fix: stdin buffer handling and terminal progress race (#1418)

* fix: stdin buffer handling improvements

* Defer terminal progress update to avoid racing twinki render cycle

Wrap syncTerminalProgress in setImmediate so the OSC 9;4 escape
sequence lands after twinki's nextTick render frame, preventing
the animation from taking priority over the actual render.

* fix: wait for slash commands before asserting agent in e2e test

The unknown-agent-fallback test was flaky because it asserted
currentAgent before slash commands finished loading. Adding
waitForSlashCommands() ensures the agent is fully initialized.

---------

Co-authored-by: Kenneth S. <kennvene@amazon.com>

Author: kensave

packages/tui/e2e_tests/unknown-agent-fallback.test.ts

@@ -22,6 +22,7 @@ describe('unknown agent fallback', () => {
       .launch();
 
     await testCase.waitForText('ask a question', 15000);
+    await testCase.waitForSlashCommands();
 
     const store = await testCase.getStore();
     expect(store.currentAgent?.name).toBe('kiro_default');

packages/tui/package.json

@@ -20,8 +20,8 @@
     "test:integ": "bun test ./integ_tests/",
     "test:e2e": "bun run scripts/run-e2e.ts",
     "bench:markdown": "bun run scripts/benchmark-markdown.ts",
-    "dev:profile": "KIRO_AGENT_PATH=../../target/debug/chat_cli_v2 KIRO_INPUT_METRICS=true KIRO_PERF_METRICS=true KIRO_TUI_LOG_FILE=/tmp/kiro-tui-perf.log bun --cpu-prof --cpu-prof-dir=./profiles --watch ./src/index.tsx",
-    "dev:profiletui": "KIRO_RENDERER=twinki KIRO_AGENT_PATH=../../target/debug/chat_cli_v2 KIRO_INPUT_METRICS=true KIRO_PERF_METRICS=true KIRO_TUI_LOG_FILE=/tmp/kiro-tui-perf.log bun --cpu-prof --cpu-prof-dir=./profiles --watch ./src/index.tsx",
+    "dev:profile": "KIRO_AGENT_PATH=../../target/debug/chat_cli KIRO_INPUT_METRICS=true KIRO_PERF_METRICS=true KIRO_TUI_LOG_FILE=/tmp/kiro-tui-perf.log bun --cpu-prof --cpu-prof-dir=./profiles --watch ./src/index.tsx",
+    "dev:profiletui": "KIRO_RENDERER=twinki KIRO_AGENT_PATH=../../target/debug/chat_cli KIRO_INPUT_METRICS=true KIRO_PERF_METRICS=true KIRO_TUI_LOG_FILE=/tmp/kiro-tui-perf.log bun --cpu-prof --cpu-prof-dir=./profiles --watch ./src/index.tsx",
     "analyze:profile": "bun run scripts/analyze-profile.ts --html"
   },
   "dependencies": {

packages/tui/src/stores/app-store.ts

@@ -1989,7 +1989,8 @@ export const createAppStore = (props: AppStoreProps) => {
     const key = `${state.agentError ?? ''}|${state.pendingApproval != null}|${state.isProcessing}|${state.isCompacting}|${state.contextUsagePercent}`;
     if (key !== lastProgressKey) {
       lastProgressKey = key;
-      syncTerminalProgress(state);
+      // Defer so the OSC 9;4 escape lands after twinki's nextTick render frame.
+      setImmediate(() => syncTerminalProgress(state));
     }
   });
 

packages/twinki/packages/twinki/src/hooks/useInput.ts

@@ -126,6 +126,9 @@ export function parseInputData(data: string): { input: string; key: Key } {
 	let input = '';
 	if (data.length === 1 && data.charCodeAt(0) >= 0x20) {
 		input = data;
+	} else if (data.length > 1 && data.charCodeAt(0) >= 0x20 && !parsed) {
+		// Multi-character printable text (batched by StdinBuffer)
+		input = data;
 	} else if (key.ctrl && data.length === 1) {
 		// Ctrl+letter (legacy): expose the letter as input, matching ink's behavior
 		const code = data.charCodeAt(0);

packages/twinki/packages/twinki/src/input/stdin-buffer.ts

@@ -207,8 +207,21 @@ function extractCompleteSequences(buffer: string): { sequences: string[]; remain
 				return { sequences, remainder: remaining };
 			}
 		} else {
-			sequences.push(remaining[0]!);
-			pos++;
+			const ch = remaining.charCodeAt(0);
+			if (ch >= 0x20) {
+				// Batch consecutive printable characters into a single sequence,
+				// matching Ink's behavior of passing whole chunks through.
+				let end = 1;
+				while (end < remaining.length && remaining.charCodeAt(end) >= 0x20 && remaining[end] !== ESC) {
+					end++;
+				}
+				sequences.push(remaining.slice(0, end));
+				pos += end;
+			} else {
+				// Control characters (0x00-0x1F except ESC) emitted individually
+				sequences.push(remaining[0]!);
+				pos++;
+			}
 		}
 	}
 

packages/twinki/packages/twinki/test/stdin-buffer.test.ts

@@ -49,14 +49,12 @@ describe('StdinBuffer', () => {
 		expect(handler).toHaveBeenCalledWith('\x1b[A');
 	});
 
-	it('splits multiple sequences in one chunk', () => {
+	it('emits plain text as a single chunk', () => {
 		const handler = vi.fn();
 		buffer.on('data', handler);
 		buffer.process('abc');
-		expect(handler).toHaveBeenCalledTimes(3);
-		expect(handler).toHaveBeenNthCalledWith(1, 'a');
-		expect(handler).toHaveBeenNthCalledWith(2, 'b');
-		expect(handler).toHaveBeenNthCalledWith(3, 'c');
+		expect(handler).toHaveBeenCalledTimes(1);
+		expect(handler).toHaveBeenCalledWith('abc');
 	});
 
 	it('handles bracketed paste', () => {