Long documents
Prompts that approach the documented context limit
GPT-5.6 Luna
GPT-5.6 Luna has the larger documented context window.
Confidence: documented
GPT-5.3-Codex-Spark vs GPT-5.6 Luna
Updated September 24, 2026. We do not rank this pair: at least one has no public score. Public scores include evidence status and uncertainty.
Both of these models will change. Get the price, version and retirement notices for the pair, each with its source. Follow model changes
Share or export
Decision reading
The public evidence has no benchmark result shared by both models, so it does not support a quality verdict. Use the documented cost, context, and runtime rows instead. 0 results are shared. Category rows resting on Estimated evidence or different benchmark sets are marked directional and do not name a winner.
- Shared results
- 0
- GPT-5.3-Codex-Spark only
- 0
- GPT-5.6 Luna only
- 29
- Like-for-like categories
- 0 / 8
Supported: GPT-5.6 LunaHow the comparison works
Which one for your work
Recommendations appear only when a shared evidence basis or an explicit operating constraint supports the call. Secondary and unsupported use cases stay disclosed below the initial list.
Show secondary and unsupported calls
Coding work
Code generation, repair, and software-engineering tasks
Not enough matched evidence
GPT-5.3-Codex-Spark is not ranked on the public lane for coding, so no winner is named for coding.
Confidence: limitedAgentic work
Tool use, computer use, and multi-step task completion
Not enough matched evidence
GPT-5.3-Codex-Spark is not ranked on the public lane for agentic, so no winner is named for agentic.
Confidence: limitedChat turn cost
1K fresh input + 500 output tokens
Not enough matched evidence
A complete comparable API-rate estimate is not available for both models.
Confidence: listed-ratesCache-heavy agent loop cost
200K cached + 20K fresh input + 10K output tokens
Not enough matched evidence
The page does not recommend a cost winner because at least one model cannot fit the stated workload in one request. GPT-5.3-Codex-Spark does not fit this workload in one request. GPT-5.3-Codex-Spark has no comparable published API token rate.
Confidence: listed-ratesRepository review cost
50K fresh input + 3K output tokens
Not enough matched evidence
A complete comparable API-rate estimate is not available for both models.
Confidence: listed-rates
Which one for a specific job
Choose a job from the LLM Selector's task catalog to see the category row it rests on, under the same basis rules as the table below. A directional row stays directional; choosing a job never creates a winner.
The same task catalog as the LLM Selector. Each job names the evidence surface it rests on; nothing here adds a new score.
—GPT-5.3-Codex-Spark64.5GPT-5.6 Luna
Not comparable · BenchAlign v5.7
The coding row is not comparable on the public lane: at least one model is not measured or not ranked there.
Coding scores combine specific tasks and setups. Match the editor, harness, and effort to your workflow.
Same basis rules as the category table below
What is actually comparable
Shared results can support a head-to-head reading. Results present for only one model describe coverage, not superiority.
29 GPT-5.6 Luna only
Shape of the matched evidence
Only shared public evidence is shown. Sparse evidence stays a ruled list rather than being closed into a radar shape.
A shared-evidence shape is not available.
BenchLM does not draw a radar or infer missing axes when the matched evidence is too sparse.
Category results, on a stated basis
Each row shows the public-lane category score for both models: the BenchAlign v5.7 lane for agentic, coding, and knowledge, and the weighted public rows elsewhere, with the same rank each model page reports. A row is like-for-like only when both scores rest on Supported evidence or the same weighted set. Directional and not-comparable rows remain visible, but they never receive a winner.
Agentic
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- 55.3
- Supported · #28/105
- Basis
- BenchAlign v5.7 lane · 0 vs 9 public rows
- Reading
- Not comparable
Coding
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- 64.5
- Supported · #9/135
- Basis
- BenchAlign v5.7 lane · 0 vs 7 public rows
- Reading
- Not comparable
Reasoning
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- 54.7
- #18/19
- Basis
- Provisional lane · 0 vs 2 weighted rows
- Reading
- Not comparable
Multimodal
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- 67.1
- #22/50
- Basis
- Provisional lane · 0 vs 1 weighted rows
- Reading
- Not comparable
Knowledge
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- 64.6
- Supported · #22/158
- Basis
- BenchAlign v5.7 lane · 0 vs 6 public rows
- Reading
- Not comparable
Multilingual
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Instruction following
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- Not ranked
- Basis
- Provisional lane · 0 vs 0 weighted rows
- Reading
- Not comparable
Math
Not comparable- GPT-5.3-Codex-Spark
- Not ranked
- GPT-5.6 Luna
- 94.2
- Unranked · 3 rankable rows
- Basis
- Provisional lane · 0 vs 2 weighted rows
- Reading
- Not comparable
| Category | GPT-5.3-Codex-Spark | GPT-5.6 Luna | Basis | Reading |
|---|---|---|---|---|
| Agentic | Not ranked | 55.3Supported · #28/105 | Not comparableBenchAlign v5.7 lane · 0 vs 9 public rows | Not comparable |
| Coding | Not ranked | 64.5Supported · #9/135 | Not comparableBenchAlign v5.7 lane · 0 vs 7 public rows | Not comparable |
| Reasoning | Not ranked | 54.7#18/19 | Not comparableProvisional lane · 0 vs 2 weighted rows | Not comparable |
| Multimodal | Not ranked | 67.1#22/50 | Not comparableProvisional lane · 0 vs 1 weighted rows | Not comparable |
| Knowledge | Not ranked | 64.6Supported · #22/158 | Not comparableBenchAlign v5.7 lane · 0 vs 6 public rows | Not comparable |
| Multilingual | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Instruction following | Not ranked | Not ranked | Not comparableProvisional lane · 0 vs 0 weighted rows | Not comparable |
| Math | Not ranked | 94.2Unranked · 3 rankable rows | Not comparableProvisional lane · 0 vs 2 weighted rows | Not comparable |
Ranks count the models scored in each category’s lane, so the agentic, coding, and knowledge denominators (BenchAlign v5.7) differ from the provisional-lane categories. Unranked scores sit on the provisional lane’s scale but never name a winner. Like-for-like rows within 0.5 points read as a practical tie.
Supported evidence per lane · bars run 0–100Methodology
What each workload costs
Three fixed token mixes turn per-token rates into comparable decisions. Each scenario states context fit and whether cached input had to fall back to the published list-input rate.
Chat turn
1K fresh input + 500 output tokens
- GPT-5.3-Codex-Spark
- API rate not published
- Fits in one request
- GPT-5.6 Luna
- $0.0008
- Fits in one request
GPT-5.3-Codex-Spark has no comparable published API token rate.
Repository review
50K fresh input + 3K output tokens
- GPT-5.3-Codex-Spark
- API rate not published
- Fits in one request
- GPT-5.6 Luna
- $0.0136
- Fits in one request
GPT-5.3-Codex-Spark has no comparable published API token rate.
Cache-heavy agent loop
200K cached + 20K fresh input + 10K output tokens
- GPT-5.3-Codex-Spark
- API rate not published
- Does not fit in one request
- Cached-input rate unavailable
- GPT-5.6 Luna
- $0.02
- Fits in one request
GPT-5.3-Codex-Spark does not fit this workload in one request. GPT-5.3-Codex-Spark has no comparable published API token rate.
Cached input falls back to the list input rate only where a cached rate is unpublished
Specification differences
Sourced differences are shown directly. Missing facts stay explicit instead of being inferred from a model name or family.
SpecificationGPT-5.3-Codex-SparkGPT-5.6 Luna
Context window
Maximum documented context; output-token limits may be lower.
GPT-5.3-Codex-Spark
GPT-5.6 Luna
1.05M
OpenAI model catalogAPI model ID
GPT-5.3-Codex-Spark
Not sourced
GPT-5.6 Luna
gpt-5.6-luna
OpenAI model catalogCached-input rate
A missing cached-input rate falls back to the listed input rate only in the stated workload estimate.
GPT-5.3-Codex-Spark
No comparable hosted API rate
GPT-5.6 Luna
$0.02 per 1M cached input tokens
OpenAI pricingDocumented inputs
GPT-5.3-Codex-Spark
GPT-5.6 Luna
text, image
OpenAI model catalogDocumented outputs
GPT-5.3-Codex-Spark
GPT-5.6 Luna
Provider availability
GPT-5.3-Codex-Spark
Limited Access · Codex for ChatGPT Pro, API design-partner program
OpenAI GPT-5.3 Codex Spark launchGPT-5.6 Luna
Generally Available · OpenAI Responses API
OpenAI model catalogReasoning profile
GPT-5.3-Codex-Spark
Reasoning
GPT-5.6 Luna
Reasoning
Weight access
GPT-5.3-Codex-Spark
Proprietary
GPT-5.6 Luna
Proprietary
License
GPT-5.3-Codex-Spark
Proprietary
GPT-5.6 Luna
Proprietary
Release date
GPT-5.3-Codex-Spark
2026-02-12
GPT-5.6 Luna
2026-07-09
If you already use one of these models
- Deployment change
- Both entries list OpenAI as the provider. Confirm endpoint, model ID, limits, and feature support before switching.
- Quality signal
- The public evidence has no benchmark result shared by both models, so it does not support a quality verdict.
- Workload cost
- A complete comparable API-rate estimate is not available for both models.
- Context tradeoff
- GPT-5.6 Luna has the larger documented window (1.05M).
Run the same representative tasks against both endpoints before changing production traffic.
Questions
Which is better, GPT-5.3-Codex-Spark or GPT-5.6 Luna?
The public evidence has no benchmark result shared by both models, so it does not support a quality verdict. The page therefore keeps the decision tied to the specific documented workload.
Which is better for coding, GPT-5.3-Codex-Spark or GPT-5.6 Luna?
GPT-5.3-Codex-Spark is not ranked on the public lane for coding, so no winner is named for coding.
Which is better for agentic tasks, GPT-5.3-Codex-Spark or GPT-5.6 Luna?
GPT-5.3-Codex-Spark is not ranked on the public lane for agentic tasks, so no winner is named for agentic tasks.
Which costs less, GPT-5.3-Codex-Spark or GPT-5.6 Luna?
Both models do not have comparable published API token rates, so this page does not name a universal price winner.
Which has the larger context window, GPT-5.3-Codex-Spark or GPT-5.6 Luna?
GPT-5.6 Luna has the larger documented context window: 1.05M, compared with 128K.
Benchmark evidence
The full public result ledger is available for audit without forcing a wide desktop table onto a phone.
Browse raw public benchmark evidence29 rows
Agentic
Terminal-Bench 3.0
GPT-5.3-Codex-Spark—GPT-5.6 Luna14.3%SourceNot directly comparable
Terminal-Bench 2.1
GPT-5.3-Codex-Spark—GPT-5.6 Luna84.7%SourceNot directly comparable
BrowseComp
GPT-5.3-Codex-Spark—GPT-5.6 Luna83.3%SourceNot directly comparable
OSWorld 2.0
GPT-5.3-Codex-Spark—GPT-5.6 Luna45.6%SourceNot directly comparable
CyberGym
GPT-5.3-Codex-Spark—GPT-5.6 Luna77.9%SourceNot directly comparable
ExploitGym
GPT-5.3-Codex-Spark—GPT-5.6 Luna12.4%SourceNot directly comparable
Toolathlon
GPT-5.3-Codex-Spark—GPT-5.6 Luna53.4%SourceNot directly comparable
Terminal-Bench 2.1 (Vals)
GPT-5.3-Codex-Spark—GPT-5.6 Luna79.0%SourceNot directly comparable
ApprenticeBench
GPT-5.3-Codex-Spark—GPT-5.6 Luna7%SourceNot directly comparable
Coding
SWE-bench Pro
GPT-5.3-Codex-Spark—GPT-5.6 Luna62.7%SourceNot directly comparable
Terminal-Bench 2.1
GPT-5.3-Codex-Spark—GPT-5.6 Luna84.7%SourceNot directly comparable
DeepSWE
GPT-5.3-Codex-Spark—GPT-5.6 Luna67.2%SourceNot directly comparable
FrontierCode 1.1 Extended
GPT-5.3-Codex-Spark—GPT-5.6 Luna55.1%SourceNot directly comparable
cursorBench32
GPT-5.3-Codex-Spark—GPT-5.6 Luna61.1%SourceNot directly comparable
VulcanBench v3
GPT-5.3-Codex-Spark—GPT-5.6 Luna85.5%SourceNot directly comparable
SWE-bench (Vals)
GPT-5.3-Codex-Spark—GPT-5.6 Luna93.0%SourceNot directly comparable
Reasoning
Multimodal
Knowledge
GPQA
GPT-5.3-Codex-Spark—GPT-5.6 Luna92.3%SourceNot directly comparable
GPQA-D
GPT-5.3-Codex-Spark—GPT-5.6 Luna92.3%SourceNot directly comparable
HealthBench Professional
GPT-5.3-Codex-Spark—GPT-5.6 Luna55.7%SourceNot directly comparable
HealthBench Hard
GPT-5.3-Codex-Spark—GPT-5.6 Luna32.0%SourceNot directly comparable
GPQA Diamond (Vals)
GPT-5.3-Codex-Spark—GPT-5.6 Luna91.7%SourceNot directly comparable
MMLU-Pro (Vals)
GPT-5.3-Codex-Spark—GPT-5.6 Luna86.0%SourceNot directly comparable
Math
29 public results · 0 shared
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Last updated September 24, 2026