diff --git a/assistant/src/daemon/handlers/sessions.ts b/assistant/src/daemon/handlers/sessions.ts
index 2c980a79e3d..548e6ddea8e 100644
--- a/assistant/src/daemon/handlers/sessions.ts
+++ b/assistant/src/daemon/handlers/sessions.ts
@@ -549,7 +549,9 @@ export function handleHistoryRequest(
   socket: net.Socket,
   ctx: HandlerContext,
 ): void {
-  const limit = msg.limit ?? 50;
+  // Default to unlimited when callers don't specify a limit, preserving
+  // backward-compatible behavior of returning full conversation history.
+  const limit = msg.limit;
 
   // Resolve include flags: explicit flags override mode, mode provides defaults.
   // Default mode is 'light' when no mode and no include flags are specified.
@@ -562,6 +564,7 @@ export function handleHistoryRequest(
     msg.sessionId,
     limit,
     msg.beforeTimestamp,
+    msg.beforeMessageId,
   );
 
   const parsed: ParsedHistoryMessage[] = dbMessages.map((m) => {
@@ -694,6 +697,9 @@ export function handleHistoryRequest(
   });
 
   const oldestTimestamp = historyMessages.length > 0 ? historyMessages[0].timestamp : undefined;
+  // Provide the oldest message ID as a tie-breaker cursor so clients can
+  // paginate without skipping same-millisecond messages at page boundaries.
+  const oldestMessageId = historyMessages.length > 0 ? historyMessages[0].id : undefined;
 
   ctx.send(socket, {
     type: 'history_response',
@@ -701,6 +707,7 @@ export function handleHistoryRequest(
     messages: historyMessages,
     hasMore,
     ...(oldestTimestamp !== undefined ? { oldestTimestamp } : {}),
+    ...(oldestMessageId ? { oldestMessageId } : {}),
   });
 
   // Surfaces are now included directly in the history_response message (in the surfaces array),
diff --git a/assistant/src/daemon/ipc-contract/sessions.ts b/assistant/src/daemon/ipc-contract/sessions.ts
index ee1c49d2a01..a171bef4099 100644
--- a/assistant/src/daemon/ipc-contract/sessions.ts
+++ b/assistant/src/daemon/ipc-contract/sessions.ts
@@ -88,10 +88,12 @@ export interface ImageGenModelSetRequest {
 export interface HistoryRequest {
   type: 'history_request';
   sessionId: string;
-  /** Max messages to return. Defaults to 50. */
+  /** Max messages to return. When omitted, all messages are returned (unlimited). */
   limit?: number;
   /** Pagination cursor: return messages with timestamp before this value. */
   beforeTimestamp?: number;
+  /** Pagination cursor tie-breaker: exclude this message ID when beforeTimestamp matches. */
+  beforeMessageId?: string;
   /** Include attachment base64 data. Defaults to false in light mode. */
   includeAttachments?: boolean;
   /** Include tool screenshot base64 data. Defaults to false in light mode. */
@@ -279,6 +281,8 @@ export interface HistoryResponse {
   hasMore: boolean;
   /** Timestamp of the oldest message in the response (client uses as next pagination cursor). */
   oldestTimestamp?: number;
+  /** ID of the oldest message in the response (tie-breaker for same-millisecond cursors). */
+  oldestMessageId?: string;
 }
 
 export interface UndoComplete {
diff --git a/assistant/src/memory/conversation-store.ts b/assistant/src/memory/conversation-store.ts
index e6c392ff2c8..12320cf674d 100644
--- a/assistant/src/memory/conversation-store.ts
+++ b/assistant/src/memory/conversation-store.ts
@@ -1,4 +1,4 @@
-import { and, asc, count, desc, eq, inArray, isNull, lt, sql } from 'drizzle-orm';
+import { and, asc, count, desc, eq, inArray, isNull, lt, lte, ne, sql } from 'drizzle-orm';
 import { v4 as uuid } from 'uuid';
 import { z } from 'zod';
 
@@ -332,16 +332,45 @@ export interface PaginatedMessagesResult {
 /**
  * Paginated variant of getMessages. Returns the most recent `limit` messages
  * (optionally before a cursor timestamp), in chronological order.
+ *
+ * When `limit` is undefined, all matching messages are returned (no pagination).
+ * When `beforeMessageId` is provided alongside `beforeTimestamp`, it acts as a
+ * tie-breaker to avoid skipping messages that share the same millisecond timestamp
+ * at page boundaries.
  */
 export function getMessagesPaginated(
   conversationId: string,
-  limit: number,
+  limit: number | undefined,
   beforeTimestamp?: number,
+  beforeMessageId?: string,
 ): PaginatedMessagesResult {
   const db = getDb();
   const conditions = [eq(messages.conversationId, conversationId)];
   if (beforeTimestamp !== undefined) {
-    conditions.push(lt(messages.createdAt, beforeTimestamp));
+    if (beforeMessageId) {
+      // Use lte + ne as a compound cursor: include messages at the same
+      // millisecond but exclude the specific boundary message already seen.
+      conditions.push(lte(messages.createdAt, beforeTimestamp));
+      conditions.push(ne(messages.id, beforeMessageId));
+    } else {
+      // Legacy callers without a message ID tie-breaker: use strict lt.
+      // This may skip same-millisecond messages at boundaries, but avoids
+      // re-fetching the boundary message. New callers should prefer the
+      // compound cursor (beforeTimestamp + beforeMessageId).
+      conditions.push(lt(messages.createdAt, beforeTimestamp));
+    }
+  }
+
+  if (limit === undefined) {
+    // Unlimited: return all messages in chronological order, no pagination.
+    const rows = db
+      .select()
+      .from(messages)
+      .where(and(...conditions))
+      .orderBy(asc(messages.createdAt))
+      .all()
+      .map(parseMessage);
+    return { messages: rows, hasMore: false };
   }
 
   // Fetch limit+1 rows ordered newest-first so we can detect hasMore
diff --git a/clients/shared/IPC/Generated/IPCContractGenerated.swift b/clients/shared/IPC/Generated/IPCContractGenerated.swift
index 109695ab360..daaf1bd71ea 100644
--- a/clients/shared/IPC/Generated/IPCContractGenerated.swift
+++ b/clients/shared/IPC/Generated/IPCContractGenerated.swift
@@ -1940,10 +1940,12 @@ public struct IPCHeartbeatRunsListResponseRun: Codable, Sendable {
 public struct IPCHistoryRequest: Codable, Sendable {
     public let type: String
     public let sessionId: String
-    /// Max messages to return. Defaults to 50.
+    /// Max messages to return. When omitted, all messages are returned (unlimited).
     public let limit: Double?
     /// Pagination cursor: return messages with timestamp before this value.
     public let beforeTimestamp: Double?
+    /// Pagination cursor tie-breaker: exclude this message ID when beforeTimestamp matches.
+    public let beforeMessageId: String?
     /// Include attachment base64 data. Defaults to false in light mode.
     public let includeAttachments: Bool?
     /// Include tool screenshot base64 data. Defaults to false in light mode.
@@ -1953,11 +1955,12 @@ public struct IPCHistoryRequest: Codable, Sendable {
     /// Shorthand: 'light' = all include flags false (default), 'full' = all include flags true.
     public let mode: String?
 
-    public init(type: String, sessionId: String, limit: Double? = nil, beforeTimestamp: Double? = nil, includeAttachments: Bool? = nil, includeToolImages: Bool? = nil, includeSurfaceData: Bool? = nil, mode: String? = nil) {
+    public init(type: String, sessionId: String, limit: Double? = nil, beforeTimestamp: Double? = nil, beforeMessageId: String? = nil, includeAttachments: Bool? = nil, includeToolImages: Bool? = nil, includeSurfaceData: Bool? = nil, mode: String? = nil) {
         self.type = type
         self.sessionId = sessionId
         self.limit = limit
         self.beforeTimestamp = beforeTimestamp
+        self.beforeMessageId = beforeMessageId
         self.includeAttachments = includeAttachments
         self.includeToolImages = includeToolImages
         self.includeSurfaceData = includeSurfaceData
@@ -1973,13 +1976,16 @@ public struct IPCHistoryResponse: Codable, Sendable {
     public let hasMore: Bool
     /// Timestamp of the oldest message in the response (client uses as next pagination cursor).
     public let oldestTimestamp: Double?
+    /// ID of the oldest message in the response (tie-breaker for same-millisecond cursors).
+    public let oldestMessageId: String?
 
-    public init(type: String, sessionId: String, messages: [IPCHistoryResponseMessage], hasMore: Bool, oldestTimestamp: Double? = nil) {
+    public init(type: String, sessionId: String, messages: [IPCHistoryResponseMessage], hasMore: Bool, oldestTimestamp: Double? = nil, oldestMessageId: String? = nil) {
         self.type = type
         self.sessionId = sessionId
         self.messages = messages
         self.hasMore = hasMore
         self.oldestTimestamp = oldestTimestamp
+        self.oldestMessageId = oldestMessageId
     }
 }