diff --git a/apps/desktop/src/routes/(window-chrome)/settings/integrations/google-drive-config.tsx b/apps/desktop/src/routes/(window-chrome)/settings/integrations/google-drive-config.tsx
index a69ffc316b6..f6d0c522180 100644
--- a/apps/desktop/src/routes/(window-chrome)/settings/integrations/google-drive-config.tsx
+++ b/apps/desktop/src/routes/(window-chrome)/settings/integrations/google-drive-config.tsx
@@ -6,6 +6,7 @@ import { commands } from "~/utils/tauri";
 import { apiClient, protectedHeaders } from "~/utils/web-api";
 import { Section, SectionCard, SettingsPageContent } from "../Setting";
 import { IntegrationConfigHeader } from "./config-header";
+import { describeS3ConfigError } from "./s3-config-error";
 
 const byteUnits = ["B", "KB", "MB", "GB", "TB", "PB"] as const;
 const googleDriveConnectionPollIntervalMs = 1500;
@@ -71,7 +72,9 @@ const fetchS3Config = async (orgId: string | null) => {
 		headers: await protectedHeaders(),
 	});
 
-	if (response.status !== 200) throw new Error("Failed to fetch S3 config");
+	if (response.status !== 200) {
+		throw new Error(describeS3ConfigError(response));
+	}
 
 	return response.body;
 };
diff --git a/apps/desktop/src/routes/(window-chrome)/settings/integrations/s3-config-error.ts b/apps/desktop/src/routes/(window-chrome)/settings/integrations/s3-config-error.ts
new file mode 100644
index 00000000000..f8a8a0fd234
--- /dev/null
+++ b/apps/desktop/src/routes/(window-chrome)/settings/integrations/s3-config-error.ts
@@ -0,0 +1,29 @@
+/**
+ * Turn a non-200 `getS3Config` response into something a user can act on or
+ * paste into an issue.
+ *
+ * The route already returns `{ error, details }` (see
+ * `apps/web/app/api/desktop/[...route]/s3Config.ts`), but both callers threw a
+ * fixed "Failed to fetch S3 config" and dropped it. Since there is no local
+ * ErrorBoundary on these pages, that string reached `CapErrorBoundary` and was
+ * all the user could see or copy — which is exactly what was reported in #1840.
+ */
+export function describeS3ConfigError(response: {
+	status: number;
+	body: unknown;
+}): string {
+	const body = response.body as
+		| { error?: unknown; details?: unknown }
+		| undefined;
+	const error = typeof body?.error === "string" ? body.error : undefined;
+	const details = typeof body?.details === "string" ? body.details : undefined;
+
+	if (response.status === 403 || error === "forbidden_org") {
+		return "You don't have access to this organization's storage settings.";
+	}
+
+	if (error && details) return `${error}: ${details}`;
+	if (error) return error;
+
+	return `Failed to fetch S3 config (HTTP ${response.status})`;
+}
diff --git a/apps/desktop/src/routes/(window-chrome)/settings/integrations/s3-config.tsx b/apps/desktop/src/routes/(window-chrome)/settings/integrations/s3-config.tsx
index cba26750e95..1cfb4552987 100644
--- a/apps/desktop/src/routes/(window-chrome)/settings/integrations/s3-config.tsx
+++ b/apps/desktop/src/routes/(window-chrome)/settings/integrations/s3-config.tsx
@@ -8,6 +8,7 @@ import { commands } from "~/utils/tauri";
 import { apiClient, protectedHeaders } from "~/utils/web-api";
 import { Section, SectionCard, SettingsPageContent } from "../Setting";
 import { IntegrationConfigHeader } from "./config-header";
+import { describeS3ConfigError } from "./s3-config-error";
 
 interface S3Config {
 	provider: string;
@@ -37,7 +38,13 @@ export default function S3ConfigPage() {
 				headers: await protectedHeaders(),
 			});
 
-			if (response.status !== 200) throw new Error("Failed to fetch S3 config");
+			if (response.status !== 200) {
+				// The server already explains what went wrong (a stored bucket row
+				// that fails to decrypt, an org the user is no longer in, ...).
+				// Throwing a fixed string discarded that and left "Failed to fetch
+				// S3 config" as the only thing the user could see or report.
+				throw new Error(describeS3ConfigError(response));
+			}
 
 			return response.body;
 		},
diff --git a/packages/web-api-contract/src/desktop.ts b/packages/web-api-contract/src/desktop.ts
index 2a0b96b529b..c3522dcfedd 100644
--- a/packages/web-api-contract/src/desktop.ts
+++ b/packages/web-api-contract/src/desktop.ts
@@ -175,6 +175,8 @@ const protectedContract = c.router(
 					source: z.enum(["default", "user", "organization"]),
 					managedByOrganization: ManagedOrganizationStorage,
 				}),
+				403: z.object({ error: z.string() }),
+				500: z.object({ error: z.string(), details: z.string().optional() }),
 			},
 		},
 		setS3Config: {