Description

When a provider using the Responses streaming path returns a wrapped error chunk such as:

{"error":{"code":"","message":"","type":"server_error"},"request_id":""}

OpenCode currently tries to validate it as a normal response.* stream event and fails with:

• Type validation failed
• invalid_union

This appears to happen before any terminal event like response.completed / response.incomplete is seen.

That makes the failure behave like a stream protocol failure before terminal event, but it is currently surfaced as a schema/type validation error instead of a retryable API/stream failure.

This is especially problematic for subagents/background tasks: the child stream can die without entering a proper terminal failed/completed state, while the parent keeps waiting for the child response indefinitely.

Based on local investigation:

• the Responses path only treats response.completed / response.incomplete as terminal
• wrapped error chunks are not normalized before schema validation
• existing retry/backoff is already wired for APICallError -> MessageV2.APIError -> SessionRetry.retryable()
• plugin hooks can modify request params/headers, but cannot intercept/normalize response stream chunks before validation

So the current behavior seems to be:

1. provider sends wrapped error chunk in stream
2. chunk is validated as normal response.* event
3. union validation fails (invalid_union)
4. failure does not enter the normal retryable API error path
5. parent/subagent waiting logic may never get a proper terminal failure signal

Plugins

oh-my-opencode

OpenCode version

Observed on recent OpenCode builds using the Responses streaming path; local repo analysis was against anomalyco/opencode dev and a local installation that surfaced the bundled stack in the TUI worker.

Steps to reproduce

1. Use a provider/model path that goes through the Responses streaming implementation.
2. Have the upstream stream return a wrapped error chunk like:

{"error":{"code":"","message":"","type":"server_error"},"request_id":""}

3. Observe that OpenCode reports a Type validation failed / invalid_union error instead of handling it like a retryable stream/API failure.
4. In subagent/background-task scenarios, observe that the parent can continue waiting because the child did not complete with a normal terminal event.

Screenshot and/or share link

Example error payload observed locally:

Type validation failed: Value: {"error":{"code":"","message":"","type":"server_error"},"request_id":""}
Error message: invalid_union ...

Operating System

Linux

Terminal

N/A

Expected behavior

Wrapped stream error chunks / premature stream failures before response.completed or response.incomplete should be treated as something like:

• stream terminated before terminal event
• or stream ended without completed response

and then mapped into the existing retry/backoff flow (for example via APICallError with the correct retryability), instead of surfacing as raw schema validation failure.

That would make this behave more like retryable HTTP/provider failures and also ensure parent sessions/subagents receive a proper terminal failure signal.

Suggested direction

For the Responses streaming path:

• skip empty/meta-only frames
• detect wrapped error chunks such as { "error": { ... } }
• normalize them before schema validation, or convert them directly into a retryable APICallError
• if the stream ends without response.completed / response.incomplete, treat that as a stream termination failure rather than a generic validation error

This would avoid the invalid_union surface error and should also prevent parent agents from waiting forever on failed child streams.