Projects & Sessions

Templates

The playground offers three project templates, matching ach init --template:

vm

A general-purpose program. This is the default template.

src/main.ach

let name = "Achronyme"
print("Hello from " + name + "!")

circuit

A ZK circuit with inline proving.

src/main.ach

let a = 6
let b = 7
let out = a * b

let proof = prove multiply(out: Public) {
    assert_eq(a * b, out)
}

print("Proof generated!")
print("Verified: " + verify_proof(proof).to_string())

prove

A program using Poseidon hashing with a prove block.

src/main.ach

let secret = 0p42
let expected = poseidon(secret, 0p0)

let proof = prove check(expected: Public) {
    let h = poseidon(secret, 0p0)
    assert_eq(h, expected)
}

print("Proof: " + proof.to_string())
print("Valid: " + verify_proof(proof).to_string())

Select a template from the dropdown in the sidebar footer. Switching templates creates a fresh project.

Project configuration

Every project includes an achronyme.toml file:

[project]
name = "my-project"
entry = "src/main.ach"

[build]
backend = "r1cs"

The playground reads this file to determine:

• entry — which file to compile and run (default: src/main.ach)
• backend — proving backend: r1cs (Groth16) or plonkish (Halo2)

See Project Configuration for all available options.

Session persistence

Your work persists across page reloads and browser restarts.

Auto-backup: every 3 seconds, all project files are backed up to localStorage. If the server loses your session (after a restart or TTL expiration), the playground automatically restores from this backup.

Session restore flow:

1. Try to reconnect to the existing server session
2. If the server lost it, create a new session and restore files from the localStorage backup
3. If no backup exists, load the default vm template

Layout preferences (sidebar width, panel position, panel visibility) are also persisted in localStorage.

Export & Import

Export

Click Export in the sidebar footer to download your project as a project.ach.json file. This includes all files and their contents.

Import

Click Import to load a previously exported project. The playground creates a fresh session and writes all files from the JSON.

The export format is simple JSON:

{
  "files": {
    "achronyme.toml": "[project]\nname = \"demo\"\nentry = \"src/main.ach\"\n",
    "src/main.ach": "print(\"Hello!\")\n"
  },
  "exportedAt": "2026-03-29T12:00:00.000Z"
}

Limits

Resource	Limit
Files per project	20
File size	32 KB
Total workspace	256 KB
Allowed extensions	.ach, achronyme.toml
Session TTL	2 hours (inactive)
Max concurrent sessions	200
Instruction budget	100M instructions
Heap size	256 MB
Execution timeout	10 seconds
Print output	1 MB