v0.189.0 spec/v0.4.0
microsoft/agent-host-protocolJun 19, 2026 → Jun 19, 20260 days between releases
What's New
Spec v0.4.0 adds a chat channel and typed message origins, with breaking changes to SessionStatus and chat state.
Breaking Changes
- SessionStatus is now an OptionSet (UInt32) instead of an Int, so existing numeric status handling must be reworked.
- ChangesetOperationTarget ranges are now nested TextRange structures rather than the previous flat range shape.
- SessionState no longer carries turns; turn data has moved into ChatState.
- The session/chatsChanged event is removed in favor of discrete chatAdded, chatRemoved, and chatUpdated actions.
New Features
- New ahp-chat: channel exposing discrete chat catalog actions for adding, removing, and updating chats.
- MessageOrigin is now a named type whose MessageKind gains Agent and Tool kinds for non-user-initiated turns.
- ChatInteractivity enum added to describe how interactive a chat is.
- ChangesetOperationStatus gains a Disabled case so clients can render unavailable operations as disabled.
- Snapshot.state now supports ResourceWatchState, and ErrorInfo gains an optional _meta provider metadata bag.
Improvements
- ChatState is flattened with inlined properties and ISO 8601 timestamps for simpler consumption.
- Per-turn chat actions accept an optional _meta slot for portable provider-specific context such as sub-agent attribution.
- ConfigPropertySchema gains an optional additionalProperties schema for object-typed config properties.
- New changeset/contentChanged action supports full-replacement batched file updates and bulk refreshes.
- ChangesetOperation gains an optional group identifier for organizing related operations in the UI.
Upgrade Notes
This is a spec-level bump, so regenerate or re-vendor any generated clients and update serializers for the new OptionSet status, nested TextRange targets, and relocated chat turns. Replace listeners on session/chatsChanged with handlers for the three discrete chat actions, and treat the new _meta and additionalProperties fields as optional. Note the two releases cover different scopes (product build vs. protocol spec), so validate compatibility against the spec version your host implements.
The Two Releases
v0.189.0
Jun 19, 2026· 4 months ago
This release focuses on dashboard improvements, proxy hardening, and SDK enhancements, including the upgrade to Tailwind v4 and better connection handling for Python clients.
Full release notesAHP 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