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Fix background task liveness probe after session resume - #215

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zevorn merged 4 commits into
PolyArch:devfrom
SwordFaith:fix/bg-task-output-path-from-transcript
Jul 17, 2026
Merged

Fix background task liveness probe after session resume#215
zevorn merged 4 commits into
PolyArch:devfrom
SwordFaith:fix/bg-task-output-path-from-transcript

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Problem

When a Claude Code session is resumed or continued, the current transcript may have a different session id from the session that originally launched a
background task. The task's .output file physically lives under the old session directory, but the stop hook's liveness probe derived the output path
from the current transcript's session id. As a result, dead/orphaned tasks were never pruned and the loop was blocked from reaching Codex review.

Fix

Teach is_bg_task_alive to look up the real output file path recorded in the transcript's launch message:

  • Add extract_bg_task_output_path_from_transcript() to parse the "Output is being written to: " line.
  • Prefer the real path when available; fall back to the derived tasks_dir path when the transcript is unreadable or the message is missing.
  • Pipe the new optional transcript_path argument through prune_dead_bg_task_ids and list_pending_background_task_ids.

Test

Add regression test AC-25: simulate a session resume with a new-session transcript that records an old-session output path, then assert the dead task is
pruned using the real path rather than the derived new-session path.

42/42 tests pass.

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Comment thread hooks/lib/loop-bg-tasks.sh Outdated
@SwordFaith
SwordFaith force-pushed the fix/bg-task-output-path-from-transcript branch from d795398 to 8929fb0 Compare June 15, 2026 12:49
SwordFaith added a commit to SwordFaith/humanize that referenced this pull request Jun 26, 2026
Fix A - TaskStop completion recognition: list_pending_background_task_ids now treats a TaskStop tool_result (.toolUseResult.message "Successfully stopped task: <id>") as a terminal completion event, because many Claude Code builds do not also emit a task_notification system record for a TaskStop. The id is read from .task_id, falling back to parsing it out of the message text when that field is absent. The message field is coerced with tostring before contains() so unrelated tool results carrying a structured (object/array/number) .message do not error and wipe the whole completed set under pipefail.

Fix B - cross-session liveness glob: is_bg_task_alive now searches sibling session dirs under the same project slug when neither the transcript-recorded output path nor the session-derived path exists. This only expands where we look, so a genuinely alive task is never wrongly pruned; a file missing everywhere still fails open as before.

Builds on the extract_bg_task_output_path_from_transcript helper landed in PolyArch#215.

Tests: 51/51. Renames existing AC-NN cases to descriptive names and adds regression coverage for TaskStop completion, the cross-session glob, and non-string .message poisoning.
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zevorn commented Jul 7, 2026

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@codex review

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Comment thread hooks/lib/loop-bg-tasks.sh Outdated
The path extractor required the trailing 'You will be notified when it
completes.' sentence. When a Claude Code launch record omits it, the
regex returned no match, so is_bg_task_alive fell back to the derived
current-session path and dead/orphaned tasks stayed pending forever on
session resume.

Bound the match by the closing JSON string quote ([^"]*) instead of the
suffix sentence, and strip the optional suffix afterwards. Add AC-25c
covering the suffix-omitted launch form.

Discussion: PolyArch#215 (comment)
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zevorn commented Jul 14, 2026

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@codex review again

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Comment thread hooks/lib/loop-bg-tasks.sh Outdated
The path extractor used grep -F "$task_id", a substring match. Probing
"bash_1" also matched an earlier "bash_10" launch line, so head -n1
selected bash_10's output path; lsof then saw a dead file and pruned
the still-running bash_1, letting the stop hook reach Codex before
bash_1 finished.

Anchor the match on the exact backgroundTaskId JSON value by wrapping
the id in literal double quotes: "bash_1" cannot match "bash_10", and
the output path never contains a double quote so the boundary cannot
fall inside a path value.

Add AC-25d (selective lsof mock: bash_1.output alive, others dead;
bash_10 launched before bash_1) asserting the alive bash_1 still
short-circuits.

Discussion: PolyArch#215 (comment)
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@codex review again

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Reviewed commit: 1034c93ad2

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Comment thread hooks/lib/loop-bg-tasks.sh Outdated
Comment on lines +172 to +174
match=$(grep -F "\"$task_id\"" "$transcript_path" 2>/dev/null \
| grep -oE 'Output is being written to: [^"]*' \
| head -n1) || true

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P2 Badge Decode JSON before using recorded output paths

When the recorded output path contains JSON-escaped characters, such as a project slug with a literal backslash, this pipeline reads the raw JSONL text and returns the escaped spelling (for example /tmp/.../foo\\bar/...) rather than the actual filesystem path (/tmp/.../foo\bar/...). [[ -f "$output_file" ]] then fails and the dead Bash task is treated as still running forever; this also regresses same-session probes that previously used the correctly derived path. Extract the text via jq/JSON decoding before passing the path to lsof.

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Root cause: extract_bg_task_output_path_from_transcript read the raw JSONL line and regex-extracted the path with grep -oE 'Output is being written to: [^"]*'. The path lives inside a JSON string value, so any character JSON must escape comes through in its escaped spelling — a literal backslash in the path is serialized as "\". [[ -f "$output_file" ]] then checked the doubled-backslash path, missed the real file, is_bg_task_alive failed open, and the dead task was treated as alive forever. The stop hook never reached Codex, and same-session probes that previously used the correctly derived path regressed too, as you noted.

Fix: keep the quote-anchored grep -F ""$task_id"" that selects the launch record by exact backgroundTaskId (so bash_1 is still not confused with bash_10), then decode that record's text field with jq -r '.message.content[]?.content[]? | select(.type == "text") | .text' so the extracted path matches the filesystem. jq is already a hard dependency of every validator hook; when it is absent the function falls back to the derived tasks_dir path (the pre-transcript-extraction behavior), preserving the fail-open contract.

Regression coverage: added AC-25e — a dead task whose recorded output path contains a literal backslash (tasks/with\backslash/...) is pruned via the decoded path. Confirmed the test has teeth: with the old raw-grep extraction AC-25e fails (escaped path → [[ -f ]] fails → treated alive → stop hook short-circuits and never reaches Codex), and with the fix it passes. Full suite 46/46.

@zevorn could you take another look?

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Codex Review: Didn't find any major issues. Nice work!

Reviewed commit: 1034c93ad2

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  • Comment "@codex review".

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extract_bg_task_output_path_from_transcript read the raw JSONL text and
regex-extracted the path, so JSON-escaped characters came through in their
escaped spelling: a literal backslash in the path was doubled to "\\".
[[ -f ]] then missed the real file, is_bg_task_alive failed open, and the
dead task was treated as alive forever -- the stop hook never reached
Codex and same-session probes regressed.

Keep the quote-anchored grep that selects the launch record by exact
backgroundTaskId, then decode the record's text field with jq -r so the
extracted path matches the filesystem. Require jq (already a hard
dependency of every validator hook) and fall back to the derived
tasks_dir path when it is absent.

Regression coverage: AC-25e -- a dead task whose recorded output path
contains a literal backslash is pruned via the decoded path. Old raw-grep
code fails AC-25e (escaped path -> [[ -f ]] fails -> treated alive);
the fix passes. Full suite 46/46.
@zevorn

zevorn commented Jul 17, 2026

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LGTM! Thanks for the contribution.

@zevorn
zevorn merged commit 075db6b into PolyArch:dev Jul 17, 2026
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SwordFaith added a commit to SwordFaith/humanize that referenced this pull request Jul 18, 2026
Fix A - TaskStop completion recognition: list_pending_background_task_ids now treats a TaskStop tool_result (.toolUseResult.message "Successfully stopped task: <id>") as a terminal completion event, because many Claude Code builds do not also emit a task_notification system record for a TaskStop. The id is read from .task_id, falling back to parsing it out of the message text when that field is absent. The message field is coerced with tostring before contains() so unrelated tool results carrying a structured (object/array/number) .message do not error and wipe the whole completed set under pipefail.

Fix B - cross-session liveness glob: is_bg_task_alive now searches sibling session dirs under the same project slug when neither the transcript-recorded output path nor the session-derived path exists. This only expands where we look, so a genuinely alive task is never wrongly pruned; a file missing everywhere still fails open as before.

Builds on the extract_bg_task_output_path_from_transcript helper landed in PolyArch#215.

Tests: 51/51. Renames existing AC-NN cases to descriptive names and adds regression coverage for TaskStop completion, the cross-session glob, and non-string .message poisoning.
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