diff --git a/src/renderer/src/components/editor/markdown-scan-ranges.test.ts b/src/renderer/src/components/editor/markdown-scan-ranges.test.ts
new file mode 100644
index 00000000000..c5914498edf
--- /dev/null
+++ b/src/renderer/src/components/editor/markdown-scan-ranges.test.ts
@@ -0,0 +1,91 @@
+import { describe, expect, it } from 'vitest'
+import { findDetailsBlockStart } from './details-markdown-html'
+import { markdownCodeSpanRanges, markdownFenceRanges } from './markdown-scan-ranges'
+
+describe('markdownCodeSpanRanges', () => {
+  it('reports a span whose backtick run closes on an equal run', () => {
+    expect(markdownCodeSpanRanges('a `<details>` b')).toEqual([[2, 13]])
+  })
+
+  it('keeps a span that contains a blank line', () => {
+    expect(markdownCodeSpanRanges('text `a\n\nb` tail')).toEqual([[5, 11]])
+  })
+
+  it('reports no span for backticks inside a fenced block', () => {
+    expect(markdownCodeSpanRanges(['```', 'a `b` c', '```'].join('\n'))).toEqual([])
+  })
+
+  it('does not pair a fence backtick with a later prose backtick', () => {
+    const content = ['~~~', 'x = `abc', '~~~', '', 'prose with `code` here'].join('\n')
+    const spans = markdownCodeSpanRanges(content)
+
+    expect(spans).toEqual([[29, 35]])
+    expect(content.slice(29, 35)).toBe('`code`')
+  })
+
+  it('does not run a span through a four-backtick fence closer', () => {
+    const content = ['```', 'code', '````', '', 'tail', '', '```', 'more', '```'].join('\n')
+
+    expect(markdownCodeSpanRanges(content)).toEqual([])
+  })
+})
+
+describe('findDetailsBlockStart with fenced content', () => {
+  it('finds a details block after a fence whose content holds an unpaired backtick', () => {
+    const content = [
+      '~~~',
+      'x = `abc',
+      '~~~',
+      '',
+      '<details>',
+      '<summary>S</summary>',
+      '',
+      'body',
+      '',
+      '</details>',
+      '',
+      'prose with `code` here'
+    ].join('\n')
+
+    expect(findDetailsBlockStart(content)).toBe(content.indexOf('<details>'))
+  })
+
+  it('finds a details block between a four-backtick closer and a later fence', () => {
+    const content = [
+      '```',
+      'code',
+      '````',
+      '',
+      '<details>',
+      '<summary>S</summary>',
+      '',
+      'x',
+      '',
+      '</details>',
+      '',
+      '```',
+      'more',
+      '```'
+    ].join('\n')
+
+    expect(findDetailsBlockStart(content)).toBe(content.indexOf('<details>'))
+  })
+
+  it('skips a details mention inside a code span that spans a blank line', () => {
+    expect(findDetailsBlockStart('text `a\n\n<details>b` tail')).toBe(-1)
+  })
+})
+
+describe('markdownFenceRanges', () => {
+  it('covers the opening delimiter, content, and closing delimiter', () => {
+    const content = ['```', 'x', '```', ''].join('\n')
+
+    expect(markdownFenceRanges(content)).toEqual([[0, 10]])
+  })
+
+  it('runs an unterminated fence to the end of the content', () => {
+    const content = ['```', 'x', 'y'].join('\n')
+
+    expect(markdownFenceRanges(content)).toEqual([[0, content.length]])
+  })
+})
diff --git a/src/renderer/src/components/editor/markdown-scan-ranges.ts b/src/renderer/src/components/editor/markdown-scan-ranges.ts
index e46a2932207..a90345e6880 100644
--- a/src/renderer/src/components/editor/markdown-scan-ranges.ts
+++ b/src/renderer/src/components/editor/markdown-scan-ranges.ts
@@ -46,14 +46,35 @@ export function isInsideRange(index: number, ranges: MarkdownFenceRanges): boole
   return ranges.some(([start, end]) => index >= start && index < end)
 }
 
+function rangeEndAt(index: number, ranges: MarkdownFenceRanges): number {
+  for (const [start, end] of ranges) {
+    if (index >= start && index < end) {
+      return end
+    }
+  }
+  return -1
+}
+
 // CommonMark code spans: a backtick run only closes on a run of the same
 // length, so `` `<details>` `` is one span even though `<details>` alone
 // isn't. Mirrors the tick-matching in raw-markdown-html.ts's inline scan.
-export function markdownCodeSpanRanges(content: string): MarkdownFenceRanges {
+// Fenced blocks are skipped whole — their delimiters and content are not
+// inline code, and scanning them pairs a fence backtick with a later prose
+// one, swallowing everything between. Blank lines are not span boundaries.
+export function markdownCodeSpanRanges(
+  content: string,
+  fenceRanges: MarkdownFenceRanges = markdownFenceRanges(content)
+): MarkdownFenceRanges {
   const ranges: [number, number][] = []
   let index = 0
 
   while (index < content.length) {
+    const fenceEnd = rangeEndAt(index, fenceRanges)
+    if (fenceEnd !== -1) {
+      index = fenceEnd
+      continue
+    }
+
     if (content[index] !== '`') {
       index += 1
       continue
@@ -72,6 +93,10 @@ export function markdownCodeSpanRanges(content: string): MarkdownFenceRanges {
       if (candidate === -1) {
         break
       }
+      if (rangeEndAt(candidate, fenceRanges) !== -1) {
+        searchFrom = candidate + 1
+        continue
+      }
       if (
         (candidate === 0 || content[candidate - 1] !== '`') &&
         content[candidate + tickCount] !== '`'