fix: prevent stale cache when editing prompts across multiple windows

Add refreshGlobalStateKey() method to ContextProxy that reads fresh values
from VS Code's globalState before performing read-modify-write operations.

This fixes a bug where editing the context condensing prompt or mode prompts
would revert to a previous value when multiple VS Code windows are open,
because each window had its own stale cache.

src/core/config/ContextProxy.ts

@@ -208,6 +208,19 @@ export class ContextProxy {
 		return this.originalContext.globalState.update(key, value)
 	}
 
+	/**
+	 * Refresh a specific key from globalState and update the cache.
+	 * This is useful for settings that may be edited across multiple VS Code windows,
+	 * ensuring we read the latest value before making modifications.
+	 * @param key The global state key to refresh
+	 * @returns The fresh value from globalState
+	 */
+	refreshGlobalStateKey<K extends GlobalStateKey>(key: K): GlobalState[K] {
+		const value = this.originalContext.globalState.get<GlobalState[K]>(key)
+		this.stateCache[key] = value
+		return value as GlobalState[K]
+	}
+
 	private getAllGlobalState(): GlobalState {
 		return Object.fromEntries(GLOBAL_STATE_KEYS.map((key) => [key, this.getGlobalState(key)]))
 	}

src/core/config/__tests__/ContextProxy.spec.ts

@@ -185,6 +185,57 @@ describe("ContextProxy", () => {
 		})
 	})
 
+	describe("refreshGlobalStateKey", () => {
+		it("should read fresh value from globalState and update cache", async () => {
+			// Set up initial cache value
+			await proxy.updateGlobalState("customSupportPrompts", { OLD: "old-prompt" })
+
+			// Simulate another window updating globalState directly (bypassing our cache)
+			const newValue = { OLD: "old-prompt", NEW: "new-prompt" }
+			mockGlobalState.get.mockReturnValue(newValue)
+
+			// Refresh the key
+			const result = proxy.refreshGlobalStateKey("customSupportPrompts")
+
+			// Should return the fresh value from globalState
+			expect(result).toEqual(newValue)
+
+			// Should have updated the cache (subsequent getGlobalState should return new value)
+			const cachedValue = proxy.getGlobalState("customSupportPrompts")
+			expect(cachedValue).toEqual(newValue)
+		})
+
+		it("should return undefined when globalState has no value", async () => {
+			// Set up initial cache value
+			await proxy.updateGlobalState("customModePrompts", { code: { roleDefinition: "test" } })
+
+			// Simulate globalState being cleared (e.g., by another window)
+			mockGlobalState.get.mockReturnValue(undefined)
+
+			// Refresh the key
+			const result = proxy.refreshGlobalStateKey("customModePrompts")
+
+			// Should return undefined
+			expect(result).toBeUndefined()
+
+			// Cache should also be updated to undefined
+			const cachedValue = proxy.getGlobalState("customModePrompts")
+			expect(cachedValue).toBeUndefined()
+		})
+
+		it("should call globalState.get with the correct key", async () => {
+			// Clear mock call history
+			mockGlobalState.get.mockClear()
+			mockGlobalState.get.mockReturnValue({ ENHANCE: "test-prompt" })
+
+			// Refresh a specific key
+			proxy.refreshGlobalStateKey("customSupportPrompts")
+
+			// Should have called get with the correct key
+			expect(mockGlobalState.get).toHaveBeenCalledWith("customSupportPrompts")
+		})
+	})
+
 	describe("getSecret", () => {
 		it("should return value from cache when it exists", async () => {
 			// Manually set a value in the cache

src/core/webview/webviewMessageHandler.ts

@@ -1485,7 +1485,9 @@ export const webviewMessageHandler = async (
 			break
 		case "updatePrompt":
 			if (message.promptMode && message.customPrompt !== undefined) {
-				const existingPrompts = getGlobalState("customModePrompts") ?? {}
+				// Use refreshGlobalStateKey to get the latest value from globalState,
+				// avoiding stale cache issues when multiple VS Code windows are open.
+				const existingPrompts = provider.contextProxy.refreshGlobalStateKey("customModePrompts") ?? {}
 				const updatedPrompts = { ...existingPrompts, [message.promptMode]: message.customPrompt }
 				await updateGlobalState("customModePrompts", updatedPrompts)
 				const currentState = await provider.getStateToPostToWebview()
@@ -1571,7 +1573,9 @@ export const webviewMessageHandler = async (
 		case "updateCondensingPrompt":
 			// Store the condensing prompt in customSupportPrompts["CONDENSE"]
 			// instead of customCondensingPrompt.
-			const currentSupportPrompts = getGlobalState("customSupportPrompts") ?? {}
+			// Use refreshGlobalStateKey to get the latest value from globalState,
+			// avoiding stale cache issues when multiple VS Code windows are open.
+			const currentSupportPrompts = provider.contextProxy.refreshGlobalStateKey("customSupportPrompts") ?? {}
 			const updatedSupportPrompts = { ...currentSupportPrompts, CONDENSE: message.text }
 			await updateGlobalState("customSupportPrompts", updatedSupportPrompts)
 			// Also update the old field for backward compatibility during migration.