nanobot/nanobot/agent/runner.py

"""Shared execution loop for tool-using agents."""

from __future__ import annotations

import asyncio
import inspect
import os
from contextlib import suppress
from copy import deepcopy
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, Callable

from loguru import logger

from nanobot.agent.hook import AgentHook, AgentHookContext, AgentRunHookContext
from nanobot.agent.tools.registry import ToolRegistry
from nanobot.providers.base import LLMProvider, LLMResponse, ToolCallRequest
from nanobot.utils.file_edit_events import (
    StreamingFileEditTracker,
    build_file_edit_end_event,
    build_file_edit_error_event,
    build_file_edit_start_event,
    prepare_file_edit_trackers,
)
from nanobot.utils.file_edit_events import (
    prepare_file_edit_tracker as _prepare_file_edit_tracker,
)
from nanobot.utils.helpers import (
    IncrementalThinkExtractor,
    build_assistant_message,
    estimate_message_tokens,
    estimate_prompt_tokens_chain,
    extract_reasoning,
    find_legal_message_start,
    maybe_persist_tool_result,
    strip_reasoning_tags,
    strip_think,
    truncate_text,
)
from nanobot.utils.progress_events import (
    invoke_file_edit_progress,
    on_progress_accepts_file_edit_events,
)
from nanobot.utils.prompt_templates import render_template
from nanobot.utils.runtime import (
    EMPTY_FINAL_RESPONSE_MESSAGE,
    build_budget_exhausted_finalization_message,
    build_finalization_retry_message,
    build_goal_continue_message,
    build_length_recovery_message,
    ensure_nonempty_tool_result,
    is_blank_text,
    repeated_external_lookup_error,
    repeated_workspace_violation_error,
)

GoalContinueMessage = str | Callable[[], str | None]

_DEFAULT_ERROR_MESSAGE = "Sorry, I encountered an error calling the AI model."
_ARREARAGE_ERROR_MESSAGE = (
    "The AI provider rejected the request because the API key is out of quota or the "
    "account is in arrears. Please top up / check the billing status of your API key and try again."
)
_PERSISTED_MODEL_ERROR_PLACEHOLDER = "[Assistant reply unavailable due to model error.]"
_MAX_EMPTY_RETRIES = 2
_MAX_LENGTH_RECOVERIES = 3
_MAX_INJECTIONS_PER_TURN = 3
_MAX_INJECTION_CYCLES = 5
_SNIP_SAFETY_BUFFER = 1024
_MICROCOMPACT_KEEP_RECENT = 10
_MICROCOMPACT_MIN_CHARS = 500
_COMPACTABLE_TOOLS = frozenset({
    "read_file", "exec", "grep", "find_files",
    "web_search", "web_fetch", "list_dir", "list_exec_sessions",
})
# read_file is the recovery path for persisted results; exempting it prevents persist->read->persist loops.
_TOOL_RESULT_OFFLOAD_EXEMPT_TOOLS = frozenset({"read_file"})
_BACKFILL_CONTENT = "[Tool result unavailable — call was interrupted or lost]"

# Backward-compatible module attribute for tests/extensions that monkeypatch
# the former single-file tracker hook. Runtime uses prepare_file_edit_trackers.
prepare_file_edit_tracker = _prepare_file_edit_tracker


@dataclass(slots=True)
class AgentRunSpec:
    """Configuration for a single agent execution."""

    initial_messages: list[dict[str, Any]]
    tools: ToolRegistry
    model: str
    max_iterations: int
    max_tool_result_chars: int
    temperature: float | None = None
    max_tokens: int | None = None
    reasoning_effort: str | None = None
    hook: AgentHook | None = None
    error_message: str | None = _DEFAULT_ERROR_MESSAGE
    max_iterations_message: str | None = None
    concurrent_tools: bool = False
    fail_on_tool_error: bool = False
    workspace: Path | None = None
    session_key: str | None = None
    context_window_tokens: int | None = None
    context_block_limit: int | None = None
    provider_retry_mode: str = "standard"
    progress_callback: Any | None = None
    stream_progress_deltas: bool = True
    retry_wait_callback: Any | None = None
    checkpoint_callback: Any | None = None
    injection_callback: Any | None = None
    llm_timeout_s: float | None = None
    goal_active_predicate: Callable[[], bool] | None = None
    goal_continue_message: GoalContinueMessage | None = None
    finalize_on_max_iterations: bool = True


@dataclass(slots=True)
class AgentRunResult:
    """Outcome of a shared agent execution."""

    final_content: str | None
    messages: list[dict[str, Any]]
    tools_used: list[str] = field(default_factory=list)
    usage: dict[str, int] = field(default_factory=dict)
    stop_reason: str = "completed"
    error: str | None = None
    tool_events: list[dict[str, str]] = field(default_factory=list)
    had_injections: bool = False


class AgentRunner:
    """Run a tool-capable LLM loop without product-layer concerns."""

    def __init__(self, provider: LLMProvider):
        self.provider = provider

    @staticmethod
    def _merge_message_content(left: Any, right: Any) -> str | list[dict[str, Any]]:
        if isinstance(left, str) and isinstance(right, str):
            return f"{left}\n\n{right}" if left else right

        def _to_blocks(value: Any) -> list[dict[str, Any]]:
            if isinstance(value, list):
                return [
                    item if isinstance(item, dict) else {"type": "text", "text": str(item)}
                    for item in value
                ]
            if value is None:
                return []
            return [{"type": "text", "text": str(value)}]

        return _to_blocks(left) + _to_blocks(right)

    @classmethod
    def _append_injected_messages(
        cls,
        messages: list[dict[str, Any]],
        injections: list[dict[str, Any]],
    ) -> None:
        """Append injected user messages while preserving role alternation."""
        for injection in injections:
            if (
                messages
                and injection.get("role") == "user"
                and messages[-1].get("role") == "user"
            ):
                merged = dict(messages[-1])
                merged["content"] = cls._merge_message_content(
                    merged.get("content"),
                    injection.get("content"),
                )
                messages[-1] = merged
                continue
            messages.append(injection)

    async def _try_drain_injections(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
        assistant_message: dict[str, Any] | None,
        injection_cycles: int,
        *,
        phase: str = "after error",
        iteration: int | None = None,
        allow_goal_continue: bool = False,
    ) -> tuple[bool, int]:
        """Drain pending injections. Returns (should_continue, updated_cycles).

        If injections are found and we haven't exceeded _MAX_INJECTION_CYCLES,
        append them to *messages* (and emit a checkpoint if *assistant_message*
        and *iteration* are both provided) and return (True, cycles+1) so the
        caller continues the iteration loop.  Otherwise return (False, cycles).
        """
        injections: list[dict[str, Any]] = []
        real_injection = False
        if injection_cycles < _MAX_INJECTION_CYCLES:
            injections = await self._drain_injections(spec)
            real_injection = bool(injections)
        if not injections and allow_goal_continue and assistant_message is not None:
            predicate = spec.goal_active_predicate
            if predicate is not None and predicate():
                injections = [self._build_goal_continue_message(spec)]
        if not injections:
            return False, injection_cycles
        if real_injection:
            injection_cycles += 1
        if assistant_message is not None:
            messages.append(assistant_message)
            if iteration is not None:
                await self._emit_checkpoint(
                    spec,
                    {
                        "phase": "final_response",
                        "iteration": iteration,
                        "model": spec.model,
                        "assistant_message": assistant_message,
                        "completed_tool_results": [],
                        "pending_tool_calls": [],
                    },
                )
        self._append_injected_messages(messages, injections)
        if real_injection:
            logger.info(
                "Injected {} follow-up message(s) {} ({}/{})",
                len(injections), phase, injection_cycles, _MAX_INJECTION_CYCLES,
            )
        else:
            logger.info("Injected sustained-goal continuation {}", phase)
        return True, injection_cycles

    def _build_goal_continue_message(self, spec: AgentRunSpec) -> dict[str, str]:
        custom = spec.goal_continue_message
        if callable(custom):
            try:
                custom = custom()
            except Exception:
                logger.exception("goal_continue_message callback failed")
                custom = None
        return build_goal_continue_message(custom)

    async def _drain_injections(self, spec: AgentRunSpec) -> list[dict[str, Any]]:
        """Drain pending user messages via the injection callback.

        Returns normalized user messages (capped by
        ``_MAX_INJECTIONS_PER_TURN``), or an empty list when there is
        nothing to inject. Messages beyond the cap are logged so they
        are not silently lost.
        """
        if spec.injection_callback is None:
            return []
        try:
            signature = inspect.signature(spec.injection_callback)
            accepts_limit = (
                "limit" in signature.parameters
                or any(
                    parameter.kind is inspect.Parameter.VAR_KEYWORD
                    for parameter in signature.parameters.values()
                )
            )
            if accepts_limit:
                items = await spec.injection_callback(limit=_MAX_INJECTIONS_PER_TURN)
            else:
                items = await spec.injection_callback()
        except Exception:
            logger.exception("injection_callback failed")
            return []
        if not items:
            return []
        injected_messages: list[dict[str, Any]] = []
        for item in items:
            if item is None:
                continue
            if isinstance(item, dict) and item.get("role") == "user" and "content" in item:
                if self._has_injection_content(item.get("content")):
                    injected_messages.append(item)
                continue
            if isinstance(item, dict):
                continue
            content = getattr(item, "content") if hasattr(item, "content") else str(item)
            if self._has_injection_content(content):
                injected_messages.append({"role": "user", "content": content})
        if len(injected_messages) > _MAX_INJECTIONS_PER_TURN:
            dropped = len(injected_messages) - _MAX_INJECTIONS_PER_TURN
            logger.warning(
                "Injection callback returned {} messages, capping to {} ({} dropped)",
                len(injected_messages), _MAX_INJECTIONS_PER_TURN, dropped,
            )
            injected_messages = injected_messages[:_MAX_INJECTIONS_PER_TURN]
        return injected_messages

    @staticmethod
    def _has_injection_content(content: Any) -> bool:
        if content is None:
            return False
        if isinstance(content, str):
            return bool(content.strip())
        if isinstance(content, list):
            return bool(content)
        return True

    async def run(self, spec: AgentRunSpec) -> AgentRunResult:
        hook = spec.hook or AgentHook()
        messages = list(spec.initial_messages)
        context = AgentRunHookContext(messages=deepcopy(messages))

        try:
            await hook.before_run(context)
            result = await self._run_core(spec, hook, messages)
        except asyncio.CancelledError as exc:
            context.messages = deepcopy(messages)
            context.stop_reason = "cancelled"
            context.error = None
            context.exception = exc
            raise
        except Exception as exc:
            context.messages = deepcopy(messages)
            context.stop_reason = "error"
            context.error = f"Error: {type(exc).__name__}: {exc}"
            context.exception = exc
            await hook.on_error(context)
            raise
        else:
            context.messages = deepcopy(result.messages)
            context.final_content = result.final_content
            context.tools_used = list(result.tools_used)
            context.usage = dict(result.usage)
            context.stop_reason = result.stop_reason
            context.error = result.error
            context.tool_events = deepcopy(result.tool_events)
            context.had_injections = result.had_injections
            context.exception = None
            if context.error is not None:
                await hook.on_error(context)
            await hook.after_run(context)
            return result
        finally:
            context.messages = deepcopy(messages)
            if context.exception is None:
                await hook.on_finally(context)
            else:
                try:
                    await hook.on_finally(context)
                except Exception:
                    logger.exception(
                        "AgentHook.on_finally error after {}",
                        context.stop_reason or "run exception",
                    )

    async def _run_core(
        self,
        spec: AgentRunSpec,
        hook: AgentHook,
        messages: list[dict[str, Any]],
    ) -> AgentRunResult:
        final_content: str | None = None
        tools_used: list[str] = []
        usage: dict[str, int] = {"prompt_tokens": 0, "completion_tokens": 0}
        error: str | None = None
        stop_reason = "completed"
        tool_events: list[dict[str, str]] = []
        external_lookup_counts: dict[str, int] = {}
        # Per-turn throttle for repeated attempts against the same outside target.
        workspace_violation_counts: dict[str, int] = {}
        empty_content_retries = 0
        length_recovery_count = 0
        had_injections = False
        injection_cycles = 0

        for iteration in range(spec.max_iterations):
            try:
                # Keep the persisted conversation untouched. Context governance
                # may repair or compact historical messages for the model, but
                # those synthetic edits must not shift the append boundary used
                # later when the caller saves only the new turn.
                messages_for_model = self._drop_orphan_tool_results(messages)
                messages_for_model = self._backfill_missing_tool_results(messages_for_model)
                messages_for_model = self._microcompact(messages_for_model)
                messages_for_model = self._apply_tool_result_budget(spec, messages_for_model)
                messages_for_model = self._snip_history(spec, messages_for_model)
                # Snipping may have created new orphans; clean them up.
                messages_for_model = self._drop_orphan_tool_results(messages_for_model)
                messages_for_model = self._backfill_missing_tool_results(messages_for_model)
            except Exception:
                logger.exception(
                    "Context governance failed on turn {} for {}; applying minimal repair",
                    iteration,
                    spec.session_key or "default",
                )
                try:
                    messages_for_model = self._drop_orphan_tool_results(messages)
                    messages_for_model = self._backfill_missing_tool_results(messages_for_model)
                except Exception:
                    messages_for_model = messages
            context = AgentHookContext(
                iteration=iteration,
                messages=messages,
                session_key=spec.session_key,
            )
            await hook.before_iteration(context)
            response = await self._request_model(spec, messages_for_model, hook, context)
            context.response = response
            context.tool_calls = list(response.tool_calls)

            reasoning_text, cleaned_content = extract_reasoning(
                response.reasoning_content,
                response.thinking_blocks,
                response.content,
            )
            response.content = cleaned_content
            raw_usage = self._usage_or_estimate(spec, messages_for_model, response)
            context.usage = dict(raw_usage)
            self._accumulate_usage(usage, raw_usage)
            if reasoning_text and not context.streamed_reasoning:
                await hook.emit_reasoning(reasoning_text)
                await hook.emit_reasoning_end()
                context.streamed_reasoning = True

            if response.should_execute_tools:
                context.tool_calls = list(response.tool_calls)
                if hook.wants_streaming():
                    await hook.on_stream_end(context, resuming=True)

                assistant_message = build_assistant_message(
                    response.content or "",
                    tool_calls=[tc.to_openai_tool_call() for tc in response.tool_calls],
                    reasoning_content=response.reasoning_content,
                    thinking_blocks=response.thinking_blocks,
                )
                messages.append(assistant_message)
                await self._emit_checkpoint(
                    spec,
                    {
                        "phase": "awaiting_tools",
                        "iteration": iteration,
                        "model": spec.model,
                        "assistant_message": assistant_message,
                        "completed_tool_results": [],
                        "pending_tool_calls": [tc.to_openai_tool_call() for tc in response.tool_calls],
                    },
                )

                await hook.before_execute_tools(context)

                results, new_events, fatal_error = await self._execute_tools(
                    spec,
                    response.tool_calls,
                    external_lookup_counts,
                    workspace_violation_counts,
                )
                tool_events.extend(new_events)
                tools_used.extend(
                    tool_call.name
                    for tool_call, event in zip(response.tool_calls, new_events)
                    if event.get("status") == "ok"
                )
                context.tool_results = list(results)
                context.tool_events = list(new_events)
                completed_tool_results: list[dict[str, Any]] = []
                for tool_call, result in zip(response.tool_calls, results):
                    tool_message = {
                        "role": "tool",
                        "tool_call_id": tool_call.id,
                        "name": tool_call.name,
                        "content": self._normalize_tool_result(
                            spec,
                            tool_call.id,
                            tool_call.name,
                            result,
                        ),
                    }
                    messages.append(tool_message)
                    completed_tool_results.append(tool_message)
                if fatal_error is not None:
                    error = f"Error: {type(fatal_error).__name__}: {fatal_error}"
                    final_content = error
                    stop_reason = "tool_error"
                    self._append_final_message(messages, final_content)
                    context.final_content = final_content
                    context.error = error
                    context.stop_reason = stop_reason
                    await hook.after_iteration(context)
                    should_continue, injection_cycles = await self._try_drain_injections(
                        spec, messages, None, injection_cycles,
                        phase="after tool error",
                    )
                    if should_continue:
                        had_injections = True
                        continue
                    break
                await self._emit_checkpoint(
                    spec,
                    {
                        "phase": "tools_completed",
                        "iteration": iteration,
                        "model": spec.model,
                        "assistant_message": assistant_message,
                        "completed_tool_results": completed_tool_results,
                        "pending_tool_calls": [],
                    },
                )
                empty_content_retries = 0
                length_recovery_count = 0
                # Checkpoint 1: drain injections after tools, before next LLM call
                _drained, injection_cycles = await self._try_drain_injections(
                    spec, messages, None, injection_cycles,
                    phase="after tool execution",
                )
                if _drained:
                    had_injections = True
                await hook.after_iteration(context)
                continue

            if response.has_tool_calls:
                logger.warning(
                    "Ignoring tool calls under finish_reason='{}' for {}",
                    response.finish_reason,
                    spec.session_key or "default",
                )

            clean = hook.finalize_content(context, response.content)
            if response.finish_reason != "error" and is_blank_text(clean):
                empty_content_retries += 1
                if empty_content_retries < _MAX_EMPTY_RETRIES:
                    logger.warning(
                        "Empty response on turn {} for {} ({}/{}); retrying",
                        iteration,
                        spec.session_key or "default",
                        empty_content_retries,
                        _MAX_EMPTY_RETRIES,
                    )
                    if hook.wants_streaming():
                        await hook.on_stream_end(context, resuming=False)
                    await hook.after_iteration(context)
                    continue
                logger.warning(
                    "Empty response on turn {} for {} after {} retries; attempting finalization",
                    iteration,
                    spec.session_key or "default",
                    empty_content_retries,
                )
                if hook.wants_streaming():
                    await hook.on_stream_end(context, resuming=False)
                retry_messages = self._finalization_retry_messages(messages_for_model)
                response = await self._request_finalization_retry(spec, messages_for_model)
                retry_usage = self._usage_or_estimate(spec, retry_messages, response)
                self._accumulate_usage(usage, retry_usage)
                raw_usage = self._merge_usage(raw_usage, retry_usage)
                context.response = response
                context.usage = dict(raw_usage)
                context.tool_calls = list(response.tool_calls)
                clean = hook.finalize_content(context, response.content)

            if response.finish_reason == "length" and not is_blank_text(clean):
                length_recovery_count += 1
                if length_recovery_count <= _MAX_LENGTH_RECOVERIES:
                    logger.info(
                        "Output truncated on turn {} for {} ({}/{}); continuing",
                        iteration,
                        spec.session_key or "default",
                        length_recovery_count,
                        _MAX_LENGTH_RECOVERIES,
                    )
                    if hook.wants_streaming():
                        await hook.on_stream_end(context, resuming=True)
                    messages.append(build_assistant_message(
                        clean,
                        reasoning_content=response.reasoning_content,
                        thinking_blocks=response.thinking_blocks,
                    ))
                    messages.append(build_length_recovery_message())
                    await hook.after_iteration(context)
                    continue

            assistant_message: dict[str, Any] | None = None
            if response.finish_reason != "error" and not is_blank_text(clean):
                assistant_message = build_assistant_message(
                    clean,
                    reasoning_content=response.reasoning_content,
                    thinking_blocks=response.thinking_blocks,
                )

            # Check for mid-turn injections BEFORE signaling stream end.
            # If injections are found we keep the stream alive (resuming=True)
            # so streaming channels don't prematurely finalize the card.
            should_continue, injection_cycles = await self._try_drain_injections(
                spec, messages, assistant_message, injection_cycles,
                phase="after final response",
                iteration=iteration,
                allow_goal_continue=True,
            )
            if should_continue:
                had_injections = True

            if hook.wants_streaming():
                await hook.on_stream_end(context, resuming=should_continue)

            if should_continue:
                await hook.after_iteration(context)
                continue

            if response.finish_reason == "error":
                if LLMProvider.is_arrearage_response(response):
                    final_content = _ARREARAGE_ERROR_MESSAGE
                else:
                    final_content = clean or spec.error_message or _DEFAULT_ERROR_MESSAGE
                stop_reason = "error"
                error = final_content
                self._append_model_error_placeholder(messages)
                context.final_content = final_content
                context.error = error
                context.stop_reason = stop_reason
                await hook.after_iteration(context)
                should_continue, injection_cycles = await self._try_drain_injections(
                    spec, messages, None, injection_cycles,
                    phase="after LLM error",
                )
                if should_continue:
                    had_injections = True
                    continue
                break
            if is_blank_text(clean):
                final_content = EMPTY_FINAL_RESPONSE_MESSAGE
                stop_reason = "empty_final_response"
                error = final_content
                self._append_final_message(messages, final_content)
                context.final_content = final_content
                context.error = error
                context.stop_reason = stop_reason
                await hook.after_iteration(context)
                should_continue, injection_cycles = await self._try_drain_injections(
                    spec, messages, None, injection_cycles,
                    phase="after empty response",
                )
                if should_continue:
                    had_injections = True
                    continue
                break

            messages.append(assistant_message or build_assistant_message(
                clean,
                reasoning_content=response.reasoning_content,
                thinking_blocks=response.thinking_blocks,
            ))
            await self._emit_checkpoint(
                spec,
                {
                    "phase": "final_response",
                    "iteration": iteration,
                    "model": spec.model,
                    "assistant_message": messages[-1],
                    "completed_tool_results": [],
                    "pending_tool_calls": [],
                },
            )
            final_content = clean
            context.final_content = final_content
            context.stop_reason = stop_reason
            await hook.after_iteration(context)
            break
        else:
            stop_reason = "max_iterations"
            # Drain any remaining injections so they are appended to the
            # conversation history instead of being re-published as
            # independent inbound messages by _dispatch's finally block.
            # We include them before the no-tools finalization pass so the
            # final response can account for every known follow-up.
            drained_after_max_iterations, injection_cycles = await self._try_drain_injections(
                spec, messages, None, injection_cycles,
                phase="after max_iterations",
            )
            if drained_after_max_iterations:
                had_injections = True
            final_content = None
            if spec.finalize_on_max_iterations:
                final_content = await self._try_finalize_after_max_iterations(
                    spec,
                    hook,
                    messages,
                    usage,
                )
            if final_content is None:
                final_content = self._max_iterations_fallback(spec)
            self._append_final_message(messages, final_content)

        return AgentRunResult(
            final_content=final_content,
            messages=messages,
            tools_used=tools_used,
            usage=usage,
            stop_reason=stop_reason,
            error=error,
            tool_events=tool_events,
            had_injections=had_injections,
        )

    def _build_request_kwargs(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
        *,
        tools: list[dict[str, Any]] | None,
    ) -> dict[str, Any]:
        kwargs: dict[str, Any] = {
            "messages": messages,
            "tools": tools,
            "model": spec.model,
            "retry_mode": spec.provider_retry_mode,
            "on_retry_wait": spec.retry_wait_callback,
        }
        if spec.temperature is not None:
            kwargs["temperature"] = spec.temperature
        if spec.max_tokens is not None:
            kwargs["max_tokens"] = spec.max_tokens
        if spec.reasoning_effort is not None:
            kwargs["reasoning_effort"] = spec.reasoning_effort
        return kwargs

    async def _request_model(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
        hook: AgentHook,
        context: AgentHookContext,
    ):
        timeout_s: float | None = spec.llm_timeout_s
        if timeout_s is None:
            # Default to a finite timeout to avoid per-session lock starvation when an LLM
            # request hangs indefinitely (e.g. gateway/network stall).
            # Set NANOBOT_LLM_TIMEOUT_S=0 to disable.
            raw = os.environ.get("NANOBOT_LLM_TIMEOUT_S", "300").strip()
            try:
                timeout_s = float(raw)
            except (TypeError, ValueError):
                timeout_s = 300.0
        if timeout_s is not None and timeout_s <= 0:
            timeout_s = None

        kwargs = self._build_request_kwargs(
            spec,
            messages,
            tools=spec.tools.get_definitions(),
        )
        wants_streaming = hook.wants_streaming()
        wants_progress_streaming = (
            not wants_streaming
            and spec.stream_progress_deltas
            and spec.progress_callback is not None
            and getattr(self.provider, "supports_progress_deltas", False) is True
        )

        progress_state: dict[str, bool] | None = None
        live_file_edits: StreamingFileEditTracker | None = None

        if (
            spec.progress_callback is not None
            and on_progress_accepts_file_edit_events(spec.progress_callback)
        ):
            async def _emit_live_file_edits(events: list[dict[str, Any]]) -> None:
                await invoke_file_edit_progress(spec.progress_callback, events)

            live_file_edits = StreamingFileEditTracker(
                workspace=spec.workspace,
                tools=spec.tools,
                emit=_emit_live_file_edits,
            )

        async def _tool_call_delta(delta: dict[str, Any]) -> None:
            if live_file_edits is not None:
                await live_file_edits.update(delta)

        if wants_streaming:
            thinking_buf = ""

            async def _stream(delta: str) -> None:
                if delta:
                    context.streamed_content = True
                await hook.on_stream(context, delta)

            async def _thinking(delta: str) -> None:
                nonlocal thinking_buf
                if not delta:
                    return
                prev_clean = strip_reasoning_tags(thinking_buf)
                thinking_buf += delta
                new_clean = strip_reasoning_tags(thinking_buf)
                incremental = new_clean[len(prev_clean):]
                if incremental:
                    context.streamed_reasoning = True
                    await hook.emit_reasoning(incremental)

            async def _stream_recover() -> None:
                await hook.on_stream_end(context, resuming=True)

            coro = self.provider.chat_stream_with_retry(
                **kwargs,
                on_content_delta=_stream,
                on_thinking_delta=_thinking,
                on_tool_call_delta=_tool_call_delta if live_file_edits is not None else None,
                on_stream_recover=_stream_recover,
            )
        elif wants_progress_streaming:
            stream_buf = ""
            think_extractor = IncrementalThinkExtractor()
            progress_state = {"reasoning_open": False}

            async def _stream_progress(delta: str) -> None:
                nonlocal stream_buf
                if not delta:
                    return
                prev_clean = strip_think(stream_buf)
                stream_buf += delta
                new_clean = strip_think(stream_buf)
                incremental = new_clean[len(prev_clean):]

                if await think_extractor.feed(stream_buf, hook.emit_reasoning):
                    context.streamed_reasoning = True
                    progress_state["reasoning_open"] = True

                if incremental:
                    if progress_state["reasoning_open"]:
                        await hook.emit_reasoning_end()
                        progress_state["reasoning_open"] = False
                    context.streamed_content = True
                    await spec.progress_callback(incremental)

            coro = self.provider.chat_stream_with_retry(
                **kwargs,
                on_content_delta=_stream_progress,
                on_tool_call_delta=_tool_call_delta if live_file_edits is not None else None,
            )
        else:
            coro = self.provider.chat_with_retry(**kwargs)

        # Streaming requests already have provider-level idle timeouts
        # (NANOBOT_STREAM_IDLE_TIMEOUT_S). Do not also apply the outer wall-clock
        # LLM timeout here, or healthy long reasoning streams can be killed just
        # because total elapsed time exceeded NANOBOT_LLM_TIMEOUT_S.
        outer_timeout_s = None if (wants_streaming or wants_progress_streaming) else timeout_s
        try:
            response = (
                await coro if outer_timeout_s is None
                else await asyncio.wait_for(coro, timeout=outer_timeout_s)
            )
            if live_file_edits is not None:
                await live_file_edits.flush()
                if response.should_execute_tools:
                    live_file_edits.apply_final_call_ids(response.tool_calls)
                await live_file_edits.error_unmatched(
                    response.tool_calls if response.should_execute_tools else [],
                    "Tool call did not complete.",
                )
        except asyncio.TimeoutError:
            if outer_timeout_s is None:
                return LLMResponse(
                    content="Error calling LLM: stream stalled",
                    finish_reason="error",
                    error_kind="timeout",
                )
            return LLMResponse(
                content=f"Error calling LLM: timed out after {outer_timeout_s:g}s",
                finish_reason="error",
                error_kind="timeout",
            )
        if progress_state and progress_state.get("reasoning_open"):
            await hook.emit_reasoning_end()
        return response

    async def _request_finalization_retry(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
    ):
        retry_messages = self._finalization_retry_messages(messages)
        return await self._request_no_tools(spec, retry_messages)

    @staticmethod
    def _finalization_retry_messages(messages: list[dict[str, Any]]) -> list[dict[str, Any]]:
        retry_messages = list(messages)
        retry_messages.append(build_finalization_retry_message())
        return retry_messages

    async def _try_finalize_after_max_iterations(
        self,
        spec: AgentRunSpec,
        hook: AgentHook,
        messages: list[dict[str, Any]],
        usage: dict[str, int],
    ) -> str | None:
        retry_messages = self._budget_exhausted_finalization_messages(messages)
        try:
            response = await self._request_no_tools(spec, retry_messages)
        except Exception:
            logger.exception(
                "Budget-exhausted finalization failed for {}; using fallback",
                spec.session_key or "default",
            )
            return None

        raw_usage = self._usage_or_estimate(spec, retry_messages, response)
        self._accumulate_usage(usage, raw_usage)
        if response.finish_reason == "error" or response.has_tool_calls:
            logger.warning(
                "Budget-exhausted finalization returned finish_reason='{}' "
                "with {} tool call(s) for {}; using fallback",
                response.finish_reason,
                len(response.tool_calls),
                spec.session_key or "default",
            )
            return None

        context = AgentHookContext(
            iteration=spec.max_iterations,
            messages=messages,
            response=response,
            usage=dict(raw_usage),
            session_key=spec.session_key,
        )
        clean = hook.finalize_content(context, response.content)
        if is_blank_text(clean):
            return None
        return clean

    async def _request_no_tools(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
    ) -> LLMResponse:
        kwargs = self._build_request_kwargs(spec, messages, tools=None)
        return await self.provider.chat_with_retry(**kwargs)

    @staticmethod
    def _budget_exhausted_finalization_messages(
        messages: list[dict[str, Any]],
    ) -> list[dict[str, Any]]:
        retry_messages = list(messages)
        retry_messages.append(build_budget_exhausted_finalization_message())
        return retry_messages

    @staticmethod
    def _max_iterations_fallback(spec: AgentRunSpec) -> str:
        if spec.max_iterations_message:
            return spec.max_iterations_message.format(
                max_iterations=spec.max_iterations,
            )
        return render_template(
            "agent/max_iterations_message.md",
            strip=True,
            max_iterations=spec.max_iterations,
        )

    def _usage_or_estimate(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
        response: LLMResponse,
    ) -> dict[str, int]:
        usage = self._usage_dict(response.usage)
        total = self._usage_total(usage)
        if total > 0:
            usage["total_tokens"] = total
            usage.setdefault("provider_tokens", total)
            return usage
        if response.finish_reason == "error":
            return {}
        return self._estimate_response_usage(spec, messages, response)

    def _estimate_response_usage(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
        response: LLMResponse,
    ) -> dict[str, int]:
        try:
            tools = spec.tools.get_definitions()
        except Exception:
            tools = None
        prompt_tokens, _ = estimate_prompt_tokens_chain(self.provider, spec.model, messages, tools)
        assistant_message = build_assistant_message(
            response.content or "",
            tool_calls=[tc.to_openai_tool_call() for tc in response.tool_calls],
            reasoning_content=response.reasoning_content,
            thinking_blocks=response.thinking_blocks,
        )
        completion_tokens = estimate_message_tokens(assistant_message)
        total_tokens = max(0, prompt_tokens) + max(0, completion_tokens)
        if total_tokens <= 0:
            return {}
        return {
            "prompt_tokens": max(0, prompt_tokens),
            "completion_tokens": max(0, completion_tokens),
            "total_tokens": total_tokens,
            "estimated_tokens": total_tokens,
        }

    @staticmethod
    def _usage_dict(usage: dict[str, Any] | None) -> dict[str, int]:
        if not usage:
            return {}
        result: dict[str, int] = {}
        for key, value in usage.items():
            try:
                result[key] = int(value or 0)
            except (TypeError, ValueError):
                continue
        return result

    @staticmethod
    def _usage_total(usage: dict[str, int]) -> int:
        return max(0, usage.get("total_tokens", 0) or (
            usage.get("prompt_tokens", 0) + usage.get("completion_tokens", 0)
        ))

    @staticmethod
    def _accumulate_usage(target: dict[str, int], addition: dict[str, int]) -> None:
        for key, value in addition.items():
            target[key] = target.get(key, 0) + value

    @staticmethod
    def _merge_usage(left: dict[str, int], right: dict[str, int]) -> dict[str, int]:
        merged = dict(left)
        for key, value in right.items():
            merged[key] = merged.get(key, 0) + value
        return merged

    async def _execute_tools(
        self,
        spec: AgentRunSpec,
        tool_calls: list[ToolCallRequest],
        external_lookup_counts: dict[str, int],
        workspace_violation_counts: dict[str, int],
    ) -> tuple[list[Any], list[dict[str, str]], BaseException | None]:
        batches = self._partition_tool_batches(spec, tool_calls)
        tool_results: list[tuple[Any, dict[str, str], BaseException | None]] = []
        for batch in batches:
            if spec.concurrent_tools and len(batch) > 1:
                batch_results = await asyncio.gather(*(
                    self._run_tool(
                        spec, tool_call, external_lookup_counts, workspace_violation_counts,
                    )
                    for tool_call in batch
                ))
                tool_results.extend(batch_results)
            else:
                batch_results = []
                for tool_call in batch:
                    result = await self._run_tool(
                        spec, tool_call, external_lookup_counts, workspace_violation_counts,
                    )
                    tool_results.append(result)
                    batch_results.append(result)

        results: list[Any] = []
        events: list[dict[str, str]] = []
        fatal_error: BaseException | None = None
        for result, event, error in tool_results:
            results.append(result)
            events.append(event)
            if error is not None and fatal_error is None:
                fatal_error = error
        return results, events, fatal_error

    async def _run_tool(
        self,
        spec: AgentRunSpec,
        tool_call: ToolCallRequest,
        external_lookup_counts: dict[str, int],
        workspace_violation_counts: dict[str, int],
    ) -> tuple[Any, dict[str, str], BaseException | None]:
        hint = "\n\n[Analyze the error above and try a different approach.]"
        lookup_error = repeated_external_lookup_error(
            tool_call.name,
            tool_call.arguments,
            external_lookup_counts,
        )
        if lookup_error:
            event = {
                "name": tool_call.name,
                "status": "error",
                "detail": "repeated external lookup blocked",
            }
            if spec.fail_on_tool_error:
                return lookup_error + hint, event, RuntimeError(lookup_error)
            return lookup_error + hint, event, None
        prepare_call = getattr(spec.tools, "prepare_call", None)
        tool, params, prep_error = None, tool_call.arguments, None
        if callable(prepare_call):
            with suppress(Exception):
                prepared = prepare_call(tool_call.name, tool_call.arguments)
                if isinstance(prepared, tuple) and len(prepared) == 3:
                    tool, params, prep_error = prepared
        if prep_error:
            event = {
                "name": tool_call.name,
                "status": "error",
                "detail": prep_error.split(": ", 1)[-1][:120],
            }
            handled = self._classify_violation(
                raw_text=prep_error,
                soft_payload=prep_error + hint,
                event=event,
                tool_call=tool_call,
                workspace_violation_counts=workspace_violation_counts,
            )
            if handled is not None:
                return handled
            return prep_error + hint, event, (
                RuntimeError(prep_error) if spec.fail_on_tool_error else None
            )
        emit_file_edit_events = (
            spec.progress_callback is not None
            and on_progress_accepts_file_edit_events(spec.progress_callback)
        )
        progress_callback = spec.progress_callback if emit_file_edit_events else None
        file_edit_trackers = (
            prepare_file_edit_trackers(
                call_id=tool_call.id,
                tool_name=tool_call.name,
                tool=tool,
                workspace=spec.workspace,
                params=params if isinstance(params, dict) else None,
            )
            if progress_callback is not None
            else None
        )
        if file_edit_trackers and progress_callback is not None:
            await invoke_file_edit_progress(
                progress_callback,
                [build_file_edit_start_event(
                    file_edit_tracker,
                    params if isinstance(params, dict) else None,
                ) for file_edit_tracker in file_edit_trackers],
            )
        try:
            if tool is not None:
                result = await tool.execute(**params)
            else:
                result = await spec.tools.execute(tool_call.name, params)
        except asyncio.CancelledError:
            raise
        except BaseException as exc:
            if file_edit_trackers and progress_callback is not None:
                await invoke_file_edit_progress(
                    progress_callback,
                    [
                        build_file_edit_error_event(file_edit_tracker, str(exc))
                        for file_edit_tracker in file_edit_trackers
                    ],
                )
            event = {
                "name": tool_call.name,
                "status": "error",
                "detail": str(exc),
            }
            payload = f"Error: {type(exc).__name__}: {exc}"
            handled = self._classify_violation(
                raw_text=str(exc),
                # Preserve legacy exception payloads without the retry hint.
                soft_payload=payload,
                event=event,
                tool_call=tool_call,
                workspace_violation_counts=workspace_violation_counts,
            )
            if handled is not None:
                return handled
            if spec.fail_on_tool_error:
                return payload, event, exc
            return payload, event, None

        if isinstance(result, str) and result.startswith("Error"):
            if file_edit_trackers and progress_callback is not None:
                await invoke_file_edit_progress(
                    progress_callback,
                    [
                        build_file_edit_error_event(file_edit_tracker, result)
                        for file_edit_tracker in file_edit_trackers
                    ],
                )
            event = {
                "name": tool_call.name,
                "status": "error",
                "detail": result.replace("\n", " ").strip()[:120],
            }
            handled = self._classify_violation(
                raw_text=result,
                soft_payload=result + hint,
                event=event,
                tool_call=tool_call,
                workspace_violation_counts=workspace_violation_counts,
            )
            if handled is not None:
                return handled
            if spec.fail_on_tool_error:
                return result + hint, event, RuntimeError(result)
            return result + hint, event, None

        if file_edit_trackers and progress_callback is not None:
            await invoke_file_edit_progress(
                progress_callback,
                [build_file_edit_end_event(
                    file_edit_tracker,
                    params if isinstance(params, dict) else None,
                ) for file_edit_tracker in file_edit_trackers],
            )

        detail = "" if result is None else str(result)
        detail = detail.replace("\n", " ").strip()
        if not detail:
            detail = "(empty)"
        elif len(detail) > 120:
            detail = detail[:120] + "..."
        return result, {"name": tool_call.name, "status": "ok", "detail": detail}, None

    # SSRF is a hard security block at the tool boundary, but the agent turn
    # should recover conversationally instead of aborting the runtime.
    _SSRF_MARKERS: tuple[str, ...] = (
        "internal/private url detected",
        "private/internal address",
        "private address",
    )
    _SSRF_BOUNDARY_NOTE: str = (
        "This is a non-bypassable security boundary. Stop trying to access "
        "private/internal URLs. Do not retry with curl, wget, encoded IPs, "
        "alternate DNS, redirects, proxies, or another tool. Ask the user for "
        "local files, logs, screenshots, or an explicit safe public URL instead. "
        "If the user explicitly trusts this private URL, ask them to whitelist "
        "the exact IP/CIDR via tools.ssrfWhitelist."
    )

    # Non-SSRF boundary markers returned to the LLM as recoverable tool errors.
    _WORKSPACE_VIOLATION_MARKERS: tuple[str, ...] = (
        "outside the configured workspace",
        "outside allowed directory",
        "working_dir is outside",
        "working_dir could not be resolved",
        "path outside working dir",
        "path traversal detected",
    )

    @classmethod
    def _is_ssrf_violation(cls, text: str) -> bool:
        if not text:
            return False
        lowered = text.lower()
        return any(marker in lowered for marker in cls._SSRF_MARKERS)

    @classmethod
    def _is_workspace_violation(cls, text: str) -> bool:
        """True when *text* looks like any policy boundary rejection."""
        if not text:
            return False
        lowered = text.lower()
        if cls._is_ssrf_violation(lowered):
            return True
        return any(marker in lowered for marker in cls._WORKSPACE_VIOLATION_MARKERS)

    def _classify_violation(
        self,
        *,
        raw_text: str,
        soft_payload: str,
        event: dict[str, str],
        tool_call: ToolCallRequest,
        workspace_violation_counts: dict[str, int],
    ) -> tuple[Any, dict[str, str], BaseException | None] | None:
        """Classify safety-boundary failures, or return ``None`` to pass through."""
        if self._is_ssrf_violation(raw_text):
            logger.warning(
                "Tool {} blocked by SSRF guard; returning non-retryable tool error: {}",
                tool_call.name,
                raw_text.replace("\n", " ").strip()[:200],
            )
            event["detail"] = self._event_detail("ssrf_violation: ", raw_text)
            return self._ssrf_soft_payload(raw_text), event, None

        if self._is_workspace_violation(raw_text):
            escalation = repeated_workspace_violation_error(
                tool_call.name,
                tool_call.arguments,
                workspace_violation_counts,
            )
            event["detail"] = self._event_detail("workspace_violation: ", raw_text)
            if escalation is not None:
                logger.warning(
                    "Tool {} hit workspace boundary repeatedly; escalating hint",
                    tool_call.name,
                )
                event["detail"] = self._event_detail(
                    "workspace_violation_escalated: ",
                    raw_text,
                )
                return escalation, event, None
            return soft_payload, event, None

        return None

    @classmethod
    def _ssrf_soft_payload(cls, raw_text: str) -> str:
        text = raw_text.strip() or "Error: request blocked by SSRF guard"
        return f"{text}\n\n{cls._SSRF_BOUNDARY_NOTE}"

    @staticmethod
    def _event_detail(prefix: str, text: str, limit: int = 160) -> str:
        return (prefix + text.replace("\n", " ").strip())[:limit]

    async def _emit_checkpoint(
        self,
        spec: AgentRunSpec,
        payload: dict[str, Any],
    ) -> None:
        callback = spec.checkpoint_callback
        if callback is not None:
            await callback(payload)

    @staticmethod
    def _append_final_message(messages: list[dict[str, Any]], content: str | None) -> None:
        if not content:
            return
        if (
            messages
            and messages[-1].get("role") == "assistant"
            and not messages[-1].get("tool_calls")
        ):
            if messages[-1].get("content") == content:
                return
            messages[-1] = build_assistant_message(content)
            return
        messages.append(build_assistant_message(content))

    @staticmethod
    def _append_model_error_placeholder(messages: list[dict[str, Any]]) -> None:
        if messages and messages[-1].get("role") == "assistant" and not messages[-1].get("tool_calls"):
            return
        messages.append(build_assistant_message(_PERSISTED_MODEL_ERROR_PLACEHOLDER))

    def _normalize_tool_result(
        self,
        spec: AgentRunSpec,
        tool_call_id: str,
        tool_name: str,
        result: Any,
    ) -> Any:
        result = ensure_nonempty_tool_result(tool_name, result)
        if tool_name in _TOOL_RESULT_OFFLOAD_EXEMPT_TOOLS:
            # Exempt tools bound their own output; skip generic offload and truncation.
            return result
        try:
            content = maybe_persist_tool_result(
                spec.workspace,
                spec.session_key,
                tool_call_id,
                result,
                max_chars=spec.max_tool_result_chars,
            )
        except Exception:
            logger.exception(
                "Tool result persist failed for {} in {}; using raw result",
                tool_call_id,
                spec.session_key or "default",
            )
            content = result
        if isinstance(content, str) and len(content) > spec.max_tool_result_chars:
            return truncate_text(content, spec.max_tool_result_chars)
        return content

    @staticmethod
    def _drop_orphan_tool_results(
        messages: list[dict[str, Any]],
    ) -> list[dict[str, Any]]:
        """Drop tool results that have no matching assistant tool_call earlier in the history."""
        declared: set[str] = set()
        updated: list[dict[str, Any]] | None = None
        for idx, msg in enumerate(messages):
            role = msg.get("role")
            if role == "assistant":
                for tc in msg.get("tool_calls") or []:
                    if isinstance(tc, dict) and tc.get("id"):
                        declared.add(str(tc["id"]))
            if role == "tool":
                tid = msg.get("tool_call_id")
                if tid and str(tid) not in declared:
                    if updated is None:
                        updated = [dict(m) for m in messages[:idx]]
                    continue
            if updated is not None:
                updated.append(dict(msg))

        if updated is None:
            return messages
        return updated

    @staticmethod
    def _backfill_missing_tool_results(
        messages: list[dict[str, Any]],
    ) -> list[dict[str, Any]]:
        """Insert synthetic error results for orphaned tool_use blocks."""
        declared: list[tuple[int, str, str]] = []  # (assistant_idx, call_id, name)
        fulfilled: set[str] = set()
        for idx, msg in enumerate(messages):
            role = msg.get("role")
            if role == "assistant":
                for tc in msg.get("tool_calls") or []:
                    if isinstance(tc, dict) and tc.get("id"):
                        name = ""
                        func = tc.get("function")
                        if isinstance(func, dict):
                            name = func.get("name", "")
                        declared.append((idx, str(tc["id"]), name))
            elif role == "tool":
                tid = msg.get("tool_call_id")
                if tid:
                    fulfilled.add(str(tid))

        missing = [(ai, cid, name) for ai, cid, name in declared if cid not in fulfilled]
        if not missing:
            return messages

        updated = list(messages)
        offset = 0
        for assistant_idx, call_id, name in missing:
            insert_at = assistant_idx + 1 + offset
            while insert_at < len(updated) and updated[insert_at].get("role") == "tool":
                insert_at += 1
            updated.insert(insert_at, {
                "role": "tool",
                "tool_call_id": call_id,
                "name": name,
                "content": _BACKFILL_CONTENT,
            })
            offset += 1
        return updated

    @staticmethod
    def _microcompact(messages: list[dict[str, Any]]) -> list[dict[str, Any]]:
        """Replace old compactable tool results with one-line summaries."""
        compactable_indices: list[int] = []
        for idx, msg in enumerate(messages):
            if msg.get("role") == "tool" and msg.get("name") in _COMPACTABLE_TOOLS:
                compactable_indices.append(idx)

        if len(compactable_indices) <= _MICROCOMPACT_KEEP_RECENT:
            return messages

        stale = compactable_indices[: len(compactable_indices) - _MICROCOMPACT_KEEP_RECENT]
        updated: list[dict[str, Any]] | None = None
        for idx in stale:
            msg = messages[idx]
            content = msg.get("content")
            if not isinstance(content, str) or len(content) < _MICROCOMPACT_MIN_CHARS:
                continue
            name = msg.get("name", "tool")
            summary = f"[{name} result omitted from context]"
            if updated is None:
                updated = [dict(m) for m in messages]
            updated[idx]["content"] = summary

        return updated if updated is not None else messages

    def _apply_tool_result_budget(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
    ) -> list[dict[str, Any]]:
        updated = messages
        for idx, message in enumerate(messages):
            if message.get("role") != "tool":
                continue
            normalized = self._normalize_tool_result(
                spec,
                str(message.get("tool_call_id") or f"tool_{idx}"),
                str(message.get("name") or "tool"),
                message.get("content"),
            )
            if normalized != message.get("content"):
                if updated is messages:
                    updated = [dict(m) for m in messages]
                updated[idx]["content"] = normalized
        return updated

    def _snip_history(
        self,
        spec: AgentRunSpec,
        messages: list[dict[str, Any]],
    ) -> list[dict[str, Any]]:
        if not messages or not spec.context_window_tokens:
            return messages

        provider_max_tokens = getattr(getattr(self.provider, "generation", None), "max_tokens", 4096)
        max_output = spec.max_tokens if isinstance(spec.max_tokens, int) else (
            provider_max_tokens if isinstance(provider_max_tokens, int) else 4096
        )
        budget = spec.context_block_limit or (
            spec.context_window_tokens - max_output - _SNIP_SAFETY_BUFFER
        )
        if budget <= 0:
            return messages

        estimate, _ = estimate_prompt_tokens_chain(
            self.provider,
            spec.model,
            messages,
            spec.tools.get_definitions(),
        )
        if estimate <= budget:
            return messages

        system_messages = [dict(msg) for msg in messages if msg.get("role") == "system"]
        non_system = [dict(msg) for msg in messages if msg.get("role") != "system"]
        if not non_system:
            return messages

        system_tokens = sum(estimate_message_tokens(msg) for msg in system_messages)
        fixed_tokens, _ = estimate_prompt_tokens_chain(
            self.provider,
            spec.model,
            system_messages,
            spec.tools.get_definitions(),
        )
        remaining_budget = max(0, budget - max(system_tokens, fixed_tokens))
        kept: list[dict[str, Any]] = []
        kept_tokens = 0
        for message in reversed(non_system):
            msg_tokens = estimate_message_tokens(message)
            if kept and kept_tokens + msg_tokens > remaining_budget:
                break
            kept.append(message)
            kept_tokens += msg_tokens
        kept.reverse()

        if kept:
            for i, message in enumerate(kept):
                if message.get("role") == "user":
                    kept = kept[i:]
                    break
            else:
                # Recover nearest user message from outside the kept window;
                # GLM rejects system→assistant (error 1214).  Budget is
                # intentionally exceeded — oversized beats invalid.
                for idx in range(len(non_system) - 1, -1, -1):
                    if non_system[idx].get("role") == "user":
                        kept = non_system[idx:]
                        break
                # If no user exists at all, _enforce_role_alternation
                # will insert a synthetic one as a safety net.
            start = find_legal_message_start(kept)
            if start:
                kept = kept[start:]
        if not kept:
            kept = non_system[-min(len(non_system), 4) :]
            start = find_legal_message_start(kept)
            if start:
                kept = kept[start:]
        return system_messages + kept

    def _partition_tool_batches(
        self,
        spec: AgentRunSpec,
        tool_calls: list[ToolCallRequest],
    ) -> list[list[ToolCallRequest]]:
        if not spec.concurrent_tools:
            return [[tool_call] for tool_call in tool_calls]

        batches: list[list[ToolCallRequest]] = []
        current: list[ToolCallRequest] = []
        for tool_call in tool_calls:
            get_tool = getattr(spec.tools, "get", None)
            tool = get_tool(tool_call.name) if callable(get_tool) else None
            can_batch = bool(tool and tool.concurrency_safe)
            if can_batch:
                current.append(tool_call)
                continue
            if current:
                batches.append(current)
                current = []
            batches.append([tool_call])
        if current:
            batches.append(current)
        return batches