diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 1b292060..cf4eb8a2 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed orphaned tool results after errored assistant messages causing Codex API errors. When an assistant message has `stopReason: "error"`, its tool calls are now excluded from pending tool tracking, preventing synthetic tool results from being generated for calls that will be dropped by provider-specific converters. ([#812](https://github.com/badlogic/pi-mono/issues/812))
+
 ## [0.48.0] - 2026-01-16
 
 ### Fixed
diff --git a/packages/ai/src/providers/transform-messages.ts b/packages/ai/src/providers/transform-messages.ts
index 14b33545..08c4cffa 100644
--- a/packages/ai/src/providers/transform-messages.ts
+++ b/packages/ai/src/providers/transform-messages.ts
@@ -111,8 +111,13 @@ export function transformMessages<TApi extends Api>(messages: Message[], model:
 			}
 
 			// Track tool calls from this assistant message
+			// Don't track tool calls from errored messages - they will be dropped by
+			// provider-specific converters, so we shouldn't create synthetic results for them
 			const assistantMsg = msg as AssistantMessage;
-			const toolCalls = assistantMsg.content.filter((b) => b.type === "toolCall") as ToolCall[];
+			const toolCalls =
+				assistantMsg.stopReason === "error"
+					? []
+					: (assistantMsg.content.filter((b) => b.type === "toolCall") as ToolCall[]);
 			if (toolCalls.length > 0) {
 				pendingToolCalls = toolCalls;
 				existingToolResultIds = new Set();