tasks

⏳ Tasks

Verdict: Tachyon does not run tasks. External system owns execution via TaskConnector functions; Tachyon keeps a revision-ordered projection cache (TaskSnapshot), maps MCP task methods to connector calls, and pushes status/progress notifications. All @ExperimentalApi.

🧱 Types

Type	Role	Proof
TaskConnector	required get, cancel, update; @LegacyApi optional list, awaitResult	TaskConnector
TaskSnapshot	taskId, status, timestamps, revision, pollInterval, result/error, meta; factories working/inputRequired/completed/failed/cancelled	TaskSnapshot
TaskState	SUBMITTED, REJECTED*, AUTH_REQUIRED, WORKING, INPUT_REQUIRED, COMPLETED*, FAILED*, CANCELLED*, UNKNOWN* (*terminal)	TaskState
TaskSupport	tool-level FORBIDDEN / OPTIONAL / REQUIRED	TaskSupport
Tasks (façade)	publish, get, remove, reportProgress	Tasks
DefaultTaskRegistry	cache + notifications + TTL janitor	DefaultTaskRegistry
TasksExtension	id io.modelcontextprotocol/tasks, ALWAYS advertised, per-request gate	TasksExtension

⚙️ Config

capabilities { tasks(connector) } ⇒ enabled + connector Builder#tasks; enabled w/o connector ⇒ ISE Builder#validateTaskConnector. TasksConfig keepAlive default 5 min, optional pollInterval, pageSize TasksConfig. Builder auto-adds TasksExtension when enabled (see overview).

Startup check: any REQUIRED tool w/o connector ⇒ IllegalStateException("Task-producing tools require a TaskConnector"); OPTIONAL w/o connector ⇒ warn DefaultTachyonServer#validateConfiguration.

🔁 Task-producing tool call

ToolMethodHandlers validateTaskRequest ToolsCallHandler#validateTaskRequest + mapResult ToolsCallHandler#mapResult:

Protocol	Rule
2025-11-25 (legacy augmentation)	client sends task-augmented call; FORBIDDEN+augmented ⇒ invalid params; REQUIRED+plain ⇒ invalid params
2026-07-28	no augmentation flag; REQUIRED ⇒ tasks extension must be declared (else -32021)

Tool returns ToolResult.task(snapshot) ⇒ checks (not FORBIDDEN, legacy must be augmented, connector configured, extension declared on modern) ⇒ tasksRegistry.publish(snapshot, progressToken) ⇒ createTaskResult, observation outcome TaskHandoff. Non-task result for REQUIRED/augmented ⇒ internal error.

🗂️ Registry semantics

DefaultTaskRegistry.publish DefaultTachyonServer:

• effective pollInterval = snapshot's or config default.
• TaskEntry.publish accepts only higher revision; taskId immutable TaskEntry#publish.
• Changed ⇒ server.notifyTaskStatus(snapshot, ownerSessionId) + ChangeSupport.fireOnChange (listeners append, like the other registries) DefaultTaskRegistry#onChange.
• Owner session captured from dispatch ThreadLocal at creation (OutboundSseStreamMessageRouter.currentSessionId()).
• reportProgress(taskId, …) needs progressToken captured at creation else dropped TaskEntry.
• Janitor every 30s removes terminal entries older than keepAlive TaskEntry#TaskEntry, TaskEntry, TaskEntry#isResultExpired.

Notification fan-out DefaultTachyonServer#notifyTaskStatus: owner session (or all ACTIVE) gets notifications/tasks/status in its protocol's shape; plus SubscriptionRegistry.notifyTaskStatus → notifications/tasks to subscriptions/listen streams filtering on taskId.

🌐 Method map

TaskMethodHandlers.register TaskMethodHandlers#register

Method	Gate	Connector	Result
tasks/list	legacy only	list (null ⇒ method not found)	list, each item re-published
tasks/get	modern: extension declared	get; TaskNotFoundException ⇒ invalid params	getTaskResult
tasks/cancel	modern: extension	cancel then (legacy) get	modern empty / legacy snapshot
tasks/result	legacy only	awaitResult (blocking)	tool call payload
tasks/update	modern only + extension	update(inputResponses)	empty

Gates thrown from decode as RequestMappingException RequestMappingException.

🔌 Temporal integration

TemporalTaskExecutionEngine → connector(); MCP task id = Workflow id; routes (TemporalTaskRoute) define workflow type, start args, status query, snapshot mapper, input update TemporalTaskExecutionEngine. Test double: tachyon-testkit/src/main/java/dev/tachyonmcp/testkit/TestTaskConnector.java. See integrations.

Related: feature-registries, extensions, protocol-versions.

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_{📄 source .llm-wiki/concepts/tasks.md · updated 2026-09-17 · verified at e5c536ea · tags [concept, tasks, experimental]}