- Add preValidateCredentialInputs to validate inputs before operations are applied
- Block invalid credential IDs (non-existent or not owned by user) from being set
- Filter out apiKey inputs for hosted models when isHosted is true
- Skip oauth-input in post-validation to preserve existing collaborator credentials
- Return validation errors for LLM feedback on blocked inputs
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>