🧯 fix: enforce allowedProviders for discovered sub-agents

Addresses the third P1 codex finding on #12740: `discoverConnectedAgents`
forwarded the caller's `endpointOption` verbatim into `initializeAgent`,
but on the OpenAI-compat routes that option's `endpoint` is the primary
agent's provider (e.g. `openai`), not `agents`. `initializeAgent` only
enforces `allowedProviders` when `isAgentsEndpoint(endpointOption.endpoint)`
is true, so handoff sub-agents silently bypassed the provider allowlist
configured under `endpoints.agents.allowedProviders`.

Override `endpointOption.endpoint` to `EModelEndpoint.agents` for every
per-sub-agent init call. The primary agent still uses the caller's
endpointOption as before — this only affects the BFS-loaded handoff
targets. Regression test asserts the override.

packages/api/src/agents/discovery.spec.ts

@@ -1,3 +1,4 @@
+import { EModelEndpoint } from 'librechat-data-provider';
 import type { Agent, GraphEdge } from 'librechat-data-provider';
 import type { Response } from 'express';
 import type { ServerRequest } from '~/types';
@@ -202,6 +203,39 @@ describe('discoverConnectedAgents', () => {
     expect(result.edges.map((e) => e.to)).toEqual(['B']);
   });
 
+  it('forces `endpoint: agents` on sub-agent init so allowedProviders is always enforced', async () => {
+    const primaryConfig = makeConfig('A', [{ from: 'A', to: 'B', edgeType: 'handoff' }]);
+    const getAgent = jest.fn(async () => makeAgent('B', []));
+    const checkPermission = jest.fn().mockResolvedValue(true);
+
+    await discoverConnectedAgents(
+      {
+        req: makeReq(),
+        res: makeRes(),
+        primaryConfig,
+        // Caller passes a non-agents endpoint (e.g. the OpenAI-compat
+        // controllers do this — endpoint = primary provider)
+        endpointOption: { endpoint: EModelEndpoint.openAI, model_parameters: {} },
+        allowedProviders: new Set(['openai']),
+        modelsConfig: { openai: ['gpt-4o'] },
+        loadTools: jest.fn(),
+      },
+      {
+        getAgent,
+        checkPermission,
+        logViolation: jest.fn(),
+        db: {} as never,
+      },
+    );
+
+    // The helper must override `endpoint` to 'agents' so
+    // `isAgentsEndpoint` is true and the allowedProviders guard in
+    // `initializeAgent` actually runs for sub-agents.
+    expect(mockInitializeAgent).toHaveBeenCalled();
+    const initArgs = mockInitializeAgent.mock.calls[0][0];
+    expect(initArgs.endpointOption.endpoint).toBe(EModelEndpoint.agents);
+  });
+
   it('passes the configured resourceType (e.g. REMOTE_AGENT) to checkPermission', async () => {
     const primaryConfig = makeConfig('A', [{ from: 'A', to: 'B', edgeType: 'handoff' }]);
     const getAgent = jest.fn(async () => makeAgent('B', []));

packages/api/src/agents/discovery.ts

@@ -1,5 +1,5 @@
 import { logger } from '@librechat/data-schemas';
-import { ResourceType, PermissionBits } from 'librechat-data-provider';
+import { ResourceType, PermissionBits, EModelEndpoint } from 'librechat-data-provider';
 import type { Agent, GraphEdge, TModelsConfig, TEndpointOption } from 'librechat-data-provider';
 import type { Response as ServerResponse } from 'express';
 import type { ServerRequest } from '~/types';
@@ -196,6 +196,20 @@ export async function discoverConnectedAgents(
       throw new Error(validation.error?.message);
     }
 
+    /**
+     * Force `endpoint: agents` on the per-sub-agent init call so
+     * `initializeAgent`'s `isAgentsEndpoint`-gated `allowedProviders`
+     * check always fires for handoff sub-agents, regardless of which
+     * endpoint the caller entered through. Without this, the OpenAI-
+     * compat routes (whose `endpointOption.endpoint` is the primary
+     * provider, not `agents`) would silently bypass the provider
+     * allowlist configured under `endpoints.agents.allowedProviders`.
+     */
+    const subAgentEndpointOption: Partial<TEndpointOption> = {
+      ...(endpointOption ?? {}),
+      endpoint: EModelEndpoint.agents,
+    };
+
     const config = await initializeAgent(
       {
         req,
@@ -205,7 +219,7 @@ export async function discoverConnectedAgents(
         requestFiles,
         conversationId,
         parentMessageId,
-        endpointOption,
+        endpointOption: subAgentEndpointOption,
         allowedProviders,
       },
       db,