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Head-to-head comparison

Claude Fable 5 vs GPT-5.3-Codex

Claude Fable 5 (Anthropic) and GPT-5.3-Codex (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.

Snapshot as of 17 August 2026

As of 17 August 2026, Claude Fable 5 holds the stronger ModelCap Index position (#1 vs #20); GPT-5.3-Codex is 3.6× cheaper per output token ($14.00/1M vs $50.00/1M); and Claude Fable 5 offers the longer context window (1M vs 400K tokens).

Which should you choose?

Choose Claude Fable 5 if…

  • you want the stronger overall ModelCap Index position — #1 against #20 (85.5 vs 66.4 points).
  • you need the longer context window — 1M tokens against 400K.
  • you want provider choice — 5 listed API providers against 2.
  • Artificial Analysis Intelligence Index is your yardstick — 62.1 against 45.5.
  • you want the more recently listed model — Claude Fable 5 was listed 9 June 2026, GPT-5.3-Codex 24 February 2026.

Choose GPT-5.3-Codex if…

  • API cost matters — $14.00/1M output tokens against $50.00/1M, about 3.6× cheaper.
  • your workload is prompt-heavy — input tokens cost $1.75/1M against $10.00/1M.

Claude Fable 5 vs GPT-5.3-Codex: specs, pricing and context

Specification comparison of Claude Fable 5 and GPT-5.3-Codex
FieldClaude Fable 5AnthropicGPT-5.3-CodexOpenAI
ModelCap Index position#1#20
Index score85.566.4
EvidenceMeasuredMeasured
Input price / 1M tokens$10.00$1.75
Output price / 1M tokens$50.00$14.00
Context window1M tokens400K tokens
Max output tokens128K128K
API providers listed52
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileText, Image, File
First listed9 June 202624 February 2026
PublisherAnthropicOpenAI

Evidence: 5 public benchmark observations across 5 boards · 1 public benchmark observation across 1 board. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Fable 5 vs GPT-5.3-Codex

Public benchmark boards where Claude Fable 5 or GPT-5.3-Codex has a published result
BoardClaude Fable 5GPT-5.3-CodexLeads
Arena codingArena (LMArena)15541546–1563—Only one result
LMArena AgentLMArena12.0%9.4%–14.6%High—Only one result
ARC-AGI-2ARC Prize Foundation89.2%Max—Only one result
Artificial Analysis Intelligence IndexArtificial Analysis62.1intelligence-index45.5intelligence-indexClaude Fable 5

Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.

Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.

Claude Fable 5 vs GPT-5.3-Codex: common questions

Is Claude Fable 5 better than GPT-5.3-Codex?

Claude Fable 5 ranks higher on the ModelCap Index as of 17 August 2026: #1 against #20. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it.

Is Claude Fable 5 cheaper than GPT-5.3-Codex?

GPT-5.3-Codex is cheaper on output tokens: $14.00/1M against $50.00/1M. Input tokens are $10.00/1M for Claude Fable 5 and $1.75/1M for GPT-5.3-Codex. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

Which has the bigger context window, Claude Fable 5 or GPT-5.3-Codex?

Claude Fable 5 has the larger context window: 1M tokens against 400K.

Which is better for coding, Claude Fable 5 or GPT-5.3-Codex?

The two models do not share a coding benchmark board on ModelCap yet, so no head-to-head coding score is published; the ModelCap Index position is the closest overall signal.

Are Claude Fable 5 and GPT-5.3-Codex open-weight models?

Claude Fable 5: API only. GPT-5.3-Codex: API only. Open weights mean the checkpoint can be downloaded and self-hosted under its licence; API-only models are available solely through hosted endpoints.

Where can I run Claude Fable 5 and GPT-5.3-Codex?

ModelCap currently lists 5 API providers for Claude Fable 5 and 2 for GPT-5.3-Codex, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Fable 5 vs GPT-5.3-Codex comparison?

Every figure comes from the sealed ModelCap dataset published 17 August 2026; the page re-renders within a minute of each data refresh, and the ModelCap Index positions are the same ones shown on the live rankings.

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