v1.0 — the agentic coding CLI

TACHYON

CODE.  AUTONOMY.  VELOCITY.

A blistering-fast terminal coding agent that runs on your keys, your models, your machine. The complete agent stack — plan mode, sandboxing, subagents — in one tiny binary. Free with your own API keys.

Model providers (BYOK)
130+
Servers your code touches
0
Enforced sandboxing
OS-level
Single fast binary
~12MB

// SEE IT RUN

The agent works.
You stay in control.

tachyon — ~/projects/api-gatewaysandbox: on · net: denied
add rate limiting to the /auth endpoints, then run the tests
Thought: 0.4s

Mapping the routes first — I'll stay in plan mode until the approach is approved, then apply edits and verify with the suite.

read · src/routes/auth.ts · 118 lines
grep · rateLimit · 0 matches
read · package.json · 76 lines
plan mode — mutating tools blocked while I map this out
  1. add express-rate-limit to auth.ts — 100 req / 15 min per IP
  2. extend auth.test.ts with a 429 case
approved · exiting plan mode
editing src/routes/auth.ts — LSP verified, 0 diagnostics
run npm test ?
  auto-allowed — read-only test command, matches safe policy
48 passing (2 new) · 0 failing  1.9s
done in 11s · /undo revert · /fork branch
ask  ·  deepseek:deepseek-v4-pro think max

Why Tachyon

Your keys. Your code. Your model choice.

Works with 130+ model providers via BYOK — you're never locked into one vendor's models or subscription. The tool is free with your own API keys, and your code never routes through our servers unless you opt in.

No lock-inFree with your keysLocal-first by default

Safe autonomy, enforced by the OS — not by promises.

Every session runs inside real OS-level sandboxing (bwrap on Linux, Seatbelt on macOS, Docker anywhere) with network access denied by default. Plan mode hard-blocks mutating tools instead of just asking nicely, and an AI permission layer auto-allows safe commands while flagging risky ones — speed without giving up control.

bwrap · Seatbelt · DockerNetwork denied by defaultPlan mode hard-block

The full agent stack in one fast binary.

Plan mode, hooks, skills, subagents, session fork / undo / redo, LSP-aware self-correcting edits, command palette and transcript search — the complete feature sweep only the biggest incumbent matches, in a tiny footprint. It even auto-imports your existing Claude Code and OpenCode MCP config, so switching takes seconds.

Zero-effort migrationAuto-imports MCP configTiny footprint

// EVERYTHING INCLUDED

One binary. The whole toolkit.

Plan mode

Map changes with mutating tools hard-blocked until you approve.

Hooks & skills

Shape behavior with lifecycle hooks and reusable skills.

Subagents

Fan out parallel work to focused agents with clean contexts.

Fork · undo · redo

Branch a session, roll back edits, and replay with confidence.

LSP-aware edits

Self-correcting edits that read diagnostics and fix themselves.

Command palette

Jump anywhere and search full transcripts instantly.

AI permissions

Auto-allow safe commands, flag the risky ones for review.

MCP auto-import

Picks up your Claude Code & OpenCode config on first run.

Install in one line.
Migrate in seconds.

Free with your own API keys. No account required to start.

curl -fsSL https://tachyon.feyncode.com/install.sh | sh

macOS · Linux · Windows (WSL)  ·  then run tachyon in any repo