fix: support bracketed IPv6 runtime URLs

dotnet/src/Client.cs

@@ -167,7 +167,7 @@ public CopilotClient(CopilotClientOptions? options = null)
                     throw new ArgumentException("GitHubToken and UseLoggedInUser cannot be combined with RuntimeConnection.ForUri (the existing runtime manages its own auth).", nameof(options));
                 }
                 var parsed = ParseRuntimeUrl(uri.Url);
-                _optionsHost = parsed.Host;
+                _optionsHost = parsed.Host.Trim('[', ']');
                 _optionsPort = parsed.Port;
                 break;
 
@@ -298,12 +298,18 @@ private static RuntimeConnection ResolveDefaultConnection(CopilotClientOptions o
     /// <summary>
     /// Parses a runtime URL into a URI with host and port.
     /// </summary>
-    /// <param name="url">The URL to parse. Supports formats: "port", "host:port", "http://host:port".</param>
+    /// <param name="url">The URL to parse. Supports formats: "port", "host:port", "[ipv6]:port", "http://host:port".</param>
     private static Uri ParseRuntimeUrl(string url)
     {
+        url = url.Trim();
+
         // If it's just a port number, treat as localhost
         if (int.TryParse(url, out var port))
         {
+            if (port <= 0 || port > 65535)
+            {
+                throw new ArgumentException($"Invalid runtime URL port: {url}");
+            }
             return new Uri($"http://localhost:{port}");
         }
 
@@ -314,7 +320,18 @@ private static Uri ParseRuntimeUrl(string url)
             url = "https://" + url;
         }
 
-        return new Uri(url);
+        if (!Uri.TryCreate(url, UriKind.Absolute, out var uri) ||
+            string.IsNullOrEmpty(uri.Host) ||
+            uri.Port <= 0 ||
+            uri.Port > 65535 ||
+            (!string.IsNullOrEmpty(uri.AbsolutePath) && uri.AbsolutePath != "/") ||
+            !string.IsNullOrEmpty(uri.Query) ||
+            !string.IsNullOrEmpty(uri.Fragment))
+        {
+            throw new ArgumentException($"Invalid runtime URL: {url}");
+        }
+
+        return uri;
     }
 
     /// <summary>

dotnet/test/Unit/RuntimeConnectionUrlParsingTests.cs

@@ -0,0 +1,51 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *--------------------------------------------------------------------------------------------*/
+
+using Xunit;
+using System.Reflection;
+
+namespace GitHub.Copilot.Test.Unit;
+
+public class RuntimeConnectionUrlParsingTests
+{
+    [Fact]
+    public void ForUri_ParsesBracketedIpv6HostPort()
+    {
+        var client = new CopilotClient(new CopilotClientOptions
+        {
+            Connection = RuntimeConnection.ForUri("[::1]:9000")
+        });
+
+        Assert.Equal("::1", GetPrivateField<string>(client, "_optionsHost"));
+        Assert.Equal(9000, GetPrivateField<int?>(client, "_optionsPort"));
+    }
+
+    [Fact]
+    public void ForUri_ParsesHttpIpv6HostPort()
+    {
+        var client = new CopilotClient(new CopilotClientOptions
+        {
+            Connection = RuntimeConnection.ForUri("http://[::1]:7000")
+        });
+
+        Assert.Equal("::1", GetPrivateField<string>(client, "_optionsHost"));
+        Assert.Equal(7000, GetPrivateField<int?>(client, "_optionsPort"));
+    }
+
+    [Fact]
+    public void ForUri_RejectsUrlPath()
+    {
+        Assert.Throws<ArgumentException>(() => new CopilotClient(new CopilotClientOptions
+        {
+            Connection = RuntimeConnection.ForUri("http://localhost:8080/path")
+        }));
+    }
+
+    private static T? GetPrivateField<T>(object instance, string name)
+    {
+        var field = instance.GetType().GetField(name, BindingFlags.Instance | BindingFlags.NonPublic);
+        Assert.NotNull(field);
+        return (T?)field.GetValue(instance);
+    }
+}

go/client.go

@@ -36,6 +36,7 @@ import (
 	"fmt"
 	"log"
 	"net"
+	neturl "net/url"
 	"os"
 	"os/exec"
 	"regexp"
@@ -372,35 +373,47 @@ func setEnvValue(env []string, key string, value string) []string {
 
 // parseCLIURL parses a CLI URL into host and port components.
 //
-// Supports formats: "host:port", "http://host:port", "https://host:port", or just "port".
+// Supports formats: "host:port", "[ipv6]:port", "http://host:port", "https://host:port", or just "port".
 // Panics if the URL format is invalid or the port is out of range.
 func parseCLIURL(url string) (string, int) {
-	// Remove protocol if present
-	cleanURL, _ := strings.CutPrefix(url, "https://")
-	cleanURL, _ = strings.CutPrefix(cleanURL, "http://")
-
-	// Parse host:port or port format
-	var host string
-	var portStr string
-	if before, after, found := strings.Cut(cleanURL, ":"); found {
-		host = before
-		portStr = after
-	} else {
-		// Only port provided
-		portStr = before
+	cleanURL := strings.TrimSpace(url)
+	if cleanURL == "" {
+		panic(fmt.Sprintf("Invalid URIConnection format: %s", url))
+	}
+
+	if _, err := strconv.Atoi(cleanURL); err == nil {
+		port := parseCLIPort(url, cleanURL)
+		return "localhost", port
+	}
+
+	parseURL := cleanURL
+	if !strings.Contains(parseURL, "://") {
+		parseURL = "tcp://" + parseURL
+	}
+
+	parsed, err := neturl.Parse(parseURL)
+	if err != nil {
+		panic(fmt.Sprintf("Invalid URIConnection format: %s", url))
+	}
+	if parsed.Host == "" || parsed.Port() == "" || parsed.RawQuery != "" || parsed.Fragment != "" || (parsed.Path != "" && parsed.Path != "/") {
+		panic(fmt.Sprintf("Invalid URIConnection format: %s", url))
 	}
 
+	port := parseCLIPort(url, parsed.Port())
+	host := parsed.Hostname()
 	if host == "" {
 		host = "localhost"
 	}
 
-	// Validate port
+	return host, port
+}
+
+func parseCLIPort(url string, portStr string) int {
 	port, err := strconv.Atoi(portStr)
 	if err != nil || port <= 0 || port > 65535 {
 		panic(fmt.Sprintf("Invalid port in URIConnection: %s", url))
 	}
-
-	return host, port
+	return port
 }
 
 // Start starts the CLI server (if not using an external server) and establishes

go/client_test.go

@@ -49,6 +49,15 @@ func TestClient_URLParsing(t *testing.T) {
 		}
 	})
 
+	t.Run("should parse bracketed IPv6 host:port URL format", func(t *testing.T) {
+		client := NewClient(&ClientOptions{
+			Connection: URIConnection{URL: "[::1]:9000"},
+		})
+		if client.actualPort != 9000 || client.actualHost != "::1" {
+			t.Errorf("Expected [::1]:9000, got %s:%d", client.actualHost, client.actualPort)
+		}
+	})
+
 	t.Run("should parse http://host:port URL format", func(t *testing.T) {
 		client := NewClient(&ClientOptions{
 			Connection: URIConnection{URL: "http://localhost:7000"},
@@ -58,6 +67,15 @@ func TestClient_URLParsing(t *testing.T) {
 		}
 	})
 
+	t.Run("should parse http://[ipv6]:port URL format", func(t *testing.T) {
+		client := NewClient(&ClientOptions{
+			Connection: URIConnection{URL: "http://[::1]:7000"},
+		})
+		if client.actualPort != 7000 || client.actualHost != "::1" {
+			t.Errorf("Expected [::1]:7000, got %s:%d", client.actualHost, client.actualPort)
+		}
+	})
+
 	t.Run("should parse https://host:port URL format", func(t *testing.T) {
 		client := NewClient(&ClientOptions{
 			Connection: URIConnection{URL: "https://example.com:443"},
@@ -76,6 +94,15 @@ func TestClient_URLParsing(t *testing.T) {
 		NewClient(&ClientOptions{Connection: URIConnection{URL: "invalid-url"}})
 	})
 
+	t.Run("should panic for URL path", func(t *testing.T) {
+		defer func() {
+			if r := recover(); r == nil {
+				t.Error("Expected panic for invalid URL path")
+			}
+		}()
+		NewClient(&ClientOptions{Connection: URIConnection{URL: "http://localhost:8080/path"}})
+	})
+
 	t.Run("should panic for invalid port - too high", func(t *testing.T) {
 		defer func() {
 			if r := recover(); r == nil {

nodejs/src/client.ts

@@ -765,27 +765,46 @@ export class CopilotClient {
 
     /**
      * Parse CLI URL into host and port
-     * Supports formats: "host:port", "http://host:port", "https://host:port", or just "port"
+     * Supports formats: "host:port", "[ipv6]:port", "http://host:port", "https://host:port", or just "port"
      */
     private parseCliUrl(url: string): { host: string; port: number } {
-        // Remove protocol if present
-        let cleanUrl = url.replace(/^https?:\/\//, "");
+        const trimmedUrl = url.trim();
 
         // Check if it's just a port number
-        if (/^\d+$/.test(cleanUrl)) {
-            return { host: "localhost", port: parseInt(cleanUrl, 10) };
+        if (/^\d+$/.test(trimmedUrl)) {
+            return { host: "localhost", port: parseInt(trimmedUrl, 10) };
         }
 
-        // Parse host:port format
-        const parts = cleanUrl.split(":");
-        if (parts.length !== 2) {
+        let parsed: URL;
+        try {
+            parsed = new URL(
+                /^[a-z][a-z0-9+.-]*:\/\//i.test(trimmedUrl) ? trimmedUrl : `tcp://${trimmedUrl}`
+            );
+        } catch {
+            if (trimmedUrl.includes(":")) {
+                throw new Error(`Invalid port in cliUrl: ${url}`);
+            }
+            throw new Error(
+                `Invalid cliUrl format: ${url}. Expected "host:port", "[ipv6]:port", "http://host:port", or "port"`
+            );
+        }
+
+        const explicitPort = trimmedUrl.match(/:(\d+)(?:[/?#]|$)/)?.[1];
+        const portString = parsed.port || explicitPort;
+
+        if (
+            !portString ||
+            (parsed.pathname !== "" && parsed.pathname !== "/") ||
+            parsed.search !== "" ||
+            parsed.hash !== ""
+        ) {
             throw new Error(
-                `Invalid cliUrl format: ${url}. Expected "host:port", "http://host:port", or "port"`
+                `Invalid cliUrl format: ${url}. Expected "host:port", "[ipv6]:port", "http://host:port", or "port"`
             );
         }
 
-        const host = parts[0] || "localhost";
-        const port = parseInt(parts[1], 10);
+        const host = parsed.hostname.replace(/^\[(.*)\]$/, "$1") || "localhost";
+        const port = parseInt(portString, 10);
 
         if (isNaN(port) || port <= 0 || port > 65535) {
             throw new Error(`Invalid port in cliUrl: ${url}`);

nodejs/test/client.test.ts

@@ -1966,6 +1966,17 @@ describe("CopilotClient", () => {
             expect((client as any).isExternalServer).toBe(true);
         });
 
+        it("should parse bracketed IPv6 host:port URL format", () => {
+            const client = new CopilotClient({
+                connection: RuntimeConnection.forUri("[::1]:9000"),
+                logLevel: "error",
+            });
+
+            expect((client as any).runtimePort).toBe(9000);
+            expect((client as any).actualHost).toBe("::1");
+            expect((client as any).isExternalServer).toBe(true);
+        });
+
         it("should parse http://host:port URL format", () => {
             const client = new CopilotClient({
                 connection: RuntimeConnection.forUri("http://localhost:7000"),
@@ -1977,6 +1988,17 @@ describe("CopilotClient", () => {
             expect((client as any).isExternalServer).toBe(true);
         });
 
+        it("should parse http://[ipv6]:port URL format", () => {
+            const client = new CopilotClient({
+                connection: RuntimeConnection.forUri("http://[::1]:7000"),
+                logLevel: "error",
+            });
+
+            expect((client as any).runtimePort).toBe(7000);
+            expect((client as any).actualHost).toBe("::1");
+            expect((client as any).isExternalServer).toBe(true);
+        });
+
         it("should parse https://host:port URL format", () => {
             const client = new CopilotClient({
                 connection: RuntimeConnection.forUri("https://example.com:443"),
@@ -1997,6 +2019,15 @@ describe("CopilotClient", () => {
             }).toThrow(/Invalid cliUrl format/);
         });
 
+        it("should throw error for URL path", () => {
+            expect(() => {
+                new CopilotClient({
+                    connection: RuntimeConnection.forUri("http://localhost:8080/path"),
+                    logLevel: "error",
+                });
+            }).toThrow(/Invalid cliUrl format/);
+        });
+
         it("should throw error for invalid port - too high", () => {
             expect(() => {
                 new CopilotClient({

python/copilot/client.py

@@ -30,6 +30,7 @@
 from datetime import UTC, datetime
 from types import TracebackType
 from typing import Any, ClassVar, Literal, TypedDict, cast, overload
+from urllib.parse import urlsplit
 
 from ._diagnostics import log_timing
 from ._ffi_runtime_host import FfiRuntimeHost
@@ -1629,8 +1630,8 @@ def _parse_cli_url(self, url: str) -> tuple[str, int]:
         """
         Parse CLI URL into host and port.
 
-        Supports formats: "host:port", "http://host:port", "https://host:port",
-        or just "port".
+        Supports formats: "host:port", "[ipv6]:port", "http://host:port",
+        "https://host:port", or just "port".
 
         Args:
             url: The CLI URL to parse.
@@ -1641,10 +1642,7 @@ def _parse_cli_url(self, url: str) -> tuple[str, int]:
         Raises:
             ValueError: If the URL format is invalid or the port is out of range.
         """
-        import re
-
-        # Remove protocol if present
-        clean_url = re.sub(r"^https?://", "", url)
+        clean_url = url.strip()
 
         # Check if it's just a port number
         if clean_url.isdigit():
@@ -1653,21 +1651,22 @@ def _parse_cli_url(self, url: str) -> tuple[str, int]:
                 raise ValueError(f"Invalid port in cli_url: {url}")
             return ("localhost", port)
 
-        # Parse host:port format
-        parts = clean_url.split(":")
-        if len(parts) != 2:
+        parsed = urlsplit(clean_url if "://" in clean_url else f"tcp://{clean_url}")
+        if parsed.path not in ("", "/") or parsed.query or parsed.fragment:
             raise ValueError(f"Invalid cli_url format: {url}")
 
-        host = parts[0] if parts[0] else "localhost"
         try:
-            port = int(parts[1])
+            port = parsed.port
         except ValueError as e:
             raise ValueError(f"Invalid port in cli_url: {url}") from e
 
+        if port is None:
+            raise ValueError(f"Invalid cli_url format: {url}")
+
         if port <= 0 or port > 65535:
             raise ValueError(f"Invalid port in cli_url: {url}")
 
-        return (host, port)
+        return (parsed.hostname or "localhost", port)
 
     async def __aenter__(self) -> CopilotClient:
         """