remove the /shared bind from agent containers

hive-c0re/src/lifecycle/host_config.rs

@@ -12,8 +12,7 @@ use hive_types::Permission;
 use crate::coordinator::{AgentPaths, HiveEnv};
 
 use super::{
-    AGENT_PREFIX, CONTAINER_RUNTIME_MOUNT, CONTAINER_SHARED_MOUNT, container_claude_mount,
-    container_name, validate,
+    AGENT_PREFIX, CONTAINER_RUNTIME_MOUNT, container_claude_mount, container_name, validate,
 };
 
 /// Re-apply the per-container host-side config: nspawn flags (bind
@@ -420,26 +419,6 @@ async fn set_nspawn_flags(
     claude_dir: &Path,
     notes_dir: &Path,
 ) -> Result<()> {
-    // Ensure /shared directory exists before binding. systemd-nspawn requires the bind source to exist.
-    let shared_root = crate::paths::shared_root();
-    std::fs::create_dir_all(&shared_root)
-        .with_context(|| format!("create {}", shared_root.display()))?;
-    // Make /shared writable by every agent. Containers share host uids (no
-    // PrivateUsers), but each agent is a distinct unix user, so a root-owned
-    // 0755 dir leaves them unable to write — the documented "read/write for
-    // all agents" contract was broken. A setgid group would need a
-    // pinned GID declared in every container plus all agent users joined to
-    // it (cross-container coordination + a rebuild cascade); instead we use
-    // the /tmp model — sticky world-writable (1777). The sticky bit lets any
-    // agent create files while protecting each agent's entries from deletion
-    // by the others, and matches /shared's documented "free-for-all, may be
-    // deleted/lost" semantics without touching any per-agent config.
-    {
-        use std::os::unix::fs::PermissionsExt as _;
-        let perms = std::fs::Permissions::from_mode(0o1777);
-        std::fs::set_permissions(&shared_root, perms)
-            .with_context(|| format!("chmod 1777 {}", shared_root.display()))?;
-    }
     // Ensure /knowledge dir exists. It may be empty until forge seeds it;
     // nspawn refuses to start if the bind source is missing entirely.
     std::fs::create_dir_all(crate::knowledge::LOCAL_DIR)
@@ -454,7 +433,6 @@ async fn set_nspawn_flags(
     // harness service's environment sets `HOME` to the same path
     // (`agent.nix` template), so no `--setenv` plumbing
     // is needed here — the bind alone is enough.
-    let claude_mount = container_claude_mount(agent_name);
 
     // The agent's own identity *at* the swarm secret store, collected under
     // this hive's certificate. Staged here rather than at spawn because this
@@ -462,28 +440,7 @@ async fn set_nspawn_flags(
     // `super::agent_identity` for the whole hop.
     let load_creds = super::agent_identity::stage(agent_name).await;
 
-    let mut binds: Vec<BindMount> = vec![
-        BindMount {
-            host_path: runtime_dir.to_string_lossy().into_owned(),
-            container_path: CONTAINER_RUNTIME_MOUNT.to_owned(),
-            read_only: false,
-        },
-        BindMount {
-            host_path: claude_dir.to_string_lossy().into_owned(),
-            container_path: claude_mount,
-            read_only: false,
-        },
-        BindMount {
-            host_path: shared_root.to_string_lossy().into_owned(),
-            container_path: CONTAINER_SHARED_MOUNT.to_owned(),
-            read_only: false,
-        },
-        BindMount {
-            host_path: crate::knowledge::LOCAL_DIR.to_owned(),
-            container_path: crate::knowledge::CONTAINER_MOUNT.to_owned(),
-            read_only: true,
-        },
-    ];
+    let mut binds = base_binds(runtime_dir, claude_dir, container_claude_mount(agent_name));
 
     // Own state, harness, work, and config dirs — same for every agent
     // including the manager. Config is RO: an agent must not edit its own
@@ -587,14 +544,55 @@ async fn set_nspawn_flags(
     .await
 }
 
+/// The binds every agent container gets, before its own state, config and
+/// role-specific dirs.
+fn base_binds(runtime_dir: &Path, claude_dir: &Path, claude_mount: String) -> Vec<BindMount> {
+    vec![
+        BindMount {
+            host_path: runtime_dir.to_string_lossy().into_owned(),
+            container_path: CONTAINER_RUNTIME_MOUNT.to_owned(),
+            read_only: false,
+        },
+        BindMount {
+            host_path: claude_dir.to_string_lossy().into_owned(),
+            container_path: claude_mount,
+            read_only: false,
+        },
+        BindMount {
+            host_path: crate::knowledge::LOCAL_DIR.to_owned(),
+            container_path: crate::knowledge::CONTAINER_MOUNT.to_owned(),
+            read_only: true,
+        },
+    ]
+}
+
 #[cfg(test)]
 mod tests {
     use super::{
-        BindMount, HostMemory, MEMORY_CAP_FILE, bind_child_agent_dirs, bind_own_agent_dirs,
-        holds_manage_root_agent, limits_to_apply, memory_cap_value, stage_limits,
+        BindMount, HostMemory, MEMORY_CAP_FILE, base_binds, bind_child_agent_dirs,
+        bind_own_agent_dirs, holds_manage_root_agent, limits_to_apply, memory_cap_value,
+        stage_limits,
     };
     use crate::coordinator::HiveEnv;
 
+    /// No agent container gets a cross-agent scratch dir; `/knowledge` is the
+    /// control that the lookup finds a bind that is there.
+    #[test]
+    fn base_binds_have_no_shared_dir() {
+        let binds = base_binds(
+            std::path::Path::new("/run/x"),
+            std::path::Path::new("/var/lib/x/claude"),
+            "/home/a/.claude".to_owned(),
+        );
+        let targets: Vec<&str> = binds.iter().map(|b| b.container_path.as_str()).collect();
+        assert!(targets.contains(&"/knowledge"), "control: {targets:?}");
+        assert!(!targets.contains(&"/shared"), "{targets:?}");
+        assert!(
+            binds.iter().all(|b| !b.host_path.ends_with("/shared")),
+            "{binds:?}"
+        );
+    }
+
     fn child_binds() -> Vec<BindMount> {
         let mut binds = Vec::new();
         bind_child_agent_dirs("kiddo", &mut binds);

hive-c0re/src/lifecycle/mod.rs

@@ -51,11 +51,6 @@ pub fn container_claude_mount(name: &str) -> String {
     format!("/home/{name}/.claude")
 }
 
-/// Mount point of the shared directory accessible to all agents.
-/// All agents can read/write here; agents should only put things they're
-/// willing to lose (other agents may delete them).
-pub const CONTAINER_SHARED_MOUNT: &str = "/shared";
-
 pub use hive_meta_flake::agent_web_port;
 
 /// Extract the bridge gateway IP from `HIVE_NETWORK_SUBNET`.

hive-c0re/src/paths.rs

@@ -6,7 +6,7 @@
 //! …). This module is the **single Rust-side source** for every host
 //! path — the strictly host-side ones grouped into subdirs (`db/`,
 //! `matrix/`, `run/`), plus the **nix-coupled** roots
-//! (`agents/`, `applied/`, `meta/`, `shared/`, `gateway/`, `knowledge/`,
+//! (`agents/`, `applied/`, `meta/`, `gateway/`, `knowledge/`,
 //! the `/run` runtime dirs).
 //!
 //! Nix-coupled paths are NOT excluded (the old stance) — they're moved
@@ -192,16 +192,6 @@ pub fn meta_rev_dir() -> PathBuf {
     state_root().join("meta-rev")
 }
 
-/// `shared/` — the cross-agent `/shared` scratch space. A `&str`, so it
-/// stays a const; [`shared_root`] wraps it.
-// nix: bind-mounted into every agent container as `/shared` (the harness nix modules) — must match.
-pub const SHARED_ROOT: &str = "/var/lib/hyperhive/shared";
-
-#[must_use]
-pub fn shared_root() -> PathBuf {
-    PathBuf::from(SHARED_ROOT)
-}
-
 /// `knowledge/` — local checkout of the `internal/knowledge` repo. A
 /// `&str` (used as a git `-C` arg / clone target throughout the knowledge
 /// worker), so it stays a const rather than a `PathBuf` fn.