Phase Transition Journal

Issue #1035 adds the durable state machine that moves one active run between compiled phase capability profiles. It builds on the Phase Capability Profiles contract without duplicating the launch propagation and tool enforcement delivered by #1036 and #1033.

Durable record

Each applied change appends one immutable phase-transition-record/v1 record. The record binds:

Workspace, task, active attempt, sequence, and idempotent operation ID
Prior and effective phase-capability-evidence/v1 documents
Added and removed scopes for every changed authority dimension
Verified actor, reason, and policy decision
Exact approval or emergency-override evidence when required
Active run-launch-manifest/v1 digest
Deterministic run-event projection reference and timestamp

File storage uses a locked, bounded JSONL journal. SQLite uses an append-only table with unique run sequence and operation constraints. Both repositories implement the same compare-and-set contract and recover the current phase as the highest sequence for the exact workspace, task, and attempt.

Compare-and-set rules

A request supplies the expected sequence, prior phase-evidence digest, and launch-manifest digest. The server also verifies that the task still has the same running attempt, executable provider, and manifest before appending.

The first transition additionally supplies the exact initial compiled evidence. Later transitions use the journal's current evidence. Stale attempt, sequence, evidence, manifest, or changed reuse of an operation ID fails closed. An exact duplicate operation returns the original record without replaying the transition.

Evidence is validated against its content digest. A blocked result or legacy identity cannot become the target of an operator transition.

Policy and approvals

The authority delta is calculated independently for filesystem read and write, command execution, network egress, credentials, external actions, and the plan artifact capability.

Same-authority and narrowing transitions apply immediately.
Any added scope creates or reuses an exact-action request in the existing run approval broker.
Approval binds the operation, prior and target evidence digests, manifest, and complete authority delta.
Pending approval returns approval-required; rejected or expired approval fails closed.
Credential or external-action expansion is classified as critical risk.

An emergency expansion requires verified admin:manage authority, a reason, and an expiry no more than 24 hours in the future. The first read after expiry appends one system-attributed override-expired transition that restores the prior evidence. Concurrent readers use compare-and-set behavior, so only one expiry record wins.

REST controls

Read the active phase and bounded history:

GET /api/agents/:taskId/phase?attemptId=attempt_123&limit=100

Request or apply a transition:

POST /api/agents/:taskId/phase/transitions
Content-Type: application/json

{
  "attemptId": "attempt_123",
  "operationId": "move-to-implement",
  "expectedSequence": 1,
  "expectedPhaseEvidenceDigest": "sha256:...",
  "expectedManifestDigest": "sha256:...",
  "reason": "The approved plan is ready to implement.",
  "targetEvidence": {
    "schemaVersion": "phase-capability-evidence/v1"
  }
}

The abbreviated targetEvidence above represents the complete compiled evidence document. Reads require agent:read; transition requests require task:write. Expansion is not applied until an administrator resolves its approval. Emergency override authority is checked independently by the service.

CLI controls

vk agent:phase TASK-001 --attempt attempt_123 --json

vk agent:transition-phase TASK-001 \
  --attempt attempt_123 \
  --operation move-to-implement \
  --target-evidence ./implement-evidence.json \
  --reason "The approved plan is ready to implement." \
  --json

vk agent:decide-phase-approval runapproval_123 \
  --decision approve \
  --note "Reviewed the exact authority delta." \
  --json

For the first transition, add --from-evidence and --manifest. The CLI reads the current durable record for later transitions and supplies its sequence, evidence digest, and manifest automatically. Retry an approved expansion with the same --operation value and the returned --approval-id.

Emergency override uses --override-until and --override-reason together. The server remains authoritative for administrator permission and maximum expiry.

Delivery boundary

The journal makes phase state, approval, expiry, restart recovery, and operator control durable. Launch propagation binds it into descendants, retries, continuations, and handoffs. Tool catalogs, mediated invocation, approvals, completion results, and the run timeline consume the same server-owned active projection.

The journal still does not prove provider enforcement by itself. ACP stdio supplies the current pre-execution mediation contract. An adapter without equivalent command and external-action controls fails an explicit phase launch closed.

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