Say it once.
Keep it as a file.

Checked before it runs. Run with the model you choose. Proven afterwards.
Nika turns the AI work you repeat into a readable workflow that stays yours. Fully open source.

_{“Read ./data/orders.csv, keep only the rows whose status is paid, and write them to ./out/paid.csv.”
One sentence becomes a checked file; yes saves it, run it keeps the two paid rows, and /proof shows what the run recorded. The real Session of nika 0.123.0, restyled; no AI model is involved.}

What is Nika?

Nika turns repeatable AI work into a small file you keep. Say what you want done, like "every Monday, pull the action items out of my meeting notes", and Nika writes it as a readable .nika workflow. Before anything runs, its check shows what the workflow will do, which models and tools it uses, what it is allowed to touch and what it can cost, without calling a model. A workflow that could read your private data, take in untrusted content and send data out is refused until it asks a person first. You run it when you decide, with the model you choose, on your machine or through a provider's API, and every run leaves a tamper-evident record you can verify. One Rust binary with a terminal Session and a command line, plus a TypeScript SDK for your applications; local-first and fully open source (AGPL-3.0).

1 · Say it	2 · Check it	3 · Run it	4 · Prove it
Describe the job; Nika writes a .nika file (or nika compile from a skeleton)	nika check audits it before any model is called	nika run with the model you choose	nika trace verify checks the run's record

See it · Control · Trifecta · Try it · Examples · Why a file · Where it works · Limits · Docs

See it in four steps

1 · Say it

Describe the job in plain words. Nika writes it as a .nika file, shows you what it will do and what it can touch, and saves it only when you say yes. Nothing runs until you ask. The clip at the top is that Session; this is its first answer, as the plain view prints it:

nika › Read ./data/orders.csv, keep only the rows whose status is paid, and write them to ./out/paid.csv.
✓ recorded 3 requirements
Nika proposes `compiled-workflow.nika`:
Does
  1. read_source · reads a file
  …
  8. write_output · writes a file
Runs
  when you ask (« run it ») · no schedule was asked
Can touch
  external effects · none
  human approval at run · none
Changes
  + `compiled-workflow.nika` · 97 lines · new
Needs
  nothing more from you
Nothing has run yet · `yes` saves these exact bytes and checks them · running is its own line (« run it »)

2 · Check it

Before anything runs, nika check reads the file and reports what it will do, what it may touch and what it can cost. It calls no model and spends nothing.

_{Two mistakes caught before anything runs, the fix, and the clean re-check. Every line is captured from the real CLI.}

3 · Run it

You run it when you decide, with the model you choose. Here a local model, through Ollama, writes a meeting's action items as typed JSON.

_{The audit first, then a real run on a local model (ollama/llama3.2:3b); the clip names the release each part was captured with. Nothing leaves the machine.}

4 · Prove it

Every run leaves a hash-chained record. nika trace verify reads it back, and when a single byte changes it names the line where the chain breaks.

Runs are also signed once this machine has a run-signing key. Mint it once with NIKA_KEYCHAIN=off nika key init: the key lands in ~/.nika/keys/ (mode 0600), where terminal runs, scripts, CI, the TypeScript SDK and nika serve all read it, and later runs report SEALED in nika trace verify and /proof. Without the variable, a terminal on a Linux desktop can keep the key in the Secret Service, which only terminal runs open (nika key align copies it to the files), and on a Mac whose keychain holds a key from Nika 0.122 or older, nika key init refuses: 0.123.0 and later never open the macOS keychain.

_{The chain read back intact, then one changed byte refused at the next line. A mock/echo rehearsal captured from the real CLI; the scan is an illustration.}

You stay in control

It refuses the lethal trifecta before a token is spent

A workflow that can read your private data, take in content nobody vetted (a web page, a tool's answer, a command's output) and send data out is one injected instruction away from a leak. Simon Willison named this the lethal trifecta. nika check reads it from the permits, then follows the untrusted content from step to step, through a model's answer and into child workflows. When all three meet, it refuses the file until a person must say yes first.

This workflow reads a note, fetches a public page, asks a local model for a digest and posts it to Slack:

nika: page-digest

model: ollama/llama3.2:3b

permits:
  fs: { read: ["./notes/today.md"] }
  net: { http: ["news.ycombinator.com", "hooks.slack.com"] }
  tools: ["nika:fetch", "nika:read", "nika:notify"]

tasks:
  page:
    invoke:
      tool: "nika:fetch"
      args: { url: "https://news.ycombinator.com/" }

  notes:
    invoke:
      tool: "nika:read"
      args: { path: "./notes/today.md" }

  digest:
    with: { page: "${{ tasks.page.output }}", notes: "${{ tasks.notes.output }}" }
    infer:
      prompt: "Pick the three stories that matter for my notes.\nNotes: ${{ with.notes }}\nPage: ${{ with.page }}"
      max_tokens: 400

  post:
    with: { digest: "${{ tasks.digest.output }}" }
    invoke:
      tool: "nika:notify"
      args: { target: "https://hooks.slack.com/services/T000/B000/XXXX", message: "${{ with.digest }}" }

The page never reaches Slack directly, only through the model's digest. The check follows it anyway and refuses the file with exit code 2:

nika check · page-digest.nika
 ✔ PLAN     3 waves · 4 tasks · max parallelism 2
 …
 ✖ TRIFECTA [NIKA-SEC-009] lethal trifecta complete · human gate required — untrusted content from `page` reaches egress task `post` while private read + untrusted ingress + external egress are all permitted …

Drop any one of the three and there is nothing to refuse. To keep all three, put a question in front of them: a nika:prompt with no default, whose answer the fetch, the read and the post each require.

  approve:
    invoke:
      tool: "nika:prompt"
      args: { message: "Read my notes, fetch Hacker News and post a digest to Slack?" }

  page:
    with: { go: "${{ tasks.approve.output }}" }
    when: ${{ with.go == true }}
    invoke:
      tool: "nika:fetch"
      args: { url: "https://news.ycombinator.com/" }

With nika:prompt added to permits.tools, and the same go binding and when: line on notes and post, the check passes with exit code 0:

 ✔ TRIFECTA no lethal trifecta over the declared permits: without a human gate
 layers · valid ✔ · access ready ✔ · capacity fit ✔ · run ready ✔

A gate that only looks like one is refused too: a prompt with a default: answers itself and guards nothing (NIKA-SEC-009 stays), and a step that still runs after a "no" fails NIKA-SEC-014. At a terminal the run asks; in CI it pauses with exit 4, as shown below. Every verdict here was captured from nika 0.124.0. NIKA-SEC-009 explains the rule; Meta's Agents Rule of Two states the same principle for agents.

It tells you the cost before the first token

nika check prices a workflow from its model's catalog price and the output limit each step declares. Set a budget below that ceiling and the run refuses to start: no model is called and nothing is spent.

_{Unbounded until one line declares max_tokens, then a hard ceiling of $0.0614; a $0.05 budget refuses the run (exit 2). Prices are catalog estimates, not invoices; no model was called.}

It asks before it acts

A step can wait for a person. At your terminal it asks; in CI, where nobody can answer, the run pauses safely with exit 4 and prints the one line that resumes it.

_{Nothing ships without a yes: asked at a terminal, paused in CI, resumed by the printed line with the finished build reused. Every terminal line is captured from the real CLI; the door is an illustration.}

Try it in two minutes

1 · Install

curl -LsSf https://nika.sh/install.sh | sh

Homebrew, npm, a container, a release archive, Nix or Windows

• Homebrew: brew install supernovae-st/tap/nika
• npm, the binary plus the TypeScript SDK: npm install @supernovae-st/nika (the nika command lands in node_modules/.bin). The package bundles the engine of its own version: check nika --version.
• A container (Linux, amd64 and arm64), built from the same release binaries: docker run --rm ghcr.io/supernovae-st/nika:0.124.1 --version. Mount a project to check or run its files, for example docker run --rm -v "$PWD:/work" -w /work ghcr.io/supernovae-st/nika:0.124.1 check hello.nika.
• A release archive: download one from the latest release. Every release ships a checksum manifest, a GitHub attestation and SLSA provenance; RELEASING.md gives the three verification commands, for example gh attestation verify nika-macos-arm64-0.124.1.tar.gz --repo supernovae-st/nika.
• Nix: nix profile install github:supernovae-st/nika/v0.124.1 builds the release from the repository's flake. Without the tag, the flake builds the default branch, which can be ahead of the latest release.
• Windows: use WSL2 and the Linux binary. Native Windows binaries are not shipped.

2 · Say what you want

This first job needs no AI account: Nika's deterministic compiler settles it without calling a model. Make a folder with a small spreadsheet and open the Session:

mkdir -p orders-demo/data && cd orders-demo
cat > data/orders.csv <<'EOF'
order_id,customer,status,amount
1001,Juniper Books,paid,18.00
1002,Kestrel Cafe,pending,9.50
1003,Linden Studio,paid,13.50
1004,Moss Supply,refunded,6.00
EOF
nika

At the prompt, type:

Read ./data/orders.csv, keep only the rows whose status is paid, and write them to ./out/paid.csv.

Nika proposes a .nika file and shows what it will do, what it can touch and the result of its check. Nothing has run yet. Type yes to save the file, then run it. out/paid.csv gets the header and the two paid rows, and /proof shows what the run's record proves, and what it does not.

Tip

Nika works only inside the folder you start it in. /show prints the proposal's exact bytes, /meaning maps your request clause by clause, and no discards it. Ctrl+T switches the view to full screen and back, and nika --plain gives the same Session as plain lines. The Session guide covers questions, changes, spending ceilings and /restore.

In a Git repository, the Session leaves .gitignore alone: before you commit, add .nika/traces/ (run records can hold file contents and model outputs) and the Session's own .nika/*.ndjson and .nika/session-state.json. After a run, the Session reminds you when traces are not ignored.

3 · Add a model

Most open-ended requests need a model to write the workflow, and workflows such as summaries call a model each time they run. Nika reads provider keys from your environment, so keep yours in your shell startup file. For DeepSeek:

# in ~/.zshrc or ~/.bashrc, then open a new terminal
export DEEPSEEK_API_KEY='your-key'

The first request that needs a model shows a numbered choice: answer 2 deepseek/deepseek-flash. Nika keeps the choice for later Sessions, and /intelligence changes it. Other API providers and local engines (Ollama, llama.cpp, LM Studio, vLLM) work too: nika catalog lists them. Your provider meters and bills these calls; Nika's cost figures are catalog estimates, not invoices.

4 · Use the file directly

A workflow is an ordinary file. The command line compiles, checks, runs and verifies it. This offline lesson needs no provider:

nika compile hello hello.nika
nika check hello.nika
nika run hello.nika
nika trace verify

▶ Watch these four commands run, exactly as captured from the CLI.

hello always uses mock/echo, a stand-in model that echoes the prompt, even when provider keys are present. It proves that the workflow runs, not that a model answered. Each run records its trace under .nika/traces/, and creating the file adds that directory to .gitignore. nika trace verify checks the latest trace's integrity, not the truth of an AI answer.

What you can hand to Nika

You say	Nika keeps	Watch
"Read ./data/orders.csv, keep only the rows whose status is paid, and write them to ./out/paid.csv."	A workflow that reads one file and writes one file. No AI model is involved.	▶ The Session
"Pull the action items out of my meeting notes."	A workflow that asks a local model and writes the items as typed JSON.	▶ A local run
"Every Friday, turn CHANGELOG.md into release notes."	A workflow your coding agent writes with the Nika plugin; the check catches its mistake before anything runs.	▶ With your agent
"Rate the risk of each pull request."	A workflow the Nika GitHub Action checks whenever a pull request changes it: one comment carries the verdict.	▶ In your pull requests

Why a file, and not a chat?

A chat answer is gone when the conversation ends, and the next one can differ. A .nika file stays: you read it, check it, run it again and review its changes like any other file in your project.

• Say it once. The request you would retype in a chat every week is kept as a file that runs again. ▶ Watch a weekly request become a file
• Read it before it runs. Every workflow has the same shape: nine sections and four kinds of step, in a file you can open and review. ▶ Watch one taken apart
• It touches only what it declares. The file lists what it may read, write and reach. The check refuses the step that reaches past it. ▶ Watch the check catch an escape
• Failures are planned for. A step can name its fallback: the run finishes, the output says it is stale, and the record keeps the failure. ▶ Watch a missing feed absorbed
• Parallel where it can be. Steps that do not depend on each other run side by side, in waves the check plans before the run. ▶ Watch a workflow run in waves

Every clip on this page shows real files and terminal lines captured from the binary, names the release it was captured with, and says what it illustrates. The media index lists them all and how they are made.

Works where you already work

Nika comes to the tools you already use. Your coding agent can write the file for you, and the check keeps it honest:

_{Your agent writes it, Nika checks it, you keep it. The agent session is an illustration; the checks and the rehearsal run are captured from the real CLI.}

Where	What you get	Watch
Your coding agent · nika-plugins	Claude Code, Codex, Cursor and others learn to write a workflow, check it and repair what the check finds.	▶ above
Your editor · nika lsp	The language server inside the binary: the check's findings as you type, in any LSP client. The VS Code extension (nika-vscode) stays at 0.120 and is not qualified with 0.124; point its nika.server.path at your 0.124 binary (known limits).	▶ The audit, as you type
Your pull requests · nika-action	One comment with the verdict, before anyone spends a token.	▶ Every pull request gets a verdict
Your app · nika-client	Run a workflow from TypeScript (the package), get a typed result and verify its receipt, with the engine the package bundles or against your nika serve.	▶ Run it from your app, prove what ran · ▶ One client, two doors

From your application

npm install @supernovae-st/nika brings the TypeScript SDK and the engine of its own version (Node.js 22 or newer, on macOS or Linux with glibc). Run NIKA_KEYCHAIN=off ./node_modules/.bin/nika key init once, so the engine your app starts can seal each run's record. Then, beside a hello.nika, this is the package's quick start:

import { Nika, isNikaRunSucceeded } from '@supernovae-st/nika';

const nika = new Nika({ cwd: process.cwd() });

// The engine checks the file first: a workflow it refuses throws here and never starts.
const run = await nika.run<{ greeting: string }>('hello.nika', { maxCostUsd: 0 });
const result = await run.result();

// A failed run is data you read, not an exception.
if (!isNikaRunSucceeded(result) || !result.receipt) {
  console.error(result.status, result.error?.code, result.error?.message);
  process.exit(1);
}
console.log(result.outputs?.greeting);

// Ask the engine to verify the run's tamper-evident record.
const proof = await nika.traceVerify(result.receipt);
console.log(proof.verified ? 'receipt verified' : `not verified: ${proof.reason}`);

Save it as demo.mts (top-level await needs a module) and run node demo.mts: Node.js 22.18 or newer runs the TypeScript as is. The SDK quick start gives the hello.nika this program runs.

To reach a nika serve instead of the bundled engine, keep the methods and change the options of two lines:

const nika = new Nika({ url, token, allowInsecureHttp: true });
const run = await nika.run<{ greeting: string }>('hello.nika', { idempotencyKey });

url and token name the server and its bearer token. Plain http:// is accepted only to a loopback host, and only with allowInsecureHttp: true. Over HTTP, run() needs an idempotencyKey you own (a retry with the same key returns the same job) and refuses maxCostUsd: the server applies its own per-run ceiling, USD 1 by default. hello.nika is then a served name, the workflow's path from the server's project root. nika-client documents the whole API.

_{Your app asks, the engine decides, the receipt proves it. The code is the quick start above, which the capture ran, with lines 3 and 6 also shown as its server driver ran them against nika serve. Every event, verdict, hash and version on screen was captured from @supernovae-st/nika 0.124.0, the engine it bundles and nika serve in a mock/echo rehearsal; the cards, lanes, packets and pacing are illustration.}

Know the limits

• 0.124 is the current release line. Work stays focused on maintenance, security and the media capabilities workflows need; native video is planned for 0.125. The 0.123.x line is the previous one, and there is no hosted service. The known limits are listed in plain words, each with a way around it: Known limits in 0.124.
• Some requests cannot be expressed. Nika then says what stopped it and writes nothing.
• A clean check is not a true answer. It describes a file's structure and boundary; it does not prove that model output is right.
• The trifecta check judges permits and flow, not words. It does not read a page or a model's answer for injected instructions, and a person who answers yes approves what follows. On a harness seat, what permits: covers is listed per seat (harness agents).
• This README describes the released 0.124.1. Compare nika --version with the changelog, which lists what each release changed. Until the next release, each change merged after 0.124.1 is described in its own file under changelog.d/, and the release folds those files into the changelog.

The four building blocks

Verb	What it does
infer	Ask a model to produce an answer
invoke	Call a native tool, MCP tool or another workflow
exec	Run a command
agent	Let a model use allowed tools for a bounded number of turns

A workflow uses only the verbs its job needs. The orders workflow at the top uses invoke alone: eight steps over five builtin tools (nika:read, nika:convert, nika:jq, nika:assert and nika:write), with no model and no shell.

Compile from the command line

nika compile --list lists exact skeletons. Preview one with nika compile <slug> --json, then answer its stable questions with repeatable --answer KEY=JSON_LITERAL. An incomplete result includes its candidate and questions; it does not write a file. Only a Ready candidate plus an explicit destination writes. Existing destinations require --force.

For an accepted source, a conservative constant edit uses the same core:

nika compile --base workflow.nika --change 'Set const.topic to "new topic"' --json

Add --output edited.nika to materialize a Ready edit. The base source remains explicit. Unresolved intent stays incomplete without a substitute workflow. --authoring-model seats a model to interpret free intent and revise text. No request count is imposed by default: creation ends on a result, a failure, no progress or a cancellation. --authoring-max-calls N sets an explicit ceiling (an ACP harness counts its invocations; its own requests are unknown), and typed repairs or samples that cannot fit under it are refused before any request. --authoring-strategy selects escalate, only, sketch or off. The compiler checks the proposed source and its fidelity to the request. This is not a guarantee of arbitrary-language understanding, and Graph editing is not implemented by this CLI.

Compile's Check preview judges source only. nika check and nika run judge the actual environment separately. For a real model, choose the provider and access explicitly; the model setup documentation explains local, API and supported harness choices. On a harness seat an agent: task runs the application's own tools: what permits: covers there, and what it does not, is listed per seat and printed by nika check.

Before sharing a workflow or a run

Share the workflow, not credentials or private data. Review file paths and tool access. Keep secrets out of source control.

Run journals can contain the data and outputs the workflow processed. The .nika/traces/ directory is a data-at-rest surface: it inherits the sensitivity of everything the run read. Exclude it from Git unless you deliberately intend to publish those records, and treat them with the same care as their source data.

After a run, nika trace verify verifies the latest journal. Compare its head with the one printed by the run. This checks the record, not the AI's judgement.

🦋 The Nika family

	Repository	What it gives you
🦋	nika	The engine and CLI: write, check, run and verify AI workflows
📖	nika-docs	The documentation, live at docs.nika.sh
📜	nika-spec	The language specification and the suite that proves an engine follows it
🧩	nika-vscode	The editor extension, frozen at 0.120 and not qualified with 0.124: use nika lsp and the JSON Schema
🟦	nika-client	Run and verify workflows from TypeScript
✅	nika-action	A GitHub Action that posts a nika check verdict on your pull requests
🚀	nika-actions-starter	A ready template: workflows, editor setup and CI from the first push
📦	nika-registry	Shareable workflows, pinned and re-verified
🤖	nika-plugins	Teaches your coding agent (Claude Code, Codex, Cursor…) to write Nika
🍺	homebrew-tap	brew install supernovae-st/tap/nika
🐙	gh-nika	The Nika CLI as a GitHub CLI extension
🏛️	nika-estate	Where each file in Nika's core repositories comes from, declared and re-checkable

This repository is the one executable: it parses, checks, runs and traces every workflow. The language is defined by the specification, and the other repositories drive this engine without adding to its authority.

Go further

Session guide · Examples · Documentation · TypeScript SDK · Editor extension (0.120, not qualified with 0.124) · Open specification · Registry · Planning archive · Website

Nika 0.124 is the current open-source release line, usable today and maintained. The engine is AGPL-3.0-or-later; the specification and the TypeScript SDK are Apache-2.0.