* Remove 3.x-era compatibility shims
* Require response_type in ctx.elicit()
* Name the utilities path for the two non-re-exported auth helpers
* Point sampling handler migration at its submodule
Deletes fastmcp/server/sampling/, Context.sample/sample_step/list_roots, and
FastMCP(sampling_handler=). The proxy's handshake-era relay now reaches the
front session through the SDK directly.
A FastMCP client now transparently completes tasked tools/call: the tasks
ClientExtension advertises the capability and claims the CreateTaskResult, and
the resolver drives the tasks/get poll loop to completion, answering in-task
input through the client's elicitation handler and returning the tool's real
result. call_tool is transparent, call_tool_mcp exposes the raw result, and
call_tool_task yields a Task handle. The client half moves to fastmcp-tasks;
the [tasks] client extension auto-wires into Client (ProxyClient opts out).
Co-Authored-By: Claude <noreply@anthropic.com>
TasksExtension serves io.modelcontextprotocol/tasks on the extension API:
a decide-and-task tools/call interceptor (era-gated to modern connections),
tasks/get with inlined results and inputRequests, tasks/update delivering
poll-based in-task elicitation, tasks/cancel, durable creation, and
auth-scoped task isolation. Wire models validate against the vendored
ext-tasks schema. Worker-side Context hooks are refcounted so sibling
servers cannot strand each other's workers.
Co-Authored-By: Claude <noreply@anthropic.com>
Engine modules (keys, context snapshot, docket lifespan, worker CLI,
client handles) move intact; SEP-1686 wire modules park in _legacy_wire
for adaptation to SEP-2663. Core keeps task=True declaration on tools
only and raises at serve time until the tasks extension is registered.
Co-Authored-By: Claude <noreply@anthropic.com>
* Add M2M client credentials auth providers
Wrap the SDK's client_credentials and private_key_jwt OAuth providers as
FastMCP-idiomatic ClientCredentialsOAuthProvider and PrivateKeyJWTOAuthProvider,
enabling browser-free client authentication via Client(auth=...).
* Fix M2M token cache collision and explicit-scope drop
Namespace the token cache by client_id so distinct clients sharing one store don't overwrite each other's tokens; pin caller-supplied scopes so the token request keeps them; fix CodeQL URL-substring check in tests; drop unused logger.
* Preserve step-up scope union, scope-aware token cache, restore token expiry
Only pin the caller's explicit scopes on initial authorization, leaving the SDK's step-up scope union intact; namespace the token cache by requested scopes as well as client_id; restore persisted absolute expiry on init so an expired stored token is re-fetched.
* Skip expiry restore for non-expiring reloaded tokens
* Distinguish expires_in=0 from omitted when restoring expiry
* Scope step-up flag to the flow via ContextVar; runnable JWT signing example
* Restore upgraded dependency checks
Generated with Codex
* Clarify settings loading and teardown logging
Generated with Codex
* Align ty checks on the upgraded version
Generated with Codex
* Preserve simultaneous caller cancellation
Generated with Codex
Resource/prompt error detail and proxy instructions/connection-error
surfacing now work on the modern protocol era, so the tests pinned to
mode="legacy" with a TODO(defect)/TODO(mode="legacy" pin) marker run
on the default auto mode again.
Remove 4 unjustified pins (proxy header passthrough, connect timeout,
two response_title validation tests that fail before any request is
dispatched). Keep 81 pins that genuinely exercise older-protocol-only
behavior (ctx.elicit back-channel, sampling, roots, ping, session IDs,
initialize handshake, client.set_logging_level).
Flags a real defect: _on_read_resource/_on_get_prompt only catch
(DisabledError, NotFoundError), unlike _on_call_tool which catches
FastMCPError broadly. A ResourceError/PromptError escapes as a raw
exception and the modern protocol's generic exception ladder masks it
as "Internal server error", losing the detailed message tool errors
still get. Left pinned with a TODO in test_client.py and
test_error_handling.py rather than hidden.
Client negotiates the newest mutual protocol era by default (probe
server/discover, fall back to the initialize handshake). ProxyClient and the
inspect utility explicitly pin the handshake era so proxy forwarding and
server_info reads are unchanged. SSE and multi-server config transports are
legacy-only. extensions= and result_claims= (SEP-2133) are thin passthroughs
to the SDK session.
* Add OAuthProxy issuer response parameter
* Cover OAuthProxy issuer error redirects
* Relax host origin guard defaults (#4439)
* Use exact issuer in authorize errors
* Restore HTTP host guard compatibility (#4472)
* Hugging Face Auth Integration (#4385)
Co-authored-by: Jeremiah Lowin <153965+jlowin@users.noreply.github.com>
* Docs: add v3.4.4 changelog entries (#4473)
* Explain unnormalized issuer; cover consent-denial path base_url
* Revert "Merge remote-tracking branch 'origin/release/3.x' into codex/oauth-proxy-rfc9207-issuer"
This reverts commit 9e34b1686c, reversing
changes made to 640dc60fe0.
* Preserve callback query bytes when appending iss/code/state params
add_query_params previously decoded the existing query with parse_qsl
and re-encoded it, mutating opaque or signed query strings (a valueless
?flag became ?flag=, non-UTF-8 percent-encoded bytes got replaced).
Append the newly-encoded params to the existing query string instead of
round-tripping it through parse/encode.
Also fixes a stray bare `httpx` reference in a test that should use
httpx2 following the SDK v2 migration.
* Attach RFC 9207 iss to authorize() success redirects too
AuthorizationHandler only added iss to error redirects from the SDK's
base handler, not to code redirects returned directly by authorize()
overrides that bypass consent/upstream (as GitHub's mocked test does).
Since metadata now unconditionally advertises
authorization_response_iss_parameter_supported, any client-facing
redirect missing iss hard-fails RFC 9207-aware clients.
Also fixes HeadlessOAuth, which parsed code/state from the redirect
but silently dropped iss, so the same regression would have masked
itself across every other provider integration test too.
* Carry RFC 9207 iss through the production OAuth callback path
OAuthProxy advertises authorization_response_iss_parameter_supported and
sends iss on every authorization redirect, but the client's production
callback chain (CallbackResponse -> OAuthCallbackResult -> OAuth.callback_handler)
had no iss field, so it was silently dropped and the SDK's
validate_authorization_response_iss rejected the callback. HeadlessOAuth
already carried iss through, which is why CI stayed green while real
clients failed.
Add iss to CallbackResponse and OAuthCallbackResult, thread it through
store_result_once for both success and error branches, and pass it into
AuthorizationCodeResult in OAuth.callback_handler.
* Don't duplicate iss when a provider redirect already carries one
* Consolidate RFC 9207 iss handling into a single redirect helper
Every client-facing authorization redirect must carry exactly one iss.
That invariant was being enforced by hand at five separate call sites,
each building its own params dict -- which is how the success-redirect
path shipped without iss in the first place, and how a registered
redirect_uri that already carries its own iss could end up duplicated.
Route all five sites through build_client_redirect(), which owns the
idempotent replace-or-append behavior so no caller can get it wrong.
---------
Co-authored-by: shaun smith <1936278+evalstate@users.noreply.github.com>
Replaces FastMCP.as_proxy() helper calls with create_proxy(), rewrites the
mount() as_proxy=/prefix= kwarg tests to plain mount() (the params are gone),
and deletes deprecation-only tests for as_proxy() and remove_tool().
* OTEL: Fix attribute compliance and improve telemetry helpers
Attribute compliance:
- Remove rpc.system/service/method (MCP is not traditional RPC)
- Add gen_ai.tool.name on tools/call spans
- Add gen_ai.prompt.name on prompts/get spans
- Fix session_id check (truthy -> is not None)
Telemetry helper improvements:
- Add is_recording() guards to skip work on non-recording spans
- Add error.type attribute with __qualname__ on error spans
- Use isinstance check for ToolError to set "tool_error" error type
- Include exception message in span status description
- Add tool_name/prompt_name params to server_span and client_span
Client call_tool enrichment:
- Reflect tool-level errors (result.isError) on client span status
so callers see ERROR even though the MCP protocol call succeeded
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* fix: remove resource URI from span names to avoid high-cardinality
Per MCP semantic conventions, resource URIs SHOULD NOT be included in
span names by default since they can be unbounded (especially with
templates like users://{id}/profile). The URI remains available via
the mcp.resource.uri attribute.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* fix: add missing gen_ai/mcp attributes to proxy and delegate spans
- Proxy tool spans: add gen_ai.tool.name
- Proxy prompt spans: add gen_ai.prompt.name
- All delegate spans: add mcp.method.name
- Docs: remove rpc.* references, update span names and attributes table
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* Hoist ToolError imports to module level, add rpc.* migration note
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* fix: resolve OpenAPI 3.x server variables in _create_default_client
When an OpenAPI spec defines server variables (e.g. `https://{region}.api.example.com/v1`),
the default values are now substituted before constructing the httpx client base URL.
Previously, the URL was used as-is, causing all requests to fail for specs that use
server variable templating.
Fixes#1681
* fix: use str.replace instead of format_map for server variable substitution
format_map applies Python string formatting rules, so variable names
like {api.version} would be treated as attribute access and raise errors.
Literal token replacement handles all valid OpenAPI variable names safely.
* fix: task.wait() now returns on input_required instead of hanging
Previously, wait() used a terminal-state allowlist (completed, failed,
cancelled), so tasks entering input_required would hang until timeout.
Replaced with inverse logic: return whenever the task exits the 'working'
state. This handles input_required and any future blocking states without
needing to update the allowlist.
Fixes#3779
* fix: include submitted in in_progress_states to avoid premature return
* fix: revert submitted, update state docstring to match MCP spec
* fix: add _wait_terminal() so result() waits for completed/failed/cancelled
wait() correctly returns on input_required for human-in-the-loop use cases,
but result() needs to wait until the task fully resolves. Add a private
_wait_terminal() helper that loops through non-terminal states and use it
in all result() implementations.
* fix: elicitation scalar return, resource auto-serialization, Client.new() state, prompt errors
- Auto-wrap scalar elicitation responses for ScalarElicitationType schemas
so handlers can return T directly for ctx.elicit("msg", str/int/float)
- Auto-serialize dict/int/float/bool/None resource returns to JSON text
instead of crashing with TypeError
- Reset _task_registry and _submitted_task_ids in Client.new() so cloned
clients have independent task tracking state
- Include original error message in prompt render errors (matching tool
error behavior)
Fixes#3856
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* Fix misleading comment and add list/tuple auto-serialization for resources
The comment said "list/tuple of primitives" but the isinstance check
didn't include list or tuple. Now it does, and the comment matches.
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* Fix TaskNotificationHandler binding in Client.new() and meta forwarding for JSON resources
Two review-identified bugs:
1. Client.new() shallow-copies _session_kwargs, so the cloned client's
TaskNotificationHandler still dispatches to the original client.
Fix: create a fresh _session_kwargs dict with a new handler bound
to the new client.
2. convert_result() for dict/int/float/bool/None fell through to
ResourceResult(raw_value) which lost component meta (CSP, permissions).
The str/bytes path correctly wrapped in ResourceContent with meta.
Fix: explicitly serialize JSON-native types and wrap with meta,
matching the str/bytes path. Other types still fall through for
error handling.
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* Preserve custom message handlers in Client.new()
Only replace the message handler with a new TaskNotificationHandler
if the current handler IS a TaskNotificationHandler. If the user
provided a custom message_handler, preserve it in the clone.
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* fix client.new and add regression tests
* Honor declared MIME type for auto-serialized JSON resources
* Fix static analysis: remove unused StdioTransport import, fix ty:ignore comment
* Exclude list[ResourceContent] from JSON auto-serialization path
A bare list[ResourceContent] would match the isinstance(list) check
and get JSON-serialized instead of passing through to ResourceResult
normalization. Check for ResourceContent items first.
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
