PLAN — P2a MCP Signal Follow-Up Claim Pack¶

Status: Shipped on main (built-in pack mcp-signal-followup)
Date: 2026-03-23
Owner: Evidence / Product

Goal¶

Productize G1/G2/G3 signals as a small companion pack (not baseline expansion): MCP-001 aligns with Trust Basis G3 via a shared predicate in assay-evidence; MCP-002/003 use existing YAML check types.

Pack identity¶

Field	Value
Name	`mcp-signal-followup`
Version	`1.0.0`
Rules	MCP-001, MCP-002, MCP-003

Engine¶

Pack engine v1.2 (see crates/assay-evidence/src/lint/packs/checks.rs ENGINE_VERSION).
MCP-001 sets engine_min_version: "1.2" for g3_authorization_context_present.

Implementation¶

src/g3_authorization_context.rs: Shared G3 v1 predicate; trust_basis::classify_authorization_context delegates to bundle_satisfies_g3_authorization_context_visible.
CheckDefinition::G3AuthorizationContextPresent: YAML type: g3_authorization_context_present.
Tests: crates/assay-evidence/tests/mcp_signal_followup_pack.rs — open/built-in parity; MCP-002/003 smoke tests; MCP-001 alignment: bundles for which Trust Basis sets authorization_context_visible to verified do not emit an MCP-001 finding; bundles for which that claim is absent do emit an MCP-001 finding (same synthetic bundles as Trust Basis tests — not a separate informal inverse).

`assay_min_version` (pack `requires`)¶

SSOT for version floors and release checklist: MIGRATION-TRUST-COMPILER-3.2.md (do not duplicate semantics elsewhere).

Pack YAML uses >=3.2.3 to track the first released Assay line with G3 evidence + Trust Card schema 2 + seven claims (git tag v3.2.3 is the reference for that prerequisite substrate; it is not the “first tag that contains this pack”).

Release truth for the built-in pack: Tag v3.2.3 does not include mcp-signal-followup, pack engine v1.2, or g3_authorization_context_present — those land with the P2a change. At crates.io / GitHub release time, either:

bump the workspace version (e.g. to 3.2.4) and set assay_min_version to >=3.2.4 (or whatever version first tags P2a), or
keep >=3.2.3 but document in release notes that the built-in mcp-signal-followup is only present in binaries from the commit range that includes P2a (the requires field then expresses evidence contract floor, not pack feature floor).

Reviewers should confirm the chosen floor against the first published Assay version that embeds this pack.

Non-goals¶

Authorization validity, issuer trust, correlation-only rules, A2A, engine-wide DSL expansion.

Semantics note¶

P2a adds no new trust-claim classification in Trust Basis: it consumes the existing G3 kernel in the pack executor. Wording like “no new classifier wave” means no new claim keys or classification rules beyond factoring shared G3 logic into g3_authorization_context.rs.