feat: add litellmProxy provider option for explicit LiteLLM compatibility

[seilk]

Summary

This PR builds on #8497 and addresses @rekram1-node's feedback from #8248:

"There are a LOT of providers that don't have this issue... ideally this would be strictly limited to litellm"

Instead of injecting the _noop tool unconditionally for all providers, this change restricts it to only LiteLLM-backed providers.

Problem

#8497 injects the _noop tool unconditionally when message history contains tool calls. While this fixes the LiteLLM compatibility issue, it unnecessarily affects providers that don't need it (Anthropic native, OpenRouter, Vertex, Bedrock, etc).

Solution

Add litellmProxy provider option and restrict _noop injection to LiteLLM providers:

const isLiteLLMProxy =
  provider.options?.["litellmProxy"] === true ||
  input.model.providerID.toLowerCase().includes("litellm") ||
  input.model.api.id.toLowerCase().includes("litellm")

if (isLiteLLMProxy && Object.keys(tools).length === 0 && hasToolCalls(input.messages)) {
  tools["_noop"] = tool({ ... })
}

Detection methods:

1. Auto-detect: Provider ID or API ID contains "litellm"
2. Explicit opt-in: Provider has litellmProxy: true option (for custom gateways)

Config example:

{
  "provider": {
    "my-gateway": {
      "api": "openai",
      "options": {
        "litellmProxy": true
      }
    }
  }
}

Changes

File	Change
packages/opencode/src/session/llm.ts	Add isLiteLLMProxy check with auto-detection + opt-in support
packages/opencode/src/session/message-v2.ts	Handle pending/running tool calls (from #8497)
packages/opencode/test/session/llm.test.ts	Tests for hasToolCalls helper (from #8497)
packages/opencode/test/session/message-v2.test.ts	Tests for pending/running tool conversion (from #8497)

Testing

• All tests pass (18 tests across 2 files)
• Manual testing with custom LiteLLM gateway confirmed working

Related

• Builds on fix: handle dangling tool_use blocks for LiteLLM proxy compatibility #8497
• Addresses feedback from fix: avoid Anthropic tool-history requests without tools #8248
• Fixes fix: Anthropic via LiteLLM/proxies rejects requests with tool history but no tools param #8246
• Fixes LiteLLM error: Anthropic doesn't support tool calling without tools= param specified #2915

Co-authored-by: Mark Henderson Mark.Henderson99@hotmail.com

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Related PR Found

PR #8497: fix: handle dangling tool_use blocks for LiteLLM proxy compatibility

Why it's related:

• PR feat: add litellmProxy provider option for explicit LiteLLM compatibility #8658 (current) explicitly builds on PR fix: handle dangling tool_use blocks for LiteLLM proxy compatibility #8497, as noted in the description
• PR fix: handle dangling tool_use blocks for LiteLLM proxy compatibility #8497 introduced the _noop tool injection for LiteLLM compatibility
• PR feat: add litellmProxy provider option for explicit LiteLLM compatibility #8658 extends this by adding an explicit litellmProxy provider option to allow opt-in support for custom gateways that don't have "litellm" in their provider ID
• Both PRs address LiteLLM proxy compatibility but at different levels of configurability

Note: This is a related follow-up PR, not a duplicate. They work together to provide progressive enhancement of LiteLLM proxy support.

[rekram1-node]

This is 100% a bug elsewhere but we can add this for now, this shouldn't ever happen

[rekram1-node]

Can we close ur other pr now?

[rekram1-node]

We should probably also document this, another idea tho we could update this:

opencode/packages/opencode/src/provider/transform.ts

Line 698 in 9b57db3

export function error(providerID: string, error: APICallError) {

To handle litellm related errors (by doing some string matching) and maybe providing some better feedback for user