[Castor-o7]

MUS-107 fixes the root cause behind the ghost rows that MUS-104's waiter ran into. robust-warbler filed it and handed it over.

The bug: both the shim and the waiter take sessionId from ~/.claude/sessions/<pid>.json. Claude leaves that file behind when it dies without cleaning up. Once the pid is reused, an unrelated process's shim or waiter would pick up a dead session's id.

The fix: manifest_is_live in crates/shim/src/session_discovery.rs trusts a manifest only when all of these hold:

• it names that pid
• a process holds the pid
• on Linux, the manifest's procStart equals field 22 of /proc/<pid>/stat, the process's start time in clock ticks; Claude records exactly that value, and I checked it against a live session on Murph
• off Linux, or when there's no procStart, the process didn't start after the manifest's startedAt, allowing 2 s of slack; macOS checks that a process holds the pid with kill(pid, 0)

Two readers apply it:

• discovery's tier 0
• canonical_session_id, which MUS-104's waiter (superseded) and the shim's drift check read

Anything that can't be read is trusted, so an older Claude's manifest, or a platform that can't report these things, behaves as it did before. A stale manifest is skipped with a warning, and discovery falls through to the other tiers.

The process probe is threaded through resolve_under, the existing test seam. The real callers pass real_liveness. Existing tests use made-up pids, so they pass unprobed, which is what the behaviour was before this change.

Tests:

• a live manifest is trusted
• a reused pid, where procStart differs, is refused
• a pid with no process is refused
• an unreadable start time is trusted
• a missing manifest returns nothing
• the wall-clock fallback (a process younger than the session is stale; the slack holds; a manifest naming another pid is stale; an old manifest with neither field is trusted)
• parsing /proc stat with a comm that contains parentheses
• the real probe on this process

Local results: fmt, clippy --workspace --all-targets -D warnings and cargo test --workspace are clean. I can't cross-compile here, so the macOS and Windows paths are covered by CI only.

🤖 Generated with Claude Code