feat: add 2026-04-22 weekly meeting notes

meetings/2026-04-22_weekly.md

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+# 2026-04-22 MCP: Transport Working Group (Regular)
+
+**TL;DR:** The April 22 meeting of the MCP Transport Working Group centered on
+tightening up the stateless Specification Enhancement Proposal (SEP). The tone
+shifted from routine specification updates to high urgency after the discovery
+of a critical, cross-SDK bug regarding protocol version negotiation. Major
+consensus was reached on deprecating resumable streams entirely, mapping JSON
+RPC request IDs as standard IO stream identifiers, and clarifying HTTP versus
+standard IO cancellation mechanisms.
+
+### Detailed Summary
+
+### Stateless SEP Cancellation Mechanisms
+*   **Tension Point:** How to handle cancellation across different transports.
+    Stephen Halter pointed out that the current streamable HTTP spec explicitly
+    notes a stream reset is *not* a cancellation, creating a capability gap with
+    standard IO. 
+*   **Consensus:** Mark Roth successfully argued that in a stateless
+    architecture, closing the HTTP stream *is* inherently a cancellation. 
+*   **Consensus:** For standard IO, cancellation will rely strictly on the
+    `cancel notification`. SDKs are expected to abstract these
+    transport-specific differences automatically so clients have a unified
+    experience.
+
+### Standard IO Semantics & Stream Identifiers
+*   **Tension Point:** Multiple `subscribe` calls over standard IO currently
+    lack a correlation ID for returning notifications, making it ambiguous which
+    notifications belong to which subscription request.
+*   **Trade-off/Debate:** Mark Roth proposed formalizing the JSON RPC request ID
+    as the standard IO stream identifier. Geoff Goodman and Luca Chang noted a
+    strict reading of JSON RPC dictates that notifications containing an ID are
+    technically treated as requests. 
+*   **Consensus:** The group agreed to include the original request ID in
+    returning notifications (potentially tucked inside an envelope or payload to
+    bypass JSON RPC violations) to effectively multiplex standard IO streams.
+    Progress notifications will follow this exact same pattern.
+
+### Deprecation of Resumable Streams
+*   **Debate:** With connection drops now implicitly triggering cancellation,
+    the existing resumable streams (SSE) feature contradicts the new stateless
+    paradigm. 
+*   **Consensus:** Resumable streams are officially deprecated and will be
+    stripped from the SEP. 
+*   **Trade-off:** Any workload requiring durability or resumability must now
+    utilize tasks rather than relying on stream resumability. 
+
+### Escalation: Critical Protocol Version Negotiation Failure
+*   **Escalation Point:** Peter Alexander revealed that zero official SDKs
+    currently return the mandated 400 Bad Request error (with JSON RPC error
+    -32602) when an unsupported protocol version is requested. Instead, they
+    perform a membership check and silently fall back to the latest supported
+    version.
+*   **Impact:** This non-compliance will cause a "bumpy rollout" for new
+    stateless features, breaking the backward compatibility fallback loop for
+    new clients speaking to old servers.
+*   **Consensus:** Immediate intervention is required. The team will file bugs
+    across the major SDKs and enforce correct negotiation logic via mandatory
+    conformance tests.
+
+### Subscription Stream Final Results
+*   **Tension Point:** Caitie McCaffrey challenged a line in the drafted SEP
+    stating that a subscription stream "closes once a final result is sent". She
+    noted there is no final result message for these streams; they simply stream
+    notifications until explicitly closed or the connection dies.
+*   **Consensus:** Kurtis Van Gent agreed to remove the inaccurate line
+    regarding a final request/result.
+
+### Next Steps & Timeline
+Between now and the June release, the priority shifts heavily toward
+implementing missing conformance tests to enforce baseline behaviors across all
+official SDKs. The stateless SEP will be updated immediately to reflect the
+removal of resumable streams, clarify the exact transport-layer cancellation
+semantics, and remove lingering stateful concepts. 
+
+### Action Items
+- [ ] **Kurtis Van Gent**: Update the stateless SEP to explicitly define HTTP
+  stream closure and standard IO `cancel notification` as standard cancellation
+  triggers.
+- [ ] **Kurtis Van Gent**: Update the stateless SEP to remove SSE stream
+  resumability and event IDs, directing users to tasks for durable workloads.
+- [ ] **Kurtis Van Gent**: Remove the language regarding a "final result" being
+  sent on subscription streams, clarifying they remain open until explicitly
+  terminated.
+- [ ] **Kurtis Van Gent**: Check with the Go SDK team to verify their specific
+  version negotiation logic implementation.
+- [ ] **Peter Alexander**: Act as DRI to investigate and file issues with
+  official SDK teams regarding correct protocol version negotiation failures.
+- [ ] **Peter Alexander**: Build a conformance test validating that unsupported
+  protocol versions correctly return a 32602 JSON RPC error and an HTTP 400
+  response.