Re-vendor 2026-07-28 schema and absorb spec #2907 error-code renumber

Bumps the draft schema pin from spec 6d441518 to 2852f30e, picking up
spec PRs #2889/#2890/#2891/#2907, and updates the hand-written code
that referenced the old shapes:

- mcp.types.jsonrpc: HEADER_MISMATCH=-32020 added,
  MISSING_REQUIRED_CLIENT_CAPABILITY -32003->-32021,
  UNSUPPORTED_PROTOCOL_VERSION -32004->-32022, allocation-policy comment
  rewritten per #2907.
- mcp.types.methods: drop the 2026-07-28 rows for
  notifications/elicitation/complete (spec #2891) and
  notifications/progress (spec #2889).
- gen_surface_types.py: NotificationMetaObject is an open _meta carrier.
- expected-failures comments: -32001 HeaderMismatch -> -32020.

SUPPORTED_PROTOCOL_VERSIONS / LATEST_PROTOCOL_VERSION are unchanged; the
renumbered constants are not used on any 2025-era code path.

Author: maxisbey

.github/actions/conformance/expected-failures.2026-07-28.yml

@@ -132,7 +132,7 @@ server:
   - input-required-result-capability-check
   # SEP-2549 (caching): no ttlMs/cacheScope support.
   - caching
-  # SEP-2243 (HTTP header standardization): -32001 HeaderMismatch handling and
+  # SEP-2243 (HTTP header standardization): -32020 HeaderMismatch handling and
   # case-insensitive/whitespace-trimmed header validation not implemented.
   - http-header-validation
   - http-custom-header-server-validation

.github/actions/conformance/expected-failures.yml

@@ -68,7 +68,7 @@ server:
   # SEP-2549 (caching): no ttlMs/cacheScope support; scenario also hits the
   # stateful-mode "Missing session ID" error.
   - caching
-  # SEP-2243 (HTTP header standardization): -32001 HeaderMismatch handling and
+  # SEP-2243 (HTTP header standardization): -32020 HeaderMismatch handling and
   # case-insensitive/whitespace-trimmed header validation not implemented.
   - http-header-validation
   - http-custom-header-server-validation

schema/2026-07-28.json

@@ -8,7 +8,7 @@
   {
     "protocol_version": "2026-07-28",
     "source_path_in_spec_repo": "schema/draft/schema.json",
-    "spec_commit": "6d441518de8a9d5adbab0b10a76a667a63f90665",
-    "sha256": "bce2e7c9622bb0b449475ba6d8d80228c71190a09250e75dabd502b280ecf3cb"
+    "spec_commit": "2852f30e26ca5fb779565741ec042094cb110abd",
+    "sha256": "ed1ad4ba94aaeb2068b78969ef901b1150f7b2f06cf86472b3032abee1380b6a"
   }
 ]

schema/PINNED.json

@@ -84,7 +84,9 @@
 # reuses class names across versions for unrelated schemas (e.g. `Data`).
 OPEN_CLASSES: dict[str, frozenset[str]] = {
     "2025-11-25": frozenset({"Meta", "InputSchema", "OutputSchema", "Result", "GetTaskPayloadResult", "Data"}),
-    "2026-07-28": frozenset({"MetaObject", "RequestMetaObject", "InputSchema", "OutputSchema", "Result"}),
+    "2026-07-28": frozenset(
+        {"MetaObject", "NotificationMetaObject", "RequestMetaObject", "InputSchema", "OutputSchema", "Result"}
+    ),
 }
 
 # Hand-written union aliases the wire-method maps reference by value; the schema

scripts/gen_surface_types.py

@@ -199,6 +199,7 @@
 # Re-export JSONRPC types
 from mcp.types.jsonrpc import (
     CONNECTION_CLOSED,
+    HEADER_MISMATCH,
     INTERNAL_ERROR,
     INVALID_PARAMS,
     INVALID_REQUEST,
@@ -423,6 +424,7 @@
     "server_result_adapter",
     # JSON-RPC types
     "CONNECTION_CLOSED",
+    "HEADER_MISMATCH",
     "INTERNAL_ERROR",
     "INVALID_PARAMS",
     "INVALID_REQUEST",

src/mcp/types/__init__.py

@@ -397,7 +397,7 @@ class ClientCapabilities(MCPModel):
 
 
 class UnsupportedProtocolVersionErrorData(MCPModel):
-    """Error data for the -32004 unsupported-protocol-version error (2026-07-28)."""
+    """Error data for the -32022 unsupported-protocol-version error (2026-07-28)."""
 
     supported: list[str]
     """Protocol versions the server supports; the client should pick one and retry."""
@@ -406,7 +406,7 @@ class UnsupportedProtocolVersionErrorData(MCPModel):
 
 
 class MissingRequiredClientCapabilityErrorData(MCPModel):
-    """Error data for the -32003 missing-required-client-capability error (2026-07-28)."""
+    """Error data for the -32021 missing-required-client-capability error (2026-07-28)."""
 
     required_capabilities: ClientCapabilities
     """The capabilities the server requires from the client to process this request."""

src/mcp/types/_types.py

@@ -41,19 +41,26 @@ class JSONRPCResponse(BaseModel):
     result: dict[str, Any]
 
 
-# MCP-specific error codes in the range [-32000, -32099]
-URL_ELICITATION_REQUIRED = -32042
-"""A URL-mode elicitation is required before the request can be processed (protocol 2025-11-25 only)."""
+# MCP error codes occupy the JSON-RPC server-error range -32000..-32099.
+# Per the 2026-07-28 spec's allocation policy:
+#   -32000..-32019  implementation-defined (SDK-local; never on the wire as a spec code)
+#   -32020..-32099  reserved for spec-defined codes, allocated sequentially from -32020
+#   -32002, -32042  reserved-never-reused (retired by earlier protocol versions)
+
+HEADER_MISMATCH = -32020
+"""HTTP headers do not match the request body, or required headers are missing/malformed (protocol 2026-07-28)."""
 
-MISSING_REQUIRED_CLIENT_CAPABILITY = -32003
+MISSING_REQUIRED_CLIENT_CAPABILITY = -32021
 """The server requires a client capability the request did not declare (protocol 2026-07-28)."""
 
-UNSUPPORTED_PROTOCOL_VERSION = -32004
+UNSUPPORTED_PROTOCOL_VERSION = -32022
 """The request's protocol version is not supported by the server (protocol 2026-07-28)."""
 
-# SDK error codes: SDK-internal allocations in the JSON-RPC server-error range
-# [-32000, -32099]; not defined by the MCP schema. New values must avoid codes
-# the spec has allocated above.
+URL_ELICITATION_REQUIRED = -32042
+"""A URL-mode elicitation is required before the request can be processed (protocol 2025-11-25 only)."""
+
+# SDK error codes: SDK-internal allocations in the implementation-defined band
+# -32000..-32019; not defined by the MCP schema.
 CONNECTION_CLOSED = -32000
 """SDK-only: the connection closed before a response arrived; never emitted on the wire."""
 

src/mcp/types/jsonrpc.py

@@ -144,9 +144,8 @@
         ("notifications/initialized", "2025-11-25"): v2025.InitializedNotification,
         ("notifications/progress", "2025-11-25"): v2025.ProgressNotification,
         ("notifications/roots/list_changed", "2025-11-25"): v2025.RootsListChangedNotification,
-        # 2026-07-28 (initialized and roots/list_changed removed)
+        # 2026-07-28 (initialized, progress and roots/list_changed removed)
         ("notifications/cancelled", "2026-07-28"): v2026.CancelledNotification,
-        ("notifications/progress", "2026-07-28"): v2026.ProgressNotification,
     }
 )
 
@@ -212,9 +211,8 @@
         ("notifications/resources/list_changed", "2025-11-25"): v2025.ResourceListChangedNotification,
         ("notifications/resources/updated", "2025-11-25"): v2025.ResourceUpdatedNotification,
         ("notifications/tools/list_changed", "2025-11-25"): v2025.ToolListChangedNotification,
-        # 2026-07-28 (adds subscriptions/acknowledged)
+        # 2026-07-28 (adds subscriptions/acknowledged; elicitation/complete removed)
         ("notifications/cancelled", "2026-07-28"): v2026.CancelledNotification,
-        ("notifications/elicitation/complete", "2026-07-28"): v2026.ElicitationCompleteNotification,
         ("notifications/message", "2026-07-28"): v2026.LoggingMessageNotification,
         ("notifications/progress", "2026-07-28"): v2026.ProgressNotification,
         ("notifications/prompts/list_changed", "2026-07-28"): v2026.PromptListChangedNotification,