Add Policy

# Adding a Configuration Policy

Policies allow enterprise administrators to lock configuration settings via OS-level mechanisms (Windows Group Policy, macOS managed preferences, Linux config files) or via Copilot account-level policy data. This skill covers the complete procedure.

## When to Use

- Adding a new `policy:` field to any configuration property
- Modifying an existing policy (rename, category change, etc.)
- Reviewing a PR that touches policy registration
- Adding account-based policy support via `IPolicyData`

## Architecture Overview

### Policy Sources (layered, last writer wins)

| Source | Implementation | How it reads policies |
|--------|---------------|----------------------|
| **OS-level** (Windows registry, macOS plist) | `NativePolicyService` via `@vscode/policy-watcher` | Watches `Software\Policies\Microsoft\{productName}` (Windows) or bundle identifier prefs (macOS) |
| **Linux file** | `FilePolicyService` | Reads `/etc/vscode/policy.json` |
| **Account/GitHub** | `AccountPolicyService` | Reads `IPolicyData` from `IDefaultAccountService.policyData`, applies `value()` function |
| **Multiplex** | `MultiplexPolicyService` | Combines OS-level + account policy services; used in desktop main |

### Key Files

| File | Purpose |
|------|---------|
| `src/vs/base/common/policy.ts` | `PolicyCategory` enum, `IPolicy` interface |
| `src/vs/platform/policy/common/policy.ts` | `IPolicyService`, `AbstractPolicyService`, `PolicyDefinition` |
| `src/vs/platform/configuration/common/configurations.ts` | `PolicyConfiguration` — bridges policies to configuration values |
| `src/vs/workbench/services/policies/common/accountPolicyService.ts` | Account/GitHub-based policy evaluation |
| `src/vs/workbench/services/policies/common/multiplexPolicyService.ts` | Combines multiple policy services |
| `src/vs/workbench/contrib/policyExport/electron-browser/policyExport.contribution.ts` | `--export-policy-data` CLI handler |
| `src/vs/base/common/defaultAccount.ts` | `IPolicyData` interface for account-level policy fields |
| `build/lib/policies/policyData.jsonc` | Auto-generated policy catalog (DO NOT edit manually) |
| `build/lib/policies/policyGenerator.ts` | Generates ADMX/ADML (Windows), plist (macOS), JSON (Linux) |
| `build/lib/test/policyConversion.test.ts` | Tests for policy artifact generation |

## Procedure

### Step 1 — Add the `policy` field to the configuration property

Find the configuration registration (typically in a `*.contribution.ts` file) and add a `policy` object to the property schema.

**Required fields:**

**Determining `minimumVersion`:** Always read `version` from the root `package.json` and use the `major.minor` portion. For example, if `package.json` has `"version": "1.112.0"`, use `minimumVersion: '1.112'`. Never hardcode an old version like `'1.99'`.

```typescript
policy: {
    name: 'MyPolicyName',                          // PascalCase, unique across all policies
    category: PolicyCategory.InteractiveSession,    // From PolicyCategory enum
    minimumVersion: '1.112',                        // Use major.minor from package.json version
    localization: {
        description: {
            key: 'my.config.key',                   // NLS key for the description
            value: nls.localize('my.config.key', "Human-readable description."),
        }
    }
}
```

**Optional: `value` function for account-based policy:**

If this policy should also be controllable via Copilot account policy data (from `IPolicyData`), add a `value` function:

```typescript
policy: {
    name: 'MyPolicyName',
    category: PolicyCategory.InteractiveSession,
    minimumVersion: '1.112',                        // Use major.minor from package