gemini-cli background tasks stuck RUNNING after child exit when stdio pipes stay open

Finding: In google-gemini/gemini-cli issue #29405 (CLI version unknown), background tasks started via run_command and polled via manage_task are reported to stay RUNNING after the child process has exited or failed. This is an external report with no KFA reproduction. Maintainers have not confirmed a cause or a fix. Reported symptom: the reporter describes a PowerShell command with a syntax error that exited at once while the task showed RUNNING for 2h52m. They cite telemetry from 49 sessions on Windows and Linux/WSL: 191 manual kills and 630 status-polling loops (https://github.com/google-gemini/gemini-cli/issues/29405). That telemetry is the reporter's own and unverified. They propose three causes: unclosed stdio pipes, interactive pagers or watch commands, and WSL 9P deadlocks on Windows mounts. None is maintainer-confirmed. Independent partial evidence: a commenter reports that on Linux/macOS, plain Node.js spawn of a shell that backgrounds a child and exits shows exit after about 5 ms but close only after about 20.5 s. The backgrounded process inherits stdout, so close waits for it (https://github.com/google-gemini/gemini-cli/issues/29405#issuecomment-5903706094). This shows one plausible mechanism, namely a task runner that waits on close rather than exit. It does not show that gemini-cli is implemented this way, and it does not cover the PowerShell or WSL cases. Proposed mitigations, not verified in gemini-cli: the commenter notes that destroying the streams on exit stops the hang but leaves the pipe-holding process running. They suggest bounding the drain after exit, then signalling the process group and reporting reaped residual processes. They also warn that a bare PID liveness check can be fooled by PID reuse, so start time should be compared and unknown state reported as unknown (same comment). The original proposals of a 15-second watchdog, a 600s default timeout and a cancel button are the reporter's suggestions only. Diagnostic takeaway: if a background task stays RUNNING after its shell has exited, check whether the command left a backgrounded descendant holding stdout or stderr. This is a hypothesis from the external comment, not a confirmed gemini-cli cause. Status: the issue is open. A contributor only asked for the CLI version (https://github.com/google-gemini/gemini-cli/issues/29405#issuecomment-5739622493). No fix or release is cited in the supplied sources. Comment coverage may be partial.