diff --git a/src/daemon.ts b/src/daemon.ts
index 3394e2d..2fec016 100644
--- a/src/daemon.ts
+++ b/src/daemon.ts
@@ -7,7 +7,7 @@ import * as net from "node:net";
 import * as path from "node:path";
 import type { FileSystemWatcher } from "vscode-languageserver-protocol";
 import { LspClient } from "./client.ts";
-import { findRoot, findServerById, pathToUri, uriToPath } from "./root.ts";
+import { findRoot, findServerById, pathToUri } from "./root.ts";
 import type { ServerConfig } from "./types.ts";
 import { WorkspaceWatcher, type FileEvent } from "./watcher.ts";
 import {
@@ -22,6 +22,8 @@ import {
 const DEFAULT_IDLE_TTL_MS = 5 * 60 * 1000;
 const WATCHER_READY_TIMEOUT_MS = 5000;
 const FILE_CHANGE_DELETED = 3;
+const WATCH_KIND_CREATE = 1;
+const WATCH_KIND_CHANGE = 2;
 const WATCH_KIND_DELETE = 4;
 
 // Client Entry - One LspClient per (server.id, rootDir), plus the bookkeeping
@@ -43,6 +45,7 @@ interface ClientEntry {
   lastUsed: number;
   watcher: WorkspaceWatcher | null;
   unsubscribeWatchers: (() => void) | null;
+  usesDerivedWatchers: boolean;
 }
 
 const entries = new Map<string, ClientEntry>();
@@ -96,6 +99,7 @@ async function getOrCreateEntry(
     lastUsed: Date.now(),
     watcher: null,
     unsubscribeWatchers: null,
+    usesDerivedWatchers: false,
   };
   entries.set(key, entry);
   try {
@@ -118,11 +122,23 @@ async function attachWatcher(entry: ClientEntry): Promise<void> {
 
 function watcherPatterns(entry: ClientEntry): FileSystemWatcher[] {
   const registered = entry.client.getFileWatchers();
-  const openedDeletes = [...entry.opened.keys()].map((uri) => ({
-    globPattern: uriToPath(uri).split(path.sep).join("/"),
-    kind: WATCH_KIND_DELETE,
-  }));
-  return [...registered, ...openedDeletes];
+  entry.usesDerivedWatchers = registered.length === 0;
+  return registered.length > 0 ? registered : derivedServerWatchers(entry.server);
+}
+
+function derivedServerWatchers(server: ServerConfig): FileSystemWatcher[] {
+  const extensions = server.match
+    .map((m) => m.replace(/^\./, ""))
+    .filter((m) => /^[A-Za-z0-9_-]+$/.test(m));
+  if (extensions.length === 0) return [];
+
+  const globPattern = extensions.length === 1
+    ? `**/*.${extensions[0]}`
+    : `**/*.{${extensions.join(",")}}`;
+  return [{
+    globPattern,
+    kind: WATCH_KIND_CREATE | WATCH_KIND_CHANGE | WATCH_KIND_DELETE,
+  }];
 }
 
 async function refreshWatcher(entry: ClientEntry): Promise<void> {
@@ -178,6 +194,9 @@ function forwardEvents(entry: ClientEntry, events: FileEvent[]): void {
     entry.client.sendNotification("workspace/didChangeWatchedFiles", {
       changes: events,
     });
+    if (entry.usesDerivedWatchers) {
+      evict(entry, "derived watcher event");
+    }
   } catch (err) {
     log(`watcher send failed`, entry.server.id, (err as Error).message);
   }
@@ -220,7 +239,6 @@ async function syncFile(
     if (prev === undefined) {
       entry.client.openDocument(filePath);
       entry.opened.set(uri, stat.mtimeMs);
-      await refreshWatcher(entry);
       return { uri, changed: true };
     } else if (prev !== stat.mtimeMs) {
       entry.client.notifyChange(filePath);
diff --git a/test/integration/watcher-typescript.test.ts b/test/integration/watcher-typescript.test.ts
index 5475ff1..30cec50 100644
--- a/test/integration/watcher-typescript.test.ts
+++ b/test/integration/watcher-typescript.test.ts
@@ -32,7 +32,7 @@ interface DiagResult {
   [serverId: string]: { diagnostics?: { message: string }[] };
 }
 
-describe("watcher: typescript handles deleted opened files", { skip: skip ?? undefined }, () => {
+describe("watcher: typescript handles derived file patterns", { skip: skip ?? undefined }, () => {
   let tmpDir: string;
   let mainFile: string;
   let helperFile: string;
@@ -81,6 +81,35 @@ describe("watcher: typescript handles deleted opened files", { skip: skip ?? und
     fs.rmSync(tmpDir, { recursive: true, force: true });
   });
 
+  it("clears missing module after an unopened imported file is created", async () => {
+    fs.rmSync(helperFile);
+
+    const missing = (await runCliJson(
+      [mainFile, "diagnostics", '{"timeoutMs":5000}'],
+      env,
+    )) as DiagResult;
+    assert.ok(
+      (missing["typescript-language-server"]?.diagnostics ?? []).some((d) =>
+        d.message.includes("Cannot find module './helper'")
+      ),
+    );
+
+    fs.writeFileSync(helperFile, "export function helper(): number {\n  return 1;\n}\n");
+
+    const result = await pollUntil(
+      async () =>
+        (await runCliJson(
+          [mainFile, "diagnostics", '{"timeoutMs":3000}'],
+          env,
+        )) as DiagResult,
+      (r) => (r["typescript-language-server"]?.diagnostics ?? []).length === 0,
+      15000,
+      500,
+    );
+
+    assert.deepEqual(result["typescript-language-server"]?.diagnostics ?? [], []);
+  });
+
   it("reports missing module after an opened imported file is deleted", async () => {
     const initial = (await runCliJson(
       [mainFile, "diagnostics", '{"timeoutMs":5000}'],