diff --git a/src/oauth/dsh.ts b/src/oauth/dsh.ts
index 6dbf5e29cff..b1ea8b3e8c3 100644
--- a/src/oauth/dsh.ts
+++ b/src/oauth/dsh.ts
@@ -9,6 +9,7 @@
  */
 
 import type { OAuthController, OAuthCredentials } from "./types";
+import { readBoundedResponseBody } from "../lib/bounded-body";
 import { homedir } from "node:os";
 import { join } from "node:path";
 import { existsSync, readFileSync } from "node:fs";
@@ -16,6 +17,20 @@ import { existsSync, readFileSync } from "node:fs";
 export const DSH_PLATFORM_ORIGIN = "https://platform.deepseek.com";
 export const DSH_INFERENCE_ORIGIN = "https://api.deepseek.com/anthropic";
 
+/**
+ * Byte ceiling for the profile document returned by /auth-api/v0/users/current.
+ *
+ * A legitimate profile is a small fixed-shape JSON object (code, data.biz_code,
+ * biz_data.id/email/id_profile{name,picture}) well under a few KiB; 64 KiB matches
+ * the shared bounded-body ceiling and still leaves orders of magnitude of
+ * headroom. Anything larger is rejected before parsing so a hostile or broken
+ * upstream cannot turn an import validation into unbounded memory work.
+ */
+export const DSH_PROFILE_MAX_BYTES = 64 * 1024;
+
+/** Wall-clock budget for the profile request and its body read, in milliseconds. */
+const DSH_PROFILE_FETCH_TIMEOUT_MS = 10_000;
+
 export interface DshAccountDetectionResult {
   detected: boolean;
   token?: string;
@@ -80,7 +95,7 @@ export async function validateDshAccountToken(
   signal?: AbortSignal,
 ): Promise<DshValidatedAccountIdentity> {
   try {
-    const timeoutSignal = AbortSignal.timeout(10_000);
+    const timeoutSignal = AbortSignal.timeout(DSH_PROFILE_FETCH_TIMEOUT_MS);
     const combinedSignal = signal ? AbortSignal.any([signal, timeoutSignal]) : timeoutSignal;
     const response = await fetch(`${DSH_PLATFORM_ORIGIN}/auth-api/v0/users/current`, {
       method: "GET",
@@ -99,7 +114,35 @@ export async function validateDshAccountToken(
       return { valid: false, error: `Platform returned HTTP ${response.status}` };
     }
 
-    const body = (await response.json()) as {
+    // A declared length past the cap is rejected without touching the stream.
+    const declaredLength = Number(response.headers.get("content-length"));
+    if (Number.isFinite(declaredLength) && declaredLength > DSH_PROFILE_MAX_BYTES) {
+      try {
+        void response.body?.cancel(
+          new DOMException("DSH profile response is too large", "QuotaExceededError"),
+        ).catch(() => undefined);
+      } catch {
+        // Best-effort cancellation only.
+      }
+      return { valid: false, error: "PROFILE_VALIDATION_FAILED" };
+    }
+
+    // Missing or understated Content-Length still meets the cap on the decoded
+    // stream itself: once an over-limit byte is observed the retained buffer is
+    // discarded and cancellation is requested on the body. Malformed UTF-8 fails
+    // closed so a replacement character can never alter the authoritative ID.
+    const bounded = await readBoundedResponseBody(response, {
+      signal: combinedSignal,
+      maxBytes: DSH_PROFILE_MAX_BYTES,
+      totalTimeoutMs: DSH_PROFILE_FETCH_TIMEOUT_MS,
+      inactivityTimeoutMs: DSH_PROFILE_FETCH_TIMEOUT_MS,
+      fatalUtf8: true,
+    });
+    if (bounded.oversized || bounded.truncated || !bounded.displaySafe) {
+      return { valid: false, error: "PROFILE_VALIDATION_FAILED" };
+    }
+
+    const body = JSON.parse(bounded.text) as {
       code?: number;
       data?: {
         biz_code?: number;
diff --git a/structure/providers/dsh-account.md b/structure/providers/dsh-account.md
index 083c5df2a15..e7285f8cedf 100644
--- a/structure/providers/dsh-account.md
+++ b/structure/providers/dsh-account.md
@@ -7,6 +7,7 @@
 `src/oauth/dsh.ts` reads `$DSH_HOME/.credentials.yaml` (default `~/.dsh/.credentials.yaml`) only inside `loginDshAccount`, which runs on `ocx login dsh-account` or the dashboard's **Log in** action for the provider. Nothing else reads the file, and nothing in opencodex writes, deletes or changes the permissions of it. The `deepseek-account-platform/default` grant record is validated against `https://platform.deepseek.com/auth-api/v0/users/current` with manual redirects before anything is stored.
 
 Only a successful business response with a nonempty authoritative account ID imports. A missing ID fails closed; email, phone and display name never supply a slot identity, so two DSH accounts sharing an email land in different slots and reauthentication uses the shared account-ID comparison in `src/oauth/index.ts`. Parser and transport failures surface fixed error codes instead of credential or profile fragments.
+The profile body is consumed under a fixed 64 KiB decoded-byte ceiling (`DSH_PROFILE_MAX_BYTES`) with the same bounded-read helper the quota path uses: a Content-Length above the cap is rejected without reading, and cancellation is requested on the streamed body once it exceeds the cap, so a hostile or broken upstream cannot turn an import validation into unbounded memory work. Malformed UTF-8 in the body fails validation instead of letting a replacement character alter the authoritative account ID.
 
 The imported copy lives in the opencodex credential store. Removing the account deletes only that copy and never signs DSH Desktop out.
 
diff --git a/tests/oauth/dsh-login.test.ts b/tests/oauth/dsh-login.test.ts
index 8c84d97a884..dcaed6acf24 100644
--- a/tests/oauth/dsh-login.test.ts
+++ b/tests/oauth/dsh-login.test.ts
@@ -8,6 +8,7 @@ import {
   loginDshAccount,
   refreshDshAccountToken,
   resolveDshCredentialsPath,
+  DSH_PROFILE_MAX_BYTES,
 } from "../../src/oauth/dsh";
 import { removeTreeWithRetry } from "../helpers/remove-tree";
 
@@ -163,6 +164,19 @@ describe("DSH Account Validation", () => {
     expect(await validateDshAccountToken("mock-token")).toEqual({ valid: false, error: "PROFILE_VALIDATION_FAILED" });
   });
 
+  test("rejects malformed UTF-8 inside the authoritative account ID instead of accepting an altered ID", async () => {
+    const encoder = new TextEncoder();
+    const prefix = encoder.encode('{"code":0,"data":{"biz_code":0,"biz_data":{"id":"user-');
+    const suffix = encoder.encode('","email":"u@example.com"}}}');
+    const malformed = new Uint8Array(prefix.length + 1 + suffix.length);
+    malformed.set(prefix);
+    malformed.set([0xff], prefix.length);
+    malformed.set(suffix, prefix.length + 1);
+    globalThis.fetch = async () => new Response(malformed, { status: 200 });
+
+    expect(await validateDshAccountToken("mock-token")).toEqual({ valid: false, error: "PROFILE_VALIDATION_FAILED" });
+  });
+
   test("returns ACCOUNT_TOKEN_INVALID when upstream returns 401", async () => {
     globalThis.fetch = async (input, init) => {
       const url = String(input);
@@ -199,6 +213,95 @@ describe("DSH Account Validation", () => {
     expect(res.valid).toBe(false);
     expect(evilTargetReceivedToken).toBe(false);
   });
+
+  test("rejects a declared oversized profile body without reading the stream", async () => {
+    let cancelReason: unknown;
+    let pulled = false;
+    const body = new ReadableStream<Uint8Array>({
+      pull(controller) {
+        // A regression that reads the body closes it instead of stalling on an
+        // open stream, so this asserts the pull flag directly instead of
+        // failing through an indirect timeout path.
+        pulled = true;
+        controller.close();
+      },
+      cancel(reason) {
+        cancelReason = reason;
+      },
+    }, { highWaterMark: 0 });
+    globalThis.fetch = async () => new Response(body, {
+      status: 200,
+      headers: { "content-length": String(DSH_PROFILE_MAX_BYTES + 1) },
+    });
+
+    const res = await validateDshAccountToken("mock-token");
+    expect(res).toEqual({ valid: false, error: "PROFILE_VALIDATION_FAILED" });
+    expect(cancelReason).toBeInstanceOf(DOMException);
+    expect((cancelReason as DOMException).name).toBe("QuotaExceededError");
+    expect(pulled).toBe(false);
+  });
+
+  test("rejects an oversized profile stream when content-length is missing or understated", async () => {
+    for (const headers of [undefined, { "content-length": "8" }]) {
+      let cancelled = false;
+      const body = new ReadableStream<Uint8Array>({
+        start(controller) {
+          controller.enqueue(new Uint8Array(DSH_PROFILE_MAX_BYTES + 1));
+        },
+        cancel() {
+          cancelled = true;
+        },
+      });
+      globalThis.fetch = async () => new Response(body, { status: 200, headers });
+
+      const res = await validateDshAccountToken("mock-token");
+      expect(res).toEqual({ valid: false, error: "PROFILE_VALIDATION_FAILED" });
+      expect(cancelled).toBe(true);
+    }
+  });
+
+  test("accepts a profile document at the byte cap and rejects one byte over a chunked boundary", async () => {
+    const base = JSON.stringify({
+      code: 0,
+      data: { biz_code: 0, biz_data: { id: "user-cap", email: "cap@example.com" } },
+    });
+    const encoder = new TextEncoder();
+    const atCap = base + " ".repeat(DSH_PROFILE_MAX_BYTES - base.length);
+    expect(encoder.encode(atCap).byteLength).toBe(DSH_PROFILE_MAX_BYTES);
+
+    globalThis.fetch = async () => new Response(atCap, { status: 200 });
+    const ok = await validateDshAccountToken("mock-token");
+    expect(ok.valid).toBe(true);
+    expect(ok.accountId).toBe("user-cap");
+
+    const overCap = encoder.encode(atCap + " ");
+    const chunked = new ReadableStream<Uint8Array>({
+      start(controller) {
+        controller.enqueue(overCap.subarray(0, DSH_PROFILE_MAX_BYTES));
+        controller.enqueue(overCap.subarray(DSH_PROFILE_MAX_BYTES));
+      },
+    });
+    globalThis.fetch = async () => new Response(chunked, { status: 200 });
+    expect(await validateDshAccountToken("mock-token")).toEqual({ valid: false, error: "PROFILE_VALIDATION_FAILED" });
+  });
+
+  test("rejects with the caller's abort reason while the profile body is still streaming", async () => {
+    const body = new ReadableStream<Uint8Array>({ start() { /* open stream, no data */ } });
+    globalThis.fetch = async () => new Response(body, { status: 200 });
+    const controller = new AbortController();
+    const reason = new DOMException("operator cancelled", "AbortError");
+    const pending = validateDshAccountToken("mock-token", controller.signal);
+    await new Promise(resolve => setTimeout(resolve, 10));
+    controller.abort(reason);
+    await expect(pending).rejects.toBe(reason);
+  });
+
+  test("surfaces a stalled profile body as PROFILE_VALIDATION_FAILED instead of hanging", async () => {
+    const body = new ReadableStream<Uint8Array>({ start() { /* open stream, no data */ } });
+    globalThis.fetch = async () => new Response(body, { status: 200 });
+    expect(await validateDshAccountToken("mock-token"))
+      .toEqual({ valid: false, error: "PROFILE_VALIDATION_FAILED" });
+  }, 30_000);
 });
 
 describe("DSH Account Login Flow", () => {