Assay

Replaces your entire infrastructure scripting toolchain. One 9 MB binary, 50 modules.

What is Assay?

A single ~9 MB static binary that replaces 50-250 MB Python/Node/kubectl containers in Kubernetes. Full-featured Lua 5.5 runtime with HTTP client/server, database, WebSocket, JWT, templates, native Temporal gRPC workflows, and 33 embedded stdlib modules for Kubernetes, monitoring, security, and AI agent integrations.

assay script.lua     # Run Lua with all builtins
assay checks.yaml    # Structured checks with retry/backoff/JSON output
assay exec -e 'log.info("hello")'   # Inline evaluation
assay context "grafana"              # LLM-ready module docs
assay modules                        # List all 50+ modules

Scripts that call http.serve() become web services. Scripts that call http.get() and exit are jobs. Same binary, same builtins.

Why Assay?

Installation

# Pre-built binary (Linux x86_64 static)
curl -L -o assay https://github.com/developerinlondon/assay/releases/latest/download/assay-linux-x86_64
chmod +x assay && sudo mv assay /usr/local/bin/

# macOS (Apple Silicon)
curl -L -o assay https://github.com/developerinlondon/assay/releases/latest/download/assay-darwin-aarch64
chmod +x assay && sudo mv assay /usr/local/bin/

# Docker
docker pull ghcr.io/developerinlondon/assay:latest

# Cargo
cargo install assay-lua

Builtins API Reference

All 17 Rust builtins are available globally in .lua scripts — no require needed.

HTTP & Networking

Serialization

Filesystem & System

Cryptography & Regex

Database, Templates & Async

Assertions & Logging

Temporal Workflow Engine (native gRPC)

Stdlib Modules

33 embedded Lua modules loaded via require("assay.<name>"). All follow the client pattern: M.client(url, opts) then c:method().

Examples

Kubernetes Health Check

#!/usr/bin/assay
local k8s = require("assay.k8s")
local c = k8s.client("https://kubernetes.default.svc", {
  token = fs.read("/var/run/secrets/kubernetes.io/serviceaccount/token"),
})

local deploy = c:deployment("default", "my-app")
assert.eq(deploy.status.readyReplicas, deploy.spec.replicas, "Not all replicas ready")
log.info("Deployment ready: " .. deploy.metadata.name)

Web Server with SSE

#!/usr/bin/assay
http.serve(8080, {
  GET = {
    ["/health"] = function(req)
      return { status = 200, json = { ok = true } }
    end,
    ["/login"] = function(req)
      -- Array header values emit the same header name multiple times.
      -- Required for setting multiple Set-Cookie values in one response.
      return {
        status = 200,
        headers = {
          ["Set-Cookie"] = {
            "session=abc; Path=/; HttpOnly",
            "csrf=xyz; Path=/",
          },
        },
        json = { ok = true },
      }
    end,
    ["/events"] = function(req)
      return {
        sse = function(send)
          send({ data = "connected" })
          for i = 1, 10 do
            sleep(1)
            send({ event = "update", data = json.encode({ count = i }), id = tostring(i) })
          end
        end
      }
    end
  }
})

Temporal Workflow

#!/usr/bin/assay
local client = temporal.connect({
  url = "temporal-frontend:7233",
  namespace = "production",
})

local handle = client:start_workflow({
  task_queue = "promotions",
  workflow_type = "PromoteToEnv",
  workflow_id = "promote-prod-v1.2.0",
  input = { version = "v1.2.0", target = "prod" },
})
log.info("Started: " .. handle.run_id)

local info = client:describe_workflow("promote-prod-v1.2.0")
log.info("Status: " .. info.status)

YAML Check Mode

timeout: 120s
retries: 3
backoff: 5s

checks:
  - name: api-health
    type: http
    url: https://api.example.com/health
    expect:
      status: 200
      json: ".status == \"healthy\""

  - name: prometheus-targets
    type: prometheus
    url: http://prometheus:9090
    query: "count(up)"
    expect:
      min: 1

assay checks.yaml   # Exit 0 if all pass, 1 if any fail

OpenClaw Integration

Assay integrates with OpenClaw as an agent tool with human approval gates:

assay run --mode tool script.lua              # Structured JSON output for agents
assay resume --token <token> --approve yes    # Resume after human approval

Install the extension: openclaw plugins install @developerinlondon/assay-openclaw-extension

Module Discovery

Find the right module before writing code:

assay context "grafana"   # Returns method signatures for LLM prompts
assay context "vault"     # Exact API docs, no hallucination
assay modules             # List all 50+ modules

Custom modules: place .lua files in ./modules/ (project) or ~/.assay/modules/ (global).

Development

cargo build --release     # Release build (~9 MB)
cargo clippy -- -D warnings
cargo test
dprint fmt                # Format (Rust, Markdown, YAML, JSON, TOML)

License

Assay is licensed under the Apache License, Version 2.0. You can use, modify, and redistribute it freely — including in commercial and proprietary products — as long as you preserve the copyright notice and the license text.

Contributing

Pull requests are welcome. See CONTRIBUTING.md for the workflow and CLA.md for the Contributor License Agreement that all contributors are required to sign (it lets the project owner relicense or incorporate contributions into commercial editions in the future, while you keep the copyright on your contribution).

Links

• Website: https://assay.rs
• Crate: https://crates.io/crates/assay-lua
• Docker: ghcr.io/developerinlondon/assay:latest
• Changelog: https://assay.rs/changelog.html
• Module Reference: https://assay.rs/modules.html
• Comparison: https://assay.rs/comparison.html
• Agent Guides: https://assay.rs/agent-guides.html
• LLM Context: https://assay.rs/llms.txt