Adopt a sealed Agent Host service graph

[roblourens]

Refactor the Agent Host node runtime to use one strict, sealed process-local service graph modeled after the VS Code shared process.

• Construct state, configuration, authentication, endpoint, proxy, and request foundations before telemetry.
• Register shared core and production host services as eagerly resolved local SyncDescriptors.
• Seal the service collection and reject late registrations while allowing descriptor resolution.
• Keep callback-bound AgentService roots in a narrow composition phase.
• Activate changeset and completion contributions separately with explicit disposal ownership.
• Inject diagnostics and edit attribution immutably into AgentService.
• Keep worktree isolation as the sole production-only post-composition bridge.
• Reduce the runtime facade so entry points resolve registered services through DI.
• Add node/AGENTS.md with service placement, descriptor, ownership, testing, and extension rules.

Validation: client typecheck and 639 targeted Agent Host tests pass. (Written by Copilot)

[Copilot]

Pull request overview

Centralizes Agent Host service construction, dependency injection, activation, and disposal under one runtime owner.

Changes:

• Splits service creation into foundation, descriptor, composition, and contribution phases.
• Replaces AgentService service getters with direct dependency injection.
• Adds service-graph tests and ownership documentation.

Show a summary per file

File	Description
.github/instructions/agentHostTesting.instructions.md	Links service-construction guidance.
src/vs/platform/agentHost/AGENTS.md	Updates architecture documentation.
src/vs/platform/agentHost/common/agentService.ts	Narrows the service interface.
src/vs/platform/agentHost/node/AGENTS.md	Documents construction and ownership rules.
src/vs/platform/agentHost/node/agentHostBootstrap.ts	Builds and owns the runtime graph.
src/vs/platform/agentHost/node/agentHostCommitOperationHandler.ts	Injects authentication directly.
src/vs/platform/agentHost/node/agentHostContributions.ts	Centralizes contribution activation.
src/vs/platform/agentHost/node/agentHostCustomizationEnablementService.ts	Updates ownership documentation.
src/vs/platform/agentHost/node/agentHostGitStateService.ts	Injects authentication directly.
src/vs/platform/agentHost/node/agentHostMain.ts	Resolves runtime services through DI.
src/vs/platform/agentHost/node/agentHostProxyResolver.ts	Constructor-injects configuration.
src/vs/platform/agentHost/node/agentHostPullRequestOperationHandler.ts	Injects authentication directly.
src/vs/platform/agentHost/node/agentHostServerMain.ts	Adopts runtime ownership and DI.
src/vs/platform/agentHost/node/agentHostServices.ts	Defines local service descriptors.
src/vs/platform/agentHost/node/agentService.ts	Accepts explicit collaborators and dependencies.
src/vs/platform/agentHost/node/agentServiceComposition.ts	Composes orchestration services.
src/vs/platform/agentHost/node/agentServiceFoundation.ts	Creates pre-DI foundation services.
src/vs/platform/agentHost/test/node/agentHostBootstrap.test.ts	Tests bootstrap and proxy initialization.
src/vs/platform/agentHost/test/node/agentHostCommitOperationHandler.test.ts	Updates authentication test fixtures.
src/vs/platform/agentHost/test/node/agentHostGitStateService.test.ts	Updates authentication test fixtures.
src/vs/platform/agentHost/test/node/agentHostPullRequestOperationHandler.test.ts	Updates authentication test fixtures.
src/vs/platform/agentHost/test/node/agentHostRequestService.test.ts	Tests constructor-bound proxy configuration.
src/vs/platform/agentHost/test/node/agentHostServices.test.ts	Tests registration, sealing, and disposal.
src/vs/platform/agentHost/test/node/agentService.test.ts	Uses composition-level test seams.
src/vs/platform/agentHost/test/node/agentServiceTestUtils.ts	Builds the production-like test graph.
src/vs/platform/agentHost/test/node/copilotAgent.test.ts	Removes obsolete proxy binding.
src/vs/platform/agentHost/test/node/protocolServerHandler.test.ts	Removes obsolete token method.

Review details

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Suppressed comments (1)

src/vs/platform/agentHost/AGENTS.md:708

• This ownership statement is outdated: these services are now registered as descriptors in registerAgentHostCoreServices, and InstantiationService constructs them. Since this is the architecture guide, naming composition as their constructor gives future service moves the wrong ownership model.

Both `IAgentHostPromptCache` and `IAgentHostSessionTitleSignal` are constructed
and registered by `createAgentServiceComposition`. Consumers resolve their
service identifiers through constructor injection; `AgentService` neither owns
nor exposes them.

• Files reviewed: 19/19 changed files
• Comments generated: 2
• Review effort level: Balanced

[Copilot]

Review details

Suppressed comments (1)

src/vs/platform/agentHost/node/agentHostContributions.ts:25

• If a later contribution/provider activation throws, this local store is never returned or disposed. The runtime catch disposes the service graph, but it does not own the createInstance contributions or workspaceFiles; previously registered contributions can therefore survive partial activation and leak their registrations. Make activation transactional by disposing store before rethrowing.

export function activateAgentHostContributions(accessor: ServicesAccessor, instantiationService: IInstantiationService): DisposableStore {
	const store = new DisposableStore();
	const changesetOperationService = accessor.get(IAgentHostChangesetOperationService);

• Files reviewed: 20/21 changed files
• Comments generated: 1
• Review effort level: Balanced