mcp 07-2026 conformance harness tracker

[filintod]

adding conformance tests to track gaps for modern mcp implementation. It includes a v2 version of everything server from typescript repo as currently everything server from conformance repo is still on previous/current version

pdf print of status.html:

• After closing stateless gap agentgateway MCP conformance 07:07.pdf
• After implementing MRTR agentgateway MCP conformance -07:08.pdf

NOTE: this is using typescript conformance test (https://github.com/modelcontextprotocol/typescript-sdk/tree/main/test/conformance) for draft (modern) as the conformance test file in the conformance repo is not currently testing all modern features

Last execution shown on top of PR #2465

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Current gaps are related to MRTR. Pending safely removing unstrip in our code strip_unsupported_client_capabilities to handle capabilities. from the code:

// Until server-to-client request routing is implemented, do not advertise
// capabilities that require the proxy to route upstream requests back to
// the downstream client and route the client's JSON-RPC response upstream.

The current stateless error requires a more thorough implementation if we ever do it for compatibility between versions

[Copilot]

Pull request overview

Adds MCP conformance-oriented behavior and tests to better track (and close) modern protocol gaps, including updated modern request validation and a new subscriptions/listen filtering/assembly path suitable for multiplexed upstreams.

Changes:

• Implement gateway-owned subscriptions/listen stream assembly with per-target filtering, subscriptionId tagging, and FailOpen/FailClosed behaviors (plus targeted tests).
• Tighten modern (2026-07-28+) request validation: required _meta fields, consistent method-not-found handling, and clearer “backend unavailable” vs “invalid request” signaling.
• Reduce backend-specific response shaping (e.g., OpenAPI upstream no longer stamps cache hints; the gateway normalizes outbound cache policy).

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
crates/agentgateway/src/proxy/mod.rs	Maps new MCP error variants to appropriate HTTP status codes (404/400/503).
crates/agentgateway/src/mcp/upstream/openapi/mod.rs	Removes cache hint stamping and treats subscriptions/listen as a long-lived/pending stream.
crates/agentgateway/src/mcp/upstream/mod.rs	Adds an explicit Unavailable upstream error and rejects unsupported listen for stdio/SSE upstreams.
crates/agentgateway/src/mcp/subscriptions.rs	New listen filtering/tagging + stream assembly implementation for multiplexing.
crates/agentgateway/src/mcp/subscriptions_tests.rs	Adds focused tests for listen filtering, tagging, error handling, and failure modes.
crates/agentgateway/src/mcp/streamablehttp.rs	Refactors modern protocol detection/validation and adds fallback classification for parse failures.
crates/agentgateway/src/mcp/session.rs	Makes stateless upstream initialization conditional and routes listen through new subscriptions pipeline with RBAC shaping.
crates/agentgateway/src/mcp/README.md	Documents listen transport limitations and failure-mode implications.
crates/agentgateway/src/mcp/mod.rs	Adds method/version helpers and new MCP error variants for modern validation.
crates/agentgateway/src/mcp/mergestream.rs	Adds a filter-map helper used by the listen pipeline (plus test-only helpers).
crates/agentgateway/src/mcp/mcp_tests.rs	Expands/updates tests for modern method-not-found, modern _meta requirements, and version error data.
crates/agentgateway/src/mcp/handler.rs	Extracts shared fanout stream-opening logic and adds a dedicated listen sender with guardrails integration.

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