diff --git a/.github/workflows/npm-telegram-beta-e2e.yml b/.github/workflows/npm-telegram-beta-e2e.yml
index d31b8354fa9a..4d734fb95c28 100644
--- a/.github/workflows/npm-telegram-beta-e2e.yml
+++ b/.github/workflows/npm-telegram-beta-e2e.yml
@@ -267,6 +267,8 @@ jobs:
             },
             ...(Array.isArray(manifest.dependencyTarballs) ? manifest.dependencyTarballs : []),
           ];
+          const packageNames = new Set();
+          const tarballNames = new Set();
           for (const entry of entries) {
             if (
               !entry.packageName ||
@@ -277,6 +279,11 @@ jobs:
             ) {
               throw new Error("package artifact manifest contains invalid tarball metadata");
             }
+            if (packageNames.has(entry.packageName) || tarballNames.has(entry.tarballName)) {
+              throw new Error("package artifact manifest contains duplicate package metadata");
+            }
+            packageNames.add(entry.packageName);
+            tarballNames.add(entry.tarballName);
             const tarballPath = path.join(packageDir, entry.tarballName);
             if (!fs.existsSync(tarballPath)) {
               throw new Error(`package artifact is missing ${entry.tarballName}`);
@@ -294,6 +301,16 @@ jobs:
               throw new Error(`package artifact metadata mismatch for ${entry.packageName}`);
             }
           }
+          const artifactTarballs = fs
+            .readdirSync(packageDir, { withFileTypes: true })
+            .filter((entry) => entry.isFile() && entry.name.endsWith(".tgz"))
+            .map((entry) => entry.name);
+          if (
+            artifactTarballs.length !== tarballNames.size ||
+            artifactTarballs.some((name) => !tarballNames.has(name))
+          ) {
+            throw new Error("package artifact tarball set does not match preflight manifest");
+          }
           process.stdout.write(path.join(packageDir, manifest.tarballName));
           NODE
               )"
diff --git a/scripts/e2e/lib/plugins/npm-registry-server.mjs b/scripts/e2e/lib/plugins/npm-registry-server.mjs
index 0fc7a14eb311..df4a5d41917c 100644
--- a/scripts/e2e/lib/plugins/npm-registry-server.mjs
+++ b/scripts/e2e/lib/plugins/npm-registry-server.mjs
@@ -114,8 +114,10 @@ async function proxyUpstream(url, response) {
     const upstreamUrl = new URL(`${url.pathname}${url.search}`, `${upstreamRegistry}/`);
     const upstreamResponse = await fetch(upstreamUrl, { redirect: "manual" });
     const body = Buffer.from(await upstreamResponse.arrayBuffer());
-    const headers = {};
-    for (const name of ["content-length", "content-type", "location"]) {
+    // Fetch decodes compressed bodies but preserves upstream length metadata.
+    // Emit the decoded size so npm clients do not truncate proxied responses.
+    const headers = { "content-length": String(body.length) };
+    for (const name of ["content-type", "location"]) {
       const value = upstreamResponse.headers.get(name);
       if (value) {
         headers[name] = value;
diff --git a/test/scripts/package-acceptance-workflow.test.ts b/test/scripts/package-acceptance-workflow.test.ts
index e4de6396d962..f0d074169eb2 100644
--- a/test/scripts/package-acceptance-workflow.test.ts
+++ b/test/scripts/package-acceptance-workflow.test.ts
@@ -1785,6 +1785,8 @@ describe("package artifact reuse", () => {
       'manifest="${package_dir}/preflight-manifest.json"',
       'candidate_manifest="${package_dir}/package-candidate.json"',
       'find "${package_dir}" -type f -name "*.tgz"',
+      "package artifact manifest contains duplicate package metadata",
+      "package artifact tarball set does not match preflight manifest",
       "package candidate manifest does not match the OpenClaw tarball",
       "package candidate digest mismatch",
       'export OPENCLAW_NPM_TELEGRAM_PACKAGE_DIR="${package_dir}"',
diff --git a/test/scripts/plugins-assertions.test.ts b/test/scripts/plugins-assertions.test.ts
index 0314ce639b47..59c63a713224 100644
--- a/test/scripts/plugins-assertions.test.ts
+++ b/test/scripts/plugins-assertions.test.ts
@@ -12,6 +12,7 @@ import {
 import { createServer, request as httpRequest } from "node:http";
 import { tmpdir } from "node:os";
 import path from "node:path";
+import { gzipSync } from "node:zlib";
 import { describe, expect, it } from "vitest";
 import { createBoundedChildOutput } from "../helpers/bounded-child-output.js";
 import { cleanupTempDirs, makeTempDir } from "../helpers/temp-dir.js";
@@ -160,7 +161,7 @@ function requestFixtureRegistry(
   port: number,
   requestPath: string,
   headers: Record<string, string> = {},
-): Promise<{ body: string; statusCode: number | undefined }> {
+): Promise<{ body: string; contentLength: string | undefined; statusCode: number | undefined }> {
   return new Promise((resolve, reject) => {
     const request = httpRequest(
       { headers, host: "127.0.0.1", method: "GET", path: requestPath, port },
@@ -171,7 +172,11 @@ function requestFixtureRegistry(
           body += chunk;
         });
         response.on("end", () => {
-          resolve({ body, statusCode: response.statusCode });
+          resolve({
+            body,
+            contentLength: response.headers["content-length"],
+            statusCode: response.statusCode,
+          });
         });
       },
     );
@@ -670,6 +675,71 @@ test -d "$OPENCLAW_PLUGINS_TMP_DIR"
     }
   });
 
+  it("recomputes proxied content length after fetch decodes the response", async () => {
+    const tempDirs: string[] = [];
+    const root = makeTempDir(tempDirs, "openclaw-plugin-npm-fixture-proxy-");
+    const portFile = path.join(root, "port");
+    const tarballPath = path.join(root, "demo-plugin.tgz");
+    const upstreamBody = JSON.stringify({ payload: "x".repeat(1_000) });
+    const compressedBody = gzipSync(upstreamBody);
+    writeFileSync(tarballPath, "fixture package archive", "utf8");
+
+    const upstream = createServer((_request, response) => {
+      response.writeHead(200, {
+        "content-encoding": "gzip",
+        "content-length": String(compressedBody.length),
+        "content-type": "application/json",
+      });
+      response.end(compressedBody);
+    });
+    await new Promise<void>((resolve) => {
+      upstream.listen(0, "127.0.0.1", resolve);
+    });
+    const upstreamAddress = upstream.address();
+    if (!upstreamAddress || typeof upstreamAddress === "string") {
+      throw new Error("expected upstream registry address");
+    }
+
+    const child = spawn(
+      process.execPath,
+      [
+        "scripts/e2e/lib/plugins/npm-registry-server.mjs",
+        portFile,
+        "@openclaw/demo-plugin-npm",
+        "1.0.0",
+        tarballPath,
+      ],
+      {
+        cwd: process.cwd(),
+        env: {
+          ...process.env,
+          OPENCLAW_NPM_REGISTRY_UPSTREAM: `http://127.0.0.1:${upstreamAddress.port}`,
+        },
+        stdio: ["ignore", "pipe", "pipe"],
+      },
+    );
+
+    try {
+      const port = await waitForPortFile(portFile);
+      const response = await requestFixtureRegistry(port, "/upstream-package");
+
+      expect(response.statusCode).toBe(200);
+      expect(response.body).toBe(upstreamBody);
+      expect(response.contentLength).toBe(String(Buffer.byteLength(upstreamBody)));
+    } finally {
+      if (child.exitCode === null) {
+        child.kill();
+        await new Promise((resolve) => {
+          child.once("close", resolve);
+        });
+      }
+      await new Promise<void>((resolve) => {
+        upstream.close(() => resolve());
+      });
+      cleanupTempDirs(tempDirs);
+    }
+  });
+
   it("rejects invalid plugin fixture log byte limits before npm fixture setup", () => {
     const root = mkdtempSync(path.join(tmpdir(), "openclaw-plugin-npm-fixture-log-invalid-"));
     try {