diff --git a/src/integrations/misc/__tests__/export-markdown.spec.ts b/src/integrations/misc/__tests__/export-markdown.spec.ts
new file mode 100644
index 00000000000..fd4c30c3d25
--- /dev/null
+++ b/src/integrations/misc/__tests__/export-markdown.spec.ts
@@ -0,0 +1,76 @@
+import { describe, it, expect } from "vitest"
+import { formatContentBlockToMarkdown, ExtendedContentBlock } from "../export-markdown"
+
+describe("export-markdown", () => {
+	describe("formatContentBlockToMarkdown", () => {
+		it("should format text blocks", () => {
+			const block = { type: "text", text: "Hello, world!" } as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("Hello, world!")
+		})
+
+		it("should format image blocks", () => {
+			const block = {
+				type: "image",
+				source: { type: "base64", media_type: "image/png", data: "data" },
+			} as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("[Image]")
+		})
+
+		it("should format tool_use blocks with string input", () => {
+			const block = { type: "tool_use", name: "read_file", id: "123", input: "file.txt" } as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("[Tool Use: read_file]\nfile.txt")
+		})
+
+		it("should format tool_use blocks with object input", () => {
+			const block = {
+				type: "tool_use",
+				name: "read_file",
+				id: "123",
+				input: { path: "file.txt", line_count: 10 },
+			} as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("[Tool Use: read_file]\nPath: file.txt\nLine_count: 10")
+		})
+
+		it("should format tool_result blocks with string content", () => {
+			const block = { type: "tool_result", tool_use_id: "123", content: "File content" } as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("[Tool]\nFile content")
+		})
+
+		it("should format tool_result blocks with error", () => {
+			const block = {
+				type: "tool_result",
+				tool_use_id: "123",
+				content: "Error message",
+				is_error: true,
+			} as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("[Tool (Error)]\nError message")
+		})
+
+		it("should format tool_result blocks with array content", () => {
+			const block = {
+				type: "tool_result",
+				tool_use_id: "123",
+				content: [
+					{ type: "text", text: "Line 1" },
+					{ type: "text", text: "Line 2" },
+				],
+			} as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("[Tool]\nLine 1\nLine 2")
+		})
+
+		it("should format reasoning blocks", () => {
+			const block = { type: "reasoning", text: "Let me think about this..." } as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("[Reasoning]\nLet me think about this...")
+		})
+
+		it("should skip thoughtSignature blocks", () => {
+			const block = { type: "thoughtSignature" } as ExtendedContentBlock
+			expect(formatContentBlockToMarkdown(block)).toBe("")
+		})
+
+		it("should handle unexpected content types", () => {
+			const block = { type: "unknown_type" as const } as any
+			expect(formatContentBlockToMarkdown(block)).toBe("[Unexpected content type: unknown_type]")
+		})
+	})
+})
diff --git a/src/integrations/misc/export-markdown.ts b/src/integrations/misc/export-markdown.ts
index 2c2207eda57..d65bb3200e4 100644
--- a/src/integrations/misc/export-markdown.ts
+++ b/src/integrations/misc/export-markdown.ts
@@ -9,7 +9,11 @@ interface ReasoningBlock {
 	text: string
 }
 
-type ExtendedContentBlock = Anthropic.Messages.ContentBlockParam | ReasoningBlock
+interface ThoughtSignatureBlock {
+	type: "thoughtSignature"
+}
+
+export type ExtendedContentBlock = Anthropic.Messages.ContentBlockParam | ReasoningBlock | ThoughtSignatureBlock
 
 export function getTaskFileName(dateTs: number): string {
 	const date = new Date(dateTs)
@@ -98,6 +102,9 @@ export function formatContentBlockToMarkdown(block: ExtendedContentBlock): strin
 		}
 		case "reasoning":
 			return `[Reasoning]\n${block.text}`
+		case "thoughtSignature":
+			// Not relevant for human-readable exports
+			return ""
 		default:
 			return `[Unexpected content type: ${block.type}]`
 	}