Common desktop screenshots can be taller than the old 2000px local resize threshold while still fitting provider request limits. Align the local image dimension cap with the Claude Vision API rejection threshold so Read and desktop attachments pass through already-small screenshots, while oversized or unprocessable images still use the existing fallback paths.
Constraint: Claude Vision API allows image dimensions up to 8000px and still has a 5MB base64 image payload limit
Rejected: Keep 2000px as a client-side hard limit | it rejects common screenshots that providers can handle
Confidence: high
Scope-risk: narrow
Related: #615
Related: #677
Tested: bun test tests/imageResizer.test.ts
Tested: bun test tests/imageResizer.test.ts tests/mediaRecoveryAndEstimation.test.ts src/services/api/errors.test.ts src/server/__tests__/proxy-transform.test.ts
Tested: bun test src/server/__tests__/conversation-attachments.test.ts tests/imageResizer.test.ts
Tested: bun run check:server
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
