diff --git a/src/ccgram/hook.py b/src/ccgram/hook.py
index 8bf7ec13..2267b023 100644
--- a/src/ccgram/hook.py
+++ b/src/ccgram/hook.py
@@ -821,11 +821,17 @@ def _closest_claude_ancestor(
 def _is_nested_session(pane_tty: str) -> bool:
     """Return True if the hook was fired by a nested (non-foreground) claude.
 
-    The "primary" claude in a tmux pane is launched by the user's shell, so
-    its PID equals the foreground process group id on the pane's tty. Any
-    claude spawned beneath that primary (e.g. an MCP-server-launched observer
-    such as claude-mem) is a *descendant* — its PID differs from the
-    foreground PGID even though it shares the pgid via inheritance.
+    A claude whose PID equals the foreground process group id on the pane's
+    tty is the primary by definition. It is not the only primary shape: a
+    launcher that starts the agent as ``bash -lc "... && claude ..."`` leaves
+    the shell leading the group, so the primary claude is a child of the
+    foreground process and its PID never equals the foreground PGID.
+
+    What actually distinguishes a nested claude (e.g. an MCP-server-launched
+    observer such as claude-mem) is that another claude sits above it in the
+    process tree. Testing ancestry rather than group leadership covers both
+    primary shapes, and is what the pgid comparison was approximating anyway,
+    since a nested claude inherits the same pgid.
 
     Fails open: returns False on any subprocess error or missing data so
     hook delivery is never made *more* fragile than the status quo.
@@ -841,7 +847,12 @@ def _is_nested_session(pane_tty: str) -> bool:
     owner = _closest_claude_ancestor(snapshot, os.getpid())
     if owner is None:
         return False
-    return owner != fg_pgid
+    if owner == fg_pgid:
+        return False
+    owner_info = snapshot.get(owner)
+    if owner_info is None:
+        return False
+    return _closest_claude_ancestor(snapshot, owner_info[0]) is not None
 
 
 def _write_event(
diff --git a/tests/ccgram/test_hook.py b/tests/ccgram/test_hook.py
index 43e05fa4..a52c2cc7 100644
--- a/tests/ccgram/test_hook.py
+++ b/tests/ccgram/test_hook.py
@@ -725,6 +725,35 @@ def test_observer_claude_is_nested(self, monkeypatch) -> None:
         monkeypatch.setattr("os.getpid", lambda: 99999)
         assert _is_nested_session("/dev/ttys005") is True
 
+    def test_shell_wrapped_primary_claude_is_not_nested(self, monkeypatch) -> None:
+        """A launcher running `bash -lc "... && claude ..."` keeps the shell as
+        group leader, so the primary claude's PID never equals the foreground
+        PGID. No claude sits above it, so it is still the primary."""
+        snapshot = {
+            14053: (1, 14053, "Ss+", "bash"),
+            14058: (14053, 14053, "S+", "claude"),
+            99999: (14058, 14053, "S+", "python"),
+        }
+        monkeypatch.setattr("ccgram.hook._ps_snapshot", lambda: snapshot)
+        monkeypatch.setattr("ccgram.hook._foreground_pgid_on_tty", lambda *_: 14053)
+        monkeypatch.setattr("os.getpid", lambda: 99999)
+        assert _is_nested_session("/dev/ttys002") is False
+
+    def test_observer_under_shell_wrapped_primary_is_nested(self, monkeypatch) -> None:
+        """The nested case must still be caught when the primary is itself a
+        child of the foreground shell rather than the group leader."""
+        snapshot = {
+            14053: (1, 14053, "Ss+", "bash"),
+            14058: (14053, 14053, "S+", "claude"),
+            14100: (14058, 14053, "S+", "bun"),
+            14200: (14100, 14053, "S+", "claude"),
+            99999: (14200, 14053, "S+", "python"),
+        }
+        monkeypatch.setattr("ccgram.hook._ps_snapshot", lambda: snapshot)
+        monkeypatch.setattr("ccgram.hook._foreground_pgid_on_tty", lambda *_: 14053)
+        monkeypatch.setattr("os.getpid", lambda: 99999)
+        assert _is_nested_session("/dev/ttys002") is True
+
     def test_empty_pane_tty_fails_open(self, monkeypatch) -> None:
         monkeypatch.setattr(
             "ccgram.hook._ps_snapshot", lambda: pytest.fail("should not be called")