Symptoms

• The error occurs before any model-specific response.
• A JSON validator reports a missing quote, comma, bracket, or invalid escape.

Likely causes

• Shell quoting changed the body or inserted an unescaped newline.
• The client sent a JavaScript object string, trailing comma, or deeply malformed structure.

How to diagnose

• Validate the exact body bytes with secrets removed.
• Confirm Content-Type is application/json.
• Replace the payload with one short user message and no optional parameters.

Fixes

• Use the SDK serializer or a JSON encoder instead of manual string concatenation.
• Correct quotes, commas, escapes, and brackets.
• Keep shell JSON in a file or a safely quoted heredoc when it becomes complex.

How to verify

The minimal JSON body parses and reaches model validation.

Resources

• Base URL and authentication
• FAQ and troubleshooting