Quick Answer
If you need one default Claude model for most daily work, start with Claude Sonnet 4.6. As of 2026-03-25, Anthropic's current API docs list Sonnet 4.6 as the best combination of speed and intelligence, with a 1M-token context window, 64K max output, and $3 input / $15 output pricing per million tokens.
Choose Claude Opus 4.6 when the task is costly to get wrong: multi-file code changes with hidden coupling, long-running agent workflows, legal or financial analysis, or document-heavy work where one buried detail changes the answer. Anthropic's current docs position Opus 4.6 as its most intelligent model for agents and coding, with the same 1M-token context window, a larger 128K max output limit, and $5 input / $25 output pricing.
The practical rule is:
- start with Sonnet 4.6 for throughput, iteration speed, and budget-sensitive daily work
- escalate to Opus 4.6 for the hardest reasoning, longest agent runs, and final review on expensive decisions
- if you need fresher built-in model knowledge without web search, Sonnet 4.6 currently has the newer official knowledge and training-data cutoffs
The Most Important Update: The Current Docs Are Better Than The Launch Headlines
One detail matters more than most side-by-side summaries mention.
Anthropic's February 2026 launch pages for Sonnet 4.6 and Opus 4.6 still describe the 1M-token context window as a beta-era capability in some places. But Anthropic's current API docs and pricing docs, checked on 2026-03-25, now state that both Claude Opus 4.6 and Claude Sonnet 4.6 include the full 1M-token context window at standard pricing.
That changes the buying decision in a real way. The question is no longer "which model can access 1M context". The useful question is:
- which model should own the cheap first pass
- which model should own the expensive uncertainty
- when is Opus quality worth more than the extra latency and token cost
My inference from Anthropic's current official docs is that the API docs and pricing pages are the more up-to-date source for developers choosing models today, even though some launch and product pages still carry older beta wording.
The Fast Comparison
| Decision point | Claude Sonnet 4.6 | Claude Opus 4.6 |
|---|---|---|
| Official positioning | best combination of speed and intelligence | most intelligent model for building agents and coding |
| Best for | daily coding, writing, doc review, first-pass research, high-volume workflows | hardest coding, long-running agents, high-stakes reasoning, final review |
| Claude app availability | available on all Claude plans; default on Free and Pro | available on Claude for Pro, Max, Team, and Enterprise users |
| API pricing | $3 input / $15 output per MTok | $5 input / $25 output per MTok |
| Context window | 1M tokens | 1M tokens |
| Max output | 64K tokens | 128K tokens |
| Comparative latency | fast | moderate |
| Adaptive thinking | yes | yes |
| Knowledge cutoff | Aug 2025 | May 2025 |
| Training data cutoff | Jan 2026 | Aug 2025 |
| Special edge | cheaper and faster default | max output, max effort, stronger long-run reasoning, fast mode |
A better way to read this table is not "which one is best overall". The better question is "which model is cheaper than the mistake I am trying to avoid?"
What Actually Changed In Claude 4.6
The current Claude 4.6 generation changed more than just the model names.
As of 2026-03-25, Anthropic's official 4.6 docs say:
- Sonnet 4.6 and Opus 4.6 both support a 1M-token context window, adaptive thinking, and all existing Claude API features
- adaptive thinking is now the recommended mode for both models, while the old
thinking: {type: "enabled"}plusbudget_tokenspath is deprecated - the effort parameter is now generally available; Anthropic explicitly suggests
mediumeffort for many Sonnet 4.6 use cases, while Opus 4.6 adds amaxeffort level for highest capability - code execution is now free when used with web search or web fetch, and both models can use dynamic filtering to reduce irrelevant context and token waste
- compaction is now in beta, which means longer-running conversations and agents can summarize their earlier context server-side instead of hitting a hard wall
- Opus 4.6 also adds a 128K output ceiling and optional fast mode at premium pricing
Those are not cosmetic release notes. They change how you should route real work between a cheaper everyday model and a stronger model for harder decisions.
Use Sonnet 4.6 First When The Task Is Clear, Bounded, And Verifiable
Sonnet 4.6 is the better default when the task has a visible edge and a cheap verification step.
Good fits:
- summarizing large document sets before a meeting
- reviewing a pull request for likely risks and missing tests
- drafting or rewriting copy under strict constraints
- comparing several product pages, docs, or policy pages
- planning a bounded code change before editing
- extracting action items from PDFs, tables, and research notes
- running high-volume API workflows where the result will be checked downstream
Why Sonnet 4.6 is the better first pass:
- it is materially cheaper per token than Opus
- Anthropic still lists it as the faster model
- it keeps the same 1M context window as Opus in the current API docs
- Anthropic's launch note and partner examples show Sonnet 4.6 closing much of the older Opus gap on coding and document-heavy reasoning
- Sonnet 4.6 currently has the newer official knowledge cutoff and training-data cutoff, which is a real advantage if you are not using web search
That last point is easy to miss. As of 2026-03-25, Anthropic's models overview lists Sonnet 4.6 with an Aug 2025 reliable knowledge cutoff and Jan 2026 training data cutoff, versus May 2025 and Aug 2025 for Opus 4.6. That does not make Sonnet smarter overall, but it does make Sonnet the safer choice when fresher built-in knowledge matters.
Use Opus 4.6 When Failure Costs More Than Latency
Opus 4.6 is worth paying for when deeper reasoning changes the answer, not just the tone.
Good fits:
- multi-file refactors where hidden coupling matters
- debugging sessions with several competing root-cause theories
- long-running agent tasks with many tool calls and changing intermediate state
- legal, finance, compliance, or security work where one missed detail changes the recommendation
- final review on an important migration or architecture change
- document-heavy analysis where key facts may be buried deep in the context
- tasks likely to require very long outputs, especially beyond what 64K output can comfortably handle
This is also where Anthropic's own guidance becomes important. Its current model-selection docs say that if you are starting with the most capable model for complex work, the sequence should begin with Claude Opus 4.6, especially for complex reasoning, scientific or mathematical applications, nuanced understanding, accuracy-sensitive applications, and advanced coding.
Anthropic's Opus 4.6 launch note reinforces that positioning. It describes Opus 4.6 as stronger on planning, longer agent runs, larger codebases, code review, debugging, and long-context retrieval. In the same launch note, Anthropic says Opus 4.6 scores 76% on the 8-needle 1M MRCR v2 long-context retrieval test, versus 18.5% for Sonnet 4.5. That is a cross-generation comparison, not an Opus 4.6 vs Sonnet 4.6 head-to-head, so you should not read it as evidence that Opus 4.6 has a similar gap over Sonnet 4.6. The narrower takeaway is that Anthropic is using long-context retrieval results to justify Opus as the model for harder, higher-risk work.
One Useful Nuance: Sonnet Is Newer, Opus Is Deeper
A lot of comparisons assume the more expensive model is better on every axis. Anthropic's current docs do not support that simplification.
As of 2026-03-25:
- Opus 4.6 is the deeper reasoning and agent model
- Sonnet 4.6 is the newer-knowledge model
- both have the same 1M-token context window in Anthropic's current API docs
- Opus still wins on max output, advanced effort control, and hard-task positioning
So if your task is "use a lot of context and think very hard," Opus is still the safer bet. But if your task is "move quickly through a large but checkable workload, and maybe rely on more recent built-in knowledge," Sonnet is not just the cheaper option. It can be the more practical one.
Cost Math: Where Opus Actually Earns Its Premium
The list-price gap is real, but it is not extreme enough to justify a lazy routing rule.
| API cost item | Sonnet 4.6 | Opus 4.6 |
|---|---|---|
| Base input | $3 / MTok | $5 / MTok |
| Base output | $15 / MTok | $25 / MTok |
| 5-minute cache write | $3.75 / MTok | $6.25 / MTok |
| 1-hour cache write | $6 / MTok | $10 / MTok |
| Cache read | $0.30 / MTok | $0.50 / MTok |
| Batch input | $1.50 / MTok | $2.50 / MTok |
| Batch output | $7.50 / MTok | $12.50 / MTok |
| Fast mode | not available | $30 input / $150 output per MTok |
Three practical conclusions follow:
- Sonnet 4.6 is the better default for high-volume routine work because the savings compound quickly.
- Opus 4.6 is usually easy to justify if it prevents one bad decision in a migration, code review, legal memo, or long agent run.
- Opus fast mode is only rational when waiting time is itself expensive. It is not a default setting. Anthropic prices it at 6x standard Opus rates.
A Better Routing Rule Than "Smartest Model Wins"
Use this routing table instead of guessing.
| Task shape | Start with Sonnet 4.6 | Escalate to Opus 4.6 |
|---|---|---|
| bounded code review | yes | if architectural risk stays unclear |
| first draft of an article, memo, or plan | yes | rarely |
| document summarization across many PDFs or notes | yes | if buried details could change the answer |
| need fresher built-in knowledge without web search | yes | only if reasoning quality later becomes the bottleneck |
| repo-wide migration planning | maybe | yes |
| hard debugging with ambiguous root cause | maybe | yes |
| long-running agent workflow with many tool calls | maybe | yes |
| final pass on legal, finance, compliance, or security reasoning | no | yes |
| very long final deliverable or large synthesis output | maybe | yes, especially if you may exceed 64K output |
| repeated daily chat and writing | yes | no |
The central judgment is simple: Sonnet 4.6 is the default model for throughput, while Opus 4.6 is the model for expensive uncertainty.
Practical Workflow: Use Both Models On The Same Job
For many teams, the best answer is not to pick one model forever. It is to split the same task into a cheap exploration stage and an expensive judgment stage.
Stage 1: Sonnet for exploration and structure
Use Sonnet 4.6 to:
- map the problem
- identify unknowns
- summarize relevant files, sources, or documents
- propose a scoped plan
- draft the first version
Copyable prompt:
You are the first-pass model for this task.
Return only:
1. what matters most
2. what is still unclear
3. the smallest safe plan
4. whether this task should be escalated to a stronger model, and why
Task:
[paste the task]
Stage 2: Opus for high-stakes reasoning
Escalate to Opus 4.6 only after the problem is scoped.
Copyable prompt:
You are the final-review model for a high-stakes task.
Review this plan and look for:
- hidden assumptions
- missing edge cases
- buried contradictions
- better alternatives with lower risk
- anything that would change the final recommendation
Context:
[paste plan, sources, or code context]
This workflow keeps most requests on the cheaper model while using the stronger model exactly where judgment quality changes the outcome.
What Not To Do
Do not make either of these mistakes:
- using Opus 4.6 for trivial drafting just because it is stronger on paper
- forcing Sonnet 4.6 to handle a task whose real difficulty is hidden judgment
A bad routing decision usually looks like this:
- you use Opus for simple drafting and pay for quality you did not need
- or you use Sonnet for an ambiguous hard task, then spend more time cleaning up a weak answer than you saved on cost
FAQ
If official Anthropic pages disagree about 1M context, which source should you trust?
As of 2026-03-25, Anthropic's current API models overview and pricing docs say Sonnet 4.6 and Opus 4.6 both include the full 1M-token context window at standard pricing. Some launch and product pages still describe 1M context as beta, especially for Opus 4.6. My read is that the current API docs are the better reference for developers choosing models now, but it is worth flagging the discrepancy if your team is doing procurement or policy review.
Does Sonnet 4.6 having a newer knowledge cutoff mean it is smarter than Opus 4.6?
No. Anthropic still positions Opus 4.6 as the more capable model for the hardest reasoning, advanced coding, and agent work. The newer Sonnet cutoff matters when fresher built-in knowledge helps, but it does not cancel Opus's advantage on difficult reasoning.
Is Opus 4.6 only for developers?
No. Anthropic positions Opus 4.6 for coding, research, finance, legal reasoning, and document-heavy work. The deciding factor is task difficulty and decision risk, not job title.
What is the safest default for most people today?
For most daily work, start with Sonnet 4.6. For the most complex or accuracy-sensitive tasks, Anthropic's own docs now point you toward Opus 4.6 first.
Bottom Line
If you want the cheapest strong default for real work, pick Claude Sonnet 4.6. If you want Anthropic's current best model for the hardest reasoning, advanced coding, and accuracy-sensitive workflows, pick Claude Opus 4.6. In practice, the most reliable setup is to start large but checkable work on Sonnet, then escalate the scoped, high-risk parts to Opus.
Verification Note
Verified on 2026-03-25 against official Anthropic sources.
Primary sources used for the current model specs and pricing:
- Models overview: https://platform.claude.com/docs/en/about-claude/models/overview
- Choosing a model: https://platform.claude.com/docs/en/about-claude/models/choosing-a-model
- Claude 4.6 updates: https://platform.claude.com/docs/en/about-claude/models/whats-new-claude-4-6
- API pricing: https://platform.claude.com/docs/en/about-claude/pricing
Primary sources used for launch positioning and plan availability:
- Sonnet 4.6 launch note: https://www.anthropic.com/news/claude-sonnet-4-6
- Opus 4.6 launch note: https://www.anthropic.com/news/claude-opus-4-6
- Opus product page: https://www.anthropic.com/claude/opus
Important source note: Anthropic's current API docs and pricing pages say Sonnet 4.6 and Opus 4.6 both include the full 1M-token context window at standard pricing, while some launch and product pages still retain older beta wording for 1M context. This article follows the current API docs as the latest developer-facing reference and calls out the discrepancy explicitly.