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## Summary by CodeRabbit
- New Features
- Added GPT-5 family and made GPT-5/-mini the new defaults for Copilot
scenarios and prompts.
- Bug Fixes
- Improved streaming chunk formats and reasoning/text semantics,
consistent attachment mediaType handling, and more reliable reranking
via log-prob handling.
- Refactor
- Unified maxOutputTokens usage; removed per-call step caps and migrated
several tools to a unified inputSchema shape.
- Chores
- Upgraded AI SDK dependencies and bumped an internal dependency
version.
- Tests
- Updated mocks and tests to reference GPT-5 variants and new stream
formats.
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