diff --git a/.devcontainer/codespaces/Dockerfile b/.devcontainer/codespaces/Dockerfile
index 8192ad35fa8..b3dd9fa209b 100644
--- a/.devcontainer/codespaces/Dockerfile
+++ b/.devcontainer/codespaces/Dockerfile
@@ -4,6 +4,7 @@ ARG NODE_VERSION=24
 FROM node:${NODE_VERSION}-bookworm
 
 ARG PLAYWRIGHT_VERSION=1.62.1
+ARG OPENCODE_VERSION=1.18.25
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     tmux sudo less jq ripgrep postgresql-client \
@@ -14,7 +15,7 @@ RUN npx -y playwright@${PLAYWRIGHT_VERSION} install-deps chromium
 
 # Agent harnesses. Self-update is off: the image is the update mechanism
 ENV DISABLE_AUTOUPDATER=1
-RUN npm install -g @anthropic-ai/claude-code opencode-ai
+RUN npm install -g @anthropic-ai/claude-code opencode-ai@${OPENCODE_VERSION}
 
 COPY codespaces-env.sh /usr/local/lib/codespaces-env.sh
 COPY codespaces-secrets.sh /etc/profile.d/codespaces-secrets.sh
diff --git a/.devcontainer/codespaces/README.md b/.devcontainer/codespaces/README.md
index 8ad8ae1805f..564d16704c4 100644
--- a/.devcontainer/codespaces/README.md
+++ b/.devcontainer/codespaces/README.md
@@ -26,8 +26,10 @@ Playwright system deps, and Docker-in-Docker (for testcontainers and
 ```bash
 pnpm session                       # attach Claude Code (creates everything on first run)
 pnpm session:shell                 # open a shell in the default checkout
-pnpm session:opencode              # attach OpenCode in auto mode
-pnpm session:opencode fix-flaky    # OpenCode in a separate worktree
+pnpm session:opencode              # connect the local OpenCode TUI
+pnpm session:opencode fix-flaky    # use a separate remote worktree
+pnpm session:opencode --web        # open OpenCode in the local browser
+pnpm session:opencode --legacy     # use the remote TUI in tmux
 pnpm session fix-flaky             # Claude Code in a separate worktree
 pnpm session ls                    # what's running
 pnpm session tunnel                # forward n8n ports (default 5678, 8080); Ctrl-C to stop
@@ -38,8 +40,9 @@ pnpm session rm                    # delete the codespace
 The dev container supports Codespaces with 2, 4, or 8 cores. The session commands
 create an 8-core Codespace by default.
 
-- **Detach** with `Ctrl-b d` — the agent keeps working without you.
-- **Scroll** with the mouse wheel (tmux mouse mode is on). To use the
+- **Detach from tmux** with `Ctrl-b d` — the agent keeps working without you.
+  Local OpenCode connections use the exit controls described below.
+- **Scroll in tmux** with the mouse wheel (tmux mouse mode is on). To use the
   terminal's own text selection, hold **Shift** and drag.
 - **Reattach** by running the same session command from any machine.
 - Each named session gets its own worktree (`/workspaces/wt-<name>`, branch
@@ -62,6 +65,105 @@ The command verifies the release checksum. It caches the bundle under
 `~/.config/opencode/plugins`. Run the command again after the lock changes.
 Restart OpenCode after the command completes.
 
+## Local OpenCode clients
+
+Run these commands from a local checkout. The TUI runs on your laptop. The
+OpenCode server, repository, tools, and builds run in the Codespace. Browser
+mode opens the remote web interface through a local connection.
+
+```bash
+pnpm session:opencode fix-flaky              # resume the saved conversation
+pnpm session:opencode fix-flaky --web        # open that conversation in a browser
+pnpm session:opencode fix-flaky --new        # start a new conversation in that worktree
+pnpm session:opencode --web --port 4100      # override the default browser port
+pnpm session:opencode --help
+```
+
+For the TUI, install the same OpenCode version as the remote server. The
+`OPENCODE_VERSION` argument in the [Dockerfile](Dockerfile) pins the version
+for new images:
+
+```bash
+pnpm add --global opencode-ai@<version>
+```
+
+The launcher checks both versions. It reports a mismatch with both version
+numbers before it opens the TUI. An existing Codespace can have a different
+version. Install that version locally, or use `--web`. Browser mode does not
+need a local OpenCode install.
+The launcher sends its bootstrap code over SSH, so an existing Codespace does
+not need a rebuild to use this connection method.
+The remote server loads the shared OpenCode harness that the Codespace
+post-start command installs. The local harness setup above is not required for
+these commands.
+
+The command prepares the worktree, starts or reuses one server, opens an SSH
+tunnel, and connects the client. Each workspace name has a saved conversation
+ID on the Codespace. TUI and browser modes open the same saved conversation.
+`--new` replaces that saved ID. It preserves the worktree and the old conversation.
+If you switch conversations inside a client, the next launcher run still opens
+the ID saved for that workspace name.
+
+- **Exit the TUI** with `/exit` or its quit shortcut. The launcher closes its
+  tunnel. The remote server stays running.
+- **Disconnect browser mode** with `Ctrl-C` in the launcher terminal. Closing
+  the browser tab does not close the tunnel. Keep the launcher running while
+  you use the browser.
+- **Reconnect** with the same command after a network interruption. After a
+  Codespace stop, the command restarts the server and opens the saved conversation.
+  A stop terminates running tools. It does not resume interrupted commands.
+- **Browser mode uses local port 4096 by default.** Use `--port` to override it.
+  TUI mode selects an available port unless you specify one.
+  A fixed browser port preserves the browser origin across runs.
+  An occupied fixed port causes an error. It does not stop the existing listener.
+- **Use model and permission controls in the client.** The new connection uses
+  the remote OpenCode configuration. It does not force the legacy `--auto` mode.
+  For the old CLI flags, use `pnpm session:opencode fix-flaky --legacy --model <model>`.
+
+Both server and tunnel bind to `127.0.0.1`. The server uses a generated password.
+The TUI receives it through its environment. Browser mode uses a local proxy
+that adds authentication and rejects requests from other browser origins. The
+proxy supports streamed responses, attachments, and terminal WebSockets. The
+password does not appear in the URL or terminal output. Other processes on
+your laptop can access the local browser proxy while it runs. Do not forward
+this proxy or the OpenCode server port to other machines.
+
+The server enables only OpenRouter. It reads `OPENROUTER_API_KEY` when it starts.
+Browser mode opens the selected conversation directly.
+The web UI stores opened projects in browser storage. If a new-session page
+shows **New project**, open `/workspaces/n8n` there once. Keep the same browser
+port when you reconnect to preserve this selection.
+
+The server runs in the detached tmux session `n8n-opencode-server`. Its log is
+`/workspaces/.n8n-opencode/server.log`. That directory also holds the server
+credentials and saved conversation IDs. It is readable only by its owner.
+An unhealthy server produces an error without stopping active work. Inspect
+the log through `pnpm session:shell`. To restart it after checking active work,
+run `tmux kill-session -t '=n8n-opencode-server'` in that shell. Then reconnect.
+Restart the server after changing provider secrets, server configuration, or
+the pinned harness release.
+
+### Limits
+
+- The launcher supports macOS and Linux. On Windows, run it in WSL. If the
+  browser does not open automatically, open the printed URL yourself.
+- Local clipboard and attachment controls depend on the client, terminal,
+  file type, and model. A laptop file path does not copy a file to the Codespace.
+  Use a supported attachment control or copy the file with `gh codespace cp`.
+- Tools and local MCP processes run on the Codespace. Laptop configuration,
+  browser sessions, and files do not sync automatically.
+- Workspace names identify worktrees. Two agents that use the same name share
+  files. Separate conversations alone do not isolate edits.
+- The server survives a client disconnect while the Codespace stays running.
+  Codespaces idle timeouts still apply. An open tunnel is not a guarantee that
+  the Codespace will stay awake. Use `pnpm session stop` to stop compute billing.
+- Existing tmux OpenCode conversations are not migrated automatically. Use
+  `--legacy` to return to them.
+
+For upstream behavior, see the [OpenCode CLI](https://opencode.ai/docs/cli/),
+[server](https://opencode.ai/docs/server/), and [web](https://opencode.ai/docs/web/)
+documentation.
+
 ## PR previews (a running instance of someone else's PR)
 
 A preview is a codespace that serves one pull request, so a reviewer can use the
diff --git a/.devcontainer/codespaces/cloud-session.test.mjs b/.devcontainer/codespaces/cloud-session.test.mjs
index 92ba28dfec4..9e5264eb21f 100644
--- a/.devcontainer/codespaces/cloud-session.test.mjs
+++ b/.devcontainer/codespaces/cloud-session.test.mjs
@@ -59,7 +59,7 @@ function remoteCommand(args) {
 }
 
 test('starts a named OpenCode session in a worktree', () => {
-	const command = remoteCommand(['--opencode', 'fix-flaky', '--model', 'test']);
+	const command = remoteCommand(['--opencode', 'fix-flaky', '--legacy', '--model', 'test']);
 
 	assert.match(command, /tmux new -As fix-flaky-opencode/);
 	assert.match(command, /unset AGENT_WORKER_TOKEN N8N_DEQUEUE_URL SLACK_BOT_TOKEN/);
@@ -71,6 +71,15 @@ test('starts a named OpenCode session in a worktree', () => {
 	assert.doesNotMatch(command, /claude plugin/);
 });
 
+test('forwards legacy flags without a workspace name to the main checkout', () => {
+	for (const flags of [['--help'], ['--model', 'test']]) {
+		const command = remoteCommand(['--opencode', '--legacy', ...flags]);
+		assert.match(command, /tmux new -As agent-opencode/);
+		assert.ok(command.includes(`cd /workspaces/n8n && opencode --auto ${flags.join(' ')}`));
+		assert.doesNotMatch(command, /git .*worktree add/);
+	}
+});
+
 test('keeps removed credentials out of the login shell', () => {
 	const command = remoteCommand(['--shell']);
 	const profile = readFileSync(new URL('./codespaces-secrets.sh', import.meta.url), 'utf8');
diff --git a/.devcontainer/codespaces/fake-bin.mjs b/.devcontainer/codespaces/fake-bin.mjs
new file mode 100644
index 00000000000..e19d8b4a49d
--- /dev/null
+++ b/.devcontainer/codespaces/fake-bin.mjs
@@ -0,0 +1,36 @@
+// Fake executables for tests. Each shim is a Node script. It receives `args`, `root`,
+// `file(name)` under the root, and `log(event)`, which appends to calls.jsonl in the root.
+import { mkdirSync, mkdtempSync, readFileSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+
+const COMMON = `
+const fs = require('node:fs');
+const path = require('node:path');
+const args = process.argv.slice(2);
+const root = process.env.TEST_ROOT;
+const file = (name) => path.join(root, name);
+const log = (event) => fs.appendFileSync(file('calls.jsonl'), JSON.stringify(event) + '\\n');
+`;
+
+export function fakeBinaries(prefix) {
+	const root = mkdtempSync(join(tmpdir(), prefix));
+	const binDir = join(root, 'bin');
+	mkdirSync(binDir);
+	const logFile = join(root, 'calls.jsonl');
+	writeFileSync(logFile, '');
+	return {
+		root,
+		env: { PATH: `${binDir}:${process.env.PATH}`, TEST_ROOT: root },
+		bin: (name, body) =>
+			writeFileSync(join(binDir, name), `#!${process.execPath}\n${COMMON}\n${body}`, {
+				mode: 0o755,
+			}),
+		calls: () =>
+			readFileSync(logFile, 'utf8')
+				.trim()
+				.split('\n')
+				.filter(Boolean)
+				.map((line) => JSON.parse(line)),
+	};
+}
diff --git a/.devcontainer/codespaces/opencode-client.test.mjs b/.devcontainer/codespaces/opencode-client.test.mjs
new file mode 100644
index 00000000000..804b1777cc4
--- /dev/null
+++ b/.devcontainer/codespaces/opencode-client.test.mjs
@@ -0,0 +1,199 @@
+import assert from 'node:assert/strict';
+import { spawn } from 'node:child_process';
+import { rmSync } from 'node:fs';
+import { test } from 'node:test';
+import { setTimeout as delay } from 'node:timers/promises';
+import { fileURLToPath } from 'node:url';
+
+import { fakeBinaries } from './fake-bin.mjs';
+import { parseOpenCodeArgs } from '../../scripts/cloud-session-opencode.mjs';
+
+const script = fileURLToPath(new URL('../../scripts/cloud-session.mjs', import.meta.url));
+const secret = 'a'.repeat(64);
+
+function fixture(t, env = {}) {
+	const { root, bin, calls, env: binEnv } = fakeBinaries('opencode-client-');
+	t.after(() => rmSync(root, { recursive: true, force: true }));
+	bin(
+		'gh',
+		`
+log({ command: 'gh', args });
+if (args[0] === 'codespace' && args[1] === 'list') {
+  console.log(JSON.stringify([
+    { name: 'dev-box', state: 'Available' },
+  ]));
+} else if (args.includes('-N')) {
+  if (process.env.TEST_TUNNEL_FAIL) process.exit(1);
+  const mapping = args[args.indexOf('-L') + 1];
+  const port = +mapping.split(':')[1];
+  const ssh = require('node:child_process').spawn(process.execPath, ['-e', 'setInterval(() => {}, 1000)'], { stdio: 'ignore' });
+  log({ event: 'ssh-child', pid: ssh.pid });
+  const server = require('node:http').createServer((req, res) => {
+    const expected = 'Basic ' + Buffer.from('opencode:' + '${secret}').toString('base64');
+    if (process.env.TEST_UNAUTHORIZED || req.headers.authorization !== expected) { res.writeHead(401).end(); return; }
+    res.setHeader('content-type', 'application/json');
+    res.end(JSON.stringify({ healthy: true, version: process.env.TEST_SERVER_VERSION || '1.2.3' }));
+  });
+  server.listen(port, '127.0.0.1');
+  if (process.env.TEST_TUNNEL_DROP) setTimeout(() => process.exit(1), 500);
+  process.on('SIGTERM', () => { log({ event: 'tunnel-stopped' }); server.closeAllConnections(); server.close(() => process.exit(0)); });
+} else if (args.at(-1).includes('node --input-type=module')) {
+  let source = '';
+  process.stdin.on('data', chunk => source += chunk);
+  process.stdin.on('end', () => {
+    log({ event: 'bootstrap', hasSource: source.includes('prepareOpenCode') });
+    if (process.env.TEST_BOOTSTRAP_FAIL) process.exit(1);
+    const name = args.at(-1).split(' ').at(-2);
+    console.log(JSON.stringify({ port: 4242, password: '${secret}', sessionID: 'ses_saved',
+      directory: name === 'agent' ? '/workspaces/n8n' : '/workspaces/wt-' + name }));
+  });
+}
+`,
+	);
+	bin(
+		'opencode',
+		`
+if (args[0] === '--version') {
+  if (process.env.TEST_NO_CLIENT) process.exit(1);
+  console.log(process.env.TEST_CLIENT_VERSION || '1.2.3');
+} else {
+  log({ command: 'opencode', args, password: process.env.OPENCODE_SERVER_PASSWORD });
+  if (process.env.TEST_CLIENT_WAIT) setInterval(() => {}, 1000);
+}
+`,
+	);
+	for (const opener of ['open', 'xdg-open']) bin(opener, `log({ command: 'browser', args });`);
+	return {
+		calls,
+		start(args) {
+			const child = spawn(process.execPath, [script, '--opencode', ...args], {
+				env: { ...process.env, ...binEnv, ...env },
+				stdio: ['ignore', 'pipe', 'pipe'],
+			});
+			let output = '';
+			child.stdout.on('data', (chunk) => {
+				output += chunk;
+			});
+			child.stderr.on('data', (chunk) => {
+				output += chunk;
+			});
+			const done = new Promise((resolve) => child.on('exit', (code) => resolve({ code, output })));
+			t.after(() => child.kill('SIGKILL'));
+			return { child, done };
+		},
+	};
+}
+
+async function waitFor(check) {
+	for (let attempt = 0; attempt < 100; attempt++) {
+		const result = check();
+		if (result) return result;
+		await delay(50);
+	}
+	throw new Error('Fixture did not become ready.');
+}
+
+test('parses options before or after the workspace and rejects unsupported flags', () => {
+	assert.equal(parseOpenCodeArgs(['--web']).port, 4096);
+	assert.equal(parseOpenCodeArgs([]).port, 0);
+	assert.equal(parseOpenCodeArgs(['--port', '4100', '--web']).port, 4100);
+	assert.deepEqual(parseOpenCodeArgs(['--web', 'fix-flaky', '--new', '--port', '4100']), {
+		name: 'fix-flaky',
+		web: true,
+		fresh: true,
+		port: 4100,
+	});
+	for (const args of [
+		['--port'],
+		['--port', '0'],
+		['--port', '65536'],
+		['--model', 'test'],
+		['a/b'],
+		['one', 'two'],
+	]) {
+		assert.throws(() => parseOpenCodeArgs(args));
+	}
+});
+
+test(
+	'attaches the local TUI to the selected workspace and closes the whole tunnel',
+	{ timeout: 15000 },
+	async (t) => {
+		const f = fixture(t);
+		const result = await f.start(['fix-flaky']).done;
+		assert.equal(result.code, 0, result.output);
+		const calls = f.calls();
+		assert.ok(calls.find((call) => call.event === 'bootstrap').hasSource);
+		assert.ok(
+			calls
+				.filter((call) => call.command === 'gh' && call.args[1] === 'ssh')
+				.every((call) => call.args[3] === 'dev-box'),
+		);
+		const tunnel = calls.find((call) => call.command === 'gh' && call.args.includes('-N'));
+		assert.match(tunnel.args.at(-1), /^127\.0\.0\.1:\d+:127\.0\.0\.1:4242$/);
+		const client = calls.find((call) => call.command === 'opencode');
+		assert.deepEqual(client.args.slice(2), [
+			'--dir',
+			'/workspaces/wt-fix-flaky',
+			'--session',
+			'ses_saved',
+		]);
+		assert.equal(client.password, secret);
+		assert.ok(!result.output.includes(secret));
+		assert.ok(calls.some((call) => call.event === 'tunnel-stopped'));
+		const pid = calls.find((call) => call.event === 'ssh-child').pid;
+		await waitFor(() => {
+			try {
+				process.kill(pid, 0);
+				return false;
+			} catch {
+				return true;
+			}
+		});
+	},
+);
+
+for (const signal of ['SIGINT', 'SIGHUP']) {
+	test(
+		`opens the saved web conversation and cleans up on ${signal}`,
+		{ timeout: 15000 },
+		async (t) => {
+			const f = fixture(t, { TEST_NO_CLIENT: '1' });
+			const run = f.start(['--web', 'fix-flaky']);
+			const browser = await waitFor(() => f.calls().find((call) => call.command === 'browser'));
+			const url = new URL(browser.args[0]);
+			assert.equal(
+				url.pathname,
+				`/${Buffer.from('/workspaces/wt-fix-flaky').toString('base64url')}/session/ses_saved`,
+			);
+			assert.equal(url.password, '');
+			const response = await fetch(`${url.origin}/global/health`);
+			assert.equal(response.status, 200);
+			await response.text();
+			run.child.kill(signal);
+			const result = await run.done;
+			assert.equal(result.code, 0, result.output);
+			assert.ok(f.calls().some((call) => call.event === 'tunnel-stopped'));
+			await assert.rejects(fetch(url.origin));
+		},
+	);
+}
+
+for (const [label, env, message] of [
+	['a version mismatch', { TEST_SERVER_VERSION: '1.14.22' }, /versions differ/],
+	['an authentication failure', { TEST_UNAUTHORIZED: '1' }, /health check failed \(401\)/],
+	['a tunnel startup failure', { TEST_TUNNEL_FAIL: '1' }, /SSH tunnel closed/],
+	['a remote preparation failure', { TEST_BOOTSTRAP_FAIL: '1' }, /Could not prepare/],
+	['a missing local client', { TEST_NO_CLIENT: '1' }, /Install OpenCode locally/],
+	['a connection loss', { TEST_CLIENT_WAIT: '1', TEST_TUNNEL_DROP: '1' }, /SSH connection closed/],
+]) {
+	test(`reports ${label} without printing credentials`, { timeout: 15000 }, async (t) => {
+		const f = fixture(t, env);
+		const result = await f.start([]).done;
+		assert.equal(result.code, 1, result.output);
+		assert.match(result.output, message);
+		assert.ok(!result.output.includes(secret));
+		if (label !== 'a connection loss')
+			assert.ok(!f.calls().some((call) => call.command === 'opencode'));
+	});
+}
diff --git a/.devcontainer/codespaces/opencode-proxy.test.mjs b/.devcontainer/codespaces/opencode-proxy.test.mjs
new file mode 100644
index 00000000000..2b357336466
--- /dev/null
+++ b/.devcontainer/codespaces/opencode-proxy.test.mjs
@@ -0,0 +1,147 @@
+import assert from 'node:assert/strict';
+import { createServer, request } from 'node:http';
+import { connect } from 'node:net';
+import { test } from 'node:test';
+
+import { openCodeProxy } from '../../scripts/cloud-session-opencode-proxy.mjs';
+
+test('proxies uploads and event streams with authentication and rejects other origins', async (t) => {
+	const requests = [];
+	const backend = createServer(async (req, res) => {
+		requests.push(req.headers);
+		res.writeHead(200, { 'content-type': 'text/event-stream' });
+		for await (const chunk of req) res.write(chunk);
+		res.end();
+	});
+	await new Promise((resolve) => backend.listen(0, '127.0.0.1', resolve));
+	t.after(() => {
+		backend.closeAllConnections();
+		backend.close();
+	});
+	const proxy = await openCodeProxy({ password: 'test-secret' });
+	proxy.targetPort = backend.address().port;
+	t.after(proxy.close);
+	const response = await fetch(`${proxy.origin}/session`, {
+		method: 'POST',
+		body: 'data: attached image\n\n',
+		headers: { origin: proxy.origin },
+	});
+	assert.equal(response.status, 200);
+	assert.equal(await response.text(), 'data: attached image\n\n');
+	assert.equal(
+		requests[0].authorization,
+		`Basic ${Buffer.from('opencode:test-secret').toString('base64')}`,
+	);
+	assert.ok(!proxy.origin.includes('test-secret'));
+	for (const headers of [
+		{ origin: 'https://example.com' },
+		{ host: 'example.com' },
+		{ 'sec-fetch-site': 'cross-site' },
+	]) {
+		const status = await new Promise((resolve, reject) => {
+			const req = request(proxy.origin, { headers }, (response) => {
+				response.resume();
+				resolve(response.statusCode);
+			});
+			req.on('error', reject);
+			req.end();
+		});
+		assert.equal(status, 403);
+	}
+	assert.equal(requests.length, 1);
+});
+
+test('forwards WebSocket upgrades and closes their sockets', async (t) => {
+	const peers = new Set();
+	const backend = createServer();
+	backend.on('upgrade', (req, socket) => {
+		assert.equal(
+			req.headers.authorization,
+			`Basic ${Buffer.from('opencode:test-secret').toString('base64')}`,
+		);
+		peers.add(socket);
+		socket.on('close', () => peers.delete(socket));
+		socket.write(
+			'HTTP/1.1 101 Switching Protocols\r\nConnection: Upgrade\r\nUpgrade: websocket\r\n\r\n',
+		);
+		socket.pipe(socket);
+	});
+	await new Promise((resolve) => backend.listen(0, '127.0.0.1', resolve));
+	t.after(() => {
+		for (const peer of peers) peer.destroy();
+		backend.close();
+	});
+	const proxy = await openCodeProxy({ password: 'test-secret' });
+	proxy.targetPort = backend.address().port;
+	t.after(proxy.close);
+	const socket = await new Promise((resolve, reject) => {
+		const req = request(`${proxy.origin}/pty/test/connect`, {
+			headers: { origin: proxy.origin, connection: 'Upgrade', upgrade: 'websocket' },
+		});
+		req.on('upgrade', (_response, peer) => resolve(peer));
+		req.on('error', reject);
+		req.end();
+	});
+	t.after(() => socket.destroy());
+	const echoed = new Promise((resolve) => socket.once('data', (data) => resolve(data.toString())));
+	socket.write('terminal input');
+	assert.equal(await echoed, 'terminal input');
+	const closed = new Promise((resolve) => socket.once('close', resolve));
+	proxy.close();
+	await closed;
+});
+
+test(
+	'closes the browser response when the upstream stream disconnects',
+	{ timeout: 5000 },
+	async (t) => {
+		const backend = createServer((_req, res) => {
+			res.writeHead(200, { 'content-type': 'text/event-stream' });
+			res.write('data: partial\n\n');
+			setTimeout(() => res.destroy(), 50);
+		});
+		await new Promise((resolve) => backend.listen(0, '127.0.0.1', resolve));
+		t.after(() => {
+			backend.closeAllConnections();
+			backend.close();
+		});
+		const proxy = await openCodeProxy({ password: 'test' });
+		proxy.targetPort = backend.address().port;
+		t.after(proxy.close);
+		const signal = AbortSignal.timeout(3000);
+		const response = await fetch(proxy.origin, { signal });
+		await assert.rejects(response.text());
+		assert.equal(
+			signal.aborted,
+			false,
+			'The proxy must close the response before the client times out.',
+		);
+	},
+);
+
+test('rejects an occupied browser port and reports a missing or closed upstream', async (t) => {
+	const proxy = await openCodeProxy({ password: 'test' });
+	t.after(proxy.close);
+	await assert.rejects(openCodeProxy({ password: 'test', port: +new URL(proxy.origin).port }), {
+		code: 'EADDRINUSE',
+	});
+	const waiting = await fetch(proxy.origin);
+	assert.equal(waiting.status, 503);
+	await waiting.text();
+	proxy.targetPort = 1;
+	const response = await fetch(proxy.origin);
+	assert.equal(response.status, 502);
+	await response.text();
+	const rejection = await new Promise((resolve) => {
+		const socket = connect(+new URL(proxy.origin).port, '127.0.0.1', () => {
+			socket.write(
+				'GET /pty/test/connect HTTP/1.1\r\nHost: example.com\r\nConnection: Upgrade\r\nUpgrade: websocket\r\n\r\n',
+			);
+		});
+		socket.once('data', (data) => {
+			socket.destroy();
+			resolve(data.toString());
+		});
+	});
+	assert.match(rejection, /403 Forbidden/);
+});
diff --git a/.devcontainer/codespaces/opencode-server.mjs b/.devcontainer/codespaces/opencode-server.mjs
new file mode 100644
index 00000000000..41027490368
--- /dev/null
+++ b/.devcontainer/codespaces/opencode-server.mjs
@@ -0,0 +1,219 @@
+#!/usr/bin/env node
+// The laptop sends this file over SSH as one standalone module. Do not import sibling files.
+// It also works in an older Codespace checkout.
+import { execFileSync, spawnSync } from 'node:child_process';
+import { randomBytes } from 'node:crypto';
+import { existsSync, mkdirSync, readFileSync, renameSync, rmSync, writeFileSync } from 'node:fs';
+import { createServer } from 'node:net';
+import { join } from 'node:path';
+import { setTimeout as delay } from 'node:timers/promises';
+
+const quote = (value) => `'${value.replaceAll("'", "'\\''")}'`;
+
+function readJson(file) {
+	try {
+		return JSON.parse(readFileSync(file, 'utf8'));
+	} catch (error) {
+		if (error.code === 'ENOENT') return undefined;
+		throw new Error(`Cannot read ${file}. Restore or remove this state file, then retry.`);
+	}
+}
+
+function saveJson(file, value) {
+	writeFileSync(`${file}.tmp`, JSON.stringify(value), { mode: 0o600 });
+	renameSync(`${file}.tmp`, file);
+}
+
+function run(command, args, options = {}) {
+	const result = spawnSync(command, args, {
+		stdio: ['ignore', 'inherit', 'inherit'],
+		...options,
+	});
+	if (result.error || result.status !== 0) {
+		throw new Error(`${command} failed. Check the output above, then retry.`);
+	}
+}
+
+async function freePort() {
+	const server = createServer();
+	await new Promise((resolve, reject) => {
+		server.once('error', reject);
+		server.listen(0, '127.0.0.1', resolve);
+	});
+	const { port } = server.address();
+	await new Promise((resolve) => server.close(resolve));
+	return port;
+}
+
+async function request(server, path, directory, options = {}, timeout = 60_000) {
+	return await fetch(`http://127.0.0.1:${server.port}${path}`, {
+		...options,
+		headers: {
+			authorization: `Basic ${Buffer.from(`opencode:${server.password}`).toString('base64')}`,
+			'x-opencode-directory': encodeURIComponent(directory),
+			'content-type': 'application/json',
+		},
+		signal: AbortSignal.timeout(timeout),
+	});
+}
+
+async function health(server, directory) {
+	try {
+		const response = await request(server, '/global/health', directory, {}, 3000);
+		if (!response.ok) return undefined;
+		const result = await response.json();
+		return result.healthy === true && typeof result.version === 'string' ? result : undefined;
+	} catch {
+		return undefined;
+	}
+}
+
+const serverFile = (stateDir) => join(stateDir, 'server.json');
+
+async function runningServer({ stateDir, mainDirectory }) {
+	const previous = readJson(serverFile(stateDir));
+	return previous && (await health(previous, mainDirectory)) ? previous : undefined;
+}
+
+async function startServer({ stateDir, mainDirectory, workspaces }) {
+	const tmuxSession = 'n8n-opencode-server';
+	if (spawnSync('tmux', ['has-session', '-t', `=${tmuxSession}`]).status === 0) {
+		throw new Error(
+			`OpenCode is still starting or is unhealthy. Check ${stateDir}/server.log, then retry. The running server was not stopped.`,
+		);
+	}
+
+	const server = { port: await freePort(), password: randomBytes(32).toString('hex') };
+	const launcher = join(stateDir, 'serve.sh');
+	// Read secrets when the server starts. Do not store provider keys in the launcher.
+	writeFileSync(
+		launcher,
+		[
+			'#!/bin/bash',
+			'. /usr/local/lib/codespaces-env.sh 2>/dev/null || true',
+			'unset AGENT_WORKER_TOKEN N8N_DEQUEUE_URL SLACK_BOT_TOKEN',
+			`export TURBO_CACHE_DIR=${quote(join(workspaces, '.turbo-cache'))}`,
+			`[ -d "$TURBO_CACHE_DIR" ] || cp -r ${quote(join(mainDirectory, '.turbo/cache'))} "$TURBO_CACHE_DIR" 2>/dev/null || mkdir -p "$TURBO_CACHE_DIR"`,
+			`export OPENCODE_SERVER_USERNAME=opencode OPENCODE_SERVER_PASSWORD=${quote(server.password)}`,
+			`export OPENCODE_CONFIG_CONTENT=${quote(
+				JSON.stringify({
+					enabled_providers: ['openrouter'],
+					provider: { openrouter: { options: { apiKey: '{env:OPENROUTER_API_KEY}' } } },
+				}),
+			)}`,
+			// Interactive sessions use the harness sandbox runtime without a profile.
+			'export N8N_AGENT_RUNTIME=sandbox; unset N8N_AGENT_PROFILE',
+			`cd ${quote(mainDirectory)} || exit 1`,
+			`exec opencode serve --hostname 127.0.0.1 --port ${server.port} >> ${quote(join(stateDir, 'server.log'))} 2>&1`,
+			'',
+		].join('\n'),
+		{ mode: 0o600 },
+	);
+	saveJson(serverFile(stateDir), server);
+	run('tmux', ['new-session', '-d', '-s', tmuxSession, `bash ${quote(launcher)}`]);
+	console.error('Starting the OpenCode server…');
+	for (let attempt = 0; attempt < 60; attempt++) {
+		if (await health(server, mainDirectory)) return server;
+		await delay(500);
+	}
+	throw new Error(`OpenCode did not become ready. Check ${stateDir}/server.log.`);
+}
+
+function prepareWorkspace({ name, directory, mainDirectory, stateDir }) {
+	if (!existsSync(directory)) {
+		console.error(`Creating worktree ${directory}…`);
+		const branch = `session/${name}`;
+		const exists =
+			spawnSync('git', [
+				'-C',
+				mainDirectory,
+				'show-ref',
+				'--verify',
+				'--quiet',
+				`refs/heads/${branch}`,
+			]).status === 0;
+		run(
+			'git',
+			[
+				'-C',
+				mainDirectory,
+				'worktree',
+				'add',
+				...(exists ? [] : ['-b', branch]),
+				directory,
+				...(exists ? [branch] : []),
+			],
+			{ stdio: ['ignore', 2, 2] },
+		);
+	}
+	// A failed install must be retried even if it left a node_modules directory.
+	const installed = join(stateDir, `${name}.installed`);
+	const installing = join(stateDir, `${name}.installing`);
+	if (
+		!existsSync(join(directory, 'node_modules')) ||
+		existsSync(installing) ||
+		(name !== 'agent' && !existsSync(installed))
+	) {
+		console.error(`Installing dependencies in ${directory}…`);
+		writeFileSync(installing, '', { mode: 0o600 });
+		run('pnpm', ['install'], { cwd: directory, stdio: ['ignore', 2, 2] });
+		writeFileSync(installed, '', { mode: 0o600 });
+		rmSync(installing);
+	}
+}
+
+async function ensureSession({ name, fresh, directory, stateDir, server }) {
+	const sessionFile = join(stateDir, `${name}.session.json`);
+	const saved = fresh ? undefined : readJson(sessionFile);
+	let session;
+	if (saved) {
+		const response = await request(server, `/session/${encodeURIComponent(saved.id)}`, directory);
+		if (response.ok) session = await response.json();
+		else if (response.status !== 404)
+			throw new Error(`Cannot resume OpenCode session (${response.status}).`);
+		if (session && session.directory !== directory)
+			throw new Error('The saved OpenCode session belongs to another directory. Use --new.');
+	}
+	if (!session) {
+		const response = await request(server, '/session', directory, {
+			method: 'POST',
+			body: JSON.stringify({ title: `n8n: ${name}` }),
+		});
+		if (!response.ok) throw new Error(`Cannot create OpenCode session (${response.status}).`);
+		session = await response.json();
+		if (typeof session.id !== 'string' || session.directory !== directory)
+			throw new Error('OpenCode returned an invalid session.');
+		saveJson(sessionFile, { id: session.id });
+	}
+	return session.id;
+}
+
+export async function prepareOpenCode({
+	name = 'agent',
+	fresh = false,
+	workspaces = '/workspaces',
+} = {}) {
+	const stateDir = join(workspaces, '.n8n-opencode');
+	const mainDirectory = join(workspaces, 'n8n');
+	if (!/^\w[\w-]*$/.test(name)) throw new Error('Invalid OpenCode workspace name.');
+	mkdirSync(stateDir, { recursive: true, mode: 0o700 });
+	const directory = name === 'agent' ? mainDirectory : join(workspaces, `wt-${name}`);
+	let server = await runningServer({ stateDir, mainDirectory });
+	// On a cold start, fail before the worktree install when OpenCode is missing on the Codespace.
+	if (!server) execFileSync('opencode', ['--version'], { stdio: ['ignore', 'pipe', 'inherit'] });
+	prepareWorkspace({ name, directory, mainDirectory, stateDir });
+	server ??= await startServer({ stateDir, mainDirectory, workspaces });
+	const sessionID = await ensureSession({ name, fresh, directory, stateDir, server });
+	// Only the parent process reads stdout. Never send this record to terminal output.
+	return { ...server, directory, sessionID };
+}
+
+if (process.argv[1] === '-') {
+	try {
+		const [name, fresh] = process.argv.slice(2);
+		console.log(JSON.stringify(await prepareOpenCode({ name, fresh: fresh === 'true' })));
+	} catch (error) {
+		console.error(error.message);
+		process.exitCode = 1;
+	}
+}
diff --git a/.devcontainer/codespaces/opencode-server.test.mjs b/.devcontainer/codespaces/opencode-server.test.mjs
new file mode 100644
index 00000000000..bdc1065d58e
--- /dev/null
+++ b/.devcontainer/codespaces/opencode-server.test.mjs
@@ -0,0 +1,201 @@
+import assert from 'node:assert/strict';
+import { mkdirSync, readFileSync, rmSync, statSync, writeFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { test } from 'node:test';
+import { setTimeout as delay } from 'node:timers/promises';
+
+import { fakeBinaries } from './fake-bin.mjs';
+import { prepareOpenCode } from './opencode-server.mjs';
+
+function fixture(t) {
+	const fake = fakeBinaries('opencode-server-');
+	const dir = fake.root;
+	mkdirSync(join(dir, 'n8n', 'node_modules'), { recursive: true });
+	const savedEnv = { ...process.env };
+	// prepareOpenCode spawns the shims in this process. Log every call before the shim body runs.
+	Object.assign(process.env, fake.env, {
+		AGENT_WORKER_TOKEN: 'test-worker',
+		N8N_DEQUEUE_URL: 'test-queue',
+		SLACK_BOT_TOKEN: 'test-slack',
+	});
+	const bin = (name, body) =>
+		fake.bin(name, `log({ command: ${JSON.stringify(name)}, args });\n${body}`);
+	bin(
+		'git',
+		`
+if (args.includes('show-ref')) process.exit(fs.existsSync(file('branch-exists')) ? 0 : 1);
+fs.mkdirSync(args.includes('-b') ? args.at(-1) : args.at(-2), { recursive: true });
+`,
+	);
+	bin(
+		'pnpm',
+		`
+fs.mkdirSync(path.join(process.cwd(), 'node_modules'), {recursive:true});
+if (process.env.TEST_INSTALL_FAIL) process.exit(1);
+`,
+	);
+	bin(
+		'tmux',
+		`
+if (args[0] === 'has-session') {
+  try { process.kill(+fs.readFileSync(file('pid'), 'utf8'), 0); } catch { process.exit(1); }
+} else {
+  const child = require('node:child_process').spawn('bash', ['-c', args.at(-1)], { detached:true, stdio:'ignore' });
+  fs.writeFileSync(file('pid'), String(child.pid)); child.unref();
+}
+`,
+	);
+	bin(
+		'opencode',
+		`
+if (args[0] === '--version') { console.log('1.2.3'); process.exit(0); }
+fs.writeFileSync(file('server-env.json'), JSON.stringify({
+  worker: !!process.env.AGENT_WORKER_TOKEN, queue: !!process.env.N8N_DEQUEUE_URL, slack: !!process.env.SLACK_BOT_TOKEN,
+  cache: process.env.TURBO_CACHE_DIR, config: JSON.parse(process.env.OPENCODE_CONFIG_CONTENT),
+  runtime: process.env.N8N_AGENT_RUNTIME, profile: process.env.N8N_AGENT_PROFILE ?? null,
+}));
+let sessions = fs.existsSync(file('sessions.json')) ? JSON.parse(fs.readFileSync(file('sessions.json'), 'utf8')) : {};
+const server = require('node:http').createServer(async (req, res) => {
+  res.setHeader('content-type', 'application/json');
+  const expected = 'Basic ' + Buffer.from('opencode:' + process.env.OPENCODE_SERVER_PASSWORD).toString('base64');
+  if (req.headers.authorization !== expected) { res.writeHead(401).end('{}'); return; }
+  if (req.url === '/global/health') { res.end(JSON.stringify({ healthy:true, version:'1.2.3' })); return; }
+  if (req.method === 'POST' && req.url === '/session') {
+    for await (const chunk of req) {}
+    const id = 'ses_' + (Object.keys(sessions).length + 1);
+    sessions[id] = { id, directory:decodeURIComponent(req.headers['x-opencode-directory']) };
+    fs.writeFileSync(file('sessions.json'), JSON.stringify(sessions));
+    res.end(JSON.stringify(sessions[id])); return;
+  }
+  if (fs.existsSync(file('reject-session'))) { res.writeHead(503).end('{}'); return; }
+  const session = sessions[req.url.split('/').at(-1)];
+  if (!session) { res.writeHead(404).end('{}'); return; }
+  res.end(JSON.stringify(session));
+});
+server.listen(+args[args.indexOf('--port') + 1], '127.0.0.1');
+`,
+	);
+	const stop = async () => {
+		try {
+			const pid = +readFileSync(join(dir, 'pid'), 'utf8');
+			process.kill(-pid, 'SIGTERM');
+			for (let count = 0; count < 100; count++) {
+				try {
+					process.kill(pid, 0);
+				} catch {
+					return;
+				}
+				await delay(20);
+			}
+			throw new Error('Fixture server did not stop.');
+		} catch (error) {
+			if (!['ENOENT', 'ESRCH'].includes(error.code)) throw error;
+		}
+	};
+	t.after(async () => {
+		await stop();
+		for (const key of Object.keys(process.env)) if (!(key in savedEnv)) delete process.env[key];
+		Object.assign(process.env, savedEnv);
+		rmSync(dir, { recursive: true, force: true });
+	});
+	return {
+		dir,
+		stop,
+		prepare: (options = {}) => prepareOpenCode({ workspaces: dir, ...options }),
+		commands: fake.calls,
+	};
+}
+
+test(
+	'reuses the server and saved conversation, creates separate workspaces, and resumes after restart',
+	{ timeout: 15000 },
+	async (t) => {
+		const f = fixture(t);
+		const first = await f.prepare({ name: 'fix-flaky' });
+		assert.equal(first.directory, join(f.dir, 'wt-fix-flaky'));
+		assert.deepEqual(await f.prepare({ name: 'fix-flaky' }), first);
+		const second = await f.prepare({ name: 'another-task' });
+		assert.equal(second.port, first.port);
+		assert.notEqual(second.sessionID, first.sessionID);
+		const fresh = await f.prepare({ name: 'fix-flaky', fresh: true });
+		assert.notEqual(fresh.sessionID, first.sessionID);
+		assert.equal((await f.prepare({ name: 'fix-flaky' })).sessionID, fresh.sessionID);
+		const env = JSON.parse(readFileSync(join(f.dir, 'server-env.json'), 'utf8'));
+		assert.deepEqual([env.worker, env.queue, env.slack], [false, false, false]);
+		assert.equal(env.cache, join(f.dir, '.turbo-cache'));
+		assert.equal(env.config.provider.openrouter.options.apiKey, '{env:OPENROUTER_API_KEY}');
+		assert.deepEqual(env.config.enabled_providers, ['openrouter']);
+		assert.deepEqual([env.runtime, env.profile], ['sandbox', null]);
+		assert.equal(statSync(join(f.dir, '.n8n-opencode')).mode & 0o777, 0o700);
+		for (const file of ['serve.sh', 'server.json', 'fix-flaky.session.json']) {
+			assert.equal(statSync(join(f.dir, '.n8n-opencode', file)).mode & 0o777, 0o600);
+		}
+		assert.ok(!f.commands().some((entry) => JSON.stringify(entry.args).includes(first.password)));
+		assert.equal(f.commands().filter((entry) => entry.command === 'pnpm').length, 2);
+		await f.stop();
+		const restarted = await f.prepare({ name: 'fix-flaky' });
+		assert.equal(restarted.sessionID, fresh.sessionID);
+		assert.notEqual(restarted.password, first.password);
+		rmSync(first.directory, { recursive: true });
+		writeFileSync(join(f.dir, 'branch-exists'), '');
+		assert.equal((await f.prepare({ name: 'fix-flaky' })).sessionID, fresh.sessionID);
+		const worktree = f
+			.commands()
+			.filter((entry) => entry.command === 'git' && entry.args.includes('add'))
+			.at(-1);
+		assert.deepEqual(worktree.args, [
+			'-C',
+			join(f.dir, 'n8n'),
+			'worktree',
+			'add',
+			first.directory,
+			'session/fix-flaky',
+		]);
+	},
+);
+
+test(
+	'retries a failed worktree install before starting the server',
+	{ timeout: 10000 },
+	async (t) => {
+		const f = fixture(t);
+		process.env.TEST_INSTALL_FAIL = '1';
+		await assert.rejects(f.prepare({ name: 'retry' }), /pnpm failed/);
+		assert.ok(!f.commands().some((entry) => entry.command === 'tmux'));
+		delete process.env.TEST_INSTALL_FAIL;
+		assert.equal((await f.prepare({ name: 'retry' })).directory, join(f.dir, 'wt-retry'));
+		assert.equal(f.commands().filter((entry) => entry.command === 'pnpm').length, 2);
+	},
+);
+
+test(
+	'retries a failed main checkout install even when node_modules exists',
+	{ timeout: 10000 },
+	async (t) => {
+		const f = fixture(t);
+		rmSync(join(f.dir, 'n8n', 'node_modules'), { recursive: true });
+		process.env.TEST_INSTALL_FAIL = '1';
+		await assert.rejects(f.prepare(), /pnpm failed/);
+		delete process.env.TEST_INSTALL_FAIL;
+		assert.equal((await f.prepare()).directory, join(f.dir, 'n8n'));
+		assert.equal(f.commands().filter((entry) => entry.command === 'pnpm').length, 2);
+	},
+);
+
+test(
+	'preserves saved sessions on API errors and replaces only missing sessions',
+	{ timeout: 10000 },
+	async (t) => {
+		const f = fixture(t);
+		const first = await f.prepare();
+		writeFileSync(join(f.dir, 'reject-session'), '');
+		await assert.rejects(f.prepare(), /Cannot resume OpenCode session \(503\)/);
+		const saved = join(f.dir, '.n8n-opencode', 'agent.session.json');
+		assert.equal(JSON.parse(readFileSync(saved, 'utf8')).id, first.sessionID);
+		rmSync(join(f.dir, 'reject-session'));
+		writeFileSync(saved, JSON.stringify({ id: 'ses_missing' }));
+		assert.notEqual((await f.prepare()).sessionID, first.sessionID);
+		writeFileSync(saved, '{');
+		await assert.rejects(f.prepare(), /Cannot read/);
+	},
+);
diff --git a/.github/workflows/ci-pull-requests.yml b/.github/workflows/ci-pull-requests.yml
index fa486b87908..308103ca6bf 100644
--- a/.github/workflows/ci-pull-requests.yml
+++ b/.github/workflows/ci-pull-requests.yml
@@ -129,9 +129,10 @@ jobs:
             workflows: .github/**
             workflow-scripts:
               .github/scripts/**
-              .devcontainer/codespaces/agent-worker*.mjs
+              .devcontainer/codespaces/*.mjs
               OWNERS
               scripts/*.test.mjs
+              scripts/cloud-session*.mjs
               scripts/codespace-env.mjs
               scripts/codespace-preview/**
               scripts/licenses/**
diff --git a/scripts/cloud-session-opencode-proxy.mjs b/scripts/cloud-session-opencode-proxy.mjs
new file mode 100644
index 00000000000..be67962ca73
--- /dev/null
+++ b/scripts/cloud-session-opencode-proxy.mjs
@@ -0,0 +1,109 @@
+// Keep browser authentication in this process. The browser URL contains no password.
+import { createServer, request } from 'node:http';
+
+export const basicAuth = (password) =>
+	`Basic ${Buffer.from(`opencode:${password}`).toString('base64')}`;
+
+// Set `targetPort` on the result once the tunnel port is known. Requests before that get 503.
+export async function openCodeProxy({ password, port = 0 }) {
+	const sockets = new Set();
+	const authorization = basicAuth(password);
+	let host;
+	let origin;
+	const proxy = {
+		targetPort: undefined,
+		close: () => {
+			for (const socket of sockets) socket.destroy();
+			server.close();
+		},
+	};
+	const allowed = (req) =>
+		req.headers.host === host &&
+		(!req.headers.origin || req.headers.origin === origin) &&
+		(!req.headers['sec-fetch-site'] ||
+			['same-origin', 'none'].includes(req.headers['sec-fetch-site'])) &&
+		req.url.startsWith('/') &&
+		!req.url.startsWith('//');
+	const upstream = (req) =>
+		request({
+			hostname: '127.0.0.1',
+			port: proxy.targetPort,
+			path: req.url,
+			method: req.method,
+			headers: { ...req.headers, authorization },
+		});
+	const waiting = 'OpenCode is still connecting. Retry in a moment.';
+	const server = createServer((req, res) => {
+		if (!allowed(req)) {
+			res.writeHead(403).end('Use the local OpenCode URL printed by pnpm session:opencode.');
+			return;
+		}
+		if (!proxy.targetPort) {
+			res.writeHead(503).end(waiting);
+			return;
+		}
+		const remote = upstream(req);
+		remote.on('response', (response) => {
+			res.writeHead(response.statusCode, response.headers);
+			response.on('error', () => res.destroy());
+			response.pipe(res);
+		});
+		remote.on('error', () => {
+			if (!res.headersSent) res.writeHead(502);
+			res.end('The OpenCode connection is unavailable. Run the session command again.');
+		});
+		res.on('close', () => remote.destroy());
+		req.pipe(remote);
+	});
+	// The web terminal uses WebSockets. Stream uploads and events without buffering.
+	server.on('upgrade', (req, socket, head) => {
+		if (!allowed(req)) {
+			socket.end('HTTP/1.1 403 Forbidden\r\nConnection: close\r\n\r\n');
+			return;
+		}
+		if (!proxy.targetPort) {
+			socket.end(`HTTP/1.1 503 Service Unavailable\r\nConnection: close\r\n\r\n${waiting}`);
+			return;
+		}
+		const remote = upstream(req);
+		remote.on('upgrade', (response, peer, remoteHead) => {
+			sockets.add(peer);
+			peer.on('close', () => {
+				sockets.delete(peer);
+				socket.destroy();
+			});
+			peer.on('error', () => socket.destroy());
+			socket.on('close', () => peer.destroy());
+			socket.on('error', () => peer.destroy());
+			const headers = response.rawHeaders;
+			socket.write(`HTTP/1.1 ${response.statusCode} ${response.statusMessage}\r\n`);
+			for (let index = 0; index < headers.length; index += 2)
+				socket.write(`${headers[index]}: ${headers[index + 1]}\r\n`);
+			socket.write('\r\n');
+			if (remoteHead.length) socket.write(remoteHead);
+			if (head.length) peer.write(head);
+			socket.pipe(peer).pipe(socket);
+		});
+		remote.on('response', (response) => {
+			response.resume();
+			socket.end(
+				`HTTP/1.1 ${response.statusCode} ${response.statusMessage}\r\nConnection: close\r\n\r\n`,
+			);
+		});
+		remote.on('error', () => socket.destroy());
+		socket.on('close', () => remote.destroy());
+		remote.end();
+	});
+	server.on('connection', (socket) => {
+		sockets.add(socket);
+		socket.on('close', () => sockets.delete(socket));
+	});
+	await new Promise((resolve, reject) => {
+		server.once('error', reject);
+		server.listen(port, '127.0.0.1', resolve);
+	});
+	host = `127.0.0.1:${server.address().port}`;
+	origin = `http://${host}`;
+	proxy.origin = origin;
+	return proxy;
+}
diff --git a/scripts/cloud-session-opencode.mjs b/scripts/cloud-session-opencode.mjs
new file mode 100644
index 00000000000..35639a0cd52
--- /dev/null
+++ b/scripts/cloud-session-opencode.mjs
@@ -0,0 +1,272 @@
+import { spawn, spawnSync } from 'node:child_process';
+import { readFileSync } from 'node:fs';
+import { createServer } from 'node:net';
+import { setTimeout as delay } from 'node:timers/promises';
+import { parseArgs } from 'node:util';
+
+import { basicAuth, openCodeProxy } from './cloud-session-opencode-proxy.mjs';
+
+const SIGNALS = ['SIGINT', 'SIGTERM', 'SIGHUP'];
+
+export function parseOpenCodeArgs(args) {
+	let parsed;
+	try {
+		parsed = parseArgs({
+			args,
+			allowPositionals: true,
+			options: { web: { type: 'boolean' }, new: { type: 'boolean' }, port: { type: 'string' } },
+		});
+	} catch (error) {
+		throw new Error(`${error.message}. Use --help. Use --legacy for remote OpenCode CLI flags.`);
+	}
+	const { positionals, values } = parsed;
+	if (positionals.length > 1 || (positionals[0] && !/^\w[\w-]*$/.test(positionals[0])))
+		throw new Error('Use one workspace name with letters, digits, - or _.');
+	let port = values.web ? 4096 : 0;
+	if (values.port !== undefined) {
+		if (!/^\d+$/.test(values.port) || +values.port < 1 || +values.port > 65535)
+			throw new Error('--port must be 1–65535.');
+		port = +values.port;
+	}
+	return { name: positionals[0] ?? 'agent', web: !!values.web, fresh: !!values.new, port };
+}
+
+function localVersion() {
+	const result = spawnSync('opencode', ['--version'], { encoding: 'utf8' });
+	if (result.error || result.status !== 0)
+		throw new Error('Install OpenCode locally, or use --web to connect with a browser.');
+	const version = result.stdout.trim();
+	if (!/^\d+\.\d+\.\d+(?:[-+][\w.-]+)?$/.test(version))
+		throw new Error('Cannot read the local OpenCode version. Use --web or --legacy.');
+	return version;
+}
+
+async function freePort() {
+	const server = createServer();
+	await new Promise((resolve, reject) => {
+		server.once('error', reject);
+		server.listen(0, '127.0.0.1', resolve);
+	});
+	const { port } = server.address();
+	await new Promise((resolve) => server.close(resolve));
+	return port;
+}
+
+function startChild(command, args, options = {}) {
+	const child = spawn(command, args, options);
+	let finished = false;
+	const done = new Promise((resolve) => {
+		child.once('error', (error) => {
+			finished = true;
+			resolve({ code: 1, error });
+		});
+		// Wait for stdout to close before parsing the SSH response.
+		child.once('close', (code, signal) => {
+			finished = true;
+			resolve({ code: code ?? (signal ? 1 : 0) });
+		});
+	});
+	const kill = (signal) => {
+		if (!child.pid) return;
+		try {
+			if (options.detached) process.kill(-child.pid, signal);
+			else child.kill(signal);
+		} catch (error) {
+			if (error.code !== 'ESRCH') throw error;
+		}
+	};
+	return {
+		child,
+		done,
+		get finished() {
+			return finished;
+		},
+		async stop() {
+			if (finished) return;
+			// gh starts ssh as a child. Terminate the process group to close the tunnel too.
+			kill('SIGTERM');
+			await Promise.race([done, delay(2000, undefined, { ref: false })]);
+			if (!finished) kill('SIGKILL');
+		},
+	};
+}
+
+async function bootstrap(codespace, options, signal) {
+	signal.throwIfAborted();
+	console.log(`Preparing OpenCode workspace '${options.name}' on ${codespace}…`);
+	const command = `umask 077; mkdir -p /workspaces/.n8n-opencode && flock --close -w 600 /workspaces/.n8n-opencode/launch.lock node --input-type=module - ${options.name} ${options.fresh}`;
+	const remote = startChild('gh', ['codespace', 'ssh', '-c', codespace, '--', command], {
+		stdio: ['pipe', 'pipe', 'inherit'],
+		detached: true,
+	});
+	let stdout = '';
+	remote.child.stdout.setEncoding('utf8');
+	remote.child.stdout.on('data', (chunk) => {
+		stdout += chunk;
+	});
+	remote.child.stdin.on('error', () => {});
+	const abort = () => {
+		void remote.stop();
+	};
+	signal.addEventListener('abort', abort, { once: true });
+	try {
+		remote.child.stdin.end(
+			readFileSync(new URL('../.devcontainer/codespaces/opencode-server.mjs', import.meta.url)),
+		);
+		const result = await remote.done;
+		signal.throwIfAborted();
+		if (result.code !== 0)
+			throw new Error('Could not prepare OpenCode. Check the SSH output above, then retry.');
+		let state;
+		try {
+			state = JSON.parse(stdout.trim().split('\n').at(-1));
+		} catch {
+			throw new Error('Invalid OpenCode server response.');
+		}
+		// The server owns the workspace layout and the credential format. Check the shape only.
+		const text = (value) => typeof value === 'string' && value.length > 0;
+		if (
+			!state ||
+			!Number.isInteger(state.port) ||
+			!text(state.password) ||
+			!text(state.sessionID) ||
+			!text(state.directory)
+		) {
+			throw new Error('Invalid OpenCode server response.');
+		}
+		return state;
+	} finally {
+		signal.removeEventListener('abort', abort);
+		await remote.stop();
+	}
+}
+
+async function waitForTunnel(url, password, tunnel, signal) {
+	for (let attempt = 0; attempt < 60; attempt++) {
+		signal.throwIfAborted();
+		if (tunnel.finished)
+			throw new Error('The SSH tunnel closed. Check the SSH output above, then reconnect.');
+		let response;
+		try {
+			response = await fetch(`${url}/global/health`, {
+				headers: { authorization: basicAuth(password) },
+				signal: AbortSignal.any([signal, AbortSignal.timeout(1000)]),
+			});
+		} catch {
+			/* The listener is not ready yet. */
+		}
+		if (response) {
+			if (!response.ok)
+				throw new Error(
+					`OpenCode health check failed (${response.status}). Reconnect after checking the remote server.`,
+				);
+			const health = await response.json();
+			if (health.healthy !== true || typeof health.version !== 'string')
+				throw new Error('Invalid OpenCode health response.');
+			return health;
+		}
+		await delay(500, undefined, { signal });
+	}
+	throw new Error('Timed out while connecting to OpenCode. Run the session command again.');
+}
+
+function openBrowser(url) {
+	const command = process.platform === 'darwin' ? 'open' : 'xdg-open';
+	const browser = spawn(command, [url], { stdio: 'ignore', detached: true });
+	browser.on('error', () => console.log('Open the URL above in your browser.'));
+	browser.on('exit', (code) => {
+		if (code) console.log('Open the URL above in your browser.');
+	});
+	browser.unref();
+}
+
+export async function connectOpenCode(options, ensureCodespace) {
+	if (process.platform === 'win32')
+		throw new Error('Run this command in WSL. Native Windows is not supported.');
+	const version = options.web ? undefined : localVersion();
+	const controller = new AbortController();
+	const interrupt = () => controller.abort();
+	for (const signal of SIGNALS) process.on(signal, interrupt);
+	let tunnel;
+	let client;
+	let proxy;
+	try {
+		const codespace = ensureCodespace();
+		const state = await bootstrap(codespace, options, controller.signal);
+		// Bind the browser port first so the tunnel cannot receive the same port.
+		if (options.web) proxy = await openCodeProxy({ password: state.password, port: options.port });
+		const port = !options.web && options.port ? options.port : await freePort();
+		const url = `http://127.0.0.1:${port}`;
+		tunnel = startChild(
+			'gh',
+			[
+				'codespace',
+				'ssh',
+				'-c',
+				codespace,
+				'--',
+				'-N',
+				'-o',
+				'ExitOnForwardFailure=yes',
+				'-o',
+				'ServerAliveInterval=15',
+				'-o',
+				'ServerAliveCountMax=3',
+				'-L',
+				`127.0.0.1:${port}:127.0.0.1:${state.port}`,
+			],
+			{ stdio: ['ignore', 'ignore', 'inherit'], detached: true },
+		);
+		const health = await waitForTunnel(url, state.password, tunnel, controller.signal);
+		if (version && health.version !== version) {
+			throw new Error(
+				`OpenCode versions differ: local ${version}, server ${health.version}. Install the matching local version, or use --web or --legacy. The remote server is still running.`,
+			);
+		}
+		const stopped = new Promise((resolve) =>
+			controller.signal.addEventListener('abort', () => resolve('interrupted'), { once: true }),
+		);
+		controller.signal.throwIfAborted();
+		if (proxy) {
+			proxy.targetPort = port;
+			const webUrl = `${proxy.origin}/${Buffer.from(state.directory).toString('base64url')}/session/${state.sessionID}`;
+			console.log(
+				`OpenCode: ${webUrl}\nKeep this command running. Press Ctrl-C to disconnect. The remote server stays running.`,
+			);
+			openBrowser(webUrl);
+		} else {
+			console.log(`Connecting to OpenCode ${health.version} in ${state.directory}…`);
+			client = startChild(
+				'opencode',
+				['attach', url, '--dir', state.directory, '--session', state.sessionID],
+				{
+					stdio: 'inherit',
+					env: {
+						...process.env,
+						OPENCODE_SERVER_PASSWORD: state.password,
+						OPENCODE_SERVER_USERNAME: 'opencode',
+					},
+				},
+			);
+		}
+		const result = await Promise.race([
+			stopped,
+			tunnel.done.then(() => 'tunnel'),
+			...(client ? [client.done] : []),
+		]);
+		if (typeof result === 'object' && result.code !== 0)
+			throw new Error(
+				'The local OpenCode client exited with an error. The remote session is saved.',
+			);
+		if (result === 'tunnel')
+			throw new Error(
+				'The SSH connection closed. Run the same command to reconnect to the saved session.',
+			);
+	} catch (error) {
+		if (!controller.signal.aborted) throw error;
+	} finally {
+		proxy?.close();
+		await Promise.all([client?.stop(), tunnel?.stop()]);
+		for (const signal of SIGNALS) process.removeListener(signal, interrupt);
+	}
+}
diff --git a/scripts/cloud-session.mjs b/scripts/cloud-session.mjs
index db741a191e3..7dc54aa00f4 100644
--- a/scripts/cloud-session.mjs
+++ b/scripts/cloud-session.mjs
@@ -6,7 +6,7 @@
 //   pnpm session                   attach Claude Code in the main checkout
 //   pnpm session <name>            attach Claude Code in a separate worktree
 //   pnpm session:shell [name]      attach a shell
-//   pnpm session:opencode [name]   attach OpenCode in auto mode
+//   pnpm session:opencode [name]   connect a local OpenCode client
 //   pnpm session ls                list Codespaces and tmux sessions
 //   pnpm session tunnel [port…]    forward ports to localhost
 //   pnpm session stop              stop the Codespace
@@ -124,6 +124,31 @@ let launcher = 'claude';
 if (args[0] === '--shell') launcher = 'shell';
 else if (args[0] === '--opencode') launcher = 'opencode';
 if (launcher !== 'claude') args.shift();
+
+// Keep the remote terminal interface available while local clients become the default.
+if (launcher === 'opencode' && !args.includes('--legacy')) {
+	if (args.includes('--help') || args.includes('-h')) {
+		console.log(`Usage: pnpm session:opencode [name] [--web] [--new] [--port PORT]
+       pnpm session:opencode [name] --legacy [OpenCode flags]
+
+The local TUI requires the same OpenCode version as the server.
+Web mode needs a browser only and uses local port 4096 by default.
+Use --port to override it. Use Ctrl-C to close the local connection.`);
+		process.exit();
+	}
+	try {
+		const { connectOpenCode, parseOpenCodeArgs } = await import('./cloud-session-opencode.mjs');
+		await connectOpenCode(parseOpenCodeArgs(args), ensureCodespace);
+	} catch (error) {
+		console.error(error.message);
+		process.exitCode = 1;
+	}
+	// Do not interpret OpenCode options as legacy session names.
+	process.exit();
+}
+if (launcher === 'opencode') args.splice(args.indexOf('--legacy'), 1);
+// Flags without a session name apply to the main checkout.
+if (args[0]?.startsWith('-')) args.unshift('agent');
 const [cmd = 'agent', ...rest] = args;
 
 switch (cmd) {
@@ -198,7 +223,7 @@ switch (cmd) {
 	}
 	default: {
 		// treat cmd as the session name; each name = an independent agent in its own worktree
-		if (!/^[\w-]+$/.test(cmd)) {
+		if (!/^\w[\w-]*$/.test(cmd)) {
 			console.error(`Invalid session name '${cmd}' — use letters, digits, - or _`);
 			process.exit(1);
 		}