Entity trail

MCP Python SDK

Source-backed findings, relationship evidence, citations, and briefing history from the public MindPattern archive.

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Corpus findings

2026-09-08 / github-pulse-researcherThe MCP Python SDK backported the same session-expiry and issuer-validation defaults to the 1.x line the same afternoonv1.30.0 shipped 2026-09-07 within two hours of v2.2.0 and carries the same behaviour changes to FastMCP: 30-minute idle session expiry, a 10,000-session cap (#3426), origin-scoped redirects (#3448), and rejection of authorization server metadata whose issuer does not match (#3431). It adds one thing 2.x does not stress: client registrations are now remembered per issuer, so a server that later points at a different authorization server triggers a fresh registration. Anyone pinned to 1.x for the older API surface gets the breaking defaults anyway.
2026-09-07 / github-pulse-researcherBoth reference MCP SDKs were re-serializing a pathless OAuth resource identifier and getting rejected by Entra ID; there is now a conformance check for itmodelcontextprotocol/conformance#488 adds `resource-parameter-matches-prm`, asserting the RFC 8707 `resource` parameter is sent byte-identical to what protected resource metadata published. The PR documents that both reference SDKs pushed a bare-origin PRM value like `https://example.com` through a URL parser and sent `https://example.com/`, which exact-match authorization servers reject — Microsoft Entra ID returns `AADSTS9010010` (typescript-sdk#1968, fixed on 2.x by #2581 with a 1.x backport #1972; python-sdk#2578/#2883, fixed by #2925). The four pre-existing RFC 8707 checks covered presence, fragment-freeness and cross-request consistency but never compared the sent value to the served one.
2026-09-05 / github-pulse-researcherMCP Python SDK adds opt-in RFC 8707 audience checking for bearer tokens, with a deprecation warning when it is left unsetPR #3447 (merged 2026-09-04) adds `AuthSettings.validate_token_resource`: when set, the bearer gate only accepts a token the `TokenVerifier` reports as issued for `resource_server_url` via `AccessToken.resource`, and a token naming another resource or none gets the same 401 as an unrecognized one. The resource-server gate had checked scopes and expiry but never compared the token's resource indicator with the server's own identifier, a gap the interaction suite tracks as the `hosting:auth:aud-validation` divergence. Leaving it unset emits an `MCPDeprecationWarning` and behaves as off; the PR says 3.0 makes it the default, so MCP server operators have one release to decide True or False.
2026-09-05 / github-pulse-researcherMCP Python SDK stops following cross-origin redirects that carried auth headers and request bodies to another hostPR #3448 (merged 2026-09-04) backports #3397 to the v1.x line: `streamable_http_client`, `streamablehttp_client`, `sse_client` and `OAuthClientProvider` now follow a redirect only when it stays on the endpoint's origin (same scheme, host and port, or an http→https upgrade on default ports), keeps the method, and carries no userinfo. Before this, the default client from `create_mcp_http_client` followed every redirect, so a `Location` naming another host moved the connection there with the endpoint's headers, auth and body attached. This is a breaking change: a cross-origin redirect or a 301/302/303 answering a POST now raises `httpx.HTTPStatusError`, and `follow_redirects=True` on a caller-supplied client is no longer consulted. Follow-up #3450 restores relative redirects for endpoint URLs that carry userinfo, which the first check refused too broadly.
2026-09-04 / github-pulse-researcherbrowser-use 0.13.10 exact-pins every dependency and stops reporting unknown MCP tool calls as successesThe 2026-09-04 release exact-pins all declared runtime, optional, development and build dependencies, migrates to MCP Python SDK 2.1.1, pins Pydantic 2.13.5 and Hatchling 1.32.0, adds pydantic-settings 2.15.0 as an explicit runtime dependency, and upgrades pypdf to 6.16.2 to clear three open Dependabot advisories. The behavioral change that matters for agent authors: an unknown MCP tool call is now reported as an application error instead of a successful result, so a model calling a tool that does not exist no longer gets a green light.
2026-09-03 / arxiv-researcherACLE-MCP Binds Each MCP Tool Call to the Workload That Was Actually AttestedThe paper names a 'post-authorization execution trust gap' in remote MCP: OAuth proves the endpoint was authorized, but not that a later tool call runs on the provider-side workload the relying party meant to trust, since execution can shift to a substituted workload, lean on stale appraisal state, reuse authority transferred from another sender, or traverse an undeclared downstream component. ACLE-MCP issues a short-lived, sender-constrained capability lease binding expected workload, freshness, operation, object and parameter bounds, downstream constraints and receipt obligations, consumed by a provider-side Execution Gate immediately before the protected tool logic runs. The runnable prototype uses Keycloak/OIDC, the MCP Python SDK server and an optional vTPM quote-verification backend; weaker authorization and connect-time-only attestation left distinct attack families open, while full ACLE-MCP blocked all evaluated families with benign tasks preserved.
2026-09-03 / github-pulse-researcherMCP Python SDK 1.x now expires idle Streamable HTTP sessions after 30 minutes and caps concurrent sessions at 10,000 by defaultPR #3426, merged 2026-09-02T15:06Z, backports session lifecycle ownership to the 1.x line: `session_idle_timeout` existed on `StreamableHTTPSessionManager` but defaulted to `None` and could not be set from `FastMCP`, so at stock settings a session whose client never sent `DELETE` stayed registered until the process exited. Both defaults are now active where there was previously no limit, and a manager beyond `max_sessions` answers 503. This is a behavior change for anyone running a stateful MCP server today, and pass `None` on either keyword to restore the old unbounded behaviour.
2026-09-03 / github-pulse-researcherThe MCP Python SDK now validates the OAuth authorization server issuer on every discovery path, including the legacy fallbackPR #3398, merged 2026-09-02T15:51Z, makes the OAuth client fix its expected issuer before fetching any authorization server metadata. On the 2025-03-26 legacy fallback path (no protected resource metadata) the document's `issuer` was never checked and stored-credential binding was re-evaluated against whatever issuer the document named, contrary to RFC 8414 section 3.3. Discovery now computes the expected issuer once, validates unconditionally, and stops rather than falling through to the legacy path when a resource-metadata location returns 5xx or 429, so a transient failure cannot walk a client with a bound registration onto the weaker path.
2026-09-01 / github-pulse-researcherFastMCP 4.0 ships stable, rebuilt on the sessionless 2026-07-28 MCP protocol so any replica behind a load balancer can answer a requestFastMCP 4.0.0 went stable on 2026-08-31 after five betas, five weeks, 23 contributors and 80+ pull requests, built on the MCP 2026-07-28 protocol revision and the rewritten Python SDK v2. Modern requests are sessionless and self-contained, so one deployment negotiates protocol version per connection and horizontal scaling no longer needs sticky sessions. Breaking changes matter for upgraders: server-initiated sampling and roots are removed (no live connection exists to call back into mid-request), ctx.elicit() is old-protocol-only, MCP model fields moved to snake_case, and background tasks moved to a separate fastmcp-tasks package.
2026-08-26 / vibe-coding-researcherMCP Python SDK Backports a FastMCP Import Warning Because Users Were Filing Bugs on the Wrong Reposv2.0.1, published 2026-08-26, is a one-off backport described as needed "due to a lot of people running into this error and making issues on other repos about it." SDK 2.0.0 moved everything under `mcp.server.fastmcp.*` to `mcp.server.mcpserver.*` and renamed the `FastMCP` class to `MCPServer`, so `pip install mcp` started producing `ModuleNotFoundError: No module named 'mcp.server.fastmcp'` in downstream servers whose maintainers had no idea why. The fix for your own project is one of two lines: pin `mcp>=1.28,<2`, or change the import and the constructor call, which leaves decorator arguments and handler signatures unchanged.
2026-08-25 / agents-researcherMCP Python SDK 2.1.0 stops leaking handler exception text to the model and extends the 4 MiB body cap to SSE and OAuthReleased 24 August, v2.1.0 changes two behaviors that will silently alter existing servers. An unexpected exception from a tool, resource or prompt handler is now logged once at ERROR locally and the client sees only 'Error executing tool <name>', so anything the model was meant to read must be raised as ToolError or ResourceError. Separately, a tool annotated to return TextContent, EmbeddedResource, Image or Audio no longer advertises outputSchema or returns structuredContent unless you pass structured_output=True. The 4 MiB request body limit now also covers the SSE transport and OAuth endpoints, and the SSE message endpoint answers 405 to non-POST.
2026-08-11 / agents-researcherOpenAI Agents SDK 0.20.0 switches the default model to gpt-5.6-luna and takes a breaking MCP v2 dependencyReleased early on Aug 11, the minor bump changes the implicit default model to gpt-5.6-luna and adds local MCP support for both Python SDK v1 and v2 across stdio, SSE, and Streamable HTTP — a potentially breaking migration for anyone with custom MCP HTTP auth or client factories, who must either match the installed MCP major version's HTTP types or pin mcp<2. The release also adds RunState.add_input() for staging durable user input before a resumed model call, GA transcription settings for realtime voice, and a batch of sandbox hardening including explicit credential-exposure acknowledgements on mounts and rejection of schemas exceeding safe recursion depth.

Graph relationships

SUPPORTS
RFC 8707
MCP Python SDK adds support for RFC 8707 bearer token audience validation
Source finding
USES
OpenTelemetry
MCP Python SDK v2.0.0 includes OpenTelemetry tracing support by default
Source finding
USES
FastMCP
FastMCP v1.30.0 backported session-expiry and authorization validation defaults from MCP Python SDK v2.2.0
Source finding
USES
FastMCP -> MCP Python SDK
FastMCP v1.30.0 backported session-expiry and authorization validation defaults from MCP Python SDK v2.2.0
Source finding

Source trail

GitHub PR #3426 The paper v2.0.1 GitHub 2026-07-28 revision confirmed it's live posted the real numbers on HN MCP Python SDK v2.0.0 TypeScript SDK went 2.0.0 spec changelog GitHub

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