fix(session): detect post-compaction no-text degradation and trigger recovery (fixes #2232)

src/hooks/preemptive-compaction-no-text-tail.ts

@@ -0,0 +1,70 @@
+import { normalizeSDKResponse } from "../shared/normalize-sdk-response"
+
+const STEP_ONLY_TYPES = new Set(["step-start", "step-finish"])
+
+interface MessagePart {
+  type?: unknown
+  text?: unknown
+}
+
+interface SessionMessage {
+  info?: {
+    id?: string
+    role?: string
+  }
+  parts?: MessagePart[]
+}
+
+export function isStepOnlyNoTextParts(parts: unknown): boolean {
+  if (!Array.isArray(parts) || parts.length === 0) return false
+
+  return parts.every((part) => {
+    const type = (part as MessagePart | undefined)?.type
+    if (typeof type !== "string") return false
+    if (!STEP_ONLY_TYPES.has(type)) return false
+
+    const text = (part as MessagePart | undefined)?.text
+    if (typeof text === "string" && text.trim().length > 0) return false
+    return true
+  })
+}
+
+function findMessageByID(messages: SessionMessage[], messageID?: string): SessionMessage | undefined {
+  if (!messageID) return undefined
+  return messages.find((message) => message.info?.id === messageID)
+}
+
+export async function resolveNoTextTailFromSession(args: {
+  client: {
+    session: {
+      messages: (input: {
+        path: { id: string }
+        query: { directory: string }
+      }) => Promise<unknown>
+    }
+  }
+  sessionID: string
+  messageID?: string
+  directory: string
+}): Promise<boolean> {
+  const { client, sessionID, messageID, directory } = args
+
+  try {
+    const response = await client.session.messages({
+      path: { id: sessionID },
+      query: { directory },
+    })
+
+    const messages = normalizeSDKResponse(response, [] as SessionMessage[], {
+      preferResponseOnMissingData: true,
+    })
+    if (!Array.isArray(messages) || messages.length === 0) return false
+
+    const target = findMessageByID(messages, messageID) ?? messages[messages.length - 1]
+    if (target.info?.role !== "assistant") return false
+
+    return isStepOnlyNoTextParts(target.parts)
+  } catch {
+    return false
+  }
+}