Zero is a terminal coding agent written in Go. It inspects a repository, edits files, runs commands, uses browser and terminal helpers, and keeps sessions on local disk, while you pick both the model and the permission level. Sessions are searchable, resumable, and forkable, and Zero does not upload them as telemetry.
There are two ways to drive it. The interactive interface offers model and provider pickers, image input for vision-capable models, slash commands, live plan and tool rendering, themes, and resume or rewind of past sessions. zero exec is the scriptable path: it takes text, JSON, or stream-JSON input and output, supports isolated worktrees and spec-first runs, and returns exit codes meant for CI. A documented stream-JSON contract covers programmatic turn-by-turn use.
Provider coverage spans OpenAI, Anthropic, Gemini, Groq, OpenRouter, DeepSeek, Mistral, xAI, Qwen, Kimi, GitHub Models, Ollama, LM Studio, and any OpenAI- or Anthropic-compatible endpoint, with presets added for AI/ML API, Meituan LongCat, Fireworks, and MiniMax. Keys come from environment variables or the setup wizard, and zero providers detect finds a local Ollama or LM Studio instance.
Side effects are made visible rather than assumed. Workspace reads are allowed by default, file writes stay inside the workspace unless --add-dir or /add-dir grants another root, and shell commands, network access, destructive commands, and elevated actions are permission-gated. Autonomous modes are explicit opt-ins, secrets are redacted from tool output and logs where Zero controls the surface, and zero sandbox policy and zero sandbox grants list show the current rules. On Linux a separate sandbox helper binary provides native sandboxing; macOS needs no extra binary.
Project guidance is appended to the system prompt from the first AGENTS.md, ZERO.md, or .zero/AGENTS.md found in each directory from the git root down to the working directory, injected general to specific and capped at 8 KiB per file and 32 KiB in total; a personal ZERO.md in the user config directory applies across every workspace.
Features
- Model choice: 25+ providers plus any OpenAI- or Anthropic-compatible endpoint, switchable mid-session with /model and /provider
- Headless execution: zero exec with text, JSON, or stream-JSON I/O, isolated worktrees, spec-first runs, and CI-meaningful exit codes
- Permission and sandbox policy: gated shell, network, destructive, and elevated actions, with per-session extra write roots and inspectable grants
- Local sessions: stored on disk, searchable, resumable, forkable, and rewindable, with /btw for an isolated side question
- Planning modes: /spec and /plan draft and review a plan before work starts
- Extension points: MCP servers, Markdown skills, plugins with tools and lifecycle hooks, and specialist subagents, all managed from the same CLI
- MCP server mode: zero serve --mcp exposes Zero's own tools over MCP stdio
- Repository tooling: zero repo-map for a deterministic map, zero verify to detect and run local checks, and zero changes to inspect and commit
- Scheduled work: zero cron runs agent jobs on a schedule, and /loop repeats a prompt or command on an interval
- Accessibility and theming: NO_COLOR, a dozen named themes, live theme preview, and status conveyed by text or glyph rather than colour alone
- Cost reporting: zero usage and /context report token use, estimated cost, and context budget
