diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index a49246fa3..cf73d98b7 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Fixed
 
 - Fixed tool-call argument parsing dropping fields when a string contains an invalid `\u` escape such as `\usepackage` ([#10868](https://github.com/earendil-works/pi/issues/10868))
+- Fixed Anthropic requests failing with a 400 when an error tool result contains images; the images are now replaced with a text note ([#10794](https://github.com/earendil-works/pi/issues/10794))
 
 ## [1.2.0] - 2026-10-12
 
diff --git a/packages/ai/src/api/anthropic-messages.ts b/packages/ai/src/api/anthropic-messages.ts
index 29e13db1d..3081c7246 100644
--- a/packages/ai/src/api/anthropic-messages.ts
+++ b/packages/ai/src/api/anthropic-messages.ts
@@ -1328,10 +1328,19 @@ function normalizeToolCallId(id: string): string {
 }
 
 function convertToolResult(msg: ToolResultMessage): ContentBlockParam {
+	// Anthropic rejects error tool results that contain anything but text, so images are replaced
+	// with a note (#10794).
+	const content = msg.isError
+		? msg.content.map((block) =>
+				block.type === "image"
+					? { type: "text" as const, text: "[image omitted: error tool results cannot contain images]" }
+					: block,
+			)
+		: msg.content;
 	return {
 		type: "tool_result",
 		tool_use_id: msg.toolCallId,
-		content: convertContentBlocks(msg.content),
+		content: convertContentBlocks(content),
 		is_error: msg.isError,
 	};
 }