refactor(provider-core): MCP provider sessions live in a McpProviderSessions service

[juliusmarminge]

The per-thread T3 MCP credentials lived in a module-level Map in provider-core/server/mcpSession.ts, behind set/read/clearMcpProviderSession functions that any module could call. That's hidden global state, and it leaked between tests.

This PR adds @t3tools/provider-core/server/McpProviderSessions, a service with set, read and clear. The server provides it once, so ProviderSessionManager and every adapter share one instance.

• Adapters yield it and read the session once per launch. The pure option builders (claudeMcpQueryOverrides, codexThreadRuntimeParams, cursorMcpServers, acpMcpContext) take the session they're given instead of looking it up.
• makeClaudeAdapterV2 and makeCodexAdapterV2 are now Effect.fn, so they can yield the service.
• Each adapter and driver env type lists McpProviderSessions. Tests get a fresh instance per layer, which replaces the old manual set/clear on the global.

Part of the provider-package audit (stack #17428).

Model: Claude Opus 5.5 via Claude Code in T3 Code.

🤖 Generated with Claude Code

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR replaces global per-thread MCP credential state with an Effect service and threads it through the session manager and numerous provider launch and runtime paths. Because the shared-infrastructure refactor changes credential lifecycle and authentication-sensitive behavior across 48 files, human review is warranted.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	5.0 KiB	—	6.8 KiB	✅
Codex	Thread snapshot wire	—	3.8 KiB	—	4.9 KiB	✅
Codex	Live turn WebSocket wire	—	1.2 KiB	—	2.0 KiB	✅
Codex	Live turn WebSocket decoded	—	20.9 KiB	—	29.3 KiB	✅
Codex	Live turn messages	—	2	—	8	✅
Claude	Total thread wire	—	5.0 KiB	—	6.8 KiB	✅
Claude	Thread snapshot wire	—	3.8 KiB	—	4.9 KiB	✅
Claude	Live turn WebSocket wire	—	1.2 KiB	—	2.0 KiB	✅
Claude	Live turn WebSocket decoded	—	21.2 KiB	—	29.3 KiB	✅
Claude	Live turn messages	—	2	—	8	✅

Baseline: unavailable · PR result: 519937b · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 108.5 KiB
• Claude decoded thread snapshot: 108.8 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between 7da182d and 519937b.

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📒 Files selected for processing (48)

• apps/server/src/mcp/OrchestratorMcpToolkit.integration.test.ts
• apps/server/src/orchestration-v2/AcpRegistryOrchestratorV2.live.test.ts
• apps/server/src/orchestration-v2/Adapters/AcpAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/AcpRegistryAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/AntigravityAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts
• apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts
• apps/server/src/orchestration-v2/Adapters/CursorAdapterV2.testkit.ts
• apps/server/src/orchestration-v2/Adapters/GrokAdapterV2.test.ts
• apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts
• apps/server/src/orchestration-v2/ClaudeAutomaticDelivery.integration.test.ts
• apps/server/src/orchestration-v2/CursorOrchestratorV2.live.test.ts
• apps/server/src/orchestration-v2/DelegatedCompletionDelivery.test.ts
• apps/server/src/orchestration-v2/GrokOrchestratorV2.live.test.ts
• apps/server/src/orchestration-v2/OpenCode2OrchestratorV2.live.test.ts
• apps/server/src/orchestration-v2/ProjectSettingsUpgrade.integration.test.ts
• apps/server/src/orchestration-v2/ProviderSessionManager.test.ts
• apps/server/src/orchestration-v2/ProviderSessionManager.ts
• apps/server/src/orchestration-v2/runtimeLayer.test.ts
• apps/server/src/orchestration-v2/testkit/ProviderReplayHarness.ts
• apps/server/src/provider/Drivers/AntigravityDriver.test.ts
• apps/server/src/provider/Drivers/AntigravityDriver.ts
• apps/server/src/provider/Drivers/CodexDriver.test.ts
• apps/server/src/provider/ProviderInstanceRegistry.test.ts
• apps/server/src/provider/ProviderRegistry.test.ts
• apps/server/src/server.ts
• packages/provider-acp-registry/src/server/adapter.ts
• packages/provider-acp/src/server/adapter.ts
• packages/provider-core/package.json
• packages/provider-core/src/server/McpProviderSessions.ts
• packages/provider-core/src/server/mcpSession.ts
• packages/provider-cursor/src/server/adapter.test.ts
• packages/provider-cursor/src/server/adapter.ts
• packages/provider-cursor/src/server/driver.test.ts
• packages/provider-grok/src/server/adapter.ts
• packages/provider-grok/src/server/driver.test.ts
• packages/provider-muse/src/server/adapter.test.ts
• packages/provider-muse/src/server/adapter.ts
• packages/provider-muse/src/server/driver.ts
• packages/provider-opencode/src/server/adapter.test.ts
• packages/provider-opencode/src/server/adapter.ts
• packages/provider-opencode/src/server/driver.test.ts
• packages/provider-opencode/src/server/v2/adapter.ts
• packages/provider-pi/src/server/adapter.test.ts
• packages/provider-pi/src/server/adapter.ts
• packages/provider-pi/src/server/driver.test.ts

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💤 Files with no reviewable changes (1)

• packages/provider-core/src/server/mcpSession.ts

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📝 Walkthrough

Walkthrough

The pull request adds an Effect-based McpProviderSessions service, removes the legacy synchronous registry, and updates provider adapters, orchestration code, runtime layers, and tests to use the service.

Changes

MCP provider session migration

Layer / File(s)	Summary
Session service and runtime wiring packages/provider-core/src/server/McpProviderSessions.ts, packages/provider-core/src/server/mcpSession.ts, packages/provider-core/package.json, apps/server/src/server.ts	The new service stores, reads, and clears thread-scoped MCP configuration. The legacy registry is removed. Shared runtime and test layers provide the new service.
Provider adapter integration packages/provider-acp/src/server/adapter.ts, packages/provider-cursor/src/server/adapter.ts, apps/server/src/orchestration-v2/Adapters/ClaudeAdapterV2.ts, apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts, packages/provider-*/src/server/adapter.ts	Adapters obtain MCP sessions from the Effect service. Several helper functions now receive resolved session configuration directly. Adapter construction gains service requirements where needed.
Provider session management apps/server/src/orchestration-v2/ProviderSessionManager.ts, apps/server/src/orchestration-v2/testkit/ProviderReplayHarness.ts	Credential preparation and cleanup use effectful service operations. Credential-ID checks remain in cleanup logic. Replay harness layers include the service.
Test environment and fixtures apps/server/src/orchestration-v2/**/*.test.ts, packages/provider-*/src/server/*.test.ts, apps/server/src/provider/**/*.test.ts	Tests provide McpProviderSessions.layer, seed sessions through set, read sessions through read, and remove direct global-registry cleanup. Adapter fixtures use effectful construction where required.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Refactor

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Merge Risk: ⚪ Minimal · up to 51993

The session migration has no identified issue requiring a fix before merge.

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check		The description clearly explains the problem and the implementation, but it omits the required Scope and approval section and focused Verification results. It references stack #17428 without providing…	Add a ## Scope and approval section with the triaged issue or explicit maintainer approval, including a link and approval comment. Add a ## Verification section that lists the focused tests or manual checks run, their observed results, …

✅ Passed checks (3 passed)

Check name	Status	Explanation
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.
Title check		The title clearly and concisely identifies the main change: moving MCP provider sessions into an McpProviderSessions service.

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Full details: Description check

Explanation

The description clearly explains the problem and the implementation, but it omits the required Scope and approval section and focused Verification results. It references stack #17428 without providing the required issue or approval link.

Resolution

Add a ## Scope and approval section with the triaged issue or explicit maintainer approval, including a link and approval comment. Add a ## Verification section that lists the focused tests or manual checks run, their observed results, and any checks not completed.

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