choosing-a-model changedabout-claude/models/choosing-a-model
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1111* **Capabilities:** What specific features or capabilities will you need the model to have to meet your needs?
1212* **Speed:** How quickly does the model need to respond in your application? [Fast mode](https://platform.claude.com/docs/en/build-with-claude/fast-mode) delivers up to 2.5x higher output speed at premium pricing on [supported models](https://platform.claude.com/docs/en/build-with-claude/fast-mode#supported-models).
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, Claude Opus 5, and Claude Sonnet 5.5, start with the default (`high`) and adjust up or down based on your evals. On Claude Opus 5.5 and Claude Haiku 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.
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 5.2, Claude Fable 5.1, Claude Opus 5, and Claude Sonnet 5.5, start with the default (`high`) and adjust up or down based on your evals. On Claude Opus 5.5 and Claude Haiku 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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43432. [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.
465. 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).
465. If your evals at `xhigh` or `max` effort still fall short on demanding reasoning or long-horizon agentic work, move to [Claude Fable 5.2](https://platform.claude.com/docs/en/models/fable-5-2/whats-new-fable-5-2).
4747
4848This approach is best for:
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5656**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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58**Claude Fable 5.1** (`claude-fable-5-1`) is Anthropic’s most capable model open to all customers. 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 only to organizations verified through Anthropic’s verification programs, such as the [Cyber Verification Program](https://support.claude.com/en/articles/14604842). 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.
58**Claude Fable 5.2** (`claude-fable-5-2`) is Anthropic’s most capable model open to all customers. It’s built for demanding reasoning and long-horizon agentic work. **Claude Mythos 5.2** (`claude-mythos-5-2`) offers the same capabilities only to organizations verified through Anthropic’s verification programs, such as the [Cyber Verification Program](https://support.claude.com/en/articles/14604842). Both models use always-on [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking). If your code edits earlier turns of a conversation, moves a conversation between models, uses the `computer_20251124` computer use tool, or uses the advisor tool, see [Claude Fable 5.2 breaking changes](https://platform.claude.com/docs/en/models/fable-5-2/whats-new-fable-5-2#breaking-changes) before switching.
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6060For context windows, output limits, and prices, see the [model comparison table](https://platform.claude.com/docs/en/models/overview#latest-models-comparison).
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6666| When you need... | Consider starting with... | Example use cases |
6767| ------------------------------------------------------------------------- | ------------------------- | --------------------------------------------------------------------------------------------------------------------------------- |
68| 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 |
68| The highest available capability | Claude Fable 5.2 | Agent sessions that run for hours, multistep deep research, analysis carried through to a finished document, spreadsheet, or deck |
6969| 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 5.5 | Code generation, data analysis, content creation, visual understanding, agentic tool use |
7171| The lowest latency and price | Claude Haiku 5.5 | Real-time applications, high-volume intelligent processing, cost-sensitive deployments needing strong reasoning, subagent tasks |
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9999 See detailed specifications and pricing for the latest Claude models
100100 </Card>
101101
102 <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">
103 Built for demanding reasoning and long-horizon agentic work
102 <Card title="What’s new in Claude Fable 5.2" icon="sparkle" href="https://platform.claude.com/docs/en/models/fable-5-2/whats-new-fable-5-2">
103 The latest Fable model: breaking changes, feature support, and pricing
104104 </Card>
105105
106106 <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">
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