In the

    United States Court of Appeals
                 For the Seventh Circuit
                     ____________________
No. 23-1718
SYSCO INDIANAPOLIS LLC,
                                                   Plaintiff-Appellee,


                                 v.

TEAMSTERS LOCAL 135,
                                               Defendant-Appellant.
                     ____________________

         Appeal from the United States District Court for the
         Southern District of Indiana, Indianapolis Division.
            No. 1:22-cv-00131 — James P. Hanlon, Judge.
                     ____________________

     ARGUED MAY 28, 2024 — DECIDED AUGUST 20, 2024
                ____________________

   Before JACKSON-AKIWUMI, LEE, and KOLAR, Circuit Judges.
   JACKSON-AKIWUMI, Circuit Judge. When John Smith did not
receive his expected monthly benefit check from his
employer, his labor union filed a grievance on his behalf. His
employer, Sysco Indianapolis, LLC, went through the first
steps of the grievance process with the labor union, Teamsters
Local 135. But Sysco balked at the last step—arbitration—
because it decided Smith’s grievance was not arbitrable under
2                                                  No. 23-1718

the parties’ collective bargaining agreement. Sysco pulled out
of the grievance process altogether and sought a declaratory
judgment from the district court. The Union counterclaimed,
seeking its own declaratory judgment.
   The district court sided with Sysco: it found that the
monthly benefit was governed by terms outside the bargain-
ing agreement and that the parties’ bargaining history
showed they did not intend for the benefit to be arbitrable.
We reach a different conclusion after our de novo review. Be-
cause Sysco failed to present the “most forceful evidence,”
United Steelworkers of Am. v. Warrior & Gulf Navigation Co., 

 (1960), showing that the parties intended to ex-
clude the monthly benefit from the arbitration provision in
the collective bargaining agreement, we reverse.
                               I
    Sysco Indianapolis, LLC, is a food service warehouse and
transportation facility in Indianapolis, Indiana. Teamsters Lo-
cal 135 represents certain employees of Sysco for the purpose
of collective bargaining. On January 8, 2019, the Union filed a
grievance alleging that Sysco was violating the parties’ 2018
collective bargaining agreement (CBA) by not providing a
Supplemental Early Retirement Benefit (SERB) of $500 per
month to certain qualified retirees and current employees.
    When a disagreement of this sort arises, the CBA obligates
the parties to resolve the dispute through a grievance process
culminating, if necessary, in arbitration. The CBA’s grievance
procedure clause defines a grievance as “any controversy,
complaint or dispute arising as to the interpretation or appli-
cation of or the compliance with any provisions on this
No. 23-1718                                                                   3

Agreement.” The clause then outlines a five-step process the
parties must take before the grievance can be heard by an ar-
bitrator. 1
    The Union initiated the five-step process by filing a griev-
ance “on behalf [of] John Smith and all future retirees.” The
grievance stated that Smith is “entitled to an additional 500 a
month until age 65. He is currently not receiving this money.
Make whole in all ways.” The grievance cited Article 18 of the
CBA and “all that may apply” as the contract provision vio-
lated. Article 18 provides:
        The previous labor agreement terminated par-
        ticipation by the Employer and the Union in the


    1 At step one of the process, the aggrieved employee must discuss the

grievance with an immediate supervisor within ten workdays of the event
that gave rise to the grievance, and the supervisor must give a verbal reply
within ten workdays of the discussion. If the grievance is not resolved, the
parties move to the next step. Step two requires the employee to put the
grievance into writing and present it to the supervisor within five work-
days of receiving a response in step one. The supervisor, employee, and
union representative must then meet to try to resolve the grievance. The
supervisor must issue a written answer to the representative within ten
workdays of the meeting. If not resolved, the grievance moves to step
three, where the business agent appeals the grievance in writing to the
branch manager within ten days of the representative’s receipt of an an-
swer in step two. The branch manager and business agent must meet, and
within ten workdays of that meeting, the branch manager must issue a
written decision. If the grievance is still not resolved, it moves to step four:
consideration by the Joint Grievance Committee, which consists of an
equal number of representatives from Sysco and the Union. Once the Joint
Grievance Committee has resolved the grievance, the losing party has ten
calendar days to appeal. But if the Joint Grievance Committee is unable to
reach a conclusion within ten workdays, the parties can proceed to step
five: arbitration.
4                                                 No. 23-1718

      Central States, Southeast and Southwest Areas
      Pension Fund. Accordingly, the Employer is no
      longer obligated to contribute to or participate
      in said Fund.
      All regular full time employees covered by this
      Agreement hired before 5/15/2018 shall be eligi-
      ble for enrollment in the Sysco Corporation Re-
      tirement Plan and the Sysco Corporation Em-
      ployees’ 401(k) Plan, subject to all rights, terms
      and conditions of this Plan including any and all
      additions, deletions or modifications made to
      any and all terms, conditions and benefits of this
      Plan made during the term of this Agreement.
      All regular full time employees hired after
      5/15/2018 shall be eligible for the Sysco En-
      hanced 401(k) program under the same terms
      and conditions as non-union employees at the
      Company.
    This was the second time the Union filed a grievance about
the $500 monthly benefit. The first was in November 2013.
That time, the Union submitted a similar grievance claiming
a violation of the same provision of the 2013 CBA. That griev-
ance went through the first four steps of the grievance process
and resulted in the Joint Grievance Committee issuing a final
and binding decision in the Union’s favor. After Sysco refused
to comply with the Joint Grievance Committee’s decision, the
Union sued Sysco in federal district court to enforce the deci-
sion. That litigation ended with a 2018 judgment in the Un-
ion’s favor ordering Sysco to pay the monthly SERB under the
parties’ 2013 CBA.
No. 23-1718                                                            5

    The district court had not issued its ruling on the 2013
grievance when the parties started negotiating the 2018 CBA.
But the Union believed that, because the Joint Committee had
already decided in its favor and the relevant contract lan-
guage in the 2013 CBA and 2018 CBA was largely the same,
the $500 monthly benefit would carry forward into the 2018
CBA. 2 Sysco had other plans.
    After going through the first four steps of the grievance
process to resolve Smith’s January 2019 grievance, Sysco
changed course. Rather than proceed to step five, which is ar-
bitration, Sysco asked the district court in January 2022 to de-
clare that the grievance was not substantively arbitrable. The
Union answered Sysco’s complaint and filed a two-count
counterclaim seeking a declaration that the grievance was ar-
bitrable and injunctive relief to compel arbitration. Sysco filed
a motion to dismiss the Union’s counterclaims. Shortly there-
after, both parties moved for summary judgment.
    The district court agreed with Sysco that the 2019
grievance was not substantively arbitrable. The court first
found that the 2018 CBA’s arbitration clause was “broad,”
which creates a presumption of arbitrability. The only way
Sysco could overcome that presumption, the court explained,
was by “produc[ing] ‘most forceful evidence of a purpose to
exclude the claim from arbitration.’” The court found that
Sysco did so by showing that (1) the SERB was not
incorporated into the CBA itself, (2) the parties’ bargaining


    2 The parties made only two changes to Article 18 between the 2013

CBA and the 2018 CBA: they changed the article’s title from “Pensions” to
“Retirement,” and they limited participation in the Retirement Plan and
401(k) Plan to employees hired before May 15, 2018.
6                                                     No. 23-1718

history demonstrates that they had considered and rejected
including language about the SERB into Article 18 of the CBA,
and (3) the CBA and the document outlining the SERB are
entirely separate documents. The court acknowledged that
the grievance identified Article 18 as the provision being
violated but reasoned that “the language of the CBA—not the
language of the grievance—determines whether a grievance
is subject to arbitration.” And here, the court found, the CBA
did not contemplate arbitration for disputes about the SERB.
As a result, the court granted Sysco’s motion for summary
judgment and denied the Union’s. The Union appeals this
decision, which we review de novo. Int’l Bhd. of Elec. Workers
Loc. 2150 v. NextEra Energy Point Beach, LLC, 

(7th Cir. 2014).
                                II
    For nearly a century, the Supreme Court has interpreted
our national labor laws as reflecting a “congressional policy
in favor of the enforcement of agreements to arbitrate griev-
ance disputes.” Textile Workers Union of Am. v. Lincoln Mills of
Ala., 

, 458–59 (1957). To effectuate Congress’s pol-
icy goal, the Court developed “a meaningful body of law to
govern the interpretation and enforcement of collective bar-
gaining agreements.” United Steelworkers of Am. v. Am. Mfg.
Co., 

 (1960). That body of law originates in a
group of cases that have come to be known as the Steelworkers
Trilogy. See id.; Warrior & Gulf, 

; United Steelworkers
of Am. v. Enter. Wheel & Car Corp., 

 (1960).
    The Steelworkers Trilogy birthed four “principles” that
guide our resolution of arbitration disputes. AT&T Techs., Inc.
v. Commc’ns Workers of Am., 

 (1986). “The first
principle gleaned from the Trilogy is that ‘arbitration is a
No. 23-1718                                                     7

matter of contract and a party cannot be required to submit to
arbitration any dispute which he has not agreed so to sub-
mit.’” 

 (quoting Warrior & Gulf, 363 U.S. at 582). This means
that, before we can compel arbitration, we must first “deter-
mine whether [the parties have] agreed to arbitrate th[e] par-
ticular dispute, for a duty to arbitrate can arise only by agree-
ment.” United Steel, Paper & Forestry, Rubber, Mfg., Energy, Al-
lied Indus. & Serv. Workers Int'l Union v. TriMas Corp., 

 (7th Cir. 2008).
    The second principle is that “the question of whether the
parties agreed to arbitrate is to be decided by the court, not
the arbitrator.” AT&T Techs., 

; see also John Wiley
& Sons, Inc. v. Livingston, 

, 546–47 (1964).
    The third principle follows from the first two: “in deciding
whether the parties have agreed to submit a particular griev-
ance to arbitration, [we are] not to rule on the potential merits
of the underlying claims.” AT&T Techs., 

. This
means we do not “weigh[] the merits of the grievance, con-
sider[] whether there is equity in a particular claim, or deter-
min[e] whether there is particular language in the written in-
strument which will support the claim.” Am. Mfg. Co., 363
U.S. at 568.
    The fourth principle derived from the Steelworkers Trilogy
is that our national labor laws establish a “presumption of ar-
bitrability.” AT&T Techs., 

. Under this presump-
tion, “[a]n order to arbitrate the particular grievance should
not be denied unless it may be said with positive assurance
that the arbitration clause is not susceptible of an interpreta-
tion that covers the asserted dispute.” Warrior & Gulf, 363 U.S.
at 582–83. Where doubts exist about whether a grievance is
8                                                    No. 23-1718

arbitrable under the terms of the agreement, those “[d]oubts
should be resolved in favor of coverage.” Id. at 583.
    These principles are not elements of a claim, but back-
ground that informs our resolution of arbitration disputes.
From these principles, our court has developed several con-
siderations relevant to determining whether a claim should
go to arbitration, including whether the parties’ agreement
explicitly contemplates (or prohibits) arbitrating a grievance,
and whether other indicators of the parties’ intent resolve the
question. These considerations, to which we turn next, com-
pel a finding of arbitrability in this case.
    A. Facial Arbitrability
    When deciding whether a dispute is arbitrable, our first
task is to determine “whether the Union is making a claim
that is, ‘on its face,’ governed by the [collective bargaining
agreement].” TriMas, 

 (quoting Am. Mfg. Co.,
363 U.S. at 568). To do so we look to (1) the language of the
CBA’s grievance and arbitration clause, and (2) the language
of the grievance itself. See Int’l Ass’n of Machinists & Aerospace
Workers, Lodge No. 1777 v. Fansteel, Inc., 

(7th Cir. 1990); NextEra Energy Point Beach, LLC, 

,
594–95. Facial arbitrability is met here.
    Article 9 of the 2018 CBA outlines the grievance and arbi-
tration procedures. It defines a grievance as “any controversy,
complaint, or dispute arising as to the interpretation or appli-
cation of or the compliance with any provisions on this Agree-
ment.” It then outlines a series of steps that an aggrieved
party must take to get the benefit of arbitration, starting with
discussing the grievance with a supervisor. Notably, the CBA
does not exclude “any category of disputes from the reach of
No. 23-1718                                                    9

the arbitration clause.” TriMas, 

. “[T]his lan-
guage is of [the] type that we have referred to, in the past, as
broad enough to trigger the presumption of arbitrability.”
NextEra Energy Point Beach, 

. That means we
will enforce the parties’ agreement to arbitrate unless Sysco
can produce “the most forceful evidence of a purpose to ex-
clude the claim from arbitration.” Warrior & Gulf, 363 U.S. at
585.
    Here, the grievance filed “on behalf [of] John Smith and all
future retirees” complained that “John is entitled to an addi-
tional 500 a month until age 65. He is currently not receiving
this money.” In the portion of the grievance that asks for a
“Contract Violation,” Smith cited Article “18 and all that may
apply.” On its face, then, Smith’s grievance simply requires
an arbitrator or adjudicator to decide whether Article 18 re-
quires that Smith be paid an additional $500 per month. The
grievance does not mention the words “Supplemental Early
Retirement Benefit” or refer to the external Retirement Plan
that establishes that benefit. Smith’s grievance is about the
scope of Article 18. In that way, it presents a “dispute [] as to
the interpretation or application of or compliance with” a pro-
vision of the CBA, which the parties agreed would be re-
solved through arbitration.
   B. The “Most Forceful Evidence”
    Failing to identify any portion of the CBA explicitly ex-
empting the $500 monthly benefit from the grievance and ar-
bitration process, Sysco argues that it has produced, to use the
Supreme Court’s language, “the most forceful evidence of a
purpose to exclude the claim from arbitration.” Warrior &
Gulf, 363 U.S. at 585. The case proving its point, according to
Sysco, is Printing Specialties & Paper Products Union Local 680
10                                                    No. 23-1718

v. Nabisco Brands, Inc., 

 (7th Cir. 1987). In that case,
we held that a pension plan’s “independence from the collec-
tive bargaining agreement, the bargaining history of the par-
ties, and the lack of Pension Plan terms in the collective bar-
gaining agreement” supported excluding grievances over
pension benefits from arbitration, even though no express ex-
clusion appeared on the face of the CBA. Nabisco, 

. Sysco contends that those same indicators of intent exist
in this case, so the same outcome should result. Not so.
    As a threshold matter, this case differs from Nabisco in an
important way: The union in Nabisco claimed that it was enti-
tled to early retirement benefits under the terms of the Pen-
sion Plan. 

. And the collective bargaining agreement
in that case included only a “passing reference” to the Pension
Plan. 

. The agreement said, “The Company agrees to
continue its present Pension Plan in full force and effect for
the term of the agreement.” 

    In this case, by contrast, Smith’s grievance does not claim
an entitlement under the terms of the Retirement Plan—it
does not even reference the Retirement Plan. The Union main-
tains that it is Article 18 of the CBA and the parties’ collective
bargaining negotiations (as discussed below)—not the terms
of the Retirement Plan—that obligate Sysco to pay the addi-
tional $500 per month. See Karl Schmidt Unisia, Inc. v. Int’l Un-
ion, United Auto., Aerospace & Agric. Implement Workers of Am.,
UAW Loc. 2357, 

 (7th Cir. 2010) (explaining
that it is the union’s understanding of their grievance claim,
not the Company’s characterization of it, that guides our con-
sideration of whether the claim is arbitrable). That is a differ-
ent question than the one we considered in Nabisco.
No. 23-1718                                                   11

    But even if we overlooked that difference and applied the
indicators that the Nabisco court concluded collectively
amounted to “most forceful evidence,” Warrior & Gulf, 363
U.S. at 585, we would still reach a different result in this case
because the parties’ bargaining history is not as straightfor-
ward as Sysco suggests, thereby distinguishing the facts of
this case from Nabisco.
    Let’s start with what Sysco gets right. We agree that the
CBA does not incorporate the Retirement Plan and that the
Retirement Plan is separate and independent of the CBA—
two indicators the Nabisco court highlighted as evidence of the
parties’ intent to exclude pension benefits grievances from ar-
bitration. Here, although Article 18 references “all rights,
terms and conditions of th[e] Plan” and includes “any and all
additions, deletions or modifications made to any and all
terms, conditions and benefits of th[e] Plan,” that language
does not amount to an incorporation of the terms of the Re-
tirement Plan. Sysco is also correct that, as with the pension
plan in Nabisco, the Retirement Plan here existed before and
apart from the parties’ CBA. Nabisco, 

. The Plan
was created in 1973 and contains its own rules for determin-
ing eligibility for benefits.
   These two indicators point in Sysco’s favor, but they are
not—alone or together—sufficient to prove that the parties in-
tended to exclude Smith’s grievance from arbitration. Those
indicators show only that the Retirement Plan was not part of
the 2018 CBA; they do not show that the parties meant to ex-
clude the $500 benefit under the language of the CBA itself–
which is what the grievance alleges.
    Sysco believes that the third indicator the Nabisco court re-
lied on—the parties’ bargaining history—puts it over the top
12                                                 No. 23-1718

because that history “clearly demonstrates” the parties did
not plan to arbitrate disputes related to the $500 monthly ben-
efit. But we do not find the bargaining history to be so clear.
   That history shows, Sysco points out, that the Union
sought to include language in the 2018 CBA that would have
more explicitly incorporated the $500 per month commit-
ment. Yet that language did not end up in the final agreement.
Sysco says that we should read that sequence of events as ev-
idence that the parties explicitly rejected such an inclusion,
and the CBA, therefore, does not guarantee the $500 monthly
benefit. The Union concedes that the language it sought to in-
clude with respect to the benefit did not make it into the final
agreement, but says that is not because Sysco refused. To the
contrary, the Union recounts, the parties understood the 2018
CBA was to be governed by however the previous grievance
under the 2013 CBA was resolved, whenever the court got
around to resolving that older grievance. Thus, in the Union’s
view, unlike in Nabisco, the entitlement to the $500 monthly
benefit stems directly from the CBA, not from the Pension
Plan.
     To support its argument, the Union points us to notes pre-
pared by Sysco’s negotiator, Scott Richardson, during the par-
ties’ negotiations over the 2018 CBA. Those notes, which
Sysco’s counsel confirmed at oral argument were written by
Richardson, reflect the Union’s proposed changes to the
agreement. In the portion of the document concerning Article
18, the Union proposed to “Reinstate the agreed to, in 2013,
extra five hundred dollars ($500) in addition.” Sysco’s Rich-
ardson annotated the document with “not neg something [in]
litigation bound by decision.” (Richardson later submitted a
declaration explaining that Sysco “would not negotiate
No. 23-1718                                                              13

benefits currently in litigation but [] would certainly comply
with—or be bound by—the decision of the Court with regard
to litigation related to the SERB and the 2013 to 2018 CBA.”)
The Union says these notes show Sysco agreed to “follow the
outcome of the litigation,” not that it “refuse[d] to pay the
benefit” once the 2018 CBA took effect.
    In response, Sysco says the notes show only that they
agreed to be bound by any court decision to provide the
monthly benefit under the 2013 CBA, but not the 2018 CBA.
Sysco, however, points to no evidence in the record showing
that was the parties’ shared understanding. And while Rich-
ardson’s notes could be read the way Sysco reads them, it is
also quite reasonable to read them as the Union does. At the
end of the day, it is not our job to speculate about what Sysco
conveyed or meant to convey during negotiations. It is
Sysco’s responsibility to dispel any doubt by marshalling “the
most forceful evidence of a purpose to exclude” the grievance
from arbitration. Warrior & Gulf, 363 U.S. at 585. Sysco has not
done so.
    C. One Final Consideration: Zipper Clauses
    While the indicators the Nabisco court considered are help-
ful in assessing whether the parties intended to arbitrate a
grievance alleging a violation of some extrinsic plan (as in
Nabisco), those indicators are neither exhaustive nor generally
applicable to all cases involving questions of arbitrability.3

    3 We have chosen to call them “indicators” here because they are

largely derivative of the factual circumstances before the court in Nabisco.
Cases with different facts might require different considerations (or offer
different “indicators”) altogether. That is true as a general matter in our
cases, but even more so in arbitration cases because of the fact-intensive
14                                                            No. 23-1718

Our analysis in arbitration cases must be driven, in the first
instance, by the principles established in the Steelworkers Tril-
ogy. And the Steelworkers Trilogy teaches that arbitration
“should not be denied unless it may be said with positive as-
surance that the arbitration clause is not susceptible of an in-
terpretation that covers the asserted dispute.” Warrior & Gulf,
363 U.S. at 582–83; see also TriMas, 

. One final
consideration deprives us of that positive assurance in this
case.
    The Union, which has no affirmative obligation to prove
that the dispute was not excluded from arbitration, argues
that the CBA’s lack of a zipper clause supports sending the
grievance to an arbitrator. As the Union sees it, a zipper clause
would have “limit[ed] [the CBA’s] provisions to those ex-
pressly set forth therein.” Such language would effectively
foreclose any debate about the parties’ unwritten understand-
ings by confining our review only to the words included in
the agreement. But because the 2018 CBA lacks a zipper
clause and because the evidence of the parties’ intent is con-
tested (as outlined above), the Union believes the arbitrator
gets to decide what the parties agreed to. We find this argu-
ment persuasive.
    A zipper clause “state[s] that the parties have had the op-
portunity to bargain over all mandatory subjects of bargain-
ing and that they waive their right to bargain over such mat-
ters during the term of the agreement.” In re Twinbrook OpCo,

nature of the question presented. In each case we look to the language of
the arbitration clause at issue and compare it to the language of the dis-
puted grievance. We must be vigilant, then, not to let the factual circum-
stances (or indicators) in one case control the arbitrability analysis in an-
other.
No. 23-1718                                                  15

LLC, No. 06–CA–283709, 

, at *2 n.4 (N.L.R.B.
Dec. 28, 2023). We have explained that zipper clauses prevent
grievances based on “unwritten promises.” Yates v. City of
Chi., 

, 910 (7th Cir. 2023).
    The lack of a zipper clause in this case makes the Union’s
argument that Sysco “promised and agreed to pay the [SERB]
in an effort to convince the employees to withdraw from Cen-
tral States and enroll in its pension plan,” and that “no
changes were made in the 2018 Agreement to the [SERB]”
more plausible. We note this argument here not to comment
on the merits of the Union’s claim—that is decidedly not our
province—but instead to demonstrate once more how, based
on the disputed evidence bearing on the question of arbitra-
bility, we cannot conclude that Sysco has presented “the most
forceful evidence of a purpose to exclude [a] claim from arbi-
tration.” Warrior & Gulf, 363 U.S. at 585.
                              III
    Because the Union’s grievance falls within the scope of the
arbitration clause on its face and because we cannot say “with
positive assurance that the arbitration clause is not suscepti-
ble of an interpretation that covers the asserted dispute,” id.
at 582–83, this grievance must be sent to arbitration. The judg-
ment of the district court is REVERSED.