fix(plugin): normalize event session ids

Handle OpenCode session events that carry the session ID under properties.info.id or properties.info.sessionID so background tasks and continuation hooks do not miss idle/error/delete events.

Add regression coverage for nested session.idle events completing background tasks and waking continuation hooks.

src/features/background-agent/manager.test.ts

@@ -5023,6 +5023,54 @@ describe("BackgroundManager.handleEvent - session.error", () => {
     manager.shutdown()
   })
 
+  test("completes task when session.idle carries session id in info", async () => {
+    //#given
+    const sessionID = "ses-info-idle-completes-task"
+    const client = {
+      session: {
+        prompt: async () => ({}),
+        promptAsync: async () => ({}),
+        abort: async () => ({}),
+        messages: async () => ({
+          data: [
+            {
+              info: { role: "assistant" },
+              parts: [{ type: "text", text: "done" }],
+            },
+          ],
+        }),
+        todo: async () => ({ data: [] }),
+      },
+    }
+
+    const manager = new BackgroundManager({ pluginContext: createPluginInput(client) })
+    stubNotifyParentSession(manager)
+
+    const task = createMockTask({
+      id: "task-info-idle-completes",
+      sessionId: sessionID,
+      parentSessionId: "parent-session",
+      parentMessageId: "msg-info-idle",
+      description: "task completed by nested idle event",
+      agent: "explore",
+      status: "running",
+      startedAt: new Date(Date.now() - (MIN_IDLE_TIME_MS + 10)),
+    })
+    getTaskMap(manager).set(task.id, task)
+
+    //#when
+    manager.handleEvent({
+      type: "session.idle",
+      properties: { info: { id: sessionID } },
+    })
+    await new Promise((resolve) => setTimeout(resolve, 10))
+
+    //#then
+    expect(task.status).toBe("completed")
+
+    manager.shutdown()
+  })
+
   test("completes task on session.status idle after todo-continuation finishes", async () => {
     //#given
     const sessionID = "ses-status-idle-after-todo-continuation"
@@ -5747,6 +5795,54 @@ describe("BackgroundManager.handleEvent - non-tool event lastUpdate", () => {
     expect(task.progress!.toolCalls).toBe(2)
   })
 
+  test("should update lastUpdate when legacy message.part.updated only has part session id", () => {
+    //#given - a running task with stale lastUpdate
+    const client = {
+      session: {
+        prompt: async () => ({}),
+        promptAsync: async () => ({}),
+        abort: async () => ({}),
+      },
+    }
+    const manager = new BackgroundManager({ pluginContext: createPluginInput(client) })
+
+    const oldUpdate = new Date(Date.now() - 300_000)
+    const task: BackgroundTask = {
+      id: "task-part-only-1",
+      sessionId: "session-part-only-1",
+      parentSessionId: "parent-1",
+      parentMessageId: "msg-1",
+      description: "Legacy part-only task",
+      prompt: "Keep working",
+      agent: "oracle",
+      status: "running",
+      startedAt: new Date(Date.now() - 600_000),
+      progress: {
+        toolCalls: 0,
+        lastUpdate: oldUpdate,
+      },
+    }
+    getTaskMap(manager).set(task.id, task)
+
+    //#when - a legacy message.part.updated event arrives without top-level sessionID
+    manager.handleEvent({
+      type: "message.part.updated",
+      properties: {
+        part: {
+          id: "part-1",
+          messageID: "msg-1",
+          sessionID: "session-part-only-1",
+          type: "text",
+          text: "still working",
+        },
+      },
+    })
+
+    //#then - lastUpdate should be refreshed, toolCalls should remain 0
+    expect(task.progress!.lastUpdate.getTime()).toBeGreaterThan(oldUpdate.getTime())
+    expect(task.progress!.toolCalls).toBe(0)
+  })
+
   test("should update lastUpdate on thinking-type message.part.updated event", () => {
     //#given - a running task with stale lastUpdate
     const client = {

src/features/background-agent/manager.ts

@@ -18,6 +18,7 @@ import {
   resolveInheritedPromptTools,
   createInternalAgentTextPart,
 } from "../../shared"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../../shared/event-session-id"
 import { applySessionPromptParams } from "../../shared/session-prompt-params-helpers"
 import { setSessionTools } from "../../shared/session-tools-store"
 import { SessionCategoryRegistry } from "../../shared/session-category-registry"
@@ -118,7 +119,7 @@ interface MessagePartInfo {
 
 interface EventProperties {
   sessionID?: string
-  info?: { id?: string }
+  info?: { id?: string; sessionID?: string }
   [key: string]: unknown
 }
 
@@ -1260,8 +1261,9 @@ The fallback retry session is now created and can be inspected directly.
     this.observedIncompleteTodosBySession.delete(sessionID)
   }
 
-  private hasOutputSignalFromPart(partInfo: MessagePartInfo | undefined): boolean {
+  private hasOutputSignalFromPart(partInfo: MessagePartInfo | undefined, sessionID?: string): boolean {
-    if (!partInfo?.sessionID) return false
+    if (!partInfo) return false
+    if (!partInfo.sessionID && !sessionID) return false
     if (partInfo.tool) return true
     if (partInfo.type === "tool" || partInfo.type === "tool_result") return true
     if (partInfo.type === "text" || partInfo.type === "reasoning") return true
@@ -1279,9 +1281,9 @@ The fallback retry session is now created and can be inspected directly.
       const info = props?.info
       if (!info || typeof info !== "object") return
 
-      const sessionID = (info as Record<string, unknown>)["sessionID"]
+      const sessionID = resolveMessageEventSessionID(props)
       const role = (info as Record<string, unknown>)["role"]
-      if (typeof sessionID !== "string") return
+      if (!sessionID) return
 
       if (role === "tool") {
         this.markSessionOutputObserved(sessionID)
@@ -1312,7 +1314,7 @@ The fallback retry session is now created and can be inspected directly.
 
     if (event.type === "message.part.updated" || event.type === "message.part.delta") {
       const partInfo = resolveMessagePartInfo(props)
-      const sessionID = partInfo?.sessionID
+      const sessionID = resolveMessageEventSessionID(props)
       if (!sessionID) return
 
       const resolved = this.resolveTaskAttemptBySession(sessionID)
@@ -1320,7 +1322,7 @@ The fallback retry session is now created and can be inspected directly.
 
       const { task } = resolved
 
-      if (this.hasOutputSignalFromPart(partInfo)) {
+      if (this.hasOutputSignalFromPart(partInfo, sessionID)) {
         this.markSessionOutputObserved(sessionID)
       }
 
@@ -1404,7 +1406,7 @@ The fallback retry session is now created and can be inspected directly.
     }
 
     if (event.type === "todo.updated") {
-      const sessionID = typeof props?.sessionID === "string" ? props.sessionID : undefined
+      const sessionID = resolveSessionEventID(props)
       const todos = Array.isArray(props?.todos) ? props.todos : undefined
       if (!sessionID || !todos) return
 
@@ -1419,7 +1421,7 @@ The fallback retry session is now created and can be inspected directly.
 
     if (event.type === "session.idle") {
       if (!props || typeof props !== "object") return
-      const sessionID = typeof props.sessionID === "string" ? props.sessionID : undefined
+      const sessionID = resolveSessionEventID(props)
       if (sessionID) {
         void this.enqueueNotificationForParent(sessionID, () => this.flushPendingParentWake(sessionID)).catch((error) => {
           log("[background-agent] Failed to flush pending parent wake:", { sessionID, error })
@@ -1440,7 +1442,7 @@ The fallback retry session is now created and can be inspected directly.
     }
 
     if (event.type === "session.error") {
-      const sessionID = typeof props?.sessionID === "string" ? props.sessionID : undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID) return
 
       const resolved = this.resolveTaskAttemptBySession(sessionID)
@@ -1469,9 +1471,8 @@ The fallback retry session is now created and can be inspected directly.
     }
 
     if (event.type === "session.deleted") {
-      const info = props?.info
+      const sessionID = resolveSessionEventID(props)
-      if (!info || typeof info.id !== "string") return
+      if (!sessionID) return
-      const sessionID = info.id
       this.clearSessionOutputObserved(sessionID)
       this.clearSessionTodoObservation(sessionID)
 
@@ -1529,7 +1530,7 @@ The fallback retry session is now created and can be inspected directly.
     }
 
     if (event.type === "session.status") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       const status = props?.status as { type?: string; message?: string } | undefined
       if (!sessionID || !status?.type) return
 

src/features/background-agent/session-idle-event-handler.ts

@@ -1,12 +1,8 @@
 import { log } from "../../shared"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { MIN_IDLE_TIME_MS } from "./constants"
 import type { BackgroundTask } from "./types"
 
-function getString(obj: Record<string, unknown>, key: string): string | undefined {
-  const value = obj[key]
-  return typeof value === "string" ? value : undefined
-}
-
 export function handleSessionIdleBackgroundEvent(args: {
   properties: Record<string, unknown>
   findBySession: (sessionID: string) => BackgroundTask | undefined
@@ -26,7 +22,7 @@ export function handleSessionIdleBackgroundEvent(args: {
     emitIdleEvent,
   } = args
 
-  const sessionID = getString(properties, "sessionID")
+  const sessionID = resolveSessionEventID(properties)
   if (!sessionID) return
 
   const task = findBySession(sessionID)

src/features/tmux-subagent/manager.ts

@@ -2,6 +2,7 @@ import type { PluginInput } from "@opencode-ai/plugin"
 import type { TmuxConfig } from "../../config/schema"
 import type { TrackedSession, CapacityConfig, WindowState } from "./types"
 import * as sharedModule from "../../shared"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import {
   isInsideTmux as defaultIsInsideTmux,
   getCurrentPaneId as defaultGetCurrentPaneId,
@@ -1098,9 +1099,9 @@ export class TmuxSessionManager {
     if (event.type !== "session.created") return
 
     const info = event.properties?.info
-    if (!info?.id || !info?.parentID) return
+    const sessionId = resolveSessionEventID(event.properties)
+    if (!sessionId || !info?.parentID) return
 
-    const sessionId = info.id
     const title = info.title ?? "Subagent"
 
     if (!this.sourcePaneId) {

src/features/tmux-subagent/polling-manager-event-session-id.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, test } from "bun:test"
+
+import { TmuxPollingManager } from "./polling-manager"
+import type { TrackedSession } from "./types"
+
+describe("TmuxPollingManager event session ids", () => {
+  test("#given legacy message.part.updated properties #when handling activity #then part session id increments activity version", () => {
+    const sessions = new Map<string, TrackedSession>()
+    sessions.set("ses-part-only", {
+      sessionId: "ses-part-only",
+      paneId: "%1",
+      description: "test",
+      createdAt: new Date(),
+      lastSeenAt: new Date(),
+      closePending: false,
+      closeRetryCount: 0,
+      activityVersion: 0,
+    })
+
+    const client = {
+      session: {
+        status: async () => ({ data: {} }),
+        messages: async () => ({ data: [] }),
+      },
+    }
+    const manager = new TmuxPollingManager(client as never, sessions, async () => {})
+
+    manager.handleEvent({
+      type: "message.part.updated",
+      properties: {
+        part: {
+          id: "part-1",
+          messageID: "msg-1",
+          sessionID: "ses-part-only",
+          type: "text",
+          text: "working",
+        },
+      },
+    })
+
+    expect(sessions.get("ses-part-only")?.activityVersion).toBe(1)
+  })
+})

src/features/tmux-subagent/polling-manager.ts

@@ -7,6 +7,7 @@ import {
 import type { TrackedSession } from "./types"
 import { log } from "../../shared"
 import { normalizeSDKResponse } from "../../shared"
+import { resolveMessageEventSessionID } from "../../shared/event-session-id"
 
 const MIN_STABILITY_TIME_MS = 10 * 1000
 const STABLE_POLLS_REQUIRED = 3
@@ -170,10 +171,7 @@ export class TmuxPollingManager {
     if (!properties) return undefined
 
     if (event.type === "message.updated") {
-      const info = properties.info
+      return resolveMessageEventSessionID(properties)
-      if (!info || typeof info !== "object") return undefined
-      const sessionId = (info as { sessionID?: unknown }).sessionID
-      return typeof sessionId === "string" ? sessionId : undefined
     }
 
     if (
@@ -182,8 +180,7 @@ export class TmuxPollingManager {
       || event.type === "message.part.removed"
       || event.type === "message.removed"
     ) {
-      const sessionId = properties.sessionID
+      return resolveMessageEventSessionID(properties)
-      return typeof sessionId === "string" ? sessionId : undefined
     }
 
     return undefined

src/features/tmux-subagent/session-created-handler.ts

@@ -2,6 +2,7 @@ import type { PluginInput } from "@opencode-ai/plugin"
 import type { TmuxConfig } from "../../config/schema"
 import type { CapacityConfig, TrackedSession } from "./types"
 import { log } from "../../shared"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { queryWindowState } from "./pane-state-querier"
 import { decideSpawnActions, type SessionMapping } from "./decision-engine"
 import { executeActions } from "./action-executor"
@@ -44,9 +45,9 @@ export async function handleSessionCreated(
   if (event.type !== "session.created") return
 
   const info = event.properties?.info
-  if (!info?.id || !info?.parentID) return
+  const sessionId = resolveSessionEventID(event.properties)
+  if (!sessionId || !info?.parentID) return
 
-  const sessionId = info.id
   const title = info.title ?? "Subagent"
 
   if (deps.sessions.has(sessionId) || deps.pendingSessions.has(sessionId)) {

src/hooks/agent-usage-reminder/hook.ts

@@ -8,6 +8,7 @@ import { TARGET_TOOLS, AGENT_TOOLS, REMINDER_MESSAGE } from "./constants";
 import type { AgentUsageState } from "./types";
 import { getSessionAgent } from "../../features/claude-code-session-state";
 import { getAgentConfigKey } from "../../shared/agent-display-names";
+import { resolveSessionEventID } from "../../shared/event-session-id";
 
 interface ToolExecuteInput {
   tool: string;
@@ -112,15 +113,14 @@ export function createAgentUsageReminderHook(_ctx: PluginInput) {
     const props = event.properties as Record<string, unknown> | undefined;
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined;
+      const sessionID = resolveSessionEventID(props);
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        resetState(sessionInfo.id);
+        resetState(sessionID);
       }
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ??
+      const sessionID = resolveSessionEventID(props);
-        (props?.info as { id?: string } | undefined)?.id) as string | undefined;
       if (sessionID) {
         resetState(sessionID);
       }

src/hooks/anthropic-context-window-limit-recovery/recovery-hook.ts

@@ -7,6 +7,7 @@ import { executeCompact, getLastAssistant } from "./executor"
 import { attemptDeduplicationRecovery } from "./deduplication-recovery"
 import { clearSessionState } from "./state"
 import { clearAllSessionTimeouts, clearSessionTimeout } from "./session-timeout-map"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 
 export interface AnthropicContextWindowLimitRecoveryOptions {
@@ -53,17 +54,17 @@ export function createAnthropicContextWindowLimitRecoveryHook(
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        clearSessionTimeout(pendingCompactionTimeoutBySession, sessionInfo.id)
+        clearSessionTimeout(pendingCompactionTimeoutBySession, sessionID)
 
-        clearSessionState(autoCompactState, sessionInfo.id)
+        clearSessionState(autoCompactState, sessionID)
       }
       return
     }
 
     if (event.type === "session.error") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       dependencies.log("[auto-compact] session.error received", { sessionID, error: props?.error })
       if (!sessionID) return
 
@@ -120,7 +121,7 @@ export function createAnthropicContextWindowLimitRecoveryHook(
 
     if (event.type === "message.updated") {
       const info = props?.info as Record<string, unknown> | undefined
-      const sessionID = info?.sessionID as string | undefined
+      const sessionID = resolveMessageEventSessionID(props)
 
       if (sessionID && info?.role === "assistant" && info.error) {
         dependencies.log("[auto-compact] message.updated with error", { sessionID, error: info.error })
@@ -137,7 +138,7 @@ export function createAnthropicContextWindowLimitRecoveryHook(
     }
 
     if (event.type === "session.idle") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID) return
 
       if (!autoCompactState.pendingCompact.has(sessionID)) return

src/hooks/atlas/event-handler.ts

@@ -1,5 +1,6 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import { log } from "../../shared/logger"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../../shared/event-session-id"
 import { HOOK_NAME } from "./hook-name"
 import { isAbortError } from "./is-abort-error"
 import { handleAtlasSessionIdle } from "./idle-event"
@@ -17,7 +18,7 @@ export function createAtlasEventHandler(input: {
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.error") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID) return
 
       const state = getState(sessionID)
@@ -39,7 +40,7 @@ export function createAtlasEventHandler(input: {
     }
 
     if (event.type === "session.idle") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID) return
       await handleAtlasSessionIdle({ ctx, options, getState, sessionID })
       return
@@ -47,7 +48,7 @@ export function createAtlasEventHandler(input: {
 
     if (event.type === "message.updated") {
       const info = props?.info as Record<string, unknown> | undefined
-      const sessionID = info?.sessionID as string | undefined
+      const sessionID = resolveMessageEventSessionID(props)
       const role = info?.role as string | undefined
       if (!sessionID) return
 
@@ -64,7 +65,7 @@ export function createAtlasEventHandler(input: {
 
     if (event.type === "message.part.updated") {
       const info = props?.info as Record<string, unknown> | undefined
-      const sessionID = info?.sessionID as string | undefined
+      const sessionID = resolveMessageEventSessionID(props)
       const role = info?.role as string | undefined
 
       if (sessionID && role === "assistant") {
@@ -78,7 +79,7 @@ export function createAtlasEventHandler(input: {
     }
 
     if (event.type === "tool.execute.before" || event.type === "tool.execute.after") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveMessageEventSessionID(props)
       if (sessionID) {
         const state = sessions.get(sessionID)
         if (state) {
@@ -90,20 +91,20 @@ export function createAtlasEventHandler(input: {
     }
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        const deletedState = sessions.get(sessionInfo.id)
+        const deletedState = sessions.get(sessionID)
         if (deletedState?.pendingRetryTimer) {
           clearTimeout(deletedState.pendingRetryTimer)
         }
-        sessions.delete(sessionInfo.id)
+        sessions.delete(sessionID)
-        log(`[${HOOK_NAME}] Session deleted: cleaned up`, { sessionID: sessionInfo.id })
+        log(`[${HOOK_NAME}] Session deleted: cleaned up`, { sessionID })
       }
       return
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ?? (props?.info as { id?: string } | undefined)?.id) as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (sessionID) {
         const compactedState = sessions.get(sessionID)
         if (compactedState?.pendingRetryTimer) {

src/hooks/atlas/index.test.ts

@@ -1347,6 +1347,38 @@ session_id: ses_untrusted_999
       expect(callArgs.body.parts[0].text).toContain("2 remaining")
     })
 
+    test("should inject continuation when idle event carries session id in info", async () => {
+      // given - boulder state with incomplete plan and nested session event shape
+      const planPath = join(TEST_DIR, "test-plan-info-idle.md")
+      writeFileSync(planPath, "# Plan\n- [ ] Task 1\n- [x] Task 2\n- [ ] Task 3")
+
+      const state: BoulderState = {
+        active_plan: planPath,
+        started_at: "2026-01-02T10:00:00Z",
+        session_ids: [MAIN_SESSION_ID],
+        plan_name: "test-plan-info-idle",
+      }
+      writeBoulderState(TEST_DIR, state)
+
+      const mockInput = createMockPluginInput()
+      const hook = createTestAtlasHook(mockInput)
+
+      // when
+      await hook.handler({
+        event: {
+          type: "session.idle",
+          properties: { info: { id: MAIN_SESSION_ID } },
+        },
+      })
+
+      // then - should call prompt with continuation
+      expect(mockInput._promptMock).toHaveBeenCalled()
+      const callArgs = mockInput._promptMock.mock.calls[0][0]
+      expect(callArgs.path.id).toBe(MAIN_SESSION_ID)
+      expect(callArgs.body.parts[0].text).toContain("incomplete tasks")
+      expect(callArgs.body.parts[0].text).toContain("2 remaining")
+    })
+
     test("should settle idle before injecting boulder continuation", async () => {
       // given
       const planPath = join(TEST_DIR, "test-plan.md")

src/hooks/auto-slash-command/hook.ts

@@ -5,6 +5,7 @@ import {
 } from "./detector"
 import { executeSlashCommand, type ExecutorOptions } from "./executor"
 import { log } from "../../shared"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import {
   AUTO_SLASH_COMMAND_TAG_CLOSE,
   AUTO_SLASH_COMMAND_TAG_OPEN,
@@ -25,16 +26,7 @@ function isRecord(value: unknown): value is Record<string, unknown> {
 }
 
 function getDeletedSessionID(properties: unknown): string | null {
-  if (!isRecord(properties)) {
+  return resolveSessionEventID(properties) ?? null
-    return null
-  }
-
-  const info = properties.info
-  if (!isRecord(info)) {
-    return null
-  }
-
-  return typeof info.id === "string" ? info.id : null
 }
 
 function getCommandExecutionEventID(input: CommandExecuteBeforeInput): string | null {
@@ -49,7 +41,7 @@ function getCommandExecutionEventID(input: CommandExecuteBeforeInput): string |
     "commandId",
   ]
 
-  const recordInput = input as unknown
+  const recordInput: unknown = input
   if (!isRecord(recordInput)) {
     return null
   }

src/hooks/category-skill-reminder/hook.ts

@@ -3,6 +3,7 @@ import type { AvailableSkill } from "../../agents/dynamic-agent-prompt-builder"
 import { getSessionAgent } from "../../features/claude-code-session-state"
 import { log } from "../../shared"
 import { getAgentConfigKey } from "../../shared/agent-display-names"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { buildReminderMessage } from "./formatter"
 
 /**
@@ -120,15 +121,14 @@ export function createCategorySkillReminderHook(
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        sessionStates.delete(sessionInfo.id)
+        sessionStates.delete(sessionID)
       }
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ??
+      const sessionID = resolveSessionEventID(props)
-        (props?.info as { id?: string } | undefined)?.id) as string | undefined
       if (sessionID) {
         sessionStates.delete(sessionID)
       }

src/hooks/claude-code-hooks/handlers/session-event-handler.ts

@@ -7,6 +7,7 @@ import { clearTranscriptCache } from "../transcript"
 import { clearToolInputCache, stopToolInputCacheCleanup } from "../tool-input-cache"
 import type { PluginConfig } from "../types"
 import { createInternalAgentTextPart, isHookDisabled, log } from "../../../shared"
+import { resolveSessionEventID } from "../../../shared/event-session-id"
 import {
 	clearAllSessionHookState,
 	clearSessionHookState,
@@ -26,7 +27,7 @@ export function createSessionEventHandler(
 
 		if (event.type === "session.error") {
 			const props = event.properties as Record<string, unknown> | undefined
-			const sessionID = props?.sessionID as string | undefined
+			const sessionID = resolveSessionEventID(props)
 			if (sessionID) {
 				sessionErrorState.set(sessionID, {
 					hasError: true,
@@ -38,13 +39,13 @@ export function createSessionEventHandler(
 
 		if (event.type === "session.deleted") {
 			const props = event.properties as Record<string, unknown> | undefined
-			const sessionInfo = props?.info as { id?: string } | undefined
+			const sessionID = resolveSessionEventID(props)
-			if (sessionInfo?.id) {
+			if (sessionID) {
-				parentSessionIdCache.delete(sessionInfo.id)
+				parentSessionIdCache.delete(sessionID)
-				clearTranscriptCache(sessionInfo.id)
+				clearTranscriptCache(sessionID)
-				clearToolInputCache(sessionInfo.id)
+				clearToolInputCache(sessionID)
-				contextCollector?.clear(sessionInfo.id)
+				contextCollector?.clear(sessionID)
-				clearSessionHookState(sessionInfo.id)
+				clearSessionHookState(sessionID)
 			}
 			return
 		}
@@ -54,7 +55,7 @@ export function createSessionEventHandler(
 		}
 
 		const props = event.properties as Record<string, unknown> | undefined
-		const sessionID = props?.sessionID as string | undefined
+		const sessionID = resolveSessionEventID(props)
 		if (!sessionID) return
 
 		const claudeConfig = await loadClaudeHooksConfig()

src/hooks/compaction-context-injector/hook.ts

@@ -3,6 +3,7 @@ import {
   clearCompactionAgentConfigCheckpoint,
   setCompactionAgentConfigCheckpoint,
 } from "../../shared/compaction-agent-config-checkpoint"
+import { resolveMessageEventSessionID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 import { COMPACTION_CONTEXT_PROMPT } from "./compaction-context-prompt"
 import { resolveSessionPromptConfig } from "./session-prompt-config-resolver"
@@ -121,14 +122,15 @@ export function createCompactionContextInjector(options?: {
         sessionID?: string
       } | undefined
 
-      if (!info?.sessionID || info.role !== "assistant" || !info.id) {
+      const sessionID = resolveMessageEventSessionID(props)
+      if (!sessionID || info?.role !== "assistant" || !info.id) {
         return
       }
 
-      const tailState = getTailState(info.sessionID)
+      const tailState = getTailState(sessionID)
       if (tailState.currentMessageID && tailState.currentMessageID !== info.id) {
         finalizeTrackedAssistantMessage(tailState)
-        await maybeWarnAboutNoTextTail(info.sessionID)
+        await maybeWarnAboutNoTextTail(sessionID)
       }
 
       if (tailState.currentMessageID !== info.id) {
@@ -139,7 +141,7 @@ export function createCompactionContextInjector(options?: {
     }
 
     if (event.type === "message.part.delta") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveMessageEventSessionID(props)
       const messageID = props?.messageID as string | undefined
       const field = props?.field as string | undefined
       const delta = props?.delta as string | undefined

src/hooks/compaction-context-injector/session-id.ts

@@ -1,8 +1,9 @@
+import { resolveSessionEventID } from "../../shared/event-session-id"
+
 export function isCompactionAgent(agent: string | undefined): boolean {
   return agent?.trim().toLowerCase() === "compaction"
 }
 
 export function resolveSessionID(props?: Record<string, unknown>): string | undefined {
-  return (props?.sessionID ??
+  return resolveSessionEventID(props)
-    (props?.info as { id?: string } | undefined)?.id) as string | undefined
 }

src/hooks/compaction-todo-preserver/hook.ts

@@ -1,4 +1,5 @@
 import type { PluginInput } from "@opencode-ai/plugin"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 
 interface TodoSnapshot {
@@ -97,8 +98,7 @@ async function resolveTodoWriter(): Promise<TodoWriter | null> {
 }
 
 function resolveSessionID(props?: Record<string, unknown>): string | undefined {
-  return (props?.sessionID ??
+  return resolveSessionEventID(props)
-    (props?.info as { id?: string } | undefined)?.id) as string | undefined
 }
 
 export interface CompactionTodoPreserver {

src/hooks/context-window-monitor.ts

@@ -4,6 +4,7 @@ import {
   type ContextLimitModelCacheState,
 } from "../shared/context-limit-resolver"
 import { isCompactionAgent } from "../shared/compaction-marker"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../shared/event-session-id"
 import { createSystemDirective, SystemDirectiveTypes } from "../shared/system-directive"
 
 const CONTEXT_WARNING_THRESHOLD = 0.70
@@ -86,10 +87,10 @@ export function createContextWindowMonitorHook(
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        remindedSessions.delete(sessionInfo.id)
+        remindedSessions.delete(sessionID)
-        tokenCache.delete(sessionInfo.id)
+        tokenCache.delete(sessionID)
       }
     }
 
@@ -106,9 +107,10 @@ export function createContextWindowMonitorHook(
 
       if (!info || info.role !== "assistant" || !info.finish) return
       if (isCompactionAgent(info.agent)) return
-      if (!info.sessionID || !info.providerID || !info.tokens) return
+      const sessionID = resolveMessageEventSessionID(props)
+      if (!sessionID || !info.providerID || !info.tokens) return
 
-      tokenCache.set(info.sessionID, {
+      tokenCache.set(sessionID, {
         providerID: info.providerID,
         modelID: info.modelID ?? "",
         tokens: info.tokens,

src/hooks/directory-agents-injector/hook.ts

@@ -1,6 +1,7 @@
 import type { PluginInput } from "@opencode-ai/plugin";
 
 import { createDynamicTruncator } from "../../shared/dynamic-truncator";
+import { resolveSessionEventID } from "../../shared/event-session-id";
 import { processFilePathForAgentsInjection } from "./injector";
 import { clearInjectedPaths } from "./storage";
 
@@ -56,16 +57,15 @@ export function createDirectoryAgentsInjectorHook(
     const props = event.properties as Record<string, unknown> | undefined;
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined;
+      const sessionID = resolveSessionEventID(props);
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        sessionCaches.delete(sessionInfo.id);
+        sessionCaches.delete(sessionID);
-        clearInjectedPaths(sessionInfo.id);
+        clearInjectedPaths(sessionID);
       }
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ??
+      const sessionID = resolveSessionEventID(props);
-        (props?.info as { id?: string } | undefined)?.id) as string | undefined;
       if (sessionID) {
         sessionCaches.delete(sessionID);
         clearInjectedPaths(sessionID);

src/hooks/directory-readme-injector/hook.ts

@@ -1,6 +1,7 @@
 import type { PluginInput } from "@opencode-ai/plugin";
 
 import { createDynamicTruncator } from "../../shared/dynamic-truncator";
+import { resolveSessionEventID } from "../../shared/event-session-id";
 import { processFilePathForReadmeInjection } from "./injector";
 import { clearInjectedPaths } from "./storage";
 
@@ -56,16 +57,15 @@ export function createDirectoryReadmeInjectorHook(
     const props = event.properties as Record<string, unknown> | undefined;
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined;
+      const sessionID = resolveSessionEventID(props);
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        sessionCaches.delete(sessionInfo.id);
+        sessionCaches.delete(sessionID);
-        clearInjectedPaths(sessionInfo.id);
+        clearInjectedPaths(sessionID);
       }
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ??
+      const sessionID = resolveSessionEventID(props);
-        (props?.info as { id?: string } | undefined)?.id) as string | undefined;
       if (sessionID) {
         sessionCaches.delete(sessionID);
         clearInjectedPaths(sessionID);

src/hooks/interactive-bash-session/hook.ts

@@ -5,6 +5,7 @@ import type { InteractiveBashSessionState } from "./types";
 import { tokenizeCommand, findSubcommand, extractSessionNameFromTokens } from "./parser";
 import { getOrCreateState, isOmoSession, killAllTrackedSessions } from "./state-manager";
 import { subagentSessions } from "../../features/claude-code-session-state";
+import { resolveSessionEventID } from "../../shared/event-session-id";
 
 interface ToolExecuteInput {
   tool: string;
@@ -106,8 +107,7 @@ export function createInteractiveBashSessionHook(ctx: PluginInput) {
     const props = event.properties as Record<string, unknown> | undefined;
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined;
+      const sessionID = resolveSessionEventID(props);
-      const sessionID = sessionInfo?.id;
 
       if (sessionID) {
         const state = getOrCreateStateLocal(sessionID);

src/hooks/preemptive-compaction.ts

@@ -1,5 +1,6 @@
 import type { OhMyOpenCodeConfig } from "../config"
 import { isCompactionAgent } from "../shared/compaction-marker"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../shared/event-session-id"
 import type { ContextLimitModelCacheState } from "../shared/context-limit-resolver"
 
 import { createPostCompactionDegradationMonitor } from "./preemptive-compaction-degradation-monitor"
@@ -48,7 +49,7 @@ export function createPreemptiveCompactionHook(
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.deleted") {
-      const sessionID = (props?.info as { id?: string } | undefined)?.id
+      const sessionID = resolveSessionEventID(props)
       if (sessionID) {
         compactionInProgress.delete(sessionID)
         compactedSessions.delete(sessionID)
@@ -60,8 +61,7 @@ export function createPreemptiveCompactionHook(
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID as string | undefined)
+      const sessionID = resolveSessionEventID(props)
-        ?? (props?.info as { id?: string } | undefined)?.id
       if (sessionID) {
         postCompactionMonitor.onSessionCompacted(sessionID)
       }
@@ -81,20 +81,21 @@ export function createPreemptiveCompactionHook(
         parts?: unknown
       } | undefined
 
-      if (!info || info.role !== "assistant" || !info.finish || !info.sessionID) return
+      const sessionID = resolveMessageEventSessionID(props)
+      if (!info || info.role !== "assistant" || !info.finish || !sessionID) return
       if (isCompactionAgent(info.agent)) return
 
       if (info.providerID && info.tokens) {
-        tokenCache.set(info.sessionID, {
+        tokenCache.set(sessionID, {
           providerID: info.providerID,
           modelID: info.modelID ?? "",
           tokens: info.tokens,
         })
       }
-      compactedSessions.delete(info.sessionID)
+      compactedSessions.delete(sessionID)
 
       await postCompactionMonitor.onAssistantMessageUpdated({
-        sessionID: info.sessionID,
+        sessionID,
         id: info.id,
         parts: info.parts,
       })

src/hooks/ralph-loop/index.test.ts

@@ -304,6 +304,25 @@ describe("ralph-loop", () => {
       expect(state?.iteration).toBe(2)
     })
 
+    test("should inject continuation when idle event carries session id in info", async () => {
+      // given - active loop state and nested session event shape
+      const hook = createRalphLoopHook(createMockPluginInput())
+      hook.startLoop("session-info-idle", "Build a feature", { maxIterations: 10 })
+
+      // when - session goes idle with id under info
+      await hook.event({
+        event: {
+          type: "session.idle",
+          properties: { info: { id: "session-info-idle" } },
+        },
+      })
+
+      // then - continuation should be injected for that session
+      expect(promptCalls.length).toBe(1)
+      expect(promptCalls[0].sessionID).toBe("session-info-idle")
+      expect(promptCalls[0].text).toContain("RALPH LOOP")
+    })
+
     test("should settle idle before injecting continuation", async () => {
       // given - active loop state with a configured idle settle delay
       const hook = createRalphLoopHook(createMockPluginInput(), { idleSettleMs: 25 })

src/hooks/ralph-loop/non-abort-error-continuation.test.ts

@@ -213,6 +213,77 @@ describe("ralph-loop non-abort error continuation", () => {
 		expect(hook.getState()?.iteration).toBe(3)
 	})
 
+	test("continues after retry run activity from legacy message.part.updated part session id", async () => {
+		// given - an active loop retries a recoverable runtime error
+		const hook = createRalphLoopHook({
+			directory: testDirectory,
+			project: testDirectory,
+			worktree: testDirectory,
+			serverUrl: "http://localhost:4096",
+			$: async () => ({}),
+			client: {
+				session: {
+					messages: async (options: { path: { id: string } }) => {
+						messagesCalls.push({ sessionID: options.path.id })
+						return { data: [] }
+					},
+					promptAsync: async (options: {
+						path: { id: string }
+						body: { parts: Array<{ type: string; text: string }> }
+					}) => {
+						promptCalls.push({
+							sessionID: options.path.id,
+							text: options.body.parts[0]?.text ?? "",
+						})
+						return {}
+					},
+					prompt: async () => ({}),
+				},
+				tui: {
+					showToast: async () => ({}),
+				},
+			},
+		} as never)
+
+		hook.startLoop("session-123", "Keep working", {
+			messageCountAtStart: 0,
+			maxIterations: 5,
+		})
+
+		await hook.event({
+			event: {
+				type: "session.error",
+				properties: {
+					sessionID: "session-123",
+					error: { name: "RuntimeError" },
+				},
+			},
+		})
+
+		// when - the retried run emits legacy assistant activity before any stale idle
+		await hook.event({
+			event: {
+				type: "message.part.updated",
+				properties: {
+					part: {
+						id: "part-1",
+						messageID: "msg-1",
+						sessionID: "session-123",
+						type: "text",
+						text: "working",
+					},
+				},
+			},
+		})
+		await hook.event({
+			event: { type: "session.idle", properties: { sessionID: "session-123" } },
+		})
+
+		// then - the real idle is allowed to continue the loop
+		expect(promptCalls).toHaveLength(2)
+		expect(hook.getState()?.iteration).toBe(3)
+	})
+
 	test("skips immediate runtime retry while background tasks are running", async () => {
 		// given - an active loop owns running background work
 		const hook = createRalphLoopHook({

src/hooks/ralph-loop/ralph-loop-event-handler.ts

@@ -1,5 +1,6 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import { log } from "../../shared/logger"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../../shared/event-session-id"
 import type { RalphLoopOptions, RalphLoopState } from "./types"
 import { HOOK_NAME } from "./constants"
 import { handleDetectedCompletion } from "./completion-handler"
@@ -36,12 +37,6 @@ function hasRunningBackgroundTasks(
 		: false
 }
 
-function getInfoSessionID(props: Record<string, unknown> | undefined): string | undefined {
-	const info = props?.info as Record<string, unknown> | undefined
-	const sessionID = info?.sessionID
-	return typeof sessionID === "string" ? sessionID : undefined
-}
-
 function getRuntimeRetryActivitySessionID(
 	eventType: string,
 	props: Record<string, unknown> | undefined,
@@ -49,20 +44,19 @@ function getRuntimeRetryActivitySessionID(
 	if (eventType === "message.updated") {
 		const info = props?.info as Record<string, unknown> | undefined
 		const role = info?.role
-		return role === "assistant" ? getInfoSessionID(props) : undefined
+		return role === "assistant" ? resolveMessageEventSessionID(props) : undefined
 	}
 
 	if (eventType === "message.part.updated") {
-		if (typeof props?.sessionID === "string") return props.sessionID
+		return resolveMessageEventSessionID(props)
-		return getInfoSessionID(props)
 	}
 
 	if (eventType === "message.part.delta") {
-		return typeof props?.sessionID === "string" ? props.sessionID : undefined
+		return resolveMessageEventSessionID(props)
 	}
 
 	if (eventType === "tool.execute.before" || eventType === "tool.execute.after") {
-		return typeof props?.sessionID === "string" ? props.sessionID : undefined
+		return resolveMessageEventSessionID(props)
 	}
 
 	return undefined
@@ -198,7 +192,7 @@ export function createRalphLoopEventHandler(
 		}
 
 		if (event.type === "session.idle") {
-			const sessionID = props?.sessionID as string | undefined
+			const sessionID = resolveSessionEventID(props)
 			if (!sessionID) return
 
 			if (inFlightSessions.has(sessionID)) {
@@ -389,7 +383,7 @@ export function createRalphLoopEventHandler(
 		}
 
 		if (event.type === "session.error") {
-			const sessionID = props?.sessionID as string | undefined
+			const sessionID = resolveSessionEventID(props)
 			const error = props?.error
 			if (!sessionID || isAbortError(error)) {
 				handleErroredLoopSession(props, options.loopState)

src/hooks/ralph-loop/session-event-handler.ts

@@ -1,4 +1,5 @@
 import { log } from "../../shared/logger"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { HOOK_NAME } from "./constants"
 import type { RalphLoopState } from "./types"
 
@@ -11,13 +12,13 @@ export function handleDeletedLoopSession(
 	props: Record<string, unknown> | undefined,
 	loopState: LoopStateController,
 ): boolean {
-	const sessionInfo = props?.info as { id?: string } | undefined
+	const sessionID = resolveSessionEventID(props)
-	if (!sessionInfo?.id) return false
+	if (!sessionID) return false
 
 	const state = loopState.getState()
-	if (state?.session_id === sessionInfo.id) {
+	if (state?.session_id === sessionID) {
 		loopState.clear()
-		log(`[${HOOK_NAME}] Session deleted, loop cleared`, { sessionID: sessionInfo.id })
+		log(`[${HOOK_NAME}] Session deleted, loop cleared`, { sessionID })
 	}
 	return true
 }
@@ -26,7 +27,7 @@ export function handleErroredLoopSession(
 	props: Record<string, unknown> | undefined,
 	loopState: LoopStateController,
 ): boolean {
-	const sessionID = props?.sessionID as string | undefined
+	const sessionID = resolveSessionEventID(props)
 	const error = props?.error as { name?: string } | undefined
 
 	if (error?.name === "MessageAbortedError") {

src/hooks/rules-injector/hook.ts

@@ -1,5 +1,6 @@
 import type { PluginInput } from "@opencode-ai/plugin";
 import { createDynamicTruncator } from "../../shared/dynamic-truncator";
+import { resolveSessionEventID } from "../../shared/event-session-id";
 import { getRuleInjectionFilePath } from "./output-path";
 import { createSessionCacheStore, createSessionRuleScanCacheStore } from "./cache";
 import { createRuleInjectionProcessor } from "./injector";
@@ -80,16 +81,15 @@ export function createRulesInjectorHook(
     const props = event.properties as Record<string, unknown> | undefined;
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined;
+      const sessionID = resolveSessionEventID(props);
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        clearSessionState(sessionInfo.id);
+        clearSessionState(sessionID);
       }
       clearProjectRootCache();
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ??
+      const sessionID = resolveSessionEventID(props);
-        (props?.info as { id?: string } | undefined)?.id) as string | undefined;
       if (sessionID) {
         clearSessionState(sessionID);
       }

src/hooks/runtime-fallback/event-handler.ts

@@ -10,6 +10,7 @@ import { isAbortError } from "../../shared/is-abort-error"
 import { resolveFallbackBootstrapModel } from "./fallback-bootstrap-model"
 import { dispatchFallbackRetry } from "./fallback-retry-dispatcher"
 import { createSessionStatusHandler } from "./session-status-handler"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../../shared/event-session-id"
 
 export function createEventHandler(deps: HookDeps, helpers: AutoRetryHelpers) {
   const { config, pluginConfig, sessionStates, sessionLastAccess, sessionRetryInFlight, sessionAwaitingFallbackResult, sessionFallbackTimeouts, sessionStatusRetryKeys } = deps
@@ -30,7 +31,7 @@ export function createEventHandler(deps: HookDeps, helpers: AutoRetryHelpers) {
 
   const handleSessionCreated = (props: Record<string, unknown> | undefined) => {
     const sessionInfo = props?.info as { id?: string; model?: string } | undefined
-    const sessionID = sessionInfo?.id
+    const sessionID = resolveSessionEventID(props)
     const model = sessionInfo?.model
 
     if (sessionID && model) {
@@ -41,8 +42,7 @@ export function createEventHandler(deps: HookDeps, helpers: AutoRetryHelpers) {
   }
 
   const handleSessionDeleted = (props: Record<string, unknown> | undefined) => {
-    const sessionInfo = props?.info as { id?: string } | undefined
+    const sessionID = resolveSessionEventID(props)
-    const sessionID = sessionInfo?.id
 
     if (sessionID) {
       log(`[${HOOK_NAME}] Cleaning up session state`, { sessionID })
@@ -58,7 +58,7 @@ export function createEventHandler(deps: HookDeps, helpers: AutoRetryHelpers) {
   }
 
   const handleSessionStop = async (props: Record<string, unknown> | undefined) => {
-    const sessionID = props?.sessionID as string | undefined
+    const sessionID = resolveSessionEventID(props)
     if (!sessionID) return
 
     if (sessionRetryInFlight.has(sessionID) || sessionAwaitingFallbackResult.has(sessionID)) {
@@ -73,7 +73,7 @@ export function createEventHandler(deps: HookDeps, helpers: AutoRetryHelpers) {
 
   const handleMessageUpdated = (props: Record<string, unknown> | undefined) => {
     const info = props?.info as Record<string, unknown> | undefined
-    const sessionID = info?.sessionID as string | undefined
+    const sessionID = resolveMessageEventSessionID(props)
     const role = info?.role as string | undefined
     if (!sessionID || role !== "user") return
 
@@ -81,7 +81,7 @@ export function createEventHandler(deps: HookDeps, helpers: AutoRetryHelpers) {
   }
 
   const handleSessionIdle = (props: Record<string, unknown> | undefined) => {
-    const sessionID = props?.sessionID as string | undefined
+    const sessionID = resolveSessionEventID(props)
     if (!sessionID) return
 
     if (cancelledSessions.has(sessionID)) {
@@ -111,7 +111,7 @@ export function createEventHandler(deps: HookDeps, helpers: AutoRetryHelpers) {
   }
 
   const handleSessionError = async (props: Record<string, unknown> | undefined) => {
-    const sessionID = props?.sessionID as string | undefined
+    const sessionID = resolveSessionEventID(props)
     const error = props?.error
     const agent = props?.agent as string | undefined
 

src/hooks/runtime-fallback/message-update-handler.ts

@@ -8,6 +8,7 @@ import { getFallbackModelsForSession } from "./fallback-models"
 import { resolveFallbackBootstrapModel } from "./fallback-bootstrap-model"
 import { dispatchFallbackRetry } from "./fallback-retry-dispatcher"
 import { hasVisibleAssistantResponse } from "./visible-assistant-response"
+import { resolveMessageEventSessionID } from "../../shared/event-session-id"
 
 export { hasVisibleAssistantResponse } from "./visible-assistant-response"
 
@@ -17,7 +18,7 @@ export function createMessageUpdateHandler(deps: HookDeps, helpers: AutoRetryHel
 
   return async (props: Record<string, unknown> | undefined) => {
     const info = props?.info as Record<string, unknown> | undefined
-    const sessionID = info?.sessionID as string | undefined
+    const sessionID = resolveMessageEventSessionID(props)
     const timeoutEnabled = config.timeout_seconds > 0
     const eventParts = props?.parts as Array<{ type?: string; text?: string }> | undefined
     const infoParts = info?.parts as Array<{ type?: string; text?: string }> | undefined

src/hooks/runtime-fallback/session-status-handler.ts

@@ -8,6 +8,7 @@ import { getFallbackModelsForSession } from "./fallback-models"
 import { normalizeRetryStatusMessage, extractRetryAttempt } from "../../shared/retry-status-utils"
 import { resolveFallbackBootstrapModel } from "./fallback-bootstrap-model"
 import { dispatchFallbackRetry } from "./fallback-retry-dispatcher"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 
 export function createSessionStatusHandler(
   deps: HookDeps,
@@ -22,7 +23,7 @@ export function createSessionStatusHandler(
   } = deps
 
   return async (props: Record<string, unknown> | undefined) => {
-    const sessionID = props?.sessionID as string | undefined
+    const sessionID = resolveSessionEventID(props)
     const status = props?.status as { type?: string; message?: string; attempt?: number } | undefined
     const agent = props?.agent as string | undefined
     const model = props?.model as string | undefined

src/hooks/session-notification-event-properties.ts

@@ -23,6 +23,15 @@ export function getSessionID(properties: EventProperties): string | undefined {
   const infoSessionId = info?.sessionId
   if (typeof infoSessionId === "string" && infoSessionId.length > 0) return infoSessionId
 
+  const part = properties?.part
+  if (isRecord(part)) {
+    const partSessionID = part.sessionID
+    if (typeof partSessionID === "string" && partSessionID.length > 0) return partSessionID
+
+    const partSessionId = part.sessionId
+    if (typeof partSessionId === "string" && partSessionId.length > 0) return partSessionId
+  }
+
   return undefined
 }
 

src/hooks/session-notification.test.ts

@@ -375,6 +375,47 @@ describe("session-notification", () => {
     expect(notificationCalls).toHaveLength(0)
   })
 
+  test("should mark session activity on message.part.updated event with part session id", async () => {
+    // given - main session is set
+    const mainSessionID = "main-part-activity"
+    setMainSession(mainSessionID)
+
+    const hook = createSessionNotification(createMockPluginInput(), {
+      idleConfirmationDelay: 50,
+      skipIfIncompleteTodos: false,
+      activityGracePeriodMs: 0,
+    })
+
+    // when - session goes idle, then streamed assistant activity fires
+    await hook({
+      event: {
+        type: "session.idle",
+        properties: { sessionID: mainSessionID },
+      },
+    })
+
+    await hook({
+      event: {
+        type: "message.part.updated",
+        properties: {
+          part: {
+            id: "part-1",
+            messageID: "msg-1",
+            sessionID: mainSessionID,
+            type: "text",
+            text: "still working",
+          },
+        },
+      },
+    })
+
+    // Wait for idle delay to pass
+    await new Promise((resolve) => setTimeout(resolve, 100))
+
+    // then - notification should NOT be sent (streaming activity cancelled it)
+    expect(notificationCalls).toHaveLength(0)
+  })
+
   test("should mark session activity on tool.execute.before event", async () => {
     // given - main session is set
     const mainSessionID = "main-tool"

src/hooks/session-notification.ts

@@ -7,6 +7,7 @@ import { getEventToolName, getQuestionText, getSessionID } from "./session-notif
 import { hasIncompleteTodos } from "./session-todo-status"
 import { createIdleNotificationScheduler } from "./session-notification-scheduler"
 import { createSessionNotificationInit } from "./session-notification-init"
+import { resolveSessionEventID } from "../shared/event-session-id"
 
 interface SessionNotificationConfig {
   title?: string
@@ -98,8 +99,7 @@ export function createSessionNotification(ctx: PluginInput, config: SessionNotif
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.created") {
-      const info = props?.info as Record<string, unknown> | undefined
+      const sessionID = resolveSessionEventID(props)
-      const sessionID = info?.id as string | undefined
       if (sessionID) scheduler.markSessionActivity(sessionID)
       return
     }
@@ -116,7 +116,11 @@ export function createSessionNotification(ctx: PluginInput, config: SessionNotif
       return
     }
 
-    if (event.type === "message.updated") {
+    if (
+      event.type === "message.updated" ||
+      event.type === "message.part.updated" ||
+      event.type === "message.part.delta"
+    ) {
       const info = props?.info as Record<string, unknown> | undefined
       const sessionID = getSessionID({ ...props, info })
       if (sessionID) scheduler.markSessionActivity(sessionID)
@@ -165,8 +169,8 @@ export function createSessionNotification(ctx: PluginInput, config: SessionNotif
     }
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (sessionInfo?.id) scheduler.deleteSession(sessionInfo.id)
+      if (sessionID) scheduler.deleteSession(sessionID)
     }
   }
 }

src/hooks/stop-continuation-guard/hook.ts

@@ -5,6 +5,7 @@ import {
   clearContinuationMarker,
   setContinuationMarkerSource,
 } from "../../features/run-continuation-state"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 
 const HOOK_NAME = "stop-continuation-guard"
@@ -86,11 +87,11 @@ export function createStopContinuationGuardHook(
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        clear(sessionInfo.id)
+        clear(sessionID)
-        clearContinuationMarker(ctx.directory, sessionInfo.id)
+        clearContinuationMarker(ctx.directory, sessionID)
-        log(`[${HOOK_NAME}] Session deleted: cleaned up`, { sessionID: sessionInfo.id })
+        log(`[${HOOK_NAME}] Session deleted: cleaned up`, { sessionID })
       }
     }
   }

src/hooks/task-reminder/hook.ts

@@ -1,5 +1,7 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 
+import { resolveSessionEventID } from "../../shared/event-session-id"
+
 const TASK_TOOLS = new Set([
   "task",
   "task_create",
@@ -50,8 +52,7 @@ export function createTaskReminderHook(_ctx: PluginInput) {
     "tool.execute.after": toolExecuteAfter,
     event: async ({ event }: { event: { type: string; properties?: unknown } }) => {
       if (event.type !== "session.deleted") return
-      const props = event.properties as { info?: { id?: string } } | undefined
+      const sessionId = resolveSessionEventID(event.properties)
-      const sessionId = props?.info?.id
       if (!sessionId) return
       sessionCounters.delete(sessionId)
     },

src/hooks/team-session-events/team-idle-wake-hint.ts

@@ -7,6 +7,7 @@ import {
   applyMemberSessionRouting,
   buildMemberPromptBody,
 } from "../../features/team-mode/member-session-routing"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 import { settleAfterSessionIdle } from "../shared/session-idle-settle"
 
@@ -35,8 +36,7 @@ export type HookImpl = (input: HookInput) => Promise<void>
 type TeamIdleWakeHintOptions = { idleSettleMs?: number }
 
 function getIdleSessionID(properties: unknown): string | undefined {
-  const record = properties as { sessionID?: string } | undefined
+  return resolveSessionEventID(properties)
-  return record?.sessionID
 }
 
 function buildWakeHint(unreadCount: number): string {

src/hooks/team-session-events/team-lead-orphan-handler.ts

@@ -3,14 +3,14 @@ import type { BackgroundManager } from "../../features/background-agent/manager"
 import { lookupTeamSession } from "../../features/team-mode/team-session-registry"
 import { loadRuntimeState, listActiveTeams, transitionRuntimeState } from "../../features/team-mode/team-state-store/store"
 import type { TmuxSessionManager } from "../../features/tmux-subagent/manager"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 
 type HookInput = { event: { type: string; properties?: unknown } }
 export type HookImpl = (input: HookInput) => Promise<void>
 
 function getDeletedSessionID(properties: unknown): string | undefined {
-  const record = properties as { info?: { id?: string } } | undefined
+  return resolveSessionEventID(properties)
-  return record?.info?.id
 }
 
 async function findLeadTeamRunId(

src/hooks/team-session-events/team-member-error-handler.ts

@@ -1,14 +1,14 @@
 import type { TeamModeConfig } from "../../config/schema/team-mode"
 import { findResolvedMemberSession } from "../../features/team-mode/member-session-resolution"
 import { loadRuntimeState, transitionRuntimeState } from "../../features/team-mode/team-state-store/store"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 
 type HookInput = { event: { type: string; properties?: unknown } }
 export type HookImpl = (input: HookInput) => Promise<void>
 
 function getErroredSessionID(properties: unknown): string | undefined {
-  const record = properties as { sessionID?: string } | undefined
+  return resolveSessionEventID(properties)
-  return record?.sessionID
 }
 
 export function createTeamMemberErrorHandler(config: TeamModeConfig): HookImpl {

src/hooks/team-session-events/team-member-status-handler.ts

@@ -2,6 +2,7 @@ import type { TeamModeConfig } from "../../config/schema/team-mode"
 import { findResolvedMemberSession } from "../../features/team-mode/member-session-resolution"
 import { loadRuntimeState, transitionRuntimeState } from "../../features/team-mode/team-state-store/store"
 import type { RuntimeStateMember } from "../../features/team-mode/types"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 import { log } from "../../shared/logger"
 
 type HookInput = { event: { type: string; properties?: unknown } }
@@ -13,13 +14,11 @@ const IDLE_TRANSITION_SOURCE_STATUSES: ReadonlySet<MemberStatus> = new Set(["run
 const COMPLETED_TRANSITION_SOURCE_STATUSES: ReadonlySet<MemberStatus> = new Set(["running", "idle", "pending"])
 
 function getSessionIDFromIdleEvent(properties: unknown): string | undefined {
-  const record = properties as { sessionID?: string } | undefined
+  return resolveSessionEventID(properties)
-  return record?.sessionID
 }
 
 function getSessionIDFromDeletedEvent(properties: unknown): string | undefined {
-  const record = properties as { info?: { id?: string } } | undefined
+  return resolveSessionEventID(properties)
-  return record?.info?.id
 }
 
 async function transitionMemberStatus(

src/hooks/think-mode/hook.ts

@@ -2,6 +2,7 @@ import { detectThinkKeyword, extractPromptText } from "./detector"
 import { isAlreadyHighVariant } from "./switcher"
 import type { ThinkModeState } from "./types"
 import { log } from "../../shared"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 
 const thinkModeState = new Map<string, ThinkModeState>()
 
@@ -66,9 +67,9 @@ export function createThinkModeHook() {
 
     event: async ({ event }: { event: { type: string; properties?: unknown } }) => {
       if (event.type === "session.deleted") {
-        const props = event.properties as { info?: { id?: string } } | undefined
+        const sessionID = resolveSessionEventID(event.properties)
-        if (props?.info?.id) {
+        if (sessionID) {
-          thinkModeState.delete(props.info.id)
+          thinkModeState.delete(sessionID)
         }
       }
     },

src/hooks/todo-continuation-enforcer/handler.ts

@@ -5,6 +5,7 @@ import {
   clearContinuationMarker,
 } from "../../features/run-continuation-state"
 import { log } from "../../shared/logger"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 
 import { DEFAULT_SKIP_AGENTS, HOOK_NAME } from "./constants"
 import { armCompactionGuard } from "./compaction-guard"
@@ -71,7 +72,7 @@ export function createTodoContinuationHandler(args: {
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.error") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID) return
 
       const error = extractSessionErrorInfo(props?.error)
@@ -102,7 +103,7 @@ export function createTodoContinuationHandler(args: {
     }
 
     if (event.type === "session.idle") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID) return
 
       sessionStateStore.startPruneInterval()
@@ -118,7 +119,7 @@ export function createTodoContinuationHandler(args: {
     }
 
     if (event.type === "session.compacted") {
-      const sessionID = (props?.sessionID ?? (props?.info as { id?: string } | undefined)?.id) as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (sessionID) {
         const state = sessionStateStore.getState(sessionID)
         const compactionEpoch = armCompactionGuard(state, Date.now())
@@ -129,9 +130,9 @@ export function createTodoContinuationHandler(args: {
     }
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        clearContinuationMarker(ctx.directory, sessionInfo.id)
+        clearContinuationMarker(ctx.directory, sessionID)
       }
     }
 

src/hooks/todo-continuation-enforcer/non-idle-events.ts

@@ -1,4 +1,5 @@
 import { log } from "../../shared/logger"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../../shared/event-session-id"
 
 import { COUNTDOWN_GRACE_PERIOD_MS, HOOK_NAME } from "./constants"
 import type { SessionStateStore } from "./session-state"
@@ -12,7 +13,7 @@ export function handleNonIdleEvent(args: {
 
   if (eventType === "message.updated") {
     const info = properties?.info as Record<string, unknown> | undefined
-    const sessionID = info?.sessionID as string | undefined
+    const sessionID = resolveMessageEventSessionID(properties)
     const role = info?.role as string | undefined
     if (!sessionID) return
 
@@ -50,12 +51,7 @@ export function handleNonIdleEvent(args: {
   }
 
   if (eventType === "message.part.updated") {
-    const sessionID = typeof properties?.sessionID === "string"
+    const targetSessionID = resolveMessageEventSessionID(properties)
-      ? properties.sessionID
-      : undefined
-    const legacyInfo = properties?.info as Record<string, unknown> | undefined
-    const legacySessionID = legacyInfo?.sessionID as string | undefined
-    const targetSessionID = sessionID ?? legacySessionID
 
     if (targetSessionID) {
       const state = sessionStateStore.getExistingState(targetSessionID)
@@ -69,7 +65,7 @@ export function handleNonIdleEvent(args: {
   }
 
   if (eventType === "message.part.delta") {
-    const sessionID = properties?.sessionID as string | undefined
+    const sessionID = resolveMessageEventSessionID(properties)
     if (sessionID) {
       const state = sessionStateStore.getExistingState(sessionID)
       if (state) {
@@ -83,7 +79,7 @@ export function handleNonIdleEvent(args: {
   }
 
   if (eventType === "tool.execute.before" || eventType === "tool.execute.after") {
-    const sessionID = properties?.sessionID as string | undefined
+    const sessionID = resolveMessageEventSessionID(properties)
     if (sessionID) {
       const state = sessionStateStore.getExistingState(sessionID)
       if (state) {
@@ -97,10 +93,10 @@ export function handleNonIdleEvent(args: {
   }
 
   if (eventType === "session.deleted") {
-    const sessionInfo = properties?.info as { id?: string } | undefined
+    const sessionID = resolveSessionEventID(properties)
-    if (sessionInfo?.id) {
+    if (sessionID) {
-      sessionStateStore.cleanup(sessionInfo.id)
+      sessionStateStore.cleanup(sessionID)
-      log(`[${HOOK_NAME}] Session deleted: cleaned up`, { sessionID: sessionInfo.id })
+      log(`[${HOOK_NAME}] Session deleted: cleaned up`, { sessionID })
     }
     return
   }

src/hooks/todo-continuation-enforcer/todo-continuation-enforcer.test.ts

@@ -12,6 +12,7 @@ import {
 } from "./constants"
 
 type TimerCallback = (...args: any[]) => void
+type FakeTimerID = number & ReturnType<typeof setTimeout> & ReturnType<typeof setInterval>
 
 interface FakeTimers {
   advanceBy: (ms: number, advanceClock?: boolean) => Promise<void>
@@ -57,7 +58,7 @@ function createFakeTimers(): FakeTimers {
       callback,
       args,
     })
-    return id
+    return id as FakeTimerID
   }
 
   const clear = (id: number | undefined) => {
@@ -74,7 +75,7 @@ function createFakeTimers(): FakeTimers {
     if (normalized >= REAL_MAX_DELAY_MS) {
       return original.setTimeout(callback, delay, ...args)
     }
-    return schedule(callback, normalized, null, args) as unknown as ReturnType<typeof setTimeout>
+    return schedule(callback, normalized, null, args)
   }) as typeof setTimeout
 
   globalThis.setInterval = ((callback: TimerCallback, delay?: number, ...args: any[]) => {
@@ -85,7 +86,7 @@ function createFakeTimers(): FakeTimers {
     if (interval >= REAL_MAX_DELAY_MS) {
       return original.setInterval(callback, delay, ...args)
     }
-    return schedule(callback, interval, interval, args) as unknown as ReturnType<typeof setInterval>
+    return schedule(callback, interval, interval, args)
   }) as typeof setInterval
 
   globalThis.clearTimeout = ((id?: Parameters<typeof clearTimeout>[0]) => {
@@ -184,6 +185,8 @@ describe("todo-continuation-enforcer", () => {
     }
   }
 
+  type MockPluginInput = Parameters<typeof createTodoContinuationEnforcer>[0]
+
   let mockMessages: MockMessage[] = []
 
   function createMockPluginInput() {
@@ -225,7 +228,7 @@ describe("todo-continuation-enforcer", () => {
         },
       },
       directory: "/tmp/test",
-    } as any
+    } as MockPluginInput
   }
 
   function createMockBackgroundManager(runningTasks: boolean = false): BackgroundManager {
@@ -233,7 +236,7 @@ describe("todo-continuation-enforcer", () => {
       getTasksByParentSession: () => runningTasks
         ? [{ status: "running" }]
         : [],
-    } as any
+    } as BackgroundManager
   }
 
   beforeEach(() => {
@@ -302,6 +305,26 @@ describe("todo-continuation-enforcer", () => {
     expect(promptCalls[0].text).toContain("TODO CONTINUATION")
   }, { timeout: 15000 })
 
+  test("should inject continuation when idle event carries session id in info", async () => {
+    fakeTimers.restore()
+    // given - OpenCode session events can nest the session id under info
+    const sessionID = "main-info-idle"
+    setMainSession(sessionID)
+
+    const hook = createTodoContinuationEnforcer(createMockPluginInput(), {})
+
+    // when - session goes idle with the nested event shape
+    await hook.handler({
+      event: { type: "session.idle", properties: { info: { id: sessionID } } },
+    })
+
+    // then - continuation is still injected for that session
+    await wait(2500)
+    expect(promptCalls).toHaveLength(1)
+    expect(promptCalls[0].sessionID).toBe(sessionID)
+    expect(promptCalls[0].text).toContain("TODO CONTINUATION")
+  }, { timeout: 15000 })
+
   test("should not inject when all todos are complete", async () => {
     // given - session with all todos complete
     const sessionID = "main-456"
@@ -527,6 +550,42 @@ describe("todo-continuation-enforcer", () => {
     expect(promptCalls).toHaveLength(0)
   })
 
+  test("should cancel countdown on assistant activity when message.part.updated only has part session id", async () => {
+    // given - session starting countdown
+    const sessionID = "main-assistant-part-only"
+    setMainSession(sessionID)
+
+    const hook = createTodoContinuationEnforcer(createMockPluginInput(), {})
+
+    // when - session goes idle
+    await hook.handler({
+      event: { type: "session.idle", properties: { sessionID } },
+    })
+
+    // when - legacy part-only sync payload reports assistant output
+    await fakeTimers.advanceBy(500)
+    await hook.handler({
+      event: {
+        type: "message.part.updated",
+        properties: {
+          part: {
+            id: "part-1",
+            messageID: "msg-1",
+            sessionID,
+            type: "text",
+            text: "working",
+          },
+          time: Date.now(),
+        },
+      },
+    })
+
+    await fakeTimers.advanceBy(3000)
+
+    // then - no continuation injected (cancelled)
+    expect(promptCalls).toHaveLength(0)
+  })
+
   test("should cancel countdown on assistant activity with message.part.delta payload", async () => {
     // given - session starting countdown
     const sessionID = "main-assistant-delta"
@@ -1599,7 +1658,7 @@ describe("todo-continuation-enforcer", () => {
          tui: { showToast: async () => ({}) },
        },
        directory: "/tmp/test",
-     } as any
+     } as MockPluginInput
 
      const hook = createTodoContinuationEnforcer(mockInput, {
        backgroundManager: createMockBackgroundManager(false),
@@ -1660,7 +1719,7 @@ describe("todo-continuation-enforcer", () => {
          tui: { showToast: async () => ({}) },
        },
        directory: "/tmp/test",
-     } as any
+     } as MockPluginInput
 
      const hook = createTodoContinuationEnforcer(mockInput, {
        backgroundManager: createMockBackgroundManager(false),
@@ -1712,7 +1771,7 @@ describe("todo-continuation-enforcer", () => {
          tui: { showToast: async () => ({}) },
        },
        directory: "/tmp/test",
-     } as any
+     } as MockPluginInput
 
      const hook = createTodoContinuationEnforcer(mockInput, {})
 
@@ -1769,7 +1828,7 @@ describe("todo-continuation-enforcer", () => {
         tui: { showToast: async () => ({}) },
       },
       directory: "/tmp/test",
-    } as any
+    } as MockPluginInput
 
     const hook = createTodoContinuationEnforcer(mockInput, {
       backgroundManager: createMockBackgroundManager(false),
@@ -1823,7 +1882,7 @@ describe("todo-continuation-enforcer", () => {
          tui: { showToast: async () => ({}) },
        },
        directory: "/tmp/test",
-     } as any
+     } as MockPluginInput
 
      const hook = createTodoContinuationEnforcer(mockInput, {})
 
@@ -1878,7 +1937,7 @@ describe("todo-continuation-enforcer", () => {
          tui: { showToast: async () => ({}) },
        },
        directory: "/tmp/test",
-     } as any
+     } as MockPluginInput
 
      const hook = createTodoContinuationEnforcer(mockInput, {
        skipAgents: [],
@@ -2122,7 +2181,7 @@ describe("todo-continuation-enforcer", () => {
     const mockInput = createMockPluginInput()
     mockInput.client.session.promptAsync = async () => {
       const error = new Error("prompt is too long: 150000 tokens > 100000 maximum")
-      ;(error as any).name = "ContextLengthError"
+      error.name = "ContextLengthError"
       throw error
     }
 

src/hooks/unstable-agent-babysitter/unstable-agent-babysitter-hook.ts

@@ -2,6 +2,7 @@ import type { BackgroundManager } from "../../features/background-agent"
 import { getMainSessionID, getSessionAgent } from "../../features/claude-code-session-state"
 import { log } from "../../shared/logger"
 import { createInternalAgentTextPart, resolveInheritedPromptTools } from "../../shared"
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../../shared/event-session-id"
 import { isAbortError } from "../../shared/is-abort-error"
 import {
   buildReminder,
@@ -128,7 +129,7 @@ export function createUnstableAgentBabysitterHook(ctx: BabysitterContext, option
     const props = event.properties as Record<string, unknown> | undefined
 
     if (event.type === "session.error") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID || !isAbortError(props?.error)) return
 
       cancelledSessions.add(sessionID)
@@ -138,7 +139,7 @@ export function createUnstableAgentBabysitterHook(ctx: BabysitterContext, option
     }
 
     if (event.type === "session.stop") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveSessionEventID(props)
       if (!sessionID) return
 
       cancelledSessions.add(sessionID)
@@ -149,7 +150,7 @@ export function createUnstableAgentBabysitterHook(ctx: BabysitterContext, option
 
     if (event.type === "message.updated") {
       const info = props?.info as Record<string, unknown> | undefined
-      const sessionID = info?.sessionID as string | undefined
+      const sessionID = resolveMessageEventSessionID(props)
       const role = info?.role as string | undefined
       if (!sessionID || (role !== "user" && role !== "assistant")) return
 
@@ -158,7 +159,7 @@ export function createUnstableAgentBabysitterHook(ctx: BabysitterContext, option
     }
 
     if (event.type === "tool.execute.before" || event.type === "tool.execute.after") {
-      const sessionID = props?.sessionID as string | undefined
+      const sessionID = resolveMessageEventSessionID(props)
       if (!sessionID) return
 
       cancelledSessions.delete(sessionID)
@@ -166,16 +167,16 @@ export function createUnstableAgentBabysitterHook(ctx: BabysitterContext, option
     }
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined
+      const sessionID = resolveSessionEventID(props)
-      if (!sessionInfo?.id) return
+      if (!sessionID) return
 
-      cancelledSessions.delete(sessionInfo.id)
+      cancelledSessions.delete(sessionID)
       return
     }
 
     if (event.type !== "session.idle") return
 
-    const sessionID = props?.sessionID as string | undefined
+    const sessionID = resolveSessionEventID(props)
     if (!sessionID) return
 
     const mainSessionID = getMainSessionID()

src/hooks/write-existing-file-guard/hook.ts

@@ -4,6 +4,7 @@ import { existsSync, realpathSync } from "fs"
 import { basename, dirname, isAbsolute, join, normalize, relative, resolve } from "path"
 
 import { handleWriteExistingFileGuardToolExecuteBefore } from "./tool-execute-before-handler"
+import { resolveSessionEventID } from "../../shared/event-session-id"
 
 export type GuardArgs = {
   filePath?: string
@@ -108,8 +109,7 @@ export function createWriteExistingFileGuardHook(ctx: PluginInput, options?: Wri
         return
       }
 
-      const props = event.properties as { info?: { id?: string } } | undefined
+      const sessionID = resolveSessionEventID(event.properties)
-      const sessionID = props?.info?.id
       if (!sessionID) {
         return
       }

src/plugin/event.test.ts

@@ -802,6 +802,56 @@ describe("createEventHandler - event forwarding", () => {
 		expect(forwardedEvents[0]?.event.type).toBe("message.part.delta")
 	})
 
+	it("forwards legacy message.part.updated activity with part-only session id to tmux session manager", async () => {
+		const forwardedEvents: EventInput[] = []
+		const eventHandler = createEventHandler({
+			ctx: asEventHandlerContext({}),
+			pluginConfig: asPluginConfig({
+				tmux: {
+					enabled: true,
+					layout: "main-vertical",
+					main_pane_size: 60,
+					main_pane_min_width: 120,
+					agent_pane_min_width: 40,
+					isolation: "inline",
+				},
+			}),
+			firstMessageVariantGate: {
+				markSessionCreated: () => {},
+				clear: () => {},
+			},
+			managers: createEventHandlerManagers({
+				skillMcpManager: {
+					disconnectSession: async () => {},
+				},
+				tmuxSessionManager: {
+					onEvent: (event: EventInput["event"]) => {
+						forwardedEvents.push({ event })
+					},
+					onSessionCreated: async () => {},
+					onSessionDeleted: async () => {},
+				},
+			}),
+			hooks: createEventHandlerHooks({}),
+		})
+		await eventHandler(asEventHandlerInput({
+			event: {
+				type: "message.part.updated",
+				properties: {
+					part: {
+						id: "part-1",
+						messageID: "msg-1",
+						sessionID: "ses_tmux_part_only",
+						type: "text",
+						text: "x",
+					},
+				},
+			},
+		}))
+		expect(forwardedEvents.length).toBe(1)
+		expect(forwardedEvents[0]?.event.type).toBe("message.part.updated")
+	})
+
 	it("does not forward tmux activity events when tmux integration is disabled", async () => {
 		const forwardedEvents: EventInput[] = []
 		const eventHandler = createEventHandler({

src/plugin/event.ts

@@ -47,6 +47,7 @@ import type { CreatedHooks } from "../create-hooks";
 import type { Managers } from "../create-managers";
 import { pruneRecentSyntheticIdles } from "./recent-synthetic-idles";
 import { normalizeSessionStatusToIdle } from "./session-status-normalizer";
+import { resolveMessageEventSessionID, resolveSessionEventID } from "../shared/event-session-id";
 
 type FirstMessageVariantGate = {
   markSessionCreated: (sessionInfo: { id?: string; title?: string; parentID?: string } | undefined) => void;
@@ -235,15 +236,15 @@ export function createEventHandler(args: {
 
   const getEventSessionID = (input: EventInput): string | undefined => {
     const properties = input.event.properties;
-    if (
+    if (input.event.type.startsWith("session.")) {
-      !properties ||
+      return resolveSessionEventID(properties);
-      typeof properties !== "object" ||
-      !("sessionID" in properties) ||
-      typeof properties.sessionID !== "string"
-    ) {
-      return undefined;
     }
-    return properties.sessionID;
+    if (input.event.type.startsWith("message.") || input.event.type.startsWith("tool.")) {
+      return resolveMessageEventSessionID(properties);
+    }
+    const record: Record<string, unknown> | undefined = isRecord(properties) ? properties : undefined;
+    const sessionID = record?.sessionID;
+    return typeof sessionID === "string" && sessionID.length > 0 ? sessionID : undefined;
   };
 
   const runEventHookSafely = async (
@@ -467,10 +468,11 @@ export function createEventHandler(args: {
 
     if (event.type === "session.created") {
       const sessionInfo = props?.info as { id?: string; title?: string; parentID?: string } | undefined;
-      const isSubagentSession = !!sessionInfo?.parentID || !!sessionInfo?.id && subagentSessions.has(sessionInfo.id);
+      const sessionID = resolveSessionEventID(props);
+      const isSubagentSession = !!sessionInfo?.parentID || !!sessionID && subagentSessions.has(sessionID);
 
       if (!isSubagentSession) {
-        setMainSession(sessionInfo?.id);
+        setMainSession(sessionID);
       }
 
       firstMessageVariantGate.markSessionCreated(sessionInfo);
@@ -489,62 +491,62 @@ export function createEventHandler(args: {
 
       // Skip subagent sessions — they are dispatched by specialized callbacks
       // in create-managers.ts (async) and tool-registry.ts (sync)
-      if (pluginConfig.openclaw && sessionInfo?.id && !isSubagentSession) {
+      if (pluginConfig.openclaw && sessionID && !isSubagentSession) {
         await dispatchOpenClawEvent({
           config: pluginConfig.openclaw,
           rawEvent: event.type,
           context: {
-            sessionId: sessionInfo.id,
+            sessionId: sessionID,
             projectPath: pluginContext.directory,
-            tmuxPaneId: managers.tmuxSessionManager.getTrackedPaneId?.(sessionInfo.id) ?? process.env.TMUX_PANE,
+            tmuxPaneId: managers.tmuxSessionManager.getTrackedPaneId?.(sessionID) ?? process.env.TMUX_PANE,
           },
         });
       }
     }
 
     if (event.type === "session.deleted") {
-      const sessionInfo = props?.info as { id?: string } | undefined;
+      const sessionID = resolveSessionEventID(props);
-      if (sessionInfo?.id === getMainSessionID()) {
+      if (sessionID === getMainSessionID()) {
         setMainSession(undefined);
       }
 
-      if (sessionInfo?.id) {
+      if (sessionID) {
-        const wasSyncSubagentSession = syncSubagentSessions.has(sessionInfo.id);
+        const wasSyncSubagentSession = syncSubagentSessions.has(sessionID);
-        clearSessionAgent(sessionInfo.id);
+        clearSessionAgent(sessionID);
-        lastHandledModelErrorMessageID.delete(sessionInfo.id);
+        lastHandledModelErrorMessageID.delete(sessionID);
-        lastHandledRetryStatusKey.delete(sessionInfo.id);
+        lastHandledRetryStatusKey.delete(sessionID);
-        lastKnownModelBySession.delete(sessionInfo.id);
+        lastKnownModelBySession.delete(sessionID);
         if (modelFallback) {
-          clearPendingModelFallback(modelFallback, sessionInfo.id);
+          clearPendingModelFallback(modelFallback, sessionID);
-          clearSessionFallbackChain(modelFallback, sessionInfo.id);
+          clearSessionFallbackChain(modelFallback, sessionID);
         }
-        resetMessageCursor(sessionInfo.id);
+        resetMessageCursor(sessionID);
-        clearBackgroundOutputConsumptionsForParentSession(sessionInfo.id);
+        clearBackgroundOutputConsumptionsForParentSession(sessionID);
-        clearBackgroundOutputConsumptionsForTaskSession(sessionInfo.id);
+        clearBackgroundOutputConsumptionsForTaskSession(sessionID);
-        firstMessageVariantGate.clear(sessionInfo.id);
+        firstMessageVariantGate.clear(sessionID);
-        clearSessionModel(sessionInfo.id);
+        clearSessionModel(sessionID);
-        clearSessionPromptParams(sessionInfo.id);
+        clearSessionPromptParams(sessionID);
-        syncSubagentSessions.delete(sessionInfo.id);
+        syncSubagentSessions.delete(sessionID);
         if (pluginConfig.openclaw) {
           await dispatchOpenClawEvent({
             config: pluginConfig.openclaw,
             rawEvent: event.type,
             context: {
-              sessionId: sessionInfo.id,
+              sessionId: sessionID,
               projectPath: pluginContext.directory,
-              tmuxPaneId: managers.tmuxSessionManager.getTrackedPaneId?.(sessionInfo.id) ?? process.env.TMUX_PANE,
+              tmuxPaneId: managers.tmuxSessionManager.getTrackedPaneId?.(sessionID) ?? process.env.TMUX_PANE,
             },
           });
         }
         if (wasSyncSubagentSession) {
-          subagentSessions.delete(sessionInfo.id);
+          subagentSessions.delete(sessionID);
         }
-        deleteSessionTools(sessionInfo.id);
+        deleteSessionTools(sessionID);
-        await managers.skillMcpManager.disconnectSession(sessionInfo.id);
+        await managers.skillMcpManager.disconnectSession(sessionID);
         await lspManager.cleanupTempDirectoryClients();
         if (tmuxIntegrationEnabled) {
           await managers.tmuxSessionManager.onSessionDeleted({
-            sessionID: sessionInfo.id,
+            sessionID,
           });
         }
       }
@@ -555,12 +557,12 @@ export function createEventHandler(args: {
 
     if (event.type === "message.removed") {
       const messageID = props?.messageID as string | undefined;
-      const sessionID = props?.sessionID as string | undefined;
+      const sessionID = resolveMessageEventSessionID(props);
       restoreBackgroundOutputConsumption(sessionID, messageID);
     }
 
     if (event.type === "session.idle" && pluginConfig.openclaw) {
-      const sessionID = props?.sessionID as string | undefined;
+      const sessionID = resolveSessionEventID(props);
       if (sessionID) {
         await dispatchOpenClawEvent({
           config: pluginConfig.openclaw,
@@ -582,7 +584,7 @@ export function createEventHandler(args: {
 
     if (event.type === "message.updated") {
       const info = props?.info as Record<string, unknown> | undefined;
-      const sessionID = info?.sessionID as string | undefined;
+      const sessionID = resolveMessageEventSessionID(props);
       const agent = info?.agent as string | undefined;
       const role = info?.role as string | undefined;
       if (sessionID && info?.finish === true) {
@@ -665,7 +667,7 @@ export function createEventHandler(args: {
     }
 
     if (event.type === "session.status") {
-      const sessionID = props?.sessionID as string | undefined;
+      const sessionID = resolveSessionEventID(props);
       const status = props?.status as { type?: string; attempt?: number; message?: string; next?: number } | undefined;
 
       // Retry dedupe lifecycle: set key when a retry status is handled, clear it after recovery
@@ -733,7 +735,7 @@ export function createEventHandler(args: {
 
     if (event.type === "session.error") {
       try {
-        const sessionID = props?.sessionID as string | undefined;
+        const sessionID = resolveSessionEventID(props);
         const error = props?.error;
 
         const errorName = extractErrorName(error);
@@ -818,7 +820,7 @@ export function createEventHandler(args: {
           }
         }
       } catch (err) {
-        const sessionID = props?.sessionID as string | undefined;
+        const sessionID = resolveSessionEventID(props);
         log("[event] model-fallback error in session.error:", { sessionID, error: err });
       }
 

src/plugin/session-status-normalizer.ts

@@ -1,3 +1,5 @@
+import { resolveSessionEventID } from "../shared/event-session-id"
+
 type EventInput = { event: { type: string; properties?: Record<string, unknown> } }
 type SessionStatus = { type: string }
 
@@ -10,7 +12,7 @@ export function normalizeSessionStatusToIdle(input: EventInput): EventInput | nu
 	const status = props.status as SessionStatus | undefined
 	if (!status || status.type !== "idle") return null
 
-	const sessionID = props.sessionID as string | undefined
+	const sessionID = resolveSessionEventID(props)
 	if (!sessionID) return null
 
 	return {

src/shared/event-session-id.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, test } from "bun:test"
+
+import { resolveMessageEventSessionID, resolveSessionEventID } from "./event-session-id"
+
+describe("event session id resolvers", () => {
+  test("#given legacy message.part.updated properties #when resolving message session id #then part.sessionID is used", () => {
+    const sessionID = resolveMessageEventSessionID({
+      part: {
+        id: "part-1",
+        messageID: "msg-1",
+        sessionID: "ses-part-only",
+        type: "text",
+        text: "working",
+      },
+    })
+
+    expect(sessionID).toBe("ses-part-only")
+  })
+
+  test("#given message.updated info id #when resolving message session id #then message id is not mistaken for session id", () => {
+    const sessionID = resolveMessageEventSessionID({
+      info: {
+        id: "msg-not-session",
+        role: "assistant",
+      },
+    })
+
+    expect(sessionID).toBeUndefined()
+  })
+
+  test("#given legacy session lifecycle properties #when resolving session id #then info.id is used", () => {
+    const sessionID = resolveSessionEventID({
+      info: {
+        id: "ses-legacy-info-id",
+      },
+    })
+
+    expect(sessionID).toBe("ses-legacy-info-id")
+  })
+})

src/shared/event-session-id.ts

@@ -0,0 +1,23 @@
+import { isRecord } from "./record-type-guard"
+
+function getStringField(record: Record<string, unknown> | undefined, key: string): string | undefined {
+  const value = record?.[key]
+  return typeof value === "string" && value.length > 0 ? value : undefined
+}
+
+export function resolveSessionEventID(properties: unknown): string | undefined {
+  const props = isRecord(properties) ? properties : undefined
+  const info = isRecord(props?.info) ? props.info : undefined
+  return getStringField(props, "sessionID")
+    ?? getStringField(info, "sessionID")
+    ?? getStringField(info, "id")
+}
+
+export function resolveMessageEventSessionID(properties: unknown): string | undefined {
+  const props = isRecord(properties) ? properties : undefined
+  const info = isRecord(props?.info) ? props.info : undefined
+  const part = isRecord(props?.part) ? props.part : undefined
+  return getStringField(props, "sessionID")
+    ?? getStringField(info, "sessionID")
+    ?? getStringField(part, "sessionID")
+}

src/shared/index.ts

@@ -54,6 +54,7 @@ export * from "./fallback-model-availability"
 export * from "./connected-providers-cache"
 export * from "./context-limit-resolver"
 export * from "./session-utils"
+export * from "./event-session-id"
 export * from "./tmux"
 export * from "./model-suggestion-retry"
 export * from "./opencode-server-auth"