diff --git a/Cargo.lock b/Cargo.lock
index ecc5b2ee0f..6844bcb1a6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2801,6 +2801,7 @@ dependencies = [
  "roc_tracing",
  "roc_types",
  "roc_unify",
+ "roc_work",
  "tempfile",
  "ven_pretty",
 ]
@@ -3216,6 +3217,15 @@ dependencies = [
  "roc_error_macros",
 ]
 
+[[package]]
+name = "roc_work"
+version = "0.0.1"
+dependencies = [
+ "roc_collections",
+ "roc_error_macros",
+ "roc_module",
+]
+
 [[package]]
 name = "rustc-demangle"
 version = "0.1.23"
diff --git a/crates/compiler/load_internal/Cargo.toml b/crates/compiler/load_internal/Cargo.toml
index e5437947c8..0f9ee8c98e 100644
--- a/crates/compiler/load_internal/Cargo.toml
+++ b/crates/compiler/load_internal/Cargo.toml
@@ -10,6 +10,7 @@ version.workspace = true
 [dependencies]
 roc_builtins = { path = "../builtins" }
 roc_can = { path = "../can" }
+roc_work = { path = "../work" }
 roc_checkmate = { path = "../checkmate" }
 roc_collections = { path = "../collections" }
 roc_constrain = { path = "../constrain" }
diff --git a/crates/compiler/load_internal/src/file.rs b/crates/compiler/load_internal/src/file.rs
index a0c5eaba65..b7788c2118 100644
--- a/crates/compiler/load_internal/src/file.rs
+++ b/crates/compiler/load_internal/src/file.rs
@@ -81,8 +81,8 @@ use {
     roc_packaging::https::{PackageMetadata, Problem},
 };
 
-pub use crate::work::Phase;
-use crate::work::{DepCycle, Dependencies};
+pub use roc_work::Phase;
+use roc_work::{DepCycle, Dependencies};
 
 #[cfg(target_family = "wasm")]
 use crate::wasm_instant::{Duration, Instant};
@@ -150,7 +150,8 @@ fn start_phase<'a>(
 ) -> Vec<BuildTask<'a>> {
     // we blindly assume all dependencies are met
 
-    use crate::work::PrepareStartPhase::*;
+    use roc_work::PrepareStartPhase::*;
+
     match state.dependencies.prepare_start_phase(module_id, phase) {
         Continue => {
             // fall through
diff --git a/crates/compiler/load_internal/src/lib.rs b/crates/compiler/load_internal/src/lib.rs
index 24226d4c6b..919832ab4f 100644
--- a/crates/compiler/load_internal/src/lib.rs
+++ b/crates/compiler/load_internal/src/lib.rs
@@ -8,7 +8,6 @@ pub mod docs;
 pub mod file;
 pub mod module;
 mod module_cache;
-mod work;
 
 #[cfg(target_family = "wasm")]
 mod wasm_instant;
diff --git a/crates/compiler/work/Cargo.toml b/crates/compiler/work/Cargo.toml
new file mode 100644
index 0000000000..6bbb4c74f2
--- /dev/null
+++ b/crates/compiler/work/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "roc_work"
+description = "This is used in loading."
+
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+version.workspace = true
+
+[dependencies]
+roc_collections = { path = "../collections" }
+roc_module = { path = "../module" }
+roc_error_macros = { path = "../../error_macros" }
diff --git a/crates/compiler/work/src/lib.rs b/crates/compiler/work/src/lib.rs
new file mode 100644
index 0000000000..6f51e383fe
--- /dev/null
+++ b/crates/compiler/work/src/lib.rs
@@ -0,0 +1,3 @@
+mod work;
+
+pub use work::*;
diff --git a/crates/compiler/load_internal/src/work.rs b/crates/compiler/work/src/work.rs
similarity index 100%
rename from crates/compiler/load_internal/src/work.rs
rename to crates/compiler/work/src/work.rs
diff --git a/crates/compiler/work/src/worker.rs b/crates/compiler/work/src/worker.rs
new file mode 100644
index 0000000000..deef2763b5
--- /dev/null
+++ b/crates/compiler/work/src/worker.rs
@@ -0,0 +1,47 @@
+use crate::work::Dependencies;
+
+/// This is a trait so that we can implement both a single-threaded and a multithreaded version.
+/// We *need* a single-threaded version for wasm, but it's also desirable in tests.
+///
+/// The general design here is "mutex granularity" - basically, try to have a mutex around each
+/// individual piece of global state, and lock it for as little time as possible.
+pub trait Worker<'global, Event, ModuleId> {
+    fn enqueue_event(&mut self, event: Event);
+    fn with_deps(&mut self, func: impl FnMut(&mut Dependencies<'global, ModuleId>));
+    // fn with_module_names(&mut self, func: impl FnMut(MutMap<ModuleId, PQModuleName<'a>>));
+
+    // /// Phases
+    // fn with_headers(&mut self, func: impl FnMut(MutMap<ModuleId, ModuleHeader<'a>>));
+    // fn with_parsed(&mut self, func: impl FnMut(MutMap<ModuleId, ParsedModule<'a>>));
+    // fn with_aliases(&mut self, func: impl FnMut(MutMap<ModuleId, MutMap<Symbol, (bool, Alias)>>));
+    // fn with_pending_abilities(&mut self, func: impl FnMut(MutMap<ModuleId, PendingAbilitiesStore>));
+    // fn with_constrained(&mut self, func: impl FnMut(MutMap<ModuleId, ConstrainedModule>));
+    // fn with_typechecked(&mut self, func: impl FnMut(MutMap<ModuleId, TypeCheckedModule<'a>>));
+    // fn with_checked(&mut self, func: impl FnMut(MutMap<ModuleId, CheckedModule>));
+    // fn with_found_specializations(
+    //     &mut self,
+    //     func: impl FnMut(MutMap<ModuleId, FoundSpecializationsModule<'a>>),
+    // );
+    // fn with_late_specializations(
+    //     &mut self,
+    //     func: impl FnMut(MutMap<ModuleId, LateSpecializationsModule<'a>>),
+    // );
+    // fn with_external_specializations_requested(
+    //     &mut self,
+    //     func: impl FnMut(MutMap<ModuleId, Vec<ExternalSpecializations<'a>>>),
+    // );
+
+    // /// Various information
+    // fn with_imports(&mut self, func: impl FnMut(MutMap<ModuleId, MutSet<ModuleId>>));
+    // fn with_exposes(&mut self, func: impl FnMut(MutMap<ModuleId, Vec<(Symbol, Variable)>>));
+    // fn with_exposed_imports(&mut self, func: impl FnMut(MutMap<ModuleId, MutMap<Symbol, Region>>));
+    // fn with_top_level_thunks(&mut self, func: impl FnMut(MutMap<ModuleId, MutSet<Symbol>>));
+    // fn with_documentation(&mut self, func: impl FnMut(VecMap<ModuleId, ModuleDocumentation>));
+    // fn with_can_problems(
+    //     &mut self,
+    //     func: impl FnMut(MutMap<ModuleId, Vec<roc_problem::can::Problem>>),
+    // );
+    // fn with_type_problems(&mut self, func: impl FnMut(MutMap<ModuleId, Vec<TypeError>>));
+
+    // fn with_sources(&mut self, func: impl FnMut(MutMap<ModuleId, (PathBuf, &'a str)>));
+}