When an assistant turn ends with stopReason="error" after a tool call
was already streamed, agent-loop synthesizes a placeholder tool result
via createAbortedToolResult() to preserve the tool_use / tool_result
pairing the provider API requires. The previous wording ("Tool
execution failed due to an error: <upstream>") and event shape
(normal tool_execution_start / tool_execution_end with empty details)
were indistinguishable from a real local tool failure — a Codex
websocket close mid-turn showed up in the CLI as a broken Edit panel,
misattributing provider-transport faults to the local tool.
Reword the "error" placeholder to state explicitly that the tool
never ran ("Tool call was not executed because the provider stream
ended with an error before the tool could run: <upstream>") and thread
a SyntheticToolResultDetails discriminator ({ __synthetic: true,
source: "assistant_stop_error" | "assistant_stop_aborted" |
"assistant_stop_skipped" | "assistant_stop_length", executed: false,
upstreamError }) through both the ToolResultMessage.details and the
tool_execution_end event's result.details, so downstream UI/telemetry/
ACP consumers can render "provider transport failed, tool not
executed" without string-matching content.
Fixes#4321
roboomp
3d86935a5e