diff --git a/crates/fayalite/examples/blinky.rs b/crates/fayalite/examples/blinky.rs
index 40b22dc..8682a33 100644
--- a/crates/fayalite/examples/blinky.rs
+++ b/crates/fayalite/examples/blinky.rs
@@ -44,7 +44,7 @@ struct ExtraArgs {
 impl ToArgs for ExtraArgs {
     fn to_args(&self, args: &mut (impl WriteArgs + ?Sized)) {
         let Self { clock_frequency } = self;
-        args.write_arg(format_args!("--clock-frequency={clock_frequency}"));
+        args.write_arg(format!("--clock-frequency={clock_frequency}"));
     }
 }
 
diff --git a/crates/fayalite/src/build.rs b/crates/fayalite/src/build.rs
index 96492cf..354d3b2 100644
--- a/crates/fayalite/src/build.rs
+++ b/crates/fayalite/src/build.rs
@@ -4,9 +4,9 @@
 use crate::{
     build::graph::JobGraph,
     bundle::{Bundle, BundleType},
-    intern::{Intern, Interned},
+    intern::{Intern, InternSlice, Interned},
     module::Module,
-    util::job_server::AcquiredJob,
+    util::{job_server::AcquiredJob, os_str_strip_prefix},
 };
 use clap::ArgAction;
 use serde::{
@@ -18,9 +18,11 @@ use std::{
     any::{Any, TypeId},
     borrow::Cow,
     cmp::Ordering,
-    ffi::OsStr,
+    ffi::{OsStr, OsString},
     fmt,
     hash::{Hash, Hasher},
+    io::Write,
+    marker::PhantomData,
     path::{Path, PathBuf},
     sync::{Arc, OnceLock},
 };
@@ -46,46 +48,14 @@ pub(crate) fn built_in_job_kinds() -> impl IntoIterator<Item = DynJobKind> {
     .chain(verilog::built_in_job_kinds())
 }
 
-#[track_caller]
-fn intern_known_utf8_path_buf(v: PathBuf) -> Interned<str> {
-    let Ok(v) = v.into_os_string().into_string().map(str::intern_owned) else {
-        unreachable!("known to be valid UTF-8");
-    };
-    v
-}
-
-#[track_caller]
-fn intern_known_utf8_str(v: impl AsRef<OsStr>) -> Interned<str> {
-    let Some(v) = v.as_ref().to_str().map(str::intern) else {
-        unreachable!("known to be valid UTF-8");
-    };
-    v
-}
-
-#[track_caller]
-fn interned_known_utf8_method<F: FnOnce(&Path) -> &OsStr>(
-    v: impl AsRef<str>,
-    f: F,
-) -> Interned<str> {
-    intern_known_utf8_str(f(v.as_ref().as_ref()))
-}
-
-#[track_caller]
-fn interned_known_utf8_path_buf_method<F: FnOnce(&Path) -> PathBuf>(
-    v: impl AsRef<str>,
-    f: F,
-) -> Interned<str> {
-    intern_known_utf8_path_buf(f(v.as_ref().as_ref()))
-}
-
 #[derive(Clone, Hash, PartialEq, Eq, Debug)]
 #[non_exhaustive]
 pub enum JobItem {
     Path {
-        path: Interned<str>,
+        path: Interned<Path>,
     },
     DynamicPaths {
-        paths: Vec<Interned<str>>,
+        paths: Vec<Interned<Path>>,
         source_job_name: Interned<str>,
     },
 }
@@ -105,7 +75,7 @@ impl JobItem {
 #[derive(Copy, Clone, Hash, PartialEq, Eq, Debug, Serialize, Deserialize)]
 #[non_exhaustive]
 pub enum JobItemName {
-    Path { path: Interned<str> },
+    Path { path: Interned<Path> },
     DynamicPaths { source_job_name: Interned<str> },
 }
 
@@ -122,7 +92,7 @@ impl JobItemName {
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
 enum JobItemNameRef<'a> {
-    Path { path: &'a str },
+    Path { path: &'a Path },
     DynamicPaths { source_job_name: &'a str },
 }
 
@@ -146,119 +116,191 @@ impl Ord for JobItemName {
 
 pub trait WriteArgs:
     for<'a> Extend<&'a str>
+    + for<'a> Extend<&'a OsStr>
+    + for<'a> Extend<&'a Path>
+    + for<'a> Extend<Cow<'a, str>>
+    + for<'a> Extend<Cow<'a, OsStr>>
+    + for<'a> Extend<Cow<'a, Path>>
     + Extend<String>
+    + Extend<OsString>
+    + Extend<PathBuf>
     + Extend<Interned<str>>
-    + for<'a> Extend<fmt::Arguments<'a>>
+    + Extend<Interned<OsStr>>
+    + Extend<Interned<Path>>
 {
-    fn write_args(&mut self, args: impl IntoIterator<Item: fmt::Display>) {
-        self.extend(args.into_iter().map(|v| format!("{v}")));
+    fn write_display_args(&mut self, args: impl IntoIterator<Item: fmt::Display>) {
+        self.extend(args.into_iter().map(|v| v.to_string()));
     }
-    fn write_string_args(&mut self, args: impl IntoIterator<Item = String>) {
-        self.extend(args);
+    fn write_owned_args(&mut self, args: impl IntoIterator<Item: Into<OsString>>) {
+        self.extend(args.into_iter().map(Into::<OsString>::into))
     }
-    fn write_str_args<'a>(&mut self, args: impl IntoIterator<Item = &'a str>) {
-        self.extend(args);
+    fn write_args<'a>(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>);
+    fn write_interned_args(&mut self, args: impl IntoIterator<Item: Into<Interned<OsStr>>>) {
+        self.extend(args.into_iter().map(Into::<Interned<OsStr>>::into))
     }
-    fn write_interned_args(&mut self, args: impl IntoIterator<Item = Interned<str>>) {
-        self.extend(args);
+    fn write_display_arg(&mut self, arg: impl fmt::Display) {
+        self.write_display_args([arg]);
     }
-    fn write_arg(&mut self, arg: impl fmt::Display) {
-        self.extend([format_args!("{arg}")]);
+    fn write_owned_arg(&mut self, arg: impl Into<OsString>) {
+        self.extend([arg.into()]);
     }
-    fn write_string_arg(&mut self, arg: String) {
-        self.extend([arg]);
+    fn write_arg(&mut self, arg: impl AsRef<OsStr>) {
+        self.extend([arg.as_ref()]);
     }
-    fn write_str_arg(&mut self, arg: &str) {
-        self.extend([arg]);
+    /// writes `--{name}={value}`
+    fn write_long_option_eq(&mut self, name: impl AsRef<OsStr>, value: impl AsRef<OsStr>) {
+        let name = name.as_ref();
+        let value = value.as_ref();
+        let mut option =
+            OsString::with_capacity(name.len().saturating_add(value.len()).saturating_add(3));
+        option.push("--");
+        option.push(name);
+        option.push("=");
+        option.push(value);
+        self.write_owned_arg(option);
     }
-    fn write_interned_arg(&mut self, arg: Interned<str>) {
-        self.extend([arg]);
+    fn write_interned_arg(&mut self, arg: impl Into<Interned<OsStr>>) {
+        self.extend([arg.into()]);
     }
     /// finds the first option that is `--{option_name}={value}` and returns `value`
-    fn get_long_option_eq(&self, option_name: impl AsRef<str>) -> Option<&str>;
+    fn get_long_option_eq(&self, option_name: impl AsRef<str>) -> Option<&OsStr>;
 }
 
-pub struct ArgsWriter<T>(pub Vec<T>);
+pub trait ArgsWriterArg:
+    AsRef<OsStr>
+    + From<Interned<OsStr>>
+    + for<'a> From<Cow<'a, OsStr>>
+    + for<'a> From<&'a OsStr>
+    + From<OsString>
+{
+}
 
-impl<T> Default for ArgsWriter<T> {
+impl ArgsWriterArg for Interned<OsStr> {}
+
+impl ArgsWriterArg for OsString {}
+
+pub struct ArgsWriter<A: ArgsWriterArg>(pub Vec<A>);
+
+impl<A: ArgsWriterArg> Default for ArgsWriter<A> {
     fn default() -> Self {
         Self(Default::default())
     }
 }
 
-impl<T: AsRef<str>> ArgsWriter<T> {
-    fn get_long_option_eq_helper(&self, option_name: &str) -> Option<&str> {
+impl<A: ArgsWriterArg> ArgsWriter<A> {
+    fn get_long_option_eq_helper(&self, option_name: &str) -> Option<&OsStr> {
         self.0.iter().find_map(|arg| {
-            arg.as_ref()
-                .strip_prefix("--")
-                .and_then(|arg| arg.strip_prefix(option_name))
-                .and_then(|arg| arg.strip_prefix("="))
+            os_str_strip_prefix(arg.as_ref(), "--")
+                .and_then(|arg| os_str_strip_prefix(arg, option_name))
+                .and_then(|arg| os_str_strip_prefix(arg, "="))
         })
     }
 }
 
-impl<'a, W> Extend<fmt::Arguments<'a>> for ArgsWriter<W>
-where
-    Self: Extend<String>,
-{
-    fn extend<T: IntoIterator<Item = fmt::Arguments<'a>>>(&mut self, iter: T) {
-        self.extend(iter.into_iter().map(|v| v.to_string()))
-    }
-}
-
-impl<'a> Extend<&'a str> for ArgsWriter<Interned<str>> {
+impl<'a, A: ArgsWriterArg> Extend<&'a str> for ArgsWriter<A> {
     fn extend<T: IntoIterator<Item = &'a str>>(&mut self, iter: T) {
-        self.extend(iter.into_iter().map(str::intern))
+        self.extend(iter.into_iter().map(AsRef::<OsStr>::as_ref))
     }
 }
 
-impl Extend<String> for ArgsWriter<Interned<str>> {
+impl<'a, A: ArgsWriterArg> Extend<&'a OsStr> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = &'a OsStr>>(&mut self, iter: T) {
+        self.0.extend(iter.into_iter().map(Into::into))
+    }
+}
+
+impl<'a, A: ArgsWriterArg> Extend<&'a Path> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = &'a Path>>(&mut self, iter: T) {
+        self.extend(iter.into_iter().map(AsRef::<OsStr>::as_ref))
+    }
+}
+
+impl<A: ArgsWriterArg> Extend<String> for ArgsWriter<A> {
     fn extend<T: IntoIterator<Item = String>>(&mut self, iter: T) {
-        self.extend(iter.into_iter().map(str::intern_owned))
+        self.extend(iter.into_iter().map(OsString::from))
     }
 }
 
-impl Extend<Interned<str>> for ArgsWriter<String> {
+impl<A: ArgsWriterArg> Extend<OsString> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = OsString>>(&mut self, iter: T) {
+        self.0.extend(iter.into_iter().map(Into::into))
+    }
+}
+
+impl<A: ArgsWriterArg> Extend<PathBuf> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = PathBuf>>(&mut self, iter: T) {
+        self.extend(iter.into_iter().map(OsString::from))
+    }
+}
+
+impl<A: ArgsWriterArg> Extend<Interned<str>> for ArgsWriter<A> {
     fn extend<T: IntoIterator<Item = Interned<str>>>(&mut self, iter: T) {
-        self.extend(iter.into_iter().map(String::from))
+        self.extend(iter.into_iter().map(Interned::<OsStr>::from))
     }
 }
 
-impl<'a> Extend<&'a str> for ArgsWriter<String> {
-    fn extend<T: IntoIterator<Item = &'a str>>(&mut self, iter: T) {
-        self.extend(iter.into_iter().map(String::from))
+impl<A: ArgsWriterArg> Extend<Interned<OsStr>> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = Interned<OsStr>>>(&mut self, iter: T) {
+        self.0.extend(iter.into_iter().map(Into::into))
     }
 }
 
-impl<I> Extend<I> for ArgsWriter<I> {
-    fn extend<T: IntoIterator<Item = I>>(&mut self, iter: T) {
-        self.0.extend(iter);
+impl<A: ArgsWriterArg> Extend<Interned<Path>> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = Interned<Path>>>(&mut self, iter: T) {
+        self.extend(iter.into_iter().map(Interned::<OsStr>::from))
     }
 }
 
-impl WriteArgs for ArgsWriter<String> {
-    fn get_long_option_eq(&self, option_name: impl AsRef<str>) -> Option<&str> {
-        self.get_long_option_eq_helper(option_name.as_ref())
+impl<'a, A: ArgsWriterArg> Extend<Cow<'a, str>> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = Cow<'a, str>>>(&mut self, iter: T) {
+        self.0.extend(iter.into_iter().map(|v| {
+            match v {
+                Cow::Borrowed(v) => Cow::<OsStr>::Borrowed(v.as_ref()),
+                Cow::Owned(v) => Cow::Owned(v.into()),
+            }
+            .into()
+        }))
     }
 }
 
-impl WriteArgs for ArgsWriter<Interned<str>> {
-    fn get_long_option_eq(&self, option_name: impl AsRef<str>) -> Option<&str> {
+impl<'a, A: ArgsWriterArg> Extend<Cow<'a, OsStr>> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = Cow<'a, OsStr>>>(&mut self, iter: T) {
+        self.0.extend(iter.into_iter().map(Into::into))
+    }
+}
+
+impl<'a, A: ArgsWriterArg> Extend<Cow<'a, Path>> for ArgsWriter<A> {
+    fn extend<T: IntoIterator<Item = Cow<'a, Path>>>(&mut self, iter: T) {
+        self.0.extend(iter.into_iter().map(|v| {
+            match v {
+                Cow::Borrowed(v) => Cow::<OsStr>::Borrowed(v.as_ref()),
+                Cow::Owned(v) => Cow::Owned(v.into()),
+            }
+            .into()
+        }))
+    }
+}
+
+impl<A: ArgsWriterArg> WriteArgs for ArgsWriter<A> {
+    fn write_args<'a>(&mut self, args: impl IntoIterator<Item: AsRef<OsStr>>) {
+        self.0.extend(args.into_iter().map(|v| v.as_ref().into()))
+    }
+    fn get_long_option_eq(&self, option_name: impl AsRef<str>) -> Option<&OsStr> {
         self.get_long_option_eq_helper(option_name.as_ref())
     }
 }
 
 pub trait ToArgs: clap::Args + 'static + Send + Sync + Hash + Eq + fmt::Debug + Clone {
     fn to_args(&self, args: &mut (impl WriteArgs + ?Sized));
-    fn to_interned_args(&self) -> Interned<[Interned<str>]> {
+    fn to_interned_args(&self) -> Interned<[Interned<OsStr>]> {
         Intern::intern_owned(self.to_interned_args_vec())
     }
-    fn to_interned_args_vec(&self) -> Vec<Interned<str>> {
+    fn to_interned_args_vec(&self) -> Vec<Interned<OsStr>> {
         let mut retval = ArgsWriter::default();
         self.to_args(&mut retval);
         retval.0
     }
-    fn to_string_args(&self) -> Vec<String> {
+    fn to_os_string_args(&self) -> Vec<OsString> {
         let mut retval = ArgsWriter::default();
         self.to_args(&mut retval);
         retval.0
@@ -361,6 +403,15 @@ pub struct JobAndDependencies<K: JobKind> {
     pub dependencies: <K::Dependencies as JobDependencies>::JobsAndKinds,
 }
 
+impl<K: JobKind> JobAndDependencies<K> {
+    pub fn get_job<J, Position>(&self) -> &J
+    where
+        Self: GetJob<J, Position>,
+    {
+        GetJob::get_job(self)
+    }
+}
+
 impl<K: JobKind> Clone for JobAndDependencies<K>
 where
     K::Job: Clone,
@@ -608,41 +659,44 @@ impl JobParams {
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub struct CommandParams {
-    pub command_line: Interned<[Interned<str>]>,
-    pub current_dir: Option<Interned<str>>,
+    pub command_line: Interned<[Interned<OsStr>]>,
+    pub current_dir: Option<Interned<Path>>,
 }
 
 impl CommandParams {
-    fn to_unix_shell_line<W: ?Sized + fmt::Write>(
+    fn to_unix_shell_line<E>(
         self,
-        output: &mut W,
-        mut escape_arg: impl FnMut(&str, &mut W) -> fmt::Result,
-    ) -> fmt::Result {
+        output: &mut String,
+        mut escape_arg: impl FnMut(&OsStr, &mut String) -> Result<(), E>,
+    ) -> Result<(), E> {
         let Self {
             command_line,
             current_dir,
         } = self;
         let mut end = None;
         let mut separator = if let Some(current_dir) = current_dir {
-            output.write_str("(cd ")?;
+            output.push_str("(cd ");
             end = Some(")");
-            if !current_dir.starts_with(|ch: char| {
-                ch.is_ascii_alphanumeric() || matches!(ch, '/' | '\\' | '.')
-            }) {
-                output.write_str("-- ")?;
+            if !current_dir
+                .as_os_str()
+                .as_encoded_bytes()
+                .first()
+                .is_some_and(|ch| ch.is_ascii_alphanumeric() || matches!(ch, b'/' | b'\\' | b'.'))
+            {
+                output.push_str("-- ");
             }
-            escape_arg(&current_dir, output)?;
+            escape_arg(current_dir.as_ref(), output)?;
             "; exec -- "
         } else {
             ""
         };
         for arg in command_line {
-            output.write_str(separator)?;
+            output.push_str(separator);
             separator = " ";
             escape_arg(&arg, output)?;
         }
         if let Some(end) = end {
-            output.write_str(end)?;
+            output.push_str(end);
         }
         Ok(())
     }
@@ -999,7 +1053,7 @@ trait DynJobArgsTrait: 'static + Send + Sync + fmt::Debug {
     fn eq_dyn(&self, other: &dyn DynJobArgsTrait) -> bool;
     fn hash_dyn(&self, state: &mut dyn Hasher);
     fn kind(&self) -> DynJobKind;
-    fn to_args_extend_vec(&self, args: Vec<Interned<str>>) -> Vec<Interned<str>>;
+    fn to_args_extend_vec(&self, args: Vec<Interned<OsStr>>) -> Vec<Interned<OsStr>>;
     fn clone_into_arc(&self) -> Arc<dyn DynJobArgsTrait>;
     fn update_from_arg_matches(
         &mut self,
@@ -1041,7 +1095,7 @@ impl<K: JobKind> DynJobArgsTrait for DynJobArgsInner<K> {
         DynJobKind::new(self.0.kind)
     }
 
-    fn to_args_extend_vec(&self, args: Vec<Interned<str>>) -> Vec<Interned<str>> {
+    fn to_args_extend_vec(&self, args: Vec<Interned<OsStr>>) -> Vec<Interned<OsStr>> {
         let mut writer = ArgsWriter(args);
         self.0.args.to_args(&mut writer);
         writer.0
@@ -1101,10 +1155,10 @@ impl DynJobArgs {
     pub fn kind(&self) -> DynJobKind {
         DynJobArgsTrait::kind(&*self.0)
     }
-    pub fn to_args_vec(&self) -> Vec<Interned<str>> {
+    pub fn to_args_vec(&self) -> Vec<Interned<OsStr>> {
         self.to_args_extend_vec(Vec::new())
     }
-    pub fn to_args_extend_vec(&self, args: Vec<Interned<str>>) -> Vec<Interned<str>> {
+    pub fn to_args_extend_vec(&self, args: Vec<Interned<OsStr>>) -> Vec<Interned<OsStr>> {
         DynJobArgsTrait::to_args_extend_vec(&*self.0, args)
     }
     fn make_mut(&mut self) -> &mut dyn DynJobArgsTrait {
@@ -1329,8 +1383,8 @@ impl DynJob {
     #[track_caller]
     pub fn internal_command_params_with_program_prefix(
         &self,
-        internal_program_prefix: &[Interned<str>],
-        extra_args: &[Interned<str>],
+        internal_program_prefix: &[Interned<OsStr>],
+        extra_args: &[Interned<OsStr>],
     ) -> CommandParams {
         let mut command_line = internal_program_prefix.to_vec();
         let command_line = match RunSingleJob::try_add_subcommand(self, &mut command_line) {
@@ -1346,7 +1400,7 @@ impl DynJob {
         }
     }
     #[track_caller]
-    pub fn internal_command_params(&self, extra_args: &[Interned<str>]) -> CommandParams {
+    pub fn internal_command_params(&self, extra_args: &[Interned<OsStr>]) -> CommandParams {
         self.internal_command_params_with_program_prefix(
             &[program_name_for_internal_jobs()],
             extra_args,
@@ -1355,8 +1409,8 @@ impl DynJob {
     #[track_caller]
     pub fn command_params_with_internal_program_prefix(
         &self,
-        internal_program_prefix: &[Interned<str>],
-        extra_args: &[Interned<str>],
+        internal_program_prefix: &[Interned<OsStr>],
+        extra_args: &[Interned<OsStr>],
     ) -> CommandParams {
         match self.external_command_params() {
             Some(v) => v,
@@ -1365,7 +1419,7 @@ impl DynJob {
         }
     }
     #[track_caller]
-    pub fn command_params(&self, extra_args: &[Interned<str>]) -> CommandParams {
+    pub fn command_params(&self, extra_args: &[Interned<OsStr>]) -> CommandParams {
         self.command_params_with_internal_program_prefix(
             &[program_name_for_internal_jobs()],
             extra_args,
@@ -1490,14 +1544,16 @@ impl RunSingleJob {
     pub const SUBCOMMAND_NAME: &'static str = "run-single-job";
     fn try_add_subcommand(
         job: &DynJob,
-        subcommand_line: &mut Vec<Interned<str>>,
+        subcommand_line: &mut Vec<Interned<OsStr>>,
     ) -> serde_json::Result<()> {
         let mut json = job.serialize_to_json_ascii()?;
         json.insert_str(0, "--json=");
         subcommand_line.extend([
-            Self::SUBCOMMAND_NAME.intern(),
-            Intern::intern_owned(format!("--name={}", job.kind().name())),
-            Intern::intern_owned(json),
+            Interned::<OsStr>::from(Self::SUBCOMMAND_NAME.intern()),
+            format!("--name={}", job.kind().name())
+                .intern_deref()
+                .into(),
+            json.intern_deref().into(),
         ]);
         Ok(())
     }
@@ -1623,10 +1679,11 @@ impl RunBuild for Completions {
         F: FnOnce(NoArgs) -> eyre::Result<JobParams>,
     {
         let Self::Completions { shell } = self;
-        let bin_name = cmd
-            .get_bin_name()
-            .map(str::intern)
-            .unwrap_or_else(|| program_name_for_internal_jobs());
+        let bin_name = cmd.get_bin_name().map(str::intern).unwrap_or_else(|| {
+            program_name_for_internal_jobs()
+                .to_interned_str()
+                .expect("program name is invalid UTF-8")
+        });
         clap_complete::aot::generate(
             shell,
             &mut cmd,
@@ -1667,6 +1724,7 @@ pub enum BuildCli<Extra: ToArgs = NoArgs> {
     RunSingleJob(RunSingleJob<Extra>),
     #[clap(flatten)]
     Completions(Completions),
+    #[cfg(unix)]
     #[clap(flatten)]
     CreateUnixShellScript(CreateUnixShellScript<Extra>),
 }
@@ -1680,11 +1738,13 @@ impl<Extra: ToArgs> RunBuild<Extra> for BuildCli<Extra> {
             BuildCli::Job(v) => v.run(make_params, cmd),
             BuildCli::RunSingleJob(v) => v.run(make_params, cmd),
             BuildCli::Completions(v) => v.run(|NoArgs {}| unreachable!(), cmd),
+            #[cfg(unix)]
             BuildCli::CreateUnixShellScript(v) => v.run(make_params, cmd),
         }
     }
 }
 
+#[cfg(unix)]
 #[derive(Clone, PartialEq, Eq, Hash, Debug, clap::Subcommand)]
 enum CreateUnixShellScriptInner<Extra: ToArgs> {
     CreateUnixShellScript {
@@ -1717,16 +1777,17 @@ impl<Extra: ToArgs> RunBuild<Extra> for CreateUnixShellScript<Extra> {
         let (job, dependencies) = args.args_to_jobs(dependencies_args, &params)?;
         let mut job_graph = JobGraph::new();
         job_graph.add_jobs([job].into_iter().chain(dependencies));
-        println!(
-            "{}",
-            job_graph.to_unix_shell_script_with_internal_program_prefix(
-                &[cmd
-                    .get_bin_name()
-                    .map(str::intern)
-                    .unwrap_or_else(|| program_name_for_internal_jobs())],
-                &extra_args,
-            )
-        );
+        std::io::stdout().write_all(
+            job_graph
+                .to_unix_shell_script_with_internal_program_prefix(
+                    &[cmd
+                        .get_bin_name()
+                        .map(|v| OsStr::new(v).intern())
+                        .unwrap_or_else(|| program_name_for_internal_jobs())],
+                    &extra_args,
+                )
+                .as_bytes(),
+        )?;
         Ok(())
     }
 }
@@ -1749,6 +1810,7 @@ impl<Extra: ToArgs> clap::FromArgMatches for CreateUnixShellScript<Extra> {
     }
 }
 
+#[cfg(unix)]
 impl<Extra: ToArgs> clap::Subcommand for CreateUnixShellScript<Extra> {
     fn augment_subcommands(cmd: clap::Command) -> clap::Command {
         CreateUnixShellScriptInner::<Extra>::augment_subcommands(cmd)
@@ -1912,10 +1974,14 @@ impl<Extra: ToArgs> RunBuild<Extra> for AnyJobSubcommand<Extra> {
     }
 }
 
-pub fn program_name_for_internal_jobs() -> Interned<str> {
-    static PROGRAM_NAME: OnceLock<Interned<str>> = OnceLock::new();
-    *PROGRAM_NAME
-        .get_or_init(|| str::intern_owned(std::env::args().next().expect("can't get program name")))
+pub fn program_name_for_internal_jobs() -> Interned<OsStr> {
+    static PROGRAM_NAME: OnceLock<Interned<OsStr>> = OnceLock::new();
+    *PROGRAM_NAME.get_or_init(|| {
+        std::env::args_os()
+            .next()
+            .expect("can't get program name")
+            .intern_deref()
+    })
 }
 
 #[derive(clap::Args, PartialEq, Eq, Hash, Debug, Clone)]
@@ -1923,7 +1989,7 @@ pub fn program_name_for_internal_jobs() -> Interned<str> {
 pub struct CreateOutputDirArgs {
     /// the directory to put the generated main output file and associated files in
     #[arg(short, long, value_hint = clap::ValueHint::DirPath)]
-    pub output: Option<String>,
+    pub output: Option<PathBuf>,
     #[arg(long, env = "FAYALITE_KEEP_TEMP_DIR")]
     pub keep_temp_dir: bool,
 }
@@ -1935,17 +2001,17 @@ impl ToArgs for CreateOutputDirArgs {
             keep_temp_dir,
         } = self;
         if let Some(output) = output {
-            args.write_arg(format_args!("--output={output}"));
+            args.write_long_option_eq("output", output);
         }
         if *keep_temp_dir {
-            args.write_str_arg("--keep-temp-dir");
+            args.write_arg("--keep-temp-dir");
         }
     }
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct CreateOutputDir {
-    output_dir: Interned<str>,
+    output_dir: Interned<Path>,
     #[serde(skip)]
     temp_dir: Option<Arc<TempDir>>,
 }
@@ -1998,20 +2064,7 @@ impl JobKind for CreateOutputDirJobKind {
             // we create the temp dir here rather than in run so other
             // jobs can have their paths based on the chosen temp dir
             let temp_dir = TempDir::new()?;
-            let output_dir = temp_dir
-                .path()
-                .as_os_str()
-                .to_str()
-                .ok_or_else(|| {
-                    std::io::Error::new(
-                        std::io::ErrorKind::InvalidFilename,
-                        format!(
-                            "temporary directory path is not valid UTF-8: {:?}",
-                            temp_dir.path()
-                        ),
-                    )
-                })?
-                .intern();
+            let output_dir = temp_dir.path().intern();
             let temp_dir = if keep_temp_dir {
                 // use TempDir::into_path() to no longer automatically delete the temp dir
                 let temp_dir_path = temp_dir.into_path();
@@ -2041,8 +2094,8 @@ impl JobKind for CreateOutputDirJobKind {
     fn outputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
         [JobItemName::Path {
             path: job.output_dir,
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
     fn name(self) -> Interned<str> {
@@ -2052,12 +2105,12 @@ impl JobKind for CreateOutputDirJobKind {
     fn external_command_params(self, job: &Self::Job) -> Option<CommandParams> {
         Some(CommandParams {
             command_line: [
-                "mkdir".intern(),
-                "-p".intern(),
-                "--".intern(),
-                job.output_dir,
-            ][..]
-                .intern(),
+                "mkdir".intern().into(),
+                "-p".intern().into(),
+                "--".intern().into(),
+                job.output_dir.into(),
+            ]
+            .intern_slice(),
             current_dir: None,
         })
     }
@@ -2084,10 +2137,10 @@ impl JobKind for CreateOutputDirJobKind {
 }
 
 impl CreateOutputDir {
-    pub fn output_dir(&self) -> Interned<str> {
+    pub fn output_dir(&self) -> Interned<Path> {
         self.output_dir
     }
-    fn compare_key(&self) -> (&str, bool) {
+    fn compare_key(&self) -> (&Path, bool) {
         let Self {
             output_dir,
             temp_dir,
@@ -2105,7 +2158,7 @@ pub struct BaseJobArgs {
     pub create_output_dir_args: CreateOutputDirArgs,
     /// the stem of the generated main output file, e.g. to get foo.v, pass --file-stem=foo
     #[arg(long)]
-    pub file_stem: Option<String>,
+    pub file_stem: Option<OsString>,
     /// run commands even if their results are already cached
     #[arg(long, env = Self::RUN_EVEN_IF_CACHED_ENV_NAME)]
     pub run_even_if_cached: bool,
@@ -2113,7 +2166,7 @@ pub struct BaseJobArgs {
 
 impl BaseJobArgs {
     pub const RUN_EVEN_IF_CACHED_ENV_NAME: &'static str = "FAYALITE_RUN_EVEN_IF_CACHED";
-    pub fn from_output_dir_and_env(output: String) -> Self {
+    pub fn from_output_dir_and_env(output: PathBuf) -> Self {
         Self {
             create_output_dir_args: CreateOutputDirArgs {
                 output: Some(output),
@@ -2134,10 +2187,10 @@ impl ToArgs for BaseJobArgs {
         } = self;
         create_output_dir_args.to_args(args);
         if let Some(file_stem) = file_stem {
-            args.write_arg(format_args!("--file-stem={file_stem}"));
+            args.write_long_option_eq("file-stem", file_stem);
         }
         if *run_even_if_cached {
-            args.write_str_arg("--run-even-if-cached");
+            args.write_arg("--run-even-if-cached");
         }
     }
 }
@@ -2147,21 +2200,21 @@ pub struct BaseJob {
     /// rather than having CreateOutputDir be a normal dependency, it's nested in BaseJob to avoid a cyclic dependency
     #[serde(flatten)]
     create_output_dir: CreateOutputDir,
-    file_stem: Interned<str>,
+    file_stem: Interned<OsStr>,
     run_even_if_cached: bool,
 }
 
 impl BaseJob {
-    pub fn output_dir(&self) -> Interned<str> {
+    pub fn output_dir(&self) -> Interned<Path> {
         self.create_output_dir.output_dir()
     }
-    pub fn file_stem(&self) -> Interned<str> {
+    pub fn file_stem(&self) -> Interned<OsStr> {
         self.file_stem
     }
-    pub fn file_with_ext(&self, ext: &str) -> Interned<str> {
-        let mut retval = std::path::Path::new(&self.output_dir()).join(self.file_stem());
+    pub fn file_with_ext(&self, ext: impl AsRef<OsStr>) -> Interned<Path> {
+        let mut retval = self.output_dir().join(self.file_stem());
         retval.set_extension(ext);
-        intern_known_utf8_path_buf(retval)
+        retval.intern_deref()
     }
     pub fn run_even_if_cached(&self) -> bool {
         self.run_even_if_cached
@@ -2195,8 +2248,8 @@ impl JobKind for BaseJobKind {
         };
         let create_output_dir = create_output_dir_args.args_to_jobs((), params)?.job.job;
         let file_stem = file_stem
-            .map(Intern::intern_owned)
-            .unwrap_or(params.main_module().name());
+            .map(Intern::intern_deref)
+            .unwrap_or(params.main_module().name().into());
         Ok(JobAndDependencies {
             job: JobAndKind {
                 kind: BaseJobKind,
@@ -2241,64 +2294,91 @@ impl JobKind for BaseJobKind {
     }
 }
 
-pub trait GetBaseJob {
-    fn base_job(&self) -> &BaseJob;
+pub trait GetJob<J, Position> {
+    fn get_job(this: &Self) -> &J;
 }
 
-impl<T: ?Sized + GetBaseJob> GetBaseJob for &'_ T {
-    fn base_job(&self) -> &BaseJob {
-        T::base_job(self)
+impl<J, Position, T: ?Sized + GetJob<J, Position>> GetJob<J, Position> for &'_ T {
+    fn get_job(this: &Self) -> &J {
+        T::get_job(this)
     }
 }
 
-impl<T: ?Sized + GetBaseJob> GetBaseJob for &'_ mut T {
-    fn base_job(&self) -> &BaseJob {
-        T::base_job(self)
+impl<J, Position, T: ?Sized + GetJob<J, Position>> GetJob<J, Position> for &'_ mut T {
+    fn get_job(this: &Self) -> &J {
+        T::get_job(this)
     }
 }
 
-impl<T: ?Sized + GetBaseJob> GetBaseJob for Box<T> {
-    fn base_job(&self) -> &BaseJob {
-        T::base_job(self)
+impl<J, Position, T: ?Sized + GetJob<J, Position>> GetJob<J, Position> for Box<T> {
+    fn get_job(this: &Self) -> &J {
+        T::get_job(this)
     }
 }
 
-impl GetBaseJob for BaseJob {
-    fn base_job(&self) -> &BaseJob {
-        self
+pub struct GetJobPositionDependencies<T>(PhantomData<T>);
+
+impl<T> Default for GetJobPositionDependencies<T> {
+    fn default() -> Self {
+        Self(Default::default())
     }
 }
 
-impl GetBaseJob for JobAndKind<BaseJobKind> {
-    fn base_job(&self) -> &BaseJob {
-        &self.job
+impl<T> fmt::Debug for GetJobPositionDependencies<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "GetJobPositionDependencies<{}>",
+            std::any::type_name::<T>()
+        )
     }
 }
 
-impl GetBaseJob for JobAndDependencies<BaseJobKind> {
-    fn base_job(&self) -> &BaseJob {
-        &self.job.job
+impl<T> Hash for GetJobPositionDependencies<T> {
+    fn hash<H: Hasher>(&self, _state: &mut H) {}
+}
+
+impl<T> Ord for GetJobPositionDependencies<T> {
+    fn cmp(&self, _other: &Self) -> Ordering {
+        Ordering::Equal
     }
 }
 
-impl<K: JobKind> GetBaseJob for JobAndDependencies<K>
-where
-    K::Dependencies: JobDependencies,
-    <K::Dependencies as JobDependencies>::JobsAndKinds: GetBaseJob,
+impl<T> PartialOrd for GetJobPositionDependencies<T> {
+    fn partial_cmp(&self, _other: &Self) -> Option<Ordering> {
+        Some(Ordering::Equal)
+    }
+}
+
+impl<T> Eq for GetJobPositionDependencies<T> {}
+
+impl<T> PartialEq for GetJobPositionDependencies<T> {
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
+impl<T> Clone for GetJobPositionDependencies<T> {
+    fn clone(&self) -> Self {
+        Self(PhantomData)
+    }
+}
+
+impl<T> Copy for GetJobPositionDependencies<T> {}
+
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Default)]
+pub struct GetJobPositionJob;
+
+impl<J, Position, K: JobKind<Dependencies: JobDependencies<JobsAndKinds: GetJob<J, Position>>>>
+    GetJob<J, GetJobPositionDependencies<Position>> for JobAndDependencies<K>
 {
-    fn base_job(&self) -> &BaseJob {
-        self.dependencies.base_job()
+    fn get_job(this: &Self) -> &J {
+        GetJob::get_job(&this.dependencies)
     }
 }
 
-impl<T: GetBaseJob, U> GetBaseJob for (T, U) {
-    fn base_job(&self) -> &BaseJob {
-        self.0.base_job()
-    }
-}
-
-impl<T: GetBaseJob, U, V> GetBaseJob for (T, U, V) {
-    fn base_job(&self) -> &BaseJob {
-        self.0.base_job()
+impl<K: JobKind> GetJob<K::Job, GetJobPositionJob> for JobAndDependencies<K> {
+    fn get_job(this: &Self) -> &K::Job {
+        &this.job.job
     }
 }
diff --git a/crates/fayalite/src/build/external.rs b/crates/fayalite/src/build/external.rs
index 021d63d..a6936e5 100644
--- a/crates/fayalite/src/build/external.rs
+++ b/crates/fayalite/src/build/external.rs
@@ -3,9 +3,9 @@
 
 use crate::{
     build::{
-        ArgsWriter, CommandParams, GetBaseJob, JobAndDependencies, JobAndKind,
+        ArgsWriter, BaseJob, CommandParams, GetJob, JobAndDependencies, JobAndKind,
         JobArgsAndDependencies, JobDependencies, JobItem, JobItemName, JobKind, JobKindAndArgs,
-        JobParams, ToArgs, WriteArgs, intern_known_utf8_path_buf,
+        JobParams, ToArgs, WriteArgs,
     },
     intern::{Intern, Interned},
     util::{job_server::AcquiredJob, streaming_read_utf8::streaming_read_utf8},
@@ -55,6 +55,25 @@ impl MaybeUtf8 {
             MaybeUtf8::Binary(v) => v,
         }
     }
+    pub fn as_os_str(&self) -> &OsStr {
+        #![allow(unreachable_code)]
+        #[cfg(unix)]
+        {
+            return std::os::unix::ffi::OsStrExt::from_bytes(self.as_bytes());
+        }
+        #[cfg(target_os = "wasi")]
+        {
+            return std::os::wasi::ffi::OsStrExt::from_bytes(self.as_bytes());
+        }
+        // implementing WTF-8 is too much of a pain so don't have a special case for windows
+        if let Ok(s) = str::from_utf8(self.as_bytes()) {
+            return OsStr::new(s);
+        }
+        panic!("invalid UTF-8 conversion to OsStr is not implemented on this platform");
+    }
+    pub fn as_path(&self) -> &Path {
+        Path::new(self.as_os_str())
+    }
 }
 
 #[derive(Serialize, Deserialize)]
@@ -107,31 +126,80 @@ impl From<String> for MaybeUtf8 {
     }
 }
 
+impl From<PathBuf> for MaybeUtf8 {
+    fn from(value: PathBuf) -> Self {
+        Self::from(value.into_os_string().into_encoded_bytes())
+    }
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Serialize, Deserialize)]
+#[serde(rename = "File")]
+pub struct ExternalJobCacheV2File<'a> {
+    pub name: MaybeUtf8,
+    pub contents: Cow<'a, MaybeUtf8>,
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
+pub struct ExternalJobCacheV2Files(pub BTreeMap<PathBuf, MaybeUtf8>);
+
+impl Serialize for ExternalJobCacheV2Files {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.collect_seq(
+            self.0
+                .iter()
+                .map(|(name, contents)| ExternalJobCacheV2File {
+                    name: name.clone().into(),
+                    contents: Cow::Borrowed(contents),
+                }),
+        )
+    }
+}
+
+impl<'de> Deserialize<'de> for ExternalJobCacheV2Files {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Ok(Self(
+            Vec::deserialize(deserializer)?
+                .into_iter()
+                .map(|ExternalJobCacheV2File { name, contents }| {
+                    (name.as_path().to_path_buf(), contents.into_owned())
+                })
+                .collect(),
+        ))
+    }
+}
+
 #[derive(Clone, PartialEq, Eq, Debug, Serialize, Deserialize)]
 #[serde(rename = "ExternalJobCache")]
 pub struct ExternalJobCacheV2 {
     pub version: ExternalJobCacheVersion,
     pub inputs_hash: blake3::Hash,
     pub stdout_stderr: String,
-    pub result: Result<BTreeMap<String, MaybeUtf8>, String>,
+    pub result: Result<ExternalJobCacheV2Files, String>,
 }
 
 impl ExternalJobCacheV2 {
-    fn read_from_file(cache_json_path: Interned<str>) -> eyre::Result<Self> {
+    fn read_from_file(cache_json_path: Interned<Path>) -> eyre::Result<Self> {
         let cache_str = std::fs::read_to_string(&*cache_json_path)
-            .wrap_err_with(|| format!("can't read {cache_json_path}"))?;
-        serde_json::from_str(&cache_str).wrap_err_with(|| format!("can't decode {cache_json_path}"))
+            .wrap_err_with(|| format!("can't read {cache_json_path:?}"))?;
+        serde_json::from_str(&cache_str)
+            .wrap_err_with(|| format!("can't decode {cache_json_path:?}"))
     }
-    fn write_to_file(&self, cache_json_path: Interned<str>) -> eyre::Result<()> {
+    fn write_to_file(&self, cache_json_path: Interned<Path>) -> eyre::Result<()> {
         let cache_str = serde_json::to_string_pretty(&self).expect("serialization can't fail");
         std::fs::write(&*cache_json_path, cache_str)
-            .wrap_err_with(|| format!("can't write {cache_json_path}"))
+            .wrap_err_with(|| format!("can't write {cache_json_path:?}"))
     }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub struct ExternalJobCaching {
-    cache_json_path: Interned<str>,
+    cache_json_path: Interned<Path>,
     run_even_if_cached: bool,
 }
 
@@ -148,8 +216,8 @@ impl JobCacheHasher {
         self.hash_size(bytes.len());
         self.0.update(bytes);
     }
-    fn hash_sized_str(&mut self, s: &str) {
-        self.hash_sized_bytes(s.as_bytes());
+    fn hash_sized_os_str(&mut self, s: &OsStr) {
+        self.hash_sized_bytes(s.as_encoded_bytes());
     }
     fn hash_iter<F: FnMut(&mut Self, I::Item), I: IntoIterator<IntoIter: ExactSizeIterator>>(
         &mut self,
@@ -193,8 +261,8 @@ fn write_file_atomically_no_clobber<F: FnOnce() -> C, C: AsRef<[u8]>>(
 }
 
 impl ExternalJobCaching {
-    pub fn get_cache_dir_from_output_dir(output_dir: &str) -> PathBuf {
-        Path::join(output_dir.as_ref(), ".fayalite-job-cache")
+    pub fn get_cache_dir_from_output_dir(output_dir: impl AsRef<Path>) -> PathBuf {
+        output_dir.as_ref().join(".fayalite-job-cache")
     }
     pub fn make_cache_dir(
         cache_dir: impl AsRef<Path>,
@@ -218,19 +286,18 @@ impl ExternalJobCaching {
         })
     }
     pub fn new(
-        output_dir: &str,
+        output_dir: impl AsRef<Path>,
         application_name: &str,
-        json_file_stem: &str,
+        json_file_stem: impl AsRef<OsStr>,
         run_even_if_cached: bool,
     ) -> std::io::Result<Self> {
         let cache_dir = Self::get_cache_dir_from_output_dir(output_dir);
         Self::make_cache_dir(&cache_dir, application_name)?;
         let mut cache_json_path = cache_dir;
-        cache_json_path.push(json_file_stem);
+        cache_json_path.push(json_file_stem.as_ref());
         cache_json_path.set_extension("json");
-        let cache_json_path = intern_known_utf8_path_buf(cache_json_path);
         Ok(Self {
-            cache_json_path,
+            cache_json_path: Path::intern_owned(cache_json_path),
             run_even_if_cached,
         })
     }
@@ -249,7 +316,7 @@ impl ExternalJobCaching {
     fn run_from_cache(
         self,
         inputs_hash: blake3::Hash,
-        output_file_paths: impl IntoIterator<Item = Interned<str>>,
+        output_file_paths: impl IntoIterator<Item = Interned<Path>>,
     ) -> Result<Result<(), String>, ()> {
         if self.run_even_if_cached {
             return Err(());
@@ -269,7 +336,7 @@ impl ExternalJobCaching {
         match result {
             Ok(outputs) => {
                 for output_file_path in output_file_paths {
-                    let Some(output_data) = outputs.get(&*output_file_path) else {
+                    let Some(output_data) = outputs.0.get(&*output_file_path) else {
                         if let Ok(true) = std::fs::exists(&*output_file_path) {
                             // assume the existing file is the correct one
                             continue;
@@ -290,7 +357,7 @@ impl ExternalJobCaching {
         }
     }
     fn make_command(
-        command_line: Interned<[Interned<str>]>,
+        command_line: Interned<[Interned<OsStr>]>,
     ) -> eyre::Result<std::process::Command> {
         ensure!(!command_line.is_empty(), "command line must not be empty");
         let mut cmd = std::process::Command::new(&*command_line[0]);
@@ -300,26 +367,26 @@ impl ExternalJobCaching {
     }
     pub fn run<F: FnOnce(std::process::Command) -> eyre::Result<()>>(
         self,
-        command_line: Interned<[Interned<str>]>,
-        input_file_paths: impl IntoIterator<Item = Interned<str>>,
-        output_file_paths: impl IntoIterator<Item = Interned<str>> + Clone,
+        command_line: Interned<[Interned<OsStr>]>,
+        input_file_paths: impl IntoIterator<Item = Interned<Path>>,
+        output_file_paths: impl IntoIterator<Item = Interned<Path>> + Clone,
         run_fn: F,
     ) -> eyre::Result<()> {
         let mut hasher = JobCacheHasher::default();
         hasher.hash_iter(command_line.iter(), |hasher, arg| {
-            hasher.hash_sized_str(arg)
+            hasher.hash_sized_os_str(arg)
         });
         let mut input_file_paths =
-            Vec::<&str>::from_iter(input_file_paths.into_iter().map(Interned::into_inner));
+            Vec::<&Path>::from_iter(input_file_paths.into_iter().map(Interned::into_inner));
         input_file_paths.sort_unstable();
         input_file_paths.dedup();
         hasher.try_hash_iter(
             &input_file_paths,
             |hasher, input_file_path| -> eyre::Result<()> {
-                hasher.hash_sized_str(input_file_path);
+                hasher.hash_sized_os_str(input_file_path.as_ref());
                 hasher.hash_sized_bytes(
                     &std::fs::read(input_file_path).wrap_err_with(|| {
-                        format!("can't read job input file: {input_file_path}")
+                        format!("can't read job input file: {input_file_path:?}")
                     })?,
                 );
                 Ok(())
@@ -338,7 +405,7 @@ impl ExternalJobCaching {
         let mut stdout_stderr = String::new();
         let result = std::thread::scope(|scope| {
             std::thread::Builder::new()
-                .name(format!("stdout:{}", command_line[0]))
+                .name(format!("stdout:{}", command_line[0].display()))
                 .spawn_scoped(scope, || {
                     let _ = streaming_read_utf8(std::io::BufReader::new(pipe_reader), |s| {
                         stdout_stderr.push_str(s);
@@ -358,17 +425,19 @@ impl ExternalJobCaching {
             inputs_hash,
             stdout_stderr,
             result: match &result {
-                Ok(()) => Ok(Result::from_iter(output_file_paths.into_iter().map(
-                    |output_file_path: Interned<str>| -> eyre::Result<_> {
-                        let output_file_path = &*output_file_path;
-                        Ok((
-                            String::from(output_file_path),
-                            MaybeUtf8::from(std::fs::read(output_file_path).wrap_err_with(
-                                || format!("can't read job output file: {output_file_path}"),
-                            )?),
-                        ))
-                    },
-                ))?),
+                Ok(()) => Ok(ExternalJobCacheV2Files(Result::from_iter(
+                    output_file_paths.into_iter().map(
+                        |output_file_path: Interned<Path>| -> eyre::Result<_> {
+                            let output_file_path = &*output_file_path;
+                            Ok((
+                                PathBuf::from(output_file_path),
+                                MaybeUtf8::from(std::fs::read(output_file_path).wrap_err_with(
+                                    || format!("can't read job output file: {output_file_path:?}"),
+                                )?),
+                            ))
+                        },
+                    ),
+                )?)),
                 Err(e) => Err(format!("{e:#}")),
             },
         }
@@ -377,9 +446,9 @@ impl ExternalJobCaching {
     }
     pub fn run_maybe_cached<F: FnOnce(std::process::Command) -> eyre::Result<()>>(
         this: Option<Self>,
-        command_line: Interned<[Interned<str>]>,
-        input_file_paths: impl IntoIterator<Item = Interned<str>>,
-        output_file_paths: impl IntoIterator<Item = Interned<str>> + Clone,
+        command_line: Interned<[Interned<OsStr>]>,
+        input_file_paths: impl IntoIterator<Item = Interned<Path>>,
+        output_file_paths: impl IntoIterator<Item = Interned<Path>> + Clone,
         run_fn: F,
     ) -> eyre::Result<()> {
         match this {
@@ -437,31 +506,22 @@ fn parse_which_result(
     which_result: which::Result<PathBuf>,
     program_name: impl Into<OsString>,
     program_path_arg_name: impl FnOnce() -> String,
-) -> Result<Interned<str>, ResolveProgramPathError> {
+) -> Result<Interned<Path>, ResolveProgramPathError> {
     let which_result = match which_result {
         Ok(v) => v,
-        Err(e) => {
+        Err(inner) => {
             return Err(ResolveProgramPathError {
-                inner: ResolveProgramPathErrorInner::Which(e),
+                inner,
                 program_name: program_name.into(),
                 program_path_arg_name: program_path_arg_name(),
             });
         }
     };
-    Ok(str::intern_owned(
-        which_result
-            .into_os_string()
-            .into_string()
-            .map_err(|_| ResolveProgramPathError {
-                inner: ResolveProgramPathErrorInner::NotValidUtf8,
-                program_name: program_name.into(),
-                program_path_arg_name: program_path_arg_name(),
-            })?,
-    ))
+    Ok(which_result.intern_deref())
 }
 
 impl clap::builder::TypedValueParser for ExternalProgramPathValueParser {
-    type Value = Interned<str>;
+    type Value = Interned<Path>;
 
     fn parse_ref(
         &self,
@@ -495,34 +555,10 @@ pub struct ExternalCommandArgs<T: ExternalCommand> {
     pub additional_args: T::AdditionalArgs,
 }
 
-#[derive(Clone)]
-enum ResolveProgramPathErrorInner {
-    Which(which::Error),
-    NotValidUtf8,
-}
-
-impl fmt::Debug for ResolveProgramPathErrorInner {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::Which(v) => v.fmt(f),
-            Self::NotValidUtf8 => f.write_str("NotValidUtf8"),
-        }
-    }
-}
-
-impl fmt::Display for ResolveProgramPathErrorInner {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::Which(v) => v.fmt(f),
-            Self::NotValidUtf8 => f.write_str("path is not valid UTF-8"),
-        }
-    }
-}
-
 #[derive(Clone, Debug)]
 pub struct ResolveProgramPathError {
-    inner: ResolveProgramPathErrorInner,
-    program_name: std::ffi::OsString,
+    inner: which::Error,
+    program_name: OsString,
     program_path_arg_name: String,
 }
 
@@ -546,7 +582,7 @@ pub fn resolve_program_path(
     program_name: Option<&OsStr>,
     default_program_name: impl AsRef<OsStr>,
     program_path_env_var_name: Option<&OsStr>,
-) -> Result<Interned<str>, ResolveProgramPathError> {
+) -> Result<Interned<Path>, ResolveProgramPathError> {
     let default_program_name = default_program_name.as_ref();
     let owned_program_name;
     let program_name = if let Some(program_name) = program_name {
@@ -564,7 +600,7 @@ pub fn resolve_program_path(
 
 impl<T: ExternalCommand> ExternalCommandArgs<T> {
     pub fn with_resolved_program_path(
-        program_path: Interned<str>,
+        program_path: Interned<Path>,
         additional_args: T::AdditionalArgs,
     ) -> Self {
         Self::new(
@@ -602,7 +638,7 @@ impl<T: ExternalCommand> ToArgs for ExternalCommandArgs<T> {
         } = *self;
         program_path.to_args(args);
         if run_even_if_cached {
-            args.write_arg(format_args!("--{}", T::run_even_if_cached_arg_name()));
+            args.write_display_arg(format_args!("--{}", T::run_even_if_cached_arg_name()));
         }
         additional_args.to_args(args);
     }
@@ -613,13 +649,13 @@ struct ExternalCommandJobParams {
     command_params: CommandParams,
     inputs: Interned<[JobItemName]>,
     outputs: Interned<[JobItemName]>,
-    output_paths: Interned<[Interned<str>]>,
+    output_paths: Interned<[Interned<Path>]>,
 }
 
 impl ExternalCommandJobParams {
     fn new<T: ExternalCommand>(job: &ExternalCommandJob<T>) -> Self {
         let output_paths = T::output_paths(job);
-        let mut command_line = ArgsWriter(vec![job.program_path]);
+        let mut command_line = ArgsWriter(vec![job.program_path.as_interned_os_str()]);
         T::command_line_args(job, &mut command_line);
         Self {
             command_params: CommandParams {
@@ -639,8 +675,8 @@ impl ExternalCommandJobParams {
 #[derive(Deserialize, Serialize)]
 pub struct ExternalCommandJob<T: ExternalCommand> {
     additional_job_data: T::AdditionalJobData,
-    program_path: Interned<str>,
-    output_dir: Interned<str>,
+    program_path: Interned<Path>,
+    output_dir: Interned<Path>,
     run_even_if_cached: bool,
     #[serde(skip)]
     params_cache: OnceLock<ExternalCommandJobParams>,
@@ -722,10 +758,10 @@ impl<T: ExternalCommand> ExternalCommandJob<T> {
     pub fn additional_job_data(&self) -> &T::AdditionalJobData {
         &self.additional_job_data
     }
-    pub fn program_path(&self) -> Interned<str> {
+    pub fn program_path(&self) -> Interned<Path> {
         self.program_path
     }
-    pub fn output_dir(&self) -> Interned<str> {
+    pub fn output_dir(&self) -> Interned<Path> {
         self.output_dir
     }
     pub fn run_even_if_cached(&self) -> bool {
@@ -741,7 +777,7 @@ impl<T: ExternalCommand> ExternalCommandJob<T> {
     pub fn inputs(&self) -> Interned<[JobItemName]> {
         self.params().inputs
     }
-    pub fn output_paths(&self) -> Interned<[Interned<str>]> {
+    pub fn output_paths(&self) -> Interned<[Interned<Path>]> {
         self.params().output_paths
     }
     pub fn outputs(&self) -> Interned<[JobItemName]> {
@@ -751,12 +787,12 @@ impl<T: ExternalCommand> ExternalCommandJob<T> {
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct ExternalProgramPath<T: ExternalProgramTrait> {
-    program_path: Interned<str>,
+    program_path: Interned<Path>,
     _phantom: PhantomData<T>,
 }
 
 impl<T: ExternalProgramTrait> ExternalProgramPath<T> {
-    pub fn with_resolved_program_path(program_path: Interned<str>) -> Self {
+    pub fn with_resolved_program_path(program_path: Interned<Path>) -> Self {
         Self {
             program_path,
             _phantom: PhantomData,
@@ -780,7 +816,7 @@ impl<T: ExternalProgramTrait> ExternalProgramPath<T> {
             _phantom: PhantomData,
         })
     }
-    pub fn program_path(&self) -> Interned<str> {
+    pub fn program_path(&self) -> Interned<Path> {
         self.program_path
     }
 }
@@ -874,8 +910,8 @@ impl<T: ExternalProgramTrait> ToArgs for ExternalProgramPath<T> {
             program_path,
             _phantom: _,
         } = self;
-        if args.get_long_option_eq(program_path_arg_name) != Some(&**program_path) {
-            args.write_arg(format_args!("--{program_path_arg_name}={program_path}"));
+        if args.get_long_option_eq(program_path_arg_name) != Some(program_path.as_os_str()) {
+            args.write_long_option_eq(program_path_arg_name, program_path);
         }
     }
 }
@@ -953,7 +989,8 @@ pub trait ExternalCommand: 'static + Send + Sync + Hash + Eq + fmt::Debug + Size
         + fmt::Debug
         + Serialize
         + DeserializeOwned;
-    type Dependencies: JobDependencies<JobsAndKinds: GetBaseJob>;
+    type BaseJobPosition;
+    type Dependencies: JobDependencies<JobsAndKinds: GetJob<BaseJob, Self::BaseJobPosition>>;
     type ExternalProgram: ExternalProgramTrait;
     fn dependencies() -> Self::Dependencies;
     fn args_to_jobs(
@@ -964,9 +1001,9 @@ pub trait ExternalCommand: 'static + Send + Sync + Hash + Eq + fmt::Debug + Size
         <Self::Dependencies as JobDependencies>::JobsAndKinds,
     )>;
     fn inputs(job: &ExternalCommandJob<Self>) -> Interned<[JobItemName]>;
-    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<str>]>;
+    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<Path>]>;
     fn command_line_args<W: ?Sized + WriteArgs>(job: &ExternalCommandJob<Self>, args: &mut W);
-    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<str>>;
+    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<Path>>;
     fn job_kind_name() -> Interned<str>;
     fn args_group_id() -> clap::Id {
         Interned::into_inner(Self::job_kind_name()).into()
@@ -1006,7 +1043,7 @@ impl<T: ExternalCommand> JobKind for ExternalCommandJobKind<T> {
                 },
         } = args.args;
         let (additional_job_data, dependencies) = T::args_to_jobs(args, params)?;
-        let base_job = dependencies.base_job();
+        let base_job = GetJob::<BaseJob, _>::get_job(&dependencies);
         let job = ExternalCommandJob {
             additional_job_data,
             program_path,
diff --git a/crates/fayalite/src/build/firrtl.rs b/crates/fayalite/src/build/firrtl.rs
index 62657f8..a04739d 100644
--- a/crates/fayalite/src/build/firrtl.rs
+++ b/crates/fayalite/src/build/firrtl.rs
@@ -8,12 +8,12 @@ use crate::{
         ToArgs, WriteArgs,
     },
     firrtl::{ExportOptions, FileBackend},
-    intern::{Intern, Interned},
+    intern::{Intern, InternSlice, Interned},
     util::job_server::AcquiredJob,
 };
 use clap::Args;
 use serde::{Deserialize, Serialize};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default, Debug)]
 pub struct FirrtlJobKind;
@@ -43,11 +43,11 @@ impl Firrtl {
     fn make_firrtl_file_backend(&self) -> FileBackend {
         FileBackend {
             dir_path: PathBuf::from(&*self.base.output_dir()),
-            top_fir_file_stem: Some(String::from(&*self.base.file_stem())),
+            top_fir_file_stem: Some(self.base.file_stem().into()),
             circuit_name: None,
         }
     }
-    pub fn firrtl_file(&self) -> Interned<str> {
+    pub fn firrtl_file(&self) -> Interned<Path> {
         self.base.file_with_ext("fir")
     }
 }
@@ -69,7 +69,7 @@ impl JobKind for FirrtlJobKind {
             params,
             |_kind, FirrtlArgs { export_options }, dependencies| {
                 Ok(Firrtl {
-                    base: dependencies.job.job.clone(),
+                    base: dependencies.get_job::<BaseJob, _>().clone(),
                     export_options,
                 })
             },
@@ -79,15 +79,15 @@ impl JobKind for FirrtlJobKind {
     fn inputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
         [JobItemName::Path {
             path: job.base.output_dir(),
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
     fn outputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
         [JobItemName::Path {
             path: job.firrtl_file(),
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
     fn name(self) -> Interned<str> {
diff --git a/crates/fayalite/src/build/formal.rs b/crates/fayalite/src/build/formal.rs
index a289c81..02515f2 100644
--- a/crates/fayalite/src/build/formal.rs
+++ b/crates/fayalite/src/build/formal.rs
@@ -3,23 +3,26 @@
 
 use crate::{
     build::{
-        CommandParams, DynJobKind, GetBaseJob, JobAndDependencies, JobArgsAndDependencies,
-        JobDependencies, JobItem, JobItemName, JobKind, JobKindAndDependencies, JobParams, ToArgs,
-        WriteArgs,
+        BaseJob, CommandParams, DynJobKind, GetJobPositionDependencies, JobAndDependencies,
+        JobArgsAndDependencies, JobDependencies, JobItem, JobItemName, JobKind,
+        JobKindAndDependencies, JobParams, ToArgs, WriteArgs,
         external::{
             ExternalCommand, ExternalCommandJob, ExternalCommandJobKind, ExternalProgramTrait,
         },
-        interned_known_utf8_method,
-        verilog::{VerilogDialect, VerilogJob, VerilogJobKind},
+        verilog::{UnadjustedVerilog, VerilogDialect, VerilogJob, VerilogJobKind},
     },
-    intern::{Intern, Interned},
+    intern::{Intern, InternSlice, Interned},
     module::NameId,
     util::job_server::AcquiredJob,
 };
 use clap::{Args, ValueEnum};
 use eyre::Context;
 use serde::{Deserialize, Serialize};
-use std::fmt;
+use std::{
+    ffi::{OsStr, OsString},
+    fmt::{self, Write},
+    path::Path,
+};
 
 #[derive(ValueEnum, Copy, Clone, Debug, PartialEq, Eq, Hash, Default, Deserialize, Serialize)]
 #[non_exhaustive]
@@ -52,7 +55,7 @@ impl fmt::Display for FormalMode {
 #[non_exhaustive]
 pub struct FormalArgs {
     #[arg(long = "sby-extra-arg", value_name = "ARG")]
-    pub sby_extra_args: Vec<String>,
+    pub sby_extra_args: Vec<OsString>,
     #[arg(long, default_value_t)]
     pub formal_mode: FormalMode,
     #[arg(long, default_value_t = Self::DEFAULT_DEPTH)]
@@ -60,7 +63,7 @@ pub struct FormalArgs {
     #[arg(long, default_value = Self::DEFAULT_SOLVER)]
     pub formal_solver: String,
     #[arg(long = "smtbmc-extra-arg", value_name = "ARG")]
-    pub smtbmc_extra_args: Vec<String>,
+    pub smtbmc_extra_args: Vec<OsString>,
 }
 
 impl FormalArgs {
@@ -77,21 +80,17 @@ impl ToArgs for FormalArgs {
             formal_solver,
             smtbmc_extra_args,
         } = self;
-        args.extend(
-            sby_extra_args
-                .iter()
-                .map(|v| format!("--sby-extra-arg={v}")),
-        );
-        args.extend([
+        for arg in sby_extra_args {
+            args.write_long_option_eq("sby-extra-arg", arg);
+        }
+        args.write_display_args([
             format_args!("--formal-mode={formal_mode}"),
             format_args!("--formal-depth={formal_depth}"),
             format_args!("--formal-solver={formal_solver}"),
         ]);
-        args.extend(
-            smtbmc_extra_args
-                .iter()
-                .map(|v| format!("--smtbmc-extra-arg={v}")),
-        );
+        for arg in smtbmc_extra_args {
+            args.write_long_option_eq("smtbmc-extra-arg", arg);
+        }
     }
 }
 
@@ -100,18 +99,18 @@ pub struct WriteSbyFileJobKind;
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Deserialize, Serialize)]
 pub struct WriteSbyFileJob {
-    sby_extra_args: Interned<[Interned<str>]>,
+    sby_extra_args: Interned<[Interned<OsStr>]>,
     formal_mode: FormalMode,
     formal_depth: u64,
     formal_solver: Interned<str>,
-    smtbmc_extra_args: Interned<[Interned<str>]>,
-    sby_file: Interned<str>,
-    output_dir: Interned<str>,
-    main_verilog_file: Interned<str>,
+    smtbmc_extra_args: Interned<[Interned<OsStr>]>,
+    sby_file: Interned<Path>,
+    output_dir: Interned<Path>,
+    main_verilog_file: Interned<Path>,
 }
 
 impl WriteSbyFileJob {
-    pub fn sby_extra_args(&self) -> Interned<[Interned<str>]> {
+    pub fn sby_extra_args(&self) -> Interned<[Interned<OsStr>]> {
         self.sby_extra_args
     }
     pub fn formal_mode(&self) -> FormalMode {
@@ -123,24 +122,24 @@ impl WriteSbyFileJob {
     pub fn formal_solver(&self) -> Interned<str> {
         self.formal_solver
     }
-    pub fn smtbmc_extra_args(&self) -> Interned<[Interned<str>]> {
+    pub fn smtbmc_extra_args(&self) -> Interned<[Interned<OsStr>]> {
         self.smtbmc_extra_args
     }
-    pub fn sby_file(&self) -> Interned<str> {
+    pub fn sby_file(&self) -> Interned<Path> {
         self.sby_file
     }
-    pub fn output_dir(&self) -> Interned<str> {
+    pub fn output_dir(&self) -> Interned<Path> {
         self.output_dir
     }
-    pub fn main_verilog_file(&self) -> Interned<str> {
+    pub fn main_verilog_file(&self) -> Interned<Path> {
         self.main_verilog_file
     }
-    fn write_sby<W: ?Sized + fmt::Write>(
+    fn write_sby(
         &self,
-        output: &mut W,
-        additional_files: &[Interned<str>],
+        output: &mut OsString,
+        additional_files: &[Interned<Path>],
         main_module_name_id: NameId,
-    ) -> Result<eyre::Result<()>, fmt::Error> {
+    ) -> eyre::Result<()> {
         let Self {
             sby_extra_args: _,
             formal_mode,
@@ -160,23 +159,21 @@ impl WriteSbyFileJob {
             \n\
             [engines]\n\
             smtbmc {formal_solver} -- --"
-        )?;
+        )
+        .expect("writing to OsString can't fail");
         for i in smtbmc_extra_args {
-            output.write_str(" ")?;
-            output.write_str(i)?;
+            output.push(" ");
+            output.push(i);
         }
-        output.write_str(
+        output.push(
             "\n\
             \n\
             [script]\n",
-        )?;
-        let all_verilog_files =
-            match VerilogJob::all_verilog_files(*main_verilog_file, additional_files) {
-                Ok(v) => v,
-                Err(e) => return Ok(Err(e)),
-            };
-        for verilog_file in all_verilog_files {
-            writeln!(output, "read_verilog -sv -formal \"{verilog_file}\"")?;
+        );
+        for verilog_file in VerilogJob::all_verilog_files(*main_verilog_file, additional_files)? {
+            output.push("read_verilog -sv -formal \"");
+            output.push(verilog_file);
+            output.push("\"\n");
         }
         let circuit_name = crate::firrtl::get_circuit_name(main_module_name_id);
         // workaround for wires disappearing -- set `keep` on all wires
@@ -186,8 +183,9 @@ impl WriteSbyFileJob {
             proc\n\
             setattr -set keep 1 w:\\*\n\
             prep",
-        )?;
-        Ok(Ok(()))
+        )
+        .expect("writing to OsString can't fail");
+        Ok(())
     }
 }
 
@@ -219,18 +217,16 @@ impl JobKind for WriteSbyFileJobKind {
                 formal_solver,
                 smtbmc_extra_args,
             } = args;
+            let base_job = dependencies.get_job::<BaseJob, _>();
             Ok(WriteSbyFileJob {
-                sby_extra_args: sby_extra_args.into_iter().map(str::intern_owned).collect(),
+                sby_extra_args: sby_extra_args.into_iter().map(Interned::from).collect(),
                 formal_mode,
                 formal_depth,
-                formal_solver: str::intern_owned(formal_solver),
-                smtbmc_extra_args: smtbmc_extra_args
-                    .into_iter()
-                    .map(str::intern_owned)
-                    .collect(),
-                sby_file: dependencies.base_job().file_with_ext("sby"),
-                output_dir: dependencies.base_job().output_dir(),
-                main_verilog_file: dependencies.job.job.main_verilog_file(),
+                formal_solver: formal_solver.intern_deref(),
+                smtbmc_extra_args: smtbmc_extra_args.into_iter().map(Interned::from).collect(),
+                sby_file: base_job.file_with_ext("sby"),
+                output_dir: base_job.output_dir(),
+                main_verilog_file: dependencies.get_job::<VerilogJob, _>().main_verilog_file(),
             })
         })
     }
@@ -238,12 +234,12 @@ impl JobKind for WriteSbyFileJobKind {
     fn inputs(self, _job: &Self::Job) -> Interned<[JobItemName]> {
         [JobItemName::DynamicPaths {
             source_job_name: VerilogJobKind.name(),
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
     fn outputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
-        [JobItemName::Path { path: job.sby_file }][..].intern()
+        [JobItemName::Path { path: job.sby_file }].intern_slice()
     }
 
     fn name(self) -> Interned<str> {
@@ -266,18 +262,16 @@ impl JobKind for WriteSbyFileJobKind {
             unreachable!();
         };
         let additional_files = VerilogJob::unwrap_additional_files(additional_files);
-        let mut contents = String::new();
-        match job.write_sby(
+        let mut contents = OsString::new();
+        job.write_sby(
             &mut contents,
             additional_files,
             params.main_module().name_id(),
-        ) {
-            Ok(result) => result?,
-            Err(fmt::Error) => unreachable!("writing to String can't fail"),
-        }
-        std::fs::write(job.sby_file, contents)
-            .wrap_err_with(|| format!("writing {} failed", job.sby_file))?;
-        Ok(vec![JobItem::Path { path: job.sby_file }])
+        )?;
+        let path = job.sby_file;
+        std::fs::write(path, contents.as_encoded_bytes())
+            .wrap_err_with(|| format!("writing {path:?} failed"))?;
+        Ok(vec![JobItem::Path { path }])
     }
 
     fn subcommand_hidden(self) -> bool {
@@ -289,7 +283,7 @@ impl JobKind for WriteSbyFileJobKind {
 pub struct Formal {
     #[serde(flatten)]
     write_sby_file: WriteSbyFileJob,
-    sby_file_name: Interned<str>,
+    sby_file_name: Interned<OsStr>,
 }
 
 impl fmt::Debug for Formal {
@@ -342,6 +336,11 @@ impl ToArgs for FormalAdditionalArgs {
 impl ExternalCommand for Formal {
     type AdditionalArgs = FormalAdditionalArgs;
     type AdditionalJobData = Formal;
+    type BaseJobPosition = GetJobPositionDependencies<
+        GetJobPositionDependencies<
+            GetJobPositionDependencies<<UnadjustedVerilog as ExternalCommand>::BaseJobPosition>,
+        >,
+    >;
     type Dependencies = JobKindAndDependencies<WriteSbyFileJobKind>;
     type ExternalProgram = Symbiyosys;
 
@@ -358,11 +357,13 @@ impl ExternalCommand for Formal {
     )> {
         args.args_to_jobs_external_simple(params, |args, dependencies| {
             let FormalAdditionalArgs {} = args.additional_args;
+            let write_sby_file = dependencies.get_job::<WriteSbyFileJob, _>().clone();
             Ok(Formal {
-                write_sby_file: dependencies.job.job.clone(),
-                sby_file_name: interned_known_utf8_method(dependencies.job.job.sby_file(), |v| {
-                    v.file_name().expect("known to have file name")
-                }),
+                sby_file_name: write_sby_file
+                    .sby_file()
+                    .interned_file_name()
+                    .expect("known to have file name"),
+                write_sby_file,
             })
         })
     }
@@ -378,22 +379,22 @@ impl ExternalCommand for Formal {
             JobItemName::DynamicPaths {
                 source_job_name: VerilogJobKind.name(),
             },
-        ][..]
-            .intern()
+        ]
+        .intern_slice()
     }
 
-    fn output_paths(_job: &ExternalCommandJob<Self>) -> Interned<[Interned<str>]> {
+    fn output_paths(_job: &ExternalCommandJob<Self>) -> Interned<[Interned<Path>]> {
         Interned::default()
     }
 
     fn command_line_args<W: ?Sized + WriteArgs>(job: &ExternalCommandJob<Self>, args: &mut W) {
         // args.write_str_arg("-j1"); // sby seems not to respect job count in parallel mode
-        args.write_str_arg("-f");
+        args.write_arg("-f");
         args.write_interned_arg(job.additional_job_data().sby_file_name);
         args.write_interned_args(job.additional_job_data().write_sby_file.sby_extra_args());
     }
 
-    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<str>> {
+    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<Path>> {
         Some(job.output_dir())
     }
 
diff --git a/crates/fayalite/src/build/graph.rs b/crates/fayalite/src/build/graph.rs
index 0cf54d5..b727715 100644
--- a/crates/fayalite/src/build/graph.rs
+++ b/crates/fayalite/src/build/graph.rs
@@ -16,9 +16,12 @@ use serde::{Deserialize, Deserializer, Serialize, Serializer, de::Error, ser::Se
 use std::{
     cell::OnceCell,
     collections::{BTreeMap, BTreeSet, VecDeque},
+    convert::Infallible,
+    ffi::OsStr,
     fmt::{self, Write},
     panic,
     rc::Rc,
+    str::Utf8Error,
     sync::mpsc,
     thread::{self, ScopedJoinHandle},
 };
@@ -138,8 +141,8 @@ impl<'a> fmt::Display for EscapeForUnixShell<'a> {
 }
 
 impl<'a> EscapeForUnixShell<'a> {
-    pub fn new(s: &'a str) -> Self {
-        Self::from_bytes(s.as_bytes())
+    pub fn new(s: &'a (impl ?Sized + AsRef<OsStr>)) -> Self {
+        Self::from_bytes(s.as_ref().as_encoded_bytes())
     }
     fn make_prefix(bytes: &[u8]) -> [u8; 3] {
         let mut prefix = [0; 3];
@@ -262,7 +265,7 @@ pub enum UnixMakefileEscapeKind {
 
 #[derive(Copy, Clone)]
 pub struct EscapeForUnixMakefile<'a> {
-    s: &'a str,
+    s: &'a OsStr,
     kind: UnixMakefileEscapeKind,
 }
 
@@ -274,9 +277,13 @@ impl<'a> fmt::Debug for EscapeForUnixMakefile<'a> {
 
 impl<'a> fmt::Display for EscapeForUnixMakefile<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.do_write(f, fmt::Write::write_str, fmt::Write::write_char, |_, _| {
-            Ok(())
-        })
+        self.do_write(
+            f,
+            fmt::Write::write_str,
+            fmt::Write::write_char,
+            |_, _| Ok(()),
+            |_| unreachable!("already checked that the input causes no UTF-8 errors"),
+        )
     }
 }
 
@@ -287,6 +294,7 @@ impl<'a> EscapeForUnixMakefile<'a> {
         write_str: impl Fn(&mut S, &str) -> Result<(), E>,
         write_char: impl Fn(&mut S, char) -> Result<(), E>,
         add_variable: impl Fn(&mut S, &'static str) -> Result<(), E>,
+        utf8_error: impl Fn(Utf8Error) -> E,
     ) -> Result<(), E> {
         let escape_recipe_char = |c| match c {
             '$' => write_str(state, "$$"),
@@ -296,24 +304,30 @@ impl<'a> EscapeForUnixMakefile<'a> {
             _ => write_char(state, c),
         };
         match self.kind {
-            UnixMakefileEscapeKind::NonRecipe => self.s.chars().try_for_each(|c| match c {
-                '=' => {
-                    add_variable(state, "EQUALS = =")?;
-                    write_str(state, "$(EQUALS)")
-                }
-                ';' => panic!("can't escape a semicolon (;) for Unix Makefile"),
-                '$' => write_str(state, "$$"),
-                '\\' | ' ' | '#' | ':' | '%' | '*' | '?' | '[' | ']' | '~' => {
-                    write_char(state, '\\')?;
-                    write_char(state, c)
-                }
-                '\0'..='\x1F' | '\x7F' => {
-                    panic!("can't escape a control character for Unix Makefile: {c:?}");
-                }
-                _ => write_char(state, c),
-            }),
+            UnixMakefileEscapeKind::NonRecipe => str::from_utf8(self.s.as_encoded_bytes())
+                .map_err(&utf8_error)?
+                .chars()
+                .try_for_each(|c| match c {
+                    '=' => {
+                        add_variable(state, "EQUALS = =")?;
+                        write_str(state, "$(EQUALS)")
+                    }
+                    ';' => panic!("can't escape a semicolon (;) for Unix Makefile"),
+                    '$' => write_str(state, "$$"),
+                    '\\' | ' ' | '#' | ':' | '%' | '*' | '?' | '[' | ']' | '~' => {
+                        write_char(state, '\\')?;
+                        write_char(state, c)
+                    }
+                    '\0'..='\x1F' | '\x7F' => {
+                        panic!("can't escape a control character for Unix Makefile: {c:?}");
+                    }
+                    _ => write_char(state, c),
+                }),
             UnixMakefileEscapeKind::RecipeWithoutShellEscaping => {
-                self.s.chars().try_for_each(escape_recipe_char)
+                str::from_utf8(self.s.as_encoded_bytes())
+                    .map_err(&utf8_error)?
+                    .chars()
+                    .try_for_each(escape_recipe_char)
             }
             UnixMakefileEscapeKind::RecipeWithShellEscaping => {
                 EscapeForUnixShell::new(self.s).try_for_each(escape_recipe_char)
@@ -321,21 +335,23 @@ impl<'a> EscapeForUnixMakefile<'a> {
         }
     }
     pub fn new(
-        s: &'a str,
+        s: &'a (impl ?Sized + AsRef<OsStr>),
         kind: UnixMakefileEscapeKind,
         needed_variables: &mut BTreeSet<&'static str>,
-    ) -> Self {
+    ) -> Result<Self, Utf8Error> {
+        let s = s.as_ref();
         let retval = Self { s, kind };
-        let Ok(()) = retval.do_write(
+        retval.do_write(
             needed_variables,
             |_, _| Ok(()),
             |_, _| Ok(()),
-            |needed_variables, variable| -> Result<(), std::convert::Infallible> {
+            |needed_variables, variable| {
                 needed_variables.insert(variable);
                 Ok(())
             },
-        );
-        retval
+            |e| e,
+        )?;
+        Ok(retval)
     }
 }
 
@@ -473,7 +489,7 @@ impl JobGraph {
             Err(e) => panic!("error: {e}"),
         }
     }
-    pub fn to_unix_makefile(&self, extra_args: &[Interned<str>]) -> String {
+    pub fn to_unix_makefile(&self, extra_args: &[Interned<OsStr>]) -> Result<String, Utf8Error> {
         self.to_unix_makefile_with_internal_program_prefix(
             &[program_name_for_internal_jobs()],
             extra_args,
@@ -481,9 +497,9 @@ impl JobGraph {
     }
     pub fn to_unix_makefile_with_internal_program_prefix(
         &self,
-        internal_program_prefix: &[Interned<str>],
-        extra_args: &[Interned<str>],
-    ) -> String {
+        internal_program_prefix: &[Interned<OsStr>],
+        extra_args: &[Interned<OsStr>],
+    ) -> Result<String, Utf8Error> {
         let mut retval = String::new();
         let mut needed_variables = BTreeSet::new();
         let mut phony_targets = BTreeSet::new();
@@ -502,10 +518,10 @@ impl JobGraph {
                                 retval,
                                 "{} ",
                                 EscapeForUnixMakefile::new(
-                                    &path,
+                                    &str::from_utf8(path.as_os_str().as_encoded_bytes())?,
                                     UnixMakefileEscapeKind::NonRecipe,
                                     &mut needed_variables
-                                )
+                                )?
                             );
                         }
                         JobItemName::DynamicPaths { source_job_name } => {
@@ -516,7 +532,7 @@ impl JobGraph {
                                     &source_job_name,
                                     UnixMakefileEscapeKind::NonRecipe,
                                     &mut needed_variables
-                                )
+                                )?
                             );
                             phony_targets.insert(Interned::into_inner(source_job_name));
                         }
@@ -535,10 +551,10 @@ impl JobGraph {
                             retval,
                             " {}",
                             EscapeForUnixMakefile::new(
-                                &path,
+                                &str::from_utf8(path.as_os_str().as_encoded_bytes())?,
                                 UnixMakefileEscapeKind::NonRecipe,
                                 &mut needed_variables
-                            )
+                            )?
                         );
                     }
                     JobItemName::DynamicPaths { source_job_name } => {
@@ -549,7 +565,7 @@ impl JobGraph {
                                 &source_job_name,
                                 UnixMakefileEscapeKind::NonRecipe,
                                 &mut needed_variables
-                            )
+                            )?
                         );
                         phony_targets.insert(Interned::into_inner(source_job_name));
                     }
@@ -558,17 +574,17 @@ impl JobGraph {
             retval.push_str("\n\t");
             job.command_params_with_internal_program_prefix(internal_program_prefix, extra_args)
                 .to_unix_shell_line(&mut retval, |arg, output| {
-                    write!(
+                    write_str!(
                         output,
                         "{}",
                         EscapeForUnixMakefile::new(
                             arg,
                             UnixMakefileEscapeKind::RecipeWithShellEscaping,
                             &mut needed_variables
-                        )
-                    )
-                })
-                .expect("writing to String never fails");
+                        )?
+                    );
+                    Ok(())
+                })?;
             retval.push_str("\n\n");
         }
         if !phony_targets.is_empty() {
@@ -581,7 +597,7 @@ impl JobGraph {
                         phony_target,
                         UnixMakefileEscapeKind::NonRecipe,
                         &mut needed_variables
-                    )
+                    )?
                 );
             }
             retval.push_str("\n");
@@ -592,9 +608,9 @@ impl JobGraph {
                 &String::from_iter(needed_variables.into_iter().map(|v| format!("{v}\n"))),
             );
         }
-        retval
+        Ok(retval)
     }
-    pub fn to_unix_shell_script(&self, extra_args: &[Interned<str>]) -> String {
+    pub fn to_unix_shell_script(&self, extra_args: &[Interned<OsStr>]) -> String {
         self.to_unix_shell_script_with_internal_program_prefix(
             &[program_name_for_internal_jobs()],
             extra_args,
@@ -602,8 +618,8 @@ impl JobGraph {
     }
     pub fn to_unix_shell_script_with_internal_program_prefix(
         &self,
-        internal_program_prefix: &[Interned<str>],
-        extra_args: &[Interned<str>],
+        internal_program_prefix: &[Interned<OsStr>],
+        extra_args: &[Interned<OsStr>],
     ) -> String {
         let mut retval = String::from(
             "#!/bin/sh\n\
@@ -613,11 +629,12 @@ impl JobGraph {
             let JobGraphNode::Job(job) = &self.graph[node_id] else {
                 continue;
             };
-            job.command_params_with_internal_program_prefix(internal_program_prefix, extra_args)
-                .to_unix_shell_line(&mut retval, |arg, output| {
-                    write!(output, "{}", EscapeForUnixShell::new(&arg))
-                })
-                .expect("writing to String never fails");
+            let Ok(()) = job
+                .command_params_with_internal_program_prefix(internal_program_prefix, extra_args)
+                .to_unix_shell_line(&mut retval, |arg, output| -> Result<(), Infallible> {
+                    write_str!(output, "{}", EscapeForUnixShell::new(&arg));
+                    Ok(())
+                });
             retval.push_str("\n");
         }
         retval
diff --git a/crates/fayalite/src/build/vendor/xilinx/yosys_nextpnr_prjxray.rs b/crates/fayalite/src/build/vendor/xilinx/yosys_nextpnr_prjxray.rs
index 3db256a..6691915 100644
--- a/crates/fayalite/src/build/vendor/xilinx/yosys_nextpnr_prjxray.rs
+++ b/crates/fayalite/src/build/vendor/xilinx/yosys_nextpnr_prjxray.rs
@@ -4,18 +4,18 @@
 use crate::{
     annotations::Annotation,
     build::{
-        CommandParams, DynJobKind, GetBaseJob, JobAndDependencies, JobArgsAndDependencies,
-        JobDependencies, JobItem, JobItemName, JobKind, JobKindAndDependencies, ToArgs, WriteArgs,
+        BaseJob, CommandParams, DynJobKind, GetJobPositionDependencies, JobAndDependencies,
+        JobArgsAndDependencies, JobDependencies, JobItem, JobItemName, JobKind,
+        JobKindAndDependencies, ToArgs, WriteArgs,
         external::{
             ExternalCommand, ExternalCommandJob, ExternalCommandJobKind, ExternalProgramTrait,
         },
-        interned_known_utf8_method, interned_known_utf8_path_buf_method,
         vendor::xilinx::{XdcIOStandardAnnotation, XdcLocationAnnotation},
-        verilog::{VerilogDialect, VerilogJob, VerilogJobKind},
+        verilog::{UnadjustedVerilog, VerilogDialect, VerilogJob, VerilogJobKind},
     },
     bundle::Bundle,
     firrtl::{ScalarizedModuleABI, ScalarizedModuleABIAnnotations, ScalarizedModuleABIPort},
-    intern::{Intern, Interned},
+    intern::{Intern, InternSlice, Interned},
     module::{Module, NameId},
     prelude::JobParams,
     util::job_server::AcquiredJob,
@@ -23,7 +23,12 @@ use crate::{
 use clap::ValueEnum;
 use eyre::Context;
 use serde::{Deserialize, Serialize};
-use std::{fmt, ops::ControlFlow};
+use std::{
+    ffi::{OsStr, OsString},
+    fmt::{self, Write},
+    ops::ControlFlow,
+    path::{Path, PathBuf},
+};
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Hash, Default)]
 pub struct YosysNextpnrXrayWriteYsFileJobKind;
@@ -39,52 +44,52 @@ impl ToArgs for YosysNextpnrXrayWriteYsFileArgs {
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
 pub struct YosysNextpnrXrayWriteYsFile {
-    main_verilog_file: Interned<str>,
-    ys_file: Interned<str>,
-    json_file: Interned<str>,
-    json_file_name: Interned<str>,
+    main_verilog_file: Interned<Path>,
+    ys_file: Interned<Path>,
+    json_file: Interned<Path>,
+    json_file_name: Interned<OsStr>,
 }
 
 impl YosysNextpnrXrayWriteYsFile {
-    pub fn main_verilog_file(&self) -> Interned<str> {
+    pub fn main_verilog_file(&self) -> Interned<Path> {
         self.main_verilog_file
     }
-    pub fn ys_file(&self) -> Interned<str> {
+    pub fn ys_file(&self) -> Interned<Path> {
         self.ys_file
     }
-    pub fn json_file(&self) -> Interned<str> {
+    pub fn json_file(&self) -> Interned<Path> {
         self.json_file
     }
-    pub fn json_file_name(&self) -> Interned<str> {
+    pub fn json_file_name(&self) -> Interned<OsStr> {
         self.json_file_name
     }
-    fn write_ys<W: ?Sized + fmt::Write>(
+    fn write_ys(
         &self,
-        output: &mut W,
-        additional_files: &[Interned<str>],
+        output: &mut OsString,
+        additional_files: &[Interned<Path>],
         main_module_name_id: NameId,
-    ) -> Result<eyre::Result<()>, fmt::Error> {
+    ) -> eyre::Result<()> {
         let Self {
             main_verilog_file,
             ys_file: _,
             json_file: _,
             json_file_name,
         } = self;
-        let all_verilog_files =
-            match VerilogJob::all_verilog_files(*main_verilog_file, additional_files) {
-                Ok(v) => v,
-                Err(e) => return Ok(Err(e)),
-            };
-        for verilog_file in all_verilog_files {
-            writeln!(output, "read_verilog -sv \"{verilog_file}\"")?;
+        for verilog_file in VerilogJob::all_verilog_files(*main_verilog_file, additional_files)? {
+            output.push("read_verilog -sv \"");
+            output.push(verilog_file);
+            output.push("\"\n");
         }
         let circuit_name = crate::firrtl::get_circuit_name(main_module_name_id);
         writeln!(
             output,
             "synth_xilinx -flatten -abc9 -nobram -arch xc7 -top {circuit_name}"
-        )?;
-        writeln!(output, "write_json \"{json_file_name}\"")?;
-        Ok(Ok(()))
+        )
+        .expect("writing to OsString can't fail");
+        output.push("write_json \"");
+        output.push(json_file_name);
+        output.push("\"\n");
+        Ok(())
     }
 }
 
@@ -110,14 +115,16 @@ impl JobKind for YosysNextpnrXrayWriteYsFileJobKind {
             .get_or_insert(VerilogDialect::Yosys);
         args.args_to_jobs_simple(params, |_kind, args, dependencies| {
             let YosysNextpnrXrayWriteYsFileArgs {} = args;
-            let json_file = dependencies.base_job().file_with_ext("json");
+            let base_job = dependencies.get_job::<BaseJob, _>();
+            let verilog_job = dependencies.get_job::<VerilogJob, _>();
+            let json_file = base_job.file_with_ext("json");
             Ok(YosysNextpnrXrayWriteYsFile {
-                main_verilog_file: dependencies.job.job.main_verilog_file(),
-                ys_file: dependencies.base_job().file_with_ext("ys"),
+                main_verilog_file: verilog_job.main_verilog_file(),
+                ys_file: base_job.file_with_ext("ys"),
                 json_file,
-                json_file_name: interned_known_utf8_method(json_file, |v| {
-                    v.file_name().expect("known to have file name")
-                }),
+                json_file_name: json_file
+                    .interned_file_name()
+                    .expect("known to have file name"),
             })
         })
     }
@@ -125,12 +132,12 @@ impl JobKind for YosysNextpnrXrayWriteYsFileJobKind {
     fn inputs(self, _job: &Self::Job) -> Interned<[JobItemName]> {
         [JobItemName::DynamicPaths {
             source_job_name: VerilogJobKind.name(),
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
     fn outputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
-        [JobItemName::Path { path: job.ys_file }][..].intern()
+        [JobItemName::Path { path: job.ys_file }].intern_slice()
     }
 
     fn name(self) -> Interned<str> {
@@ -153,18 +160,16 @@ impl JobKind for YosysNextpnrXrayWriteYsFileJobKind {
             unreachable!();
         };
         let additional_files = VerilogJob::unwrap_additional_files(additional_files);
-        let mut contents = String::new();
-        match job.write_ys(
+        let mut contents = OsString::new();
+        job.write_ys(
             &mut contents,
             additional_files,
             params.main_module().name_id(),
-        ) {
-            Ok(result) => result?,
-            Err(fmt::Error) => unreachable!("writing to String can't fail"),
-        }
-        std::fs::write(job.ys_file, contents)
-            .wrap_err_with(|| format!("writing {} failed", job.ys_file))?;
-        Ok(vec![JobItem::Path { path: job.ys_file }])
+        )?;
+        let path = job.ys_file;
+        std::fs::write(path, contents.as_encoded_bytes())
+            .wrap_err_with(|| format!("writing {path:?} failed"))?;
+        Ok(vec![JobItem::Path { path }])
     }
 
     fn subcommand_hidden(self) -> bool {
@@ -185,7 +190,7 @@ impl ToArgs for YosysNextpnrXraySynthArgs {
 pub struct YosysNextpnrXraySynth {
     #[serde(flatten)]
     write_ys_file: YosysNextpnrXrayWriteYsFile,
-    ys_file_name: Interned<str>,
+    ys_file_name: Interned<OsStr>,
 }
 
 impl fmt::Debug for YosysNextpnrXraySynth {
@@ -211,19 +216,19 @@ impl fmt::Debug for YosysNextpnrXraySynth {
 }
 
 impl YosysNextpnrXraySynth {
-    pub fn main_verilog_file(&self) -> Interned<str> {
+    pub fn main_verilog_file(&self) -> Interned<Path> {
         self.write_ys_file.main_verilog_file()
     }
-    pub fn ys_file(&self) -> Interned<str> {
+    pub fn ys_file(&self) -> Interned<Path> {
         self.write_ys_file.ys_file()
     }
-    pub fn ys_file_name(&self) -> Interned<str> {
+    pub fn ys_file_name(&self) -> Interned<OsStr> {
         self.ys_file_name
     }
-    pub fn json_file(&self) -> Interned<str> {
+    pub fn json_file(&self) -> Interned<Path> {
         self.write_ys_file.json_file()
     }
-    pub fn json_file_name(&self) -> Interned<str> {
+    pub fn json_file_name(&self) -> Interned<OsStr> {
         self.write_ys_file.json_file_name()
     }
 }
@@ -240,6 +245,11 @@ impl ExternalProgramTrait for Yosys {
 impl ExternalCommand for YosysNextpnrXraySynth {
     type AdditionalArgs = YosysNextpnrXraySynthArgs;
     type AdditionalJobData = Self;
+    type BaseJobPosition = GetJobPositionDependencies<
+        GetJobPositionDependencies<
+            GetJobPositionDependencies<<UnadjustedVerilog as ExternalCommand>::BaseJobPosition>,
+        >,
+    >;
     type Dependencies = JobKindAndDependencies<YosysNextpnrXrayWriteYsFileJobKind>;
     type ExternalProgram = Yosys;
 
@@ -258,9 +268,12 @@ impl ExternalCommand for YosysNextpnrXraySynth {
             let YosysNextpnrXraySynthArgs {} = args.additional_args;
             Ok(Self {
                 write_ys_file: dependencies.job.job.clone(),
-                ys_file_name: interned_known_utf8_method(dependencies.job.job.ys_file(), |v| {
-                    v.file_name().expect("known to have file name")
-                }),
+                ys_file_name: dependencies
+                    .job
+                    .job
+                    .ys_file()
+                    .interned_file_name()
+                    .expect("known to have file name"),
             })
         })
     }
@@ -276,20 +289,20 @@ impl ExternalCommand for YosysNextpnrXraySynth {
             JobItemName::DynamicPaths {
                 source_job_name: VerilogJobKind.name(),
             },
-        ][..]
-            .intern()
+        ]
+        .intern_slice()
     }
 
-    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<str>]> {
-        [job.additional_job_data().json_file()][..].intern()
+    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<Path>]> {
+        [job.additional_job_data().json_file()].intern_slice()
     }
 
     fn command_line_args<W: ?Sized + WriteArgs>(job: &ExternalCommandJob<Self>, args: &mut W) {
-        args.write_str_arg("-s");
+        args.write_arg("-s");
         args.write_interned_arg(job.additional_job_data().ys_file_name());
     }
 
-    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<str>> {
+    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<Path>> {
         Some(job.output_dir())
     }
 
@@ -317,8 +330,8 @@ impl ToArgs for YosysNextpnrXrayWriteXdcFileArgs {
 #[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
 pub struct YosysNextpnrXrayWriteXdcFile {
     firrtl_export_options: crate::firrtl::ExportOptions,
-    output_dir: Interned<str>,
-    xdc_file: Interned<str>,
+    output_dir: Interned<Path>,
+    xdc_file: Interned<Path>,
 }
 
 struct WriteXdcContentsError(eyre::Report);
@@ -424,10 +437,11 @@ impl JobKind for YosysNextpnrXrayWriteXdcFileJobKind {
             .export_options;
         args.args_to_jobs_simple(params, |_kind, args, dependencies| {
             let YosysNextpnrXrayWriteXdcFileArgs {} = args;
+            let base_job = dependencies.get_job::<BaseJob, _>();
             Ok(YosysNextpnrXrayWriteXdcFile {
                 firrtl_export_options,
-                output_dir: dependencies.base_job().output_dir(),
-                xdc_file: dependencies.base_job().file_with_ext("xdc"),
+                output_dir: base_job.output_dir(),
+                xdc_file: base_job.file_with_ext("xdc"),
             })
         })
     }
@@ -435,12 +449,12 @@ impl JobKind for YosysNextpnrXrayWriteXdcFileJobKind {
     fn inputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
         [JobItemName::Path {
             path: job.output_dir,
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
     fn outputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
-        [JobItemName::Path { path: job.xdc_file }][..].intern()
+        [JobItemName::Path { path: job.xdc_file }].intern_slice()
     }
 
     fn name(self) -> Interned<str> {
@@ -611,7 +625,7 @@ impl fmt::Display for Device {
 #[derive(Clone, PartialEq, Eq, Hash, Debug, clap::Args)]
 pub struct YosysNextpnrXrayRunNextpnrArgs {
     #[arg(long, env = "CHIPDB_DIR", value_hint = clap::ValueHint::DirPath)]
-    pub nextpnr_xilinx_chipdb_dir: String,
+    pub nextpnr_xilinx_chipdb_dir: PathBuf,
     #[arg(long)]
     pub device: Device,
     #[arg(long, default_value_t = 0)]
@@ -625,42 +639,43 @@ impl ToArgs for YosysNextpnrXrayRunNextpnrArgs {
             device,
             nextpnr_xilinx_seed,
         } = self;
-        args.write_args([
-            format_args!("--nextpnr-xilinx-chipdb-dir={nextpnr_xilinx_chipdb_dir}"),
-            format_args!("--device={device}"),
-            format_args!("--nextpnr-xilinx-seed={nextpnr_xilinx_seed}"),
-        ]);
+        args.write_long_option_eq("nextpnr-xilinx-chipdb-dir", nextpnr_xilinx_chipdb_dir);
+        args.write_long_option_eq("device", device.as_str());
+        args.write_display_arg(format_args!("--nextpnr-xilinx-seed={nextpnr_xilinx_seed}"));
     }
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
 pub struct YosysNextpnrXrayRunNextpnr {
-    nextpnr_xilinx_chipdb_dir: Interned<str>,
+    nextpnr_xilinx_chipdb_dir: Interned<Path>,
     device: Device,
     nextpnr_xilinx_seed: i32,
-    xdc_file: Interned<str>,
-    xdc_file_name: Interned<str>,
-    json_file: Interned<str>,
-    json_file_name: Interned<str>,
-    routed_json_file: Interned<str>,
-    routed_json_file_name: Interned<str>,
-    fasm_file: Interned<str>,
-    fasm_file_name: Interned<str>,
+    xdc_file: Interned<Path>,
+    xdc_file_name: Interned<OsStr>,
+    json_file: Interned<Path>,
+    json_file_name: Interned<OsStr>,
+    routed_json_file: Interned<Path>,
+    routed_json_file_name: Interned<OsStr>,
+    fasm_file: Interned<Path>,
+    fasm_file_name: Interned<OsStr>,
 }
 
 impl YosysNextpnrXrayRunNextpnr {
-    fn chipdb_file(&self) -> Interned<str> {
-        interned_known_utf8_path_buf_method(self.nextpnr_xilinx_chipdb_dir, |chipdb_dir| {
-            let mut retval = chipdb_dir.join(self.device.xray_device());
-            retval.set_extension("bin");
-            retval
-        })
+    fn chipdb_file(&self) -> Interned<Path> {
+        let mut retval = self
+            .nextpnr_xilinx_chipdb_dir
+            .join(self.device.xray_device());
+        retval.set_extension("bin");
+        retval.intern_deref()
     }
 }
 
 impl ExternalCommand for YosysNextpnrXrayRunNextpnr {
     type AdditionalArgs = YosysNextpnrXrayRunNextpnrArgs;
     type AdditionalJobData = Self;
+    type BaseJobPosition = GetJobPositionDependencies<
+        GetJobPositionDependencies<<YosysNextpnrXraySynth as ExternalCommand>::BaseJobPosition>,
+    >;
     type Dependencies = JobKindAndDependencies<YosysNextpnrXrayWriteXdcFileJobKind>;
     type ExternalProgram = NextpnrXilinx;
 
@@ -681,37 +696,30 @@ impl ExternalCommand for YosysNextpnrXrayRunNextpnr {
                 device,
                 nextpnr_xilinx_seed,
             } = args.additional_args;
-            let xdc_file = dependencies.job.job.xdc_file;
-            let routed_json_file = dependencies.base_job().file_with_ext("routed.json");
-            let fasm_file = dependencies.base_job().file_with_ext("fasm");
+            let base_job = dependencies.get_job::<BaseJob, _>();
+            let write_xdc_file = dependencies.get_job::<YosysNextpnrXrayWriteXdcFile, _>();
+            let synth = dependencies.get_job::<ExternalCommandJob<YosysNextpnrXraySynth>, _>();
+            let routed_json_file = base_job.file_with_ext("routed.json");
+            let fasm_file = base_job.file_with_ext("fasm");
             Ok(Self {
-                nextpnr_xilinx_chipdb_dir: str::intern_owned(nextpnr_xilinx_chipdb_dir),
+                nextpnr_xilinx_chipdb_dir: nextpnr_xilinx_chipdb_dir.intern_deref(),
                 device,
                 nextpnr_xilinx_seed,
-                xdc_file,
-                xdc_file_name: interned_known_utf8_method(xdc_file, |v| {
-                    v.file_name().expect("known to have file name")
-                }),
-                json_file: dependencies
-                    .dependencies
-                    .job
-                    .job
-                    .additional_job_data()
-                    .json_file(),
-                json_file_name: dependencies
-                    .dependencies
-                    .job
-                    .job
-                    .additional_job_data()
-                    .json_file_name(),
+                xdc_file: write_xdc_file.xdc_file,
+                xdc_file_name: write_xdc_file
+                    .xdc_file
+                    .interned_file_name()
+                    .expect("known to have file name"),
+                json_file: synth.additional_job_data().json_file(),
+                json_file_name: synth.additional_job_data().json_file_name(),
                 routed_json_file,
-                routed_json_file_name: interned_known_utf8_method(routed_json_file, |v| {
-                    v.file_name().expect("known to have file name")
-                }),
+                routed_json_file_name: routed_json_file
+                    .interned_file_name()
+                    .expect("known to have file name"),
                 fasm_file,
-                fasm_file_name: interned_known_utf8_method(fasm_file, |v| {
-                    v.file_name().expect("known to have file name")
-                }),
+                fasm_file_name: fasm_file
+                    .interned_file_name()
+                    .expect("known to have file name"),
             })
         })
     }
@@ -724,16 +732,16 @@ impl ExternalCommand for YosysNextpnrXrayRunNextpnr {
             JobItemName::Path {
                 path: job.additional_job_data().xdc_file,
             },
-        ][..]
-            .intern()
+        ]
+        .intern_slice()
     }
 
-    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<str>]> {
+    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<Path>]> {
         [
             job.additional_job_data().routed_json_file,
             job.additional_job_data().fasm_file,
-        ][..]
-            .intern()
+        ]
+        .intern_slice()
     }
 
     fn command_line_args<W: ?Sized + WriteArgs>(job: &ExternalCommandJob<Self>, args: &mut W) {
@@ -745,17 +753,15 @@ impl ExternalCommand for YosysNextpnrXrayRunNextpnr {
             fasm_file_name,
             ..
         } = job.additional_job_data();
-        args.write_args([
-            format_args!("--chipdb={}", job_data.chipdb_file()),
-            format_args!("--xdc={xdc_file_name}"),
-            format_args!("--json={json_file_name}"),
-            format_args!("--write={routed_json_file_name}"),
-            format_args!("--fasm={fasm_file_name}"),
-            format_args!("--seed={nextpnr_xilinx_seed}"),
-        ]);
+        args.write_long_option_eq("chipdb", job_data.chipdb_file());
+        args.write_long_option_eq("xdc", xdc_file_name);
+        args.write_long_option_eq("json", json_file_name);
+        args.write_long_option_eq("write", routed_json_file_name);
+        args.write_long_option_eq("fasm", fasm_file_name);
+        args.write_display_arg(format_args!("--seed={nextpnr_xilinx_seed}"));
     }
 
-    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<str>> {
+    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<Path>> {
         Some(job.output_dir())
     }
 
@@ -780,47 +786,48 @@ impl ExternalProgramTrait for Xcfasm {
 #[derive(Clone, PartialEq, Eq, Hash, Debug, clap::Args)]
 pub struct YosysNextpnrXrayArgs {
     #[arg(long, env = "DB_DIR", value_hint = clap::ValueHint::DirPath)]
-    pub prjxray_db_dir: String,
+    pub prjxray_db_dir: PathBuf,
 }
 
 impl ToArgs for YosysNextpnrXrayArgs {
     fn to_args(&self, args: &mut (impl WriteArgs + ?Sized)) {
         let Self { prjxray_db_dir } = self;
-        args.write_arg(format_args!("--prjxray-db-dir={prjxray_db_dir}"));
+        args.write_long_option_eq("prjxray-db-dir", prjxray_db_dir);
     }
 }
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug, Serialize, Deserialize)]
 pub struct YosysNextpnrXray {
-    prjxray_db_dir: Interned<str>,
+    prjxray_db_dir: Interned<Path>,
     device: Device,
-    fasm_file: Interned<str>,
-    fasm_file_name: Interned<str>,
-    frames_file: Interned<str>,
-    frames_file_name: Interned<str>,
-    bit_file: Interned<str>,
-    bit_file_name: Interned<str>,
+    fasm_file: Interned<Path>,
+    fasm_file_name: Interned<OsStr>,
+    frames_file: Interned<Path>,
+    frames_file_name: Interned<OsStr>,
+    bit_file: Interned<Path>,
+    bit_file_name: Interned<OsStr>,
 }
 
 impl YosysNextpnrXray {
-    fn db_root(&self) -> Interned<str> {
-        interned_known_utf8_path_buf_method(self.prjxray_db_dir, |prjxray_db_dir| {
-            prjxray_db_dir.join(self.device.xray_family())
-        })
+    fn db_root(&self) -> Interned<Path> {
+        self.prjxray_db_dir
+            .join(self.device.xray_family())
+            .intern_deref()
     }
-    fn part_file(&self) -> Interned<str> {
-        interned_known_utf8_path_buf_method(self.prjxray_db_dir, |prjxray_db_dir| {
-            let mut retval = prjxray_db_dir.join(self.device.xray_family());
-            retval.push(self.device.xray_part());
-            retval.push("part.yaml");
-            retval
-        })
+    fn part_file(&self) -> Interned<Path> {
+        let mut retval = self.prjxray_db_dir.join(self.device.xray_family());
+        retval.push(self.device.xray_part());
+        retval.push("part.yaml");
+        retval.intern_deref()
     }
 }
 
 impl ExternalCommand for YosysNextpnrXray {
     type AdditionalArgs = YosysNextpnrXrayArgs;
     type AdditionalJobData = Self;
+    type BaseJobPosition = GetJobPositionDependencies<
+        <YosysNextpnrXrayRunNextpnr as ExternalCommand>::BaseJobPosition,
+    >;
     type Dependencies = JobKindAndDependencies<ExternalCommandJobKind<YosysNextpnrXrayRunNextpnr>>;
     type ExternalProgram = Xcfasm;
 
@@ -837,21 +844,22 @@ impl ExternalCommand for YosysNextpnrXray {
     )> {
         args.args_to_jobs_external_simple(params, |args, dependencies| {
             let YosysNextpnrXrayArgs { prjxray_db_dir } = args.additional_args;
-            let frames_file = dependencies.base_job().file_with_ext("frames");
-            let bit_file = dependencies.base_job().file_with_ext("bit");
+            let base_job = dependencies.get_job::<BaseJob, _>();
+            let frames_file = base_job.file_with_ext("frames");
+            let bit_file = base_job.file_with_ext("bit");
             Ok(Self {
-                prjxray_db_dir: str::intern_owned(prjxray_db_dir),
+                prjxray_db_dir: prjxray_db_dir.intern_deref(),
                 device: dependencies.job.job.additional_job_data().device,
                 fasm_file: dependencies.job.job.additional_job_data().fasm_file,
                 fasm_file_name: dependencies.job.job.additional_job_data().fasm_file_name,
                 frames_file,
-                frames_file_name: interned_known_utf8_method(frames_file, |v| {
-                    v.file_name().expect("known to have file name")
-                }),
+                frames_file_name: frames_file
+                    .interned_file_name()
+                    .expect("known to have file name"),
                 bit_file,
-                bit_file_name: interned_known_utf8_method(bit_file, |v| {
-                    v.file_name().expect("known to have file name")
-                }),
+                bit_file_name: bit_file
+                    .interned_file_name()
+                    .expect("known to have file name"),
             })
         })
     }
@@ -859,16 +867,16 @@ impl ExternalCommand for YosysNextpnrXray {
     fn inputs(job: &ExternalCommandJob<Self>) -> Interned<[JobItemName]> {
         [JobItemName::Path {
             path: job.additional_job_data().fasm_file,
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
-    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<str>]> {
+    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<Path>]> {
         [
             job.additional_job_data().frames_file,
             job.additional_job_data().bit_file,
-        ][..]
-            .intern()
+        ]
+        .intern_slice()
     }
 
     fn command_line_args<W: ?Sized + WriteArgs>(job: &ExternalCommandJob<Self>, args: &mut W) {
@@ -879,18 +887,16 @@ impl ExternalCommand for YosysNextpnrXray {
             bit_file_name,
             ..
         } = job.additional_job_data();
-        args.write_args([
-            format_args!("--sparse"),
-            format_args!("--db-root={}", job_data.db_root()),
-            format_args!("--part={}", device.xray_part()),
-            format_args!("--part_file={}", job_data.part_file()),
-            format_args!("--fn_in={fasm_file_name}"),
-            format_args!("--frm_out={frames_file_name}"),
-            format_args!("--bit_out={bit_file_name}"),
-        ]);
+        args.write_arg("--sparse");
+        args.write_long_option_eq("db-root", job_data.db_root());
+        args.write_long_option_eq("part", device.xray_part());
+        args.write_long_option_eq("part_file", job_data.part_file());
+        args.write_long_option_eq("fn_in", fasm_file_name);
+        args.write_long_option_eq("frm_out", frames_file_name);
+        args.write_long_option_eq("bit_out", bit_file_name);
     }
 
-    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<str>> {
+    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<Path>> {
         Some(job.output_dir())
     }
 
diff --git a/crates/fayalite/src/build/verilog.rs b/crates/fayalite/src/build/verilog.rs
index 39334f2..6ecae2c 100644
--- a/crates/fayalite/src/build/verilog.rs
+++ b/crates/fayalite/src/build/verilog.rs
@@ -3,22 +3,25 @@
 
 use crate::{
     build::{
-        CommandParams, DynJobKind, GetBaseJob, JobAndDependencies, JobArgsAndDependencies,
-        JobDependencies, JobItem, JobItemName, JobKind, JobKindAndDependencies, JobParams, ToArgs,
-        WriteArgs,
+        BaseJob, CommandParams, DynJobKind, GetJobPositionDependencies, GetJobPositionJob,
+        JobAndDependencies, JobArgsAndDependencies, JobDependencies, JobItem, JobItemName, JobKind,
+        JobKindAndDependencies, JobParams, ToArgs, WriteArgs,
         external::{
             ExternalCommand, ExternalCommandJob, ExternalCommandJobKind, ExternalProgramTrait,
         },
-        firrtl::FirrtlJobKind,
-        interned_known_utf8_method, interned_known_utf8_path_buf_method,
+        firrtl::{Firrtl, FirrtlJobKind},
     },
-    intern::{Intern, Interned},
+    intern::{Intern, InternSlice, Interned},
     util::job_server::AcquiredJob,
 };
 use clap::Args;
 use eyre::{Context, bail};
 use serde::{Deserialize, Serialize};
-use std::{fmt, mem};
+use std::{
+    ffi::{OsStr, OsString},
+    fmt, mem,
+    path::Path,
+};
 
 /// based on [LLVM Circt's recommended lowering options][lowering-options]
 ///
@@ -70,7 +73,7 @@ impl VerilogDialect {
 #[non_exhaustive]
 pub struct UnadjustedVerilogArgs {
     #[arg(long = "firtool-extra-arg", value_name = "ARG")]
-    pub firtool_extra_args: Vec<String>,
+    pub firtool_extra_args: Vec<OsString>,
     /// adapt the generated Verilog for a particular toolchain
     #[arg(long)]
     pub verilog_dialect: Option<VerilogDialect>,
@@ -85,16 +88,14 @@ impl ToArgs for UnadjustedVerilogArgs {
             verilog_dialect,
             verilog_debug,
         } = *self;
-        args.extend(
-            firtool_extra_args
-                .iter()
-                .map(|arg| format!("--firtool-extra-arg={arg}")),
-        );
+        for arg in firtool_extra_args {
+            args.write_long_option_eq("firtool-extra-arg", arg);
+        }
         if let Some(verilog_dialect) = verilog_dialect {
-            args.write_arg(format_args!("--verilog-dialect={verilog_dialect}"));
+            args.write_long_option_eq("verilog-dialect", verilog_dialect.as_str());
         }
         if verilog_debug {
-            args.write_str_arg("--verilog-debug");
+            args.write_arg("--verilog-debug");
         }
     }
 }
@@ -110,23 +111,23 @@ impl ExternalProgramTrait for Firtool {
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug, Deserialize, Serialize)]
 pub struct UnadjustedVerilog {
-    firrtl_file: Interned<str>,
-    firrtl_file_name: Interned<str>,
-    unadjusted_verilog_file: Interned<str>,
-    unadjusted_verilog_file_name: Interned<str>,
-    firtool_extra_args: Interned<[Interned<str>]>,
+    firrtl_file: Interned<Path>,
+    firrtl_file_name: Interned<OsStr>,
+    unadjusted_verilog_file: Interned<Path>,
+    unadjusted_verilog_file_name: Interned<OsStr>,
+    firtool_extra_args: Interned<[Interned<OsStr>]>,
     verilog_dialect: Option<VerilogDialect>,
     verilog_debug: bool,
 }
 
 impl UnadjustedVerilog {
-    pub fn firrtl_file(&self) -> Interned<str> {
+    pub fn firrtl_file(&self) -> Interned<Path> {
         self.firrtl_file
     }
-    pub fn unadjusted_verilog_file(&self) -> Interned<str> {
+    pub fn unadjusted_verilog_file(&self) -> Interned<Path> {
         self.unadjusted_verilog_file
     }
-    pub fn firtool_extra_args(&self) -> Interned<[Interned<str>]> {
+    pub fn firtool_extra_args(&self) -> Interned<[Interned<OsStr>]> {
         self.firtool_extra_args
     }
     pub fn verilog_dialect(&self) -> Option<VerilogDialect> {
@@ -140,6 +141,7 @@ impl UnadjustedVerilog {
 impl ExternalCommand for UnadjustedVerilog {
     type AdditionalArgs = UnadjustedVerilogArgs;
     type AdditionalJobData = UnadjustedVerilog;
+    type BaseJobPosition = GetJobPositionDependencies<GetJobPositionJob>;
     type Dependencies = JobKindAndDependencies<FirrtlJobKind>;
     type ExternalProgram = Firtool;
 
@@ -165,21 +167,18 @@ impl ExternalCommand for UnadjustedVerilog {
                 .job
                 .job
                 .file_with_ext("unadjusted.v");
+            let firrtl_job = dependencies.get_job::<Firrtl, _>();
             Ok(UnadjustedVerilog {
-                firrtl_file: dependencies.job.job.firrtl_file(),
-                firrtl_file_name: interned_known_utf8_method(
-                    dependencies.job.job.firrtl_file(),
-                    |v| v.file_name().expect("known to have file name"),
-                ),
+                firrtl_file: firrtl_job.firrtl_file(),
+                firrtl_file_name: firrtl_job
+                    .firrtl_file()
+                    .interned_file_name()
+                    .expect("known to have file name"),
                 unadjusted_verilog_file,
-                unadjusted_verilog_file_name: interned_known_utf8_method(
-                    unadjusted_verilog_file,
-                    |v| v.file_name().expect("known to have file name"),
-                ),
-                firtool_extra_args: firtool_extra_args
-                    .into_iter()
-                    .map(str::intern_owned)
-                    .collect(),
+                unadjusted_verilog_file_name: unadjusted_verilog_file
+                    .interned_file_name()
+                    .expect("known to have file name"),
+                firtool_extra_args: firtool_extra_args.into_iter().map(Interned::from).collect(),
                 verilog_dialect,
                 verilog_debug,
             })
@@ -189,12 +188,12 @@ impl ExternalCommand for UnadjustedVerilog {
     fn inputs(job: &ExternalCommandJob<Self>) -> Interned<[JobItemName]> {
         [JobItemName::Path {
             path: job.additional_job_data().firrtl_file,
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
-    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<str>]> {
-        [job.additional_job_data().unadjusted_verilog_file][..].intern()
+    fn output_paths(job: &ExternalCommandJob<Self>) -> Interned<[Interned<Path>]> {
+        [job.additional_job_data().unadjusted_verilog_file].intern_slice()
     }
 
     fn command_line_args<W: ?Sized + WriteArgs>(job: &ExternalCommandJob<Self>, args: &mut W) {
@@ -208,18 +207,18 @@ impl ExternalCommand for UnadjustedVerilog {
             verilog_debug,
         } = *job.additional_job_data();
         args.write_interned_arg(firrtl_file_name);
-        args.write_str_arg("-o");
+        args.write_arg("-o");
         args.write_interned_arg(unadjusted_verilog_file_name);
         if verilog_debug {
-            args.write_str_args(["-g", "--preserve-values=all"]);
+            args.write_args(["-g", "--preserve-values=all"]);
         }
         if let Some(dialect) = verilog_dialect {
-            args.write_str_args(dialect.firtool_extra_args().iter().copied());
+            args.write_args(dialect.firtool_extra_args().iter().copied());
         }
         args.write_interned_args(firtool_extra_args);
     }
 
-    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<str>> {
+    fn current_dir(job: &ExternalCommandJob<Self>) -> Option<Interned<Path>> {
         Some(job.output_dir())
     }
 
@@ -251,23 +250,23 @@ impl ToArgs for VerilogJobArgs {
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Serialize, Deserialize)]
 pub struct VerilogJob {
-    output_dir: Interned<str>,
-    unadjusted_verilog_file: Interned<str>,
-    main_verilog_file: Interned<str>,
+    output_dir: Interned<Path>,
+    unadjusted_verilog_file: Interned<Path>,
+    main_verilog_file: Interned<Path>,
 }
 
 impl VerilogJob {
-    pub fn output_dir(&self) -> Interned<str> {
+    pub fn output_dir(&self) -> Interned<Path> {
         self.output_dir
     }
-    pub fn unadjusted_verilog_file(&self) -> Interned<str> {
+    pub fn unadjusted_verilog_file(&self) -> Interned<Path> {
         self.unadjusted_verilog_file
     }
-    pub fn main_verilog_file(&self) -> Interned<str> {
+    pub fn main_verilog_file(&self) -> Interned<Path> {
         self.main_verilog_file
     }
     #[track_caller]
-    pub fn unwrap_additional_files(additional_files: &JobItem) -> &[Interned<str>] {
+    pub fn unwrap_additional_files(additional_files: &JobItem) -> &[Interned<Path>] {
         match additional_files {
             JobItem::DynamicPaths {
                 paths,
@@ -277,31 +276,31 @@ impl VerilogJob {
         }
     }
     pub fn all_verilog_files(
-        main_verilog_file: Interned<str>,
-        additional_files: &[Interned<str>],
-    ) -> eyre::Result<Interned<[Interned<str>]>> {
+        main_verilog_file: Interned<Path>,
+        additional_files: &[Interned<Path>],
+    ) -> eyre::Result<Interned<[Interned<Path>]>> {
         let mut retval = Vec::with_capacity(additional_files.len().saturating_add(1));
         for verilog_file in [main_verilog_file].iter().chain(additional_files) {
-            if !(verilog_file.ends_with(".v") || verilog_file.ends_with(".sv")) {
+            if !["v", "sv"]
+                .iter()
+                .any(|extension| verilog_file.extension() == Some(extension.as_ref()))
+            {
                 continue;
             }
-            let verilog_file = std::path::absolute(verilog_file)
-                .and_then(|v| {
-                    v.into_os_string().into_string().map_err(|_| {
-                        std::io::Error::new(std::io::ErrorKind::Other, "path is not valid UTF-8")
-                    })
-                })
-                .wrap_err_with(|| {
-                    format!("converting {verilog_file:?} to an absolute path failed")
-                })?;
-            if verilog_file.contains(|ch: char| {
-                (ch != ' ' && ch != '\t' && ch.is_ascii_whitespace()) || ch == '"'
-            }) {
+            let verilog_file = std::path::absolute(verilog_file).wrap_err_with(|| {
+                format!("converting {verilog_file:?} to an absolute path failed")
+            })?;
+            if verilog_file
+                .as_os_str()
+                .as_encoded_bytes()
+                .iter()
+                .any(|&ch| (ch != b' ' && ch != b'\t' && ch.is_ascii_whitespace()) || ch == b'"')
+            {
                 bail!("verilog file path contains characters that aren't permitted");
             }
-            retval.push(str::intern_owned(verilog_file));
+            retval.push(verilog_file.intern_deref());
         }
-        Ok(Intern::intern_owned(retval))
+        Ok(retval.intern_slice())
     }
 }
 
@@ -320,14 +319,15 @@ impl JobKind for VerilogJobKind {
     ) -> eyre::Result<JobAndDependencies<Self>> {
         args.args_to_jobs_simple(params, |_kind, args, dependencies| {
             let VerilogJobArgs {} = args;
+            let base_job = dependencies.get_job::<BaseJob, _>();
             Ok(VerilogJob {
-                output_dir: dependencies.base_job().output_dir(),
+                output_dir: base_job.output_dir(),
                 unadjusted_verilog_file: dependencies
                     .job
                     .job
                     .additional_job_data()
                     .unadjusted_verilog_file(),
-                main_verilog_file: dependencies.base_job().file_with_ext("v"),
+                main_verilog_file: base_job.file_with_ext("v"),
             })
         })
     }
@@ -335,8 +335,8 @@ impl JobKind for VerilogJobKind {
     fn inputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
         [JobItemName::Path {
             path: job.unadjusted_verilog_file,
-        }][..]
-            .intern()
+        }]
+        .intern_slice()
     }
 
     fn outputs(self, job: &Self::Job) -> Interned<[JobItemName]> {
@@ -347,8 +347,8 @@ impl JobKind for VerilogJobKind {
             JobItemName::DynamicPaths {
                 source_job_name: self.name(),
             },
-        ][..]
-            .intern()
+        ]
+        .intern_slice()
     }
 
     fn name(self) -> Interned<str> {
@@ -384,8 +384,7 @@ impl JobKind for VerilogJobKind {
                     );
                 };
                 input = rest;
-                let next_file_name =
-                    interned_known_utf8_path_buf_method(job.output_dir, |v| v.join(next_file_name));
+                let next_file_name = job.output_dir.join(next_file_name).intern_deref();
                 additional_outputs.push(next_file_name);
                 (chunk, Some(next_file_name))
             } else {
diff --git a/crates/fayalite/src/bundle.rs b/crates/fayalite/src/bundle.rs
index 55843ea..a0de189 100644
--- a/crates/fayalite/src/bundle.rs
+++ b/crates/fayalite/src/bundle.rs
@@ -7,7 +7,7 @@ use crate::{
         ops::{ArrayLiteral, BundleLiteral, ExprPartialEq},
     },
     int::{Bool, DynSize},
-    intern::{Intern, Interned},
+    intern::{Intern, InternSlice, Interned},
     sim::value::{SimValue, SimValuePartialEq, ToSimValue, ToSimValueWithType},
     source_location::SourceLocation,
     ty::{
@@ -549,7 +549,7 @@ macro_rules! impl_tuples {
             type FilledBuilder = TupleBuilder<($(Expr<$T>,)*)>;
             fn fields(&self) -> Interned<[BundleField]> {
                 let ($($var,)*) = self;
-                [$(BundleField { name: stringify!($num).intern(), flipped: false, ty: $var.canonical() }),*][..].intern()
+                [$(BundleField { name: stringify!($num).intern(), flipped: false, ty: $var.canonical() }),*].intern_slice()
             }
         }
         impl<$($T: Type,)*> TypeWithDeref for ($($T,)*) {
@@ -580,7 +580,7 @@ macro_rules! impl_tuples {
                 $(let $var = $var.to_expr();)*
                 let ty = ($(Expr::ty($var),)*);
                 let field_values = [$(Expr::canonical($var)),*];
-                BundleLiteral::new(ty, field_values[..].intern()).to_expr()
+                BundleLiteral::new(ty, field_values.intern_slice()).to_expr()
             }
         }
         impl<$($T: Type,)*> ToExpr for TupleBuilder<($(Expr<$T>,)*)> {
@@ -590,7 +590,7 @@ macro_rules! impl_tuples {
                 let ($($var,)*) = self.0;
                 let ty = ($(Expr::ty($var),)*);
                 let field_values = [$(Expr::canonical($var)),*];
-                BundleLiteral::new(ty, field_values[..].intern()).to_expr()
+                BundleLiteral::new(ty, field_values.intern_slice()).to_expr()
             }
         }
         impl<$($T: ToSimValueWithType<CanonicalType>,)*> ToSimValueWithType<CanonicalType> for ($($T,)*) {
diff --git a/crates/fayalite/src/firrtl.rs b/crates/fayalite/src/firrtl.rs
index a83f269..4bb71c0 100644
--- a/crates/fayalite/src/firrtl.rs
+++ b/crates/fayalite/src/firrtl.rs
@@ -49,6 +49,7 @@ use std::{
     cmp::Ordering,
     collections::{BTreeMap, VecDeque},
     error::Error,
+    ffi::OsString,
     fmt::{self, Write},
     fs,
     hash::Hash,
@@ -2452,7 +2453,7 @@ impl<T: ?Sized + FileBackendTrait> FileBackendTrait for &'_ mut T {
 pub struct FileBackend {
     pub dir_path: PathBuf,
     pub circuit_name: Option<String>,
-    pub top_fir_file_stem: Option<String>,
+    pub top_fir_file_stem: Option<OsString>,
 }
 
 impl FileBackend {
@@ -2501,7 +2502,7 @@ impl FileBackendTrait for FileBackend {
     ) -> Result<(), Self::Error> {
         let top_fir_file_stem = self
             .top_fir_file_stem
-            .get_or_insert_with(|| circuit_name.clone());
+            .get_or_insert_with(|| circuit_name.clone().into());
         self.circuit_name = Some(circuit_name);
         let mut path = self.dir_path.join(top_fir_file_stem);
         if let Some(parent) = path.parent().filter(|v| !v.as_os_str().is_empty()) {
@@ -2777,7 +2778,7 @@ impl ToArgs for ExportOptions {
             __private: ExportOptionsPrivate(()),
         } = *self;
         if !simplify_memories {
-            args.write_str_arg("--no-simplify-memories");
+            args.write_arg("--no-simplify-memories");
         }
         let simplify_enums = simplify_enums.map(|v| {
             clap::ValueEnum::to_possible_value(&v).expect("there are no skipped variants")
@@ -2786,7 +2787,7 @@ impl ToArgs for ExportOptions {
             None => OptionSimplifyEnumsKindValueParser::NONE_NAME,
             Some(v) => v.get_name(),
         };
-        args.write_arg(format_args!("--simplify-enums={simplify_enums}"));
+        args.write_long_option_eq("simplify-enums", simplify_enums);
     }
 }
 
diff --git a/crates/fayalite/src/int/uint_in_range.rs b/crates/fayalite/src/int/uint_in_range.rs
index 5ddd38c..39f4051 100644
--- a/crates/fayalite/src/int/uint_in_range.rs
+++ b/crates/fayalite/src/int/uint_in_range.rs
@@ -8,7 +8,7 @@ use crate::{
         ops::{ExprCastTo, ExprPartialEq, ExprPartialOrd},
     },
     int::{Bool, DynSize, KnownSize, Size, SizeType, UInt, UIntType},
-    intern::{Intern, Interned},
+    intern::{Intern, InternSlice, Interned},
     phantom_const::PhantomConst,
     sim::value::{SimValue, SimValuePartialEq, ToSimValueWithType},
     source_location::SourceLocation,
@@ -112,8 +112,8 @@ impl BundleType for UIntInRangeMaskType {
                 flipped: false,
                 ty: range.canonical(),
             },
-        ][..]
-            .intern()
+        ]
+        .intern_slice()
     }
 }
 
@@ -409,8 +409,8 @@ macro_rules! define_uint_in_range_type {
                         flipped: false,
                         ty: range.canonical(),
                     },
-                ][..]
-                    .intern()
+                ]
+                .intern_slice()
             }
         }
 
diff --git a/crates/fayalite/src/intern.rs b/crates/fayalite/src/intern.rs
index 9d57146..b68140b 100644
--- a/crates/fayalite/src/intern.rs
+++ b/crates/fayalite/src/intern.rs
@@ -9,13 +9,13 @@ use std::{
     any::{Any, TypeId},
     borrow::{Borrow, Cow},
     cmp::Ordering,
-    ffi::OsStr,
+    ffi::{OsStr, OsString},
     fmt,
     hash::{BuildHasher, Hash, Hasher},
     iter::FusedIterator,
     marker::PhantomData,
     ops::Deref,
-    path::Path,
+    path::{Path, PathBuf},
     sync::{Mutex, RwLock},
 };
 
@@ -289,15 +289,266 @@ impl InternedCompare for BitSlice {
     }
 }
 
-impl InternedCompare for str {
-    type InternedCompareKey = PtrEqWithMetadata<Self>;
-    fn interned_compare_key_ref(this: &Self) -> Self::InternedCompareKey {
-        PtrEqWithMetadata(this)
+/// Safety: `as_bytes` and `from_bytes_unchecked` must return the same pointer as the input.
+/// all values returned by `as_bytes` must be valid to pass to `from_bytes_unchecked`.
+/// `into_bytes` must return the exact same thing as `as_bytes`.
+/// `Interned<Self>` must contain the exact same references as `Interned<[u8]>`,
+/// so they can be safely interconverted without needing re-interning.
+unsafe trait InternStrLike: ToOwned {
+    fn as_bytes(this: &Self) -> &[u8];
+    fn into_bytes(this: Self::Owned) -> Vec<u8>;
+    /// Safety: `bytes` must be a valid sequence of bytes for this type. All UTF-8 sequences are valid.
+    unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self;
+}
+
+macro_rules! impl_intern_str_like {
+    ($ty:ty, owned = $Owned:ty) => {
+        impl InternedCompare for $ty {
+            type InternedCompareKey = PtrEqWithMetadata<[u8]>;
+            fn interned_compare_key_ref(this: &Self) -> Self::InternedCompareKey {
+                PtrEqWithMetadata(InternStrLike::as_bytes(this))
+            }
+        }
+        impl Intern for $ty {
+            fn intern(&self) -> Interned<Self> {
+                Self::intern_cow(Cow::Borrowed(self))
+            }
+            fn intern_cow(this: Cow<'_, Self>) -> Interned<Self> {
+                Interned::cast_unchecked(
+                    <[u8]>::intern_cow(match this {
+                        Cow::Borrowed(v) => Cow::Borrowed(<Self as InternStrLike>::as_bytes(v)),
+                        Cow::Owned(v) => {
+                            // verify $Owned is correct
+                            let v: $Owned = v;
+                            Cow::Owned(<Self as InternStrLike>::into_bytes(v))
+                        }
+                    }),
+                    // Safety: guaranteed safe because we got the bytes from `as_bytes`/`into_bytes`
+                    |v| unsafe { <Self as InternStrLike>::from_bytes_unchecked(v) },
+                )
+            }
+        }
+        impl Default for Interned<$ty> {
+            fn default() -> Self {
+                // Safety: safe because the empty sequence is valid UTF-8
+                unsafe { <$ty as InternStrLike>::from_bytes_unchecked(&[]) }.intern()
+            }
+        }
+        impl<'de> Deserialize<'de> for Interned<$ty> {
+            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+            where
+                D: serde::Deserializer<'de>,
+            {
+                Cow::<'de, $ty>::deserialize(deserializer).map(Intern::intern_cow)
+            }
+        }
+        impl From<$Owned> for Interned<$ty> {
+            fn from(v: $Owned) -> Self {
+                v.intern_deref()
+            }
+        }
+        impl From<Interned<$ty>> for $Owned {
+            fn from(v: Interned<$ty>) -> Self {
+                Interned::into_inner(v).into()
+            }
+        }
+        impl From<Interned<$ty>> for Box<$ty> {
+            fn from(v: Interned<$ty>) -> Self {
+                Interned::into_inner(v).into()
+            }
+        }
+    };
+}
+
+// Safety: satisfies `InternStrLike`'s requirements where the valid sequences for `from_bytes_unchecked` matches `str`
+unsafe impl InternStrLike for str {
+    fn as_bytes(this: &Self) -> &[u8] {
+        this.as_bytes()
+    }
+    fn into_bytes(this: Self::Owned) -> Vec<u8> {
+        this.into_bytes()
+    }
+    unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self {
+        // Safety: `bytes` is guaranteed UTF-8 by the caller
+        unsafe { str::from_utf8_unchecked(bytes) }
+    }
+}
+
+impl_intern_str_like!(str, owned = String);
+
+// Safety: satisfies `InternStrLike`'s requirements where the valid sequences for `from_bytes_unchecked` matches `OsStr`
+unsafe impl InternStrLike for OsStr {
+    fn as_bytes(this: &Self) -> &[u8] {
+        this.as_encoded_bytes()
+    }
+    fn into_bytes(this: Self::Owned) -> Vec<u8> {
+        this.into_encoded_bytes()
+    }
+    unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self {
+        // Safety: `bytes` is guaranteed valid for `OsStr` by the caller
+        unsafe { OsStr::from_encoded_bytes_unchecked(bytes) }
+    }
+}
+
+impl_intern_str_like!(OsStr, owned = OsString);
+
+// Safety: satisfies `InternStrLike`'s requirements where the valid sequences for `from_bytes_unchecked` matches `OsStr`
+unsafe impl InternStrLike for Path {
+    fn as_bytes(this: &Self) -> &[u8] {
+        this.as_os_str().as_encoded_bytes()
+    }
+    fn into_bytes(this: Self::Owned) -> Vec<u8> {
+        this.into_os_string().into_encoded_bytes()
+    }
+    unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self {
+        // Safety: `bytes` is guaranteed valid for `OsStr` by the caller
+        unsafe { Path::new(OsStr::from_encoded_bytes_unchecked(bytes)) }
+    }
+}
+
+impl_intern_str_like!(Path, owned = PathBuf);
+
+impl Interned<str> {
+    pub fn from_utf8(v: Interned<[u8]>) -> Result<Self, std::str::Utf8Error> {
+        Interned::try_cast_unchecked(v, str::from_utf8)
+    }
+    pub fn as_interned_bytes(self) -> Interned<[u8]> {
+        Interned::cast_unchecked(self, str::as_bytes)
+    }
+    pub fn as_interned_os_str(self) -> Interned<OsStr> {
+        Interned::cast_unchecked(self, AsRef::as_ref)
+    }
+    pub fn as_interned_path(self) -> Interned<Path> {
+        Interned::cast_unchecked(self, AsRef::as_ref)
+    }
+}
+
+impl From<Interned<str>> for Interned<OsStr> {
+    fn from(value: Interned<str>) -> Self {
+        value.as_interned_os_str()
+    }
+}
+
+impl From<Interned<str>> for Interned<Path> {
+    fn from(value: Interned<str>) -> Self {
+        value.as_interned_path()
+    }
+}
+
+impl Interned<OsStr> {
+    pub fn as_interned_encoded_bytes(self) -> Interned<[u8]> {
+        Interned::cast_unchecked(self, OsStr::as_encoded_bytes)
+    }
+    pub fn to_interned_str(self) -> Option<Interned<str>> {
+        Interned::try_cast_unchecked(self, |v| v.to_str().ok_or(())).ok()
+    }
+    pub fn display(self) -> std::ffi::os_str::Display<'static> {
+        Self::into_inner(self).display()
+    }
+    pub fn as_interned_path(self) -> Interned<Path> {
+        Interned::cast_unchecked(self, AsRef::as_ref)
+    }
+}
+
+impl From<Interned<OsStr>> for Interned<Path> {
+    fn from(value: Interned<OsStr>) -> Self {
+        value.as_interned_path()
+    }
+}
+
+impl Interned<Path> {
+    pub fn as_interned_os_str(self) -> Interned<OsStr> {
+        Interned::cast_unchecked(self, AsRef::as_ref)
+    }
+    pub fn to_interned_str(self) -> Option<Interned<str>> {
+        Interned::try_cast_unchecked(self, |v| v.to_str().ok_or(())).ok()
+    }
+    pub fn display(self) -> std::path::Display<'static> {
+        Self::into_inner(self).display()
+    }
+    pub fn interned_file_name(self) -> Option<Interned<OsStr>> {
+        Some(self.file_name()?.intern())
+    }
+}
+
+impl From<Interned<Path>> for Interned<OsStr> {
+    fn from(value: Interned<Path>) -> Self {
+        value.as_interned_os_str()
+    }
+}
+
+pub trait InternSlice: Sized {
+    type Element: 'static + Send + Sync + Clone + Hash + Eq;
+    fn intern_slice(self) -> Interned<[Self::Element]>;
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq> InternSlice for Box<[T]> {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        self.into_vec().intern_slice()
+    }
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq> InternSlice for Vec<T> {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        self.intern_deref()
+    }
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq> InternSlice for &'_ [T] {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        self.intern()
+    }
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq> InternSlice for &'_ mut [T] {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        self.intern()
+    }
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq, const N: usize> InternSlice for [T; N] {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        (&self).intern_slice()
+    }
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq, const N: usize> InternSlice for Box<[T; N]> {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        let this: Box<[T]> = self;
+        this.intern_slice()
+    }
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq, const N: usize> InternSlice for &'_ [T; N] {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        let this: &[T] = self;
+        this.intern()
+    }
+}
+
+impl<T: 'static + Send + Sync + Clone + Hash + Eq, const N: usize> InternSlice for &'_ mut [T; N] {
+    type Element = T;
+    fn intern_slice(self) -> Interned<[Self::Element]> {
+        let this: &[T] = self;
+        this.intern()
     }
 }
 
 pub trait Intern: Any + Send + Sync {
     fn intern(&self) -> Interned<Self>;
+    fn intern_deref(self) -> Interned<Self::Target>
+    where
+        Self: Sized + Deref<Target: Intern + ToOwned<Owned = Self>>,
+    {
+        Self::Target::intern_owned(self)
+    }
     fn intern_sized(self) -> Interned<Self>
     where
         Self: Clone,
@@ -318,6 +569,30 @@ pub trait Intern: Any + Send + Sync {
     }
 }
 
+impl<T: ?Sized + Intern + ToOwned> From<Cow<'_, T>> for Interned<T> {
+    fn from(value: Cow<'_, T>) -> Self {
+        Intern::intern_cow(value)
+    }
+}
+
+impl<T: ?Sized + Intern> From<&'_ T> for Interned<T> {
+    fn from(value: &'_ T) -> Self {
+        Intern::intern(value)
+    }
+}
+
+impl<T: Intern + Clone> From<T> for Interned<T> {
+    fn from(value: T) -> Self {
+        Intern::intern_sized(value)
+    }
+}
+
+impl<T: ?Sized + 'static + Send + Sync + ToOwned> From<Interned<T>> for Cow<'_, T> {
+    fn from(value: Interned<T>) -> Self {
+        Cow::Borrowed(Interned::into_inner(value))
+    }
+}
+
 struct InternerState<T: ?Sized + 'static + Send + Sync> {
     table: HashTable<&'static T>,
     hasher: DefaultBuildHasher,
@@ -383,12 +658,6 @@ impl Interner<BitSlice> {
     }
 }
 
-impl Interner<str> {
-    fn intern_str(&self, value: Cow<'_, str>) -> Interned<str> {
-        self.intern(|value| value.into_owned().leak(), value)
-    }
-}
-
 pub struct Interned<T: ?Sized + 'static + Send + Sync> {
     inner: &'static T,
 }
@@ -418,9 +687,9 @@ forward_fmt_trait!(Pointer);
 forward_fmt_trait!(UpperExp);
 forward_fmt_trait!(UpperHex);
 
-impl<T: ?Sized + 'static + Send + Sync> AsRef<T> for Interned<T> {
-    fn as_ref(&self) -> &T {
-        self
+impl<T: ?Sized + 'static + Send + Sync + AsRef<U>, U: ?Sized> AsRef<U> for Interned<T> {
+    fn as_ref(&self) -> &U {
+        T::as_ref(self)
     }
 }
 
@@ -498,19 +767,25 @@ where
     String: FromIterator<I>,
 {
     fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {
-        str::intern_owned(FromIterator::from_iter(iter))
+        String::from_iter(iter).intern_deref()
     }
 }
 
-impl AsRef<OsStr> for Interned<str> {
-    fn as_ref(&self) -> &OsStr {
-        str::as_ref(self)
+impl<I> FromIterator<I> for Interned<Path>
+where
+    PathBuf: FromIterator<I>,
+{
+    fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {
+        PathBuf::from_iter(iter).intern_deref()
     }
 }
 
-impl AsRef<Path> for Interned<str> {
-    fn as_ref(&self) -> &Path {
-        str::as_ref(self)
+impl<I> FromIterator<I> for Interned<OsStr>
+where
+    OsString: FromIterator<I>,
+{
+    fn from_iter<T: IntoIterator<Item = I>>(iter: T) -> Self {
+        OsString::from_iter(iter).intern_deref()
     }
 }
 
@@ -550,24 +825,12 @@ impl<T: 'static + Clone + Send + Sync> From<Interned<[T]>> for Box<[T]> {
     }
 }
 
-impl From<Interned<str>> for String {
-    fn from(value: Interned<str>) -> Self {
-        String::from(&*value)
-    }
-}
-
 impl<I> Default for Interned<[I]>
 where
     [I]: Intern,
 {
     fn default() -> Self {
-        [][..].intern()
-    }
-}
-
-impl Default for Interned<str> {
-    fn default() -> Self {
-        "".intern()
+        Intern::intern(&[])
     }
 }
 
@@ -698,15 +961,6 @@ impl<'de> Deserialize<'de> for Interned<BitSlice> {
     }
 }
 
-impl<'de> Deserialize<'de> for Interned<str> {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: serde::Deserializer<'de>,
-    {
-        String::deserialize(deserializer).map(Intern::intern_owned)
-    }
-}
-
 impl<T: Clone + Send + Sync + 'static + Hash + Eq> Intern for T {
     fn intern(&self) -> Interned<Self> {
         Self::intern_cow(Cow::Borrowed(self))
@@ -767,26 +1021,6 @@ impl Intern for BitSlice {
     }
 }
 
-impl Intern for str {
-    fn intern(&self) -> Interned<Self> {
-        Self::intern_cow(Cow::Borrowed(self))
-    }
-
-    fn intern_owned(this: <Self as ToOwned>::Owned) -> Interned<Self>
-    where
-        Self: ToOwned,
-    {
-        Self::intern_cow(Cow::Owned(this))
-    }
-
-    fn intern_cow(this: Cow<'_, Self>) -> Interned<Self>
-    where
-        Self: ToOwned,
-    {
-        Interner::get().intern_str(this)
-    }
-}
-
 pub trait MemoizeGeneric: 'static + Send + Sync + Hash + Eq + Copy {
     type InputRef<'a>: 'a + Send + Sync + Hash + Copy;
     type InputOwned: 'static + Send + Sync;
diff --git a/crates/fayalite/src/module/transform/simplify_enums.rs b/crates/fayalite/src/module/transform/simplify_enums.rs
index 0839881..bd5f7d5 100644
--- a/crates/fayalite/src/module/transform/simplify_enums.rs
+++ b/crates/fayalite/src/module/transform/simplify_enums.rs
@@ -10,7 +10,7 @@ use crate::{
     },
     hdl,
     int::UInt,
-    intern::{Intern, Interned, Memoize},
+    intern::{Intern, InternSlice, Interned, Memoize},
     memory::{DynPortType, Mem, MemPort},
     module::{
         Block, Id, Module, NameId, ScopedNameId, Stmt, StmtConnect, StmtIf, StmtMatch, StmtWire,
@@ -620,7 +620,7 @@ fn match_int_tag(
                 block,
                 Block {
                     memories: Default::default(),
-                    stmts: [Stmt::from(retval)][..].intern(),
+                    stmts: [Stmt::from(retval)].intern_slice(),
                 },
             ],
         };
diff --git a/crates/fayalite/src/sim.rs b/crates/fayalite/src/sim.rs
index 1717aec..fabe6d8 100644
--- a/crates/fayalite/src/sim.rs
+++ b/crates/fayalite/src/sim.rs
@@ -12,7 +12,9 @@ use crate::{
         },
     },
     int::BoolOrIntType,
-    intern::{Intern, Interned, InternedCompare, PtrEqWithTypeId, SupportsPtrEqWithTypeId},
+    intern::{
+        Intern, InternSlice, Interned, InternedCompare, PtrEqWithTypeId, SupportsPtrEqWithTypeId,
+    },
     module::{
         ModuleIO,
         transform::visit::{Fold, Folder, Visit, Visitor},
@@ -262,7 +264,7 @@ impl_trace_decl! {
         }),
         Instance(TraceInstance {
             fn children(self) -> _ {
-                [self.instance_io.into(), self.module.into()][..].intern()
+                [self.instance_io.into(), self.module.into()].intern_slice()
             }
             name: Interned<str>,
             instance_io: TraceBundle,
@@ -282,7 +284,7 @@ impl_trace_decl! {
         }),
         MemPort(TraceMemPort {
             fn children(self) -> _ {
-                [self.bundle.into()][..].intern()
+                [self.bundle.into()].intern_slice()
             }
             name: Interned<str>,
             bundle: TraceBundle,
@@ -290,7 +292,7 @@ impl_trace_decl! {
         }),
         Wire(TraceWire {
             fn children(self) -> _ {
-                [*self.child][..].intern()
+                [*self.child].intern_slice()
             }
             name: Interned<str>,
             child: Interned<TraceDecl>,
@@ -298,7 +300,7 @@ impl_trace_decl! {
         }),
         Reg(TraceReg {
             fn children(self) -> _ {
-                [*self.child][..].intern()
+                [*self.child].intern_slice()
             }
             name: Interned<str>,
             child: Interned<TraceDecl>,
@@ -306,7 +308,7 @@ impl_trace_decl! {
         }),
         ModuleIO(TraceModuleIO {
             fn children(self) -> _ {
-                [*self.child][..].intern()
+                [*self.child].intern_slice()
             }
             name: Interned<str>,
             child: Interned<TraceDecl>,
diff --git a/crates/fayalite/src/sim/compiler.rs b/crates/fayalite/src/sim/compiler.rs
index 2b291be..fbede7b 100644
--- a/crates/fayalite/src/sim/compiler.rs
+++ b/crates/fayalite/src/sim/compiler.rs
@@ -14,7 +14,7 @@ use crate::{
         },
     },
     int::BoolOrIntType,
-    intern::{Intern, Interned, Memoize},
+    intern::{Intern, InternSlice, Interned, Memoize},
     memory::PortKind,
     module::{
         AnnotatedModuleIO, Block, ExternModuleBody, Id, InstantiatedModule, ModuleBody, NameId,
@@ -3950,8 +3950,8 @@ impl Compiler {
                     [Cond {
                         body: CondBody::IfTrue { cond },
                         source_location: reg.source_location(),
-                    }][..]
-                        .intern(),
+                    }]
+                    .intern_slice(),
                     lhs,
                     init,
                     reg.source_location(),
diff --git a/crates/fayalite/src/testing.rs b/crates/fayalite/src/testing.rs
index 47c7cfa..30a8243 100644
--- a/crates/fayalite/src/testing.rs
+++ b/crates/fayalite/src/testing.rs
@@ -14,7 +14,6 @@ use crate::{
     module::Module,
     util::HashMap,
 };
-use eyre::eyre;
 use serde::Deserialize;
 use std::{
     fmt::Write,
@@ -107,12 +106,7 @@ fn make_assert_formal_args(
 ) -> eyre::Result<JobArgsAndDependencies<ExternalCommandJobKind<Formal>>> {
     let args = JobKindAndArgs {
         kind: BaseJobKind,
-        args: BaseJobArgs::from_output_dir_and_env(
-            get_assert_formal_target_path(&test_name)
-                .into_os_string()
-                .into_string()
-                .map_err(|_| eyre!("path is not valid UTF-8"))?,
-        ),
+        args: BaseJobArgs::from_output_dir_and_env(get_assert_formal_target_path(&test_name)),
     };
     let dependencies = JobArgsAndDependencies {
         args,
diff --git a/crates/fayalite/src/util.rs b/crates/fayalite/src/util.rs
index 23a6852..cc8f8b0 100644
--- a/crates/fayalite/src/util.rs
+++ b/crates/fayalite/src/util.rs
@@ -38,9 +38,9 @@ pub(crate) use misc::chain;
 pub use misc::{
     BitSliceWriteWithBase, DebugAsDisplay, DebugAsRawString, MakeMutSlice, RcWriter,
     SerdeJsonEscapeIf, SerdeJsonEscapeIfFormatter, SerdeJsonEscapeIfTest,
-    SerdeJsonEscapeIfTestResult, interned_bit, iter_eq_by, serialize_to_json_ascii,
-    serialize_to_json_ascii_pretty, serialize_to_json_ascii_pretty_with_indent, slice_range,
-    try_slice_range,
+    SerdeJsonEscapeIfTestResult, interned_bit, iter_eq_by, os_str_strip_prefix,
+    os_str_strip_suffix, serialize_to_json_ascii, serialize_to_json_ascii_pretty,
+    serialize_to_json_ascii_pretty_with_indent, slice_range, try_slice_range,
 };
 
 pub mod job_server;
diff --git a/crates/fayalite/src/util/misc.rs b/crates/fayalite/src/util/misc.rs
index 6c9acee..bd5c53f 100644
--- a/crates/fayalite/src/util/misc.rs
+++ b/crates/fayalite/src/util/misc.rs
@@ -4,6 +4,7 @@ use crate::intern::{Intern, Interned};
 use bitvec::{bits, order::Lsb0, slice::BitSlice, view::BitView};
 use std::{
     cell::Cell,
+    ffi::OsStr,
     fmt::{self, Debug, Write},
     io,
     ops::{Bound, Range, RangeBounds},
@@ -564,3 +565,23 @@ pub fn serialize_to_json_ascii_pretty_with_indent<T: serde::Serialize + ?Sized>(
         serde_json::ser::PrettyFormatter::with_indent(indent.as_bytes()),
     )
 }
+
+pub fn os_str_strip_prefix<'a>(os_str: &'a OsStr, prefix: impl AsRef<str>) -> Option<&'a OsStr> {
+    os_str
+        .as_encoded_bytes()
+        .strip_prefix(prefix.as_ref().as_bytes())
+        .map(|bytes| {
+            // Safety: we removed a UTF-8 prefix so bytes starts with a valid boundary
+            unsafe { OsStr::from_encoded_bytes_unchecked(bytes) }
+        })
+}
+
+pub fn os_str_strip_suffix<'a>(os_str: &'a OsStr, suffix: impl AsRef<str>) -> Option<&'a OsStr> {
+    os_str
+        .as_encoded_bytes()
+        .strip_suffix(suffix.as_ref().as_bytes())
+        .map(|bytes| {
+            // Safety: we removed a UTF-8 suffix so bytes ends with a valid boundary
+            unsafe { OsStr::from_encoded_bytes_unchecked(bytes) }
+        })
+}
diff --git a/crates/fayalite/tests/ui/simvalue_is_not_internable.stderr b/crates/fayalite/tests/ui/simvalue_is_not_internable.stderr
index 03c62bf..1fd291c 100644
--- a/crates/fayalite/tests/ui/simvalue_is_not_internable.stderr
+++ b/crates/fayalite/tests/ui/simvalue_is_not_internable.stderr
@@ -156,7 +156,7 @@ note: required by a bound in `intern_sized`
    |
    | pub trait Intern: Any + Send + Sync {
    |                                ^^^^ required by this bound in `Intern::intern_sized`
-   |     fn intern(&self) -> Interned<Self>;
+...
    |     fn intern_sized(self) -> Interned<Self>
    |        ------------ required by a bound in this associated function
 help: consider dereferencing here
@@ -188,7 +188,7 @@ note: required by a bound in `intern_sized`
    |
    | pub trait Intern: Any + Send + Sync {
    |                                ^^^^ required by this bound in `Intern::intern_sized`
-   |     fn intern(&self) -> Interned<Self>;
+...
    |     fn intern_sized(self) -> Interned<Self>
    |        ------------ required by a bound in this associated function
 help: consider dereferencing here
@@ -255,7 +255,7 @@ note: required by a bound in `intern_sized`
    |
    | pub trait Intern: Any + Send + Sync {
    |                         ^^^^ required by this bound in `Intern::intern_sized`
-   |     fn intern(&self) -> Interned<Self>;
+...
    |     fn intern_sized(self) -> Interned<Self>
    |        ------------ required by a bound in this associated function
 help: consider dereferencing here