# WebAssembly Skill Runtime

> Package agent skills as WebAssembly modules with explicit capability manifests — untrusted third-party skills run in strong isolation without container overhead.

- **Category**: Agentic AI
- **Subcategory**: Tool Use & Environment
- **Canonical URL**: https://designpattern.fyi/patterns/wasm_skill_runtime/

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## Description
**Intent**: Accept skills from external authors in any language and enforce per-skill capability limits at the runtime level.

**Context**: You run an enterprise agent platform that must execute skills authored by external users or partners on shared infrastructure. Skills come in Rust, Python-to-Wasm, TypeScript, and Go. Per-skill limits on CPU, memory, network, and filesystem must be enforced while serving at request-rate throughput.

**Solution**: Define a Wasm Component Model interface for skills. Each skill compiles to a Wasm module and ships with a manifest declaring (filesystem paths, network hosts, env vars, syscalls) it needs. The host runtime instantiates a fresh sandbox per call with only those capabilities. Missing-capability calls fail at the boundary. Polyglot by design — any language that compiles to Wasm works.


## Use Cases
- Enterprise platforms must accept user- or partner-authored skills in multiple languages.
- Per-skill capabilities (filesystem, network, env, syscalls) must be enforced at the runtime level.
- Per-call container overhead is too heavy for request-rate execution.





## Trade-offs


### Advantages

- Polyglot skill ecosystem with one runtime — Rust, Python, TypeScript, Go all welcome.

- Strong capability isolation; the manifest is the audit surface.

- Wasm cold-start is fast enough to run per request, unlike containers.




### Considerations & Drawbacks

- Wasm ecosystem maturity varies by language — Rust is strong, Python is heavier.

- Capability manifest design is the real engineering problem; get it wrong and isolation is theater.

- Some workloads (GPU, large data processing) don't fit Wasm well.







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**Reference**: [Original Source](https://www.agentpatternscatalog.org/patterns/wasm-skill-runtime/)