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spec/v0.4.0 clients/go/v0.4.0

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microsoft/agent-host-protocolJun 19, 2026 → Jun 19, 20260 days between releases

What's New

Go client v0.4.0 implements AHP 0.4.0 with typed message origins, reducer parity, and Go-specific breaking API changes.

Breaking Changes

  • Go `Message.Origin` changed from untyped `json.RawMessage` to typed `MessageOrigin`/`MessageKind`, requiring code updates for origin handling.
  • `ChangesetOperationTargetRange` now uses a nested `TextRange` structure, breaking existing range construction and parsing.
  • `ToolResultSubagentContent.Resource` now denotes a worker chat URI (`ahp-chat:/<cid>`) instead of a session URI, changing sub-agent resource semantics.

New Features

  • Added `SessionDefaultChatChangedAction` for steering input.
  • Added `ErrorInfo.Meta` map for provider-specific error metadata.
  • Added optional `RootState._meta` property bag.
  • Added support for `ChatInteractivity` enum values.
  • Implemented full reducers for `ApplyActionToChangeset`, `Annotations`, and `ResourceWatch`.

Improvements

  • Flattened `ChatState` structure to match the spec and Swift implementation.
  • Typed `MessageOrigin` and `MessageKind` improve message attribution safety.
  • Achieved reducer parity with spec and Swift for changeset, annotations, and resource watch.
  • Fixed `ActionEnvelope.Origin` encoding to omit when absent.

Bug Fixes

  • Fixed `ActionEnvelope.Origin` encoding so it is omitted when absent.

Upgrade Notes

This is the Go client implementation of AHP 0.4.0, not a drop-in upgrade from the spec release; update Go code for typed `MessageOrigin`, nested `TextRange`, and chat-URI subagent resources. Regenerate or adjust serialization for `ActionEnvelope.Origin` and any code relying on untyped origins. Verify reducer behavior against the spec/Swift parity expectations.

The Two Releases

spec/v0.4.0

AHP Spec v0.4.0

Jun 19, 2026· 4 months ago

Core protocol update introducing the chat channel, typed message origins, and metadata fields for per-event context.

Full release notes
clients/go/v0.4.0

Go module v0.4.0

Jun 19, 2026· 4 months ago

Go module implementation of AHP 0.4.0, matching Swift and Spec changes with typed origins and reducer parity.

Full release notes