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storkit: create 453_bug_agent_pty_crashes_with_fatal_runtime_error_on_restart_after_gate_failure

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dave
2026-03-31 14:13:22 +00:00
parent 49a8a23d75
commit 3f97e34f21
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@@ -9,11 +9,14 @@ name: "Agent PTY crashes with fatal runtime error on restart after gate failure"
When an agent completes coding and the acceptance gates fail (e.g. a test failure), the pipeline restarts the agent on the same worktree. The restarted Claude Code PTY process crashes immediately with `fatal runtime error: assertion failed: output.write(&bytes).is_ok(), aborting`. The process exits in the same second it spawns (Session: None), burns through all 3 retries, and blocks the story. When an agent completes coding and the acceptance gates fail (e.g. a test failure), the pipeline restarts the agent on the same worktree. The restarted Claude Code PTY process crashes immediately with `fatal runtime error: assertion failed: output.write(&bytes).is_ok(), aborting`. The process exits in the same second it spawns (Session: None), burns through all 3 retries, and blocks the story.
Key observations: Key observations:
- Running `claude -p "hello"` manually in the same worktree works fine (no crash) - The crash is **deterministic, not intermittent**: the first PTY spawn in a worktree always works; the second spawn (restart) always crashes
- The crash happens specifically when spawned via portable-pty in `agents/pty.rs` - Running `claude -p "hello"` manually in the same worktree works fine (no crash) — the issue is specific to spawning via portable-pty
- The worktree is clean (all changes committed) — the agent has nothing to do but fix the gate failure - The worktree is clean (all changes committed) — the agent has nothing to do but fix the gate failure
- The crash is inside the Claude Code binary, not storkit code - The crash is inside the Claude Code binary, not storkit code
- Observed on stories 449 and 450 — both had their coding done but failed the same unrelated test - Observed on every story that needed a restart: 329, 400, 420, 438, 446, 449, 450
- Stories that passed gates on the first run were never affected — they never triggered a second spawn
Likely cause: the reader thread spawned by `std::thread::spawn` in `pty.rs` (line 248-255) is never joined. After `run_agent_pty_streaming` returns, the pipeline immediately calls `start_agent` for the retry, but the old reader thread may still be running and holding a cloned PTY reader fd. The new PTY allocation could collide with the still-open fd from the previous session.
The root cause is unknown. It is NOT caused by zombie process accumulation (that is a separate issue in #452). The root cause is unknown. It is NOT caused by zombie process accumulation (that is a separate issue in #452).