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claude-code - 💡(How to fix) Fix [Bug] Opus 4.8 on Bedrock: "thinking.type.enabled" not supported — regression from #51439

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Claude Code 2.1.156 sends thinking.type: "enabled" when using aws.claude-opus-4.8 on AWS Bedrock, but this model only accepts thinking.type: "adaptive" with output_config.effort. This results in a 400 error, making Opus 4.8 unusable on Bedrock.

This is a regression of the same issue previously fixed in #51439 / #50100 (fixed in v2.1.121 for Opus 4.7). The fix apparently does not cover the new Opus 4.8 model ID.

Error Message

API Error: 400 "thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.
(Service: BedrockRuntime, Status Code: 400, Request ID: 4ca3008d-466e-4042-b0fb-6c21618cf8a9)

Root Cause

Claude Code 2.1.156 sends thinking.type: "enabled" when using aws.claude-opus-4.8 on AWS Bedrock, but this model only accepts thinking.type: "adaptive" with output_config.effort. This results in a 400 error, making Opus 4.8 unusable on Bedrock.

This is a regression of the same issue previously fixed in #51439 / #50100 (fixed in v2.1.121 for Opus 4.7). The fix apparently does not cover the new Opus 4.8 model ID.

Fix Action

Workaround

Switch to aws.claude-opus-4.6-b which works correctly.

Code Example

API Error: 400 "thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.
(Service: BedrockRuntime, Status Code: 400, Request ID: 4ca3008d-466e-4042-b0fb-6c21618cf8a9)
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Summary

Claude Code 2.1.156 sends thinking.type: "enabled" when using aws.claude-opus-4.8 on AWS Bedrock, but this model only accepts thinking.type: "adaptive" with output_config.effort. This results in a 400 error, making Opus 4.8 unusable on Bedrock.

This is a regression of the same issue previously fixed in #51439 / #50100 (fixed in v2.1.121 for Opus 4.7). The fix apparently does not cover the new Opus 4.8 model ID.

Error

API Error: 400 "thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.
(Service: BedrockRuntime, Status Code: 400, Request ID: 4ca3008d-466e-4042-b0fb-6c21618cf8a9)

Steps to reproduce

  1. Configure Claude Code to use AWS Bedrock as the provider
  2. /model aws.claude-opus-4.8
  3. Send any message

Expected behavior

Claude Code should use thinking.type: "adaptive" for Opus 4.8, same as it does for Opus 4.7 on Bedrock.

Actual behavior

Immediate 400 error on every message sent.

Workaround

Switch to aws.claude-opus-4.6-b which works correctly.

Environment

  • Claude Code version: 2.1.156
  • Platform: macOS (Darwin, ARM64)
  • Provider: AWS Bedrock
  • Model: aws.claude-opus-4.8

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FAQ

Expected behavior

Claude Code should use thinking.type: "adaptive" for Opus 4.8, same as it does for Opus 4.7 on Bedrock.

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claude-code - 💡(How to fix) Fix [Bug] Opus 4.8 on Bedrock: "thinking.type.enabled" not supported — regression from #51439