fix(mcp): resolve userId before JWT generation for agent block auth

[waleedlatif1]

Summary

• MCP tools called from Agent blocks fail with "Authentication failed" because the internal JWT is generated without userId
• The security hardening in fix(security): harden auth, SSRF, injection, and CORS across API routes #3792 removed the query-param fallback for userId in auth, but executeMcpTool was relying on that fallback when executionContext isn't passed (agent block path)
• Fix: resolve tool scope (which reads params._context.userId) before generating the JWT token, so userId is embedded in the token itself

Fixes #3922

Type of Change

• Bug fix

Testing

Tested manually

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Apr 4, 2026 2:01am

[cursor]

PR Summary

Medium Risk
Adjusts internal auth token generation for MCP tool execution; incorrect user scoping could break MCP calls or inadvertently authenticate as the wrong user if scope resolution is wrong.

Overview
Fixes MCP tool auth for agent block executions by resolving ToolExecutionScope (including params._context.userId) before calling generateInternalToken, ensuring the JWT embeds the correct userId even when executionContext is missing.

Adds a unit test that mocks generateInternalToken and asserts it is invoked with the _context.userId when executing an MCP tool without an explicit executionContext.

^{Reviewed by Cursor Bugbot for commit f182eb5. Configure here.}

[greptile-apps]

Greptile Summary

This PR fixes a bug where MCP tools called from Agent blocks would fail authentication because generateInternalToken was called with executionContext?.userId before resolveToolScope had been invoked — meaning the fallback to params._context.userId (the agent block path) was never reached. The fix is a minimal 3-line reorder: resolveToolScope(params, executionContext) is now called before JWT generation so mcpScope.userId is properly populated from either the execution context or the _context param embedded by the agent block. A targeted regression test is also added that verifies generateInternalToken receives the correct userId when executionContext is undefined.

Key changes:

• apps/sim/tools/index.ts: Moved resolveToolScope call above JWT token generation so mcpScope.userId is resolved from params._context.userId when executionContext is absent (agent block path).
• apps/sim/tools/index.test.ts: Added regression test inside describe('MCP Tool Execution') that calls executeTool with _context.userId but no executionContext, asserting mockGenerateInternalToken is called with the correct user ID.

Confidence Score: 5/5

Safe to merge — the fix is correct, minimal, and well-tested with a focused regression test.

The change is a 3-line reorder with no new logic: moving resolveToolScope above JWT generation so the fallback to params._context.userId is exercised. The regression test directly validates the fixed behavior. No P0/P1 concerns remain.

No files require special attention.

Important Files Changed

Filename	Overview
apps/sim/tools/index.ts	Minimal reorder fix: resolveToolScope now executes before generateInternalToken, correctly populating mcpScope.userId from params._context.userId in the agent block path.
apps/sim/tools/index.test.ts	Regression test added in the MCP Tool Execution describe block; verifies generateInternalToken receives the correct userId from params._context when executionContext is undefined, following the project's established hoisted-mock pattern.

_{Reviews (2): Last reviewed commit: "test(mcp): add regression test for agent..." | Re-trigger Greptile}

[waleedlatif1]

@greptile

[waleedlatif1]

@cursor review

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^{Reviewed by Cursor Bugbot for commit f182eb5. Configure here.}