Add --dangerously-force-json flag for syncback

Adds a CLI flag that forces syncback to use JSON representations
instead of binary .rbxm files. Instances with children become
directories with init.meta.json; leaf instances become .model.json.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -23,6 +23,3 @@
 # Macos file system junk
 ._*
 .DS_STORE
-
-# JetBrains IDEs
-/.idea/

CHANGELOG.md

@@ -31,14 +31,10 @@ Making a new release? Simply add the new header with the version and date undern
 
 ## Unreleased
 * Fixed a bug caused by having reference properties (such as `ObjectValue.Value`) that point to an Instance not included in syncback. ([#1179])
-* Implemented support for the "name" property in meta/model JSON files. ([#1187])
 * Fixed instance replacement fallback failing when too many instances needed to be replaced. ([#1192])
-* Fixed a bug where MacOS paths weren't being handled correctly. ([#1201])
 
 [#1179]: https://github.com/rojo-rbx/rojo/pull/1179
-[#1187]: https://github.com/rojo-rbx/rojo/pull/1187
 [#1192]: https://github.com/rojo-rbx/rojo/pull/1192
-[#1201]: https://github.com/rojo-rbx/rojo/pull/1201
 
 ## [7.7.0-rc.1] (November 27th, 2025)
 

Cargo.lock

@@ -1319,7 +1319,6 @@ dependencies = [
  "fs-err",
  "notify",
  "serde",
- "tempfile",
 ]
 
 [[package]]

crates/memofs/CHANGELOG.md

@@ -1,7 +1,6 @@
 # memofs Changelog
 
 ## Unreleased Changes
-* Added `Vfs::canonicalize`. [#1201]
 
 ## 0.3.1 (2025-11-27)
 * Added `Vfs::exists`. [#1169]

crates/memofs/Cargo.toml

@@ -19,6 +19,3 @@ crossbeam-channel = "0.5.12"
 fs-err = "2.11.0"
 notify = "4.0.17"
 serde = { version = "1.0.197", features = ["derive"] }
-
-[dev-dependencies]
-tempfile = "3.10.1"

crates/memofs/src/in_memory_fs.rs

@@ -232,33 +232,6 @@ impl VfsBackend for InMemoryFs {
         }
     }
 
-    // TODO: We rely on Rojo to prepend cwd to any relative path before storing paths
-    // in MemoFS. The current implementation will error if no prepended absolute path
-    // is found. It really only normalizes paths within the provided path's context.
-    // Example: "/Users/username/project/../other/file.txt" ->
-    // "/Users/username/other/file.txt"
-    // Erroneous example: "/Users/../../other/file.txt" -> "/other/file.txt"
-    // This is not very robust. We should implement proper path normalization here or otherwise
-    // warn if we are missing context and can not fully canonicalize the path correctly.
-    fn canonicalize(&mut self, path: &Path) -> io::Result<PathBuf> {
-        let mut normalized = PathBuf::new();
-        for component in path.components() {
-            match component {
-                std::path::Component::ParentDir => {
-                    normalized.pop();
-                }
-                std::path::Component::CurDir => {}
-                _ => normalized.push(component),
-            }
-        }
-
-        let inner = self.inner.lock().unwrap();
-        match inner.entries.get(&normalized) {
-            Some(_) => Ok(normalized),
-            None => not_found(&normalized),
-        }
-    }
-
     fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
         let inner = self.inner.lock().unwrap();
 

crates/memofs/src/lib.rs

@@ -77,7 +77,6 @@ pub trait VfsBackend: sealed::Sealed + Send + 'static {
     fn metadata(&mut self, path: &Path) -> io::Result<Metadata>;
     fn remove_file(&mut self, path: &Path) -> io::Result<()>;
     fn remove_dir_all(&mut self, path: &Path) -> io::Result<()>;
-    fn canonicalize(&mut self, path: &Path) -> io::Result<PathBuf>;
 
     fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent>;
     fn watch(&mut self, path: &Path) -> io::Result<()>;
@@ -226,11 +225,6 @@ impl VfsInner {
         self.backend.metadata(path)
     }
 
-    fn canonicalize<P: AsRef<Path>>(&mut self, path: P) -> io::Result<PathBuf> {
-        let path = path.as_ref();
-        self.backend.canonicalize(path)
-    }
-
     fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
         self.backend.event_receiver()
     }
@@ -419,19 +413,6 @@ impl Vfs {
         self.inner.lock().unwrap().metadata(path)
     }
 
-    /// Normalize a path via the underlying backend.
-    ///
-    /// Roughly equivalent to [`std::fs::canonicalize`][std::fs::canonicalize]. Relative paths are
-    /// resolved against the backend's current working directory (if applicable) and errors are
-    /// surfaced directly from the backend.
-    ///
-    /// [std::fs::canonicalize]: https://doc.rust-lang.org/stable/std/fs/fn.canonicalize.html
-    #[inline]
-    pub fn canonicalize<P: AsRef<Path>>(&self, path: P) -> io::Result<PathBuf> {
-        let path = path.as_ref();
-        self.inner.lock().unwrap().canonicalize(path)
-    }
-
     /// Retrieve a handle to the event receiver for this `Vfs`.
     #[inline]
     pub fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
@@ -559,13 +540,6 @@ impl VfsLock<'_> {
         self.inner.metadata(path)
     }
 
-    /// Normalize a path via the underlying backend.
-    #[inline]
-    pub fn normalize<P: AsRef<Path>>(&mut self, path: P) -> io::Result<PathBuf> {
-        let path = path.as_ref();
-        self.inner.canonicalize(path)
-    }
-
     /// Retrieve a handle to the event receiver for this `Vfs`.
     #[inline]
     pub fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
@@ -581,9 +555,7 @@ impl VfsLock<'_> {
 
 #[cfg(test)]
 mod test {
-    use crate::{InMemoryFs, StdBackend, Vfs, VfsSnapshot};
+    use crate::{InMemoryFs, Vfs, VfsSnapshot};
-    use std::io;
-    use std::path::PathBuf;
 
     /// https://github.com/rojo-rbx/rojo/issues/899
     #[test]
@@ -599,62 +571,4 @@ mod test {
             "bar\nfoo\n\n"
         );
     }
-
-    /// https://github.com/rojo-rbx/rojo/issues/1200
-    #[test]
-    fn canonicalize_in_memory_success() {
-        let mut imfs = InMemoryFs::new();
-        let contents = "Lorem ipsum dolor sit amet.".to_string();
-
-        imfs.load_snapshot("/test/file.txt", VfsSnapshot::file(contents.to_string()))
-            .unwrap();
-
-        let vfs = Vfs::new(imfs);
-
-        assert_eq!(
-            vfs.canonicalize("/test/nested/../file.txt").unwrap(),
-            PathBuf::from("/test/file.txt")
-        );
-        assert_eq!(
-            vfs.read_to_string(vfs.canonicalize("/test/nested/../file.txt").unwrap())
-                .unwrap()
-                .to_string(),
-            contents.to_string()
-        );
-    }
-
-    #[test]
-    fn canonicalize_in_memory_missing_errors() {
-        let imfs = InMemoryFs::new();
-        let vfs = Vfs::new(imfs);
-
-        let err = vfs.canonicalize("test").unwrap_err();
-        assert_eq!(err.kind(), io::ErrorKind::NotFound);
-    }
-
-    #[test]
-    fn canonicalize_std_backend_success() {
-        let contents = "Lorem ipsum dolor sit amet.".to_string();
-        let dir = tempfile::tempdir().unwrap();
-        let file_path = dir.path().join("file.txt");
-        fs_err::write(&file_path, contents.to_string()).unwrap();
-
-        let vfs = Vfs::new(StdBackend::new());
-        let canonicalized = vfs.canonicalize(&file_path).unwrap();
-        assert_eq!(canonicalized, file_path.canonicalize().unwrap());
-        assert_eq!(
-            vfs.read_to_string(&canonicalized).unwrap().to_string(),
-            contents.to_string()
-        );
-    }
-
-    #[test]
-    fn canonicalize_std_backend_missing_errors() {
-        let dir = tempfile::tempdir().unwrap();
-        let file_path = dir.path().join("test");
-
-        let vfs = Vfs::new(StdBackend::new());
-        let err = vfs.canonicalize(&file_path).unwrap_err();
-        assert_eq!(err.kind(), io::ErrorKind::NotFound);
-    }
 }

crates/memofs/src/noop_backend.rs

@@ -1,5 +1,5 @@
 use std::io;
-use std::path::{Path, PathBuf};
+use std::path::Path;
 
 use crate::{Metadata, ReadDir, VfsBackend, VfsEvent};
 
@@ -50,10 +50,6 @@ impl VfsBackend for NoopBackend {
         Err(io::Error::other("NoopBackend doesn't do anything"))
     }
 
-    fn canonicalize(&mut self, _path: &Path) -> io::Result<PathBuf> {
-        Err(io::Error::other("NoopBackend doesn't do anything"))
-    }
-
     fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
         crossbeam_channel::never()
     }

crates/memofs/src/std_backend.rs

@@ -106,10 +106,6 @@ impl VfsBackend for StdBackend {
         })
     }
 
-    fn canonicalize(&mut self, path: &Path) -> io::Result<PathBuf> {
-        fs_err::canonicalize(path)
-    }
-
     fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
         self.watcher_receiver.clone()
     }

rojo-test/build-test-snapshots/end_to_end__tests__build__json_model_legacy_name.snap

@@ -0,0 +1,16 @@
+---
+source: tests/tests/build.rs
+expression: contents
+---
+<roblox version="4">
+  <Item class="Folder" referent="0">
+    <Properties>
+      <string name="Name">json_model_legacy_name</string>
+    </Properties>
+    <Item class="Folder" referent="1">
+      <Properties>
+        <string name="Name">Expected Name</string>
+      </Properties>
+    </Item>
+  </Item>
+</roblox>

rojo-test/build-test-snapshots/end_to_end__tests__build__model_json_name_input.snap

@@ -1,23 +0,0 @@
----
-source: tests/tests/build.rs
-assertion_line: 109
-expression: contents
----
-<roblox version="4">
-  <Item class="DataModel" referent="0">
-    <Properties>
-      <string name="Name">model_json_name_input</string>
-    </Properties>
-    <Item class="Workspace" referent="1">
-      <Properties>
-        <string name="Name">Workspace</string>
-        <bool name="NeedsPivotMigration">false</bool>
-      </Properties>
-      <Item class="StringValue" referent="2">
-        <Properties>
-          <string name="Name">/Bar</string>
-        </Properties>
-      </Item>
-    </Item>
-  </Item>
-</roblox>

rojo-test/build-test-snapshots/end_to_end__tests__build__slugified_name_roundtrip.snap

@@ -1,20 +0,0 @@
----
-source: tests/tests/build.rs
-assertion_line: 108
-expression: contents
----
-<roblox version="4">
-  <Item class="Folder" referent="0">
-    <Properties>
-      <string name="Name">slugified_name_roundtrip</string>
-    </Properties>
-    <Item class="Script" referent="1">
-      <Properties>
-        <string name="Name">/Script</string>
-        <token name="RunContext">0</token>
-        <string name="Source"><![CDATA[print("Hello world!")
-]]></string>
-      </Properties>
-    </Item>
-  </Item>
-</roblox>

rojo-test/build-tests/json_model_legacy_name/default.project.json

@@ -0,0 +1,6 @@
+{
+  "name": "json_model_legacy_name",
+  "tree": {
+    "$path": "folder"
+  }
+}

rojo-test/build-tests/json_model_legacy_name/folder/Expected Name.model.json

@@ -0,0 +1,4 @@
+{
+  "Name": "Overridden Name",
+  "ClassName": "Folder"
+}

rojo-test/build-tests/model_json_name_input/default.project.json

@@ -1,11 +0,0 @@
-{
-  "name": "model_json_name_input",
-  "tree": {
-    "$className": "DataModel",
-    "Workspace": {
-      "$className": "Workspace",
-      "$path": "src"
-    }
-  }
-}
-

rojo-test/build-tests/model_json_name_input/src/Bar.model.json

@@ -1,5 +0,0 @@
-{
-  "name": "/Bar",
-  "className": "StringValue"
-}
-

rojo-test/build-tests/slugified_name_roundtrip/_Script/init.meta.json

@@ -1,4 +0,0 @@
-{
-  "name": "/Script"
-}
-

rojo-test/build-tests/slugified_name_roundtrip/_Script/init.server.luau

@@ -1,2 +0,0 @@
-print("Hello world!")
-

rojo-test/build-tests/slugified_name_roundtrip/default.project.json

@@ -1,6 +0,0 @@
-{
-  "name": "slugified_name_roundtrip",
-  "tree": {
-    "$path": "src"
-  }
-}

rojo-test/build-tests/slugified_name_roundtrip/src/_Script/init.meta.json

@@ -1,3 +0,0 @@
-{
-  "name": "/Script"
-}

rojo-test/build-tests/slugified_name_roundtrip/src/_Script/init.server.luau

@@ -1 +0,0 @@
-print("Hello world!")

rojo-test/syncback-test-snapshots/end_to_end__rojo_test__syncback_util__model_json_name-stdout.snap

@@ -1,6 +0,0 @@
----
-source: tests/rojo_test/syncback_util.rs
-assertion_line: 101
-expression: "String::from_utf8_lossy(&output.stdout)"
----
-

rojo-test/syncback-test-snapshots/end_to_end__rojo_test__syncback_util__rbxm_fallback-src__ChildWithDuplicates.rbxm.snap

@@ -0,0 +1,73 @@
+---
+source: tests/rojo_test/syncback_util.rs
+expression: src/ChildWithDuplicates.rbxm
+---
+num_types: 1
+num_instances: 3
+chunks:
+  - Inst:
+      type_id: 0
+      type_name: Folder
+      object_format: 0
+      referents:
+        - 0
+        - 1
+        - 2
+  - Prop:
+      type_id: 0
+      prop_name: AttributesSerialize
+      prop_type: String
+      values:
+        - ""
+        - ""
+        - ""
+  - Prop:
+      type_id: 0
+      prop_name: Capabilities
+      prop_type: SecurityCapabilities
+      values:
+        - 0
+        - 0
+        - 0
+  - Prop:
+      type_id: 0
+      prop_name: Name
+      prop_type: String
+      values:
+        - DuplicateChild
+        - DuplicateChild
+        - ChildWithDuplicates
+  - Prop:
+      type_id: 0
+      prop_name: DefinesCapabilities
+      prop_type: Bool
+      values:
+        - false
+        - false
+        - false
+  - Prop:
+      type_id: 0
+      prop_name: SourceAssetId
+      prop_type: Int64
+      values:
+        - -1
+        - -1
+        - -1
+  - Prop:
+      type_id: 0
+      prop_name: Tags
+      prop_type: String
+      values:
+        - ""
+        - ""
+        - ""
+  - Prnt:
+      version: 0
+      links:
+        - - 0
+          - 2
+        - - 1
+          - 2
+        - - 2
+          - -1
+  - End

rojo-test/syncback-test-snapshots/end_to_end__rojo_test__syncback_util__rbxm_fallback-stdout.snap

@@ -1,12 +1,9 @@
 ---
 source: tests/rojo_test/syncback_util.rs
-assertion_line: 101
 expression: "String::from_utf8_lossy(&output.stdout)"
 ---
-Writing src/ChildWithDuplicates/DuplicateChild/.gitkeep
+Writing src/ChildWithDuplicates.rbxm
-Writing src/ChildWithDuplicates/DuplicateChild1/.gitkeep
 Writing src/ChildWithoutDuplicates/Child/.gitkeep
-Writing src/ChildWithDuplicates/DuplicateChild
-Writing src/ChildWithDuplicates/DuplicateChild1
 Writing src/ChildWithoutDuplicates
 Writing src/ChildWithoutDuplicates/Child
+Removing src/ChildWithDuplicates

rojo-test/syncback-test-snapshots/end_to_end__rojo_test__syncback_util__slugified_name-stdout.snap

@@ -1,13 +0,0 @@
----
-source: tests/rojo_test/syncback_util.rs
-assertion_line: 101
-expression: "String::from_utf8_lossy(&output.stdout)"
----
-Writing default.project.json
-Writing src/Camera.rbxm
-Writing src/Terrain.rbxm
-Writing src/_Folder/init.meta.json
-Writing src/_Script.meta.json
-Writing src/_Script.server.luau
-Writing src
-Writing src/_Folder

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__model_json_name-src__foo.model.json.snap

@@ -1,9 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/foo.model.json
----
-{
-  "name": "/Bar",
-  "className": "StringValue"
-}

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__rbxm_fallback-src__ChildWithDuplicates__DuplicateChild1__.gitkeep.snap

@@ -1,6 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/ChildWithDuplicates/DuplicateChild1/.gitkeep
----
-

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__rbxm_fallback-src__ChildWithDuplicates__DuplicateChild__.gitkeep.snap

@@ -1,6 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/ChildWithDuplicates/DuplicateChild/.gitkeep
----
-

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__slugified_name-src___Folder.model.json.snap

@@ -1,8 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/_Folder.model.json
----
-{
-  "className": "Folder"
-}

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__slugified_name-src___Folder__init.meta.json.snap

@@ -1,8 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/_Folder/init.meta.json
----
-{
-  "name": "/Folder"
-}

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__slugified_name-src___Script.meta.json.snap

@@ -1,8 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/_Script.meta.json
----
-{
-  "name": "/Script"
-}

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__slugified_name-src___Script.server.luau.snap

@@ -1,6 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/_Script.server.luau
----
-print("Hello world!")

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__slugified_name-src___Script__init.meta.json.snap

@@ -1,8 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/_Script/init.meta.json
----
-{
-  "name": "/Script"
-}

rojo-test/syncback-test-snapshots/end_to_end__tests__syncback__slugified_name-src___Script__init.server.luau.snap

@@ -1,6 +0,0 @@
----
-source: tests/tests/syncback.rs
-assertion_line: 31
-expression: src/_Script/init.server.luau
----
-print("Hello world!")

rojo-test/syncback-tests/model_json_name/input-project/default.project.json

@@ -1,11 +0,0 @@
-{
-  "name": "model_json_name",
-  "tree": {
-    "$className": "DataModel",
-    "Workspace": {
-      "$className": "Workspace",
-      "$path": "src"
-    }
-  }
-}
-

rojo-test/syncback-tests/model_json_name/input-project/src/foo.model.json

@@ -1,5 +0,0 @@
-{
-  "name": "/Bar",
-  "className": "StringValue"
-}
-

rojo-test/syncback-tests/slugified_name/input-project/default.project.json

@@ -1,10 +0,0 @@
-{
-  "name": "slugified_name",
-  "tree": {
-    "$className": "DataModel",
-    "Workspace": {
-      "$className": "Workspace",
-      "$path": "src"
-    }
-  }
-}

src/change_processor.rs

@@ -1,13 +1,13 @@
-use crossbeam_channel::{select, Receiver, RecvError, Sender};
-use jod_thread::JoinHandle;
-use memofs::{IoResultExt, Vfs, VfsEvent};
-use rbx_dom_weak::types::{Ref, Variant};
-use std::path::PathBuf;
 use std::{
     fs,
     sync::{Arc, Mutex},
 };
 
+use crossbeam_channel::{select, Receiver, RecvError, Sender};
+use jod_thread::JoinHandle;
+use memofs::{IoResultExt, Vfs, VfsEvent};
+use rbx_dom_weak::types::{Ref, Variant};
+
 use crate::{
     message_queue::MessageQueue,
     snapshot::{
@@ -114,49 +114,6 @@ struct JobThreadContext {
 }
 
 impl JobThreadContext {
-    /// Computes and applies patches to the DOM for a given file path.
-    ///
-    /// This function finds the nearest ancestor to the given path that has associated instances
-    /// in the tree.
-    /// It then computes and applies changes for each affected instance ID and
-    /// returns a vector of applied patch sets.
-    fn apply_patches(&self, path: PathBuf) -> Vec<AppliedPatchSet> {
-        let mut tree = self.tree.lock().unwrap();
-        let mut applied_patches = Vec::new();
-
-        // Find the nearest ancestor to this path that has
-        // associated instances in the tree. This helps make sure
-        // that we handle additions correctly, especially if we
-        // receive events for descendants of a large tree being
-        // created all at once.
-        let mut current_path = path.as_path();
-        let affected_ids = loop {
-            let ids = tree.get_ids_at_path(current_path);
-
-            log::trace!("Path {} affects IDs {:?}", current_path.display(), ids);
-
-            if !ids.is_empty() {
-                break ids.to_vec();
-            }
-
-            log::trace!("Trying parent path...");
-            match current_path.parent() {
-                Some(parent) => current_path = parent,
-                None => break Vec::new(),
-            }
-        };
-
-        for id in affected_ids {
-            if let Some(patch) = compute_and_apply_changes(&mut tree, &self.vfs, id) {
-                if !patch.is_empty() {
-                    applied_patches.push(patch);
-                }
-            }
-        }
-
-        applied_patches
-    }
-
     fn handle_vfs_event(&self, event: VfsEvent) {
         log::trace!("Vfs event: {:?}", event);
 
@@ -168,16 +125,41 @@ impl JobThreadContext {
         // For a given VFS event, we might have many changes to different parts
         // of the tree. Calculate and apply all of these changes.
         let applied_patches = match event {
-            VfsEvent::Create(path) | VfsEvent::Write(path) => {
+            VfsEvent::Create(path) | VfsEvent::Remove(path) | VfsEvent::Write(path) => {
-                self.apply_patches(self.vfs.canonicalize(&path).unwrap())
+                let mut tree = self.tree.lock().unwrap();
-            }
+                let mut applied_patches = Vec::new();
-            VfsEvent::Remove(path) => {
+
-                // MemoFS does not track parent removals yet, so we can canonicalize
+                // Find the nearest ancestor to this path that has
-                // the parent path safely and then append the removed path's file name.
+                // associated instances in the tree. This helps make sure
-                let parent = path.parent().unwrap();
+                // that we handle additions correctly, especially if we
-                let file_name = path.file_name().unwrap();
+                // receive events for descendants of a large tree being
-                let parent_normalized = self.vfs.canonicalize(parent).unwrap();
+                // created all at once.
-                self.apply_patches(parent_normalized.join(file_name))
+                let mut current_path = path.as_path();
+                let affected_ids = loop {
+                    let ids = tree.get_ids_at_path(current_path);
+
+                    log::trace!("Path {} affects IDs {:?}", current_path.display(), ids);
+
+                    if !ids.is_empty() {
+                        break ids.to_vec();
+                    }
+
+                    log::trace!("Trying parent path...");
+                    match current_path.parent() {
+                        Some(parent) => current_path = parent,
+                        None => break Vec::new(),
+                    }
+                };
+
+                for id in affected_ids {
+                    if let Some(patch) = compute_and_apply_changes(&mut tree, &self.vfs, id) {
+                        if !patch.is_empty() {
+                            applied_patches.push(patch);
+                        }
+                    }
+                }
+
+                applied_patches
             }
             _ => {
                 log::warn!("Unhandled VFS event: {:?}", event);

src/cli/syncback.rs

@@ -54,6 +54,11 @@ pub struct SyncbackCommand {
     /// If provided, the prompt for writing to the file system is skipped.
     #[clap(long, short = 'y')]
     pub non_interactive: bool,
+
+    /// If provided, forces syncback to use JSON model files instead of binary
+    /// .rbxm files for instances that would otherwise serialize as binary.
+    #[clap(long)]
+    pub dangerously_force_json: bool,
 }
 
 impl SyncbackCommand {
@@ -104,6 +109,7 @@ impl SyncbackCommand {
             &mut dom_old,
             dom_new,
             session_old.root_project(),
+            self.dangerously_force_json,
         )?;
         log::debug!(
             "Syncback finished in {:.02}s!",

src/snapshot/metadata.rs

@@ -70,12 +70,6 @@ pub struct InstanceMetadata {
     /// A schema provided via a JSON file, if one exists. Will be `None` for
     /// all non-JSON middleware.
     pub schema: Option<String>,
-
-    /// A custom name specified via meta.json or model.json files. If present,
-    /// this name will be used for the instance while the filesystem name will
-    /// be slugified to remove illegal characters.
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub specified_name: Option<String>,
 }
 
 impl InstanceMetadata {
@@ -88,7 +82,6 @@ impl InstanceMetadata {
             specified_id: None,
             middleware: None,
             schema: None,
-            specified_name: None,
         }
     }
 
@@ -137,13 +130,6 @@ impl InstanceMetadata {
     pub fn schema(self, schema: Option<String>) -> Self {
         Self { schema, ..self }
     }
-
-    pub fn specified_name(self, specified_name: Option<String>) -> Self {
-        Self {
-            specified_name,
-            ..self
-        }
-    }
 }
 
 impl Default for InstanceMetadata {

src/snapshot_middleware/csv.rs

@@ -42,7 +42,7 @@ pub fn snapshot_csv(
         .metadata(
             InstanceMetadata::new()
                 .instigating_source(path)
-                .relevant_paths(vec![vfs.canonicalize(path)?]),
+                .relevant_paths(vec![path.to_path_buf()]),
         );
 
     AdjacentMetadata::read_and_apply_all(vfs, path, name, &mut snapshot)?;
@@ -109,14 +109,8 @@ pub fn syncback_csv<'sync>(
 
         if !meta.is_empty() {
             let parent = snapshot.path.parent_err()?;
-            let file_name = snapshot
-                .path
-                .file_name()
-                .and_then(|n| n.to_str())
-                .unwrap_or("");
-            let meta_stem = file_name.strip_suffix(".csv").unwrap_or(file_name);
             fs_snapshot.add_file(
-                parent.join(format!("{meta_stem}.meta.json")),
+                parent.join(format!("{}.meta.json", new_inst.name)),
                 serde_json::to_vec_pretty(&meta).context("cannot serialize metadata")?,
             )
         }

src/snapshot_middleware/dir.rs

@@ -8,13 +8,10 @@ use memofs::{DirEntry, Vfs};
 
 use crate::{
     snapshot::{InstanceContext, InstanceMetadata, InstanceSnapshot, InstigatingSource},
-    syncback::{
+    syncback::{hash_instance, FsSnapshot, SyncbackReturn, SyncbackSnapshot},
-        extension_for_middleware, hash_instance, FsSnapshot, SyncbackReturn,
-        SyncbackSnapshot,
-    },
 };
 
-use super::{meta_file::DirectoryMetadata, snapshot_from_vfs, Middleware};
+use super::{meta_file::DirectoryMetadata, snapshot_from_vfs};
 
 const EMPTY_DIR_KEEP_NAME: &str = ".gitkeep";
 
@@ -65,19 +62,18 @@ pub fn snapshot_dir_no_meta(
         }
     }
 
-    let normalized_path = vfs.canonicalize(path)?;
     let relevant_paths = vec![
-        normalized_path.clone(),
+        path.to_path_buf(),
         // TODO: We shouldn't need to know about Lua existing in this
         // middleware. Should we figure out a way for that function to add
         // relevant paths to this middleware?
-        normalized_path.join("init.lua"),
+        path.join("init.lua"),
-        normalized_path.join("init.luau"),
+        path.join("init.luau"),
-        normalized_path.join("init.server.lua"),
+        path.join("init.server.lua"),
-        normalized_path.join("init.server.luau"),
+        path.join("init.server.luau"),
-        normalized_path.join("init.client.lua"),
+        path.join("init.client.lua"),
-        normalized_path.join("init.client.luau"),
+        path.join("init.client.luau"),
-        normalized_path.join("init.csv"),
+        path.join("init.csv"),
     ];
 
     let snapshot = InstanceSnapshot::new()
@@ -94,22 +90,6 @@ pub fn snapshot_dir_no_meta(
     Ok(Some(snapshot))
 }
 
-/// Splits a filesystem name into (stem, extension) based on middleware type.
-/// For directory middleware, the extension is empty. For file middleware,
-/// the extension comes from `extension_for_middleware`.
-fn split_name_and_ext(name: &str, middleware: Middleware) -> (&str, &str) {
-    if middleware.is_dir() {
-        (name, "")
-    } else {
-        let ext = extension_for_middleware(middleware);
-        if let Some(stem) = name.strip_suffix(&format!(".{ext}")) {
-            (stem, ext)
-        } else {
-            (name, "")
-        }
-    }
-}
-
 pub fn syncback_dir<'sync>(
     snapshot: &SyncbackSnapshot<'sync>,
 ) -> anyhow::Result<SyncbackReturn<'sync>> {
@@ -153,128 +133,65 @@ pub fn syncback_dir_no_meta<'sync>(
     let mut children = Vec::new();
     let mut removed_children = Vec::new();
 
-    // Build the old child map early so it can be used for deduplication below.
+    // We have to enforce unique child names for the file system.
-    let mut old_child_map = HashMap::new();
+    let mut child_names = HashSet::with_capacity(new_inst.children().len());
+    let mut duplicate_set = HashSet::new();
+    for child_ref in new_inst.children() {
+        let child = snapshot.get_new_instance(*child_ref).unwrap();
+        if !child_names.insert(child.name.to_lowercase()) {
+            duplicate_set.insert(child.name.as_str());
+        }
+    }
+    if !duplicate_set.is_empty() {
+        if duplicate_set.len() <= 25 {
+            anyhow::bail!(
+                "Instance has children with duplicate name (case may not exactly match):\n {}",
+                duplicate_set.into_iter().collect::<Vec<&str>>().join(", ")
+            );
+        }
+        anyhow::bail!("Instance has more than 25 children with duplicate names");
+    }
+
     if let Some(old_inst) = snapshot.old_inst() {
+        let mut old_child_map = HashMap::with_capacity(old_inst.children().len());
         for child in old_inst.children() {
             let inst = snapshot.get_old_instance(*child).unwrap();
             old_child_map.insert(inst.name(), inst);
         }
-    }
 
-    // --- Two-pass collision resolution ---
+        for new_child_ref in new_inst.children() {
-    //
+            let new_child = snapshot.get_new_instance(*new_child_ref).unwrap();
-    // Pass 1: Collect each child's base filesystem name and old ref, applying
+            if let Some(old_child) = old_child_map.remove(new_child.name.as_str()) {
-    // skip conditions. Track which names are used (lowercased) so we can
+                if old_child.metadata().relevant_paths.is_empty() {
-    // detect collisions.
+                    log::debug!(
-    struct ChildEntry {
+                        "Skipping instance {} because it doesn't exist on the disk",
-        new_ref: rbx_dom_weak::types::Ref,
+                        old_child.name()
-        old_ref: Option<rbx_dom_weak::types::Ref>,
+                    );
-        base_name: String,
+                    continue;
-        middleware: Middleware,
+                } else if matches!(
-        skip: bool,
+                    old_child.metadata().instigating_source,
-    }
+                    Some(InstigatingSource::ProjectNode { .. })
-
+                ) {
-    let mut entries = Vec::with_capacity(new_inst.children().len());
+                    log::debug!(
-    let mut used_names: HashSet<String> = HashSet::with_capacity(new_inst.children().len());
+                        "Skipping instance {} because it originates in a project file",
-    let mut collision_indices: Vec<usize> = Vec::new();
+                        old_child.name()
-
+                    );
-    for new_child_ref in new_inst.children() {
+                    continue;
-        let new_child = snapshot.get_new_instance(*new_child_ref).unwrap();
+                }
-
+                // This child exists in both doms. Pass it on.
-        // Determine old_ref and apply skip conditions.
+                children.push(snapshot.with_joined_path(*new_child_ref, Some(old_child.id()))?);
-        let old_child = if snapshot.old_inst().is_some() {
-            old_child_map.remove(new_child.name.as_str())
-        } else {
-            None
-        };
-
-        let mut skip = false;
-        if let Some(ref old) = old_child {
-            if old.metadata().relevant_paths.is_empty() {
-                log::debug!(
-                    "Skipping instance {} because it doesn't exist on the disk",
-                    old.name()
-                );
-                skip = true;
-            } else if matches!(
-                old.metadata().instigating_source,
-                Some(InstigatingSource::ProjectNode { .. })
-            ) {
-                log::debug!(
-                    "Skipping instance {} because it originates in a project file",
-                    old.name()
-                );
-                skip = true;
-            }
-        }
-
-        let old_ref = old_child.as_ref().map(|o| o.id());
-
-        if skip {
-            entries.push(ChildEntry {
-                new_ref: *new_child_ref,
-                old_ref,
-                base_name: String::new(),
-                middleware: Middleware::Dir,
-                skip: true,
-            });
-            continue;
-        }
-
-        let (middleware, base_name) =
-            snapshot.child_middleware_and_name(*new_child_ref, old_ref)?;
-
-        let idx = entries.len();
-        let lower = base_name.to_lowercase();
-        if !used_names.insert(lower) {
-            // Name already claimed — needs resolution.
-            collision_indices.push(idx);
-        }
-
-        entries.push(ChildEntry {
-            new_ref: *new_child_ref,
-            old_ref,
-            base_name,
-            middleware,
-            skip: false,
-        });
-    }
-
-    // Pass 2: Resolve collisions by appending incrementing suffixes.
-    for idx in collision_indices {
-        let entry = &entries[idx];
-        let (stem, ext) = split_name_and_ext(&entry.base_name, entry.middleware);
-        let mut counter = 1u32;
-        loop {
-            let candidate = if ext.is_empty() {
-                format!("{stem}{counter}")
             } else {
-                format!("{stem}{counter}.{ext}")
+                // The child only exists in the the new dom
-            };
+                children.push(snapshot.with_joined_path(*new_child_ref, None)?);
-            let lower = candidate.to_lowercase();
-            if used_names.insert(lower) {
-                // Safe to mutate — we only visit each collision index once.
-                let entry = &mut entries[idx];
-                entry.base_name = candidate;
-                break;
             }
-            counter += 1;
         }
-    }
+        // Any children that are in the old dom but not the new one are removed.
-
-    // Create snapshots from resolved entries.
-    for entry in &entries {
-        if entry.skip {
-            continue;
-        }
-        let resolved_path = snapshot.path.join(&entry.base_name);
-        children.push(snapshot.with_new_path(resolved_path, entry.new_ref, entry.old_ref));
-    }
-
-    // Any children that are in the old dom but not the new one are removed.
-    if snapshot.old_inst().is_some() {
         removed_children.extend(old_child_map.into_values());
+    } else {
+        // There is no old instance. Just add every child.
+        for new_child_ref in new_inst.children() {
+            children.push(snapshot.with_joined_path(*new_child_ref, None)?);
+        }
     }
     let mut fs_snapshot = FsSnapshot::new();
 
@@ -307,12 +224,6 @@ pub fn syncback_dir_no_meta<'sync>(
 mod test {
     use super::*;
 
-    use std::path::PathBuf;
-
-    use crate::{
-        snapshot::{InstanceMetadata, InstanceSnapshot},
-        Project, RojoTree, SyncbackData, SyncbackSnapshot,
-    };
     use memofs::{InMemoryFs, VfsSnapshot};
 
     #[test]
@@ -349,302 +260,4 @@ mod test {
 
         insta::assert_yaml_snapshot!(instance_snapshot);
     }
-
-    fn make_project() -> Project {
-        serde_json::from_str(r#"{"tree": {"$className": "DataModel"}}"#).unwrap()
-    }
-
-    fn make_vfs() -> Vfs {
-        let mut imfs = InMemoryFs::new();
-        imfs.load_snapshot("/root", VfsSnapshot::empty_dir()).unwrap();
-        Vfs::new(imfs)
-    }
-
-    /// Two children whose Roblox names are identical when lowercased ("Alpha"
-    /// and "alpha") but live at different filesystem paths because of the
-    /// `name` property ("Beta/" and "Alpha/" respectively). The dedup check
-    /// must use the actual filesystem paths, not the raw Roblox names, to
-    /// avoid a false-positive duplicate error.
-    #[test]
-    fn syncback_no_false_duplicate_with_name_prop() {
-        use rbx_dom_weak::{InstanceBuilder, WeakDom};
-
-        // Old child A: Roblox name "Alpha", on disk at "/root/Beta"
-        //   (name property maps "Alpha" → "Beta" on the filesystem)
-        let old_child_a = InstanceSnapshot::new()
-            .name("Alpha")
-            .class_name("Folder")
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root/Beta"))
-                    .relevant_paths(vec![PathBuf::from("/root/Beta")]),
-            );
-        // Old child B: Roblox name "alpha", on disk at "/root/Alpha"
-        let old_child_b = InstanceSnapshot::new()
-            .name("alpha")
-            .class_name("Folder")
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root/Alpha"))
-                    .relevant_paths(vec![PathBuf::from("/root/Alpha")]),
-            );
-        let old_parent = InstanceSnapshot::new()
-            .name("Parent")
-            .class_name("Folder")
-            .children(vec![old_child_a, old_child_b])
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root"))
-                    .relevant_paths(vec![PathBuf::from("/root")]),
-            );
-        let old_tree = RojoTree::new(old_parent);
-
-        // New state: same two children in Roblox.
-        let mut new_tree = WeakDom::new(InstanceBuilder::new("ROOT"));
-        let new_parent = new_tree.insert(
-            new_tree.root_ref(),
-            InstanceBuilder::new("Folder").with_name("Parent"),
-        );
-        new_tree.insert(new_parent, InstanceBuilder::new("Folder").with_name("Alpha"));
-        new_tree.insert(new_parent, InstanceBuilder::new("Folder").with_name("alpha"));
-
-        let vfs = make_vfs();
-        let project = make_project();
-        let data = SyncbackData::for_test(&vfs, &old_tree, &new_tree, &project);
-        let snapshot = SyncbackSnapshot {
-            data,
-            old: Some(old_tree.get_root_id()),
-            new: new_parent,
-            path: PathBuf::from("/root"),
-            middleware: None,
-        };
-
-        let result = syncback_dir_no_meta(&snapshot);
-        assert!(
-            result.is_ok(),
-            "should not error when two children have the same lowercased Roblox \
-             name but map to distinct filesystem paths: {:?}",
-            result.as_ref().err(),
-        );
-    }
-
-    /// Two completely new children with the same name get resolved via
-    /// incrementing suffixes instead of erroring.
-    #[test]
-    fn syncback_resolves_sibling_duplicate_names() {
-        use rbx_dom_weak::{InstanceBuilder, WeakDom};
-
-        let old_parent = InstanceSnapshot::new()
-            .name("Parent")
-            .class_name("Folder")
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root"))
-                    .relevant_paths(vec![PathBuf::from("/root")]),
-            );
-        let old_tree = RojoTree::new(old_parent);
-
-        let mut new_tree = WeakDom::new(InstanceBuilder::new("ROOT"));
-        let new_parent = new_tree.insert(
-            new_tree.root_ref(),
-            InstanceBuilder::new("Folder").with_name("Parent"),
-        );
-        new_tree.insert(new_parent, InstanceBuilder::new("Folder").with_name("Foo"));
-        new_tree.insert(new_parent, InstanceBuilder::new("Folder").with_name("Foo"));
-
-        let vfs = make_vfs();
-        let project = make_project();
-        let data = SyncbackData::for_test(&vfs, &old_tree, &new_tree, &project);
-        let snapshot = SyncbackSnapshot {
-            data,
-            old: Some(old_tree.get_root_id()),
-            new: new_parent,
-            path: PathBuf::from("/root"),
-            middleware: None,
-        };
-
-        let result = syncback_dir_no_meta(&snapshot);
-        assert!(
-            result.is_ok(),
-            "should resolve duplicate names with suffixes, not error: {:?}",
-            result.as_ref().err(),
-        );
-        let children = result.unwrap().children;
-        let mut names: Vec<String> = children
-            .iter()
-            .map(|c| c.path.file_name().unwrap().to_string_lossy().into_owned())
-            .collect();
-        names.sort();
-        assert_eq!(names, vec!["Foo", "Foo1"]);
-    }
-
-    /// A new child named "Init" (as a ModuleScript) would naively become
-    /// "Init.luau", which case-insensitively matches the parent's reserved
-    /// "init.luau". Syncback must resolve this automatically by prefixing the
-    /// filesystem name with '_' (→ "_Init.luau") rather than erroring.
-    #[test]
-    fn syncback_resolves_init_name_conflict() {
-        use rbx_dom_weak::{InstanceBuilder, WeakDom};
-
-        let old_parent = InstanceSnapshot::new()
-            .name("Parent")
-            .class_name("Folder")
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root"))
-                    .relevant_paths(vec![PathBuf::from("/root")]),
-            );
-        let old_tree = RojoTree::new(old_parent);
-
-        let mut new_tree = WeakDom::new(InstanceBuilder::new("ROOT"));
-        let new_parent = new_tree.insert(
-            new_tree.root_ref(),
-            InstanceBuilder::new("Folder").with_name("Parent"),
-        );
-        new_tree.insert(
-            new_parent,
-            InstanceBuilder::new("ModuleScript").with_name("Init"),
-        );
-
-        let vfs = make_vfs();
-        let project = make_project();
-        let data = SyncbackData::for_test(&vfs, &old_tree, &new_tree, &project);
-        let snapshot = SyncbackSnapshot {
-            data,
-            old: Some(old_tree.get_root_id()),
-            new: new_parent,
-            path: PathBuf::from("/root"),
-            middleware: None,
-        };
-
-        let result = syncback_dir_no_meta(&snapshot);
-        assert!(
-            result.is_ok(),
-            "should resolve init-name conflict by prefixing '_', not error: {:?}",
-            result.as_ref().err(),
-        );
-        // The child should have been placed at "_Init.luau", not "Init.luau".
-        let child_file_name = result
-            .unwrap()
-            .children
-            .into_iter()
-            .next()
-            .and_then(|c| c.path.file_name().map(|n| n.to_string_lossy().into_owned()))
-            .unwrap_or_default();
-        assert!(
-            child_file_name.starts_with('_'),
-            "child filesystem name should start with '_' to avoid init collision, \
-             got: {child_file_name}",
-        );
-    }
-
-    /// A child whose filesystem name is stored with a slugified prefix (e.g.
-    /// "_Init") must NOT be blocked — only the bare "init" stem is reserved.
-    #[test]
-    fn syncback_allows_slugified_init_name() {
-        use rbx_dom_weak::{InstanceBuilder, WeakDom};
-
-        // Existing child: on disk as "_Init" (slugified from a name with an
-        // illegal character), its stem is "_init" which is not reserved.
-        let old_child = InstanceSnapshot::new()
-            .name("Init")
-            .class_name("Folder")
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root/_Init"))
-                    .relevant_paths(vec![PathBuf::from("/root/_Init")]),
-            );
-        let old_parent = InstanceSnapshot::new()
-            .name("Parent")
-            .class_name("Folder")
-            .children(vec![old_child])
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root"))
-                    .relevant_paths(vec![PathBuf::from("/root")]),
-            );
-        let old_tree = RojoTree::new(old_parent);
-
-        let mut new_tree = WeakDom::new(InstanceBuilder::new("ROOT"));
-        let new_parent = new_tree.insert(
-            new_tree.root_ref(),
-            InstanceBuilder::new("Folder").with_name("Parent"),
-        );
-        new_tree.insert(new_parent, InstanceBuilder::new("Folder").with_name("Init"));
-
-        let vfs = make_vfs();
-        let project = make_project();
-        let data = SyncbackData::for_test(&vfs, &old_tree, &new_tree, &project);
-        let snapshot = SyncbackSnapshot {
-            data,
-            old: Some(old_tree.get_root_id()),
-            new: new_parent,
-            path: PathBuf::from("/root"),
-            middleware: None,
-        };
-
-        let result = syncback_dir_no_meta(&snapshot);
-        assert!(
-            result.is_ok(),
-            "should allow a child whose filesystem name is slugified away from \
-             the reserved 'init' stem: {:?}",
-            result.as_ref().err(),
-        );
-    }
-
-    /// Two new children both named "Init" (ModuleScripts) should get
-    /// "_Init.luau" and "_Init1.luau" respectively.
-    #[test]
-    fn syncback_resolves_multiple_init_conflicts() {
-        use rbx_dom_weak::{InstanceBuilder, WeakDom};
-
-        let old_parent = InstanceSnapshot::new()
-            .name("Parent")
-            .class_name("Folder")
-            .metadata(
-                InstanceMetadata::new()
-                    .instigating_source(PathBuf::from("/root"))
-                    .relevant_paths(vec![PathBuf::from("/root")]),
-            );
-        let old_tree = RojoTree::new(old_parent);
-
-        let mut new_tree = WeakDom::new(InstanceBuilder::new("ROOT"));
-        let new_parent = new_tree.insert(
-            new_tree.root_ref(),
-            InstanceBuilder::new("Folder").with_name("Parent"),
-        );
-        new_tree.insert(
-            new_parent,
-            InstanceBuilder::new("ModuleScript").with_name("Init"),
-        );
-        new_tree.insert(
-            new_parent,
-            InstanceBuilder::new("ModuleScript").with_name("Init"),
-        );
-
-        let vfs = make_vfs();
-        let project = make_project();
-        let data = SyncbackData::for_test(&vfs, &old_tree, &new_tree, &project);
-        let snapshot = SyncbackSnapshot {
-            data,
-            old: Some(old_tree.get_root_id()),
-            new: new_parent,
-            path: PathBuf::from("/root"),
-            middleware: None,
-        };
-
-        let result = syncback_dir_no_meta(&snapshot);
-        assert!(
-            result.is_ok(),
-            "should resolve multiple init conflicts with suffixes: {:?}",
-            result.as_ref().err(),
-        );
-        let children = result.unwrap().children;
-        let mut names: Vec<String> = children
-            .iter()
-            .map(|c| c.path.file_name().unwrap().to_string_lossy().into_owned())
-            .collect();
-        names.sort();
-        assert_eq!(names, vec!["_Init.luau", "_Init1.luau"]);
-    }
 }

src/snapshot_middleware/json.rs

@@ -32,7 +32,7 @@ pub fn snapshot_json(
         .metadata(
             InstanceMetadata::new()
                 .instigating_source(path)
-                .relevant_paths(vec![vfs.canonicalize(path)?])
+                .relevant_paths(vec![path.to_path_buf()])
                 .context(context),
         );
 

src/snapshot_middleware/json_model.rs

@@ -35,14 +35,20 @@ pub fn snapshot_json_model(
         format!("File is not a valid JSON model: {}", path.display())
     })?;
 
-    // If the JSON has a name property, preserve it in metadata for syncback
+    if let Some(top_level_name) = &instance.name {
-    let specified_name = instance.name.clone();
+        let new_name = format!("{}.model.json", top_level_name);
 
-    // Use the name from JSON if present, otherwise fall back to filename-derived name
+        log::warn!(
-    if instance.name.is_none() {
+            "Model at path {} had a top-level Name field. \
-        instance.name = Some(name.to_owned());
+            This field has been ignored since Rojo 6.0.\n\
+            Consider removing this field and renaming the file to {}.",
+            new_name,
+            path.display()
+        );
     }
 
+    instance.name = Some(name.to_owned());
+
     let id = instance.id.take().map(RojoRef::new);
     let schema = instance.schema.take();
 
@@ -53,11 +59,10 @@ pub fn snapshot_json_model(
     snapshot.metadata = snapshot
         .metadata
         .instigating_source(path)
-        .relevant_paths(vec![vfs.canonicalize(path)?])
+        .relevant_paths(vec![path.to_path_buf()])
         .context(context)
         .specified_id(id)
-        .schema(schema)
+        .schema(schema);
-        .specified_name(specified_name);
 
     Ok(Some(snapshot))
 }
@@ -76,7 +81,6 @@ pub fn syncback_json_model<'sync>(
         // schemas will ever exist in one project for it to matter, but it
         // could have a performance cost.
         model.schema = old_inst.metadata().schema.clone();
-        model.name = old_inst.metadata().specified_name.clone();
     }
 
     Ok(SyncbackReturn {

src/snapshot_middleware/lua.rs

@@ -88,7 +88,7 @@ pub fn snapshot_lua(
         .metadata(
             InstanceMetadata::new()
                 .instigating_source(path)
-                .relevant_paths(vec![vfs.canonicalize(path)?])
+                .relevant_paths(vec![path.to_path_buf()])
                 .context(context),
         );
 
@@ -158,23 +158,8 @@ pub fn syncback_lua<'sync>(
 
         if !meta.is_empty() {
             let parent_location = snapshot.path.parent_err()?;
-            let file_name = snapshot
-                .path
-                .file_name()
-                .and_then(|n| n.to_str())
-                .unwrap_or("");
-            let meta_stem = file_name
-                .strip_suffix(".server.luau")
-                .or_else(|| file_name.strip_suffix(".server.lua"))
-                .or_else(|| file_name.strip_suffix(".client.luau"))
-                .or_else(|| file_name.strip_suffix(".client.lua"))
-                .or_else(|| file_name.strip_suffix(".plugin.luau"))
-                .or_else(|| file_name.strip_suffix(".plugin.lua"))
-                .or_else(|| file_name.strip_suffix(".luau"))
-                .or_else(|| file_name.strip_suffix(".lua"))
-                .unwrap_or(file_name);
             fs_snapshot.add_file(
-                parent_location.join(format!("{meta_stem}.meta.json")),
+                parent_location.join(format!("{}.meta.json", new_inst.name)),
                 serde_json::to_vec_pretty(&meta).context("cannot serialize metadata")?,
             );
         }

src/snapshot_middleware/meta_file.rs

@@ -10,10 +10,7 @@ use rbx_dom_weak::{
 use serde::{Deserialize, Serialize};
 
 use crate::{
-    json,
+    json, resolution::UnresolvedValue, snapshot::InstanceSnapshot, syncback::SyncbackSnapshot,
-    resolution::UnresolvedValue,
-    snapshot::InstanceSnapshot,
-    syncback::{validate_file_name, SyncbackSnapshot},
     RojoRef,
 };
 
@@ -39,9 +36,6 @@ pub struct AdjacentMetadata {
     #[serde(default, skip_serializing_if = "IndexMap::is_empty")]
     pub attributes: IndexMap<String, UnresolvedValue>,
 
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub name: Option<String>,
-
     #[serde(skip)]
     pub path: PathBuf,
 }
@@ -150,26 +144,6 @@ impl AdjacentMetadata {
             }
         }
 
-        let name = snapshot
-            .old_inst()
-            .and_then(|inst| inst.metadata().specified_name.clone())
-            .or_else(|| {
-                // Write name when name_for_inst would produce a different
-                // filesystem stem (slugification or init-prefix).
-                if snapshot.old_inst().is_none() {
-                    let instance_name = &snapshot.new_inst().name;
-                    if validate_file_name(instance_name).is_err()
-                        || instance_name.to_lowercase() == "init"
-                    {
-                        Some(instance_name.clone())
-                    } else {
-                        None
-                    }
-                } else {
-                    None
-                }
-            });
-
         Ok(Some(Self {
             ignore_unknown_instances: if ignore_unknown_instances {
                 Some(true)
@@ -181,7 +155,6 @@ impl AdjacentMetadata {
             path,
             id: None,
             schema,
-            name,
         }))
     }
 
@@ -240,26 +213,11 @@ impl AdjacentMetadata {
         Ok(())
     }
 
-    fn apply_name(&mut self, snapshot: &mut InstanceSnapshot) -> anyhow::Result<()> {
-        if self.name.is_some() && snapshot.metadata.specified_name.is_some() {
-            anyhow::bail!(
-                "cannot specify a name using {} (instance has a name from somewhere else)",
-                self.path.display()
-            );
-        }
-        if let Some(name) = &self.name {
-            snapshot.name = name.clone().into();
-        }
-        snapshot.metadata.specified_name = self.name.take();
-        Ok(())
-    }
-
     pub fn apply_all(&mut self, snapshot: &mut InstanceSnapshot) -> anyhow::Result<()> {
         self.apply_ignore_unknown_instances(snapshot);
         self.apply_properties(snapshot)?;
         self.apply_id(snapshot)?;
         self.apply_schema(snapshot)?;
-        self.apply_name(snapshot)?;
         Ok(())
     }
 
@@ -268,13 +226,11 @@ impl AdjacentMetadata {
     ///
     /// - The number of properties and attributes is 0
     /// - `ignore_unknown_instances` is None
-    /// - `name` is None
     #[inline]
     pub fn is_empty(&self) -> bool {
         self.attributes.is_empty()
             && self.properties.is_empty()
             && self.ignore_unknown_instances.is_none()
-            && self.name.is_none()
     }
 
     // TODO: Add method to allow selectively applying parts of metadata and
@@ -306,9 +262,6 @@ pub struct DirectoryMetadata {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub class_name: Option<Ustr>,
 
-    #[serde(skip_serializing_if = "Option::is_none")]
-    pub name: Option<String>,
-
     #[serde(skip)]
     pub path: PathBuf,
 }
@@ -419,26 +372,6 @@ impl DirectoryMetadata {
             }
         }
 
-        let name = snapshot
-            .old_inst()
-            .and_then(|inst| inst.metadata().specified_name.clone())
-            .or_else(|| {
-                // Write name when name_for_inst would produce a different
-                // directory name (slugification or init-prefix).
-                if snapshot.old_inst().is_none() {
-                    let instance_name = &snapshot.new_inst().name;
-                    if validate_file_name(instance_name).is_err()
-                        || instance_name.to_lowercase() == "init"
-                    {
-                        Some(instance_name.clone())
-                    } else {
-                        None
-                    }
-                } else {
-                    None
-                }
-            });
-
         Ok(Some(Self {
             ignore_unknown_instances: if ignore_unknown_instances {
                 Some(true)
@@ -451,7 +384,6 @@ impl DirectoryMetadata {
             path,
             id: None,
             schema,
-            name,
         }))
     }
 
@@ -461,7 +393,6 @@ impl DirectoryMetadata {
         self.apply_properties(snapshot)?;
         self.apply_id(snapshot)?;
         self.apply_schema(snapshot)?;
-        self.apply_name(snapshot)?;
 
         Ok(())
     }
@@ -533,33 +464,17 @@ impl DirectoryMetadata {
         snapshot.metadata.schema = self.schema.take();
         Ok(())
     }
-
-    fn apply_name(&mut self, snapshot: &mut InstanceSnapshot) -> anyhow::Result<()> {
-        if self.name.is_some() && snapshot.metadata.specified_name.is_some() {
-            anyhow::bail!(
-                "cannot specify a name using {} (instance has a name from somewhere else)",
-                self.path.display()
-            );
-        }
-        if let Some(name) = &self.name {
-            snapshot.name = name.clone().into();
-        }
-        snapshot.metadata.specified_name = self.name.take();
-        Ok(())
-    }
     /// Returns whether the metadata is 'empty', meaning it doesn't have anything
     /// worth persisting in it. Specifically:
     ///
     /// - The number of properties and attributes is 0
     /// - `ignore_unknown_instances` is None
     /// - `class_name` is either None or not Some("Folder")
-    /// - `name` is None
     #[inline]
     pub fn is_empty(&self) -> bool {
         self.attributes.is_empty()
             && self.properties.is_empty()
             && self.ignore_unknown_instances.is_none()
-            && self.name.is_none()
             && if let Some(class) = &self.class_name {
                 class == "Folder"
             } else {

src/snapshot_middleware/rbxm.rs

@@ -28,7 +28,7 @@ pub fn snapshot_rbxm(
             .metadata(
                 InstanceMetadata::new()
                     .instigating_source(path)
-                    .relevant_paths(vec![vfs.canonicalize(path)?])
+                    .relevant_paths(vec![path.to_path_buf()])
                     .context(context),
             );
 

src/snapshot_middleware/rbxmx.rs

@@ -31,7 +31,7 @@ pub fn snapshot_rbxmx(
             .metadata(
                 InstanceMetadata::new()
                     .instigating_source(path)
-                    .relevant_paths(vec![vfs.canonicalize(path)?])
+                    .relevant_paths(vec![path.to_path_buf()])
                     .context(context),
             );
 

src/snapshot_middleware/toml.rs

@@ -31,7 +31,7 @@ pub fn snapshot_toml(
         .metadata(
             InstanceMetadata::new()
                 .instigating_source(path)
-                .relevant_paths(vec![vfs.canonicalize(path)?])
+                .relevant_paths(vec![path.to_path_buf()])
                 .context(context),
         );
 

src/snapshot_middleware/txt.rs

@@ -28,7 +28,7 @@ pub fn snapshot_txt(
         .metadata(
             InstanceMetadata::new()
                 .instigating_source(path)
-                .relevant_paths(vec![vfs.canonicalize(path)?])
+                .relevant_paths(vec![path.to_path_buf()])
                 .context(context),
         );
 
@@ -58,14 +58,8 @@ pub fn syncback_txt<'sync>(
 
         if !meta.is_empty() {
             let parent = snapshot.path.parent_err()?;
-            let file_name = snapshot
-                .path
-                .file_name()
-                .and_then(|n| n.to_str())
-                .unwrap_or("");
-            let meta_stem = file_name.strip_suffix(".txt").unwrap_or(file_name);
             fs_snapshot.add_file(
-                parent.join(format!("{meta_stem}.meta.json")),
+                parent.join(format!("{}.meta.json", new_inst.name)),
                 serde_json::to_vec_pretty(&meta).context("could not serialize metadata")?,
             );
         }

src/snapshot_middleware/yaml.rs

@@ -37,7 +37,7 @@ pub fn snapshot_yaml(
         .metadata(
             InstanceMetadata::new()
                 .instigating_source(path)
-                .relevant_paths(vec![vfs.canonicalize(path)?])
+                .relevant_paths(vec![path.to_path_buf()])
                 .context(context),
         );
 

src/syncback/file_names.rs

@@ -8,11 +8,11 @@ use rbx_dom_weak::Instance;
 
 use crate::{snapshot::InstanceWithMeta, snapshot_middleware::Middleware};
 
-pub fn name_for_inst<'a>(
+pub fn name_for_inst<'old>(
     middleware: Middleware,
-    new_inst: &'a Instance,
+    new_inst: &Instance,
-    old_inst: Option<InstanceWithMeta<'a>>,
+    old_inst: Option<InstanceWithMeta<'old>>,
-) -> anyhow::Result<Cow<'a, str>> {
+) -> anyhow::Result<Cow<'old, str>> {
     if let Some(old_inst) = old_inst {
         if let Some(source) = old_inst.metadata().relevant_paths.first() {
             source
@@ -35,34 +35,14 @@ pub fn name_for_inst<'a>(
             | Middleware::CsvDir
             | Middleware::ServerScriptDir
             | Middleware::ClientScriptDir
-            | Middleware::ModuleScriptDir => {
+            | Middleware::ModuleScriptDir => Cow::Owned(new_inst.name.clone()),
-                let name = if validate_file_name(&new_inst.name).is_err() {
-                    Cow::Owned(slugify_name(&new_inst.name))
-                } else {
-                    Cow::Borrowed(new_inst.name.as_str())
-                };
-                // Prefix "init" to avoid colliding with reserved init files.
-                if name.to_lowercase() == "init" {
-                    Cow::Owned(format!("_{name}"))
-                } else {
-                    name
-                }
-            }
             _ => {
                 let extension = extension_for_middleware(middleware);
-                let slugified;
+                let name = &new_inst.name;
-                let stem: &str = if validate_file_name(&new_inst.name).is_err() {
+                validate_file_name(name).with_context(|| {
-                    slugified = slugify_name(&new_inst.name);
+                    format!("name '{name}' is not legal to write to the file system")
-                    &slugified
+                })?;
-                } else {
+                Cow::Owned(format!("{name}.{extension}"))
-                    &new_inst.name
-                };
-                // Prefix "init" stems to avoid colliding with reserved init files.
-                if stem.to_lowercase() == "init" {
-                    Cow::Owned(format!("_{stem}.{extension}"))
-                } else {
-                    Cow::Owned(format!("{stem}.{extension}"))
-                }
             }
         })
     }
@@ -114,39 +94,6 @@ const INVALID_WINDOWS_NAMES: [&str; 22] = [
 /// in a file's name.
 const FORBIDDEN_CHARS: [char; 9] = ['<', '>', ':', '"', '/', '|', '?', '*', '\\'];
 
-/// Slugifies a name by replacing forbidden characters with underscores
-/// and ensuring the result is a valid file name
-pub fn slugify_name(name: &str) -> String {
-    let mut result = String::with_capacity(name.len());
-
-    for ch in name.chars() {
-        if FORBIDDEN_CHARS.contains(&ch) {
-            result.push('_');
-        } else {
-            result.push(ch);
-        }
-    }
-
-    // Handle Windows reserved names by appending an underscore
-    let result_lower = result.to_lowercase();
-    for forbidden in INVALID_WINDOWS_NAMES {
-        if result_lower == forbidden.to_lowercase() {
-            result.push('_');
-            break;
-        }
-    }
-
-    while result.ends_with(' ') || result.ends_with('.') {
-        result.pop();
-    }
-
-    if result.is_empty() || result.chars().all(|c| c == '_') {
-        result = "instance".to_string();
-    }
-
-    result
-}
-
 /// Validates a provided file name to ensure it's allowed on the file system. An
 /// error is returned if the name isn't allowed, indicating why.
 /// This takes into account rules for Windows, MacOS, and Linux.

src/syncback/mod.rs

@@ -52,6 +52,7 @@ pub fn syncback_loop(
     old_tree: &mut RojoTree,
     mut new_tree: WeakDom,
     project: &Project,
+    force_json: bool,
 ) -> anyhow::Result<FsSnapshot> {
     let ignore_patterns = project
         .syncback_rules
@@ -153,6 +154,7 @@ pub fn syncback_loop(
         old_tree,
         new_tree: &new_tree,
         project,
+        force_json,
     };
 
     let mut snapshots = vec![SyncbackSnapshot {
@@ -197,7 +199,7 @@ pub fn syncback_loop(
             }
         }
 
-        let middleware = get_best_middleware(&snapshot);
+        let middleware = get_best_middleware(&snapshot, force_json);
 
         log::trace!(
             "Middleware for {inst_path} is {:?} (path is {})",
@@ -213,10 +215,14 @@ pub fn syncback_loop(
         let syncback = match middleware.syncback(&snapshot) {
             Ok(syncback) => syncback,
             Err(err) if middleware == Middleware::Dir => {
-                let new_middleware = match env::var(DEBUG_MODEL_FORMAT_VAR) {
+                let new_middleware = if force_json {
-                    Ok(value) if value == "1" => Middleware::Rbxmx,
+                    Middleware::JsonModel
-                    Ok(value) if value == "2" => Middleware::JsonModel,
+                } else {
-                    _ => Middleware::Rbxm,
+                    match env::var(DEBUG_MODEL_FORMAT_VAR) {
+                        Ok(value) if value == "1" => Middleware::Rbxmx,
+                        Ok(value) if value == "2" => Middleware::JsonModel,
+                        _ => Middleware::Rbxm,
+                    }
                 };
                 let file_name = snapshot
                     .path
@@ -295,7 +301,7 @@ pub struct SyncbackReturn<'sync> {
     pub removed_children: Vec<InstanceWithMeta<'sync>>,
 }
 
-pub fn get_best_middleware(snapshot: &SyncbackSnapshot) -> Middleware {
+pub fn get_best_middleware(snapshot: &SyncbackSnapshot, force_json: bool) -> Middleware {
     // At some point, we're better off using an O(1) method for checking
     // equality for classes like this.
     static JSON_MODEL_CLASSES: OnceLock<HashSet<&str>> = OnceLock::new();
@@ -361,10 +367,18 @@ pub fn get_best_middleware(snapshot: &SyncbackSnapshot) -> Middleware {
     }
 
     if middleware == Middleware::Rbxm {
-        middleware = match env::var(DEBUG_MODEL_FORMAT_VAR) {
+        middleware = if force_json {
-            Ok(value) if value == "1" => Middleware::Rbxmx,
+            if !inst.children().is_empty() {
-            Ok(value) if value == "2" => Middleware::JsonModel,
+                Middleware::Dir
-            _ => Middleware::Rbxm,
+            } else {
+                Middleware::JsonModel
+            }
+        } else {
+            match env::var(DEBUG_MODEL_FORMAT_VAR) {
+                Ok(value) if value == "1" => Middleware::Rbxmx,
+                Ok(value) if value == "2" => Middleware::JsonModel,
+                _ => Middleware::Rbxm,
+            }
         }
     }
 

src/syncback/snapshot.rs

@@ -20,6 +20,7 @@ pub struct SyncbackData<'sync> {
     pub(super) old_tree: &'sync RojoTree,
     pub(super) new_tree: &'sync WeakDom,
     pub(super) project: &'sync Project,
+    pub(super) force_json: bool,
 }
 
 pub struct SyncbackSnapshot<'sync> {
@@ -31,25 +32,6 @@ pub struct SyncbackSnapshot<'sync> {
 }
 
 impl<'sync> SyncbackSnapshot<'sync> {
-    /// Computes the middleware and filesystem name for a child without
-    /// creating a full snapshot. Uses the same logic as `with_joined_path`.
-    pub fn child_middleware_and_name(
-        &self,
-        new_ref: Ref,
-        old_ref: Option<Ref>,
-    ) -> anyhow::Result<(Middleware, String)> {
-        let temp = Self {
-            data: self.data,
-            old: old_ref,
-            new: new_ref,
-            path: PathBuf::new(),
-            middleware: None,
-        };
-        let middleware = get_best_middleware(&temp, self.data.force_json);
-        let name = name_for_inst(middleware, temp.new_inst(), temp.old_inst())?;
-        Ok((middleware, name.into_owned()))
-    }
-
     /// Constructs a SyncbackSnapshot from the provided refs
     /// while inheriting this snapshot's path and data. This should be used for
     /// directories.
@@ -62,7 +44,7 @@ impl<'sync> SyncbackSnapshot<'sync> {
             path: PathBuf::new(),
             middleware: None,
         };
-        let middleware = get_best_middleware(&snapshot);
+        let middleware = get_best_middleware(&snapshot, self.data.force_json);
         let name = name_for_inst(middleware, snapshot.new_inst(), snapshot.old_inst())?;
         snapshot.path = self.path.join(name.as_ref());
 
@@ -88,7 +70,7 @@ impl<'sync> SyncbackSnapshot<'sync> {
             path: PathBuf::new(),
             middleware: None,
         };
-        let middleware = get_best_middleware(&snapshot);
+        let middleware = get_best_middleware(&snapshot, self.data.force_json);
         let name = name_for_inst(middleware, snapshot.new_inst(), snapshot.old_inst())?;
         snapshot.path = base_path.join(name.as_ref());
 
@@ -256,25 +238,6 @@ pub fn inst_path(dom: &WeakDom, referent: Ref) -> String {
     path.join("/")
 }
 
-impl<'sync> SyncbackData<'sync> {
-    /// Constructs a `SyncbackData` for use in unit tests.
-    #[cfg(test)]
-    pub fn for_test(
-        vfs: &'sync Vfs,
-        old_tree: &'sync RojoTree,
-        new_tree: &'sync WeakDom,
-        project: &'sync Project,
-    ) -> Self {
-        Self {
-            vfs,
-            old_tree,
-            new_tree,
-            project,
-            force_json: false,
-        }
-    }
-}
-
 #[cfg(test)]
 mod test {
     use rbx_dom_weak::{InstanceBuilder, WeakDom};

tests/tests/build.rs

@@ -41,6 +41,7 @@ gen_build_tests! {
     issue_546,
     json_as_lua,
     json_model_in_folder,
+    json_model_legacy_name,
     module_in_folder,
     module_init,
     nested_runcontext,
@@ -54,8 +55,6 @@ gen_build_tests! {
     script_meta_disabled,
     server_in_folder,
     server_init,
-    slugified_name_roundtrip,
-    model_json_name_input,
     txt,
     txt_in_folder,
     unresolved_values,

tests/tests/syncback.rs

@@ -60,8 +60,8 @@ syncback_tests! {
     // Ensures that projects can be reserialized by syncback and that
     // default.project.json doesn't change unexpectedly.
     project_reserialize => ["attribute_mismatch.luau", "property_mismatch.project.json"],
-    // Confirms that duplicate children are resolved with incrementing suffixes
+    // Confirms that Instances that cannot serialize as directories serialize as rbxms
-    rbxm_fallback => ["src/ChildWithDuplicates/DuplicateChild/.gitkeep", "src/ChildWithDuplicates/DuplicateChild1/.gitkeep"],
+    rbxm_fallback => ["src/ChildWithDuplicates.rbxm"],
     // Ensures that ref properties are linked properly on the file system
     ref_properties => ["src/pointer.model.json", "src/target.model.json"],
     // Ensures that ref properties are linked when no attributes are manually
@@ -86,9 +86,4 @@ syncback_tests! {
     sync_rules => ["src/module.modulescript", "src/text.text"],
     // Ensures that the `syncUnscriptable` setting works
     unscriptable_properties => ["default.project.json"],
-    // Ensures that instances with names containing illegal characters get slugified filenames
-    // and preserve their original names in meta.json without forcing directories for leaf scripts
-    slugified_name => ["src/_Script.meta.json", "src/_Script.server.luau", "src/_Folder/init.meta.json"],
-    // Ensures that .model.json files preserve the name property
-    model_json_name => ["src/foo.model.json"],
 }