[dezren39]

Fixes the diagnosability half of #290 (the Nix-build flake itself does not reproduce locally — see below).

Problem

TestTerminateOrphanedSessionEndsTheUpstreamSession flaked in the Nix build gate with the orphaned session saw 0 DELETE(s) (PR #275's run 39121884524), and the test discarded the evidence that would identify the cause:

• the mock upstream counted only DELETEs for live sessions — a DELETE for a session the upstream had forgotten is answered 404 and counted as nothing, indistinguishable from no DELETE arriving at all;
• the test never captured the upstream.session.orphaned events, which are exactly where TerminateOrphanedSession reports why a termination failed.

Fix (test-only)

• sessionUpstream records every DELETE attempt and its session id (the daemon package's orphanUpstream mock already does this — the pool mock now matches it).
• The test captures terminated and orphaned events via a new lifecycleCapture helper (the existing lifecycleEvents hook can hold only one kind), and its failure message reports attempts, session ids, and orphaned reasons.

The three failure modes now read differently:

• no DELETE arrived → attempts=0 (+ orphaned reason if the dial errored);
• DELETE arrived for a forgotten session → attempts=1, deleted=[sess-1], deletes=0, terminated still fires (404 is success by design in closeSession);
• DELETE errored → orphaned event carries the reason.

Verification

• Sabotage run (upstream forgets the session before termination) produced exactly the second signature above, confirming the diagnostics distinguish the modes.
• Full internal/pool suite green; target test -count=200, GOMAXPROCS=1 -count=100 and -race green locally. The flake is Nix-sandbox-only (100/100 local passes pre-fix, per mcpx: TestTerminateOrphanedSessionEndsTheUpstreamSession flakes in the Nix build (0 DELETEs) and hides its own failure reason #290), so mcpx: TestTerminateOrphanedSessionEndsTheUpstreamSession flakes in the Nix build (0 DELETEs) and hides its own failure reason #290 stays open until a future Nix-build flake prints its mode — or repeated green builds close it.
• Mirrored to dezren39/nix in the same run (mcpx set; the test file was byte-identical in both repos), referencing this issue.

Refs #290

---

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Summary by CodeRabbit

• Tests
  • Expanded coverage for session cleanup when an upstream deletion attempt returns “not found.”
  • Added checks for orphaned and terminated session lifecycle events, including verification of the reported session details.

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-19T06:09:47.187100Z	—	PR opened

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📥 Commits

Reviewing files that changed from the base of the PR and between 7b081c3 and 9ecdeae.

📒 Files selected for processing: 1

• pkgs/mcpx/internal/pool/upstream_session_test.go

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📝 Walkthrough

The upstream session test mock now records DELETE attempts, including attempts that receive 404. The orphan-termination test captures termination and orphan lifecycle events and checks that exactly one termination event identifies remote and sess-1.

Changes: Upstream session termination tests

Layer / File(s)	Summary
DELETE and lifecycle event assertions pkgs/mcpx/internal/pool/upstream_session_test.go	The mock records attempted session IDs before checking whether a session is live. The test captures termination and orphan events, checks the expected termination event, and includes attempt and event details in failure messages.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 9ecde

This change updates test observability and assertions without changing production behavior. No concrete merge-blocking risk remains.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly describes the main change: improving the orphaned-session test so its failure mode is identifiable.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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