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/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
-      if (!info || typeof info !== "object") return undefined
-      const sessionId = (info as { sessionID?: unknown }).sessionID
-      return typeof sessionId === "string" ? sessionId : undefined
+      return resolveMessageEventSessionID(properties)
     }
 
     if (
@@ -182,8 +180,7 @@ export class TmuxPollingManager {
       || event.type === "message.part.removed"
       || event.type === "message.removed"
     ) {
-      const sessionId = properties.sessionID
-      return typeof sessionId === "string" ? sessionId : undefined
+      return resolveMessageEventSessionID(properties)
     }
 
     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)) {