fix: buffer split reasoning wrapper deltas

maintainer edit: native reasoning streams can split <thinking> wrapper tags across chunks. Buffer the stream and emit only cleaned incremental reasoning so raw partial tags do not reach WebUI.

nanobot/agent/runner.py

@@ -771,18 +771,24 @@ class AgentRunner:
                 await live_file_edits.update(delta)
 
         if wants_streaming:
+            thinking_buf = ""
+
             async def _stream(delta: str) -> None:
                 if delta:
                     context.streamed_content = True
                 await hook.on_stream(context, delta)
 
             async def _thinking(delta: str) -> None:
+                nonlocal thinking_buf
                 if not delta:
                     return
-                delta = strip_reasoning_tags(delta)
-                if delta:
+                prev_clean = strip_reasoning_tags(thinking_buf)
+                thinking_buf += delta
+                new_clean = strip_reasoning_tags(thinking_buf)
+                incremental = new_clean[len(prev_clean):]
+                if incremental:
                     context.streamed_reasoning = True
-                    await hook.emit_reasoning(delta)
+                    await hook.emit_reasoning(incremental)
 
             async def _stream_recover() -> None:
                 await hook.on_stream_end(context, resuming=True)

nanobot/utils/helpers.py

@@ -134,10 +134,15 @@ def strip_reasoning_tags(text: object) -> str:
     """Remove wrapper tags from text that is already known to be reasoning."""
     if not isinstance(text, str):
         return ""
+    partial_reasoning_tag = (
+        r"</?(?:t|th|thi|thin|think|thinki|thinkin|thinking|tho|thou|thoug|though|thought)>?"
+    )
+    text = re.sub(rf"^\s*(?:{partial_reasoning_tag})$", "", text)
     text = re.sub(r"^\s*<(?:think|thinking|thought)/>\s*", "", text)
     text = re.sub(r"\s*<(?:think|thinking|thought)/>\s*$", "", text)
     text = re.sub(r"^\s*<(?:think|thinking|thought)>\s*", "", text)
     text = re.sub(r"\s*</(?:think|thinking|thought)>\s*$", "", text)
+    text = re.sub(rf"\s*(?:{partial_reasoning_tag})$", "", text)
     return text.strip()
 
 

tests/agent/test_runner_reasoning.py

@@ -381,8 +381,8 @@ async def test_runner_strips_thinking_tags_from_native_thinking_deltas():
         *, on_content_delta=None, on_thinking_delta=None, **kwargs
     ):
         if on_thinking_delta:
-            await on_thinking_delta("<thinking>")
-            await on_thinking_delta("Preparing final response")
+            await on_thinking_delta("<thinking")
+            await on_thinking_delta(">Preparing final response")
             await on_thinking_delta("</thinking>")
         if on_content_delta:
             await on_content_delta("done")