diff --git a/src/hooks/atlas/index.test.ts b/src/hooks/atlas/index.test.ts
index 109ed3de..a1b165e7 100644
--- a/src/hooks/atlas/index.test.ts
+++ b/src/hooks/atlas/index.test.ts
@@ -858,8 +858,8 @@ describe("atlas hook", () => {
       expect(callArgs.body.parts[0].text).toContain("2 remaining")
     })
 
-     test("should not inject when last agent is not Atlas", async () => {
-       // given - boulder state with incomplete plan, but last agent is NOT Atlas
+     test("should not inject when last agent does not match boulder agent", async () => {
+       // given - boulder state with incomplete plan, but last agent does NOT match
        const planPath = join(TEST_DIR, "test-plan.md")
        writeFileSync(planPath, "# Plan\n- [ ] Task 1\n- [ ] Task 2")
 
@@ -868,10 +868,11 @@ describe("atlas hook", () => {
          started_at: "2026-01-02T10:00:00Z",
          session_ids: [MAIN_SESSION_ID],
          plan_name: "test-plan",
+         agent: "atlas",
        }
        writeBoulderState(TEST_DIR, state)
 
-       // given - last agent is NOT Atlas
+       // given - last agent is NOT the boulder agent
        cleanupMessageStorage(MAIN_SESSION_ID)
        setupMessageStorage(MAIN_SESSION_ID, "sisyphus")
 
@@ -886,10 +887,44 @@ describe("atlas hook", () => {
          },
        })
 
-       // then - should NOT call prompt because agent is not Atlas
+       // then - should NOT call prompt because agent does not match
        expect(mockInput._promptMock).not.toHaveBeenCalled()
      })
 
+     test("should inject when last agent matches boulder agent even if non-Atlas", async () => {
+       // given - boulder state expects sisyphus and last agent is sisyphus
+       const planPath = join(TEST_DIR, "test-plan.md")
+       writeFileSync(planPath, "# Plan\n- [ ] Task 1\n- [ ] Task 2")
+
+       const state: BoulderState = {
+         active_plan: planPath,
+         started_at: "2026-01-02T10:00:00Z",
+         session_ids: [MAIN_SESSION_ID],
+         plan_name: "test-plan",
+         agent: "sisyphus",
+       }
+       writeBoulderState(TEST_DIR, state)
+
+       cleanupMessageStorage(MAIN_SESSION_ID)
+       setupMessageStorage(MAIN_SESSION_ID, "sisyphus")
+
+       const mockInput = createMockPluginInput()
+       const hook = createAtlasHook(mockInput)
+
+       // when
+       await hook.handler({
+         event: {
+           type: "session.idle",
+           properties: { sessionID: MAIN_SESSION_ID },
+         },
+       })
+
+       // then - should call prompt for sisyphus
+       expect(mockInput._promptMock).toHaveBeenCalled()
+       const callArgs = mockInput._promptMock.mock.calls[0][0]
+       expect(callArgs.body.agent).toBe("sisyphus")
+     })
+
     test("should debounce rapid continuation injections (prevent infinite loop)", async () => {
       // given - boulder state with incomplete plan
       const planPath = join(TEST_DIR, "test-plan.md")
diff --git a/src/hooks/atlas/index.ts b/src/hooks/atlas/index.ts
index 2583606e..3bf4e78a 100644
--- a/src/hooks/atlas/index.ts
+++ b/src/hooks/atlas/index.ts
@@ -26,6 +26,13 @@ function isSisyphusPath(filePath: string): boolean {
 
 const WRITE_EDIT_TOOLS = ["Write", "Edit", "write", "edit"]
 
+function getLastAgentFromSession(sessionID: string): string | null {
+  const messageDir = getMessageDir(sessionID)
+  if (!messageDir) return null
+  const nearest = findNearestMessageWithFields(messageDir)
+  return nearest?.agent?.toLowerCase() ?? null
+}
+
 const DIRECT_WORK_REMINDER = `
 
 ---
@@ -549,8 +556,14 @@ export function createAtlasHook(
           return
         }
 
-        if (!isCallerOrchestrator(sessionID)) {
-          log(`[${HOOK_NAME}] Skipped: last agent is not Atlas`, { sessionID })
+        const requiredAgent = (boulderState.agent ?? "atlas").toLowerCase()
+        const lastAgent = getLastAgentFromSession(sessionID)
+        if (!lastAgent || lastAgent !== requiredAgent) {
+          log(`[${HOOK_NAME}] Skipped: last agent does not match boulder agent`, {
+            sessionID,
+            lastAgent: lastAgent ?? "unknown",
+            requiredAgent,
+          })
           return
         }