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2026.4.1

juliangarnier/anime2026.4.1Apr 24, 2026by GabrielBianconi

AI Summary

This release updates observability to async writes by default, removes the Autopilot Sessions UI page, and adds TypeScript evaluators, vLLM reasoning support, and enhanced UI and trace data.

Key Highlights

  • Gateway defaults to async observability writes to reduce tail latency.
  • Removed TensorZero Autopilot 'Sessions' page from the UI.
  • Added TypeScript evaluators, vLLM reasoning support, and aggregated variant usage data.
  • Added inference cost data to exported OpenTelemetry traces.

Breaking Changes

  • The gateway now defaults to async observability writes.

New Features

  • Added TypeScript evaluators (for inference evaluations).
  • Added support for vLLM's new `reasoning` field.
  • Added aggregated variant usage data (tokens, cost, etc.) to the UI.
  • Added inference cost data to exported OpenTelemetry traces.
  • Added `export.otlp.traces.include_content` configuration field.

Full Release Notes

> [!CAUTION]
> **Breaking Changes**
>
> - The gateway now defaults to async observability writes to reduce tail latency: inferences are sent to the client before they are persisted in the database. To restore the previous behavior, set `observability.async_writes = false`. **[[docs]](https://www.tensorzero.com/docs/gateway/configuration-reference)**

> [!WARNING]
> **Deprecations**
>
> - Removed the TensorZero Autopilot "Sessions" page from the UI. We recently added a TensorZero MCP that integrates nicely with coding agents, and we'll re-introduce advanced TensorZero Autopilot workflows in a platform-agnostic format soon.

**Bug Fixes**

- Return HTTP code 429 for rate limiting errors.
- Fixed a bug affecting ClickHouse database names with hyphens. (thanks @ianliuy!)

**New Features**

- Added TypeScript evaluators (for inference evaluations).
- Added support for vLLM's new `reasoning` field.
- Added aggregated variant usage data (tokens, cost, etc.) to the UI.
- Added inference cost data to exported OpenTelemetry traces. (thanks @kimsehwan96!)
- Added `export.otlp.traces.include_content` (default false) configuration field to include inference content (e.g. prompts, messages) in exported OpenTelemetry GenAI traces.

_& multiple under-the-hood and UI improvements_