Quick answer. Grok 4.5 is SpaceXAI's (xAI's) new flagship, launched July 8, 2026 for developers and July 9 for the public. Musk pitches it as an "Opus-class model, but faster, more token-efficient and lower cost." It ships a 500K-token context window at $2 per million input tokens and $6 per million output tokens (cached input $0.50). Independent testing by Artificial Analysis ranks it #4 of 168 models on its Intelligence Index (score 54) — near the frontier, at a fraction of rivals' cost per task.
SpaceXAI — SpaceX's AI division, still widely referred to as xAI — is moving fast again. On July 8, 2026 it shipped Grok 4.5 to developers through Grok Build, Cursor, and the SpaceXAI API, with the public rollout on grok.com and the X app the next day. Elon Musk's framing was deliberate: an "Opus-class model, but faster, more token-efficient and lower cost." His internal read was more measured — "roughly comparable to Opus 4.7, but much faster."
Unlike the pre-launch guesses, the real numbers are now confirmed. Here's what Grok 4.5 actually is, how much it costs, how it benchmarks against Claude Opus and GPT, and whether it's worth switching to.
What is Grok 4.5?
Grok 4.5 is the newest model in the Grok family and the successor to Grok 4.3. It's the first frontier model SpaceXAI has released since acquiring the AI coding startup Cursor — and that acquisition is the real story behind it. According to Cursor, Grok 4.5 is a mixture-of-experts model, jointly trained by Cursor and SpaceXAI on trillions of tokens of real developer-agent data — the debugging traces, tool interactions, and multi-step coding sessions Cursor sees every day.
SpaceXAI has not published an official parameter count or spec sheet; some secondary reports cite a "~1.5 trillion-parameter V9 foundation," but that figure isn't confirmed by the company or by independent trackers, so treat it as unverified. What is confirmed is the positioning: a near-frontier reasoning model tuned hard for agentic coding and knowledge work, sold on price and efficiency rather than raw benchmark supremacy.
One naming note worth getting right: recent launch materials and coverage use SpaceXAI, though "xAI" still appears interchangeably. The model itself is called grok-4.5 in the API.
What did Elon Musk say about Grok 4.5?
Musk's announcement leaned on three claimed advantages:
- Opus-class capability — benchmarked internally against Claude Opus, which SpaceXAI set as its target. His more precise phrasing was that it's "roughly comparable to Opus 4.7," not that it beats Anthropic's current frontier (Opus 4.8).
- Faster — higher throughput than comparable reasoning models (though, with reasoning on by default, time-to-first-token is relatively slow).
- More token-efficient and lower cost — it aims to reach the same answer using far fewer tokens, which is where the real savings show up at scale.
He credited "strong positive feedback from customers in our beta test program" — SpaceX and Tesla engineering teams that ran it privately in late June — as the trigger for the public release. SpaceXAI has also said it plans to ship a new foundation model roughly every month through the end of 2026, an aggressive cadence aimed at closing the gap with Anthropic, OpenAI, and Google.
Grok 4.5 specs and architecture
Here's the confirmed spec sheet, cross-checked against OpenRouter and Artificial Analysis rather than vendor marketing alone:
| Attribute | Grok 4.5 | Grok 4.3 |
|---|---|---|
| Maker | SpaceXAI (xAI) | xAI |
| Architecture | Mixture-of-experts, co-trained with Cursor | V8-small |
| Context window | 500K tokens | 1M tokens |
| Input | Text + image | Text, image, video |
| Output | Text only | Text |
| Reasoning | "High" effort on by default (non-disableable) | Always-on reasoning |
| Measured throughput | ~86.7 tokens/sec (Artificial Analysis) | — |
| API model string | grok-4.5 | grok-4.3 |
| Status | Live (July 2026) | Live |
Two details stand out. First, the context window actually shrank — 500K tokens versus Grok 4.3's 1M — so if you rely on very long contexts, 4.3 still has the edge there. Second, the model supports the full modern tool-use stack: native function calling, structured JSON outputs, web search, X (Twitter) search, and code execution, with "high" reasoning always on. That last point means slower time-to-first-token (Artificial Analysis measured ~16.7 seconds) in exchange for stronger multi-step results. The Cursor co-training is aimed squarely at where Claude Opus has historically been strongest — real agentic coding — which makes 4.5 a genuine option for agentic coding workflows.
How much does Grok 4.5 cost?
SpaceXAI's API pricing is confirmed:
| Model | Input / 1M | Output / 1M | Cached input / 1M |
|---|---|---|---|
| Grok 4.5 | $2.00 | $6.00 | $0.50 (−75%) |
| Claude Opus 4.8 | $5.00 | $25.00 | — |
| GPT-5.5 / 5.6 | $5.00 | $30.00 | — |
| Claude Fable 5 | $10.00 | $50.00 | — |
A high-context surcharge applies above 200K tokens. Note the nuance: Grok 4.5's output price ($6) is actually higher than Grok 4.3's ($2.50) — the "lower cost" framing is relative to rivals like Opus and GPT, not to its own predecessor. Against those rivals the gap is large: Grok 4.5 undercuts Claude Opus 4.8 by roughly 4× on output and Claude Fable 5 by more than 8×. Competitor prices above are from SpaceXAI's own comparison table, reported by The Decoder.
The bigger cost story is token efficiency. SpaceXAI says Grok 4.5 used 4.2× fewer output tokens than Opus 4.8 on SWE-Bench Pro (about 15,954 tokens per task versus 67,020). Fewer tokens per task multiplied by a low per-token price is what actually shows up on the monthly bill — and it's why Artificial Analysis measured a cost of roughly $0.31 per task on its Intelligence Index and about $2.59 per coding task, versus around $11.80 for Claude Fable 5.
How does Grok 4.5 perform on benchmarks?
The most credible independent read comes from Artificial Analysis, which tests models on a common harness. Its verdict: Grok 4.5 scores 54 on the Intelligence Index and ranks #4 of 168 models, behind only Claude Fable 5, GPT-5.5, and Claude Opus 4.8 — a jump of about +16 points over Grok 4.3. On agentic work it's stronger still: a Coding Agent Index of 76 (on par with GPT-5.5's Codex) and the top score on τ³-Banking, a tool-use benchmark, at 33% versus GPT-5.5's 31%. Artificial Analysis places it squarely on the price-performance Pareto frontier, calling it "one of the most cost-efficient models to run for near-frontier intelligence."
SpaceXAI's own launch table leads with coding and agentic benchmarks (not the GPQA/AIME reasoning tests it stayed quiet on), and the honest read is that Grok 4.5 mostly trails Opus 4.8 on raw scores — it wins on cost, not on the leaderboard:
| Benchmark (vendor-reported) | Grok 4.5 | Opus 4.8 | GPT-5.5 | Fable 5 |
|---|---|---|---|---|
| Terminal-Bench 2.1 | 83.3% | 78.9% | 83.4% | 84.3% |
| SWE-Bench Pro (resolve) | 64.7% | 69.2% | 58.6% | 80.4% |
| DeepSWE 1.1 | 53% | 59% | 67% | 70% |
SpaceXAI also claims the #1 spot on Harvey's Legal Agent Benchmark. One caveat worth flagging: Artificial Analysis measured a high hallucination rate (roughly 54% on its AA-Omniscience test) even as raw accuracy improved — so for high-stakes factual work, verification still matters. All vendor numbers here are SpaceXAI's own; independent per-benchmark reasoning splits (GPQA, AIME, ARC-AGI) weren't published at launch, so don't trust any specific figure for those yet.
Grok 4.5 vs Claude Opus 4.8 vs GPT-5.6
Grok 4.5 shipped into the same competitive window as OpenAI's GPT-5.6. Here's the practical framing:
- vs Claude Opus 4.8 — Opus stays the reference for coding and long-horizon reasoning quality, and it beats Grok 4.5 on most raw benchmarks. Grok's pitch is "the same class, ~4× cheaper and much faster." For a current head-to-head on coding, see our Grok vs Claude Opus vs Gemini comparison and the Claude Opus complete guide.
- vs GPT-5.6 — OpenAI's ecosystem and tooling breadth remain a key reason teams stay on GPT models. Grok's edge is price, token efficiency, and its tight integration with X and SpaceXAI's own dev stack.
- vs Grok 4.3 — 4.5 is the quality and agentic-tooling step up (MoE, Cursor co-training, +16 Intelligence Index points); 4.3 keeps a longer 1M-token context and a lower output price if that's what your workload needs.
The honest summary: Grok 4.5's claim isn't "smartest model." It's near-frontier intelligence at a fraction of the cost per task, with best-in-class agentic tool-use efficiency. That price-and-efficiency wedge — not benchmark leadership — is the whole story, and it's why analysts think it could pressure Anthropic and OpenAI on margins.
How to access Grok 4.5
Grok 4.5 is live across SpaceXAI's surfaces:
- Grok Build — it's now the default model. See our Grok Build, Skills and Connectors guide and the Grok Build CLI walkthrough.
- Cursor — available on all plans, with doubled usage in the first week of launch.
- SpaceXAI API / console — for developers, priced per token as above (
grok-4.5). - grok.com and the X app — for X Premium+ and SuperGrok subscribers.
One important limitation: Grok 4.5 was not available in the EU at launch, with SpaceXAI expecting EU access around mid-July 2026. If you're building for European users, confirm availability before you commit.
Should you switch to Grok 4.5?
If you're running production workloads, the sensible play is to test before you switch. Grok 4.5's cost-and-speed story is genuinely strong, and the Cursor-trained coding focus is aimed at the workloads engineering teams care about most. But it trails Opus 4.8 on raw benchmarks and its hallucination rate is a real caveat, so the "Opus-class" label is best read as "near-frontier at a fraction of the price," not "better than Anthropic."
Practical approach: run your own eval set — your real prompts, your real code — against Grok 4.5 and your current model, and compare quality and total token cost per task. For teams standardizing on agentic coding tools, our AI coding agents guide covers how these models plug into day-to-day workflows.
FAQ
When was Grok 4.5 released?
SpaceXAI launched Grok 4.5 on July 8, 2026 for developers (via Grok Build, Cursor, and the API) and opened public access on grok.com and the X app on July 9, 2026, after a private beta with SpaceX and Tesla teams.
How much does Grok 4.5 cost?
The API is $2.00 per million input tokens and $6.00 per million output tokens, with cached input at $0.50 per million (a 75% discount) and a higher-context surcharge above 200K tokens. That's roughly 4× cheaper than Claude Opus 4.8 on output.
How big is Grok 4.5's context window?
500,000 tokens — which is actually smaller than Grok 4.3's 1M-token window. It supports text and image input and produces text output.
Is Grok 4.5 as good as Claude Opus?
On raw benchmarks, mostly no — Grok 4.5 trails Claude Opus 4.8 on tests like SWE-Bench Pro and DeepSWE. Independent testing (Artificial Analysis) ranks it #4 overall, behind Fable 5, GPT-5.5, and Opus 4.8. Its advantage is cost and speed: near-frontier quality at a fraction of the price per task.
What is Grok 4.5 built on?
It's a mixture-of-experts model, jointly trained by Cursor and SpaceXAI on trillions of tokens of developer-agent session data after SpaceXAI acquired Cursor. SpaceXAI hasn't published an official parameter count; the widely-repeated "1.5 trillion parameter V9" figure is unconfirmed.
Is Grok 4.5 available in the EU?
Not at launch. SpaceXAI expected EU availability around mid-July 2026, so European developers should confirm access before building on it.
Is Grok 4.5 the same as Grok 5?
No. Grok 4.5 is the current flagship. SpaceXAI has said it plans to release a new foundation model roughly every month through the end of 2026, so a larger next-generation flagship is expected to follow.
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