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Model comparison

GPT-5.3 Codex vs Grok Code Fast 1

Data verified

Head-to-head evidence from 12 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

66.69/100
Margin
28.0pts
← winning
38.64/100
0 category wins1 category wins

Public leaderboard positions: GPT-5.3 Codex #26 (Supported); Grok Code Fast 1 #180 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. GPT-5.3 Codex and Grok Code Fast 1 share 12 comparable benchmark results. 1 of 8 categories are comparable. 9 results are unique to GPT-5.3 Codex; 0 to Grok Code Fast 1.

Updated July 20, 2026
Shared results
12
GPT-5.3 Codex only
9
Grok Code Fast 1 only
0
Comparable categories
1 / 8

Pick GPT-5.3 Codex if you want the stronger benchmark profile. Grok Code Fast 1 only becomes the better choice if coding is the priority or you want the cheaper token bill.

Confidence note. This is a partial-evidence comparison with 12 shared benchmark results across 5 evidence categories; 1 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.

Why this result

GPT-5.3 Codex is clearly ahead on the BenchAlign aggregate, 66.69 to 38.64. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

GPT-5.3 Codex is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $0.20 input / $1.50 output per 1M tokens for Grok Code Fast 1. That is roughly 9.3x on output cost alone. GPT-5.3 Codex is the reasoning model in the pair, while Grok Code Fast 1 is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. GPT-5.3 Codex gives you the larger context window at 400K, compared with 256K for Grok Code Fast 1.

Category breakdown

Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.

Category scores and score margins for GPT-5.3 Codex and Grok Code Fast 1
CategoryGPT-5.3 CodexΔGrok Code Fast 1
CodingGPT-5.3 Codex67.2Margin→ 3.6Grok Code Fast 170.8
AgenticGPT-5.3 Codex71.4MarginNo overlapGrok Code Fast 1Not measured

Decisive benchmark drivers

The largest measured benchmark gaps in this matchup, with exact reported values.

More
A · GPT-5.3 CodexB · Grok Code Fast 1

  1. SWE-bench Verified

    Coding
    Source ↗
    A 85%B 70.8%
    Winner: GPT-5.3 CodexΔ 14.2
    SWE-bench Verified: GPT-5.3 Codex scored 85%; Grok Code Fast 1 scored 70.8%. GPT-5.3 Codex wins this benchmark.

Operational comparison

Runtime and commercial metrics are compared only when both models have a complete sourced value.

MetricGPT-5.3 CodexGrok Code Fast 1Comparison
Input / output priceUSD per 1M tokensGPT-5.3 Codex$1.75 input / $14 outputGrok Code Fast 1$0.2 input / $1.5 outputGrok Code Fast 1 has the lower combined listed price.
Generation speedtokens per secondGPT-5.3 Codex79 tok/sGrok Code Fast 1172 tok/sGrok Code Fast 1 has the higher measured throughput.
First-answer latencyseconds to first tokenGPT-5.3 Codex88.26 sGrok Code Fast 12.81 sGrok Code Fast 1 reaches the first token sooner.
Context windowmaximum listed tokensGPT-5.3 Codex400KGrok Code Fast 1256KGPT-5.3 Codex lists the larger context window.

Benchmark Deep Dive

Agentic
BenchmarkGPT-5.3 CodexGrok Code Fast 1Result
Terminal-Bench 2.0Source 77.3%—Not comparable
OSWorld-VerifiedSource 64.7%—Not comparable
τ²-bench resultsSource 86%75.7%GPT-5.3 Codex leads
Gert LabsSource 57.47%—Not comparable
JobBenchSource 33.7%—Not comparable
CodingGrok Code Fast 1 wins
BenchmarkGPT-5.3 CodexGrok Code Fast 1Result
SWE-bench VerifiedSource 85%70.8%GPT-5.3 Codex leads
SWE-bench ProSource 56.8%—Not comparable
SWE-RebenchSource 58.2%—Not comparable
Vibe Code BenchSource 61.77%—Not comparable
AA-SciCodeSource 53.2%36.2%GPT-5.3 Codex leads
Reasoning
BenchmarkGPT-5.3 CodexGrok Code Fast 1Result
AA-LCRSource 74.0%48.3%GPT-5.3 Codex leads
CritPtSource 16.9%0.0%GPT-5.3 Codex leads
Knowledge
BenchmarkGPT-5.3 CodexGrok Code Fast 1Result
Artificial Analysis Intelligence IndexSource 44.3%21.6%GPT-5.3 Codex leads
AA-GPQA DiamondSource 91.5%72.7%GPT-5.3 Codex leads
AA-HLESource 39.9%7.5%GPT-5.3 Codex leads
AA-Omniscience IndexSource 9.9%-36.0%GPT-5.3 Codex leads
AA-Omniscience AccuracySource 51.8%23.8%GPT-5.3 Codex leads
AA-Omniscience Hallucination RateSource 86.9%78.5%Grok Code Fast 1 leads
Multimodal
BenchmarkGPT-5.3 CodexGrok Code Fast 1Result
AA-MMMU-ProSource 78.5%—Not comparable
Design Arena WebsiteSource 1195—Not comparable
Inst. Following
BenchmarkGPT-5.3 CodexGrok Code Fast 1Result
AA-IFBenchSource 75.4%41.4%GPT-5.3 Codex leads
Frequently Asked Questions (2)

Which is better, GPT-5.3 Codex or Grok Code Fast 1?

GPT-5.3 Codex is ahead on BenchLM's BenchAlign leaderboard, 66.69 to 38.64. The biggest single separator in this matchup is SWE-bench Verified, where the scores are 85% and 70.8%.

Which is better for coding, GPT-5.3 Codex or Grok Code Fast 1?

Grok Code Fast 1 has the edge for coding in this comparison, averaging 70.8 versus 67.2. Inside this category, AA-SciCode is the benchmark that creates the most daylight between them.

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