diff --git a/docs/conventions.md b/docs/conventions.md
index 909a7646..894b6f48 100644
--- a/docs/conventions.md
+++ b/docs/conventions.md
@@ -332,13 +332,16 @@ binary flavor.
 | `scheduling` | `request_schedule_prompt`, `fire_schedule_now`, `cancel_schedule`, `edit_schedule`, `list_schedules` *(privileged)* |
 | `diagnostics` | `get_logs` *(privileged)* |
 
-**Always-on tools** — `set_status` is exposed to every agent regardless of
-which groups it holds (`ToolGroup::ALWAYS_ON_TOOLS`). The operator dashboard
-depends on every agent being able to report its status chip, and the
-server-side `SetStatus` handler has no tool-group check (only length
-validation), so gating it would only desync the `--allowedTools` list from
-what the host actually accepts. Revoking `meta` therefore drops
-`get_agent_meta` but never `set_status`.
+**Always-on tools** — `set_status`, `compact`, and `mark_todos_done` are
+exposed to every agent regardless of which groups it holds
+(`ToolGroup::ALWAYS_ON_TOOLS`). The operator dashboard depends on every agent
+being able to report its status chip, and the server-side `SetStatus` handler
+has no tool-group check (only length validation), so gating it would only
+desync the `--allowedTools` list from what the host actually accepts.
+Revoking `meta` therefore drops `get_agent_meta` but never `set_status`.
+`mark_todos_done` is here because todos are pushed to an agent independent of
+whether it holds `inbox` — an agent without that group still needs a way to
+clear them.
 
 **Config storage** — per-agent tool groups live in
 `/var/lib/hyperhive/meta/tool-groups.json` (hive-c0re-owned, committed to the
diff --git a/hive-agent/src/mcp_config.rs b/hive-agent/src/mcp_config.rs
index 2f4820c7..a36fce3a 100644
--- a/hive-agent/src/mcp_config.rs
+++ b/hive-agent/src/mcp_config.rs
@@ -423,6 +423,22 @@ mod tests {
         );
     }
 
+    #[test]
+    fn mark_todos_done_present_with_no_groups() {
+        // Regression: mark_todos_done was declared as a
+        // tool but never added to any ToolGroup, so no agent could ever
+        // get it into --allowedTools regardless of which groups it held —
+        // including `inbox`, which only gates get_loose_ends/
+        // cancel_loose_end/remind.
+        let tools = allowed_mcp_tools(&[]);
+        assert!(
+            tools.contains(&qualified("mark_todos_done")),
+            "mark_todos_done missing from empty-group allow-list: {tools:?}"
+        );
+        let tools = allowed_mcp_tools(&[ToolGroup::Inbox]);
+        assert!(tools.contains(&qualified("mark_todos_done")));
+    }
+
     #[test]
     fn set_status_present_without_meta_group() {
         let tools = allowed_mcp_tools(&[ToolGroup::Messaging, ToolGroup::Inbox]);
diff --git a/hive-sh4re/src/lib.rs b/hive-sh4re/src/lib.rs
index 6509778f..a9c9cef0 100644
--- a/hive-sh4re/src/lib.rs
+++ b/hive-sh4re/src/lib.rs
@@ -639,7 +639,19 @@ impl ToolGroup {
     /// than on tool groups, and every agent should be able to reach for it
     /// regardless of which optional groups it's been granted — same
     /// reasoning as `set_status`.
-    pub const ALWAYS_ON_TOOLS: &'static [&'static str] = &["set_status", "compact"];
+    ///
+    /// `mark_todos_done` too (a critical bug every agent hit): it was
+    /// declared as a `#[tool]` fn but never added to *any*
+    /// group's [`tools`](Self::tools), including `Inbox`, so no agent could
+    /// ever get it into `--allowedTools` and every call prompted for
+    /// approval it can't get. Todos are pushed to an agent independent of
+    /// whether it holds `Inbox` (that group only gates
+    /// `get_loose_ends`/`cancel_loose_end`/`remind`), so an agent without
+    /// `Inbox` could accumulate todos it can never clear — same
+    /// "every agent needs this regardless of optional groups" shape as
+    /// `set_status`/`compact`, not a narrower `Inbox`-only fix.
+    pub const ALWAYS_ON_TOOLS: &'static [&'static str] =
+        &["set_status", "compact", "mark_todos_done"];
 
     /// The Claude built-in tool names enabled by this group. Only
     /// `WebTools` returns a non-empty slice; all other groups return `&[]`