fix(runner): use export endpoint for get_session_events to prevent freeze

[Gkrumbach07]

Summary

• Root cause: acp_get_session_status was calling the /agui/events endpoint, which is an SSE (Server-Sent Events) stream that never closes. urllib.request.urlopen blocks waiting for the response to finish, causing the agent to freeze for 30 seconds (the timeout).
• Fix: Switch to the /export endpoint which returns all historical AG-UI events as a regular JSON response, no streaming.

Follows up on #1006.

Test plan

• 22 tests pass
• Manual: call acp_get_session_status on a running session — should return immediately with status + recent messages

🤖 Generated with Claude Code

[coderabbitai]

Walkthrough

Session events retrieval was changed to use the session /export endpoint and a fixed max-events approach. The BackendAPIClient signature removed thread_id and limit in favor of max_events and now parses aguiEvents (list or JSON string). Caller code was updated to call the API with only the session identifier.

Changes

Cohort / File(s)	Summary
Backend API — session export components/runners/ambient-runner/ambient_runner/tools/backend_api.py	Replaced /agui/events SSE-style fetch with /export fetch. Removed thread_id/limit parameters; added max_events and class constant _MAX_EXPORT_EVENTS = 200. Parses aguiEvents as list or JSON string and returns the last N events.
Caller update — session status components/runners/ambient-runner/ambient_runner/bridges/claude/backend_tools.py	Updated acp_get_session_status to call get_session_events(session_name=...) without heuristic limit scaling; removed the related explanatory comment. Event extraction/truncation logic unchanged.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: switching from the SSE /agui/events endpoint to the /export endpoint to prevent agent freeze.
Description check	✅ Passed	The description is directly related to the changeset, explaining the root cause (SSE streaming blocking behavior) and the solution (switching to /export endpoint).
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch worktree-better-acp-tools

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@components/runners/ambient-runner/ambient_runner/tools/backend_api.py`:
- Around line 293-305: The current export call fetches the entire session
history which can be huge; modify the request to use a bounded contract (append
a limit query param to the path variable before calling _make_request, e.g.
"/projects/{self.project_name}/agentic-sessions/{session_name}/export?limit={MAX_EXPORT_EVENTS}")
and introduce a local cap constant (e.g. MAX_EXPORT_EVENTS) to guard
client-side; after receiving response in the current method, parse as before but
if events is a list or a decoded JSON string, trim/slice it to MAX_EXPORT_EVENTS
before returning to avoid full-history transfers and parses.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 7799a783-198f-493b-9f57-18604988ff32

📥 Commits

Reviewing files that changed from the base of the PR and between 0467664 and a3a71bb.

📒 Files selected for processing (2)

• components/runners/ambient-runner/ambient_runner/bridges/claude/backend_tools.py
• components/runners/ambient-runner/ambient_runner/tools/backend_api.py

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@components/runners/ambient-runner/ambient_runner/tools/backend_api.py`:
- Around line 277-278: The constant _MAX_EXPORT_EVENTS was lowered to 200, which
breaks the previous behavior of fetching limit=max_messages * 10 events; to fix
this, update the call in backend_tools.py that fetches exported events (the call
that currently only passes max_messages) to pass an explicit
max_events=max_messages * 10 (or alternatively restore _MAX_EXPORT_EVENTS to
500) so the event fetch retains the previous multiplier and sparse
TEXT_MESSAGE_CONTENT events don't drop messages.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 60b14e65-42a5-4d9a-b7e2-173c4231797a

📥 Commits

Reviewing files that changed from the base of the PR and between a3a71bb and c2b7a32.

📒 Files selected for processing (1)

• components/runners/ambient-runner/ambient_runner/tools/backend_api.py