backlog(p3): B-0530 — cron-sentinel mutex to prevent multi-Otto-CLI self-contention

[AceHack]

Summary

Files B-0530 (P3, effort S) for the cron-sentinel-mutex mitigation candidate identified in PR #3370's worktree-prune-race root-cause analysis.

The pattern: two concurrent Otto-CLI claude-code sessions firing autonomous-loop ticks in parallel both invoke git worktree add, both contend on shared .git/objects/pack, both get rolled back by git's own automatic cleanup. The substrate-honest first mitigation is a top-of-tick pgrep check that defers when peer Otto-CLI is detected.

Why P3

• Failure mode is operationally observable via bus envelopes (substrate-honest fallback channel already established)
• Contention windows resolve naturally within minutes (peer's stuck git reset eventually exits)
• Not blocking ongoing work; just causing extra round-trips for affected ticks

Composes with

• B-0506 — sibling worktree-hygiene mechanization
• B-0519 — adjacent failure-mode family; Pattern 8 of the multi-Otto contamination space
• PR shard(tick): 0615Z — worktree-prune-race root cause identified (multi-Otto-CLI self-contention) #3370 — landed the root-cause analysis this row implements

Test plan

• Markdownlint clean locally
• CI green
• Auto-merge fires

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds a new P3 backlog row for B-0530, documenting a proposed cron-sentinel mutex to reduce multi-Otto-CLI contention around shared Git worktree operations.

Changes:

• Adds B-0530 with origin, problem statement, mitigation sketch, alternatives, acceptance criteria, and empirical anchors.
• Cross-links related backlog rows and operational rule surfaces.

Comments suppressed due to low confidence (1)

docs/backlog/P3/B-0530-cron-sentinel-mutex-prevent-otto-cli-self-contention-2026-05-15.md:73

• P1: Comparing the matched claude-code PID to process.pid does not exclude the current Otto-CLI session if this check runs as a child TypeScript process; process.pid is the checker process, while pgrep returns the parent claude-code process. That would make every tick see its own session as a peer and defer forever unless the implementation compares against the current process tree/session instead.

  const parts = line.trim().split(/\s+/);
  const pid = parseInt(parts[0] ?? "", 10);
  return pid && pid !== MY_PID;