From 7a783c7c15999caaf5be36f62995a2d699fd2558 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 16 Jan 2026 11:10:17 +0000
Subject: [PATCH 1/8] Initial plan


From 8abac8956fddb640f22e815ec6636a43d7881548 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 16 Jan 2026 11:16:22 +0000
Subject: [PATCH 2/8] Add ENABLE_COMPILE_CONFIG_LOGGING environment variable to
 control debug logs

Co-authored-by: RodgeFu <6038235+RodgeFu@users.noreply.github.com>
---
 .../compiler/src/server/compile-service.ts    | 19 ++++++++++++-------
 packages/compiler/src/server/constants.ts     |  1 +
 .../src/server/entrypoint-resolver.ts         | 15 ++++++++++-----
 packages/compiler/src/server/serverlib.ts     |  9 +++++++--
 4 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/packages/compiler/src/server/compile-service.ts b/packages/compiler/src/server/compile-service.ts
index 2c41249149e..342e009689d 100644
--- a/packages/compiler/src/server/compile-service.ts
+++ b/packages/compiler/src/server/compile-service.ts
@@ -19,7 +19,7 @@ import { deepClone, distinctArray } from "../utils/misc.js";
 import { getLocationInYamlScript } from "../yaml/diagnostics.js";
 import { parseYaml } from "../yaml/parser.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
-import { serverOptions } from "./constants.js";
+import { ENABLE_COMPILE_CONFIG_LOGGING, serverOptions } from "./constants.js";
 import { resolveEntrypointFile } from "./entrypoint-resolver.js";
 import { FileService } from "./file-service.js";
 import { FileSystemCache } from "./file-system-cache.js";
@@ -90,6 +90,11 @@ export function createCompileService({
   const eventListeners = new Map<string, (...args: unknown[]) => void | Promise<void>>();
   const compileManager = new ServerCompileManager(updateManager, compilerHost, log);
   let configFilePath: string | undefined;
+  const { getEnvironmentVariable } = serverHost;
+  const logDebug =
+    getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true"
+      ? log
+      : () => {};
 
   return { compile, getScript, on, notifyChange, getMainFileForDocument };
 
@@ -129,7 +134,7 @@ export function createCompileService({
     }
     const mainFile = await getMainFileForDocument(path);
     if (mainFile === undefined) {
-      log({ level: "debug", message: `failed to resolve main file for ${path}` });
+      logDebug({ level: "debug", message: `failed to resolve main file for ${path}` });
       return undefined;
     }
     if (!mainFile.endsWith(".tsp")) {
@@ -137,7 +142,7 @@ export function createCompileService({
     }
     const config = await getConfig(mainFile);
     configFilePath = config.filename;
-    log({ level: "debug", message: `config resolved`, detail: config });
+    logDebug({ level: "debug", message: `config resolved`, detail: config });
     const [optionsFromConfig, _] = resolveOptionsFromConfig(config, {
       cwd: getDirectoryPath(path),
     });
@@ -217,7 +222,7 @@ export function createCompileService({
       ) {
         // If the file that changed wasn't imported by anything from the main
         // file, retry using the file itself as the main file.
-        log({
+        logDebug({
           level: "debug",
           message: `target file was not included in compiling, try to compile ${path} as main file directly`,
         });
@@ -246,7 +251,7 @@ export function createCompileService({
         const [yamlScript] = parseYaml(await serverHost.compilerHost.readFile(configFilePath));
         const target = getLocationInYamlScript(yamlScript, ["emit", emitterName], "key");
         if (target.pos === 0) {
-          log({
+          logDebug({
             level: "debug",
             message: `Unexpected situation, can't find emitter '${emitterName}' in config file '${configFilePath}'`,
           });
@@ -286,7 +291,7 @@ export function createCompileService({
     const lookupDir = entrypointStat.isDirectory() ? mainFile : getDirectoryPath(mainFile);
     const configPath = await findTypeSpecConfigPath(compilerHost, lookupDir, true);
     if (!configPath) {
-      log({
+      logDebug({
         level: "debug",
         message: `can't find path with config file, try to use default config`,
       });
@@ -337,7 +342,7 @@ export function createCompileService({
    */
   async function getMainFileForDocument(path: string) {
     if (path.startsWith("untitled:")) {
-      log({ level: "debug", message: `untitled document treated as its own main file: ${path}` });
+      logDebug({ level: "debug", message: `untitled document treated as its own main file: ${path}` });
       return path;
     }
 
diff --git a/packages/compiler/src/server/constants.ts b/packages/compiler/src/server/constants.ts
index 1bb0333bd04..e96c3610654 100644
--- a/packages/compiler/src/server/constants.ts
+++ b/packages/compiler/src/server/constants.ts
@@ -18,3 +18,4 @@ export const Commands = {
  */
 export const ENABLE_SERVER_COMPILE_LOGGING = "ENABLE_SERVER_COMPILE_LOGGING";
 export const ENABLE_UPDATE_MANAGER_LOGGING = "ENABLE_UPDATE_MANAGER_LOGGING";
+export const ENABLE_COMPILE_CONFIG_LOGGING = "ENABLE_COMPILE_CONFIG_LOGGING";
diff --git a/packages/compiler/src/server/entrypoint-resolver.ts b/packages/compiler/src/server/entrypoint-resolver.ts
index 4865b44d4c6..134f970308d 100644
--- a/packages/compiler/src/server/entrypoint-resolver.ts
+++ b/packages/compiler/src/server/entrypoint-resolver.ts
@@ -2,7 +2,8 @@ import { formatDiagnostic } from "../core/logger/console-sink.js";
 import { getDirectoryPath, joinPaths } from "../core/path-utils.js";
 import { SystemHost, Diagnostic as TypeSpecDiagnostic } from "../core/types.js";
 import { doIO, loadFile } from "../utils/io.js";
-import { resolveTspMain } from "../utils/misc.js";
+import { getEnvironmentVariable, resolveTspMain } from "../utils/misc.js";
+import { ENABLE_COMPILE_CONFIG_LOGGING } from "./constants.js";
 import { FileSystemCache } from "./file-system-cache.js";
 import { ServerLog } from "./types.js";
 
@@ -14,6 +15,10 @@ export async function resolveEntrypointFile(
   log: (log: ServerLog) => void,
 ): Promise<string | undefined> {
   const options = { allowFileNotFound: true };
+  const logDebug =
+    getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true"
+      ? log
+      : () => {};
 
   const pathStat = await doIO(() => host.stat(path), path, logMainFileSearchDiagnostic, options);
   const isFilePath = pathStat?.isFile() ?? false;
@@ -36,14 +41,14 @@ export async function resolveEntrypointFile(
 
     const tspMain = resolveTspMain(pkg);
     if (typeof tspMain === "string") {
-      log({
+      logDebug({
         level: "debug",
         message: `tspMain resolved from package.json (${pkgPath}) as ${tspMain}`,
       });
 
       const packageJsonEntrypoint = await existingFile(dir, tspMain);
       if (packageJsonEntrypoint) {
-        log({ level: "debug", message: `entrypoint file found as ${packageJsonEntrypoint}` });
+        logDebug({ level: "debug", message: `entrypoint file found as ${packageJsonEntrypoint}` });
         return packageJsonEntrypoint;
       }
     }
@@ -51,7 +56,7 @@ export async function resolveEntrypointFile(
     for (const entrypoint of entrypoints) {
       const candidate = await existingFile(dir, entrypoint);
       if (candidate) {
-        log({
+        logDebug({
           level: "debug",
           message: `main file found using client provided entrypoint: ${candidate}`,
         });
@@ -67,7 +72,7 @@ export async function resolveEntrypointFile(
     dir = parentDir;
   }
 
-  log({ level: "debug", message: `reached directory root, using '${path}' as main file` });
+  logDebug({ level: "debug", message: `reached directory root, using '${path}' as main file` });
   return isFilePath ? path : undefined;
 
   function logMainFileSearchDiagnostic(diagnostic: TypeSpecDiagnostic) {
diff --git a/packages/compiler/src/server/serverlib.ts b/packages/compiler/src/server/serverlib.ts
index 50ad2b12057..900e3858f83 100644
--- a/packages/compiler/src/server/serverlib.ts
+++ b/packages/compiler/src/server/serverlib.ts
@@ -104,7 +104,7 @@ import { getSemanticTokens } from "./classify.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
 import { createCompileService } from "./compile-service.js";
 import { resolveCompletion } from "./completion.js";
-import { Commands } from "./constants.js";
+import { Commands, ENABLE_COMPILE_CONFIG_LOGGING } from "./constants.js";
 import { convertDiagnosticToLsp } from "./diagnostics.js";
 import { createFileService } from "./file-service.js";
 import { createFileSystemCache } from "./file-system-cache.js";
@@ -1138,7 +1138,7 @@ export function createServer(
           compilerHost,
           emitterProvider,
           linterProvider,
-          log,
+          log: logCompileConfig,
         });
         return CompletionList.create(items);
       }
@@ -1412,6 +1412,11 @@ export function createServer(
     host.log(log);
   }
 
+  const logCompileConfig =
+    host.getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true"
+      ? log
+      : () => {};
+
   function sendDiagnostics(document: TextDocument, diagnostics: VSDiagnostic[]) {
     host.sendDiagnostics({
       uri: document.uri,

From 9750838b8f316cd5a12c31c329fe5e028feb9264 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 16 Jan 2026 11:28:20 +0000
Subject: [PATCH 3/8] Fix JavaScript hoisting issue with logCompileConfig
 function

Co-authored-by: RodgeFu <6038235+RodgeFu@users.noreply.github.com>
---
 packages/compiler/src/server/compile-service.ts |  3 +--
 packages/compiler/src/server/serverlib.ts       | 11 ++++++-----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/packages/compiler/src/server/compile-service.ts b/packages/compiler/src/server/compile-service.ts
index 342e009689d..cb4a13b85c1 100644
--- a/packages/compiler/src/server/compile-service.ts
+++ b/packages/compiler/src/server/compile-service.ts
@@ -15,7 +15,7 @@ import { CompilerOptions } from "../core/options.js";
 import { parse } from "../core/parser.js";
 import { getBaseFileName, getDirectoryPath } from "../core/path-utils.js";
 import type { CompilerHost, TypeSpecScriptNode } from "../core/types.js";
-import { deepClone, distinctArray } from "../utils/misc.js";
+import { deepClone, distinctArray, getEnvironmentVariable } from "../utils/misc.js";
 import { getLocationInYamlScript } from "../yaml/diagnostics.js";
 import { parseYaml } from "../yaml/parser.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
@@ -90,7 +90,6 @@ export function createCompileService({
   const eventListeners = new Map<string, (...args: unknown[]) => void | Promise<void>>();
   const compileManager = new ServerCompileManager(updateManager, compilerHost, log);
   let configFilePath: string | undefined;
-  const { getEnvironmentVariable } = serverHost;
   const logDebug =
     getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true"
       ? log
diff --git a/packages/compiler/src/server/serverlib.ts b/packages/compiler/src/server/serverlib.ts
index 900e3858f83..c000298f875 100644
--- a/packages/compiler/src/server/serverlib.ts
+++ b/packages/compiler/src/server/serverlib.ts
@@ -99,7 +99,7 @@ import { scaffoldNewProject } from "../init/scaffold.js";
 import { typespecVersion } from "../manifest.js";
 import { resolveModule, ResolveModuleHost } from "../module-resolver/index.js";
 import { listAllFilesInDir } from "../utils/fs-utils.js";
-import { getNormalizedRealPath, resolveTspMain } from "../utils/misc.js";
+import { getEnvironmentVariable, getNormalizedRealPath, resolveTspMain } from "../utils/misc.js";
 import { getSemanticTokens } from "./classify.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
 import { createCompileService } from "./compile-service.js";
@@ -1412,10 +1412,11 @@ export function createServer(
     host.log(log);
   }
 
-  const logCompileConfig =
-    host.getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true"
-      ? log
-      : () => {};
+  function logCompileConfig(logMessage: ServerLog) {
+    if (getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true") {
+      log(logMessage);
+    }
+  }
 
   function sendDiagnostics(document: TextDocument, diagnostics: VSDiagnostic[]) {
     host.sendDiagnostics({

From 94bf93fe58e0ef4bc1349f2071175a8dc0bc83b4 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 17 Jan 2026 05:20:28 +0000
Subject: [PATCH 4/8] Refactor to use Node.js DEBUG pattern instead of
 individual env vars

Changed from individual ENABLE_*_LOGGING environment variables to
Node.js style DEBUG pattern supporting comma-separated areas and wildcards.

Usage examples:
  DEBUG=typespec:compile
  DEBUG=typespec:*
  DEBUG=typespec:compile,typespec:config

Debug areas:
  - typespec:compile (previously ENABLE_SERVER_COMPILE_LOGGING)
  - typespec:update (previously ENABLE_UPDATE_MANAGER_LOGGING)
  - typespec:config (previously ENABLE_COMPILE_CONFIG_LOGGING)

Co-authored-by: RodgeFu <6038235+RodgeFu@users.noreply.github.com>
---
 .../compiler/src/server/compile-service.ts    |  9 ++--
 packages/compiler/src/server/constants.ts     | 45 +++++++++++++++++--
 .../src/server/entrypoint-resolver.ts         |  9 ++--
 .../src/server/server-compile-manager.ts      |  9 ++--
 packages/compiler/src/server/serverlib.ts     |  6 +--
 .../compiler/src/server/update-manager.ts     | 13 +++---
 6 files changed, 60 insertions(+), 31 deletions(-)

diff --git a/packages/compiler/src/server/compile-service.ts b/packages/compiler/src/server/compile-service.ts
index cb4a13b85c1..2d9ff267005 100644
--- a/packages/compiler/src/server/compile-service.ts
+++ b/packages/compiler/src/server/compile-service.ts
@@ -15,11 +15,11 @@ import { CompilerOptions } from "../core/options.js";
 import { parse } from "../core/parser.js";
 import { getBaseFileName, getDirectoryPath } from "../core/path-utils.js";
 import type { CompilerHost, TypeSpecScriptNode } from "../core/types.js";
-import { deepClone, distinctArray, getEnvironmentVariable } from "../utils/misc.js";
+import { deepClone, distinctArray } from "../utils/misc.js";
 import { getLocationInYamlScript } from "../yaml/diagnostics.js";
 import { parseYaml } from "../yaml/parser.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
-import { ENABLE_COMPILE_CONFIG_LOGGING, serverOptions } from "./constants.js";
+import { DebugAreas, isDebugEnabled, serverOptions } from "./constants.js";
 import { resolveEntrypointFile } from "./entrypoint-resolver.js";
 import { FileService } from "./file-service.js";
 import { FileSystemCache } from "./file-system-cache.js";
@@ -90,10 +90,7 @@ export function createCompileService({
   const eventListeners = new Map<string, (...args: unknown[]) => void | Promise<void>>();
   const compileManager = new ServerCompileManager(updateManager, compilerHost, log);
   let configFilePath: string | undefined;
-  const logDebug =
-    getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true"
-      ? log
-      : () => {};
+  const logDebug = isDebugEnabled(DebugAreas.COMPILE_CONFIG) ? log : () => {};
 
   return { compile, getScript, on, notifyChange, getMainFileForDocument };
 
diff --git a/packages/compiler/src/server/constants.ts b/packages/compiler/src/server/constants.ts
index e96c3610654..c4cf398320e 100644
--- a/packages/compiler/src/server/constants.ts
+++ b/packages/compiler/src/server/constants.ts
@@ -1,4 +1,5 @@
 import { CompilerOptions } from "../core/options.js";
+import { getEnvironmentVariable } from "../utils/misc.js";
 
 export const serverOptions: CompilerOptions = {
   dryRun: true,
@@ -14,8 +15,44 @@ export const Commands = {
 };
 
 /**
- * Environment variables to enable some logging when needed
+ * Debug areas that can be enabled via DEBUG environment variable.
+ * Usage: DEBUG=typespec:compile,typespec:config
  */
-export const ENABLE_SERVER_COMPILE_LOGGING = "ENABLE_SERVER_COMPILE_LOGGING";
-export const ENABLE_UPDATE_MANAGER_LOGGING = "ENABLE_UPDATE_MANAGER_LOGGING";
-export const ENABLE_COMPILE_CONFIG_LOGGING = "ENABLE_COMPILE_CONFIG_LOGGING";
+export const DebugAreas = {
+  SERVER_COMPILE: "typespec:compile",
+  UPDATE_MANAGER: "typespec:update",
+  COMPILE_CONFIG: "typespec:config",
+} as const;
+
+/**
+ * Check if a debug area is enabled via the DEBUG environment variable.
+ * Supports Node.js DEBUG pattern with wildcards and comma-separated values.
+ * Examples:
+ *   DEBUG=typespec:compile
+ *   DEBUG=typespec:*
+ *   DEBUG=typespec:compile,typespec:config
+ */
+export function isDebugEnabled(area: string): boolean {
+  const debug = getEnvironmentVariable("DEBUG");
+  if (!debug) {
+    return false;
+  }
+
+  const areas = debug.split(",").map((a) => a.trim());
+  
+  return areas.some((pattern) => {
+    // Exact match
+    if (pattern === area) {
+      return true;
+    }
+    
+    // Wildcard pattern matching
+    if (pattern.includes("*")) {
+      const regexPattern = pattern.replace(/\*/g, ".*");
+      const regex = new RegExp(`^${regexPattern}$`);
+      return regex.test(area);
+    }
+    
+    return false;
+  });
+}
diff --git a/packages/compiler/src/server/entrypoint-resolver.ts b/packages/compiler/src/server/entrypoint-resolver.ts
index 134f970308d..ab2162c7fc8 100644
--- a/packages/compiler/src/server/entrypoint-resolver.ts
+++ b/packages/compiler/src/server/entrypoint-resolver.ts
@@ -2,8 +2,8 @@ import { formatDiagnostic } from "../core/logger/console-sink.js";
 import { getDirectoryPath, joinPaths } from "../core/path-utils.js";
 import { SystemHost, Diagnostic as TypeSpecDiagnostic } from "../core/types.js";
 import { doIO, loadFile } from "../utils/io.js";
-import { getEnvironmentVariable, resolveTspMain } from "../utils/misc.js";
-import { ENABLE_COMPILE_CONFIG_LOGGING } from "./constants.js";
+import { resolveTspMain } from "../utils/misc.js";
+import { DebugAreas, isDebugEnabled } from "./constants.js";
 import { FileSystemCache } from "./file-system-cache.js";
 import { ServerLog } from "./types.js";
 
@@ -15,10 +15,7 @@ export async function resolveEntrypointFile(
   log: (log: ServerLog) => void,
 ): Promise<string | undefined> {
   const options = { allowFileNotFound: true };
-  const logDebug =
-    getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true"
-      ? log
-      : () => {};
+  const logDebug = isDebugEnabled(DebugAreas.COMPILE_CONFIG) ? log : () => {};
 
   const pathStat = await doIO(() => host.stat(path), path, logMainFileSearchDiagnostic, options);
   const isFilePath = pathStat?.isFile() ?? false;
diff --git a/packages/compiler/src/server/server-compile-manager.ts b/packages/compiler/src/server/server-compile-manager.ts
index 552c0551893..c84168e97d2 100644
--- a/packages/compiler/src/server/server-compile-manager.ts
+++ b/packages/compiler/src/server/server-compile-manager.ts
@@ -9,7 +9,7 @@ import {
   ServerLog,
 } from "../index.js";
 import { getEnvironmentVariable } from "../utils/misc.js";
-import { ENABLE_SERVER_COMPILE_LOGGING } from "./constants.js";
+import { DebugAreas, isDebugEnabled } from "./constants.js";
 import { trackActionFunc } from "./server-track-action-task.js";
 import { UpdateManager } from "./update-manager.js";
 
@@ -45,10 +45,9 @@ export class ServerCompileManager {
     private compilerHost: CompilerHost,
     private log: (log: ServerLog) => void,
   ) {
-    this.logDebug =
-      getEnvironmentVariable(ENABLE_SERVER_COMPILE_LOGGING)?.toLowerCase() === "true"
-        ? (msg) => this.log({ level: "debug", message: msg })
-        : () => {};
+    this.logDebug = isDebugEnabled(DebugAreas.SERVER_COMPILE)
+      ? (msg) => this.log({ level: "debug", message: msg })
+      : () => {};
   }
 
   async compile(
diff --git a/packages/compiler/src/server/serverlib.ts b/packages/compiler/src/server/serverlib.ts
index c000298f875..d8c7ac3b2e4 100644
--- a/packages/compiler/src/server/serverlib.ts
+++ b/packages/compiler/src/server/serverlib.ts
@@ -99,12 +99,12 @@ import { scaffoldNewProject } from "../init/scaffold.js";
 import { typespecVersion } from "../manifest.js";
 import { resolveModule, ResolveModuleHost } from "../module-resolver/index.js";
 import { listAllFilesInDir } from "../utils/fs-utils.js";
-import { getEnvironmentVariable, getNormalizedRealPath, resolveTspMain } from "../utils/misc.js";
+import { getNormalizedRealPath, resolveTspMain } from "../utils/misc.js";
 import { getSemanticTokens } from "./classify.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
 import { createCompileService } from "./compile-service.js";
 import { resolveCompletion } from "./completion.js";
-import { Commands, ENABLE_COMPILE_CONFIG_LOGGING } from "./constants.js";
+import { Commands, DebugAreas, isDebugEnabled } from "./constants.js";
 import { convertDiagnosticToLsp } from "./diagnostics.js";
 import { createFileService } from "./file-service.js";
 import { createFileSystemCache } from "./file-system-cache.js";
@@ -1413,7 +1413,7 @@ export function createServer(
   }
 
   function logCompileConfig(logMessage: ServerLog) {
-    if (getEnvironmentVariable(ENABLE_COMPILE_CONFIG_LOGGING)?.toLowerCase() === "true") {
+    if (isDebugEnabled(DebugAreas.COMPILE_CONFIG)) {
       log(logMessage);
     }
   }
diff --git a/packages/compiler/src/server/update-manager.ts b/packages/compiler/src/server/update-manager.ts
index 0d650dbc359..1b88e622439 100644
--- a/packages/compiler/src/server/update-manager.ts
+++ b/packages/compiler/src/server/update-manager.ts
@@ -1,7 +1,7 @@
 import { TextDocumentIdentifier } from "vscode-languageserver";
 import { TextDocument } from "vscode-languageserver-textdocument";
 import { getEnvironmentVariable } from "../utils/misc.js";
-import { ENABLE_UPDATE_MANAGER_LOGGING } from "./constants.js";
+import { DebugAreas, isDebugEnabled } from "./constants.js";
 import { ServerLog } from "./types.js";
 
 interface PendingUpdate {
@@ -43,12 +43,11 @@ export class UpdateManager<T = void> {
     log: (sl: ServerLog) => void,
     getDebounceDelay?: () => number,
   ) {
-    this._log =
-      getEnvironmentVariable(ENABLE_UPDATE_MANAGER_LOGGING)?.toLowerCase() === "true"
-        ? (sl: ServerLog) => {
-            log({ ...sl, message: `#FromUpdateManager(${this.name}): ${sl.message}` });
-          }
-        : () => {};
+    this._log = isDebugEnabled(DebugAreas.UPDATE_MANAGER)
+      ? (sl: ServerLog) => {
+          log({ ...sl, message: `#FromUpdateManager(${this.name}): ${sl.message}` });
+        }
+      : () => {};
 
     // Set the debounce delay function once during construction
     this.getDebounceDelay = getDebounceDelay ?? this.getAdaptiveDebounceDelay;

From b4bcd2dbe31a5ece75a532907fd9eaa33184afca Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 17 Jan 2026 08:12:45 +0000
Subject: [PATCH 5/8] Keep original naming convention for debug areas

Changed debug area names to preserve the original convention:
- typespec:server_compile (was typespec:compile)
- typespec:update_manager (was typespec:update)
- typespec:compile_config (was typespec:config)

This maintains consistency with the original ENABLE_*_LOGGING variable names.

Co-authored-by: RodgeFu <6038235+RodgeFu@users.noreply.github.com>
---
 packages/compiler/src/server/constants.ts | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/packages/compiler/src/server/constants.ts b/packages/compiler/src/server/constants.ts
index c4cf398320e..2dc109aa8ea 100644
--- a/packages/compiler/src/server/constants.ts
+++ b/packages/compiler/src/server/constants.ts
@@ -16,21 +16,21 @@ export const Commands = {
 
 /**
  * Debug areas that can be enabled via DEBUG environment variable.
- * Usage: DEBUG=typespec:compile,typespec:config
+ * Usage: DEBUG=typespec:server_compile,typespec:compile_config
  */
 export const DebugAreas = {
-  SERVER_COMPILE: "typespec:compile",
-  UPDATE_MANAGER: "typespec:update",
-  COMPILE_CONFIG: "typespec:config",
+  SERVER_COMPILE: "typespec:server_compile",
+  UPDATE_MANAGER: "typespec:update_manager",
+  COMPILE_CONFIG: "typespec:compile_config",
 } as const;
 
 /**
  * Check if a debug area is enabled via the DEBUG environment variable.
  * Supports Node.js DEBUG pattern with wildcards and comma-separated values.
  * Examples:
- *   DEBUG=typespec:compile
+ *   DEBUG=typespec:server_compile
  *   DEBUG=typespec:*
- *   DEBUG=typespec:compile,typespec:config
+ *   DEBUG=typespec:server_compile,typespec:compile_config
  */
 export function isDebugEnabled(area: string): boolean {
   const debug = getEnvironmentVariable("DEBUG");

From 451c4e0b3651cd2270a2cc1904f30c7559e12c91 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 17 Jan 2026 08:21:28 +0000
Subject: [PATCH 6/8] Refactor to use debug npm package and update launch.json
 comments

- Added `debug` package (v4.4.0) as dependency
- Added `@types/debug` as dev dependency
- Replaced custom isDebugEnabled() with debug package loggers
- Updated .vscode/launch.json to document DEBUG env var usage
- Removed old ENABLE_*_LOGGING environment variable comments

The debug package provides standard Node.js debugging with namespace support,
wildcards, and better performance than the custom implementation.

Co-authored-by: RodgeFu <6038235+RodgeFu@users.noreply.github.com>
---
 .vscode/launch.json                           |  8 ++-
 packages/compiler/package.json                |  2 +
 .../compiler/src/server/compile-service.ts    |  5 +-
 packages/compiler/src/server/constants.ts     | 50 ++++---------------
 .../src/server/entrypoint-resolver.ts         |  5 +-
 .../src/server/server-compile-manager.ts      |  5 +-
 packages/compiler/src/server/serverlib.ts     |  4 +-
 .../compiler/src/server/update-manager.ts     |  5 +-
 pnpm-lock.yaml                                |  6 +++
 9 files changed, 39 insertions(+), 51 deletions(-)

diff --git a/.vscode/launch.json b/.vscode/launch.json
index ed76356799c..a204103d10c 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -141,8 +141,12 @@
         // Set the telemetry key environment variable to use if you dont want to set it in package.json
         //"TYPESPEC_VSCODE_TELEMETRY_KEY": "{The instrumentation key of your Application Insights}",
 
-        //"ENABLE_SERVER_COMPILE_LOGGING": "true",
-        //"ENABLE_UPDATE_MANAGER_LOGGING": "true",
+        // Enable debug logging for specific areas using DEBUG environment variable
+        // Examples:
+        //   "DEBUG": "typespec:server_compile"           - Enable server compilation debug logs
+        //   "DEBUG": "typespec:*"                        - Enable all typespec debug logs
+        //   "DEBUG": "typespec:server_compile,typespec:compile_config" - Enable multiple areas
+        //"DEBUG": "typespec:server_compile,typespec:update_manager,typespec:compile_config",
         //"ENABLE_LM_LOGGING": "true",
 
         "TYPESPEC_SERVER_NODE_OPTIONS": "--nolazy --inspect-brk=4242",
diff --git a/packages/compiler/package.json b/packages/compiler/package.json
index bd834faa5fa..cf791847742 100644
--- a/packages/compiler/package.json
+++ b/packages/compiler/package.json
@@ -109,6 +109,7 @@
     "@inquirer/prompts": "^8.0.1",
     "ajv": "~8.17.1",
     "change-case": "~5.4.4",
+    "debug": "~4.4.0",
     "env-paths": "^3.0.0",
     "globby": "~16.0.0",
     "is-unicode-supported": "^2.1.0",
@@ -125,6 +126,7 @@
   },
   "devDependencies": {
     "@types/babel__code-frame": "~7.0.6",
+    "@types/debug": "~4.1.12",
     "@types/mustache": "~4.2.5",
     "@types/node": "~25.0.2",
     "@types/semver": "^7.5.8",
diff --git a/packages/compiler/src/server/compile-service.ts b/packages/compiler/src/server/compile-service.ts
index 2d9ff267005..8db4db2da72 100644
--- a/packages/compiler/src/server/compile-service.ts
+++ b/packages/compiler/src/server/compile-service.ts
@@ -19,7 +19,7 @@ import { deepClone, distinctArray } from "../utils/misc.js";
 import { getLocationInYamlScript } from "../yaml/diagnostics.js";
 import { parseYaml } from "../yaml/parser.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
-import { DebugAreas, isDebugEnabled, serverOptions } from "./constants.js";
+import { debugLoggers, serverOptions } from "./constants.js";
 import { resolveEntrypointFile } from "./entrypoint-resolver.js";
 import { FileService } from "./file-service.js";
 import { FileSystemCache } from "./file-system-cache.js";
@@ -90,7 +90,8 @@ export function createCompileService({
   const eventListeners = new Map<string, (...args: unknown[]) => void | Promise<void>>();
   const compileManager = new ServerCompileManager(updateManager, compilerHost, log);
   let configFilePath: string | undefined;
-  const logDebug = isDebugEnabled(DebugAreas.COMPILE_CONFIG) ? log : () => {};
+  const debug = debugLoggers.compileConfig;
+  const logDebug = debug.enabled ? log : () => {};
 
   return { compile, getScript, on, notifyChange, getMainFileForDocument };
 
diff --git a/packages/compiler/src/server/constants.ts b/packages/compiler/src/server/constants.ts
index 2dc109aa8ea..70e99a7b2a8 100644
--- a/packages/compiler/src/server/constants.ts
+++ b/packages/compiler/src/server/constants.ts
@@ -1,5 +1,5 @@
 import { CompilerOptions } from "../core/options.js";
-import { getEnvironmentVariable } from "../utils/misc.js";
+import createDebug from "debug";
 
 export const serverOptions: CompilerOptions = {
   dryRun: true,
@@ -15,44 +15,16 @@ export const Commands = {
 };
 
 /**
- * Debug areas that can be enabled via DEBUG environment variable.
+ * Debug loggers for different areas. Can be enabled via DEBUG environment variable.
  * Usage: DEBUG=typespec:server_compile,typespec:compile_config
- */
-export const DebugAreas = {
-  SERVER_COMPILE: "typespec:server_compile",
-  UPDATE_MANAGER: "typespec:update_manager",
-  COMPILE_CONFIG: "typespec:compile_config",
-} as const;
-
-/**
- * Check if a debug area is enabled via the DEBUG environment variable.
- * Supports Node.js DEBUG pattern with wildcards and comma-separated values.
+ * 
  * Examples:
- *   DEBUG=typespec:server_compile
- *   DEBUG=typespec:*
- *   DEBUG=typespec:server_compile,typespec:compile_config
+ *   DEBUG=typespec:server_compile      - Enable server compilation debug logs
+ *   DEBUG=typespec:*                   - Enable all typespec debug logs
+ *   DEBUG=typespec:server_compile,typespec:compile_config - Enable multiple areas
  */
-export function isDebugEnabled(area: string): boolean {
-  const debug = getEnvironmentVariable("DEBUG");
-  if (!debug) {
-    return false;
-  }
-
-  const areas = debug.split(",").map((a) => a.trim());
-  
-  return areas.some((pattern) => {
-    // Exact match
-    if (pattern === area) {
-      return true;
-    }
-    
-    // Wildcard pattern matching
-    if (pattern.includes("*")) {
-      const regexPattern = pattern.replace(/\*/g, ".*");
-      const regex = new RegExp(`^${regexPattern}$`);
-      return regex.test(area);
-    }
-    
-    return false;
-  });
-}
+export const debugLoggers = {
+  serverCompile: createDebug("typespec:server_compile"),
+  updateManager: createDebug("typespec:update_manager"),
+  compileConfig: createDebug("typespec:compile_config"),
+} as const;
diff --git a/packages/compiler/src/server/entrypoint-resolver.ts b/packages/compiler/src/server/entrypoint-resolver.ts
index ab2162c7fc8..0885021f3e2 100644
--- a/packages/compiler/src/server/entrypoint-resolver.ts
+++ b/packages/compiler/src/server/entrypoint-resolver.ts
@@ -3,7 +3,7 @@ import { getDirectoryPath, joinPaths } from "../core/path-utils.js";
 import { SystemHost, Diagnostic as TypeSpecDiagnostic } from "../core/types.js";
 import { doIO, loadFile } from "../utils/io.js";
 import { resolveTspMain } from "../utils/misc.js";
-import { DebugAreas, isDebugEnabled } from "./constants.js";
+import { debugLoggers } from "./constants.js";
 import { FileSystemCache } from "./file-system-cache.js";
 import { ServerLog } from "./types.js";
 
@@ -15,7 +15,8 @@ export async function resolveEntrypointFile(
   log: (log: ServerLog) => void,
 ): Promise<string | undefined> {
   const options = { allowFileNotFound: true };
-  const logDebug = isDebugEnabled(DebugAreas.COMPILE_CONFIG) ? log : () => {};
+  const debug = debugLoggers.compileConfig;
+  const logDebug = debug.enabled ? log : () => {};
 
   const pathStat = await doIO(() => host.stat(path), path, logMainFileSearchDiagnostic, options);
   const isFilePath = pathStat?.isFile() ?? false;
diff --git a/packages/compiler/src/server/server-compile-manager.ts b/packages/compiler/src/server/server-compile-manager.ts
index c84168e97d2..d600c4825d6 100644
--- a/packages/compiler/src/server/server-compile-manager.ts
+++ b/packages/compiler/src/server/server-compile-manager.ts
@@ -9,7 +9,7 @@ import {
   ServerLog,
 } from "../index.js";
 import { getEnvironmentVariable } from "../utils/misc.js";
-import { DebugAreas, isDebugEnabled } from "./constants.js";
+import { debugLoggers } from "./constants.js";
 import { trackActionFunc } from "./server-track-action-task.js";
 import { UpdateManager } from "./update-manager.js";
 
@@ -45,7 +45,8 @@ export class ServerCompileManager {
     private compilerHost: CompilerHost,
     private log: (log: ServerLog) => void,
   ) {
-    this.logDebug = isDebugEnabled(DebugAreas.SERVER_COMPILE)
+    const debug = debugLoggers.serverCompile;
+    this.logDebug = debug.enabled
       ? (msg) => this.log({ level: "debug", message: msg })
       : () => {};
   }
diff --git a/packages/compiler/src/server/serverlib.ts b/packages/compiler/src/server/serverlib.ts
index d8c7ac3b2e4..ea6ee86823b 100644
--- a/packages/compiler/src/server/serverlib.ts
+++ b/packages/compiler/src/server/serverlib.ts
@@ -104,7 +104,7 @@ import { getSemanticTokens } from "./classify.js";
 import { ClientConfigProvider } from "./client-config-provider.js";
 import { createCompileService } from "./compile-service.js";
 import { resolveCompletion } from "./completion.js";
-import { Commands, DebugAreas, isDebugEnabled } from "./constants.js";
+import { Commands, debugLoggers } from "./constants.js";
 import { convertDiagnosticToLsp } from "./diagnostics.js";
 import { createFileService } from "./file-service.js";
 import { createFileSystemCache } from "./file-system-cache.js";
@@ -1413,7 +1413,7 @@ export function createServer(
   }
 
   function logCompileConfig(logMessage: ServerLog) {
-    if (isDebugEnabled(DebugAreas.COMPILE_CONFIG)) {
+    if (debugLoggers.compileConfig.enabled) {
       log(logMessage);
     }
   }
diff --git a/packages/compiler/src/server/update-manager.ts b/packages/compiler/src/server/update-manager.ts
index 1b88e622439..d3e1aac41e7 100644
--- a/packages/compiler/src/server/update-manager.ts
+++ b/packages/compiler/src/server/update-manager.ts
@@ -1,7 +1,7 @@
 import { TextDocumentIdentifier } from "vscode-languageserver";
 import { TextDocument } from "vscode-languageserver-textdocument";
 import { getEnvironmentVariable } from "../utils/misc.js";
-import { DebugAreas, isDebugEnabled } from "./constants.js";
+import { debugLoggers } from "./constants.js";
 import { ServerLog } from "./types.js";
 
 interface PendingUpdate {
@@ -43,7 +43,8 @@ export class UpdateManager<T = void> {
     log: (sl: ServerLog) => void,
     getDebounceDelay?: () => number,
   ) {
-    this._log = isDebugEnabled(DebugAreas.UPDATE_MANAGER)
+    const debug = debugLoggers.updateManager;
+    this._log = debug.enabled
       ? (sl: ServerLog) => {
           log({ ...sl, message: `#FromUpdateManager(${this.name}): ${sl.message}` });
         }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 8af70bccd41..5dc7cd89b01 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -314,6 +314,9 @@ importers:
       change-case:
         specifier: ~5.4.4
         version: 5.4.4
+      debug:
+        specifier: ~4.4.0
+        version: 4.4.3(supports-color@8.1.1)
       env-paths:
         specifier: ^3.0.0
         version: 3.0.0
@@ -357,6 +360,9 @@ importers:
       '@types/babel__code-frame':
         specifier: ~7.0.6
         version: 7.0.6
+      '@types/debug':
+        specifier: ~4.1.12
+        version: 4.1.12
       '@types/mustache':
         specifier: ~4.2.5
         version: 4.2.6

From ca30a7456fd321bd6a15ca6520c33bacb298c964 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 19 Jan 2026 06:20:02 +0000
Subject: [PATCH 7/8] Add documentation comment for ENABLE_LM_LOGGING in
 launch.json

Added a comment to clarify that ENABLE_LM_LOGGING is separate from
the DEBUG environment variable logging system and is used specifically
for Language Model logging in the typespec-vscode extension.

Co-authored-by: RodgeFu <6038235+RodgeFu@users.noreply.github.com>
---
 .vscode/launch.json | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.vscode/launch.json b/.vscode/launch.json
index a204103d10c..fb092407602 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -147,6 +147,8 @@
         //   "DEBUG": "typespec:*"                        - Enable all typespec debug logs
         //   "DEBUG": "typespec:server_compile,typespec:compile_config" - Enable multiple areas
         //"DEBUG": "typespec:server_compile,typespec:update_manager,typespec:compile_config",
+
+        // Enable Language Model logging (separate from DEBUG logging)
         //"ENABLE_LM_LOGGING": "true",
 
         "TYPESPEC_SERVER_NODE_OPTIONS": "--nolazy --inspect-brk=4242",

From 42c1d4fb0cbbf70ef17add28010ba8ea60e3f3ad Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 19 Jan 2026 06:29:34 +0000
Subject: [PATCH 8/8] Refactor typespec-vscode to use debug package for LM
 logging

- Added `debug@~4.4.0` as dependency to typespec-vscode
- Added `@types/debug@~4.1.12` as dev dependency
- Replaced ENABLE_LM_LOGGING with debug logger (typespec:lm)
- Updated const.ts to export debugLoggers.lm
- Updated language-model.ts to use debugLoggers.lm.enabled
- Updated .vscode/launch.json to document DEBUG=typespec:lm usage

Language Model logging now follows the same DEBUG pattern as compiler
logging, enabling it with DEBUG=typespec:lm or DEBUG=typespec:*

Co-authored-by: RodgeFu <6038235+RodgeFu@users.noreply.github.com>
---
 .vscode/launch.json                               |  6 ++----
 packages/typespec-vscode/package.json             |  6 +++++-
 packages/typespec-vscode/src/const.ts             | 11 ++++++++++-
 packages/typespec-vscode/src/lm/language-model.ts |  5 +++--
 pnpm-lock.yaml                                    |  7 +++++++
 5 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/.vscode/launch.json b/.vscode/launch.json
index fb092407602..384e8a86605 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -144,12 +144,10 @@
         // Enable debug logging for specific areas using DEBUG environment variable
         // Examples:
         //   "DEBUG": "typespec:server_compile"           - Enable server compilation debug logs
+        //   "DEBUG": "typespec:lm"                       - Enable Language Model debug logs  
         //   "DEBUG": "typespec:*"                        - Enable all typespec debug logs
         //   "DEBUG": "typespec:server_compile,typespec:compile_config" - Enable multiple areas
-        //"DEBUG": "typespec:server_compile,typespec:update_manager,typespec:compile_config",
-
-        // Enable Language Model logging (separate from DEBUG logging)
-        //"ENABLE_LM_LOGGING": "true",
+        //"DEBUG": "typespec:server_compile,typespec:update_manager,typespec:compile_config,typespec:lm",
 
         "TYPESPEC_SERVER_NODE_OPTIONS": "--nolazy --inspect-brk=4242",
         "TYPESPEC_DEVELOPMENT_MODE": "true"
diff --git a/packages/typespec-vscode/package.json b/packages/typespec-vscode/package.json
index 7fb914d9b4f..f31f8da8b3a 100644
--- a/packages/typespec-vscode/package.json
+++ b/packages/typespec-vscode/package.json
@@ -309,6 +309,10 @@
     "vitest": "^4.0.15",
     "vscode-languageclient": "~9.0.1",
     "which": "^6.0.0",
-    "yaml": "~2.8.2"
+    "yaml": "~2.8.2",
+    "@types/debug": "~4.1.12"
+  },
+  "dependencies": {
+    "debug": "~4.4.0"
   }
 }
diff --git a/packages/typespec-vscode/src/const.ts b/packages/typespec-vscode/src/const.ts
index 39df7d9279c..e0726239f8e 100644
--- a/packages/typespec-vscode/src/const.ts
+++ b/packages/typespec-vscode/src/const.ts
@@ -1,5 +1,14 @@
+import createDebug from "debug";
+
 export const StartFileName = "main.tsp";
 export const TspConfigFileName = "tspconfig.yaml";
 export const EmptyGuid = "00000000-0000-0000-0000-000000000000";
 
-export const ENABLE_LM_LOGGING = "ENABLE_LM_LOGGING";
+/**
+ * Debug logger for Language Model operations.
+ * Can be enabled via DEBUG environment variable.
+ * Usage: DEBUG=typespec:lm
+ */
+export const debugLoggers = {
+  lm: createDebug("typespec:lm"),
+} as const;
diff --git a/packages/typespec-vscode/src/lm/language-model.ts b/packages/typespec-vscode/src/lm/language-model.ts
index 3dfb8d581d6..064358199f3 100644
--- a/packages/typespec-vscode/src/lm/language-model.ts
+++ b/packages/typespec-vscode/src/lm/language-model.ts
@@ -1,6 +1,6 @@
 import { inspect } from "util";
 import { LanguageModelChat, LanguageModelChatMessage, lm } from "vscode";
-import { ENABLE_LM_LOGGING } from "../const";
+import { debugLoggers } from "../const";
 import logger, { LogItem } from "../log/logger";
 import { RetryResult, runWithRetry, runWithTimingLog } from "../utils";
 
@@ -23,7 +23,8 @@ export async function sendLmChatRequest(
   /** Only for logging purpose */
   id?: string,
 ): Promise<string | undefined> {
-  const logEnabled = process.env[ENABLE_LM_LOGGING] === "true";
+  const debug = debugLoggers.lm;
+  const logEnabled = debug.enabled;
   const lmLog = (item: LogItem) => {
     if (logEnabled || item.level === "error" || item.level === "warning") {
       logger.log(
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 5dc7cd89b01..eaa178f7ede 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2361,10 +2361,17 @@ importers:
         version: link:../typespec-vscode
 
   packages/typespec-vscode:
+    dependencies:
+      debug:
+        specifier: ~4.4.0
+        version: 4.4.3(supports-color@8.1.1)
     devDependencies:
       '@types/cross-spawn':
         specifier: ~6.0.6
         version: 6.0.6
+      '@types/debug':
+        specifier: ~4.1.12
+        version: 4.1.12
       '@types/mocha':
         specifier: ^10.0.9
         version: 10.0.10