agents@0.27.0
Cloudflare Agents SDK 0.27.0 introduces four experimental harnesses, a web search tool integration, and a breaking architectural rewrite of the Channels API around conversations and turns.
Why this signal matters
agents@0.27.0 delivers breaking changes by completely removing the first pass of the agents/channels entry points (including ChannelHost , composite fallbacks/fanouts, and early AI SDK/TanStack/Voice helpers) and moving the functionality to agents/experimental/channels . The Channels subsystem is redesigned around conversations and turns, introducing ChannelGateway , Web Channel clients, an AI SDK chat transport, and a terminal TUI client. Slack, Telegram, and Email adapters have also been shifted to agents/experimental/channels/ . Additionally, four experimental agent harnesses matching the shape of PiHarness are introduced: AiSdkHarness (with Durable Object session persistence), ThinkHarness , ContainerHarness (for Claude Code or Codex in containers), and OpenCodeHarness . A new agents/websearch tool adds Cloudflare Web Search API support across Pi, AI SDK, and TanStack AI setups. Patches resolve multiple issues including MCP credential cleanup on removeServer() , AiSdkHarness startup failures due to concurrent Durable Object kv.list() operations, and early abort signal handling.
Actionable summary
Cloudflare Agents SDK v0.27.0 removes legacy agents/channels entry points and relocates the reworked architecture to agents/experimental/channels . It introduces AiSdkHarness , ThinkHarness , ContainerHarness , and OpenCodeHarness , alongside agents/websearch and bug fixes for Streams, Tasks, and MCP credential handling.
- Agent usefulness
- 94/100
- Confidence
- 96%
- Canonical data
- JSON + Markdown
What builders should check
- Migrate any legacy imports from agents/channels to agents/experimental/channels , including Slack, Telegram, and Email modules.
- Replace usage of ChannelHost and removed first-pass composites with the new ChannelGateway and Channels.forHarness pattern.
- Implement the required participant callback on ingress channels, as ChannelGateway no longer assigns sender identity automatically.
- If using AiSdkHarness , update to the new agents/harness/ai-sdk entry point.