diff --git a/apps/backend/internal/utility/models/models.go b/apps/backend/internal/utility/models/models.go
index 6d8bc22fb2..5fa4c9e136 100644
--- a/apps/backend/internal/utility/models/models.go
+++ b/apps/backend/internal/utility/models/models.go
@@ -3,13 +3,13 @@ package models
 import "time"
 
 // UtilityAgent represents a configured utility agent for quick one-shot tasks.
-// It references an inference-capable agent (like claude-code, amp) by ID.
+// It references an inference-capable agent (like claude-acp, amp) by ID.
 type UtilityAgent struct {
 	ID          string    `json:"id" db:"id"`
 	Name        string    `json:"name" db:"name"`
 	Description string    `json:"description" db:"description"`
 	Prompt      string    `json:"prompt" db:"prompt"`
-	AgentID     string    `json:"agent_id" db:"agent_id"` // Reference to inference agent (e.g., "claude-code")
+	AgentID     string    `json:"agent_id" db:"agent_id"` // Reference to inference agent (e.g., "claude-acp")
 	Model       string    `json:"model" db:"model"`       // Model to use (e.g., "claude-haiku-4-5")
 	Builtin     bool      `json:"builtin" db:"builtin"`   // Built-in agents cannot be deleted
 	Enabled     bool      `json:"enabled" db:"enabled"`   // Whether agent is enabled
diff --git a/apps/backend/internal/utility/service/service.go b/apps/backend/internal/utility/service/service.go
index 75ea71bc6a..cb2c2e6853 100644
--- a/apps/backend/internal/utility/service/service.go
+++ b/apps/backend/internal/utility/service/service.go
@@ -211,7 +211,7 @@ func (s *Service) PreparePromptRequest(ctx context.Context, utilityID string, tm
 type PromptRequest struct {
 	UtilityID      string
 	ResolvedPrompt string
-	AgentCLI       string // The inference agent ID (e.g., "claude-code", "amp")
+	AgentCLI       string // The inference agent ID (e.g., "claude-acp", "amp")
 	Model          string // The model to use
 }
 
diff --git a/apps/backend/internal/utility/store/builtins.go b/apps/backend/internal/utility/store/builtins.go
index 5c9070f38d..f632c8fe49 100644
--- a/apps/backend/internal/utility/store/builtins.go
+++ b/apps/backend/internal/utility/store/builtins.go
@@ -40,6 +40,11 @@ var builtinDefs = []builtinDef{
 	{"builtin-summarize-session", "summarize-session", "Summarize a session conversation for context handover", "summarize-session"},
 }
 
+// builtinSeedAgentID is the inference-agent ID embedded in seeded built-in
+// rows. Kept aligned with the schema DEFAULT so a row that survives every
+// migration path still maps to a registered inference agent.
+const builtinSeedAgentID = "claude-acp"
+
 // getBuiltinAgents returns the predefined built-in utility agents with prompts from embedded files.
 func getBuiltinAgents() []*models.UtilityAgent {
 	now := time.Now().UTC()
@@ -50,6 +55,7 @@ func getBuiltinAgents() []*models.UtilityAgent {
 			Name:        d.name,
 			Description: d.description,
 			Prompt:      utilcfg.Get(d.promptFile),
+			AgentID:     builtinSeedAgentID,
 			Builtin:     true,
 			Enabled:     false,
 			CreatedAt:   now,
diff --git a/apps/backend/internal/utility/store/sqlite.go b/apps/backend/internal/utility/store/sqlite.go
index 112950f043..6241cadb91 100644
--- a/apps/backend/internal/utility/store/sqlite.go
+++ b/apps/backend/internal/utility/store/sqlite.go
@@ -47,7 +47,7 @@ func (r *sqliteRepository) initSchema() error {
 			name TEXT NOT NULL UNIQUE,
 			description TEXT NOT NULL DEFAULT '',
 			prompt TEXT NOT NULL,
-			agent_id TEXT NOT NULL DEFAULT 'claude-code',
+			agent_id TEXT NOT NULL DEFAULT 'claude-acp',
 			model TEXT NOT NULL DEFAULT '',
 			builtin INTEGER NOT NULL DEFAULT 0,
 			enabled INTEGER NOT NULL DEFAULT 1,
@@ -99,6 +99,17 @@ func (r *sqliteRepository) initSchema() error {
 		  AND agent_id <> '' AND model <> ''
 		  AND updated_at = created_at`)
 
+	// Legacy-data backfill: rewrite the old "claude-code" identifier and any
+	// pre-fix builtin rows that were persisted with an empty agent_id to the
+	// registered inference agent ID "claude-acp". The Claude agent was
+	// renamed during the ACP migration (#566), and seedBuiltinAgents()
+	// historically inserted rows with agent_id = "" — combined with its
+	// ON CONFLICT(id) DO NOTHING contract, those stale rows survived
+	// untouched on every restart. Current seeds now use builtinSeedAgentID
+	// (see builtins.go), so this migration only repairs existing deployments.
+	_, _ = r.db.Exec(`UPDATE utility_agents SET agent_id = 'claude-acp'
+		WHERE agent_id IN ('claude-code', '')`)
+
 	// Seed built-in agents
 	if err := r.seedBuiltinAgents(); err != nil {
 		return fmt.Errorf("failed to seed built-in agents: %w", err)
diff --git a/apps/backend/internal/utility/store/sqlite_migration_test.go b/apps/backend/internal/utility/store/sqlite_migration_test.go
new file mode 100644
index 0000000000..21e8a135a1
--- /dev/null
+++ b/apps/backend/internal/utility/store/sqlite_migration_test.go
@@ -0,0 +1,119 @@
+package store
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/jmoiron/sqlx"
+
+	"github.com/kandev/kandev/internal/db"
+)
+
+// openTestDB opens a fresh SQLite file under t.TempDir and registers cleanup.
+func openTestDB(t *testing.T) *sqlx.DB {
+	t.Helper()
+	tmpDir := t.TempDir()
+	conn, err := db.OpenSQLite(filepath.Join(tmpDir, "test.db"))
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	sqlxDB := sqlx.NewDb(conn, "sqlite3")
+	t.Cleanup(func() {
+		_ = sqlxDB.Close()
+	})
+	return sqlxDB
+}
+
+// TestInitSchema_MigratesLegacyClaudeCodeAgentID guards against the #1269
+// regression: a stale "claude-code" agent_id (and the empty agent_id seeded
+// into pre-fix built-in rows) must be rewritten to the registered inference
+// agent ID "claude-acp" on schema init, so the utility-agent dialog's model
+// dropdown can resolve to a valid agent.
+func TestInitSchema_MigratesLegacyClaudeCodeAgentID(t *testing.T) {
+	sqlxDB := openTestDB(t)
+
+	// Bootstrap the schema once so we can seed legacy rows directly.
+	if _, err := newSQLiteRepositoryWithDB(sqlxDB, sqlxDB); err != nil {
+		t.Fatalf("initial schema init: %v", err)
+	}
+
+	now := time.Now().UTC()
+	rows := []struct {
+		id, agentID string
+	}{
+		{"legacy-claude-code", "claude-code"},
+		{"legacy-empty", ""},
+		{"untouched-amp", "amp"},
+	}
+	for _, r := range rows {
+		if _, err := sqlxDB.Exec(`INSERT OR REPLACE INTO utility_agents
+			(id, name, description, prompt, agent_id, model, builtin, enabled, created_at, updated_at)
+			VALUES (?, ?, '', '', ?, '', 0, 1, ?, ?)`,
+			r.id, r.id, r.agentID, now, now); err != nil {
+			t.Fatalf("seed %s: %v", r.id, err)
+		}
+	}
+
+	// Re-run schema init — this fires the agent_id backfill migration.
+	if _, err := newSQLiteRepositoryWithDB(sqlxDB, sqlxDB); err != nil {
+		t.Fatalf("re-init schema: %v", err)
+	}
+
+	want := map[string]string{
+		"legacy-claude-code": "claude-acp",
+		"legacy-empty":       "claude-acp",
+		"untouched-amp":      "amp",
+	}
+	for id, expected := range want {
+		var got string
+		if err := sqlxDB.QueryRowx(`SELECT agent_id FROM utility_agents WHERE id = ?`, id).
+			Scan(&got); err != nil {
+			t.Fatalf("read %s: %v", id, err)
+		}
+		if got != expected {
+			t.Errorf("%s: agent_id = %q, want %q", id, got, expected)
+		}
+	}
+}
+
+// TestSeedBuiltinAgents_UsesClaudeACP pins the seed contract: every built-in
+// row inserted on first run already references the registered inference
+// agent, with no reliance on the dialog fallback or the backfill migration.
+func TestSeedBuiltinAgents_UsesClaudeACP(t *testing.T) {
+	sqlxDB := openTestDB(t)
+
+	if _, err := newSQLiteRepositoryWithDB(sqlxDB, sqlxDB); err != nil {
+		t.Fatalf("schema init: %v", err)
+	}
+
+	ctx := context.Background()
+	rowsxDB, err := sqlxDB.QueryxContext(ctx, `SELECT id, agent_id FROM utility_agents WHERE builtin = 1`)
+	if err != nil {
+		t.Fatalf("query builtins: %v", err)
+	}
+	t.Cleanup(func() {
+		if err := rowsxDB.Close(); err != nil {
+			t.Errorf("close rows: %v", err)
+		}
+	})
+
+	var count int
+	for rowsxDB.Next() {
+		var id, agentID string
+		if err := rowsxDB.Scan(&id, &agentID); err != nil {
+			t.Fatalf("scan: %v", err)
+		}
+		count++
+		if agentID != "claude-acp" {
+			t.Errorf("builtin %s: agent_id = %q, want %q", id, agentID, "claude-acp")
+		}
+	}
+	if err := rowsxDB.Err(); err != nil {
+		t.Fatalf("rows iteration error: %v", err)
+	}
+	if count == 0 {
+		t.Fatalf("expected at least one built-in row, found 0")
+	}
+}
diff --git a/apps/web/components/settings/utility-agent-dialog.tsx b/apps/web/components/settings/utility-agent-dialog.tsx
index f2cc4c132f..ae384c692b 100644
--- a/apps/web/components/settings/utility-agent-dialog.tsx
+++ b/apps/web/components/settings/utility-agent-dialog.tsx
@@ -39,7 +39,7 @@ const defaultFormState: FormState = {
   name: "",
   description: "",
   prompt: "",
-  agent_id: "claude-code",
+  agent_id: "claude-acp",
   model: "",
 };
 
@@ -209,7 +209,7 @@ export function UtilityAgentDialog({ open, onOpenChange, agent, onSuccess }: Pro
         name: agent.name,
         description: agent.description,
         prompt: agent.prompt,
-        agent_id: agent.agent_id || "claude-code",
+        agent_id: agent.agent_id || "claude-acp",
         model: agent.model || "",
       });
     } else {