diff --git a/luprex/core/cpp/eng-malloc.hpp b/luprex/core/cpp/eng-malloc.hpp
index 30afaf53..27a06d78 100644
--- a/luprex/core/cpp/eng-malloc.hpp
+++ b/luprex/core/cpp/eng-malloc.hpp
@@ -142,6 +142,9 @@ namespace eng {
 
 // eng::nevernew.  A class containing private operator new and
 // operator delete, making it impossible to 'new' the class.
+// This means the class must be embedded as a field in some other
+// class, and it gets allocated when its enclosing object gets
+// allocated.
 namespace eng {
     class nevernew {
     private:
diff --git a/luprex/core/cpp/http.cpp b/luprex/core/cpp/http.cpp
index 5042701c..5db07712 100644
--- a/luprex/core/cpp/http.cpp
+++ b/luprex/core/cpp/http.cpp
@@ -189,6 +189,9 @@ public:
 HttpOutRequest::HttpOutRequest() {
     verify_certificate_ = true;
     port_ = 0;
+    request_id_ = 0;
+    place_id_ = 0;
+    thread_id_ = 0;
 }
 
 void HttpOutRequest::fail(string_view s) {
@@ -395,8 +398,6 @@ void HttpOutRequest::set_config(LuaStack &LS0, LuaSlot tab) {
             set_port(LS, val);
         } else if (kstr == "path") {
             set_path(LS, val);
-        } else if (kstr == "encodedpath") {
-            set_path(LS, val);
         } else if (kstr == "params") {
             set_params(LS, val);
         } else if (kstr == "url") {
@@ -430,6 +431,7 @@ eng::string HttpOutRequest::check() const {
     return "";
 }
 
+
 void HttpOutRequest::send_internal(StreamBuffer *sb, bool debug_string) const {
     // If there's an error in the request, handle it.  In debug string mode,
     // we just put the error into the output.  In production mode, we assert
@@ -469,18 +471,78 @@ void HttpOutRequest::send_internal(StreamBuffer *sb, bool debug_string) const {
     sb->write_bytes("User-agent: Mozilla 5.0 (luprex)");
     sb->write_bytes(linebreak);
 
+    // Add the requester IDs (debug string only)
+    if (debug_string && ((request_id_ != 0) || (place_id_ != 0) || (thread_id_ != 0))) {
+        sb->write_bytes("X-Requester-Ids: ");
+        sb->ostream() << "rid=" << request_id_ << "; pid=" << place_id_ << "; tid=" << thread_id_;
+        sb->write_bytes(linebreak);
+    }
+
     // Send the extra linebreak.
     if (!debug_string) {
         sb->write_bytes(linebreak);
     }
 }
 
+void HttpOutRequest::serialize(StreamBuffer *sb) const {
+    sb->write_int64(request_id_);
+    sb->write_int64(place_id_);
+    sb->write_int64(thread_id_);
+    sb->write_string(error_);
+    sb->write_bool(verify_certificate_);
+    sb->write_string(method_);
+    sb->write_string(host_);
+    sb->write_int32(port_);
+    sb->write_string(path_);
+    sb->write_int32(params_.size());
+    for (const auto &pair : params_) {
+        sb->write_string(pair.first);
+        sb->write_string(pair.second);
+    }
+}
+
+void HttpOutRequest::deserialize(StreamBuffer *sb) {
+    request_id_ = sb->read_int64();
+    place_id_ = sb->read_int64();
+    thread_id_ = sb->read_int64();
+    error_ = sb->read_string();
+    verify_certificate_ = sb->read_bool();
+    method_ = sb->read_string();
+    host_ = sb->read_string();
+    port_ = sb->read_int32();
+    path_ = sb->read_string();
+    int32_t nparams = sb->read_int32();
+    params_.clear();
+    for (int i = 0; i < nparams; i++) {
+        eng::string k = sb->read_string();
+        eng::string v = sb->read_string();
+        params_[k] = v;
+    }
+}
+
 eng::string HttpOutRequest::DebugString() {
     StreamBuffer sb;
     send_internal(&sb, true);
     return eng::string(sb.view());
 }
 
+void HttpOutRequestMap::serialize(StreamBuffer *sb) const {
+    sb->write_int32(size());
+    for (const auto &pair : *this) {
+        pair.second.serialize(sb);
+    }
+}
+
+void HttpOutRequestMap::deserialize(StreamBuffer *sb) {
+    int32_t count = sb->read_int32();
+    clear();
+    HttpOutRequest req;
+    for (int i = 0; i < count; i++) {
+        req.deserialize(sb);
+        (*this)[req.request_id()] = req;
+    }
+}
+
 HttpInResponse::HttpInResponse() {
     status_code_ = 0;
     response_length_ = 0;
@@ -513,7 +575,7 @@ void HttpInResponse::fail(int code, string_view message) {
 
 void HttpInResponse::incomplete(bool closed) {
     if (closed) {
-        fail(500, "response truncated");
+        fail(500, "internal server error: response truncated");
     } else {
         fail(0, "response not yet fully received");
     }
@@ -526,7 +588,7 @@ void HttpInResponse::parse_content_encoding(string_view value) {
 void HttpInResponse::parse_content_length(string_view value) {
     int64_t code = sv::to_int64(value);
     if ((code < 0) || (code > INT_MAX)) {
-        fail(500, util::ss("unparseable content-length: ", value));
+        fail(500, util::ss("internal server error: unparseable content-length: ", value));
     }
     content_length_ = code;
 }
@@ -536,7 +598,7 @@ void HttpInResponse::parse_content_type(string_view value) {
     string_view ctview(ctype);
     mime_type_ = sv::trim(sv::read_to_sep(ctview, ';'));
     if (mime_type_.empty()) {
-        fail(500, util::ss("unparseable content-type: ", value));
+        fail(500, util::ss("internal server error: unparseable content-type: ", value));
         return;
     }
     while (true) {
@@ -571,14 +633,14 @@ void HttpInResponse::parse_header(string_view header, string_view value) {
     } else if (header == "transfer-encoding") {
         parse_transfer_encoding(value);
     } else if (header == "content-range") {
-        fail(500, util::ss("unsupported response header: ", header));
+        fail(406, util::ss("not acceptable: unsupported response header: ", header));
     }
 }
 
 bool HttpInResponse::parse_content_basic(std::string_view &view, bool closed) {
     if (content_length_ >= 0) {
         if (content_length_ > MAX_CONTENT_LENGTH) {
-            fail(500, "content too long");
+            fail(413, util::ss("payload too large: luprex limit=", MAX_CONTENT_LENGTH));
             return false;
         }
         if (int(view.size()) < content_length_) {
@@ -588,7 +650,7 @@ bool HttpInResponse::parse_content_basic(std::string_view &view, bool closed) {
         content_ = sv::read_nbytes(view, content_length_);
     } else {
         if (int64_t(view.size()) > MAX_CONTENT_LENGTH) {
-            fail(500, "content too long");
+            fail(413, util::ss("payload too large: luprex limit=", MAX_CONTENT_LENGTH));
             return false;
         }
         if (!closed) {
@@ -611,17 +673,17 @@ bool HttpInResponse::parse_content_chunked(std::string_view &view, bool closed)
         }
         int64_t chunk_size = sv::to_hex64(chunk_header, -1);
         if (chunk_size < 0) {
-            fail(500, "unparseable chunk header");
+            fail(500, "internal server error: unparseable chunk header");
             return false;
         }
         if (chunk_size > MAX_CONTENT_LENGTH) {
-            fail(500, "content too long");
+            fail(413, util::ss("payload too large: luprex limit=", MAX_CONTENT_LENGTH));
             return false;
         }
         if (chunk_size == 0) break;
         total_size += chunk_size;
         if (total_size > MAX_CONTENT_LENGTH) {
-            fail(500, "content too long");
+            fail(413, util::ss("payload too large: luprex limit=", MAX_CONTENT_LENGTH));
             return false;
         }
         std::string_view chunk = sv::read_nbytes(view, chunk_size);
@@ -631,7 +693,7 @@ bool HttpInResponse::parse_content_chunked(std::string_view &view, bool closed)
         }
         std::string_view newline = sv::read_to_line(view);
         if (!newline.empty()) {
-            fail(500, "corrupted chunk encoding");
+            fail(500, "internal server error: corrupted chunk encoding");
             return false;
         }
         if (sv::isnull(view)) {
@@ -665,7 +727,7 @@ void HttpInResponse::parse(const StreamBuffer *sb, bool closed) {
     string_view scode = sv::read_to_space(status);
     int64_t code = sv::to_int64(scode, 0);
     if ((code < 100) || (code > 599)) {
-        fail(500, util::ss("protocol error: invalid response code: ", scode));
+        fail(500, util::ss("internal server error: invalid response code: ", scode));
     }
     status_code_ = code;
 
@@ -690,11 +752,11 @@ void HttpInResponse::parse(const StreamBuffer *sb, bool closed) {
         }
         eng::string command = util::ascii_tolower(sv::trim(sv::read_to_sep(header, ':')));
         if (sv::isnull(header)) {
-            fail(500, util::ss("protocol error: no colon in header line: ", command));
+            fail(500, util::ss("internal server error: no colon in header line: ", command));
             return;
         }
         if (!words_separated_by_dashes(command)) {
-            fail(500, util::ss("protocol error: invalid header: ", command));
+            fail(500, util::ss("internal server error: invalid header: ", command));
             return;
         }
         parse_header(command, sv::trim(header));
@@ -716,7 +778,7 @@ void HttpInResponse::parse(const StreamBuffer *sb, bool closed) {
     // If it's not a redirect, disallow 'location'.
     if ((status_code_ < 300) || (status_code_ > 399)) {
         if (!location_.empty()) {
-            fail(500, util::ss("redirect specified, but result code not 300-399: ", code));
+            fail(500, util::ss("internal server error: location specified, but result code not 300-399: ", code));
             return;
         }
     }
@@ -734,18 +796,18 @@ void HttpInResponse::parse(const StreamBuffer *sb, bool closed) {
 
     // If it's multipart, reject it.
     if (sv::has_prefix(mime_type_, "multipart/")) {
-        fail(500, "multipart messages not implemented");
+        fail(406, "not acceptable: multipart messages not supported");
         return;
     }
 
     // If it's text, demand a reasonable charset.  Otherwise,
     // ignore the charset.
     if (sv::has_prefix(mime_type_, "text/")) {
-        if (charset_.empty()) {
+        if (charset_.empty() || (charset_ == "ascii")) {
             charset_ = "utf-8";
         }
         if (charset_ != "utf-8") {
-            fail(500, util::ss("charset not supported: ", charset_));
+            fail(406, util::ss("not acceptable: charset not supported: ", charset_));
             return;
         }
     } else {
@@ -755,7 +817,7 @@ void HttpInResponse::parse(const StreamBuffer *sb, bool closed) {
     // Uncompress the content.
     if ((content_encoding_ == "") || (content_encoding_ == "identity")) {
     } else {
-        fail(500, util::ss("content-encoding not supported: ", content_encoding_));
+        fail(406, util::ss("not acceptable: content-encoding not supported: ", content_encoding_));
         return;
     }
 
@@ -767,7 +829,7 @@ void HttpInResponse::parse(const StreamBuffer *sb, bool closed) {
     }
 }
 
-void HttpInResponse::store(LuaStack &LS0, LuaSlot tab) {
+void HttpInResponse::store(LuaStack &LS0, LuaSlot tab) const {
     LuaStack LS(LS0.state());
 
     LS.newtable(tab);
@@ -784,10 +846,24 @@ void HttpInResponse::store(LuaStack &LS0, LuaSlot tab) {
     }
 
     // Debugging fields.  Do not use for lua programming.
-    LS.rawset(tab, "dbg-content-length", content_length_);
-    LS.rawset(tab, "dbg-transfer-encoding", transfer_encoding_);
-    LS.rawset(tab, "dbg-charset", charset_);
-    LS.rawset(tab, "dbg-response-length", response_length_);
+    if (content_length_ >= 0) {
+        LS.rawset(tab, "dbg_contentlength", content_length_);
+    }
+    if (!transfer_encoding_.empty()) {
+        LS.rawset(tab, "dbg_transferencoding", transfer_encoding_);
+    }
+    if (!charset_.empty()) {
+        LS.rawset(tab, "dbg_charset", charset_);
+    }
+    if (response_length_ != 0) {
+        LS.rawset(tab, "dbg_responselength", response_length_);
+    }
+}
+
+void HttpInResponse::store_fail(LuaStack &LS, LuaSlot tab, int status_code, std::string_view error) {
+    HttpInResponse response;
+    response.fail(status_code, error);
+    response.store(LS, tab);
 }
 
 LuaDefine(http_fixurl, "url", "validate URL and repair minor flaws in the URL syntax") {
@@ -804,36 +880,35 @@ LuaDefine(http_fixurl, "url", "validate URL and repair minor flaws in the URL sy
 }
 
 
-LuaDefine(http_request, "reqtab",
-    "|Given an HTTP request in the form of a table, returns the same "
-    "|request as a string, to assist with debugging."
+LuaDefine(http_request, "request",
+    "|Takes an HTTP request in the form of a lua table."
+    "|The table may contain these fields:"
     "|"
-    "|The table can contain:"
-    "|"
-    "|  method             (ie, GET, HEAD, POST, etc)"
+    "|  method             (ie, 'GET', 'POST', etc)"
     "|  host               (ie, 'google.com')"
     "|  port               (default: 443)"
-    "|  url                (ie, '/index.html')"
+    "|  path               (ie, '/index.html')"
     "|  params             (a table of url parameters)"
     "|  verifycertificate  (default: true)"
+    "|  url                (ie, 'https://host:port/path.html?a=b&c=d')"
     "|"
-    "|The url can start with 'https://', or with '/'.  If it starts"
-    "|with 'https://', then the URL includes the host and port, which"
-    "|then must not be specified separately."
+    "|You can specify url components separately (host, port, path,"
+    "|and params), or you can specify the entire url as a unit. "
+    "|If you specify components, they must not be url-encoded. "
+    "|If you specify the url as a whole, it must already be url-encoded."
     "|"
-    "|Note that plain HTTP is not supported - we only allow HTTPS."
+    "|You can omit the port, in which case it defaults to the"
+    "|standard https port.  You can omit verifycertificate, in which"
+    "|case it defaults to true.  You can omit the method if the"
+    "|method is implied by the function you called (eg, 'http.get')."
+    "|"
+    "|Note that unencrypted http is not supported - we only allow https."
     "|However, you can talk to a server that has a dummy certificate"
     "|by specifying verifycertificate=false."
     "|"
-    "|This module will automatically url encode everything for you."
-    "|Therefore, you shouldn't url encode anything, otherwise,"
-    "|you'll end up double-encoding."
-    "|"
-    "|You cannot include url parameters as part of the url.  If you try,"
-    "|then your ?, &, and = characters will get url encoded, which will"
-    "|cause them to not function.  To use url parameters, you must"
-    "|use the separate params table."
-    "|") {
+    "|This routine, http.request, returns a debug string for the "
+    "|request.  The debug string looks like the actual http headers"
+    "|that would be sent.") {
     LuaArg tab;
     LuaRet str;
     LuaStack LS(L, tab, str);
@@ -849,7 +924,48 @@ LuaDefine(http_request, "reqtab",
     return LS.result();
 }
 
-LuaDefine(http_response, "text", "") {
+LuaDefine(http_response, "response",
+    "|Returns an HTTP response in the form of a lua table."
+    "|The table will contain these important fields:"
+    "|"
+    "|  responsecode - 3-digit HTTP response code."
+    "|  error        - an error message, or nil if no error."
+    "|  content      - on success, the content, as a string."
+    "|  mimetype     - on success, the mime type of the content."
+    "|  location     - for HTTP redirects, the target url."
+    "|"
+    "|If the mimetype is a text mimetype, then the content"
+    "|is automatically converted to utf-8."
+    "|"
+    "|The table may also contain these debugging-only fields."
+    "|"
+    "|  dbg_transferencoding - If there was a Transfer-Encoding header."
+    "|  dbg_contentlength    - If there was a Content-length header."
+    "|  dbg_charset          - Original character set for text mime types."
+    "|  dbg_responselength   - Total bytes in the response."
+    "|"
+    "|None of the dbg fields is needed to understand the response."
+    "|For example, consider dbg_charset.  When text content is"
+    "|passed to lua, the content is automatically converted to utf-8."
+    "|So dbg_charset only tells you what the character set used"
+    "|to be, before it was converted to utf-8."
+    "|"
+    "|If an http routine generates an error, that error will be"
+    "|expressed as a status code.  These locally-generated status"
+    "|codes can be:"
+    "|"
+    "|   400 (bad request)          - the request was malformed"
+    "|   503 (service unavailable)  - dns fail, connect fail, or ssl fail"
+    "|   500 (internal server error)- the response contains invalid HTTP"
+    "|   406 (not acceptable)       - the response used a feature we don't support yet"
+    "|   413 (payload too large)    - we refuse to download something so big"
+    "|   425 (can't resume)         - reloaded a save game with a pending request"
+    "|"
+    "|In this case, the error message will be the stock"
+    "|error message, followed by more information."
+    "|"
+    "|This routine, http.response, generates a response by parsing"
+    "|an actual HTTP response string.  This is for debugging only.") {
     LuaArg text;
     LuaRet tab;
     LuaStack LS(L, text, tab);
diff --git a/luprex/core/cpp/http.hpp b/luprex/core/cpp/http.hpp
index 8f274d8f..c315cf49 100644
--- a/luprex/core/cpp/http.hpp
+++ b/luprex/core/cpp/http.hpp
@@ -24,6 +24,11 @@ using UrlParameters = eng::map<eng::string, eng::string>;
 
 class HttpOutRequest : public eng::nevernew {    
 private:
+    // Request IDs.
+    int64_t request_id_;
+    int64_t place_id_;
+    int64_t thread_id_;
+    
     // If the request contains an error, the error
     // message is stored here.
     eng::string error_;
@@ -32,38 +37,36 @@ private:
     // True is the default.
     bool verify_certificate_;
 
-    // Method: GET, HEAD, POST, etc.
+    // Method: GET, HEAD, POST, etc.  Must be all-caps.
     eng::string method_;
 
-    // The hostname.  This is used both for DNS lookup,
-    // and to create an HTTP Host header.
+    // The hostname. Not yet url-encoded.
     eng::string host_;
 
     // Port number.
     int port_;
 
-    // You may specify either path or encoded_path.
-    // The path is not url-encoded, and must not include URL parameters.
+    // The path.  Not yet url-encoded.  Can not include URL parameters.
     eng::string path_;
     
-    // If params is nonempty, then we will add URL parameters
-    // to the URL.  The contents of the params field should not be
-    // urlencoded, the urlencoding is done automatically when the
-    // request is sent.  If you specify encoded_path, then the
-    // params must be empty, because the encoded path already contains
-    // the params.
+    // URL parameters to append to the path.  Not yet url-encoded.
     UrlParameters params_;
-    
+
 private:
     void fail(std::string_view error);
-
     void send_internal(StreamBuffer *target, bool debug_string) const;
+
 public:
     // Construct an empty HTTP request.
     // All of the fields have empty values.
     HttpOutRequest();
     
-    // Get fields.
+    // Get the request IDs.
+    int64_t request_id() const { return request_id_; }
+    int64_t place_id() const { return place_id_; }
+    int64_t thread_id() const { return thread_id_; }
+
+    // Get request-related fields.
     const eng::string &error() const { return error_; }
     bool verify_certificate() const { return verify_certificate_; }
     const eng::string &method() const { return method_; }
@@ -74,6 +77,11 @@ public:
     // Get the network target, eg, "cert:host:port"
     eng::string target() const;
 
+    // Set the request IDs.
+    void set_request_id(int64_t request_id) { request_id_ = request_id; }
+    void set_place_id(int64_t place_id) { place_id_ = place_id; }
+    void set_thread_id(int64_t thread_id) { thread_id_ = thread_id; }
+    
     // Populate an HTTP request a piece at a time.
     // If you pass an invalid value, or if the field is
     // already set, the routine will generate an error message
@@ -113,10 +121,20 @@ public:
     // Put the request into the stream, assuming HTTP/1.1
     void send(StreamBuffer *target) const { send_internal(target, false); }
 
+    // Serialize and deserialize.
+    void serialize(StreamBuffer *sb) const;
+    void deserialize(StreamBuffer *sb);
+
     // Get the request as a debug string.
     eng::string DebugString();
 };
 
+class HttpOutRequestMap : public eng::map<int64_t, HttpOutRequest> {
+public:
+    void serialize(StreamBuffer *sb) const;
+    void deserialize(StreamBuffer *sb);
+};
+
 class HttpInResponse {
 private:
     // The HTTP response status code.
@@ -201,10 +219,13 @@ public:
     void parse(const StreamBuffer *sb, bool closed);
 
     // Convert the HTTP response to a lua table.
-    void store(LuaStack &LS, LuaSlot tab);
+    void store(LuaStack &LS, LuaSlot tab) const;
 
     // Convert to a debug string.
     eng::string DebugString() const;
+
+    // Synthesize an error response and store it in lua.
+    static void store_fail(LuaStack &LS, LuaSlot tab, int status_code, std::string_view error);
 };
 
 #endif // HTTP_HPP
diff --git a/luprex/core/cpp/lpxserver.cpp b/luprex/core/cpp/lpxserver.cpp
index 0095ece3..6d5ae362 100644
--- a/luprex/core/cpp/lpxserver.cpp
+++ b/luprex/core/cpp/lpxserver.cpp
@@ -91,6 +91,10 @@ public:
         stop_driver();
     }
 
+    void do_aborthttp_command(const util::StringVec &words) {
+        master_->abort_all_http_requests(425, "http requests aborted from the server command line");
+    }
+
     void do_command(const util::StringVec &words) {
         if (words.empty()) return;
         else if (words[0] == "luainvoke") do_luainvoke_command(words);
@@ -101,6 +105,7 @@ public:
         else if (words[0] == "tick") do_tick_command(words);
         else if (words[0] == "cpl") do_cpl_command(words);
         else if (words[0] == "quit") do_quit_command(words);
+        else if (words[0] == "aborthttp") do_aborthttp_command(words);
         else {
             stdostream() << "Unsupported command: " << words[0] << std::endl;
         }
diff --git a/luprex/core/cpp/luaconsole.cpp b/luprex/core/cpp/luaconsole.cpp
index 5f6204bc..55093169 100644
--- a/luprex/core/cpp/luaconsole.cpp
+++ b/luprex/core/cpp/luaconsole.cpp
@@ -94,6 +94,10 @@ void LuaConsole::simplify(const StringVec &words) {
         if (words.size() != 1) {
             synerr("/work takes no arguments");
         }
+    } else if (words[0] == "aborthttp") {
+        if (words.size() != 1) {
+            synerr("/aborthttp takes no arguments");
+        }
     } else {
         synerr("unrecognized command");
     }
diff --git a/luprex/core/cpp/world-accessor.cpp b/luprex/core/cpp/world-accessor.cpp
index 6bbea6e2..769fbeda 100644
--- a/luprex/core/cpp/world-accessor.cpp
+++ b/luprex/core/cpp/world-accessor.cpp
@@ -295,6 +295,9 @@ LuaDefine(tangible_scan, "plane,x,y,radius,omit_nowhere",
 LuaDefine(wait, "nticks",
     "|Wait the specified number of ticks.") {
     World *w = World::fetch_global_pointer(L);
+    w->guard_blockable(L, "wait");
+
+    // Parse the argument.
     LuaArg seconds;
     LuaStack LS(L, seconds);
     int64_t n = LS.ckinteger(seconds);
@@ -302,30 +305,19 @@ LuaDefine(wait, "nticks",
         luaL_error(L, "Argument to wait must be between 0 and 1000000");
         return LS.result();
     }
-    if (!lua_isyieldable(L)) {
-        // in a probe, wait throws an error.
-        luaL_error(L, "cannot wait in a probe.");
-        return LS.result();
-    } else if (!w->is_authoritative()) {
-        // in a nonauth model, yield is converted to nopredict.
-        lua_yield(L, 0);
-        return LS.result();
-    } else {
-        // in an authoritative model, wait schedules a continuation.
-        w->schedule(w->clock_ + n, w->lthread_thread_id_, w->lthread_place_id_);
-        lua_yield(L, 0);
-        return LS.result();
-    }
+
+    // Schedule a continuation.
+    w->schedule(w->clock_ + n, w->lthread_thread_id_, w->lthread_place_id_);
+    return lua_yield(L, 0);
 }
 
 LuaDefine(nopredict, "",
     "|Stop predictive execution of this thread.") {
-    if (lua_gettop(L) != 0) {
-        luaL_error(L, "tangible.nopredict takes no arguments");
-    }
     World *w = World::fetch_global_pointer(L);
-    if (lua_isyieldable(L) && !w->is_authoritative()) {
-        return lua_yield(L, 0);
+    w->guard_nopredict(L, "nopredict");
+
+    if (lua_gettop(L) != 0) {
+        luaL_error(L, "nopredict takes no arguments");
     }
     return 0;
 }
@@ -529,4 +521,36 @@ LuaDefine(doc, "function",
     }
     (*ostream) << doc;
     return LS.result();
+}
+
+LuaDefine(http_get, "request",
+    "|Make an HTTP GET request.  Returns an HTTP response."
+    "|See doc(http.request) and doc(http.response).") {
+    World *w = World::fetch_global_pointer(L);
+    w->guard_blockable(L, "http.get");
+
+    LuaArg request;
+    LuaRet response;
+    LuaStack LS(L, request, response);
+    HttpOutRequest req;
+    
+    // Parse the request and make sure it's valid.
+    req.set_config(LS, request);
+    req.set_defaults();
+    eng::string error = req.check();
+    if (!error.empty()) {
+        HttpInResponse::store_fail(LS, response, 400, util::ss("bad request: ", error));
+        return LS.result();
+    }
+
+    // Give the request an ID.
+    req.set_request_id(w->id_global_pool_.get_one());
+    req.set_place_id(w->lthread_place_id_);
+    req.set_thread_id(w->lthread_thread_id_);
+
+    // Store it in the global request table.
+    w->http_requests_[req.request_id()] = req;
+
+    // Block.
+    return lua_yield(L, 0);
 }
\ No newline at end of file
diff --git a/luprex/core/cpp/world-core.cpp b/luprex/core/cpp/world-core.cpp
index adadb8cb..ee03bb03 100644
--- a/luprex/core/cpp/world-core.cpp
+++ b/luprex/core/cpp/world-core.cpp
@@ -393,6 +393,66 @@ void World::update_source(const util::LuaSourceVec &source) {
     assert(stack_is_clear());
 }
 
+void World::http_response(int64_t request_id, const HttpInResponse &response) {
+    // Find the request.
+    auto iter = http_requests_.find(request_id);
+    if (iter == http_requests_.end()) {
+        return;
+    }
+    HttpOutRequest request = iter->second;
+    http_requests_.erase(iter);
+
+    // Get the place and thread as lua objects.
+    LuaVar tangibles, place, mt, threads, thinfo, thread;
+    LuaStack LS(state(), tangibles, place, mt, threads, thinfo, thread);
+    LS.rawget(tangibles, LuaRegistry, "tangibles");
+    LS.rawget(place, tangibles, request.place_id());
+    if (!LS.istable(place)) {
+        return;
+    }
+    LS.getmetatable(mt, place);
+    if (!LS.istable(mt)) {
+        return;
+    }
+    LS.rawget(threads, mt, "threads");
+    if (!LS.istable(threads)) {
+        return;
+    }
+    LS.rawget(thinfo, threads, request.thread_id());
+    if (!LS.istable(thinfo)) {
+        return;
+    }
+    LS.rawget(thread, thinfo, "thread");
+    if (!LS.isthread(thread)) {
+        return;
+    }
+    lua_State *CO = LS.ckthread(thread);
+
+    // Push the response onto the awakening thread.
+    LuaRet responsetable;
+    LuaStack LSCO(CO, responsetable);
+    response.store(LSCO, responsetable);
+
+    // Clean up lua stacks.
+    LSCO.result();
+    LS.result();
+    assert(stack_is_clear());
+
+    // Awaken the thread, with its new return value.
+    schedule(0, request.thread_id(), request.place_id());
+    run_scheduled_threads();
+}
+
+void World::abort_all_http_requests(int status_code, std::string_view error) {
+    HttpInResponse abortresponse;
+    abortresponse.fail(status_code, error);
+    while (true) {
+        auto iter = http_requests_.begin();
+        if (iter == http_requests_.end()) break;
+        http_response(iter->second.request_id(), abortresponse);
+    }
+}
+
 void World::run_unittests() {
     assert(stack_is_clear());
     source_db_.run_unittests();
@@ -635,6 +695,30 @@ void World::invoke_lua_source(int64_t actor_id, int64_t place_id, const eng::str
     }
 }
 
+void World::guard_blockable(lua_State *L, const char *fn) {
+    if (lthread_thread_id_ == 0) {
+        // in a probe, http.get throws an error.
+        luaL_error(L, "cannot %s in a probe", fn);
+        assert(false);
+    }
+    if (!is_authoritative()) {
+        // in a nonauth model, http.get is converted to nopredict.
+        lua_yield(L, 0);
+        luaL_error(L, "unexplained nopredict failure in %s", fn);
+        assert(false);
+    }
+}
+
+void World::guard_nopredict(lua_State *L, const char *fn) {
+    if (lthread_thread_id_ == 0) {
+        return;
+    }
+    if (!is_authoritative()) {
+        lua_yield(L, 0);
+        luaL_error(L, "unexplained nopredict failure in %s", fn);
+    }
+}
+
 void World::schedule(int64_t clk, int64_t thid, int64_t plid) {
     assert(is_authoritative());
     thread_sched_.add(clk, thid, plid);
@@ -796,6 +880,7 @@ void World::serialize(StreamBuffer *sb) {
     id_global_pool_.serialize(sb);
     sb->write_int64(clock_);
     thread_sched_.serialize(sb);
+    http_requests_.serialize(sb);
     sb->write_uint32(tangibles_.size());
     for (const auto &p : tangibles_) {
         sb->write_int64(p.first);
@@ -813,6 +898,7 @@ void World::deserialize(StreamBuffer *sb) {
     id_global_pool_.deserialize(sb);
     clock_ = sb->read_int64();
     thread_sched_.deserialize(sb);
+    http_requests_.deserialize(sb);
     // Mark all tangibles for deletion by setting ID to zero.
     for (const auto &p : tangibles_) {
         p.second->plane_item_.set_id(0);
@@ -837,6 +923,8 @@ void World::deserialize(StreamBuffer *sb) {
             ++iter;
         }
     }
+    // After a save and load, http requests no longer should exist
+    abort_all_http_requests(425, "http requests aborted by loading a save game");
     assert(stack_is_clear());
 }
 
diff --git a/luprex/core/cpp/world.hpp b/luprex/core/cpp/world.hpp
index fc9dba33..66ef47a1 100644
--- a/luprex/core/cpp/world.hpp
+++ b/luprex/core/cpp/world.hpp
@@ -18,6 +18,7 @@
 #include "debugcollector.hpp"
 #include "printbuffer.hpp"
 #include "sched.hpp"
+#include "http.hpp"
 #include "source.hpp"
 #include "gui.hpp"
 #include "luasnap.hpp"
@@ -188,6 +189,9 @@ public:
     // This is the primary dispatcher for all operations that mutate a world model.
     // To mutate a world model, create an invocation, then invoke it.
     //
+    // It is legal to mutate a world model without using 'Invoke', but
+    // only in authoritative world models.
+    //
     void invoke(const Invocation &inv);
     
     // Get the PrintBuffer of the actor.
@@ -201,6 +205,14 @@ public:
     void update_source(const util::LuaSourcePtr &source);
     void update_source(const util::LuaSourceVec &source);
     
+    // Supply an HTTP response to an outstanding HTTP request.
+    void http_response(int64_t request_id, const HttpInResponse &response);
+
+    // Abort all HTTP requests.  This is typically used after
+    // reloading a world from a save-game.  The http requests that
+    // were in progress are long-since dead.
+    void abort_all_http_requests(int status_code, std::string_view error);
+
     // Run all unit tests.
     //
     void run_unittests();
@@ -216,6 +228,10 @@ public:
     //
     bool is_authoritative() const { return (world_type_ == util::WORLD_TYPE_MASTER) || (world_type_ == util::WORLD_TYPE_STANDALONE); }
 
+    // Get a table showing all outstanding HTTP requests.
+    //
+    const HttpOutRequestMap &http_requests() const { return http_requests_; }
+
     // Serialize and deserialize.
     //
     void serialize(StreamBuffer *sb);
@@ -263,6 +279,16 @@ public:
     //
     int64_t alloc_id_predictable();
     
+    // If we're in a probe, generate an error.
+    // If we're in a nonauthoritative model, do a nopredict yield.
+    // Otherwise, return.
+    void guard_blockable(lua_State *L, const char *fn);
+    
+    // If we're in a probe, return.
+    // If we're in a nonauthoritative model, do a nopredict yield.
+    // Otherwise, return.
+    void guard_nopredict(lua_State *L, const char *fn);
+
 private:
     // Add a thread to the scheduler queue.
     //
@@ -478,6 +504,7 @@ private:
     eng::unordered_map<int64_t, UniqueTangible> tangibles_;
 
     // Current time.
+    //
     int64_t clock_;
 
     // Thread schedule: must include every thread, except
@@ -485,7 +512,13 @@ private:
     //
     Schedule thread_sched_;
 
+    // Outstanding HTTP requests, indexed by request ID.
+    // Authoritative models only.
+    //
+    HttpOutRequestMap http_requests_;
+
     // Serialized snapshot of world model.
+    //
     StreamBuffer snapshot_;
 
     // Redirects.
@@ -513,6 +546,7 @@ private:
     friend int lfn_math_randomstate(lua_State *L);
     friend int lfn_wait(lua_State *L);
     friend int lfn_nopredict(lua_State *L);
+    friend int lfn_http_get(lua_State *L);
 };
 
 using UniqueWorld = std::unique_ptr<World>;
diff --git a/luprex/core/lua/login.lua b/luprex/core/lua/login.lua
index 04b9bd0a..8b166b6e 100644
--- a/luprex/core/lua/login.lua
+++ b/luprex/core/lua/login.lua
@@ -42,3 +42,9 @@ function setfoo(n)
 function buildq()
     return tangible.build{class="login", x=10, y=0, z=0, plane="nowhere", graphic="what"}
     end
+
+function htest()
+    print("hi")
+    pprint(http.get{url="https://mit.edu/"})
+    print("bye")
+    end