fix(MAT-273): parse text-based tool calls instead of leaking to Matrix

Some LiteLLM-proxied models emit tool calls as <tool_call>fn(args)
text instead of using the OpenAI function-calling API. This caused
raw markup to be streamed as visible chat text with no tool execution.

After streaming completes, detect <tool_call> patterns, parse into
proper tool_calls, strip markup from content, and re-edit the Matrix
message.

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

bot.py

@@ -3827,6 +3827,49 @@ class Bot:
         tc_list = None
         if tool_calls_acc:
             tc_list = [tool_calls_acc[i] for i in sorted(tool_calls_acc.keys())]
+
+        # Fallback: some models emit tool calls as text instead of using the
+        # function-calling API.  Detect patterns like:
+        #   <tool_call>web_search(query: "...")</tool_call>
+        #   <tool_call>web_search(query: "...")
+        # Parse them into proper tool_calls and strip from visible content.
+        if not tc_list and content:
+            _TC_RE = re.compile(
+                r"<tool[-_]?call>\s*(\w+)\(([^)]*)\)\s*(?:</tool[-_]?call>)?",
+                re.DOTALL,
+            )
+            text_tcs = list(_TC_RE.finditer(content))
+            if text_tcs:
+                tc_list = []
+                for m in text_tcs:
+                    fn_name = m.group(1)
+                    raw_args = m.group(2).strip()
+                    # Parse key: "value" pairs into JSON dict
+                    args = {}
+                    for kv in re.finditer(r'(\w+)\s*[:=]\s*"([^"]*)"', raw_args):
+                        args[kv.group(1)] = kv.group(2)
+                    if not args and raw_args:
+                        # Single unnamed argument — treat as "query"
+                        cleaned = raw_args.strip().strip('"').strip("'")
+                        if cleaned:
+                            args["query"] = cleaned
+                    tc_list.append({
+                        "id": f"text_tc_{uuid.uuid4().hex[:8]}",
+                        "name": fn_name,
+                        "arguments": json.dumps(args),
+                    })
+                # Strip the tool-call markup from visible content
+                content = _TC_RE.sub("", content).rstrip()
+                # If we already streamed the raw text to Matrix, edit it to remove the markup
+                if event_id:
+                    await self._send_stream_edit(
+                        room_id, event_id, content or "...", final=not content,
+                    )
+                logger.info(
+                    "[stream] parsed %d text-based tool call(s) from content",
+                    len(tc_list),
+                )
+
         logger.info(
             "[stream] model=%s chars=%d tool_calls=%d streamed_to_matrix=%s",
             model, len(content), len(tc_list or []), event_id is not None,