OpenAI-compatible cost chunk omits required stream fields

Description

Zen appends an invalid cost event to OpenAI-compatible streams:

{"choices":[],"cost":"0"}

The event omits id, object, created, and model. Strict OpenAI chunk decoders parse every SSE data: event and fail with missing field id before they can ignore the cost metadata. Expected: retain cost inside a valid chat-completion chunk envelope.

Plugins

N/A

OpenCode version

Zen production endpoint, observed 2026-07-27

Steps to reproduce

1. Send a streaming request through the Zen OpenAI-compatible endpoint.
2. Parse every data: JSON event as an OpenAI chat completion chunk.
3. Observe the final cost event fail schema deserialization because id is missing.

Screenshot and/or share link

N/A — failure occurs in the raw SSE response shown above.

Operating System

Linux

Terminal

zsh