Split the monolithic Client class into focused mixin classes:
- ClientToolsMixin (tools_client.py)
- ClientPromptsMixin (prompts.py)
- ClientResourcesMixin (resources.py)
- ClientTaskManagementMixin (task_management.py)
Also:
- Extract timeout normalization helpers to utilities/timeout.py
- Split SSETransport into its own module (transports/sse.py)
- Clean up unused imports across client modules
- Fix bare except clauses to catch specific McpError
Note: ty reports unresolved-attribute errors on mixin classes because
it doesn't understand that mixins will be composed with Client. This is
a known limitation of mixin typing in Python. The code is functionally
correct and all tests pass.
Remove send_notification_sync() method, notification queue, and background flusher task. Component add/remove operations happen outside sessions and no longer need notifications.
Rename Visibility to Enabled, collapse VisibilityRule into the transform,
and move enabled filtering from Provider to Server level so server-level
transforms can override provider-level disables.
Updates FastMCP's telemetry to align with the new MCP semantic conventions
from open-telemetry/semantic-conventions#2083. This gives us interoperability
with other MCP implementations while keeping fastmcp.* attributes for things
unique to our framework.
Changes:
- Span names now follow `{method} {target}` format (e.g., `tools/call greet`)
- Added `mcp.method.name` and `mcp.resource.uri` attributes
- Renamed `fastmcp.session.id` to standard `mcp.session.id`
- Kept fastmcp.* attributes for server name, component info, provider details
🤖 Generated with Claude Code
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Validates that session_id is captured on both client and server
spans when using HTTP transport, and that they share the same ID.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Adds opt-in distributed tracing via OpenTelemetry for observability into
FastMCP server and client operations.
Server spans are created for tool calls, resource reads, and prompt
renders with attributes like component key, component type, provider
type, session ID, and auth context. Client spans wrap outgoing calls
with trace context propagation via W3C headers in request meta.
Components provide their own span attributes through a `get_span_attributes()`
method that subclasses override - this lets LocalProvider, FastMCPProvider,
and ProxyProvider each include relevant context (original names, backend URIs).
To enable: configure an OpenTelemetry SDK with a TracerProvider before
importing fastmcp. Traces export to any OTLP-compatible backend.
Closes ENG-2813
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
pydocket 0.16.3 fixes a race condition in `_worker_loop` where cancellation
arriving between `_worker_done.clear()` and the try block would cause
`_worker_done.set()` to never run, blocking `Worker.__aexit__` forever.
Also fixes:
- Simplified `_docket_lifespan` cleanup (timeout wrapper no longer needed)
- Fixed `nested_server` test fixture to use graceful uvicorn shutdown
- Fixed uv transport tests to use local fastmcp in dev mode
Closes#2679🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
* Move OpenAPI to providers/openapi/ submodule
Migrates the OpenAPI implementation to the provider pattern:
- Creates src/fastmcp/server/providers/openapi/ submodule with provider.py,
components.py, and routing.py
- Converts server/openapi/ to deprecated re-export stubs
- FastMCPOpenAPI remains as deprecated wrapper that uses OpenAPIProvider
- Updates experimental/server/openapi to import from new canonical location
* Update tests and FastMCP methods to use OpenAPIProvider
- Update FastMCP.from_openapi() and from_fastapi() to use OpenAPIProvider
directly, returning FastMCP instead of deprecated FastMCPOpenAPI
- Move tests from tests/server/openapi/ to tests/server/providers/openapi/
- Update all test imports to use new canonical location
- Add tests/deprecated/openapi/ for backward compatibility testing
- Update tests/client/test_openapi.py to use new imports
* Fix deprecation warning tests and address CodeRabbit feedback
- Use importlib.reload() to ensure deprecation warnings fire in tests
- Change logger.error to logger.exception for better stack traces
* Replace type: ignore[attr-defined] with isinstance assertions in tests
* Fix isinstance assertions in failing tests
- Fix enum test to check for ResponseEnum instead of str
- Fix binary resource test to check for BlobResourceContents instead of TextResourceContents
- Fix Root type tests to check attributes directly instead of isinstance checks
* Fix type errors without using type: ignore
- Remove execution methods from TransformingProvider (only handles transformations)
- Add execution methods to base Provider class with default implementations
- Fix type narrowing in tests using cast() instead of type: ignore
- Fix PromptResult type handling in prompt render tests
- Fix type narrowing in middleware test for arguments and structured_content
* Simplify Provider interface and consolidate docket registration
- Remove get_http_routes from Provider (unused)
- Remove ProviderLifespanConfig, _base_lifespan, _register_tasks
- Remove supports_tasks flag from Provider.__init__
- Consolidate all docket registration in server._docket_lifespan()
- Simplify lifespan() to take no parameters
- Move MountedProvider to separate module
* Fix control flow in ComponentService resource methods
* Move providers to server/providers
* Ensure MountedProvider get_* methods go through middleware
* Fix get_resource to only return concrete resources
Reverts template-checking in get_resource that broke task execution.
Tasks need access to the original template, not instantiated resources.
* Move prefix utilities into mounted.py, deprecate import_server
- Add resource prefix functions (add/remove/has_resource_prefix) to mounted.py
- Deprecate import_server with warning to use mount() instead
- Add tool_names uniqueness validation in MountedProvider
* Fix provider iteration order and remove dead _is_mounted flag
- Remove unused _is_mounted flag (MountedProvider.lifespan() calls _lifespan
not _lifespan_manager, so the flag was never checked)
- Fix provider iteration: change reversed() to forward order in execution
methods (_call_tool, _read_resource_middleware, _get_prompt_content_middleware)
to match documented "first non-None wins" semantics
- Fix ComponentService to handle prefix-less mounted servers using
_strip_tool_prefix()/_strip_resource_prefix() methods
- Update conflict resolution tests to expect first-registered provider wins
- Add regression tests for Docket behavior and prefix-less ComponentService
* Add TaskComponents type and exception handling for provider task registration
- Create TaskComponents dataclass with FunctionTool/FunctionResource/etc. types
for proper typing of get_tasks() return value
- Add try/except wrapper around provider.get_tasks() in _docket_lifespan for
consistent error handling (warn + continue or raise based on settings)
- Remove type: ignore comments from server.py task registration loop
* Add AnthropicSamplingHandler
Adds a sampling handler for the Anthropic API at
fastmcp.client.sampling.handlers.anthropic, alongside the existing
OpenAI handler. Includes full support for tool calling.
Install with: pip install fastmcp[anthropic]
* Update default model
* Update sampling docs to cover both OpenAI and Anthropic handlers
* Use AsyncAnthropic, fix falsy value handling, handle tool_choice none
* Propagate isError to Anthropic, join multiple text blocks, fix docs
* Unify SamplingHandler and promote OpenAI handler
Consolidates ServerSamplingHandler and ClientSamplingHandler into a single
SamplingHandler type alias. Moves OpenAISamplingHandler from experimental
to fastmcp.client.sampling.handlers.openai as the canonical location.
Backwards compatibility maintained for imports from experimental.
* Remove unreachable code paths in OpenAI handler
* Fix docstring and use elif for mutually exclusive branches
* MCP → SDK (vocab change only)
* WIP: Sampling API with SamplingResult[T] and result_type
* SEP-1577: Sampling with tools
- Add tools and result_type parameters to ctx.sample()
- Update OpenAI handler for tool content types
- Client advertises sampling.tools capability by default
- Collect tool results into single message with list content
* Fix tool result content handling in OpenAI handler
* Remove @sampling_tool decorator - pass functions directly to sample()
Functions passed to ctx.sample(tools=[...]) are now auto-converted
via SamplingTool.from_function(). Users can still use that method
directly for custom name/description overrides.
* Remove auto-conversion of MCP tools to sampling tools
Users want MCP tools passed to ctx.sample() to go through the full MCP
machinery (middleware, native responses) rather than being auto-converted
to direct function calls. Now only SamplingTool and plain callables are
accepted - passing a FastMCP Tool raises a clear TypeError.
Also bumps mcp dependency to >=1.24.0 for required sampling features.
* Refactor sampling API: replace sample_iter() with sample_step()
Replace the mutable SampleRun/sample_iter() pattern with a simpler stateless
sample_step() function. sample_step() makes a single LLM call and returns a
SampleStep with the response and history. sample() now loops sample_step()
internally.
Key changes:
- Add sample_step() for fine-grained control over the sampling loop
- Remove SampleRun class and sample_iter() method
- Structured output uses tool description only (no prompt modification)
- execute_tools parameter controls automatic vs manual tool execution
* Address CodeRabbit nitpicks
* Address CodeRabbit review feedback for sampling tools
- Fix temperature=0.0 being dropped due to falsy evaluation
- Add ToolChoice.name support for forcing specific tools
- Replace assert statements with explicit RuntimeError checks
- Add mask_error_details parameter to sample()/sample_step() with ToolError escape hatch
- Fix hasattr patterns with proper isinstance checks
- Document mask_error_details and add OpenAI prerequisites to docs
* Address additional CodeRabbit review feedback
- Catch ValidationError specifically instead of bare Exception
- Update result_type docs to mention dataclasses and basic types
- Raise ValueError for unknown tool_choice modes
- Validate sampling_handler_behavior to catch typos
- Remove ToolChoice.name handling (not part of MCP spec)
- Validate tool_choice string in sample_step()
* Review fixes for sampling tools PR
- Remove internal functions from sampling __init__.py exports
- Remove fragile is_text property, use not is_tool_use instead
- Inline call_client into context.py, remove from run.py
- Fix SamplingMessage docs to use TextContent
- Handle result.text being None in doc examples
- Simplify client sampling docs to recommend OpenAISamplingHandler
- Add sampling_capabilities override documentation
- Raise iteration limit from 50 to 100
- Remove _parse_model_preferences duplication
- Use AsyncOpenAI in OpenAISamplingHandler
- Fix tool_choice docstring
* Fix OpenAI handler tests to use AsyncOpenAI
* Address remaining CodeRabbit review comments
- Fix message ordering in OpenAI handler: tool results now correctly
follow assistant message with tool_calls
- sample_step() now always includes assistant message in history
- Raise ValueError on JSON parse errors instead of silent {}
- Add has_sampling capability check when behavior is None
- Raise RuntimeError when structured output receives text response
- Wrap primitive result_type schemas in object wrapper
- Fix docs example using invalid SamplingMessage construction
- Add comprehensive client_sampling_test.py example
* Add return type annotation to OpenAISamplingHandler.__init__
* Use explicit 'is not None' check for sampling_capabilities defaulting
---------
Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
Co-authored-by: Bill Easton <strawgate@users.noreply.github.com>
When a prompt function returned `mcp.types.PromptMessage` objects directly
and was executed as a task, the result serialization failed with
"'PromptMessage' object has no attribute 'to_mcp'".
The task result converter was calling `.to_mcp()` on what it thought was a
FastMCP wrapper type, but the import actually pulls in `mcp.types.PromptMessage`
directly, which is already the final MCP type. Removed the unnecessary
conversion.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
* [feat] expose get_session_id callback
* [test] add test for session id callback
* [fix] add test for uninitialized case and default to None
* [fix] add in changes based on reviewers
* SEP-1330 enum schema support for elicitation
* Add version badges for 2.14.0 elicitation features
* Fix Context.elicit() to handle SEP-1330 enum syntaxes
* Guard against empty list in elicit response_type
* Add guards for empty dict/list edge cases in elicit
* Refactor elicit: extract parsing and response handling to elicitation.py
The task protocol (SEP-1686) is now always enabled - server always
registers task handlers and advertises task capabilities. Users still
opt into background execution at the server level (tasks=True) or
component level (task=True on tools, prompts, resources).
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Co-Authored-By: Claude <noreply@anthropic.com>
* Fix type errors for ty 0.0.1-alpha.31 upgrade
Add type ignores and fixes for ty's stricter checking:
- Path(None) guards in cli.py
- isinstance checks for ElicitRequestFormParams (URL elicitation support)
- TODO(ty) comments for match/isinstance narrowing bugs
- Method override type ignores for generic covariance
- Starlette Middleware typing workarounds
- Dynamic type construction ignores in json_schema_type.py
* Fix remaining type errors for ty 0.0.1-alpha.31
- Add asserts for optional attribute access in tests
- Add type ignores for dynamic httpx transport internals
- Add TODO(ty) comments for `in` operator on str|bytes
- Add TODO(ty) comments for Starlette Middleware typing
- Use cast for prompt.fn async validation in server.py
* Upgrade ty to 0.0.1-alpha.31
Fixes additional test file type errors discovered after upgrade.
Docket provides background task execution and is now always available
for all FastMCP servers. Only `enable_tasks` remains to control the
SEP-1686 task protocol support.
Changes:
- Remove `enable_docket` setting and related validation
- Docket/Worker lifecycle is always active in server lifespan
- CurrentDocket and CurrentWorker dependencies work without config
- Add server readiness signaling via `_started` event
- Fix test timing issues with proper port probing
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Co-Authored-By: Claude <noreply@anthropic.com>
* Implement MCP background tasks (SEP-1686) using Docket
Adds support for background task execution via the MCP task protocol,
powered by Docket for task queue management.
- Tools, resources, and prompts can be marked with `task=True` to run async
- Progress dependency for tracking task progress
- CurrentDocket and CurrentWorker dependencies for advanced use cases
- Client API with `.call_tool(..., task=True)` returns task handles
- Task status notifications via subscriptions
- CLI worker command for distributed task processing
Configuration via environment:
- FASTMCP_ENABLE_DOCKET=true
- FASTMCP_ENABLE_TASKS=true
- FASTMCP_DOCKET_URL=redis://... (or memory:// for single-process)
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Co-Authored-By: Claude <noreply@anthropic.com>
* Fix tasks example import (TaskStatusResponse → GetTaskResult)
The example was using a non-existent TaskStatusResponse type.
Updated to use mcp.types.GetTaskResult which is what the
on_status_change callback actually receives.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
* Fix env var name in Docket error messages
The error messages referenced FASTMCP_EXPERIMENTAL_ENABLE_DOCKET but the
actual setting is FASTMCP_ENABLE_DOCKET.
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Co-Authored-By: Claude <noreply@anthropic.com>
* Remove deprecated code re-added from pre-#2329 branch
- Remove ExtendedEnvSettingsSource (FASTMCP_SERVER_ prefix support)
- Remove dependencies parameter from FastMCP.__init__
* Replace fakeredis git pin with PyPI release
* Remove redundant fakeredis dev dep (pulled via pydocket)
---------
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Jeremiah Lowin <153965+jlowin@users.noreply.github.com>
- Bump mcp SDK to >=1.23.1
- Add `client_secret_basic` authentication support (SDK PR #1334)
- TokenHandler now wraps SDK's handle() to transform `unauthorized_client`
to `invalid_client` on 401 responses per OAuth 2.1 spec
- Update `sample()` return type to use SDK's SamplingMessageContentBlock
- Update test expectations for new SDK fields (`task`, `_meta`)
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Co-Authored-By: Claude <noreply@anthropic.com>
* Initialize 2.14 deprecation removal branch
* Remove deprecated FASTMCP_SERVER_ environment variable prefix (#2330)
* Remove deprecated Context.get_http_request method (#2332)
* Remove fastmcp.Image top-level import (deprecated 2.8.1) (#2334)
* Remove test warnings (#2331)
* Create new branch and fix issue
* Remove deprecated client parameter from FastMCPProxy (#2333)
* Remove deprecated run_streamable_http_async method (#2338)
* Remove deprecated sse_app method (#2337)
* Remove deprecated run_sse_async method (#2335)
* Remove deprecated run_sse_async method
* Update CLI and tests to use run_http_async(transport="sse")
- Change CLI to call run_http_async with transport="sse" instead of run_sse_async
- Update test to mock run_http_async with create=True for v1 servers
* Revert CLI changes - v1 servers do have run_sse_async
- Keep CLI calling run_sse_async() for v1 compatibility
- Update test to mock run_sse_async (which exists on v1)
* Remove unnecessary type ignore for run_sse_async
Method exists on v1 FastMCP class, no type error
* Remove unused imports after test deletion
* Remove deprecated streamable_http_app method (#2336)
* Remove deprecated dependencies parameter from FastMCP constructor (#2340)
* Remove output_schema=False support (deprecated 2.11.4) (#2339)
* Remove deprecated client parameter from FastMCPProxy (#2333)
* Delete deprecated test_output_schema_false.py
Tests functionality that has been removed
* Remove deprecated BearerAuthProvider module (#2341)
* Remove resource_prefix_format="protocol" support (deprecated 2.4.0) (#2342)
* Remove resource_prefix_format="protocol" support (fixes#2195)
Removes deprecated protocol format (prefix+resource://path) and keeps only
path format (resource://prefix/path). Since only one format remains:
- Removed resource_prefix_format from settings, FastMCP.__init__, and helpers
- Simplified add_resource_prefix, remove_resource_prefix, has_resource_prefix
- Removed MountedServer.resource_prefix_format field
- Deleted tests for protocol format
All resource prefixes now use path format exclusively.
* Clean up resource_prefix_format references
- Remove from test files
- Update documentation to remove protocol format section
- Move custom HTTP routes note to mounting section
- Remove resource_prefix_format from settings docs
* Use inline version note instead of badge for prefix format
* Remove obsolete test functions and update docs
- Delete test functions that no longer assert anything
- Remove proxy.mdx reference to deleted prefix format section
* Format error messages per ruff
* Remove from_client classmethod (deprecated 2.8.0) (#2343)
* Remove deprecated from_client classmethod (fixes#2192)
* Remove unused Client import
* Remove add_resource_fn method (deprecated 2.7.0) (#2345)
* Update SDK
* Add missing imports for exclude_args deprecation warning
* Allow OAuth instance to use the same httpx factory as the Transport
* Fix test
* Update SSL verification mode assertion in tests
* This is actually not needed
* Creating a Client instance is not needed for this test
* Fix test
* Apply httpx_client_factory fix to SSETransport
Extends the OAuth httpx_client_factory changes to SSETransport.
SSETransport had the same issues as StreamableHttpTransport where it
wasn't passing the custom httpx client factory to OAuth, causing
certificate verification settings to be ignored during OAuth flows.
Changes:
- Set httpx_client_factory before calling _set_auth()
- Pass httpx_client_factory to OAuth constructor
- Add test for SSETransport OAuth client factory propagation
---------
Co-authored-by: Jeremiah Lowin <153965+jlowin@users.noreply.github.com>
* feat: Add optional meta parameter to Client tool call methods
* fix: Add support for mcp<1.19
* chore: cleaner solution
* Refactor call_tool to directly accept meta parameter and add tests for meta functionality
---------
Co-authored-by: Jeremiah Lowin <153965+jlowin@users.noreply.github.com>
* Add manual initialization control to Client
- Add auto_initialize parameter (default True) to control automatic initialization
- Make initialize() method public with idempotent caching
- Add comprehensive test suite for initialization behavior
* Document client initialization control and server instructions
- Expand documentation to cover auto_initialize parameter
- Show manual initialization for advanced use cases
- Document accessing server instructions via initialize_result
* Update client.mdx
* Bump ty to >=0.0.1a25 with type fixes
Follow-up to #2295. Updates ty and fixes compatibility issues with alpha 25, including:
- Updated ignore comment syntax (possibly-unbound-attribute → possibly-missing-attribute)
- Fixed async generator type handling with anext()
- Fixed type narrowing for timeout parameters
- Converted base_url assignments to AnyHttpUrl after string manipulation
- Added CallToolResult to return type annotations
- Removed redundant type casts
- Fixed test form data to use strings instead of bytes
ty alpha 25 has limitations with isinstance() narrowing on unions (see pyproject.toml for details), requiring some targeted type ignores.
* Pin ty to ==0.0.1a25
Alpha releases can have breaking changes, so pin to the tested version.
* Use anyio as testing backend
* Remove asyncio markers
* Update streamable http tests
* Replace all subprocess tests
* Replace anyio task groups with asyncio context managers in tests
- Convert run_server_async from anyio task group pattern to asyncio.create_task with async context manager
- Remove task_group fixture from conftest
- Update all test fixtures to use async with run_server_async pattern
- Remove TaskGroup imports from all test files
- Tests now work with pytest-asyncio instead of pytest-anyio
* Update test_github_provider_integration.py
