diff --git a/internal/api/handler_ladder_test.go b/internal/api/handler_ladder_test.go
index cbecfd6be..17c1f1635 100644
--- a/internal/api/handler_ladder_test.go
+++ b/internal/api/handler_ladder_test.go
@@ -2,6 +2,7 @@ package api
 
 import (
 	"context"
+	"fmt"
 	"testing"
 
 	"github.com/LeanerCloud/cloud-commitments-platform/internal/config"
@@ -50,6 +51,52 @@ func newLadderHandler(t *testing.T) (*Handler, *MockConfigStore, **config.Ladder
 
 const ladderValidRamp = `"ramp_schedule":{"steps":[{"after_days":0,"fraction":1.0}]}`
 
+// cloud_accounts.id is a UUID column, so the ladder tests use UUID ids: a
+// non-UUID id is now refused before any lookup (#1430).
+const (
+	ladderTestAccount  = "33333333-3333-4333-8333-333333333333"
+	ladderGhostAccount = "44444444-4444-4444-8444-444444444444"
+	ladderBadAccountID = "not-a-uuid"
+)
+
+// failNonUUIDLookups makes the mock store answer GetCloudAccount the way
+// Postgres does for a non-UUID id: a plain (non-client) error, which
+// handleRequestError would turn into a 500.
+func failNonUUIDLookups(mockStore *MockConfigStore) {
+	mockStore.GetCloudAccountFn = func(_ context.Context, id string) (*config.CloudAccount, error) {
+		if !uuidRegex.MatchString(id) {
+			return nil, fmt.Errorf(`pq: invalid input syntax for type uuid: %q`, id)
+		}
+		return &config.CloudAccount{ID: id, Provider: "aws"}, nil
+	}
+}
+
+// requireInvalidAccountID asserts a 400 ClientError that never reached the
+// account lookup.
+func requireInvalidAccountID(t *testing.T, mockStore *MockConfigStore, result any, err error) {
+	t.Helper()
+	require.Error(t, err)
+	assert.Nil(t, result)
+	ce, ok := IsClientError(err)
+	require.True(t, ok, "a non-UUID account id must be a 400 ClientError, not a 500; got %T: %v", err, err)
+	assert.Equal(t, 400, ce.code)
+	mockStore.AssertNotCalled(t, "GetCloudAccount", mock.Anything, ladderBadAccountID)
+	mockStore.AssertNotCalled(t, "UpsertLadderConfig", mock.Anything, mock.Anything)
+}
+
+// TestUpsertLadderConfig_NonUUIDAccountIDIs400 pins #1430: a cloud_account_id
+// that is not a UUID answers 400 instead of letting Postgres's uuid syntax
+// error surface as a 500.
+func TestUpsertLadderConfig_NonUUIDAccountIDIs400(t *testing.T) {
+	ctx := context.Background()
+	handler, mockStore, _ := newLadderHandler(t)
+	failNonUUIDLookups(mockStore)
+
+	body := `{"cloud_account_id":"` + ladderBadAccountID + `","provider":"aws","mode":"email_approval","cadence":"daily",` + ladderValidRamp + `}`
+	result, err := handler.upsertLadderConfig(ctx, ladderReq(body))
+	requireInvalidAccountID(t, mockStore, result, err)
+}
+
 // TestUpsertLadderConfig_BufferFractionExplicitZeroSurvives asserts that an
 // explicit buffer_fraction:0 ("no buffer") reaches the store unchanged rather
 // than being silently rewritten to DefaultLadderBufferFraction.
@@ -57,7 +104,7 @@ func TestUpsertLadderConfig_BufferFractionExplicitZeroSurvives(t *testing.T) {
 	ctx := context.Background()
 	handler, _, captured := newLadderHandler(t)
 
-	body := `{"cloud_account_id":"acct-1","provider":"aws","mode":"email_approval","cadence":"daily","buffer_fraction":0,` + ladderValidRamp + `}`
+	body := `{"cloud_account_id":"` + ladderTestAccount + `","provider":"aws","mode":"email_approval","cadence":"daily","buffer_fraction":0,` + ladderValidRamp + `}`
 	_, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.NoError(t, err)
 	require.NotNil(t, *captured, "store should have been reached")
@@ -71,7 +118,7 @@ func TestUpsertLadderConfig_BufferFractionOmittedDefaults(t *testing.T) {
 	ctx := context.Background()
 	handler, _, captured := newLadderHandler(t)
 
-	body := `{"cloud_account_id":"acct-1","provider":"aws","mode":"email_approval","cadence":"daily",` + ladderValidRamp + `}`
+	body := `{"cloud_account_id":"` + ladderTestAccount + `","provider":"aws","mode":"email_approval","cadence":"daily",` + ladderValidRamp + `}`
 	_, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.NoError(t, err)
 	require.NotNil(t, *captured, "store should have been reached")
@@ -86,7 +133,7 @@ func TestUpsertLadderConfig_ExplicitZeroTargetCoverageRejected(t *testing.T) {
 	ctx := context.Background()
 	handler, mockStore, _ := newLadderHandler(t)
 
-	body := `{"cloud_account_id":"acct-1","provider":"aws","mode":"email_approval","cadence":"daily","target_coverage":0,` + ladderValidRamp + `}`
+	body := `{"cloud_account_id":"` + ladderTestAccount + `","provider":"aws","mode":"email_approval","cadence":"daily","target_coverage":0,` + ladderValidRamp + `}`
 	result, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.Error(t, err)
 	assert.Nil(t, result)
@@ -103,7 +150,7 @@ func TestUpsertLadderConfig_ShortAWSLookbackRejected(t *testing.T) {
 	ctx := context.Background()
 	handler, mockStore, _ := newLadderHandler(t)
 
-	body := `{"cloud_account_id":"acct-1","provider":"aws","mode":"email_approval","cadence":"daily","lookback_days":9,` + ladderValidRamp + `}`
+	body := `{"cloud_account_id":"` + ladderTestAccount + `","provider":"aws","mode":"email_approval","cadence":"daily","lookback_days":9,` + ladderValidRamp + `}`
 	result, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.Error(t, err)
 	assert.Nil(t, result)
@@ -124,7 +171,7 @@ func TestUpsertLadderConfig_MultiStepRampAccepted(t *testing.T) {
 	handler, _, captured := newLadderHandler(t)
 
 	const ramp = `"ramp_schedule":{"steps":[{"after_days":0,"fraction":0.5},{"after_days":30,"fraction":0.3},{"after_days":60,"fraction":0.2}]}`
-	body := `{"cloud_account_id":"acct-1","provider":"aws","mode":"email_approval","cadence":"daily",` + ramp + `}`
+	body := `{"cloud_account_id":"` + ladderTestAccount + `","provider":"aws","mode":"email_approval","cadence":"daily",` + ramp + `}`
 	result, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.NoError(t, err)
 	require.NotNil(t, result)
@@ -142,7 +189,7 @@ func TestUpsertLadderConfig_UnknownFieldRejected(t *testing.T) {
 	ctx := context.Background()
 	handler, mockStore, _ := newLadderHandler(t)
 
-	body := `{"cloud_account_id":"acct-1","provider":"aws","mode":"email_approval","cadence":"daily","max_hourly_commit_per_runn":5,` + ladderValidRamp + `}`
+	body := `{"cloud_account_id":"` + ladderTestAccount + `","provider":"aws","mode":"email_approval","cadence":"daily","max_hourly_commit_per_runn":5,` + ladderValidRamp + `}`
 	result, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.Error(t, err)
 	assert.Nil(t, result)
@@ -159,7 +206,7 @@ func TestUpsertLadderConfig_ProviderMismatchRejected(t *testing.T) {
 	ctx := context.Background()
 	handler, mockStore, _ := newLadderHandler(t)
 
-	body := `{"cloud_account_id":"acct-1","provider":"azure","mode":"email_approval","cadence":"daily",` + ladderValidRamp + `}`
+	body := `{"cloud_account_id":"` + ladderTestAccount + `","provider":"azure","mode":"email_approval","cadence":"daily",` + ladderValidRamp + `}`
 	result, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.Error(t, err)
 	assert.Nil(t, result)
@@ -181,9 +228,9 @@ func TestUpsertLadderConfig_ProviderMismatchRejected(t *testing.T) {
 func TestUpsertLadderConfig_NonexistentAccountRejected(t *testing.T) {
 	ctx := context.Background()
 	handler, mockStore, _ := newLadderHandler(t)
-	mockStore.On("GetCloudAccount", ctx, "ghost").Return(nil, nil)
+	mockStore.On("GetCloudAccount", ctx, ladderGhostAccount).Return(nil, nil)
 
-	body := `{"cloud_account_id":"ghost","provider":"aws","mode":"email_approval","cadence":"daily",` + ladderValidRamp + `}`
+	body := `{"cloud_account_id":"` + ladderGhostAccount + `","provider":"aws","mode":"email_approval","cadence":"daily",` + ladderValidRamp + `}`
 	result, err := handler.upsertLadderConfig(ctx, ladderReq(body))
 	require.Error(t, err)
 	assert.Nil(t, result)
diff --git a/internal/api/handler_ladder_timeline_test.go b/internal/api/handler_ladder_timeline_test.go
index 7f522ceb4..f544a2432 100644
--- a/internal/api/handler_ladder_timeline_test.go
+++ b/internal/api/handler_ladder_timeline_test.go
@@ -129,3 +129,22 @@ func TestLadderTimelineMalformedRateReturnsFixedError(t *testing.T) {
 	require.NotContains(t, clientErr.Error(), "row 9")
 	require.Nil(t, result)
 }
+
+// TestLadderTimelineNonUUIDAccountIDIs400 pins #1430 for both timeline reads:
+// an account_id that is not a UUID answers 400 instead of letting Postgres's
+// uuid syntax error surface as a 500.
+func TestLadderTimelineNonUUIDAccountIDIs400(t *testing.T) {
+	for _, path := range []string{"/api/ladder/tranches", "/api/ladder/runs"} {
+		t.Run(path, func(t *testing.T) {
+			h, original := ladderScopedHandler(t)
+			failNonUUIDLookups(original)
+			store := &timelineTestStore{MockConfigStore: original}
+			h.config = store
+			req := ladderScopedReq("")
+			req.QueryStringParameters = map[string]string{"account_id": ladderBadAccountID, "provider": "aws"}
+			result, err := NewRouter(h).Route(context.Background(), "GET", path, req)
+			requireInvalidAccountID(t, original, result, err)
+			require.False(t, store.called)
+		})
+	}
+}
diff --git a/internal/api/scoping.go b/internal/api/scoping.go
index 12ec34c26..bbeac7dc6 100644
--- a/internal/api/scoping.go
+++ b/internal/api/scoping.go
@@ -23,7 +23,16 @@ import (
 //
 // requirePermission must be called before this helper so the verb gate fires
 // first; callers pass the session it returned.
+//
+// A non-UUID accountID is refused with a 400 before the lookup:
+// cloud_accounts.id is a UUID column, so Postgres would reject the value with
+// a syntax error that handleRequestError turns into a 500. The ladder routes
+// pass caller-supplied ids (body or query string) straight here, without the
+// validateUUID the account path handlers run first.
 func (h *Handler) requireAccountAccess(ctx context.Context, session *Session, accountID string) (*config.CloudAccount, error) {
+	if !uuidRegex.MatchString(accountID) {
+		return nil, NewClientError(400, "invalid account id: must be a valid UUID")
+	}
 	account, err := h.config.GetCloudAccount(ctx, accountID)
 	if err != nil {
 		return nil, fmt.Errorf("accounts: %w", err)