Fix theme updating when VS Code auto theme detection is on

.gitignore

@@ -17,3 +17,4 @@ public/dist
 /.luarc.json
 .vscode-test
 *.vsix
+*.timestamp-*.mjs

apps/lsp/src/config.ts

@@ -136,6 +136,8 @@ export class ConfigurationManager extends Disposable {
 
   private _settings: Settings;
   private _logger: ILogger;
+  private _activeColorThemeKind: "light" | "dark" = "dark";
+  private _themeExplicitlySet = false;
 
   constructor(
     private readonly connection_: Connection,
@@ -177,6 +179,18 @@ export class ConfigurationManager extends Disposable {
         }
       }
     };
+
+    // Fallback: try to detect theme from name if we haven't received an explicit notification yet
+    // This is a best-effort approach for compatibility, but won't work with autoDetectColorScheme
+    // Only apply fallback if theme hasn't been explicitly set via notification
+    if (!this._themeExplicitlySet) {
+      if (settings.workbench.colorTheme.includes("Light")) {
+        this._activeColorThemeKind = "light";
+      } else if (settings.workbench.colorTheme.includes("Dark")) {
+        this._activeColorThemeKind = "dark";
+      }
+    }
+
     this._onDidChangeConfiguration.fire(this._settings);
   }
 
@@ -202,6 +216,18 @@ export class ConfigurationManager extends Disposable {
   public getSettings(): Settings {
     return this._settings;
   }
+
+  public setActiveColorThemeKind(kind: "light" | "dark") {
+    if (this._activeColorThemeKind !== kind) {
+      this._activeColorThemeKind = kind;
+      this._themeExplicitlySet = true;
+      this._onDidChangeConfiguration.fire(this._settings);
+    }
+  }
+
+  public getActiveColorThemeKind(): "light" | "dark" {
+    return this._activeColorThemeKind;
+  }
 }
 
 export function lsConfiguration(configManager: ConfigurationManager): LsConfiguration {
@@ -226,8 +252,7 @@ export function lsConfiguration(configManager: ConfigurationManager): LsConfigur
       }
     },
     get colorTheme(): "light" | "dark" {
-      const settings = configManager.getSettings();
-      return settings.workbench.colorTheme.includes("Light") ? "light" : "dark";
+      return configManager.getActiveColorThemeKind();
     },
     get mathjaxScale(): number {
       return configManager.getSettings().quarto.mathjax.scale;

apps/lsp/src/index.ts

@@ -224,6 +224,17 @@ connection.onInitialized(async () => {
     logger.setConfigurationManager(configManager);
   }
 
+  // listen for color theme changes from the client
+  connection.onNotification("quarto/didChangeActiveColorTheme", (params: { kind: string; }) => {
+    logger.logNotification('didChangeActiveColorTheme');
+    // Validate the theme kind before using it
+    if (params.kind === "light" || params.kind === "dark") {
+      configManager.setActiveColorThemeKind(params.kind);
+    } else {
+      logger.logError(`Invalid theme kind received: ${params.kind}`);
+    }
+  });
+
   // initialize connection to quarto
   const workspaceFolders = await connection.workspace.getWorkspaceFolders();
   const workspaceDir = workspaceFolders?.length

apps/vscode/src/lsp/client.ts

@@ -24,7 +24,9 @@ import {
   Definition,
   LogOutputChannel,
   Uri,
-  Diagnostic
+  Diagnostic,
+  window,
+  ColorThemeKind
 } from "vscode";
 import {
   LanguageClient,
@@ -151,12 +153,33 @@ export async function activateLsp(
     clientOptions
   );
 
+  // Helper to send current theme to LSP server
+  const sendThemeNotification = () => {
+    if (client) {
+      // Map VS Code theme kinds to light/dark. HighContrast themes are treated as dark
+      // since they typically have light text on dark backgrounds
+      const kind = (window.activeColorTheme.kind === ColorThemeKind.Light || window.activeColorTheme.kind === ColorThemeKind.HighContrastLight) ? "light" : "dark";
+      client.sendNotification("quarto/didChangeActiveColorTheme", { kind });
+    }
+  };
+
+  // Listen for theme changes and notify the server
+  context.subscriptions.push(
+    window.onDidChangeActiveColorTheme(() => {
+      sendThemeNotification();
+    })
+  );
+
   // return once the server is running
   return new Promise<LanguageClient>((resolve, reject) => {
 
     const handler = client.onDidChangeState(e => {
       if (e.newState === State.Running) {
         handler.dispose();
+        // Send initial theme on startup, slightly delayed to ensure server is ready
+        setTimeout(() => {
+          sendThemeNotification();
+        }, 100);
         resolve(client);
       } else if (e.newState === State.Stopped) {
         reject(new Error("Failed to start Quarto LSP Server"));