Install Sidekick, choose Kay or Codex, and delegate your first coding task from Claude Code or Codex. If you're not sure where to begin, read Start Here first.
Sidekick is a Claude Code and Codex plugin that gives the active host two implementation sidekicks. Kay routes work through the Kay runtime and kay exec. Codex routes work through the local OpenAI Codex CLI and codex exec, pinned to gpt-5.4-mini with extra-high reasoning.
When you activate a sidekick, the host stops making direct implementation edits. The selected sidekick writes files and runs commands, while the host stays responsible for architecture, review, verification, and communication.
You need the following before installing Sidekick:
kay exec path. Codex needs the real OpenAI Codex CLI with codex exec support; Sidekick rejects Kay compatibility aliases masquerading as Codex.Install Sidekick through the plugin surface for the host you use:
Restart the host after installation so the hook surface loads before you start a Kay or Codex session. Sidekick does not install SessionStart hooks; runtime readiness is checked when delegation starts for the current session.
Codex users should install the Codex-facing Sidekick package through the Codex plugin surface. That path exposes the shared skill bodies and runtime guidance without duplicating writable state from Claude Code.
After installing, verify the runtime for the sidekick path you plan to use.
In the host, run:
On activation, Codex mode verifies that the real OpenAI Codex CLI is available, is not Kay's compatibility alias, and supports codex exec --ask-for-approval. Sidekick then creates the current-session marker, writes active-sidekick=codex, and routes implementation through codex exec.
A successful health check means the child command can run with Sidekick's managed defaults:
For the Kay path, verify that the Kay runtime is reachable. Claude Code and Codex both start Kay mode through /sidekick:kay-delegate; active Kay mode then routes implementation through the native kay exec child runtime while Sidekick maintains .kay/conversations.idx.
Once the health check passes, the host is in Codex sidekick mode. Every implementation task you give the host is delegated to the local OpenAI Codex CLI through codex exec.
Tell the host what you need in plain language. It will prepare a focused implementation prompt with the relevant files, constraints, and success criteria.
The host delegates through codex exec. Sidekick injects -m gpt-5.4-mini, -c model_reasoning_effort=xhigh, --sandbox workspace-write, and --ask-for-approval never automatically.
The host watches bounded, redacted Codex output and checks whether the child process completed the requested work.
The host verifies the diff, integration points, and relevant commands before reporting success. If verification fails, it relaunches Codex with focused correction context.
Start Kay mode through /sidekick:kay-delegate. Use /sidekick:kay-delegate xiaomi for Xiaomi routing, /sidekick:kay-delegate ocg to force OpenCode Go routing, or SIDEKICK_KAY_PROVIDER as an environment override.
Once Kay mode is active, the hook keeps kay exec as the child runtime command, surfaces bounded redacted output, and preserves project-local .kay/conversations.idx lookup metadata.
Sidekick relies on repository instructions such as AGENTS.md. The host and sidekick both treat those instructions as project context when preparing implementation and verification work.
You can edit AGENTS.md at any time to add project-specific rules, supported sidekicks, testing expectations, release discipline, and verification requirements.
Current Sidekick keeps canonical workflows under skills/ and renders host bundles under agents/claude/ and agents/codex/. Do not hand-edit generated copies unless the canonical skill and renderer contract change with them.
Now that Kay or Codex is configured, explore the rest of the documentation: