This template provides conservative defaults for a browser extension with an optional server. A generated product must review these rules against its actual permissions, data flows, and providers.

• Manifest V3 extension pages use an explicit script-src 'self'; object-src 'self'; content security policy.
• Do not add inline scripts, dynamic code evaluation, or unnecessary permissions.
• Values exposed through VITE_ variables are public and may be bundled into the extension. Never put admin keys, server credentials, or other secrets in them.
• Treat captured page content as untrusted input. Bound and validate it before transport or storage.
• Keep browser-specific API calls behind the platform adapter so target differences do not bypass the extension's validation and permission boundaries.

• Parse runtime environment values with Zod at startup and fail clearly on invalid configuration.
• Do not fetch arbitrary user-supplied URLs from the server. If a product needs server-side fetching, define an allowlist and validate URL, scheme, redirects, response size, and timeout explicitly.
• Keep provider credentials and prompt construction on the server side.
• The built-in provider adapters read credentials from server-only settings (OPENAI_API_KEY, ANTHROPIC_API_KEY, or the selected-provider AI_API_KEY fallback); never put these values in VITE_ variables or extension code.
• Resolve the selected provider during server composition so missing credentials and unsupported provider IDs fail before handling user analysis requests.
• Do not log page content, credentials, or complete provider prompts by default.

• Keep local .env files ignored and commit only .env.example placeholders.
• Review new permissions, endpoints, storage, dependencies, and data retention in the product definition and an ADR when the decision is non-trivial.
• Replace the Firefox manifest's template extension ID and data_collection_permissions declaration with product-owned values before signing or publishing an add-on.