diff --git a/packages/app/src/components/markdown/html-ish.test.ts b/packages/app/src/components/markdown/html-ish.test.ts
index ac6f2ad8b..c47a718fe 100644
--- a/packages/app/src/components/markdown/html-ish.test.ts
+++ b/packages/app/src/components/markdown/html-ish.test.ts
@@ -256,6 +256,12 @@ describe("splitHtmlishMarkdown", () => {
     expect(splitHtmlishMarkdown(source)).toEqual([{ kind: "markdown", text: source }]);
   });
 
+  it("terminates when an unmatched backtick follows a closed inline code span", () => {
+    const source = "Use `<details><summary>Example</summary>Body</details>` before `dangling";
+
+    expect(splitHtmlishMarkdown(source)).toEqual([{ kind: "markdown", text: source }]);
+  });
+
   it("still parses normal details outside code", () => {
     expect(splitHtmlishMarkdown("`code`\n<details><summary>Real</summary>Body</details>")).toEqual([
       { kind: "markdown", text: "`code`\n" },
diff --git a/packages/app/src/components/markdown/html-ish.ts b/packages/app/src/components/markdown/html-ish.ts
index b68e734b5..7a92f0d20 100644
--- a/packages/app/src/components/markdown/html-ish.ts
+++ b/packages/app/src/components/markdown/html-ish.ts
@@ -651,8 +651,13 @@ function getInlineCodeRanges(
     }
 
     const marker = open[0];
-    const close = findClosingBacktickRun(source, BACKTICK_RUN_RE.lastIndex, marker, fencedRanges);
+    const afterOpen = BACKTICK_RUN_RE.lastIndex;
+    const close = findClosingBacktickRun(source, afterOpen, marker, fencedRanges);
     if (!close) {
+      // Unmatched backtick run — skip past it so the loop doesn't restart from 0.
+      // findClosingBacktickRun exhausts the global regex, which resets lastIndex
+      // to 0 when exec() returns null (ECMAScript §22.2.7.2).
+      BACKTICK_RUN_RE.lastIndex = afterOpen;
       continue;
     }