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GLM 5.3 Flash vs GPT-6 Luna

Updated October 21, 2026. 87 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GLM 5.3 Flash Replace GPT-6 Luna
GLM 5.3 FlashZ.ai
Coding
71.0
Overall
41.8
Output $/M
$0.50
60
GPT-6 LunaOpenAI
Coding
71.4
Overall
38.1
Output $/M
$0.50
26
vs boards won of 87 shared, 1 tied

Decision reading

GLM 5.3 Flash and GPT-6 Luna are level for coding, 71.0 against 71.4 on the Vibe Coding Index, so price and context decide.

Pick GLM 5.3 Flash when what matters is LMArena WebDev or Terminal-Bench 4 (Vals AI), where it leads. Pick GPT-6 Luna when the context window is larger, 1.05M against 1.05M tokens, or when what matters is LiveBench coding or Vibe Code Bench (Vals AI), where it leads.

Model AGLM 5.3 FlashZ.ai71.0/1002 independent benchmarks$0.02 per solved taskModel BGPT-6 LunaOpenAI71.4/1002 independent benchmarksNo cost per solved task
Shared results
87
GLM 5.3 Flash only
15
GPT-6 Luna only
15
Like-for-like categories
8 of 9

Shared results can support a head-to-head reading. Results only one model has describe coverage, not superiority.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

At a glance

Coding index
GLM 5.3 Flash 71.0 from 2 benchmarks, GPT-6 Luna 71.4 from 2 benchmarks.
Widest category
Math, 22.9 points apart on average over 6 shared benchmarks.
Widest single gap
Vibe Code Bench (Vals AI): GLM 5.3 Flash 30.8% against GPT-6 Luna 81.7%, 50.9 points apart on a 0 to 100 scale.
Output price
Both cost $0.50 per million output tokens.
Context window
GLM 5.3 Flash takes 1.05M tokens, GPT-6 Luna 1.05M.

Benchmark by benchmark

First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.

Boards won, where both have a result
CategoryGLM 5.3 FlashBarsGPT-6 LunaTies
Coding611
Intelligence11
Agentic work74
Reasoning93
Math24
Knowledge40
Web design711 tie
General242
All shared boards60261 tie
CodingLike-for-likeFour of these boards feed the Vibe Coding Index611
Coding benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
LiveBench coding80.6%84.5%GPT-6 Luna
LMArena WebDev16071578GLM 5.3 Flash
AA Coding Index71.5Not measuredOnly GLM 5.3 Flash measured
LiveCodeBench (Vals AI)80.5%Not measuredOnly GLM 5.3 Flash measured
SWE-bench Verified (Vals AI)92.0%Not measuredOnly GLM 5.3 Flash measured
Terminal-Bench 4 (Vals AI)37.4%13.6%GLM 5.3 Flash
Vibe Code Bench (Vals AI)30.8%81.7%GPT-6 Luna
Code migration (Vals AI)20.5%42.5%GPT-6 Luna
ProgramBench (Vals AI)0.0%0.5%GPT-6 Luna
IOI (Vals AI)52.5%55.6%GPT-6 Luna
Terminal-Bench 2.1 (Vals AI)62.9%73.0%GPT-6 Luna
SWE-bench Multimodal (Vals AI)Not measured37.5%Only GPT-6 Luna measured
Vibe Code Bench 1-100 (Vals AI)16.0%Not measuredOnly GLM 5.3 Flash measured
SkillsBench (Vals AI)40.2%Not measuredOnly GLM 5.3 Flash measured
CyberBench (Vals AI)67.9%76.3%GPT-6 Luna
SciCode51.6%54.6%GPT-6 Luna
FrontierCode31.8%42.4%GPT-6 Luna
FrontierSWE18.1%Not measuredOnly GLM 5.3 Flash measured
ALE-Bench303.61576.9GPT-6 Luna
LMArena Text: coding15071437GLM 5.3 Flash
LMArena Text: software and IT15001423GLM 5.3 Flash
LMArena WebDev: React16241573GLM 5.3 Flash
LMArena WebDev: HTML15771595GPT-6 Luna
LMArena WebDev: from an image15781571GLM 5.3 Flash
Neither model has a result on the other 14 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index11
Intelligence benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
AA Intelligence Index41.838.1GLM 5.3 Flash
Epoch Capabilities Index153.1156.8GPT-6 Luna
Agentic workLike-for-likePublic boards, shown as published, kept out of the index74
Agentic work benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
AA Agentic Index50.9Not measuredOnly GLM 5.3 Flash measured
Design Arena: agents building web appsNot measured1189Only GPT-6 Luna measured
Design Arena: agents building full-stack appsNot measured1158Only GPT-6 Luna measured
Design Arena: agents building mobile appsNot measured1133Only GPT-6 Luna measured
LiveBench research70.1%43.5%GLM 5.3 Flash
LiveBench browser84.0%72.0%GLM 5.3 Flash
LiveBench long agentic28.4%48.1%GPT-6 Luna
SREBench (Vals AI)0.8%2.7%GPT-6 Luna
Finance Agent (Vals AI)57.9%49.9%GLM 5.3 Flash
Tax Agent Bench (Vals AI)31.6%19.9%GLM 5.3 Flash
Legal Research Bench (Vals AI)45.2%30.3%GLM 5.3 Flash
Harvey's Legal Agent Benchmark (Vals AI)10.4%4.2%GLM 5.3 Flash
Excel Modeling Benchmark (Vals AI)55.9%68.5%GPT-6 Luna
BioMysteryBench (Vals AI)Not measured61.5%Only GPT-6 Luna measured
Terminal-Bench-Science (Vals AI)2.9%4.3%GPT-6 Luna
Vals Science IndexNot measured28.4%Only GPT-6 Luna measured
APEX-Agents52.8%44.3%GLM 5.3 Flash
SpireClimbNot measured0.0%Only GPT-6 Luna measured
Neither model has a result on the other 21 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index93
Reasoning benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
GPQA Diamond86.4%Not measuredOnly GLM 5.3 Flash measured
LiveBench reasoning77.6%81.8%GPT-6 Luna
MysteryMechanism (Vals AI)Not measured19.4%Only GPT-6 Luna measured
MMMU Pro (Vals AI)86.0%Not measuredOnly GLM 5.3 Flash measured
GPQA Diamond (Artificial Analysis run)91.2%Not measuredOnly GLM 5.3 Flash measured
Humanity's Last Exam (Artificial Analysis run)39.9%38.5%GLM 5.3 Flash
GPQA Diamond (Epoch AI run)90.2%90.5%GPT-6 Luna
ARC-AGI91.0%86.7%GLM 5.3 Flash
ARC-AGI-265.8%59.3%GLM 5.3 Flash
Chess puzzles21.0%36.0%GPT-6 Luna
Mystery game puzzles8.0%7.0%GLM 5.3 Flash
LMArena Text: hard prompts14901410GLM 5.3 Flash
LMArena Text: expert15111442GLM 5.3 Flash
LMArena Text: hard prompts in English14881410GLM 5.3 Flash
LMArena Vision: diagrams13171245GLM 5.3 Flash
LMArena Vision: homework13181261GLM 5.3 Flash
Neither model has a result on the other 5 boards here
MathLike-for-likePublic boards, shown as published, kept out of the index24
Math benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
OTIS Mock AIME93.9%98.9%GPT-6 Luna
FrontierMath, tiers 1 to 355.8%78.9%GPT-6 Luna
FrontierMath, tier 417.1%56.1%GPT-6 Luna
ProofBench21.0%64.0%GPT-6 Luna
LMArena Text: math15031409GLM 5.3 Flash
LMArena Text: mathematical work14971427GLM 5.3 Flash
Neither model has a result on the other 7 boards here
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index40
Knowledge benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
MMLU Pro86.1%Not measuredOnly GLM 5.3 Flash measured
LegalBench (Vals AI)83.9%Not measuredOnly GLM 5.3 Flash measured
TaxEval (Vals AI)75.6%Not measuredOnly GLM 5.3 Flash measured
MedCode (Vals AI)Not measured44.7%Only GPT-6 Luna measured
SimpleQA VerifiedNot measured41.4%Only GPT-6 Luna measured
LMArena Text: science14841386GLM 5.3 Flash
LMArena Text: medicine and healthcare14751352GLM 5.3 Flash
LMArena Text: legal and government14731400GLM 5.3 Flash
LMArena Text: business and finance14601388GLM 5.3 Flash
Neither model has a result on the other 8 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index71
Web design benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
Design Arena: websites12721272Tie
Design Arena: UI components13161297GLM 5.3 Flash
Design Arena: game dev12791259GLM 5.3 Flash
Design Arena: data viz12621215GLM 5.3 Flash
Design Arena: 3D13161217GLM 5.3 Flash
Design Arena: all code categories12821271GLM 5.3 Flash
Design Arena: SVG12841253GLM 5.3 Flash
Design Arena: ASCII art12691156GLM 5.3 Flash
LiveBench design77.2%82.5%GPT-6 Luna
GeneralLike-for-likePublic boards, shown as published, kept out of the index242
General benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
Vals Index50.9%52.3%GPT-6 Luna
LiveBench data analysis76.4%73.4%GLM 5.3 Flash
Public Benefits Bench (Vals AI)Not measured57.6%Only GPT-6 Luna measured
SAGE (Vals AI)Not measured48.1%Only GPT-6 Luna measured
MedScribe (Vals AI)88.9%83.7%GLM 5.3 Flash
Long context reasoning (AA-LCR)80.0%83.3%GPT-6 Luna
DTBenchNot measured90.1%Only GPT-6 Luna measured
LMCANot measured44.5%Only GPT-6 Luna measured
Surface Evolver Bench52.5%Not measuredOnly GLM 5.3 Flash measured
Furniture assemblyNot measured44.2%Only GPT-6 Luna measured
LMArena Text14711389GLM 5.3 Flash
LMArena Text: instruction following14781408GLM 5.3 Flash
LMArena Text: creative writing14411363GLM 5.3 Flash
LMArena Vision12941216GLM 5.3 Flash
LMArena Text: English14741393GLM 5.3 Flash
LMArena Text: non-English14621381GLM 5.3 Flash
LMArena Text: Chinese15311427GLM 5.3 Flash
LMArena Text: German14621376GLM 5.3 Flash
LMArena Text: Japanese14441369GLM 5.3 Flash
LMArena Text: Korean14361359GLM 5.3 Flash
LMArena Text: French14911408GLM 5.3 Flash
LMArena Text: Spanish14751391GLM 5.3 Flash
LMArena Text: Russian14651392GLM 5.3 Flash
LMArena Text: Polish14501383GLM 5.3 Flash
LMArena Text: multi-turn14691392GLM 5.3 Flash
LMArena Text: longer queries14811408GLM 5.3 Flash
LMArena Text: writing and language14551384GLM 5.3 Flash
LMArena Text: entertainment and media14401364GLM 5.3 Flash
LMArena Vision: English12951204GLM 5.3 Flash
LMArena Vision: Chinese13631266GLM 5.3 Flash
LMArena Vision: reading text12991225GLM 5.3 Flash
LMArena Vision: humor1279Not measuredOnly GLM 5.3 Flash measured
LMArena Vision: creative writing12701205GLM 5.3 Flash
Neither model has a result on the other 13 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GLM 5.3 Flash and GPT-6 Luna
BenchmarkGLM 5.3 FlashGPT-6 LunaLeader
Neither model has a result on 5 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

GLM 5.3 Flash$0.0004Fits in one request
GPT-6 Luna$0.0003Fits in one request

GPT-6 Luna costs less

Repository review

50K input + 3K output tokens

GLM 5.3 Flash$0.0090Fits in one request
GPT-6 Luna$0.0065Fits in one request

GPT-6 Luna costs less

Agent loop

200K input + 10K output tokens

GLM 5.3 Flash$0.035Fits in one request
GPT-6 Luna$0.025Fits in one request

GPT-6 Luna costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of GLM 5.3 Flash and GPT-6 Luna
SpecificationZ.ai GLM 5.3 FlashOpenAI GPT-6 Luna
MakerZ.aiOpenAI
WeightsOpen weightsNo public weights listed
ReleasedAugust 26, 2026September 22, 2026
Context window1.05M1.05M
Input $/Mtok$0.15$0.10
Output $/Mtok$0.50$0.50
Coding index71.071.4
Independent measurements behind it22
Cost per solved task$0.02Not computable
SourceOpenRouter listingOpenRouter listing

Questions

Is GLM 5.3 Flash better than GPT-6 Luna for coding?

GLM 5.3 Flash and GPT-6 Luna are level for coding, 71.0 against 71.4 on the Vibe Coding Index, so price and context decide. Pick GLM 5.3 Flash when what matters is LMArena WebDev or Terminal-Bench 4 (Vals AI), where it leads. Pick GPT-6 Luna when the context window is larger, 1.05M against 1.05M tokens, or when what matters is LiveBench coding or Vibe Code Bench (Vals AI), where it leads.

Which is cheaper, GLM 5.3 Flash or GPT-6 Luna?

GLM 5.3 Flash costs $0.15 per million input tokens and $0.50 per million output tokens; GPT-6 Luna costs $0.10 and $0.50. Cost per solved task is known for GLM 5.3 Flash only.

Which has the bigger context window, GLM 5.3 Flash or GPT-6 Luna?

GPT-6 Luna, with 1.05M tokens against 1.05M.

How many benchmarks is the GLM 5.3 Flash vs GPT-6 Luna comparison based on?

87 benchmarks have a result for both models as of October 21, 2026. GLM 5.3 Flash's coding index rests on 2 independent benchmarks and GPT-6 Luna's on 2. Where only one model has a result, the page says so instead of naming a winner.

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<p style="font:13px/1.4 sans-serif;margin:6px 0 0">Source: <a href="https://llmbenchmark.ai/compare/glm-5-3-flash-vs-gpt-6-luna">LLMBenchmark.ai, GLM 5.3 Flash vs GPT-6 Luna</a></p>