Claude Sonnet 5 Pricing Jumps 50% on September 1, 2026

Claude Sonnet 5's introductory API pricing of $2 per million input tokens and $10 per million output tokens ends August 31, 2026. Starting September 1, 2026, Anthropic's standard rate of $3/$15 per million tokens takes over — a 50% increase on both the input and output legs, confirmed on Anthropic's pricing documentation. Any workload running on Sonnet 5 today will cost 50% more from that date unless you act first.

What changes on September 1, 2026

Every rate that derives from the base input and output price moves by the same 50%, because Anthropic's cache and batch multipliers are fixed percentages of the base rate rather than independent numbers.

Pricing category	Through Aug 31, 2026	From Sep 1, 2026	Change
Base input	$2 / MTok	$3 / MTok	+50%
Output	$10 / MTok	$15 / MTok	+50%
5-minute cache write	$2.50 / MTok	$3.75 / MTok	+50%
1-hour cache write	$4 / MTok	$6 / MTok	+50%
Cache hit (read)	$0.20 / MTok	$0.30 / MTok	+50%
Batch input	$1 / MTok	$1.50 / MTok	+50%
Batch output	$5 / MTok	$7.50 / MTok	+50%

MTok = million tokens. These are first-party Claude API rates; Amazon Bedrock and Google Cloud pricing tracks the same token rates plus their own platform fees, per Anthropic's documentation.

Why this is happening

Anthropic launched Claude Sonnet 5 on June 30, 2026, describing it as "the most agentic Sonnet model yet" with performance "close to that of Opus 4.8, but at lower prices." The $2/$10 introductory rate was documented as temporary from the day of launch, with the $3/$15 standard rate and its September 1 start date published on the same pricing page at release, not added later. In other words, this is a scheduled reversion to a rate Anthropic announced up front, not a mid-cycle hike — though the practical effect for a budget or invoice is identical either way.

The change lands in the same week OpenAI cut GPT-5.6 Luna and Terra pricing by up to 80%, a reminder that frontier and near-frontier API pricing is moving in both directions across vendors this quarter, not trending uniformly down.

What this costs in practice

For a workload processing 10 million input tokens and 2 million output tokens in a month with no caching:

• Through August 31: (10M × $2) + (2M × $10) = $20 + $20 = $40
• From September 1: (10M × $3) + (2M × $15) = $30 + $30 = $60

That's a $20 increase on a $40 bill — the 50% figure holds regardless of your input-to-output token ratio, since both legs moved by the same percentage. Heavier users of prompt caching see the same 50% jump on cache-write and cache-read line items, since those are fixed multipliers of the base rate rather than separately negotiated numbers.

Where Sonnet 5 sits after the increase

Even at $3/$15, Sonnet 5 remains cheaper than Claude Opus 5, which costs $5 input / $25 output per million tokens, and matches the price Anthropic already charges for the prior Sonnet 4.6 and Sonnet 4.5 models — the standard rate isn't a new high-water mark for the Sonnet line, it's a return to where Sonnet pricing has sat since Sonnet 4. For a full cross-vendor view including GPT-5.6, Gemini 3.6 Flash, Grok 4.5 and Kimi K3, see this site's AI model API pricing comparison.

What to do before August 31, 2026

• Re-run cost forecasts now. Any budget or customer-facing pricing built on the $2/$10 introductory rate needs a 50% adjustment before the switch, not after an invoice surprises someone.
• Check contracts and internal pricing tied to Sonnet 5 cost. If your product prices a feature based on Sonnet 5's per-token cost, that margin shrinks on September 1 unless you rebuild it around $3/$15.
• Re-test prompt caching now, not later. A cache hit still costs 10% of the base input price after the change, so the relative payoff of caching is unchanged — but confirm your cache-hit ratio is high enough to justify the now-higher absolute cache-write cost.
• Don't switch models reactively. A price change on Sonnet 5 doesn't change which model performs best on your task; only re-route to Haiku 4.5, Opus 5, or a competing model if your own evals already support it at the new numbers.
• If usage is elastic, front-load work before the deadline. Batch jobs, backfills or non-time-sensitive processing scheduled for early September can run under the introductory rate if shifted earlier, cutting that portion of the cost by a third.

The deadline is fixed and public, which makes this one of the more predictable pricing changes in the current API market — the only open question is whether your own budgeting catches up to it before August 31.