Motivation

Fix IGW routing where External runtime workers were sent to the regular HTTP router instead of the OpenAI router, so OpenAI-compatible backends received SGLang-specific fields (e.g., priority) and returned “Unknown parameter”.

#16544

Modifications

• In RouterManager::get_router_for_model, detect RuntimeType::External workers and prefer HTTP_OPENAI, preventing External workers from being handled by the regular router.
• Keep the existing gRPC/PD/Regular priority ordering unchanged.

Accuracy Tests

N/A

Benchmarking and Profiling

N/A

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.
• Follow the SGLang code style guidance.

Review Process

1. Ping Merge Oncalls to start the PR flow. See the PR Merge Process.
2. Get approvals from CODEOWNERS and other reviewers.
3. Trigger CI tests with comments (/tag-run-ci-label, /rerun-failed-ci, /tag-and-rerun-ci) or contact authorized users to do so.
4. After green CI and required approvals, ask Merge Oncalls to merge.