NEXO 7.8.2 — hook_runs sid observability closed

Published 2026-04-23. Patch release over v7.8.1.

v7.8.0 shipped compaction continuity (PostCompact as a real registered hook, exact SID via CLAUDE_SESSION_ID, per-conv sidecar, fail-closed on mismatch). v7.8.1 patched the Layer-2 emergency auto-diary and Layer-3 record_auto_flush to use the same exact target SID instead of "latest active session". Francisco audited the resulting telemetry and found one remaining gap: hook_runs.session_id was empty for 7 out of 8 recent compaction rows, and when populated it stored the raw Claude Code token instead of the NEXO sid. Per-session queries over hook_runs for compact events therefore could not be joined back to the NEXO session that actually compacted.

What v7.8.2 changes

New src/hooks/compact_session_resolver.py with resolve_nexo_sid(claude_session_id). It walks the same rails the shell uses: sessions.claude_session_id match, then session_claude_aliases.claude_session_id (most recent last_seen wins), then the per-conversation sidecar under runtime/data/compacting/<safe-claude-id>.txt, then the legacy global sidecar for single-conversation setups. Returns (nexo_sid, source).
src/hooks/pre_compact.py and src/hooks/post_compact.py now call the resolver and store the real NEXO sid in hook_runs.session_id. Both wrappers also stash {claude_session_id, sid_source} in hook_runs.metadata, so "why is this row still empty?" becomes a one-query answer.

Tests — the empty-state rail is the one we actually care about

Nine new tests in tests/test_hook_runs_compact_sid_resolution.py:

Five resolver rails: sessions match, alias match (newest wins), per-conv sidecar fallback, legacy global sidecar, and the none outcome when nothing matches.
Malformed sidecar rejection: non-NEXO-shaped content must not poison hook_runs.session_id — the resolver returns ("", "none") instead.
Pre-compact and post-compact wrappers end-to-end via a stubbed hook_observability: assert both session_id and metadata are captured with the correct values on a sessions hit and an alias hit respectively.
Empty-state wrapper path: when nothing resolves, the row is still written with session_id='' and sid_source='none' so the audit trail stays diffable instead of being silently skipped.

No Desktop bump

Entirely Brain-side. Desktop v0.27.0 continues to ship.

Live smoke

First compaction after the update emitted a hook_runs row carrying the resolved NEXO sid (nexo-NNNNNN-N) plus the raw Claude token in metadata.claude_session_id and metadata.sid_source='alias'. Per-session SELECT * FROM hook_runs WHERE session_id = ? joins work again end-to-end.