v0.13.0 - Coordination Under Contention

Agent Memory Bridge 0.13 makes signal coordination easier to trust when several
agents or sessions poll the same namespace.

Thesis

0.13.0 = coordination under contention without turning the bridge into a task queue.

The public MCP surface remains the same 10 tools. The change is in the signal
contract: claim_signal(...) assigns work, extend_signal_lease(...) renews
ownership, and stale work must be reclaimed before it can be acknowledged.

What Shipped

• active same-owner claim_signal(...) calls no longer behave like lease renewal
• initial claims are capped by the signal hard expiry
• stale owners cannot ack_signal(...) after lease expiry
• generic claim selection filters eligible rows before the contention window, so
  active claims do not starve later pending work
• failed explicit claims return clearer reason codes such as already-claimed,
  claimed-by-other, expired, or lease-expired
• a signal contention benchmark slice for multi-consumer claim/reclaim/ack
  semantics
• release contract coverage for the new contention benchmark snapshot

Evidence

Current release snapshot:

• pytest: 194 passed
• public MCP tools: 10
• deterministic proof: 4/4 checks
• signal contention benchmark:
  • signal_contention_case_count = 5
  • signal_contention_case_pass_rate = 1.0
  • unique_active_claim_rate = 1.0
  • duplicate_active_claim_count = 0
  • active_reclaim_block_rate = 1.0
  • stale_ack_blocked_rate = 1.0
  • stale_reclaim_success_rate = 1.0
  • pending_under_pressure_claim_rate = 1.0
  • initial_hard_expiry_cap_rate = 1.0

Why It Matters

AMB is not only a memory store. It also carries lightweight handoff state. Under
repeated polling, stale leases, and competing consumers, that state needs to stay
legible. This release makes the ownership boundaries sharper without adding a
scheduler, worker runtime, or new MCP tools.

Honest Boundaries

0.13.0 does not mean:

• scheduler
• active worker runtime
• general queue platform
• distributed lock
• exactly-once distributed coordination
• dead-letter system

The contention benchmark is a repeatable serialized contract slice. It is not a
throughput benchmark or a claim that AMB is a full queueing system.

Next

Likely next candidates:

• pre-compaction capture before model-side context loss
• broader reviewed retrieval fixtures
• deeper real multi-client contention dogfood
• stronger write-side calibration for promotion quality

Pick one thesis for the next release instead of bundling them all together.