fix(terminal): swallow Shift+Enter keypress so it no longer submits

xterm runs the custom key handler for keypress too and drops Ctrl/Alt
keypresses but not Shift-only ones, so the stray \r submitted the prompt
after the newline. Swallow every event type for Shift/Ctrl+Enter and send
only on keydown, in the primary pane and Pane B. Adds a static guard and a
real xterm + Chromium browser test.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.changeset/shift-enter-keypress.md

@@ -0,0 +1,5 @@
+---
+"aicodeman": patch
+---
+
+Shift+Enter no longer submits the prompt after inserting the newline. The terminal key handler swallowed only `keydown`, so xterm's `keypress` for Shift+Enter (which, unlike Ctrl/Alt, it does not discard) still sent a bare `\r`.

config/test-suites.ts

@@ -31,6 +31,7 @@ export const BROWSER_TEST_GLOBS = [
   'test/capture-geometry-retry.browser.test.ts',
   'test/codex-predictive-echo.test.ts', // also needs a real codex binary
   'test/split-pane-terminal.browser.test.ts',
+  'test/shift-enter-keypress.browser.test.ts',
   'test/split-pane-orchestration.browser.test.ts',
   'test/split-pane-auto-collapse.browser.test.ts',
 ];

src/web/public/terminal-split.js

@@ -169,14 +169,17 @@
         // session (this.sessionId), never the primary pane's
         // activeSessionId, and has no local-echo overlay of its own to flush
         // first (Pane B is deliberately plainer — see the fileoverview).
-        if (ev.key === 'Enter' && (ev.shiftKey || ev.ctrlKey) && ev.type === 'keydown') {
+        // Swallow keypress/keyup too (xterm would send \r for a Shift-only keypress); only keydown sends.
-          fetch(`/api/sessions/${this.sessionId}/send-key`, {
+        if (ev.key === 'Enter' && (ev.shiftKey || ev.ctrlKey)) {
-            method: 'POST',
+          if (ev.type === 'keydown') {
-            headers: { 'Content-Type': 'application/json' },
+            fetch(`/api/sessions/${this.sessionId}/send-key`, {
-            body: JSON.stringify({ key: ev.ctrlKey ? 'C-Enter' : 'S-Enter' }),
+              method: 'POST',
-          }).catch(() => {
+              headers: { 'Content-Type': 'application/json' },
-            /* Best-effort, matching this pane's tolerance elsewhere. */
+              body: JSON.stringify({ key: ev.ctrlKey ? 'C-Enter' : 'S-Enter' }),
-          });
+            }).catch(() => {
+              /* Best-effort, matching this pane's tolerance elsewhere. */
+            });
+          }
           return false;
         }
         // Smart copy (mirrors terminal-ui.js's Ctrl+C gate, #211): with a

src/web/public/terminal-ui.js

@@ -447,8 +447,11 @@ Object.assign(CodemanApp.prototype, {
       // xterm.js sends plain \r for all Enter variants, so Claude Code (Ink) can't
       // distinguish them. We use tmux send-keys -H to send a line feed byte (0x0a)
       // which the inner application recognizes as "insert newline" vs carriage return.
-      if (ev.key === 'Enter' && (ev.shiftKey || ev.ctrlKey) && ev.type === 'keydown') {
+      // This handler also runs for keypress/keyup: xterm drops a keypress carrying Ctrl/Alt
-        if (this.activeSessionId) {
+      // but NOT one carrying only Shift, so unless every event type is swallowed here,
+      // Shift+Enter's keypress sends a bare \r (submit) after the newline. Only keydown sends.
+      if (ev.key === 'Enter' && (ev.shiftKey || ev.ctrlKey)) {
+        if (ev.type === 'keydown' && this.activeSessionId) {
           if (this._localEchoEnabled) {
             const text = this._localEchoOverlay?.pendingText || '';
             this._localEchoOverlay?.clear();

test/shift-enter-keypress-swallowed.test.ts

@@ -0,0 +1,21 @@
+// @vitest-environment node
+// Regression guard: xterm runs the custom key handler for keydown AND keypress.
+// It discards a keypress carrying Ctrl/Alt but not one carrying only Shift, so
+// a handler that returns false for keydown alone lets Shift+Enter's keypress
+// through as a bare \r (submit). The Enter gate must therefore not be keyed on
+// ev.type === 'keydown'; only the send-key fetch is.
+
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { describe, expect, it } from 'vitest';
+
+const PUBLIC = join(new URL('.', import.meta.url).pathname, '../src/web/public');
+
+describe.each(['terminal-ui.js', 'terminal-split.js'])('%s Shift/Ctrl+Enter handler', (file) => {
+  const src = readFileSync(join(PUBLIC, file), 'utf8');
+
+  it('swallows every event type for Shift/Ctrl+Enter', () => {
+    expect(src).toMatch(/ev\.key === 'Enter' && \(ev\.shiftKey \|\| ev\.ctrlKey\)\) \{/);
+    expect(src).not.toMatch(/ev\.key === 'Enter' && \(ev\.shiftKey \|\| ev\.ctrlKey\) && ev\.type === 'keydown'/);
+  });
+});

test/shift-enter-keypress.browser.test.ts

@@ -0,0 +1,81 @@
+// @vitest-environment node
+// Real xterm.js in real Chromium, real keystrokes. xterm runs the custom key handler for
+// keydown AND keypress, and drops a keypress that carries Ctrl/Alt but NOT a Shift-only one,
+// so a handler that returns false for keydown alone lets Shift+Enter fall through to a bare
+// \r (submit). That is why Ctrl+Enter and Alt+Enter inserted a newline while Shift+Enter
+// submitted. Self-contained: no server, only the xterm bundle.
+
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { chromium, type Browser, type Page } from 'playwright';
+
+const XTERM = readFileSync(join(process.cwd(), 'node_modules/@xterm/xterm/lib/xterm.js'), 'utf8');
+
+declare global {
+  interface Window {
+    __t: Record<string, { term: { focus(): void }; sent: string[] }>;
+    Terminal: new () => {
+      open(el: HTMLElement): void;
+      focus(): void;
+      onData(cb: (d: string) => void): void;
+      attachCustomKeyEventHandler(cb: (ev: KeyboardEvent) => boolean): void;
+    };
+  }
+}
+
+describe('Shift/Ctrl+Enter reach the PTY as a bare \\r only if the handler lets keypress through', () => {
+  let browser: Browser;
+  let page: Page;
+
+  beforeAll(async () => {
+    browser = await chromium.launch({ headless: true });
+    page = await browser.newPage();
+    await page.setContent('<body></body>');
+    await page.addScriptTag({ content: XTERM });
+    await page.evaluate(() => {
+      const mk = (handler: (ev: KeyboardEvent) => boolean) => {
+        const host = document.createElement('div');
+        document.body.appendChild(host);
+        const term = new window.Terminal();
+        term.open(host);
+        const sent: string[] = [];
+        term.onData((d) => sent.push(d));
+        term.attachCustomKeyEventHandler(handler);
+        return { term, sent };
+      };
+      // The shipped predicate (terminal-ui.js / terminal-split.js) and the one it replaced.
+      const shipped = (ev: KeyboardEvent) => !(ev.key === 'Enter' && (ev.shiftKey || ev.ctrlKey));
+      const keydownOnly = (ev: KeyboardEvent) =>
+        !(ev.key === 'Enter' && (ev.shiftKey || ev.ctrlKey) && ev.type === 'keydown');
+      window.__t = { shipped: mk(shipped), keydownOnly: mk(keydownOnly) };
+    });
+  });
+  afterAll(async () => {
+    await browser?.close();
+  });
+
+  async function typed(which: 'shipped' | 'keydownOnly', key: string): Promise<string[]> {
+    await page.evaluate((w) => {
+      window.__t[w].sent.length = 0;
+      window.__t[w].term.focus();
+    }, which);
+    await page.keyboard.press(key);
+    return page.evaluate((w) => [...window.__t[w].sent], which);
+  }
+
+  it('reproduces the bug with the old keydown-only handler', async () => {
+    expect(await typed('keydownOnly', 'Shift+Enter')).toEqual(['\r']);
+    expect(await typed('keydownOnly', 'Control+Enter')).toEqual([]);
+  });
+
+  it('sends nothing for Shift+Enter and Ctrl+Enter with the shipped handler (the send-key route supplies the newline)', async () => {
+    expect(await typed('shipped', 'Shift+Enter')).toEqual([]);
+    expect(await typed('shipped', 'Control+Enter')).toEqual([]);
+  });
+
+  it('leaves plain Enter and Alt+Enter alone', async () => {
+    expect(await typed('shipped', 'Enter')).toEqual(['\r']);
+    expect(await typed('shipped', 'Alt+Enter')).toEqual(['\x1b\r']);
+  });
+});