diff --git a/docker-compose.dev.yml b/docker-compose.dev.yml
index 11c1426..832b1de 100644
--- a/docker-compose.dev.yml
+++ b/docker-compose.dev.yml
@@ -30,6 +30,8 @@ services:
       - APP_ENV=development
       - ENVIRONMENT=development
       - START_MODE=dev
+      - CC_COMPOSE_PROJECT=api-dev
+      - CC_COMPOSE_SERVICE=backend-dev
       - RUN_INIT=false
       - INIT_MODE=infra
     ports:
@@ -54,6 +56,9 @@ services:
       - BACKEND_DEV_MODE=true
       - APP_ENV=development
       - ENVIRONMENT=development
+      - START_MODE=dev
+      - CC_COMPOSE_PROJECT=api-dev
+      - CC_COMPOSE_SERVICE=backend-test
       - API_HEALTH_URL=http://192.168.0.64:18000/health
     depends_on:
       redis-dev:
diff --git a/docker-compose.yml b/docker-compose.yml
index e7c45df..e378a32 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -46,6 +46,11 @@ services:
       - .env
     environment:
       - REDIS_HOST=redis
+      - START_MODE=prod
+      - APP_ENV=production
+      - ENVIRONMENT=production
+      - CC_COMPOSE_PROJECT=api
+      - CC_COMPOSE_SERVICE=backend
       - RUN_INIT=${RUN_INIT:-false} # Set to 'true' to run init on startup
       - INIT_MODE=${INIT_MODE:-infra} # Which init tasks to run
     ports:
diff --git a/main.py b/main.py
index 3834e82..7dd9e35 100644
--- a/main.py
+++ b/main.py
@@ -10,6 +10,7 @@ logger = initialise_logger(__name__, os.getenv("LOG_LEVEL"), os.getenv("LOG_PATH
 from fastapi import FastAPI, HTTPException
 import uvicorn
 import requests
+from urllib.parse import urlparse
 from typing import Dict, Any, Optional
 from modules.database.tools.neo4j_driver_tools import get_driver
 
@@ -22,15 +23,59 @@ from modules.queue_system import ServiceType
 app = FastAPI()
 setup_cors(app)
 
+def _truthy_env(name: str) -> bool:
+    return os.getenv(name, "").lower() in {"1", "true", "yes", "on"}
+
+
+def _runtime_environment() -> str:
+    """Return the API runtime role used for dev/prod backing-service selection."""
+    start_mode = os.getenv("START_MODE", "prod").lower()
+    if start_mode == "dev" or _truthy_env("BACKEND_DEV_MODE"):
+        return "dev"
+    return "prod"
+
+
+def _url_host(url: Optional[str]) -> Optional[str]:
+    if not url:
+        return None
+    parsed = urlparse(url)
+    return parsed.hostname
+
+
+def _runtime_identity() -> Dict[str, Any]:
+    """Non-secret runtime identity for agents and smoke tests.
+
+    This intentionally exposes only modes, labels, and URL hosts. It must not
+    include API keys, passwords, bearer tokens, or full URLs that may embed
+    credentials.
+    """
+    return {
+        "api_runtime_role": _runtime_environment(),
+        "start_mode": os.getenv("START_MODE", "prod"),
+        "app_environment": os.getenv("APP_ENV"),
+        "environment": os.getenv("ENVIRONMENT"),
+        "backend_dev_mode": _truthy_env("BACKEND_DEV_MODE"),
+        "compose_project": os.getenv("COMPOSE_PROJECT_NAME") or os.getenv("CC_COMPOSE_PROJECT"),
+        "compose_service": os.getenv("COMPOSE_SERVICE") or os.getenv("CC_COMPOSE_SERVICE"),
+        "supabase_url_host": _url_host(os.getenv("SUPABASE_URL")),
+    }
+
+
 # Health check endpoint
 @app.get("/health")
 async def health_check() -> Dict[str, Any]:
     """Health check endpoint that verifies all service dependencies"""
+    runtime_identity = _runtime_identity()
     health_status = {
         "status": "healthy",
+        "runtime": runtime_identity,
         "services": {
             "neo4j": {"status": "healthy", "message": "Connected"},
-            "supabase": {"status": "healthy", "message": "Connected"},
+            "supabase": {
+                "status": "healthy",
+                "message": "Connected",
+                "url_host": runtime_identity["supabase_url_host"],
+            },
             "redis": {"status": "healthy", "message": "Connected"}
         }
     }
@@ -77,8 +122,8 @@ async def health_check() -> Dict[str, Any]:
         # Check Redis using new Redis manager
         from modules.redis_manager import get_redis_manager
         
-        # Determine environment
-        environment = 'dev' if os.getenv('BACKEND_DEV_MODE', 'true').lower() == 'true' else 'prod'
+        # Determine environment from explicit startup/runtime identity.
+        environment = runtime_identity["api_runtime_role"]
         redis_manager = get_redis_manager(environment)
         
         # Get comprehensive health check
diff --git a/tests/test_dev_stack.py b/tests/test_dev_stack.py
index 4e0d3d2..c056990 100644
--- a/tests/test_dev_stack.py
+++ b/tests/test_dev_stack.py
@@ -38,7 +38,18 @@ def test_dev_api_health_endpoint_is_healthy():
     assert response.status_code == 200
     payload = response.json()
     assert payload['status'] == 'healthy'
+
+    runtime = payload['runtime']
+    assert runtime['api_runtime_role'] == 'dev'
+    assert runtime['start_mode'] == 'dev'
+    assert runtime['app_environment'] == 'development'
+    assert runtime['environment'] == 'development'
+    assert runtime['backend_dev_mode'] is True
+    assert runtime['compose_project'] == 'api-dev'
+    assert runtime['supabase_url_host'] == '192.168.0.94'
+
     assert payload['services']['supabase']['status'] == 'healthy'
+    assert payload['services']['supabase']['url_host'] == '192.168.0.94'
     assert payload['services']['redis']['status'] == 'healthy'
     assert payload['services']['redis']['environment'] == 'dev'
     assert payload['services']['redis']['database'] == 0
@@ -53,3 +64,19 @@ def test_supabase_dev_seed_core_counts():
 def test_supabase_dev_seed_timetable_counts():
     assert _rest_count('classes') == 17
     assert _rest_count('taught_lessons') == 1462
+
+
+def test_runtime_identity_does_not_expose_secret_values():
+    health_url = os.getenv('API_HEALTH_URL', 'http://192.168.0.64:18000/health')
+    response = requests.get(health_url, timeout=15)
+    assert response.status_code == 200
+    payload_text = response.text
+    for secret_name in ('SERVICE_ROLE_KEY', 'ANON_KEY', 'SUPABASE_JWT_SECRET', 'REDIS_PASSWORD'):
+        secret_value = os.getenv(secret_name)
+        if secret_value:
+            assert secret_value not in payload_text
+
+    runtime = response.json()['runtime']
+    assert 'supabase_url' not in runtime
+    assert 'service_role_key' not in runtime
+    assert 'anon_key' not in runtime