Add 'meshmc/' from commit 'fad6a1066616b69d7f5fef01178efdf014c59537'

git-subtree-dir: meshmc
git-subtree-mainline: 934382c8a1ce738589dee9ee0f14e1cec812770e
git-subtree-split: fad6a1066616b69d7f5fef01178efdf014c59537

16 files changed, 1615 insertions, 0 deletions

diff --git a/meshmc/libraries/katabasis/.gitignore b/meshmc/libraries/katabasis/.gitignore
new file mode 100644
index 0000000000..35e189c5ef
--- /dev/null
+++ b/meshmc/libraries/katabasis/.gitignore
@@ -0,0 +1,2 @@
+build/
+*.kdev4
diff --git a/meshmc/libraries/katabasis/CMakeLists.txt b/meshmc/libraries/katabasis/CMakeLists.txt
new file mode 100644
index 0000000000..a42fb3057d
--- /dev/null
+++ b/meshmc/libraries/katabasis/CMakeLists.txt
@@ -0,0 +1,53 @@
+cmake_minimum_required(VERSION 3.25)
+
+string(COMPARE EQUAL "${CMAKE_SOURCE_DIR}" "${CMAKE_BUILD_DIR}" IS_IN_SOURCE_BUILD)
+if(IS_IN_SOURCE_BUILD)
+    message(FATAL_ERROR "You are building Katabasis in-source. Please separate the build tree from the source tree.")
+endif()
+
+if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    if(CMAKE_HOST_SYSTEM_VERSION MATCHES ".*[Mm]icrosoft.*" OR
+        CMAKE_HOST_SYSTEM_VERSION MATCHES ".*WSL.*"
+    )
+        message(FATAL_ERROR "Building Katabasis is not supported in Linux-on-Windows distributions. Use a real Linux machine, not a fraudulent one.")
+    endif()
+endif()
+
+project(Katabasis)
+enable_testing()
+
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+set(CMAKE_CXX_STANDARD_REQUIRED true)
+set(CMAKE_C_STANDARD_REQUIRED true)
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_C_STANDARD 11)
+
+find_package(Qt6 COMPONENTS Core Network REQUIRED)
+
+set( katabasis_PRIVATE
+    src/DeviceFlow.cpp
+    src/JsonResponse.cpp
+    src/JsonResponse.h
+    src/PollServer.cpp
+    src/Reply.cpp
+)
+
+set( katabasis_PUBLIC
+    include/katabasis/DeviceFlow.h
+    include/katabasis/Globals.h
+    include/katabasis/PollServer.h
+    include/katabasis/Reply.h
+    include/katabasis/RequestParameter.h
+)
+
+add_library( Katabasis STATIC ${katabasis_PRIVATE} ${katabasis_PUBLIC} )
+target_link_libraries(Katabasis Qt6::Core Qt6::Network)
+
+# needed for statically linked Katabasis in shared libs on x86_64
+set_target_properties(Katabasis
+    PROPERTIES POSITION_INDEPENDENT_CODE TRUE
+)
+
+target_include_directories(Katabasis PUBLIC include PRIVATE src include/katabasis)
diff --git a/meshmc/libraries/katabasis/LICENSE b/meshmc/libraries/katabasis/LICENSE
new file mode 100644
index 0000000000..9ac8d42fb0
--- /dev/null
+++ b/meshmc/libraries/katabasis/LICENSE
@@ -0,0 +1,23 @@
+Copyright (c) 2012, Akos Polster
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without 
+modification, are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice, 
+this list of conditions and the following disclaimer in the documentation 
+and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE 
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/meshmc/libraries/katabasis/README.md b/meshmc/libraries/katabasis/README.md
new file mode 100644
index 0000000000..646a128670
--- /dev/null
+++ b/meshmc/libraries/katabasis/README.md
@@ -0,0 +1,36 @@
+# Katabasis - MS-flavoerd OAuth for Qt, derived from the O2 library
+
+This library's sole purpose is to make interacting with MSA and various MSA and XBox authenticated services less painful.
+
+It may be possible to backport some of the changes to O2 in the future, but for the sake of going fast, all compatibility concerns have been ignored.
+
+[You can find the original library's git repository here.](https://github.com/pipacs/o2)
+
+Notes to contributors:
+
+   * Please follow the coding style of the existing source, where reasonable
+   * Code contributions are released under Simplified BSD License, as specified in LICENSE. Do not contribute if this license does not suit your code
+   * If you are interested in working on this, come to the MeshMC Discord server and talk first
+
+## Installation
+
+Clone the Github repository, integrate the it into your CMake build system.
+
+The library is static only, dynamic linking and system-wide installation are out of scope and undesirable.
+
+## Usage
+
+At this stage, don't, unless you want to help with the library itself.
+
+This is an experimental fork of the O2 library and is undergoing a big design/architecture shift in order to support different features:
+
+* Multiple accounts
+* Multi-stage authentication/authorization schemes
+* Tighter control over token chains and their storage
+* Talking to complex APIs and individually authorized microservices
+* Token lifetime management, 'offline mode' and resilience in face of network failures
+* Token and claims/entitlements validation
+* Caching of some API results
+* XBox magic
+* Mojang magic
+* Generally, magic that you would spend weeks on researching while getting confused by contradictory/incomplete documentation (if any is available)
diff --git a/meshmc/libraries/katabasis/acknowledgements.md b/meshmc/libraries/katabasis/acknowledgements.md
new file mode 100644
index 0000000000..c1c8a3d49e
--- /dev/null
+++ b/meshmc/libraries/katabasis/acknowledgements.md
@@ -0,0 +1,110 @@
+# O2 library by Akos Polster and contributors
+
+[The origin of this fork.](https://github.com/pipacs/o2)
+
+> Copyright (c) 2012, Akos Polster
+> All rights reserved.
+>
+> Redistribution and use in source and binary forms, with or without
+> modification, are permitted provided that the following conditions are met:
+>
+>  * Redistributions of source code must retain the above copyright notice, this
+> list of conditions and the following disclaimer.
+>
+>  * Redistributions in binary form must reproduce the above copyright notice,
+> this list of conditions and the following disclaimer in the documentation
+> and/or other materials provided with the distribution.
+>
+> THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+> AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+> IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+> DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+> DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+> SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+> CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+> OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+> OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+# SimpleCrypt by Andre Somers
+
+Cryptographic methods for Qt.
+
+> Copyright (c) 2011, Andre Somers
+> All rights reserved.
+> 
+> Redistribution and use in source and binary forms, with or without
+> modification, are permitted provided that the following conditions are met:
+> 
+>    * Redistributions of source code must retain the above copyright
+>      notice, this list of conditions and the following disclaimer.
+>    * Redistributions in binary form must reproduce the above copyright
+>      notice, this list of conditions and the following disclaimer in the
+>      documentation and/or other materials provided with the distribution.
+>    * Neither the name of the Rathenau Instituut, Andre Somers nor the
+>      names of its contributors may be used to endorse or promote products
+>      derived from this software without specific prior written permission.
+> 
+> THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+> ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+> WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+> DISCLAIMED. IN NO EVENT SHALL ANDRE SOMERS BE LIABLE FOR ANY
+> DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+> (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+> LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+> ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+> (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+> SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# Mandeep Sandhu <mandeepsandhu.chd@gmail.com>
+
+Configurable settings storage, Twitter XAuth specialization, new demos, cleanups.
+
+> "Hi Akos,
+> 
+> I'm writing this mail to confirm that my contributions to the O2 library, available here https://github.com/pipacs/o2, can be freely distributed according to the project's license (as shown in the LICENSE file).
+> 
+> Regards,
+> -mandeep"
+
+# Sergey Gavrushkin <https://github.com/ncux>
+
+FreshBooks specialization
+
+# Theofilos Intzoglou <https://github.com/parapente>
+
+Hubic specialization
+
+# Dimitar
+
+SurveyMonkey specialization
+
+# David Brooks <https://github.com/dbrnz>
+
+CMake related fixes and improvements.
+
+# Lukas Vogel <https://github.com/lukedirtwalker>
+
+Spotify support
+
+# Alan Garny <https://github.com/agarny>
+
+Windows DLL build support
+
+# MartinMikita <https://github.com/MartinMikita>
+
+Bug fixes
+
+# Larry Shaffer <https://github.com/dakcarto>
+
+Versioning, shared lib, install target and header support
+
+# Gilmanov Ildar <https://github.com/gilmanov-ildar>
+
+Bug fixes, support for ```qml``` module
+
+# Fabian Vogt <https://github.com/Vogtinator>
+
+Bug fixes, support for building without Qt keywords enabled
+
diff --git a/meshmc/libraries/katabasis/include/katabasis/Bits.h b/meshmc/libraries/katabasis/include/katabasis/Bits.h
new file mode 100644
index 0000000000..bd0aed8508
--- /dev/null
+++ b/meshmc/libraries/katabasis/include/katabasis/Bits.h
@@ -0,0 +1,57 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <QString>
+#include <QDateTime>
+#include <QMap>
+#include <QVariantMap>
+
+namespace Katabasis
+{
+	enum class Activity {
+		Idle,
+		LoggingIn,
+		LoggingOut,
+		Refreshing,
+		FailedSoft, //!< soft failure. this generally means the user auth
+					//!< details haven't been invalidated
+		FailedHard, //!< hard failure. auth is invalid
+		FailedGone, //!< hard failure. auth is invalid, and the account no
+					//!< longer exists
+		Succeeded
+	};
+
+	enum class Validity { None, Assumed, Certain };
+
+	struct Token {
+		QDateTime issueInstant;
+		QDateTime notAfter;
+		QString token;
+		QString refresh_token;
+		QVariantMap extra;
+
+		Validity validity = Validity::None;
+		bool persistent = true;
+	};
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/include/katabasis/DeviceFlow.h b/meshmc/libraries/katabasis/include/katabasis/DeviceFlow.h
new file mode 100644
index 0000000000..37f39cc658
--- /dev/null
+++ b/meshmc/libraries/katabasis/include/katabasis/DeviceFlow.h
@@ -0,0 +1,178 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <QNetworkAccessManager>
+#include <QNetworkRequest>
+#include <QNetworkReply>
+#include <QPair>
+
+#include "Reply.h"
+#include "RequestParameter.h"
+#include "Bits.h"
+
+namespace Katabasis
+{
+
+	class ReplyServer;
+	class PollServer;
+
+	/// Simple OAuth2 Device Flow authenticator.
+	class DeviceFlow : public QObject
+	{
+		Q_OBJECT
+	  public:
+		Q_ENUMS(GrantFlow)
+
+	  public:
+		struct Options {
+			QString userAgent = QStringLiteral("Katabasis/1.0");
+			QString responseType = QStringLiteral("code");
+			QString scope;
+			QString clientIdentifier;
+			QString clientSecret;
+			QUrl authorizationUrl;
+			QUrl accessTokenUrl;
+		};
+
+	  public:
+		/// Are we authenticated?
+		bool linked();
+
+		/// Authentication token.
+		QString token();
+
+		/// Provider-specific extra tokens, available after a successful
+		/// authentication
+		QVariantMap extraTokens();
+
+	  public:
+		// TODO: put in `Options`
+		/// User-defined extra parameters to append to request URL
+		QVariantMap extraRequestParams();
+		void setExtraRequestParams(const QVariantMap& value);
+
+		// TODO: split up the class into multiple, each implementing one OAuth2
+		// flow
+		/// Grant type (if non-standard)
+		QString grantType();
+		void setGrantType(const QString& value);
+
+	  public:
+		/// Constructor.
+		/// @param  parent  Parent object.
+		explicit DeviceFlow(Options& opts, Token& token, QObject* parent = 0,
+							QNetworkAccessManager* manager = 0);
+
+		/// Get refresh token.
+		QString refreshToken();
+
+		/// Get token expiration time
+		QDateTime expires();
+
+	  public slots:
+		/// Authenticate.
+		void login();
+
+		/// De-authenticate.
+		void logout();
+
+		/// Refresh token.
+		bool refresh();
+
+		/// Handle situation where reply server has opted to close its
+		/// connection
+		void serverHasClosed(bool paramsfound = false);
+
+	  signals:
+		/// Emitted when client needs to open a web browser window, with the
+		/// given URL.
+		void openBrowser(const QUrl& url);
+
+		/// Emitted when client can close the browser window.
+		void closeBrowser();
+
+		/// Emitted when client needs to show a verification uri and user code
+		void showVerificationUriAndCode(const QUrl& uri, const QString& code,
+										int expiresIn);
+
+		/// Emitted when the internal state changes
+		void activityChanged(Activity activity);
+
+	  public slots:
+		/// Handle verification response.
+		void onVerificationReceived(QMap<QString, QString>);
+
+	  protected slots:
+		/// Handle completion of a Device Authorization Request
+		void onDeviceAuthReplyFinished();
+
+		/// Handle completion of a refresh request.
+		void onRefreshFinished();
+
+		/// Handle failure of a refresh request.
+		void onRefreshError(QNetworkReply::NetworkError error,
+							QNetworkReply* reply);
+
+	  protected:
+		/// Set refresh token.
+		void setRefreshToken(const QString& v);
+
+		/// Set token expiration time.
+		void setExpires(QDateTime v);
+
+		/// Start polling authorization server
+		void startPollServer(const QVariantMap& params, int expiresIn);
+
+		/// Set authentication token.
+		void setToken(const QString& v);
+
+		/// Set the linked state
+		void setLinked(bool v);
+
+		/// Set extra tokens found in OAuth response
+		void setExtraTokens(QVariantMap extraTokens);
+
+		/// Set local poll server
+		void setPollServer(PollServer* server);
+
+		PollServer* pollServer() const;
+
+		void updateActivity(Activity activity);
+
+	  protected:
+		Options options_;
+
+		QVariantMap extraReqParams_;
+		QNetworkAccessManager* manager_ = nullptr;
+		ReplyList timedReplies_;
+		QString grantType_;
+
+	  protected:
+		Token& token_;
+
+	  private:
+		PollServer* pollServer_ = nullptr;
+		Activity activity_ = Activity::Idle;
+	};
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/include/katabasis/Globals.h b/meshmc/libraries/katabasis/include/katabasis/Globals.h
new file mode 100644
index 0000000000..cf6fa39b21
--- /dev/null
+++ b/meshmc/libraries/katabasis/include/katabasis/Globals.h
@@ -0,0 +1,82 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+namespace Katabasis
+{
+
+	// Common constants
+	const char ENCRYPTION_KEY[] = "12345678";
+	const char MIME_TYPE_XFORM[] = "application/x-www-form-urlencoded";
+	const char MIME_TYPE_JSON[] = "application/json";
+
+	// OAuth 1/1.1 Request Parameters
+	const char OAUTH_CALLBACK[] = "oauth_callback";
+	const char OAUTH_CONSUMER_KEY[] = "oauth_consumer_key";
+	const char OAUTH_NONCE[] = "oauth_nonce";
+	const char OAUTH_SIGNATURE[] = "oauth_signature";
+	const char OAUTH_SIGNATURE_METHOD[] = "oauth_signature_method";
+	const char OAUTH_TIMESTAMP[] = "oauth_timestamp";
+	const char OAUTH_VERSION[] = "oauth_version";
+	// OAuth 1/1.1 Response Parameters
+	const char OAUTH_TOKEN[] = "oauth_token";
+	const char OAUTH_TOKEN_SECRET[] = "oauth_token_secret";
+	const char OAUTH_CALLBACK_CONFIRMED[] = "oauth_callback_confirmed";
+	const char OAUTH_VERFIER[] = "oauth_verifier";
+
+	// OAuth 2 Request Parameters
+	const char OAUTH2_RESPONSE_TYPE[] = "response_type";
+	const char OAUTH2_CLIENT_ID[] = "client_id";
+	const char OAUTH2_CLIENT_SECRET[] = "client_secret";
+	const char OAUTH2_USERNAME[] = "username";
+	const char OAUTH2_PASSWORD[] = "password";
+	const char OAUTH2_REDIRECT_URI[] = "redirect_uri";
+	const char OAUTH2_SCOPE[] = "scope";
+	const char OAUTH2_GRANT_TYPE_CODE[] = "code";
+	const char OAUTH2_GRANT_TYPE_TOKEN[] = "token";
+	const char OAUTH2_GRANT_TYPE_PASSWORD[] = "password";
+	const char OAUTH2_GRANT_TYPE_DEVICE[] =
+		"urn:ietf:params:oauth:grant-type:device_code";
+	const char OAUTH2_GRANT_TYPE[] = "grant_type";
+	const char OAUTH2_API_KEY[] = "api_key";
+	const char OAUTH2_STATE[] = "state";
+	const char OAUTH2_CODE[] = "code";
+
+	// OAuth 2 Response Parameters
+	const char OAUTH2_ACCESS_TOKEN[] = "access_token";
+	const char OAUTH2_REFRESH_TOKEN[] = "refresh_token";
+	const char OAUTH2_EXPIRES_IN[] = "expires_in";
+	const char OAUTH2_DEVICE_CODE[] = "device_code";
+	const char OAUTH2_USER_CODE[] = "user_code";
+	const char OAUTH2_VERIFICATION_URI[] = "verification_uri";
+	const char OAUTH2_VERIFICATION_URL[] = "verification_url"; // Google sign-in
+	const char OAUTH2_VERIFICATION_URI_COMPLETE[] = "verification_uri_complete";
+	const char OAUTH2_INTERVAL[] = "interval";
+
+	// Parameter values
+	const char AUTHORIZATION_CODE[] = "authorization_code";
+
+	// Standard HTTP headers
+	const char HTTP_HTTP_HEADER[] = "HTTP";
+	const char HTTP_AUTHORIZATION_HEADER[] = "Authorization";
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/include/katabasis/PollServer.h b/meshmc/libraries/katabasis/include/katabasis/PollServer.h
new file mode 100644
index 0000000000..d070131f49
--- /dev/null
+++ b/meshmc/libraries/katabasis/include/katabasis/PollServer.h
@@ -0,0 +1,73 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <QByteArray>
+#include <QMap>
+#include <QNetworkRequest>
+#include <QObject>
+#include <QString>
+#include <QTimer>
+
+class QNetworkAccessManager;
+
+namespace Katabasis
+{
+
+	/// Poll an authorization server for token
+	class PollServer : public QObject
+	{
+		Q_OBJECT
+
+	  public:
+		explicit PollServer(QNetworkAccessManager* manager,
+							const QNetworkRequest& request,
+							const QByteArray& payload, int expiresIn,
+							QObject* parent = 0);
+
+		/// Seconds to wait between polling requests
+		Q_PROPERTY(int interval READ interval WRITE setInterval)
+		int interval() const;
+		void setInterval(int interval);
+
+	  signals:
+		void verificationReceived(QMap<QString, QString>);
+		void serverClosed(bool); // whether it has found parameters
+
+	  public slots:
+		void startPolling();
+
+	  protected slots:
+		void onPollTimeout();
+		void onExpiration();
+		void onReplyFinished();
+
+	  protected:
+		QNetworkAccessManager* manager_;
+		const QNetworkRequest request_;
+		const QByteArray payload_;
+		const int expiresIn_;
+		QTimer expirationTimer;
+		QTimer pollTimer;
+	};
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/include/katabasis/Reply.h b/meshmc/libraries/katabasis/include/katabasis/Reply.h
new file mode 100644
index 0000000000..dbfa939829
--- /dev/null
+++ b/meshmc/libraries/katabasis/include/katabasis/Reply.h
@@ -0,0 +1,92 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <QList>
+#include <QTimer>
+#include <QNetworkRequest>
+#include <QNetworkReply>
+#include <QNetworkAccessManager>
+#include <QByteArray>
+
+namespace Katabasis
+{
+
+	constexpr int defaultTimeout = 30 * 1000;
+
+	/// A network request/reply pair that can time out.
+	class Reply : public QTimer
+	{
+		Q_OBJECT
+
+	  public:
+		Reply(QNetworkReply* reply, int timeOut = defaultTimeout,
+			  QObject* parent = 0);
+
+	  signals:
+		void error(QNetworkReply::NetworkError);
+
+	  public slots:
+		/// When time out occurs, the QNetworkReply's error() signal is
+		/// triggered.
+		void onTimeOut();
+
+	  public:
+		QNetworkReply* reply;
+		bool timedOut = false;
+	};
+
+	/// List of O2Replies.
+	class ReplyList
+	{
+	  public:
+		ReplyList()
+		{
+			ignoreSslErrors_ = false;
+		}
+
+		/// Destructor.
+		/// Deletes all O2Reply instances in the list.
+		virtual ~ReplyList();
+
+		/// Create a new O2Reply from a QNetworkReply, and add it to this list.
+		void add(QNetworkReply* reply, int timeOut = defaultTimeout);
+
+		/// Add an O2Reply to the list, while taking ownership of it.
+		void add(Reply* reply);
+
+		/// Remove item from the list that corresponds to a QNetworkReply.
+		void remove(QNetworkReply* reply);
+
+		/// Find an O2Reply in the list, corresponding to a QNetworkReply.
+		/// @return Matching O2Reply or NULL.
+		Reply* find(QNetworkReply* reply);
+
+		bool ignoreSslErrors();
+		void setIgnoreSslErrors(bool ignoreSslErrors);
+
+	  protected:
+		QList<Reply*> replies_;
+		bool ignoreSslErrors_;
+	};
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/include/katabasis/RequestParameter.h b/meshmc/libraries/katabasis/include/katabasis/RequestParameter.h
new file mode 100644
index 0000000000..e7ff1efda3
--- /dev/null
+++ b/meshmc/libraries/katabasis/include/katabasis/RequestParameter.h
@@ -0,0 +1,42 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+namespace Katabasis
+{
+
+	/// Request parameter (name-value pair) participating in authentication.
+	struct RequestParameter {
+		RequestParameter(const QByteArray& n, const QByteArray& v)
+			: name(n), value(v)
+		{
+		}
+		bool operator<(const RequestParameter& other) const
+		{
+			return (name == other.name) ? (value < other.value)
+										: (name < other.name);
+		}
+		QByteArray name;
+		QByteArray value;
+	};
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/src/DeviceFlow.cpp b/meshmc/libraries/katabasis/src/DeviceFlow.cpp
new file mode 100644
index 0000000000..d03b3efd8f
--- /dev/null
+++ b/meshmc/libraries/katabasis/src/DeviceFlow.cpp
@@ -0,0 +1,539 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <QList>
+#include <QPair>
+#include <QDebug>
+#include <QTcpServer>
+#include <QMap>
+#include <QNetworkRequest>
+#include <QNetworkReply>
+#include <QNetworkAccessManager>
+#include <QDateTime>
+#include <QCryptographicHash>
+#include <QTimer>
+#include <QVariantMap>
+#include <QUuid>
+#include <QDataStream>
+
+#include <QUrlQuery>
+
+#include "katabasis/DeviceFlow.h"
+#include "katabasis/PollServer.h"
+#include "katabasis/Globals.h"
+
+#include "JsonResponse.h"
+
+namespace
+{
+	// ref: https://tools.ietf.org/html/rfc8628#section-3.2
+	// Exception: Google sign-in uses "verification_url" instead of "*_uri" -
+	// we'll accept both.
+	bool hasMandatoryDeviceAuthParams(const QVariantMap& params)
+	{
+		if (!params.contains(Katabasis::OAUTH2_DEVICE_CODE))
+			return false;
+
+		if (!params.contains(Katabasis::OAUTH2_USER_CODE))
+			return false;
+
+		if (!(params.contains(Katabasis::OAUTH2_VERIFICATION_URI) ||
+			  params.contains(Katabasis::OAUTH2_VERIFICATION_URL)))
+			return false;
+
+		if (!params.contains(Katabasis::OAUTH2_EXPIRES_IN))
+			return false;
+
+		return true;
+	}
+
+	QByteArray
+	createQueryParameters(const QList<Katabasis::RequestParameter>& parameters)
+	{
+		QByteArray ret;
+		bool first = true;
+		for (auto& h : parameters) {
+			if (first) {
+				first = false;
+			} else {
+				ret.append("&");
+			}
+			ret.append(QUrl::toPercentEncoding(h.name) + "=" +
+					   QUrl::toPercentEncoding(h.value));
+		}
+		return ret;
+	}
+} // namespace
+
+namespace Katabasis
+{
+
+	DeviceFlow::DeviceFlow(Options& opts, Token& token, QObject* parent,
+						   QNetworkAccessManager* manager)
+		: QObject(parent), token_(token)
+	{
+		manager_ = manager ? manager : new QNetworkAccessManager(this);
+		qRegisterMetaType<QNetworkReply::NetworkError>(
+			"QNetworkReply::NetworkError");
+		options_ = opts;
+	}
+
+	bool DeviceFlow::linked()
+	{
+		return token_.validity != Validity::None;
+	}
+	void DeviceFlow::setLinked(bool v)
+	{
+		qDebug() << "DeviceFlow::setLinked:" << (v ? "true" : "false");
+		token_.validity = v ? Validity::Certain : Validity::None;
+	}
+
+	void DeviceFlow::updateActivity(Activity activity)
+	{
+		if (activity_ == activity) {
+			return;
+		}
+
+		activity_ = activity;
+		switch (activity) {
+			case Katabasis::Activity::Idle:
+			case Katabasis::Activity::LoggingIn:
+			case Katabasis::Activity::LoggingOut:
+			case Katabasis::Activity::Refreshing:
+				// non-terminal states...
+				break;
+			case Katabasis::Activity::FailedSoft:
+				// terminal state, tokens did not change
+				break;
+			case Katabasis::Activity::FailedHard:
+			case Katabasis::Activity::FailedGone:
+				// terminal state, tokens are invalid
+				token_ = Token();
+				break;
+			case Katabasis::Activity::Succeeded:
+				setLinked(true);
+				break;
+		}
+		emit activityChanged(activity_);
+	}
+
+	QString DeviceFlow::token()
+	{
+		return token_.token;
+	}
+	void DeviceFlow::setToken(const QString& v)
+	{
+		token_.token = v;
+	}
+
+	QVariantMap DeviceFlow::extraTokens()
+	{
+		return token_.extra;
+	}
+
+	void DeviceFlow::setExtraTokens(QVariantMap extraTokens)
+	{
+		token_.extra = extraTokens;
+	}
+
+	void DeviceFlow::setPollServer(PollServer* server)
+	{
+		if (pollServer_)
+			pollServer_->deleteLater();
+
+		pollServer_ = server;
+	}
+
+	PollServer* DeviceFlow::pollServer() const
+	{
+		return pollServer_;
+	}
+
+	QVariantMap DeviceFlow::extraRequestParams()
+	{
+		return extraReqParams_;
+	}
+
+	void DeviceFlow::setExtraRequestParams(const QVariantMap& value)
+	{
+		extraReqParams_ = value;
+	}
+
+	QString DeviceFlow::grantType()
+	{
+		if (!grantType_.isEmpty())
+			return grantType_;
+
+		return OAUTH2_GRANT_TYPE_DEVICE;
+	}
+
+	void DeviceFlow::setGrantType(const QString& value)
+	{
+		grantType_ = value;
+	}
+
+	// First get the URL and token to display to the user
+	void DeviceFlow::login()
+	{
+		qDebug() << "DeviceFlow::link";
+
+		updateActivity(Activity::LoggingIn);
+		setLinked(false);
+		setToken("");
+		setExtraTokens(QVariantMap());
+		setRefreshToken(QString());
+		setExpires(QDateTime());
+
+		QList<RequestParameter> parameters;
+		parameters.append(RequestParameter(OAUTH2_CLIENT_ID,
+										   options_.clientIdentifier.toUtf8()));
+		parameters.append(
+			RequestParameter(OAUTH2_SCOPE, options_.scope.toUtf8()));
+		QByteArray payload = createQueryParameters(parameters);
+
+		QUrl url(options_.authorizationUrl);
+		QNetworkRequest deviceRequest(url);
+		deviceRequest.setHeader(QNetworkRequest::ContentTypeHeader,
+								"application/x-www-form-urlencoded");
+		QNetworkReply* tokenReply = manager_->post(deviceRequest, payload);
+
+		connect(tokenReply, &QNetworkReply::finished, this,
+				&DeviceFlow::onDeviceAuthReplyFinished, Qt::QueuedConnection);
+	}
+
+	// Then, once we get them, present them to the user
+	void DeviceFlow::onDeviceAuthReplyFinished()
+	{
+		qDebug() << "DeviceFlow::onDeviceAuthReplyFinished";
+		QNetworkReply* tokenReply = qobject_cast<QNetworkReply*>(sender());
+		if (!tokenReply) {
+			qDebug() << "DeviceFlow::onDeviceAuthReplyFinished: reply is null";
+			return;
+		}
+		if (tokenReply->error() == QNetworkReply::NoError) {
+			QByteArray replyData = tokenReply->readAll();
+
+			// Dump replyData
+			// SENSITIVE DATA in RelWithDebInfo or Debug builds
+			// qDebug() << "DeviceFlow::onDeviceAuthReplyFinished: replyData\n";
+			// qDebug() << QString( replyData );
+
+			QVariantMap params = parseJsonResponse(replyData);
+
+			// Dump tokens
+			qDebug()
+				<< "DeviceFlow::onDeviceAuthReplyFinished: Tokens returned:\n";
+			foreach (QString key, params.keys()) {
+				// SENSITIVE DATA in RelWithDebInfo or Debug builds, so it is
+				// truncated first
+				qDebug() << key << ": " << params.value(key).toString();
+			}
+
+			// Check for mandatory parameters
+			if (hasMandatoryDeviceAuthParams(params)) {
+				qDebug() << "DeviceFlow::onDeviceAuthReplyFinished: Device "
+							"auth request response";
+
+				const QString userCode =
+					params.take(OAUTH2_USER_CODE).toString();
+				QUrl uri = params.take(OAUTH2_VERIFICATION_URI).toUrl();
+				if (uri.isEmpty())
+					uri = params.take(OAUTH2_VERIFICATION_URL).toUrl();
+
+				if (params.contains(OAUTH2_VERIFICATION_URI_COMPLETE))
+					emit openBrowser(
+						params.take(OAUTH2_VERIFICATION_URI_COMPLETE).toUrl());
+
+				bool ok = false;
+				int expiresIn = params[OAUTH2_EXPIRES_IN].toInt(&ok);
+				if (!ok) {
+					qWarning() << "DeviceFlow::startPollServer: No expired_in "
+								  "parameter";
+					updateActivity(Activity::FailedHard);
+					return;
+				}
+
+				emit showVerificationUriAndCode(uri, userCode, expiresIn);
+
+				startPollServer(params, expiresIn);
+			} else {
+				qWarning() << "DeviceFlow::onDeviceAuthReplyFinished: "
+							  "Mandatory parameters missing from response";
+				updateActivity(Activity::FailedHard);
+			}
+		}
+		tokenReply->deleteLater();
+	}
+
+	// Spin up polling for the user completing the login flow out of band
+	void DeviceFlow::startPollServer(const QVariantMap& params, int expiresIn)
+	{
+		qDebug()
+			<< "DeviceFlow::startPollServer: device_ and user_code expires in"
+			<< expiresIn << "seconds";
+
+		QUrl url(options_.accessTokenUrl);
+		QNetworkRequest authRequest(url);
+		authRequest.setHeader(QNetworkRequest::ContentTypeHeader,
+							  "application/x-www-form-urlencoded");
+
+		const QString deviceCode = params[OAUTH2_DEVICE_CODE].toString();
+		const QString grantType =
+			grantType_.isEmpty() ? OAUTH2_GRANT_TYPE_DEVICE : grantType_;
+
+		QList<RequestParameter> parameters;
+		parameters.append(RequestParameter(OAUTH2_CLIENT_ID,
+										   options_.clientIdentifier.toUtf8()));
+		if (!options_.clientSecret.isEmpty()) {
+			parameters.append(RequestParameter(OAUTH2_CLIENT_SECRET,
+											   options_.clientSecret.toUtf8()));
+		}
+		parameters.append(RequestParameter(OAUTH2_CODE, deviceCode.toUtf8()));
+		parameters.append(
+			RequestParameter(OAUTH2_GRANT_TYPE, grantType.toUtf8()));
+		QByteArray payload = createQueryParameters(parameters);
+
+		PollServer* pollServer =
+			new PollServer(manager_, authRequest, payload, expiresIn, this);
+		if (params.contains(OAUTH2_INTERVAL)) {
+			bool ok = false;
+			int interval = params[OAUTH2_INTERVAL].toInt(&ok);
+			if (ok) {
+				pollServer->setInterval(interval);
+			}
+		}
+		connect(pollServer, &PollServer::verificationReceived, this,
+				&DeviceFlow::onVerificationReceived);
+		connect(pollServer, &PollServer::serverClosed, this,
+				&DeviceFlow::serverHasClosed);
+		setPollServer(pollServer);
+		pollServer->startPolling();
+	}
+
+	// Once the user completes the flow, update the internal state and report it
+	// to observers
+	void
+	DeviceFlow::onVerificationReceived(const QMap<QString, QString> response)
+	{
+		qDebug()
+			<< "DeviceFlow::onVerificationReceived: Emitting closeBrowser()";
+		emit closeBrowser();
+
+		if (response.contains("error")) {
+			qWarning()
+				<< "DeviceFlow::onVerificationReceived: Verification failed:"
+				<< response;
+			updateActivity(Activity::FailedHard);
+			return;
+		}
+
+		// Check for mandatory tokens
+		if (response.contains(OAUTH2_ACCESS_TOKEN)) {
+			qDebug() << "DeviceFlow::onVerificationReceived: Access token "
+						"returned for implicit or device flow";
+			setToken(response.value(OAUTH2_ACCESS_TOKEN));
+			if (response.contains(OAUTH2_EXPIRES_IN)) {
+				bool ok = false;
+				int expiresIn = response.value(OAUTH2_EXPIRES_IN).toInt(&ok);
+				if (ok) {
+					qDebug() << "DeviceFlow::onVerificationReceived: Token "
+								"expires in"
+							 << expiresIn << "seconds";
+					setExpires(
+						QDateTime::currentDateTimeUtc().addSecs(expiresIn));
+				}
+			}
+			if (response.contains(OAUTH2_REFRESH_TOKEN)) {
+				setRefreshToken(response.value(OAUTH2_REFRESH_TOKEN));
+			}
+			updateActivity(Activity::Succeeded);
+		} else {
+			qWarning() << "DeviceFlow::onVerificationReceived: Access token "
+						  "missing from response for implicit or device flow";
+			updateActivity(Activity::FailedHard);
+		}
+	}
+
+	// Or if the flow fails or the polling times out, update the internal state
+	// with error and report it to observers
+	void DeviceFlow::serverHasClosed(bool paramsfound)
+	{
+		if (!paramsfound) {
+			// server has probably timed out after receiving first response
+			updateActivity(Activity::FailedHard);
+		}
+		// poll server is not re-used for later auth requests
+		setPollServer(NULL);
+	}
+
+	void DeviceFlow::logout()
+	{
+		qDebug() << "DeviceFlow::unlink";
+		updateActivity(Activity::LoggingOut);
+		// FIXME: implement logout flows... if they exist
+		token_ = Token();
+		updateActivity(Activity::FailedHard);
+	}
+
+	QDateTime DeviceFlow::expires()
+	{
+		return token_.notAfter;
+	}
+	void DeviceFlow::setExpires(QDateTime v)
+	{
+		token_.notAfter = v;
+	}
+
+	QString DeviceFlow::refreshToken()
+	{
+		return token_.refresh_token;
+	}
+
+	void DeviceFlow::setRefreshToken(const QString& v)
+	{
+#ifndef NDEBUG
+		qDebug() << "DeviceFlow::setRefreshToken" << v << "...";
+#endif
+		token_.refresh_token = v;
+	}
+
+	namespace
+	{
+		QByteArray buildRequestBody(const QMap<QString, QString>& parameters)
+		{
+			QByteArray body;
+			bool first = true;
+			foreach (QString key, parameters.keys()) {
+				if (first) {
+					first = false;
+				} else {
+					body.append("&");
+				}
+				QString value = parameters.value(key);
+				body.append(QUrl::toPercentEncoding(key) +
+							QString("=").toUtf8() +
+							QUrl::toPercentEncoding(value));
+			}
+			return body;
+		}
+	} // namespace
+
+	bool DeviceFlow::refresh()
+	{
+		qDebug() << "DeviceFlow::refresh: Token: ..."
+				 << refreshToken().right(7);
+
+		updateActivity(Activity::Refreshing);
+
+		if (refreshToken().isEmpty()) {
+			qWarning() << "DeviceFlow::refresh: No refresh token";
+			onRefreshError(QNetworkReply::AuthenticationRequiredError, nullptr);
+			return false;
+		}
+		if (options_.accessTokenUrl.isEmpty()) {
+			qWarning() << "DeviceFlow::refresh: Refresh token URL not set";
+			onRefreshError(QNetworkReply::AuthenticationRequiredError, nullptr);
+			return false;
+		}
+
+		QNetworkRequest refreshRequest(options_.accessTokenUrl);
+		refreshRequest.setHeader(QNetworkRequest::ContentTypeHeader,
+								 MIME_TYPE_XFORM);
+		QMap<QString, QString> parameters;
+		parameters.insert(OAUTH2_CLIENT_ID, options_.clientIdentifier);
+		if (!options_.clientSecret.isEmpty()) {
+			parameters.insert(OAUTH2_CLIENT_SECRET, options_.clientSecret);
+		}
+		parameters.insert(OAUTH2_REFRESH_TOKEN, refreshToken());
+		parameters.insert(OAUTH2_GRANT_TYPE, OAUTH2_REFRESH_TOKEN);
+
+		QByteArray data = buildRequestBody(parameters);
+		QNetworkReply* refreshReply = manager_->post(refreshRequest, data);
+		timedReplies_.add(refreshReply);
+		connect(refreshReply, &QNetworkReply::finished, this,
+				&DeviceFlow::onRefreshFinished, Qt::QueuedConnection);
+		return true;
+	}
+
+	void DeviceFlow::onRefreshFinished()
+	{
+		QNetworkReply* refreshReply = qobject_cast<QNetworkReply*>(sender());
+
+		auto networkError = refreshReply->error();
+		if (networkError == QNetworkReply::NoError) {
+			QByteArray reply = refreshReply->readAll();
+			QVariantMap tokens = parseJsonResponse(reply);
+			setToken(tokens.value(OAUTH2_ACCESS_TOKEN).toString());
+			setExpires(QDateTime::currentDateTimeUtc().addSecs(
+				tokens.value(OAUTH2_EXPIRES_IN).toInt()));
+			QString refreshToken =
+				tokens.value(OAUTH2_REFRESH_TOKEN).toString();
+			if (!refreshToken.isEmpty()) {
+				setRefreshToken(refreshToken);
+			} else {
+				qDebug() << "No new refresh token. Keep the old one.";
+			}
+			timedReplies_.remove(refreshReply);
+			refreshReply->deleteLater();
+			updateActivity(Activity::Succeeded);
+			qDebug() << "New token expires in" << expires() << "seconds";
+		} else {
+			// FIXME: differentiate the error more here
+			onRefreshError(networkError, refreshReply);
+		}
+	}
+
+	void DeviceFlow::onRefreshError(QNetworkReply::NetworkError error,
+									QNetworkReply* refreshReply)
+	{
+		QString errorString = "No Reply";
+		if (refreshReply) {
+			timedReplies_.remove(refreshReply);
+			errorString = refreshReply->errorString();
+		}
+
+		switch (error) {
+			// used for invalid credentials and similar errors. Fall through.
+			case QNetworkReply::AuthenticationRequiredError:
+			case QNetworkReply::ContentAccessDenied:
+			case QNetworkReply::ContentOperationNotPermittedError:
+			case QNetworkReply::ProtocolInvalidOperationError:
+				updateActivity(Activity::FailedHard);
+				break;
+			case QNetworkReply::ContentGoneError: {
+				updateActivity(Activity::FailedGone);
+				break;
+			}
+			case QNetworkReply::TimeoutError:
+			case QNetworkReply::OperationCanceledError:
+			case QNetworkReply::SslHandshakeFailedError:
+			default:
+				updateActivity(Activity::FailedSoft);
+				return;
+		}
+		if (refreshReply) {
+			refreshReply->deleteLater();
+		}
+		qDebug() << "DeviceFlow::onRefreshFinished: Error" << (int)error
+				 << " - " << errorString;
+	}
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/src/JsonResponse.cpp b/meshmc/libraries/katabasis/src/JsonResponse.cpp
new file mode 100644
index 0000000000..8daee82ebb
--- /dev/null
+++ b/meshmc/libraries/katabasis/src/JsonResponse.cpp
@@ -0,0 +1,51 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "JsonResponse.h"
+
+#include <QByteArray>
+#include <QDebug>
+#include <QJsonDocument>
+#include <QJsonObject>
+
+namespace Katabasis
+{
+
+	QVariantMap parseJsonResponse(const QByteArray& data)
+	{
+		QJsonParseError err;
+		QJsonDocument doc = QJsonDocument::fromJson(data, &err);
+		if (err.error != QJsonParseError::NoError) {
+			qWarning() << "parseTokenResponse: Failed to parse token response "
+						  "due to err:"
+					   << err.errorString();
+			return QVariantMap();
+		}
+
+		if (!doc.isObject()) {
+			qWarning() << "parseTokenResponse: Token response is not an object";
+			return QVariantMap();
+		}
+
+		return doc.object().toVariantMap();
+	}
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/src/JsonResponse.h b/meshmc/libraries/katabasis/src/JsonResponse.h
new file mode 100644
index 0000000000..0662c8ff61
--- /dev/null
+++ b/meshmc/libraries/katabasis/src/JsonResponse.h
@@ -0,0 +1,34 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <QVariantMap>
+
+class QByteArray;
+
+namespace Katabasis
+{
+
+	/// Parse JSON data into a QVariantMap
+	QVariantMap parseJsonResponse(const QByteArray& data);
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/src/PollServer.cpp b/meshmc/libraries/katabasis/src/PollServer.cpp
new file mode 100644
index 0000000000..1c8556aa98
--- /dev/null
+++ b/meshmc/libraries/katabasis/src/PollServer.cpp
@@ -0,0 +1,147 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <QNetworkAccessManager>
+#include <QNetworkReply>
+
+#include "katabasis/PollServer.h"
+#include "JsonResponse.h"
+
+namespace
+{
+	QMap<QString, QString> toVerificationParams(const QVariantMap& map)
+	{
+		QMap<QString, QString> params;
+		for (QVariantMap::const_iterator i = map.constBegin();
+			 i != map.constEnd(); ++i) {
+			params[i.key()] = i.value().toString();
+		}
+		return params;
+	}
+} // namespace
+
+namespace Katabasis
+{
+
+	PollServer::PollServer(QNetworkAccessManager* manager,
+						   const QNetworkRequest& request,
+						   const QByteArray& payload, int expiresIn,
+						   QObject* parent)
+		: QObject(parent), manager_(manager), request_(request),
+		  payload_(payload), expiresIn_(expiresIn)
+	{
+		expirationTimer.setTimerType(Qt::VeryCoarseTimer);
+		expirationTimer.setInterval(expiresIn * 1000);
+		expirationTimer.setSingleShot(true);
+		connect(&expirationTimer, SIGNAL(timeout()), this,
+				SLOT(onExpiration()));
+		expirationTimer.start();
+
+		pollTimer.setTimerType(Qt::VeryCoarseTimer);
+		pollTimer.setInterval(5 * 1000);
+		pollTimer.setSingleShot(true);
+		connect(&pollTimer, SIGNAL(timeout()), this, SLOT(onPollTimeout()));
+	}
+
+	int PollServer::interval() const
+	{
+		return pollTimer.interval() / 1000;
+	}
+
+	void PollServer::setInterval(int interval)
+	{
+		pollTimer.setInterval(interval * 1000);
+	}
+
+	void PollServer::startPolling()
+	{
+		if (expirationTimer.isActive()) {
+			pollTimer.start();
+		}
+	}
+
+	void PollServer::onPollTimeout()
+	{
+		qDebug() << "PollServer::onPollTimeout: retrying";
+		QNetworkReply* reply = manager_->post(request_, payload_);
+		connect(reply, SIGNAL(finished()), this, SLOT(onReplyFinished()));
+	}
+
+	void PollServer::onExpiration()
+	{
+		pollTimer.stop();
+		emit serverClosed(false);
+	}
+
+	void PollServer::onReplyFinished()
+	{
+		QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
+
+		if (!reply) {
+			qDebug() << "PollServer::onReplyFinished: reply is null";
+			return;
+		}
+
+		QByteArray replyData = reply->readAll();
+		QMap<QString, QString> params =
+			toVerificationParams(parseJsonResponse(replyData));
+
+		// Dump replyData
+		// SENSITIVE DATA in RelWithDebInfo or Debug builds
+		// qDebug() << "PollServer::onReplyFinished: replyData\n";
+		// qDebug() << QString( replyData );
+
+		if (reply->error() == QNetworkReply::TimeoutError) {
+			// rfc8628#section-3.2
+			// "On encountering a connection timeout, clients MUST unilaterally
+			// reduce their polling frequency before retrying.  The use of an
+			// exponential backoff algorithm to achieve this, such as doubling
+			// the polling interval on each such connection timeout, is
+			// RECOMMENDED."
+			setInterval(interval() * 2);
+			pollTimer.start();
+		} else {
+			QString error = params.value("error");
+			if (error == "slow_down") {
+				// rfc8628#section-3.2
+				// "A variant of 'authorization_pending', the authorization
+				// request is still pending and polling should continue, but the
+				// interval MUST be increased by 5 seconds for this and all
+				// subsequent requests."
+				setInterval(interval() + 5);
+				pollTimer.start();
+			} else if (error == "authorization_pending") {
+				// keep trying - rfc8628#section-3.2
+				// "The authorization request is still pending as the end user
+				// hasn't yet completed the user-interaction steps
+				// (Section 3.3)."
+				pollTimer.start();
+			} else {
+				expirationTimer.stop();
+				emit serverClosed(true);
+				// let O2 handle the other cases
+				emit verificationReceived(params);
+			}
+		}
+		reply->deleteLater();
+	}
+
+} // namespace Katabasis
diff --git a/meshmc/libraries/katabasis/src/Reply.cpp b/meshmc/libraries/katabasis/src/Reply.cpp
new file mode 100644
index 0000000000..c19113ac50
--- /dev/null
+++ b/meshmc/libraries/katabasis/src/Reply.cpp
@@ -0,0 +1,96 @@
+/* SPDX-FileCopyrightText: 2026 Project Tick
+ * SPDX-FileContributor: Project Tick
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ *
+ *   MeshMC - A Custom Launcher for Minecraft
+ *   Copyright (C) 2026 Project Tick
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <QTimer>
+#include <QNetworkReply>
+
+#include "katabasis/Reply.h"
+
+namespace Katabasis
+{
+
+	Reply::Reply(QNetworkReply* r, int timeOut, QObject* parent)
+		: QTimer(parent), reply(r)
+	{
+		setSingleShot(true);
+		connect(this, &Reply::timeout, this, &Reply::onTimeOut,
+				Qt::QueuedConnection);
+		start(timeOut);
+	}
+
+	void Reply::onTimeOut()
+	{
+		timedOut = true;
+		reply->abort();
+	}
+
+	// ----------------------------
+
+	ReplyList::~ReplyList()
+	{
+		foreach (Reply* timedReply, replies_) {
+			delete timedReply;
+		}
+	}
+
+	void ReplyList::add(QNetworkReply* reply, int timeOut)
+	{
+		if (reply && ignoreSslErrors()) {
+			reply->ignoreSslErrors();
+		}
+		add(new Reply(reply, timeOut));
+	}
+
+	void ReplyList::add(Reply* reply)
+	{
+		replies_.append(reply);
+	}
+
+	void ReplyList::remove(QNetworkReply* reply)
+	{
+		Reply* o2Reply = find(reply);
+		if (o2Reply) {
+			o2Reply->stop();
+			(void)replies_.removeOne(o2Reply);
+		}
+	}
+
+	Reply* ReplyList::find(QNetworkReply* reply)
+	{
+		foreach (Reply* timedReply, replies_) {
+			if (timedReply->reply == reply) {
+				return timedReply;
+			}
+		}
+		return 0;
+	}
+
+	bool ReplyList::ignoreSslErrors()
+	{
+		return ignoreSslErrors_;
+	}
+
+	void ReplyList::setIgnoreSslErrors(bool ignoreSslErrors)
+	{
+		ignoreSslErrors_ = ignoreSslErrors;
+	}
+
+} // namespace Katabasis