@@ -539,10 +539,13 @@ describe('Settings Module', () => {
         notification_days_before: 3,
         // Grace-period inputs default to 7 per provider when the DOM
         // doesn't include the new inputs (older test harness setup).
-        // The save helper reads missing elements as "empty" → default 7.
+        // The save helper reads missing elements as "empty" -> default 7.
         grace_period_days: { aws: 7, azure: 7, gcp: 7 },
         recommendations_cache_stale_hours: 24,
         recommendations_lookback_days: 7,
+        // offering_class select is absent in this test harness (no DOM element);
+        // saveGlobalSettings falls back to 'convertible'.
+        offering_class: 'convertible',
       });
     });
 
 
@@ -289,6 +289,10 @@ export interface Config {
   // Keys: 'aws' / 'azure' / 'gcp'. A missing key defaults to 7 on
   // the backend. Explicit 0 disables the feature for that provider.
   grace_period_days?: Record<string, number>;
+  // EC2 Reserved Instance offering class. "convertible" (default) allows
+  // future exchanges for different families/sizes/OS; "standard" is
+  // ~5% cheaper but locked to the exact instance type for the full term.
+  offering_class?: 'convertible' | 'standard';
   ri_exchange_enabled?: boolean;
   ri_exchange_mode?: string;
   ri_exchange_utilization_threshold?: number;
 
@@ -497,6 +497,22 @@ <h2>Purchasing Settings</h2>
                         </div>
                     </fieldset>
 
+                    <fieldset class="settings-category" id="ec2-ri-offering-class">
+                        <legend><span class="provider-badge aws">AWS</span> Reserved Instance Class</legend>
+                        <p class="settings-help">Controls whether EC2 Reserved Instances are purchased as Convertible or Standard. Convertible RIs can be exchanged for a different instance family, size, OS, or region later. Standard RIs are approximately 5% cheaper but are locked to the exact instance type for the full term and cannot be exchanged.</p>
+                        <div class="setting-row">
+                            <div class="setting-info">
+                                <label for="setting-ec2-offering-class">Reserved Instance class</label>
+                            </div>
+                            <div class="setting-input">
+                                <select id="setting-ec2-offering-class">
+                                    <option value="convertible" selected>Convertible (default -- exchangeable for different families/sizes/OS later)</option>
+                                    <option value="standard">Standard (~5% cheaper, locked to the exact instance for the full term)</option>
+                                </select>
+                            </div>
+                        </div>
+                    </fieldset>
+
                     <!-- AWS Settings -->
                     <fieldset class="settings-category provider-settings" id="aws-settings">
                         <legend><span class="provider-badge aws">AWS</span> Service Defaults</legend>
 
@@ -3202,6 +3202,16 @@ export async function loadGlobalSettings(): Promise<void> {
       populateGraceInput('setting-grace-azure', gpMap['azure']);
       populateGraceInput('setting-grace-gcp', gpMap['gcp']);
 
+      // EC2 RI offering class. Absent/null from the API means "convertible"
+      // (backend default). Only "convertible" and "standard" are valid; any
+      // other value from a future API version falls back to "convertible" so
+      // the dropdown always has a valid selection.
+      const offeringClassSelect = byId<HTMLSelectElement>('setting-ec2-offering-class');
+      if (offeringClassSelect) {
+        const oc = data.global.offering_class;
+        offeringClassSelect.value = (oc === 'standard') ? 'standard' : 'convertible';
+      }
+
       // Recommendations cycle params
       const staleHoursInput = byId<HTMLInputElement>('setting-recs-stale-hours');
       if (staleHoursInput) {
@@ -3476,6 +3486,9 @@ export async function saveGlobalSettings(e: Event): Promise<void> {
     return;
   }
 
+  const rawOfferingClass = byId<HTMLSelectElement>('setting-ec2-offering-class')?.value ?? 'convertible';
+  const offeringClass: 'convertible' | 'standard' = (rawOfferingClass === 'standard') ? 'standard' : 'convertible';
+
   const settings: api.Config = {
     enabled_providers: enabledProviders,
     notification_email: byId<HTMLInputElement>('setting-notification-email')?.value || '',
@@ -3488,6 +3501,7 @@ export async function saveGlobalSettings(e: Event): Promise<void> {
     grace_period_days: gracePeriodDays,
     recommendations_cache_stale_hours: rawStaleHours,
     recommendations_lookback_days: parseInt(byId<HTMLSelectElement>('setting-recs-lookback-days')?.value || '7', 10),
+    offering_class: offeringClass,
   };
 
   // Include laddering_enabled in the payload when the Purchasing panel's
@@ -3625,6 +3639,9 @@ export async function resetSettings(): Promise<void> {
   populateGraceInput('setting-grace-azure', 7);
   populateGraceInput('setting-grace-gcp', 7);
 
+  const offeringClassSelect = byId<HTMLSelectElement>('setting-ec2-offering-class');
+  if (offeringClassSelect) offeringClassSelect.value = 'convertible';
+
   const staleHoursInput = byId<HTMLInputElement>('setting-recs-stale-hours');
   if (staleHoursInput) staleHoursInput.value = '24';
   const lookbackSelect = byId<HTMLSelectElement>('setting-recs-lookback-days');
 
@@ -373,6 +373,8 @@ export interface GlobalConfig {
   // suppression feature. Keys: 'aws' / 'azure' / 'gcp'. Missing keys
   // fall back to the backend default (7). Explicit 0 = disabled.
   grace_period_days?: Record<string, number>;
+  // EC2 Reserved Instance offering class. "convertible" (default) or "standard".
+  offering_class?: 'convertible' | 'standard';
   // Age (hours) after which the recommendations cache triggers a background
   // stale-while-revalidate refresh. 0 disables automatic background refresh.
   // Valid range: 0–8760. Default: 24.
 
@@ -81,7 +81,8 @@ func getGlobalConfigFrom(ctx context.Context, q globalConfigExecutor) (*GlobalCo
 		       recommendations_cache_stale_hours, recommendations_lookback_days,
 		       COALESCE(purchase_delay_hours, 0),
 		       COALESCE(laddering_enabled, false),
-		       COALESCE(ladder_execution_enabled, false)
+		       COALESCE(ladder_execution_enabled, false),
+		       offering_class
 		FROM global_config
 		WHERE id = 1
 	`
@@ -113,6 +114,7 @@ func getGlobalConfigFrom(ctx context.Context, q globalConfigExecutor) (*GlobalCo
 		&config.PurchaseDelayHours,
 		&config.LadderingEnabled,
 		&config.LadderExecutionEnabled,
+		&config.OfferingClass,
 	)
 
 	if err != nil {
@@ -135,6 +137,7 @@ func getGlobalConfigFrom(ctx context.Context, q globalConfigExecutor) (*GlobalCo
 				RecommendationsCacheStaleHours: DefaultRecommendationsCacheStaleHours,
 				RecommendationsLookbackDays:    DefaultRecommendationsLookbackDays,
 				PurchaseDelayHours:             DefaultPurchaseDelayHours,
+				OfferingClass:                  "convertible",
 			}, nil
 		}
 		return nil, fmt.Errorf("failed to get global config: %w", err)
@@ -211,8 +214,8 @@ func saveGlobalConfigWith(ctx context.Context, q globalConfigExecutor, config *G
 			auto_collect, collection_schedule, notification_days_before,
 			grace_period_days,
 			recommendations_cache_stale_hours, recommendations_lookback_days,
-			purchase_delay_hours, laddering_enabled, ladder_execution_enabled
-		) VALUES (1, $1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19, $20, $21, $22)
+			purchase_delay_hours, laddering_enabled, ladder_execution_enabled, offering_class
+		) VALUES (1, $1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19, $20, $21, $22, $23)
 		ON CONFLICT (id) DO UPDATE SET
 			enabled_providers = $1,
 			notification_email = $2,
@@ -236,6 +239,7 @@ func saveGlobalConfigWith(ctx context.Context, q globalConfigExecutor, config *G
 			purchase_delay_hours = $20,
 			laddering_enabled = $21,
 			ladder_execution_enabled = $22,
+			offering_class = $23,
 			updated_at = NOW()
 	`
 
@@ -259,7 +263,7 @@ func saveGlobalConfigWith(ctx context.Context, q globalConfigExecutor, config *G
 		riExchangeUtilizationThreshold = 95.0
 	}
 
-	// Marshal GracePeriodDays → JSON text column. Empty map encodes as
+	// Marshal GracePeriodDays -> JSON text column. Empty map encodes as
 	// "{}" so the DB column is never NULL and GetGlobalConfig can
 	// treat "{}" and "" uniformly as "no explicit entries".
 	gracePeriodJSON := "{}"
@@ -271,6 +275,14 @@ func saveGlobalConfigWith(ctx context.Context, q globalConfigExecutor, config *G
 		gracePeriodJSON = string(gpBytes)
 	}
 
+	// Default offering_class to "convertible" when unset so the DB column
+	// never stores an empty string (the NOT NULL DEFAULT 'convertible'
+	// column handles inserts, but upserts overwrite with whatever we pass).
+	offeringClass := config.OfferingClass
+	if offeringClass == "" {
+		offeringClass = "convertible"
+	}
+
 	_, err := q.Exec(ctx, query,
 		config.EnabledProviders,
 		config.NotificationEmail,
@@ -294,6 +306,7 @@ func saveGlobalConfigWith(ctx context.Context, q globalConfigExecutor, config *G
 		config.PurchaseDelayHours,
 		config.LadderingEnabled,
 		config.LadderExecutionEnabled,
+		offeringClass,
 	)
 
 	if err != nil {
 
@@ -5,7 +5,9 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pashagolub/pgxmock/v4"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 // These tests exercise the real PostgresStore methods to gain code coverage.
@@ -535,3 +537,75 @@ func TestPostgresStore_GetAllPurchaseHistory_NilDB(t *testing.T) {
 
 	assert.True(t, panicked, "expected panic with nil db connection")
 }
+
+// TestSaveGlobalConfig_OfferingClassBindsAt23 is the HOLE 2 regression guard
+// (issue #694): the real PostgresStore.SaveGlobalConfig must bind offering_class
+// as the 23rd positional argument ($23), with laddering_enabled at $21 and
+// ladder_execution_enabled at $22.
+// The testablePostgresStore in store_postgres_mock_test.go is a hand-maintained
+// copy that omits the field entirely, so no fast test guarded the placeholder
+// count until now.
+//
+// Using pgxmock directly against the real PostgresStore (not the hand-maintained
+// testablePostgresStore wrapper) ensures the live query is tested, not a stale copy.
+func TestSaveGlobalConfig_OfferingClassBindsAt23(t *testing.T) {
+	ctx := context.Background()
+	mock, err := pgxmock.NewPool()
+	require.NoError(t, err)
+	defer mock.Close()
+
+	// Wire the pgxmock pool directly into the real PostgresStore via the
+	// unexported db field (test is in package config so this is allowed).
+	store := &PostgresStore{db: mock}
+
+	email := "ops@example.com"
+	cfg := &GlobalConfig{
+		EnabledProviders:    []string{"aws"},
+		NotificationEmail:   &email,
+		ApprovalRequired:    true,
+		DefaultTerm:         12,
+		DefaultPayment:      "all-upfront",
+		DefaultCoverage:     80.0,
+		DefaultRampSchedule: "immediate",
+		OfferingClass:       "standard",
+	}
+
+	// Expect exactly 23 args; pgxmock validates arg count and types.
+	// The 21st arg is laddering_enabled; the 22nd is ladder_execution_enabled;
+	// the 23rd arg must be "standard" (offering_class).
+	// If the real query regresses to a different arg count, pgxmock
+	// will return an unexpected-call error and the test will fail.
+	mock.ExpectExec(`INSERT INTO global_config`).
+		WithArgs(
+			pgxmock.AnyArg(), // $1  enabled_providers
+			pgxmock.AnyArg(), // $2  notification_email
+			pgxmock.AnyArg(), // $3  approval_required
+			pgxmock.AnyArg(), // $4  default_term
+			pgxmock.AnyArg(), // $5  default_payment
+			pgxmock.AnyArg(), // $6  default_coverage
+			pgxmock.AnyArg(), // $7  default_ramp_schedule
+			pgxmock.AnyArg(), // $8  ri_exchange_enabled
+			pgxmock.AnyArg(), // $9  ri_exchange_mode
+			pgxmock.AnyArg(), // $10 ri_exchange_utilization_threshold
+			pgxmock.AnyArg(), // $11 ri_exchange_max_per_exchange_usd
+			pgxmock.AnyArg(), // $12 ri_exchange_max_daily_usd
+			pgxmock.AnyArg(), // $13 ri_exchange_lookback_days
+			pgxmock.AnyArg(), // $14 auto_collect
+			pgxmock.AnyArg(), // $15 collection_schedule
+			pgxmock.AnyArg(), // $16 notification_days_before
+			pgxmock.AnyArg(), // $17 grace_period_days
+			pgxmock.AnyArg(), // $18 recommendations_cache_stale_hours
+			pgxmock.AnyArg(), // $19 recommendations_lookback_days
+			pgxmock.AnyArg(), // $20 purchase_delay_hours
+			pgxmock.AnyArg(), // $21 laddering_enabled
+			pgxmock.AnyArg(), // $22 ladder_execution_enabled
+			"standard",       // $23 offering_class -- the field this test guards
+		).
+		WillReturnResult(pgxmock.NewResult("INSERT", 1))
+
+	err = store.SaveGlobalConfig(ctx, cfg)
+	require.NoError(t, err, "SaveGlobalConfig must succeed when the DB accepts all 23 args")
+
+	require.NoError(t, mock.ExpectationsWereMet(),
+		"offering_class must be bound as the 23rd argument to SaveGlobalConfig")
+}
@@ -61,6 +61,7 @@ func TestPGXMock_GetGlobalConfig_Success(t *testing.T) {
 		"purchase_delay_hours",
 		"laddering_enabled",
 		"ladder_execution_enabled",
+		"offering_class",
 	}
 	rows := pgxmock.NewRows(cols).AddRow(
 		[]string{"aws"}, strPtr("ops@example.com"), true,
@@ -73,6 +74,7 @@ func TestPGXMock_GetGlobalConfig_Success(t *testing.T) {
 		0,
 		false,
 		false,
+		"convertible",
 	)
 	mock.ExpectQuery("SELECT").WillReturnRows(rows)
 
@@ -83,6 +85,7 @@ func TestPGXMock_GetGlobalConfig_Success(t *testing.T) {
 	assert.Equal(t, "ops@example.com", *cfg.NotificationEmail)
 	assert.Equal(t, 24, cfg.RecommendationsCacheStaleHours)
 	assert.Equal(t, 7, cfg.RecommendationsLookbackDays)
+	assert.Equal(t, "convertible", cfg.OfferingClass)
 	assert.NoError(t, mock.ExpectationsWereMet())
 }
 
@@ -115,6 +118,7 @@ func TestPGXMock_GetGlobalConfig_GracePeriodDays(t *testing.T) {
 		"purchase_delay_hours",
 		"laddering_enabled",
 		"ladder_execution_enabled",
+		"offering_class",
 	}
 	baseRow := func(graceJSON string) []any {
 		return []any{
@@ -128,6 +132,7 @@ func TestPGXMock_GetGlobalConfig_GracePeriodDays(t *testing.T) {
 			0,
 			false,
 			false,
+			"convertible",
 		}
 	}
 
@@ -186,6 +191,7 @@ var globalConfigCols = []string{
 	"purchase_delay_hours",
 	"laddering_enabled",
 	"ladder_execution_enabled",
+	"offering_class",
 }
 
 // TestPGXMock_UpdateGlobalConfigAtomic_LockedReadModifyWrite proves the F2
@@ -213,8 +219,9 @@ func TestPGXMock_UpdateGlobalConfigAtomic_LockedReadModifyWrite(t *testing.T) {
 		"{}",
 		24, 7,
 		48,
-		false, // laddering_enabled = false
-		false, // ladder_execution_enabled = false
+		false,         // laddering_enabled = false
+		false,         // ladder_execution_enabled = false
+		"convertible", // offering_class
 	)
 
 	// Strict order: the SELECT and the UPSERT must sit between the same
@@ -223,7 +230,7 @@ func TestPGXMock_UpdateGlobalConfigAtomic_LockedReadModifyWrite(t *testing.T) {
 	mock.ExpectExec("pg_advisory_xact_lock").WithArgs(pgxmock.AnyArg()).
 		WillReturnResult(pgxmock.NewResult("SELECT", 1))
 	mock.ExpectQuery("FROM global_config").WillReturnRows(seeded)
-	mock.ExpectExec("INSERT INTO global_config").WithArgs(anyArgsCfg(22)...).
+	mock.ExpectExec("INSERT INTO global_config").WithArgs(anyArgsCfg(23)...).
 		WillReturnResult(pgxmock.NewResult("INSERT", 1))
 	mock.ExpectCommit()
 
@@ -270,6 +277,7 @@ func TestPGXMock_UpdateGlobalConfigAtomic_ApplyErrorRollsBack(t *testing.T) {
 		0,
 		false,
 		false,
+		"convertible",
 	)
 
 	mock.ExpectBegin()
 
@@ -50,7 +50,7 @@ type GlobalConfig struct {
 
 	// RecommendationsLookbackDays is the AWS Cost Explorer lookback window
 	// (days) used when fetching fresh recommendations. Must be one of 7,
-	// 30, or 60 — the AWS Cost Explorer LookbackPeriodInDays enum.
+	// 30, or 60 -- the AWS Cost Explorer LookbackPeriodInDays enum.
 	// GCP CUD Recommender has no equivalent lookback parameter (fixed
 	// internally); this setting applies to AWS only.
 	// Default: 7.
@@ -78,6 +78,14 @@ type GlobalConfig struct {
 	// operator explicitly opts in. Fail-loud: wireLadderWriteSide returns
 	// a typed ErrLadderExecutionDisabled when this is false.
 	LadderExecutionEnabled bool `json:"ladder_execution_enabled" db:"ladder_execution_enabled"`
+
+	// OfferingClass controls the EC2 Reserved Instance offering class used
+	// during purchase. Accepted values: "convertible" (default) and
+	// "standard". Convertible RIs can be exchanged for a different
+	// instance family/size/region/OS; Standard RIs are locked to the exact
+	// instance type for the full term but are ~5% cheaper.
+	// Unknown values are rejected at purchase time with an explicit error.
+	OfferingClass string `json:"offering_class,omitempty" dynamodbav:"offering_class,omitempty"`
 }
 
 // DefaultGracePeriodDays is the fallback window used when a provider