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2026.4.1

scottschiller/SoundManager22026.4.1Apr 24, 2026by GabrielBianconi

AI Summary

This release changes observability behavior to async writes by default and removes the Autopilot Sessions page, while adding TypeScript evaluators and vLLM support.

Key Highlights

  • Gateway defaults to async observability writes
  • Removed TensorZero Autopilot 'Sessions' page
  • Added TypeScript evaluators for inference evaluations
  • Added support for vLLM's new `reasoning` field

Breaking Changes

  • The gateway now defaults to async observability writes

New Features

  • 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
  • Return HTTP code 429 for rate limiting errors
  • Fixed ClickHouse database names with hyphens

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_