Model comparison

Claude Opus 5 vs GPT-5.6 Luna

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

Recorded profile verification October 1, 2026Individual provider fields may changeEvidence confidence: Medium — see receipts below

Anthropic

Claude Opus 5

Frontier

OpenAI

GPT-5.6 Luna

Budget

AI model capability comparison
Specification	Claude Opus 5	GPT-5.6 Luna
Provider
Provider	Anthropic	OpenAI
Tier
Tier	Frontier	Budget
Context window
Context window	1M	Winner: 1.05M
Max output
Max output	128K	128K
Input / 1M tokens
Input / 1M tokens	$5	Winner: $0.20
Output / 1M tokens
Output / 1M tokens	$25	Winner: $1.20
Weights
Weights	Closed	Closed
Parameters
Parameters	Not verifiedUnverified	Not verifiedUnverified
Reasoning levels
Reasoning levels	low, medium, high, xhigh, max	none, low, medium, high, xhigh, max
Modalities
Modalities	text, image	text, image
API model id
API model id	claude-opus-5	gpt-5.6-luna
Released
Released	July 24, 2026	July 9, 2026
Humanity's Last Exam · source date Claude Opus 5: 2026-09-01
Humanity's Last Exam · source date Claude Opus 5: 2026-09-01	63.6	Not verifiedUnverified
Terminal-Bench 2.1 · source date Claude Opus 5: 2026-09-02
Terminal-Bench 2.1 · source date Claude Opus 5: 2026-09-02	89.1	Not verifiedUnverified
Terminal-Bench 2.1 · source date GPT-5.6 Luna: 2026-07-09
Terminal-Bench 2.1 · source date GPT-5.6 Luna: 2026-07-09	Not verifiedUnverified	84.7
LiveBench · source date GPT-5.6 Luna: 2026-09-05
LiveBench · source date GPT-5.6 Luna: 2026-09-05	Not verifiedUnverified	73.6

Dates beside benchmark scores refer to the linked source’s publication or capture date unless that source explicitly states when it measured the result. A shared URL alone does not establish comparable runs; unverified setups are marked. Prices are USD per million tokens at standard rates, excluding batch and caching discounts. 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.

Source date2026-09-05
LiveBench official leaderboard (benchmark-owned), max effort
Contamination-resistant general capability across reasoning, coding, math, data analysis, and language, with monthly question refreshes.
Comparable with caveatCompare only observations confirmed to use the same exact question-set version. Date proximity (including within one month) does not establish identical questions; when the version is unavailable, treat the scores as unaligned.
Source date2026-09-02
Google Gemini 3.8 Flash evaluation table quoting public leaderboard / Artificial Analysis, Terminus 2; not a Google-run Opus evaluation (Cross-provider quotation; common effort and experiment date unverified)
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.
Source date2026-09-01
Anthropic Fable 5.1 comparison table (vendor, with tools; 56.6 no tools)
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.
Source date2026-07-09
OpenAI GPT-5.6 launch table (vendor-reported; effort and experiment date unspecified) (Vendor launch table; complete common run settings unverified)
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: Standard $5/$25 per MTok with no long-context surcharge. Cache reads $0.50; 5-minute writes $6.25 and 1-hour writes $10. Batch $2.50/$12.50. First-party Fast research preview $10/$50, unavailable with Batch. US-only inference adds 10% where supported. Batch 300K output requires output-300k-2026-03-24; standard stays 128K. Knowledge cutoff May 2026; retirement not sooner than July 24, 2027.

GPT-5.6 Luna: Launch $1/$6, reduced to $0.20/$1.20 on July 30. Above 272K input the full request bills $0.40/$1.80. Cached input $0.02; cache writes $0.25 at short context. Batch $0.10/$0.60 at short context. Regional/FedRAMP processing adds 10% where eligible.

FrontierRecord checked October 1, 2026

Claude Opus 5

Claude Opus 5 is Anthropic's July 2026 agentic-coding model, now 'Active (legacy)'. Its successor Opus 5.5 has lower base input/output prices ($4/$20 vs $5/$25 per million tokens); performance depends on the workload and evaluation settings.

Best for

Complex agentic coding
Enterprise work
Long-context analysis

Watch out

Active legacy, superseded by Opus 5.5. Test migration: Opus 5.5 makes adaptive thinking always on, rejects forced tool use and the older computer-use tool, and changes thinking-block/progress behavior. Partner cloud lifecycles and prices can differ.

BudgetRecord checked October 1, 2026

GPT-5.6 Luna

OpenAI’s GPT-5.6 budget tier, succeeded by GPT-6 Luna on September 22. The newer model halves input pricing ($0.20→$0.10) and lowers output pricing from $1.20 to $0.50.

Best for

Classification
High-volume chat
Latency-sensitive pipelines

Watch out

Superseded by GPT-6 Luna and still listed in the API. Historical index captures are not current evidence of equal quality; the successor has lower Standard input and output prices.

When the cheaper one wins

GPT-5.6 Luna is cheaper on output at $1.20 per million tokens against $25 for Claude Opus 5 — about 21×. 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. On DeepSWE 1.1, GPT-5.6 Luna is 67.2% Pass@1 at $3.03/task versus Claude Opus 5 at 73.6% / $11.84/task. This compares standard short-context token rates, not total cost per accepted task. Include input, cache, context tiers, schedules, retries and review in your pilot.

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Evidence confidence: Medium

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.
No directly aligned benchmark setup — No benchmark has matching cited sources, source dates, units, effort and recorded run details on both models.
Verified within the last 90 days — Older of the two catalog checks was 25 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: Claude model overview — whole-profile source check October 1 (accessed 2026-10-01)
Claude Opus 5: Claude current API pricing, caching and inference geography (accessed 2026-10-01)
Claude Opus 5: Anthropic — Claude Opus 5 (accessed 2026-08-29)
Claude Opus 5: Anthropic news — Claude Opus 5 (accessed 2026-08-29)
Claude Opus 5: Anthropic — Claude Opus 5.5 (Opus 5 successor) (accessed 2026-09-26)
Claude Opus 5: Anthropic selectable effort levels (separate from adaptive thinking mode) (accessed 2026-10-01)
GPT-5.6 Luna: OpenAI model card — whole-profile source check October 1 (accessed 2026-10-01)
GPT-5.6 Luna: OpenAI current API pricing and processing tiers (accessed 2026-10-01)
GPT-5.6 Luna: OpenAI — GPT-5.6 (accessed 2026-08-29)
GPT-5.6 Luna: OpenAI API pricing (gpt-5.6-luna $0.20/$1.20) (accessed 2026-08-29)
GPT-5.6 Luna: OpenAI — Introducing GPT-6 Sol and Luna (GPT-5.6 Luna successor) (accessed 2026-09-26)

Related comparisons

Diving deeper on one model? Claude Opus 5 · GPT-5.6 Luna

Common questions

Claude Opus 5 vs GPT-5.6 Luna

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

Is Claude Opus 5 or GPT-5.6 Luna cheaper for input?

GPT-5.6 Luna is cheaper at $0.20 per million input tokens, against $5 for Claude Opus 5 — roughly 25× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Opus 5: Standard $5/$25 per MTok with no long-context surcharge. Cache reads $0.50; 5-minute writes $6.25 and 1-hour writes $10. Batch $2.50/$12.50. First-party Fast research preview $10/$50, unavailable with Batch. US-only inference adds 10% where supported. Batch 300K output requires output-300k-2026-03-24; standard stays 128K. Knowledge cutoff May 2026; retirement not sooner than July 24, 2027. GPT-5.6 Luna: Launch $1/$6, reduced to $0.20/$1.20 on July 30. Above 272K input the full request bills $0.40/$1.80. Cached input $0.02; cache writes $0.25 at short context. Batch $0.10/$0.60 at short context. Regional/FedRAMP processing adds 10% where eligible.

Is Claude Opus 5 or GPT-5.6 Luna cheaper for output?

GPT-5.6 Luna is cheaper at $1.20 per million output tokens, against $25 for Claude Opus 5 — roughly 21× the price. Estimate both input and output token volume for your workload. These are base rates; Claude Opus 5: Standard $5/$25 per MTok with no long-context surcharge. Cache reads $0.50; 5-minute writes $6.25 and 1-hour writes $10. Batch $2.50/$12.50. First-party Fast research preview $10/$50, unavailable with Batch. US-only inference adds 10% where supported. Batch 300K output requires output-300k-2026-03-24; standard stays 128K. Knowledge cutoff May 2026; retirement not sooner than July 24, 2027. GPT-5.6 Luna: Launch $1/$6, reduced to $0.20/$1.20 on July 30. Above 272K input the full request bills $0.40/$1.80. Cached input $0.02; cache writes $0.25 at short context. Batch $0.10/$0.60 at short context. Regional/FedRAMP processing adds 10% where eligible.

Which has the larger context window, Claude Opus 5 or GPT-5.6 Luna?

GPT-5.6 Luna accepts 1.05M tokens against 1M for Claude Opus 5. This only matters if you routinely send very long documents or large codebases.

Do Claude Opus 5 and GPT-5.6 Luna support the same reasoning levels?

Claude Opus 5 exposes low, medium, high, xhigh, max, while GPT-5.6 Luna exposes none, low, medium, high, xhigh, max.

Should I use Claude Opus 5 or GPT-5.6 Luna?

We classify Claude Opus 5 in the frontier tier and GPT-5.6 Luna in the budget tier. Test whether either meets your accuracy, tool-use and latency requirements before choosing on price.

Next step

Choosing between them

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

Input price: GPT-5.6 Luna costs $0.20 per 1M tokens versus $5 for Claude Opus 5 — a 25x difference at the headline tier.
Context: GPT-5.6 Luna takes 1.05M against 1M for Claude Opus 5 — only decisive if your prompts approach the smaller window.
Positioning: Claude Opus 5 sits in the frontier tier, GPT-5.6 Luna in the budget tier. Compare accuracy, reliability, latency, and cost on representative tasks before choosing.

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