diff --git a/src/main/apiServer/routes/agents/handlers/messages.ts b/src/main/apiServer/routes/agents/handlers/messages.ts
index 0f731fe089..4364868dac 100644
--- a/src/main/apiServer/routes/agents/handlers/messages.ts
+++ b/src/main/apiServer/routes/agents/handlers/messages.ts
@@ -12,7 +12,7 @@ const verifyAgentAndSession = async (agentId: string, sessionId: string) => {
     throw { status: 404, code: 'agent_not_found', message: 'Agent not found' }
   }
 
-  const session = await sessionService.getSession(sessionId)
+  const session = await sessionService.getSession(agentId, sessionId)
   if (!session) {
     throw { status: 404, code: 'session_not_found', message: 'Session not found' }
   }
diff --git a/src/main/apiServer/routes/agents/handlers/sessions.ts b/src/main/apiServer/routes/agents/handlers/sessions.ts
index d9f45833c1..f164d6cd52 100644
--- a/src/main/apiServer/routes/agents/handlers/sessions.ts
+++ b/src/main/apiServer/routes/agents/handlers/sessions.ts
@@ -64,7 +64,7 @@ export const getSession = async (req: Request, res: Response): Promise<Response>
     const { agentId, sessionId } = req.params
     logger.info(`Getting session: ${sessionId} for agent: ${agentId}`)
 
-    const session = await sessionService.getSession(sessionId)
+    const session = await sessionService.getSession(agentId, sessionId)
 
     if (!session) {
       logger.warn(`Session not found: ${sessionId}`)
@@ -119,7 +119,7 @@ export const updateSession = async (req: Request, res: Response): Promise<Respon
     logger.debug('Update data:', req.body)
 
     // First check if session exists and belongs to agent
-    const existingSession = await sessionService.getSession(sessionId)
+    const existingSession = await sessionService.getSession(agentId, sessionId)
     if (!existingSession || existingSession.agent_id !== agentId) {
       logger.warn(`Session ${sessionId} not found for agent ${agentId}`)
       return res.status(404).json({
@@ -133,7 +133,7 @@ export const updateSession = async (req: Request, res: Response): Promise<Respon
 
     // For PUT, we replace the entire resource
     const sessionData = { ...req.body, main_agent_id: agentId }
-    const session = await sessionService.updateSession(sessionId, sessionData)
+    const session = await sessionService.updateSession(agentId, sessionId, sessionData)
 
     if (!session) {
       logger.warn(`Session not found for update: ${sessionId}`)
@@ -167,7 +167,7 @@ export const patchSession = async (req: Request, res: Response): Promise<Respons
     logger.debug('Patch data:', req.body)
 
     // First check if session exists and belongs to agent
-    const existingSession = await sessionService.getSession(sessionId)
+    const existingSession = await sessionService.getSession(agentId, sessionId)
     if (!existingSession || existingSession.agent_id !== agentId) {
       logger.warn(`Session ${sessionId} not found for agent ${agentId}`)
       return res.status(404).json({
@@ -180,7 +180,7 @@ export const patchSession = async (req: Request, res: Response): Promise<Respons
     }
 
     const updateSession = { ...existingSession, ...req.body }
-    const session = await sessionService.updateSession(sessionId, updateSession)
+    const session = await sessionService.updateSession(agentId, sessionId, updateSession)
 
     if (!session) {
       logger.warn(`Session not found for patch: ${sessionId}`)
@@ -213,7 +213,7 @@ export const deleteSession = async (req: Request, res: Response): Promise<Respon
     logger.info(`Deleting session: ${sessionId} for agent: ${agentId}`)
 
     // First check if session exists and belongs to agent
-    const existingSession = await sessionService.getSession(sessionId)
+    const existingSession = await sessionService.getSession(agentId, sessionId)
     if (!existingSession || existingSession.agent_id !== agentId) {
       logger.warn(`Session ${sessionId} not found for agent ${agentId}`)
       return res.status(404).json({
@@ -225,7 +225,7 @@ export const deleteSession = async (req: Request, res: Response): Promise<Respon
       })
     }
 
-    const deleted = await sessionService.deleteSession(sessionId)
+    const deleted = await sessionService.deleteSession(agentId, sessionId)
 
     if (!deleted) {
       logger.warn(`Session not found for deletion: ${sessionId}`)
@@ -287,7 +287,7 @@ export const getSessionById = async (req: Request, res: Response): Promise<Respo
     const { sessionId } = req.params
     logger.info(`Getting session: ${sessionId}`)
 
-    const session = await sessionService.getSession(sessionId)
+    const session = await sessionService.getSessionById(sessionId)
 
     if (!session) {
       logger.warn(`Session not found: ${sessionId}`)
diff --git a/src/main/services/agents/services/SessionMessageService.ts b/src/main/services/agents/services/SessionMessageService.ts
index 362ab4539d..b0a08e6efb 100644
--- a/src/main/services/agents/services/SessionMessageService.ts
+++ b/src/main/services/agents/services/SessionMessageService.ts
@@ -9,7 +9,7 @@ import type {
 } from '@types'
 import { ModelMessage, UIMessage, UIMessageChunk } from 'ai'
 import { convertToModelMessages, readUIMessageStream } from 'ai'
-import { count, eq } from 'drizzle-orm'
+import { eq } from 'drizzle-orm'
 
 import { BaseService } from '../BaseService'
 import { InsertSessionMessageRow, sessionMessagesTable } from '../database/schema'
@@ -148,17 +148,9 @@ export class SessionMessageService extends BaseService {
   async listSessionMessages(
     sessionId: string,
     options: ListOptions = {}
-  ): Promise<{ messages: AgentSessionMessageEntity[]; total: number }> {
+  ): Promise<{ messages: AgentSessionMessageEntity[] }> {
     this.ensureInitialized()
 
-    // Get total count
-    const totalResult = await this.database
-      .select({ count: count() })
-      .from(sessionMessagesTable)
-      .where(eq(sessionMessagesTable.session_id, sessionId))
-
-    const total = totalResult[0].count
-
     // Get messages with pagination
     const baseQuery = this.database
       .select()
@@ -175,7 +167,7 @@ export class SessionMessageService extends BaseService {
 
     const messages = result.map((row) => this.deserializeSessionMessage(row)) as AgentSessionMessageEntity[]
 
-    return { messages, total }
+    return { messages }
   }
 
   async saveUserMessage(
diff --git a/src/main/services/agents/services/SessionService.ts b/src/main/services/agents/services/SessionService.ts
index 1141a26014..63a64c1efb 100644
--- a/src/main/services/agents/services/SessionService.ts
+++ b/src/main/services/agents/services/SessionService.ts
@@ -78,7 +78,25 @@ export class SessionService extends BaseService {
     return this.deserializeJsonFields(result[0]) as AgentSessionEntity
   }
 
-  async getSession(id: string): Promise<GetAgentSessionResponse | null> {
+  async getSession(agentId: string, id: string): Promise<GetAgentSessionResponse | null> {
+    this.ensureInitialized()
+
+    const result = await this.database
+      .select()
+      .from(sessionsTable)
+      .where(and(eq(sessionsTable.id, id), eq(sessionsTable.agent_id, agentId)))
+      .limit(1)
+
+    if (!result[0]) {
+      return null
+    }
+
+    const session = this.deserializeJsonFields(result[0]) as GetAgentSessionResponse
+
+    return session
+  }
+
+  async getSessionById(id: string): Promise<GetAgentSessionResponse | null> {
     this.ensureInitialized()
 
     const result = await this.database.select().from(sessionsTable).where(eq(sessionsTable.id, id)).limit(1)
@@ -92,14 +110,6 @@ export class SessionService extends BaseService {
     return session
   }
 
-  async getSessionWithAgent(id: string): Promise<any | null> {
-    this.ensureInitialized()
-
-    // TODO: Implement join query with agents table when needed
-    // For now, just return the session
-    return await this.getSession(id)
-  }
-
   async listSessions(
     agentId?: string,
     options: ListOptions = {}
@@ -139,11 +149,11 @@ export class SessionService extends BaseService {
     return { sessions, total }
   }
 
-  async updateSession(id: string, updates: UpdateSessionRequest): Promise<GetAgentSessionResponse | null> {
+  async updateSession(agentId: string, id: string, updates: UpdateSessionRequest): Promise<GetAgentSessionResponse | null> {
     this.ensureInitialized()
 
     // Check if session exists
-    const existing = await this.getSession(id)
+    const existing = await this.getSession(agentId, id)
     if (!existing) {
       return null
     }
@@ -173,24 +183,26 @@ export class SessionService extends BaseService {
 
     await this.database.update(sessionsTable).set(updateData).where(eq(sessionsTable.id, id))
 
-    return await this.getSession(id)
+    return await this.getSession(agentId, id)
   }
 
-  async deleteSession(id: string): Promise<boolean> {
+  async deleteSession(agentId: string, id: string): Promise<boolean> {
     this.ensureInitialized()
 
-    const result = await this.database.delete(sessionsTable).where(eq(sessionsTable.id, id))
+    const result = await this.database
+      .delete(sessionsTable)
+      .where(and(eq(sessionsTable.id, id), eq(sessionsTable.agent_id, agentId)))
 
     return result.rowsAffected > 0
   }
 
-  async sessionExists(id: string): Promise<boolean> {
+  async sessionExists(agentId: string, id: string): Promise<boolean> {
     this.ensureInitialized()
 
     const result = await this.database
       .select({ id: sessionsTable.id })
       .from(sessionsTable)
-      .where(eq(sessionsTable.id, id))
+      .where(and(eq(sessionsTable.id, id), eq(sessionsTable.agent_id, agentId)))
       .limit(1)
 
     return result.length > 0
diff --git a/src/renderer/src/types/agent.ts b/src/renderer/src/types/agent.ts
index cad935d0e8..ecce2941cf 100644
--- a/src/renderer/src/types/agent.ts
+++ b/src/renderer/src/types/agent.ts
@@ -2,7 +2,7 @@
  * Database entity types for Agent, Session, and SessionMessage
  * Shared between main and renderer processes
  */
-import { ModelMessage, modelMessageSchema, TextStreamPart, UIMessageChunk } from 'ai'
+import { ModelMessage, modelMessageSchema, TextStreamPart } from 'ai'
 import { z } from 'zod'
 
 // ------------------ Core enums and helper types ------------------
@@ -119,14 +119,6 @@ export type AgentSessionMessageEntity = z.infer<typeof AgentSessionMessageEntity
 
 // ------------------ Session message payload ------------------
 
-// Structured content for session messages that preserves both AI SDK and raw data
-export interface SessionMessageContent {
-  chunk: UIMessageChunk[] // UI-friendly AI SDK chunks for rendering
-  raw: any[] // Original agent-specific messages for data integrity (agent-agnostic)
-  agentResult?: any // Complete result from the underlying agent service
-  agentType: string // The type of agent that generated this message (e.g., 'claude-code', 'openai', etc.)
-}
-
 // Not implemented fields:
 // - plan_model: Optional model for planning/thinking tasks
 // - small_model: Optional lightweight model for quick responses