diff --git a/scripts/test_long_task_gate_lock.mjs b/scripts/test_long_task_gate_lock.mjs
new file mode 100644
index 0000000..bd02eb9
--- /dev/null
+++ b/scripts/test_long_task_gate_lock.mjs
@@ -0,0 +1,197 @@
+#!/usr/bin/env node
+import assert from 'node:assert/strict';
+import { spawnSync } from 'node:child_process';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+const gateScript = path.join(__dirname, 'long_task_gate_lock.mjs');
+
+const scenarios = [
+  {
+    name: 'ordinary chat -> gateStatus=not_applicable',
+    input: {
+      classification: 'ordinary_chat',
+      message: 'just answer directly',
+    },
+    expected: {
+      gateRequired: false,
+      gateStatus: 'not_applicable',
+      reasonIncludes: 'classification is not long_task',
+      allowedResponseModesIncludes: 'direct_reply',
+      requiredEvidenceLength: 0,
+    },
+  },
+  {
+    name: 'long-task missing externalized checkpoint -> gateStatus=fail',
+    input: {
+      classification: 'long_task',
+      silentContinuation: true,
+    },
+    expected: {
+      gateRequired: true,
+      gateStatus: 'fail',
+      reasonIncludes: 'silent long-task cannot continue without externalized checkpoint path',
+      allowedResponseModesIncludes: 'non_silent_follow_up',
+      requiredEvidenceKey: 'externalizedCheckpoint',
+    },
+  },
+  {
+    name: 'long-task with explicit externalized checkpoint + concrete next action -> gateStatus=pass',
+    input: {
+      classification: 'long_task',
+      silentContinuation: true,
+      claimedExecution: true,
+      externalizedCheckpointPath: 'checkpoints/task-42.md',
+      concreteNextAction: 'Run the queued verifier and report back with output.',
+    },
+    expected: {
+      gateRequired: true,
+      gateStatus: 'pass',
+      reasonIncludes: 'required long-task gate evidence is present or no gated condition was triggered',
+      allowedResponseModesIncludes: 'silent_continuation',
+      allowedResponseModesIncludesAlso: 'direct_reply',
+      requiredEvidenceLength: 0,
+    },
+  },
+  {
+    name: 'owner decision without button-path -> gateStatus=fail',
+    input: {
+      classification: 'long_task',
+      needsOwnerDecision: true,
+      replyClosureMode: 'plain_text',
+    },
+    expected: {
+      gateRequired: true,
+      gateStatus: 'fail',
+      reasonIncludes: 'owner decision flow must end in button-path, not plain text',
+      allowedResponseModesIncludes: 'button_path',
+      requiredEvidenceKey: 'buttonPathMode',
+    },
+  },
+  {
+    name: 'owner decision with button-path -> gateStatus=pass',
+    input: {
+      classification: 'long_task',
+      needsOwnerDecision: true,
+      replyClosureMode: 'button_path',
+    },
+    expected: {
+      gateRequired: true,
+      gateStatus: 'pass',
+      reasonIncludes: 'required long-task gate evidence is present or no gated condition was triggered',
+      allowedResponseModesIncludes: 'button_path',
+      requiredEvidenceLength: 0,
+    },
+  },
+];
+
+function runGate(input) {
+  const result = spawnSync(process.execPath, [gateScript, '--compact'], {
+    input: JSON.stringify(input),
+    encoding: 'utf8',
+  });
+
+  if (result.status !== 0) {
+    throw new Error(`gate script failed with status=${result.status}: ${result.stderr || result.stdout}`);
+  }
+
+  let parsed;
+  try {
+    parsed = JSON.parse(result.stdout);
+  } catch (error) {
+    throw new Error(`gate script returned invalid JSON: ${error.message}\nstdout=${result.stdout}`);
+  }
+
+  return parsed;
+}
+
+function requireCoreFields(output) {
+  assert.equal(typeof output.gateRequired, 'boolean', 'gateRequired should be boolean');
+  assert.equal(typeof output.gateStatus, 'string', 'gateStatus should be string');
+  assert.ok(Array.isArray(output.reasons), 'reasons should be an array');
+  assert.ok(Array.isArray(output.requiredEvidence), 'requiredEvidence should be an array');
+  assert.ok(Array.isArray(output.allowedResponseModes), 'allowedResponseModes should be an array');
+}
+
+function assertScenario(output, expected) {
+  assert.equal(output.gateRequired, expected.gateRequired, 'gateRequired mismatch');
+  assert.equal(output.gateStatus, expected.gateStatus, 'gateStatus mismatch');
+
+  if (expected.reasonIncludes) {
+    assert.ok(
+      output.reasons.some((reason) => reason.includes(expected.reasonIncludes)),
+      `expected reasons to include: ${expected.reasonIncludes}`,
+    );
+  }
+
+  if (expected.allowedResponseModesIncludes) {
+    assert.ok(
+      output.allowedResponseModes.includes(expected.allowedResponseModesIncludes),
+      `expected allowedResponseModes to include: ${expected.allowedResponseModesIncludes}`,
+    );
+  }
+
+  if (expected.allowedResponseModesIncludesAlso) {
+    assert.ok(
+      output.allowedResponseModes.includes(expected.allowedResponseModesIncludesAlso),
+      `expected allowedResponseModes to include: ${expected.allowedResponseModesIncludesAlso}`,
+    );
+  }
+
+  if (typeof expected.requiredEvidenceLength === 'number') {
+    assert.equal(
+      output.requiredEvidence.length,
+      expected.requiredEvidenceLength,
+      'requiredEvidence length mismatch',
+    );
+  }
+
+  if (expected.requiredEvidenceKey) {
+    assert.ok(
+      output.requiredEvidence.some((entry) => entry && entry.evidenceKey === expected.requiredEvidenceKey),
+      `expected requiredEvidence to include key: ${expected.requiredEvidenceKey}`,
+    );
+  }
+}
+
+const results = [];
+let failed = false;
+
+for (const scenario of scenarios) {
+  try {
+    const output = runGate(scenario.input);
+    requireCoreFields(output);
+    assertScenario(output, scenario.expected);
+
+    results.push({
+      scenario: scenario.name,
+      ok: true,
+      gateRequired: output.gateRequired,
+      gateStatus: output.gateStatus,
+      reasons: output.reasons,
+      requiredEvidenceKeys: output.requiredEvidence.map((entry) => entry.evidenceKey),
+      allowedResponseModes: output.allowedResponseModes,
+      assertion: 'pass',
+    });
+  } catch (error) {
+    failed = true;
+    results.push({
+      scenario: scenario.name,
+      ok: false,
+      assertion: 'fail',
+      error: error instanceof Error ? error.message : String(error),
+    });
+  }
+}
+
+const summary = {
+  total: results.length,
+  passed: results.filter((entry) => entry.ok).length,
+  failed: results.filter((entry) => !entry.ok).length,
+};
+
+process.stdout.write(`${JSON.stringify({ summary, results }, null, 2)}\n`);
+
+if (failed) process.exit(1);