I'm trying to add a chat script to layout/theme.liquid in a Shopify store using the Admin API.

GET request works fine (200 OK), and I successfully retrieve the asset content. PUT request fails with a 404 Not Found error when trying to update the asset.

    asset_url = f"https://{shop}/admin/api/2025-01/themes/{theme_id}/assets.json"
    params = {"asset[key]": "layout/theme.liquid"}
    # here 200
    asset_resp = requests.get(asset_url, headers=headers, params=params)
    if asset_resp.status_code != 200:
        return {"error": "Failed to get theme.liquid", "details": asset_resp.json()}
    asset_data = asset_resp.json().get("asset", {})
    current_content = asset_data.get("value", "")

    script_tag = f'<script type="module" src="{SCRIPT_URL}"></script>'
    if script_tag in current_content:
        return {"message": "Script already injected in theme.liquid"}

    if "</body>" in current_content:
        new_content = current_content.replace("</body>", script_tag + "\n</body>")
        print("script iputed")
    else:
        new_content = current_content + "\n" + script_tag

    update_payload = {"asset": {"key": "layout/theme.liquid", "value": new_content}}
    update_url = f"https://{shop}/admin/api/2025-01/themes/{theme_id}/assets.json"

    # BUT here 404
    update_resp = requests.put(update_url, headers=headers, json=update_payload)
    print(update_resp.url)
    print(update_resp.status_code)

API version is consistent (2025-01 for both GET and PUT). Access token is correct (same token works for GET). The asset key exists (GET confirms it). I’m using JSON body for PUT (not params).