Bedrock: configured output limit never sent, long reasoning turns truncate at 4096 tokens

Description

V2 sends Bedrock Converse requests without inferenceConfig.maxTokens, even when the model config sets limit.output: 128000. The prepared model request only carries generation values set by hooks/context, so the resolved limit never reaches the provider and Bedrock applies a much lower implicit budget.

With adaptive thinking (reasoningConfig: adaptive, effort xhigh), reasoning and text share that budget. Long-thinking turns finish as max_tokens at exactly 4096 output tokens, often reasoning-only with no visible text.

Captured request (via a session.hook("http.request") plugin, sanitized): additionalModelRequestFields.thinking is present, inferenceConfig is absent:

{
  "url": "https://bedrock-runtime.us-east-1.amazonaws.com/model/global.anthropic.claude-fable-5/converse-stream",
  "modelId": "global.anthropic.claude-fable-5",
  "inferenceConfig": null,
  "additionalModelRequestFields": { "thinking": { "type": "adaptive", "display": "summarized" }, "output_config": { "effort": "xhigh" } }
}

Auditing ~1,500 sessions across two workspaces: 1,098 assistant turns finished max_tokens at exactly 4,096 output tokens; 552 of them contained reasoning only.

The Bedrock protocol already serializes generation.maxTokens as inferenceConfig.maxTokens; it just never receives a value. I have a fix ready (projects resolved.limit.output into the request with hook/model/route defaults taking precedence) and will open a PR.

Plugins

opencode-bedrock-rotate (bearer token rotation; not related, reproduced with it failing to load)

OpenCode version

0.0.0-beta-18743, also reproduced on 0.0.0-dev-18806

Steps to reproduce

1. Configure a Bedrock Claude model with limit.output: 128000 and an adaptive reasoning variant.
2. Log outgoing requests with a plugin hooked on session.hook("http.request").
3. The request has no inferenceConfig; turns with long reasoning truncate at 4096 output tokens.