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Model comparison

Claude Fable 5 vs GLM 5.3

Anthropic against Z.ai, compared on context, price, and attributed benchmark results.

Recorded profile verification October 2, 2026Individual provider fields may changeEvidence confidence: Medium — see receipts below

Anthropic

Claude Fable 5

Frontier

vs

Z.ai

GLM 5.3

Frontier · Open weights

AI model capability comparison
SpecificationClaude Fable 5GLM 5.3
ProviderAnthropicZ.ai
TierFrontierFrontier
Context window1M1M
Max output128KWinner: 131K
Input / 1M tokens$10Winner: $1.40
Output / 1M tokens$50Winner: $4.40
WeightsClosedOpen
ParametersNot verifiedUnverified753B total (MoE; active count not verified)
Reasoning levelslow, medium, high, xhigh, maxlow, high, max
Modalitiestext, imagetext
LicenseNot verifiedUnverifiedGLM-5.3 License (custom)
API model idclaude-fable-5glm-5.3
ReleasedJune 9, 2026August 14, 2026
Artificial Analysis Intelligence Index [max] · source date GLM 5.3: 2026-10-01Not verifiedUnverified45
Terminal-Bench 2.1 · source date GLM 5.3: 2026-08-14Not verifiedUnverified88.2
DeepSWE 1.1 · source date GLM 5.3: 2026-08-14Not verifiedUnverified66.9
Humanity's Last Exam · source date GLM 5.3: 2026-08-14Not verifiedUnverified62.5

Dates beside benchmark scores refer to the linked source’s publication or capture date unless that source explicitly states when it measured the result. A shared URL alone does not establish comparable runs; unverified setups are marked. Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

  • Source date2026-10-01
    Artificial Analysis (GLM-5.3 (max))

    Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.

    Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check the cited source and its date.

  • Source date2026-08-14
    Z.ai GLM-5.3 blog + HF model card (vendor, with tools, full set)

    Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise.

    Comparable with caveatSubset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.

  • Source date2026-08-14
    Z.ai GLM-5.3 blog + HF model card (vendor, mini-swe-agent family)

    Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task.

    Directly comparable

  • Source date2026-08-14
    Z.ai GLM-5.3 blog + HF model card eval results (vendor, Claude Code harness)

    Agentic terminal work: multi-step tasks executed in a sandboxed shell environment.

    Comparable with caveatNot comparable with Terminal-Bench 3.0 or 4.0 (different task sets) or v1; harness configuration (container, time limits) also shifts results.

Pricing tiers

Claude Fable 5: Standard $10/$50 per MTok with no long-context surcharge. Cache reads $1; 5-minute writes $12.50 and 1-hour writes $20. Batch $5/$25. US-only inference adds 10% where supported. Adaptive thinking is always on, default effort high. Reliable knowledge cutoff Jan 2026; retirement not sooner than June 9, 2027. Access was suspended June 12 and restored July 1, 2026.

GLM 5.3: Z.ai token API $1.40/$4.40 per MTok; cached input $0.26. Cache storage is listed as limited-time free, with no verified end date. Coding Plan points are separate: off-peak/weekend calls consume half the standard points. API docs advertise 1M context and specify a 131,072 output ceiling.

FrontierRecord checked October 1, 2026

Claude Fable 5

Claude Fable 5 is Anthropic's June 2026 long-running-agent model, now 'Active (legacy)' behind Fable 5.1 at the same $10/$50 price.

Best for

  • Long-running agents
  • Frontier reasoning
  • Enterprise work

Watch out

Superseded: Fable 5.1 has the same base input/output prices and lower cache-read pricing ($0.25 vs $1 per million tokens). Savings depend on eligible cached requests; evaluate the successor against your pinned workloads.

FrontierOpen weightsRecord checked October 2, 2026

GLM 5.3

Z.ai's text-only GLM flagship, with a 753B-total MoE checkpoint and always-enabled reasoning. Published benchmark figures identify particular harnesses and settings.

Best for

  • Coding Plan subscribers
  • Long-horizon coding
  • Chinese + English

Watch out

Custom licence: model-as-a-service operators whose licensee/affiliate aggregate revenue exceeds $10B in any consecutive 12 months require Z.AI security review before commercial use; the definition excludes embedded end-user features/harnesses and mere relays. Keep attribution/permission notices. Reasoning defaults to max; disabling it fails. Accounts that ever subscribed to Coding Plan, including expired subscriptions, currently have Model API access only through the Chat Completions-compatible protocol. Active parameter count and exact initial weight-publication day remain unverified.

When the cheaper one wins

GLM 5.3 is cheaper on output at $4.40 per million tokens against $50 for Claude Fable 5 — 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. On DeepSWE 1.1, GLM 5.3 is 69% Pass@1 at $3.99/task versus Claude Fable 5 at 69.9% / $13.41/task. This compares standard short-context token rates, not total cost per accepted task. Include input, cache, context tiers, schedules, retries and review in your pilot.

Run the model picker

Evidence confidence: Medium

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.
  • No directly aligned benchmark setup — No benchmark has matching cited sources, source dates, units, effort and recorded run details on both models.
  • Verified within the last 90 days — Older of the two catalog checks was 25 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.

Related comparisons

Diving deeper on one model? Claude Fable 5 · GLM 5.3

Common questions

Claude Fable 5 vs GLM 5.3

Answered from the verified figures on this page rather than general guidance.

Is Claude Fable 5 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 — roughly 7.1× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Fable 5: Standard $10/$50 per MTok with no long-context surcharge. Cache reads $1; 5-minute writes $12.50 and 1-hour writes $20. Batch $5/$25. US-only inference adds 10% where supported. Adaptive thinking is always on, default effort high. Reliable knowledge cutoff Jan 2026; retirement not sooner than June 9, 2027. Access was suspended June 12 and restored July 1, 2026. GLM 5.3: Z.ai token API $1.40/$4.40 per MTok; cached input $0.26. Cache storage is listed as limited-time free, with no verified end date. Coding Plan points are separate: off-peak/weekend calls consume half the standard points. API docs advertise 1M context and specify a 131,072 output ceiling.
Is Claude Fable 5 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 — roughly 11× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Fable 5: Standard $10/$50 per MTok with no long-context surcharge. Cache reads $1; 5-minute writes $12.50 and 1-hour writes $20. Batch $5/$25. US-only inference adds 10% where supported. Adaptive thinking is always on, default effort high. Reliable knowledge cutoff Jan 2026; retirement not sooner than June 9, 2027. Access was suspended June 12 and restored July 1, 2026. GLM 5.3: Z.ai token API $1.40/$4.40 per MTok; cached input $0.26. Cache storage is listed as limited-time free, with no verified end date. Coding Plan points are separate: off-peak/weekend calls consume half the standard points. API docs advertise 1M context and specify a 131,072 output ceiling.
Which has the larger context window, Claude Fable 5 or GLM 5.3?
Both accept about 1M tokens of context, so document length will not decide between them.
Do Claude Fable 5 and GLM 5.3 support the same reasoning levels?
Claude Fable 5 exposes low, medium, high, xhigh, max, while GLM 5.3 exposes low, high, max.
Should I use Claude Fable 5 or GLM 5.3?
Both are classified in our frontier tier; this editorial grouping does not imply equal capability. Claude Fable 5 is a candidate for long-running agents; GLM 5.3 is a candidate for coding plan subscribers. Compare accuracy, tool reliability, latency and cost on representative tasks.
Can I self-host Claude Fable 5 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 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 — a 7.1x difference at the headline tier.
  • Deployment: GLM 5.3 publishes weights you can self-host; the other is API-only.
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