From 42d7884fb1fc751c83e274db2c7ef89959f670fb Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Tue, 1 Sep 2026 21:09:29 +0000
Subject: [PATCH 01/12] add p3 feature

---
 Cargo.toml      | 70 ++++++++++++++++++++++++++++++++++++++++++++++---
 axum/Cargo.toml | 19 +++++++++++++-
 axum/src/lib.rs |  1 +
 src/lib.rs      | 40 +++++++++++++++++++++-------
 4 files changed, 116 insertions(+), 14 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 386afa8..3b4a3b9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,9 +13,13 @@ repository.workspace = true
 rust-version.workspace = true
 
 [features]
-default = ["json"]
+default = ["json", "p2"]
 json = ["dep:serde", "dep:serde_json"]
 
+# WASI backend selection. Exactly one of these must be enabled.
+p2 = ["dep:wasip2"]
+p3 = ["dep:wasip3"]
+
 [dependencies]
 anyhow.workspace = true
 async-task.workspace = true
@@ -27,9 +31,11 @@ http.workspace = true
 itoa.workspace = true
 pin-project-lite.workspace = true
 slab.workspace = true
-wasip2.workspace = true
 wstd-macro.workspace = true
 
+wasip2 = { workspace = true, optional = true }
+wasip3 = { workspace = true, optional = true }
+
 # optional
 serde = { workspace = true, optional = true }
 serde_json = { workspace = true, optional = true }
@@ -43,6 +49,62 @@ humantime.workspace = true
 serde = { workspace = true, features = ["derive"] }
 serde_json.workspace = true
 
+[[test]]
+name = "http_first_byte_timeout"
+required-features = ["p2"]
+
+[[test]]
+name = "http_get"
+required-features = ["p2"]
+
+[[test]]
+name = "http_get_json"
+required-features = ["p2"]
+
+[[test]]
+name = "http_handle_error_code"
+required-features = ["p2"]
+
+[[test]]
+name = "http_post"
+required-features = ["p2"]
+
+[[test]]
+name = "http_post_json"
+required-features = ["p2"]
+
+[[test]]
+name = "http_timeout"
+required-features = ["p2"]
+
+[[test]]
+name = "sleep"
+required-features = ["p2"]
+
+[[example]]
+name = "complex_http_client"
+required-features = ["p2"]
+
+[[example]]
+name = "http_client"
+required-features = ["p2"]
+
+[[example]]
+name = "http_server"
+required-features = ["p2"]
+
+[[example]]
+name = "http_server_proxy"
+required-features = ["p2"]
+
+[[example]]
+name = "tcp_echo_server"
+required-features = ["p2"]
+
+[[example]]
+name = "tcp_stream_client"
+required-features = ["p2"]
+
 [workspace]
 members = [
     "axum",
@@ -95,13 +157,13 @@ test-programs = { path = "test-programs" }
 tower-service = "0.3.3"
 ureq = { version = "3.1", default-features = false, features = ["json"] }
 wasip2 = "1.0"
-wstd = { path = ".", version = "=0.6.8" }
+wasip3 = "0.8"
+wstd = { path = ".", version = "=0.6.8", default-features = false }
 wstd-axum = { path = "./axum", version = "=0.6.8" }
 wstd-axum-macro = { path = "./axum/macro", version = "=0.6.8" }
 wstd-macro = { path = "./macro", version = "=0.6.8" }
 
 [package.metadata.docs.rs]
-all-features = true
 targets = [
     "wasm32-wasip2"
 ]
diff --git a/axum/Cargo.toml b/axum/Cargo.toml
index 154a021..baa5da4 100644
--- a/axum/Cargo.toml
+++ b/axum/Cargo.toml
@@ -13,12 +13,29 @@ rust-version.workspace = true
 [dependencies]
 axum.workspace = true
 tower-service.workspace = true
-wstd.workspace = true
+wstd = { workspace = true, features = ["json"] }
 wstd-axum-macro.workspace = true
 
+[features]
+default = ["p2"]
+p2 = ["wstd/p2"]
+p3 = ["wstd/p3"]
+
 [dev-dependencies]
 anyhow.workspace = true
 futures-concurrency.workspace = true
 serde = { workspace = true, features = ["derive"] }
 serde_qs.workspace = true
 axum = { workspace = true, features = ["query", "json", "macros"] }
+
+[[example]]
+name = "hello_world"
+required-features = ["p2"]
+
+[[example]]
+name = "hello_world_nomacro"
+required-features = ["p2"]
+
+[[example]]
+name = "weather"
+required-features = ["p2"]
diff --git a/axum/src/lib.rs b/axum/src/lib.rs
index 3272b91..9536c89 100644
--- a/axum/src/lib.rs
+++ b/axum/src/lib.rs
@@ -1,3 +1,4 @@
+#![cfg(feature = "p2")]
 //! Support for the [`axum`] web server framework in wasi-http components, via
 //! [`wstd`].
 //!
diff --git a/src/lib.rs b/src/lib.rs
index ebc673d..0dc8ed7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,7 +18,7 @@
 //! **TCP echo server**
 //!
 //! ```rust,no_run
-#![doc = include_str!("../examples/tcp_echo_server.rs")]
+#![cfg_attr(feature = "p2", doc = include_str!("../examples/tcp_echo_server.rs"))]
 //! ```
 //!
 //! **HTTP Client**
@@ -30,7 +30,7 @@
 //! **HTTP Server**
 //!
 //! ```rust,no_run
-#![doc = include_str!("../examples/http_server.rs")]
+#![cfg_attr(feature = "p2", doc = include_str!("../examples/http_server.rs"))]
 //! ```
 //!
 //! # Design Decisions
@@ -55,30 +55,52 @@
 //! These are unique capabilities provided by WASI 0.2, and because this library
 //! is specific to that are exposed from here.
 
+// Exactly one WASI backend must be selected. See the `p2`/`p3` features.
+#[cfg(all(feature = "p2", feature = "p3"))]
+compile_error!(
+    "the `p2` and `p3` features are mutually exclusive — enable exactly one WASI backend"
+);
+#[cfg(not(any(feature = "p2", feature = "p3")))]
+compile_error!("exactly one of the `p2` or `p3` features must be enabled");
+
+#[cfg(feature = "p2")]
 pub mod future;
+#[cfg(feature = "p2")]
 #[macro_use]
 pub mod http;
+#[cfg(feature = "p2")]
 pub mod io;
 pub mod iter;
+#[cfg(feature = "p2")]
 pub mod net;
+#[cfg(feature = "p2")]
 pub mod rand;
+#[cfg(feature = "p2")]
 pub mod runtime;
+#[cfg(feature = "p2")]
 pub mod task;
+#[cfg(feature = "p2")]
 pub mod time;
 
-pub use wstd_macro::attr_macro_http_server as http_server;
-pub use wstd_macro::attr_macro_main as main;
-pub use wstd_macro::attr_macro_test as test;
+#[cfg(feature = "p2")]
+pub use wstd_macro::{
+    attr_macro_http_server as http_server, attr_macro_main as main, attr_macro_test as test,
+};
 
-// Re-export the wasip2 crate for use only by `wstd-macro` macros. The proc
-// macros need to generate code that uses these definitions, but we don't want
-// to treat it as part of our public API with regards to semver, so we keep it
-// under `__internal` as well as doc(hidden) to indicate it is private.
+// Re-export the active WASI backend crate for use only by `wstd-macro` macros.
+// The proc macros need to generate code that uses these definitions, but we
+// don't want to treat it as part of our public API with regards to semver, so
+// we keep it under `__internal` as well as doc(hidden) to indicate it is
+// private.
 #[doc(hidden)]
 pub mod __internal {
+    #[cfg(feature = "p2")]
     pub use wasip2;
+    #[cfg(feature = "p3")]
+    pub use wasip3;
 }
 
+#[cfg(feature = "p2")]
 pub mod prelude {
     pub use crate::future::FutureExt as _;
     pub use crate::io::AsyncRead as _;

From 4a6e65cc71b452d39000f998e47c04e605c38dd0 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 2 Sep 2026 12:24:53 +0000
Subject: [PATCH 02/12] add p3 test CI job

---
 .github/workflows/ci.yaml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 1362609..9681c60 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -54,6 +54,9 @@ jobs:
     - name: wstd tests
       run: cargo test -p wstd -p wstd-axum --target wasm32-wasip2 -- --nocapture
 
+    - name: p3 wstd tests
+      run: cargo test -p wstd -p wstd-axum --target wasm32-wasip2 --no-default-features --features p3 -- --nocapture
+
     - name: test-programs tests
       run: cargo test -p test-programs -- --nocapture
       if: steps.creds.outcome == 'success'

From ea32edf32998964ef18ab766043b98a226fbf5f4 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Thu, 3 Sep 2026 14:00:43 +0000
Subject: [PATCH 03/12] use cfg alias

---
 Cargo.toml      |  4 ++++
 axum/Cargo.toml |  3 +++
 axum/build.rs   | 10 ++++++++++
 axum/src/lib.rs |  2 +-
 build.rs        | 10 ++++++++++
 src/lib.rs      | 32 ++++++++++++++++----------------
 6 files changed, 44 insertions(+), 17 deletions(-)
 create mode 100644 axum/build.rs
 create mode 100644 build.rs

diff --git a/Cargo.toml b/Cargo.toml
index 3b4a3b9..90a90cd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -20,6 +20,9 @@ json = ["dep:serde", "dep:serde_json"]
 p2 = ["dep:wasip2"]
 p3 = ["dep:wasip3"]
 
+[build-dependencies]
+cfg_aliases.workspace = true
+
 [dependencies]
 anyhow.workspace = true
 async-task.workspace = true
@@ -134,6 +137,7 @@ async-task = "4.7"
 axum = { version = "0.8.6", default-features = false }
 bytes = "1.10.1"
 cargo_metadata = "0.22"
+cfg_aliases = "0.2"
 clap = { version = "4.5.26", features = ["derive"] }
 futures-core = "0.3.19"
 futures-lite = "1.12.0"
diff --git a/axum/Cargo.toml b/axum/Cargo.toml
index baa5da4..a27ce78 100644
--- a/axum/Cargo.toml
+++ b/axum/Cargo.toml
@@ -21,6 +21,9 @@ default = ["p2"]
 p2 = ["wstd/p2"]
 p3 = ["wstd/p3"]
 
+[build-dependencies]
+cfg_aliases.workspace = true
+
 [dev-dependencies]
 anyhow.workspace = true
 futures-concurrency.workspace = true
diff --git a/axum/build.rs b/axum/build.rs
new file mode 100644
index 0000000..5a5f457
--- /dev/null
+++ b/axum/build.rs
@@ -0,0 +1,10 @@
+use cfg_aliases::cfg_aliases;
+
+fn main() {
+    cfg_aliases! {
+        // TODO https://github.com/bytecodealliance/wstd/issues/147: Swap these
+        // to use `target_env` instead.
+        p2: { feature = "p2" },
+        p3: { feature = "p3" },
+    }
+}
diff --git a/axum/src/lib.rs b/axum/src/lib.rs
index 9536c89..c730fd2 100644
--- a/axum/src/lib.rs
+++ b/axum/src/lib.rs
@@ -1,4 +1,4 @@
-#![cfg(feature = "p2")]
+#![cfg(p2)]
 //! Support for the [`axum`] web server framework in wasi-http components, via
 //! [`wstd`].
 //!
diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000..5a5f457
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,10 @@
+use cfg_aliases::cfg_aliases;
+
+fn main() {
+    cfg_aliases! {
+        // TODO https://github.com/bytecodealliance/wstd/issues/147: Swap these
+        // to use `target_env` instead.
+        p2: { feature = "p2" },
+        p3: { feature = "p3" },
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 0dc8ed7..64ac672 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,7 +18,7 @@
 //! **TCP echo server**
 //!
 //! ```rust,no_run
-#![cfg_attr(feature = "p2", doc = include_str!("../examples/tcp_echo_server.rs"))]
+#![cfg_attr(p2, doc = include_str!("../examples/tcp_echo_server.rs"))]
 //! ```
 //!
 //! **HTTP Client**
@@ -30,7 +30,7 @@
 //! **HTTP Server**
 //!
 //! ```rust,no_run
-#![cfg_attr(feature = "p2", doc = include_str!("../examples/http_server.rs"))]
+#![cfg_attr(p2, doc = include_str!("../examples/http_server.rs"))]
 //! ```
 //!
 //! # Design Decisions
@@ -56,33 +56,33 @@
 //! is specific to that are exposed from here.
 
 // Exactly one WASI backend must be selected. See the `p2`/`p3` features.
-#[cfg(all(feature = "p2", feature = "p3"))]
+#[cfg(all(p2, p3))]
 compile_error!(
     "the `p2` and `p3` features are mutually exclusive — enable exactly one WASI backend"
 );
-#[cfg(not(any(feature = "p2", feature = "p3")))]
+#[cfg(not(any(p2, p3)))]
 compile_error!("exactly one of the `p2` or `p3` features must be enabled");
 
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod future;
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 #[macro_use]
 pub mod http;
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod io;
 pub mod iter;
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod net;
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod rand;
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod runtime;
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod task;
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod time;
 
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub use wstd_macro::{
     attr_macro_http_server as http_server, attr_macro_main as main, attr_macro_test as test,
 };
@@ -94,13 +94,13 @@ pub use wstd_macro::{
 // private.
 #[doc(hidden)]
 pub mod __internal {
-    #[cfg(feature = "p2")]
+    #[cfg(p2)]
     pub use wasip2;
-    #[cfg(feature = "p3")]
+    #[cfg(p3)]
     pub use wasip3;
 }
 
-#[cfg(feature = "p2")]
+#[cfg(p2)]
 pub mod prelude {
     pub use crate::future::FutureExt as _;
     pub use crate::io::AsyncRead as _;

From adb35fcb17d5d6620bf34464b4909c3b4aeacb9c Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 00:49:00 +0000
Subject: [PATCH 04/12] switch from feature to target

---
 .cargo/config.toml                      |  6 ++
 .github/actions/install-rust/action.yml |  5 ++
 .github/workflows/ci.yaml               |  8 +--
 Cargo.toml                              | 75 +++----------------------
 axum/Cargo.toml                         | 20 -------
 axum/build.rs                           | 10 ----
 axum/examples/hello_world.rs            |  3 +
 axum/examples/hello_world_nomacro.rs    |  3 +
 axum/examples/weather.rs                |  3 +
 axum/src/lib.rs                         |  2 +-
 build.rs                                | 10 ----
 examples/complex_http_client.rs         |  3 +
 examples/http_client.rs                 |  3 +
 examples/http_server.rs                 |  3 +
 examples/http_server_proxy.rs           |  3 +
 examples/tcp_echo_server.rs             |  3 +
 examples/tcp_stream_client.rs           |  3 +
 src/lib.rs                              | 36 +++++-------
 tests/http_first_byte_timeout.rs        |  2 +
 tests/http_get.rs                       |  2 +
 tests/http_get_json.rs                  |  2 +
 tests/http_handle_error_code.rs         |  2 +
 tests/http_post.rs                      |  2 +
 tests/http_post_json.rs                 |  2 +
 tests/http_timeout.rs                   |  2 +
 tests/sleep.rs                          |  2 +
 26 files changed, 80 insertions(+), 135 deletions(-)
 delete mode 100644 axum/build.rs
 delete mode 100644 build.rs

diff --git a/.cargo/config.toml b/.cargo/config.toml
index e9a242c..aa3925b 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -3,3 +3,9 @@
 # * AWS auth environment variables, for running the wstd-aws integration tests.
 # * . directory is available at .
 runner = "wasmtime run -Shttp --env AWS_ACCESS_KEY_ID --env AWS_SECRET_ACCESS_KEY --env AWS_SESSION_TOKEN --dir .::."
+
+[target.wasm32-wasip3]
+# wasmtime is given:
+# * AWS auth environment variables, for running the wstd-aws integration tests.
+# * . directory is available at .
+runner = "wasmtime run -Shttp -Sp3 --env AWS_ACCESS_KEY_ID --env AWS_SECRET_ACCESS_KEY --env AWS_SESSION_TOKEN --dir .::."
diff --git a/.github/actions/install-rust/action.yml b/.github/actions/install-rust/action.yml
index 0d11907..57cc11c 100644
--- a/.github/actions/install-rust/action.yml
+++ b/.github/actions/install-rust/action.yml
@@ -31,6 +31,11 @@ runs:
         rustup update "${{ steps.select.outputs.version }}" --no-self-update
         rustup default "${{ steps.select.outputs.version }}"
 
+        # Required for -Zbuild-std for the wasip3 target.
+        if [ "${{ inputs.toolchain }}" = "nightly" ]; then
+          rustup component add rust-src
+        fi
+
         # Save disk space by avoiding incremental compilation. Also turn down
         # debuginfo from 2 to 0 to help save disk space.
         cat >> "$GITHUB_ENV" <<EOF
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 9681c60..9e2f537 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -51,11 +51,12 @@ jobs:
     - name: check
       run: cargo check --workspace --all --bins --examples
 
-    - name: wstd tests
+    - name: wstd p2 tests
       run: cargo test -p wstd -p wstd-axum --target wasm32-wasip2 -- --nocapture
 
-    - name: p3 wstd tests
-      run: cargo test -p wstd -p wstd-axum --target wasm32-wasip2 --no-default-features --features p3 -- --nocapture
+    - name: wstd p3 tests
+      if: matrix.rust == 'nightly'
+      run: cargo test -p wstd -p wstd-axum --target wasm32-wasip3 -Z build-std=std,panic_abort -- --nocapture
 
     - name: test-programs tests
       run: cargo test -p test-programs -- --nocapture
@@ -93,4 +94,3 @@ jobs:
     - run: ./publish bump
     # Make sure the tree is publish-able as-is
     - run: ./publish verify
-
diff --git a/Cargo.toml b/Cargo.toml
index 90a90cd..fc43b0f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,16 +13,9 @@ repository.workspace = true
 rust-version.workspace = true
 
 [features]
-default = ["json", "p2"]
+default = ["json"]
 json = ["dep:serde", "dep:serde_json"]
 
-# WASI backend selection. Exactly one of these must be enabled.
-p2 = ["dep:wasip2"]
-p3 = ["dep:wasip3"]
-
-[build-dependencies]
-cfg_aliases.workspace = true
-
 [dependencies]
 anyhow.workspace = true
 async-task.workspace = true
@@ -36,13 +29,16 @@ pin-project-lite.workspace = true
 slab.workspace = true
 wstd-macro.workspace = true
 
-wasip2 = { workspace = true, optional = true }
-wasip3 = { workspace = true, optional = true }
-
 # optional
 serde = { workspace = true, optional = true }
 serde_json = { workspace = true, optional = true }
 
+[target.'cfg(target_env = "p2")'.dependencies]
+wasip2.workspace = true
+
+[target.'cfg(target_env = "p3")'.dependencies]
+wasip3.workspace = true
+
 [dev-dependencies]
 anyhow.workspace = true
 clap.workspace = true
@@ -52,62 +48,6 @@ humantime.workspace = true
 serde = { workspace = true, features = ["derive"] }
 serde_json.workspace = true
 
-[[test]]
-name = "http_first_byte_timeout"
-required-features = ["p2"]
-
-[[test]]
-name = "http_get"
-required-features = ["p2"]
-
-[[test]]
-name = "http_get_json"
-required-features = ["p2"]
-
-[[test]]
-name = "http_handle_error_code"
-required-features = ["p2"]
-
-[[test]]
-name = "http_post"
-required-features = ["p2"]
-
-[[test]]
-name = "http_post_json"
-required-features = ["p2"]
-
-[[test]]
-name = "http_timeout"
-required-features = ["p2"]
-
-[[test]]
-name = "sleep"
-required-features = ["p2"]
-
-[[example]]
-name = "complex_http_client"
-required-features = ["p2"]
-
-[[example]]
-name = "http_client"
-required-features = ["p2"]
-
-[[example]]
-name = "http_server"
-required-features = ["p2"]
-
-[[example]]
-name = "http_server_proxy"
-required-features = ["p2"]
-
-[[example]]
-name = "tcp_echo_server"
-required-features = ["p2"]
-
-[[example]]
-name = "tcp_stream_client"
-required-features = ["p2"]
-
 [workspace]
 members = [
     "axum",
@@ -137,7 +77,6 @@ async-task = "4.7"
 axum = { version = "0.8.6", default-features = false }
 bytes = "1.10.1"
 cargo_metadata = "0.22"
-cfg_aliases = "0.2"
 clap = { version = "4.5.26", features = ["derive"] }
 futures-core = "0.3.19"
 futures-lite = "1.12.0"
diff --git a/axum/Cargo.toml b/axum/Cargo.toml
index a27ce78..74141e9 100644
--- a/axum/Cargo.toml
+++ b/axum/Cargo.toml
@@ -16,29 +16,9 @@ tower-service.workspace = true
 wstd = { workspace = true, features = ["json"] }
 wstd-axum-macro.workspace = true
 
-[features]
-default = ["p2"]
-p2 = ["wstd/p2"]
-p3 = ["wstd/p3"]
-
-[build-dependencies]
-cfg_aliases.workspace = true
-
 [dev-dependencies]
 anyhow.workspace = true
 futures-concurrency.workspace = true
 serde = { workspace = true, features = ["derive"] }
 serde_qs.workspace = true
 axum = { workspace = true, features = ["query", "json", "macros"] }
-
-[[example]]
-name = "hello_world"
-required-features = ["p2"]
-
-[[example]]
-name = "hello_world_nomacro"
-required-features = ["p2"]
-
-[[example]]
-name = "weather"
-required-features = ["p2"]
diff --git a/axum/build.rs b/axum/build.rs
deleted file mode 100644
index 5a5f457..0000000
--- a/axum/build.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-use cfg_aliases::cfg_aliases;
-
-fn main() {
-    cfg_aliases! {
-        // TODO https://github.com/bytecodealliance/wstd/issues/147: Swap these
-        // to use `target_env` instead.
-        p2: { feature = "p2" },
-        p3: { feature = "p3" },
-    }
-}
diff --git a/axum/examples/hello_world.rs b/axum/examples/hello_world.rs
index 90a9cbd..8cf124c 100644
--- a/axum/examples/hello_world.rs
+++ b/axum/examples/hello_world.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 //! Run with
 //!
 //! ```sh
diff --git a/axum/examples/hello_world_nomacro.rs b/axum/examples/hello_world_nomacro.rs
index f3068d1..44744e5 100644
--- a/axum/examples/hello_world_nomacro.rs
+++ b/axum/examples/hello_world_nomacro.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 //! Run with
 //!
 //! ```sh
diff --git a/axum/examples/weather.rs b/axum/examples/weather.rs
index 5163fcc..f404c0f 100644
--- a/axum/examples/weather.rs
+++ b/axum/examples/weather.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 //! This demo app shows a Axum based wasi-http server making an arbitrary
 //! number of http requests as part of serving a single response.
 //!
diff --git a/axum/src/lib.rs b/axum/src/lib.rs
index c730fd2..d113410 100644
--- a/axum/src/lib.rs
+++ b/axum/src/lib.rs
@@ -1,4 +1,4 @@
-#![cfg(p2)]
+#![cfg(target_env = "p2")]
 //! Support for the [`axum`] web server framework in wasi-http components, via
 //! [`wstd`].
 //!
diff --git a/build.rs b/build.rs
deleted file mode 100644
index 5a5f457..0000000
--- a/build.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-use cfg_aliases::cfg_aliases;
-
-fn main() {
-    cfg_aliases! {
-        // TODO https://github.com/bytecodealliance/wstd/issues/147: Swap these
-        // to use `target_env` instead.
-        p2: { feature = "p2" },
-        p3: { feature = "p3" },
-    }
-}
diff --git a/examples/complex_http_client.rs b/examples/complex_http_client.rs
index 703e931..7dadebf 100644
--- a/examples/complex_http_client.rs
+++ b/examples/complex_http_client.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 use anyhow::{Result, anyhow};
 use clap::{ArgAction, Parser};
 use std::str::FromStr;
diff --git a/examples/http_client.rs b/examples/http_client.rs
index f4465a8..6850d60 100644
--- a/examples/http_client.rs
+++ b/examples/http_client.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 use anyhow::{Result, anyhow};
 use clap::{ArgAction, Parser};
 use wstd::http::{Body, BodyExt, Client, Method, Request, Uri};
diff --git a/examples/http_server.rs b/examples/http_server.rs
index 8449f83..5486f0c 100644
--- a/examples/http_server.rs
+++ b/examples/http_server.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 use anyhow::{Context, Result};
 use futures_lite::stream::{once_future, unfold};
 use http_body_util::{BodyExt, StreamBody};
diff --git a/examples/http_server_proxy.rs b/examples/http_server_proxy.rs
index ccad608..77bb231 100644
--- a/examples/http_server_proxy.rs
+++ b/examples/http_server_proxy.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 //! Run the example with:
 //! ```sh
 //! cargo build --example http_server_proxy --target=wasm32-wasip2
diff --git a/examples/tcp_echo_server.rs b/examples/tcp_echo_server.rs
index f1dd895..3e8aef2 100644
--- a/examples/tcp_echo_server.rs
+++ b/examples/tcp_echo_server.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 use wstd::io;
 use wstd::iter::AsyncIterator;
 use wstd::net::TcpListener;
diff --git a/examples/tcp_stream_client.rs b/examples/tcp_stream_client.rs
index 2e93faf..c14b267 100644
--- a/examples/tcp_stream_client.rs
+++ b/examples/tcp_stream_client.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 use wstd::io::{self, AsyncRead, AsyncWrite};
 use wstd::net::TcpStream;
 
diff --git a/src/lib.rs b/src/lib.rs
index 64ac672..c3442aa 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,7 +18,7 @@
 //! **TCP echo server**
 //!
 //! ```rust,no_run
-#![cfg_attr(p2, doc = include_str!("../examples/tcp_echo_server.rs"))]
+#![doc = include_str!("../examples/tcp_echo_server.rs")]
 //! ```
 //!
 //! **HTTP Client**
@@ -30,7 +30,7 @@
 //! **HTTP Server**
 //!
 //! ```rust,no_run
-#![cfg_attr(p2, doc = include_str!("../examples/http_server.rs"))]
+#![doc = include_str!("../examples/http_server.rs")]
 //! ```
 //!
 //! # Design Decisions
@@ -55,34 +55,26 @@
 //! These are unique capabilities provided by WASI 0.2, and because this library
 //! is specific to that are exposed from here.
 
-// Exactly one WASI backend must be selected. See the `p2`/`p3` features.
-#[cfg(all(p2, p3))]
-compile_error!(
-    "the `p2` and `p3` features are mutually exclusive — enable exactly one WASI backend"
-);
-#[cfg(not(any(p2, p3)))]
-compile_error!("exactly one of the `p2` or `p3` features must be enabled");
-
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod future;
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 #[macro_use]
 pub mod http;
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod io;
 pub mod iter;
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod net;
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod rand;
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod runtime;
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod task;
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod time;
 
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub use wstd_macro::{
     attr_macro_http_server as http_server, attr_macro_main as main, attr_macro_test as test,
 };
@@ -94,13 +86,13 @@ pub use wstd_macro::{
 // private.
 #[doc(hidden)]
 pub mod __internal {
-    #[cfg(p2)]
+    #[cfg(target_env = "p2")]
     pub use wasip2;
-    #[cfg(p3)]
+    #[cfg(target_env = "p3")]
     pub use wasip3;
 }
 
-#[cfg(p2)]
+#[cfg(target_env = "p2")]
 pub mod prelude {
     pub use crate::future::FutureExt as _;
     pub use crate::io::AsyncRead as _;
diff --git a/tests/http_first_byte_timeout.rs b/tests/http_first_byte_timeout.rs
index 5fd47be..fb22cd3 100644
--- a/tests/http_first_byte_timeout.rs
+++ b/tests/http_first_byte_timeout.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use wstd::http::{Body, Client, Request, error::ErrorCode};
 
 #[wstd::main]
diff --git a/tests/http_get.rs b/tests/http_get.rs
index e7a3a5a..5660e0e 100644
--- a/tests/http_get.rs
+++ b/tests/http_get.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use std::error::Error;
 use wstd::http::{Body, Client, HeaderValue, Request};
 
diff --git a/tests/http_get_json.rs b/tests/http_get_json.rs
index a4f42b6..5596e0b 100644
--- a/tests/http_get_json.rs
+++ b/tests/http_get_json.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use serde::Deserialize;
 use std::error::Error;
 use wstd::http::{Body, Client, Request};
diff --git a/tests/http_handle_error_code.rs b/tests/http_handle_error_code.rs
index 6affb90..0bbdd1d 100644
--- a/tests/http_handle_error_code.rs
+++ b/tests/http_handle_error_code.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use wstd::http::{Body, Client, Request, error::ErrorCode};
 
 /// Test that `outgoing_handler::handle` errors are properly propagated.
diff --git a/tests/http_post.rs b/tests/http_post.rs
index 5de184d..522c47b 100644
--- a/tests/http_post.rs
+++ b/tests/http_post.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use std::error::Error;
 use wstd::http::{Client, HeaderValue, Request};
 
diff --git a/tests/http_post_json.rs b/tests/http_post_json.rs
index f9fcf07..1dc07f2 100644
--- a/tests/http_post_json.rs
+++ b/tests/http_post_json.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use serde::{Deserialize, Serialize};
 use std::error::Error;
 use wstd::http::{Body, Client, HeaderValue, Request};
diff --git a/tests/http_timeout.rs b/tests/http_timeout.rs
index 96d40de..04f60fc 100644
--- a/tests/http_timeout.rs
+++ b/tests/http_timeout.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use wstd::future::FutureExt;
 use wstd::http::{Body, Client, Request};
 use wstd::time::Duration;
diff --git a/tests/sleep.rs b/tests/sleep.rs
index eb55ea0..ac8c72a 100644
--- a/tests/sleep.rs
+++ b/tests/sleep.rs
@@ -1,3 +1,5 @@
+#![cfg(target_env = "p2")]
+
 use std::error::Error;
 use wstd::task::sleep;
 use wstd::time::Duration;

From 26bea8b9d41bc11f1c8b9f52d0b758618ccc8408 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 13:03:53 +0000
Subject: [PATCH 05/12] merge fixes

---
 examples/udp_echo_server.rs   | 3 +++
 examples/udp_stream_client.rs | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/examples/udp_echo_server.rs b/examples/udp_echo_server.rs
index f840107..7c10bc3 100644
--- a/examples/udp_echo_server.rs
+++ b/examples/udp_echo_server.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 use wstd::io;
 use wstd::net::UdpSocket;
 
diff --git a/examples/udp_stream_client.rs b/examples/udp_stream_client.rs
index 013caee..68626d6 100644
--- a/examples/udp_stream_client.rs
+++ b/examples/udp_stream_client.rs
@@ -1,3 +1,6 @@
+#![cfg_attr(not(target_env = "p2"), no_main)]
+#![cfg(target_env = "p2")]
+
 use wstd::io;
 use wstd::net::{UdpSocket, UdpStream};
 

From 6435d57d3330a76224630a92c6aeff371354f255 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 13:12:01 +0000
Subject: [PATCH 06/12] add job printing rust version

---
 .github/workflows/ci.yaml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 9e2f537..46cbec8 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -48,6 +48,9 @@ jobs:
         role-to-assume: arn:aws:iam::313377415443:role/wstd-aws-ci-role
         role-session-name: github-ci
 
+    - name: rust version
+      run: cargo --version
+
     - name: check
       run: cargo check --workspace --all --bins --examples
 

From 663c532863e5734eadfc2051f9b712c2d0de3062 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 13:24:11 +0000
Subject: [PATCH 07/12] try override instead of default

---
 .github/actions/install-rust/action.yml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/.github/actions/install-rust/action.yml b/.github/actions/install-rust/action.yml
index 57cc11c..c39c4be 100644
--- a/.github/actions/install-rust/action.yml
+++ b/.github/actions/install-rust/action.yml
@@ -29,7 +29,9 @@ runs:
       run: |
         rustup set profile minimal
         rustup update "${{ steps.select.outputs.version }}" --no-self-update
-        rustup default "${{ steps.select.outputs.version }}"
+        # `rustup default` gets overwritten by rust-toolchain.toml, `rustup
+        # override` has higher precedence though.
+        rustup override set "${{ steps.select.outputs.version }}"
 
         # Required for -Zbuild-std for the wasip3 target.
         if [ "${{ inputs.toolchain }}" = "nightly" ]; then

From d306e06e369563de71ea16cfae143ff3944700bf Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 13:26:41 +0000
Subject: [PATCH 08/12] explicitly add wasi targets

---
 .github/actions/install-rust/action.yml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/.github/actions/install-rust/action.yml b/.github/actions/install-rust/action.yml
index c39c4be..18957d4 100644
--- a/.github/actions/install-rust/action.yml
+++ b/.github/actions/install-rust/action.yml
@@ -33,8 +33,11 @@ runs:
         # override` has higher precedence though.
         rustup override set "${{ steps.select.outputs.version }}"
 
+        rustup target add wasm32-wasip2
+
         # Required for -Zbuild-std for the wasip3 target.
         if [ "${{ inputs.toolchain }}" = "nightly" ]; then
+          rustup target add wasm32-wasip3
           rustup component add rust-src
         fi
 

From 2f8c1c2c449946dbb7f6c710ec784a0d7c76cbf8 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 13:32:48 +0000
Subject: [PATCH 09/12] bump msrv to latest version with p3 target_env

---
 Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Cargo.toml b/Cargo.toml
index e990b9e..9b903c1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -64,7 +64,7 @@ license = "Apache-2.0 WITH LLVM-exception"
 repository = "https://github.com/bytecodealliance/wstd"
 keywords = ["WebAssembly", "async", "stdlib", "Components"]
 categories = ["wasm", "asynchronous"]
-rust-version = "1.91.1"
+rust-version = "1.92.0"
 authors = [
     "Yoshua Wuyts <rust@yosh.is>",
     "Pat Hickey <pat@moreproductive.org>",

From 5841233cbe314258dfa55c836c32fd517e23f084 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 13:38:36 +0000
Subject: [PATCH 10/12] include target_os in directives

---
 Cargo.toml                           |  4 ++--
 axum/examples/hello_world.rs         |  4 ++--
 axum/examples/hello_world_nomacro.rs |  4 ++--
 axum/examples/weather.rs             |  4 ++--
 axum/src/lib.rs                      |  2 +-
 examples/complex_http_client.rs      |  4 ++--
 examples/http_client.rs              |  4 ++--
 examples/http_server.rs              |  4 ++--
 examples/http_server_proxy.rs        |  4 ++--
 examples/tcp_echo_server.rs          |  4 ++--
 examples/tcp_stream_client.rs        |  4 ++--
 examples/udp_echo_server.rs          |  4 ++--
 examples/udp_stream_client.rs        |  4 ++--
 src/lib.rs                           | 24 ++++++++++++------------
 tests/http_first_byte_timeout.rs     |  2 +-
 tests/http_get.rs                    |  2 +-
 tests/http_get_json.rs               |  2 +-
 tests/http_handle_error_code.rs      |  2 +-
 tests/http_post.rs                   |  2 +-
 tests/http_post_json.rs              |  2 +-
 tests/http_timeout.rs                |  2 +-
 tests/sleep.rs                       |  2 +-
 22 files changed, 45 insertions(+), 45 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 9b903c1..2a7e28b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,10 +33,10 @@ wstd-macro.workspace = true
 serde = { workspace = true, optional = true }
 serde_json = { workspace = true, optional = true }
 
-[target.'cfg(target_env = "p2")'.dependencies]
+[target.'cfg(all(target_os = "wasi", target_env = "p2"))'.dependencies]
 wasip2.workspace = true
 
-[target.'cfg(target_env = "p3")'.dependencies]
+[target.'cfg(all(target_os = "wasi", target_env = "p3"))'.dependencies]
 wasip3.workspace = true
 
 [dev-dependencies]
diff --git a/axum/examples/hello_world.rs b/axum/examples/hello_world.rs
index 8cf124c..9931344 100644
--- a/axum/examples/hello_world.rs
+++ b/axum/examples/hello_world.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 //! Run with
 //!
diff --git a/axum/examples/hello_world_nomacro.rs b/axum/examples/hello_world_nomacro.rs
index 44744e5..bc0a39b 100644
--- a/axum/examples/hello_world_nomacro.rs
+++ b/axum/examples/hello_world_nomacro.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 //! Run with
 //!
diff --git a/axum/examples/weather.rs b/axum/examples/weather.rs
index f404c0f..0df8f97 100644
--- a/axum/examples/weather.rs
+++ b/axum/examples/weather.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 //! This demo app shows a Axum based wasi-http server making an arbitrary
 //! number of http requests as part of serving a single response.
diff --git a/axum/src/lib.rs b/axum/src/lib.rs
index d113410..c5a2af1 100644
--- a/axum/src/lib.rs
+++ b/axum/src/lib.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 //! Support for the [`axum`] web server framework in wasi-http components, via
 //! [`wstd`].
 //!
diff --git a/examples/complex_http_client.rs b/examples/complex_http_client.rs
index 7dadebf..7c3e470 100644
--- a/examples/complex_http_client.rs
+++ b/examples/complex_http_client.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use anyhow::{Result, anyhow};
 use clap::{ArgAction, Parser};
diff --git a/examples/http_client.rs b/examples/http_client.rs
index 6850d60..178fbeb 100644
--- a/examples/http_client.rs
+++ b/examples/http_client.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use anyhow::{Result, anyhow};
 use clap::{ArgAction, Parser};
diff --git a/examples/http_server.rs b/examples/http_server.rs
index 5486f0c..fa67518 100644
--- a/examples/http_server.rs
+++ b/examples/http_server.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use anyhow::{Context, Result};
 use futures_lite::stream::{once_future, unfold};
diff --git a/examples/http_server_proxy.rs b/examples/http_server_proxy.rs
index 77bb231..8d0cf01 100644
--- a/examples/http_server_proxy.rs
+++ b/examples/http_server_proxy.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 //! Run the example with:
 //! ```sh
diff --git a/examples/tcp_echo_server.rs b/examples/tcp_echo_server.rs
index 3e8aef2..319f911 100644
--- a/examples/tcp_echo_server.rs
+++ b/examples/tcp_echo_server.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use wstd::io;
 use wstd::iter::AsyncIterator;
diff --git a/examples/tcp_stream_client.rs b/examples/tcp_stream_client.rs
index c14b267..a269b8c 100644
--- a/examples/tcp_stream_client.rs
+++ b/examples/tcp_stream_client.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use wstd::io::{self, AsyncRead, AsyncWrite};
 use wstd::net::TcpStream;
diff --git a/examples/udp_echo_server.rs b/examples/udp_echo_server.rs
index 7c10bc3..c441d87 100644
--- a/examples/udp_echo_server.rs
+++ b/examples/udp_echo_server.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use wstd::io;
 use wstd::net::UdpSocket;
diff --git a/examples/udp_stream_client.rs b/examples/udp_stream_client.rs
index 68626d6..f26f5d5 100644
--- a/examples/udp_stream_client.rs
+++ b/examples/udp_stream_client.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(target_env = "p2"), no_main)]
-#![cfg(target_env = "p2")]
+#![cfg_attr(not(all(target_os = "wasi", target_env = "p2")), no_main)]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use wstd::io;
 use wstd::net::{UdpSocket, UdpStream};
diff --git a/src/lib.rs b/src/lib.rs
index c3442aa..e7abd6f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -55,26 +55,26 @@
 //! These are unique capabilities provided by WASI 0.2, and because this library
 //! is specific to that are exposed from here.
 
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod future;
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 #[macro_use]
 pub mod http;
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod io;
 pub mod iter;
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod net;
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod rand;
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod runtime;
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod task;
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod time;
 
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub use wstd_macro::{
     attr_macro_http_server as http_server, attr_macro_main as main, attr_macro_test as test,
 };
@@ -86,13 +86,13 @@ pub use wstd_macro::{
 // private.
 #[doc(hidden)]
 pub mod __internal {
-    #[cfg(target_env = "p2")]
+    #[cfg(all(target_os = "wasi", target_env = "p2"))]
     pub use wasip2;
-    #[cfg(target_env = "p3")]
+    #[cfg(all(target_os = "wasi", target_env = "p3"))]
     pub use wasip3;
 }
 
-#[cfg(target_env = "p2")]
+#[cfg(all(target_os = "wasi", target_env = "p2"))]
 pub mod prelude {
     pub use crate::future::FutureExt as _;
     pub use crate::io::AsyncRead as _;
diff --git a/tests/http_first_byte_timeout.rs b/tests/http_first_byte_timeout.rs
index fb22cd3..2162294 100644
--- a/tests/http_first_byte_timeout.rs
+++ b/tests/http_first_byte_timeout.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use wstd::http::{Body, Client, Request, error::ErrorCode};
 
diff --git a/tests/http_get.rs b/tests/http_get.rs
index 5660e0e..1735d22 100644
--- a/tests/http_get.rs
+++ b/tests/http_get.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use std::error::Error;
 use wstd::http::{Body, Client, HeaderValue, Request};
diff --git a/tests/http_get_json.rs b/tests/http_get_json.rs
index 5596e0b..641c2b7 100644
--- a/tests/http_get_json.rs
+++ b/tests/http_get_json.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use serde::Deserialize;
 use std::error::Error;
diff --git a/tests/http_handle_error_code.rs b/tests/http_handle_error_code.rs
index 0bbdd1d..fa72e0c 100644
--- a/tests/http_handle_error_code.rs
+++ b/tests/http_handle_error_code.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use wstd::http::{Body, Client, Request, error::ErrorCode};
 
diff --git a/tests/http_post.rs b/tests/http_post.rs
index 522c47b..1082a40 100644
--- a/tests/http_post.rs
+++ b/tests/http_post.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use std::error::Error;
 use wstd::http::{Client, HeaderValue, Request};
diff --git a/tests/http_post_json.rs b/tests/http_post_json.rs
index 1dc07f2..f67d050 100644
--- a/tests/http_post_json.rs
+++ b/tests/http_post_json.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use serde::{Deserialize, Serialize};
 use std::error::Error;
diff --git a/tests/http_timeout.rs b/tests/http_timeout.rs
index 04f60fc..6a156d9 100644
--- a/tests/http_timeout.rs
+++ b/tests/http_timeout.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use wstd::future::FutureExt;
 use wstd::http::{Body, Client, Request};
diff --git a/tests/sleep.rs b/tests/sleep.rs
index ac8c72a..c888302 100644
--- a/tests/sleep.rs
+++ b/tests/sleep.rs
@@ -1,4 +1,4 @@
-#![cfg(target_env = "p2")]
+#![cfg(all(target_os = "wasi", target_env = "p2"))]
 
 use std::error::Error;
 use wstd::task::sleep;

From 14e1bceb47b0d122b5fb35c8fec342a54b9d1a23 Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Wed, 9 Sep 2026 14:44:57 +0000
Subject: [PATCH 11/12] remove build-std

---
 .github/actions/install-rust/action.yml | 2 --
 .github/workflows/ci.yaml               | 2 +-
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/.github/actions/install-rust/action.yml b/.github/actions/install-rust/action.yml
index 18957d4..3c16f0c 100644
--- a/.github/actions/install-rust/action.yml
+++ b/.github/actions/install-rust/action.yml
@@ -35,10 +35,8 @@ runs:
 
         rustup target add wasm32-wasip2
 
-        # Required for -Zbuild-std for the wasip3 target.
         if [ "${{ inputs.toolchain }}" = "nightly" ]; then
           rustup target add wasm32-wasip3
-          rustup component add rust-src
         fi
 
         # Save disk space by avoiding incremental compilation. Also turn down
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 46cbec8..598dd5f 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -59,7 +59,7 @@ jobs:
 
     - name: wstd p3 tests
       if: matrix.rust == 'nightly'
-      run: cargo test -p wstd -p wstd-axum --target wasm32-wasip3 -Z build-std=std,panic_abort -- --nocapture
+      run: cargo test -p wstd -p wstd-axum --target wasm32-wasip3 -- --nocapture
 
     - name: test-programs tests
       run: cargo test -p test-programs -- --nocapture

From fb62b45f63f79043ad1c76996e5f02a6eaea385d Mon Sep 17 00:00:00 2001
From: Adam Bratschi-Kaye <a.bratschi-kaye@f5.com>
Date: Thu, 10 Sep 2026 13:10:19 +0000
Subject: [PATCH 12/12] cleanup Cargo.tomls after feature removal

---
 Cargo.toml      | 3 ++-
 axum/Cargo.toml | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 2a7e28b..6db1876 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -101,12 +101,13 @@ tower-service = "0.3.3"
 ureq = { version = "3.1", default-features = false, features = ["json"] }
 wasip2 = "1.0"
 wasip3 = "0.8"
-wstd = { path = ".", version = "=0.6.8", default-features = false }
+wstd = { path = ".", version = "=0.6.8" }
 wstd-axum = { path = "./axum", version = "=0.6.8" }
 wstd-axum-macro = { path = "./axum/macro", version = "=0.6.8" }
 wstd-macro = { path = "./macro", version = "=0.6.8" }
 
 [package.metadata.docs.rs]
+all-features = true
 targets = [
     "wasm32-wasip2"
 ]
diff --git a/axum/Cargo.toml b/axum/Cargo.toml
index 74141e9..154a021 100644
--- a/axum/Cargo.toml
+++ b/axum/Cargo.toml
@@ -13,7 +13,7 @@ rust-version.workspace = true
 [dependencies]
 axum.workspace = true
 tower-service.workspace = true
-wstd = { workspace = true, features = ["json"] }
+wstd.workspace = true
 wstd-axum-macro.workspace = true
 
 [dev-dependencies]