Claude Code: Fix A2A communication - add error logging and diagnostics

- Add specific exception handling in /a2a/jsonrpc endpoint (ImportError, RecursionError, general Exception)
- Add diagnostic logging for brain import failures
- Include brain_error in A2A response when brain processing fails
- Add error type to outer exception handler response
- Add startup verification of openclaw and brain_minimal imports
- Add A2A endpoint registration messages at startup
- Update cain_status.json to include stage field and A2A config
- Add detailed logging in /a2a/health endpoint for debugging

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

app.py

@@ -181,6 +181,7 @@ async def a2a_jsonrpc(request: Request):
             # CRITICAL: Always provide a default response
             response = f"Cain received: {message_text}"
 
+            brain_error = None
             try:
                 import openclaw  # Sets up sys.path
                 from agents import brain_minimal
@@ -194,12 +195,18 @@ async def a2a_jsonrpc(request: Request):
                             enhanced_response = result.get("response", "")
                             if enhanced_response and not enhanced_response.startswith("Error:"):
                                 response = enhanced_response
-            except (ImportError, RecursionError, Exception):
-                # Brain not available - use default fallback response
-                pass
+            except ImportError as e:
+                brain_error = f"ImportError: {e}"
+                print(f">>> CAIN A2A: Brain import error: {e}", flush=True)
+            except RecursionError as e:
+                brain_error = f"RecursionError: {e}"
+                print(f">>> CAIN A2A: Recursion error (circular import): {e}", flush=True)
+            except Exception as e:
+                brain_error = f"{type(e).__name__}: {e}"
+                print(f">>> CAIN A2A: Brain processing error: {type(e).__name__}: {e}", flush=True)
 
             # Build A2A JSON-RPC response (ALWAYS succeeds with valid response)
-            return {
+            result_response = {
                 "jsonrpc": "2.0",
                 "id": msg_id,
                 "result": {
@@ -211,6 +218,10 @@ async def a2a_jsonrpc(request: Request):
                     }
                 }
             }
+            # Add brain error as diagnostic info if present
+            if brain_error:
+                result_response["result"]["brain_error"] = brain_error
+            return result_response
 
         # Unknown method
         return JSONResponse(
@@ -219,9 +230,10 @@ async def a2a_jsonrpc(request: Request):
         )
 
     except Exception as e:
+        print(f">>> CAIN A2A: Unhandled error: {type(e).__name__}: {e}", flush=True)
         return JSONResponse(
             status_code=500,
-            content={"jsonrpc": "2.0", "id": "", "error": {"code": -32603, "message": str(e)}}
+            content={"jsonrpc": "2.0", "id": "", "error": {"code": -32603, "message": str(e), "type": type(e).__name__}}
         )
 
 
@@ -285,23 +297,29 @@ async def a2a_health():
         if not hasattr(brain_minimal, 'get_brain'):
             brain_status = "error"
             error_details = "get_brain method not found"
+            print(f">>> CAIN A2A Health: brain_minimal missing get_brain method", flush=True)
         else:
             brain = brain_minimal.get_brain(agent_name="cain", legacy_mode=True)
             if hasattr(brain, '_conversation_process'):
                 brain_status = "ready"
                 brain_ready = True
+                print(f">>> CAIN A2A Health: Brain ready (agent={brain.agent_name if hasattr(brain, 'agent_name') else 'unknown'})", flush=True)
             else:
                 brain_status = "error"
                 error_details = "_conversation_process method not found"
+                print(f">>> CAIN A2A Health: Brain missing _conversation_process", flush=True)
     except ImportError as e:
         brain_status = "import_error"
         error_details = str(e)
+        print(f">>> CAIN A2A Health: ImportError - {e}", flush=True)
     except RecursionError as e:
         brain_status = "recursion_error"
         error_details = "Circular import detected - openclaw init issue"
+        print(f">>> CAIN A2A Health: RecursionError - {e}", flush=True)
     except Exception as e:
         brain_status = "error"
         error_details = str(e)
+        print(f">>> CAIN A2A Health: Exception - {type(e).__name__}: {e}", flush=True)
 
     # A2A endpoint is ALWAYS available (this endpoint responding proves it)
     # Brain readiness is informational, not blocking
@@ -320,6 +338,18 @@ async def a2a_health():
     }
 
 print(">>> CAIN: FastAPI app created successfully", flush=True)
+print(">>> CAIN: A2A endpoint registered at /a2a/jsonrpc", flush=True)
+print(">>> CAIN: A2A health check at /a2a/health", flush=True)
+print(">>> CAIN: A2A diagnostics at /a2a/diagnostics", flush=True)
+
+# Verify openclaw can be imported at startup
+try:
+    import openclaw
+    print(f">>> CAIN: openclaw imported from {openclaw.__file__}", flush=True)
+    from agents import brain_minimal
+    print(">>> CAIN: brain_minimal module available", flush=True)
+except Exception as e:
+    print(f">>> CAIN WARNING: Could not import brain modules at startup: {e}", flush=True)
 
 # ============================================================================
 # STARTUP DIAGNOSTIC ENDPOINT

openclaw/.openclaw/agents/cain_status.json

@@ -1,5 +1,10 @@
 {
   "current_state": "idle",
-  "last_updated": "2026-03-16T07:28:04.536278+00:00",
-  "agent": "cain"
+  "stage": "RUNNING",
+  "last_updated": "2026-03-16T10:20:00.000000+00:00",
+  "agent": "cain",
+  "a2a": {
+    "endpoint": "/a2a/jsonrpc",
+    "enabled": true
+  }
 }