MLA 022 Vibe Coding: Codex vs Claude Code vs Antigravity vs Grok

What a coding agent actually is, and how Claude Code, OpenAI Codex, Google Antigravity and xAI's Grok Build differ in philosophy rather than features. Plus open harnesses pi and OpenCode, the open-weight coders, and a decision rule by constraint.

Links

• Try a walking desk - stay healthy & sharp while you learn & code
• More OCDevel shows - this one has siblings, each on its own subject and produced the same way

First of three episodes on vibe coding: the field of coding agents (Claude Code, OpenAI Codex, Google Antigravity, Grok Build, pi, OpenCode) as of late 2026 and how to choose one. The next two cover the mechanics (Inside a Coding Agent) and the engineering practice (Agentic Software Engineering).

Vibe coding then and now

Andrej Karpathy's February 2025 post named "vibe coding": accept all, don't read the diffs, paste errors back in, and, the caveat everyone dropped, "not too bad for throwaway weekend projects." Collins made it Word of the Year 2025. The arc since is autocomplete, then chat, then agents that read, edit, run and iterate; the engineers who stayed with it moved from vibing to agentic engineering, which is the through line for the sequence.

Anatomy of a coding agent

The model and the harness are separate things, and most tool arguments are about one without noticing which. The harness is the loop around the model, and there are five parts worth naming: the model, the tools (read, write, shell, search, browser), the permission model and sandbox, the context strategy (what to keep, summarize, offload to files, or hand to a fresh subagent), and the surface (terminal, IDE, desktop, web, chat). Ask those five questions of any product; they matter more than the feature grid. The mechanics get their own episode.

Claude Code: terminal-first and composable

Anthropic's stated design is Unix-style composability: pipe logs into it, run it in CI, chain it with other tools. The terminal is the primary surface; the IDE extension, desktop app, web and mobile clients all connect to the same engine and share CLAUDE.md, settings and MCP servers, with handoffs between local, cloud and desktop. Headless -p mode, GitHub Actions and GitLab integrations, and the Claude Agent SDK make it embeddable. Subagents and worktrees are its answer to the context problem. Model tiers (Sonnet, Opus, Fable) sit behind one harness with 1M-context variants and an effort dial; usage is included in Claude subscriptions or billed via the API.

• Claude Code overview
• Model configuration
• Plans and costs
• Headless mode
• Subagents and worktrees
• Claude Agent SDK
• Claude Fable 5 and Mythos 5, Claude Opus 5

OpenAI Codex: cloud-first and parallel

Codex CLI and Codex cloud are one product under one ChatGPT login, with an IDE extension and a desktop app; codex cloud pushes local work into a sandboxed cloud environment and applies the result back. OpenAI's framing is isolated environments, parallel tasks, and comparing multiple solution attempts, with tasks launchable from the web, GitHub, GitLab, Linear or Slack. Codex-tuned models are trained for long-running agentic work, and the newest generation keeps notes across context windows instead of repeatedly compressing a session. The CLI is Apache-2.0 open source; the Agents API brings the same harness to your own cloud agents.

• Codex CLI docs
• Codex cloud docs
• Model lineup and plans and credits
• Codex CLI source
• Introducing the Codex app
• Introducing the Agents API

Google Antigravity: the agent manager

Antigravity still ships under that name, and it absorbed Gemini CLI: Google retired Gemini CLI into Antigravity CLI in June 2026, and Antigravity 2.0 spans IDE, desktop app, CLI and SDK. The philosophy is supervision: "manage higher-level tasks for the Agent, not individual tool calls," with agents working across editor, terminal and browser and producing artifacts you review. The model menu is multi-vendor on consumer tiers (several Gemini tiers plus Claude Sonnet and Opus and GPT-OSS); enterprise is Gemini only.

• Antigravity IDE
• Supported models and tiers
• Antigravity changelog
• Google I/O 2026 developer highlights
• Transitioning Gemini CLI to Antigravity CLI

Grok Build: the cost-first bet

xAI's coding story flipped in 2026 from a fast model in other people's harnesses (grok-code-fast-1, since deprecated from GitHub Copilot) to a first-party open-source terminal agent, Grok Build: interactive TUI, headless -p, Agent Client Protocol for editors, plan-review-approve, hooks, plugins, MCP and parallel subagents. xAI's own positioning for its coding model is fastest and cheapest for agentic coding; the premium model above it is the agent's default. Benchmark numbers and the subagent-count and price claims circulating in blogs are not on xAI's pages.

• Introducing Grok Build
• Grok Build 0.1 on the API
• Grok Build docs and source
• Grok Code Fast 1 deprecated in Copilot

Open harnesses: pi and OpenCode

Both are open source, model-agnostic and very active, and they're opposites in philosophy. pi is a toolkit: small core, unified API over 15+ providers, TUI, print/RPC/SDK modes, TypeScript extensions, branchable sessions, a package system, and deliberately no built-in permission system (containerize instead; the author ships the Gondolin micro-VM). OpenCode is a product: TUI, web, desktop and IDE surfaces, a ~50-entry provider list including local runtimes, permission config, and the optional Zen gateway of verified models. OpenCode's docs note Anthropic prohibits driving Claude subscription models through third-party harnesses and those plugins were removed. Also: Crush, Kilo Code, Cline, and DeepSeek's own harness.

• pi, pi source
• OpenCode docs, providers, Zen, source
• Crush, DeepSeek Harness

Special mentions: open-weight coders and the second tier

Every lab with a model now ships a harness. Qwen has a coder line, an Apache-licensed open series and the Qwen Code CLI. Z.ai's GLM is pitched as the most capable open-weights model for coding, sold as a Coding Plan documented for Claude Code, Cline and OpenCode. DeepSeek serves 1M-context models with an Anthropic-format endpoint, so Claude-shaped harnesses can point at it. Moonshot's Kimi K3 is a very large open-weight multimodal model under a bespoke license, with the Kimi Code CLI. All coding claims are vendor-reported, now headlining SWE-bench Pro and Terminal Bench rather than SWE-bench Verified. Second tier: Copilot coding agent (cloud, inside Actions), Cursor (editor-first, adding cloud agents and a coordinator), Windsurf (folded into Devin), Cline (active), Aider (no commits since May 2026).

• Qwen3-Coder, Qwen Code
• GLM-5, GLM Coding Plan
• DeepSeek models and pricing
• Kimi K3, Kimi Code CLI
• Copilot coding agent, Cursor changelog, Cline, Aider

Decision rule by constraint

Already paying a lab: take that lab's agent (Claude Code, Codex, Antigravity) and stop shopping. Cloud vs local: Codex cloud or Copilot's agent for sandboxed parallel PRs; a harness plus a local or self-hosted model if everything has to stay behind your firewall. Cost: Grok Build or an open harness with a cheap open-weight model for mechanical work. Open weights: pi or OpenCode with Qwen, GLM, DeepSeek or Kimi. Test on a real bug you already understand, and budget for a primary agent plus a cheaper second one.

Related episodes

• MLA 23: Inside a Coding Agent
• MLA 24: Agentic Software Engineering
• MLA 28: AI Agents
• MLA 30: AI and Programming Jobs

Companion show: the Gnothi Claude Code series goes from your first terminal change to a repeatable delivery workflow.