Tasks: io.modelcontextprotocol/tasks extension on modern servers (era fork) (#1731)

* Tasks: modern io.modelcontextprotocol/tasks extension (era fork core)

Core + test-server implementation of the SEP-2663 tasks extension for modern
(2026-07-28) connections, forked from the legacy 2025-11-25 tasks path.

SDK v2 removed all tasks support AND era-gates the tasks/* spec methods out of
the modern era on both the client (outbound) and server (inbound) sides, and its
codec rejects a resultType:"task" result outright. So the Inspector drives the
extension itself: task creation rides tools/call (a modern method) with the
resultType:"task" frame rewritten at the transport to a CallToolResult carrying
the handle in _meta; tasks/get/update/cancel go over a raw-wire request channel
that bypasses the era gate (full modern envelope, string ids, consumed by the
transport). input_required tasks reuse the existing pending-request modal via
fulfilInputRequests, answered with tasks/update. No tasks/list, no tasks/result.

Tab + run-as-task gate on the negotiated extension; the managed task store's
refresh re-polls known handles on modern (no server list). Test server serves
the extension via an Express interceptor (SDK can't) + a shared poll-driven
runtime. Full integration coverage of both eras.

Refs #1631

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Tasks modern era: tests + coverage (raw-wire, schemas, era integration)

Adds unit coverage for modernTaskSchemas and the raw-wire request channel
(transport-null guard, send failure, timeout, error response, teardown), plus
end-to-end era integration tests (create/poll/input-required/update/cancel,
synchronous passthrough, unknown-id error, modern store re-poll). Fixes the App
and constructor-capabilities tests for the always-on tasks extension.

Refs #1631

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Tasks modern era: docs + share test servers per era to de-flake coverage

Document the tasks era-fork test configs in README and the new core/test-server
files in AGENTS.md. Share one modern + one legacy test server across the era
integration block (started lazily, stopped in afterAll) — starting a fresh
Express server per test made connection negotiation flaky under the heavy
concurrent coverage run.

Refs #1631

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Restore pr-screenshots deleted inadvertently

The logging/subscriptions PR screenshots + README were staged-deleted in the
working tree before this branch; restore them from v2/main so this PR doesn't
remove other PRs' artifacts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Tasks modern era: offer Run-as-task for any tool + PR screenshots

On modern (SEP-2663) task creation is server-directed — the client declares the
extension once and any tool may return a task — so the Tools screen now offers
'Run as task' for every tool on a modern connection (threaded via a modernTasks
prop through InspectorView → ToolsScreen → ToolDetailPanel), rather than gating
on the legacy per-tool taskSupport. Verified end-to-end in the web UI (remote
proxy): create → poll tasks/get → input_required elicitation → tasks/update →
inline result, plus the unchanged legacy tasks/list/result flow. Adds proof
screenshots.

Refs #1631

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Tasks modern era: address two follow-ups (task-input note + ordinary-path auto-poll)

1. The pending-request note now distinguishes a modern task round from an MRTR
   round: a new 'task-input-required' PendingRequestOrigin threads through
   fulfilInputRequests → the pending-request modal → MrtrOriginNote, which shows
   'submitted via a tasks/update request (SEP-2663), not a retry' instead of the
   MRTR retry copy.

2. The ordinary (non-run-as-task) modern callTool path now auto-polls an
   unsolicited task handle: attemptToolCall detects the rewritten handle in the
   result _meta and drives it to termination (get → input_required/update →
   inline result), dispatching task events so the Tasks tab + toasts track it and
   the tool result resolves to the task's final result. The poll loop is shared
   with the streaming path via extracted helpers (submitModernTaskInput /
   modernTaskTerminalOutcome / modernTaskPollInterval).

Refs #1631

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Tasks modern era: address review (negotiated envelope version, input-round cap, clarifying comment) + fresh smoke screenshots

Review of #1731:
1. withModernTaskEnvelope now stamps the NEGOTIATED protocol version
   (getProtocolVersion() ?? MODERN_PROTOCOL_VERSION) so the envelope matches the
   MCP-Protocol-Version header instead of a hardcoded constant.
2. A never-completing input_required task is now bounded by MRTR_MAX_ROUNDS in the
   shared submitModernTaskInput (threaded through both poll loops), so a
   non-conformant server can't re-prompt the user forever. New modern_loop_task
   test-server tool + integration test cover the cap.
3. ToolDetailPanel: comment clarifying that per-tool taskSupport:"forbidden" is
   deliberately ignored on modern (task creation is server-directed under SEP-2663).

(The abort-during-poll observation is addressed in the PR reply: the cancel path
uses tasks/cancel and disconnect rejects the in-flight raw request, so the poll
stops; matches legacy.)

Fresh web-UI smoke screenshots (modern connected, task completed, input_required
with the corrected tasks/update note, input completed).

Refs #1631

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Tasks modern era: fix uncancelable input-required loop + sticky cancel

Two bug fixes reported during manual testing of the tasks era-fork (#1631):

1. A modern task paused at `input_required` (e.g. `modern_loop_task`, which
   never advances) could not be cancelled: the poll loop blocked on the
   pending-request modal, so `cancelRequestorTask` sent `tasks/cancel` but the
   modal kept re-prompting. Now each modern poll loop registers a per-task
   AbortController (`registerTaskInputAbort`), `cancelRequestorTask` aborts it
   to reject the pending elicitation and unblock the poll, and the embedded
   input requests are tagged with their owning task id
   (`RELATED_TASK_META_KEY`) so the pending-request UI's Cancel action cancels
   the TASK rather than sending a "cancel" answer the server would re-prompt on.

2. On the legacy server, cancelling a task briefly showed CANCELLED then
   flipped to COMPLETED when the in-flight tool call resolved. Cancellation is
   a deliberate terminal decision, so `ManagedRequestorTasksState` now remembers
   cancelled task ids and ignores any later non-cancelled status update.

Also: move the compact task id onto its own line in the embedded monitoring
sidebar so the status badge / Cancel Task control don't wrap; DRY the duplicated
task poll-interval logic into a shared `taskPollInterval` helper.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Refresh tasks PR screenshots + capture both bug-fix scenarios

Recapture the five tasks flow screenshots against the current build and add
two demonstrating the post-review fixes: modern_loop_task cancelled from the
pending-request modal (uncancelable-loop fix) and a legacy task staying
CANCELLED after the in-flight call resolves (sticky-cancel fix).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* Address re-review: sticky cancel on legacy refresh + App cancel-routing test

Re-review of the cancelable-loop / sticky-cancel fix raised two non-blocking
hardening items:

1. The legacy tasks/list refresh() rebuilt the list from the server, honoring
   only dismissedTaskIds — so a cooperative-cancel server that re-lists a
   user-cancelled task as completed could un-stick the cancel on a manual
   Refresh. The refresh path now pins a cancelledTaskIds task to "cancelled"
   (keeping it visible-as-cancelled, matching the live-merge handlers) rather
   than dropping it. Covered by a new state test.

2. Added an App.test.tsx case locking in the user-facing half of the fix: Cancel
   on a task-input-required elicitation calls cancelRequestorTask (not respond).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -120,6 +120,8 @@ A streamable-HTTP server can also serve the **modern (2026-07-28) protocol era**
 
 `test-servers/configs/subscriptions-legacy-http.json` and `test-servers/configs/subscriptions-modern-http.json` are the **resource-subscription era-fork showcase** (#1630). Both serve three `numbered_resources` with `subscriptions: true`; the legacy one also serves an `update_resource` tool, and the modern one sets `transport.modern: true`. Connect to the **legacy** server, open a resource in the **Resources** tab and click **Subscribe** — the client sends `resources/subscribe` (Network/Protocol view) and the Subscriptions section lists the URI with no stream chrome; call `update_resource` with that URI and the server updates the content and emits `notifications/resources/updated`, stamping the subscribed tile's last-updated time. Connect to the **modern** server with **Protocol Era = Modern** and the same Subscribe instead sends **`subscriptions/listen`** (its filter carries `resourceSubscriptions` + the `resourcesListChanged` opt-in) and resolves on `notifications/subscriptions/acknowledged`; the Subscriptions section then shows the stream-status badge (`Connecting…` → `Listening`) in its header, and if the long-lived stream drops it reconnects by re-listing. The modern config deliberately **omits** `update_resource`: the SDK's modern leg is stateless/per-request (`createMcpHandler(() => createMcpServer(config))`), so the tool would run against a throwaway server instance — the content change wouldn't persist for the next `resources/read`, and its `resources/updated` wouldn't reach the (separate) listen stream — which is more confusing than useful. The live update-notification round-trip is therefore demonstrated on the legacy (stateful-session) server; the modern server is for the subscribe/listen/badge behavior. (The Inspector's *receive* path is era-transparent, so a real stateful modern server that routes `resources/updated` onto the listen stream drives the subscribed tile the same way.)
 
+`test-servers/configs/tasks-legacy-http.json` and `test-servers/configs/tasks-modern-http.json` are the **Tasks era-fork showcase** (#1631). The legacy server advertises `capabilities.tasks` (`tasks: { list, cancel }`) with the `simple_task` / `progress_task` / `elicitation_task` presets — connect to it, run one of those tools with **Run as task** on, and the **Tasks** tab lists it (populated via `tasks/list`), polls `tasks/get`, fetches the payload with the blocking `tasks/result`, and cancels with `tasks/cancel`. The modern server sets `transport.modern: true` and `tasksExtension: true`, advertising the `io.modelcontextprotocol/tasks` extension (SEP-2663) and serving the `modern_task` / `modern_input_task` tools. Connect with **Protocol Era = Modern**: the **Tasks** tab is now gated on the negotiated extension (not `capabilities.tasks`). Run `modern_task` as a task — the `tools/call` returns a `CreateTaskResult` (`resultType: "task"`, visible in the Protocol/Network tabs), the client polls **`tasks/get`** (no `tasks/list`), and the completed task inlines its result (no blocking `tasks/result`). Run `modern_input_task` and the task moves to `input_required`, surfacing an embedded elicitation through the pending-request modal; answering it sends **`tasks/update`** with the `inputResponses`, and the next poll completes. SDK v2 removed all tasks support **and** era-gates the `tasks/*` spec methods out of the modern era on both sides — so the Inspector drives the extension itself (the `resultType: "task"` frame is rewritten at the transport into a `CallToolResult` carrying the handle; `tasks/get`/`update`/`cancel` ride a raw-wire request channel with the full modern envelope), and the test server serves `tasks/*` from an Express interceptor ahead of the SDK handler (the SDK's modern leg would answer them `-32601`). The Tasks tab's **Refresh** re-polls the handles already known to the client (modern has no server-side task list).
+
 ## Building
 
 ```bash