* fix(model): decode metadata-bearing input-required results
The draft permits every Result, including InputRequiredResult, to carry
_meta and recommends that servers include
io.modelcontextprotocol/serverInfo on every response. It also requires
an InputRequiredResult to contain inputRequests or requestState so the
client knows what to provide or how to resume the request.
ServerResult uses untagged deserialization and attempts CallToolResult
before InputRequiredResult. Because CallToolResult accepts _meta and
defaults missing content to an empty list, it consumed valid
input_required results carrying metadata. Unknown inputRequests and
requestState fields were then discarded, leaving clients without the
information needed to continue.
Reject resultType input_required when deserializing CallToolResult so
Serde proceeds to the InputRequiredResult variant. Add regression
coverage proving that inputRequests, requestState, and serverInfo
metadata are preserved.
Spec:
41d9e938e9/schema/draft/schema.ts (L137-L151)41d9e938e9/schema/draft/schema.ts (L198-L224)41d9e938e9/schema/draft/schema.ts (L541-L565)
Signed-off-by: Filinto Duran <1373693+filintod@users.noreply.github.com>
* incorporate feedback - close gap in inputrequired not properly checking that at least one of inputRequest or requestState is present
Signed-off-by: Filinto Duran <1373693+filintod@users.noreply.github.com>
---------
Signed-off-by: Filinto Duran <1373693+filintod@users.noreply.github.com>
* fix: stamp server info on graceful subscription results
* fix: expose subscription server info metadata
---------
Co-authored-by: mrcs64 <9069178+mrcs64@users.noreply.github.com>
* feat!: implement SEP-2663 Tasks extension, removing the experimental 2025-11-25 tasks design
Reshape tasks from the experimental SEP-1319/1686 core-protocol feature into
the official io.modelcontextprotocol/tasks extension (SEP-2663):
Model:
- Re-model Task (statusMessage, ttlMs nullable, pollIntervalMs) and add
DetailedTask with status-discriminated payloads (inputRequests/result/error
inlined per spec)
- CreateTaskResult now flattens Task with resultType: "task";
add ResultType::TASK and CallToolResponse::Task
- Add tasks/update (UpdateTaskParams with MRTR InputResponses); tasks/get and
tasks/cancel reworked; remove tasks/list, tasks/result
- notifications/tasks now carries a full DetailedTask; removed from client
notifications (SEP-2260)
Capabilities:
- Remove core TasksCapability et al; tasks are declared via the extensions
map (enable_tasks() builders, supports_tasks() accessors)
- Remove tool-level execution.taskSupport and the _meta.task /
TaskMetadata / with_task() opt-in: task creation is server-directed and
gated on the per-request client capability
Runtime:
- Replace OperationProcessor with TaskManager: durable-before-response task
creation, input_required round-trips via tasks/update, cooperative
cancellation, TTL expiry
- Client peer helpers get_task/update_task/cancel_task
- Emit Mcp-Name routing header from params.taskId for tasks/* methods
(SEP-2243/2663)
Macros:
- Remove #[task_handler] and the tool execution() attribute
Tests/examples/docs updated; schema snapshots regenerated.
BREAKING CHANGE: the 2025-11-25 experimental tasks API is removed without a
compatibility shim. Clients that do not declare the tasks extension always
receive synchronous results.
* feat: gate tasks/* methods on the client tasks-extension capability (SEP-2663)
When the server advertises io.modelcontextprotocol/tasks but the client did
not declare it (per-request _meta clientCapabilities, or initialize-time
capabilities in session mode), tasks/get, tasks/update, and tasks/cancel now
return -32021 Missing Required Client Capability with the required extension
in the error data, instead of falling through to the handler's -32601
default. Servers that do not advertise the extension keep returning -32601.
Also add regression tests confirming that unknown taskIds yield -32602 and
that a legacy 2025-11-25 'task' param on tools/call is silently ignored.
* feat: pass SEP-2663 Tasks extension conformance suite
Conformance fixtures (conformance/src/bin/server.rs):
- Add the required fixture tools: greet (sync-only), slow_compute,
failing_job (task support: required), protocol_error_job, confirm_delete,
multi_input, and test_tool_with_task (MRTR -> task escalation), all backed
by TaskManager with server-directed task creation gated on the client's
tasks-extension capability
- Advertise io.modelcontextprotocol/tasks in server capabilities and wire
get_task/update_task/cancel_task handlers
- Task-required tools reject with -32021 when the client did not declare the
extension
SDK wire-shape fixes surfaced by the suite:
- Add resultType: "complete" to GetTaskResult and introduce TaskAckResult
so tasks/update and tasks/cancel acks carry the SEP-2322 discriminator
(spec: every non-CreateTaskResult response on the tasks surface is
resultType complete); dispatch now returns ServerResult::task_ack
- CreateTaskResult gets a strict deserializer requiring resultType: "task"
so it does not shadow task-shaped results in untagged unions
- Client update_task/cancel_task accept both TaskAckResult and EmptyResult
All 9 runnable Tasks extension server scenarios now pass (35/35 checks;
tasks-status-notifications remains upstream-skipped), so the corresponding
entries are removed from conformance/expected-failures-extensions.yaml.
2025-11-25 server suite (40/40), 2026-07-28 server suite (114/114), draft
client suite, and extensions client suite all pass their baselines.
* fix: address PR 1020 review feedback on DetailedTask schema and cooperative cancel
- DetailedTask's JsonSchema now derives from the actual flattened wire shape
(DetailedTaskWire: base Task + optional inputRequests/result/error) instead
of approximating with the base Task schema, so generated schemas for
GetTaskResult and notifications/tasks document the status-specific payload
fields. Golden message schemas regenerated.
- TaskManager::cancel_task no longer aborts the underlying future. It records
the observable cancelled state and acks immediately (spec's eventually
consistent semantics), but lets the operation keep running so it can observe
is_cancel_requested() or the error from a woken request_input() and perform
cleanup; any late result is discarded. New unit tests cover both the
cooperative-cleanup path and waking parked input requests.
* fix: make tasks/cancel truly cooperative per SEP-2663 (FEEDBACK_2)
- TaskManager::cancel_task no longer forces terminal 'cancelled'. It records
the cancellation intent, acks immediately, and wakes parked request_input
awaits, but the operation decides its own terminal state: a post-cancel
error settles as 'cancelled', while an operation that finishes its work
settles as 'completed' — per the spec, 'the task may still reach a
non-cancelled terminal status'.
- Add TaskContext::cancelled(), a watch-based await for use with
tokio::select! as the cooperative cancellation exit path.
- Correct the unsupported-notification method string from
'notifications/tasks/status' to 'notifications/tasks' and document that
task status notifications are not yet routable through subscriptions/listen
(SubscriptionFilter has no taskIds field; upstream check still skipped).
- Update conformance slow_compute fixture, task_demo example, and tests to
honor cancellation via ctx.cancelled(); lifecycle conformance still 8/8
(all 9 scenarios remain green, 35/35 checks).
* fix: sweep and evict expired tasks from TaskManager (FEEDBACK_3)
TTL handling previously only ran from get_task and only flipped overdue
non-terminal tasks to 'failed', never removing entries — an unbounded leak
for long-lived servers, and it made ttl_ms: None = 'unlimited retention'
meaningless since everything was retained forever.
- Rename expire_overdue to sweep_expired and run it from every entry point
(spawn, get_task, update_task, cancel_task).
- Track terminal_at on each entry; terminal tasks are evicted after being
retained for one further ttl_ms window past their terminal transition, so
well-behaved pollers can observe the final state before late tasks/get
calls return -32602 (spec: servers may delete expired tasks at any time,
and returning task-not-found for purged tasks is compliant behavior).
- ttl_ms: None entries are never evicted (spec: unlimited retention);
document the retention model on TaskManager, including that there is no
background sweeper.
- New tests: retention-window eviction, sweep of abandoned tasks via other
entry points, unlimited-TTL retention, and error-code assertions
(-32602) for unknown ids across get/update/cancel.
Reviewed the second feedback item (dedicated task-not-found error code)
against SEP-2663 §Protocol Errors and it is incorrect: the SEP explicitly
specifies -32602 (Invalid params) for invalid or nonexistent taskIds, which
is what unknown_task already returns. Kept -32602; strengthened tests to
assert the code.
* fix: address Copilot review feedback on PR #1020
- TaskManager: drop the JoinHandle as soon as the operation settles instead
of retaining it for the whole retention window, and only store it at spawn
time if the task is still non-terminal (avoids keeping a completed handle
that the completion path could never clear).
- Use RequestContext::client_capabilities() (which applies the initialize-time
fallback for session peers) instead of raw context.meta.client_capabilities()
in the task_demo example, the README snippet, and the test server — the
meta-only form would wrongly treat session-declared tasks clients as
unsupported.
All 9 Tasks extension conformance scenarios remain green (35/35 checks).
* fix: enforce SEP-2663 task-result gating in tools/call dispatch
A handler could return CallToolResponse::Task without checking whether the
request declared the io.modelcontextprotocol/tasks extension, sending a
CreateTaskResult to a client that cannot parse it. The SDK dispatch now
rejects that case with -32021 Missing Required Client Capability before the
response leaves the server, using RequestContext::client_capabilities()
(per-request _meta with initialize-time fallback).
Adds a regression test with a deliberately misbehaving handler that always
materializes a task; all Tasks extension conformance scenarios remain green
(35/35 checks).
* fix: align TTL boundary comparisons in sweep_expired
Copilot review: ttlMs: 0 never expired immediately because phase 1 used a
strict 'elapsed > ttl_ms' comparison, and phase 2 retained terminal tasks
at exactly the TTL boundary ('elapsed <= ttl_ms'). Treat elapsed >= ttl_ms
as expired in phase 1 and evict when elapsed >= ttl_ms in phase 2, so both
phases agree at the boundary and ttlMs: 0 expires/evicts on the first sweep.
* fix: strict TaskAckResult deserializer and TASK_REQUIRED_TOOLS consistency
- TaskAckResult carried only resultType (+ optional _meta) with a derived
Deserialize, so inside the untagged ServerResult union it greedily matched
any result object containing a resultType key, shadowing CustomResult and
losing data (verified with a probe). Replace with a strict deserializer:
deny_unknown_fields and require resultType == "complete". Regression
tests cover both the non-matching shapes and the genuine ack shape.
- Conformance fixtures: confirm_delete and multi_input rejected non-tasks
clients inline, contradicting the TASK_REQUIRED_TOOLS doc/constant. Move
them into TASK_REQUIRED_TOOLS (they park on in-task elicitation and have
no synchronous fallback) so the upfront -32021 gate is the single source
of truth, and drop the now-unreachable inline checks.
All 9 Tasks extension conformance scenarios remain green (35/35 checks).
* fix: let the operation decide its terminal state via TaskExit
After tasks/cancel, any operation error was coerced to terminal
'cancelled', masking real failures (e.g. an unrelated error landing just
after a late cancel request) and contradicting the documented 'operation
decides its own terminal state' contract.
Change TaskFuture's error type from McpError to a new TaskExit enum:
- TaskExit::Cancelled — an explicit cooperative-cancellation exit;
settles as terminal 'cancelled'.
- TaskExit::Error(McpError) — a real failure; settles as terminal
'failed' with the error inlined, even after tasks/cancel was received.
From<McpError> for TaskExit keeps '?' ergonomic in task bodies, and
request_input() now returns TaskExit directly (its wake-on-cancel path
yields TaskExit::Cancelled), so parked operations that propagate it with
'?' settle as 'cancelled' automatically.
Update the conformance fixtures, task_demo example, and tests; add a
regression test asserting a post-cancel unrelated error settles as
'failed' with its error payload preserved.
All 9 Tasks extension conformance scenarios remain green (35/35 checks).
* fix: allow TaskExit enum to be exhaustive
* fix: close spawn/shutdown race, sweep in running_task_count, clarify TTL retention docs
Addresses branch-review findings:
- spawn() raced with shutdown(): if shutdown drained the task map between
the entry insert and the JoinHandle store, the handle was dropped and the
operation kept running detached. If the entry is gone at store time, the
handle is now aborted instead.
- running_task_count() now runs the TTL sweep like every other entry point,
so it no longer reports overdue tasks as running (matching the documented
sweep-on-every-entry-point behavior). Regression test added.
- Document that terminal-task retention intentionally extends one ttl_ms
window past the terminal transition (observation grace period) beyond the
creation-based lifetime ttlMs advertises on the wire — compliant since
SEP-2663 allows deleting expired tasks at any time after the TTL.
* feat!: add MRTR behavior support
* feat: harden SEP-2322 MRTR support
* ci: diff public API only on features common to base and head
cargo public-api builds both revisions with the same feature set, so a
feature introduced (or removed) by a PR broke the build of the other
revision. Restrict the all-features diff to features present in both the
base and head revisions.
* docs(server): document Err vs Ok(CallToolResult::error) visibility contract
The MCP spec separates two failure modes that surface very differently in
clients:
- Err(ErrorData) is a JSON-RPC protocol error. Most MCP clients render
it opaquely ("Tool result missing due to internal error") - the
caller does not see the message text.
- Ok(CallToolResult::error(content)) is a tool-level error. Clients
render the content; the caller reads the message.
The right shape for "the tool didn't work" is the latter, but Err is
what most handlers reach for because it looks like the natural Rust
return value. This commit adds rustdoc on both ServerHandler::call_tool
and CallToolResult::error pointing handlers at the correct shape, with
a worked example showing protocol errors (-32602 invalid_params) vs
tool errors (empty result, downstream failure).
This is the docs half of the visibility-contract ask. A follow-up may
introduce a typed ToolOutcome sum type to enforce the distinction at
compile time; this PR is the lower-risk version that unblocks the
class immediately.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* docs: update crates/rmcp/src/handler/server.rs
* docs: update crates/rmcp/src/model.rs
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Dale Seo <5466341+DaleSeo@users.noreply.github.com>
* feat: implement SEP-2164 resource not found errors
* test: update protocol version utility expectations
* feat: gate not-found code at server boundary
---------
Co-authored-by: Michael Neale <michael.neale@gmail.com>
* feat: add theme field to Icon
* fix: update IconThem crates/rmcp/src/model.rs (non_exhaustive)
Co-authored-by: Dale Seo <5466341+DaleSeo@users.noreply.github.com>
* fix: update IconThem crates/rmcp/src/model.rs (eq, hash)
Co-authored-by: Dale Seo <5466341+DaleSeo@users.noreply.github.com>
* fix: update docs with full descriptions of theme from mcp spec
---------
Co-authored-by: Dale Seo <5466341+DaleSeo@users.noreply.github.com>
The `#[serde(default)]` on `CallToolResult.content` (added in #752) made
all fields optional, causing `CallToolResult` to greedily match any JSON
object during `#[serde(untagged)]` deserialization of `ServerResult`.
Similarly, `GetTaskPayloadResult(Value)` matched everything before
`CustomResult(Value)` could be reached.
Fix by replacing derived `Deserialize` impls with custom ones:
- `CallToolResult`: require at least one known field to be present
- `GetTaskPayloadResult`: always fail (indistinguishable from
`CustomResult` in JSON; construct programmatically via `::new()`)
* fix: builder with_* methods take T instead of Option<T>
* fix: emit conditional builder calls for optional fields in macros
* fix: convert with_task, with_stop_reason, with_logger, with_content to proper builders
* fix: update test callers for new builder signatures
* fix: simplify make_task helper and remove unused import
* fix: update sampling_stdio example for new with_stop_reason signature
* fix: make annotations and execution Option<Expr> consistent with other fields
* fix: remove unused none_expr import
Move CustomRequest and CustomResult to end of their respective untagged
enums to ensure specific task variants match before catch-all custom types.
Add deny_unknown_fields to GetTaskInfoResult to prevent matching arbitrary
JSON objects.
Fixes issue where tasks/get, tasks/list, tasks/result, and tasks/cancel
incorrectly deserialized as CustomRequest instead of their typed variants.
* feat: implement SEP-1319 Decouple Request Payload from RPC Methods
* test: update tests
* fix: update handler trait methods to use new types
* fix: update examples
* fix: correct deprecation version
* fix: update wrapper macros to use new *Params type names
#580 and #556 introduced support for custom notifications,
so this PR takes the next logical step and adds support for custom requests:
- Introduces `CustomRequest` and `CustomResult` model types, wires them into the client/server
request and result unions, and allows `ClientRequest::method()` to return the dynamic method
name.
- Implements serde and meta handling for `CustomRequest` so `_meta` is carried through
extensions; adds default `on_custom_request` handlers that return `METHOD_NOT_FOUND` unless
overridden.
- Updates JSON schema fixtures to include the new request/result shapes and `EmptyObject`
strictness.
- Adds tests for custom request roundtrips and end-to-end client↔server handling.
- Focused integration test in `crates/rmcp/tests/test_custom_request.rs`.
For additional testing, I used this locally to update Codex to use a custom
request instead of a custom notification so that it gets an "ack" from the MCP
server to ensure it has processed the update before sending more messages:
https://github.com/openai/codex/pull/8142.
https://github.com/modelcontextprotocol/rust-sdk/pull/556 introduced support for
custom client notifications, so this PR makes the complementary change, adding
support for custom server notifications.
MCP clients, particularly ones that offer "experimental" capabilities,
may wish to handle custom server notifications that are not part of the
standard MCP specification. This change introduces a new
`CustomServerNotification` type that allows a client to process
such custom notifications.
- introduces `CustomServerNotification` to carry arbitrary methods/params while
still preserving meta/extensions; wires it into the `ServerNotification` union
and `serde` so `params` can be decoded with `params_as`
- allows client handlers to receive custom notifications via a new
`on_custom_notification` hook
- adds integration coverage that sends a custom server notification end-to-end
and asserts the client sees the method and payload
Test:
```shell
cargo test -p rmcp --features client test_custom_server_notification_reaches_client
```
