feat: include SQL scripts in schema diff

Backtick-wrapped defaults (e.g. from GORM tags like `now()`) were only
stripped in the CREATE TABLE column-definition path, leaving raw
backticks in the ALTER COLUMN ... SET DEFAULT migration statement and
in the migration-generated CREATE TABLE template, producing invalid
SQL. Default-drift comparisons also compared raw values, so a
backtick-wrapped model default never matched the live DB default and
kept re-emitting redundant ALTER statements.

cmd/relspec/diff.go

@@ -16,6 +16,7 @@ import (
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/drawdb"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/json"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/pgsql"
+	"git.warky.dev/wdevs/relspecgo/pkg/readers/sqldir"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/sqlite"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/yaml"
 )
@@ -87,11 +88,11 @@ Examples:
 }
 
 func init() {
-	diffCmd.Flags().StringVar(&sourceType, "from", "", "Source database format (dbml, dctx, drawdb, json, yaml, pgsql)")
+	diffCmd.Flags().StringVar(&sourceType, "from", "", "Source database format (dbml, dctx, drawdb, json, yaml, pgsql, sqldir)")
 	diffCmd.Flags().StringVar(&sourcePath, "from-path", "", "Source file path (for file-based formats)")
 	diffCmd.Flags().StringVar(&sourceConn, "from-conn", "", "Source connection string (for database formats)")
 
-	diffCmd.Flags().StringVar(&targetType, "to", "", "Target database format (dbml, dctx, drawdb, json, yaml, pgsql)")
+	diffCmd.Flags().StringVar(&targetType, "to", "", "Target database format (dbml, dctx, drawdb, json, yaml, pgsql, sqldir)")
 	diffCmd.Flags().StringVar(&targetPath, "to-path", "", "Target file path (for file-based formats)")
 	diffCmd.Flags().StringVar(&targetConn, "to-conn", "", "Target connection string (for database formats)")
 
@@ -129,10 +130,12 @@ func runDiff(cmd *cobra.Command, args []string) error {
 
 	fmt.Fprintf(os.Stderr, "      ✓ Successfully read database '%s'\n", sourceDB.Name)
 	sourceTables := 0
+	sourceScripts := 0
 	for _, schema := range sourceDB.Schemas {
 		sourceTables += len(schema.Tables)
+		sourceScripts += len(schema.Scripts)
 	}
-	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s)\n\n", len(sourceDB.Schemas), sourceTables)
+	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s), %d script(s)\n\n", len(sourceDB.Schemas), sourceTables, sourceScripts)
 
 	// Read target database
 	fmt.Fprintf(os.Stderr, "[2/3] Reading target schema...\n")
@@ -151,10 +154,12 @@ func runDiff(cmd *cobra.Command, args []string) error {
 
 	fmt.Fprintf(os.Stderr, "      ✓ Successfully read database '%s'\n", targetDB.Name)
 	targetTables := 0
+	targetScripts := 0
 	for _, schema := range targetDB.Schemas {
 		targetTables += len(schema.Tables)
+		targetScripts += len(schema.Scripts)
 	}
-	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s)\n\n", len(targetDB.Schemas), targetTables)
+	fmt.Fprintf(os.Stderr, "      Found: %d schema(s), %d table(s), %d script(s)\n\n", len(targetDB.Schemas), targetTables, targetScripts)
 
 	// Compare databases
 	fmt.Fprintf(os.Stderr, "[3/3] Comparing schemas...\n")
@@ -165,7 +170,8 @@ func runDiff(cmd *cobra.Command, args []string) error {
 		summary.Tables.Missing + summary.Tables.Extra + summary.Tables.Modified +
 		summary.Columns.Missing + summary.Columns.Extra + summary.Columns.Modified +
 		summary.Indexes.Missing + summary.Indexes.Extra + summary.Indexes.Modified +
-		summary.Constraints.Missing + summary.Constraints.Extra + summary.Constraints.Modified
+		summary.Constraints.Missing + summary.Constraints.Extra + summary.Constraints.Modified +
+		summary.Scripts.Missing + summary.Scripts.Extra + summary.Scripts.Modified
 
 	fmt.Fprintf(os.Stderr, "      ✓ Comparison complete\n")
 	fmt.Fprintf(os.Stderr, "      Found: %d difference(s)\n\n", totalDiffs)
@@ -249,6 +255,12 @@ func readDatabase(dbType, filePath, connString, label string) (*models.Database,
 		}
 		reader = yaml.NewReader(&readers.ReaderOptions{FilePath: filePath})
 
+	case "sqldir", "scripts", "scriptdir":
+		if filePath == "" {
+			return nil, fmt.Errorf("%s: file path is required for SQL directory format", label)
+		}
+		reader = sqldir.NewReader(&readers.ReaderOptions{FilePath: filePath})
+
 	case "pgsql", "postgres", "postgresql":
 		if connString == "" {
 			return nil, fmt.Errorf("%s: connection string is required for PostgreSQL format", label)

cmd/relspec/diff_sqldir_test.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestReadDatabaseSupportsSQLDir(t *testing.T) {
+	tempDir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(tempDir, "1_001_create_users.sql"), []byte("CREATE TABLE users (id int);"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(tempDir, "1_002_seed_users.pgsql"), []byte("INSERT INTO users (id) VALUES (1);"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	db, err := readDatabase("sqldir", tempDir, "", "source")
+	if err != nil {
+		t.Fatalf("readDatabase failed: %v", err)
+	}
+	if len(db.Schemas) != 1 {
+		t.Fatalf("expected 1 schema, got %d", len(db.Schemas))
+	}
+	if got := len(db.Schemas[0].Scripts); got != 2 {
+		t.Fatalf("expected 2 scripts, got %d", got)
+	}
+}

linux/arch/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Hein (Warky Devs) <hein@warky.dev>
 pkgname=relspec
-pkgver=1.0.66
+pkgver=1.0.69
 pkgrel=1
 pkgdesc="RelSpec is a comprehensive database relations management tool that reads, transforms, and writes database table specifications across multiple formats and ORMs."
 arch=('x86_64' 'aarch64')

linux/centos/relspec.spec

@@ -1,5 +1,5 @@
 Name:           relspec
-Version:        1.0.66
+Version:        1.0.69
 Release:        1%{?dist}
 Summary:        RelSpec is a comprehensive database relations management tool that reads, transforms, and writes database table specifications across multiple formats and ORMs.
 

pkg/diff/diff.go

@@ -1,6 +1,7 @@
 package diff
 
 import (
+	"fmt"
 	"reflect"
 	"sort"
 
@@ -96,6 +97,13 @@ func compareSchemaDetails(source, target *models.Schema) *SchemaChange {
 		hasChanges = true
 	}
 
+	// Compare scripts
+	scriptDiff := compareScripts(source.Scripts, target.Scripts)
+	if !isEmpty(scriptDiff) {
+		change.Scripts = scriptDiff
+		hasChanges = true
+	}
+
 	if !hasChanges {
 		return nil
 	}
@@ -543,6 +551,79 @@ func compareSequenceDetails(source, target *models.Sequence) map[string]any {
 	return changes
 }
 
+func compareScripts(source, target []*models.Script) *ScriptDiff {
+	diff := &ScriptDiff{
+		Missing:  make([]*models.Script, 0),
+		Extra:    make([]*models.Script, 0),
+		Modified: make([]*ScriptChange, 0),
+	}
+
+	sourceMap := make(map[string]*models.Script)
+	targetMap := make(map[string]*models.Script)
+
+	for _, s := range source {
+		sourceMap[scriptCompareKey(s)] = s
+	}
+	for _, s := range target {
+		targetMap[scriptCompareKey(s)] = s
+	}
+
+	for _, name := range sortedKeys(sourceMap) {
+		srcScript := sourceMap[name]
+		if tgtScript, exists := targetMap[name]; !exists {
+			diff.Missing = append(diff.Missing, srcScript)
+		} else if changes := compareScriptDetails(srcScript, tgtScript); len(changes) > 0 {
+			diff.Modified = append(diff.Modified, &ScriptChange{
+				Name:    srcScript.Name,
+				Source:  srcScript,
+				Target:  tgtScript,
+				Changes: changes,
+			})
+		}
+	}
+
+	for _, name := range sortedKeys(targetMap) {
+		tgtScript := targetMap[name]
+		if _, exists := sourceMap[name]; !exists {
+			diff.Extra = append(diff.Extra, tgtScript)
+		}
+	}
+
+	return diff
+}
+
+func scriptCompareKey(script *models.Script) string {
+	return fmt.Sprintf("%d:%d:%s", script.Priority, script.Sequence, script.SQLName())
+}
+
+func compareScriptDetails(source, target *models.Script) map[string]any {
+	changes := make(map[string]any)
+
+	if source.SQL != target.SQL {
+		changes["sql"] = map[string]string{"source": source.SQL, "target": target.SQL}
+	}
+	if source.Rollback != target.Rollback {
+		changes["rollback"] = map[string]string{"source": source.Rollback, "target": target.Rollback}
+	}
+	if !reflect.DeepEqual(source.RunAfter, target.RunAfter) {
+		changes["run_after"] = map[string][]string{"source": source.RunAfter, "target": target.RunAfter}
+	}
+	if source.Schema != target.Schema {
+		changes["schema"] = map[string]string{"source": source.Schema, "target": target.Schema}
+	}
+	if source.Version != target.Version {
+		changes["version"] = map[string]string{"source": source.Version, "target": target.Version}
+	}
+	if source.Priority != target.Priority {
+		changes["priority"] = map[string]int{"source": source.Priority, "target": target.Priority}
+	}
+	if source.Sequence != target.Sequence {
+		changes["sequence"] = map[string]uint{"source": source.Sequence, "target": target.Sequence}
+	}
+
+	return changes
+}
+
 // Helper function to check if a diff is empty
 func isEmpty(v any) bool {
 	switch d := v.(type) {
@@ -560,6 +641,8 @@ func isEmpty(v any) bool {
 		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
 	case *SequenceDiff:
 		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
+	case *ScriptDiff:
+		return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
 	default:
 		return false
 	}
@@ -616,6 +699,11 @@ func ComputeSummary(result *DiffResult) *Summary {
 				summary.Sequences.Extra += len(schemaChange.Sequences.Extra)
 				summary.Sequences.Modified += len(schemaChange.Sequences.Modified)
 			}
+			if schemaChange.Scripts != nil {
+				summary.Scripts.Missing += len(schemaChange.Scripts.Missing)
+				summary.Scripts.Extra += len(schemaChange.Scripts.Extra)
+				summary.Scripts.Modified += len(schemaChange.Scripts.Modified)
+			}
 		}
 	}
 

pkg/diff/diff_test.go

@@ -525,6 +525,78 @@ func TestCompareSchemas(t *testing.T) {
 	}
 }
 
+func TestCompareScripts(t *testing.T) {
+	tests := []struct {
+		name   string
+		source []*models.Script
+		target []*models.Script
+		want   func(*ScriptDiff) bool
+	}{
+		{
+			name:   "identical scripts",
+			source: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);", Priority: 1, Sequence: 1}},
+			target: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);", Priority: 1, Sequence: 1}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 0 && len(d.Extra) == 0 && len(d.Modified) == 0
+			},
+		},
+		{
+			name:   "missing script",
+			source: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);"}},
+			target: []*models.Script{},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 1 && d.Missing[0].Name == "create_users"
+			},
+		},
+		{
+			name:   "extra script",
+			source: []*models.Script{},
+			target: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);"}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Extra) == 1 && d.Extra[0].Name == "create_users"
+			},
+		},
+		{
+			name:   "modified script sql",
+			source: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id int);"}},
+			target: []*models.Script{{Name: "create_users", SQL: "CREATE TABLE users (id bigint);"}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Modified) == 1 && d.Modified[0].Name == "create_users" && d.Modified[0].Changes["sql"] != nil
+			},
+		},
+		{
+			name:   "different script order is different identity",
+			source: []*models.Script{{Name: "create_users", SQL: "SELECT 1;", Priority: 1, Sequence: 1}},
+			target: []*models.Script{{Name: "create_users", SQL: "SELECT 1;", Priority: 2, Sequence: 3}},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 1 && len(d.Extra) == 1 && len(d.Modified) == 0
+			},
+		},
+		{
+			name: "same descriptive names remain distinct",
+			source: []*models.Script{
+				{Name: "alter_users", SQL: "SELECT 1;", Priority: 1, Sequence: 1},
+				{Name: "alter_users", SQL: "SELECT 2;", Priority: 1, Sequence: 2},
+			},
+			target: []*models.Script{
+				{Name: "alter_users", SQL: "SELECT 1;", Priority: 1, Sequence: 1},
+			},
+			want: func(d *ScriptDiff) bool {
+				return len(d.Missing) == 1 && d.Missing[0].Sequence == 2
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := compareScripts(tt.source, tt.target)
+			if !tt.want(got) {
+				t.Errorf("compareScripts() result doesn't match expectations")
+			}
+		})
+	}
+}
+
 func TestIsEmpty(t *testing.T) {
 	tests := []struct {
 		name string
@@ -540,6 +612,8 @@ func TestIsEmpty(t *testing.T) {
 		{"TableDiff with extra", &TableDiff{Missing: []*models.Table{}, Extra: []*models.Table{{Name: "users"}}, Modified: []*TableChange{}}, false},
 		{"empty ConstraintDiff", &ConstraintDiff{Missing: []*models.Constraint{}, Extra: []*models.Constraint{}, Modified: []*ConstraintChange{}}, true},
 		{"empty RelationshipDiff", &RelationshipDiff{Missing: []*models.Relationship{}, Extra: []*models.Relationship{}, Modified: []*RelationshipChange{}}, true},
+		{"empty ScriptDiff", &ScriptDiff{Missing: []*models.Script{}, Extra: []*models.Script{}, Modified: []*ScriptChange{}}, true},
+		{"ScriptDiff with modified", &ScriptDiff{Missing: []*models.Script{}, Extra: []*models.Script{}, Modified: []*ScriptChange{{Name: "create_users"}}}, false},
 	}
 
 	for _, tt := range tests {
@@ -586,6 +660,26 @@ func TestComputeSummary(t *testing.T) {
 				return s.Schemas.Missing == 1 && s.Schemas.Extra == 2 && s.Schemas.Modified == 1
 			},
 		},
+		{
+			name: "scripts with differences",
+			result: &DiffResult{
+				Schemas: &SchemaDiff{
+					Modified: []*SchemaChange{
+						{
+							Name: "public",
+							Scripts: &ScriptDiff{
+								Missing:  []*models.Script{{Name: "missing_script"}},
+								Extra:    []*models.Script{{Name: "extra_script"}, {Name: "seed_data"}},
+								Modified: []*ScriptChange{{Name: "changed_script"}},
+							},
+						},
+					},
+				},
+			},
+			want: func(s *Summary) bool {
+				return s.Scripts.Missing == 1 && s.Scripts.Extra == 2 && s.Scripts.Modified == 1
+			},
+		},
 	}
 
 	for _, tt := range tests {

pkg/diff/formatters.go

@@ -158,6 +158,21 @@ func formatSummary(result *DiffResult, w io.Writer) error {
 		fmt.Fprintf(w, "\n")
 	}
 
+	// Scripts
+	if summary.Scripts.Missing > 0 || summary.Scripts.Extra > 0 || summary.Scripts.Modified > 0 {
+		fmt.Fprintf(w, "Scripts:\n")
+		if summary.Scripts.Missing > 0 {
+			fmt.Fprintf(w, "  Missing:  %d\n", summary.Scripts.Missing)
+		}
+		if summary.Scripts.Extra > 0 {
+			fmt.Fprintf(w, "  Extra:    %d\n", summary.Scripts.Extra)
+		}
+		if summary.Scripts.Modified > 0 {
+			fmt.Fprintf(w, "  Modified: %d\n", summary.Scripts.Modified)
+		}
+		fmt.Fprintf(w, "\n")
+	}
+
 	// Check if there are no differences
 	if summary.Schemas.Missing == 0 && summary.Schemas.Extra == 0 && summary.Schemas.Modified == 0 &&
 		summary.Tables.Missing == 0 && summary.Tables.Extra == 0 && summary.Tables.Modified == 0 &&
@@ -166,7 +181,8 @@ func formatSummary(result *DiffResult, w io.Writer) error {
 		summary.Constraints.Missing == 0 && summary.Constraints.Extra == 0 && summary.Constraints.Modified == 0 &&
 		summary.Relationships.Missing == 0 && summary.Relationships.Extra == 0 && summary.Relationships.Modified == 0 &&
 		summary.Views.Missing == 0 && summary.Views.Extra == 0 && summary.Views.Modified == 0 &&
-		summary.Sequences.Missing == 0 && summary.Sequences.Extra == 0 && summary.Sequences.Modified == 0 {
+		summary.Sequences.Missing == 0 && summary.Sequences.Extra == 0 && summary.Sequences.Modified == 0 &&
+		summary.Scripts.Missing == 0 && summary.Scripts.Extra == 0 && summary.Scripts.Modified == 0 {
 		fmt.Fprintf(w, "No differences found.\n")
 	}
 
@@ -448,6 +464,26 @@ const htmlTemplate = `<!DOCTYPE html>
                 </div>
             </div>
             {{end}}
+
+            {{if or .Summary.Scripts.Missing .Summary.Scripts.Extra .Summary.Scripts.Modified}}
+            <div class="summary-item">
+                <h3>Scripts</h3>
+                <div class="count-group">
+                    <div class="count">
+                        <span class="count-label">Missing</span>
+                        <span class="count-value missing">{{.Summary.Scripts.Missing}}</span>
+                    </div>
+                    <div class="count">
+                        <span class="count-label">Extra</span>
+                        <span class="count-value extra">{{.Summary.Scripts.Extra}}</span>
+                    </div>
+                    <div class="count">
+                        <span class="count-label">Modified</span>
+                        <span class="count-value modified">{{.Summary.Scripts.Modified}}</span>
+                    </div>
+                </div>
+            </div>
+            {{end}}
         </div>
     </div>
 
@@ -588,6 +624,35 @@ const htmlTemplate = `<!DOCTYPE html>
                 </ul>
                 {{end}}
             {{end}}
+
+            {{if .Scripts}}
+                {{if .Scripts.Missing}}
+                <h4>Missing Scripts</h4>
+                <ul class="item-list">
+                    {{range .Scripts.Missing}}
+                    <li class="missing">{{.Name}}</li>
+                    {{end}}
+                </ul>
+                {{end}}
+
+                {{if .Scripts.Extra}}
+                <h4>Extra Scripts</h4>
+                <ul class="item-list">
+                    {{range .Scripts.Extra}}
+                    <li class="extra">{{.Name}}</li>
+                    {{end}}
+                </ul>
+                {{end}}
+
+                {{if .Scripts.Modified}}
+                <h4>Modified Scripts</h4>
+                <ul class="item-list">
+                    {{range .Scripts.Modified}}
+                    <li class="modified">{{.Name}}</li>
+                    {{end}}
+                </ul>
+                {{end}}
+            {{end}}
         </div>
         {{end}}
     </div>

pkg/diff/formatters_test.go

@@ -104,6 +104,26 @@ func TestFormatSummary(t *testing.T) {
 			},
 			wantStr: []string{"Tables:", "Missing:  1", "Extra:    1", "Modified: 1"},
 		},
+		{
+			name: "with script differences",
+			result: &DiffResult{
+				Source: "source",
+				Target: "target",
+				Schemas: &SchemaDiff{
+					Modified: []*SchemaChange{
+						{
+							Name: "public",
+							Scripts: &ScriptDiff{
+								Missing:  []*models.Script{{Name: "create_users"}},
+								Extra:    []*models.Script{{Name: "seed_users"}},
+								Modified: []*ScriptChange{{Name: "add_indexes"}},
+							},
+						},
+					},
+				},
+			},
+			wantStr: []string{"Scripts:", "Missing:  1", "Extra:    1", "Modified: 1"},
+		},
 	}
 
 	for _, tt := range tests {
@@ -237,6 +257,31 @@ func TestFormatHTML(t *testing.T) {
 				"text",
 			},
 		},
+		{
+			name: "with script modifications",
+			result: &DiffResult{
+				Source: "source",
+				Target: "target",
+				Schemas: &SchemaDiff{
+					Modified: []*SchemaChange{
+						{
+							Name: "public",
+							Scripts: &ScriptDiff{
+								Missing:  []*models.Script{{Name: "create_users"}},
+								Extra:    []*models.Script{{Name: "seed_users"}},
+								Modified: []*ScriptChange{{Name: "add_indexes"}},
+							},
+						},
+					},
+				},
+			},
+			wantStr: []string{
+				"Scripts",
+				"create_users",
+				"seed_users",
+				"add_indexes",
+			},
+		},
 	}
 
 	for _, tt := range tests {

pkg/diff/types.go

@@ -22,6 +22,7 @@ type SchemaChange struct {
 	Tables    *TableDiff    `json:"tables,omitempty"`
 	Views     *ViewDiff     `json:"views,omitempty"`
 	Sequences *SequenceDiff `json:"sequences,omitempty"`
+	Scripts   *ScriptDiff   `json:"scripts,omitempty"`
 }
 
 // TableDiff represents differences in tables
@@ -131,6 +132,21 @@ type SequenceChange struct {
 	Changes map[string]any   `json:"changes"`
 }
 
+// ScriptDiff represents differences in migration scripts.
+type ScriptDiff struct {
+	Missing  []*models.Script `json:"missing"`  // Scripts in source but not in target
+	Extra    []*models.Script `json:"extra"`    // Scripts in target but not in source
+	Modified []*ScriptChange  `json:"modified"` // Scripts that exist in both but differ
+}
+
+// ScriptChange represents a modified migration script.
+type ScriptChange struct {
+	Name    string         `json:"name"`
+	Source  *models.Script `json:"source"`
+	Target  *models.Script `json:"target"`
+	Changes map[string]any `json:"changes"`
+}
+
 // Summary provides counts for quick overview
 type Summary struct {
 	Schemas       SchemaSummary       `json:"schemas"`
@@ -141,6 +157,7 @@ type Summary struct {
 	Relationships RelationshipSummary `json:"relationships"`
 	Views         ViewSummary         `json:"views"`
 	Sequences     SequenceSummary     `json:"sequences"`
+	Scripts       ScriptSummary       `json:"scripts"`
 }
 
 type SchemaSummary struct {
@@ -190,3 +207,9 @@ type SequenceSummary struct {
 	Extra    int `json:"extra"`
 	Modified int `json:"modified"`
 }
+
+type ScriptSummary struct {
+	Missing  int `json:"missing"`
+	Extra    int `json:"extra"`
+	Modified int `json:"modified"`
+}

pkg/writers/pgsql/migration_writer.go

@@ -409,14 +409,7 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 
 		if !exists {
 			// Column doesn't exist, add it
-			defaultVal := ""
-			if modelCol.Default != nil {
-				if value, ok := modelCol.Default.(string); ok {
-					defaultVal = writers.QuoteDefaultValue(value, modelCol.Type)
-				} else {
-					defaultVal = fmt.Sprintf("%v", modelCol.Default)
-				}
-			}
+			_, defaultVal := formatColumnDefaultSQL(modelCol)
 
 			sql, err := w.executor.ExecuteAddColumn(AddColumnData{
 				SchemaName: schema.Name,
@@ -442,12 +435,14 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 		} else if !columnsEqual(modelCol, currentCol) {
 			// Column exists but properties changed
 			if !columnTypesEqual(modelCol, currentCol) {
-				sql, err := w.executor.ExecuteAlterColumnType(AlterColumnTypeData{
+				newType := effectiveAlterColumnSQLType(modelCol)
+				sql, err := w.executor.ExecuteAlterColumnTypeWithCheck(AlterColumnTypeWithCheckData{
 					SchemaName:      schema.Name,
 					TableName:       modelTable.Name,
 					ColumnName:      modelCol.Name,
-					NewType:    effectiveAlterColumnSQLType(modelCol),
-					UsingExpr:  buildAlterColumnUsingExpression(modelCol.Name, effectiveAlterColumnSQLType(modelCol)),
+					NewType:         newType,
+					EquivalentTypes: equivalentTypeListSQL(newType),
+					UsingExpr:       buildAlterColumnUsingExpression(modelCol.Name, newType),
 				})
 				if err != nil {
 					return nil, err
@@ -465,18 +460,10 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 			}
 
 			// Check default value changes
-			if fmt.Sprintf("%v", modelCol.Default) != fmt.Sprintf("%v", currentCol.Default) {
-				setDefault := modelCol.Default != nil
-				defaultVal := ""
-				if setDefault {
-					if value, ok := modelCol.Default.(string); ok {
-						defaultVal = writers.QuoteDefaultValue(value, modelCol.Type)
-					} else {
-						defaultVal = fmt.Sprintf("%v", modelCol.Default)
-					}
-				}
+			if !columnDefaultsEqual(modelCol.Default, currentCol.Default) {
+				setDefault, defaultVal := formatColumnDefaultSQL(modelCol)
 
-				sql, err := w.executor.ExecuteAlterColumnDefault(AlterColumnDefaultData{
+				sql, err := w.executor.ExecuteAlterColumnDefaultWithCheck(AlterColumnDefaultWithCheckData{
 					SchemaName:   schema.Name,
 					TableName:    modelTable.Name,
 					ColumnName:   modelCol.Name,
@@ -497,6 +484,29 @@ func (w *MigrationWriter) generateAlterTableScripts(schema *models.Schema, model
 				}
 				scripts = append(scripts, script)
 			}
+
+			// Check nullability changes
+			if modelCol.NotNull != currentCol.NotNull {
+				sql, err := w.executor.ExecuteAlterColumnNullabilityWithCheck(AlterColumnNullabilityWithCheckData{
+					SchemaName: schema.Name,
+					TableName:  modelTable.Name,
+					ColumnName: modelCol.Name,
+					NotNull:    modelCol.NotNull,
+				})
+				if err != nil {
+					return nil, err
+				}
+
+				script := MigrationScript{
+					ObjectName: fmt.Sprintf("%s.%s.%s", schema.Name, modelTable.Name, modelCol.Name),
+					ObjectType: "alter column nullability",
+					Schema:     schema.Name,
+					Priority:   145,
+					Sequence:   len(scripts),
+					Body:       sql,
+				}
+				scripts = append(scripts, script)
+			}
 		}
 	}
 
@@ -946,7 +956,24 @@ func columnsEqual(col1, col2 *models.Column) bool {
 	}
 	return columnTypesEqual(col1, col2) &&
 		col1.NotNull == col2.NotNull &&
-		fmt.Sprintf("%v", col1.Default) == fmt.Sprintf("%v", col2.Default)
+		columnDefaultsEqual(col1.Default, col2.Default)
+}
+
+// columnDefaultsEqual compares column defaults for drift detection, stripping
+// MySQL-style backticks (e.g. from GORM tags) so a model default of
+// "`now()`" is recognised as equal to a live default of "now()".
+func columnDefaultsEqual(default1, default2 interface{}) bool {
+	return normalizeDefaultForCompare(default1) == normalizeDefaultForCompare(default2)
+}
+
+func normalizeDefaultForCompare(value interface{}) string {
+	if value == nil {
+		return ""
+	}
+	if s, ok := value.(string); ok {
+		return strings.TrimSpace(stripBackticks(s))
+	}
+	return fmt.Sprintf("%v", value)
 }
 
 func columnTypesEqual(col1, col2 *models.Column) bool {

pkg/writers/pgsql/migration_writer_test.go

@@ -136,6 +136,89 @@ func TestWriteMigration_AltersColumnTypeWhenActualTypeDiffers(t *testing.T) {
 	}
 }
 
+func TestWriteMigration_AltersColumnTypeFallsBackToRenameAndAddOnConversionFailure(t *testing.T) {
+	current := models.InitDatabase("testdb")
+	currentSchema := models.InitSchema("public")
+	currentTable := models.InitTable("learnings", "public")
+	currentDetails := models.InitColumn("details", "learnings", "public")
+	currentDetails.Type = "varchar(50)"
+	currentTable.Columns["details"] = currentDetails
+	currentSchema.Tables = append(currentSchema.Tables, currentTable)
+	current.Schemas = append(current.Schemas, currentSchema)
+
+	model := models.InitDatabase("testdb")
+	modelSchema := models.InitSchema("public")
+	modelTable := models.InitTable("learnings", "public")
+	modelDetails := models.InitColumn("details", "learnings", "public")
+	modelDetails.Type = "integer"
+	modelTable.Columns["details"] = modelDetails
+	modelSchema.Tables = append(modelSchema.Tables, modelTable)
+	model.Schemas = append(model.Schemas, modelSchema)
+
+	var buf bytes.Buffer
+	writer, err := NewMigrationWriter(&writers.WriterOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create writer: %v", err)
+	}
+	writer.writer = &buf
+
+	if err := writer.WriteMigration(model, current); err != nil {
+		t.Fatalf("WriteMigration failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "EXCEPTION WHEN OTHERS THEN") {
+		t.Fatalf("expected migration to guard the type conversion with an exception handler, got:\n%s", output)
+	}
+	if !strings.Contains(output, "RENAME COLUMN details TO %I") {
+		t.Fatalf("expected migration to rename the old column (derived from the live type) on conversion failure, got:\n%s", output)
+	}
+	if !strings.Contains(output, "renamed_column := 'details_' || trim(both '_' from regexp_replace(lower(current_type)") {
+		t.Fatalf("expected migration to derive the renamed column name from the live type, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ADD COLUMN details integer") {
+		t.Fatalf("expected migration to add a fresh column with the new type on conversion failure, got:\n%s", output)
+	}
+}
+
+func TestWriteMigration_AltersColumnNullabilityWhenNotNullDiffers(t *testing.T) {
+	current := models.InitDatabase("testdb")
+	currentSchema := models.InitSchema("public")
+	currentTable := models.InitTable("service_instance", "public")
+	currentType := models.InitColumn("rid_service_instance_type", "service_instance", "public")
+	currentType.Type = "text"
+	currentType.NotNull = true
+	currentTable.Columns["rid_service_instance_type"] = currentType
+	currentSchema.Tables = append(currentSchema.Tables, currentTable)
+	current.Schemas = append(current.Schemas, currentSchema)
+
+	model := models.InitDatabase("testdb")
+	modelSchema := models.InitSchema("public")
+	modelTable := models.InitTable("service_instance", "public")
+	modelType := models.InitColumn("rid_service_instance_type", "service_instance", "public")
+	modelType.Type = "text"
+	modelType.NotNull = false
+	modelTable.Columns["rid_service_instance_type"] = modelType
+	modelSchema.Tables = append(modelSchema.Tables, modelTable)
+	model.Schemas = append(model.Schemas, modelSchema)
+
+	var buf bytes.Buffer
+	writer, err := NewMigrationWriter(&writers.WriterOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create writer: %v", err)
+	}
+	writer.writer = &buf
+
+	if err := writer.WriteMigration(model, current); err != nil {
+		t.Fatalf("WriteMigration failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "ALTER COLUMN rid_service_instance_type DROP NOT NULL") {
+		t.Fatalf("expected migration to drop NOT NULL on existing column, got:\n%s", output)
+	}
+}
+
 func TestWriteMigration_UsesStorageTypeForSerialAlterStatements(t *testing.T) {
 	current := models.InitDatabase("testdb")
 	currentSchema := models.InitSchema("public")

pkg/writers/pgsql/templates.go

@@ -89,15 +89,10 @@ type AddColumnData struct {
 	NotNull    bool
 }
 
-// AlterColumnTypeData contains data for alter column type template
-type AlterColumnTypeData struct {
-	SchemaName string
-	TableName  string
-	ColumnName string
-	NewType    string
-	UsingExpr  string
-}
-
+// AlterColumnTypeWithCheckData contains data for the guarded alter column
+// type template, which only alters existing columns whose live type
+// differs from the desired one, and falls back to renaming the old column
+// and adding a fresh one when the in-place conversion is not possible.
 type AlterColumnTypeWithCheckData struct {
 	SchemaName      string
 	TableName       string
@@ -107,8 +102,10 @@ type AlterColumnTypeWithCheckData struct {
 	UsingExpr       string
 }
 
-// AlterColumnDefaultData contains data for alter column default template
-type AlterColumnDefaultData struct {
+// AlterColumnDefaultWithCheckData contains data for the guarded alter
+// column default template, which only alters existing columns whose live
+// default differs from the desired one.
+type AlterColumnDefaultWithCheckData struct {
 	SchemaName   string
 	TableName    string
 	ColumnName   string
@@ -116,6 +113,16 @@ type AlterColumnDefaultData struct {
 	DefaultValue string
 }
 
+// AlterColumnNullabilityWithCheckData contains data for the guarded alter
+// column nullability template, which only alters existing columns whose
+// live NOT NULL state differs from the desired one.
+type AlterColumnNullabilityWithCheckData struct {
+	SchemaName string
+	TableName  string
+	ColumnName string
+	NotNull    bool
+}
+
 // CreatePrimaryKeyData contains data for create primary key template
 type CreatePrimaryKeyData struct {
 	SchemaName     string
@@ -302,16 +309,9 @@ func (te *TemplateExecutor) ExecuteAddColumn(data AddColumnData) (string, error)
 	return buf.String(), nil
 }
 
-// ExecuteAlterColumnType executes the alter column type template
-func (te *TemplateExecutor) ExecuteAlterColumnType(data AlterColumnTypeData) (string, error) {
-	var buf bytes.Buffer
-	err := te.templates.ExecuteTemplate(&buf, "alter_column_type.tmpl", data)
-	if err != nil {
-		return "", fmt.Errorf("failed to execute alter_column_type template: %w", err)
-	}
-	return buf.String(), nil
-}
-
+// ExecuteAlterColumnTypeWithCheck executes the guarded alter column type
+// template shared by the full-schema writer and the diff-based migration
+// writer.
 func (te *TemplateExecutor) ExecuteAlterColumnTypeWithCheck(data AlterColumnTypeWithCheckData) (string, error) {
 	var buf bytes.Buffer
 	err := te.templates.ExecuteTemplate(&buf, "alter_column_type_with_check.tmpl", data)
@@ -321,12 +321,25 @@ func (te *TemplateExecutor) ExecuteAlterColumnTypeWithCheck(data AlterColumnType
 	return buf.String(), nil
 }
 
-// ExecuteAlterColumnDefault executes the alter column default template
-func (te *TemplateExecutor) ExecuteAlterColumnDefault(data AlterColumnDefaultData) (string, error) {
+// ExecuteAlterColumnDefaultWithCheck executes the guarded alter column
+// default template shared by the full-schema writer and the diff-based
+// migration writer.
+func (te *TemplateExecutor) ExecuteAlterColumnDefaultWithCheck(data AlterColumnDefaultWithCheckData) (string, error) {
 	var buf bytes.Buffer
-	err := te.templates.ExecuteTemplate(&buf, "alter_column_default.tmpl", data)
+	err := te.templates.ExecuteTemplate(&buf, "alter_column_default_with_check.tmpl", data)
 	if err != nil {
-		return "", fmt.Errorf("failed to execute alter_column_default template: %w", err)
+		return "", fmt.Errorf("failed to execute alter_column_default_with_check template: %w", err)
+	}
+	return buf.String(), nil
+}
+
+// ExecuteAlterColumnNullabilityWithCheck executes the guarded alter column
+// nullability template.
+func (te *TemplateExecutor) ExecuteAlterColumnNullabilityWithCheck(data AlterColumnNullabilityWithCheckData) (string, error) {
+	var buf bytes.Buffer
+	err := te.templates.ExecuteTemplate(&buf, "alter_column_nullability_with_check.tmpl", data)
+	if err != nil {
+		return "", fmt.Errorf("failed to execute alter_column_nullability_with_check template: %w", err)
 	}
 	return buf.String(), nil
 }
@@ -517,7 +530,7 @@ func BuildCreateTableData(schemaName string, table *models.Table) CreateTableDat
 		}
 		if col.Default != nil {
 			if value, ok := col.Default.(string); ok {
-				colData.Default = writers.QuoteDefaultValue(value, col.Type)
+				colData.Default = writers.QuoteDefaultValue(stripBackticks(value), col.Type)
 			} else {
 				colData.Default = fmt.Sprintf("%v", col.Default)
 			}

pkg/writers/pgsql/templates/alter_column_default.tmpl

@@ -1,7 +0,0 @@
-{{- if .SetDefault -}}
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} SET DEFAULT {{.DefaultValue}};
-{{- else -}}
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} DROP DEFAULT;
-{{- end -}}

pkg/writers/pgsql/templates/alter_column_default_with_check.tmpl

@@ -0,0 +1,29 @@
+DO $$
+DECLARE
+  current_default text;
+BEGIN
+  SELECT pg_catalog.pg_get_expr(d.adbin, d.adrelid)
+    INTO current_default
+  FROM pg_attribute a
+  JOIN pg_class t ON t.oid = a.attrelid
+  JOIN pg_namespace n ON n.oid = t.relnamespace
+  LEFT JOIN pg_attrdef d ON d.adrelid = a.attrelid AND d.adnum = a.attnum
+  WHERE n.nspname = '{{.SchemaName}}'
+    AND t.relname = '{{.TableName}}'
+    AND a.attname = '{{.ColumnName}}'
+    AND a.attnum > 0
+    AND NOT a.attisdropped;
+
+{{- if .SetDefault }}
+  IF current_default IS DISTINCT FROM {{quote .DefaultValue}} THEN
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} SET DEFAULT {{.DefaultValue}};
+  END IF;
+{{- else }}
+  IF current_default IS NOT NULL THEN
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} DROP DEFAULT;
+  END IF;
+{{- end }}
+END;
+$$;

pkg/writers/pgsql/templates/alter_column_nullability_with_check.tmpl

@@ -0,0 +1,26 @@
+DO $$
+DECLARE
+  current_not_null boolean;
+BEGIN
+  SELECT a.attnotnull
+    INTO current_not_null
+  FROM pg_attribute a
+  JOIN pg_class t ON t.oid = a.attrelid
+  JOIN pg_namespace n ON n.oid = t.relnamespace
+  WHERE n.nspname = '{{.SchemaName}}'
+    AND t.relname = '{{.TableName}}'
+    AND a.attname = '{{.ColumnName}}'
+    AND a.attnum > 0
+    AND NOT a.attisdropped;
+
+  IF current_not_null IS NOT NULL AND current_not_null IS DISTINCT FROM {{.NotNull}} THEN
+{{- if .NotNull }}
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} SET NOT NULL;
+{{- else }}
+    ALTER TABLE {{qual_table .SchemaName .TableName}}
+      ALTER COLUMN {{quote_ident .ColumnName}} DROP NOT NULL;
+{{- end }}
+  END IF;
+END;
+$$;

pkg/writers/pgsql/templates/alter_column_type.tmpl

@@ -1,2 +0,0 @@
-ALTER TABLE {{qual_table .SchemaName .TableName}}
-  ALTER COLUMN {{quote_ident .ColumnName}} TYPE {{.NewType}}{{if .UsingExpr}} USING {{.UsingExpr}}{{end}};

pkg/writers/pgsql/templates/alter_column_type_with_check.tmpl

@@ -1,6 +1,7 @@
 DO $$
 DECLARE
   current_type text;
+  renamed_column text;
 BEGIN
   SELECT pg_catalog.format_type(a.atttypid, a.atttypmod)
     INTO current_type
@@ -15,8 +16,15 @@ BEGIN
 
   IF current_type IS NOT NULL
      AND current_type <> ALL(ARRAY[{{.EquivalentTypes}}]) THEN
+    BEGIN
       ALTER TABLE {{qual_table .SchemaName .TableName}}
         ALTER COLUMN {{quote_ident .ColumnName}} TYPE {{.NewType}}{{if .UsingExpr}} USING {{.UsingExpr}}{{end}};
+    EXCEPTION WHEN OTHERS THEN
+      renamed_column := '{{.ColumnName}}_' || trim(both '_' from regexp_replace(lower(current_type), '[^a-z0-9]+', '_', 'g'));
+      EXECUTE format('ALTER TABLE {{qual_table .SchemaName .TableName}} RENAME COLUMN {{quote_ident .ColumnName}} TO %I', renamed_column);
+      ALTER TABLE {{qual_table .SchemaName .TableName}}
+        ADD COLUMN {{quote_ident .ColumnName}} {{.NewType}};
+    END;
   END IF;
 END;
 $$;

pkg/writers/pgsql/writer.go

@@ -475,6 +475,75 @@ func (w *Writer) GenerateAlterColumnTypeStatements(schema *models.Schema) ([]str
 	return statements, nil
 }
 
+// GenerateAlterColumnDefaultStatements generates guarded ALTER TABLE
+// statements to bring existing columns' DEFAULT clause in line with the
+// model, safe to run against a database that already has the columns.
+func (w *Writer) GenerateAlterColumnDefaultStatements(schema *models.Schema) ([]string, error) {
+	statements := []string{}
+
+	statements = append(statements, fmt.Sprintf("-- Alter column defaults for schema: %s", schema.Name))
+
+	for _, table := range schema.Tables {
+		columns := getSortedColumns(table.Columns)
+		for _, col := range columns {
+			setDefault, defaultVal := formatColumnDefaultSQL(col)
+			stmt, err := w.executor.ExecuteAlterColumnDefaultWithCheck(AlterColumnDefaultWithCheckData{
+				SchemaName:   schema.Name,
+				TableName:    table.Name,
+				ColumnName:   col.Name,
+				SetDefault:   setDefault,
+				DefaultValue: defaultVal,
+			})
+			if err != nil {
+				return nil, fmt.Errorf("failed to generate alter column default for %s.%s.%s: %w", schema.Name, table.Name, col.Name, err)
+			}
+			statements = append(statements, stmt)
+		}
+	}
+
+	return statements, nil
+}
+
+// formatColumnDefaultSQL renders a column's model-level default into the
+// SQL literal/expression used by ALTER COLUMN ... SET DEFAULT, shared by
+// the full-schema writer and the diff-based migration writer.
+func formatColumnDefaultSQL(col *models.Column) (setDefault bool, defaultVal string) {
+	if col.Default == nil {
+		return false, ""
+	}
+	if value, ok := col.Default.(string); ok {
+		return true, writers.QuoteDefaultValue(stripBackticks(value), col.Type)
+	}
+	return true, fmt.Sprintf("%v", col.Default)
+}
+
+// GenerateAlterColumnNullabilityStatements generates guarded ALTER TABLE
+// statements to bring existing columns' NOT NULL state in line with the
+// model, safe to run against a database that already has the columns.
+func (w *Writer) GenerateAlterColumnNullabilityStatements(schema *models.Schema) ([]string, error) {
+	statements := []string{}
+
+	statements = append(statements, fmt.Sprintf("-- Alter column nullability for schema: %s", schema.Name))
+
+	for _, table := range schema.Tables {
+		columns := getSortedColumns(table.Columns)
+		for _, col := range columns {
+			stmt, err := w.executor.ExecuteAlterColumnNullabilityWithCheck(AlterColumnNullabilityWithCheckData{
+				SchemaName: schema.Name,
+				TableName:  table.Name,
+				ColumnName: col.Name,
+				NotNull:    col.NotNull,
+			})
+			if err != nil {
+				return nil, fmt.Errorf("failed to generate alter column nullability for %s.%s.%s: %w", schema.Name, table.Name, col.Name, err)
+			}
+			statements = append(statements, stmt)
+		}
+	}
+
+	return statements, nil
+}
+
 // GenerateAddColumnsForDatabase generates ALTER TABLE ADD COLUMN statements for the entire database
 func (w *Writer) GenerateAddColumnsForDatabase(db *models.Database) ([]string, error) {
 	statements := []string{}
@@ -641,6 +710,14 @@ func (w *Writer) WriteSchema(schema *models.Schema) error {
 		return err
 	}
 
+	if err := w.writeAlterColumnDefaults(schema); err != nil {
+		return err
+	}
+
+	if err := w.writeAlterColumnNullability(schema); err != nil {
+		return err
+	}
+
 	// Phase 4: Create primary keys (priority 160)
 	if err := w.writePrimaryKeys(schema); err != nil {
 		return err
@@ -859,6 +936,36 @@ func (w *Writer) writeAlterColumnTypes(schema *models.Schema) error {
 	return nil
 }
 
+func (w *Writer) writeAlterColumnDefaults(schema *models.Schema) error {
+	fmt.Fprintf(w.writer, "-- Alter column defaults for schema: %s\n", schema.Name)
+
+	statements, err := w.GenerateAlterColumnDefaultStatements(schema)
+	if err != nil {
+		return err
+	}
+	for _, stmt := range statements[1:] {
+		fmt.Fprint(w.writer, stmt)
+		fmt.Fprint(w.writer, "\n")
+	}
+
+	return nil
+}
+
+func (w *Writer) writeAlterColumnNullability(schema *models.Schema) error {
+	fmt.Fprintf(w.writer, "-- Alter column nullability for schema: %s\n", schema.Name)
+
+	statements, err := w.GenerateAlterColumnNullabilityStatements(schema)
+	if err != nil {
+		return err
+	}
+	for _, stmt := range statements[1:] {
+		fmt.Fprint(w.writer, stmt)
+		fmt.Fprint(w.writer, "\n")
+	}
+
+	return nil
+}
+
 // writePrimaryKeys generates ALTER TABLE statements for primary keys
 func (w *Writer) writePrimaryKeys(schema *models.Schema) error {
 	fmt.Fprintf(w.writer, "-- Primary keys for schema: %s\n", schema.Name)

pkg/writers/pgsql/writer_test.go

@@ -1106,6 +1106,144 @@ func TestWriteSchema_EmitsGuardedAlterColumnTypeStatements(t *testing.T) {
 	}
 }
 
+func TestWriteSchema_EmitsGuardedAlterColumnDefaultStatements(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("agent_skills", "public")
+
+	statusCol := models.InitColumn("status", "agent_skills", "public")
+	statusCol.Type = "text"
+	statusCol.Default = "active"
+	table.Columns["status"] = statusCol
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "-- Alter column defaults for schema: public") {
+		t.Fatalf("expected alter column default section, got:\n%s", output)
+	}
+	if !strings.Contains(output, "pg_get_expr(d.adbin, d.adrelid)") {
+		t.Fatalf("expected guarded live-default check, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ALTER COLUMN status SET DEFAULT 'active'") {
+		t.Fatalf("expected guarded SET DEFAULT for status column, got:\n%s", output)
+	}
+}
+
+func TestWriteSchema_AlterColumnDefaultStripsBackticksFromFunctionExpression(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("agent_skills", "public")
+
+	updatedAtCol := models.InitColumn("updatedat", "agent_skills", "public")
+	updatedAtCol.Type = "timestamp"
+	updatedAtCol.Default = "`now()`"
+	table.Columns["updatedat"] = updatedAtCol
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+	if strings.Contains(output, "`") {
+		t.Fatalf("expected no backticks in generated SQL, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ALTER COLUMN updatedat SET DEFAULT now()") {
+		t.Fatalf("expected guarded SET DEFAULT now() without backticks, got:\n%s", output)
+	}
+}
+
+func TestWriteSchema_GuardedAlterColumnTypeFallsBackOnConversionFailure(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("agent_skills", "public")
+
+	nameCol := models.InitColumn("name", "agent_skills", "public")
+	nameCol.Type = "integer"
+	table.Columns["name"] = nameCol
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "EXCEPTION WHEN OTHERS THEN") {
+		t.Fatalf("expected guarded alter to fall back on conversion failure, got:\n%s", output)
+	}
+	if !strings.Contains(output, "renamed_column := 'name_' || trim(both '_' from regexp_replace(lower(current_type)") {
+		t.Fatalf("expected fallback to derive a renamed column name from the live type, got:\n%s", output)
+	}
+	if !strings.Contains(output, "RENAME COLUMN name TO %I") {
+		t.Fatalf("expected fallback to rename the existing column, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ADD COLUMN name integer") {
+		t.Fatalf("expected fallback to add a fresh column with the new type, got:\n%s", output)
+	}
+}
+
+func TestWriteSchema_EmitsGuardedAlterColumnNullabilityStatements(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("origin")
+
+	table := models.InitTable("service_instance", "origin")
+
+	typeCol := models.InitColumn("rid_service_instance_type", "service_instance", "origin")
+	typeCol.Type = "text"
+	typeCol.NotNull = false
+	table.Columns["rid_service_instance_type"] = typeCol
+
+	schema.Tables = append(schema.Tables, table)
+	db.Schemas = append(db.Schemas, schema)
+
+	var buf bytes.Buffer
+	writer := NewWriter(&writers.WriterOptions{})
+	writer.writer = &buf
+
+	if err := writer.WriteDatabase(db); err != nil {
+		t.Fatalf("WriteDatabase failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "-- Alter column nullability for schema: origin") {
+		t.Fatalf("expected alter column nullability section, got:\n%s", output)
+	}
+	if !strings.Contains(output, "a.attnotnull") {
+		t.Fatalf("expected guarded live-nullability check, got:\n%s", output)
+	}
+	if !strings.Contains(output, "current_not_null IS DISTINCT FROM false") {
+		t.Fatalf("expected guard comparing live nullability against desired value, got:\n%s", output)
+	}
+	if !strings.Contains(output, "ALTER COLUMN rid_service_instance_type DROP NOT NULL") {
+		t.Fatalf("expected guarded DROP NOT NULL for nullable column, got:\n%s", output)
+	}
+}
+
 func TestWriteSchema_UsesStorageTypeForSerialAlterStatements(t *testing.T) {
 	db := models.InitDatabase("testdb")
 	schema := models.InitSchema("public")