diff --git a/src/features/workspaces/files/workspace-file-upload.test.ts b/src/features/workspaces/files/workspace-file-upload.test.ts
new file mode 100644
index 00000000..2e11f362
--- /dev/null
+++ b/src/features/workspaces/files/workspace-file-upload.test.ts
@@ -0,0 +1,77 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import { runWorkspaceFileUploadBatch } from "#/features/workspaces/files/workspace-file-upload";
+
+vi.mock("sonner", () => ({
+	toast: {
+		error: vi.fn(),
+		promise: vi.fn(),
+	},
+}));
+
+function pptxFile(name: string) {
+	return new File(["deck"], name, {
+		type: "application/vnd.openxmlformats-officedocument.presentationml.presentation",
+	});
+}
+
+function conversionFailureResponse() {
+	return new Response(
+		JSON.stringify({
+			requestId: "req_test",
+			code: "CONVERSION_FAILED",
+			message: "Unable to convert this file to PDF right now.",
+			details: { message: "LibreOffice conversion failed: timed out." },
+		}),
+		{ status: 422, headers: { "content-type": "application/json" } },
+	);
+}
+
+afterEach(() => {
+	vi.restoreAllMocks();
+});
+
+describe("runWorkspaceFileUploadBatch", () => {
+	it("surfaces the real server reason when a single office conversion fails", async () => {
+		vi.stubGlobal(
+			"fetch",
+			vi.fn(async () => conversionFailureResponse()),
+		);
+
+		await expect(
+			runWorkspaceFileUploadBatch({
+				workspaceId: "ws_1",
+				parentId: null,
+				files: [pptxFile("23. Special Topic Limb Loss.pptx")],
+				onSuccess: () => {},
+			}),
+		).rejects.toMatchObject({
+			message:
+				"Failed to upload 23. Special Topic Limb Loss.pptx. Unable to convert this file to PDF right now.",
+		});
+
+		vi.unstubAllGlobals();
+	});
+
+	it("attaches the underlying failure as the error cause", async () => {
+		vi.stubGlobal(
+			"fetch",
+			vi.fn(async () => conversionFailureResponse()),
+		);
+
+		const error = await runWorkspaceFileUploadBatch({
+			workspaceId: "ws_1",
+			parentId: null,
+			files: [pptxFile("deck.pptx")],
+			onSuccess: () => {},
+		}).catch((caught: unknown) => caught);
+
+		expect(error).toBeInstanceOf(Error);
+		expect((error as Error).cause).toBeInstanceOf(Error);
+		expect(((error as Error).cause as Error).message).toBe(
+			"Unable to convert this file to PDF right now.",
+		);
+
+		vi.unstubAllGlobals();
+	});
+});
diff --git a/src/features/workspaces/files/workspace-file-upload.ts b/src/features/workspaces/files/workspace-file-upload.ts
index 7c1faea4..cf46477b 100644
--- a/src/features/workspaces/files/workspace-file-upload.ts
+++ b/src/features/workspaces/files/workspace-file-upload.ts
@@ -122,10 +122,17 @@ function uploadAcceptedFiles(input: {
 	const total = jobs.length;
 
 	return new Promise((resolve, reject) => {
+		const uploadErrors: Error[] = [];
+
 		new AsyncQueuer<WorkspaceFileUploadJob>(postWorkspaceFileUpload, {
 			concurrency: workspaceFileUploadLimits.concurrency,
 			throwOnError: false,
 			initialItems: jobs,
+			onError: (error) => {
+				// The queuer swallows per-job failures (throwOnError: false), so hold on to
+				// them here — otherwise the real server reason never reaches error tracking.
+				uploadErrors.push(error);
+			},
 			onSuccess: (command) => {
 				input.onSuccess(command);
 			},
@@ -137,13 +144,7 @@ function uploadAcceptedFiles(input: {
 				const { successCount, errorCount } = queuer.store.state;
 
 				if (successCount === 0) {
-					reject(
-						new Error(
-							total === 1
-								? `Failed to upload ${input.files[0]?.name ?? "file"}.`
-								: `Failed to upload ${total} files.`,
-						),
-					);
+					reject(buildUploadFailureError(input.files, total, uploadErrors));
 					return;
 				}
 
@@ -153,6 +154,37 @@ function uploadAcceptedFiles(input: {
 	});
 }
 
+function buildUploadFailureError(
+	files: readonly File[],
+	total: number,
+	errors: readonly Error[],
+): Error {
+	const summary =
+		total === 1
+			? `Failed to upload ${files[0]?.name ?? "file"}.`
+			: `Failed to upload ${total} files.`;
+
+	const reason = summarizeUploadErrors(errors);
+	const error = new Error(reason ? `${summary} ${reason}` : summary);
+
+	if (errors.length > 0) {
+		// Preserve the underlying failures so error tracking keeps the server context.
+		error.cause = errors.length === 1 ? errors[0] : errors;
+	}
+
+	return error;
+}
+
+function summarizeUploadErrors(errors: readonly Error[]): string | null {
+	const messages = [
+		...new Set(
+			errors.map((error) => getErrorMessage(error, "").trim()).filter((message) => message !== ""),
+		),
+	];
+
+	return messages.length > 0 ? messages.join(" ") : null;
+}
+
 async function getWorkspaceFileUploadErrorMessage(response: Response) {
 	const fallback = "Unable to upload file to workspace storage.";