**Problem to solve** Self-hosted models are still using the v2 code generation endpoint, which does not include any of the enriched context information. Support for open tabs as context is on the v3 endpoint, and as such is not supported on the v2 endpoint and the current self-hosted models deployment **Impact** - From historical data, open tabs context increases acceptance rate by significant basis points - This quality improvement is largely consistent among models for which Code Creation has data: code-gecko, Codestral, Qwen 2.5 7B.  - Each of these are FIM code completion models - we don’t have historical data for any chat/instruct tuned models used for code completion. ### **Definition of Done** * Migrate [AiGatewaySelfHostedMessages](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/code_suggestions/prompts/code_generation/ai_gateway_self_hosted_messages.rb#L6-6) to match or replace it with [AiGatewayMessages](https://gitlab.com/gitlab-org/gitlab/blob/master/ee/lib/code_suggestions/prompts/code_generation/ai_gateway_messages.rb#L6-6). * Ensure that the self-hosted Code Suggestion feature using Claude 3.5 Sonnet v3 works as expected for both code completion and code generation.