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Model comparison

Claude Sonnet 5 vs GLM 5.3 Flash

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 Sonnet 5

Balanced

vs

Z.ai

GLM 5.3 Flash

Balanced · Open weights

AI model capability comparison
SpecificationClaude Sonnet 5GLM 5.3 Flash
ProviderAnthropicZ.ai
TierBalancedBalanced
Context window1MWinner: 1.05M
Max output128KWinner: 131K
Input / 1M tokens$2Winner: $0.15
Output / 1M tokens$10Winner: $0.50
WeightsClosedOpen
ParametersNot disclosedUnverified320B total / 18B active (MoE)
Reasoning levelsadaptiveNot verifiedUnverified
Modalitiestext, imagetext, image, video
LicenseNot disclosedUnverifiedMIT
API model idclaude-sonnet-5Not publishedUnverified
ReleasedJune 30, 2026August 26, 2026
Artificial Analysis Intelligence Index (2026-08-14)55Winner: 57
Terminal-Bench 2.1 (2026-06-30)80.4Winner: 84.3
Humanity's Last Exam (2026-06-30)Winner: 57.455.3
SWE-bench Verified (2026-09-01)79.6Winner: 92
LiveBench (2026-09-05)76Not verifiedUnverified
DeepSWE 1.1 (2026-08)Not verifiedUnverified63.4

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: LiveBench official leaderboard (benchmark-owned), xhigh effortContamination-resistant general capability across reasoning, coding, math, data analysis, and language, with monthly question refreshes. Comparability: comparable with caveat — Rolling question set: observations months apart measure different question mixes. Record the measurement date and compare within ~1 month windows.
  • 2026-09-01: vals.ai SWE-bench Verified leaderboard (independent, mini-swe-agent bash-only); not published by Z.aiReal 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.
  • 2026-08-26: 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).
  • 2026-08: Z.ai GLM-5.3-Flash blog (vendor, mini-swe-agent, 400K context)Agentic software engineering: pass@1 on real repo tasks with reported cost per completed task. Comparability: directly comparable
  • 2026-08: GLM-5.3-Flash 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.
  • 2026-06-30: Anthropic announcement (vendor, with 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.
  • 2026-06-30: Anthropic announcement table (vendor, default effort; via Vellum transcription)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.

Pricing tiers: Claude Sonnet 5: Standard $2/$10 per MTok; cache reads 10% of base input. Knowledge cutoff Jan 2026. · GLM 5.3 Flash: $0.15/$0.50 per MTok is the standard first-party and third-party rate (Z.ai docs; GMI, Novita, Together). A 50% promo tier runs $0.075/$0.25 — confirm which rate your account quotes.

BalancedRecord checked September 3, 2026

Claude Sonnet 5

Claude Sonnet 5 is Anthropic's best speed/intelligence balance for high-volume agentic work at $2/$10.

Best for

  • Everyday generation
  • High-volume agents
  • Cost-sensitive work

Watch out

A step below Opus 5 on the hardest tasks; pick Opus when quality is paramount.

BalancedOpen weightsRecord checked September 3, 2026

GLM 5.3 Flash

GLM 5.3 Flash is Z.ai's natively multimodal open-weight workhorse — 1M context, hybrid sparse/linear attention, near-flagship Intelligence Index at a fraction of the cost.

Best for

  • Cost-efficient long-context
  • Multimodal input
  • Coding agents

Watch out

Self-hosting needs ~186GB GPU memory at 4-bit (multi-GPU). Third-party hosts charge more than Z.ai's own API.

When the cheaper one wins

GLM 5.3 Flash is cheaper on output at $0.50 per million tokens against $10 for Claude Sonnet 5 — about 20×. 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 picker

Evidence 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.
  • 3/5 core specs verified on both sides — Not published for at least one side: parameter count, reasoning levels.
  • 4 shared named benchmarks with differing scores — Measured on: Artificial Analysis Intelligence Index, Terminal-Bench 2.1, Humanity's Last Exam, SWE-bench Verified.
  • 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.

Related comparisons

Diving deeper on one model? Claude Sonnet 5 · GLM 5.3 Flash

Common questions

Claude Sonnet 5 vs GLM 5.3 Flash

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

Is Claude Sonnet 5 or GLM 5.3 Flash cheaper for input?

GLM 5.3 Flash is cheaper at $0.15 per million input tokens, against $2 for Claude Sonnet 5 — roughly 13× 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 Sonnet 5 has tiered pricing: Standard $2/$10 per MTok; cache reads 10% of base input. Knowledge cutoff Jan 2026. GLM 5.3 Flash has tiered pricing: $0.15/$0.50 per MTok is the standard first-party and third-party rate (Z.ai docs; GMI, Novita, Together). A 50% promo tier runs $0.075/$0.25 — confirm which rate your account quotes.

Is Claude Sonnet 5 or GLM 5.3 Flash cheaper for output?

GLM 5.3 Flash is cheaper at $0.50 per million output tokens, against $10 for Claude Sonnet 5 — roughly 20× 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 Sonnet 5 has tiered pricing: Standard $2/$10 per MTok; cache reads 10% of base input. Knowledge cutoff Jan 2026. GLM 5.3 Flash has tiered pricing: $0.15/$0.50 per MTok is the standard first-party and third-party rate (Z.ai docs; GMI, Novita, Together). A 50% promo tier runs $0.075/$0.25 — confirm which rate your account quotes.

Which has the larger context window, Claude Sonnet 5 or GLM 5.3 Flash?

GLM 5.3 Flash accepts 1.05M tokens against 1M for Claude Sonnet 5. This only matters if you routinely send very long documents or large codebases.

Should I use Claude Sonnet 5 or GLM 5.3 Flash?

Both sit in the balanced tier, so the choice usually comes down to price and context rather than capability. Claude Sonnet 5 suits everyday generation; GLM 5.3 Flash suits cost-efficient long-context.

Can I self-host Claude Sonnet 5 or GLM 5.3 Flash?

GLM 5.3 Flash publishes open weights, but self-hosting and third-party provider access depend on the licence, hardware, serving support, and availability. Claude Sonnet 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 Flash costs $0.15 per 1M tokens versus $2 for Claude Sonnet 5 — a 13.3x difference at the headline tier.
  • Context: GLM 5.3 Flash takes 1.05M against 1M for Claude Sonnet 5 — only decisive if your prompts approach the smaller window.
  • Measured capability: GLM 5.3 Flash leads Artificial Analysis Intelligence Index 57 to 55 (measured 2026-08-14).
  • Deployment: GLM 5.3 Flash publishes weights you can self-host; the other is API-only.
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