diff --git a/packages/coding-agent/src/cli.ts b/packages/coding-agent/src/cli.ts
index fea8044d7..e6e512f38 100755
--- a/packages/coding-agent/src/cli.ts
+++ b/packages/coding-agent/src/cli.ts
@@ -6,6 +6,14 @@
 import { type CommandEntry, run } from "@oh-my-pi/pi-utils/cli";
 import { APP_NAME, VERSION } from "./config";
 
+// Detect known Bun errata that cause TUI crashes (e.g. Bun.stringWidth mishandling OSC sequences).
+if (Bun.stringWidth("\x1b[0m\x1b]8;;\x07") !== 0) {
+	process.stderr.write(
+		`error: Bun runtime errata detected (v${Bun.version}). Please update Bun: bun upgrade\n`,
+	);
+	process.exit(1);
+}
+
 process.title = APP_NAME;
 
 const commands: CommandEntry[] = [