diff --git a/packages/app/src/components/markdown/fence/mermaid/segments.ts b/packages/app/src/components/markdown/fence/mermaid/segments.ts
index 1958a3c016..dc21db3b1e 100644
--- a/packages/app/src/components/markdown/fence/mermaid/segments.ts
+++ b/packages/app/src/components/markdown/fence/mermaid/segments.ts
@@ -1,40 +1,54 @@
 import { fromMarkdown } from "mdast-util-from-markdown";
-import type { RootContent } from "mdast";
+import type { Definition, RootContent } from "mdast";
 
 interface Segment {
   kind: "markdown" | "mermaid";
-  offset: number;
+  id: string;
   source: string;
 }
 
 /** Native enriched-markdown has no fenced-block override. Only diagrams leave its engine. */
 export function splitMermaidFences(markdown: string): Segment[] {
-  if (!/mermaid/i.test(markdown)) return [{ kind: "markdown", offset: 0, source: markdown }];
+  if (!/mermaid/i.test(markdown)) return [{ kind: "markdown", id: "0", source: markdown }];
   const segments: Segment[] = [];
+  const definitions: Definition[] = [];
   let cursor = 0;
   function visit(node: RootContent): void {
+    if (node.type === "definition") definitions.push(node);
     if (node.type === "code" && node.lang?.toLowerCase() === "mermaid" && node.position) {
       const start = node.position.start.offset!;
       const end = node.position.end.offset!;
       if (start > cursor)
-        segments.push({ kind: "markdown", offset: cursor, source: markdown.slice(cursor, start) });
-      segments.push({ kind: "mermaid", offset: start, source: node.value });
+        segments.push({
+          kind: "markdown",
+          id: String(segments.length),
+          source: markdown.slice(cursor, start),
+        });
+      segments.push({ kind: "mermaid", id: String(segments.length), source: node.value });
       cursor = end;
     } else if ("children" in node) node.children.forEach(visit);
   }
   const tree = fromMarkdown(markdown);
   tree.children.forEach(visit);
   if (cursor < markdown.length || segments.length === 0)
-    segments.push({ kind: "markdown", offset: cursor, source: markdown.slice(cursor) });
+    segments.push({
+      kind: "markdown",
+      id: String(segments.length),
+      source: markdown.slice(cursor),
+    });
   // Reference links keep their document-wide scope on both sides of a diagram.
   if (segments.some((segment) => segment.kind === "mermaid")) {
-    const definitions = tree.children
-      .filter((node) => node.type === "definition")
-      .map((node) => markdown.slice(node.position!.start.offset, node.position!.end.offset))
+    const referenceSource = definitions
+      .map((node) => {
+        const label = node.identifier.replace(/[\\[\]]/g, "\\$&");
+        const url = node.url.replace(/[\\<>]/g, "\\$&");
+        const title = node.title ? ` "${node.title.replace(/[\\"]/g, "\\$&")}"` : "";
+        return `[${label}]: <${url}>${title}`;
+      })
       .join("\n");
-    if (definitions)
+    if (referenceSource)
       for (const segment of segments) {
-        if (segment.kind === "markdown") segment.source += `\n\n${definitions}`;
+        if (segment.kind === "markdown") segment.source += `\n\n${referenceSource}`;
       }
   }
   return segments;
diff --git a/packages/app/src/components/markdown/renderer.test.ts b/packages/app/src/components/markdown/renderer.test.ts
index 60315ac460..068fc1f2f4 100644
--- a/packages/app/src/components/markdown/renderer.test.ts
+++ b/packages/app/src/components/markdown/renderer.test.ts
@@ -85,12 +85,12 @@ it("extracts only Mermaid fences for the native diagram host", async () => {
   const source =
     "First.\n\n```ts\nconst n = 1;\n```\n\n```mermaid\ngraph TD\nA-->B\n```\n\n> Last.";
   expect(splitMermaidFences(source)).toEqual([
-    { kind: "markdown", offset: 0, source: "First.\n\n```ts\nconst n = 1;\n```\n\n" },
-    { kind: "mermaid", offset: 32, source: "graph TD\nA-->B" },
-    { kind: "markdown", offset: 61, source: "\n\n> Last." },
+    { kind: "markdown", id: "0", source: "First.\n\n```ts\nconst n = 1;\n```\n\n" },
+    { kind: "mermaid", id: "1", source: "graph TD\nA-->B" },
+    { kind: "markdown", id: "2", source: "\n\n> Last." },
   ]);
   expect(splitMermaidFences("```md\n```mermaid\n```")).toEqual([
-    { kind: "markdown", offset: 0, source: "```md\n```mermaid\n```" },
+    { kind: "markdown", id: "0", source: "```md\n```mermaid\n```" },
   ]);
 });
 
@@ -100,12 +100,31 @@ it("keeps reference links available across native Mermaid boundaries", async ()
     "[Before][file]\n\n```mermaid\ngraph TD\nA-->B\n```\n\n[After][file]\n\n[file]: src/file.ts",
   );
   for (const part of parts.filter((candidate) => candidate.kind === "markdown"))
-    expect(part.source).toContain("[file]: src/file.ts");
+    expect(part.source).toContain("[file]: <src/file.ts>");
 });
 
 it("recognizes mixed-case Mermaid fence info and incomplete streaming fences", async () => {
   const { splitMermaidFences } = await import("./fence/mermaid/segments");
   expect(splitMermaidFences("```Mermaid title\ngraph TD\nA-->B")).toEqual([
-    { kind: "mermaid", offset: 0, source: "graph TD\nA-->B" },
+    { kind: "mermaid", id: "0", source: "graph TD\nA-->B" },
   ]);
 });
+
+it("carries reference definitions nested in quotes across a diagram", async () => {
+  const { splitMermaidFences } = await import("./fence/mermaid/segments");
+  const parts = splitMermaidFences(
+    "[open][file]\n\n```mermaid\ngraph TD\nA-->B\n```\n\n> [file]: src/file.ts",
+  );
+  expect(parts[0].source).toContain("[file]: <src/file.ts>");
+});
+
+it("keeps diagram identity when an earlier workspace image resolves", async () => {
+  const { splitMermaidFences } = await import("./fence/mermaid/segments");
+  const source = "![image](a.png)\n\n```mermaid\ngraph TD\nA-->B\n```";
+  const before = splitMermaidFences(source).find((part) => part.kind === "mermaid");
+  const after = splitMermaidFences(
+    source.replace("a.png", "file:///long/cache/path/image.png"),
+  ).find((part) => part.kind === "mermaid");
+  expect(before).toHaveProperty("id");
+  expect(after?.id).toBe(before?.id);
+});
diff --git a/packages/app/src/components/markdown/renderer.tsx b/packages/app/src/components/markdown/renderer.tsx
index 97fe981fc8..057eebd7e3 100644
--- a/packages/app/src/components/markdown/renderer.tsx
+++ b/packages/app/src/components/markdown/renderer.tsx
@@ -158,17 +158,17 @@ export const MarkdownRenderer = memo(function MarkdownRenderer({
   const closeImage = useStableEvent(() => setImage(null));
   const segments = useMemo(
     () =>
-      isWeb ? [{ kind: "markdown", offset: 0, source: markdown }] : splitMermaidFences(markdown),
+      isWeb ? [{ kind: "markdown", id: "0", source: markdown }] : splitMermaidFences(markdown),
     [markdown],
   );
   const content = (
     <MermaidStreamingContext.Provider value={streaming}>
       {segments.map((segment) =>
         segment.kind === "mermaid" ? (
-          <MermaidFence key={segment.offset} code={segment.source} />
+          <MermaidFence key={`${segment.kind}:${segment.id}`} code={segment.source} />
         ) : (
           <ThemedMarkdown
-            key={segment.offset}
+            key={`${segment.kind}:${segment.id}`}
             markdown={segment.source}
             containerStyle={isWeb ? WEB_CONTAINER : undefined}
             uniProps={compact ? compactStyle : regularStyle}