Two years ago, choosing a coding agent meant choosing a philosophy: how it planned, how it ran tools, whether it could spawn helpers, whether you could script it. In July 2026, xAI's Grok Build and Anthropic's Claude Code answer every one of those questions the same way. Both run from a terminal. Both spawn parallel subagents into isolated git worktrees. Both load MCP servers, support skills and hooks, read an AGENTS.md project contract, offer a plan/read-only mode before anything touches disk, and run headless with -p for CI and scripts. Grok Build embeds over ACP; Claude Code embeds over its Agent SDK. The feature grids have collapsed into each other.

That convergence is the decision. When two agents drive identically, "which harness is more capable" stops being the question. What's left is money — the model's token bill, and the subscription you're already paying. Here's how to choose on those two axes.

The harness is now a commodity#

Run down the checklist a founder cared about a year ago and the columns match: interactive terminal UI, parallel subagents, worktree isolation, MCP tool servers, a skills mechanism, lifecycle hooks, a plan mode that reads-and-proposes before it edits, a headless mode for automation, and an AGENTS.md file both tools honor as the project's operating manual. Grok Build even mirrors Claude Code's safety instinct: its MCP permission prompts now show the planned arguments so you can judge what a tool will actually do before you approve it — the same "surface the request, don't auto-run it" design Claude Code shipped for background subagents. We mapped that supervision fight in Claude Code vs Cursor vs Cline; the notable thing now is that Grok Build arrived already holding the consensus answer.

So don't shop on features. Shop on the two things that still differ.

Axis one: the model bill#

Grok Build runs Grok 4.5 by default — $2 per million input tokens, $6 per million output, $0.50 for cached input, a 500K-token context window, served around 80 tokens/sec, and Cursor-trained on coding and engineering tasks. Claude Code runs Claude Opus 4.8 by default — $5 input, $25 output per million on the API (with steep cached-input discounts), on a 200K context (1M in beta on some tiers).

On raw tokens, Grok 4.5 is roughly 2.5 to 4x cheaper. For a coding agent — which burns input tokens re-reading your repo on every turn and output tokens writing diffs — that gap compounds fast at volume. If you're running agents across a large codebase all day, the token math alone can favor Grok Build by hundreds of dollars a month. The counterweight is capability: on the hardest multi-step engineering tasks, Opus 4.8 still tends to finish what cheaper models stall on, and one completed gnarly refactor can be worth a lot of cheap failed attempts. The honest framing is the one from our coding-agent model-backend breakdown: cheap tokens win the routine, the strongest model wins the tail.

Axis two: the subscription you already have#

The token price is the API story. Most solo founders don't touch the API — they live inside a subscription, and that changes the math entirely.

If you already pay for SuperGrok or X Premium Plus, Grok Build is bundled — free at the margin. If you already pay for Claude Pro or Max (roughly $20 to $200/month), Claude Code is bundled the same way. Paying twice to run two agents rarely makes sense for a team of one, so the pragmatic default is: use the coding agent that ships with the subscription you're already inside. You've effectively pre-paid for one of these harnesses; the other is a second bill for a nearly identical tool.

The actual recommendation#

The convergence is good news for founders. When the harness is a commodity, you stop betting on a vendor's roadmap and start optimizing the one thing you control: what each token costs you. Pick the cheaper engine when the task is routine, the stronger one when it isn't, and let the subscription you already pay break the tie.