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

stella (zsh)
$ 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. The docs list 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 draft plan. The sources line names the files the graph links to the issue and 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. The merge stays blocked meanwhile, 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