Short-lived GPU sandboxes,
created and destroyed by code.

Python

import fantasti

fx = fantasti.Client()         # reads FANTASTI_API_KEY

def rollout(policy, seed):
    # one sandbox per episode; its TTL cleans up after it
    sb = fx.sandboxes.create(image="ghcr.io/acme/env:latest",
                             ttl="15m", network="closed")
    obs = sb.exec(f"python env.py reset --seed {seed}").stdout
    total = 0.0
    for _ in range(MAX_STEPS):
        step = sb.exec(f"python env.py step {policy.act(obs)}")
        obs, reward, done = parse(step.stdout)
        total += reward
        if done:
            break
    return total               # nothing to tear down

CLI

$ fantasti sandbox create --image ghcr.io/acme/env:latest \
    --ttl 15m --network closed
$ fantasti sandbox exec sb_41c9 -- python env.py reset --seed 7

sb_41c9  placing   cpu · ttl 15m · network closed
sb_41c9  ready
sb_41c9  running   python env.py reset --seed 7
sb_41c9  exit 0    {"obs": [0.02, -0.41, 0.03, 0.27]}

Python

import fantasti

fx = fantasti.Client()         # reads FANTASTI_API_KEY

cases = load_cases("evals/swe-tasks.jsonl")

# one clean sandbox per case: nothing leaks or caches between
boxes = fx.sandboxes.create(n=len(cases), gpu="L40S",
                            image="ghcr.io/acme/eval:latest",
                            ttl="20m", network="closed")

results = [box.exec(case.command)
           for box, case in zip(boxes, cases)]
passed = sum(run.exit_code == 0 for run in results)
print(f"{passed} of {len(cases)} cases passed")

CLI

$ fantasti sandbox create --gpu L40S --ttl 20m \
    --network closed --image ghcr.io/acme/eval:latest
$ fantasti sandbox exec sb_7q2m -- python grade.py --case 0412

sb_7q2m  placing   L40S:1 · ttl 20m · network closed
sb_7q2m  ready
sb_7q2m  running   python grade.py --case 0412
sb_7q2m  exit 1    case 0412 · 3 of 5 checks passed

Python

import sys
import fantasti

fx = fantasti.Client()         # reads FANTASTI_API_KEY

# a fresh GPU for this pull request; a hung job ends at the TTL
with fx.sandboxes.create(
    gpu="L40S", image="ghcr.io/acme/ci:latest", ttl="30m",
    network="restricted",
    allow_domains=["pypi.org", "files.pythonhosted.org"],
) as sb:
    run = sb.exec("pytest -q tests/gpu", timeout="20m")
    print(run.stdout[-2000:])

sys.exit(run.exit_code)        # the sandbox has already ended

CLI

$ fantasti sandbox create --gpu L40S --ttl 30m --network closed
$ fantasti sandbox exec sb_41c9 -- pytest -q tests/gpu
$ fantasti sandbox delete sb_41c9

sb_41c9  placing   L40S:1 · ttl 30m · network closed
sb_41c9  ready
sb_41c9  running   pytest -q tests/gpu
sb_41c9  exit 0    212 passed
sb_41c9  ended     disk deleted · metering stopped

Python

import fantasti

fx = fantasti.Client()         # reads FANTASTI_API_KEY

with fx.sandboxes.create(
    gpu="L40S", ttl="15m", network="closed",
) as sb:
    sb.files.write("/work/patch.py", patch)
    run = sb.exec("python /work/patch.py --check", timeout="5m")
    print(run.exit_code, run.stdout[-2000:])
# ends here, or at its TTL, whichever comes sooner

MCP

{
  "mcpServers": {
    "fantasti": {
      "type": "http",
      "url": "https://mcp.fantasti.ai/mcp"
    }
  }
}

sandboxes_create
sandboxes_exec
sandboxes_read_file
sandboxes_write_file
sandboxes_delete        asks for confirmation

REST

curl -X POST https://api.fantasti.ai/v1/sandboxes \
  -H "Authorization: Bearer $FANTASTI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "gpu": "L40S", "ttl": "15m", "network": "closed" }'
# { "id": "sb_41c9…", "status": "placing" }