fix(atlas): skip compaction in last-agent recovery

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/atlas/session-last-agent.ts

@@ -1,24 +1,65 @@
-import type { PluginInput } from "@opencode-ai/plugin"
+import { readFileSync, readdirSync } from "node:fs"
+import { join } from "node:path"
 
-import { findNearestMessageWithFields } from "../../features/hook-message-injector"
-import { findNearestMessageWithFieldsFromSDK } from "../../features/hook-message-injector"
-import { getMessageDir, isSqliteBackend } from "../../shared"
+import { getMessageDir, isSqliteBackend, normalizeSDKResponse } from "../../shared"
 
-type OpencodeClient = PluginInput["client"]
+type SessionMessagesClient = {
+  session: {
+    messages: (input: { path: { id: string } }) => Promise<unknown>
+  }
+}
+
+function isCompactionAgent(agent: unknown): boolean {
+  return typeof agent === "string" && agent.toLowerCase() === "compaction"
+}
+
+function getLastAgentFromMessageDir(messageDir: string): string | null {
+  try {
+    const files = readdirSync(messageDir)
+      .filter((fileName) => fileName.endsWith(".json"))
+      .sort()
+      .reverse()
+
+    for (const fileName of files) {
+      try {
+        const content = readFileSync(join(messageDir, fileName), "utf-8")
+        const parsed = JSON.parse(content) as { agent?: unknown }
+        if (typeof parsed.agent === "string" && !isCompactionAgent(parsed.agent)) {
+          return parsed.agent.toLowerCase()
+        }
+      } catch {
+        continue
+      }
+    }
+  } catch {
+    return null
+  }
+
+  return null
+}
 
 export async function getLastAgentFromSession(
   sessionID: string,
-  client?: OpencodeClient
+  client?: SessionMessagesClient
 ): Promise<string | null> {
-  let nearest = null
-
   if (isSqliteBackend() && client) {
-    nearest = await findNearestMessageWithFieldsFromSDK(client, sessionID)
-  } else {
-    const messageDir = getMessageDir(sessionID)
-    if (!messageDir) return null
-    nearest = findNearestMessageWithFields(messageDir)
+    const response = await client.session.messages({ path: { id: sessionID } })
+    const messages = normalizeSDKResponse(response, [] as Array<{ info?: { agent?: string } }>, {
+      preferResponseOnMissingData: true,
+    })
+
+    for (let i = messages.length - 1; i >= 0; i--) {
+      const agent = messages[i].info?.agent
+      if (typeof agent === "string" && !isCompactionAgent(agent)) {
+        return agent.toLowerCase()
+      }
+    }
+
+    return null
   }
 
-  return nearest?.agent?.toLowerCase() ?? null
+  const messageDir = getMessageDir(sessionID)
+  if (!messageDir) return null
+
+  return getLastAgentFromMessageDir(messageDir)
 }