---
title: I Made Grok 4.5 My Default Coding Model for One Client Week
dek: >-
  Cursor co-trained it. The price undercuts the usual suspects. Here is what
  held up on a real repo, what did not, and the verdict I would put my own money
  on.
slug: grok-45-default-coding-week
publishedAt: '2026-07-16'
author: agnel-nieves
pillar: the-stack
tags:
  - grok
  - cursor
  - coding-agents
  - xai
  - tool-review
  - mcp
summary: >-
  Grok 4.5 shipped July 8, 2026, co-trained with Cursor and priced around $2 /
  $6 per million tokens. I made it the default for one client week on a Next.js
  plus MCP codebase, tracked spend and rework, and compared it to my Claude Code
  and Sonnet habits. Verdict: buy for iterative editing inside Cursor, wait
  before making it the only agent for unsupervised multi-file refactors, skip if
  you need the absolute safest long agent run tonight.
draft: false
featured: false
listen: true
heroImage: /blog/grok-45-default-coding-week.webp
heroImageAlt: >-
  Engraved illustration of an open book with quill pen and gold nib atop stacked
  papers on a stone pedestal against a deep blue background with floral borders,
  hourglasses, pocket watch, and radiating lines.
heroVideo: /blog/grok-45-default-coding-week.mp4
ogImage: /blog/grok-45-default-coding-week-og.jpg
assetCredit: Hero illustration and animation generated with Grok.
---

On July 8, Cursor and SpaceXAI put Grok 4.5 in front of every Cursor subscriber who would click the model picker. The pitch was simple: frontier-ish coding and agent work, trained with real Cursor interaction data, cheap enough that token anxiety stops being the main character.

I did what I always do when a tool claims it belongs in the daily path. I made it the default for one week on a real client repo and wrote down what broke.

This is not a benchmark re-score. It is a work log.

## The task I actually ran

Client context, sanitized: a Next.js App Router publication with content validation, MCP servers for ads and analytics reads, and a pre-commit asset pipeline. The week had three jobs that match how I actually bill time.

1. **Ship a feature branch** with two new MDX routes, shared components, and schema fields that had to pass `bun run validate`.
2. **Debug a flaky integration** where an MCP tool returned partial JSON and the agent kept "fixing" it by inventing keys.
3. **Drive a multi-file refactor** that touched route handlers, a Zod schema, and a small TypeScript helper without breaking static generation.

I used Cursor as the shell the whole week. Grok 4.5 as the default model. Same MCP config I already trust. No special harness beyond what a mid-size agency repo already has.

## What worked, with receipts

**Speed on the boring middle.** Autocomplete-plus-edit on component props, frontmatter keys, and test stubs felt fast. Not magically smarter than Opus-class on hard architecture. Noticeably cheaper per loop when I was iterating ten times on the same file. For the kind of work that is 70% of a billable day, that matters more than a one-point leaderboard bump.

**Cursor-native habits.** This is the underrated part of "trained with Cursor data." The model was less confused by multi-cursor edits, partial selections, and "apply this diff but keep my comment." That is not a general intelligence claim. It is a product claim, and on this repo it held.

**Price as a product feature.** At roughly $2 input / $6 output per million tokens (and lower on cached), I stopped doing the mental math that makes people under-prompt. I asked for the second rewrite. I asked for the third. The quality of the *session* went up because I stopped rationing turns. That is a real effect, even when single-shot quality is a wash.

Rough week spend on the client branch, all-in model cost through Cursor: under what a single heavy Claude Max-style day used to burn on comparable volume. Your numbers will differ. The direction did not.

## What broke first

**Unsupervised multi-file refactors.** When I pointed it at "migrate these three modules and keep generateStaticParams honest," it produced a plausible plan and then a half-applied migration. Two files updated. One left mid-state. Tests red. Claude Code on the same prompt the next morning finished the graph more cleanly, with fewer "I will fix the types in a follow-up" lies.

**Confident wrong tools.** On the MCP JSON bug, Grok 4.5 was eager. It rewrote the client twice before it agreed to log the raw payload. Claude's slower, slightly pedantic loop would have asked for the log earlier. Eager is not free. Eager costs review time.

**Long context discipline.** On a chat that had already eaten a big schema dump, it started compressing my constraints into vibes. I had to re-paste the Zod refine rules mid-thread. Not unique to Grok. Worse here than my Sonnet baseline on the same thread length.

## How it compares on the jobs that matter

| Job | Grok 4.5 in Cursor | My Claude Code / Sonnet baseline |
| --- | --- | --- |
| Tight UI and content schema edits | **Winner** on speed + cost | Fine, pricier per loop |
| MCP / tool debugging | Mixed; needs tighter human steering | **Winner** on "slow down and inspect" |
| Multi-file refactors with static guarantees | Risky without babysitting | **Winner** for unsupervised depth |
| "Just ship the PR" Friday afternoon | Strong if you stay in the editor | Strong if you live in the terminal agent |

The posture split from the public discourse is real. Cursor assumes you are editing. Claude Code assumes you are delegating. Grok 4.5 inherits the Cursor posture even when you ask it to act like an agent. That is not a bug if you wanted a co-pilot. It is a bug if you wanted a night-shift senior.

## Verdict

**Buy** Grok 4.5 as a default *inside Cursor* for iterative product work if you already live in that editor and your pain is token cost plus turn latency.

**Wait** before making it the only model for unattended multi-file agents or production refactors that touch codegen boundaries. Keep a heavier model one hotkey away.

**Skip** if your whole workflow is terminal-agent and you already have Claude Code tuned. Switching shells just to chase a model is a tax.

I am not deleting Claude from the stack. I am not writing a "Grok won coding forever" post. I am changing my default for the 70% path and keeping the expensive brain for the 30% path that ships the scary PR.

Six months ago I would have told you to pick one model and learn it deeply. I no longer believe that is the right advice for coding agents. The July wave made routing the skill. Grok 4.5 is a strong cheap route, not a religion.

## What I will re-test in 30 days

1. Same multi-file refactor with whatever patch they ship after the first wave of forum complaints.
2. Token spend on a pure greenfield app versus this brownfield content site.
3. Whether "double usage first week" promo pricing was hiding a bill shock at steady state.

If any of those flip the verdict, I will update this page in public. That is the deal on The Stack.

## Sources

- [Cursor, Introducing Grok 4.5](https://cursor.com/blog/grok-4-5)
- [DevOps.com on Grok 4.5 pricing and Cursor collab](https://devops.com/spacexais-grok-4-5-undercuts-anthropic-and-openai-on-coding-agent-pricing/)
- [Nimbalyst, Claude Code vs Cursor posture](https://nimbalyst.com/blog/claude-code-vs-cursor/)
- Prior Promptway stack note: [Connecting Claude to Google Ads and GA4 via MCP](/blog/connecting-claude-to-google-ads-and-ga4-via-mcp)
---