refactor(session): effectify session processor (#19485)

packages/opencode/src/session/overflow.ts

@@ -0,0 +1,22 @@
+import type { Config } from "@/config/config"
+import type { Provider } from "@/provider/provider"
+import { ProviderTransform } from "@/provider/transform"
+import type { MessageV2 } from "./message-v2"
+
+const COMPACTION_BUFFER = 20_000
+
+export function isOverflow(input: { cfg: Config.Info; tokens: MessageV2.Assistant["tokens"]; model: Provider.Model }) {
+  if (input.cfg.compaction?.auto === false) return false
+  const context = input.model.limit.context
+  if (context === 0) return false
+
+  const count =
+    input.tokens.total || input.tokens.input + input.tokens.output + input.tokens.cache.read + input.tokens.cache.write
+
+  const reserved =
+    input.cfg.compaction?.reserved ?? Math.min(COMPACTION_BUFFER, ProviderTransform.maxOutputTokens(input.model))
+  const usable = input.model.limit.input
+    ? input.model.limit.input - reserved
+    : context - ProviderTransform.maxOutputTokens(input.model)
+  return count >= usable
+}