GPT-5.6 Sol vs Claude Sonnet 5: Flagship or Balanced Claude? (2026)

GPT-5.6 Sol and Claude Sonnet 5 sit in different tiers: Sol is OpenAI's premium flagship, Claude Sonnet 5 is Anthropic's balanced value model. On the independent Artificial Analysis Intelligence Index, Sol scores 59 to Sonnet 5's 53, adds a second-place Coding Agent Index v1.3 placement at 66.57 (Sonnet 5 is not charted), an ultra multi-agent reasoning mode, a 1,050,000-token context to Sonnet 5's 1,000,000, and the only LMArena Elo of the pair at 1486. Claude Sonnet 5 answers on price, speed, and reach: $2 per million input tokens and $10 per million output against Sol's promotional $4 and $20 — exactly half on both sides — a measured 79 output tokens per second against Sol's 74.5, and the free default model on Claude.ai. Best for peak capability and agentic coding: GPT-5.6 Sol. Best for the lowest price and widest free reach: Claude Sonnet 5. There is no single overall winner — the question is whether you need the flagship or the balanced Claude is enough.

Quick Verdict

This is a split verdict between a flagship and a value tier: GPT-5.6 Sol owns measured capability, coding, and reasoning depth, while Claude Sonnet 5 owns price, measured speed, and free reach — so the real question is not which is better, but whether your workload needs the flagship. GPT-5.6 Sol reached general availability on July 9, 2026, and Claude Sonnet 5 on June 30, and both are reachable through our own OpenAI and Anthropic API keys, so we have run them side-by-side on the same tasks — Sonnet 5 since its June 30 launch and Sol since July 9, which makes our Sol notes first impressions rather than a settled verdict. We lean on attributed third-party numbers from Artificial Analysis and LMArena wherever our own time is too short, and every figure below carries its source, per OpenAI's own announcement. Here is the short version.

• Best on the independent intelligence aggregate: GPT-5.6 Sol. Artificial Analysis scores it 59 on the Intelligence Index against Claude Sonnet 5's 53 — a six-point gap on the same harness.
• Best on the independent coding index: GPT-5.6 Sol. It places second at 66.57 on the AA Coding Agent Index v1.3, through the Codex harness at max reasoning effort; Sonnet 5 is not charted there, so this is a difference in available evidence rather than a decisive head-to-head win.
• Best for reasoning depth: GPT-5.6 Sol. Its ultra tier runs up to sixteen reasoning agents in parallel, a ceiling Sonnet 5's adaptive thinking does not match.
• Best for price: Claude Sonnet 5, decisively. Its $2 input and $10 output per million tokens undercut Sol's promotional $4 and $20 by exactly 50 percent on both sides, and Sol's long-context rate of $8 and $30 by 75 and 67 percent.
• Best for measured output speed: Claude Sonnet 5. Artificial Analysis clocks it at 79 output tokens per second against Sol's 74.5 — a genuine head-to-head, since both are measured.
• Best for free and consumer reach: Claude Sonnet 5. It is the default model on the free and Pro plans of Claude.ai; Sol requires a paid ChatGPT plan or API access.
• Best for context and newest knowledge: GPT-5.6 Sol, marginally. Its 1,050,000-token window is five percent larger than Sonnet 5's 1,000,000, and its February 16, 2026 cutoff is about a month newer.
• No single overall winner: Sol wins capability, coding, and reasoning; Sonnet 5 wins price, speed, and reach. The right pick is whichever axis is binding for you.

The honest caveats up front: Sol is only days old at the time of writing, so we treat our hands-on notes as first impressions. Neither model has been submitted to the independently run SWE-bench Verified suite, so there is no third-party verified-coding number for either, and we will not paper over that gap with self-reported figures. One fact complicates Sonnet 5's price advantage without erasing it: Anthropic states its newer tokenizer counts roughly 30 percent more tokens for the same text, which narrows the effective-cost gap. Even after both adjustments Sonnet 5 stays clearly cheaper than Sol. We only declare a winner where both models were measured on the same independent benchmark, and we keep self-reported and third-party numbers strictly apart.

GPT-5.6 Sol vs Claude Sonnet 5 — Overview

What Is GPT-5.6 Sol?

GPT-5.6 Sol is the flagship capability tier of OpenAI's GPT-5.6 generation, generally available July 9, 2026 after a gated preview on June 26. In OpenAI's naming scheme the number is the generation and the names — Sol, Terra, and Luna — are durable capability tiers rather than sizes; Sol is the tier aimed at the hardest problems, from complex coding and long-horizon agents to cyber, science, and computer use, per OpenAI's announcement. Its balanced sibling GPT-5.6 Terra and the prior flagship GPT-5.5 both remain active, and our GPT-5.6 rollout explainer covers how the generation reached the public. Per OpenAI's model documentation, Sol runs a 1,050,000-token context window with up to 128,000 output tokens and a February 16, 2026 knowledge cutoff, handles text and image inputs to text output, and introduces two new reasoning levels above xhigh: max, and ultra, a multi-agent mode that runs up to sixteen reasoning agents in parallel. It carries Programmatic Tool Calling, where the model writes and executes JavaScript in an isolated, ephemeral runtime to orchestrate its own tools. API pricing is $4 per million input tokens and $20 per million output on requests up to 272,000 input tokens, with cached input at $0.40 per million — promotional rates cut on August 21, 2026 — rising to $8 and $30 above that threshold. On the independent leaderboards it is a frontier model: 59 on the Artificial Analysis Intelligence Index and second at 66.57 on the Coding Agent Index v1.3. Our full GPT-5.6 Sol review covers the hands-on detail.

What Is Claude Sonnet 5?

Claude Sonnet 5 is Anthropic's midsize model, generally available June 30, 2026, and positioned as the best combination of speed and intelligence in the Claude family — the balanced workhorse tier below the Claude Opus 4.8 flagship. Anthropic markets it as its most agentic midsize model, reporting near-Opus results at a fraction of the price, and our Sonnet 5 launch analysis covers why it matters that Anthropic made it the default model. Per Anthropic's model documentation, Sonnet 5 runs a 1,000,000-token context window with up to 128,000 output tokens — 300,000 through a Batch API beta header — a January 2026 knowledge cutoff, adaptive thinking with an effort dial that defaults to high, and text and image inputs to text output. API pricing is $2 per million input tokens and $10 per million output, which we confirmed on Anthropic's pricing documentation. Anthropic also notes Sonnet 5 uses a newer tokenizer that produces roughly 30 percent more tokens for the same text. Critically, it is the default model on the free and Pro plans of Claude.ai and is available in Claude Code and via the API at model id claude-sonnet-5.

How We Compared Them — and What We Did Not Do

Method transparency matters here, because this is a flagship against a value tier, Sol is days old at the time of writing, and the cost comparison hinges on a date and a tokenizer detail that a casual read of the rate cards misses. Here is exactly what we did and did not do, and where every number comes from.

• Pricing: both rate cards are vendor-verified. We re-confirmed Sol's $4 input and $20 output per million tokens — its promotional short-context rate — directly on OpenAI's API pricing documentation on August 28, 2026, and Sonnet 5's $2 and $10 on Anthropic's pricing documentation. No relayed figures. Our AI model pricing explainer breaks down how input, output, and cached-token rates translate into real bills.
• Independent benchmarks: we lean on Artificial Analysis for the Intelligence Index, the Coding Agent Index, cost per task, and output speed, and on LMArena for human-preference Elo. We only declare a benchmark winner where both models were measured on the same suite. Where one model is absent — as Sonnet 5 is on the Coding Agent Index and LMArena in our sources, and both are on SWE-bench Verified — we say so and do not substitute a self-reported number.
• Self-reported figures: OpenAI's Terminal-Bench 2.1 number for Sol and Anthropic's SWE-bench Pro and OSWorld-Verified numbers for Sonnet 5 are labeled as vendor-reported, measured on different suites, and not treated as head-to-head evidence. Our agentic coding model explainer covers why coding-agent scores and chatbot scores measure different things.
• Hands-on: we have run both models through our own OpenAI and Anthropic API keys — Sonnet 5 since June 30 and Sol since July 9. That gives us more time with Sonnet 5 and only first impressions of Sol, and we scope every observation accordingly.
• Disclosure: we have no affiliate relationship with OpenAI or Anthropic. There are no sponsored links on this page. We flag the tokenizer difference prominently because it changes the cost conclusion, not because it favors one vendor.

Features and Benchmarks Comparison

The table below lists every dimension we could verify or attribute. Read the Winner column carefully: it distinguishes vendor-verified pricing, independent benchmarks, and self-reported figures, and it flags where a result is one-sided ("where measured"), genuinely tied, or date-dependent. Every benchmark figure carries its source. Sources for the independent scores are Artificial Analysis, LMArena, and vals.ai.

Synthesis: read top to bottom, the table splits along the flagship-versus-value line. Every pricing row still goes to Claude Sonnet 5, though by less than it did before August 21, 2026: after OpenAI's cut, Sonnet 5 is exactly half Sol's promotional short-context rate on both input and output, rather than the roughly two-thirds discount it held against Sol's old $5 and $30. The capability rows go to GPT-5.6 Sol on the independent yardsticks the two share or that only Sol appears on: six points on the Intelligence Index, a second-place Coding Agent Index v1.3 placement where Sonnet 5 is absent, the only LMArena Elo, a marginally larger context, a newer cutoff, and a deeper reasoning ceiling. Two rows are honest ties on independent grounds — neither model is on SWE-bench Verified, and each vendor's self-reported coding number lives in its own harness — and one row runs against the pricing trend: measured output speed goes to Sonnet 5 at 79 tokens per second against Sol's 74.5, a genuine head-to-head since both are measured. The per-task cost row is not a clean win for either: Sol has the only published figure at about $1.04, but that is high, consistent with a flagship, not an economy advantage. That leaves the decision exactly where the two tiers put it: peak capability against price, speed, and reach.

Pricing — GPT-5.6 Sol vs Claude Sonnet 5 in 2026

Pricing is the sharpest contrast in this comparison, because it is a flagship rate card against a value one. Claude Sonnet 5 is far cheaper on both sides. But a tokenizer detail complicates the headline, and the one independent per-task measurement is a reminder that flagship capability is not free. Both rate cards below come straight from OpenAI's and Anthropic's own documentation, and our pricing explainer covers how these translate into real spend.

GPT-5.6 Sol Pricing

Context pricing is not flat for Sol: above 272,000 input tokens the long-context rate of $8 and $30 applies to the entire request, so a 900,000-token prompt costs twice as much per input token as a short one. Claude Sonnet 5 is the opposite — Anthropic states that Claude 4.6 and later models carry the full 1,000,000-token window at standard pricing, so a 900,000-token request there bills at the same per-token rate as a 9,000-token one.

These are promotional rates, and OpenAI's own pages disagree on how long they last. The company cut Sol's API and credit pricing on August 21, 2026. Its GPT-5.6 launch page carries an update reading: "OpenAI dropped the API and credit pricing of GPT-5.6 Sol by over 20% for the next 3 months." Its API pricing page states: "GPT-5.6 Sol's promotional pricing is available at least through November 21, 2026." One phrasing closes a window; the other sets a floor and leaves the end open. We are not going to pick between them. Sol's standard rate before the cut was $5 input and $30 output per million, which is where the two-thirds output discount Sonnet 5 used to hold came from. Budget for both readings, and do not plan around the rate reverting on a specific date, because neither page says it will.

Claude Sonnet 5 Pricing

Pricing verdict: Claude Sonnet 5 wins price, and it is not close in either window. On a representative call of 50,000 input tokens and 5,000 output tokens — comfortably inside Sol's short-context tier — Sol costs about $0.30 at its promotional rate card ($4 times 0.05 input plus $20 times 0.005 output), while Sonnet 5 costs about $0.15 ($2 times 0.05 plus $10 times 0.005) — exactly half of Sol's cost. Two things move the effective comparison, though neither erases Sonnet 5's advantage. First, Artificial Analysis measures Sol at about $1.04 per task to run its Intelligence Index and publishes no equivalent per-task figure for Sonnet 5 in our sources; that $1.04 is high, reflecting Sol's flagship rate, and we read it in July 2026, before the August 21 price cut, so it overstates what the same run would cost today; either way it is a reminder that peak capability carries a premium, not a point in Sol's favor on cost. Second, Anthropic states Sonnet 5's newer tokenizer counts roughly 30 percent more tokens for the same text, so an identical document is billed more tokens on Sonnet 5; even after inflating its token count by 30 percent, Sonnet 5's effective cost stays about a third below Sol's. The lesson is not that one rate card is wrong — both are real — but that the sticker price decides your bill only if your token counts match. Test on your own prompts before assuming the capability lead is worth the premium.

Hands-On Notes — What Side-by-Side Testing Showed

We owe you precision about what this section is and is not. We have run both models through our own OpenAI and Anthropic API keys on the same tasks, but the windows are uneven: Claude Sonnet 5 has been generally available since June 30, 2026, and GPT-5.6 Sol only since July 9, so our Sol observations are first impressions rather than a settled read. Take everything below as scoped, and weight the attributed benchmarks and OpenAI's model documentation above it.

Where Sol stood out: the hardest single problems. On a deliberately tricky algorithm task, Sol wrote a correct implementation on the first try and reasoned cleanly through a multi-step logic puzzle; on a source-comprehension prompt it correctly refused to invent a fact the text withheld rather than guessing. Turned up to its higher reasoning levels, and especially in the ultra multi-agent mode, it produced visibly more thorough plans on a hard architecture task — at a higher token bill and slower wall-clock time for that call. This lines up with its 59 Intelligence Index and its second-place Coding Agent Index v1.3 placement without proving either in a few days.

Where Sonnet 5 stood out: fast, clean production work at a fraction of the cost. On multi-document summarization and support-style question answering, Sonnet 5's tool-error recovery felt mature, matching Anthropic's positioning of it as its most agentic midsize model, and its prose came out tight with less editing on our drafting tasks. Its measured 79 tokens per second showed up as snappy interactive responses, and being the default model on Claude.ai meant we could sanity-check behavior in the chat interface for free before spending API tokens — a practical advantage Sol does not offer at the free tier.

What we watched carefully: whether Sol's capability lead actually changed outcomes on ordinary work. On many everyday prompts — routine refactors, standard summaries, straightforward drafting — the two produced comparable results, and Sonnet 5 did so faster and far cheaper. Sol's edge showed up on the hardest tasks, not the average one, which is exactly what a flagship-versus-value split predicts. We did not run a controlled token-accounting benchmark across a full workload mix, so we present these as scoped observations rather than measured results.

What we cannot tell you yet: Sol's behavior over weeks, controlled latency for both under identical conditions, and per-task economics across a representative production mix. We will update this comparison as our side-by-side time accumulates and as more independent harnesses publish results for both models.

Winner per Category

Best on the Independent Intelligence Index: GPT-5.6 Sol

On the Artificial Analysis Intelligence Index, GPT-5.6 Sol scores 59 against Claude Sonnet 5's 53 — a six-point gap on the aggregate independent measure, and a real one for a flagship against a value tier. It is not a rounding difference: on the hardest reasoning tasks, a gap of that size regularly decides whether a multi-step answer is correct or merely plausible. Sonnet 5's 53 is a strong result for a balanced midsize model, and for many everyday prompts the two will feel closer than the numbers suggest. For context, the top of that chart is around 60, where Claude Fable 5 sits one point above Sol, so Sol lands right at the frontier while Sonnet 5 sits a tier below by design. If your workload leans on the toughest reasoning you have, Sol is the pick of these two on the independent evidence — and our GPT-5.6 Sol review covers where that headroom shows up.

Independent Coding Agent Index: Only GPT-5.6 Sol Is Charted

The Artificial Analysis Coding Agent Index is the sharpest capability separator here, and it is one-sided by absence: Sol places second at 66.57, through the Codex harness at max reasoning effort, while Claude Sonnet 5 is not charted on that index at all, so there is no independent agentic-coding score to place beside Sol's. That is a difference in what has been measured, not a demonstration that Sol codes better. Neither model has been submitted to the independently run SWE-bench Verified suite, so there is no third-party verified-coding number for either; for reference, Claude Opus 4.8 posts 88.6 percent on that suite, the flagship Sonnet 5 is measured against as near-Opus. Each vendor publishes its own coding headline on a different suite — OpenAI reports Sol at 88.8 percent on Terminal-Bench 2.1, Anthropic reports Sonnet 5 at 63.2 percent on SWE-bench Pro and 81.2 percent on OSWorld-Verified — and because the suites differ, those numbers are not comparable. On independent evidence, Sol has the only agentic-coding index; on verified coding, both are blank, and our agentic coding explainer covers why the suite matters as much as the score.

Best for Price: Claude Sonnet 5

This one is not close, and it runs against the capability rows. Claude Sonnet 5 costs $2 per million input tokens against Sol's promotional $4, and $10 per million output against $20 — exactly 50 percent cheaper on both sides, both re-verified on August 28, 2026 on Anthropic's documentation and OpenAI's. Anthropic cancelled the increase it had scheduled for September 1, 2026, so Sonnet 5's side of that gap is settled; Sol's is not, because $4 and $20 is a promotional rate OpenAI has committed to only for a limited window, and above 272,000 input tokens Sol already bills $8 and $30, which widens the gap to 75 and 67 percent. The honest complication is the tokenizer: Anthropic's newer tokenizer counts roughly 30 percent more tokens for the same text, which narrows but does not close the effective gap. For high-volume, cost-sensitive, output-heavy workloads, Sonnet 5 delivers twice the output per dollar of Sol on short prompts and three times it on long ones — the single largest advantage in this matchup, and the reason a value tier exists alongside a flagship.

Best for Measured Output Speed: Claude Sonnet 5

Speed is a rare category here where both models carry an independent number, so it is a true head-to-head rather than a one-sided gap. Artificial Analysis measures Claude Sonnet 5 at 79 output tokens per second and GPT-5.6 Sol at about 74.5, so Sonnet 5 is modestly faster on measured throughput. The margin is small and both sit mid-pack rather than at the top of the speed charts, so for most interactive work neither will feel dramatically quicker. Speed also depends on Sol's reasoning effort: pushed to xhigh, max, or ultra, Sol spends more time reasoning before it answers, which lowers effective throughput on hard tasks in exchange for better answers. For latency-sensitive, high-throughput work where the balanced model already clears your quality bar, Sonnet 5's measured edge is the pick; for the hardest tasks, Sol's slower, deeper reasoning is the point.

Best for Context and Newest Knowledge: GPT-5.6 Sol

Sol owns the envelope, narrowly. Per OpenAI's documentation, it runs a 1,050,000-token context against Sonnet 5's 1,000,000 — five percent larger, a marginal edge rather than an architectural gulf, and one partly offset by Sonnet 5's heavier tokenizer counting more tokens per document. Both cap standard output at 128,000 tokens, though Sonnet 5 can reach 300,000 through a Batch beta header, so the output ceiling actually favors Sonnet 5 for very long generations. Where Sol pulls clearly ahead is knowledge freshness — its February 16, 2026 cutoff is about a month newer than Sonnet 5's January 2026 — and reasoning depth, since its ultra tier runs up to sixteen agents in parallel where Sonnet 5 offers a single adaptive-thinking dial. For workloads that lean on the freshest knowledge and the deepest reasoning, Sol is the pick; for the largest single outputs, Sonnet 5's batch ceiling is the edge.

Best for Free Reach and Ecosystem: Claude Sonnet 5

Reach is where Sonnet 5 wins on structure, not benchmarks. It is the default model on the free and Pro plans of Claude.ai, which puts it in front of a vast consumer audience at no cost and lets developers sanity-check behavior in the chat interface before spending API tokens. GPT-5.6 Sol is a flagship you reach through the API, Codex, or a paid ChatGPT plan — it is selectable for Plus, Pro, Business, and Enterprise subscribers, but it is not the model a free ChatGPT user talks to. Sonnet 5 also plugs into the mature Claude Code and Claude API ecosystem, and it carries the only measured output-speed figure of the pair. For teams that value a free consumer default, chat-first prototyping, and a proven balanced-tier ecosystem, Sonnet 5 is the pick; for those who need the flagship and will pay for a seat or API access, Sol is reachable but never free.

Pros and Cons

GPT-5.6 Sol Pros and Cons

What we like about GPT-5.6 Sol

• Highest measured capability of the pair. 59 on the Artificial Analysis Intelligence Index against Sonnet 5's 53, and second at 66.57 on the Coding Agent Index v1.3 where Sonnet 5 is not charted.
• Exclusive ultra multi-agent reasoning mode. Up to sixteen parallel reasoning agents for the hardest long-horizon problems — a ceiling Sonnet 5's adaptive thinking does not match.
• The only charted human-preference Elo. 1486 on LMArena for its Xhigh configuration, where Sonnet 5 is not charted in our sources.
• Marginally larger context and newer knowledge. A 1,050,000-token window and a February 16, 2026 cutoff, about a month ahead of Sonnet 5.
• Disciplined hands-on behavior. In our runs it wrote a correct hard algorithm on the first try and refused to hallucinate a withheld fact rather than guessing.

Where GPT-5.6 Sol falls short

• Twice the price on every line, and worse above 272,000 tokens. $4 input and $20 output per million on promotional rates against Sonnet 5's $2 and $10, rising to $8 and $30 once a request passes 272,000 input tokens.
• Slower on measured output speed. About 74.5 tokens per second against Sonnet 5's 79 on Artificial Analysis.
• No free consumer tier. Selectable only on paid ChatGPT plans or through the API and Codex, not the model a free user reaches.
• Absent from independent SWE-bench Verified. Not submitted, so it has no third-party verified-coding number — the same gap as Sonnet 5.
• Days old at the time of writing. Its production behavior over weeks is unproven, so our hands-on notes are first impressions.

Claude Sonnet 5 Pros and Cons

What we like about Claude Sonnet 5

• Half the price on both sides, with no long-context tier. $2 input and $10 output per million against Sol's promotional $4 and $20, and Anthropic bills Sonnet 5's full 1,000,000-token window at that same rate.
• The free consumer default on Claude.ai. Free and Pro users get it by default, and developers can test it in chat before spending API tokens.
• Faster on measured output speed. 79 tokens per second on Artificial Analysis against Sol's 74.5 — a genuine head-to-head.
• Higher output ceiling. Up to 300,000 output tokens through a Batch beta header, against Sol's 128,000.
• Mature agentic tooling. Strong tool-error recovery and a proven Claude Code and API ecosystem, positioned as Anthropic's most agentic midsize model.

Where Claude Sonnet 5 falls short

• Behind Sol on the independent capability indices. Intelligence Index 53 to 59, and it is not separately charted on the Coding Agent Index or LMArena in our sources.
• No ultra multi-agent reasoning tier. A single adaptive-thinking dial rather than Sol's parallel multi-agent mode.
• Heavier tokenizer. Anthropic notes roughly 30 percent more tokens for the same text, which erodes part of the per-token discount.
• Absent from independent SWE-bench Verified. Not listed, so it too has no third-party verified-coding number.

When to Pick GPT-5.6 Sol vs Claude Sonnet 5

Pick GPT-5.6 Sol if...

• Your workload is the hardest coding, long-horizon agents, science, or reasoning, where the six-point intelligence lead and Sol's charted coding-index result actually change outcomes.
• You want the ultra multi-agent reasoning mode (up to sixteen parallel agents) that Sonnet 5 does not offer.
• A correct answer on a hard task is worth far more to you than the token bill, so paying flagship rates for capability you use is rational.
• You need the newest training knowledge — a February 16, 2026 cutoff, about a month ahead of Sonnet 5 — or the marginally larger context.
• You already build on the OpenAI API, Codex, or a paid ChatGPT plan and want code-orchestrated tool use via Programmatic Tool Calling.

Pick Claude Sonnet 5 if...

• Price is the deciding factor — its $2 input and $10 output per million are half Sol's promotional rate, and a quarter to a third of Sol's long-context rate.
• Your work is high-volume, cost-sensitive, or output-heavy, where a balanced model that clears your quality bar beats paying for capability you do not use.
• Free consumer reach matters — it is the default model on the free and Pro plans of Claude.ai, where a free user cannot reach Sol.
• You want measured output speed (79 tokens per second) or a higher 300,000-token output ceiling for very long generations.
• You want a proven, mature agentic ecosystem in Claude Code and the Claude API, with strong tool-error recovery, and the option to test in chat before paying for tokens.

Frequently Asked Questions

Is GPT-5.6 Sol better than Claude Sonnet 5 in 2026?

On raw measured capability, yes, but they sit in different tiers, so there is no single winner. On the independent Artificial Analysis Intelligence Index, GPT-5.6 Sol scores 59 against Claude Sonnet 5's 53, a six-point gap on the same harness, and Sol places second at 66.57 on the Coding Agent Index v1.3 while Sonnet 5 is not charted there. Sol also carries an ultra multi-agent reasoning mode, a marginally larger 1,050,000-token context, and the only LMArena Elo of the pair at 1486. But Sol is OpenAI's flagship tier and is priced like one: $4 per million input tokens and $20 per million output on promotional rates up to 272,000 input tokens, rising to $8 and $30 above that, against Sonnet 5's flat $2 and $10. Claude Sonnet 5 is Anthropic's balanced value tier — cheaper on every line, faster on measured output speed, and the free default on Claude.ai. For the hardest reasoning and agentic coding, Sol is the stronger model; for price, speed, and everyday production work, the balanced Claude is often enough. It depends on whether your workload actually needs the flagship.

How much do GPT-5.6 Sol and Claude Sonnet 5 cost?

GPT-5.6 Sol costs $4 per million input tokens and $20 per million output tokens on requests up to 272,000 input tokens, with cached input at $0.40 per million; above that threshold the rate is $8 and $30 on the whole request. Those are promotional rates OpenAI cut on August 21, 2026, and we re-confirmed them directly on OpenAI's API pricing documentation on August 28, 2026. Claude Sonnet 5 runs $2 per million input tokens and $10 per million output, with cache reads at $0.20, flat across its full context window; we confirmed this on Anthropic's pricing documentation. So Sonnet 5 is exactly 50 percent cheaper than Sol on both input and output on short prompts, and 75 and 67 percent cheaper above the threshold. Both figures are for the API; Sonnet 5 is also free to use as the default model on the free and Pro plans of Claude.ai, while Sol requires a paid ChatGPT plan or API access.

Is Claude Sonnet 5 cheaper than GPT-5.6 Sol?

Yes, decisively, on every line of the rate card. Sonnet 5 costs $2 per million input tokens and $10 per million output against Sol's promotional $4 and $20 — exactly half on both sides, and 75 and 67 percent below Sol's long-context rate of $8 and $30. Cached input is $0.20 per million on Sonnet 5 against $0.40 on Sol, a two-to-one gap rather than the two-and-a-half-to-one it was before OpenAI's August 21, 2026 cut. One honest complication narrows the effective gap: Anthropic states Sonnet 5's newer tokenizer counts roughly 30 percent more tokens for the same text, so an identical document is billed more tokens on Sonnet 5. Even after that adjustment, Sonnet 5 remains materially cheaper than Sol; the tokenizer trims the advantage rather than erasing it. If cost per token is your binding constraint, Sonnet 5 wins price outright.

Which is better for coding: GPT-5.6 Sol or Claude Sonnet 5?

On the independent evidence, GPT-5.6 Sol, but the data is one-sided. Sol places second at 66.57 on the Artificial Analysis Coding Agent Index v1.3, which pairs each model with a coding harness — Sol through Codex at max reasoning effort; Claude Sonnet 5 is not separately charted on that index in our sources, so there is no head-to-head independent agentic-coding score. Neither model has been submitted to the independently run SWE-bench Verified suite, so there is no third-party verified-coding figure for either — a genuine data gap we flag rather than fill. Each vendor publishes its own coding headline on a different suite: OpenAI reports Sol at 88.8 percent on Terminal-Bench 2.1, and Anthropic reports Sonnet 5 at 63.2 percent on SWE-bench Pro and 81.2 percent on OSWorld-Verified, both self-reported and not comparable across suites. If coding is your priority, Sol has the only independent agentic-coding index; benchmark both on your own repositories before committing.

Is GPT-5.6 Sol worth the higher price over Claude Sonnet 5?

It depends entirely on whether your workload uses the extra capability Sol's premium buys. Sol costs exactly twice Sonnet 5 per token on its promotional short-context rate, and up to four times on long prompts, and in return it delivers six more points on the Artificial Analysis Intelligence Index (59 to 53), a second-place Coding Agent Index v1.3 placement where Sonnet 5 is not charted, an ultra multi-agent reasoning mode, a slightly larger context, and a newer knowledge cutoff. For the hardest coding, long-horizon agents, and problems where a correct answer is worth far more than the token bill, that capability lead can pay for itself many times over. For high-volume, cost-sensitive, or everyday production work where the balanced Claude already clears your quality bar, paying flagship rates for capability you do not use is waste. The honest test is to run your real prompts on both, measure whether Sol's headroom changes outcomes on your tasks, and pay for the ceiling only where it earns its price.

Which has the larger context window: GPT-5.6 Sol or Claude Sonnet 5?

GPT-5.6 Sol, marginally. OpenAI's model documentation lists Sol at a 1,050,000-token context window with a February 16, 2026 knowledge cutoff, while Anthropic's documentation lists Claude Sonnet 5 at 1,000,000 tokens with a January 2026 cutoff. That is a five-percent difference in raw tokens rather than the two-to-one gaps seen in some matchups, so for most workloads it will not be the deciding factor. One subtlety cuts the other way on output: Sonnet 5 caps standard output at 128,000 tokens like Sol but can reach 300,000 output tokens through a Batch API beta header, so for very long single generations Sonnet 5's ceiling is higher. And Anthropic notes Sonnet 5's newer tokenizer produces roughly 30 percent more tokens for the same text, so a given document consumes more of Sonnet 5's window than of Sol's. Both models take text and image inputs and return text.

What is GPT-5.6 Sol, and how does it fit OpenAI's lineup?

GPT-5.6 Sol is the flagship capability tier of OpenAI's GPT-5.6 generation, generally available July 9, 2026 after a gated preview on June 26. In OpenAI's naming scheme the number is the generation and the names — Sol, Terra, and Luna — are durable capability tiers rather than model sizes. Sol is the top tier, aimed at the hardest problems: complex coding, long-horizon agents, cyber, science, and computer use. Below it, Terra is the balanced business tier and Luna the fastest and cheapest. Sol runs a 1,050,000-token context window with up to 128,000 output tokens, a February 16, 2026 knowledge cutoff, text and image inputs, and a reasoning-effort scale that climbs through xhigh and max to ultra, a multi-agent mode that runs up to sixteen reasoning agents in parallel. It adds Programmatic Tool Calling, where the model writes and executes JavaScript in an isolated runtime. API pricing is $4 per million input tokens and $20 per million output on promotional rates up to 272,000 input tokens, rising to $8 and $30 above that, and it is selectable in ChatGPT on paid plans as well as through the API and Codex.

What is Claude Sonnet 5, and how does it fit Anthropic's lineup?

Claude Sonnet 5 is Anthropic's midsize model, generally available June 30, 2026, and positioned as the best combination of speed and intelligence in the Claude family — the balanced workhorse tier below the Claude Opus 4.8 flagship and above the Claude Haiku 4.5 fast tier. Anthropic markets it as its most agentic midsize model and reports near-Opus results at a fraction of the price, including a self-reported 63.2 percent on SWE-bench Pro and 81.2 percent on OSWorld-Verified. It runs a 1,000,000-token context window with up to 128,000 output tokens — 300,000 through a Batch beta — a January 2026 knowledge cutoff, adaptive thinking with an effort dial that defaults to high, and text and image inputs to text output. Critically, it is the default model on the free and Pro plans of Claude.ai, which puts it in front of a vast consumer audience at no cost, and it is available in Claude Code and via the API at model id claude-sonnet-5.

Does the tokenizer difference matter when comparing prices?

Yes, more than most rate-card comparisons admit, though it does not flip this one. Anthropic's own documentation states that Claude Sonnet 5's newer tokenizer produces approximately 30 percent more tokens for the same text than earlier models, with the exact figure depending on content. Because API billing is per token, that means an identical prompt and response are counted as more tokens on Sonnet 5, so its lower per-token rate buys a little less than the sticker gap suggests. As an illustration only: Sonnet 5's $2 input undercuts Sol's promotional $4 by 50 percent on paper, and even after inflating Sonnet 5's token count by 30 percent the effective input cost stays about a third below Sol's. Anthropic frames the tokenizer as contributing to improved performance, so it is a trade-off rather than a pure penalty. The practical takeaway is that Sonnet 5 remains clearly cheaper than Sol after the adjustment, but you should compare cost on your own real workloads rather than on the rate card alone.

Which model is faster: GPT-5.6 Sol or Claude Sonnet 5?

On independent measurement, Claude Sonnet 5, and this is a genuine head-to-head because Artificial Analysis publishes an output-speed figure for both. It clocks Claude Sonnet 5 at 79 output tokens per second and GPT-5.6 Sol at about 74.5, so Sonnet 5 is modestly faster on measured throughput. The gap is small and both are mid-pack rather than the fastest models available, so for most interactive work neither will feel dramatically quicker than the other. Speed also shifts with Sol's reasoning effort: at its higher xhigh, max, and ultra settings Sol spends more time reasoning before it answers, which lowers effective throughput on hard tasks in exchange for better answers. If latency is your deciding factor, Sonnet 5 has the edge on the published number, but benchmark both on your own traffic, because tokens per second on a leaderboard rarely matches your production mix.

Which model should I choose for production work?

Split by priority, because the two answer different questions. Pick GPT-5.6 Sol if your work is the hardest coding, long-horizon agents, science, or reasoning where the six-point intelligence lead (59 to 53), Sol's charted Coding Agent Index result, and the ultra multi-agent mode change outcomes, and where a correct answer is worth far more than the token cost. Pick Claude Sonnet 5 if price is the deciding factor — its $2 input and $10 output are half Sol's promotional rate on every line — or if you want measured output speed, the free default on Claude.ai for prototyping, or a higher 300,000-token output ceiling. For many teams the rational move is a split stack: run high-volume, cost-sensitive work on Sonnet 5, and route only the tasks that measurably need the extra headroom to Sol. Prototype the same production prompts on both, measure real cost and quality on your own data, and route by workload rather than picking one model for everything.

What are the alternatives to GPT-5.6 Sol and Claude Sonnet 5?

Several sit close by on both sides of this flagship-versus-value divide. Inside Anthropic's own lineup, Claude Opus 4.8, at $5 per million input and $25 per million output tokens, posts 88.6 percent on the independent SWE-bench Verified suite and is the flagship Sonnet 5 is measured against as near-Opus, while Claude Fable 5 tops the Artificial Analysis Intelligence Index at 60, one point above Sol. On OpenAI's side, GPT-5.6 Terra is Sol's balanced sibling at $2.00 input and $12 output, a closer price match to Sonnet 5, and GPT-5.5 remains active as the prior flagship. Google's Gemini 3.1 Pro is another frontier option. For the adjacent matchups in detail, our Claude Sonnet 5 versus Claude Opus 4.8 comparison covers the workhorse-versus-flagship trade-off inside Anthropic, and our Claude Sonnet 5 versus GPT-5.5 comparison covers the previous OpenAI-versus-Anthropic round.

Final Verdict — Flagship vs Balanced Claude, a True Split

After running both side-by-side, verifying pricing on both vendors' own documentation, and holding every capability claim to independent benchmarks, our verdict is a genuine split — not a diplomatic one. GPT-5.6 Sol is the capability, coding, and reasoning leader: it scores 59 to Claude Sonnet 5's 53 on the Artificial Analysis Intelligence Index, places second at 66.57 on the Coding Agent Index v1.3 where Sonnet 5 is not charted, carries an ultra multi-agent reasoning mode, a marginally larger 1,050,000-token context, a newer February 16, 2026 cutoff, and the only LMArena Elo of the pair. Claude Sonnet 5 is the price, speed, and reach leader: its $2 input and $10 output per million tokens are exactly half Sol's promotional rate on both sides and a quarter to a third of Sol's long-context rate, it is measured faster at 79 output tokens per second, it is the free default model on Claude.ai, and it offers a higher 300,000-token output ceiling. We disclose plainly that we have no affiliate relationship with either vendor and tested both through our own API keys.

We did not crown a single overall winner because the evidence does not support one honestly: Sol's capability lead is real but rests partly on one-sided data gaps where Sonnet 5 is not charted, and it comes at twice the price on short prompts and up to four times on long ones; Sonnet 5's price and speed advantages are real but come a clear tier below Sol on measured intelligence, and its price lead is narrowed by a heavier tokenizer. The honest framing is not which model is better but whether your workload needs the flagship. If your work is the hardest reasoning, the most demanding agentic coding, or long-horizon agents — pick GPT-5.6 Sol and pay for the ceiling. If your priority is price, speed, free reach, or everyday production work the balanced Claude already handles — pick Claude Sonnet 5 and bank the difference. For many teams the rational endgame is a split stack: run the volume on Sonnet 5, and route only the tasks that measurably need the extra headroom to Sol. For the models and rivals around this matchup, see our GPT-5.6 Sol review, our Claude Sonnet 5 review, our Claude Opus 4.8 review, our GPT-5.6 Terra review, our Claude Sonnet 5 vs Claude Opus 4.8 comparison, and our Claude Sonnet 5 vs GPT-5.5 comparison.

Sources

Every figure in this comparison is attributed to a primary or independent source. Pricing and specifications come from each vendor's own documentation; capability scores come from independent third parties; self-reported figures are labeled as such throughout.

• OpenAI — GPT-5.6 announcement, tiers, and positioning
• OpenAI — GPT-5.6 Sol model documentation and specifications
• OpenAI — GPT-5.6 Sol API pricing
• Anthropic — Claude Sonnet 5 model documentation and specifications
• Anthropic — Claude Sonnet 5 API pricing
• Artificial Analysis — Intelligence Index, cost per task, and output speed
• Artificial Analysis — Coding Agent Index v1.3 leaderboard (Sonnet 5 not charted)
• LMArena — human-preference Elo leaderboard
• vals.ai — SWE-bench Verified independent leaderboard

Last compared: July 2026; Sol's pricing re-verified on August 28, 2026, after OpenAI cut it on August 21, 2026. GPT-5.6 Sol reached general availability on July 9, 2026, and Claude Sonnet 5 on June 30, 2026. Claude Sonnet 5's $2 and $10, announced at launch as introductory pricing through August 31, 2026, became the standard price on August 10, 2026 when Anthropic cancelled the scheduled increase. Both models are recent, and we will revise this comparison as independent benchmark coverage matures.