[JacobStephens2]

Summary

Live Sessions remain interruptible after CLI exit, and unread prompts cannot block supervision. Sessions, Muse/OpenCode checks and OpenCode export share one Harness process owner.

spawn child + stdout + optional stdin/stderr workers
supervise until child exits AND every worker finishes
on interruption or transport failure:
  adapter.stop → reap child → join all started workers
return exit status + consumed output

Session logging preserves raw bytes and live progress. Consumer failures retain the partial stream for after-exit recovery, warnings and elapsed/usage reporting before returning the original error. The old captured-execution module is removed.

Evidence

• Before: interrupting_a_live_session_after_cli_exit_stops_the_command_holding_stdout failed on main: interruption waited for the finite stdout holder's natural expiry.
  After: passes with the under-two-second SIGINT bound and owned-command termination assertion. The equivalent captured regression uses the same bound.
• Before: the review regression a_log_failure_still_recovers_and_reports_warnings_and_usage failed because a logging error skipped the warning and recovered usage summary.
  After: passes, preserving the original BrokenPipe error, once-only warning and exported usage summary.
• Validation: cargo fmt --check, cargo check --all-targets, cargo clippy --all-targets -- -D warnings, and full cargo test passed on Linux: 1,184 tests passed, 0 failed, across 39 test binaries.
• Seams under test: Harness process output and streaming; the thirdshift CLI in process-isolated Scenario regressions. Coverage includes exact captured bytes/status, raw streamed bytes, stdin transport/closure, EOF before exit, retained stdout/stderr after exit, unread/broken prompts, consumer failure/panic, escaped-group cleanup and normal background-work survival.
• Review against main: Standards had no findings; Spec finding P1 was addressed and both reviewers rechecked the final diff.

Merge Danger

Door: two-way

The implementation can be reverted without a configuration or data migration.

Blast Radius: Harness

Changes session/check/export process lifetimes across all six Harnesses. Adapter stop signals and ten-second grace periods are retained.

Unaddressed findings

Standards

None. No Standards findings were raised.

Spec

None. P1 was addressed; no Spec findings were skipped.

Closes #448

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