fix(cli): report an unknown install target as an argument error

cli/commands/install/handler.test.ts

@@ -151,6 +151,17 @@ describe("commands/install/handler", () => {
     it("reads the positional for uninstall too", () => {
       assertEquals(parseCommandLine(["uninstall", "agents"]).target, "agents");
     });
+
+    it("fails argument parsing for an unknown positional tool id", () => {
+      const result = parseInstallArgs(parseCliArgs(["install", "not-a-tool"]));
+      assertEquals(result.success, false);
+      assertEquals(result.error?.message.includes("Valid targets"), true);
+    });
+
+    it("fails argument parsing for an unknown --target too", () => {
+      const result = parseInstallArgs(parseCliArgs(["install", "--target", "not-a-tool"]));
+      assertEquals(result.success, false);
+    });
   });
 
   describe("uninstall argument extraction", () => {

cli/commands/install/handler.ts

@@ -3,14 +3,19 @@
  */
 
 import { defineSchema, lazySchema } from "veryfront/schemas";
-import { installCommand } from "./install.ts";
+import { installCommand, isValidTargetSpec, VALID_TARGET_VALUES } from "./install.ts";
 import { uninstallCommand } from "./uninstall.ts";
 import { CommonArgs, createArgParser, parseArgsOrThrow } from "#cli/shared/args";
 import type { ParsedArgs } from "#cli/shared/types";
 
 const getInstallArgsSchema = defineSchema((v) =>
   v.object({
-    target: v.string().optional(),
+    // Validated here rather than at install time so an unknown tool id is an
+    // argument error (exit 2), not a runtime failure (exit 1).
+    target: v.string().optional().refine(
+      (value) => value === undefined || isValidTargetSpec(value),
+      { message: `unknown tool. Valid targets: ${VALID_TARGET_VALUES}` },
+    ),
     global: v.boolean().default(false),
     force: v.boolean().default(false),
   })

cli/commands/install/install.integration.test.ts

@@ -194,8 +194,23 @@ describe("install command integration", () => {
     });
 
     it("fails instead of installing something else for an unknown target", async () => {
-      const { code } = await runInstallArgs(["unknown-tool", "--force", "--no-input"]);
-      assertEquals(code, 1);
+      const { code, output } = await runInstallArgs(["unknown-tool", "--force", "--no-input"]);
+      // AGENTS.md reserves exit 2 for usage and argument errors.
+      assertEquals(code, 2);
+      assertEquals(output.includes("Valid targets"), true);
+
+      await assertFileNotExists(join(tempDir, "SKILL.md"));
+      await assertFileNotExists(join(tempDir, "AGENTS.md"));
+    });
+
+    it("fails an unknown --target with the same usage exit code", async () => {
+      const { code } = await runInstallArgs([
+        "--target",
+        "unknown-tool",
+        "--force",
+        "--no-input",
+      ]);
+      assertEquals(code, 2);
 
       await assertFileNotExists(join(tempDir, "SKILL.md"));
       await assertFileNotExists(join(tempDir, "AGENTS.md"));

cli/commands/install/install.ts

@@ -37,6 +37,14 @@ export function parseTargetFlag(target: string): AIToolId[] {
   return TargetFlagSchema.parse(target);
 }
 
+/** Valid target values, for messages and argument validation. */
+export const VALID_TARGET_VALUES = [...AI_TOOLS.map((t) => t.id), "all"].join(", ");
+
+/** True when the value names at least one known tool (or `all`). */
+export function isValidTargetSpec(target: string): boolean {
+  return TargetFlagSchema.safeParse(target).success;
+}
+
 const getAIToolIdArraySchema = defineSchema((v) => v.array(AIToolIdSchema).min(1));
 
 const AIToolIdArraySchema = lazySchema(getAIToolIdArraySchema);