feat: dynamic-scopeの実装

Cargo.lock

@@ -82,6 +82,15 @@ version = "1.0.102"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
 
+[[package]]
+name = "arc-swap"
+version = "1.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a3a1fd6f75306b68087b831f025c712524bcb19aad54e557b1129cfa0a2b207"
+dependencies = [
+ "rustversion",
+]
+
 [[package]]
 name = "assert-json-diff"
 version = "2.0.2"
@@ -1696,6 +1705,7 @@ dependencies = [
 name = "manifest"
 version = "0.1.0"
 dependencies = [
+ "arc-swap",
  "llm-worker",
  "protocol",
  "serde",

crates/manifest/Cargo.toml

@@ -5,6 +5,7 @@ edition.workspace = true
 license.workspace = true
 
 [dependencies]
+arc-swap = "1"
 llm-worker = { workspace = true }
 protocol = { workspace = true }
 serde = { workspace = true, features = ["derive"] }

crates/manifest/src/lib.rs

@@ -15,7 +15,7 @@ pub use model::{
 };
 pub use paths::user_manifest_path;
 pub use protocol::{Permission, ScopeRule};
-pub use scope::{Scope, ScopeError};
+pub use scope::{Scope, ScopeError, SharedScope};
 
 use std::collections::HashMap;
 use std::num::NonZeroU32;

crates/manifest/src/scope.rs

@@ -8,6 +8,9 @@
 
 use std::ffi::OsString;
 use std::path::{Path, PathBuf};
+use std::sync::{Arc, Mutex};
+
+use arc_swap::{ArcSwap, Guard};
 
 use crate::{Permission, ScopeConfig, ScopeRule};
 
@@ -182,6 +185,38 @@ impl Scope {
             .map(|r| r.target.as_path())
     }
 
+    /// Build a new [`Scope`] equal to `self` with `extra_allow` appended
+    /// to the allow set. Used by dynamic-scope grow paths
+    /// (e.g. controller adding the bash-output Read rule, future
+    /// external `GrantScope`).
+    pub fn with_added_allow_rules(
+        &self,
+        extra_allow: impl IntoIterator<Item = ScopeRule>,
+    ) -> Result<Self, ScopeError> {
+        let mut config = ScopeConfig {
+            allow: self.allow_rules(),
+            deny: self.deny_rules(),
+        };
+        config.allow.extend(extra_allow);
+        Self::from_config(&config)
+    }
+
+    /// Build a new [`Scope`] equal to `self` with `extra_deny` appended
+    /// to the deny set. Used by dynamic-scope shrink paths
+    /// (e.g. SpawnPod-style delegation that strips Write from the
+    /// spawner without touching its allow rules).
+    pub fn with_added_deny_rules(
+        &self,
+        extra_deny: impl IntoIterator<Item = ScopeRule>,
+    ) -> Result<Self, ScopeError> {
+        let mut config = ScopeConfig {
+            allow: self.allow_rules(),
+            deny: self.deny_rules(),
+        };
+        config.deny.extend(extra_deny);
+        Self::from_config(&config)
+    }
+
     /// Human-readable grouping of allow rules, suitable for embedding in
     /// LLM system prompts. Deny rules are intentionally omitted — they
     /// only cap effective permission and surface them would mislead the
@@ -230,6 +265,81 @@ impl Scope {
     }
 }
 
+/// Shared, atomically-swappable view of a [`Scope`].
+///
+/// Built around [`ArcSwap`] so the hot path (permission checks inside
+/// `ScopedFs`) reads the current scope lock-free. Mutators are
+/// serialised by an internal `Mutex` so concurrent `update` calls do
+/// not lose each other's contributions.
+///
+/// All clones share the same underlying state — a `SharedScope` cloned
+/// out to multiple consumers (Pod, ScopedFs, future grant/revoke
+/// callers) sees every update.
+#[derive(Debug, Clone)]
+pub struct SharedScope {
+    inner: Arc<SharedScopeInner>,
+}
+
+#[derive(Debug)]
+struct SharedScopeInner {
+    scope: ArcSwap<Scope>,
+    /// Serialises read-modify-write update transactions so a producer
+    /// can read the current scope, build a derived one, and store it
+    /// without losing concurrent updates.
+    write_lock: Mutex<()>,
+}
+
+impl SharedScope {
+    /// Wrap an owned [`Scope`] in a shared, atomically-swappable handle.
+    pub fn new(scope: Scope) -> Self {
+        Self {
+            inner: Arc::new(SharedScopeInner {
+                scope: ArcSwap::from_pointee(scope),
+                write_lock: Mutex::new(()),
+            }),
+        }
+    }
+
+    /// Snapshot the current scope. Cheap and lock-free; the returned
+    /// guard borrows the live scope for as long as it is held.
+    pub fn load(&self) -> Guard<Arc<Scope>> {
+        self.inner.scope.load()
+    }
+
+    /// Snapshot the current scope into an owned `Arc<Scope>`. Useful
+    /// when the caller needs a value that outlives the load guard
+    /// (e.g. cloning into another struct).
+    pub fn snapshot(&self) -> Arc<Scope> {
+        self.inner.scope.load_full()
+    }
+
+    /// Replace the current scope wholesale. Equivalent to building a
+    /// fresh [`Scope`] from a [`ScopeConfig`] and storing it. Concurrent
+    /// `update` callers in the middle of a read-modify-write will see
+    /// this store reflected on their next iteration if their derived
+    /// scope cannot be built from the now-stale snapshot.
+    pub fn store(&self, scope: Scope) {
+        let _guard = self.inner.write_lock.lock().expect("scope mutex poisoned");
+        self.inner.scope.store(Arc::new(scope));
+    }
+
+    /// Read-modify-write transaction. `f` is called with the current
+    /// scope and returns a derived one (or an error). The internal
+    /// write lock ensures that two concurrent `update` calls see each
+    /// other's results — the second observes the first's output as its
+    /// input.
+    pub fn update<F>(&self, f: F) -> Result<(), ScopeError>
+    where
+        F: FnOnce(&Scope) -> Result<Scope, ScopeError>,
+    {
+        let _guard = self.inner.write_lock.lock().expect("scope mutex poisoned");
+        let current = self.inner.scope.load();
+        let new = f(&current)?;
+        self.inner.scope.store(Arc::new(new));
+        Ok(())
+    }
+}
+
 impl ResolvedRule {
     fn matches(&self, path: &Path) -> bool {
         if self.recursive {
@@ -545,4 +655,87 @@ mod tests {
         let deep = dir.path().join("a/b/c/new.txt");
         assert!(scope.is_writable(&deep));
     }
+
+    #[test]
+    fn with_added_allow_rules_grows_readable_set() {
+        let dir = TempDir::new().unwrap();
+        let extra = TempDir::new().unwrap();
+        let base = Scope::writable(dir.path()).unwrap();
+        assert!(!base.is_readable(&extra.path().join("x")));
+        let extended = base
+            .with_added_allow_rules([ScopeRule {
+                target: extra.path().to_path_buf(),
+                permission: Permission::Read,
+                recursive: true,
+            }])
+            .unwrap();
+        assert!(extended.is_readable(&extra.path().join("x")));
+        assert!(extended.is_writable(&dir.path().join("y")));
+    }
+
+    #[test]
+    fn with_added_deny_rules_demotes_write_to_read() {
+        let dir = TempDir::new().unwrap();
+        let sub = dir.path().join("sub");
+        std::fs::create_dir(&sub).unwrap();
+        let base = Scope::writable(dir.path()).unwrap();
+        let demoted = base
+            .with_added_deny_rules([ScopeRule {
+                target: sub.clone(),
+                permission: Permission::Write,
+                recursive: true,
+            }])
+            .unwrap();
+        let f = sub.join("a.txt");
+        assert_eq!(demoted.permission_at(&f), Some(Permission::Read));
+        assert_eq!(
+            demoted.permission_at(&dir.path().join("top.txt")),
+            Some(Permission::Write)
+        );
+    }
+
+    #[test]
+    fn shared_scope_load_returns_current_value() {
+        let dir = TempDir::new().unwrap();
+        let shared = SharedScope::new(Scope::writable(dir.path()).unwrap());
+        assert!(shared.load().is_writable(&dir.path().join("a.txt")));
+    }
+
+    #[test]
+    fn shared_scope_update_replaces_view_atomically() {
+        let dir = TempDir::new().unwrap();
+        let sub = dir.path().join("sub");
+        std::fs::create_dir(&sub).unwrap();
+        let shared = SharedScope::new(Scope::writable(dir.path()).unwrap());
+        let target = sub.join("a.txt");
+        assert_eq!(shared.load().permission_at(&target), Some(Permission::Write));
+        shared
+            .update(|cur| {
+                cur.with_added_deny_rules([ScopeRule {
+                    target: sub.clone(),
+                    permission: Permission::Write,
+                    recursive: true,
+                }])
+            })
+            .unwrap();
+        assert_eq!(shared.load().permission_at(&target), Some(Permission::Read));
+    }
+
+    #[test]
+    fn shared_scope_clones_share_state() {
+        let dir = TempDir::new().unwrap();
+        let extra = TempDir::new().unwrap();
+        let a = SharedScope::new(Scope::writable(dir.path()).unwrap());
+        let b = a.clone();
+        assert!(!b.load().is_readable(&extra.path().join("x")));
+        a.update(|cur| {
+            cur.with_added_allow_rules([ScopeRule {
+                target: extra.path().to_path_buf(),
+                permission: Permission::Read,
+                recursive: true,
+            }])
+        })
+        .unwrap();
+        assert!(b.load().is_readable(&extra.path().join("x")));
+    }
 }

crates/pod/src/controller.rs

@@ -83,7 +83,7 @@ impl PodController {
 
         // Snapshot pod-immutable values needed for tool factories so the
         // mutable worker borrow below doesn't conflict with reads on `pod`.
-        let scope_for_tools = pod.scope().clone();
+        let scope_handle = pod.scope().clone();
         let pwd_for_tools = pod.pwd().to_path_buf();
         let spawner_name = pod.manifest().pod.name.clone();
         let spawner_model = pod.manifest().model.clone();
@@ -230,11 +230,14 @@ impl PodController {
             // touching.
             //
             // Bash spills long outputs to a per-pod subdir under the
-            // runtime dir. We layer a recursive `allow(Read)` rule for
-            // that path on top of the user-facing scope so the agent can
-            // `Read` the saved files without polluting the workspace.
-            // Same approach memory takes for its deny rules: round-trip
-            // through `ScopeConfig` and rebuild via `from_config`.
+            // runtime dir. Push a recursive `allow(Read)` for that path
+            // into the Pod's runtime scope so the agent can `Read` the
+            // saved files without polluting the workspace. The Pod's
+            // SharedScope is the single source of truth — the same
+            // handle backs every ScopedFs (builtin tools, fs_view,
+            // compact worker), and any future scope mutation
+            // (SpawnPod-style revoke, future GrantScope) propagates
+            // through it.
             let bash_output_dir = runtime_dir.path().join("bash-output");
             std::fs::create_dir_all(&bash_output_dir).map_err(|e| {
                 std::io::Error::other(format!(
@@ -242,18 +245,16 @@ impl PodController {
                     bash_output_dir.display()
                 ))
             })?;
-            let mut scope_config = manifest::ScopeConfig {
-                allow: scope_for_tools.allow_rules(),
-                deny: scope_for_tools.deny_rules(),
-            };
-            scope_config.allow.push(manifest::ScopeRule {
-                target: bash_output_dir.clone(),
-                permission: manifest::Permission::Read,
-                recursive: true,
-            });
-            let scope_with_bash = manifest::Scope::from_config(&scope_config)
+            scope_handle
+                .update(|cur| {
+                    cur.with_added_allow_rules([manifest::ScopeRule {
+                        target: bash_output_dir.clone(),
+                        permission: manifest::Permission::Read,
+                        recursive: true,
+                    }])
+                })
                 .map_err(std::io::Error::other)?;
-            let fs = tools::ScopedFs::new(scope_with_bash, pwd_for_tools.clone());
+            let fs = tools::ScopedFs::with_shared_scope(scope_handle.clone(), pwd_for_tools.clone());
             let tracker = tools::Tracker::new();
             // The same ScopedFs also powers the IPC `ListCompletions`
             // query — keep a clone for the FS view we attach below,
@@ -292,6 +293,7 @@ impl PodController {
                 spawned_registry.clone(),
                 self_parent_socket.clone(),
                 spawner_model.clone(),
+                scope_handle.clone(),
             ));
             worker.register_tool(send_to_pod_tool(spawned_registry.clone()));
             worker.register_tool(read_pod_output_tool(spawned_registry.clone()));
@@ -873,7 +875,7 @@ where
         cwd: pod.pwd().display().to_string(),
         provider: provider_name,
         model: model_id,
-        scope_summary: pod.scope().summary(),
+        scope_summary: pod.scope_snapshot().summary(),
         tools: tool_names,
     }
 }

crates/pod/src/pod.rs

@@ -10,7 +10,10 @@ use llm_worker::{ToolOutputLimits, UsageRecord, Worker, WorkerError, WorkerResul
 use session_store::{EntryHash, SessionId, SessionStartState, Store, StoreError};
 use tracing::{info, warn};
 
-use manifest::{PodManifest, PodManifestConfig, ResolveError, Scope, ScopeError, WorkerManifest};
+use manifest::{
+    PodManifest, PodManifestConfig, ResolveError, Scope, ScopeError, ScopeRule, SharedScope,
+    WorkerManifest,
+};
 
 use crate::compact::state::CompactState;
 use crate::compact::usage_tracker::UsageTracker;
@@ -60,8 +63,11 @@ pub struct Pod<C: LlmClient, St: Store> {
     head_hash: Option<EntryHash>,
     /// Absolute working directory of the Pod.
     pwd: PathBuf,
-    /// Resolved scope — always present.
-    scope: Scope,
+    /// Shared, atomically-swappable view of the Pod's resolved scope.
+    /// Cloned out to `ScopedFs` instances (builtin tools, fs_view,
+    /// compact worker) so scope updates propagate to every consumer
+    /// at the next permission check.
+    scope: SharedScope,
     hook_builder: HookRegistryBuilder,
     interceptor_installed: bool,
     /// Shared compaction state (present when compact_threshold is configured).
@@ -185,7 +191,7 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
             session_id,
             head_hash: None,
             pwd,
-            scope,
+            scope: SharedScope::new(scope),
             hook_builder: HookRegistryBuilder::new(),
             interceptor_installed: false,
             compact_state: None,
@@ -252,11 +258,46 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
         &self.pwd
     }
 
-    /// The Pod's directory scope.
-    pub fn scope(&self) -> &Scope {
+    /// The Pod's directory scope, as a shared atomically-swappable
+    /// handle. Clone it to share scope state with another consumer
+    /// (e.g. a tool that needs to mutate scope dynamically).
+    pub fn scope(&self) -> &SharedScope {
         &self.scope
     }
 
+    /// Snapshot the current scope as an owned `Arc<Scope>`. Subsequent
+    /// scope mutations do not affect the returned snapshot.
+    pub fn scope_snapshot(&self) -> Arc<Scope> {
+        self.scope.snapshot()
+    }
+
+    /// Apply `extra_allow` to the Pod's runtime scope. Future tool
+    /// permission checks (read/write/glob/grep) reflect the broadened
+    /// scope; in-flight tool calls keep the snapshot they captured at
+    /// invocation time.
+    pub fn add_scope_rules(
+        &self,
+        extra_allow: impl IntoIterator<Item = ScopeRule>,
+    ) -> Result<(), ScopeError> {
+        let extra: Vec<ScopeRule> = extra_allow.into_iter().collect();
+        self.scope
+            .update(|cur| cur.with_added_allow_rules(extra.clone()))
+    }
+
+    /// Strip `revoke` rules from the Pod's runtime scope by adding
+    /// matching deny rules. A `Permission::Write` revoke caps effective
+    /// access at `Read` (mirroring the pod-registry `effective_write`
+    /// semantics — Write is the only permission tracked across Pods).
+    /// A `Permission::Read` revoke removes access entirely.
+    pub fn revoke_scope_rules(
+        &self,
+        revoke: impl IntoIterator<Item = ScopeRule>,
+    ) -> Result<(), ScopeError> {
+        let revoke: Vec<ScopeRule> = revoke.into_iter().collect();
+        self.scope
+            .update(|cur| cur.with_added_deny_rules(revoke.clone()))
+    }
+
     /// Direct access to the underlying Worker.
     pub fn worker(&self) -> &Worker<C, Mutable> {
         self.worker.as_ref().expect("worker taken during run")
@@ -582,10 +623,11 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
             } else {
                 None
             };
+        let scope_snapshot = self.scope.snapshot();
         let ctx = SystemPromptContext {
             now: chrono::Utc::now(),
             cwd: &self.pwd,
-            scope: &self.scope,
+            scope: &scope_snapshot,
             tool_names,
             agents_md: agents_md_read.body,
             resident_knowledge: resident_slice,
@@ -667,7 +709,7 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
     /// are skipped — the unresolved placeholder stays in the flattened
     /// user message so the LLM still sees the intent.
     fn resolve_file_refs(&self, segments: &[Segment]) -> Vec<Item> {
-        let view = crate::fs_view::PodFsView::new(tools::ScopedFs::new(
+        let view = crate::fs_view::PodFsView::new(tools::ScopedFs::with_shared_scope(
             self.scope.clone(),
             self.pwd.clone(),
         ));
@@ -1078,7 +1120,7 @@ impl<C: LlmClient, St: Store> Pod<C, St> {
         // with the main Pod (reads go through the same policy) but the
         // Tracker is fresh — compact-time reads must not pollute the
         // main session's recency list, which feeds `default_refs` above.
-        let scoped_fs = tools::ScopedFs::new(self.scope.clone(), self.pwd.clone());
+        let scoped_fs = tools::ScopedFs::with_shared_scope(self.scope.clone(), self.pwd.clone());
         let summary_tracker = tools::Tracker::new();
         let summary_client: Box<dyn LlmClient> = self.build_compactor_client()?;
         let summary_system_prompt = self
@@ -1801,7 +1843,7 @@ impl<St: Store> Pod<Box<dyn LlmClient>, St> {
             session_id,
             head_hash: None,
             pwd: common.pwd,
-            scope: common.scope,
+            scope: SharedScope::new(common.scope),
             hook_builder: HookRegistryBuilder::new(),
             interceptor_installed: false,
             compact_state: None,
@@ -1859,7 +1901,7 @@ impl<St: Store> Pod<Box<dyn LlmClient>, St> {
             session_id,
             head_hash: None,
             pwd: common.pwd,
-            scope: common.scope,
+            scope: SharedScope::new(common.scope),
             hook_builder: HookRegistryBuilder::new(),
             interceptor_installed: false,
             compact_state: None,
@@ -1967,7 +2009,7 @@ impl<St: Store> Pod<Box<dyn LlmClient>, St> {
             session_id,
             head_hash: state.head_hash,
             pwd: common.pwd,
-            scope: common.scope,
+            scope: SharedScope::new(common.scope),
             hook_builder: HookRegistryBuilder::new(),
             interceptor_installed: false,
             compact_state: None,

crates/pod/src/spawn/tool.rs

@@ -15,7 +15,7 @@ use async_trait::async_trait;
 use llm_worker::tool::{Tool, ToolDefinition, ToolError, ToolMeta, ToolOutput};
 use manifest::{
     ModelManifest, Permission, PodManifestConfig, PodMetaConfig, ScopeConfig, ScopeRule,
-    WorkerManifestConfig,
+    SharedScope, WorkerManifestConfig,
 };
 use protocol::Method;
 use protocol::stream::JsonLineWriter;
@@ -119,6 +119,14 @@ pub struct SpawnPodTool {
     /// configuration in the manifest cascade. Per-spawn override is
     /// out of scope here (see `tickets/spawn-inherit-provider.md`).
     spawner_model: ModelManifest,
+    /// Spawner's runtime scope. After a successful spawn, the
+    /// `Permission::Write` rules in the delegated scope are revoked
+    /// from the spawner's in-memory view (a `deny(Write, target)` is
+    /// pushed on top, downgrading the spawner's effective access on
+    /// those paths to `Read`). Mirrors the pod-registry's
+    /// `effective_write` semantics: Write is the only permission
+    /// tracked across Pods, so revocation only touches Write.
+    spawner_scope: SharedScope,
 }
 
 impl SpawnPodTool {
@@ -130,6 +138,7 @@ impl SpawnPodTool {
         registry: Arc<SpawnedPodRegistry>,
         parent_socket: Option<PathBuf>,
         spawner_model: ModelManifest,
+        spawner_scope: SharedScope,
     ) -> Self {
         Self {
             spawner_name,
@@ -139,6 +148,7 @@ impl SpawnPodTool {
             registry,
             parent_socket,
             spawner_model,
+            spawner_scope,
         }
     }
 }
@@ -217,6 +227,27 @@ impl Tool for SpawnPodTool {
 
         // Child is live. Post-start errors propagate but do not roll
         // back the scope allocation — the child already owns it.
+        //
+        // Mirror that ownership transfer in the spawner's in-memory
+        // scope: every `Permission::Write` rule in the delegated scope
+        // is shadowed by a `deny(Write, target)` so subsequent tool
+        // calls (Edit/Write) on the delegated paths fail with
+        // `ReadOnly`. Read access is left intact — the registry only
+        // arbitrates Write, and keeping Read lets the spawner observe
+        // the child's intermediate output through Read/Glob/Grep.
+        let revoke_write: Vec<ScopeRule> = scope_allow
+            .iter()
+            .filter(|r| r.permission == Permission::Write)
+            .cloned()
+            .collect();
+        if !revoke_write.is_empty() {
+            self.spawner_scope
+                .update(|cur| cur.with_added_deny_rules(revoke_write.clone()))
+                .map_err(|e| {
+                    ToolError::ExecutionFailed(format!("revoke spawner scope: {e}"))
+                })?;
+        }
+
         send_run(&predicted_socket, &input.task).await?;
 
         let record = SpawnedPodRecord {
@@ -456,6 +487,7 @@ pub fn spawn_pod_tool(
     registry: Arc<SpawnedPodRegistry>,
     parent_socket: Option<PathBuf>,
     spawner_model: ModelManifest,
+    spawner_scope: SharedScope,
 ) -> ToolDefinition {
     Arc::new(move || {
         let schema = schemars::schema_for!(SpawnPodInput);
@@ -471,6 +503,7 @@ pub fn spawn_pod_tool(
             registry.clone(),
             parent_socket.clone(),
             spawner_model.clone(),
+            spawner_scope.clone(),
         ));
         (meta, tool)
     })

crates/pod/tests/spawn_pod_test.rs

@@ -11,7 +11,7 @@ use std::path::{Path, PathBuf};
 use std::sync::{LazyLock, Mutex};
 
 use llm_worker::tool::{ToolError, ToolOutput};
-use manifest::{AuthRef, ModelManifest, Permission, SchemeKind, ScopeRule};
+use manifest::{AuthRef, ModelManifest, Permission, SchemeKind, Scope, ScopeRule, SharedScope};
 use pod::runtime::dir::{RuntimeDir, SpawnedPodRecord};
 use pod::runtime::pod_registry::{self, LockFileGuard};
 use pod::spawn::registry::SpawnedPodRegistry;
@@ -149,6 +149,14 @@ fn dummy_model() -> ModelManifest {
     }
 }
 
+/// Spawner-side `SharedScope` mirroring the `allow_root` granted by
+/// `setup_spawner`. The tool revokes Write rules from this scope on
+/// successful spawn — tests can `load()` it to assert the
+/// revocation took effect.
+fn shared_scope_for(allow_root: &Path) -> SharedScope {
+    SharedScope::new(Scope::writable(allow_root).unwrap())
+}
+
 fn clear_env() {
     unsafe {
         std::env::remove_var("INSOMNIA_RUNTIME_DIR");
@@ -169,6 +177,7 @@ async fn spawn_pod_delegates_scope_and_sends_run() {
     let received = accept_one_method(listener);
 
     let registry = SpawnedPodRegistry::new(spawner_rd.clone());
+    let spawner_scope = shared_scope_for(allow_root.path());
     let def = spawn_pod_tool(
         "root".into(),
         spawner_socket.clone(),
@@ -177,6 +186,7 @@ async fn spawn_pod_delegates_scope_and_sends_run() {
         registry,
         None,
         dummy_model(),
+        spawner_scope.clone(),
     );
     let (_meta, tool) = def();
 
@@ -190,6 +200,13 @@ async fn spawn_pod_delegates_scope_and_sends_run() {
     })
     .to_string();
 
+    // Pre-spawn: the spawner can write to the delegated path.
+    assert!(
+        spawner_scope
+            .load()
+            .is_writable(&allow_root.path().join("a.txt"))
+    );
+
     let output: ToolOutput = tool.execute(&input).await.unwrap();
     assert!(
         output.summary.contains("child"),
@@ -225,6 +242,15 @@ async fn spawn_pod_delegates_scope_and_sends_run() {
     assert_eq!(records[0].pod_name, "child");
     assert_eq!(records[0].callback_address, spawner_socket);
 
+    // Post-spawn: the spawner's runtime scope has been demoted on the
+    // delegated path. Write is gone, Read remains.
+    let post = spawner_scope.load();
+    assert_eq!(
+        post.permission_at(&allow_root.path().join("a.txt")),
+        Some(Permission::Read),
+        "spawner should still be able to read delegated path"
+    );
+
     clear_env();
 }
 
@@ -239,6 +265,7 @@ async fn spawn_pod_rejects_scope_outside_spawner() {
     point_pod_command_at_true();
 
     let registry = SpawnedPodRegistry::new(spawner_rd);
+    let spawner_scope = shared_scope_for(allow_root.path());
     let def = spawn_pod_tool(
         "root".into(),
         spawner_socket,
@@ -247,6 +274,7 @@ async fn spawn_pod_rejects_scope_outside_spawner() {
         registry,
         None,
         dummy_model(),
+        spawner_scope.clone(),
     );
     let (_meta, tool) = def();
 
@@ -277,6 +305,13 @@ async fn spawn_pod_rejects_scope_outside_spawner() {
     let guard = LockFileGuard::open(&lock_path).unwrap();
     assert!(guard.data().find("child").is_none());
 
+    // Failed spawn must not have demoted the spawner's scope either.
+    assert!(
+        spawner_scope
+            .load()
+            .is_writable(&allow_root.path().join("a.txt"))
+    );
+
     clear_env();
 }
 
@@ -301,6 +336,7 @@ async fn spawn_pod_rolls_back_reservation_when_socket_never_appears() {
     // by running this test alone when iterating.
 
     let registry = SpawnedPodRegistry::new(spawner_rd);
+    let spawner_scope = shared_scope_for(allow_root.path());
     let def = spawn_pod_tool(
         "root".into(),
         spawner_socket,
@@ -309,6 +345,7 @@ async fn spawn_pod_rolls_back_reservation_when_socket_never_appears() {
         registry,
         None,
         dummy_model(),
+        spawner_scope.clone(),
     );
     let (_meta, tool) = def();
 
@@ -341,5 +378,13 @@ async fn spawn_pod_rolls_back_reservation_when_socket_never_appears() {
         "allocation was not rolled back after socket wait timed out"
     );
 
+    // Spawner's runtime scope must also be untouched — revoke is
+    // performed only after exec_child succeeds.
+    assert!(
+        spawner_scope
+            .load()
+            .is_writable(&allow_root.path().join("a.txt"))
+    );
+
     clear_env();
 }

crates/tools/src/scoped_fs.rs

@@ -13,17 +13,23 @@ use std::io::Write as _;
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
-use manifest::Scope;
+use manifest::{Scope, SharedScope};
 
 use crate::error::ToolsError;
 
 #[derive(Debug)]
 struct ScopedFsInner {
-    scope: Scope,
+    scope: SharedScope,
     pwd: PathBuf,
 }
 
 /// Scope-aware filesystem handle. Clone-cheap (`Arc` inside).
+///
+/// The wrapped [`SharedScope`] is shared with every clone of this
+/// `ScopedFs` and with whoever else holds the same `SharedScope`
+/// handle (typically the owning Pod). Mutations to that `SharedScope`
+/// propagate atomically; the next permission check inside any
+/// `ScopedFs` reads the new view.
 #[derive(Debug, Clone)]
 pub struct ScopedFs {
     inner: Arc<ScopedFsInner>,
@@ -37,15 +43,34 @@ pub struct WriteOutcome {
 }
 
 impl ScopedFs {
-    /// Create a new [`ScopedFs`] wrapping the given [`Scope`] and pwd.
+    /// Create a new [`ScopedFs`] wrapping `scope` and `pwd` in a fresh
+    /// [`SharedScope`]. Use [`ScopedFs::with_shared_scope`] when you
+    /// need the resulting `ScopedFs` to share scope state with another
+    /// holder of the `SharedScope` (typically the Pod).
     pub fn new(scope: Scope, pwd: PathBuf) -> Self {
+        Self::with_shared_scope(SharedScope::new(scope), pwd)
+    }
+
+    /// Build a [`ScopedFs`] over an existing [`SharedScope`]. The
+    /// resulting handle and any future updates the caller pushes to
+    /// `scope` are observed by every clone of this `ScopedFs`.
+    pub fn with_shared_scope(scope: SharedScope, pwd: PathBuf) -> Self {
         Self {
             inner: Arc::new(ScopedFsInner { scope, pwd }),
         }
     }
 
-    /// The underlying [`Scope`].
-    pub fn scope(&self) -> &Scope {
+    /// Snapshot the current scope. Cheap; the returned `Arc<Scope>` is
+    /// a coherent point-in-time view that subsequent mutations do not
+    /// affect.
+    pub fn scope(&self) -> Arc<Scope> {
+        self.inner.scope.snapshot()
+    }
+
+    /// Shared scope handle backing this `ScopedFs`. Cloning it lets a
+    /// caller (usually the Pod) hold the same view and push updates
+    /// that are immediately reflected in subsequent permission checks.
+    pub fn shared_scope(&self) -> &SharedScope {
         &self.inner.scope
     }
 
@@ -67,7 +92,7 @@ impl ScopedFs {
         if !path.is_absolute() {
             return Err(ToolsError::RelativePath(path.to_path_buf()));
         }
-        if !self.inner.scope.is_readable(path) {
+        if !self.inner.scope.load().is_readable(path) {
             return Err(ToolsError::OutOfScope(path.to_path_buf()));
         }
         let meta = std::fs::metadata(path).map_err(|e| match e.kind() {
@@ -100,13 +125,15 @@ impl ScopedFs {
         if !path.is_absolute() {
             return Err(ToolsError::RelativePath(path.to_path_buf()));
         }
-        if !self.inner.scope.is_writable(path) {
-            return Err(if self.inner.scope.is_readable(path) {
+        let scope = self.inner.scope.load();
+        if !scope.is_writable(path) {
+            return Err(if scope.is_readable(path) {
                 ToolsError::ReadOnly(path.to_path_buf())
             } else {
                 ToolsError::OutOfScope(path.to_path_buf())
             });
         }
+        drop(scope);
 
         // Reject existing directory targets.
         match std::fs::metadata(path) {
@@ -299,4 +326,118 @@ mod tests {
         let err = fs.write(dir.path(), b"x").unwrap_err();
         assert!(matches!(err, ToolsError::IsDirectory(_)));
     }
+
+    // -------------------------------------------------------------------------
+    // Dynamic scope: SharedScope mutations propagate into ScopedFs decisions
+    // -------------------------------------------------------------------------
+
+    #[test]
+    fn add_allow_rule_through_shared_scope_grows_readable_set() {
+        use manifest::SharedScope;
+
+        let dir = TempDir::new().unwrap();
+        let extra = TempDir::new().unwrap();
+        let extra_file = extra.path().join("x.txt");
+        fs::write(&extra_file, b"hi").unwrap();
+
+        let shared = SharedScope::new(Scope::writable(dir.path()).unwrap());
+        let fs = ScopedFs::with_shared_scope(shared.clone(), dir.path().to_path_buf());
+
+        // Before: extra is out of scope.
+        let err = fs.read_bytes(&extra_file).unwrap_err();
+        assert!(matches!(err, ToolsError::OutOfScope(_)));
+
+        // Push an allow(Read) rule.
+        shared
+            .update(|cur| {
+                cur.with_added_allow_rules([ScopeRule {
+                    target: extra.path().to_path_buf(),
+                    permission: Permission::Read,
+                    recursive: true,
+                }])
+            })
+            .unwrap();
+
+        // After: read goes through.
+        assert_eq!(fs.read_bytes(&extra_file).unwrap(), b"hi");
+        // But write still fails — allow only granted Read.
+        let err = fs.write(&extra.path().join("y.txt"), b"x").unwrap_err();
+        assert!(
+            matches!(err, ToolsError::ReadOnly(_)),
+            "expected ReadOnly, got {err:?}"
+        );
+    }
+
+    #[test]
+    fn revoke_write_through_shared_scope_blocks_subsequent_writes() {
+        use manifest::SharedScope;
+
+        let dir = TempDir::new().unwrap();
+        let sub = dir.path().join("sub");
+        fs::create_dir(&sub).unwrap();
+        let target = sub.join("a.txt");
+
+        let shared = SharedScope::new(Scope::writable(dir.path()).unwrap());
+        let fs = ScopedFs::with_shared_scope(shared.clone(), dir.path().to_path_buf());
+
+        // Write succeeds initially.
+        fs.write(&target, b"first").unwrap();
+
+        // Revoke Write on `sub` (push a deny(Write) rule).
+        shared
+            .update(|cur| {
+                cur.with_added_deny_rules([ScopeRule {
+                    target: sub.clone(),
+                    permission: Permission::Write,
+                    recursive: true,
+                }])
+            })
+            .unwrap();
+
+        // Subsequent write fails with ReadOnly — Read is preserved.
+        let err = fs.write(&target, b"second").unwrap_err();
+        assert!(
+            matches!(err, ToolsError::ReadOnly(_)),
+            "expected ReadOnly after revoke, got {err:?}"
+        );
+        // Read still works.
+        assert_eq!(fs.read_bytes(&target).unwrap(), b"first");
+    }
+
+    #[test]
+    fn shared_scope_changes_propagate_across_clones() {
+        use manifest::SharedScope;
+
+        let dir = TempDir::new().unwrap();
+        let target = dir.path().join("a.txt");
+
+        let shared = SharedScope::new(Scope::writable(dir.path()).unwrap());
+        let fs1 = ScopedFs::with_shared_scope(shared.clone(), dir.path().to_path_buf());
+        let fs2 = fs1.clone();
+
+        // fs1 writes; both clones see the file.
+        fs1.write(&target, b"hi").unwrap();
+        assert_eq!(fs2.read_bytes(&target).unwrap(), b"hi");
+
+        // Revoke write through the original handle.
+        shared
+            .update(|cur| {
+                cur.with_added_deny_rules([ScopeRule {
+                    target: dir.path().to_path_buf(),
+                    permission: Permission::Write,
+                    recursive: true,
+                }])
+            })
+            .unwrap();
+
+        // Both clones reject writes now — they share the same SharedScope.
+        assert!(matches!(
+            fs1.write(&target, b"x").unwrap_err(),
+            ToolsError::ReadOnly(_)
+        ));
+        assert!(matches!(
+            fs2.write(&target, b"x").unwrap_err(),
+            ToolsError::ReadOnly(_)
+        ));
+    }
 }