⚠️ Enforcement note: The writeback contract (task_update + thought_record) is a design-level requirement. In the reference implementation (AMS), enforcement is at convention level — agents that skip writeback are flagged but not blocked at runtime. Colibri’s implementation WILL enforce this at runtime (hard block).

S15 — GSD Contract

Defines the task execution state machine used by the orchestration layer.

States

GATHER → SYNC → DISPATCH → VERIFY → DONE
                                ↓
                             RETRY → GATHER

State	Purpose
GATHER	Collect task definition, dependencies, context, memory
SYNC	Validate preconditions, resolve dependency order, check blockers
DISPATCH	Assign to agent pool, execute phase work, track progress
VERIFY	Run acceptance criteria, tests, lint, generate proofs
DONE	Write results, update task status, seal audit trail
RETRY	Classify error, backoff, re-enter GATHER or DISPATCH

Multi-phase workflows

A task may decompose into ordered phases:

1. Audit (research)
2. Contract (define interface)
3. Execution packet (plan implementation)
4. Implementation (write code)
5. Verification (test and prove)

Each phase gets an agent pool allocation. Phases execute sequentially — phase N+1 starts only when phase N completes.

Writeback contract

Every completed task must produce:

• task_update: status=done, progress=100
• thought_record: task_id, branch, commit SHA, tests run, summary, blockers

Failure to write back marks the task as orphaned.

Enforcement note: Writeback tools are available but enforcement is at convention level, not runtime. No hard block prevents a task from closing without writeback. Orphan detection is a warning scan, not an automated rollback.

Error recovery

1. Classify: transient (timeout, rate limit) vs permanent (invalid input)
2. Retry: exponential backoff, max 3 attempts for transient errors
3. Fallback: simpler execution path or partial completion
4. Escalate: mark as blocked, log error, notify parent workflow

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Implementation Status

⚠ Donor genealogy table — not a Phase 0 claim. The table below was assembled in R40 against the pre-R53 donor AMS runtime in projects/unified-mcp/src/. That source tree no longer exists — src/ was deleted in R53 and every src/controllers/*.js, src/gsd/*.js, and src/intelligence/*.js reference in the table below is heritage genealogy only. Phase 0 Colibri has zero code for GSD (colibri_code: none across the entire β axis). The authoritative Phase 0 β state model is the 8-state FSM INIT → GATHER → ANALYZE → PLAN → APPLY → VERIFY → DONE (+ CANCELLED) in ../concepts/β-task-pipeline.md, not the GATHER → SYNC → DISPATCH → VERIFY → DONE spec draft at the top of this file. When Colibri’s β engine actually ships, this table should be rebuilt against the then-current src/domains/tasks/ tree.

Runtime: Verified against donor AMS Node.js (projects/unified-mcp/src/, deleted R53); not yet ported to Colibri Node.js

Verified against source: 2026-04-06 (donor, pre-R53)

Claim	Status	Notes
State machine: GATHER -> SYNC -> DISPATCH -> VERIFY -> DONE -> RETRY	Partial	Autonomous pipeline uses INIT -> GATHER -> ANALYZE -> PLAN -> [DRY_RUN/APPLY] -> VERIFY -> DONE (7 steps in src/controllers/autonomous/intents.js). SYNC and DISPATCH do not exist as named states. GSD workflow engine (src/gsd/engine.js) uses PENDING -> RUNNING -> PAUSED -> COMPLETED -> FAILED -> ROLLED_BACK. Neither matches the spec exactly.
GATHER: collect task definition, dependencies, context, memory	Implemented	gatherPhase() in src/controllers/autonomous.js collects project context, git state, roadmap, codebase scan
SYNC: validate preconditions, resolve dependency order	Partial	Precondition validation happens inside initPhase() (project existence, auto-register). No dedicated SYNC state.
DISPATCH: assign to agent pool, execute phase work	Implemented	src/gsd/agent-pool.js provides full agent pool with lifecycle management, load balancing; src/gsd/task-queue.js handles dispatch with priority queuing
VERIFY: run acceptance criteria, tests, lint, generate proofs	Implemented	verifyPhase() in autonomous controller; src/gsd/verifier.js provides goal-backward verification, artifact checking, quality gates
DONE: write results, update task status, seal audit trail	Implemented	Autonomous pipeline marks session complete, updates DB status
RETRY: classify error, backoff, re-enter	Implemented	src/gsd/task-queue.js classifies errors, retries with exponential backoff (default 3 attempts), re-queues to PENDING
Multi-phase workflows (5 ordered phases)	Implemented	src/gsd/engine.js supports ordered phases with dependency graphs; src/gsd/planner.js provides sequential/parallel/DAG/pipeline templates
Phase N+1 starts only when phase N completes	Implemented	Sequential dependency pattern enforced; phase dependencies normalized in normalizePhaseDependencies()
Writeback: task_update with status=done, progress=100	Implemented	task_update tool in src/controllers/tasks.js accepts id, status, progress fields
Writeback: thought_record with task_id, branch, commit SHA	Partial	thought_record tool in src/controllers/thought.js accepts session_id, thought_type, content – but no explicit task_id, branch, or commit SHA fields in schema; these go in the content string
Failure to write back marks task as orphaned	Spec-only	No automatic orphan detection for missing writebacks found in source
Exponential backoff, max 3 attempts for transient errors	Implemented	src/gsd/task-queue.js: retry.attempts = 3, backoff = "exponential", delay calculated as delay * 2^(attempts-1)
Fallback: simpler execution path or partial completion	Spec-only	No fallback-to-simpler-path logic found; tasks fail after max retries
Escalate: mark as blocked, log error, notify parent workflow	Partial	Tasks emit “failed” event with error details; no explicit “blocked” marking or parent workflow notification
Agent pool allocation per phase	Implemented	src/gsd/agent-pool.js manages pools with max agents (default 20), health checks (30s interval), agent types (worker/orchestrator/specialist/supervisor)
Checkpoint and rollback	Implemented	src/gsd/checkpoint.js provides state snapshots, rollback; autonomous controller uses git-checkpoint for rollback on failure
Default timeout 5 minutes	Implemented	src/gsd/engine.js: DEFAULT_TIMEOUT_MS = 5 * 60 * 1000; src/gsd/task-queue.js: default timeout 30s per task