diff --git a/Cargo.toml b/Cargo.toml
index 0a74905..d771507 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,8 +1,73 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 # Cargo.toml
 #
-# Workspace manifest for the Noctua project.
+# Noctua COSMIC desktop application
 
-[workspace]
-members = ["core", "ui"]
-resolver = "2"
+[package]
+name = "noctua"
+version = "0.1.0"
+edition = "2021"
+description = "Noctua – a document viewer for the COSMIC™ desktop"
+repository = "https://codeberg.org/wfx/noctua"
+authors = ["Wolfgang Morawetz <wfx@mailbox.org>"]
+license = "GPL-3.0-or-later"
+
+[features]
+default = ["image", "vector", "portable"]
+image = ["dep:image", "dep:kamadak-exif"]
+vector = ["dep:resvg"]
+portable = ["dep:pdfium-render"]
+full = ["image", "vector", "portable"]
+
+[dependencies]
+# Serialization
+serde = { version = "1", features = ["derive"] }
+ron = "0.8"
+
+# Feature-gated document backends
+image = { version = "0.25", optional = true }
+kamadak-exif = { version = "0.5", optional = true }
+pdfium-render = { version = "0.8", optional = true }
+resvg = { version = "0.45", optional = true }
+
+# Logging
+log = "0.4"
+env_logger = "0.11"
+
+# i18n / localization
+i18n-embed = { version = "0.16", features = [
+    "fluent-system",
+    "desktop-requester",
+] }
+i18n-embed-fl = "0.10"
+
+# Resource embedding
+rust-embed = "8"
+
+# Open files/URLs with the system default application
+open = "5"
+
+# Thumbnail cache (freedesktop.org spec)
+dirs = "5.0"
+md5 = "0.7"
+png = "0.17"
+
+# CLI argument parsing
+clap = { version = "4", features = ["derive"] }
+
+# Async runtime (required by libcosmic)
+tokio = { version = "1", features = ["rt", "rt-multi-thread", "macros"] }
+
+[dependencies.libcosmic]
+git = "https://github.com/pop-os/libcosmic.git"
+features = [
+    "a11y",
+    "about",
+    "dbus-config",
+    "multi-window",
+    "single-instance",
+    "tokio",
+    "winit",
+    "wayland",
+    "wgpu",
+]
diff --git a/core/Cargo.toml b/core/Cargo.toml
deleted file mode 100644
index d582fe8..0000000
--- a/core/Cargo.toml
+++ /dev/null
@@ -1,48 +0,0 @@
-# SPDX-License-Identifier: GPL-3.0-or-later
-# core/Cargo.toml
-#
-# Core library crate – no UI dependencies.
-
-[package]
-name = "noctua_core"
-version = "0.1.0"
-edition = "2021"
-description = "Document core library for the Noctua viewer"
-repository = "https://codeberg.org/wfx/noctua"
-authors = ["Wolfgang Morawetz <wfx@mailbox.org>"]
-license = "GPL-3.0-or-later"
-
-[lib]
-name = "noctua_core"
-path = "src/lib.rs"
-
-[features]
-default = ["image", "vector", "portable"]
-image = ["dep:image", "dep:kamadak-exif"]
-vector = ["dep:resvg"]
-portable = ["dep:pdfium-render"]
-full = ["image", "vector", "portable"]
-
-[dependencies]
-# Serialization
-serde = { version = "1", features = ["derive"] }
-ron = "0.8"
-
-# Feature-gated document backends
-image = { version = "0.25", optional = true }
-kamadak-exif = { version = "0.5", optional = true }
-pdfium-render = { version = "0.8", optional = true }
-resvg = { version = "0.45", optional = true }
-
-# Logging interface
-log = "0.4"
-
-# Thumbnail cache (freedesktop.org spec)
-dirs = "5.0"
-md5 = "0.7"
-png = "0.17"
-
-[dev-dependencies]
-# CLI test harness (examples/cli.rs only)
-clap = { version = "4", features = ["derive"] }
-env_logger = "0.11"
diff --git a/core/src/lib.rs b/core/src/lib.rs
deleted file mode 100644
index b337937..0000000
--- a/core/src/lib.rs
+++ /dev/null
@@ -1,14 +0,0 @@
-// SPDX-License-Identifier: GPL-3.0-or-later
-// src/lib.rs
-//
-// Public API of the noctua_core library.
-
-pub mod error;
-
-pub mod document;
-pub mod render;
-
-pub use document::command::DocumentCommand;
-pub use document::manager::DocumentManager;
-pub use document::session::SessionCommand;
-pub use document::types::RawImage;
diff --git a/justfile b/justfile
index c04c9d0..65263c9 100644
--- a/justfile
+++ b/justfile
@@ -60,13 +60,9 @@ check-json: (check '--message-format=json')
 test *args:
     cargo test --workspace {{args}}
 
-# Runs the COSMIC UI application
+# Runs the application (no args = COSMIC UI, with args = CLI mode)
 run *args:
-    env RUST_BACKTRACE=full cargo run --release -p noctua_ui {{args}}
-
-# Runs the CLI test harness (core only, no UI deps)
-run-cli *args:
-    env RUST_BACKTRACE=full cargo run --example cli -p noctua_core {{args}}
+    env RUST_BACKTRACE=full cargo run --release {{args}}
 
 # Installs files
 install:
diff --git a/core/src/document/command.rs b/src/document/command.rs
similarity index 100%
rename from core/src/document/command.rs
rename to src/document/command.rs
diff --git a/core/src/document/loader.rs b/src/document/loader.rs
similarity index 100%
rename from core/src/document/loader.rs
rename to src/document/loader.rs
diff --git a/core/src/document/manager.rs b/src/document/manager.rs
similarity index 100%
rename from core/src/document/manager.rs
rename to src/document/manager.rs
diff --git a/core/src/document/mod.rs b/src/document/mod.rs
similarity index 87%
rename from core/src/document/mod.rs
rename to src/document/mod.rs
index c719136..f620821 100644
--- a/core/src/document/mod.rs
+++ b/src/document/mod.rs
@@ -14,7 +14,7 @@ use self::model::{PortableModel, RasterModel, VectorModel};
 
 /// The decoded content of a loaded document.
 ///
-/// This enum is internal to `noctua_core`. The UI only ever sees a `RawImage`
+/// This enum is internal to Noctua. The UI only ever sees a `RawImage`
 /// produced by the render subsystem – it never matches on this type.
 #[derive(Debug)]
 pub enum DocumentContent {
diff --git a/core/src/document/model/mod.rs b/src/document/model/mod.rs
similarity index 100%
rename from core/src/document/model/mod.rs
rename to src/document/model/mod.rs
diff --git a/core/src/document/model/portable.rs b/src/document/model/portable.rs
similarity index 100%
rename from core/src/document/model/portable.rs
rename to src/document/model/portable.rs
diff --git a/core/src/document/model/raster.rs b/src/document/model/raster.rs
similarity index 100%
rename from core/src/document/model/raster.rs
rename to src/document/model/raster.rs
diff --git a/core/src/document/model/vector.rs b/src/document/model/vector.rs
similarity index 100%
rename from core/src/document/model/vector.rs
rename to src/document/model/vector.rs
diff --git a/core/src/document/session/command.rs b/src/document/session/command.rs
similarity index 100%
rename from core/src/document/session/command.rs
rename to src/document/session/command.rs
diff --git a/core/src/document/session/data.rs b/src/document/session/data.rs
similarity index 100%
rename from core/src/document/session/data.rs
rename to src/document/session/data.rs
diff --git a/core/src/document/session/mod.rs b/src/document/session/mod.rs
similarity index 67%
rename from core/src/document/session/mod.rs
rename to src/document/session/mod.rs
index 1e82946..5d25ca6 100644
--- a/core/src/document/session/mod.rs
+++ b/src/document/session/mod.rs
@@ -6,6 +6,3 @@
 pub mod command;
 pub mod data;
 pub mod store;
-
-pub use command::SessionCommand;
-pub use data::{CollectionKind, SessionData, SessionItem};
diff --git a/core/src/document/session/store.rs b/src/document/session/store.rs
similarity index 100%
rename from core/src/document/session/store.rs
rename to src/document/session/store.rs
diff --git a/core/src/document/types/image.rs b/src/document/types/image.rs
similarity index 100%
rename from core/src/document/types/image.rs
rename to src/document/types/image.rs
diff --git a/core/src/document/types/layout.rs b/src/document/types/layout.rs
similarity index 100%
rename from core/src/document/types/layout.rs
rename to src/document/types/layout.rs
diff --git a/core/src/document/types/mod.rs b/src/document/types/mod.rs
similarity index 91%
rename from core/src/document/types/mod.rs
rename to src/document/types/mod.rs
index eae29b1..7a5f836 100644
--- a/core/src/document/types/mod.rs
+++ b/src/document/types/mod.rs
@@ -7,6 +7,5 @@ pub mod image;
 pub mod layout;
 pub mod viewbox;
 
-pub use image::RawImage;
 pub use layout::PageLayout;
 pub use viewbox::ViewBox;
diff --git a/core/src/document/types/viewbox.rs b/src/document/types/viewbox.rs
similarity index 100%
rename from core/src/document/types/viewbox.rs
rename to src/document/types/viewbox.rs
diff --git a/core/src/error.rs b/src/error.rs
similarity index 86%
rename from core/src/error.rs
rename to src/error.rs
index c17566b..402a70a 100644
--- a/core/src/error.rs
+++ b/src/error.rs
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 // src/error.rs
 //
-// Central error and result types for noctua_core.
+// Central error and result types for Noctua.
 
 use std::fmt;
 
@@ -13,8 +13,6 @@ pub enum Error {
     NotFound(String),
     /// The file format or operation is not supported.
     Unsupported(String),
-    /// A rendering operation failed.
-    Render(String),
     /// A session could not be loaded or saved.
     Session(String),
     /// An underlying I/O error.
@@ -26,7 +24,6 @@ impl fmt::Display for Error {
         match self {
             Error::NotFound(msg) => write!(f, "Not found: {msg}"),
             Error::Unsupported(msg) => write!(f, "Unsupported: {msg}"),
-            Error::Render(msg) => write!(f, "Render error: {msg}"),
             Error::Session(msg) => write!(f, "Session error: {msg}"),
             Error::Io(err) => write!(f, "I/O error: {err}"),
         }
diff --git a/core/examples/cli.rs b/src/main.rs
similarity index 72%
rename from core/examples/cli.rs
rename to src/main.rs
index 7d4edb3..da53220 100644
--- a/core/examples/cli.rs
+++ b/src/main.rs
@@ -1,13 +1,17 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
-// examples/cli.rs
+// src/main.rs
 //
-// CLI test harness for the noctua_core document foundation.
+// Entry point for the Noctua COSMIC application.
 
-use clap::{ArgGroup, Parser};
-use noctua_core::document::manager::{DocumentManager, DocumentState};
-use noctua_core::document::session::command::SessionCommand;
-use noctua_core::document::session::data::{CollectionKind, SessionData};
-use std::path::PathBuf;
+mod document;
+mod error;
+mod render;
+
+use clap::Parser;
+use document::manager::{DocumentManager, DocumentState};
+use document::session::command::SessionCommand;
+use document::session::data::{CollectionKind, SessionData};
+use std::path::{Path, PathBuf};
 
 // ANSI helpers
 
@@ -87,50 +91,45 @@ fn print_active_session(mgr: &DocumentManager) {
 }
 
 #[derive(Parser, Debug)]
-#[command(
-    name = "noctua",
-    about = "A document viewer for the COSMIC desktop",
-    group(
-        ArgGroup::new("source")
-            .required(true)
-            .args(["open_document", "open_directory", "open_session"])
-    )
-)]
-struct Opt {
+#[command(name = "noctua", about = "A document viewer for the COSMIC desktop")]
+struct Args {
     /// Open a document (raster, vector, portable)
-    #[arg(long, value_name = "PATH")]
-    open_document: Option<PathBuf>,
+    #[arg(long = "open-document", value_name = "PATH")]
+    document: Option<PathBuf>,
 
     /// Open a directory
-    #[arg(long, value_name = "PATH")]
-    open_directory: Option<PathBuf>,
+    #[arg(long = "open-directory", value_name = "PATH")]
+    directory: Option<PathBuf>,
 
     /// Open a session file (.ron)
-    #[arg(long, value_name = "PATH")]
-    open_session: Option<PathBuf>,
+    #[arg(long = "open-session", value_name = "PATH")]
+    session: Option<PathBuf>,
 }
 
 fn main() {
     env_logger::init();
 
-    let cli = Opt::parse();
-    let mut mgr = DocumentManager::new();
+    let args = Args::parse();
 
-    // Open source
+    if args.document.is_none() && args.directory.is_none() && args.session.is_none() {
+        // TODO: Launch COSMIC UI.
+        return;
+    }
 
-    heading("Opening source");
+    run_cli(args);
+}
 
-    if let Some(path) = cli.open_session {
+fn open_source(mgr: &mut DocumentManager, args: Args) {
+    if let Some(path) = args.session {
         exec(
-            &mut mgr,
+            mgr,
             "Open session file",
             SessionCommand::OpenSession { path },
         );
-    } else if let Some(path) = cli.open_document {
+    } else if let Some(path) = args.document {
         let dir = path
             .parent()
-            .map(|p| p.to_path_buf())
-            .unwrap_or_else(|| PathBuf::from("."));
+            .map_or_else(|| PathBuf::from("."), Path::to_path_buf);
 
         let session_name = dir
             .file_name()
@@ -139,30 +138,30 @@ fn main() {
             .to_string();
 
         exec(
-            &mut mgr,
+            mgr,
             &format!("New session '{session_name}'"),
             SessionCommand::NewSession {
                 name: session_name.clone(),
             },
         );
         exec(
-            &mut mgr,
+            mgr,
             &format!("Select '{session_name}'"),
             SessionCommand::SelectSession {
                 name: session_name.clone(),
             },
         );
         exec(
-            &mut mgr,
+            mgr,
             &format!("Add directory {}", dir.display()),
             SessionCommand::AddDirectoryToSession { dir },
         );
         exec(
-            &mut mgr,
+            mgr,
             &format!("Add document {}", path.display()),
             SessionCommand::AddDocumentToSession { path },
         );
-    } else if let Some(path) = cli.open_directory {
+    } else if let Some(path) = args.directory {
         let session_name = path
             .file_name()
             .and_then(|n| n.to_str())
@@ -170,69 +169,44 @@ fn main() {
             .to_string();
 
         exec(
-            &mut mgr,
+            mgr,
             &format!("New session '{session_name}'"),
             SessionCommand::NewSession {
                 name: session_name.clone(),
             },
         );
         exec(
-            &mut mgr,
+            mgr,
             &format!("Select '{session_name}'"),
             SessionCommand::SelectSession {
                 name: session_name.clone(),
             },
         );
         exec(
-            &mut mgr,
+            mgr,
             &format!("Add directory {}", path.display()),
             SessionCommand::AddDirectoryToSession { dir: path },
         );
     }
+}
 
-    // State summary
-
-    heading("State after open");
-
-    match &mgr.state {
-        DocumentState::Empty => info("No document loaded"),
-        DocumentState::Loading => info("Loading…"),
-        DocumentState::Error(e) => err(&format!("{e}")),
-        DocumentState::Loaded(_) => ok("Document loaded"),
-    }
-
-    let active_name = match mgr.active_session().map(|s| s.name.clone()) {
-        Some(n) => n,
-        None => {
-            info("No active session – nothing more to test.");
-            return;
-        }
-    };
-
-    print_active_session(&mgr);
-
-    // Navigation
-
+fn run_navigation_test(mgr: &mut DocumentManager) {
     heading("Navigation");
 
-    exec(&mut mgr, "NextDocument", SessionCommand::NextDocument);
+    exec(mgr, "NextDocument", SessionCommand::NextDocument);
     ok(&format!(
         "After NextDocument       → index {:?}",
         mgr.active_document_index()
     ));
 
-    exec(
-        &mut mgr,
-        "PreviousDocument",
-        SessionCommand::PreviousDocument,
-    );
+    exec(mgr, "PreviousDocument", SessionCommand::PreviousDocument);
     ok(&format!(
         "After PreviousDocument   → index {:?}",
         mgr.active_document_index()
     ));
 
     exec(
-        &mut mgr,
+        mgr,
         "SelectDocument { index: 0 }",
         SessionCommand::SelectDocument { index: 0 },
     );
@@ -241,42 +215,36 @@ fn main() {
         mgr.active_document_index()
     ));
 
-    // Move operations
-
     heading("Move operations");
 
     step("Before MoveDocumentDown:");
-    print_active_session(&mgr);
+    print_active_session(mgr);
 
-    exec(
-        &mut mgr,
-        "MoveDocumentDown",
-        SessionCommand::MoveDocumentDown,
-    );
+    exec(mgr, "MoveDocumentDown", SessionCommand::MoveDocumentDown);
     ok(&format!(
         "After MoveDocumentDown   → index {:?}",
         mgr.active_document_index()
     ));
 
-    exec(&mut mgr, "MoveDocumentUp", SessionCommand::MoveDocumentUp);
+    exec(mgr, "MoveDocumentUp", SessionCommand::MoveDocumentUp);
     ok(&format!(
         "After MoveDocumentUp     → index {:?}",
         mgr.active_document_index()
     ));
+}
 
-    // Copy / Paste
-
+fn run_copy_paste_test(mgr: &mut DocumentManager, active_name: &str) {
     heading("Copy / Paste");
 
     exec(
-        &mut mgr,
+        mgr,
         "New session 'Favorites'",
         SessionCommand::NewSession {
             name: "Favorites".to_string(),
         },
     );
     exec(
-        &mut mgr,
+        mgr,
         "New session 'Workspace'",
         SessionCommand::NewSession {
             name: "Workspace".to_string(),
@@ -288,61 +256,56 @@ fn main() {
         print_session(session, None);
     }
 
-    // SelectSession source → SelectDocument → CopyDocument → SelectSession target → PasteDocument
     exec(
-        &mut mgr,
+        mgr,
         &format!("SelectSession '{active_name}'"),
         SessionCommand::SelectSession {
-            name: active_name.clone(),
+            name: active_name.to_string(),
         },
     );
     exec(
-        &mut mgr,
+        mgr,
         "SelectDocument { index: 0 }",
         SessionCommand::SelectDocument { index: 0 },
     );
-    exec(&mut mgr, "CopyDocument", SessionCommand::CopyDocument);
+    exec(mgr, "CopyDocument", SessionCommand::CopyDocument);
     exec(
-        &mut mgr,
+        mgr,
         "SelectSession 'Favorites'",
         SessionCommand::SelectSession {
             name: "Favorites".to_string(),
         },
     );
-    exec(&mut mgr, "PasteDocument", SessionCommand::PasteDocument);
+    exec(mgr, "PasteDocument", SessionCommand::PasteDocument);
 
     step("Favorites after paste:");
-    print_active_session(&mgr);
-
-    // Move pasted item to front via MoveDocumentTo
+    print_active_session(mgr);
 
     exec(
-        &mut mgr,
+        mgr,
         "MoveDocumentTo { index: 0 }",
         SessionCommand::MoveDocumentTo { index: 0 },
     );
     step("Favorites after MoveDocumentTo(0):");
-    print_active_session(&mgr);
+    print_active_session(mgr);
 
-    // Remove active document
-
-    exec(&mut mgr, "RemoveDocument", SessionCommand::RemoveDocument);
+    exec(mgr, "RemoveDocument", SessionCommand::RemoveDocument);
     step("Favorites after RemoveDocument:");
-    print_active_session(&mgr);
-
-    // Session operations
+    print_active_session(mgr);
+}
 
+fn run_session_test(mgr: &mut DocumentManager, active_name: &str) {
     heading("Session operations");
 
     exec(
-        &mut mgr,
+        mgr,
         &format!("SelectSession '{active_name}'"),
         SessionCommand::SelectSession {
-            name: active_name.clone(),
+            name: active_name.to_string(),
         },
     );
     exec(
-        &mut mgr,
+        mgr,
         "DuplicateSession 'Snapshot'",
         SessionCommand::DuplicateSession {
             new_name: "Snapshot".to_string(),
@@ -355,14 +318,14 @@ fn main() {
     }
 
     exec(
-        &mut mgr,
+        mgr,
         "SelectSession 'Workspace'",
         SessionCommand::SelectSession {
             name: "Workspace".to_string(),
         },
     );
     exec(
-        &mut mgr,
+        mgr,
         "RenameSession 'Archive'",
         SessionCommand::RenameSession {
             name: "Archive".to_string(),
@@ -371,9 +334,7 @@ fn main() {
 
     step("All sessions after rename:");
     for session in mgr.sessions() {
-        let is_active = mgr
-            .active_session()
-            .map_or(false, |a| a.name == session.name);
+        let is_active = mgr.active_session().is_some_and(|a| a.name == session.name);
         let marker = if is_active {
             format!("{GREEN}*{RESET}")
         } else {
@@ -383,7 +344,7 @@ fn main() {
     }
 
     exec(
-        &mut mgr,
+        mgr,
         "CloseSession (closes 'Archive')",
         SessionCommand::CloseSession,
     );
@@ -392,6 +353,33 @@ fn main() {
     for session in mgr.sessions() {
         println!("    {DIM}-{RESET} {}", session.name);
     }
+}
+
+fn run_cli(args: Args) {
+    let mut mgr = DocumentManager::new();
+
+    heading("Opening source");
+    open_source(&mut mgr, args);
+
+    heading("State after open");
+
+    match &mgr.state {
+        DocumentState::Empty => info("No document loaded"),
+        DocumentState::Loading => info("Loading…"),
+        DocumentState::Error(e) => err(&format!("{e}")),
+        DocumentState::Loaded(_) => ok("Document loaded"),
+    }
+
+    let Some(active_name) = mgr.active_session().map(|s| s.name.clone()) else {
+        info("No active session – nothing more to test.");
+        return;
+    };
+
+    print_active_session(&mgr);
+
+    run_navigation_test(&mut mgr);
+    run_copy_paste_test(&mut mgr, &active_name);
+    run_session_test(&mut mgr, &active_name);
 
     heading("Done");
 }
diff --git a/core/src/render/converter.rs b/src/render/converter.rs
similarity index 100%
rename from core/src/render/converter.rs
rename to src/render/converter.rs
diff --git a/core/src/render/mod.rs b/src/render/mod.rs
similarity index 100%
rename from core/src/render/mod.rs
rename to src/render/mod.rs
diff --git a/core/src/render/thumbnail.rs b/src/render/thumbnail.rs
similarity index 100%
rename from core/src/render/thumbnail.rs
rename to src/render/thumbnail.rs
diff --git a/ui/Cargo.toml b/ui/Cargo.toml
deleted file mode 100644
index 98bb336..0000000
--- a/ui/Cargo.toml
+++ /dev/null
@@ -1,50 +0,0 @@
-# SPDX-License-Identifier: GPL-3.0-or-later
-# ui/Cargo.toml
-#
-# Binary crate for the Noctua COSMIC desktop application.
-
-[package]
-name = "noctua"
-version = "0.1.0"
-edition = "2021"
-description = "Noctua – a document viewer for the COSMIC™ desktop"
-repository = "https://codeberg.org/wfx/noctua"
-authors = ["Wolfgang Morawetz <wfx@mailbox.org>"]
-license = "GPL-3.0-or-later"
-
-[dependencies]
-noctua_core = { path = "../core" }
-
-# Logging
-log = "0.4"
-env_logger = "0.11"
-
-# i18n / localization
-i18n-embed = { version = "0.16", features = [
-    "fluent-system",
-    "desktop-requester",
-] }
-i18n-embed-fl = "0.10"
-
-# Resource embedding
-rust-embed = "8"
-
-# Open files/URLs with the system default application
-open = "5"
-
-# Async runtime (required by libcosmic)
-tokio = { version = "1", features = ["rt", "rt-multi-thread", "macros"] }
-
-[dependencies.libcosmic]
-git = "https://github.com/pop-os/libcosmic.git"
-features = [
-    "a11y",
-    "about",
-    "dbus-config",
-    "multi-window",
-    "single-instance",
-    "tokio",
-    "winit",
-    "wayland",
-    "wgpu",
-]
diff --git a/ui/src/main.rs b/ui/src/main.rs
deleted file mode 100644
index 7269760..0000000
--- a/ui/src/main.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-// SPDX-License-Identifier: GPL-3.0-or-later
-// src/main.rs
-//
-// Entry point for the Noctua COSMIC application.
-
-fn main() {
-    // TODO: Initialize the COSMIC application.
-}