Google Chat Spaces API: Enterprise Integration Architecture in 2026
Google Chat's developer platform went through a major architectural reset in 2024–2025. The legacy "Hangouts Chat" API endpoints were fully deprecated, the concept of "rooms" was replaced by "spaces," and the Pub/Sub-based event delivery model replaced the previous webhook system for enterprise configurations.
If your Google Chat integration was written before 2025, parts of it are broken or deprecated. This post covers the current (2026) architecture and what it means for cross-platform messaging bridges.
Spaces vs Rooms: What Changed
The legacy API used "rooms" as the primary container for group conversations. The current Spaces API uses "spaces" with three distinct types:
- SPACE: Persistent named spaces, equivalent to Slack channels or Teams team channels
- GROUP_CHAT: Unnamed group direct messages
- DIRECT_MESSAGE: 1:1 DMs
For enterprise bridge implementations, you will primarily work with SPACE type. The distinction matters because several API operations (notably, listing messages with the spaces.messages.list method) behave differently depending on space type, and some operations require the Chat API to be explicitly enabled in the Google Workspace admin console — unlike legacy rooms which were accessible with basic OAuth scopes.
Authentication: Service Account vs OAuth 2.0
For enterprise integrations running as background services (not user-initiated), Google Chat requires a domain-wide delegation service account rather than standard OAuth 2.0 user consent flow.
Domain-wide delegation allows the service account to impersonate workspace users and act on their behalf. The key scopes required for a full messaging bridge:
https://www.googleapis.com/auth/chat.spaces
https://www.googleapis.com/auth/chat.messages
https://www.googleapis.com/auth/chat.messages.create
https://www.googleapis.com/auth/chat.memberships
The critical security consideration: domain-wide delegation grants the service account access to impersonate ANY user in the workspace. For SOC 2 compliance, the service account must be scoped to the minimum required permissions, access must be logged, and the service account keys must be rotated on a schedule. Many enterprise security reviews will flag domain-wide delegation as a high-risk configuration and require detailed documentation.
Event Delivery: Pub/Sub vs HTTP
The legacy Google Chat webhook model (HTTP POST to a user-specified URL) still works for simple bot integrations, but for enterprise-scale bridges, the Pub/Sub model is required.
With the Pub/Sub model:
- A Google Cloud Pub/Sub topic is created in your GCP project
- The Chat API is configured to publish space events to that topic
- Your service subscribes to the topic and processes events
This model provides much stronger delivery guarantees (at-least-once delivery, configurable acknowledgment deadlines) and decouples event production from your processing pipeline, which is essential for handling large Google Workspace deployments where hundreds of spaces may be active simultaneously.
The tradeoff: you now own a Pub/Sub subscription that requires operational maintenance. Dead letter topics, subscription acknowledgment monitoring, and per-message processing idempotency all become your responsibility.
Message Threading in Google Chat Spaces
Google Chat has a threading model that is fundamentally different from both Slack and Teams. In Google Chat:
- All messages in a Space belong to a thread
- New top-level messages automatically create a new thread
- Reply chains are nested under their parent thread
- The thread ID (
threadName) is stable and can be used for routing
For a cross-platform bridge, mapping threads correctly is the hardest part. When a Slack thread reply arrives, the bridge must determine whether a corresponding Google Chat thread already exists (from a previous bridged message in the same thread) or whether to create a new thread.
The correct approach: maintain a thread mapping table with (slack_thread_ts, google_chat_thread_name) pairs. On each bridged message, look up the parent thread ID from the table. If not found, create a new Google Chat thread and record the mapping.
Rate Limits (2026)
Current Google Chat API rate limits:
- Create message: 3,000 requests per minute per project
- List messages: 3,000 requests per minute per project
- Get space: 3,000 requests per minute per project
- Create membership: 3,000 requests per minute per project
These are substantially more generous than Teams Graph API limits, making Google Chat the least likely platform to throttle your bridge at enterprise scale — but only if you stay within Google's per-project limit rather than multiplying the limit by space count.
Bridge Google Chat to Teams → | Bridge Google Chat to Slack →
