Fix minimal TUI submitted-line duplicate appearance

docs/plans/state.json

@@ -3,6 +3,18 @@
   "updated_at": "2026-02-23",
   "description": "Tracks the status of all Flynn plans and implementation phases",
   "plans": {
+    "minimal-tui-submitted-line-dedupe": {
+      "status": "completed",
+      "date": "2026-02-23",
+      "updated": "2026-02-23",
+      "summary": "Fixed duplicate-looking user messages in minimal TUI by clearing the just-submitted readline prompt line before rendering the timestamped `You` block, so sent content is shown once in the conversation transcript.",
+      "files_modified": [
+        "src/frontends/tui/minimal.ts",
+        "src/frontends/tui/minimal.test.ts",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/frontends/tui/minimal.test.ts passing"
+    },
     "dashboard-local-backend-update-actions": {
       "status": "completed",
       "date": "2026-02-23",
@@ -6010,7 +6022,7 @@
     }
   },
   "overall_progress": {
-    "total_test_count": 1941,
+    "total_test_count": 1942,
     "all_tests_passing": true,
     "p0_completion": "3/3 (100%)",
     "p1_completion": "4/4 (100%)",

src/frontends/tui/minimal.test.ts

@@ -39,6 +39,7 @@ function minimalTuiPrivates(value: MinimalTui): {
   handleCommand: (command: unknown) => Promise<void>;
   handleEscapeAction: () => boolean;
   handleCtrlCPress: (nowMs?: number) => boolean;
+  clearSubmittedPromptLine: () => boolean;
   prompt: (text: string) => Promise<string>;
   rl: {
     once: (event: string, cb: () => void) => void;
@@ -61,6 +62,7 @@ function minimalTuiPrivates(value: MinimalTui): {
     handleCommand: (command: unknown) => Promise<void>;
     handleEscapeAction: () => boolean;
     handleCtrlCPress: (nowMs?: number) => boolean;
+    clearSubmittedPromptLine: () => boolean;
     prompt: (text: string) => Promise<string>;
     rl: {
       once: (event: string, cb: () => void) => void;
@@ -428,6 +430,46 @@ describe('MinimalTui backend command', () => {
 });
 
 describe('MinimalTui prompt cancellation', () => {
+  it('omits leading newline when submitted prompt line was cleared', async () => {
+    const mockSession = {
+      id: 'test',
+      getHistory: () => [],
+      addMessage: vi.fn(),
+      clear: vi.fn(),
+      replaceHistory: vi.fn(),
+    };
+
+    const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    const writeSpy = vi.spyOn(process.stdout, 'write').mockImplementation(() => true);
+    try {
+      const mockAgent = {
+        process: vi.fn(async () => 'ok'),
+      };
+
+      const tui = new MinimalTui({
+        session: asSession(mockSession),
+        modelClient: asRouter({}),
+        agent: asAgent(mockAgent),
+        systemPrompt: 'test',
+      });
+
+      const clearSpy = vi.fn(() => true);
+      minimalTuiPrivates(tui).clearSubmittedPromptLine = clearSpy;
+
+      await minimalTuiPrivates(tui).handleCommand({ type: 'message', content: 'hello' });
+
+      expect(clearSpy).toHaveBeenCalledOnce();
+      const userHeader = writeSpy.mock.calls
+        .map(([chunk]) => String(chunk))
+        .find((chunk) => chunk.includes('You'));
+      expect(userHeader).toBeDefined();
+      expect(userHeader?.startsWith('\n')).toBe(false);
+    } finally {
+      writeSpy.mockRestore();
+      logSpy.mockRestore();
+    }
+  });
+
   it('cancels an active prompt without closing the TUI', async () => {
     const mockSession = {
       id: 'test',

src/frontends/tui/minimal.ts

@@ -237,6 +237,21 @@ export class MinimalTui {
     }
   }
 
+  private clearSubmittedPromptLine(): boolean {
+    if (!process.stdout.isTTY) {
+      return false;
+    }
+
+    try {
+      readline.moveCursor(process.stdout, 0, -1);
+      readline.clearLine(process.stdout, 0);
+      readline.cursorTo(process.stdout, 0);
+      return true;
+    } catch {
+      return false;
+    }
+  }
+
   private handleToolEvent(event: ToolUseEvent): void {
     if (!this.verbose) {
       return;
@@ -1309,9 +1324,10 @@ export class MinimalTui {
   }
 
   private async handleMessage(content: string): Promise<void> {
+    const clearedPromptLine = this.clearSubmittedPromptLine();
     const userTimestamp = formatMessageTimestampParts(Date.now());
     process.stdout.write(
-      `\n${colors.blue}${colors.bold}You${colors.reset} ${colors.gray}[${userTimestamp.date} | ${userTimestamp.time}]${colors.reset}\n`,
+      `${clearedPromptLine ? '' : '\n'}${colors.blue}${colors.bold}You${colors.reset} ${colors.gray}[${userTimestamp.date} | ${userTimestamp.time}]${colors.reset}\n`,
     );
     process.stdout.write(`${content}\n`);