diff --git a/internal/store/sqlitestore/agents_update_null_coerce_test.go b/internal/store/sqlitestore/agents_update_null_coerce_test.go
new file mode 100644
index 00000000..71ffa3aa
--- /dev/null
+++ b/internal/store/sqlitestore/agents_update_null_coerce_test.go
@@ -0,0 +1,136 @@
+//go:build sqlite || sqliteonly
+
+package sqlitestore
+
+import (
+	"database/sql"
+	"path/filepath"
+	"testing"
+
+	"github.com/google/uuid"
+)
+
+// Regression test for PR #897 — fresh SQLite DBs crash on agent setting save
+// when UI sends null for NOT NULL columns (other_config, tools_config,
+// self_evolve, skill_evolve, is_default). Update() must coerce nil to the
+// column's default value ({}, false) to satisfy NOT NULL constraints.
+func TestSQLiteAgentStore_Update_CoerceNullForNotNullColumns(t *testing.T) {
+	db, tenantID, agentID := newAgentUpdateTestFixture(t)
+	store := NewSQLiteAgentStore(db)
+	ctx := sqliteTenantCtx(tenantID)
+
+	// Simulate UI sending null for every NOT NULL column that can be toggled off.
+	updates := map[string]any{
+		"other_config":          nil,
+		"tools_config":          nil,
+		"reasoning_config":      nil,
+		"workspace_sharing":     nil,
+		"chatgpt_oauth_routing": nil,
+		"shell_deny_groups":     nil,
+		"kg_dedup_config":       nil,
+		"self_evolve":           nil,
+		"skill_evolve":          nil,
+		"is_default":            nil,
+		"skill_nudge_interval":  nil,
+		"max_tokens":            nil,
+		"emoji":                 nil,
+		"agent_description":     nil,
+		"thinking_level":        nil,
+	}
+
+	if err := store.Update(ctx, agentID, updates); err != nil {
+		t.Fatalf("Update with null NOT NULL columns: %v", err)
+	}
+
+	// Verify JSON columns became '{}', BOOL → 0, INT → 0, TEXT → ''.
+	var (
+		otherCfg, toolsCfg, reasoningCfg, wsSharing, oauthRouting, shellDeny, kgDedup string
+		selfEvolve, skillEvolve, isDefault                                            bool
+		skillNudge, maxTokens                                                         int
+		emoji, agentDesc, thinkingLvl                                                 string
+	)
+	err := db.QueryRowContext(ctx,
+		`SELECT other_config, tools_config, reasoning_config, workspace_sharing,
+			chatgpt_oauth_routing, shell_deny_groups, kg_dedup_config,
+			self_evolve, skill_evolve, is_default,
+			skill_nudge_interval, max_tokens,
+			emoji, agent_description, thinking_level
+		 FROM agents WHERE id = ?`, agentID).Scan(
+		&otherCfg, &toolsCfg, &reasoningCfg, &wsSharing, &oauthRouting, &shellDeny, &kgDedup,
+		&selfEvolve, &skillEvolve, &isDefault,
+		&skillNudge, &maxTokens,
+		&emoji, &agentDesc, &thinkingLvl,
+	)
+	if err != nil {
+		t.Fatalf("scan back: %v", err)
+	}
+
+	jsonCols := map[string]string{
+		"other_config": otherCfg, "tools_config": toolsCfg,
+		"reasoning_config": reasoningCfg, "workspace_sharing": wsSharing,
+		"chatgpt_oauth_routing": oauthRouting, "shell_deny_groups": shellDeny,
+		"kg_dedup_config": kgDedup,
+	}
+	for name, got := range jsonCols {
+		if got != "{}" {
+			t.Errorf("%s: got %q, want %q", name, got, "{}")
+		}
+	}
+
+	boolCols := map[string]bool{
+		"self_evolve": selfEvolve, "skill_evolve": skillEvolve, "is_default": isDefault,
+	}
+	for name, got := range boolCols {
+		if got {
+			t.Errorf("%s: got true, want false", name)
+		}
+	}
+
+	intCols := map[string]int{
+		"skill_nudge_interval": skillNudge, "max_tokens": maxTokens,
+	}
+	for name, got := range intCols {
+		if got != 0 {
+			t.Errorf("%s: got %d, want 0", name, got)
+		}
+	}
+
+	textCols := map[string]string{
+		"emoji": emoji, "agent_description": agentDesc, "thinking_level": thinkingLvl,
+	}
+	for name, got := range textCols {
+		if got != "" {
+			t.Errorf("%s: got %q, want empty string", name, got)
+		}
+	}
+}
+
+// newAgentUpdateTestFixture opens a fresh SQLite DB with schema loaded and
+// inserts a minimal tenant + agent for Update() tests.
+func newAgentUpdateTestFixture(t *testing.T) (*sql.DB, uuid.UUID, uuid.UUID) {
+	t.Helper()
+	db, err := OpenDB(filepath.Join(t.TempDir(), "agent_update_test.db"))
+	if err != nil {
+		t.Fatalf("OpenDB: %v", err)
+	}
+	if err := EnsureSchema(db); err != nil {
+		db.Close()
+		t.Fatalf("EnsureSchema: %v", err)
+	}
+	t.Cleanup(func() { db.Close() })
+
+	tenantID := uuid.Must(uuid.NewV7())
+	agentID := uuid.Must(uuid.NewV7())
+	if _, err := db.Exec(
+		`INSERT INTO tenants (id, name, slug, status) VALUES (?,?,?,'active')`,
+		tenantID.String(), "agent-upd-"+tenantID.String()[:8], "au"+tenantID.String()[:8]); err != nil {
+		t.Fatalf("seed tenant: %v", err)
+	}
+	if _, err := db.Exec(
+		`INSERT INTO agents (id, tenant_id, agent_key, agent_type, status, provider, model, owner_id)
+		 VALUES (?,?,?,'predefined','active','test','test-model','owner')`,
+		agentID.String(), tenantID.String(), "au-"+agentID.String()[:8]); err != nil {
+		t.Fatalf("seed agent: %v", err)
+	}
+	return db, tenantID, agentID
+}