claude-on-amazon-bedrock-legacy changedbuild-with-claude/claude-on-amazon-bedrock-legacy
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757757### Mid-conversation system messages on Bedrock
758758
759[Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) are available through the InvokeModel API for Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, and Claude Sonnet 5.5. As described in the note under [API model IDs](https://platform.claude.com/docs/en/build-with-claude/claude-on-amazon-bedrock-legacy#api-model-ids), these requests are served by the same infrastructure as the [Claude in Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock) endpoint. No beta header is required. This feature is not available on Claude Sonnet 5. Use the top-level `system` field instead. It is not available for the ARN-versioned models in the model table on this page.
759[Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) are available through the InvokeModel API for Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, and Claude Sonnet 5.5. As described in the note under [API model IDs](https://platform.claude.com/docs/en/build-with-claude/claude-on-amazon-bedrock-legacy#api-model-ids), these requests are served by the same infrastructure as the [Claude in Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock) endpoint. No beta header is required for mid-conversation system messages. This feature is not available on Claude Sonnet 5. Use the top-level `system` field instead. It is not available for the ARN-versioned models in the model table on this page.
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761A `role: "system"` message can also set `output_config.effort` to [change effort mid-conversation](https://platform.claude.com/docs/en/build-with-claude/effort#change-effort-mid-conversation-beta) on Claude Fable 5.1 and Claude Opus 5.5. This is in beta: add `mid-conversation-output-config-2026-07-01` to the `anthropic_beta` array in the request body. Without that value, or on Claude Fable 5, Claude Opus 5, or Claude Opus 4.8, the request returns a 400 error: `messages.N.output_config: Extra inputs are not permitted`. In the error, `N` is the index of the `system` message in `messages`.
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761763**For Converse API users:** the Converse API accepts system instructions through its top-level [`system` parameter](https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_Converse.html). To add system instructions mid-conversation, use the InvokeModel API.
762764
763765### Context window
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765Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, Claude Sonnet 5.5, Claude Sonnet 5, and Claude Sonnet 4.6 have a [1M-token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows) on Amazon Bedrock. Other Claude models, including Sonnet 4.5 and Sonnet 4 (deprecated), have a 200k-token context window.
767Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, Claude Sonnet 5.5, Claude Sonnet 5, and Claude Sonnet 4.6 have a [1M-token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows) on Amazon Bedrock. Other Claude models, including Sonnet 4.5 (deprecated) and Sonnet 4 (deprecated), have a 200k-token context window.
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767769Bedrock limits request payloads to 20 MB. When sending large documents or many images, you may reach this limit before the token limit.
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776778Regional endpoints include a 10% pricing premium over global endpoints.
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778780<Note>
779 This applies to Claude Sonnet 4.5 and future models only. Older models (Claude Sonnet 4 (deprecated) and earlier) maintain their existing pricing structures.
781 This applies to Claude Sonnet 4.5 (deprecated) and future models only. Older models (Claude Sonnet 4 (deprecated) and earlier) maintain their existing pricing structures.
780782</Note>
781783
782784### When to use each option
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798800### Implementation
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800**Using global endpoints (default for Opus 4.6, Sonnet 4.6, and Sonnet 4.5):**
802**Using global endpoints (default for Opus 4.6, Sonnet 4.6, and Sonnet 4.5 (deprecated)):**
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802The model IDs for Claude Opus 4.6, Sonnet 4.6, and Sonnet 4.5 already include the `global.` prefix:
804The model IDs for Claude Opus 4.6, Sonnet 4.6, and Sonnet 4.5 (deprecated) already include the `global.` prefix:
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