diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
index 2717b200..8bdad5b6 100644
--- a/.github/workflows/checks.yml
+++ b/.github/workflows/checks.yml
@@ -24,6 +24,8 @@ jobs:
       - run: RUSTFLAGS="-D warnings" cargo check --all-targets
       - run: RUSTFLAGS="-D warnings" cargo check --all-targets --features trace
       - run: RUSTFLAGS="-D warnings" cargo check --all-targets --no-default-features
+      - run: cargo install cargo-no-std-check
+      - run: cargo no-std-check --workspace --exclude hvm64 --no-default-features
   clippy:
     runs-on: ubuntu-latest
     timeout-minutes: 10
diff --git a/Cargo.lock b/Cargo.lock
index f2335691..b1daa4d7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5,8 +5,7 @@ version = 3
 [[package]]
 name = "TSPL"
 version = "0.0.12"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "52dfd6238b1461b99635b26585a85b4e7b9c786cc0481b3c540ae5f590b6dfb6"
+source = "git+https://github.com/tjjfvi/TSPL?branch=no_std#35e172d6369794c6a81c9cd1bb249277e66e79c6"
 dependencies = [
  "highlight_error",
 ]
@@ -266,8 +265,7 @@ checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 [[package]]
 name = "highlight_error"
 version = "0.1.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "809e18805660d7b6b2e2b9f316a5099521b5998d5cba4dda11b5157a21aaef03"
+source = "git+https://github.com/tjjfvi/rust_highlight_error/?branch=no_std#e4136b3dd5a80699ecbab8fe708433da21ff1be1"
 
 [[package]]
 name = "hvm64"
@@ -320,7 +318,6 @@ dependencies = [
  "hvm64-runtime",
  "hvm64-util",
  "ordered-float",
- "thiserror",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index c25e4188..ffeb91ab 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -35,7 +35,7 @@ debug = "full"
 [dependencies]
 clap = { version = "4.5.4", features = ["derive"] }
 libloading = { version = "0.8.3", default-features = false }
-ordered-float = { version = "4.2.0" }
+ordered-float = { version = "4.2.0", default-features = false }
 thiserror = "1.0.58"
 
 hvm64-ast = { path = "./ast" }
@@ -52,3 +52,6 @@ serial_test = "3.0.0"
 default = ["std"]
 std = []
 trace = ["hvm64-runtime/trace"]
+
+[patch.crates-io]
+highlight_error = { git = "https://github.com/tjjfvi/rust_highlight_error/", branch = "no_std" }
diff --git a/ast/Cargo.toml b/ast/Cargo.toml
index b2894996..4a6d9a3f 100644
--- a/ast/Cargo.toml
+++ b/ast/Cargo.toml
@@ -8,13 +8,13 @@ path = "src/ast.rs"
 
 [dependencies]
 ordered-float = { version = "4.2.0", default-features = false }
-TSPL = { version = "0.0.12", optional = true }
+TSPL = { git = "https://github.com/tjjfvi/TSPL", branch = "no_std", optional = true }
 
-hvm64-util = { path = "../util" }
+hvm64-util = { path = "../util", default-features = false }
 
 [features]
 default = ["std", "parser"]
-std = []
+std = ["hvm64-util/std"]
 parser = ["dep:TSPL"]
 
 [lints]
diff --git a/ast/src/ast.rs b/ast/src/ast.rs
index 33d2f942..2dee343d 100644
--- a/ast/src/ast.rs
+++ b/ast/src/ast.rs
@@ -9,6 +9,7 @@
 //! The AST is based on the [interaction calculus].
 //!
 //! [interaction calculus]: https://en.wikipedia.org/wiki/Interaction_nets#Interaction_calculus
+#![cfg_attr(not(feature = "std"), no_std)]
 
 include!("../../prelude.rs");
 
diff --git a/host/Cargo.toml b/host/Cargo.toml
index 3a5b2901..e337a6d5 100644
--- a/host/Cargo.toml
+++ b/host/Cargo.toml
@@ -7,13 +7,13 @@ edition = "2021"
 path = "src/host.rs"
 
 [dependencies]
-hvm64-util = { path = "../util" }
+hvm64-util = { path = "../util", default-features = false }
 hvm64-ast = { path = "../ast", default-features = false }
 hvm64-runtime = { path = "../runtime", default-features = false }
 
 [features]
 default = ["std"]
-std = ["hvm64-ast/std", "hvm64-runtime/std"]
+std = ["hvm64-util/std", "hvm64-ast/std", "hvm64-runtime/std"]
 
 [lints]
 workspace = true
diff --git a/runtime/Cargo.toml b/runtime/Cargo.toml
index d05a9e7d..c8cc6661 100644
--- a/runtime/Cargo.toml
+++ b/runtime/Cargo.toml
@@ -7,11 +7,11 @@ edition = "2021"
 path = "src/runtime.rs"
 
 [dependencies]
-hvm64-util = { path = "../util" }
+hvm64-util = { path = "../util", default-features = false }
 
 [features]
 default = ["std"]
-std = []
+std = ["hvm64-util/std"]
 trace = ["std"]
 
 [lints]
diff --git a/runtime/src/runtime.rs b/runtime/src/runtime.rs
index 7b35dcf7..9a14ee34 100644
--- a/runtime/src/runtime.rs
+++ b/runtime/src/runtime.rs
@@ -19,6 +19,7 @@
 //! - active pairs are thus stored in a dedicated vector, `net.redexes`
 #![feature(const_type_id, extern_types, inline_const, new_uninit)]
 #![cfg_attr(feature = "trace", feature(const_type_name))]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 include!("../../prelude.rs");
 
diff --git a/transform/Cargo.toml b/transform/Cargo.toml
index 3ccccf36..1024942e 100644
--- a/transform/Cargo.toml
+++ b/transform/Cargo.toml
@@ -8,16 +8,15 @@ path = "src/transform.rs"
 
 [dependencies]
 ordered-float = { version = "4.2.0", default-features = false }
-thiserror = "1.0.58"
 
-hvm64-util = { path = "../util" }
+hvm64-util = { path = "../util", default-features = false }
 hvm64-runtime = { path = "../runtime", default-features = false }
 hvm64-ast = { path = "../ast", default-features = false }
 hvm64-host = { path = "../host", default-features = false }
 
 [features]
 default = ["std"]
-std = ["hvm64-runtime/std", "hvm64-ast/std", "hvm64-host/std"]
+std = ["hvm64-util/std", "hvm64-runtime/std", "hvm64-ast/std", "hvm64-host/std"]
 
 [lints]
 workspace = true
diff --git a/transform/src/transform.rs b/transform/src/transform.rs
index 4ef6f811..b6bfcc4f 100644
--- a/transform/src/transform.rs
+++ b/transform/src/transform.rs
@@ -2,6 +2,8 @@
 
 include!("../../prelude.rs");
 
+use crate::prelude::*;
+
 use hvm64_ast::Book;
 
 pub mod eta_reduce;
@@ -16,12 +18,18 @@ use prune::Prune;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[non_exhaustive]
-#[cfg_attr(feature = "std", derive(thiserror::Error))]
 pub enum TransformError {
-  #[cfg_attr(feature = "std", error("infinite reference cycle in `@{0}`"))]
   InfiniteRefCycle(String),
 }
 
+impl fmt::Display for TransformError {
+  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    match self {
+      TransformError::InfiniteRefCycle(name) => write!(f, "infinite reference cycle in `@{name}`"),
+    }
+  }
+}
+
 pub trait Transform {
   fn transform(&mut self, passes: TransformPasses, opts: &TransformOpts) -> Result<(), TransformError>;
 }
diff --git a/util/Cargo.toml b/util/Cargo.toml
index 304adf21..b2cfbf56 100644
--- a/util/Cargo.toml
+++ b/util/Cargo.toml
@@ -4,7 +4,11 @@ version = "0.3.0"
 edition = "2021"
 
 [dependencies]
-stacker = { version = "0.1.15" }
+stacker = { version = "0.1.15", optional = true }
+
+[features]
+default = ["std"]
+std = ["dep:stacker"]
 
 [lints]
 workspace = true
diff --git a/util/src/lib.rs b/util/src/lib.rs
index be7b857e..d080f897 100644
--- a/util/src/lib.rs
+++ b/util/src/lib.rs
@@ -1,3 +1,5 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+
 include!("../../prelude.rs");
 
 pub mod ops;
diff --git a/util/src/maybe_grow.rs b/util/src/maybe_grow.rs
index 11c04cf8..2025d57b 100644
--- a/util/src/maybe_grow.rs
+++ b/util/src/maybe_grow.rs
@@ -1,4 +1,10 @@
 /// Guard against stack overflows in recursive functions.
+#[cfg(feature = "std")]
 pub fn maybe_grow<R>(f: impl FnOnce() -> R) -> R {
   stacker::maybe_grow(1024 * 32, 1024 * 1024, f)
 }
+
+#[cfg(not(feature = "std"))]
+pub fn maybe_grow<R>(f: impl FnOnce() -> R) -> R {
+  f()
+}