Switch Agent0 from MCP to REST API (/api/api_message)

MCP endpoint returns 403 (wrong token) and the mcp library's TaskGroup
error is opaque. The REST API (X-API-KEY header, /api/api_message) is
already validated in connectivity tests and returns proper responses.

mcp_key field is reused as the X-API-KEY value.
context_id replaces chat_id for conversation continuity.

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

server.py

@@ -268,60 +268,50 @@ async def handle_agent0_mcp(
     valid_poses: list[str],
 ) -> ChatResponse:
     """
-    Send a message to a live Agent Zero instance via its MCP streamable-http
-    server and return the response as a ChatResponse.
+    Send a message to a live Agent Zero instance via its REST API
+    (POST /api/api_message, X-API-KEY header).
 
-    MCP URL format: {endpoint}/mcp/t-{mcp_key}/http
-    Tool called: send_message (built into every Agent Zero instance)
-
-    Conversation continuity is maintained via Agent Zero's chat_id, which maps
-    to a gnommoweb conversation_id in _a0_sessions (in-memory).
+    Conversation continuity is maintained via Agent Zero's context_id, which
+    maps to a gnommoweb conversation_id in _a0_sessions (in-memory).
     """
-    from mcp.client.streamable_http import streamablehttp_client
-    from mcp import ClientSession
-
     endpoint = (model.endpoint or "").strip().rstrip("/")
-    mcp_key  = model.mcp_key or ""
-    mcp_url  = f"{endpoint}/mcp/t-{mcp_key}/http"
+    api_key  = model.mcp_key or ""   # stored in mcp_key field; used as X-API-KEY
+    api_url  = f"{endpoint}/api/api_message"
 
-    # Retrieve existing Agent0 chat_id for this conversation (if any)
-    a0_chat_id = _a0_sessions.get(req.conversation_id) if req.conversation_id else None
+    # Retrieve existing Agent0 context_id for this conversation (if any)
+    a0_context_id = _a0_sessions.get(req.conversation_id) if req.conversation_id else None
 
     log.info(
-        f"[{agent.name}] → Agent0 MCP  url={mcp_url}  "
-        f"conv={req.conversation_id}  a0_chat={a0_chat_id or 'new'}  "
+        f"[{agent.name}] → Agent0 REST  url={api_url}  "
+        f"conv={req.conversation_id}  a0_ctx={a0_context_id or 'new'}  "
         f"msg='{req.message[:60]}'"
     )
 
     try:
-        async with streamablehttp_client(mcp_url) as (read, write, _):
-            async with ClientSession(read, write) as session:
-                await session.initialize()
+        payload: dict = {
+            "message":       req.message,
+            "lifetime_hours": 24,
+        }
+        if a0_context_id:
+            payload["context_id"] = a0_context_id
 
-                tool_args: dict = {
-                    "message":        req.message,
-                    "persistent_chat": True,
-                }
-                if a0_chat_id:
-                    tool_args["chat_id"] = a0_chat_id
+        async with httpx.AsyncClient(timeout=120.0) as client:
+            r = await client.post(
+                api_url,
+                headers={"X-API-KEY": api_key, "Content-Type": "application/json"},
+                json=payload,
+            )
+            r.raise_for_status()
 
-                result = await session.call_tool("send_message", tool_args)
+        data = r.json()
+        log.info(f"[{agent.name}] ← Agent0 REST: {str(data)[:300]}")
 
-        # The tool returns a JSON-serialised ToolResponse / ToolError
-        raw = result.content[0].text if result.content else "{}"
-        log.info(f"[{agent.name}] ← Agent0 MCP raw: {raw[:300]}")
+        response_text  = data.get("response", "")
+        new_context_id = data.get("context_id", "")
 
-        parsed = json.loads(raw)
-
-        if parsed.get("status") == "error":
-            raise RuntimeError(parsed.get("error", "Unknown Agent0 error"))
-
-        response_text = parsed.get("response", "")
-        new_chat_id   = parsed.get("chat_id", "")
-
-        # Persist the Agent0 chat_id so the next turn continues the same context
-        if new_chat_id and req.conversation_id is not None:
-            _a0_sessions[req.conversation_id] = new_chat_id
+        # Persist context_id for conversation continuity
+        if new_context_id and req.conversation_id is not None:
+            _a0_sessions[req.conversation_id] = new_context_id
 
         pose = pick_pose(response_text, valid_poses)
 
@@ -334,7 +324,7 @@ async def handle_agent0_mcp(
         )
 
     except Exception as e:
-        log.error(f"[{agent.name}] Agent0 MCP error: {e}")
+        log.error(f"[{agent.name}] Agent0 REST error: {e}")
         fallback_pose = next(
             (p for p in ("sorry", "annoyed", "neutral") if p in valid_poses),
             valid_poses[0],