stella is a terminal coding agent that proves its work finished.

It runs on the API keys you already have, speaks ten providers' own protocols, and ends a run on evidence — a test that failed before the change and passes after — rather than on a model's say-so. Nothing is proxied through a hosted service, and telemetry never leaves your disk.

Install it:

$ curl -fsSL https://stella.oxagen.sh/install.sh | sh
Read the docs
Source on GitHub

created by @macanderson — star stella on GitHub and follow for examples and updates.

One run, start to finish

zsh — stella
$ export ANTHROPIC_API_KEY=…
$ stella run "fix the failing test"
  ▶ read_file(path=src/parser.rs)
  ± modified src/parser.rs +3 −1
  ▶ bash(command=cargo test -p parser)
    ✓ ok in 1174ms — test result: ok. 12 passed; 0 failed

  ◆ claude-sonnet-5 · $0.0413 · 18.6s

A plain stella run is the raw step loop: it reports what it changed and what the turn cost, and claims nothing about proof. The rows and the metering are stella's own; the figures illustrate a run rather than a benchmark. Verification is opt-in — a wrapper plugin gathers the evidence, or goal mode judges rounds.

The deck

Two moments decide whether you can trust an agent with a branch: what it does before it starts, and what it does when a check goes red. Running stella with no subcommand opens the interactive deck, where both of them look like this — every tab, and what each one holds.

An issue being turned into a draft plan: the sources it was built from, four tasks each with a done-means clause, and an estimate of cost, tokens and time above an approval row.
stellaAn issue becomes a plan while you watch. The sources line names exactly what went in — the issue text, the coupled files from the graph, the memory rules that applied — and nothing is touched before you approve it.
A gate board with four gates green and an end-to-end smoke test red, the failing case and its assertion quoted underneath, and a proposed plan revision awaiting approval while the merge stays blocked.
stellaA red gate is not something the model can argue with. It answers with a proposed plan revision naming the cause, and nothing runs until you approve it — while the merge stays blocked and the verify work keeps costing $0.00.

Step inside

The rest of this page tells you what stella is. The engine tour shows you the machine: the turn loop, the tool bay, vera's deterministic verification chamber, the governance plane, and the deck where stella rebuilds itself from your team's traces.

Take the engine tour

Providers

Anthropic · OpenAI · Google Gemini · Google Vertex AI · Amazon Bedrock · xAI · DeepSeek · Z.ai · OpenRouter · Local server

stella speaks each vendor's own wire protocol rather than normalising everything through one OpenAI-shaped adapter, so thinking blocks, cache control, and tool-call shapes are native rather than emulated. Override any base URL, key, or model in settings.json.

Start here