fix(coding-agent): reject invalid session files

closes #6002

packages/coding-agent/src/main.ts

@@ -241,6 +241,16 @@ function validateSessionIdFlags(parsed: Args): void {
 	}
 }
 
+function openSessionOrExit(path: string, sessionDir?: string): SessionManager {
+	try {
+		return SessionManager.open(path, sessionDir);
+	} catch (error: unknown) {
+		const message = error instanceof Error ? error.message : String(error);
+		console.error(chalk.red(`Error: ${message}`));
+		process.exit(1);
+	}
+}
+
 function forkSessionOrExit(sourcePath: string, cwd: string, sessionDir?: string, sessionId?: string): SessionManager {
 	try {
 		return SessionManager.forkFrom(sourcePath, cwd, sessionDir, { id: sessionId });
@@ -290,7 +300,7 @@ async function createSessionManager(
 		switch (resolved.type) {
 			case "path":
 			case "local":
-				return SessionManager.open(resolved.path, sessionDir);
+				return openSessionOrExit(resolved.path, sessionDir);
 
 			case "global": {
 				console.log(chalk.yellow(`Session found in different project: ${resolved.cwd}`));