diff --git a/src/activate/registerCommands.ts b/src/activate/registerCommands.ts
index 8f0529574a..ae9080101c 100644
--- a/src/activate/registerCommands.ts
+++ b/src/activate/registerCommands.ts
@@ -228,13 +228,38 @@ const getCommandsMap = ({ context, outputChannel, provider }: RegisterCommandOpt
 		}
 
 		try {
-			const projectId = await generateProjectId(workspacePath)
-			vscode.window.showInformationMessage(t("common:info.project_id_generated", { projectId }))
+			// Check if project ID already exists
+			const { getProjectId } = await import("../utils/projectId")
+			const existingId = await getProjectId(workspacePath)
 
-			// Notify the provider to update any cached state
+			if (existingId) {
+				vscode.window.showInformationMessage(
+					t("common:info.project_id_already_exists", { projectId: existingId }),
+				)
+				return
+			}
+
+			const projectId = await generateProjectId(workspacePath)
+
+			// Migrate existing tasks to use the new project ID
 			const visibleProvider = getVisibleProviderOrLog(outputChannel)
 			if (visibleProvider) {
+				const migrated = await visibleProvider.migrateTasksToProjectId(workspacePath, projectId)
+
+				if (migrated > 0) {
+					vscode.window.showInformationMessage(
+						t("common:info.project_id_generated_with_migration", {
+							projectId,
+							count: migrated,
+						}),
+					)
+				} else {
+					vscode.window.showInformationMessage(t("common:info.project_id_generated", { projectId }))
+				}
+
 				await visibleProvider.postStateToWebview()
+			} else {
+				vscode.window.showInformationMessage(t("common:info.project_id_generated", { projectId }))
 			}
 		} catch (error) {
 			vscode.window.showErrorMessage(
diff --git a/src/core/webview/ClineProvider.ts b/src/core/webview/ClineProvider.ts
index ed8f8a27d1..5b5ad68028 100644
--- a/src/core/webview/ClineProvider.ts
+++ b/src/core/webview/ClineProvider.ts
@@ -1643,6 +1643,16 @@ export class ClineProvider
 		const currentMode = mode ?? defaultModeSlug
 		const hasSystemPromptOverride = await this.hasFileBasedSystemPromptOverride(currentMode)
 
+		// Get the workspace storage key (project ID or workspace path)
+		const { getWorkspaceStorageKey } = await import("../../utils/projectId")
+		const workspaceStorageKey = await getWorkspaceStorageKey(cwd)
+
+		// Filter task history to only show tasks for the current workspace
+		const filteredTaskHistory = (taskHistory || [])
+			.filter((item: HistoryItem) => item.workspace === workspaceStorageKey)
+			.filter((item: HistoryItem) => item.ts && item.task)
+			.sort((a: HistoryItem, b: HistoryItem) => b.ts - a.ts)
+
 		return {
 			version: this.context.extension?.packageJSON?.version ?? "",
 			apiConfiguration,
@@ -1664,12 +1674,10 @@ export class ClineProvider
 			autoCondenseContextPercent: autoCondenseContextPercent ?? 100,
 			uriScheme: vscode.env.uriScheme,
 			currentTaskItem: this.getCurrentCline()?.taskId
-				? (taskHistory || []).find((item: HistoryItem) => item.id === this.getCurrentCline()?.taskId)
+				? filteredTaskHistory.find((item: HistoryItem) => item.id === this.getCurrentCline()?.taskId)
 				: undefined,
 			clineMessages: this.getCurrentCline()?.clineMessages || [],
-			taskHistory: (taskHistory || [])
-				.filter((item: HistoryItem) => item.ts && item.task)
-				.sort((a: HistoryItem, b: HistoryItem) => b.ts - a.ts),
+			taskHistory: filteredTaskHistory,
 			soundEnabled: soundEnabled ?? false,
 			ttsEnabled: ttsEnabled ?? false,
 			ttsSpeed: ttsSpeed ?? 1.0,
@@ -2114,6 +2122,32 @@ export class ClineProvider
 			...gitInfo,
 		}
 	}
+
+	/**
+	 * Migrate existing tasks to use the new project ID
+	 * @param workspacePath The workspace path to migrate from
+	 * @param projectId The new project ID to migrate to
+	 * @returns The number of tasks migrated
+	 */
+	async migrateTasksToProjectId(workspacePath: string, projectId: string): Promise<number> {
+		const taskHistory = this.getGlobalState("taskHistory") ?? []
+		let migratedCount = 0
+
+		// Update all tasks that match the workspace path
+		const updatedHistory = taskHistory.map((item: HistoryItem) => {
+			if (item.workspace === workspacePath) {
+				migratedCount++
+				return { ...item, workspace: projectId }
+			}
+			return item
+		})
+
+		if (migratedCount > 0) {
+			await this.updateGlobalState("taskHistory", updatedHistory)
+		}
+
+		return migratedCount
+	}
 }
 
 class OrganizationAllowListViolationError extends Error {
diff --git a/src/i18n/locales/en/common.json b/src/i18n/locales/en/common.json
index c8deee5cf4..7b5c61c22e 100644
--- a/src/i18n/locales/en/common.json
+++ b/src/i18n/locales/en/common.json
@@ -120,7 +120,11 @@
 		"image_copied_to_clipboard": "Image data URI copied to clipboard",
 		"image_saved": "Image saved to {{path}}",
 		"mode_exported": "Mode '{{mode}}' exported successfully",
-		"mode_imported": "Mode imported successfully"
+		"mode_imported": "Mode imported successfully",
+		"project_id_generated": "Project ID generated: {{projectId}}",
+		"project_id_already_exists": "Project ID already exists: {{projectId}}",
+		"project_id_generated_with_migration": "Project ID generated: {{projectId}}. Migrated {{count}} task(s) to use the new ID.",
+		"project_id_generation_failed": "Failed to generate project ID: {{error}}"
 	},
 	"answers": {
 		"yes": "Yes",
diff --git a/src/utils/__tests__/projectId.test.ts b/src/utils/__tests__/projectId.test.ts
index 3598fe61f2..8ea43dbe0a 100644
--- a/src/utils/__tests__/projectId.test.ts
+++ b/src/utils/__tests__/projectId.test.ts
@@ -76,6 +76,7 @@ describe("projectId", () => {
 
 	describe("generateProjectId", () => {
 		it("should generate and save a new project ID", async () => {
+			vi.mocked(fileExistsAtPath).mockResolvedValue(false)
 			vi.mocked(fs.writeFile).mockResolvedValue()
 
 			const result = await generateProjectId(mockWorkspaceRoot)
@@ -84,7 +85,18 @@ describe("projectId", () => {
 			expect(fs.writeFile).toHaveBeenCalledWith(mockProjectIdPath, result, "utf8")
 		})
 
+		it("should return existing project ID if already exists", async () => {
+			vi.mocked(fileExistsAtPath).mockResolvedValue(true)
+			vi.mocked(fs.readFile).mockResolvedValue(mockProjectId)
+
+			const result = await generateProjectId(mockWorkspaceRoot)
+
+			expect(result).toBe(mockProjectId)
+			expect(fs.writeFile).not.toHaveBeenCalled()
+		})
+
 		it("should throw error if write fails", async () => {
+			vi.mocked(fileExistsAtPath).mockResolvedValue(false)
 			vi.mocked(fs.writeFile).mockRejectedValue(new Error("Write failed"))
 
 			await expect(generateProjectId(mockWorkspaceRoot)).rejects.toThrow("Write failed")
diff --git a/src/utils/projectId.ts b/src/utils/projectId.ts
index 5d022a6e51..e231e311a5 100644
--- a/src/utils/projectId.ts
+++ b/src/utils/projectId.ts
@@ -38,11 +38,18 @@ export async function getProjectId(workspaceRoot: string): Promise<string | null
 
 /**
  * Generates a new project ID and writes it to the .rooprojectid file.
+ * If a project ID already exists, returns the existing one.
  *
  * @param workspaceRoot The root directory of the workspace
- * @returns The generated project ID
+ * @returns The generated or existing project ID
  */
 export async function generateProjectId(workspaceRoot: string): Promise<string> {
+	// Check if project ID already exists
+	const existingId = await getProjectId(workspaceRoot)
+	if (existingId) {
+		return existingId
+	}
+
 	const projectId = uuidv4()
 	const projectIdPath = path.join(workspaceRoot, PROJECT_ID_FILENAME)