On October 27, Meta's Ad API Stops Returning Three Delivery Estimate Fields. Pinning Your Version Won't Save You.

On October 27, Meta's Advertising API stopped returning three important fields from its Delivery Estimate API response: daily_outcomes_curve, budget_guardrail, and estimate_dau. If your code relied on these fields to forecast reach, size a budget, or show advertisers campaign performance, you would experience a quiet failure on that day.

The GET request to /{ad-account-id}/delivery_estimate still returned a 200 status code, and the response object appeared valid. However, the three fields were simply no longer present in the response. No error messages were generated to alert developers to the issue. This change applied to all supported versions of the API, including unversioned calls, making it particularly dangerous for developers who had pinned their integration to an older version, thinking it provided protection.

Many applications that rely on accurate delivery estimates are at risk, including budget pacing tools, campaign planners, advertiser dashboards, automated bidding systems, and agency reporting layers. The change effectively rendered the Delivery Estimate endpoint useless for planning and reporting purposes. Meta also announced the deprecation of the story value for Messenger placements on the same date.

When creating or updating an ad set, if the story value is included, it will be silently removed, and the API will return a success response without indicating the change. This silent modification of user-specified targeting can lead to unexpected ad targeting and performance. Both changes affected all supported versions of the Marketing API, including unversioned calls.

Pinning to an older API version did not prevent these changes from impacting applications. The announcement from Meta provided a three-month window for developers to migrate their code, but the fact that these changes applied to all supported versions meant that the migration window had effectively closed for everyone by October 27.

Developers who had relied on version pinning as a protection measure found that it did not provide the intended safeguard.