release

MSBuild Release Orchestration

This skill guides an agent through the MSBuild release process defined in documentation/release-checklist.md. The checklist is the single source of truth — this skill provides context on how to execute it.

Overview

MSBuild is a component that gets inserted into Visual Studio. VS ships monthly; MSBuild must branch and prepare its bits before VS is ready to take them. See the release process doc for the full timeline diagram.

The insertion pipeline routes MSBuild branches to VS branches:

• main → VS main (daily canary)
• vs* release branch → VS main (replaces main → main after branch snap)

VS handles the progression from main → rel/insiders → rel/stable on its own schedule. MSBuild's responsibility is to have final-branded bits in VS main before the insiders snap date.

Each monthly VS release produces:

• A new vs* branch from main
• Final branding on that branch
• A version bump in main
• DARC channel/subscription updates
• A VS insertion
• Post-GA publishing to nuget.org and docs

The process is organized into 6 timeline-gated phases (0–5), each with an explicit trigger.

Execution model: This skill is designed for an interactive Copilot session. The agent walks through each phase step-by-step, but every command that modifies state (git push, DARC writes, pipeline changes, PR creation) requires user approval before execution. Read-only queries (DARC get-*, git log, etc.) can run without approval.

Required Inputs

Before starting any phase, ensure you have these values (the user must provide them — version increments are irregular and cannot be computed):

Input	Example	How to determine
PREVIOUS_RELEASE_VERSION	18.5	Previous entry in the merge-flow chain
THIS_RELEASE_VERSION	18.6	Current VersionPrefix in eng/Versions.props (drop .0)
NEXT_VERSION	18.7	User-provided — not computable from current version
BRANCH_SNAP_DATE	2026-04-08	From VS-Dates wiki — when MSBuild branches vs* from main, insertion targets VS main
INSIDERS_SNAP_DATE	2026-04-22	From VS-Dates wiki — when VS snaps main → rel/insiders; final-branded bits must be in VS main before this
STABLE_SNAP_DATE	2026-05-06	From VS-Dates wiki — when VS promotes rel/insiders → rel/stable
VS_SHIP_DATE	2026-05-12	When VS ships publicly (GA) — triggers post-release tasks

Prerequisites

• gh cli
• az cli
• darc cli

Phase Summary

Phase	Trigger	Key Actions
0: Instantiate	User-initiated	Validate inputs, create GitHub tracking issue
1: Branch & Prepare	BRANCH_SNAP_DATE	Create vs* branch, DARC channel setup (batched PR), merge-flow config, VisualStudio.ChannelName
2: Bump Main	Phase 1 branch exists	Branding PR in main (version bump, baseline, pipeline YAML)
3: DARC Updates	Phase 2 merged	Channel reassignment, subscription updates (batched PR), verification
4: Final Branding	7 days before INSIDERS_SNAP_DATE	Public API promotion, Stabilize-Release.ps1, OptProf bootstrap, get final-branded bits into VS main before insiders snap
5: Post-GA	VS shipped (VS_SHIP_DATE)	nuget.org publish, docs, GitHub release, cleanup

DARC Batching

DARC write commands push to the maestro-configuration repo. Batch related changes into one PR:

1. Choose a branch name like release/msbuild-{{THIS_RELEASE_VERSION}}
2. Add --configuration-branch <name> --no-pr to every write command except the last
3. Last command: use --configuration-branch <name> without --no-pr to create the PR
4. Get the PR reviewed and merged

Read-only commands (get-default-channels, get-subscriptions, get-channel) don't need these flags.

Executing a Phase

When asked to execute a specific phase:

1. Read the full phase from documentation/release-checklist.md
2. Verify the trigger condition is met (previous phases completed)
3. Execute steps in order — respect sequential/parallel annotations
4. For DARC commands: batch writes into one configuration PR per phase
5. Record all output URLs in the tracking issue's artifact table
6. Mark checkboxes as completed in the tracking issue

Key Files

File	Purpose
documentation/release-checklist.md	Operational checklist — the source of truth
documentation/release.md	Process description: final branding, public API, major version steps
eng/Versions.props	VersionPrefix, PackageValidationBaselineVersion, BootstrapSdkVersion
.config/git-merge-flow-config.jsonc	Branch merge chain — update each release
azure-pipelines/vs-insertion.yml	VS insertion pipeline — AutoInsertTargetBranch mappings
azure-pipelines/vs-insertion-experimental.yml	Experimental insertion — TargetBranch parameter values
scripts/Stabilize-Release.ps1	Final branding automation (-DryRun to preview)
.vsts-dotnet.yml	Build pipeline — VisualStudio.ChannelName setting

Validation

After completing all phases, verify:

1. Branch vs{{THIS_RELEASE_VERSION}} exists and has final branding
2. Main has VersionPrefix = {{NEXT_VERSION}}.0
3. DARC: main → VS {{NEXT_VERSION}} channel, release branch → VS {{THIS_RELEASE_VERSION}} channel
4. VS insertion PR merged
5. Packages published to nuget.org
6. GitHub release created with tag v{{THIS_RELEASE_EXACT_VERSION}}

Error Recovery

• Branch already exists: Release was partially started — check the tracking issue for progress
• DARC channel already exists: Safe to continue — add-channel is idempotent
• Stabilize-Release.ps1 says "already stabilized": Skip — idempotent
• OptProf fails on first build: Expected — that's why we use main's OptProf data as fallback
• DARC configuration PR conflicts: Rebase the configuration branch on production and force-push

Major Version Releases

If NEXT_VERSION is a new major version (e.g., 18.x → 19.0), additional steps are needed after Phase 5. See release.md for:

• src/Shared/BuildEnvironmentHelper.cs — VS major version constants
• src/Shared/Constants.cs — version constants
• src/Framework/Telemetry/TelemetryConstants.cs — telemetry version