T-Mobile US, Inc. v. Kaifi LLC

Case: 25-1006 Document: 82 Page: 1 Filed: 08/28/2026

United States Court of Appeals for the Federal Circuit

______________________

T-MOBILE US, INC., T-MOBILE USA, INC.,

Plaintiffs-Appellants v. KAIFI LLC, Defendant-Appellee ______________________ 2025-1006 ______________________

Appeal from the United States District Court for the Eastern District of Texas in No. 2:22-cv-00192-JRG, Judge J. Rodney Gilstrap.

______________________ Decided: August 28, 2026 ______________________

GREGG COSTA, Gibson, Dunn & Crutcher LLP, Hou- ston, TX, argued for plaintiffs-appellants. Also repre- sented by KOHL VINCENT ANDERSON, JACK DISORBO; NATHAN ROBERT CURTIS, Dallas, TX; KATHERINE QUINN DOMINGUEZ, JOSH KREVITT, New York, NY; ANDREW WILLIAM ROBB, Palo Alto, CA.

PHILIP J. WARRICK, Irell & Manella LLP, Washington, DC, argued for defendant-appellee. Also represented by GREGORY ALBANO, JASON SHEASBY, Los Angeles, CA; ANDREW CHOUNG, JENNIFER HAYES, Nixon Peabody LLP, 2 T‑MOBILE US, INC. v. KAIFI LLC Los Angeles, CA; ANDREW TICE INGRAM, GRANT MARTINEZ, CONSTANCE PFEIFFER, Yetter Coleman, LLP, Houston, TX.

______________________

Before TARANTO, SCHALL, and CHEN, Circuit Judges. CHEN, Circuit Judge.

T-Mobile US, Inc. and T-Mobile USA, Inc. (collectively, T-Mobile) and patent owner KAIFI LLC (KAIFI) settled a lawsuit in which KAIFI alleged that T-Mobile infringed several claims of U.S. Patent No. 6,922,728 (’728 patent). At the time of settlement, an ex parte reexamination (EPR) of the ’728 patent, which T-Mobile had initiated, was pend- ing at the United States Patent and Trademark Office (Pa- tent Office). Under the settlement agreement, T-Mobile agreed to make an immediate payment to KAIFI for a cer- tain amount, which it did. T-Mobile also agreed to make an additional payment to KAIFI at the conclusion of the reexamination “if any Asserted Claim survives the EPR.” After the Patent Office confirmed the patentability of mul- tiple claims, without amendment, that had been asserted in the lawsuit, T-Mobile sought a declaratory judgment that no asserted claims “survive[d]” the EPR and that therefore it had not breached the settlement agreement by refusing to make the additional payment. The district court granted summary judgment in KAIFI’s favor on all claims, including its counterclaim for breach of contract, and ordered T-Mobile to make the additional payment to KAIFI.

Both parties contend that we have appellate jurisdic- tion over this case concerning the interpretation of the set- tlement agreement phrase “survives the EPR.” We disagree. Because the dispute here is a matter of contract interpretation, which is a state law issue that does not nec- essarily depend on resolving a substantial patent law ques- tion, we lack subject-matter jurisdiction. We therefore transfer the case to the United States Court of Appeals for the Fifth Circuit, which has appellate jurisdiction over cases from the District Court for the Eastern District of Texas.

BACKGROUND I

On August 28, 2020, KAIFI brought a patent infringe- ment action against T-Mobile in the United States District Court for the Eastern District of Texas, alleging infringe- ment of the ’728 patent, which is directed to a Wi-Fi calling technology. On July 13, 2021, T-Mobile, in turn, filed a re- quest for an ex parte reexamination (EPR) of the ’728 pa- tent, and the Patent Office ordered the EPR on August 19, 2021. Just days before the trial, and before the outcome of the EPR was available, the parties settled.

Under the “Settlement and Patent License Agreement” that the parties executed on January 12, 2022 (Settlement Agreement), T-Mobile was granted a license under the ’728 patent, agreed to make an initial upfront payment, and agreed to make an additional, contingent payment, re- ferred to as the “EPR Payment,” “if any Asserted Claim survives the EPR.” J.A. 109, §§ 2.1, 2.3 (footnote omitted). The Settlement Agreement defines “Asserted Claims” as “claims 1, 2, 3, 5, 7, 10, 11 and 20 of the Patent-In-Suit [’728 patent],” which were the patent claims KAIFI alleged in the district court litigation that T-Mobile infringed. J.A. 108, § 1.23. The Settlement Agreement also provides that Licensee T-Mobile “covenants not to . . . challenge the va- lidity or enforceability of the Licensed Patents” and that “Licensee’s prior filing of the request for EPR is not a breach of this covenant.” Id. at 109–10, § 4.1; see also id. at 208. The Settlement Agreement is governed by Texas law. Id. at 119, § 17.1.

After the parties executed the Settlement Agreement, the Patent Office concluded the reexamination and issued a Reexamination Certificate confirming multiple asserted 4 T‑MOBILE US, INC. v. KAIFI LLC claims—1, 2, 3, 5, 10, 11, and 20—patentable without amendment. 1 J.A. 6543.

II

T-Mobile did not make the EPR Payment. Instead, cit- ing diversity of citizenship as a jurisdictional basis, T-Mo- bile sought a declaratory judgment that none of the asserted claims “survive[d]” the EPR. J.A. 52–104. T-Mo- bile asserted several causes of action 2 that relate to the in- terpretation of “survives the EPR.” In its first two causes of action, T-Mobile contended that for a patent claim to “survive” the reexamination, it must retain a claim scope sufficient to support KAIFI’s previously asserted infringe- ment case against T-Mobile. In particular, T-Mobile al- leged that (1) KAIFI impermissibly altered the claim scope from what it had staked out during the district court liti- gation by arguing for materially different claim construc- tion positions before the Patent Office and (2) KAIFI’s inequitable conduct during the EPR (by failing to disclose to the Patent Office its prior inconsistent claim-construc- tion positions taken in district court) rendered the claims unenforceable. In its remaining causes of action, T-Mobile alleged frustration of purpose and lack of mutual assent. KAIFI counterclaimed for breach of contract and sought to recover the EPR payment. The parties then filed cross-mo- tions for summary judgment.

The district court granted summary judgment on KAIFI’s counterclaims after concluding that “the Settle- ment Agreement [is] clear and unambiguous that a claim ‘survives the EPR’ if it is confirmed as patentable in the Patent Office’s Reexamination Certificate.” J.A. 21, 24. In reaching its conclusion, the court agreed with KAIFI that “T-Mobile’s causes of action rise and fall with [the] inter- pretation of the term ‘survives,’” and determined that T-Mobile’s inequitable conduct allegations have “no bear- ing on whether any of the claims ‘survived the EPR.’” J.A. 12, 16. The court also noted that T-Mobile has repeatedly represented that it was not seeking a declaration of unen- forceability, in light of its obligation under § 4.1 of the Set- tlement Agreement to not challenge the patent’s enforceability. Id. at 12. The court ordered T-Mobile to pay KAIFI the EPR Payment. J.A. 25.

T‑Mobile timely appealed. 3

DISCUSSION

“We review issues of jurisdiction de novo.” Prasco, LLC v. Medicis Pharm. Corp., 537 F.3d 1329, 1335 (Fed. Cir. 2008).

Our court has exclusive jurisdiction to decide “an ap- peal from a final decision of a district court . . . in any civil action arising under . . . any Act of Congress relating to pa- tents.” 28 U.S.C. § 1295(a)(1) (emphasis added). The Su- preme Court interpreted this language 4 to mean that our 6 T‑MOBILE US, INC. v. KAIFI LLC jurisdiction extends “only to those cases in which a well- pleaded complaint establishes either [1] that federal patent law creates the cause of action or [2] that the plaintiff’s right to relief necessarily depends on resolution of a sub- stantial question of federal patent law, in that patent law is a necessary element of one of the well-pleaded claims.” Christianson v. Colt Indus. Operating Corp., 486 U.S. 800, 808–09 (1988); see also Gunn v. Minton, 568 U.S. 251, 257– 58 (2013). To assess whether a case falls within that latter “special and small category” of cases, where “a claim finds its origins in state rather than federal law” but neverthe- less arises under federal law, Gunn, 568 U.S. at 258, we apply the four-part Gunn test. See, e.g., Inspired Dev. Grp., LLC v. Inspired Prods. Grp., LLC, 938 F.3d 1355, 1361 (Fed. Cir. 2019).

Under Gunn, a state law claim can be said to arise un- der federal law when a federal issue is “(1) necessarily raised, (2) actually disputed, (3) substantial, and (4) capa- ble of resolution in federal court without disrupting the fed- eral-state balance approved by Congress.” 568 U.S. at 258 (citation omitted). In determining whether we have appel- late jurisdiction over the appeal of a district court judgment in a diversity case, we “look to whether the four- part Gunn test is met on the basis of the cause of action pled and the facts as they existed at the time the complaint or any compulsory counterclaim is filed.” Jang v. Bos. Sci. Corp., 767 F.3d 1334, 1338 (Fed. Cir. 2014).

For a declaratory judgment action like this one, we look to “the character of the threatened action, and not of the defense” and “examine[] the declaratory defendant’s See Chandler v. Phoenix Servs. LLC, 1 F.4th 1013, 1017 (Fed. Cir. 2021). Accordingly, the Supreme Court’s inter- pretation of § 1338, in the context of the pre-amended § 1295(a)(1), applies with equal force to the amended § 1295(a)(1). Id. hypothetical well-pleaded complaint to determine if subject matter jurisdiction exists.” ABB Inc. v. Cooper Indus., LLC, 635 F.3d 1345, 1349 (Fed. Cir. 2011) (first quoting Pub. Serv. Comm’n of Utah v. Wycoff Co., 344 U.S. 237, 248 (1952); and then citing Franchise Tax Bd. of State of Cal. v. Constr. Laborers Vacation Tr. for S. Cal., 463 U.S. 1, 16, 19 (1983)). Here, the hypothetical complaint is the same as KAIFI’s counterclaim: breach of contract.

The parties focus on the first and third Gunn require- ments, contending that the state law breach of contract claim necessarily raises a substantial patent law issue. T-Mobile argues that determining whether any asserted patent claim “survives the EPR” requires addressing two “imbedded” patent law issues, namely (1) whether KAIFI’s conduct before the Patent Office materially altered the claim scope and (2) whether KAIFI engaged in inequitable conduct during the EPR. Appellant Br. 27; see also Appel- lant Reply Br. 3–9. T-Mobile also contends that setting standards and regulating conduct before the Patent Office present substantial questions of patent law. Appellant Re- ply Br. 8.

Although KAIFI previously moved to transfer for lack of jurisdiction, ECF No. 15, it now argues that we have ju- risdiction because the term “survives” has a particular meaning in patent law and because the effect of reexami- nation proceedings presents a substantial question of pa- tent law. Appellee Br. 29–31. “We must independently assure ourselves of our jurisdiction over an appeal ‘even though the parties are prepared to concede it.’” Wawrzyn- ski v. H.J. Heinz Co., 728 F.3d 1374, 1378 (Fed. Cir. 2013) (citation omitted). We conclude that we lack appellate ju- risdiction.

I

We begin with Gunn’s first requirement, which asks whether a federal issue is “necessarily raised.” Gunn, 568 U.S. at 258. “That is, if there is a theory of liability for each 8 T‑MOBILE US, INC. v. KAIFI LLC of the asserted claims for which it is not necessary to re- solve an issue of federal patent law, the district court lacked jurisdiction under section 1338, and we correspond- ingly lack jurisdiction under section 1295.” ClearPlay, Inc. v. Abecassis, 602 F.3d 1364, 1367 (Fed. Cir. 2010).

Focusing on KAIFI’s breach of contract counterclaim, we do not see how determining whether any of the asserted patent claims “survive[d] the EPR” necessarily raises a pa- tent law issue. That is because “there is at least one theory of relief that would not require the resolution of a patent law issue.” ClearPlay, 602 F.3d at 1368. For example, one way to resolve the relevant contract interpretive question would be the way the district court here approached it—by simply looking at the Reexamination Certificate and ob- serving that the Patent Office confirmed the patentability of many of the asserted claims without amendment. J.A. 7.

Reexamination is an administrative proceeding “to pro- vide an important ‘quality check’ on patents that would al- low the government to remove defective and erroneously granted patents.” In re Swanson, 540 F.3d 1368, 1375 (Fed. Cir. 2008) (citations omitted); see 35 U.S.C. § 304 (“If . . . the Director finds that a substantial new question of patentability affecting any claim of a patent is raised, the determination will include an order for reexamination of the patent for resolution of the question.”). At bottom, a reexamination of patent claims by the Patent Office puts the validity of those claims to the test in light of a new question of patentability. At the conclusion of an ex parte reexamination, the Patent Office issues a Reexamination Certificate, “canceling any claim of the patent finally deter- mined to be unpatentable, confirming any claim of the pa- tent determined to be patentable, and incorporating in the patent any proposed amended or new claim determined to be patentable.” 35 U.S.C. § 307(a) (emphases added). In other words, it could be said that a confirmed claim sur- vives a reexamination unscathed whereas a canceled claim does not. That straightforward, ordinary understanding of “survives” applied by the district court does not implicate a patent law question.

T-Mobile’s alternate reading of “survives” would re- quire an investigation into whether KAIFI’s arguments made during the EPR materially changed the scope of the claims such that the original claim scope did not “survive” even if the claim language remained unaltered. T-Mobile additionally argues that the term “survives” must take into account KAIFI’s alleged inequitable conduct during the EPR in failing to submit relevant documents from the dis- trict court litigation to the Patent Office. According to T-Mobile, if that allegation is proven, the patent would be unenforceable, and none of the claims could be said to “sur- vive.”

Even assuming, for jurisdictional purposes, that we look to T-Mobile’s theories of the meaning of “survives,” which would require a court to address patent-law issues like prosecution disclaimer and inequitable conduct, it is less than clear to us that the contractual term “survives” demands such in-depth patent-law inquiries. The text of the Settlement Agreement wholly lacks any hint to that ef- fect. Demonstrating altered claim scope or inequitable con- duct instead appears to be part of T-Mobile’s “defense” to KAIFI’s breach of contract action and “is not the only way” of resolving it. Inspired Dev. Grp., 938 F.3d at 1363 (find- ing that on an unjust enrichment claim, a patent infringe- ment question is not necessarily raised because “[d]emonstrating infringement . . . is not the only way that [plaintiff] could succeed on its claim”); see also Acorda Therapeutics, Inc. v. Alkermes PLC, 145 F.4th 1299, 1307 (Fed. Cir. 2025) (finding that a patent law issue is not nec- essarily raised where alternative ground for relief is pre- sented). As we explained above, mere review of a Reexamination Certificate, as the district court did, is one possible resolution to KAIFI’s breach of contract claim. 10 T‑MOBILE US, INC. v. KAIFI LLC

Nonetheless, T-Mobile argues that the patent law is- sues it raises are “logically antecedent” to the contract claim. Appellant Br. 33. First, T-Mobile cites our decision in Jang v. Boston Scientific Corp., where we held that we had jurisdiction over a state law contract dispute regarding royalties under a patent license because we had to address a question of infringement. Appellant Reply Br. 7–8; see Jang, 767 F.3d at 1336–38. T-Mobile analogizes this case to Jang, arguing that to determine whether a claim “sur- vives,” we must determine whether KAIFI obtained confir- mation of the claims through inequitable conduct. Appellant Reply Br. 8. Second, T-Mobile analogizes its in- equitable conduct allegations to fraud in a fraudulent-in- ducement contract case to argue that we must first resolve underlying issues of prosecution disclaimer and inequita- ble conduct before interpreting the term “survives.” Appel- lant Br. 33 (citing Italian Cowboy Partners, Ltd. v. Prudential Ins. Co. of Am., 341 S.W.3d 323, 334–35 (Tex. 2011)); see also Appellant Reply Br. 15 n.2.

We are not persuaded by T-Mobile’s analogies. First, T-Mobile’s reliance on Jang is misplaced because Jang pre- sented a necessary patent law question—infringement—in deciding whether Jang could seek royalty payments for the period during which the defendant allegedly practiced the patented technology before the claims were invalidated. See Jang, 767 F.3d at 1336–38 (explaining that “resolution of the contract claim itself requires resolution of underlying issues of infringement”). Here, unlike Jang, interpreting “survives” does not necessarily require resolving underly- ing issues of prosecution disclaimer and inequitable con- duct. Moreover, T-Mobile’s argument that none of the asserted patent claims survived the EPR because KAIFI engaged in inequitable conduct, if accepted, would appear to clash with its obligation under the Settlement Agree- ment “not to . . . challenge the validity or enforceability of the Licensed Patents.” J.A. 109–110, § 4.1; J.A. 12 (the dis- trict court noting the same). But the theory underlying its declaratory judgment action is, in effect, making an en- forceability challenge. Second, T-Mobile has not ade- quately made the case for why prosecution disclaimer of claim scope or alleged inequitable conduct are required threshold issues for resolving the breach of contract claim, akin to the fraud issue in Italian Cowboy Partners, where fraud was a threshold issue in the fraudulent inducement claim. See 341 S.W.3d at 327–28.

Next, T-Mobile stresses the “commercial realities” sur- rounding the Settlement Agreement to contend that the parties understood the term “survives” as referring to whether KAIFI’s patent-infringement theory, which was based on a particular understanding of the patent claims, survived the EPR. Appellant Br. 42–46. In doing so, T-Mo- bile does not point to the text of the Settlement Agreement but rather relies on extrinsic evidence, e.g., drafting history and testimony of the attorney who negotiated the Settle- ment Agreement. See J.A. 1948–2002 (drafting history), 2004–10 (attorney testimony).

Looking at the text of the Settlement Agreement, we do not see support for T-Mobile’s particularized understand- ing of “survives.” The Settlement Agreement, in the lan- guage at issue, requires the additional payment if “any Asserted Claim survives the EPR” and defines Asserted Claims as “claims 1, 2, 3, 5, 7, 10, 11 and 20 of the Patent- In-Suit [’728 patent].” J.A. 108–09, §§ 1.23, 2.3. T-Mobile’s reading would effectively rewrite the Settlement Agree- ment to refer to “litigated infringement claims” instead of the “asserted claims.” Nor does the extrinsic evidence cited by T-Mobile support its position. Instead, it reflects a dif- ferent point, namely the parties’ disagreement during the negotiation whether ”an Asserted Claim that is amended during the EPR ‘survives the EPR,’” which is memorialized as a footnote in the Settlement Agreement. J.A. 109 n.1 (emphasis added). But here the Patent Office confirmed the patentability of many of the Asserted Claims without amendment. J.A. 7. Whatever disagreement the parties 12 T‑MOBILE US, INC. v. KAIFI LLC may have had regarding amended claims is therefore not relevant. In sum, we cannot say that T-Mobile’s theory of the meaning of “survives” is necessarily the only way to read that term.

For KAIFI’s part, it now argues that we have jurisdic- tion because the term “survives” has a special patent law meaning. 5 Appellee Br. 29–31. In so arguing, however, KAIFI does not identify any use of the term in the patent statute or patent regulations, and we are aware of none. Rather, KAIFI points simply to the fact that we have used the word in our decisions. KAIFI points to Spectrum Inter- national, Inc. v. Sterilite Corp., 164 F.3d 1372, 1374 (Fed. Cir. 1998), where we used the term “survived” in the reex- amination context. See id. (“[C]laims 2, 11, and 14–16 sur- vived reexamination.”). KAIFI also points to other decisions, where we used the term “survived” in the inter partes review context. See, e.g., Pavo Sols. LLC v. Kingston Tech. Co., 35 F.4th 1367, 1372 (Fed. Cir. 2022) (“A subset of the ’544 patent’s claims survived IPR”).

But in none of these cases did we ever suggest we were assigning a particularized patent-law meaning to “sur- vives.” Our occasional use of that term, as in the cases on which KAIFI relies, is merely an employment of this ordi- nary word in the ordinary sense, i.e., “to continue to live or to exist, esp. after a dangerous event,” CAMBRIDGE DICTIONARY, https://dictionary.cambridge.org/diction- ary/english/survive. See Spectrum Int’l, 164 F.3d at 1374 (using the term “claims . . . survived reexamination” to mean that claims continue to live, i.e., were not determined to be unpatentable); see also Pavo Sols., 35 F.4th at 1372 (using the term “claims survived IPR” to mean that a claim is not held unpatentable, and hence slated for cancellation, through the IPR process). We thus find KAIFI’s argument unpersuasive. A patent law question is not a “necessary element” of the breach of contract claim, which might well succeed on the theory that the term is being used in this contract in its ordinary-language sense as applied to the plain formal results of the EPR process.

II

Although our inquiry could end here, this court addi- tionally lacks jurisdiction because the third Gunn require- ment is not satisfied. That is, “the federal issue in this case is not substantial in the relevant sense.” Gunn, 568 U.S. at 260. “The substantiality inquiry” looks to “the im- portance of the issue to the federal system as a whole.” Id. “[I]t is not enough [for] the federal issue [to] be significant to the particular parties in the immediate suit.” Id. Fol- lowing the Supreme Court’s guidance in Gunn, we look to “three nonexclusive factors that may help to inform the substantiality inquiry.” NeuroRepair, Inc. v. Nath L. Grp., 781 F.3d 1340, 1345 (Fed. Cir. 2015) (citations omitted). A “substantial” federal issue is more likely to be present if (1) “a pure issue of federal law is dispositive of the case,” (2) “the court’s resolution of the issue will control numerous other cases,” and (3) “if the Government has a direct inter- est in the availability of a federal forum to vindicate its own administrative action.” Id. (cleaned up) (citations omitted). None of the three factors indicates substantiality here.

First, there is no dispositive federal law issue. The un- derlying patent infringement action was settled, and this case presents a breach of contract claim. As explained above, there is an independent basis for resolving the breach of contract claim without reaching any question of patent law, and therefore this appeal presents “no pure is- sue of federal law [that] is dispositive.” NeuroRepair, 781 F.3d at 1345–46; see Inspired Dev. Grp., 938 F.3d at 1364. For the same reason, we are not persuaded by T-Mobile’s 14 T‑MOBILE US, INC. v. KAIFI LLC generic argument that “setting standards and regulating conduct before the Patent Office” is a substantial patent law issue. See Appellant Reply Br. 8–9.

Second, resolution of the issue will not control numer- ous other cases. We reiterate that as pled, T-Mobile’s claims do not formally challenge validity or enforceability of the ’728 patent. Rather, the dispute is over the interpre- tation of the contractual term “survives,” which we find to be “backward-looking” and “fact-bound and situation-spe- cific,” characteristics the Supreme Court explained are “not sufficient to establish federal arising under jurisdiction.” Gunn, 568 U.S. at 261–63 (citations omitted); see also In- spired Dev. Grp., 938 F.3d at 1368 (“[Defendant] ignores the limited nature of the claim. As pled, this claim is about a particular relationship.”).

Nor will the resolution of this case undermine the uni- formity of patent law. See Inspired Dev. Grp., 938 F.3d at 1364 (“[T]he touchstone for ‘substantiality’ is whether al- lowing state courts to resolve the case would undermine ‘the development of a uniform body of patent law.’” (quoting Gunn, 568 U.S. at 261)). Neither party provided any evi- dence that the contractual term “survives” is used in other settlement agreements or patent licensing contracts. And whatever meaning is assigned to “survives” in the context of the Settlement Agreement, future parties can contract around that meaning, if they wish, by using a different term. For example, if “survives” requires an inquiry into the patent owner’s inequitable conduct during the EPR and parties wish to avoid such a requirement, they can choose to draft a settlement agreement referring, for example, to “any asserted claim that is confirmed to be patentable in the reexamination proceeding.”

We also note that the ’728 patent has been expired since January 2024, further weakening any case for sub- stantiality. In Xitronix, we transferred an appeal, involv- ing a Walker Process monopolization claim based on alleged fraud on the Patent Office, to the Fifth Circuit, on the ground that the case did not present a substantial issue of patent law. Xitronix Corp. v. KLA-Tencor Corp., 882 F.3d 1075, 1077–80 (Fed. Cir. 2018) (Xitronix I). The Fifth Cir- cuit, however, disagreed with our conclusion. Xitronix Corp. v. KLA-Tencor Corp., 916 F.3d 429, 441 (5th Cir. 2019) (Xitronix II). In its view, the case “concerns a patent that is currently valid and enforceable” and a substantial patent law issue was present because the case “has the po- tential to render that patent effectively unenforceable.” Id.; see also Jang, 767 F.3d at 1338 (“Permitting regional circuits to adjudicate questions of patent validity, for ex- ample, could result in inconsistent judgments between a regional circuit and the Federal Circuit.”). Here, those con- cerns about the case’s effect on future cases involving the patent have much less force, given that the ’728 patent has expired and there is no other pending litigation involving it. Thus, regardless of our disagreement with the Fifth Cir- cuit’s Xitronix II opinion, see, e.g.,. Chandler v. Phoenix Servs. LLC, 1 F.4th 1013, 1016–19 (Fed. Cir. 2021) (noting disagreements with Xitronix II), the facts and circum- stances of this case are materially different from Xitronix I and II.

Third, “the government has no direct interest in this contract dispute between private parties.” See Inspired Dev. Grp., 938 F.3d at 1368. This stands in contrast to Gra- ble & Sons Metal Products, Inc. v. Darue Engineering & Manufacturing, 545 U.S. 308 (2005), where the Supreme Court noted the government’s “strong interest in the ‘prompt and certain collection of delinquent taxes.’” Gra- ble, 545 U.S. at 315 (citation omitted). Here, considering the fact-bound nature of the dispute over the contractual term, we do not find a comparable governmental interest like the one recognized in Grable.

All three NeuroRepair factors, although not exhaus- tive, confirm that this case does not present a “substantial” issue of federal law. And T-Mobile and KAIFI do not argue 16 T‑MOBILE US, INC. v. KAIFI LLC that any other factors are relevant to our substantiality in- quiry. Nor do they explain how this case presents a patent law issue more than a “case within a case.” 6 Having con- cluded that this case does not necessarily raise a substan- tial patent law issue, we need not reach whether the second and fourth requirements of Gunn are satisfied. Accord- ingly, we see no basis to conclude that the state law claim here raises an important issue “to the federal system as a whole.” Gunn, 568 U.S. at 260.

CONCLUSION

We have considered the parties’ remaining arguments and find them unpersuasive. We lack appellate jurisdic- tion over this case. Because the Eastern District of Texas had diversity jurisdiction and at the time this appeal was filed, the Fifth Circuit would have had jurisdiction over this case, we transfer it to the Fifth Circuit.

TRANSFERRED COSTS

The parties shall bear their own costs.