diff --git a/runtime/actions.cpp b/runtime/actions.cpp
index acdfaf0..c57594b 100644
--- a/runtime/actions.cpp
+++ b/runtime/actions.cpp
@@ -1,5 +1,11 @@
 #include "actions.hpp"
+#include "json.hpp"
 #include "vm_provider.hpp"
+#include <cstdlib>
+#include <iostream>
+#include <memory>
+
+using namespace sliger::rpc::action;
 
 auto sliger::rpc::action::RunDebug::perform_action(
     std::unique_ptr<sliger::rpc::BufferedWriter> writer,
@@ -38,3 +44,35 @@ auto sliger::rpc::action::CodeCoverage::perform_action(
     }
     writer->flush();
 };
+
+auto sliger::rpc::action::action_from_json(const sliger::json::Value& value)
+    -> std::unique_ptr<Action>
+{
+    auto& obj = value.as<sliger::json::Object>();
+    auto type = obj.fields.at("type")->as<sliger::json::String>();
+
+    if (type.value == "flame-graph") {
+        auto action = FlameGraph();
+        return std::make_unique<FlameGraph>(action);
+    }
+
+    if (type.value == "code-coverage") {
+        auto action = CodeCoverage();
+        return std::make_unique<CodeCoverage>(action);
+    }
+
+    if (type.value == "run-debug") {
+        sliger::json::ArrayValues values = std::move(
+            obj.fields.at("program")->as<sliger::json::Array>().values);
+        auto instructions = std::vector<uint32_t>();
+        for (auto& v : values) {
+            std::unique_ptr<sliger::json::Value> moved = std::move(v);
+            auto value = moved->as<sliger::json::Number>().value;
+            instructions.push_back((uint32_t)value);
+        }
+        auto action = RunDebug(instructions);
+        return std::make_unique<RunDebug>(action);
+    }
+    std::cout << "error: TODO " << __FILE__ << ":" << __LINE__ << "\n";
+    exit(1);
+};
diff --git a/runtime/actions.hpp b/runtime/actions.hpp
index cab5dd2..80916c7 100644
--- a/runtime/actions.hpp
+++ b/runtime/actions.hpp
@@ -5,24 +5,24 @@
 namespace sliger::rpc::action {
 
 struct Action {
-    virtual auto perform_action(
-        std::unique_ptr<sliger::rpc::BufferedWriter> writer,
-        sliger::rpc::vm_provider::VmProvider& vm_provider) -> void = 0;
+    virtual auto perform_action(std::unique_ptr<BufferedWriter> writer,
+        vm_provider::VmProvider& vm_provider) -> void
+        = 0;
     virtual ~Action() = default;
 };
 
 class FlameGraph : public Action {
 public:
     FlameGraph() { }
-    auto perform_action(std::unique_ptr<sliger::rpc::BufferedWriter> writer,
-        sliger::rpc::vm_provider::VmProvider& vm_provider) -> void;
+    auto perform_action(std::unique_ptr<BufferedWriter> writer,
+        vm_provider::VmProvider& vm_provider) -> void;
 };
 
 class CodeCoverage : public Action {
 public:
     CodeCoverage() { }
-    auto perform_action(std::unique_ptr<sliger::rpc::BufferedWriter> writer,
-        sliger::rpc::vm_provider::VmProvider& vm_provider) -> void;
+    auto perform_action(std::unique_ptr<BufferedWriter> writer,
+        vm_provider::VmProvider& vm_provider) -> void;
 };
 
 class RunDebug : public Action {
@@ -31,41 +31,13 @@ public:
         : instructions(instructions)
     {
     }
-    auto perform_action(std::unique_ptr<sliger::rpc::BufferedWriter> writer,
-        sliger::rpc::vm_provider::VmProvider& vm_provider) -> void;
+    auto perform_action(std::unique_ptr<BufferedWriter> writer,
+        vm_provider::VmProvider& vm_provider) -> void;
 
 private:
     std::vector<uint32_t> instructions;
 };
 
-static inline auto action_from_json(
-    std::unique_ptr<json::Value> value) -> std::unique_ptr<Action>
-{
-    auto& obj = value->as<sliger::json::Object>();
-    auto type = obj.fields.at("type")->as<sliger::json::String>();
+auto action_from_json(const json::Value& value) -> std::unique_ptr<Action>;
 
-    if (type.value == "flame-graph") {
-        auto action = FlameGraph();
-        return std::make_unique<FlameGraph>(action);
-    }
-
-    if (type.value == "code-coverage") {
-        auto action = CodeCoverage();
-        return std::make_unique<CodeCoverage>(action);
-    }
-
-    if (type.value == "run-debug") {
-        sliger::json::ArrayValues values = std::move(
-            obj.fields.at("program")->as<sliger::json::Array>().values);
-        auto instructions = std::vector<uint32_t>();
-        for (auto& v : values) {
-            std::unique_ptr<json::Value> moved = std::move(v);
-            auto value = moved->as<sliger::json::Number>().value;
-            instructions.push_back((uint32_t)value);
-        }
-        auto action = RunDebug(instructions);
-        return std::make_unique<RunDebug>(action);
-    }
-    throw "todo";
-};
 }
diff --git a/runtime/json.cpp b/runtime/json.cpp
index 660e689..1359393 100644
--- a/runtime/json.cpp
+++ b/runtime/json.cpp
@@ -238,3 +238,14 @@ auto Parser::parse_val() -> Res<std::unique_ptr<Value>>
             "internal error, could not parse '{}'", tok_typ_to_string(cur.typ)),
     };
 }
+
+auto Parser::unexpected_tok_err(TokTyp expected, std::string_view msg)
+    -> Res<std::unique_ptr<Value>>
+{
+    return Err {
+        .pos = this->cur.val().pos,
+        .msg = std::format("{}, expected '{}', got '{}'", msg,
+            tok_typ_to_string(expected),
+            tok_typ_to_string(this->cur.val().typ)),
+    };
+}
diff --git a/runtime/json.hpp b/runtime/json.hpp
index c22eca2..554ef7e 100644
--- a/runtime/json.hpp
+++ b/runtime/json.hpp
@@ -2,7 +2,6 @@
 
 #include <concepts>
 #include <cstddef>
-#include <format>
 #include <memory>
 #include <optional>
 #include <string>
@@ -97,6 +96,13 @@ struct Value {
     {
         return static_cast<T&>(*this);
     }
+
+    template <typename T>
+        requires std::derived_from<T, Value>
+    inline auto as() const& -> const T&
+    {
+        return static_cast<const T&>(*this);
+    }
 };
 
 struct Null final : public Value {
@@ -275,16 +281,8 @@ public:
     auto parse_val() -> Res<std::unique_ptr<Value>>;
 
 private:
-    inline auto unexpected_tok_err(
-        TokTyp expected, std::string_view msg) -> Res<std::unique_ptr<Value>>
-    {
-        return Err {
-            .pos = this->cur.val().pos,
-            .msg = std::format("{}, expected '{}', got '{}'", msg,
-                tok_typ_to_string(expected),
-                tok_typ_to_string(this->cur.val().typ)),
-        };
-    }
+    auto unexpected_tok_err(TokTyp expected, std::string_view msg)
+        -> Res<std::unique_ptr<Value>>;
 
     inline auto step() -> Res<void>
     {
diff --git a/runtime/main.cpp b/runtime/main.cpp
index ce28b71..f751e95 100644
--- a/runtime/main.cpp
+++ b/runtime/main.cpp
@@ -6,6 +6,7 @@
 #include <cstdint>
 #include <format>
 #include <fstream>
+#include <iostream>
 #include <string>
 #include <vector>
 
@@ -52,7 +53,7 @@ int main(int argc, char** argv)
     auto rpc = sliger::rpc::RpcServer(
         [&](std::unique_ptr<sliger::json::Value> req,
             std::unique_ptr<sliger::rpc::BufferedWriter> writer) {
-            auto action = sliger::rpc::action::action_from_json(std::move(req));
+            auto action = sliger::rpc::action::action_from_json(*req);
             action->perform_action(std::move(writer), state);
         });
 
diff --git a/runtime/rpc_server.cpp b/runtime/rpc_server.cpp
index c720470..4642713 100644
--- a/runtime/rpc_server.cpp
+++ b/runtime/rpc_server.cpp
@@ -1,37 +1,104 @@
 #include "rpc_server.hpp"
+
+extern "C" {
+#include <arpa/inet.h>
+#include <asm-generic/socket.h>
+#include <netdb.h>
 #include <netinet/in.h>
+#include <stdlib.h>
+#include <string>
 #include <sys/socket.h>
 #include <unistd.h>
+}
 
-auto sliger::rpc::BufferedWriter::write(std::string message) -> Res<Unit>
+using namespace sliger::rpc;
+
+static auto create_address(uint16_t port) -> sockaddr_in
 {
-    for (size_t i = 0; i < message.length(); ++i) {
-        auto res = this->write((uint8_t)message[i]);
-        if (!res.is_ok()) {
+    return {
+        .sin_family = AF_INET,
+        .sin_port = ::htons(port),
+        .sin_addr = { .s_addr = ::inet_addr("127.0.0.1") },
+        .sin_zero = { 0 },
+    };
+}
+
+auto Socket::init() -> Res<void>
+{
+    this->socket_fd = ::socket(AF_INET, SOCK_STREAM, 0);
+    if (socket_fd < 0) {
+        return Err { .msg
+            = std::format("could not get socket ({})", socket_fd) };
+    };
+    this->initialized = true;
+
+    int trueValue = 1;
+    ::setsockopt(
+        this->socket_fd, SOL_SOCKET, SO_REUSEADDR, &trueValue, sizeof(int));
+
+    int err;
+
+    auto address = create_address(13370);
+    err = ::bind(socket_fd, (struct sockaddr*)&address, sizeof(address));
+    if (err < 0) {
+        return Err { .msg = std::format("could not bind ({})", err) };
+    };
+
+    err = ::listen(socket_fd, 0);
+    if (err < 0) {
+        return Err { .msg = std::format("could not listen ({})", err) };
+    }
+    return {};
+}
+
+auto Socket::accept() -> Res<std::unique_ptr<Client>>
+{
+    auto client_address = create_address(13370);
+    socklen_t address_size = sizeof(client_address);
+    int client
+        = ::accept(socket_fd, (struct sockaddr*)&client_address, &address_size);
+    if (client < 0) {
+        return Err { .msg = std::format("could not accept ({})", client) };
+    }
+    return std::make_unique<Client>(client);
+}
+auto Client::read(int8_t* buffer, size_t buffer_size) -> ssize_t
+{
+    return ::read(this->client_sock, buffer, buffer_size);
+}
+auto Client::write(uint8_t* buffer, size_t buffer_size) -> ssize_t
+{
+    return ::write(this->client_sock, buffer, buffer_size);
+}
+
+auto BufferedWriter::write(std::string message) -> Res<void>
+{
+    for (auto ch : message) {
+        if (auto res = this->write((uint8_t)ch); !res.is_ok()) {
             return res.err();
         }
     }
-    return Unit {};
+    return {};
 }
 
-auto sliger::rpc::BufferedWriter::write(uint8_t byte) -> Res<Unit>
+auto BufferedWriter::write(uint8_t byte) -> Res<void>
 {
     if (this->occupied >= length) {
-        auto res = this->flush();
-        if (!res.is_ok()) {
+        if (auto res = this->flush(); !res.is_ok()) {
             return res.err();
         }
     }
     this->buffer[this->occupied] = byte;
     this->occupied += 1;
-    return Unit {};
+
+    return {};
 }
 
-auto sliger::rpc::BufferedWriter::flush() -> Res<size_t>
+auto BufferedWriter::flush() -> Res<size_t>
 {
-    auto result = ::write(this->fd, this->buffer, this->occupied);
+    auto result = this->client->write(this->buffer, this->occupied);
     if (result < 0) {
-        return { { "unable to write" } };
+        return Err("unable to write");
     }
     this->occupied = 0;
     return (size_t)result;
diff --git a/runtime/rpc_server.hpp b/runtime/rpc_server.hpp
index 98f6c9d..2994e23 100644
--- a/runtime/rpc_server.hpp
+++ b/runtime/rpc_server.hpp
@@ -1,11 +1,8 @@
 #pragma once
 
 #include "json.hpp"
-#include <arpa/inet.h>
-#include <netdb.h>
-#include <stdlib.h>
-#include <string>
-#include <unistd.h>
+#include <format>
+#include <iostream>
 
 namespace sliger::rpc {
 
@@ -16,17 +13,18 @@ struct Err {
 template <typename T> class Res {
 public:
     Res(T value)
+        : holds_value(true)
+        , value(std::move(value))
     {
-        this->value = value;
-        this->holds_value = true;
     }
     Res(Err error)
+        : holds_value(false)
+        , error(error)
     {
-        this->error = error;
-        this->holds_value = false;
     }
     auto is_ok() -> bool { return this->holds_value; }
-    auto ok() -> T { return this->value; }
+    auto ok() & -> T& { return this->value; }
+    auto ok() && -> T&& { return std::move(this->value); }
     auto err() -> Err { return this->error; }
 
 private:
@@ -35,6 +33,25 @@ private:
     Err error;
 };
 
+template <> class Res<void> {
+public:
+    Res()
+        : holds_value(true)
+    {
+    }
+    Res(Err error)
+        : holds_value(false)
+        , error(error)
+    {
+    }
+    auto is_ok() -> bool { return this->holds_value; }
+    auto err() -> Err { return this->error; }
+
+private:
+    bool holds_value;
+    Err error;
+};
+
 class BracketFinder {
 public:
     BracketFinder()
@@ -55,43 +72,70 @@ private:
     int layers;
 };
 
-struct Unit { };
+#define DONT_COPY_OR_MOVE(T)                                                   \
+    T(const T&) = delete;                                                      \
+    T operator=(const T&) = delete;                                            \
+    T(T&&) = delete;                                                           \
+    T operator=(T&&) = delete;
+
+class Client;
+
+class Socket {
+public:
+    DONT_COPY_OR_MOVE(Socket);
+    Socket() = default;
+
+    ~Socket()
+    {
+        if (this->initialized) {
+            close(this->socket_fd);
+        }
+    }
+
+    auto init() -> Res<void>;
+    auto accept() -> Res<std::unique_ptr<Client>>;
+
+private:
+    int socket_fd = 0;
+    bool initialized = false;
+};
+
+class Client {
+public:
+    DONT_COPY_OR_MOVE(Client);
+    Client(int client_sock)
+        : client_sock(client_sock)
+    {
+    }
+
+    ~Client() { close(client_sock); }
+
+    auto read(int8_t* buffer, size_t buffer_size) -> ssize_t;
+    auto write(uint8_t* buffer, size_t buffer_size) -> ssize_t;
+    void flush();
+
+private:
+    int client_sock;
+};
 
 class BufferedWriter {
 public:
-    BufferedWriter(int fd)
-        : fd(fd)
+    BufferedWriter(Client& client)
+        : client(&client)
     {
     }
-    BufferedWriter(const BufferedWriter&) = delete;
-    BufferedWriter operator=(const BufferedWriter&) = delete;
-    BufferedWriter(BufferedWriter&&) = delete;
-    BufferedWriter operator=(BufferedWriter&&) = delete;
-    ~BufferedWriter() { close(fd); }
 
     auto flush() -> Res<size_t>;
-    auto write(uint8_t byte) -> Res<Unit>;
-    auto write(std::string message) -> Res<Unit>;
+    auto write(uint8_t byte) -> Res<void>;
+    auto write(std::string message) -> Res<void>;
 
 private:
     static const size_t length = 1024;
     size_t occupied = 0;
     uint8_t buffer[length];
-    int fd;
+    Client* client;
 };
 
-namespace {
-    static inline auto create_address(uint16_t port) -> sockaddr_in
-    {
-        return {
-            .sin_family = AF_INET,
-            .sin_port = htons(port),
-            .sin_addr = { .s_addr = inet_addr("127.0.0.1") },
-            .sin_zero = { 0 },
-        };
-    }
-}
-
 /// - load code
 ///     - program input
 /// - run
@@ -107,54 +151,31 @@ namespace {
 template <typename Functor> class RpcServer {
 public:
     RpcServer(Functor&& functor)
-        : functor(functor) {};
+        : functor(functor) { };
 
-    auto listen() -> Res<Unit>
+    auto listen() -> Res<void>
     {
-        int socket;
-        {
-            socket = ::socket(AF_INET, SOCK_STREAM, 0);
-            if (socket < 0) {
-                return Err { .msg
-                    = std::format("could not get socket ({})", socket) };
-            };
-        }
-        {
-            auto address = create_address(13370);
-            auto err
-                = ::bind(socket, (struct sockaddr*)&address, sizeof(address));
-            if (err < 0) {
-                close(socket);
-                return Err { .msg = std::format("could not bind ({})", err) };
-            };
-        }
-        {
-            auto err = ::listen(socket, 0);
-            if (err < 0) {
-                close(socket);
-                return Err { .msg = std::format("could not listen ({})", err) };
-            }
+        auto socket = Socket();
+        if (auto res = socket.init(); not res.is_ok()) {
+            return res.err();
         }
         while (true) {
-
-            auto client_address = create_address(13370);
-            socklen_t address_size = sizeof(client_address);
-            int client = ::accept(
-                socket, (struct sockaddr*)&client_address, &address_size);
-            if (client < 0) {
-                close(socket);
-                return Err { .msg
-                    = std::format("could not accept ({})", client) };
+            auto client_res = socket.accept();
+            if (!client_res.is_ok()) {
+                return client_res.err();
             }
+            auto client = std::move(client_res.ok());
+
             const size_t buf_len = 1024;
             int8_t buffer[buf_len] = {};
             auto bracket_finder = BracketFinder();
             std::string message = {};
             while (true) {
-                ssize_t bytes_read = read(client, buffer, buf_len);
+                ssize_t bytes_read = client->read(buffer, buf_len);
                 if (bytes_read <= 0) {
                     break;
                 }
+
                 for (size_t i = 0; i < (size_t)bytes_read; ++i) {
                     message += buffer[i];
                     bracket_finder.feed(buffer[i]);
@@ -167,18 +188,17 @@ public:
                         auto msg = std::format(
                             "error parsing rpc message: '{}' @ {}:{}\n",
                             err.msg, err.pos.line, err.pos.col);
-                        close(client);
-                        close(socket);
                         return Err {
                             .msg = msg,
                         };
                     }
-                    auto writer = std::make_unique<BufferedWriter>(client);
+                    auto writer = std::make_unique<BufferedWriter>(*client);
                     this->functor(std::move(req.val()), std::move(writer));
                     message.clear();
-                    break;
+                    goto message_done;
                 }
             }
+        message_done:
         }
         std::unreachable();
     };
diff --git a/runtime/value.cpp b/runtime/value.cpp
new file mode 100644
index 0000000..12a259a
--- /dev/null
+++ b/runtime/value.cpp
@@ -0,0 +1,34 @@
+#include "value.hpp"
+#include <format>
+#include <iostream>
+
+using namespace sliger;
+
+auto Value::to_string() const -> std::string
+{
+    switch (this->m_type) {
+        case ValueType::Null:
+            return "null";
+        case ValueType::Int:
+            return std::to_string(as_int().value);
+        case ValueType::Bool:
+            return as_bool().value ? "true" : "false";
+        case ValueType::String:
+            return std::format("\"{}\"", escape_string(as_string().value));
+        case ValueType::Ptr:
+            return std::to_string(as_ptr().value);
+    }
+    std::unreachable();
+}
+
+auto Value::to_repr_string() const -> std::string
+{
+    return std::format(
+        "{}({:.4s})", value_type_to_string(this->m_type), to_string());
+}
+
+void Value::print_tried_to_unwrap_error_message(ValueType vt) const
+{
+    std::cerr << std::format("error: tried to unwrap {} as {}\n",
+        value_type_to_string(this->m_type), value_type_to_string(vt));
+}
diff --git a/runtime/value.hpp b/runtime/value.hpp
index 7380d52..e1e3d52 100644
--- a/runtime/value.hpp
+++ b/runtime/value.hpp
@@ -2,8 +2,6 @@
 
 #include <cstdint>
 #include <cstdlib>
-#include <format>
-#include <iostream>
 #include <string>
 #include <utility>
 #include <variant>
@@ -126,8 +124,7 @@ public:
         try {
             return std::get<typename ValueTypeToType<VT>::Type>(value);
         } catch (const std::bad_variant_access& ex) {
-            std::cerr << std::format("error: tried to unwrap {} as {}\n",
-                value_type_to_string(this->m_type), value_type_to_string(VT));
+            print_tried_to_unwrap_error_message(VT);
             std::exit(1);
         }
     }
@@ -138,8 +135,7 @@ public:
         try {
             return std::get<typename ValueTypeToType<VT>::Type>(value);
         } catch (const std::bad_variant_access& ex) {
-            std::cerr << std::format("error: tried to unwrap {} as {}\n",
-                value_type_to_string(this->m_type), value_type_to_string(VT));
+            print_tried_to_unwrap_error_message(VT);
             std::exit(1);
         }
     }
@@ -158,30 +154,12 @@ public:
     inline auto as_ptr() const -> const Ptr& { return as<ValueType::Ptr>(); }
     // clang-format on
 
-    inline auto to_string() const -> std::string
-    {
-        switch (this->m_type) {
-            case ValueType::Null:
-                return "null";
-            case ValueType::Int:
-                return std::to_string(as_int().value);
-            case ValueType::Bool:
-                return as_bool().value ? "true" : "false";
-            case ValueType::String:
-                return std::format("\"{}\"", escape_string(as_string().value));
-            case ValueType::Ptr:
-                return std::to_string(as_ptr().value);
-        }
-        std::unreachable();
-    }
-
-    inline auto to_repr_string() const -> std::string
-    {
-        return std::format(
-            "{}({:.4s})", value_type_to_string(this->m_type), to_string());
-    }
+    auto to_string() const -> std::string;
+    auto to_repr_string() const -> std::string;
 
 private:
+    void print_tried_to_unwrap_error_message(ValueType vt) const;
+
     ValueType m_type;
     std::variant<Null, Int, Bool, String, Ptr> value;
 };
diff --git a/runtime/vm.cpp b/runtime/vm.cpp
index 1324d13..dd9b412 100644
--- a/runtime/vm.cpp
+++ b/runtime/vm.cpp
@@ -131,7 +131,7 @@ void VM::run_instruction()
             this->pc = fn_ptr.as_ptr().value;
             this->bp = static_cast<uint32_t>(this->stack.size());
             for (auto&& arg = arguments.rbegin(); arg != arguments.rend();
-                 ++arg) {
+                ++arg) {
                 stack_push(*arg);
             }
             if (this->opts.flame_graph) {
@@ -399,3 +399,44 @@ void VM::run_builtin(Builtin builtin_id)
         }
     }
 }
+auto VM::stack_repr_string(size_t max_items) const -> std::string
+{
+    auto result = std::string();
+    result += "→";
+    const auto& stack = view_stack();
+    for (size_t i = 0; i < stack.size() and i < max_items; ++i) {
+        if (i != 0) {
+            result += " ";
+        }
+        result += std::format(
+            "{:<11}", stack[stack.size() - i - 1].to_repr_string());
+    }
+    if (stack.size() > max_items) {
+        result += std::format(" ... + {}", stack.size() - max_items);
+    }
+    return result;
+};
+
+void VM::assert_fn_stack_has(size_t count)
+{
+    if (this->stack.size() - this->bp < count) {
+        std::cerr << std::format("stack underflow, pc = {}\n", this->pc);
+        std::exit(1);
+    }
+}
+
+void VM::assert_stack_has(size_t count)
+{
+    if (this->stack.size() < count) {
+        std::cerr << std::format("stack underflow, pc = {}\n", this->pc);
+        std::exit(1);
+    }
+}
+
+void VM::assert_program_has(size_t count)
+{
+    if (this->pc + count > program_size) {
+        std::cerr << std::format("malformed program, pc = {}", this->pc);
+        std::exit(1);
+    }
+}
diff --git a/runtime/vm.hpp b/runtime/vm.hpp
index 5a1bc45..04e29d5 100644
--- a/runtime/vm.hpp
+++ b/runtime/vm.hpp
@@ -6,8 +6,6 @@
 #include "value.hpp"
 #include <cstddef>
 #include <cstdint>
-#include <format>
-#include <iostream>
 #include <string>
 #include <vector>
 
@@ -173,23 +171,7 @@ public:
         return this->stack;
     }
 
-    inline auto stack_repr_string(size_t max_items) const -> std::string
-    {
-        auto result = std::string();
-        result += "→";
-        const auto& stack = view_stack();
-        for (size_t i = 0; i < stack.size() and i < max_items; ++i) {
-            if (i != 0) {
-                result += " ";
-            }
-            result += std::format(
-                "{:<11}", stack[stack.size() - i - 1].to_repr_string());
-        }
-        if (stack.size() > max_items) {
-            result += std::format(" ... + {}", stack.size() - max_items);
-        }
-        return result;
-    }
+    auto stack_repr_string(size_t max_items) const -> std::string;
 
 private:
     void run_builtin(Builtin builtin_id);
@@ -238,20 +220,8 @@ private:
     {
         return this->stack.at(this->bp + idx);
     }
-    inline void assert_fn_stack_has(size_t count)
-    {
-        if (this->stack.size() - this->bp < count) {
-            std::cerr << std::format("stack underflow, pc = {}\n", this->pc);
-            std::exit(1);
-        }
-    }
-    inline void assert_stack_has(size_t count)
-    {
-        if (this->stack.size() < count) {
-            std::cerr << std::format("stack underflow, pc = {}\n", this->pc);
-            std::exit(1);
-        }
-    }
+    void assert_fn_stack_has(size_t count);
+    void assert_stack_has(size_t count);
     inline void stack_push(Value&& value) { this->stack.push_back(value); }
     inline void stack_push(Value& value) { this->stack.push_back(value); }
     inline auto stack_pop() -> Value
@@ -260,14 +230,7 @@ private:
         this->stack.pop_back();
         return value;
     }
-
-    inline auto assert_program_has(size_t count)
-    {
-        if (this->pc + count > program_size) {
-            std::cerr << std::format("malformed program, pc = {}", this->pc);
-            std::exit(1);
-        }
-    }
+    void assert_program_has(size_t count);
 
     VMOpts opts;
     uint32_t pc = 0;
diff --git a/web/main.ts b/web/main.ts
index e2eb0f6..9be0750 100644
--- a/web/main.ts
+++ b/web/main.ts
@@ -17,7 +17,7 @@ const filepath = flags._[0] as string;
 const text = await Deno.readTextFile(filepath);
 
 const runtime = new Runtime(13370);
-await runtime.start();
+// await runtime.start();
 
 async function compileProgram(filepath: string) {
     const result = await compiler.compileWithDebug(filepath);
@@ -25,14 +25,18 @@ async function compileProgram(filepath: string) {
 }
 
 async function runProgramWithDebug(program: number[]) {
+    console.log("connecting");
     const connection = await runtime.connect();
+    console.log("conneced");
     connection.send({
         type: "run-debug",
         program,
     });
+    console.log("sent");
     const res = await connection.receive<{
         ok: boolean;
     }>();
+    console.log("received");
     connection.close();
     if (!res.ok) {
         throw new Error("could not run code");
diff --git a/web/runtime.ts b/web/runtime.ts
index b80e931..bf47d2c 100644
--- a/web/runtime.ts
+++ b/web/runtime.ts
@@ -33,17 +33,22 @@ export class Runtime {
     }
 
     async connect(): Promise<RuntimeConnection> {
-        return await new Promise((resolve) => {
-            setTimeout(async () => {
-                resolve(
-                    new RuntimeConnection(
-                        await Deno.connect({
-                            port: this.port,
-                        }),
-                    ),
-                );
-            }, 1000);
-        });
+        // return await new Promise((resolve) => {
+        //     setTimeout(async () => {
+        //         resolve(
+        //             new RuntimeConnection(
+        //                 await Deno.connect({
+        //                     port: this.port,
+        //                 }),
+        //             ),
+        //         );
+        //     }, 100);
+        // });
+        return new RuntimeConnection(
+            await Deno.connect({
+                port: this.port,
+            }),
+        );
     }
 }