Write what the user does. Decisium runs it in Playwright:

@url:https://www.saucedemo.com/
Feature: Checkout

  Scenario: Checkout requires a first name
    When I log in as "standard_user" with password "$SAUCE_PASSWORD"
    And I add "Sauce Labs Backpack" to the cart
    And I open the cart
    And I start the checkout
    And I try to continue without filling in the form
    Then the error should say "First Name is required"

No selectors, no page objects, no step definitions.

How it works

Each Step is executed by Jev, TypeSafe's decision model. Jev does not generate text or code. It picks among the options Decisium enumerates from the page (elements, actions, check kinds) and returns a probability for each. Code, not the model, decides whether a Step passed: a value check compares the element's value with the quoted one, a presence check looks for the text, a state check reads the control's state. No LLM, no prompts, no invented selectors.

What each Step resolved to is recorded in a cassette next to the feature. CI replays it with zero model calls, the same outcome every run; a real UI change fails as UI_CHANGED.

Install

Global, one decisium command for every project:

npm install -g decisium
decisium install                     # the Chromium build Decisium drives

Or per project, with the version pinned in package.json (run commands as npx decisium …):

npm install --save-dev decisium
npx decisium install

Then:

echo 'TYPESAFE_API_KEY=...' >> .env   # live runs only; replays need no key
decisium doctor

Node 22.18+ or 23.6+.

Use

decisium lint checkout.feature                 # how each Step will be read; flags known-bad wordings
decisium run checkout.feature                  # live: asks Jev, records checkout.cassette.json
decisium run checkout.feature --record none    # replay: zero model calls (CI)
decisium step "I open the cart" --url https://www.saucedemo.com/   # try one wording

A failed run prints the reason under each Step and writes <reportDir>/<timestamp>/report.md (reportDir defaults to runs): the Step, Jev's answers, the page text around the element, a screenshot, a Playwright trace and a rerun command, ready for you or a coding agent.

Decisium runs inside cucumber-js: your cucumber.mjs, profiles, formatters (--format junit:junit.xml) and your own step definitions (--import, with this.page and this.context) keep working.

Configuration

Put Decisium options in worldParameters.decisium in your project's cucumber.mjs. decisium run loads it automatically:

// cucumber.mjs
export default {
  worldParameters: {
    decisium: {
      url: "http://localhost:3000",
      reportDir: "e2e/runs",
      checkTimeout: 10000, // milliseconds to wait for the expected state
      actionTimeout: 10000, // milliseconds to wait for the page to settle after an action
      maxTurns: 12, // action Turns allowed per Step
      confidence: { target: 0.5, answer: 0.8 }, // default confidence thresholds
    },
  },
};

Precedence: CLI flag > DECISIUM_* environment variable > configuration > default. For example, --check-timeout 15000 overrides both DECISIUM_CHECK_TIMEOUT and checkTimeout in the file.

Raise timeouts for slow apps; raise maxTurns for long flows, or split the Step. Reword ambiguous Steps before changing confidence. Lowering confidence.answer below 0.6 warns because a wrong reading can pass.

See Configuration for every option, default, flag, environment variable, and reporter setup.

Docs

andletenkov.github.io/decisium

• Quick start
• Writing features
• Writing Steps: every kind of action and check, and how to word it
• Client steps · Browser context · Network replay
• Record and replay · CI · Configuration
• Examples against real public sites
• Agent skill for coding agents: designs CUJ-first scenarios from app code or requirements, writes and repairs features. Install with npx skills add andletenkov/decisium (also ships in the package: $(npm root -g)/decisium/skills/decisium/SKILL.md)

Jev and your data

Live runs call Jev through the TypeSafe API and need a TypeSafe API key; Jev is TypeSafe's hosted service under its own terms. Per Turn it receives the Step's text and a text snapshot of the page (the accessibility tree: roles, names, visible text, link URLs). No screenshots, cookies or network traffic. Write credentials as "$NAME": only the token leaves your machine. Replays send nothing.

License

MIT © Andrei Letenkov