Features

Arcturn is one runtime with two front ends: a terminal coding agent and an embeddable TypeScript harness. Here is what it does, grouped four ways.

Four pillars

What Arcturn does

Control before the fact

A rule-based permission engine at a single choke point in the tool dispatcher. Allow, deny, ask — scoped session over project over user, with plan, acceptEdits and yolo modes when you want a different posture.

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Accountability after it

The session is an append-only tree on disk, so replay, bisect and blame are ordinary operations — and /rewind restores files by forking the conversation instead of deleting it.

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Extensible without a build step

MCP servers, markdown skills, shell hooks with veto power, sub-agents, file-defined workflows — and TypeScript custom tools when you need real code.

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Every provider, one interface

Anthropic, OpenAI and any OpenAI-compatible endpoint, Google Gemini, Bedrock, Vertex, Azure — with streaming, tool calls, thinking, prompt caching and cost tracking.

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Orchestration

A pipeline in a file, and roles the engine bounds

More than one agent, without the honour system. When a role hits a question only a person can settle, it writes ORG-ASK: and the run pauses on its durable journal instead of guessing — your reply becomes that step’s output, and nothing that already succeeded runs twice.

Workflows

A numbered markdown list is the control flow: top-level items are stages that run in order, indented bullets are parallel branches. Their outputs join in written order, never completion order, so the same file always produces the same pipe — and every [tag] naming a model resolves before the first step spends a token.

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Agent organizations

Give each step a named role and its declared tools: pick its lane — read, exec or write. A reviewer holding bash and no write tool gets a real worktree to run things in, and that worktree’s diff is discarded on every path, success and failure alike. The finding has nowhere to go but the report.

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Also included