V2 Bedrock: sessions silently die mid-turn (opus 5.5 and fable 5.1 confirmed) #51063

Description

The maxTokens value is omitted, so Bedrock defaults to 4096. In Claude Code the value is 128,000 for Opus 5.5, and 64.000 for Fable 5.1.

When Claude models think for more than 4k tokens, the turn ends without any answer, error or retry. Usually in the middle of a thinking block.

A workaround is to add this to opencode.jsonc:

  "providers": {
    "amazon-bedrock": {
      "models": {
        "global.anthropic.claude-fable-5-1": {
          "body": {
            "inferenceConfig": {
              "maxTokens": 64000,
            },
          },
        },
        "global.anthropic.claude-opus-5-5": {
          "body": {
            "inferenceConfig": {
              "maxTokens": 128000,
            },
          },
        },
      },
    },
  },

• Confirmed with Fable 5.1 and Opus 5.5, could be more models through Bedrock.
• Only tested in V2

Plugins

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OpenCode version

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Steps to reproduce

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Screenshot and/or share link

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Operating System

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Terminal

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