diff --git a/src/app/(payload)/admin/importMap.js b/src/app/(payload)/admin/importMap.js
index ff5af9b..ebdc4e2 100644
--- a/src/app/(payload)/admin/importMap.js
+++ b/src/app/(payload)/admin/importMap.js
@@ -7,6 +7,7 @@ import { HeadingFeatureClient as HeadingFeatureClient_e70f5e05f09f93e00b997edb1e
 import { default as default_d9c22b951ac6762f436db59b889da382 } from '@/components/admin/awards/CommendationColorField'
 import { default as default_c3ea68702b5e5f8f2f98055e01c43c8d } from '@/components/admin/awards/RibbonDesigner'
 import { default as default_2f2033acccb3be245f1a85f7b4271dac } from '@/components/admin/awards/MedalDesigner'
+import { default as default_4b88a624e9f0b376cffcc6814d459adb } from '@/components/admin/assignments/AssignmentMembersField'
 import { default as default_0edde40a6ccd30c893b1227360f69360 } from '@/components/static/TickDurationDescription'
 import { default as default_2d468cc5cf0b647ffca3201592c20825 } from '@/components/static/WarningMessage'
 import { default as default_7fa52484aec46e988e9cfb5e86c0c759 } from '@/components/admin/narrative-flow/NarrativeFlowEditor'
@@ -32,6 +33,7 @@ export const importMap = {
   "@/components/admin/awards/CommendationColorField#default": default_d9c22b951ac6762f436db59b889da382,
   "@/components/admin/awards/RibbonDesigner#default": default_c3ea68702b5e5f8f2f98055e01c43c8d,
   "@/components/admin/awards/MedalDesigner#default": default_2f2033acccb3be245f1a85f7b4271dac,
+  "@/components/admin/assignments/AssignmentMembersField#default": default_4b88a624e9f0b376cffcc6814d459adb,
   "@/components/static/TickDurationDescription#default": default_0edde40a6ccd30c893b1227360f69360,
   "@/components/static/WarningMessage#default": default_2d468cc5cf0b647ffca3201592c20825,
   "@/components/admin/narrative-flow/NarrativeFlowEditor#default": default_7fa52484aec46e988e9cfb5e86c0c759,
diff --git a/src/app/(payload)/custom.scss b/src/app/(payload)/custom.scss
index ead5dda..03106d9 100644
--- a/src/app/(payload)/custom.scss
+++ b/src/app/(payload)/custom.scss
@@ -22,4 +22,4 @@
 
 @layer utilities {
   @import 'tailwindcss/utilities.css';
-}
\ No newline at end of file
+}
diff --git a/src/collections/users/Assignments.ts b/src/collections/users/Assignments.ts
index e4d84c8..e76b463 100644
--- a/src/collections/users/Assignments.ts
+++ b/src/collections/users/Assignments.ts
@@ -88,6 +88,9 @@ export const Assignments: CollectionConfig = {
       relationTo: "users",
       hasMany: true,
       admin: {
+        components: {
+          Field: "@/components/admin/assignments/AssignmentMembersField",
+        },
         description: "Add individuals as members of this team/assignment.",
       },
     },
diff --git a/src/components/admin/assignments/AssignmentMembersField.tsx b/src/components/admin/assignments/AssignmentMembersField.tsx
new file mode 100644
index 0000000..a75b99c
--- /dev/null
+++ b/src/components/admin/assignments/AssignmentMembersField.tsx
@@ -0,0 +1,231 @@
+"use client";
+
+import {
+  ConfirmationModal,
+  RelationshipInput,
+  toast,
+  useDocumentInfo,
+  useField,
+  useModal,
+} from "@payloadcms/ui";
+import type { RelationshipFieldClientComponent } from "payload";
+import { useCallback, useId, useMemo, useState } from "react";
+
+type ExistingAssignment = {
+  id: number;
+  name: string;
+};
+
+type PendingSelection = {
+  value: Array<{ relationTo: string; value: number | string }>;
+  conflicts: ExistingAssignment[];
+};
+
+const getId = (value: number | string | { value?: number | string }) =>
+  typeof value === "object" ? value.value : value;
+
+/**
+ * Keeps Payload's relationship picker, but asks before putting an operator in
+ * more than one assignment. “Replace” updates existing assignments through
+ * the admin API; “Add as new” only changes this unsaved assignment form.
+ */
+const AssignmentMembersField: RelationshipFieldClientComponent = (props) => {
+  const { field, path: pathFromProps, readOnly, validate } = props;
+  const { id: documentId } = useDocumentInfo();
+  const { openModal } = useModal();
+  const modalSlug = useId().replaceAll(":", "");
+  const {
+    customComponents: { AfterInput, BeforeInput, Description, Error: ErrorComponent, Label } = {},
+    disabled,
+    filterOptions,
+    initialValue,
+    path,
+    setValue,
+    showError,
+    value: currentValue,
+  } = useField<Array<number | string>>({
+    potentiallyStalePath: pathFromProps,
+    // RelationshipInput performs the field validation itself. Its validation
+    // type is intentionally broader than useField's internal callback type.
+  });
+  const [pending, setPending] = useState<PendingSelection | null>(null);
+
+  const {
+    admin: {
+      allowCreate = true,
+      allowEdit = true,
+      appearance = "select",
+      className,
+      description,
+      isSortable = true,
+      placeholder,
+      sortOptions,
+    } = {},
+    hasMany,
+    label,
+    localized,
+    relationTo,
+    required,
+  } = field;
+
+  const relation = typeof relationTo === "string" ? relationTo : relationTo[0];
+  const selectedIds = useMemo(
+    () =>
+      Array.isArray(currentValue) ? currentValue.map((item) => getId(item)).filter(Boolean) : [],
+    [currentValue],
+  );
+
+  const applyValue = useCallback(
+    (next: Array<{ relationTo: string; value: number | string }>) => {
+      setValue(next.map((item) => item.value));
+    },
+    [setValue],
+  );
+
+  const handleChange = useCallback(
+    async (next: Array<{ relationTo: string; value: number | string }>) => {
+      const added = next.filter((item) => !selectedIds.includes(item.value));
+      if (added.length === 0) {
+        applyValue(next);
+        return;
+      }
+
+      const responses = await Promise.all(
+        added.map(async (item) => {
+          const query = new URLSearchParams({
+            depth: "0",
+            limit: "100",
+            "where[or][0][members][contains]": String(item.value),
+            "where[or][1][leader][equals]": String(item.value),
+          });
+          const response = await fetch(`/api/assignments?${query.toString()}`);
+          if (!response.ok) throw new Error("Could not check existing assignments.");
+          return (await response.json()).docs as ExistingAssignment[];
+        }),
+      );
+      const conflicts = responses.flat().filter((assignment, index, assignments) => {
+        if (String(assignment.id) === String(documentId)) return false;
+        return assignments.findIndex((item) => item.id === assignment.id) === index;
+      });
+
+      if (conflicts.length > 0) {
+        setPending({ value: next, conflicts });
+        openModal(modalSlug);
+      } else {
+        applyValue(next);
+      }
+    },
+    [applyValue, documentId, modalSlug, openModal, selectedIds],
+  );
+
+  const replaceAssignments = async () => {
+    if (!pending) return;
+    try {
+      for (const assignment of pending.conflicts) {
+        const response = await fetch(`/api/assignments/${assignment.id}?depth=0`);
+        if (!response.ok) throw new Error("Could not load an existing assignment.");
+        const existing = await response.json();
+        const members = (existing.members ?? [])
+          .map((member: number | { id?: number }) =>
+            typeof member === "object" ? member.id : member,
+          )
+          .filter(
+            (member: number | undefined) =>
+              member !== undefined &&
+              !pending.value.some((item) => String(item.value) === String(member)),
+          );
+        const leaderId =
+          typeof existing.leader === "object" ? existing.leader?.id : existing.leader;
+        const update = await fetch(`/api/assignments/${assignment.id}`, {
+          method: "PATCH",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({
+            members,
+            ...(pending.value.some((item) => String(item.value) === String(leaderId))
+              ? { leader: null }
+              : {}),
+          }),
+        });
+        if (!update.ok) throw new Error(`Could not remove the operator from ${assignment.name}.`);
+      }
+      applyValue(pending.value);
+    } catch (error) {
+      toast.error(
+        error instanceof Error ? error.message : "Could not replace the existing assignment.",
+      );
+    }
+    setPending(null);
+  };
+
+  return (
+    <>
+      <RelationshipInput
+        AfterInput={AfterInput}
+        allowCreate={allowCreate}
+        allowEdit={allowEdit}
+        appearance={appearance}
+        BeforeInput={BeforeInput}
+        className={className}
+        Description={Description}
+        description={description}
+        Error={ErrorComponent}
+        filterOptions={filterOptions}
+        Label={Label}
+        label={label}
+        localized={localized}
+        maxResultsPerRequest={10}
+        isSortable={isSortable}
+        path={path}
+        placeholder={placeholder}
+        readOnly={readOnly || disabled}
+        relationTo={[relation]}
+        required={required}
+        showError={showError}
+        sortOptions={sortOptions}
+        hasMany={true}
+        initialValue={
+          Array.isArray(initialValue)
+            ? initialValue.map((value) => ({ relationTo: relation, value }))
+            : undefined
+        }
+        value={
+          Array.isArray(currentValue)
+            ? currentValue.map((value) => ({ relationTo: relation, value }))
+            : null
+        }
+        onChange={handleChange}
+      />
+
+      <ConfirmationModal
+        body={
+          <>
+            <p>
+              This operator is already assigned to{" "}
+              {pending?.conflicts.length === 1 ? "an assignment" : "these assignments"}:
+            </p>
+            <ul>
+              {pending?.conflicts.map((assignment) => (
+                <li key={assignment.id}>{assignment.name}</li>
+              ))}
+            </ul>
+            <p>
+              Replace the existing assignment, or add this operator to the new assignment as well?
+            </p>
+          </>
+        }
+        cancelLabel="Add as new"
+        confirmingLabel="Replacing..."
+        confirmLabel="Replace existing"
+        heading="Operator already assigned"
+        modalSlug={modalSlug}
+        onCancel={() => {
+          if (pending) applyValue(pending.value);
+          setPending(null);
+        }}
+        onConfirm={replaceAssignments}
+      />
+    </>
+  );
+};
+
+export default AssignmentMembersField;