fix(ai): handle unknown finish_reason in openai-completions gracefully

Map unknown finish_reason values (e.g. "end" from Ollama/LM Studio) to
"stop" instead of throwing, since assistant content is already produced.

fixes #2142

packages/ai/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Handle `finish_reason: "end"` from Ollama/LM Studio by mapping it to `"stop"` instead of throwing ([#2142](https://github.com/badlogic/pi-mono/issues/2142))
+
 ## [0.58.0] - 2026-03-14
 
 ### Added

packages/ai/src/providers/openai-completions.ts

@@ -730,10 +730,11 @@ function parseChunkUsage(
 	return usage;
 }
 
-function mapStopReason(reason: ChatCompletionChunk.Choice["finish_reason"]): StopReason {
+function mapStopReason(reason: ChatCompletionChunk.Choice["finish_reason"] | string): StopReason {
 	if (reason === null) return "stop";
 	switch (reason) {
 		case "stop":
+		case "end":
 			return "stop";
 		case "length":
 			return "length";
@@ -743,7 +744,7 @@ function mapStopReason(reason: ChatCompletionChunk.Choice["finish_reason"]): Sto
 		case "content_filter":
 			return "error";
 		default: {
-			const _exhaustive: never = reason;
+			const _exhaustive: never = reason as never;
 			throw new Error(`Unhandled stop reason: ${_exhaustive}`);
 		}
 	}