Title generator leaking think/reasoning blocks from LLM output

Fixes on record

Merged to main. A stamp counts the issues a fix is linked to.

• #56298 fix(title_generator): strip think blocks from LLM output before extracting title

  merged to main

  files: agent/title_generator.py, scripts/release.py, tests/agent/test_title_generator.py

  Show the diff

  • agent/title_generator.py

    @@ -87,7 +87,15 @@ def generate_title(
                 timeout=timeout,
                 main_runtime=main_runtime,
             )
    -        title = (response.choices[0].message.content or "").strip()
    +        content = response.choices[0].message.content or ""
    +        # Strip thinking/reasoning blocks that think-enabled models
    +        # (MiniMax M2.7, DeepSeek, etc.) emit even for simple prompts like
    +        # title generation. Without this the raw <think>...</think> XML
    +        # leaks into session titles. Reuses the canonical scrubber so all
    +        # tag variants (unterminated blocks, orphan closes, mixed case)
    +        # are handled, not just a single literal <think> pair.
    +        from agent.agent_runtime_helpers import strip_think_blocks
    +        title = strip_think_blocks(None, content).strip()
             # Clean up: remove quotes, trailing punctuation, prefixes like "Title: "
             title = title.strip('"\'')
             if title.lower().startswith("title:"):

  • scripts/release.py

    @@ -48,6 +48,7 @@
         "[redacted:email]": "bitcryptic-gw",  # PR #53997 salvage (Matrix E2EE: resolve device_id via query_keys({mxid: []}) when whoami returns none; guard verification call sites so query_keys is never sent [null]; reset _device_id_unverified at connect() start; disconnect before reconnect)
         "[redacted:email]": "abchiaravalle",  # PR #46997 salvage (recover resume_pending sessions: dual freshness signal + empty-turn safety net so restart auto-resume never sends a blank user turn)
         "[redacted:email]": "swissly",  # PR #47167 salvage (wrap cron delivery thread-pool fallback in its own try/except so a per-target failure can't escape the except-RuntimeError block and crash the multi-target delivery loop; #47163)
    +    "[redacted:email]": "shawchanshek",  # PR #44126 salvage (strip <think>...</think> reasoning blocks from title-generator LLM output via the canonical strip_think_blocks scrubber so reasoning-model output can't leak into session titles)
         "[redacted:email]": "YLChen-007",  # PR #27289 salvage (case-insensitive streaming reasoning-tag filter in cli.py _stream_delta + gateway stream_consumer so mixed-case variants like <Think>/<ThInK> are suppressed, not just the hardcoded case literals)
         "[redacted:email]": "kangsoo-bit",  # PR #47508 salvage (keep Telegram gateway alive on transient bootstrap network errors: best-effort deleteWebhook + resilient start_polling degrade to background recovery instead of failing startup)
         "[redacted:email]": "testingbuddies24",  # PR #43192 salvage (strip orphan think-tag close tags in progressive gateway stream so a bare </think> whose open was dropped upstream can't leak to the user)

  • tests/agent/test_title_generator.py

    @@ -68,6 +68,37 @@ def test_strips_quotes(self):
                 title = generate_title("how do I set up docker", "First install...")
                 assert title == "Setting Up Docker Environment"
     
    +    def test_strips_think_blocks(self):
    +        """Reasoning-model output wrapped in <think>...</think> must not
    +        leak into the session title."""
    +        mock_response = MagicMock()
    +        mock_response.choices = [MagicMock()]
    +        mock_response.choices[0].message.content = (
    +            "<think>The user wants a title. I'll summarize the topic "
    +            "concisely.</think>Debugging Python Import Errors"
    +        )
    +
    +        with patch("agent.title_generator.call_llm", return_value=mock_response):
    +            title = generate_title("help me fix this import", "Sure...")
    +            assert title == "Debugging Python Import Errors"
    +            assert "<think>" not in title
    +            assert "summarize" not in title
    +
    +    def test_strips_unterminated_think_block(self):
    +        """An unterminated <think> block (no close tag) must still be
    +        stripped so the leaked reasoning doesn't become the title."""
    +        mock_response = MagicMock()
    +        mock_response.choices = [MagicMock()]
    +        mock_response.choices[0].message.content = (
    +            "<think>Let me reason about a good title for this session"
    +        )
    +
    +        with patch("agent.title_generator.call_llm", return_value=mock_response):
    +            title = generate_title("hello", "hi there")
    +            # Everything from the unterminated open tag onward is stripped,
    +            # leaving nothing → None.
    +            assert title is None
    +
         def test_strips_title_prefix(self):
             mock_response = MagicMock()
             mock_response.choices = [MagicMock()]