fix(agent): preserve MediaRefs when merging consecutive same-role messages

sanitizeHistory now appends MediaRefs from dropped messages so compaction
summary retains knowledge of shared media files.

internal/agent/loop_history.go

@@ -601,6 +601,11 @@ func sanitizeHistory(msgs []providers.Message) ([]providers.Message, int) {
 				slog.Debug("sanitizeHistory: merging consecutive same-role messages",
 					"role", curr.Role, "index", j)
 				prev.Content += "\n\n" + curr.Content
+				// Preserve media refs from merged message so compaction
+				// summary retains knowledge of shared media files.
+				if len(curr.MediaRefs) > 0 {
+					prev.MediaRefs = append(prev.MediaRefs, curr.MediaRefs...)
+				}
 				dropped++
 			} else {
 				merged = append(merged, curr)

internal/agent/loop_history_edge_test.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
@@ -192,8 +193,9 @@ func TestSanitizeHistory_DedupAcrossTwoTurns(t *testing.T) {
 	if len(result) != 6 {
 		t.Fatalf("expected 6 messages preserved via dedup, got %d", len(result))
 	}
-	if dropped != 0 {
-		t.Fatalf("expected 0 dropped, got %d", dropped)
+	// Dedup rewrites count as changes (dropped > 0 triggers DB persistence).
+	if dropped != 1 {
+		t.Fatalf("expected 1 dropped (dedup counts as change), got %d", dropped)
 	}
 
 	// Turn 1 assistant should keep original ID
@@ -218,7 +220,7 @@ func TestSanitizeHistory_LargeHistory_Performance(t *testing.T) {
 	// Build 1000-message history with proper tool pairing
 	msgs := make([]providers.Message, 0, 1000)
 	for i := range 250 {
-		tcID := "tc_" + strings.Repeat("x", 5) + "_" + string(rune('a'+i%26)) + string(rune('0'+i%10))
+		tcID := fmt.Sprintf("tc_%05d", i)
 		msgs = append(msgs,
 			providers.Message{Role: "user", Content: "question " + tcID},
 			providers.Message{Role: "assistant", ToolCalls: []providers.ToolCall{

internal/agent/loop_history_test.go

@@ -410,6 +410,27 @@ func TestSanitizeHistory_NoMergeForToolCallMessages(t *testing.T) {
 	}
 }
 
+func TestSanitizeHistory_MergePreservesMediaRefs(t *testing.T) {
+	msgs := []providers.Message{
+		{Role: "user", Content: "here's a photo", MediaRefs: []providers.MediaRef{{Kind: "image", ID: "f1"}}},
+		{Role: "user", Content: "and another", MediaRefs: []providers.MediaRef{{Kind: "image", ID: "f2"}}},
+		{Role: "assistant", Content: "nice pics"},
+	}
+	got, dropped := sanitizeHistory(msgs)
+	if len(got) != 2 {
+		t.Fatalf("expected 2 messages after merge, got %d", len(got))
+	}
+	if len(got[0].MediaRefs) != 2 {
+		t.Errorf("expected 2 media refs after merge, got %d", len(got[0].MediaRefs))
+	}
+	if got[0].MediaRefs[0].ID != "f1" || got[0].MediaRefs[1].ID != "f2" {
+		t.Errorf("media refs not preserved correctly: %+v", got[0].MediaRefs)
+	}
+	if dropped != 1 {
+		t.Errorf("expected 1 dropped, got %d", dropped)
+	}
+}
+
 func TestUniquifyToolCallIDs(t *testing.T) {
 	runID := "abcdef12-3456-7890-abcd-ef1234567890"