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Grok 4.5 vs Claude Opus 4.8 vs GPT-5.6 in Cursor: which model to run in July 2026
Grok 4.5 charges $6 per million output tokens, per Cursor's launch post. Claude Opus 4.8 charges $25, per Anthropic's published API pricing. Same agent run, roughly a quarter of the output bill. That gap, not the benchmark chart, is what changed the model-selection question for Cursor users on July 8.
Here is the short version before the reasoning. For most Cursor agent work today, Grok 4.5 base is the default pick: it is close enough on capability and it is priced to make the comparison about cost. Keep Opus 4.8 in the rotation for the precision jobs where the accuracy gap actually shows, and skip both for plain autocomplete. EU users cannot run it yet. The rest of this piece is the cost math, the benchmark reality, and the six tasks where the pick flips.
What landed on July 8
SpaceXAI and Cursor released Grok 4.5 jointly on July 8, 2026, a mixture-of-experts model trained on "trillions of tokens of Cursor data" that captures how developers and agents actually work inside a codebase, per Cursor's launch post. It is Cursor's first model built for more than software engineering, with the training mix deliberately widened to cover data science, finance, and legal work. The model is available today across Cursor desktop, web, iOS, the CLI, and the SDK, included in individual and team plans as a first-party model with doubled usage for the first week.
The backdrop is corporate. Grok 4.5 is the first shipped product of SpaceX's $60 billion all-stock acquisition of Cursor, a deal reported by Axios and Bloomberg on July 8. Elon Musk's own framing was that the model is "roughly comparable to Opus 4.7, but much faster," per VentureBeat's July 8 report. That is a pricing play dressed as a model launch, and it works.
The pricing, side by side
Two things matter here. Inside a Cursor plan, Grok 4.5 draws from the included first-party usage pool, so most users never see a per-token invoice until they exhaust that pool or call the API directly. The per-token rates below are what bite on usage-based billing and on the SpaceXAI API, and they are the numbers that decide a heavy agent day.
| Model | Input $/M | Output $/M | Cursor plan access | Source |
|---|---|---|---|---|
| Grok 4.5 base | $2 | $6 | Included, first-party pool | Cursor |
| Grok 4.5 fast | $4 | $18 | Included, first-party pool | Cursor |
| Claude Opus 4.8 | $5 | $25 | Included / usage-based | Anthropic |
| GPT-5.6 Sol | ~$5 | ~$30 | Included / usage-based | ChatForest summary |
Pricing per vendor pages and a third-party launch summary, as of July 12, 2026. The GPT-5.6 Sol figures come from a third-party roundup rather than an OpenAI first-party page, so treat them as directional. On output tokens, the plain fact is that Grok 4.5 base at $6 sits about 76% below Opus 4.8 at $25, per Cursor and Anthropic. Even the fast variant at $18 undercuts Opus.
What the benchmarks say, and don't
The launch chart is mixed, and Cursor is candid that the third-party scores are self-reported. Anthropic's Fable 5 tops most of the coding evals; Opus 4.8 and Grok 4.5 trade rows. Here is the head-to-head on the four benchmarks worth watching, as transcribed from the Cursor launch chart by Agentpedia.
| Benchmark | Grok 4.5 | Opus 4.8 | Winner | Source |
|---|---|---|---|---|
| Terminal-Bench 2.1 | 83.3% | 78.9% | Grok 4.5 | Agentpedia |
| DeepSWE 1.0 | 62.0% | 55.8% | Grok 4.5 | Agentpedia |
| SWE-Bench Pro | 64.7% | 69.2% | Opus 4.8 | Agentpedia |
| DeepSWE 1.1 | 53% | 59% | Opus 4.8 | Agentpedia |
One caveat changes how you read that table: the effort settings differ. Grok 4.5 ran at high while Opus 4.8 ran at max on the launch chart, per Agentpedia, so this is not a like-for-like grid. Independent scoring lands in the same neighborhood. Artificial Analysis ranked Grok 4.5 fourth on its GDPval-AA v2 index of real-world agentic work, at an Elo of 1543, behind the latest Claude releases, per VentureBeat.
The number that reframes the whole comparison is a vendor claim. xAI says Grok 4.5 uses roughly 4.2 times fewer output tokens than Opus 4.8 to finish an SWE-Bench Pro task, per ChatForest's builder evaluation. If that holds up on your codebase, a task that costs 4.2 times more Grok output tokens still lands at about the same raw dollar figure as one Opus run, and Grok output is already priced at a quarter of Opus. That is a big if, and it is self-reported. The benchmarks are close. The cost math is not.
The cost math for a real agent run
Skip the marketing and price one run. Say a single long agent session reads 400,000 input tokens and writes 200,000 output tokens. Those counts are illustrative, not measured, but the ratios are what matter. Drop the current per-token rates into a few lines of Python:
# Example token counts for one long agent run (hypothetical, not measured)
input_tokens = 400_000
output_tokens = 200_000
models = {
"Grok 4.5 base": (2, 6), # ($/M input, $/M output)
"Grok 4.5 fast": (4, 18),
"Claude Opus 4.8": (5, 25),
}
for name, (inp, out) in models.items():
cost = input_tokens / 1e6 * inp + output_tokens / 1e6 * out
print(f"{name:16} ${cost:.2f}")Expected output:
Grok 4.5 base $2.00
Grok 4.5 fast $5.20
Claude Opus 4.8 $7.00One run, and Grok base comes in at $2.00 against Opus 4.8's $7.00 on the rates from Cursor and Anthropic. Now scale it to an overnight audit that emits 2 million output tokens against 1 million input: Grok base is about $14, Opus 4.8 about $55. The output multiplier is where the bill lives, and long agentic runs are almost all output. That is the entire reason this launch matters for anyone running Cursor agents past coffee-break length.
Switching the model, and calling it outside Cursor
Inside the editor there is no setup. Open the Composer or chat input, click the model name in the bottom bar, and pick grok-4.5 from the first-party pool. Cursor doubled the included usage for launch week, so it is a cheap week to A/B it against whatever you run now. If you want Cursor itself, the download and plan details are on their site.
For a one-off call outside the editor, the SpaceXAI API is OpenAI-compatible. Grab a key from the console at console.x.ai and point a standard chat-completions request at it:
curl https://api.x.ai/v1/chat/completions \
-H "Authorization: Bearer $XAI_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "grok-4.5",
"messages": [
{"role": "user", "content": "Summarize the failing test in tests/auth_spec.ts"}
]
}'That is the same request shape you already use for OpenAI or Anthropic-compatible endpoints, so wiring Grok 4.5 into an existing script is a base-URL and key swap, not a rewrite.
Which model to run, by task
Not every task flips to Grok. The pick tracks where each model actually leads, and the routing below is the practical takeaway to bookmark.
| Task | Best pick | Why (one sentence) |
|---|---|---|
| Tab autocomplete | Cursor Tab / Composer 2.5 | Autocomplete needs sub-second latency, not frontier reasoning, and Cursor built Composer 2.5 as the fast coding specialist (Cursor). |
| Agent session under 30 min | Grok 4.5 base | Comparable capability at $6/M output versus Opus 4.8's $25/M, served at about 80 tokens per second so short runs stay snappy (Agentpedia). |
| Agent session over 30 min | Grok 4.5 base | Output-token cost dominates long runs, and Grok's low rate plus the claimed 4.2x token efficiency compound in its favor (ChatForest). |
| PR review run (Bugbot) | Claude Opus 4.8 | Review rewards precision on multi-file diffs, where Opus 4.8 leads on SWE-Bench Pro, 69.2% to 64.7% (Agentpedia). |
| Data analysis / notebook | Grok 4.5 base | Cursor widened the training mix across STEM and data-science work and aimed the model at non-engineering knowledge tasks (Cursor). |
| Legal or finance document | Grok 4.5 base | xAI reports Grok 4.5 at number one on Harvey's Legal Agent Benchmark, its strongest single result (Agentpedia). |
The two rows to weigh are the flips. On a big multi-file refactor or a precision debugging pass, the DeepSWE 1.1 and SWE-Bench Pro gaps are where Opus 4.8 earns its price, so keep it for the runs where a wrong edit costs more than the tokens saved. Everything else that runs long and mostly writes code favors Grok on cost.
What "trained on Cursor data" actually buys you
Most frontier models learn from public code corpora. Grok 4.5 learned from trillions of tokens of how developers and agents move through real codebases inside Cursor, per Cursor's launch post. That is a different signal. A general model has read a lot of finished code; this one has watched a lot of the process, including how an agent calls a tool, reads the result, recovers from a bad edit, and verifies the fix.
The practical payoff is in the agent loop. A model that has seen how Cursor tools get called is likelier to format a tool call correctly the first time and less likely to burn a retry on a malformed request. Fewer retries is fewer round trips, and fewer round trips is both faster and cheaper, which is the same throughput-and-cost story the pricing tells from the other end. Cursor did flag one honest asterisk: an earlier snapshot of its own codebase was accidentally in the training data, which inflates the model's CursorBench score, so they excluded that benchmark, per Cursor. Take the CursorBench number with salt; the routing picks above do not lean on it.
There is a ceiling to the effect. On the hardest reasoning-heavy engineering tasks, the DeepSWE 1.1 gap says process familiarity does not fully close a capability gap. Grok knows the Cursor environment well. It is not the smartest model on the chart, and on the jobs where that last point of accuracy matters, the training edge does not save it.
EU users and availability
One hard limit. Grok 4.5 is not available to EU users in any SpaceXAI product or the API console yet, with EU availability expected around mid-July 2026, per Agentpedia. If your team is in the EU, keep a fallback model set as your Cursor default until it clears review. For everyone else, it is live now on individual and team plans with the launch-week usage bonus, which makes this a low-cost week to run it side by side against Opus 4.8 on your own repo before you commit.
The verdict
For most Cursor users running agent sessions today, Grok 4.5 base is the default pick as of July 12, 2026: it is close enough on capability and priced at roughly a quarter of Opus 4.8 on output tokens, which is where long agent runs spend their budget. Keep Claude Opus 4.8 assigned to precision jobs, the multi-file refactors and PR reviews where its SWE-Bench Pro lead is worth the extra dollars, and leave autocomplete to Cursor's Tab model. EU teams wait for the mid-July availability and hold a fallback default in the meantime. Switch it inside Cursor during the double-usage week and let your own agent bill make the call. For the wider editor decision behind all of this, our Cursor review and GitHub Copilot review cover the tools these models run inside.