// the engine

One coding-agent CLI, over Claude or Codex.

The first-party coding agent that runs in every worktree — one REPL and one contract over two engines: Claude via the Agent SDK, or OpenAI Codex. Live engine switching, diff approval, and MCP. Drive it by hand, or let Zevyn Studio orchestrate it.

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// dual-engine replclaude · codex · one contract

◆anthropic·claude-opus-4-8·subscriptionzevyn cli

›add idempotency keys to the stripe webhook

●Readsrc/webhooks/stripe.ts✓ 0.4s

●Editsrc/webhooks/stripe.ts✓ +24 −3

●Bashpnpm test✓ 124 passed · 2.1s

/provideropenai · gpt-5.5switched · fresh thread

✦Working… (3s · esc to interrupt)claude sdk · codex · one contract

live·cli·claude sdk · codex · one frozen contract

Zevyn CLI

A first-party agent CLI behind one REPL and contract. Swap Claude for Codex mid-session; Zevyn drives it exactly like it drives everything else.

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Two engines, one REPL

Claude runs in-process via the Agent SDK; OpenAI Codex runs as a subprocess. Same REPL, same tools, same cards — switch mid-session without losing the thread.

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Any model, any host

Point the openai engine at any OpenAI-compatible host. A built-in Chat→Responses bridge means OpenRouter, Groq, Together, and local Ollama all just work.

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Ready to try Zevyn CLI?

Zevyn Studio is launching soon. Join the waitlist to be first in line.

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