Commit a36af0637a63ebf316beb5db5670be226df01cbc | the-knife

author	Theo Browne <me@t3.gg> 2026-09-24 15:10:39-07:00
committer	GitHub <noreply@github.com> 2026-09-24 15:10:39-07:00
log	a36af0637a63ebf316beb5db5670be226df01cbc
tree	e3766ff0a3ff780a446c4976733d0203409e56c8
parent	8251c8de78a021014b83ffe986dc52a480d71e41
signature	Signed by PGP key B5690EEEBB952194

fix(server): streamed section titles wait for the text under them (#13504)

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

2 files changed, 80 insertions(+), 2 deletions(-)

apps
- server
  - src
    orchestration
    Layers
    ProviderRuntimeIngestion.test.ts
    ProviderRuntimeIngestion.ts

apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.test.ts+55

...	@@ -5174,4 +5174,59 @@ describe("splitBufferedAssistantText", () => {	...	@@ -5174,4 +5174,59 @@ describe("splitBufferedAssistantText", () => {
5174	rest: "```\n- one\n- two\n",	5174	rest: "```\n- one\n- two\n",
5175	});	5175	});
5176	});	5176	});
		5177
		5178	it("holds a heading until the block under it is done", () => {
		5179	expect(splitBufferedAssistantText("intro\n\n## Setup\n\nInstall it")).toEqual({
		5180	ready: "intro\n\n",
		5181	rest: "## Setup\n\nInstall it",
		5182	});
		5183	expect(
		5184	splitBufferedAssistantText("intro\n\n# Plan\n\n## Setup\n\nInstall it.\n\nNext"),
		5185	).toEqual({
		5186	ready: "intro\n\n# Plan\n\n## Setup\n\nInstall it.\n\n",
		5187	rest: "Next",
		5188	});
		5189	});
		5190
		5191	it("delivers the paragraph above a heading with no blank line between them", () => {
		5192	expect(splitBufferedAssistantText("para\n## Setup\n\nInstall")).toEqual({
		5193	ready: "para\n",
		5194	rest: "## Setup\n\nInstall",
		5195	});
		5196	// A bold line there continues the paragraph, so both stay buffered.
		5197	expect(splitBufferedAssistantText("para\nSetup\n\nInstall")).toEqual({
		5198	ready: "",
		5199	rest: "para\nSetup\n\nInstall",
		5200	});
		5201	});
		5202
		5203	it("holds a line of only bold text like a heading", () => {
		5204	expect(splitBufferedAssistantText("Risk by area:\n\n\| a \|\n\|---\|\n")).toEqual({
		5205	ready: "",
		5206	rest: "Risk by area:\n\n\| a \|\n\|---\|\n",
		5207	});
		5208	expect(splitBufferedAssistantText("*Use npm* now**\n\nInstall it")).toEqual({
		5209	ready: "",
		5210	rest: "*Use npm* now**\n\nInstall it",
		5211	});
		5212	expect(splitBufferedAssistantText("Note: read this.\n\nNext")).toEqual({
		5213	ready: "Note: read this.\n\n",
		5214	rest: "Next",
		5215	});
		5216	});
		5217
		5218	it("delivers a held heading with its first list item or its whole code block", () => {
		5219	expect(splitBufferedAssistantText("## Steps\n\n- one\n- tw")).toEqual({
		5220	ready: "## Steps\n\n- one\n",
		5221	rest: "- tw",
		5222	});
		5223	expect(splitBufferedAssistantText("## Code\n\n```ts\na\n\nb\n")).toEqual({
		5224	ready: "",
		5225	rest: "## Code\n\n```ts\na\n\nb\n",
		5226	});
		5227	expect(splitBufferedAssistantText("## Code\n\n```ts\na\n```\nafter")).toEqual({
		5228	ready: "## Code\n\n```ts\na\n```\n",
		5229	rest: "after",
		5230	});
		5231	});
5177	});	5232	});

apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.ts+25-2

 @@ -211,6 +211,12 @@ const BLANK_LINE_PATTERN = /^[ \t]*$/;
 // nested items count. The trailing space is required, so a partial `-` or
 // `1.` never matches before the model finishes the marker.
 const LIST_ITEM_START_PATTERN = /^[ \t]*(?:[-*+]|\d{1,9}[.)])[ \t]/;
+// A section title: an ATX heading, or a line of only bold text, which models
+// often use as a heading.
+const SECTION_TITLE_PATTERN = /^ {0,3}(?:#{1,6}(?:[ \t]|$)|\*\*(?:[^*]|\*(?!\*))+\*\*:?$)/;
+// An unindented ATX heading ends the paragraph or list above it, even with no
+// blank line between them. A bold line would continue the paragraph instead.
+const TOP_LEVEL_HEADING_PATTERN = /^#{1,6}(?:[ \t]|$)/;
 /**
  * Splits buffered assistant text at the last blank line, closing code fence,
 @@ -221,17 +227,26 @@ const LIST_ITEM_START_PATTERN = /^[ \t]*(?:[-*+]|\d{1,9}[.)])[ \t]/;
  * never leaks; a list item start is the one lookahead that may sit on the
  * partial line, since tight lists have no blank lines between items and would
  * otherwise land all at once.
+ *
+ * A section title holds the boundary until a content line follows it, so a
+ * title never lands alone and waits above a block that is still streaming.
  */
 export function splitBufferedAssistantText(text: string): { ready: string; rest: string } {
   let openFence: { marker: string; indent: number } | null = null;
   let boundary = -1;
   let lineStart = 0;
+  let titleAwaitingContent = false;
   for (;;) {
     const newline = text.indexOf("\n", lineStart);
     const line = text
       .slice(lineStart, newline === -1 ? text.length : newline)
       .replace(/[ \t\r]+$/, "");
-    if (openFence === null && lineStart > 0 && LIST_ITEM_START_PATTERN.test(line)) {
+    if (
+      openFence === null &&
+      lineStart > 0 &&
+      !titleAwaitingContent &&
+      LIST_ITEM_START_PATTERN.test(line)
+    ) {
       boundary = lineStart;
     }
     if (newline === -1) {
 @@ -243,6 +258,7 @@ export function splitBufferedAssistantText(text: string): { ready: string; rest:
       const marker = fenceMatch[2]!;
       if (openFence === null) {
         openFence = { marker, indent };
+        titleAwaitingContent = false;
       } else if (
         marker[0] === openFence.marker[0] &&
         marker.length >= openFence.marker.length &&
 @@ -254,7 +270,14 @@ export function splitBufferedAssistantText(text: string): { ready: string; rest:
         boundary = newline + 1;
       }
     } else if (openFence === null && BLANK_LINE_PATTERN.test(line) && lineStart > 0) {
-      boundary = newline + 1;
+      if (!titleAwaitingContent) {
+        boundary = newline + 1;
+      }
+    } else if (openFence === null) {
+      if (lineStart > 0 && !titleAwaitingContent && TOP_LEVEL_HEADING_PATTERN.test(line)) {
+        boundary = lineStart;
+      }
+      titleAwaitingContent = SECTION_TITLE_PATTERN.test(line);
     }
     lineStart = newline + 1;
   }