phase5.md

Phase 5: The Brain (Compute-over-Data / WASM Transforms)

Phase 5 embeds a sandboxed WASM runtime into the storage pipeline so capsules can be transformed in-flight during reads (lazy) or during ingestion (eager).

Goals

• Compute-to-data: move transformation logic (WASM) to the storage node.
• Streaming-first: process data chunk-by-chunk; no full-capsule buffering required.
• Sandboxed safety: traps/timeouts prevent buggy modules from crashing the node.

Policy Schema

Policy.transform is an ordered chain. Output of transform i feeds transform i+1.

transform:
  - name: resize_1080p
    image: capsule://wasm-registry/resize.wasm
    trigger: on-read
    args:
      width: "1920"
      height: "1080"
    resources:
      max_memory_pages: 16
      fuel_limit: 10000000
    verification:
      sha256: "<hex>"
      signature: "<optional ed25519 sig>"

Execution Model

• OnRead (default): decrypt -> decompress -> transform chain -> client stream
• OnWrite: transform chain -> compress/dedup -> encrypt -> persist

WASM ABI (v0)

WASM modules are loaded as raw binaries. The guest exports:

• memory (linear memory)
• alloc(len: u32) -> u32
• dealloc(ptr: u32, len: u32)
• process(ptr: u32, len: u32) -> u64 returning (out_ptr << 32) | out_len

The host copies the input chunk into guest memory, calls process, then copies the output back out (streaming, bounded by chunk size).

Notes

• file://... and capsule://<UUID> module images are supported.
• capsule://... images are intended to be stored in SPACE itself (dogfooding).
• verification.signature is reserved for trusted publishers (signature verification is planned).
• Derived-output caching is a planned optimization (transform hash + args).
• Enable the implementation by building pipeline with --features phase5, or via higher-level flags like spacectl --features phase5 (which enables the modular pipeline path).