diff --git a/ui-tui/src/__tests__/createGatewayEventHandler.test.ts b/ui-tui/src/__tests__/createGatewayEventHandler.test.ts
index 071f8141a0..517b2be0c2 100644
--- a/ui-tui/src/__tests__/createGatewayEventHandler.test.ts
+++ b/ui-tui/src/__tests__/createGatewayEventHandler.test.ts
@@ -175,6 +175,26 @@ describe('createGatewayEventHandler', () => {
     expect(appended[0]?.text).toContain(cleaned)
   })
 
+  it('does not append inline_diff twice when assistant text already contains it', () => {
+    const appended: Msg[] = []
+    const onEvent = createGatewayEventHandler(buildCtx(appended))
+    const cleaned = '--- a/foo.ts\n+++ b/foo.ts\n@@\n-old\n+new'
+    const assistantText = `Done. Here's the inline diff:\n\n\`\`\`diff\n${cleaned}\n\`\`\``
+
+    onEvent({
+      payload: { inline_diff: cleaned, summary: 'patched', tool_id: 'tool-1' },
+      type: 'tool.complete'
+    } as any)
+    onEvent({
+      payload: { text: assistantText },
+      type: 'message.complete'
+    } as any)
+
+    expect(appended).toHaveLength(1)
+    expect(appended[0]?.text).toBe(assistantText)
+    expect((appended[0]?.text.match(/```diff/g) ?? []).length).toBe(1)
+  })
+
   it('shows setup panel for missing provider startup error', () => {
     const appended: Msg[] = []
     const onEvent = createGatewayEventHandler(buildCtx(appended))
diff --git a/ui-tui/src/app/turnController.ts b/ui-tui/src/app/turnController.ts
index db312d20e2..005eed4bcb 100644
--- a/ui-tui/src/app/turnController.ts
+++ b/ui-tui/src/app/turnController.ts
@@ -187,7 +187,7 @@ class TurnController {
   queueInlineDiff(diffText: string) {
     const text = diffText.trim()
 
-    if (!text) {
+    if (!text || this.pendingInlineDiffs.includes(text)) {
       return
     }
 
@@ -239,8 +239,9 @@ class TurnController {
     const rawText = (payload.rendered ?? payload.text ?? this.bufRef).trimStart()
     const split = splitReasoning(rawText)
     const finalText = split.text
-    const inlineDiffBlock = this.pendingInlineDiffs.length
-      ? `\`\`\`diff\n${this.pendingInlineDiffs.join('\n\n')}\n\`\`\``
+    const remainingInlineDiffs = this.pendingInlineDiffs.filter(diff => !finalText.includes(diff))
+    const inlineDiffBlock = remainingInlineDiffs.length
+      ? `\`\`\`diff\n${remainingInlineDiffs.join('\n\n')}\n\`\`\``
       : ''
     const mergedText = [finalText, inlineDiffBlock].filter(Boolean).join('\n\n')
     const existingReasoning = this.reasoningText.trim() || String(payload.reasoning ?? '').trim()