Give both hosts a focused implementation sidekick. Activate Kay or Codex for bounded coding work while the host AI stays responsible for planning, review, verification, and communication.
Sidekick keeps the host AI in charge. The active sidekick writes files and runs commands; the host compares the result against the original prompt, checks integration points, runs verification, and relaunches the sidekick when a requirement is missed.
You stay in Claude Code or Codex. The host AI agent shapes the task, Sidekick activates Kay or Codex, and the host reviews, corrects, verifies, and reports the final state.
The host AI stays in the advisor role: it breaks down work, delegates to Kay or Codex, then synthesizes and reviews the result.
Kay and Codex enforcement stays dormant until delegation starts for the current session, then activates through the session marker and shared selector.
PostToolUse hooks emit compact Kay or Codex summaries, while `.kay` and `.codex` indexes keep durable task lookup metadata.
Host review classifies missed requirements, wrong logic, integration errors, regressions, and external failures before any result is accepted.
The current Sidekick surface ships two implementation sidekicks. Claude Code and Codex hosts can activate either one for the current session.
/sidekick:kay-delegateKay is the Kay/OpenCode Go execution sidekick. It uses kay exec for child implementation work, supports the xiaomi and ocg selectors, and keeps SIDEKICK_KAY_PROVIDER as an environment override.
/sidekick:codex-delegateCodex delegates implementation to the local OpenAI Codex CLI through codex exec. Sidekick pins the child runtime to gpt-5.4-mini with extra-high reasoning, workspace-write sandboxing, and no approval prompts.
The sidekick can claim success, but the host must prove it. Every task ends with a host verification pass against the original prompt, surrounding repository behavior, and the required test evidence.
Sidekick's current contract is explicit: Kay and Codex perform implementation, but the host AI owns final correctness. A sidekick task is not accepted until the host checks the result against the prompt and surrounding repository behavior.
| Gate | Evidence | Failure handled | Recovery |
|---|---|---|---|
| Prompt match | Diff and final state match the requested objective and success criteria. | MISSED_REQUIREMENT, MISUNDERSTOOD_TASK | Relaunch the active sidekick with focused correction context. |
| Integration check | Imports, file paths, signatures, config, and touched behavior are inspected. | INTEGRATION_ERROR, WRONG_FILE, WRONG_LOGIC | Handhold the sidekick with exact files, APIs, and examples. |
| Verification command | Run the smallest meaningful tests, linters, builds, or runtime checks. | REGRESSION, SYNTAX_ERROR | Retry after evidence identifies the failing boundary. |
| External failures | Provider, API, CLI, or environment failures are treated as blockers. | TRIAL_INCOMPLETE, API_FAILURE, EXECUTION_ERROR_EXTERNAL | Retry only after the external condition is usable, or report the blocker. |
Release gate: bash tests/run_unit.bash, bash tests/run_all.bash, and Kay-hosted live release checks with SIDEKICK_LIVE_CODEX=1.
Sidekick keeps runtime ownership explicit. Kay owns its provider routing; Codex sidekick mode owns the local OpenAI Codex CLI command and model flags.
| Sidekick | Runtime | Routing | Notes |
|---|---|---|---|
|
Kay Kay sidekick |
kay exec | default | Starts with /sidekick:kay-delegate; Sidekick records Kay session state and progress metadata. |
|
Kay Provider selectors |
kay exec | xiaomi / ocg | Use /sidekick:kay-delegate xiaomi, /sidekick:kay-delegate ocg, or SIDEKICK_KAY_PROVIDER. |
|
Codex OpenAI CLI sidekick |
codex exec | gpt-5.4-mini / xhigh | Starts with /sidekick:codex-delegate; Sidekick injects model, reasoning, sandbox, and approval flags. |
Only one sidekick is active per host session. The shared active-sidekick selector contains kay or codex.
For the user, setup is API access, plugin install, then per-session delegation. Sidekick checks runtime readiness when delegation starts.
Prepare the runtime you want to use. Kay requires a working Kay runtime; Codex sidekick mode requires the real OpenAI Codex CLI, not a Kay compatibility alias.
Install the plugin through the host's plugin surface, then restart the host so Sidekick hooks load before a Kay or Codex session.
Start the sidekick workflow for the current session. The host stays in the planning and verification role while Kay or Codex performs implementation work.
Add Sidekick to your host plugin surface and keep implementation work with the right sidekick while the host owns correctness.