fix(prompt): scale bracketed-paste delay by line count to prevent stuck initial prompts (#107)

* fix(prompt): scale bracketed-paste delay by line count to prevent stuck initial prompts

When an agent enables bracketed paste mode (CSI ? 2004 h), synthetic prompt
sends wrap the text in \x1b[200~...\x1b[201~ to avoid Codex's paste-burst
guard. However, TUI agents like Claude Code process the paste asynchronously —
if \r arrives while the paste is still being consumed, it is absorbed into the
input buffer as a newline rather than submitting the prompt.

The previous fixed 50ms delay was sufficient for short prompts but too short
for large ones (e.g. a 31-line initial task prompt). The symptom is the agent
sitting in INSERT mode with "[Pasted text #1 +N lines]" in its input, never
sending.

Fix:
- Track bracketed paste mode (CSI ? 2004 h/l) in AgentTrackingState via
  updateBracketedPasteMode(), called on each PTY data chunk in markAgentOutput()
- Export isAgentBracketedPasteEnabled() so sendPrompt can conditionally wrap
- Scale the pre-Enter delay: max(50ms, lines * 15ms), capped at 500ms —
  a 31-line prompt now waits ~465ms instead of 50ms

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test(prompt): add pasteDelayMs regression tests; export fn; fix duplicate constants

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: brooksc

src/store/tasks.test.ts

@@ -74,7 +74,7 @@ vi.mock('../lib/log', () => ({
   warn: vi.fn(),
 }));
 
-import { sendPrompt } from './tasks';
+import { pasteDelayMs, sendPrompt } from './tasks';
 
 function writePayloads(): string[] {
   return mockInvoke.mock.calls
@@ -180,3 +180,19 @@ describe('sendPrompt', () => {
     expect(writePayloads()[1]).toContain('IMPORTANT: Maintain .claude/steps.json');
   });
 });
+
+describe('pasteDelayMs', () => {
+  it('returns 50ms for a short single-line prompt', () => {
+    expect(pasteDelayMs('hello')).toBe(50);
+  });
+
+  it('scales by line count for a ~31-line prompt', () => {
+    const text = Array.from({ length: 31 }, (_, i) => `line ${i + 1}`).join('\n');
+    expect(pasteDelayMs(text)).toBe(Math.min(500, Math.max(50, 31 * 15)));
+  });
+
+  it('caps at 500ms for a very large prompt', () => {
+    const text = Array.from({ length: 100 }, (_, i) => `line ${i + 1}`).join('\n');
+    expect(pasteDelayMs(text)).toBe(500);
+  });
+});

src/store/tasks.ts

@@ -60,6 +60,17 @@ function sleep(ms: number): Promise<void> {
   return new Promise((resolve) => setTimeout(resolve, ms));
 }
 
+// Delay between writing pasted text and the Enter key.  Claude Code (and other
+// TUI agents) process bracketed paste asynchronously — if \r arrives before
+// the paste is fully consumed, it gets absorbed into the input buffer instead
+// of submitting it.  We scale the delay by line count so large prompts (e.g.
+// initial task prompts of 30+ lines) reliably submit.  Cap at 500ms to avoid
+// noticeable lag on normal sends.
+export function pasteDelayMs(text: string): number {
+  const lines = text.split('\n').length;
+  return Math.min(500, Math.max(50, lines * 15));
+}
+
 function isAgentNotFoundError(err: unknown): boolean {
   return String(err).toLowerCase().includes('agent not found');
 }
@@ -496,13 +507,12 @@ export async function sendPrompt(taskId: string, agentId: string, text: string):
   // bracketed paste, wrap only the prompt text; this avoids Codex's paste-burst
   // guard treating rapid synthetic keystrokes plus Enter as a paste.
   setTaskLastInputAt(taskId);
+  const useBracketed = isAgentBracketedPasteEnabled(agentId);
   await writeToAgentWhenReady(
     agentId,
-    isAgentBracketedPasteEnabled(agentId)
-      ? `${BRACKETED_PASTE_START}${effectiveText}${BRACKETED_PASTE_END}`
-      : effectiveText,
+    useBracketed ? `${BRACKETED_PASTE_START}${effectiveText}${BRACKETED_PASTE_END}` : effectiveText,
   );
-  await new Promise((r) => setTimeout(r, 50));
+  await new Promise((r) => setTimeout(r, pasteDelayMs(effectiveText)));
   await writeToAgentWhenReady(agentId, '\r');
   setStore('tasks', taskId, 'lastPrompt', text);
   if (task && !hasPromptedAgent) {