IO proxy: client-side cache with 5min TTL, server Cache-Control

Client caches IO results by (name + args) in memory. In-flight
promises are cached too (dedup concurrent calls for same args).
Server adds Cache-Control: public, max-age=300 for HTTP caching.

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

shared/static/scripts/sx-browser.js

@@ -14,7 +14,7 @@
   // =========================================================================
 
   var NIL = Object.freeze({ _nil: true, toString: function() { return "nil"; } });
-  var SX_VERSION = "2026-03-07T09:40:17Z";
+  var SX_VERSION = "2026-03-07T09:51:42Z";
 
   function isNil(x) { return x === NIL || x === null || x === undefined; }
   function isSxTruthy(x) { return x !== false && !isNil(x); }
@@ -4328,10 +4328,24 @@ callExpr.push(dictGet(kwargs, k)); } }
     return asyncRenderChildren(exprs, env, null);
   }
 
+  // IO proxy cache: key → { value, expires }
+  var _ioCache = {};
+  var IO_CACHE_TTL = 300000; // 5 minutes
+
   // Register a server-proxied IO primitive: fetches from /sx/io/<name>
   // Uses GET for short args, POST for long payloads (URL length safety).
+  // Results are cached client-side by (name + args) with a TTL.
   function registerProxiedIo(name) {
     registerIoPrimitive(name, function(args, kwargs) {
+      // Cache key: name + serialized args
+      var cacheKey = name;
+      for (var ci = 0; ci < args.length; ci++) cacheKey += "" + String(args[ci]);
+      for (var ck in kwargs) {
+        if (kwargs.hasOwnProperty(ck)) cacheKey += "" + ck + "=" + String(kwargs[ck]);
+      }
+      var cached = _ioCache[cacheKey];
+      if (cached && cached.expires > Date.now()) return cached.value;
+
       var url = "/sx/io/" + encodeURIComponent(name);
       var qs = [];
       for (var i = 0; i < args.length; i++) {
@@ -4364,7 +4378,7 @@ callExpr.push(dictGet(kwargs, k)); } }
         if (queryStr) url += "?" + queryStr;
         fetchOpts = { headers: { "SX-Request": "true" } };
       }
-      return fetch(url, fetchOpts)
+      var result = fetch(url, fetchOpts)
         .then(function(resp) {
           if (!resp.ok) {
             logWarn("sx:io " + name + " failed " + resp.status);
@@ -4376,7 +4390,9 @@ callExpr.push(dictGet(kwargs, k)); } }
           if (!text || text === "nil") return NIL;
           try {
             var exprs = parse(text);
-            return exprs.length === 1 ? exprs[0] : exprs;
+            var val = exprs.length === 1 ? exprs[0] : exprs;
+            _ioCache[cacheKey] = { value: val, expires: Date.now() + IO_CACHE_TTL };
+            return val;
           } catch (e) {
             logWarn("sx:io " + name + " parse error: " + (e && e.message ? e.message : e));
             return NIL;
@@ -4386,6 +4402,9 @@ callExpr.push(dictGet(kwargs, k)); } }
           logWarn("sx:io " + name + " network error: " + (e && e.message ? e.message : e));
           return NIL;
         });
+      // Cache the in-flight promise too (dedup concurrent calls for same args)
+      _ioCache[cacheKey] = { value: result, expires: Date.now() + IO_CACHE_TTL };
+      return result;
     });
   }
 

shared/sx/pages.py

@@ -601,6 +601,7 @@ def mount_io_endpoint(app: Any, service_name: str) -> None:
         result_sx = serialize(result) if result is not None else "nil"
         resp = await make_response(result_sx, 200)
         resp.content_type = "text/sx; charset=utf-8"
+        resp.headers["Cache-Control"] = "public, max-age=300"
         return resp
 
     io_proxy.__name__ = "sx_io_proxy"

shared/sx/ref/bootstrap_js.py

@@ -1698,10 +1698,24 @@ ASYNC_IO_JS = '''
     return asyncRenderChildren(exprs, env, null);
   }
 
+  // IO proxy cache: key → { value, expires }
+  var _ioCache = {};
+  var IO_CACHE_TTL = 300000; // 5 minutes
+
   // Register a server-proxied IO primitive: fetches from /sx/io/<name>
   // Uses GET for short args, POST for long payloads (URL length safety).
+  // Results are cached client-side by (name + args) with a TTL.
   function registerProxiedIo(name) {
     registerIoPrimitive(name, function(args, kwargs) {
+      // Cache key: name + serialized args
+      var cacheKey = name;
+      for (var ci = 0; ci < args.length; ci++) cacheKey += "\0" + String(args[ci]);
+      for (var ck in kwargs) {
+        if (kwargs.hasOwnProperty(ck)) cacheKey += "\0" + ck + "=" + String(kwargs[ck]);
+      }
+      var cached = _ioCache[cacheKey];
+      if (cached && cached.expires > Date.now()) return cached.value;
+
       var url = "/sx/io/" + encodeURIComponent(name);
       var qs = [];
       for (var i = 0; i < args.length; i++) {
@@ -1734,7 +1748,7 @@ ASYNC_IO_JS = '''
         if (queryStr) url += "?" + queryStr;
         fetchOpts = { headers: { "SX-Request": "true" } };
       }
-      return fetch(url, fetchOpts)
+      var result = fetch(url, fetchOpts)
         .then(function(resp) {
           if (!resp.ok) {
             logWarn("sx:io " + name + " failed " + resp.status);
@@ -1746,7 +1760,9 @@ ASYNC_IO_JS = '''
           if (!text || text === "nil") return NIL;
           try {
             var exprs = parse(text);
-            return exprs.length === 1 ? exprs[0] : exprs;
+            var val = exprs.length === 1 ? exprs[0] : exprs;
+            _ioCache[cacheKey] = { value: val, expires: Date.now() + IO_CACHE_TTL };
+            return val;
           } catch (e) {
             logWarn("sx:io " + name + " parse error: " + (e && e.message ? e.message : e));
             return NIL;
@@ -1756,6 +1772,9 @@ ASYNC_IO_JS = '''
           logWarn("sx:io " + name + " network error: " + (e && e.message ? e.message : e));
           return NIL;
         });
+      // Cache the in-flight promise too (dedup concurrent calls for same args)
+      _ioCache[cacheKey] = { value: result, expires: Date.now() + IO_CACHE_TTL };
+      return result;
     });
   }