Is claude-sonnet-5-5 cheaper than claude-sonnet-4-5-20250929?

Yes. The labeled example monthly cost is $60 for the old model and $40 for the replacement.

Does claude-sonnet-5-5 have a bigger context window than claude-sonnet-4-5-20250929?

Yes. The context window changes from 200,000 to 1,000,000 tokens.

claude-sonnet-4-5-20250929 to claude-sonnet-5-5: price, context, and code

The official replacement is claude-sonnet-5-5. claude-sonnet-4-5-20250929 shuts down on 2026-11-30 per Anthropic's deprecation page (checked 2026-10-17). On the labeled example of 10 million input tokens and 2 million output tokens, claude-sonnet-5-5 costs $40 a month, lower than $60 for claude-sonnet-4-5-20250929.

claude-sonnet-4-5-20250929 to claude-sonnet-5-5

All values from official sources Checked 2026-10-17.

Price per 1M tokens

Price comparison. Example monthly cost for 10M input tokens and 2M output tokens. Labeled example, not a bill.
Field	Old	New	Change
Input	$3	$2	-33.3% (lower)
Output	$15	$10	-33.3% (lower)
Cached input	$0.3	$0.1	Not published
Example monthly cost	$60	$40	Example only

Context and max output

Token limits
Limit	Old	New	Change
Context window	200,000	1,000,000	+400% (higher)
Max output	64,000	128,000	+100% (higher)

Capabilities that differ

No differing capability values are published for both models.

API changes

No parameter change is listed on the official pages we checked. The sample below only swaps the model id.

Code

python typescript curl

python before

import anthropic
client = anthropic.Anthropic()
message = client.messages.create(
    model="claude-sonnet-4-5-20250929",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}],
)

python after

import anthropic
client = anthropic.Anthropic()
message = client.messages.create(
    model="claude-sonnet-5-5",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello"}],
)

typescript before

import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const message = await client.messages.create({
  model: "claude-sonnet-4-5-20250929",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Hello" }],
});

typescript after

import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const message = await client.messages.create({
  model: "claude-sonnet-5-5",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Hello" }],
});

curl before

curl https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-4-5-20250929","max_tokens":1024,"messages":[{"role":"user","content":"Hello"}]}'

curl after

curl https://api.anthropic.com/v1/messages \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "content-type: application/json" \
  -d '{"model":"claude-sonnet-5-5","max_tokens":1024,"messages":[{"role":"user","content":"Hello"}]}'

Checklist

Read the shutdown date for claude-sonnet-4-5-20250929 on the linked official page.
Point your requests at claude-sonnet-5-5.
Re-check price, context, and parameters on the provider pages linked here.
Ship the change before the published shutdown date.

Replacement for claude-sonnet-4-5-20250929: what changes when you switch