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Hello LiveAvatar Support,

We are unable to create a LiveAvatar session because the token endpoint returns a 422 validation error related to the discriminator field mode.

Summary

• Endpoint: POST {LIVEAVATAR_API_BASE}/v1/sessions/token
• Result: HTTP 422
• Error message: “Request validation errors. body: Unable to extract tag using discriminator 'mode'”
• Because the token request fails, we cannot proceed to POST /v1/sessions/start and therefore never receive a ws_url (our client normally writes ws_url to a local artifact file, which is missing as a consequence).

Expected behavior

1. POST /v1/sessions/token returns a valid session token (and related session identifiers).
2. POST /v1/sessions/start (Authorization: Bearer <session_token>) returns the connection details including ws_url for CUSTOM mode.
3. We then connect to ws_url to continue the session.

Actual behavior

• Step 1 fails consistently with 422, preventing session creation.

• Error returned:

  • code: 4000
  • message: “Request validation errors. body: Unable to extract tag using discriminator 'mode'”

Time of occurrence

• 2026-01-26 22:19:57Z (from our run logs)

Environment

• OS: macOS
• Node.js: v22.20.0
• npm: 10.9.3
• Python (for tooling only): 3.12.4
• API Base: https://api.liveavatar.com

What we need from you

1. Please confirm the exact request schema for POST /v1/sessions/token in CUSTOM mode:

   • Where mode must appear (top-level vs nested)
   • Allowed values for mode and whether they are case-sensitive
   • Any required fields that are conditionally required for CUSTOM mode

2. If there has been a recent schema change/regression: please confirm and share the updated expected payload.

Attachments (redacted)

1. step12e_report.json (shows the 422 status and error message)
2. step12e.stderr.log (full stderr for the run)
3. token_request_body_redacted.json (exact payload we send, with secrets removed)
4. token_request_headers_redacted.txt (headers minus secrets)

Thank you — if you need a minimal cURL reproduction, tell us the exact expected payload shape for CUSTOM mode and we will provide a one-command repro immediately.

Best regards,
Christopher