Model comparison
Claude Fable 5.1 vs GLM 5.3
Anthropic against Z.ai, compared on context, price, and verified benchmark results.
Catalog record checked September 3, 2026Individual provider fields may changeEvidence confidence: High — see receipts below
Anthropic
Claude Fable 5.1
Frontier
Z.ai
GLM 5.3
Frontier · Open weights
| Specification | Claude Fable 5.1 | GLM 5.3 |
|---|---|---|
| Provider | Anthropic | Z.ai |
| Tier | Frontier | Frontier |
| Context window | 1M | 1M |
| Max output | 128K | 128K |
| Input / 1M tokens | $10 | Winner: $1.40 |
| Output / 1M tokens | $50 | Winner: $4.40 |
| Weights | Closed | Open |
| Parameters | Not disclosedUnverified | 753B total (MoE; active count unpublished) |
| Reasoning levels | adaptive | low, high, max |
| Modalities | text, image | text |
| License | Not disclosedUnverified | glm-5.3 (custom) |
| API model id | claude-fable-5-1 | glm-5.3 |
| Released | September 1, 2026 | August 14, 2026 |
| Artificial Analysis Intelligence Index (2026-08-14) | 66 | Not verifiedUnverified |
| Artificial Analysis Intelligence Index [max] (2026-08-14) | Not verifiedUnverified | 60 |
| Humanity's Last Exam (2026-09-01) | Winner: 65 | 62.5 |
| Terminal-Bench 2.1 (2026-09-05) | Winner: 91.4 | 88.2 |
| DeepSWE 1.1 (2026-09-03) | Winner: 67.4 | 66.9 |
| SWE-bench Verified (2026-09-01) | Not verifiedUnverified | 95.4 |
Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Bold indicates the better figure where one is objectively better. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.
Benchmark receipts
- 2026-09-05: Artificial Analysis Terminal-Bench v2.1 (independent, Terminus 2, max effort — current AA leader)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-09-03: OpenAI GPT-6 Astra launch chart (independent cross-vendor; Fable 5.1 not on the official Datacurve leaderboard)Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task. Comparability: directly comparable
- 2026-09-01: vals.ai SWE-bench Verified leaderboard (independent, mini-swe-agent bash-only); Zhipu docs list 77.8 inherited from GLM-5 — attribution contested, both notedReal GitHub issue resolution: does the model's patch pass the hidden tests. Comparability: comparable with caveat — Post-audit vendor claims and pre-audit scores sit on different task trust levels; scaffolding (agent harness, compute budget) also dominates results. Never aggregate across scaffolds.
- 2026-09-01: Anthropic announcement comparison table (vendor, with tools; 60.9 no tools)Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise. Comparability: comparable with caveat — Subset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.
- 2026-08-14: Z.ai GLM-5.3 blog + HF model card (vendor, with tools, full set)Agentic terminal work: multi-step tasks executed in a sandboxed shell environment. Comparability: comparable with caveat — Scores across Terminal-Bench major versions (v1 vs v2) are NOT comparable; harness configuration (container, time limits) also shifts results.
- 2026-08-14: Artificial AnalysisComposite index blending reasoning, knowledge, and coding evals into one 0–100 score. Comparability: directly comparable — AA occasionally rebaselines the index scale between snapshots — a score captured on one date is only comparable to same-snapshot scores (check measuredAt).
Pricing tiers: Claude Fable 5.1: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day. · GLM 5.3: Token API listed at $1.40/$4.40 per MTok from 2026-08-18 (cached input $0.26); Coding Plan access on a points quota. 1M context, 128K max output per official docs; thinking always on. 753B total MoE per the Hugging Face card (active count unpublished).
Claude Fable 5.1
Claude Fable 5.1 is Anthropic's September 2026 flagship refresh, debuting at the top of LiveBench and the Artificial Analysis Intelligence Index.
Best for
- Frontier agents
- Hardest reasoning work
- Fable 5 workloads at the same price
Watch out
Early-life model: leaderboard position is from launch-week boards; recheck before committing spend.
GLM 5.3
GLM 5.3 is Zhipu's flagship (~753B MoE), near the top of the leaderboards, and the current GLM Coding Plan default.
Best for
- Coding Plan subscribers
- Long-horizon coding
- Chinese + English
Watch out
Open weights dropped 2026-08-28 under Z.ai's custom glm-5.3 licence (not a standard open-source licence — review before commercial use; secondary coverage says >$10B-revenue providers need a security review). 5.2/5.1 Coding Plan requests route to 5.3.
When the cheaper one wins
GLM 5.3 is cheaper on output at $4.40 per million tokens against $50 for Claude Fable 5.1 — about 11×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. These are standard-tier API rates, excluding batch and cache discounts.
Run the model pickerEvidence confidence: High
How strong and complete the evidence behind this comparison is — not a prediction of which model is better.
- Pricing verified on both sides — Input and output rates are verified for both models.
- 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
- 4 shared named benchmarks with differing scores — Measured on: Artificial Analysis Intelligence Index, Humanity's Last Exam, Terminal-Bench 2.1, DeepSWE 1.1.
- Verified within the last 90 days — Newest catalog check was 8 days ago.
- Both models carry source citations — Each side has at least two catalog sources on record.
Source receipts
Each catalog figure was checked against the provider or an independent second source on the date shown.
- Claude Fable 5.1: Anthropic pricing — Fable 5.1/Mythos 5.1 $10/$50 (accessed 2026-09-03)
- Claude Fable 5.1: Anthropic models overview — Fable 5.1 (1M context, 128K output) (accessed 2026-09-03)
- Claude Fable 5.1: Artificial Analysis — Fable 5.1 Intelligence Index 66 #1 (accessed 2026-09-01)
- GLM 5.3: Z.ai GLM-5.3 announcement (accessed 2026-08-29)
- GLM 5.3: Hugging Face — zai-org/GLM-5.3 (weights, 2026-08-28) (accessed 2026-08-30)
Related comparisons
- GLM 5.3 vs Grok 4.5
- Claude Fable 5.1 vs Claude Haiku 4.5
- Claude Fable 5.1 vs Claude Mythos 5.1
- Claude Fable 5.1 vs Claude Opus 5
- Claude Fable 5.1 vs Claude Sonnet 5
- Claude Fable 5.1 vs DeepSeek V4 Pro
Diving deeper on one model? Claude Fable 5.1 · GLM 5.3
Common questions
Claude Fable 5.1 vs GLM 5.3
Answered from the verified figures on this page rather than general guidance.
Is Claude Fable 5.1 or GLM 5.3 cheaper for input?
GLM 5.3 is cheaper at $1.40 per million input tokens, against $10 for Claude Fable 5.1 — roughly 7.1× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Fable 5.1 has tiered pricing: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day. GLM 5.3 has tiered pricing: Token API listed at $1.40/$4.40 per MTok from 2026-08-18 (cached input $0.26); Coding Plan access on a points quota. 1M context, 128K max output per official docs; thinking always on. 753B total MoE per the Hugging Face card (active count unpublished).
Is Claude Fable 5.1 or GLM 5.3 cheaper for output?
GLM 5.3 is cheaper at $4.40 per million output tokens, against $50 for Claude Fable 5.1 — roughly 11× the price. Output tokens usually dominate a real bill, so weigh the output rate more heavily than the input rate. These are base rates; Claude Fable 5.1 has tiered pricing: Priced with Fable 5 at $10/$50 per MTok; cache reads cut 75% to $0.25/MTok. Adaptive thinking always on (default effort high); knowledge cutoff Jun 2026. Sibling Mythos 5.1 launched the same day. GLM 5.3 has tiered pricing: Token API listed at $1.40/$4.40 per MTok from 2026-08-18 (cached input $0.26); Coding Plan access on a points quota. 1M context, 128K max output per official docs; thinking always on. 753B total MoE per the Hugging Face card (active count unpublished).
Which has the larger context window, Claude Fable 5.1 or GLM 5.3?
Both accept about 1M tokens of context, so document length will not decide between them.
Do Claude Fable 5.1 and GLM 5.3 support the same reasoning levels?
Claude Fable 5.1 exposes adaptive, while GLM 5.3 exposes low, high, max.
Should I use Claude Fable 5.1 or GLM 5.3?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Fable 5.1 suits frontier agents; GLM 5.3 suits coding plan subscribers.
Can I self-host Claude Fable 5.1 or GLM 5.3?
GLM 5.3 publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. Claude Fable 5.1 is a closed model whose supported access paths are controlled by its provider.
Next step
Choosing between them
The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.
- Input price: GLM 5.3 costs $1.40 per 1M tokens versus $10 for Claude Fable 5.1 — a 7.1x difference at the headline tier.
- Measured capability: Claude Fable 5.1 leads Artificial Analysis Intelligence Index 66 to 60 (measured 2026-08-14).
- Deployment: GLM 5.3 publishes weights you can self-host; the other is API-only.
Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.