Fork a sandbox and let a model try three fixes

bash
API=https://beta-api.b3os.orgAUTH="Authorization: Bearer $B3OS_API_KEY"post() { curl -s "$API$1" -H "$AUTH" -H "Content-Type: application/json" -d @-; }SRC=$(echo '{"template": "base", "timeout_s": 300, "forkable": true, "egress": {"mode": "deny"},  "api": {"scopes": ["infer:run"], "spend_cap_usd": 1}}' | post /v1/sandboxes | jq -r .id)for f in slug.py test_slug.py fix.py; do  curl -s -X PUT "$API/v1/sandboxes/$SRC/files?path=/workspace/$f" -H "$AUTH" \    -H "Content-Type: application/octet-stream" --data-binary @"$f" > /dev/nulldoneecho '{"cmd": ["python3", "/workspace/fix.py", "--tests-only"]}' | post "/v1/sandboxes/$SRC/exec" | jq -r .stdout# Three copies of the source's memory and disk, then one try per temperature, at onceFORKS=$(echo '{"count": 3}' | post "/v1/sandboxes/$SRC/fork" | jq -r '.data[].id')i=0for id in $FORKS; do  i=$((i + 1))  t=$(echo "0 0.6 1.0" | cut -d' ' -f$i)  jq -n --arg t "$t" '{cmd: ["python3", "/workspace/fix.py"], env: {TEMPERATURE: $t}, timeout_ms: 58000}' \    | post "/v1/sandboxes/$id/exec" | jq -r '.stdout | split("\n") | map(select(. != "")) | last' &donewaitfor id in $SRC $FORKS; do curl -s -X DELETE "$API/v1/sandboxes/$id" -H "$AUTH" > /dev/null; done

ts
import { readFileSync } from "node:fs";const API = "https://beta-api.b3os.org";const auth = { authorization: `Bearer ${process.env.B3OS_API_KEY}` };const call = async (method: string, path: string, body?: unknown): Promise<any> =>  (    await fetch(`${API}${path}`, {      method,      headers: { ...auth, "content-type": "application/json" },      body: body === undefined ? undefined : JSON.stringify(body),    })  ).json();const last = (r: { stdout: string }) => JSON.parse(r.stdout.trim().split("\n").at(-1) ?? "{}");const src = await call("POST", "/v1/sandboxes", {  template: "base",  timeout_s: 300,  forkable: true,  api: { scopes: ["infer:run"], spend_cap_usd: 1 },  egress: { mode: "deny" },});for (const f of ["slug.py", "test_slug.py", "fix.py"])  await fetch(`${API}/v1/sandboxes/${src.id}/files?path=/workspace/${f}`, {    method: "PUT",    headers: { ...auth, "content-type": "application/octet-stream" },    body: readFileSync(f, "utf8"),  });console.log(last(await call("POST", `/v1/sandboxes/${src.id}/exec`, { cmd: ["python3", "/workspace/fix.py", "--tests-only"] })));const temperatures = [0, 0.6, 1.0];const fork = await call("POST", `/v1/sandboxes/${src.id}/fork`, { count: temperatures.length });const tries = await Promise.all(  fork.data.map(async (c: { id: string }, i: number) => {    const r = await call("POST", `/v1/sandboxes/${c.id}/exec`, {      cmd: ["python3", "/workspace/fix.py"],      env: { TEMPERATURE: String(temperatures[i]) },      timeout_ms: 58000,    });    return { temperature: temperatures[i], ...(r.exit_code === 0 ? last(r) : { error: r.stderr }) };  }),);console.log(tries);for (const id of [src.id, ...fork.data.map((c: { id: string }) => c.id)])  await call("DELETE", `/v1/sandboxes/${id}`);

python
import jsonimport osfrom concurrent.futures import ThreadPoolExecutorimport requestsAPI = "https://beta-api.b3os.org"s = requests.Session()s.headers["Authorization"] = f"Bearer {os.environ['B3OS_API_KEY']}"def last(r):    return json.loads(r["stdout"].strip().split("\n")[-1])src = s.post(f"{API}/v1/sandboxes", json={    "template": "base", "timeout_s": 300, "forkable": True, "egress": {"mode": "deny"},    "api": {"scopes": ["infer:run"], "spend_cap_usd": 1},}).json()["id"]for f in ["slug.py", "test_slug.py", "fix.py"]:    with open(f, "rb") as fh:        s.put(f"{API}/v1/sandboxes/{src}/files", params={"path": f"/workspace/{f}"}, data=fh.read(),              headers={"Content-Type": "application/octet-stream"})print(last(s.post(f"{API}/v1/sandboxes/{src}/exec",                  json={"cmd": ["python3", "/workspace/fix.py", "--tests-only"]}).json()))temperatures = [0, 0.6, 1.0]forks = [c["id"] for c in s.post(f"{API}/v1/sandboxes/{src}/fork", json={"count": 3}).json()["data"]]def attempt(pair):    sbx, t = pair    r = s.post(f"{API}/v1/sandboxes/{sbx}/exec", json={        "cmd": ["python3", "/workspace/fix.py"], "env": {"TEMPERATURE": str(t)}, "timeout_ms": 58000,    }).json()    return {"temperature": t, **(last(r) if r["exit_code"] == 0 else {"error": r["stderr"]})}with ThreadPoolExecutor(3) as pool:    print(list(pool.map(attempt, zip(forks, temperatures))))for sbx in [src, *forks]:    s.delete(f"{API}/v1/sandboxes/{sbx}")

The MCP sandbox_create tool takes neither forkable nor an api grant, so create the source sandbox with the API, with the same B3OS_API_KEY your MCP client sends:

bash
curl -s https://beta-api.b3os.org/v1/sandboxes -H "Authorization: Bearer $B3OS_API_KEY" \  -H "Content-Type: application/json" -d '{"template": "base", "timeout_s": 600, "forkable": true,  "egress": {"mode": "deny"}, "api": {"scopes": ["infer:run"], "spend_cap_usd": 1}}' | jq -r .id

sandbox_fork is in the sandboxes toolset, so connect to the remote B3OS MCP server as https://beta-api.b3os.org/mcp?toolsets=sandboxes. Then, with the three files' contents in the conversation, ask your agent:

text
In sandbox <id>, write slug.py, test_slug.py and fix.py to /workspace and runpython3 /workspace/fix.py --tests-only. Then fork it into three copies and in each run python3 /workspace/fix.pywith TEMPERATURE set to 0, 0.6 and 1.0 and a 58 second timeout. Tell me which temperatures pass all seven tests,then delete all four sandboxes.

The agent calls sandbox_write_file three times, sandbox_exec, sandbox_fork, sandbox_exec once per fork and sandbox_delete four times.