fix(server): hold streamed section titles with content

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

@@ -7363,4 +7363,63 @@ describe("splitBufferedAssistantText", () => {
       rest: "```\n- one\n- two\n",
     });
   });
+
+  it("holds headings until the following block is ready", () => {
+    expect(splitBufferedAssistantText("intro\n\n## Setup\n\nInstall it")).toEqual({
+      ready: "intro\n\n",
+      rest: "## Setup\n\nInstall it",
+    });
+    expect(
+      splitBufferedAssistantText("intro\n\n# Plan\n\n## Setup\n\nInstall it.\n\nNext"),
+    ).toEqual({
+      ready: "intro\n\n# Plan\n\n## Setup\n\nInstall it.\n\n",
+      rest: "Next",
+    });
+    expect(splitBufferedAssistantText("para\n## Setup\n\nInstall")).toEqual({
+      ready: "para\n",
+      rest: "## Setup\n\nInstall",
+    });
+    expect(splitBufferedAssistantText("intro\n\n## ")).toEqual({
+      ready: "intro\n\n",
+      rest: "## ",
+    });
+  });
+
+  it("holds standalone bold titles, but not bold text within a paragraph", () => {
+    expect(splitBufferedAssistantText("**Risk by area:**\n\n| a |\n|---|\n")).toEqual({
+      ready: "",
+      rest: "**Risk by area:**\n\n| a |\n|---|\n",
+    });
+    expect(splitBufferedAssistantText("**Use *npm* now**\n\nInstall it")).toEqual({
+      ready: "",
+      rest: "**Use *npm* now**\n\nInstall it",
+    });
+    expect(splitBufferedAssistantText("**Note:** read this.\n\nNext")).toEqual({
+      ready: "**Note:** read this.\n\n",
+      rest: "Next",
+    });
+    expect(splitBufferedAssistantText("para\n**Setup**\n\nInstall")).toEqual({
+      ready: "",
+      rest: "para\n**Setup**\n\nInstall",
+    });
+  });
+
+  it("delivers a title with its first list item or completed code block", () => {
+    expect(splitBufferedAssistantText("## Steps\n\n- one\n- tw")).toEqual({
+      ready: "## Steps\n\n- one\n",
+      rest: "- tw",
+    });
+    expect(splitBufferedAssistantText("## Code\n\n```ts\na\n\nb\n")).toEqual({
+      ready: "",
+      rest: "## Code\n\n```ts\na\n\nb\n",
+    });
+    expect(splitBufferedAssistantText("## Code\n\n```ts\na\n```\nafter")).toEqual({
+      ready: "## Code\n\n```ts\na\n```\n",
+      rest: "after",
+    });
+    expect(splitBufferedAssistantText("```md\n## Inside\n\ntext\n")).toEqual({
+      ready: "",
+      rest: "```md\n## Inside\n\ntext\n",
+    });
+  });
 });

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

@@ -275,18 +275,28 @@ const MARKDOWN_FENCE_PATTERN = /^( *)(`{3,}|~{3,})/;
 const BLANK_LINE_PATTERN = /^[ \t]*$/;
 // A complete list marker lets the previous item land before the next is done.
 const LIST_ITEM_START_PATTERN = /^[ \t]*(?:[-*+]|\d{1,9}[.)])[ \t]/;
+// Models also use a line of bold text as a section title.
+const SECTION_TITLE_PATTERN = /^ {0,3}(?:#{1,6}(?:[ \t]|$)|\*\*(?:[^*]|\*(?!\*))+\*\*:?$)/;
+// A top-level heading ends the paragraph above it even without a blank line.
+const TOP_LEVEL_HEADING_PATTERN = /^#{1,6}(?:[ \t]|$)/;
 
 /** Return text whose Markdown shape is complete, leaving the active block buffered. */
 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) break;
@@ -296,6 +306,7 @@ 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 &&
@@ -306,7 +317,14 @@ 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;
   }