diff --git a/scripts/build-portal-runtime.mjs b/scripts/build-portal-runtime.mjs
index e779328..4eba621 100755
--- a/scripts/build-portal-runtime.mjs
+++ b/scripts/build-portal-runtime.mjs
@@ -367,6 +367,7 @@ async function writeMetadata() {
       '  bash scripts/install-runtime-metrics-agent.sh',
       '  node scripts/runtime-slo-report.mjs',
       '  node scripts/runtime-slo-report.mjs --write-report',
+      '  node scripts/runtime-slo-report.mjs --write-report --prune --retention-days 30',
       '  bash scripts/install-runtime-slo-report-agent.sh',
       '  node scripts/runtime-worker-drain.mjs drain goosed-3',
       '  node scripts/runtime-worker-drain.mjs undrain goosed-3',
diff --git a/scripts/install-runtime-slo-report-agent.sh b/scripts/install-runtime-slo-report-agent.sh
index 336f84c..058b9b2 100644
--- a/scripts/install-runtime-slo-report-agent.sh
+++ b/scripts/install-runtime-slo-report-agent.sh
@@ -11,6 +11,7 @@ GUI="gui/$(id -u)"
 HOUR="${MEMIND_RUNTIME_SLO_HOUR:-23}"
 MINUTE="${MEMIND_RUNTIME_SLO_MINUTE:-55}"
 REPORT_DIR="${MEMIND_RUNTIME_REPORT_DIR:-$ROOT/reports/runtime-slo}"
+RETENTION_DAYS="${MEMIND_RUNTIME_SLO_RETENTION_DAYS:-30}"
 
 mkdir -p "$HOME/Library/LaunchAgents" "$HOME/Library/Logs" "$REPORT_DIR"
 
@@ -34,6 +35,9 @@ cat > "$PLIST" <<EOF
     <string>$NODE_BIN</string>
     <string>$SCRIPT</string>
     <string>--write-report</string>
+    <string>--prune</string>
+    <string>--retention-days</string>
+    <string>$RETENTION_DAYS</string>
     <string>--report-dir</string>
     <string>$REPORT_DIR</string>
   </array>
@@ -69,4 +73,5 @@ echo "installed $PLIST"
 echo "script: $SCRIPT"
 echo "schedule: daily ${HOUR}:${MINUTE}"
 echo "report_dir: $REPORT_DIR"
+echo "retention_days: $RETENTION_DAYS"
 echo "log: $LOG"
diff --git a/scripts/runtime-slo-report.mjs b/scripts/runtime-slo-report.mjs
index 77309cf..da34e2d 100755
--- a/scripts/runtime-slo-report.mjs
+++ b/scripts/runtime-slo-report.mjs
@@ -90,27 +90,85 @@ function uniquePaths(paths) {
 function parseArgs(argv) {
   const args = {
     writeReport: false,
+    prune: false,
+    retentionDays: Number(process.env.MEMIND_RUNTIME_SLO_RETENTION_DAYS || 30),
     reportDir: process.env.MEMIND_RUNTIME_REPORT_DIR || '',
   };
   for (let i = 0; i < argv.length; i += 1) {
     const item = argv[i];
     if (item === '--write-report') args.writeReport = true;
+    else if (item === '--prune') args.prune = true;
+    else if (item === '--retention-days') args.retentionDays = Number(argv[++i] ?? args.retentionDays);
     else if (item === '--report-dir') args.reportDir = String(argv[++i] ?? args.reportDir);
     else if (item === '--help' || item === '-h') args.help = true;
   }
+  if (!Number.isFinite(args.retentionDays) || args.retentionDays < 1) {
+    throw new Error(`Invalid --retention-days: ${args.retentionDays}`);
+  }
   return args;
 }
 
 function printHelp() {
   console.log([
     'Usage:',
-    '  node scripts/runtime-slo-report.mjs [--write-report] [--report-dir <dir>]',
+    '  node scripts/runtime-slo-report.mjs [--write-report] [--prune] [--retention-days <days>] [--report-dir <dir>]',
     '',
     'Default behavior is read-only and writes nothing.',
     '--write-report writes JSON and Markdown snapshots to an operations report directory.',
+    '--prune deletes old .json/.md snapshots in the report directory only.',
   ].join('\n'));
 }
 
+function pruneReportDir(reportDir, retentionDays) {
+  const resolvedDir = path.resolve(reportDir);
+  const cutoffMs = Date.now() - retentionDays * 24 * 60 * 60 * 1000;
+  const result = {
+    enabled: true,
+    reportDir: resolvedDir,
+    retentionDays,
+    deleted: [],
+    kept: 0,
+    skipped: 0,
+    errors: [],
+  };
+  let entries = [];
+  try {
+    entries = fs.readdirSync(resolvedDir, { withFileTypes: true });
+  } catch (err) {
+    result.errors.push(err instanceof Error ? err.message : String(err));
+    return result;
+  }
+  for (const entry of entries) {
+    if (!entry.isFile()) {
+      result.skipped += 1;
+      continue;
+    }
+    if (!entry.name.endsWith('.json') && !entry.name.endsWith('.md')) {
+      result.skipped += 1;
+      continue;
+    }
+    const full = path.join(resolvedDir, entry.name);
+    let stat = null;
+    try {
+      stat = fs.statSync(full);
+    } catch (err) {
+      result.errors.push(`${entry.name}: ${err instanceof Error ? err.message : String(err)}`);
+      continue;
+    }
+    if (stat.mtimeMs >= cutoffMs) {
+      result.kept += 1;
+      continue;
+    }
+    try {
+      fs.unlinkSync(full);
+      result.deleted.push(entry.name);
+    } catch (err) {
+      result.errors.push(`${entry.name}: ${err instanceof Error ? err.message : String(err)}`);
+    }
+  }
+  return result;
+}
+
 function tableCountQueries() {
   return [
     ['h5_users', 'users'],
@@ -257,6 +315,17 @@ if (runtimeSummary?.toolQueue?.inFlight > runtimeSummary?.toolQueue?.maxConcurre
   failures.push('tool_queue_concurrency_exceeded');
 }
 
+const reportDir = path.resolve(args.reportDir || path.join(appRoot, 'reports', 'runtime-slo'));
+if (args.writeReport || args.prune) {
+  fs.mkdirSync(reportDir, { recursive: true });
+}
+const reportPrune = args.prune
+  ? pruneReportDir(reportDir, args.retentionDays)
+  : { enabled: false, reportDir, retentionDays: args.retentionDays };
+for (const error of reportPrune.errors ?? []) {
+  failures.push(`report_prune_error:${error}`);
+}
+
 const report = {
   ok: failures.length === 0,
   checkedAt: new Date().toISOString(),
@@ -274,7 +343,9 @@ const report = {
     mindSpace: false,
     redis: false,
     report: Boolean(args.writeReport),
+    reportPrune: Boolean(args.prune),
   },
+  reportPrune,
 };
 
 function markdownReport(payload) {
@@ -319,13 +390,17 @@ function markdownReport(payload) {
     JSON.stringify(payload.writes, null, 2),
     '```',
     '',
+    '## Report Prune',
+    '',
+    '```json',
+    JSON.stringify(payload.reportPrune ?? null, null, 2),
+    '```',
+    '',
   );
   return lines.join('\n');
 }
 
 if (args.writeReport) {
-  const reportDir = path.resolve(args.reportDir || path.join(appRoot, 'reports', 'runtime-slo'));
-  fs.mkdirSync(reportDir, { recursive: true });
   const stamp = new Date().toISOString().replace(/[:.]/g, '-');
   report.reportFiles = {
     json: path.join(reportDir, `${stamp}.json`),