diff --git a/features/package-install.feature b/features/package-install.feature
index bfa9338d..ff76ccbe 100644
--- a/features/package-install.feature
+++ b/features/package-install.feature
@@ -243,7 +243,7 @@ Feature: Install WP-CLI packages
       """
     And the {PACKAGE_PATH}composer.json file should not contain:
       """
-      "wp-cli/google-sitemap-generator-cli": "dev-master"
+      "wp-cli/google-sitemap-generator-cli":
       """
     And the {PACKAGE_PATH}composer.json file should not contain:
       """
@@ -474,8 +474,9 @@ Feature: Install WP-CLI packages
   Scenario: Install a package from Git using a shortened package identifier
     Given an empty directory
 
-    When I run `wp package install wp-cli-test/github-test-command`
-    Then STDOUT should contain:
+    When I try `wp package install wp-cli-test/github-test-command`
+    Then the return code should be 0
+    And STDOUT should contain:
       """
       Installing package wp-cli-test/github-test-command (dev-master)
       """
@@ -792,7 +793,7 @@ Feature: Install WP-CLI packages
       """
       Warning: Package name mismatch...Updating from git name 'GeekPress/wp-rocket-cli' to composer.json name 'wp-media/wp-rocket-cli'.
       """
-    And STDOUT should match /Installing package wp-media\/wp-rocket-cli \(dev-/
+    And STDOUT should match /Installing package wp-media\/wp-rocket-cli \([^)]+\)/
     # This path is sometimes changed on Macs to prefix with /private
     And STDOUT should contain:
       """
@@ -957,7 +958,7 @@ Feature: Install WP-CLI packages
 
   Scenario: Install a package from a local zip
     Given an empty directory
-    And I run `wget -q -O google-sitemap-generator-cli.zip https://github.com/wp-cli/google-sitemap-generator-cli/archive/master.zip`
+    And I run `curl -fSsL -o google-sitemap-generator-cli.zip https://github.com/wp-cli/google-sitemap-generator-cli/archive/main.zip`
 
     When I run `wp package install google-sitemap-generator-cli.zip`
     Then STDOUT should contain:
@@ -1093,7 +1094,7 @@ Feature: Install WP-CLI packages
       Error: Couldn't download package from 'https://github.com/wp-cli/google-sitemap-generator.zip' (HTTP code 404).
       """
 
-    When I run `wp package install https://github.com/wp-cli/google-sitemap-generator-cli/archive/master.zip`
+    When I run `wp package install https://github.com/wp-cli/google-sitemap-generator-cli/archive/main.zip`
     Then STDOUT should contain:
       """
       Installing package wp-cli/google-sitemap-generator-cli (dev-
@@ -1201,9 +1202,9 @@ Feature: Install WP-CLI packages
       """
       {PACKAGE_PATH}composer.json to require the package...
       """
+    And STDOUT should match /Registering .*?path-command as a path repository\.\.\./
     And STDOUT should contain:
       """
-      Registering {CURRENT_PATH}/path-command as a path repository...
       Using Composer to install the package...
       """
     And STDOUT should contain:
@@ -1290,9 +1291,9 @@ Feature: Install WP-CLI packages
       """
       {PACKAGE_PATH}composer.json to require the package...
       """
+    And STDOUT should match /Registering .*?path-command as a path repository\.\.\./
     And STDOUT should contain:
       """
-      Registering {CURRENT_PATH}/path-command as a path repository...
       Using Composer to install the package...
       """
     And STDOUT should contain:
@@ -1374,11 +1375,11 @@ Feature: Install WP-CLI packages
       """
     And STDOUT should be empty
 
-    When I try `wp package install https://example.com/non-existent-zip-asdfasdf.zip`
+    When I try `wp package install http://example.com/non-existent-zip-asdfasdf.zip`
     Then the return code should be 1
     And STDERR should contain:
       """
-      Error: Couldn't download package from 'https://example.com/non-existent-zip-asdfasdf.zip'
+      Error: Couldn't download package from 'http://example.com/non-existent-zip-asdfasdf.zip'
       """
     And STDOUT should be empty
 
diff --git a/features/package-update.feature b/features/package-update.feature
index 6d36ea89..3aa12ef3 100644
--- a/features/package-update.feature
+++ b/features/package-update.feature
@@ -62,7 +62,7 @@ Feature: Update WP-CLI packages
       | name                           | update    |
       | wp-cli-test/updateable-package | available |
 
-    When I run `sed -i.bak s/v1.0.0/\>=1.0.0/g {PACKAGE_PATH}/composer.json`
+    When I run `wp eval "file_put_contents( '{PACKAGE_PATH}composer.json', str_replace( 'v1.0.0', '>=1.0.0', file_get_contents( '{PACKAGE_PATH}composer.json' ) ) );" --skip-wordpress`
     Then the return code should be 0
 
     When I run `cat {PACKAGE_PATH}/composer.json`
@@ -114,7 +114,7 @@ Feature: Update WP-CLI packages
       Success: Package installed.
       """
 
-    When I run `sed -i.bak s/v1.0.0/\>=1.0.0/g {PACKAGE_PATH}/composer.json`
+    When I run `wp eval "file_put_contents( '{PACKAGE_PATH}composer.json', str_replace( 'v1.0.0', '>=1.0.0', file_get_contents( '{PACKAGE_PATH}composer.json' ) ) );" --skip-wordpress`
     Then the return code should be 0
 
     When I run `wp package update wp-cli-test/updateable-package`
@@ -147,7 +147,7 @@ Feature: Update WP-CLI packages
       Success: Package installed.
       """
 
-    When I run `sed -i.bak s/v1.0.0/\>=1.0.0/g {PACKAGE_PATH}/composer.json`
+    When I run `wp eval "file_put_contents( '{PACKAGE_PATH}composer.json', str_replace( 'v1.0.0', '>=1.0.0', file_get_contents( '{PACKAGE_PATH}composer.json' ) ) );" --skip-wordpress`
     Then the return code should be 0
 
     When I run `wp package update wp-cli-test/updateable-package danielbachhuber/wp-cli-reset-post-date-command`
diff --git a/src/Package_Command.php b/src/Package_Command.php
index 1b24df3d..3b1ed22c 100644
--- a/src/Package_Command.php
+++ b/src/Package_Command.php
@@ -358,7 +358,7 @@ public function install( $args, $assoc_args ) {
 		$this->register_revert_shutdown_function( $json_path, $composer_backup, $revert );
 
 		// Add the 'require' to composer.json
-		WP_CLI::log( sprintf( 'Updating %s to require the package...', $json_path ) );
+		WP_CLI::log( sprintf( 'Updating %s to require the package...', Path::normalize( $json_path ) ) );
 		$json_manipulator = new JsonManipulator( $composer_backup );
 		$json_manipulator->addMainKey( 'name', 'wp-cli/wp-cli' );
 		$json_manipulator->addMainKey( 'version', self::get_wp_cli_version_composer() );
@@ -526,12 +526,12 @@ public function list_( $args, $assoc_args ) {
 	public function path( $args ) {
 		$packages_dir = WP_CLI::get_runner()->get_packages_dir_path();
 		if ( ! empty( $args ) ) {
-			$packages_dir .= 'vendor/' . $args[0];
+			$packages_dir .= 'vendor' . DIRECTORY_SEPARATOR . $args[0];
 			if ( ! is_dir( $packages_dir ) ) {
 				WP_CLI::error( 'Invalid package name.' );
 			}
 		}
-		WP_CLI::line( $packages_dir );
+		WP_CLI::line( Path::normalize( $packages_dir ) );
 	}
 
 	/**
@@ -835,12 +835,12 @@ public function uninstall( $args, $assoc_args ) {
 		$this->register_revert_shutdown_function( $json_path, $composer_backup, $revert );
 
 		// Remove the 'require' from composer.json.
-		WP_CLI::log( sprintf( 'Removing require statement for package \'%s\' from %s', $package_name, $json_path ) );
+		WP_CLI::log( sprintf( 'Removing require statement for package \'%s\' from %s', $package_name, Path::normalize( $json_path ) ) );
 		$manipulator = new JsonManipulator( $composer_backup );
 		$manipulator->removeSubNode( 'require', $package_name, true /*caseInsensitive*/ );
 
 		// Remove the 'repository' details from composer.json.
-		WP_CLI::log( sprintf( 'Removing repository details from %s', $json_path ) );
+		WP_CLI::log( sprintf( 'Removing repository details from %s', Path::normalize( $json_path ) ) );
 		$manipulator->removeSubNode( 'repositories', $package_name, true /*caseInsensitive*/ );
 
 		file_put_contents( $json_path, $manipulator->getContents() );
@@ -1158,7 +1158,7 @@ private function get_installed_package_by_name( $package_name ) {
 	 * @return array Two-element array containing package name and version.
 	 */
 	private static function get_package_name_and_version_from_dir_package( $dir_package ) {
-		$composer_file = $dir_package . '/composer.json';
+		$composer_file = Path::normalize( $dir_package . '/composer.json' );
 		if ( ! file_exists( $composer_file ) ) {
 			WP_CLI::error( sprintf( "Invalid package: composer.json file '%s' not found.", $composer_file ) );
 		}
@@ -1192,21 +1192,12 @@ private function get_composer_json_path() {
 
 		if ( null === $composer_path || getenv( 'WP_CLI_TEST_PACKAGE_GET_COMPOSER_JSON_PATH' ) ) {
 
-			if ( getenv( 'WP_CLI_PACKAGES_DIR' ) ) {
-				$composer_path = Path::trailingslashit( getenv( 'WP_CLI_PACKAGES_DIR' ) ) . 'composer.json';
-			} else {
-				$composer_path = Path::trailingslashit( Path::get_home_dir() ) . '.wp-cli/packages/composer.json';
-			}
+			$packages_dir  = WP_CLI::get_runner()->get_packages_dir_path();
+			$composer_path = rtrim( $packages_dir, '/\\' ) . DIRECTORY_SEPARATOR . 'composer.json';
 
 			// `composer.json` and its directory might need to be created
 			if ( ! file_exists( $composer_path ) ) {
 				$composer_path = $this->create_default_composer_json( $composer_path );
-			} else {
-				$composer_path = realpath( $composer_path );
-				if ( false === $composer_path ) {
-					$error = error_get_last();
-					WP_CLI::error( sprintf( "Composer path '%s' for packages/composer.json not found: %s", $composer_path, $error['message'] ) );
-				}
 			}
 		}
 
@@ -1238,11 +1229,7 @@ private function create_default_composer_json( $composer_path ) {
 			}
 		}
 
-		$composer_dir = realpath( $composer_dir );
-		if ( false === $composer_dir ) {
-			$error = error_get_last();
-			WP_CLI::error( sprintf( "Composer directory '%s' for packages not found: %s", $composer_dir, $error['message'] ) );
-		}
+		// No realpath() here to preserve short names on Windows if applicable.
 
 		$composer_path = Path::trailingslashit( $composer_dir ) . Path::basename( $composer_path );
 
@@ -1346,6 +1333,10 @@ private function maybe_add_git_suffix( $package_name ) {
 		if ( preg_match( '#\.git(?::[^:]+)?$#i', $package_name ) ) {
 			return $package_name;
 		}
+		// Skip if it looks like a zip file.
+		if ( preg_match( '#\.zip$#i', $package_name ) ) {
+			return $package_name;
+		}
 		// Append .git for GitHub/GitLab HTTPS or SSH URLs, preserving any :version suffix.
 		// Pattern: (https?://github.com/<user>/<repo>[...subgroups...] or git@github.com:<user>/<repo>[...subgroups...])(:version)?
 		if ( preg_match( '#^((?:https?://(?:github|gitlab)\.com/|git@(?:github|gitlab)\.com:)[^/:]+(?:/[^/:]+)*)(:.*)?$#i', $package_name, $matches ) ) {
diff --git a/tests/phpunit/ComposerJsonTest.php b/tests/phpunit/ComposerJsonTest.php
index c1cdf9b6..21af48fb 100644
--- a/tests/phpunit/ComposerJsonTest.php
+++ b/tests/phpunit/ComposerJsonTest.php
@@ -37,7 +37,12 @@ public function set_up() {
 		}
 		$class_wp_cli_capture_exit->setValue( null, true );
 
-		$this->temp_dir = Utils\get_temp_dir() . uniqid( 'wp-cli-test-package-composer-json-', true ) . '/';
+		$temp_dir = Utils\get_temp_dir();
+		if ( Utils\is_windows() ) {
+			$temp_dir = realpath( $temp_dir ) ?: $temp_dir;
+			$temp_dir = str_replace( '\\', '/', $temp_dir );
+		}
+		$this->temp_dir = rtrim( $temp_dir, '/' ) . '/' . uniqid( 'wp-cli-test-package-composer-json-', true ) . '/';
 		mkdir( $this->temp_dir );
 	}
 
@@ -80,7 +85,7 @@ public function test_create_default_composer_json() {
 		// Succeed.
 		$expected = $this->temp_dir . 'packages/composer.json';
 		$actual   = $create_default_composer_json->invoke( $package, $expected );
-		$this->assertSame( $expected, $this->mac_safe_path( $actual ) );
+		$this->assertSame( $this->mac_safe_path( realpath( $expected ) ?: $expected ), $this->mac_safe_path( realpath( $actual ) ?: $actual ) );
 		$this->assertTrue( false !== strpos( file_get_contents( $actual ), 'wp-cli/wp-cli' ) );
 		unlink( $actual );
 		rmdir( dirname( $actual ) );
@@ -105,7 +110,7 @@ public function test_get_composer_json_path() {
 		putenv( 'WP_CLI_PACKAGES_DIR' );
 		$expected = $this->temp_dir . '.wp-cli/packages/composer.json';
 		$actual   = $get_composer_json_path->invoke( $package );
-		$this->assertSame( $expected, $this->mac_safe_path( $actual ) );
+		$this->assertSame( $this->mac_safe_path( realpath( $expected ) ?: $expected ), $this->mac_safe_path( realpath( $actual ) ?: $actual ) );
 		$this->assertTrue( false !== strpos( file_get_contents( $actual ), 'wp-cli/wp-cli' ) );
 		unlink( $actual );
 		rmdir( dirname( $actual ) );
@@ -115,7 +120,7 @@ public function test_get_composer_json_path() {
 		putenv( 'WP_CLI_PACKAGES_DIR=' . $this->temp_dir . 'packages' );
 		$expected = $this->temp_dir . 'packages/composer.json';
 		$actual   = $get_composer_json_path->invoke( $package );
-		$this->assertSame( $expected, $this->mac_safe_path( $actual ) );
+		$this->assertSame( $this->mac_safe_path( realpath( $expected ) ?: $expected ), $this->mac_safe_path( realpath( $actual ) ?: $actual ) );
 		$this->assertTrue( false !== strpos( file_get_contents( $actual ), 'wp-cli/wp-cli' ) );
 		unlink( $actual );
 		rmdir( dirname( $actual ) );
@@ -126,7 +131,7 @@ public function test_get_composer_json_path() {
 		mkdir( $this->temp_dir . 'packages' );
 		touch( $expected );
 		$actual = $get_composer_json_path->invoke( $package );
-		$this->assertSame( $expected, $this->mac_safe_path( $actual ) );
+		$this->assertSame( $this->mac_safe_path( realpath( $expected ) ?: $expected ), $this->mac_safe_path( realpath( $actual ) ?: $actual ) );
 		$this->assertSame( 0, filesize( $actual ) );
 		unlink( $actual );
 		rmdir( dirname( $actual ) );
@@ -170,7 +175,7 @@ public function test_get_composer_json_path_backup_decoded() {
 		// Succeed with newly created.
 		$expected                           = $this->temp_dir . 'packages/composer.json';
 		list( $actual, $content, $decoded ) = $get_composer_json_path_backup_decoded->invoke( $package );
-		$this->assertSame( $expected, $this->mac_safe_path( $actual ) );
+		$this->assertSame( $this->mac_safe_path( realpath( $expected ) ?: $expected ), $this->mac_safe_path( realpath( $actual ) ?: $actual ) );
 		$this->assertTrue( false !== strpos( file_get_contents( $actual ), 'wp-cli/wp-cli' ) );
 		$this->assertSame( file_get_contents( $actual ), $content );
 		$this->assertFalse( empty( $decoded ) );
@@ -182,7 +187,7 @@ public function test_get_composer_json_path_backup_decoded() {
 		mkdir( $this->temp_dir . 'packages' );
 		file_put_contents( $expected, '{}' );
 		list( $actual, $content, $decoded ) = $get_composer_json_path_backup_decoded->invoke( $package );
-		$this->assertSame( $expected, $this->mac_safe_path( $actual ) );
+		$this->assertSame( $this->mac_safe_path( realpath( $expected ) ?: $expected ), $this->mac_safe_path( realpath( $actual ) ?: $actual ) );
 		$this->assertSame( '{}', $content );
 		$this->assertTrue( empty( $decoded ) );
 		unlink( $expected );
@@ -193,6 +198,8 @@ public function test_get_composer_json_path_backup_decoded() {
 	}
 
 	private function mac_safe_path( $path ) {
-		return preg_replace( '#^/private/(var|tmp)/#i', '/$1/', $path );
+		$path = \WP_CLI\Path::normalize( $path );
+		$path = preg_replace( '#^/private/(var|tmp)/#i', '/$1/', $path );
+		return $path;
 	}
 }
diff --git a/tests/phpunit/JsonManipulatorTest.php b/tests/phpunit/JsonManipulatorTest.php
index 156ab7f9..579e6867 100644
--- a/tests/phpunit/JsonManipulatorTest.php
+++ b/tests/phpunit/JsonManipulatorTest.php
@@ -25,7 +25,7 @@ public function testAddLink($json, $type, $package, $constraint, $expected)
     {
         $manipulator = new JsonManipulator($json);
         $this->assertTrue($manipulator->addLink($type, $package, $constraint));
-        $this->assertEquals($expected, $manipulator->getContents());
+        $this->assertJsonEquals($expected, $manipulator->getContents());
     }
 
     public static function linkProvider()
@@ -1297,7 +1297,7 @@ public function testAddLinkAndSortPackages($json, $type, $package, $constraint,
     {
         $manipulator = new JsonManipulator($json);
         $this->assertTrue($manipulator->addLink($type, $package, $constraint, $sortPackages));
-        $this->assertEquals($expected, $manipulator->getContents());
+        $this->assertJsonEquals($expected, $manipulator->getContents());
     }
 
     public static function providerAddLinkAndSortPackages()
@@ -1380,7 +1380,7 @@ public function testRemoveSubNode($json, $name, $expected, $expectedContent = nu
 
         $this->assertEquals($expected, $manipulator->removeSubNode('repositories', $name));
         if (null !== $expectedContent) {
-            $this->assertEquals($expectedContent, $manipulator->getContents());
+            $this->assertJsonEquals($expectedContent, $manipulator->getContents());
         }
     }
 
@@ -2167,10 +2167,11 @@ public function testAddMainKeyWithContentHavingDollarSignFollowedByDigit2()
         $manipulator = new JsonManipulator('{}');
 
         $this->assertTrue($manipulator->addMainKey('foo', '$1bar'));
-        $this->assertEquals('{
+        $expected = '{
     "foo": "$1bar"
 }
-', $manipulator->getContents());
+';
+        $this->assertEquals( preg_replace( '/\R/', "\n", $expected ), preg_replace( '/\R/', "\n", $manipulator->getContents() ) );
     }
 
     public function testUpdateMainKey()
@@ -2301,9 +2302,10 @@ public function testRemoveMainKey()
 
         $this->assertTrue($manipulator->removeMainKey('require'));
         $this->assertTrue($manipulator->removeMainKey('require-dev'));
-        $this->assertEquals('{
+        $expected = '{
 }
-', $manipulator->getContents());
+';
+        $this->assertEquals( preg_replace( '/\R/', "\n", $expected ), preg_replace( '/\R/', "\n", $manipulator->getContents() ) );
     }
 
     public function testIndentDetection()
@@ -2576,4 +2578,7 @@ public static function providerRemoveSubNodeCaseInsensitive()
 	}
 	// WP_CLI: end caseInsensitive.
 
+	private function assertJsonEquals( $expected, $actual ) {
+		$this->assertEquals( preg_replace( '/\R/', "\n", $expected ), preg_replace( '/\R/', "\n", $actual ) );
+	}
 }