Send smart-router recipe as an inference request header

src/ucode/agents/claude.py

@@ -28,6 +28,7 @@
     MCP_USER_SCOPE,
     MODEL_PROVIDER_SERVICE_HEADER,
     MODEL_SERVICE_PARENT_SCHEMA_HEADER,
+    SMART_ROUTER_RECIPE_HEADER,
 )
 from ucode.custom_oauth import (
     CustomOAuthConfig,
@@ -62,6 +63,7 @@
     remove_smart_routing_hooks,
     sync_smart_routing_hooks,
 )
+from ucode.smart_routing.routing import configured_router_name
 from ucode.state import MANAGED_OVERLAY_KEY, is_tool_managed, mark_tool_managed, save_state
 from ucode.telemetry import agent_version, ug_version
 from ucode.ui import print_note, print_success, print_warning
@@ -204,6 +206,7 @@ def _otel_trace_env(workspace: str) -> dict[str, str]:
         "user-agent",
         MODEL_PROVIDER_SERVICE_HEADER.casefold(),
         MODEL_SERVICE_PARENT_SCHEMA_HEADER.casefold(),
+        SMART_ROUTER_RECIPE_HEADER.casefold(),
     }
 )
 # Relayed drops the user scope to deliberately omit the stale apiKeyHelper. Only applied to relayed
@@ -389,6 +392,8 @@ def render_overlay(
         header_lines.append(f"{MODEL_PROVIDER_SERVICE_HEADER}: {provider}")
     elif parent_schema:
         header_lines.append(f"{MODEL_SERVICE_PARENT_SCHEMA_HEADER}: {parent_schema}")
+    if smart_routing_v2.smart_routing_enabled():
+        header_lines.append(f"{SMART_ROUTER_RECIPE_HEADER}: {configured_router_name()}")
     # Relayed: the X-Databricks-AI-Gateway-Token swap header is added per request
     # by the refresh proxy, not here — a static value would go stale mid-session.
     custom_headers = "\n".join(header_lines)

src/ucode/agents/codex.py

@@ -34,6 +34,7 @@
 from ucode.constants import (
     MODEL_PROVIDER_SERVICE_HEADER,
     MODEL_SERVICE_PARENT_SCHEMA_HEADER,
+    SMART_ROUTER_RECIPE_HEADER,
 )
 from ucode.custom_oauth import (
     CUSTOM_OAUTH_TIMEOUT_MS,
@@ -69,6 +70,7 @@
     sync_smart_routing_hooks,
 )
 from ucode.smart_routing.codex_routing import codex_model_id
+from ucode.smart_routing.routing import configured_router_name
 from ucode.state import get_provider_service, is_tool_managed, mark_tool_managed, save_state
 from ucode.telemetry import agent_version, ug_version
 from ucode.ui import print_warning_err
@@ -197,6 +199,8 @@ def _provider_block(
         http_headers[MODEL_PROVIDER_SERVICE_HEADER] = provider
     elif parent_schema:
         http_headers[MODEL_SERVICE_PARENT_SCHEMA_HEADER] = parent_schema
+    if smart_routing_v2.smart_routing_enabled():
+        http_headers[SMART_ROUTER_RECIPE_HEADER] = configured_router_name()
     return {
         "name": "Databricks AI Gateway",
         "base_url": base_url,

src/ucode/constants.py

@@ -5,6 +5,8 @@
 
 MODEL_PROVIDER_SERVICE_HEADER = "Databricks-Model-Provider-Service"
 MODEL_SERVICE_PARENT_SCHEMA_HEADER = "Databricks-Model-Service-Parent-Schema"
+# Names the smart-router recipe (e.g. `task_v3`) in use; sent only when smart routing is enabled.
+SMART_ROUTER_RECIPE_HEADER = "Databricks-Smart-Router-Recipe"
 
 # MCP server registration scopes. Claude Code supports local/project/user; the
 # other CLIs only take the user-scope name. Kept here (a leaf module) so both