'Semantic Segmentation with Polygons' template issues with labels

[zdunecki]

Describe the bug
I'm trying to use a template, 'Semantic Segmentation with Polygons, and labels are not saved correctly. Once updated, I don't see saved results on export or UI.

To Reproduce
Steps to reproduce the behavior:

1. Install label-studio
2. Create a project
3. Pick sample data set
4. Pick 'Semantic Segmentation with Polygons...' template
5. Annotate
6. After the updated annotations are not saved (export

Expected behavior
It should just work like Choices, where I see results on UI and exported JSON.

Screenshots

[
    {
        "id": 1,
        "annotations": [
            {
                "id": 8,
                "completed_by": 1,
                "result": [],
                "was_cancelled": false,
                "ground_truth": false,
                "created_at": "2025-11-11T17:01:08.950898Z",
                "updated_at": "2025-11-11T17:01:08.950921Z",
                "draft_created_at": null,
                "lead_time": 7.276,
                "prediction": {},
                "result_count": 0,
                "unique_id": "ae9deacb-018e-4862-a72a-f5b03f345423",
                "import_id": null,
                "last_action": null,
                "bulk_created": false,
                "task": 1,
                "project": 1,
                "updated_by": 1,
                "parent_prediction": null,
                "parent_annotation": null,
                "last_created_by": null
            }
        ],
        "file_upload": "2b19584d-coco_2017_val_100tasks.json",
        "drafts": [],
        "predictions": [],
        "data": {
            "image": "https:\/\/hs-sandbox-pub.s3.us-east-1.amazonaws.com\/sample_data\/coco_2017_val_100tasks\/000000491757.jpg"
        },
        "meta": {},
        "created_at": "2025-11-11T16:54:46.403062Z",
        "updated_at": "2025-11-11T17:01:08.965789Z",
        "inner_id": 1,
        "total_annotations": 1,
        "cancelled_annotations": 0,
        "total_predictions": 0,
        "comment_count": 0,
        "unresolved_comment_count": 0,
        "last_comment_updated_at": null,
        "project": 1,
        "updated_by": 1,
        "comment_authors": []
    },
    {
        "id": 2,
        "annotations": [
            {
                "id": 2,
                "completed_by": 1,
                "result": [],
                "was_cancelled": false,
                "ground_truth": false,
                "created_at": "2025-11-11T16:57:18.384573Z",
                "updated_at": "2025-11-11T16:57:18.384592Z",
                "draft_created_at": null,
                "lead_time": 2.998,
                "prediction": {},
                "result_count": 0,
                "unique_id": "48ae29c9-ca78-4f9b-af9f-88cb6b66e3fa",
                "import_id": null,
                "last_action": null,
                "bulk_created": false,
                "task": 2,
                "project": 1,
                "updated_by": 1,
                "parent_prediction": null,
                "parent_annotation": null,
                "last_created_by": null
            },
            {
                "id": 13,
                "completed_by": 1,
                "result": [],
                "was_cancelled": false,
                "ground_truth": false,
                "created_at": "2025-11-11T17:04:51.486007Z",
                "updated_at": "2025-11-11T17:04:51.486020Z",
                "draft_created_at": null,
                "lead_time": 7.496,
                "prediction": {},
                "result_count": 0,
                "unique_id": "afb0b8a8-454b-4368-82f6-9a1c4f29b26b",
                "import_id": null,
                "last_action": null,
                "bulk_created": false,
                "task": 2,
                "project": 1,
                "updated_by": 1,
                "parent_prediction": null,
                "parent_annotation": null,
                "last_created_by": null
            },
            {
                "id": 14,
                "completed_by": 1,
                "result": [],
                "was_cancelled": false,
                "ground_truth": false,
                "created_at": "2025-11-11T17:05:10.834222Z",
                "updated_at": "2025-11-11T17:05:10.834242Z",
                "draft_created_at": null,
                "lead_time": 2.294,
                "prediction": {},
                "result_count": 0,
                "unique_id": "784e88d2-4f6e-4edf-909a-3e87026daa20",
                "import_id": null,
                "last_action": null,
                "bulk_created": false,
                "task": 2,
                "project": 1,
                "updated_by": 1,
                "parent_prediction": null,
                "parent_annotation": null,
                "last_created_by": null
            },
            {
                "id": 15,
                "completed_by": 1,
                "result": [],
                "was_cancelled": false,
                "ground_truth": false,
                "created_at": "2025-11-11T17:05:13.794423Z",
                "updated_at": "2025-11-11T17:05:13.794441Z",
                "draft_created_at": null,
                "lead_time": 1.824,
                "prediction": {},
                "result_count": 0,
                "unique_id": "e027ec1f-27d5-4697-815a-433a61069c36",
                "import_id": null,
                "last_action": null,
                "bulk_created": false,
                "task": 2,
                "project": 1,
                "updated_by": 1,
                "parent_prediction": null,
                "parent_annotation": null,
                "last_created_by": null
            }
        ],
        "file_upload": "2b19584d-coco_2017_val_100tasks.json",
        "drafts": [],
        "predictions": [],
        "data": {
            "image": "https:\/\/hs-sandbox-pub.s3.us-east-1.amazonaws.com\/sample_data\/coco_2017_val_100tasks\/000000045472.jpg"
        },
        "meta": {},
        "created_at": "2025-11-11T16:54:46.403133Z",
        "updated_at": "2025-11-11T17:05:13.811219Z",
        "inner_id": 2,
        "total_annotations": 4,
        "cancelled_annotations": 0,
        "total_predictions": 0,
        "comment_count": 0,
        "unresolved_comment_count": 0,
        "last_comment_updated_at": null,
        "project": 1,
        "updated_by": 1,
        "comment_authors": []
    }
]

Environment (please complete the following information):

• OS: macOS Tahoe 26.0.1
• Label Studio Version: 1.20.0

Additional context
Add any other context about the problem here.