diff --git a/josh-core/src/cache.rs b/josh-core/src/cache.rs
index 91d222472..0af7b9d07 100644
--- a/josh-core/src/cache.rs
+++ b/josh-core/src/cache.rs
@@ -73,6 +73,9 @@ pub struct Transaction {
 
 impl Transaction {
     pub fn open(path: &std::path::Path, ref_prefix: Option<&str>) -> JoshResult<Transaction> {
+        if !path.exists() {
+            return Err(josh_error("path does not exist"));
+        }
         Ok(Transaction::new(
             git2::Repository::open_ext(
                 path,
diff --git a/josh-core/src/query.rs b/josh-core/src/query.rs
index 591f3316e..d226ad0c1 100644
--- a/josh-core/src/query.rs
+++ b/josh-core/src/query.rs
@@ -23,7 +23,20 @@ impl GraphQLHelper {
             .join(path);
         let path = normalize_path(&path);
 
-        let transaction = cache::Transaction::open(&self.repo_path, Some(&self.ref_prefix))?;
+        let transaction = if let Ok(to) =
+            cache::Transaction::open(&self.repo_path.join("mirror"), Some(&self.ref_prefix))
+        {
+            to.repo().odb()?.add_disk_alternate(
+                self.repo_path
+                    .join("overlay")
+                    .join("objects")
+                    .to_str()
+                    .unwrap(),
+            )?;
+            to
+        } else {
+            cache::Transaction::open(&self.repo_path, Some(&self.ref_prefix))?
+        };
 
         let tree = transaction.repo().find_commit(self.commit_id)?.tree()?;
 
@@ -41,8 +54,26 @@ impl GraphQLHelper {
             variables.insert(k.to_string(), juniper::InputValue::scalar(v.render()));
         }
 
-        let transaction = cache::Transaction::open(&self.repo_path, None)?;
-        let transaction_overlay = cache::Transaction::open(&self.repo_path, None)?;
+        let (transaction, transaction_overlay) =
+            if let Ok(to) = cache::Transaction::open(&self.repo_path.join("overlay"), None) {
+                to.repo().odb()?.add_disk_alternate(
+                    self.repo_path
+                        .join("mirror")
+                        .join("objects")
+                        .to_str()
+                        .unwrap(),
+                )?;
+                (
+                    cache::Transaction::open(&self.repo_path.join("mirror"), None)?,
+                    to,
+                )
+            } else {
+                (
+                    cache::Transaction::open(&self.repo_path, None)?,
+                    cache::Transaction::open(&self.repo_path, None)?,
+                )
+            };
+
         let (res, _errors) = juniper::execute_sync(
             &query,
             None,
@@ -77,7 +108,7 @@ impl handlebars::HelperDef for GraphQLHelper {
                 h.hash(),
                 rc.get_current_template_name().unwrap_or(&"/".to_owned()),
             )
-            .map_err(|_| handlebars::RenderError::new("josh"))?,
+            .map_err(|e| handlebars::RenderError::new(format!("{}", e)))?,
         ));
     }
 }
@@ -91,6 +122,7 @@ pub fn render(
     ref_prefix: &str,
     commit_id: git2::Oid,
     query_and_params: &str,
+    split_odb: bool,
 ) -> JoshResult<Option<String>> {
     let mut parameters = query_and_params.split('&');
     let query = parameters
@@ -162,13 +194,24 @@ pub fn render(
     drop(obj);
     drop(tree);
 
+    let repo_path = if split_odb {
+        transaction
+            .repo()
+            .path()
+            .parent()
+            .ok_or(josh_error("parent"))?
+            .to_owned()
+    } else {
+        transaction.repo().path().to_owned()
+    };
+
     let mut handlebars = handlebars::Handlebars::new();
     handlebars.register_template_string(path, template)?;
     handlebars.register_helper("concat", Box::new(helpers::concat_helper));
     handlebars.register_helper(
         "graphql",
         Box::new(GraphQLHelper {
-            repo_path: transaction.repo().path().to_owned(),
+            repo_path: repo_path,
             ref_prefix: ref_prefix.to_owned(),
             commit_id,
         }),
diff --git a/josh-filter/src/bin/josh-filter.rs b/josh-filter/src/bin/josh-filter.rs
index 730622d1b..9a7ca62f8 100644
--- a/josh-filter/src/bin/josh-filter.rs
+++ b/josh-filter/src/bin/josh-filter.rs
@@ -424,7 +424,7 @@ fn run_filter(args: Vec<String>) -> josh::JoshResult<i32> {
         let commit_id = transaction.repo().refname_to_id(update_target)?;
         print!(
             "{}",
-            josh::query::render(&transaction, "", commit_id, query,)?
+            josh::query::render(&transaction, "", commit_id, query, false)?
                 .unwrap_or("File not found".to_string())
         );
     }
diff --git a/josh-proxy/src/bin/josh-proxy.rs b/josh-proxy/src/bin/josh-proxy.rs
index 307c15317..e0f22ce48 100644
--- a/josh-proxy/src/bin/josh-proxy.rs
+++ b/josh-proxy/src/bin/josh-proxy.rs
@@ -1358,7 +1358,7 @@ async fn serve_query(
         let commit_id =
             josh::filter_commit(&transaction, filter, commit_id, josh::filter::empty())?;
 
-        josh::query::render(&transaction, "", commit_id, &q)
+        josh::query::render(&transaction, "", commit_id, &q, true)
     })
     .in_current_span()
     .await?;
diff --git a/tests/proxy/query.t b/tests/proxy/query.t
index 0c399a5a5..50b6dc654 100644
--- a/tests/proxy/query.t
+++ b/tests/proxy/query.t
@@ -16,10 +16,20 @@
   $ git add sub2
   $ git commit -m "add file2" 1> /dev/null
 
+  $ cat > x.graphql <<EOF
+  > query {
+  >  hash
+  > }
+  > EOF
+
   $ cat > tmpl_file <<EOF
   > param: {{ param_val }}
+  > {{ #with (graphql file="x.graphql") as |gql| }}
+  > sha: {{ gql.hash }}
+  > {{ /with }}
   > EOF
 
+  $ git add x.graphql
   $ git add tmpl_file
   $ git commit -m "add tmpl_file" 1> /dev/null
 
@@ -47,6 +57,7 @@
   JoshError(Error rendering "tmpl_file" line 1, col 8: Variable "param_val" not found in strict mode.) (no-eol)
   $ curl -s http://localhost:8002/real_repo.git?render=tmpl_file\&param_val=12345
   param: 12345
+  sha: 002d20d28aab1ebe3892b01ec1dfc60d43fc598f
   $ curl -s http://localhost:8002/real_repo.git?get=sub1/file1
   contents1
   $ curl -s http://localhost:8002/real_repo.git@refs/changes/123/2:nop.git?get=sub2/on_change