[Router] Interfaces + fixtures stub (foundation)

.github/workflows/cpp_server_build_test_release.yml

@@ -276,8 +276,9 @@ jobs:
           cmake --preset default
           cmake --build --preset default --target test_directory_watcher
           cmake --build --preset default --target test_latest_version_fallback
+          cmake --build --preset default --target test_routing_policy_contract
           cd build
-          ctest --output-on-failure -R "DirectoryWatcher|LatestVersionFallback"
+          ctest --output-on-failure -R "DirectoryWatcher|LatestVersionFallback|RoutingPolicyContract"
 
       - name: Upload .deb package
         uses: actions/upload-artifact@v7
@@ -536,8 +537,9 @@ jobs:
         run: |
           cmake --build --preset default --target test_directory_watcher
           cmake --build --preset default --target test_latest_version_fallback
+          cmake --build --preset default --target test_routing_policy_contract
           cd build
-          ctest --output-on-failure -R "DirectoryWatcher|LatestVersionFallback"
+          ctest --output-on-failure -R "DirectoryWatcher|LatestVersionFallback|RoutingPolicyContract"
 
       - name: Upload .pkg package
         if: steps.check_signing.outputs.has_signing == 'true'

.github/workflows/routing_schema_tests.yml

@@ -0,0 +1,31 @@
+name: Routing Schema Tests
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+  merge_group:
+
+permissions:
+  contents: read
+
+jobs:
+  routing-schema-tests:
+    name: Routing schema + fixtures
+    runs-on: ubuntu-latest
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}
+      cancel-in-progress: true
+    steps:
+      - uses: actions/checkout@v5
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - name: Install dependencies
+        run: python -m pip install --upgrade pip jsonschema
+      # Pure-python, no server binary needed — fast PR gate for the routing
+      # policy/decision schemas. Keeps the back-compat guardrails enforced.
+      - name: Validate fixtures against the JSON schemas
+        run: python test/test_routing_fixtures.py
+      - name: Verify frozen-major schema lock
+        run: python test/test_schema_lock.py

CMakeLists.txt

@@ -1788,6 +1788,30 @@ if(EXISTS "${_INSTALL_ATOMICITY_TEST_SRC}")
     add_test(NAME InstallAtomicityTest COMMAND test_install_atomicity)
 endif()
 
+# Routing engine contract surface (issue #2407). Header-only foundation: the
+# shared types/interfaces in routing_policy.h plus the fake ClassifierServices.
+# The test loads the L0a-L3 fixtures from the source tree via ROUTING_FIXTURE_DIR.
+set(_ROUTING_CONTRACT_TEST_SRC
+    "${CMAKE_CURRENT_SOURCE_DIR}/test/cpp/test_routing_policy_contract.cpp"
+)
+if(EXISTS "${_ROUTING_CONTRACT_TEST_SRC}")
+    add_executable(test_routing_policy_contract
+        test/cpp/test_routing_policy_contract.cpp
+    )
+    target_include_directories(test_routing_policy_contract PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/src/cpp/include
+        ${CMAKE_CURRENT_SOURCE_DIR}/test/cpp
+        ${CMAKE_CURRENT_BINARY_DIR}/include
+    )
+    target_link_libraries(test_routing_policy_contract PRIVATE nlohmann_json::nlohmann_json)
+    target_compile_definitions(test_routing_policy_contract PRIVATE
+        ROUTING_FIXTURE_DIR="${CMAKE_CURRENT_SOURCE_DIR}/test/cpp/fixtures/routing"
+    )
+
+    include(CTest)
+    add_test(NAME RoutingPolicyContractTest COMMAND test_routing_policy_contract)
+endif()
+
 # Auto-tune: GGUF array storage, scalar derivation, weighted KV cache computation.
 # Covers head_count_kv_per_layer, sliding_window_pattern, SWA precise weighted sum,
 # full_attention_interval exact count, and scalar fallback paths.