Don't steal focus when an agent spawns a child via MCP

CHANGELOG.md

@@ -20,6 +20,12 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   child agent, even though you were still within that thread.
 
 ### Changed
+- Agent-initiated `spawn_agent` and `spawn_process` MCP calls no
+  longer steal viewport focus from the currently active tab. The
+  new child still appears in the sidebar and tab bar; switch to it
+  explicitly via the palette or `select_process`. Palette-initiated
+  spawns and persistence restores are unchanged — they still auto-
+  focus the new pane.
 - Sidebar rows (Processes, Agent Tree, Scratchpads) now truncate
   overflowing names with a trailing `…` instead of spilling into
   the main viewport. The focused row marquees its name when it

internal/app/app.go

@@ -700,8 +700,26 @@ func (st *uiState) scratchpadsChanged() {
 	}
 }
 
-// OnChildSpawned auto-focuses the new child.
+// OnChildSpawned auto-focuses the new child when the spawn came from
+// the user (palette, persistence restore, or an external MCP client with
+// no resolved identity). When ParentID is set — meaning a patterm-managed
+// agent spawned this child via spawn_agent/spawn_process — focus stays
+// on whatever the user was watching; the new child is still surfaced in
+// the sidebar/tab bar so it's reachable via the palette or select_process.
 func (st *uiState) OnChildSpawned(c *Child) {
+	if c.ParentID != "" {
+		st.mu.Lock()
+		if st.palette != nil {
+			st.palette.children = st.sess.Children()
+			st.palette.focused = st.focusedID
+			st.palette.rebuild()
+			st.renderPaletteLocked()
+		}
+		st.mu.Unlock()
+		st.drawTabBar()
+		st.drawSidebar()
+		return
+	}
 	st.marquee.reset()
 	layout := st.layoutSnapshot()
 	onAlt := childIsOnAlt(c)

internal/app/spawn_focus_test.go

@@ -0,0 +1,46 @@
+package app
+
+import (
+	"testing"
+)
+
+// TestOnChildSpawnedAgentChildKeepsFocus verifies that when a child is
+// spawned with a ParentID set (i.e. a patterm-managed agent caused the
+// spawn over MCP), OnChildSpawned does NOT steal viewport focus from
+// the currently focused child.
+func TestOnChildSpawnedAgentChildKeepsFocus(t *testing.T) {
+	sess := NewSession(t.TempDir(), "test")
+	st := &uiState{sess: sess}
+
+	parent := newChildEntry("p_parent", "parent", KindAgent, nil, nil, "", "", "")
+	st.focusedID = parent.ID
+	st.focusedName = parent.Name
+
+	subAgent := newChildEntry("p_sub", "sub", KindAgent, nil, nil, parent.ID, "", "")
+
+	st.OnChildSpawned(subAgent)
+
+	if got := st.focusedID; got != parent.ID {
+		t.Fatalf("agent-initiated spawn should not change focusedID: want %q, got %q", parent.ID, got)
+	}
+	if got := st.focusedName; got != parent.Name {
+		t.Fatalf("focusedName changed: want %q, got %q", parent.Name, got)
+	}
+}
+
+// TestOnChildSpawnedPaletteChildTakesFocus verifies the legacy path is
+// preserved: spawns with an empty ParentID (palette, restore, external
+// MCP caller) still auto-focus the new child.
+func TestOnChildSpawnedPaletteChildTakesFocus(t *testing.T) {
+	sess := NewSession(t.TempDir(), "test")
+	st := &uiState{sess: sess}
+	st.lastExit.Store(-1)
+
+	c := newChildEntry("p_new", "newchild", KindAgent, nil, nil, "", "", "")
+
+	st.OnChildSpawned(c)
+
+	if got := st.focusedID; got != c.ID {
+		t.Fatalf("palette-initiated spawn should auto-focus: want %q, got %q", c.ID, got)
+	}
+}