diff --git a/src/features/boulder-state/storage.test.ts b/src/features/boulder-state/storage.test.ts
index f1a2671c6..9d685e798 100644
--- a/src/features/boulder-state/storage.test.ts
+++ b/src/features/boulder-state/storage.test.ts
@@ -246,5 +246,33 @@ describe("boulder-state", () => {
       expect(state.plan_name).toBe("auth-refactor")
       expect(state.started_at).toBeDefined()
     })
+
+    test("should include agent field when provided", () => {
+      //#given - plan path, session id, and agent type
+      const planPath = "/path/to/feature.md"
+      const sessionId = "ses-xyz789"
+      const agent = "atlas"
+
+      //#when - createBoulderState is called with agent
+      const state = createBoulderState(planPath, sessionId, agent)
+
+      //#then - state should include the agent field
+      expect(state.agent).toBe("atlas")
+      expect(state.active_plan).toBe(planPath)
+      expect(state.session_ids).toEqual([sessionId])
+      expect(state.plan_name).toBe("feature")
+    })
+
+    test("should allow agent to be undefined", () => {
+      //#given - plan path and session id without agent
+      const planPath = "/path/to/legacy.md"
+      const sessionId = "ses-legacy"
+
+      //#when - createBoulderState is called without agent
+      const state = createBoulderState(planPath, sessionId)
+
+      //#then - state should not have agent field (backward compatible)
+      expect(state.agent).toBeUndefined()
+    })
   })
 })
diff --git a/src/features/boulder-state/storage.ts b/src/features/boulder-state/storage.ts
index 99aed0106..c42fc8812 100644
--- a/src/features/boulder-state/storage.ts
+++ b/src/features/boulder-state/storage.ts
@@ -139,12 +139,14 @@ export function getPlanName(planPath: string): string {
  */
 export function createBoulderState(
   planPath: string,
-  sessionId: string
+  sessionId: string,
+  agent?: string
 ): BoulderState {
   return {
     active_plan: planPath,
     started_at: new Date().toISOString(),
     session_ids: [sessionId],
     plan_name: getPlanName(planPath),
+    ...(agent !== undefined ? { agent } : {}),
   }
 }
diff --git a/src/features/boulder-state/types.ts b/src/features/boulder-state/types.ts
index b231e165f..f56dcdaa2 100644
--- a/src/features/boulder-state/types.ts
+++ b/src/features/boulder-state/types.ts
@@ -14,6 +14,8 @@ export interface BoulderState {
   session_ids: string[]
   /** Plan name derived from filename */
   plan_name: string
+  /** Agent type to use when resuming (e.g., 'atlas') */
+  agent?: string
 }
 
 export interface PlanProgress {
diff --git a/src/hooks/atlas/index.ts b/src/hooks/atlas/index.ts
index 3d70859e6..2583606e5 100644
--- a/src/hooks/atlas/index.ts
+++ b/src/hooks/atlas/index.ts
@@ -431,7 +431,7 @@ export function createAtlasHook(
     return state
   }
 
-  async function injectContinuation(sessionID: string, planName: string, remaining: number, total: number): Promise<void> {
+  async function injectContinuation(sessionID: string, planName: string, remaining: number, total: number, agent?: string): Promise<void> {
     const hasRunningBgTasks = backgroundManager
       ? backgroundManager.getTasksByParentSession(sessionID).some(t => t.status === "running")
       : false
@@ -477,7 +477,7 @@ export function createAtlasHook(
        await ctx.client.session.prompt({
          path: { id: sessionID },
          body: {
-            agent: "atlas",
+            agent: agent ?? "atlas",
            ...(model !== undefined ? { model } : {}),
            parts: [{ type: "text", text: prompt }],
          },
@@ -568,7 +568,7 @@ export function createAtlasHook(
 
         state.lastContinuationInjectedAt = now
         const remaining = progress.total - progress.completed
-        injectContinuation(sessionID, boulderState.plan_name, remaining, progress.total)
+        injectContinuation(sessionID, boulderState.plan_name, remaining, progress.total, boulderState.agent)
         return
       }
 
diff --git a/src/hooks/start-work/index.ts b/src/hooks/start-work/index.ts
index ce432e46e..600814bd5 100644
--- a/src/hooks/start-work/index.ts
+++ b/src/hooks/start-work/index.ts
@@ -102,7 +102,7 @@ All ${progress.total} tasks are done. Create a new plan with: /plan "your task"`
             if (existingState) {
               clearBoulderState(ctx.directory)
             }
-            const newState = createBoulderState(matchedPlan, sessionId)
+            const newState = createBoulderState(matchedPlan, sessionId, "atlas")
             writeBoulderState(ctx.directory, newState)
             
             contextInfo = `
@@ -187,7 +187,7 @@ All ${plans.length} plan(s) are complete. Create a new plan with: /plan "your ta
         } else if (incompletePlans.length === 1) {
           const planPath = incompletePlans[0]
           const progress = getPlanProgress(planPath)
-          const newState = createBoulderState(planPath, sessionId)
+          const newState = createBoulderState(planPath, sessionId, "atlas")
           writeBoulderState(ctx.directory, newState)
 
           contextInfo += `