What each product actually is
Codex sits in OpenAI's multi-surface coding stack. Vendor positioning frames the same agent across ChatGPT, the IDE extension, and the CLI, with cloud environments, worktrees, skills, scheduled background work, and code review as first-class loops. The published aicoolies review still treats it as a cloud-leaning agentic tool for async, sandboxed tasks: define the job, let it run, then review the output. ChatGPT-plan managed surfaces and API-key CLI/SDK/IDE paths coexist in the catalog story. Buyers already inside the OpenAI ecosystem are the natural audience.
Grok Build sits in the terminal. Catalog and review framing emphasize a TUI/CLI loop with planning controls, subagents, permission rules, parallel implementation attempts, and headless JSON output. It is less of a "browser cloud SWE desk" and more of a shell-native xAI agent for teams already on SuperGrok / X Premium+ or xAI API metering.
Scoreboard with dates (no re-test)
Codex (tested 2026-03-25): overall 80, speed 72, privacy 68, developer experience 79 (v0.9.4).
Grok Build (tested 2026-05-28): overall 82, speed 84, privacy 72, developer experience 80 (v0.9.4).
On these dated Score v1 rows, Grok Build leads every published dimension, with the clearest gap on speed (84 vs 72) and a narrow overall edge (82 vs 80). Both dates belong on the live page; the May 2026-05-28 Grok Build hands-on must stay explicit so readers do not assume a matched March dual test. Editorial winner status does not rewrite or re-date these numbers.
Workflow — async multi-surface vs shell-native agents
Choose Codex when the loop is "hand off a well-scoped coding task into OpenAI-managed or cloud surfaces, then review" — especially if you want one agent across ChatGPT, editor, and terminal with skills, worktrees, and always-on background jobs. The review's trade-off — less real-time pairing for more autonomous execution — is the fit signal, not a bug.
Choose Grok Build when the loop is terminal-first: plan in the CLI, run subagents, use worktrees, and keep automation close to the shell. Speed 84 (tested 2026-05-28) supports that interactive/parallel terminal story relative to Codex's 72 (tested 2026-03-25). Peer context: Grok Build vs OpenCode is already live for OSS-terminal buyers; Amp vs Codex covers Amp's terminal intelligence shelf. This page is the OpenAI ↔ xAI commercial CLI cut.
Billing and ecosystem posture
Codex access in the catalog is tied to ChatGPT subscription plans for managed app/cloud/GitHub-review surfaces, with API-key pay-as-you-go for CLI, SDK, and IDE paths. Grok Build interactive CLI access is described as included with SuperGrok or X Premium+ subscriptions, with headless/programmatic access via metered xAI API usage. Cite catalog summaries; do not invent new plan math in CMS copy.
Ecosystem lock-in is the real buyer filter: OpenAI stack vs xAI stack. Score v1 does not replace that commercial reality — and the dated scoreboard still favors Grok Build on overall and speed even when the editorial pick is Codex for OpenAI-native teams.
Who should pick which — and the winner guide
Pick Codex if OpenAI multi-surface / async cloud coding is the constraint and ChatGPT or API access is how you already buy models. Pick Grok Build if you want the dated Score v1 overall lead (82) and a terminal-native xAI agent with a clear speed advantage (84 vs 72).