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99When choosing a Claude model, consider first evaluating these factors:
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1111* **Capabilities:** What specific features or capabilities will you need the model to have to meet your needs?
12* **Speed:** How quickly does the model need to respond in your application? Claude Opus 5 and Claude Opus 4.8 support [fast mode](https://platform.claude.com/docs/en/build-with-claude/fast-mode) (research preview), which delivers up to 2.5x higher output speed at premium pricing.
12* **Speed:** How quickly does the model need to respond in your application? Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8 support [fast mode](https://platform.claude.com/docs/en/build-with-claude/fast-mode) (research preview), which delivers up to 2.5x higher output speed at premium pricing.
1313* **Cost:** What's your budget for both development and production usage?
14* **Effort:** Several Claude models support an [effort parameter](https://platform.claude.com/docs/en/build-with-claude/effort) that trades intelligence for latency and cost within a single model. Tuning effort is often a better lever than switching models. On Claude Fable 5.1 and Claude Opus 5, start with the default (`high`) and adjust up or down based on your evals. On Claude Opus 4.8 and Claude Opus 4.7, the `xhigh` effort level, between `high` and `max`, is the best setting for most coding and agentic use cases.
14* **Effort:** Several Claude models support an [effort parameter](https://platform.claude.com/docs/en/build-with-claude/effort) that trades intelligence for latency and cost within a single model. Tuning effort is often a better lever than switching models. On Claude Fable 5.1 and Claude Opus 5, start with the default (`high`) and adjust up or down based on your evals. On Claude Opus 5.5 the default is `medium`; start there and adjust the same way. On Claude Opus 4.8 and Claude Opus 4.7, the `xhigh` effort level, between `high` and `max`, is the best setting for most coding and agentic use cases.
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1616***
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3939
4040For complex tasks where intelligence and advanced capabilities are paramount, you may want to start capability-first: implement with the strongest starting point for your task, then optimize to more efficient models down the line:
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421. Implement with Claude Opus 5.
432. [Optimize your prompts](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-opus-5) for this model.
421. Implement with Claude Opus 5.5.
432. [Optimize your prompts](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-opus-5-5) for this model.
44443. Evaluate if performance meets your requirements.
45454. Consider increasing efficiency by lowering [effort](https://platform.claude.com/docs/en/build-with-claude/effort) or downgrading models over time with greater workflow optimization.
46465. If your evals at `xhigh` or `max` effort still fall short on demanding reasoning or long-horizon agentic work, move to [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/whats-new-fable-5-1).
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5353* Applications where accuracy outweighs cost considerations
5454* Advanced coding and high-autonomy agentic work
5555
56**Claude Opus 5** (`claude-opus-5`) is built for complex agentic coding and enterprise work, with deep reasoning, long-horizon tasks, and test-time compute scaling.
56**Claude Opus 5.5** (`claude-opus-5-5`) is built for long-running agentic coding and knowledge work, with [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking) always on. If your integration forces tool use (`tool_choice` of type `any` or `tool`), turns thinking off, or uses the `computer_20251124` computer use tool, see [Breaking changes](https://platform.claude.com/docs/en/models/opus-5-5/whats-new-opus-5-5#breaking-changes) before switching.
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5858**Claude Fable 5.1** (`claude-fable-5-1`) is Anthropic's most capable widely released model. It extends Claude Fable 5 with stronger long-running agentic coding, knowledge work, and research at the same input and output prices, with cache reads at a quarter of the cost. **Claude Mythos 5.1** (`claude-mythos-5-1`) offers the same capabilities to [Project Glasswing](https://anthropic.com/glasswing) participants only. Both models use always-on [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking). See [What's new in Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/whats-new-fable-5-1) for details.
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60Claude Fable 5 and Claude Mythos 5 are also available. See [Introducing Claude Fable 5 and Claude Mythos 5](https://platform.claude.com/docs/en/models/fable-5/introducing-claude-fable-5-and-claude-mythos-5) for details. For context windows, output limits, and prices, see the [model comparison table](https://platform.claude.com/docs/en/models/overview#latest-models-comparison).
60For context windows, output limits, and prices, see the [model comparison table](https://platform.claude.com/docs/en/models/overview#latest-models-comparison).
6161
6262## Model selection matrix
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64Most workloads start with Claude Opus 5.
64Most workloads start with Claude Opus 5.5.
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6666| When you need... | Consider starting with... | Example use cases |
6767| ------------------------------------------------------------------------- | ------------------------- | --------------------------------------------------------------------------------------------------------------------------------- |
6868| The highest available capability | Claude Fable 5.1 | Agent sessions that run for hours, multistep deep research, analysis carried through to a finished document, spreadsheet, or deck |
69| Complex agentic coding and enterprise work | Claude Opus 5 | Multihour autonomous coding agents, large-scale refactoring, complex systems engineering, vision-heavy workflows, computer use |
69| Complex agentic coding and enterprise work | Claude Opus 5.5 | Multihour autonomous coding agents, large-scale refactoring, complex systems engineering, vision-heavy workflows, computer use |
7070| Speed and capability for everyday coding, agent, and enterprise workloads | Claude Sonnet 5 | Code generation, data analysis, content creation, visual understanding, agentic tool use |
7171| The lowest latency and price, with extended thinking | Claude Haiku 4.5 | Real-time applications, high-volume intelligent processing, cost-sensitive deployments needing strong reasoning, sub-agent tasks |
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102102 <Card title="What's new in Claude Fable 5.1" icon="sparkle" href="https://platform.claude.com/docs/en/models/fable-5-1/whats-new-fable-5-1">
103103 Built for demanding reasoning and long-horizon agentic work
104 </Card>
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106 <Card title="What's new in Claude Opus 5.5" icon="sparkle" href="https://platform.claude.com/docs/en/models/opus-5-5/whats-new-opus-5-5">
107 The latest Opus model: breaking changes, new features, and behavior differences
104108 </Card>
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106110 <Card title="What's new in Claude Opus 5" icon="sparkle" href="https://platform.claude.com/docs/en/models/opus-5/whats-new-opus-5">