Skip to main content
AI Choice Engine

Model comparison

Claude Opus 5.5 vs GPT-5.6 Sol

Anthropic against OpenAI, compared on context, price, and verified benchmark results.

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

Anthropic

Claude Opus 5.5

Frontier

vs

OpenAI

GPT-5.6 Sol

Frontier

AI model capability comparison
SpecificationClaude Opus 5.5GPT-5.6 Sol
ProviderAnthropicOpenAI
TierFrontierFrontier
Context window1MWinner: 1.05M
Max output128K128K
Input / 1M tokens$4$4
Output / 1M tokens$20$20
WeightsClosedClosed
ParametersNot disclosedUnverifiedprevious-generation reasoning + coding model
Reasoning levelsadaptivenone, low, medium, high, xhigh, max
Modalitiestext, imagetext, image
API model idclaude-opus-5-5gpt-5.6-sol
ReleasedSeptember 22, 2026July 9, 2026
Artificial Analysis Intelligence Index [max] (2026-09-26)Winner: 57.647
Humanity's Last Exam [max] (2026-09-26)61.4Not verifiedUnverified
Terminal-Bench 4.0 [max] (2026-09-26)59.6Not verifiedUnverified
Terminal-Bench 4.0 [xhigh] (2026-09-22)66.4Not verifiedUnverified
Terminal-Bench 2.1 (2026-07-09)Not verifiedUnverified88.8
GPQA Diamond (2026-07-09)Not verifiedUnverified94.6

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.

  • 2026-09-26
    Artificial Analysis Terminal-Bench 4.0 (independent AA run, part of Intelligence Index v4.3.2)

    Agentic terminal work: long multi-step tasks executed in a sandboxed shell environment.

    Comparable with caveatNOT comparable with Terminal-Bench 2.x or 3.0 — 4.0 uses a new, non-overlapping task set. Within 4.0, scores from different harnesses (tbench.ai agent entries vs Artificial Analysis runs) are not interchangeable.

  • 2026-09-26
    Artificial Analysis Humanity's Last Exam (independent, 2,158 text-only questions)

    Frontier-knowledge ceiling: extremely hard multi-domain questions written to be near-impossible without deep expertise.

    Comparable with caveatSubset/tool configurations (text-only vs with-tools) differ between vendors and materially change scores; must match configuration to compare.

  • 2026-09-26
    Artificial Analysis

    Composite index blending reasoning, knowledge, and coding evals into one 0–100 score.

    Comparable with caveatOnly same-version scores are comparable. v4.3.2 was rebaselined (the top score fell from 66 on v4.1.1 to ~58), so v4.1.1 figures must not be compared with v4.3.2 figures — check measuredAt.

  • 2026-09-22
    Anthropic — Claude Opus 5.5 announcement (vendor; conflicts with AA's independent 59.6 — harness difference preserved)

    Agentic terminal work: long multi-step tasks executed in a sandboxed shell environment.

    Comparable with caveatNOT comparable with Terminal-Bench 2.x or 3.0 — 4.0 uses a new, non-overlapping task set. Within 4.0, scores from different harnesses (tbench.ai agent entries vs Artificial Analysis runs) are not interchangeable.

  • 2026-07-09
    OpenAI — GPT-5.6 evals table (vendor)

    Agentic terminal work: multi-step tasks executed in a sandboxed shell environment.

    Comparable with caveatNot comparable with Terminal-Bench 3.0 or 4.0 (different task sets) or v1; harness configuration (container, time limits) also shifts results.

Pricing tiers

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.

GPT-5.6 Sol: Launch list was $5/$30; cut to $4/$20 on 2026-08-21, promo held at least through 2026-11-21. Above 272K input the whole request bills 2x input / 1.5x output ($8/$30). Cached input $0.40/MTok; cache writes 1.25x input; batch $2/$10. Knowledge cutoff Feb 16 2026.

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.

FrontierRecord checked September 26, 2026

GPT-5.6 Sol

GPT-5.6 Sol was OpenAI's GPT-5.6 flagship for complex reasoning and coding with a 1.05M-token context — superseded on 2026-09-22 by GPT-6 Sol at half the price.

Best for

  • Complex reasoning
  • Agentic coding
  • Hard knowledge work

Watch out

Superseded: GPT-6 Sol lists $2/$10, half this row's $4/$20 promo rate, and scores higher on the Artificial Analysis index. Still served; 'max' effort and 'ultra' multi-agent mode multiply token use.

When the cheaper one wins

Both charge $20 per million output tokens at standard rates, so output price is not the split. Prefer the row whose “best for” line matches the job, then confirm the live vendor rate.

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.
  • 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
  • 1 shared named benchmark with differing scores — Measured on: Artificial Analysis Intelligence Index.
  • 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 5.5 · GPT-5.6 Sol

Common questions

Claude Opus 5.5 vs GPT-5.6 Sol

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

Is Claude Opus 5.5 or GPT-5.6 Sol cheaper for input?
Both cost $4 per million input tokens at standard rates, so input price is not a deciding factor between them.
Is Claude Opus 5.5 or GPT-5.6 Sol cheaper for output?
Both cost $20 per million output tokens at standard rates, so output price is not a deciding factor between them.
Which has the larger context window, Claude Opus 5.5 or GPT-5.6 Sol?
GPT-5.6 Sol accepts 1.05M tokens against 1M for Claude Opus 5.5. This only matters if you routinely send very long documents or large codebases.
Do Claude Opus 5.5 and GPT-5.6 Sol support the same reasoning levels?
Claude Opus 5.5 exposes adaptive, while GPT-5.6 Sol exposes none, low, medium, high, xhigh, max.
Should I use Claude Opus 5.5 or GPT-5.6 Sol?
Both sit in the frontier tier, so the choice usually comes down to price and context rather than capability. Claude Opus 5.5 suits complex agentic coding; GPT-5.6 Sol suits complex reasoning.

Next step

Choosing between them

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

  • Context: GPT-5.6 Sol takes 1.05M against 1M for Claude Opus 5.5 — only decisive if your prompts approach the smaller window.
  • Measured capability: Claude Opus 5.5 leads Artificial Analysis Intelligence Index 57.6 to 47 (measured 2026-09-26).
Run the model pickerEstimate stack costAll model comparisons

Choosing a harness rather than a model — Cursor, Copilot, Claude Code, Windsurf, or Lovable? Compare agentic harnesses · Latest releases.