policy: DeprecatedEditModeHidden (#300290)

* Add 'DeprecatedEditModeHidden' policy

* Add 'add-policy' skill

.github/skills/add-policy/SKILL.md

@@ -0,0 +1,139 @@
+---
+name: add-policy
+description: Use when adding, modifying, or reviewing VS Code configuration policies. Covers the full policy lifecycle from registration to export to platform-specific artifacts. Run on ANY change that adds a `policy:` field to a configuration property.
+---
+
+# 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.json version
+    value: (policyData) => policyData.my_field === false ? false : undefined,
+    localization: { /* ... */ }
+}
+```
+
+The `value` function receives `IPolicyData` (from `src/vs/base/common/defaultAccount.ts`) and should:
+- Return a concrete value to **override** the user's setting
+- Return `undefined` to **not apply** any account-level override (falls through to OS policy or user setting)
+
+If you need a new field on `IPolicyData`, add it to the interface in `src/vs/base/common/defaultAccount.ts`.
+
+**Optional: `enumDescriptions` for enum/string policies:**
+
+```typescript
+localization: {
+    description: { key: '...', value: nls.localize('...', "...") },
+    enumDescriptions: [
+        { key: 'opt.none', value: nls.localize('opt.none', "No access.") },
+        { key: 'opt.all', value: nls.localize('opt.all', "Full access.") },
+    ]
+}
+```
+
+### Step 2 — Ensure `PolicyCategory` is imported
+
+```typescript
+import { PolicyCategory } from '../../../../base/common/policy.js';
+```
+
+Existing categories in the `PolicyCategory` enum:
+- `Extensions`
+- `IntegratedTerminal`
+- `InteractiveSession` (used for all chat/Copilot policies)
+- `Telemetry`
+- `Update`
+
+If you need a new category, add it to `PolicyCategory` in `src/vs/base/common/policy.ts` and add corresponding `PolicyCategoryData` localization.
+
+### Step 3 — Validate TypeScript compilation
+
+Check the `VS Code - Build` watch task output, or run:
+
+```bash
+npm run compile-check-ts-native
+```
+
+### Step 4 — Export the policy data
+
+Regenerate the auto-generated policy catalog:
+
+```bash
+npm run transpile-client && ./scripts/code.sh --export-policy-data
+```
+
+This updates `build/lib/policies/policyData.jsonc`. **Never edit this file manually.** Verify your new policy appears in the output.  You will need code review from a codeowner to merge the change to main.
+
+
+## Policy for extension-provided settings
+
+For an extension author to provide policies for their extension's settings, a change must be made in `vscode-distro` to the `product.json`.
+
+## Examples
+
+Search the codebase for `policy:` to find all the examples of different policy configurations.

build/lib/policies/policyData.jsonc

@@ -169,6 +169,20 @@
             "type": "boolean",
             "default": true
         },
+        {
+            "key": "chat.editMode.hidden",
+            "name": "DeprecatedEditModeHidden",
+            "category": "InteractiveSession",
+            "minimumVersion": "1.112",
+            "localization": {
+                "description": {
+                    "key": "chat.editMode.hidden",
+                    "value": "When enabled, hides the Edit mode from the chat mode picker."
+                }
+            },
+            "type": "boolean",
+            "default": true
+        },
         {
             "key": "chat.useHooks",
             "name": "ChatHooks",

src/vs/workbench/contrib/chat/browser/chat.contribution.ts

@@ -728,6 +728,17 @@ configurationRegistry.registerConfiguration({
 			tags: ['experimental'],
 			experiment: {
 				mode: 'auto'
+			},
+			policy: {
+				name: 'DeprecatedEditModeHidden',
+				category: PolicyCategory.InteractiveSession,
+				minimumVersion: '1.112',
+				localization: {
+					description: {
+						key: 'chat.editMode.hidden',
+						value: nls.localize('chat.editMode.hidden', "When enabled, hides the Edit mode from the chat mode picker."),
+					}
+				}
 			}
 		},
 		[ChatConfiguration.EnableMath]: {