Empty Turns

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Valid empty assistant turns

An assistant turn can finish normally without visible text. OmniRoute preserves such a turn when the selected execution used a supported native endpoint and the original upstream response supplied the protocol's normal terminal. An empty response without that evidence retains the existing empty-content guard.

The execution boundary records this policy internally on the response identity. Client headers, a provider name, a planned connection, and a terminal synthesized by translation cannot grant the exception. The context survives response wrappers, JSON-to-SSE conversion, and non-streaming deduplication. It contains protocol and terminal flags, not credentials or a URL exposed to clients.

Supported execution endpoints

Execution	Endpoint contract
OpenAI Chat	The registered https://api.openai.com/v1/chat/completions endpoint
Anthropic Messages, including Claude connections	The registered https://api.anthropic.com/v1/messages endpoint
Codex Responses	The registered https://chatgpt.com/backend-api/codex/responses endpoint
OpenRouter Chat	The registered https://openrouter.ai/api/v1/chat/completions endpoint
Azure OpenAI / Foundry Responses	HTTPS resource hosts ending exactly in .openai.azure.com or .services.ai.azure.com, with /openai/v1/responses
Azure Foundry Anthropic	HTTPS resource hosts ending exactly in .services.ai.azure.com, with /anthropic/v1/messages

The Azure paths follow Microsoft's endpoint documentation, Responses REST API, and Anthropic SDK guidance. Nonstandard Azure ports, URL credentials, lookalike hostname suffixes, and other custom endpoints do not inherit this policy.

Terminal and error handling

• OpenAI Chat requires a native finish_reason: "stop".
• Claude requires end_turn or stop_sequence and a completed message lifecycle. A lifecycle that opened a block but produced no useful output remains guarded.
• Responses requires a native completed response. An initial response.created followed by EOF cannot use the translator's synthetic stop as proof.
• Native errors take priority over normal terminals. Existing quota errors, missing-terminal handling, token-limit exemptions, reasoning output, and tool output retain their separate classification.

For a valid empty turn, direct requests return the completion, and combos stop without generating a response from a sibling target. Deduplicated callers share the policy of the execution they joined. The empty-turn exception does not write connection cooldown or model lockout state.

A native terminal describes protocol completion; it cannot establish whether the model intended silence or a backend malfunctioned. Origin checks use the actual response URL when available and otherwise the effective request URL returned by the executor. An executor that rebuilds its response before this boundary can hide the final destination of an HTTP redirect; this is not a redirect attestation mechanism.

Regression evidence

The HTTP regression suite uses the real API routes, stored synthetic connections, provider executors, translation, and combos. It intercepts outbound transport and counts generation requests. It covers official endpoint shapes, native JSON and SSE, unknown origins, errors, deduplication, and the optional empty-turn retry. These tests do not contact real provider accounts or reproduce the reporter's deployment or token totals.

node --import tsx/esm --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit tests/unit/valid-empty-stop-dispatch-16072.test.ts

The policy implementation is in emptyTurnPolicy.ts; combo validation reads the execution's native terminal after consuming the response.