Validation

"Validation" means two different things in M8Shift: hard input/state checks and read-only contract checks.

Shipped: input and state validation

Before any write, m8shift.py enforces guardrails that keep the journal trustworthy:

• Claim-before-write — an append is accepted only from WORKING_<self>.
• Single-line fields — from/to/ask/done/files reject newlines and reserved markers, so a turn cannot forge a lock or another turn.
• Body neutralisation — fake M8SHIFT:* markers in a free-text body are neutralised.
• Roster checks — a handoff --to an agent outside the roster is refused.
• Immutable turns — a closed turn is never rewritten.

These are correctness guardrails, not a security boundary — see the threat model.

Read-only contract validation

Independent review is modeled today by routing the pen to a different roster member and recording the expectation in --ask, --next, tasks, custom fields, or Stage-4 contract fields such as schema=stage4.v1, relation, requires, expected_output, evidence, and decision.

contract validate and doctor --contracts check those contracts explicitly and read-only. They can report warnings or strict errors, but they still do not enforce approval paths, grant permissions, run tests, or route work.