fix(coding-agent): handle stdio write stream errors

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- Fixed stdout/stderr write-stream failures from embedded terminal hosts, including Node's `errno -122` case, crashing Caveman Code with an unhandled `WriteStream` error.
 - Added missing `@sinclair/typebox` runtime dependency. Fixes `ERR_MODULE_NOT_FOUND` on `caveman-code` startup when installed globally ([#6](https://github.com/JuliusBrussee/caveman-code/issues/6)).
 - Fixed broken extensions-migration links in the hooks-folder warning — now point to `JuliusBrussee/caveman-code` instead of the renamed-away `caveman-cli` repo ([#8](https://github.com/JuliusBrussee/caveman-code/issues/8)).
 - Self-update check now queries the correct GitHub repo (`caveman-code`) for releases.

packages/coding-agent/src/cli.ts

@@ -11,6 +11,42 @@ process.emitWarning = (() => {}) as typeof process.emitWarning;
 import { EnvHttpProxyAgent, setGlobalDispatcher } from "undici";
 import { main } from "./main.js";
 
+type StdioWriteError = Error & {
+	code?: string;
+	errno?: number | string;
+	syscall?: string;
+};
+
+function isClosedStdioWrite(error: StdioWriteError): boolean {
+	if (error.syscall !== "write") return false;
+	if (error.code === "EPIPE" || error.code === "ERR_STREAM_DESTROYED") return true;
+	// Some embedded PTY hosts surface a failed output stream as libuv EDQUOT
+	// (errno -122) instead of a more specific stream error on recent Node versions.
+	return error.errno === -122 || error.errno === "-122" || error.code === "Unknown system error -122";
+}
+
+function getStdioWriteExitCode(error: StdioWriteError): number {
+	return error.errno === -122 || error.errno === "-122" || error.code === "Unknown system error -122" ? 1 : 0;
+}
+
+function installStdioWriteErrorHandlers(): void {
+	let exiting = false;
+	const handleError = (error: Error) => {
+		if (!isClosedStdioWrite(error)) {
+			throw error;
+		}
+		if (exiting) return;
+		exiting = true;
+		const exitCode = getStdioWriteExitCode(error);
+		process.exitCode = exitCode;
+		setImmediate(() => process.exit(exitCode));
+	};
+
+	process.stdout.on("error", handleError);
+	process.stderr.on("error", handleError);
+}
+
 setGlobalDispatcher(new EnvHttpProxyAgent());
+installStdioWriteErrorHandlers();
 
 main(process.argv.slice(2));