Bump conformance harness to 0.2.0-alpha.11

alpha.11 adds a client scenario, json-schema-2020-12-preservation, that
lists tools and echoes the focal tool's inputSchema back through
json_schema_echo so the harness can detect 2020-12 keywords being
stripped in transit. client.py had no handler for it, so both client
legs failed with "Unknown scenario"; with the handler it passes 9/9 at
the default, 2025-11-25 and 2026-07-28 wires.

Everything else in the release (JSON-schema validation of every wire
message, the server-session-lifecycle scenario, a DELETE after each
stateful server scenario, the new --requirements mode) passes against
main without baseline changes: server active 73/0, draft 103/0,
all@2026-07-28 151/0, all 204/25 (the nine tasks-* entries, unchanged);
client all 458/9 (the nine per-check DPoP/WIF entries, unchanged),
all@2026-07-28 381/0.

Also correct the client.py docstring: the exit budget is the harness
--timeout (60s in CI), and the scenario list was missing
http-custom-headers.

No-Verification-Needed: CI config and conformance fixture only

Author: maxisbey

.github/actions/conformance/client.py

@@ -11,16 +11,18 @@
       --spec-version is omitted the harness picks per-scenario (LATEST_SPEC_VERSION
       for active scenarios, DRAFT_PROTOCOL_VERSION for draft-only ones).
     - Server URL as last CLI argument (sys.argv[1])
-    - Must exit 0 within 30 seconds
+    - Must exit 0 within the harness --timeout (CI passes 60s; the default is 30s)
 
 Scenarios:
     initialize                              - Connect, initialize, list tools, close
     tools_call                              - Connect, call add_numbers(a=5, b=3), close
     sse-retry                               - Connect, call test_reconnection, close
     json-schema-ref-no-deref                - Connect, list tools (no $ref deref)
+    json-schema-2020-12-preservation        - List tools, echo the focal inputSchema back verbatim
     request-metadata                        - Connect with all callbacks; client stamps _meta
     http-standard-headers                   - Connect, call a tool (Mcp-* headers checked)
     http-invalid-tool-headers               - List tools, call every surfaced tool (x-mcp-header filter)
+    http-custom-headers                     - Replay the harness's toolCalls (x-mcp-header -> Mcp-Param-*)
     elicitation-sep1034-client-defaults     - Elicitation with default accept callback
     sep-2322-client-request-state           - Drive the MRTR auto-loop (SEP-2322)
     auth/client-credentials-jwt             - Client credentials with private_key_jwt
@@ -252,6 +254,21 @@ async def run_json_schema_ref_no_deref(server_url: str) -> None:
         await client.list_tools()
 
 
+@register("json-schema-2020-12-preservation")
+async def run_json_schema_2020_12_preservation(server_url: str) -> None:
+    """List tools, then echo the focal tool's inputSchema back verbatim (SEP-1613 / SEP-2106).
+
+    The harness diffs what the client round-trips through `json_schema_echo` against its
+    fixture to detect 2020-12 keywords ($schema, $defs, $anchor, additionalProperties,
+    allOf/anyOf, if/then/else) being stripped while parsing tools/list. Unlike
+    json-schema-ref-no-deref, this mock is version-aware, so client_mode() applies.
+    """
+    async with Client(server_url, mode=client_mode()) as client:
+        listed = await client.list_tools()
+        focal = next(tool for tool in listed.tools if tool.name == "json_schema_2020_12_tool")
+        await client.call_tool("json_schema_echo", {"schema": focal.input_schema})
+
+
 @register("tools_call")
 async def run_tools_call(server_url: str) -> None:
     """Connect, list tools, call add_numbers(a=5, b=3), close."""

.github/workflows/conformance.yml

@@ -17,7 +17,7 @@ env:
   # Pinned conformance harness package spec (passed verbatim to `npx --yes`).
   # Bump deliberately and reconcile both
   # .github/actions/conformance/expected-failures*.yml files in the same change.
-  CONFORMANCE_PKG: "@modelcontextprotocol/conformance@0.2.0-alpha.10"
+  CONFORMANCE_PKG: "@modelcontextprotocol/conformance@0.2.0-alpha.11"
 
 jobs:
   server-conformance: