Model comparison

Claude Opus 5.5 vs Upstage Solar Pro 4

Anthropic against Upstage, 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

Upstage

Upstage Solar Pro 4

Frontier

AI model capability comparison
Specification	Claude Opus 5.5	Upstage Solar Pro 4
Provider
Provider	Anthropic	Upstage
Tier
Tier	Frontier	Frontier
Context window
Context window	Winner: 1M	524K
Max output
Max output	128K	128K
Input / 1M tokens
Input / 1M tokens	$4	Winner: $0.30
Output / 1M tokens
Output / 1M tokens	$20	Winner: $1.20
Weights
Weights	Closed	Closed
Parameters
Parameters	Not disclosedUnverified	Not disclosedUnverified
Reasoning levels
Reasoning levels	adaptive	low, medium, high
Modalities
Modalities	text, image	text
API model id
API model id	claude-opus-5-5	solar-pro4
Released
Released	September 22, 2026	August 10, 2026
Artificial Analysis Intelligence Index [max] (2026-09-26)
Artificial Analysis Intelligence Index [max] (2026-09-26)	57.6	Not verifiedUnverified
Artificial Analysis Intelligence Index (2026-09-26)
Artificial Analysis Intelligence Index (2026-09-26)	Not verifiedUnverified	28.2
Humanity's Last Exam [max] (2026-09-26)
Humanity's Last Exam [max] (2026-09-26)	61.4	Not verifiedUnverified
Terminal-Bench 4.0 [max] (2026-09-26)
Terminal-Bench 4.0 [max] (2026-09-26)	59.6	Not verifiedUnverified
Terminal-Bench 4.0 [xhigh] (2026-09-22)
Terminal-Bench 4.0 [xhigh] (2026-09-22)	66.4	Not verifiedUnverified

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 (AA-estimated)
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.

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.

Upstage Solar Pro 4: List $0.30/$1.20 per MTok; cached input $0.06. The 90%-off launch promo ended 2026-09-10. Closed API. 524K context with up to 128K output.

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

Upstage Solar Pro 4

Solar Pro 4 is Upstage's closed flagship with a 524K context at a low $0.30/$1.20 list price.

Best for

Long-context
Cost-sensitive API
Korean + English

Watch out

Closed API; the launch promo has ended, so budget at the $0.30/$1.20 list rate.

When the cheaper one wins

Upstage Solar Pro 4 is cheaper on output at $1.20 per million tokens against $20 for Claude Opus 5.5 — about 17×. 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.

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.

Claude Opus 5.5: Anthropic — Claude Opus 5.5 (accessed 2026-09-26)
Claude Opus 5.5: Anthropic docs — Opus 5.5 overview (1M context, 128K output) (accessed 2026-09-26)
Claude Opus 5.5: Anthropic pricing (claude-opus-5-5 $4/$20, cache reads $0.20) (accessed 2026-09-26)
Claude Opus 5.5: Artificial Analysis — Intelligence Index v4.3.2 (Opus 5.5 #1) (accessed 2026-09-26)
Upstage Solar Pro 4: Upstage — Solar Pro 4 (accessed 2026-08-29)
Upstage Solar Pro 4: Upstage (accessed 2026-08-29)

Related comparisons

Diving deeper on one model? Claude Opus 5.5 · Upstage Solar Pro 4

Common questions

Claude Opus 5.5 vs Upstage Solar Pro 4

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

Is Claude Opus 5.5 or Upstage Solar Pro 4 cheaper for input?

Upstage Solar Pro 4 is cheaper at $0.30 per million input tokens, against $4 for Claude Opus 5.5 — roughly 13× 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 5.5 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. Upstage Solar Pro 4 has tiered pricing: List $0.30/$1.20 per MTok; cached input $0.06. The 90%-off launch promo ended 2026-09-10. Closed API. 524K context with up to 128K output.

Is Claude Opus 5.5 or Upstage Solar Pro 4 cheaper for output?

Upstage Solar Pro 4 is cheaper at $1.20 per million output tokens, against $20 for Claude Opus 5.5 — roughly 17× 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 5.5 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. Upstage Solar Pro 4 has tiered pricing: List $0.30/$1.20 per MTok; cached input $0.06. The 90%-off launch promo ended 2026-09-10. Closed API. 524K context with up to 128K output.

Which has the larger context window, Claude Opus 5.5 or Upstage Solar Pro 4?

Claude Opus 5.5 accepts 1M tokens against 524K for Upstage Solar Pro 4. This only matters if you routinely send very long documents or large codebases.

Do Claude Opus 5.5 and Upstage Solar Pro 4 support the same reasoning levels?

Claude Opus 5.5 exposes adaptive, while Upstage Solar Pro 4 exposes low, medium, high.

Should I use Claude Opus 5.5 or Upstage Solar Pro 4?

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; Upstage Solar Pro 4 suits long-context.

Next step

Choosing between them

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

Input price: Upstage Solar Pro 4 costs $0.30 per 1M tokens versus $4 for Claude Opus 5.5 — a 13.3x difference at the headline tier.
Context: Claude Opus 5.5 takes 1M against 524K for Upstage Solar Pro 4 — only decisive if your prompts approach the smaller window.

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