Support encryption configuration

**Problem**
When working with validation, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

No file, test, or entry point is named. Start by locating validation and encryption-configuration handling in the terminal agent, then determine which failures currently produce vague messages. Done means the supported encryption configuration is clear and validation errors provide detailed, useful context.

Written by the indexing model from the issue text.