diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index ec4b4b9b..0fab372d 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -18,6 +18,8 @@ jobs:
     - uses: actions/checkout@v3
     - name: Add musl target
       run: rustup target add x86_64-unknown-linux-musl
+    - name: Add no_std target
+      run: rustup target add thumbv7m-none-eabi
     - name: Install musl-gcc
       run: sudo apt update && sudo apt install -y musl-tools
     - name: Format Check
@@ -26,6 +28,8 @@ jobs:
       run: cargo build -r --all-features --verbose
     - name: Build
       run: cargo build -r --verbose
+    - name: Build no_std
+      run: cd tests/ensure_no_std && cargo build -r --target thumbv7m-none-eabi
     - name: Doc Tests
       run: cargo test -r --doc
     - name: Run tests
diff --git a/Cargo.toml b/Cargo.toml
index 7d753bbf..1401833c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,6 +6,7 @@ members = [
     "bindings/wasm",
     "bindings/java",
     "bindings/ruby/ext/regorusrb",
+    "tests/ensure_no_std",
 ]
 
 [package]
@@ -33,14 +34,15 @@ crypto = ["dep:constant_time_eq", "dep:hmac", "dep:hex", "dep:md-5", "dep:sha1",
 deprecated = []
 hex = ["dep:data-encoding"]
 http = []
-jwt = ["dep:jsonwebtoken", "dep:data-encoding"]
 glob = ["dep:wax"]
 graph = []
 jsonschema = ["dep:jsonschema"]
+jwt = ["dep:jsonwebtoken", "dep:data-encoding", "dep:itertools"]
+no_std = ["lazy_static/spin_no_std"]
 opa-runtime = []
 regex = ["dep:regex"]
 semver = ["dep:semver"]
-std = ["serde_json/std"]
+std = ["rand", "serde_json/std"]
 time = ["dep:chrono", "dep:chrono-tz"]
 uuid = ["dep:uuid"]
 urlquery = ["dep:url"]
@@ -67,39 +69,58 @@ full-opa = [
     "yaml"
 ]
 
+# Features that can be used in no_std environments.
+# Note that: the spin_no_std feature in lazy_static must be specified.
+opa-no-std = [
+  "arc",
+  "base64",
+  "base64url",
+  "coverage",
+  "crypto",
+  "deprecated",
+  "graph",
+  "hex",
+  "no_std",
+  "opa-runtime",
+  "regex",
+  "semver",
+  # Configure lazy_static to use spinlocks.
+  "lazy_static/spin_no_std"
+]
+
 # This feature enables some testing utils for OPA tests.
 opa-testutil = []
 
 [dependencies]
-anyhow = { version = "1.0.45", default-features=false }
+anyhow = { version = "1.0.45", default-features = false }
 serde = {version = "1.0.150", default-features = false, features = ["derive", "rc"] }
-serde_json = { version = "1.0.89", default-features=false, features = ["alloc"] }
-serde_yaml = {version = "0.9.16", optional = true }
-lazy_static = "1.4.0"
-rand = "0.8.5"
-num = "0.4.1"
+serde_json = { version = "1.0.89", default-features = false, features = ["alloc"] }
+lazy_static =  { version = "1.4.0", default-features = false }
 
 # Crypto
-constant_time_eq = {version = "0.3.0", optional = true}
-hmac = {version = "0.12.1", optional = true}
-sha2 = {version= "0.10.8", optional = true}
-hex = {version = "0.4.3", optional = true}
-sha1 = {version = "0.10.6", optional = true}
-md-5 = {version = "0.10.6", optional = true}
-
-data-encoding = { version = "2.4.0", optional = true }
+constant_time_eq = {version = "0.3.0", optional = true, default-features = false }
+hmac = {version = "0.12.1", optional = true, default-features = false}
+sha2 = {version= "0.10.8", optional = true, default-features = false }
+hex = {version = "0.4.3", optional = true, default-features = false, features = ["alloc"] }
+sha1 = {version = "0.10.6", optional = true, default-features = false }
+md-5 = {version = "0.10.6", optional = true, default-features = false }
+
+data-encoding = { version = "2.4.0", optional = true, default-features=false, features = ["alloc"] }
 scientific = { version = "0.5.2" }
 
-regex = {version = "1.10.2", optional = true}
-semver = {version = "1.0.20", optional = true}
+regex = {version = "1.10.2", optional = true, default-features = false }
+semver = {version = "1.0.20", optional = true, default-features = false }
 wax = { version = "0.6.0", features = [], default-features = false, optional = true }
 url = { version = "2.5.0", optional = true }
-uuid = { version = "1.6.1", features = ["v4", "fast-rng"], optional = true }
+uuid = { version = "1.6.1", default-features = false, features = ["v4", "fast-rng"], optional = true }
 jsonschema = { version = "0.17.1", default-features = false, optional = true }
 chrono = { version = "0.4.31", optional = true }
 chrono-tz = { version = "0.8.5", optional = true }
 jsonwebtoken = { version = "9.2.0", optional = true }
-itertools = "0.12.1"
+itertools = { version = "0.12.1", default-features = false, optional = true }
+
+serde_yaml = {version = "0.9.16", default-features = false, optional = true }
+rand = { version = "0.8.5", default-features = false, optional = true } 
 
 [dev-dependencies]
 cfg-if = "1.0.0"
diff --git a/scripts/pre-push b/scripts/pre-push
index 7a2bec87..09577591 100755
--- a/scripts/pre-push
+++ b/scripts/pre-push
@@ -5,17 +5,24 @@
 set -eo pipefail
 
 if [ -f Cargo.toml ]; then
-   # Run precommit checks
+   # Run precommit checks.
    dir=$(dirname "${BASH_SOURCE[0]}")
    "$dir/pre-commit"
 
-   # Ensure that the public API works
+   # Ensure that the public API works.
    cargo test -r --doc
 
-   # Ensure that we can build with all features
+   # Ensure that no_std build succeeds.
+   # Build for a target that has no std available.
+   if command -v rustup > /dev/null; then
+       rustup target add thumbv7m-none-eabi
+       (cd tests/ensure_no_std; cargo build -r --target thumbv7m-none-eabi)
+   fi
+   
+   # Ensure that we can build with all features.
    cargo build -r --all-features
    
-   # Ensure that all tests pass
+   # Ensure that all tests pass.
    cargo test -r
    cargo test -r --test aci
    cargo test -r --test kata
diff --git a/src/builtins/debugging.rs b/src/builtins/debugging.rs
index 003e1383..1e407080 100644
--- a/src/builtins/debugging.rs
+++ b/src/builtins/debugging.rs
@@ -43,7 +43,7 @@ pub fn print_to_string(
 // Additionally interpreter must allow undefined inputs to print.
 fn print(span: &Span, params: &[Ref<Expr>], args: &[Value], strict: bool) -> Result<Value> {
     let msg = print_to_string(span, params, args, strict)?;
-
+    let _ = core::convert::identity(&msg);
     #[cfg(feature = "std")]
     if !msg.is_empty() {
         std::eprintln!("{}", &msg[1..]);
diff --git a/src/builtins/encoding.rs b/src/builtins/encoding.rs
index 6c05a056..0c89ab8a 100644
--- a/src/builtins/encoding.rs
+++ b/src/builtins/encoding.rs
@@ -63,7 +63,13 @@ fn base64_decode(
     ensure_args_count(span, name, params, args, 1)?;
 
     let encoded_str = ensure_string(name, &params[0], &args[0])?;
-    let decoded_bytes = data_encoding::BASE64.decode(encoded_str.as_bytes())?;
+    let decoded_bytes = data_encoding::BASE64
+        .decode(encoded_str.as_bytes())
+        .map_err(|e| {
+            params[0]
+                .span()
+                .error(&format!("decode failed\nCaused by\n{e}"))
+        })?;
     Ok(Value::String(
         String::from_utf8_lossy(&decoded_bytes).into(),
     ))
@@ -173,7 +179,13 @@ fn hex_decode(span: &Span, params: &[Ref<Expr>], args: &[Value], _strict: bool)
     ensure_args_count(span, name, params, args, 1)?;
 
     let encoded_str = ensure_string(name, &params[0], &args[0])?;
-    let decoded_bytes = data_encoding::HEXLOWER_PERMISSIVE.decode(encoded_str.as_bytes())?;
+    let decoded_bytes = data_encoding::HEXLOWER_PERMISSIVE
+        .decode(encoded_str.as_bytes())
+        .map_err(|e| {
+            params[0]
+                .span()
+                .error(&format!("decode failure\nCaused by\n{e}"))
+        })?;
     Ok(Value::String(
         String::from_utf8_lossy(&decoded_bytes).into(),
     ))
@@ -361,11 +373,9 @@ fn json_is_valid(
 fn json_marshal(span: &Span, params: &[Ref<Expr>], args: &[Value], _strict: bool) -> Result<Value> {
     let name = "json.marshal";
     ensure_args_count(span, name, params, args, 1)?;
-    Ok(Value::String(
-        serde_json::to_string(&args[0])
-            .with_context(|| span.error("could not serialize to json"))?
-            .into(),
-    ))
+    Ok(Value::from(serde_json::to_string(&args[0]).map_err(
+        |e| span.error(&format!("could not serialize to json\nCaused by\n{e}")),
+    )?))
 }
 
 fn json_marshal_with_options(
@@ -406,15 +416,13 @@ fn json_marshal_with_options(
     }
 
     if !pretty || options.is_empty() {
-        return Ok(Value::String(
-            serde_json::to_string(&args[0])
-                .with_context(|| span.error("could not serialize to json"))?
-                .into(),
-        ));
+        return Ok(Value::from(serde_json::to_string(&args[0]).map_err(
+            |e| span.error(&format!("could not serialize to json\nCaused by\n{e}")),
+        )?));
     }
 
     let lines: Vec<String> = serde_json::to_string_pretty(&args[0])
-        .with_context(|| span.error("could not serialize to json"))?
+        .map_err(|e| span.error(&format!("could not serialize to json\nCaused by\n{e}")))?
         .split('\n')
         .map(|line| {
             let mut line = line.to_string();
diff --git a/src/builtins/numbers.rs b/src/builtins/numbers.rs
index a3bf55cc..87675386 100644
--- a/src/builtins/numbers.rs
+++ b/src/builtins/numbers.rs
@@ -3,13 +3,15 @@
 
 use crate::ast::{ArithOp, Expr, Ref};
 use crate::builtins;
-use crate::builtins::utils::{ensure_args_count, ensure_numeric, ensure_string};
+use crate::builtins::utils::{ensure_args_count, ensure_numeric};
 use crate::lexer::Span;
 use crate::number::Number;
 use crate::value::Value;
 use crate::*;
 
 use anyhow::{bail, Result};
+
+#[cfg(feature = "std")]
 use rand::{thread_rng, Rng};
 
 pub fn register(m: &mut builtins::BuiltinsMap<&'static str, builtins::BuiltinFcn>) {
@@ -18,6 +20,7 @@ pub fn register(m: &mut builtins::BuiltinsMap<&'static str, builtins::BuiltinFcn
     m.insert("floor", (floor, 1));
     m.insert("numbers.range", (range, 2));
     m.insert("numbers.range_step", (range_step, 3));
+    #[cfg(feature = "std")]
     m.insert("rand.intn", (intn, 2));
     m.insert("round", (round, 1));
 }
@@ -155,10 +158,11 @@ fn round(span: &Span, params: &[Ref<Expr>], args: &[Value], _strict: bool) -> Re
     ))
 }
 
+#[cfg(feature = "std")]
 fn intn(span: &Span, params: &[Ref<Expr>], args: &[Value], _strict: bool) -> Result<Value> {
     let fcn = "rand.intn";
     ensure_args_count(span, fcn, params, args, 2)?;
-    let _ = ensure_string(fcn, &params[0], &args[0])?;
+    let _ = crate::builtins::utils::ensure_string(fcn, &params[0], &args[0])?;
     let n = ensure_numeric(fcn, &params[0], &args[1])?;
 
     Ok(match n.as_u64() {
diff --git a/src/builtins/opa.rs b/src/builtins/opa.rs
index fc388650..b427b779 100644
--- a/src/builtins/opa.rs
+++ b/src/builtins/opa.rs
@@ -38,6 +38,7 @@ fn opa_runtime(span: &Span, params: &[Ref<Expr>], args: &[Value], _strict: bool)
     );
 
     // Emitting environment variables could lead to confidential data being leaked.
+    #[cfg(feature = "std")]
     if false {
         obj.insert(
             Value::String("env".into()),
diff --git a/src/builtins/semver.rs b/src/builtins/semver.rs
index 8154fd38..6f4c916d 100644
--- a/src/builtins/semver.rs
+++ b/src/builtins/semver.rs
@@ -24,8 +24,8 @@ fn compare(span: &Span, params: &[Ref<Expr>], args: &[Value], _strict: bool) ->
 
     let v1 = ensure_string(name, &params[0], &args[0])?;
     let v2 = ensure_string(name, &params[1], &args[1])?;
-    let version1 = Version::parse(&v1)?;
-    let version2 = Version::parse(&v2)?;
+    let version1 = Version::parse(&v1).map_err(|_| params[0].span().error("invalid semver"))?;
+    let version2 = Version::parse(&v2).map_err(|_| params[0].span().error("invalid semver"))?;
     let result = match version1.cmp_precedence(&version2) {
         Ordering::Less => -1,
         Ordering::Equal => 0,
diff --git a/src/builtins/test.rs b/src/builtins/test.rs
index 0fe42d06..7a6d5264 100644
--- a/src/builtins/test.rs
+++ b/src/builtins/test.rs
@@ -7,6 +7,7 @@ use crate::builtins::time;
 use crate::builtins::utils::{ensure_args_count, ensure_string};
 use crate::lexer::Span;
 use crate::value::Value;
+use crate::*;
 
 use std::thread;
 
@@ -21,7 +22,8 @@ fn sleep(span: &Span, params: &[Ref<Expr>], args: &[Value], _strict: bool) -> Re
     ensure_args_count(span, name, params, args, 1)?;
 
     let val = ensure_string(name, &params[0], &args[0])?;
-    let dur = time::compat::parse_duration(val.as_ref())?;
+    let dur = time::compat::parse_duration(val.as_ref())
+        .map_err(|e| params[0].span().error(&format!("{e}")))?;
 
     thread::sleep(dur.to_std()?);
 
diff --git a/src/builtins/time.rs b/src/builtins/time.rs
index 12cf4743..8bc2ffa6 100644
--- a/src/builtins/time.rs
+++ b/src/builtins/time.rs
@@ -147,7 +147,7 @@ fn parse_duration_ns(
     ensure_args_count(span, name, params, args, 1)?;
 
     let value = ensure_string(name, &params[0], &args[0])?;
-    let dur = compat::parse_duration(value.as_ref())?;
+    let dur = compat::parse_duration(value.as_ref()).map_err(anyhow::Error::msg)?;
     safe_timestamp_nanos(span, strict, dur.num_nanoseconds())
 }
 
diff --git a/src/builtins/time/compat.rs b/src/builtins/time/compat.rs
index e2e0b440..0d491d04 100644
--- a/src/builtins/time/compat.rs
+++ b/src/builtins/time/compat.rs
@@ -34,7 +34,6 @@
 use crate::*;
 use core::fmt;
 use core::iter;
-use std::error::Error;
 
 use chrono::TimeZone;
 use chrono::{
@@ -72,8 +71,6 @@ impl fmt::Display for ParseDurationError {
     }
 }
 
-impl Error for ParseDurationError {}
-
 // Parses a duration string in the form of `10h12m45s`.
 //
 // Adapted from Go's `time.ParseDuration`:
diff --git a/src/interpreter.rs b/src/interpreter.rs
index caa0a299..30d7b059 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -1743,9 +1743,9 @@ impl Interpreter {
                                     span.col,
                                     format!(
 					"value for key `{}` generated multiple times: `{}` and `{}`",
-					serde_json::to_string_pretty(&key)?,
-					serde_json::to_string_pretty(&pv)?,
-					serde_json::to_string_pretty(&value)?,
+					serde_json::to_string_pretty(&key).map_err(anyhow::Error::msg)?,
+					serde_json::to_string_pretty(&pv).map_err(anyhow::Error::msg)?,
+					serde_json::to_string_pretty(&value).map_err(anyhow::Error::msg)?,
                                     )
                                     .as_str(),
                                 ));
diff --git a/src/lib.rs b/src/lib.rs
index f30546c1..a63befbe 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -404,30 +404,29 @@ pub mod coverage {
         /// <img src="https://github.com/microsoft/regorus/blob/main/docs/coverage.png?raw=true">
 
         pub fn to_colored_string(&self) -> anyhow::Result<String> {
-            use std::io::Write;
-            let mut s = Vec::new();
-            writeln!(&mut s, "COVERAGE REPORT:")?;
+            let mut s = String::default();
+            s.push_str("COVERAGE REPORT:\n");
             for file in self.files.iter() {
                 if file.not_covered.is_empty() {
-                    writeln!(&mut s, "{} has full coverage", file.path)?;
+                    s.push_str(&format!("{} has full coverage\n", file.path));
                     continue;
                 }
 
-                writeln!(&mut s, "{}:", file.path)?;
+                s.push_str(&format!("{}:", file.path));
                 for (line, code) in file.code.split('\n').enumerate() {
                     let line = line as u32 + 1;
                     if file.not_covered.contains(&line) {
-                        writeln!(&mut s, "\x1b[31m {line:4}  {code}\x1b[0m")?;
+                        s.push_str(&format!("\x1b[31m {line:4}  {code}\x1b[0m\n"));
                     } else if file.covered.contains(&line) {
-                        writeln!(&mut s, "\x1b[32m {line:4}  {code}\x1b[0m")?;
+                        s.push_str(&format!("\x1b[32m {line:4}  {code}\x1b[0m\n"));
                     } else {
-                        writeln!(&mut s, " {line:4}  {code}")?;
+                        s.push_str(&format!(" {line:4}  {code}\n"));
                     }
                 }
             }
 
-            writeln!(&mut s)?;
-            Ok(core::str::from_utf8(&s)?.to_string())
+            s.push('\n');
+            Ok(s)
         }
     }
 }
diff --git a/src/parser.rs b/src/parser.rs
index 3f34eab0..e9621f29 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -74,6 +74,7 @@ impl<'source> Parser<'source> {
         let msg = format!(
             "`{kw}` will be treated as identifier due to missing `import future.keywords.{kw}`"
         );
+        let _ = core::convert::identity(&msg);
         #[cfg(feature = "std")]
         std::println!(
             "{}",
diff --git a/src/scheduler.rs b/src/scheduler.rs
index 98f96c52..727266fc 100644
--- a/src/scheduler.rs
+++ b/src/scheduler.rs
@@ -47,7 +47,6 @@ pub fn schedule<Str: Clone + cmp::Ord + fmt::Debug>(
     empty: &Str,
 ) -> Result<SortResult> {
     let num_statements = infos.len();
-    let orig_infos: Vec<&StmtInfo<Str>> = infos.iter().collect();
 
     // Mapping from each var to the list of statements that define it.
     let mut defining_stmts: BTreeMap<Str, Vec<usize>> = BTreeMap::new();
@@ -198,7 +197,7 @@ pub fn schedule<Str: Clone + cmp::Ord + fmt::Debug>(
 
     if order.len() != num_statements {
         #[cfg(feature = "std")]
-        std::eprintln!("could not schedule all statements {order:?} {orig_infos:?}");
+        std::eprintln!("could not schedule all statements {order:?}");
         return Ok(SortResult::Order(
             (0..num_statements).map(|i| i as u16).collect(),
         ));
diff --git a/src/value.rs b/src/value.rs
index 212aee38..758368ca 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -406,6 +406,7 @@ impl Value {
 
     /// Deserialize a value from a file containing YAML.
     /// Note: Deserialization from YAML does not support arbitrary precision numbers.
+    #[cfg(feature = "std")]
     #[cfg(feature = "yaml")]
     pub fn from_yaml_file(path: &String) -> Result<Value> {
         match std::fs::read_to_string(path) {
diff --git a/tests/ensure_no_std/Cargo.toml b/tests/ensure_no_std/Cargo.toml
new file mode 100644
index 00000000..bcf7745f
--- /dev/null
+++ b/tests/ensure_no_std/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "ensure_no_std"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = { version = "1.0.83", default-features = false }
+regorus = { path = "../..", default-features = false, features = ["opa-no-std"] }
diff --git a/tests/ensure_no_std/src/main.rs b/tests/ensure_no_std/src/main.rs
new file mode 100644
index 00000000..d4aff8a4
--- /dev/null
+++ b/tests/ensure_no_std/src/main.rs
@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+#![no_std]
+#![no_main]
+
+use core::panic::PanicInfo;
+
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {}
+}
+
+#[no_mangle]
+pub extern "C" fn _start() -> ! {
+    loop {}
+}