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Model comparison

DeepSeek V4 Flash (High) vs GPT-5.3 Codex

Data verified

Head-to-head evidence from 15 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

53.95/100
Margin
12.7pts
winning →
66.69/100
1 category wins1 category wins

Public leaderboard positions: DeepSeek V4 Flash (High) #92 (Estimated); GPT-5.3 Codex #26 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. DeepSeek V4 Flash (High) and GPT-5.3 Codex share 15 comparable benchmark results. 2 of 8 categories are comparable. 23 results are unique to DeepSeek V4 Flash (High); 6 to GPT-5.3 Codex.

Updated July 23, 2026
Shared results
15
DeepSeek V4 Flash (High) only
23
GPT-5.3 Codex only
6
Comparable categories
2 / 8

Pick GPT-5.3 Codex if you want the stronger benchmark profile. DeepSeek V4 Flash (High) 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 15 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 BenchAlign aggregate, 66.69 to 53.95. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

GPT-5.3 Codex's sharpest advantage is in agentic, where it averages 71.4 against 55.3. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 56.6% to 77.3%. DeepSeek V4 Flash (High) does hit back in coding, so the answer changes if that is the part of the workload you care about most.

GPT-5.3 Codex is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $0.14 input / $0.28 output per 1M tokens for DeepSeek V4 Flash (High). That is roughly 50.0x on output cost alone. DeepSeek V4 Flash (High) gives you the larger context window at 1M, compared with 400K for GPT-5.3 Codex.

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 DeepSeek V4 Flash (High) and GPT-5.3 Codex
CategoryDeepSeek V4 Flash (High)ΔGPT-5.3 Codex
AgenticDeepSeek V4 Flash (High)55.3Margin→ 16.1GPT-5.3 Codex71.4
CodingDeepSeek V4 Flash (High)68.5Margin← 1.3GPT-5.3 Codex67.2
KnowledgeDeepSeek V4 Flash (High)52.1MarginNo overlapGPT-5.3 CodexNot measured
MathDeepSeek V4 Flash (High)91.9MarginNo overlapGPT-5.3 CodexNot measured

Decisive benchmark drivers

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

More
A · DeepSeek V4 Flash (High)B · GPT-5.3 Codex

  1. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 56.6%B 77.3%
    Winner: GPT-5.3 CodexΔ 20.7
    Terminal-Bench 2.0: DeepSeek V4 Flash (High) scored 56.6%; GPT-5.3 Codex scored 77.3%. GPT-5.3 Codex wins this benchmark.

  2. SWE-bench Verified

    Coding
    Source ↗
    A 78.6%B 85%
    Winner: GPT-5.3 CodexΔ 6.4
    SWE-bench Verified: DeepSeek V4 Flash (High) scored 78.6%; GPT-5.3 Codex scored 85%. GPT-5.3 Codex wins this benchmark.

  3. SWE-bench Pro

    Coding
    Source ↗
    A 52.3%B 56.8%
    Winner: GPT-5.3 CodexΔ 4.5
    SWE-bench Pro: DeepSeek V4 Flash (High) scored 52.3%; GPT-5.3 Codex scored 56.8%. GPT-5.3 Codex wins this benchmark.

Operational comparison

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

MetricDeepSeek V4 Flash (High)GPT-5.3 CodexComparison
Input / output priceUSD per 1M tokensDeepSeek V4 Flash (High)$0.14 input / $0.28 outputGPT-5.3 Codex$1.75 input / $14 outputDeepSeek V4 Flash (High) has the lower combined listed price.
Generation speedtokens per secondDeepSeek V4 Flash (High)Not availableGPT-5.3 Codex79 tok/sA complete speed comparison is not available.
First-answer latencyseconds to first tokenDeepSeek V4 Flash (High)Not availableGPT-5.3 Codex88.26 sA complete latency comparison is not available.
Context windowmaximum listed tokensDeepSeek V4 Flash (High)1MGPT-5.3 Codex400KDeepSeek V4 Flash (High) lists the larger context window.

Benchmark Deep Dive

AgenticGPT-5.3 Codex wins
BenchmarkDeepSeek V4 Flash (High)GPT-5.3 CodexResult
Terminal-Bench 2.0Source 56.6%77.3%GPT-5.3 Codex leads
BrowseCompSource 53.5%—Not comparable
HLE w/ toolsSource 40.3%—Not comparable
MCP AtlasSource 67.4%—Not comparable
ToolathlonSource 43.5%—Not comparable
τ²-bench resultsSource 95.6%86%DeepSeek V4 Flash (High) leads
AA Agentic IndexSource 28.2%—Not comparable
GDPval-AASource 32.4%—Not comparable
GDPval-AASource 1147—Not comparable
OSWorld-VerifiedSource —64.7%Not comparable
Gert LabsSource —57.47%Not comparable
JobBenchSource —33.7%Not comparable
CodingDeepSeek V4 Flash (High) wins
BenchmarkDeepSeek V4 Flash (High)GPT-5.3 CodexResult
CodeforcesSource 2816.0—Not comparable
SWE-bench VerifiedSource 78.6%85%GPT-5.3 Codex leads
SWE-bench ProSource 52.3%56.8%GPT-5.3 Codex leads
SWE MultilingualSource 70.2%—Not comparable
Terminal-Bench 2.0Source 56.6%—Not comparable
AA-SciCodeSource 42.0%53.2%GPT-5.3 Codex leads
AA Coding IndexSource 52.0%—Not comparable
SWE-RebenchSource —58.2%Not comparable
Vibe Code BenchSource —61.77%Not comparable
Reasoning
BenchmarkDeepSeek V4 Flash (High)GPT-5.3 CodexResult
MRCR 1MSource 76.9%—Not comparable
CorpusQA 1MSource 59.3%—Not comparable
AA-LCRSource 62.7%74.0%GPT-5.3 Codex leads
CritPtSource 3.4%16.9%GPT-5.3 Codex leads
Knowledge
BenchmarkDeepSeek V4 Flash (High)GPT-5.3 CodexResult
MMLU-ProSource 86.4%—Not comparable
SimpleQASource 28.9%—Not comparable
Chinese-SimpleQASource 73.2%—Not comparable
GPQASource 87.4%—Not comparable
GPQA-DSource 87.4%—Not comparable
HLESource 29.4%—Not comparable
Artificial Analysis Intelligence IndexSource 37.5%44.3%GPT-5.3 Codex leads
AA-GPQA DiamondSource 86.7%91.5%GPT-5.3 Codex leads
AA-HLESource 27.8%39.9%GPT-5.3 Codex leads
AA-Omniscience IndexSource -22.3%9.9%GPT-5.3 Codex leads
AA-Omniscience AccuracySource 35.5%51.8%GPT-5.3 Codex leads
AA-Omniscience Hallucination RateSource 89.7%86.9%GPT-5.3 Codex leads
Math
BenchmarkDeepSeek V4 Flash (High)GPT-5.3 CodexResult
HMMT Feb 2026Source 91.9%—Not comparable
IMOAnswerBenchSource 85.1%—Not comparable
ApexSource 19.1%—Not comparable
Apex ShortlistSource 72.1%—Not comparable
Multimodal
BenchmarkDeepSeek V4 Flash (High)GPT-5.3 CodexResult
Design Arena WebsiteSource 12381193DeepSeek V4 Flash (High) leads
AA-MMMU-ProSource —78.5%Not comparable
Inst. Following
BenchmarkDeepSeek V4 Flash (High)GPT-5.3 CodexResult
AA-IFBenchSource 73.5%75.4%GPT-5.3 Codex leads
Frequently Asked Questions (3)

Which is better, DeepSeek V4 Flash (High) or GPT-5.3 Codex?

GPT-5.3 Codex is ahead on BenchLM's BenchAlign leaderboard, 66.69 to 53.95. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 56.6% and 77.3%.

Which is better for coding, DeepSeek V4 Flash (High) or GPT-5.3 Codex?

DeepSeek V4 Flash (High) has the edge for coding in this comparison, averaging 68.5 versus 67.2. Inside this category, AA-SciCode is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, DeepSeek V4 Flash (High) or GPT-5.3 Codex?

GPT-5.3 Codex has the edge for agentic tasks in this comparison, averaging 71.4 versus 55.3. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

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