agent: More sandboxing changes (#60111)

Large change to sandboxing:
- fixes a nasty TOCTOU relating to a symlink swap attack, documented in
the `sandboxing/README.md`
- Adds UI and restrictions when in an untrusted workspace
- Adds tests for (soon to be removed) git support


---

Release Notes:

- N/A or Added/Fixed/Improved ...

Cargo.lock

@@ -288,6 +288,7 @@ dependencies = [
  "quick-xml 0.38.3",
  "rand 0.9.4",
  "regex",
+ "release_channel",
  "reqwest_client",
  "rust-embed",
  "sandbox",
@@ -11441,6 +11442,7 @@ dependencies = [
  "cfg-if",
  "cfg_aliases 0.2.1",
  "libc",
+ "memoffset",
 ]
 
 [[package]]
@@ -15972,6 +15974,7 @@ dependencies = [
  "http_proxy",
  "libc",
  "log",
+ "nix 0.29.0",
  "serde",
  "serde_json",
  "smol",

crates/acp_thread/src/acp_thread.rs

@@ -3952,14 +3952,15 @@ impl AcpThread {
                     let (task_command, task_args) = builder
                         .redirect_stdin_to_dev_null()
                         .build(Some(command.clone()), &args);
-                    let (task_command, task_args, task_env, sandbox) = prepare_sandbox_wrap(
-                        task_command,
-                        task_args,
-                        cwd.clone(),
-                        sandbox_wrap,
-                        env,
-                    )
-                    .await?;
+                    let (task_command, task_args, task_env, sandbox) = cx
+                        .background_spawn(prepare_sandbox_wrap(
+                            task_command,
+                            task_args,
+                            cwd.clone(),
+                            sandbox_wrap,
+                            env,
+                        ))
+                        .await?;
                     (task_command, task_args, task_env, sandbox, cwd.clone())
                 };
                 let terminal = project

crates/acp_thread/src/terminal.rs

@@ -59,6 +59,13 @@ pub struct SandboxWrap {
     /// enforcing proxy binds a loopback port on this host, so it can only
     /// confine local commands; a remote terminal can't reach it.
     pub is_local: bool,
+    /// Windows/WSL only: `(release channel, version)` of the Linux `zed` to
+    /// provision inside WSL as the sandbox helper (version `latest` for dev
+    /// builds). Resolved by the agent (which can read the running app's release
+    /// info) and forwarded to the sandbox. `None` on other platforms, or when
+    /// the release can't be determined, in which case the WSL backend falls back
+    /// to running bwrap without in-sandbox bind validation.
+    pub wsl_zed_release: Option<(String, String)>,
 }
 
 #[derive(Clone, Debug, Default)]
@@ -137,26 +144,32 @@ impl SandboxWrap {
     /// (fail-open), or refuse (fail-closed). It runs a brief probe subprocess on
     /// Linux, so call it off the main thread. On platforms whose sandbox can't
     /// fail to set up this way it always returns `Ok`.
-    pub fn can_create_sandbox(
-        &self,
-        cwd: Option<&std::path::Path>,
-    ) -> Result<(), LinuxWslSandboxError> {
-        sandbox::Sandbox::can_create(&self.to_policy(), cwd).map_err(LinuxWslSandboxError::from)
+    pub fn can_create_sandbox(&self) -> Result<(), LinuxWslSandboxError> {
+        sandbox::Sandbox::can_create(&self.to_policy()).map_err(LinuxWslSandboxError::from)
     }
 
     /// Translate this request into the cross-platform [`sandbox::SandboxPolicy`].
+    ///
+    /// This is the enforcement-policy construction point, so it **captures** each
+    /// grant as a [`sandbox::HostFilesystemLocation`] (pinning the inode / canonical
+    /// path) rather than passing a re-resolvable path. A location that can't be
+    /// captured (e.g. it doesn't exist) is dropped from the grant — fail-closed.
     fn to_policy(&self) -> sandbox::SandboxPolicy {
         let fs = if self.allow_fs_write {
             sandbox::SandboxFsPolicy::Unrestricted
         } else {
-            sandbox::SandboxFsPolicy::Restricted {
-                writable_paths: self
-                    .writable_paths
-                    .iter()
-                    .cloned()
-                    .chain(self.extra_write_paths.iter().cloned())
-                    .collect(),
-            }
+            let writable_paths = self
+                .writable_paths
+                .iter()
+                .chain(self.extra_write_paths.iter())
+                .filter_map(|path| {
+                    // Create not-yet-existing writable grants (e.g. an approved
+                    // scratch dir) so they can be captured and bound; best-effort.
+                    let _ = std::fs::create_dir_all(path);
+                    sandbox::HostFilesystemLocation::new(path).ok()
+                })
+                .collect();
+            sandbox::SandboxFsPolicy::Restricted { writable_paths }
         };
         let network = match &self.network {
             SandboxNetworkAccess::None => sandbox::SandboxNetPolicy::Blocked,
@@ -169,7 +182,11 @@ impl SandboxWrap {
                     .collect(),
             },
         };
-        let git_dirs = self.git_dirs.clone();
+        let git_dirs = self
+            .git_dirs
+            .iter()
+            .filter_map(|path| sandbox::HostFilesystemLocation::new(path).ok())
+            .collect();
         let git = if self.allow_git_access {
             sandbox::GitSandboxPolicy::Allowed { git_dirs }
         } else {
@@ -238,6 +255,12 @@ pub(crate) async fn prepare_sandbox_wrap(
 
     let mut sandbox =
         sandbox::Sandbox::new(sandbox_wrap.to_policy()).map_err(anyhow::Error::new)?;
+    // Windows/WSL only: tell the sandbox which Linux `zed` to provision inside
+    // WSL as its `--wsl-sandbox-helper`. A no-op (and a no-op setter) elsewhere.
+    #[cfg(target_os = "windows")]
+    if let Some((channel, version)) = sandbox_wrap.wsl_zed_release.clone() {
+        sandbox.set_wsl_zed_release(channel, version);
+    }
     let command = sandbox::CommandAndArgs {
         program,
         args,

crates/agent/Cargo.toml

@@ -79,6 +79,11 @@ web_search.workspace = true
 zed_env_vars.workspace = true
 zstd.workspace = true
 
+# Used only on Windows to resolve the running release channel/version so the WSL
+# sandbox helper can fetch a matching Linux `zed`.
+[target.'cfg(target_os = "windows")'.dependencies]
+release_channel.workspace = true
+
 [dev-dependencies]
 assets.workspace = true
 async-io.workspace = true

crates/agent/src/sandboxing.rs

@@ -30,7 +30,9 @@ use feature_flags::{FeatureFlagAppExt as _, SandboxingFeatureFlag};
 use gpui::App;
 use http_proxy::HostPattern;
 use project::Project;
-use sandbox::{GitSandboxPolicy, SandboxFsPolicy, SandboxNetPolicy, SandboxPolicy};
+use sandbox::{
+    GitSandboxPolicy, HostFilesystemLocation, SandboxFsPolicy, SandboxNetPolicy, SandboxPolicy,
+};
 use settings::Settings;
 use std::path::PathBuf;
 
@@ -126,6 +128,13 @@ impl ThreadSandbox {
         match self {
             ThreadSandbox::Unsandboxed => ThreadSandbox::Unsandboxed,
             ThreadSandbox::Sandboxed(policy) => {
+                // Capture each `.git` location (pinning its inode / canonical
+                // path). A location that can't be captured (e.g. doesn't exist)
+                // is dropped — fail-closed.
+                let git_dirs = git_dirs
+                    .into_iter()
+                    .filter_map(|path| HostFilesystemLocation::new(path).ok())
+                    .collect();
                 let git = if allowed {
                     GitSandboxPolicy::Allowed { git_dirs }
                 } else {
@@ -158,7 +167,11 @@ pub fn settings_sandbox_policy(persistent: &SandboxPermissions) -> SandboxPolicy
         SandboxFsPolicy::Unrestricted
     } else {
         SandboxFsPolicy::Restricted {
-            writable_paths: persistent.write_paths.clone(),
+            writable_paths: persistent
+                .write_paths
+                .iter()
+                .filter_map(|path| HostFilesystemLocation::new(path).ok())
+                .collect(),
         }
     };
     let network = if persistent.allow_all_hosts {
@@ -437,7 +450,11 @@ impl ThreadSandboxGrants {
             SandboxFsPolicy::Unrestricted
         } else {
             SandboxFsPolicy::Restricted {
-                writable_paths: self.write_paths.clone(),
+                writable_paths: self
+                    .write_paths
+                    .iter()
+                    .filter_map(|path| HostFilesystemLocation::new(path).ok())
+                    .collect(),
             }
         };
         let network = if self.network_any_host {
@@ -613,6 +630,7 @@ pub(crate) fn insert_host_pattern(set: &mut Vec<HostPattern>, pattern: HostPatte
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::path::Path;
 
     fn hosts(list: &[&str]) -> NetworkRequest {
         NetworkRequest::Hosts(
@@ -644,9 +662,19 @@ mod tests {
 
     #[test]
     fn thread_sandbox_merge_unsandboxed_wins_else_unions_scopes() {
-        let policy = |paths: &[&str], hosts: &[&str]| SandboxPolicy {
+        // Writable paths are captured as real `HostFilesystemLocation`s (which
+        // open an fd and key on the inode), so the test uses real directories.
+        let dir_a = tempfile::tempdir().expect("create temp dir a");
+        let dir_b = tempfile::tempdir().expect("create temp dir b");
+        let path_a = dir_a.path();
+        let path_b = dir_b.path();
+
+        let policy = |paths: &[&Path], hosts: &[&str]| SandboxPolicy {
             fs: SandboxFsPolicy::Restricted {
-                writable_paths: paths.iter().map(PathBuf::from).collect(),
+                writable_paths: paths
+                    .iter()
+                    .map(|p| HostFilesystemLocation::new(p).expect("capture temp dir"))
+                    .collect(),
             },
             network: if hosts.is_empty() {
                 SandboxNetPolicy::Blocked
@@ -661,20 +689,20 @@ mod tests {
         // Unsandboxed on either side wins — the agent runs with ambient access.
         assert!(
             ThreadSandbox::Unsandboxed
-                .merge(ThreadSandbox::Sandboxed(policy(&["/a"], &["a.com"])))
+                .merge(ThreadSandbox::Sandboxed(policy(&[path_a], &["a.com"])))
                 .is_unsandboxed()
         );
         assert!(
-            ThreadSandbox::Sandboxed(policy(&["/a"], &["a.com"]))
+            ThreadSandbox::Sandboxed(policy(&[path_a], &["a.com"]))
                 .merge(ThreadSandbox::Unsandboxed)
                 .is_unsandboxed()
         );
 
         // Two sandboxed layers union their scopes.
         assert_eq!(
-            ThreadSandbox::Sandboxed(policy(&["/a"], &["a.com"]))
-                .merge(ThreadSandbox::Sandboxed(policy(&["/b"], &["b.com"]))),
-            ThreadSandbox::Sandboxed(policy(&["/a", "/b"], &["a.com", "b.com"]))
+            ThreadSandbox::Sandboxed(policy(&[path_a], &["a.com"]))
+                .merge(ThreadSandbox::Sandboxed(policy(&[path_b], &["b.com"]))),
+            ThreadSandbox::Sandboxed(policy(&[path_a, path_b], &["a.com", "b.com"]))
         );
     }
 
@@ -743,13 +771,19 @@ mod tests {
     fn thread_grants_to_policy_maps_paths_and_domains() {
         use sandbox::{SandboxFsPolicy, SandboxNetPolicy};
 
+        // `to_policy` captures real `HostFilesystemLocation`s, so use a real dir.
+        let build_dir = tempfile::tempdir().expect("create temp build dir");
+        let build_path = build_dir.path().to_str().expect("utf-8 temp path");
+
         let mut grants = ThreadSandboxGrants::default();
-        grants.record(&request(hosts(&["github.com"]), false, &["/tmp/build"]));
+        grants.record(&request(hosts(&["github.com"]), false, &[build_path]));
         let policy = grants.to_policy();
         assert_eq!(
             policy.fs,
             SandboxFsPolicy::Restricted {
-                writable_paths: vec![PathBuf::from("/tmp/build")]
+                writable_paths: vec![
+                    HostFilesystemLocation::new(build_dir.path()).expect("capture temp dir")
+                ]
             }
         );
         assert_eq!(
@@ -781,8 +815,10 @@ mod tests {
     fn settings_policy_maps_persistent_permissions() {
         use sandbox::{SandboxFsPolicy, SandboxNetPolicy};
 
+        // `settings_sandbox_policy` captures real `HostFilesystemLocation`s.
+        let log_dir = tempfile::tempdir().expect("create temp log dir");
         let persistent = SandboxPermissions {
-            write_paths: vec![PathBuf::from("/var/log")],
+            write_paths: vec![log_dir.path().to_path_buf()],
             network_hosts: vec!["*.npmjs.org".to_string()],
             ..Default::default()
         };
@@ -790,7 +826,9 @@ mod tests {
         assert_eq!(
             policy.fs,
             SandboxFsPolicy::Restricted {
-                writable_paths: vec![PathBuf::from("/var/log")]
+                writable_paths: vec![
+                    HostFilesystemLocation::new(log_dir.path()).expect("capture temp dir")
+                ]
             }
         );
         assert_eq!(

crates/agent/src/thread.rs

@@ -18,8 +18,8 @@ use crate::sandboxing::{
 use crate::tools::{SandboxGitPathCandidates, sandbox_git_paths};
 use agent_client_protocol::schema::v1 as acp;
 use agent_settings::{
-    AgentProfileId, AgentSettings, AutoCompactThreshold, COMPACTION_PROMPT,
-    SUMMARIZE_THREAD_DETAILED_PROMPT, SUMMARIZE_THREAD_PROMPT,
+    AgentProfileId, AgentProfileSettings, AgentSettings, AutoCompactThreshold, COMPACTION_PROMPT,
+    SUMMARIZE_THREAD_DETAILED_PROMPT, SUMMARIZE_THREAD_PROMPT, builtin_profiles,
 };
 use anyhow::{Context as _, Result, anyhow};
 use chrono::{DateTime, Local, Utc};
@@ -46,7 +46,7 @@ use language_model::{
     LanguageModelToolUse, LanguageModelToolUseId, MessageContent, Role, SelectedModel, Speed,
     StopReason, TokenUsage, ZED_CLOUD_PROVIDER_ID,
 };
-use project::Project;
+use project::{Project, trusted_worktrees::TrustedWorktrees};
 use prompt_store::ProjectContext;
 use schemars::{JsonSchema, Schema};
 use serde::de::DeserializeOwned;
@@ -1226,6 +1226,9 @@ pub struct Thread {
     initial_project_snapshot: Shared<Task<Option<Arc<ProjectSnapshot>>>>,
     pub(crate) context_server_registry: Entity<ContextServerRegistry>,
     profile_id: AgentProfileId,
+    /// Whether `profile_id` was downgraded to `minimal` at thread start because
+    /// the workspace is restricted. Used purely to surface a warning in the UI.
+    profile_downgraded_for_restricted_workspace: bool,
     project_context: Entity<ProjectContext>,
     pub(crate) templates: Arc<Templates>,
     model: ThreadModel,
@@ -1320,7 +1323,8 @@ impl Thread {
         cx: &mut Context<Self>,
     ) -> Self {
         let settings = AgentSettings::get_global(cx);
-        let profile_id = settings.default_profile.clone();
+        let (profile_id, profile_downgraded_for_restricted_workspace) =
+            Self::profile_for_restricted_workspace(settings.default_profile.clone(), &project, cx);
         let enable_thinking = settings
             .default_model
             .as_ref()
@@ -1363,6 +1367,7 @@ impl Thread {
             },
             context_server_registry,
             profile_id,
+            profile_downgraded_for_restricted_workspace,
             project_context,
             templates,
             model,
@@ -1395,6 +1400,8 @@ impl Thread {
         self.thinking_effort = parent.thinking_effort.clone();
         self.summarization_model = parent.summarization_model.clone();
         self.profile_id = parent.profile_id.clone();
+        self.profile_downgraded_for_restricted_workspace =
+            parent.profile_downgraded_for_restricted_workspace;
     }
 
     fn apply_model_selection(
@@ -1738,6 +1745,7 @@ impl Thread {
             initial_project_snapshot: Task::ready(db_thread.initial_project_snapshot).shared(),
             context_server_registry,
             profile_id,
+            profile_downgraded_for_restricted_workspace: false,
             project_context,
             templates,
             model,
@@ -2195,7 +2203,44 @@ impl Thread {
         &self.profile_id
     }
 
+    /// Whether this thread's profile was downgraded to `minimal` at thread start
+    /// because the workspace is restricted.
+    pub fn profile_was_downgraded(&self) -> bool {
+        self.profile_downgraded_for_restricted_workspace
+    }
+
+    /// Computes the profile a thread should start with, given the user's chosen
+    /// profile. In a restricted workspace, the built-in `write`/`ask` profiles
+    /// are downgraded to `minimal` — but only when both the chosen profile and
+    /// `minimal` are unmodified, shipped defaults, so we never override a user's
+    /// custom or customized profiles.
+    ///
+    /// Returns the (possibly downgraded) profile and whether a downgrade
+    /// happened.
+    fn profile_for_restricted_workspace(
+        profile_id: AgentProfileId,
+        project: &Entity<Project>,
+        cx: &App,
+    ) -> (AgentProfileId, bool) {
+        let is_write_or_ask = profile_id.as_str() == builtin_profiles::WRITE
+            || profile_id.as_str() == builtin_profiles::ASK;
+        let minimal = AgentProfileId(builtin_profiles::MINIMAL.into());
+        if is_write_or_ask
+            && TrustedWorktrees::has_restricted_worktrees(&project.read(cx).worktree_store(), cx)
+            && AgentProfileSettings::is_unmodified_default(&profile_id, cx)
+            && AgentProfileSettings::is_unmodified_default(&minimal, cx)
+        {
+            (minimal, true)
+        } else {
+            (profile_id, false)
+        }
+    }
+
     pub fn set_profile(&mut self, profile_id: AgentProfileId, cx: &mut Context<Self>) {
+        // An explicit selection means any earlier automatic downgrade no longer
+        // applies, even if the user re-selects the same profile.
+        self.profile_downgraded_for_restricted_workspace = false;
+
         if self.profile_id == profile_id {
             return;
         }
@@ -3458,6 +3503,26 @@ impl Thread {
         cancellation_rx: watch::Receiver<bool>,
         cx: &mut Context<Self>,
     ) -> Task<LanguageModelToolResult> {
+        // A workspace can become restricted after a thread has already started.
+        // Tools that aren't allowed in restricted workspaces must never run in
+        // that state, even though they were exposed to the model earlier.
+        if !tool.allow_in_restricted_mode()
+            && TrustedWorktrees::has_restricted_worktrees(
+                &self.project.read(cx).worktree_store(),
+                cx,
+            )
+        {
+            return Task::ready(LanguageModelToolResult {
+                tool_use_id,
+                tool_name,
+                is_error: true,
+                content: vec![LanguageModelToolResultContent::Text(Arc::from(
+                    "workspace has become restricted",
+                ))],
+                output: None,
+            });
+        }
+
         let fs = self.project.read(cx).fs().clone();
         let tool_event_stream = ToolCallEventStream::new(
             tool_use_id.clone(),
@@ -3936,9 +4001,16 @@ impl Thread {
         // to the model under that name.
         let use_sandboxed_terminal = sandboxing_enabled_for_project(self.project.read(cx), cx);
 
+        // Tools that aren't allowed in restricted workspaces must never be
+        // provided to the model while the workspace is restricted, regardless
+        // of what the active profile enables.
+        let is_restricted =
+            TrustedWorktrees::has_restricted_worktrees(&self.project.read(cx).worktree_store(), cx);
+
         let mut tools = self
             .tools
             .iter()
+            .filter(|(_, tool)| !is_restricted || tool.allow_in_restricted_mode())
             .filter_map(|(tool_name, tool)| {
                 let terminal_variant = matches!(
                     tool_name.as_ref(),
@@ -4904,6 +4976,14 @@ where
         true
     }
 
+    /// Whether this tool may be provided to an agent in a restricted workspace.
+    ///
+    /// Tools that return `false` are never exposed to the model while the
+    /// workspace is restricted, and will fail if invoked in that state.
+    fn allow_in_restricted_mode() -> bool {
+        true
+    }
+
     /// Runs the tool with the provided input.
     ///
     /// Returns `Result<Self::Output, Self::Output>` rather than `Result<Self::Output, anyhow::Error>`
@@ -4967,6 +5047,9 @@ pub trait AnyAgentTool {
     fn supports_provider(&self, _provider: &LanguageModelProviderId) -> bool {
         true
     }
+    fn allow_in_restricted_mode(&self) -> bool {
+        true
+    }
     /// See [`AgentTool::run`] for why this returns `Result<AgentToolOutput, AgentToolOutput>`.
     fn run(
         self: Arc<Self>,
@@ -5018,6 +5101,10 @@ where
         T::supports_provider(provider)
     }
 
+    fn allow_in_restricted_mode(&self) -> bool {
+        T::allow_in_restricted_mode()
+    }
+
     fn run(
         self: Arc<Self>,
         input: ToolInput<serde_json::Value>,

crates/agent/src/tools.rs

@@ -138,6 +138,18 @@ macro_rules! tools {
             false
         }
 
+        /// Returns whether the tool with the given name may be provided to an
+        /// agent in a restricted workspace. Unknown tools (e.g. MCP tools) are
+        /// considered allowed.
+        pub fn tool_allowed_in_restricted_mode(name: &str) -> bool {
+            $(
+                if name == <$tool>::NAME {
+                    return <$tool>::allow_in_restricted_mode();
+                }
+            )*
+            true
+        }
+
         /// A list of all built-in tools
         pub fn built_in_tools() -> impl Iterator<Item = LanguageModelRequestTool> {
             fn language_model_tool<T: AgentTool>() -> LanguageModelRequestTool {
@@ -219,3 +231,25 @@ pub fn tool_feature_flag_enabled(tool_name: &str, cx: &App) -> bool {
         _ => true,
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn fetch_and_terminal_are_forbidden_in_restricted_mode() {
+        assert!(!tool_allowed_in_restricted_mode(FetchTool::NAME));
+        assert!(!tool_allowed_in_restricted_mode(TerminalTool::NAME));
+
+        // Every other built-in tool, and unknown (e.g. MCP) tools, are allowed.
+        for name in ALL_TOOL_NAMES {
+            let expected = *name != FetchTool::NAME && *name != TerminalTool::NAME;
+            assert_eq!(
+                tool_allowed_in_restricted_mode(name),
+                expected,
+                "unexpected restricted-mode policy for tool `{name}`"
+            );
+        }
+        assert!(tool_allowed_in_restricted_mode("some_mcp_tool"));
+    }
+}

crates/agent/src/tools/fetch_tool.rs

@@ -124,6 +124,10 @@ impl AgentTool for FetchTool {
         acp::ToolKind::Fetch
     }
 
+    fn allow_in_restricted_mode() -> bool {
+        false
+    }
+
     fn initial_title(
         &self,
         input: Result<Self::Input, serde_json::Value>,

crates/agent/src/tools/terminal_tool.rs

@@ -298,6 +298,10 @@ impl AgentTool for TerminalTool {
         acp::ToolKind::Execute
     }
 
+    fn allow_in_restricted_mode() -> bool {
+        false
+    }
+
     fn initial_title(
         &self,
         input: Result<Self::Input, serde_json::Value>,
@@ -336,6 +340,10 @@ impl AgentTool for SandboxedTerminalTool {
         acp::ToolKind::Execute
     }
 
+    fn allow_in_restricted_mode() -> bool {
+        false
+    }
+
     fn initial_title(
         &self,
         input: Result<Self::Input, serde_json::Value>,
@@ -372,6 +380,32 @@ fn terminal_initial_title(input: Result<String, serde_json::Value>) -> SharedStr
     }
 }
 
+/// Windows only: resolve the `(release channel, version)` of the Linux `zed` to
+/// provision inside WSL as the sandbox helper. Dev (source) builds have no
+/// matching release, so they pull the latest nightly; every other channel pins
+/// its exact running version (stripped of pre-release/build metadata, which the
+/// release API doesn't key on).
+#[cfg(target_os = "windows")]
+fn wsl_zed_release(cx: &App) -> Option<(String, String)> {
+    use release_channel::{AppVersion, ReleaseChannel};
+    match *release_channel::RELEASE_CHANNEL {
+        ReleaseChannel::Dev => Some(("nightly".to_string(), "latest".to_string())),
+        channel => {
+            let version = AppVersion::global(cx);
+            Some((
+                channel.dev_name().to_string(),
+                format!("{}.{}.{}", version.major, version.minor, version.patch),
+            ))
+        }
+    }
+}
+
+/// Non-Windows platforms don't route through WSL, so there's no helper to fetch.
+#[cfg(not(target_os = "windows"))]
+fn wsl_zed_release(_cx: &App) -> Option<(String, String)> {
+    None
+}
+
 async fn run_terminal_tool(
     project: Entity<Project>,
     environment: Rc<dyn ThreadEnvironment>,
@@ -382,17 +416,26 @@ async fn run_terminal_tool(
     let selection = input.selection;
     let sandbox_input = input.sandbox.clone().unwrap_or_default();
 
-    let (working_dir, authorize, sandboxing, is_local_project) = cx.update(|cx| {
-        let working_dir = working_dir(&input.cd, &project, cx).map_err(|err| err.to_string())?;
-        let context =
-            crate::ToolPermissionContext::new(TerminalTool::NAME, vec![input.command.clone()]);
-        let authorize =
-            event_stream.authorize(SharedString::new(input.command.clone()), context, cx);
-        let sandboxing =
-            input.sandbox.is_some() && sandboxing_enabled_for_project(project.read(cx), cx);
-        let is_local_project = project.read(cx).is_local();
-        Result::<_, String>::Ok((working_dir, authorize, sandboxing, is_local_project))
-    })?;
+    let (working_dir, authorize, sandboxing, is_local_project, wsl_zed_release) =
+        cx.update(|cx| {
+            let working_dir =
+                working_dir(&input.cd, &project, cx).map_err(|err| err.to_string())?;
+            let context =
+                crate::ToolPermissionContext::new(TerminalTool::NAME, vec![input.command.clone()]);
+            let authorize =
+                event_stream.authorize(SharedString::new(input.command.clone()), context, cx);
+            let sandboxing =
+                input.sandbox.is_some() && sandboxing_enabled_for_project(project.read(cx), cx);
+            let is_local_project = project.read(cx).is_local();
+            let wsl_zed_release = wsl_zed_release(cx);
+            Result::<_, String>::Ok((
+                working_dir,
+                authorize,
+                sandboxing,
+                is_local_project,
+                wsl_zed_release,
+            ))
+        })?;
 
     authorize.await.map_err(|e| e.to_string())?;
 
@@ -621,6 +664,7 @@ async fn run_terminal_tool(
                 network: network_request_to_sandbox_network_access(&effective.network),
                 allow_fs_write: effective.allow_fs_write_all,
                 is_local: is_local_project,
+                wsl_zed_release: wsl_zed_release.clone(),
             };
 
             // The viability check runs a brief probe subprocess, so do it off
@@ -637,10 +681,9 @@ async fn run_terminal_tool(
                 let mut retries = 0usize;
                 loop {
                     let probe_wrap = wrap.clone();
-                    let probe_cwd = working_dir.clone();
                     let error = match cx
                         .background_executor()
-                        .spawn(async move { probe_wrap.can_create_sandbox(probe_cwd.as_deref()) })
+                        .spawn(async move { probe_wrap.can_create_sandbox() })
                         .await
                     {
                         Ok(()) => break Some(wrap),
@@ -686,10 +729,9 @@ async fn run_terminal_tool(
             #[cfg(not(target_os = "linux"))]
             {
                 let probe_wrap = wrap.clone();
-                let probe_cwd = working_dir.clone();
                 match cx
                     .background_executor()
-                    .spawn(async move { probe_wrap.can_create_sandbox(probe_cwd.as_deref()) })
+                    .spawn(async move { probe_wrap.can_create_sandbox() })
                     .await
                 {
                     Ok(()) => Some(wrap),

crates/agent_settings/src/agent_profile.rs

@@ -7,7 +7,7 @@ use fs::Fs;
 use gpui::{App, SharedString};
 use settings::{
     AgentProfileContent, ContextServerPresetContent, LanguageModelSelection, Settings as _,
-    SettingsContent, update_settings_file,
+    SettingsContent, SettingsStore, update_settings_file,
 };
 use util::ResultExt as _;
 
@@ -116,6 +116,32 @@ impl AgentProfileSettings {
         self.tools.get(tool_name) == Some(&true)
     }
 
+    /// Whether the built-in profile with the given id still matches the shipped
+    /// default — i.e. the user has neither customized the built-in profile nor
+    /// shadowed it with a custom profile of the same id. Custom profile ids are
+    /// never considered unmodified defaults.
+    pub fn is_unmodified_default(profile_id: &AgentProfileId, cx: &App) -> bool {
+        if !builtin_profiles::is_builtin(profile_id) {
+            return false;
+        }
+        let store = cx.global::<SettingsStore>();
+        let profile_in = |content: &SettingsContent| {
+            content
+                .agent
+                .as_ref()
+                .and_then(|agent| agent.profiles.as_ref())
+                .and_then(|profiles| profiles.get(profile_id.as_str()))
+                .cloned()
+        };
+        match (
+            profile_in(store.merged_settings()),
+            profile_in(store.raw_default_settings()),
+        ) {
+            (Some(merged), Some(default)) => merged == default,
+            _ => false,
+        }
+    }
+
     pub fn is_context_server_tool_enabled(&self, server_id: &str, tool_name: &str) -> bool {
         self.context_servers
             .get(server_id)
@@ -247,4 +273,37 @@ mod tests {
         assert!(!profile.is_context_server_tool_enabled("server", "other_tool"));
         assert!(!profile.is_context_server_tool_enabled("other_server", "any_tool"));
     }
+
+    #[gpui::test]
+    fn unmodified_default_detection(cx: &mut gpui::App) {
+        use gpui::UpdateGlobal as _;
+
+        let store = SettingsStore::test(cx);
+        cx.set_global(store);
+        project::DisableAiSettings::register(cx);
+        AgentSettings::register(cx);
+
+        let write = AgentProfileId(builtin_profiles::WRITE.into());
+        let minimal = AgentProfileId(builtin_profiles::MINIMAL.into());
+        let custom = AgentProfileId("custom".into());
+
+        // Fresh defaults: the shipped built-in profiles are unmodified.
+        assert!(AgentProfileSettings::is_unmodified_default(&write, cx));
+        assert!(AgentProfileSettings::is_unmodified_default(&minimal, cx));
+        // Custom (non-built-in) ids are never considered unmodified defaults.
+        assert!(!AgentProfileSettings::is_unmodified_default(&custom, cx));
+
+        // The user customizes the `write` profile; `minimal` stays untouched.
+        SettingsStore::update_global(cx, |store, cx| {
+            store
+                .set_user_settings(
+                    r#"{ "agent": { "profiles": { "write": { "name": "Write", "tools": { "fetch": false } } } } }"#,
+                    cx,
+                )
+                .unwrap();
+        });
+
+        assert!(!AgentProfileSettings::is_unmodified_default(&write, cx));
+        assert!(AgentProfileSettings::is_unmodified_default(&minimal, cx));
+    }
 }

crates/agent_ui/src/conversation_view.rs

@@ -244,6 +244,17 @@ impl ProfileProvider for Entity<agent::Thread> {
     fn model_selected(&self, cx: &App) -> bool {
         self.read(cx).model().is_some()
     }
+
+    fn is_restricted(&self, cx: &App) -> bool {
+        project::trusted_worktrees::TrustedWorktrees::has_restricted_worktrees(
+            &self.read(cx).project().read(cx).worktree_store(),
+            cx,
+        )
+    }
+
+    fn profile_downgraded(&self, cx: &App) -> bool {
+        self.read(cx).profile_was_downgraded()
+    }
 }
 
 #[derive(Default)]

crates/agent_ui/src/conversation_view/thread_view.rs

@@ -4645,7 +4645,7 @@ impl ThreadView {
             // Sandboxed by settings, but disabled for this thread: show the
             // settings scope (greyed) for context above the disabled status.
             (ThreadSandbox::Sandboxed(settings_policy), ThreadSandbox::Unsandboxed) => {
-                let settings = augment_settings_sandbox_policy(settings_policy, baseline);
+                let settings = augment_settings_sandbox_policy(&settings_policy, baseline);
                 SandboxStatusTooltip::disabled_for_thread(sandbox_section(
                     "Defined in your settings:",
                     &settings,
@@ -4656,10 +4656,11 @@ impl ThreadView {
                 ThreadSandbox::Sandboxed(settings_policy),
                 ThreadSandbox::Sandboxed(thread_policy),
             ) => {
-                let settings = augment_settings_sandbox_policy(settings_policy, baseline);
+                let settings = augment_settings_sandbox_policy(&settings_policy, baseline);
+                let thread = SandboxPolicyDisplay::from_policy(&thread_policy);
                 // Omit the per-thread section when it grants nothing extra.
-                let thread = (!sandbox_policy_grants_nothing(&thread_policy))
-                    .then(|| sandbox_section("Allowed for this thread:", &thread_policy, false));
+                let thread = (!sandbox_policy_grants_nothing(&thread))
+                    .then(|| sandbox_section("Allowed for this thread:", &thread, false));
                 SandboxStatusTooltip::enabled(
                     sandbox_section("Defined in your settings:", &settings, true),
                     thread,
@@ -5604,6 +5605,83 @@ impl Render for TokenUsageTooltip {
     }
 }
 
+/// A display-ready snapshot of a sandbox policy for the status tooltip.
+///
+/// The opaque `HostFilesystemLocation`s in a policy are stringified up front,
+/// when this is built, so the tooltip state (which outlives the build and is
+/// captured by the lazy tooltip closure) never holds the locations' fds open.
+#[derive(Clone)]
+struct SandboxPolicyDisplay {
+    fs: SandboxFsDisplay,
+    network: SandboxNetPolicy,
+    git: SandboxGitDisplay,
+}
+
+/// The filesystem write-access portion of a [`SandboxPolicyDisplay`].
+#[derive(Clone)]
+enum SandboxFsDisplay {
+    Unrestricted,
+    Restricted(Vec<WritableEntryDisplay>),
+}
+
+/// A single writable entry to display in the sandbox tooltip: either a real host
+/// location (already stringified for display) or the Linux-only host-isolated
+/// `/tmp` overlay, which has no backing host path and is purely a label.
+#[derive(Clone)]
+enum WritableEntryDisplay {
+    Path(String),
+    // Only ever constructed on Linux (the bwrap `--tmpfs /tmp` overlay), so the
+    // variant is gated to match and avoid dead-code warnings elsewhere.
+    #[cfg(target_os = "linux")]
+    IsolatedTmp,
+}
+
+/// The Git-access portion of a [`SandboxPolicyDisplay`]: whether `.git` writes
+/// are granted, and the (display-only) `.git` directories the policy governs.
+#[derive(Clone)]
+struct SandboxGitDisplay {
+    allowed: bool,
+    git_dirs: Vec<String>,
+}
+
+impl SandboxPolicyDisplay {
+    /// Display a policy verbatim (used for the per-thread overrides, which carry
+    /// no implicit baseline grants). Takes the policy by reference and stringifies
+    /// its locations immediately, so no fd is retained past this call.
+    fn from_policy(policy: &SandboxPolicy) -> Self {
+        let fs = match &policy.fs {
+            SandboxFsPolicy::Unrestricted => SandboxFsDisplay::Unrestricted,
+            SandboxFsPolicy::Restricted { writable_paths } => SandboxFsDisplay::Restricted(
+                writable_paths
+                    .iter()
+                    .map(|location| {
+                        WritableEntryDisplay::Path(location.untrusted_path_display().to_string())
+                    })
+                    .collect(),
+            ),
+        };
+        SandboxPolicyDisplay {
+            fs,
+            network: policy.network.clone(),
+            git: SandboxGitDisplay::from_policy(&policy.git),
+        }
+    }
+}
+
+impl SandboxGitDisplay {
+    /// Stringify a Git policy's `.git` directories for display, retaining no fds.
+    fn from_policy(git: &GitSandboxPolicy) -> Self {
+        SandboxGitDisplay {
+            allowed: git.allows_writes(),
+            git_dirs: git
+                .git_dirs()
+                .iter()
+                .map(|location| location.untrusted_path_display().to_string())
+                .collect(),
+        }
+    }
+}
+
 /// Fold the always-granted baseline writable paths (the project's worktree
 /// roots, derived from the same source the terminal tool uses) and, on Linux,
 /// the host-isolated `/tmp` overlay into a settings policy for display. These
@@ -5612,27 +5690,51 @@ impl Render for TokenUsageTooltip {
 /// section rather than stored. A no-op when the fs is unrestricted (rendered as
 /// "All paths"), since there's nothing to scope.
 fn augment_settings_sandbox_policy(
-    mut policy: SandboxPolicy,
+    policy: &SandboxPolicy,
     baseline: Vec<PathBuf>,
-) -> SandboxPolicy {
-    if let SandboxFsPolicy::Restricted { writable_paths } = &mut policy.fs {
-        let mut merged = baseline;
-        for path in writable_paths.drain(..) {
-            if !merged.contains(&path) {
-                merged.push(path);
+) -> SandboxPolicyDisplay {
+    let fs = match &policy.fs {
+        SandboxFsPolicy::Unrestricted => SandboxFsDisplay::Unrestricted,
+        SandboxFsPolicy::Restricted { writable_paths } => {
+            // Dedup by display string. We deliberately don't open the locations'
+            // fds to dedup by inode here: this is a display-only tooltip and the
+            // string is the location's identity for that purpose. The string can
+            // only diverge from the captured inode while a symlink-swap is
+            // actively in progress, and in that case the bind validator refuses
+            // to run the command at all (see the `sandbox` crate) — so showing the
+            // requested path is always safe, and not worth a blocking syscall on
+            // the render path.
+            let mut merged: Vec<String> = Vec::new();
+            let baseline_paths = baseline.iter().map(|path| path.display().to_string());
+            let granted_paths = writable_paths
+                .iter()
+                .map(|location| location.untrusted_path_display().to_string());
+            for path in baseline_paths.chain(granted_paths) {
+                if !merged.contains(&path) {
+                    merged.push(path);
+                }
             }
+            // `mut` is only needed on Linux, where the isolated `/tmp` entry is
+            // pushed below.
+            #[cfg_attr(not(target_os = "linux"), allow(unused_mut))]
+            let mut entries: Vec<WritableEntryDisplay> =
+                merged.into_iter().map(WritableEntryDisplay::Path).collect();
+            // The ephemeral, host-isolated tmpfs at /tmp is Linux-specific (the
+            // bwrap `--tmpfs /tmp` overlay). It's a display-only label, not a
+            // real host path, so it can't be a captured location.
+            #[cfg(target_os = "linux")]
+            entries.push(WritableEntryDisplay::IsolatedTmp);
+            SandboxFsDisplay::Restricted(entries)
         }
-        // The ephemeral, host-isolated tmpfs at /tmp is Linux-specific (the
-        // bwrap `--tmpfs /tmp` overlay). It's a display-only label, not a real
-        // host path, so it can't come from the path source above.
-        #[cfg(target_os = "linux")]
-        merged.push(PathBuf::from("/tmp (isolated)"));
-        *writable_paths = merged;
+    };
+    SandboxPolicyDisplay {
+        fs,
+        network: policy.network.clone(),
+        git: SandboxGitDisplay::from_policy(&policy.git),
     }
-    policy
 }
 
-fn sandbox_section(title: &str, policy: &SandboxPolicy, show_empty: bool) -> SandboxSection {
+fn sandbox_section(title: &str, policy: &SandboxPolicyDisplay, show_empty: bool) -> SandboxSection {
     let write_empty = fs_grants_nothing(&policy.fs);
     let network_empty = network_grants_nothing(&policy.network);
     let git_empty = git_grants_nothing(&policy.git);
@@ -5659,7 +5761,7 @@ fn sandbox_section(title: &str, policy: &SandboxPolicy, show_empty: bool) -> San
 
 /// Whether a policy grants nothing worth surfacing, used to decide whether to
 /// show the per-thread overrides section at all.
-fn sandbox_policy_grants_nothing(policy: &SandboxPolicy) -> bool {
+fn sandbox_policy_grants_nothing(policy: &SandboxPolicyDisplay) -> bool {
     fs_grants_nothing(&policy.fs)
         && network_grants_nothing(&policy.network)
         && git_grants_nothing(&policy.git)
@@ -5667,24 +5769,26 @@ fn sandbox_policy_grants_nothing(policy: &SandboxPolicy) -> bool {
 
 /// Git access grants nothing to surface unless `.git` writes are allowed *and*
 /// at least one `.git` directory is known.
-fn git_grants_nothing(git: &GitSandboxPolicy) -> bool {
-    !git.allows_writes() || git.git_dirs().is_empty()
+fn git_grants_nothing(git: &SandboxGitDisplay) -> bool {
+    !git.allowed || git.git_dirs.is_empty()
 }
 
 /// Rows for the Git-access group: one row per writable `.git` directory (these
 /// may live outside the project for a linked worktree).
-fn sandbox_git_rows(git: &GitSandboxPolicy) -> Vec<SandboxRow> {
-    match git {
-        GitSandboxPolicy::Allowed { git_dirs } if !git_dirs.is_empty() => git_dirs
-            .iter()
-            .map(|path| SandboxRow::git(path.clone()))
-            .collect(),
-        _ => Vec::new(),
+fn sandbox_git_rows(git: &SandboxGitDisplay) -> Vec<SandboxRow> {
+    if !git.allowed {
+        return Vec::new();
     }
+    git.git_dirs
+        .iter()
+        // The display string was captured up front; reconstruct a throwaway path
+        // here purely to render a label + icon (never used as an identity).
+        .map(|dir| SandboxRow::git(PathBuf::from(dir)))
+        .collect()
 }
 
-fn fs_grants_nothing(fs: &SandboxFsPolicy) -> bool {
-    matches!(fs, SandboxFsPolicy::Restricted { writable_paths } if writable_paths.is_empty())
+fn fs_grants_nothing(fs: &SandboxFsDisplay) -> bool {
+    matches!(fs, SandboxFsDisplay::Restricted(entries) if entries.is_empty())
 }
 
 fn network_grants_nothing(network: &SandboxNetPolicy) -> bool {
@@ -5697,15 +5801,22 @@ fn network_grants_nothing(network: &SandboxNetPolicy) -> bool {
 
 /// Rows for the write-access group: a message for the "all"/"none" cases, or one
 /// row per granted path.
-fn sandbox_fs_rows(fs: &SandboxFsPolicy) -> Vec<SandboxRow> {
+fn sandbox_fs_rows(fs: &SandboxFsDisplay) -> Vec<SandboxRow> {
     match fs {
-        SandboxFsPolicy::Unrestricted => vec![SandboxRow::message("All paths (unrestricted)")],
-        SandboxFsPolicy::Restricted { writable_paths } if writable_paths.is_empty() => {
+        SandboxFsDisplay::Unrestricted => vec![SandboxRow::message("All paths (unrestricted)")],
+        SandboxFsDisplay::Restricted(entries) if entries.is_empty() => {
             vec![SandboxRow::message("None")]
         }
-        SandboxFsPolicy::Restricted { writable_paths } => writable_paths
+        SandboxFsDisplay::Restricted(entries) => entries
             .iter()
-            .map(|path| SandboxRow::path(path.clone()))
+            .map(|entry| match entry {
+                // The display string was captured up front; see `sandbox_git_rows`.
+                WritableEntryDisplay::Path(path) => SandboxRow::path(PathBuf::from(path)),
+                #[cfg(target_os = "linux")]
+                WritableEntryDisplay::IsolatedTmp => {
+                    SandboxRow::path(PathBuf::from("/tmp (isolated)"))
+                }
+            })
             .collect(),
     }
 }
@@ -8265,27 +8376,23 @@ impl ThreadView {
                         }),
                 )
                 .when(has_host_list && is_open, |this| {
-                    this.child(
-                        v_flex()
-                            .id(("sandbox-network-hosts-list", entry_ix))
-                            .max_h_40()
-                            .overflow_y_scroll()
-                            .children(hosts.iter().enumerate().map(|(host_ix, host)| {
-                                h_flex()
-                                    .min_w_0()
-                                    .px_2()
-                                    .py_1p5()
-                                    .bg(cx.theme().colors().editor_background)
-                                    .when(host_ix < hosts.len() - 1, |this| {
-                                        this.border_b_1().border_color(cx.theme().colors().border)
-                                    })
-                                    .child(
-                                        Label::new(host.clone())
-                                            .size(LabelSize::XSmall)
-                                            .buffer_font(cx),
-                                    )
-                            })),
-                    )
+                    this.child(v_flex().children(hosts.iter().enumerate().map(
+                        |(host_ix, host)| {
+                            h_flex()
+                                .min_w_0()
+                                .px_2()
+                                .py_1p5()
+                                .bg(cx.theme().colors().editor_background)
+                                .when(host_ix < hosts.len() - 1, |this| {
+                                    this.border_b_1().border_color(cx.theme().colors().border)
+                                })
+                                .child(
+                                    Label::new(host.clone())
+                                        .size(LabelSize::XSmall)
+                                        .buffer_font(cx),
+                                )
+                        },
+                    )))
                 })
         });
 
@@ -8368,21 +8475,17 @@ impl ThreadView {
                         }),
                 )
                 .when(has_path_list && is_open, |this| {
-                    this.child(
-                        v_flex()
-                            .id(("sandbox-authorization-paths-list", entry_ix))
-                            .max_h_40()
-                            .overflow_y_scroll()
-                            .children(paths.iter().enumerate().map(|(path_ix, path)| {
-                                self.render_sandbox_authorization_path_row(
-                                    entry_ix,
-                                    path_ix,
-                                    path,
-                                    path_ix < paths.len() - 1,
-                                    cx,
-                                )
-                            })),
-                    )
+                    this.child(v_flex().children(paths.iter().enumerate().map(
+                        |(path_ix, path)| {
+                            self.render_sandbox_authorization_path_row(
+                                entry_ix,
+                                path_ix,
+                                path,
+                                path_ix < paths.len() - 1,
+                                cx,
+                            )
+                        },
+                    )))
                 })
         });
 
@@ -8439,9 +8542,9 @@ impl ThreadView {
         v_flex()
             .border_t_1()
             .border_color(self.tool_card_border_color(cx))
+            .children(git_access_section)
             .children(network_section)
             .children(write_section)
-            .children(git_access_section)
             .children(unsandboxed_section)
             .children(reason_section)
             .into_any_element()

crates/agent_ui/src/profile_selector.rs

@@ -18,8 +18,9 @@ use std::{
 };
 use ui::{
     DocumentationAside, HighlightedLabel, KeyBinding, LabelSize, ListItem, ListItemSpacing,
-    PopoverMenuHandle, Tooltip, prelude::*,
+    PopoverMenuHandle, TintColor, Tooltip, prelude::*,
 };
+use workspace::ToggleWorktreeSecurity;
 
 /// Trait for types that can provide and manage agent profiles
 pub trait ProfileProvider {
@@ -34,6 +35,22 @@ pub trait ProfileProvider {
 
     /// Check if there is a model selected in the current context.
     fn model_selected(&self, cx: &App) -> bool;
+
+    /// Whether the current workspace is restricted (has untrusted worktrees).
+    ///
+    /// In a restricted workspace, profiles that enable tools forbidden in
+    /// restricted mode are flagged, and the active built-in `write`/`ask`
+    /// profiles are downgraded to `minimal`.
+    fn is_restricted(&self, _cx: &App) -> bool {
+        false
+    }
+
+    /// Whether the active profile has been downgraded to `minimal` because the
+    /// workspace is restricted (i.e. the user selected `write`/`ask`, but those
+    /// profiles aren't honored while restricted).
+    fn profile_downgraded(&self, _cx: &App) -> bool {
+        false
+    }
 }
 
 pub struct ProfileSelector {
@@ -188,9 +205,23 @@ impl Render for ProfileSelector {
             IconName::ChevronDown
         };
 
+        // Warn when the active profile is affected by a restricted workspace:
+        // either it was downgraded to `minimal`, or it still enables tools that
+        // are forbidden while restricted.
+        let show_warning = self.provider.is_restricted(cx)
+            && (self.provider.profile_downgraded(cx)
+                || !ProfilePickerDelegate::restricted_forbidden_tools(&profile_id, cx).is_empty());
+
         let trigger_button = Button::new("profile-selector", selected_profile)
             .label_size(LabelSize::Small)
             .color(Color::Muted)
+            .when(show_warning, |this| {
+                this.start_icon(
+                    Icon::new(IconName::Warning)
+                        .size(IconSize::XSmall)
+                        .color(Color::Warning),
+                )
+            })
             .end_icon(Icon::new(icon).size(IconSize::XSmall).color(Color::Muted));
 
         let tooltip: Box<dyn Fn(&mut Window, &mut App) -> AnyView> = Box::new(Tooltip::element({
@@ -339,6 +370,22 @@ impl ProfilePickerDelegate {
             .collect()
     }
 
+    /// Tools enabled by a profile that are forbidden while the workspace is
+    /// restricted. Returns an empty list for profiles that are safe to use.
+    fn restricted_forbidden_tools(profile_id: &AgentProfileId, cx: &App) -> Vec<SharedString> {
+        let Some(profile) = AgentSettings::get_global(cx).profiles.get(profile_id) else {
+            return Vec::new();
+        };
+        profile
+            .tools
+            .iter()
+            .filter(|(name, enabled)| {
+                **enabled && !agent::tool_allowed_in_restricted_mode(name.as_ref())
+            })
+            .map(|(name, _)| SharedString::from(name.to_string()))
+            .collect()
+    }
+
     fn documentation(candidate: &ProfileCandidate) -> Option<&'static str> {
         match candidate.id.as_str() {
             builtin_profiles::WRITE => Some("Get help to write anything."),
@@ -594,10 +641,17 @@ impl PickerDelegate for ProfilePickerDelegate {
                 let is_active = active_id == candidate.id;
                 let has_documentation = Self::documentation(candidate).is_some();
 
+                let has_warning = self.provider.is_restricted(cx)
+                    && !Self::restricted_forbidden_tools(&candidate.id, cx).is_empty();
+                // The warning details are merged into the documentation aside,
+                // so hovering either the row or the icon shows a single popup.
+                let track_hover = has_documentation || has_warning;
+                let has_end_slot = is_active || has_warning;
+
                 Some(
                     div()
                         .id(("profile-picker-item", ix))
-                        .when(has_documentation, |this| {
+                        .when(track_hover, |this| {
                             this.on_hover(cx.listener(move |picker, hovered, _, cx| {
                                 if *hovered {
                                     picker.delegate.hovered_index = Some(ix);
@@ -616,11 +670,23 @@ impl PickerDelegate for ProfilePickerDelegate {
                                     candidate.name.clone(),
                                     entry.positions.clone(),
                                 ))
-                                .when(is_active, |this| {
+                                .when(has_end_slot, |this| {
                                     this.end_slot(
-                                        div()
+                                        h_flex()
+                                            .gap_1()
                                             .pr_2()
-                                            .child(Icon::new(IconName::Check).color(Color::Accent)),
+                                            .when(has_warning, |this| {
+                                                this.child(
+                                                    Icon::new(IconName::Warning)
+                                                        .size(IconSize::Small)
+                                                        .color(Color::Warning),
+                                                )
+                                            })
+                                            .when(is_active, |this| {
+                                                this.child(
+                                                    Icon::new(IconName::Check).color(Color::Accent),
+                                                )
+                                            }),
                                     )
                                 }),
                         )
@@ -644,13 +710,61 @@ impl PickerDelegate for ProfilePickerDelegate {
         };
 
         let candidate = self.candidates.get(entry.candidate_index)?;
-        let docs_aside = Self::documentation(candidate)?.to_string();
+        let description = Self::documentation(candidate).map(|docs| docs.to_string());
+        let forbidden_tools = if self.provider.is_restricted(cx) {
+            Self::restricted_forbidden_tools(&candidate.id, cx)
+        } else {
+            Vec::new()
+        };
+
+        // Nothing to show: no description and no restricted-tool warning.
+        if description.is_none() && forbidden_tools.is_empty() {
+            return None;
+        }
 
         let side = documentation_aside_side(cx);
 
         Some(DocumentationAside {
             side,
-            render: Rc::new(move |_| Label::new(docs_aside.clone()).into_any_element()),
+            render: Rc::new(move |cx| {
+                v_flex()
+                    .gap_1p5()
+                    .when_some(description.clone(), |this, description| {
+                        this.child(Label::new(description))
+                    })
+                    .when(!forbidden_tools.is_empty(), |this| {
+                        this.when(description.is_some(), |this| {
+                            this.child(
+                                div()
+                                    .border_t_1()
+                                    .border_color(cx.theme().colors().border_variant),
+                            )
+                        })
+                        .child(
+                            v_flex()
+                                .gap_0p5()
+                                .child(
+                                    h_flex()
+                                        .gap_1()
+                                        .child(
+                                            Icon::new(IconName::Warning)
+                                                .size(IconSize::XSmall)
+                                                .color(Color::Warning),
+                                        )
+                                        .child(
+                                            Label::new("Disabled in Restricted Mode")
+                                                .size(LabelSize::Small),
+                                        ),
+                                )
+                                .children(forbidden_tools.iter().map(|tool| {
+                                    Label::new(format!("• {tool}"))
+                                        .size(LabelSize::Small)
+                                        .color(Color::Muted)
+                                })),
+                        )
+                    })
+                    .into_any_element()
+            }),
         })
     }
 
@@ -664,29 +778,66 @@ impl PickerDelegate for ProfilePickerDelegate {
         cx: &mut Context<Picker<Self>>,
     ) -> Option<gpui::AnyElement> {
         let focus_handle = self.focus_handle.clone();
+        let is_restricted = self.provider.is_restricted(cx);
 
         Some(
-            h_flex()
+            v_flex()
                 .w_full()
-                .border_t_1()
-                .border_color(cx.theme().colors().border_variant)
-                .p_1p5()
                 .child(
-                    Button::new("configure", "Configure")
-                        .full_width()
-                        .style(ButtonStyle::Outlined)
-                        .key_binding(
-                            KeyBinding::for_action_in(
-                                &ManageProfiles::default(),
-                                &focus_handle,
-                                cx,
-                            )
-                            .map(|kb| kb.size(rems_from_px(12.))),
-                        )
-                        .on_click(|_, window, cx| {
-                            window.dispatch_action(ManageProfiles::default().boxed_clone(), cx);
-                        }),
+                    h_flex()
+                        .w_full()
+                        .border_t_1()
+                        .border_color(cx.theme().colors().border_variant)
+                        .p_1p5()
+                        .child(
+                            Button::new("configure", "Configure")
+                                .full_width()
+                                .style(ButtonStyle::Outlined)
+                                .key_binding(
+                                    KeyBinding::for_action_in(
+                                        &ManageProfiles::default(),
+                                        &focus_handle,
+                                        cx,
+                                    )
+                                    .map(|kb| kb.size(rems_from_px(12.))),
+                                )
+                                .on_click(|_, window, cx| {
+                                    window.dispatch_action(
+                                        ManageProfiles::default().boxed_clone(),
+                                        cx,
+                                    );
+                                }),
+                        ),
                 )
+                .when(is_restricted, |this| {
+                    this.child(
+                        h_flex()
+                            .w_full()
+                            .border_t_1()
+                            .border_color(cx.theme().colors().border_variant)
+                            .p_1p5()
+                            .child(
+                                Button::new("restricted-mode", "Restricted Mode")
+                                    .full_width()
+                                    .style(ButtonStyle::Tinted(TintColor::Warning))
+                                    .color(Color::Warning)
+                                    .start_icon(
+                                        Icon::new(IconName::Warning)
+                                            .size(IconSize::Small)
+                                            .color(Color::Warning),
+                                    )
+                                    .tooltip(Tooltip::text(
+                                        "Some tools are disabled. Click to review trust settings.",
+                                    ))
+                                    .on_click(|_, window, cx| {
+                                        window.dispatch_action(
+                                            ToggleWorktreeSecurity.boxed_clone(),
+                                            cx,
+                                        );
+                                    }),
+                            ),
+                    )
+                })
                 .into_any(),
         )
     }

crates/docs_preprocessor/src/main.rs

@@ -395,10 +395,21 @@ fn template_and_validate_json_snippets(book: &mut Book, errors: &mut HashSet<Pre
     let settings_validator = jsonschema::validator_for(&settings_schema)
         .expect("failed to compile settings JSON schema");
 
-    let keymap_schema =
-        keymap_schema_for_actions(&ALL_ACTIONS.actions, &ALL_ACTIONS.schema_definitions);
-    let keymap_validator =
-        jsonschema::validator_for(&keymap_schema).expect("failed to compile keymap JSON schema");
+    // The keymap schema is built from the action manifest. When `actions.json`
+    // is unavailable (e.g. when running outside of CI without first generating
+    // it) there are no actions, which produces an invalid schema (an empty
+    // `anyOf`). In that case we skip keymap snippet validation rather than
+    // panicking, consistent with the action validation skipped above.
+    let keymap_validator = if actions_available() {
+        let keymap_schema =
+            keymap_schema_for_actions(&ALL_ACTIONS.actions, &ALL_ACTIONS.schema_definitions);
+        Some(
+            jsonschema::validator_for(&keymap_schema)
+                .expect("failed to compile keymap JSON schema"),
+        )
+    } else {
+        None
+    };
 
     fn for_each_labeled_code_block_mut(
         book: &mut Book,
@@ -499,19 +510,22 @@ fn template_and_validate_json_snippets(book: &mut Book, errors: &mut HashSet<Pre
                 }
             }
             "keymap" => {
-                if !snippet_json_fixed.starts_with('[') || !snippet_json_fixed.ends_with(']') {
-                    snippet_json_fixed.insert(0, '[');
-                    snippet_json_fixed.push_str("\n]");
-                }
+                if let Some(keymap_validator) = &keymap_validator {
+                    if !snippet_json_fixed.starts_with('[') || !snippet_json_fixed.ends_with(']') {
+                        snippet_json_fixed.insert(0, '[');
+                        snippet_json_fixed.push_str("\n]");
+                    }
 
-                let value =
-                    settings::parse_json_with_comments::<serde_json::Value>(&snippet_json_fixed)?;
-                let validation_errors: Vec<String> = keymap_validator
-                    .iter_errors(&value)
-                    .map(|err| err.to_string())
-                    .collect();
-                if !validation_errors.is_empty() {
-                    anyhow::bail!("{}", validation_errors.join("\n"));
+                    let value = settings::parse_json_with_comments::<serde_json::Value>(
+                        &snippet_json_fixed,
+                    )?;
+                    let validation_errors: Vec<String> = keymap_validator
+                        .iter_errors(&value)
+                        .map(|err| err.to_string())
+                        .collect();
+                    if !validation_errors.is_empty() {
+                        anyhow::bail!("{}", validation_errors.join("\n"));
+                    }
                 }
             }
             "debug" => {

crates/sandbox/Cargo.toml

@@ -55,6 +55,9 @@ serde_json = { workspace = true, optional = true }
 
 [target.'cfg(target_os = "linux")'.dependencies]
 libc.workspace = true
+# Safe wrappers for the SCM_RIGHTS fd-passing and `fstat` the bind validator
+# needs, so that code doesn't hand-roll `msghdr`/`CMSG_*`/`mem::zeroed` unsafe.
+nix = { workspace = true, features = ["fs", "socket", "uio"] }
 
 [target.'cfg(target_os = "linux")'.dev-dependencies]
 tempfile.workspace = true

crates/sandbox/README.md

@@ -0,0 +1,261 @@
+# `sandbox`
+
+Cross-platform sandboxing for shell commands.
+
+## Overview
+
+This crate allows creating a `Sandbox` according to some `SandboxPolicy`. A
+`SandboxPolicy` expresses:
+- what filesystem operations are allowed
+- which kinds of networking operations are allowed
+- whether git metadata is protected
+
+Once you have a `Sandbox`, you can use it to run commands that are constrained
+by that policy.
+
+## Security model
+
+The sandbox itself assumes all untrusted code is maximally hostile. It does
+*not* assume that the untrusted code is written by a
+well-meaning-but-perhaps-marginally-unaligned AI agent.
+
+However, practical limitations make the default profile in Zed not secure
+against attacks. An attacker with read/write access to the current directory can:
+- create a new Rust project in the current dir
+- create a proc macro library containing malicious code
+- use that macro in the project somewhere
+- rust-analyzer will run that proc macro outside the sandbox
+
+This can be mitigated by:
+- disabling any language servers with the capability to run untrusted code
+- not granting git access (since write access to `.git` can similarly be
+  escalated to unsandboxed code execution via `$EDITOR` and various other
+  methods)
+
+## Implementation
+
+The implementations are highly platform-specific:
+- Mac support comes from Seatbelt
+- Linux support comes from [bubblewrap], implemented via Linux [namespaces].
+- Windows:
+  - WSL: same as Linux
+  - non-WSL: not supported
+
+Note that WSL shells can be used on all Windows projects, regardless of whether
+the files are stored in the Linux filesystem or not.
+
+## Architecture
+
+Filesystem restrictions are different on all platforms. Network restrictions
+however largely follow a similar approach (details omitted):
+- Disable networking in the sandbox, except for one localhost port
+- Within the sandbox, set `HTTP_PROXY` and friends to tell programs to
+  communicate with that socket
+- On the Zed host side, there is a proxy that listens to that port that enforces
+  domain filtering
+
+On Linux specifically, there is an intermediate socket that allows data to flow
+out of the sandbox. This is required because, unlike seatbelt, bubblewrap runs
+sandboxed programs in an entirely separate network stack (i.e. it has a
+different `localhost`).
+
+### Linux
+
+A naive implementation on Linux would work roughly like:
+- Figure out which paths are read-only and which are read/write
+- Run the sandboxed program through `bwrap` with `--ro-bind` for read-only and
+  `--bind` for read/write
+
+However, this fails because of a nasty TOCTOU.
+
+#### The nasty TOCTOU
+
+Consider the following case:
+- an attacker has convinced the user to open `project`, which contains an evil
+  `AGENTS.md`
+- They have also convinced the user to allow git access
+- This means that the user will have given the following permissions to the sandbox:
+  - read/write access to `project`
+  - read/write access to `project/.git`
+  - read/write access to an isolated `/tmp`
+  - read-only access to `/`
+- The `AGENTS.md` instructs the LLM to do the following:
+  - spawn two subagents
+  - the first subagent tries to swap `project/.git` with a symlink to
+    `/home/alice` [`renameat2(2)`][renameat2] with the `RENAME_EXCHANGE`
+    flag set
+  - the second subagent tries to run `echo 'export PATH="proj/obfuscated.../evil_eavesdropping_sudo/bin:$PATH"' >> proj/.git/.bashrc`
+- The user sends a prompt, we pick up the evil `AGENTS.md` instructions, and the
+  agent does them
+- Zed checks whether paths are symlinks outside the allowable paths before
+  passing them to bubblewrap, but there is a **time delay** between this check
+  and when bubblewrap mounts them.
+- In this delay, the `renameat2` may succeed, which means that:
+  - At check time, `proj/.git` is a subdirectory of `proj`
+  - At bind time, `proj/.git` is a symlink to `/home/alice`
+- The attacker is now running code in a sandbox which has **read/write** access
+  to `/home/alice`, and so the second command to inject the malicious
+  credential-stealing sudo succeeds.
+
+
+```mermaid
+sequenceDiagram
+    participant Agent as Zed Agent
+    participant S1 as Subagent 1 swapper
+    participant S2 as Subagent 2 writer
+    participant Zed as Zed path validation
+    participant BW as bubblewrap
+
+    Note over Agent: Evil AGENTS.md picked up, git access granted
+    Note over Agent: Grants rw project, rw project/.git, rw /tmp, ro /
+    Agent->>S1: spawn swap project/.git for a symlink to /home/alice
+    Agent->>S2: spawn append PATH hijack to project/.git/.bashrc
+    Zed->>Zed: check project/.git is not an out-of-bounds symlink
+    Note over Zed: at check time it is a real subdirectory, so OK
+    Note over Zed,BW: time delay, time-of-check to time-of-use
+    S1->>S1: renameat2 RENAME_EXCHANGE wins the race
+    Note over S1: project/.git is now a symlink to /home/alice
+    Zed->>BW: bind project/.git into the sandbox
+    BW->>BW: re-resolve project/.git, following symlink to /home/alice
+    S2->>BW: write project/.git/.bashrc
+    BW-->>S2: write lands in /home/alice/.bashrc
+    Note over S2: escalation, project-scoped grant becomes arbitrary write
+```
+
+Note that this attack requires *two nested directories*, each with read/write
+grants. A single grant is insufficient, because you must mutate *a path which is
+used as a `--bind` argument*. If you cannot mutate a parent (because we are
+assuming no nested directories), then the only part you can mutate is the the
+read/write grant path itself (i.e. `/home/alice/project`). But, in bubblewrap's
+model, doing this requires write access to the *parent* (i.e. `/home/alice`),
+which we have assumed is not present.
+
+`./bind_source_toctou_test.sh` is a small bash script demonstrating this
+behaviour. It tries to replace the current dir with a symlink, and it fails due
+to invalid permissions.
+
+#### The naive (and incorrect) fix
+
+It is tempting to read the previous paragraph and think "that's simple, just
+disallow nested directories". In theory, this would work. A read/write grant to `/foo` and `/foo/bar` is logically equivalent to a read/write grant to just `/foo`. And the following is *true*: 
+
+> If there is no pair of read/write grants such that one is an ancestor of the
+> other, this TOCTOU attack is impossible.
+
+However, this is not a viable countermeasure for two reasons:
+
+1. It requires that no two grants of this kind ever exist at the same time
+   *globally across the whole system*. For example, opening `/foo` in one zed
+   window and `/foo/bar` in another would re-open this exploit. Even if we did
+   mitigate this by widening `/foo/bar` to have access to `/foo` (which in
+   itself is an unacceptable privilege escalation), we still wouldn't be able to
+   control non-Zed processes.
+2. It prevents the potentially useful pattern of:
+  - read/write access to `/foo`
+  - read-only access to `/foo/bar`
+  - read/write access to `/foo/bar/baz`
+
+Because of this, we need something more robust.
+
+#### The correct fix
+
+The correct fix involves using file descriptors as the source of truth, rather
+than paths. This is important because file descriptors are stable once opened,
+regardless of what happens to the path. The symlink swap attack will not change
+which inode the FD points to.
+
+This leads to a different question: how do we tell `bwrap` to use FDs instead of paths?
+
+`bwrap` does support `--bind-fd`, but this has another issue: "how do you get
+FDs into the `bwrap` process?
+
+There are two options:
+1. open the FDs in zed, clear `CLOEXEC`, then fork/exec into bwrap with the FD arguments
+2. send them into a helper process inside the sandbox using an `SCM_RIGHTS`
+  socket, and validate from the inside of the sandbox.
+
+We chose option 2 because we already have a helper process inside the sandbox
+(to set up the HTTP proxy).
+
+The flow for this approach in detail is:
+- open each *writable* path we `--bind` and get an `O_PATH` FD (which pins the
+  inode without granting read/write on its contents)
+- create an `SCM_RIGHTS` socket over which we can send the FDs
+- run `bwrap --bind /path1 /path1 ... -- zed --zed-linux-sandbox-launcher <untrusted program args>`
+  - note: we use (potentially swapped) paths
+  - we also mount the socket in the sandbox
+- the sandbox bridge reads the FDs from the socket, does the following for each
+  read/write bind:
+  - `fstat` the FD to get the `(device, inode)`
+  - `lstat` the corresponding mount path to get its `(device, inode)`
+  - check that they match
+
+  Note that this is essentially the check that `bwrap --bind-fd` does internally.
+- if all binds match, run the untrusted command, otherwise refuse to execute
+
+```mermaid
+sequenceDiagram
+    participant Zed as Zed host
+    participant BW as bubblewrap
+    participant Bridge as sandbox-bridge in sandbox
+    participant Prog as untrusted program
+
+    Zed->>Zed: open O_PATH FD per writable path, pinning the inode
+    Zed->>Zed: create SCM_RIGHTS socket
+    Zed->>BW: exec bwrap, binding paths, then zed --zed-linux-sandbox-launcher
+    Note over Zed,BW: binds use possibly-swapped paths, socket mounted in sandbox
+    Zed->>Bridge: send FDs over the SCM_RIGHTS socket
+    loop each writable bind
+        Bridge->>Bridge: fstat the FD to get device and inode
+        Bridge->>Bridge: lstat the mount path to get device and inode
+        Bridge->>Bridge: compare the two pairs
+    end
+    alt all binds match
+        Bridge->>Prog: exec the untrusted command
+    else any mismatch, a path was swapped
+        Bridge-->>Zed: refuse to execute
+    end
+```
+
+If the attacker managed to change a path to point to a different inode to when
+the FD was captured, the check will fail, and we don't run the untrusted
+command.
+
+### Windows
+
+> [!NOTE] The Windows implementation depends heavily on the details of the Linux
+  implementation. 
+
+The Linux approach works perfectly on WSL in theory (WSL uses a "regular linux
+kernel"), but there is one practical thorn: the zed host code that creates the
+FD is now running on Windows, but we need Linux file descriptors.
+
+To work around this, we launch `zed --wsl-sandbox-helper` in WSL, which is a
+shim that captures the FDs and sets up the socket. We download this to
+`~/.local/libexec/zed`, so that it does not conflict with the Windows `zed.exe`
+binary that WSL will inject into the Linux `$PATH` (yes the `.exe` is stripped).
+## Code design
+
+### `HostFilesystemLocation`
+
+As mentioned above, TOCTOUs are a real issue. MacOS is not vulnerable to the
+TOCTOU that affected Linux, but there is still a risk if we canonicalize paths
+twice with a time delay between. 
+
+To mitigate this, sensitive APIs take a `HostFilesystemLocation`. This is:
+- an `Arc<OwnedFd>` on Linux
+- a `PathBuf` on MacOS
+
+This type does not expose its inner value, and so this encourages the developer
+to capture and validate the path once, before passing it into this type.
+
+### `SandboxFilesystemLocation`
+
+A thin wrapper around a `PathBuf` representing a location *inside* the sandbox.
+No hardening is required - the worst a tampered in-sandbox path can do is expose
+already-granted host files at a different in-sandbox path.
+
+
+[bubblewrap]: https://github.com/containers/bubblewrap
+[namespaces]: https://en.wikipedia.org/wiki/Linux_namespaces
+[renameat2]: https://man.archlinux.org/man/renameat2.2.en

crates/sandbox/bind_source_toctou_test.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+set -u
+command -v bwrap >/dev/null || { echo "bwrap not found" >&2; exit 2; }
+
+ROOT="$(mktemp -d)"; trap 'rm -rf "$ROOT"' EXIT
+READ_WRITE_DIR="$ROOT/foo/bar"
+ATTACK_TARGET="$ROOT/baz"
+mkdir -p "$READ_WRITE_DIR" "$ATTACK_TARGET"
+
+# /foo (parent of the grant) is read-only; only /foo/bar is writable, so staging
+# then renaming a symlink over /foo/bar fails.
+# 
+# Writable access to `/foo/bar` should not result in the ability to make
+# `/foo/bar` into a symlink.
+bwrap \
+  --ro-bind / / \
+  --bind "$READ_WRITE_DIR" "$READ_WRITE_DIR" \
+  --unshare-user \
+  --setenv READ_WRITE_DIR "$READ_WRITE_DIR" \
+  --setenv ATTACK_TARGET "$ATTACK_TARGET" \
+  /bin/sh -c '
+    ln -s "$ATTACK_TARGET" "$READ_WRITE_DIR.link" && mv -fT "$READ_WRITE_DIR.link" "$READ_WRITE_DIR" && exit 7
+    exit 0
+  '
+rc=$?
+
+if [ "$rc" -eq 7 ] || [ -L "$READ_WRITE_DIR" ]; then echo "FAIL: grant redirected"; exit 1; fi
+[ "$rc" -eq 0 ] || { echo "bwrap error (rc=$rc)" >&2; exit 2; }
+echo "PASS: swap blocked"

crates/sandbox/src/bwrap_test_helper.rs

@@ -30,12 +30,13 @@ fn main() {
 mod imp {
     use std::io::{Read as _, Write as _};
     use std::net::TcpStream;
-    use std::path::{Path, PathBuf};
+    use std::path::Path;
     use std::time::Duration;
 
     use anyhow::{Context as _, Result, bail};
     use sandbox::{
-        CommandAndArgs, Sandbox, SandboxError, SandboxFsPolicy, SandboxNetPolicy, SandboxPolicy,
+        CommandAndArgs, GitSandboxPolicy, HostFilesystemLocation, Sandbox, SandboxError,
+        SandboxFsPolicy, SandboxNetPolicy, SandboxPolicy,
     };
     use serde::Deserialize;
 
@@ -111,6 +112,14 @@ mod imp {
         network_access: NetMode,
         #[serde(default)]
         allowed_domains: Vec<String>,
+        /// `.git` directories to protect (contents read-only on Linux). Selects a
+        /// `Denied` Git policy. Mutually exclusive with `gitAllowed`.
+        #[serde(default)]
+        git_disabled: Vec<String>,
+        /// `.git` directories to make writable. Selects an `Allowed` Git policy.
+        /// Mutually exclusive with `gitDisabled`.
+        #[serde(default)]
+        git_allowed: Vec<String>,
 
         // ---- operation (exactly one) ----
         /// Read this host path from inside the sandbox.
@@ -169,12 +178,24 @@ mod imp {
         checks.finish()
     }
 
-    fn policy_of(check: &Check) -> SandboxPolicy {
+    fn policy_of(check: &Check) -> Result<SandboxPolicy> {
         let fs = match check.fs {
             FsMode::Unrestricted => SandboxFsPolicy::Unrestricted,
-            FsMode::Restricted => SandboxFsPolicy::Restricted {
-                writable_paths: check.writable_paths.iter().map(PathBuf::from).collect(),
-            },
+            FsMode::Restricted => {
+                let mut writable_paths = Vec::new();
+                for path in &check.writable_paths {
+                    // Mirror production (`acp_thread::SandboxWrap::to_policy`):
+                    // the directory must exist before its inode can be pinned, so
+                    // create it up front, then capture it.
+                    std::fs::create_dir_all(path)
+                        .with_context(|| format!("failed to create writable path {path}"))?;
+                    writable_paths.push(
+                        HostFilesystemLocation::new(path)
+                            .with_context(|| format!("failed to capture writable path {path}"))?,
+                    );
+                }
+                SandboxFsPolicy::Restricted { writable_paths }
+            }
         };
         let network = match check.network_access {
             NetMode::Unrestricted => SandboxNetPolicy::Unrestricted,
@@ -183,18 +204,47 @@ mod imp {
                 allowed_domains: check.allowed_domains.clone(),
             },
         };
-        SandboxPolicy {
-            fs,
-            network,
-            git: sandbox::GitSandboxPolicy::default(),
-        }
+        // `gitAllowed` and `gitDisabled` are mutually exclusive; `gitAllowed`
+        // wins if both are (mistakenly) set. With neither, the default protects
+        // an empty set of dirs, which is a no-op.
+        let git = if !check.git_allowed.is_empty() {
+            GitSandboxPolicy::Allowed {
+                git_dirs: capture_git_dirs(&check.git_allowed),
+            }
+        } else if !check.git_disabled.is_empty() {
+            GitSandboxPolicy::Denied {
+                git_dirs: capture_git_dirs(&check.git_disabled),
+            }
+        } else {
+            GitSandboxPolicy::default()
+        };
+        Ok(SandboxPolicy { fs, network, git })
+    }
+
+    /// Capture each already-existing `.git` directory, mirroring production's
+    /// fail-closed `filter_map(HostFilesystemLocation::new(..).ok())`: a `.git`
+    /// that does not yet exist can't be pinned and is simply skipped (the
+    /// documented Linux gap). Unlike writable paths, these are never created
+    /// here — whether one exists is exactly what several checks turn on.
+    fn capture_git_dirs(paths: &[String]) -> Vec<HostFilesystemLocation> {
+        paths
+            .iter()
+            .filter_map(|path| HostFilesystemLocation::new(path).ok())
+            .collect()
     }
 
     fn describe(check: &Check) -> String {
         if let Some(name) = &check.name {
             return name.clone();
         }
-        let policy = format!("fs={:?},net={:?}", check.fs, check.network_access);
+        let git = if !check.git_allowed.is_empty() {
+            format!(",git_allowed={:?}", check.git_allowed)
+        } else if !check.git_disabled.is_empty() {
+            format!(",git_disabled={:?}", check.git_disabled)
+        } else {
+            String::new()
+        };
+        let policy = format!("fs={:?},net={:?}{git}", check.fs, check.network_access);
         let op = if let Some(path) = &check.read {
             format!("read {path}")
         } else if let Some(path) = &check.write {
@@ -211,10 +261,10 @@ mod imp {
 
     fn run_check(check: &Check, echo_port: &str, checks: &mut Checks) -> Result<()> {
         let label = describe(check);
-        let policy = policy_of(check);
 
         if let Some(expect_can_create) = check.can_create {
-            let outcome = Sandbox::can_create(&policy, None);
+            let policy = policy_of(check)?;
+            let outcome = Sandbox::can_create(&policy);
             let passed = match (&outcome, expect_can_create) {
                 (Ok(()), true) => true,
                 (Ok(()), false) => false,
@@ -234,11 +284,11 @@ mod imp {
             .with_context(|| format!("check {label:?} has an operation but no `succeeds`"))?;
 
         let actual = if let Some(path) = &check.read {
-            run_read(&policy, path)?
+            run_read(check, path)?
         } else if let Some(path) = &check.write {
-            run_write(&policy, path)?
+            run_write(check, path)?
         } else if let Some(host) = &check.network {
-            run_network(&policy, host, echo_port)?
+            run_network(check, host, echo_port)?
         } else {
             bail!("check {label:?} has no operation");
         };
@@ -250,7 +300,7 @@ mod imp {
     /// Seed a host file, then `cat` it from inside the sandbox. Reads are always
     /// granted (root is bound read-only), so this proves the sandbox doesn't
     /// *block* reads of existing host files.
-    fn run_read(policy: &SandboxPolicy, path: &str) -> Result<bool> {
+    fn run_read(check: &Check, path: &str) -> Result<bool> {
         let path = Path::new(path);
         if let Some(parent) = path.parent() {
             std::fs::create_dir_all(parent)
@@ -259,7 +309,10 @@ mod imp {
         std::fs::write(path, b"sandbox-test\n")
             .with_context(|| format!("failed to seed readable file {}", path.display()))?;
 
-        let mut sandbox = Sandbox::new(policy.clone()).map_err(sandbox_err)?;
+        // Build the policy only after the fixtures exist: capturing a
+        // `HostFilesystemLocation` pins the inode, so the path must be present.
+        let policy = policy_of(check)?;
+        let mut sandbox = Sandbox::new(policy).map_err(sandbox_err)?;
         run_command(
             &mut sandbox,
             "sh",
@@ -271,18 +324,22 @@ mod imp {
     /// the command exited 0 *and* the bytes actually landed on the host file —
     /// a write that only hits the sandbox's ephemeral tmpfs counts as blocked,
     /// since it never escaped the sandbox.
-    fn run_write(policy: &SandboxPolicy, path: &str) -> Result<bool> {
+    fn run_write(check: &Check, path: &str) -> Result<bool> {
         let path = Path::new(path);
         if let Some(parent) = path.parent() {
             // Create the parent on the host so the only thing under test is the
-            // sandbox's write permission, not a missing directory.
+            // sandbox's write permission, not a missing directory. This also
+            // makes a `.git` parent exist before the policy captures it.
             std::fs::create_dir_all(parent)
                 .with_context(|| format!("failed to create parent of {}", path.display()))?;
         }
         // Start from a clean slate so `exists()` afterwards is meaningful.
         let _ = std::fs::remove_file(path);
 
-        let mut sandbox = Sandbox::new(policy.clone()).map_err(sandbox_err)?;
+        // Build the policy only after the fixtures exist: capturing a
+        // `HostFilesystemLocation` pins the inode, so the path must be present.
+        let policy = policy_of(check)?;
+        let mut sandbox = Sandbox::new(policy).map_err(sandbox_err)?;
         let command_ok = run_command(
             &mut sandbox,
             "sh",
@@ -297,14 +354,15 @@ mod imp {
     /// Connect to `host` (`hostname` or `hostname:port`) from inside the
     /// sandbox via the `__echo_check` subcommand, which honors `HTTP_PROXY` for
     /// the restricted-network case.
-    fn run_network(policy: &SandboxPolicy, host: &str, echo_port: &str) -> Result<bool> {
+    fn run_network(check: &Check, host: &str, echo_port: &str) -> Result<bool> {
         let target = if host.contains(':') {
             host.to_string()
         } else {
             format!("{host}:{echo_port}")
         };
         let exe = current_exe_str()?;
-        let mut sandbox = Sandbox::new(policy.clone()).map_err(sandbox_err)?;
+        let policy = policy_of(check)?;
+        let mut sandbox = Sandbox::new(policy).map_err(sandbox_err)?;
         run_command(&mut sandbox, &exe, &[SUBCOMMAND_ECHO_CHECK, &target])
     }
 

crates/sandbox/src/macos_seatbelt.rs

@@ -209,21 +209,19 @@ fn generate_seatbelt_config(
     allowed_unix_socket_paths: &[&Path],
     permissions: SandboxPermissions,
 ) -> Result<String> {
-    // Canonicalize each writable path to resolve symlinks (e.g.,
-    // /var -> /private/var on macOS). Fall back to the original path if
-    // canonicalization fails.
+    // These paths are already the canonical identities captured once, at
+    // validation time, inside each `HostFilesystemLocation` (resolving symlinks
+    // and, for a not-yet-created `.git`, its existing parent). We deliberately do
+    // NOT re-canonicalize here: re-resolving a path at profile-generation time
+    // is the time-of-check-to-time-of-use hole this design closes. Use them
+    // verbatim as Seatbelt rule literals.
     let canonical_writable_directories: Vec<PathBuf> = writable_directories
         .iter()
-        .map(|path| path.canonicalize().unwrap_or_else(|_| path.to_path_buf()))
+        .map(|path| path.to_path_buf())
         .collect();
-    // Use `canonicalize_allowing_missing_leaf` rather than a plain
-    // `canonicalize` so a not-yet-created `.git` (before `git init`) still
-    // resolves through its existing parent and matches the canonicalized
-    // writable worktree above; otherwise the deny rule would miss the real path
-    // on a symlinked root (`/tmp` -> `/private/tmp`).
     let canonical_protected_paths: Vec<PathBuf> = protected_paths
         .iter()
-        .map(|path| crate::canonicalize_allowing_missing_leaf(path))
+        .map(|path| path.to_path_buf())
         .collect();
     // Unlike file paths, Unix socket literals are emitted verbatim: it isn't
     // guaranteed whether Seatbelt resolves symlinks before matching a
@@ -564,7 +562,11 @@ mod tests {
         use std::process::Command;
 
         let temp_dir = tempfile::tempdir().unwrap();
-        let protected_file = temp_dir.path().join(".gitignore");
+        // Canonicalize so the policy paths resolve the macOS `/var` -> `/private/var`
+        // symlink; Seatbelt matches rules against the resolved path, as production
+        // does via `HostFilesystemLocation`.
+        let dir = std::fs::canonicalize(temp_dir.path()).unwrap();
+        let protected_file = dir.join(".gitignore");
         std::fs::write(&protected_file, "target\n").unwrap();
 
         let (program, args, _config_file) = wrap_invocation(
@@ -578,7 +580,7 @@ mod tests {
                     protected_file.display(),
                 ),
             ],
-            &[temp_dir.path()],
+            &[dir.as_path()],
             &[protected_file.as_path()],
             &[],
             SandboxPermissions::default(),
@@ -607,7 +609,10 @@ mod tests {
         use std::process::Command;
 
         let temp_dir = tempfile::tempdir().unwrap();
-        let protected_file = temp_dir.path().join(".gitignore");
+        // See the sibling protected-path test: canonicalize so policy paths resolve
+        // the macOS `/var` -> `/private/var` symlink that Seatbelt matches against.
+        let dir = std::fs::canonicalize(temp_dir.path()).unwrap();
+        let protected_file = dir.join(".gitignore");
         std::fs::write(&protected_file, "target\n").unwrap();
 
         let (program, args, _config_file) = wrap_invocation(
@@ -620,7 +625,7 @@ mod tests {
                     protected_file.display(),
                 ),
             ],
-            &[temp_dir.path()],
+            &[dir.as_path()],
             &[protected_file.as_path()],
             &[],
             SandboxPermissions {
@@ -870,7 +875,11 @@ mod tests {
 
         let project_dir = tempfile::tempdir().unwrap();
         let scratch_dir = tempfile::tempdir().unwrap();
-        let test_file = scratch_dir.path().join("test_write.txt");
+        // Canonicalize so the writable subpaths resolve the macOS `/var` ->
+        // `/private/var` symlink that Seatbelt matches against.
+        let project_path = std::fs::canonicalize(project_dir.path()).unwrap();
+        let scratch_path = std::fs::canonicalize(scratch_dir.path()).unwrap();
+        let test_file = scratch_path.join("test_write.txt");
 
         let (program, args, _config_file) = wrap_invocation(
             "/bin/sh",
@@ -878,7 +887,7 @@ mod tests {
                 "-c".to_string(),
                 format!("echo 'hello' > '{}'", test_file.display()),
             ],
-            &[project_dir.path(), scratch_dir.path()],
+            &[project_path.as_path(), scratch_path.as_path()],
             &[],
             &[],
             SandboxPermissions::default(),
@@ -903,7 +912,10 @@ mod tests {
         use std::process::Command;
 
         let temp_dir = tempfile::tempdir().unwrap();
-        let test_file = temp_dir.path().join("test_write.txt");
+        // Canonicalize so the writable subpath resolves the macOS `/var` ->
+        // `/private/var` symlink that Seatbelt matches against.
+        let dir = std::fs::canonicalize(temp_dir.path()).unwrap();
+        let test_file = dir.join("test_write.txt");
 
         let (program, args, _config_file) = wrap_invocation(
             "/bin/sh",
@@ -911,7 +923,7 @@ mod tests {
                 "-c".to_string(),
                 format!("echo 'hello' > '{}'", test_file.display()),
             ],
-            &[temp_dir.path()],
+            &[dir.as_path()],
             &[],
             &[],
             SandboxPermissions::default(),

crates/sandbox/src/sandbox.rs

@@ -29,6 +29,249 @@ mod windows_wsl;
 #[cfg(target_os = "windows")]
 pub(crate) const WSL_SANDBOX_UNAVAILABLE_PREFIX: &str = "Windows sandboxing via WSL is unavailable";
 
+/// An opaque handle to a location on the **host** filesystem the sandbox may
+/// grant access to (a writable subtree, a `.git` directory, …).
+///
+/// The entire purpose of this type is to capture the *security-relevant identity*
+/// of a host location once, up front, in a form the enforcement layer can use
+/// without re-resolving a path string later. Re-resolving a path at enforcement
+/// time is the classic time-of-check-to-time-of-use hole: a path that was
+/// verified as safe can be swapped for a symlink before the sandbox actually
+/// binds/allows it, redirecting the grant to an arbitrary host location.
+///
+/// What is captured is platform-specific:
+/// - **macOS**: the fully-canonicalized path, used verbatim as the Seatbelt rule
+///   literal. Seatbelt matches the *resolved* access path against this literal,
+///   so a post-capture swap of a path component fails closed (denied) rather
+///   than redirecting the grant.
+/// - **Linux**: an `O_PATH` file descriptor pinned to the target inode. bwrap is
+///   launched by a PTY that can't inherit extra fds, so we can't use bwrap's own
+///   `--bind-fd`; instead the bind uses an ordinary `--bind <path>` and an
+///   in-sandbox validator compares `fstat` of this descriptor against `lstat` of
+///   the mounted path after the mounts, failing closed on a post-capture swap
+///   (see `linux_bubblewrap::validate_binds` and `README.md`).
+/// - **Windows**: nothing — a Windows process holds no Linux fds, so the real
+///   capture-at-validation happens inside WSL (in the `--wsl-sandbox-helper`),
+///   and the value here carries only the requested path as untrusted intent.
+///
+/// The type is deliberately **opaque**: it does not `Deref`, and it never hands
+/// back its trusted value. The only thing readable is a *display-only* path via
+/// [`HostFilesystemLocation::untrusted_path_display`], suitable for showing a
+/// human but which must never be passed back into a sandbox API as the
+/// location's identity. Equality reflects the actual filesystem object (same
+/// inode), not the textual path.
+#[derive(Clone)]
+pub struct HostFilesystemLocation {
+    /// macOS: the canonicalized path, resolved exactly once at capture time and
+    /// used directly as the Seatbelt rule literal.
+    #[cfg(target_os = "macos")]
+    canonical_path: PathBuf,
+    /// Linux: an `O_PATH` descriptor pinned to the captured inode. Wrapped in an
+    /// `Arc` only so the surrounding policy types can stay `Clone`; cloning
+    /// shares the same underlying descriptor.
+    #[cfg(target_os = "linux")]
+    fd: std::sync::Arc<std::os::fd::OwnedFd>,
+    /// The path exactly as the caller requested it. Kept **only** so the UI can
+    /// show the user which location is being granted. This is never consulted by
+    /// any enforcement path — treat it as untrusted, attacker-influenced text.
+    untrusted_path_for_display: PathBuf,
+}
+
+impl HostFilesystemLocation {
+    /// Capture `path` as a host sandbox location, resolving its identity up front.
+    ///
+    /// On macOS this canonicalizes the path; on Linux it opens an `O_PATH`
+    /// descriptor to it; on Windows it records nothing. The caller is
+    /// responsible for having already *validated* `path` (e.g. confirmed it is
+    /// inside the project, or that a `.git` is not a symlink) — capturing it here
+    /// pins that decision against later tampering. To be race-free, capture
+    /// should happen as part of, or immediately after, that validation, and the
+    /// resulting value should be passed around unchanged from then on (never
+    /// re-derived from a path).
+    pub fn new(path: impl AsRef<Path>) -> std::io::Result<Self> {
+        let path = path.as_ref();
+        let untrusted_path_for_display = path.to_path_buf();
+
+        #[cfg(target_os = "macos")]
+        {
+            // `canonicalize_allowing_missing_leaf` resolves through the existing
+            // parent so a not-yet-created leaf (e.g. a `.git` before `git init`)
+            // still yields the real path Seatbelt will match against.
+            let canonical_path = canonicalize_allowing_missing_leaf(path);
+            Ok(Self {
+                canonical_path,
+                untrusted_path_for_display,
+            })
+        }
+        #[cfg(target_os = "linux")]
+        {
+            use std::os::unix::fs::OpenOptionsExt as _;
+            // `O_PATH` opens a handle that refers to the inode without granting
+            // read/write on its contents, which is exactly what a bind source
+            // needs. `O_CLOEXEC` keeps the descriptor from leaking into
+            // unrelated children; the bind step re-publishes it deliberately
+            // when launching bwrap.
+            let file = std::fs::OpenOptions::new()
+                .read(true)
+                .custom_flags(libc::O_PATH | libc::O_CLOEXEC)
+                .open(path)?;
+            Ok(Self {
+                fd: std::sync::Arc::new(std::os::fd::OwnedFd::from(file)),
+                untrusted_path_for_display,
+            })
+        }
+        #[cfg(not(any(target_os = "macos", target_os = "linux")))]
+        {
+            Ok(Self {
+                untrusted_path_for_display,
+            })
+        }
+    }
+
+    /// The requested path, for **display only** (e.g. the permission-request UI).
+    ///
+    /// This intentionally returns the untrusted, as-requested path — never the
+    /// captured trusted identity. Do not feed the result back into any sandbox
+    /// API as if it identified this location.
+    pub fn untrusted_path_display(&self) -> std::path::Display<'_> {
+        self.untrusted_path_for_display.display()
+    }
+
+    /// macOS: the canonical path captured once at construction, used verbatim as
+    /// the Seatbelt rule literal. Trusted — never re-resolved. Falls back to the
+    /// requested path for a display-only location (which must never reach
+    /// enforcement).
+    #[cfg(target_os = "macos")]
+    pub(crate) fn macos_canonical_path(&self) -> &Path {
+        &self.canonical_path
+    }
+
+    /// Linux: a borrowed handle to the pinned inode, for deriving a bind source
+    /// path and for `fstat`-based identity checks.
+    #[cfg(target_os = "linux")]
+    pub(crate) fn linux_fd(&self) -> std::os::fd::BorrowedFd<'_> {
+        use std::os::fd::AsFd as _;
+        self.fd.as_fd()
+    }
+
+    /// Linux: an independent `O_PATH` descriptor to the same pinned inode,
+    /// duplicated (with `O_CLOEXEC`) so the validation server can own and send it
+    /// over `SCM_RIGHTS` without affecting this location's descriptor.
+    #[cfg(target_os = "linux")]
+    pub(crate) fn linux_dup_fd(&self) -> std::io::Result<std::os::fd::OwnedFd> {
+        use std::os::fd::AsFd as _;
+        self.fd.as_fd().try_clone_to_owned()
+    }
+
+    /// Windows: the requested path, to be mapped into WSL and handed to the
+    /// in-WSL helper. Windows captures no identity itself (it holds no Linux
+    /// fds); the real capture-at-validation happens WSL-side in the helper, so
+    /// here the requested path *is* the location.
+    #[cfg(target_os = "windows")]
+    pub(crate) fn windows_path(&self) -> &Path {
+        &self.untrusted_path_for_display
+    }
+}
+
+impl fmt::Debug for HostFilesystemLocation {
+    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // Only the display path is shown; the trusted identity stays opaque.
+        formatter
+            .debug_struct("HostFilesystemLocation")
+            .field(
+                "untrusted_path_for_display",
+                &self.untrusted_path_for_display,
+            )
+            .finish_non_exhaustive()
+    }
+}
+
+impl PartialEq for HostFilesystemLocation {
+    /// Two locations are equal when they refer to the **same filesystem object**,
+    /// determined from the captured identity (the inode behind the `O_PATH` fd on
+    /// Linux, the canonical path on macOS) — never from the textual
+    /// display path. This is what lets policy bookkeeping dedupe "the same
+    /// location named two different ways," and refuse to treat "two different
+    /// objects that happen to share a path string" as one.
+    fn eq(&self, other: &Self) -> bool {
+        #[cfg(target_os = "linux")]
+        {
+            match (linux_fd_identity(&self.fd), linux_fd_identity(&other.fd)) {
+                (Some(a), Some(b)) => a == b,
+                // An `fstat` on an `O_PATH` fd we own should never fail; if it
+                // somehow does we can't prove identity, so report "not equal"
+                // (the safe answer) and leave a trace.
+                _ => {
+                    log::error!(
+                        "failed to fstat an O_PATH descriptor while comparing sandbox locations"
+                    );
+                    false
+                }
+            }
+        }
+        #[cfg(target_os = "macos")]
+        {
+            // Canonicalization is a bijection on real paths, so equal canonical
+            // paths mean the same directory/file.
+            self.canonical_path == other.canonical_path
+        }
+        #[cfg(not(any(target_os = "linux", target_os = "macos")))]
+        {
+            // No enforcement and no captured identity on these platforms; fall
+            // back to the requested path purely so the type can still be used in
+            // collections.
+            self.untrusted_path_for_display == other.untrusted_path_for_display
+        }
+    }
+}
+
+impl Eq for HostFilesystemLocation {}
+
+/// The `(device, inode)` pair behind an `O_PATH` descriptor, used to decide
+/// whether two [`HostFilesystemLocation`]s refer to the same filesystem object.
+#[cfg(target_os = "linux")]
+fn linux_fd_identity(fd: &std::os::fd::OwnedFd) -> Option<(u64, u64)> {
+    use std::os::fd::AsRawFd as _;
+    let stat = nix::sys::stat::fstat(fd.as_raw_fd()).ok()?;
+    Some((stat.st_dev as u64, stat.st_ino as u64))
+}
+
+/// A path *inside the sandbox* — i.e. where a host location is exposed in the
+/// sandboxed process's view of the filesystem (for example, a bind-mount
+/// destination on Linux).
+///
+/// Unlike [`HostFilesystemLocation`], this needs no hardening and is just a thin
+/// wrapper around a [`PathBuf`]. It only names a location within the sandbox's
+/// own namespace: the worst a tampered sandbox-side path can do is expose the
+/// (already-granted) host files at a *different* path inside the sandbox — it can
+/// never widen which host files are reachable. It is therefore fine to build one
+/// from an ordinary, even attacker-influenced, path.
+#[derive(Clone, Debug, Eq, PartialEq, Hash)]
+pub struct SandboxFilesystemLocation(PathBuf);
+
+impl SandboxFilesystemLocation {
+    /// Name a location inside the sandbox's filesystem view.
+    pub fn new(path: impl Into<PathBuf>) -> Self {
+        Self(path.into())
+    }
+
+    /// The in-sandbox path. Safe to read: this is not a trusted host identity.
+    pub fn as_path(&self) -> &Path {
+        &self.0
+    }
+
+    /// Consume this wrapper, yielding the underlying in-sandbox path.
+    pub fn into_path_buf(self) -> PathBuf {
+        self.0
+    }
+}
+
+impl From<PathBuf> for SandboxFilesystemLocation {
+    fn from(path: PathBuf) -> Self {
+        Self(path)
+    }
+}
+
 /// What a command is allowed to do, expressed as intent. This is the entire
 /// public configuration surface; how each policy is enforced (Seatbelt rules,
 /// Bubblewrap flags, a loopback proxy, …) is an implementation detail.
@@ -44,9 +287,13 @@ pub struct SandboxPolicy {
 pub enum SandboxFsPolicy {
     /// Allow unrestricted filesystem writes.
     Unrestricted,
-    /// Reads are allowed everywhere; writes are confined to these directory
-    /// subtrees (and the standard ephemeral locations the platform provides).
-    Restricted { writable_paths: Vec<PathBuf> },
+    /// Reads are allowed everywhere; writes are confined to these locations
+    /// (and the standard ephemeral locations the platform provides). Each is a
+    /// [`HostFilesystemLocation`] captured at validation time, never a bare path
+    /// the enforcement layer would re-resolve.
+    Restricted {
+        writable_paths: Vec<HostFilesystemLocation>,
+    },
 }
 
 /// Outbound-network policy for a sandboxed command.
@@ -72,9 +319,13 @@ pub enum GitSandboxPolicy {
     /// `.git` contents are protected: read-only on Linux and Windows/WSL;
     /// content reads and writes denied on macOS (metadata stays visible either
     /// way).
-    Denied { git_dirs: Vec<PathBuf> },
+    Denied {
+        git_dirs: Vec<HostFilesystemLocation>,
+    },
     /// `.git` contents are writable (these dirs are made writable).
-    Allowed { git_dirs: Vec<PathBuf> },
+    Allowed {
+        git_dirs: Vec<HostFilesystemLocation>,
+    },
 }
 
 impl Default for GitSandboxPolicy {
@@ -88,7 +339,7 @@ impl Default for GitSandboxPolicy {
 
 impl GitSandboxPolicy {
     /// The `.git` directories this policy governs, regardless of variant.
-    pub fn git_dirs(&self) -> &[PathBuf] {
+    pub fn git_dirs(&self) -> &[HostFilesystemLocation] {
         match self {
             GitSandboxPolicy::Denied { git_dirs } | GitSandboxPolicy::Allowed { git_dirs } => {
                 git_dirs
@@ -285,7 +536,7 @@ impl std::error::Error for SandboxError {}
 /// Resolved filesystem setup derived from [`SandboxFsPolicy`].
 struct FsSetup {
     allow_fs_write: bool,
-    writable_paths: Vec<PathBuf>,
+    writable_paths: Vec<HostFilesystemLocation>,
 }
 
 /// Resolved network plan derived from [`SandboxNetPolicy`]. For the restricted
@@ -317,6 +568,23 @@ pub struct Sandbox {
     /// In-process network proxy for the restricted-network case, spawned on the
     /// first `wrap`. Dropped on a background thread (the join blocks).
     proxy: Option<ProxyHandle>,
+    /// Linux only: the host endpoint that hands the in-sandbox validator the
+    /// captured `O_PATH` fds over a unix socket. Runs entirely in-process (a
+    /// short-lived background thread, never a separate process) and is owned by
+    /// this `Sandbox` — which is created per command — so it comes up when the
+    /// command is wrapped and is torn down (thread stopped, socket removed) when
+    /// the command finishes. Holds the fds, keeping their inodes pinned until
+    /// then. Created lazily on the wrap that first needs it (a restricted-fs run
+    /// with writable binds); a `Sandbox` normally wraps a single command.
+    #[cfg(target_os = "linux")]
+    validation_fd_sender: Option<linux_bubblewrap::ValidationFdSender>,
+    /// Windows only: `(release channel, version)` of the Linux `zed` to
+    /// provision inside WSL as the `--wsl-sandbox-helper` (version `latest` for
+    /// dev builds). Set by the caller (which has the running release info);
+    /// `None` falls back to exec'ing bwrap directly without in-sandbox bind
+    /// validation.
+    #[cfg(target_os = "windows")]
+    wsl_zed_release: Option<(String, String)>,
     #[cfg(target_os = "macos")]
     seatbelt_config: Option<macos_seatbelt::SeatbeltConfigFile>,
 }
@@ -353,29 +621,48 @@ impl Sandbox {
             network,
             git: policy.git,
             proxy: None,
+            #[cfg(target_os = "linux")]
+            validation_fd_sender: None,
+            #[cfg(target_os = "windows")]
+            wsl_zed_release: None,
             #[cfg(target_os = "macos")]
             seatbelt_config: None,
         })
     }
 
-    /// Check whether the platform sandbox can be created for `policy` without
+    /// Windows only: record the `(release channel, version)` of the Linux `zed`
+    /// to provision inside WSL as the sandbox helper (version `latest` for dev
+    /// builds). The caller resolves these from the running app's release info
+    /// (which this low-level crate can't read) and sets them before `wrap`. When
+    /// unset, the WSL backend falls back to exec'ing bwrap directly without
+    /// in-sandbox bind validation.
+    #[cfg(target_os = "windows")]
+    pub fn set_wsl_zed_release(&mut self, channel: String, version: String) {
+        self.wsl_zed_release = Some((channel, version));
+    }
+
+    /// Check whether the platform sandbox can be created on this host without
     /// actually building a command or spawning the proxy. On Linux this runs a
     /// brief `bwrap` probe (call it off the main thread).
-    pub fn can_create(policy: &SandboxPolicy, cwd: Option<&Path>) -> Result<(), SandboxError> {
+    ///
+    /// This answers a purely *environmental* question — is a bwrap sandbox
+    /// possible here at all (a usable `bwrap`, plus the unprivileged user
+    /// namespace and mount scaffolding we rely on)? It deliberately does **not**
+    /// depend on any command's writable grants or working directory: the probe
+    /// runs a bare, representative sandbox and runs `true` in it. (Unlike the
+    /// former Landlock probe, bwrap needs no ABI-matching against the real
+    /// ruleset, so there's no reason to mirror the real command's mounts.)
+    pub fn can_create(policy: &SandboxPolicy) -> Result<(), SandboxError> {
         #[cfg(target_os = "linux")]
         {
-            let writable = policy_writable_paths(policy);
-            let writable: Vec<&Path> = writable.iter().map(PathBuf::as_path).collect();
             let permissions = linux_bubblewrap::SandboxPermissions {
                 network: linux_probe_network(&policy.network),
                 allow_fs_write: matches!(policy.fs, SandboxFsPolicy::Unrestricted),
             };
-            linux_bubblewrap::check_can_create_sandbox(&writable, permissions, cwd)
-                .map_err(map_linux_status)
+            linux_bubblewrap::check_can_create_sandbox(permissions).map_err(map_linux_status)
         }
         #[cfg(target_os = "windows")]
         {
-            let _ = cwd;
             if matches!(policy.network, SandboxNetPolicy::Restricted { .. }) {
                 return Err(unsupported_restricted_network_on_windows());
             }
@@ -383,7 +670,7 @@ impl Sandbox {
         }
         #[cfg(not(any(target_os = "linux", target_os = "windows")))]
         {
-            let _ = (policy, cwd);
+            let _ = policy;
             Ok(())
         }
     }
@@ -491,7 +778,7 @@ impl Sandbox {
     /// is empty (Git protection is moot); otherwise `Allowed` git dirs are
     /// writable and `Denied` git dirs are protected.
     #[cfg(any(target_os = "macos", target_os = "linux", target_os = "windows"))]
-    fn git_path_split(&self) -> (Vec<PathBuf>, Vec<PathBuf>) {
+    fn git_path_split(&self) -> (Vec<HostFilesystemLocation>, Vec<HostFilesystemLocation>) {
         if self.fs.allow_fs_write {
             return (Vec::new(), Vec::new());
         }
@@ -520,14 +807,61 @@ impl Sandbox {
             allow_fs_write: self.fs.allow_fs_write,
         };
         let (git_writable, git_protected) = self.git_path_split();
-        let mut writable: Vec<&Path> = self
-            .fs
-            .writable_paths
+        // Build the writable binds as (captured fd, bind path) pairs in lockstep.
+        // The bind *path* is derived from the pinned inode (readlink of the
+        // captured `O_PATH` fd), never from an attacker-influenceable string; the
+        // *fd* is what the in-sandbox validator compares the mounted inode
+        // against. The two lists stay in the same order so each fd lines up with
+        // its path on the validator side.
+        let mut writable_owned: Vec<PathBuf> = Vec::new();
+        let mut writable_fds: Vec<std::os::fd::OwnedFd> = Vec::new();
+        for location in self.fs.writable_paths.iter().chain(git_writable.iter()) {
+            let Some(path) = linux_location_path(location) else {
+                continue;
+            };
+            match location.linux_dup_fd() {
+                Ok(fd) => {
+                    writable_owned.push(path);
+                    writable_fds.push(fd);
+                }
+                Err(error) => {
+                    // Fail closed: a bind we can't pin a verifiable fd for is
+                    // dropped rather than bound unverified.
+                    log::warn!(
+                        "[sandbox] could not duplicate fd for writable bind {}: {error}",
+                        path.display()
+                    );
+                }
+            }
+        }
+        let writable: Vec<&Path> = writable_owned.iter().map(PathBuf::as_path).collect();
+        let protected_owned: Vec<PathBuf> = git_protected
             .iter()
-            .map(PathBuf::as_path)
+            .filter_map(linux_location_path)
             .collect();
-        writable.extend(git_writable.iter().map(PathBuf::as_path));
-        let protected_git_dirs: Vec<&Path> = git_protected.iter().map(PathBuf::as_path).collect();
+        let protected_git_dirs: Vec<&Path> = protected_owned.iter().map(PathBuf::as_path).collect();
+
+        // Stand up the host endpoint that sends the captured fds to the
+        // in-sandbox validator, when this run has writable binds to verify. It's
+        // an in-process background thread owned by this (per-command) `Sandbox`,
+        // so it lives only for the command's duration. The sender serves its
+        // descriptors to exactly one client and then tears itself down, so each
+        // wrap creates a fresh one (replacing any from a prior wrap); a
+        // `Sandbox` normally wraps a single command.
+        if !self.fs.allow_fs_write && !writable_fds.is_empty() {
+            let sender =
+                linux_bubblewrap::ValidationFdSender::spawn(writable_fds).map_err(|error| {
+                    SandboxError::Io(format!("failed to start sandbox bind validator: {error}"))
+                })?;
+            self.validation_fd_sender = Some(sender);
+        }
+        let validation_socket =
+            self.validation_fd_sender
+                .as_ref()
+                .map(|sender| linux_bubblewrap::ValidationSocket {
+                    host_socket_path: sender.host_socket_path(),
+                    sandbox_socket_path: sender.sandbox_socket_path(),
+                });
 
         let bridge_program = std::env::current_exe()
             .map_err(|error| SandboxError::BridgeExecutableUnavailable(error.to_string()))?;
@@ -547,6 +881,7 @@ impl Sandbox {
             &command.program,
             &command.args,
             proxy_socket_path.as_deref(),
+            validation_socket,
         )
         .map_err(map_anyhow_error)?;
 
@@ -576,14 +911,28 @@ impl Sandbox {
             allow_fs_write: self.fs.allow_fs_write,
         };
         let (git_writable, git_protected) = self.git_path_split();
+        // Each location's canonical path was resolved exactly once at capture
+        // time; pass it straight through as the Seatbelt rule literal. The
+        // profile generator must NOT re-canonicalize (that reopened the
+        // verify-vs-enforce gap); see `generate_seatbelt_config`.
         let mut writable: Vec<&Path> = self
             .fs
             .writable_paths
             .iter()
-            .map(PathBuf::as_path)
+            .map(HostFilesystemLocation::macos_canonical_path)
             .collect();
-        writable.extend(git_writable.iter().map(PathBuf::as_path));
-        let protected: Vec<&Path> = git_protected.iter().map(PathBuf::as_path).collect();
+        writable.extend(
+            git_writable
+                .iter()
+                .map(HostFilesystemLocation::macos_canonical_path),
+        );
+        let protected: Vec<&Path> = git_protected
+            .iter()
+            .map(HostFilesystemLocation::macos_canonical_path)
+            .collect();
+
+        // SSH-agent socket handling (commit signing) is deferred, so no unix
+        // sockets are allowed for now.
         let (program, args, config) = macos_seatbelt::wrap_invocation(
             &command.program,
             &command.args,
@@ -614,16 +963,34 @@ impl Sandbox {
             allow_network: matches!(self.network, NetSetup::Unrestricted),
             allow_fs_write: self.fs.allow_fs_write,
         };
-        let (writable_git_paths, protected_git_paths) = self.git_path_split();
+        // On Windows the location carries only the requested path; the in-WSL
+        // helper performs the real capture-at-validation. These are mapped into
+        // WSL by `wrap_invocation`.
+        let writable_paths: Vec<PathBuf> = self
+            .fs
+            .writable_paths
+            .iter()
+            .map(|location| location.windows_path().to_path_buf())
+            .collect();
+        let (writable_git_locations, protected_git_locations) = self.git_path_split();
+        let writable_git_paths: Vec<PathBuf> = writable_git_locations
+            .iter()
+            .map(|location| location.windows_path().to_path_buf())
+            .collect();
+        let protected_git_paths: Vec<PathBuf> = protected_git_locations
+            .iter()
+            .map(|location| location.windows_path().to_path_buf())
+            .collect();
         let (program, args) = windows_wsl::wrap_invocation(
             command.program.clone(),
             command.args.clone(),
-            self.fs.writable_paths.clone(),
+            writable_paths,
             writable_git_paths,
             protected_git_paths,
             permissions,
             command.cwd.clone(),
             command.env.clone(),
+            self.wsl_zed_release.clone(),
         )
         .await
         .map_err(map_anyhow_error)?;
@@ -650,23 +1017,47 @@ impl Drop for Sandbox {
     }
 }
 
-/// Handle a possible re-exec of this binary as an in-sandbox helper.
+/// Argv flag that marks the WSL-side sandbox-helper re-exec. Shared so the
+/// Windows side (`windows_wsl`, which builds the `wsl.exe` invocation) and the
+/// Linux side (`linux_bubblewrap`, which parses it inside WSL) can't drift.
 ///
-/// Linux restricted-network runs launch this binary in bridge mode inside the
-/// sandbox network namespace before spawning the real command. Call this at the
-/// top of `main`, before normal argument parsing.
+/// Only referenced by those two cfg-gated modules, so it's gated to match;
+/// otherwise it's dead code on macOS.
+#[cfg(any(target_os = "linux", target_os = "windows"))]
+pub(crate) const WSL_SANDBOX_HELPER_FLAG: &str = "--wsl-sandbox-helper";
+
+/// Handle a possible re-exec of this binary as a sandbox helper.
+///
+/// Two Linux re-exec modes funnel through here, neither of which returns if it
+/// matches:
+/// - the in-sandbox launcher (bind validator + restricted-network bridge), run
+///   by bwrap before the real command; and
+/// - the WSL-side helper, run inside WSL to capture fds + drive bwrap (the moral
+///   equivalent of `Sandbox::wrap` on native Linux).
+///
+/// Call this at the top of `main`, before normal argument parsing.
 #[doc(hidden)]
 pub fn run_sandbox_launcher_if_invoked() {
     #[cfg(target_os = "linux")]
-    linux_bubblewrap::run_launcher_if_invoked();
+    {
+        linux_bubblewrap::run_launcher_if_invoked();
+        linux_bubblewrap::run_wsl_helper_if_invoked();
+    }
 }
 
+// The createability probe only needs to know whether a sandbox *can* be built
+// (namespaces, `bwrap` availability); it does not enforce any grant, so it runs
+// with no writable binds rather than re-deriving paths from the opaque
+// locations.
+
+/// The current path of the inode pinned by a [`HostFilesystemLocation`]'s
+/// `O_PATH` fd, via `/proc/self/fd`. This resolves to the *pinned inode*, so it
+/// reflects the object captured at validation even if its name was changed,
+/// rather than re-resolving an attacker-influenceable path string.
 #[cfg(target_os = "linux")]
-fn policy_writable_paths(policy: &SandboxPolicy) -> Vec<PathBuf> {
-    match &policy.fs {
-        SandboxFsPolicy::Unrestricted => Vec::new(),
-        SandboxFsPolicy::Restricted { writable_paths } => writable_paths.clone(),
-    }
+fn linux_location_path(location: &HostFilesystemLocation) -> Option<PathBuf> {
+    use std::os::fd::AsRawFd as _;
+    std::fs::read_link(format!("/proc/self/fd/{}", location.linux_fd().as_raw_fd())).ok()
 }
 
 #[cfg(not(target_os = "windows"))]
@@ -842,20 +1233,25 @@ mod tests {
 
     #[test]
     fn fs_merge_unrestricted_dominates_else_unions_paths() {
+        // Writable paths are captured as real `HostFilesystemLocation`s (keyed on
+        // the inode), so the union/dedup test needs three distinct real dirs.
+        let dir_a = tempfile::tempdir().expect("create temp dir a");
+        let dir_b = tempfile::tempdir().expect("create temp dir b");
+        let dir_c = tempfile::tempdir().expect("create temp dir c");
+        let location = |dir: &tempfile::TempDir| {
+            HostFilesystemLocation::new(dir.path()).expect("capture temp dir")
+        };
+
         let a = SandboxFsPolicy::Restricted {
-            writable_paths: vec![PathBuf::from("/a"), PathBuf::from("/b")],
+            writable_paths: vec![location(&dir_a), location(&dir_b)],
         };
         let b = SandboxFsPolicy::Restricted {
-            writable_paths: vec![PathBuf::from("/b"), PathBuf::from("/c")],
+            writable_paths: vec![location(&dir_b), location(&dir_c)],
         };
         assert_eq!(
             a.clone().merge(b),
             SandboxFsPolicy::Restricted {
-                writable_paths: vec![
-                    PathBuf::from("/a"),
-                    PathBuf::from("/b"),
-                    PathBuf::from("/c")
-                ],
+                writable_paths: vec![location(&dir_a), location(&dir_b), location(&dir_c)],
             }
         );
         assert_eq!(
@@ -864,7 +1260,7 @@ mod tests {
         );
         assert_eq!(
             SandboxFsPolicy::Unrestricted.merge(SandboxFsPolicy::Restricted {
-                writable_paths: vec![PathBuf::from("/a")],
+                writable_paths: vec![location(&dir_a)],
             }),
             SandboxFsPolicy::Unrestricted
         );

crates/sandbox/src/windows_wsl.rs

@@ -58,6 +58,101 @@ const BWRAP_UNUSABLE_EXIT_CODE: i32 = 42;
 /// of any stdout noise printed by the login shell's profile scripts.
 const PROBE_RESULT_PREFIX: &str = "zed-wsl-probe:";
 
+/// Prefix of the helper-provisioning script's single result line (the absolute
+/// in-WSL path of the Linux `zed` to run as the sandbox helper), picked out of
+/// login-shell stdout noise just like [`PROBE_RESULT_PREFIX`].
+const HELPER_RESULT_PREFIX: &str = "zed-wsl-helper:";
+
+/// Ensures a Linux `zed` matching the running release is available inside WSL to
+/// act as the sandbox helper (`--wsl-sandbox-helper`), and prints its absolute
+/// in-WSL path on a [`HELPER_RESULT_PREFIX`] line. `$1` is the release channel,
+/// `$2` the version (`latest` for dev builds, which have no matching release and
+/// so track the latest nightly); both are passed as argv, never interpolated, so
+/// a version/channel string can't inject shell.
+///
+/// Unlike a normal Linux install, this deliberately does **not** consult the WSL
+/// `PATH`: inside WSL `zed` typically resolves to the *Windows* `zed.exe` via
+/// interop, which is not a Linux binary and so can't be the helper. It also does
+/// not use the public install script (`install.sh`), which puts `zed` on the
+/// user's `PATH` and writes desktop entries we don't want. Instead the Windows
+/// side resolves the exact channel+version (see `wsl_zed_release`) and this
+/// script downloads that release's Linux tarball straight from
+/// `cloud.zed.dev/releases` and unpacks it into a private, off-`PATH` location
+/// (`~/.local/libexec/zed/<channel>`, the conventional spot for executables run
+/// by other programs rather than directly by the user). One managed copy per
+/// channel is kept, tracked by a marker file so an exact channel+version match
+/// is reused rather than re-downloaded.
+///
+/// We ship no `zed` (nor `bwrap`) into WSL ourselves; this downloads `zed` on
+/// demand. A missing `curl`/`wget` (or a failed download) is a hard error the
+/// caller surfaces to the user, exactly like a missing `bwrap`.
+const HELPER_PROVISION_SCRIPT: &str = r#"
+set -eu
+channel="$1"
+version="$2"
+dest="$HOME/.local/libexec/zed/$channel"
+marker="$dest/.zed-wsl-helper-version"
+want="$channel $version"
+
+# Reuse an exact, already-installed channel+version.
+if [ "$(cat "$marker" 2>/dev/null || true)" = "$want" ]; then
+    helper=$(find "$dest" -type f -path '*/bin/zed' -print 2>/dev/null | head -n 1 || true)
+    if [ -n "$helper" ] && [ -x "$helper" ]; then
+        printf 'zed-wsl-helper: %s\n' "$helper"
+        exit 0
+    fi
+fi
+
+arch=$(uname -m)
+case "$arch" in
+    x86_64 | amd64) arch="x86_64" ;;
+    aarch64 | arm64) arch="aarch64" ;;
+    *) echo "unsupported WSL architecture for the zed sandbox helper: $arch" >&2; exit 1 ;;
+esac
+url="https://cloud.zed.dev/releases/$channel/$version/download?asset=zed&arch=$arch&os=linux&source=zed-wsl-sandbox"
+
+tmp=$(mktemp -d "${TMPDIR:-/tmp}/zed-wsl-helper-XXXXXX")
+trap 'rm -rf "$tmp"' EXIT
+tarball="$tmp/zed.tar.gz"
+if command -v curl >/dev/null 2>&1; then
+    curl -fL "$url" -o "$tarball"
+elif command -v wget >/dev/null 2>&1; then
+    wget -O "$tarball" "$url"
+else
+    echo 'neither curl nor wget is available in WSL to download zed' >&2
+    exit 1
+fi
+
+mkdir -p "$tmp/unpacked"
+tar -xzf "$tarball" -C "$tmp/unpacked"
+helper_src=$(find "$tmp/unpacked" -type f -path '*/bin/zed' -print 2>/dev/null | head -n 1 || true)
+if [ -z "$helper_src" ]; then
+    echo 'the downloaded zed tarball did not contain a bin/zed binary' >&2
+    exit 1
+fi
+app=$(dirname "$(dirname "$helper_src")")
+
+# Install atomically: stage the unpacked app next to the destination on the same
+# filesystem, then swap it into place so a concurrent run never sees (or execs) a
+# partially-written install. The whole app dir is kept so the binary's bundled
+# libraries ($ORIGIN/../lib) remain alongside it.
+mkdir -p "$(dirname "$dest")"
+rm -rf "$dest.new" "$dest.old"
+cp -a "$app" "$dest.new"
+if [ -e "$dest" ]; then mv "$dest" "$dest.old"; fi
+mv "$dest.new" "$dest"
+rm -rf "$dest.old"
+printf '%s' "$want" > "$marker"
+
+helper=$(find "$dest" -type f -path '*/bin/zed' -print 2>/dev/null | head -n 1 || true)
+if [ -z "$helper" ] || [ ! -x "$helper" ]; then
+    echo "the installed zed sandbox helper is missing or not executable under $dest" >&2
+    exit 1
+fi
+printf 'zed-wsl-helper: %s\n' "$helper"
+exit 0
+"#;
+
 /// Marks a failure of the Windows WSL sandboxing *environment*: WSL is missing
 /// or won't start, there's no usable `bwrap`, or the probe / path-resolution
 /// stdout protocol broke down. Returned as the root of the `anyhow::Error` so
@@ -177,6 +272,13 @@ pub async fn wrap_invocation<S: std::hash::BuildHasher>(
     permissions: SandboxPermissions,
     cwd: Option<PathBuf>,
     env: HashMap<String, String, S>,
+    // `(release channel, version)` of the Linux `zed` to provision inside WSL as
+    // the `--wsl-sandbox-helper` (the version is `latest` for dev builds). When
+    // `None`, no helper is used and bwrap is exec'd directly — the legacy path,
+    // which binds writable paths by string and so carries the bind-source TOCTOU
+    // the helper closes. Callers that can determine the running release should
+    // always pass `Some`.
+    wsl_zed_release: Option<(String, String)>,
 ) -> Result<(String, Vec<String>)> {
     // Mapping failures are bad requests (a path that doesn't exist or has a
     // shape WSL can't address), not environment problems, so no
@@ -279,21 +381,50 @@ pub async fn wrap_invocation<S: std::hash::BuildHasher>(
     if let Some(cwd) = &cwd {
         wsl_args.extend(["--cd".to_string(), cwd.clone()]);
     }
-    // Use the absolute path the probe validated: `wsl --exec` searches only
-    // the default WSL PATH, which may not include a profile-managed location
-    // where the probe's login shell found `bwrap`.
-    wsl_args.extend(["--exec".to_string(), environment.bwrap_path.clone()]);
-    wsl_args.extend(build_bwrap_args(
+
+    // The bwrap *options* (everything before the trailing `-- cmd`): root bind,
+    // `/tmp` tmpfs, writable binds, interop blocking, `--setenv`s, `--chdir`,
+    // namespace flags. Identical whether or not we route through the helper.
+    let bwrap_options = build_bwrap_args(
         &writable_paths,
         &protected_git_paths,
         permissions,
         cwd.as_deref(),
         environment.mask_interop_dir,
         &env,
-    ));
-    wsl_args.push("--".to_string());
-    wsl_args.push(program);
-    wsl_args.extend(args);
+    );
+
+    match wsl_zed_release {
+        // Preferred path: run the in-WSL `zed` as the sandbox helper, which
+        // captures the writable binds' inodes WSL-side and validates them after
+        // bwrap's mounts (the same in-sandbox check native Linux performs).
+        Some((channel, version)) => {
+            let helper =
+                ensure_wsl_zed_helper(&wsl_exe, distro.as_deref(), &channel, &version).await?;
+            wsl_args.extend(["--exec".to_string(), helper]);
+            // Protocol (decoded by `linux_bubblewrap::decode_wsl_helper_args`):
+            //   <flag> <bwrap_path> <n_base> <base...> <n_writable> <writable...> -- <prog> <args>
+            wsl_args.push(crate::WSL_SANDBOX_HELPER_FLAG.to_string());
+            wsl_args.push(environment.bwrap_path.clone());
+            wsl_args.push(bwrap_options.len().to_string());
+            wsl_args.extend(bwrap_options);
+            wsl_args.push(writable_paths.len().to_string());
+            wsl_args.extend(writable_paths.iter().cloned());
+            wsl_args.push("--".to_string());
+            wsl_args.push(program);
+            wsl_args.extend(args);
+        }
+        // Legacy path: exec bwrap directly (no in-sandbox bind validation). Use
+        // the absolute path the probe validated, since `wsl --exec` searches
+        // only the default WSL PATH.
+        None => {
+            wsl_args.extend(["--exec".to_string(), environment.bwrap_path.clone()]);
+            wsl_args.extend(bwrap_options);
+            wsl_args.push("--".to_string());
+            wsl_args.push(program);
+            wsl_args.extend(args);
+        }
+    }
 
     Ok((wsl_exe.to_string_lossy().into_owned(), wsl_args))
 }
@@ -509,6 +640,94 @@ fn parse_probe_output(stdout: &str) -> Result<EnvironmentProbe> {
     })
 }
 
+/// Ensure a Linux `zed` of the given release `channel`/`version` is available
+/// inside WSL and return its absolute in-WSL path, to be `--exec`'d as the
+/// `--wsl-sandbox-helper`. Runs [`HELPER_PROVISION_SCRIPT`] (which downloads the
+/// matching release tarball into an off-`PATH` location on first use).
+///
+/// Successful resolutions are cached per `(distro, channel, version)` for the
+/// life of the process — once provisioned, the path won't change. Failures are
+/// not cached, so a user who installs `curl` (or fixes networking) after an
+/// error can retry without restarting Zed.
+async fn ensure_wsl_zed_helper(
+    wsl_exe: &Path,
+    distro: Option<&str>,
+    channel: &str,
+    version: &str,
+) -> Result<String> {
+    type HelperCache = HashMap<(Option<String>, String, String), String>;
+    static CACHE: OnceLock<Mutex<HelperCache>> = OnceLock::new();
+    let cache = CACHE.get_or_init(|| Mutex::new(HashMap::new()));
+
+    let key = (
+        distro.map(str::to_string),
+        channel.to_string(),
+        version.to_string(),
+    );
+    if let Some(path) = cache
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+        .get(&key)
+    {
+        return Ok(path.clone());
+    }
+
+    // A login shell (`-lc`) is used so a profile-managed PATH (where `zed` or
+    // `curl` may live) is honored. `channel`/`version` are passed as positional
+    // args (`$1`/`$2`), never interpolated into the script body.
+    let output = run_wsl_command(
+        wsl_exe,
+        distro,
+        [
+            "--exec",
+            "sh",
+            "-lc",
+            HELPER_PROVISION_SCRIPT,
+            "zed-wsl-sandbox-helper",
+            channel,
+            version,
+        ],
+        "provision the Linux `zed` sandbox helper",
+    )
+    .await?;
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        let stderr = stderr.trim();
+        return Err(unavailable(format!(
+            "failed to provision a Linux `zed` sandbox helper in {}{}",
+            wsl_distro_label(distro),
+            if stderr.is_empty() {
+                String::new()
+            } else {
+                format!(": {stderr}")
+            }
+        )));
+    }
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let path = stdout
+        .lines()
+        .rev()
+        .find_map(|line| line.strip_prefix(HELPER_RESULT_PREFIX))
+        .map(|path| path.trim().to_string())
+        .with_context(|| {
+            unavailable(format!(
+                "no helper result line in sandbox-helper provisioning output from {}: {stdout:?}",
+                wsl_distro_label(distro)
+            ))
+        })?;
+    ensure!(
+        path.starts_with('/'),
+        "the WSL `zed` sandbox helper resolved to {path:?} rather than an absolute path"
+    );
+
+    cache
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+        .insert(key, path.clone());
+    Ok(path)
+}
+
 /// Shell script that resolves and existence-checks paths in a single WSL
 /// round-trip. Arguments come in triples `(kind, path, fallback)`: kind `W`
 /// is a native Windows path to translate with `wslpath -u` (falling back to
@@ -1105,6 +1324,7 @@ mod tests {
             SandboxPermissions::default(),
             None,
             HashMap::<String, String>::new(),
+            None,
         ));
     }
 

crates/sandbox/src/wsl_sandbox_test_helper.rs

@@ -48,8 +48,8 @@ mod imp {
 
     use anyhow::{Context as _, Result, bail, ensure};
     use sandbox::{
-        CommandAndArgs, GitSandboxPolicy, Sandbox, SandboxError, SandboxFsPolicy, SandboxNetPolicy,
-        SandboxPolicy,
+        CommandAndArgs, GitSandboxPolicy, HostFilesystemLocation, Sandbox, SandboxError,
+        SandboxFsPolicy, SandboxNetPolicy, SandboxPolicy,
     };
 
     /// Network access for a helper run, translated into a `SandboxNetPolicy` in
@@ -513,7 +513,12 @@ mod imp {
                 SandboxFsPolicy::Unrestricted
             } else {
                 SandboxFsPolicy::Restricted {
-                    writable_paths: writable_paths.to_vec(),
+                    // On Windows the location only records the requested path;
+                    // the real capture happens WSL-side in the helper.
+                    writable_paths: writable_paths
+                        .iter()
+                        .filter_map(|path| HostFilesystemLocation::new(path).ok())
+                        .collect(),
                 }
             },
             network: match permissions.network {

docs/README.md

@@ -13,6 +13,17 @@ mdbook serve docs
 
 The first command dumps an action manifest to `crates/docs_preprocessor/actions.json`. Without it, the preprocessor cannot validate keybinding and action references in the docs and will report errors. You only need to re-run it when actions change.
 
+If you use Nix, the development shell provides a pinned `mdbook` (0.4.40) and a
+prebuilt docs preprocessor, so you can build the docs without installing anything
+or compiling the preprocessor on every run:
+
+```sh
+nix develop -c mdbook build docs
+```
+
+(When `actions.json` has not been generated, action/keybinding validation is
+skipped with a warning rather than failing the build.)
+
 It's important to note the version number above. For an unknown reason, as of 2025-04-23, running 0.4.48 will cause odd URL behavior that breaks things.
 
 Before committing, verify that the docs are formatted in the way Prettier expects with:
@@ -25,7 +36,7 @@ cd docs && pnpm dlx prettier@3.5.0 . --write && cd ..
 
 We have a custom mdBook preprocessor for interfacing with our crates (`crates/docs_preprocessor`).
 
-If for some reason you need to bypass the docs preprocessor, you can comment out `[preprocessor.zed_docs_preprocessor]` from the `book.toml`.
+If for some reason you need to bypass the docs preprocessor, you can comment out `[preprocessor.zed-docs-preprocessor]` from the `book.toml`.
 
 ## Images and videos
 

docs/book.toml

@@ -106,6 +106,6 @@ enable = false
 # and other docs-related functions.
 #
 # Comment the below section out if you need to bypass the preprocessor for some reason.
-[preprocessor.zed_docs_preprocessor]
+[preprocessor.zed-docs-preprocessor]
 command = "cargo run -p docs_preprocessor --"
 renderer = ["html", "zed-html"]

nix/build.nix

@@ -311,6 +311,13 @@ craneLib.buildPackage (
   lib.recursiveUpdate commonArgs {
     inherit cargoArtifacts;
 
+    # Expose the crane builder and shared arguments so other derivations (e.g.
+    # the docs preprocessor in the devshell) can build sibling workspace crates
+    # without duplicating all of the build inputs and environment setup.
+    passthru = {
+      inherit craneLib commonArgs cargoArtifacts;
+    };
+
     dontUseCmakeConfigure = true;
 
     # without the env var generate-licenses fails due to crane's fetchCargoVendor, see:

nix/dev/flake.lock

@@ -16,8 +16,25 @@
         "type": "github"
       }
     },
+    "nixpkgs-mdbook": {
+      "locked": {
+        "lastModified": 1721153957,
+        "narHash": "sha256-3xc3Tvk+AivI7TKctzgg3Q/4cLeqtarUuWLgTv2rPPM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "6ecabf9e3f617aeec1a23a27d0080cab066a9d5b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "6ecabf9e3f617aeec1a23a27d0080cab066a9d5b",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
+        "nixpkgs-mdbook": "nixpkgs-mdbook",
         "treefmt-nix": "treefmt-nix"
       }
     },

nix/dev/flake.nix

@@ -3,6 +3,10 @@
 
   inputs = {
     treefmt-nix.url = "github:numtide/treefmt-nix";
+    # Pinned to a nixpkgs revision that packages mdBook 0.4.40, the version the
+    # docs require (see `crates/docs_preprocessor/Cargo.toml`). Newer mdBook
+    # releases break the docs' double-nested subdirectories.
+    nixpkgs-mdbook.url = "github:NixOS/nixpkgs/6ecabf9e3f617aeec1a23a27d0080cab066a9d5b";
   };
 
   # This flake is only used for its inputs.

nix/modules/devshells.nix

@@ -1,13 +1,41 @@
 { inputs, ... }:
 {
   perSystem =
-    { pkgs, ... }:
+    { pkgs, system, ... }:
     let
       # NOTE: Duplicated because this is in a separate flake-parts partition
       # than ./packages.nix
       mkZed = import ../toolchain.nix { inherit inputs; };
       zed-editor = mkZed pkgs;
 
+      # mdBook pinned to 0.4.40 via a dedicated nixpkgs input, because the docs
+      # rely on behavior that newer mdBook releases break (see
+      # `crates/docs_preprocessor/Cargo.toml`).
+      mdbook = (import inputs.nixpkgs-mdbook { inherit system; }).mdbook;
+
+      # Prebuilt docs preprocessor/postprocessor binary. `docs/book.toml`
+      # defaults to `cargo run -p docs_preprocessor` so non-Nix contributors are
+      # unaffected; in the devshell we point mdBook at this prebuilt binary via
+      # the `MDBOOK_*` env vars below so `mdbook build docs` doesn't have to
+      # compile the preprocessor on every run.
+      #
+      # We reuse `zed-editor`'s crane builder and shared arguments (exposed via
+      # `passthru`) rather than `overrideAttrs`, because crane bakes
+      # `cargoExtraArgs` into the build command at evaluation time.
+      docs-preprocessor = zed-editor.passthru.craneLib.buildPackage (
+        zed-editor.passthru.commonArgs
+        // {
+          inherit (zed-editor.passthru) cargoArtifacts;
+          pname = "zed-docs-preprocessor";
+          cargoExtraArgs = "-p docs_preprocessor --locked";
+          dontUseCmakeConfigure = true;
+          meta = {
+            description = "mdBook preprocessor and postprocessor for the Zed docs";
+            mainProgram = "docs_preprocessor";
+          };
+        }
+      );
+
       rustBin = inputs.rust-overlay.lib.mkRustBin { } pkgs;
       rustToolchain = rustBin.fromRustupToolchainFile ../../rust-toolchain.toml;
 
@@ -54,6 +82,10 @@
             nodejs_22
             zig
 
+            # Documentation tooling: `nix develop -c mdbook build docs`
+            mdbook
+            docs-preprocessor
+
             # A11y testing infra
             gobject-introspection
             at-spi2-core
@@ -81,6 +113,14 @@
               ];
             };
             PROTOC = "${pkgs.protobuf}/bin/protoc";
+
+            # Point mdBook at the prebuilt preprocessor/postprocessor binary
+            # instead of `cargo run`. mdBook lowercases these keys and turns `_`
+            # into `-`, so they map to `preprocessor.zed-docs-preprocessor.command`
+            # and `output.zed-html.command` in `docs/book.toml`.
+            MDBOOK_PREPROCESSOR__ZED_DOCS_PREPROCESSOR__COMMAND = "${docs-preprocessor}/bin/docs_preprocessor";
+            MDBOOK_OUTPUT__ZED_HTML__COMMAND = "${docs-preprocessor}/bin/docs_preprocessor postprocess";
+
             ZED_ZSTD_MUSL_LIB = "${pkgs.pkgsCross.musl64.pkgsStatic.zstd.out}/lib";
             # For aws-lc-sys musl cross-compilation
             CC_x86_64_unknown_linux_musl = "${muslCross.stdenv.cc}/bin/x86_64-unknown-linux-musl-gcc";

nix/tests/sandboxing/default.nix

@@ -31,6 +31,11 @@
 #   writablePaths = [ ];        # writable subtrees when fs = "restricted"
 #   networkAccess = "blocked";  # or "unrestricted" / "restricted"
 #   allowedDomains = [ ];       # allowed hosts when networkAccess = "restricted"
+#   gitDisabled = [ ];          # `.git` dirs whose contents are protected
+#                               # (read-only on Linux). Mutually exclusive with
+#                               # gitAllowed.
+#   gitAllowed = [ ];           # `.git` dirs whose contents are made writable.
+#                               # Mutually exclusive with gitDisabled.
 #
 # Two echo servers (`echo1`, `echo2`) on separate nodes give the network checks
 # real peers, so a restricted-network policy that allowlists `echo1` can be
@@ -232,6 +237,138 @@ in
         succeeds = true;
       }
 
+      # ---- Git protection ----------------------------------------------------
+      # The worktree is writable, but the `.git` directory inside it can be
+      # protected (Git disabled) or opened up (Git allowed) independently. On
+      # Linux a protected `.git` is re-bound read-only *over* the writable
+      # worktree, so its contents stay readable but writes are denied.
+
+      # Git disabled: the worktree is writable but `.git` is protected, so a
+      # write into `.git` is denied. This is the core case the feature exists
+      # for — an agent editing the project must not be able to corrupt Git
+      # metadata.
+      {
+        fs = "restricted";
+        writablePaths = [ "/sandbox-test/repo" ];
+        gitDisabled = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo/.git/test";
+        succeeds = false;
+      }
+
+      # Git allowed: the same write into `.git` now succeeds because the policy
+      # makes `.git` writable.
+      {
+        fs = "restricted";
+        writablePaths = [ "/sandbox-test/repo" ];
+        gitAllowed = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo/.git/test";
+        succeeds = true;
+      }
+
+      # Git disabled protects only `.git`: ordinary writes elsewhere in the
+      # writable worktree are unaffected.
+      {
+        fs = "restricted";
+        writablePaths = [ "/sandbox-test/repo" ];
+        gitDisabled = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo/src/main.rs";
+        succeeds = true;
+      }
+
+      # Git disabled is a subtree protection: a write to something nested deep
+      # inside `.git` is denied too, not just a top-level file.
+      {
+        fs = "restricted";
+        writablePaths = [ "/sandbox-test/repo" ];
+        gitDisabled = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo/.git/hooks/pre-commit";
+        succeeds = false;
+      }
+
+      # Git disabled blocks writes but NOT reads: on Linux a protected `.git` is
+      # read-only, so its contents remain readable from inside the sandbox
+      # (Git status, log, diff, … must keep working).
+      {
+        fs = "restricted";
+        writablePaths = [ "/sandbox-test/repo" ];
+        gitDisabled = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        read = "/sandbox-test/repo/.git/HEAD";
+        succeeds = true;
+      }
+
+      # Git allowed grants writes to `.git` on its own, even when the worktree
+      # itself is not in `writablePaths`. The policy's Git dirs are made
+      # writable directly.
+      {
+        fs = "restricted";
+        writablePaths = [ ];
+        gitAllowed = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo/.git/test";
+        succeeds = true;
+      }
+
+      # ...and that grant is scoped to `.git`: it does not make the surrounding
+      # worktree writable. A write next to `.git` (not in `writablePaths`) is
+      # still denied.
+      {
+        fs = "restricted";
+        writablePaths = [ ];
+        gitAllowed = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo/README.md";
+        succeeds = false;
+      }
+
+      # Multiple repositories: each protected `.git` is independently denied.
+      # This exercises the list handling — a write into the *second* repo's
+      # `.git` must still be blocked.
+      {
+        fs = "restricted";
+        writablePaths = [
+          "/sandbox-test/repo-a"
+          "/sandbox-test/repo-b"
+        ];
+        gitDisabled = [
+          "/sandbox-test/repo-a/.git"
+          "/sandbox-test/repo-b/.git"
+        ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo-b/.git/test";
+        succeeds = false;
+      }
+
+      # The fs escape hatch supersedes Git protection: when filesystem writes
+      # are unrestricted there is no read-only bind to protect `.git`, so the
+      # write succeeds. This documents that `gitDisabled` only has teeth under a
+      # restricted filesystem policy.
+      {
+        fs = "unrestricted";
+        gitDisabled = [ "/sandbox-test/repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/repo/.git/test";
+        succeeds = true;
+      }
+
+      # Documented Linux gap: a `.git` that does not yet exist when the sandbox
+      # is built cannot be re-bound read-only, so it is skipped. Writing the
+      # `.git` entry itself (its parent worktree is writable, and `.git` does
+      # not exist beforehand) therefore succeeds. macOS denies this even before
+      # `.git` exists; bwrap cannot, and this test pins that difference.
+      {
+        fs = "restricted";
+        writablePaths = [ "/sandbox-test/fresh-repo" ];
+        gitDisabled = [ "/sandbox-test/fresh-repo/.git" ];
+        networkAccess = "blocked";
+        write = "/sandbox-test/fresh-repo/.git";
+        succeeds = true;
+      }
+
       # Blocked network: the echo server is unreachable.
       {
         fs = "restricted";