[Veld101]

Issue for this PR

Closes #57043

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Some OpenAI-compatible gateways (LiteLLM in the report) stream the title model's reasoning inline in the text channel instead of as a separate reasoning part. The title code keeps the first non-empty line of that text, so a title model that writes <think>…</think> followed by the title produced this as the session title:

<think>The user message is "/mcps". Need a brief title.</think>

and the real title on the next line was never used.

This strips <think>…</think> blocks before selecting the line, which is what v1 did before the session rewrite (ad8a4bc744, #1325). The strip runs after the deltas join, so a block split across stream deltas still matches:

return chunks
  .join("")
  .replace(/<think>[\s\S]*?<\/think>\s*/g, "")
  .split("\n")
  .map((line) => line.trim())
  .find((line) => line.length > 0)

If the model emits nothing but reasoning, the result is empty and no rename happens, so a session keeps its fallback title instead of gaining a reasoning-only one.

Relationship to #52006

#52006 also touches this function, but it addresses a different input: it filters chunks whose providerMetadata.phase is commentary, which is structured OpenAI Responses commentary. Inline <think> text inside an ordinary text chunk carries no phase, so it is not covered by that change. The two are complementary; whichever lands second will need a trivial rebase.

How did you verify your code works?

Two cases in packages/core/test/session-title.test.ts, both confirmed to fail without the change (reverting only title.ts turns both red, and the first reproduces the reported title verbatim):

• drops inline reasoning blocks from the generated title — the reported shape, <think>…</think> then the title on the next line.
• drops inline reasoning blocks split across stream deltas — pins that the strip happens after the join, which a per-delta strip would miss.

bun test test/session-title.test.ts   # 17 pass, 0 fail
bun typecheck                         # packages/core, clean
bunx prettier --check                 # clean
bun run lint                          # exit 0, no new findings

Screenshots / recordings

Not applicable; no UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

---

Added by the opencode bot (AI-generated).

Related: #54401, #54185

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

[opencode-agent]

Looks good. I ran the #57043 reproduction (a simulated title model that streams <think>…</think> and then the title) against the base and this branch. On the base the tab title is the raw reasoning; with this change it's MCP servers list. session-title.test.ts passes (17/17) and packages/core typechecks.

Public API: unchanged.

One thing worth handling: a reasoning block that is never closed (or uses uppercase tags) still ends up in the title. See the inline comment.

Related: #54401, #54185

[opencode-agent]

This only matches a closed, lowercase block. If the title output is cut off mid-reasoning (more likely once #54411 adds an output limit), the text is just <think>… and that becomes the title, which is the same symptom as #57043. A stray </think> or <THINK> also gets through. Could you make the match case-insensitive and also drop a trailing unclosed <think>… up to the end of the output, plus any leftover lone tags? For example:

.replace(/<think>[\s\S]*?(<\/think>|$)\s*/gi, "")
.replace(/<\/?think>/gi, "")

Then reasoning-only or truncated output falls through to undefined and keeps the fallback title.

[Veld101]

Applied both parts of the suggestion in 0d0704d:

.replace(/<think>[\s\S]*?(<\/think>|$)\s*/gi, "")
.replace(/<\/?think>/gi, "")

• Case-insensitive, so <THINK> and mixed case match.
• |$ closes an unterminated block, so a stream truncated mid-reasoning is dropped to the end of the output instead of becoming the title.
• The second pass drops a leftover lone tag, e.g. a leading </think> with no opening block.

Reasoning-only or truncated output now yields no title, so the session keeps its fallback rather than storing a tag.

Two cases added, both red against the previous single-pattern version:

• drops an unclosed or uppercase reasoning block — <THINK>Need a brief title. with no close; asserts the title stays undefined.
• strips a stray closing tag that has no opening block — </think>MCP servers list; asserts MCP servers list.

session-title.test.ts is 19 pass / 0 fail, packages/core typechecks, prettier is clean.