Reduce MCP token usage

internal/app/host_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/hjbdev/patterm/internal/mcp"
+	"github.com/hjbdev/patterm/internal/scratchpad"
 )
 
 // mkChild builds a Child without starting a PTY. Use sparingly — the
@@ -134,6 +135,42 @@ func TestWrapSubAgentPromptEmptyStaysEmpty(t *testing.T) {
 	}
 }
 
+func TestMCPContentCapsPreferRecentStreamBytes(t *testing.T) {
+	got, gotBytes, truncated, dropped := capBytesTail([]byte("abcdefghijklmnop"), 6)
+	if got != "klmnop" || gotBytes != 6 || !truncated || dropped != 10 {
+		t.Fatalf("capBytesTail = (%q, %d, %v, %d)", got, gotBytes, truncated, dropped)
+	}
+}
+
+func TestMCPGridCapKeepsHeadAndTail(t *testing.T) {
+	got, gotBytes, truncated, dropped := capTextMiddle("abcdefghijklmnopqrstuvwxyz", 24)
+	if gotBytes != 24 || !truncated || dropped != 2 {
+		t.Fatalf("capTextMiddle metadata = (%d, %v, %d), content %q", gotBytes, truncated, dropped, got)
+	}
+	if !strings.Contains(got, "...[truncated]...") {
+		t.Fatalf("capTextMiddle missing marker: %q", got)
+	}
+}
+
+func TestScratchpadReadPagesLargeContent(t *testing.T) {
+	t.Setenv("XDG_DATA_HOME", t.TempDir())
+	store, err := scratchpad.Open("test-project")
+	if err != nil {
+		t.Fatalf("scratchpad open: %v", err)
+	}
+	if _, err := store.Write("notes.md", "abcdefghijklmnopqrstuvwxyz", ""); err != nil {
+		t.Fatalf("scratchpad write: %v", err)
+	}
+	h := &toolHost{pads: store}
+	res, err := h.ScratchpadRead(mcp.ScratchpadReadArgs{Name: "notes.md", Offset: 5, MaxBytes: 7})
+	if err != nil {
+		t.Fatalf("ScratchpadRead: %v", err)
+	}
+	if res.Content != "fghijkl" || !res.Truncated || res.NextOffset != 12 || res.TotalBytes != 26 {
+		t.Fatalf("ScratchpadRead result = %+v", res)
+	}
+}
+
 func TestHelpLifecycleTopicCoversCleanup(t *testing.T) {
 	resp := helpFor("lifecycle")
 	if resp.Topic != "lifecycle" {