diff --git a/apps/client/src/features/editor/gitmost/gitmost-recording.test.ts b/apps/client/src/features/editor/gitmost/gitmost-recording.test.ts
index 29149822..bcd31451 100644
--- a/apps/client/src/features/editor/gitmost/gitmost-recording.test.ts
+++ b/apps/client/src/features/editor/gitmost/gitmost-recording.test.ts
@@ -4,19 +4,31 @@ import { Document } from "@tiptap/extension-document";
 import { Paragraph } from "@tiptap/extension-paragraph";
 import { Text } from "@tiptap/extension-text";
 import { Heading } from "@tiptap/extension-heading";
+import { Bold } from "@tiptap/extension-bold";
+import { Italic } from "@tiptap/extension-italic";
+import { Link } from "@tiptap/extension-link";
 import { gitmostInsertTranscriptIntoEditor } from "./gitmost-recording.ts";
 
+const ZWSP = "​"; // U+200B, the helper's block-trigger neutralizer
+
 /**
  * #377 — the web-side bridge must append the native host's transcript below the
  * recording. These exercise the pure insert helper through a REAL Tiptap editor
- * (Document/Paragraph/Text/Heading), asserting the resulting document rather
- * than mocking the editor: transcript present -> "Transcript" heading + one
- * paragraph per non-empty line (verbatim); absent/empty/non-string -> no-op.
+ * (Document/Paragraph/Text/Heading + Bold/Italic/Link marks so an HTML-parsing
+ * regression would be caught), asserting the resulting document rather than
+ * mocking the editor: transcript present -> "Transcript" heading + one paragraph
+ * per non-empty line; content is inserted as LITERAL TEXT (no HTML/markdown
+ * parsing); col-0 markdown block triggers are neutralized so git-sync keeps them
+ * paragraphs; absent/empty/non-string -> no-op.
  */
 describe("gitmostInsertTranscriptIntoEditor", () => {
   const makeEditor = () =>
     new Editor({
-      extensions: [Document, Paragraph, Text, Heading],
+      // Bold/Italic/Link are registered specifically so that IF the helper ever
+      // regressed to inserting an HTML/markdown string (instead of a text node),
+      // TipTap would parse `<b>`/`*..*`/`[..](..)` into marks and the literal-
+      // text assertions below would fail.
+      extensions: [Document, Paragraph, Text, Heading, Bold, Italic, Link],
       // Start from a single empty paragraph (a fresh page's baseline). The
       // helper appends at the end of the doc, i.e. below existing content.
       content: { type: "doc", content: [{ type: "paragraph" }] },
@@ -49,6 +61,73 @@ describe("gitmostInsertTranscriptIntoEditor", () => {
     editor.destroy();
   });
 
+  it("inserts HTML + markdown metacharacters as LITERAL text (no injection / no mark parsing)", () => {
+    const editor = makeEditor();
+    const line =
+      "You: <b>bold</b> <script>alert(1)</script> and *stars* and [link](x)";
+
+    const inserted = gitmostInsertTranscriptIntoEditor(editor, line);
+    expect(inserted).toBe(true);
+
+    const paras = (editor.getJSON().content ?? []).filter(
+      (n: any) => n.type === "paragraph",
+    ) as any[];
+    // The transcript line is exactly ONE paragraph holding a SINGLE text node
+    // whose text is the verbatim string — not split into bold/link/other nodes,
+    // not carrying any marks, not raw HTML. This FAILS if the helper switched to
+    // insertContent(htmlString): TipTap would then parse <b>/[link](x)/*stars*.
+    const content = paras[paras.length - 1].content;
+    expect(content).toHaveLength(1);
+    expect(content[0].type).toBe("text");
+    expect(content[0].marks ?? []).toEqual([]);
+    expect(content[0].text).toBe(line);
+    // And no bold/italic/link mark exists anywhere in the document.
+    const html = editor.getHTML();
+    expect(html).not.toMatch(/<(strong|b|em|i|a)\b/);
+    // The angle brackets survived as escaped entities (literal text), not a live
+    // <script>/<b> element.
+    expect(html).not.toMatch(/<script/i);
+
+    editor.destroy();
+  });
+
+  it("neutralizes col-0 markdown block triggers with a leading ZWSP (git-sync safety)", () => {
+    const editor = makeEditor();
+    // Trigger lines (some with a leaked indent) + a normal prefixed line.
+    const inserted = gitmostInsertTranscriptIntoEditor(
+      editor,
+      [
+        "- dash",
+        "  > quote", // leading indent must be trimmed then neutralized
+        "# hash",
+        "1. one",
+        "> [!info] note",
+        "```js",
+        "You: normal line",
+      ].join("\n"),
+    );
+    expect(inserted).toBe(true);
+
+    const texts = (editor.getJSON().content ?? [])
+      .filter((n: any) => n.type === "paragraph")
+      .map((n: any) => n.content?.[0]?.text)
+      .filter((t: any) => typeof t === "string") as string[];
+
+    // Every block-trigger line is prefixed with the invisible ZWSP (indent
+    // trimmed first); the normal `You:` line is left byte-exact.
+    expect(texts).toEqual([
+      ZWSP + "- dash",
+      ZWSP + "> quote",
+      ZWSP + "# hash",
+      ZWSP + "1. one",
+      ZWSP + "> [!info] note",
+      ZWSP + "```js",
+      "You: normal line",
+    ]);
+
+    editor.destroy();
+  });
+
   it("is a no-op for undefined / empty / whitespace-only / non-string transcripts", () => {
     for (const value of [undefined, "", "   \n  \n", 42, {}, null]) {
       const editor = makeEditor();
diff --git a/apps/client/src/features/editor/gitmost/gitmost-recording.ts b/apps/client/src/features/editor/gitmost/gitmost-recording.ts
index 2b5017cb..bb37297b 100644
--- a/apps/client/src/features/editor/gitmost/gitmost-recording.ts
+++ b/apps/client/src/features/editor/gitmost/gitmost-recording.ts
@@ -240,23 +240,57 @@ export async function gitmostUploadFileToEditor(
   }
 }
 
+// Zero-width space (U+200B). Prepended to a transcript line that begins with a
+// markdown BLOCK trigger: it is invisible in the rendered doc but shifts the
+// trigger off column 0, so the git-sync doc->markdown->doc round-trip keeps the
+// line a plain paragraph (see GITMOST_MD_BLOCK_TRIGGER_RE).
+const GITMOST_ZWSP = "​";
+
+// A markdown BLOCK-level construct that, sitting at column 0 of a paragraph
+// line, the git-sync markdown serializer (packages/prosemirror-markdown
+// markdown-converter.ts, `case "paragraph"`) would re-parse into a NON-paragraph
+// block on the doc->markdown->doc cycle. That serializer emits paragraph text
+// verbatim with NO block-escape (the pre-existing root cause), so a leading
+// `#`/`-`/`*`/`+`/`>`, an ordered-list `N.`/`N)`, a code fence ```/~~~, a table
+// `|`, or a `> [!info]` callout opener would silently become a heading / list /
+// quote / code block / table / callout. This matches a TRIMMED line's start;
+// the transcript's own `You:` / `Speaker N:` prefix begins with a letter and
+// never matches, so prefixed lines are left byte-exact.
+const GITMOST_MD_BLOCK_TRIGGER_RE =
+  /^(#{1,6}(\s|$)|[-*+](\s|$)|>|\d+[.)](\s|$)|```|~~~|\|)/;
+
 // Append a transcript block BELOW the recording's audio node in a live editor:
 // a "Transcript" heading followed by one paragraph per non-empty transcript
 // line. The transcript is plain text, `\n`-separated, each line already
-// formatted as `You: ...` / `Speaker N: ...` by the native host — lines are
-// inserted VERBATIM as text nodes (never HTML), so there is no injection
-// surface. This is best-effort and meant to run AFTER the audio has already
-// been inserted; the caller must guard against a throw so a transcript failure
-// never fails the (already successful) recording. Returns true when a block was
-// inserted, false when there was nothing to insert (transcript undefined/empty/
-// not-a-string). A non-string value is a no-op, not an error.
+// formatted as `You: ...` / `Speaker N: ...` by the native host — line text is
+// inserted as a TEXT node (never HTML/markdown), so there is no injection or
+// mark-parsing surface. Each kept line is trimmed (drops an indent that would
+// both leak into the display and, at col 0, form a markdown block trigger) and,
+// if it still begins with a col-0 markdown block trigger, gets an invisible
+// zero-width space prepended so the git-sync round-trip cannot turn it into a
+// list/quote/heading/callout/code/table (defensive boundary against the
+// serializer's missing block-escape). This is best-effort and meant to run
+// AFTER the audio has already been inserted; the caller must guard against a
+// throw so a transcript failure never fails the (already successful) recording.
+// Returns true when a block was inserted, false when there was nothing to
+// insert (transcript undefined/empty/not-a-string). A non-string value is a
+// no-op, not an error.
 export function gitmostInsertTranscriptIntoEditor(
   editor: Editor,
   transcript: unknown,
 ): boolean {
   if (typeof transcript !== "string") return false;
-  // Keep each line's text verbatim; only drop blank (whitespace-only) lines.
-  const lines = transcript.split("\n").filter((line) => line.trim().length > 0);
+  const lines = transcript
+    .split("\n")
+    // Trim each line and drop blank (whitespace-only) ones.
+    .map((line) => line.trim())
+    .filter((line) => line.length > 0)
+    // Neutralize a col-0 markdown block trigger with an invisible ZWSP so the
+    // git-sync round-trip keeps the line a paragraph. Host lines (`You:` /
+    // `Speaker N:`) never match and stay byte-exact.
+    .map((line) =>
+      GITMOST_MD_BLOCK_TRIGGER_RE.test(line) ? GITMOST_ZWSP + line : line,
+    );
   if (lines.length === 0) return false;
 
   const content = [
diff --git a/packages/prosemirror-markdown/test/gitmost-transcript-neutralization.test.ts b/packages/prosemirror-markdown/test/gitmost-transcript-neutralization.test.ts
new file mode 100644
index 00000000..ad60b8c8
--- /dev/null
+++ b/packages/prosemirror-markdown/test/gitmost-transcript-neutralization.test.ts
@@ -0,0 +1,104 @@
+import { describe, expect, it } from "vitest";
+// Import DIRECTLY from src (NOT the docmost-client barrel, which pulls in
+// collaboration.ts and mutates global DOM at import time).
+import { convertProseMirrorToMarkdown } from "../src/lib/markdown-converter.js";
+import { markdownToProseMirror } from "../src/lib/markdown-to-prosemirror.js";
+
+/**
+ * gitmost #377 (round-1 review, finding #1) — proof, against the REAL
+ * converter, that the transcript-insert boundary defense survives git-sync.
+ *
+ * The web bridge (apps/client .../gitmost/gitmost-recording.ts,
+ * `gitmostInsertTranscriptIntoEditor`) appends each transcript line as a
+ * PARAGRAPH text node. The paragraph serializer here (`case "paragraph"`) emits
+ * that text VERBATIM with no block-escape, so a line whose text begins with a
+ * col-0 markdown block trigger would, on the doc -> markdown -> doc git-sync
+ * cycle, silently re-parse into a heading / list / quote / callout / code block.
+ * That missing block-escape is the pre-existing root cause; the bridge's
+ * boundary defense prepends an invisible zero-width space (U+200B) to a line
+ * that begins with such a trigger, shifting it off column 0.
+ *
+ * This test keeps a COPY of the bridge's trigger regex (the bridge is in a
+ * different package and can't be imported here) and asserts:
+ *   1. bare trigger lines DO corrupt (documents the root cause), and
+ *   2. the ZWSP-neutralized form round-trips as a single PARAGRAPH with the
+ *      text byte-preserved.
+ */
+
+const ZWSP = "​"; // U+200B
+
+// MUST stay in sync with GITMOST_MD_BLOCK_TRIGGER_RE in the client bridge.
+const MD_BLOCK_TRIGGER_RE =
+  /^(#{1,6}(\s|$)|[-*+](\s|$)|>|\d+[.)](\s|$)|```|~~~|\|)/;
+
+const doc = (...nodes: any[]) => ({ type: "doc", content: nodes });
+const para = (t: string) => ({
+  type: "paragraph",
+  content: [{ type: "text", text: t }],
+});
+
+const roundtrip = async (text: string) => {
+  const md = convertProseMirrorToMarkdown(doc(para(text)));
+  const back = await markdownToProseMirror(md);
+  return back.content as any[];
+};
+
+describe("gitmost transcript neutralization (git-sync round-trip)", () => {
+  // Lines that, at column 0, the serializer's missing block-escape would let
+  // git-sync re-parse into a non-paragraph block.
+  const triggerLines = [
+    "- dash",
+    "* star",
+    "+ plus",
+    "> quote",
+    "# hash",
+    "1. one",
+    "1) one",
+    "> [!info] note",
+    "```js",
+    "~~~",
+  ];
+
+  it("BARE trigger lines corrupt into non-paragraph blocks (root cause)", async () => {
+    for (const line of triggerLines) {
+      const blocks = await roundtrip(line);
+      // At least one produced block is NOT a paragraph — i.e. corruption.
+      const allParagraphs = blocks.every((b) => b.type === "paragraph");
+      expect(
+        allParagraphs,
+        `expected "${line}" to corrupt when inserted bare`,
+      ).toBe(false);
+    }
+  });
+
+  it("ZWSP-neutralized trigger lines round-trip as a single paragraph, text preserved", async () => {
+    for (const line of triggerLines) {
+      // The regex must actually classify each as a trigger.
+      expect(MD_BLOCK_TRIGGER_RE.test(line), `regex missed "${line}"`).toBe(
+        true,
+      );
+      const neutralized = ZWSP + line;
+      const blocks = await roundtrip(neutralized);
+
+      expect(blocks).toHaveLength(1);
+      expect(blocks[0].type).toBe("paragraph");
+      // Text is byte-preserved (ZWSP + original line), so the display is the
+      // original line with only an invisible leading character.
+      expect(blocks[0].content[0].text).toBe(neutralized);
+    }
+  });
+
+  it("normal host-prefixed lines never match the trigger regex and round-trip byte-exact", async () => {
+    for (const line of [
+      "You: hello there",
+      "Speaker 1: - and then a dash mid-line",
+      "Speaker 2: 1. not a list",
+    ]) {
+      expect(MD_BLOCK_TRIGGER_RE.test(line)).toBe(false);
+      const blocks = await roundtrip(line);
+      expect(blocks).toHaveLength(1);
+      expect(blocks[0].type).toBe("paragraph");
+      expect(blocks[0].content[0].text).toBe(line);
+    }
+  });
+});