LibreChat

LibreChat supports custom OpenAI-compatible endpoints via librechat.yaml. Its placeholder substitution system lets you forward the logged-in user's email to CoreCube on every request — no special header mode needs to be enabled on the LibreChat side.

Prerequisites

• CoreCube running and accessible from your LibreChat instance
• LibreChat with a librechat.yaml configuration file
• An admin account on CoreCube

Step 1 — Create a service API key

In the CoreCube admin console, go to Settings → API Keys and create a new key:

Field	Value
Key Name	LibreChat Production (or any label)
Key Type	Service — proxy app
Integration	Generic
Owner User	Select an admin user as key owner
Auto-provision users	Enable if you want CoreCube to create accounts automatically for new LibreChat users
Default scope	Select the scope new users should receive (required when auto-provision is on)

Save the key — copy the raw value now, it is shown only once.

Why Generic?

LibreChat lets you choose the header name yourself. The Generic preset uses X-Cube-User, which LibreChat populates with the user's email via the {{LIBRECHAT_USER_EMAIL}} placeholder.

Step 2 — Configure librechat.yaml

Add CoreCube as a custom endpoint in your librechat.yaml. The key line is the X-Cube-User header with the {{LIBRECHAT_USER_EMAIL}} placeholder — LibreChat replaces this with the logged-in user's email on every request.

endpoints:
  custom:
    - name: 'CoreCube'
      apiKey: 'cc_YOUR_SERVICE_KEY'
      baseURL: 'http://corecube:7400/v1'
      models:
        default: ['claude-sonnet-4-5']
        fetch: true
      headers:
        X-Cube-User: '{{LIBRECHAT_USER_EMAIL}}'
      titleConvo: true
      titleModel: 'claude-sonnet-4-5'
      summarize: false
      summaryModel: 'claude-sonnet-4-5'
      forcePrompt: false
      modelDisplayLabel: 'CoreCube'

Replace cc_YOUR_SERVICE_KEY with the key from Step 1, and adjust baseURL to match your setup.

Model name is cosmetic

With fetch: true, LibreChat calls GET /v1/models and receives a single model named after your CoreCube instance (default CoreCube). The default model name you list is only a display label — the upstream LLM that answers each request is chosen by CoreCube's own routing, not selected in LibreChat.

Available placeholders

LibreChat supports additional user fields as placeholders:

Placeholder	Value
{{LIBRECHAT_USER_EMAIL}}	User's email address (recommended)
{{LIBRECHAT_USER_ID}}	Internal LibreChat user ID
{{LIBRECHAT_USER_NAME}}	Display name
{{LIBRECHAT_USER_USERNAME}}	Username

Use {{LIBRECHAT_USER_EMAIL}} — CoreCube matches users by email.

Step 3 — Ensure users exist in CoreCube

CoreCube resolves the user from the forwarded email. Each LibreChat user must have a matching account in CoreCube with the same email address.

Option A — Manual: Create users in CoreCube admin (Settings → Users) with matching email addresses.

Option B — Auto-provision: Enable the auto-provision toggle on the service key (Step 1). New users are created automatically on their first query.

Auto-provisioned users

Auto-provisioned users receive a no_access role and the default scope only. They cannot log into the CoreCube admin console. Adjust their scope and role in CoreCube admin after provisioning if needed.

Step 4 — Assign knowledge scopes

In CoreCube admin, go to Access Control → Scopes and assign each user to the appropriate scope. Users without a scope assignment will receive empty search results.

How it works end-to-end

Alice logs into LibreChat
  → sends a chat message
  → LibreChat calls POST /v1/chat/completions
    with: Authorization: Bearer cc_SERVICE_KEY
          X-Cube-User: alice@company.com   ← injected from {{LIBRECHAT_USER_EMAIL}}
  → CoreCube resolves alice, applies her scopes
  → searches only compartments alice can access
  → returns cited response

Troubleshooting

"User not found" errors The email in LibreChat does not match any CoreCube user. Check that the {{LIBRECHAT_USER_EMAIL}} placeholder is correctly placed in librechat.yaml under headers, not parameters.

Placeholder not substituted (literal {{LIBRECHAT_USER_EMAIL}} sent) LibreChat version is too old, or librechat.yaml is not being loaded. Check that your LibreChat instance is reading the config file and is at a version that supports user field placeholders.

Requests fail with 400 MISSING_USER The headers block is missing or misconfigured, so no X-Cube-User value reaches CoreCube. A service key with no forwarded identity is rejected with 400 MISSING_USER ("Service keys require X-Cube-User header") rather than returning shared results. Confirm the X-Cube-User header is present under headers and that the {{LIBRECHAT_USER_EMAIL}} placeholder is substituting correctly.