When Meta launched Graph API and Marketing API v26.0 on July 29, a set of breaking changes applied only to calls made on v26. On October 27, 90 days later, Meta extends several of them to every supported version, including unversioned calls. If you run campaigns through a third-party tool, a launcher script or an in-house dashboard, this is the week to check it.
What breaks on October 27
Meta's July 29 developer blog post lists these changes as moving from v26-only to all versions on October 27, and the v26.0 changelog gives the field-level detail. None of them has a replacement unless noted.
- Poll ads: creating poll creatives, or switching an ad to a poll creative, is rejected. Remove poll_spec and the poll type from interactive_components_spec. Edits that don't touch the creative still work.
- Web-only app links: creatives with applink_treatment set to web_only can't be used in campaigns optimising for website and app conversions. Switch to automatic or deeplink_with_web_fallback.
- Delivery estimate fields: daily_outcomes_curve, budget_guardrail and estimate_dau are removed from the delivery_estimate endpoints. Meta says they already return zero or empty data.
- Messenger Stories: the story value in messenger_positions is removed for all versions (the changelog page gives an earlier date, so if you still send it, remove it now). Advantage+ Placements need no action.
- Commerce order management: the 47 blocked order endpoints are removed from the remaining Graph API versions.
One more change to watch: advantage_audience
Since v26, new or copied ad sets that use constrained targeting, such as custom audience inclusions or detailed targeting, must explicitly set advantage_audience to 1 or 0, or the call returns an error. Updates to existing ad sets are unaffected. Bulk launchers that duplicate ad sets are the most likely place for this to fail quietly, because a copy counts as a new ad set.
Who it affects
Anyone who creates or edits ads outside the Ads Manager interface: agencies with bulk-launch scripts, affiliates using third-party launchers, and teams with reporting dashboards that read delivery estimates. If you build everything by hand in Ads Manager, the practical impact is small: poll ads and the Messenger Stories placement simply stop being options.
Older tools pinned to v24 or v25 were shielded from these changes until now. After October 27 that version pin no longer protects them, so a script that worked yesterday can start throwing errors with no change on your side.
What to do this week
Ask your tool vendor or developer to confirm they have tested against v26 behaviour, then run one test launch before October 27 rather than discovering errors in the middle of a Q4 scale-up. Search your code and templates for poll_spec, web_only, messenger_positions and the three delivery estimate field names, and update any dashboard that charts estimated daily outcomes so it doesn't show silent zeros. If a launch does fail, the API error message names the field at fault, which makes these changes quick to trace.
What it means for you
- From October 27, poll creatives and web_only app links are rejected on every API version.
- Remove story from messenger_positions; Advantage+ Placements are unaffected.
- Set advantage_audience explicitly on new or copied ad sets with constrained targeting.
- Run a test launch through your tools before October 27, not during a scale-up.
Sources
- Meta for Developers: Introducing Graph API v26 and Marketing API v26
- Meta Marketing API changelog: Version 26.0
