fix(server): streamed section titles wait for the text under them

[t3dotgg]

In paragraph streaming mode, a section title showed up alone and then sat there until the block under it finished. You got a title, waited, got the paragraph, then got the next title almost at once, and waited again.

In local chat history, 31% of titles in paragraph-mode messages sat alone like this. The median wait was 1.0s. The longest was 5.4s, for a title above a table.

The splitter now holds a section title until a content line follows it. The title then ships with its paragraph, its first list item, or its whole table or code block. A section title is an ATX heading or a line of only bold text (**Risk by area**). Claude and Codex both use bold lines as titles, and about a third of the titles that sat alone were bold lines.

Nothing else is delayed. A held title still flushes on tool calls, at turn end, and at the buffer cap. The change is server only, so every client gets it. Reasoning uses the same splitter (in paragraph and token mode), so bold titles in reasoning summaries also wait for their text.

📹 screen recording

The demo replays one token stream (240 chars/s, the median rate in local history) through the old and new splitter with the server's 400ms pacing, and renders both side by side with react-markdown. It is not a recording of the T3 Code app.

Created with Claude Opus 5.5 in Claude Code.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved how streamed Markdown is divided into readable sections. Headings stay with the content that follows, including the first list item, and paragraphs can end cleanly before a heading.
  • Bold-only title lines, including titles with nested emphasis, stay with their following content, while bold text within a paragraph continues to flow normally.
  • Headings followed by unfinished code blocks remain together until the code block is complete.

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	+41 B (+0.3%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	+10 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.5 KiB	+31 B (+0.5%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.2 KiB	56.3 KiB	+44 B (+0.1%)	66.4 KiB	✅
Codex	Live turn messages	9	10	+1 (+11.1%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	−4 B (−0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	−4 B (−0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.4 KiB	0 B (0.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 0109670 · PR result: 792cfcf · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 114.0 KiB
• Claude decoded thread snapshot: 114.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[macroscopeapp]

Approvability

Verdict: Approved at 792cfcf

Macroscope's review found this PR approvable — This is a narrowly scoped server-side streaming bug fix that keeps headings and bold-only titles with their following content while preserving existing buffering and flush safeguards. Focused regression tests cover the changed Markdown cases, with no schema, deployment, security, billing, default, or static-analysis configuration impact.

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ℹ️ Recent review info

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Reviewing files that changed from the base of the PR and between a35ade2 and 792cfcf.

📒 Files selected for processing (2)

• apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.test.ts
• apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.test.ts
• apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.ts

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📝 Walkthrough

Walkthrough

splitBufferedAssistantText now handles section titles and top-level ATX headings when splitting buffered assistant text. Tests cover heading, paragraph, list-item, and fenced-code boundaries.

Changes

Assistant text buffering

Layer / File(s)	Summary
Heading and content boundaries apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.ts, apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.test.ts	The splitter recognizes ATX headings and bold-only title lines, including titles with nested emphasis. It delays boundaries while a title awaits content, treats an unindented ATX heading as a boundary before itself, and clears pending-title state when a code fence opens. Tests cover these boundaries and adjacent paragraphs, lists, and fenced code.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 792cf

Headings are held with following content in the inspected paths. No actionable merge-blocking issue remains after normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main server-side change: streamed section titles now wait for the text under them.
Description check	✅ Passed	The description clearly explains what changed and why. It includes UI demonstration links and states that the change is server-only. It omits the template headings and checklist, but the required info…
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

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Inline comments:
In `@apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.ts`:
- Line 216: Update SECTION_TITLE_PATTERN to recognize bold-only title lines that
contain nested emphasis, such as “**Use *npm* now**”, while still requiring the
line to end after the bold span (optionally with a colon). Ensure these titles
are held until following content is available.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository: pingdotgg/t3code/.coderabbit.yaml

Review profile: CHILL

Plan: Advanced

Run ID: 5373f84f-6b66-4061-95b4-d4841360537b

📥 Commits

Reviewing files that changed from the base of the PR and between 0109670 and a35ade2.

📒 Files selected for processing (2)

• apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.test.ts
• apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 6 remain after this review.

Dismissing prior approval to re-evaluate 792cfcf