I’m generating videos with the Google Gen AI SDK on Vertex AI using the Veo 2 model. My code sets a pubsubTopic in GenerateVideosConfig, but I don’t receive any Pub/Sub messages about generation progress.

private final Client client;

public VertexAiVideoGenerator() throws IOException {
    var clientBuilder = Client.builder();
    clientBuilder.vertexAI(true);
    clientBuilder.project(PROJECT_ID);
    clientBuilder.location(LOCATION);
    clientBuilder.credentials(GoogleCredentials.getApplicationDefault());
    this.client = clientBuilder.build();
}

public GenerateVideosOperation generate(String modelId, String prompt) {
    Image image = Image.builder()
            .gcsUri("gs://test-bucket/test.jpg")
            .mimeType("image/jpeg")
            .build();
    var videoConfig = GenerateVideosConfig.builder()
            .durationSeconds(10)
            .numberOfVideos(2)
            .outputGcsUri("gs://test-bucket")
            .pubsubTopic("projects/PROJECT_ID/topics/TOPIC_NAME")
            .build();

    var operation = client.models.generateVideos(modelId, prompt, image, videoConfig);
    return operation;

}

What I’ve tried:

Verified the topic exists and I created a subscription to it.

Checked that outputGcsUri is valid and the video is generated successfully in GCS.

Waited for several generations — still no Pub/Sub messages.

Question: What is required to make Vertex AI publish progress updates to my Pub/Sub topic for Veo video generation? Is there a specific service account or IAM role I need to grant on the topic?

Environment: Google Gen AI Java SDK, Veo 2 (veo-2.0-generate-001), Vertex AI on GCP.