fix(browse): sidebar Terminal — drop the duplicate WS subprotocol header, stop doubling CJK IME input

The terminal client passed the auth token as the WS subprotocol AND echoed
it in a second header, which some Chromium builds reject; and composition
events double-sent CJK input (each IME commit arrived once from the
composition handler and once from the data handler). One auth path, one
input path; also fixes the terminal-agent test that failed on clean main.

Contributed by @mindsurf0176 (PR #2515).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

browse/test/terminal-agent-integration.test.ts

@@ -227,6 +227,45 @@ describe('terminal-agent: PTY round-trip via real WebSocket (Cookie auth)', () =
     expect(resp.headers.get('sec-websocket-protocol')).toBe(`gstack-pty.${token}`);
   });
 
+  test('upgrade response contains exactly ONE Sec-WebSocket-Protocol header', async () => {
+    // RFC 6455: the server MUST select at most one subprotocol. Bun >= 1.3
+    // auto-echoes the first offered protocol in server.upgrade(), so a
+    // manual echo on top of that produced TWO Sec-WebSocket-Protocol
+    // headers — and strict clients (Chromium, python websockets) reject the
+    // handshake, leaving the sidebar terminal permanently disconnected.
+    //
+    // Headers.get() normalizes duplicates away, so this test handshakes
+    // over a raw socket and counts header lines in the response head.
+    const token = 'dup-proto-token-must-be-at-least-seventeen-chars';
+    await grantToken(token);
+
+    const head = await new Promise<string>((resolve, reject) => {
+      const req =
+        'GET /ws HTTP/1.1\r\n' +
+        `Host: 127.0.0.1:${agentPort}\r\n` +
+        'Connection: Upgrade\r\n' +
+        'Upgrade: websocket\r\n' +
+        'Sec-WebSocket-Version: 13\r\n' +
+        'Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==\r\n' +
+        `Sec-WebSocket-Protocol: gstack-pty.${token}\r\n` +
+        'Origin: chrome-extension://test-extension-id\r\n' +
+        '\r\n';
+      let buf = '';
+      const socket = require('net').connect(agentPort, '127.0.0.1', () => socket.write(req));
+      socket.setTimeout(5000, () => { socket.destroy(); reject(new Error('handshake timeout')); });
+      socket.on('data', (chunk: Buffer) => {
+        buf += chunk.toString('utf8');
+        const end = buf.indexOf('\r\n\r\n');
+        if (end !== -1) { socket.destroy(); resolve(buf.slice(0, end)); }
+      });
+      socket.on('error', reject);
+    });
+
+    expect(head).toContain('101');
+    const protoLines = head.split('\r\n').filter(l => l.toLowerCase().startsWith('sec-websocket-protocol:'));
+    expect(protoLines).toEqual([`Sec-WebSocket-Protocol: gstack-pty.${token}`]);
+  });
+
   test('Sec-WebSocket-Protocol auth: rejects unknown token even with valid Origin', async () => {
     const resp = await fetch(`http://127.0.0.1:${agentPort}/ws`, {
       headers: {

browse/test/terminal-agent.test.ts

@@ -131,15 +131,18 @@ describe('Source-level guard: terminal-agent', () => {
     expect(wsHandler).toContain('validTokens.has');
   });
 
-  test('Sec-WebSocket-Protocol auth: strips gstack-pty. prefix and echoes back', () => {
+  test('Sec-WebSocket-Protocol auth: strips gstack-pty. prefix, no manual echo', () => {
     const wsHandler = AGENT_SRC.slice(AGENT_SRC.indexOf("if (url.pathname === '/ws')"));
     // Browsers send `Sec-WebSocket-Protocol: gstack-pty.<token>`. The agent
-    // must strip the prefix before checking validTokens, AND echo the
-    // protocol back in the upgrade response — without the echo, the
-    // browser closes the connection immediately.
+    // must strip the prefix before checking validTokens. The protocol echo
+    // is Bun's job: Bun >= 1.3 auto-echoes the first offered protocol in the
+    // 101 response. A manual echo on top produced a DUPLICATE
+    // Sec-WebSocket-Protocol header, which strict clients (Chromium, python
+    // websockets) reject per RFC 6455 — the sidebar terminal could never
+    // connect. Pin the invariant: no manual echo in the upgrade call.
     expect(wsHandler).toContain("'gstack-pty.'");
-    expect(wsHandler).toContain('Sec-WebSocket-Protocol');
-    expect(wsHandler).toContain('acceptedProtocol');
+    expect(wsHandler).toContain('sec-websocket-protocol');
+    expect(wsHandler).not.toContain("headers: { 'Sec-WebSocket-Protocol'");
   });
 
   test('lazy spawn: claude PTY is spawned in message handler, not on upgrade', () => {
@@ -155,6 +158,8 @@ describe('Source-level guard: terminal-agent', () => {
     expect(upgradeBlock).not.toContain('spawnClaude(');
     expect(upgradeBlock).not.toContain('maybeSpawnPty(');
     // Spawn must be invoked from the message handler (lazy on first byte).
+    // v1.44 routes both spawn triggers (explicit {type:"start"} text frame
+    // and the lazy binary-frame path) through the maybeSpawnPty helper.
     const messageHandler = AGENT_SRC.slice(AGENT_SRC.indexOf('message(ws, raw)'));
     expect(messageHandler).toContain('maybeSpawnPty(');
     expect(messageHandler).toContain('!session.spawned');