Berk v. Choy

(Slip Opinion) OCTOBER TERM, 2025 1

 Syllabus

 NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
 being done in connection with this case, at the time the opinion is issued.
 The syllabus constitutes no part of the opinion of the Court but has been
 prepared by the Reporter of Decisions for the convenience of the reader.
 See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337 .

SUPREME COURT OF THE UNITED STATES

 Syllabus

 BERK v. CHOY ET AL.

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
 THE THIRD CIRCUIT

 No. 24–440. Argued October 6, 2025—Decided January 20, 2026

Delaware law provides that a plaintiff may not sue for medical malprac-
 tice unless a medical professional attests to the suit’s merit in an “af-
 fidavit of merit” that “accompanie[s]” the plaintiff’s complaint. Del.
 Code, Tit. 18, §6853(a)(1). Petitioner Harold Berk sued Dr. Wilson
 Choy and Beebe Medical Center in federal court for medical malprac-
 tice under Delaware law, but failed to provide the affidavit required by
 §6853. Berk argued that §6853 is not enforceable in federal court be-
 cause it is displaced by the Federal Rules of Civil Procedure. The Dis-
 trict Court dismissed Berk’s lawsuit for failure to comply with Dela-
 ware’s affidavit law. The Third Circuit affirmed.
Held: Delaware’s affidavit law does not apply in federal court. Pp. 3–11.
 (a) When a plaintiff brings a state-law claim in federal court, the
 court faces a choice-of-law problem: whether to apply state or federal
 law. The Rules of Decision Act directs federal courts to apply state
 substantive law unless the Constitution, a treaty, or a statute other-
 wise requires or provides. 28 U. S. C. §1652 . The Rules Enabling Act,
 which authorizes the Supreme Court to adopt uniform rules of proce-
 dure for district courts, provides for the application of federal law.
 §2072(a). So, when a valid Federal Rule of Civil Procedure is on point,
 it displaces contrary state law even if the state law would qualify as
 substantive under Erie R. Co. v. Tompkins, 304 U. S. 64 . The analysis
 is straightforward: The Court first asks whether a Federal Rule an-
 swers the disputed question. If a Federal Rule does, it governs, unless
 it “exceeds statutory authorization or Congress’s rulemaking power.”
 Shady Grove Orthopedic Associates, P. A. v. Allstate Ins. Co., 559 U. S.
 393, 398 . Pp. 3–4.
2 BERK v. CHOY

 Syllabus

 (b) Here, Rule 8 answers the disputed question whether Berk’s law-
 suit may be dismissed because his complaint was not accompanied by
 an affidavit. Rule 8 prescribes the information a plaintiff must present
 about the merits of his claim at the outset of litigation: “a short and
 plain statement of the claim showing that [he] is entitled to relief.”
 Fed. Rule Civ. Proc. 8(a)(2). By requiring no more than a statement of
 the claim, Rule 8 establishes “implicitly, but with unmistakable clar-
 ity,” Hanna v. Plumer, 380 U. S. 460, 470 , that evidence of the claim is
 not required. Rule 12 reinforces the point by providing only one ground
 for dismissal based on the merits—“failure to state a claim upon which
 relief can be granted,” Rule 12(b)(6)—and prohibiting courts from con-
 sidering “matters outside the pleadings” when evaluating whether a
 plaintiff has stated a claim, Rule 12(d). The court instead asks only
 whether the complaint’s factual allegations, if taken as true, “state a
 claim to relief that is plausible on its face.” Bell Atlantic Corp. v.
 Twombly, 550 U. S. 544, 570 . This Court has consistently rejected ef-
 forts by lower federal courts to require more information than Rule 8
 requires. Delaware’s law and Rule 8 thus give different answers to the
 question whether Berk’s complaint can be dismissed as insufficient be-
 cause it was unaccompanied by an affidavit.
 Defendants offer a workaround: They rewrite Delaware’s law. After
 defendants’ edits, the Delaware law is no longer a pleading require-
 ment but a free-floating evidentiary requirement that can serve as the
 basis for an early dismissal. But that requirement could not be en-
 forced under the Federal Rules. Defendants concede that the absence
 of an affidavit is not grounds for dismissal under Rule 12(b)(6). And
 Rule 56 already prescribes the mechanism for putting a plaintiff to his
 proof: a motion for summary judgment.
 Finally, defendants’ argument that Rule 11’s proviso concerning af-
 fidavits incorporates state affidavit laws like §6853 fails because the
 proviso cannot be read to address affidavits from third parties. Pp. 4–
 10.
 (c) Because Rule 8 and §6853 answer the same question, Rule 8 gov-
 erns so long as it is valid under the Rules Enabling Act, which requires
 that Federal Rules be procedural rather than substantive. 28 U. S. C.
 §2072 (b). Rule 8 is valid under the Rules Enabling Act because it “re-
 ally regulates procedure.” Sibbach v. Wilson & Co., 312 U. S. 1, 14 .
 Defendants argue that determining whether a Rule is valid under the
 Rules Enabling Act requires also asking whether the displaced state
 law is substantive, but “the substantive nature of [a state] law, or its
 substantive purpose, makes no difference” to the analysis of a Federal
 Rule’s validity. Shady Grove, 559 U. S., at 409 . Pp. 10–11.
Reversed and remanded.
 Cite as: 607 U. S. ___ (2026) 3

 Syllabus

 BARRETT, J., delivered the opinion of the Court, in which ROBERTS,
C. J., and THOMAS, ALITO, SOTOMAYOR, KAGAN, GORSUCH, and
KAVANAUGH, JJ., joined. JACKSON, J., filed an opinion concurring in the
judgment.
 Cite as: 607 U. S. ____ (2026) 1

 Opinion of the Court

 NOTICE: This opinion is subject to formal revision before publication in the
 United States Reports. Readers are requested to notify the Reporter of
 Decisions, Supreme Court of the United States, Washington, D. C. 20543,
 pio@supremecourt.gov, of any typographical or other formal errors.

SUPREME COURT OF THE UNITED STATES
 _________________

 No. 24–440
 _________________

 HAROLD R. BERK, PETITIONER v.
 WILSON C. CHOY, ET AL.
 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF
 APPEALS FOR THE THIRD CIRCUIT
 [January 20, 2026]

 JUSTICE BARRETT delivered the opinion of the Court.
 The cost of malpractice insurance for doctors and hospi-
tals has significantly increased in some areas of the coun-
try. In response, several States have imposed a screening
mechanism on malpractice suits, requiring plaintiffs to sub-
mit an affidavit from a medical professional attesting to the
suit’s merit. We consider whether Delaware’s affidavit re-
quirement applies in federal court and hold that it does not.
 I
 While on a trip to Delaware, Harold Berk fell out of bed.
According to his complaint, he was taken by ambulance to
a hospital owned by Beebe Medical Center, Inc., where an
X ray revealed a fractured ankle. Dr. Wilson Choy recom-
mended that Berk be fitted with a protective boot.
 The fitting did not go well. Hospital employees forced
Berk’s leg into the boot, twisting his fractured ankle. Still,
Dr. Choy did not immediately order another X ray; he told
Berk to keep weight off his ankle, proposed a follow-up ap-
pointment in two weeks, and sent Berk on his way. At the
follow-up, Berk got a second X ray, which showed that his
2 BERK v. CHOY

 Opinion of the Court

ankle was not just fractured but also severely deformed, re-
quiring surgery.
 Berk sued Beebe Medical Center and Dr. Choy (whom we
will call defendants) for medical malpractice under Dela-
ware law. Because Berk and defendants are citizens of dif-
ferent States, Berk could sue in federal court based on di-
versity jurisdiction.
 Under Delaware law, a plaintiff may not sue for medical
malpractice unless an affidavit of merit “accompanie[s]” the
complaint. Del. Code, Tit. 18, §6853(a)(1) (2025). The affi-
davit must be signed by a medical professional, §6853(c),
and it must state that there are “reasonable grounds to be-
lieve that there has been health-care medical negligence
committed by each defendant,” §6853(a)(1). A plaintiff with
“good cause” may secure a single 60-day extension of time
in which to file the affidavit, ibid., but he must file the ex-
tension motion before or when he files the complaint,
§6853(a)(2). If an affidavit does not accompany the com-
plaint and the plaintiff has not filed a timely extension mo-
tion, then the clerk of court shall “refuse to file the com-
plaint and it shall not be docketed.” §6853(a)(1). The
defendants need not take any action with respect to the
complaint until 20 days after the affidavit of merit is filed.
§6853(a)(4). Upon the defendants’ motion, the court must
determine in camera if the affidavit satisfies the statutory
requirements. §6853(d).
 Attempting to comply with §6853, Berk immediately
moved for an extension of time to file an affidavit. The Dis-
trict Court granted Berk’s motion, and Berk tried to track
down a doctor willing to provide an affidavit (an ordeal
spawning separate litigation). But the clock ran out, and
coming up empty-handed, Berk instead filed his medical
records under seal. Defendants moved the District Court to
review Berk’s submissions in camera to determine whether
they complied with §6853. Berk countered that §6853 is not
enforceable in federal court because it is displaced by the
 Cite as: 607 U. S. ____ (2026) 3

 Opinion of the Court

Federal Rules of Civil Procedure. The District Court disa-
greed with Berk and dismissed his lawsuit for failure to
comply with Delaware’s affidavit law. See 2023 WL
2770573 , *1–*2 (D Del., Apr. 4, 2023).
 The Third Circuit affirmed, holding that §6853 applies in
federal court. See 2024 WL 3534482 , *4 (July 25, 2024).
The court concluded that the Federal Rules of Civil Proce-
dure are silent as to whether an affidavit must accompany
the complaint. Id., at *2–*3. Where the Federal Rules are
silent, state law applies if it is substantive. See Erie R. Co.
v. Tompkins, 304 U. S. 64, 78 (1938). A state law is sub-
stantive if (1) it is outcome determinative, and (2) failing to
apply it in federal court would promote forum shopping and
the inequitable administration of the law. See Hanna v.
Plumer, 380 U. S. 460 , 467–469 (1965). After applying this
test, the Third Circuit concluded that §6853 is substantive
and affirmed the dismissal of Berk’s suit. See 2024 WL
3534482 , *3–*4.
 We granted certiorari. 604 U. S. 1193 (2025).
 II
 State-law claims are usually brought in state court. But
if the parties are citizens of different States and the amount
in controversy exceeds a certain threshold, a plaintiff may
choose to sue in federal court. 28 U. S. C. §1332 . In that
event, the federal court faces a choice-of-law problem:
whether to apply state or federal law. The Rules of Decision
Act directs federal courts to apply state substantive law,
leaving federal law to cover the rest. §1652. Following that
direction is harder than it looks, because determining
whether a state law is substantive requires a court to enter
“Erie’s murky waters.” Shady Grove Orthopedic Associates,
P. A. v. Allstate Ins. Co., 559 U. S. 393, 398 (2010).
 Yet when a Federal Rule of Civil Procedure is on point, a
federal court bypasses Erie’s inquiry altogether. That is be-
cause the Rules of Decision Act dictates that state
4 BERK v. CHOY

 Opinion of the Court

substantive law must yield if the Constitution, a treaty, or
a statute “otherwise require[s] or provide[s].” §1652. And
the Rules Enabling Act, which authorizes the Supreme
Court to adopt uniform rules of procedure for district courts,
provides for the application of federal law. §2072(a); see
also Fed. Rule Civ. Proc. 1 (“These rules govern the proce-
dure in all civil actions and proceedings in the United
States district courts . . . ”). Thus, a valid Rule of Civil Pro-
cedure displaces contrary state law even if the state law
would qualify as substantive under Erie’s test. See Hanna,
380 U. S., at 469–474.
 Analyzing whether a Federal Rule displaces state law is
straightforward. We first ask whether the Federal Rule
“answers the question in dispute.” Shady Grove, 559 U. S.,
at 398 . In doing so, we interpret the Federal Rules the same
way we interpret federal laws more generally: by giving
them their “plain meaning.” Walker v. Armco Steel Corp.,
 446 U. S. 740, 750, n. 9 (1980). If a Federal Rule answers
the disputed question, it governs, unless it “exceeds statu-
tory authorization or Congress’s rulemaking power.”
Shady Grove, 559 U. S., at 398 .
 A
 In this case, the disputed question is whether Berk’s law-
suit may be dismissed because his complaint was not ac-
companied by an expert affidavit.1 Rule 8 gives the answer.
——————
 1 The concurrence objects to our framing the disputed question around

dismissal because doing so “assumes that Berk’s lawsuit has already
been . . . filed and docketed.” Post, at 4 (JACKSON, J., concurring in judg-
ment). But Berk’s lawsuit has already been filed and docketed, see
No. 1:22–cv–01506 (D Del., Nov. 18, 2022), ECF Doc. 1, which is how it
found its way here. The only question in dispute is whether Berk’s law-
suit may be dismissed—indeed, that is the question on which we granted
certiorari. See Pet. for Cert. i. The concurrence reframes the question
in dispute as “what is required to start a medical malpractice case.” Post,
at 4. But because no one argues that the court violated §6853 by docket-
ing Berk’s complaint, the concurrence is ultimately forced to grapple with
 Cite as: 607 U. S. ____ (2026) 5

 Opinion of the Court

It prescribes the information a plaintiff must present about
the merits of his claim at the outset of litigation: “a short
and plain statement of the claim showing that [he] is enti-
tled to relief.” Fed. Rule Civ. Proc. 8(a)(2). By requiring no
more than a statement of the claim, Rule 8 establishes “im-
plicitly, but with unmistakable clarity,” Hanna, 380 U. S.,
at 470 , that evidence of the claim is not required. Cf. Bur-
lington Northern R. Co. v. Woods, 480 U. S. 1 , 7–8 (1987)
(declining to apply a state statute where a Federal Rule “oc-
cupies the statute’s field of operation”).
 Rule 12 reinforces the point. It provides only one ground
for dismissal based on the merits: “failure to state a claim
upon which relief can be granted.” Fed. Rule Civ.
Proc. 12(b)(6). When evaluating whether a plaintiff has
stated a claim, the court cannot consider “matters outside
the pleadings.” Rule 12(d). The court instead asks only
whether the complaint’s factual allegations, if taken as
true, “state a claim to relief that is plausible on its face.”
Bell Atlantic Corp. v. Twombly, 550 U. S. 544, 570 (2007).
A complaint that satisfies this standard is “well-pleaded”
and “may proceed even if it strikes a savvy judge that actual
proof of the facts alleged is improbable.” Id., at 556 .
 By design, this system of pleading makes it relatively
easy for plaintiffs to subject defendants to discovery—even
for claims that are likely to fail. To protect defendants from
this burden, lower federal courts have sometimes tried to
require more information for certain kinds of claims: 42
U. S. C. §1983 actions against municipalities, Leatherman
v. Tarrant County Narcotics Intelligence and Coordination
Unit, 507 U. S. 163 (1993); employment discrimination
suits, Swierkiewicz v. Sorema N. A., 534 U. S. 506 (2002);
and prisoner suits, Jones v. Bock, 549 U. S. 199 (2007). We

——————
the question whether Berk’s lawsuit may be “dismiss[ed].” Post, at 11.
By focusing on dismissal from the start, we do not “jum[p] the gun,” post,
at 4, but rather cut to the chase.
6 BERK v. CHOY

 Opinion of the Court

have consistently rejected such efforts. As we explained in
Leatherman—which dealt with a demand that plaintiffs
plead certain §1983 claims with added specificity—
Rule 8(a)(2) requires “only” a “ ‘short and plain statement of
the claim.’ ” 507 U. S., at 165 , 168 (quoting Rule 8(a)(2)).
Unless the Federal Rules single out a claim for special
treatment, see, e.g., Fed. Rule Civ. Proc. 9, Rule 8 sets a
ceiling on the information that plaintiffs can be required to
provide about the merits of their claims.
 Delaware’s affidavit requirement is at odds with Rule 8
because it demands more: A medical malpractice suit can-
not proceed “unless the complaint is accompanied by . . .
[a]n affidavit of merit.” §6853(a)(1). Under Rule 8, factual
allegations are sufficient, but under the Delaware law, the
plaintiff needs evidence too. See Dishmon v. Fucci, 32 A. 3d
338, 344 (Del. 2011) (describing §6853 as imposing a “prima
facie evidentiary requiremen[t]”); see also Brief for Re-
spondent Beebe 23 (same). The two rules thus give differ-
ent answers to the question whether Berk’s complaint can
be dismissed as insufficient because it was unaccompanied
by an affidavit.
 It is true, as defendants and the concurrence are quick to
point out, that an affidavit of merit is a document separate
from the “pleading,” and that, by its literal terms, Rule 8
defines only what the “pleading . . . must contain.” But we
think it is fair to infer that by specifying what information
about the merits is required in the “pleading,” Rule 8 ex-
cludes the possibility of requiring even more information on
the same topic—whether in the “pleading” itself or on a sep-
arate sheet of paper attached to it. Cf. Jones, 549 U. S., at
205 , 212–217 (rejecting requirement that prisoners “attach
proof of exhaustion . . . to their complaints” as inconsistent
with Rule 8). Rule 8 addresses what information a plaintiff
must provide about the merits of his claim at the outset of
 Cite as: 607 U. S. ____ (2026) 7

 Opinion of the Court

litigation. Section 6853 addresses the same issue—and in
doing so, imposes a different standard.2
 Resisting this conclusion, defendants cite Cohen v. Bene-
ficial Industrial Loan Corp., 337 U. S. 541 (1949), for the
broad proposition that all state “preconditions to proceed-
ing” are consistent with the Federal Rules. Brief for Re-
spondent Beebe 26–27; see Brief for Respondent Choy 20–
21. They substantially overread Cohen. There, a state law
rendered an unsuccessful plaintiff in a shareholder deriva-
tive suit liable for all the defendant’s expenses, including
attorney’s fees, and as security for that potential liability,
required the plaintiff to post a bond before proceeding with
the action. 337 U. S., at 543 . The plaintiffs argued that the
bond requirement was displaced by then-Rule 23, which
governed shareholder derivative suits in federal court. Id.,
at 556 . Cohen held that there was no conflict because the
state law and Rule 23 addressed different issues: The state
law created a liability, while Rule 23 dealt with “disclosure
to the court and notice to the parties in interest.” Id., at
555–556.
 Cohen thus did not identify and exempt a broad category
of so-called preconditions to proceeding from conflict with
——————
 2 The concurrence accuses us—and the “many Courts of Appeals” that

agree with us—of “contorting” Rule 8 by reading it to implicitly preclude
courts from requiring plaintiffs to provide additional information. Post,
at 10, and n. 6. Yet drawing a negative inference from text is sometimes
the best way to understand it. See A. Scalia & B. Garner, Reading Law:
The Interpretation of Legal Texts 107–111 (2012) (negative-implication
canon). And while the concurrence criticizes the negative inference we
draw as “inattentively capacious,” post, at 8, its Rule 3 analysis depends
on an analogous inference. Rule 3 establishes what happens once a com-
plaint is filed: “A civil action is commenced by filing a complaint with the
court.” Fed. Rule Civ. Proc. 3. Section 6853, meanwhile, establishes
what is required “to file the complaint . . . with the court”: an affidavit of
merit or an extension motion. §6853(a)(1). The concurrence finds a col-
lision only by reading Rule 3 to implicitly foreclose any precondition to
filing the complaint. So if a negative inference is a “contortion,” the con-
currence’s argument fails by its own measure.
8 BERK v. CHOY

 Opinion of the Court

the Federal Rules. It held that a particular state law ad-
dressed a matter that was unaddressed by the relevant
Federal Rule. Here, by contrast, the state law and the Fed-
eral Rule address the same issue: the information that a
plaintiff must provide about the merits of his claim at the
outset of litigation. Describing the affidavit requirement as
a “preconditio[n] to proceeding” does not magically dispel
the conflict.
 Defendants offer a workaround: They rewrite Delaware’s
law. While §6853 provides that an affidavit must “accom-
pan[y]” the complaint, defendants suggest that the district
court can simply require it “early in [a] case.” Brief for Re-
spondent Beebe 13; see also Brief for Respondent Choy 36
(suggesting affidavit can be filed “weeks” or “months” after
the complaint). This proposal is inspired by §6853’s allow-
ance for an extension of time in which to file the affidavit.
But defendants treat this exception—which is available
only “for good cause shown”—as the rule and rework the
exception to boot. In federal court, apparently, an extension
motion need not precede or accompany the complaint; nor
is the district court limited to granting one 60-day exten-
sion. See, e.g., Brief for Respondent Beebe 23–25. And de-
fendants’ proposed changes do not stop there: They would
also have us delete the provision that absolves a defendant
from “tak[ing] any action with respect to the complaint” un-
til the affidavit is filed. §6853(a)(4). Under Federal Rule
12(a)(1), service of the summons and complaint triggers a
defendant’s obligation to respond, and defendants admit
that the Federal Rule controls on this point.
 After defendants’ edits, the Delaware law is no longer a
pleading requirement that serves a gatekeeping function; it
is a free-floating evidentiary requirement that can serve as
the basis for an early dismissal. Yet even were it acceptable
to take creative license with the Delaware law, there would
be no way to enforce such a requirement. Defendants con-
cede that the absence of an affidavit is not grounds for
 Cite as: 607 U. S. ____ (2026) 9

 Opinion of the Court

dismissal under Rule 12(b)(6). They float the possibility of
dismissal for failure to prosecute, but that does not work
because Berk actively participated in the litigation. De-
fendants’ first choice is the course the District Court took
here: dismissal based on the court’s inherent authority.
The problem, however, is that the Federal Rules already
prescribe a mechanism for putting a plaintiff to his proof: a
motion for summary judgment. See Fed. Rule Civ. Proc. 56.
And that does not offer defendants the protection they
want, because before ruling on the motion, the court must
allow the nonmovant “adequate time for discovery.” Celotex
Corp. v. Catrett, 477 U. S. 317, 322 (1986); see also Rule
12(d) (requiring a “reasonable opportunity to present all the
[pertinent] material” if motion to dismiss is converted to
motion for summary judgment). That defendants cannot fit
the affidavit requirement into the Federal Rules illustrates
that it has no place there.
 Perhaps recognizing this, defendants devote most of their
energy to arguing that the Federal Rules contain a loophole.
According to defendants, a proviso tucked into Rule 11
makes state affidavit laws applicable in federal court even
if they conflict with other Federal Rules. Rule 11 provides
that “[u]nless a rule or statute specifically states otherwise,
a pleading need not be verified or accompanied by an affi-
davit.” Fed. Rule Civ. Proc. 11(a). Defendants argue that
§6853 is a “statute [that] specifically states otherwise,”
ibid., and it therefore applies in federal court regardless of
whether it conflicts with other Federal Rules.
 Even if Rule 11 incorporates some state affidavit laws, it
does not incorporate this one. Rule 11 governs the conduct
of those who practice before courts: the “attorney of record”
or the “party personally if the party is unrepresented.”
Ibid. It requires the attorney or pro se party to certify, after
“reasonable” inquiry, that the legal and factual representa-
tions made to the court are warranted. Rule 11(b). The
sentence on which defendants rely simply “acknowledges”
10 BERK v. CHOY

 Opinion of the Court

that although Rule 11 generally puts the onus on the attor-
ney or pro se party to vouch for representations, “in some
situations represented parties are required by rule or stat-
ute to verify pleadings or sign affidavits.” Business Guides,
Inc. v. Chromatic Communications Enterprises, Inc., 498
U. S. 533, 542 (1991) (emphasis added); see, e.g., Fed. Rule
Civ. Proc. 23.1 (requiring complaints in shareholder deriv-
ative actions to be verified). The sentence has nothing to do
with affidavits from third parties. Accordingly, Rule 11
does not shield Delaware’s law from displacement by
Rule 8.
 B
 Because Rule 8 and §6853 answer the same question,
Rule 8 governs so long as it is valid under the Rules Ena-
bling Act, which requires that Federal Rules be procedural
rather than substantive. 28 U. S. C. §2072 (b) (“Such rules
shall not abridge, enlarge or modify any substantive right”).
The line between substance and procedure is hazy, and we
draw it differently in different contexts. See Hanna, 380
U. S., at 471 (“The line between ‘substance’ and ‘procedure’
shifts as the legal context changes”). For purposes of the
Rules Enabling Act, we use a modest test: whether the Fed-
eral Rule “really regulates procedure.” Sibbach v. Wilson
& Co., 312 U. S. 1, 14 (1941). Or put differently, “[w]hat
matters is what the Rule itself regulates: If it governs only
‘the manner and the means’ by which the litigants’ rights
are ‘enforced,’ it is valid.” Shady Grove, 559 U. S., at 407
(plurality opinion) (quoting Mississippi Publishing Corp. v.
Murphree, 326 U. S. 438, 446 (1946)).
 In applying this analysis, we have “rejected every statu-
tory challenge to a Federal Rule that has come before us.”
Shady Grove, 559 U. S., at 407 (plurality opinion). We have
upheld Rules governing the certification of class actions,
 id., at 408 (Rule 23); see id., at 416, 436 (Stevens, J., con-
curring in part and concurring in judgment) (Rule 23);
 Cite as: 607 U. S. ____ (2026) 11

 Opinion of the Court

service of process, Mississippi Publishing Corp., 326 U. S.,
at 445–446 (Rule 4(f )); compelled mental and physical ex-
aminations, Sibbach, 312 U. S., at 14–16 (Rule 35); sanc-
tions for frivolous appeals, Burlington, 480 U. S., at 8 (Rule
38); and sanctions for signing court papers without reason-
ably investigating the facts asserted, Business Guides, 498
U. S., at 551–554 (Rule 11).
 Like those Rules, Rule 8 “really regulates procedure.”
Sibbach, 312 U. S., at 14 . It determines what plaintiffs
must present to the court about their claims at the outset
of litigation. Although the Rule may have some “practical
effect on the parties’ rights,” it regulates “only the process
for enforcing those rights,” not “the rights themselves, the
available remedies, or the rules of decision.” Shady Grove,
559 U. S., at 407–408 (plurality opinion).
 Defendants do not contend otherwise. Instead, they ar-
gue that determining whether a Rule is valid under the
Rules Enabling Act requires asking a second question:
whether the displaced state law is substantive. We rejected
that approach eight decades ago and decline to reconsider
it now. See Sibbach, 312 U. S., at 14 . On the contrary, we
underscore that “the substantive nature of [a state] law, or
its substantive purpose, makes no difference.” Shady Grove,
 559 U. S., at 409 (plurality opinion). To determine whether
a Rule is valid under the Rules Enabling Act, the only ques-
tion is whether it “really regulates procedure.” Sibbach,
 312 U. S., at 14 . Rule 8 does, so it governs, and Delaware’s
affidavit law does not apply in federal court.
 * * *
 The judgment of the Court of Appeals is reversed, and the
case is remanded for further proceedings consistent with
this opinion.
 It is so ordered.
 Cite as: 607 U. S. ____ (2026) 1

 JACKSON, J., concurring in judgment

SUPREME COURT OF THE UNITED STATES
 _________________

 No. 24–440
 _________________

 HAROLD R. BERK, PETITIONER v.
 WILSON C. CHOY, ET AL.
 ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF
 APPEALS FOR THE THIRD CIRCUIT
 [January 20, 2026]

 JUSTICE JACKSON, concurring in the judgment.
 I agree with the Court that Delaware’s affidavit require-
ment cannot apply in federal court. I write separately be-
cause, in my view, the relevant conflicts are with Federal
Rules of Civil Procedure 3 and 12, not Rule 8.
 I
 As the majority explains, Delaware’s law is, at bottom, an
“affidavit requirement.” Ante, at 1. If a medical malprac-
tice plaintiff wants her complaint deemed “filed” and his
case docketed, the statute mandates that an affidavit of
merit signed by a medical professional (or a motion for an
extension of time to file the affidavit) must accompany the
complaint. See Del. Code, Tit. 18, §6853(a)(1) (2025). By
contrast, the Federal Rules require no such additional fil-
ing. Rather, “[a] civil action is commenced by filing a com-
plaint with the court.” Fed. Rule Civ. Proc. 3.
 Thus, §6853 and Rule 3 conflict regarding the require-
ments to “commence” a medical malpractice action. If a fed-
eral court were to follow Delaware’s law, a plaintiff would
have to do more than merely tender the complaint in order
for his medical malpractice lawsuit to be filed and docketed.
But, under the language of Rule 3, civil suits commence as
soon as the complaint—and only the complaint—has been
2 BERK v. CHOY

 JACKSON, J., concurring in judgment

filed by the plaintiff. In my view, this clash warrants re-
versal here.
 As the majority explains, our cases make clear beyond
cavil that “a valid [Federal] Rule of Civil Procedure dis-
places contrary state law.” Ante, at 4. Thus, the nub of the
conflict inquiry is to determine whether the State’s require-
ment is, in fact, contrary to a Federal Rule. Over time, we
have expressed this central inquiry in various ways. See,
e.g., Hanna v. Plumer, 380 U. S. 460, 472 (1965) (asking
whether “the applicable Federal Rule is in direct collision
with the [state] law”); Burlington Northern R. Co. v. Woods,
 480 U. S. 1 , 4–5 (1987) (asking whether the scope of the
Federal Rule is “ ‘sufficiently broad’ ” to “ ‘control the issue’ ”
before the Court, “thereby leaving no room for the opera-
tion” of the state law (quoting Walker v. Armco Steel Corp.,
 446 U. S. 740 , 749–750, and n. 9 (1980))). But as the ma-
jority acknowledges, our most up-to-date approach to iden-
tifying the necessary conflict is to ask whether the Federal
Rule and the state statute “attemp[t] to answer the same
question.” Shady Grove Orthopedic Associates, P. A. v. All-
state Ins. Co., 559 U. S. 393, 399 (2010); see also ante, at 4.1
——————
 1 To the extent that the Court suggests that the Federal Rule’s plain

text is all that matters when answering this question, that is not what
our precedents hold. In Gasperini v. Center for Humanities, Inc., 518
U. S. 415 (1996), we explained that Federal Rules must be interpreted
not solely based on their text—as the much earlier case of Walker v.
Armco Steel Corp. had suggested in a footnote—but also “with sensitivity
to important state interests and regulatory policies,” 518 U. S., at 427,
n. 7 . The majority opinion in Shady Grove subsequently criticized
Gasperini’s “search for state interests and policies that are ‘important’ ”
as “standardless.” 559 U. S., at 405, n. 7 . But five Justices in that case
(i.e., a majority) agreed nevertheless with Gasperini’s approach to inter-
preting the Federal Rules in this context. See 559 U. S., at 437 (Gins-
burg, J., dissenting) (writing for three other Justices that the Court
should “continue to interpret Federal Rules with awareness of, and sen-
sitivity to, important state regulatory policies”); id., at 418 (Stevens, J.,
concurring in part and concurring in judgment) (explaining that the
 Cite as: 607 U. S. ____ (2026) 3

 JACKSON, J., concurring in judgment

 Per Shady Grove, once a conflict between the State’s re-
quirement and a Federal Rule has been identified, the Fed-
eral Rule displaces the State’s requirement so long as the
Rule is “valid,” meaning that it “governs only ‘the manner
and the means’ by which the litigants’ rights are ‘enforced.’ ”
 559 U. S., at 407 (plurality opinion) (quoting Mississippi
Publishing Corp. v. Murphree, 326 U. S. 438, 446 (1946));
see also 28 U. S. C. §2072 (b) (Rules Enabling Act). And for
similar reasons to those given in Part II–B of the majority
opinion, Rule 3 easily satisfies this standard. See ante, at
10–11; see also Shady Grove, 559 U. S., at 407 (plurality
opinion) (noting that we have “rejected every statutory
challenge to a Federal Rule that has come before us”).
 Accordingly, Delaware’s affidavit requirement cannot ap-
ply in federal court.
 II
 The majority and I start in the same place and ultimately
reach the same conclusion, but we have taken different
paths, marked by different assumptions and nuances. I
agree with the majority that the first step of today’s analy-
sis is to identify the relevant conflict by ascertaining the
question that the Delaware law and the Federal Rule “at-
temp[t] to answer.” Shady Grove, 559 U. S., at 399 ; see
ante, at 4. But I disagree that, in this case, “the disputed
question is whether Berk’s lawsuit may be dismissed be-
cause his complaint was not accompanied by an expert affi-
davit.” Ante, at 4. Here is why.

——————
Federal Rules “must be interpreted with some degree of ‘sensitivity to
important state interests and regulatory policies’ ” (quoting Gasperini,
 518 U. S., at 427, n. 7 )). So, under our precedents, courts must be mind-
ful of state interests and policies when determining whether a Federal
Rule conflicts with state law.
4 BERK v. CHOY

 JACKSON, J., concurring in judgment

 A
 First and foremost, that formulation of the question as-
sumes that Berk’s lawsuit has already been properly ac-
cepted by the court clerk (i.e., filed and docketed) and thus
that §6853 is answering whether the “lawsuit may be dis-
missed” for want of the required affidavit. Ante, at 4. But
that assumption jumps the gun. Delaware’s law states that
“[n]o health-care negligence lawsuit shall be filed in this
State unless the complaint is accompanied by: (1) [a]n affi-
davit of merit” or (2) “a motion to extend the time to file said
affidavit.” §6853(a)(1) (emphasis added). The statute fur-
ther specifies that “[i]f the required affidavit does not ac-
company the complaint or if a motion to extend the time to
file said affidavit . . . has not been filed with the court, then
the . . . clerk of the court shall refuse to file the complaint
and it shall not be docketed with the court.” Ibid. (emphasis
added).
 Accordingly, the text of §6853 makes clear that the stat-
ute’s first order of business is not to address the require-
ments for dismissal of an affidavit-free lawsuit such as
Berk’s. Instead, §6853 most directly answers the threshold
question of what is required to start a civil action for medi-
cal malpractice under Delaware law. Delaware’s response
is that the plaintiff must submit an affidavit of merit, or a
motion for an extension of time to file such affidavit, be-
cause (to repeat) the clerk cannot “file the complaint” or
“docke[t]” the case without that additional filing.
§6853(a)(1).
 Rule 3 provides a completely different answer to the ques-
tion of what is required to start a medical malpractice case.
As explained above, under that Rule, “[a] civil action is com-
menced by filing a complaint with the court”—period. That
answer leaves “no room” for Delaware’s insistence that an
affidavit of merit (or a motion for an extension) must be sub-
mitted in order to commence this kind of legal action. Bur-
lington, 480 U. S., at 5 . Indeed, Rule 3 uses the
 Cite as: 607 U. S. ____ (2026) 5

 JACKSON, J., concurring in judgment

uncompromising, declarative phrase “is commenced,”
plainly indicating that Congress meant for the “filing [of] a
complaint” to be both necessary and sufficient to begin any
civil case (including a malpractice action) in federal court.
Cf. Walker, 446 U. S., at 750, n. 10 (“ ‘Rule 3 simply provides
that an action is commenced by filing the complaint and has
as its primary purpose the measuring of time periods that
begin running from the date of commencement’ ” (quoting 4
C. Wright & A. Miller, Federal Practice and Procedure
§1057, p. 191 (1969))); Hallstrom v. Tillamook County, 493
U. S. 20, 26 (1989) (reading Rule 3 to mean that “filing a
complaint with the court” is synonymous with “fil[ing]
suit”).2
 Resisting this conclusion, defendants rely on three cases
from 1949, arguing that “this Court has long found applica-
ble in federal court” “state-law condition[s] on allowing
suits to proceed.” Brief for Respondent Beebe 26–27, and
——————
 2 The majority contends that its dismissal-focused formulation of the

question is the right one because, in this case, “Berk’s lawsuit has al-
ready been filed and docketed,” and “we granted certiorari” on the ques-
tion “whether Berk’s lawsuit may be dismissed.” Ante, at 4, n. 1. That
argument conflates the question presented with the “question” that, un-
der Shady Grove, is supposed to serve as the linchpin of our conflict anal-
ysis. 559 U. S., at 401 . The latter comes not from the facts of the case,
but rather from our interpretations of the potentially conflicting state
law and Federal Rule. So, while it may be that the question presented is
“whether Berk’s lawsuit may be dismissed,” the relevant question for our
Shady Grove analysis is “what is required to start a medical malpractice
case,” because that is the question that §6853 and, as it happens, Rule 3,
“attemp[t] to answer,” Id., at 399.
 Nor is the majority correct that, regardless, I am “ultimately forced to
grapple with the question whether Berk’s lawsuit may be ‘dismiss[ed].’ ”
Ante, at 4, n. 1 (alteration in original). As I stated above, §6853’s conflict
with Rule 3 is enough to hold that the law cannot apply in federal court.
And, as I have shown, the Rule 3 analysis is about the commencement of
the action, not its dismissal. Once we determine that §6853 and Rule 3
answer the same commencement-related question, §6853 cannot apply
in federal court, meaning that Berk’s lawsuit cannot be thwarted for fail-
ure to satisfy the requirements of that state law.
6 BERK v. CHOY

 JACKSON, J., concurring in judgment

n. 11; see also Brief for Respondent Choy 36–37. But that
argument mischaracterizes our past rulings. See Cohen v.
Beneficial Industrial Loan Corp., 337 U. S. 541 (1949);
Woods v. Interstate Realty Co., 337 U. S. 535 (1949); Walker
v. Armco Steel Corp., 446 U. S. 740 .
 The majority has already ably explained that defendants
“substantially overread” Cohen for the proposition that “all
state ‘preconditions to proceeding’ are consistent with the
Federal Rules.” Ante, at 7. I think Walker and Woods are
also easily distinguishable.
 As with Cohen, respondents overstate the effect of
Walker. There, we held that a federal court sitting in diver-
sity must apply an Oklahoma law that deemed an action
“commenced” upon service of the summons for purposes of
the State’s statute of limitations. 446 U. S., at 742 . Rule 3,
we explained, “governs the date from which various timing
requirements of the Federal Rules begin to run, but does
not affect state statutes of limitations.” Id., at 751 . Here,
by contrast, §6853 and Rule 3 serve precisely the same func-
tion, in the same context: Both establish when a malprac-
tice lawsuit is deemed initiated (i.e., filed and docketed) for
purposes of determining “the date from which various tim-
ing requirements of the Federal Rules begin to run.” Ibid.
That is precisely the kind of conflict that bars the applica-
tion of state law in federal court under our precedents.3
 Defendants’ reliance on Woods is similarly unavailing.
There, we held that a federal court sitting in diversity must
apply a Mississippi law prohibiting out-of-state
——————
 3 Proving this point, another provision of the Delaware law,

§6853(a)(4), provides that a defendant is “not required to take any action
with respect to the complaint . . . until 20 days after plaintiff has filed
the affidavit.” Under the Federal Rules, however, the deadline for a re-
sponsive act by the defendant is anchored to the filing of the complaint.
See Fed. Rules Civ. Proc. 4(m) (a plaintiff must serve the complaint and
summons “within 90 days after the complaint is filed”) and 12(a)(1)(A)(i)
(a defendant “must serve an answer . . . within 21 days after being served
with the summons and complaint”).
 Cite as: 607 U. S. ____ (2026) 7

 JACKSON, J., concurring in judgment

corporations from bringing suit in the State unless they
designated an agent for service of process. 337 U. S., at 536,
n. 1. Mississippi’s law was enacted to ensure that only
those out-of-state corporations that consented to being sued
in Mississippi had the privilege of accessing Mississippi’s
courts. See ibid. In other words, Mississippi’s law had a
broad substantive purpose and effect that went well beyond
what the Federal Rules addressed. That was why we had
to wade through “Erie’s murky waters” to decide the con-
flicts question that case presented. See Shady Grove, 559
U. S., at 398 ; see Erie R. Co. v. Tompkins, 304 U. S. 64
(1938). Delaware’s affidavit requirement, by contrast, is
plainly procedural in scope and well within the territory of
the Federal Rules.
 In short, our precedents establish that when a state law
and a valid Federal Rule conflict—because they answer the
same procedural question—the State’s requirement is inap-
plicable in federal court. Because §6853 answers the same
question about what is required to commence a medical
malpractice action as the unquestionably valid Rule 3, Del-
aware’s law must give way. See Hanna, 380 U. S., at 469–
474.
 B
 If we accept, for the sake of argument, that the question
Delaware’s law attempts to answer is “whether [a medical
malpractice complaint] may be dismissed because [it] was
not accompanied by an expert affidavit,” ante, at 4, a prob-
lem arises: The Federal Rule the majority points to does not
answer that same question.
 The majority discerns a conflict with Rule 8 by reasoning
as follows. With respect to the dismissal-related question
quoted above, Delaware’s law says that such a complaint
must be dismissed because the affidavit of merit is missing,
whereas Rule 8 prescribes all “the information a plaintiff
must present about the merits of his claim at the outset of
8 BERK v. CHOY

 JACKSON, J., concurring in judgment

litigation”—namely, “ ‘a short and plain statement of the
claim showing that [he] is entitled to relief.’ ” Ante, at 5
(quoting Fed. Rule Civ. Proc. 8(a)(2)). “By requiring no
more than a statement of the claim,” the majority contin-
ues, “Rule 8 establishes ‘implicitly, but with unmistakable
clarity,’ . . . that evidence of the claim is not required.’ ”
Ante, at 5.
 The problem with this reasoning is not that it is based on
“a negative inference” about Rule 8, id., at 7, n. 2, but rather
the inattentively capacious scope of that negative inference.
I agree that Rule 8(a)’s finite list “preclude[s] courts” from
imposing additional requirements. Ibid.; see Leatherman
v. Tarrant County Narcotics Intelligence and Coordination
Unit, 507 U. S. 163, 168 (1993). But context is critical: Rule
8 does not purport to establish all that a medical malprac-
tice plaintiff can be required to say about the merits of his
claims at the beginning of the case, much less that nothing
more than the filing of a complaint can be mandated. Ra-
ther, it (more narrowly) addresses what any “pleading”
stating a claim for relief must contain. See Rule 8(a) (“A
pleading that states a claim for relief must contain . . .” (em-
phasis added)). The majority neither holds nor suggests
that §6853’s affidavit of merit is, itself, a “pleading”; to the
contrary, the majority admits that the affidavit is not. Ante,
at 6. So, as I see it, Delaware’s law—which prescribes what
a plaintiff must submit in addition to his pleadings in order
for his complaint to be filed and his case docketed—does not
actually conflict with Rule 8.
 The majority acknowledges this “pleading” problem and
offers, apparently as a solution, yet another formulation of
the question that Rule 8 is answering: Rule 8, it says, tells
us “what information a plaintiff must provide about the
merits of his claim.” Ante, at 6. But, again, this description
fails to acknowledge that Rule 8 operates entirely within a
specific universe: the pleadings. The majority’s unbounded
characterization subtly frees Rule 8 from the constraint of
 Cite as: 607 U. S. ____ (2026) 9

 JACKSON, J., concurring in judgment

its subject matter, allowing it to expand until it collides
with Delaware’s law.4
 When properly construed, Rule 8 addresses a particular
(and particularly important) procedural question: “What
must a pleading that states a claim for relief contain?”5 In
my view, this narrower formulation of the question—the
one tethered to the required contents of a “pleading”—keeps
Rule 8 within the bounds of its plain meaning, consistent
with Gasperini’s command not to overread the Federal
Rules at the expense of “important state interests and reg-
ulatory policies” in cases such as this one. Gasperini v. Cen-
ter for Humanities, Inc., 518 U. S. 415, 427, n. 7 (1996); see
also n. 1, supra.
 Accordingly, because §6853 does not address or govern
the required contents of a pleading, Delaware’s law does not
answer the same question as Rule 8. Instead, the State’s
affidavit requirement (which, incidentally, neither de-
scribes the affidavit of merit in relation to a plaintiff ’s obli-
gation to state a claim for relief nor treats it as evidence) is
an additional filing requirement for commencing any med-
ical malpractice civil action under state law. See
§6853(a)(1) (“No health-care negligence lawsuit shall be
——————
 4 The majority’s description of Rule 8’s work is inaccurate even if con-

fined to the universe of pleadings. Rule 8 does not “addres[s] what infor-
mation a plaintiff must provide about the merits of his claim” in the
pleadings. Ante, at 6 (emphasis added). Instead, with respect to a plead-
ing that states a claim for relief (as opposed to one that does not, see Rule
7), Rule 8 governs how much a plaintiff must say concerning his claim.
Rule 8’s primary purpose is to install a “simplified pleading system” that
requires a complaint to include nothing more than “ ‘short and plain
statement[s]’ ” of the claim, the grounds for jurisdiction, and the relief
sought. Swierkiewicz v. Sorema N. A., 534 U. S. 506, 512, 514 (2002). In
other words, Rule 8’s innovation is the “short and plain” bit, not the sub-
stance of what is required to be stated in that manner.
 5 The answer, under the Rule, is (1) “a short and plain statement of the

grounds for . . . jurisdiction,” (2) “a short and plain statement of the claim
showing that the pleader is entitled to relief,” and (3) “a demand for the
relief sought.” Rule 8(a).
10 BERK v. CHOY

 JACKSON, J., concurring in judgment

filed in [Delaware] unless the complaint is accompanied by
. . . [a]n affidavit of merit”). Finding a Rule 8 conflict, as
the majority does, thus requires contorting both Rule 8 and
§6853. There is no need to do so here, especially given the
ready conflict with Rule 3 (discussed above) and Rule 12
(described below).6
 III
 The majority and I appear to agree that Delaware’s affi-
davit requirement—as interpreted by the Delaware Su-
preme Court—conflicts with Rule 12(d). See ante, at 5.
That conflict suffices to displace §6853’s requirement. But
to the extent that the majority ties its Rule 12 analysis to
the purported Rule 8 conflict, see ibid., I think the majority
has gone further than it needs to, introducing incoherence
in the process.
 While the statute itself does not so specify, the Delaware
Supreme Court has interpreted §6853 to mean that (assum-
ing the clerk of court accepts an affidavit-free medical mal-
practice action and dockets the case notwithstanding the
statute’s prohibition) “[t]he filing of a healthcare negligence

——————
 6 To be sure, many Courts of Appeals have also relied on a conflict with

Rule 8 to hold that state affidavit-of-merit laws like Delaware’s do not
apply in federal court. See Albright v. Christensen, 24 F. 4th 1039 , 1048–
1049 (CA6 2022); Gallivan v. United States, 943 F. 3d 291, 293 (CA6
2019); Pledger v. Lynch, 5 F. 4th 511, 519 (CA4 2021); Young v. United
States, 942 F. 3d 349, 351 (CA7 2019). But a closer look at the relevant
cases reveals that these courts, like the majority, got there by manipu-
lating the relevant question. In Gallivan, for example, the Sixth Circuit
posed as the pertinent question: “[D]oes someone need an affidavit of
merit to state a claim for medical negligence?” 943 F. 3d, at 293 . This
leading question not only ignores (as the majority does) that Rule 8 is
solely about “pleadings,” but, worse, also preordains a conflict by naming
the very thing that the state law requires but the Federal Rule does not
(i.e., an affidavit). The Fourth and Seventh Circuits make the same er-
ror. See Pledger, 5 F. 4th, at 519 (asking “whether a medical malpractice
plaintiff must provide pre-suit expert support for his claim”); Young, 942
F. 3d, at 351 (asking whether Rule 8 “require[s] attachments”).
 Cite as: 607 U. S. ____ (2026) 11

 JACKSON, J., concurring in judgment

action without the requisite affidavit of merit constitutes
grounds of dismissal of medical negligence claims as a mat-
ter of law.” Hall v. Sorouri, 996 A. 2d 793 (Del. 2010) (Ta-
ble). That reading of Delaware law answers the question,
“What can a court consider when dismissing a medical mal-
practice case?” Because “[t]he highest state court is the fi-
nal authority on state law,” Fidelity Union Trust Co. v.
Field, 311 U. S. 169, 177 (1940), we must read this statute
as that court does, i.e., as establishing dismissal require-
ments for medical malpractice cases. Thus, if a valid Fed-
eral Rule answers that same dismissal question, §6853 can-
not govern in federal court. See Shady Grove, 559 U. S., at
398 .
 Enter Rule 12. As the majority correctly explains, Rule
12(b)(6) provides the “only . . . ground for dismissal based
on the merits,” and Rule 12(d) prohibits courts from consid-
ering “ ‘matters outside the pleadings’ ” in deciding motions
to dismiss brought under Rule 12(b)(6). Ante, at 5; see also
Stanley v. City of Sanford, 606 U. S. 46, 49 (2025) (explain-
ing that, under Rule 12(d), a judge considering a motion to
dismiss must “take as true the well-pleaded facts in the
plaintiff ’s complaint, . . . and [must] not consider evidence
beyond that pleading”). Furthermore, by all accounts, the
affidavit required by Delaware’s law is a “matte[r] outside
the pleadings.” Rule 12(d); see ante, at 6 (“It is true . . . that
an affidavit of merit is a document separate from the ‘plead-
ing’ ”).
 We know the affidavit of merit qualifies as a “matter out-
side the pleadings” for several reasons. For one thing, Del-
aware law provides that the affidavit is to “accompany” the
complaint. §6853(a)(1). A thing cannot “accompany” that
of which it is already a part.7 Indeed, Delaware’s
——————
 7 To be sure, plaintiffs can, in limited contexts, “incorporat[e]” certain

documents “into the complaint by reference.” Tellabs, Inc. v. Makor
12 BERK v. CHOY

 JACKSON, J., concurring in judgment

Legislature apparently felt so strongly about the affidavit
not being part of the complaint that it mandated physical
separation: By statute, the affidavit must be filed in its own
sealed envelope, alongside (but apart from) the complaint.
See ibid. Nor do the Federal Rules suggest that affidavits
of the nature specified by the Delaware law can qualify as
“pleadings.” Rule 7, which sets forth a list of “[p]leadings
[a]llowed” in federal court, does not include an “affidavit”
(or anything like it) on its list.
 Pulling these threads together, Delaware’s law, as inter-
preted by the Delaware Supreme Court, requires judges to
account for a matter outside the pleadings—i.e., the exist-
ence or sufficiency of an affidavit of merit (or lack
thereof )—when deciding whether to dismiss a medical mal-
practice case. Rule 12(d), however, forbids such extraneous
considerations. And Rule 12 is valid under the Rules Ena-
bling Act (for similar reasons as the Court lays out in its
opinion, see ante, at 10–11). So Delaware’s law cannot be
enforced in federal court.
 As far as I can tell, then, there is no daylight between my
view of the Rule 12 conflict and the majority’s assessment.
But far from “reinforc[ing]” a conflict with Rule 8, ante, at
5, our shared evaluation of Rule 12 is, to me, yet another
reason why Delaware’s law is not in conflict with Rule 8.
See Part II–B, supra. The conflicts analysis concerning
these two Rules is based on diametrically opposed charac-
terizations of Delaware’s affidavit of merit: The affidavit
must be either a “matter outside the pleadings” (and thus
§6853 conflicts with Rule 12, per the Delaware Supreme
Court’s decision in Hall) or it is part of what the pleadings
must contain (giving rise to the purported conflict with Rule
8). A coherent conflicts analysis cannot have it both ways.

——————
Issues & Rights, Ltd., 551 U. S. 308, 322 (2007). But the affidavit of merit
is not such a document because its content is neither discoverable nor
admissible. See §6853(d).
 Cite as: 607 U. S. ____ (2026) 13

 JACKSON, J., concurring in judgment

 * * *
 Read for what they are—by their “plain meaning,” sensi-
tive to context yet without distortions created by the task of
checking for a conflict, see Walker, 446 U. S., at 750, n. 9 ;
Gasperini, 518 U. S., at 427 , n. 7—Rules 3 and 12 answer
the same questions as Delaware’s affidavit requirement.
That means that the majority and I share the same conclu-
sion: There is a conflict between state law and valid Federal
Rules, precluding application of Delaware’s affidavit re-
quirement in federal court. For the reasons discussed
above, I think the majority is wrong to further maintain
that §6853 answers the same question as Rule 8. And I
cannot see how the affidavit that the Delaware law requires
can be a “matter outside the pleadings” (for Rule 12-conflict
purposes) and also part of the “pleadings” (for Rule 8-con-
flict purposes). Therefore, I concur only in the judgment.