ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Claude Opus 5.5 vs GLM-5.3-Flash

GLM-5.3-Flash comes out ahead, 80 to 70 on our weighted score, and it is the cheaper option too.

  1. Anthropic

    Claude Opus 5.5

    Released Sep 22, 2026

    70/100
    • ECI167.4
    • Price$4.00 / $20.00
    • Context1M
    Full specs Remove Claude Opus 5.5
  2. 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

  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 Opus 5.5 (70). It leads on price and inputs & features. Claude Opus 5.5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Opus 5.5Capabilities Index (ECI): Claude Opus 5.5 167.4 · GLM-5.3-Flash 151.9
  • Lowest priceGLM-5.3-FlashGLM-5.3-Flash $0.237 · Claude Opus 5.5 $8.00 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameClaude Opus 5.5 1,000,000 · GLM-5.3-Flash 1,000,000 tokens
  • Widest inputsGLM-5.3-FlashClaude Opus 5.5: Text, Images, PDFs · GLM-5.3-Flash: Text, Images, PDFs, Video
  • Self-hostingGLM-5.3-FlashPublishes downloadable weights
How the score is built
MeasureWeightClaude Opus 5.5GLM-5.3-Flash
CapabilityCapabilities Index (ECI)50%10081
Price25%779
Inputs & features15%8090
Context window10%6060
Overall100%70/10080/100
02 — Side by side

Every spec in one table

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

Claude Opus 5.5 vs GLM-5.3-Flash specifications side by side
SpecificationClaude Opus 5.5AnthropicGLM-5.3-FlashZ.ai (Zhipu)
Capability
Capabilities Index (ECI)167.4 (best)151.9
ECI rank#1 of 148 (best)#42 of 148
GPQA DiamondGraduate-level science questions90.6% (best)90.2%
FrontierMath Tiers 1–3Research-level mathematics91.2% (best)55.8%
OTIS Mock AIME 2024–2025Competition mathematics100% (best)93.9%
SimpleQA VerifiedShort factual questions72.2%—
Price per million tokens
Input$4.00$0.15 (best)
Output$20.00$0.50 (best)
Cached input$0.20$0.03 (best)
Blended (3:1)$8.00$0.237 (best)
Long-context rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial Z.AI API
Limits
Context window1,000,000 tokens1,000,000 tokens
Max output128,000 tokens131,072 tokens (best)
Inputs and features
TextYesYes
ImagesYesYes
PDFsYesYes
AudioNoNo
VideoNoYes
ReasoningYeslow · medium · high · xhigh · maxYeslow · high · max
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryOpen
API model IDclaude-opus-5-5glm-5.3-flash
API providers2865 (best)
ReleasedSep 22, 2026Aug 26, 2026
Knowledge cutoffJun 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.

  • Claude Opus 5.5$80.00
  • GLM-5.3-Flash$2.50
04 — Questions

Which should you choose?

Which is better: Claude Opus 5.5 or GLM-5.3-Flash?

GLM-5.3-Flash is the better all-round choice, scoring 80/100 against Claude Opus 5.5 (70). It leads on price and inputs & features. Claude Opus 5.5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Opus 5.5 or GLM-5.3-Flash?

GLM-5.3-Flash is cheaper at $0.15 input / $0.50 output per million tokens (official Z.AI API price). Claude Opus 5.5 costs $4.00 input / $20.00 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 $8.00 for Claude Opus 5.5 (34× as much).

Which scores higher on benchmarks?

Claude Opus 5.5 scores higher on the Capabilities Index (ECI): Claude Opus 5.5 167.4 (#1 of 148) and GLM-5.3-Flash 151.9 (#42 of 148). Their confidence ranges do not overlap (164.0–172.0 vs 149.4–154.3), so the gap is a real one. On individual benchmarks: GPQA Diamond — Claude Opus 5.5 90.6%, GLM-5.3-Flash 90.2%; FrontierMath Tiers 1–3 — Claude Opus 5.5 91.2%, GLM-5.3-Flash 55.8%; OTIS Mock AIME 2024–2025 — Claude Opus 5.5 100%, GLM-5.3-Flash 93.9%.

Which is better for coding?

There are no published SWE-bench Verified results for Claude Opus 5.5 and GLM-5.3-Flash yet, so there is no like-for-like coding score. On overall capability, Claude Opus 5.5 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?

Claude Opus 5.5 and GLM-5.3-Flash share the same 1,000,000-token context window. Maximum output per response: Claude Opus 5.5 up to 128,000, GLM-5.3-Flash up to 131,072 tokens.

Which can read images, PDFs, audio or video?

Claude Opus 5.5 accepts text, images and PDFs; GLM-5.3-Flash accepts text, images, PDFs and video. 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 Opus 5.5 is proprietary.

Which is newer?

Claude Opus 5.5 is the newest, released Sep 22, 2026. GLM-5.3-Flash came out Aug 26, 2026. Knowledge cutoff: Claude Opus 5.5 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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