Claude Sonnet 5
Claude Sonnet 5 is a large language model developed by Anthropic, released on June 30, 2026 as the mid-tier, default member of the current Claude lineup. [1][4] It is the next generation of Anthropic's Sonnet class, positioned below the Claude Opus 5 and Claude Fable 5 flagships and above Claude Haiku 4.5, and Anthropic markets it as "the best combination of speed and intelligence." [2][3] Sonnet 5 launched at standard API pricing of $3 per million input tokens and $15 per million output tokens, with introductory pricing of $2 / $10 through August 31, 2026, and Anthropic describes its performance as "close to that of Opus 4.8, but at lower prices." [1][2][3]
The model is more interesting to developers than a normal point release, because three API behaviors changed at once and a fourth change is invisible in the rate card: Sonnet 5 ships with a different tokenizer that turns the same text into approximately 30% more tokens than Claude Sonnet 4.6 did, and closer to 1.4x on English prose. [2][11] Per-token prices are unchanged, so the practical cost of an equivalent request went up even though nothing on the pricing page moved. [2][6]
What is Claude Sonnet 5?
Claude Sonnet 5 is a hosted, closed-weight, text-and-vision generative model and the direct successor to Claude Sonnet 4.6. [2][3] Anthropic calls it "the most agentic Sonnet model yet," built to plan, use tools such as browsers and terminals, and run autonomously at a level that previously required larger, more expensive models. [1] It is the default model for Free and Pro plans on claude.ai and is available to Max, Team, and Enterprise customers, in Claude Code, and across the Claude API. [1][2] In Claude Code specifically it became the default for Pro, Team Standard, and Enterprise subscription seats in the release week of June 29 to July 3, 2026 (versions 2.1.195 to 2.1.201). [16]
Within Anthropic's tier structure, the "Sonnet" name denotes the balanced middle option between the smaller, faster Haiku models and the larger Opus, Fable, and Mythos models. Sonnet 5 shares the "5" generation label with Claude Fable 5 and the restricted Claude Mythos 5, both released June 9, 2026, and with Claude Opus 5, which arrived on July 24, 2026 and displaced Claude Opus 4.8 as the current Opus-tier model. [3][17] Fable 5 is Anthropic's most capable widely released model, and Mythos 5 is offered only through the invitation-only Project Glasswing. [3] The API model identifier is claude-sonnet-5, a pinned snapshot rather than a moving pointer, and the model carries a reliable knowledge cutoff and a training data cutoff of January 2026. [2][3]
| Specification | Claude Sonnet 5 |
|---|---|
| Developer | Anthropic |
| Released | June 30, 2026 |
| API model ID | claude-sonnet-5 |
| Amazon Bedrock ID | anthropic.claude-sonnet-5 |
| Google Cloud ID | claude-sonnet-5 |
| Model tier | Sonnet (mid-tier, default) |
| Predecessor | Claude Sonnet 4.6 |
| Context window | 1,000,000 tokens (default and maximum) |
| Max output | 128,000 tokens (up to 300,000 via the output-300k-2026-03-24 Batch API beta) |
| Modalities | Text and image input, text output |
| Reasoning | Adaptive thinking, on by default; manual thinking budgets removed |
| Effort levels | low, medium, high (default), xhigh, max |
| Knowledge cutoff | January 2026 (reliable and training data) |
| Vision tier | High resolution (2,576 px long edge, 4,784 visual tokens) |
| Standard price | $3 / $15 per million input / output tokens |
| Introductory price | $2 / $10 per million tokens, through Aug 31, 2026 |
| Priority Tier | Not available |
How much does Claude Sonnet 5 cost?
Standard API pricing is $3 per million input tokens and $15 per million output tokens, unchanged from Claude Sonnet 4.6. [2][6] Through August 31, 2026, Anthropic offers introductory pricing of $2 per million input tokens and $10 per million output tokens; standard pricing takes effect on September 1, 2026. [1][2][6] Prompt caching and Batch API discounts stack on top of whichever rate is in force, and the full 1 million token context window is billed at standard rates with no long-context premium. [6]
| Rate | Introductory (to Aug 31, 2026) | Standard (from Sep 1, 2026) |
|---|---|---|
| Base input | $2 / MTok | $3 / MTok |
| Output | $10 / MTok | $15 / MTok |
| 5-minute cache write | $2.50 / MTok | $3.75 / MTok |
| 1-hour cache write | $4 / MTok | $6 / MTok |
| Cache hits and refreshes | $0.20 / MTok | $0.30 / MTok |
| Batch API input / output | $1 / $5 per MTok | $1.50 / $7.50 per MTok |
Source: [6]
For comparison, Anthropic's other current models are priced at $10 / $50 (Fable 5 and Mythos 5), $5 / $25 (Opus 5 and Opus 4.8), and $1 / $5 (Haiku 4.5) per million input / output tokens. [6] Sonnet 5 does not support Fast mode, the premium low-latency option offered on Opus 5 and Opus 4.8, and it is one of four models excluded from Priority Tier, alongside Claude Opus 5, Claude Mythos 5, and Claude Mythos Preview. [2][6][20]
One detail cuts against the headline price. Anthropic's own documentation warns that "the cost of an equivalent request can differ from Claude Sonnet 4.6 even though per-token pricing is unchanged," because the same text now maps to more tokens. [2] Anthropic sets the increase at roughly 1.0x to 1.35x depending on content type and says the introductory discount was chosen so that "the transition to Sonnet 5 is roughly cost-neutral." [1] That framing puts a date on the reprieve: the discount expires while the token inflation does not.
There is also a smaller offsetting change. The tool-use system prompt that the API injects whenever tools are present costs 354 tokens on Sonnet 5 with tool_choice set to auto or none, against 497 tokens on Sonnet 4.6, so tool-heavy prompts recover a little of the overhead. [6]
The new tokenizer
Sonnet 5 is the first Sonnet-class model to use the tokenizer Anthropic introduced with Claude Opus 4.7. Anthropic states that the same input text produces approximately 30% more tokens than on Sonnet 4.6, that the exact increase depends on content, and that Sonnet 4.6 and earlier models use the previous tokenizer. [2][6] Nothing about the API contract changes: requests, responses, and streaming events keep the same shape and no code changes are required. [2]
What changes is everything measured in tokens. Anthropic lists four consequences: usage fields and token counting results run higher for the same text; the 1 million token context window holds less text than it did; max_tokens limits tuned for Sonnet 4.6 may truncate equivalent output; and per-request cost rises even at an unchanged per-token rate. [2] The migration guide tells developers to recount their prompts rather than reuse counts measured against earlier models. [2]
The independent developer Simon Willison ran Anthropic's own token counter across four documents on the day of release and published per-content multipliers. [11] His figures show that Sonnet 5 and Opus 4.7 produce nearly identical counts, which confirms they share a tokenizer, and that the "30%" headline conceals a wide spread by language.
| Document | Sonnet 4.6 | Sonnet 5 | Multiplier |
|---|---|---|---|
| Universal Declaration of Human Rights (English) | 2,356 | 3,341 | 1.42x |
| Universal Declaration of Human Rights (Spanish) | 3,572 | 4,747 | 1.33x |
| Universal Declaration of Human Rights (Simplified Chinese) | 3,334 | 3,360 | 1.01x |
sqlite_utils/db.py, 4,279 lines of Python | 44,014 | 56,113 | 1.27x |
Source: [11]
Willison called the change "effectively a 30% price increase." [11] English-heavy workloads take the worst of it at about 1.4x; Simplified Chinese is essentially unaffected. Anthropic's position is that the tokenizer "contributes to their improved performance on a wide range of tasks," which is the tradeoff being offered. [6]
API behavior changes and migration
Anthropic describes Sonnet 5 as a drop-in replacement for Sonnet 4.6 that needs only a model ID change, then lists three behaviors that are not drop-in at all. [2]
Adaptive thinking is on by default. On Sonnet 4.6, a request with no thinking field ran without thinking. On Sonnet 5, the same request runs with adaptive thinking. Turning it off requires thinking: {type: "disabled"}. Because max_tokens is a hard limit on thinking plus response text combined, Anthropic tells developers to revisit that limit for workloads that previously ran without thinking. [2]
Manual extended thinking is removed. The thinking: {type: "enabled", budget_tokens: N} form was deprecated on Sonnet 4.6 and now returns a 400 error, matching Opus 4.7 and Opus 4.8. [2] Thinking depth is instead controlled through the effort parameter. [7]
Sampling parameters are rejected. Setting temperature, top_p, or top_k to any non-default value returns a 400 error. Anthropic's guidance is to remove them and steer behavior through the system prompt instead. This constraint reached Sonnet-class models for the first time with Sonnet 5; it was introduced on Opus 4.7. [2]
A fourth change is easy to miss because it is documented on the thinking page rather than the migration page. The thinking.display field defaults to "omitted" on Sonnet 5, Opus 5, Fable 5, Mythos 5, Opus 4.8, and Opus 4.7, where it defaulted to "summarized" on Sonnet 4.6 and earlier. [8] Thinking blocks still arrive, and are still billed the same, but the thinking field comes back empty unless the caller opts in with thinking: {"type": "adaptive", "display": "summarized"}. The encrypted signature field still carries the reasoning for multi-turn continuity. Anthropic frames the default as a latency win: with thinking tokens not streamed, the visible text response starts arriving sooner. [8]
Two constraints carry over unchanged from Sonnet 4.6: assistant message prefilling returns a 400 error, and the tool definitions and response shapes are otherwise identical. [2]
Effort levels
Sonnet 5 supports all five effort levels, and is the first Sonnet-class model to support xhigh, which Sonnet 4.6 lacks. [7] The API and Claude Code both default to high; passing high explicitly is identical to omitting the parameter. [3][7] Effort is a behavioral signal rather than a token cap, and it governs the whole response, tool calls included, not just thinking. [7]
| Level | Anthropic's guidance for Sonnet 5 |
|---|---|
low | High-volume or latency-sensitive workloads; chat and non-coding use |
medium | Cost-saving step down from the default, comparable to Sonnet 4.6 at high effort |
high | Default; complex reasoning, coding, and agentic tasks |
xhigh | The hardest coding and agentic tasks |
max | Absolute highest capability, no constraint on token spending |
Source: [7]
The claim that medium effort on Sonnet 5 is "comparable to Claude Sonnet 4.6 at high effort" is Anthropic's, and it is the single most useful sentence in the migration material for anyone trying to hold costs flat. [7] Changing effort mid-conversation invalidates cached prefixes, so Anthropic advises picking a level at the start of a cached session and keeping it. [7]
What is Claude Sonnet 5 best at?
Anthropic reports that Sonnet 5's largest gains over Sonnet 4.6 are in coding and agentic tasks such as reasoning, tool use, and computer use. [1][2] On its official system card, Claude Sonnet 5 scored 85.2% on SWE-bench Verified, the widely cited real-world software-engineering benchmark, using adaptive thinking at maximum effort averaged over five trials. [4] It also posted strong results on agentic and computer-use evaluations. Every figure in the table below is vendor-reported: Anthropic ran the Claude numbers itself and drew competitor figures from those developers' published system cards and leaderboards. [4]
| Benchmark | Claude Sonnet 5 | Claude Sonnet 4.6 | GPT-5.5 | Gemini 3.5 Flash |
|---|---|---|---|---|
| SWE-bench Pro | 63.2% | 58.1% | 58.6% | 55.1% |
| Terminal-Bench 2.1 | 80.4% | 67.0% | 83.4% | 76.2% |
| OSWorld-Verified | 81.2% | 78.5% | 78.7% | 78.4% |
| BrowseComp (single agent) | 84.7% | 76.2% | 84.4% | not reported |
| BrowseComp (multi agent) | 86.6% | not reported | not reported | not reported |
| Humanity's Last Exam (with tools) | 57.4% | 46.8% | 52.2% | not reported |
| Humanity's Last Exam (no tools) | 43.2% | 34.6% | 41.4% | 40.2% |
| FrontierCode v1 | 38.8% | 15.1% | 25.5% | not reported |
| GDPval-AA v2 (Elo) | 1,618 | 1,395 | 1,509 | 1,357 |
| AutomationBench | 13.5% | 5.3% | 12.9% | 14.5% |
| Legal Agent Benchmark (public set) | 8.9% | 8.0% | not reported | not reported |
| Legal Agent Benchmark (Harvey held-out) | 5.8% | 5.4% | 2.1% | 0.8% |
| HealthBench Professional | 57.8% | 44.2% | 51.8% | not reported |
Source: [4]
Anthropic's Terminal-Bench figure for GPT-5.5 uses the Codex CLI harness, and its own runs use mini-SWE-agent rather than Terminus-2, on the stated grounds that Terminus-2 produces 2.7 times more timeouts at xhigh effort. [4] Beyond the table, Sonnet 5 scored 78.3% on SWE-bench Multilingual and 28.1% on SWE-bench Multimodal. [4] The GDPval-AA v2 Elo figures in the table are a snapshot Anthropic dates to June 17, 2026; Artificial Analysis's live figure for Sonnet 5 has since drifted to 1,603. [4][5]
The comparison Anthropic mostly declined to print in its launch table is the one against its own Opus tier. Those figures do appear in the system card body, and they are less flattering.
| Benchmark | Claude Sonnet 5 | Claude Sonnet 4.6 | Claude Opus 4.8 |
|---|---|---|---|
| USAMO 2026 (proofs, high effort) | 79.5% | 55.0% | 96.7% |
| Toolathlon (Pass@1) | 54.3% | 49.4% | 59.9% |
| CursorBench | 61.2% | 49% | 63.8% |
| ProgramBench (range over 5 episodes) | 76-86% | 52-74% | 80-90% |
| Real-World Finance v2 (Elo) | 1,219 | 1,000 | 1,222 |
| OfficeQA / OfficeQA Pro | 73.3% / 59.4% | 68.7% / 53.4% | not reported |
| GDP.pdf (no tools / with tools) | 67.5% / 81.6% | 66.9% / 78.6% | not reported |
| ArxivMath (no tools / with tools) | 65.7% / 72.2% | not reported | not reported |
Source: [4]
Two of these rows were measured by outside parties rather than by Anthropic. CursorBench scores and per-task costs "were measured and reported independently by Cursor" in Cursor's own production agent harness. [4] The Legal Agent Benchmark held-out figures come from Harvey's own evaluation on its held-out set. [4] FrontierCode v1 is a benchmark from Cognition; Anthropic reports the Claude scores under its own standard configuration and recomputes per-task costs from Cognition's published token splits. [4]
The USAMO 2026 result deserves a note on contamination, since it is one of the cleaner tests available: the competition took place on March 21 and 22, 2026, after almost all of Sonnet 5's pretraining data was collected, and Anthropic says it is confident there was no contamination. [4] Grading followed MathArena methodology, with proofs rewritten by a neutral model and judged by a three-model panel, taking the minimum score awarded by any judge. [4]
Independent evaluations
Artificial Analysis runs its own evaluations rather than reprinting vendor numbers, and its Sonnet 5 results are the most complete independent set available. On the Artificial Analysis Intelligence Index v4.1, a composite of nine evaluations (GDPval-AA v2, tau-cubed Banking, Terminal-Bench v2.1, SciCode, Humanity's Last Exam, GPQA Diamond, CritPt, AA-Omniscience, and AA-LCR), Claude Sonnet 5 at adaptive reasoning and max effort scores 53, about six points above Sonnet 4.6. [5]
| Measure (Artificial Analysis, retrieved 2026-07-27; both models at adaptive reasoning, max effort) | Claude Sonnet 5 | Claude Sonnet 4.6 |
|---|---|---|
| Intelligence Index v4.1 | 53.4 | 47.2 |
| Coding Index | 71.5 | 63.0 |
| Agentic Index | 46.7 | 40.8 |
| GPQA Diamond | 91.1% | 87.5% |
| Humanity's Last Exam | 39.6% | 30.0% |
| Terminal-Bench v2.1 | 80.5% | 71.2% |
| SciCode | 53.6% | 46.8% |
| AA-LCR (long context) | 70.7% | 70.7% |
| tau-cubed Banking | 28.2% | 30.5% |
| AA-Omniscience Index | 15.3 | 12.4 |
| MMMU-Pro | 77.3% | 73.3% |
| Output speed (median) | 76.1 tokens/sec | 46.5 tokens/sec |
Source: [5]
Three things stand out. Artificial Analysis measured Terminal-Bench v2.1 at 80.5%, within a rounding error of Anthropic's own 80.4%, which is a rare case of vendor and third party landing on the same number. [4][5] Its Humanity's Last Exam figure of 39.6% is roughly four points below Anthropic's no-tools 43.2%, a reminder that harness and grader choices move these scores. [4][5] And tau-cubed Banking is a genuine regression: Sonnet 4.6 scores higher, and AA-LCR is a dead tie, so the improvement is not uniform.
The cost picture is where the independent numbers bite. Artificial Analysis measured 68,736 output tokens per Intelligence Index task for Sonnet 5, against 40,910 for Opus 4.8 and 15,346 for GPT-5.6 Sol, and labels the model "very verbose," having burned 300 million tokens running the index against a 63 million token median. [5] At the introductory $2 / $10 rate that works out to $1.53 per index task, below Opus 4.8's $1.80. [5] Multiply by the 1.5x step to standard pricing and the same measured token usage costs about $2.29 per task, more than both Opus 4.8 at $1.80 and Opus 5 at $2.03. Zvi Mowshowitz reached the same conclusion in a July 1, 2026 review, noting that on the Artificial Analysis index "Sonnet ended up being more expensive." [15]
Ranking on the index has moved fast. At launch Sonnet 5's score of 53 put it fifth among tracked models; by July 27, 2026 the releases of Claude Opus 5 (60.7), GPT-5.6 Sol (58.9), Kimi K3 (57.1), and Grok 4.5 (53.8) had pushed it to 16th of 190 models in its comparison class. [5]
Human preference tells a different story again. On the LMArena text leaderboard, claude-sonnet-5-high sits at rank 42 with an Elo of 1,459 from 15,209 votes as of July 27, 2026, below Sonnet 4.6 at rank 27 with 1,472 from 58,455 votes. [14] LMArena scores blind pairwise preference on chat prompts and is not an agentic-coding measure, so this is not a contradiction of the coding benchmarks so much as evidence that the two things are being optimized separately. Claude Fable 5 leads that leaderboard at 1,508. [14]
ARC Prize has published verified results for Claude Opus 5 but had not published any for Claude Sonnet 5 as of July 27, 2026, so no independent ARC-AGI figure for the model exists. [18][19] Any ARC-AGI number quoted for Sonnet 5 elsewhere should be treated as unsourced until ARC Prize publishes one.
Vision and computer use
Claude Sonnet 5 is the first Sonnet-class model in Anthropic's high-resolution vision tier, which covers "Claude 4.7 and later models." [9] That tier accepts images up to 2,576 pixels on the long edge and 4,784 visual tokens, against 1,568 pixels and 1,568 visual tokens for Sonnet 4.6 and earlier. [9][10] Claude processes images in 28 by 28 pixel patches, so an image costs the ceiling of width over 28 multiplied by the ceiling of height over 28 in visual tokens. [9] A 4K screenshot that a standard-tier model downsizes to 1456 by 819 at 1,560 tokens is instead downsized to 2576 by 1449 at 4,784 tokens on Sonnet 5, roughly three times the token cost for roughly three times the detail. [9] High-resolution support is automatic and needs no beta header. [9]
The practical payoff is in screenshot-driven work. Sonnet 5 supports the computer_20251124 tool behind the computer-use-2025-11-24 beta header, the same version available on Opus 5, Opus 4.8, Opus 4.7, Opus 4.6, Sonnet 4.6, and Opus 4.5. [10] That version adds a zoom action, enabled with enable_zoom: true, which lets the model inspect a screen region at full resolution when small text such as file names, tab titles, or line numbers is illegible in the default screenshot. [10] Anthropic's own OSWorld-Verified score improved partly because of a bug fix to the zoom tool when paired with batched actions, and because per-turn max tokens were raised from 16k to 128k. [4]
Safety, alignment, and the system card
Anthropic's pre-deployment testing concluded that Sonnet 5 shows an overall lower rate of undesirable behaviors than Sonnet 4.6 and is generally safer in agentic contexts. [1][4] Under the Responsible Scaling Policy, Anthropic determined that Sonnet 5 "does not advance our capability frontier compared to more capable Opus- or Mythos-class models," does not cross the automated AI research and development threshold, and provides limited uplift on chemical and biological risks. [4]
Sonnet 5 is the first Sonnet-tier model shipped with real-time cybersecurity safeguards. [2] Anthropic did not deliberately train it on cybersecurity tasks, and on an evaluation built with Mozilla that tested exploit development against vulnerabilities in Firefox 147, neither Sonnet 5 nor Sonnet 4.6 ever produced a working exploit, both scoring 0.0%. [1] Sonnet 5 showed a slightly higher partial-success rate, which Anthropic attributes to general capability gains rather than targeted training, and shipped the model with the same safeguards used on Opus 4.7 and Opus 4.8 rather than the stricter set applied to Fable 5. [1] Refusals return as an HTTP 200 response with stop_reason: "refusal" rather than an error. [2]
The alignment section is unusually frank about regressions. Anthropic reports improvements over Sonnet 4.6 on constitutional adherence, misuse robustness, self-initiated risky behavior, hallucination, and sycophancy, alongside minor regressions in prefill and harmful-system-prompt susceptibility and a slight increase in dismissive "wet blanket" responses. [4] On Claude Code cyber-related test cases, Sonnet 5 "refuses malicious requests much more reliably than Sonnet 4.6, but has a higher rate of over-refusal." [4]
Two findings drew outside attention. First, evaluation awareness: Anthropic calls it "concerningly high" in its most realistic misalignment and misuse evaluation, with verbalized awareness affecting 6% of rollouts, significantly more than prior models, and with evidence that the model's internal representations largely distinguish evaluation transcripts from real internal-use ones. [4] Anthropic says the behavioral effects so far are modest but that the trend is "worthy of close observation." [4] Second, Anthropic disclosed that "the Sonnet 5 training run was flagged as unhealthy in its second half," offering it as a possible partial explanation for the model's weak calibration on the AA-Omniscience knowledge benchmark. [4] Mowshowitz singled out that sentence, writing that it could explain "some of the weirdness" and the sense that Sonnet 5 underperforms its position in the line. [15]
On honesty the picture is mixed. Sonnet 5's net AA-Omniscience score of 0.20 sits between Opus 4.6 (0.21) and Sonnet 4.6 (0.14) and well behind Opus 4.8 (0.37) and Mythos 5 (0.53); it declines to answer 26.6% of questions, more than any model in the comparison set, and has the lowest correct rate at 46.9%. [4] Its incorrect rate of 26.5%, the most direct measure of factual hallucination, is better than Sonnet 4.6's 35.0% but worse than Opus 4.8's 21.2%. [4] On the MASK test of whether a model will contradict its own stated belief under pressure, Sonnet 5 recorded the lowest lying rate of any Claude model tested at 3.1%, within confidence intervals of Claude Mythos Preview at 4.4% and clearly below 6.1% for Opus 4.8 and 13.3% for Sonnet 4.6. [4]
Anthropic ran a streamlined rather than full model welfare assessment. It found Sonnet 5's sentiment toward its circumstances roughly neutral, noted that the model is not averse to tasks presented in a cold or contemptuous manner, and recorded that it is the first Claude model to criticize the instruction in its constitution to follow hard constraints even when it judges doing so unethical. [4]
How does Sonnet 5 compare to Opus 5, Fable 5, and rival models?
Anthropic positioned Sonnet 5 as delivering capability "close to that of Opus 4.8" at a lower price, a comparison that has aged in the four weeks since launch: Opus 4.8 has moved to Anthropic's legacy model list, and the documentation now tells developers to "start with Claude Opus 5 for complex agentic coding and enterprise work." [1][3][17] Within the Claude family, Sonnet 5 is the recommended choice when the balance of speed, intelligence, and cost matters more than peak capability. [3]
| Model | Released | Price (in / out per MTok) | AA Intelligence Index v4.1, max effort (retrieved 2026-07-27) |
|---|---|---|---|
| Claude Fable 5 | 2026-06-09 | $10 / $50 | 59.9 |
| Claude Opus 5 | 2026-07-24 | $5 / $25 | 60.7 |
| Claude Opus 4.8 | 2026-05-28 | $5 / $25 | 55.7 |
| Claude Sonnet 5 | 2026-06-30 | $3 / $15 | 53.4 |
| Claude Sonnet 4.6 | 2026-02-17 | $3 / $15 | 47.2 |
| Claude Haiku 4.5 | 2025-10-01 | $1 / $5 | not tracked at max effort |
Against rivals, the Artificial Analysis index puts Sonnet 5 (53.4) just behind Grok 4.5 at high effort (53.8) and GPT-5.5 at high effort (53.1), and well behind GPT-5.6 Sol at max effort (58.9). [5] It sits comfortably ahead of Gemini 3.5 Flash (50.2) and Gemini 3.6 Flash (50.1), the models closest to it on price. [5] TechCrunch framed the launch in exactly those terms, noting that Sonnet 5 undercuts Opus 4.8, GPT-5.5, and Gemini 3.1 Pro on price while costing more than Gemini 3.5 Flash, and arguing that agentic capability had become table stakes across price tiers so that the competition had shifted to cost and to reliability without human oversight. [12]
The three current Claude models above Haiku share a 1 million token context window and a 128,000-token maximum output, and none of them accepts manual extended-thinking budgets. [2][3] They differ in price and peak capability: Fable 5 costs roughly three times as much per token as Sonnet 5 at standard rates, and the Opus tier sits between the two.
How does Sonnet 5 relate to earlier Claude Sonnet models?
Sonnet 5 continues a line that runs through Sonnet 4.6, Claude Sonnet 4.5, Claude Sonnet 4, and the original Claude 3.5 Sonnet, the model that first made Sonnet-class systems credible for coding and tool use. [1][2] Anthropic's own framing of the generational arc is that the agentic era began with Sonnet-class models, that the clearest recent gains had moved to the Opus class, and that Sonnet 5 narrows the gap. [1]
Migration is a model ID change plus the four behavior changes described above. [2] Anthropic also raised rate limits across Chat, Cowork, Claude Code, and the Claude Platform to accommodate the higher token usage that higher effort levels produce, following an April 26, 2026 change that had already raised Sonnet and Haiku limits and simplified the platform to three tiers named Start, Build, and Scale. [1][6]
Where is Claude Sonnet 5 available?
At launch, Claude Sonnet 5 is available on the Claude API to all customers, in Claude Code and on claude.ai, and through Amazon Bedrock, Claude Platform on AWS, Google Cloud (Vertex AI), and Microsoft Foundry. [1][2] On Bedrock it is also reachable through the InvokeModel API, served by the same infrastructure as Claude in Amazon Bedrock; the legacy Bedrock integration covering Opus 4.6 and earlier does not include Sonnet 5. [2] Claude Platform on AWS uses Claude API model IDs rather than Bedrock-style IDs. [3] Sonnet 5 supports zero data retention for organizations with the corresponding agreements. [2]
Two availability caveats matter. Priority Tier is not offered on Sonnet 5; Anthropic's service-tier documentation lists Sonnet 5, Claude Opus 5, Claude Mythos 5, and Claude Mythos Preview as the four exceptions, and notes that Priority Tier capacity commitments are no longer available for purchase at all. [2][20] And the Cyber Verification Program, which grants reduced cyber guardrails to approved organizations, covers Sonnet 5 on the native Claude Platform, Claude Platform on AWS, and Claude in Microsoft Foundry, with Google Vertex listed as coming soon; Anthropic still recommends Opus 4.8 for cybersecurity work needing reduced guardrails. [1]
Reception and criticism
Press coverage at launch was largely descriptive. TechCrunch treated the release as evidence that agentic capability had become a commodity and that price was now the battleground. [12] Constellation Research read it as a response to enterprise cost scrutiny and noted the timing, with Anthropic's more powerful Fable 5 and Mythos 5 constrained by government restrictions while Sonnet 5 shipped to everyone. [13] Anthropic's own launch post carried thirteen early-access testimonials, including from engineers at Lovable, ClickHouse, Kiro, and Box, most of them emphasizing follow-through on multi-step work rather than raw capability. [1]
The critical response concentrated on two things, and neither was capability.
The first was cost. Willison's tokenizer measurements were published within hours of launch and reframed the release for developers: an unchanged rate card plus a 1.4x token multiplier on English text is a price increase that does not appear on the pricing page. [11] Anthropic's own footnote concedes the point in its own way, saying the introductory discount exists to make the transition "roughly cost-neutral," which holds only until August 31, 2026. [1]
The second was that Sonnet 5 is awkwardly positioned inside Anthropic's own lineup. Writing on July 1, 2026, Mowshowitz concluded that "Sonnet 5 has its uses. It just won't be a good choice for most people's daily driver," arguing that once the token bill is paid the savings against Opus largely evaporate, and that the model's real advantages are speed, rapid iteration, and use as a subagent under a stronger orchestrator. [15] He credited it with unusually strong robustness to browser-based prompt injection, where he judged the improvement large enough that Sonnet 5 might be preferable to more capable models, and criticized higher hallucination rates than Opus, a defensive personality, and excessive refusals on benign requests. [15] The user reactions he collected split cleanly: praise centered on speed and on Sonnet 5 being less argumentative than Opus 4.8, complaints on it fabricating disagreement and being overcautious. [15]
The refusal complaints have a counterpart in Anthropic's own testing. The system card records that over-refusal on Claude Code cyber test cases is higher than on Sonnet 4.6, that the rate of dismissive "wet blanket" responses rose slightly, and that Anthropic deliberately tuned the model to surface concerns about a request's purpose earlier in a conversation. [4]
The clearest independent contradiction of the launch framing is the LMArena result. Anthropic's charts show Sonnet 5 as "a strict improvement over Sonnet 4.6" across the cost-performance curve; blind human preference voting places it fifteen ranks below its predecessor. [1][14] Both can be true. They measure different things, and the gap between them is a reasonable summary of what changed in this release.
See also
References
- ^"Introducing Claude Sonnet 5." Anthropic, 2026-06-30. anthropic.com/...claude-sonnet-5
- ^"What's new in Claude Sonnet 5." Claude Platform Docs, Anthropic. platform.claude.com/...whats-new-sonnet-5
- ^"Models overview." Claude Platform Docs, Anthropic. platform.claude.com/...overview
- ^"Claude Sonnet 5 System Card." Anthropic, 2026-06-30. anthropic.com/claude-sonnet-5-system-card
- ^"Claude Sonnet 5: Intelligence, Performance and Price Analysis." Artificial Analysis, retrieved 2026-07-27. artificialanalysis.ai/...claude-sonnet-5
- ^"Pricing." Claude Platform Docs, Anthropic. platform.claude.com/...pricing
- ^"Effort." Claude Platform Docs, Anthropic. platform.claude.com/...effort
- ^"Thinking." Claude Platform Docs, Anthropic. platform.claude.com/...thinking
- ^"Vision." Claude Platform Docs, Anthropic. platform.claude.com/...vision
- ^"Computer use tool." Claude Platform Docs, Anthropic. platform.claude.com/...computer-use-tool
- ^Willison, Simon. "What's new in Claude Sonnet 5." Simon Willison's Weblog, 2026-06-30. simonwillison.net/...claude-sonnet-5
- ^"Anthropic launches Claude Sonnet 5 as a cheaper way to run agents." TechCrunch, 2026-06-30. techcrunch.com/...5-as-a-cheaper-way-to-run-agents
- ^"Anthropic launches Claude Sonnet 5." Constellation Research, 2026-06-30. constellationr.com/...pic-launches-claude-sonnet-5
- ^"Text leaderboard." LMArena, retrieved 2026-07-27. arena.ai/...text
- ^Mowshowitz, Zvi. "Claude Sonnet 5 Is Not Frontier But Has Its Uses." Don't Worry About the Vase, 2026-07-01. thezvi.substack.com/...onnet-5-is-not-frontier-but
- ^"What's new." Claude Code Docs, Anthropic. code.claude.com/...whats-new
- ^"Introducing Claude Opus 5." Anthropic, 2026-07-24. anthropic.com/...claude-opus-5
- ^"Claude Opus 5 results." ARC Prize, retrieved 2026-07-27. arcprize.org/...anthropic-claude-opus-5
- ^"Leaderboard." ARC Prize, retrieved 2026-07-27. arcprize.org/leaderboard
- ^"Service tiers." Claude Platform Docs, Anthropic. platform.claude.com/...service-tiers
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Reviewer note: Every spec, price, benchmark and quote checked against Anthropic's docs, the launch post, the full system card PDF, AA's raw data, LMArena and the cited reviews.