enable session pruning and allow disabling with OPENCODE_DISABLE_PRUNE

packages/opencode/src/session/compaction.ts

@@ -11,8 +11,12 @@ import z from "zod/v4"
 import type { ModelsDev } from "../provider/models"
 import { SessionPrompt } from "./prompt"
 import { Flag } from "../flag/flag"
+import { Token } from "../util/token"
+import { Log } from "../util/log"
 
 export namespace SessionCompaction {
+  const log = Log.create({ service: "session.compaction" })
+
   export const Event = {
     Compacted: Bus.event(
       "session.compacted",
@@ -32,6 +36,46 @@ export namespace SessionCompaction {
     return count > usable
   }
 
+  // goes backwards through parts until there are 40_000 tokens worth of tool
+  // calls. then erases output of previous tool calls. idea is to throw away old
+  // tool calls that are no longer relevant.
+  export async function prune(input: { sessionID: string }) {
+    if (Flag.OPENCODE_DISABLE_PRUNE) return
+    log.info("pruning")
+    const msgs = await Session.messages(input.sessionID)
+    let total = 0
+    let pruned = 0
+    const toPrune = []
+
+    loop: for (let msgIndex = msgs.length - 2; msgIndex >= 0; msgIndex--) {
+      const msg = msgs[msgIndex]
+      if (msg.info.role === "assistant" && msg.info.summary) return
+      for (let partIndex = msg.parts.length - 1; partIndex >= 0; partIndex--) {
+        const part = msg.parts[partIndex]
+        if (part.type === "tool")
+          if (part.state.status === "completed") {
+            if (part.state.time.compacted) break loop
+            const estimate = Token.estimate(part.state.output)
+            total += estimate
+            if (total > 40_000) {
+              pruned += estimate
+              toPrune.push(part)
+            }
+          }
+      }
+    }
+    log.info("found", { pruned, total })
+    if (pruned > 20_000) {
+      for (const part of toPrune) {
+        if (part.state.status === "completed") {
+          part.state.time.compacted = Date.now()
+          await Session.updatePart(part)
+        }
+      }
+      log.info("pruned", { count: toPrune.length })
+    }
+  }
+
   export async function run(input: { sessionID: string; providerID: string; modelID: string }) {
     await Session.update(input.sessionID, (draft) => {
       draft.time.compacting = Date.now()