# Show HN: Jevpipe – a fast System 1 for AI agents, as a Unix pipe

> Source: <https://github.com/fabianboth/jevpipe>
> Published: 2026-09-28 13:15:05+00:00

**Give your coding agent a System 1.**

Fast, cheap judgments over thousands of files, lines or records in one shell command,

so your agent decides at scale instead of reading everything itself.

[Quick start](https://github.com/fabianboth/jevpipe#quick-start) ·
[Example](https://github.com/fabianboth/jevpipe#example) ·
[Use cases](https://github.com/fabianboth/jevpipe#use-cases) ·
[Measured](https://github.com/fabianboth/jevpipe#measured) ·
[Cost](https://github.com/fabianboth/jevpipe#cost-and-speed)

```
uv tool install jevpipe                             # the CLI
jevpipe auth set-key                                # your OpenRouter key, kept in the system keychain
npx skills add fabianboth/jevpipe --skill jevpipe   # teaches your agent when and how to use it
```

You need an [OpenRouter API key](https://openrouter.ai/settings/keys). Where there is no keychain,
as in containers, CI or headless Linux, set `OPENROUTER_API_KEY` instead; it also takes precedence.
No uv yet? [Install it](https://docs.astral.sh/uv/getting-started/installation/) or use pipx.

## Without uv, or with the GitHub CLI

```
pipx install jevpipe                                # instead of uv
gh skill install fabianboth/jevpipe jevpipe         # the skill, with the GitHub CLI
```

Which of the 19 commits in ripgrep 15.1 are new features? Ask each commit message:

```
# in a clone of https://github.com/BurntSushi/ripgrep
git log --format=%s 15.0.0..15.1.0 | jevpipe filter "Is this a new feature?"
# the commit messages that match the question
ignore/types: add `ssa` type
printer: add Cursor hyperlink alias

# the summary, on standard error
jevpipe: 19 records, 2 kept, 0 skipped, 0 failed, $0.000225, 1.1s
```

## Typed answers with `map`: sort every commit into feature, fix, docs or internal

```
# in a clone of https://github.com/BurntSushi/ripgrep
git log --format=%s 15.0.0..15.1.0 | jevpipe map -q '{
  "kind": {
    "type": "choice",
    "instructions": "What kind of change is this, for the release notes?",
    "criteria": {
      "feature": "a new capability for users",
      "fix": "a bug fix users would notice",
      "docs": "documentation only",
      "internal": "refactoring, tests, CI, dependencies or release chores"
    }
  }
}'
```

Every commit becomes one JSON line. One of the 19:

```
{
  "record": "printer: add Cursor hyperlink alias",
  "answers": {
    "kind": {
      "type": "choice",
      "choice": "feature",
      "probabilities": {"docs": 0.05, "feature": 0.87, "fix": 0.03, "internal": 0.05},
      "confidence": 0.82
    }
  }
}
```

All 19 took 1.1 seconds and cost $0.0003. Pick from them with jq, for example the fixes:
`jq -r 'select(.answers.kind.choice == "fix") | .record'`. A low confidence marks an answer worth
a second look.

Each item is judged on its own, so ask what the item itself can answer:

| Job | Question for every item | Answer | 
|---|---|---|
| Search code by meaning | Does this file retry failed requests? | yes/no | 
| Triage CI failures | Timeout, network error, failed assertion or crash? | choice | 
| Review a large diff | Does this change touch authentication or permissions? | yes/no | 
| Label an issue backlog | Bug report, feature request or question? | choice | 
| Route a support inbox | Which team? How urgent? | choice, score | 
| Moderate a comment queue | Fine, spam or abusive? | choice | 
| Screen papers | How relevant is this abstract to my question? | score 1 to 5 | 

**Classification.** Jev against general LLMs on intent routing and prompt-injection detection,
from an [independent study](https://www.ayautomate.com/blog/jev-vs-llm-benchmark):

**Code search.** jevpipe in an agent's hands: 470 searches from the
[extended CodeSearchNet Challenge](https://huggingface.co/datasets/Scoolar/codesearchnet-challenge-extended)
in five languages, each over every function of its language.

**[Read the full benchmark](https://github.com/fabianboth/jevpipe/blob/main/bench/README.md)**:
every language, speed and cost, and the searches where jevpipe loses.

|  | Asks | Prints | 
|---|---|---|
| `jevpipe filter "question"` | one yes/no question | the lines answered yes, like grep | 
| `jevpipe map -q '{...}'` | several typed questions: yes/no, one choice, a score | one JSON line per record | 

Both read their input like grep: lines through a pipe or from the files you name. With
`--read-files`, each line is a path, and the file it names is judged instead:

```
git log --format=%s | jevpipe filter "Is this a new feature?"                       # each commit message
jevpipe filter "Is this an error worth a closer look?" app.log                      # each line of app.log
git ls-files | jevpipe filter "Does this file retry failed requests?" --read-files  # each file
```

`jevpipe <command> --help` has the rest.

Every record is one request billed to your [OpenRouter](https://openrouter.ai) credit, and the
cost follows the size of each record: about a cent per 1,000 commit messages, 4 to 18 cents per
1,000 source files. Asking several questions at once barely changes it. Up to 100 records run at
the same time, so hundreds take seconds.

`--max-cost 0.50` stops sending requests once the run has spent $0.50; it then exits with status 3
and names the line to resume from.
To cap every run by default, run `jevpipe config set max-cost 0.50` once; `jevpipe config --help`
lists the other defaults you can set.

[Apache-2.0](https://github.com/fabianboth/jevpipe/blob/main/LICENSE). jevpipe is an independent
project, not affiliated with or endorsed by TypeSafe AI; the answers come from
[Jev](https://typesafe.ai), TypeSafe AI's calibrated decision model, through OpenRouter. Building
from source needs Rust (rustup picks the pinned toolchain) and PowerShell 7 for `./check.ps1`.