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Comparison · 2 models · Updated Oct 4, 2026

Claude Fable 5 vs GPT-5.3 Codex

Too close to call on our weighted score (Claude Fable 5 65, GPT-5.3 Codex 64). The right pick depends on what you value most.

  1. Anthropic

    Claude Fable 5

    Released Jun 9, 2026

    65/100
    • ECI162.2
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5

  2. OpenAI

    GPT-5.3 Codex

    Released Feb 5, 2026

    64/100
    • ECI156.8
    • Price$1.75 / $14.00
    • Context400K
    Full specs Remove GPT-5.3 Codex

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01 — Verdict

Too close to call

It is close. Our weighted score puts them within a point (Claude Fable 5 65/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: Claude Fable 5 for raw capability and GPT-5.3 Codex on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Fable 5Capabilities Index (ECI): Claude Fable 5 162.2 · GPT-5.3 Codex 156.8
  • Lowest priceGPT-5.3 CodexGPT-5.3 Codex $4.81 · Claude Fable 5 $20.00 per 1M tokens (3:1 blend)
  • Longest contextClaude Fable 5Claude Fable 5 1,000,000 · GPT-5.3 Codex 400,000 tokens
  • Widest inputsSame inputsClaude Fable 5: Text, Images, PDFs · GPT-5.3 Codex: Text, Images, PDFs
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightClaude Fable 5GPT-5.3 Codex
CapabilityCapabilities Index (ECI)50%9487
Price25%018
Inputs & features15%8080
Context window10%6044
Overall100%65/10064/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Claude Fable 5 vs GPT-5.3 Codex specifications side by side
SpecificationClaude Fable 5AnthropicGPT-5.3 CodexOpenAI
Capability
Capabilities Index (ECI)162.2 (best)156.8
ECI rank#7 of 148 (best)#18 of 148
GPQA DiamondGraduate-level science questions85.9%—
FrontierMath Tiers 1–3Research-level mathematics87.0%—
OTIS Mock AIME 2024–2025Competition mathematics100%—
SWE-bench VerifiedFixing real GitHub issues—74.8%
SimpleQA VerifiedShort factual questions70.7%—
Price per million tokens
Input$10.00$1.75 (best)
Output$50.00$14.00 (best)
Cached input$1.00$0.175 (best)
Blended (3:1)$20.00$4.81 (best)
Long-context rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial OpenAI API
Limits
Context window1,000,000 tokens (best)400,000 tokens
Max output128,000 tokens128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoNo
ReasoningYeslow · medium · high · xhigh · maxYeslow · medium · high · xhigh
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryProprietary
API model IDclaude-fable-5gpt-5.3-codex
API providers38 (best)19
ReleasedJun 9, 2026Feb 5, 2026
Knowledge cutoffJan 31, 2026Aug 31, 2025
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Claude Fable 5$200.00
  • GPT-5.3 Codex$45.50
04 — Questions

Which should you choose?

Which is better: Claude Fable 5 or GPT-5.3 Codex?

It is close. Our weighted score puts them within a point (Claude Fable 5 65/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: Claude Fable 5 for raw capability and GPT-5.3 Codex on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Fable 5 or GPT-5.3 Codex?

GPT-5.3 Codex is cheaper at $1.75 input / $14.00 output per million tokens (official OpenAI API price). Claude Fable 5 costs $10.00 input / $50.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $4.81 per million tokens for GPT-5.3 Codex versus $20.00 for Claude Fable 5 (4.2× as much).

Which scores higher on benchmarks?

Claude Fable 5 scores higher on the Capabilities Index (ECI): Claude Fable 5 162.2 (#7 of 148) and GPT-5.3 Codex 156.8 (#18 of 148). The confidence ranges of the top two overlap (159.6–166.1 vs 153.5–160.8), so treat the gap as small.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Fable 5 yet, so there is no like-for-like coding score. On overall capability, Claude Fable 5 leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Claude Fable 5 has the largest context window at 1,000,000 tokens, against 400,000 for GPT-5.3 Codex. Maximum output per response: Claude Fable 5 up to 128,000, GPT-5.3 Codex up to 128,000 tokens.

Which can read images, PDFs, audio or video?

Claude Fable 5 accepts text, images and PDFs; GPT-5.3 Codex accepts text, images and PDFs. They handle the same number of input types.

Are any of these open source?

No. Claude Fable 5 and GPT-5.3 Codex are proprietary and only available through APIs and apps.

Which is newer?

Claude Fable 5 is the newest, released Jun 9, 2026. GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: Claude Fable 5 Jan 31, 2026, GPT-5.3 Codex Aug 31, 2025.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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