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

MIT

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