Agent State Migration v2

Status: HOSTED GREEN for the bounded v0.4.0 migration implementation.

Audience: runtime integrators and compiler contributors.

The v0.4.0 release baseline supersedes the former local-only status for pure-call, cumulative-accounting, and joined-runtime integration from an actual durable Suspend.

migrate_suspended_agent_runtime_v2 consumes three independently bound inputs: the previous AgentRuntimeV2, the AgentRuntimeV2DurableEvidence produced by that runtime's live durable invocation, and a newly bound destination runtime. The previous and destination execution revisions are checked against caller supplied expectations; the durable evidence must belong to the previous revision; and the program roots must differ. A terminal result, an effect failure, a fabricated checkpoint, or stale revision is refused before migration or destination host work.

The producer must have reached an actual Suspend. Its checkpoint journal is parsed only to count the producer's acknowledged stage reservations, while the retained state is taken from the checked lifecycle run. Evidence and checkpoint bytes carry no migration authority. The old state is required to be a bounded flat record with persistent identity and scalar or byte leaves. The destination must retain the old state schema and provide a second bounded flat state schema.

The selected migration function is checked as a pure, deterministic OldState -> NewState call. It is evaluated twice against the exact retained state and both outcomes must match. The result must be a destination nominal record. Migration fuel is reserved cumulatively with prior usage and bounded by the supplied ceiling; prior calls, bytes, iterations, and stage reservations must fit the destination ceilings before the pure call is admitted.

On success the destination runtime receives the checked migrated state through an internal seed. Its next live invocation obtains fresh stage authorizations and may perform new injected host work. Migration evidence reports the previous and destination roots, the pure migration root, cumulative usage, and the destination typed effect evidence. No checkpoint authority, host capability, filesystem, network, provider, or publication authority crosses the migration boundary.

The focused integration gate uses the shared typed fixture, mutates the old reducer to produce a real Suspend, adds a pure state extension to the destination source, and verifies three prior calls plus three post-migration calls, cumulative bytes and reserved fuel, increased stage counts, stale revision rejection, and destination ceiling exhaustion before host work.

The integration also verifies that the destination does not execute initialize, that the migrated State survives a different destination task input, and that an exhausted pure migration returns its reserved fuel in failure accounting. This v2 destination continuation produces in-memory execution evidence. Persisted handoff, checkpoint recovery, and repeated migration chains are implemented by the additive v3 contract rather than added to this frozen v2 profile. Automatic reconciliation remains separate functionality.

Durable migration v3 extends this consuming preparation with persisted handoff and destination recovery. Its release evidence is hosted green under the same v0.4.0 baseline, with its own wire and trust boundaries.