ADR-0153 - MCP parity and compatibility

Context

The MCP check tool accepted one primary path, so it could not expose the CLI's cross-file checks. It trusted CLI JSON without complete runtime validation and repeated verdict disclaimers in every response even though the data model already contains no verdict.

Decision

1. MCP accepts a path set. suspec_check takes a non-empty paths array of absolute primary artifact paths, passes the set through one CLI invocation, and preserves input order.
2. Review companions stay explicit. specPath and taskPath may accompany one review target. Multiple review targets with shared companions are rejected as ambiguous.
3. Compatibility is exact. The adapter validates every success and error payload at runtime and requires checks-contract version 0.18.0. A malformed payload or incompatible version fails structurally.
4. The envelope is lean. Responses contain ok, source, data, optional note, and responseFormat. No verdict flag or repeated no-verdict prose ships.
5. The boundary stays narrow. MCP retains the artifact check, checks-contract tool, and checks-contract resource. It adds no storage, discovery, orchestration, promotion, lifecycle, or artifact-management surface.

Narrowed decisions

• ADR-0085: shell-out architecture stands; runtime validation and exact contract compatibility are mandatory.
• ADR-0143: explicit primary paths and review companions stand; MCP now preserves multi-path CLI behavior.

Consequences

• MCP-capable runners receive the same cross-file facts as CLI users.
• Contract drift fails immediately.
• Responses spend no fields restating the absence of acceptance authority.

Status

Accepted (2026-07-13).