feat(coding-agent): add --no-extensions flag to disable extension discovery

Adds --no-extensions CLI flag that skips automatic extension discovery
while still allowing explicit -e paths. Three modes now available:

1. Default: auto-discover + any -e additions
2. --no-extensions: no extensions at all
3. --no-extensions -e foo.js: only load explicit extensions

Useful for debugging or running subagent instances without auto-discovered
extensions.

closes #524

packages/coding-agent/CHANGELOG.md

@@ -14,6 +14,7 @@
 
 ### Added
 
+- `--no-extensions` flag to disable extension discovery while still allowing explicit `-e` paths ([#524](https://github.com/badlogic/pi-mono/pull/524) by [@cv](https://github.com/cv))
 - SDK: `InteractiveMode`, `runPrintMode()`, `runRpcMode()` exported for building custom run modes. See `docs/sdk.md`.
 - `PI_SKIP_VERSION_CHECK` environment variable to disable new version notifications at startup ([#549](https://github.com/badlogic/pi-mono/pull/549) by [@aos](https://github.com/aos))
 - `thinkingBudgets` setting to customize token budgets per thinking level for token-based providers ([#529](https://github.com/badlogic/pi-mono/pull/529) by [@melihmucuk](https://github.com/melihmucuk))

packages/coding-agent/README.md

@@ -1125,6 +1125,7 @@ pi [options] [@files...] [messages...]
 | `--tools <tools>` | Comma-separated tool list (default: `read,bash,edit,write`) |
 | `--thinking <level>` | Thinking level: `off`, `minimal`, `low`, `medium`, `high` |
 | `--extension <path>`, `-e` | Load an extension file (can be used multiple times) |
+| `--no-extensions` | Disable extension discovery (explicit `-e` paths still work) |
 | `--no-skills` | Disable skills discovery and loading |
 | `--skills <patterns>` | Comma-separated glob patterns to filter skills (e.g., `git-*,docker`) |
 | `--export <file> [output]` | Export session to HTML |

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

@@ -27,6 +27,7 @@ export interface Args {
 	models?: string[];
 	tools?: ToolName[];
 	extensions?: string[];
+	noExtensions?: boolean;
 	print?: boolean;
 	export?: string;
 	noSkills?: boolean;
@@ -116,6 +117,8 @@ export function parseArgs(args: string[], extensionFlags?: Map<string, { type: "
 		} else if ((arg === "--extension" || arg === "-e") && i + 1 < args.length) {
 			result.extensions = result.extensions ?? [];
 			result.extensions.push(args[++i]);
+		} else if (arg === "--no-extensions") {
+			result.noExtensions = true;
 		} else if (arg === "--no-skills") {
 			result.noSkills = true;
 		} else if (arg === "--skills" && i + 1 < args.length) {
@@ -175,6 +178,7 @@ ${chalk.bold("Options:")}
                                  Available: read, bash, edit, write, grep, find, ls
   --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                Disable extensions discovery and loading
   --no-skills                    Disable skills discovery and loading
   --skills <patterns>            Comma-separated glob patterns to filter skills (e.g., git-*,docker)
   --export <file>                Export session file to HTML and exit

packages/coding-agent/src/main.ts

@@ -16,7 +16,7 @@ import { selectSession } from "./cli/session-picker.js";
 import { CONFIG_DIR_NAME, getAgentDir, getModelsPath, VERSION } from "./config.js";
 import { createEventBus } from "./core/event-bus.js";
 import { exportFromFile } from "./core/export-html/index.js";
-import { discoverAndLoadExtensions, type LoadExtensionsResult } from "./core/extensions/index.js";
+import { discoverAndLoadExtensions, type LoadExtensionsResult, loadExtensions } from "./core/extensions/index.js";
 import type { ModelRegistry } from "./core/model-registry.js";
 import { resolveModelScope, type ScopedModel } from "./core/model-resolver.js";
 import { type CreateAgentSessionOptions, createAgentSession, discoverAuthStorage, discoverModels } from "./core/sdk.js";
@@ -209,16 +209,25 @@ export async function main(args: string[]) {
 	const firstPass = parseArgs(args);
 	time("parseArgs-firstPass");
 
-	// Early load extensions to discover their CLI flags
+	// Early load extensions to discover their CLI flags (unless --no-extensions)
 	const cwd = process.cwd();
 	const agentDir = getAgentDir();
 	const eventBus = createEventBus();
 	const settingsManager = SettingsManager.create(cwd);
 	time("SettingsManager.create");
-	// Merge CLI --extension args with settings.json extensions
-	const extensionPaths = [...settingsManager.getExtensionPaths(), ...(firstPass.extensions ?? [])];
-	const extensionsResult = await discoverAndLoadExtensions(extensionPaths, cwd, agentDir, eventBus);
-	time("discoverExtensionFlags");
+
+	let extensionsResult: LoadExtensionsResult;
+	if (firstPass.noExtensions) {
+		// --no-extensions disables discovery, but explicit -e flags still work
+		const explicitPaths = firstPass.extensions ?? [];
+		extensionsResult = await loadExtensions(explicitPaths, cwd, eventBus);
+		time("loadExtensions");
+	} else {
+		// Merge CLI --extension args with settings.json extensions
+		const extensionPaths = [...settingsManager.getExtensionPaths(), ...(firstPass.extensions ?? [])];
+		extensionsResult = await discoverAndLoadExtensions(extensionPaths, cwd, agentDir, eventBus);
+		time("discoverExtensionFlags");
+	}
 
 	// Collect all extension flags
 	const extensionFlags = new Map<string, { type: "boolean" | "string" }>();

packages/coding-agent/test/args.test.ts

@@ -150,6 +150,26 @@ describe("parseArgs", () => {
 		});
 	});
 
+	describe("--no-extensions flag", () => {
+		test("parses --no-extensions flag", () => {
+			const result = parseArgs(["--no-extensions"]);
+			expect(result.noExtensions).toBe(true);
+		});
+
+		test("parses --no-extensions with explicit -e flags", () => {
+			const result = parseArgs(["--no-extensions", "-e", "foo.ts", "-e", "bar.ts"]);
+			expect(result.noExtensions).toBe(true);
+			expect(result.extensions).toEqual(["foo.ts", "bar.ts"]);
+		});
+	});
+
+	describe("--no-skills flag", () => {
+		test("parses --no-skills flag", () => {
+			const result = parseArgs(["--no-skills"]);
+			expect(result.noSkills).toBe(true);
+		});
+	});
+
 	describe("messages and file args", () => {
 		test("parses plain text messages", () => {
 			const result = parseArgs(["hello", "world"]);

packages/coding-agent/test/extensions-discovery.test.ts

@@ -443,4 +443,34 @@ describe("extensions discovery", () => {
 		expect(result.extensions).toHaveLength(1);
 		expect(result.extensions[0].flags.has("--my-flag")).toBe(true);
 	});
+
+	it("loadExtensions only loads explicit paths without discovery", async () => {
+		// Create discoverable extensions (would be found by discoverAndLoadExtensions)
+		fs.writeFileSync(path.join(extensionsDir, "discovered.ts"), extensionCodeWithTool("discovered"));
+
+		// Create explicit extension outside discovery path
+		const explicitPath = path.join(tempDir, "explicit.ts");
+		fs.writeFileSync(explicitPath, extensionCodeWithTool("explicit"));
+
+		// Use loadExtensions directly to skip discovery
+		const { loadExtensions } = await import("../src/core/extensions/loader.js");
+		const result = await loadExtensions([explicitPath], tempDir);
+
+		expect(result.errors).toHaveLength(0);
+		expect(result.extensions).toHaveLength(1);
+		expect(result.extensions[0].tools.has("explicit")).toBe(true);
+		expect(result.extensions[0].tools.has("discovered")).toBe(false);
+	});
+
+	it("loadExtensions with no paths loads nothing", async () => {
+		// Create discoverable extensions (would be found by discoverAndLoadExtensions)
+		fs.writeFileSync(path.join(extensionsDir, "discovered.ts"), extensionCode);
+
+		// Use loadExtensions directly with empty paths
+		const { loadExtensions } = await import("../src/core/extensions/loader.js");
+		const result = await loadExtensions([], tempDir);
+
+		expect(result.errors).toHaveLength(0);
+		expect(result.extensions).toHaveLength(0);
+	});
 });