feat: add memory file count hard limit (500) and archive cap (20)

Prevents memory/ from growing unbounded by capping STATE_ARCHIVE
files at 20 per type and enforcing a 500-file hard limit on the
entire memory directory.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

skills/memory-continuity/SKILL.md

@@ -130,6 +130,22 @@ Update the file by **overwriting** it, not appending, at these moments:
 | Before handoff / subagent exit | Preserves outputs and unsurfaced results |
 | After a substantive state change | Keeps checkpoint aligned with actual work |
 
+### Override rule
+
+**CURRENT_STATE.md must always be overwritten when:**
+- A new task or objective starts — regardless of what is currently in the file
+- The previous objective is complete or abandoned
+- The user gives a new task that supersedes the previous one
+
+Having content in CURRENT_STATE.md does NOT mean it should be preserved.
+Content only matters if Objective is still active and work is genuinely in progress.
+
+Checking before overwrite:
+- Read the file
+- If Objective matches the current task → update in place (overwrite)
+- If Objective does NOT match → overwrite the entire file with the new state
+- Never append. Never skip the update because "there's already something there".
+
 ### 4. Keep the checkpoint small
 
 `CURRENT_STATE.md` should usually stay under about 40 lines and be readable in

skills/memory-continuity/plugin/lifecycle-prototype.ts

@@ -1,6 +1,18 @@
 import fs from "node:fs";
 import path from "node:path";
 
+const MAX_ARCHIVE_COUNT = 20;
+const MAX_MEMORY_FILES = 500;
+
+// Protected files that should never be auto-deleted
+const PROTECTED_FILES = new Set([
+  "CURRENT_STATE.md",
+  "MEMORY.md",
+  "INDEX.md",
+  "dev_principles.md",
+  "oracle_cloud.md",
+]);
+
 const PLACEHOLDER_VALUES = new Set([
   "",
   "none",
@@ -82,11 +94,70 @@ function formatArchiveStamp(date = new Date()) {
   ].join("-") + `_${pad(date.getHours())}-${pad(date.getMinutes())}`;
 }
 
+function pruneArchives(dir: string, pattern: RegExp, max: number) {
+  try {
+    const files = fs.readdirSync(dir)
+      .filter((f: string) => pattern.test(f))
+      .sort();
+    const excess = files.length - max;
+    if (excess > 0) {
+      for (let i = 0; i < excess; i++) {
+        fs.unlinkSync(path.join(dir, files[i]));
+      }
+      console.log(`[memory-continuity] pruned ${excess} old archive(s) in ${dir}`);
+    }
+  } catch {}
+}
+
+function enforceFileLimit(memoryDir: string) {
+  try {
+    const allFiles = fs.readdirSync(memoryDir, { recursive: true }) as string[];
+    // Only count files, not directories
+    const fileList = allFiles
+      .map((f: string) => ({ name: String(f), full: path.join(memoryDir, String(f)) }))
+      .filter((f) => {
+        try { return fs.statSync(f.full).isFile(); } catch { return false; }
+      });
+
+    if (fileList.length <= MAX_MEMORY_FILES) return;
+
+    // Sort deletable files by mtime (oldest first), skip protected
+    const deletable = fileList
+      .filter((f) => {
+        const base = path.basename(f.name);
+        if (PROTECTED_FILES.has(base)) return false;
+        if (base.endsWith(".json")) return false; // automation state
+        return true;
+      })
+      .map((f) => ({ ...f, mtime: fs.statSync(f.full).mtimeMs }))
+      .sort((a, b) => a.mtime - b.mtime);
+
+    const toDelete = fileList.length - 450; // bring down to 450 for headroom
+    const deleted = Math.min(toDelete, deletable.length);
+    for (let i = 0; i < deleted; i++) {
+      fs.unlinkSync(deletable[i].full);
+    }
+    if (deleted > 0) {
+      console.log(`[memory-continuity] enforced file limit: deleted ${deleted} oldest files (${fileList.length} → ${fileList.length - deleted})`);
+    }
+  } catch {}
+}
+
 function appendArchive(workspaceDir: string, markdown: string) {
   const stamp = formatArchiveStamp();
   const archiveDir = path.join(workspaceDir, "memory", "session_archive");
   fs.mkdirSync(archiveDir, { recursive: true });
   fs.writeFileSync(path.join(archiveDir, `${stamp}.md`), markdown, "utf8");
+
+  // Prune session_archive/ beyond MAX_ARCHIVE_COUNT
+  pruneArchives(archiveDir, /\.md$/, MAX_ARCHIVE_COUNT);
+
+  // Also prune STATE_ARCHIVE_*.md in memory/ root (generated by OpenClaw native)
+  const memoryDir = path.join(workspaceDir, "memory");
+  pruneArchives(memoryDir, /^STATE_ARCHIVE_.*\.md$/, MAX_ARCHIVE_COUNT);
+
+  // Hard cap: total files in memory/ must not exceed MAX_MEMORY_FILES
+  enforceFileLimit(memoryDir);
 }
 
 export default function register(api: any) {