logLevel: don't impose any default, match C#/Go

Instead of defaulting to 'info' on the SDK side, omit the --log-level
flag entirely when the caller didn't set one and let the runtime use
its own default. Matches dotnet/Client.cs and go/client.go, which both
only pass --log-level when explicitly provided.

CopilotClientOptions.logLevel JSDoc and README updated to describe this
('When omitted, the runtime uses its own default').

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

nodejs/README.md

@@ -85,7 +85,7 @@ new CopilotClient(options?: CopilotClientOptions)
     - `RuntimeConnection.forUri(url, { connectionToken? })` — connect to an already-running runtime (mutually exclusive with `gitHubToken`/`useLoggedInUser`).
 - `cwd?: string` - Working directory for the runtime process (default: current process cwd).
 - `baseDirectory?: string` - Base directory for Copilot data (session state, config, etc.). Sets `COPILOT_HOME` on the spawned runtime. When not set, the runtime defaults to `~/.copilot`. Ignored when connecting via `RuntimeConnection.forUri`.
-- `logLevel?: string` - Log level (default: "info").
+- `logLevel?: string` - Log level. When omitted, the runtime uses its own default (currently `"info"`).
 - `gitHubToken?: string` - GitHub token for authentication. When provided, takes priority over other auth methods.
 - `useLoggedInUser?: boolean` - Whether to use logged-in user for authentication (default: true, but false when `gitHubToken` is provided). Cannot be used with `RuntimeConnection.forUri`.
 - `telemetry?: TelemetryConfig` - OpenTelemetry configuration for the runtime process. Providing this object enables telemetry — no separate flag needed. See [Telemetry](#telemetry) below.

nodejs/src/client.ts

@@ -229,7 +229,7 @@ export class CopilotClient {
     private resolvedEnv: Record<string, string | undefined>;
     private options: {
         cwd: string;
-        logLevel: string;
+        logLevel?: string;
         gitHubToken?: string;
         useLoggedInUser: boolean;
         telemetry?: TelemetryConfig;
@@ -375,7 +375,7 @@ export class CopilotClient {
 
         this.options = {
             cwd: options.cwd ?? process.cwd(),
-            logLevel: options.logLevel || "info",
+            logLevel: options.logLevel,
             gitHubToken: options.gitHubToken,
             // Default useLoggedInUser to false when gitHubToken is provided, otherwise true.
             useLoggedInUser: options.useLoggedInUser ?? (options.gitHubToken ? false : true),
@@ -1491,13 +1491,11 @@ export class CopilotClient {
             // Clear stderr buffer for fresh capture
             this.stderrBuffer = "";
 
-            const args = [
-                ...this.connectionExtraArgs,
-                "--headless",
-                "--no-auto-update",
-                "--log-level",
-                this.options.logLevel,
-            ];
+            const args = [...this.connectionExtraArgs, "--headless", "--no-auto-update"];
+
+            if (this.options.logLevel) {
+                args.push("--log-level", this.options.logLevel);
+            }
 
             // Choose transport mode based on the resolved connection config.
             if (this.connectionConfig.kind === "stdio") {

nodejs/src/types.ts

@@ -187,7 +187,8 @@ export interface CopilotClientOptions {
     baseDirectory?: string;
 
     /**
-     * Log level for the Copilot runtime.
+     * Log level for the Copilot runtime. When omitted, the runtime uses its
+     * own default (currently `"info"`).
      */
     logLevel?: "none" | "error" | "warning" | "info" | "debug" | "all";