feat(plugin): widen the RPC surface to LibraryInstaller-based plugins

An installer that extends LibraryInstaller reaches for the Composer object
graph in ways the proxy did not answer: the download manager and the config,
the writable repository methods, a React promise as its own return value, and
`new Package(...)` from its supports() path.

* `Composer::getConfig`/`getDownloadManager` are dispatched, and both classes
  become generated proxy stubs. Their reads and mutators answer from the Rust
  entity; the surfaces needing stubs of their own (ConfigSourceInterface,
  DownloaderInterface) stay explicit errors.
* The download manager's futures are driven to completion and handed back as
  already-settled React promises, since PHP declares a non-nullable
  PromiseInterface there. A promise a plugin returns is drained the same way:
  settled yields its value, rejected re-raises, pending is an explicit error.
* Proxy stubs now carry the real class's constructor and ask the Rust side to
  allocate the entity; reviving a stub for an existing entity binds the handle
  without running it. Classes Rust cannot build name themselves in the error.
* The package proxy covers `Package`'s own setters, `CompletePackage`'s
  metadata, `RootPackage`'s root-only state, and `BasePackage::$id`.

Link values and release dates still have no wire image, so the methods
carrying them remain explicit errors.

17 files changed, 539 insertions, 83 deletions

diff --git a/crates/shirabe-php-rpc/php/runtime/Composer/EventDispatcher/Event.php b/crates/shirabe-php-rpc/php/runtime/Composer/EventDispatcher/Event.php
index 0d35ac55..e2c63439 100644
--- a/crates/shirabe-php-rpc/php/runtime/Composer/EventDispatcher/Event.php
+++ b/crates/shirabe-php-rpc/php/runtime/Composer/EventDispatcher/Event.php
@@ -4,9 +4,10 @@
 // lives in both worlds at once: an instance revived from a Rust handle proxies every call over
 // RPC (like a generated stub), while an instance constructed natively — real Composer code in
 // this process does `new PreCommandRunEvent(...)`, whose parent constructor lands here — is a
-// faithful in-process port of the real base class. The two modes are told apart by the
-// constructor arguments; `__shirabeRustHandleDescriptor()` returns null in native mode so the
-// wire codec registers the object in the P table instead of treating it as a Rust handle.
+// faithful in-process port of the real base class. Proxy revival binds the handle without
+// running the constructor, so the constructor below is the native mode alone;
+// `__shirabeRustHandleDescriptor()` returns null there so the wire codec registers the object in
+// the P table instead of treating it as a Rust handle.
 
 namespace Composer\EventDispatcher;
 
@@ -29,29 +30,20 @@ class Event implements \ShirabeRustStub
     /** @var bool Whether the event should not be passed to more listeners (native mode) */
     private $propagationStopped = false;
 
-    /**
-     * Proxy revival passes (int $rhandle, int $epoch); the real class's constructor is
-     * (string $name, array $args = [], array $flags = []).
-     */
-    public function __construct($name = null, $args = [], $flags = [])
+    public function __construct(string $name, array $args = [], array $flags = [])
     {
-        if (is_int($name) && func_num_args() === 2 && is_int($args)) {
-            $this->__rhandle = $name;
-            $this->__epoch = $args;
-
-            return;
-        }
-        if (!is_string($name)) {
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process without an event name'
-            );
-        }
         $this->__rhandle = null;
         $this->name = $name;
         $this->args = $args;
         $this->flags = $flags;
     }
 
+    public function __shirabeBind(int $rhandle, int $epoch): void
+    {
+        $this->__rhandle = $rhandle;
+        $this->__epoch = $epoch;
+    }
+
     public function __destruct()
     {
         if ($this->__rhandle !== null) {
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Config.php b/crates/shirabe-php-rpc/php/stubs/Composer/Config.php
new file mode 100644
index 00000000..bccb8dcb
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Config.php
@@ -0,0 +1,212 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Proxy stub for Composer\Config: the public surface forwards to the Rust-side entity over RPC.
+
+namespace Composer;
+
+use Composer\Advisory\Auditor;
+use Composer\Config\ConfigSourceInterface;
+use Composer\IO\IOInterface;
+use Composer\Util\ProcessExecutor;
+
+class Config implements \ShirabeRustStub
+{
+    /** @var int */
+    protected $__rhandle;
+    /** @var int */
+    protected $__epoch;
+
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
+    {
+        $this->__rhandle = $rhandle;
+        $this->__epoch = $epoch;
+    }
+
+    public function __destruct()
+    {
+        \ShirabeRustObjectRegistry::release($this->__rhandle);
+    }
+
+    public function __shirabeRustHandleDescriptor(): array
+    {
+        return [
+            '__rhandle' => $this->__rhandle,
+            '__class' => static::class,
+            '__epoch' => $this->__epoch,
+        ];
+    }
+
+    public function __clone()
+    {
+        // PHP has already shallow-copied this stub, so both copies would point at one
+        // entity and release it twice. The Rust side clones the entity instead, applying
+        // whatever __clone semantics the real class defines, and this copy rebinds to the
+        // fresh handle. Entities without clone semantics answer with an explicit error.
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust($this->__rhandle, '__shirabeClone', []);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
+    public function __construct(bool $useEnvironment = true, ?string $baseDir = null)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$useEnvironment, $baseDir]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
+    public const SOURCE_DEFAULT = 'default';
+    public const SOURCE_COMMAND = 'command';
+    public const SOURCE_UNKNOWN = 'unknown';
+    public const RELATIVE_PATHS = 1;
+
+    public static $defaultConfig = [
+        'process-timeout' => 300,
+        'use-include-path' => false,
+        'allow-plugins' => [],
+        'use-parent-dir' => 'prompt',
+        'preferred-install' => 'dist',
+        'audit' => ['ignore' => [], 'abandoned' => Auditor::ABANDONED_FAIL],
+        'notify-on-install' => true,
+        'github-protocols' => ['https', 'ssh', 'git'],
+        'gitlab-protocol' => null,
+        'vendor-dir' => 'vendor',
+        'bin-dir' => '{$vendor-dir}/bin',
+        'cache-dir' => '{$home}/cache',
+        'data-dir' => '{$home}',
+        'cache-files-dir' => '{$cache-dir}/files',
+        'cache-repo-dir' => '{$cache-dir}/repo',
+        'cache-vcs-dir' => '{$cache-dir}/vcs',
+        'cache-ttl' => 15552000, // 6 months
+        'cache-files-ttl' => null, // fallback to cache-ttl
+        'cache-files-maxsize' => '300MiB',
+        'cache-read-only' => false,
+        'bin-compat' => 'auto',
+        'discard-changes' => false,
+        'autoloader-suffix' => null,
+        'sort-packages' => false,
+        'optimize-autoloader' => false,
+        'classmap-authoritative' => false,
+        'apcu-autoloader' => false,
+        'prepend-autoloader' => true,
+        'update-with-minimal-changes' => false,
+        'github-domains' => ['github.com'],
+        'bitbucket-expose-hostname' => true,
+        'disable-tls' => false,
+        'secure-http' => true,
+        'secure-svn-domains' => [],
+        'cafile' => null,
+        'capath' => null,
+        'github-expose-hostname' => true,
+        'gitlab-domains' => ['gitlab.com'],
+        'store-auths' => 'prompt',
+        'platform' => [],
+        'archive-format' => 'tar',
+        'archive-dir' => '.',
+        'htaccess-protect' => true,
+        'use-github-api' => true,
+        'lock' => true,
+        'platform-check' => 'php-only',
+        'bitbucket-oauth' => [],
+        'github-oauth' => [],
+        'gitlab-oauth' => [],
+        'gitlab-token' => [],
+        'http-basic' => [],
+        'bearer' => [],
+        'custom-headers' => [],
+        'bump-after-update' => false,
+        'allow-missing-requirements' => false,
+        'client-certificate' => [],
+        'forgejo-domains' => ['codeberg.org'],
+        'forgejo-token' => [],
+    ];
+    public static $defaultRepositories = [
+        'packagist.org' => [
+            'type' => 'composer',
+            'url' => 'https://repo.packagist.org',
+        ],
+    ];
+
+    public static function disableProcessTimeout(): void
+    {
+        // Override global timeout set earlier by environment or config
+        ProcessExecutor::setTimeout(0);
+    }
+
+    public function setBaseDir(?string $baseDir): void
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setBaseDir', [$baseDir]);
+    }
+
+    public function setConfigSource(ConfigSourceInterface $source): void
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setConfigSource', [$source]);
+    }
+
+    public function getConfigSource(): ConfigSourceInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getConfigSource', []);
+    }
+
+    public function setAuthConfigSource(ConfigSourceInterface $source): void
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setAuthConfigSource', [$source]);
+    }
+
+    public function getAuthConfigSource(): ConfigSourceInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getAuthConfigSource', []);
+    }
+
+    public function setLocalAuthConfigSource(ConfigSourceInterface $source): void
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setLocalAuthConfigSource', [$source]);
+    }
+
+    public function getLocalAuthConfigSource(): ?ConfigSourceInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getLocalAuthConfigSource', []);
+    }
+
+    public function merge(array $config, string $source = self::SOURCE_UNKNOWN): void
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'merge', [$config, $source]);
+    }
+
+    public function getRepositories(): array
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getRepositories', []);
+    }
+
+    public function get(string $key, int $flags = 0)
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'get', [$key, $flags]);
+    }
+
+    public function all(int $flags = 0): array
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'all', [$flags]);
+    }
+
+    public function getSourceOfValue(string $key): string
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getSourceOfValue', [$key]);
+    }
+
+    public function raw(): array
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'raw', []);
+    }
+
+    public function has(string $key): bool
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'has', [$key]);
+    }
+
+    public function prohibitUrlByConfig(string $url, ?IOInterface $io = null, array $repoOptions = []): void
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'prohibitUrlByConfig', [$url, $io, $repoOptions]);
+    }
+}
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Downloader/DownloadManager.php b/crates/shirabe-php-rpc/php/stubs/Composer/Downloader/DownloadManager.php
new file mode 100644
index 00000000..3828ac4a
--- /dev/null
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Downloader/DownloadManager.php
@@ -0,0 +1,128 @@
+<?php
+
+// Generated by scripts/plugin-stub-generator; do not edit by hand.
+// Proxy stub for Composer\Downloader\DownloadManager: the public surface forwards to the Rust-side entity over RPC.
+
+namespace Composer\Downloader;
+
+use Composer\Package\PackageInterface;
+use Composer\IO\IOInterface;
+use Composer\Util\Filesystem;
+use React\Promise\PromiseInterface;
+
+class DownloadManager implements \ShirabeRustStub
+{
+    /** @var int */
+    protected $__rhandle;
+    /** @var int */
+    protected $__epoch;
+
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
+    {
+        $this->__rhandle = $rhandle;
+        $this->__epoch = $epoch;
+    }
+
+    public function __destruct()
+    {
+        \ShirabeRustObjectRegistry::release($this->__rhandle);
+    }
+
+    public function __shirabeRustHandleDescriptor(): array
+    {
+        return [
+            '__rhandle' => $this->__rhandle,
+            '__class' => static::class,
+            '__epoch' => $this->__epoch,
+        ];
+    }
+
+    public function __clone()
+    {
+        // PHP has already shallow-copied this stub, so both copies would point at one
+        // entity and release it twice. The Rust side clones the entity instead, applying
+        // whatever __clone semantics the real class defines, and this copy rebinds to the
+        // fresh handle. Entities without clone semantics answer with an explicit error.
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust($this->__rhandle, '__shirabeClone', []);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
+    public function __construct(IOInterface $io, bool $preferSource = false, ?Filesystem $filesystem = null)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$io, $preferSource, $filesystem]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
+    public function setPreferSource(bool $preferSource): self
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setPreferSource', [$preferSource]);
+        return $this;
+    }
+
+    public function setPreferDist(bool $preferDist): self
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setPreferDist', [$preferDist]);
+        return $this;
+    }
+
+    public function setPreferences(array $preferences): self
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setPreferences', [$preferences]);
+        return $this;
+    }
+
+    public function setDownloader(string $type, DownloaderInterface $downloader): self
+    {
+        \ShirabeRpcRuntime::callRust($this->__rhandle, 'setDownloader', [$type, $downloader]);
+        return $this;
+    }
+
+    public function getDownloader(string $type): DownloaderInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getDownloader', [$type]);
+    }
+
+    public function getDownloaderForPackage(PackageInterface $package): ?DownloaderInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getDownloaderForPackage', [$package]);
+    }
+
+    public function getDownloaderType(DownloaderInterface $downloader): string
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getDownloaderType', [$downloader]);
+    }
+
+    public function download(PackageInterface $package, string $targetDir, ?PackageInterface $prevPackage = null): PromiseInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'download', [$package, $targetDir, $prevPackage]);
+    }
+
+    public function prepare(string $type, PackageInterface $package, string $targetDir, ?PackageInterface $prevPackage = null): PromiseInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'prepare', [$type, $package, $targetDir, $prevPackage]);
+    }
+
+    public function install(PackageInterface $package, string $targetDir): PromiseInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'install', [$package, $targetDir]);
+    }
+
+    public function update(PackageInterface $initial, PackageInterface $target, string $targetDir): PromiseInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'update', [$initial, $target, $targetDir]);
+    }
+
+    public function remove(PackageInterface $package, string $targetDir): PromiseInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'remove', [$package, $targetDir]);
+    }
+
+    public function cleanup(string $type, PackageInterface $package, string $targetDir, ?PackageInterface $prevPackage = null): PromiseInterface
+    {
+        return \ShirabeRpcRuntime::callRust($this->__rhandle, 'cleanup', [$type, $package, $targetDir, $prevPackage]);
+    }
+}
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/EventDispatcher/EventDispatcher.php b/crates/shirabe-php-rpc/php/stubs/Composer/EventDispatcher/EventDispatcher.php
index 30f8c0e8..e2369ed2 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/EventDispatcher/EventDispatcher.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/EventDispatcher/EventDispatcher.php
@@ -6,8 +6,11 @@
 namespace Composer\EventDispatcher;
 
 use Composer\DependencyResolver\Transaction;
+use Composer\IO\IOInterface;
+use Composer\PartialComposer;
 use Composer\DependencyResolver\Operation\OperationInterface;
 use Composer\Repository\RepositoryInterface;
+use Composer\Util\ProcessExecutor;
 
 class EventDispatcher implements \ShirabeRustStub
 {
@@ -16,16 +19,12 @@ class EventDispatcher implements \ShirabeRustStub
     /** @var int */
     protected $__epoch;
 
-    public function __construct(int $rhandle = 0, int $epoch = 0)
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
     {
-        if (func_num_args() < 2) {
-            // Constructing the class from plugin code (a common idiom for e.g. `new BufferIO()`)
-            // is an open question of the plugin design; only proxy instantiation passes a
-            // Rust handle. Fail with a diagnosable message instead of an ArgumentCountError.
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process yet'
-            );
-        }
         $this->__rhandle = $rhandle;
         $this->__epoch = $epoch;
     }
@@ -54,6 +53,12 @@ class EventDispatcher implements \ShirabeRustStub
         \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
     }
 
+    public function __construct(PartialComposer $composer, IOInterface $io, ?ProcessExecutor $process = null)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$composer, $io, $process]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function setRunScripts(bool $runScripts = true): self
     {
         \ShirabeRpcRuntime::callRust($this->__rhandle, 'setRunScripts', [$runScripts]);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/IO/BaseIO.php b/crates/shirabe-php-rpc/php/stubs/Composer/IO/BaseIO.php
index b3e0fb51..ecb4db2f 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/IO/BaseIO.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/IO/BaseIO.php
@@ -14,16 +14,12 @@ abstract class BaseIO implements IOInterface, \ShirabeRustStub
     /** @var int */
     protected $__epoch;
 
-    public function __construct(int $rhandle = 0, int $epoch = 0)
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
     {
-        if (func_num_args() < 2) {
-            // Constructing the class from plugin code (a common idiom for e.g. `new BufferIO()`)
-            // is an open question of the plugin design; only proxy instantiation passes a
-            // Rust handle. Fail with a diagnosable message instead of an ArgumentCountError.
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process yet'
-            );
-        }
         $this->__rhandle = $rhandle;
         $this->__epoch = $epoch;
     }
@@ -52,6 +48,12 @@ abstract class BaseIO implements IOInterface, \ShirabeRustStub
         \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
     }
 
+    public function __construct()
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, []]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function isInteractive()
     {
         return \ShirabeRpcRuntime::callRust($this->__rhandle, 'isInteractive', []);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/IO/BufferIO.php b/crates/shirabe-php-rpc/php/stubs/Composer/IO/BufferIO.php
index d5e59e90..b2e84d2b 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/IO/BufferIO.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/IO/BufferIO.php
@@ -5,8 +5,17 @@
 
 namespace Composer\IO;
 
+use Symfony\Component\Console\Output\StreamOutput;
+use Symfony\Component\Console\Formatter\OutputFormatterInterface;
+
 class BufferIO extends ConsoleIO
 {
+    public function __construct(string $input = '', int $verbosity = StreamOutput::VERBOSITY_NORMAL, ?OutputFormatterInterface $formatter = null)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$input, $verbosity, $formatter]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function getOutput(): string
     {
         return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getOutput', []);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/IO/ConsoleIO.php b/crates/shirabe-php-rpc/php/stubs/Composer/IO/ConsoleIO.php
index 0041363a..b68f50ff 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/IO/ConsoleIO.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/IO/ConsoleIO.php
@@ -6,10 +6,19 @@
 namespace Composer\IO;
 
 use Composer\Pcre\Preg;
+use Symfony\Component\Console\Helper\HelperSet;
 use Symfony\Component\Console\Helper\Table;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
 
 class ConsoleIO extends BaseIO
 {
+    public function __construct(InputInterface $input, OutputInterface $output, HelperSet $helperSet)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$input, $output, $helperSet]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public static function sanitize($messages, bool $allowNewlines = true)
     {
         // Match ANSI escape sequences:
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Installer/InstallationManager.php b/crates/shirabe-php-rpc/php/stubs/Composer/Installer/InstallationManager.php
index d458d30b..7f41f6b9 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/Installer/InstallationManager.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Installer/InstallationManager.php
@@ -13,6 +13,8 @@ use Composer\DependencyResolver\Operation\UpdateOperation;
 use Composer\DependencyResolver\Operation\UninstallOperation;
 use Composer\DependencyResolver\Operation\MarkAliasInstalledOperation;
 use Composer\DependencyResolver\Operation\MarkAliasUninstalledOperation;
+use Composer\EventDispatcher\EventDispatcher;
+use Composer\Util\Loop;
 use React\Promise\PromiseInterface;
 
 class InstallationManager implements \ShirabeRustStub
@@ -22,16 +24,12 @@ class InstallationManager implements \ShirabeRustStub
     /** @var int */
     protected $__epoch;
 
-    public function __construct(int $rhandle = 0, int $epoch = 0)
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
     {
-        if (func_num_args() < 2) {
-            // Constructing the class from plugin code (a common idiom for e.g. `new BufferIO()`)
-            // is an open question of the plugin design; only proxy instantiation passes a
-            // Rust handle. Fail with a diagnosable message instead of an ArgumentCountError.
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process yet'
-            );
-        }
         $this->__rhandle = $rhandle;
         $this->__epoch = $epoch;
     }
@@ -60,6 +58,12 @@ class InstallationManager implements \ShirabeRustStub
         \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
     }
 
+    public function __construct(Loop $loop, IOInterface $io, ?EventDispatcher $eventDispatcher = null)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$loop, $io, $eventDispatcher]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function reset(): void
     {
         \ShirabeRpcRuntime::callRust($this->__rhandle, 'reset', []);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Package/BasePackage.php b/crates/shirabe-php-rpc/php/stubs/Composer/Package/BasePackage.php
index de8037ca..9fca286a 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/Package/BasePackage.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Package/BasePackage.php
@@ -14,16 +14,12 @@ abstract class BasePackage implements PackageInterface, \ShirabeRustStub
     /** @var int */
     protected $__epoch;
 
-    public function __construct(int $rhandle = 0, int $epoch = 0)
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
     {
-        if (func_num_args() < 2) {
-            // Constructing the class from plugin code (a common idiom for e.g. `new BufferIO()`)
-            // is an open question of the plugin design; only proxy instantiation passes a
-            // Rust handle. Fail with a diagnosable message instead of an ArgumentCountError.
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process yet'
-            );
-        }
         $this->__rhandle = $rhandle;
         $this->__epoch = $epoch;
     }
@@ -52,6 +48,12 @@ abstract class BasePackage implements PackageInterface, \ShirabeRustStub
         \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
     }
 
+    public function __construct(string $name)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$name]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public const STABILITY_STABLE = 0;
     public const STABILITY_RC = 5;
     public const STABILITY_BETA = 10;
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Package/Package.php b/crates/shirabe-php-rpc/php/stubs/Composer/Package/Package.php
index 5b80060d..238dde3b 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/Package/Package.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Package/Package.php
@@ -7,6 +7,12 @@ namespace Composer\Package;
 
 class Package extends BasePackage
 {
+    public function __construct(string $name, string $version, string $prettyVersion)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$name, $version, $prettyVersion]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function setType(string $type): void
     {
         \ShirabeRpcRuntime::callRust($this->__rhandle, 'setType', [$type]);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/PartialComposer.php b/crates/shirabe-php-rpc/php/stubs/Composer/PartialComposer.php
index c60edbb2..a48133cb 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/PartialComposer.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/PartialComposer.php
@@ -18,16 +18,12 @@ class PartialComposer implements \ShirabeRustStub
     /** @var int */
     protected $__epoch;
 
-    public function __construct(int $rhandle = 0, int $epoch = 0)
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
     {
-        if (func_num_args() < 2) {
-            // Constructing the class from plugin code (a common idiom for e.g. `new BufferIO()`)
-            // is an open question of the plugin design; only proxy instantiation passes a
-            // Rust handle. Fail with a diagnosable message instead of an ArgumentCountError.
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process yet'
-            );
-        }
         $this->__rhandle = $rhandle;
         $this->__epoch = $epoch;
     }
@@ -56,6 +52,12 @@ class PartialComposer implements \ShirabeRustStub
         \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
     }
 
+    public function __construct()
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, []]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function setPackage(RootPackageInterface $package): void
     {
         \ShirabeRpcRuntime::callRust($this->__rhandle, 'setPackage', [$package]);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Repository/ArrayRepository.php b/crates/shirabe-php-rpc/php/stubs/Composer/Repository/ArrayRepository.php
index 51e6a462..a5358ff2 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/Repository/ArrayRepository.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Repository/ArrayRepository.php
@@ -14,16 +14,12 @@ class ArrayRepository implements RepositoryInterface, \ShirabeRustStub
     /** @var int */
     protected $__epoch;
 
-    public function __construct(int $rhandle = 0, int $epoch = 0)
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
     {
-        if (func_num_args() < 2) {
-            // Constructing the class from plugin code (a common idiom for e.g. `new BufferIO()`)
-            // is an open question of the plugin design; only proxy instantiation passes a
-            // Rust handle. Fail with a diagnosable message instead of an ArgumentCountError.
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process yet'
-            );
-        }
         $this->__rhandle = $rhandle;
         $this->__epoch = $epoch;
     }
@@ -52,6 +48,12 @@ class ArrayRepository implements RepositoryInterface, \ShirabeRustStub
         \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
     }
 
+    public function __construct(array $packages = [])
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$packages]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function hasPackage(PackageInterface $package)
     {
         return \ShirabeRpcRuntime::callRust($this->__rhandle, 'hasPackage', [$package]);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Repository/FilesystemRepository.php b/crates/shirabe-php-rpc/php/stubs/Composer/Repository/FilesystemRepository.php
index 00e42ac6..99c225cf 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/Repository/FilesystemRepository.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Repository/FilesystemRepository.php
@@ -5,10 +5,19 @@
 
 namespace Composer\Repository;
 
+use Composer\Json\JsonFile;
+use Composer\Package\RootPackageInterface;
 use Composer\Pcre\Preg;
+use Composer\Util\Filesystem;
 
 class FilesystemRepository extends WritableArrayRepository
 {
+    public function __construct(JsonFile $repositoryFile, bool $dumpVersions = false, ?RootPackageInterface $rootPackage = null, ?Filesystem $filesystem = null)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$repositoryFile, $dumpVersions, $rootPackage, $filesystem]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public static function safelyLoadInstalledVersions(string $path): bool
     {
         $installedVersionsData = @file_get_contents($path);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Repository/RepositoryManager.php b/crates/shirabe-php-rpc/php/stubs/Composer/Repository/RepositoryManager.php
index 5635c0dc..9f3567d3 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/Repository/RepositoryManager.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Repository/RepositoryManager.php
@@ -5,7 +5,12 @@
 
 namespace Composer\Repository;
 
+use Composer\IO\IOInterface;
+use Composer\Config;
+use Composer\EventDispatcher\EventDispatcher;
 use Composer\Package\PackageInterface;
+use Composer\Util\HttpDownloader;
+use Composer\Util\ProcessExecutor;
 
 class RepositoryManager implements \ShirabeRustStub
 {
@@ -14,16 +19,12 @@ class RepositoryManager implements \ShirabeRustStub
     /** @var int */
     protected $__epoch;
 
-    public function __construct(int $rhandle = 0, int $epoch = 0)
+    /**
+     * Binds a stub the registry built for an existing entity. Proxy instantiation bypasses
+     * the constructor, which belongs to plugin code building a new entity instead.
+     */
+    public function __shirabeBind(int $rhandle, int $epoch): void
     {
-        if (func_num_args() < 2) {
-            // Constructing the class from plugin code (a common idiom for e.g. `new BufferIO()`)
-            // is an open question of the plugin design; only proxy instantiation passes a
-            // Rust handle. Fail with a diagnosable message instead of an ArgumentCountError.
-            throw new \RuntimeException(
-                'Shirabe does not support constructing ' . static::class . ' inside the plugin process yet'
-            );
-        }
         $this->__rhandle = $rhandle;
         $this->__epoch = $epoch;
     }
@@ -52,6 +53,12 @@ class RepositoryManager implements \ShirabeRustStub
         \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
     }
 
+    public function __construct(IOInterface $io, Config $config, HttpDownloader $httpDownloader, ?EventDispatcher $eventDispatcher = null, ?ProcessExecutor $process = null)
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$io, $config, $httpDownloader, $eventDispatcher, $process]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function findPackage(string $name, $constraint): ?PackageInterface
     {
         return \ShirabeRpcRuntime::callRust($this->__rhandle, 'findPackage', [$name, $constraint]);
diff --git a/crates/shirabe-php-rpc/php/stubs/Composer/Script/Event.php b/crates/shirabe-php-rpc/php/stubs/Composer/Script/Event.php
index a93d0dfc..065e79e2 100644
--- a/crates/shirabe-php-rpc/php/stubs/Composer/Script/Event.php
+++ b/crates/shirabe-php-rpc/php/stubs/Composer/Script/Event.php
@@ -11,6 +11,12 @@ use Composer\EventDispatcher\Event as BaseEvent;
 
 class Event extends BaseEvent
 {
+    public function __construct(string $name, Composer $composer, IOInterface $io, bool $devMode = false, array $args = [], array $flags = [])
+    {
+        [$this->__rhandle, $this->__epoch] = \ShirabeRpcRuntime::callRust(0, '__shirabeConstruct', [static::class, [$name, $composer, $io, $devMode, $args, $flags]]);
+        \ShirabeRustObjectRegistry::adopt($this->__rhandle, $this);
+    }
+
     public function getComposer(): Composer
     {
         return \ShirabeRpcRuntime::callRust($this->__rhandle, 'getComposer', []);
diff --git a/crates/shirabe-php-rpc/php/worker.php b/crates/shirabe-php-rpc/php/worker.php
index 12297c83..9a36abdd 100644
--- a/crates/shirabe-php-rpc/php/worker.php
+++ b/crates/shirabe-php-rpc/php/worker.php
@@ -25,6 +25,9 @@ interface ShirabeRustStub
      * @return ?array{__rhandle: int, __class: string, __epoch: int}
      */
     public function __shirabeRustHandleDescriptor(): ?array;
+
+    /** Binds this stub to an existing Rust entity, in place of running its constructor. */
+    public function __shirabeBind(int $rhandle, int $epoch): void;
 }
 
 /** Interns proxy stubs so the same Rust handle always yields the same stub instance. */
@@ -46,7 +49,10 @@ final class ShirabeRustObjectRegistry
                 "no proxy stub class is available for {$class}"
             );
         }
-        $stub = new $class($rhandle, $epoch);
+        // The stub's constructor belongs to plugin code building a *new* entity; an entity that
+        // already exists is bound directly, so proxying never runs it.
+        $stub = (new ReflectionClass($class))->newInstanceWithoutConstructor();
+        $stub->__shirabeBind($rhandle, $epoch);
         self::$internTable[$rhandle] = WeakReference::create($stub);
         return $stub;
     }
@@ -626,6 +632,53 @@ ShirabeRpcRuntime::$dispatch = [
         }
         return true;
     },
+    // An already-fulfilled promise for a Rust-side call whose PHP signature declares
+    // PromiseInterface. The Rust future ran to completion before this is called, so there is
+    // nothing left to defer; see .ken/plugin-arch/design.md §10.1.6.
+    '__shirabe_resolved_promise' => static function ($args) {
+        if (!function_exists('React\\Promise\\resolve')) {
+            throw new RuntimeException(
+                'react/promise is not loaded in the plugin process, so a PromiseInterface cannot be built'
+            );
+        }
+        return \React\Promise\resolve($args[0]);
+    },
+    // Drains a promise a plugin returned to the Rust side. React settles promises
+    // synchronously, so an already-settled one runs these handlers during then(); one that is
+    // still pending is an explicit error rather than a silently dropped continuation.
+    '__shirabe_settle_promise' => static function ($args) {
+        $promise = $args[0];
+        if (!$promise instanceof \React\Promise\PromiseInterface) {
+            throw new RuntimeException('__shirabe_settle_promise expects a promise handle');
+        }
+        $settled = false;
+        $value = null;
+        $rejected = false;
+        $reason = null;
+        $promise->then(
+            static function ($result) use (&$settled, &$value) {
+                $settled = true;
+                $value = $result;
+            },
+            static function ($error) use (&$settled, &$rejected, &$reason) {
+                $settled = true;
+                $rejected = true;
+                $reason = $error;
+            }
+        );
+        if (!$settled) {
+            throw new RuntimeException(
+                'the promise returned to Shirabe is still pending; deferred resolution across the'
+                . ' RPC boundary is not implemented yet'
+            );
+        }
+        if ($rejected) {
+            throw $reason instanceof Throwable
+                ? $reason
+                : new RuntimeException('the promise returned to Shirabe was rejected with ' . gettype($reason));
+        }
+        return $value;
+    },
     // For testing only: reads a public property of a P-table entity (PHPUnit asserts like
     // `$plugins[0]->version` have no method to call).
     '__shirabe_get_property' => static function ($args) {
diff --git a/crates/shirabe-php-rpc/src/lib.rs b/crates/shirabe-php-rpc/src/lib.rs
index ef11d542..4f9ba6b5 100644
--- a/crates/shirabe-php-rpc/src/lib.rs
+++ b/crates/shirabe-php-rpc/src/lib.rs
@@ -579,6 +579,14 @@ const STUB_FILES: &[(&str, &str)] = &[
         include_str!("../php/stubs/Composer/Composer.php"),
     ),
     (
+        "Composer/Config.php",
+        include_str!("../php/stubs/Composer/Config.php"),
+    ),
+    (
+        "Composer/Downloader/DownloadManager.php",
+        include_str!("../php/stubs/Composer/Downloader/DownloadManager.php"),
+    ),
+    (
         "Composer/IO/BaseIO.php",
         include_str!("../php/stubs/Composer/IO/BaseIO.php"),
     ),