Tool call streaming fails with 'missing id or name' on OpenAI-compatible APIs that send empty-string deltas

[Garfier]

Description

When using an OpenAI-compatible API (DashScope token-plan endpoint with GLM-5.2), tool calls fail with:

OpenAI Chat tool call delta is missing id or name

The root cause is that some OpenAI-compatible APIs send empty strings ("") for id and function.name on subsequent tool call deltas instead of omitting them or sending null. For example:

delta 1: {"id":"call_8c1f...","function":{"name":"calculator","arguments":"{"}}
delta 2: {"id":"","function":{"name":"","arguments":"\"expression\": "}}
delta 3: {"id":"","function":{"name":"","arguments":"\"2"}}

In ToolStream.appendOrStart, the nullish coalescing operator (??) does not treat "" as absent, so the fallback to accumulated values never triggers. The !id check then fails on the empty string.

OpenCode version

v2 branch (also affects published opencode2 next builds)

Steps to reproduce

1. Configure an OpenAI-compatible provider pointing to DashScope token-plan endpoint (token-plan.cn-beijing.maas.aliyuncs.com/compatible-mode/v1)
2. Add a model like glm-5.2 with tool_call: true
3. Send a prompt that triggers a tool call
4. The streaming response fails on the second tool call delta

Operating System

Linux (x86_64)

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• V2: spawning subagent failure and errors "OpenAI Chat tool call delta is missing id or name" in the UI #36299: Reports the same error message ("OpenAI Chat tool call delta is missing id or name") with a different OpenAI-compatible provider

If these are the same root cause, it would be helpful to consolidate discussion there. If your issue is distinct (e.g., specifically about empty-string deltas vs. missing fields), please note that in a comment.

[Garfier]

Already fixed in v2 branch — upstream changed appendOrStart to prefer accumulated identity (current?.id ?? delta.id), which handles empty-string deltas correctly.