fix(call-chain): x-sim-via propagation for API blocks and MCP tools

apps/docs/content/docs/en/execution/basics.mdx

@@ -97,6 +97,7 @@ Understanding these core principles will help you build better workflows:
 3. **Smart Data Flow**: Outputs flow automatically to connected blocks
 4. **Error Handling**: Failed blocks stop their execution path but don't affect independent paths
 5. **State Persistence**: All block outputs and execution details are preserved for debugging
+6. **Cycle Protection**: Workflows that call other workflows (via Workflow blocks, MCP tools, or API blocks) are tracked with a call chain. If the chain exceeds 25 hops, execution is stopped to prevent infinite loops
 
 ## Next Steps
 

apps/sim/app/api/mcp/tools/execute/route.ts

@@ -3,6 +3,7 @@ import type { NextRequest } from 'next/server'
 import { getHighestPrioritySubscription } from '@/lib/billing/core/plan'
 import { getExecutionTimeout } from '@/lib/core/execution-limits'
 import type { SubscriptionPlan } from '@/lib/core/rate-limiter/types'
+import { SIM_VIA_HEADER } from '@/lib/execution/call-chain'
 import { getParsedBody, withMcpAuth } from '@/lib/mcp/middleware'
 import { mcpService } from '@/lib/mcp/service'
 import type { McpTool, McpToolCall, McpToolResult } from '@/lib/mcp/types'
@@ -178,8 +179,14 @@ export const POST = withMcpAuth('read')(
         'sync'
       )
 
+      const simViaHeader = request.headers.get(SIM_VIA_HEADER)
+      const extraHeaders: Record<string, string> = {}
+      if (simViaHeader) {
+        extraHeaders[SIM_VIA_HEADER] = simViaHeader
+      }
+
       const result = await Promise.race([
-        mcpService.executeTool(userId, serverId, toolCall, workspaceId),
+        mcpService.executeTool(userId, serverId, toolCall, workspaceId, extraHeaders),
         new Promise<never>((_, reject) =>
           setTimeout(() => reject(new Error('Tool execution timeout')), executionTimeout)
         ),

apps/sim/executor/constants.ts

@@ -158,7 +158,6 @@ export const DEFAULTS = {
   MAX_LOOP_ITERATIONS: 1000,
   MAX_FOREACH_ITEMS: 1000,
   MAX_PARALLEL_BRANCHES: 20,
-  MAX_WORKFLOW_DEPTH: 10,
   MAX_SSE_CHILD_DEPTH: 3,
   EXECUTION_TIME: 0,
   TOKENS: {

apps/sim/executor/handlers/agent/agent-handler.test.ts

@@ -123,7 +123,6 @@ describe('AgentBlockHandler', () => {
   let handler: AgentBlockHandler
   let mockBlock: SerializedBlock
   let mockContext: ExecutionContext
-  let originalPromiseAll: any
 
   beforeEach(() => {
     handler = new AgentBlockHandler()
@@ -135,8 +134,6 @@ describe('AgentBlockHandler', () => {
       configurable: true,
     })
 
-    originalPromiseAll = Promise.all
-
     mockBlock = {
       id: 'test-agent-block',
       metadata: { id: BlockType.AGENT, name: 'Test Agent' },
@@ -209,8 +206,6 @@ describe('AgentBlockHandler', () => {
   })
 
   afterEach(() => {
-    Promise.all = originalPromiseAll
-
     try {
       Object.defineProperty(global, 'window', {
         value: undefined,
@@ -271,38 +266,7 @@ describe('AgentBlockHandler', () => {
       expect(result).toEqual(expectedOutput)
     })
 
-    it('should preserve executeFunction for custom tools with different usageControl settings', async () => {
-      let capturedTools: any[] = []
-
-      Promise.all = vi.fn().mockImplementation((promises: Promise<any>[]) => {
-        const result = originalPromiseAll.call(Promise, promises)
-
-        result.then((tools: any[]) => {
-          if (tools?.length) {
-            capturedTools = tools.filter((t) => t !== null)
-          }
-        })
-
-        return result
-      })
-
-      mockExecuteProviderRequest.mockResolvedValueOnce({
-        content: 'Using tools to respond',
-        model: 'mock-model',
-        tokens: { input: 10, output: 20, total: 30 },
-        toolCalls: [
-          {
-            name: 'auto_tool',
-            arguments: { input: 'test input for auto tool' },
-          },
-          {
-            name: 'force_tool',
-            arguments: { input: 'test input for force tool' },
-          },
-        ],
-        timing: { total: 100 },
-      })
-
+    it('should preserve usageControl for custom tools and filter out "none"', async () => {
       const inputs = {
         model: 'gpt-4o',
         userPrompt: 'Test custom tools with different usageControl settings',
@@ -372,51 +336,21 @@ describe('AgentBlockHandler', () => {
 
       await handler.execute(mockContext, mockBlock, inputs)
 
-      expect(Promise.all).toHaveBeenCalled()
+      const providerCall = mockExecuteProviderRequest.mock.calls[0]
+      const tools = providerCall[1].tools
 
-      expect(capturedTools.length).toBe(2)
+      expect(tools.length).toBe(2)
 
-      const autoTool = capturedTools.find((t) => t.name === 'auto_tool')
-      const forceTool = capturedTools.find((t) => t.name === 'force_tool')
-      const noneTool = capturedTools.find((t) => t.name === 'none_tool')
+      const autoTool = tools.find((t: any) => t.name === 'auto_tool')
+      const forceTool = tools.find((t: any) => t.name === 'force_tool')
+      const noneTool = tools.find((t: any) => t.name === 'none_tool')
 
       expect(autoTool).toBeDefined()
       expect(forceTool).toBeDefined()
       expect(noneTool).toBeUndefined()
 
       expect(autoTool.usageControl).toBe('auto')
       expect(forceTool.usageControl).toBe('force')
-
-      expect(typeof autoTool.executeFunction).toBe('function')
-      expect(typeof forceTool.executeFunction).toBe('function')
-
-      await autoTool.executeFunction({ input: 'test input' })
-      expect(mockExecuteTool).toHaveBeenCalledWith(
-        'function_execute',
-        expect.objectContaining({
-          code: 'return { result: "auto tool executed", input }',
-          input: 'test input',
-        }),
-        false, // skipPostProcess
-        expect.any(Object) // execution context
-      )
-
-      await forceTool.executeFunction({ input: 'another test' })
-      expect(mockExecuteTool).toHaveBeenNthCalledWith(
-        2, // Check the 2nd call
-        'function_execute',
-        expect.objectContaining({
-          code: 'return { result: "force tool executed", input }',
-          input: 'another test',
-        }),
-        false, // skipPostProcess
-        expect.any(Object) // execution context
-      )
-
-      const providerCall = mockExecuteProviderRequest.mock.calls[0]
-      const requestBody = providerCall[1]
-
-      expect(requestBody.tools.length).toBe(2)
     })
 
     it('should filter out tools with usageControl set to "none"', async () => {
@@ -1763,6 +1697,52 @@ describe('AgentBlockHandler', () => {
       expect(providerCallArgs[1].tools[0].name).toBe('search_files')
     })
 
+    it('should pass callChain to executeProviderRequest for MCP cycle detection', async () => {
+      mockFetch.mockImplementation(() =>
+        Promise.resolve({ ok: true, json: () => Promise.resolve({}) })
+      )
+
+      const inputs = {
+        model: 'gpt-4o',
+        userPrompt: 'Search for files',
+        apiKey: 'test-api-key',
+        tools: [
+          {
+            type: 'mcp',
+            title: 'search_files',
+            schema: {
+              type: 'object',
+              properties: {
+                query: { type: 'string', description: 'Search query' },
+              },
+              required: ['query'],
+            },
+            params: {
+              serverId: 'mcp-search-server',
+              toolName: 'search_files',
+              serverName: 'search',
+            },
+            usageControl: 'auto' as const,
+          },
+        ],
+      }
+
+      const contextWithCallChain = {
+        ...mockContext,
+        workspaceId: 'test-workspace-123',
+        workflowId: 'test-workflow-456',
+        callChain: ['wf-parent', 'test-workflow-456'],
+      }
+
+      mockGetProviderFromModel.mockReturnValue('openai')
+
+      await handler.execute(contextWithCallChain, mockBlock, inputs)
+
+      expect(mockExecuteProviderRequest).toHaveBeenCalled()
+      const providerCallArgs = mockExecuteProviderRequest.mock.calls[0][1]
+      expect(providerCallArgs.callChain).toEqual(['wf-parent', 'test-workflow-456'])
+    })
+
     it('should handle multiple MCP tools from the same server efficiently', async () => {
       const fetchCalls: any[] = []
 
@@ -2139,21 +2119,10 @@ describe('AgentBlockHandler', () => {
         expect(tools.length).toBe(0)
       })
 
-      it('should use DB code for executeFunction when customToolId resolves', async () => {
+      it('should use DB schema when customToolId resolves', async () => {
         const toolId = 'custom-tool-123'
         mockFetchForCustomTool(toolId)
 
-        let capturedTools: any[] = []
-        Promise.all = vi.fn().mockImplementation((promises: Promise<any>[]) => {
-          const result = originalPromiseAll.call(Promise, promises)
-          result.then((tools: any[]) => {
-            if (tools?.length) {
-              capturedTools = tools.filter((t) => t !== null)
-            }
-          })
-          return result
-        })
-
         const inputs = {
           model: 'gpt-4o',
           userPrompt: 'Format a report',
@@ -2174,19 +2143,12 @@ describe('AgentBlockHandler', () => {
 
         await handler.execute(mockContext, mockBlock, inputs)
 
-        expect(capturedTools.length).toBe(1)
-        expect(typeof capturedTools[0].executeFunction).toBe('function')
-
-        await capturedTools[0].executeFunction({ title: 'Q1', format: 'pdf' })
+        expect(mockExecuteProviderRequest).toHaveBeenCalled()
+        const providerCall = mockExecuteProviderRequest.mock.calls[0]
+        const tools = providerCall[1].tools
 
-        expect(mockExecuteTool).toHaveBeenCalledWith(
-          'function_execute',
-          expect.objectContaining({
-            code: dbCode,
-          }),
-          false,
-          expect.any(Object)
-        )
+        expect(tools.length).toBe(1)
+        expect(tools[0].name).toBe('formatReport')
       })
 
       it('should not fetch from DB when no customToolId is present', async () => {