Claude Sonnet 5.5 for everyday coding and documents
Use Claude Sonnet 5.5 for code reviews and document questions. $1.60 / 1M input, $8.00 / 1M output.
- Adaptive thinking
- 1M-token context
- Images and PDFs
- Prompt caching
- Streaming
Try Claude Sonnet 5.5
Test Claude Sonnet 5.5 with text or files. Inspect answers and usage.
claude-sonnet-5-5$1.60 in · $8.00 out per 1M tokens
Check compatibility notes before using advanced options.
Claude Sonnet 5.5 output
Unedited answer at default effort.
Explain a database index to a new backend developer in three concise sentences. Include one trade-off.
A database index is a separate data structure (typically a B-tree) that stores the values of one or more columns in sorted order along with pointers to the corresponding rows, so the database can find matching rows without scanning the entire table. Think of it like a book's index: instead of reading every page to find a topic, you look it up and jump straight to the right place. The trade-off is that indexes speed up reads but slow down writes (INSERT, UPDATE, DELETE) and consume extra storage, because every change to the table must also be applied to each relevant index.
October 1, 2026: 65 input, 170 output tokens. Results vary.
Claude Sonnet 5.5 pricing
Claude Sonnet 5.5 prices match your account rates.
Illustrative sizes; charges follow reported usage.
| Item | Counted as | Rate | Billing |
|---|---|---|---|
| Input | Uncached prompt tokens | $1.60 / 1M | Per 1M tokens |
| Output | Answer and thinking tokens | $8.00 / 1M | Per 1M tokens |
| Cache read | Cached prompt tokens | $0.16 / 1M | Per 1M tokens |
| Cache write, 5 minutes | Five-minute cache creation | $2.00 / 1M | Per 1M tokens |
| Cache write, 1 hour | One-hour cache creation | $3.20 / 1M | Per 1M tokens |
| Failed request | Any request that returns an error | Free | Not charged |
What is Claude Sonnet 5.5?
Claude Sonnet 5.5 is Anthropic's coding and document model, with 1M context and 128K output limits.
Claude Sonnet 5.5 defaults to high-effort adaptive thinking. Between-tools skips up-front thinking. Advanced features have compatibility limits.
Text, images and PDFs in; text out.
Connect your app or coding agent
Connect Claude Sonnet 5.5 to your backend or coding agent.
Call it from your backend
Call Claude Sonnet 5.5 with the Anthropic SDK and your SeedRouter key.
- 1Create an API key
- 2Set https://api.seedrouter.ai as base URL
- 3Choose claude-sonnet-5-5
Hand it to your coding agent
Ask your agent to prepare a Claude Sonnet 5.5 request and cost estimate for approval.
- 1Copy the prompt
- 2Paste it into your agent
- 3Approve the request
Work with code and documents
Give Claude Sonnet 5.5 a task with context you can verify.
Review code
Find edge cases with Claude Sonnet 5.5 and request tests.
Compare sources
Compare reports and request section references for each conclusion.
Read files
Ask about screenshots or PDFs; verify details against the original.
Call tools
Give Claude Sonnet 5.5 tools, inspect arguments and return results.
Choose thinking
Compare Claude Sonnet 5.5 thinking modes; higher effort alone proves no improvement.
Reuse context
Cache repeated Claude Sonnet 5.5 instructions for five minutes or one hour.
Build around your workflow
Code reviews
Draft findings with Claude Sonnet 5.5; keep a developer reviewing.
Support drafts
Ground Claude Sonnet 5.5 replies in your help articles. Review before sending.
Document extraction
Extract JSON with Claude Sonnet 5.5; check values against the document.
Start with Claude Sonnet 5.5
- 01
Create a key
Create a key and add credit for Claude Sonnet 5.5.
- 02
Set the base URL
Anthropic: https://api.seedrouter.ai. OpenAI: append /v1.
- 03
Choose your model
Set claude-sonnet-5-5 and max_tokens for your Claude Sonnet 5.5 request.
- 04
Review usage
Review Claude Sonnet 5.5 tokens and charges in usage records.
Claude Sonnet 5.5 at a glance
Tested limits are in the API reference.
| Feature | Claude Sonnet 5.5 |
|---|---|
| Anthropic Messages API | Native format; tested limits apply |
| OpenAI Chat Completions | Basic requests verified |
| OpenAI Responses | Basic requests verified |
| Image and PDF input | Base64 examples verified |
| Prompt caching | 5-minute and 1-hour |
| Forced tool use | Unsupported by this model |
| Failed requests | Not charged |
Claude Sonnet 5.5 batch processing and fast mode are not offered here.
Limits and compatibility to check
Context and output
Claude Sonnet 5.5 lists 1M context and 128K output; these ceilings remain untested here.
Thinking restrictions
Claude Sonnet 5.5 rejects disabled/manual thinking. Between-tools accepts low, medium or high effort.
Sampling restrictions
Omit sampling settings; accepted compatibility values are documented separately.
Prewarming and stops
Claude Sonnet 5.5 tests rejected zero-output prewarming and continued past a stop string.
Signed compaction
The compaction test returned ordinary text without a signed block.
Instructions and history
Per-message effort recall and conflicting system-instruction tests found issues.
Why use SeedRouter?
One key
Call Claude Sonnet 5.5 with Messages or basic OpenAI-format requests.
Pay as you go
Spend your balance across models. No subscription.
Failures are free
Claude Sonnet 5.5 requests that return errors are not charged.
Live prices
Claude Sonnet 5.5 prices come from billing data.
Prompt caching
Claude Sonnet 5.5 passed both cache-usage checks; official minimum: 512 tokens.
Images and PDFs
Image and PDF examples passed; full media boundaries remain unverified.
Streaming
Stream Claude Sonnet 5.5 output; handle thinking, tools and errors.
Related models
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View pricingClaude Sonnet 5.5 FAQ
What is Claude Sonnet 5.5?+
Claude Sonnet 5.5 is Anthropic's coding and document model. It accepts text and images, returning text or tool requests.
How does it compare with Opus 5.5?+
Claude Sonnet 5.5 defaults to high effort and offers between-tools thinking. Opus defaults to medium. Compare both on your workload.
What does Claude Sonnet 5.5 cost?+
Claude Sonnet 5.5 costs $1.60 / 1M input and $8.00 / 1M output. Cache rates appear above; charges follow reported tokens.
Can I disable thinking?+
Claude Sonnet 5.5 rejects disabled thinking. Between-tools skips up-front thinking at low, medium or high effort.
When was Claude Sonnet 5.5 released?+
Claude Sonnet 5.5 launched September 28, 2026, with a June 2026 knowledge cutoff. The release guide covers changes.
Which model ID do I use?+
Use claude-sonnet-5-5 for Claude Sonnet 5.5. Messages requires model, max_tokens and messages. Keep keys server-side.
Does Claude Sonnet 5.5 support OpenAI SDKs?+
Basic Claude Sonnet 5.5 Chat Completions and Responses requests passed testing. Use Messages for native Claude parameters.
Are failed requests charged?+
Claude Sonnet 5.5 requests that return errors are not charged, including Playground requests.
Put Claude Sonnet 5.5 to work
Try one task in the Playground, then connect your application.