diff --git a/docs/cli-reference.md b/docs/cli-reference.md
index b9a4899e..1db77c3b 100644
--- a/docs/cli-reference.md
+++ b/docs/cli-reference.md
@@ -20,7 +20,7 @@ Use this page when you know what you want to run and need the command shape. For
 | Check chat channel setup | `nanobot channels status` | Useful before starting `nanobot gateway` |
 | Manage optional features | `nanobot plugins list` | Shows channels and optional capabilities you can turn on |
 | Log in to QR/OAuth-style channels | `nanobot channels login <channel>` | Used by channels such as WhatsApp and WeChat |
-| Log in to OAuth model providers | `nanobot provider login <provider>` | Used by OAuth providers such as OpenAI Codex and GitHub Copilot |
+| Log in to OAuth model providers | `nanobot provider login <provider>` | Used by OpenAI Codex, xAI subscription, and GitHub Copilot providers |
 
 ## Global
 
@@ -287,8 +287,10 @@ remain accepted as no-op compatibility aliases.
 | Command | Description |
 |---|---|
 | `nanobot provider login openai-codex --set-main` | Authenticate Codex and select its current default model |
+| `nanobot provider login xai-grok --set-main` | Authenticate an eligible X Premium / Grok subscription and select Grok 4.5; hosted X Search is enabled for models that advertise support |
 | `nanobot provider login github-copilot --set-main` | Authenticate GitHub Copilot and select its current default model |
 | `nanobot provider logout openai-codex` | Remove OpenAI Codex OAuth state |
+| `nanobot provider logout xai-grok --config <path>` | Remove the selected nanobot instance's xAI OAuth state |
 | `nanobot provider logout github-copilot` | Remove GitHub Copilot OAuth state |
 
 See [`providers.md`](./providers.md#oauth-providers) for when OAuth providers need explicit provider/model selection.
diff --git a/docs/configuration.md b/docs/configuration.md
index c69ad7d2..404cb772 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -260,7 +260,7 @@ Tracing covers the providers that go through nanobot's OpenAI-compatible client
 > - **Xiaomi MiMo thinking mode**: MiMo models (e.g. `mimo-v2.5-pro`) default to enabled thinking. Use `agents.defaults.reasoningEffort: "none"` to disable it, or `"low"` / `"medium"` / `"high"` to keep it on. Omitting the field preserves the provider's per-model default.
 > - **Xiaomi MiMo Token Plan**: If you're on MiMo's token plan, set `"apiBase": "https://token-plan-sgp.xiaomimimo.com/v1"` in your xiaomi_mimo provider config.
 > - **Custom OpenAI-compatible providers**: Besides the built-in `custom` provider, any extra key under `providers` can define its own OpenAI-compatible endpoint. For example, `providers.companyProxy.apiBase` plus `modelPresets.primary.provider: "companyProxy"` creates a separate custom provider. Set `apiBase`; set `apiKey` only when the endpoint requires it. This named-custom path uses the OpenAI-compatible request format only. For Anthropic-compatible proxies, use `providers.anthropic.apiBase` with `provider: "anthropic"`.
-> - **Provider-scoped proxy**: `providers.<name>.proxy` routes only that provider through an HTTP proxy. It is supported for OpenAI-compatible providers and `openai_codex`. Native provider backends such as `anthropic`, `bedrock`, `azure_openai`, and `github_copilot` reject `proxy`.
+> - **Provider-scoped proxy**: `providers.<name>.proxy` routes only that provider through an HTTP proxy. It is supported for OpenAI-compatible providers, `openai_codex`, and `xai_grok`. Native provider backends such as `anthropic`, `bedrock`, `azure_openai`, and `github_copilot` reject `proxy`.
 
 | Provider | Purpose | Get API Key |
 |----------|---------|-------------|
@@ -305,6 +305,7 @@ Tracing covers the providers that go through nanobot's OpenAI-compatible client
 | `vllm` | LLM (local, any OpenAI-compatible server) | — |
 | `nvidia` | LLM (NVIDIA NIM) | [build.nvidia.com](https://build.nvidia.com/) |
 | `openai_codex` | LLM (Codex, OAuth) | `nanobot provider login openai-codex --set-main` |
+| `xai_grok` | LLM (Grok, OAuth) | `nanobot provider login xai-grok --set-main` |
 | `github_copilot` | LLM (GitHub Copilot, OAuth) | `nanobot provider login github-copilot` |
 | `qianfan` | LLM (Baidu Qianfan) | [cloud.baidu.com](https://cloud.baidu.com/doc/qianfan/s/Hmh4suq26) |
 
@@ -702,6 +703,51 @@ For proxy, remote/headless login, model-name, or config-key errors, see [`troubl
 </details>
 
 
+<details>
+<summary><b>xAI Grok (OAuth)</b></summary>
+
+Use an eligible X Premium / Grok subscription without putting an API key in
+`config.json`:
+
+```bash
+nanobot provider login xai-grok --set-main
+nanobot agent -m "Hello from Grok."
+```
+
+The default model is `xai-grok/grok-4.5` with a 500,000-token context window.
+The provider reads xAI's model catalog and includes the server-hosted `x_search`
+tool only when the selected model advertises `supportsBackendSearch`. Models
+without that capability continue normally without hosted X Search. When enabled,
+searches run inside xAI's Responses API and citations arrive as inline links.
+
+This is xAI subscription OAuth, not X Developer OAuth. nanobot follows the
+public OAuth client and proxy contract used by
+[Grok Build](https://github.com/xai-org/grok-build/blob/main/crates/codegen/xai-grok-pager/docs/user-guide/02-authentication.md).
+The browser flow uses a random loopback callback and PKCE. The resulting token
+is stored in the active instance's `auth/xai.json` (normally
+`~/.nanobot/auth/xai.json`), separately from Grok Build so rotating refresh
+tokens cannot invalidate one another.
+
+To use a provider-specific proxy, merge this into `config.json` before login:
+
+```json
+{
+  "providers": {
+    "xaiGrok": {
+      "proxy": "http://127.0.0.1:7890"
+    }
+  }
+}
+```
+
+The proxy applies to OAuth discovery, token exchange/refresh, model-catalog
+lookups, and subscription model requests. Because this integration depends on
+xAI's public Grok Build client contract, an upstream contract change may require
+a nanobot update.
+
+</details>
+
+
 <details>
 <summary><b>GitHub Copilot (OAuth)</b></summary>
 
diff --git a/docs/providers.md b/docs/providers.md
index 9ce3135e..2d2ea452 100644
--- a/docs/providers.md
+++ b/docs/providers.md
@@ -63,11 +63,11 @@ These fields answer different questions:
 | `model` | `modelPresets.<name>.model` | The model ID expected by that provider or gateway. |
 | `apiKey` | `providers.<provider>.apiKey` | Credential for that provider. Use `${ENV_VAR}` for secrets. |
 | `apiBase` | `providers.<provider>.apiBase` | HTTP base URL of the provider endpoint. |
-| `proxy` | `providers.<provider>.proxy` | Optional HTTP proxy for this provider only. Supported for OpenAI-compatible providers and OpenAI Codex. |
+| `proxy` | `providers.<provider>.proxy` | Optional HTTP proxy for this provider only. Supported for OpenAI-compatible providers, OpenAI Codex, and xAI OAuth. |
 
 You usually omit `apiBase` for hosted built-in providers such as OpenRouter, Anthropic direct, OpenAI direct, Groq, or Bedrock because nanobot knows their default endpoints. Set `apiBase` for `custom`, local OpenAI-compatible servers, provider proxies, regional endpoints, or subscription endpoints. Include the API version path when the endpoint requires it, for example `https://api.example.com/v1` or `http://localhost:11434/v1`.
 
-Use `proxy` when one provider must send HTTP traffic through a proxy without changing process-wide `HTTP_PROXY` / `HTTPS_PROXY`. This is supported for providers that use nanobot's OpenAI-compatible client, including `openai`, `custom`, named custom providers, OpenRouter-style gateways, local OpenAI-compatible servers, and similar registry entries. It is also supported for `openai_codex`, including Codex OAuth token exchange/refresh and Codex Responses API requests. Native provider backends such as `anthropic`, `bedrock`, `azure_openai`, and `github_copilot` reject `proxy`; use their endpoint-specific configuration instead.
+Use `proxy` when one provider must send HTTP traffic through a proxy without changing process-wide `HTTP_PROXY` / `HTTPS_PROXY`. This is supported for providers that use nanobot's OpenAI-compatible client, including `openai`, `custom`, named custom providers, OpenRouter-style gateways, local OpenAI-compatible servers, and similar registry entries. It is also supported for `openai_codex` and `xai_grok`, including OAuth token exchange/refresh and model requests. Native provider backends such as `anthropic`, `bedrock`, `azure_openai`, and `github_copilot` reject `proxy`; use their endpoint-specific configuration instead.
 
 ## Common Provider Patterns
 
@@ -433,6 +433,25 @@ For OpenAI Codex:
 nanobot provider login openai-codex --set-main
 ```
 
+For an eligible X Premium / Grok subscription:
+
+```bash
+nanobot provider login xai-grok --set-main
+```
+
+This selects `xai-grok/grok-4.5`. The provider reads xAI's model catalog and
+exposes the hosted `x_search` tool only when the selected model advertises
+`supportsBackendSearch`; otherwise the model runs without hosted X Search.
+When enabled, Grok can search current X posts and return inline source links
+without invoking a local nanobot tool. Credentials are stored under the
+active instance's `auth/xai.json` (normally `~/.nanobot/auth/xai.json`), not in
+`config.json` and not in Grok Build's credential file.
+
+The login is xAI subscription OAuth, not X Developer OAuth. It follows the
+public client contract documented and implemented by
+[Grok Build](https://github.com/xai-org/grok-build/blob/main/crates/codegen/xai-grok-pager/docs/user-guide/02-authentication.md);
+xAI may change that upstream contract independently of nanobot.
+
 For GitHub Copilot:
 
 ```bash
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index ba89dadc..c3b9d977 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -135,12 +135,17 @@ If you need a known-good snippet instead of diagnosis, use [`provider-cookbook.m
 | Provider cannot be inferred | Pin `modelPresets.<name>.provider` in the active preset instead of using `"auto"`. For legacy direct configs, pin `agents.defaults.provider`. |
 | Local model connection refused | Ollama, vLLM, LM Studio, or another local server is not running, or `apiBase` points to the wrong port. |
 | Bedrock validation error | Check AWS region, credentials, model access, model ID, and whether the model supports Converse. |
-| OAuth provider fails | Run `nanobot provider login openai-codex --set-main` or `nanobot provider login github-copilot --set-main`. |
+| OAuth provider fails | Run the matching login command: `openai-codex`, `xai-grok`, or `github-copilot`, normally with `--set-main`. |
 | Codex OAuth needs a proxy | Set `providers.openaiCodex.proxy` before running the login command. The proxy applies to login, token refresh, and Codex API requests. |
 | Codex login runs on a remote/headless machine | Open the printed URL in a local browser, then paste the final `http://localhost:1455/auth/callback?...` URL back into the terminal. |
 | Codex login runs in Docker | Start the container with `docker run -it` so the OAuth flow has an interactive terminal. |
 | Codex says a model is not supported with a ChatGPT account | Use provider `openai_codex` with a Codex model such as `openai-codex/gpt-5.6-sol`. Do not use the direct-API `openai/...` prefix with Codex OAuth. |
 | Config says `providers.openai_codex` conflicts with the built-in provider | Under `providers`, keep only the canonical `openaiCodex` settings key and remove a duplicate `openai_codex` key. A model preset's `provider` value remains `openai_codex`. |
+| xAI OAuth needs a proxy | Set `providers.xaiGrok.proxy` before login. It applies to OAuth discovery, token exchange/refresh, and Grok subscription requests. |
+| xAI login runs on a remote/headless machine | In the WebUI, finish sign-in in your local browser; if the loopback redirect cannot reach the server, copy the final URL from the address bar into the WebUI dialog. From the CLI, run `nanobot provider login xai-grok` interactively, open the printed URL elsewhere, and paste the final callback URL or authorization code when prompted. |
+| xAI returns 403 or subscription access denied | Confirm the signed-in account has an eligible X Premium / Grok subscription, then run `nanobot provider login xai-grok` again. This provider does not use an xAI API key or X Developer OAuth. |
+| xAI returns 400 `invalid-argument` | Read the bounded `Response body` appended to the provider error. Hosted `x_search` is sent only when xAI's model catalog advertises `supportsBackendSearch`; the model ID `grok-4.5` itself is valid. |
+| xAI model or X Search stops working after an upstream release | The integration follows Grok Build's public OAuth/proxy client contract. Update nanobot if xAI changes that contract. |
 
 ## Langfuse Problems
 
diff --git a/nanobot/cli/commands.py b/nanobot/cli/commands.py
index 9b35b68b..d96c92c8 100644
--- a/nanobot/cli/commands.py
+++ b/nanobot/cli/commands.py
@@ -2662,11 +2662,13 @@ _LOGOUT_HANDLERS: dict[str, Callable[[], None]] = {}
 
 _PROVIDER_DISPLAY: dict[str, str] = {
     "openai_codex": "OpenAI Codex",
+    "xai_grok": "xAI Grok",
     "github_copilot": "GitHub Copilot",
 }
 
 _OAUTH_PROVIDER_DEFAULT_MODELS: dict[str, str] = {
     "openai_codex": "openai-codex/gpt-5.6-sol",
+    "xai_grok": "xai-grok/grok-4.5",
     "github_copilot": "github-copilot/gpt-5.4-mini",
 }
 
@@ -2720,6 +2722,8 @@ def _set_oauth_provider_as_main(
     config.agents.defaults.model_preset = None
     config.agents.defaults.provider = provider_name
     config.agents.defaults.model = selected_model
+    if provider_name == "xai_grok" and selected_model == "xai-grok/grok-4.5":
+        config.agents.defaults.context_window_tokens = 500_000
     save_config(config, resolved_config_path)
 
     saved_path = resolved_config_path or get_config_path()
@@ -2732,7 +2736,10 @@ def _set_oauth_provider_as_main(
 
 @provider_app.command("login")
 def provider_login(
-    provider: str = typer.Argument(..., help="OAuth provider (e.g. 'openai-codex', 'github-copilot')"),
+    provider: str = typer.Argument(
+        ...,
+        help="OAuth provider (e.g. 'openai-codex', 'xai-grok', 'github-copilot')",
+    ),
     set_main: bool = typer.Option(
         False,
         "--set-main",
@@ -2770,7 +2777,11 @@ def provider_login(
 
 @provider_app.command("logout")
 def provider_logout(
-    provider: str = typer.Argument(..., help="OAuth provider (e.g. 'openai-codex', 'github-copilot')"),
+    provider: str = typer.Argument(
+        ...,
+        help="OAuth provider (e.g. 'openai-codex', 'xai-grok', 'github-copilot')",
+    ),
+    config: str | None = typer.Option(None, "--config", "-c", help="Path to config file"),
 ):
     """Log out from an OAuth provider."""
     spec = _resolve_oauth_provider(provider)
@@ -2780,6 +2791,13 @@ def provider_logout(
         console.print(f"[red]Logout not implemented for {spec.label}[/red]")
         raise typer.Exit(1)
 
+    if config:
+        from nanobot.config.loader import set_config_path
+
+        resolved_config_path = Path(config).expanduser().resolve()
+        set_config_path(resolved_config_path)
+        console.print(f"[dim]Using config: {resolved_config_path}[/dim]")
+
     console.print(f"{__logo__} OAuth Logout - {spec.label}\n")
     handler()
 
@@ -2830,6 +2848,55 @@ def _logout_openai_codex() -> None:
     _delete_oauth_files(storage.get_token_path(), _PROVIDER_DISPLAY["openai_codex"])
 
 
+@_register_login("xai_grok")
+def _login_xai_grok() -> None:
+    """Authenticate with xAI using the Grok subscription OAuth contract."""
+    from nanobot.config.loader import load_config, resolve_config_env_vars
+    from nanobot.providers.xai_oauth import get_xai_oauth_token, login_xai_oauth
+
+    try:
+        proxy = resolve_config_env_vars(load_config()).providers.xai_grok.proxy or None
+    except ValueError as exc:
+        console.print(f"[red]{exc}[/red]")
+        raise typer.Exit(1) from exc
+
+    token = None
+    with suppress(Exception):
+        token = get_xai_oauth_token(proxy=proxy)
+    if not (token and token.access):
+        console.print(
+            "[cyan]Starting xAI browser sign-in for your X Premium / Grok subscription...[/cyan]\n"
+        )
+        try:
+            token = login_xai_oauth(
+                print_fn=lambda message: console.print(message),
+                prompt_fn=lambda prompt: typer.prompt(prompt),
+                proxy=proxy,
+            )
+        except Exception as exc:
+            console.print(f"[red]Authentication error: {exc}[/red]")
+            raise typer.Exit(1) from exc
+    account = token.account_id or "xAI account"
+    console.print(f"[green]✓ Authenticated with xAI[/green]  [dim]{account}[/dim]")
+    console.print(
+        "[dim]Hosted X Search is enabled automatically when the selected model supports it.[/dim]"
+    )
+
+
+@_register_logout("xai_grok")
+def _logout_xai_grok() -> None:
+    """Clear local xAI OAuth credentials for this nanobot instance."""
+    from nanobot.providers.xai_oauth import get_xai_oauth_storage_path, logout_xai_oauth
+
+    token_path = get_xai_oauth_storage_path()
+    provider_label = _PROVIDER_DISPLAY["xai_grok"]
+    if logout_xai_oauth():
+        console.print(f"[green]✓ Logged out from {provider_label}[/green]")
+        console.print(f"[dim]Removed: {token_path}[/dim]")
+    else:
+        console.print(f"[yellow]! No local OAuth credentials found for {provider_label}[/yellow]")
+
+
 @_register_logout("github_copilot")
 def _logout_github_copilot() -> None:
     """Clear local OAuth credentials for GitHub Copilot."""
diff --git a/nanobot/config/loader.py b/nanobot/config/loader.py
index 743ab8a0..347c1c29 100644
--- a/nanobot/config/loader.py
+++ b/nanobot/config/loader.py
@@ -81,10 +81,20 @@ def save_config(config: Config, config_path: Path | None = None) -> None:
     path.parent.mkdir(parents=True, exist_ok=True)
 
     data = config.model_dump(mode="json", by_alias=True)
-    if config.providers.openai_codex.proxy is not None:
-        data.setdefault("providers", {})["openaiCodex"] = {
-            "proxy": config.providers.openai_codex.proxy,
-        }
+    # OAuth credentials live in dedicated token stores. Persist only the
+    # non-credential request settings consumed by these provider backends.
+    for alias, provider in (
+        ("openaiCodex", config.providers.openai_codex),
+        ("xaiGrok", config.providers.xai_grok),
+    ):
+        settings = provider.model_dump(
+            mode="json",
+            by_alias=True,
+            include={"proxy", "extra_body"},
+            exclude_none=True,
+        )
+        if settings:
+            data.setdefault("providers", {})[alias] = settings
 
     # Temp + replace so a crash mid-write cannot leave a truncated config.json.
     _write_text_atomic(path, json.dumps(data, indent=2, ensure_ascii=False))
diff --git a/nanobot/config/schema.py b/nanobot/config/schema.py
index 95e7d68c..47c04ae2 100644
--- a/nanobot/config/schema.py
+++ b/nanobot/config/schema.py
@@ -269,6 +269,7 @@ class ProvidersConfig(Base):
     byteplus: ProviderConfig = Field(default_factory=ProviderConfig)  # BytePlus (VolcEngine international)
     byteplus_coding_plan: ProviderConfig = Field(default_factory=ProviderConfig)  # BytePlus Coding Plan
     openai_codex: ProviderConfig = Field(default_factory=ProviderConfig, exclude=True)  # OpenAI Codex (OAuth)
+    xai_grok: ProviderConfig = Field(default_factory=ProviderConfig, exclude=True)  # xAI Grok (OAuth)
     github_copilot: ProviderConfig = Field(default_factory=ProviderConfig, exclude=True)  # Github Copilot (OAuth)
     qianfan: ProviderConfig = Field(default_factory=ProviderConfig)  # Qianfan (百度千帆)
     nvidia: ProviderConfig = Field(default_factory=ProviderConfig)  # NVIDIA NIM (nvapi- keys)
diff --git a/nanobot/providers/__init__.py b/nanobot/providers/__init__.py
index f5834b73..4eea5d3d 100644
--- a/nanobot/providers/__init__.py
+++ b/nanobot/providers/__init__.py
@@ -13,6 +13,7 @@ __all__ = [
     "AnthropicProvider",
     "OpenAICompatProvider",
     "OpenAICodexProvider",
+    "XAIGrokProvider",
     "GitHubCopilotProvider",
     "AzureOpenAIProvider",
     "BedrockProvider",
@@ -22,6 +23,7 @@ _LAZY_IMPORTS = {
     "AnthropicProvider": ".anthropic_provider",
     "OpenAICompatProvider": ".openai_compat_provider",
     "OpenAICodexProvider": ".openai_codex_provider",
+    "XAIGrokProvider": ".xai_grok_provider",
     "GitHubCopilotProvider": ".github_copilot_provider",
     "AzureOpenAIProvider": ".azure_openai_provider",
     "BedrockProvider": ".bedrock_provider",
@@ -34,6 +36,7 @@ if TYPE_CHECKING:
     from nanobot.providers.github_copilot_provider import GitHubCopilotProvider
     from nanobot.providers.openai_codex_provider import OpenAICodexProvider
     from nanobot.providers.openai_compat_provider import OpenAICompatProvider
+    from nanobot.providers.xai_grok_provider import XAIGrokProvider
 
 
 def __getattr__(name: str):
diff --git a/nanobot/providers/factory.py b/nanobot/providers/factory.py
index ead2e023..7fdec1a3 100644
--- a/nanobot/providers/factory.py
+++ b/nanobot/providers/factory.py
@@ -60,10 +60,10 @@ def _make_provider_core(
     if spec and spec.is_transcription_only:
         raise ValueError(f"Provider '{provider_name}' only supports transcription.")
     backend = spec.backend if spec else "openai_compat"
-    if p and p.proxy and backend not in {"openai_compat", "openai_codex"}:
+    if p and p.proxy and backend not in {"openai_compat", "openai_codex", "xai_grok"}:
         raise ValueError(
             f"providers.{provider_name}.proxy is only supported for "
-            "OpenAI-compatible providers and OpenAI Codex."
+            "OpenAI-compatible providers, OpenAI Codex, and xAI Grok."
         )
 
     if backend == "azure_openai":
@@ -91,6 +91,14 @@ def _make_provider_core(
             proxy=getattr(p, "proxy", None) if p else None,
             extra_body=p.extra_body if p else None,
         )
+    elif backend == "xai_grok":
+        from nanobot.providers.xai_grok_provider import XAIGrokProvider
+
+        provider = XAIGrokProvider(
+            default_model=model,
+            proxy=getattr(p, "proxy", None) if p else None,
+            extra_body=p.extra_body if p else None,
+        )
     elif backend == "azure_openai":
         from nanobot.providers.azure_openai_provider import AzureOpenAIProvider
 
diff --git a/nanobot/providers/registry.py b/nanobot/providers/registry.py
index 59db09a4..d5acd0de 100644
--- a/nanobot/providers/registry.py
+++ b/nanobot/providers/registry.py
@@ -47,7 +47,8 @@ class ProviderSpec:
     settings_alias_for: str = ""  # compatibility alias grouped under this provider in Settings
 
     # which provider implementation to use
-    # "openai_compat" | "anthropic" | "azure_openai" | "openai_codex" | "github_copilot" | "bedrock"
+    # "openai_compat" | "anthropic" | "azure_openai" | "openai_codex" | "xai_grok"
+    # | "github_copilot" | "bedrock"
     backend: str = "openai_compat"
 
     # extra env vars / request headers supplied by the provider integration.
@@ -420,6 +421,25 @@ PROVIDERS: tuple[ProviderSpec, ...] = (
         default_api_base="https://chatgpt.com/backend-api",
         is_oauth=True,
     ),
+    # xAI subscription: OAuth-based, with capability-gated server-hosted X Search.
+    ProviderSpec(
+        name="xai_grok",
+        keywords=("xai-grok", "xai_grok"),
+        env_key="",
+        display_name="xAI Grok",
+        model_catalog="builtin",
+        builtin_models=(
+            ProviderModelSpec(
+                id="xai-grok/grok-4.5",
+                label="Grok 4.5",
+                description="Grok via xAI subscription; X Search is enabled when supported.",
+                context_window=500000,
+            ),
+        ),
+        backend="xai_grok",
+        default_api_base="https://cli-chat-proxy.grok.com/v1",
+        is_oauth=True,
+    ),
     # GitHub Copilot: OAuth-based
     ProviderSpec(
         name="github_copilot",
diff --git a/nanobot/providers/xai_grok_provider.py b/nanobot/providers/xai_grok_provider.py
new file mode 100644
index 00000000..c503d89d
--- /dev/null
+++ b/nanobot/providers/xai_grok_provider.py
@@ -0,0 +1,545 @@
+"""xAI subscription provider with capability-gated hosted X Search."""
+
+from __future__ import annotations
+
+import asyncio
+import base64
+import json
+import re
+import time
+import uuid
+from collections.abc import Awaitable, Callable
+from typing import Any
+
+import httpx
+from loguru import logger
+
+from nanobot import __version__
+from nanobot.providers.base import (
+    LLMProvider,
+    LLMResponse,
+    ToolCallRequest,
+    resolve_stream_idle_timeout_s,
+)
+from nanobot.providers.openai_responses import (
+    consume_sse_with_reasoning,
+    convert_messages,
+    convert_tools,
+)
+from nanobot.providers.xai_oauth import (
+    XAI_CLIENT_VERSION,
+    XAIToken,
+    get_xai_oauth_token,
+)
+
+DEFAULT_XAI_GROK_URL = "https://cli-chat-proxy.grok.com/v1/responses"
+DEFAULT_XAI_GROK_MODELS_URL = "https://cli-chat-proxy.grok.com/v1/models"
+DEFAULT_XAI_GROK_MODEL = "xai-grok/grok-4.5"
+_MODEL_CAPABILITIES_TTL_S = 5 * 60
+_MAX_ERROR_BODY_CHARS = 1000
+_SENSITIVE_ERROR_KEYS = {
+    "accesstoken",
+    "apikey",
+    "authorization",
+    "idtoken",
+    "refreshtoken",
+}
+
+
+class XAIGrokProvider(LLMProvider):
+    """Call xAI's subscription proxy and expose supported hosted tools."""
+
+    supports_progress_deltas = True
+
+    def __init__(
+        self,
+        default_model: str = DEFAULT_XAI_GROK_MODEL,
+        proxy: str | None = None,
+        extra_body: dict[str, Any] | None = None,
+    ):
+        super().__init__(api_key=None, api_base=None)
+        self.default_model = default_model
+        self.proxy = proxy or None
+        self._extra_body = dict(extra_body or {})
+        self._model_capabilities: dict[str, bool] | None = None
+        self._model_capabilities_fetched_at = 0.0
+
+    async def _supports_backend_search(self, token: XAIToken, model: str) -> bool:
+        now = time.monotonic()
+        capabilities = self._model_capabilities
+        if (
+            capabilities is None
+            or now - self._model_capabilities_fetched_at >= _MODEL_CAPABILITIES_TTL_S
+        ):
+            try:
+                capabilities = await _fetch_xai_model_capabilities(
+                    DEFAULT_XAI_GROK_MODELS_URL,
+                    _build_model_headers(token),
+                    proxy=self.proxy,
+                )
+            except Exception as exc:
+                logger.warning(
+                    "xAI model capability lookup failed; hosted X Search disabled for model {}: "
+                    "type={} error={}",
+                    model,
+                    type(exc).__name__,
+                    str(exc).strip() or "unexpected error",
+                )
+                capabilities = {}
+                self._model_capabilities = capabilities
+                self._model_capabilities_fetched_at = now
+            else:
+                self._model_capabilities = capabilities
+                self._model_capabilities_fetched_at = now
+        return capabilities.get(model, False)
+
+    async def _call_xai(
+        self,
+        messages: list[dict[str, Any]],
+        tools: list[dict[str, Any]] | None,
+        model: str | None,
+        max_tokens: int,
+        temperature: float,
+        reasoning_effort: str | None,
+        tool_choice: str | dict[str, Any] | None,
+        on_content_delta: Callable[[str], Awaitable[None]] | None = None,
+        on_thinking_delta: Callable[[str], Awaitable[None]] | None = None,
+        on_tool_call_delta: Callable[[dict[str, Any]], Awaitable[None]] | None = None,
+    ) -> LLMResponse:
+        wire_model = _strip_model_prefix(model or self.default_model)
+        system_prompt, input_items = convert_messages(messages)
+
+        stage = "oauth_token"
+        try:
+            token = await asyncio.to_thread(get_xai_oauth_token, proxy=self.proxy)
+            stage = "model_capabilities"
+            supports_backend_search = await self._supports_backend_search(token, wire_model)
+            converted_tools = convert_tools(tools or [])
+            if supports_backend_search:
+                converted_tools = [
+                    tool for tool in converted_tools if tool.get("name") != "x_search"
+                ]
+                converted_tools.append({"type": "x_search"})
+
+            body: dict[str, Any] = {
+                "model": wire_model,
+                "store": False,
+                "stream": True,
+                "instructions": system_prompt,
+                "input": input_items,
+                "include": ["reasoning.encrypted_content"],
+                "tools": converted_tools,
+                "tool_choice": tool_choice or "auto",
+                "parallel_tool_calls": True,
+                "stream_tool_calls": True,
+                "max_output_tokens": max_tokens,
+                "temperature": temperature,
+                "reasoning": _build_reasoning_options(reasoning_effort),
+            }
+            if self._extra_body:
+                body.update(self._extra_body)
+
+            headers = _build_headers(token.access, wire_model)
+            stage = "xai_request"
+            try:
+                result = await _request_xai(
+                    DEFAULT_XAI_GROK_URL,
+                    headers,
+                    body,
+                    proxy=self.proxy,
+                    on_content_delta=on_content_delta,
+                    on_thinking_delta=on_thinking_delta,
+                    on_tool_call_delta=on_tool_call_delta,
+                )
+            except _XAIHTTPError as exc:
+                if exc.status_code != 401:
+                    raise
+                stage = "oauth_refresh"
+                token = await asyncio.to_thread(
+                    get_xai_oauth_token,
+                    proxy=self.proxy,
+                    force_refresh=True,
+                )
+                self._model_capabilities = None
+                self._model_capabilities_fetched_at = 0.0
+                headers = _build_headers(token.access, wire_model)
+                stage = "xai_request_retry"
+                result = await _request_xai(
+                    DEFAULT_XAI_GROK_URL,
+                    headers,
+                    body,
+                    proxy=self.proxy,
+                    on_content_delta=on_content_delta,
+                    on_thinking_delta=on_thinking_delta,
+                    on_tool_call_delta=on_tool_call_delta,
+                )
+
+            content, tool_calls, finish_reason, usage, reasoning_content = result
+            return LLMResponse(
+                content=content,
+                tool_calls=tool_calls,
+                finish_reason=finish_reason,
+                usage=usage,
+                reasoning_content=reasoning_content,
+            )
+        except Exception as exc:
+            response = _xai_error_response(exc)
+            logger.warning(
+                "xAI subscription request failed: stage={} type={} retryable={} status={} "
+                "error_type={} error_code={} response_body={}",
+                stage,
+                type(exc).__name__,
+                response.error_should_retry,
+                response.error_status_code,
+                response.error_type,
+                response.error_code,
+                getattr(exc, "response_body", None),
+            )
+            return response
+
+    async def chat(
+        self,
+        messages: list[dict[str, Any]],
+        tools: list[dict[str, Any]] | None = None,
+        model: str | None = None,
+        max_tokens: int = 4096,
+        temperature: float = 0.7,
+        reasoning_effort: str | None = None,
+        tool_choice: str | dict[str, Any] | None = None,
+    ) -> LLMResponse:
+        return await self._call_xai(
+            messages, tools, model, max_tokens, temperature, reasoning_effort, tool_choice
+        )
+
+    async def chat_stream(
+        self,
+        messages: list[dict[str, Any]],
+        tools: list[dict[str, Any]] | None = None,
+        model: str | None = None,
+        max_tokens: int = 4096,
+        temperature: float = 0.7,
+        reasoning_effort: str | None = None,
+        tool_choice: str | dict[str, Any] | None = None,
+        on_content_delta: Callable[[str], Awaitable[None]] | None = None,
+        on_thinking_delta: Callable[[str], Awaitable[None]] | None = None,
+        on_tool_call_delta: Callable[[dict[str, Any]], Awaitable[None]] | None = None,
+    ) -> LLMResponse:
+        return await self._call_xai(
+            messages,
+            tools,
+            model,
+            max_tokens,
+            temperature,
+            reasoning_effort,
+            tool_choice,
+            on_content_delta,
+            on_thinking_delta,
+            on_tool_call_delta,
+        )
+
+    def get_default_model(self) -> str:
+        return self.default_model
+
+
+def _strip_model_prefix(model: str) -> str:
+    if model.startswith("xai-grok/") or model.startswith("xai_grok/"):
+        return model.split("/", 1)[1]
+    return model
+
+
+def _build_reasoning_options(reasoning_effort: str | None) -> dict[str, str]:
+    options = {"summary": "concise"}
+    if reasoning_effort and reasoning_effort.lower() != "none":
+        options["effort"] = reasoning_effort
+    return options
+
+
+def _build_headers(token: str, model: str) -> dict[str, str]:
+    conversation_id = str(uuid.uuid4())
+    return {
+        "Authorization": f"Bearer {token}",
+        "X-XAI-Token-Auth": "xai-grok-cli",
+        "x-authenticateresponse": "authenticate-response",
+        "x-grok-client-version": XAI_CLIENT_VERSION,
+        "x-grok-client-identifier": "nanobot",
+        "x-grok-client-mode": "headless",
+        "x-grok-conv-id": conversation_id,
+        "x-grok-req-id": str(uuid.uuid4()),
+        "x-grok-model-override": model,
+        "x-grok-session-id": conversation_id,
+        "x-grok-agent-id": str(uuid.uuid4()),
+        "User-Agent": f"nanobot/{__version__} (python)",
+        "accept": "text/event-stream",
+        "content-type": "application/json",
+    }
+
+
+def _build_model_headers(token: XAIToken) -> dict[str, str]:
+    headers = {
+        "Authorization": f"Bearer {token.access}",
+        "X-XAI-Token-Auth": "xai-grok-cli",
+        "x-grok-client-version": XAI_CLIENT_VERSION,
+        "x-grok-client-identifier": "nanobot",
+        "x-grok-client-mode": "headless",
+        "User-Agent": f"nanobot/{__version__} (python)",
+        "accept": "application/json",
+    }
+    claims = _decode_access_token_claims(token.access)
+    user_id = claims.get("sub")
+    if claims.get("principal_type") == "Team":
+        user_id = claims.get("principal_id") or user_id
+    if isinstance(user_id, str) and user_id:
+        headers["x-userid"] = user_id
+    email = claims.get("email")
+    if not isinstance(email, str) or "@" not in email:
+        email = token.account_id if token.account_id and "@" in token.account_id else None
+    if email:
+        headers["x-email"] = email
+    return headers
+
+
+def _decode_access_token_claims(token: str) -> dict[str, Any]:
+    """Read identity hints from the signed token; the server still authenticates it."""
+    parts = token.split(".")
+    if len(parts) < 2 or not parts[1]:
+        return {}
+    payload = parts[1]
+    try:
+        decoded = base64.urlsafe_b64decode(payload + "=" * (-len(payload) % 4))
+        claims = json.loads(decoded)
+    except (ValueError, TypeError):
+        return {}
+    return claims if isinstance(claims, dict) else {}
+
+
+class _XAIHTTPError(RuntimeError):
+    def __init__(
+        self,
+        message: str,
+        *,
+        status_code: int,
+        retry_after: float | None = None,
+        error_type: str | None = None,
+        error_code: str | None = None,
+        should_retry: bool | None = None,
+        response_body: str | None = None,
+    ):
+        super().__init__(message)
+        self.status_code = status_code
+        self.retry_after = retry_after
+        self.error_type = error_type
+        self.error_code = error_code
+        self.should_retry = should_retry
+        self.response_body = response_body
+
+
+async def _fetch_xai_model_capabilities(
+    url: str,
+    headers: dict[str, str],
+    *,
+    proxy: str | None = None,
+) -> dict[str, bool]:
+    client_kwargs: dict[str, Any] = {"timeout": 10.0, "follow_redirects": False}
+    if proxy:
+        client_kwargs.update(proxy=proxy, trust_env=False)
+    async with httpx.AsyncClient(**client_kwargs) as client:
+        response = await client.get(url, headers=headers)
+    if response.status_code != 200:
+        raw = response.content.decode("utf-8", "ignore")
+        raise _build_xai_http_error(response.status_code, response.headers, raw)
+    try:
+        payload = response.json()
+    except ValueError as exc:
+        raise RuntimeError("xAI model catalog returned invalid JSON.") from exc
+    return _parse_xai_model_capabilities(payload)
+
+
+def _parse_xai_model_capabilities(payload: Any) -> dict[str, bool]:
+    if isinstance(payload, dict):
+        rows = payload.get("data")
+        if not isinstance(rows, list):
+            rows = payload.get("models")
+    else:
+        rows = payload
+    if not isinstance(rows, list):
+        return {}
+
+    capabilities: dict[str, bool] = {}
+    for row in rows:
+        if not isinstance(row, dict):
+            continue
+        meta = row.get("_meta") if isinstance(row.get("_meta"), dict) else {}
+        support_value = row.get("supportsBackendSearch")
+        if not isinstance(support_value, bool):
+            support_value = row.get("supports_backend_search")
+        if not isinstance(support_value, bool):
+            support_value = meta.get("supportsBackendSearch")
+        if not isinstance(support_value, bool):
+            support_value = meta.get("supports_backend_search")
+        supports_backend_search = support_value if isinstance(support_value, bool) else False
+
+        identifiers = (
+            row.get("model"),
+            row.get("modelId"),
+            row.get("id"),
+            meta.get("model"),
+            meta.get("modelId"),
+        )
+        for identifier in identifiers:
+            if isinstance(identifier, str) and identifier.strip():
+                capabilities[_strip_model_prefix(identifier.strip())] = supports_backend_search
+    return capabilities
+
+
+async def _request_xai(
+    url: str,
+    headers: dict[str, str],
+    body: dict[str, Any],
+    *,
+    proxy: str | None = None,
+    on_content_delta: Callable[[str], Awaitable[None]] | None = None,
+    on_thinking_delta: Callable[[str], Awaitable[None]] | None = None,
+    on_tool_call_delta: Callable[[dict[str, Any]], Awaitable[None]] | None = None,
+) -> tuple[str, list[ToolCallRequest], str, dict[str, int], str | None]:
+    client_kwargs: dict[str, Any] = {"timeout": resolve_stream_idle_timeout_s()}
+    if proxy:
+        client_kwargs.update(proxy=proxy, trust_env=False)
+    async with httpx.AsyncClient(**client_kwargs) as client:
+        async with client.stream("POST", url, headers=headers, json=body) as response:
+            if response.status_code != 200:
+                content = await response.aread()
+                raw = content.decode("utf-8", "ignore")
+                raise _build_xai_http_error(response.status_code, response.headers, raw)
+            return await consume_sse_with_reasoning(
+                response,
+                on_content_delta=on_content_delta,
+                on_tool_call_delta=on_tool_call_delta,
+                on_reasoning_delta=on_thinking_delta,
+            )
+
+
+def _build_xai_http_error(
+    status_code: int,
+    headers: httpx.Headers,
+    raw: str,
+) -> _XAIHTTPError:
+    retry_after = LLMProvider._extract_retry_after_from_headers(headers)
+    error_type, error_code = LLMProvider._extract_error_type_code(raw)
+    response_body = _bounded_error_body(raw)
+    return _XAIHTTPError(
+        _friendly_error(status_code, response_body),
+        status_code=status_code,
+        retry_after=retry_after,
+        error_type=error_type,
+        error_code=error_code,
+        should_retry=_should_retry_status(status_code, error_type, error_code, raw),
+        response_body=response_body,
+    )
+
+
+def _bounded_error_body(raw: str) -> str | None:
+    text = raw.strip()
+    if not text:
+        return None
+
+    try:
+        payload = json.loads(text)
+    except (TypeError, ValueError):
+        pass
+    else:
+        text = json.dumps(
+            _redact_error_payload(payload),
+            ensure_ascii=False,
+            separators=(",", ":"),
+        )
+
+    text = re.sub(r"(?i)(bearer\s+)[a-z0-9._~+/=-]+", r"\1[REDACTED]", text)
+    text = " ".join(text.split())
+    if len(text) > _MAX_ERROR_BODY_CHARS:
+        return f"{text[:_MAX_ERROR_BODY_CHARS]}…"
+    return text
+
+
+def _redact_error_payload(payload: Any) -> Any:
+    if isinstance(payload, dict):
+        return {
+            key: "[REDACTED]" if _is_sensitive_error_key(key) else _redact_error_payload(value)
+            for key, value in payload.items()
+        }
+    if isinstance(payload, list):
+        return [_redact_error_payload(value) for value in payload]
+    return payload
+
+
+def _is_sensitive_error_key(key: str) -> bool:
+    normalized = re.sub(r"[^a-z0-9]", "", key.casefold())
+    return normalized in _SENSITIVE_ERROR_KEYS
+
+
+def _friendly_error(status_code: int, response_body: str | None = None) -> str:
+    if status_code == 401:
+        message = "xAI rejected the login. Sign in again with `nanobot provider login xai-grok`."
+    elif status_code == 403:
+        message = "This xAI account or subscription cannot access the Grok subscription endpoint."
+    elif status_code == 426:
+        message = "xAI requires a newer Grok client version. Update nanobot and try again."
+    elif status_code == 429:
+        message = "xAI usage quota or rate limit reached. Please try again later."
+    else:
+        message = f"xAI subscription endpoint returned HTTP {status_code}."
+    if response_body:
+        return f"{message} Response body: {response_body}"
+    return message
+
+
+def _xai_error_response(exc: Exception) -> LLMResponse:
+    status_code = getattr(exc, "status_code", None)
+    should_retry = getattr(exc, "should_retry", None)
+    error_kind: str | None = None
+    if isinstance(exc, (httpx.TimeoutException, asyncio.TimeoutError)):
+        error_kind = "timeout"
+        should_retry = True if should_retry is None else should_retry
+    elif isinstance(exc, (httpx.NetworkError, httpx.TransportError)):
+        error_kind = "connection"
+        should_retry = True if should_retry is None else should_retry
+    elif isinstance(exc, _XAIHTTPError):
+        error_kind = "http"
+    if status_code is not None and should_retry is None:
+        should_retry = _should_retry_status(
+            int(status_code),
+            getattr(exc, "error_type", None),
+            getattr(exc, "error_code", None),
+            None,
+        )
+    message = str(exc).strip() or "unexpected error"
+    retry_after = getattr(exc, "retry_after", None)
+    return LLMResponse(
+        content=f"Error calling xAI ({type(exc).__name__}): {message}",
+        finish_reason="error",
+        retry_after=retry_after,
+        error_status_code=int(status_code) if status_code is not None else None,
+        error_kind=error_kind,
+        error_type=getattr(exc, "error_type", None),
+        error_code=getattr(exc, "error_code", None),
+        error_retry_after_s=retry_after,
+        error_should_retry=should_retry,
+    )
+
+
+def _should_retry_status(
+    status_code: int,
+    error_type: str | None,
+    error_code: str | None,
+    content: str | None,
+) -> bool:
+    if status_code == 429:
+        return LLMProvider._is_retryable_429_response(
+            LLMResponse(
+                content=content or "",
+                finish_reason="error",
+                error_status_code=status_code,
+                error_type=error_type,
+                error_code=error_code,
+            )
+        )
+    return status_code in LLMProvider._RETRYABLE_STATUS_CODES or status_code >= 500
diff --git a/nanobot/providers/xai_oauth.py b/nanobot/providers/xai_oauth.py
new file mode 100644
index 00000000..ca5e0dda
--- /dev/null
+++ b/nanobot/providers/xai_oauth.py
@@ -0,0 +1,745 @@
+"""xAI subscription OAuth (Authorization Code + PKCE) support.
+
+This integration follows the public OAuth client contract used by Grok Build.
+Credentials are stored separately from Grok Build so rotating refresh tokens are
+never shared between the two applications.
+"""
+
+from __future__ import annotations
+
+import base64
+import hashlib
+import hmac
+import json
+import os
+import queue
+import secrets
+import threading
+import time
+import webbrowser
+from collections.abc import Callable
+from contextlib import suppress
+from dataclasses import asdict, dataclass
+from http import HTTPStatus
+from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
+from pathlib import Path
+from typing import Any
+from urllib.parse import parse_qs, urlencode, urlsplit
+
+import httpx
+from filelock import FileLock
+from loguru import logger
+
+from nanobot.config.paths import get_data_dir
+from nanobot.utils.helpers import _write_text_atomic
+
+XAI_OAUTH_ISSUER = "https://auth.x.ai"
+XAI_CLIENT_ID = "b1a00492-073a-47ea-816f-4c329264a828"
+XAI_CLIENT_VERSION = "0.2.109"
+XAI_ALLOWED_CALLBACK_ORIGIN = "https://accounts.x.ai"
+XAI_OAUTH_SCOPES = (
+    "openid",
+    "profile",
+    "email",
+    "offline_access",
+    "grok-cli:access",
+    "api:access",
+    "conversations:read",
+    "conversations:write",
+    "workspaces:read",
+    "workspaces:write",
+)
+
+_DISCOVERY_URL = f"{XAI_OAUTH_ISSUER}/.well-known/openid-configuration"
+_TOKEN_REFRESH_MARGIN_MS = 5 * 60 * 1000
+_DEFAULT_TOKEN_TTL_S = 60 * 60
+_HTTP_TIMEOUT_S = 15.0
+
+
+class XAIOAuthError(RuntimeError):
+    """An actionable xAI OAuth failure with no credential material."""
+
+
+@dataclass(frozen=True)
+class XAIToken:
+    """Persisted xAI OAuth token material."""
+
+    access: str
+    refresh: str | None
+    expires: int
+    account_id: str | None = None
+
+    @classmethod
+    def from_dict(cls, value: Any) -> XAIToken | None:
+        if not isinstance(value, dict):
+            return None
+        access = value.get("access")
+        if not isinstance(access, str) or not access:
+            return None
+        refresh = value.get("refresh")
+        if not isinstance(refresh, str) or not refresh:
+            refresh = None
+        try:
+            expires = int(value.get("expires") or 0)
+        except (TypeError, ValueError):
+            expires = 0
+        account_id = value.get("account_id")
+        if not isinstance(account_id, str) or not account_id:
+            account_id = None
+        return cls(access=access, refresh=refresh, expires=expires, account_id=account_id)
+
+
+@dataclass(frozen=True)
+class _Discovery:
+    authorization_endpoint: str
+    token_endpoint: str
+    userinfo_endpoint: str | None
+
+
+@dataclass(frozen=True)
+class _CallbackResult:
+    code: str | None = None
+    state: str | None = None
+    error: str | None = None
+
+
+class XAIOAuthLoginFlow:
+    """Pending xAI OAuth login that can finish through loopback or an authorization code."""
+
+    def __init__(
+        self,
+        *,
+        authorization_url: str,
+        redirect_uri: str,
+        verifier: str,
+        state: str,
+        discovery: _Discovery,
+        proxy: str | None,
+        result_queue: queue.Queue[_CallbackResult],
+        server: ThreadingHTTPServer,
+        timeout_s: float,
+    ) -> None:
+        self.authorization_url = authorization_url
+        self.redirect_uri = redirect_uri
+        self._verifier = verifier
+        self._state = state
+        self._discovery = discovery
+        self._proxy = proxy
+        self._result_queue = result_queue
+        self._server = server
+        self._expires_at = time.monotonic() + timeout_s
+        self._lock = threading.Lock()
+        self._stop_event = threading.Event()
+        self._token: XAIToken | None = None
+        self._error: Exception | None = None
+        self._closed = False
+        self._server_thread = threading.Thread(
+            target=_serve_callback_server,
+            args=(server, self._stop_event),
+            name="nanobot-xai-grok-oauth-callback",
+            daemon=True,
+        )
+        self._server_thread.start()
+        self._timeout_timer = threading.Timer(timeout_s, self._expire)
+        self._timeout_timer.daemon = True
+        self._timeout_timer.start()
+
+    @property
+    def expired(self) -> bool:
+        return time.monotonic() >= self._expires_at
+
+    @property
+    def remaining_seconds(self) -> int:
+        return max(0, int(self._expires_at - time.monotonic()))
+
+    def complete(self, authorization_code: str | None = None) -> XAIToken | None:
+        """Complete this flow, or return ``None`` while loopback is still pending."""
+        with self._lock:
+            if self._token is not None:
+                return self._token
+            self._raise_if_finished()
+
+        callback: _CallbackResult | None
+        if authorization_code is not None:
+            callback = _CallbackResult(code=authorization_code.strip())
+        else:
+            try:
+                callback = self._result_queue.get_nowait()
+            except queue.Empty:
+                callback = None
+        if callback is None:
+            with self._lock:
+                if self._token is not None:
+                    return self._token
+                self._raise_if_finished()
+                if self.expired:
+                    self._expire_locked()
+                    self._raise_if_finished()
+            return None
+        return self._finish(callback)
+
+    def wait(self, timeout_s: float) -> XAIToken:
+        """Wait for the loopback callback and complete this flow."""
+        with self._lock:
+            if self._token is not None:
+                return self._token
+            self._raise_if_finished()
+        try:
+            callback = self._result_queue.get(timeout=timeout_s)
+        except queue.Empty as exc:
+            with self._lock:
+                if self._error is not None:
+                    raise self._error
+            raise XAIOAuthError(
+                "Timed out waiting for xAI sign-in. Run "
+                "`nanobot provider login xai-grok` to try again."
+            ) from exc
+        return self._finish(callback)
+
+    def cancel(self) -> None:
+        """Stop the callback listener for an abandoned flow."""
+        with self._lock:
+            if self._token is None and self._error is None:
+                self._error = XAIOAuthError("xAI sign-in was cancelled.")
+            self._close_locked()
+
+    def _finish(self, callback: _CallbackResult) -> XAIToken:
+        with self._lock:
+            if self._token is not None:
+                return self._token
+            self._raise_if_finished()
+            self._close_locked()
+            try:
+                token = _exchange_callback(
+                    callback,
+                    expected_state=self._state,
+                    discovery=self._discovery,
+                    verifier=self._verifier,
+                    redirect_uri=self.redirect_uri,
+                    proxy=self._proxy,
+                )
+                with _token_lock():
+                    _write_token(token)
+            except Exception as exc:
+                self._error = exc
+                raise
+            self._token = token
+            return token
+
+    def _expire(self) -> None:
+        with self._lock:
+            if self._token is not None or self._error is not None:
+                return
+            self._expire_locked()
+
+    def _expire_locked(self) -> None:
+        self._error = XAIOAuthError("xAI sign-in expired. Start a new sign-in flow.")
+        self._close_locked()
+
+    def _raise_if_finished(self) -> None:
+        if self._token is not None:
+            return
+        if self._error is not None:
+            raise self._error
+
+    def _close_locked(self) -> None:
+        if self._closed:
+            return
+        self._closed = True
+        self._timeout_timer.cancel()
+        self._stop_event.set()
+        if threading.current_thread() is not self._server_thread:
+            self._server_thread.join(timeout=2)
+
+
+def get_xai_oauth_storage_path() -> Path:
+    """Return the instance-scoped xAI OAuth credential path."""
+    return get_data_dir() / "auth" / "xai.json"
+
+
+def get_xai_oauth_login_status() -> XAIToken | None:
+    """Return locally stored login state without making a network request."""
+    return _load_token()
+
+
+def logout_xai_oauth() -> bool:
+    """Remove this instance's credentials while excluding token refreshes."""
+    path = get_xai_oauth_storage_path()
+    with _token_lock():
+        try:
+            path.unlink()
+        except FileNotFoundError:
+            return False
+    return True
+
+
+def login_xai_oauth(
+    *,
+    print_fn: Callable[[str], None] = print,
+    prompt_fn: Callable[[str], str] | None = None,
+    proxy: str | None = None,
+    callback_timeout_s: float = 600,
+    browser_opener: Callable[[str], bool] = webbrowser.open,
+) -> XAIToken:
+    """Run xAI's browser-based OAuth flow and persist the resulting token.
+
+    ``prompt_fn`` is used only when no local browser could be opened. It lets a
+    headless user paste either the final callback URL or its authorization code.
+    """
+    flow = start_xai_oauth_login(proxy=proxy, timeout_s=callback_timeout_s)
+
+    try:
+        print_fn("Opening xAI sign-in in your browser...")
+        print_fn(f"If it does not open automatically, visit:\n{flow.authorization_url}")
+        opened = False
+        with suppress(Exception):
+            opened = bool(browser_opener(flow.authorization_url))
+
+        if not opened and prompt_fn is not None:
+            pasted = prompt_fn("Paste the final callback URL (or authorization code)")
+            token = flow.complete(pasted)
+            if token is None:  # pragma: no cover - pasted input always resolves a callback
+                raise XAIOAuthError("xAI sign-in returned no authorization code.")
+            return token
+        return flow.wait(callback_timeout_s)
+    finally:
+        flow.cancel()
+
+
+def start_xai_oauth_login(
+    *,
+    proxy: str | None = None,
+    timeout_s: float = 600,
+) -> XAIOAuthLoginFlow:
+    """Create a non-blocking OAuth flow for browser or pasted-callback completion."""
+    discovery = _discover(proxy)
+    verifier, challenge = _generate_pkce()
+    state = secrets.token_urlsafe(32)
+    nonce = secrets.token_urlsafe(32)
+    result_queue: queue.Queue[_CallbackResult] = queue.Queue(maxsize=1)
+    server = _make_callback_server(state, result_queue)
+    redirect_uri = f"http://127.0.0.1:{server.server_port}/callback"
+    authorization_url = _build_authorize_url(
+        discovery.authorization_endpoint,
+        redirect_uri=redirect_uri,
+        challenge=challenge,
+        state=state,
+        nonce=nonce,
+    )
+    return XAIOAuthLoginFlow(
+        authorization_url=authorization_url,
+        redirect_uri=redirect_uri,
+        verifier=verifier,
+        state=state,
+        discovery=discovery,
+        proxy=proxy,
+        result_queue=result_queue,
+        server=server,
+        timeout_s=timeout_s,
+    )
+
+
+def complete_xai_oauth_login(
+    flow: XAIOAuthLoginFlow,
+    authorization_code: str | None = None,
+) -> XAIToken | None:
+    """Complete a pending login from loopback state or a pasted authorization code."""
+    return flow.complete(authorization_code)
+
+
+def get_xai_oauth_token(
+    *,
+    proxy: str | None = None,
+    min_ttl_ms: int = _TOKEN_REFRESH_MARGIN_MS,
+    force_refresh: bool = False,
+) -> XAIToken:
+    """Load a usable token, refreshing it under an inter-process lock when needed."""
+    token = _load_token()
+    if token is None:
+        raise XAIOAuthError(
+            "xAI is not signed in. Run `nanobot provider login xai-grok` first."
+        )
+    if not force_refresh and _token_is_fresh(token, min_ttl_ms):
+        return token
+    if not token.refresh:
+        if not force_refresh and token.expires > _now_ms():
+            return token
+        raise XAIOAuthError(
+            "The xAI login has expired and cannot be refreshed. "
+            "Run `nanobot provider login xai-grok` again."
+        )
+
+    with _token_lock():
+        latest = _load_token()
+        if latest is None:
+            raise XAIOAuthError(
+                "xAI is not signed in. Run `nanobot provider login xai-grok` first."
+            )
+        if not force_refresh and _token_is_fresh(latest, min_ttl_ms):
+            return latest
+        if not latest.refresh:
+            raise XAIOAuthError(
+                "The xAI login has expired and cannot be refreshed. "
+                "Run `nanobot provider login xai-grok` again."
+            )
+        refreshed = _refresh_token(latest, proxy)
+        _write_token(refreshed)
+        return refreshed
+
+
+def _discover(proxy: str | None) -> _Discovery:
+    try:
+        with _http_client(proxy) as client:
+            response = client.get(_DISCOVERY_URL)
+    except httpx.HTTPError as exc:
+        raise XAIOAuthError(f"Could not reach xAI sign-in: {type(exc).__name__}.") from exc
+    if response.status_code != HTTPStatus.OK:
+        raise _oauth_http_error(response, "discovery")
+    try:
+        payload = response.json()
+    except ValueError as exc:
+        raise XAIOAuthError("xAI sign-in discovery returned invalid JSON.") from exc
+    if payload.get("issuer", "").rstrip("/") != XAI_OAUTH_ISSUER:
+        raise XAIOAuthError("xAI sign-in discovery returned an unexpected issuer.")
+    authorization_endpoint = _validate_xai_endpoint(
+        payload.get("authorization_endpoint"), "authorization"
+    )
+    token_endpoint = _validate_xai_endpoint(payload.get("token_endpoint"), "token")
+    userinfo_raw = payload.get("userinfo_endpoint")
+    userinfo_endpoint = (
+        _validate_xai_endpoint(userinfo_raw, "userinfo") if userinfo_raw else None
+    )
+    return _Discovery(authorization_endpoint, token_endpoint, userinfo_endpoint)
+
+
+def _validate_xai_endpoint(value: Any, label: str) -> str:
+    if not isinstance(value, str):
+        raise XAIOAuthError(f"xAI sign-in discovery omitted the {label} endpoint.")
+    parsed = urlsplit(value)
+    try:
+        port = parsed.port
+    except ValueError as exc:
+        raise XAIOAuthError(
+            f"xAI sign-in discovery returned an unsafe {label} endpoint."
+        ) from exc
+    if (
+        parsed.scheme != "https"
+        or parsed.hostname != "auth.x.ai"
+        or parsed.username is not None
+        or parsed.password is not None
+        or port not in (None, 443)
+    ):
+        raise XAIOAuthError(f"xAI sign-in discovery returned an unsafe {label} endpoint.")
+    return value
+
+
+def _generate_pkce() -> tuple[str, str]:
+    verifier = _base64url(secrets.token_bytes(32))
+    challenge = _base64url(hashlib.sha256(verifier.encode("ascii")).digest())
+    return verifier, challenge
+
+
+def _base64url(value: bytes) -> str:
+    return base64.urlsafe_b64encode(value).rstrip(b"=").decode("ascii")
+
+
+def _build_authorize_url(
+    endpoint: str,
+    *,
+    redirect_uri: str,
+    challenge: str,
+    state: str,
+    nonce: str,
+) -> str:
+    params = {
+        "response_type": "code",
+        "client_id": XAI_CLIENT_ID,
+        "redirect_uri": redirect_uri,
+        "scope": " ".join(XAI_OAUTH_SCOPES),
+        "code_challenge": challenge,
+        "code_challenge_method": "S256",
+        "state": state,
+        "nonce": nonce,
+        "referrer": "nanobot",
+    }
+    return f"{endpoint}?{urlencode(params)}"
+
+
+def _make_callback_server(
+    expected_state: str,
+    result_queue: queue.Queue[_CallbackResult],
+) -> ThreadingHTTPServer:
+    class CallbackHandler(BaseHTTPRequestHandler):
+        def do_OPTIONS(self) -> None:  # noqa: N802
+            if self.path.split("?", 1)[0] != "/callback":
+                self.send_error(HTTPStatus.NOT_FOUND)
+                return
+            self.send_response(HTTPStatus.NO_CONTENT)
+            self._send_cors_headers()
+            self.send_header("Access-Control-Allow-Methods", "GET, OPTIONS")
+            self.send_header("Access-Control-Allow-Headers", "Content-Type")
+            self.send_header("Access-Control-Allow-Private-Network", "true")
+            self.end_headers()
+
+        def do_GET(self) -> None:  # noqa: N802
+            parsed = urlsplit(self.path)
+            if parsed.path != "/callback":
+                self.send_error(HTTPStatus.NOT_FOUND)
+                return
+            params = parse_qs(parsed.query)
+            code = _first(params, "code")
+            received_state = _first(params, "state")
+            error = _first(params, "error_description") or _first(params, "error")
+            if code and received_state and hmac.compare_digest(received_state, expected_state):
+                result = _CallbackResult(code=code, state=received_state)
+                title = "Signed in to xAI"
+                message = "You can close this tab and return to nanobot."
+            elif code:
+                result = _CallbackResult(error="OAuth state mismatch")
+                title = "Sign-in failed"
+                message = "The sign-in response could not be verified. Return to nanobot and retry."
+            else:
+                result = _CallbackResult(error=error or "access denied")
+                title = "Access denied"
+                message = "Return to nanobot and try signing in again."
+            with suppress(queue.Full):
+                result_queue.put_nowait(result)
+            body = _callback_page(title, message)
+            encoded = body.encode("utf-8")
+            self.send_response(HTTPStatus.OK)
+            self._send_cors_headers()
+            self.send_header("Content-Type", "text/html; charset=utf-8")
+            self.send_header("Content-Length", str(len(encoded)))
+            self.send_header("Cache-Control", "no-store")
+            self.end_headers()
+            self.wfile.write(encoded)
+
+        def _send_cors_headers(self) -> None:
+            origin = self.headers.get("Origin")
+            if origin == XAI_ALLOWED_CALLBACK_ORIGIN:
+                self.send_header("Access-Control-Allow-Origin", origin)
+                self.send_header("Vary", "Origin")
+            self.send_header("Access-Control-Allow-Private-Network", "true")
+
+        def log_message(self, _format: str, *_args: Any) -> None:
+            # Callback query strings contain an authorization code.
+            return
+
+    return ThreadingHTTPServer(("127.0.0.1", 0), CallbackHandler)
+
+
+def _serve_callback_server(
+    server: ThreadingHTTPServer,
+    stop_event: threading.Event,
+) -> None:
+    server.timeout = 0.2
+    try:
+        while not stop_event.is_set():
+            server.handle_request()
+    finally:
+        server.server_close()
+
+
+def _first(params: dict[str, list[str]], key: str) -> str | None:
+    values = params.get(key)
+    return values[0] if values else None
+
+
+def _callback_page(title: str, message: str) -> str:
+    return f"""<!doctype html>
+<html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width">
+<title>{title}</title><style>
+body{{margin:0;min-height:100vh;display:grid;place-items:center;background:#f5f7fb;color:#172033;
+font:16px/1.5 system-ui,sans-serif}}main{{max-width:30rem;margin:1.5rem;padding:2rem;border:1px solid #dfe4ee;
+border-radius:18px;background:white;box-shadow:0 16px 50px #17203318}}h1{{margin:0 0 .65rem;font-size:1.5rem}}
+p{{margin:0;color:#526078}}</style></head><body><main><h1>{title}</h1><p>{message}</p></main></body></html>"""
+
+
+def _exchange_callback(
+    callback: _CallbackResult,
+    *,
+    expected_state: str,
+    discovery: _Discovery,
+    verifier: str,
+    redirect_uri: str,
+    proxy: str | None,
+) -> XAIToken:
+    if callback.error:
+        raise XAIOAuthError(f"xAI sign-in was not completed: {callback.error}")
+    if not callback.code:
+        raise XAIOAuthError("xAI sign-in returned no authorization code.")
+    if callback.state and not hmac.compare_digest(callback.state, expected_state):
+        raise XAIOAuthError("xAI sign-in failed because the OAuth state did not match.")
+
+    payload = _exchange_code(
+        discovery.token_endpoint,
+        code=callback.code,
+        verifier=verifier,
+        redirect_uri=redirect_uri,
+        proxy=proxy,
+    )
+    account_id = _fetch_account(discovery.userinfo_endpoint, payload["access_token"], proxy)
+    return _token_from_response(payload, account_id=account_id)
+
+
+def _exchange_code(
+    token_endpoint: str,
+    *,
+    code: str,
+    verifier: str,
+    redirect_uri: str,
+    proxy: str | None,
+) -> dict[str, Any]:
+    data = {
+        "grant_type": "authorization_code",
+        "code": code,
+        "redirect_uri": redirect_uri,
+        "client_id": XAI_CLIENT_ID,
+        "code_verifier": verifier,
+    }
+    try:
+        with _http_client(proxy) as client:
+            response = client.post(
+                token_endpoint,
+                data=data,
+                headers={"x-grok-client-version": XAI_CLIENT_VERSION},
+            )
+    except httpx.HTTPError as exc:
+        raise XAIOAuthError(f"Could not exchange the xAI sign-in code: {type(exc).__name__}.") from exc
+    if not response.is_success:
+        raise _oauth_http_error(response, "token exchange")
+    return _token_payload(response)
+
+
+def _refresh_token(token: XAIToken, proxy: str | None) -> XAIToken:
+    data = {
+        "grant_type": "refresh_token",
+        "refresh_token": token.refresh or "",
+        "client_id": XAI_CLIENT_ID,
+    }
+    try:
+        with _http_client(proxy) as client:
+            response = client.post(
+                f"{XAI_OAUTH_ISSUER}/oauth2/token",
+                data=data,
+                headers={"x-grok-client-version": XAI_CLIENT_VERSION},
+            )
+    except httpx.HTTPError as exc:
+        raise XAIOAuthError(f"Could not refresh the xAI login: {type(exc).__name__}.") from exc
+    if not response.is_success:
+        raise _oauth_http_error(response, "token refresh")
+    payload = _token_payload(response)
+    return _token_from_response(
+        payload,
+        account_id=token.account_id,
+        previous_refresh=token.refresh,
+    )
+
+
+def _token_payload(response: httpx.Response) -> dict[str, Any]:
+    try:
+        payload = response.json()
+    except ValueError as exc:
+        raise XAIOAuthError("xAI sign-in returned an invalid token response.") from exc
+    if not isinstance(payload, dict) or not isinstance(payload.get("access_token"), str):
+        raise XAIOAuthError("xAI sign-in returned no access token.")
+    return payload
+
+
+def _token_from_response(
+    payload: dict[str, Any],
+    *,
+    account_id: str | None,
+    previous_refresh: str | None = None,
+) -> XAIToken:
+    try:
+        expires_in = max(1, int(payload.get("expires_in") or _DEFAULT_TOKEN_TTL_S))
+    except (TypeError, ValueError):
+        expires_in = _DEFAULT_TOKEN_TTL_S
+    refresh = payload.get("refresh_token")
+    if not isinstance(refresh, str) or not refresh:
+        refresh = previous_refresh
+    return XAIToken(
+        access=payload["access_token"],
+        refresh=refresh,
+        expires=_now_ms() + expires_in * 1000,
+        account_id=account_id,
+    )
+
+
+def _fetch_account(endpoint: str | None, access_token: str, proxy: str | None) -> str | None:
+    if not endpoint:
+        return None
+    try:
+        with _http_client(proxy) as client:
+            response = client.get(endpoint, headers={"Authorization": f"Bearer {access_token}"})
+        if not response.is_success:
+            return None
+        payload = response.json()
+    except (httpx.HTTPError, ValueError):
+        return None
+    if not isinstance(payload, dict):
+        return None
+    for key in ("email", "preferred_username", "name", "sub"):
+        value = payload.get(key)
+        if isinstance(value, str) and value:
+            return value
+    return None
+
+
+def _oauth_http_error(response: httpx.Response, action: str) -> XAIOAuthError:
+    code: str | None = None
+    description: str | None = None
+    with suppress(ValueError):
+        payload = response.json()
+        if isinstance(payload, dict):
+            raw_code = payload.get("error")
+            raw_description = payload.get("error_description") or payload.get("message")
+            code = raw_code[:80] if isinstance(raw_code, str) else None
+            description = raw_description[:200] if isinstance(raw_description, str) else None
+    detail = ": ".join(value for value in (code, description) if value)
+    suffix = f" ({detail})" if detail else ""
+    return XAIOAuthError(f"xAI OAuth {action} failed with HTTP {response.status_code}{suffix}.")
+
+
+def _http_client(proxy: str | None) -> httpx.Client:
+    kwargs: dict[str, Any] = {"timeout": _HTTP_TIMEOUT_S}
+    if proxy:
+        kwargs.update(proxy=proxy, trust_env=False)
+    return httpx.Client(**kwargs)
+
+
+def _token_lock() -> FileLock:
+    path = get_xai_oauth_storage_path()
+    path.parent.mkdir(parents=True, exist_ok=True)
+    return FileLock(str(path.with_suffix(".lock")), timeout=15)
+
+
+def _load_token() -> XAIToken | None:
+    path = get_xai_oauth_storage_path()
+    try:
+        payload = json.loads(path.read_text(encoding="utf-8"))
+    except FileNotFoundError:
+        return None
+    except (OSError, ValueError, TypeError) as exc:
+        logger.warning("Could not read xAI OAuth credentials: {}", type(exc).__name__)
+        return None
+    return XAIToken.from_dict(payload)
+
+
+def _write_token(token: XAIToken) -> None:
+    path = get_xai_oauth_storage_path()
+    path.parent.mkdir(parents=True, exist_ok=True)
+    with suppress(OSError):
+        os.chmod(path.parent, 0o700)
+    _write_text_atomic(path, json.dumps(asdict(token), indent=2, ensure_ascii=False))
+    with suppress(OSError):
+        os.chmod(path, 0o600)
+
+
+def _token_is_fresh(token: XAIToken, min_ttl_ms: int) -> bool:
+    return bool(token.access and token.expires > _now_ms() + max(0, min_ttl_ms))
+
+
+def _now_ms() -> int:
+    return int(time.time() * 1000)
diff --git a/nanobot/webui/settings_api.py b/nanobot/webui/settings_api.py
index 113b26e1..152e5a0c 100644
--- a/nanobot/webui/settings_api.py
+++ b/nanobot/webui/settings_api.py
@@ -8,6 +8,8 @@ from __future__ import annotations
 
 import os
 import re
+import secrets
+import threading
 import time
 from contextlib import suppress
 from typing import Any, Literal
@@ -121,7 +123,12 @@ _IMAGE_GENERATION_ASPECT_RATIOS = {
     "2:3",
     "21:9",
 }
-_CONTEXT_WINDOW_TOKEN_OPTIONS = {65_536, 200_000, 262_144, 1_048_576}
+_CONTEXT_WINDOW_TOKEN_OPTIONS = {65_536, 200_000, 262_144, 500_000, 1_048_576}
+_OAUTH_PROXY_PROVIDERS = {"openai_codex", "xai_grok"}
+_XAI_WEBUI_OAUTH_TIMEOUT_S = 600
+_XAI_WEBUI_OAUTH_MAX_FLOWS = 8
+_xai_webui_oauth_flows: dict[str, Any] = {}
+_xai_webui_oauth_flows_lock = threading.Lock()
 _MODEL_CONFIGURATION_SLUG_RE = re.compile(r"[^a-z0-9_-]+")
 _ENV_REF_RE = re.compile(r"\$\{([A-Za-z_][A-Za-z0-9_]*)\}")
 
@@ -304,6 +311,32 @@ def _oauth_provider_status(spec: Any) -> dict[str, Any]:
             "login_supported": True,
         }
 
+    if spec.name == "xai_grok":
+        try:
+            from nanobot.providers.xai_oauth import get_xai_oauth_login_status
+        except Exception:
+            return {
+                "configured": False,
+                "account": None,
+                "expires_at": None,
+                "login_supported": False,
+            }
+        token = None
+        with suppress(Exception):
+            token = get_xai_oauth_login_status()
+        expires_at = getattr(token, "expires", None) if token else None
+        now_ms = int(time.time() * 1000)
+        return {
+            "configured": bool(
+                token
+                and token.access
+                and (getattr(token, "refresh", None) or (expires_at and expires_at > now_ms))
+            ),
+            "account": getattr(token, "account_id", None) if token else None,
+            "expires_at": expires_at,
+            "login_supported": True,
+        }
+
     return {"configured": False, "account": None, "expires_at": None, "login_supported": False}
 
 
@@ -374,6 +407,8 @@ def _provider_settings_row(
         row["oauth_account"] = oauth_status["account"]
         row["oauth_expires_at"] = oauth_status["expires_at"]
         row["oauth_login_supported"] = oauth_status["login_supported"]
+    if spec.name in _OAUTH_PROXY_PROVIDERS:
+        row["proxy"] = provider_config.proxy
     if spec.name == "openai":
         row["api_type"] = provider_config.api_type
     return row
@@ -635,7 +670,7 @@ def _parse_context_window_tokens(value: str | None) -> int | None:
         raise WebUISettingsError("context_window_tokens must be an integer") from None
     if parsed not in _CONTEXT_WINDOW_TOKEN_OPTIONS:
         raise WebUISettingsError(
-            "context_window_tokens must be 65536, 200000, 262144, or 1048576"
+            "context_window_tokens must be 65536, 200000, 262144, 500000, or 1048576"
         )
     return parsed
 
@@ -1171,7 +1206,23 @@ def update_provider_settings(query: QueryParams) -> dict[str, Any]:
         raise WebUISettingsError("unknown provider")
     spec, provider_key, provider_config = resolved_provider
     if spec.is_oauth:
-        raise WebUISettingsError("unknown provider")
+        if spec.name not in _OAUTH_PROXY_PROVIDERS:
+            raise WebUISettingsError("unknown provider")
+        if any(
+            key in query
+            for key in ("api_key", "apiKey", "api_base", "apiBase", "api_type")
+        ):
+            raise WebUISettingsError("OAuth provider only supports proxy settings")
+
+        changed = False
+        if "proxy" in query:
+            proxy = (_query_first(query, "proxy") or "").strip() or None
+            if provider_config.proxy != proxy:
+                provider_config.proxy = proxy
+                changed = True
+        if changed:
+            save_config(config)
+        return settings_payload()
 
     changed = False
     if "api_key" in query or "apiKey" in query:
@@ -1263,9 +1314,68 @@ def login_oauth_provider(query: QueryParams) -> dict[str, Any]:
             raise WebUISettingsError("OAuth login failed", status=401)
         return settings_payload()
 
+    if spec.name == "xai_grok":
+        from nanobot.providers.xai_oauth import start_xai_oauth_login
+
+        try:
+            proxy = resolve_config_env_vars(load_config()).providers.xai_grok.proxy or None
+        except ValueError as e:
+            raise WebUISettingsError(str(e), status=400) from e
+        try:
+            flow = start_xai_oauth_login(
+                proxy=proxy,
+                timeout_s=_XAI_WEBUI_OAUTH_TIMEOUT_S,
+            )
+        except Exception as e:
+            raise WebUISettingsError(f"xAI OAuth login failed: {e}", status=502) from e
+        flow_id = secrets.token_urlsafe(24)
+        _register_xai_webui_oauth_flow(flow_id, flow)
+        return {
+            "status": "authorization_required",
+            "provider": spec.name,
+            "flow_id": flow_id,
+            "authorization_url": flow.authorization_url,
+            "expires_in": flow.remaining_seconds,
+        }
+
     raise WebUISettingsError("OAuth login is not supported for this provider")
 
 
+def complete_oauth_provider(
+    query: QueryParams,
+    authorization_code: str | None = None,
+) -> dict[str, Any]:
+    provider_name = (_query_first(query, "provider") or "").strip()
+    flow_id = (_query_first(query, "flow_id") or "").strip()
+    spec = find_by_name(provider_name)
+    if spec is None or spec.name != "xai_grok":
+        raise WebUISettingsError("OAuth completion is not supported for this provider")
+    if not flow_id:
+        raise WebUISettingsError("flow_id is required")
+
+    flow = _get_xai_webui_oauth_flow(flow_id)
+    if flow is None:
+        raise WebUISettingsError("xAI sign-in expired. Start again.", status=410)
+
+    from nanobot.providers.xai_oauth import complete_xai_oauth_login
+
+    try:
+        token = complete_xai_oauth_login(flow, authorization_code)
+    except Exception as e:
+        _remove_xai_webui_oauth_flow(flow_id, flow)
+        raise WebUISettingsError(f"xAI OAuth login failed: {e}", status=502) from e
+    if token is None:
+        return {
+            "status": "pending",
+            "provider": spec.name,
+            "flow_id": flow_id,
+        }
+    _remove_xai_webui_oauth_flow(flow_id, flow, cancel=False)
+    if not token.access:
+        raise WebUISettingsError("OAuth login failed", status=401)
+    return settings_payload()
+
+
 def logout_oauth_provider(query: QueryParams) -> dict[str, Any]:
     provider_name = (_query_first(query, "provider") or "").strip()
     if not provider_name:
@@ -1291,6 +1401,12 @@ def logout_oauth_provider(query: QueryParams) -> dict[str, Any]:
                 "oauth_cli_kit not installed. Run: pip install oauth-cli-kit", status=500
             ) from None
         token_path = get_storage().get_token_path()
+    elif spec.name == "xai_grok":
+        from nanobot.providers.xai_oauth import logout_xai_oauth
+
+        _clear_xai_webui_oauth_flows()
+        logout_xai_oauth()
+        return settings_payload()
     else:
         raise WebUISettingsError("OAuth logout is not supported for this provider")
 
@@ -1300,6 +1416,51 @@ def logout_oauth_provider(query: QueryParams) -> dict[str, Any]:
     return settings_payload()
 
 
+def _register_xai_webui_oauth_flow(flow_id: str, flow: Any) -> None:
+    discarded: list[Any] = []
+    with _xai_webui_oauth_flows_lock:
+        for existing_id, existing in list(_xai_webui_oauth_flows.items()):
+            if existing.expired:
+                discarded.append(_xai_webui_oauth_flows.pop(existing_id))
+        while len(_xai_webui_oauth_flows) >= _XAI_WEBUI_OAUTH_MAX_FLOWS:
+            oldest_id = next(iter(_xai_webui_oauth_flows))
+            discarded.append(_xai_webui_oauth_flows.pop(oldest_id))
+        _xai_webui_oauth_flows[flow_id] = flow
+    for existing in discarded:
+        existing.cancel()
+
+
+def _get_xai_webui_oauth_flow(flow_id: str) -> Any | None:
+    with _xai_webui_oauth_flows_lock:
+        flow = _xai_webui_oauth_flows.get(flow_id)
+        if flow is None or not flow.expired:
+            return flow
+        _xai_webui_oauth_flows.pop(flow_id, None)
+    flow.cancel()
+    return None
+
+
+def _remove_xai_webui_oauth_flow(
+    flow_id: str,
+    flow: Any,
+    *,
+    cancel: bool = True,
+) -> None:
+    with _xai_webui_oauth_flows_lock:
+        if _xai_webui_oauth_flows.get(flow_id) is flow:
+            _xai_webui_oauth_flows.pop(flow_id)
+    if cancel:
+        flow.cancel()
+
+
+def _clear_xai_webui_oauth_flows() -> None:
+    with _xai_webui_oauth_flows_lock:
+        flows = list(_xai_webui_oauth_flows.values())
+        _xai_webui_oauth_flows.clear()
+    for flow in flows:
+        flow.cancel()
+
+
 def update_network_safety_settings(query: QueryParams) -> dict[str, Any]:
     raw_allow = (
         _query_first_alias(query, "webui_allow_local_service_access", "webuiAllowLocalServiceAccess")
diff --git a/nanobot/webui/settings_routes.py b/nanobot/webui/settings_routes.py
index 1464b8bb..1060f0f2 100644
--- a/nanobot/webui/settings_routes.py
+++ b/nanobot/webui/settings_routes.py
@@ -37,6 +37,7 @@ from nanobot.optional_features import (
 )
 from nanobot.pairing import approve_code, deny_code, list_pending
 from nanobot.webui.cli_apps_api import cli_apps_action, cli_apps_payload
+from nanobot.webui.http_utils import case_insensitive_header
 from nanobot.webui.http_utils import is_local_browser_request as _is_local_browser_request
 from nanobot.webui.http_utils import query_first as _query_first
 from nanobot.webui.mcp_presets_api import mcp_presets_settings_action
@@ -47,6 +48,7 @@ from nanobot.webui.nanobot_features_api import (
 )
 from nanobot.webui.settings_api import (
     WebUISettingsError,
+    complete_oauth_provider,
     create_model_configuration,
     decorate_settings_payload,
     login_oauth_provider,
@@ -73,6 +75,8 @@ _CHANNEL_VALUES_HEADER = "X-Nanobot-Channel-Values"
 _CHANNEL_VALUES_HEADER_MAX_BYTES = 64 * 1024
 _API_SERVICE_VALUES_HEADER = "X-Nanobot-API-Service-Values"
 _API_SERVICE_VALUES_HEADER_MAX_BYTES = 8 * 1024
+_OAUTH_CODE_HEADER = "X-Nanobot-OAuth-Code"
+_OAUTH_CODE_HEADER_MAX_BYTES = 8 * 1024
 
 _SKIP_FIELD = object()
 _CHANNEL_CONNECT_ACTIONS = frozenset({"start", "poll", "cancel"})
@@ -146,6 +150,8 @@ class WebUISettingsRouter:
             return await self._handle_settings_provider_models(request)
         if path == "/api/settings/provider/oauth-login":
             return await self._handle_settings_provider_oauth(request, "login")
+        if path == "/api/settings/provider/oauth-login/complete":
+            return await self._handle_settings_provider_oauth(request, "complete")
         if path == "/api/settings/provider/oauth-logout":
             return await self._handle_settings_provider_oauth(request, "logout")
         if path == "/api/settings/web-search/update":
@@ -378,10 +384,24 @@ class WebUISettingsRouter:
         try:
             if action == "login":
                 payload = await asyncio.to_thread(login_oauth_provider, query)
+            elif action == "complete":
+                authorization_code = case_insensitive_header(
+                    request.headers,
+                    _OAUTH_CODE_HEADER,
+                )
+                if len(authorization_code.encode("utf-8")) > _OAUTH_CODE_HEADER_MAX_BYTES:
+                    raise WebUISettingsError("OAuth authorization code is too large")
+                payload = await asyncio.to_thread(
+                    complete_oauth_provider,
+                    query,
+                    authorization_code or None,
+                )
             else:
                 payload = await asyncio.to_thread(logout_oauth_provider, query)
         except WebUISettingsError as e:
             return self._error_response(e.status, e.message)
+        if payload.get("status") in {"authorization_required", "pending"}:
+            return self._json_response(payload)
         return self._json_response(self._with_restart_state(payload))
 
     def _handle_settings_web_search_update(self, request: WsRequest) -> Response:
diff --git a/tests/cli/test_commands.py b/tests/cli/test_commands.py
index 9843f6d2..0b9ba4d8 100644
--- a/tests/cli/test_commands.py
+++ b/tests/cli/test_commands.py
@@ -478,6 +478,7 @@ def test_config_dump_excludes_oauth_provider_blocks():
     providers = config.model_dump(by_alias=True)["providers"]
 
     assert "openaiCodex" not in providers
+    assert "xaiGrok" not in providers
     assert "githubCopilot" not in providers
 
 
@@ -541,6 +542,47 @@ def test_provider_logout_openai_codex_succeeds_when_no_local_oauth_file(monkeypa
     assert "No local OAuth credentials found for OpenAI Codex" in result.stdout
 
 
+def test_provider_logout_xai_grok_removes_instance_credentials(tmp_path, monkeypatch):
+    token_path = tmp_path / "auth" / "xai.json"
+    lock_path = token_path.with_suffix(".lock")
+    token_path.parent.mkdir(parents=True, exist_ok=True)
+    token_path.write_text("{}", encoding="utf-8")
+    lock_path.write_text("", encoding="utf-8")
+    monkeypatch.setattr(
+        "nanobot.providers.xai_oauth.get_xai_oauth_storage_path",
+        lambda: token_path,
+    )
+
+    result = runner.invoke(app, ["provider", "logout", "xai-grok"])
+
+    assert result.exit_code == 0
+    assert not token_path.exists()
+    assert "Logged out from xAI Grok" in result.stdout
+
+
+def test_provider_logout_xai_grok_uses_explicit_config_path(tmp_path, monkeypatch):
+    from nanobot.config import loader
+
+    default_config = tmp_path / "default" / "config.json"
+    selected_config = tmp_path / "selected" / "config.json"
+    default_token = default_config.parent / "auth" / "xai.json"
+    selected_token = selected_config.parent / "auth" / "xai.json"
+    for token_path in (default_token, selected_token):
+        token_path.parent.mkdir(parents=True, exist_ok=True)
+        token_path.write_text("{}", encoding="utf-8")
+    monkeypatch.setattr(loader, "_current_config_path", default_config)
+
+    result = runner.invoke(
+        app,
+        ["provider", "logout", "xai-grok", "--config", str(selected_config)],
+    )
+
+    assert result.exit_code == 0
+    assert default_token.exists()
+    assert not selected_token.exists()
+    assert "Using config:" in result.stdout
+
+
 def test_provider_logout_github_copilot_removes_local_oauth_files(tmp_path, monkeypatch):
     token_path = tmp_path / "auth" / "github-copilot.json"
     lock_path = token_path.with_suffix(".lock")
@@ -579,12 +621,17 @@ def test_provider_logout_paths_resolve_to_expected_files():
     from oauth_cli_kit.storage import FileTokenStorage
 
     from nanobot.providers.github_copilot_provider import get_storage
+    from nanobot.providers.xai_oauth import get_xai_oauth_storage_path
 
     codex_storage = FileTokenStorage(token_filename=OPENAI_CODEX_PROVIDER.token_filename)
     codex_path = codex_storage.get_token_path()
     assert codex_path.name == "codex.json"
     assert codex_path.parent.name == "auth"
 
+    xai_path = get_xai_oauth_storage_path()
+    assert xai_path.name == "xai.json"
+    assert xai_path.parent.name == "auth"
+
     gh_storage = get_storage()
     gh_path = gh_storage.get_token_path()
     assert gh_path.name == "github-copilot.json"
@@ -663,6 +710,36 @@ def test_provider_login_can_set_github_copilot_as_main_provider(tmp_path):
     assert make_provider(saved).__class__.__name__ == "GitHubCopilotProvider"
 
 
+def test_provider_login_can_set_xai_grok_as_main_provider(tmp_path):
+    config_path = tmp_path / "config.json"
+    original = cli_commands._LOGIN_HANDLERS["xai_grok"]
+    cli_commands._LOGIN_HANDLERS["xai_grok"] = lambda: None
+    try:
+        result = runner.invoke(
+            app,
+            [
+                "provider",
+                "login",
+                "xai-grok",
+                "--set-main",
+                "--config",
+                str(config_path),
+            ],
+        )
+    finally:
+        cli_commands._LOGIN_HANDLERS["xai_grok"] = original
+
+    assert result.exit_code == 0
+    assert "Set xai-grok as the main provider" in result.stdout
+
+    saved = Config.model_validate(json.loads(config_path.read_text(encoding="utf-8")))
+    assert saved.agents.defaults.provider == "xai_grok"
+    assert saved.agents.defaults.model == "xai-grok/grok-4.5"
+    assert saved.agents.defaults.context_window_tokens == 500_000
+    assert saved.agents.defaults.model_preset is None
+    assert make_provider(saved).__class__.__name__ == "XAIGrokProvider"
+
+
 def test_provider_login_model_implies_set_main_provider(tmp_path):
     config_path = tmp_path / "config.json"
     original = cli_commands._LOGIN_HANDLERS["github_copilot"]
@@ -792,6 +869,33 @@ def test_provider_login_openai_codex_resolves_proxy_env_ref(monkeypatch):
     assert captured["proxy"] == proxy
 
 
+def test_provider_login_xai_grok_runs_browser_flow_with_configured_proxy(monkeypatch):
+    proxy = "http://127.0.0.1:23458"
+    monkeypatch.setattr(
+        "nanobot.config.loader.load_config",
+        lambda: Config.model_validate({"providers": {"xaiGrok": {"proxy": proxy}}}),
+    )
+    monkeypatch.setattr(
+        "nanobot.providers.xai_oauth.get_xai_oauth_token",
+        lambda **_kwargs: (_ for _ in ()).throw(RuntimeError("not signed in")),
+    )
+    captured: dict[str, object] = {}
+
+    def fake_login(*, print_fn, prompt_fn, proxy=None):
+        captured.update(print_fn=print_fn, prompt_fn=prompt_fn, proxy=proxy)
+        return SimpleNamespace(access="access-token", account_id="user@example.com")
+
+    monkeypatch.setattr("nanobot.providers.xai_oauth.login_xai_oauth", fake_login)
+
+    result = runner.invoke(app, ["provider", "login", "xai-grok"])
+
+    assert result.exit_code == 0
+    assert captured["proxy"] == proxy
+    assert callable(captured["print_fn"])
+    assert callable(captured["prompt_fn"])
+    assert "Hosted X Search is enabled automatically when the selected model supports it" in result.stdout
+
+
 def test_config_matches_explicit_ollama_prefix_without_api_key():
     config = Config()
     config.agents.defaults.model = "ollama/llama3.2"
diff --git a/tests/config/test_env_interpolation.py b/tests/config/test_env_interpolation.py
index 329010cc..fb01bda9 100644
--- a/tests/config/test_env_interpolation.py
+++ b/tests/config/test_env_interpolation.py
@@ -111,6 +111,7 @@ class TestResolveConfig:
                     "agents": {"defaults": {"dream": {"cron": "0 */4 * * *"}}},
                     "providers": {
                         "openaiCodex": {"apiKey": "codex-secret"},
+                        "xaiGrok": {"apiKey": "xai-secret"},
                         "githubCopilot": {"apiKey": "copilot-secret"},
                         "groq": {"apiKey": "groq-secret"},
                     },
@@ -125,6 +126,7 @@ class TestResolveConfig:
         saved = json.loads(config_path.read_text(encoding="utf-8"))
         assert saved["agents"]["defaults"]["dream"]["cron"] == "0 */4 * * *"
         assert "openaiCodex" not in saved["providers"]
+        assert "xaiGrok" not in saved["providers"]
         assert "githubCopilot" not in saved["providers"]
         assert saved["providers"]["groq"]["apiKey"] == "groq-secret"
 
@@ -137,6 +139,7 @@ class TestResolveConfig:
                     "openaiCodex": {
                         "apiKey": "codex-secret",
                         "proxy": proxy,
+                        "extraBody": {"service_tier": "priority"},
                     },
                     "groq": {"apiKey": "groq-secret"},
                 }
@@ -146,13 +149,77 @@ class TestResolveConfig:
         save_config(config, config_path)
 
         saved = json.loads(config_path.read_text(encoding="utf-8"))
-        assert saved["providers"]["openaiCodex"] == {"proxy": proxy}
+        assert saved["providers"]["openaiCodex"] == {
+            "extraBody": {"service_tier": "priority"},
+            "proxy": proxy,
+        }
         assert saved["providers"]["groq"]["apiKey"] == "groq-secret"
 
         reloaded = load_config(config_path)
         assert reloaded.providers.openai_codex.proxy == proxy
+        assert reloaded.providers.openai_codex.extra_body == {"service_tier": "priority"}
         assert reloaded.providers.openai_codex.api_key is None
 
+    def test_save_preserves_xai_grok_proxy_but_never_credentials(self, tmp_path):
+        config_path = tmp_path / "config.json"
+        proxy = "http://127.0.0.1:23458"
+        config = Config.model_validate(
+            {
+                "providers": {
+                    "xaiGrok": {
+                        "apiKey": "must-not-be-saved",
+                        "proxy": proxy,
+                        "extraBody": {"parallel_tool_calls": False},
+                    }
+                }
+            }
+        )
+
+        save_config(config, config_path)
+
+        saved = json.loads(config_path.read_text(encoding="utf-8"))
+        assert saved["providers"]["xaiGrok"] == {
+            "extraBody": {"parallel_tool_calls": False},
+            "proxy": proxy,
+        }
+        assert "must-not-be-saved" not in config_path.read_text(encoding="utf-8")
+
+        reloaded = load_config(config_path)
+        assert reloaded.providers.xai_grok.proxy == proxy
+        assert reloaded.providers.xai_grok.extra_body == {"parallel_tool_calls": False}
+        assert reloaded.providers.xai_grok.api_key is None
+
+    def test_save_preserves_settings_across_oauth_provider_blocks(self, tmp_path):
+        config_path = tmp_path / "config.json"
+        config = Config.model_validate(
+            {
+                "providers": {
+                    "openaiCodex": {
+                        "apiKey": "codex-secret",
+                        "extraBody": {"service_tier": "${CODEX_SERVICE_TIER}"},
+                    },
+                    "xaiGrok": {
+                        "apiKey": "xai-secret",
+                        "proxy": "http://127.0.0.1:7890",
+                        "extraBody": {"parallel_tool_calls": False},
+                    },
+                }
+            }
+        )
+
+        save_config(config, config_path)
+
+        saved = json.loads(config_path.read_text(encoding="utf-8"))
+        assert saved["providers"]["openaiCodex"] == {
+            "extraBody": {"service_tier": "${CODEX_SERVICE_TIER}"}
+        }
+        assert saved["providers"]["xaiGrok"] == {
+            "extraBody": {"parallel_tool_calls": False},
+            "proxy": "http://127.0.0.1:7890",
+        }
+        assert "codex-secret" not in config_path.read_text(encoding="utf-8")
+        assert "xai-secret" not in config_path.read_text(encoding="utf-8")
+
     def test_preserves_excluded_fields_when_no_env_refs(self, tmp_path):
         """Regression: fields with ``exclude=True`` (e.g. ProviderConfig.openai_codex)
         must survive ``resolve_config_env_vars`` when the config has no
diff --git a/tests/providers/test_providers_init.py b/tests/providers/test_providers_init.py
index 707a3f68..f3c3b51c 100644
--- a/tests/providers/test_providers_init.py
+++ b/tests/providers/test_providers_init.py
@@ -7,43 +7,61 @@ import sys
 
 
 def test_importing_providers_package_is_lazy(monkeypatch) -> None:
+    original_package = sys.modules["nanobot.providers"]
     monkeypatch.delitem(sys.modules, "nanobot.providers", raising=False)
     monkeypatch.delitem(sys.modules, "nanobot.providers.anthropic_provider", raising=False)
     monkeypatch.delitem(sys.modules, "nanobot.providers.openai_compat_provider", raising=False)
     monkeypatch.delitem(sys.modules, "nanobot.providers.openai_codex_provider", raising=False)
+    monkeypatch.delitem(sys.modules, "nanobot.providers.xai_oauth", raising=False)
+    monkeypatch.delitem(sys.modules, "nanobot.providers.xai_grok_provider", raising=False)
     monkeypatch.delitem(sys.modules, "nanobot.providers.github_copilot_provider", raising=False)
     monkeypatch.delitem(sys.modules, "nanobot.providers.azure_openai_provider", raising=False)
     monkeypatch.delitem(sys.modules, "nanobot.providers.bedrock_provider", raising=False)
 
-    providers = importlib.import_module("nanobot.providers")
+    try:
+        providers = importlib.import_module("nanobot.providers")
 
-    assert "nanobot.providers.anthropic_provider" not in sys.modules
-    assert "nanobot.providers.openai_compat_provider" not in sys.modules
-    assert "nanobot.providers.openai_codex_provider" not in sys.modules
-    assert "nanobot.providers.github_copilot_provider" not in sys.modules
-    assert "nanobot.providers.azure_openai_provider" not in sys.modules
-    assert "nanobot.providers.bedrock_provider" not in sys.modules
-    assert providers.__all__ == [
-        "LLMProvider",
-        "LLMResponse",
-        "AnthropicProvider",
-        "OpenAICompatProvider",
-        "OpenAICodexProvider",
-        "GitHubCopilotProvider",
-        "AzureOpenAIProvider",
-        "BedrockProvider",
-    ]
+        assert "nanobot.providers.anthropic_provider" not in sys.modules
+        assert "nanobot.providers.openai_compat_provider" not in sys.modules
+        assert "nanobot.providers.openai_codex_provider" not in sys.modules
+        assert "nanobot.providers.xai_oauth" not in sys.modules
+        assert "nanobot.providers.xai_grok_provider" not in sys.modules
+        assert "nanobot.providers.github_copilot_provider" not in sys.modules
+        assert "nanobot.providers.azure_openai_provider" not in sys.modules
+        assert "nanobot.providers.bedrock_provider" not in sys.modules
+        assert providers.__all__ == [
+            "LLMProvider",
+            "LLMResponse",
+            "AnthropicProvider",
+            "OpenAICompatProvider",
+            "OpenAICodexProvider",
+            "XAIGrokProvider",
+            "GitHubCopilotProvider",
+            "AzureOpenAIProvider",
+            "BedrockProvider",
+        ]
+    finally:
+        # Importing a replacement subpackage also replaces nanobot.providers on the
+        # parent package. Restore both views so this isolation test cannot pollute
+        # later tests that resolve a module through a dotted monkeypatch target.
+        monkeypatch.undo()
+        setattr(sys.modules["nanobot"], "providers", original_package)
 
 
 def test_explicit_provider_import_still_works(monkeypatch) -> None:
+    original_package = sys.modules["nanobot.providers"]
     monkeypatch.delitem(sys.modules, "nanobot.providers", raising=False)
     monkeypatch.delitem(sys.modules, "nanobot.providers.anthropic_provider", raising=False)
 
-    namespace: dict[str, object] = {}
-    exec("from nanobot.providers import AnthropicProvider", namespace)
+    try:
+        namespace: dict[str, object] = {}
+        exec("from nanobot.providers import AnthropicProvider", namespace)
 
-    assert namespace["AnthropicProvider"].__name__ == "AnthropicProvider"
-    assert "nanobot.providers.anthropic_provider" in sys.modules
+        assert namespace["AnthropicProvider"].__name__ == "AnthropicProvider"
+        assert "nanobot.providers.anthropic_provider" in sys.modules
+    finally:
+        monkeypatch.undo()
+        setattr(sys.modules["nanobot"], "providers", original_package)
 
 
 def test_openai_codex_supports_progress_deltas() -> None:
diff --git a/tests/providers/test_xai_grok_provider.py b/tests/providers/test_xai_grok_provider.py
new file mode 100644
index 00000000..46fc6255
--- /dev/null
+++ b/tests/providers/test_xai_grok_provider.py
@@ -0,0 +1,526 @@
+from __future__ import annotations
+
+import base64
+import json
+import time
+from types import SimpleNamespace
+from typing import Any
+
+import httpx
+import pytest
+
+from nanobot.config.schema import Config
+from nanobot.providers.factory import make_provider
+from nanobot.providers.registry import find_by_name
+from nanobot.providers.xai_grok_provider import (
+    DEFAULT_XAI_GROK_MODEL,
+    DEFAULT_XAI_GROK_MODELS_URL,
+    XAIGrokProvider,
+    _bounded_error_body,
+    _build_headers,
+    _build_model_headers,
+    _build_reasoning_options,
+    _build_xai_http_error,
+    _fetch_xai_model_capabilities,
+    _parse_xai_model_capabilities,
+    _request_xai,
+    _xai_error_response,
+    _XAIHTTPError,
+)
+
+
+def _token(access: str = "subscription-token") -> SimpleNamespace:
+    return SimpleNamespace(
+        access=access,
+        refresh="refresh-token",
+        expires=int(time.time() * 1000) + 3_600_000,
+        account_id="account",
+    )
+
+
+def _mock_token(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(
+        "nanobot.providers.xai_grok_provider.get_xai_oauth_token",
+        lambda **_kwargs: _token(),
+    )
+
+
+def _mock_model_capabilities(
+    monkeypatch: pytest.MonkeyPatch,
+    *,
+    supports_backend_search: bool,
+) -> None:
+    async def fake_fetch(*_args, **_kwargs):
+        return {"grok-4.5": supports_backend_search}
+
+    monkeypatch.setattr(
+        "nanobot.providers.xai_grok_provider._fetch_xai_model_capabilities",
+        fake_fetch,
+    )
+
+
+def test_xai_grok_registry_exposes_curated_x_search_model() -> None:
+    spec = find_by_name("xai_grok")
+
+    assert spec is not None
+    assert spec.is_oauth is True
+    assert spec.backend == "xai_grok"
+    assert spec.builtin_models[0].id == DEFAULT_XAI_GROK_MODEL
+    assert spec.builtin_models[0].context_window == 500000
+    assert "when supported" in spec.builtin_models[0].description
+
+
+def test_reasoning_options_omit_disabled_effort() -> None:
+    assert _build_reasoning_options("none") == {"summary": "concise"}
+
+
+@pytest.mark.asyncio
+async def test_provider_injects_hosted_x_search_and_required_proxy_headers(monkeypatch) -> None:
+    _mock_token(monkeypatch)
+    _mock_model_capabilities(monkeypatch, supports_backend_search=True)
+    calls: list[tuple[str, dict[str, str], dict[str, Any]]] = []
+
+    async def fake_request(url, headers, body, **_kwargs):
+        calls.append((url, headers, body))
+        return "answer [[1]](https://x.com/example/status/1)", [], "stop", {}, None
+
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider._request_xai", fake_request)
+    provider = XAIGrokProvider()
+    tools = [
+        {
+            "type": "function",
+            "function": {
+                "name": "read_file",
+                "description": "Read a file",
+                "parameters": {"type": "object"},
+            },
+        },
+        {
+            "type": "function",
+            "function": {
+                "name": "x_search",
+                "description": "A colliding local tool",
+                "parameters": {"type": "object"},
+            },
+        },
+    ]
+
+    response = await provider.chat(
+        [{"role": "user", "content": "What is happening on X?"}],
+        tools=tools,
+        max_tokens=1234,
+        temperature=0.2,
+        reasoning_effort="high",
+    )
+
+    assert response.content == "answer [[1]](https://x.com/example/status/1)"
+    url, headers, body = calls[0]
+    assert url == "https://cli-chat-proxy.grok.com/v1/responses"
+    assert body["model"] == "grok-4.5"
+    assert body["tools"] == [
+        {
+            "type": "function",
+            "name": "read_file",
+            "description": "Read a file",
+            "parameters": {"type": "object"},
+        },
+        {"type": "x_search"},
+    ]
+    assert body["max_output_tokens"] == 1234
+    assert body["temperature"] == 0.2
+    assert body["stream_tool_calls"] is True
+    assert body["reasoning"] == {"summary": "concise", "effort": "high"}
+    assert body["store"] is False
+    assert headers["Authorization"] == "Bearer subscription-token"
+    assert headers["X-XAI-Token-Auth"] == "xai-grok-cli"
+    assert headers["x-authenticateresponse"] == "authenticate-response"
+    assert headers["x-grok-client-identifier"] == "nanobot"
+    assert headers["x-grok-client-mode"] == "headless"
+    assert headers["x-grok-model-override"] == "grok-4.5"
+
+
+@pytest.mark.asyncio
+async def test_provider_keeps_local_x_search_when_model_does_not_support_hosted_search(
+    monkeypatch,
+) -> None:
+    _mock_token(monkeypatch)
+    _mock_model_capabilities(monkeypatch, supports_backend_search=False)
+    bodies: list[dict[str, Any]] = []
+
+    async def fake_request(_url, _headers, body, **_kwargs):
+        bodies.append(body)
+        return "ok", [], "stop", {}, None
+
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider._request_xai", fake_request)
+    provider = XAIGrokProvider()
+    tools = [
+        {
+            "type": "function",
+            "function": {
+                "name": "x_search",
+                "description": "A local search fallback",
+                "parameters": {"type": "object"},
+            },
+        }
+    ]
+
+    response = await provider.chat([{"role": "user", "content": "search"}], tools=tools)
+
+    assert response.content == "ok"
+    assert bodies[0]["tools"] == [
+        {
+            "type": "function",
+            "name": "x_search",
+            "description": "A local search fallback",
+            "parameters": {"type": "object"},
+        }
+    ]
+
+
+@pytest.mark.asyncio
+async def test_provider_fails_closed_and_caches_model_catalog_failure(monkeypatch) -> None:
+    _mock_token(monkeypatch)
+    fetch_calls = 0
+    bodies: list[dict[str, Any]] = []
+
+    async def failing_fetch(*_args, **_kwargs):
+        nonlocal fetch_calls
+        fetch_calls += 1
+        raise httpx.ConnectError("catalog unavailable")
+
+    async def fake_request(_url, _headers, body, **_kwargs):
+        bodies.append(body)
+        return "ok", [], "stop", {}, None
+
+    monkeypatch.setattr(
+        "nanobot.providers.xai_grok_provider._fetch_xai_model_capabilities",
+        failing_fetch,
+    )
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider._request_xai", fake_request)
+    provider = XAIGrokProvider()
+
+    await provider.chat([{"role": "user", "content": "first"}])
+    await provider.chat([{"role": "user", "content": "second"}])
+
+    assert fetch_calls == 1
+    assert all({"type": "x_search"} not in body["tools"] for body in bodies)
+
+
+@pytest.mark.asyncio
+async def test_provider_refreshes_and_retries_exactly_once_after_401(monkeypatch) -> None:
+    _mock_model_capabilities(monkeypatch, supports_backend_search=False)
+    token_calls: list[tuple[str | None, bool]] = []
+
+    def fake_token(*, proxy=None, force_refresh=False):
+        token_calls.append((proxy, force_refresh))
+        return _token("fresh-token" if force_refresh else "stale-token")
+
+    monkeypatch.setattr(
+        "nanobot.providers.xai_grok_provider.get_xai_oauth_token",
+        fake_token,
+    )
+    request_tokens: list[str] = []
+
+    async def fake_request(_url, headers, _body, **_kwargs):
+        request_tokens.append(headers["Authorization"])
+        if len(request_tokens) == 1:
+            raise _XAIHTTPError("unauthorized", status_code=401, should_retry=False)
+        return "ok", [], "stop", {}, None
+
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider._request_xai", fake_request)
+    provider = XAIGrokProvider(proxy="http://127.0.0.1:7890")
+
+    response = await provider.chat([{"role": "user", "content": "hello"}])
+
+    assert response.content == "ok"
+    assert token_calls == [
+        ("http://127.0.0.1:7890", False),
+        ("http://127.0.0.1:7890", True),
+    ]
+    assert request_tokens == ["Bearer stale-token", "Bearer fresh-token"]
+
+
+@pytest.mark.asyncio
+async def test_second_401_is_non_retryable_and_prompts_reauthentication(monkeypatch) -> None:
+    _mock_token(monkeypatch)
+    _mock_model_capabilities(monkeypatch, supports_backend_search=False)
+
+    async def always_unauthorized(*_args, **_kwargs):
+        raise _XAIHTTPError(
+            "xAI rejected the login. Sign in again with `nanobot provider login xai-grok`.",
+            status_code=401,
+            should_retry=False,
+        )
+
+    monkeypatch.setattr(
+        "nanobot.providers.xai_grok_provider._request_xai",
+        always_unauthorized,
+    )
+    provider = XAIGrokProvider()
+
+    response = await provider.chat([{"role": "user", "content": "hello"}])
+
+    assert response.finish_reason == "error"
+    assert response.error_status_code == 401
+    assert response.error_kind == "http"
+    assert response.error_should_retry is False
+    assert "nanobot provider login xai-grok" in (response.content or "")
+
+
+@pytest.mark.asyncio
+async def test_factory_builds_xai_provider_and_applies_explicit_body_overrides(monkeypatch) -> None:
+    _mock_token(monkeypatch)
+    _mock_model_capabilities(monkeypatch, supports_backend_search=True)
+    bodies: list[dict[str, Any]] = []
+
+    async def fake_request(_url, _headers, body, **_kwargs):
+        bodies.append(body)
+        return "ok", [], "stop", {}, None
+
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider._request_xai", fake_request)
+    config = Config.model_validate(
+        {
+            "agents": {
+                "defaults": {
+                    "model": "xai-grok/grok-4.5",
+                    "provider": "xai_grok",
+                }
+            },
+            "providers": {
+                "xaiGrok": {
+                    "proxy": "http://127.0.0.1:7890",
+                    "extraBody": {"parallel_tool_calls": False},
+                }
+            },
+        }
+    )
+
+    provider = make_provider(config)
+    response = await provider.chat([{"role": "user", "content": "hello"}])
+
+    assert isinstance(provider, XAIGrokProvider)
+    assert provider.proxy == "http://127.0.0.1:7890"
+    assert response.content == "ok"
+    assert bodies[0]["parallel_tool_calls"] is False
+    assert {"type": "x_search"} in bodies[0]["tools"]
+
+
+@pytest.mark.asyncio
+async def test_raw_response_request_streams_text_usage_and_inline_citations(monkeypatch) -> None:
+    original_client = httpx.AsyncClient
+    captured: dict[str, Any] = {}
+    events = [
+        {"type": "response.output_text.delta", "delta": "Live result "},
+        {
+            "type": "response.output_text.delta",
+            "delta": "[[1]](https://x.com/example/status/1)",
+        },
+        {
+            "type": "response.completed",
+            "response": {
+                "status": "completed",
+                "usage": {"input_tokens": 8, "output_tokens": 4, "total_tokens": 12},
+            },
+        },
+    ]
+    content = "".join(f"data: {json.dumps(event)}\n\n" for event in events)
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        captured["request"] = request
+        captured["json"] = json.loads(request.content)
+        return httpx.Response(200, content=content, request=request)
+
+    def fake_client(**kwargs) -> httpx.AsyncClient:
+        captured["kwargs"] = kwargs
+        return original_client(
+            transport=httpx.MockTransport(handler),
+            timeout=kwargs["timeout"],
+        )
+
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider.httpx.AsyncClient", fake_client)
+    deltas: list[str] = []
+
+    result = await _request_xai(
+        "https://cli-chat-proxy.grok.com/v1/responses",
+        _build_headers("secret", "grok-4.5"),
+        {"model": "grok-4.5", "tools": [{"type": "x_search"}]},
+        on_content_delta=lambda delta: _append(deltas, delta),
+    )
+
+    assert result[0] == "Live result [[1]](https://x.com/example/status/1)"
+    assert result[2] == "stop"
+    assert result[3] == {"prompt_tokens": 8, "completion_tokens": 4, "total_tokens": 12}
+    assert deltas == ["Live result ", "[[1]](https://x.com/example/status/1)"]
+    assert captured["json"]["tools"] == [{"type": "x_search"}]
+
+
+def test_model_capabilities_follow_upstream_aliases_and_default_to_disabled() -> None:
+    capabilities = _parse_xai_model_capabilities(
+        {
+            "data": [
+                {"id": "grok-4.5", "supportsBackendSearch": False},
+                {
+                    "model": "grok-search",
+                    "supports_backend_search": True,
+                },
+                {
+                    "modelId": "grok-meta",
+                    "_meta": {"supportsBackendSearch": True},
+                },
+                {"id": "grok-unknown"},
+            ]
+        }
+    )
+
+    assert capabilities == {
+        "grok-4.5": False,
+        "grok-search": True,
+        "grok-meta": True,
+        "grok-unknown": False,
+    }
+
+
+@pytest.mark.asyncio
+async def test_model_capability_request_uses_subscription_headers(monkeypatch) -> None:
+    original_client = httpx.AsyncClient
+    captured: dict[str, Any] = {}
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        captured["request"] = request
+        return httpx.Response(
+            200,
+            json={"data": [{"id": "grok-search", "supportsBackendSearch": True}]},
+            request=request,
+        )
+
+    def fake_client(**kwargs) -> httpx.AsyncClient:
+        captured["kwargs"] = kwargs
+        return original_client(
+            transport=httpx.MockTransport(handler),
+            timeout=kwargs["timeout"],
+            follow_redirects=kwargs["follow_redirects"],
+        )
+
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider.httpx.AsyncClient", fake_client)
+    payload = base64.urlsafe_b64encode(
+        json.dumps({"sub": "user-42", "email": "user@example.com"}).encode()
+    ).decode().rstrip("=")
+    access_token = f"header.{payload}.signature"
+    headers = _build_model_headers(_token(access_token))
+
+    capabilities = await _fetch_xai_model_capabilities(
+        DEFAULT_XAI_GROK_MODELS_URL,
+        headers,
+    )
+
+    request = captured["request"]
+    assert isinstance(request, httpx.Request)
+    assert request.method == "GET"
+    assert str(request.url) == DEFAULT_XAI_GROK_MODELS_URL
+    assert request.headers["Authorization"] == f"Bearer {access_token}"
+    assert request.headers["X-XAI-Token-Auth"] == "xai-grok-cli"
+    assert request.headers["x-userid"] == "user-42"
+    assert request.headers["x-email"] == "user@example.com"
+    assert captured["kwargs"] == {"timeout": 10.0, "follow_redirects": False}
+    assert capabilities == {"grok-search": True}
+
+
+@pytest.mark.asyncio
+async def test_raw_response_error_preserves_bounded_redacted_body(monkeypatch) -> None:
+    original_client = httpx.AsyncClient
+    raw = json.dumps(
+        {
+            "code": "invalid-argument",
+            "message": "Hosted x_search is not supported by grok-4.5",
+            "access_token": "must-not-leak",
+        }
+    )
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        return httpx.Response(400, content=raw, request=request)
+
+    def fake_client(**kwargs) -> httpx.AsyncClient:
+        return original_client(
+            transport=httpx.MockTransport(handler),
+            timeout=kwargs["timeout"],
+        )
+
+    monkeypatch.setattr("nanobot.providers.xai_grok_provider.httpx.AsyncClient", fake_client)
+
+    with pytest.raises(_XAIHTTPError) as caught:
+        await _request_xai(
+            "https://cli-chat-proxy.grok.com/v1/responses",
+            _build_headers("secret", "grok-4.5"),
+            {"model": "grok-4.5"},
+        )
+
+    error = caught.value
+    assert error.status_code == 400
+    assert error.error_code == "invalid-argument"
+    assert error.should_retry is False
+    assert error.response_body == (
+        '{"code":"invalid-argument","message":"Hosted x_search is not supported by '
+        'grok-4.5","access_token":"[REDACTED]"}'
+    )
+    assert f"Response body: {error.response_body}" in str(error)
+    assert "must-not-leak" not in str(error)
+
+    provider_response = _xai_error_response(error)
+    assert provider_response.error_status_code == 400
+    assert provider_response.error_code == "invalid-argument"
+    assert error.response_body in (provider_response.content or "")
+
+
+def test_plain_error_body_is_single_line_and_bounded() -> None:
+    detail = _bounded_error_body("Bearer secret-token\n" + "x" * 1100)
+
+    assert detail is not None
+    assert detail.startswith("Bearer [REDACTED] ")
+    assert detail.endswith("…")
+    assert len(detail) == 1001
+
+
+def test_client_version_rejection_explains_update_and_preserves_body() -> None:
+    raw = json.dumps(
+        {
+            "code": "upgrade-required",
+            "message": "Client version 0.2.109 is no longer supported",
+        }
+    )
+
+    error = _build_xai_http_error(426, httpx.Headers(), raw)
+    response = _xai_error_response(error)
+
+    assert error.status_code == 426
+    assert error.should_retry is False
+    assert error.response_body == (
+        '{"code":"upgrade-required","message":"Client version 0.2.109 is no longer supported"}'
+    )
+    assert "xAI requires a newer Grok client version. Update nanobot and try again." in str(error)
+    assert error.response_body in str(error)
+    assert response.error_status_code == 426
+    assert error.response_body in (response.content or "")
+
+
+def test_large_json_error_body_redacts_camel_case_credentials_before_bounding() -> None:
+    detail = _bounded_error_body(
+        json.dumps(
+            {
+                "accessToken": "access-must-not-leak",
+                "refresh-token": "refresh-must-not-leak",
+                "padding": "x" * 33_000,
+            }
+        )
+    )
+
+    assert detail is not None
+    assert '"accessToken":"[REDACTED]"' in detail
+    assert '"refresh-token":"[REDACTED]"' in detail
+    assert "access-must-not-leak" not in detail
+    assert "refresh-must-not-leak" not in detail
+    assert detail.endswith("…")
+    assert len(detail) == 1001
+
+
+async def _append(target: list[str], value: str) -> None:
+    target.append(value)
diff --git a/tests/providers/test_xai_oauth.py b/tests/providers/test_xai_oauth.py
new file mode 100644
index 00000000..1da7d478
--- /dev/null
+++ b/tests/providers/test_xai_oauth.py
@@ -0,0 +1,340 @@
+from __future__ import annotations
+
+import json
+import queue
+import threading
+import time
+from urllib.parse import parse_qs, urlencode, urlsplit
+
+import httpx
+import pytest
+
+import nanobot.providers.xai_oauth as xai_oauth
+from nanobot.providers.xai_oauth import (
+    XAI_CLIENT_ID,
+    XAI_OAUTH_SCOPES,
+    XAIOAuthError,
+    XAIToken,
+    _build_authorize_url,
+    _CallbackResult,
+    _Discovery,
+    _generate_pkce,
+    _make_callback_server,
+    _validate_xai_endpoint,
+    complete_xai_oauth_login,
+    get_xai_oauth_login_status,
+    get_xai_oauth_storage_path,
+    get_xai_oauth_token,
+    login_xai_oauth,
+    logout_xai_oauth,
+    start_xai_oauth_login,
+)
+
+
+def _use_temp_credentials(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
+    monkeypatch.setattr(xai_oauth, "get_data_dir", lambda: tmp_path)
+
+
+def test_authorize_url_uses_pkce_and_frozen_xai_scope_contract() -> None:
+    verifier, challenge = _generate_pkce()
+
+    url = _build_authorize_url(
+        "https://auth.x.ai/oauth2/authorize",
+        redirect_uri="http://127.0.0.1:54321/callback",
+        challenge=challenge,
+        state="state-value",
+        nonce="nonce-value",
+    )
+
+    params = parse_qs(urlsplit(url).query)
+    assert len(verifier) >= 43
+    assert params == {
+        "response_type": ["code"],
+        "client_id": [XAI_CLIENT_ID],
+        "redirect_uri": ["http://127.0.0.1:54321/callback"],
+        "scope": [" ".join(XAI_OAUTH_SCOPES)],
+        "code_challenge": [challenge],
+        "code_challenge_method": ["S256"],
+        "state": ["state-value"],
+        "nonce": ["nonce-value"],
+        "referrer": ["nanobot"],
+    }
+
+
+@pytest.mark.parametrize(
+    "endpoint",
+    [
+        "http://auth.x.ai/oauth2/token",
+        "https://evil.example/oauth2/token",
+        "https://auth.x.ai:444/oauth2/token",
+        "https://user@auth.x.ai/oauth2/token",
+        "https://auth.x.ai:invalid/oauth2/token",
+    ],
+)
+def test_discovery_rejects_unsafe_endpoints(endpoint: str) -> None:
+    with pytest.raises(XAIOAuthError, match="unsafe token endpoint"):
+        _validate_xai_endpoint(endpoint, "token")
+
+
+def test_callback_server_accepts_only_matching_state_and_allows_accounts_origin() -> None:
+    results: queue.Queue[_CallbackResult] = queue.Queue(maxsize=1)
+    server = _make_callback_server("expected-state", results)
+    thread = threading.Thread(target=server.serve_forever, daemon=True)
+    thread.start()
+    try:
+        response = httpx.get(
+            f"http://127.0.0.1:{server.server_port}/callback",
+            params={"code": "one-time-code", "state": "expected-state"},
+            headers={"Origin": "https://accounts.x.ai"},
+        )
+        result = results.get(timeout=1)
+    finally:
+        server.shutdown()
+        server.server_close()
+        thread.join(timeout=2)
+
+    assert response.status_code == 200
+    assert response.headers["access-control-allow-origin"] == "https://accounts.x.ai"
+    assert response.headers["access-control-allow-private-network"] == "true"
+    assert result == _CallbackResult(code="one-time-code", state="expected-state")
+    assert "one-time-code" not in response.text
+
+
+def test_login_uses_random_loopback_callback_and_saves_separate_credentials(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+) -> None:
+    _use_temp_credentials(monkeypatch, tmp_path)
+    discovery = _Discovery(
+        authorization_endpoint="https://auth.x.ai/oauth2/authorize",
+        token_endpoint="https://auth.x.ai/oauth2/token",
+        userinfo_endpoint="https://auth.x.ai/oauth2/userinfo",
+    )
+    monkeypatch.setattr(xai_oauth, "_discover", lambda _proxy: discovery)
+    exchanged: dict[str, str] = {}
+
+    def fake_exchange(endpoint: str, **kwargs):
+        exchanged.update(endpoint=endpoint, **kwargs)
+        return {
+            "access_token": "access-secret",
+            "refresh_token": "refresh-secret",
+            "expires_in": 3600,
+        }
+
+    monkeypatch.setattr(xai_oauth, "_exchange_code", fake_exchange)
+    monkeypatch.setattr(
+        xai_oauth,
+        "_fetch_account",
+        lambda endpoint, access, proxy: "user@example.com",
+    )
+    opened_urls: list[str] = []
+
+    def complete_in_browser(authorize_url: str) -> bool:
+        opened_urls.append(authorize_url)
+        params = parse_qs(urlsplit(authorize_url).query)
+        callback_url = params["redirect_uri"][0]
+        callback_query = urlencode({"code": "auth-code", "state": params["state"][0]})
+        response = httpx.get(f"{callback_url}?{callback_query}")
+        assert response.status_code == 200
+        return True
+
+    token = login_xai_oauth(
+        print_fn=lambda _message: None,
+        browser_opener=complete_in_browser,
+        callback_timeout_s=1,
+    )
+
+    assert token.account_id == "user@example.com"
+    assert exchanged["code"] == "auth-code"
+    assert exchanged["redirect_uri"].startswith("http://127.0.0.1:")
+    assert exchanged["verifier"]
+    assert opened_urls
+    assert get_xai_oauth_storage_path() == tmp_path / "auth" / "xai.json"
+    saved = json.loads(get_xai_oauth_storage_path().read_text(encoding="utf-8"))
+    assert saved["access"] == "access-secret"
+    assert saved["refresh"] == "refresh-secret"
+    assert get_xai_oauth_login_status() == token
+
+
+def test_pending_login_accepts_authorization_code_from_remote_browser(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+) -> None:
+    _use_temp_credentials(monkeypatch, tmp_path)
+    discovery = _Discovery(
+        authorization_endpoint="https://auth.x.ai/oauth2/authorize",
+        token_endpoint="https://auth.x.ai/oauth2/token",
+        userinfo_endpoint=None,
+    )
+    monkeypatch.setattr(xai_oauth, "_discover", lambda _proxy: discovery)
+    exchanged: dict[str, str] = {}
+
+    def fake_exchange(endpoint: str, **kwargs):
+        exchanged.update(endpoint=endpoint, **kwargs)
+        return {"access_token": "remote-access", "expires_in": 3600}
+
+    monkeypatch.setattr(xai_oauth, "_exchange_code", fake_exchange)
+
+    flow = start_xai_oauth_login(timeout_s=5)
+    try:
+        params = parse_qs(urlsplit(flow.authorization_url).query)
+        callback_url = params["redirect_uri"][0]
+
+        token = complete_xai_oauth_login(flow, "remote-code")
+    finally:
+        flow.cancel()
+
+    assert token is not None
+    assert token.access == "remote-access"
+    assert exchanged["code"] == "remote-code"
+    assert exchanged["redirect_uri"] == callback_url
+    assert get_xai_oauth_login_status() == token
+
+
+def test_expired_token_refreshes_once_and_persists_rotated_refresh_token(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+) -> None:
+    _use_temp_credentials(monkeypatch, tmp_path)
+    expired = XAIToken(
+        access="old-access",
+        refresh="old-refresh",
+        expires=int(time.time() * 1000) - 1,
+        account_id="account",
+    )
+    xai_oauth._write_token(expired)
+    calls: list[tuple[XAIToken, str | None]] = []
+
+    def fake_refresh(token: XAIToken, proxy: str | None) -> XAIToken:
+        calls.append((token, proxy))
+        return XAIToken(
+            access="new-access",
+            refresh="new-refresh",
+            expires=int(time.time() * 1000) + 3_600_000,
+            account_id=token.account_id,
+        )
+
+    monkeypatch.setattr(xai_oauth, "_refresh_token", fake_refresh)
+
+    refreshed = get_xai_oauth_token(proxy="http://127.0.0.1:7890")
+
+    assert refreshed.access == "new-access"
+    assert refreshed.refresh == "new-refresh"
+    assert calls == [(expired, "http://127.0.0.1:7890")]
+    assert get_xai_oauth_login_status() == refreshed
+
+
+def test_missing_credentials_returns_actionable_login_command(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+) -> None:
+    _use_temp_credentials(monkeypatch, tmp_path)
+
+    with pytest.raises(XAIOAuthError, match="nanobot provider login xai-grok"):
+        get_xai_oauth_token()
+
+
+def test_logout_waits_for_inflight_refresh_and_removes_rotated_token(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+) -> None:
+    _use_temp_credentials(monkeypatch, tmp_path)
+    expired = XAIToken(
+        access="old-access",
+        refresh="old-refresh",
+        expires=int(time.time() * 1000) - 1,
+    )
+    xai_oauth._write_token(expired)
+    refresh_started = threading.Event()
+    finish_refresh = threading.Event()
+    logout_started = threading.Event()
+    logout_finished = threading.Event()
+    refresh_errors: list[Exception] = []
+    logout_results: list[bool] = []
+
+    def fake_refresh(token: XAIToken, _proxy: str | None) -> XAIToken:
+        refresh_started.set()
+        assert finish_refresh.wait(timeout=2)
+        return XAIToken(
+            access="new-access",
+            refresh=token.refresh,
+            expires=int(time.time() * 1000) + 3_600_000,
+        )
+
+    def refresh() -> None:
+        try:
+            get_xai_oauth_token()
+        except Exception as exc:  # pragma: no cover - asserted below
+            refresh_errors.append(exc)
+
+    def logout() -> None:
+        logout_started.set()
+        logout_results.append(logout_xai_oauth())
+        logout_finished.set()
+
+    monkeypatch.setattr(xai_oauth, "_refresh_token", fake_refresh)
+    refresh_thread = threading.Thread(target=refresh)
+    refresh_thread.start()
+    assert refresh_started.wait(timeout=2)
+
+    logout_thread = threading.Thread(target=logout)
+    logout_thread.start()
+    assert logout_started.wait(timeout=2)
+    assert not logout_finished.wait(timeout=0.05)
+    finish_refresh.set()
+    refresh_thread.join(timeout=2)
+    logout_thread.join(timeout=2)
+
+    assert not refresh_thread.is_alive()
+    assert not logout_thread.is_alive()
+    assert refresh_errors == []
+    assert logout_results == [True]
+    assert not get_xai_oauth_storage_path().exists()
+
+
+def test_refresh_does_not_restore_credentials_removed_after_its_initial_read(
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path,
+) -> None:
+    _use_temp_credentials(monkeypatch, tmp_path)
+    expired = XAIToken(
+        access="old-access",
+        refresh="old-refresh",
+        expires=int(time.time() * 1000) - 1,
+    )
+    xai_oauth._write_token(expired)
+    real_load_token = xai_oauth._load_token
+    initial_read_finished = threading.Event()
+    continue_refresh = threading.Event()
+    refresh_errors: list[Exception] = []
+    first_load = True
+
+    def gated_load_token() -> XAIToken | None:
+        nonlocal first_load
+        token = real_load_token()
+        if first_load:
+            first_load = False
+            initial_read_finished.set()
+            assert continue_refresh.wait(timeout=2)
+        return token
+
+    def refresh() -> None:
+        try:
+            get_xai_oauth_token()
+        except Exception as exc:
+            refresh_errors.append(exc)
+
+    monkeypatch.setattr(xai_oauth, "_load_token", gated_load_token)
+    refresh_thread = threading.Thread(target=refresh)
+    refresh_thread.start()
+    assert initial_read_finished.wait(timeout=2)
+
+    assert logout_xai_oauth() is True
+    continue_refresh.set()
+    refresh_thread.join(timeout=2)
+
+    assert not refresh_thread.is_alive()
+    assert len(refresh_errors) == 1
+    assert isinstance(refresh_errors[0], XAIOAuthError)
+    assert "not signed in" in str(refresh_errors[0])
+    assert not get_xai_oauth_storage_path().exists()
diff --git a/tests/webui/test_settings_api.py b/tests/webui/test_settings_api.py
index 13cdc9ff..9c8ec2e9 100644
--- a/tests/webui/test_settings_api.py
+++ b/tests/webui/test_settings_api.py
@@ -16,8 +16,10 @@ from nanobot.webui.settings_api import (
     _model_catalog_kind,
     _oauth_provider_status,
     _reasoning_effort_values_for,
+    complete_oauth_provider,
     create_model_configuration,
     login_oauth_provider,
+    logout_oauth_provider,
     provider_models_payload,
     settings_payload,
     settings_usage_payload,
@@ -344,6 +346,63 @@ def test_update_provider_settings_updates_dynamic_custom_provider(
     assert dynamic_provider.api_key == "sk-test"
 
 
+@pytest.mark.parametrize(
+    ("provider_name", "config_attr"),
+    [
+        ("openai_codex", "openai_codex"),
+        ("xai_grok", "xai_grok"),
+    ],
+)
+def test_update_provider_settings_updates_and_clears_oauth_proxy(
+    provider_name: str,
+    config_attr: str,
+    tmp_path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    config_path = tmp_path / "config.json"
+    config = Config()
+    getattr(config.providers, config_attr).proxy = "http://127.0.0.1:7000"
+    save_config(config, config_path)
+    monkeypatch.setattr("nanobot.config.loader._current_config_path", config_path)
+    monkeypatch.setattr(
+        "nanobot.webui.settings_api._oauth_provider_status",
+        lambda _spec: {
+            "configured": False,
+            "account": None,
+            "expires_at": None,
+            "login_supported": True,
+        },
+    )
+
+    payload = update_provider_settings(
+        {"provider": [provider_name], "proxy": [" http://127.0.0.1:7890 "]}
+    )
+
+    providers = {row["name"]: row for row in payload["providers"]}
+    assert providers[provider_name]["proxy"] == "http://127.0.0.1:7890"
+    assert getattr(load_config(config_path).providers, config_attr).proxy == (
+        "http://127.0.0.1:7890"
+    )
+
+    cleared = update_provider_settings({"provider": [provider_name], "proxy": ["  "]})
+
+    providers = {row["name"]: row for row in cleared["providers"]}
+    assert providers[provider_name]["proxy"] is None
+    assert getattr(load_config(config_path).providers, config_attr).proxy is None
+
+
+def test_update_provider_settings_keeps_oauth_credentials_read_only(
+    tmp_path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    config_path = tmp_path / "config.json"
+    save_config(Config(), config_path)
+    monkeypatch.setattr("nanobot.config.loader._current_config_path", config_path)
+
+    with pytest.raises(WebUISettingsError, match="only supports proxy settings"):
+        update_provider_settings({"provider": ["openai_codex"], "apiKey": ["not-allowed"]})
+
+
 def test_update_agent_settings_accepts_context_window_options(
     tmp_path,
     monkeypatch: pytest.MonkeyPatch,
@@ -396,7 +455,7 @@ def test_update_context_window_rejects_unknown_values(
 
     with pytest.raises(
         WebUISettingsError,
-        match="context_window_tokens must be 65536, 200000, 262144, or 1048576",
+        match="context_window_tokens must be 65536, 200000, 262144, 500000, or 1048576",
     ):
         update_agent_settings({"context_window_tokens": ["128000"]})
 
@@ -1020,6 +1079,30 @@ def test_openai_codex_oauth_status_rejects_unavailable_token(
     assert status["account"] is None
 
 
+def test_xai_grok_status_accepts_refreshable_login(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    token = SimpleNamespace(
+        access="access-token",
+        refresh="refresh-token",
+        expires=1,
+        account_id="user@example.com",
+    )
+    monkeypatch.setattr(
+        "nanobot.providers.xai_oauth.get_xai_oauth_login_status",
+        lambda: token,
+    )
+
+    status = _oauth_provider_status(find_by_name("xai_grok"))
+
+    assert status == {
+        "configured": True,
+        "account": "user@example.com",
+        "expires_at": 1,
+        "login_supported": True,
+    }
+
+
 def test_openai_codex_oauth_login_passes_configured_proxy(
     tmp_path,
     monkeypatch: pytest.MonkeyPatch,
@@ -1089,6 +1172,118 @@ def test_github_copilot_oauth_login_reports_missing_oauth_cli_kit(
     assert "oauth_cli_kit not installed. Run: pip install oauth-cli-kit" in str(exc.value)
 
 
+def test_xai_grok_login_starts_fresh_browser_flow_with_proxy(
+    tmp_path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    proxy = "http://127.0.0.1:23458"
+    config_path = tmp_path / "config.json"
+    save_config(Config.model_validate({"providers": {"xaiGrok": {"proxy": proxy}}}), config_path)
+    monkeypatch.setattr("nanobot.config.loader._current_config_path", config_path)
+    captured: dict[str, object] = {}
+
+    class FakeFlow:
+        authorization_url = "https://auth.x.ai/oauth2/authorize?state=test"
+        remaining_seconds = 600
+        expired = False
+
+        def cancel(self) -> None:
+            captured["cancelled"] = True
+
+    def fake_start(*, proxy=None, timeout_s=None):
+        captured.update(proxy=proxy, timeout_s=timeout_s)
+        return FakeFlow()
+
+    monkeypatch.setattr("nanobot.providers.xai_oauth.start_xai_oauth_login", fake_start)
+
+    payload = login_oauth_provider({"provider": ["xai-grok"]})
+
+    assert captured["proxy"] == proxy
+    assert captured["timeout_s"] == 600
+    assert payload["status"] == "authorization_required"
+    assert payload["provider"] == "xai_grok"
+    assert payload["authorization_url"] == FakeFlow.authorization_url
+    assert payload["flow_id"]
+
+    callbacks: list[str | None] = []
+
+    def fake_complete(_flow, callback):
+        callbacks.append(callback)
+        if callback is None:
+            return None
+        return SimpleNamespace(access="access-token")
+
+    monkeypatch.setattr(
+        "nanobot.providers.xai_oauth.complete_xai_oauth_login",
+        fake_complete,
+    )
+    monkeypatch.setattr(
+        "nanobot.webui.settings_api.settings_payload",
+        lambda: {"settings": "ready"},
+    )
+
+    pending = complete_oauth_provider(
+        {"provider": ["xai-grok"], "flow_id": [payload["flow_id"]]},
+    )
+    completed = complete_oauth_provider(
+        {"provider": ["xai-grok"], "flow_id": [payload["flow_id"]]},
+        "secret",
+    )
+
+    assert pending == {
+        "status": "pending",
+        "provider": "xai_grok",
+        "flow_id": payload["flow_id"],
+    }
+    assert completed == {"settings": "ready"}
+    assert callbacks == [None, "secret"]
+
+
+def test_xai_grok_login_reports_upstream_failure_as_bad_gateway(
+    tmp_path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    config_path = tmp_path / "config.json"
+    save_config(Config(), config_path)
+    monkeypatch.setattr("nanobot.config.loader._current_config_path", config_path)
+    failure = RuntimeError("Could not reach xAI sign-in: ConnectError.")
+
+    def fake_start(**_kwargs):
+        raise failure
+
+    monkeypatch.setattr("nanobot.providers.xai_oauth.start_xai_oauth_login", fake_start)
+
+    with pytest.raises(WebUISettingsError) as exc:
+        login_oauth_provider({"provider": ["xai-grok"]})
+
+    assert exc.value.status == 502
+    assert str(exc.value) == (
+        "xAI OAuth login failed: Could not reach xAI sign-in: ConnectError."
+    )
+    assert exc.value.__cause__ is failure
+
+
+def test_xai_grok_logout_removes_token_through_shared_lock(
+    tmp_path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    config_path = tmp_path / "config.json"
+    save_config(Config(), config_path)
+    monkeypatch.setattr("nanobot.config.loader._current_config_path", config_path)
+    token_path = tmp_path / "auth" / "xai.json"
+    token_path.parent.mkdir(parents=True)
+    token_path.write_text("{}", encoding="utf-8")
+    token_path.with_suffix(".lock").write_text("", encoding="utf-8")
+    monkeypatch.setattr(
+        "nanobot.providers.xai_oauth.get_xai_oauth_storage_path",
+        lambda: token_path,
+    )
+
+    logout_oauth_provider({"provider": ["xai-grok"]})
+
+    assert not token_path.exists()
+
+
 def test_provider_models_payload_fetches_openai_compatible_models(
     tmp_path,
     monkeypatch: pytest.MonkeyPatch,
@@ -1144,6 +1339,22 @@ def test_provider_models_payload_returns_curated_openai_codex_models() -> None:
     ]
 
 
+def test_provider_models_payload_returns_xai_grok_model() -> None:
+    payload = provider_models_payload({"provider": ["xai_grok"]})
+
+    assert payload["status"] == "available"
+    assert payload["catalog_kind"] == "builtin"
+    assert payload["models"] == [
+        {
+            "id": "xai-grok/grok-4.5",
+            "label": "Grok 4.5",
+            "description": "Grok via xAI subscription; X Search is enabled when supported.",
+            "owned_by": "xAI Grok",
+            "context_window": 500000,
+        }
+    ]
+
+
 def test_provider_models_payload_fetches_dynamic_custom_provider_models(
     tmp_path,
     monkeypatch: pytest.MonkeyPatch,
diff --git a/tests/webui/test_settings_routes.py b/tests/webui/test_settings_routes.py
new file mode 100644
index 00000000..9a87abc3
--- /dev/null
+++ b/tests/webui/test_settings_routes.py
@@ -0,0 +1,72 @@
+from __future__ import annotations
+
+import json
+from types import SimpleNamespace
+from urllib.parse import parse_qs, urlsplit
+
+import pytest
+from websockets.datastructures import Headers
+
+from nanobot.webui.http_utils import http_json_response
+from nanobot.webui.settings_routes import WebUISettingsRouter
+
+
+@pytest.mark.asyncio
+async def test_xai_oauth_completion_reads_code_from_private_header(monkeypatch) -> None:
+    captured: dict[str, object] = {}
+
+    def complete(query, authorization_code=None):
+        captured.update(query=query, authorization_code=authorization_code)
+        return {
+            "status": "pending",
+            "provider": "xai_grok",
+            "flow_id": "flow-123",
+        }
+
+    monkeypatch.setattr("nanobot.webui.settings_routes.complete_oauth_provider", complete)
+    router = WebUISettingsRouter(
+        bus=SimpleNamespace(),
+        logger=SimpleNamespace(exception=lambda *_args: None),
+        check_api_token=lambda _request: True,
+        parse_query=lambda path: parse_qs(urlsplit(path).query),
+        json_response=http_json_response,
+        error_response=lambda status, message: http_json_response(
+            {"error": message},
+            status=status,
+        ),
+        runtime_surface="browser",
+        runtime_capabilities={},
+    )
+    request = SimpleNamespace(
+        path=(
+            "/api/settings/provider/oauth-login/complete"
+            "?provider=xai_grok&flow_id=flow-123"
+        ),
+        headers=Headers(
+            [
+                (
+                    "X-Nanobot-OAuth-Code",
+                    "secret",
+                )
+            ]
+        ),
+    )
+
+    response = await router.dispatch(
+        None,
+        request,
+        "/api/settings/provider/oauth-login/complete",
+    )
+
+    assert response is not None
+    assert response.status_code == 200
+    assert json.loads(response.body) == {
+        "status": "pending",
+        "provider": "xai_grok",
+        "flow_id": "flow-123",
+    }
+    assert captured == {
+        "query": {"provider": ["xai_grok"], "flow_id": ["flow-123"]},
+        "authorization_code": "secret",
+    }
+    assert "secret" not in request.path
diff --git a/webui/src/components/settings/SettingsView.tsx b/webui/src/components/settings/SettingsView.tsx
index 24810cea..2a4a0f7e 100644
--- a/webui/src/components/settings/SettingsView.tsx
+++ b/webui/src/components/settings/SettingsView.tsx
@@ -98,6 +98,7 @@ import { Textarea } from "@/components/ui/textarea";
 import { isLoopbackHost } from "@/lib/network";
 import {
   checkVersion,
+  completeProviderOAuth,
   createModelConfiguration,
   disableNanobotFeature,
   enableNanobotFeature,
@@ -166,6 +167,10 @@ import type {
   NanobotFeaturesPayload,
   NetworkSafetySettingsUpdate,
   ProviderModelsPayload,
+  ProviderOAuthAuthorizationRequired,
+  ProviderOAuthCompletionResult,
+  ProviderOAuthLoginResult,
+  ProviderOAuthPending,
   SessionAutomationJob,
   SettingsPayload,
   SkillSummary,
@@ -188,6 +193,18 @@ export type SettingsSectionKey =
   | "runtime"
   | "advanced";
 
+function isProviderOAuthAuthorizationRequired(
+  payload: ProviderOAuthLoginResult,
+): payload is ProviderOAuthAuthorizationRequired {
+  return (payload as ProviderOAuthAuthorizationRequired).status === "authorization_required";
+}
+
+function isProviderOAuthPending(
+  payload: ProviderOAuthCompletionResult,
+): payload is ProviderOAuthPending {
+  return (payload as ProviderOAuthPending).status === "pending";
+}
+
 type AppsKindFilter = "ready" | "cli" | "mcp";
 type AutomationFilter = "all" | "active" | "paused" | "failed" | "system";
 type AutomationSort = "next" | "last" | "updated" | "name";
@@ -223,10 +240,16 @@ type RestartAwarePayload = {
   runtime_capabilities?: SettingsPayload["runtime_capabilities"];
 };
 type ProviderApiType = "auto" | "chat_completions" | "responses";
-type ProviderForm = { apiKey: string; apiBase: string; apiType: ProviderApiType };
+type ProviderForm = {
+  apiKey: string;
+  apiBase: string;
+  apiType: ProviderApiType;
+  proxy: string;
+};
 type CustomMcpTransport = "stdio" | "streamableHttp" | "sse";
 
-const CONTEXT_WINDOW_TOKEN_OPTIONS = [65_536, 200_000, 262_144, 1_048_576] as const;
+const CONTEXT_WINDOW_TOKEN_OPTIONS = [65_536, 200_000, 262_144, 500_000, 1_048_576] as const;
+const OAUTH_PROXY_PROVIDERS = new Set(["openai_codex", "xai_grok"]);
 const DEFERRED_MODEL_LIST_PROVIDERS = new Set([
   "aihubmix",
   "atomic_chat",
@@ -541,6 +564,8 @@ export function SettingsView({
   const { t } = useTranslation();
   const { token } = useClient();
   const pageVisible = usePageVisibility();
+  const remoteBrowserAccess =
+    typeof window !== "undefined" && !isLoopbackHost(window.location.hostname);
   const [settings, setSettings] = useState<SettingsPayload | null>(() => initialSettings);
   const [cliApps, setCliApps] = useState<CliAppsPayload | null>(null);
   const [nanobotFeatures, setNanobotFeatures] = useState<NanobotFeaturesPayload | null>(null);
@@ -565,6 +590,11 @@ export function SettingsView({
   const [nanobotFeatureConfirm, setNanobotFeatureConfirm] = useState<NanobotFeatureInfo | null>(null);
   const [mcpPresetAction, setMcpPresetAction] = useState<string | null>(null);
   const [providerSaving, setProviderSaving] = useState<string | null>(null);
+  const [xaiOAuthFlow, setXaiOAuthFlow] =
+    useState<ProviderOAuthAuthorizationRequired | null>(null);
+  const xaiOAuthFlowRef = useRef<ProviderOAuthAuthorizationRequired | null>(null);
+  const [xaiOAuthCode, setXaiOAuthCode] = useState("");
+  const [xaiOAuthCompleting, setXaiOAuthCompleting] = useState(false);
   const [webSearchSaving, setWebSearchSaving] = useState(false);
   const [imageGenerationSaving, setImageGenerationSaving] = useState(false);
   const [transcriptionSaving, setTranscriptionSaving] = useState(false);
@@ -658,6 +688,46 @@ export function SettingsView({
     onSettingsChange?.(payload);
   }, [onSettingsChange]);
 
+  const closeXaiOAuthFlow = useCallback(() => {
+    xaiOAuthFlowRef.current = null;
+    setXaiOAuthFlow(null);
+    setXaiOAuthCode("");
+    setXaiOAuthCompleting(false);
+  }, []);
+
+  useEffect(() => {
+    if (!xaiOAuthFlow) return;
+    let cancelled = false;
+    let timer: number | null = null;
+    const poll = async () => {
+      try {
+        const payload = await completeProviderOAuth(
+          token,
+          xaiOAuthFlow.provider,
+          xaiOAuthFlow.flow_id,
+        );
+        if (cancelled || xaiOAuthFlowRef.current?.flow_id !== xaiOAuthFlow.flow_id) return;
+        if (isProviderOAuthPending(payload)) {
+          timer = window.setTimeout(() => void poll(), 1000);
+          return;
+        }
+        applyPayload(payload);
+        setExpandedProvider(xaiOAuthFlow.provider);
+        setError(null);
+        closeXaiOAuthFlow();
+      } catch (err) {
+        if (cancelled || xaiOAuthFlowRef.current?.flow_id !== xaiOAuthFlow.flow_id) return;
+        setError((err as Error).message);
+        closeXaiOAuthFlow();
+      }
+    };
+    timer = window.setTimeout(() => void poll(), 1000);
+    return () => {
+      cancelled = true;
+      if (timer !== null) window.clearTimeout(timer);
+    };
+  }, [applyPayload, closeXaiOAuthFlow, token, xaiOAuthFlow]);
+
   useEffect(() => {
     if (!initialSettings || settings !== null) return;
     applyPayload(initialSettings);
@@ -882,6 +952,7 @@ export function SettingsView({
           apiKey: next[provider.name]?.apiKey ?? "",
           apiBase: next[provider.name]?.apiBase ?? provider.api_base ?? provider.default_api_base ?? "",
           apiType: next[provider.name]?.apiType ?? provider.api_type ?? "auto",
+          proxy: next[provider.name]?.proxy ?? provider.proxy ?? "",
         };
       }
       return next;
@@ -1229,11 +1300,16 @@ export function SettingsView({
     if (providerSaving) return;
     const provider = settings?.providers.find((item) => item.name === providerName);
     if (!provider) return;
-    if (provider.auth_type === "oauth") return;
-    const providerForm = providerForms[providerName] ?? { apiKey: "", apiBase: "", apiType: "auto" };
+    const isOauthProvider = provider.auth_type === "oauth";
+    const providerForm = providerForms[providerName] ?? {
+      apiKey: "",
+      apiBase: "",
+      apiType: "auto",
+      proxy: provider.proxy ?? "",
+    };
     const apiKey = providerForm.apiKey.trim();
     const apiKeyRequired = provider.api_key_required ?? true;
-    if (!provider.configured && apiKeyRequired && !apiKey) {
+    if (!isOauthProvider && !provider.configured && apiKeyRequired && !apiKey) {
       setError(t("settings.byok.apiKeyRequired"));
       return;
     }
@@ -1245,12 +1321,20 @@ export function SettingsView({
           ? "azure"
           : null;
       if (supportName && !(await installCapabilities([supportName]))) return;
-      const payload = await updateProviderSettings(token, {
-        provider: providerName,
-        apiKey: apiKey || undefined,
-        apiBase: providerForm.apiBase.trim(),
-        apiType: providerForm.apiType,
-      });
+      const payload = await updateProviderSettings(
+        token,
+        isOauthProvider
+          ? {
+              provider: providerName,
+              proxy: providerForm.proxy.trim(),
+            }
+          : {
+              provider: providerName,
+              apiKey: apiKey || undefined,
+              apiBase: providerForm.apiBase.trim(),
+              apiType: providerForm.apiType,
+            },
+      );
       applyPayload(payload);
       if (payload.requires_restart) {
         setPendingRestartSections((prev) => ({ ...prev, image: true }));
@@ -1262,6 +1346,7 @@ export function SettingsView({
           apiKey: "",
           apiBase: providerForm.apiBase.trim(),
           apiType: providerForm.apiType,
+          proxy: providerForm.proxy.trim(),
         },
       }));
       setVisibleProviderKeys((prev) => ({ ...prev, [providerName]: false }));
@@ -1276,22 +1361,75 @@ export function SettingsView({
 
   const runProviderOAuth = async (providerName: string, action: "login" | "logout") => {
     if (providerSaving) return;
+    let popup: Window | null = null;
+    if (action === "login" && providerName === "xai_grok" && !remoteBrowserAccess) {
+      try {
+        popup = window.open("about:blank", "_blank");
+        if (popup) popup.opener = null;
+      } catch {
+        popup = null;
+      }
+    }
     setProviderSaving(providerName);
     try {
       const payload =
         action === "login"
           ? await loginProviderOAuth(token, providerName)
           : await logoutProviderOAuth(token, providerName);
+      if (isProviderOAuthAuthorizationRequired(payload)) {
+        try {
+          if (popup && !popup.closed) popup.location.href = payload.authorization_url;
+        } catch {
+          // The dialog keeps the authorization link available when the popup was closed.
+        }
+        xaiOAuthFlowRef.current = payload;
+        setXaiOAuthFlow(payload);
+        setXaiOAuthCode("");
+        setExpandedProvider(providerName);
+        setError(null);
+        return;
+      }
+      popup?.close();
+      closeXaiOAuthFlow();
       applyPayload(payload);
       setExpandedProvider(providerName);
       setError(null);
     } catch (err) {
+      popup?.close();
       setError((err as Error).message);
     } finally {
       setProviderSaving(null);
     }
   };
 
+  const completeXaiOAuth = async () => {
+    const flow = xaiOAuthFlowRef.current;
+    const authorizationCode = xaiOAuthCode.trim();
+    if (!flow || !authorizationCode || xaiOAuthCompleting) return;
+    setXaiOAuthCompleting(true);
+    try {
+      const payload = await completeProviderOAuth(
+        token,
+        flow.provider,
+        flow.flow_id,
+        authorizationCode,
+      );
+      if (xaiOAuthFlowRef.current?.flow_id !== flow.flow_id) return;
+      if (isProviderOAuthPending(payload)) return;
+      applyPayload(payload);
+      setExpandedProvider(flow.provider);
+      setError(null);
+      closeXaiOAuthFlow();
+    } catch (err) {
+      if (xaiOAuthFlowRef.current?.flow_id === flow.flow_id) {
+        setError((err as Error).message);
+        closeXaiOAuthFlow();
+      }
+    } finally {
+      setXaiOAuthCompleting(false);
+    }
+  };
+
   const saveWebSearch = async () => {
     if (!settings || webSearchSaving) return;
     const provider = settings.web_search.providers.find((item) => item.name === webSearchForm.provider);
@@ -1364,6 +1502,7 @@ export function SettingsView({
         apiKey: "",
         apiBase: provider.api_base ?? provider.default_api_base ?? "",
         apiType: provider.api_type ?? "auto",
+        proxy: provider.proxy ?? "",
       },
     }));
     setVisibleProviderKeys((prev) => ({ ...prev, [providerName]: false }));
@@ -1418,6 +1557,7 @@ export function SettingsView({
             apiKey: "",
             apiBase: forms[providerName]?.apiBase ?? "",
             apiType: forms[providerName]?.apiType ?? "auto",
+            proxy: forms[providerName]?.proxy ?? "",
           },
         }));
         setVisibleProviderKeys((visible) => ({ ...visible, [providerName]: false }));
@@ -1671,6 +1811,7 @@ export function SettingsView({
               providerSaving={providerSaving}
               query={providerQuery}
               showBrandLogos={localPrefs.brandLogos}
+              remoteBrowserAccess={remoteBrowserAccess}
               onQueryChange={setProviderQuery}
               onToggleProvider={handleToggleProvider}
               onToggleProviderKey={toggleProviderKeyVisibility}
@@ -1682,6 +1823,7 @@ export function SettingsView({
                     apiKey: prev[provider]?.apiKey ?? "",
                     apiBase: prev[provider]?.apiBase ?? "",
                     apiType: prev[provider]?.apiType ?? "auto",
+                    proxy: prev[provider]?.proxy ?? "",
                     ...value,
                   },
                 }))
@@ -1917,6 +2059,21 @@ export function SettingsView({
         onSave={handleCreateModelConfiguration}
       />
 
+      <XaiOAuthLoginDialog
+        flow={xaiOAuthFlow}
+        authorizationCode={xaiOAuthCode}
+        completing={xaiOAuthCompleting}
+        remoteBrowserAccess={remoteBrowserAccess}
+        onAuthorizationCodeChange={setXaiOAuthCode}
+        onOpenAuthorization={() => {
+          if (!xaiOAuthFlow) return;
+          const opened = window.open(xaiOAuthFlow.authorization_url, "_blank", "noopener,noreferrer");
+          if (opened) opened.opener = null;
+        }}
+        onComplete={() => void completeXaiOAuth()}
+        onClose={closeXaiOAuthFlow}
+      />
+
       <NanobotFeatureInstallDialog
         feature={nanobotFeatureConfirm}
         installing={nanobotFeatureAction === `enable:${nanobotFeatureConfirm?.name ?? ""}`}
@@ -2523,6 +2680,82 @@ function AppearanceSettings({
   );
 }
 
+function XaiOAuthLoginDialog({
+  flow,
+  authorizationCode,
+  completing,
+  remoteBrowserAccess,
+  onAuthorizationCodeChange,
+  onOpenAuthorization,
+  onComplete,
+  onClose,
+}: {
+  flow: ProviderOAuthAuthorizationRequired | null;
+  authorizationCode: string;
+  completing: boolean;
+  remoteBrowserAccess: boolean;
+  onAuthorizationCodeChange: (value: string) => void;
+  onOpenAuthorization: () => void;
+  onComplete: () => void;
+  onClose: () => void;
+}) {
+  const { t } = useTranslation();
+
+  return (
+    <Dialog
+      open={Boolean(flow)}
+      onOpenChange={(open) => {
+        if (!open) onClose();
+      }}
+    >
+      <DialogContent className="w-[min(calc(100vw-2rem),28rem)] rounded-[24px]">
+        <form
+          className="space-y-4"
+          onSubmit={(event) => {
+            event.preventDefault();
+            onComplete();
+          }}
+        >
+          <DialogHeader>
+            <DialogTitle>xAI Grok</DialogTitle>
+            <DialogDescription>
+              {remoteBrowserAccess
+                ? t("settings.oauth.remoteCodeHelp")
+                : t("settings.oauth.localCodeHelp")}
+            </DialogDescription>
+          </DialogHeader>
+          <div className="space-y-2">
+            <label
+              htmlFor="xai-oauth-code"
+              className="block text-xs font-medium text-foreground"
+            >
+              {t("settings.oauth.authorizationCode")}
+            </label>
+            <Input
+              id="xai-oauth-code"
+              value={authorizationCode}
+              onChange={(event) => onAuthorizationCodeChange(event.target.value)}
+              placeholder={t("settings.oauth.authorizationCode")}
+              aria-label={t("settings.oauth.authorizationCode")}
+              autoComplete="off"
+              spellCheck={false}
+            />
+          </div>
+          <DialogFooter className="gap-2 sm:space-x-0">
+            <Button type="button" variant="outline" onClick={onOpenAuthorization}>
+              <ExternalLink className="mr-2 h-4 w-4" aria-hidden />
+              {t("settings.oauth.signIn")}
+            </Button>
+            <Button type="submit" disabled={!authorizationCode.trim() || completing}>
+              {completing ? t("settings.oauth.signingIn") : t("settings.oauth.finishSignIn")}
+            </Button>
+          </DialogFooter>
+        </form>
+      </DialogContent>
+    </Dialog>
+  );
+}
+
 function NewModelConfigurationDialog({
   open,
   draft,
@@ -2827,11 +3060,13 @@ function ModelsSettings({
                 label:
                   tokens === 1_048_576
                     ? "1M"
-                    : tokens === 262_144
-                      ? "256K"
-                      : tokens === 200_000
-                        ? "200K"
-                        : "64K",
+                    : tokens === 500_000
+                      ? "500K"
+                      : tokens === 262_144
+                        ? "256K"
+                        : tokens === 200_000
+                          ? "200K"
+                          : "64K",
               }))}
               onChange={(value) =>
                 setForm((prev) => ({
@@ -2871,6 +3106,7 @@ function ProvidersSettings({
   providerSaving,
   query,
   showBrandLogos,
+  remoteBrowserAccess,
   onQueryChange,
   onToggleProvider,
   onToggleProviderKey,
@@ -2895,6 +3131,7 @@ function ProvidersSettings({
   providerSaving: string | null;
   query: string;
   showBrandLogos: boolean;
+  remoteBrowserAccess: boolean;
   onQueryChange: (query: string) => void;
   onToggleProvider: (provider: string) => void;
   onToggleProviderKey: (provider: string) => void;
@@ -2923,14 +3160,20 @@ function ProvidersSettings({
       apiKey: "",
       apiBase: provider.api_base ?? provider.default_api_base ?? "",
       apiType: provider.api_type ?? "auto",
+      proxy: provider.proxy ?? "",
     };
     const saving = providerSaving === provider.name;
     const isOauthProvider = provider.auth_type === "oauth";
+    const supportsOauthProxy = isOauthProvider && OAUTH_PROXY_PROVIDERS.has(provider.name);
     const keyVisible = !!visibleProviderKeys[provider.name];
     const editingKey = !provider.configured || !!editingProviderKeys[provider.name];
     const apiKeyRequired = provider.api_key_required ?? true;
     const apiKey = form.apiKey.trim();
     const apiBase = form.apiBase.trim();
+    const proxy = form.proxy.trim();
+    const oauthProxyDirty = supportsOauthProxy && proxy !== (provider.proxy ?? "").trim();
+    const oauthProxySaving = saving && oauthProxyDirty;
+    const oauthActionBusy = saving && !oauthProxySaving;
     const missingRequiredApiKey = !isOauthProvider && apiKeyRequired && !provider.configured && !apiKey;
     const missingOptionalCredential =
       !isOauthProvider && !apiKeyRequired && !provider.configured && !apiKey && !apiBase;
@@ -2990,48 +3233,120 @@ function ProvidersSettings({
               <p className="text-[12px] text-destructive">{capabilityError}</p>
             ) : null}
             {isOauthProvider ? (
-              <div className="flex flex-col gap-3 rounded-[18px] border border-border/45 bg-background/75 px-4 py-3 sm:flex-row sm:items-center sm:justify-between">
-                <div className="min-w-0">
-                  <p className="text-[13px] font-semibold text-foreground">
-                    {tx("settings.oauth.authentication", "OAuth authentication")}
-                  </p>
-                  <p className="mt-1 truncate text-[12px] text-muted-foreground">
-                    {provider.configured
-                      ? t("settings.oauth.signedInAs", {
-                          account: provider.oauth_account || provider.label,
-                          defaultValue: "Signed in as {{account}}",
-                        })
-                      : tx("settings.oauth.signInHelp", "Sign in from this device; no API key is stored in config.")}
-                  </p>
-                </div>
-                <div className="flex shrink-0 justify-end gap-2">
-                  {provider.configured ? (
+              <>
+                <div className="flex flex-col gap-3 rounded-[18px] border border-border/45 bg-background/75 px-4 py-3 sm:flex-row sm:items-center sm:justify-between">
+                  <div className="min-w-0">
+                    <p className="text-[13px] font-semibold text-foreground">
+                      {tx("settings.oauth.authentication", "OAuth authentication")}
+                    </p>
+                    <p className="mt-1 text-[12px] text-muted-foreground">
+                      {provider.configured
+                        ? t("settings.oauth.signedInAs", {
+                            account: provider.oauth_account || provider.label,
+                            defaultValue: "Signed in as {{account}}",
+                          })
+                        : provider.name === "xai_grok" && remoteBrowserAccess
+                          ? tx(
+                              "settings.oauth.remoteSignInHelp",
+                              "Select Sign in to open xAI on your computer, then paste the authorization code shown after login.",
+                            )
+                          : tx("settings.oauth.signInHelp", "Sign in from this device; no API key is stored in config.")}
+                    </p>
+                  </div>
+                  <div className="flex shrink-0 justify-end gap-2">
+                    {provider.configured ? (
+                      <Button
+                        size="sm"
+                        variant="ghost"
+                        onClick={() => onProviderOAuthLogout(provider.name)}
+                        disabled={saving}
+                        className="rounded-full"
+                      >
+                        {tx("settings.oauth.signOut", "Sign out")}
+                      </Button>
+                    ) : null}
                     <Button
                       size="sm"
-                      variant="ghost"
-                      onClick={() => onProviderOAuthLogout(provider.name)}
-                      disabled={saving}
+                      variant="outline"
+                      onClick={() => onProviderOAuthLogin(provider.name)}
+                      disabled={saving || oauthProxyDirty || !provider.oauth_login_supported}
+                      title={
+                        oauthProxyDirty
+                          ? tx(
+                              "settings.oauth.proxySaveBeforeSignIn",
+                              "Save proxy changes before signing in.",
+                            )
+                          : undefined
+                      }
                       className="rounded-full"
                     >
-                      {tx("settings.oauth.signOut", "Sign out")}
+                      {oauthActionBusy ? (
+                        <Loader2 className="mr-1.5 h-3.5 w-3.5 animate-spin" aria-hidden />
+                      ) : null}
+                      {oauthActionBusy
+                        ? tx("settings.oauth.signingIn", "Signing in...")
+                        : provider.configured
+                          ? tx("settings.oauth.signInAgain", "Sign in again")
+                          : tx("settings.oauth.signIn", "Sign in")}
                     </Button>
-                  ) : null}
-                  <Button
-                    size="sm"
-                    variant="outline"
-                    onClick={() => onProviderOAuthLogin(provider.name)}
-                    disabled={saving || !provider.oauth_login_supported}
-                    className="rounded-full"
-                  >
-                    {saving ? <Loader2 className="mr-1.5 h-3.5 w-3.5 animate-spin" aria-hidden /> : null}
-                    {saving
-                      ? tx("settings.oauth.signingIn", "Signing in...")
-                      : provider.configured
-                        ? tx("settings.oauth.signInAgain", "Sign in again")
-                        : tx("settings.oauth.signIn", "Sign in")}
-                  </Button>
+                  </div>
                 </div>
-              </div>
+                {supportsOauthProxy ? (
+                  <div className="rounded-[18px] border border-border/45 bg-background/75 px-4 py-3.5">
+                    <div className="flex items-center gap-3">
+                      <span className="flex h-8 w-8 shrink-0 items-center justify-center rounded-full bg-muted text-muted-foreground">
+                        <Globe2 className="h-4 w-4" aria-hidden />
+                      </span>
+                      <label
+                        htmlFor={`provider-${provider.name}-proxy`}
+                        className="text-[13px] font-semibold text-foreground"
+                      >
+                        {tx("settings.oauth.proxyLabel", "Network proxy")}
+                      </label>
+                    </div>
+                    <div className="mt-3 flex flex-col gap-2 sm:flex-row sm:items-center">
+                      <Input
+                        id={`provider-${provider.name}-proxy`}
+                        value={form.proxy}
+                        onChange={(event) =>
+                          onChangeProviderForm(provider.name, { proxy: event.target.value })
+                        }
+                        placeholder="http://127.0.0.1:7890"
+                        autoCapitalize="none"
+                        autoComplete="off"
+                        autoCorrect="off"
+                        spellCheck={false}
+                        className="h-9 min-w-0 flex-1 rounded-full font-mono text-[12px]"
+                      />
+                      <div className="flex shrink-0 justify-end gap-2">
+                        <Button
+                          size="sm"
+                          variant="ghost"
+                          onClick={() => onResetProviderDraft(provider.name)}
+                          disabled={saving || !oauthProxyDirty}
+                          className="rounded-full"
+                        >
+                          {t("settings.actions.cancel")}
+                        </Button>
+                        <Button
+                          size="sm"
+                          variant="outline"
+                          onClick={() => onSaveProvider(provider.name)}
+                          disabled={saving || !oauthProxyDirty}
+                          className="rounded-full"
+                        >
+                          {oauthProxySaving ? (
+                            <Loader2 className="mr-1.5 h-3.5 w-3.5 animate-spin" aria-hidden />
+                          ) : null}
+                          {oauthProxySaving
+                            ? t("settings.actions.saving")
+                            : tx("settings.oauth.saveProxy", "Save proxy")}
+                        </Button>
+                      </div>
+                    </div>
+                  </div>
+                ) : null}
+              </>
             ) : (
               <>
             <label className="block space-y-1.5">
diff --git a/webui/src/i18n/locales/en/common.json b/webui/src/i18n/locales/en/common.json
index 35bd6901..8b1b3c47 100644
--- a/webui/src/i18n/locales/en/common.json
+++ b/webui/src/i18n/locales/en/common.json
@@ -719,10 +719,18 @@
       "signOut": "Sign out",
       "signedInAs": "Signed in as {{account}}",
       "signInHelp": "Sign in from this device; no API key is stored in config.",
+      "remoteSignInHelp": "Select Sign in to open xAI on your computer, then paste the authorization code shown after login.",
       "signInRequired": "Sign in required",
       "signInBeforeSaving": "Sign in before saving this OAuth provider as the active model provider.",
       "signedIn": "Signed in",
-      "notSignedIn": "Not signed in"
+      "notSignedIn": "Not signed in",
+      "proxyLabel": "Network proxy",
+      "proxySaveBeforeSignIn": "Save proxy changes before signing in.",
+      "saveProxy": "Save proxy",
+      "localCodeHelp": "Complete sign-in in your browser. Nanobot usually finishes automatically; if it does not, paste the authorization code below.",
+      "remoteCodeHelp": "Select Sign in to open xAI on your computer. After signing in, paste the authorization code shown by xAI below.",
+      "authorizationCode": "Authorization code",
+      "finishSignIn": "Finish sign-in"
     },
     "skills": {
       "description": "Review the instruction skills this agent can load during a conversation.",
diff --git a/webui/src/i18n/locales/es/common.json b/webui/src/i18n/locales/es/common.json
index 8edba150..50db9a7f 100644
--- a/webui/src/i18n/locales/es/common.json
+++ b/webui/src/i18n/locales/es/common.json
@@ -706,10 +706,18 @@
       "signOut": "Cerrar sesión",
       "signedInAs": "Sesión iniciada como {{account}}",
       "signInHelp": "Inicia sesión desde este dispositivo; no se guarda API key en config.",
+      "remoteSignInHelp": "Selecciona Iniciar sesión para abrir xAI en tu computadora y luego pega el código de autorización que se muestra tras iniciar sesión.",
       "signInRequired": "Inicio de sesión requerido",
       "signInBeforeSaving": "Inicia sesión antes de guardar este proveedor OAuth como proveedor activo.",
       "signedIn": "Sesión iniciada",
-      "notSignedIn": "Sin sesión"
+      "notSignedIn": "Sin sesión",
+      "proxyLabel": "Proxy de red",
+      "proxySaveBeforeSignIn": "Guarda los cambios del proxy antes de iniciar sesión.",
+      "saveProxy": "Guardar proxy",
+      "localCodeHelp": "Completa el inicio de sesión en el navegador. nanobot suele finalizar automáticamente; si no lo hace, pega el código de autorización abajo.",
+      "remoteCodeHelp": "Selecciona Iniciar sesión para abrir xAI en tu computadora. Después de iniciar sesión, pega abajo el código de autorización que muestra xAI.",
+      "authorizationCode": "Código de autorización",
+      "finishSignIn": "Completar inicio de sesión"
     },
     "skills": {
       "description": "Revisa las habilidades de instrucciones que este agente puede cargar durante una conversación.",
diff --git a/webui/src/i18n/locales/fr/common.json b/webui/src/i18n/locales/fr/common.json
index ffb125ee..dd1252f3 100644
--- a/webui/src/i18n/locales/fr/common.json
+++ b/webui/src/i18n/locales/fr/common.json
@@ -705,10 +705,18 @@
       "signOut": "Se déconnecter",
       "signedInAs": "Connecté en tant que {{account}}",
       "signInHelp": "Inicia sesión desde este dispositivo; no se guarda API key en config.",
+      "remoteSignInHelp": "Sélectionnez Se connecter pour ouvrir xAI sur votre ordinateur, puis collez le code d’autorisation affiché après la connexion.",
       "signInRequired": "Connexion requise",
       "signInBeforeSaving": "Inicia sesión antes de guardar este proveedor OAuth como proveedor activo.",
       "signedIn": "Connecté",
-      "notSignedIn": "Non connecté"
+      "notSignedIn": "Non connecté",
+      "proxyLabel": "Proxy réseau",
+      "proxySaveBeforeSignIn": "Enregistrez les modifications du proxy avant de vous connecter.",
+      "saveProxy": "Enregistrer le proxy",
+      "localCodeHelp": "Terminez la connexion dans votre navigateur. nanobot termine généralement automatiquement ; sinon, collez le code d’autorisation ci-dessous.",
+      "remoteCodeHelp": "Sélectionnez Se connecter pour ouvrir xAI sur votre ordinateur. Après la connexion, collez ci-dessous le code d’autorisation affiché par xAI.",
+      "authorizationCode": "Code d’autorisation",
+      "finishSignIn": "Terminer la connexion"
     },
     "skills": {
       "description": "Consultez les compétences d’instruction que cet agent peut charger pendant une conversation.",
diff --git a/webui/src/i18n/locales/id/common.json b/webui/src/i18n/locales/id/common.json
index 8109b897..5c59c889 100644
--- a/webui/src/i18n/locales/id/common.json
+++ b/webui/src/i18n/locales/id/common.json
@@ -705,10 +705,18 @@
       "signOut": "Keluar",
       "signedInAs": "Masuk sebagai {{account}}",
       "signInHelp": "Inicia sesión desde este dispositivo; no se guarda API key en config.",
+      "remoteSignInHelp": "Pilih Masuk untuk membuka xAI di komputer Anda, lalu tempel kode otorisasi yang ditampilkan setelah masuk.",
       "signInRequired": "Perlu masuk",
       "signInBeforeSaving": "Inicia sesión antes de guardar este proveedor OAuth como proveedor activo.",
       "signedIn": "Sudah masuk",
-      "notSignedIn": "Belum masuk"
+      "notSignedIn": "Belum masuk",
+      "proxyLabel": "Proksi jaringan",
+      "proxySaveBeforeSignIn": "Simpan perubahan proksi sebelum login.",
+      "saveProxy": "Simpan proksi",
+      "localCodeHelp": "Selesaikan proses masuk di browser. nanobot biasanya menyelesaikannya secara otomatis; jika tidak, tempel kode otorisasi di bawah.",
+      "remoteCodeHelp": "Pilih Masuk untuk membuka xAI di komputer Anda. Setelah masuk, tempel kode otorisasi yang ditampilkan xAI di bawah.",
+      "authorizationCode": "Kode otorisasi",
+      "finishSignIn": "Selesaikan masuk"
     },
     "skills": {
       "description": "Tinjau skill instruksi yang dapat dimuat agent ini selama percakapan.",
diff --git a/webui/src/i18n/locales/ja/common.json b/webui/src/i18n/locales/ja/common.json
index d8ef34bf..2cac48ee 100644
--- a/webui/src/i18n/locales/ja/common.json
+++ b/webui/src/i18n/locales/ja/common.json
@@ -705,10 +705,18 @@
       "signOut": "サインアウト",
       "signedInAs": "{{account}} としてサインイン済み",
       "signInHelp": "このデバイスからサインインします。API key は config に保存されません。",
+      "remoteSignInHelp": "「サインイン」を選択して自分のコンピューターで xAI を開き、サインイン後に表示される認証コードを貼り付けてください。",
       "signInRequired": "サインインが必要です",
       "signInBeforeSaving": "この OAuth プロバイダーをアクティブなモデルプロバイダーとして保存する前にサインインしてください。",
       "signedIn": "サインイン済み",
-      "notSignedIn": "未サインイン"
+      "notSignedIn": "未サインイン",
+      "proxyLabel": "ネットワークプロキシ",
+      "proxySaveBeforeSignIn": "サインイン前にプロキシの変更を保存してください。",
+      "saveProxy": "プロキシを保存",
+      "localCodeHelp": "ブラウザーでサインインを完了してください。通常は nanobot が自動で完了します。完了しない場合は、認証コードを下に貼り付けてください。",
+      "remoteCodeHelp": "「サインイン」を選択して自分のコンピューターで xAI を開いてください。サインイン後、xAI に表示された認証コードを下に貼り付けてください。",
+      "authorizationCode": "認証コード",
+      "finishSignIn": "サインインを完了"
     },
     "skills": {
       "description": "このエージェントが会話中に読み込める指示スキルを確認します。",
diff --git a/webui/src/i18n/locales/ko/common.json b/webui/src/i18n/locales/ko/common.json
index 44b5c41b..e3a66af5 100644
--- a/webui/src/i18n/locales/ko/common.json
+++ b/webui/src/i18n/locales/ko/common.json
@@ -705,10 +705,18 @@
       "signOut": "로그아웃",
       "signedInAs": "{{account}}로 로그인됨",
       "signInHelp": "이 기기에서 로그인합니다. API key는 config에 저장되지 않습니다.",
+      "remoteSignInHelp": "로그인을 선택하여 사용자 컴퓨터에서 xAI를 연 다음, 로그인 후 표시되는 인증 코드를 붙여 넣으세요.",
       "signInRequired": "로그인이 필요합니다",
       "signInBeforeSaving": "이 OAuth 제공자를 활성 모델 제공자로 저장하기 전에 로그인하세요.",
       "signedIn": "로그인됨",
-      "notSignedIn": "로그인 안 됨"
+      "notSignedIn": "로그인 안 됨",
+      "proxyLabel": "네트워크 프록시",
+      "proxySaveBeforeSignIn": "로그인하기 전에 프록시 변경 사항을 저장하세요.",
+      "saveProxy": "프록시 저장",
+      "localCodeHelp": "브라우저에서 로그인을 완료하세요. 일반적으로 nanobot이 자동으로 완료합니다. 완료되지 않으면 인증 코드를 아래에 붙여 넣으세요.",
+      "remoteCodeHelp": "로그인을 선택하여 사용자 컴퓨터에서 xAI를 여세요. 로그인 후 xAI에 표시된 인증 코드를 아래에 붙여 넣으세요.",
+      "authorizationCode": "인증 코드",
+      "finishSignIn": "로그인 완료"
     },
     "skills": {
       "description": "이 에이전트가 대화 중에 불러올 수 있는 지시 스킬을 확인합니다.",
diff --git a/webui/src/i18n/locales/pt-BR/common.json b/webui/src/i18n/locales/pt-BR/common.json
index fa8ccbf6..549ff2cd 100644
--- a/webui/src/i18n/locales/pt-BR/common.json
+++ b/webui/src/i18n/locales/pt-BR/common.json
@@ -719,10 +719,18 @@
       "signOut": "Sair",
       "signedInAs": "Conectado como {{account}}",
       "signInHelp": "Entre por este dispositivo; nenhuma chave de API é armazenada em config.",
+      "remoteSignInHelp": "Selecione Entrar para abrir a xAI no seu computador e depois cole o código de autorização exibido após o login.",
       "signInRequired": "Login necessário",
       "signInBeforeSaving": "Entre antes de salvar este provedor OAuth como provedor de modelo ativo.",
       "signedIn": "Conectado",
-      "notSignedIn": "Desconectado"
+      "notSignedIn": "Desconectado",
+      "proxyLabel": "Proxy de rede",
+      "proxySaveBeforeSignIn": "Salve as alterações do proxy antes de entrar.",
+      "saveProxy": "Salvar proxy",
+      "localCodeHelp": "Conclua o login no navegador. O nanobot geralmente termina automaticamente; caso contrário, cole o código de autorização abaixo.",
+      "remoteCodeHelp": "Selecione Entrar para abrir a xAI no seu computador. Após o login, cole abaixo o código de autorização exibido pela xAI.",
+      "authorizationCode": "Código de autorização",
+      "finishSignIn": "Concluir login"
     },
     "skills": {
       "description": "Revise as skills de instrução que este agente pode carregar durante uma conversa.",
diff --git a/webui/src/i18n/locales/vi/common.json b/webui/src/i18n/locales/vi/common.json
index 0717952c..011ab288 100644
--- a/webui/src/i18n/locales/vi/common.json
+++ b/webui/src/i18n/locales/vi/common.json
@@ -705,10 +705,18 @@
       "signOut": "Đăng xuất",
       "signedInAs": "Đã đăng nhập bằng {{account}}",
       "signInHelp": "Inicia sesión desde este dispositivo; no se guarda API key en config.",
+      "remoteSignInHelp": "Chọn Đăng nhập để mở xAI trên máy tính của bạn, sau đó dán mã ủy quyền được hiển thị sau khi đăng nhập.",
       "signInRequired": "Cần đăng nhập",
       "signInBeforeSaving": "Inicia sesión antes de guardar este proveedor OAuth como proveedor activo.",
       "signedIn": "Đã đăng nhập",
-      "notSignedIn": "Chưa đăng nhập"
+      "notSignedIn": "Chưa đăng nhập",
+      "proxyLabel": "Proxy mạng",
+      "proxySaveBeforeSignIn": "Hãy lưu thay đổi proxy trước khi đăng nhập.",
+      "saveProxy": "Lưu proxy",
+      "localCodeHelp": "Hoàn tất đăng nhập trong trình duyệt. nanobot thường tự động hoàn tất; nếu không, hãy dán mã ủy quyền bên dưới.",
+      "remoteCodeHelp": "Chọn Đăng nhập để mở xAI trên máy tính của bạn. Sau khi đăng nhập, hãy dán mã ủy quyền do xAI hiển thị bên dưới.",
+      "authorizationCode": "Mã ủy quyền",
+      "finishSignIn": "Hoàn tất đăng nhập"
     },
     "skills": {
       "description": "Xem các kỹ năng chỉ dẫn mà agent này có thể tải trong cuộc trò chuyện.",
diff --git a/webui/src/i18n/locales/zh-CN/common.json b/webui/src/i18n/locales/zh-CN/common.json
index 8e85854d..5e787845 100644
--- a/webui/src/i18n/locales/zh-CN/common.json
+++ b/webui/src/i18n/locales/zh-CN/common.json
@@ -719,10 +719,18 @@
       "signOut": "退出登录",
       "signedInAs": "已登录为 {{account}}",
       "signInHelp": "从这台设备登录；不会在配置中保存 API key。",
+      "remoteSignInHelp": "点击“登录”在你的电脑上打开 xAI，完成登录后粘贴页面显示的授权码。",
       "signInRequired": "需要登录",
       "signInBeforeSaving": "将此 OAuth 提供商设为当前模型提供商前，请先登录。",
       "signedIn": "已登录",
-      "notSignedIn": "未登录"
+      "notSignedIn": "未登录",
+      "proxyLabel": "网络代理",
+      "proxySaveBeforeSignIn": "请先保存代理更改再登录。",
+      "saveProxy": "保存代理",
+      "localCodeHelp": "请在浏览器中完成登录。nanobot 通常会自动完成；若未自动完成，请将授权码粘贴到下方。",
+      "remoteCodeHelp": "点击“登录”在你的电脑上打开 xAI。完成登录后，请将 xAI 显示的授权码粘贴到下方。",
+      "authorizationCode": "授权码",
+      "finishSignIn": "完成登录"
     },
     "skills": {
       "description": "查看此 agent 在对话中可以加载的指令技能。",
diff --git a/webui/src/i18n/locales/zh-TW/common.json b/webui/src/i18n/locales/zh-TW/common.json
index e7c07a64..aac4c6b0 100644
--- a/webui/src/i18n/locales/zh-TW/common.json
+++ b/webui/src/i18n/locales/zh-TW/common.json
@@ -705,10 +705,18 @@
       "signOut": "登出",
       "signedInAs": "已使用 {{account}} 登入",
       "signInHelp": "請從這臺裝置登入；系統不會將 API 金鑰儲存在設定中。",
+      "remoteSignInHelp": "點擊「登入」在你的電腦上開啟 xAI，完成登入後貼上頁面顯示的授權碼。",
       "signInRequired": "需要登入",
       "signInBeforeSaving": "將此 OAuth 供應商設為目前模型供應商前，請先登入。",
       "signedIn": "已登入",
-      "notSignedIn": "未登入"
+      "notSignedIn": "未登入",
+      "proxyLabel": "網路代理",
+      "proxySaveBeforeSignIn": "請先儲存代理變更再登入。",
+      "saveProxy": "儲存代理",
+      "localCodeHelp": "請在瀏覽器中完成登入。nanobot 通常會自動完成；若未自動完成，請將授權碼貼到下方。",
+      "remoteCodeHelp": "點擊「登入」在你的電腦上開啟 xAI。完成登入後，請將 xAI 顯示的授權碼貼到下方。",
+      "authorizationCode": "授權碼",
+      "finishSignIn": "完成登入"
     },
     "skills": {
       "description": "檢閱此 Agent 可在對話期間載入的指令技能。",
diff --git a/webui/src/lib/api.ts b/webui/src/lib/api.ts
index 378bec84..0c022be5 100644
--- a/webui/src/lib/api.ts
+++ b/webui/src/lib/api.ts
@@ -16,6 +16,8 @@ import type {
   NetworkSafetySettingsUpdate,
   PairingPayload,
   ProviderModelsPayload,
+  ProviderOAuthCompletionResult,
+  ProviderOAuthLoginResult,
   ProviderSettingsUpdate,
   SessionDeleteResult,
   SessionAutomationsPayload,
@@ -51,6 +53,7 @@ function isSlashCommandLifecycle(value: unknown): value is SlashCommandLifecycle
 }
 const CHANNEL_VALUES_HEADER = "X-Nanobot-Channel-Values";
 const API_SERVICE_VALUES_HEADER = "X-Nanobot-API-Service-Values";
+const OAUTH_CODE_HEADER = "X-Nanobot-OAuth-Code";
 
 export class ApiError extends Error {
   status: number;
@@ -809,6 +812,7 @@ export async function updateProviderSettings(
   if (update.apiKey !== undefined) query.set("api_key", update.apiKey);
   if (update.apiBase !== undefined) query.set("api_base", update.apiBase);
   if (update.apiType !== undefined) query.set("api_type", update.apiType);
+  if (update.proxy !== undefined) query.set("proxy", update.proxy);
   return request<SettingsPayload>(
     `${base}/api/settings/provider/update?${query}`,
     token,
@@ -819,12 +823,31 @@ export async function loginProviderOAuth(
   token: string,
   provider: string,
   base: string = "",
-): Promise<SettingsPayload> {
+): Promise<ProviderOAuthLoginResult> {
   const query = new URLSearchParams();
   query.set("provider", provider);
-  return request<SettingsPayload>(
+  return request<ProviderOAuthLoginResult>(
     `${base}/api/settings/provider/oauth-login?${query}`,
     token,
+    { cache: "no-store" },
+  );
+}
+
+export async function completeProviderOAuth(
+  token: string,
+  provider: string,
+  flowId: string,
+  authorizationCode?: string,
+  base: string = "",
+): Promise<ProviderOAuthCompletionResult> {
+  const query = new URLSearchParams();
+  query.set("provider", provider);
+  query.set("flow_id", flowId);
+  const headers = authorizationCode ? { [OAUTH_CODE_HEADER]: authorizationCode } : undefined;
+  return request<ProviderOAuthCompletionResult>(
+    `${base}/api/settings/provider/oauth-login/complete?${query}`,
+    token,
+    { cache: "no-store", ...(headers ? { headers } : {}) },
   );
 }
 
diff --git a/webui/src/lib/provider-brand.ts b/webui/src/lib/provider-brand.ts
index a7404e50..0019bcae 100644
--- a/webui/src/lib/provider-brand.ts
+++ b/webui/src/lib/provider-brand.ts
@@ -131,6 +131,8 @@ export const PROVIDER_BRAND_ALIASES: Record<string, string> = {
   minimaxAnthropic: "minimax",
   minimax_anthropic: "minimax",
   openai_codex: "openai",
+  "xai-grok": "xai",
+  xai_grok: "xai",
   xiaomi: "xiaomi_mimo",
   volcengine_coding_plan: "volcengine",
 };
@@ -141,6 +143,8 @@ export const PROVIDER_LABEL_ALIASES: Record<string, string> = {
   minimaxAnthropic: "MiniMax",
   minimax_anthropic: "MiniMax",
   openai_codex: "OpenAI",
+  "xai-grok": "xAI",
+  xai_grok: "xAI",
   volcengine_coding_plan: "Volcengine",
 };
 
@@ -194,6 +198,7 @@ const PROVIDER_BRANDS: Record<string, ProviderBrand> = {
   xiaomi_mimo: brand("mimo.xiaomi.com", "#FF6900", "MI", [
     "https://mimo.xiaomi.com/mimo-v2-pro/assets/logo.svg",
   ]),
+  xai: brand("x.ai", "#111827", "xAI"),
   zhipu: brand("z.ai", "#155EEF", "Z", [
     "https://z-cdn.chatglm.cn/z-ai/static/logo.svg",
     "https://www.google.com/s2/favicons?domain=z.ai&sz=64",
diff --git a/webui/src/lib/types.ts b/webui/src/lib/types.ts
index 1d2f0e3f..10430e99 100644
--- a/webui/src/lib/types.ts
+++ b/webui/src/lib/types.ts
@@ -377,6 +377,23 @@ export interface ProviderModelsPayload {
   fetched_at?: number;
 }
 
+export interface ProviderOAuthAuthorizationRequired {
+  status: "authorization_required";
+  provider: string;
+  flow_id: string;
+  authorization_url: string;
+  expires_in: number;
+}
+
+export interface ProviderOAuthPending {
+  status: "pending";
+  provider: string;
+  flow_id: string;
+}
+
+export type ProviderOAuthLoginResult = SettingsPayload | ProviderOAuthAuthorizationRequired;
+export type ProviderOAuthCompletionResult = SettingsPayload | ProviderOAuthPending;
+
 export interface SettingsPayload {
   surface?: RuntimeSurface;
   runtime_surface?: RuntimeSurface;
@@ -430,6 +447,7 @@ export interface SettingsPayload {
     oauth_account?: string | null;
     oauth_expires_at?: number | null;
     oauth_login_supported?: boolean;
+    proxy?: string | null;
   }>;
   web_search: {
     provider: string;
@@ -936,6 +954,7 @@ export interface ProviderSettingsUpdate {
   apiKey?: string;
   apiBase?: string;
   apiType?: "auto" | "chat_completions" | "responses";
+  proxy?: string;
 }
 
 export interface WebSearchSettingsUpdate {
diff --git a/webui/src/tests/api.test.ts b/webui/src/tests/api.test.ts
index 0bae3fd2..7979f1af 100644
--- a/webui/src/tests/api.test.ts
+++ b/webui/src/tests/api.test.ts
@@ -2,6 +2,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import {
   configureChannel,
+  completeProviderOAuth,
   createModelConfiguration,
   deleteSession,
   fetchFilePreview,
@@ -431,6 +432,20 @@ describe("webui API helpers", () => {
     );
   });
 
+  it("serializes OAuth provider proxy updates", async () => {
+    await updateProviderSettings("tok", {
+      provider: "xai_grok",
+      proxy: "http://127.0.0.1:7890",
+    });
+
+    expect(fetch).toHaveBeenCalledWith(
+      "/api/settings/provider/update?provider=xai_grok&proxy=http%3A%2F%2F127.0.0.1%3A7890",
+      expect.objectContaining({
+        headers: { Authorization: "Bearer tok" },
+      }),
+    );
+  });
+
   it("fetches provider model lists", async () => {
     await fetchProviderModels("tok", "deepseek");
 
@@ -451,6 +466,30 @@ describe("webui API helpers", () => {
       }),
     );
 
+    await completeProviderOAuth("tok", "xai_grok", "flow-123");
+    expect(fetch).toHaveBeenCalledWith(
+      "/api/settings/provider/oauth-login/complete?provider=xai_grok&flow_id=flow-123",
+      expect.objectContaining({
+        headers: { Authorization: "Bearer tok" },
+      }),
+    );
+
+    await completeProviderOAuth(
+      "tok",
+      "xai_grok",
+      "flow-123",
+      "secret",
+    );
+    expect(fetch).toHaveBeenCalledWith(
+      "/api/settings/provider/oauth-login/complete?provider=xai_grok&flow_id=flow-123",
+      expect.objectContaining({
+        headers: {
+          Authorization: "Bearer tok",
+          "X-Nanobot-OAuth-Code": "secret",
+        },
+      }),
+    );
+
     await logoutProviderOAuth("tok", "openai_codex");
     expect(fetch).toHaveBeenCalledWith(
       "/api/settings/provider/oauth-logout?provider=openai_codex",
diff --git a/webui/src/tests/provider-brand.test.ts b/webui/src/tests/provider-brand.test.ts
index 86c63332..b48c5520 100644
--- a/webui/src/tests/provider-brand.test.ts
+++ b/webui/src/tests/provider-brand.test.ts
@@ -74,6 +74,11 @@ describe("provider brand logos", () => {
     expect(providerBrand("openrouter")?.initials).toBe("OR");
   });
 
+  it("maps both xAI Grok spellings to the xAI brand", () => {
+    expect(providerBrand("xai_grok")?.logoUrls).toContain("https://x.ai/favicon.ico");
+    expect(providerBrand("xai-grok")?.initials).toBe("xAI");
+  });
+
   it("keeps AssemblyAI voice settings on the first-party brand domain", () => {
     expect(providerBrand("assemblyai")?.logoUrls).toContain("https://assemblyai.com/favicon.ico");
     expect(providerBrand("assemblyai")?.initials).toBe("AA");
diff --git a/webui/src/tests/settings-view.test.tsx b/webui/src/tests/settings-view.test.tsx
index ae5d5278..043c386d 100644
--- a/webui/src/tests/settings-view.test.tsx
+++ b/webui/src/tests/settings-view.test.tsx
@@ -1973,9 +1973,310 @@ describe("SettingsView Apps catalog", () => {
     expect(screen.getByRole("button", { name: "64K" })).toBeInTheDocument();
     expect(screen.getByRole("button", { name: "200K" })).toBeInTheDocument();
     expect(screen.getByRole("button", { name: "256K" })).toBeInTheDocument();
+    expect(screen.getByRole("button", { name: "500K" })).toBeInTheDocument();
     expect(screen.getByRole("button", { name: "1M" })).toBeInTheDocument();
   });
 
+  it("signs in to the xAI Grok provider", async () => {
+    const base = settingsPayload();
+    const xaiProvider = {
+      name: "xai_grok",
+      label: "xAI Grok",
+      configured: false,
+      auth_type: "oauth" as const,
+      api_key_required: false,
+      api_key_hint: null,
+      api_base: null,
+      default_api_base: "https://cli-chat-proxy.grok.com/v1",
+      model_catalog: "builtin",
+      oauth_account: null,
+      oauth_expires_at: null,
+      oauth_login_supported: true,
+    };
+    const payload: SettingsPayload = { ...base, providers: [xaiProvider] };
+    const signedIn: SettingsPayload = {
+      ...payload,
+      providers: [{ ...xaiProvider, configured: true, oauth_account: "user@example.com" }],
+    };
+    const authorization = {
+      status: "authorization_required",
+      provider: "xai_grok",
+      flow_id: "flow-123",
+      authorization_url: "https://auth.x.ai/oauth2/authorize?state=test",
+      expires_in: 600,
+    };
+    const fetchMock = vi.fn(async (input: RequestInfo | URL, init?: RequestInit) => {
+      const url = String(input);
+      if (url === "/api/settings") return jsonResponse(payload);
+      if (url === "/api/settings/provider/oauth-login?provider=xai_grok") {
+        return jsonResponse(authorization);
+      }
+      if (
+        url ===
+        "/api/settings/provider/oauth-login/complete?provider=xai_grok&flow_id=flow-123"
+      ) {
+        expect(init?.headers).toMatchObject({
+          "X-Nanobot-OAuth-Code": "secret",
+        });
+        return jsonResponse(signedIn);
+      }
+      if (url === "/api/settings/cli-apps") {
+        return jsonResponse({ apps: [], installed_count: 0 });
+      }
+      if (url === "/api/settings/mcp-presets") {
+        return jsonResponse({ presets: [], installed_count: 0 });
+      }
+      return jsonResponse({});
+    });
+    vi.stubGlobal("fetch", fetchMock);
+    const popup = {
+      opener: window,
+      location: { href: "about:blank" },
+      close: vi.fn(),
+    };
+    vi.stubGlobal("open", vi.fn(() => popup));
+
+    renderSettingsView({ initialSection: "models", initialSettings: payload });
+
+    const providerLabel = await screen.findByText("xAI Grok");
+    fireEvent.click(providerLabel.closest("button")!);
+
+    fireEvent.click(screen.getByRole("button", { name: "Sign in" }));
+
+    await waitFor(() =>
+      expect(fetchMock).toHaveBeenCalledWith(
+        "/api/settings/provider/oauth-login?provider=xai_grok",
+        expect.objectContaining({ headers: { Authorization: "Bearer tok" } }),
+      ),
+    );
+    expect(popup.opener).toBeNull();
+    expect(popup.location.href).toBe(authorization.authorization_url);
+
+    expect(
+      screen.getByText(
+        "Complete sign-in in your browser. Nanobot usually finishes automatically; if it does not, paste the authorization code below.",
+      ),
+    ).toBeInTheDocument();
+    const callbackInput = await screen.findByRole("textbox", {
+      name: "Authorization code",
+    });
+    fireEvent.change(callbackInput, {
+      target: { value: "secret" },
+    });
+    fireEvent.click(screen.getByRole("button", { name: "Finish sign-in" }));
+
+    await waitFor(() =>
+      expect(fetchMock).toHaveBeenCalledWith(
+        "/api/settings/provider/oauth-login/complete?provider=xai_grok&flow_id=flow-123",
+        expect.objectContaining({
+          headers: expect.objectContaining({
+            "X-Nanobot-OAuth-Code": "secret",
+          }),
+        }),
+      ),
+    );
+    expect(await screen.findByText("Signed in as user@example.com")).toBeInTheDocument();
+  });
+
+  it("recognizes remote access before starting xAI Grok sign-in", async () => {
+    const happyWindow = window as typeof window & {
+      happyDOM: { setURL: (url: string) => void };
+    };
+    const originalUrl = window.location.href;
+    happyWindow.happyDOM.setURL("http://203.0.113.10:18887/#/settings?section=models");
+
+    try {
+      const base = settingsPayload();
+      const xaiProvider = {
+        name: "xai_grok",
+        label: "xAI Grok",
+        configured: false,
+        auth_type: "oauth" as const,
+        api_key_required: false,
+        api_key_hint: null,
+        api_base: null,
+        default_api_base: "https://cli-chat-proxy.grok.com/v1",
+        model_catalog: "builtin",
+        oauth_account: null,
+        oauth_expires_at: null,
+        oauth_login_supported: true,
+      };
+      const payload: SettingsPayload = { ...base, providers: [xaiProvider] };
+      const authorization = {
+        status: "authorization_required",
+        provider: "xai_grok",
+        flow_id: "flow-remote",
+        authorization_url: "https://auth.x.ai/oauth2/authorize?state=remote",
+        expires_in: 600,
+      };
+      const fetchMock = vi.fn(async (input: RequestInfo | URL) => {
+        const url = String(input);
+        if (url === "/api/settings") return jsonResponse(payload);
+        if (url === "/api/settings/provider/oauth-login?provider=xai_grok") {
+          return jsonResponse(authorization);
+        }
+        if (
+          url ===
+          "/api/settings/provider/oauth-login/complete?provider=xai_grok&flow_id=flow-remote"
+        ) {
+          return jsonResponse({
+            status: "pending",
+            provider: "xai_grok",
+            flow_id: "flow-remote",
+          });
+        }
+        if (url === "/api/settings/cli-apps") {
+          return jsonResponse({ apps: [], installed_count: 0 });
+        }
+        if (url === "/api/settings/mcp-presets") {
+          return jsonResponse({ presets: [], installed_count: 0 });
+        }
+        return jsonResponse({});
+      });
+      vi.stubGlobal("fetch", fetchMock);
+      const popup = {
+        opener: window,
+        location: { href: "about:blank" },
+        close: vi.fn(),
+      };
+      const openMock = vi.fn(() => popup);
+      vi.stubGlobal("open", openMock);
+
+      renderSettingsView({ initialSection: "models", initialSettings: payload });
+
+      fireEvent.click((await screen.findByText("xAI Grok")).closest("button")!);
+      expect(
+        screen.getByText(
+          "Select Sign in to open xAI on your computer, then paste the authorization code shown after login.",
+        ),
+      ).toBeInTheDocument();
+
+      fireEvent.click(screen.getByRole("button", { name: "Sign in" }));
+      const dialog = await screen.findByRole("dialog");
+
+      expect(openMock).not.toHaveBeenCalled();
+      expect(
+        within(dialog).getByText(
+          "Select Sign in to open xAI on your computer. After signing in, paste the authorization code shown by xAI below.",
+        ),
+      ).toBeInTheDocument();
+      expect(
+        within(dialog).queryByRole("textbox", { name: "xAI sign-in URL" }),
+      ).not.toBeInTheDocument();
+      expect(
+        within(dialog).queryByRole("button", { name: "Copy" }),
+      ).not.toBeInTheDocument();
+      expect(
+        within(dialog).getByRole("textbox", { name: "Authorization code" }),
+      ).toBeInTheDocument();
+
+      fireEvent.click(within(dialog).getByRole("button", { name: "Sign in" }));
+      expect(openMock).toHaveBeenCalledWith(
+        authorization.authorization_url,
+        "_blank",
+        "noopener,noreferrer",
+      );
+      expect(popup.opener).toBeNull();
+    } finally {
+      happyWindow.happyDOM.setURL(originalUrl);
+    }
+  });
+
+  it("saves scoped proxies for xAI and OpenAI Codex OAuth providers", async () => {
+    const base = settingsPayload();
+    const providers: SettingsPayload["providers"] = [
+      {
+        name: "xai_grok",
+        label: "xAI Grok",
+        configured: false,
+        auth_type: "oauth",
+        api_key_required: false,
+        api_key_hint: null,
+        api_base: null,
+        default_api_base: "https://cli-chat-proxy.grok.com/v1",
+        model_catalog: "builtin",
+        oauth_account: null,
+        oauth_expires_at: null,
+        oauth_login_supported: true,
+        proxy: "http://127.0.0.1:7000",
+      },
+      {
+        name: "openai_codex",
+        label: "OpenAI Codex",
+        configured: false,
+        auth_type: "oauth",
+        api_key_required: false,
+        api_key_hint: null,
+        api_base: null,
+        default_api_base: "https://chatgpt.com/backend-api",
+        model_catalog: "builtin",
+        oauth_account: null,
+        oauth_expires_at: null,
+        oauth_login_supported: true,
+        proxy: null,
+      },
+    ];
+    let payload: SettingsPayload = { ...base, providers };
+    const fetchMock = vi.fn(async (input: RequestInfo | URL) => {
+      const url = String(input);
+      if (url === "/api/settings") return jsonResponse(payload);
+      if (url.startsWith("/api/settings/provider/update?")) {
+        const query = new URLSearchParams(url.split("?")[1]);
+        const providerName = query.get("provider");
+        const proxy = query.get("proxy");
+        payload = {
+          ...payload,
+          providers: payload.providers.map((provider) =>
+            provider.name === providerName ? { ...provider, proxy } : provider,
+          ),
+        };
+        return jsonResponse(payload);
+      }
+      if (url === "/api/settings/cli-apps") {
+        return jsonResponse({ apps: [], installed_count: 0 });
+      }
+      if (url === "/api/settings/mcp-presets") {
+        return jsonResponse({ presets: [], installed_count: 0 });
+      }
+      return jsonResponse({});
+    });
+    vi.stubGlobal("fetch", fetchMock);
+
+    renderSettingsView({ initialSection: "models", initialSettings: payload });
+
+    fireEvent.click((await screen.findByText("xAI Grok")).closest("button")!);
+    const xaiProxy = screen.getByLabelText("Network proxy");
+    expect(xaiProxy).toHaveValue("http://127.0.0.1:7000");
+    fireEvent.change(xaiProxy, { target: { value: "http://127.0.0.1:7890" } });
+    expect(screen.getByRole("button", { name: "Sign in" })).toBeDisabled();
+    expect(screen.getByRole("button", { name: "Sign in" })).toHaveAttribute(
+      "title",
+      "Save proxy changes before signing in.",
+    );
+    fireEvent.click(screen.getByRole("button", { name: "Save proxy" }));
+
+    await waitFor(() =>
+      expect(fetchMock).toHaveBeenCalledWith(
+        "/api/settings/provider/update?provider=xai_grok&proxy=http%3A%2F%2F127.0.0.1%3A7890",
+        expect.objectContaining({ headers: { Authorization: "Bearer tok" } }),
+      ),
+    );
+    await waitFor(() => expect(screen.getByRole("button", { name: "Sign in" })).toBeEnabled());
+
+    fireEvent.click(screen.getByText("OpenAI Codex").closest("button")!);
+    const codexProxy = screen.getByLabelText("Network proxy");
+    expect(codexProxy).toHaveValue("");
+    fireEvent.change(codexProxy, { target: { value: "http://proxy.example:8080" } });
+    fireEvent.click(screen.getByRole("button", { name: "Save proxy" }));
+
+    await waitFor(() =>
+      expect(fetchMock).toHaveBeenCalledWith(
+        "/api/settings/provider/update?provider=openai_codex&proxy=http%3A%2F%2Fproxy.example%3A8080",
+        expect.objectContaining({ headers: { Authorization: "Bearer tok" } }),
+      ),
+    );
+  });
+
   it("keeps the default model distinct from the active named configuration", async () => {
     const base = settingsPayload();
     const payload: SettingsPayload = {