[ty] Support LSP client settings (#19614)

## Summary

This PR implements support for providing LSP client settings.

The complementary PR in the ty VS Code extension:
astral-sh/ty-vscode#106.

Notes for the previous iteration of this PR is in
https://github.com/astral-sh/ruff/pull/19614#issuecomment-3136477864
(click on "Details").

Specifically, this PR splits the client settings into 3 distinct groups.
Keep in mind that these groups are not visible to the user, they're
merely an implementation detail. The groups are:
1. `GlobalOptions` - these are the options that are global to the
language server and will be the same for all the workspaces that are
handled by the server
2. `WorkspaceOptions` - these are the options that are specific to a
workspace and will be applied only when running any logic for that
workspace
3. `InitializationOptions` - these are the options that can be specified
during initialization

The initialization options are a superset that contains both the global
and workspace options flattened into a 1-dimensional structure. This
means that the user can specify any and all fields present in
`GlobalOptions` and `WorkspaceOptions` in the initialization options in
addition to the fields that are _specific_ to initialization options.

From the current set of available settings, following are only available
during initialization because they are required at that time, are static
during the runtime of the server and changing their values require a
restart to take effect:
- `logLevel`
- `logFile`

And, following are available under `GlobalOptions`:
- `diagnosticMode`

And, following under `WorkspaceOptions`:
- `disableLanguageServices`
- `pythonExtension` (Python environment information that is populated by
the ty VS Code extension)

### `workspace/configuration`

This request allows server to ask the client for configuration to a
specific workspace. But, this is only supported by the client that has
the `workspace.configuration` client capability set to `true`. What to
do for clients that don't support pulling configurations?

In that case, the settings needs to be provided in the initialization
options and updating the values of those settings can only be done by
restarting the server. With the way this is implemented, this means that
if the client does not support pulling workspace configuration then
there's no way to specify settings specific to a workspace. Earlier,
this would've been possible by providing an array of client options with
an additional field which specifies which workspace the options belong
to but that adds complexity and clients that actually do not support
`workspace/configuration` would usually not support multiple workspaces
either.

Now, for the clients that do support this, the server will initiate the
request to get the configuration for all the workspaces at the start of
the server. Once the server receives these options, it will resolve them
for each workspace as follows:
1. Combine the client options sent during initialization with the
options specific to the workspace creating the final client options
that's specific to this workspace
2. Create a global options by combining the global options from (1) for
all workspaces which in turn will also combine the global options sent
during initialization

The global options are resolved into the global settings and are
available on the `Session` which is initialized with the default global
settings. The workspace options are resolved into the workspace settings
and are available on the respective `Workspace`.

The `SessionSnapshot` contains the global settings while the document
snapshot contains the workspace settings. We could add the global
settings to the document snapshot but that's currently not needed.

### Document diagnostic dynamic registration

Currently, the document diagnostic server capability is created based on
the `diagnosticMode` sent during initialization. But, that wouldn't
provide us with the complete picture. This means the server needs to
defer registering the document diagnostic capability at a later point
once the settings have been resolved.

This is done using dynamic registration for clients that support it. For
clients that do not support dynamic registration for document diagnostic
capability, the server advertises itself as always supporting workspace
diagnostics and work done progress token.

This dynamic registration now allows us to change the server capability
for workspace diagnostics based on the resolved `diagnosticMode` value.
In the future, once `workspace/didChangeConfiguration` is supported, we
can avoid the server restart when users have changed any client
settings.

## Test Plan

Add integration tests and recorded videos on the user experience in
various editors:

### VS Code

For VS Code users, the settings experience is unchanged because the
extension defines it's own interface on how the user can specify the
server setting. This means everything is under the `ty.*` namespace as
usual.


https://github.com/user-attachments/assets/c2e5ba5c-7617-406e-a09d-e397ce9c3b93

### Zed

For Zed, the settings experience has changed. Users can specify settings
during initialization:

```json
{
  "lsp": {
    "ty": {
      "initialization_options": {
        "logLevel": "debug",
        "logFile": "~/.cache/ty.log",
        "diagnosticMode": "workspace",
        "disableLanguageServices": true
      }
    },
  }
}
```

Or, can specify the options under the `settings` key:

```json
{
  "lsp": {
    "ty": {
      "settings": {
        "ty": {
          "diagnosticMode": "openFilesOnly",
          "disableLanguageServices": true
        }
      },
      "initialization_options": {
        "logLevel": "debug",
        "logFile": "~/.cache/ty.log"
      }
    },
  }
}
```

The `logLevel` and `logFile` setting still needs to go under the
initialization options because they're required by the server during
initialization.

We can remove the nesting of the settings under the "ty" namespace by
updating the return type of
db9ea0cdfd/src/tychecker.rs (L45-L49)
to be wrapped inside `ty` directly so that users can avoid doing the
double nesting.

There's one issue here which is that if the `diagnosticMode` is
specified in both the initialization option and settings key, then the
resolution is a bit different - if either of them is set to be
`workspace`, then it wins which means that in the following
configuration, the diagnostic mode is `workspace`:

```json
{
  "lsp": {
    "ty": {
      "settings": {
        "ty": {
          "diagnosticMode": "openFilesOnly"
        }
      },
      "initialization_options": {
        "diagnosticMode": "workspace"
      }
    },
  }
}
```

This behavior is mainly a result of combining global options from
various workspace configuration results. Users should not be able to
provide global options in multiple workspaces but that restriction
cannot be done on the server side. The ty VS Code extension restricts
these global settings to only be set in the user settings and not in
workspace settings but we do not control extensions in other editors.


https://github.com/user-attachments/assets/8e2d6c09-18e6-49e5-ab78-6cf942fe1255

### Neovim

Same as in Zed.

### Other

Other editors that do not support `workspace/configuration`, the users
would need to provide the server settings during initialization.

Cargo.lock

@@ -4208,6 +4208,7 @@ dependencies = [
  "tracing",
  "tracing-flame",
  "tracing-subscriber",
+ "ty_combine",
  "ty_project",
  "ty_python_semantic",
  "ty_server",
@@ -4215,6 +4216,16 @@ dependencies = [
  "wild",
 ]
 
+[[package]]
+name = "ty_combine"
+version = "0.0.0"
+dependencies = [
+ "ordermap",
+ "ruff_db",
+ "ruff_python_ast",
+ "ty_python_semantic",
+]
+
 [[package]]
 name = "ty_ide"
 version = "0.0.0"
@@ -4267,6 +4278,7 @@ dependencies = [
  "thiserror 2.0.12",
  "toml 0.9.4",
  "tracing",
+ "ty_combine",
  "ty_python_semantic",
  "ty_vendored",
 ]
@@ -4338,6 +4350,7 @@ dependencies = [
  "lsp-types",
  "regex",
  "ruff_db",
+ "ruff_macros",
  "ruff_notebook",
  "ruff_python_ast",
  "ruff_source_file",
@@ -4351,6 +4364,7 @@ dependencies = [
  "thiserror 2.0.12",
  "tracing",
  "tracing-subscriber",
+ "ty_combine",
  "ty_ide",
  "ty_project",
  "ty_python_semantic",

Cargo.toml

@@ -40,6 +40,7 @@ ruff_text_size = { path = "crates/ruff_text_size" }
 ruff_workspace = { path = "crates/ruff_workspace" }
 
 ty = { path = "crates/ty" }
+ty_combine = { path = "crates/ty_combine" }
 ty_ide = { path = "crates/ty_ide" }
 ty_project = { path = "crates/ty_project", default-features = false }
 ty_python_semantic = { path = "crates/ty_python_semantic" }

crates/ruff_macros/src/combine.rs

@@ -12,14 +12,14 @@ pub(crate) fn derive_impl(input: DeriveInput) -> syn::Result<proc_macro2::TokenS
                 .map(|member| {
 
                     quote_spanned!(
-                        member.span() => crate::combine::Combine::combine_with(&mut self.#member, other.#member)
+                        member.span() => ty_combine::Combine::combine_with(&mut self.#member, other.#member)
                     )
                 })
                 .collect();
 
             Ok(quote! {
                 #[automatically_derived]
-                impl crate::combine::Combine for #ident {
+                impl ty_combine::Combine for #ident {
                     #[allow(deprecated)]
                     fn combine_with(&mut self, other: Self) {
                         #(

crates/ruff_macros/src/lib.rs

@@ -47,8 +47,8 @@ pub fn derive_combine_options(input: TokenStream) -> TokenStream {
         .into()
 }
 
-/// Automatically derives a `ty_project::project::Combine` implementation for the attributed type
+/// Automatically derives a `ty_combine::Combine` implementation for the attributed type
-/// that calls `ty_project::project::Combine::combine` for each field.
+/// that calls `ty_combine::Combine::combine` for each field.
 ///
 /// The derive macro can only be used on structs. Enums aren't yet supported.
 #[proc_macro_derive(Combine)]

crates/ty/Cargo.toml

@@ -16,6 +16,7 @@ license.workspace = true
 [dependencies]
 ruff_db = { workspace = true, features = ["os", "cache"] }
 ruff_python_ast = { workspace = true }
+ty_combine = { workspace = true }
 ty_python_semantic = { workspace = true }
 ty_project = { workspace = true, features = ["zstd"] }
 ty_server = { workspace = true }

crates/ty/src/args.rs

@@ -3,7 +3,7 @@ use crate::python_version::PythonVersion;
 use clap::error::ErrorKind;
 use clap::{ArgAction, ArgMatches, Error, Parser};
 use ruff_db::system::SystemPathBuf;
-use ty_project::combine::Combine;
+use ty_combine::Combine;
 use ty_project::metadata::options::{EnvironmentOptions, Options, SrcOptions, TerminalOptions};
 use ty_project::metadata::value::{RangedValue, RelativeGlobPattern, RelativePathBuf, ValueSource};
 use ty_python_semantic::lint;

crates/ty_combine/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "ty_combine"
+version = "0.0.0"
+edition.workspace = true
+rust-version.workspace = true
+homepage.workspace = true
+documentation.workspace = true
+repository.workspace = true
+authors.workspace = true
+license.workspace = true
+
+[dependencies]
+ruff_db = { workspace = true }
+ruff_python_ast = { workspace = true }
+ty_python_semantic = { workspace = true }
+
+ordermap = { workspace = true }
+
+[lints]
+workspace = true

crates/ty_combine/src/lib.rs

@@ -161,10 +161,11 @@ impl_noop_combine!(String);
 
 #[cfg(test)]
 mod tests {
-    use crate::combine::Combine;
     use ordermap::OrderMap;
     use std::collections::HashMap;
 
+    use super::Combine;
+
     #[test]
     fn combine_option() {
         assert_eq!(Some(1).combine(Some(2)), Some(1));

crates/ty_project/Cargo.toml

@@ -19,6 +19,7 @@ ruff_options_metadata = { workspace = true }
 ruff_python_ast = { workspace = true, features = ["serde"] }
 ruff_python_formatter = { workspace = true, optional = true }
 ruff_text_size = { workspace = true }
+ty_combine = { workspace = true }
 ty_python_semantic = { workspace = true, features = ["serde"] }
 ty_vendored = { workspace = true }
 

crates/ty_project/src/db.rs

@@ -107,8 +107,10 @@ impl ProjectDatabase {
 
     /// Set the check mode for the project.
     pub fn set_check_mode(&mut self, mode: CheckMode) {
-        tracing::debug!("Updating project to check {mode}");
+        if self.project().check_mode(self) != mode {
-        self.project().set_check_mode(self).to(mode);
+            tracing::debug!("Updating project to check {mode}");
+            self.project().set_check_mode(self).to(mode);
+        }
     }
 
     /// Returns a mutable reference to the system.

crates/ty_project/src/lib.rs

@@ -28,8 +28,6 @@ use ty_python_semantic::lint::{LintRegistry, LintRegistryBuilder, RuleSelection}
 use ty_python_semantic::types::check_types;
 use ty_python_semantic::{add_inferred_python_version_hint_to_diagnostic, register_lints};
 
-pub mod combine;
-
 mod db;
 mod files;
 mod glob;

crates/ty_project/src/metadata.rs

@@ -4,9 +4,9 @@ use ruff_db::vendored::VendoredFileSystem;
 use ruff_python_ast::name::Name;
 use std::sync::Arc;
 use thiserror::Error;
+use ty_combine::Combine;
 use ty_python_semantic::ProgramSettings;
 
-use crate::combine::Combine;
 use crate::metadata::options::ProjectOptionsOverrides;
 use crate::metadata::pyproject::{Project, PyProject, PyProjectError, ResolveRequiresPythonError};
 use crate::metadata::value::ValueSource;

crates/ty_project/src/metadata/options.rs

@@ -1,5 +1,4 @@
 use crate::Db;
-use crate::combine::Combine;
 use crate::glob::{ExcludeFilter, IncludeExcludeFilter, IncludeFilter, PortableGlobKind};
 use crate::metadata::settings::{OverrideSettings, SrcSettings};
 
@@ -28,6 +27,7 @@ use std::hash::BuildHasherDefault;
 use std::ops::Deref;
 use std::sync::Arc;
 use thiserror::Error;
+use ty_combine::Combine;
 use ty_python_semantic::lint::{GetLintError, Level, LintSource, RuleSelection};
 use ty_python_semantic::{
     ProgramSettings, PythonEnvironment, PythonPlatform, PythonVersionFileSource,

crates/ty_project/src/metadata/settings.rs

@@ -1,10 +1,11 @@
 use std::sync::Arc;
 
 use ruff_db::files::File;
+use ty_combine::Combine;
 use ty_python_semantic::lint::RuleSelection;
 
 use crate::metadata::options::{InnerOverrideOptions, OutputFormat};
-use crate::{Db, combine::Combine, glob::IncludeExcludeFilter};
+use crate::{Db, glob::IncludeExcludeFilter};
 
 /// The resolved [`super::Options`] for the project.
 ///

crates/ty_project/src/metadata/value.rs

@@ -1,5 +1,4 @@
 use crate::Db;
-use crate::combine::Combine;
 use crate::glob::{
     AbsolutePortableGlobPattern, PortableGlobError, PortableGlobKind, PortableGlobPattern,
 };
@@ -15,6 +14,7 @@ use std::hash::{Hash, Hasher};
 use std::ops::{Deref, DerefMut};
 use std::sync::Arc;
 use toml::Spanned;
+use ty_combine::Combine;
 
 #[derive(Clone, Debug)]
 pub enum ValueSource {

crates/ty_server/Cargo.toml

@@ -12,11 +12,13 @@ license = { workspace = true }
 
 [dependencies]
 ruff_db = { workspace = true, features = ["os"] }
+ruff_macros = { workspace = true }
 ruff_notebook = { workspace = true }
 ruff_python_ast = { workspace = true }
 ruff_source_file = { workspace = true }
 ruff_text_size = { workspace = true }
 
+ty_combine = { workspace = true }
 ty_ide = { workspace = true }
 ty_project = { workspace = true }
 ty_python_semantic = { workspace = true }

crates/ty_server/src/capabilities.rs

@@ -1,4 +1,4 @@
-use lsp_types::{ClientCapabilities, MarkupKind};
+use lsp_types::{ClientCapabilities, DiagnosticOptions, MarkupKind, WorkDoneProgressOptions};
 
 bitflags::bitflags! {
     /// Represents the resolved client capabilities for the language server.
@@ -18,7 +18,9 @@ bitflags::bitflags! {
         const SIGNATURE_ACTIVE_PARAMETER_SUPPORT = 1 << 9;
         const HIERARCHICAL_DOCUMENT_SYMBOL_SUPPORT = 1 << 10;
         const WORK_DONE_PROGRESS = 1 << 11;
-        const DID_CHANGE_WATCHED_FILES_DYNAMIC_REGISTRATION= 1 << 12;
+        const FILE_WATCHER_SUPPORT = 1 << 12;
+        const DIAGNOSTIC_DYNAMIC_REGISTRATION = 1 << 13;
+        const WORKSPACE_CONFIGURATION = 1 << 14;
     }
 }
 
@@ -28,6 +30,11 @@ impl ResolvedClientCapabilities {
         self.contains(Self::WORKSPACE_DIAGNOSTIC_REFRESH)
     }
 
+    /// Returns `true` if the client supports workspace configuration.
+    pub(crate) const fn supports_workspace_configuration(self) -> bool {
+        self.contains(Self::WORKSPACE_CONFIGURATION)
+    }
+
     /// Returns `true` if the client supports inlay hint refresh.
     pub(crate) const fn supports_inlay_hint_refresh(self) -> bool {
         self.contains(Self::INLAY_HINT_REFRESH)
@@ -83,9 +90,14 @@ impl ResolvedClientCapabilities {
         self.contains(Self::WORK_DONE_PROGRESS)
     }
 
-    /// Returns `true` if the client supports dynamic registration for watched files changes.
+    /// Returns `true` if the client supports file watcher capabilities.
-    pub(crate) const fn supports_did_change_watched_files_dynamic_registration(self) -> bool {
+    pub(crate) const fn supports_file_watcher(self) -> bool {
-        self.contains(Self::DID_CHANGE_WATCHED_FILES_DYNAMIC_REGISTRATION)
+        self.contains(Self::FILE_WATCHER_SUPPORT)
+    }
+
+    /// Returns `true` if the client supports dynamic registration for diagnostic capabilities.
+    pub(crate) const fn supports_diagnostic_dynamic_registration(self) -> bool {
+        self.contains(Self::DIAGNOSTIC_DYNAMIC_REGISTRATION)
     }
 
     pub(super) fn new(client_capabilities: &ClientCapabilities) -> Self {
@@ -101,6 +113,13 @@ impl ResolvedClientCapabilities {
             flags |= Self::WORKSPACE_DIAGNOSTIC_REFRESH;
         }
 
+        if workspace
+            .and_then(|workspace| workspace.configuration)
+            .unwrap_or_default()
+        {
+            flags |= Self::WORKSPACE_CONFIGURATION;
+        }
+
         if workspace
             .and_then(|workspace| workspace.inlay_hint.as_ref()?.refresh_support)
             .unwrap_or_default()
@@ -108,10 +127,24 @@ impl ResolvedClientCapabilities {
             flags |= Self::INLAY_HINT_REFRESH;
         }
 
+        if workspace
+            .and_then(|workspace| workspace.did_change_watched_files?.dynamic_registration)
+            .unwrap_or_default()
+        {
+            flags |= Self::FILE_WATCHER_SUPPORT;
+        }
+
         if text_document.is_some_and(|text_document| text_document.diagnostic.is_some()) {
             flags |= Self::PULL_DIAGNOSTICS;
         }
 
+        if text_document
+            .and_then(|text_document| text_document.diagnostic.as_ref()?.dynamic_registration)
+            .unwrap_or_default()
+        {
+            flags |= Self::DIAGNOSTIC_DYNAMIC_REGISTRATION;
+        }
+
         if text_document
             .and_then(|text_document| text_document.type_definition?.link_support)
             .unwrap_or_default()
@@ -212,15 +245,20 @@ impl ResolvedClientCapabilities {
             flags |= Self::WORK_DONE_PROGRESS;
         }
 
-        if client_capabilities
-            .workspace
-            .as_ref()
-            .and_then(|workspace| workspace.did_change_watched_files?.dynamic_registration)
-            .unwrap_or_default()
-        {
-            flags |= Self::DID_CHANGE_WATCHED_FILES_DYNAMIC_REGISTRATION;
-        }
-
         flags
     }
 }
+
+/// Creates the default [`DiagnosticOptions`] for the server.
+pub(crate) fn server_diagnostic_options(workspace_diagnostics: bool) -> DiagnosticOptions {
+    DiagnosticOptions {
+        identifier: Some(crate::DIAGNOSTIC_NAME.to_string()),
+        inter_file_dependencies: true,
+        workspace_diagnostics,
+        work_done_progress_options: WorkDoneProgressOptions {
+            // Currently, the server only supports reporting work done progress for "workspace"
+            // diagnostic mode.
+            work_done_progress: Some(workspace_diagnostics),
+        },
+    }
+}

crates/ty_server/src/lib.rs

@@ -10,6 +10,7 @@ pub use crate::session::{ClientOptions, DiagnosticMode};
 pub use document::{NotebookDocument, PositionEncoding, TextDocument};
 pub(crate) use session::{DocumentQuery, Session};
 
+mod capabilities;
 mod document;
 mod logging;
 mod server;

crates/ty_server/src/server.rs

@@ -2,10 +2,12 @@
 
 use self::schedule::spawn_main_loop;
 use crate::PositionEncoding;
-use crate::session::{AllOptions, ClientOptions, DiagnosticMode, Session};
+use crate::capabilities::{ResolvedClientCapabilities, server_diagnostic_options};
+use crate::session::{InitializationOptions, Session};
+use anyhow::Context;
 use lsp_server::Connection;
 use lsp_types::{
-    ClientCapabilities, DeclarationCapability, DiagnosticOptions, DiagnosticServerCapabilities,
+    ClientCapabilities, DeclarationCapability, DiagnosticServerCapabilities,
     HoverProviderCapability, InitializeParams, InlayHintOptions, InlayHintServerCapabilities,
     MessageType, SelectionRangeProviderCapability, SemanticTokensLegend, SemanticTokensOptions,
     SemanticTokensServerCapabilities, ServerCapabilities, SignatureHelpOptions,
@@ -47,23 +49,38 @@ impl Server {
         in_test: bool,
     ) -> crate::Result<Self> {
         let (id, init_value) = connection.initialize_start()?;
-        let init_params: InitializeParams = serde_json::from_value(init_value)?;
 
-        let AllOptions {
+        let InitializeParams {
-            global: global_options,
+            initialization_options,
-            workspace: mut workspace_options,
+            capabilities: client_capabilities,
-        } = AllOptions::from_value(
+            workspace_folders,
-            init_params
+            ..
-                .initialization_options
+        } = serde_json::from_value(init_value)
-                .unwrap_or_else(|| serde_json::Value::Object(serde_json::Map::default())),
+            .context("Failed to deserialize initialization parameters")?;
-        );
 
-        let client_capabilities = init_params.capabilities;
+        let (initialization_options, deserialization_error) =
+            InitializationOptions::from_value(initialization_options);
+
+        if !in_test {
+            crate::logging::init_logging(
+                initialization_options.log_level.unwrap_or_default(),
+                initialization_options.log_file.as_deref(),
+            );
+        }
+
+        if let Some(error) = deserialization_error {
+            tracing::error!("Failed to deserialize initialization options: {error}");
+        }
+
+        tracing::debug!("Initialization options: {initialization_options:?}");
+
+        let resolved_client_capabilities = ResolvedClientCapabilities::new(&client_capabilities);
         let position_encoding = Self::find_best_position_encoding(&client_capabilities);
         let server_capabilities =
-            Self::server_capabilities(position_encoding, global_options.diagnostic_mode());
+            Self::server_capabilities(position_encoding, resolved_client_capabilities);
 
         let version = ruff_db::program_version().unwrap_or("Unknown");
+        tracing::debug!("Version: {version}");
 
         connection.initialize_finish(
             id,
@@ -81,37 +98,14 @@ impl Server {
         let (main_loop_sender, main_loop_receiver) = crossbeam::channel::bounded(32);
         let client = Client::new(main_loop_sender.clone(), connection.sender.clone());
 
-        if !in_test {
+        // Get workspace URLs without settings - settings will come from workspace/configuration
-            crate::logging::init_logging(
+        let workspace_urls = workspace_folders
-                global_options.tracing.log_level.unwrap_or_default(),
-                global_options.tracing.log_file.as_deref(),
-            );
-        }
-
-        tracing::debug!("Version: {version}");
-
-        let mut workspace_for_url = |url: Url| {
-            let Some(workspace_settings) = workspace_options.as_mut() else {
-                return (url, ClientOptions::default());
-            };
-            let settings = workspace_settings.remove(&url).unwrap_or_else(|| {
-                tracing::warn!(
-                    "No workspace options found for {}, using default options",
-                    url
-                );
-                ClientOptions::default()
-            });
-            (url, settings)
-        };
-
-        let workspaces = init_params
-            .workspace_folders
             .filter(|folders| !folders.is_empty())
             .map(|folders| {
                 folders
                     .into_iter()
-                    .map(|folder| workspace_for_url(folder.uri))
+                    .map(|folder| folder.uri)
-                    .collect()
+                    .collect::<Vec<_>>()
             })
             .or_else(|| {
                 let current_dir = native_system
@@ -125,7 +119,7 @@ impl Server {
                     current_dir.display()
                 );
                 let uri = Url::from_file_path(current_dir).ok()?;
-                Some(vec![workspace_for_url(uri)])
+                Some(vec![uri])
             })
             .ok_or_else(|| {
                 anyhow::anyhow!(
@@ -134,19 +128,19 @@ impl Server {
                 )
             })?;
 
-        let workspaces = if workspaces.len() > 1 {
+        let workspace_urls = if workspace_urls.len() > 1 {
-            let first_workspace = workspaces.into_iter().next().unwrap();
+            let first_workspace = workspace_urls.into_iter().next().unwrap();
             tracing::warn!(
                 "Multiple workspaces are not yet supported, using the first workspace: {}",
-                &first_workspace.0
+                &first_workspace
             );
             client.show_warning_message(format_args!(
                 "Multiple workspaces are not yet supported, using the first workspace: {}",
-                &first_workspace.0,
+                &first_workspace,
             ));
             vec![first_workspace]
         } else {
-            workspaces
+            workspace_urls
         };
 
         Ok(Self {
@@ -155,10 +149,10 @@ impl Server {
             main_loop_receiver,
             main_loop_sender,
             session: Session::new(
-                &client_capabilities,
+                resolved_client_capabilities,
                 position_encoding,
-                global_options,
+                workspace_urls,
-                workspaces,
+                initialization_options,
                 native_system,
                 in_test,
             )?,
@@ -190,21 +184,26 @@ impl Server {
             .unwrap_or_default()
     }
 
+    // TODO: Move this to `capabilities.rs`?
     fn server_capabilities(
         position_encoding: PositionEncoding,
-        diagnostic_mode: DiagnosticMode,
+        resolved_client_capabilities: ResolvedClientCapabilities,
     ) -> ServerCapabilities {
+        let diagnostic_provider =
+            if resolved_client_capabilities.supports_diagnostic_dynamic_registration() {
+                // If the client supports dynamic registration, we will register the diagnostic
+                // capabilities dynamically based on the `ty.diagnosticMode` setting.
+                None
+            } else {
+                // Otherwise, we always advertise support for workspace diagnostics.
+                Some(DiagnosticServerCapabilities::Options(
+                    server_diagnostic_options(true),
+                ))
+            };
+
         ServerCapabilities {
             position_encoding: Some(position_encoding.into()),
-            diagnostic_provider: Some(DiagnosticServerCapabilities::Options(DiagnosticOptions {
+            diagnostic_provider,
-                identifier: Some(crate::DIAGNOSTIC_NAME.into()),
-                inter_file_dependencies: true,
-                // TODO: Dynamically register for workspace diagnostics.
-                workspace_diagnostics: diagnostic_mode.is_workspace(),
-                work_done_progress_options: WorkDoneProgressOptions {
-                    work_done_progress: Some(diagnostic_mode.is_workspace()),
-                },
-            })),
             text_document_sync: Some(TextDocumentSyncCapability::Options(
                 TextDocumentSyncOptions {
                     open_close: Some(true),

crates/ty_server/src/server/api/diagnostics.rs

@@ -199,12 +199,7 @@ pub(crate) fn publish_settings_diagnostics(
     // Note we DO NOT respect the fact that clients support pulls because these are
     // files they *specifically* won't pull diagnostics from us for, because we don't
     // claim to be an LSP for them.
-    let has_workspace_diagnostics = session
+    if session.global_settings().diagnostic_mode().is_workspace() {
-        .workspaces()
-        .for_path(&path)
-        .map(|workspace| workspace.settings().diagnostic_mode().is_workspace())
-        .unwrap_or(false);
-    if has_workspace_diagnostics {
         return;
     }
 

crates/ty_server/src/server/api/notifications/did_close.rs

@@ -53,6 +53,20 @@ impl SyncNotificationHandler for DidCloseTextDocumentHandler {
                     // interned in the lookup table (`Files`).
                     tracing::warn!("Salsa file does not exists for {}", system_path);
                 }
+
+                // For non-virtual files, we clear diagnostics if:
+                //
+                // 1. The file does not belong to any workspace e.g., opening a random file from
+                //    outside the workspace because closing it acts like the file doesn't exists
+                // 2. The diagnostic mode is set to open-files only
+                if session.workspaces().for_path(system_path).is_none()
+                    || session
+                        .global_settings()
+                        .diagnostic_mode()
+                        .is_open_files_only()
+                {
+                    clear_diagnostics(&key, client);
+                }
             }
             AnySystemPath::SystemVirtual(virtual_path) => {
                 if let Some(virtual_file) = db.files().try_virtual_file(virtual_path) {
@@ -61,14 +75,11 @@ impl SyncNotificationHandler for DidCloseTextDocumentHandler {
                 } else {
                     tracing::warn!("Salsa virtual file does not exists for {}", virtual_path);
                 }
-            }
-        }
 
-        if !session.global_settings().diagnostic_mode().is_workspace() {
+                // Always clear diagnostics for virtual files, as they don't really exist on disk
-            // The server needs to clear the diagnostics regardless of whether the client supports
+                // which means closing them is like deleting the file.
-            // pull diagnostics or not. This is because the client only has the capability to fetch
+                clear_diagnostics(&key, client);
-            // the diagnostics but does not automatically clear them when a document is closed.
+            }
-            clear_diagnostics(&key, client);
         }
 
         Ok(())

crates/ty_server/src/server/api/requests/completion.rs

@@ -34,7 +34,10 @@ impl BackgroundDocumentRequestHandler for CompletionRequestHandler {
     ) -> crate::server::Result<Option<CompletionResponse>> {
         let start = Instant::now();
 
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/doc_highlights.rs

@@ -30,7 +30,10 @@ impl BackgroundDocumentRequestHandler for DocumentHighlightRequestHandler {
         _client: &Client,
         params: DocumentHighlightParams,
     ) -> crate::server::Result<Option<Vec<DocumentHighlight>>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/document_symbols.rs

@@ -32,7 +32,10 @@ impl BackgroundDocumentRequestHandler for DocumentSymbolRequestHandler {
         _client: &Client,
         params: DocumentSymbolParams,
     ) -> crate::server::Result<Option<lsp_types::DocumentSymbolResponse>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/goto_declaration.rs

@@ -30,7 +30,10 @@ impl BackgroundDocumentRequestHandler for GotoDeclarationRequestHandler {
         _client: &Client,
         params: GotoDeclarationParams,
     ) -> crate::server::Result<Option<GotoDefinitionResponse>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/goto_definition.rs

@@ -30,7 +30,10 @@ impl BackgroundDocumentRequestHandler for GotoDefinitionRequestHandler {
         _client: &Client,
         params: GotoDefinitionParams,
     ) -> crate::server::Result<Option<GotoDefinitionResponse>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/goto_references.rs

@@ -30,7 +30,10 @@ impl BackgroundDocumentRequestHandler for ReferencesRequestHandler {
         _client: &Client,
         params: ReferenceParams,
     ) -> crate::server::Result<Option<Vec<Location>>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/goto_type_definition.rs

@@ -30,7 +30,10 @@ impl BackgroundDocumentRequestHandler for GotoTypeDefinitionRequestHandler {
         _client: &Client,
         params: GotoTypeDefinitionParams,
     ) -> crate::server::Result<Option<GotoDefinitionResponse>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/hover.rs

@@ -30,7 +30,10 @@ impl BackgroundDocumentRequestHandler for HoverRequestHandler {
         _client: &Client,
         params: HoverParams,
     ) -> crate::server::Result<Option<lsp_types::Hover>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/inlay_hints.rs

@@ -29,7 +29,10 @@ impl BackgroundDocumentRequestHandler for InlayHintRequestHandler {
         _client: &Client,
         params: InlayHintParams,
     ) -> crate::server::Result<Option<Vec<lsp_types::InlayHint>>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/selection_range.rs

@@ -30,7 +30,10 @@ impl BackgroundDocumentRequestHandler for SelectionRangeRequestHandler {
         _client: &Client,
         params: SelectionRangeParams,
     ) -> crate::server::Result<Option<Vec<LspSelectionRange>>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/semantic_tokens.rs

@@ -26,7 +26,10 @@ impl BackgroundDocumentRequestHandler for SemanticTokensRequestHandler {
         _client: &Client,
         _params: SemanticTokensParams,
     ) -> crate::server::Result<Option<SemanticTokensResult>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/semantic_tokens_range.rs

@@ -28,7 +28,10 @@ impl BackgroundDocumentRequestHandler for SemanticTokensRangeRequestHandler {
         _client: &Client,
         params: SemanticTokensRangeParams,
     ) -> crate::server::Result<Option<SemanticTokensRangeResult>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/signature_help.rs

@@ -32,7 +32,10 @@ impl BackgroundDocumentRequestHandler for SignatureHelpRequestHandler {
         _client: &Client,
         params: SignatureHelpParams,
     ) -> crate::server::Result<Option<SignatureHelp>> {
-        if snapshot.client_settings().is_language_services_disabled() {
+        if snapshot
+            .workspace_settings()
+            .is_language_services_disabled()
+        {
             return Ok(None);
         }
 

crates/ty_server/src/server/api/requests/workspace_diagnostic.rs

@@ -103,9 +103,7 @@ impl BackgroundRequestHandler for WorkspaceDiagnosticRequestHandler {
         client: &Client,
         params: WorkspaceDiagnosticParams,
     ) -> Result<WorkspaceDiagnosticReportResult> {
-        let index = snapshot.index();
+        if !snapshot.global_settings().diagnostic_mode().is_workspace() {
-
-        if !index.global_settings().diagnostic_mode().is_workspace() {
             tracing::debug!("Workspace diagnostics is disabled; returning empty report");
             return Ok(WorkspaceDiagnosticReportResult::Report(
                 WorkspaceDiagnosticReport { items: vec![] },

crates/ty_server/src/server/api/requests/workspace_symbols.rs

@@ -23,15 +23,6 @@ impl BackgroundRequestHandler for WorkspaceSymbolRequestHandler {
         _client: &Client,
         params: WorkspaceSymbolParams,
     ) -> crate::server::Result<Option<WorkspaceSymbolResponse>> {
-        // Check if language services are disabled
-        if snapshot
-            .index()
-            .global_settings()
-            .is_language_services_disabled()
-        {
-            return Ok(None);
-        }
-
         let query = &params.query;
         let mut all_symbols = Vec::new();
 

crates/ty_server/src/server/lazy_work_done_progress.rs

@@ -1,4 +1,4 @@
-use crate::session::ResolvedClientCapabilities;
+use crate::capabilities::ResolvedClientCapabilities;
 use crate::session::client::Client;
 use lsp_types::request::WorkDoneProgressCreate;
 use lsp_types::{

crates/ty_server/src/server/main_loop.rs

@@ -5,7 +5,7 @@ use crate::session::{ClientOptions, SuspendedWorkspaceDiagnosticRequest};
 use anyhow::anyhow;
 use crossbeam::select;
 use lsp_server::Message;
-use lsp_types::notification::Notification;
+use lsp_types::notification::{DidChangeWatchedFiles, Notification};
 use lsp_types::{
     ConfigurationParams, DidChangeWatchedFilesRegistrationOptions, FileSystemWatcher, Url,
 };
@@ -194,12 +194,43 @@ impl Server {
     }
 
     fn initialize(&mut self, client: &Client) {
+        self.request_workspace_configurations(client);
+        self.try_register_file_watcher(client);
+    }
+
+    /// Requests workspace configurations from the client for all the workspaces in the session.
+    ///
+    /// If the client does not support workspace configuration, it initializes the workspaces
+    /// using the initialization options provided by the client.
+    fn request_workspace_configurations(&mut self, client: &Client) {
+        if !self
+            .session
+            .client_capabilities()
+            .supports_workspace_configuration()
+        {
+            tracing::info!(
+                "Client does not support workspace configuration, initializing workspaces \
+                using the initialization options"
+            );
+            self.session.initialize_workspaces(
+                self.session
+                    .workspaces()
+                    .urls()
+                    .cloned()
+                    .map(|url| (url, self.session.initialization_options().options.clone()))
+                    .collect::<Vec<_>>(),
+                client,
+            );
+            return;
+        }
+
         let urls = self
             .session
             .workspaces()
             .urls()
             .cloned()
             .collect::<Vec<_>>();
+
         let items = urls
             .iter()
             .map(|root| lsp_types::ConfigurationItem {
@@ -209,95 +240,109 @@ impl Server {
             .collect();
 
         tracing::debug!("Requesting workspace configuration for workspaces");
-        client
+        client.send_request::<lsp_types::request::WorkspaceConfiguration>(
-            .send_request::<lsp_types::request::WorkspaceConfiguration>(
+            &self.session,
-                &self.session,
+            ConfigurationParams { items },
-                ConfigurationParams { items },
+            |client, result: Vec<Value>| {
-                |client, result: Vec<Value>| {
+                tracing::debug!("Received workspace configurations, initializing workspaces");
-                    tracing::debug!("Received workspace configurations, initializing workspaces");
-                    assert_eq!(result.len(), urls.len());
 
-                    let workspaces_with_options: Vec<_> = urls
+                // This shouldn't fail because, as per the spec, the client needs to provide a
-                        .into_iter()
+                // `null` value even if it cannot provide a configuration for a workspace.
-                        .zip(result)
+                assert_eq!(
-                        .map(|(url, value)| {
+                    result.len(),
-                            let options: ClientOptions = serde_json::from_value(value).unwrap_or_else(|err| {
+                    urls.len(),
-                                tracing::warn!("Failed to deserialize workspace options for {url}: {err}. Using default options.");
+                    "Mismatch in number of workspace URLs ({}) and configuration results ({})",
+                    urls.len(),
+                    result.len()
+                );
+
+                let workspaces_with_options: Vec<_> = urls
+                    .into_iter()
+                    .zip(result)
+                    .map(|(url, value)| {
+                        if value.is_null() {
+                            tracing::debug!(
+                                "No workspace options provided for {url}, using default options"
+                            );
+                            return (url, ClientOptions::default());
+                        }
+                        let options: ClientOptions =
+                            serde_json::from_value(value).unwrap_or_else(|err| {
+                                tracing::error!(
+                                    "Failed to deserialize workspace options for {url}: {err}. \
+                                        Using default options"
+                                );
                                 ClientOptions::default()
                             });
-
+                        (url, options)
-                            (url, options)
-                        })
-                        .collect();
-
-
-                    client.queue_action(Action::InitializeWorkspaces(workspaces_with_options));
-                },
-            );
-
-        let fs_watcher = self
-            .session
-            .client_capabilities()
-            .supports_did_change_watched_files_dynamic_registration();
-
-        if fs_watcher {
-            let registration = lsp_types::Registration {
-                id: "workspace/didChangeWatchedFiles".to_owned(),
-                method: "workspace/didChangeWatchedFiles".to_owned(),
-                register_options: Some(
-                    serde_json::to_value(DidChangeWatchedFilesRegistrationOptions {
-                        watchers: vec![
-                            FileSystemWatcher {
-                                glob_pattern: lsp_types::GlobPattern::String("**/ty.toml".into()),
-                                kind: None,
-                            },
-                            FileSystemWatcher {
-                                glob_pattern: lsp_types::GlobPattern::String(
-                                    "**/.gitignore".into(),
-                                ),
-                                kind: None,
-                            },
-                            FileSystemWatcher {
-                                glob_pattern: lsp_types::GlobPattern::String("**/.ignore".into()),
-                                kind: None,
-                            },
-                            FileSystemWatcher {
-                                glob_pattern: lsp_types::GlobPattern::String(
-                                    "**/pyproject.toml".into(),
-                                ),
-                                kind: None,
-                            },
-                            FileSystemWatcher {
-                                glob_pattern: lsp_types::GlobPattern::String("**/*.py".into()),
-                                kind: None,
-                            },
-                            FileSystemWatcher {
-                                glob_pattern: lsp_types::GlobPattern::String("**/*.pyi".into()),
-                                kind: None,
-                            },
-                            FileSystemWatcher {
-                                glob_pattern: lsp_types::GlobPattern::String("**/*.ipynb".into()),
-                                kind: None,
-                            },
-                        ],
                     })
-                    .unwrap(),
+                    .collect();
-                ),
-            };
-            let response_handler = move |_: &Client, ()| {
-                tracing::info!("File watcher successfully registered");
-            };
 
-            client.send_request::<lsp_types::request::RegisterCapability>(
+                client.queue_action(Action::InitializeWorkspaces(workspaces_with_options));
-                &self.session,
+            },
-                lsp_types::RegistrationParams {
+        );
-                    registrations: vec![registration],
+    }
-                },
+
-                response_handler,
+    /// Try to register the file watcher provided by the client if the client supports it.
-            );
+    fn try_register_file_watcher(&mut self, client: &Client) {
-        } else {
+        static FILE_WATCHER_REGISTRATION_ID: &str = "ty/workspace/didChangeWatchedFiles";
-            tracing::warn!("The client does not support file system watching.");
+
+        if !self.session.client_capabilities().supports_file_watcher() {
+            tracing::warn!("Client does not support file system watching");
+            return;
         }
+
+        let registration = lsp_types::Registration {
+            id: FILE_WATCHER_REGISTRATION_ID.to_owned(),
+            method: DidChangeWatchedFiles::METHOD.to_owned(),
+            register_options: Some(
+                serde_json::to_value(DidChangeWatchedFilesRegistrationOptions {
+                    watchers: vec![
+                        FileSystemWatcher {
+                            glob_pattern: lsp_types::GlobPattern::String("**/ty.toml".into()),
+                            kind: None,
+                        },
+                        FileSystemWatcher {
+                            glob_pattern: lsp_types::GlobPattern::String("**/.gitignore".into()),
+                            kind: None,
+                        },
+                        FileSystemWatcher {
+                            glob_pattern: lsp_types::GlobPattern::String("**/.ignore".into()),
+                            kind: None,
+                        },
+                        FileSystemWatcher {
+                            glob_pattern: lsp_types::GlobPattern::String(
+                                "**/pyproject.toml".into(),
+                            ),
+                            kind: None,
+                        },
+                        FileSystemWatcher {
+                            glob_pattern: lsp_types::GlobPattern::String("**/*.py".into()),
+                            kind: None,
+                        },
+                        FileSystemWatcher {
+                            glob_pattern: lsp_types::GlobPattern::String("**/*.pyi".into()),
+                            kind: None,
+                        },
+                        FileSystemWatcher {
+                            glob_pattern: lsp_types::GlobPattern::String("**/*.ipynb".into()),
+                            kind: None,
+                        },
+                    ],
+                })
+                .unwrap(),
+            ),
+        };
+
+        client.send_request::<lsp_types::request::RegisterCapability>(
+            &self.session,
+            lsp_types::RegistrationParams {
+                registrations: vec![registration],
+            },
+            |_: &Client, ()| {
+                tracing::info!("File watcher registration completed successfully");
+            },
+        );
     }
 }
 

crates/ty_server/src/session.rs

@@ -4,25 +4,33 @@ use anyhow::{Context, anyhow};
 use index::DocumentQueryError;
 use lsp_server::{Message, RequestId};
 use lsp_types::notification::{Exit, Notification};
-use lsp_types::request::{Request, Shutdown, WorkspaceDiagnosticRequest};
+use lsp_types::request::{
-use lsp_types::{ClientCapabilities, TextDocumentContentChangeEvent, Url};
+    DocumentDiagnosticRequest, RegisterCapability, Request, Shutdown, UnregisterCapability,
+    WorkspaceDiagnosticRequest,
+};
+use lsp_types::{
+    DiagnosticRegistrationOptions, DiagnosticServerCapabilities, Registration, RegistrationParams,
+    TextDocumentContentChangeEvent, Unregistration, UnregistrationParams, Url,
+};
 use options::GlobalOptions;
 use ruff_db::Db;
 use ruff_db::files::File;
 use ruff_db::system::{System, SystemPath, SystemPathBuf};
+use settings::GlobalSettings;
 use std::collections::{BTreeMap, VecDeque};
 use std::ops::{Deref, DerefMut};
 use std::panic::RefUnwindSafe;
 use std::sync::Arc;
+use ty_combine::Combine;
 use ty_project::metadata::Options;
 use ty_project::watch::ChangeEvent;
-use ty_project::{ChangeResult, Db as _, ProjectDatabase, ProjectMetadata};
+use ty_project::{ChangeResult, CheckMode, Db as _, ProjectDatabase, ProjectMetadata};
 
-pub(crate) use self::capabilities::ResolvedClientCapabilities;
 pub(crate) use self::index::DocumentQuery;
-pub(crate) use self::options::AllOptions;
+pub(crate) use self::options::InitializationOptions;
 pub use self::options::{ClientOptions, DiagnosticMode};
-pub(crate) use self::settings::ClientSettings;
+pub(crate) use self::settings::WorkspaceSettings;
+use crate::capabilities::{ResolvedClientCapabilities, server_diagnostic_options};
 use crate::document::{DocumentKey, DocumentVersion, NotebookDocument};
 use crate::server::{Action, publish_settings_diagnostics};
 use crate::session::client::Client;
@@ -31,7 +39,6 @@ use crate::system::{AnySystemPath, LSPSystem};
 use crate::{PositionEncoding, TextDocument};
 use index::Index;
 
-mod capabilities;
 pub(crate) mod client;
 pub(crate) mod index;
 mod options;
@@ -65,6 +72,12 @@ pub(crate) struct Session {
     /// That's what we use the default project for.
     default_project: DefaultProject,
 
+    /// Initialization options that were provided by the client during server initialization.
+    initialization_options: InitializationOptions,
+
+    /// Resolved global settings that are shared across all workspaces.
+    global_settings: Arc<GlobalSettings>,
+
     /// The global position encoding, negotiated during LSP initialization.
     position_encoding: PositionEncoding,
 
@@ -77,6 +90,9 @@ pub(crate) struct Session {
     /// Has the client requested the server to shutdown.
     shutdown_requested: bool,
 
+    /// Whether the server has dynamically registered the diagnostic capability with the client.
+    diagnostic_capability_registered: bool,
+
     /// Is the connected client a `TestServer` instance.
     in_test: bool,
 
@@ -121,18 +137,20 @@ pub(crate) struct ProjectState {
 
 impl Session {
     pub(crate) fn new(
-        client_capabilities: &ClientCapabilities,
+        resolved_client_capabilities: ResolvedClientCapabilities,
         position_encoding: PositionEncoding,
-        global_options: GlobalOptions,
+        workspace_urls: Vec<Url>,
-        workspace_folders: Vec<(Url, ClientOptions)>,
+        initialization_options: InitializationOptions,
         native_system: Arc<dyn System + 'static + Send + Sync + RefUnwindSafe>,
         in_test: bool,
     ) -> crate::Result<Self> {
-        let index = Arc::new(Index::new(global_options.into_settings()));
+        let index = Arc::new(Index::new());
 
         let mut workspaces = Workspaces::default();
-        for (url, workspace_options) in workspace_folders {
+        // Register workspaces with default settings - they'll be initialized with real settings
-            workspaces.register(url, workspace_options.into_settings())?;
+        // when workspace/configuration response is received
+        for url in workspace_urls {
+            workspaces.register(url)?;
         }
 
         Ok(Self {
@@ -142,10 +160,13 @@ impl Session {
             deferred_messages: VecDeque::new(),
             index: Some(index),
             default_project: DefaultProject::new(),
+            initialization_options,
+            global_settings: Arc::new(GlobalSettings::default()),
             projects: BTreeMap::new(),
-            resolved_client_capabilities: ResolvedClientCapabilities::new(client_capabilities),
+            resolved_client_capabilities,
             request_queue: RequestQueue::new(),
             shutdown_requested: false,
+            diagnostic_capability_registered: false,
             in_test,
             suspended_workspace_diagnostics_request: None,
             revision: 0,
@@ -155,10 +176,15 @@ impl Session {
     pub(crate) fn request_queue(&self) -> &RequestQueue {
         &self.request_queue
     }
+
     pub(crate) fn request_queue_mut(&mut self) -> &mut RequestQueue {
         &mut self.request_queue
     }
 
+    pub(crate) fn initialization_options(&self) -> &InitializationOptions {
+        &self.initialization_options
+    }
+
     pub(crate) fn is_shutdown_requested(&self) -> bool {
         self.shutdown_requested
     }
@@ -414,11 +440,27 @@ impl Session {
         client: &Client,
     ) {
         assert!(!self.workspaces.all_initialized());
+
+        // These are the options combined from all the global options received by the server for
+        // each workspace via the workspace configuration request.
+        let mut combined_global_options: Option<GlobalOptions> = None;
+
         for (url, options) in workspace_settings {
             tracing::debug!("Initializing workspace `{url}`");
 
-            let settings = options.into_settings();
+            // Combine the global options specified during initialization with the
-            let Some((root, workspace)) = self.workspaces.initialize(&url, settings) else {
+            // workspace-specific options to create the final workspace options.
+            let ClientOptions { global, workspace } = self
+                .initialization_options
+                .options
+                .clone()
+                .combine(options.clone());
+
+            combined_global_options.combine_with(Some(global));
+
+            let workspace_settings = workspace.into_settings();
+            let Some((root, workspace)) = self.workspaces.initialize(&url, workspace_settings)
+            else {
                 continue;
             };
 
@@ -445,17 +487,16 @@ impl Session {
                 });
 
             let (root, db) = match project {
-                Ok(mut db) => {
+                Ok(db) => (root, db),
-                    db.set_check_mode(workspace.settings.diagnostic_mode().into_check_mode());
-                    (root, db)
-                }
                 Err(err) => {
                     tracing::error!(
-                        "Failed to create project for `{root}`: {err:#}. Falling back to default settings"
+                        "Failed to create project for `{root}`: {err:#}. \
+                        Falling back to default settings"
                     );
 
                     client.show_error_message(format!(
-                        "Failed to load project rooted at {root}. Please refer to the logs for more details.",
+                        "Failed to load project rooted at {root}. \
+                        Please refer to the logs for more details.",
                     ));
 
                     let db_with_default_settings =
@@ -488,6 +529,18 @@ impl Session {
             publish_settings_diagnostics(self, client, root);
         }
 
+        if let Some(global_options) = combined_global_options.take() {
+            let global_settings = global_options.into_settings();
+            if global_settings.diagnostic_mode().is_workspace() {
+                for project in self.projects.values_mut() {
+                    project.db.set_check_mode(CheckMode::AllFiles);
+                }
+            }
+            self.global_settings = Arc::new(global_settings);
+        }
+
+        self.register_diagnostic_capability(client);
+
         assert!(
             self.workspaces.all_initialized(),
             "All workspaces should be initialized after calling `initialize_workspaces`"
@@ -502,17 +555,83 @@ impl Session {
         }
     }
 
+    /// Sends a registration notification to the client to enable / disable workspace diagnostics
+    /// as per the `diagnostic_mode`.
+    ///
+    /// This method is a no-op if the client doesn't support dynamic registration of diagnostic
+    /// capabilities.
+    fn register_diagnostic_capability(&mut self, client: &Client) {
+        static DIAGNOSTIC_REGISTRATION_ID: &str = "ty/textDocument/diagnostic";
+
+        if !self
+            .resolved_client_capabilities
+            .supports_diagnostic_dynamic_registration()
+        {
+            return;
+        }
+
+        let diagnostic_mode = self.global_settings.diagnostic_mode;
+
+        if self.diagnostic_capability_registered {
+            client.send_request::<UnregisterCapability>(
+                self,
+                UnregistrationParams {
+                    unregisterations: vec![Unregistration {
+                        id: DIAGNOSTIC_REGISTRATION_ID.into(),
+                        method: DocumentDiagnosticRequest::METHOD.into(),
+                    }],
+                },
+                |_: &Client, ()| {
+                    tracing::debug!("Unregistered diagnostic capability");
+                },
+            );
+        }
+
+        let registration = Registration {
+            id: DIAGNOSTIC_REGISTRATION_ID.into(),
+            method: DocumentDiagnosticRequest::METHOD.into(),
+            register_options: Some(
+                serde_json::to_value(DiagnosticServerCapabilities::RegistrationOptions(
+                    DiagnosticRegistrationOptions {
+                        diagnostic_options: server_diagnostic_options(
+                            diagnostic_mode.is_workspace(),
+                        ),
+                        ..Default::default()
+                    },
+                ))
+                .unwrap(),
+            ),
+        };
+
+        client.send_request::<RegisterCapability>(
+            self,
+            RegistrationParams {
+                registrations: vec![registration],
+            },
+            move |_: &Client, ()| {
+                tracing::debug!(
+                    "Registered diagnostic capability in {diagnostic_mode:?} diagnostic mode"
+                );
+            },
+        );
+
+        self.diagnostic_capability_registered = true;
+    }
+
     /// Creates a document snapshot with the URL referencing the document to snapshot.
     pub(crate) fn take_document_snapshot(&self, url: Url) -> DocumentSnapshot {
-        let index = self.index();
+        let key = self
+            .key_from_url(url)
+            .map_err(DocumentQueryError::InvalidUrl);
         DocumentSnapshot {
             resolved_client_capabilities: self.resolved_client_capabilities,
-            client_settings: index.global_settings(),
+            workspace_settings: key
+                .as_ref()
+                .ok()
+                .and_then(|key| self.workspaces.settings_for_path(key.path().as_system()?))
+                .unwrap_or_else(|| Arc::new(WorkspaceSettings::default())),
             position_encoding: self.position_encoding,
-            document_query_result: self
+            document_query_result: key.and_then(|key| self.index().make_document_ref(key)),
-                .key_from_url(url)
-                .map_err(DocumentQueryError::InvalidUrl)
-                .and_then(|key| index.make_document_ref(key)),
         }
     }
 
@@ -526,6 +645,7 @@ impl Session {
                 .cloned()
                 .collect(),
             index: self.index.clone().unwrap(),
+            global_settings: self.global_settings.clone(),
             position_encoding: self.position_encoding,
             in_test: self.in_test,
             resolved_client_capabilities: self.resolved_client_capabilities,
@@ -582,6 +702,7 @@ impl Session {
     /// Calling this multiple times for the same document is a logic error.
     pub(crate) fn close_document(&mut self, key: &DocumentKey) -> crate::Result<()> {
         self.index_mut().close_document(key)?;
+        self.bump_revision();
         Ok(())
     }
 
@@ -626,8 +747,8 @@ impl Session {
         self.resolved_client_capabilities
     }
 
-    pub(crate) fn global_settings(&self) -> Arc<ClientSettings> {
+    pub(crate) fn global_settings(&self) -> &GlobalSettings {
-        self.index().global_settings()
+        &self.global_settings
     }
 
     pub(crate) fn position_encoding(&self) -> PositionEncoding {
@@ -678,7 +799,7 @@ impl Drop for MutIndexGuard<'_> {
 #[derive(Debug)]
 pub(crate) struct DocumentSnapshot {
     resolved_client_capabilities: ResolvedClientCapabilities,
-    client_settings: Arc<ClientSettings>,
+    workspace_settings: Arc<WorkspaceSettings>,
     position_encoding: PositionEncoding,
     document_query_result: Result<DocumentQuery, DocumentQueryError>,
 }
@@ -694,9 +815,9 @@ impl DocumentSnapshot {
         self.position_encoding
     }
 
-    /// Returns the client settings for this document.
+    /// Returns the client settings for the workspace that this document belongs to.
-    pub(crate) fn client_settings(&self) -> &ClientSettings {
+    pub(crate) fn workspace_settings(&self) -> &WorkspaceSettings {
-        &self.client_settings
+        &self.workspace_settings
     }
 
     /// Returns the result of the document query for this snapshot.
@@ -726,6 +847,7 @@ impl DocumentSnapshot {
 /// An immutable snapshot of the current state of [`Session`].
 pub(crate) struct SessionSnapshot {
     index: Arc<Index>,
+    global_settings: Arc<GlobalSettings>,
     position_encoding: PositionEncoding,
     resolved_client_capabilities: ResolvedClientCapabilities,
     in_test: bool,
@@ -752,6 +874,10 @@ impl SessionSnapshot {
         &self.index
     }
 
+    pub(crate) fn global_settings(&self) -> &GlobalSettings {
+        &self.global_settings
+    }
+
     pub(crate) fn position_encoding(&self) -> PositionEncoding {
         self.position_encoding
     }
@@ -783,7 +909,9 @@ impl Workspaces {
     /// the workspace are announced to the server during the `initialize` request, but the
     /// resolved settings are only available after the client has responded to the `workspace/configuration`
     /// request.
-    pub(crate) fn register(&mut self, url: Url, settings: ClientSettings) -> anyhow::Result<()> {
+    ///
+    /// [`initialize`]: Workspaces::initialize
+    pub(crate) fn register(&mut self, url: Url) -> anyhow::Result<()> {
         let path = url
             .to_file_path()
             .map_err(|()| anyhow!("Workspace URL is not a file or directory: {url:?}"))?;
@@ -792,8 +920,13 @@ impl Workspaces {
         let system_path = SystemPathBuf::from_path_buf(path)
             .map_err(|_| anyhow!("Workspace URL is not valid UTF8"))?;
 
-        self.workspaces
+        self.workspaces.insert(
-            .insert(system_path, Workspace { url, settings });
+            system_path,
+            Workspace {
+                url,
+                settings: Arc::new(WorkspaceSettings::default()),
+            },
+        );
 
         self.uninitialized += 1;
 
@@ -808,7 +941,7 @@ impl Workspaces {
     pub(crate) fn initialize(
         &mut self,
         url: &Url,
-        settings: ClientSettings,
+        settings: WorkspaceSettings,
     ) -> Option<(SystemPathBuf, &mut Workspace)> {
         let path = url.to_file_path().ok()?;
 
@@ -816,7 +949,7 @@ impl Workspaces {
         let system_path = SystemPathBuf::from_path_buf(path).ok()?;
 
         if let Some(workspace) = self.workspaces.get_mut(&system_path) {
-            workspace.settings = settings;
+            workspace.settings = Arc::new(settings);
             self.uninitialized -= 1;
             Some((system_path, workspace))
         } else {
@@ -824,6 +957,8 @@ impl Workspaces {
         }
     }
 
+    /// Returns a reference to the workspace for the given path, [`None`] if there's no workspace
+    /// registered for the path.
     pub(crate) fn for_path(&self, path: impl AsRef<SystemPath>) -> Option<&Workspace> {
         self.workspaces
             .range(..=path.as_ref().to_path_buf())
@@ -831,10 +966,22 @@ impl Workspaces {
             .map(|(_, db)| db)
     }
 
+    /// Returns the client settings for the workspace at the given path, [`None`] if there's no
+    /// workspace registered for the path.
+    pub(crate) fn settings_for_path(
+        &self,
+        path: impl AsRef<SystemPath>,
+    ) -> Option<Arc<WorkspaceSettings>> {
+        self.for_path(path).map(Workspace::settings_arc)
+    }
+
     pub(crate) fn urls(&self) -> impl Iterator<Item = &Url> + '_ {
         self.workspaces.values().map(Workspace::url)
     }
 
+    /// Returns `true` if all workspaces have been [initialized].
+    ///
+    /// [initialized]: Workspaces::initialize
     pub(crate) fn all_initialized(&self) -> bool {
         self.uninitialized == 0
     }
@@ -853,7 +1000,7 @@ impl<'a> IntoIterator for &'a Workspaces {
 pub(crate) struct Workspace {
     /// The workspace root URL as sent by the client during initialization.
     url: Url,
-    settings: ClientSettings,
+    settings: Arc<WorkspaceSettings>,
 }
 
 impl Workspace {
@@ -861,9 +1008,13 @@ impl Workspace {
         &self.url
     }
 
-    pub(crate) fn settings(&self) -> &ClientSettings {
+    pub(crate) fn settings(&self) -> &WorkspaceSettings {
         &self.settings
     }
+
+    pub(crate) fn settings_arc(&self) -> Arc<WorkspaceSettings> {
+        self.settings.clone()
+    }
 }
 
 /// Thin wrapper around the default project database that ensures it only gets initialized
@@ -899,11 +1050,8 @@ impl DefaultProject {
             )
             .unwrap();
 
-            let mut db = ProjectDatabase::new(metadata, system).unwrap();
-            db.set_check_mode(index.global_settings().diagnostic_mode().into_check_mode());
-
             ProjectState {
-                db,
+                db: ProjectDatabase::new(metadata, system).unwrap(),
                 untracked_files_with_pushed_diagnostics: Vec::new(),
             }
         })

crates/ty_server/src/session/index.rs

@@ -5,7 +5,6 @@ use ruff_db::Db;
 use ruff_db::files::{File, system_path_to_file};
 use rustc_hash::FxHashMap;
 
-use crate::session::settings::ClientSettings;
 use crate::{
     PositionEncoding, TextDocument,
     document::{DocumentKey, DocumentVersion, NotebookDocument},
@@ -20,17 +19,13 @@ pub(crate) struct Index {
 
     /// Maps opaque cell URLs to a notebook path (document)
     notebook_cells: FxHashMap<Url, AnySystemPath>,
-
-    /// Global settings provided by the client.
-    global_settings: Arc<ClientSettings>,
 }
 
 impl Index {
-    pub(super) fn new(global_settings: ClientSettings) -> Self {
+    pub(super) fn new() -> Self {
         Self {
             documents: FxHashMap::default(),
             notebook_cells: FxHashMap::default(),
-            global_settings: Arc::new(global_settings),
         }
     }
 
@@ -188,10 +183,6 @@ impl Index {
         Ok(())
     }
 
-    pub(crate) fn global_settings(&self) -> Arc<ClientSettings> {
-        self.global_settings.clone()
-    }
-
     fn document_controller_for_key(
         &mut self,
         key: &DocumentKey,

crates/ty_server/src/session/options.rs

@@ -1,98 +1,145 @@
 use lsp_types::Url;
 use ruff_db::system::SystemPathBuf;
+use ruff_macros::Combine;
 use ruff_python_ast::PythonVersion;
-use rustc_hash::FxHashMap;
 use serde::{Deserialize, Serialize};
-use ty_project::CheckMode;
+use serde_json::Value;
-use ty_project::metadata::Options;
+
+use ty_combine::Combine;
+use ty_project::metadata::Options as TyOptions;
 use ty_project::metadata::options::ProjectOptionsOverrides;
 use ty_project::metadata::value::{RangedValue, RelativePathBuf};
 
 use crate::logging::LogLevel;
-use crate::session::ClientSettings;
 
-pub(crate) type WorkspaceOptionsMap = FxHashMap<Url, ClientOptions>;
+use super::settings::{GlobalSettings, WorkspaceSettings};
 
-#[derive(Debug, Deserialize, Default)]
+/// Initialization options that are set once at server startup that never change.
-#[cfg_attr(test, derive(PartialEq, Eq))]
+///
+/// There are two sets of options that are defined here:
+/// 1. Options that are static, set once and are required at server startup. Any changes to these
+///    options require a server restart to take effect.
+/// 2. Options that are dynamic and can change during the runtime of the server, such as the
+///    diagnostic mode.
+///
+/// The dynamic options are also accepted during the initialization phase, so that we can support
+/// clients that do not support the `workspace/didChangeConfiguration` notification.
+///
+/// Note that this structure has a limitation in that there's no way to specify different options
+/// for different workspaces in the initialization options which means that the server will not
+/// support multiple workspaces for clients that do not implement the `workspace/configuration`
+/// endpoint. Most editors support this endpoint, so this is not a significant limitation.
+#[derive(Clone, Debug, Deserialize, Default)]
 #[serde(rename_all = "camelCase")]
-pub(crate) struct GlobalOptions {
+pub(crate) struct InitializationOptions {
+    /// The log level for the language server.
+    pub(crate) log_level: Option<LogLevel>,
+
+    /// Path to the log file, defaults to stderr if not set.
+    ///
+    /// Tildes (`~`) and environment variables (e.g., `$HOME`) are expanded.
+    pub(crate) log_file: Option<SystemPathBuf>,
+
+    /// The remaining options that are dynamic and can change during the runtime of the server.
     #[serde(flatten)]
-    client: ClientOptions,
+    pub(crate) options: ClientOptions,
-
-    // These settings are only needed for tracing, and are only read from the global configuration.
-    // These will not be in the resolved settings.
-    #[serde(flatten)]
-    pub(crate) tracing: TracingOptions,
 }
 
-impl GlobalOptions {
+impl InitializationOptions {
-    pub(crate) fn into_settings(self) -> ClientSettings {
+    /// Create the initialization options from the given JSON value that corresponds to the
-        self.client.into_settings()
+    /// initialization options sent by the client.
-    }
+    ///
-
+    /// It returns a tuple of the initialization options and an optional error if the JSON value
-    pub(crate) fn diagnostic_mode(&self) -> DiagnosticMode {
+    /// could not be deserialized into the initialization options. In case of an error, the default
-        self.client.diagnostic_mode.unwrap_or_default()
+    /// initialization options are returned.
-    }
+    pub(crate) fn from_value(
-}
+        options: Option<Value>,
-
+    ) -> (InitializationOptions, Option<serde_json::Error>) {
-/// This is a direct representation of the workspace settings schema, which inherits the schema of
+        let Some(options) = options else {
-/// [`ClientOptions`] and adds extra fields to describe the workspace it applies to.
+            return (InitializationOptions::default(), None);
-#[derive(Debug, Deserialize)]
+        };
-#[cfg_attr(test, derive(PartialEq, Eq))]
+        match serde_json::from_value(options) {
-#[serde(rename_all = "camelCase")]
+            Ok(options) => (options, None),
-struct WorkspaceOptions {
+            Err(err) => (InitializationOptions::default(), Some(err)),
-    #[serde(flatten)]
-    options: ClientOptions,
-    workspace: Url,
-}
-
-/// This is a direct representation of the settings schema sent by the client.
-#[derive(Clone, Debug, Serialize, Deserialize, Default)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
-#[serde(rename_all = "camelCase")]
-pub struct ClientOptions {
-    /// Settings under the `python.*` namespace in VS Code that are useful for the ty language
-    /// server.
-    python: Option<Python>,
-    /// Diagnostic mode for the language server.
-    diagnostic_mode: Option<DiagnosticMode>,
-
-    python_extension: Option<PythonExtension>,
-}
-
-/// Diagnostic mode for the language server.
-#[derive(Clone, Copy, Debug, Default, Serialize, Deserialize)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
-#[serde(rename_all = "camelCase")]
-pub enum DiagnosticMode {
-    /// Check only currently open files.
-    #[default]
-    OpenFilesOnly,
-    /// Check all files in the workspace.
-    Workspace,
-}
-
-impl DiagnosticMode {
-    pub(crate) fn is_workspace(self) -> bool {
-        matches!(self, DiagnosticMode::Workspace)
-    }
-
-    pub(crate) fn into_check_mode(self) -> CheckMode {
-        match self {
-            DiagnosticMode::OpenFilesOnly => CheckMode::OpenFiles,
-            DiagnosticMode::Workspace => CheckMode::AllFiles,
         }
     }
 }
 
+/// Options that configure the behavior of the language server.
+///
+/// This is the direct representation of the options that the client sends to the server when
+/// asking for workspace configuration. These options are dynamic and can change during the runtime
+/// of the server via the `workspace/didChangeConfiguration` notification.
+///
+/// The representation of the options is split into two parts:
+/// 1. Global options contains options that are global to the language server. They are applied to
+///    all workspaces managed by the language server.
+/// 2. Workspace options contains options that are specific to a workspace. They are applied to the
+///    workspace these options are associated with.
+#[derive(Clone, Combine, Debug, Serialize, Deserialize, Default)]
+#[serde(rename_all = "camelCase")]
+pub struct ClientOptions {
+    #[serde(flatten)]
+    pub(crate) global: GlobalOptions,
+
+    #[serde(flatten)]
+    pub(crate) workspace: WorkspaceOptions,
+}
+
 impl ClientOptions {
-    /// Returns the client settings that are relevant to the language server.
+    #[must_use]
-    pub(crate) fn into_settings(self) -> ClientSettings {
+    pub fn with_diagnostic_mode(mut self, diagnostic_mode: DiagnosticMode) -> Self {
+        self.global.diagnostic_mode = Some(diagnostic_mode);
+        self
+    }
+
+    #[must_use]
+    pub fn with_disable_language_services(mut self, disable_language_services: bool) -> Self {
+        self.workspace.disable_language_services = Some(disable_language_services);
+        self
+    }
+}
+
+/// Options that are global to the language server.
+///
+/// These are the dynamic options that are applied to all workspaces managed by the language
+/// server.
+#[derive(Clone, Combine, Debug, Serialize, Deserialize, Default)]
+#[serde(rename_all = "camelCase")]
+pub(crate) struct GlobalOptions {
+    /// Diagnostic mode for the language server.
+    diagnostic_mode: Option<DiagnosticMode>,
+}
+
+impl GlobalOptions {
+    pub(crate) fn into_settings(self) -> GlobalSettings {
+        GlobalSettings {
+            diagnostic_mode: self.diagnostic_mode.unwrap_or_default(),
+        }
+    }
+}
+
+/// Options that are specific to a workspace.
+///
+/// These are the dynamic options that are applied to a specific workspace.
+#[derive(Clone, Combine, Debug, Serialize, Deserialize, Default)]
+#[serde(rename_all = "camelCase")]
+pub(crate) struct WorkspaceOptions {
+    /// Whether to disable language services like code completions, hover, etc.
+    disable_language_services: Option<bool>,
+
+    /// Information about the currently active Python environment in the VS Code Python extension.
+    ///
+    /// This is relevant only for VS Code and is populated by the ty VS Code extension.
+    python_extension: Option<PythonExtension>,
+}
+
+impl WorkspaceOptions {
+    pub(crate) fn into_settings(self) -> WorkspaceSettings {
         let overrides = self.python_extension.and_then(|extension| {
             let active_environment = extension.active_environment?;
 
-            let mut overrides = ProjectOptionsOverrides::new(None, Options::default());
+            let mut overrides = ProjectOptionsOverrides::new(None, TyOptions::default());
 
             overrides.fallback_python = if let Some(environment) = &active_environment.environment {
                 environment.folder_uri.to_file_path().ok().and_then(|path| {
@@ -116,59 +163,84 @@ impl ClientOptions {
 
             if let Some(python) = &overrides.fallback_python {
                 tracing::debug!(
-                    "Using the Python environment selected in the VS Code Python extension in case the configuration doesn't specify a Python environment: {python}",
+                    "Using the Python environment selected in the VS Code Python extension \
+                    in case the configuration doesn't specify a Python environment: {python}",
                     python = python.path()
                 );
             }
 
             if let Some(version) = &overrides.fallback_python_version {
                 tracing::debug!(
-                    "Using the Python version selected in the VS Code Python extension: {version} in case the configuration doesn't specify a Python version",
+                    "Using the Python version selected in the VS Code Python extension: {version} \
+                    in case the configuration doesn't specify a Python version",
                 );
             }
 
             Some(overrides)
         });
 
-        ClientSettings {
+        WorkspaceSettings {
-            disable_language_services: self
+            disable_language_services: self.disable_language_services.unwrap_or_default(),
-                .python
-                .and_then(|python| python.ty)
-                .and_then(|ty| ty.disable_language_services)
-                .unwrap_or_default(),
-            diagnostic_mode: self.diagnostic_mode.unwrap_or_default(),
             overrides,
         }
     }
+}
 
-    /// Create a new `ClientOptions` with the specified diagnostic mode
+/// Diagnostic mode for the language server.
-    #[must_use]
+#[derive(Clone, Copy, Debug, Default, PartialEq, Serialize, Deserialize)]
-    pub fn with_diagnostic_mode(mut self, mode: DiagnosticMode) -> Self {
+#[serde(rename_all = "camelCase")]
-        self.diagnostic_mode = Some(mode);
+pub enum DiagnosticMode {
-        self
+    /// Check only currently open files.
+    #[default]
+    OpenFilesOnly,
+    /// Check all files in the workspace.
+    Workspace,
+}
+
+impl DiagnosticMode {
+    /// Returns `true` if the diagnostic mode is set to check all files in the workspace.
+    pub(crate) const fn is_workspace(self) -> bool {
+        matches!(self, DiagnosticMode::Workspace)
+    }
+
+    /// Returns `true` if the diagnostic mode is set to check only currently open files.
+    pub(crate) const fn is_open_files_only(self) -> bool {
+        matches!(self, DiagnosticMode::OpenFilesOnly)
     }
 }
 
-// TODO(dhruvmanila): We need to mirror the "python.*" namespace on the server side but ideally it
+impl Combine for DiagnosticMode {
-// would be useful to instead use `workspace/configuration` instead. This would be then used to get
+    fn combine_with(&mut self, other: Self) {
-// all settings and not just the ones in "python.*".
+        // Diagnostic mode is a global option but as it can be updated without a server restart,
-
+        // it is part of the dynamic option set. But, there's no easy way to enforce the fact that
-#[derive(Clone, Debug, Serialize, Deserialize, Default)]
+        // this option should not be set for individual workspaces. The ty VS Code extension
-#[cfg_attr(test, derive(PartialEq, Eq))]
+        // enforces this but we're not in control of other clients.
-#[serde(rename_all = "camelCase")]
+        //
-struct Python {
+        // So, this is a workaround to ensure that if the diagnostic mode is set to `workspace` in
-    ty: Option<Ty>,
+        // either an initialization options or one of the workspace options, it is always set to
+        // `workspace` in the global options.
+        if other.is_workspace() {
+            *self = DiagnosticMode::Workspace;
+        }
+    }
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize, Default)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
 #[serde(rename_all = "camelCase")]
 struct PythonExtension {
     active_environment: Option<ActiveEnvironment>,
 }
 
+impl Combine for PythonExtension {
+    fn combine_with(&mut self, _other: Self) {
+        panic!(
+            "`python_extension` is not expected to be combined with the initialization options as \
+            it's only set by the ty VS Code extension in the `workspace/configuration` request."
+        );
+    }
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
 #[serde(rename_all = "camelCase")]
 pub(crate) struct ActiveEnvironment {
     pub(crate) executable: PythonExecutable,
@@ -177,7 +249,6 @@ pub(crate) struct ActiveEnvironment {
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
 #[serde(rename_all = "camelCase")]
 pub(crate) struct EnvironmentVersion {
     pub(crate) major: i64,
@@ -189,7 +260,6 @@ pub(crate) struct EnvironmentVersion {
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
 #[serde(rename_all = "camelCase")]
 pub(crate) struct PythonEnvironment {
     pub(crate) folder_uri: Url,
@@ -201,100 +271,9 @@ pub(crate) struct PythonEnvironment {
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
 #[serde(rename_all = "camelCase")]
 pub(crate) struct PythonExecutable {
     #[allow(dead_code)]
     pub(crate) uri: Url,
     pub(crate) sys_prefix: SystemPathBuf,
 }
-
-#[derive(Clone, Debug, Serialize, Deserialize, Default)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
-#[serde(rename_all = "camelCase")]
-struct Ty {
-    disable_language_services: Option<bool>,
-}
-
-/// This is a direct representation of the settings schema sent by the client.
-/// Settings needed to initialize tracing. These will only be read from the global configuration.
-#[derive(Debug, Deserialize, Default)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
-#[serde(rename_all = "camelCase")]
-pub(crate) struct TracingOptions {
-    pub(crate) log_level: Option<LogLevel>,
-
-    /// Path to the log file - tildes and environment variables are supported.
-    pub(crate) log_file: Option<SystemPathBuf>,
-}
-
-/// This is the exact schema for initialization options sent in by the client during
-/// initialization.
-#[derive(Debug, Deserialize)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
-#[serde(untagged)]
-enum InitializationOptions {
-    #[serde(rename_all = "camelCase")]
-    HasWorkspaces {
-        #[serde(rename = "globalSettings")]
-        global: GlobalOptions,
-        #[serde(rename = "settings")]
-        workspace: Vec<WorkspaceOptions>,
-    },
-    GlobalOnly {
-        #[serde(default)]
-        settings: GlobalOptions,
-    },
-}
-
-impl Default for InitializationOptions {
-    fn default() -> Self {
-        Self::GlobalOnly {
-            settings: GlobalOptions::default(),
-        }
-    }
-}
-
-/// Built from the initialization options provided by the client.
-#[derive(Debug)]
-pub(crate) struct AllOptions {
-    pub(crate) global: GlobalOptions,
-    /// If this is `None`, the client only passed in global settings.
-    pub(crate) workspace: Option<WorkspaceOptionsMap>,
-}
-
-impl AllOptions {
-    /// Initializes the controller from the serialized initialization options. This fails if
-    /// `options` are not valid initialization options.
-    pub(crate) fn from_value(options: serde_json::Value) -> Self {
-        Self::from_init_options(
-            serde_json::from_value(options)
-                .map_err(|err| {
-                    tracing::error!("Failed to deserialize initialization options: {err}. Falling back to default client settings...");
-                })
-                .unwrap_or_default(),
-        )
-    }
-
-    fn from_init_options(options: InitializationOptions) -> Self {
-        let (global_options, workspace_options) = match options {
-            InitializationOptions::GlobalOnly { settings: options } => (options, None),
-            InitializationOptions::HasWorkspaces {
-                global: global_options,
-                workspace: workspace_options,
-            } => (global_options, Some(workspace_options)),
-        };
-
-        Self {
-            global: global_options,
-            workspace: workspace_options.map(|workspace_options| {
-                workspace_options
-                    .into_iter()
-                    .map(|workspace_options| {
-                        (workspace_options.workspace, workspace_options.options)
-                    })
-                    .collect()
-            }),
-        }
-    }
-}

crates/ty_server/src/session/settings.rs

@@ -2,26 +2,33 @@ use super::options::DiagnosticMode;
 
 use ty_project::metadata::options::ProjectOptionsOverrides;
 
-/// Resolved client settings for a specific document. These settings are meant to be
+/// Resolved client settings that are shared across all workspaces.
-/// used directly by the server, and are *not* a 1:1 representation with how the client
+#[derive(Clone, Default, Debug, PartialEq)]
-/// sends them.
+pub(crate) struct GlobalSettings {
-#[derive(Clone, Debug)]
-#[cfg_attr(test, derive(PartialEq, Eq))]
-pub(crate) struct ClientSettings {
-    pub(super) disable_language_services: bool,
     pub(super) diagnostic_mode: DiagnosticMode,
+}
+
+impl GlobalSettings {
+    pub(crate) fn diagnostic_mode(&self) -> DiagnosticMode {
+        self.diagnostic_mode
+    }
+}
+
+/// Resolved client settings for a specific workspace.
+///
+/// These settings are meant to be used directly by the server, and are *not* a 1:1 representation
+/// with how the client sends them.
+#[derive(Clone, Default, Debug)]
+pub(crate) struct WorkspaceSettings {
+    pub(super) disable_language_services: bool,
     pub(super) overrides: Option<ProjectOptionsOverrides>,
 }
 
-impl ClientSettings {
+impl WorkspaceSettings {
     pub(crate) fn is_language_services_disabled(&self) -> bool {
         self.disable_language_services
     }
 
-    pub(crate) fn diagnostic_mode(&self) -> DiagnosticMode {
-        self.diagnostic_mode
-    }
-
     pub(crate) fn project_options_overrides(&self) -> Option<&ProjectOptionsOverrides> {
         self.overrides.as_ref()
     }

crates/ty_server/tests/e2e/initialize.rs

@@ -1,6 +1,7 @@
 use anyhow::Result;
+use lsp_types::{Position, request::RegisterCapability};
 use ruff_db::system::SystemPath;
-use ty_server::ClientOptions;
+use ty_server::{ClientOptions, DiagnosticMode};
 
 use crate::TestServerBuilder;
 
@@ -21,7 +22,7 @@ fn empty_workspace_folders() -> Result<()> {
 fn single_workspace_folder() -> Result<()> {
     let workspace_root = SystemPath::new("foo");
     let server = TestServerBuilder::new()?
-        .with_workspace(workspace_root, ClientOptions::default())?
+        .with_workspace(workspace_root, None)?
         .build()?
         .wait_until_workspaces_are_initialized()?;
 
@@ -31,3 +32,353 @@ fn single_workspace_folder() -> Result<()> {
 
     Ok(())
 }
+
+/// Tests that the server sends a registration request for diagnostics if workspace diagnostics
+/// are enabled via initialization options and dynamic registration is enabled, even if the
+/// workspace configuration is not supported by the client.
+#[test]
+fn workspace_diagnostic_registration_without_configuration() -> Result<()> {
+    let workspace_root = SystemPath::new("foo");
+    let mut server = TestServerBuilder::new()?
+        .with_initialization_options(
+            ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace),
+        )
+        .with_workspace(workspace_root, None)?
+        .enable_workspace_configuration(false)
+        .enable_diagnostic_dynamic_registration(true)
+        .build()?;
+
+    // No need to wait for workspaces to initialize as the client does not support workspace
+    // configuration.
+
+    let (_, params) = server.await_request::<RegisterCapability>()?;
+    let [registration] = params.registrations.as_slice() else {
+        panic!(
+            "Expected a single registration, got: {:#?}",
+            params.registrations
+        );
+    };
+
+    insta::assert_json_snapshot!(registration, @r#"
+    {
+      "id": "ty/textDocument/diagnostic",
+      "method": "textDocument/diagnostic",
+      "registerOptions": {
+        "documentSelector": null,
+        "identifier": "ty",
+        "interFileDependencies": true,
+        "workDoneProgress": true,
+        "workspaceDiagnostics": true
+      }
+    }
+    "#);
+
+    Ok(())
+}
+
+/// Tests that the server sends a registration request for diagnostics if open files diagnostics
+/// are enabled via initialization options and dynamic registration is enabled, even if the
+/// workspace configuration is not supported by the client.
+#[test]
+fn open_files_diagnostic_registration_without_configuration() -> Result<()> {
+    let workspace_root = SystemPath::new("foo");
+    let mut server = TestServerBuilder::new()?
+        .with_initialization_options(
+            ClientOptions::default().with_diagnostic_mode(DiagnosticMode::OpenFilesOnly),
+        )
+        .with_workspace(workspace_root, None)?
+        .enable_workspace_configuration(false)
+        .enable_diagnostic_dynamic_registration(true)
+        .build()?;
+
+    // No need to wait for workspaces to initialize as the client does not support workspace
+    // configuration.
+
+    let (_, params) = server.await_request::<RegisterCapability>()?;
+    let [registration] = params.registrations.as_slice() else {
+        panic!(
+            "Expected a single registration, got: {:#?}",
+            params.registrations
+        );
+    };
+
+    insta::assert_json_snapshot!(registration, @r#"
+    {
+      "id": "ty/textDocument/diagnostic",
+      "method": "textDocument/diagnostic",
+      "registerOptions": {
+        "documentSelector": null,
+        "identifier": "ty",
+        "interFileDependencies": true,
+        "workDoneProgress": false,
+        "workspaceDiagnostics": false
+      }
+    }
+    "#);
+
+    Ok(())
+}
+
+/// Tests that the server sends a registration request for diagnostics if workspace diagnostics
+/// are enabled via initialization options and dynamic registration is enabled.
+#[test]
+fn workspace_diagnostic_registration_via_initialization() -> Result<()> {
+    let workspace_root = SystemPath::new("foo");
+    let mut server = TestServerBuilder::new()?
+        .with_initialization_options(
+            ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace),
+        )
+        .with_workspace(workspace_root, None)?
+        .enable_diagnostic_dynamic_registration(true)
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    let (_, params) = server.await_request::<RegisterCapability>()?;
+    let [registration] = params.registrations.as_slice() else {
+        panic!(
+            "Expected a single registration, got: {:#?}",
+            params.registrations
+        );
+    };
+
+    insta::assert_json_snapshot!(registration, @r#"
+    {
+      "id": "ty/textDocument/diagnostic",
+      "method": "textDocument/diagnostic",
+      "registerOptions": {
+        "documentSelector": null,
+        "identifier": "ty",
+        "interFileDependencies": true,
+        "workDoneProgress": true,
+        "workspaceDiagnostics": true
+      }
+    }
+    "#);
+
+    Ok(())
+}
+
+/// Tests that the server sends a registration request for diagnostics if open files diagnostics
+/// are enabled via initialization options and dynamic registration is enabled.
+#[test]
+fn open_files_diagnostic_registration_via_initialization() -> Result<()> {
+    let workspace_root = SystemPath::new("foo");
+    let mut server = TestServerBuilder::new()?
+        .with_initialization_options(
+            ClientOptions::default().with_diagnostic_mode(DiagnosticMode::OpenFilesOnly),
+        )
+        .with_workspace(workspace_root, None)?
+        .enable_diagnostic_dynamic_registration(true)
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    let (_, params) = server.await_request::<RegisterCapability>()?;
+    let [registration] = params.registrations.as_slice() else {
+        panic!(
+            "Expected a single registration, got: {:#?}",
+            params.registrations
+        );
+    };
+
+    insta::assert_json_snapshot!(registration, @r#"
+    {
+      "id": "ty/textDocument/diagnostic",
+      "method": "textDocument/diagnostic",
+      "registerOptions": {
+        "documentSelector": null,
+        "identifier": "ty",
+        "interFileDependencies": true,
+        "workDoneProgress": false,
+        "workspaceDiagnostics": false
+      }
+    }
+    "#);
+
+    Ok(())
+}
+
+/// Tests that the server sends a registration request for diagnostics if workspace diagnostics
+/// are enabled and dynamic registration is enabled.
+#[test]
+fn workspace_diagnostic_registration() -> Result<()> {
+    let workspace_root = SystemPath::new("foo");
+    let mut server = TestServerBuilder::new()?
+        .with_workspace(
+            workspace_root,
+            Some(ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace)),
+        )?
+        .enable_diagnostic_dynamic_registration(true)
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    let (_, params) = server.await_request::<RegisterCapability>()?;
+    let [registration] = params.registrations.as_slice() else {
+        panic!(
+            "Expected a single registration, got: {:#?}",
+            params.registrations
+        );
+    };
+
+    insta::assert_json_snapshot!(registration, @r#"
+    {
+      "id": "ty/textDocument/diagnostic",
+      "method": "textDocument/diagnostic",
+      "registerOptions": {
+        "documentSelector": null,
+        "identifier": "ty",
+        "interFileDependencies": true,
+        "workDoneProgress": true,
+        "workspaceDiagnostics": true
+      }
+    }
+    "#);
+
+    Ok(())
+}
+
+/// Tests that the server sends a registration request for diagnostics if workspace diagnostics are
+/// disabled and dynamic registration is enabled.
+#[test]
+fn open_files_diagnostic_registration() -> Result<()> {
+    let workspace_root = SystemPath::new("foo");
+    let mut server = TestServerBuilder::new()?
+        .with_workspace(
+            workspace_root,
+            Some(ClientOptions::default().with_diagnostic_mode(DiagnosticMode::OpenFilesOnly)),
+        )?
+        .enable_diagnostic_dynamic_registration(true)
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    let (_, params) = server.await_request::<RegisterCapability>()?;
+    let [registration] = params.registrations.as_slice() else {
+        panic!(
+            "Expected a single registration, got: {:#?}",
+            params.registrations
+        );
+    };
+
+    insta::assert_json_snapshot!(registration, @r#"
+    {
+      "id": "ty/textDocument/diagnostic",
+      "method": "textDocument/diagnostic",
+      "registerOptions": {
+        "documentSelector": null,
+        "identifier": "ty",
+        "interFileDependencies": true,
+        "workDoneProgress": false,
+        "workspaceDiagnostics": false
+      }
+    }
+    "#);
+
+    Ok(())
+}
+
+/// Tests that the server can disable language services for a workspace via initialization options.
+#[test]
+fn disable_language_services_set_on_initialization() -> Result<()> {
+    let workspace_root = SystemPath::new("src");
+    let foo = SystemPath::new("src/foo.py");
+    let foo_content = "\
+def foo() -> str:
+    return 42
+";
+
+    let mut server = TestServerBuilder::new()?
+        .with_initialization_options(ClientOptions::default().with_disable_language_services(true))
+        .with_workspace(workspace_root, None)?
+        .enable_pull_diagnostics(true)
+        .with_file(foo, foo_content)?
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    server.open_text_document(foo, &foo_content, 1);
+    let hover = server.hover_request(foo, Position::new(0, 5))?;
+
+    assert!(
+        hover.is_none(),
+        "Expected no hover information, got: {hover:?}"
+    );
+
+    Ok(())
+}
+
+/// Tests that the server can disable language services for a workspace via workspace configuration
+/// request.
+#[test]
+fn disable_language_services_set_on_workspace() -> Result<()> {
+    let workspace_root = SystemPath::new("src");
+    let foo = SystemPath::new("src/foo.py");
+    let foo_content = "\
+def foo() -> str:
+    return 42
+";
+
+    let mut server = TestServerBuilder::new()?
+        .with_workspace(
+            workspace_root,
+            Some(ClientOptions::default().with_disable_language_services(true)),
+        )?
+        .enable_pull_diagnostics(true)
+        .with_file(foo, foo_content)?
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    server.open_text_document(foo, &foo_content, 1);
+    let hover = server.hover_request(foo, Position::new(0, 5))?;
+
+    assert!(
+        hover.is_none(),
+        "Expected no hover information, got: {hover:?}"
+    );
+
+    Ok(())
+}
+
+/// Tests that the server can disable language services for one workspace while keeping them
+/// enabled for another.
+#[test]
+#[ignore = "Requires multiple workspace support in the server and test server"]
+fn disable_language_services_for_one_workspace() -> Result<()> {
+    let workspace_a = SystemPath::new("src/a");
+    let workspace_b = SystemPath::new("src/b");
+    let foo = SystemPath::new("src/a/foo.py");
+    let bar = SystemPath::new("src/b/bar.py");
+    let foo_content = "\
+def foo() -> str:
+    return 42
+";
+    let bar_content = "\
+def bar() -> str:
+    return 42
+";
+
+    let mut server = TestServerBuilder::new()?
+        .with_workspace(
+            workspace_a,
+            Some(ClientOptions::default().with_disable_language_services(true)),
+        )?
+        .with_workspace(workspace_b, None)?
+        .enable_pull_diagnostics(true)
+        .with_file(foo, foo_content)?
+        .with_file(bar, bar_content)?
+        .build()?
+        .wait_until_workspaces_are_initialized()?;
+
+    server.open_text_document(foo, &foo_content, 1);
+    let hover_foo = server.hover_request(foo, Position::new(0, 5))?;
+    assert!(
+        hover_foo.is_none(),
+        "Expected no hover information for workspace A, got: {hover_foo:?}"
+    );
+
+    server.open_text_document(bar, &bar_content, 1);
+    let hover_bar = server.hover_request(bar, Position::new(0, 5))?;
+    assert!(
+        hover_bar.is_some(),
+        "Expected hover information for workspace B, got: {hover_bar:?}"
+    );
+
+    Ok(())
+}

crates/ty_server/tests/e2e/main.rs

@@ -48,24 +48,23 @@ use lsp_types::notification::{
     Initialized, Notification,
 };
 use lsp_types::request::{
-    DocumentDiagnosticRequest, Initialize, Request, Shutdown, WorkspaceConfiguration,
+    DocumentDiagnosticRequest, HoverRequest, Initialize, Request, Shutdown, WorkspaceConfiguration,
     WorkspaceDiagnosticRequest,
 };
 use lsp_types::{
     ClientCapabilities, ConfigurationParams, DiagnosticClientCapabilities,
     DidChangeTextDocumentParams, DidChangeWatchedFilesClientCapabilities,
     DidChangeWatchedFilesParams, DidCloseTextDocumentParams, DidOpenTextDocumentParams,
-    DocumentDiagnosticParams, DocumentDiagnosticReportResult, FileEvent, InitializeParams,
+    DocumentDiagnosticParams, DocumentDiagnosticReportResult, FileEvent, Hover, HoverParams,
-    InitializeResult, InitializedParams, NumberOrString, PartialResultParams, PreviousResultId,
+    InitializeParams, InitializeResult, InitializedParams, NumberOrString, PartialResultParams,
-    PublishDiagnosticsClientCapabilities, TextDocumentClientCapabilities,
+    Position, PreviousResultId, PublishDiagnosticsClientCapabilities,
-    TextDocumentContentChangeEvent, TextDocumentIdentifier, TextDocumentItem, Url,
+    TextDocumentClientCapabilities, TextDocumentContentChangeEvent, TextDocumentIdentifier,
-    VersionedTextDocumentIdentifier, WorkDoneProgressParams, WorkspaceClientCapabilities,
+    TextDocumentItem, TextDocumentPositionParams, Url, VersionedTextDocumentIdentifier,
-    WorkspaceDiagnosticParams, WorkspaceDiagnosticReportResult, WorkspaceFolder,
+    WorkDoneProgressParams, WorkspaceClientCapabilities, WorkspaceDiagnosticParams,
+    WorkspaceDiagnosticReportResult, WorkspaceFolder,
 };
 use ruff_db::system::{OsSystem, SystemPath, SystemPathBuf, TestSystem};
 use rustc_hash::FxHashMap;
-use serde::de::DeserializeOwned;
-use serde_json::json;
 use tempfile::TempDir;
 
 use ty_server::{ClientOptions, LogLevel, Server, init_logging};
@@ -149,9 +148,6 @@ pub(crate) struct TestServer {
     /// Workspace configurations for `workspace/configuration` requests
     workspace_configurations: HashMap<Url, ClientOptions>,
 
-    /// Capabilities registered by the server
-    registered_capabilities: Vec<String>,
-
     /// Whether a Shutdown request has been sent by the test
     /// and the exit sequence should be skipped during `Drop`
     shutdown_requested: bool,
@@ -160,7 +156,7 @@ pub(crate) struct TestServer {
 impl TestServer {
     /// Create a new test server with the given workspace configurations
     fn new(
-        workspaces: Vec<(WorkspaceFolder, ClientOptions)>,
+        workspaces: Vec<(WorkspaceFolder, Option<ClientOptions>)>,
         test_context: TestContext,
         capabilities: ClientCapabilities,
         initialization_options: Option<ClientOptions>,
@@ -197,7 +193,7 @@ impl TestServer {
 
         let workspace_configurations = workspaces
             .into_iter()
-            .map(|(folder, options)| (folder.uri, options))
+            .filter_map(|(folder, options)| Some((folder.uri, options?)))
             .collect::<HashMap<_, _>>();
 
         Self {
@@ -210,13 +206,16 @@ impl TestServer {
             requests: VecDeque::new(),
             initialize_response: None,
             workspace_configurations,
-            registered_capabilities: Vec::new(),
             shutdown_requested: false,
         }
         .initialize(workspace_folders, capabilities, initialization_options)
     }
 
     /// Perform LSP initialization handshake
+    ///
+    /// # Panics
+    ///
+    /// If the `initialization_options` cannot be serialized to JSON
     fn initialize(
         mut self,
         workspace_folders: Vec<WorkspaceFolder>,
@@ -226,15 +225,16 @@ impl TestServer {
         let init_params = InitializeParams {
             capabilities,
             workspace_folders: Some(workspace_folders),
-            // TODO: This should be configurable by the test server builder. This might not be
+            initialization_options: initialization_options.map(|options| {
-            // required after client settings are implemented in the server.
+                serde_json::to_value(options)
-            initialization_options: initialization_options
+                    .context("Failed to serialize initialization options to `ClientOptions`")
-                .map(|options| json!({ "settings": options})),
+                    .unwrap()
+            }),
             ..Default::default()
         };
 
         let init_request_id = self.send_request::<Initialize>(init_params);
-        self.initialize_response = Some(self.await_response::<InitializeResult>(&init_request_id)?);
+        self.initialize_response = Some(self.await_response::<Initialize>(&init_request_id)?);
         self.send_notification::<Initialized>(InitializedParams {});
 
         Ok(self)
@@ -365,7 +365,10 @@ impl TestServer {
     /// called once per request ID.
     ///
     /// [`send_request`]: TestServer::send_request
-    pub(crate) fn await_response<T: DeserializeOwned>(&mut self, id: &RequestId) -> Result<T> {
+    pub(crate) fn await_response<R>(&mut self, id: &RequestId) -> Result<R::Result>
+    where
+        R: Request,
+    {
         loop {
             if let Some(response) = self.responses.remove(id) {
                 match response {
@@ -374,7 +377,7 @@ impl TestServer {
                         result: Some(result),
                         ..
                     } => {
-                        return Ok(serde_json::from_value::<T>(result)?);
+                        return Ok(serde_json::from_value::<R::Result>(result)?);
                     }
                     Response {
                         error: Some(err),
@@ -574,19 +577,26 @@ impl TestServer {
             };
             let config_value = if let Some(options) = self.workspace_configurations.get(scope_uri) {
                 // Return the configuration for the specific workspace
+                //
+                // As per the spec:
+                //
+                // > If the client can't provide a configuration setting for a given scope
+                // > then null needs to be present in the returned array.
                 match item.section.as_deref() {
                     Some("ty") => serde_json::to_value(options)?,
-                    Some(_) | None => {
+                    Some(section) => {
-                        // TODO: Handle `python` section once it's implemented in the server
+                        tracing::debug!("Unrecognized section `{section}` for {scope_uri}");
-                        // As per the spec:
+                        serde_json::Value::Null
-                        //
+                    }
-                        // > If the client can't provide a configuration setting for a given scope
+                    None => {
-                        // > then null needs to be present in the returned array.
+                        tracing::debug!(
+                            "No section specified for workspace configuration of {scope_uri}",
+                        );
                         serde_json::Value::Null
                     }
                 }
             } else {
-                tracing::warn!("No workspace configuration found for {scope_uri}");
+                tracing::debug!("No workspace configuration provided for {scope_uri}");
                 serde_json::Value::Null
             };
             results.push(config_value);
@@ -677,7 +687,7 @@ impl TestServer {
             partial_result_params: PartialResultParams::default(),
         };
         let id = self.send_request::<DocumentDiagnosticRequest>(params);
-        self.await_response::<DocumentDiagnosticReportResult>(&id)
+        self.await_response::<DocumentDiagnosticRequest>(&id)
     }
 
     /// Send a `workspace/diagnostic` request with optional previous result IDs.
@@ -694,7 +704,26 @@ impl TestServer {
         };
 
         let id = self.send_request::<WorkspaceDiagnosticRequest>(params);
-        self.await_response::<WorkspaceDiagnosticReportResult>(&id)
+        self.await_response::<WorkspaceDiagnosticRequest>(&id)
+    }
+
+    /// Send a `textDocument/hover` request for the document at the given path and position.
+    pub(crate) fn hover_request(
+        &mut self,
+        path: impl AsRef<SystemPath>,
+        position: Position,
+    ) -> Result<Option<Hover>> {
+        let params = HoverParams {
+            text_document_position_params: TextDocumentPositionParams {
+                text_document: TextDocumentIdentifier {
+                    uri: self.file_uri(path),
+                },
+                position,
+            },
+            work_done_progress_params: WorkDoneProgressParams::default(),
+        };
+        let id = self.send_request::<HoverRequest>(params);
+        self.await_response::<HoverRequest>(&id)
     }
 }
 
@@ -708,7 +737,6 @@ impl fmt::Debug for TestServer {
             .field("server_requests", &self.requests)
             .field("initialize_response", &self.initialize_response)
             .field("workspace_configurations", &self.workspace_configurations)
-            .field("registered_capabilities", &self.registered_capabilities)
             .finish_non_exhaustive()
     }
 }
@@ -723,7 +751,7 @@ impl Drop for TestServer {
         // it dropped the client connection.
         let shutdown_error = if self.server_thread.is_some() && !self.shutdown_requested {
             let shutdown_id = self.send_request::<Shutdown>(());
-            match self.await_response::<()>(&shutdown_id) {
+            match self.await_response::<Shutdown>(&shutdown_id) {
                 Ok(()) => {
                     self.send_notification::<Exit>(());
                     None
@@ -761,7 +789,7 @@ impl Drop for TestServer {
 /// Builder for creating test servers with specific configurations
 pub(crate) struct TestServerBuilder {
     test_context: TestContext,
-    workspaces: Vec<(WorkspaceFolder, ClientOptions)>,
+    workspaces: Vec<(WorkspaceFolder, Option<ClientOptions>)>,
     initialization_options: Option<ClientOptions>,
     client_capabilities: ClientCapabilities,
 }
@@ -769,10 +797,13 @@ pub(crate) struct TestServerBuilder {
 impl TestServerBuilder {
     /// Create a new builder
     pub(crate) fn new() -> Result<Self> {
-        // Default client capabilities for the test server. These are assumptions made by the real
+        // Default client capabilities for the test server:
-        // server and are common for most clients:
         //
+        // These are common capabilities that all clients support:
         // - Supports publishing diagnostics
+        //
+        // These are enabled by default for convenience but can be disabled using the builder
+        // methods:
         // - Supports pulling workspace configuration
         let client_capabilities = ClientCapabilities {
             text_document: Some(TextDocumentClientCapabilities {
@@ -794,6 +825,7 @@ impl TestServerBuilder {
         })
     }
 
+    /// Set the initial client options for the test server
     pub(crate) fn with_initialization_options(mut self, options: ClientOptions) -> Self {
         self.initialization_options = Some(options);
         self
@@ -803,10 +835,13 @@ impl TestServerBuilder {
     ///
     /// This option will be used to respond to the `workspace/configuration` request that the
     /// server will send to the client.
+    ///
+    /// If `options` is `None`, the test server will respond with `null` for this workspace
+    /// when the server sends a `workspace/configuration` request.
     pub(crate) fn with_workspace(
         mut self,
         workspace_root: &SystemPath,
-        options: ClientOptions,
+        options: Option<ClientOptions>,
     ) -> Result<Self> {
         // TODO: Support multiple workspaces in the test server
         if self.workspaces.len() == 1 {
@@ -830,7 +865,6 @@ impl TestServerBuilder {
     }
 
     /// Enable or disable pull diagnostics capability
-    #[must_use]
     pub(crate) fn enable_pull_diagnostics(mut self, enabled: bool) -> Self {
         self.client_capabilities
             .text_document
@@ -843,8 +877,27 @@ impl TestServerBuilder {
         self
     }
 
+    /// Enable or disable dynamic registration of diagnostics capability
+    pub(crate) fn enable_diagnostic_dynamic_registration(mut self, enabled: bool) -> Self {
+        self.client_capabilities
+            .text_document
+            .get_or_insert_with(Default::default)
+            .diagnostic
+            .get_or_insert_with(Default::default)
+            .dynamic_registration = Some(enabled);
+        self
+    }
+
+    /// Enable or disable workspace configuration capability
+    pub(crate) fn enable_workspace_configuration(mut self, enabled: bool) -> Self {
+        self.client_capabilities
+            .workspace
+            .get_or_insert_with(Default::default)
+            .configuration = Some(enabled);
+        self
+    }
+
     /// Enable or disable file watching capability
-    #[must_use]
     #[expect(dead_code)]
     pub(crate) fn enable_did_change_watched_files(mut self, enabled: bool) -> Self {
         self.client_capabilities
@@ -859,7 +912,6 @@ impl TestServerBuilder {
     }
 
     /// Set custom client capabilities (overrides any previously set capabilities)
-    #[must_use]
     #[expect(dead_code)]
     pub(crate) fn with_client_capabilities(mut self, capabilities: ClientCapabilities) -> Self {
         self.client_capabilities = capabilities;

crates/ty_server/tests/e2e/publish_diagnostics.rs

@@ -1,7 +1,6 @@
 use anyhow::Result;
 use lsp_types::notification::PublishDiagnostics;
 use ruff_db::system::SystemPath;
-use ty_server::ClientOptions;
 
 use crate::TestServerBuilder;
 
@@ -15,7 +14,7 @@ def foo() -> str:
 ";
 
     let mut server = TestServerBuilder::new()?
-        .with_workspace(workspace_root, ClientOptions::default())?
+        .with_workspace(workspace_root, None)?
         .with_file(foo, foo_content)?
         .enable_pull_diagnostics(false)
         .build()?

crates/ty_server/tests/e2e/pull_diagnostics.rs

@@ -23,7 +23,7 @@ def foo() -> str:
 ";
 
     let mut server = TestServerBuilder::new()?
-        .with_workspace(workspace_root, ClientOptions::default())?
+        .with_workspace(workspace_root, None)?
         .with_file(foo, foo_content)?
         .enable_pull_diagnostics(true)
         .build()?
@@ -49,7 +49,7 @@ def foo() -> str:
 ";
 
     let mut server = TestServerBuilder::new()?
-        .with_workspace(workspace_root, ClientOptions::default())?
+        .with_workspace(workspace_root, None)?
         .with_file(foo, foo_content)?
         .enable_pull_diagnostics(true)
         .build()?
@@ -105,7 +105,7 @@ def foo() -> str:
 ";
 
     let mut server = TestServerBuilder::new()?
-        .with_workspace(workspace_root, ClientOptions::default())?
+        .with_workspace(workspace_root, None)?
         .with_file(foo, foo_content_v1)?
         .enable_pull_diagnostics(true)
         .build()?
@@ -217,14 +217,11 @@ def foo() -> str:
     return 42  # Same error: expected str, got int
 ";
 
-    let global_options = ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace);
-
     let mut server = TestServerBuilder::new()?
-        .with_workspace(
+        .with_workspace(workspace_root, None)?
-            workspace_root,
+        .with_initialization_options(
             ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace),
-        )?
+        )
-        .with_initialization_options(global_options)
         .with_file(file_a, file_a_content)?
         .with_file(file_b, file_b_content_v1)?
         .with_file(file_c, file_c_content_v1)?
@@ -335,12 +332,12 @@ def foo() -> str:
     return 42
 ";
 
-    let global_options = ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace);
-
     let mut server = TestServerBuilder::new()?
-        .with_workspace(workspace_root, global_options.clone())?
+        .with_workspace(workspace_root, None)?
         .with_file(foo, foo_content)?
-        .with_initialization_options(global_options)
+        .with_initialization_options(
+            ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace),
+        )
         .enable_pull_diagnostics(true)
         .build()?
         .wait_until_workspaces_are_initialized()?;
@@ -431,14 +428,11 @@ def foo() -> str:
     return 42  # Type error: expected str, got int
 ";
 
-    let global_options = ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace);
-
     let mut builder = TestServerBuilder::new()?
-        .with_workspace(
+        .with_workspace(workspace_root, None)?
-            workspace_root,
+        .with_initialization_options(
             ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace),
-        )?
+        );
-        .with_initialization_options(global_options);
 
     for i in 0..NUM_FILES {
         let file_path_string = format!("src/file_{i:03}.py");
@@ -467,7 +461,7 @@ def foo() -> str:
 
     // First, read the response of the workspace diagnostic request.
     // Note: This response comes after the progress notifications but it simplifies the test to read it first.
-    let final_response = server.await_response::<WorkspaceDiagnosticReportResult>(&request_id)?;
+    let final_response = server.await_response::<WorkspaceDiagnosticRequest>(&request_id)?;
 
     // Process the final report.
     // This should always be a partial report. However, the type definition in the LSP specification
@@ -523,11 +517,11 @@ fn workspace_diagnostic_streaming_with_caching() -> Result<()> {
     let error_content = "def foo() -> str:\n    return 42  # Error";
     let changed_content = "def foo() -> str:\n    return true  # Error";
 
-    let global_options = ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace);
-
     let mut builder = TestServerBuilder::new()?
-        .with_workspace(workspace_root, global_options.clone())?
+        .with_workspace(workspace_root, None)?
-        .with_initialization_options(global_options);
+        .with_initialization_options(
+            ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace),
+        );
 
     for i in 0..NUM_FILES {
         let file_path_string = format!("src/error_{i}.py");
@@ -596,7 +590,7 @@ fn workspace_diagnostic_streaming_with_caching() -> Result<()> {
             },
         });
 
-    let final_response2 = server.await_response::<WorkspaceDiagnosticReportResult>(&request2_id)?;
+    let final_response2 = server.await_response::<WorkspaceDiagnosticRequest>(&request2_id)?;
 
     let mut all_items = Vec::new();
 
@@ -739,8 +733,7 @@ def hello() -> str:
     );
 
     // The workspace diagnostic request should now complete with the new diagnostic
-    let workspace_response =
+    let workspace_response = server.await_response::<WorkspaceDiagnosticRequest>(&request_id)?;
-        server.await_response::<WorkspaceDiagnosticReportResult>(&request_id)?;
 
     // Verify we got a report with one file containing the new diagnostic
     assert_debug_snapshot!(
@@ -782,7 +775,7 @@ def hello() -> str:
     server.cancel(&request_id);
 
     // The workspace diagnostic request should now respond with a cancellation response (Err).
-    let result = server.await_response::<WorkspaceDiagnosticReportResult>(&request_id);
+    let result = server.await_response::<WorkspaceDiagnosticRequest>(&request_id);
     assert_debug_snapshot!(
         "workspace_diagnostic_long_polling_cancellation_result",
         result
@@ -840,7 +833,7 @@ def hello() -> str:
     );
 
     // First request should complete with diagnostics
-    let first_response = server.await_response::<WorkspaceDiagnosticReportResult>(&request_id_1)?;
+    let first_response = server.await_response::<WorkspaceDiagnosticRequest>(&request_id_1)?;
 
     // Extract result IDs from the first response for the second request
     let previous_result_ids = extract_result_ids_from_response(&first_response);
@@ -873,8 +866,7 @@ def hello() -> str:
     );
 
     // Second request should complete with the fix (no diagnostics)
-    let second_response =
+    let second_response = server.await_response::<WorkspaceDiagnosticRequest>(&request_id_2)?;
-        server.await_response::<WorkspaceDiagnosticReportResult>(&request_id_2)?;
 
     // Snapshot both responses to verify the full cycle
     assert_debug_snapshot!(
@@ -895,12 +887,12 @@ fn create_workspace_server_with_file(
     file_path: &SystemPath,
     file_content: &str,
 ) -> Result<TestServer> {
-    let global_options = ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace);
-
     TestServerBuilder::new()?
-        .with_workspace(workspace_root, global_options.clone())?
+        .with_workspace(workspace_root, None)?
         .with_file(file_path, file_content)?
-        .with_initialization_options(global_options)
+        .with_initialization_options(
+            ClientOptions::default().with_diagnostic_mode(DiagnosticMode::Workspace),
+        )
         .enable_pull_diagnostics(true)
         .build()?
         .wait_until_workspaces_are_initialized()
@@ -930,10 +922,10 @@ fn shutdown_and_await_workspace_diagnostic(
     let shutdown_id = server.send_request::<lsp_types::request::Shutdown>(());
 
     // The workspace diagnostic request should now respond with an empty report
-    let workspace_response = server.await_response::<WorkspaceDiagnosticReportResult>(request_id);
+    let workspace_response = server.await_response::<WorkspaceDiagnosticRequest>(request_id);
 
     // Complete shutdown sequence
-    server.await_response::<()>(&shutdown_id)?;
+    server.await_response::<lsp_types::request::Shutdown>(&shutdown_id)?;
     server.send_notification::<lsp_types::notification::Exit>(());
 
     workspace_response
@@ -944,7 +936,7 @@ fn assert_workspace_diagnostics_suspends_for_long_polling(
     server: &mut TestServer,
     request_id: &lsp_server::RequestId,
 ) {
-    match server.await_response::<WorkspaceDiagnosticReportResult>(request_id) {
+    match server.await_response::<WorkspaceDiagnosticRequest>(request_id) {
         Ok(_) => {
             panic!("Expected workspace diagnostic request to suspend for long-polling.");
         }

crates/ty_server/tests/e2e/snapshots/e2e__initialize__initialization.snap

@@ -64,8 +64,8 @@ expression: initialization_result
     "diagnosticProvider": {
       "identifier": "ty",
       "interFileDependencies": true,
-      "workspaceDiagnostics": false,
+      "workspaceDiagnostics": true,
-      "workDoneProgress": false
+      "workDoneProgress": true
     }
   },
   "serverInfo": {

crates/ty_server/tests/e2e/snapshots/e2e__initialize__initialization_with_workspace.snap

@@ -64,8 +64,8 @@ expression: initialization_result
     "diagnosticProvider": {
       "identifier": "ty",
       "interFileDependencies": true,
-      "workspaceDiagnostics": false,
+      "workspaceDiagnostics": true,
-      "workDoneProgress": false
+      "workDoneProgress": true
     }
   },
   "serverInfo": {