When should a request ask for more input, and when should it become a Task?

2026-07-28 core · deterministic JSON-RPC fixtures

Atlas Release Evidence Server. Read-only evidence, deterministic scoring, and an explicit evaluation Task across replicas and protocol eras.

01 · Smallest useful mechanism

Use MRTR for bounded clarification and Tasks for durable long-running work.

Modern multi-round-trip requests return input_required and the client retries the original request with inputResponses. The official Tasks extension adds task handles and lifecycle operations after extension negotiation.

Both flows keep continuation explicit, typed, correlated, and subject to current authority.

02 · Experiment

Test the prediction

Deterministic protocol fixture

This workbench uses inspectable JSON-RPC fixtures and injected failures. It does not make live calls or execute external effects.

Protocol workbench · atlas-tasks-v1

Choose the flow for profile selection followed by a ten-minute evaluation.

Injected failure

The client disconnects after starting work and later requests cancellation.

Choose the implementation

Keep one HTTP request openHold process memory for clarification and ten minutes of work.Create a Task for every questionUse durable tasks even for one immediate choice.Use MRTR, then a TaskCollect the bounded choice, negotiate Tasks, and persist the evaluation handle.

The trace has not run.

Commit to an implementation, then inject the failure and inspect the actual state transitions.

03 · Implementation brief

Build it, break it, prove the outcome.

Implement: Model one MRTR clarification and one durable Task with explicit states, limits, and current authorization.
Break it on purpose: Disconnect, duplicate creation, refuse input, race cancellation with completion, expire a handle, and swap tenants.
Completion evidence: The product can resume truthfully, never exposes another tenant, and distinguishes requested, running, cancelled, failed, and completed outcomes.

Your learning artifact

Write the argument you would defend

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Your response

04 · Check your understanding

How are Tasks available in MCP 2026-07-28?

Primary sources · verified 2026-08-02

What the fixture does not prove

Treating every pause as a Task creates infrastructure overhead; treating durable work as an in-memory clarification loses recovery, cancellation, and observability.

Common mistake: Tasks are still part of the modern core protocol. Tasks moved into the official io.modelcontextprotocol/tasks extension and must be negotiated by both parties.

Transfer exercise: Use MRTR to choose an evaluation profile, then run the selected evaluation as a Task that survives client disconnect.

MCP — 2026-07-28 key changesOfficial migration summary covering session removal, discovery, MRTR, extensions, Tasks, caching, and deprecations.MCP — Extensions overviewOfficial opt-in extension framework and current extensions, including Tasks, MCP Apps, and Skills over MCP.MCP Tasks extensionOfficial lifecycle for negotiated long-running work using explicit task handles and task operations.

Optional referenceDeep dive / reference chapterOpen the complete essay, diagrams, mathematics, exercises, glossary, and sources when you want more depth.on demand

Next: Explicit continuations are only useful if identity, authorization, hostile content, compatibility, and contract tests hold around every call.