From 93a262d185fcba2d919692c32e88ce0f97a9ec98 Mon Sep 17 00:00:00 2001
From: Joshen Lim <joshenlimek@gmail.com>
Date: Tue, 29 Sep 2026 16:34:03 +0800
Subject: [PATCH] Check region selection for project creation (#51012)

## Context

Previously added telemetry for `selectedRegionOption` and
`selectedRegionOptionType`
[here](https://github.com/supabase/supabase/issues/50851) if the best
available region option is available for users

Opting to extend this telemetry (still just for Free plan orgs)
irregardless if best available region was selected and include
`initialRecommendedRegion`

Main thing to understand is what regions users are spinning projects up
in outside of the recommended option

## To test
- [ ] Verify the telemetry network request after creating projects
- [ ] Non-free plan: Telemetry request doesn't have
`initialRecommendedRegion` in the payload
- [ ] Free plan: Telemetry request has `initialRecommendedRegion` in the
payload
- Sends correctly if best available region option is available (default
behaviour for staging)
- Sends correctly if best available region option is NOT available
(override with dev tools the configcat flag)
---
 .../ProjectCreation/ProjectCreationForm.tsx   | 19 ++++++++++++++++-
 packages/common/telemetry-constants.ts        | 21 ++++++++++++++++---
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/apps/studio/components/interfaces/ProjectCreation/ProjectCreationForm.tsx b/apps/studio/components/interfaces/ProjectCreation/ProjectCreationForm.tsx
index 0ad0e897952..dca2cafbeb7 100644
--- a/apps/studio/components/interfaces/ProjectCreation/ProjectCreationForm.tsx
+++ b/apps/studio/components/interfaces/ProjectCreation/ProjectCreationForm.tsx
@@ -152,6 +152,9 @@ export const ProjectCreationForm = ({
     showBestAvailableRegionFeature && showBestAvailableRegionFlag && isFreePlan
   const [isBestAvailableSelected, setIsBestAvailableSelected] = useState(false)
 
+  const shouldTrackRegionRecommendation = isFreePlan && showBestAvailableRegionFeature
+  const initialRecommendedRegionRef = useRef<string | undefined>(undefined)
+
   // Read the raw flag for telemetry — coerce-undefined-to-false would record false for
   // users whose flags haven't loaded yet. The raw value preserves undefined (omitted from
   // PostHog) so we only record an actual value (boolean true/false, or a variant string
@@ -302,6 +305,16 @@ export const ProjectCreationForm = ({
     ? availableRegionsData?.recommendations.smartGroup.name
     : ''
 
+  if (
+    initialRecommendedRegionRef.current === undefined &&
+    flagsLoaded &&
+    shouldTrackRegionRecommendation
+  ) {
+    initialRecommendedRegionRef.current = showBestAvailableRegionOption
+      ? 'best_available'
+      : recommendedSmartRegion || undefined
+  }
+
   const fixedDefaultRegion = PROVIDERS[selectedCloudProvider].default_region.displayName
   const regionError = smartRegionEnabled ? availableRegionsError : defaultRegionError
   const defaultRegion = resolveDefaultDbRegion({
@@ -374,7 +387,11 @@ export const ProjectCreationForm = ({
           ...(dataApiRevokeOnCreateDefaultFlag !== undefined && {
             dataApiRevokeOnCreateDefaultEnabled: dataApiRevokeOnCreateDefaultFlag,
           }),
-          ...(showBestAvailableRegionOption && { selectedRegionOption, selectedRegionOptionType }),
+          ...(shouldTrackRegionRecommendation && {
+            selectedRegionOption,
+            selectedRegionOptionType,
+            initialRecommendedRegion: initialRecommendedRegionRef.current,
+          }),
         },
         {
           project: res.ref,
diff --git a/packages/common/telemetry-constants.ts b/packages/common/telemetry-constants.ts
index dbddceff257..473b6b7169f 100644
--- a/packages/common/telemetry-constants.ts
+++ b/packages/common/telemetry-constants.ts
@@ -450,9 +450,12 @@ export interface ProjectCreationSimpleVersionSubmittedEvent {
      */
     dataApiRevokeOnCreateDefaultEnabled?: boolean | string
     /**
-     * Which region option was submitted. Only present when the "Best available region" option
-     * was shown to the user (see `showBestAvailableRegionOption` in RegionSelector.tsx); omitted
-     * entirely for users who never saw that option.
+     * Which region option was submitted. Only present for the region-recommendation experiment's
+     * eligible cohort (free plan + `project_creation:show_best_available_region` feature enabled —
+     * see `shouldTrackRegionRecommendation` in ProjectCreationForm.tsx). This is cohort-level
+     * eligibility, not "the option was shown" — it's present for both the PostHog flag's control
+     * and test arms so the two can be compared; omitted entirely outside the cohort (e.g. paid
+     * plans, or providers like AWS_NIMBUS where the feature is disabled).
      * 'best_available' = the "Best available region" shortcut was used
      * otherwise = the name of the region that was directly selected (e.g. 'Americas', 'ap-southeast-1')
      */
@@ -464,6 +467,18 @@ export interface ProjectCreationSimpleVersionSubmittedEvent {
      * 'specific' = picked from the "Specific regions" list
      */
     selectedRegionOptionType?: 'general' | 'specific'
+    /**
+     * The region that was recommended/defaulted to on initial render, before any user
+     * interaction. Present under the same cohort gate as `selectedRegionOption`. Frozen the
+     * first time it's known, so a later refetch (e.g. switching cloud provider or instance size)
+     * doesn't overwrite what was actually shown to the user initially.
+     * 'best_available' = the user was in the PostHog flag's test arm, so the form defaulted to
+     * the "Best available region" shortcut
+     * otherwise = the name of the smart-group region recommended by the `available-regions`
+     * endpoint (e.g. 'Americas'), for users in the flag's control arm
+     * undefined = no recommendation had loaded yet at submission time
+     */
+    initialRecommendedRegion?: string
   }
   groups: TelemetryGroups
 }