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/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"