ADR-0159 - Companion and task binding

Context

A task could claim any source spec and still check clean. Review companions bypassed their own hard checks. The task method required dependency order, but C022 did not.

Decision

1. Task checks bind a spec. Every checked task receives an explicit --spec companion. The spec must be ready, clear its hard checks, and match the task's source: list. One companion may bind several task paths only when they all name that spec.
2. Review companions clear their hard checks. A review does not reconcile against a malformed spec or task. Companion warnings remain advisory.
3. C022 owns dependency handoff. Run order is required exactly once. It carries non-empty Starts after: and May run with: values; None is explicit and valid.
4. The contract advances to 0.21.0. No check ID is added or repurposed. C022 gains the shape it already claimed; companion failures remain usage errors.
5. MCP stays thin. specPath may accompany task paths or one review. taskPath remains valid only for one review. The adapter forwards; the CLI decides validity.

Narrowed decisions

• ADR-0143: task source specs join explicit review companions.
• ADR-0152: C022 includes dependency handoff.
• ADR-0153: exact compatibility advances to 0.21.0.
• ADR-0154: spec-backed task authority is enforced at check time.
• ADR-0158: companions must be valid before their identity can bind another artifact.

Consequences

• Missing, stale, draft, malformed, or mismatched task sources cannot dispatch cleanly.
• A review cannot launder a malformed companion into a clean reconciliation.
• Split tasks always state their dependency position.

Status

Accepted (2026-07-13). Narrows ADR-0143 and ADR-0152 through ADR-0154 and ADR-0158.