test: stop the CLI no-socket regression waiting 90 s for an app it never starts

CLI/cmux.swift

@@ -4197,7 +4197,19 @@ struct CMUXCLI {
     /// Restored terminals start the app and then race its listener bind. Keep
     /// the implicit restore connection alive long enough for that lifecycle,
     /// while explicit socket paths retain their immediate failure semantics.
-    private static let restoreSocketStartupTimeoutSeconds: TimeInterval = 45
+    private static let defaultRestoreSocketStartupTimeoutSeconds: TimeInterval = 45
+    /// Tests that exercise the "still opening" failure set
+    /// `CMUX_RESTORE_SOCKET_STARTUP_TIMEOUT_SECONDS` so they do not wait out
+    /// the full startup budget. It can only shorten the default.
+    private static var restoreSocketStartupTimeoutSeconds: TimeInterval {
+        let key = "CMUX_RESTORE_SOCKET_STARTUP_TIMEOUT_SECONDS"
+        guard let raw = ProcessInfo.processInfo.environment[key]?.trimmingCharacters(in: .whitespacesAndNewlines),
+              let value = TimeInterval(raw),
+              value.isFinite else {
+            return defaultRestoreSocketStartupTimeoutSeconds
+        }
+        return min(max(value, 0.05), defaultRestoreSocketStartupTimeoutSeconds)
+    }
     // Stable per-user slot for the pinned Cloud VM. This value is intentionally reused as
     // both the backend create idempotency key and the local daemon slot so every open,
     // reconnect, session restore, and mobile attach targets the same provider VM once

cmuxTests/CMUXCLIErrorOutputRegressionTests.swift

@@ -2351,6 +2351,9 @@ import Testing
         }
         environment["CMUX_CLI_SENTRY_DISABLED"] = "1"
         environment["CFFIXED_USER_HOME"] = home.path
+        // restore and fork wait for the app's socket before reporting that
+        // cmux is still opening; the default 45 s wait made this test 90 s.
+        environment["CMUX_RESTORE_SOCKET_STARTUP_TIMEOUT_SECONDS"] = "1"
 
         let cases: [(arguments: [String], expectedError: String)] = [
             (["settings", "invalid-target"], "Unknown settings subcommand 'invalid-target'"),