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AI Choice Engine

Model comparison

GPT-5.3-Codex vs Muse Spark 1.2

OpenAI against Meta, compared on context, price, and verified benchmark results.

Catalog record checked September 26, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

OpenAI

GPT-5.3-Codex

Frontier

vs

Meta

Muse Spark 1.2

Frontier

AI model capability comparison
SpecificationGPT-5.3-CodexMuse Spark 1.2
ProviderOpenAIMeta
TierFrontierFrontier
Context window400KWinner: 1.05M
Max output128KNot verifiedUnverified
Input / 1M tokens$1.75Winner: $1.25
Output / 1M tokens$14Winner: $4.25
WeightsClosedClosed
ParametersNot disclosedUnverifiedMeta frontier model
Reasoning levelslow, medium, high, xhighminimal, low, medium, high, xhigh, max
Modalitiestext, imagetext, image, video, audio, pdf
API model idgpt-5.3-codexmuse-spark-1.2
ReleasedFebruary 5, 2026August 5, 2026
Artificial Analysis Intelligence Index [xhigh] (2026-09-26)32.5Winner: 39.6

Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

  • 2026-09-26
    Artificial Analysis

    Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.

    Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check measuredAt.

Pricing tiers

GPT-5.3-Codex: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Still listed in the API as a coding-specialised model.

Muse Spark 1.2: $1.25/$4.25 per MTok on Meta's Model API (Standard tier shared with Muse Spark 1.3; cached input $0.15). Closed weights.

FrontierRecord checked September 26, 2026

GPT-5.3-Codex

GPT-5.3-Codex is OpenAI's coding-specialised API model at $1.75/$14 — the Codex agent itself now runs GPT-6 Sol, Luna and Astra.

Best for

  • Autonomous coding
  • Repo-scale refactors
  • Test generation

Watch out

Tuned for coding, not general chat; for new coding work compare GPT-6 Sol ($2/$10) first.

FrontierRecord checked September 26, 2026

Muse Spark 1.2

Muse Spark 1.2 is Meta's closed frontier model until the 1.3 refresh (2026-09-02) — still served and ranked in the LMArena text top 10 as of mid-2026.

Best for

  • Frontier reasoning
  • Meta ecosystem
  • Agentic work

Watch out

Closed-weights (unlike Llama 4); Meta's post-Llama-4 frontier branding.

When the cheaper one wins

Muse Spark 1.2 is cheaper on output at $4.25 per million tokens against $14 for GPT-5.3-Codex — about 3.3×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.

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Evidence confidence: High

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

  • Pricing verified on both sides — Input and output rates are verified for both models.
  • 3/5 core specs verified on both sides — Not published for at least one side: max output, parameter count.
  • 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
  • Verified within the last 90 days — Newest catalog check was 2 days ago.
  • Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Related comparisons

Diving deeper on one model? GPT-5.3-Codex · Muse Spark 1.2

Common questions

GPT-5.3-Codex vs Muse Spark 1.2

Answered from the verified figures on this page rather than general guidance.

Is GPT-5.3-Codex or Muse Spark 1.2 cheaper for input?
Muse Spark 1.2 is cheaper at $1.25 per million input tokens, against $1.75 for GPT-5.3-Codex — roughly 1.4× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.3-Codex has tiered pricing: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Still listed in the API as a coding-specialised model. Muse Spark 1.2 has tiered pricing: $1.25/$4.25 per MTok on Meta's Model API (Standard tier shared with Muse Spark 1.3; cached input $0.15). Closed weights.
Is GPT-5.3-Codex or Muse Spark 1.2 cheaper for output?
Muse Spark 1.2 is cheaper at $4.25 per million output tokens, against $14 for GPT-5.3-Codex — roughly 3.3× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; GPT-5.3-Codex has tiered pricing: Standard $1.75/$14 per MTok; cached input $0.175/MTok; Fast mode $3.50/$28. Still listed in the API as a coding-specialised model. Muse Spark 1.2 has tiered pricing: $1.25/$4.25 per MTok on Meta's Model API (Standard tier shared with Muse Spark 1.3; cached input $0.15). Closed weights.
Which has the larger context window, GPT-5.3-Codex or Muse Spark 1.2?
Muse Spark 1.2 accepts 1.05M tokens against 400K for GPT-5.3-Codex. This only matters if you routinely send very long documents or large codebases.
Do GPT-5.3-Codex and Muse Spark 1.2 support the same reasoning levels?
GPT-5.3-Codex exposes low, medium, high, xhigh, while Muse Spark 1.2 exposes minimal, low, medium, high, xhigh, max.
Should I use GPT-5.3-Codex or Muse Spark 1.2?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. GPT-5.3-Codex suits autonomous coding; Muse Spark 1.2 suits frontier reasoning.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

  • Input price: Muse Spark 1.2 costs $1.25 per 1M tokens versus $1.75 for GPT-5.3-Codex — a 1.4x difference at the headline tier.
  • Context: Muse Spark 1.2 takes 1.05M against 400K for GPT-5.3-Codex — only decisive if your prompts approach the smaller window.
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