Calls to an unknown tool are reported as completed (ACP status "completed") #54238

Description

If the model calls a tool OpenCode doesn't have, experimental_repairToolCall
(packages/opencode/src/session/llm.ts) sends the call to the invalid tool.
That tool returns the error with Effect.succeed
(packages/opencode/src/tool/invalid.ts), so the part ends as completed.

The model gets the right message ("Model tried to call unavailable tool
'write_file'. Available tools: ..."), but everything else treats the call as
a success. ACP clients get tool_call_update with status: "completed" (in
Zed it shows as a succeeded step titled "Invalid Tool"), and the part is
stored as completed. Other tool failures (e.g. read on a missing file)
end as error / failed.

Expected: the call ends as an error, with the same message for the model.

Plugins

No response

OpenCode version

1.18.34 (commit 1ddb087). invalid.ts is unchanged on dev.

Steps to reproduce

1. Run opencode acp from an ACP client (e.g. Zed), with a model that calls
   a tool name OpenCode doesn't offer (e.g. write_file). We used a scripted
   OpenAI-compatible endpoint that returns that call.
2. Look at the tool_call_update for that call: its status is completed.
3. For comparison, a read of a missing file reports failed.

Screenshot and/or share link

No response

Operating System

Linux (Ubuntu VM)

Terminal

No response