[tbyfield]

📖 Description

Adds a proposed design for an experimental Windows 365 for Agents (W365A) backend and links it from the development documentation. No implementation changes.

🔗 References

Refs #1615

🔍 Validation

• git diff --check origin/main...HEAD — passed.
• Runtime tests not run (documentation-only).

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• For features or changes requiring a spec: linked the issue with maintainer-applied feature-accepted
• For implementation: linked the required approved and merged design/API spec, or explained why no spec is required
• Feature issue remains open unless this PR completes all agreed implementation, validation, and documentation
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)
• If this PR changes Cargo.lock, the dependency-feed-check check passes (see pull request builds)

Implementation, Copilot-instruction and Cargo.lock checks are not applicable to this design-only PR. CLA status has not been verified.

📋 Issue Type

• Bug fix
• Feature
• Task

Microsoft Reviewers: Open in CodeFlow

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.

[Copilot]

🟡 Changes recommended

The design treats transport loss or a remote error as normal execution completion with exit code -1, obscuring structured error and outcome-uncertainty details while colliding with a valid Windows exit code.

1 open issue

• Report uncertain transport loss instead of synthetic exit -1 · New

What changed in this PR

Proposes an experimental Windows 365 for Agents backend for MXC’s container lifecycle operations, supporting the remote Cloud PC workflow described in #1615. This PR changes documentation only.

Changes:

• Defines reservation, readiness, command execution, release, and failure-recovery behavior.
• Specifies development-contract settings, security boundaries, staged delivery, and planned CI and manual validation.
• Links the proposal from the development documentation.

File	Description
docs/​development/​README.md	Adds a link to the backend proposal.
docs/​development/​architecture/​designs/​1615-w365a-backend/​README.md	Defines the proposed backend’s scope, lifecycle, contracts, security, and validation plan.

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

The checkout mismatch assertion discards a valid session ID needed for stop/deprovision cleanup, so the error handling must preserve that identity or attempt release while retaining it if cleanup fails.

No open issues 🎉

1 previously missed issue

In code that hasn't changed since last review

Preserve reservation identity when checkout computer ID mismatches

docs/​development/​architecture/​designs/​1615-w365a-backend/​README.md:414

[P2] When checkout returns a valid sessionId but a different computerId, this assertion discards a known reservation identity, leaving the caller without the ID required by stop/deprovision. Keep execution refused, but preserve an identity for cleanup in the structured error, or attempt release and retain that identity if cleanup fails. Align the identity and recovery sections with that choice, and distinguish this recoverable mismatch from a lost or malformed session ID in the fixture.

1 resolved since last review

• Report uncertain transport loss instead of synthetic exit -1

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Service-owner confirmation of pooled-ID equivalence and delegated-identity omission rules remains pending, alongside maintainer agreement on deferred nightly live validation and infrastructure ownership.

No open issues 🎉

_{Review effort: Balanced}

[Branden Bonaby (bbonaby)]

note: tbyfield looks like we're missing a api.md file to show the usage of this feature:
See: https://github.com/microsoft/mxc/blob/main/docs/development/guides/authoring-a-new-feature.md#write-the-spec

This will let us see how users are expected to use the new backend in the SDKs.