diff --git a/crates/cli/tests/fixtures/apollo.mjs b/crates/cli/tests/fixtures/apollo.mjs
index 35aad76..b7fd189 100644
--- a/crates/cli/tests/fixtures/apollo.mjs
+++ b/crates/cli/tests/fixtures/apollo.mjs
@@ -54,7 +54,7 @@ if (fetched.url !== "https://example.test/") {
 }
 
 const request = { url: "https://example.test/" };
-await init(new URL("./app.wasm", import.meta.url), {
+const exports = await init(new URL("./app.wasm", import.meta.url), {
   "regulus/js": {
     request_text(input) {
       return `${input} from JS`;
@@ -71,15 +71,30 @@ await init(new URL("./app.wasm", import.meta.url), {
   },
 });
 
+const initialMark = exports.__regulus_arena_mark();
 const result = callString("main", "hello");
 if (result !== "hello from JS") {
   throw new Error(`unexpected result: ${result}`);
 }
+if (exports.__regulus_arena_mark() !== initialMark) {
+  throw new Error("adapter callString did not reset the arena");
+}
+
+const secondResult = callString("main", "again");
+if (secondResult !== "again from JS") {
+  throw new Error(`unexpected second result: ${secondResult}`);
+}
+if (exports.__regulus_arena_mark() !== initialMark) {
+  throw new Error("repeated adapter callString did not reuse arena memory");
+}
 
 const described = call("describe_from_js", 7n, 2.5, true, "shape");
 if (described !== "shape:7:2.5:true") {
   throw new Error(`unexpected described result: ${described}`);
 }
+if (exports.__regulus_arena_mark() !== initialMark) {
+  throw new Error("adapter call did not reset scalar/string argument allocations");
+}
 
 const kept = call("keep_bool", true);
 if (kept !== true) {
@@ -90,6 +105,9 @@ const response = call("response");
 if (response.tag !== "Response" || response.fields.status !== 200n || response.fields.body !== "ok") {
   throw new Error(`unexpected response: ${response.tag}`);
 }
+if (exports.__regulus_arena_mark() !== initialMark) {
+  throw new Error("adapter call did not reset structured return allocations");
+}
 
 const names = call("names");
 if (names.join(",") !== "Ada,Joe") {
diff --git a/crates/core/src/adapter.js b/crates/core/src/adapter.js
index b18b19b..417ee42 100644
--- a/crates/core/src/adapter.js
+++ b/crates/core/src/adapter.js
@@ -213,8 +213,13 @@ export function callExport(name, paramTypes = [], returnType = "Nil", ...args) {
       `Regulus export "${name}" expects ${paramTypes.length} argument(s), got ${args.length}`,
     );
   }
-  const wasmArgs = args.map((arg, index) => toWasmValue(paramTypes[index], arg));
-  return fromWasmValue(returnType, fn(...wasmArgs));
+  const mark = instance.exports.__regulus_arena_mark();
+  try {
+    const wasmArgs = args.map((arg, index) => toWasmValue(paramTypes[index], arg));
+    return fromWasmValue(returnType, fn(...wasmArgs));
+  } finally {
+    instance.exports.__regulus_arena_reset(mark);
+  }
 }
 
 /**
diff --git a/crates/core/src/wasm/codegen.rs b/crates/core/src/wasm/codegen.rs
index b380e00..2dd0ca8 100644
--- a/crates/core/src/wasm/codegen.rs
+++ b/crates/core/src/wasm/codegen.rs
@@ -371,6 +371,8 @@ impl<'a> StructuredEmitter<'a> {
     fn emit_js_host_abi_helpers(&mut self) {
         self.ensure_memory();
         self.runtime_helper_roots.insert("__alloc".into());
+        self.runtime_helper_roots.insert("__arena_mark".into());
+        self.runtime_helper_roots.insert("__arena_reset".into());
         self.runtime_helper_roots.insert("__string_new".into());
         self.runtime_helper_roots.insert("__string_len".into());
         self.runtime_helper_roots.insert("__string_data".into());
@@ -382,6 +384,15 @@ impl<'a> StructuredEmitter<'a> {
     call $__alloc
   )
   (export "__regulus_alloc" (func $__regulus_alloc))
+  (func $__regulus_arena_mark (result i32)
+    call $__arena_mark
+  )
+  (export "__regulus_arena_mark" (func $__regulus_arena_mark))
+  (func $__regulus_arena_reset (param $mark i32)
+    local.get $mark
+    call $__arena_reset
+  )
+  (export "__regulus_arena_reset" (func $__regulus_arena_reset))
   (func $__regulus_string_new (param $data i32) (param $len i32) (result i32)
     local.get $data
     local.get $len
diff --git a/crates/core/src/wasm/tests.rs b/crates/core/src/wasm/tests.rs
index 0c57309..91474a4 100644
--- a/crates/core/src/wasm/tests.rs
+++ b/crates/core/src/wasm/tests.rs
@@ -874,6 +874,8 @@ pub fn main(input: String) -> String { request_text(input) }"#,
     );
     for name in [
         "__regulus_alloc",
+        "__regulus_arena_mark",
+        "__regulus_arena_reset",
         "__regulus_string_new",
         "__regulus_string_len",
         "__regulus_string_data",
diff --git a/docs/website/development/runtime-memory.md b/docs/website/development/runtime-memory.md
index c085702..0ad0b4b 100644
--- a/docs/website/development/runtime-memory.md
+++ b/docs/website/development/runtime-memory.md
@@ -123,9 +123,15 @@ Reset invalidates every dynamic object allocated after the mark. Static data and
 dynamic objects allocated before the mark remain valid. Later allocations may
 reuse reset-owned memory.
 
-Automatic call/request reset boundaries are not yet generated. Host adapters
-and compiler-generated code must not return or retain pointers allocated after
-a mark that will be reset.
+Generated JavaScript adapters wrap exported Gleam calls in an arena scope. The
+adapter marks before encoding JS arguments, calls the Wasm export, decodes the
+return into JS-owned data, and resets in a `finally` block. Raw Wasm and
+Wasmtime exports are not automatically reset because those callers may inspect
+borrowed managed pointers after the call.
+
+Compiler-generated code must not return or retain pointers allocated after a
+mark that will be reset. General internal reset scopes still require escape
+analysis or region tracking.
 
 Reference counting is not the selected strategy for this milestone. It would
 require generated retain/release operations for every managed assignment, field