From 257eb9277ba21f372700beae22d0f8c9f0b2ad6a Mon Sep 17 00:00:00 2001
From: YeonGyu-Kim <code.yeon.gyu@gmail.com>
Date: Tue, 10 Feb 2026 22:15:28 +0900
Subject: [PATCH] fix(atlas): restrict boulder continuation to sessions in
 boulder session_ids

Main session was unconditionally allowed through the boulder session guard,
causing continuation injection into sessions not part of the active boulder.
Now only sessions explicitly in boulder's session_ids (or background tasks)
receive boulder continuation, matching todo-continuation-enforcer behavior.
---
 src/hooks/atlas/event-handler.ts | 10 ++++------
 src/hooks/atlas/index.test.ts    | 28 ++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/hooks/atlas/event-handler.ts b/src/hooks/atlas/event-handler.ts
index f9024776..8e57aea8 100644
--- a/src/hooks/atlas/event-handler.ts
+++ b/src/hooks/atlas/event-handler.ts
@@ -1,6 +1,6 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import { getPlanProgress, readBoulderState } from "../../features/boulder-state"
-import { getMainSessionID, subagentSessions } from "../../features/claude-code-session-state"
+import { subagentSessions } from "../../features/claude-code-session-state"
 import { log } from "../../shared/logger"
 import { HOOK_NAME } from "./hook-name"
 import { isAbortError } from "./is-abort-error"
@@ -43,13 +43,11 @@ export function createAtlasEventHandler(input: {
       const boulderState = readBoulderState(ctx.directory)
       const isBoulderSession = boulderState?.session_ids.includes(sessionID) ?? false
 
-      const mainSessionID = getMainSessionID()
-      const isMainSession = sessionID === mainSessionID
       const isBackgroundTaskSession = subagentSessions.has(sessionID)
 
-      // Allow continuation if: main session OR background task OR boulder session
-      if (mainSessionID && !isMainSession && !isBackgroundTaskSession && !isBoulderSession) {
-        log(`[${HOOK_NAME}] Skipped: not main, background task, or boulder session`, { sessionID })
+      // Allow continuation only if: session is in boulder's session_ids OR is a background task
+      if (!isBackgroundTaskSession && !isBoulderSession) {
+        log(`[${HOOK_NAME}] Skipped: not boulder or background task session`, { sessionID })
         return
       }
 
diff --git a/src/hooks/atlas/index.test.ts b/src/hooks/atlas/index.test.ts
index 88722682..1713789b 100644
--- a/src/hooks/atlas/index.test.ts
+++ b/src/hooks/atlas/index.test.ts
@@ -691,6 +691,34 @@ describe("atlas hook", () => {
       expect(mockInput._promptMock).not.toHaveBeenCalled()
     })
 
+    test("should not inject when main session is not in boulder session_ids", async () => {
+      // given - boulder state exists but current (main) session is NOT in session_ids
+      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: ["some-other-session-id"],
+        plan_name: "test-plan",
+      }
+      writeBoulderState(TEST_DIR, state)
+
+      const mockInput = createMockPluginInput()
+      const hook = createAtlasHook(mockInput)
+
+      // when - main session fires idle but is NOT in boulder's session_ids
+      await hook.handler({
+        event: {
+          type: "session.idle",
+          properties: { sessionID: MAIN_SESSION_ID },
+        },
+      })
+
+      // then - should NOT call prompt because session is not part of this boulder
+      expect(mockInput._promptMock).not.toHaveBeenCalled()
+    })
+
     test("should not inject when boulder plan is complete", async () => {
       // given - boulder state with complete plan
       const planPath = join(TEST_DIR, "complete-plan.md")