diff --git a/config/scripts/record-ime-trace.mjs b/config/scripts/record-ime-trace.mjs
index 32a6fec66f7..a4ed1da82b2 100644
--- a/config/scripts/record-ime-trace.mjs
+++ b/config/scripts/record-ime-trace.mjs
@@ -100,6 +100,7 @@ let initial = snapshot()
 
 function snapshot() {
   return {
+    selectionDirection: target.selectionDirection ?? 'none',
     selectionEnd: target.selectionEnd ?? 0,
     selectionStart: target.selectionStart ?? 0,
     value: target.value
@@ -114,20 +115,24 @@ function record(event) {
   } else if (event instanceof InputEvent) {
     entry.data = event.data ?? null
     entry.inputType = event.inputType
-    // Safari reports undefined rather than false and the distinction is load-bearing,
-    // so it is preserved instead of coerced.
-    entry.isComposing = event.isComposing
+    // Safari reports undefined rather than false and the distinction is load-bearing.
+    // JSON.stringify drops an undefined value outright, so null carries it instead;
+    // transcribe it back to undefined in the fixture.
+    entry.isComposing = event.isComposing ?? null
   } else if (event instanceof KeyboardEvent) {
     entry.code = event.code
     entry.isComposing = event.isComposing
     entry.key = event.key
     entry.keyCode = event.keyCode
+    // The accent panel a macOS press-and-hold opens is only recognisable by this.
+    entry.repeat = event.repeat
   }
   events.push(entry)
   countEl.textContent = String(events.length)
   const detail = [
     entry.key ? 'key=' + entry.key : '',
     entry.keyCode === undefined ? '' : 'keyCode=' + entry.keyCode,
+    entry.repeat ? 'repeat' : '',
     entry.inputType ? entry.inputType : '',
     entry.data === undefined ? '' : 'data=' + JSON.stringify(entry.data),
     'isComposing=' + entry.isComposing,
diff --git a/config/scripts/record-ime-trace.test.mjs b/config/scripts/record-ime-trace.test.mjs
new file mode 100644
index 00000000000..bf22be6650a
--- /dev/null
+++ b/config/scripts/record-ime-trace.test.mjs
@@ -0,0 +1,55 @@
+import { readFileSync } from 'node:fs'
+import path from 'node:path'
+import { describe, expect, it } from 'vitest'
+
+// The recorder writes traces that the fixture schema has to be able to hold. The two
+// live in different languages and different build graphs, so nothing but this checks
+// that a field one of them learns about ever reaches the other.
+
+const scriptsDir = import.meta.dirname
+const projectDir = path.resolve(scriptsDir, '../..')
+
+const recorderSource = readFileSync(path.join(scriptsDir, 'record-ime-trace.mjs'), 'utf8')
+const schemaSource = readFileSync(
+  path.join(projectDir, 'src/renderer/src/lib/ime-composition-trace.test-fixtures.ts'),
+  'utf8'
+)
+
+function declaredSchemaFields(typeName) {
+  const body = schemaSource.match(new RegExp(`export type ${typeName} = [^{]*\\{([^}]*)\\}`))?.[1]
+  if (!body) {
+    throw new Error(`${typeName} not found in the fixture schema`)
+  }
+  return new Set(Array.from(body.matchAll(/^\s{2}(\w+)\??:/gm), (match) => match[1]))
+}
+
+describe('record-ime-trace', () => {
+  it('captures nothing the trace schema cannot express', () => {
+    const captured = new Set(Array.from(recorderSource.matchAll(/entry\.(\w+) =/g), (m) => m[1]))
+    const expressible = new Set([
+      ...declaredSchemaFields('ImeTraceKeyEvent'),
+      ...declaredSchemaFields('ImeTraceInputEvent'),
+      ...declaredSchemaFields('ImeTraceCompositionEvent')
+    ])
+
+    expect(captured.size).toBeGreaterThan(0)
+    expect([...captured].filter((field) => !expressible.has(field))).toEqual([])
+  })
+
+  it('records the fields the platform quirks are recognised by', () => {
+    // repeat distinguishes a held key from the first press, which is the only signal
+    // a macOS press-and-hold accent panel produces; selectionDirection is the only way
+    // a backward preedit range survives as anything but a caret.
+    expect(recorderSource).toMatch(/entry\.repeat = event\.repeat/)
+    expect(recorderSource).toMatch(/selectionDirection: target\.selectionDirection/)
+    expect(declaredSchemaFields('ImeTraceKeyEvent')).toContain('repeat')
+    expect(declaredSchemaFields('ImeTraceTargetState')).toContain('selectionDirection')
+  })
+
+  it('carries an undefined isComposing as null rather than dropping the key', () => {
+    // JSON.stringify omits undefined-valued keys outright, so coercing here would
+    // erase the one bit a Safari trace is recorded to preserve.
+    expect(recorderSource).toMatch(/entry\.isComposing = event\.isComposing \?\? null/)
+    expect(JSON.stringify({ isComposing: undefined })).toBe('{}')
+  })
+})