v3.8.6 spec/v0.2.0
microsoft/agent-host-protocolMay 25, 2026 → May 28, 20263 days between releases
What's New
Spec v0.2.0 overhauls protocol channels, resources, and telemetry; unrelated to v3.8.6 maintenance fixes.
Breaking Changes
- Every command and notification now carries a top-level `channel: URI`, with per-channel state types and action unions relocated under `types/channels-*/`.
- Customizations are redesigned as a typed two-level tree, replacing the previous flat representation.
- The content-bearing `resource*` family is now formally bidirectional and appears in `ServerCommandMap`, changing method directionality.
- `resourceWrite` gains `mode`, `position`, and `ifMatch` parameters, and a new `Conflict` (-32011) error code is returned for stale conditional writes.
New Features
- New `otlp/*` notifications (`exportLogs`, `exportTraces`, `exportMetrics`) for telemetry export.
- New `resourceResolve` (stat + realpath, throwing `NotFound`) and `resourceMkdir` (`mkdir -p` semantics) requests.
- New `createResourceWatch` request plus the `ahp-resource-watch:/<id>` channel with a `resourceWatch/changed` action for long-lived file-change streams.
- New `session/agentChanged`, `session/customizationRemoved`, `session/changesetsChanged` notifications and the `changeset/*` action family.
- `UserMessage._meta` field added for provider-specific metadata.
Improvements
- First release produced by the unified spec release pipeline (`spec/v*` tags) with schema artifacts attached to the GitHub Release.
- Optimistic concurrency support for resource writes via `ifMatch`.
- Channel-scoped state and action types are now organized into dedicated `types/channels-*/` modules for clearer structure.
Upgrade Notes
This is a spec-level release, not a continuation of the v3.8.6 code line, so treat it as a fresh major integration rather than a patch upgrade. Consumers must migrate to the top-level `channel` URI model, rebuild customization handling against the new two-level tree, and handle the new `Conflict` error when using `ifMatch` on writes. Regenerate clients from the attached schema artifacts and verify any resource-write call sites for the added `mode`/`position` parameters.
The Two Releases
v3.8.6
May 25, 2026· 5 months ago
A maintenance release that adds Indonesian model support, fixes interpolation handling for NaN values, and hardens CI workflows.
Full release notesAHP Spec v0.2.0
May 28, 2026· 5 months ago
First unified spec release introducing channel reorganization, resource management, and telemetry notifications.
Full release notes