thephpleague/flysystem · error · League\Flysystem\PhpseclibV3\UnableToLoadPrivateKey

Unable to load private key.

Error message

Unable to load private key.

What it means

Error "Unable to load private key." thrown in thephpleague/flysystem.

Source

Thrown at src/PhpseclibV3/SftpConnectionProvider.php:209

        }

        throw UnableToAuthenticate::withPrivateKey($connection->getLastError());
    }

    private function loadPrivateKey(): AsymmetricKey
    {
        if (("---" !== substr($this->privateKey, 0, 3) || "PuTTY" !== substr($this->privateKey, 0, 5)) && is_file($this->privateKey)) {
            $this->privateKey = file_get_contents($this->privateKey);
        }

        try {
            if ($this->passphrase !== null) {
                return PublicKeyLoader::load($this->privateKey, $this->passphrase);
            }

            return PublicKeyLoader::load($this->privateKey);
        } catch (NoKeyLoadedException $exception) {
            throw new UnableToLoadPrivateKey(null, $exception);
        }
    }

    private function authenticateWithAgent(SFTP $connection): void
    {
        $agent = new Agent();

        if ( ! $connection->login($this->username, $agent)) {
            throw UnableToAuthenticate::withSshAgent($connection->getLastError());
        }
    }
}

View on GitHub (pinned to b277b5dc3d)

When it happens

Trigger: Thrown at src/PhpseclibV3/SftpConnectionProvider.php:209 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of thephpleague/flysystem@b277b5dc3d (2026-08-17). Data as JSON: /api/errors/5e309ebc6239921b. Report an issue: GitHub.