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Model comparison

GPT-5.3 Codex vs Kimi K2.6

Data verified

Head-to-head evidence from 20 shared benchmark results across 6 categories. Overall scores shown here use BenchLM's provisional ranking lane.

82/100
Margin
8.0pts
← winning
Kimi K2.6
Moonshot AI
74/100
0 category wins2 category wins

Verified leaderboard positions: GPT-5.3 Codex unranked; Kimi K2.6 #13

Evidence parity. GPT-5.3 Codex and Kimi K2.6 share 20 comparable benchmark results. 2 of 8 categories are comparable. 2 results are unique to GPT-5.3 Codex; 40 to Kimi K2.6.

Updated July 13, 2026
Shared results
20
GPT-5.3 Codex only
2
Kimi K2.6 only
40
Comparable categories
2 / 8

Pick GPT-5.3 Codex if you want the stronger benchmark profile. Kimi K2.6 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 20 shared benchmark results across 6 evidence categories; 2 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 provisional aggregate, 82 to 74. 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 $0.95 input / $4.00 output per 1M tokens for Kimi K2.6. That is roughly 3.5x on output cost alone. GPT-5.3 Codex gives you the larger context window at 400K, compared with 256K for Kimi K2.6.

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 Kimi K2.6
CategoryGPT-5.3 CodexΔKimi K2.6
CodingGPT-5.3 Codex64.4Margin→ 8.2Kimi K2.672.6
AgenticGPT-5.3 Codex71.4Margin→ 2.1Kimi K2.673.5
KnowledgeGPT-5.3 CodexNot measuredMarginNo overlapKimi K2.642.2
MathGPT-5.3 CodexNot measuredMarginNo overlapKimi K2.667.1
MultimodalGPT-5.3 CodexNot measuredMarginNo overlapKimi K2.679.8

Decisive benchmark drivers

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

More
A · GPT-5.3 CodexB · Kimi K2.6

  1. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 77.3%B 66.7%
    Winner: GPT-5.3 CodexΔ 10.6
    Terminal-Bench 2.0: GPT-5.3 Codex scored 77.3%; Kimi K2.6 scored 66.7%. GPT-5.3 Codex wins this benchmark.

  2. OSWorld-Verified

    Agentic
    Source ↗
    A 64.7%B 73.1%
    Winner: Kimi K2.6Δ 8.4
    OSWorld-Verified: GPT-5.3 Codex scored 64.7%; Kimi K2.6 scored 73.1%. Kimi K2.6 wins this benchmark.

  3. SWE-bench Verified

    Coding
    Source ↗
    A 85%B 80.2%
    Winner: GPT-5.3 CodexΔ 4.8
    SWE-bench Verified: GPT-5.3 Codex scored 85%; Kimi K2.6 scored 80.2%. GPT-5.3 Codex wins this benchmark.

  4. SWE-bench Pro

    Coding
    Source ↗
    A 56.8%B 58.6%
    Winner: Kimi K2.6Δ 1.8
    SWE-bench Pro: GPT-5.3 Codex scored 56.8%; Kimi K2.6 scored 58.6%. Kimi K2.6 wins this benchmark.

Operational comparison

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

MetricGPT-5.3 CodexKimi K2.6Comparison
Input / output priceUSD per 1M tokensGPT-5.3 Codex$1.75 input / $14 outputKimi K2.6$0.95 input / $4 outputKimi K2.6 has the lower combined listed price.
Generation speedtokens per secondGPT-5.3 Codex79 tok/sKimi K2.6Not availableA complete speed comparison is not available.
First-answer latencyseconds to first tokenGPT-5.3 Codex88.26 sKimi K2.6Not availableA complete latency comparison is not available.
Context windowmaximum listed tokensGPT-5.3 Codex400KKimi K2.6256KGPT-5.3 Codex lists the larger context window.

Benchmark Deep Dive

AgenticKimi K2.6 wins
BenchmarkGPT-5.3 CodexKimi K2.6Result
Terminal-Bench 2.0Source 77.3%66.7%GPT-5.3 Codex leads
OSWorld-VerifiedSource 64.7%73.1%Kimi K2.6 leads
Tau2-TelecomSource 86%95.9%Kimi K2.6 leads
Gert LabsSource 57.47%56.82%GPT-5.3 Codex leads
JobBenchSource 33.7%—Not comparable
BrowseCompSource —83.2%Not comparable
ToolathlonSource —50%Not comparable
MCP AtlasSource —55.9%Not comparable
Claw-EvalSource —62.3%Not comparable
DeepSearchQASource —92.5%Not comparable
WideResearchSource —80.8%Not comparable
AA Agentic IndexSource —30.3%Not comparable
GDPval-AASource —34.5%Not comparable
GDPval-AASource —1190Not comparable
APEX-Agents-AASource —28.5%Not comparable
ResearchClawBenchSource —18.0%Not comparable
OSWorld 2.0Source —4.6%Not comparable
AA BriefcaseSource —809Not comparable
AA AutomationBenchSource —19.6%Not comparable
AA EnterpriseOps-GymSource —38.5%Not comparable
AA Harvey LABSource —0.0%Not comparable
AA ITBenchSource —31.2%Not comparable
AA Tau3 BankingSource —20.6%Not comparable
CodingKimi K2.6 wins
BenchmarkGPT-5.3 CodexKimi K2.6Result
SWE-bench VerifiedSource 85%80.2%GPT-5.3 Codex leads
SWE-bench ProSource 56.8%58.6%Kimi K2.6 leads
SWE-RebenchSource 58.2%—Not comparable
Vibe Code BenchSource 61.77%37.89%GPT-5.3 Codex leads
Terminal-Bench HardSource 53.0%43.9%GPT-5.3 Codex leads
AA-SciCodeSource 53.2%53.5%Kimi K2.6 leads
LiveCodeBenchSource —89.6%Not comparable
LiveCodeBench v6Source —89.6%Not comparable
SWE MultilingualSource —76.7%Not comparable
SciCodeSource —52.2%Not comparable
Terminal-Bench 2.0Source —66.7%Not comparable
cursorBench31Source —47.6%Not comparable
AA Coding IndexSource —61.8%Not comparable
AA Terminal-Bench 2.1Source —65.9%Not comparable
Reasoning
BenchmarkGPT-5.3 CodexKimi K2.6Result
AA-LCRSource 74.0%69.7%GPT-5.3 Codex leads
CritPtSource 16.9%8.0%GPT-5.3 Codex leads
Knowledge
BenchmarkGPT-5.3 CodexKimi K2.6Result
Artificial Analysis Intelligence IndexSource 44.3%44.2%GPT-5.3 Codex leads
AA-GPQA DiamondSource 91.5%91.1%GPT-5.3 Codex leads
AA-HLESource 39.9%35.9%GPT-5.3 Codex leads
AA-Omniscience IndexSource 9.9%6.4%GPT-5.3 Codex leads
AA-Omniscience AccuracySource 51.8%32.8%GPT-5.3 Codex leads
AA-Omniscience Hallucination RateSource 86.9%39.3%Kimi K2.6 leads
GPQASource —90.5%Not comparable
GPQA-DSource —90.5%Not comparable
HLESource —34.7%Not comparable
AA Openness IndexSource —33.3%Not comparable
Math
BenchmarkGPT-5.3 CodexKimi K2.6Result
AIME26Source —96.4%Not comparable
HMMT Feb 2026Source —92.7%Not comparable
MMAnswerBenchSource —86.0%Not comparable
FrontierMath v2 (Tiers 1-3)Source —38.966%Not comparable
FrontierMath v2 (Tier 4)Source —14.580%Not comparable
Multimodal
BenchmarkGPT-5.3 CodexKimi K2.6Result
AA-MMMU-ProSource 78.5%79.4%Kimi K2.6 leads
Design Arena WebsiteSource 12051318Kimi K2.6 leads
MMMU-ProSource —79.4%Not comparable
MMMU-Pro w/ PythonSource —80.1%Not comparable
CharXivSource —80.4%Not comparable
MathVisionSource —87.4%Not comparable
V*Source —96.9%Not comparable
Inst. Following
BenchmarkGPT-5.3 CodexKimi K2.6Result
AA-IFBenchSource 75.4%76.0%Kimi K2.6 leads
Frequently Asked Questions (3)

Which is better, GPT-5.3 Codex or Kimi K2.6?

GPT-5.3 Codex is ahead on BenchLM's provisional leaderboard, 82 to 74. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 77.3% and 66.7%.

Which is better for coding, GPT-5.3 Codex or Kimi K2.6?

Kimi K2.6 has the edge for coding in this comparison, averaging 72.6 versus 64.4. Inside this category, Vibe Code Bench is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, GPT-5.3 Codex or Kimi K2.6?

Kimi K2.6 has the edge for agentic tasks in this comparison, averaging 73.5 versus 71.4. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

Self-host vs API cost

Estimates at 50,000 req/day · 1000 tokens/req average.

GPT-5.3 Codex
API / mo$11,813
Self-host / moNot listed
Break-even—
Proprietary model — self-hosting not applicable.
Kimi K2.6
API / mo$3,713
Self-host / mo$18,221
Break-even326M/day
Model the full break-even

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