diff --git a/Cargo.lock b/Cargo.lock
index 41c6dbd4..8bbba0b8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -316,9 +316,9 @@ checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
 
 [[package]]
 name = "chacha20"
-version = "0.10.1"
+version = "0.10.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d524456ba66e72eb8b115ff89e01e497f8e6d11d78b70b1aa13c0fbd97540a81"
+checksum = "65c35e4b699c7e15ccbe7ee35c005e4fc0a278d22238a2857e6ce2dadeda1b06"
 dependencies = [
  "cfg-if",
  "cpufeatures 0.3.0",
@@ -1229,9 +1229,9 @@ dependencies = [
 
 [[package]]
 name = "h2"
-version = "0.4.15"
+version = "0.4.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6cb093c84e8bd9b188d4c4a8cb6579fc016968d14c99882163cd3ff402a4f155"
+checksum = "a9f37a958b41b3b19ee2707c06439c0e9e547e847223eb791ecb0cb821c65e27"
 dependencies = [
  "atomic-waker",
  "bytes",
diff --git a/crates/iroh-http-adapter/src/lib.rs b/crates/iroh-http-adapter/src/lib.rs
index 6eb5b329..6893ab2f 100644
--- a/crates/iroh-http-adapter/src/lib.rs
+++ b/crates/iroh-http-adapter/src/lib.rs
@@ -10,6 +10,7 @@
 
 use iroh_http_core::{
     respond, CoreError, ErrorCode, HandleStore, RequestPayload, ResponseHeadEntry,
+    DEFAULT_MAX_REQUEST_BODY_BYTES, DEFAULT_MAX_RESPONSE_BODY_BYTES,
 };
 
 /// Maximum number of header rows accepted at an adapter boundary.
@@ -20,8 +21,10 @@ pub const MAX_HEADER_NAME_LEN: usize = 256;
 pub const MAX_HEADER_VALUE_LEN: usize = 8_192;
 /// Maximum adapter-level timeout in milliseconds.
 pub const MAX_TIMEOUT_MS: u64 = 300_000;
-/// Maximum adapter-level body cap in bytes.
-pub const MAX_BODY_BYTES: usize = 16 * 1024 * 1024;
+/// Maximum adapter-level request body cap in bytes.
+pub const MAX_BODY_BYTES: usize = DEFAULT_MAX_REQUEST_BODY_BYTES;
+/// Maximum adapter-level response body cap in bytes.
+pub const MAX_RESPONSE_BODY_BYTES: usize = DEFAULT_MAX_RESPONSE_BODY_BYTES;
 /// Maximum total simultaneous connections a served endpoint will accept.
 pub const MAX_TOTAL_CONNECTIONS: usize = 100_000;
 /// Maximum header block size in bytes accepted for a served endpoint.
@@ -418,7 +421,7 @@ pub fn coerce_fetch_options(raw: RawFetchOptions) -> Result<FetchOptions, Adapte
         .transpose()?;
     let max_response_body_bytes = raw
         .max_response_body_bytes
-        .map(|b| safe_f64_to_usize(b, "maxResponseBodyBytes", MAX_BODY_BYTES))
+        .map(|b| safe_f64_to_usize(b, "maxResponseBodyBytes", MAX_RESPONSE_BODY_BYTES))
         .transpose()?;
     Ok(FetchOptions {
         node_id: raw.node_id,
@@ -836,10 +839,10 @@ mod tests {
             f64::INFINITY,
             -1.0,
             1.5,
-            (MAX_BODY_BYTES + 1) as f64,
+            (MAX_RESPONSE_BODY_BYTES + 1) as f64,
         ] {
             assert!(matches!(
-                safe_f64_to_usize(value, "maxResponseBodyBytes", MAX_BODY_BYTES),
+                safe_f64_to_usize(value, "maxResponseBodyBytes", MAX_RESPONSE_BODY_BYTES),
                 Err(AdapterInputError::InvalidArgument {
                     field: "maxResponseBodyBytes",
                     ..
@@ -991,6 +994,47 @@ mod tests {
         ));
     }
 
+    #[test]
+    fn coerce_fetch_options_accepts_response_limits_through_core_default() {
+        const CORE_DEFAULT_MAX_RESPONSE_BODY_BYTES: usize = 256 * 1024 * 1024;
+
+        for value in [
+            MAX_BODY_BYTES,
+            64 * 1024 * 1024,
+            CORE_DEFAULT_MAX_RESPONSE_BODY_BYTES,
+        ] {
+            let options = coerce_fetch_options(RawFetchOptions {
+                node_id: "aaaa".to_string(),
+                url: "httpi://peer/".to_string(),
+                method: "GET".to_string(),
+                direct_addrs: None,
+                headers: vec![],
+                timeout_ms: None,
+                max_response_body_bytes: Some(value as f64),
+            })
+            .expect("response limit through the core default should be accepted");
+
+            assert_eq!(options.max_response_body_bytes, Some(value));
+        }
+
+        let too_large = coerce_fetch_options(RawFetchOptions {
+            node_id: "aaaa".to_string(),
+            url: "httpi://peer/".to_string(),
+            method: "GET".to_string(),
+            direct_addrs: None,
+            headers: vec![],
+            timeout_ms: None,
+            max_response_body_bytes: Some((CORE_DEFAULT_MAX_RESPONSE_BODY_BYTES + 1) as f64),
+        });
+        assert!(matches!(
+            too_large,
+            Err(AdapterInputError::InvalidArgument {
+                field: "maxResponseBodyBytes",
+                ..
+            })
+        ));
+    }
+
     #[test]
     fn coerce_endpoint_options_validates_and_coerces() {
         let ok = coerce_endpoint_options(RawEndpointOptions {
@@ -1068,5 +1112,21 @@ mod tests {
                 ..
             })
         ));
+
+        for bad in [
+            RawServeOptions {
+                max_request_body_wire_bytes: Some((MAX_BODY_BYTES + 1) as f64),
+                ..Default::default()
+            },
+            RawServeOptions {
+                max_request_body_decoded_bytes: Some((MAX_BODY_BYTES + 1) as f64),
+                ..Default::default()
+            },
+        ] {
+            assert!(matches!(
+                coerce_serve_options(bad),
+                Err(AdapterInputError::InvalidArgument { .. })
+            ));
+        }
     }
 }
diff --git a/crates/iroh-http-core/src/http/server/mod.rs b/crates/iroh-http-core/src/http/server/mod.rs
index 875ce848..3a77b3ac 100644
--- a/crates/iroh-http-core/src/http/server/mod.rs
+++ b/crates/iroh-http-core/src/http/server/mod.rs
@@ -35,7 +35,7 @@ use crate::{Body, ConnectionEvent, IrohEndpoint};
 use self::accept::{accept_loop, AcceptConfig};
 use self::options::{
     DEFAULT_CONCURRENCY, DEFAULT_DRAIN_TIMEOUT_MS, DEFAULT_MAX_CONNECTIONS_PER_PEER,
-    DEFAULT_MAX_REQUEST_BODY_BYTES, DEFAULT_REQUEST_TIMEOUT_MS,
+    DEFAULT_REQUEST_TIMEOUT_MS,
 };
 
 // Re-exported from sub-modules so external paths
@@ -44,8 +44,9 @@ use self::options::{
 // unchanged after Slice C.7 split.
 pub(crate) use self::error_layer::HandleLayerErrorLayer;
 pub use self::handle::ServeHandle;
-pub use self::options::ServeOptions;
-pub(crate) use self::options::DEFAULT_MAX_RESPONSE_BODY_BYTES;
+pub use self::options::{
+    ServeOptions, DEFAULT_MAX_REQUEST_BODY_BYTES, DEFAULT_MAX_RESPONSE_BODY_BYTES,
+};
 
 // ── Connection-event callback type ───────────────────────────────────────────
 
diff --git a/crates/iroh-http-core/src/http/server/options.rs b/crates/iroh-http-core/src/http/server/options.rs
index d16e8ab0..f2d591d4 100644
--- a/crates/iroh-http-core/src/http/server/options.rs
+++ b/crates/iroh-http-core/src/http/server/options.rs
@@ -47,8 +47,8 @@ pub(crate) const DEFAULT_DRAIN_TIMEOUT_MS: u64 = 30_000;
 /// 16 MiB — applied when `max_request_body_wire_bytes` or
 /// `max_request_body_decoded_bytes` is not explicitly set.
 /// Prevents memory exhaustion from unbounded request bodies.
-pub(crate) const DEFAULT_MAX_REQUEST_BODY_BYTES: usize = 16 * 1024 * 1024;
+pub const DEFAULT_MAX_REQUEST_BODY_BYTES: usize = 16 * 1024 * 1024;
 /// 256 MiB — applied when `max_response_body_bytes` is not explicitly set.
 /// Prevents memory exhaustion from a malicious server sending a compressed
 /// response that expands to an unbounded size (compression bomb).
-pub(crate) const DEFAULT_MAX_RESPONSE_BODY_BYTES: usize = 256 * 1024 * 1024;
+pub const DEFAULT_MAX_RESPONSE_BODY_BYTES: usize = 256 * 1024 * 1024;
diff --git a/crates/iroh-http-core/src/lib.rs b/crates/iroh-http-core/src/lib.rs
index 3489408f..cf71cf87 100644
--- a/crates/iroh-http-core/src/lib.rs
+++ b/crates/iroh-http-core/src/lib.rs
@@ -36,7 +36,10 @@ pub mod registry {
 // ── Pure-Rust HTTP API surface (`mod http`) ───────────────────────────────────
 pub use http::body::{Body, BoxError};
 pub use http::client::{fetch_request, FetchError};
-pub use http::server::{serve, serve_with_events, RemoteNodeId, ServeHandle, ServeOptions};
+pub use http::server::{
+    serve, serve_with_events, RemoteNodeId, ServeHandle, ServeOptions,
+    DEFAULT_MAX_REQUEST_BODY_BYTES, DEFAULT_MAX_RESPONSE_BODY_BYTES,
+};
 
 // ── FFI bridge surface (`mod ffi`) ────────────────────────────────
 pub use ffi::dispatcher::{ffi_serve, ffi_serve_with_callback, respond};
diff --git a/docs/specification.md b/docs/specification.md
index 90e4217c..9bb3d780 100644
--- a/docs/specification.md
+++ b/docs/specification.md
@@ -188,6 +188,15 @@ interface IrohFetchInit extends RequestInit {
   directAddrs?: string[];
   /** Explicit home relay URL, usually obtained from peer discovery. */
   relayUrl?: string;
+  /** Per-request timeout in milliseconds. Maximum: 300 000. */
+  requestTimeout?: number;
+  /** Whether to decompress the response body. Default: true. */
+  decompress?: boolean;
+  /**
+   * Maximum decompressed response body size in bytes for this request.
+   * Range: 0 through 268 435 456 (256 MiB). Default: 256 MiB.
+   */
+  maxResponseBodyBytes?: number;
 }
 ```
 
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index 17bcd71d..5cd03ecf 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -145,7 +145,7 @@ mDNS uses UDP multicast on port 5353. Common blockers:
 | `InvalidInput` | `IrohArgumentError` | Bad node ID, invalid URL scheme, invalid header | Check input format; URLs must use `httpi://` scheme |
 | `ConnectionFailed` | `IrohConnectError` | No network path, peer offline | See [connection errors](#networkerror-on-fetch--connection-refused-or-connection-failed) |
 | `Timeout` | `IrohConnectError` | Peer too slow, network timeout | Increase `requestTimeout`; retry with backoff |
-| `BodyTooLarge` | `IrohProtocolError` | Request body exceeds `maxRequestBodyWireBytes` / `maxRequestBodyDecodedBytes` | Send smaller payload or increase limit |
+| `BodyTooLarge` | `IrohProtocolError` | A request body exceeds `maxRequestBodyWireBytes` / `maxRequestBodyDecodedBytes`, or a response exceeds `maxResponseBodyBytes` | Send a smaller payload or increase the corresponding limit within its supported range |
 | `HeaderTooLarge` | `IrohProtocolError` | Header block exceeds `maxHeaderBytes` | Reduce header count/size or increase limit |
 | `PeerRejected` | `IrohConnectError` | Peer rejected connection at app layer | See [peer rejected](#networkerror--peer-rejected) |
 | `Cancelled` | `IrohAbortError` | `AbortSignal` fired or `fetch()` cancelled | Handle `AbortError` in caller; do not retry cancelled requests |
diff --git a/package-lock.json b/package-lock.json
index 5e952fc0..dd3507e9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1353,9 +1353,9 @@
       "license": "MIT"
     },
     "node_modules/js-yaml": {
-      "version": "4.3.0",
-      "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.3.0.tgz",
-      "integrity": "sha512-1td788aAnnZ5qs7V2QIRl1owjtYpbKt749Y3xauqQgwIIGF/xXWz1wMTEBx5O3LK3lXLVuqXPdPxj2BoFHaW9Q==",
+      "version": "4.3.2",
+      "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.3.2.tgz",
+      "integrity": "sha512-SFNOvSJ+Dgf/9An904Yx+CgSlIPCkIpao4qo51lpee25TIRejdH3rhR4EZMGoNx3/TP3O+wzWuiTFl4sqbltzA==",
       "dev": true,
       "funding": [
         {
@@ -1507,7 +1507,9 @@
       }
     },
     "node_modules/nanoid": {
-      "version": "3.3.15",
+      "version": "3.3.18",
+      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.18.tgz",
+      "integrity": "sha512-DTg4MJbGMWkfi6VZFdNt2/caMbQy4Ou+Op/hJQvGEWcnVfoA1QA+xzRKAzw9jD6+GVOOeYr/mIcuDSdug6F6+w==",
       "dev": true,
       "funding": [
         {
@@ -1569,7 +1571,9 @@
       }
     },
     "node_modules/postcss": {
-      "version": "8.5.15",
+      "version": "8.5.26",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.26.tgz",
+      "integrity": "sha512-u82N74LFzG8ca+dD8puPnplTXoGH4fTPpVGuIbt36G3qvNlkvfD0lEAZSxaly3KX8TS/L1A1gsCEmvKmBcVbkQ==",
       "dev": true,
       "funding": [
         {
@@ -1587,7 +1591,7 @@
       ],
       "license": "MIT",
       "dependencies": {
-        "nanoid": "^3.3.12",
+        "nanoid": "^3.3.17",
         "picocolors": "^1.1.1",
         "source-map-js": "^1.2.1"
       },
@@ -1804,7 +1808,9 @@
       }
     },
     "node_modules/undici": {
-      "version": "7.28.0",
+      "version": "7.29.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-7.29.0.tgz",
+      "integrity": "sha512-IDxfleLmmbSskfWSUATiN1nfn2rDuvnMOqb5CWR92iIfojA0Ud+ulOAAEQ57LPr9rWmsreUyf5lwyao+7GNNVw==",
       "dev": true,
       "license": "MIT",
       "engines": {
diff --git a/packages/iroh-http-node/lib.ts b/packages/iroh-http-node/lib.ts
index a8acae4d..99bd1a81 100644
--- a/packages/iroh-http-node/lib.ts
+++ b/packages/iroh-http-node/lib.ts
@@ -54,6 +54,7 @@ import {
 
 import {
   classifyBindError,
+  classifyError,
   type DiscoveryInfo,
   IrohNode,
   type IrohNodeWithSecret,
@@ -182,7 +183,14 @@ class NodeAdapter extends IrohAdapter {
     try {
       const chunk = jsTryNextChunk(this.#eh, handle);
       return Promise.resolve(chunk ? new Uint8Array(chunk) : null);
-    } catch {
+    } catch (error) {
+      const classified = classifyError(error);
+      if (
+        classified.code !== "INTERNAL" ||
+        !classified.message.startsWith("try_next_chunk:")
+      ) {
+        throw classified;
+      }
       // Channel empty or lock contended — fall back to async.
       return jsNextChunk(this.#eh, handle);
     }
diff --git a/packages/iroh-http-node/test/adapter.test.mjs b/packages/iroh-http-node/test/adapter.test.mjs
index ac1ebc85..422e5a7e 100644
--- a/packages/iroh-http-node/test/adapter.test.mjs
+++ b/packages/iroh-http-node/test/adapter.test.mjs
@@ -85,7 +85,7 @@ test("fetch numeric validation rejects invalid values instead of defaulting", as
   const { id } = await node.addr();
   const url = `httpi://${id}/validation`;
   const maxTimeoutMs = 300_000;
-  const maxBodyBytes = 16 * 1024 * 1024;
+  const maxResponseBodyBytes = 256 * 1024 * 1024;
 
   try {
     for (
@@ -110,7 +110,7 @@ test("fetch numeric validation rejects invalid values instead of defaulting", as
         Number.POSITIVE_INFINITY,
         -1,
         1.5,
-        maxBodyBytes + 1,
+        maxResponseBodyBytes + 1,
       ]
     ) {
       await assert.rejects(
diff --git a/packages/iroh-http-shared/src/IrohAdapter.ts b/packages/iroh-http-shared/src/IrohAdapter.ts
index ed2c1063..766b13c3 100644
--- a/packages/iroh-http-shared/src/IrohAdapter.ts
+++ b/packages/iroh-http-shared/src/IrohAdapter.ts
@@ -102,8 +102,9 @@ export interface IrohFetchInit extends RequestInit {
    */
   decompress?: boolean;
   /**
-   * Per-call response body byte limit.  When set, overrides the endpoint-wide
-   * `maxResponseBodyBytes` default for this single request.
+   * Maximum decompressed response body bytes accepted for this request.
+   * Must be an integer from 0 through 268_435_456 (256 MiB). When omitted,
+   * the core default is 256 MiB.
    */
   maxResponseBodyBytes?: number;
 }
@@ -118,7 +119,7 @@ export interface FetchOptions {
   timeoutMs?: number;
   /** When `false`, the response body is not decompressed. @default true */
   decompress?: boolean;
-  /** Per-call response body byte limit.  Overrides endpoint default. */
+  /** Per-call response body byte limit. Range: 0 through 256 MiB. */
   maxResponseBodyBytes?: number;
 }
 
diff --git a/packages/iroh-http-shared/src/streams.ts b/packages/iroh-http-shared/src/streams.ts
index 74f7a672..05c90e9b 100644
--- a/packages/iroh-http-shared/src/streams.ts
+++ b/packages/iroh-http-shared/src/streams.ts
@@ -6,6 +6,7 @@
  */
 
 import type { IrohAdapter } from "./IrohAdapter.js";
+import { classifyError } from "./errors.js";
 
 /**
  * Wrap a `BodyReader` handle in a web-standard `ReadableStream<Uint8Array>`.
@@ -25,12 +26,17 @@ export function makeReadable(
 ): ReadableStream<Uint8Array> {
   return new ReadableStream<Uint8Array>({
     async pull(controller) {
-      const chunk = await adapter.nextChunk(handle);
-      if (chunk === null) {
-        controller.close();
+      try {
+        const chunk = await adapter.nextChunk(handle);
+        if (chunk === null) {
+          controller.close();
+          onClose?.();
+        } else {
+          controller.enqueue(chunk);
+        }
+      } catch (error) {
         onClose?.();
-      } else {
-        controller.enqueue(chunk);
+        throw classifyError(error);
       }
     },
     cancel() {
diff --git a/packages/iroh-http-tauri/Cargo.lock b/packages/iroh-http-tauri/Cargo.lock
index 16fb5575..5881e183 100644
--- a/packages/iroh-http-tauri/Cargo.lock
+++ b/packages/iroh-http-tauri/Cargo.lock
@@ -490,9 +490,9 @@ checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
 
 [[package]]
 name = "chacha20"
-version = "0.10.1"
+version = "0.10.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d524456ba66e72eb8b115ff89e01e497f8e6d11d78b70b1aa13c0fbd97540a81"
+checksum = "65c35e4b699c7e15ccbe7ee35c005e4fc0a278d22238a2857e6ce2dadeda1b06"
 dependencies = [
  "cfg-if",
  "cpufeatures 0.3.0",
@@ -1857,9 +1857,9 @@ dependencies = [
 
 [[package]]
 name = "h2"
-version = "0.4.15"
+version = "0.4.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6cb093c84e8bd9b188d4c4a8cb6579fc016968d14c99882163cd3ff402a4f155"
+checksum = "a9f37a958b41b3b19ee2707c06439c0e9e547e847223eb791ecb0cb821c65e27"
 dependencies = [
  "atomic-waker",
  "bytes",
diff --git a/packages/iroh-http-tauri/guest-js/index.ts b/packages/iroh-http-tauri/guest-js/index.ts
index 68955d04..cc983308 100644
--- a/packages/iroh-http-tauri/guest-js/index.ts
+++ b/packages/iroh-http-tauri/guest-js/index.ts
@@ -7,6 +7,7 @@ import { installForegroundHealthCheck } from "./lifecycle.js";
 import {
   bigintToSafeNumber,
   classifyBindError,
+  classifyError,
   encodeBase64,
   IrohNode,
   type IrohNodeWithSecret,
@@ -93,15 +94,23 @@ class TauriAdapter extends IrohAdapter {
         const v = new Uint8Array(buf);
         return v.length > 0 && v[0] !== 0 ? v.subarray(1) : null;
       },
-      // Channel empty or lock contended — fall back to async.
-      () =>
-        invoke<ArrayBuffer>(`${PLUGIN}|next_chunk`, {
+      (error) => {
+        const classified = classifyError(error);
+        if (
+          classified.code !== "INTERNAL" ||
+          !classified.message.startsWith("try_next_chunk:")
+        ) {
+          throw classified;
+        }
+        // Channel empty or lock contended — fall back to async.
+        return invoke<ArrayBuffer>(`${PLUGIN}|next_chunk`, {
           endpointHandle: this.#epHandle,
           handle: safeHandle,
         }).then((buf) => {
           const v = new Uint8Array(buf);
           return v.length > 0 && v[0] !== 0 ? v.subarray(1) : null;
-        }),
+        });
+      },
     );
   }
 
diff --git a/tests/suites/adapter-validation.mjs b/tests/suites/adapter-validation.mjs
index c9a58c7f..8cb3afab 100644
--- a/tests/suites/adapter-validation.mjs
+++ b/tests/suites/adapter-validation.mjs
@@ -6,7 +6,7 @@
  */
 
 const MAX_TIMEOUT_MS = 300_000;
-const MAX_BODY_BYTES = 16 * 1024 * 1024;
+const MAX_RESPONSE_BODY_BYTES = 256 * 1024 * 1024;
 
 export function adapterValidationTests({
   createNode,
@@ -63,7 +63,6 @@ export function adapterValidationTests({
         Number.POSITIVE_INFINITY,
         -1,
         1.5,
-        MAX_BODY_BYTES + 1,
       ];
 
       for (const value of timeoutValues) {
@@ -76,11 +75,40 @@ export function adapterValidationTests({
           await node.fetch(url, { maxResponseBodyBytes: value });
         }, `maxResponseBodyBytes=${String(value)}`);
       }
+
+      const overCapError = await assertThrows(async () => {
+        await node.fetch(url, {
+          maxResponseBodyBytes: MAX_RESPONSE_BODY_BYTES + 1,
+        });
+      }, "maxResponseBodyBytes over cap");
+      assertEqual(overCapError.code, "INVALID_ARGUMENT");
+      assertEqual(overCapError.name, "TypeError");
     } finally {
       await node.close();
     }
   });
 
+  test("adapter validation enforces the configured response body limit", async () => {
+    const node = await createNode({ disableNetworking: true });
+    let handle;
+    try {
+      const { id } = await node.addr();
+      handle = node.serve(() => new Response(new Uint8Array(1025)));
+
+      const error = await assertThrows(async () => {
+        const res = await node.fetch(`httpi://${id}/response-limit`, {
+          maxResponseBodyBytes: 1024,
+        });
+        await res.arrayBuffer();
+      }, "response body above configured cap");
+
+      assertEqual(error.code, "BODY_TOO_LARGE");
+    } finally {
+      await node.close();
+      if (handle) await handle.finished.catch(() => {});
+    }
+  });
+
   test("adapter validation rejects invalid fetch inputs", async () => {
     const node = await createNode({ disableNetworking: true });
     try {
@@ -169,19 +197,27 @@ export function adapterValidationTests({
         });
       });
 
-      const res = await node.fetch(`httpi://${id}/validation`, {
-        headers: [["x-conformance", "ok"]],
-        requestTimeout: 30_000,
-        maxResponseBodyBytes: 1024,
-      });
+      for (
+        const maxResponseBodyBytes of [
+          16 * 1024 * 1024,
+          64 * 1024 * 1024,
+          MAX_RESPONSE_BODY_BYTES,
+        ]
+      ) {
+        const res = await node.fetch(`httpi://${id}/validation`, {
+          headers: [["x-conformance", "ok"]],
+          requestTimeout: 30_000,
+          maxResponseBodyBytes,
+        });
 
-      assertEqual(res.status, 200, "valid request should succeed");
-      assertEqual(await res.text(), "ok", "valid header should pass through");
-      assertEqual(
-        res.headers.get("x-conformance-response"),
-        "ok",
-        "valid response header should pass through",
-      );
+        assertEqual(res.status, 200, "valid request should succeed");
+        assertEqual(await res.text(), "ok", "valid header should pass through");
+        assertEqual(
+          res.headers.get("x-conformance-response"),
+          "ok",
+          "valid response header should pass through",
+        );
+      }
     } finally {
       await node.close();
       if (handle) await handle.finished.catch(() => {});