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Head-to-head comparison

Claude Fable 5 vs o3

Claude Fable 5 (Anthropic) and o3 (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 18 August 2026

As of 18 August 2026, Claude Fable 5 holds the stronger ModelCap Index position (#1 vs #37); o3 is 6.3× cheaper per output token ($8.00/1M vs $50.00/1M); and Claude Fable 5 offers the longer context window (1M vs 200K tokens).

Which should you choose?

Choose Claude Fable 5 if…

  • you want the stronger overall ModelCap Index position — #1 against #37 (84.2 vs 55.1 points).
  • you need the longer context window — 1M tokens against 200K.
  • you want provider choice — 5 listed API providers against 1.
  • Arena coding is your yardstick — 1554 against 1460.
  • ARC-AGI-2 is your yardstick — 89.2% against 6.5%.
  • Artificial Analysis Intelligence Index is your yardstick — 62.1 against 31.1.
  • you want the more recently listed model — Claude Fable 5 was listed 9 June 2026, o3 16 April 2025.

Choose o3 if…

  • API cost matters — $8.00/1M output tokens against $50.00/1M, about 6.3× cheaper.
  • your workload is prompt-heavy — input tokens cost $2.00/1M against $10.00/1M.

Claude Fable 5 vs o3: specs, pricing and context

Specification comparison of Claude Fable 5 and o3
FieldClaude Fable 5Anthropico3OpenAI
ModelCap Index position#1#37
Index score84.255.1
EvidenceMeasuredMeasured
Input price / 1M tokens$10.00$2.00
Output price / 1M tokens$50.00$8.00
Context window1M tokens200K tokens
Max output tokens128K100K
API providers listed51
Weight accessAPI onlyAPI only
Input modalitiesText, Image, FileImage, Text, File
First listed9 June 202616 April 2025
PublisherAnthropicOpenAI

Evidence: 7 public benchmark observations across 7 boards · 4 public benchmark observations across 4 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.

Benchmark scores: Claude Fable 5 vs o3

Public benchmark boards where Claude Fable 5 or o3 has a published result
BoardClaude Fable 5o3Leads
Arena codingArena (LMArena)15541546–156314601453–1466Claude Fable 5
LMArena AgentLMArena12.0%9.4%–14.6%High—Only one result
ARC-AGI-2ARC Prize Foundation89.2%Max6.5%HighClaude Fable 5
SWE-benchSWE-bench (Princeton / SWE-agent team)—58.4%Only one result
BFCL V4UC Berkeley (Gorilla)—63.1PromptOnly one result
Terminal-Bench 2.1 Terminus 2Terminal-Bench80.4High—Only one result
WildClawBench OpenClawWildClawBench62.0—Only one result
Artificial Analysis Intelligence IndexArtificial Analysis62.1intelligence-index31.1intelligence-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 o3: common questions

Is Claude Fable 5 better than o3?

Claude Fable 5 ranks higher on the ModelCap Index as of 18 August 2026: #1 against #37. 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 o3?

o3 is cheaper on output tokens: $8.00/1M against $50.00/1M. Input tokens are $10.00/1M for Claude Fable 5 and $2.00/1M for o3. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens.

Which has the bigger context window, Claude Fable 5 or o3?

Claude Fable 5 has the larger context window: 1M tokens against 200K.

Which is better for coding, Claude Fable 5 or o3?

Arena coding: Claude Fable 5 1554, o3 1460 — Claude Fable 5 leads.

Are Claude Fable 5 and o3 open-weight models?

Claude Fable 5: API only. o3: 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 o3?

ModelCap currently lists 5 API providers for Claude Fable 5 and 1 for o3, 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 o3 comparison?

Every figure comes from the sealed ModelCap dataset published 18 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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