diff --git a/docs/.vitepress/modules/posthog.ts b/docs/.vitepress/modules/posthog.ts
index 890821d65..a77d72bd6 100644
--- a/docs/.vitepress/modules/posthog.ts
+++ b/docs/.vitepress/modules/posthog.ts
@@ -1,9 +1,12 @@
 import posthog from 'posthog-js'
 
-import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY_DOCS } from '../../../posthog.config'
+import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY } from '../../../posthog.config'
 
 if (!import.meta.env.DEV) {
-  posthog.init(POSTHOG_PROJECT_KEY_DOCS, {
+  posthog.init(POSTHOG_PROJECT_KEY, {
     ...DEFAULT_POSTHOG_CONFIG,
   })
+  // Tag docs-site traffic so it can be told apart from the app surfaces
+  // inside the shared project.
+  posthog.register({ surface: 'docs' })
 }
diff --git a/packages/stage-ui/src/stores/analytics/posthog.ts b/packages/stage-ui/src/stores/analytics/posthog.ts
index 140cb0a9f..2f5f64104 100644
--- a/packages/stage-ui/src/stores/analytics/posthog.ts
+++ b/packages/stage-ui/src/stores/analytics/posthog.ts
@@ -7,21 +7,23 @@ import { isStageCapacitor, isStageTamagotchi } from '@proj-airi/stage-shared'
 import {
   DEFAULT_POSTHOG_CONFIG,
   POSTHOG_ENABLED,
-  POSTHOG_PROJECT_KEY_DESKTOP,
-  POSTHOG_PROJECT_KEY_POCKET,
-  POSTHOG_PROJECT_KEY_WEB,
+  POSTHOG_PROJECT_KEY,
 } from '../../../../../posthog.config'
 
 let posthogInitialized = false
 
-function getPosthogProjectKey(): string {
+// All AIRI surfaces (web, desktop, mobile) capture into a single PostHog
+// project. The platform is carried on every event via the `surface` super
+// property (registered at init), so cross-platform funnels live in one
+// project instead of being split across per-platform projects.
+function currentSurface(): 'web' | 'mobile' | 'electron' {
   if (isStageTamagotchi())
-    return POSTHOG_PROJECT_KEY_DESKTOP
+    return 'electron'
 
   if (isStageCapacitor())
-    return POSTHOG_PROJECT_KEY_POCKET
+    return 'mobile'
 
-  return POSTHOG_PROJECT_KEY_WEB
+  return 'web'
 }
 
 export function isPosthogAvailableInBuild(): boolean {
@@ -35,10 +37,13 @@ export function ensurePosthogInitialized(enabled: boolean): boolean {
   if (posthogInitialized)
     return true
 
-  posthog.init(getPosthogProjectKey(), {
+  posthog.init(POSTHOG_PROJECT_KEY, {
     ...DEFAULT_POSTHOG_CONFIG,
     opt_out_capturing_by_default: !enabled,
   })
+  // Tag every event (including autocapture / pageview) with the platform so
+  // the single project can still be broken down by web / desktop / mobile.
+  posthog.register({ surface: currentSurface() })
   posthogInitialized = true
   return true
 }
diff --git a/posthog.config.ts b/posthog.config.ts
index de9c1588f..573c21519 100644
--- a/posthog.config.ts
+++ b/posthog.config.ts
@@ -12,22 +12,11 @@ function isEnvFlagEnabled(value: string | undefined): boolean {
 // For Release workflows set `VITE_ENABLE_POSTHOG=true`.
 export const POSTHOG_ENABLED = isEnvFlagEnabled(import.meta.env.VITE_ENABLE_POSTHOG)
 
-export const POSTHOG_PROJECT_KEY_WEB
-  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_WEB
-    ?? 'phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9' // cspell:disable-line
-
-export const POSTHOG_PROJECT_KEY_DESKTOP
-  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_DESKTOP
-    ?? 'phc_rljw376z5gt6vXJlc3sTr7hFbXodciY9THEQXIRnW53'// cspell:disable-line
-
-// FIXME: Using the same key for 'web' for now.
-export const POSTHOG_PROJECT_KEY_POCKET
-  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_POCKET
-    ?? 'phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9' // cspell:disable-line
-
-// FIXME: Using the same key for 'web' for now.
-export const POSTHOG_PROJECT_KEY_DOCS
-  = import.meta.env.VITE_POSTHOG_PROJECT_KEY_DOCS
+// Single PostHog project for every AIRI surface (web / desktop / mobile).
+// Platforms are told apart by the `surface` super property set at init, not
+// by routing to separate per-platform projects.
+export const POSTHOG_PROJECT_KEY
+  = import.meta.env.VITE_POSTHOG_PROJECT_KEY
     ?? 'phc_pzjziJjrVZpa9SqnQqq0QEKvkmuCPH7GDTA6TbRTEf9' // cspell:disable-line
 
 export const DEFAULT_POSTHOG_CONFIG = {
diff --git a/vite-env.d.ts b/vite-env.d.ts
index 11dc7cd1d..27e806e4b 100644
--- a/vite-env.d.ts
+++ b/vite-env.d.ts
@@ -4,10 +4,7 @@ interface ImportMetaEnv {
   readonly VITE_DISABLE_FLUX_PURCHASE?: string
   readonly VITE_DISABLE_CUSTOM_PROVIDERS?: string
   readonly VITE_ENABLE_POSTHOG?: string
-  readonly VITE_POSTHOG_PROJECT_KEY_WEB?: string
-  readonly VITE_POSTHOG_PROJECT_KEY_DESKTOP?: string
-  readonly VITE_POSTHOG_PROJECT_KEY_POCKET?: string
-  readonly VITE_POSTHOG_PROJECT_KEY_DOCS?: string
+  readonly VITE_POSTHOG_PROJECT_KEY?: string
 }
 
 interface ImportMeta {