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GPT-5.3-Codex vs Muse Spark Open

Updated October 21, 2026. 11 benchmarks have a result for both. Coding is ranked on the Vibe Coding Index; every other board is shown as published.

Replace GPT-5.3-Codex Replace Muse Spark Open
GPT-5.3-CodexOpenAI
Coding
29.5
Overall
32.5
Output $/M
$14.00
4
Muse Spark OpenMeta
Coding
62.1
Overall
No data
Output $/M
$4.25
7
vs boards won of 11 shared

Decision reading

Pick Muse Spark Open for coding: it scores 62.1 on the Vibe Coding Index against 29.5 for GPT-5.3-Codex.

Pick GPT-5.3-Codex when what matters is ALE-Bench or Epoch Capabilities Index, where it leads.

Model AGPT-5.3-CodexOpenAI29.5/1001 independent benchmark$0.59 per solved taskModel BMuse Spark OpenMeta62.1/1002 independent benchmarksNo cost per solved task
Shared results
11
GPT-5.3-Codex only
23
Muse Spark Open only
15
Like-for-like categories
5 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
GPT-5.3-Codex 29.5 from 1 benchmark, Muse Spark Open 62.1 from 2 benchmarks.
Widest category
Web design, 17.3 points apart on average over 2 shared benchmarks.
Widest single gap
LMArena WebDev: React: GPT-5.3-Codex 1395 against Muse Spark Open 1529, 22.4 points apart on a 0 to 100 scale.
Output price
GPT-5.3-Codex $14.00 against Muse Spark Open $4.25 per million output tokens, 3.3x apart.
Context window
GPT-5.3-Codex takes 400K tokens, Muse Spark Open 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
CategoryGPT-5.3-CodexBarsMuse Spark OpenTies
Coding14
Intelligence10
Reasoning11
Web design02
General10
All shared boards47
CodingLike-for-likeFour of these boards feed the Vibe Coding Index14
Coding benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
LiveBench codingNot measured73.6%Only Muse Spark Open measured
LMArena WebDev14071528Muse Spark Open
LiveCodeBench (Vals AI)87.3%Not measuredOnly GPT-5.3-Codex measured
SWE-bench Verified (Vals AI)78.0%Not measuredOnly GPT-5.3-Codex measured
Terminal-Bench 4 (Vals AI)Not measured6.6%Only Muse Spark Open measured
Vibe Code Bench (Vals AI)61.8%76.2%Muse Spark Open
Code migration (Vals AI)Not measured21.2%Only Muse Spark Open measured
IOI (Vals AI)53.8%Not measuredOnly GPT-5.3-Codex measured
SciCodeNot measured58.4%Only Muse Spark Open measured
Terminal-Bench Hard (Artificial Analysis run)53.0%Not measuredOnly GPT-5.3-Codex measured
Terminal-Bench78.4%Not measuredOnly GPT-5.3-Codex measured
WeirdML79.3%Not measuredOnly GPT-5.3-Codex measured
ALE-Bench1655.21590.1GPT-5.3-Codex
LMArena WebDev: React13951529Muse Spark Open
LMArena WebDev: HTML14221495Muse Spark Open
LMArena WebDev: from an image1443Not measuredOnly GPT-5.3-Codex measured
Neither model has a result on the other 22 boards here
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index10
Intelligence benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
AA Intelligence Index32.5Not measuredOnly GPT-5.3-Codex measured
Epoch Capabilities Index157.1155.1GPT-5.3-Codex
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index16 boards, none shared
Agentic work benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
Design Arena: agents building web apps1033Not measuredOnly GPT-5.3-Codex measured
Design Arena: agents building full-stack apps983Not measuredOnly GPT-5.3-Codex measured
Design Arena: agents building mobile apps1054Not measuredOnly GPT-5.3-Codex measured
Design Arena: agents building Android apps1084Not measuredOnly GPT-5.3-Codex measured
Design Arena: agents building Godot games1124Not measuredOnly GPT-5.3-Codex measured
LiveBench researchNot measured80.3%Only Muse Spark Open measured
LiveBench browserNot measured36.0%Only Muse Spark Open measured
LiveBench long agenticNot measured18.9%Only Muse Spark Open measured
Finance Agent (Vals AI)Not measured61.3%Only Muse Spark Open measured
Tax Agent Bench (Vals AI)Not measured26.3%Only Muse Spark Open measured
Legal Research Bench (Vals AI)Not measured38.5%Only Muse Spark Open measured
Excel Modeling Benchmark (Vals AI)Not measured53.7%Only Muse Spark Open measured
τ²-Bench Telecom86.0%Not measuredOnly GPT-5.3-Codex measured
APEX-AgentsNot measured33.4%Only Muse Spark Open measured
METR time horizons74.5%Not measuredOnly GPT-5.3-Codex measured
Vending-Bench 2$5,940Not measuredOnly GPT-5.3-Codex measured
Neither model has a result on the other 23 boards here
ReasoningLike-for-likePublic boards, shown as published, kept out of the index11
Reasoning benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
LiveBench reasoningNot measured73.7%Only Muse Spark Open measured
GPQA Diamond (Artificial Analysis run)91.5%89.0%GPT-5.3-Codex
Humanity's Last Exam (Artificial Analysis run)42.5%43.9%Muse Spark Open
Neither model has a result on the other 18 boards here
MathNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Math benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
Neither model has a result on 13 boards here
KnowledgeNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Knowledge benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
Neither model has a result on 17 boards here
Web designLike-for-likePublic boards, shown as published, kept out of the index02
Web design benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
Design Arena: websites11631311Muse Spark Open
Design Arena: UI components1137Not measuredOnly GPT-5.3-Codex measured
Design Arena: game dev11621290Muse Spark Open
Design Arena: data viz1164Not measuredOnly GPT-5.3-Codex measured
Design Arena: 3D1008Not measuredOnly GPT-5.3-Codex measured
Design Arena: all code categories1145Not measuredOnly GPT-5.3-Codex measured
Design Arena: SVG1129Not measuredOnly GPT-5.3-Codex measured
Design Arena: ASCII art1151Not measuredOnly GPT-5.3-Codex measured
LiveBench designNot measured60.3%Only Muse Spark Open measured
GeneralLike-for-likePublic boards, shown as published, kept out of the index10
General benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
LiveBench data analysisNot measured60.2%Only Muse Spark Open measured
IFBench75.4%Not measuredOnly GPT-5.3-Codex measured
Long context reasoning (AA-LCR)83.3%78.3%GPT-5.3-Codex
Neither model has a result on the other 43 boards here
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
Image generation benchmarks for GPT-5.3-Codex and Muse Spark Open
BenchmarkGPT-5.3-CodexMuse Spark OpenLeader
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

GPT-5.3-Codex$0.0088Fits in one request
Muse Spark Open$0.0034Fits in one request

Muse Spark Open costs less

Repository review

50K input + 3K output tokens

GPT-5.3-Codex$0.130Fits in one request
Muse Spark Open$0.075Fits in one request

Muse Spark Open costs less

Agent loop

200K input + 10K output tokens

GPT-5.3-Codex$0.490Fits in one request
Muse Spark Open$0.292Fits in one request

Muse Spark Open 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 GPT-5.3-Codex and Muse Spark Open
SpecificationOpenAI GPT-5.3-CodexMeta Muse Spark Open
MakerOpenAIMeta
WeightsNo public weights listedOpen weights
ReleasedFebruary 24, 2026October 15, 2026
Context window400K1.05M
Input $/Mtok$1.75$1.25
Output $/Mtok$14.00$4.25
Coding index29.562.1
Independent measurements behind it12
Cost per solved task$0.59Not computable
SourceOpenRouter listingOpenRouter listing

Questions

Is GPT-5.3-Codex better than Muse Spark Open for coding?

Pick Muse Spark Open for coding: it scores 62.1 on the Vibe Coding Index against 29.5 for GPT-5.3-Codex. Pick GPT-5.3-Codex when what matters is ALE-Bench or Epoch Capabilities Index, where it leads.

Which is cheaper, GPT-5.3-Codex or Muse Spark Open?

GPT-5.3-Codex costs $1.75 per million input tokens and $14.00 per million output tokens; Muse Spark Open costs $1.25 and $4.25. Cost per solved task is known for GPT-5.3-Codex only.

Which has the bigger context window, GPT-5.3-Codex or Muse Spark Open?

Muse Spark Open, with 1.05M tokens against 400K.

How many benchmarks is the GPT-5.3-Codex vs Muse Spark Open comparison based on?

11 benchmarks have a result for both models as of October 21, 2026. GPT-5.3-Codex's coding index rests on 1 independent benchmark and Muse Spark Open's on 2. Where only one model has a result, the page says so instead of naming a winner.

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