--- name: agent-state-machine description: Use when designing or implementing states for AI agent tasks, background jobs, local model runs, queues, and notifications — one shared set of states, only legal transitions, and a recovery path out of every failure. --- # Agent State Machine Model every agent / task / run with **one shared state machine**: a fixed set of states, only the transitions that are legal between them, and a recovery path out of every failure or wait. This kills the most common agent-UX bug — random status strings invented per screen. ## When to use - Active runs, task queues, AI generation, local model jobs - Agent progress, notifications, error recovery - Retry / stop / cancel behavior and "needs review" states ## Core rule Agent UX needs clear **states**, legal **transitions**, and **recovery** paths. Do not invent random labels per screen. ## State vocabulary ``` Draft Queued Starting Thinking Running Waiting Blocked Paused Cancelling Cancelled Failed Completed Needs Review Archived ``` ## State meanings ``` Draft Created but not ready to run Queued Ready and waiting Starting Preparing environment/model/files Thinking Planning/reasoning before action Running Executing work Waiting Waiting for external service/user/system Blocked Cannot continue without user action Paused Temporarily stopped, can resume Cancelling Stop requested, cleanup in progress Cancelled Stopped by user/system Failed Ended with error Completed Finished successfully Needs Review User should inspect result Archived Hidden from active workflow ``` ## Legal transitions ``` Draft → Queued Queued → Starting Starting → Thinking Thinking → Running Running → Waiting Waiting → Running Running → Needs Review Running → Completed Running → Failed Running → Blocked Running → Cancelling Cancelling → Cancelled Failed → Queued Blocked → Queued Needs Review → Archived Completed → Archived Paused → Running ``` Avoid impossible transitions unless explicitly handled. ## Reference implementation Swift shown below, but the pattern is language-agnostic — one enum, one validator. ```swift enum AgentRunState: String, Codable, CaseIterable, Hashable { case draft case queued case starting case thinking case running case waiting case blocked case paused case cancelling case cancelled case failed case completed case needsReview case archived var title: String { switch self { case .draft: "Draft" case .queued: "Queued" case .starting: "Starting" case .thinking: "Thinking" case .running: "Running" case .waiting: "Waiting" case .blocked: "Blocked" case .paused: "Paused" case .cancelling: "Cancelling" case .cancelled: "Cancelled" case .failed: "Failed" case .completed: "Completed" case .needsReview: "Needs Review" case .archived: "Archived" } } var symbol: String { switch self { case .draft: "doc" case .queued: "list.bullet.rectangle" case .starting: "play.circle" case .thinking: "brain" case .running: "bolt.circle" case .waiting: "clock" case .blocked: "xmark.octagon" case .paused: "pause.circle" case .cancelling: "xmark.circle" case .cancelled: "xmark.circle" case .failed: "exclamationmark.triangle" case .completed: "checkmark.circle" case .needsReview: "checkmark.seal" case .archived: "archivebox" } } } ``` State transition validator: ```swift extension AgentRunState { func canTransition(to next: AgentRunState) -> Bool { switch (self, next) { case (.draft, .queued), (.queued, .starting), (.starting, .thinking), (.thinking, .running), (.running, .waiting), (.waiting, .running), (.running, .needsReview), (.running, .completed), (.running, .failed), (.running, .blocked), (.running, .cancelling), (.cancelling, .cancelled), (.failed, .queued), (.blocked, .queued), (.needsReview, .archived), (.completed, .archived), (.paused, .running): return true default: return false } } } ``` ## User-facing actions per state ``` Draft: Edit, Queue, Delete Queued: Run Now, Remove from Queue, Edit Starting: Cancel Thinking: Cancel Running: Stop, Open Logs Waiting: Retry, Cancel, Open Settings if service issue Blocked: Resolve, Retry, Cancel Paused: Resume, Cancel Failed: Retry, View Error, Archive Completed: Review, Archive, Run Again Needs Review: Review, Approve, Archive Archived: Restore ``` ## Notifications per state Notify only for: ``` Completed Failed Blocked Needs Review ``` Do not notify for every transition. ## Progress rules Use real progress only when measurable. For agent tasks, prefer step labels over a fake bar: ``` Planning Editing files Running checks Summarizing changes Waiting for review ``` Avoid fake percentages. ## Persistence fields Each run should store: ``` id title projectId state createdAt startedAt updatedAt completedAt model provider currentStep errorMessage outputSummary outputPath retryCount ``` ## Recovery rules Every failed / blocked / waiting state needs a way out. ``` Failed → show error + Retry Blocked → show what the user must fix Waiting → show what service/input is missing Offline → open settings / retry ``` ## Review checklist ``` [ ] Uses one shared state enum [ ] States have clear user-facing titles [ ] States have consistent icons [ ] Illegal transitions are prevented or handled [ ] Failed/blocked/waiting states have recovery [ ] Notifications fire only for important states [ ] No fake progress percentages [ ] Needs Review exists before archive/done [ ] Retry behavior is defined [ ] Cancel/stop behavior is defined ``` ## Common mistakes ``` Random status strings across files Done/failed only, no waiting/blocked/review No transition rules No recovery actions Notification spam Fake progress Cancelling instantly becomes cancelled without cleanup Completed work disappears before review ``` ## Prompt template Drop this into any coding agent (Claude Code, Codex, Cursor, …) to apply the skill: ``` Use the agent-state-machine skill to implement or clean up agent/task/run states. Rules: - Use a single shared state enum. - Use clear user-facing titles and consistent icons. - Define legal transitions and prevent or handle illegal ones. - Add user-facing actions per state. - Add recovery for failed, blocked, waiting, and offline states. - Notify only for completed, failed, blocked, and needs-review. - Avoid fake progress percentages. - Store enough run metadata for review and retry. After coding: 1. List states added/changed. 2. Explain transition rules. 3. Explain actions per state. 4. Explain notification behavior. 5. Give manual test steps. ```