# Custom\_attribute\_values on an ITEM silently don't persist (sandbox) — reproduced without the SDK

**URL:** <https://developer.squareup.com/forums/t/custom-attribute-values-on-an-item-silently-dont-persist-sandbox-reproduced-without-the-sdk/27162>\
**Category:** Questions\
**Tags:** catalog-api, sandbox\
**Created:** [August 11, 2026, 9:37pm UTC](https://developer.squareup.com/forums/t/custom-attribute-values-on-an-item-silently-dont-persist-sandbox-reproduced-without-the-sdk/27162 "2026-08-11T21:37:26Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![UKM.sr](https://avatars.discourse-cdn.com/v4/letter/u/e274bd/32.png) [@UKM.sr](https://developer.squareup.com/forums/u/UKM.sr)\
**Post date:** [August 11, 2026, 9:37pm UTC](https://developer.squareup.com/forums/t/custom-attribute-values-on-an-item-silently-dont-persist-sandbox-reproduced-without-the-sdk/27162/1 "2026-08-11T21:37:26Z")

</div>

I’m building a Catalog API integration against a sandbox test account and can’t get `custom_attribute_values` to persist on an `ITEM` object. The write reports success (200, no `errors` array) but the value is never present on read-back — not even in the write response itself.

**Environment:** Sandbox, `Square-Version: 2025-02-20`, app id `sandbox-sq0idb-f-65nNciqV7hMiXosjEfGg`.

**What I’ve ruled out** , each tested independently:

- **SDK vs raw REST** — reproduced identically calling `fetch()` directly against `connect.squareupsandbox.com/v2/catalog/object`, bypassing the `square` npm SDK entirely, using your own documented example payload from the custom attributes guide ([Add Custom Attributes](http://developer.squareup.com/docs/catalog-api/add-custom-attributes)) almost verbatim.
- 
  - **SELECTION vs STRING type** — same result on both a `SELECTION`-type attribute and a fresh, minimal `STRING`-type attribute.
  - 
    - **Map key = definition id vs definition `key`** — tried both; your docs specify the `key` string should be the map key, tested that exactly.
    - 
      - **Selection UID** — tried both a client-supplied `#`-prefixed temp UID and the real server-assigned UID (fetched after the definition was created).
      - 
        - **`app_visibility`** — tried both `APP_VISIBILITY_HIDDEN` (my original attributes) and a brand-new attribute created with `APP_VISIBILITY_READ_WRITE_VALUES`, in case the “creating app always has access” guarantee in your docs doesn’t apply as documented. Same result.
        - 
          - **API version** — pinned to `2025-02-20` to match your own working doc example exactly (rather than the SDK’s default `2026-07-15`).
          - 
            - **Stale version** — confirmed I’m always sending the freshly-fetched `version` before the write (ruled out `VERSION_MISMATCH` as a red herring).

          - **Minimal repro:**

        - 
          1. Create a `CUSTOM_ATTRIBUTE_DEFINITION` (type `STRING`, `allowed_object_types: ["ITEM"]`, key `test_string`).
          2. 
            1. Create/update an `ITEM` with:

          3. “custom\_attribute\_values”: {
          4. “test\_string”: {
          5. 

```auto
"key": "test_string",

```

          6. 

```auto
"custom_attribute_definition_id": "<the definition id>",

```

          7. 

```auto
"type": "STRING",

```

          8. 

```auto
"string_value": "hello"

```

          9. }

        1. }

        - 
          1. Response to that very write already omits `custom_attribute_values` from the returned object.
          2. 
            1. A subsequent `RetrieveCatalogObject` on that item also shows no `custom_attribute_values`.

          3. Is this a known sandbox-specific issue, or is there an undocumented requirement I’m missing? Happy to share the exact request/response bodies if useful.

        - (Context: this blocks a taxonomy mapping — technique, frame shape, prescription type, brand — for an e-commerce catalog sync. Once resolved, worth re-testing against the production account too, in case it’s sandbox-specific.)

---

<div class="post-metadata">

**Author:** ![jseok](https://avatars.discourse-cdn.com/v4/letter/j/f475e1/32.png) [@jseok](https://developer.squareup.com/forums/u/jseok)\
**Post date:** [August 12, 2026, 3:59pm UTC](https://developer.squareup.com/forums/t/custom-attribute-values-on-an-item-silently-dont-persist-sandbox-reproduced-without-the-sdk/27162/4 "2026-08-12T15:59:24Z")

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Hi @UKM.sr - thanks for sharing. Custom attributes are operating as expected in sandbox, with the same parameters as described. Could you please try the following:

- Check that you are using a unique idempotency key for every attempt
- Replicate this same process using the most recent API version
- Replicate this process in production
- Replicate with both the most recent API version and in production

If none of those work, please provide the exact timestamp of the request, the request itself, and the response that was received.