feat(coding-agent): allow explicit -e flags with --no-extensions

--no-extensions now skips discovery but still loads extensions
specified via -e flags. This gives users three modes:

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

fixes #524

packages/coding-agent/src/main.ts

@@ -18,7 +18,12 @@ import type { AgentSession } from "./core/agent-session.js";
 
 import { createEventBus } from "./core/event-bus.js";
 import { exportFromFile } from "./core/export-html/index.js";
-import { discoverAndLoadExtensions, type ExtensionUIContext, type LoadedExtension } from "./core/extensions/index.js";
+import {
+	discoverAndLoadExtensions,
+	type ExtensionUIContext,
+	type LoadedExtension,
+	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";
@@ -328,7 +333,15 @@ export async function main(args: string[]) {
 	time("SettingsManager.create");
 
 	let loadedExtensions: LoadedExtension[] = [];
-	if (!firstPass.noExtensions) {
+	if (firstPass.noExtensions) {
+		// --no-extensions disables discovery, but explicit -e flags still work
+		const explicitPaths = firstPass.extensions ?? [];
+		if (explicitPaths.length > 0) {
+			const result = await loadExtensions(explicitPaths, cwd, eventBus);
+			loadedExtensions = result.extensions;
+			time("loadExtensions");
+		}
+	} else {
 		// Merge CLI --extension args with settings.json extensions
 		const extensionPaths = [...settingsManager.getExtensionPaths(), ...(firstPass.extensions ?? [])];
 		const result = await discoverAndLoadExtensions(extensionPaths, cwd, agentDir, eventBus);

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

@@ -155,6 +155,12 @@ describe("parseArgs", () => {
 			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", () => {

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);
+	});
 });