From 1fdd3592d365720a4997fbc9dbdf91417461283d Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Tue, 13 Jan 2026 05:58:35 +0000
Subject: [PATCH] fix: tune compaction safeguard schema (#700) (thanks
 @thewilloftheshadow)

---
 CHANGELOG.md                                  |  1 +
 .../pi-extensions/compaction-safeguard.ts     | 54 ++++++++++++++-----
 src/config/zod-schema.ts                      |  4 +-
 3 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index edb9c220c..2dfd801be 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Changes
 - Cron: accept ISO timestamps for one-shot schedules (UTC) and allow optional delete-after-run; wired into CLI + macOS editor.
 - Gateway: add Tailscale binary discovery, custom bind mode, and probe auth retry for password changes. (#740 — thanks @jeffersonwarrior)
+- Agents: add compaction mode config with optional safeguard summarization for long histories. (#700 — thanks @thewilloftheshadow)
 
 ## 2026.1.12-4
 
diff --git a/src/agents/pi-extensions/compaction-safeguard.ts b/src/agents/pi-extensions/compaction-safeguard.ts
index 198fb99ab..4b374c258 100644
--- a/src/agents/pi-extensions/compaction-safeguard.ts
+++ b/src/agents/pi-extensions/compaction-safeguard.ts
@@ -2,13 +2,9 @@ import type { AgentMessage } from "@mariozechner/pi-agent-core";
 import type {
   ExtensionAPI,
   ExtensionContext,
+  FileOperations,
 } from "@mariozechner/pi-coding-agent";
-import {
-  computeFileLists,
-  formatFileOperations,
-  generateSummary,
-  estimateTokens,
-} from "@mariozechner/pi-coding-agent";
+import { estimateTokens, generateSummary } from "@mariozechner/pi-coding-agent";
 
 import { DEFAULT_CONTEXT_TOKENS } from "../defaults.js";
 
@@ -16,10 +12,40 @@ const MAX_CHUNK_RATIO = 0.4;
 const FALLBACK_SUMMARY =
   "Summary unavailable due to context limits. Older messages were truncated.";
 const TURN_PREFIX_INSTRUCTIONS =
-  "This summary covers the prefix of a split turn. Focus on the original request,"
-  + " early progress, and any details needed to understand the retained suffix.";
+  "This summary covers the prefix of a split turn. Focus on the original request," +
+  " early progress, and any details needed to understand the retained suffix.";
 
-function chunkMessages(messages: AgentMessage[], maxTokens: number): AgentMessage[][] {
+function computeFileLists(fileOps: FileOperations): {
+  readFiles: string[];
+  modifiedFiles: string[];
+} {
+  const modified = new Set([...fileOps.edited, ...fileOps.written]);
+  const readFiles = [...fileOps.read].filter((f) => !modified.has(f)).sort();
+  const modifiedFiles = [...modified].sort();
+  return { readFiles, modifiedFiles };
+}
+
+function formatFileOperations(
+  readFiles: string[],
+  modifiedFiles: string[],
+): string {
+  const sections: string[] = [];
+  if (readFiles.length > 0) {
+    sections.push(`<read-files>\n${readFiles.join("\n")}\n</read-files>`);
+  }
+  if (modifiedFiles.length > 0) {
+    sections.push(
+      `<modified-files>\n${modifiedFiles.join("\n")}\n</modified-files>`,
+    );
+  }
+  if (sections.length === 0) return "";
+  return `\n\n${sections.join("\n\n")}`;
+}
+
+function chunkMessages(
+  messages: AgentMessage[],
+  maxTokens: number,
+): AgentMessage[][] {
   if (messages.length === 0) return [];
 
   const chunks: AgentMessage[][] = [];
@@ -28,10 +54,7 @@ function chunkMessages(messages: AgentMessage[], maxTokens: number): AgentMessag
 
   for (const message of messages) {
     const messageTokens = estimateTokens(message);
-    if (
-      currentChunk.length > 0 &&
-      currentTokens + messageTokens > maxTokens
-    ) {
+    if (currentChunk.length > 0 && currentTokens + messageTokens > maxTokens) {
       chunks.push(currentChunk);
       currentChunk = [];
       currentTokens = 0;
@@ -144,7 +167,10 @@ export default function compactionSafeguardExtension(api: ExtensionAPI): void {
       });
 
       let summary = historySummary;
-      if (preparation.isSplitTurn && preparation.turnPrefixMessages.length > 0) {
+      if (
+        preparation.isSplitTurn &&
+        preparation.turnPrefixMessages.length > 0
+      ) {
         const prefixSummary = await summarizeChunks({
           messages: preparation.turnPrefixMessages,
           model,
diff --git a/src/config/zod-schema.ts b/src/config/zod-schema.ts
index 1fb119124..cacd7fcfb 100644
--- a/src/config/zod-schema.ts
+++ b/src/config/zod-schema.ts
@@ -1210,7 +1210,9 @@ const AgentDefaultsSchema = z
       .optional(),
     compaction: z
       .object({
-        mode: z.union([z.literal("default"), z.literal("safeguard")]).optional(),
+        mode: z
+          .union([z.literal("default"), z.literal("safeguard")])
+          .optional(),
         reserveTokensFloor: z.number().int().nonnegative().optional(),
         memoryFlush: z
           .object({