Harden cross-suite E2E process cleanup

[stephentoub]

Summary

• fix shared proxy shutdown at the source by rejecting late connections and force-closing active HTTP/TLS connections before awaiting server close
• centralize bounded Node test-child shutdown with graceful SIGTERM, SIGKILL escalation, and race-safe timer/listener cleanup
• bound Python and Go replay-proxy shutdown, including Windows process-tree termination and visible cleanup failures
• replace nested PowerShell startup in .NET and Rust Windows zero-timeout shell E2Es with cmd-native delays; strengthen Rust coverage by proving the process remains killable

These are test harness reliability fixes only; SDK runtime behavior is unchanged. Release-artifact checksum retry behavior is untouched.

Validation

• shared harness: full suite (69 passed), including active-response shutdown regression coverage
• Node: typecheck, focused Prettier/ESLint, build, and affected E2Es (9 passed)
• Python: focused Ruff/ty checks and OAuth E2Es (4 passed)
• Go: test harness package/vet and OAuth E2E; one unrelated direct-RPC OAuth status retry passed when isolated
• Rust: nightly formatting, check/Clippy, and targeted Windows zero-timeout E2E
• .NET: targeted Windows zero-timeout E2E

The final design and repository-wide occurrence audit were independently reviewed with Claude Opus 5.

[Copilot]

Copilot review overview

🟢 Approval recommended

The teardown changes are scoped, race-safe, and preserve the intended E2E assertions.

Review tier: Balanced
Findings: None

What changed in this PR

Hardens cross-platform E2E teardown without changing SDK runtime behavior.

Changes:

• Adds bounded graceful shutdown with SIGKILL escalation for the Node OAuth MCP helper.
• Replaces nested PowerShell startup with a cmd-native Windows test command.

File	Description
nodejs/​test/​e2e/​mcp_oauth.e2e.test.ts	Adds race-safe, bounded child-process teardown.
dotnet/​test/​E2E/​RpcAdditionalEdgeCasesE2ETests.cs	Simplifies Windows delay and marker handling.

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[github-actions]

SDK Consistency Review

This PR is scoped entirely to test/E2E harness infrastructure, not public SDK client APIs. No files under nodejs/src/, python/copilot/, go/ (non-test), dotnet/src/, java/sdk/src/main/, or rust/src/ are modified.

Changes reviewed:

• Graceful shutdown for the replaying proxy child process (SIGTERM → wait → SIGKILL/taskkill, with timeouts) added to the Go (testharness/proxy.go) and Python (testharness/proxy.py) E2E harnesses.
• A new stopChildProcess helper with the same graceful-then-forceful shutdown pattern added to the Node.js E2E harness (sdkTestHelper.ts), replacing ad-hoc kill logic in extension_env_access.e2e.test.ts and mcp_oauth.e2e.test.ts.
• test/harness/connectProxy.ts (shared harness used by Node E2E tests) gets idempotent/concurrent-safe stop() and rejects in-flight requests while stopping.
• .NET and Rust E2E tests get an unrelated but related fix: adjusted zero-timeout shell test commands, and the Rust test now explicitly kills the leaked shell process via ShellKillRequest at the end of the test (good cleanup hygiene) — this exercises an existing public API rather than adding one.

Consistency assessment: Since this is test-harness-only (no public SDK API surface changed), there's no API naming/parameter/return-type parity issue to flag under the review criteria.

Minor, non-blocking observation: the "wait, then escalate to force-kill with a timeout" pattern was applied to the Go, Python, and Node.js test harnesses, but not to the Java or .NET E2E test harnesses' proxy-stop logic (only a command-string tweak landed in dotnet/test/E2E/RpcAdditionalEdgeCasesE2ETests.cs). If proxy processes have been observed to hang on stop in CI for those languages too, it may be worth applying the same graceful-shutdown pattern there in a follow-up for infra consistency — but this is test tooling, not a user-facing API, so it's a suggestion rather than a blocking issue.

No inline code comments needed; nothing here creates a cross-language SDK API inconsistency.

Generated by SDK Consistency Review Agent for #2539 · copilot · sonnet50 · 31.9 AIC · ⌖ 12.1 AIC · ⊞ 9.7K · ◷