diff --git a/Cargo.Bazel.json.lock b/Cargo.Bazel.json.lock
index ae3a6e269f4..da588ed0203 100644
--- a/Cargo.Bazel.json.lock
+++ b/Cargo.Bazel.json.lock
@@ -1,5 +1,5 @@
 {
-  "checksum": "c940ed0c71e779f38de47e366662d71cd883022d89016936e1952a55719fe089",
+  "checksum": "5eb904c0c07c6b91be340371eabc73c69bb12f120fa709cc3b1d8488b1a5de6b",
   "crates": {
     "abnf 0.12.0": {
       "name": "abnf",
@@ -10027,7 +10027,7 @@
               "target": "canbench_rs"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -10122,7 +10122,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -10209,14 +10209,14 @@
       ],
       "license_file": null
     },
-    "candid 0.10.10": {
+    "candid 0.10.12": {
       "name": "candid",
-      "version": "0.10.10",
+      "version": "0.10.12",
       "package_url": "https://github.com/dfinity/candid",
       "repository": {
         "Http": {
-          "url": "https://static.crates.io/crates/candid/0.10.10/download",
-          "sha256": "6c30ee7f886f296b6422c0ff017e89dd4f831521dfdcc76f3f71aae1ce817222"
+          "url": "https://static.crates.io/crates/candid/0.10.12/download",
+          "sha256": "51e129c4051c57daf943586e01ef72faae48b04a8f692d5f646febf17a264c38"
         }
       },
       "targets": [
@@ -10323,7 +10323,7 @@
           ],
           "selects": {}
         },
-        "version": "0.10.10"
+        "version": "0.10.12"
       },
       "license": "Apache-2.0",
       "license_ids": [
@@ -10438,7 +10438,7 @@
               "target": "anyhow"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -18346,7 +18346,7 @@
               "target": "canbench_rs"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -18609,6 +18609,11 @@
               "id": "ic-cdk 0.16.0",
               "target": "ic_cdk"
             },
+            {
+              "id": "ic-cdk 0.18.0-alpha.1",
+              "target": "ic_cdk",
+              "alias": "ic_cdk_next"
+            },
             {
               "id": "ic-cdk-timers 0.11.0",
               "target": "ic_cdk_timers"
@@ -19505,6 +19510,11 @@
               "id": "ic-cdk-macros 0.9.0",
               "target": "ic_cdk_macros"
             },
+            {
+              "id": "ic-cdk-macros 0.18.0-alpha.1",
+              "target": "ic_cdk_macros",
+              "alias": "ic_cdk_macros_next"
+            },
             {
               "id": "indoc 1.0.9",
               "target": "indoc"
@@ -23076,7 +23086,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -29827,7 +29837,7 @@
               "target": "cached"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30298,7 +30308,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30402,7 +30412,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30489,7 +30499,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30552,7 +30562,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30620,7 +30630,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30688,7 +30698,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30724,6 +30734,81 @@
       ],
       "license_file": "LICENSE"
     },
+    "ic-cdk 0.18.0-alpha.1": {
+      "name": "ic-cdk",
+      "version": "0.18.0-alpha.1",
+      "package_url": "https://github.com/dfinity/cdk-rs",
+      "repository": {
+        "Git": {
+          "remote": "https://github.com/dfinity/cdk-rs.git",
+          "commitish": {
+            "Rev": "4e287ce51636b0e70768c193da38d2fc5324ea15"
+          },
+          "strip_prefix": "ic-cdk"
+        }
+      },
+      "targets": [
+        {
+          "Library": {
+            "crate_name": "ic_cdk",
+            "crate_root": "src/lib.rs",
+            "srcs": {
+              "allow_empty": true,
+              "include": [
+                "**/*.rs"
+              ]
+            }
+          }
+        }
+      ],
+      "library_target_name": "ic_cdk",
+      "common_attrs": {
+        "compile_data_glob": [
+          "**"
+        ],
+        "deps": {
+          "common": [
+            {
+              "id": "candid 0.10.12",
+              "target": "candid"
+            },
+            {
+              "id": "ic0 0.24.0-alpha.1",
+              "target": "ic0"
+            },
+            {
+              "id": "serde 1.0.217",
+              "target": "serde"
+            },
+            {
+              "id": "serde_bytes 0.11.15",
+              "target": "serde_bytes"
+            },
+            {
+              "id": "thiserror 2.0.3",
+              "target": "thiserror"
+            }
+          ],
+          "selects": {}
+        },
+        "edition": "2021",
+        "proc_macro_deps": {
+          "common": [
+            {
+              "id": "ic-cdk-macros 0.18.0-alpha.1",
+              "target": "ic_cdk_macros"
+            }
+          ],
+          "selects": {}
+        },
+        "version": "0.18.0-alpha.1"
+      },
+      "license": "Apache-2.0",
+      "license_ids": [
+        "Apache-2.0"
+      ],
+      "license_file": "LICENSE"
+    },
     "ic-cdk-macros 0.8.4": {
       "name": "ic-cdk-macros",
       "version": "0.8.4",
@@ -30756,7 +30841,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30823,7 +30908,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30890,7 +30975,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30957,7 +31042,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -30992,6 +31077,76 @@
       ],
       "license_file": "LICENSE"
     },
+    "ic-cdk-macros 0.18.0-alpha.1": {
+      "name": "ic-cdk-macros",
+      "version": "0.18.0-alpha.1",
+      "package_url": "https://github.com/dfinity/cdk-rs",
+      "repository": {
+        "Git": {
+          "remote": "https://github.com/dfinity/cdk-rs.git",
+          "commitish": {
+            "Rev": "4e287ce51636b0e70768c193da38d2fc5324ea15"
+          },
+          "strip_prefix": "ic-cdk-macros"
+        }
+      },
+      "targets": [
+        {
+          "ProcMacro": {
+            "crate_name": "ic_cdk_macros",
+            "crate_root": "src/lib.rs",
+            "srcs": {
+              "allow_empty": true,
+              "include": [
+                "**/*.rs"
+              ]
+            }
+          }
+        }
+      ],
+      "library_target_name": "ic_cdk_macros",
+      "common_attrs": {
+        "compile_data_glob": [
+          "**"
+        ],
+        "deps": {
+          "common": [
+            {
+              "id": "candid 0.10.12",
+              "target": "candid"
+            },
+            {
+              "id": "proc-macro2 1.0.89",
+              "target": "proc_macro2"
+            },
+            {
+              "id": "quote 1.0.37",
+              "target": "quote"
+            },
+            {
+              "id": "serde 1.0.217",
+              "target": "serde"
+            },
+            {
+              "id": "serde_tokenstream 0.2.1",
+              "target": "serde_tokenstream"
+            },
+            {
+              "id": "syn 2.0.87",
+              "target": "syn"
+            }
+          ],
+          "selects": {}
+        },
+        "edition": "2021",
+        "version": "0.18.0-alpha.1"
+      },
+      "license": "Apache-2.0",
+      "license_ids": [
+        "Apache-2.0"
+      ],
+      "license_file": "LICENSE"
+    },
     "ic-cdk-timers 0.11.0": {
       "name": "ic-cdk-timers",
       "version": "0.11.0",
@@ -31095,7 +31250,7 @@
               "target": "cached"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -31370,7 +31525,7 @@
               "target": "base64"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -31449,7 +31604,7 @@
               "target": "bytes"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -31625,7 +31780,7 @@
               "target": "base64"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -31822,7 +31977,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -31881,7 +32036,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -31965,7 +32120,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -32059,7 +32214,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -32337,7 +32492,7 @@
               "target": "anyhow"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -32412,7 +32567,7 @@
         "deps": {
           "common": [
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -32545,6 +32700,47 @@
       ],
       "license_file": "LICENSE"
     },
+    "ic0 0.24.0-alpha.1": {
+      "name": "ic0",
+      "version": "0.24.0-alpha.1",
+      "package_url": "https://github.com/dfinity/cdk-rs",
+      "repository": {
+        "Git": {
+          "remote": "https://github.com/dfinity/cdk-rs.git",
+          "commitish": {
+            "Rev": "4e287ce51636b0e70768c193da38d2fc5324ea15"
+          },
+          "strip_prefix": "ic0"
+        }
+      },
+      "targets": [
+        {
+          "Library": {
+            "crate_name": "ic0",
+            "crate_root": "src/lib.rs",
+            "srcs": {
+              "allow_empty": true,
+              "include": [
+                "**/*.rs"
+              ]
+            }
+          }
+        }
+      ],
+      "library_target_name": "ic0",
+      "common_attrs": {
+        "compile_data_glob": [
+          "**"
+        ],
+        "edition": "2021",
+        "version": "0.24.0-alpha.1"
+      },
+      "license": "Apache-2.0",
+      "license_ids": [
+        "Apache-2.0"
+      ],
+      "license_file": "LICENSE"
+    },
     "ic_bls12_381 0.10.0": {
       "name": "ic_bls12_381",
       "version": "0.10.0",
@@ -32753,7 +32949,7 @@
               "target": "anyhow"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -32824,7 +33020,7 @@
               "target": "anyhow"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -49217,7 +49413,7 @@
               "target": "base64"
             },
             {
-              "id": "candid 0.10.10",
+              "id": "candid 0.10.12",
               "target": "candid"
             },
             {
@@ -87297,7 +87493,7 @@
     "cached 0.49.2",
     "canbench 0.1.8",
     "canbench-rs 0.1.8",
-    "candid 0.10.10",
+    "candid 0.10.12",
     "candid_parser 0.1.2",
     "cargo_metadata 0.14.2",
     "cc 1.1.37",
@@ -87364,7 +87560,9 @@
     "ic-canister-sig-creation 1.1.0",
     "ic-cbor 3.0.2",
     "ic-cdk 0.16.0",
+    "ic-cdk 0.18.0-alpha.1",
     "ic-cdk-macros 0.9.0",
+    "ic-cdk-macros 0.18.0-alpha.1",
     "ic-cdk-timers 0.11.0",
     "ic-certificate-verification 3.0.2",
     "ic-certification 3.0.2",
diff --git a/Cargo.Bazel.toml.lock b/Cargo.Bazel.toml.lock
index a81cc6d2d52..fc8871c416f 100644
--- a/Cargo.Bazel.toml.lock
+++ b/Cargo.Bazel.toml.lock
@@ -1746,9 +1746,9 @@ dependencies = [
 
 [[package]]
 name = "candid"
-version = "0.10.10"
+version = "0.10.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c30ee7f886f296b6422c0ff017e89dd4f831521dfdcc76f3f71aae1ce817222"
+checksum = "51e129c4051c57daf943586e01ef72faae48b04a8f692d5f646febf17a264c38"
 dependencies = [
  "anyhow",
  "binread",
@@ -3069,6 +3069,8 @@ dependencies = [
  "ic-canister-sig-creation",
  "ic-cbor",
  "ic-cdk 0.16.0",
+ "ic-cdk 0.18.0-alpha.1",
+ "ic-cdk-macros 0.18.0-alpha.1",
  "ic-cdk-macros 0.9.0",
  "ic-cdk-timers",
  "ic-certificate-verification",
@@ -5113,6 +5115,19 @@ dependencies = [
  "serde_bytes",
 ]
 
+[[package]]
+name = "ic-cdk"
+version = "0.18.0-alpha.1"
+source = "git+https://github.com/dfinity/cdk-rs.git?branch=next#4e287ce51636b0e70768c193da38d2fc5324ea15"
+dependencies = [
+ "candid",
+ "ic-cdk-macros 0.18.0-alpha.1",
+ "ic0 0.24.0-alpha.1",
+ "serde",
+ "serde_bytes",
+ "thiserror 2.0.3",
+]
+
 [[package]]
 name = "ic-cdk-macros"
 version = "0.8.4"
@@ -5169,6 +5184,19 @@ dependencies = [
  "syn 2.0.87",
 ]
 
+[[package]]
+name = "ic-cdk-macros"
+version = "0.18.0-alpha.1"
+source = "git+https://github.com/dfinity/cdk-rs.git?branch=next#4e287ce51636b0e70768c193da38d2fc5324ea15"
+dependencies = [
+ "candid",
+ "proc-macro2",
+ "quote",
+ "serde",
+ "serde_tokenstream 0.2.1",
+ "syn 2.0.87",
+]
+
 [[package]]
 name = "ic-cdk-timers"
 version = "0.11.0"
@@ -5472,6 +5500,11 @@ version = "0.23.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8de254dd67bbd58073e23dc1c8553ba12fa1dc610a19de94ad2bbcd0460c067f"
 
+[[package]]
+name = "ic0"
+version = "0.24.0-alpha.1"
+source = "git+https://github.com/dfinity/cdk-rs.git?branch=next#4e287ce51636b0e70768c193da38d2fc5324ea15"
+
 [[package]]
 name = "ic_bls12_381"
 version = "0.10.0"
diff --git a/Cargo.lock b/Cargo.lock
index da683f8ccbc..967ae2e10bc 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6344,6 +6344,19 @@ dependencies = [
  "serde_bytes",
 ]
 
+[[package]]
+name = "ic-cdk"
+version = "0.18.0-alpha.1"
+source = "git+https://github.com/dfinity/cdk-rs?branch=next#4e287ce51636b0e70768c193da38d2fc5324ea15"
+dependencies = [
+ "candid",
+ "ic-cdk-macros 0.18.0-alpha.1",
+ "ic0 0.24.0-alpha.1",
+ "serde",
+ "serde_bytes",
+ "thiserror 2.0.11",
+]
+
 [[package]]
 name = "ic-cdk-macros"
 version = "0.8.4"
@@ -6414,6 +6427,19 @@ dependencies = [
  "syn 2.0.96",
 ]
 
+[[package]]
+name = "ic-cdk-macros"
+version = "0.18.0-alpha.1"
+source = "git+https://github.com/dfinity/cdk-rs?branch=next#4e287ce51636b0e70768c193da38d2fc5324ea15"
+dependencies = [
+ "candid",
+ "proc-macro2",
+ "quote",
+ "serde",
+ "serde_tokenstream 0.2.2",
+ "syn 2.0.96",
+]
+
 [[package]]
 name = "ic-cdk-timers"
 version = "0.7.0"
@@ -13714,6 +13740,11 @@ version = "0.23.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8de254dd67bbd58073e23dc1c8553ba12fa1dc610a19de94ad2bbcd0460c067f"
 
+[[package]]
+name = "ic0"
+version = "0.24.0-alpha.1"
+source = "git+https://github.com/dfinity/cdk-rs?branch=next#4e287ce51636b0e70768c193da38d2fc5324ea15"
+
 [[package]]
 name = "ic_bls12_381"
 version = "0.10.0"
@@ -15589,7 +15620,7 @@ dependencies = [
  "dfn_candid",
  "ic-agent",
  "ic-base-types",
- "ic-cdk 0.16.0",
+ "ic-cdk 0.18.0-alpha.1",
  "ic-registry-subnet-type",
  "ic-system-test-driver",
  "ic-types",
@@ -22996,8 +23027,8 @@ version = "0.9.0"
 dependencies = [
  "candid",
  "futures",
- "ic-cdk 0.16.0",
- "ic-cdk-macros 0.9.0",
+ "ic-cdk 0.18.0-alpha.1",
+ "ic-cdk-macros 0.18.0-alpha.1",
  "rand 0.8.5",
  "rand_pcg 0.3.1",
  "serde",
diff --git a/bazel/external_crates.bzl b/bazel/external_crates.bzl
index f25afadc154..0da3fafe937 100644
--- a/bazel/external_crates.bzl
+++ b/bazel/external_crates.bzl
@@ -592,6 +592,18 @@ def external_crates_repository(name, cargo_lockfile, lockfile, sanitizers_enable
             "ic-cdk-macros": crate.spec(
                 version = "^0.9.0",
             ),
+            "ic-cdk-macros-next": crate.spec(
+                package = "ic-cdk-macros",
+                git = "https://github.com/dfinity/cdk-rs.git",
+                branch = "next",
+                # rev = "4e287ce51636b0e70768c193da38d2fc5324ea15",
+            ),
+            "ic-cdk-next": crate.spec(
+                package = "ic-cdk",
+                git = "https://github.com/dfinity/cdk-rs.git",
+                branch = "next",
+                # rev = "4e287ce51636b0e70768c193da38d2fc5324ea15",
+            ),
             "ic-certified-map": crate.spec(
                 version = "^0.3.1",
             ),
diff --git a/rs/config/src/embedders.rs b/rs/config/src/embedders.rs
index 9c6ef4db9d7..4e599ea4c5a 100644
--- a/rs/config/src/embedders.rs
+++ b/rs/config/src/embedders.rs
@@ -121,7 +121,7 @@ impl FeatureFlags {
             write_barrier: FlagStatus::Disabled,
             wasm_native_stable_memory: FlagStatus::Enabled,
             wasm64: FlagStatus::Enabled,
-            best_effort_responses: FlagStatus::Disabled,
+            best_effort_responses: FlagStatus::Enabled,
             canister_backtrace: FlagStatus::Enabled,
         }
     }
diff --git a/rs/messaging/tests/queue_tests.rs b/rs/messaging/tests/queue_tests.rs
index 2107d111210..33adfbedcbb 100644
--- a/rs/messaging/tests/queue_tests.rs
+++ b/rs/messaging/tests/queue_tests.rs
@@ -102,7 +102,9 @@ impl SubnetPairProxy {
         Encode!(&StartArgs {
             network_topology,
             canister_to_subnet_rate,
-            payload_size_bytes,
+            request_payload_size_bytes: payload_size_bytes,
+            request_timeout_seconds: 0,
+            response_payload_size_bytes: payload_size_bytes,
         })
     }
 
diff --git a/rs/rust_canisters/xnet_test/BUILD.bazel b/rs/rust_canisters/xnet_test/BUILD.bazel
index 4382e3ffc46..38a68d9ef14 100644
--- a/rs/rust_canisters/xnet_test/BUILD.bazel
+++ b/rs/rust_canisters/xnet_test/BUILD.bazel
@@ -7,7 +7,7 @@ DEPENDENCIES = [
     # Keep sorted.
     "@crate_index//:candid",
     "@crate_index//:futures",
-    "@crate_index//:ic-cdk",
+    "@crate_index//:ic_cdk_next",
     "@crate_index//:rand",
     "@crate_index//:rand_pcg",
     "@crate_index//:serde",
@@ -16,7 +16,7 @@ DEPENDENCIES = [
 
 MACRO_DEPENDENCIES = [
     # Keep sorted.
-    "@crate_index//:ic-cdk-macros",
+    "@crate_index//:ic_cdk_macros_next",
 ]
 
 rust_library(
diff --git a/rs/rust_canisters/xnet_test/Cargo.toml b/rs/rust_canisters/xnet_test/Cargo.toml
index 48384c1838b..92285baf255 100644
--- a/rs/rust_canisters/xnet_test/Cargo.toml
+++ b/rs/rust_canisters/xnet_test/Cargo.toml
@@ -13,8 +13,8 @@ path = "src/main.rs"
 [dependencies]
 candid = { workspace = true }
 futures = { workspace = true }
-ic-cdk = { workspace = true }
-ic-cdk-macros = { workspace = true }
+ic-cdk = { git = "https://github.com/dfinity/cdk-rs", branch = "next" }
+ic-cdk-macros = { git = "https://github.com/dfinity/cdk-rs", branch = "next" }
 rand = { workspace = true }
 rand_pcg = "0.3"
 serde = { workspace = true }
diff --git a/rs/rust_canisters/xnet_test/src/lib.rs b/rs/rust_canisters/xnet_test/src/lib.rs
index 0ab8122568f..19b52556f8a 100644
--- a/rs/rust_canisters/xnet_test/src/lib.rs
+++ b/rs/rust_canisters/xnet_test/src/lib.rs
@@ -14,7 +14,9 @@ pub type NetworkTopology = Vec<Vec<CanisterId>>;
 pub struct StartArgs {
     pub network_topology: NetworkTopology,
     pub canister_to_subnet_rate: u64,
-    pub payload_size_bytes: u64,
+    pub request_payload_size_bytes: u64,
+    pub request_timeout_seconds: u32,
+    pub response_payload_size_bytes: u64,
 }
 
 /// Metrics observed by this canister.
diff --git a/rs/rust_canisters/xnet_test/src/main.rs b/rs/rust_canisters/xnet_test/src/main.rs
index 6b2767f689f..81a5c97d02d 100644
--- a/rs/rust_canisters/xnet_test/src/main.rs
+++ b/rs/rust_canisters/xnet_test/src/main.rs
@@ -8,19 +8,14 @@
 use candid::{CandidType, Deserialize, Principal};
 use futures::future::join_all;
 use ic_cdk::api::management_canister::provisional::CanisterId;
-use ic_cdk::{
-    api::{
-        call::{call, call_with_payment},
-        caller, canister_balance, id, time,
-    },
-    setup,
-};
+use ic_cdk::api::{canister_cycle_balance, canister_self, msg_caller, time};
+use ic_cdk::call::{Call, CallError, ConfigurableCall, SendableCall};
+use ic_cdk::setup;
 use ic_cdk_macros::{heartbeat, query, update};
 use rand::Rng;
 use rand_pcg::Lcg64Xsh32;
 use std::cell::RefCell;
 use std::collections::BTreeMap;
-use std::str::FromStr;
 use std::time::Duration;
 use xnet_test::{Metrics, NetworkTopology, StartArgs};
 
@@ -38,8 +33,14 @@ thread_local! {
     /// Number of requests to send to each subnet (other than ours) every round.
     static PER_SUBNET_RATE: RefCell<u64> = const { RefCell::new(1) };
 
-    /// Pad requests AND responses to this size (in bytes) if smaller.
-    static PAYLOAD_SIZE: RefCell<u64> = const { RefCell::new(1024) };
+    /// Pad requests to this size (in bytes) if smaller.
+    static REQUEST_PAYLOAD_SIZE: RefCell<u64> = const { RefCell::new(1024) };
+
+    /// Timeout to set on requests. Zero for guaranteed response calls.
+    static REQUEST_TIMEOUT_SECONDS: RefCell<u32> = const { RefCell::new(0) };
+
+    /// Pad responses to this size (in bytes) if smaller.
+    static RESPONSE_PAYLOAD_SIZE: RefCell<u64> = const { RefCell::new(1024) };
 
     /// State of the messaging that we use to check invariants (e.g., sequence
     /// numbers).
@@ -151,7 +152,9 @@ fn start(start_args: StartArgs) -> String {
         *canisters.borrow_mut() = start_args.network_topology;
     });
     PER_SUBNET_RATE.with(|r| *r.borrow_mut() = start_args.canister_to_subnet_rate);
-    PAYLOAD_SIZE.with(|r| *r.borrow_mut() = start_args.payload_size_bytes);
+    REQUEST_PAYLOAD_SIZE.with(|r| *r.borrow_mut() = start_args.request_payload_size_bytes);
+    REQUEST_TIMEOUT_SECONDS.with(|r| *r.borrow_mut() = start_args.request_timeout_seconds);
+    RESPONSE_PAYLOAD_SIZE.with(|r| *r.borrow_mut() = start_args.response_payload_size_bytes);
 
     RUNNING.with(|r| *r.borrow_mut() = true);
 
@@ -169,10 +172,12 @@ fn stop() -> String {
 /// Invoked by the canister heartbeat handler as long as `RUNNING` is `true`
 /// (`start()` was and `stop()` was not yet called).
 async fn fanout() {
-    let self_id = id();
+    let self_id = canister_self();
 
     let network_topology =
         NETWORK_TOPOLOGY.with(|network_topology| network_topology.borrow().clone());
+    let timeout_seconds = REQUEST_TIMEOUT_SECONDS.with(|p| *p.borrow());
+    let payload_size = REQUEST_PAYLOAD_SIZE.with(|p| *p.borrow()) as usize;
 
     let mut futures = vec![];
     for canisters in network_topology {
@@ -191,15 +196,19 @@ async fn fanout() {
 
             let seq_no = STATE.with(|s| s.borrow_mut().next_out_seq_no(canister));
 
-            let payload_size = PAYLOAD_SIZE.with(|p| *p.borrow()) as usize;
             let payload = Request {
                 seq_no,
                 time_nanos: time(),
                 padding: vec![0; payload_size.saturating_sub(16)],
             };
 
-            let res = call::<(Request,), (Reply,)>(canister, "handle_request", (payload,));
-            futures.push(res);
+            let call = Call::new(canister, "handle_request").with_args((payload,));
+            let call = if timeout_seconds == 0 {
+                call.with_guaranteed_response()
+            } else {
+                call.change_timeout(timeout_seconds)
+            };
+            futures.push(call.call::<Reply>());
             METRICS.with(move |m| m.borrow_mut().calls_attempted += 1);
         }
     }
@@ -208,25 +217,32 @@ async fn fanout() {
 
     for res in results {
         match res {
-            Ok((reply,)) => {
+            Ok(reply) => {
                 let elapsed = Duration::from_nanos(time() - reply.time_nanos);
                 METRICS.with(|m| m.borrow_mut().latency_distribution.observe(elapsed));
             }
-            Err((err_code, err_message)) => {
-                // Catch whether the call failed due to a synchronous or
-                // asynchronous error. Based on the current implementation of
-                // the Rust CDK, a synchronous error will contain a specific
-                // error message.
-                if err_message.contains("Couldn't send message") {
-                    log(&format!(
-                        "{} call failed with {:?}",
-                        time() / 1_000_000,
-                        err_code
-                    ));
-                    METRICS.with(|m| m.borrow_mut().call_errors += 1);
-                } else {
-                    METRICS.with(|m| m.borrow_mut().reject_responses += 1);
-                }
+            Err(CallError::CallRejected(rejection)) if rejection.is_sync() => {
+                // Call failed due to a synchronous error.
+                log(&format!(
+                    "{} sync failure {:?} {}",
+                    time() / 1_000_000,
+                    rejection.reject_code(),
+                    rejection.reject_message()
+                ));
+                METRICS.with(|m| m.borrow_mut().call_errors += 1);
+            }
+            Err(CallError::CallRejected(rejection)) => {
+                log(&format!(
+                    "{} rejected {:?} {}",
+                    time() / 1_000_000,
+                    rejection.reject_code(),
+                    rejection.reject_message()
+                ));
+                METRICS.with(|m| m.borrow_mut().reject_responses += 1);
+            }
+            Err(CallError::CandidDecodeFailed(err)) => {
+                log(&format!("{} call failed: {}", time() / 1_000_000, err));
+                METRICS.with(|m| m.borrow_mut().call_errors += 1);
             }
         }
     }
@@ -235,14 +251,14 @@ async fn fanout() {
 /// Endpoint that handles requests from canisters located on remote subnets.
 #[update]
 fn handle_request(req: Request) -> Reply {
-    let caller = caller();
+    let caller = msg_caller();
     let in_seq_no = STATE.with(|s| s.borrow_mut().set_in_seq_no(caller, req.seq_no));
 
     if req.seq_no <= in_seq_no {
         METRICS.with(|m| m.borrow_mut().seq_errors += 1);
     }
 
-    let payload_size = PAYLOAD_SIZE.with(|p| *p.borrow()) as usize;
+    let payload_size = RESPONSE_PAYLOAD_SIZE.with(|p| *p.borrow()) as usize;
     Reply {
         time_nanos: req.time_nanos,
         padding: vec![0; payload_size.saturating_sub(8)],
@@ -252,14 +268,14 @@ fn handle_request(req: Request) -> Reply {
 /// Deposits the cycles this canister has minus 1T at the given destination.
 #[update]
 async fn return_cycles(canister_id_record: CanisterIdRecord) -> String {
-    let cycle_refund = canister_balance().saturating_sub(1_000_000_000_000);
-    let _ = call_with_payment::<(CanisterIdRecord,), ()>(
-        Principal::from_str("aaaaa-aa").unwrap(),
-        "deposit_cycles",
-        (canister_id_record,),
-        cycle_refund,
-    )
-    .await;
+    let cycle_refund = canister_cycle_balance().saturating_sub(1_000_000_000_000);
+    Call::new(Principal::from_text("aaaaa-aa").unwrap(), "deposit_cycles")
+        .with_arg(canister_id_record)
+        .with_guaranteed_response()
+        .with_cycles(cycle_refund)
+        .call::<()>()
+        .await
+        .unwrap();
 
     "ok".to_string()
 }
diff --git a/rs/tests/message_routing/BUILD.bazel b/rs/tests/message_routing/BUILD.bazel
index ba42cad9e36..541505b545c 100644
--- a/rs/tests/message_routing/BUILD.bazel
+++ b/rs/tests/message_routing/BUILD.bazel
@@ -26,7 +26,7 @@ system_test_nns(
         "//rs/tests/driver:ic-system-test-driver",
         "@crate_index//:anyhow",
         "@crate_index//:candid",
-        "@crate_index//:ic-cdk",
+        "@crate_index//:ic_cdk_next",
         "@crate_index//:itertools",
         "@crate_index//:slog",
         "@crate_index//:tokio",
diff --git a/rs/tests/message_routing/Cargo.toml b/rs/tests/message_routing/Cargo.toml
index bbba932178f..5e3c54769a3 100644
--- a/rs/tests/message_routing/Cargo.toml
+++ b/rs/tests/message_routing/Cargo.toml
@@ -11,7 +11,7 @@ anyhow = { workspace = true }
 candid = { workspace = true }
 canister-test = { path = "../../rust_canisters/canister_test" }
 dfn_candid = { path = "../../rust_canisters/dfn_candid" }
-ic-cdk = { workspace = true }
+ic-cdk = { git = "https://github.com/dfinity/cdk-rs", branch = "next" }
 ic-registry-subnet-type = { path = "../../registry/subnet_type" }
 ic-system-test-driver = { path = "../driver" }
 itertools = { workspace = true }
diff --git a/rs/tests/message_routing/common/common.rs b/rs/tests/message_routing/common/common.rs
index 2a1d826616e..3516e6c714b 100644
--- a/rs/tests/message_routing/common/common.rs
+++ b/rs/tests/message_routing/common/common.rs
@@ -13,7 +13,9 @@ use xnet_test::StartArgs;
 /// given parameters.
 pub async fn start_all_canisters(
     canisters: &[Vec<Canister<'_>>],
-    payload_size_bytes: u64,
+    request_payload_size_bytes: u64,
+    request_timeout_seconds: u32,
+    response_payload_size_bytes: u64,
     canister_to_subnet_rate: u64,
 ) {
     let topology: Vec<Vec<CanisterId>> = canisters
@@ -33,7 +35,9 @@ pub async fn start_all_canisters(
         let input = StartArgs {
             network_topology: topology.clone(),
             canister_to_subnet_rate,
-            payload_size_bytes,
+            request_payload_size_bytes,
+            request_timeout_seconds,
+            response_payload_size_bytes,
         };
         futures.push(async move {
             let _: String = canister
diff --git a/rs/tests/message_routing/global_reboot_test.rs b/rs/tests/message_routing/global_reboot_test.rs
index b1060cb2580..bf9a8fcfe94 100644
--- a/rs/tests/message_routing/global_reboot_test.rs
+++ b/rs/tests/message_routing/global_reboot_test.rs
@@ -189,7 +189,9 @@ pub fn start_all_canisters(
             let input = StartArgs {
                 network_topology: topology.clone(),
                 canister_to_subnet_rate,
-                payload_size_bytes,
+                request_payload_size_bytes: payload_size_bytes,
+                request_timeout_seconds: 0,
+                response_payload_size_bytes: payload_size_bytes,
             };
             let _: String = canister
                 .update_("start", candid, (input,))
diff --git a/rs/tests/message_routing/xnet/BUILD.bazel b/rs/tests/message_routing/xnet/BUILD.bazel
index 8b77eea3cda..7cf39ffc0c6 100644
--- a/rs/tests/message_routing/xnet/BUILD.bazel
+++ b/rs/tests/message_routing/xnet/BUILD.bazel
@@ -25,6 +25,27 @@ system_test_nns(
     ],
 )
 
+system_test_nns(
+    name = "xnet_slo_3_subnets_best_effort_test",
+    env = {
+        "XNET_TEST_CANISTER_WASM_PATH": "$(rootpath //rs/rust_canisters/xnet_test:xnet-test-canister)",
+    },
+    extra_head_nns_tags = ["manual"],  # only run this test with the mainnet NNS canisters.
+    flaky = False,
+    tags = [
+        "k8s",
+        "system_test_nightly",
+    ],
+    target_compatible_with = ["@platforms//os:linux"],  # requires libssh that does not build on Mac OS
+    test_timeout = "long",
+    runtime_deps = GUESTOS_RUNTIME_DEPS + XNET_TEST_CANISTER_RUNTIME_DEPS + GRAFANA_RUNTIME_DEPS,
+    deps = [
+        "//rs/tests/driver:ic-system-test-driver",
+        "//rs/tests/message_routing/xnet/slo_test_lib:xnet_slo_test_lib",
+        "@crate_index//:anyhow",
+    ],
+)
+
 system_test_nns(
     name = "xnet_slo_3_subnets_hotfix_test",
     env = {
diff --git a/rs/tests/message_routing/xnet/Cargo.toml b/rs/tests/message_routing/xnet/Cargo.toml
index 4cdb5ff722e..400b76a4ac0 100644
--- a/rs/tests/message_routing/xnet/Cargo.toml
+++ b/rs/tests/message_routing/xnet/Cargo.toml
@@ -26,6 +26,10 @@ path = "xnet_compatibility.rs"
 name = "xnet_malicious_slices"
 path = "xnet_malicious_slices.rs"
 
+[[bin]]
+name = "xnet_slo_3_subnets_best_effort_test"
+path = "xnet_slo_3_subnets_best_effort_test.rs"
+
 [[bin]]
 name = "xnet_slo_3_subnets_hotfix_test"
 path = "xnet_slo_3_subnets_hotfix_test.rs"
diff --git a/rs/tests/message_routing/xnet/slo_test_lib/xnet_slo_test_lib.rs b/rs/tests/message_routing/xnet/slo_test_lib/xnet_slo_test_lib.rs
index 102a82a8caa..808922a3c0e 100644
--- a/rs/tests/message_routing/xnet/slo_test_lib/xnet_slo_test_lib.rs
+++ b/rs/tests/message_routing/xnet/slo_test_lib/xnet_slo_test_lib.rs
@@ -28,7 +28,7 @@ use canister_test::{Canister, Runtime};
 use dfn_candid::candid;
 use futures::future::join_all;
 use ic_registry_subnet_type::SubnetType;
-use ic_system_test_driver::driver::ic::{InternetComputer, Subnet};
+use ic_system_test_driver::driver::ic::{InternetComputer, Subnet, VmResources};
 use ic_system_test_driver::driver::pot_dsl::{PotSetupFn, SysTestFn};
 use ic_system_test_driver::driver::prometheus_vm::{HasPrometheus, PrometheusVm};
 use ic_system_test_driver::driver::test_env::TestEnv;
@@ -48,7 +48,7 @@ const PAYLOAD_SIZE_BYTES: u64 = 1024;
 /// filling up its output queue). This should be estimated as:
 ///
 /// `queue_capacity / 10 /* max_rounds roundtrip */`
-const MAX_CANISTER_TO_CANISTER_RATE: usize = 30;
+const MAX_CANISTER_TO_CANISTER_RATE: usize = 5;
 const SEND_RATE_THRESHOLD: f64 = 0.3;
 const ERROR_PERCENTAGE_THRESHOLD: f64 = 5.0;
 const TARGETED_LATENCY_SECONDS: u64 = 20;
@@ -58,13 +58,16 @@ pub struct Config {
     subnets: usize,
     nodes_per_subnet: usize,
     runtime: Duration,
-    payload_size_bytes: u64,
+    request_payload_size_bytes: u64,
+    request_timeout_seconds: u32,
+    response_payload_size_bytes: u64,
     send_rate_threshold: f64,
     error_percentage_threshold: f64,
     targeted_latency_seconds: u64,
     subnet_to_subnet_rate: usize,
     canisters_per_subnet: usize,
     canister_to_subnet_rate: usize,
+    vm_resources: Option<VmResources>,
     with_prometheus: bool,
 }
 
@@ -106,23 +109,56 @@ impl Config {
             subnets,
             nodes_per_subnet,
             runtime,
-            payload_size_bytes: PAYLOAD_SIZE_BYTES,
+            request_payload_size_bytes: PAYLOAD_SIZE_BYTES,
+            request_timeout_seconds: 0,
+            response_payload_size_bytes: PAYLOAD_SIZE_BYTES,
             send_rate_threshold,
             error_percentage_threshold,
             targeted_latency_seconds,
             subnet_to_subnet_rate,
             canisters_per_subnet,
             canister_to_subnet_rate,
+            vm_resources: None,
             with_prometheus: false,
         }
     }
 
+    pub fn with_vm_resources(mut self, resources: VmResources) -> Self {
+        self.vm_resources = Some(resources);
+        self
+    }
+
     pub fn with_prometheus(self) -> Self {
         let mut config = self.clone();
         config.with_prometheus = true;
         config
     }
 
+    pub fn with_best_effort_response(self, timeout_seconds: u32) -> Self {
+        let mut config = self.clone();
+        config.request_timeout_seconds = timeout_seconds;
+        config
+    }
+
+    pub fn with_payload_bytes(self, payload_size_bytes: u64) -> Self {
+        let mut config = self.clone();
+        config.request_payload_size_bytes = payload_size_bytes;
+        config.response_payload_size_bytes = payload_size_bytes;
+        config
+    }
+
+    pub fn with_request_payload_size_bytes(self, request_payload_size_bytes: u64) -> Self {
+        let mut config = self.clone();
+        config.request_payload_size_bytes = request_payload_size_bytes;
+        config
+    }
+
+    pub fn with_response_payload_size_bytes(self, response_payload_size_bytes: u64) -> Self {
+        let mut config = self.clone();
+        config.response_payload_size_bytes = response_payload_size_bytes;
+        config
+    }
+
     /// Builds the IC instance.
     pub fn build(self) -> impl PotSetupFn {
         move |env: TestEnv| setup(env, self)
@@ -136,8 +172,12 @@ impl Config {
 
 // Generic setup
 fn setup(env: TestEnv, config: Config) {
+    let mut ic = InternetComputer::new();
+    if let Some(resources) = config.vm_resources {
+        ic = ic.with_default_vm_resources(resources);
+    }
     (0..config.subnets)
-        .fold(InternetComputer::new(), |ic, _idx| {
+        .fold(ic, |ic, _idx| {
             ic.add_subnet(Subnet::new(SubnetType::Application).add_nodes(config.nodes_per_subnet))
         })
         .setup_and_start(&env)
@@ -226,7 +266,9 @@ pub async fn deploy_and_start<'a, 'b>(
 
     start_all_canisters(
         &canisters,
-        config.payload_size_bytes,
+        config.request_payload_size_bytes,
+        config.request_timeout_seconds,
+        config.response_payload_size_bytes,
         config.canister_to_subnet_rate as u64,
     )
     .await;
@@ -234,10 +276,12 @@ pub async fn deploy_and_start<'a, 'b>(
         config.canister_to_subnet_rate * config.canisters_per_subnet * (config.subnets - 1);
     info!(
         logger,
-        "Starting chatter: {} messages/round * {} bytes = {} bytes/round",
+        "Starting chatter: {} messages/round * {}/{} bytes = {} bytes/round",
         msgs_per_round,
-        config.payload_size_bytes,
-        msgs_per_round * config.payload_size_bytes as usize
+        config.request_payload_size_bytes,
+        config.response_payload_size_bytes,
+        msgs_per_round
+            * (config.request_payload_size_bytes + config.response_payload_size_bytes) as usize
     );
 
     canisters
diff --git a/rs/tests/message_routing/xnet/xnet_malicious_slices.rs b/rs/tests/message_routing/xnet/xnet_malicious_slices.rs
index 74bb2195973..acc5e2d97db 100644
--- a/rs/tests/message_routing/xnet/xnet_malicious_slices.rs
+++ b/rs/tests/message_routing/xnet/xnet_malicious_slices.rs
@@ -154,6 +154,8 @@ pub async fn test_async(env: TestEnv, config: Config) {
     info!(logger, "Calling start() on all canisters...");
     start_all_canisters(
         &canisters, 1024, // send messages with 1024 byte payloads
+        0,    // guaranteed response calls
+        1024, // same response size
         10,   // each canister sends 10 RPS
     )
     .await;
diff --git a/rs/tests/message_routing/xnet/xnet_slo_3_subnets_best_effort_test.rs b/rs/tests/message_routing/xnet/xnet_slo_3_subnets_best_effort_test.rs
new file mode 100644
index 00000000000..92e1358fd90
--- /dev/null
+++ b/rs/tests/message_routing/xnet/xnet_slo_3_subnets_best_effort_test.rs
@@ -0,0 +1,27 @@
+use anyhow::Result;
+use ic_system_test_driver::driver::group::SystemTestGroup;
+use ic_system_test_driver::systest;
+use std::time::Duration;
+use xnet_slo_test_lib::Config;
+
+const SUBNETS: usize = 3;
+const NODES_PER_SUBNET: usize = 4;
+const RUNTIME: Duration = Duration::from_secs(60);
+const REQUEST_RATE: usize = 100;
+const RESPONSE_TIMEOUT_SECONDS: u32 = 300;
+
+const PER_TASK_TIMEOUT: Duration = Duration::from_secs(15 * 60);
+const OVERALL_TIMEOUT: Duration = Duration::from_secs(25 * 60);
+
+fn main() -> Result<()> {
+    let config = Config::new(SUBNETS, NODES_PER_SUBNET, RUNTIME, REQUEST_RATE)
+        .with_best_effort_response(RESPONSE_TIMEOUT_SECONDS);
+    let test = config.clone().test();
+    SystemTestGroup::new()
+        .with_setup(config.build())
+        .add_test(systest!(test))
+        .with_timeout_per_test(PER_TASK_TIMEOUT) // each task (including the setup function) may take up to `per_task_timeout`.
+        .with_overall_timeout(OVERALL_TIMEOUT) // the entire group may take up to `overall_timeout`.
+        .execute_from_args()?;
+    Ok(())
+}