OPINION & ORDER Two bicycle rental companies that operate out of Central Park dispute which is entitled to use the “Bike Rental Central Park” trademark. On October 23, 2019, Go New York Tours (“Plaintiff”) sued Tour Central Park Inc. (“Defendant”) for trademark infringement and related claims. See Compl., Dkt. 1. On October 30, 2020, the parties informed the Court that they had reached an amicable resolution of the matter. Letter, Dkt. 44. As a result of the parties’ purported settlement, the Court dismissed the case with prejudice. See Order, Dkt. 45 at 1. Several days later, Defense counsel informed the Court that his client had misunderstood a key term of the settlement agreement and asked the Court to reopen the case for immediate trial. Letter, Dkt. 48. On January 11, 2021, Plaintiff moved to reopen the case so that the Court could either enforce the settlement agreement or allow Plaintiff to amend its complaint to add a breach of contract claim. See Notice of Mot, Dkt. 52 at 1. For the reasons discussed below, Plaintiff’s motion is DENIED WITHOUT PREJUDICE. BACKGROUND The parties dispute which is entitled to use the trademark “Bike Rental Central Park” and to use other phrases like “Bike Rent NYC.” See generally Compl., Dkt. 1; Ans., Dkt. 15. The parties tried to reach an early settlement through mediation. See Order, Dkt. 17 (referring the parties to the Court-sponsored mediation program). When mediation through the Court sponsored program was unsuccessful, see Letter, Dkt. 25, the parties next turned to a private mediator, Letter, Dkt. 41. On October 30, 2020, the parties jointly submitted a letter to the Court stating that they “were able to reach an amicable resolution of this action.” Letter, Dkt. 44 at 1. As a result of the parties’ purported settlement, on November 2, 2020, the Court dismissed the case with prejudice. See Order, Dkt. 45 at 1. The Order provided that the parties could apply to reopen the case within thirty days if they could show “good cause for holding the case open in light of the parties’ settlement.” Id. Additionally, the Court informed the parties that if they “wish for the Court to retain jurisdiction to enforce their settlement agreement, they must submit within the same 30-day period: (1) their settlement agreement to the Court in accordance with Rule [7].A of the Court’s Individual Practices and (2) a request that the Court issue an order expressly retaining jurisdiction to enforce the settlement agreement.” See Id. at 1- 2 (citing Hendrickson v. United States, 791 F.3d 354 (2d Cir. 2015) (cleaned up)). Rule 7.A of the undersigned’s Individual Practices in Civil Cases notes that if parties would like the Court to retain jurisdiction to enforce their settlement agreement, they must file the agreement on the public docket (or make a request to file the agreement under seal) so that the Court may determine whether to retain jurisdiction for the limited purpose of enforcing the settlement agreement. See Ind. Prac. R. 7.A. Plaintiff’s counsel reports that on November 4, 2020, two days after the Court dismissed the case, Defense counsel informed him that the Defendant “intended to back out of the settlement” because he would not accept certain terms, namely the provision allowing both parties to continue using the terms “Central Park Bike Rent” and “Central Park Rent Bike.” See Letter, Dkt. 46 at 1-2. Defense counsel claims that there had been a misunderstanding1 and that no settlement was ever reached because (a) his client never would have agreed that both businesses could use those terms and (b) his client felt stressed and pressured during the mediation.2 See Letter, Dkt. 48 at 2-3. To give the parties more time to see if the problem could be resolved, the Court extended the application window for reopening the case with good cause by another sixty days, until January 12, 2021. See Order, Dkt. 49. In an attempt to resolve the case without further court intervention, the parties returned to mediation, but they failed to reach an agreement. See Ross Decl., Dkt. 53 15; Nohavicka Decl, Dkt. 55 13. On January 11, 2021, Plaintiff moved to reopen the case and enforce the settlement agreement, or alternatively, for leave to amend its Complaint to add a breach of contract claim.3 See Notice of Mot. at 1-2. Defendant joined Plaintiff’s application to reopen the case but argued that the matter should proceed to immediate trial on the merits because the “case was not settled.” See Resp., Dkt. 56 at 1. DISCUSSION At issue is whether the parties have established good cause to reopen the case. Plaintiff argues that the need for the Court to enforce the settlement agreement constitutes good cause. See Mem. of Law, Dkt. 54 at 11-12. Defendant joins the application to reopen the case; Defendant argues, however, that good cause to reopen exists because there was no settlement and Defendant wishes to proceed to trial on the merits. See Resp. at 1. The Court agrees that if the case were not settled, then there would be good cause to reopen it. Accordingly, for good cause to be established under either party’s theory, the Court must determine whether a settlement agreement has been reached and, if so, whether the Court can enforce it. But the Court can only make that determination if it has subject-matter jurisdiction to do so. In short, whether there is good cause to reopen this case depends on whether a settlement was reached, and making that determination requires subject matter jurisdiction.4 I. Supplemental Jurisdiction Plaintiff’s proposed breach of contract claim would be one means to determine whether a settlement agreement existed, and if so, whether it was breached. Plaintiff seeks leave to amend its Complaint to add a breach of contract claim pursuant to Rule 15 of the Federal Rules of Civil Procedure. See Mem. of Law, at 14-15; Proposed Am. Compl., Dkt. 53-10
89-104. The Court may deny leave to amend a complaint pursuant to Rule 15 if the amendment would be futile. See Ruotolo v. City of New York, 514 F.3d 184, 191 (2d Cir. 2008) (citing Foman v. Davis, 371 U.S. 178, 182 (1962)). If the Court lacks subject-matter jurisdiction over the proposed breach of contract claim, then amending the complaint would be a futile endeavor. The Court has federal question jurisdiction over the original trademark claims in this case, but a breach of contract claim is premised on New York state law. Because the parties are not diverse, see Compl.