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Deno on Miren

Miren auto-detects Node and Bun, but not Deno — so you deploy Deno with a Dockerfile.miren built on the official Deno image. It runs TypeScript directly, so there's no separate build step for most apps.

Let your agent do this

Ask your AI coding agent to "set up this Deno app on Miren" after installing the Miren agent skills. It adds the Dockerfile.miren, confirms your server binds 0.0.0.0:$PORT, sets the runtime permissions, and deploys — using this page as its reference.

Do you need a Dockerfile?​

Yes. Miren's JavaScript detection covers Node and Bun (see JavaScript on Miren); Deno needs a Dockerfile.miren. Miren builds from it instead of guessing the stack — see Using Dockerfile.miren.

Want native support?

Miren auto-detects and builds common stacks (Python, Node, Bun, Go, Ruby, Rust) without a Dockerfile. This language isn't one of them yet — if you'd like first-class support, request it.

Bind to the injected port​

Miren injects PORT and routes traffic to it, so your server must read PORT and listen on 0.0.0.0. With the built-in Deno.serve:

const port = Number(Deno.env.get("PORT") ?? "8080");

Deno.serve({ port, hostname: "0.0.0.0" }, () =>
  new Response("Hello from Deno on Miren!\n", {
    headers: { "content-type": "text/plain" },
  }));

Frameworks like Oak or Fresh accept the same port/hostname — pass the injected PORT and bind 0.0.0.0.

The Dockerfile​

Create Dockerfile.miren in your project root:

FROM denoland/deno:2.1.4

WORKDIR /app
COPY . .
RUN deno cache main.ts

EXPOSE 8080
CMD ["run", "--allow-net", "--allow-env", "main.ts"]

deno cache pre-fetches and compiles your dependencies into the image so startup is fast. Deno runs with no permissions by default, so grant exactly what your app needs — --allow-net to listen, --allow-env to read PORT, and any others (--allow-read, --allow-write) your code requires.

.dockerignore​

.git

Set up the app​

Even with a Dockerfile.miren, Miren needs at least one service defined — it doesn't use the image's CMD as the start command. Add a Procfile with the full deno run command (including permissions):

web: deno run --allow-net --allow-env main.ts

Then create .miren/app.toml naming your app and deploy from your project root:

name = "deno-bench"
miren deploy
Deploying without a service fails

If no service is defined, the build succeeds but the deploy stops with no services defined: please define at least one service in a Procfile or .miren/app.toml.

Environment variables​

Set variables with miren env set — -e for plain values, -s for secrets (masked in output and logs). Read them with Deno.env.get("KEY") (needs --allow-env):

miren env set -e LOG_LEVEL=info
miren env set -s DATABASE_URL
miren env set -s API_TOKEN

You can also declare variables in .miren/app.toml:

[[env]]
key = "DATABASE_URL"
value = ""
required = true
sensitive = true
description = "Postgres connection string"

See App Configuration — Environment Variables.

Agent quick reference​

  • Detection: none — requires Dockerfile.miren (Node/Bun are detected, Deno is not)
  • Base image: denoland/deno:<version>; deno cache main.ts warms deps
  • Service is required: define a Procfile (web: deno run --allow-net --allow-env main.ts) — the image CMD is not used
  • Permissions: grant --allow-net + --allow-env at minimum; add others as needed
  • Port: read Deno.env.get("PORT"); bind 0.0.0.0 via Deno.serve
  • Env vars: miren env set -e/-s, or [[env]] in app.toml; read with Deno.env.get

Next steps​