diff --git a/.devcontainer/codespaces/cloud-session.test.mjs b/.devcontainer/codespaces/cloud-session.test.mjs
index 9e5264eb21f..ac41a012279 100644
--- a/.devcontainer/codespaces/cloud-session.test.mjs
+++ b/.devcontainer/codespaces/cloud-session.test.mjs
@@ -27,6 +27,14 @@ if (args[0] === 'codespace' && args[1] === 'list') {
 `,
 	);
 	chmodSync(mockGh, 0o755);
+	for (const [name, script] of Object.entries({
+		infocmp: '[ "$1" = "$SUPPORTED_TERM" ]',
+		tmux: 'printf "%s" "$TERM"',
+	})) {
+		const executable = join(fixtureDir, name);
+		writeFileSync(executable, `#!/bin/sh\n${script}\n`);
+		chmodSync(executable, 0o755);
+	}
 });
 
 after(() => rmSync(fixtureDir, { recursive: true, force: true }));
@@ -58,6 +66,34 @@ function remoteCommand(args) {
 	return invocationArgs[6];
 }
 
+for (const { name, supportedTerm, expectedTerm } of [
+	{
+		name: 'uses xterm-256color when the remote terminal definition is missing',
+		supportedTerm: 'xterm-256color',
+		expectedTerm: 'xterm-256color',
+	},
+	{
+		name: 'keeps the terminal type when the remote definition is available',
+		supportedTerm: 'xterm-ghostty',
+		expectedTerm: 'xterm-ghostty',
+	},
+]) {
+	test(name, () => {
+		const result = spawnSync('/bin/sh', ['-c', remoteCommand(['--opencode', '--legacy'])], {
+			encoding: 'utf8',
+			env: {
+				...process.env,
+				PATH: `${fixtureDir}:${process.env.PATH}`,
+				TERM: 'xterm-ghostty',
+				SUPPORTED_TERM: supportedTerm,
+			},
+		});
+
+		assert.equal(result.status, 0, result.stderr);
+		assert.equal(result.stdout, expectedTerm);
+	});
+}
+
 test('starts a named OpenCode session in a worktree', () => {
 	const command = remoteCommand(['--opencode', 'fix-flaky', '--legacy', '--model', 'test']);
 
diff --git a/scripts/cloud-session.mjs b/scripts/cloud-session.mjs
index 7dc54aa00f4..e84e840e686 100644
--- a/scripts/cloud-session.mjs
+++ b/scripts/cloud-session.mjs
@@ -23,6 +23,11 @@ const MACHINE = 'premiumLinux';
 const gh = (...args) => execFileSync('gh', args, { encoding: 'utf8' }).trim();
 const ghTty = (...args) => spawnSync('gh', args, { stdio: 'inherit' });
 
+// Check the remote terminal database before tmux starts. Older images can lack
+// terminal definitions such as xterm-ghostty.
+const TERMINAL_FALLBACK =
+	'if ! infocmp "$TERM" >/dev/null 2>&1; then export TERM=xterm-256color; fi';
+
 function findCodespace(retry = false) {
 	try {
 		const list = JSON.parse(gh('codespace', 'list', '-R', REPO, '--json', 'name,state'));
@@ -237,7 +242,7 @@ switch (cmd) {
 			name,
 			'--',
 			'-t',
-			`tmux new -As ${tmuxSession} '${remoteCommand(cmd, launcher, rest.join(' '))}'`,
+			`${TERMINAL_FALLBACK}; tmux new -As ${tmuxSession} '${remoteCommand(cmd, launcher, rest.join(' '))}'`,
 		);
 		process.exitCode = status ?? 1;
 	}