Both are xAI models. Grok 4.5 is the newer, generally stronger default; reach for Grok Code Fast 1 when its lower price or a specific cost or latency profile matters more than the latest capabilities.
Grok 4.5 and Grok Code Fast 1 are both xAI models, so the real question is not which lab to trust but which tier fits your workload and budget. Grok 4.5 is xAI's first coding-focused model — pitched as Opus-class but faster, more token-efficient, and cheaper, undercutting GPT-5.5-Codex. Grok Code Fast 1 is xAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
Key differences
Price: Grok Code Fast 1 is about 10× cheaper on input ($0.2/$1.5 per 1M tokens vs $2/$6 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
Context window: Grok 4.5 holds 2× more — 500K (~750 pages) vs 256K (~384 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: Grok 4.5 is the newer model by about 10 months (released July 8, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Grok 4.5
Grok Code Fast 1
Provider
xAI (US)
xAI (US)
Released
July 8, 2026
August 28, 2025
Context window
500K (~750 pages)
256K (~384 pages)
Price (in/out)
$2/$6 per 1M tokens
$0.2/$1.5 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Cheap, token-efficient agentic coding — about GPT-5.5-Codex quality at roughly half the cost: Grok 4.5 — Its 500K window holds about 2× more than Grok Code Fast 1's 256K in a single prompt.
Extreme token efficiency — around 4x fewer output tokens per task than Opus 4.8: Grok 4.5 — XAI's first coding-focused model — pitched as Opus-class but faster, more token-efficient, and cheaper, undercutting GPT-5.5-Codex — and it carries the larger 500K context.
In-IDE coding, trained on real Cursor developer sessions and shipped natively in Cursor: Grok 4.5 — Grok Code Fast 1 is comparatively weak here — a speed-tier coding model, not a frontier reasoner
Fast, cheap agentic coding at $0.20/$1.50: Grok Code Fast 1 — At $0.2/$1.5 per 1M tokens it undercuts Grok 4.5 ($2/$6 per 1M tokens), and that gap compounds at volume.
Low-latency code generation and terminal tasks: Grok Code Fast 1 — Grok 4.5 is comparatively weak here — smaller 500K context (halved from the 1M generation), with pricing that doubles above 200K tokens
High-volume coding pipelines where speed beats peak quality: Grok Code Fast 1 — XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it runs cheaper at $0.2/$1.5 per 1M tokens.
Lowest cost at scale: Grok Code Fast 1 — At $0.2/$1.5 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: Grok 4.5 — Its 500K window is about 2× larger than Grok Code Fast 1's 256K, fitting roughly 750 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: Grok Code Fast 1 — At $0.2/$1.5 per 1M tokens it undercuts Grok 4.5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: Grok 4.5 — Larger 500K window fits more in one prompt.
Anyone whose priority is cheap, token-efficient agentic coding — about gpt-5.5-codex quality at roughly half the cost: Grok 4.5 — It is specifically built for that.
Anyone whose priority is fast, cheap agentic coding at $0.20/$1.50: Grok Code Fast 1 — That is its strongest area.
Grok 4.5: where it fits
XAI's first coding-focused model — pitched as Opus-class but faster, more token-efficient, and cheaper, undercutting GPT-5.5-Codex. Released July 8, 2026 by xAI, it is built for cheap, token-efficient agentic coding — about GPT-5.5-Codex quality at roughly half the cost, extreme token efficiency — around 4x fewer output tokens per task than Opus 4.8, in-IDE coding, trained on real Cursor developer sessions and shipped natively in Cursor, and top-tier placement on the Artificial Analysis Intelligence Index.
Its trade-offs are real: smaller 500K context (halved from the 1M generation), with pricing that doubles above 200K tokens, and eU launch delayed; no open weights. At $2 in / $6 out per million tokens, it sits in the mid price band.
Grok Code Fast 1: where it fits
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Released August 28, 2025 by xAI, it is built for fast, cheap agentic coding at $0.20/$1.50, low-latency code generation and terminal tasks, high-volume coding pipelines where speed beats peak quality, and a 256K window sized for real codebases.
Its trade-offs: text and code only — no image, audio or video input, xAI did not publish a SWE-Bench Verified score, a speed-tier coding model, not a frontier reasoner, and narrow focus — built for code, not general knowledge work. At $0.2 in / $1.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Because Grok 4.5 and Grok Code Fast 1 come from the same lab (xAI), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. Grok 4.5 is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to Grok 4.5 and drop down only with a concrete reason.
Frequently asked questions
Is Grok 4.5 or Grok Code Fast 1 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Grok 4.5 leans toward cheap, token-efficient agentic coding — about gpt-5.5-codex quality at roughly half the cost while Grok Code Fast 1 leans toward fast, cheap agentic coding at $0.20/$1.50, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Grok 4.5 or Grok Code Fast 1?
Grok Code Fast 1 is cheaper — $2/$6 per 1M tokens vs $0.2/$1.5 per 1M tokens, roughly 10× apart on input.
Which has the bigger context window?
Grok 4.5 — 500K vs 256K, about 2× larger. Useful only if the model actually reasons over the full window, which not all do.
Should I upgrade from Grok Code Fast 1 to Grok 4.5?
Since both are xAI models, the newer one (Grok 4.5) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, Grok 4.5 or Grok Code Fast 1?
Grok 4.5 — released July 8, 2026, about 10 months after Grok Code Fast 1.
Grok 4.5 vs Grok Code Fast 1
xAI · US | xAI · US · Updated June 2026
Quick verdict
Both are xAI models. Grok 4.5 is the newer, generally stronger default; reach for Grok Code Fast 1 when its lower price or a specific cost or latency profile matters more than the latest capabilities.
Grok 4.5 and Grok Code Fast 1 are both xAI models, so the real question is not which lab to trust but which tier fits your workload and budget. Grok 4.5 is xAI's first coding-focused model — pitched as Opus-class but faster, more token-efficient, and cheaper, undercutting GPT-5.5-Codex. Grok Code Fast 1 is xAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Since both come from the same lab, the comparison below focuses on the tier-and-cost trade-offs that actually separate them.
Key differences at a glance
▸Price: Grok Code Fast 1 is about 10× cheaper on input ($0.2/$1.5 per 1M tokens vs $2/$6 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
▸Context window: Grok 4.5 holds 2× more — 500K (~750 pages) vs 256K (~384 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: Grok 4.5 is the newer model by about 10 months (released July 8, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Grok 4.5
Grok Code Fast 1
Provider
xAI (US)
xAI (US)
Released
July 8, 2026
August 28, 2025
Context window
500K (~750 pages)
256K (~384 pages)
Price (in/out)
$2/$6 per 1M tokens
$0.2/$1.5 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Cheap, token-efficient agentic coding — about GPT-5.5-Codex quality at roughly half the cost
Grok 4.5
Its 500K window holds about 2× more than Grok Code Fast 1's 256K in a single prompt.
Extreme token efficiency — around 4x fewer output tokens per task than Opus 4.8
Grok 4.5
XAI's first coding-focused model — pitched as Opus-class but faster, more token-efficient, and cheaper, undercutting GPT-5.5-Codex — and it carries the larger 500K context.
In-IDE coding, trained on real Cursor developer sessions and shipped natively in Cursor
Grok 4.5
Grok Code Fast 1 is comparatively weak here — a speed-tier coding model, not a frontier reasoner
Fast, cheap agentic coding at $0.20/$1.50
Grok Code Fast 1
At $0.2/$1.5 per 1M tokens it undercuts Grok 4.5 ($2/$6 per 1M tokens), and that gap compounds at volume.
Low-latency code generation and terminal tasks
Grok Code Fast 1
Grok 4.5 is comparatively weak here — smaller 500K context (halved from the 1M generation), with pricing that doubles above 200K tokens
High-volume coding pipelines where speed beats peak quality
Grok Code Fast 1
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it runs cheaper at $0.2/$1.5 per 1M tokens.
Lowest cost at scale
Grok Code Fast 1
At $0.2/$1.5 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
Grok 4.5
Its 500K window is about 2× larger than Grok Code Fast 1's 256K, fitting roughly 750 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Grok Code Fast 1
At $0.2/$1.5 per 1M tokens it undercuts Grok 4.5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ Grok 4.5
Larger 500K window fits more in one prompt.
Anyone whose priority is cheap, token-efficient agentic coding — about gpt-5.5-codex quality at roughly half the cost
→ Grok 4.5
It is specifically built for that.
Anyone whose priority is fast, cheap agentic coding at $0.20/$1.50
→ Grok Code Fast 1
That is its strongest area.
Grok 4.5: where it fits
XAI's first coding-focused model — pitched as Opus-class but faster, more token-efficient, and cheaper, undercutting GPT-5.5-Codex. Released July 8, 2026 by xAI, it is built for cheap, token-efficient agentic coding — about GPT-5.5-Codex quality at roughly half the cost, extreme token efficiency — around 4x fewer output tokens per task than Opus 4.8, in-IDE coding, trained on real Cursor developer sessions and shipped natively in Cursor, and top-tier placement on the Artificial Analysis Intelligence Index.
Its trade-offs are real: smaller 500K context (halved from the 1M generation), with pricing that doubles above 200K tokens, and eU launch delayed; no open weights. At $2 in / $6 out per million tokens, it sits in the mid price band.
Grok Code Fast 1: where it fits
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Released August 28, 2025 by xAI, it is built for fast, cheap agentic coding at $0.20/$1.50, low-latency code generation and terminal tasks, high-volume coding pipelines where speed beats peak quality, and a 256K window sized for real codebases.
Its trade-offs: text and code only — no image, audio or video input, xAI did not publish a SWE-Bench Verified score, a speed-tier coding model, not a frontier reasoner, and narrow focus — built for code, not general knowledge work. At $0.2 in / $1.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Because Grok 4.5 and Grok Code Fast 1 come from the same lab (xAI), they share the same training philosophy and ecosystem — the decision is purely tier vs. cost. Grok 4.5 is the more capable, more recent option; the other earns its place only when its price or latency profile fits a specific job better. Most teams should default to Grok 4.5 and drop down only with a concrete reason.
Want both Grok 4.5 and Grok Code Fast 1 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Is Grok 4.5 or Grok Code Fast 1 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Grok 4.5 leans toward cheap, token-efficient agentic coding — about gpt-5.5-codex quality at roughly half the cost while Grok Code Fast 1 leans toward fast, cheap agentic coding at $0.20/$1.50, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Grok 4.5 or Grok Code Fast 1?
Grok Code Fast 1 is cheaper — $2/$6 per 1M tokens vs $0.2/$1.5 per 1M tokens, roughly 10× apart on input.
Which has the bigger context window?
Grok 4.5 — 500K vs 256K, about 2× larger. Useful only if the model actually reasons over the full window, which not all do.
Should I upgrade from Grok Code Fast 1 to Grok 4.5?
Since both are xAI models, the newer one (Grok 4.5) is usually the better default unless you need a specific cost or latency profile from the other.
Which is newer, Grok 4.5 or Grok Code Fast 1?
Grok 4.5 — released July 8, 2026, about 10 months after Grok Code Fast 1.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.