fix(lsp): add legacy alias for renamed kotlin-language-server key

Users with existing lsp.json overrides referencing the old
"kotlin-language-server" key would silently lose their Kotlin
LSP config after the rename to "kotlin-lsp". LEGACY_ALIASES
map remaps old keys during mergeServers() so overrides still
merge correctly.

packages/pi-coding-agent/src/core/lsp/config.ts

@@ -12,6 +12,11 @@ import type { ServerConfig } from "./types.js";
 const require = createRequire(import.meta.url);
 const DEFAULTS = require("./defaults.json") as Record<string, Partial<ServerConfig>>;
 
+/** Map legacy server keys to their current names so user overrides still merge. */
+const LEGACY_ALIASES: Record<string, string> = {
+	"kotlin-language-server": "kotlin-lsp",
+};
+
 export interface LspConfig {
 	servers: Record<string, ServerConfig>;
 	/** Idle timeout in milliseconds. If set, LSP clients will be shutdown after this period of inactivity. Disabled by default. */
@@ -109,7 +114,8 @@ function mergeServers(
 	overrides: Record<string, Partial<ServerConfig>>,
 ): Record<string, ServerConfig> {
 	const merged: Record<string, ServerConfig> = { ...base };
-	for (const [name, config] of Object.entries(overrides)) {
+	for (const [rawName, config] of Object.entries(overrides)) {
+		const name = LEGACY_ALIASES[rawName] ?? rawName;
 		if (merged[name]) {
 			const candidate = { ...merged[name], ...config };
 			const normalized = normalizeServerConfig(name, candidate);

packages/pi-coding-agent/src/core/lsp/lsp-legacy-alias.test.ts

@@ -0,0 +1,70 @@
+// GSD2 — Regression test for LSP legacy server key aliases
+// Copyright (c) 2026 Jeremy McSpadden <jeremy@fluxlabs.net>
+
+/**
+ * When a default server key is renamed (e.g., kotlin-language-server → kotlin-lsp),
+ * user overrides referencing the old key must still merge correctly via LEGACY_ALIASES.
+ *
+ * This test exercises the merge path through loadConfig() with a temp project
+ * containing an lsp.json that uses the legacy key.
+ */
+
+import { describe, it, beforeEach, afterEach } from "node:test";
+import assert from "node:assert/strict";
+import * as fs from "node:fs";
+import * as path from "node:path";
+import * as os from "node:os";
+import { loadConfig } from "./config.js";
+
+describe("LSP legacy server key aliases", () => {
+	let tmpDir: string;
+
+	beforeEach(() => {
+		tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "lsp-alias-test-"));
+	});
+
+	afterEach(() => {
+		fs.rmSync(tmpDir, { recursive: true, force: true });
+	});
+
+	it("merges user override with legacy key 'kotlin-language-server' into 'kotlin-lsp'", () => {
+		// Write an lsp.json that uses the old key name with a command that exists (node)
+		// so resolveCommand doesn't filter it out.
+		const overrideConfig = {
+			servers: {
+				"kotlin-language-server": {
+					command: "node",
+				},
+			},
+		};
+		fs.writeFileSync(
+			path.join(tmpDir, "lsp.json"),
+			JSON.stringify(overrideConfig),
+		);
+
+		// Also add root markers so the server is detected
+		fs.writeFileSync(path.join(tmpDir, "build.gradle.kts"), "");
+
+		const config = loadConfig(tmpDir);
+
+		// The merged config should have kotlin-lsp (new key) with the user's command override
+		const kotlinServer = config.servers["kotlin-lsp"];
+		assert.ok(kotlinServer, "kotlin-lsp should exist in merged config");
+		assert.equal(
+			kotlinServer.command,
+			"node",
+			"command should be overridden from user config via legacy alias",
+		);
+		assert.ok(
+			kotlinServer.fileTypes.includes(".kt"),
+			"fileTypes should be inherited from defaults",
+		);
+
+		// The old key should NOT appear as a separate entry
+		assert.equal(
+			config.servers["kotlin-language-server"],
+			undefined,
+			"legacy key should not appear as separate server",
+		);
+	});
+});