diff --git a/package.json b/package.json
index f1f0b4d851f..b237a56c18a 100644
--- a/package.json
+++ b/package.json
@@ -101,10 +101,7 @@
     "agentmail": "^0.5.31",
     "cross-env": "^10.1.0",
     "esbuild": "^0.28.2",
-    "remark-gfm": "4.0.1",
-    "remark-parse": "11.0.0",
     "typescript": "^7.0.2",
-    "unified": "11.0.5",
     "vitest": "^5.0.3",
     "yaml": "^2.8.1",
     "turbo": "2.11.10"
diff --git a/tests/runner-e2e/PRODUCT-JOURNEYS.md b/tests/runner-e2e/PRODUCT-JOURNEYS.md
index 014a9ff6fe6..daee209ef45 100644
--- a/tests/runner-e2e/PRODUCT-JOURNEYS.md
+++ b/tests/runner-e2e/PRODUCT-JOURNEYS.md
@@ -116,7 +116,7 @@ reply path. A finish summary by itself, an earlier turn, a progress
 bubble, or a cancelled run cannot satisfy it. Private receipts record the run,
 thread anchor and observed text; classic protocol comment matchers stay strict.
 Markdown replies compare complete text and exact link destinations after parsing
-with the production GFM and issue-reference plugins. The observer receives the
+through the UI-owned projection of its existing Markdown renderer and GFM/issue-reference plugins. The observer receives the
 same visible-company prefix list used by the UI, so bare issue keys and URLs
 match their rendered links. Whitespace and inline formatting can change during rendering. A
 document or issue chip can replace a link label, but must retain its destination.
diff --git a/tests/runner-e2e/task-reply-content.ts b/tests/runner-e2e/task-reply-content.ts
index a79397bb57b..6b35116c0f3 100644
--- a/tests/runner-e2e/task-reply-content.ts
+++ b/tests/runner-e2e/task-reply-content.ts
@@ -1,11 +1,8 @@
-import { unified } from "unified";
-import remarkParse from "remark-parse";
-import remarkGfm from "remark-gfm";
+import { markdownReplyContent } from "../../ui/src/lib/markdown-reply-content.js";
 import { applyCompanyPrefix, extractCompanyPrefixFromPath } from "../../ui/src/lib/company-routes.js";
-import { parseIssueReferenceFromHref, remarkLinkIssueReferences } from "../../ui/src/lib/issue-reference.js";
+import { parseIssueReferenceFromHref } from "../../ui/src/lib/issue-reference.js";
 
 export type ReplyContentPart = { text: string } | { href: string; label?: string; decorated?: boolean };
-type MarkdownNode = { type: string; value?: string; url?: string; children?: MarkdownNode[] };
 
 function normalized(parts: ReplyContentPart[], pageUrl: string, source = false) {
   const result: ReplyContentPart[] = [];
@@ -43,23 +40,8 @@ export function taskReplyContentMatches(
     const displayed = observation.content.map(part => "text" in part ? part.text : part.label!).join("").replace(/\s+/g, " ").trim();
     if (displayed !== observation.body.replace(/\s+/g, " ").trim()) return false;
   }
-  const parts: ReplyContentPart[] = [];
-  const inlineLabel = (node: MarkdownNode): boolean => ["text", "inlineCode", "strong", "emphasis", "delete"].includes(node.type)
-    && (node.children ?? []).every(inlineLabel);
-  const labelText = (node: MarkdownNode): string => node.value ?? (node.children ?? []).map(labelText).join("");
-  function visit(node: MarkdownNode): boolean {
-    if (node.type === "text" || node.type === "inlineCode") { parts.push({ text: node.value ?? "" }); return true; }
-    if (node.type === "break") { parts.push({ text: " " }); return true; }
-    if (node.type === "link" && node.url && (node.children ?? []).every(inlineLabel)) { parts.push({ href: node.url, label: labelText(node) }); return true; }
-    if (!["root", "paragraph", "heading", "blockquote", "list", "listItem", "strong", "emphasis", "delete"].includes(node.type)) return false;
-    for (const child of node.children ?? []) if (!visit(child)) return false;
-    if (!["strong", "emphasis", "delete"].includes(node.type)) parts.push({ text: " " });
-    return true;
-  }
-  const parser = unified().use(remarkParse).use(remarkGfm);
-  const tree = parser.runSync(parser.parse(markdown)) as MarkdownNode;
-  remarkLinkIssueReferences({ knownPrefixes: observation.knownCompanyPrefixes })(tree);
-  if (!visit(tree)) return false;
+  const parts = markdownReplyContent(markdown, observation.knownCompanyPrefixes);
+  if (!parts) return false;
   const pageUrl = observation.pageUrl ?? observation.origin ?? "https://reply.invalid";
   const expected = normalized(parts, pageUrl, true);
   const actual = normalized(observation.content ?? [{ text: observation.body }], pageUrl);
diff --git a/ui/src/lib/markdown-reply-content.ts b/ui/src/lib/markdown-reply-content.ts
new file mode 100644
index 00000000000..1855b58272a
--- /dev/null
+++ b/ui/src/lib/markdown-reply-content.ts
@@ -0,0 +1,52 @@
+import { Fragment, isValidElement, type ReactNode } from "react";
+import Markdown from "react-markdown";
+import remarkGfm from "remark-gfm";
+import { remarkLinkIssueReferences } from "./issue-reference.js";
+
+export type MarkdownReplyPart = { text: string } | { href: string; label: string };
+type AstNode = { type: string; children?: AstNode[] };
+
+/** The reply observer consumes the UI's existing parser without adding a
+ * parallel Markdown dependency graph. Unsupported structures fail closed. */
+export function markdownReplyContent(markdown: string, knownPrefixes?: string[]): MarkdownReplyPart[] | null {
+  let rawHtml = false;
+  function rejectHtml() {
+    return (tree: AstNode) => {
+      const nodes = [tree];
+      while (nodes.length) {
+        const node = nodes.pop()!;
+        if (node.type === "html") rawHtml = true;
+        nodes.push(...node.children ?? []);
+      }
+    };
+  }
+  const rendered = Markdown({ children: markdown,
+    remarkPlugins: [remarkGfm, [remarkLinkIssueReferences, { knownPrefixes }], rejectHtml] });
+  if (rawHtml) return null;
+  const parts: MarkdownReplyPart[] = [];
+  function visit(node: ReactNode, label?: string[]): boolean {
+    if (node == null || typeof node === "boolean") return true;
+    if (typeof node === "string" || typeof node === "number") {
+      if (label) label.push(String(node)); else parts.push({ text: String(node) });
+      return true;
+    }
+    if (Array.isArray(node)) return node.every(child => visit(child, label));
+    if (!isValidElement<{ children?: ReactNode; href?: string }>(node)) return false;
+    if (node.type === Fragment) return visit(node.props.children, label);
+    if (node.type === "a" && !label && node.props.href) {
+      const words: string[] = [];
+      if (!visit(node.props.children, words)) return false;
+      parts.push({ href: node.props.href, label: words.join("") });
+      return true;
+    }
+    if (node.type === "br") { if (label) label.push(" "); else parts.push({ text: " " }); return true; }
+    if (["strong", "em", "del", "code"].includes(String(node.type))) return visit(node.props.children, label);
+    if (!label && ["p", "ul", "ol", "li", "blockquote", "h1", "h2", "h3", "h4", "h5", "h6"].includes(String(node.type))) {
+      if (!visit(node.props.children)) return false;
+      parts.push({ text: " " });
+      return true;
+    }
+    return false;
+  }
+  return visit(rendered) ? parts : null;
+}