Arm A: honker-core linked on our rusqlite (bridge per REQ-TTY-01, honker's watcher). Arm B: honker extension .so over sqlx-sqlite (natively async call path, own watcher, per-pool-connection extension + bootstrap — stress-testing what the CI proof script doesn't cover: pool wiring, lost connections, full surface). Option 2 (honker-rs-as-substrate) dropped from scope with reasoning: its mutex-pinned sync transaction model is subsumed by both other postures' trade space. Five probes (async seam, watcher, transactional contract, packaging, cross-process interop), a decision gate including a legitimate hybrid verdict, and out-of-scope boundaries (postgres side, full surface, extension-as-consumer-feature regardless of outcome). Phase-0: POC register added, plan/frontmatter updated; AGENTS.md: POC-register convention codified.
