fix(cli): suppress legacy task spinner when stdout is not a TTY

apps/cli/src/shared/output/output.layer.ts

@@ -181,6 +181,20 @@ export const textOutputLayer = Layer.effect(
           : Effect.sync(() => log.info(JSON.stringify(event))),
       task: (message: string) =>
         Effect.sync(() => {
+          if (!tty.stdoutIsTty) {
+            // Non-TTY stdout (CI, pipe, redirect) — suppress the @clack spinner,
+            // which writes cursor-hide and animated-frame ANSI to stdout and
+            // pollutes machine-parsed output. See supabase/cli#5397.
+            const noop = () => Effect.void;
+            return {
+              message: noop,
+              succeed: noop,
+              fail: noop,
+              info: noop,
+              cancel: noop,
+              clear: noop,
+            };
+          }
           let shown = false;
           let settled = false;
           let currentMessage = message;

apps/cli/src/shared/output/output.layer.unit.test.ts

@@ -154,6 +154,21 @@ describe("Output", () => {
         }).pipe(Effect.provide(layer)),
     );
 
+    it.effect("task suppresses the spinner entirely when stdout is not a TTY", () =>
+      Effect.gen(function* () {
+        vi.useFakeTimers();
+        const out = yield* Output;
+        const task = yield* out.task("Fetching branches...");
+        vi.advanceTimersByTime(1000);
+        yield* task.clear();
+
+        expect(mockClack.spinnerFactory).not.toHaveBeenCalled();
+        expect(mockClack.spinnerHandle.start).not.toHaveBeenCalled();
+      }).pipe(
+        Effect.provide(textOutputLayer.pipe(Layer.provide(mockTty({ stdoutIsTty: false })))),
+      ),
+    );
+
     it.effect("task prefixes continuation lines for multiline completions", () =>
       Effect.gen(function* () {
         vi.useFakeTimers();