diff --git a/src/agent/agent_loop.rs b/src/agent/agent_loop.rs
index 3b31ac1..3af02e4 100644
--- a/src/agent/agent_loop.rs
+++ b/src/agent/agent_loop.rs
@@ -1,11 +1,11 @@
 use crate::bus::ChatMessage;
-use crate::bus::message::ContentBlock;
 use crate::bus::message::ToolMessageState;
 use crate::config::LLMProviderConfig;
+use crate::domain::messages::{ContentBlock, ToolCall};
 use crate::observability::{
     Observer, ObserverEvent, ToolExecutionOutcome, ToolExecutionState, truncate_args,
 };
-use crate::providers::{ChatCompletionRequest, LLMProvider, Message, ToolCall, create_provider};
+use crate::providers::{ChatCompletionRequest, LLMProvider, Message, create_provider};
 use crate::skills::SkillRuntime;
 use crate::storage::SessionStore;
 use crate::text::{char_count, take_prefix_chars, take_suffix_chars};
diff --git a/src/bus/message.rs b/src/bus/message.rs
index 75c03d8..cdf7ac3 100644
--- a/src/bus/message.rs
+++ b/src/bus/message.rs
@@ -1,7 +1,7 @@
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
-use crate::providers::ToolCall;
+use crate::domain::messages::ToolCall;
 
 pub const SYSTEM_CONTEXT_AGENT_PROMPT: &str = "agent_prompt";
 pub const SYSTEM_CONTEXT_SCHEDULED_PROMPT: &str = "scheduled_system_prompt";
@@ -14,38 +14,6 @@ pub enum ToolMessageState {
     PendingUserAction,
 }
 
-// ============================================================================
-// ContentBlock - Multimodal content representation (OpenAI-style)
-// ============================================================================
-
-#[derive(Debug, Clone, Serialize, Deserialize)]
-#[serde(tag = "type", rename_all = "snake_case")]
-pub enum ContentBlock {
-    #[serde(rename = "text")]
-    Text { text: String },
-    #[serde(rename = "image_url")]
-    ImageUrl { image_url: ImageUrlBlock },
-}
-
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct ImageUrlBlock {
-    pub url: String,
-}
-
-impl ContentBlock {
-    pub fn text(content: impl Into<String>) -> Self {
-        Self::Text {
-            text: content.into(),
-        }
-    }
-
-    pub fn image_url(url: impl Into<String>) -> Self {
-        Self::ImageUrl {
-            image_url: ImageUrlBlock { url: url.into() },
-        }
-    }
-}
-
 // ============================================================================
 // MediaItem - Media metadata for messages
 // ============================================================================
@@ -566,7 +534,7 @@ fn current_timestamp() -> i64 {
 #[cfg(test)]
 mod tests {
     use super::{ChatMessage, OutboundEventKind, OutboundMessage, ToolMessageState};
-    use crate::providers::ToolCall;
+    use crate::domain::messages::ToolCall;
     use serde_json::json;
     use std::collections::HashMap;
 
diff --git a/src/bus/mod.rs b/src/bus/mod.rs
index 77e642c..c0325b0 100644
--- a/src/bus/mod.rs
+++ b/src/bus/mod.rs
@@ -1,11 +1,11 @@
 pub mod dispatcher;
 pub mod message;
 
+pub use crate::domain::messages::ContentBlock;
 pub use dispatcher::OutboundDispatcher;
 pub use message::{
-    ChatMessage, ContentBlock, InboundMessage, MediaItem, OutboundMessage,
-    SYSTEM_CONTEXT_AGENT_PROMPT, SYSTEM_CONTEXT_HISTORY_COMPACTION,
-    SYSTEM_CONTEXT_SCHEDULED_PROMPT,
+    ChatMessage, InboundMessage, MediaItem, OutboundMessage, SYSTEM_CONTEXT_AGENT_PROMPT,
+    SYSTEM_CONTEXT_HISTORY_COMPACTION, SYSTEM_CONTEXT_SCHEDULED_PROMPT,
 };
 
 use std::sync::Arc;
diff --git a/src/domain/messages.rs b/src/domain/messages.rs
new file mode 100644
index 0000000..174880b
--- /dev/null
+++ b/src/domain/messages.rs
@@ -0,0 +1,36 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum ContentBlock {
+    #[serde(rename = "text")]
+    Text { text: String },
+    #[serde(rename = "image_url")]
+    ImageUrl { image_url: ImageUrlBlock },
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ImageUrlBlock {
+    pub url: String,
+}
+
+impl ContentBlock {
+    pub fn text(content: impl Into<String>) -> Self {
+        Self::Text {
+            text: content.into(),
+        }
+    }
+
+    pub fn image_url(url: impl Into<String>) -> Self {
+        Self::ImageUrl {
+            image_url: ImageUrlBlock { url: url.into() },
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ToolCall {
+    pub id: String,
+    pub name: String,
+    pub arguments: serde_json::Value,
+}
diff --git a/src/domain/mod.rs b/src/domain/mod.rs
new file mode 100644
index 0000000..ba63992
--- /dev/null
+++ b/src/domain/mod.rs
@@ -0,0 +1 @@
+pub mod messages;
diff --git a/src/gateway/agent_task_executor.rs b/src/gateway/agent_task_executor.rs
index a77376b..1b2e7ce 100644
--- a/src/gateway/agent_task_executor.rs
+++ b/src/gateway/agent_task_executor.rs
@@ -1,8 +1,13 @@
 use crate::agent::AgentError;
 use crate::bus::OutboundMessage;
+use crate::scheduler::{
+    AgentTaskExecutor as SchedulerAgentTaskExecutor, MaintenanceExecutor, MaintenanceRunSummary,
+    ScheduledAgentTaskOptions,
+};
+use async_trait::async_trait;
 
 use super::memory_maintenance::MemoryMaintenanceScopeResult;
-use super::session::{ScheduledAgentTaskOptions, SessionManager};
+use super::session::SessionManager;
 
 #[derive(Clone)]
 pub struct AgentTaskExecutor {
@@ -14,7 +19,7 @@ impl AgentTaskExecutor {
         Self { session_manager }
     }
 
-    pub(crate) async fn execute(
+    async fn execute_agent_task(
         &self,
         channel_name: &str,
         chat_id: &str,
@@ -27,6 +32,21 @@ impl AgentTaskExecutor {
     }
 }
 
+#[async_trait]
+impl SchedulerAgentTaskExecutor for AgentTaskExecutor {
+    async fn execute(
+        &self,
+        channel_name: &str,
+        chat_id: &str,
+        prompt: &str,
+        options: ScheduledAgentTaskOptions,
+    ) -> anyhow::Result<Vec<OutboundMessage>> {
+        self.execute_agent_task(channel_name, chat_id, prompt, options)
+            .await
+            .map_err(|error| anyhow::anyhow!(error.to_string()))
+    }
+}
+
 #[derive(Clone)]
 pub struct SchedulerMaintenanceService {
     session_manager: SessionManager,
@@ -37,11 +57,11 @@ impl SchedulerMaintenanceService {
         Self { session_manager }
     }
 
-    pub(crate) async fn cleanup_expired_sessions(&self) -> usize {
+    async fn cleanup_sessions(&self) -> usize {
         self.session_manager.cleanup_expired_sessions().await
     }
 
-    pub(crate) async fn run_memory_maintenance_for_all_scopes(
+    async fn run_memory_maintenance(
         &self,
         updated_since: Option<i64>,
     ) -> Result<Vec<MemoryMaintenanceScopeResult>, AgentError> {
@@ -50,3 +70,33 @@ impl SchedulerMaintenanceService {
             .await
     }
 }
+
+#[async_trait]
+impl MaintenanceExecutor for SchedulerMaintenanceService {
+    async fn cleanup_expired_sessions(&self) -> usize {
+        self.cleanup_sessions().await
+    }
+
+    async fn run_memory_maintenance_for_all_scopes(
+        &self,
+        updated_since: Option<i64>,
+    ) -> anyhow::Result<Vec<MaintenanceRunSummary>> {
+        self.run_memory_maintenance(updated_since)
+            .await
+            .map(|results| {
+                results
+                    .into_iter()
+                    .map(|result| MaintenanceRunSummary {
+                        scope_key: result.scope_key,
+                        user_facts: result.output.user_facts.len(),
+                        preferences: result.output.preferences.len(),
+                        behavior_patterns: result.output.behavior_patterns.len(),
+                        merges: result.output.merges.len(),
+                        conflicts: result.output.conflicts.len(),
+                        low_value: result.output.low_value_ids.len(),
+                    })
+                    .collect()
+            })
+            .map_err(|error| anyhow::anyhow!(error.to_string()))
+    }
+}
diff --git a/src/gateway/session.rs b/src/gateway/session.rs
index 612119a..6e1435d 100644
--- a/src/gateway/session.rs
+++ b/src/gateway/session.rs
@@ -4,6 +4,7 @@ use crate::bus::SYSTEM_CONTEXT_SCHEDULED_PROMPT;
 use crate::bus::{ChatMessage, MessageBus, OutboundMessage};
 use crate::config::LLMProviderConfig;
 use crate::protocol::WsOutbound;
+use crate::scheduler::ScheduledAgentTaskOptions;
 use crate::skills::SkillRuntime;
 use crate::storage::{SessionRecord, SessionStore, persistent_session_id};
 use crate::tools::ToolRegistry;
@@ -66,15 +67,6 @@ pub struct BusToolCallEmitter {
     show_tool_results: bool,
 }
 
-#[derive(Debug, Clone, Default)]
-pub struct ScheduledAgentTaskOptions {
-    pub sender_id: Option<String>,
-    pub fresh_session: bool,
-    pub system_prompt: Option<String>,
-    pub metadata: HashMap<String, String>,
-    pub agent: Option<String>,
-}
-
 impl BusToolCallEmitter {
     pub fn new(
         bus: Arc<MessageBus>,
diff --git a/src/gateway/ws_adapter.rs b/src/gateway/ws_adapter.rs
index c013a7b..c59a5fb 100644
--- a/src/gateway/ws_adapter.rs
+++ b/src/gateway/ws_adapter.rs
@@ -118,7 +118,7 @@ pub(crate) fn ws_outbound_from_outbound_message(message: &OutboundMessage) -> Ve
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::providers::ToolCall;
+    use crate::domain::messages::ToolCall;
     use serde_json::json;
 
     #[test]
diff --git a/src/lib.rs b/src/lib.rs
index c99e424..9e5e8c6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,6 +4,7 @@ pub mod channels;
 pub mod cli;
 pub mod client;
 pub mod config;
+pub mod domain;
 pub mod gateway;
 pub mod logging;
 pub mod observability;
diff --git a/src/providers/anthropic.rs b/src/providers/anthropic.rs
index f5563f0..a2632fe 100644
--- a/src/providers/anthropic.rs
+++ b/src/providers/anthropic.rs
@@ -6,7 +6,7 @@ use std::time::Duration;
 
 use super::traits::Usage;
 use super::{ChatCompletionRequest, ChatCompletionResponse, LLMProvider, Tool, ToolCall};
-use crate::bus::message::ContentBlock;
+use crate::domain::messages::ContentBlock;
 
 fn format_error_chain(error: &(dyn std::error::Error + 'static)) -> String {
     let mut details = vec![error.to_string()];
diff --git a/src/providers/mod.rs b/src/providers/mod.rs
index f4f0675..8e1f25a 100644
--- a/src/providers/mod.rs
+++ b/src/providers/mod.rs
@@ -6,9 +6,9 @@ pub use self::anthropic::AnthropicProvider;
 pub use self::openai::OpenAIProvider;
 
 use crate::config::LLMProviderConfig;
+pub use crate::domain::messages::ToolCall;
 pub use traits::{
-    ChatCompletionRequest, ChatCompletionResponse, LLMProvider, Message, Tool, ToolCall,
-    ToolFunction, Usage,
+    ChatCompletionRequest, ChatCompletionResponse, LLMProvider, Message, Tool, ToolFunction, Usage,
 };
 
 pub fn create_provider(config: LLMProviderConfig) -> Result<Box<dyn LLMProvider>, ProviderError> {
diff --git a/src/providers/openai.rs b/src/providers/openai.rs
index 05a3f96..fa1329a 100644
--- a/src/providers/openai.rs
+++ b/src/providers/openai.rs
@@ -7,7 +7,7 @@ use std::time::Duration;
 
 use super::traits::Usage;
 use super::{ChatCompletionRequest, ChatCompletionResponse, LLMProvider, ToolCall};
-use crate::bus::message::ContentBlock;
+use crate::domain::messages::ContentBlock;
 
 const INTERNAL_MODEL_EXTRA_KEYS: &[&str] = &["tool_call_arguments_json", "mock_response_content"];
 
diff --git a/src/providers/traits.rs b/src/providers/traits.rs
index a1ace3c..9fd8ae8 100644
--- a/src/providers/traits.rs
+++ b/src/providers/traits.rs
@@ -1,4 +1,4 @@
-use crate::bus::message::ContentBlock;
+use crate::domain::messages::{ContentBlock, ToolCall};
 use async_trait::async_trait;
 use serde::{Deserialize, Serialize};
 
@@ -91,13 +91,6 @@ pub struct ToolFunction {
     pub parameters: serde_json::Value,
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct ToolCall {
-    pub id: String,
-    pub name: String,
-    pub arguments: serde_json::Value,
-}
-
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ChatCompletionRequest {
     pub messages: Vec<Message>,
diff --git a/src/scheduler/mod.rs b/src/scheduler/mod.rs
index 2144bba..cf7d4ca 100644
--- a/src/scheduler/mod.rs
+++ b/src/scheduler/mod.rs
@@ -2,6 +2,7 @@ use std::collections::HashMap;
 use std::str::FromStr;
 use std::sync::Arc;
 
+use async_trait::async_trait;
 use chrono::{DateTime, Duration as ChronoDuration, TimeZone, Utc};
 use chrono_tz::Tz;
 use tokio::sync::watch;
@@ -11,37 +12,80 @@ use crate::config::{
     SchedulerConfig, SchedulerJobConfig, SchedulerJobKind, SchedulerJobTarget,
     SchedulerMisfirePolicy, SchedulerSchedule,
 };
-use crate::gateway::agent_task_executor::{AgentTaskExecutor, SchedulerMaintenanceService};
-use crate::gateway::session::ScheduledAgentTaskOptions;
 use crate::storage::{
     SchedulerJobRecord, SchedulerJobState, SchedulerJobStatus, SchedulerJobUpsert, SessionStore,
 };
 
+#[derive(Debug, Clone, Default)]
+pub struct ScheduledAgentTaskOptions {
+    pub sender_id: Option<String>,
+    pub fresh_session: bool,
+    pub system_prompt: Option<String>,
+    pub metadata: HashMap<String, String>,
+    pub agent: Option<String>,
+}
+
+#[derive(Debug, Clone)]
+pub struct MaintenanceRunSummary {
+    pub scope_key: String,
+    pub user_facts: usize,
+    pub preferences: usize,
+    pub behavior_patterns: usize,
+    pub merges: usize,
+    pub conflicts: usize,
+    pub low_value: usize,
+}
+
+#[async_trait]
+pub trait AgentTaskExecutor: Send + Sync {
+    async fn execute(
+        &self,
+        channel_name: &str,
+        chat_id: &str,
+        prompt: &str,
+        options: ScheduledAgentTaskOptions,
+    ) -> anyhow::Result<Vec<OutboundMessage>>;
+}
+
+#[async_trait]
+pub trait MaintenanceExecutor: Send + Sync {
+    async fn cleanup_expired_sessions(&self) -> usize;
+
+    async fn run_memory_maintenance_for_all_scopes(
+        &self,
+        updated_since: Option<i64>,
+    ) -> anyhow::Result<Vec<MaintenanceRunSummary>>;
+}
+
 pub struct Scheduler {
     bus: Arc<MessageBus>,
     config: SchedulerConfig,
     timezone: Tz,
     store: Arc<SessionStore>,
-    agent_task_executor: AgentTaskExecutor,
-    maintenance_service: SchedulerMaintenanceService,
+    agent_task_executor: Arc<dyn AgentTaskExecutor>,
+    maintenance_executor: Arc<dyn MaintenanceExecutor>,
 }
 
 impl Scheduler {
-    pub fn new(
+    pub fn new<A, M>(
         bus: Arc<MessageBus>,
         config: SchedulerConfig,
         timezone: Tz,
         store: Arc<SessionStore>,
-        agent_task_executor: AgentTaskExecutor,
-        maintenance_service: SchedulerMaintenanceService,
-    ) -> Self {
+        agent_task_executor: A,
+        maintenance_executor: M,
+    ) -> Self
+    where
+        A: AgentTaskExecutor + 'static,
+        M: MaintenanceExecutor + 'static,
+    {
         Self {
             bus,
             config,
             timezone,
             store,
-            agent_task_executor,
-            maintenance_service,
+            agent_task_executor: Arc::new(agent_task_executor),
+            maintenance_executor: Arc::new(maintenance_executor),
         }
     }
 
@@ -171,11 +215,11 @@ impl Scheduler {
                 self.bus.publish_outbound(message).await?;
             }
             SchedulerJobKind::InternalEvent => {
-                execute_internal_event(&self.maintenance_service, job).await?;
+                execute_internal_event(self.maintenance_executor.as_ref(), job).await?;
             }
             SchedulerJobKind::AgentTask => {
                 let outbound_messages = execute_agent_task(
-                    &self.agent_task_executor,
+                    self.agent_task_executor.as_ref(),
                     job,
                     required_notification_chat_id(job, "agent_task")?,
                 )
@@ -187,7 +231,8 @@ impl Scheduler {
             SchedulerJobKind::SilentAgentTask => {
                 let execution_chat_id = resolve_execution_chat_id(job)?;
                 if let Err(error) =
-                    execute_agent_task(&self.agent_task_executor, job, &execution_chat_id).await
+                    execute_agent_task(self.agent_task_executor.as_ref(), job, &execution_chat_id)
+                        .await
                 {
                     if let Err(notify_error) =
                         self.notify_silent_agent_task_failure(job, &error).await
@@ -590,7 +635,7 @@ fn build_outbound_message(job: &RuntimeJob) -> anyhow::Result<OutboundMessage> {
 }
 
 async fn execute_internal_event(
-    maintenance_service: &SchedulerMaintenanceService,
+    maintenance_executor: &dyn MaintenanceExecutor,
     job: &RuntimeJob,
 ) -> anyhow::Result<()> {
     let event = job
@@ -601,24 +646,24 @@ async fn execute_internal_event(
 
     match event {
         "session_cleanup" => {
-            let removed = maintenance_service.cleanup_expired_sessions().await;
+            let removed = maintenance_executor.cleanup_expired_sessions().await;
             tracing::info!(job_id = %job.id, removed, "Scheduler session cleanup completed");
             Ok(())
         }
         "memory_maintenance" => {
-            let results = maintenance_service
+            let results = maintenance_executor
                 .run_memory_maintenance_for_all_scopes(job.last_fired_at)
                 .await?;
             for result in &results {
                 tracing::info!(
                     job_id = %job.id,
                     scope_key = %result.scope_key,
-                    user_facts = result.output.user_facts.len(),
-                    preferences = result.output.preferences.len(),
-                    behavior_patterns = result.output.behavior_patterns.len(),
-                    merges = result.output.merges.len(),
-                    conflicts = result.output.conflicts.len(),
-                    low_value = result.output.low_value_ids.len(),
+                    user_facts = result.user_facts,
+                    preferences = result.preferences,
+                    behavior_patterns = result.behavior_patterns,
+                    merges = result.merges,
+                    conflicts = result.conflicts,
+                    low_value = result.low_value,
                     "Scheduler completed memory maintenance model run"
                 );
             }
@@ -630,7 +675,7 @@ async fn execute_internal_event(
 }
 
 async fn execute_agent_task(
-    agent_task_executor: &AgentTaskExecutor,
+    agent_task_executor: &dyn AgentTaskExecutor,
     job: &RuntimeJob,
     execution_chat_id: &str,
 ) -> anyhow::Result<Vec<OutboundMessage>> {
@@ -649,7 +694,6 @@ async fn execute_agent_task(
     agent_task_executor
         .execute(channel_name, execution_chat_id, prompt, options)
         .await
-        .map_err(|error| anyhow::anyhow!(error.to_string()))
 }
 
 fn required_notification_chat_id<'a>(
@@ -966,52 +1010,44 @@ impl TryFrom<serde_json::Value> for SchedulerJobTarget {
 mod tests {
     use super::*;
     use crate::bus::MessageBus;
-    use crate::config::{BUILTIN_MEMORY_MAINTENANCE_JOB_ID, LLMProviderConfig};
-    use crate::gateway::agent_task_executor::{AgentTaskExecutor, SchedulerMaintenanceService};
-    use crate::gateway::session::SessionManager;
-    use crate::skills::SkillRuntime;
+    use crate::config::BUILTIN_MEMORY_MAINTENANCE_JOB_ID;
     use crate::storage::{SchedulerJobUpsert, SessionStore};
-    use std::collections::HashMap;
 
-    fn test_provider_config() -> LLMProviderConfig {
-        LLMProviderConfig {
-            provider_type: "openai".to_string(),
-            name: "default".to_string(),
-            base_url: "http://localhost".to_string(),
-            api_key: "test-key".to_string(),
-            extra_headers: HashMap::new(),
-            llm_timeout_secs: 30,
-            model_id: "test-model".to_string(),
-            temperature: Some(0.0),
-            max_tokens: None,
-            context_window_tokens: None,
-            model_extra: HashMap::new(),
-            max_tool_iterations: 4,
-            tool_result_max_chars: 20_000,
-            context_tool_result_trim_chars: 20_000,
+    #[derive(Clone)]
+    struct TestAgentTaskExecutor;
+
+    #[async_trait::async_trait]
+    impl AgentTaskExecutor for TestAgentTaskExecutor {
+        async fn execute(
+            &self,
+            _channel_name: &str,
+            _chat_id: &str,
+            _prompt: &str,
+            _options: ScheduledAgentTaskOptions,
+        ) -> anyhow::Result<Vec<OutboundMessage>> {
+            Ok(Vec::new())
         }
     }
 
-    fn test_session_manager() -> SessionManager {
-        let provider_config = test_provider_config();
-        SessionManager::new(
-            4,
-            100,
-            false,
-            "Asia/Shanghai".to_string(),
-            provider_config.clone(),
-            HashMap::from([("default".to_string(), provider_config)]),
-            Arc::new(SkillRuntime::default()),
-        )
-        .unwrap()
+    #[derive(Clone)]
+    struct TestMaintenanceExecutor;
+
+    #[async_trait::async_trait]
+    impl MaintenanceExecutor for TestMaintenanceExecutor {
+        async fn cleanup_expired_sessions(&self) -> usize {
+            0
+        }
+
+        async fn run_memory_maintenance_for_all_scopes(
+            &self,
+            _updated_since: Option<i64>,
+        ) -> anyhow::Result<Vec<MaintenanceRunSummary>> {
+            Ok(Vec::new())
+        }
     }
 
-    fn test_scheduler_services() -> (AgentTaskExecutor, SchedulerMaintenanceService) {
-        let session_manager = test_session_manager();
-        (
-            AgentTaskExecutor::new(session_manager.clone()),
-            SchedulerMaintenanceService::new(session_manager),
-        )
+    fn test_scheduler_services() -> (TestAgentTaskExecutor, TestMaintenanceExecutor) {
+        (TestAgentTaskExecutor, TestMaintenanceExecutor)
     }
 
     #[test]
diff --git a/src/storage/mod.rs b/src/storage/mod.rs
index 2bdde00..42a0dc7 100644
--- a/src/storage/mod.rs
+++ b/src/storage/mod.rs
@@ -1802,7 +1802,7 @@ fn quote_fts_or_query(queries: &[String]) -> String {
 mod tests {
     use super::*;
     use crate::bus::SYSTEM_CONTEXT_AGENT_PROMPT;
-    use crate::providers::ToolCall;
+    use crate::domain::messages::ToolCall;
 
     #[test]
     fn test_persistent_session_id_for_cli_and_channel() {