build_tool_start renders every ACP (Zed) tool call — on the live tool-progress
callback (acp_adapter/events.py) and during session history replay
(acp_adapter/server.py). It called build_tool_title and extract_locations
directly, so a model that emits a malformed argument crashed the render:
- terminal `command` as null/number -> TypeError (len() in build_tool_title)
- delegate_task `goal` as a number -> TypeError (len())
- read_file `path` as a non-string -> pydantic ValidationError building a
ToolCallLocation
A live crash breaks the tool-call event; a persisted one breaks history replay
on every resume of that session. The sibling CLI label builder
get_cute_tool_message was already wrapped for exactly this reason
(agent/display.py: "display must never abort a turn").
Wrap build_tool_start the same way: on any builder failure, fall back to a
minimal, valid start event (tool name as title, resolved kind). The happy path
is unchanged.
Adds tests for the non-string command, path, and goal cases.
05473428cb