fix(ci): select migrated E2E parity entrypoint

.github/actions/ci-cli-coverage-shard/action.yaml

@@ -91,7 +91,15 @@ runs:
             exit 0
             ;;
         esac
-        npx tsx scripts/checks/e2e-mock-parity.ts --base "$base" --head "$head"
+        parity_check=scripts/checks/e2e-mock-parity.mts
+        if [ ! -f "$parity_check" ]; then
+          parity_check=scripts/checks/e2e-mock-parity.ts
+        fi
+        if [ ! -f "$parity_check" ]; then
+          echo "::error title=Missing E2E mock parity entrypoint::Expected scripts/checks/e2e-mock-parity.mts or scripts/checks/e2e-mock-parity.ts."
+          exit 1
+        fi
+        npx tsx "$parity_check" --base "$base" --head "$head"
 
     - name: Build TypeScript plugin
       shell: bash

test/e2e-mock-parity.test.ts

@@ -1,12 +1,17 @@
 // SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+import { type SpawnSyncReturns, spawnSync } from "node:child_process";
+import { existsSync, mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 import { describe, expect, it } from "vitest";
 import {
   isMockParityRelevantSourceChange,
   type MockParityManifest,
   validateMockParity,
 } from "../scripts/checks/e2e-mock-parity";
+import { type CompositeAction, readYaml } from "./helpers/e2e-workflow-contract";
 
 const live = "test/e2e/live/example.test.ts";
 const fast = "test/e2e/support/example.test.ts";
@@ -108,3 +113,85 @@ describe("changed live E2E mock parity", () => {
     ).toEqual([`${live}: liveOnlyReason must be a string`]);
   });
 });
+
+describe("trusted E2E parity entrypoint selection", () => {
+  const action = readYaml<CompositeAction>(".github/actions/ci-cli-coverage-shard/action.yaml");
+  const parityStep = action.runs.steps.find(
+    (step) => step.name === "Validate changed live E2E mock parity",
+  );
+  const parityRun = parityStep?.run ?? "";
+  const parityEnv = parityStep?.env ?? {};
+  const stem = "scripts/checks/e2e-mock-parity";
+
+  function withParityEntrypoints(
+    extensions: readonly string[],
+    verify: (result: SpawnSyncReturns<string>, commandLog: string) => void,
+  ): void {
+    const temp = mkdtempSync(join(tmpdir(), "nemoclaw-e2e-parity-entrypoint-"));
+    const fakeBin = join(temp, "bin");
+    const commandLog = join(temp, "command.json");
+    mkdirSync(fakeBin);
+    mkdirSync(join(temp, "scripts", "checks"), { recursive: true });
+    writeFileSync(
+      join(fakeBin, "npx"),
+      [
+        "#!/usr/bin/env node",
+        'const fs = require("node:fs");',
+        "fs.appendFileSync(process.env.COMMAND_LOG, `${JSON.stringify(process.argv.slice(2))}\\n`);",
+      ].join("\n"),
+      { mode: 0o755 },
+    );
+    for (const extension of extensions) {
+      writeFileSync(join(temp, `${stem}.${extension}`), "// fixture\n");
+    }
+
+    try {
+      verify(
+        spawnSync("bash", ["-c", parityRun], {
+          cwd: temp,
+          encoding: "utf8",
+          env: {
+            ...process.env,
+            ...parityEnv,
+            COMMAND_LOG: commandLog,
+            EVENT_NAME: "pull_request",
+            PATH: `${fakeBin}:${process.env.PATH ?? ""}`,
+            PUSH_BASE_SHA: "unused",
+          },
+          timeout: 5_000,
+        }),
+        commandLog,
+      );
+    } finally {
+      rmSync(temp, { force: true, recursive: true });
+    }
+  }
+
+  it.each([
+    {
+      extensions: ["mts", "ts"],
+      expected: `${stem}.mts`,
+      title: "prefers .mts when both entrypoints exist",
+    },
+    { extensions: ["mts"], expected: `${stem}.mts`, title: "runs the migrated .mts entrypoint" },
+    { extensions: ["ts"], expected: `${stem}.ts`, title: "falls back to the .ts entrypoint" },
+  ])("$title (#6921)", ({ extensions, expected }) => {
+    withParityEntrypoints(extensions, (result, commandLog) => {
+      expect(result.status, String(result.stderr)).toBe(0);
+      expect(
+        readFileSync(commandLog, "utf8")
+          .trim()
+          .split("\n")
+          .map((line) => JSON.parse(line)),
+      ).toEqual([["tsx", expected, "--base", "HEAD^1", "--head", "HEAD^2"]]);
+    });
+  });
+
+  it("rejects a missing parity entrypoint (#6921)", () => {
+    withParityEntrypoints([], (result, commandLog) => {
+      expect(result.status, String(result.stderr)).toBe(1);
+      expect(existsSync(commandLog)).toBe(false);
+      expect(String(result.stdout)).toContain("Missing E2E mock parity entrypoint");
+    });
+  });
+});

test/pr-workflow-contract.test.ts

@@ -975,9 +975,6 @@ describe("pull request and main workflow contracts", () => {
     expect(parityStep.run).toContain("base=HEAD^1");
     expect(parityStep.run).toContain("head=HEAD^2");
     expect(parityStep.run).toContain('base="$PUSH_BASE_SHA"');
-    expect(parityStep.run).toContain(
-      'npx tsx scripts/checks/e2e-mock-parity.ts --base "$base" --head "$head"',
-    );
 
     const trustedCapabilityProbe = requiredWorkflowStep(
       prWorkflow.jobs["cli-test-shards"],