litellm.UnsupportedParamsError when Task subagents use Bedrock provider

[pt-james-woszczynski]

Bug Report

Environment:

• Model: us.anthropic.claude-opus-4-6-v1 via Bedrock (litellm)
• OS: macOS
• OpenCode version: latest

Error

litellm.UnsupportedParamsError: Bedrock doesn't support tool calling without `tools=` param specified. Pass `tools=` param OR set `litellm.modify_params = True` // `litellm_settings::modify_params: True` to add dummy tool to the request.. Received Model Group=us.anthropic.claude-opus-4-6-v1
Available Model Group Fallbacks=None

Context

This error occurs when a Task subagent is spawned to perform work that involves MCP tool calls (e.g. Atlassian Confluence, Jira, Miro, Todoist). The subagent session appears to not pass the tools= parameter to the Bedrock API, which is required by litellm when using Bedrock as the provider.

Reproduction Steps

1. Configure OpenCode with a Bedrock-hosted model via litellm (e.g. us.anthropic.claude-opus-4-6-v1)
2. Have MCP servers configured (e.g. Atlassian, Todoist)
3. Trigger a task that causes the primary agent to spawn a Task subagent
4. The subagent attempts to use MCP tools → error fires

Expected Behaviour

Task subagents should correctly pass the tools= parameter to the model provider when MCP tools are available, or litellm's modify_params should be set to handle this case gracefully.

Workaround

Added AGENTS.md rules to prevent the primary agent from delegating MCP/external service calls to Task subagents. This avoids the error but limits parallelism.

Suggestion

Either:

1. Ensure the tools= param is forwarded to subagent sessions when using Bedrock via litellm
2. Set litellm.modify_params = True / litellm_settings::modify_params: True as a default when Bedrock is the provider
3. Document the limitation clearly for Bedrock users

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• LiteLLM error: Anthropic doesn't support tool calling without tools= param specified #2915: Same litellm.UnsupportedParamsError — tool calling without tools= param (LiteLLM proxy + Anthropic)
• LiteLLM proxy error: "Anthropic doesn't support tool calling without tools=" even with litellmProxy: true (v1.1.31) #10037: Same error with LiteLLM proxy even after attempted fix (v1.1.31)
• Compaction fails with Bedrock: toolConfig not included when conversation has tool history #10259: Related — Bedrock requires toolConfig/tools= when conversation history contains tool calls (compaction context)

These were closed after fixes were applied. If the issue persists specifically for Task subagent sessions (as opposed to the main agent), it may be a regression or a gap in the existing fix coverage.