`[2026-06-30]` **Verify-against-the-real-spec-before-committing caught a real upstream gap.** Holding the v0.18.3 commit to verify against demo's OpenAPI surfaced that the FROZEN OpenAPI 2.1.0 didn't document the 409/503 the heads-up described (`agent_not_available` was in the ErrorCode enum, but NO 503/turn-launch code). worldtree-dev confirmed it was THEIR gap (#331 added the statuses without extending the #328 `openapi()` override), shipped the fix in **v1.0.0b2 / OpenAPI 2.2.0** (409/503 now enumerated, 503 code finalized as `not_ready`). "The consumer-oracle earning its keep." Lesson: a provider's prose heads-up can diverge from its frozen machine-readable spec — verify the actual spec before committing a consumer adaptation.