diff --git a/Cargo.lock b/Cargo.lock
index cd2f631f31..d87306562e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3060,6 +3060,7 @@ dependencies = [
  "roc_derive_key",
  "roc_error_macros",
  "roc_exhaustive",
+ "roc_load",
  "roc_module",
  "roc_packaging",
  "roc_parse",
@@ -3072,6 +3073,7 @@ dependencies = [
  "roc_types",
  "roc_unify",
  "tempfile",
+ "test_solve_helpers",
 ]
 
 [[package]]
@@ -3094,42 +3096,6 @@ dependencies = [
  "bitflags 1.3.2",
 ]
 
-[[package]]
-name = "roc_solve_tests"
-version = "0.0.1"
-dependencies = [
- "arrayvec 0.7.4",
- "bumpalo",
- "indoc",
- "insta",
- "lazy_static",
- "libtest-mimic",
- "pretty_assertions",
- "regex",
- "roc_builtins",
- "roc_can",
- "roc_checkmate",
- "roc_collections",
- "roc_debug_flags",
- "roc_derive",
- "roc_derive_key",
- "roc_error_macros",
- "roc_exhaustive",
- "roc_load_internal",
- "roc_module",
- "roc_packaging",
- "roc_parse",
- "roc_problem",
- "roc_region",
- "roc_reporting",
- "roc_solve_problem",
- "roc_solve_schema",
- "roc_target",
- "roc_types",
- "roc_unify",
- "tempfile",
-]
-
 [[package]]
 name = "roc_std"
 version = "0.0.1"
diff --git a/crates/lang_srv/src/analysis.rs b/crates/lang_srv/src/analysis.rs
index 072bf1673a..69f26ea26b 100644
--- a/crates/lang_srv/src/analysis.rs
+++ b/crates/lang_srv/src/analysis.rs
@@ -309,6 +309,8 @@ pub struct DocInfo {
     pub version: i32,
 }
 impl DocInfo {
+    #[cfg(debug_assertions)]
+    #[allow(unused)]
     fn debug_log_prefix(&self, offset: u32) {
         eprintln!("prefix source{:?}", self.source);
 
diff --git a/crates/lang_srv/src/registry.rs b/crates/lang_srv/src/registry.rs
index 20b0d6795d..07f16b1c3f 100644
--- a/crates/lang_srv/src/registry.rs
+++ b/crates/lang_srv/src/registry.rs
@@ -1,6 +1,6 @@
 use std::{collections::HashMap, sync::Arc};
 
-use tokio::sync::{Mutex, MutexGuard};
+use tokio::sync::{Mutex, MutexGuard, RwLock, RwLockWriteGuard};
 use tower_lsp::lsp_types::{
     CompletionResponse, Diagnostic, GotoDefinitionResponse, Hover, Position, SemanticTokensResult,
     TextEdit, Url,
@@ -10,51 +10,34 @@ use crate::analysis::{AnalyzedDocument, DocInfo};
 
 #[derive(Debug)]
 pub(crate) struct LatestDocument {
-    info: DocInfo,
-    //We can hold this mutex locked during updating while the latest and doc_info are out of sync
-    //the lock should be aquired and immediately freed by and task looking to get a copy of info
-    //At the top level we will need to store our lock
-    latest: tokio::sync::watch::Receiver<Option<Arc<AnalyzedDocument>>>,
-    latest_sender: tokio::sync::watch::Sender<Option<Arc<AnalyzedDocument>>>,
+    pub info: DocInfo,
+    analyzed: tokio::sync::RwLock<Option<Arc<AnalyzedDocument>>>,
 }
 impl LatestDocument {
     pub(crate) async fn get_latest(&self) -> Arc<AnalyzedDocument> {
-        let mut my_reciever = self.latest.clone();
-
-        let a = my_reciever.wait_for(|x| x.is_some()).await.unwrap();
-        match a.as_ref() {
-            Some(latest) => latest.clone(),
-            None => todo!(),
-        }
+        self.analyzed.read().await.as_ref().unwrap().clone()
     }
-    pub(crate) fn set_latest(&self, latest: Arc<AnalyzedDocument>) {
-        self.latest_sender.send(Some(latest)).unwrap()
-    }
-    pub(crate) fn waiting_for_doc(&self) -> bool {
-        self.latest.borrow().is_none()
+    pub(crate) fn get_lock(&self) -> RwLockWriteGuard<Option<Arc<AnalyzedDocument>>> {
+        self.analyzed.blocking_write()
     }
     pub(crate) fn new(doc_info: DocInfo) -> LatestDocument {
-        let chan = tokio::sync::watch::channel(None);
+        let val = RwLock::new(None);
         LatestDocument {
             info: doc_info,
-            latest_sender: chan.0,
-            latest: chan.1,
+            analyzed: val,
         }
     }
-    pub(crate) fn new_initialised(doc: Arc<AnalyzedDocument>) -> LatestDocument {
-        let info = doc.doc_info.clone();
-        let chan = tokio::sync::watch::channel(Some(doc));
+    pub(crate) fn new_initialised(analyzed: Arc<AnalyzedDocument>) -> LatestDocument {
         LatestDocument {
-            info,
-            latest_sender: chan.0,
-            latest: chan.1,
+            info: analyzed.doc_info.clone(),
+            analyzed: RwLock::new(Some(analyzed)),
         }
     }
 }
 
 #[derive(Debug)]
 pub(crate) struct DocumentPair {
-    latest_document: LatestDocument,
+    latest_document: Arc<LatestDocument>,
     last_good_document: Arc<AnalyzedDocument>,
 }
 
@@ -64,26 +47,28 @@ pub(crate) struct Registry {
 }
 
 impl Registry {
+    pub async fn get_latest_version(&self, url: &Url) -> Option<i32> {
+        self.documents
+            .lock()
+            .await
+            .get(&url)
+            .map(|x| x.latest_document.info.version)
+    }
     fn update_document<'a>(
         documents: &mut MutexGuard<'a, HashMap<Url, DocumentPair>>,
         document: AnalyzedDocument,
     ) {
         let url = document.url().clone();
         let document = Arc::new(document);
-        let latest_doc = LatestDocument::new_initialised(document.clone());
+        let latest_doc = Arc::new(LatestDocument::new_initialised(document.clone()));
         match documents.get_mut(&url) {
             Some(old_doc) => {
-                //This is a special case where we know we should
-                if old_doc.latest_document.waiting_for_doc() {
-                    old_doc.latest_document.set_latest(document.clone());
-                }
                 if document.type_checked() {
                     *old_doc = DocumentPair {
                         latest_document: latest_doc,
                         last_good_document: document,
                     };
                 } else {
-                    //TODO this seems ugly but for now i'll let it slide. shoudl be immutable
                     *old_doc = DocumentPair {
                         latest_document: latest_doc,
                         last_good_document: old_doc.last_good_document.clone(),
@@ -102,7 +87,12 @@ impl Registry {
         }
     }
 
-    pub async fn apply_changes(&self, analysed_docs: Vec<AnalyzedDocument>) -> () {
+    pub async fn apply_changes<'a>(
+        &self,
+        analysed_docs: Vec<AnalyzedDocument>,
+        mut partial_writer: RwLockWriteGuard<'a, Option<Arc<AnalyzedDocument>>>,
+        updating_url: Url,
+    ) {
         let mut documents = self.documents.lock().await;
         eprintln!(
             "finised doc analysis updating docs {:?}",
@@ -111,13 +101,21 @@ impl Registry {
                 .map(|a| a.doc_info.url.to_string())
                 .collect::<Vec<_>>()
         );
+        let updates = analysed_docs.into_iter().filter_map(|a| {
+            if a.doc_info.url == updating_url {
+                *partial_writer = Some(Arc::new(a));
+                None
+            } else {
+                Some(a)
+            }
+        });
 
-        for document in analysed_docs {
+        for document in updates {
             Registry::update_document(&mut documents, document);
         }
     }
 
-    pub async fn apply_doc_info_changes(&self, url: Url, partial: DocInfo) {
+    pub async fn apply_doc_info_changes(&self, url: Url, partial: Arc<LatestDocument>) {
         let mut lock = self.documents.lock().await;
         let doc = lock.get_mut(&url);
         match doc {
@@ -125,10 +123,10 @@ impl Registry {
                 eprintln!(
                     "set the docInfo for {:?} to version:{:?}",
                     url.as_str(),
-                    partial.version
+                    partial.info.version
                 );
 
-                a.latest_document = LatestDocument::new(partial);
+                a.latest_document = partial;
             }
 
             None => (),
diff --git a/crates/lang_srv/src/server.rs b/crates/lang_srv/src/server.rs
index c2a5d334bf..3d98b14e97 100644
--- a/crates/lang_srv/src/server.rs
+++ b/crates/lang_srv/src/server.rs
@@ -1,14 +1,15 @@
 use analysis::HIGHLIGHT_TOKENS_LEGEND;
 use registry::Registry;
 use std::future::Future;
+use tokio::sync::RwLock;
 
 use std::sync::Arc;
-use std::time::Duration;
 use tower_lsp::jsonrpc::Result;
 use tower_lsp::lsp_types::*;
 use tower_lsp::{Client, LanguageServer, LspService, Server};
 
 use crate::analysis::global_analysis;
+use crate::registry::LatestDocument;
 
 mod analysis;
 mod convert;
@@ -21,34 +22,21 @@ struct RocLs {
 #[derive(Debug)]
 struct Inner {
     client: Client,
-    registry: Registry,
-    change_cancel_handle: parking_lot::Mutex<(
-        tokio::sync::watch::Sender<i32>,
-        tokio::sync::watch::Receiver<i32>,
-    )>,
-    documents_updating: tokio::sync::Semaphore,
+    registry: RwLock<Registry>,
 }
 
 impl std::panic::RefUnwindSafe for RocLs {}
-const SEMLIMIT: u32 = 20;
 
 impl RocLs {
     pub fn new(client: Client) -> Self {
         Self {
             inner: Arc::new(Inner {
                 client,
-                registry: Registry::default(),
-                change_cancel_handle: parking_lot::Mutex::new(tokio::sync::watch::channel(0)),
-                ///Used for identifying if the intial stage of a document update is complete
-                documents_updating: tokio::sync::Semaphore::new(SEMLIMIT as usize),
+                registry: RwLock::new(Registry::default()),
             }),
         }
     }
     ///Wait for all the semaphores associated with an in-progress document_info update to be released
-    async fn wait_for_changes(&self) {
-        //We don't actually need to return the permit, all we want is to have it momenterily which guarentees that any updates started before the call to this are complete
-        drop(self.inner.documents_updating.acquire_many(SEMLIMIT).await.expect("semaphore permits could not be aquired for the document updating process. This is unrecoverable"));
-    }
     pub fn capabilities() -> ServerCapabilities {
         let text_document_sync = TextDocumentSyncCapability::Options(
             // TODO: later on make this incremental
@@ -104,89 +92,72 @@ impl RocLs {
     /// Records a document content change.
     async fn change(&self, fi: Url, text: String, version: i32) {
         eprintln!("starting change");
-
-        let (updating_doc_info, mut new_change) = self.change_preamble(version).await;
-        tokio::time::sleep(Duration::from_millis(20)).await;
-        if new_change.has_changed().unwrap() {
-            eprintln!("newer task started almost immediately");
-            return;
-        }
+        let registry_write_lock = self.inner.registry.write().await;
 
         eprintln!("finished checking for cancellation");
         let (results, partial) = global_analysis(fi.clone(), text, version);
+        let partial_document = Arc::new(LatestDocument::new(partial.clone()));
+        let partial_doc_write_lock = partial_document.get_lock();
 
-        self.inner
-            .registry
-            .apply_doc_info_changes(fi.clone(), partial)
+        registry_write_lock
+            .apply_doc_info_changes(fi.clone(), partial_document.clone())
             .await;
-        drop(updating_doc_info);
+        //Now that we've got our new partial document written and we hold the exclusive write_handle to its analysis we can allow other tasks to access the registry and the doc_info inside this partial document
+        drop(registry_write_lock);
 
         eprintln!("finished updating docinfo, starting analysis ",);
 
         let inner_ref = self.inner.clone();
-        let handle = async {
+        let updating_result = async {
             let results = match tokio::task::spawn_blocking(results).await {
                 Err(e) => return Err(format!("document analysis failed. reason:{:?}", e)),
                 Ok(a) => a,
             };
+            let latest_version = inner_ref
+                .registry
+                .read()
+                .await
+                .get_latest_version(&fi)
+                .await;
 
-            inner_ref.registry().apply_changes(results).await;
+            //if this version is not the latest another change must have come in and this analysis is useless
+            //if there is no older version we can just proceed with the update
+            if let Some(latest_version) = latest_version {
+                return Err(format!(
+                    "version {0} doesn't match latest: {1} discarding analysis  ",
+                    version, latest_version
+                ));
+            }
+
+            inner_ref
+                .registry
+                .write()
+                .await
+                .apply_changes(results, partial_doc_write_lock, fi.clone())
+                .await;
             Ok(())
-        };
-
-        eprintln!("waiting on analysis or cancel");
+        }
+        .await;
 
         //The analysis task can be cancelled by another change coming in which will update the watched variable
-        let finished = tokio::select! {
-            a=handle=>a,
-            _=new_change.changed()=>Err("Cancellation triggered from change".to_string())
-        };
-        match finished {
-            Err(e) => {
-                eprintln!("cancelled change. Reason:{:?}", e);
-                return;
-            }
-            Ok(_) => (),
+        if let Err(e) = updating_result {
+            eprintln!("cancelled change. Reason:{:?}", e);
+            return;
         }
         eprintln!("applied_change getting and returning diagnostics");
 
-        let diagnostics = self.inner.registry().diagnostics(&fi).await;
+        let diagnostics = self.inner.registry().await.diagnostics(&fi).await;
 
         self.inner
             .client
             .publish_diagnostics(fi, diagnostics, Some(version))
             .await;
     }
-    /// Does some bookkeeping before the change.
-    ///aquires a semphore permit to let future functions know that there is a change ongoing
-    ///sends a message to the watched change_handle to cancel other changes
-    ///returns a copy of the watcher to use in our own cancellation  
-    async fn change_preamble(
-        &self,
-        version: i32,
-    ) -> (
-        tokio::sync::SemaphorePermit<'_>,
-        tokio::sync::watch::Receiver<i32>,
-    ) {
-        let updating_doc_info = self.inner.documents_updating.acquire().await.unwrap();
-        let new_change = {
-            let cancel_handle = self.inner.change_cancel_handle.lock();
-            //This will cancel any other onging changes in favour of this one
-            cancel_handle
-                .0
-                .send(version)
-                .expect("change_handle disposed, this shouldn't happen");
-            let mut watched = cancel_handle.1.clone();
-            watched.borrow_and_update();
-            watched
-        };
-        (updating_doc_info, new_change)
-    }
 }
 
 impl Inner {
-    fn registry(&self) -> &Registry {
-        &self.registry
+    fn registry(&self) -> impl Future<Output = tokio::sync::RwLockReadGuard<Registry>> {
+        self.registry.read()
     }
 
     async fn close(&self, _fi: Url) {
@@ -250,6 +221,7 @@ impl LanguageServer for RocLs {
         panic_wrapper_async(|| async {
             self.inner
                 .registry()
+                .await
                 .hover(&text_document.uri, position)
                 .await
         })
@@ -273,6 +245,7 @@ impl LanguageServer for RocLs {
         panic_wrapper_async(|| async {
             self.inner
                 .registry()
+                .await
                 .goto_definition(&text_document.uri, position)
                 .await
         })
@@ -286,7 +259,8 @@ impl LanguageServer for RocLs {
             work_done_progress_params: _,
         } = params;
 
-        panic_wrapper_async(|| async { self.inner.registry().formatting(&text_document.uri) }).await
+        panic_wrapper_async(|| async { self.inner.registry().await.formatting(&text_document.uri) })
+            .await
     }
 
     async fn semantic_tokens_full(
@@ -299,24 +273,25 @@ impl LanguageServer for RocLs {
             partial_result_params: _,
         } = params;
 
-        panic_wrapper_async(|| async { self.inner.registry().semantic_tokens(&text_document.uri) })
-            .await
+        panic_wrapper_async(|| async {
+            self.inner
+                .registry()
+                .await
+                .semantic_tokens(&text_document.uri)
+        })
+        .await
     }
     async fn completion(&self, params: CompletionParams) -> Result<Option<CompletionResponse>> {
         let doc = params.text_document_position;
         eprintln!("starting completion");
-        eprintln!(
-            "permits::{:?} ",
-            self.inner.documents_updating.available_permits()
-        );
 
         //We need to wait untill any changes that were in progress when we requested completion have applied
-        self.wait_for_changes().await;
         eprintln!("waited for doc update to get sorted ");
 
         let res = panic_wrapper_async(|| async {
             self.inner
                 .registry()
+                .await
                 .completion_items(&doc.text_document.uri, doc.position)
                 .await
         })
@@ -327,12 +302,6 @@ impl LanguageServer for RocLs {
     }
 }
 
-fn panic_wrapper<T>(f: impl FnOnce() -> Option<T> + std::panic::UnwindSafe) -> Result<Option<T>> {
-    match std::panic::catch_unwind(f) {
-        Ok(r) => Ok(r),
-        Err(_) => Err(tower_lsp::jsonrpc::Error::internal_error()),
-    }
-}
 async fn panic_wrapper_async<Fut, T>(
     f: impl FnOnce() -> Fut + std::panic::UnwindSafe,
 ) -> Result<Option<T>>