publisher: access token used as user_id in carousel child create for accounts with NULL user_id (THApiException #100)

[ajianaz]

Evidence (2026-09-23, prod v0.9.4)

Carousel publish on an account with user_id = NULL (manual-form account) failed at child container #1:

Threads API error: Unsupported post request. Object with ID
'THAASBUF8ygJdBYmJZAb0RfMFFQemdLQjNueG44RS1EWVJFMm9mbzBmVlVaalJETV94TkNkeFhaRFRJblNiQkh4cG4wUmI3MnM2REQ3TzMtUkxuU0UxZAGc1NEdvNmpnSnIzLTRVcTFVRUgwUzhFRWduM1RMUnRKaWVPbkNmenhVM1BpdlctVW9hUEFDR01yWnNjVVVreTJrQzJCRFZAlSjVZAMjcwU3ZAsQQZDZD'
does not exist ... [THApiException #100] (HTTP 400)

That "object ID" is not a Threads container ID — it is an encoded access token (length, alphabet, and prefix pattern match a Graph API token; the account's real user_id was NULL at the time). The publish path (or the #264 self-heal) passed the access token where a numeric user ID belongs, so Meta rejected the request.

Additionally, the #264 self-heal did not persist a corrected user_id: GET /api/accounts still showed user_id: null for this account after publish attempts and after a scheduler restart.

Impact

• Any manual-form account (the very accounts that need the self-heal) cannot publish CAROUSEL/IMAGE/TEXT posts that address the user graph object.
• The failure message gives no hint that identity resolution produced garbage.

Proposed fixes

1. Before publish, require a numeric user_id; if missing, resolve via GET /me?fields=id,username and fail loudly (do not fall back to any non-numeric value) if resolution fails.
2. Guard by format: user_id must match ^\d{15,20}$ before being used in any Graph path; log and reject otherwise (this turns the confusing fix: register migration 008 in store.migrate() #100 into a clear internal error).
3. Persist the healed user_id back to the account row (currently it appears to stay NULL).
4. Same format guard on the OAuth exchange path: the response's user_id should be validated before storage.

Repro: account added via manual form (user_id null) → schedule any CAROUSEL → approve → observe #100 with a token-shaped ID in the error.