Experimenting with the Proposed Cross-Origin Storage API in Transformers.js

Transformers.js allows web developers to run AI models in the browser via task-specific pipelines. However, popular models like Xenova/whisper-tiny.en are downloaded and cached separately per origin, leading to duplicate storage (e.g., 177 MB for a simple ASR example). Even Wasm runtime files like ort-wasm-simd-threaded.asyncify.wasm from ONNX Runtime are cached redundantly across origins, despite identical content. This is due to browser cache isolation using Network Isolation Keys based on top-level and current-frame sites. The proposed Cross-Origin Storage (COS) API introduces `navigator.crossOriginStorage` that stores files identified by a cryptographic hash (e.g., SHA-256). Apps can request a file handle by hash; if present, they read directly; if not, they download and store it with options for visibility: `origins: '*'` for global sharing, a list of origins for restricted sharing, or same-site only. The browser verifies the hash on write for integrity, and visibility can only be upgraded, not downgraded, to prevent malicious narrowing. COS is an early-stage proposal not yet natively implemented, but can be tested via a browser extension.