feat(webapp): admin UI for feature flag overrides (#3291)

Adds a dialog to the admin orgs page for viewing and editing per-org
feature flag overrides. Flags are introspected from the catalog so the
UI stays in sync with available flags automatically. Also adds a new tab
for global flags.

Refactors featureFlags.server.ts to split catalog definition (shared)
from server-only runtime (flags(), makeSetMultipleFlags). The shared
module exports flag metadata and validation so both the UI and API
routes can use it without pulling in server dependencies.

Author: nicktrn

.server-changes/admin-feature-flags-dialog.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: feature
+---
+
+Add admin UI for viewing and editing feature flags (org-level overrides and global defaults).

apps/webapp/CLAUDE.md

@@ -98,3 +98,12 @@ The `app/v3/` directory name is misleading - most code is actively used by V2. O
 - `app/v3/sharedSocketConnection.ts`
 
 Some services (e.g., `cancelTaskRun.server.ts`, `batchTriggerV3.server.ts`) branch on `RunEngineVersion` to support both V1 and V2. When editing these, only modify V2 code paths.
+
+## Prisma Query Patterns
+
+- **Always use `findFirst` instead of `findUnique`.** Prisma's `findUnique` has an implicit DataLoader that batches concurrent calls into a single `IN` query. This batching cannot be disabled and has active bugs even in Prisma 6.x: uppercase UUIDs returning null (#25484, confirmed 6.4.1), composite key SQL correctness issues (#22202), and 5-10x worse performance than manual DataLoader (#6573, open since 2021). `findFirst` is never batched and avoids this entire class of issues.
+
+## React Patterns
+
+- Only use `useCallback`/`useMemo` for context provider values, expensive derived data that is a dependency elsewhere, or stable refs required by a dependency array. Don't wrap ordinary event handlers or trivial computations.
+- Use named constants for sentinel/placeholder values (e.g. `const UNSET_VALUE = "__unset__"`) instead of raw string literals scattered across comparisons.

apps/webapp/app/components/admin/FeatureFlagsDialog.tsx

@@ -0,0 +1,290 @@
+import { useFetcher } from "@remix-run/react";
+import { useEffect, useState } from "react";
+import stableStringify from "json-stable-stringify";
+import {
+  Dialog,
+  DialogContent,
+  DialogHeader,
+  DialogDescription,
+  DialogFooter,
+} from "~/components/primitives/Dialog";
+import { Button } from "~/components/primitives/Buttons";
+import { Callout } from "~/components/primitives/Callout";
+import { LockClosedIcon } from "@heroicons/react/20/solid";
+import { CheckboxWithLabel } from "~/components/primitives/Checkbox";
+import { cn } from "~/utils/cn";
+import { FEATURE_FLAG, ORG_LOCKED_FLAGS, type FlagControlType } from "~/v3/featureFlags";
+import {
+  UNSET_VALUE,
+  BooleanControl,
+  EnumControl,
+  StringControl,
+  WorkerGroupControl,
+  type WorkerGroup,
+} from "./FlagControls";
+
+type LoaderData = {
+  org: { id: string; title: string; slug: string };
+  orgFlags: Record<string, unknown>;
+  globalFlags: Record<string, unknown>;
+  controlTypes: Record<string, FlagControlType>;
+  workerGroupName?: string;
+  workerGroups?: WorkerGroup[];
+  isManagedCloud?: boolean;
+};
+
+type ActionData = {
+  success?: boolean;
+  error?: string;
+};
+
+type FeatureFlagsDialogProps = {
+  orgId: string | null;
+  orgTitle: string;
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+};
+
+export function FeatureFlagsDialog({
+  orgId,
+  orgTitle,
+  open,
+  onOpenChange,
+}: FeatureFlagsDialogProps) {
+  const loadFetcher = useFetcher<LoaderData>();
+  const saveFetcher = useFetcher<ActionData>();
+
+  const [overrides, setOverrides] = useState<Record<string, unknown>>({});
+  const [initialOverrides, setInitialOverrides] = useState<Record<string, unknown>>({});
+  const [saveError, setSaveError] = useState<string | null>(null);
+  const [unlocked, setUnlocked] = useState(false);
+
+  const isLocked = (key: string) => !unlocked && ORG_LOCKED_FLAGS.includes(key);
+
+  useEffect(() => {
+    if (open && orgId) {
+      setSaveError(null);
+      setOverrides({});
+      setInitialOverrides({});
+      loadFetcher.load(`/admin/api/v2/orgs/${orgId}/feature-flags`);
+    }
+  }, [open, orgId]);
+
+  useEffect(() => {
+    if (loadFetcher.data) {
+      const loaded = loadFetcher.data.orgFlags ?? {};
+      setOverrides({ ...loaded });
+      setInitialOverrides({ ...loaded });
+    }
+  }, [loadFetcher.data]);
+
+  useEffect(() => {
+    if (saveFetcher.data?.success) {
+      onOpenChange(false);
+    } else if (saveFetcher.data?.error) {
+      setSaveError(saveFetcher.data.error);
+    }
+  }, [saveFetcher.data]);
+
+  const isDirty = stableStringify(overrides) !== stableStringify(initialOverrides);
+
+  const setFlagValue = (key: string, value: unknown) => {
+    setOverrides((prev) => ({ ...prev, [key]: value }));
+  };
+
+  const unsetFlag = (key: string) => {
+    setOverrides((prev) => {
+      const next = { ...prev };
+      delete next[key];
+      return next;
+    });
+  };
+
+  const handleSave = () => {
+    if (!orgId) return;
+    const body = Object.keys(overrides).length === 0 ? null : overrides;
+    saveFetcher.submit(JSON.stringify(body), {
+      method: "POST",
+      action: `/admin/api/v2/orgs/${orgId}/feature-flags`,
+      encType: "application/json",
+    });
+  };
+
+  const data = loadFetcher.data;
+  const isLoading = loadFetcher.state === "loading";
+  const isSaving = saveFetcher.state === "submitting";
+
+  const jsonPreview =
+    Object.keys(overrides).length === 0 ? "null" : JSON.stringify(overrides, null, 2);
+
+  const sortedFlagKeys = data ? Object.keys(data.controlTypes).sort() : [];
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="sm:max-w-lg">
+        <DialogHeader>Feature flags - {orgTitle}</DialogHeader>
+        <DialogDescription>
+          Org-level overrides. Unset flags inherit from global defaults.
+        </DialogDescription>
+
+        {data && (
+          <div className={data.isManagedCloud ? "cursor-not-allowed" : undefined}>
+            <CheckboxWithLabel
+              variant="simple/small"
+              label={
+                data.isManagedCloud
+                  ? "Unlock read-only flags (only in unmanaged cloud)"
+                  : "Unlock read-only flags"
+              }
+              defaultChecked={unlocked}
+              onChange={setUnlocked}
+              disabled={data.isManagedCloud}
+              className={data.isManagedCloud ? "pointer-events-none" : undefined}
+            />
+          </div>
+        )}
+
+        <div className="max-h-[60vh] overflow-y-auto">
+          {isLoading ? (
+            <div className="py-8 text-center text-sm text-text-dimmed">Loading flags...</div>
+          ) : data ? (
+            <div className="flex flex-col gap-1.5">
+              {sortedFlagKeys.map((key) => {
+                const control = data.controlTypes[key];
+                const locked = isLocked(key);
+                const globalValue = data.globalFlags[key as keyof typeof data.globalFlags];
+                const isWorkerGroup = key === FEATURE_FLAG.defaultWorkerInstanceGroupId;
+                const globalDisplay =
+                  isWorkerGroup && data.workerGroupName && globalValue !== undefined
+                    ? `${data.workerGroupName} (${String(globalValue).slice(0, 8)}...)`
+                    : globalValue !== undefined
+                      ? String(globalValue)
+                      : "unset";
+
+                if (locked) {
+                  return (
+                    <div
+                      key={key}
+                      className="flex items-center justify-between rounded-md border border-transparent bg-charcoal-750 px-3 py-2.5"
+                      title="Global-level setting - not editable per org"
+                    >
+                      <div className="min-w-0 flex-1">
+                        <div className="truncate text-sm text-text-dimmed">{key}</div>
+                        <div className="text-xs text-charcoal-400">global: {globalDisplay}</div>
+                      </div>
+                      <LockClosedIcon className="size-4 text-charcoal-500" />
+                    </div>
+                  );
+                }
+
+                const isOverridden = key in overrides;
+
+                return (
+                  <div
+                    key={key}
+                    className={cn(
+                      "flex items-center justify-between rounded-md border px-3 py-2.5",
+                      isOverridden
+                        ? "border-indigo-500/20 bg-indigo-500/5"
+                        : "border-transparent bg-charcoal-750"
+                    )}
+                  >
+                    <div className="min-w-0 flex-1">
+                      <div
+                        className={cn(
+                          "truncate text-sm",
+                          isOverridden ? "text-text-bright" : "text-text-dimmed"
+                        )}
+                      >
+                        {key}
+                      </div>
+                      <div className="text-xs text-charcoal-400">global: {globalDisplay}</div>
+                    </div>
+
+                    <div className="flex items-center gap-2">
+                      <Button
+                        variant="minimal/small"
+                        onClick={() => unsetFlag(key)}
+                        className={cn(!isOverridden && "invisible")}
+                      >
+                        unset
+                      </Button>
+
+                      {isWorkerGroup && data.workerGroups ? (
+                        <WorkerGroupControl
+                          value={isOverridden ? (overrides[key] as string) : undefined}
+                          workerGroups={data.workerGroups as WorkerGroup[]}
+                          onChange={(val) => {
+                            if (val === UNSET_VALUE) {
+                              unsetFlag(key);
+                            } else {
+                              setFlagValue(key, val);
+                            }
+                          }}
+                          dimmed={!isOverridden}
+                        />
+                      ) : control.type === "boolean" ? (
+                        <BooleanControl
+                          value={isOverridden ? (overrides[key] as boolean) : undefined}
+                          onChange={(val) => setFlagValue(key, val)}
+                          dimmed={!isOverridden}
+                        />
+                      ) : control.type === "enum" ? (
+                        <EnumControl
+                          value={isOverridden ? (overrides[key] as string) : undefined}
+                          options={control.options}
+                          onChange={(val) => {
+                            if (val === UNSET_VALUE) {
+                              unsetFlag(key);
+                            } else {
+                              setFlagValue(key, val);
+                            }
+                          }}
+                          dimmed={!isOverridden}
+                        />
+                      ) : control.type === "string" ? (
+                        <StringControl
+                          value={isOverridden ? (overrides[key] as string) : ""}
+                          onChange={(val) => {
+                            if (val === "") {
+                              unsetFlag(key);
+                            } else {
+                              setFlagValue(key, val);
+                            }
+                          }}
+                          dimmed={!isOverridden}
+                        />
+                      ) : null}
+                    </div>
+                  </div>
+                );
+              })}
+            </div>
+          ) : null}
+        </div>
+
+        {data && (
+          <details className="mt-2">
+            <summary className="cursor-pointer text-xs text-text-dimmed hover:text-text-bright">
+              Preview JSON
+            </summary>
+            <pre className="mt-1 max-h-40 overflow-auto rounded bg-charcoal-800 p-2 text-xs text-text-dimmed">
+              {jsonPreview}
+            </pre>
+          </details>
+        )}
+
+        {saveError && <Callout variant="error">{saveError}</Callout>}
+
+        <DialogFooter>
+          <Button variant="tertiary/small" onClick={() => onOpenChange(false)}>
+            Cancel
+          </Button>
+          <Button variant="primary/small" onClick={handleSave} disabled={!isDirty || isSaving}>
+            {isSaving ? "Saving..." : "Save changes"}
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}