diff --git a/.github/actions/conformance/client.py b/.github/actions/conformance/client.py
index 0784ef190d..18e59a8ac6 100644
--- a/.github/actions/conformance/client.py
+++ b/.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."""
diff --git a/.github/workflows/conformance.yml b/.github/workflows/conformance.yml
index c7e5097a72..0222296888 100644
--- a/.github/workflows/conformance.yml
+++ b/.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: