diff --git a/crates/cpp/src/lib.rs b/crates/cpp/src/lib.rs
index 2d7b30099..27f6fdf31 100644
--- a/crates/cpp/src/lib.rs
+++ b/crates/cpp/src/lib.rs
@@ -3300,13 +3300,17 @@ impl<'a, 'b> Bindgen for FunctionBindgen<'a, 'b> {
                     &self.namespace,
                     Flavor::InStruct,
                 );
+                // Bind payloads by reference: the payload's heap data must
+                // stay owned by `op0` (which outlives the lowered call). A
+                // by-value binding would free that data at the end of the
+                // `if`/`else` block below, before the flat ABI consumes it.
                 let bind_ok = if let Some(_ok) = result.ok.as_ref() {
-                    format!("{ok_ty} {ok_payload} = std::move({op0}).value();")
+                    format!("{ok_ty}&& {ok_payload} = std::move({op0}).value();")
                 } else {
                     String::new()
                 };
                 let bind_err = if let Some(_err) = result.err.as_ref() {
-                    format!("{err_ty} {err_payload} = std::move({op0}).error();")
+                    format!("{err_ty}&& {err_payload} = std::move({op0}).error();")
                 } else {
                     String::new()
                 };
diff --git a/crates/test/src/cpp.rs b/crates/test/src/cpp.rs
index d33cefa11..436116797 100644
--- a/crates/test/src/cpp.rs
+++ b/crates/test/src/cpp.rs
@@ -146,8 +146,13 @@ impl LanguageMethods for Cpp {
         .arg(&bindings_object);
         runner.run_command(&mut cmd)?;
 
-        // Now compile the runner's source code to with the above object and the
-        // component-type object into a final component.
+        // Now link the runner's source code with the above object and the
+        // component-type object into a core module, then componentize with
+        // the workspace's `wit-component` (mirroring the C harness). This
+        // skips the WIT processing of the wasi-sdk's bundled
+        // `wasm-component-ld`, which may predate component-model features
+        // used by the embedded metadata (e.g. `map`).
+        let output = compile.output.with_extension("core.wasm");
         let mut cmd = Command::new(compiler);
         cmd.arg(&compile.component.path)
             .arg(&bindings_object)
@@ -170,12 +175,17 @@ impl LanguageMethods for Cpp {
             .arg("-std=c++20")
             .arg("-g")
             .arg("-o")
-            .arg(&compile.output);
+            .arg(&output);
         for flag in Vec::from(config.cflags) {
             cmd.arg(flag);
         }
         cmd.arg("-mexec-model=reactor");
+        cmd.arg("-Wl,--skip-wit-component");
         runner.run_command(&mut cmd)?;
+
+        runner
+            .convert_p1_to_component(&output, compile)
+            .with_context(|| format!("failed to convert {output:?}"))?;
         Ok(())
     }
 
diff --git a/tests/runtime/map/runner.cpp b/tests/runtime/map/runner.cpp
new file mode 100644
index 000000000..7d8281c0f
--- /dev/null
+++ b/tests/runtime/map/runner.cpp
@@ -0,0 +1,229 @@
+//@ wasmtime-flags = '-Wcomponent-model-map'
+
+#include <assert.h>
+#include <runner_cpp.h>
+
+#include <cstring>
+#include <string>
+#include <vector>
+
+namespace to_test = ::test::maps::to_test;
+
+using wit::string;
+using wit::unordered_map;
+
+static bool str_eq(string const& a, std::string_view b) { return a.get_view() == b; }
+
+template <class V>
+static V const* find(unordered_map<string, V> const& m, std::string_view key) {
+    for (auto const& [k, v] : m) {
+        if (k.get_view() == key) {
+            return &v;
+        }
+    }
+    return nullptr;
+}
+
+template <class V>
+static V const* find(unordered_map<uint32_t, V> const& m, uint32_t key) {
+    for (auto const& [k, v] : m) {
+        if (k == key) {
+            return &v;
+        }
+    }
+    return nullptr;
+}
+
+static unordered_map<uint32_t, string> make_names(
+    std::initializer_list<std::pair<uint32_t, std::string_view>> entries) {
+    auto result = unordered_map<uint32_t, string>::allocate(entries.size());
+    size_t i = 0;
+    for (auto const& [key, value] : entries) {
+        result.initialize(i++, std::make_pair(key, string::from_view(value)));
+    }
+    return result;
+}
+
+static void test_named_roundtrip() {
+    std::vector<std::pair<uint32_t, std::string_view>> input{{1, "uno"}, {2, "two"}};
+    auto result = to_test::NamedRoundtrip(input);
+    assert(result.size() == 2);
+    auto uno = find(result, "uno");
+    assert(uno && *uno == 1);
+    auto two = find(result, "two");
+    assert(two && *two == 2);
+}
+
+static void test_bytes_roundtrip() {
+    uint8_t const world_bytes[] = {'w', 'o', 'r', 'l', 'd'};
+    uint8_t const bin_bytes[] = {0, 1, 2};
+    std::vector<std::pair<std::string_view, std::span<uint8_t const>>> input{
+        {"hello", world_bytes},
+        {"bin", bin_bytes},
+    };
+    auto result = to_test::BytesRoundtrip(input);
+    assert(result.size() == 2);
+    auto hello = find(result, "hello");
+    assert(hello && hello->size() == 5);
+    assert(memcmp(hello->data(), "world", 5) == 0);
+    auto bin = find(result, "bin");
+    assert(bin && bin->size() == 3);
+    assert((*bin)[0] == 0 && (*bin)[1] == 1 && (*bin)[2] == 2);
+}
+
+static void test_empty_roundtrip() {
+    auto result = to_test::EmptyRoundtrip({});
+    assert(result.empty());
+}
+
+static void test_option_roundtrip() {
+    std::vector<std::pair<std::string_view, std::optional<uint32_t>>> input{
+        {"some", 42},
+        {"none", std::nullopt},
+    };
+    auto result = to_test::OptionRoundtrip(input);
+    assert(result.size() == 2);
+    auto some = find(result, "some");
+    assert(some && some->has_value() && **some == 42);
+    auto none = find(result, "none");
+    assert(none && !none->has_value());
+}
+
+static void test_record_roundtrip() {
+    to_test::LabeledEntry input{
+        string::from_view("test-label"),
+        make_names({{10, "ten"}, {20, "twenty"}}),
+    };
+    auto result = to_test::RecordRoundtrip(std::move(input));
+    assert(str_eq(result.label, "test-label"));
+    assert(result.values.size() == 2);
+    auto ten = find(result.values, 10);
+    assert(ten && str_eq(*ten, "ten"));
+    auto twenty = find(result.values, 20);
+    assert(twenty && str_eq(*twenty, "twenty"));
+}
+
+static void test_inline_roundtrip() {
+    std::vector<std::pair<uint32_t, std::string_view>> input{{1, "one"}, {2, "two"}};
+    auto result = to_test::InlineRoundtrip(input);
+    assert(result.size() == 2);
+    auto one = find(result, "one");
+    assert(one && *one == 1);
+    auto two = find(result, "two");
+    assert(two && *two == 2);
+}
+
+static void test_large_roundtrip() {
+    size_t const n = 100;
+    std::vector<std::string> storage;
+    storage.reserve(n);
+    std::vector<std::pair<uint32_t, std::string_view>> input;
+    input.reserve(n);
+    for (size_t i = 0; i < n; i++) {
+        storage.push_back("value-" + std::to_string(i));
+        input.emplace_back(uint32_t(i), storage.back());
+    }
+    auto result = to_test::LargeRoundtrip(input);
+    assert(result.size() == n);
+    auto value = find(result, 42);
+    assert(value && str_eq(*value, "value-42"));
+}
+
+static void test_multi_param_roundtrip() {
+    std::vector<std::pair<uint32_t, std::string_view>> names{{1, "one"}, {2, "two"}};
+    uint8_t const payload[] = {42};
+    std::vector<std::pair<std::string_view, std::span<uint8_t const>>> bytes{{"key", payload}};
+    auto [ids, bytes_out] = to_test::MultiParamRoundtrip(names, bytes);
+    assert(ids.size() == 2);
+    auto one = find(ids, "one");
+    assert(one && *one == 1);
+    auto two = find(ids, "two");
+    assert(two && *two == 2);
+    assert(bytes_out.size() == 1);
+    auto key = find(bytes_out, "key");
+    assert(key && key->size() == 1 && (*key)[0] == 42);
+}
+
+static void test_nested_roundtrip() {
+    std::vector<std::pair<uint32_t, std::string_view>> inner_a{{1, "one"}, {2, "two"}};
+    std::vector<std::pair<uint32_t, std::string_view>> inner_b{{10, "ten"}};
+    std::vector<std::pair<std::string_view, std::span<std::pair<uint32_t, std::string_view> const>>>
+        outer{
+            {"group-a", inner_a},
+            {"group-b", inner_b},
+        };
+    auto result = to_test::NestedRoundtrip(outer);
+    assert(result.size() == 2);
+    auto group_a = find(result, "group-a");
+    assert(group_a && group_a->size() == 2);
+    auto two = find(*group_a, 2);
+    assert(two && str_eq(*two, "two"));
+    auto group_b = find(result, "group-b");
+    assert(group_b && group_b->size() == 1);
+    auto ten = find(*group_b, 10);
+    assert(ten && str_eq(*ten, "ten"));
+}
+
+static void test_variant_roundtrip() {
+    to_test::MapOrString map_input{to_test::MapOrString::AsMap{make_names({{1, "one"}})}};
+    auto map_result = to_test::VariantRoundtrip(std::move(map_input));
+    auto* as_map = std::get_if<to_test::MapOrString::AsMap>(&map_result.variants);
+    assert(as_map && as_map->value.size() == 1);
+    auto one = find(as_map->value, 1);
+    assert(one && str_eq(*one, "one"));
+
+    to_test::MapOrString string_input{to_test::MapOrString::AsString{string::from_view("hello")}};
+    auto string_result = to_test::VariantRoundtrip(std::move(string_input));
+    auto* as_string = std::get_if<to_test::MapOrString::AsString>(&string_result.variants);
+    assert(as_string && str_eq(as_string->value, "hello"));
+}
+
+static void test_result_roundtrip() {
+    std::expected<unordered_map<uint32_t, string>, string> ok_input{make_names({{5, "five"}})};
+    auto ok_result = to_test::ResultRoundtrip(std::move(ok_input));
+    assert(ok_result.has_value());
+    assert(ok_result->size() == 1);
+    auto five = find(*ok_result, 5);
+    assert(five && str_eq(*five, "five"));
+
+    std::expected<unordered_map<uint32_t, string>, string> err_input{
+        std::unexpected(string::from_view("bad input"))};
+    auto err_result = to_test::ResultRoundtrip(std::move(err_input));
+    assert(!err_result.has_value());
+    assert(str_eq(err_result.error(), "bad input"));
+}
+
+static void test_tuple_roundtrip() {
+    std::vector<std::pair<uint32_t, std::string_view>> entries{{7, "seven"}};
+    auto result = to_test::TupleRoundtrip(std::make_tuple(
+        std::span<std::pair<uint32_t, std::string_view> const>(entries), uint64_t(42)));
+    auto& [values, number] = result;
+    assert(values.size() == 1);
+    auto seven = find(values, 7);
+    assert(seven && str_eq(*seven, "seven"));
+    assert(number == 42);
+}
+
+static void test_single_entry_roundtrip() {
+    std::vector<std::pair<uint32_t, std::string_view>> input{{99, "ninety-nine"}};
+    auto result = to_test::SingleEntryRoundtrip(input);
+    assert(result.size() == 1);
+    auto value = find(result, 99);
+    assert(value && str_eq(*value, "ninety-nine"));
+}
+
+void exports::runner::Run() {
+    test_named_roundtrip();
+    test_bytes_roundtrip();
+    test_empty_roundtrip();
+    test_option_roundtrip();
+    test_record_roundtrip();
+    test_inline_roundtrip();
+    test_large_roundtrip();
+    test_multi_param_roundtrip();
+    test_nested_roundtrip();
+    test_variant_roundtrip();
+    test_result_roundtrip();
+    test_tuple_roundtrip();
+    test_single_entry_roundtrip();
+}
diff --git a/tests/runtime/map/test.cpp b/tests/runtime/map/test.cpp
new file mode 100644
index 000000000..f06f781b6
--- /dev/null
+++ b/tests/runtime/map/test.cpp
@@ -0,0 +1,76 @@
+#include <test_cpp.h>
+
+namespace test_exports = ::exports::test::maps::to_test;
+
+using wit::string;
+using wit::unordered_map;
+using wit::vector;
+
+static unordered_map<string, uint32_t> invert(unordered_map<uint32_t, string> a) {
+    auto result = unordered_map<string, uint32_t>::allocate(a.size());
+    size_t i = 0;
+    for (auto& [id, name] : a) {
+        result.initialize(i++, std::make_pair(std::move(name), id));
+    }
+    return result;
+}
+
+unordered_map<string, uint32_t> test_exports::NamedRoundtrip(unordered_map<uint32_t, string> a) {
+    return invert(std::move(a));
+}
+
+unordered_map<string, vector<uint8_t>> test_exports::BytesRoundtrip(
+    unordered_map<string, vector<uint8_t>> a) {
+    return a;
+}
+
+unordered_map<uint32_t, string> test_exports::EmptyRoundtrip(unordered_map<uint32_t, string> a) {
+    return a;
+}
+
+unordered_map<string, std::optional<uint32_t>> test_exports::OptionRoundtrip(
+    unordered_map<string, std::optional<uint32_t>> a) {
+    return a;
+}
+
+test_exports::LabeledEntry test_exports::RecordRoundtrip(test_exports::LabeledEntry a) {
+    return a;
+}
+
+unordered_map<string, uint32_t> test_exports::InlineRoundtrip(unordered_map<uint32_t, string> a) {
+    return invert(std::move(a));
+}
+
+unordered_map<uint32_t, string> test_exports::LargeRoundtrip(unordered_map<uint32_t, string> a) {
+    return a;
+}
+
+std::tuple<unordered_map<string, uint32_t>, unordered_map<string, vector<uint8_t>>>
+test_exports::MultiParamRoundtrip(unordered_map<uint32_t, string> a,
+                                  unordered_map<string, vector<uint8_t>> b) {
+    return std::make_tuple(invert(std::move(a)), std::move(b));
+}
+
+unordered_map<string, unordered_map<uint32_t, string>> test_exports::NestedRoundtrip(
+    unordered_map<string, unordered_map<uint32_t, string>> a) {
+    return a;
+}
+
+test_exports::MapOrString test_exports::VariantRoundtrip(test_exports::MapOrString a) {
+    return a;
+}
+
+std::expected<unordered_map<uint32_t, string>, string> test_exports::ResultRoundtrip(
+    std::expected<unordered_map<uint32_t, string>, string> a) {
+    return a;
+}
+
+std::tuple<unordered_map<uint32_t, string>, uint64_t> test_exports::TupleRoundtrip(
+    std::tuple<unordered_map<uint32_t, string>, uint64_t> a) {
+    return a;
+}
+
+unordered_map<uint32_t, string> test_exports::SingleEntryRoundtrip(
+    unordered_map<uint32_t, string> a) {
+    return a;
+}