Quickstart

Use this Quickstart to get Cosine set up and complete your first task.

Cosine is your AI-powered software engineer. It connects to your codebase, works on tasks in the background, and proposes code changes for you to review. This guide focuses on the fastest path to getting started: setting up Cosine, connecting a project, and running your first task on the Cosine platform.

Choose your environment

Cosine is one product across three starting points: Platform, CLI, and VS Code. These environments are connected by design, so you can begin in one place and move to another later without changing products or starting from scratch. This Quickstart is platform-first, but it helps to know how each environment fits together before you begin.

CLI

The Cosine CLI is your coding agent in the terminal. It brings Cosine directly into your local development environment and is best for terminal-native workflows, scripting, and working close to the code. If you want to get started in the terminal first, use the CLI quick start guide.

Platform

The Cosine Platform is the remote workspace where you can connect repositories, start tasks, review plans and code changes, and keep work moving in the background. It is the fastest way to see the full Cosine workflow, which is why this Quickstart uses the Platform for the step-by-step setup.

VS Code

Cosine for VS Code brings the full Cosine agent natively into your editor. It fits best when you want an in-editor experience while keeping the rest of the Cosine workflow close at hand. To get started, install it from the VS Code Marketplace.

Before you start - checklist

✅ Access to your GitHub to add integrations
✅ Permission to read/write to at least one repo
✅ (Optional) Your team’s task tool (Jira/Linear/Asana) and Slack
✅ (Optional) A small, non‑critical task you’re happy to try first

Quick start in 10 steps

Create your account
- Open the Cosine platform and sign up with your work email.
Connect your code
- Link your GitHub/other git provider and import one or more repos you want Cosine to work on (you can also start a new project from a template).
Pick a project
- From the Projects page (second tab at the top), select the repo/project you just imported.
Tell Cosine what you want
- Use the New task / prompt box. Be simple: describe the bug or feature and any acceptance criteria (what “done” looks like).
(Optional) Kick off from Jira/Linear/Slack
- Instead of typing a prompt, you can trigger tasks by tagging/labelling a ticket in Jira/Linear or by mentioning @cosine in a Slack thread. Details below.
Start the task — then walk away
- Cosine works asynchronously. Don’t babysit it. Queue several tasks if you like.
Come back to review
- Open the task to see what Cosine did: the plan, code changes and validation runs.
Review the pull request (PR)
- Read the diff, view test/CI status, and add comments if you want tweaks.
Ask for changes or iterate
- Type follow‑ups (e.g., “Make the button blue and add a test”). Cosine updates the branch/PR.
Merge
- When happy, merge the PR from Cosine or from your git host. To do this, select the PR icon on the right-hand side (second from the top) and click Merge. Done.

What are the icons on the Cosine platform?

In order:

Explorer: allows you to look in and select specific files for Cosine to work in. You can search over file names and paths.
PR: allows you to view PRs and merge.
Source control: lets you view the code changes directly.
Search: lets you search in the actual code base of files.
Preview: shows you the impact of the change on the site.
Tickets: can integrate with Jira / Linear / Slack.
Workflows: shows you CI checks and their status.
Settings: lets you change the underlying model you’re using, and choose where to merge your PR into.

Common ways to give Cosine a task

A. On the platform (fastest):

Open your project → New task / prompt → Describe the change → Submit.

B. From Jira/Linear:

Add your integration once.
On a ticket, apply the Cosine label/tag your workspace uses (e.g., “cosine”). That’s it — Cosine will pick it up and start.

C. From Slack:

In a relevant channel/thread, mention @cosine and say what you want (or ask it to take the ticket discussed above).
Or open the Cosine side‑panel in Slack to get the full app experience without leaving Slack.

What you’ll see on the platform

Task timeline & plan
- What it intends to do and why.
Code changes
- Diffs grouped by file (Third icon on the right-hand side).
Validation
- Local code execution and CI status for the PR (Second last icon on the right-hand side).
Controls
- Ask for changes, re‑run, or merge when satisfied.

Tips that 10x results

Don’t hover: Kick off 5–10 small tasks; come back later to review.
Add acceptance criteria: Tell it how you’ll judge “done”.
Start small: Non‑critical bugs/UX tweaks are perfect first wins.
Let it clarify: If your ask is vague, Cosine will ask you questions; answer briefly and keep moving.
Turn on AutoDoc when you want docs: It writes and keeps project docs up‑to‑date as code changes. (To do so, enter a Project and then select “Autodoc” rather than “Tasks” in the header)

Troubleshooting basics

Nothing happened? Check the task page for errors; re‑submit or slightly narrow the ask.
It asked questions. That’s normal — answer directly; it will continue.
Tests failing? Ask Cosine to fix failing tests and re‑run.
Private repos okay? Yes — as long as your user has access.

First‑task ideas you can try today

“Fix the header logo alignment on mobile (<768px). Add a test.”
“Add a ‘Resend verification email’ button on the account page with success/error toasts.”
“Refactor legacy utils/date.js to TypeScript, add unit tests for parseDate and formatDate.”