## Why
Incremental tool declarations were limited to Responses Lite. Regular OpenAI Responses requests sent the full current tool catalog on each request.
## What changed
- Add the disabled-by-default `incremental_tools_legacy` feature for regular OpenAI Responses, independently of the Responses Lite `incremental_tools` flag.
- Support tool declarations and updates in conversation history, including during compaction, while preserving existing history prefixes.
- Keep hosted `web_search` configuration in top-level `tools` rather than `additional_tools`, including in compaction requests.
## Testing
Extend request-history scenarios and snapshots to cover regular Responses catalog updates, model switches, compaction, and MCP tool removal and restoration. Assert that incremental requests preserve input prefixes and keep web search out of history declarations.
GitOrigin-RevId: fa347409e387aa973ce2e41df8505769b7db1ec2
## Why
Incremental-tool windows recorded base instructions only at setup, so a catalog refresh for the same model could leave active instructions stale. Instruction changes need to reach the model without rewriting the existing history prefix.
## What changed
- Track model identity and instruction content independently, appending a `model_instructions` developer message when either changes. Explicitly mark replacement or removal of base instructions, and avoid repeating unchanged updates.
- Start new windows after compaction with the latest model instructions while preserving custom base instructions.
- Preserve the recorded window base during local compaction retries, including empty instructions, and rebuild current model instructions when reconstructing child context.
## Testing
Add integration tests and request snapshots for catalog refreshes, instruction removal, model switches, compaction, restart, and forks. Extend regression coverage for legacy snapshots and local compaction retries.
GitOrigin-RevId: eeca69067b4d9cd91c817732d79b4d5c1faa18b9
Alex Kira