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litellm.UnsupportedParamsError when Task subagents use Bedrock provider #29428
Description
Bug Report
Environment:
- Model:
us.anthropic.claude-opus-4-6-v1via 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
- Configure OpenCode with a Bedrock-hosted model via litellm (e.g.
us.anthropic.claude-opus-4-6-v1) - Have MCP servers configured (e.g. Atlassian, Todoist)
- Trigger a task that causes the primary agent to spawn a Task subagent
- 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:
- Ensure the
tools=param is forwarded to subagent sessions when using Bedrock via litellm - Set
litellm.modify_params = True/litellm_settings::modify_params: Trueas a default when Bedrock is the provider - Document the limitation clearly for Bedrock users
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github-actions commentedon May 26, 2026
This issue might be a duplicate of existing issues. Please check:
litellm.UnsupportedParamsError— tool calling withouttools=param (LiteLLM proxy + Anthropic)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.
serejaris commentedon May 27, 2026
I looked through the related history (#2915, #10037, #10259) and the newer PR #29474. This looks like a specific remaining Task subagent + LiteLLM/Bedrock/tool-history path, but #29474 already attempted the likely
_noopcompatibility fix and was closed unmerged.Before opening another PR in the same direction: was #29474 closed because opencode should not add provider-specific LiteLLM/Bedrock compatibility here, or would a narrower/opt-in shape be acceptable (for example only when
litellmProxyis enabled)?github-actions commentedon Jul 27, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.