CliAgentEnv: add TASK_FINISHED stop-signal hook

[rasdani]

Summary

Adds an opt-in task_finished_signal: str | None = None parameter to CliAgentEnv and a matching @vf.stop hook (task_finished_signal_emitted) that terminates the rollout when the configured signal (e.g. "TASK_FINISHED") appears in the trailing tool-role messages of the agent's latest intercepted request.

The default (None) is a no-op, so existing envs are unaffected.

Motivation

rlm-style agents already expose a passive-stop path when the model returns tool_calls=[], but the model rarely takes that exit on its own. Analysis of v4-p1 step-27 rollouts showed a 54.5% rate of "summary-while-still-tool-calling" — the agent narrates that it's done while continuing to issue tool calls — whereas mini_swe_agent_plus's analogous MINI_SWE_AGENT_FINAL_OUTPUT ritual is emitted in 97.4% of its rollouts.

Giving CliAgentEnv the same "I'm done" ritual + automatic stop hook gives the engine a reliable way to terminate when the model commits to a fix.

Companion PR

This hook is paired with PrimeIntellect-ai/rlm-harness#60, which instructs the rlm agent (when bash is an active tool) to emit exactly one bash tool call with the command echo "TASK_FINISHED" when confident the task is complete. Either PR alone is a no-op; both together close the loop.

Design notes

• task_finished_signal defaults to None so the hook is opt-in; existing CliAgentEnv subclasses (e.g. rlm-swe harness configs) are not surprised.
• The scan only walks the trailing run of tool messages in the latest trajectory step's prompt; it does not traverse full history.
• Handles both Pydantic ToolMessage and dict-shaped intercepted messages.
• Substring match on content (not exact equality) so echo wrappers or output framing don't defeat detection.

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Note

Low Risk
Low risk: behavior is unchanged by default (task_finished_signal=None), and the new stop condition only triggers when explicitly configured based on recent tool-message content.

Overview
Adds an opt-in task_finished_signal parameter to CliAgentEnv and stores it on the instance.

Introduces a new @vf.stop check (task_finished_signal_emitted) that terminates the rollout when the configured signal is detected in the latest step’s trailing tool-role messages, allowing agents to end runs via a deliberate tool output marker.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Missing documentation for new task_finished_signal parameter

Low Severity

The new task_finished_signal parameter and its corresponding @vf.stop hook task_finished_signal_emitted add user-facing functionality to CliAgentEnv, but docs/environments.md (line 888) — which explicitly enumerates CliAgentEnv constructor parameters — was not updated to mention the new parameter or describe the stop-signal behavior. This violates the documentation update rule for changes to core user-facing functionality described in docs/.

 

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