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AI Choice Engine

Model comparison

Claude Opus 5 vs Claude Opus 5.5

Two Anthropic tiers compared on the figures that decide which one a workload actually needs.

Catalog record checked September 26, 2026Individual provider fields may changeEvidence confidence: High — see receipts below

Anthropic

Claude Opus 5

Frontier

vs

Anthropic

Claude Opus 5.5

Frontier

AI model capability comparison
SpecificationClaude Opus 5Claude Opus 5.5
ProviderAnthropicAnthropic
TierFrontierFrontier
Context window1M1M
Max output128K128K
Input / 1M tokens$5Winner: $4
Output / 1M tokens$25Winner: $20
WeightsClosedClosed
ParametersNot disclosedUnverifiedNot disclosedUnverified
Reasoning levelsadaptiveadaptive
Modalitiestext, imagetext, image
API model idclaude-opus-5claude-opus-5-5
ReleasedJuly 24, 2026September 22, 2026
Artificial Analysis Intelligence Index [max] (2026-09-26)50.8Winner: 57.6
Humanity's Last Exam (2026-09-01)63.6Not verifiedUnverified
Humanity's Last Exam [max] (2026-09-26)Not verifiedUnverified61.4
Terminal-Bench 2.1 (2026-09-03)86.7Not verifiedUnverified
Terminal-Bench 4.0 [max] (2026-09-26)Not verifiedUnverified59.6
Terminal-Bench 4.0 [xhigh] (2026-09-22)Not verifiedUnverified66.4

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

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

Pricing tiers

Claude Opus 5: Standard $5/$25 per MTok; cache reads 10% of base input. Knowledge cutoff May 2026.

Claude Opus 5.5: $4/$20 per MTok, no long-context surcharge. Cache reads $0.20; 5-minute cache writes $5, 1-hour writes $8. Batch $2/$10; Fast mode $8/$40. Batches API allows 300K output with the output-300k-2026-03-24 beta header. Knowledge cutoff Jun 2026; retirement not before 2027-09-22.

FrontierRecord checked September 26, 2026

Claude Opus 5

Claude Opus 5 is Anthropic's July 2026 agentic-coding model, now 'Active (legacy)': Opus 5.5 is cheaper ($4/$20 vs $5/$25) and stronger.

Best for

  • Complex agentic coding
  • Enterprise work
  • Long-context analysis

Watch out

Superseded by Opus 5.5 — migrate new work, but note Opus 5.5's breaking changes (adaptive thinking always on; forced tool use errors). Output costs 5x input.

FrontierRecord checked September 26, 2026

Claude Opus 5.5

Claude Opus 5.5 is Anthropic's default model for agentic coding and knowledge work — Anthropic says it performs near Fable 5.1 on most work at about 40% lower running cost than Opus 5, and it leads the Artificial Analysis Intelligence Index v4.3.2.

Best for

  • Complex agentic coding
  • Enterprise knowledge work
  • Default frontier model

Watch out

Breaking changes from Opus 5: adaptive thinking cannot be disabled (effort runs low to max, default medium) and forced tool use returns an error. Verbose at max effort, so cap output on cost-sensitive routes.

When the cheaper one wins

Claude Opus 5.5 is cheaper on output at $20 per million tokens against $25 for Claude Opus 5 — about 1.3×. 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.

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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.
  • 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
  • 2 shared named benchmarks with differing scores — Measured on: Artificial Analysis Intelligence Index, Humanity's Last Exam.
  • Verified within the last 90 days — Newest catalog check was 2 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 Opus 5 · Claude Opus 5.5

Common questions

Claude Opus 5 vs Claude Opus 5.5

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

Is Claude Opus 5 or Claude Opus 5.5 cheaper for input?
Claude Opus 5.5 is cheaper at $4 per million input tokens, against $5 for Claude Opus 5 — roughly 1.3× 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 Opus 5 has tiered pricing: Standard $5/$25 per MTok; cache reads 10% of base input. Knowledge cutoff May 2026. Claude Opus 5.5 has tiered pricing: $4/$20 per MTok, no long-context surcharge. Cache reads $0.20; 5-minute cache writes $5, 1-hour writes $8. Batch $2/$10; Fast mode $8/$40. Batches API allows 300K output with the output-300k-2026-03-24 beta header. Knowledge cutoff Jun 2026; retirement not before 2027-09-22.
Is Claude Opus 5 or Claude Opus 5.5 cheaper for output?
Claude Opus 5.5 is cheaper at $20 per million output tokens, against $25 for Claude Opus 5 — roughly 1.3× 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 Opus 5 has tiered pricing: Standard $5/$25 per MTok; cache reads 10% of base input. Knowledge cutoff May 2026. Claude Opus 5.5 has tiered pricing: $4/$20 per MTok, no long-context surcharge. Cache reads $0.20; 5-minute cache writes $5, 1-hour writes $8. Batch $2/$10; Fast mode $8/$40. Batches API allows 300K output with the output-300k-2026-03-24 beta header. Knowledge cutoff Jun 2026; retirement not before 2027-09-22.
Which has the larger context window, Claude Opus 5 or Claude Opus 5.5?
Both accept about 1M tokens of context, so document length will not decide between them.
Do Claude Opus 5 and Claude Opus 5.5 support the same reasoning levels?
Yes — both accept the same effort settings: "adaptive". Higher effort costs more and takes longer, so start low and raise it only where output quality actually improves.
Should I use Claude Opus 5 or Claude Opus 5.5?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Opus 5 suits complex agentic coding; Claude Opus 5.5 suits complex agentic coding.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

  • Input price: Claude Opus 5.5 costs $4 per 1M tokens versus $5 for Claude Opus 5 — a 1.3x difference at the headline tier.
  • Measured capability: Claude Opus 5.5 leads Artificial Analysis Intelligence Index 57.6 to 50.8 (measured 2026-09-26).
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