Closes Stream H Task 7 (H7). Prevents two Claude sessions on the same
workspace from concurrently mutating files — addresses the cross-session
worktree collisions seen on 28.05/29.05 (deploy branch hijack + push
non-fast-forward incidents).
Architecture:
- Pure module tools/parallel-session-lock.mjs with injectable I/O
(readLock/writeLock/deleteLock) so unit tests cover all branches without
touching the real filesystem. Exports acquire(), refresh(), release(),
computeWorkspaceHash(), LOCK_DEFAULT_TTL_MS (5 minutes).
- Lock record schema (schema_version=1): {session_id, pid, acquired_at, ttl_ms}.
Stored at ~/.claude/runtime/session-lock-<workspaceHash>.json (production
binding handled in deferred batch). Workspace hash is MD5 first-12 hex of
the resolved workspace path.
- Acquisition semantics: stale (past TTL) → take over; same-session → idempotent
re-acquire; other-session fresh → block. refresh() is same-session only
(never steals). release() is same-session only (never deletes other's lock).
- Wrapper tools/enforce-parallel-session-lock.mjs exports decide(acquireResult,
sessionId) → {block, reason?}. Fail-open if acquireResult is missing
(internal-error safety net — avoids the Stream G Task 8 self-lockout
pattern). Block message names the other holder's pid for human triage
("parallel session lock held by <other> (pid N) — wait or close that
session first").
Defensive design:
- main() is a no-op (exit 0) until settings.json registration AND a Stop-hook
release pathway are wired together in the batched activation step. Activating
this hook before release-on-Stop would lock the user out of their own
session on first abnormal exit.
Regression: vitest tools 1763/1763 GREEN (was 1748; +10 pure-module tests
under "parallel-session-lock pure module (Stream H Task 7)" and
"computeWorkspaceHash (Stream H Task 7)" describe blocks; +5 wrapper-decide
tests under "enforce-parallel-session-lock wrapper (Stream H Task 7)").
DEFERRED: .claude/settings.json registration (PreToolUse matcher
"Edit|Write|MultiEdit|NotebookEdit|Bash", block-mode, timeout 3000ms);
Stop-hook release wiring; PostToolUse refresh-on-success wiring.
Batched at end of Phase H-α/H-β.
Stream H Task 7 of 11. Plan: docs/superpowers/plans/2026-05-30-router-gate-v4-stream-H.md
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