---
title: "Budget a task before you scale it"
description: "Run a task small, read its cost on the receipt, then decide how many boxes to fork."
order: 7
verified:
  cli: "0.0.0-mock"
  date: "2026-10-20"
---

Run a small fork first and read its cost with `vakna receipt <task> --money cost`. A fork's cost grows with its count, so fifty boxes tell you what a thousand will cost.

## How much did a small run cost?

```sh
$ vakna fork api --count 50 -- go test -run TestRetry ./retry/...
$ vakna receipt prove-flaky-retry --money cost
```

```prints
snapshot snp_eu1a_z7a8b9c0 taken 0.19s
forked api ×50 from snapshot · 0.34s each
task prove-flaky-retry tsk_eu1a_0k1m2n3p
ran go test -run TestRetry ./retry/... in 50 boxes · 42 exit 0, 8 failed 2m 11s
errors: 2 signatures
  assertion in retry_test.go:88 ×6
  timeout after 30s ×2
receipt: prove-flaky-retry · 50 boxes · 8 failed · 2m 11s · $0.46 · mocked
receipt · task prove-flaky-retry
tsk_eu1a_0k1m2n3p                                                         mocked
────────────────────────────────────────────────────────────────────────────────
boxes       50                                                       took 2m 11s
started     forked ×50 from snapshot                                  0.34s each
passed      42 of 50
errors      2 signatures
            assertion in retry_test.go:88 ×6
            timeout after 30s ×2
wall clock                                                                1h 18m
cost                                                                       $0.46
```

## How do I scale it once the cost is right?

```sh
$ vakna fork api --count 1000 --name prove-hypothesis-42 -- pytest -k slow
```

```prints
snapshot snp_eu1a_z7a8b9c0 taken 0.19s
forked api ×1,000 from snapshot · 0.34s each
task prove-hypothesis-42 tsk_eu1a_4x5y6z7a
ran pytest -k slow in 1,000 boxes · 994 exit 0, 6 failed 3m 20s
errors: 3 signatures
  OOM in test runner ×3
  port 5432 already in use ×2
  timeout after 45s ×1
receipt: prove-hypothesis-42 · 1,000 boxes · 6 failed · 3m 20s · $4.12 · mocked
```

There is no spending cap flag yet. One task holds up to 1,000 boxes, and a larger `--count` is an error that says so.