Firebase's JS SDK deprecates VertexAIBackend for AgentPlatformBackend, and the new class defaults to global instead of us-central1.
Firebase AI Logic’s JavaScript SDK deprecated VertexAIBackend
in version 12.17.0, released July 30, 2026, replacing it with a new AgentPlatformBackend
class (Firebase JS SDK releases, July 2026). The rename isn’t cosmetic: the new class defaults to a different region than the old one, a behavior change developers can miss if they treat this as a find-and-replace.
What actually changed #
The swap follows Google’s April 22, 2026 rebrand of Vertex AI into the Gemini Enterprise Agent Platform, announced at Cloud Next 2026 (Google Cloud, April 2026). Google said at the time that future Vertex AI capability would ship exclusively through the new Agent Platform rather than as a standalone product. Firebase’s client SDK is now catching up to that shift, three months later: what Firebase’s docs called the “Vertex AI Gemini API” is now the “Agent Platform Gemini API,” one of the two backend options in Firebase AI Logic alongside the Gemini Developer API (Firebase AI Logic docs).
VertexAIBackend
still works. Google hasn’t pulled it, but it’s deprecated, and new features will only land on AgentPlatformBackend
going forward.
The part that actually breaks things #
The two classes aren’t drop-in equivalents. VertexAIBackend
defaults to the us-central1
region if you don’t specify one. AgentPlatformBackend
defaults to global
(Firebase AI Logic docs, location reference). Swap the class name without setting a location explicitly, and a call that ran in us-central1
now runs wherever Google routes “global” traffic, which matters for latency-sensitive apps or anyone with a data-residency requirement tied to a specific region.
Firebase’s own docs point out why the default flipped rather than just carrying us-central1
forward: most of Google’s newer Gemini models aren’t available in us-central1
at all. Pinning the old regional default into the new class would have quietly cut off access to current models. Developers who need us-central1
specifically have to ask for it: new AgentPlatformBackend('us-central1')
.
Where this fits #
This is Firebase’s second rename in this exact spot in about a year. “Vertex AI in Firebase” became “Firebase AI Logic” in May 2025, and the underlying package went from firebase-vertexai
to firebase-ai
at the same time. That first rename was mostly cosmetic: it reflected Firebase AI Logic adding support for the Gemini Developer API alongside Vertex AI, not a change in how existing code behaved. This one is different: it’s Firebase’s SDK inheriting a platform-wide rebrand from Google Cloud, and it ships with a default that changes where your requests actually go.
Firerun’s take: the version bump itself is easy to skip past. SDK release notes are exactly the kind of change that gets batch-approved in a dependency update PR without a close read. Anyone on VertexAIBackend
today should treat this one differently. Read the region section of the migration notes before swapping classes, and if the target region matters to your app, set it explicitly rather than trust the new default to match the old one.