Harden Agent Host E2E and protocol integration tests

[roblourens]

Hardens the Agent Host E2E and protocol integration tests following the failures reported in this PR comment.

Changes

• use platform-aware protocol operation timeouts with extra Windows and coverage headroom
• register pending JSON-RPC calls before sending to avoid fast-response races
• centralize bounded graceful server shutdown with forced termination fallback
• await server shutdown across protocol suites to avoid process overlap
• track and clean up secondary WebSocket clients on failure paths
• replace wall-clock sleeps with protocol barriers and turn-specific notification matching
• add retry-backed temporary resource cleanup for Windows

Validation

• npm run typecheck-client
• npm run precommit
• Agent Host protocol integration tests: 115 passing, 1 pending
• reported terminal E2E cases for Claude: 2 passing
• reported terminal E2E cases for Copilot: 2 passing
• final code review: no findings

(Written by Copilot)

[Copilot]

Pull request overview

Note

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Hardens Agent Host E2E + protocol integration tests to reduce flakiness (timeouts/races), improve shutdown/cleanup reliability, and avoid cross-suite process overlap.

Changes:

• Introduces platform/coverage-aware protocol operation timeouts and removes wall-clock sleeps in favor of protocol barriers.
• Registers pending JSON-RPC calls before sending to avoid fast-response races; improves client cleanup paths.
• Centralizes graceful server shutdown with a bounded timeout and SIGKILL fallback; updates protocol suites to await shutdown.

Show a summary per file

File	Description
src/vs/platform/agentHost/test/node/serverIntegrationTestHelpers.ts	Adds protocol timeouts, fixes JSON-RPC call ordering race, and centralizes bounded server shutdown (stopServer).
src/vs/platform/agentHost/test/node/protocol/turnExecution.integrationTest.ts	Replaces sleeps with turn-specific notification matching and uses shared stopServer.
src/vs/platform/agentHost/test/node/protocol/toolApproval.integrationTest.ts	Switches suite teardown to await stopServer with extended timeout.
src/vs/platform/agentHost/test/node/protocol/sessionLifecycle.integrationTest.ts	Tracks/cleans secondary clients; replaces sleeps with protocol barriers; awaits server shutdown.
src/vs/platform/agentHost/test/node/protocol/sessionFeatures.integrationTest.ts	Switches suite teardown to await stopServer with extended timeout.
src/vs/platform/agentHost/test/node/protocol/sessionDiffs.integrationTest.ts	Switches suite teardown to await stopServer with extended timeout.
src/vs/platform/agentHost/test/node/protocol/sessionConfig.integrationTest.ts	Replaces bespoke stdin-close shutdown with centralized stopServer.
src/vs/platform/agentHost/test/node/protocol/resourceOperations.integrationTest.ts	Adds retry-backed temp dir cleanup (Windows-friendly) and secondary client cleanup; awaits server shutdown.
src/vs/platform/agentHost/test/node/protocol/otlpLogs.integrationTest.ts	Updates timeouts and suite teardown to await stopServer.
src/vs/platform/agentHost/test/node/protocol/networkDiagnostics.integrationTest.ts	Awaits target close and server shutdown with extended timeout.
src/vs/platform/agentHost/test/node/protocol/multiClient.integrationTest.ts	Tracks/cleans secondary clients; replaces sleeps with protocol barriers; awaits server shutdown.
src/vs/platform/agentHost/test/node/protocol/handshake.integrationTest.ts	Improves raw client cleanup with try/finally; updates timeouts and server teardown.
src/vs/platform/agentHost/test/node/protocol/clientTools.integrationTest.ts	Switches suite teardown to await stopServer with extended timeout.
src/vs/platform/agentHost/test/node/protocol/agentHostServer.integrationTest.ts	Switches suite teardown to await stopServer with extended timeout.
src/vs/platform/agentHost/test/node/e2e/harness/agentHostE2ETestHarness.ts	Removes local shutdown helper and reuses shared stopServer.

Review details

Comments suppressed due to low confidence (1)

src/vs/platform/agentHost/test/node/serverIntegrationTestHelpers.ts:1

• In the catch block, reject(error) can reject with a non-Error value (unknown), while the rest of this helper (and IPendingCall.reject) assumes Error. To keep error handling consistent and predictable across tests, coerce error into an Error instance before rejecting (e.g., error instanceof Error ? error : new Error(String(error))).

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• Files reviewed: 15/15 changed files
• Comments generated: 2
• Review effort level: Low