feat(terminal): newline chord as registry data, plus a Key tester in Settings

capabilities.newline replaces choosing the Shift+Enter bytes in the send-key
route. Key tester shows the keydown/keypress/keyup a browser reports.

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

.changeset/newline-capability-key-tester.md

@@ -0,0 +1,5 @@
+---
+"aicodeman": patch
+---
+
+Shift+Enter's newline chord is now registry data (`capabilities.newline`: `line-feed` by default, `esc-enter` for Codex) instead of being chosen in the `send-key` route, so a CLI with a different composer is one line in `stock.ts`. Adds a Key tester under Settings → Terminal & Input that shows the keydown/keypress/keyup events a browser reports, to diagnose a device where a shortcut behaves differently.

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/key-tester.browser.test.ts',
   'test/split-pane-orchestration.browser.test.ts',
   'test/split-pane-auto-collapse.browser.test.ts',
 ];

docs/cli-registry.md

@@ -118,6 +118,10 @@ sure its row is one the agent cannot write.
 
 `test/cli-capability-predicates.test.ts` asserts that no two of the three are equivalent across the catalog, so collapsing them fails the build rather than a user's session.
 
+## The newline chord
+
+`capabilities.newline` (`'line-feed'` | `'esc-enter'`, absent = line feed) is the byte sequence the `send-key` route types into the pane for Shift+Enter. A line feed (`0x0a`, also Ctrl+Enter) is what Claude Code's Ink input reads as "insert a newline"; `esc-enter` (`ESC CR`, the Option/Alt+Enter chord) is for a composer that ignores a bare line feed, which Codex does in some terminals (#495). It is an enum rather than a byte string on purpose: config never carries bytes that get typed into a pane. Settings → Terminal & Input → **Key tester** prints what a browser reports for keydown/keypress/keyup, to see whether a device is sending what you think.
+
 ## Arg-template safety
 
 The composed command line is interpolated into `bash -c "…"` inside tmux, which makes command construction a security boundary. Four independent layers keep config out of it:

src/config/cli-registry/schema.ts

@@ -377,6 +377,7 @@ const capabilitiesSchema = z
     privilegedEnvKeys: z.array(envName).max(8),
     gates: z.record(z.string(), z.object({ minVersion: z.string().max(20), failClosed: z.boolean() }).strict()),
     maxFrameBytes: z.number().int().positive().optional(),
+    newline: z.enum(['line-feed', 'esc-enter']).optional(),
     customModelInjection: z.discriminatedUnion('kind', [
       z
         .object({

src/config/cli-registry/stock.ts

@@ -620,6 +620,9 @@ const CODEX: CliEntry = {
     // `dangerouslyBypassApprovals` on the wire), so it is the one that would have caught a
     // regression; `schema.ts` now rejects a name that is not a declared param.
     privilegedParams: [{ param: 'bypassApprovals', clampTo: false }],
+    // Codex's composer ignores a bare line feed in some terminals (Windows browsers, #495); the
+    // Esc+Enter chord is the one its own Option+Enter uses.
+    newline: 'esc-enter',
     // Verified by hand against a real llama.cpp server. Written to an isolated CODEX_HOME
     // so the user's real ~/.codex/config.toml is never touched.
     customModelInjection: {

src/config/cli-registry/types.ts

@@ -90,6 +90,9 @@ export interface CliVariant {
   args: ArgSpec[];
 }
 
+/** The newline chord a CLI's composer reads as "insert a line break" (see `CliCapabilities.newline`). */
+export type NewlineSequence = 'line-feed' | 'esc-enter';
+
 export interface CliLaunch {
   params: Record<string, ParamSpec>;
   /**
@@ -511,6 +514,14 @@ export interface CliCapabilities {
   gates: Record<string, { minVersion: string; failClosed: boolean }>;
   /** Cap on a single terminal frame, when this CLI needs a tighter one than the default. */
   maxFrameBytes?: number;
+  /**
+   * The bytes the web UI types into this CLI's pane for Shift+Enter (the `send-key` route).
+   * `line-feed` (`0x0a`, also what Ctrl+Enter sends) is what Claude Code's Ink input and most TUIs
+   * read as "insert a newline"; `esc-enter` (`ESC` `CR`, the same chord as Option/Alt+Enter and
+   * the mobile ⌥Enter key) is for a TUI that ignores a bare line feed. Absent = `line-feed`.
+   * Data, not a branch on the CLI id, so supporting another CLI's quirk is one line here.
+   */
+  newline?: NewlineSequence;
   /**
    * How this CLI is pointed at a user-supplied custom OpenAI-compatible
    * endpoint (local, e.g. llama.cpp, or cloud, e.g. Azure AI Foundry) — the

src/web/public/index.html

@@ -1822,6 +1822,22 @@
                   </div>
                 </div>
               </div>
+            
+              <div class="set-group">
+                <div class="set-group-head"><h4>Key tester</h4><span class="set-scope">device</span></div>
+                <div class="set-group-body">
+                  <div class="set-row has-field" data-search="key tester keyboard shift enter newline diagnose keydown keypress">
+                    <div class="set-row-text">
+                      <span class="set-row-label">Key tester</span>
+                      <span class="set-row-desc">Click the box and press keys to see what this browser reports (key, code, modifiers) for keydown, keypress and keyup. Useful when a shortcut such as Shift+Enter behaves differently on one device. Nothing is sent to a session.</span>
+                    </div>
+                    <input type="text" id="keyTesterInput" class="set-select" readonly autocomplete="off" spellcheck="false"
+                      placeholder="Click here, then press keys"
+                      onkeydown="app.keyTesterEvent(event)" onkeypress="app.keyTesterEvent(event)" onkeyup="app.keyTesterEvent(event)">
+                  </div>
+                  <pre id="keyTesterLog" class="set-note mono" style="display:none;white-space:pre-wrap" data-i18n-skip></pre>
+                </div>
+              </div>
             </section>
 
             <!-- ══ Header &amp; Panels ═══════════════════════════════════════ -->

src/web/public/settings-ui.js

@@ -1114,6 +1114,27 @@ Object.assign(CodemanApp.prototype, {
     this._updateCheck = null;
   },
 
+  /**
+   * Settings → Terminal & Input → Key tester: prints what the browser reports for each key event.
+   * Read-only and local; it never reaches a session. keypress is shown on purpose: that event is
+   * why a Shift-only Enter used to submit (xterm drops Ctrl/Alt keypresses, not Shift ones).
+   */
+  keyTesterEvent(ev) {
+    const log = document.getElementById('keyTesterLog');
+    if (!log) return;
+    // Never preventDefault on keydown: that suppresses the keypress this panel exists to show.
+    // The field is readonly, so nothing is typed into it either way.
+    const mods = ['ctrlKey', 'shiftKey', 'altKey', 'metaKey'].filter((m) => ev[m]).map((m) => m.replace('Key', ''));
+    const line =
+      `${ev.type.padEnd(8)} key=${JSON.stringify(ev.key)} code=${ev.code || '-'} ` +
+      `mods=${mods.join('+') || 'none'}` +
+      (ev.type === 'keypress' ? ` charCode=${ev.charCode}` : '') +
+      (ev.repeat ? ' (repeat)' : '');
+    const lines = (log.textContent ? log.textContent.split('\n') : []).concat(line);
+    log.textContent = lines.slice(-14).join('\n');
+    log.style.display = 'block';
+  },
+
   _setUpdateResult(html) {
     const el = this.$('updateResult');
     if (el) { el.style.display = 'block'; el.innerHTML = html; }

src/web/routes/session-routes.ts

@@ -107,6 +107,7 @@ import { buildAgentCaseMarker, writeAgentCaseMarker } from '../../agent-case-mar
 import { canUsernameRunPrivilegedCommands, resolveClaudeModeForUsername } from '../../user-store.js';
 import { clampEnvOverridesForOwner } from '../../session-env-clamp.js';
 import { enabledClis, getCli } from '../../config/cli-registry/registry.js';
+import type { NewlineSequence } from '../../config/cli-registry/types.js';
 import { resolveCliLaunchError } from '../../utils/cli-launcher.js';
 import { legacyConfigForMode } from '../../session-cli-registry-bridge.js';
 import { isMultiUserMode } from '../../config/multiuser.js';
@@ -2100,13 +2101,7 @@ export function registerSessionRoutes(
     const body = req.body as Record<string, unknown>;
     const key = typeof body?.key === 'string' ? body.key : '';
 
-    // Map key names to hex byte sequences
-    const KEY_HEX_MAP: Record<string, string[]> = {
-      'S-Enter': ['0a'], // \n (line feed)
-      'C-Enter': ['0a'], // \n (line feed)
-    };
-    const hex = KEY_HEX_MAP[key];
-    if (!hex) {
+    if (key !== 'S-Enter' && key !== 'C-Enter') {
       return createErrorResponse(ApiErrorCode.INVALID_INPUT, `Key not allowed: ${key}`);
     }
 
@@ -2116,6 +2111,18 @@ export function registerSessionRoutes(
       return createErrorResponse(ApiErrorCode.INVALID_INPUT, 'No tmux session');
     }
 
+    // Key names map to hex byte sequences. Ctrl+Enter is always a line feed; Shift+Enter is the
+    // CLI's own newline chord (`capabilities.newline`, default line feed), so a CLI that wants
+    // Esc+Enter declares it in the registry instead of being special-cased here.
+    const NEWLINE_HEX: Record<NewlineSequence, string[]> = {
+      'line-feed': ['0a'], // \n
+      'esc-enter': ['1b', '0d'], // ESC CR, the Alt/Option+Enter chord
+    };
+    const hex =
+      key === 'C-Enter'
+        ? NEWLINE_HEX['line-feed']
+        : NEWLINE_HEX[getCli(session.mode)?.capabilities.newline ?? 'line-feed'];
+
     try {
       // Route through the dedicated Codeman socket — bare `tmux` would target the
       // user's default server and never find this session (same #80 regression class).

test/cli-newline-capability.test.ts

@@ -0,0 +1,37 @@
+// @vitest-environment node
+// capabilities.newline: the bytes Shift+Enter types into a CLI's pane. Data in the registry, not
+// a branch on the CLI id (test/cli-registry-no-id-branching.test.ts keeps the latter true).
+
+import { describe, expect, it } from 'vitest';
+import { CliEntrySchema } from '../src/config/cli-registry/schema.js';
+import { STOCK_CLIS } from '../src/config/cli-registry/stock.js';
+import type { CliEntry } from '../src/config/cli-registry/types.js';
+
+const claude = () => structuredClone(STOCK_CLIS.find((e) => (e.id as string) === 'claude')!) as CliEntry;
+
+describe('capabilities.newline', () => {
+  it('only codex declares a non-default chord today', () => {
+    const declared = Object.fromEntries(
+      STOCK_CLIS.filter((e) => e.capabilities.newline).map((e) => [e.id as string, e.capabilities.newline])
+    );
+    expect(declared).toEqual({ codex: 'esc-enter' });
+  });
+
+  it.each(['line-feed', 'esc-enter'])('schema accepts %s', (value) => {
+    const e = claude();
+    (e.capabilities as Record<string, unknown>).newline = value;
+    expect(CliEntrySchema.safeParse(e).success).toBe(true);
+  });
+
+  it.each(['lf', 'crlf', '\x1b\r', '', 0])('schema rejects %j (no free-form byte strings in config)', (value) => {
+    const e = claude();
+    (e.capabilities as Record<string, unknown>).newline = value;
+    expect(CliEntrySchema.safeParse(e).success).toBe(false);
+  });
+
+  it('is optional, so an entry that declares nothing keeps the line feed', () => {
+    const e = claude();
+    delete (e.capabilities as Record<string, unknown>).newline;
+    expect(CliEntrySchema.safeParse(e).success).toBe(true);
+  });
+});

test/key-tester.browser.test.ts

@@ -0,0 +1,53 @@
+/** @fileoverview Settings → Terminal & Input → Key tester, driven with real keystrokes in Chromium. */
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { chromium, type Browser, type Page } from 'playwright';
+import { WebServer } from '../src/web/server.js';
+
+const PORT = 3197;
+
+describe('Key tester in a real browser', () => {
+  let server: WebServer;
+  let browser: Browser;
+  let page: Page;
+
+  beforeAll(async () => {
+    server = new WebServer(PORT, false, true);
+    await server.start();
+    browser = await chromium.launch({ headless: true });
+    page = await browser.newPage();
+    await page.goto(`http://localhost:${PORT}`, { waitUntil: 'domcontentloaded' });
+    await page.waitForFunction(() => (window as any).app?.terminal, null, { timeout: 30000 });
+    await page.evaluate(() => (window as any).app.openAppSettings());
+    await page.focus('#keyTesterInput');
+  }, 90000);
+
+  afterAll(async () => {
+    if (browser) await browser.close();
+    if (server) await server.stop();
+  }, 60000);
+
+  const log = () => page.evaluate(() => document.getElementById('keyTesterLog')!.textContent ?? '');
+
+  it('shows keydown, keypress and keyup for Shift+Enter, with the modifier and charCode', async () => {
+    await page.keyboard.press('Shift+Enter');
+    const text = await log();
+    expect(text).toMatch(/keydown\s+key="Enter" code=Enter mods=shift/);
+    // The keypress is the event that used to leak a bare \r to the PTY.
+    expect(text).toMatch(/keypress\s+key="Enter" code=Enter mods=shift charCode=13/);
+    expect(text).toMatch(/keyup\s+key="Enter" code=Enter mods=shift/);
+  });
+
+  it('shows Ctrl+Enter without a keypress, as xterm would never see one for Ctrl', async () => {
+    await page.evaluate(() => (document.getElementById('keyTesterLog')!.textContent = ''));
+    await page.keyboard.press('Control+Enter');
+    const text = await log();
+    expect(text).toMatch(/keydown\s+key="Enter" code=Enter mods=ctrl/);
+    expect(text).toMatch(/keyup/);
+  });
+
+  it('keeps only the last 14 lines and never types into the field', async () => {
+    for (let i = 0; i < 8; i++) await page.keyboard.press('a');
+    expect((await log()).split('\n').length).toBeLessThanOrEqual(14);
+    expect(await page.inputValue('#keyTesterInput')).toBe('');
+  });
+});

test/routes/session-routes.test.ts

@@ -165,6 +165,48 @@ describe('session-routes', () => {
       expect(argv).toContain('-H');
     });
 
+    describe('newline chord comes from the CLI registry (capabilities.newline)', () => {
+      const sentHex = async (mode: string, key: string): Promise<string[]> => {
+        execFile.mockReset();
+        execFile.mockImplementation((_bin: string, _argv: string[], _opts: unknown, cb: (e: Error | null) => void) =>
+          cb(null)
+        );
+        const session = harness.ctx._session as unknown as { mode: string };
+        const before = session.mode;
+        session.mode = mode;
+        try {
+          const res = await harness.app.inject({
+            method: 'POST',
+            url: '/api/sessions/test-session-1/send-key',
+            payload: { key },
+          });
+          expect(res.statusCode).toBe(200);
+        } finally {
+          session.mode = before;
+        }
+        const argv = execFile.mock.calls[0][1] as string[];
+        return argv.slice(argv.indexOf('-H') + 3); // after "-H -t <pane>"
+      };
+
+      it('sends a line feed for Shift+Enter to a CLI that declares nothing', async () => {
+        expect(await sentHex('claude', 'S-Enter')).toEqual(['0a']);
+        expect(await sentHex('opencode', 'S-Enter')).toEqual(['0a']);
+      });
+
+      it('sends Esc+Enter for Shift+Enter to a CLI that declares esc-enter', async () => {
+        expect(await sentHex('codex', 'S-Enter')).toEqual(['1b', '0d']);
+      });
+
+      it('always sends a line feed for Ctrl+Enter', async () => {
+        expect(await sentHex('codex', 'C-Enter')).toEqual(['0a']);
+        expect(await sentHex('claude', 'C-Enter')).toEqual(['0a']);
+      });
+
+      it('falls back to a line feed for a mode the registry does not know', async () => {
+        expect(await sentHex('no-such-cli', 'S-Enter')).toEqual(['0a']);
+      });
+    });
+
     it('rejects keys outside the hex allowlist without invoking tmux', async () => {
       execFile.mockReset();
       const res = await harness.app.inject({