Status: accepted · ADR-8 · Filed 2026-04-17
Decision
Add a new MCP verb hd_exec (short for ‘handoff execute’ / ‘handoff pickup’). Symmetric counterpart to prism_wrap: prism_wrap closes a session, hd_exec opens one for an inherited thread. Behavior: (1) resolve PID from project_dir match or prompt; (2) fetch last prism_handoff doc for this PID; (3) return structured payload with status_card (last handoff author+timestamp, focus field, next_agent), recent session deltas, TODOs tagged to the handoff focus, ADRs in the recent window, retros for current phase, any Ring 4 drift warnings; (4) set a session marker so the subsequent prism_wrap knows this was a handoff pickup (enables Ring 4 enforcement: ‘you picked up a handoff but didn’t address the focus items’). CC and Codex should surface hd_exec as a lightweight entry point — a single verb/command agents type or run on session start when continuing another agent’s work.
Rationale
Today prism_handoff writes the handoff doc but there is no symmetric verb to READ it as the pickup ritual. Agents continuing another agent’s work must manually call prism_start + search past chats + reconstruct the thread. hd_exec makes cross-agent continuity a single tool call. The session-marker semantics matter: without it, Ring 4 enforcement cannot distinguish ‘fresh session on this project’ from ‘picking up a handoff’ — and those have different accounting obligations. This is the verb that operationalizes the shared-memory thesis of Prism.
Alternatives Considered
Overload prism_handoff with a mode parameter (handoff write-mode vs read-mode) — conflates two verbs with opposite directions. Use prism_start for handoff pickup — but prism_start is project-level; hd_exec is handoff-level (pick up a specific thread, not just project state). Make it a CC slash-command only — but then Codex and other MCP clients can’t use it.
