diff --git a/docs/cli-reference.md b/docs/cli-reference.md
index 3056e920..b9a4899e 100644
--- a/docs/cli-reference.md
+++ b/docs/cli-reference.md
@@ -286,8 +286,8 @@ remain accepted as no-op compatibility aliases.
 
 | Command | Description |
 |---|---|
-| `nanobot provider login openai-codex` | Authenticate OpenAI Codex provider |
-| `nanobot provider login github-copilot` | Authenticate GitHub Copilot provider |
+| `nanobot provider login openai-codex --set-main` | Authenticate Codex and select its current default model |
+| `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 github-copilot` | Remove GitHub Copilot OAuth state |
 
diff --git a/docs/configuration.md b/docs/configuration.md
index cae55e6a..b347e8e2 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -298,7 +298,7 @@ Tracing covers the providers that go through nanobot's OpenAI-compatible client
 | `ovms` | LLM (local, OpenVINO Model Server) | [docs.openvino.ai](https://docs.openvino.ai/2026/model-server/ovms_docs_llm_quickstart.html) |
 | `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` |
+| `openai_codex` | LLM (Codex, OAuth) | `nanobot provider login openai-codex --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) |
 
@@ -660,61 +660,19 @@ nanobot agent -m "Reply with one short sentence."
 <details>
 <summary><b>OpenAI Codex (OAuth)</b></summary>
 
-Codex uses OAuth instead of API keys. Requires a ChatGPT Plus or Pro account. `nanobot provider login` stores the OAuth session outside config. A `providers.openai_codex` block is optional and is only needed for provider-specific settings such as a proxy.
+Codex uses OAuth instead of API keys and requires a ChatGPT Plus or Pro account. Authenticate it and make the current flagship model the active agent model with one command:
 
-**1. Login:**
 ```bash
-nanobot provider login openai-codex
+nanobot provider login openai-codex --set-main
 ```
 
-If the machine running nanobot cannot open a graphical browser, copy the printed URL into a real browser. For remote SSH login, open the URL locally, then paste the final `http://localhost:1455/auth/callback?...` redirect URL back into the terminal when prompted.
+Then run:
 
-**2. Optional proxy** (merge into `~/.nanobot/config.json` if Codex OAuth or Codex API traffic must use a proxy):
-
-```json
-{
-  "providers": {
-    "openai_codex": {
-      "proxy": "http://127.0.0.1:7890"
-    }
-  }
-}
-```
-
-The proxy applies to Codex OAuth token refresh, interactive token exchange, and Codex Responses API requests. It does not affect other providers; configure `proxy` separately on each supported provider that needs it.
-
-**3. Set model** (merge into `~/.nanobot/config.json`):
-```json
-{
-  "modelPresets": {
-    "codex": {
-      "provider": "openai_codex",
-      "model": "gpt-5.1-codex",
-      "reasoningEffort": "high"
-    }
-  },
-  "agents": {
-    "defaults": {
-      "modelPreset": "codex"
-    }
-  }
-}
-```
-
-Use `reasoningEffort` in the preset to send a Codex reasoning effort such as `"low"`, `"medium"`, `"high"`, or another value supported by the selected model. When `provider` is explicitly `openai_codex`, the model name does not need the `openai-codex/` prefix.
-
-**4. Chat:**
 ```bash
 nanobot agent -m "Hello!"
-
-# Target a specific workspace/config locally
-nanobot agent -c ~/.nanobot-telegram/config.json -m "Hello!"
-
-# One-off workspace override on top of that config
-nanobot agent -c ~/.nanobot-telegram/config.json -w /tmp/nanobot-telegram-test -m "Hello!"
 ```
 
-> Docker users: use `docker run -it` for interactive OAuth login.
+For proxy, remote/headless login, model-name, or config-key errors, see [`troubleshooting.md`](./troubleshooting.md#provider-and-model-problems).
 
 </details>
 
diff --git a/docs/providers.md b/docs/providers.md
index 028d92b2..141b7e5c 100644
--- a/docs/providers.md
+++ b/docs/providers.md
@@ -418,38 +418,19 @@ See [`configuration.md#providers`](./configuration.md#providers) for Bedrock-spe
 
 Some providers do not use API keys in `config.json`.
 
+For OpenAI Codex:
+
 ```bash
-nanobot provider login openai-codex
-nanobot provider login github-copilot
+nanobot provider login openai-codex --set-main
 ```
 
-Then explicitly select the provider and model in a preset. OAuth providers are not valid automatic fallbacks.
+For GitHub Copilot:
 
-For OpenAI Codex, add `providers.openai_codex.proxy` only when Codex OAuth/token refresh or Codex API requests must use a proxy:
-
-```json
-{
-  "providers": {
-    "openai_codex": {
-      "proxy": "http://127.0.0.1:7890"
-    }
-  },
-  "modelPresets": {
-    "codex": {
-      "provider": "openai_codex",
-      "model": "gpt-5.1-codex",
-      "reasoningEffort": "high"
-    }
-  },
-  "agents": {
-    "defaults": {
-      "modelPreset": "codex"
-    }
-  }
-}
+```bash
+nanobot provider login github-copilot --set-main
 ```
 
-If you run the login command on a remote/headless machine and open the authorization URL in a local browser, paste the final `http://localhost:1455/auth/callback?...` redirect URL back into the terminal when prompted. See [`configuration.md#providers`](./configuration.md#providers) for the full OAuth provider notes.
+Each command authenticates the selected provider and makes its current default model active. OAuth providers are not valid automatic fallbacks. See [`troubleshooting.md`](./troubleshooting.md#provider-and-model-problems) for proxy, headless-login, model-name, and config-key errors.
 
 ## Provider Resolution
 
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index 70b940e8..ba89dadc 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -135,7 +135,12 @@ 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` or `nanobot provider login github-copilot`, then select the provider explicitly. |
+| OAuth provider fails | Run `nanobot provider login openai-codex --set-main` or `nanobot provider login github-copilot --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`. |
 
 ## Langfuse Problems
 
diff --git a/nanobot/cli/commands.py b/nanobot/cli/commands.py
index 9c3609df..5900d7e4 100644
--- a/nanobot/cli/commands.py
+++ b/nanobot/cli/commands.py
@@ -2646,7 +2646,7 @@ _PROVIDER_DISPLAY: dict[str, str] = {
 }
 
 _OAUTH_PROVIDER_DEFAULT_MODELS: dict[str, str] = {
-    "openai_codex": "openai-codex/gpt-5.4-mini",
+    "openai_codex": "openai-codex/gpt-5.6-sol",
     "github_copilot": "github-copilot/gpt-5.4-mini",
 }
 
diff --git a/nanobot/providers/openai_codex_provider.py b/nanobot/providers/openai_codex_provider.py
index b544bad4..a89e3cac 100644
--- a/nanobot/providers/openai_codex_provider.py
+++ b/nanobot/providers/openai_codex_provider.py
@@ -35,7 +35,7 @@ class OpenAICodexProvider(LLMProvider):
 
     def __init__(
         self,
-        default_model: str = "openai-codex/gpt-5.1-codex",
+        default_model: str = "openai-codex/gpt-5.6-sol",
         proxy: str | None = None,
     ):
         super().__init__(api_key=None, api_base=None)
diff --git a/tests/cli/test_commands.py b/tests/cli/test_commands.py
index dce93986..0ec0b582 100644
--- a/tests/cli/test_commands.py
+++ b/tests/cli/test_commands.py
@@ -450,11 +450,21 @@ def test_config_matches_github_copilot_codex_with_hyphen_prefix():
 
 def test_config_matches_openai_codex_with_hyphen_prefix():
     config = Config()
-    config.agents.defaults.model = "openai-codex/gpt-5.1-codex"
+    config.agents.defaults.model = "openai-codex/gpt-5.6-sol"
 
     assert config.get_provider_name() == "openai_codex"
 
 
+def test_openai_codex_oauth_default_matches_curated_flagship():
+    spec = find_by_name("openai_codex")
+
+    assert spec is not None
+    assert spec.builtin_models
+    assert cli_commands._OAUTH_PROVIDER_DEFAULT_MODELS["openai_codex"] == (
+        spec.builtin_models[0].id
+    )
+
+
 def test_config_dump_excludes_oauth_provider_blocks():
     config = Config()
 
@@ -605,7 +615,7 @@ def test_provider_login_can_set_openai_codex_as_main_provider(tmp_path):
 
     saved = Config.model_validate(json.loads(config_path.read_text(encoding="utf-8")))
     assert saved.agents.defaults.provider == "openai_codex"
-    assert saved.agents.defaults.model == "openai-codex/gpt-5.4-mini"
+    assert saved.agents.defaults.model == "openai-codex/gpt-5.6-sol"
     assert saved.agents.defaults.model_preset is None
     assert make_provider(saved).__class__.__name__ == "OpenAICodexProvider"
 
@@ -1071,8 +1081,8 @@ async def test_github_copilot_provider_refreshes_client_api_key_before_chat():
 
 
 def test_openai_codex_strip_prefix_supports_hyphen_and_underscore():
-    assert _strip_model_prefix("openai-codex/gpt-5.1-codex") == "gpt-5.1-codex"
-    assert _strip_model_prefix("openai_codex/gpt-5.1-codex") == "gpt-5.1-codex"
+    assert _strip_model_prefix("openai-codex/gpt-5.6-sol") == "gpt-5.6-sol"
+    assert _strip_model_prefix("openai_codex/gpt-5.6-sol") == "gpt-5.6-sol"
 
 
 def test_make_provider_passes_extra_headers_to_custom_provider():
diff --git a/tests/providers/test_openai_codex_provider.py b/tests/providers/test_openai_codex_provider.py
index 8cba9df0..560b25e7 100644
--- a/tests/providers/test_openai_codex_provider.py
+++ b/tests/providers/test_openai_codex_provider.py
@@ -18,6 +18,7 @@ from nanobot.providers.openai_codex_provider import (
     _request_codex,
     _should_retry_status,
 )
+from nanobot.providers.registry import find_by_name
 
 
 def _mock_codex_token(monkeypatch: pytest.MonkeyPatch) -> None:
@@ -30,6 +31,14 @@ def _mock_codex_token(monkeypatch: pytest.MonkeyPatch) -> None:
     )
 
 
+def test_codex_default_model_matches_curated_flagship() -> None:
+    spec = find_by_name("openai_codex")
+
+    assert spec is not None
+    assert spec.builtin_models
+    assert OpenAICodexProvider().get_default_model() == spec.builtin_models[0].id
+
+
 class _WarningCaptureLogger:
     def __init__(self) -> None:
         self.calls: list[tuple[str, tuple[Any, ...]]] = []
diff --git a/tests/webui/test_settings_api.py b/tests/webui/test_settings_api.py
index 3e91ca30..299b4af2 100644
--- a/tests/webui/test_settings_api.py
+++ b/tests/webui/test_settings_api.py
@@ -1220,7 +1220,7 @@ def test_create_model_configuration_accepts_configured_oauth_provider(
         {
             "label": ["Codex"],
             "provider": ["openai_codex"],
-            "model": ["openai-codex/gpt-5.1-codex"],
+            "model": ["openai-codex/gpt-5.6-sol"],
         }
     )