fix(gcp/computeengine): fail loud when a non-empty idempotency token cannot form a request ID

providers/gcp/go.mod

@@ -8,7 +8,7 @@ require (
 	cloud.google.com/go/redis v1.18.3
 	cloud.google.com/go/resourcemanager v1.10.7
 	cloud.google.com/go/storage v1.59.2
-	github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261015085730-498b74f31f01
+	github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261017012250-2bf23fbd8c2a
 	github.com/googleapis/gax-go/v2 v2.21.0
 	github.com/stretchr/testify v1.11.1
 	golang.org/x/oauth2 v0.36.0

providers/gcp/go.sum

@@ -36,8 +36,8 @@ github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/cloudmock v0
 github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/cloudmock v0.54.0/go.mod h1:vB2GH9GAYYJTO3mEn8oYwzEdhlayZIdQz6zdzgUIRvA=
 github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/resourcemapping v0.54.0 h1:s0WlVbf9qpvkh1c/uDAPElam0WrL7fHRIidgZJ7UqZI=
 github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/resourcemapping v0.54.0/go.mod h1:Mf6O40IAyB9zR/1J8nGDDPirZQQPbYJni8Yisy7NTMc=
-github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261015085730-498b74f31f01 h1:R2EQAvwLAxPrdlZXmF+bI7ioQYh1CxBkethx5hq6WWA=
-github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261015085730-498b74f31f01/go.mod h1:8RTmzPazA8IeVZfn7wNaU7ILx0VK5eHZQozO21Mvtq8=
+github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261017012250-2bf23fbd8c2a h1:TggoJtZRb3MHRRhJ8Q1uu5SGGmhL1YbHiG08Xv9hqDw=
+github.com/LeanerCloud/cloud-commitments-go/pkg v0.0.0-20261017012250-2bf23fbd8c2a/go.mod h1:SCDEgHG6evjPh0RsoXof+J3aMmGXNFMrwbJIle7rMpQ=
 github.com/aws/aws-sdk-go-v2 v1.41.5 h1:dj5kopbwUsVUVFgO4Fi5BIT3t4WyqIDjGKCangnV/yY=
 github.com/aws/aws-sdk-go-v2 v1.41.5/go.mod h1:mwsPRE8ceUUpiTgF7QmQIJ7lgsKUPQOUl3o72QBrE1o=
 github.com/aws/smithy-go v1.24.2 h1:FzA3bu/nt/vDvmnkg+R8Xl46gmzEDam6mZ1hzmwXFng=

providers/gcp/services/computeengine/client.go

@@ -870,7 +870,11 @@ func (c *Client) buildInsertRequest(rec common.Recommendation, opts common.Purch
 		Region:             c.region,
 		CommitmentResource: commitment,
 	}
-	if requestID := common.IdempotencyGUID(opts.IdempotencyToken); requestID != "" {
+	requestID, err := common.OrderIDFromToken(opts.IdempotencyToken, "")
+	if err != nil {
+		return nil, "", fmt.Errorf("derive GCP request ID: %w", err)
+	}
+	if requestID != "" {
 		insertReq.RequestId = stringPtr(requestID)
 		log.Printf("GCP CUD purchase using idempotent request ID for token %s (commitment %s); a re-drive will not double-purchase (issue #654)",
 			common.MaskToken(opts.IdempotencyToken), commitmentName)
@@ -1438,16 +1442,14 @@ func idempotentCommitmentName(token string) (string, error) {
 		return fmt.Sprintf("cud-%d", time.Now().Unix()), nil
 	}
 	if !idempotencyTokenPattern.MatchString(token) {
-		return "", fmt.Errorf("%w: must be a lowercase hex digest to derive a GCP commitment name (got %d chars)", errInvalidIdempotencyToken, len(token))
+		return "", fmt.Errorf("%w: must be a lowercase hex digest to derive a GCP commitment name (got %d chars)", common.ErrInvalidIdempotencyToken, len(token))
 	}
 	if len(token) > idempotentNameTokenLen {
 		token = token[:idempotentNameTokenLen]
 	}
 	return "cud-" + token, nil
 }
 
-var errInvalidIdempotencyToken = errors.New("invalid idempotency token")
-
 var idempotencyTokenPattern = regexp.MustCompile(`^[0-9a-f]+$`)
 
 // Helper functions.

providers/gcp/services/computeengine/client_test.go

@@ -2442,14 +2442,39 @@ func TestPurchaseCommitment_RejectsNonHexIdempotencyToken(t *testing.T) {
 
 			result, err := client.PurchaseCommitment(ctx, rec, common.PurchaseOptions{IdempotencyToken: token})
 			require.Error(t, err)
-			assert.ErrorIs(t, err, errInvalidIdempotencyToken)
+			assert.ErrorIs(t, err, common.ErrInvalidIdempotencyToken)
 			assert.Contains(t, err.Error(), "lowercase hex digest")
 			assert.False(t, result.Success)
 			assert.Empty(t, mockSvc.insertReqs, "Insert must not be called for an invalid token")
 		})
 	}
 }
 
+// A short or partly non-hex token passes the name check but cannot form a
+// RequestId; it must fail before Insert instead of dropping idempotency.
+func TestPurchaseCommitment_UnformableRequestIDTokenFailsLoud(t *testing.T) {
+	ctx := context.Background()
+	rec := common.Recommendation{
+		ResourceType: "n1-standard-1",
+		Term:         "1yr",
+		Count:        5,
+		Details:      common.ComputeDetails{MemoryGB: 20.0},
+	}
+	for _, token := range []string{"abc", strings.Repeat("a", 31)} {
+		t.Run(token, func(t *testing.T) {
+			client, _ := NewClient(ctx, "test-project", "us-central1")
+			mockSvc := &MockCommitmentsService{operation: &MockOperation{}}
+			client.SetCommitmentsService(mockSvc)
+
+			result, err := client.PurchaseCommitment(ctx, rec, common.PurchaseOptions{IdempotencyToken: token})
+			require.Error(t, err)
+			assert.ErrorIs(t, err, common.ErrInvalidIdempotencyToken)
+			assert.False(t, result.Success)
+			assert.Empty(t, mockSvc.insertReqs, "Insert must not be called")
+		})
+	}
+}
+
 func TestBuildInsertRequest_RejectedTokenWrapsSentinel(t *testing.T) {
 	client, _ := NewClient(context.Background(), "test-project", "us-central1")
 	rec := common.Recommendation{
@@ -2459,7 +2484,7 @@ func TestBuildInsertRequest_RejectedTokenWrapsSentinel(t *testing.T) {
 		Details:      common.ComputeDetails{MemoryGB: 20.0},
 	}
 	_, _, err := client.buildInsertRequest(rec, common.PurchaseOptions{IdempotencyToken: "NOT-HEX"})
-	require.ErrorIs(t, err, errInvalidIdempotencyToken)
+	require.ErrorIs(t, err, common.ErrInvalidIdempotencyToken)
 }
 
 // A full 64-char SHA-256 digest must be truncated so the name stays within