diff --git a/src-tauri/icons/icon.ico b/src-tauri/icons/icon.ico
new file mode 100644
index 0000000..a34a461
Binary files /dev/null and b/src-tauri/icons/icon.ico differ
diff --git a/src-tauri/src/audio/mod.rs b/src-tauri/src/audio/mod.rs
new file mode 100644
index 0000000..31a5ac6
--- /dev/null
+++ b/src-tauri/src/audio/mod.rs
@@ -0,0 +1,61 @@
+use serde::{Deserialize, Serialize};
+
+use crate::error::{AppError, AppResult};
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum RecordingStatus {
+    Idle,
+    Recording,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct RecordingSession {
+    pub status: RecordingStatus,
+    pub sequence: u64,
+}
+
+impl Default for RecordingSession {
+    fn default() -> Self {
+        Self {
+            status: RecordingStatus::Idle,
+            sequence: 0,
+        }
+    }
+}
+
+impl RecordingSession {
+    pub fn start(&mut self) -> AppResult<()> {
+        if self.status == RecordingStatus::Recording {
+            return Err(AppError::RecordingAlreadyActive);
+        }
+
+        self.sequence += 1;
+        self.status = RecordingStatus::Recording;
+        Ok(())
+    }
+
+    pub fn stop(&mut self) -> AppResult<u64> {
+        if self.status == RecordingStatus::Idle {
+            return Err(AppError::NoActiveRecording);
+        }
+
+        self.status = RecordingStatus::Idle;
+        Ok(self.sequence)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn recording_session_requires_start_before_stop() {
+        let mut session = RecordingSession::default();
+
+        assert_eq!(session.stop(), Err(AppError::NoActiveRecording));
+        session.start().expect("start should work");
+        assert_eq!(session.stop(), Ok(1));
+    }
+}
diff --git a/src-tauri/src/error.rs b/src-tauri/src/error.rs
new file mode 100644
index 0000000..c5cc2c0
--- /dev/null
+++ b/src-tauri/src/error.rs
@@ -0,0 +1,27 @@
+use serde::Serialize;
+use thiserror::Error;
+
+pub type AppResult<T> = Result<T, AppError>;
+
+#[derive(Debug, Error, Serialize, Clone, PartialEq, Eq)]
+#[serde(tag = "code", content = "message")]
+pub enum AppError {
+    #[error("modelo offline não instalado: {0}")]
+    ModelNotInstalled(String),
+    #[error("sidecar CrispASR não configurado")]
+    SidecarNotConfigured,
+    #[error("gravação já está em andamento")]
+    RecordingAlreadyActive,
+    #[error("nenhuma gravação ativa")]
+    NoActiveRecording,
+    #[error("operação ainda não suportada neste ambiente: {0}")]
+    Unsupported(String),
+    #[error("erro de configuração: {0}")]
+    Configuration(String),
+}
+
+impl From<AppError> for String {
+    fn from(value: AppError) -> Self {
+        value.to_string()
+    }
+}
diff --git a/src-tauri/src/injection/mod.rs b/src-tauri/src/injection/mod.rs
new file mode 100644
index 0000000..29c969a
--- /dev/null
+++ b/src-tauri/src/injection/mod.rs
@@ -0,0 +1,116 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct FocusTarget {
+    pub platform: Platform,
+    pub display_server: DisplayServer,
+    pub window_title: Option<String>,
+    pub process_name: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum Platform {
+    Windows,
+    Linux,
+    Unknown,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum DisplayServer {
+    Windows,
+    X11,
+    Wayland,
+    Unknown,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum InsertCapability {
+    Full,
+    Partial,
+    Unsupported,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum InsertMethod {
+    ClipboardPaste,
+    KeyTyping,
+    ManualCopy,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct InsertRequest {
+    pub text: String,
+    pub target: Option<FocusTarget>,
+    pub method: InsertMethod,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct InsertResult {
+    pub capability: InsertCapability,
+    pub method_used: InsertMethod,
+    pub message: String,
+}
+
+pub trait TextInjector {
+    fn can_insert(&self, target: Option<&FocusTarget>) -> InsertCapability;
+    fn insert_text(&self, request: InsertRequest) -> InsertResult;
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct FallbackInjector;
+
+impl TextInjector for FallbackInjector {
+    fn can_insert(&self, target: Option<&FocusTarget>) -> InsertCapability {
+        match target.map(|target| &target.display_server) {
+            Some(DisplayServer::Windows | DisplayServer::X11) => InsertCapability::Full,
+            Some(DisplayServer::Wayland) => InsertCapability::Partial,
+            _ => InsertCapability::Unsupported,
+        }
+    }
+
+    fn insert_text(&self, request: InsertRequest) -> InsertResult {
+        let capability = self.can_insert(request.target.as_ref());
+        let message = match capability {
+            InsertCapability::Full => {
+                "Inserção automática preparada; implementação nativa será conectada ao adaptador."
+            }
+            InsertCapability::Partial => {
+                "Wayland pode bloquear automação. Texto mantido para cópia manual com Ctrl+V."
+            }
+            InsertCapability::Unsupported => {
+                "Destino não confiável. Copie o texto manualmente a partir do modal."
+            }
+        };
+
+        InsertResult {
+            capability,
+            method_used: request.method,
+            message: message.to_string(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn wayland_reports_partial_insert_capability() {
+        let injector = FallbackInjector;
+        let target = FocusTarget {
+            platform: Platform::Linux,
+            display_server: DisplayServer::Wayland,
+            window_title: Some("Editor".to_string()),
+            process_name: Some("app".to_string()),
+        };
+
+        assert_eq!(injector.can_insert(Some(&target)), InsertCapability::Partial);
+    }
+}
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 7b4614e..39f56de 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -1,4 +1,10 @@
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
+pub mod audio;
+pub mod error;
+pub mod injection;
+pub mod models;
+pub mod settings;
+pub mod transcription;
 pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_opener::init())
diff --git a/src-tauri/src/settings/mod.rs b/src-tauri/src/settings/mod.rs
new file mode 100644
index 0000000..b8c76db
--- /dev/null
+++ b/src-tauri/src/settings/mod.rs
@@ -0,0 +1,105 @@
+use serde::{Deserialize, Serialize};
+
+use crate::models::DEFAULT_MODEL_ID;
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct AppSettings {
+    pub transcription: TranscriptionSettings,
+    pub insertion: InsertionSettings,
+    pub storage: StorageSettings,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct TranscriptionSettings {
+    pub mode: TranscriptionMode,
+    pub model_id: String,
+    pub language: Option<String>,
+    pub openai_compatible: OpenAiCompatibleSettings,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum TranscriptionMode {
+    LocalFirst,
+    ApiOnly,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct OpenAiCompatibleSettings {
+    pub endpoint: String,
+    pub api_key_configured: bool,
+    pub model: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct InsertionSettings {
+    pub method: InsertionMethod,
+    pub restore_clipboard: bool,
+    pub wayland_manual_fallback: bool,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum InsertionMethod {
+    ClipboardPaste,
+    KeyTyping,
+    ManualCopy,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct StorageSettings {
+    pub keep_audio: bool,
+    pub audio_format: AudioFormat,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "lowercase")]
+pub enum AudioFormat {
+    Wav,
+    Ogg,
+    Mp3,
+}
+
+impl Default for AppSettings {
+    fn default() -> Self {
+        Self {
+            transcription: TranscriptionSettings {
+                mode: TranscriptionMode::LocalFirst,
+                model_id: DEFAULT_MODEL_ID.to_string(),
+                language: None,
+                openai_compatible: OpenAiCompatibleSettings {
+                    endpoint: "https://api.openai.com/v1/audio/transcriptions".to_string(),
+                    api_key_configured: false,
+                    model: "whisper-1".to_string(),
+                },
+            },
+            insertion: InsertionSettings {
+                method: InsertionMethod::ClipboardPaste,
+                restore_clipboard: true,
+                wayland_manual_fallback: true,
+            },
+            storage: StorageSettings {
+                keep_audio: false,
+                audio_format: AudioFormat::Wav,
+            },
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn default_language_is_optional_for_auto_detecting_model() {
+        let settings = AppSettings::default();
+
+        assert_eq!(settings.transcription.language, None);
+        assert_eq!(settings.transcription.mode, TranscriptionMode::LocalFirst);
+    }
+}
diff --git a/src-tauri/src/transcription/crispasr.rs b/src-tauri/src/transcription/crispasr.rs
new file mode 100644
index 0000000..01068ad
--- /dev/null
+++ b/src-tauri/src/transcription/crispasr.rs
@@ -0,0 +1,80 @@
+use std::path::PathBuf;
+
+use serde::{Deserialize, Serialize};
+
+use crate::error::{AppError, AppResult};
+
+use super::{Transcriber, TranscriptionInput, TranscriptionResult};
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct CrispAsrConfig {
+    pub sidecar_name: Option<String>,
+    pub model_path: Option<PathBuf>,
+}
+
+#[derive(Debug, Clone)]
+pub struct CrispAsrTranscriber {
+    config: CrispAsrConfig,
+}
+
+impl CrispAsrTranscriber {
+    pub fn new(config: CrispAsrConfig) -> Self {
+        Self { config }
+    }
+
+    pub fn config(&self) -> &CrispAsrConfig {
+        &self.config
+    }
+}
+
+impl Transcriber for CrispAsrTranscriber {
+    fn transcribe(&self, input: TranscriptionInput) -> AppResult<TranscriptionResult> {
+        let Some(model_path) = &self.config.model_path else {
+            return Err(AppError::ModelNotInstalled(input.options.model_id));
+        };
+
+        if self.config.sidecar_name.is_none() {
+            return Err(AppError::SidecarNotConfigured);
+        }
+
+        Ok(TranscriptionResult {
+            text: format!(
+                "Transcrição local pendente via CrispASR para {} usando {}.",
+                input.audio_path.display(),
+                model_path.display()
+            ),
+            backend: "crispasr".to_string(),
+            model_id: input.options.model_id,
+            detected_language: input.options.language,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::PathBuf;
+
+    use crate::error::AppError;
+    use crate::models::DEFAULT_MODEL_ID;
+    use crate::transcription::{Transcriber, TranscriptionInput, TranscriptionOptions};
+
+    use super::{CrispAsrConfig, CrispAsrTranscriber};
+
+    #[test]
+    fn missing_model_returns_clear_error() {
+        let transcriber = CrispAsrTranscriber::new(CrispAsrConfig {
+            sidecar_name: Some("crispasr".to_string()),
+            model_path: None,
+        });
+
+        let err = transcriber
+            .transcribe(TranscriptionInput {
+                audio_path: PathBuf::from("sample.wav"),
+                options: TranscriptionOptions::default(),
+            })
+            .expect_err("modelo ausente deve falhar");
+
+        assert_eq!(err, AppError::ModelNotInstalled(DEFAULT_MODEL_ID.to_string()));
+    }
+}
diff --git a/src-tauri/src/transcription/mod.rs b/src-tauri/src/transcription/mod.rs
new file mode 100644
index 0000000..b8216f6
--- /dev/null
+++ b/src-tauri/src/transcription/mod.rs
@@ -0,0 +1,47 @@
+use std::path::PathBuf;
+
+use serde::{Deserialize, Serialize};
+
+use crate::error::AppResult;
+use crate::models::DEFAULT_MODEL_ID;
+
+pub mod crispasr;
+pub mod openai;
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct TranscriptionInput {
+    pub audio_path: PathBuf,
+    pub options: TranscriptionOptions,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct TranscriptionOptions {
+    pub model_id: String,
+    pub language: Option<String>,
+    pub timestamps: bool,
+}
+
+impl Default for TranscriptionOptions {
+    fn default() -> Self {
+        Self {
+            model_id: DEFAULT_MODEL_ID.to_string(),
+            language: None,
+            timestamps: false,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct TranscriptionResult {
+    pub text: String,
+    pub backend: String,
+    pub model_id: String,
+    pub detected_language: Option<String>,
+}
+
+pub trait Transcriber {
+    fn transcribe(&self, input: TranscriptionInput) -> AppResult<TranscriptionResult>;
+}
diff --git a/src-tauri/src/transcription/openai.rs b/src-tauri/src/transcription/openai.rs
new file mode 100644
index 0000000..4c13569
--- /dev/null
+++ b/src-tauri/src/transcription/openai.rs
@@ -0,0 +1,19 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub struct OpenAiTranscriptionConfig {
+    pub endpoint: String,
+    pub model: String,
+    pub language: Option<String>,
+}
+
+impl Default for OpenAiTranscriptionConfig {
+    fn default() -> Self {
+        Self {
+            endpoint: "https://api.openai.com/v1/audio/transcriptions".to_string(),
+            model: "whisper-1".to_string(),
+            language: None,
+        }
+    }
+}