Desktop image attachments were sent as @path references, which made the model invoke Read on the original file before the existing CLI image resizing path could run. This aligns desktop attachment materialization with the CLI behavior by resizing image data locally and sending SDK image content blocks, while preserving @path fallback for non-image files and failed image normalization.
Constraint: Desktop still needs local source paths for UI/context metadata while model input should avoid first-turn Read for images
Rejected: Route all attachments through @path | keeps the oversized image failure path for desktop images
Confidence: high
Scope-risk: moderate
Directive: Keep desktop image attachments aligned with CLI pasted-image processing before changing this path
Tested: bun test src/server/__tests__/conversation-attachments.test.ts
Tested: bun run check:server
Not-tested: Live GPT-5.5 proxy request with real provider credentials
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