Claude Code: Add global exception handler and better startup logging for health check debugging

- Add global exception handler to catch all unhandled errors
- Add try/except around app initialization with proper exit on failure
- Add flush=True to all startup prints for immediate log output
- Add service name to root endpoint response
- Add shutdown event handler for cleaner logs
- Log full tracebacks for debugging

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app.py

@@ -6,20 +6,23 @@ FastAPI with lazy imports to avoid startup blocking.
 import os
 import sys
 import time
+import traceback
 
 # EXPLICIT STARTUP PRINTS (visible in container logs)
-print(">>> CAIN: Python app.py loading...")
-print(">>> CAIN: Python version:", sys.version.split()[0])
-print(">>> CAIN: Working directory:", os.getcwd())
-print(">>> CAIN: PORT =", os.environ.get('PORT', '7860'))
-print(">>> CAIN: sys.stdout flush...", flush=True)
+print(">>> CAIN: Python app.py loading...", flush=True)
+print(">>> CAIN: Python version:", sys.version.split()[0], flush=True)
+print(">>> CAIN: Working directory:", os.getcwd(), flush=True)
+print(">>> CAIN: PORT =", os.environ.get('PORT', '7860'), flush=True)
 
 # Lazy import FastAPI to avoid blocking init
 def get_app():
     """Create FastAPI app with imports inside function."""
-    from fastapi import FastAPI
+    from fastapi import FastAPI, Request, HTTPException
+    from fastapi.responses import JSONResponse
     import logging
 
+    print(">>> CAIN: Creating FastAPI app...", flush=True)
+
     # Configure stdout logging
     logging.basicConfig(
         level=logging.INFO,
@@ -27,8 +30,6 @@ def get_app():
         handlers=[logging.StreamHandler(sys.stdout)]
     )
     logger = logging.getLogger(__name__)
-
-    print(">>> CAIN: Creating FastAPI app...", flush=True)
     logger.info(">>> CAIN: FastAPI initialization starting")
 
     app = FastAPI(title="HuggingClaw - Cain", version="0.0.1")
@@ -38,25 +39,48 @@ def get_app():
     @app.get("/")
     async def root():
         """Root endpoint - simple alive status."""
-        return {"status": "alive"}
+        return {"status": "alive", "service": "cain"}
 
     @app.get("/health")
     async def health():
         """Health check endpoint for external monitoring."""
         return {"status": "healthy", "uptime": round(time.time() - START_TIME, 2)}
 
+    @app.exception_handler(Exception)
+    async def global_exception_handler(request: Request, exc: Exception):
+        """Global exception handler to catch all errors."""
+        logger.error(f"Unhandled exception: {type(exc).__name__}: {str(exc)}")
+        logger.error(f"Traceback: {traceback.format_exc()}")
+        return JSONResponse(
+            status_code=500,
+            content={"error": True, "message": str(exc), "type": type(exc).__name__}
+        )
+
     @app.on_event("startup")
     async def startup():
         """Log startup complete."""
         print(">>> CAIN: Startup complete - ready to serve", flush=True)
         logger.info(">>> CAIN: Ready to serve requests on port %s", os.environ.get('PORT', '7860'))
 
+    @app.on_event("shutdown")
+    async def shutdown():
+        """Log shutdown."""
+        print(">>> CAIN: Shutdown triggered", flush=True)
+        logger.info(">>> CAIN: Shutting down")
+
     print(">>> CAIN: FastAPI app created successfully", flush=True)
     return app
 
 
 # Create app at module level for uvicorn
-app = get_app()
+try:
+    print(">>> CAIN: Initializing app...", flush=True)
+    app = get_app()
+    print(">>> CAIN: App initialization complete", flush=True)
+except Exception as e:
+    print(f">>> CAIN: FATAL - App initialization failed: {e}", flush=True)
+    print(f">>> CAIN: Traceback: {traceback.format_exc()}", flush=True)
+    sys.exit(1)
 
 
 if __name__ == "__main__":