From 0e4dc69ec0d4dd45dd142f8e4ddaf60919d47e0f Mon Sep 17 00:00:00 2001
From: RainbowBird <git@luoling.moe>
Date: Fri, 10 Jul 2026 13:54:23 +0800
Subject: [PATCH] fix(analytics): normalize PostHog event semantics (#2041)

---
 .../docs/ai-context/metrics-ownership.md      |  18 +-
 .../product-analytics-dashboard-setup.md      |  26 +-
 .../product-analytics-instrumentation.md      |  43 +--
 .../posthog-forwarding-and-pageview.md        |   2 +-
 .../verifications/product-analytics-smoke.md  |  58 +++-
 .../services/domain/product-events.test.ts    |   4 +-
 .../src/services/domain/product-events.ts     |   8 +-
 .../src/modules/analytics.test.ts             |  48 ++++
 apps/ui-server-auth/src/modules/analytics.ts  |  21 +-
 apps/ui-server-auth/src/pages/sign-in.vue     |   6 +-
 docs/.vitepress/modules/posthog.ts            |   2 +-
 .../runtime/chat-orchestrator-runtime.test.ts |  91 +++++-
 .../src/runtime/chat-orchestrator-runtime.ts  | 112 ++++++--
 .../stage-pages/src/pages/settings/flux.vue   |  14 +-
 .../src/composables/use-analytics.test.ts     | 259 +++++++++---------
 .../stage-ui/src/composables/use-analytics.ts | 223 +++++++--------
 .../stage-ui/src/stores/analytics/index.ts    |   8 +-
 .../src/stores/analytics/posthog.test.ts      |  35 +++
 .../stage-ui/src/stores/analytics/posthog.ts  |   4 +-
 .../stage-ui/src/stores/chat.contract.test.ts | 143 +++++++++-
 packages/stage-ui/src/stores/chat.ts          |  89 +++---
 packages/stage-ui/src/stores/providers.ts     |   4 +-
 posthog.config.ts                             |   2 +-
 23 files changed, 808 insertions(+), 412 deletions(-)
 create mode 100644 apps/ui-server-auth/src/modules/analytics.test.ts
 create mode 100644 packages/stage-ui/src/stores/analytics/posthog.test.ts

diff --git a/apps/server/docs/ai-context/metrics-ownership.md b/apps/server/docs/ai-context/metrics-ownership.md
index 18099d893..a35810136 100644
--- a/apps/server/docs/ai-context/metrics-ownership.md
+++ b/apps/server/docs/ai-context/metrics-ownership.md
@@ -112,17 +112,17 @@
 ### PostHog（前端 / 外部数据源，产品侧）
 
 已接入：
-- 前端 `posthog-js` 通过 `packages/stage-ui/src/stores/analytics/posthog.ts` 初始化，三个 app（web / desktop / pocket）按 `isStageTamagotchi()` 等选 project key
-- Server 不接入 `posthog-node`。后端产品事件写 `product_events`，Grafana 展示低基数聚合；需要 PostHog revenue/person analytics 时优先用 PostHog Stripe source connector 或离线导入，不允许在 API 请求路径同步发 PostHog。
+- 前端 `posthog-js` 通过 `packages/stage-ui/src/stores/analytics/posthog.ts` 初始化；web / desktop / pocket / auth / docs 共用一个 project key，以 `app_surface` 区分运行端。
+- Server 先把产品事实写入 `product_events`，再异步 best-effort 转发注册、支付、订阅等白名单业务事实到 PostHog；LLM / TTS per-request 事件不转发，PostHog 失败也不能影响请求主链路。
 - 前端 identity：`useSharedAnalyticsStore.initialize()` watch `authStore.isAuthenticated` 自动调 `posthog.identify(user.id)` / `reset()`
-- Conversation controls 事件的 `surface` 由 `packages/stage-ui/src/composables/use-analytics.ts` 统一按 runtime 推断，UI 调用点只传业务字段。
+- 平台统一写入 `app_surface`；`entry_surface` 只表示 `settings_flux` 这类业务入口，避免同名字段混用或覆盖 PostHog super property。
 
 已埋点：
 
 | 域 | 事件 | 来源 | 落点 | Truth |
 |---|---|---|---|---|
 | 付费漏斗 | `pricing_page_viewed` / `plan_selected` / `checkout_started` | 前端 | `packages/stage-pages/src/pages/settings/flux.vue` | PostHog |
-| 付费漏斗终点 | `payment_completed` | 后端 webhook | `product_events` + Grafana；PostHog 走 Stripe source connector/离线导入 | Postgres |
+| 付费漏斗终点 | `payment_completed` | 后端 webhook | `product_events` + Grafana，并 best-effort 转发 PostHog | Postgres |
 | Activation / Retention | `first_model_selected` / `model_switched` | 前端（consciousness store watcher） | `packages/stage-ui/src/stores/analytics/index.ts` | PostHog |
 | Retention | `character_created` | 前端 | `apps/stage-web/src/pages/settings/characters/components/CharacterDialog.vue` | PostHog |
 | Retention | `chat_session_started` | 前端 | `packages/stage-ui/src/components/scenarios/chat/components/sessions-drawer.vue` | PostHog |
@@ -131,13 +131,15 @@
 | Conversation controls | `tts_stop_clicked` | 前端 | `packages/stage-layouts/src/composables/useStopSpeakingButton.ts` | PostHog |
 | Churn | `subscription_cancelled`（带 cancellation_reason） | 外部 Stripe 数据源 | PostHog Stripe source connector | Stripe/Postgres |
 | 老事件 | `provider_card_clicked` | 前端 | `packages/stage-ui/src/composables/use-analytics.ts` | PostHog |
-| 已退役 | `first_message_sent` / `user_signed_up`（前端版） | 无生产者 | wrapper 已删除；激活口径用 `chat_activation_succeeded`，注册事实用服务端转发的 `signup_completed` | PostHog 历史数据仍在 |
+| 兼容指标 | `first_message_sent` | 前端 | 仍有生产者，仅供历史 dashboard；新激活口径使用 `chat_activation_succeeded` | PostHog |
+| 聊天轮次 | `message_send_started` / `message_sent` / `llm_*` / `message_round` / `message_round_failed` | 前端 core runtime | 以 `conversation_id` / `round_id` / `turn_index` 关联；成功和失败各有唯一终点事件 | PostHog |
+| 注册 UI | `signup_form_completed` | auth SPA | 匿名表单完成信号，不计作注册事实 | PostHog |
+| 注册事实 | `signup_completed` | Better Auth user create hook | 仅服务端生产，以 Better Auth user id 识别 | Postgres + PostHog |
 
 待埋点（API 已在 `use-analytics.ts` 暴露但调用点未接入）：
 
 | 域 | 事件 | 状态 |
 |---|---|---|
-| Activation | `user_signed_up` | 等接到 auth callback 完成事件（Better Auth 的 signUp 成功 hook） |
 | Retention | `voice_mode_activated` | 需要先在 hearing store 加显式 `enableVoiceMode` action — 当前 hearing 没有单一"用户主动启用"那一刻的 trigger，被动监听 + 录音 action 不构成 user intent 信号 |
 | Feature adoption | `flux_image_generated` | 等图片生成 feature 上线 |
 
@@ -155,7 +157,7 @@
 
 ### 阶段 1（P0 — 付费漏斗 + activation）
 
-所有 surface 共用根目录 `posthog.config.ts`（单一 project key，`surface` super property 区分端）。初始化实况：
+所有运行端共用根目录 `posthog.config.ts`（单一 project key，`app_surface` super property 区分端）。初始化实况：
 
 ```ts
 import { DEFAULT_POSTHOG_CONFIG, POSTHOG_PROJECT_KEY } from '../posthog.config'
@@ -184,7 +186,7 @@ posthog.init(import.meta.env.VITE_POSTHOG_KEY, {
 
 埋点事件清单（P0）：
 
-- 前端：`pricing_page_viewed`、`plan_selected`、`checkout_started`、`signup_completed`（ui-server-auth 邮箱注册路径）、`first_model_selected`
+- 前端：`pricing_page_viewed`、`plan_selected`、`checkout_started`、`signup_form_completed`（ui-server-auth 匿名邮箱表单里程碑）、`first_model_selected`
 - 后端：`product_events` 是事实账本；其中业务事实白名单（`signup_completed`、`payment_completed`、`subscription_started/renewed/cancelled`）由 product-events 服务经 posthog-node 转发一份到 PostHog（`apps/server/src/services/domain/product-events.ts`，distinctId = Better Auth user id）。LLM / TTS 等 per-request 事件不转发
 
 PostHog UI 配两个 funnel：
diff --git a/apps/server/docs/ai-context/product-analytics-dashboard-setup.md b/apps/server/docs/ai-context/product-analytics-dashboard-setup.md
index dadc86833..530dae32e 100644
--- a/apps/server/docs/ai-context/product-analytics-dashboard-setup.md
+++ b/apps/server/docs/ai-context/product-analytics-dashboard-setup.md
@@ -60,7 +60,7 @@ Steps:
 Breakdowns:
 
 - `provider_mode`
-- `surface`
+- `app_surface`
 
 Filters:
 
@@ -116,6 +116,26 @@ Watch for:
 - `failure_stage = model_list`
 - `failure_stage = llm_response`
 
+### Insight 2a: All Message Round Failures
+
+Type: Trends
+
+Event:
+
+- `message_round_failed`
+
+Breakdowns:
+
+- `failure_stage`
+- `error_code`
+- `provider_id`
+- `app_surface`
+
+Watch for:
+
+- Failures where `turn_index > 1`, which are intentionally outside the activation-failure series.
+- Repeated failures for the same `conversation_id` with different `round_id` values.
+
 ### Insight 3: Provider Configuration Health
 
 Type: Funnel
@@ -213,7 +233,7 @@ Breakdowns:
 
 - `stt_provider_id`
 - `error_code`
-- `surface`
+- `app_surface`
 
 ### Insight 7: Feedback And Bug Reports
 
@@ -229,7 +249,7 @@ Breakdowns:
 - `category`
 - `severity`
 - `entrypoint`
-- `surface`
+- `app_surface`
 
 Watch for:
 
diff --git a/apps/server/docs/ai-context/product-analytics-instrumentation.md b/apps/server/docs/ai-context/product-analytics-instrumentation.md
index 53555391f..74d095151 100644
--- a/apps/server/docs/ai-context/product-analytics-instrumentation.md
+++ b/apps/server/docs/ai-context/product-analytics-instrumentation.md
@@ -127,7 +127,8 @@ Grafana 当前不能回答：
 
 | Field | Values | Notes |
 |---|---|---|
-| `surface` | `web` / `desktop` / `mobile` | 所有关键前端事件必带 |
+| `app_surface` | `web` / `electron` / `mobile` / `auth` / `docs` / `server` | 所有关键事件的平台 / 运行端 |
+| `entry_surface` | `settings_flux` / `onboarding` / `chat_toolbar` 等受控枚举 | 业务入口；不得用于表示运行端 |
 | `provider_mode` | `official` / `custom` / `unknown` | 官方开箱即用 vs 用户自配置 |
 | `provider_id` | 白名单 ID | 不传 raw URL / raw key / 用户输入 |
 | `model_id` | 白名单或归一化后的 ID | 自定义模型用 `is_custom_model = true` |
@@ -147,6 +148,7 @@ Grafana 当前不能回答：
 | `chat_activation_started` | frontend | PostHog | 用户进入首次聊天路径或点击发送第一条消息前 |
 | `chat_activation_succeeded` | frontend | PostHog | 首次消息完成并看到 assistant response |
 | `chat_activation_failed` | frontend | PostHog | 首次消息未完成，包含配置、网络、鉴权、余额、模型等失败 |
+| `message_round_failed` | frontend | PostHog | 任意用户轮次在 assistant response 完成前失败；成功轮次的唯一终点仍为 `message_round` |
 | `official_provider_selected` | frontend | PostHog | 官方 Provider 被默认落地或在设置页被手动选择，记录 provider id 与是否自动选择 |
 | `second_turn_started` | frontend | PostHog | 同一会话开始第二轮对话 |
 
@@ -157,11 +159,13 @@ Grafana 当前不能回答：
 | `provider_mode` | yes | `official` / `custom` |
 | `provider_id` | yes | 归一化 ID |
 | `model_id` | yes | 归一化 ID |
-| `surface` | yes | web / desktop / mobile |
+| `app_surface` | yes | web / electron / mobile |
+| `conversation_id` | yes | 应用会话 ID；同一 conversation 的聊天事件保持一致 |
+| `round_id` | yes | 单轮关联 ID，复用该轮 user message id；同一轮所有聊天主链路事件保持一致 |
+| `turn_index` | yes | conversation 内从 `1` 开始的用户轮次；`second_turn_started` 固定为 `2` |
 | `time_to_first_message_ms` | success only | 从 app start 或 onboarding complete 到首次成功 |
 | `error_code` | failed only | 稳定错误码 |
 | `failure_stage` | failed only | `provider_config` / `model_list` / `message_send` / `llm_response` / `tts` |
-| `turn_index` | second turn only | 固定为 `2`，用于首轮成功后的二轮启动 |
 | `auto_selected` | official provider only | 官方默认 Provider 自动落地时为 `true` |
 
 推荐看板：
@@ -169,6 +173,7 @@ Grafana 当前不能回答：
 - 新用户 `chat_activation_started -> chat_activation_succeeded` 漏斗。
 - 按 `provider_mode` 拆分 activation conversion。
 - `chat_activation_failed` 按 `failure_stage` / `provider_id` 排名。
+- `message_round_failed` 按 `turn_index` / `failure_stage` / `provider_id` 排名，用于分析激活后的聊天失败。
 
 异常提醒：
 
@@ -282,14 +287,14 @@ Grafana 当前不能回答：
 | Field | Required | Notes |
 |---|---|---|
 | `stt_provider_id` | yes | 归一化 ID |
-| `surface` | yes | web / desktop / mobile |
+| `app_surface` | yes | web / electron / mobile |
 | `duration_ms` | no | 用户按住或录音时长 |
 | `error_code` | failed only | `permission_denied` / `device_unavailable` / `provider_error` / `timeout` |
 
 推荐看板：
 
 - Voice input start -> STT success funnel。
-- Permission denied rate by browser / surface。
+- Permission denied rate by browser / app surface。
 - STT failure rate by Provider。
 
 ### Feedback And Bug Reports
@@ -312,7 +317,7 @@ Grafana 当前不能回答：
 | `severity` | yes | `blocker` / `major` / `minor` / `suggestion` |
 | `user_type` | yes | `new_user` / `paid_user` / `overseas_user` / `developer_user` / `role_chat_user` / `unknown` |
 | `entrypoint` | yes | `about_update_error` / `community_manual_tag` 等低基数入口 |
-| `surface` | in-app | web / desktop / mobile |
+| `app_surface` | in-app | web / electron / mobile |
 | `provider_mode` | no | 可从最近一次配置状态补齐 |
 | `description_length_bucket` | bug report | `empty` / `short` / `medium` / `long`，不要上传正文 |
 | `include_triage_context` | bug report | 是否附带页面上下文 |
@@ -395,7 +400,7 @@ Grafana 当前不能回答：
 - `has_voice`
 - `latency_ms`
 - `error_code`
-- `surface`
+- `app_surface`
 
 看板：
 
@@ -420,7 +425,7 @@ Grafana 当前不能回答：
 - `character_type`: `built_in` / `imported` / `custom`
 - `has_voice`
 - `voice_type`
-- `surface`
+- `app_surface`
 
 看板：
 
@@ -438,7 +443,7 @@ Grafana 当前不能回答：
 
 字段：
 
-- `surface`
+- `entry_surface`（付费入口，例如 `settings_flux`；运行端使用 `app_surface`）
 - `balance_state`
 - `plan_id`
 - `currency`
@@ -457,6 +462,8 @@ Grafana 当前不能回答：
 |---|---|---|
 | `first_message_sent` | 保留历史指标 | 继续用于老 dashboard；新激活口径用 `chat_activation_succeeded` |
 | `chat_activation_started` / `chat_activation_succeeded` / `chat_activation_failed` | 新核心 activation 口径 | 用来回答“用户能不能正常开始聊天” |
+| `message_send_started` / `message_sent` / `llm_*` / `message_round` / `message_round_failed` | 聊天主链路 | 共享 `conversation_id` / `round_id` / `turn_index`；`message_round` 和 `message_round_failed` 分别是单轮成功 / 失败的唯一终点；不再重复发送 `chat_started`、`assistant_response_completed`、`chat_failed` 或 chat 的通用 `feature_used` 别名 |
+| `signup_form_completed` / `signup_completed` | UI 里程碑 / 注册事实 | 前者可匿名；后者只由服务端按 Better Auth user id 发送，禁止复用同名客户端事件 |
 | `provider_card_clicked` | 保留入口点击 | 不等于配置成功；成功 / 失败看 `provider_config_succeeded` / `provider_config_failed` |
 | `first_model_selected` / `model_switched` | 保留模型选择行为 | 配置链路和模型列表健康看 `model_list_loaded` / `model_list_failed` |
 | `stt_started` / `stt_succeeded` / `stt_failed` | 保留 STT Provider 结果 | 权限和设备问题用新增 `microphone_*` / `audio_device_unavailable` 拆开 |
@@ -495,7 +502,8 @@ PostHog 线上已经能看到 `model` / `model_id` 存在自由文本风险。
 | `voice_pack_id` | medium | 只进 PostHog / Postgres，不进 Prometheus label |
 | `error_code` | low | enum |
 | `source` | low | enum |
-| `surface` | low | enum |
+| `app_surface` | low | runtime enum |
+| `entry_surface` | low | 低基数业务入口 enum；不得复用为 runtime |
 
 Prometheus label 不放 `user_id`、`session_id`、`voice_pack_id`、自定义模型名、自定义音色名。
 
@@ -673,7 +681,7 @@ Prometheus label 不放 `user_id`、`session_id`、`voice_pack_id`、自定义
 
 - Top failing providers: <list>
 - Top failing error codes: <list>
-- Rage-click pages / surfaces: <list>
+- Rage-click pages / app surfaces: <list>
 - Discord / QQ feedback categories:
   - performance: <count>
   - config: <count>
@@ -709,7 +717,7 @@ Prometheus label 不放 `user_id`、`session_id`、`voice_pack_id`、自定义
 给负责上手体验的人看：
 
 - Funnel：`app_loaded -> chat_activation_started -> provider_config_succeeded -> model_list_loaded -> chat_activation_succeeded`
-- Breakdown：`provider_mode`、`surface`、`region`
+- Breakdown：`provider_mode`、`app_surface`、`region`
 - Table：Top `provider_config_failed` by `provider_id` / `error_code`
 - Timeseries：`time_to_first_message_ms` p50 / p95
 
@@ -729,7 +737,7 @@ Prometheus label 不放 `user_id`、`session_id`、`voice_pack_id`、自定义
 
 - Grafana：5xx、LLM latency、provider failure、TTS blocked
 - PostHog：rage-click trend、failed frontend events
-- Table：Top error_code by surface / provider
+- Table：Top error_code by app surface / provider
 - Community tags：Discord / QQ 反馈分类趋势
 
 ### 分析方法
@@ -763,7 +771,7 @@ Prometheus label 不放 `user_id`、`session_id`、`voice_pack_id`、自定义
 - `chat_activation_failed` by `failure_stage`
 - `provider_config_failed` by `error_code`
 - `model_list_failed` by `provider_id`
-- `$rageclick` by page / surface
+- `$rageclick` by page / `app_surface`
 - Discord / QQ `category = bug` 的高频词
 
 日报只报异常；周报把异常和社区反馈合并成“优先修复建议”。
@@ -863,11 +871,14 @@ Prometheus label 不放 `user_id`、`session_id`、`voice_pack_id`、自定义
 10. 建异常检查：activation、provider config、model list、STT、TTS blocked、bug report。
 11. 建周报模板：自动填指标，社区负责人补充 Discord / QQ 反馈解释和下周建议。
 
-### 当前接入状态（2026-06-30）
+### 当前接入状态（2026-07-10）
 
 已接入代码：
 
-- Chat activation：`chat_activation_started`、`chat_activation_succeeded`、`chat_activation_failed`、`second_turn_started`；官方 Provider 选择事件为 `official_provider_selected`，实际聊天使用口径看 activation events 的 `provider_mode = official`。
+- Chat activation：`chat_activation_started`、`chat_activation_succeeded`、`chat_activation_failed` 只覆盖每个 conversation 首次 assistant response 之前的尝试；后续轮次继续发 message / latency events，第二轮单独发 `second_turn_started`。
+- Chat correlation：每次发送以 user message id 作为 `round_id`；activation、message、LLM latency、render、`message_round` 和 `message_round_failed` 事件共享 `conversation_id`、`round_id`、`turn_index`。
+- Identity：匿名 auth SPA 发 `signup_form_completed`；只有服务端 Better Auth user create hook 发 identified `signup_completed`。平台统一使用 `app_surface`，业务入口统一使用 `entry_surface`。
+- Chat event reuse：主链路使用 `message_send_started`、`message_sent`、`llm_*`、`message_round`、`message_round_failed`；每轮成功 / 失败各自只有一个终点事件，不再发送 `chat_started`、`assistant_response_completed`、`chat_failed` 和 chat 的通用 `feature_used` 别名。
 - Model list：`model_list_loaded`、`model_list_failed`。
 - Provider config：`provider_config_started`、`provider_config_succeeded`、`provider_config_failed`。
 - TTS voice：`tts_provider_selected`、`voice_selected`、`voice_preview_played`、`voice_pack_bound`、`official_tts_exposed`、`official_tts_preview_started`、`official_tts_preview_succeeded`、`official_tts_auto_enabled`。
diff --git a/apps/server/docs/ai-context/verifications/posthog-forwarding-and-pageview.md b/apps/server/docs/ai-context/verifications/posthog-forwarding-and-pageview.md
index 40987a8fa..e1687bca3 100644
--- a/apps/server/docs/ai-context/verifications/posthog-forwarding-and-pageview.md
+++ b/apps/server/docs/ai-context/verifications/posthog-forwarding-and-pageview.md
@@ -16,7 +16,7 @@ Environment: commit 689f02ac4 + 本次工作区改动；posthog-node 5.39.4；po
 |---|---|---|
 | 转发白名单与映射 | `pnpm exec vitest run src/services/domain/product-events.test.ts`（apps/server） | 6 passed：`payment_completed` 原名转发、`user_signed_up→signup_completed` 映射、per-request 动作不转发、sink 抛错时 DB 行仍落库且 track 不抛 |
 | posthog-node 真实传输 | `node posthog-smoke.mjs`（captureImmediate → us.i.posthog.com，生产 project key，事件名 `server_forwarding_smoke_test`） | `captureImmediate resolved in 1380ms` + `shutdown clean` |
-| SPA 路由 pageview | `VITE_ENABLE_POSTHOG=true pnpm -F @proj-airi/stage-web dev` + agent-browser 两次 `history.pushState` | 两条 `$pageview`，`$pathname` 分别为 `/settings/flux`、`/settings/airi-card`，`navigation_type: pushState`，携带 `$prev_pageview_duration` 与 `surface: web` super property；批量 POST `us.i.posthog.com/e/` 返回 200 |
+| SPA 路由 pageview | `VITE_ENABLE_POSTHOG=true pnpm -F @proj-airi/stage-web dev` + agent-browser 两次 `history.pushState` | 两条 `$pageview`，`$pathname` 分别为 `/settings/flux`、`/settings/airi-card`，`navigation_type: pushState`，携带 `$prev_pageview_duration` 与 `app_surface: web` super property；批量 POST `us.i.posthog.com/e/` 返回 200 |
 | 服务端 typecheck / lint | `pnpm -F @proj-airi/server typecheck`、eslint 改动文件 | 均通过 |
 
 ## 注意事项
diff --git a/apps/server/docs/ai-context/verifications/product-analytics-smoke.md b/apps/server/docs/ai-context/verifications/product-analytics-smoke.md
index 35948a7b3..5db13df56 100644
--- a/apps/server/docs/ai-context/verifications/product-analytics-smoke.md
+++ b/apps/server/docs/ai-context/verifications/product-analytics-smoke.md
@@ -2,7 +2,7 @@
 
 Status: **code-level instrumentation verified; live PostHog dashboard updated; Grafana dashboard updated; alert setup pending**
 Owner: Community / Product Analytics
-Last updated: 2026-07-01
+Last updated: 2026-07-10
 Related:
 - [`product-analytics-instrumentation.md`](../product-analytics-instrumentation.md)
 - [`product-analytics-dashboard-setup.md`](../product-analytics-dashboard-setup.md)
@@ -20,6 +20,7 @@ Related:
 |---|---|
 | Frontend analytics API | `packages/stage-ui/src/composables/use-analytics.test.ts` 覆盖 activation、model list、provider config、voice selection、voice input、feedback event API |
 | Chat activation hooks | `packages/core-agent/src/runtime/chat-orchestrator-runtime.test.ts` 覆盖 activation started / succeeded / failed hook |
+| Chat round failures | core runtime 与 stage contract tests 覆盖激活前和激活后的 `message_round_failed`，并验证 `conversation_id` / `round_id` / `turn_index` |
 | Voice input failures | `packages/stage-ui/src/composables/audio/audio-device.test.ts` 与 `packages/stage-ui/src/stores/modules/hearing.analytics.test.ts` 覆盖 permission / device / cancel / STT failed |
 | Server TTS metadata | `apps/server/src/routes/openai/v1/route.test.ts` 与 `apps/server/src/routes/audio-speech-ws/route.test.ts` 覆盖 REST / WS TTS `voice_id`、`voice_type`、`voice_pack_id` metadata |
 | Grafana product row | `apps/server/otel/grafana/dashboards/build.test.ts` 覆盖 Product Analytics panels、layout references、PromQL 不包含 high-cardinality voice / user fields |
@@ -51,8 +52,10 @@ Required properties:
 provider_mode = official
 provider_id = <official provider id>
 model_id = <selected model id>
-surface = web | mobile | electron
-turn_index = 2
+app_surface = web | mobile | electron
+conversation_id = <same application session id across the chat chain>
+round_id = <same id across one message round; different between the first and second round>
+turn_index = 1 for the first round; 2 for second_turn_started and the second round
 ```
 
 Fail if:
@@ -60,9 +63,52 @@ Fail if:
 - `chat_activation_started` appears but `chat_activation_succeeded` never appears for a successful chat.
 - The second message is sent but `second_turn_started` does not appear.
 - `provider_mode` is missing or always `unknown`.
-- `surface` is missing.
+- `app_surface` is missing.
+- Any chat-chain event is missing `conversation_id`, `round_id`, or `turn_index`.
+- Events from one round disagree on `round_id`, or two different rounds reuse the same `round_id`.
 
-### 1b. PostHog: official provider selection
+### 1a. PostHog: message round failure
+
+Action:
+
+1. Complete a successful first chat round.
+2. Force the second round to fail before the assistant response completes.
+
+Expected PostHog events:
+
+```text
+message_round_failed
+```
+
+Required properties:
+
+```text
+conversation_id = <same application session id as the successful first round>
+round_id = <the failed round's user message id>
+turn_index = 2
+provider_id = <active provider id>
+model_id = <selected model id>
+failure_stage = llm_response
+error_code = llm_response_failed
+app_surface = web | mobile | electron
+```
+
+Fail if:
+
+- The failed second round has no `message_round_failed` event.
+- The failed round emits `message_round`, `chat_failed`, or `assistant_response_completed` as an alias.
+- A new `chat_activation_failed` appears after the conversation already completed its first assistant response.
+- Correlation keys disagree with the failed round's preceding message / LLM events.
+
+### 1b. Signup identity ownership
+
+1. Complete an email signup in the auth SPA.
+2. Confirm the auth SPA emits `signup_form_completed` with `app_surface = auth`.
+3. Confirm the Better Auth user-create hook emits exactly one `signup_completed` with `app_surface = server` and the Better Auth user id as `distinctId`.
+
+Fail if the auth SPA emits `signup_completed`, or if the server event lands on a different PostHog person from later identified onboarding events.
+
+### 1c. PostHog: official provider selection
 
 Action:
 
@@ -219,7 +265,7 @@ paywall_seen
 Required properties:
 
 ```text
-surface = settings_flux
+entry_surface = settings_flux
 reason = manual_topup
 flux_balance_bucket = zero | 1_100 | 101_1000 | 1001_10000 | 10000_plus | unknown
 ```
diff --git a/apps/server/src/services/domain/product-events.test.ts b/apps/server/src/services/domain/product-events.test.ts
index 05526bdbf..c5109ca81 100644
--- a/apps/server/src/services/domain/product-events.test.ts
+++ b/apps/server/src/services/domain/product-events.test.ts
@@ -162,7 +162,7 @@ describe('productEventService', () => {
       distinctId: 'user-1',
       event: 'payment_completed',
       properties: {
-        surface: 'server',
+        app_surface: 'server',
         feature: 'billing',
         status: 'succeeded',
         source: 'stripe.webhook',
@@ -174,7 +174,7 @@ describe('productEventService', () => {
       distinctId: 'user-2',
       event: 'signup_completed',
       properties: {
-        surface: 'server',
+        app_surface: 'server',
         feature: 'auth',
         status: 'succeeded',
       },
diff --git a/apps/server/src/services/domain/product-events.ts b/apps/server/src/services/domain/product-events.ts
index 036238eb0..888acfee8 100644
--- a/apps/server/src/services/domain/product-events.ts
+++ b/apps/server/src/services/domain/product-events.ts
@@ -82,9 +82,9 @@ export interface ProductEventAggregateRow {
  * a funnel are forwarded — per-request LLM/TTS volume stays in Postgres and
  * Grafana where it belongs (see `docs/ai-context/metrics-ownership.md`).
  *
- * `user_signed_up` maps to `signup_completed` because that is the canonical
- * activation-funnel step name the browser surfaces emit; the server copy
- * covers OAuth signups the auth UI cannot classify client-side.
+ * `user_signed_up` maps to `signup_completed` because the identified server
+ * hook is the canonical registration fact for every signup method. Anonymous
+ * auth UI progress uses `signup_form_completed` and never reuses this name.
  */
 const POSTHOG_FORWARDED_ACTIONS: Partial<Record<ProductAction, string>> = {
   user_signed_up: 'signup_completed',
@@ -175,7 +175,7 @@ export function createProductEventService(db: Database, metrics?: ProductMetrics
             distinctId: input.userId,
             event: forwardedEvent,
             properties: {
-              surface: 'server',
+              app_surface: 'server',
               feature: input.feature,
               status: input.status,
               ...(input.source && { source: input.source }),
diff --git a/apps/ui-server-auth/src/modules/analytics.test.ts b/apps/ui-server-auth/src/modules/analytics.test.ts
new file mode 100644
index 000000000..064e91966
--- /dev/null
+++ b/apps/ui-server-auth/src/modules/analytics.test.ts
@@ -0,0 +1,48 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+import { initAuthAnalytics, trackSignupFormCompleted } from './analytics'
+
+const posthogMocks = vi.hoisted(() => ({
+  capture: vi.fn(),
+  init: vi.fn(),
+  register: vi.fn(),
+}))
+
+vi.mock('posthog-js', () => ({
+  default: posthogMocks,
+}))
+
+vi.mock('../../../../posthog.config', () => ({
+  DEFAULT_POSTHOG_CONFIG: {},
+  POSTHOG_ENABLED: true,
+  POSTHOG_PROJECT_KEY: 'test-project-key',
+}))
+
+describe('auth product analytics', () => {
+  beforeEach(() => {
+    posthogMocks.capture.mockClear()
+    posthogMocks.init.mockClear()
+    posthogMocks.register.mockClear()
+  })
+
+  // ROOT CAUSE:
+  //
+  // The auth SPA emitted `signup_completed` before it knew the Better Auth
+  // user id, while the server emitted the same canonical event with that id.
+  // PostHog therefore counted one email signup as two unrelated persons.
+  //
+  // The anonymous UI milestone must use its own name. The identified server
+  // event remains the only canonical `signup_completed` business fact.
+  it('keeps anonymous signup UI completion separate from the canonical server signup fact', () => {
+    expect(initAuthAnalytics()).toBe(true)
+    expect(posthogMocks.register).toHaveBeenCalledWith({ app_surface: 'auth' })
+
+    trackSignupFormCompleted({ source: 'email', requires_verification: true })
+
+    expect(posthogMocks.capture).toHaveBeenCalledWith(
+      'signup_form_completed',
+      { source: 'email', requires_verification: true },
+      undefined,
+    )
+  })
+})
diff --git a/apps/ui-server-auth/src/modules/analytics.ts b/apps/ui-server-auth/src/modules/analytics.ts
index 6d3d61807..ab2e9c3d5 100644
--- a/apps/ui-server-auth/src/modules/analytics.ts
+++ b/apps/ui-server-auth/src/modules/analytics.ts
@@ -1,12 +1,11 @@
 /**
  * PostHog product analytics for the auth-only SPA (`apps/ui-server-auth`).
  *
- * This surface is the top of the activation funnel: sign-up, sign-in, email
- * verification, password recovery. Events captured here are the funnel
- * entry that the in-app surfaces (`signup_completed → onboarding_started →
- * first message`) join against, keyed by the Better Auth user id passed to
- * {@link identifyAuthUser} — the same id the server uses as `distinctId`
- * for its own events, so the person profiles merge.
+ * This surface captures anonymous auth-UI milestones such as form completion,
+ * sign-in attempts, email verification, and password recovery. Canonical
+ * registration facts come from the server as identified `signup_completed`
+ * events; the auth SPA intentionally uses `signup_form_completed` so an event
+ * emitted before {@link identifyAuthUser} cannot double-count a new user.
  *
  * Unlike the stage apps there is no in-app analytics consent toggle here
  * (the user isn't signed in yet, so there's no settings store to read).
@@ -43,9 +42,9 @@ export function initAuthAnalytics(): boolean {
     return true
 
   posthog.init(POSTHOG_PROJECT_KEY, { ...DEFAULT_POSTHOG_CONFIG })
-  // Same single-project setup as the stage apps: the `surface` super
+  // Same single-project setup as the stage apps: the `app_surface` super
   // property is how auth traffic is told apart in shared dashboards.
-  posthog.register({ surface: 'auth' })
+  posthog.register({ app_surface: 'auth' })
   initialized = true
   return true
 }
@@ -81,9 +80,9 @@ function capture(event: string, properties: Record<string, unknown>, options?: C
   )
 }
 
-/** Activation funnel step 1 — the account now exists (email flow). */
-export function trackSignupCompleted(properties: { source: AuthMethod, requires_verification: boolean }): void {
-  capture('signup_completed', properties, { beforeNavigation: !properties.requires_verification })
+/** Anonymous email-signup UI milestone; the server owns the registration fact. */
+export function trackSignupFormCompleted(properties: { source: AuthMethod, requires_verification: boolean }): void {
+  capture('signup_form_completed', properties, { beforeNavigation: !properties.requires_verification })
 }
 
 /**
diff --git a/apps/ui-server-auth/src/pages/sign-in.vue b/apps/ui-server-auth/src/pages/sign-in.vue
index 4c79c9d8d..6e18dd1f6 100644
--- a/apps/ui-server-auth/src/pages/sign-in.vue
+++ b/apps/ui-server-auth/src/pages/sign-in.vue
@@ -12,7 +12,7 @@ import {
   trackLoginFailed,
   trackLoginStarted,
   trackLoginSucceeded,
-  trackSignupCompleted,
+  trackSignupFormCompleted,
 } from '../modules/analytics'
 import { buildCurrentOriginAuthUiUrl } from '../modules/auth-ui-base'
 import {
@@ -247,7 +247,7 @@ async function handleEmailSignUp(event: Event) {
     })
 
     if (result.requiresVerification) {
-      trackSignupCompleted({ source: 'email', requires_verification: true })
+      trackSignupFormCompleted({ source: 'email', requires_verification: true })
       await router.push({
         path: '/verify-email',
         query: {
@@ -260,7 +260,7 @@ async function handleEmailSignUp(event: Event) {
 
     // Verification disabled at server config: session is live, fall through
     // to the OIDC continuation just like sign-in.
-    trackSignupCompleted({ source: 'email', requires_verification: false })
+    trackSignupFormCompleted({ source: 'email', requires_verification: false })
     window.location.href = effectiveCallbackURL.value
   }
   catch (error) {
diff --git a/docs/.vitepress/modules/posthog.ts b/docs/.vitepress/modules/posthog.ts
index a77d72bd6..7f06faf38 100644
--- a/docs/.vitepress/modules/posthog.ts
+++ b/docs/.vitepress/modules/posthog.ts
@@ -8,5 +8,5 @@ if (!import.meta.env.DEV) {
   })
   // Tag docs-site traffic so it can be told apart from the app surfaces
   // inside the shared project.
-  posthog.register({ surface: 'docs' })
+  posthog.register({ app_surface: 'docs' })
 }
diff --git a/packages/core-agent/src/runtime/chat-orchestrator-runtime.test.ts b/packages/core-agent/src/runtime/chat-orchestrator-runtime.test.ts
index 738013a10..20b880e6c 100644
--- a/packages/core-agent/src/runtime/chat-orchestrator-runtime.test.ts
+++ b/packages/core-agent/src/runtime/chat-orchestrator-runtime.test.ts
@@ -43,6 +43,7 @@ function createHarness() {
     llmFirstToken: [] as unknown[],
     assistantResponseRendered: [] as unknown[],
     messageRound: [] as unknown[],
+    messageRoundFailed: [] as unknown[],
   }
   const stream = vi.fn(async (_model: string, _chatProvider: ChatProvider, _messages: Message[], options?: {
     onStreamEvent?: (event: StreamEvent) => Promise<void> | void
@@ -100,6 +101,7 @@ function createHarness() {
     onLlmFirstToken: event => telemetry.llmFirstToken.push(event),
     onAssistantResponseRendered: event => telemetry.assistantResponseRendered.push(event),
     onMessageRound: event => telemetry.messageRound.push(event),
+    onMessageRoundFailed: event => telemetry.messageRoundFailed.push(event),
   })
 
   return {
@@ -308,42 +310,86 @@ describe('createChatOrchestratorRuntime', () => {
     })
 
     expect(harness.telemetry.messageSendStarted).toEqual([{
+      conversationId: 'session-1',
+      roundId: 'user-id',
       source: 'voice',
       model: 'gpt-test',
+      turnIndex: 1,
     }])
     expect(harness.telemetry.llmRequestStarted).toEqual([{
+      conversationId: 'session-1',
+      roundId: 'user-id',
       model: 'gpt-test',
       provider: 'mock-provider',
       hasVoice: true,
+      turnIndex: 1,
     }])
     expect(harness.telemetry.llmFirstToken).toEqual([{
+      conversationId: 'session-1',
+      roundId: 'user-id',
       model: 'gpt-test',
       ttfbMs: 100,
+      turnIndex: 1,
     }])
     expect(harness.telemetry.assistantResponseRendered).toEqual([{
+      conversationId: 'session-1',
+      roundId: 'user-id',
       model: 'gpt-test',
       latencyMs: 250,
+      turnIndex: 1,
     }])
     expect(harness.telemetry.messageRound).toEqual([{
+      conversationId: 'session-1',
+      roundId: 'user-id',
       durationMs: 360,
       hasVoice: true,
       model: 'gpt-test',
+      turnIndex: 1,
     }])
     expect(harness.telemetry.chatActivationStarted).toEqual([{
+      conversationId: 'session-1',
       model: 'gpt-test',
       provider: 'mock-provider',
-      sessionId: 'session-1',
+      roundId: 'user-id',
       source: 'voice',
+      turnIndex: 1,
     }])
     expect(harness.telemetry.chatActivationSucceeded).toEqual([{
+      conversationId: 'session-1',
       durationMs: 360,
       model: 'gpt-test',
       provider: 'mock-provider',
+      roundId: 'user-id',
       source: 'voice',
+      turnIndex: 1,
     }])
     expect(harness.telemetry.chatActivationFailed).toEqual([])
   })
 
+  // ROOT CAUSE:
+  //
+  // Activation callbacks were emitted for every chat round, so production
+  // `chat_activation_*` volume tracked message traffic instead of the first
+  // successful assistant response in a conversation.
+  it('emits activation milestones only until the conversation gets its first assistant response', async () => {
+    const harness = createHarness()
+
+    await harness.runtime.ingest('first turn', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })
+    await harness.runtime.ingest('second turn', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })
+
+    expect(harness.telemetry.chatActivationStarted).toHaveLength(1)
+    expect(harness.telemetry.chatActivationSucceeded).toHaveLength(1)
+    expect(harness.telemetry.chatActivationFailed).toHaveLength(0)
+    expect(harness.telemetry.messageSendStarted).toHaveLength(2)
+    expect(harness.telemetry.messageRound).toHaveLength(2)
+  })
+
   /**
    * @example
    * await expect(runtime.ingest('hello', { model, chatProvider })).rejects.toThrow('provider rejected')
@@ -358,19 +404,60 @@ describe('createChatOrchestratorRuntime', () => {
     })).rejects.toThrow('provider rejected')
 
     expect(harness.telemetry.chatActivationStarted).toEqual([{
+      conversationId: 'session-1',
       model: 'gpt-test',
       provider: 'mock-provider',
-      sessionId: 'session-1',
+      roundId: 'user-id',
       source: 'text',
+      turnIndex: 1,
     }])
     expect(harness.telemetry.chatActivationSucceeded).toEqual([])
     expect(harness.telemetry.chatActivationFailed).toEqual([{
+      conversationId: 'session-1',
       errorCode: 'llm_response_failed',
       failureStage: 'llm_response',
       model: 'gpt-test',
       provider: 'mock-provider',
+      roundId: 'user-id',
       source: 'text',
+      turnIndex: 1,
     }])
+    expect(harness.telemetry.messageRoundFailed).toEqual([{
+      conversationId: 'session-1',
+      errorCode: 'llm_response_failed',
+      failureStage: 'llm_response',
+      model: 'gpt-test',
+      provider: 'mock-provider',
+      roundId: 'user-id',
+      source: 'text',
+      turnIndex: 1,
+    }])
+  })
+
+  it('emits a round failure for later turns without repeating activation failure', async () => {
+    const harness = createHarness()
+
+    await harness.runtime.ingest('first turn succeeds', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })
+    harness.stream.mockRejectedValueOnce(new Error('later turn rejected'))
+
+    await expect(harness.runtime.ingest('second turn fails', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })).rejects.toThrow('later turn rejected')
+
+    expect(harness.telemetry.chatActivationFailed).toEqual([])
+    expect(harness.telemetry.messageRoundFailed).toEqual([
+      expect.objectContaining({
+        conversationId: 'session-1',
+        errorCode: 'llm_response_failed',
+        failureStage: 'llm_response',
+        roundId: expect.any(String),
+        turnIndex: 2,
+      }),
+    ])
   })
 
   /**
diff --git a/packages/core-agent/src/runtime/chat-orchestrator-runtime.ts b/packages/core-agent/src/runtime/chat-orchestrator-runtime.ts
index 221f05e31..5ed767960 100644
--- a/packages/core-agent/src/runtime/chat-orchestrator-runtime.ts
+++ b/packages/core-agent/src/runtime/chat-orchestrator-runtime.ts
@@ -156,6 +156,16 @@ export interface ChatOrchestratorRuntimeState {
   pendingQueuedSendCount: number
 }
 
+/** Correlation keys shared by every analytics milestone from one user-to-assistant round. */
+interface ChatRoundCorrelation {
+  /** Application conversation that owns the round. */
+  conversationId: string
+  /** Stable round key; the runtime reuses the persisted user-message ID. */
+  roundId: string
+  /** One-based user turn position within the conversation. */
+  turnIndex: number
+}
+
 /**
  * Dependency surface used by the platform-agnostic chat orchestrator runtime.
  */
@@ -190,22 +200,21 @@ export interface ChatOrchestratorRuntimeDeps {
   onSendSettled?: (event: { sessionId: string }) => void
   /** Called when a send starts and the first assistant placeholder is created. */
   onTrackFirstMessage?: () => void
-  /** Called when a user starts a chat activation attempt. */
-  onChatActivationStarted?: (event: {
-    sessionId: string
+  /** Called for attempts made before the conversation has its first assistant response. */
+  onChatActivationStarted?: (event: ChatRoundCorrelation & {
     source: 'text' | 'voice'
     model: string
     provider: string
   }) => void
-  /** Called after one user-to-assistant message round completes successfully. */
-  onChatActivationSucceeded?: (event: {
+  /** Called when the conversation reaches its first successful assistant response. */
+  onChatActivationSucceeded?: (event: ChatRoundCorrelation & {
     source: 'text' | 'voice'
     model: string
     provider: string
     durationMs: number
   }) => void
-  /** Called after a chat activation attempt fails before assistant completion. */
-  onChatActivationFailed?: (event: {
+  /** Called when a pre-activation attempt fails before assistant completion. */
+  onChatActivationFailed?: (event: ChatRoundCorrelation & {
     source: 'text' | 'voice'
     model: string
     provider: string
@@ -213,32 +222,40 @@ export interface ChatOrchestratorRuntimeDeps {
     errorCode: 'llm_response_failed'
   }) => void
   /** Called when a user message send begins. */
-  onMessageSendStarted?: (event: {
+  onMessageSendStarted?: (event: ChatRoundCorrelation & {
     source: 'text' | 'voice'
     model: string
   }) => void
   /** Called immediately before the provider LLM request starts. */
-  onLlmRequestStarted?: (event: {
+  onLlmRequestStarted?: (event: ChatRoundCorrelation & {
     model: string
     provider: string
     hasVoice: boolean
   }) => void
   /** Called when the first text token arrives from the provider stream. */
-  onLlmFirstToken?: (event: {
+  onLlmFirstToken?: (event: ChatRoundCorrelation & {
     model: string
     ttfbMs: number
   }) => void
   /** Called after the assistant stream is parsed and rendered into runtime state. */
-  onAssistantResponseRendered?: (event: {
+  onAssistantResponseRendered?: (event: ChatRoundCorrelation & {
     model: string
     latencyMs: number
   }) => void
   /** Called after one user-to-assistant message round completes successfully. */
-  onMessageRound?: (event: {
+  onMessageRound?: (event: ChatRoundCorrelation & {
     durationMs: number
     hasVoice: boolean
     model: string
   }) => void
+  /** Called whenever a user-to-assistant round fails before completion. */
+  onMessageRoundFailed?: (event: ChatRoundCorrelation & {
+    source: 'text' | 'voice'
+    model: string
+    provider: string
+    failureStage: 'llm_response'
+    errorCode: 'llm_response_failed'
+  }) => void
   /** Called for context/prompt lifecycle observability. */
   onLifecycle?: (record: ChatOrchestratorLifecycleRecord) => void
   /** Called with the final provider prompt projection. */
@@ -251,6 +268,7 @@ export interface ChatOrchestratorRuntimeDeps {
     source: 'text' | 'voice'
     model: string
     provider: string
+    roundId: string
     turnIndex: number
   }) => void
   /** Called after the assistant message has been finalized into session history. */
@@ -386,6 +404,14 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
 
     deps.session.ensureSession(sessionId)
 
+    const existingSessionMessages = deps.session.getSessionMessages(sessionId)
+    const turnIndex = existingSessionMessages.filter(message => message.role === 'user').length + 1
+
+    // Activation measures whether a conversation reaches its first assistant
+    // response. Later turns still emit message and latency telemetry, but they
+    // must not inflate the one-time activation milestones.
+    const isActivationAttempt = !existingSessionMessages.some(message => message.role === 'assistant')
+
     // Datetime is no longer injected through the side-channel context store.
     // It is applied at message-assembly time (see below) as a system-prompt
     // date anchor + per-message [HH:MM] prefixes, which is more KV-cache
@@ -429,14 +455,25 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
     patchForegroundStream(sessionId, buildingMessage)
     const sendSource = options.input ? 'voice' : 'text'
     const activeProvider = deps.getActiveProvider?.() ?? ''
+    // The user message is the durable start of a round, so its ID also serves
+    // as the correlation key for every telemetry milestone emitted by it.
+    const roundId = createId()
+    const correlation: ChatRoundCorrelation = {
+      conversationId: sessionId,
+      roundId,
+      turnIndex,
+    }
     deps.onTrackFirstMessage?.()
-    deps.onChatActivationStarted?.({
-      sessionId,
-      source: sendSource,
-      model: options.model,
-      provider: activeProvider,
-    })
+    if (isActivationAttempt) {
+      deps.onChatActivationStarted?.({
+        ...correlation,
+        source: sendSource,
+        model: options.model,
+        provider: activeProvider,
+      })
+    }
     deps.onMessageSendStarted?.({
+      ...correlation,
       source: sendSource,
       model: options.model,
     })
@@ -473,15 +510,13 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
       if (shouldAbort())
         return
 
-      const userMessageId = createId()
       const userMessage = {
         role: 'user' as const,
         content: finalContent,
         createdAt: sendingCreatedAt,
-        id: userMessageId,
+        id: roundId,
       }
       deps.session.appendSessionMessage(sessionId, userMessage)
-      const userTurnIndex = deps.session.getSessionMessages(sessionId).filter(message => message.role === 'user').length
 
       // Cloud sync v1: only the raw text part round-trips; image attachments
       // and other non-text parts stay local.
@@ -492,7 +527,8 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
         source: sendSource,
         model: options.model,
         provider: activeProvider,
-        turnIndex: userTurnIndex,
+        roundId,
+        turnIndex,
       })
 
       const sessionMessagesForSend = deps.session.getSessionMessages(sessionId)
@@ -644,6 +680,7 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
       const llmRequestStartedAt = monotonicNow()
       let llmFirstTokenEmitted = false
       deps.onLlmRequestStarted?.({
+        ...correlation,
         model: options.model,
         provider: deps.getActiveProvider() || 'unknown',
         hasVoice: !!options.input,
@@ -684,6 +721,7 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
               if (!llmFirstTokenEmitted) {
                 llmFirstTokenEmitted = true
                 deps.onLlmFirstToken?.({
+                  ...correlation,
                   model: options.model,
                   ttfbMs: Math.round(monotonicNow() - llmRequestStartedAt),
                 })
@@ -718,6 +756,7 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
 
       await parser.end()
       deps.onAssistantResponseRendered?.({
+        ...correlation,
         model: options.model,
         latencyMs: Math.round(monotonicNow() - llmRequestStartedAt),
       })
@@ -751,26 +790,41 @@ export function createChatOrchestratorRuntime(deps: ChatOrchestratorRuntimeDeps)
       resetForegroundStream(sessionId)
       const durationMs = Math.round(monotonicNow() - roundStartedAt)
       deps.onMessageRound?.({
+        ...correlation,
         durationMs,
         hasVoice: !!options.input,
         model: options.model,
       })
-      deps.onChatActivationSucceeded?.({
-        durationMs,
-        source: sendSource,
-        model: options.model,
-        provider: activeProvider,
-      })
+      if (isActivationAttempt) {
+        deps.onChatActivationSucceeded?.({
+          ...correlation,
+          durationMs,
+          source: sendSource,
+          model: options.model,
+          provider: activeProvider,
+        })
+      }
     }
     catch (error) {
       console.error('Error sending message:', error)
-      deps.onChatActivationFailed?.({
+      deps.onMessageRoundFailed?.({
+        ...correlation,
         source: sendSource,
         model: options.model,
         provider: activeProvider,
         failureStage: 'llm_response',
         errorCode: 'llm_response_failed',
       })
+      if (isActivationAttempt) {
+        deps.onChatActivationFailed?.({
+          ...correlation,
+          source: sendSource,
+          model: options.model,
+          provider: activeProvider,
+          failureStage: 'llm_response',
+          errorCode: 'llm_response_failed',
+        })
+      }
       throw error
     }
     finally {
diff --git a/packages/stage-pages/src/pages/settings/flux.vue b/packages/stage-pages/src/pages/settings/flux.vue
index 551af2b0c..4f34b146c 100644
--- a/packages/stage-pages/src/pages/settings/flux.vue
+++ b/packages/stage-pages/src/pages/settings/flux.vue
@@ -284,11 +284,11 @@ onMounted(async () => {
 
   // PostHog funnel step 1: pricing surface view. Today this is an in-app
   // settings page (already-authenticated users); when we add a public
-  // pricing landing page the surface label changes but the event stays the
+  // pricing landing page the entry-surface label changes but the event stays the
   // same, so the funnel definition in PostHog doesn't need re-wiring.
   if (!fluxPurchaseDisabled) {
     trackPaywallSeen({
-      surface: 'settings_flux',
+      entry_surface: 'settings_flux',
       reason: 'manual_topup',
       flux_balance_bucket: fluxBalanceBucket(credits.value),
     })
@@ -317,7 +317,10 @@ async function handleBuy(stripePriceId: string) {
     current_plan: 'flux',
     trigger: 'manual_topup',
   })
-  trackPlanSelected(stripePriceId, { currency: selectedCurrency.value })
+  trackPlanSelected(stripePriceId, {
+    currency: selectedCurrency.value,
+    entry_surface: 'settings_flux',
+  })
   try {
     const res = await client.api.v1.stripe.checkout.$post({ json: { stripePriceId, currency: selectedCurrency.value } })
     if (!res.ok) {
@@ -330,7 +333,10 @@ async function handleBuy(stripePriceId: string) {
       // PostHog funnel step 3: about to redirect to Stripe. Capture before
       // the page nav so the event is sent (PostHog's beforeunload handler
       // would otherwise race the navigation).
-      trackCheckoutStarted(stripePriceId, { currency: selectedCurrency.value })
+      trackCheckoutStarted(stripePriceId, {
+        currency: selectedCurrency.value,
+        entry_surface: 'settings_flux',
+      })
       // Electron renderer runs from file:// and cannot navigate to Stripe in-window
       // (the settings window would load checkout.stripe.com and never come back).
       // window.open routes through setWindowOpenHandler -> shell.openExternal, so the
diff --git a/packages/stage-ui/src/composables/use-analytics.test.ts b/packages/stage-ui/src/composables/use-analytics.test.ts
index b5c76dd60..3bf53234b 100644
--- a/packages/stage-ui/src/composables/use-analytics.test.ts
+++ b/packages/stage-ui/src/composables/use-analytics.test.ts
@@ -70,7 +70,7 @@ describe('useAnalytics conversation product events', () => {
     analyticsMocks.isPosthogAvailableInBuildMock.mockClear()
   })
 
-  it('infers the web surface for browser conversation actions', () => {
+  it('uses app_surface for the web runtime without occupying the event entry surface', () => {
     const analytics = useAnalytics()
 
     analytics.trackTtsStopClicked({
@@ -78,7 +78,7 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenCalledWith('tts_stop_clicked', {
-      surface: 'web',
+      app_surface: 'web',
       reason: 'manual-chat',
     })
   })
@@ -94,7 +94,7 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenCalledWith('chat_session_selected', {
-      surface: 'mobile',
+      app_surface: 'mobile',
       source: 'sessions_drawer',
       message_count: 4,
       cloud_synced: true,
@@ -118,36 +118,42 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'chat_message_deleted', {
-      surface: 'electron',
+      app_surface: 'electron',
       source: 'history',
       message_role: 'assistant',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'chat_messages_cleared', {
-      surface: 'electron',
+      app_surface: 'electron',
       source: 'chat_controls',
       message_count: 3,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'chat_message_retried', {
-      surface: 'electron',
+      app_surface: 'electron',
       source: 'history',
     })
   })
 
   /**
    * @example
-   * analytics.trackChatActivationStarted({ provider_mode: 'official', provider_id: 'official-provider', model_id: 'gpt-test', source: 'text' })
-   * expect(posthog.capture).toHaveBeenCalledWith('chat_activation_started', expect.objectContaining({ surface: 'web' }))
+   * analytics.trackChatActivationStarted({ conversation_id: 'session-1', round_id: 'round-1', turn_index: 1, provider_mode: 'official', provider_id: 'official-provider', model_id: 'gpt-test', source: 'text' })
+   * expect(posthog.capture).toHaveBeenCalledWith('chat_activation_started', expect.objectContaining({ app_surface: 'web' }))
    */
   it('emits chat activation milestones with inferred surface and normalized fields', () => {
     const analytics = useAnalytics()
 
     analytics.trackChatActivationStarted({
+      conversation_id: 'session-1',
+      round_id: 'round-1',
+      turn_index: 1,
       provider_mode: 'official',
       provider_id: 'official-provider',
       model_id: 'gpt-test',
       source: 'text',
     })
     analytics.trackChatActivationSucceeded({
+      conversation_id: 'session-1',
+      round_id: 'round-1',
+      turn_index: 1,
       provider_mode: 'official',
       provider_id: 'official-provider',
       model_id: 'gpt-test',
@@ -155,6 +161,9 @@ describe('useAnalytics conversation product events', () => {
       source: 'voice',
     })
     analytics.trackChatActivationFailed({
+      conversation_id: 'session-1',
+      round_id: 'round-1',
+      turn_index: 1,
       provider_mode: 'custom',
       provider_id: 'openai-compatible',
       model_id: 'custom',
@@ -164,14 +173,20 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'chat_activation_started', {
-      surface: 'web',
+      app_surface: 'web',
+      conversation_id: 'session-1',
+      round_id: 'round-1',
+      turn_index: 1,
       provider_mode: 'official',
       provider_id: 'official-provider',
       model_id: 'gpt-test',
       source: 'text',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'chat_activation_succeeded', {
-      surface: 'web',
+      app_surface: 'web',
+      conversation_id: 'session-1',
+      round_id: 'round-1',
+      turn_index: 1,
       provider_mode: 'official',
       provider_id: 'official-provider',
       model_id: 'gpt-test',
@@ -179,7 +194,10 @@ describe('useAnalytics conversation product events', () => {
       source: 'voice',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'chat_activation_failed', {
-      surface: 'web',
+      app_surface: 'web',
+      conversation_id: 'session-1',
+      round_id: 'round-1',
+      turn_index: 1,
       provider_mode: 'custom',
       provider_id: 'openai-compatible',
       model_id: 'custom',
@@ -225,13 +243,13 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'tts_provider_selected', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider',
       tts_model_id: 'stepfun/tts',
       source: 'settings',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'voice_selected', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider',
       tts_model_id: 'stepfun/tts',
       voice_id: 'longxiaochun_v2',
@@ -239,7 +257,7 @@ describe('useAnalytics conversation product events', () => {
       source: 'settings',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'voice_preview_played', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider',
       tts_model_id: 'stepfun/tts',
       voice_id: 'longxiaochun_v2',
@@ -247,7 +265,7 @@ describe('useAnalytics conversation product events', () => {
       source: 'manual_preview',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'voice_pack_bound', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider',
       tts_model_id: 'stepfun/tts',
       voice_id: 'longxiaochun_v2',
@@ -272,15 +290,17 @@ describe('useAnalytics conversation product events', () => {
       model_id: 'chat-auto',
     })
     analytics.trackSecondTurnStarted({
+      conversation_id: 'session-1',
       provider_id: 'official-provider',
       provider_mode: 'official',
       model_id: 'chat-auto',
+      round_id: 'round-2',
       source: 'text',
       turn_index: 2,
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'official_provider_selected', {
-      surface: 'web',
+      app_surface: 'web',
       provider_id: 'official-provider',
       provider_mode: 'official',
       source: 'default_auto',
@@ -288,10 +308,12 @@ describe('useAnalytics conversation product events', () => {
       model_id: 'chat-auto',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'second_turn_started', {
-      surface: 'web',
+      app_surface: 'web',
+      conversation_id: 'session-1',
       provider_id: 'official-provider',
       provider_mode: 'official',
       model_id: 'chat-auto',
+      round_id: 'round-2',
       source: 'text',
       turn_index: 2,
     })
@@ -333,13 +355,13 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'official_tts_exposed', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider-speech',
       tts_model_id: 'stepfun/tts',
       source: 'post_first_chat',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'official_tts_preview_started', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider-speech',
       tts_model_id: 'stepfun/tts',
       voice_id: 'longxiaochun_v2',
@@ -347,7 +369,7 @@ describe('useAnalytics conversation product events', () => {
       source: 'manual_preview',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'official_tts_preview_succeeded', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider-speech',
       tts_model_id: 'stepfun/tts',
       voice_id: 'longxiaochun_v2',
@@ -356,7 +378,7 @@ describe('useAnalytics conversation product events', () => {
       duration_ms: 320,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'official_tts_auto_enabled', {
-      surface: 'web',
+      app_surface: 'web',
       tts_provider_id: 'official-provider-speech',
       tts_model_id: 'stepfun/tts',
       source: 'settings',
@@ -368,23 +390,55 @@ describe('useAnalytics conversation product events', () => {
     const analytics = useAnalytics()
 
     analytics.trackPaywallSeen({
-      surface: 'settings_flux',
+      entry_surface: 'settings_flux',
       reason: 'manual_topup',
       flux_balance_bucket: '1_100',
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenCalledWith('paywall_seen', {
-      surface: 'settings_flux',
       app_surface: 'web',
+      entry_surface: 'settings_flux',
       reason: 'manual_topup',
       flux_balance_bucket: '1_100',
     })
   })
 
+  it('uses entry_surface across the pricing funnel without emitting surface', () => {
+    const analytics = useAnalytics()
+
+    analytics.trackPricingViewed('settings_flux', 'one_time')
+    analytics.trackPlanSelected('price-1', {
+      currency: 'USD',
+      entry_surface: 'settings_flux',
+    })
+    analytics.trackCheckoutStarted('price-1', {
+      currency: 'USD',
+      entry_surface: 'settings_flux',
+    })
+
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'pricing_page_viewed', {
+      entry_surface: 'settings_flux',
+      plan_period: 'one_time',
+    })
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'plan_selected', {
+      currency: 'USD',
+      entry_surface: 'settings_flux',
+      plan_id: 'price-1',
+    })
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'checkout_started', {
+      currency: 'USD',
+      entry_surface: 'settings_flux',
+      plan_id: 'price-1',
+    }, {
+      send_instantly: true,
+      transport: 'sendBeacon',
+    })
+  })
+
   /**
    * @example
    * analytics.trackMicrophonePermissionDenied({ stt_provider_id: 'browser-web-speech-api' })
-   * expect(posthog.capture).toHaveBeenCalledWith('microphone_permission_denied', expect.objectContaining({ surface: 'web' }))
+   * expect(posthog.capture).toHaveBeenCalledWith('microphone_permission_denied', expect.objectContaining({ app_surface: 'web' }))
    */
   it('emits voice input friction events with low-cardinality error fields', () => {
     const analytics = useAnalytics()
@@ -409,29 +463,29 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'voice_input_started', {
-      surface: 'web',
+      app_surface: 'web',
       stt_provider_id: 'browser-web-speech-api',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'voice_input_used', {
-      surface: 'web',
+      app_surface: 'web',
       stt_provider_id: 'browser-web-speech-api',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'microphone_permission_requested', {
-      surface: 'web',
+      app_surface: 'web',
       stt_provider_id: 'browser-web-speech-api',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'microphone_permission_denied', {
-      surface: 'web',
+      app_surface: 'web',
       stt_provider_id: 'browser-web-speech-api',
       error_code: 'permission_denied',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(5, 'audio_device_unavailable', {
-      surface: 'web',
+      app_surface: 'web',
       stt_provider_id: 'browser-web-speech-api',
       error_code: 'device_unavailable',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(6, 'voice_input_cancelled', {
-      surface: 'web',
+      app_surface: 'web',
       stt_provider_id: 'browser-web-speech-api',
       duration_ms: 420,
     })
@@ -459,14 +513,14 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'model_list_loaded', {
-      surface: 'web',
+      app_surface: 'web',
       provider_id: 'official-provider',
       provider_mode: 'official',
       model_count: 3,
       duration_ms: 25,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'model_list_failed', {
-      surface: 'web',
+      app_surface: 'web',
       provider_id: 'openai-compatible',
       provider_mode: 'custom',
       error_code: 'provider_error',
@@ -502,20 +556,20 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'provider_config_started', {
-      surface: 'web',
+      app_surface: 'web',
       provider_id: 'openai-compatible',
       provider_mode: 'custom',
       step: 'settings_auto_validate',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'provider_config_succeeded', {
-      surface: 'web',
+      app_surface: 'web',
       provider_id: 'official-provider',
       provider_mode: 'official',
       step: 'manual_chat_ping',
       duration_ms: 18,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'provider_config_completed', {
-      surface: 'web',
+      app_surface: 'web',
       provider_id: 'official-provider',
       provider_mode: 'official',
       provider_type: 'official',
@@ -526,12 +580,12 @@ describe('useAnalytics conversation product events', () => {
       success: true,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'official_provider_enabled', {
-      surface: 'web',
+      app_surface: 'web',
       provider_name: 'official-provider',
       entry: 'settings',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(5, 'provider_config_failed', {
-      surface: 'web',
+      app_surface: 'web',
       provider_id: 'openai-compatible',
       provider_mode: 'custom',
       step: 'settings_auto_validate',
@@ -540,14 +594,9 @@ describe('useAnalytics conversation product events', () => {
     })
   })
 
-  it('emits P0 activation, chat, quota, and feature events using canonical names', () => {
+  it('emits P0 onboarding, message, quota, and feature events using canonical names', () => {
     const analytics = useAnalytics()
 
-    analytics.trackSignupCompleted({
-      source: 'google',
-      locale: 'en',
-      utm_source: 'launch',
-    })
     analytics.trackOnboardingStarted({
       entry: 'app_start',
     })
@@ -556,41 +605,19 @@ describe('useAnalytics conversation product events', () => {
       selected_provider_id: 'official-provider',
       selected_use_case: 'role_chat',
     })
-    analytics.trackChatStarted({
-      conversation_id: 'session-1',
-      provider_type: 'official',
-      provider_name: 'official-provider',
-      model: 'gpt-test',
-      entry: 'chat',
-      is_paid_user: true,
-    })
     analytics.trackMessageSent({
       conversation_id: 'session-1',
       provider_type: 'official',
       provider_name: 'official-provider',
       model: 'gpt-test',
       message_id: 'message-1',
+      round_id: 'message-1',
+      turn_index: 1,
       message_index: 2,
       message_length: 24,
       has_attachment: false,
       mode: 'text',
     })
-    analytics.trackAssistantResponseCompleted({
-      conversation_id: 'session-1',
-      provider_type: 'official',
-      provider_name: 'official-provider',
-      model: 'gpt-test',
-      latency_ms: 350,
-      completion_length: 120,
-    })
-    analytics.trackChatFailed({
-      conversation_id: 'session-1',
-      provider_type: 'custom',
-      provider_name: 'openai-compatible',
-      model: 'custom',
-      failure_stage: 'llm_response',
-      error_code: 'provider_error',
-    })
     analytics.trackQuotaLimitReached({
       limit_type: 'flux',
       current_usage: 0,
@@ -609,73 +636,43 @@ describe('useAnalytics conversation product events', () => {
       success: true,
     })
 
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'signup_completed', {
-      source: 'google',
-      locale: 'en',
-      utm_source: 'launch',
-    })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'onboarding_started', {
-      surface: 'web',
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'onboarding_started', {
+      app_surface: 'web',
       entry: 'app_start',
     })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'onboarding_completed', {
-      surface: 'web',
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'onboarding_completed', {
+      app_surface: 'web',
       selected_provider_type: 'official',
       selected_provider_id: 'official-provider',
       selected_use_case: 'role_chat',
     })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'chat_started', {
-      surface: 'web',
-      conversation_id: 'session-1',
-      provider_type: 'official',
-      provider_name: 'official-provider',
-      model: 'gpt-test',
-      entry: 'chat',
-      is_paid_user: true,
-    })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(5, 'message_sent', {
-      surface: 'web',
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'message_sent', {
+      app_surface: 'web',
       conversation_id: 'session-1',
       provider_type: 'official',
       provider_name: 'official-provider',
       model: 'gpt-test',
       message_id: 'message-1',
+      round_id: 'message-1',
+      turn_index: 1,
       message_index: 2,
       message_length: 24,
       has_attachment: false,
       mode: 'text',
     })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(6, 'assistant_response_completed', {
-      surface: 'web',
-      conversation_id: 'session-1',
-      provider_type: 'official',
-      provider_name: 'official-provider',
-      model: 'gpt-test',
-      latency_ms: 350,
-      completion_length: 120,
-    })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(7, 'chat_failed', {
-      surface: 'web',
-      conversation_id: 'session-1',
-      provider_type: 'custom',
-      provider_name: 'openai-compatible',
-      model: 'custom',
-      failure_stage: 'llm_response',
-      error_code: 'provider_error',
-    })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(8, 'quota_limit_reached', {
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'quota_limit_reached', {
       limit_type: 'flux',
       current_usage: 0,
       limit_value: 0,
       entry: 'pricing',
     })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(9, 'upgrade_clicked', {
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(5, 'upgrade_clicked', {
       source_page: 'settings_flux',
       current_plan: 'flux',
       trigger: 'manual_topup',
     })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(10, 'feature_used', {
-      surface: 'web',
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(6, 'feature_used', {
+      app_surface: 'web',
       feature_name: 'chat',
       business_domain: 'conversation',
       entry: 'chat',
@@ -736,43 +733,43 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'conversation_created', {
-      surface: 'web',
+      app_surface: 'web',
       conversation_id: 'session-1',
       source: 'new_session',
       character_id: 'character-1',
       cloud_synced: true,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'conversation_renamed', {
-      surface: 'web',
+      app_surface: 'web',
       conversation_id: 'session-1',
       source: 'sessions_drawer',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'conversation_shared', {
-      surface: 'web',
+      app_surface: 'web',
       conversation_id: 'session-1',
       source: 'share_button',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'conversation_deleted', {
-      surface: 'web',
+      app_surface: 'web',
       conversation_id: 'session-1',
       message_count: 6,
       cloud_synced: true,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(5, 'attachment_uploaded', {
-      surface: 'web',
+      app_surface: 'web',
       attachment_type: 'image',
       size_bytes: 2048,
       source: 'chat',
       success: true,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(6, 'preset_used', {
-      surface: 'web',
+      app_surface: 'web',
       preset_id: 'preset-live2d-1',
       preset_type: 'stage_model',
       source: 'settings',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(7, 'provider_switched', {
-      surface: 'web',
+      app_surface: 'web',
       from_provider: 'openai-compatible',
       to_provider: 'official-provider',
       from_provider_type: 'custom',
@@ -780,14 +777,14 @@ describe('useAnalytics conversation product events', () => {
       reason: 'manual',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(8, 'settings_changed', {
-      surface: 'web',
+      app_surface: 'web',
       setting_name: 'analytics_enabled',
       previous_value: false,
       new_value: true,
       source: 'settings',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(9, 'support_contacted', {
-      surface: 'web',
+      app_surface: 'web',
       channel: 'discord',
       source: 'settings',
       category: 'payment',
@@ -821,7 +818,7 @@ describe('useAnalytics conversation product events', () => {
     })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'bug_report_submitted', {
-      surface: 'web',
+      app_surface: 'web',
       source: 'app',
       category: 'update',
       severity: 'major',
@@ -832,7 +829,7 @@ describe('useAnalytics conversation product events', () => {
       screenshot_attached: true,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'feedback_submitted', {
-      surface: 'web',
+      app_surface: 'web',
       source: 'discord',
       category: 'voice_input',
       severity: 'minor',
@@ -851,21 +848,21 @@ describe('useAnalytics conversation product events', () => {
     analytics.trackAccountDeletionRequested()
     analytics.trackOauthCallbackFailed({ stage: 'missing_flow_state' })
 
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'password_changed', { surface: 'web' })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'password_reset_requested', { surface: 'web' })
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'password_changed', { app_surface: 'web' })
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'password_reset_requested', { app_surface: 'web' })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(
       3,
       'oauth_provider_link_started',
-      { surface: 'web', provider: 'github' },
+      { app_surface: 'web', provider: 'github' },
       { send_instantly: true, transport: 'sendBeacon' },
     )
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(4, 'oauth_provider_unlinked', {
-      surface: 'web',
+      app_surface: 'web',
       provider: 'google',
     })
-    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(5, 'account_deletion_requested', { surface: 'web' })
+    expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(5, 'account_deletion_requested', { app_surface: 'web' })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(6, 'oauth_callback_failed', {
-      surface: 'web',
+      app_surface: 'web',
       stage: 'missing_flow_state',
     })
   })
@@ -879,16 +876,16 @@ describe('useAnalytics conversation product events', () => {
     analytics.trackCharacterUpdated({ character_id: 'character-1' })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'card_edited', {
-      surface: 'web',
+      app_surface: 'web',
       card_id: 'card-1',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'scene_background_set', {
-      surface: 'web',
+      app_surface: 'web',
       source: 'card_gallery',
       cleared: false,
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(3, 'scene_background_set', {
-      surface: 'web',
+      app_surface: 'web',
       source: 'scene_settings',
       cleared: true,
     })
@@ -904,11 +901,11 @@ describe('useAnalytics conversation product events', () => {
     analytics.trackDataAction({ action: 'app_data_cleared' })
 
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(1, 'data_action', {
-      surface: 'web',
+      app_surface: 'web',
       action: 'chats_exported',
     })
     expect(analyticsMocks.posthogCaptureMock).toHaveBeenNthCalledWith(2, 'data_action', {
-      surface: 'web',
+      app_surface: 'web',
       action: 'app_data_cleared',
     })
   })
diff --git a/packages/stage-ui/src/composables/use-analytics.ts b/packages/stage-ui/src/composables/use-analytics.ts
index 08e492955..9f212d8fd 100644
--- a/packages/stage-ui/src/composables/use-analytics.ts
+++ b/packages/stage-ui/src/composables/use-analytics.ts
@@ -51,7 +51,13 @@ export type OauthCallbackFailureStage
     | 'parse'
     | 'relay_unreachable'
 
-interface ChatActivationBaseProperties {
+interface ChatRoundCorrelationProperties {
+  conversation_id: string
+  round_id: string
+  turn_index: number
+}
+
+interface ChatActivationBaseProperties extends ChatRoundCorrelationProperties {
   provider_mode: ProviderMode
   provider_id: string
   model_id: string
@@ -167,23 +173,23 @@ export function useAnalytics() {
    * - Any UI surface that shows Flux packages / subscription plans renders.
    *   Current surfaces: `settings_flux` (in-app billing settings). Future
    *   surfaces (a public pricing landing page, an upsell modal) just pass a
-   *   different `surface` so the funnel split stays clean.
+   *   different `entry_surface` so the funnel split stays clean.
    *
    * Expects:
-   * - `surface` is a stable identifier — don't rename without coordinating
+   * - `entry_surface` is a stable identifier — don't rename without coordinating
    *   PostHog funnel definitions in `docs/ai-context/metrics-ownership.md`.
    */
-  function trackPricingViewed(surface: string, planPeriod?: 'monthly' | 'annual' | 'one_time') {
+  function trackPricingViewed(entrySurface: string, planPeriod?: 'monthly' | 'annual' | 'one_time') {
     if (!canCapture())
       return
-    posthog.capture('pricing_page_viewed', { surface, ...(planPeriod && { plan_period: planPeriod }) })
+    posthog.capture('pricing_page_viewed', { entry_surface: entrySurface, ...(planPeriod && { plan_period: planPeriod }) })
   }
 
   /**
    * Pricing funnel — step 2. Fires when the user picks a plan/package but
    * hasn't yet kicked off the Stripe checkout redirect.
    */
-  function trackPlanSelected(planId: string, properties?: { price_minor_unit?: number, currency?: string }) {
+  function trackPlanSelected(planId: string, properties: { entry_surface: string, price_minor_unit?: number, currency?: string }) {
     if (!canCapture())
       return
     posthog.capture('plan_selected', { plan_id: planId, ...properties })
@@ -206,7 +212,7 @@ export function useAnalytics() {
    * `apps/server/src/services/domain/product-events.ts`), keyed by the
    * Better Auth user id.
    */
-  function trackCheckoutStarted(planId: string, properties: { checkout_session_id?: string, price_minor_unit?: number, currency?: string }) {
+  function trackCheckoutStarted(planId: string, properties: { entry_surface: string, checkout_session_id?: string, price_minor_unit?: number, currency?: string }) {
     if (!canCapture())
       return
     posthog.capture(
@@ -217,14 +223,14 @@ export function useAnalytics() {
   }
 
   function trackPaywallSeen(properties: {
-    surface: string
+    entry_surface: string
     reason: 'manual_topup' | 'insufficient_balance' | 'checkout_recovery' | 'unknown'
     flux_balance_bucket: FluxBalanceBucket
   }) {
     if (!canCapture())
       return
     posthog.capture('paywall_seen', {
-      surface: properties.surface,
+      entry_surface: properties.entry_surface,
       app_surface: getConversationAnalyticsSurface(),
       reason: properties.reason,
       flux_balance_bucket: properties.flux_balance_bucket,
@@ -243,7 +249,7 @@ export function useAnalytics() {
       return
     posthog.capture('oauth_callback_failed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -253,13 +259,13 @@ export function useAnalytics() {
   function trackPasswordChanged() {
     if (!canCapture())
       return
-    posthog.capture('password_changed', { surface: getConversationAnalyticsSurface() })
+    posthog.capture('password_changed', { app_surface: getConversationAnalyticsSurface() })
   }
 
   function trackPasswordResetRequested() {
     if (!canCapture())
       return
-    posthog.capture('password_reset_requested', { surface: getConversationAnalyticsSurface() })
+    posthog.capture('password_reset_requested', { app_surface: getConversationAnalyticsSurface() })
   }
 
   function trackOauthProviderLinkStarted(properties: { provider: string }) {
@@ -272,7 +278,7 @@ export function useAnalytics() {
       'oauth_provider_link_started',
       {
         ...properties,
-        surface: getConversationAnalyticsSurface(),
+        app_surface: getConversationAnalyticsSurface(),
       },
       { send_instantly: true, transport: 'sendBeacon' },
     )
@@ -283,7 +289,7 @@ export function useAnalytics() {
       return
     posthog.capture('oauth_provider_unlinked', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -295,21 +301,7 @@ export function useAnalytics() {
   function trackAccountDeletionRequested() {
     if (!canCapture())
       return
-    posthog.capture('account_deletion_requested', { surface: getConversationAnalyticsSurface() })
-  }
-
-  function trackSignupCompleted(properties: {
-    source: string
-    referrer?: string
-    country?: string
-    locale?: string
-    utm_source?: string
-    utm_medium?: string
-    utm_campaign?: string
-  }) {
-    if (!canCapture())
-      return
-    posthog.capture('signup_completed', properties)
+    posthog.capture('account_deletion_requested', { app_surface: getConversationAnalyticsSurface() })
   }
 
   function trackOnboardingStarted(properties: { entry: ProductAnalyticsEntry }) {
@@ -317,7 +309,7 @@ export function useAnalytics() {
       return
     posthog.capture('onboarding_started', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -326,7 +318,7 @@ export function useAnalytics() {
       return
     posthog.capture('onboarding_completed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -357,7 +349,7 @@ export function useAnalytics() {
       from_model: fromModel,
       to_model: toModel,
       reason,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -379,39 +371,55 @@ export function useAnalytics() {
   // (per-request volume stays in DB/Grafana). These client emits supply the
   // user-facing latency picture (TTFT, render time) the server cannot see.
 
-  function trackMessageSendStarted(properties: { source: 'text' | 'voice', model?: string }) {
+  function trackMessageSendStarted(properties: ChatRoundCorrelationProperties & { source: 'text' | 'voice', model?: string }) {
     if (!canCapture())
       return
     posthog.capture('message_send_started', properties)
   }
 
-  function trackLlmRequestStarted(properties: { model: string, provider: string, has_voice: boolean }) {
+  function trackLlmRequestStarted(properties: ChatRoundCorrelationProperties & { model: string, provider: string, has_voice: boolean }) {
     if (!canCapture())
       return
     posthog.capture('llm_request_started', properties)
   }
 
   /** First token from a streaming LLM response — perceived responsiveness anchor. */
-  function trackLlmFirstToken(properties: { model: string, ttfb_ms: number }) {
+  function trackLlmFirstToken(properties: ChatRoundCorrelationProperties & { model: string, ttfb_ms: number }) {
     if (!canCapture())
       return
     posthog.capture('llm_first_token', properties)
   }
 
   /** Stream finished and the UI has fully rendered the assistant message. */
-  function trackAssistantResponseRendered(properties: { model: string, latency_ms: number }) {
+  function trackAssistantResponseRendered(properties: ChatRoundCorrelationProperties & { model: string, latency_ms: number }) {
     if (!canCapture())
       return
     posthog.capture('assistant_response_rendered', properties)
   }
 
   /** Closing event for one full message round (user send → assistant render). */
-  function trackMessageRound(properties: { duration_ms: number, has_voice: boolean, model: string }) {
+  function trackMessageRound(properties: ChatRoundCorrelationProperties & { duration_ms: number, has_voice: boolean, model: string }) {
     if (!canCapture())
       return
     posthog.capture('message_round', properties)
   }
 
+  /** Canonical failure event for every user-to-assistant round, including post-activation turns. */
+  function trackMessageRoundFailed(properties: ChatRoundCorrelationProperties & {
+    provider_id: string
+    model_id: string
+    source: 'text' | 'voice'
+    error_code: string
+    failure_stage: ChatActivationFailureStage
+  }) {
+    if (!canCapture())
+      return
+    posthog.capture('message_round_failed', {
+      ...properties,
+      app_surface: getConversationAnalyticsSurface(),
+    })
+  }
+
   // ─── Chat activation events ──────────────────────────────────────────
 
   function trackChatActivationStarted(properties: ChatActivationBaseProperties) {
@@ -419,7 +427,7 @@ export function useAnalytics() {
       return
     posthog.capture('chat_activation_started', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -428,7 +436,7 @@ export function useAnalytics() {
       return
     posthog.capture('chat_activation_succeeded', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -440,19 +448,7 @@ export function useAnalytics() {
       return
     posthog.capture('chat_activation_failed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
-    })
-  }
-
-  function trackChatStarted(properties: ConversationBaseProperties & {
-    entry: ProductAnalyticsEntry
-    is_paid_user?: boolean
-  }) {
-    if (!canCapture())
-      return
-    posthog.capture('chat_started', {
-      ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -467,11 +463,13 @@ export function useAnalytics() {
       return
     posthog.capture('official_provider_selected', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
   function trackMessageSent(properties: ConversationBaseProperties & {
+    round_id: string
+    turn_index: number
     message_id?: string
     message_index?: number
     message_length?: number
@@ -482,40 +480,16 @@ export function useAnalytics() {
       return
     posthog.capture('message_sent', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
-  function trackAssistantResponseCompleted(properties: ConversationBaseProperties & {
-    latency_ms?: number
-    completion_length?: number
-  }) {
-    if (!canCapture())
-      return
-    posthog.capture('assistant_response_completed', {
-      ...properties,
-      surface: getConversationAnalyticsSurface(),
-    })
-  }
-
-  function trackChatFailed(properties: ConversationBaseProperties & {
-    failure_stage: ChatActivationFailureStage
-    error_code: string
-  }) {
-    if (!canCapture())
-      return
-    posthog.capture('chat_failed', {
-      ...properties,
-      surface: getConversationAnalyticsSurface(),
-    })
-  }
-
-  function trackSecondTurnStarted(properties: ChatActivationBaseProperties & { turn_index: number }) {
+  function trackSecondTurnStarted(properties: ChatActivationBaseProperties) {
     if (!canCapture())
       return
     posthog.capture('second_turn_started', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -529,7 +503,7 @@ export function useAnalytics() {
       return
     posthog.capture('model_list_loaded', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -543,7 +517,7 @@ export function useAnalytics() {
       return
     posthog.capture('model_list_failed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -552,7 +526,7 @@ export function useAnalytics() {
       return
     posthog.capture('provider_config_started', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -561,7 +535,7 @@ export function useAnalytics() {
       return
     posthog.capture('provider_config_succeeded', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
     trackProviderConfigCompleted({
       ...properties,
@@ -583,7 +557,7 @@ export function useAnalytics() {
       return
     posthog.capture('provider_config_failed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -599,7 +573,7 @@ export function useAnalytics() {
       provider_type: properties.provider_mode,
       provider_name: properties.provider_id,
       entry_page: properties.step,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -611,7 +585,7 @@ export function useAnalytics() {
       return
     posthog.capture('official_provider_enabled', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -622,7 +596,7 @@ export function useAnalytics() {
       return
     posthog.capture('tts_stop_clicked', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -631,7 +605,7 @@ export function useAnalytics() {
       return
     posthog.capture('chat_session_selected', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -640,7 +614,7 @@ export function useAnalytics() {
       return
     posthog.capture('chat_message_deleted', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -649,7 +623,7 @@ export function useAnalytics() {
       return
     posthog.capture('chat_messages_cleared', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -658,7 +632,7 @@ export function useAnalytics() {
       return
     posthog.capture('chat_message_retried', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -672,7 +646,7 @@ export function useAnalytics() {
       return
     posthog.capture('conversation_created', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -684,7 +658,7 @@ export function useAnalytics() {
       return
     posthog.capture('conversation_renamed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -696,7 +670,7 @@ export function useAnalytics() {
       return
     posthog.capture('conversation_shared', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -709,7 +683,7 @@ export function useAnalytics() {
       return
     posthog.capture('conversation_deleted', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -738,11 +712,11 @@ export function useAnalytics() {
       return
     posthog.capture('voice_input_started', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
     posthog.capture('voice_input_used', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -751,7 +725,7 @@ export function useAnalytics() {
       return
     posthog.capture('microphone_permission_requested', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -760,7 +734,7 @@ export function useAnalytics() {
       return
     posthog.capture('microphone_permission_denied', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -769,7 +743,7 @@ export function useAnalytics() {
       return
     posthog.capture('audio_device_unavailable', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -778,7 +752,7 @@ export function useAnalytics() {
       return
     posthog.capture('voice_input_cancelled', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -793,7 +767,7 @@ export function useAnalytics() {
       return
     posthog.capture('bug_report_submitted', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -802,7 +776,7 @@ export function useAnalytics() {
       return
     posthog.capture('feedback_submitted', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -848,7 +822,7 @@ export function useAnalytics() {
       return
     posthog.capture('tts_provider_selected', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -861,7 +835,7 @@ export function useAnalytics() {
       return
     posthog.capture('voice_selected', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -874,7 +848,7 @@ export function useAnalytics() {
       return
     posthog.capture('voice_preview_played', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -886,7 +860,7 @@ export function useAnalytics() {
       return
     posthog.capture('voice_pack_bound', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -900,7 +874,7 @@ export function useAnalytics() {
       return
     posthog.capture('attachment_uploaded', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -909,7 +883,7 @@ export function useAnalytics() {
       return
     posthog.capture('official_tts_exposed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -922,7 +896,7 @@ export function useAnalytics() {
       return
     posthog.capture('preset_used', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -936,7 +910,7 @@ export function useAnalytics() {
       return
     posthog.capture('official_tts_preview_started', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -951,7 +925,7 @@ export function useAnalytics() {
       return
     posthog.capture('official_tts_preview_succeeded', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -966,7 +940,7 @@ export function useAnalytics() {
       return
     posthog.capture('provider_switched', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -980,7 +954,7 @@ export function useAnalytics() {
       return
     posthog.capture('settings_changed', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -993,7 +967,7 @@ export function useAnalytics() {
       return
     posthog.capture('support_contacted', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -1005,7 +979,7 @@ export function useAnalytics() {
       return
     posthog.capture('official_tts_auto_enabled', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -1029,7 +1003,7 @@ export function useAnalytics() {
       return
     posthog.capture('card_edited', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -1039,7 +1013,7 @@ export function useAnalytics() {
       return
     posthog.capture('scene_background_set', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -1097,7 +1071,7 @@ export function useAnalytics() {
     posthog.capture('flux_low_warning_shown', properties)
   }
 
-  function trackFluxTopupClicked(properties: { balance: number, surface: string }) {
+  function trackFluxTopupClicked(properties: { balance: number, entry_surface: string }) {
     if (!canCapture())
       return
     posthog.capture('flux_topup_clicked', properties)
@@ -1134,7 +1108,7 @@ export function useAnalytics() {
       return
     posthog.capture('feature_used', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -1153,7 +1127,7 @@ export function useAnalytics() {
       return
     posthog.capture('data_action', {
       ...properties,
-      surface: getConversationAnalyticsSurface(),
+      app_surface: getConversationAnalyticsSurface(),
     })
   }
 
@@ -1243,7 +1217,6 @@ export function useAnalytics() {
     trackPlanSelected,
     trackCheckoutStarted,
     trackPaywallSeen,
-    trackSignupCompleted,
     trackOauthCallbackFailed,
     trackPasswordChanged,
     trackPasswordResetRequested,
@@ -1261,11 +1234,9 @@ export function useAnalytics() {
     trackLlmRequestStarted,
     trackLlmFirstToken,
     trackAssistantResponseRendered,
-    trackAssistantResponseCompleted,
     trackMessageRound,
-    trackChatStarted,
+    trackMessageRoundFailed,
     trackMessageSent,
-    trackChatFailed,
     trackChatActivationStarted,
     trackChatActivationSucceeded,
     trackChatActivationFailed,
diff --git a/packages/stage-ui/src/stores/analytics/index.ts b/packages/stage-ui/src/stores/analytics/index.ts
index 0a4ead9d7..8e785617d 100644
--- a/packages/stage-ui/src/stores/analytics/index.ts
+++ b/packages/stage-ui/src/stores/analytics/index.ts
@@ -59,7 +59,7 @@ export const useSharedAnalyticsStore = defineStore('analytics-shared', () => {
         previous_value: previousEnabled,
         new_value: enabled,
         source: 'settings',
-        surface: analyticsSurface(),
+        app_surface: analyticsSurface(),
       })
     }
 
@@ -71,7 +71,7 @@ export const useSharedAnalyticsStore = defineStore('analytics-shared', () => {
           previous_value: previousEnabled,
           new_value: enabled,
           source: 'settings',
-          surface: analyticsSurface(),
+          app_surface: analyticsSurface(),
         })
       }
 
@@ -189,7 +189,7 @@ export const useSharedAnalyticsStore = defineStore('analytics-shared', () => {
             from_provider_type: providerMode(prev.provider),
             to_provider_type: providerMode(next.provider),
             reason: 'manual',
-            surface: analyticsSurface(),
+            app_surface: analyticsSurface(),
           })
         }
 
@@ -204,7 +204,7 @@ export const useSharedAnalyticsStore = defineStore('analytics-shared', () => {
             to_model: next.model,
             provider: next.provider,
             reason: 'manual',
-            surface: analyticsSurface(),
+            app_surface: analyticsSurface(),
           })
         }
       },
diff --git a/packages/stage-ui/src/stores/analytics/posthog.test.ts b/packages/stage-ui/src/stores/analytics/posthog.test.ts
new file mode 100644
index 000000000..57bf31533
--- /dev/null
+++ b/packages/stage-ui/src/stores/analytics/posthog.test.ts
@@ -0,0 +1,35 @@
+import { describe, expect, it, vi } from 'vitest'
+
+import { ensurePosthogInitialized } from './posthog'
+
+const posthogMocks = vi.hoisted(() => ({
+  init: vi.fn(),
+  register: vi.fn(),
+}))
+
+vi.mock('posthog-js', () => ({
+  default: posthogMocks,
+}))
+
+vi.mock('@proj-airi/stage-shared', () => ({
+  isStageCapacitor: () => false,
+  isStageTamagotchi: () => false,
+}))
+
+vi.mock('../../../../../posthog.config', () => ({
+  DEFAULT_POSTHOG_CONFIG: {},
+  POSTHOG_ENABLED: true,
+  POSTHOG_PROJECT_KEY: 'test-project-key',
+}))
+
+describe('stage PostHog initialization', () => {
+  // ROOT CAUSE:
+  //
+  // `surface` was registered as the runtime platform but individual events
+  // also used `surface` for entry points such as `settings_flux`. Event
+  // properties overwrite super properties, so platform breakdowns drifted.
+  it('registers the runtime under the dedicated app_surface property', () => {
+    expect(ensurePosthogInitialized(true)).toBe(true)
+    expect(posthogMocks.register).toHaveBeenCalledWith({ app_surface: 'web' })
+  })
+})
diff --git a/packages/stage-ui/src/stores/analytics/posthog.ts b/packages/stage-ui/src/stores/analytics/posthog.ts
index 2a226bdf8..f9eff92f3 100644
--- a/packages/stage-ui/src/stores/analytics/posthog.ts
+++ b/packages/stage-ui/src/stores/analytics/posthog.ts
@@ -13,7 +13,7 @@ import {
 let posthogInitialized = false
 
 // All AIRI surfaces (web, desktop, mobile) capture into a single PostHog
-// project. The platform is carried on every event via the `surface` super
+// project. The platform is carried on every event via the `app_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' {
@@ -43,7 +43,7 @@ export function ensurePosthogInitialized(enabled: boolean): boolean {
   })
   // 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() })
+  posthog.register({ app_surface: currentSurface() })
   posthogInitialized = true
   return true
 }
diff --git a/packages/stage-ui/src/stores/chat.contract.test.ts b/packages/stage-ui/src/stores/chat.contract.test.ts
index 7aa1c9b2f..4004825f5 100644
--- a/packages/stage-ui/src/stores/chat.contract.test.ts
+++ b/packages/stage-ui/src/stores/chat.contract.test.ts
@@ -39,7 +39,26 @@ const ioTracerMocks = vi.hoisted(() => {
 
 const llmStreamMock = vi.fn()
 const trackFirstMessageMock = vi.fn()
-const trackSecondTurnStartedMock = vi.fn()
+const chatAnalyticsMocks = vi.hoisted(() => ({
+  trackAssistantResponseRendered: vi.fn(),
+  trackChatActivationFailed: vi.fn(),
+  trackChatActivationStarted: vi.fn(),
+  trackChatActivationSucceeded: vi.fn(),
+  trackLlmFirstToken: vi.fn(),
+  trackLlmRequestStarted: vi.fn(),
+  trackMessageRound: vi.fn(),
+  trackMessageRoundFailed: vi.fn(),
+  trackMessageSendStarted: vi.fn(),
+  trackMessageSent: vi.fn(),
+  trackSecondTurnStarted: vi.fn(),
+}))
+const trackSecondTurnStartedMock = chatAnalyticsMocks.trackSecondTurnStarted
+const redundantChatAnalyticsMocks = vi.hoisted(() => ({
+  trackAssistantResponseCompleted: vi.fn(),
+  trackChatFailed: vi.fn(),
+  trackChatStarted: vi.fn(),
+  trackFeatureUsed: vi.fn(),
+}))
 const ingestContextMessageMock = vi.fn()
 const getContextsSnapshotMock = vi.fn()
 const createMinecraftContextMock = vi.fn()
@@ -65,19 +84,20 @@ vi.mock('pinia', async () => {
 vi.mock('../composables', () => ({
   useAnalytics: () => ({
     trackFirstMessage: trackFirstMessageMock,
-    trackChatFailed: vi.fn(),
-    trackChatStarted: vi.fn(),
-    trackMessageSendStarted: vi.fn(),
-    trackMessageSent: vi.fn(),
-    trackLlmRequestStarted: vi.fn(),
-    trackLlmFirstToken: vi.fn(),
-    trackAssistantResponseRendered: vi.fn(),
-    trackAssistantResponseCompleted: vi.fn(),
-    trackMessageRound: vi.fn(),
-    trackFeatureUsed: vi.fn(),
-    trackChatActivationStarted: vi.fn(),
-    trackChatActivationSucceeded: vi.fn(),
-    trackChatActivationFailed: vi.fn(),
+    trackChatFailed: redundantChatAnalyticsMocks.trackChatFailed,
+    trackChatStarted: redundantChatAnalyticsMocks.trackChatStarted,
+    trackMessageSendStarted: chatAnalyticsMocks.trackMessageSendStarted,
+    trackMessageSent: chatAnalyticsMocks.trackMessageSent,
+    trackLlmRequestStarted: chatAnalyticsMocks.trackLlmRequestStarted,
+    trackLlmFirstToken: chatAnalyticsMocks.trackLlmFirstToken,
+    trackAssistantResponseRendered: chatAnalyticsMocks.trackAssistantResponseRendered,
+    trackAssistantResponseCompleted: redundantChatAnalyticsMocks.trackAssistantResponseCompleted,
+    trackMessageRound: chatAnalyticsMocks.trackMessageRound,
+    trackMessageRoundFailed: chatAnalyticsMocks.trackMessageRoundFailed,
+    trackFeatureUsed: redundantChatAnalyticsMocks.trackFeatureUsed,
+    trackChatActivationStarted: chatAnalyticsMocks.trackChatActivationStarted,
+    trackChatActivationSucceeded: chatAnalyticsMocks.trackChatActivationSucceeded,
+    trackChatActivationFailed: chatAnalyticsMocks.trackChatActivationFailed,
     trackSecondTurnStarted: trackSecondTurnStartedMock,
   }),
 }))
@@ -166,7 +186,12 @@ describe('chat orchestrator contract', () => {
     setActivePinia(createPinia())
     llmStreamMock.mockReset()
     trackFirstMessageMock.mockReset()
-    trackSecondTurnStartedMock.mockReset()
+    for (const analyticsMock of Object.values(chatAnalyticsMocks))
+      analyticsMock.mockReset()
+    redundantChatAnalyticsMocks.trackAssistantResponseCompleted.mockReset()
+    redundantChatAnalyticsMocks.trackChatFailed.mockReset()
+    redundantChatAnalyticsMocks.trackChatStarted.mockReset()
+    redundantChatAnalyticsMocks.trackFeatureUsed.mockReset()
     ingestContextMessageMock.mockReset()
     getContextsSnapshotMock.mockReset()
     getContextsSnapshotMock.mockReturnValue({})
@@ -190,6 +215,39 @@ describe('chat orchestrator contract', () => {
     sessionMessages['session-1'] = [{ role: 'system', content: 'system prompt', createdAt: 1, id: 'system' }]
   })
 
+  it('forwards one correlation identity across every PostHog chat milestone', async () => {
+    llmStreamMock.mockImplementation(async (_model: string, _chatProvider: ChatProvider, _messages: Message[], options: any) => {
+      await options.onStreamEvent({ type: 'text-delta', text: 'ok' })
+      await options.onStreamEvent({ type: 'finish', finishReason: 'stop' })
+    })
+
+    const store = useChatOrchestratorStore()
+    await store.ingest('hello', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })
+
+    const messageProperties = chatAnalyticsMocks.trackMessageSent.mock.calls[0]?.[0]
+    expect(messageProperties).toMatchObject({
+      conversation_id: 'session-1',
+      round_id: messageProperties.message_id,
+      turn_index: 1,
+    })
+
+    const correlation = {
+      conversation_id: 'session-1',
+      round_id: messageProperties.round_id,
+      turn_index: 1,
+    }
+    expect(chatAnalyticsMocks.trackMessageSendStarted).toHaveBeenCalledWith(expect.objectContaining(correlation))
+    expect(chatAnalyticsMocks.trackLlmRequestStarted).toHaveBeenCalledWith(expect.objectContaining(correlation))
+    expect(chatAnalyticsMocks.trackLlmFirstToken).toHaveBeenCalledWith(expect.objectContaining(correlation))
+    expect(chatAnalyticsMocks.trackAssistantResponseRendered).toHaveBeenCalledWith(expect.objectContaining(correlation))
+    expect(chatAnalyticsMocks.trackMessageRound).toHaveBeenCalledWith(expect.objectContaining(correlation))
+    expect(chatAnalyticsMocks.trackChatActivationStarted).toHaveBeenCalledWith(expect.objectContaining(correlation))
+    expect(chatAnalyticsMocks.trackChatActivationSucceeded).toHaveBeenCalledWith(expect.objectContaining(correlation))
+  })
+
   it('emits second turn analytics from chat sends', async () => {
     activeProviderRef.value = 'official-provider'
     llmStreamMock.mockImplementation(async (_model: string, _chatProvider: ChatProvider, _messages: Message[], options: any) => {
@@ -210,9 +268,64 @@ describe('chat orchestrator contract', () => {
 
     expect(trackSecondTurnStartedMock).toHaveBeenCalledTimes(1)
     expect(trackSecondTurnStartedMock).toHaveBeenCalledWith({
+      conversation_id: 'session-1',
       provider_id: 'official-provider',
       provider_mode: 'official',
       model_id: 'chat-auto',
+      round_id: expect.any(String),
+      source: 'text',
+      turn_index: 2,
+    })
+  })
+
+  // ROOT CAUSE:
+  //
+  // One successful send emitted both the canonical message/latency events
+  // and four generic aliases, multiplying PostHog volume without adding a
+  // distinct product decision.
+  it('does not emit redundant generic chat aliases for a successful send', async () => {
+    llmStreamMock.mockImplementation(async (_model: string, _chatProvider: ChatProvider, _messages: Message[], options: any) => {
+      await options.onStreamEvent({ type: 'text-delta', text: 'ok' })
+      await options.onStreamEvent({ type: 'finish', finishReason: 'stop' })
+    })
+
+    const store = useChatOrchestratorStore()
+    await store.ingest('hello', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })
+
+    expect(redundantChatAnalyticsMocks.trackChatStarted).not.toHaveBeenCalled()
+    expect(redundantChatAnalyticsMocks.trackAssistantResponseCompleted).not.toHaveBeenCalled()
+    expect(redundantChatAnalyticsMocks.trackChatFailed).not.toHaveBeenCalled()
+    expect(redundantChatAnalyticsMocks.trackFeatureUsed).not.toHaveBeenCalled()
+  })
+
+  it('forwards later-turn failures to the canonical round failure event', async () => {
+    llmStreamMock.mockImplementationOnce(async (_model: string, _chatProvider: ChatProvider, _messages: Message[], options: any) => {
+      await options.onStreamEvent({ type: 'text-delta', text: 'ok' })
+      await options.onStreamEvent({ type: 'finish', finishReason: 'stop' })
+    })
+    llmStreamMock.mockRejectedValueOnce(new Error('later turn rejected'))
+
+    const store = useChatOrchestratorStore()
+    await store.ingest('first turn', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })
+    await expect(store.ingest('second turn', {
+      model: 'gpt-test',
+      chatProvider: provider,
+    })).rejects.toThrow('later turn rejected')
+
+    expect(chatAnalyticsMocks.trackChatActivationFailed).not.toHaveBeenCalled()
+    expect(chatAnalyticsMocks.trackMessageRoundFailed).toHaveBeenCalledWith({
+      conversation_id: 'session-1',
+      error_code: 'llm_response_failed',
+      failure_stage: 'llm_response',
+      model_id: 'gpt-test',
+      provider_id: 'mock-provider',
+      round_id: expect.any(String),
       source: 'text',
       turn_index: 2,
     })
diff --git a/packages/stage-ui/src/stores/chat.ts b/packages/stage-ui/src/stores/chat.ts
index 08b57ce45..665c57eeb 100644
--- a/packages/stage-ui/src/stores/chat.ts
+++ b/packages/stage-ui/src/stores/chat.ts
@@ -51,16 +51,13 @@ export const useChatOrchestratorStore = defineStore('chat-orchestrator', () => {
   const { activeModel, activeProvider } = storeToRefs(consciousnessStore)
   const {
     trackFirstMessage,
-    trackChatFailed,
-    trackChatStarted,
     trackMessageSendStarted,
     trackMessageSent,
     trackLlmRequestStarted,
     trackLlmFirstToken,
     trackAssistantResponseRendered,
-    trackAssistantResponseCompleted,
     trackMessageRound,
-    trackFeatureUsed,
+    trackMessageRoundFailed,
     trackChatActivationStarted,
     trackChatActivationSucceeded,
     trackChatActivationFailed,
@@ -185,109 +182,119 @@ export const useChatOrchestratorStore = defineStore('chat-orchestrator', () => {
     onStateChange: syncRuntimeState,
     onSendSettled: settleOwnedActiveTurnSpan,
     onTrackFirstMessage: trackFirstMessage,
-    onMessageSendStarted: ({ source, model }) => {
+    onMessageSendStarted: ({ conversationId, roundId, turnIndex, source, model }) => {
       lastSendSource = source
       trackMessageSendStarted({
+        conversation_id: conversationId,
+        round_id: roundId,
+        turn_index: turnIndex,
         source,
         model,
       })
-      trackChatStarted({
-        conversation_id: activeSessionId.value || 'unknown',
-        provider_type: providerMode(activeProvider.value),
-        provider_name: activeProvider.value || 'unknown',
-        model: model || 'unknown',
-        entry: 'chat',
-      })
     },
-    onLlmRequestStarted: ({ model, provider, hasVoice }) => trackLlmRequestStarted({
+    onLlmRequestStarted: ({ conversationId, roundId, turnIndex, model, provider, hasVoice }) => trackLlmRequestStarted({
+      conversation_id: conversationId,
+      round_id: roundId,
+      turn_index: turnIndex,
       model,
       provider,
       has_voice: hasVoice,
     }),
-    onLlmFirstToken: ({ model, ttfbMs }) => trackLlmFirstToken({
+    onLlmFirstToken: ({ conversationId, roundId, turnIndex, model, ttfbMs }) => trackLlmFirstToken({
+      conversation_id: conversationId,
+      round_id: roundId,
+      turn_index: turnIndex,
       model,
       ttfb_ms: ttfbMs,
     }),
-    onAssistantResponseRendered: ({ model, latencyMs }) => {
+    onAssistantResponseRendered: ({ conversationId, roundId, turnIndex, model, latencyMs }) => {
       trackAssistantResponseRendered({
+        conversation_id: conversationId,
+        round_id: roundId,
+        turn_index: turnIndex,
         model,
         latency_ms: latencyMs,
       })
-      trackAssistantResponseCompleted({
-        conversation_id: activeSessionId.value || 'unknown',
-        provider_type: providerMode(activeProvider.value),
-        provider_name: activeProvider.value || 'unknown',
-        model: model || 'unknown',
-        latency_ms: latencyMs,
-      })
     },
-    onMessageRound: ({ durationMs, hasVoice, model }) => trackMessageRound({
+    onMessageRound: ({ conversationId, roundId, turnIndex, durationMs, hasVoice, model }) => trackMessageRound({
+      conversation_id: conversationId,
+      round_id: roundId,
+      turn_index: turnIndex,
       duration_ms: durationMs,
       has_voice: hasVoice,
       model,
     }),
-    onChatActivationStarted: ({ model, provider, source }) => {
+    onMessageRoundFailed: ({ conversationId, roundId, turnIndex, model, provider, errorCode, failureStage, source }) => trackMessageRoundFailed({
+      conversation_id: conversationId,
+      round_id: roundId,
+      turn_index: turnIndex,
+      provider_id: provider || 'unknown',
+      model_id: model || 'unknown',
+      source,
+      error_code: errorCode,
+      failure_stage: failureStage,
+    }),
+    onChatActivationStarted: ({ conversationId, roundId, turnIndex, model, provider, source }) => {
       const mode = providerMode(provider)
       const providerId = provider || 'unknown'
       const modelId = model || 'unknown'
 
       trackChatActivationStarted({
+        conversation_id: conversationId,
         provider_mode: mode,
         provider_id: providerId,
         model_id: modelId,
+        round_id: roundId,
         source,
+        turn_index: turnIndex,
       })
     },
-    onChatActivationSucceeded: ({ model, provider, durationMs, source }) => trackChatActivationSucceeded({
+    onChatActivationSucceeded: ({ conversationId, roundId, turnIndex, model, provider, durationMs, source }) => trackChatActivationSucceeded({
+      conversation_id: conversationId,
       provider_mode: providerMode(provider),
       provider_id: provider || 'unknown',
       model_id: model || 'unknown',
+      round_id: roundId,
       time_to_first_message_ms: durationMs,
       source,
+      turn_index: turnIndex,
     }),
-    onChatActivationFailed: ({ model, provider, errorCode, failureStage, source }) => {
+    onChatActivationFailed: ({ conversationId, roundId, turnIndex, model, provider, errorCode, failureStage, source }) => {
       trackChatActivationFailed({
+        conversation_id: conversationId,
         provider_mode: providerMode(provider),
         provider_id: provider || 'unknown',
         model_id: model || 'unknown',
+        round_id: roundId,
         error_code: errorCode,
         failure_stage: failureStage,
         source,
-      })
-      trackChatFailed({
-        conversation_id: activeSessionId.value || 'unknown',
-        provider_type: providerMode(provider),
-        provider_name: provider || 'unknown',
-        model: model || 'unknown',
-        failure_stage: failureStage,
-        error_code: errorCode,
+        turn_index: turnIndex,
       })
     },
     onLifecycle: record => contextObservability.recordLifecycle(record),
     onPromptProjection: payload => contextObservability.capturePromptProjection(payload),
-    onUserMessageAppended: ({ sessionId, message, messageText, source, model, provider, turnIndex }) => {
+    onUserMessageAppended: ({ sessionId, message, messageText, source, model, provider, roundId, turnIndex }) => {
       trackMessageSent({
         conversation_id: sessionId,
         provider_type: providerMode(activeProvider.value),
         provider_name: activeProvider.value || 'unknown',
         model: activeModel.value || 'unknown',
         message_id: message.id,
+        round_id: roundId,
+        turn_index: turnIndex,
         message_index: chatSession.getSessionMessages(sessionId).length,
         message_length: messageText.length,
         has_attachment: false,
         mode: lastSendSource,
       })
-      trackFeatureUsed({
-        feature_name: 'chat',
-        business_domain: 'conversation',
-        entry: 'chat',
-        success: true,
-      })
       if (turnIndex === 2) {
         trackSecondTurnStarted({
+          conversation_id: sessionId,
           provider_mode: providerMode(provider),
           provider_id: provider || 'unknown',
           model_id: model || 'unknown',
+          round_id: roundId,
           source,
           turn_index: turnIndex,
         })
diff --git a/packages/stage-ui/src/stores/providers.ts b/packages/stage-ui/src/stores/providers.ts
index cb9d34a41..c7e31846a 100644
--- a/packages/stage-ui/src/stores/providers.ts
+++ b/packages/stage-ui/src/stores/providers.ts
@@ -132,7 +132,7 @@ function trackModelListLoaded(properties: {
 
   capturePosthogEvent('model_list_loaded', {
     ...properties,
-    surface: analyticsSurface(),
+    app_surface: analyticsSurface(),
   })
 }
 
@@ -150,7 +150,7 @@ function trackModelListFailed(properties: {
 
   capturePosthogEvent('model_list_failed', {
     ...properties,
-    surface: analyticsSurface(),
+    app_surface: analyticsSurface(),
   })
 }
 
diff --git a/posthog.config.ts b/posthog.config.ts
index c65392814..7111999c3 100644
--- a/posthog.config.ts
+++ b/posthog.config.ts
@@ -13,7 +13,7 @@ function isEnvFlagEnabled(value: string | undefined): boolean {
 export const POSTHOG_ENABLED = isEnvFlagEnabled(import.meta.env.VITE_ENABLE_POSTHOG)
 
 // Single PostHog project for every AIRI surface (web / desktop / mobile).
-// Platforms are told apart by the `surface` super property set at init, not
+// Platforms are told apart by the `app_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