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GPT-5.5 vs Claude Opus 4.8

RANKED BY EPOCH CAPABILITIES INDEX (ECI) #8 VS #10 CHECKED 28 SEPT 2026

Side by side

Verdict

GPT-5.5 ranks #8 of 20 on Epoch Capabilities Index (ECI) (159.25); Claude Opus 4.8 ranks #10 (158.30).

Rank 08 of 20 · leads

GPT-5.5

Epoch Capabilities Index (ECI)

159.25

MakerOpenAI

Date2026

Verified—

Evidence

Epoch AI epoch_capabilities_index/eci_scores.csv (LLM Benchmark Data ZIP, fetched 2026-09-28). ECI 159.25, accessibility API access, release date 2026-04-23. Pricing/context via Statlyte (statlyte.com/models/openai/gpt-5-5), MIT licensed.

Rank 10 of 20

Claude Opus 4.8

Epoch Capabilities Index (ECI)

158.30

MakerAnthropic

Date2026

Verified—

Evidence

Epoch AI epoch_capabilities_index/eci_scores.csv (LLM Benchmark Data ZIP, fetched 2026-09-28). ECI 158.3, accessibility API access, release date 2026-05-28. Pricing/context via Statlyte (statlyte.com/models/anthropic/claude-opus-4-8), MIT licensed.

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More GPT-5.5 matchups

Source Ranking: Epoch AI, AI Benchmarking Hub, Epoch Capabilities Index (epoch.ai/data/benchmark_data.zip, CC BY 4.0). Per-entry pricing/context:… Last checked 28 Sept 2026

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