Research: mission-create idempotency guard
Decision 1 — Duplicate key = same mission_slug AND mission_type (operator-decided)
Refuse only when a prior non-abandoned mission shares BOTH the slug and the type. A research and a software-dev mission named alike are different work. Rationale: matches the #4033 symptom (re-running the same command) with minimal false refusals.
Decision 2 — Abandonment-aware auto-allow (operator-decided)
A prior same-key mission that is abandoned does NOT trigger the guard. "Abandoned" = canceled, OR genesis / no lifecycle progress (no status.events.jsonl beyond scaffold / spec never committed). Source of truth = the status event log (reduced), consistent with the append-only status model. Rationale: the common "gave up and re-ran" path must not need a flag. Fail closed (C-002): if abandonment can't be read, treat as live and refuse.
Decision 3 — Escape hatch = explicit allow_duplicate (operator-decided)
create_mission_core(allow_duplicate=False) new param (mirrors existing opt-in flags); --allow-duplicate on agent mission create and /spec-kitty.specify; factory passes it. Not a blind same-slug refusal (the factory creates at volume) — the flag + abandonment awareness together cover the legitimate cases.
Seam grounding
_create_mission_core_impl (mission_creation.py) already funnels all callers and hosts the early guards (git-repo, unborn-HEAD, detached-HEAD) before scaffold write — the guard slots there. _list_mission_scaffolds() is the detection primitive.
Supply-chain
No dependency added/removed.