docs(19.7-02): record deferred items from the pier session router

.planning/phases/19.7-generic-mcp-module/deferred-items.md

@@ -22,3 +22,25 @@ was changed by the plan that recorded it.
   at `schema_types.go:376`, not a duplicate of the new `RecordAction.Prompt`;
   the criterion's "prints 1" was written without that line in mind. No change
   needed.
+- Stateful pier sessions cannot carry the SDK's protocol-version context value (found during 19.7-02 Task 3)
+  status: open
+  **What:** go-sdk v1.8.0's `StreamableHTTPHandler.ServeHTTP` stores the
+  `Mcp-Protocol-Version` header under an unexported context key that the
+  transport's `servePOST`/`serveGET` read; pier's own session router (needed
+  for Redis-shared sessions, D-25) serves `StreamableServerTransport`
+  directly and cannot set that key, so stateful streams run with the SDK's
+  2025-03-26 defaults for stream close/reconnect hints and the JSON-RPC
+  batch rule (lenient, spec-compliant for older clients; 2026-07-28 clients
+  go through the SDK's own stateless handler). Revisit if a later SDK
+  exports the key or a transport-level setter; plan 05 may add a test
+  pinning the behaviour.
+- `notifications/initialized` landing on another instance than `initialize` (found during 19.7-02 Task 3)
+  status: open
+  **What:** the session state is persisted after `initialize` and again
+  after the client's `initialized` notification; when a load balancer sends
+  the notification to a second instance, the first instance's local copy
+  keeps `InitializedParams` nil and refuses calls until that copy is
+  dropped (session end, revocation or process restart) while the second
+  instance serves them. Sticky sessions or a per-request re-read of the
+  stored `initialized` flag would close the gap; not needed for the
+  single-instance demo.