ZMIME
Comparison · 2 models · Updated Oct 4, 2026

GLM-5.3-Flash vs Claude Fable 5.1

GLM-5.3-Flash comes out ahead, 80 to 66 on our weighted score, and it is the cheaper option too.

  1. Our pick

    Z.ai (Zhipu)

    GLM-5.3-Flash

    Released Aug 26, 2026

    80/100
    • ECI151.9
    • Price$0.15 / $0.50
    • Context1M
    Full specs Remove GLM-5.3-Flash

  2. Anthropic

    Claude Fable 5.1

    Released Sep 1, 2026

    66/100
    • ECI164.8
    • Price$10.00 / $50.00
    • Context1M
    Full specs Remove Claude Fable 5.1

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

GLM-5.3-Flash is our pick

GLM-5.3-Flash is the better all-round choice, scoring 80/100 against Claude Fable 5.1 (66). It leads on price and inputs & features. Claude Fable 5.1 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Fable 5.1Capabilities Index (ECI): Claude Fable 5.1 164.8 · GLM-5.3-Flash 151.9
  • Lowest priceGLM-5.3-FlashGLM-5.3-Flash $0.237 · Claude Fable 5.1 $20.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameGLM-5.3-Flash 1,000,000 · Claude Fable 5.1 1,000,000 tokens
  • Widest inputsGLM-5.3-FlashGLM-5.3-Flash: Text, Images, PDFs, Video · Claude Fable 5.1: Text, Images, PDFs
  • Self-hostingGLM-5.3-FlashPublishes downloadable weights
How the score is built
MeasureWeightGLM-5.3-FlashClaude Fable 5.1
CapabilityCapabilities Index (ECI)50%8197
Price25%790
Inputs & features15%9080
Context window10%6060
Overall100%80/10066/100
02 — Side by side

Every spec in one table

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

GLM-5.3-Flash vs Claude Fable 5.1 specifications side by side
SpecificationGLM-5.3-FlashZ.ai (Zhipu)Claude Fable 5.1Anthropic
Capability
Capabilities Index (ECI)151.9164.8 (best)
ECI rank#42 of 148#4 of 148 (best)
GPQA DiamondGraduate-level science questions90.2%—
FrontierMath Tiers 1–3Research-level mathematics55.8%90.2% (best)
OTIS Mock AIME 2024–2025Competition mathematics93.9%100% (best)
SimpleQA VerifiedShort factual questions—70.8%
Price per million tokens
Input$0.15 (best)$10.00
Output$0.50 (best)$50.00
Cached input$0.03 (best)$0.25
Blended (3:1)$0.237 (best)$20.00
Long-context rateSame rateSame rate
Price sourceOfficial Z.AI APIOfficial Anthropic API
Limits
Context window1,000,000 tokens1,000,000 tokens
Max output131,072 tokens (best)128,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoYesNo
ReasoningYeslow · high · maxYeslow · medium · high · xhigh · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsOpenProprietary
API model IDglm-5.3-flashclaude-fable-5-1
API providers65 (best)29
ReleasedAug 26, 2026Sep 1, 2026
Knowledge cutoff—Jun 2026
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.

  • GLM-5.3-Flash$2.50
  • Claude Fable 5.1$200.00
04 — Questions

Which should you choose?

Which is better: GLM-5.3-Flash or Claude Fable 5.1?

GLM-5.3-Flash is the better all-round choice, scoring 80/100 against Claude Fable 5.1 (66). It leads on price and inputs & features. Claude Fable 5.1 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, GLM-5.3-Flash or Claude Fable 5.1?

GLM-5.3-Flash is cheaper at $0.15 input / $0.50 output per million tokens (official Z.AI API price). Claude Fable 5.1 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 $0.237 per million tokens for GLM-5.3-Flash versus $20.00 for Claude Fable 5.1 (84× as much).

Which scores higher on benchmarks?

Claude Fable 5.1 scores higher on the Capabilities Index (ECI): Claude Fable 5.1 164.8 (#4 of 148) and GLM-5.3-Flash 151.9 (#42 of 148). Their confidence ranges do not overlap (161.8–169.1 vs 149.4–154.3), so the gap is a real one. On individual benchmarks: FrontierMath Tiers 1–3 — Claude Fable 5.1 90.2%, GLM-5.3-Flash 55.8%; OTIS Mock AIME 2024–2025 — Claude Fable 5.1 100%, GLM-5.3-Flash 93.9%.

Which is better for coding?

There are no published SWE-bench Verified results for GLM-5.3-Flash and Claude Fable 5.1 yet, so there is no like-for-like coding score. On overall capability, Claude Fable 5.1 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?

GLM-5.3-Flash and Claude Fable 5.1 share the same 1,000,000-token context window. Maximum output per response: GLM-5.3-Flash up to 131,072, Claude Fable 5.1 up to 128,000 tokens.

Which can read images, PDFs, audio or video?

GLM-5.3-Flash accepts text, images, PDFs and video; Claude Fable 5.1 accepts text, images and PDFs. GLM-5.3-Flash handles the widest range of inputs.

Are any of these open source?

GLM-5.3-Flash publishes its weights and can be self-hosted; Claude Fable 5.1 is proprietary.

Which is newer?

Claude Fable 5.1 is the newest, released Sep 1, 2026. GLM-5.3-Flash came out Aug 26, 2026. Knowledge cutoff: Claude Fable 5.1 Jun 2026.

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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