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fix(agent): ignore empty advanced MCP bindings #7397

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Merged
TheodoreSpeaks merged 1 commit into from
Sep 2, 2026
Merged

fix(agent): ignore empty advanced MCP bindings #7397

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26 changes: 26 additions & 0 deletions apps/sim/executor/handlers/agent/agent-handler.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3779,6 +3779,32 @@ describe('AgentBlockHandler', () => {
])
})

it('does not create tools for a blank advanced MCP server binding', async () => {
await handler.execute(
{
...mockContext,
workspaceId: 'test-workspace-123',
workflowId: 'test-workflow-456',
},
mockBlock,
{
model: 'gpt-4o',
userPrompt: 'Continue without MCP tools',
apiKey: 'test-api-key',
tools: [
{
type: 'mcp-server-advanced',
params: { serverId: '' },
usageControl: 'auto' as const,
},
],
}
)

expect(mockDiscoverMcpServerToolsAsExecutor).not.toHaveBeenCalled()
expect(mockExecuteProviderRequest.mock.calls[0][1].tools).toEqual([])
})

describe('customToolId resolution - DB as source of truth', () => {
const staleInlineSchema = {
function: {
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2 changes: 2 additions & 0 deletions apps/sim/executor/handlers/agent/agent-handler.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -803,6 +803,8 @@ export class AgentBlockHandler implements BlockHandler {
if (entry.tool.type === 'mcp') {
mcpTools.push(entry)
} else if (entry.tool.type === MCP_SERVER_ADVANCED_TOOL_TYPE) {
const serverId = entry.tool.params?.serverId
if (typeof serverId === 'string' && !serverId.trim()) continue
advancedMcpServers.push(entry)
} else {
otherTools.push(entry)
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19 changes: 19 additions & 0 deletions apps/sim/executor/handlers/mothership/mothership-handler.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1030,6 +1030,25 @@ describe('MothershipBlockHandler', () => {
])
})

it('does not forward tools for a blank advanced MCP server binding', async () => {
fetchMock.mockResolvedValue(createJsonResponse({ content: 'done', toolCalls: [] }))

await handler.execute(context, block, {
prompt: 'Continue without MCP tools',
tools: [
{
type: 'mcp-server-advanced',
params: { serverId: '' },
usageControl: 'auto',
},
],
})

expect(mockDiscoverMcpServerToolsAsExecutor).not.toHaveBeenCalled()
const [, options] = fetchMock.mock.calls[0] as [string, RequestInit]
expect(JSON.parse(String(options.body))).not.toHaveProperty('mcpTools')
})

it('does not scan arbitrary Mothership metadata, attachment names, or payloads', async () => {
const secret = 'boundary-secret'
const registry = new ResolvedSecretTraceRegistry([
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3 changes: 2 additions & 1 deletion apps/sim/executor/handlers/mothership/mothership-handler.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -161,9 +161,10 @@ async function expandMothershipMcpTools(
throw new Error('MCP Server (Advanced) requires params.serverId')
}
const serverId = candidate.params.serverId
if (typeof serverId !== 'string' || !serverId.trim()) {
if (typeof serverId !== 'string') {
throw new Error('MCP Server (Advanced) requires params.serverId')
}
if (!serverId.trim()) return []
const usageControl: 'auto' | 'force' = candidate.usageControl === 'force' ? 'force' : 'auto'
return [{ serverId, usageControl }]
}
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11 changes: 10 additions & 1 deletion apps/sim/lib/mcp/shared.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -46,9 +46,18 @@ describe('assertValidMcpServerToolBindings', () => {
).not.toThrow()
})

it('ignores server-wide bindings with blank server IDs', () => {
expect(() =>
assertValidMcpServerToolBindings([
{ type: 'mcp-server-advanced', params: { serverId: '' } },
{ type: 'mcp-server-advanced', params: { serverId: ' ' } },
])
).not.toThrow()
})

it('fails fast on a malformed active server-wide binding', () => {
expect(() =>
assertValidMcpServerToolBindings([{ type: 'mcp-server-advanced', params: { serverId: '' } }])
assertValidMcpServerToolBindings([{ type: 'mcp-server-advanced', params: {} }])
).toThrow('requires params.serverId')
})
})
3 changes: 2 additions & 1 deletion apps/sim/lib/mcp/shared.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -49,9 +49,10 @@ export function assertValidMcpServerToolBindings(value: unknown): void {
}
if (tool.type !== MCP_SERVER_ADVANCED_TOOL_TYPE) continue
const serverId = tool.params?.serverId
if (typeof serverId !== 'string' || !serverId.trim()) {
if (typeof serverId !== 'string') {
throw new Error('MCP Server (Advanced) requires params.serverId')
}
if (!serverId.trim()) continue

@cubic-dev-ai cubic-dev-ai Bot Sep 2, 2026 •
edited
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P2: When MCP tools are disabled for a workspace, a blank advanced binding now blocks the agent run even though it is intended to be inactive: validateToolPermissions sees the advanced entry before formatTools ignores it. Filter blank advanced bindings before the permission check, or make the permission check consider only active MCP bindings.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At apps/sim/lib/mcp/shared.ts, line 55:

<comment>When MCP tools are disabled for a workspace, a blank advanced binding now blocks the agent run even though it is intended to be inactive: `validateToolPermissions` sees the advanced entry before `formatTools` ignores it. Filter blank advanced bindings before the permission check, or make the permission check consider only active MCP bindings.</comment>

<file context>
@@ -49,9 +49,10 @@ export function assertValidMcpServerToolBindings(value: unknown): void {
+    if (typeof serverId !== 'string') {
       throw new Error('MCP Server (Advanced) requires params.serverId')
     }
+    if (!serverId.trim()) continue
     if (advancedServerIds.has(serverId)) {
       throw new Error(`Duplicate MCP Server (Advanced) binding for ${serverId}`)
</file context>
Fix with cubic

if (advancedServerIds.has(serverId)) {
throw new Error(`Duplicate MCP Server (Advanced) binding for ${serverId}`)
}
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