diff --git a/src/hooks/shared/compaction-model-resolver.ts b/src/hooks/shared/compaction-model-resolver.ts
new file mode 100644
index 00000000..b21cc980
--- /dev/null
+++ b/src/hooks/shared/compaction-model-resolver.ts
@@ -0,0 +1,35 @@
+import type { OhMyOpenCodeConfig } from "../../config"
+import { getSessionAgent } from "../../features/claude-code-session-state"
+import { getAgentConfigKey } from "../../shared/agent-display-names"
+
+export function resolveCompactionModel(
+  pluginConfig: OhMyOpenCodeConfig,
+  sessionID: string,
+  originalProviderID: string,
+  originalModelID: string
+): { providerID: string; modelID: string } {
+  const sessionAgentName = getSessionAgent(sessionID)
+  
+  if (!sessionAgentName || !pluginConfig.agents) {
+    return { providerID: originalProviderID, modelID: originalModelID }
+  }
+
+  const agentConfigKey = getAgentConfigKey(sessionAgentName)
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  const agentConfig = (pluginConfig.agents as any)[agentConfigKey]
+  const compactionConfig = agentConfig?.compaction
+
+  if (!compactionConfig?.model) {
+    return { providerID: originalProviderID, modelID: originalModelID }
+  }
+
+  const modelParts = compactionConfig.model.split("/")
+  if (modelParts.length < 2) {
+    return { providerID: originalProviderID, modelID: originalModelID }
+  }
+
+  return {
+    providerID: modelParts[0],
+    modelID: modelParts.slice(1).join("/"),
+  }
+}