diff --git a/Cargo.lock b/Cargo.lock
index 9b1e9966..c842a1cb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -45,9 +45,9 @@ checksum = "ec8ad6edb4840b78c5c3d88de606b22252d552b55f3a4699fbb10fc070ec3049"
 
 [[package]]
 name = "anyhow"
-version = "1.0.65"
+version = "1.0.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "98161a4e3e2184da77bb14f02184cdd111e83bbbcc9979dfee3c44b9a85f5602"
+checksum = "216261ddc8289130e551ddcd5ce8a064710c0d064a4d2895c67151c92b5443f6"
 
 [[package]]
 name = "arrayvec"
@@ -57,9 +57,9 @@ checksum = "8da52d66c7071e2e3fa2a1e5c6d088fec47b593032b254f5e980de8ea54454d6"
 
 [[package]]
 name = "async-trait"
-version = "0.1.57"
+version = "0.1.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "76464446b8bc32758d7e88ee1a804d9914cd9b1cb264c029899680b0be29826f"
+checksum = "1e805d94e6b5001b651426cf4cd446b1ab5f319d27bab5c644f61de0a804360c"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -85,9 +85,9 @@ checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
 
 [[package]]
 name = "base64"
-version = "0.13.0"
+version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"
+checksum = "9e1b586273c5702936fe7b7d6896644d8be71e6314cfe09d3167c95f712589e8"
 
 [[package]]
 name = "bincode"
@@ -115,9 +115,9 @@ dependencies = [
 
 [[package]]
 name = "bumpalo"
-version = "3.11.0"
+version = "3.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c1ad822118d20d2c234f427000d5acc36eabe1e29a348c89b63dd60b13f28e5d"
+checksum = "572f695136211188308f16ad2ca5c851a712c464060ae6974944458eb83880ba"
 
 [[package]]
 name = "byteorder"
@@ -146,7 +146,7 @@ dependencies = [
  "cap-primitives",
  "cap-std",
  "io-lifetimes",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
@@ -163,7 +163,7 @@ dependencies = [
  "maybe-owned",
  "rustix",
  "winapi-util",
- "windows-sys",
+ "windows-sys 0.36.1",
  "winx",
 ]
 
@@ -204,9 +204,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.0.73"
+version = "1.0.74"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2fff2a6927b3bb87f9595d67196a70493f627687a71d87a0d692242c33f58c11"
+checksum = "581f5dba903aac52ea3feb5ec4810848460ee833876f1f9b0fdeab1f19091574"
 dependencies = [
  "jobserver",
 ]
@@ -219,9 +219,9 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "clap"
-version = "4.0.18"
+version = "4.0.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "335867764ed2de42325fafe6d18b8af74ba97ee0c590fa016f157535b42ab04b"
+checksum = "8e67816e006b17427c9b4386915109b494fec2d929c63e3bd3561234cbf1bf1e"
 dependencies = [
  "atty",
  "bitflags",
@@ -290,25 +290,25 @@ dependencies = [
 
 [[package]]
 name = "cranelift-bforest"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "be5e1ee4c22871d24a95196ea7047d58c1d978e46c88037d3d397b3b3e0af360"
+checksum = "e4d6bb61f78cc312fbdebbb8a11b5aea6c16355ee682c57b89914691f3d57d0d"
 dependencies = [
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
 ]
 
 [[package]]
 name = "cranelift-codegen"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "70f600a52d59eed56a85f33750873b3b42d61e35ca777cd792369893f9e1f9dd"
+checksum = "b4f8572ccd8b99df7a8244d64feaa37f37877e47eccc245aa5e27f15dd336d7e"
 dependencies = [
  "arrayvec",
  "bumpalo",
  "cranelift-bforest",
  "cranelift-codegen-meta",
  "cranelift-codegen-shared",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "cranelift-isle",
  "gimli",
  "log",
@@ -319,18 +319,18 @@ dependencies = [
 
 [[package]]
 name = "cranelift-codegen-meta"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8418218d0953d73e9b96e9d9ffec56145efa4f18988251530b5872ae4410563"
+checksum = "15f2f284f49249a9fda931332f3feed56492651f47c330ffe1aa5a51f2b9d6b6"
 dependencies = [
  "cranelift-codegen-shared",
 ]
 
 [[package]]
 name = "cranelift-codegen-shared"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f01be0cfd40aba59153236ab4b99062131b5bbe6f9f3d4bcb238bd2f96ff5262"
+checksum = "8f6190411c55dfd88e68f506dfdbd028da0551dca40793d40811ea03cb6e0f4a"
 
 [[package]]
 name = "cranelift-entity"
@@ -340,18 +340,18 @@ checksum = "0b65673279d75d34bf11af9660ae2dbd1c22e6d28f163f5c72f4e1dc56d56103"
 
 [[package]]
 name = "cranelift-entity"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ddae4fec5d6859233ffa175b61d269443c473b3971a2c3e69008c8d3e83d5825"
+checksum = "ed8aa1104f54509dfb386520711cd8a6a0992ae42ce2df06fdebdfff4de2c2dd"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "cranelift-frontend"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2cc3deb0df97748434cf9f7e404f1f5134f6a253fc9a6bca25c5cd6804c08d3"
+checksum = "d48087600d6c055f625754b1d9cc9cab36a0d26a365cbcb388825e331e0041ff"
 dependencies = [
  "cranelift-codegen",
  "log",
@@ -361,18 +361,15 @@ dependencies = [
 
 [[package]]
 name = "cranelift-isle"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc3bb54287de9c36ba354eb849fefb77b5e73955058745fd08f12cfdfa181866"
-dependencies = [
- "rayon",
-]
+checksum = "eead4df80ce3c68b913d071683790692a0316a67e3518b32e273169238876f0a"
 
 [[package]]
 name = "cranelift-native"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d8c2a4f2efdce1de1f94e74f12b3b4144e3bcafa6011338b87388325d72d2120"
+checksum = "3adde571ff9c6a77320b69ac03920c5ce70fed94f5f9ac53f5c0600a69fc142e"
 dependencies = [
  "cranelift-codegen",
  "libc",
@@ -381,12 +378,12 @@ dependencies = [
 
 [[package]]
 name = "cranelift-wasm"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f918c37eb01f5b5ccc632e0ef3b4bf9ee03b5d4c267d3d2d3b62720a6bce0180"
+checksum = "5ebe9c1a3e90365d3dfa8cf12899cd96e4da327ef37ad58e060a93705ddf5937"
 dependencies = [
  "cranelift-codegen",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "cranelift-frontend",
  "itertools",
  "log",
@@ -545,9 +542,9 @@ checksum = "4443176a9f2c162692bd3d352d745ef9413eec5782a80d8fd6f8a1ac692a07f7"
 
 [[package]]
 name = "fastly-shared"
-version = "0.8.7"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "238fb7af2219391cb024673302861adffd96cb3dbe4b602c2c7abef11ce5a5f9"
+checksum = "6f79939bdbbab8b1de759d584f386319454f8623681400675a07f9ad35f2b158"
 dependencies = [
  "bitflags",
  "http",
@@ -606,14 +603,14 @@ checksum = "a267b6a9304912e018610d53fe07115d8b530b160e85db4d2d3a59f3ddde1aec"
 dependencies = [
  "io-lifetimes",
  "rustix",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "futures"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f21eda599937fba36daeb58a22e8f5cee2d14c4a17b5b7739c7c8e5e3b8230c"
+checksum = "38390104763dc37a5145a53c29c63c1290b5d316d6086ec32c293f6736051bb0"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -626,9 +623,9 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "30bdd20c28fadd505d0fd6712cdfcb0d4b5648baf45faef7f852afb2399bb050"
+checksum = "52ba265a92256105f45b719605a571ffe2d1f0fea3807304b522c1d778f79eed"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -636,15 +633,15 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4e5aa3de05362c3fb88de6531e6296e85cde7739cccad4b9dfeeb7f6ebce56bf"
+checksum = "04909a7a7e4633ae6c4a9ab280aeb86da1236243a77b694a49eacd659a4bd3ac"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9ff63c23854bee61b6e9cd331d523909f238fc7636290b96826e9cfa5faa00ab"
+checksum = "7acc85df6714c176ab5edf386123fafe217be88c0840ec11f199441134a074e2"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -653,15 +650,15 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bbf4d2a7a308fd4578637c0b17c7e1c7ba127b8f6ba00b29f717e9655d85eb68"
+checksum = "00f5fb52a06bdcadeb54e8d3671f8888a39697dcb0b81b23b55174030427f4eb"
 
 [[package]]
 name = "futures-macro"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "42cd15d1c7456c04dbdf7e88bcd69760d74f3a798d6444e16974b505b0e62f17"
+checksum = "bdfb8ce053d86b91919aad980c220b1fb8401a9394410e1c289ed7e66b61835d"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -670,21 +667,21 @@ dependencies = [
 
 [[package]]
 name = "futures-sink"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "21b20ba5a92e727ba30e72834706623d94ac93a725410b6a6b6fbc1b07f7ba56"
+checksum = "39c15cf1a4aa79df40f1bb462fb39676d0ad9e366c2a33b590d7c66f4f81fcf9"
 
 [[package]]
 name = "futures-task"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a6508c467c73851293f390476d4491cf4d227dbabcd4170f3bb6044959b294f1"
+checksum = "2ffb393ac5d9a6eaa9d3fdf37ae2776656b706e200c8e16b1bdb227f5198e6ea"
 
 [[package]]
 name = "futures-util"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "44fb6cb1be61cc1d2e43b262516aafcf63b241cffdb1d3fa115f91d9c7b09c90"
+checksum = "197676987abd2f9cadff84926f410af1c183608d36641465df73ae8211dc65d6"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -719,9 +716,9 @@ dependencies = [
 
 [[package]]
 name = "getrandom"
-version = "0.2.7"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4eb1a864a501629691edf6c15a593b7a51eebaa1e8468e9ddc623de7c9b58ec6"
+checksum = "c05aeb6a22b8f62540c194aac980f2115af067bfe15a0734d7277a768d396b31"
 dependencies = [
  "cfg-if",
  "libc",
@@ -741,9 +738,9 @@ dependencies = [
 
 [[package]]
 name = "h2"
-version = "0.3.14"
+version = "0.3.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5ca32592cf21ac7ccab1825cd87f6c9b3d9022c44d086172ed0966bec8af30be"
+checksum = "5f9f29bc9dda355256b2916cf526ab02ce0aeaaaf2bad60d65ef3f12f11dd0f4"
 dependencies = [
  "bytes",
  "fnv",
@@ -833,9 +830,9 @@ checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
 
 [[package]]
 name = "hyper"
-version = "0.14.20"
+version = "0.14.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02c929dc5c39e335a03c405292728118860721b10190d98c2a0f0efd5baafbac"
+checksum = "abfba89e19b959ca163c7752ba59d737c1ceea53a5d31a149c805446fc958064"
 dependencies = [
  "bytes",
  "futures-channel",
@@ -892,17 +889,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a5d8c2ab5becd8720e30fd25f8fa5500d8dc3fceadd8378f05859bd7b46fc49"
 dependencies = [
  "io-lifetimes",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "io-lifetimes"
-version = "0.7.3"
+version = "0.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ea37f355c05dde75b84bba2d767906ad522e97cd9e2eef2be7a4ab7fb442c06"
+checksum = "59ce5ef949d49ee85593fc4d3f3f95ad61657076395cbbce23e2121fc5542074"
 dependencies = [
  "libc",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -920,7 +917,7 @@ dependencies = [
  "hermit-abi 0.2.6",
  "io-lifetimes",
  "rustix",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
@@ -990,9 +987,9 @@ checksum = "884e2677b40cc8c339eaefcb701c32ef1fd2493d71118dc0ca4b6a736c93bd67"
 
 [[package]]
 name = "libc"
-version = "0.2.135"
+version = "0.2.137"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68783febc7782c6c5cb401fbda4de5a9898be1762314da0bb2c10ced61f18b0c"
+checksum = "fc7fcc620a3bff7cdd7a365be3376c97191aeaccc2a603e600951e452615bf89"
 
 [[package]]
 name = "linux-raw-sys"
@@ -1078,14 +1075,14 @@ dependencies = [
 
 [[package]]
 name = "mio"
-version = "0.8.4"
+version = "0.8.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "57ee1c23c7c63b0c9250c339ffdc69255f110b298b901b9f6c82547b7b87caaf"
+checksum = "e5d732bc30207a6423068df043e3d02e0735b155ad7ce1a6f76fe2baa5b158de"
 dependencies = [
  "libc",
  "log",
  "wasi",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -1100,9 +1097,9 @@ dependencies = [
 
 [[package]]
 name = "num_cpus"
-version = "1.13.1"
+version = "1.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "19e64526ebdee182341572e50e9ad03965aa510cd94427a4549448f285e957a1"
+checksum = "f6058e64324c71e02bc2b150e4f3bc8286db6c83092132ffa3f6b1eab0f9def5"
 dependencies = [
  "hermit-abi 0.1.19",
  "libc",
@@ -1122,9 +1119,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.15.0"
+version = "1.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
+checksum = "86f0b0d4bf799edbc74508c1e8bf170ff5f41238e5f8225603ca7caaae2b7860"
 
 [[package]]
 name = "opaque-debug"
@@ -1162,15 +1159,15 @@ dependencies = [
 
 [[package]]
 name = "parking_lot_core"
-version = "0.9.3"
+version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09a279cbf25cb0757810394fbc1e359949b59e348145c643a939a525692e6929"
+checksum = "4dc9e0dc2adc1c69d09143aff38d3d30c5c3f0df0dad82e6d25547af174ebec0"
 dependencies = [
  "cfg-if",
  "libc",
  "redox_syscall",
  "smallvec",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -1350,9 +1347,9 @@ dependencies = [
 
 [[package]]
 name = "regalloc2"
-version = "0.4.1"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "69025b4a161879ba90719837c06621c3d73cffa147a000aeacf458f6a9572485"
+checksum = "91b2eab54204ea0117fe9a060537e0b07a4e72f7c7d182361ecc346cab2240e5"
 dependencies = [
  "fxhash",
  "log",
@@ -1418,9 +1415,9 @@ checksum = "7ef03e0a2b150c7a90d01faf6254c9c48a41e95fb2a8c2ac1c6f0d2b9aefc342"
 
 [[package]]
 name = "rustix"
-version = "0.35.11"
+version = "0.35.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fbb2fda4666def1433b1b05431ab402e42a1084285477222b72d6c564c417cef"
+checksum = "727a1a6d65f786ec22df8a81ca3121107f235970dc1705ed681d3e6e8b9cd5f9"
 dependencies = [
  "bitflags",
  "errno",
@@ -1429,7 +1426,7 @@ dependencies = [
  "libc",
  "linux-raw-sys",
  "once_cell",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -1470,7 +1467,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "88d6731146462ea25d9244b2ed5fd1d716d25c52e4d54aa4fb0f3c4e9854dbe2"
 dependencies = [
  "lazy_static",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
@@ -1529,18 +1526,18 @@ checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 
 [[package]]
 name = "serde"
-version = "1.0.145"
+version = "1.0.147"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "728eb6351430bccb993660dfffc5a72f91ccc1295abaa8ce19b27ebe4f75568b"
+checksum = "d193d69bae983fc11a79df82342761dfbf28a99fc8d203dca4c3c1b590948965"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.145"
+version = "1.0.147"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "81fa1584d3d1bcacd84c277a0dfe21f5b0f6accf4a23d04d4c6d61f1af522b4c"
+checksum = "4f1d362ca8fc9c3e3a7484440752472d68a6caa98f1ab81d99b5dfe517cec852"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1549,9 +1546,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.86"
+version = "1.0.87"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "41feea4228a6f1cd09ec7a3593a682276702cd67b5273544757dae23c096f074"
+checksum = "6ce777b7b150d76b9cf60d28b55f5847135a003f7d7350c6be7a773508ce7d45"
 dependencies = [
  "itoa",
  "ryu",
@@ -1649,9 +1646,9 @@ checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"
 
 [[package]]
 name = "syn"
-version = "1.0.102"
+version = "1.0.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3fcd952facd492f9be3ef0d0b7032a6e442ee9b361d4acc2b1d0c4aaa5f613a1"
+checksum = "a864042229133ada95abf3b54fdc62ef5ccabe9515b64717bcb9a1919e59445d"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1670,7 +1667,7 @@ dependencies = [
  "cap-std",
  "io-lifetimes",
  "rustix",
- "windows-sys",
+ "windows-sys 0.36.1",
  "winx",
 ]
 
@@ -2035,9 +2032,9 @@ checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
 
 [[package]]
 name = "wasi-cap-std-sync"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6fa9ddcfc9d85e89a10c27801376ea57d2e9421ad91336326160c56044049b49"
+checksum = "ea3e0d556c3f9c2481c2d15eee7ad4b0b25db206d034aa80b16ff1299e7cd679"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -2054,14 +2051,14 @@ dependencies = [
  "system-interface",
  "tracing",
  "wasi-common",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasi-common"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fd86a0cd870709441a25d63737bd416db6cf8eb6229c0da08d29d7ab79108bbb"
+checksum = "5e924b71f77144f65e173478d43be57ee9e16a9b8f7b8a41223b689051b3c176"
 dependencies = [
  "anyhow",
  "bitflags",
@@ -2072,14 +2069,14 @@ dependencies = [
  "thiserror",
  "tracing",
  "wiggle",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasi-tokio"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "50eae69cf1ad9de30bb7d604c5433d38d2aec1e32dac6bc89ef30ab7a0860381"
+checksum = "a2ab5198e9d48ad1991c507eef9a4dca953ed0077fc1597b09e808cae74c05b5"
 dependencies = [
  "anyhow",
  "cap-std",
@@ -2148,9 +2145,9 @@ checksum = "1c38c045535d93ec4f0b4defec448e4291638ee608530863b1e2ba115d4fff7f"
 
 [[package]]
 name = "wasm-encoder"
-version = "0.18.0"
+version = "0.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c64ac98d5d61192cc45c701b7e4bd0b9aff91e2edfc7a088406cfe2288581e2c"
+checksum = "c5816e88e8ea7335016aa62eb0485747f786136d505a9b3890f8c400211d9b5f"
 dependencies = [
  "leb128",
 ]
@@ -2166,9 +2163,9 @@ dependencies = [
 
 [[package]]
 name = "wasmtime"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f5fc5bb3329415030796cfa5530b2481ccef5c4f1e5150733ba94318ab004fe1"
+checksum = "63e4f0c3cbaed050686095e5fde04f28eada1ef6196b456ffce7df2115cc2a38"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -2192,23 +2189,23 @@ dependencies = [
  "wasmtime-jit",
  "wasmtime-runtime",
  "wat",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-asm-macros"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "db36545ff0940ad9bf4e9ab0ec2a4e1eaa5ebe2aa9227bcbc4af905375d9e482"
+checksum = "41f17b9bf1ff3ed08f35dd3faa8fe0dc34693939252e47a3a056073d28fcd6d7"
 dependencies = [
  "cfg-if",
 ]
 
 [[package]]
 name = "wasmtime-cache"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2c2101b211d9db7db8bcfb2ffa69e119fa99a20266d0e5f19bb989cb6c3280d7"
+checksum = "ba1bfca72e269de2b96dc77a8fe64816d9cc6c6ad416a3aba9a51f4ff6bcefc1"
 dependencies = [
  "anyhow",
  "base64",
@@ -2220,19 +2217,19 @@ dependencies = [
  "serde",
  "sha2",
  "toml",
- "windows-sys",
+ "windows-sys 0.36.1",
  "zstd",
 ]
 
 [[package]]
 name = "wasmtime-cranelift"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0409e93b5eceaa4e5f498a4bce1cffc7ebe071d14582b5437c10af4aecc23f54"
+checksum = "d4d237bf7d2bcaea5e8018e088668e80b4448e002667d58c414fdcbb8f56ba0e"
 dependencies = [
  "anyhow",
  "cranelift-codegen",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "cranelift-frontend",
  "cranelift-native",
  "cranelift-wasm",
@@ -2247,12 +2244,12 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-environ"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "55240389c604f68d2e1d2573d7d3740246ab9ea2fa4fe79e10ccd51faf9b9500"
+checksum = "c432df5094f397e43467eca9775254850231d9047b3513a8e1f28a5778a90dfc"
 dependencies = [
  "anyhow",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "gimli",
  "indexmap",
  "log",
@@ -2266,22 +2263,22 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-fiber"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "abb9b7b94f7b40d98665feca2338808cf449fa671d01be7176861f8d9aa4a012"
+checksum = "331439bc204d5395b89a018d5aa11aaeb5819c733db40fe8bd1d4ce88bf85be1"
 dependencies = [
  "cc",
  "cfg-if",
  "rustix",
  "wasmtime-asm-macros",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-jit"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bc15e285b7073ee566e62ea4b6dd38b80465ade0ea8cd4cee13c7ac2e295cfca"
+checksum = "f0e1f06e0ab975f0e9dd6b2db9364209272625d5348d02b0b846cf62f102e89c"
 dependencies = [
  "addr2line",
  "anyhow",
@@ -2300,14 +2297,14 @@ dependencies = [
  "wasmtime-environ",
  "wasmtime-jit-debug",
  "wasmtime-runtime",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-jit-debug"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bee06d206bcf7a875eacd1e1e957c2a63f64a92934d2535dd8e15cde6d3a9ffe"
+checksum = "07ca7aeb81909fc7688e1318fc247de2fb7ef2b638aa7501b45f7f6ad710f989"
 dependencies = [
  "object",
  "once_cell",
@@ -2316,9 +2313,9 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-runtime"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9969ff36cbf57f18c2d24679db57d0857ea7cc7d839534afc26ecc8003e9914b"
+checksum = "16069dff65b648d121d9b5ecbeb7319035f9a5aafd370d713c90a7f23db4d823"
 dependencies = [
  "anyhow",
  "cc",
@@ -2337,16 +2334,16 @@ dependencies = [
  "wasmtime-environ",
  "wasmtime-fiber",
  "wasmtime-jit-debug",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-types"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df64c737fc9b3cdf7617bcc65e8b97cb713ceb9c9c58530b20788a8a3482b5d1"
+checksum = "8926344aff6324e6469aa17345bbb29ef9de4fe934bde30a05be28ebf21e0a23"
 dependencies = [
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "serde",
  "thiserror",
  "wasmparser",
@@ -2354,9 +2351,9 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-wasi"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fb41d16dfd153d2078ea2347d311cee6c74f2a4ecc109cd9acaf860709137fdb"
+checksum = "26e67b408714dc3fe9f7eaab091a45b9bbfed9f983bd16e0dc209fa4456d903f"
 dependencies = [
  "anyhow",
  "wasi-cap-std-sync",
@@ -2377,9 +2374,9 @@ dependencies = [
 
 [[package]]
 name = "wast"
-version = "47.0.1"
+version = "48.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02b98502f3978adea49551e801a6687678e6015317d7d9470a67fe813393f2a8"
+checksum = "84825b5ac7164df8260c9e2b2e814075334edbe7ac426f2469b93a5eeac23cce"
 dependencies = [
  "leb128",
  "memchr",
@@ -2389,11 +2386,11 @@ dependencies = [
 
 [[package]]
 name = "wat"
-version = "1.0.49"
+version = "1.0.50"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7aab4e20c60429fbba9670a6cae0fff9520046ba0aa3e6d0b1cd2653bea14898"
+checksum = "129da4a03ec6d2a815f42c88f641824e789d5be0d86d2f90aa8a218c7068e0be"
 dependencies = [
- "wast 47.0.1",
+ "wast 48.0.0",
 ]
 
 [[package]]
@@ -2418,9 +2415,9 @@ dependencies = [
 
 [[package]]
 name = "wiggle"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2943156975c608cab1b44d28becba4196b07f18be92ea28f1e7f3372a12d81dd"
+checksum = "d55b0d7302192e47c1c2b1706790dab42cd42342ac58c4acb3d589daf56cddf0"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -2434,9 +2431,9 @@ dependencies = [
 
 [[package]]
 name = "wiggle-generate"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0321263a6b1ba1e0a97174524891a14907cee68cfa183fd5389088dffbeab668"
+checksum = "e164de81eea233c6b4e430e6cba4ff3953e3594fd0068633651994a5f0750a0a"
 dependencies = [
  "anyhow",
  "heck",
@@ -2449,9 +2446,9 @@ dependencies = [
 
 [[package]]
 name = "wiggle-macro"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa3d3794e5d68ef69f30e65f267c6bf18c920750d3ccd2a3ac04e77d95f66b96"
+checksum = "829a1543aa92a51f64e38f1dfcf16adfe447aefff3a2c281cf8ddf35c9797255"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2496,43 +2493,100 @@ version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ea04155a16a59f9eab786fe12a4a450e75cdb175f9e0d80da1e17db09f55b8d2"
 dependencies = [
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_msvc",
+ "windows_aarch64_msvc 0.36.1",
+ "windows_i686_gnu 0.36.1",
+ "windows_i686_msvc 0.36.1",
+ "windows_x86_64_gnu 0.36.1",
+ "windows_x86_64_msvc 0.36.1",
+]
+
+[[package]]
+name = "windows-sys"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a3e1820f08b8513f676f7ab6c1f99ff312fb97b553d30ff4dd86f9f15728aa7"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc 0.42.0",
+ "windows_i686_gnu 0.42.0",
+ "windows_i686_msvc 0.42.0",
+ "windows_x86_64_gnu 0.42.0",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc 0.42.0",
 ]
 
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41d2aa71f6f0cbe00ae5167d90ef3cfe66527d6f613ca78ac8024c3ccab9a19e"
+
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9bb8c3fd39ade2d67e9874ac4f3db21f0d710bee00fe7cab16949ec184eeaa47"
 
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd0f252f5a35cac83d6311b2e795981f5ee6e67eb1f9a7f64eb4500fbc4dcdb4"
+
 [[package]]
 name = "windows_i686_gnu"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "180e6ccf01daf4c426b846dfc66db1fc518f074baa793aa7d9b9aaeffad6a3b6"
 
+[[package]]
+name = "windows_i686_gnu"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fbeae19f6716841636c28d695375df17562ca208b2b7d0dc47635a50ae6c5de7"
+
 [[package]]
 name = "windows_i686_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2e7917148b2812d1eeafaeb22a97e4813dfa60a3f8f78ebe204bcc88f12f024"
 
+[[package]]
+name = "windows_i686_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "84c12f65daa39dd2babe6e442988fc329d6243fdce47d7d2d155b8d874862246"
+
 [[package]]
 name = "windows_x86_64_gnu"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4dcd171b8776c41b97521e5da127a2d86ad280114807d0b2ab1e462bc764d9e1"
 
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf7b1b21b5362cbc318f686150e5bcea75ecedc74dd157d874d754a2ca44b0ed"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09d525d2ba30eeb3297665bd434a54297e4170c7f1a44cad4ef58095b4cd2028"
+
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"
 
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f40009d85759725a34da6d89a94e63d7bdc50a862acf0dbc7c8e488f1edcb6f5"
+
 [[package]]
 name = "winx"
 version = "0.33.0"
@@ -2541,7 +2595,7 @@ checksum = "b7b01e010390eb263a4518c8cebf86cb67469d1511c00b749a47b64c39e8054d"
 dependencies = [
  "bitflags",
  "io-lifetimes",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
diff --git a/cli/tests/integration/async_io.rs b/cli/tests/integration/async_io.rs
new file mode 100644
index 00000000..77af6f63
--- /dev/null
+++ b/cli/tests/integration/async_io.rs
@@ -0,0 +1,230 @@
+use crate::common::Test;
+use crate::common::TestResult;
+use hyper::Body;
+use hyper::Request;
+use hyper::Response;
+use hyper::StatusCode;
+use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::Ordering;
+use std::sync::Arc;
+use tokio::sync::Barrier;
+
+// On Windows, streaming body backpressure doesn't seem to work as expected, either
+// due to the Hyper client or server too eagerly clearing the chunk buffer. This issue does
+// not appear related to async I/O hostcalls; the behavior is seen within the streaming body
+// implementation in general. For the time being, this test is unix-only.
+//
+// https://github.com/fastly/Viceroy/issues/207 tracks the broader issue.
+#[cfg(target_family = "unix")]
+#[tokio::test(flavor = "multi_thread")]
+async fn async_io_methods() -> TestResult {
+    let request_count = Arc::new(AtomicUsize::new(0));
+    let req_count_1 = request_count.clone();
+    let req_count_2 = request_count.clone();
+    let req_count_3 = request_count.clone();
+
+    let barrier = Arc::new(Barrier::new(3));
+    let barrier_1 = barrier.clone();
+    let barrier_2 = barrier.clone();
+
+    let test = Test::using_fixture("async_io.wasm")
+        .backend("Simple", "http://127.0.0.1:9000/", None)
+        .async_host(9000, move |req: Request<Body>| {
+            assert_eq!(req.headers()["Host"], "simple.org");
+            let req_count_1 = req_count_1.clone();
+            let barrier_1 = barrier_1.clone();
+            Box::new(async move {
+                match req_count_1.load(Ordering::Relaxed) {
+                    0 => {
+                        barrier_1.wait().await;
+                        Response::builder()
+                            .status(StatusCode::OK)
+                            .body(Body::empty())
+                            .unwrap()
+                    }
+                    1 => Response::builder()
+                        .status(StatusCode::OK)
+                        .body(Body::empty())
+                        .unwrap(),
+                    2 => {
+                        barrier_1.wait().await;
+                        Response::builder()
+                            .status(StatusCode::OK)
+                            .body(Body::empty())
+                            .unwrap()
+                    }
+                    3 => {
+                        barrier_1.wait().await;
+                        Response::builder()
+                            .status(StatusCode::OK)
+                            .body(Body::empty())
+                            .unwrap()
+                    }
+                    _ => unreachable!(),
+                }
+            })
+        })
+        .backend("ReadBody", "http://127.0.0.1:9001/", None)
+        .async_host(9001, move |req: Request<Body>| {
+            assert_eq!(req.headers()["Host"], "readbody.org");
+            let req_count_2 = req_count_2.clone();
+            Box::new(async move {
+                match req_count_2.load(Ordering::Relaxed) {
+                    0 => Response::builder()
+                        .header("Transfer-Encoding", "chunked")
+                        .status(StatusCode::OK)
+                        .body(Body::empty())
+                        .unwrap(),
+                    1 => Response::builder()
+                        .header("Transfer-Encoding", "chunked")
+                        .status(StatusCode::OK)
+                        .body(Body::empty())
+                        .unwrap(),
+                    2 => Response::builder()
+                        .status(StatusCode::OK)
+                        .body(Body::empty())
+                        .unwrap(),
+                    3 => Response::builder()
+                        .header("Transfer-Encoding", "chunked")
+                        .status(StatusCode::OK)
+                        .body(Body::empty())
+                        .unwrap(),
+                    _ => unreachable!(),
+                }
+            })
+        })
+        .backend("WriteBody", "http://127.0.0.1:9002/", None)
+        .async_host(9002, move |req: Request<Body>| {
+            assert_eq!(req.headers()["Host"], "writebody.org");
+            let req_count_3 = req_count_3.clone();
+            let barrier_2 = barrier_2.clone();
+            Box::new(async move {
+                match req_count_3.load(Ordering::Relaxed) {
+                    0 => {
+                        barrier_2.wait().await;
+                        Response::builder()
+                            .status(StatusCode::OK)
+                            .body(Body::empty())
+                            .unwrap()
+                    }
+                    1 => {
+                        barrier_2.wait().await;
+                        Response::builder()
+                            .status(StatusCode::OK)
+                            .body(Body::empty())
+                            .unwrap()
+                    }
+                    2 => {
+                        barrier_2.wait().await;
+                        Response::builder()
+                            .status(StatusCode::OK)
+                            .body(Body::empty())
+                            .unwrap()
+                    }
+                    3 => {
+                        let _body = hyper::body::to_bytes(req.into_body()).await;
+                        Response::builder()
+                            .status(StatusCode::OK)
+                            .body(Body::empty())
+                            .unwrap()
+                    }
+                    _ => unreachable!(),
+                }
+            })
+        });
+
+    // request_count is 0 here
+    let resp = test
+        .against(
+            Request::builder()
+                .header("Host", "example.org")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await;
+
+    assert_eq!(resp.status(), StatusCode::OK);
+    assert_eq!(resp.headers()["Simple-Ready"], "false");
+    assert_eq!(resp.headers()["Read-Ready"], "false");
+    assert_eq!(resp.headers()["Write-Ready"], "false");
+    assert_eq!(resp.headers()["Ready-Index"], "timeout");
+
+    barrier.wait().await;
+
+    request_count.store(1, Ordering::Relaxed);
+    let resp = test
+        .against(
+            Request::builder()
+                .header("Host", "example.org")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await;
+    assert_eq!(resp.status(), StatusCode::OK);
+    assert_eq!(resp.headers()["Simple-Ready"], "true");
+    assert_eq!(resp.headers()["Read-Ready"], "false");
+    assert_eq!(resp.headers()["Write-Ready"], "false");
+    assert_eq!(resp.headers()["Ready-Index"], "0");
+    let temp_barrier = barrier.clone();
+    let _task = tokio::task::spawn(async move { temp_barrier.wait().await });
+    barrier.wait().await;
+
+    request_count.store(2, Ordering::Relaxed);
+    let resp = test
+        .against(
+            Request::builder()
+                .header("Host", "example.org")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await;
+    assert_eq!(resp.status(), StatusCode::OK);
+    assert_eq!(resp.headers()["Simple-Ready"], "false");
+    assert_eq!(resp.headers()["Read-Ready"], "true");
+    assert_eq!(resp.headers()["Write-Ready"], "false");
+    assert_eq!(resp.headers()["Ready-Index"], "1");
+    barrier.wait().await;
+
+    request_count.store(3, Ordering::Relaxed);
+    let resp = test
+        .against(
+            Request::builder()
+                .header("Host", "example.org")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await;
+    assert_eq!(resp.status(), StatusCode::OK);
+    assert_eq!(resp.headers()["Simple-Ready"], "false");
+    assert_eq!(resp.headers()["Read-Ready"], "false");
+    assert_eq!(resp.headers()["Write-Ready"], "true");
+    assert_eq!(resp.headers()["Ready-Index"], "2");
+    let temp_barrier = barrier.clone();
+    let _task = tokio::task::spawn(async move { temp_barrier.wait().await });
+    barrier.wait().await;
+
+    let resp = test
+        .against(
+            Request::builder()
+                .header("Host", "example.org")
+                .header("Empty-Select-Timeout", "0")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await;
+    assert_eq!(resp.status(), StatusCode::INTERNAL_SERVER_ERROR);
+
+    let resp = test
+        .against(
+            Request::builder()
+                .header("Host", "example.org")
+                .header("Empty-Select-Timeout", "1")
+                .body(Body::empty())
+                .unwrap(),
+        )
+        .await;
+    assert_eq!(resp.status(), StatusCode::OK);
+    assert_eq!(resp.headers()["Ready-Index"], "timeout");
+
+    Ok(())
+}
diff --git a/cli/tests/integration/common.rs b/cli/tests/integration/common.rs
index 50dbc304..3e3e097d 100644
--- a/cli/tests/integration/common.rs
+++ b/cli/tests/integration/common.rs
@@ -3,7 +3,7 @@
 
 use futures::stream::StreamExt;
 use hyper::{service, Body as HyperBody, Request, Response, Server};
-use std::{convert::Infallible, net::SocketAddr, path::PathBuf, sync::Arc};
+use std::{convert::Infallible, future::Future, net::SocketAddr, path::PathBuf, sync::Arc};
 use tokio::sync::Mutex;
 use tracing_subscriber::filter::EnvFilter;
 use viceroy_lib::{
@@ -126,7 +126,17 @@ impl Test {
         HostFn: Fn(Request<Vec<u8>>) -> Response<Vec<u8>>,
         HostFn: Send + Sync + 'static,
     {
-        let service = Arc::new(service);
+        let service = Arc::new(TestService::Sync(Arc::new(service)));
+        self.hosts.push(HostSpec { port, service });
+        self
+    }
+
+    pub fn async_host<HostFn>(mut self, port: u16, service: HostFn) -> Self
+    where
+        HostFn: Fn(Request<HyperBody>) -> AsyncResp,
+        HostFn: Send + Sync + 'static,
+    {
+        let service = Arc::new(TestService::Async(Arc::new(service)));
         self.hosts.push(HostSpec { port, service });
         self
     }
@@ -273,7 +283,7 @@ impl Test {
 /// The specification of a mock host, as part of a `Test` builder.
 struct HostSpec {
     port: u16,
-    service: Arc<dyn Fn(Request<Vec<u8>>) -> Response<Vec<u8>> + Send + Sync>,
+    service: Arc<TestService>,
 }
 
 /// A handle to a running mock host, used to gracefully shut down the host on test completion.
@@ -292,21 +302,26 @@ impl HostSpec {
         // we transform `service` into an async function that consumes Hyper bodies. that requires a bit
         // of `Arc` and `move` operations because each invocation needs to produce a distinct `Future`
         let async_service = Arc::new(move |req: Request<HyperBody>| {
-            let (parts, body) = req.into_parts();
-            let mut body = Box::new(body); // for pinning
             let service = service.clone();
 
             async move {
-                // read out all of the bytes from the body into a vector, then re-assemble the request
-                let mut body_bytes = Vec::new();
-                while let Some(chunk) = body.next().await {
-                    body_bytes.extend_from_slice(&chunk.unwrap());
-                }
-                let req = Request::from_parts(parts, body_bytes);
-
-                // pass the request through the host function, then convert its body into the form
-                // that Hyper wants
-                let resp = service(req).map(HyperBody::from);
+                let resp = match &*service {
+                    TestService::Sync(s) => {
+                        let (parts, body) = req.into_parts();
+                        let mut body = Box::new(body); // for pinning
+                                                       // read out all of the bytes from the body into a vector, then re-assemble the request
+                        let mut body_bytes = Vec::new();
+                        while let Some(chunk) = body.next().await {
+                            body_bytes.extend_from_slice(&chunk.unwrap());
+                        }
+                        let req = Request::from_parts(parts, body_bytes);
+
+                        // pass the request through the host function, then convert its body into the form
+                        // that Hyper wants
+                        s(req).map(HyperBody::from)
+                    }
+                    TestService::Async(s) => Box::into_pin(s(req)).await.map(HyperBody::from),
+                };
 
                 let res: Result<_, hyper::Error> = Ok(resp);
                 res
@@ -345,8 +360,16 @@ impl HostHandle {
         self.terminate_signal
             .send(())
             .expect("could not send terminate signal to mock host");
-        self.task_handle
-            .await
-            .expect("mock host did not terminate cleanly")
+        if !self.task_handle.is_finished() {
+            self.task_handle.abort();
+        }
     }
 }
+
+#[derive(Clone)]
+pub enum TestService {
+    Sync(Arc<dyn Fn(Request<Vec<u8>>) -> Response<Vec<u8>> + Send + Sync>),
+    Async(Arc<dyn Fn(Request<HyperBody>) -> AsyncResp + Send + Sync>),
+}
+
+type AsyncResp = Box<dyn Future<Output = Response<HyperBody>> + Send + Sync>;
diff --git a/cli/tests/integration/main.rs b/cli/tests/integration/main.rs
index 10790c23..60e9b2c2 100644
--- a/cli/tests/integration/main.rs
+++ b/cli/tests/integration/main.rs
@@ -1,3 +1,4 @@
+mod async_io;
 mod body;
 mod common;
 mod dictionary_lookup;
diff --git a/cli/tests/trap-test/Cargo.lock b/cli/tests/trap-test/Cargo.lock
index d2952ffd..9e154805 100644
--- a/cli/tests/trap-test/Cargo.lock
+++ b/cli/tests/trap-test/Cargo.lock
@@ -63,9 +63,9 @@ dependencies = [
 
 [[package]]
 name = "anyhow"
-version = "1.0.65"
+version = "1.0.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "98161a4e3e2184da77bb14f02184cdd111e83bbbcc9979dfee3c44b9a85f5602"
+checksum = "216261ddc8289130e551ddcd5ce8a064710c0d064a4d2895c67151c92b5443f6"
 
 [[package]]
 name = "arrayvec"
@@ -75,9 +75,9 @@ checksum = "8da52d66c7071e2e3fa2a1e5c6d088fec47b593032b254f5e980de8ea54454d6"
 
 [[package]]
 name = "async-trait"
-version = "0.1.57"
+version = "0.1.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "76464446b8bc32758d7e88ee1a804d9914cd9b1cb264c029899680b0be29826f"
+checksum = "1e805d94e6b5001b651426cf4cd446b1ab5f319d27bab5c644f61de0a804360c"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -103,9 +103,9 @@ checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
 
 [[package]]
 name = "base64"
-version = "0.13.0"
+version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"
+checksum = "9e1b586273c5702936fe7b7d6896644d8be71e6314cfe09d3167c95f712589e8"
 
 [[package]]
 name = "bincode"
@@ -133,9 +133,9 @@ dependencies = [
 
 [[package]]
 name = "bumpalo"
-version = "3.11.0"
+version = "3.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c1ad822118d20d2c234f427000d5acc36eabe1e29a348c89b63dd60b13f28e5d"
+checksum = "572f695136211188308f16ad2ca5c851a712c464060ae6974944458eb83880ba"
 
 [[package]]
 name = "byteorder"
@@ -164,7 +164,7 @@ dependencies = [
  "cap-primitives",
  "cap-std",
  "io-lifetimes",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
@@ -181,7 +181,7 @@ dependencies = [
  "maybe-owned",
  "rustix",
  "winapi-util",
- "windows-sys",
+ "windows-sys 0.36.1",
  "winx",
 ]
 
@@ -222,9 +222,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.0.73"
+version = "1.0.74"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2fff2a6927b3bb87f9595d67196a70493f627687a71d87a0d692242c33f58c11"
+checksum = "581f5dba903aac52ea3feb5ec4810848460ee833876f1f9b0fdeab1f19091574"
 dependencies = [
  "jobserver",
 ]
@@ -293,25 +293,25 @@ dependencies = [
 
 [[package]]
 name = "cranelift-bforest"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "be5e1ee4c22871d24a95196ea7047d58c1d978e46c88037d3d397b3b3e0af360"
+checksum = "e4d6bb61f78cc312fbdebbb8a11b5aea6c16355ee682c57b89914691f3d57d0d"
 dependencies = [
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
 ]
 
 [[package]]
 name = "cranelift-codegen"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "70f600a52d59eed56a85f33750873b3b42d61e35ca777cd792369893f9e1f9dd"
+checksum = "b4f8572ccd8b99df7a8244d64feaa37f37877e47eccc245aa5e27f15dd336d7e"
 dependencies = [
  "arrayvec",
  "bumpalo",
  "cranelift-bforest",
  "cranelift-codegen-meta",
  "cranelift-codegen-shared",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "cranelift-isle",
  "gimli",
  "log",
@@ -322,18 +322,18 @@ dependencies = [
 
 [[package]]
 name = "cranelift-codegen-meta"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8418218d0953d73e9b96e9d9ffec56145efa4f18988251530b5872ae4410563"
+checksum = "15f2f284f49249a9fda931332f3feed56492651f47c330ffe1aa5a51f2b9d6b6"
 dependencies = [
  "cranelift-codegen-shared",
 ]
 
 [[package]]
 name = "cranelift-codegen-shared"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f01be0cfd40aba59153236ab4b99062131b5bbe6f9f3d4bcb238bd2f96ff5262"
+checksum = "8f6190411c55dfd88e68f506dfdbd028da0551dca40793d40811ea03cb6e0f4a"
 
 [[package]]
 name = "cranelift-entity"
@@ -343,18 +343,18 @@ checksum = "0b65673279d75d34bf11af9660ae2dbd1c22e6d28f163f5c72f4e1dc56d56103"
 
 [[package]]
 name = "cranelift-entity"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ddae4fec5d6859233ffa175b61d269443c473b3971a2c3e69008c8d3e83d5825"
+checksum = "ed8aa1104f54509dfb386520711cd8a6a0992ae42ce2df06fdebdfff4de2c2dd"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "cranelift-frontend"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2cc3deb0df97748434cf9f7e404f1f5134f6a253fc9a6bca25c5cd6804c08d3"
+checksum = "d48087600d6c055f625754b1d9cc9cab36a0d26a365cbcb388825e331e0041ff"
 dependencies = [
  "cranelift-codegen",
  "log",
@@ -364,18 +364,15 @@ dependencies = [
 
 [[package]]
 name = "cranelift-isle"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc3bb54287de9c36ba354eb849fefb77b5e73955058745fd08f12cfdfa181866"
-dependencies = [
- "rayon",
-]
+checksum = "eead4df80ce3c68b913d071683790692a0316a67e3518b32e273169238876f0a"
 
 [[package]]
 name = "cranelift-native"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d8c2a4f2efdce1de1f94e74f12b3b4144e3bcafa6011338b87388325d72d2120"
+checksum = "3adde571ff9c6a77320b69ac03920c5ce70fed94f5f9ac53f5c0600a69fc142e"
 dependencies = [
  "cranelift-codegen",
  "libc",
@@ -384,12 +381,12 @@ dependencies = [
 
 [[package]]
 name = "cranelift-wasm"
-version = "0.89.0"
+version = "0.89.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f918c37eb01f5b5ccc632e0ef3b4bf9ee03b5d4c267d3d2d3b62720a6bce0180"
+checksum = "5ebe9c1a3e90365d3dfa8cf12899cd96e4da327ef37ad58e060a93705ddf5937"
 dependencies = [
  "cranelift-codegen",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "cranelift-frontend",
  "itertools",
  "log",
@@ -452,9 +449,9 @@ dependencies = [
 
 [[package]]
 name = "cxx"
-version = "1.0.79"
+version = "1.0.80"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3f83d0ebf42c6eafb8d7c52f7e5f2d3003b89c7aa4fd2b79229209459a849af8"
+checksum = "6b7d4e43b25d3c994662706a1d4fcfc32aaa6afd287502c111b237093bb23f3a"
 dependencies = [
  "cc",
  "cxxbridge-flags",
@@ -464,9 +461,9 @@ dependencies = [
 
 [[package]]
 name = "cxx-build"
-version = "1.0.79"
+version = "1.0.80"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "07d050484b55975889284352b0ffc2ecbda25c0c55978017c132b29ba0818a86"
+checksum = "84f8829ddc213e2c1368e51a2564c552b65a8cb6a28f31e576270ac81d5e5827"
 dependencies = [
  "cc",
  "codespan-reporting",
@@ -479,15 +476,15 @@ dependencies = [
 
 [[package]]
 name = "cxxbridge-flags"
-version = "1.0.79"
+version = "1.0.80"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "99d2199b00553eda8012dfec8d3b1c75fce747cf27c169a270b3b99e3448ab78"
+checksum = "e72537424b474af1460806647c41d4b6d35d09ef7fe031c5c2fa5766047cc56a"
 
 [[package]]
 name = "cxxbridge-macro"
-version = "1.0.79"
+version = "1.0.80"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcb67a6de1f602736dd7eaead0080cf3435df806c61b24b13328db128c58868f"
+checksum = "309e4fb93eed90e1e14bea0da16b209f81813ba9fc7830c20ed151dd7bc0a4d7"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -592,9 +589,9 @@ checksum = "4443176a9f2c162692bd3d352d745ef9413eec5782a80d8fd6f8a1ac692a07f7"
 
 [[package]]
 name = "fastly-shared"
-version = "0.8.7"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "238fb7af2219391cb024673302861adffd96cb3dbe4b602c2c7abef11ce5a5f9"
+checksum = "6f79939bdbbab8b1de759d584f386319454f8623681400675a07f9ad35f2b158"
 dependencies = [
  "bitflags",
  "http",
@@ -644,14 +641,14 @@ checksum = "a267b6a9304912e018610d53fe07115d8b530b160e85db4d2d3a59f3ddde1aec"
 dependencies = [
  "io-lifetimes",
  "rustix",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "futures"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f21eda599937fba36daeb58a22e8f5cee2d14c4a17b5b7739c7c8e5e3b8230c"
+checksum = "38390104763dc37a5145a53c29c63c1290b5d316d6086ec32c293f6736051bb0"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -664,9 +661,9 @@ dependencies = [
 
 [[package]]
 name = "futures-channel"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "30bdd20c28fadd505d0fd6712cdfcb0d4b5648baf45faef7f852afb2399bb050"
+checksum = "52ba265a92256105f45b719605a571ffe2d1f0fea3807304b522c1d778f79eed"
 dependencies = [
  "futures-core",
  "futures-sink",
@@ -674,15 +671,15 @@ dependencies = [
 
 [[package]]
 name = "futures-core"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4e5aa3de05362c3fb88de6531e6296e85cde7739cccad4b9dfeeb7f6ebce56bf"
+checksum = "04909a7a7e4633ae6c4a9ab280aeb86da1236243a77b694a49eacd659a4bd3ac"
 
 [[package]]
 name = "futures-executor"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9ff63c23854bee61b6e9cd331d523909f238fc7636290b96826e9cfa5faa00ab"
+checksum = "7acc85df6714c176ab5edf386123fafe217be88c0840ec11f199441134a074e2"
 dependencies = [
  "futures-core",
  "futures-task",
@@ -691,15 +688,15 @@ dependencies = [
 
 [[package]]
 name = "futures-io"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bbf4d2a7a308fd4578637c0b17c7e1c7ba127b8f6ba00b29f717e9655d85eb68"
+checksum = "00f5fb52a06bdcadeb54e8d3671f8888a39697dcb0b81b23b55174030427f4eb"
 
 [[package]]
 name = "futures-macro"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "42cd15d1c7456c04dbdf7e88bcd69760d74f3a798d6444e16974b505b0e62f17"
+checksum = "bdfb8ce053d86b91919aad980c220b1fb8401a9394410e1c289ed7e66b61835d"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -708,21 +705,21 @@ dependencies = [
 
 [[package]]
 name = "futures-sink"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "21b20ba5a92e727ba30e72834706623d94ac93a725410b6a6b6fbc1b07f7ba56"
+checksum = "39c15cf1a4aa79df40f1bb462fb39676d0ad9e366c2a33b590d7c66f4f81fcf9"
 
 [[package]]
 name = "futures-task"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a6508c467c73851293f390476d4491cf4d227dbabcd4170f3bb6044959b294f1"
+checksum = "2ffb393ac5d9a6eaa9d3fdf37ae2776656b706e200c8e16b1bdb227f5198e6ea"
 
 [[package]]
 name = "futures-util"
-version = "0.3.24"
+version = "0.3.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "44fb6cb1be61cc1d2e43b262516aafcf63b241cffdb1d3fa115f91d9c7b09c90"
+checksum = "197676987abd2f9cadff84926f410af1c183608d36641465df73ae8211dc65d6"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -757,9 +754,9 @@ dependencies = [
 
 [[package]]
 name = "getrandom"
-version = "0.2.7"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4eb1a864a501629691edf6c15a593b7a51eebaa1e8468e9ddc623de7c9b58ec6"
+checksum = "c05aeb6a22b8f62540c194aac980f2115af067bfe15a0734d7277a768d396b31"
 dependencies = [
  "cfg-if",
  "libc",
@@ -779,9 +776,9 @@ dependencies = [
 
 [[package]]
 name = "h2"
-version = "0.3.14"
+version = "0.3.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5ca32592cf21ac7ccab1825cd87f6c9b3d9022c44d086172ed0966bec8af30be"
+checksum = "5f9f29bc9dda355256b2916cf526ab02ce0aeaaaf2bad60d65ef3f12f11dd0f4"
 dependencies = [
  "bytes",
  "fnv",
@@ -871,9 +868,9 @@ checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
 
 [[package]]
 name = "hyper"
-version = "0.14.20"
+version = "0.14.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02c929dc5c39e335a03c405292728118860721b10190d98c2a0f0efd5baafbac"
+checksum = "abfba89e19b959ca163c7752ba59d737c1ceea53a5d31a149c805446fc958064"
 dependencies = [
  "bytes",
  "futures-channel",
@@ -895,9 +892,9 @@ dependencies = [
 
 [[package]]
 name = "iana-time-zone"
-version = "0.1.51"
+version = "0.1.53"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f5a6ef98976b22b3b7f2f3a806f858cb862044cfa66805aa3ad84cb3d3b785ed"
+checksum = "64c122667b287044802d6ce17ee2ddf13207ed924c712de9a66a5814d5b64765"
 dependencies = [
  "android_system_properties",
  "core-foundation-sys",
@@ -945,17 +942,17 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a5d8c2ab5becd8720e30fd25f8fa5500d8dc3fceadd8378f05859bd7b46fc49"
 dependencies = [
  "io-lifetimes",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "io-lifetimes"
-version = "0.7.3"
+version = "0.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ea37f355c05dde75b84bba2d767906ad522e97cd9e2eef2be7a4ab7fb442c06"
+checksum = "59ce5ef949d49ee85593fc4d3f3f95ad61657076395cbbce23e2121fc5542074"
 dependencies = [
  "libc",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -973,7 +970,7 @@ dependencies = [
  "hermit-abi 0.2.6",
  "io-lifetimes",
  "rustix",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
@@ -1043,9 +1040,9 @@ checksum = "884e2677b40cc8c339eaefcb701c32ef1fd2493d71118dc0ca4b6a736c93bd67"
 
 [[package]]
 name = "libc"
-version = "0.2.135"
+version = "0.2.137"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68783febc7782c6c5cb401fbda4de5a9898be1762314da0bb2c10ced61f18b0c"
+checksum = "fc7fcc620a3bff7cdd7a365be3376c97191aeaccc2a603e600951e452615bf89"
 
 [[package]]
 name = "link-cplusplus"
@@ -1140,14 +1137,14 @@ dependencies = [
 
 [[package]]
 name = "mio"
-version = "0.8.4"
+version = "0.8.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "57ee1c23c7c63b0c9250c339ffdc69255f110b298b901b9f6c82547b7b87caaf"
+checksum = "e5d732bc30207a6423068df043e3d02e0735b155ad7ce1a6f76fe2baa5b158de"
 dependencies = [
  "libc",
  "log",
  "wasi",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -1171,9 +1168,9 @@ dependencies = [
 
 [[package]]
 name = "num_cpus"
-version = "1.13.1"
+version = "1.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "19e64526ebdee182341572e50e9ad03965aa510cd94427a4549448f285e957a1"
+checksum = "f6058e64324c71e02bc2b150e4f3bc8286db6c83092132ffa3f6b1eab0f9def5"
 dependencies = [
  "hermit-abi 0.1.19",
  "libc",
@@ -1193,9 +1190,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.15.0"
+version = "1.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
+checksum = "86f0b0d4bf799edbc74508c1e8bf170ff5f41238e5f8225603ca7caaae2b7860"
 
 [[package]]
 name = "opaque-debug"
@@ -1221,15 +1218,15 @@ dependencies = [
 
 [[package]]
 name = "parking_lot_core"
-version = "0.9.3"
+version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09a279cbf25cb0757810394fbc1e359949b59e348145c643a939a525692e6929"
+checksum = "4dc9e0dc2adc1c69d09143aff38d3d30c5c3f0df0dad82e6d25547af174ebec0"
 dependencies = [
  "cfg-if",
  "libc",
  "redox_syscall",
  "smallvec",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -1385,9 +1382,9 @@ dependencies = [
 
 [[package]]
 name = "regalloc2"
-version = "0.4.1"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "69025b4a161879ba90719837c06621c3d73cffa147a000aeacf458f6a9572485"
+checksum = "91b2eab54204ea0117fe9a060537e0b07a4e72f7c7d182361ecc346cab2240e5"
 dependencies = [
  "fxhash",
  "log",
@@ -1444,9 +1441,9 @@ checksum = "7ef03e0a2b150c7a90d01faf6254c9c48a41e95fb2a8c2ac1c6f0d2b9aefc342"
 
 [[package]]
 name = "rustix"
-version = "0.35.11"
+version = "0.35.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fbb2fda4666def1433b1b05431ab402e42a1084285477222b72d6c564c417cef"
+checksum = "727a1a6d65f786ec22df8a81ca3121107f235970dc1705ed681d3e6e8b9cd5f9"
 dependencies = [
  "bitflags",
  "errno",
@@ -1455,7 +1452,7 @@ dependencies = [
  "libc",
  "linux-raw-sys",
  "once_cell",
- "windows-sys",
+ "windows-sys 0.42.0",
 ]
 
 [[package]]
@@ -1496,7 +1493,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "88d6731146462ea25d9244b2ed5fd1d716d25c52e4d54aa4fb0f3c4e9854dbe2"
 dependencies = [
  "lazy_static",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
@@ -1561,18 +1558,18 @@ checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 
 [[package]]
 name = "serde"
-version = "1.0.145"
+version = "1.0.147"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "728eb6351430bccb993660dfffc5a72f91ccc1295abaa8ce19b27ebe4f75568b"
+checksum = "d193d69bae983fc11a79df82342761dfbf28a99fc8d203dca4c3c1b590948965"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.145"
+version = "1.0.147"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "81fa1584d3d1bcacd84c277a0dfe21f5b0f6accf4a23d04d4c6d61f1af522b4c"
+checksum = "4f1d362ca8fc9c3e3a7484440752472d68a6caa98f1ab81d99b5dfe517cec852"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1581,9 +1578,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.86"
+version = "1.0.87"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "41feea4228a6f1cd09ec7a3593a682276702cd67b5273544757dae23c096f074"
+checksum = "6ce777b7b150d76b9cf60d28b55f5847135a003f7d7350c6be7a773508ce7d45"
 dependencies = [
  "itoa",
  "ryu",
@@ -1675,9 +1672,9 @@ checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 
 [[package]]
 name = "syn"
-version = "1.0.102"
+version = "1.0.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3fcd952facd492f9be3ef0d0b7032a6e442ee9b361d4acc2b1d0c4aaa5f613a1"
+checksum = "a864042229133ada95abf3b54fdc62ef5ccabe9515b64717bcb9a1919e59445d"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1696,7 +1693,7 @@ dependencies = [
  "cap-std",
  "io-lifetimes",
  "rustix",
- "windows-sys",
+ "windows-sys 0.36.1",
  "winx",
 ]
 
@@ -2054,9 +2051,9 @@ checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
 
 [[package]]
 name = "wasi-cap-std-sync"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6fa9ddcfc9d85e89a10c27801376ea57d2e9421ad91336326160c56044049b49"
+checksum = "ea3e0d556c3f9c2481c2d15eee7ad4b0b25db206d034aa80b16ff1299e7cd679"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -2073,14 +2070,14 @@ dependencies = [
  "system-interface",
  "tracing",
  "wasi-common",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasi-common"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fd86a0cd870709441a25d63737bd416db6cf8eb6229c0da08d29d7ab79108bbb"
+checksum = "5e924b71f77144f65e173478d43be57ee9e16a9b8f7b8a41223b689051b3c176"
 dependencies = [
  "anyhow",
  "bitflags",
@@ -2091,14 +2088,14 @@ dependencies = [
  "thiserror",
  "tracing",
  "wiggle",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasi-tokio"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "50eae69cf1ad9de30bb7d604c5433d38d2aec1e32dac6bc89ef30ab7a0860381"
+checksum = "a2ab5198e9d48ad1991c507eef9a4dca953ed0077fc1597b09e808cae74c05b5"
 dependencies = [
  "anyhow",
  "cap-std",
@@ -2167,9 +2164,9 @@ checksum = "1c38c045535d93ec4f0b4defec448e4291638ee608530863b1e2ba115d4fff7f"
 
 [[package]]
 name = "wasm-encoder"
-version = "0.18.0"
+version = "0.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c64ac98d5d61192cc45c701b7e4bd0b9aff91e2edfc7a088406cfe2288581e2c"
+checksum = "c5816e88e8ea7335016aa62eb0485747f786136d505a9b3890f8c400211d9b5f"
 dependencies = [
  "leb128",
 ]
@@ -2185,9 +2182,9 @@ dependencies = [
 
 [[package]]
 name = "wasmtime"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f5fc5bb3329415030796cfa5530b2481ccef5c4f1e5150733ba94318ab004fe1"
+checksum = "63e4f0c3cbaed050686095e5fde04f28eada1ef6196b456ffce7df2115cc2a38"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -2211,23 +2208,23 @@ dependencies = [
  "wasmtime-jit",
  "wasmtime-runtime",
  "wat",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-asm-macros"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "db36545ff0940ad9bf4e9ab0ec2a4e1eaa5ebe2aa9227bcbc4af905375d9e482"
+checksum = "41f17b9bf1ff3ed08f35dd3faa8fe0dc34693939252e47a3a056073d28fcd6d7"
 dependencies = [
  "cfg-if",
 ]
 
 [[package]]
 name = "wasmtime-cache"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2c2101b211d9db7db8bcfb2ffa69e119fa99a20266d0e5f19bb989cb6c3280d7"
+checksum = "ba1bfca72e269de2b96dc77a8fe64816d9cc6c6ad416a3aba9a51f4ff6bcefc1"
 dependencies = [
  "anyhow",
  "base64",
@@ -2239,19 +2236,19 @@ dependencies = [
  "serde",
  "sha2",
  "toml",
- "windows-sys",
+ "windows-sys 0.36.1",
  "zstd",
 ]
 
 [[package]]
 name = "wasmtime-cranelift"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0409e93b5eceaa4e5f498a4bce1cffc7ebe071d14582b5437c10af4aecc23f54"
+checksum = "d4d237bf7d2bcaea5e8018e088668e80b4448e002667d58c414fdcbb8f56ba0e"
 dependencies = [
  "anyhow",
  "cranelift-codegen",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "cranelift-frontend",
  "cranelift-native",
  "cranelift-wasm",
@@ -2266,12 +2263,12 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-environ"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "55240389c604f68d2e1d2573d7d3740246ab9ea2fa4fe79e10ccd51faf9b9500"
+checksum = "c432df5094f397e43467eca9775254850231d9047b3513a8e1f28a5778a90dfc"
 dependencies = [
  "anyhow",
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "gimli",
  "indexmap",
  "log",
@@ -2285,22 +2282,22 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-fiber"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "abb9b7b94f7b40d98665feca2338808cf449fa671d01be7176861f8d9aa4a012"
+checksum = "331439bc204d5395b89a018d5aa11aaeb5819c733db40fe8bd1d4ce88bf85be1"
 dependencies = [
  "cc",
  "cfg-if",
  "rustix",
  "wasmtime-asm-macros",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-jit"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bc15e285b7073ee566e62ea4b6dd38b80465ade0ea8cd4cee13c7ac2e295cfca"
+checksum = "f0e1f06e0ab975f0e9dd6b2db9364209272625d5348d02b0b846cf62f102e89c"
 dependencies = [
  "addr2line",
  "anyhow",
@@ -2319,14 +2316,14 @@ dependencies = [
  "wasmtime-environ",
  "wasmtime-jit-debug",
  "wasmtime-runtime",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-jit-debug"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bee06d206bcf7a875eacd1e1e957c2a63f64a92934d2535dd8e15cde6d3a9ffe"
+checksum = "07ca7aeb81909fc7688e1318fc247de2fb7ef2b638aa7501b45f7f6ad710f989"
 dependencies = [
  "object",
  "once_cell",
@@ -2335,9 +2332,9 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-runtime"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9969ff36cbf57f18c2d24679db57d0857ea7cc7d839534afc26ecc8003e9914b"
+checksum = "16069dff65b648d121d9b5ecbeb7319035f9a5aafd370d713c90a7f23db4d823"
 dependencies = [
  "anyhow",
  "cc",
@@ -2356,16 +2353,16 @@ dependencies = [
  "wasmtime-environ",
  "wasmtime-fiber",
  "wasmtime-jit-debug",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
 name = "wasmtime-types"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df64c737fc9b3cdf7617bcc65e8b97cb713ceb9c9c58530b20788a8a3482b5d1"
+checksum = "8926344aff6324e6469aa17345bbb29ef9de4fe934bde30a05be28ebf21e0a23"
 dependencies = [
- "cranelift-entity 0.89.0",
+ "cranelift-entity 0.89.1",
  "serde",
  "thiserror",
  "wasmparser",
@@ -2373,9 +2370,9 @@ dependencies = [
 
 [[package]]
 name = "wasmtime-wasi"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fb41d16dfd153d2078ea2347d311cee6c74f2a4ecc109cd9acaf860709137fdb"
+checksum = "26e67b408714dc3fe9f7eaab091a45b9bbfed9f983bd16e0dc209fa4456d903f"
 dependencies = [
  "anyhow",
  "wasi-cap-std-sync",
@@ -2396,9 +2393,9 @@ dependencies = [
 
 [[package]]
 name = "wast"
-version = "47.0.1"
+version = "48.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02b98502f3978adea49551e801a6687678e6015317d7d9470a67fe813393f2a8"
+checksum = "84825b5ac7164df8260c9e2b2e814075334edbe7ac426f2469b93a5eeac23cce"
 dependencies = [
  "leb128",
  "memchr",
@@ -2408,11 +2405,11 @@ dependencies = [
 
 [[package]]
 name = "wat"
-version = "1.0.49"
+version = "1.0.50"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7aab4e20c60429fbba9670a6cae0fff9520046ba0aa3e6d0b1cd2653bea14898"
+checksum = "129da4a03ec6d2a815f42c88f641824e789d5be0d86d2f90aa8a218c7068e0be"
 dependencies = [
- "wast 47.0.1",
+ "wast 48.0.0",
 ]
 
 [[package]]
@@ -2437,9 +2434,9 @@ dependencies = [
 
 [[package]]
 name = "wiggle"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2943156975c608cab1b44d28becba4196b07f18be92ea28f1e7f3372a12d81dd"
+checksum = "d55b0d7302192e47c1c2b1706790dab42cd42342ac58c4acb3d589daf56cddf0"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -2453,9 +2450,9 @@ dependencies = [
 
 [[package]]
 name = "wiggle-generate"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0321263a6b1ba1e0a97174524891a14907cee68cfa183fd5389088dffbeab668"
+checksum = "e164de81eea233c6b4e430e6cba4ff3953e3594fd0068633651994a5f0750a0a"
 dependencies = [
  "anyhow",
  "heck",
@@ -2468,9 +2465,9 @@ dependencies = [
 
 [[package]]
 name = "wiggle-macro"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa3d3794e5d68ef69f30e65f267c6bf18c920750d3ccd2a3ac04e77d95f66b96"
+checksum = "829a1543aa92a51f64e38f1dfcf16adfe447aefff3a2c281cf8ddf35c9797255"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2515,43 +2512,100 @@ version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ea04155a16a59f9eab786fe12a4a450e75cdb175f9e0d80da1e17db09f55b8d2"
 dependencies = [
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_msvc",
+ "windows_aarch64_msvc 0.36.1",
+ "windows_i686_gnu 0.36.1",
+ "windows_i686_msvc 0.36.1",
+ "windows_x86_64_gnu 0.36.1",
+ "windows_x86_64_msvc 0.36.1",
 ]
 
+[[package]]
+name = "windows-sys"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a3e1820f08b8513f676f7ab6c1f99ff312fb97b553d30ff4dd86f9f15728aa7"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc 0.42.0",
+ "windows_i686_gnu 0.42.0",
+ "windows_i686_msvc 0.42.0",
+ "windows_x86_64_gnu 0.42.0",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc 0.42.0",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41d2aa71f6f0cbe00ae5167d90ef3cfe66527d6f613ca78ac8024c3ccab9a19e"
+
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9bb8c3fd39ade2d67e9874ac4f3db21f0d710bee00fe7cab16949ec184eeaa47"
 
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd0f252f5a35cac83d6311b2e795981f5ee6e67eb1f9a7f64eb4500fbc4dcdb4"
+
 [[package]]
 name = "windows_i686_gnu"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "180e6ccf01daf4c426b846dfc66db1fc518f074baa793aa7d9b9aaeffad6a3b6"
 
+[[package]]
+name = "windows_i686_gnu"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fbeae19f6716841636c28d695375df17562ca208b2b7d0dc47635a50ae6c5de7"
+
 [[package]]
 name = "windows_i686_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2e7917148b2812d1eeafaeb22a97e4813dfa60a3f8f78ebe204bcc88f12f024"
 
+[[package]]
+name = "windows_i686_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "84c12f65daa39dd2babe6e442988fc329d6243fdce47d7d2d155b8d874862246"
+
 [[package]]
 name = "windows_x86_64_gnu"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4dcd171b8776c41b97521e5da127a2d86ad280114807d0b2ab1e462bc764d9e1"
 
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf7b1b21b5362cbc318f686150e5bcea75ecedc74dd157d874d754a2ca44b0ed"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09d525d2ba30eeb3297665bd434a54297e4170c7f1a44cad4ef58095b4cd2028"
+
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"
 
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f40009d85759725a34da6d89a94e63d7bdc50a862acf0dbc7c8e488f1edcb6f5"
+
 [[package]]
 name = "winx"
 version = "0.33.0"
@@ -2560,7 +2614,7 @@ checksum = "b7b01e010390eb263a4518c8cebf86cb67469d1511c00b749a47b64c39e8054d"
 dependencies = [
  "bitflags",
  "io-lifetimes",
- "windows-sys",
+ "windows-sys 0.36.1",
 ]
 
 [[package]]
diff --git a/lib/compute-at-edge-abi/compute-at-edge.witx b/lib/compute-at-edge-abi/compute-at-edge.witx
index 575ca97a..36319394 100644
--- a/lib/compute-at-edge-abi/compute-at-edge.witx
+++ b/lib/compute-at-edge-abi/compute-at-edge.witx
@@ -508,6 +508,36 @@
     )
 )
 
+(module $fastly_async_io
+    ;;; Blocks until one of the given objects is ready for I/O, or the optional timeout expires.
+    ;;;
+    ;;; Valid object handles includes bodies and pending requests. See the `async_item_handle`
+    ;;; definition for more details, including what I/O actions are associated with each handle
+    ;;; type.
+    ;;;
+    ;;; The timeout is specified in milliseconds, or 0 if no timeout is desired.
+    ;;;
+    ;;; Returns the _index_ (not handle!) of the first object that is ready, or u32::MAX if the
+    ;;; timeout expires before any objects are ready for I/O.
+    (@interface func (export "select")
+        (param $hs (list $async_item_handle))
+        (param $timeout_ms u32)
+        (result $err (expected $ready_idx (error $fastly_status)))
+    )
+
+    ;;; Returns 1 if the given async item is "ready" for its associated I/O action, 0 otherwise.
+    ;;;
+    ;;; If an object is ready, the I/O action is guaranteed to complete without blocking.
+    ;;;
+    ;;; Valid object handles includes bodies and pending requests. See the `async_item_handle`
+    ;;; definition for more details, including what I/O actions are associated with each handle
+    ;;; type.
+    (@interface func (export "is_ready")
+        (param $handle $async_item_handle)
+        (result $err (expected $is_done (error $fastly_status)))
+    )
+)
+
 (module $fastly_purge
     (@interface func (export "purge_surrogate_key")
         (param $surrogate_key string)
diff --git a/lib/compute-at-edge-abi/typenames.witx b/lib/compute-at-edge-abi/typenames.witx
index ee1aa96e..4d1a9b42 100644
--- a/lib/compute-at-edge-abi/typenames.witx
+++ b/lib/compute-at-edge-abi/typenames.witx
@@ -94,6 +94,19 @@
 (typename $dictionary_handle (handle))
 ;;; A handle to an Object Store.
 (typename $object_store_handle (handle))
+;;; A handle to an object supporting generic async operations.
+;;; Can be either a `body_handle` or a `pending_request_handle`.
+;;;
+;;; Each async item has an associated I/O action:
+;;;
+;;; * Pending requests: awaiting the response headers / `Response` object
+;;; * Normal bodies: reading bytes from the body
+;;; * Streaming bodies: writing bytes to the body
+;;;
+;;; For writing bytes, note that there is a large host-side buffer that bytes can eagerly be written
+;;; into, even before the origin itself consumes that data.
+(typename $async_item_handle (handle))
+
 
 ;;; A "multi-value" cursor.
 (typename $multi_value_cursor u32)
@@ -117,6 +130,7 @@
 (typename $is_done u32)
 (typename $done_idx u32)
 (typename $inserted u32)
+(typename $ready_idx u32)
 
 (typename $content_encodings
     (flags (@witx repr u32)
diff --git a/lib/src/async_io.rs b/lib/src/async_io.rs
new file mode 100644
index 00000000..ee7a8cc2
--- /dev/null
+++ b/lib/src/async_io.rs
@@ -0,0 +1,50 @@
+use {
+    crate::{
+        error::Error,
+        session::Session,
+        wiggle_abi::{fastly_async_io::FastlyAsyncIo, types::AsyncItemHandle},
+    },
+    futures::{FutureExt, TryFutureExt},
+    std::time::Duration,
+    tokio::time::timeout,
+    wiggle::GuestPtr,
+};
+
+#[wiggle::async_trait]
+impl FastlyAsyncIo for Session {
+    async fn select<'a>(
+        &mut self,
+        handles: &GuestPtr<'a, [AsyncItemHandle]>,
+        timeout_ms: u32,
+    ) -> Result<u32, Error> {
+        let handles = handles.as_slice()?;
+        if handles.len() == 0 && timeout_ms == 0 {
+            return Err(Error::InvalidArgument);
+        }
+
+        let select_fut = self
+            .select_impl(handles.iter().copied().map(Into::into))
+            .map_ok(|done_idx| done_idx as u32);
+
+        if timeout_ms == 0 {
+            select_fut.await
+        } else {
+            timeout(Duration::from_millis(timeout_ms as u64), select_fut)
+                .await
+                .unwrap_or(Ok(u32::MAX))
+        }
+    }
+    fn is_ready(&mut self, handle: AsyncItemHandle) -> Result<u32, Error> {
+        if self
+            .async_item_mut(handle.into())?
+            .unwrap()
+            .await_ready()
+            .now_or_never()
+            .is_some()
+        {
+            Ok(1)
+        } else {
+            Ok(0)
+        }
+    }
+}
diff --git a/lib/src/body.rs b/lib/src/body.rs
index 047cbf76..e26186f7 100644
--- a/lib/src/body.rs
+++ b/lib/src/body.rs
@@ -131,6 +131,16 @@ impl Body {
     pub async fn read_into_string(self) -> Result<String, error::Error> {
         Ok(String::from_utf8(self.read_into_vec().await?).expect("Body was not UTF-8"))
     }
+
+    /// Block until the body has a chunk ready (or is known to be empty).
+    pub async fn await_ready(&mut self) {
+        // Attempt to read a chunk, blocking until one is available (or `None` signals end of stream)
+        if let Some(Ok(chunk)) = self.data().await {
+            // If we did get a chunk, put it back; subsequent read attempts will find this chunk without
+            // additional blocking.
+            self.chunks.push_front(chunk.into())
+        }
+    }
 }
 
 impl<T: Into<Chunk>> From<T> for Body {
diff --git a/lib/src/error.rs b/lib/src/error.rs
index b3684ece..5156c77d 100644
--- a/lib/src/error.rs
+++ b/lib/src/error.rs
@@ -222,10 +222,12 @@ pub enum HandleError {
     /// A dictionary handle was not valid.
     #[error("Invalid dictionary handle: {0}")]
     InvalidDictionaryHandle(crate::wiggle_abi::types::DictionaryHandle),
-
     /// An object-store handle was not valid.
     #[error("Invalid object-store handle: {0}")]
     InvalidObjectStoreHandle(crate::wiggle_abi::types::ObjectStoreHandle),
+    /// An async item handle was not valid.
+    #[error("Invalid async item handle: {0}")]
+    InvalidAsyncItemHandle(crate::wiggle_abi::types::AsyncItemHandle),
 }
 
 /// Errors that can occur in a worker thread running a guest module.
diff --git a/lib/src/lib.rs b/lib/src/lib.rs
index 408be855..9abcf1c7 100644
--- a/lib/src/lib.rs
+++ b/lib/src/lib.rs
@@ -19,6 +19,7 @@ pub mod error;
 pub mod logging;
 pub mod session;
 
+mod async_io;
 mod downstream;
 mod execute;
 mod headers;
diff --git a/lib/src/linking.rs b/lib/src/linking.rs
index be5bd278..55197202 100644
--- a/lib/src/linking.rs
+++ b/lib/src/linking.rs
@@ -90,6 +90,7 @@ pub fn link_host_functions(linker: &mut Linker<WasmCtx>) -> Result<(), Error> {
     wiggle_abi::fastly_object_store::add_to_linker(linker, WasmCtx::session)?;
     wiggle_abi::fastly_purge::add_to_linker(linker, WasmCtx::session)?;
     wiggle_abi::fastly_uap::add_to_linker(linker, WasmCtx::session)?;
+    wiggle_abi::fastly_async_io::add_to_linker(linker, WasmCtx::session)?;
     link_legacy_aliases(linker)?;
     Ok(())
 }
diff --git a/lib/src/session.rs b/lib/src/session.rs
index 03139e8f..d8d923a6 100644
--- a/lib/src/session.rs
+++ b/lib/src/session.rs
@@ -3,8 +3,10 @@
 mod async_item;
 mod downstream;
 
+pub use async_item::AsyncItem;
+
 use {
-    self::{async_item::AsyncItem, downstream::DownstreamResponse},
+    self::downstream::DownstreamResponse,
     crate::{
         body::Body,
         config::{Backend, Backends, Dictionaries, Dictionary, DictionaryName, Geolocation},
@@ -14,13 +16,14 @@ use {
         streaming_body::StreamingBody,
         upstream::{PendingRequest, SelectTarget, TlsConfig},
         wiggle_abi::types::{
-            BodyHandle, ContentEncodings, DictionaryHandle, EndpointHandle, ObjectStoreHandle,
-            PendingRequestHandle, RequestHandle, ResponseHandle,
+            self, BodyHandle, ContentEncodings, DictionaryHandle, EndpointHandle,
+            ObjectStoreHandle, PendingRequestHandle, RequestHandle, ResponseHandle,
         },
     },
     cranelift_entity::{entity_impl, PrimaryMap},
+    futures::future::{self, FutureExt},
     http::{request, response, HeaderMap, Request, Response},
-    std::{collections::HashMap, net::IpAddr, path::PathBuf, sync::Arc},
+    std::{collections::HashMap, future::Future, net::IpAddr, path::PathBuf, sync::Arc},
     tokio::sync::oneshot::Sender,
 };
 
@@ -695,26 +698,36 @@ impl Session {
             .ok_or(HandleError::InvalidPendingRequestHandle(handle))
     }
 
+    pub fn reinsert_pending_request(
+        &mut self,
+        handle: PendingRequestHandle,
+        pending_req: PendingRequest,
+    ) -> Result<(), HandleError> {
+        *self
+            .async_items
+            .get_mut(handle.into())
+            .ok_or(HandleError::InvalidPendingRequestHandle(handle))? =
+            Some(AsyncItem::PendingReq(pending_req));
+        Ok(())
+    }
+
     /// Take ownership of multiple [`PendingRequest`]s in preparation for a `select`.
     ///
     /// Returns a [`HandleError`] if any of the handles are not associated with a pending
     /// request in the session.
     pub fn prepare_select_targets(
         &mut self,
-        handles: &[PendingRequestHandle],
+        handles: impl IntoIterator<Item = AsyncItemHandle>,
     ) -> Result<Vec<SelectTarget>, HandleError> {
         // Prepare a vector of targets from the given handles; if any of the handles are invalid,
         // put back all the targets we've extracted so far
         let mut targets = vec![];
-        for handle in handles.iter().copied() {
-            if let Ok(pending_req) = self.take_pending_request(handle) {
-                targets.push(SelectTarget {
-                    handle,
-                    pending_req,
-                });
+        for handle in handles {
+            if let Ok(item) = self.take_async_item(handle) {
+                targets.push(SelectTarget { handle, item });
             } else {
                 self.reinsert_select_targets(targets);
-                return Err(HandleError::InvalidPendingRequestHandle(handle));
+                return Err(HandleError::InvalidPendingRequestHandle(handle.into()));
             }
         }
         Ok(targets)
@@ -724,8 +737,7 @@ impl Session {
     /// stored within each [`SelectTarget`].
     pub fn reinsert_select_targets(&mut self, targets: Vec<SelectTarget>) {
         for target in targets {
-            let async_handle: AsyncItemHandle = target.handle.into();
-            self.async_items[async_handle] = Some(AsyncItem::PendingReq(target.pending_req));
+            self.async_items[target.handle] = Some(target.item);
         }
     }
 
@@ -738,6 +750,73 @@ impl Session {
     pub fn config_path(&self) -> &Arc<Option<PathBuf>> {
         &self.config_path
     }
+
+    pub fn async_item_mut(
+        &mut self,
+        handle: AsyncItemHandle,
+    ) -> Result<Option<&mut AsyncItem>, HandleError> {
+        self.async_items
+            .get_mut(handle)
+            .map(|ai| ai.as_mut())
+            .ok_or_else(|| HandleError::InvalidAsyncItemHandle(handle.into()))
+    }
+
+    pub fn take_async_item(&mut self, handle: AsyncItemHandle) -> Result<AsyncItem, HandleError> {
+        // check that this is an async item before removing it
+        let _ = self.async_item_mut(handle)?;
+
+        self.async_items
+            .get_mut(handle)
+            .and_then(|tracked| tracked.take())
+            .ok_or_else(|| HandleError::InvalidAsyncItemHandle(handle.into()))
+    }
+
+    pub async fn select_impl(
+        &mut self,
+        handles: impl IntoIterator<Item = AsyncItemHandle>,
+    ) -> Result<usize, Error> {
+        // we have to temporarily move the async items out of the session table,
+        // because we need &mut borrows of all of them simultaneously.
+        let targets = self.prepare_select_targets(handles)?;
+        let mut selected = SelectedTargets::new(self, targets);
+        let done_index = selected.future().await;
+
+        Ok(done_index)
+    }
+}
+
+pub struct SelectedTargets<'session> {
+    session: &'session mut Session,
+    targets: Vec<SelectTarget>,
+}
+
+impl<'session> SelectedTargets<'session> {
+    fn new(session: &'session mut Session, targets: Vec<SelectTarget>) -> Self {
+        Self { session, targets }
+    }
+
+    fn future(&mut self) -> Box<dyn Future<Output = usize> + Unpin + Send + Sync + '_> {
+        // for each target, we produce a future for checking on the "readiness"
+        // of the associated primary I/O operation
+        let mut futures = Vec::new();
+        for target in &mut *self.targets {
+            futures.push(Box::pin(target.item.await_ready()))
+        }
+        if futures.is_empty() {
+            // if there are no futures, we wait forever; this waiting will always be bounded by a timeout,
+            // since the `select` hostcall requires a timeout when no handles are given.
+            Box::new(future::pending())
+        } else {
+            Box::new(future::select_all(futures).map(|f| f.1))
+        }
+    }
+}
+
+impl<'session> Drop for SelectedTargets<'session> {
+    fn drop(&mut self) {
+        let targets = std::mem::replace(&mut self.targets, Vec::new());
+        self.session.reinsert_select_targets(targets);
+    }
 }
 
 /// Additional Viceroy-specific metadata for requests.
@@ -788,3 +867,15 @@ impl From<AsyncItemHandle> for PendingRequestHandle {
         PendingRequestHandle::from(h.as_u32())
     }
 }
+
+impl From<types::AsyncItemHandle> for AsyncItemHandle {
+    fn from(h: types::AsyncItemHandle) -> AsyncItemHandle {
+        AsyncItemHandle::from_u32(h.into())
+    }
+}
+
+impl From<AsyncItemHandle> for types::AsyncItemHandle {
+    fn from(h: AsyncItemHandle) -> types::AsyncItemHandle {
+        types::AsyncItemHandle::from(h.as_u32())
+    }
+}
diff --git a/lib/src/session/async_item.rs b/lib/src/session/async_item.rs
index fe0c3930..75a4c95d 100644
--- a/lib/src/session/async_item.rs
+++ b/lib/src/session/async_item.rs
@@ -85,4 +85,12 @@ impl AsyncItem {
             _ => None,
         }
     }
+
+    pub async fn await_ready(&mut self) {
+        match self {
+            Self::StreamingBody(body) => body.await_ready().await,
+            Self::Body(body) => body.await_ready().await,
+            Self::PendingReq(req) => req.await_ready().await,
+        }
+    }
 }
diff --git a/lib/src/streaming_body.rs b/lib/src/streaming_body.rs
index 3eafe068..78c3d427 100644
--- a/lib/src/streaming_body.rs
+++ b/lib/src/streaming_body.rs
@@ -5,7 +5,7 @@ use tokio::sync::mpsc;
 //
 // this isn't a tremendously useful size limiter, as it controls the number of chunks that can be in
 // flight before applying backpressure, as opposed to the size of data in those chunks
-const STREAMING_CHANNEL_SIZE: usize = 128;
+const STREAMING_CHANNEL_SIZE: usize = 8;
 
 /// The "write end" of a streaming body, used for writing to the body of a streaming upstream request
 /// or a streaming downstream response.
@@ -33,4 +33,9 @@ impl StreamingBody {
             .await
             .map_err(|_| Error::StreamingChunkSend)
     }
+
+    /// Block until the body has room for writing additional chunks.
+    pub async fn await_ready(&mut self) {
+        let _ = self.sender.reserve().await;
+    }
 }
diff --git a/lib/src/upstream.rs b/lib/src/upstream.rs
index 2b75c4a0..1f8f8e2a 100644
--- a/lib/src/upstream.rs
+++ b/lib/src/upstream.rs
@@ -3,8 +3,8 @@ use crate::{
     config::Backend,
     error::Error,
     headers::filter_outgoing_headers,
-    session::ViceroyRequestMetadata,
-    wiggle_abi::types::{ContentEncodings, PendingRequestHandle},
+    session::{AsyncItem, AsyncItemHandle, ViceroyRequestMetadata},
+    wiggle_abi::types::ContentEncodings,
 };
 use futures::Future;
 use http::{uri, HeaderValue};
@@ -19,7 +19,7 @@ use std::{
 use tokio::{
     io::{AsyncRead, AsyncWrite, ReadBuf},
     net::TcpStream,
-    sync::oneshot,
+    sync::oneshot::{self, error::TryRecvError},
 };
 use tokio_rustls::{client::TlsStream, TlsConnector};
 use tracing::warn;
@@ -272,13 +272,14 @@ pub fn send_request(
 }
 
 /// The type ultimately yielded by a `PendingRequest`.
-pub type ResponseResult = Result<Response<Body>, Error>;
+pub type PendingRequestResult = Result<Response<Body>, Error>;
 
 /// An asynchronous request awaiting a response.
 #[derive(Debug)]
-pub struct PendingRequest {
+pub enum PendingRequest {
     // NB: we use channels rather than a `JoinHandle` in order to support the `poll` API.
-    receiver: oneshot::Receiver<ResponseResult>,
+    Waiting(oneshot::Receiver<PendingRequestResult>),
+    Complete(PendingRequestResult),
 }
 
 impl PendingRequest {
@@ -289,26 +290,44 @@ impl PendingRequest {
     ) -> Self {
         let (sender, receiver) = oneshot::channel();
         tokio::task::spawn(async move { sender.send(req.await) });
-        Self { receiver }
+        Self::Waiting(receiver)
     }
 
     /// Check whether a response happens to be available for this pending request.
     ///
     /// This function does _not_ block, nor does it require being in an `async` context.
-    pub fn poll(&mut self) -> Option<ResponseResult> {
-        match self.receiver.try_recv() {
-            Err(oneshot::error::TryRecvError::Closed) => {
-                panic!("Pending request sender was dropped")
-            }
-            // the request is still in flight
-            Err(oneshot::error::TryRecvError::Empty) => None,
-            Ok(res) => Some(res),
+    pub fn poll(&mut self) {
+        match self {
+            Self::Waiting(ref mut rx) => match rx.try_recv() {
+                Err(TryRecvError::Closed) => {
+                    panic!("Pending request sender was dropped")
+                }
+                // the request is still in flight
+                Err(TryRecvError::Empty) => {}
+                Ok(res) => *self = Self::Complete(res),
+            },
+            // the request is already completed
+            Self::Complete(_) => {}
         }
     }
 
     /// Block until the response is ready, and then return it.
-    pub async fn wait(self) -> ResponseResult {
-        self.receiver.await.expect("Pending request receiver error")
+    pub async fn wait(mut self) -> PendingRequestResult {
+        self.await_ready().await;
+        match self {
+            Self::Complete(res) => res,
+            Self::Waiting(_) => unreachable!("PendingRequest should have completed"),
+        }
+    }
+
+    pub async fn await_ready(&mut self) {
+        if let Self::Waiting(rx) = self {
+            let res = match rx.await {
+                Err(_) => panic!("Pending request was unable to complete"),
+                Ok(res) => res,
+            };
+            *self = Self::Complete(res);
+        }
     }
 }
 
@@ -319,21 +338,8 @@ impl PendingRequest {
 /// the leftover futures. We have to build our own future to keep the handle-receiver association.
 #[derive(Debug)]
 pub struct SelectTarget {
-    pub handle: PendingRequestHandle,
-    pub pending_req: PendingRequest,
-}
-
-impl Future for SelectTarget {
-    type Output = ResponseResult;
-
-    fn poll(
-        mut self: std::pin::Pin<&mut Self>,
-        cx: &mut std::task::Context,
-    ) -> std::task::Poll<Self::Output> {
-        std::pin::Pin::new(&mut self.pending_req.receiver)
-            .poll(cx)
-            .map(|res| res.expect("Pending request receiver was dropped"))
-    }
+    pub handle: AsyncItemHandle,
+    pub item: AsyncItem,
 }
 
 // Boilerplate forwarding implementations for `Connection`:
diff --git a/lib/src/wiggle_abi.rs b/lib/src/wiggle_abi.rs
index 92d55998..707872c3 100644
--- a/lib/src/wiggle_abi.rs
+++ b/lib/src/wiggle_abi.rs
@@ -65,6 +65,7 @@ wiggle::from_witx!({
     witx: ["$CARGO_MANIFEST_DIR/compute-at-edge-abi/compute-at-edge.witx"],
     errors: { fastly_status => Error },
     async: {
+        fastly_async_io::{select},
         fastly_object_store::{insert},
         fastly_http_body::{append, read, write},
         fastly_http_req::{pending_req_select, pending_req_wait, send},
diff --git a/lib/src/wiggle_abi/entity.rs b/lib/src/wiggle_abi/entity.rs
index e878bf65..3efa55af 100644
--- a/lib/src/wiggle_abi/entity.rs
+++ b/lib/src/wiggle_abi/entity.rs
@@ -3,8 +3,8 @@
 //! [ref]: https://docs.rs/cranelift-entity/latest/cranelift_entity/trait.EntityRef.html
 
 use super::types::{
-    BodyHandle, DictionaryHandle, EndpointHandle, ObjectStoreHandle, PendingRequestHandle,
-    RequestHandle, ResponseHandle,
+    AsyncItemHandle, BodyHandle, DictionaryHandle, EndpointHandle, ObjectStoreHandle,
+    PendingRequestHandle, RequestHandle, ResponseHandle,
 };
 
 /// Macro which implements a 32-bit entity reference for handles generated by Wiggle.
@@ -46,3 +46,4 @@ wiggle_entity!(EndpointHandle);
 wiggle_entity!(PendingRequestHandle);
 wiggle_entity!(DictionaryHandle);
 wiggle_entity!(ObjectStoreHandle);
+wiggle_entity!(AsyncItemHandle);
diff --git a/lib/src/wiggle_abi/req_impl.rs b/lib/src/wiggle_abi/req_impl.rs
index 101eef10..60b93dac 100644
--- a/lib/src/wiggle_abi/req_impl.rs
+++ b/lib/src/wiggle_abi/req_impl.rs
@@ -4,7 +4,7 @@ use {
     crate::{
         config::Backend,
         error::Error,
-        session::{Session, ViceroyRequestMetadata},
+        session::{AsyncItem, Session, ViceroyRequestMetadata},
         upstream::{self, PendingRequest},
         wiggle_abi::{
             fastly_http_req::FastlyHttpReq,
@@ -569,17 +569,22 @@ impl FastlyHttpReq for Session {
         &mut self,
         pending_req_handle: PendingRequestHandle,
     ) -> Result<(u32, ResponseHandle, BodyHandle), Error> {
-        let pending_req = self.pending_request_mut(pending_req_handle)?;
-
-        let outcome = match pending_req.poll() {
-            None => (0, INVALID_REQUEST_HANDLE.into(), INVALID_BODY_HANDLE.into()),
-            Some(resp) => {
-                // the request is done; remove it from the map
-                drop(self.take_pending_request(pending_req_handle)?);
+        let mut pending_req = self.take_pending_request(pending_req_handle)?;
+        pending_req.poll();
+
+        let outcome = match pending_req {
+            PendingRequest::Waiting(_) => {
+                // Make sure to reinsert if pending
+                self.reinsert_pending_request(pending_req_handle, pending_req)?;
+                (0, INVALID_REQUEST_HANDLE.into(), INVALID_BODY_HANDLE.into())
+            }
+            PendingRequest::Complete(resp) => {
+                // the request is done so we will not reinsert it into the map
                 let (resp_handle, resp_body_handle) = self.insert_response(resp?);
                 (1, resp_handle, resp_body_handle)
             }
         };
+
         Ok(outcome)
     }
 
@@ -599,26 +604,38 @@ impl FastlyHttpReq for Session {
         if pending_req_handles.len() == 0 {
             return Err(Error::InvalidArgument);
         }
-        let targets = self.prepare_select_targets(&pending_req_handles.as_slice()?)?;
 
         // perform the select operation
-        let (fut_result, done_index, rest) = futures::future::select_all(targets).await;
-
-        // reinsert the other receivers before doing anything else, so they don't get dropped
-        self.reinsert_select_targets(rest);
-
-        let outcome = match fut_result {
-            Ok(resp) => {
-                let (resp_handle, body_handle) = self.insert_response(resp);
-                (done_index as u32, resp_handle, body_handle)
-            }
-            // Unfortunately, the ABI provides no means of returning error information
-            // from completed `select`.
-            Err(_) => (
-                done_index as u32,
-                INVALID_RESPONSE_HANDLE.into(),
-                INVALID_BODY_HANDLE.into(),
-            ),
+        let done_index = self
+            .select_impl(
+                pending_req_handles
+                    .as_slice()?
+                    .iter()
+                    .map(|handle| handle.to_owned().into()),
+            )
+            .await? as u32;
+
+        let item =
+            self.take_async_item(pending_req_handles.get(done_index).unwrap().read()?.into())?;
+
+        let outcome = match item {
+            AsyncItem::PendingReq(res) => match res {
+                PendingRequest::Complete(resp) => match resp {
+                    Ok(resp) => {
+                        let (resp_handle, body_handle) = self.insert_response(resp);
+                        (done_index, resp_handle, body_handle)
+                    }
+                    // Unfortunately, the ABI provides no means of returning error information
+                    // from completed `select`.
+                    Err(_) => (
+                        done_index,
+                        INVALID_RESPONSE_HANDLE.into(),
+                        INVALID_BODY_HANDLE.into(),
+                    ),
+                },
+                _ => panic!("Pending request was not completed"),
+            },
+            _ => panic!("AsyncItem was not a pending request"),
         };
 
         Ok(outcome)
diff --git a/test-fixtures/Cargo.lock b/test-fixtures/Cargo.lock
index b609fb1a..7a8b79ce 100644
--- a/test-fixtures/Cargo.lock
+++ b/test-fixtures/Cargo.lock
@@ -4,9 +4,9 @@ version = 3
 
 [[package]]
 name = "anyhow"
-version = "1.0.65"
+version = "1.0.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "98161a4e3e2184da77bb14f02184cdd111e83bbbcc9979dfee3c44b9a85f5602"
+checksum = "216261ddc8289130e551ddcd5ce8a064710c0d064a4d2895c67151c92b5443f6"
 
 [[package]]
 name = "bitflags"
@@ -61,12 +61,13 @@ dependencies = [
 
 [[package]]
 name = "fastly"
-version = "0.8.7"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ac81708c039cd2f95e09f3b700d36b46976de382dd47cf46e3f18a51aa70427d"
+checksum = "0d14ee2f12a3191582449a2e080287eff8898fc52da61c437869d91c41b3ae2a"
 dependencies = [
  "anyhow",
  "bytes 0.5.6",
+ "cfg-if",
  "fastly-macros",
  "fastly-shared",
  "fastly-sys",
@@ -84,9 +85,9 @@ dependencies = [
 
 [[package]]
 name = "fastly-macros"
-version = "0.8.7"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "99060e78d03bd1436bd4055c54cc5c62b1926e9c894b9bf00c40e8e5c276fd99"
+checksum = "e3d1b2980c09148cb84bfd18591943ee449a350dc1ff1ead69edbf012f7e2eef"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -95,9 +96,9 @@ dependencies = [
 
 [[package]]
 name = "fastly-shared"
-version = "0.8.7"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "238fb7af2219391cb024673302861adffd96cb3dbe4b602c2c7abef11ce5a5f9"
+checksum = "6f79939bdbbab8b1de759d584f386319454f8623681400675a07f9ad35f2b158"
 dependencies = [
  "bitflags",
  "http",
@@ -106,9 +107,9 @@ dependencies = [
 
 [[package]]
 name = "fastly-sys"
-version = "0.8.7"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa50606a08d3ee623033013d063e1843c5cb8c928fce3bd0f2c8ce4eaa460d8d"
+checksum = "1d01e98274a6b12c85c0eef22924871cc12c54b5322268947322463e59d09336"
 dependencies = [
  "bitflags",
  "fastly-shared",
@@ -174,9 +175,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.135"
+version = "0.2.137"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68783febc7782c6c5cb401fbda4de5a9898be1762314da0bb2c10ced61f18b0c"
+checksum = "fc7fcc620a3bff7cdd7a365be3376c97191aeaccc2a603e600951e452615bf89"
 
 [[package]]
 name = "mime"
@@ -184,15 +185,6 @@ version = "0.3.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2a60c7ce501c71e03a9c9c0d35b861413ae925bd979cc7a4e30d060069aaac8d"
 
-[[package]]
-name = "num_threads"
-version = "0.1.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2819ce041d2ee131036f4fc9d6ae7ae125a3a40e97ba64d04fe799ad9dabbb44"
-dependencies = [
- "libc",
-]
-
 [[package]]
 name = "opaque-debug"
 version = "0.3.0"
@@ -231,18 +223,18 @@ checksum = "4501abdff3ae82a1c1b477a17252eb69cee9e66eb915c1abaa4f44d873df9f09"
 
 [[package]]
 name = "serde"
-version = "1.0.145"
+version = "1.0.147"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "728eb6351430bccb993660dfffc5a72f91ccc1295abaa8ce19b27ebe4f75568b"
+checksum = "d193d69bae983fc11a79df82342761dfbf28a99fc8d203dca4c3c1b590948965"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.145"
+version = "1.0.147"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "81fa1584d3d1bcacd84c277a0dfe21f5b0f6accf4a23d04d4c6d61f1af522b4c"
+checksum = "4f1d362ca8fc9c3e3a7484440752472d68a6caa98f1ab81d99b5dfe517cec852"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -251,9 +243,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.86"
+version = "1.0.87"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "41feea4228a6f1cd09ec7a3593a682276702cd67b5273544757dae23c096f074"
+checksum = "6ce777b7b150d76b9cf60d28b55f5847135a003f7d7350c6be7a773508ce7d45"
 dependencies = [
  "itoa",
  "ryu",
@@ -287,9 +279,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.102"
+version = "1.0.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3fcd952facd492f9be3ef0d0b7032a6e442ee9b361d4acc2b1d0c4aaa5f613a1"
+checksum = "a864042229133ada95abf3b54fdc62ef5ccabe9515b64717bcb9a1919e59445d"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -330,13 +322,28 @@ dependencies = [
 
 [[package]]
 name = "time"
-version = "0.3.15"
+version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d634a985c4d4238ec39cacaed2e7ae552fbd3c476b552c1deac3021b7d7eaf0c"
+checksum = "a561bf4617eebd33bca6434b988f39ed798e527f51a1e797d0ee4f61c0a38376"
 dependencies = [
- "libc",
- "num_threads",
  "serde",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e153e1f1acaef8acc537e68b44906d2db6436e2b35ac2c6b42640fff91f00fd"
+
+[[package]]
+name = "time-macros"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d967f99f534ca7e495c575c62638eebc2898a8c84c119b89e250477bc4ba16b2"
+dependencies = [
+ "time-core",
 ]
 
 [[package]]
diff --git a/test-fixtures/Cargo.toml b/test-fixtures/Cargo.toml
index 57b9b840..bdd23455 100644
--- a/test-fixtures/Cargo.toml
+++ b/test-fixtures/Cargo.toml
@@ -8,9 +8,9 @@ license = "Apache-2.0 WITH LLVM-exception"
 publish = false
 
 [dependencies]
-fastly = "=0.8.7"
-fastly-shared = "=0.8.7"
-fastly-sys = "=0.8.7"
+fastly = "=0.8.9"
+fastly-shared = "=0.8.9"
+fastly-sys = "=0.8.9"
 bytes = "1.0.0"
 http = "0.2.1"
 serde = "1.0.114"
diff --git a/test-fixtures/src/bin/async_io.rs b/test-fixtures/src/bin/async_io.rs
new file mode 100644
index 00000000..87856d38
--- /dev/null
+++ b/test-fixtures/src/bin/async_io.rs
@@ -0,0 +1,143 @@
+//! Tests the `async_io` hostcalls by setting up one of each kind of async item, each against
+//! a distinct backend. Checks each for readiness, and then does a select with timeout against
+//! all of them.
+
+use std::str::FromStr;
+
+use fastly::handle::{BodyHandle, RequestHandle, ResponseHandle};
+use fastly::http::{HeaderName, HeaderValue, Method, StatusCode, Url};
+use fastly::Error;
+use fastly_shared::{CacheOverride, FastlyStatus};
+
+fn is_ready(handle: u32) -> bool {
+    let mut ready_out: u32 = 0;
+    unsafe {
+        let status = fastly_sys::fastly_async_io::is_ready(handle, &mut ready_out);
+        assert_eq!(status, FastlyStatus::OK);
+    }
+    ready_out == 1
+}
+
+fn append_header(resp: &mut ResponseHandle, header: impl ToString, value: impl ToString) {
+    resp.append_header(
+        &HeaderName::from_str(&header.to_string()).unwrap(),
+        &HeaderValue::from_str(&value.to_string()).unwrap(),
+    )
+}
+
+fn test_select() -> Result<(), Error> {
+    let mut ds_resp = ResponseHandle::new();
+    let pass = CacheOverride::pass();
+
+    // The "simple" case is a pending request, where the async item is awaiting the response headers
+    let mut simple_req = RequestHandle::new();
+    simple_req.set_url(&Url::parse("http://simple.org/")?);
+    simple_req.set_cache_override(&pass);
+    let simple_pending_req = simple_req.send_async(BodyHandle::new(), "Simple")?;
+    let simple_pending_req_handle = simple_pending_req.as_u32();
+
+    // The "read body" case involves a sync `send`, followed by treating the response body as an async item
+    // to read from
+    let mut read_body_req = RequestHandle::new();
+    read_body_req.set_url(&Url::parse("http://readbody.org/")?);
+    read_body_req.set_cache_override(&pass);
+    let (_read_body_resp, read_body) = read_body_req.send(BodyHandle::new(), "ReadBody")?;
+    let read_body_handle = unsafe { read_body.as_u32() };
+
+    // The "write body" case involves a `send_async_streaming` call, where the streaming body is the
+    // async item of interest. To test readiness, we need to ensure the body is large enough that Hyper
+    // won't try to buffer it, and hence we can see backpressure on streaming. We do this by including
+    // a large (4MB) prefix of the body _prior to_ streaming.
+    const INITIAL_BYTE_COUNT: usize = 4 * 1024 * 1024;
+    let mut write_body_req = RequestHandle::new();
+    write_body_req.set_url(&Url::parse("http://writebody.org/")?);
+    write_body_req.set_cache_override(&pass);
+    write_body_req.set_method(&Method::POST);
+    let mut write_body_initial = BodyHandle::new();
+    let initial_bytes = write_body_initial.write_bytes(&vec![0; INITIAL_BYTE_COUNT]);
+    assert_eq!(initial_bytes, INITIAL_BYTE_COUNT);
+    let (mut write_body, _write_body_pending_req) =
+        write_body_req.send_async_streaming(write_body_initial, "WriteBody")?;
+    let write_body_handle = unsafe { write_body.as_u32() };
+
+    // Now we attempt to stream chunks into the body until we encounter backpressure. That backpressure
+    // should result from the fixed channel-size, and the fact that the test server waits to read the
+    // body we are streaming to it.
+    let one_chunk = vec![0; 8 * 1024];
+    while is_ready(write_body_handle) {
+        let nwritten = write_body.write_bytes(&one_chunk);
+        assert!(nwritten > 0);
+    }
+
+    // Give the servers a chance to do their thing. This is needed to resolve a race between the servers
+    // initiating responses / reading buffers and the guest snapshotting readiness or performing `select`
+    //
+    // If this ever becomes flaky, an alternative would be to introduce an additional backend that
+    // responds only when the other backends have reached their steady state, via a VTC semaphore, and
+    // block on THAT backend here.
+    std::thread::sleep(std::time::Duration::from_millis(100));
+
+    append_header(
+        &mut ds_resp,
+        "Simple-Ready",
+        is_ready(simple_pending_req_handle),
+    );
+    append_header(&mut ds_resp, "Read-Ready", is_ready(read_body_handle));
+    append_header(&mut ds_resp, "Write-Ready", is_ready(write_body_handle));
+
+    let handles = vec![
+        simple_pending_req_handle,
+        read_body_handle,
+        write_body_handle,
+    ];
+    let mut ready_idx = 0;
+    unsafe {
+        fastly_sys::fastly_async_io::select(handles.as_ptr(), handles.len(), 20, &mut ready_idx);
+    };
+    if ready_idx == u32::MAX {
+        append_header(&mut ds_resp, "Ready-Index", "timeout");
+    } else {
+        append_header(&mut ds_resp, "Ready-Index", ready_idx);
+    }
+
+    // check that handles are still available after the select, by explicitly closing one of them:
+    assert!(read_body.close().is_ok());
+
+    ds_resp.send_to_client(BodyHandle::new());
+    Ok(())
+}
+
+fn test_empty_select(timeout: u32) {
+    let mut ds_resp = ResponseHandle::new();
+
+    let empty_handles = Vec::new();
+    let mut ready_idx = 0;
+
+    let res = unsafe {
+        fastly_sys::fastly_async_io::select(empty_handles.as_ptr(), 0, timeout, &mut ready_idx)
+    };
+
+    if res == FastlyStatus::OK {
+        if ready_idx == u32::MAX {
+            append_header(&mut ds_resp, "Ready-Index", "timeout");
+        } else {
+            append_header(&mut ds_resp, "Ready-Index", ready_idx);
+        }
+    } else {
+        ds_resp.set_status(StatusCode::INTERNAL_SERVER_ERROR);
+    }
+
+    ds_resp.send_to_client(BodyHandle::new());
+}
+
+fn main() -> Result<(), Error> {
+    let client_req = RequestHandle::from_client();
+    if let Ok(Some(val)) =
+        client_req.get_header_value(&HeaderName::from_str("Empty-Select-Timeout").unwrap(), 1024)
+    {
+        test_empty_select(val.to_str().unwrap().parse().unwrap());
+        Ok(())
+    } else {
+        test_select()
+    }
+}