* Add prefab auto-wiring for MCP Apps (#3119)
Tools that return prefab types (UIResponse, Component) automatically get
wired to the shared prefab renderer resource. Works via app=True,
return type inference, or both.
* Prefab compatibility updates
* Use published prefab-ui >=0.6.0, remove local source override
* Migrate UIResponse to PrefabApp for Prefab UI integration
PrefabApp is a pure data object with to_json(), html(), and csp()
methods. Tools can return PrefabApp, bare Components, or
ToolResult with structured_content for custom LLM fallback text.
* Add Prefab UI apps documentation
* Add mini apps and full apps documentation pages
Mini apps covers the common single-screen patterns: charts (bar, line,
area, pie), data tables with sorting/search/pagination, forms (manual
and Pydantic-generated), status displays, conditional content, and
layout composition with tabs and accordions.
Full apps covers multi-page applications using Pages/Page components,
shared state across pages, and using ToolCall with result_key for
server-driven state updates.
* Reframe apps docs around motivation, add generative UIs page
The docs now lead with the problem — MCP tools stuff data into the LLM
context window, and building HTML/JS/CSS frontends is a non-starter for
Python developers — before introducing Prefab as the solution. Mini apps
are framed as the primary use case: focused, single-purpose UIs that
present data visually and collect structured input.
New generative UIs page covers the concept of LLMs producing component
JSON directly, enabling adaptive dashboards, tailored forms, and
exploratory workflows.
* Tag Prefab docs pages as SOON instead of NEW
* Rename Low-Level API to Custom HTML Apps
The page is about using the MCP Apps extension directly, not a FastMCP
or Prefab internal API. Reframed to make clear this is the open MCP
protocol with FastMCP providing convenience wrappers.
* Tighten apps docs and widen content area
Strip editorial motivation from all app doc pages — let code examples
do the talking. Add content-area max-width override (44rem) to style.css.
* Restructure apps docs, fix code issues
Rename Prefab UI → Prefab Apps, mini-apps → patterns, remove
generative-uis and full-apps pages. Rewrite prefab page to lead with
what users do (declare a UI, return it) before explaining internals.
Patterns page now has fully self-contained copy-pasteable examples with
explicit imports and links to prefab docs. Forms show the two-tool
pattern (form + handler). Add patterns_server.py example.
Code fixes: move get_args to module-level import, remove dead
AuthCheckCallable type alias, fix ToolCall→CallTool in all docs.
* Remove unused ToolResult import from chart_server
* Handle composite Prefab types in type inference and schema suppression
_has_prefab_return_type and the output schema suppression logic only
checked bare classes, missing unions (Column | None) and Annotated
wrappers (Annotated[PrefabApp | None, ...]). Recurse through Union,
types.UnionType, and Annotated to detect Prefab types in composite
annotations.
* code mode
* update uv.lock for monty optional dep
🤖 Generated with Claude Code
* retry CI
* Address PR review comments on CodeMode transform
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
* Fix ty unresolved-attribute error on search_helper
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
* more idiomacy
* harden
* fix docs
* harden
* fix red CI
* Refactor CodeMode to use CatalogTransform base class
Removes the duplicate ContextVar bypass pattern in favor of the shared
CatalogTransform machinery. Also fixes a pre-existing bug where
`from __future__ import annotations` caused NameError for Annotated
in nested function scopes at runtime.
* Remove redundant _get_visible_tools wrapper in CodeMode
* Rewrite CodeMode docs with proper motivation and structure
* Fix type narrowing in collision test
* Stop unwrapping tool results in CodeMode's call_tool
call_tool() inside execute blocks now returns structured content as-is,
preserving the {"result": value} wrapping. This means the output schema
shown in search results accurately describes what call_tool() returns,
so LLMs can trust the schema when writing code.
Also adds examples/code_mode/ with a server and narrated client demo.
* Simplify call_tool return type: dict | str
* Fix example client to unwrap structured results
* Let server resolve tool versions instead of pinning first match
* Rewrite CodeMode docs to match current behavior
* Rename optional extra from monty to code-mode
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Jeremiah Lowin <153965+jlowin@users.noreply.github.com>
* feat: Add search transforms for tool discovery
RegexSearchTransform and BM25SearchTransform collapse large tool
catalogs into a search interface so LLMs discover tools on demand
instead of receiving the full listing.
* chore: Update SDK documentation
* fix: call_tool recursion guard, atomic BM25 rebuild, hash includes descriptions
* Extract CatalogTransform base class for catalog-aware transforms
Transforms that replace list_tools() with synthetic components (like
search) need to read the real catalog at call time without triggering
their own replacement logic. CatalogTransform handles the re-entrant
bypass via per-instance ContextVar, exposing transform_tools() as the
subclass hook and get_tool_catalog() for catalog access.
* Add search transform examples for regex and BM25
* Add README for search transform examples
* Polish search example clients with rich output
* Remove hardcoded tool counts from search example subtitles
* Clarify that review bot feedback should be evaluated on its merits
* Expand search transform docs with proper hierarchy
---------
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
* Fix ty 0.0.19 type errors
🤖 Generated with Claude Code
* Fix ruff formatting in sampling/run.py
🤖 Generated with Claude Code
https://claude.ai/code/session_01GWzbyF1vHvVeS4yJ5bhScf
---------
Co-authored-by: Claude <noreply@anthropic.com>
* Fix background Context request correlation
* Make OptionalCurrentContext type-safe
Refactor OptionalCurrentContext to wrap CurrentContext instead of overriding __aenter__ with a wider return type. Adds a background-task origin_request_id round-trip test and applies ruff formatting.
* Fix ty ignore syntax in OpenAPI provider
* Fix flaky rate limiting and ping timing tests
* Assert rate limit error message in flaky test fix
* Catch only ToolError in rate limiting test
* Fix NameError with future annotations and Context/Depends parameters
Closes#3238, closes#905
* chore: Update SDK documentation
* Drop unnecessary pre-resolution of annotations
Pydantic (even 2.11.7) uses __module__ not __globals__ to resolve
annotations, so setting __module__ alone is sufficient.
* chore: Update SDK documentation
* Restore annotation pre-resolution for Pydantic compat
The wrapper's __globals__ is read-only and points to dependencies.py,
so some Pydantic versions use it instead of __module__ when resolving
string annotations. Pre-resolving via get_type_hints on the original
function ensures annotations are type objects before Pydantic sees them.
* chore: Update SDK documentation
---------
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
* Fix non-serializable state lost between middleware and tools
Inherit _request_state dict from parent Context in __aenter__ so
middleware and tool contexts share the same in-memory state.
Closes#3228
* chore: Update SDK documentation
---------
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
* Use standard traceparent/tracestate keys per OTel MCP semconv
The OTel semantic conventions for MCP (https://opentelemetry.io/docs/specs/semconv/gen-ai/mcp/)
put `traceparent` and `tracestate` directly in `params._meta` without a prefix.
FastMCP was using `fastmcp.traceparent` / `fastmcp.tracestate`, which meant
non-FastMCP clients sending the standard keys couldn't propagate traces.
Switches injection to the bare keys and adds fallback extraction for the old
prefixed keys so older FastMCP clients still work.
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
* chore: Update SDK documentation
* Drop legacy fastmcp.-prefixed trace key fallback
🤖 Generated with Claude Code
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
* chore: Update SDK documentation
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
* Update repository references from jlowin/fastmcp to prefecthq/fastmcp
* Retrigger CI after repo transfer
* chore: Update SDK documentation
* Only run deep triage on bug issues for jlowin
---------
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
* Add consent binding cookie to prevent confused deputy attacks (GHSA-rww4-4w9c-7733)
The OAuthProxy's consent page verified user intent but didn't bind the
consenting browser to the IdP callback. An attacker could intercept the
upstream authorization URL after consent and send it to a victim, whose
browser would complete the flow without having the consent cookie.
This adds a signed consent binding cookie set during consent approval
(both manual and auto-approve paths) and verified in the IdP callback
handler. A different browser won't have this cookie and gets a 403.
* Use startswith for URL assertion in consent binding test
* Store consent bindings as per-transaction map to support parallel flows
* Only accept __Host- consent binding cookie on HTTPS
* chore: Update SDK documentation
---------
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
* fix: restore request context in StatefulProxyClient handlers
StatefulProxyClient reuses sessions across requests, so its receive-loop
task inherits a stale request_ctx ContextVar from the first request.
Server-initiated messages (elicitation, sampling, etc.) that depend on
related_request_id routing get sent to a closed stream and hang forever.
Closes#3169
* chore: Update SDK documentation
---------
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
* fix: guard client pagination loops against misbehaving servers
Treat empty/falsy nextCursor as end-of-pagination and detect cursor
cycles across all client list methods and the server context proxy
helper.
* chore: Update SDK documentation
---------
Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
Moves relay_elicitation() into elicitation.py so it can reuse
handle_task_input() for the Redis push instead of duplicating that logic.
notifications.py just detects the trigger and calls it.
Also fixes the related-task metadata key from modelcontextprotocol.io/ to
io.modelcontextprotocol/ to match the current spec:
https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/tasks
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
