Taskpenny

Frontier prices only for frontier work.

Taskpenny splits a request only when it expects splitting to pay, gives each task to the cheapest model that does it well, checks every result, and shows you the receipt. Open source, Python, one command to try.

A real run replayed at 4x. Watch it in your browser: live demo (no key, no cost). The saving on the page is the receipt's estimate against Claude Opus 5.5; the benchmark below runs the models it compares with for real.

Measured, not promised

On 50 English tasks Taskpenny had never seen (40 Arena-Hard prompts and 10 requests with four asks each), judged pair by pair by Gemini 3.1 Pro (full report):

Against	Taskpenny's setup	Taskpenny cost	As good or better
Claude Sonnet 5 alone	Sonnet 5 as its strongest model, on equal footing (same worker instruction and reasoning cap)	38% less (19 to 56)	74% (62 to 86): 11 wins, 26 ties, 13 losses
Claude Opus 5.5 alone	the default	78% less (66 to 86)	50% (35 to 65): 1 win, 23 ties, 24 losses

The ranges are 95% intervals: fifty tasks give a direction, not a precise figure. What they say:

• Sonnet-class answers for less, on equal footing. Basic and standard tasks cost about a tenth (88% less), as good or better in 77%.
• Most of an Opus bill saved, but not Opus quality on hard prompts. Taskpenny's cheap tiers were judged worse than Opus about half the time; critical tasks go to Opus itself and tied. If every answer must match Opus, Taskpenny is not there yet.
• Labelling customer messages (first benchmark): 95% cheaper than Sonnet 5, same accuracy (96 of 100 on both sides).

Costs are the ones the gateway reported for each call, with Jev at its list price (it was billed in the Opus run and free before; the report has both). Each pair was judged twice with the order swapped, and a tie includes the pairs where the two orders disagreed. The judge prefers longer answers, and Taskpenny's workers are told to show the key steps while the baselines get no instruction; Taskpenny also caps hidden reasoning (off on tiers 1 and 2, low on tiers 3 and 4) while the baselines use each model's default, so part of the saving comes from that setting and not from routing. The control that gives the baseline both the same worker instruction and the same reasoning cap was run on 1 October 2026: on equal footing the saving is 38% (not 52.5%) and Taskpenny is as good or better in 74% (not 82%), which is the headline above. See the full report. The author also voted blind on 20 pairs (as good or better in 18, where the judge said 14), with limits the report spells out.

We publish where Taskpenny loses too: against Opus, in the first full run (only 13% cheaper than Sonnet 5), and in Catalan, our weakest set. It is all in the report.

Try it

pip install taskpenny
taskpenny demo                     # replays a real run in the terminal: no key, no cost

Then give it a key:

export AI_GATEWAY_API_KEY=...      # one Vercel AI Gateway key: Jev decides, and it reaches Claude, GPT and Gemini
taskpenny run "Write a short email to move tomorrow's meeting to Thursday"
taskpenny ui                       # the live task tree in your browser

The Vercel key is required: every decision is Jev's, and Jev is reached through Vercel AI Gateway. Your own OpenAI, Anthropic or Gemini keys can be added next to it; see "Keys" below.

Every run is saved in runs/ as JSON. taskpenny export runs/<id>.json turns one into a Markdown report.

Who it is for

• You send most of your requests to one strong model, and the bill grows with usage.
• Your requests mix easy and hard parts: a summary plus a decision, ten labels plus a reply, a plan plus copy.
• You want to see why each model was chosen and what each step cost.

Who it is not for (yet): if every answer must match Claude Opus on hard prompts (see above), or if your calls are one short classification each, where a per-request router is enough. Tool calling, images and JSON mode are not supported yet; Taskpenny returns a clear error.

How it is different

Project	What it routes	What Taskpenny adds
RouteLLM, OpenRouter Auto, Not Diamond, LiteLLM's auto router	A whole request, to one model	It can split a request when the parts go to cheaper models, and Jev checks every result before the answer goes out
ROMA	Subtasks, recursively, with a model set for each module	Jev picks the tier of every subtask and the cheapest model of that tier does it; a plan is dropped when splitting would not pay
JevRouter	The steps of a plan, with Jev deciding	Taskpenny also does the work, checks it and gives you the cost receipt

From each project's own README and docs, September 2026. All of them are good at what they do, several report what each request cost, and several can sit next to Taskpenny: it speaks the OpenAI API.

How it works

request
  |
  v
[gate]       Jev: split it? which tier (1-4)? what kind of work? what form of answer?
  |                                   |
  | clearly worth splitting           | one task
  v                                   v
[planner]    subtasks with prompt,  [router]    closed question -> Jev answers it
  success criteria and                         anything else -> cheapest model of the tier
  dependencies; each one goes                  |
  back to the gate                             v
  |                                 [worker]    result + notes for the tasks that depend on it
  |                                            |
  |                                            v
  |                                 [check]     Jev: does it meet the criteria?
  |                                            no -> repair, then one tier up (at most 2)
  v
[assembly]   an outline from a cheap model; the parts are stitched in, not rewritten
  |
  v
[final check] Jev against the request; only what is missing gets written
  |
  v
answer + cost receipt + full task tree

Every decision is a closed question (split or not, which tier, is this good enough), and closed questions are what Jev, TypeSafe AI's decision model, answers well and cheaply. When a request, or a part of a plan, is itself a closed question about texts it gives (label these messages, yes or no for each email, rate each ticket), Jev answers it item by item; the cheapest model only writes the question, and answers the items Jev is unsure about. Jev does not solve problems: maths, code and quiz questions always go to a language model.

Splitting uses more tokens in total. The saving is in money: most tokens go to models that cost a fraction of a frontier model, and Taskpenny drops a plan when the parts would not go to clearly cheaper models (5 of 11 plans in the Sonnet-ceiling run on the 50 new tasks). Details, thresholds and fallbacks: docs/how-it-works.md. Every option and variable: docs/configuration.md.

Reading the live page

• What Taskpenny did: how many Jev decisions, plans, model calls, Jev-solved tasks and checks the run needed.
• Task tree: every task with its tier (1 basic to 4 critical), who did it (a model, or JEV) and what it cost. Click a task to see its prompt, what Jev decided about it, each attempt and its result.
• Warnings: when a result did not pass Jev's check, a check could not run or a part failed, the page says so above the answer, and the task is marked in the tree.
• Cost receipt: planning, work, Jev decisions, checks and assembly add up to the total. The comparison with one strong model (Claude Opus 5.5) is an estimate: the same request sent once, with an answer as long as Taskpenny's, scaled by the hidden reasoning Taskpenny's own models used in that run.

Use it from any tool

taskpenny serve starts an OpenAI-compatible endpoint on http://127.0.0.1:8765/v1, with the live page on the same address. Change only the base URL:

from openai import OpenAI
client = OpenAI(base_url="http://127.0.0.1:8765/v1", api_key="unused", max_retries=0)  # each call is a paid run
reply = client.chat.completions.create(
    model="taskpenny",             # or "taskpenny/anthropic" to use only Claude models
    messages=[{"role": "user", "content": "Draft a polite reminder for an unpaid invoice."}],
)
print(reply.choices[0].message.content)
print(reply.model_extra["taskpenny"])   # run id, status, warnings, cost in USD, baseline estimate, saving

• Chat Completions and Responses both work, so n8n's OpenAI Chat Model node needs only the new base URL. A ready-to-import workflow: examples/n8n.
• Every request is one Taskpenny run, saved in runs/ and visible live on the page while it works.
• System messages and earlier turns are passed as context; the last user message is the request.
• stream: true works, but the answer arrives in one piece at the end: Taskpenny checks the work before answering. The headers and a keep-alive line go out at once.
• Nothing fails in silence: taskpenny.status says done, unverified (complete, but a check did not pass or could not run) or partial (stopped early, finish_reason: "length"), with the reasons in taskpenny.warnings; a run with no answer is an HTTP 502 error.
• Each request is a paid run: set max_retries=0 in your client, or send an Idempotency-Key header so a retry gets the first run's answer. A client that disconnects without that header cancels its run.
• TASKPENNY_CEILING=anthropic/claude-sonnet-5 makes the model you use today the strongest one Taskpenny may use.
• Per request: "taskpenny": {"max_cost": 0.2, "no_split": true} in the body, or the header X-Taskpenny-Max-Cost.
• The server listens only on your machine. If you open it, set a long random TASKPENNY_API_KEY (openssl rand -hex 24) and put an https proxy in front: then the API and the page need the key (the page asks for it once). A request's budget is a ceiling, and it can ask for at most TASKPENNY_MAX_COST (2 USD by default).

Docker

docker compose up                  # page and API on http://127.0.0.1:8765
# or: docker build -t taskpenny . && docker run -p 127.0.0.1:8765:8765 -e AI_GATEWAY_API_KEY taskpenny

Keys come from your environment and are never written into the image. Runs are kept in the taskpenny-runs volume.

Keys

You set	What Taskpenny does
AI_GATEWAY_API_KEY (required)	Jev decides every step and every model is reached through Vercel AI Gateway, with the real cost of every call.
That, plus TASKPENNY_DIRECT=anthropic,openai and those providers' keys	Those providers' models go straight to their own API; everything else, Jev included, through Vercel.
That, plus TASKPENNY_LOCAL	Basic tasks go first to a free local model (below).

Without the Vercel key there is no real run: Taskpenny tells you so, and taskpenny demo and --dry-run still work. taskpenny doctor shows what your keys reach and whether each model name exists on its provider's API, without spending tokens.

Local models (free)

With Ollama running, basic tasks can run on your machine at no cost:

ollama pull qwen3:4b
export TASKPENNY_LOCAL=qwen3:4b          # tier 1 goes local; "qwen3:8b@2" also covers tier 2; "auto" = all installed

Jev still checks every result. A weak answer is first repaired by the same local model, then moves one tier up, where a cloud model does it unless a local model covers that tier too. Use a model of at least 3 to 4 billion parameters: tiny ones answer fast but badly.

What leaves your machine

Your prompt goes to Jev and the models through Vercel AI Gateway, and to any provider you call directly. Keys are read from environment variables only and are never written to disk, run files or logs; set the server's own key with TASKPENNY_API_KEY too, since a key on the command line shows in the process list. Saved runs contain your requests and answers. The page loads nothing from other sites (its fonts come with it). See SECURITY.md.

All results

With Jev at its list price. The report also has the figures with Jev free, as it was during the run.

What Taskpenny did	Tasks	Taskpenny cost	As good or better
Basic and standard tasks, one cheap model	103	92% less	76%
Of those, labelling customer messages (true labels)	10	95% less	same accuracy, 96 of 100
Advanced tasks, one model	16	11% less	69%
Critical tasks, sent to Claude Opus	8	2.0x as much	100%
Requests split into parts	15	2.2x as much	73%
All	142	13% less	76%

That run is why the ceiling and the "split only when it pays" rule exist. The 50 new tasks above were run after both changes. Method, raw data and how to rerun it: bench/public.

What we have learned so far

• Jev's gate chooses well when to split and what kind of answer is expected (41 of 42 on our development set).
• The saving comes from everyday requests going to models that cost a small fraction of a frontier model.
• Splitting only pays when the parts can go to cheaper tiers than the whole; at advanced level it did not.
• Cheap models give correct but bare answers. The automatic judge prefers more explanation; in a blind check of 20 pairs, the author often preferred the short answer that did only what was asked.
• Against Opus 5.5 the cheap tiers are not enough on hard prompts. The next thing to measure is a setting that sends more of that work to the strong tiers.

FAQ

Can you trust an LLM judge? It is from a third provider, compares each pair twice in both orders, and counts a tie when the two orders disagree. It does like longer answers: many of Taskpenny's losses on basic tasks were short, correct answers against longer ones. You can rerun the benchmark with your own judge, or give the baseline Taskpenny's own worker instruction (--baseline-system worker) to see how much that matters.

Do I need Vercel? Yes. Every decision in Taskpenny is Jev's, and Jev is only reached through Vercel AI Gateway. Earlier versions let a small language model stand in for Jev; it made decisions that cost more and were never measured for accuracy, so it is gone. Your own provider keys still work next to the Vercel key.

Why Jev? Every decision Taskpenny makes is a closed question. Jev answers those with a probability and a confidence, costs about 4 cents per thousand decisions at list price (about 1,000 tokens each in our benchmark), and never writes text.

What if Jev changes? The development cases (bench/run_dev.py) show quickly whether its decisions moved, and the thresholds that use them are in one place (Settings in decider.py).

Contributing

Adding a model is a few lines in models.yaml. Translations of the page and good first issues: CONTRIBUTING.md and docs/good-first-issues.md.

If Taskpenny saves you money, a star helps other people find it.

License

The code is MIT. The benchmark's task texts keep their own licences (Apache 2.0, CC BY-SA 3.0, CC BY 4.0): see bench/public/LICENSES.md. Made by Cinto Casals · SerIA Nativa.