ZMIME
Comparison · 3 models · Updated Oct 4, 2026

Claude Opus 4.5 vs GLM-5.1 vs GPT-5.1

Too close to call on our weighted score (GPT-5.1 60, GLM-5.1 57, Claude Opus 4.5 55). The right pick depends on what you value most.

  1. Anthropic

    Claude Opus 4.5

    Released Nov 24, 2025

    55/100
    • ECI150.1
    • Price$5.00 / $25.00
    • Context200K
    Full specs Remove Claude Opus 4.5

  2. Z.ai (Zhipu)

    GLM-5.1

    Released Apr 7, 2026

    57/100
    • ECI149.9
    • Price$1.40 / $4.40
    • Context200K
    Full specs Remove GLM-5.1

  3. OpenAI

    GPT-5.1

    Released Nov 13, 2025

    60/100
    • ECI149.7
    • Price$1.25 / $10.00
    • Context400K
    Full specs Remove GPT-5.1
01 — Verdict

Too close to call

It is close. Our weighted score puts them within 2 points (GPT-5.1 60/100, GLM-5.1 57/100, Claude Opus 4.5 55/100), so choose by what matters most for your work: Claude Opus 4.5 for raw capability, GLM-5.1 on price and GPT-5.1 for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityClaude Opus 4.5Capabilities Index (ECI): Claude Opus 4.5 150.1 · GLM-5.1 149.9 · GPT-5.1 149.7
  • Lowest priceGLM-5.1GLM-5.1 $2.15 · GPT-5.1 $3.44 · Claude Opus 4.5 $10.00 per 1M tokens (3:1 blend)
  • Longest contextGPT-5.1GPT-5.1 400,000 · Claude Opus 4.5 200,000 · GLM-5.1 200,000 tokens
  • Widest inputsClaude Opus 4.5Claude Opus 4.5: Text, Images, PDFs · GLM-5.1: Text · GPT-5.1: Text, Images
  • Self-hostingGLM-5.1Publishes downloadable weights
How the score is built
MeasureWeightClaude Opus 4.5GLM-5.1GPT-5.1
CapabilityCapabilities Index (ECI)50%787878
Price25%23424
Inputs & features15%804570
Context window10%323244
Overall100%55/10057/10060/100
02 — Side by side

Every spec in one table

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

Claude Opus 4.5 vs GLM-5.1 vs GPT-5.1 specifications side by side
SpecificationClaude Opus 4.5AnthropicGLM-5.1Z.ai (Zhipu)GPT-5.1OpenAI
Capability
Capabilities Index (ECI)150.1 (best)149.9149.7
ECI rank#48 of 148 (best)#51 of 148#52 of 148
GPQA DiamondGraduate-level science questions86.1%89.9% (best)87.6%
FrontierMath Tiers 1–3Research-level mathematics34.4%36.8% (best)—
OTIS Mock AIME 2024–2025Competition mathematics86.1%93.3% (best)88.6%
SWE-bench VerifiedFixing real GitHub issues76.7% (best)74.2%68.0%
SimpleQA VerifiedShort factual questions45.7%34.0%48.0% (best)
Price per million tokens
Input$5.00$1.40$1.25 (best)
Output$25.00$4.40 (best)$10.00
Cached input$0.50$0.26$0.125 (best)
Blended (3:1)$10.00$2.15 (best)$3.44
Long-context rateSame rateSame rateSame rate
Price sourceOfficial Anthropic APIOfficial Z.AI APIOfficial OpenAI API
Limits
Context window200,000 tokens200,000 tokens400,000 tokens (best)
Max output64,000 tokens131,072 tokens (best)128,000 tokens
Inputs and features
TextYesYesYes
ImagesYesNoYes
PDFsYesNoNo
AudioNoNoNo
VideoNoNoNo
ReasoningYeslow · medium · highYesYeslow · medium · high
Tool callingYesYesYes
Structured outputYesYesYes
Availability
WeightsProprietaryOpenProprietary
API model IDclaude-opus-4-5glm-5.1gpt-5.1
API providers2840 (best)21
ReleasedNov 24, 2025Apr 7, 2026Nov 13, 2025
Knowledge cutoffMay 2025—Sep 30, 2024
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 4.5$100.00
  • GLM-5.1$22.80
  • GPT-5.1$32.50
04 — Questions

Which should you choose?

Which is better: Claude Opus 4.5, GLM-5.1 or GPT-5.1?

It is close. Our weighted score puts them within 2 points (GPT-5.1 60/100, GLM-5.1 57/100, Claude Opus 4.5 55/100), so choose by what matters most for your work: Claude Opus 4.5 for raw capability, GLM-5.1 on price and GPT-5.1 for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Claude Opus 4.5, GLM-5.1 or GPT-5.1?

GLM-5.1 is cheaper at $1.40 input / $4.40 output per million tokens (official Z.AI API price). GPT-5.1 costs $1.25 input / $10.00 output per million tokens (official OpenAI API price); Claude Opus 4.5 costs $5.00 input / $25.00 output per million tokens (official Anthropic API price). At a typical mix of three input tokens to one output token, that is $2.15 per million tokens for GLM-5.1 versus $3.44 for GPT-5.1 (1.6× as much) and $10.00 for Claude Opus 4.5 (4.7× as much).

Which scores higher on benchmarks?

Claude Opus 4.5 scores higher on the Capabilities Index (ECI): Claude Opus 4.5 150.1 (#48 of 148), GLM-5.1 149.9 (#51 of 148) and GPT-5.1 149.7 (#52 of 148). The confidence ranges of the top two overlap (147.9–153.0 vs 148.0–151.6), so treat the gap as small. On individual benchmarks: GPQA Diamond — GLM-5.1 89.9%, GPT-5.1 87.6%, Claude Opus 4.5 86.1%; OTIS Mock AIME 2024–2025 — GLM-5.1 93.3%, GPT-5.1 88.6%, Claude Opus 4.5 86.1%; SWE-bench Verified — Claude Opus 4.5 76.7%, GLM-5.1 74.2%, GPT-5.1 68.0%; SimpleQA Verified — GPT-5.1 48.0%, Claude Opus 4.5 45.7%, GLM-5.1 34.0%.

Which is better for coding?

Claude Opus 4.5 resolves more real GitHub issues on SWE-bench Verified: Claude Opus 4.5 76.7%, GLM-5.1 74.2% and GPT-5.1 68.0%. All three support tool calling for agent workflows.

Which has the bigger context window?

GPT-5.1 has the largest context window at 400,000 tokens, against 200,000 for Claude Opus 4.5 and 200,000 for GLM-5.1. Maximum output per response: Claude Opus 4.5 up to 64,000, GLM-5.1 up to 131,072, GPT-5.1 up to 128,000 tokens.

Which can read images, PDFs, audio or video?

Claude Opus 4.5 accepts text, images and PDFs; GLM-5.1 accepts text; GPT-5.1 accepts text and images. Claude Opus 4.5 handles the widest range of inputs.

Are any of these open source?

GLM-5.1 publishes its weights and can be self-hosted; Claude Opus 4.5 and GPT-5.1 is proprietary.

Which is newer?

GLM-5.1 is the newest, released Apr 7, 2026. Claude Opus 4.5 came out Nov 24, 2025; GPT-5.1 came out Nov 13, 2025. Knowledge cutoff: Claude Opus 4.5 May 2025, GPT-5.1 Sep 30, 2024.

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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