fix(coding-agent): restore builtin-only tool disabling

closes #3592

packages/coding-agent/src/cli/args.ts

@@ -28,6 +28,7 @@ export interface Args {
 	models?: string[];
 	tools?: string[];
 	noTools?: boolean;
+	noBuiltinTools?: boolean;
 	extensions?: string[];
 	noExtensions?: boolean;
 	print?: boolean;
@@ -100,9 +101,11 @@ export function parseArgs(args: string[]): Args {
 			result.sessionDir = args[++i];
 		} else if (arg === "--models" && i + 1 < args.length) {
 			result.models = args[++i].split(",").map((s) => s.trim());
-		} else if (arg === "--no-tools") {
+		} else if (arg === "--no-tools" || arg === "-nt") {
 			result.noTools = true;
-		} else if (arg === "--tools" && i + 1 < args.length) {
+		} else if (arg === "--no-builtin-tools" || arg === "-nbt") {
+			result.noBuiltinTools = true;
+		} else if ((arg === "--tools" || arg === "-t") && i + 1 < args.length) {
 			result.tools = args[++i]
 				.split(",")
 				.map((s) => s.trim())
@@ -221,9 +224,10 @@ ${chalk.bold("Options:")}
   --no-session                   Don't save session (ephemeral)
   --models <patterns>            Comma-separated model patterns for Ctrl+P cycling
                                  Supports globs (anthropic/*, *sonnet*) and fuzzy matching
-  --no-tools                     Disable all tools by default (built-in and extension)
-  --tools <tools>                Comma-separated allowlist of tool names to enable
-                                 Applies to built-in and extension tools
+  --no-tools, -nt                Disable all tools by default (built-in and extension)
+  --no-builtin-tools, -nbt       Disable built-in tools by default but keep extension/custom tools enabled
+  --tools, -t <tools>            Comma-separated allowlist of tool names to enable
+                                 Applies to built-in, extension, and custom tools
   --thinking <level>             Set thinking level: off, minimal, low, medium, high, xhigh
   --extension, -e <path>         Load an extension file (can be used multiple times)
   --no-extensions, -ne           Disable extension discovery (explicit -e paths still work)

packages/coding-agent/src/core/sdk.ts

@@ -47,11 +47,19 @@ export interface CreateAgentSessionOptions {
 	/** Models available for cycling (Ctrl+P in interactive mode) */
 	scopedModels?: Array<{ model: Model<any>; thinkingLevel?: ThinkingLevel }>;
 
+	/**
+	 * Optional default tool suppression mode when no explicit allowlist is provided.
+	 *
+	 * - "all": start with no tools enabled
+	 * - "builtin": disable the default built-in tools (read, bash, edit, write)
+	 *   but keep extension/custom tools enabled
+	 */
+	noTools?: "all" | "builtin";
 	/**
 	 * Optional allowlist of tool names.
 	 *
 	 * When omitted, pi enables the default built-in tools (read, bash, edit, write)
-	 * and leaves extension/custom tools enabled.
+	 * and leaves extension/custom tools enabled unless `noTools` changes that default.
 	 * When provided, only the listed tool names are enabled.
 	 */
 	tools?: string[];
@@ -245,7 +253,12 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 	}
 
 	const defaultActiveToolNames: ToolName[] = ["read", "bash", "edit", "write"];
-	const initialActiveToolNames: string[] = options.tools ? [...options.tools] : defaultActiveToolNames;
+	const allowedToolNames = options.tools ?? (options.noTools === "all" ? [] : undefined);
+	const initialActiveToolNames: string[] = options.tools
+		? [...options.tools]
+		: options.noTools
+			? []
+			: defaultActiveToolNames;
 
 	let agent: Agent;
 
@@ -366,7 +379,7 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 		customTools: options.customTools,
 		modelRegistry,
 		initialActiveToolNames,
-		allowedToolNames: options.tools,
+		allowedToolNames,
 		extensionRunnerRef,
 		sessionStartEvent: options.sessionStartEvent,
 	});

packages/coding-agent/src/main.ts

@@ -366,10 +366,11 @@ function buildSessionOptions(
 
 	// Tools
 	if (parsed.noTools) {
-		// --no-tools: start with no built-in tools
-		// --tools can still add specific ones back, including extension tools.
-		options.tools = parsed.tools && parsed.tools.length > 0 ? [...parsed.tools] : [];
-	} else if (parsed.tools) {
+		options.noTools = "all";
+	} else if (parsed.noBuiltinTools) {
+		options.noTools = "builtin";
+	}
+	if (parsed.tools) {
 		options.tools = [...parsed.tools];
 	}