Codex desktop can hang when two long-running tool calls start in parallel in one turn

Bug Summary

Codex desktop can lose tool outputs and leave a turn permanently unfinished when two long-running tool calls are started in parallel in the same turn.

Environment

• Codex desktop app
• WSL enabled
• Workspace: /mnt/d/codex_app/the_answer_2
• Shell shown in UI: PowerShell
• Agent tool execution used bash/WSL
• Date observed: March 10, 2026
• Thread ID: 019cd7af-bd08-7f00-be1f-f75845805c4d
• Stuck turn ID: 019cd81a-8a4e-7832-a644-965a4e2da267

Repro Steps

1. Open a repo in Codex desktop.
2. Have the agent run two long-running verification commands in parallel in the same turn:

• flutter test
• flutter analyze

1. Wait for both tool calls to start.

Expected

• Each tool call returns function_call_output
• The agent receives both results
• The turn emits a final answer and task_complete

Actual

• At 2026-03-10T14:20:57Z, the turn emitted two function_call events for flutter test and flutter analyze
• No later function_call_output arrived for either call
• No task_complete event was emitted
• The session appeared stuck indefinitely

Evidence

• Last agent message before the hang:
• 分類功能主流程已通。現在跑完整 flutter test 與 flutter analyze，確認沒有回歸與 lint 問題。
• Rollout file:
• C:\Users\love1\.codex\sessions\2026\03\10\rollout-2026-03-10T20-19-04-019cd7af-bd08-7f00-be1f-f75845805c4d.jsonl
• The rollout stream shows both tool calls being issued, then no tool outputs and no task_complete
• A later session in the same repo completed successfully, so the repository itself was not in a broken state

Important Non-Causes

• No lingering flutter or git subprocesses were present when inspected
• The repository later verified cleanly in a separate session
• Failed to create shell snapshot for powershell: Shell snapshot not supported yet for PowerShell appeared in logs but does not look like the direct cause
• This looks more like tool transport / turn orchestration failure than project code failure

Likely Trigger

Parallel long-running tool calls in one turn, especially flutter test plus flutter analyze