diff --git a/packages/commercial-development-agent/src/opencode-install-contract.test.mjs b/packages/commercial-development-agent/src/opencode-install-contract.test.mjs
new file mode 100644
index 00000000..0dacf21c
--- /dev/null
+++ b/packages/commercial-development-agent/src/opencode-install-contract.test.mjs
@@ -0,0 +1,48 @@
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+import { describe, expect, it } from 'vitest';
+
+const WORKSPACE_PATH = resolve(
+  import.meta.dirname,
+  '../../../pnpm-workspace.yaml',
+);
+const PACKAGE_PATH = resolve(import.meta.dirname, '../package.json');
+
+const workspace = readFileSync(WORKSPACE_PATH, 'utf8');
+const packageJson = JSON.parse(readFileSync(PACKAGE_PATH, 'utf8'));
+
+function parseTopLevelYamlSequence(document, key) {
+  const lines = document.replace(/\r\n?/gu, '\n').split('\n');
+  const headerIndex = lines.findIndex((line) => line === `${key}:`);
+  if (headerIndex === -1) {
+    throw new Error(`Missing required YAML sequence: ${key}`);
+  }
+
+  const values = [];
+  for (const line of lines.slice(headerIndex + 1)) {
+    if (line.length === 0) {
+      continue;
+    }
+    if (!line.startsWith(' ')) {
+      break;
+    }
+
+    const item = /^  -\s+([^#]+?)\s*$/u.exec(line);
+    if (!item) {
+      throw new Error(`Unsupported ${key} YAML entry: ${line}`);
+    }
+    values.push(item[1].trim());
+  }
+
+  return values;
+}
+
+describe('OpenCode installation boundary', () => {
+  it('allows only the reviewed exact OpenCode dependency to run install lifecycle scripts', () => {
+    expect(packageJson.devDependencies['opencode-ai']).toBe('1.18.9');
+    expect(
+      parseTopLevelYamlSequence(workspace, 'onlyBuiltDependencies'),
+    ).toEqual(['opencode-ai']);
+    expect(workspace).not.toContain('dangerouslyAllowAllBuilds');
+  });
+});
diff --git a/pnpm-workspace.yaml b/pnpm-workspace.yaml
index 76553917..cfe685dd 100644
--- a/pnpm-workspace.yaml
+++ b/pnpm-workspace.yaml
@@ -2,3 +2,6 @@ packages:
   - apps/*
   - packages/*
   - infra/tests
+
+onlyBuiltDependencies:
+  - opencode-ai