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Head-to-head comparison

Claude Fable 5.1 vs GLM 5.3 Flash

Claude Fable 5.1 (Anthropic) and GLM 5.3 Flash (Z.ai) 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 9 September 2026

As of 9 September 2026, Claude Fable 5.1 holds the stronger ModelCap Index position (#3 vs #11); GLM 5.3 Flash is 200× cheaper per output token ($0.25/1M vs $50.00/1M); GLM 5.3 Flash offers the longer context window (1.3M vs 1M tokens); and GLM 5.3 Flash ships open weights.

Which should you choose?

Choose Claude Fable 5.1 if…

  • you want the stronger overall ModelCap Index position — #3 against #11 (87.7 vs 78.7 points).
  • LMArena Agent is your yardstick — 14.5% against 2.0%.
  • AA Intelligence Index is your yardstick — 53.4 against 41.9.
  • AA Terminal-Bench 2.1 is your yardstick — 91.4% against 84.3%.
  • AA Humanity's Last Exam is your yardstick — 59.1% against 39.9%.
  • you want the more recently listed model — Claude Fable 5.1 was listed 1 September 2026, GLM 5.3 Flash 26 August 2026.

Choose GLM 5.3 Flash if…

  • API cost matters — $0.25/1M output tokens against $50.00/1M, about 200× cheaper.
  • your workload is prompt-heavy — input tokens cost $0.075/1M against $10.00/1M.
  • you need the longer context window — 1.3M tokens against 1M.
  • you want to self-host: GLM 5.3 Flash ships open weights while Claude Fable 5.1 is api only.
  • you want provider choice — 26 listed API providers against 4.
  • Arena coding is your yardstick — 1534 against 1517.

Claude Fable 5.1 vs GLM 5.3 Flash: specs, pricing and context

Specification comparison of Claude Fable 5.1 and GLM 5.3 Flash
FieldClaude Fable 5.1AnthropicGLM 5.3 FlashZ.ai
ModelCap Index position#3#11
Index score87.778.7
EvidenceMeasuredMeasured
Input price / 1M tokens$10.00$0.075
Output price / 1M tokens$50.00$0.25
Context window1M tokens1.3M tokens
Max output tokens128K131K
API providers listed426
Weight accessAPI onlyOpen weights
Input modalitiesText, Image, FileText, Image, Video
First listed1 September 202626 August 2026
PublisherAnthropicZ.ai

Evidence: 5 public benchmark observations across 5 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 5.1 vs GLM 5.3 Flash

Public benchmark boards where Claude Fable 5.1 or GLM 5.3 Flash has a published result
BoardClaude Fable 5.1GLM 5.3 FlashLeads
Arena codingArena (LMArena)15171491–1542Max15341517–1551GLM 5.3 Flash
LMArena AgentLMArena14.5%12.6%–16.4%Max2.0%1.1%–2.9%Claude Fable 5.1
ARC-AGI-2ARC Prize Foundation90.0%Max—Only one result
AA Intelligence IndexArtificial Analysis53.4intelligence-index:v4.3:reasoning-unspecified41.9intelligence-index:v4.3:reasoning-unspecifiedClaude Fable 5.1
AA Terminal-Bench 2.1Artificial Analysis91.4%terminal-bench:2.1:terminus-2:e2b:pass-at-1:3-repeats:source-model="Claude Fable 5.1 (max with fallback)":reasoning=true84.3%terminal-bench:2.1:terminus-2:e2b:pass-at-1:3-repeats:source-model="GLM-5.3-Flash":reasoning=trueClaude Fable 5.1
AA Humanity's Last ExamArtificial Analysis59.1%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="Claude Fable 5.1 (max with fallback)":reasoning=true39.9%hle:may-2025:text-only-2158:no-tools:pass-at-1:source-model="GLM-5.3-Flash":reasoning=trueClaude Fable 5.1
Terminal-Bench 4.0Terminal-Bench (Laude Institute)57.9%54.1%–61.6%Claude Code · Max—Only one result

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 5.1 vs GLM 5.3 Flash: common questions

Is Claude Fable 5.1 better than GLM 5.3 Flash?

Claude Fable 5.1 ranks higher on the ModelCap Index as of 9 September 2026: #3 against #11. 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. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.

Is Claude Fable 5.1 cheaper than GLM 5.3 Flash?

GLM 5.3 Flash is cheaper on output tokens: $0.25/1M against $50.00/1M. Input tokens are $10.00/1M for Claude Fable 5.1 and $0.075/1M for GLM 5.3 Flash. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $45.00 for Claude Fable 5.1 versus $0.28 for GLM 5.3 Flash. GLM 5.3 Flash costs 99.4% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.

Which has the bigger context window, Claude Fable 5.1 or GLM 5.3 Flash?

GLM 5.3 Flash has the larger context window: 1.3M tokens against 1M.

Which is better for coding, Claude Fable 5.1 or GLM 5.3 Flash?

Arena coding: Claude Fable 5.1 1517, GLM 5.3 Flash 1534 — GLM 5.3 Flash leads. AA Terminal-Bench 2.1: Claude Fable 5.1 91.4%, GLM 5.3 Flash 84.3% — Claude Fable 5.1 leads.

Are Claude Fable 5.1 and GLM 5.3 Flash open-weight models?

Claude Fable 5.1: API only. GLM 5.3 Flash: Open weights. 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 5.1 and GLM 5.3 Flash?

ModelCap currently lists 4 API providers for Claude Fable 5.1 and 26 for GLM 5.3 Flash, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.

How current is this Claude Fable 5.1 vs GLM 5.3 Flash comparison?

Every figure comes from the sealed ModelCap dataset published 9 September 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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