diff --git a/scripts/e2e/lib/plugins/assertions.mjs b/scripts/e2e/lib/plugins/assertions.mjs
index c99d4c10a9f4..ed85eff9a288 100644
--- a/scripts/e2e/lib/plugins/assertions.mjs
+++ b/scripts/e2e/lib/plugins/assertions.mjs
@@ -324,13 +324,18 @@ function assertSimplePlugin(jsonFile, inspectFile, pluginId, method) {
   }
 }
 
-function assertUpdateOutput(logFile, expectedSnippet) {
-  if (!fileContainsText(logFile, expectedSnippet)) {
-    const outputTail = readTextFileTail(logFile, ERROR_DETAIL_TAIL_BYTES);
-    throw new Error(
-      `expected update output to include ${JSON.stringify(expectedSnippet)}. Output tail:\n${outputTail}`,
-    );
+function assertTextFileIncludes(file, expectedSnippet, label) {
+  if (fileContainsText(file, expectedSnippet)) {
+    return;
   }
+  const outputTail = readTextFileTail(file, ERROR_DETAIL_TAIL_BYTES);
+  throw new Error(
+    `expected ${label} to include ${JSON.stringify(expectedSnippet)}. Output tail:\n${outputTail}`,
+  );
+}
+
+function assertUpdateOutput(logFile, expectedSnippet) {
+  assertTextFileIncludes(logFile, expectedSnippet, "update output");
 }
 
 function assertClaudeBundleDisabled() {
@@ -504,10 +509,11 @@ function assertGitPlugin() {
     throw new Error(`expected demo-git cli command, got ${inspect.cliCommands?.join(", ")}`);
   }
 
-  const cliOutput = fs.readFileSync(scratchFile("plugins-git-cli.txt"), "utf8");
-  if (!cliOutput.includes("demo-plugin-git:pong")) {
-    throw new Error(`unexpected git plugin cli output: ${cliOutput.trim()}`);
-  }
+  assertTextFileIncludes(
+    scratchFile("plugins-git-cli.txt"),
+    "demo-plugin-git:pong",
+    "git plugin CLI output",
+  );
 
   const record = getInstallRecords()["demo-plugin-git"];
   if (!record) {
@@ -690,10 +696,11 @@ function assertNpmPlugin() {
     throw new Error(`expected demo-npm cli command, got ${inspect.cliCommands?.join(", ")}`);
   }
 
-  const cliOutput = fs.readFileSync(scratchFile("plugins-npm-cli.txt"), "utf8");
-  if (!cliOutput.includes("demo-plugin-npm:pong")) {
-    throw new Error(`unexpected npm plugin cli output: ${cliOutput.trim()}`);
-  }
+  assertTextFileIncludes(
+    scratchFile("plugins-npm-cli.txt"),
+    "demo-plugin-npm:pong",
+    "npm plugin CLI output",
+  );
 
   const record = getInstallRecords()["demo-plugin-npm"];
   if (!record) {
@@ -781,13 +788,12 @@ function assertNpmPluginRemoved() {
 
 function assertInvalidOpenClawExtensionsRejected() {
   const pluginId = "demo-plugin-invalid-metadata";
-  const output = fs.readFileSync(scratchFile("plugins-invalid-openclaw-extensions.log"), "utf8");
   for (const expected of ["openclaw.extensions[1]", "non-empty string"]) {
-    if (!output.includes(expected)) {
-      throw new Error(
-        `expected malformed metadata install output to include ${JSON.stringify(expected)}:\n${output}`,
-      );
-    }
+    assertTextFileIncludes(
+      scratchFile("plugins-invalid-openclaw-extensions.log"),
+      expected,
+      "malformed metadata install output",
+    );
   }
 
   const list = readJson(scratchFile("plugins-invalid-openclaw-extensions-list.json"));
@@ -835,10 +841,11 @@ function assertGitPluginUpdated() {
     throw new Error(`expected demo-git-update cli command, got ${inspect.cliCommands?.join(", ")}`);
   }
 
-  const cliOutput = fs.readFileSync(scratchFile("plugins-git-update-cli.txt"), "utf8");
-  if (!cliOutput.includes("demo-plugin-git-update:pong-v2")) {
-    throw new Error(`unexpected updated git plugin cli output: ${cliOutput.trim()}`);
-  }
+  assertTextFileIncludes(
+    scratchFile("plugins-git-update-cli.txt"),
+    "demo-plugin-git-update:pong-v2",
+    "updated git plugin CLI output",
+  );
 
   const record = getInstallRecords()["demo-plugin-git-update"];
   if (!record) {
@@ -1037,10 +1044,11 @@ function assertClawHubRemoved() {
 }
 
 function assertClawHubUpdated() {
-  const output = fs.readFileSync(scratchFile("plugins-clawhub-update.log"), "utf8");
-  if (!output.includes(`${process.env.CLAWHUB_PLUGIN_ID} already at `)) {
-    throw new Error(`expected ClawHub update to report already-at version:\n${output}`);
-  }
+  assertTextFileIncludes(
+    scratchFile("plugins-clawhub-update.log"),
+    `${process.env.CLAWHUB_PLUGIN_ID} already at `,
+    "ClawHub update output",
+  );
   assertClawHubInstalled();
 }
 
diff --git a/test/scripts/plugins-assertions.test.ts b/test/scripts/plugins-assertions.test.ts
index bccff578c026..4a3e0858d316 100644
--- a/test/scripts/plugins-assertions.test.ts
+++ b/test/scripts/plugins-assertions.test.ts
@@ -208,7 +208,7 @@ test -d "$OPENCLAW_PLUGINS_TMP_DIR"
     }
   });
 
-  it("scans plugin update logs without echoing whole files on failure", async () => {
+  it("scans plugin assertion logs without echoing whole files on failure", async () => {
     const root = mkdtempSync(path.join(tmpdir(), "openclaw-plugin-update-log-"));
     try {
       const passRoot = path.join(root, "pass");
@@ -237,6 +237,27 @@ test -d "$OPENCLAW_PLUGINS_TMP_DIR"
       expect(fail.stderr).toContain("Output tail:");
       expect(fail.stderr).toContain("missing marker tail");
       expect(fail.stderr.length).toBeLessThan(20 * 1024);
+
+      const invalidRoot = path.join(root, "invalid");
+      const invalidHome = path.join(root, "home");
+      mkdirSync(invalidRoot, { recursive: true });
+      mkdirSync(invalidHome, { recursive: true });
+      writeFileSync(
+        path.join(invalidRoot, "plugins-invalid-openclaw-extensions.log"),
+        `openclaw.extensions[1]\n${"x".repeat(256 * 1024)}\nmissing validation tail`,
+        "utf8",
+      );
+      writeJson(path.join(invalidRoot, "plugins-invalid-openclaw-extensions-list.json"), {
+        plugins: [],
+      });
+      const invalid = await runAssertionAsync(["invalid-openclaw-extensions"], {
+        HOME: invalidHome,
+        OPENCLAW_PLUGINS_TMP_DIR: invalidRoot,
+      });
+      expect(invalid.status).toBe(1);
+      expect(invalid.stderr).toContain("malformed metadata install output");
+      expect(invalid.stderr).toContain("missing validation tail");
+      expect(invalid.stderr.length).toBeLessThan(20 * 1024);
     } finally {
       rmSync(root, { recursive: true, force: true });
     }