diff --git a/packages/linejs/base/obs/mod.ts b/packages/linejs/base/obs/mod.ts
index 7e005f5c..d0b4ca3f 100644
--- a/packages/linejs/base/obs/mod.ts
+++ b/packages/linejs/base/obs/mod.ts
@@ -356,20 +356,19 @@ export class LineObs {
 			} else {
 				previewEdata = edata;
 			}
-			const { objId: objId2, headers } = await this.uploadObjectForService({
+			const { objId: objId2 } = await this.uploadObjectForService({
 				data: previewEdata,
 				oType: "file",
 				obsPath: `${serviceName}/${obsNamespace}/${objId}__ud-preview`,
 				params,
 			});
 			if (objId !== objId2) {
-				throw new InternalError(
-					"ObsError",
-					"objId not match: " + JSON.stringify(Object.fromEntries(headers)),
-					{
-						headers: Object.fromEntries(headers),
-					},
-				);
+				// The response headers stay out: they can carry the next access
+				// token. Object IDs are no credential; fetching one needs the token.
+				throw new InternalError("ObsError", "objId not match", {
+					objId,
+					previewObjId: objId2,
+				});
 			}
 		}
 
diff --git a/packages/linejs/base/obs/upload_e2ee.test.ts b/packages/linejs/base/obs/upload_e2ee.test.ts
index 80121522..82a4ea78 100644
--- a/packages/linejs/base/obs/upload_e2ee.test.ts
+++ b/packages/linejs/base/obs/upload_e2ee.test.ts
@@ -1,5 +1,7 @@
 import { assert, test } from "vite-plus/test";
+import { assertRejects } from "../../test/assert.ts";
 import { Buffer } from "node:buffer";
+import { InternalError } from "../core/mod.ts";
 import { LineObs } from "./mod.ts";
 
 /** Per-call record of (data.size, obsPath) so tests can assert which
@@ -248,3 +250,34 @@ test("uploadMediaByE2EE — video duration preserves encrypted preview and messa
 	assert.deepEqual(message.contentType, 2);
 	assert.deepEqual(message.chunks, [new Uint8Array()]);
 });
+
+// The preview upload answering a different object ID used to put every
+// response header into the error, and those can carry the next access token.
+test("uploadMediaByE2EE — an object ID mismatch names no response headers", async () => {
+	const nextAccess = "NEXT-ACCESS-MARKER";
+	const { obs, fake } = makeObs();
+	obs.uploadObjectForService = ((opts: { data: Blob; obsPath: string }) => {
+		fake.records.push({ size: opts.data.size, obsPath: opts.obsPath });
+		return Promise.resolve({
+			objId: `OBJ-${fake.records.length}`,
+			headers: new Headers({ "x-line-next-access": nextAccess }),
+		});
+	}) as never;
+
+	const error = await assertRejects(
+		() =>
+			obs.uploadMediaByE2EE({
+				data: new Blob([new Uint8Array(1_000)]),
+				oType: "image",
+				to: "u-recipient",
+			}),
+		InternalError,
+	);
+
+	assert.deepEqual(error.name, "ObsError");
+	assert.notInclude(error.message, nextAccess);
+	assert.notInclude(JSON.stringify(error.data), nextAccess);
+	assert.deepEqual(error.data, { objId: "OBJ-1", previewObjId: "OBJ-2" });
+	assert.deepEqual(fake.records.length, 2);
+	assert.deepEqual(fake.sendMessageCalls.length, 0);
+});
diff --git a/packages/linejs/base/request/mod.test.ts b/packages/linejs/base/request/mod.test.ts
new file mode 100644
index 00000000..36a7a8a9
--- /dev/null
+++ b/packages/linejs/base/request/mod.test.ts
@@ -0,0 +1,51 @@
+import { assert, test } from "vite-plus/test";
+import { assertRejects } from "../../test/assert.ts";
+import { BaseClient } from "../core/mod.ts";
+
+const nextAccess = "NEXT-ACCESS-MARKER";
+const bodyText = "<html>BODY-MARKER</html>";
+const pathToken = "PATH-MARKER";
+
+/** Every place a logger or error serializer reads an error from. */
+function errorText(error: Error): string {
+	return [
+		error.message,
+		error.stack ?? "",
+		JSON.stringify({ ...error }),
+		String(error.cause ?? ""),
+	].join("\n");
+}
+
+// A gateway error page is not Thrift, so the parse fails. That error used to
+// print every response header, x-line-next-access included, and the body as
+// hex, and callers copy the message into logs and tool output. A caller's
+// path may carry a query string, so the error leaves the path out too.
+test("request — an unparsable response names no headers, body or path", async () => {
+	const base = new BaseClient({
+		device: "DESKTOPWIN",
+		fetch: () =>
+			Promise.resolve(
+				new Response(bodyText, {
+					status: 503,
+					headers: { "x-line-next-access": nextAccess },
+				}),
+			),
+	});
+	const body = new TextEncoder().encode(bodyText);
+
+	const error = await assertRejects(() =>
+		base.request.request([], "getProfile", 3, true, `/S3?token=${pathToken}`),
+	);
+
+	assert.strictEqual(Object.getPrototypeOf(error), Error.prototype);
+	const text = errorText(error);
+	assert.notInclude(text, nextAccess);
+	assert.notInclude(text, bodyText);
+	assert.notInclude(text, pathToken);
+	assert.notInclude(text, [...body].map((byte) => byte.toString(16)).join(" "));
+	assert.deepEqual(error.cause, undefined);
+	assert.deepEqual(
+		error.message,
+		`Request internal failed: status=503 method=getProfile bodyLength=${body.length}`,
+	);
+});
diff --git a/packages/linejs/base/request/mod.ts b/packages/linejs/base/request/mod.ts
index 6f84872a..ba087160 100644
--- a/packages/linejs/base/request/mod.ts
+++ b/packages/linejs/base/request/mod.ts
@@ -173,10 +173,12 @@ export class RequestClient {
 		try {
 			res = this.client.thrift.readThrift(parsedBody, protocol);
 		} catch {
+			// Callers log and print this message, so it names no response
+			// headers (x-line-next-access carries the next access token), no
+			// body bytes and no path, which a caller may give a query string.
 			throw new Error(
 				`Request internal failed: status=${response.status} ` +
-					`headers=${JSON.stringify([...response.headers.entries()])} ` +
-					`body=<${[...parsedBody].map((e) => e.toString(16)).join(" ")}>`,
+					`method=${methodName} bodyLength=${parsedBody.length}`,
 			);
 		}
 		if (!res.data[0] && Object.keys(res.data).length) {