feat(coding-agent): allowed toggling workspace tree in system prompt

- Added `includeWorkspaceTree` configuration setting to optionally render the workspace directory tree.
- Configured the system prompt template and SDK to respect this toggle, allowing users to disable the tree to prevent prompt cache invalidation.

packages/coding-agent/src/config/settings-schema.ts

@@ -967,6 +967,18 @@ export const SETTINGS_SCHEMA = {
 		},
 	},
 
+	includeWorkspaceTree: {
+		type: "boolean",
+		default: false,
+		ui: {
+			tab: "model",
+			group: "Prompt",
+			label: "Include Workspace Tree",
+			description:
+				"Render the workspace directory tree in the system prompt. WARNING: This can bust prompt caching across sessions when files are modified.",
+		},
+	},
+
 	personality: {
 		type: "enum",
 		values: ["default", "friendly", "pragmatic", "none"] as const,

packages/coding-agent/src/prompts/system/project-prompt.md

@@ -29,6 +29,7 @@ Before making changes within these directories, you MUST read:
 The context files above are loaded automatically. You NEVER `search`/`find` for `AGENTS.md`, `CLAUDE.md`, `.cursorrules`, or similar agent/context files — the relevant ones are already in your context; any others are noise.
 {{/ifAny}}
 
+{{#if includeWorkspaceTree}}
 {{#if workspaceTree.rendered}}
 <workspace-tree>
 Working directory layout (sorted by mtime, recent first; depth ≤ 3):
@@ -38,6 +39,7 @@ Working directory layout (sorted by mtime, recent first; depth ≤ 3):
 {{/if}}
 </workspace-tree>
 {{/if}}
+{{/if}}
 
 Today is {{date}}, and the current working directory is '{{cwd}}'.
 

packages/coding-agent/src/sdk.ts

@@ -796,6 +796,7 @@ export interface BuildSystemPromptOptions {
 	customPrompt?: string;
 	appendPrompt?: string;
 	inlineToolDescriptors?: boolean;
+	includeWorkspaceTree?: boolean;
 }
 
 /**
@@ -813,6 +814,7 @@ export async function buildSystemPrompt(options: BuildSystemPromptOptions = {}):
 		contextFiles: options.contextFiles,
 		appendSystemPrompt: options.appendPrompt,
 		inlineToolDescriptors: options.inlineToolDescriptors,
+		includeWorkspaceTree: options.includeWorkspaceTree,
 		toolNames: options.tools?.map(tool => tool.name),
 		tools: toolMap ? buildSystemPromptToolMetadata(toolMap) : undefined,
 	});
@@ -1120,9 +1122,12 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 	// startup does not perform a second recursive filesystem search. Subagents
 	// inherit the parent's resolved values via options.
 	const STARTUP_SCAN_DEADLINE_MS = 5000;
+	const includeWorkspaceTree = settings.get("includeWorkspaceTree") ?? false;
 	const workspaceTreePromise: Promise<WorkspaceTree> = options.workspaceTree
 		? Promise.resolve(options.workspaceTree)
-		: logger.time("buildWorkspaceTree", () => buildWorkspaceTree(cwd, { timeoutMs: STARTUP_SCAN_DEADLINE_MS }));
+		: includeWorkspaceTree
+			? logger.time("buildWorkspaceTree", () => buildWorkspaceTree(cwd, { timeoutMs: STARTUP_SCAN_DEADLINE_MS }))
+			: Promise.resolve({ rootPath: cwd, rendered: "", truncated: false, totalLines: 0, agentsMdFiles: [] });
 	workspaceTreePromise.catch(() => {});
 
 	// Independent discoveries that depend only on cwd/agentDir — kicked off in parallel and awaited
@@ -2101,6 +2106,7 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 		const eagerTasks = settings.get("task.eager") !== "default";
 		const eagerTasksAlways = settings.get("task.eager") === "always";
 		const intentField = $flag("PI_INTENT_TRACING", settings.get("tools.intentTracing")) ? INTENT_FIELD : undefined;
+		const includeWorkspaceTree = settings.get("includeWorkspaceTree") ?? false;
 		const rebuildSystemPrompt = async (
 			toolNames: string[],
 			tools: Map<string, AgentTool>,
@@ -2194,6 +2200,7 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 				taskBatch: settings.get("task.batch"),
 				secretsEnabled,
 				workspaceTree: workspaceTreePromise,
+				includeWorkspaceTree,
 				memoryRootEnabled: memoryBackend.id === "local",
 				model: settings.get("includeModelInPrompt") ? getActiveModelString() : undefined,
 				personality: agentKind === "sub" ? "none" : settings.get("personality"),

packages/coding-agent/src/system-prompt.ts

@@ -421,6 +421,8 @@ export interface BuildSystemPromptOptions {
 	model?: string;
 	/** Personality preset rendered into the default system prompt. "none" omits the block. Default: "default" */
 	personality?: Personality;
+	/** Whether to include the workspace directory tree in the system prompt. Default: false */
+	includeWorkspaceTree?: boolean;
 }
 
 /** Result of building provider-facing system prompt messages. */
@@ -461,6 +463,7 @@ export async function buildSystemPrompt(options: BuildSystemPromptOptions = {}):
 		memoryRootEnabled = false,
 		model,
 		personality = "default",
+		includeWorkspaceTree = false,
 	} = options;
 	const inlineToolDescriptors = providedInlineToolDescriptors ?? false;
 	const resolvedCwd = cwd ?? getProjectDir();
@@ -523,9 +526,17 @@ export async function buildSystemPrompt(options: BuildSystemPromptOptions = {}):
 	const workspaceTreePromise =
 		providedWorkspaceTree !== undefined
 			? Promise.resolve(providedWorkspaceTree)
-			: logger.time("buildWorkspaceTree", () =>
-					buildWorkspaceTree(resolvedCwd, { timeoutMs: SYSTEM_PROMPT_PREP_TIMEOUT_MS }),
-				);
+			: includeWorkspaceTree
+				? logger.time("buildWorkspaceTree", () =>
+						buildWorkspaceTree(resolvedCwd, { timeoutMs: SYSTEM_PROMPT_PREP_TIMEOUT_MS }),
+					)
+				: Promise.resolve({
+						rootPath: resolvedCwd,
+						rendered: "",
+						truncated: false,
+						totalLines: 0,
+						agentsMdFiles: [],
+					});
 	const skillsPromise: Promise<Skill[]> =
 		providedSkills !== undefined
 			? Promise.resolve(providedSkills)
@@ -670,6 +681,7 @@ export async function buildSystemPrompt(options: BuildSystemPromptOptions = {}):
 		secretsEnabled,
 		hasMemoryRoot: memoryRootEnabled,
 		hasObsidian: hasObsidian(),
+		includeWorkspaceTree,
 	};
 	const rendered = prompt.render(resolvedCustomPrompt ? customSystemPromptTemplate : systemPromptTemplate, data);
 	const systemPrompt = [rendered];

packages/coding-agent/test/system-prompt-dedup.test.ts

@@ -121,6 +121,7 @@ describe("SYSTEM.md prompt assembly", () => {
 			rules: [],
 			toolNames: ["read"],
 			tools: READ_TOOL,
+			includeWorkspaceTree: true,
 			workspaceTree: {
 				rootPath: projectDir,
 				rendered: ".\n  - nested/",