Wasm Nodes

Wasm nodes run sandboxed WebAssembly plugins for safe, portable custom logic using Wasmtime.

Use Cases

• Text transforms, validation, formatting
• Scoring, ranking, classification
• Tenant-defined business logic
• Cross-language portable extensions

Not For

• ffmpeg / yt-dlp — use the Tool runtime
• AI inference — use the Provider runtime
• Unrestricted OS/process/network access

Configuration

NodeDefinition::wasm("format", "text.transform", "fabric://modules/formatter@v1")
    .requires("wasm.execute")

WasmRuntimeConfig

Field	Default	Description
module	required	Module reference (fabric://modules/name@version)
memory_limit_bytes	64 MB	Maximum memory
fuel_limit	1B instructions	CPU fuel limit

Planned ABI

describe() -> module metadata
validate(input, config) -> validation result
execute(input, context, config) -> output

Host Capabilities (Planned)

• Logging
• Limited asset metadata reads
• Metrics emission
• Approved context value reads
• Structured output return

Sandboxing

All Wasm modules run in a sandboxed environment with strict limits:

• Memory limits enforced
• CPU/fuel limits enforced
• Timeout enforced
• Capability allowlist (only explicitly granted capabilities)

Security Boundaries

Concern	Policy
Filesystem	Denied
Network	Denied
Process spawning	Denied
Environment variables	Denied
Secrets	Denied
Context reads	Allowlisted paths only
Output	Structured JSON only

Wasm modules cannot access the filesystem, network, spawn processes, read environment variables, or access secrets. They can only read allowlisted context paths and return structured JSON output.