diff --git a/.env.local.example b/.env.local.example
index f75dd2a..7340c1a 100644
--- a/.env.local.example
+++ b/.env.local.example
@@ -43,6 +43,13 @@ NOTEBOOK_PUBLIC_URL=http://notebook.local.knowhereto.ai:3001
 # to Better Auth's standard cookie names.
 # SESSION_COOKIE_NAMES=better-auth.session_token,__Secure-better-auth.session_token
 
+# --- Product analytics (client-side) ---
+# PostHog Project API key. When unset, Notebook skips analytics initialization.
+# NEXT_PUBLIC_POSTHOG_KEY=phc_your_project_api_key
+#
+# PostHog ingestion host. Keep default for US PostHog Cloud.
+# NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com
+
 # --- Database (server-side only) ---
 # Neon Postgres connection string (Vercel Marketplace free tier).
 # Provisioned by the owner; do not commit a real value.
diff --git a/README.md b/README.md
index 5e4e239..efde58d 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,8 @@ Upload documents, explore parsed content, and ask questions about your knowledge
 2. Fill in your API keys in `.env.local`:
    - `AI_GATEWAY_API_KEY` — your Vercel AI Gateway key for chat (optional `CHAT_MODEL` override)
    - `KNOWHERE_API_KEY` — optional development override that skips Dashboard auth and calls Knowhere directly
+   - `NEXT_PUBLIC_POSTHOG_KEY` — PostHog Project API key for front-end event tracking
+   - `NEXT_PUBLIC_POSTHOG_HOST` — PostHog ingestion host (default `https://us.i.posthog.com`)
 
 3. Install dependencies and run:
    ```bash
@@ -21,6 +23,43 @@ Upload documents, explore parsed content, and ask questions about your knowledge
 
 4. Open [http://localhost:3000](http://localhost:3000)
 
+## PostHog Tracking
+
+Notebook sends these product analytics events when PostHog is configured:
+
+- `notebook_upload_button_clicked`
+- `notebook_document_upload_completed` (`uploaded_count`, `file_types`, `total_size_bytes`)
+- `notebook_assistant_question_submitted` (`selected_sources_count`, `message_length`)
+- `notebook_dashboard_link_clicked`
+
+Notebook also calls PostHog `identify` for authenticated users and `reset` for
+guest sessions so insights can be grouped by user.
+
+### Connect Notebook to PostHog
+
+1. In PostHog, create/select a project.
+2. Copy the project API key and ingestion host.
+3. Set these values in `.env.local`:
+   ```bash
+   NEXT_PUBLIC_POSTHOG_KEY=phc_your_project_api_key
+   NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com
+   ```
+4. Restart `pnpm dev` (or `npm run dev`), then trigger a few actions in Notebook.
+5. Open PostHog `Events` and filter by the event names above to verify ingestion.
+
+### Where to view the metrics
+
+Create four Trends insights in PostHog:
+
+1. Upload button clicks: count of `notebook_upload_button_clicked`
+2. Uploaded documents: `sum(uploaded_count)` on `notebook_document_upload_completed`
+3. Avg sources per question: `avg(selected_sources_count)` on `notebook_assistant_question_submitted`
+4. Users opening dashboard: `Unique users` on `notebook_dashboard_link_clicked`
+
+Pin those four insights to a `Notebook Tracking` dashboard for team reporting.
+
+GA4 field and event alignment guidance lives in `docs/ga4-alignment.md`.
+
 ## Tech Stack
 
 - **Framework**: [Next.js 16](https://nextjs.org) with App Router and Server Components
diff --git a/docs/ga4-alignment.md b/docs/ga4-alignment.md
new file mode 100644
index 0000000..aee8443
--- /dev/null
+++ b/docs/ga4-alignment.md
@@ -0,0 +1,41 @@
+# GA4 Alignment for Notebook Storytelling v2
+
+This document maps the Notebook storytelling events to GA4 naming and parameters.
+
+## Naming policy
+
+- Keep the same event names in PostHog and GA4.
+- Keep the same parameter names and meanings in both systems.
+
+## Shared user properties
+
+- `workspace_id`
+- `workspace_namespace`
+- `is_guest`
+
+## Event mapping
+
+- `notebook_upload_button_clicked`
+  - params: `source_count_snapshot`, `surface`
+- `notebook_document_upload_completed`
+  - params: `uploaded_count`, `file_types`, `total_size_bytes`, `source_count_before`, `source_count_after`
+- `notebook_document_upload_failed`
+  - params: `file_type`, `file_size_bytes`, `error_type`, `error_message`
+- `notebook_assistant_question_submitted`
+  - params: `thread_id`, `selected_sources_count`, `source_count_snapshot`, `message_length`
+- `notebook_assistant_answer_completed`
+  - params: `thread_id`, `latency_ms`
+- `notebook_assistant_answer_failed`
+  - params: `thread_id`, `latency_ms`, `error_type`, `error_message`
+- `notebook_dashboard_link_clicked`
+  - params: `from_page`, `target_url`, `has_sources`, `has_chats`
+- `notebook_workspace_first_document_uploaded`
+  - params: `surface`
+- `notebook_workspace_first_question_asked`
+  - params: `selected_sources_count`, `surface`
+
+## GA4 implementation notes
+
+- Send GA4 events from the same trigger points as PostHog.
+- Attach `workspace_id`, `workspace_namespace`, and `is_guest` as GA4 user properties after auth state resolves.
+- Keep `error_message` truncated to avoid oversized payloads.
diff --git a/docs/posthog-notebook-tracking.md b/docs/posthog-notebook-tracking.md
new file mode 100644
index 0000000..499a276
--- /dev/null
+++ b/docs/posthog-notebook-tracking.md
@@ -0,0 +1,34 @@
+# PostHog Notebook Tracking Setup
+
+This runbook configures the four baseline insights for Knowhere Notebook usage.
+
+## Events
+
+- `notebook_upload_button_clicked`
+- `notebook_document_upload_completed`
+- `notebook_assistant_question_submitted`
+- `notebook_dashboard_link_clicked`
+
+## Create the Insights
+
+1. Open PostHog `Product Analytics -> Insights`.
+2. Create a `Trends` insight named `Notebook - Upload Button Clicks`.
+   - Series: event `notebook_upload_button_clicked`
+   - Math: `Total count`
+3. Create `Notebook - Uploaded Documents`.
+   - Series: event `notebook_document_upload_completed`
+   - Math: `Sum`
+   - Property: `uploaded_count`
+4. Create `Notebook - Avg Sources Per Question`.
+   - Series: event `notebook_assistant_question_submitted`
+   - Math: `Average`
+   - Property: `selected_sources_count`
+5. Create `Notebook - Dashboard Click Users`.
+   - Series: event `notebook_dashboard_link_clicked`
+   - Math: `Unique users`
+
+## Dashboard
+
+1. Open PostHog `Dashboards` and create `Notebook Tracking`.
+2. Add all four insights above to this dashboard.
+3. Use a rolling `Last 30 days` filter for product reviews.
diff --git a/package-lock.json b/package-lock.json
index d5a79bb..f543f10 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,7 +11,7 @@
         "@ai-sdk/react": "^3.0.177",
         "@effect/platform": "^0.96.1",
         "@neondatabase/serverless": "^1.1.0",
-        "@ontos-ai/knowhere-sdk": "^0.4.0",
+        "@ontos-ai/knowhere-sdk": "^0.6.0",
         "@radix-ui/react-alert-dialog": "^1.1.15",
         "@radix-ui/react-checkbox": "^1.3.3",
         "@radix-ui/react-dialog": "^1.1.15",
@@ -39,6 +39,7 @@
         "next-themes": "^0.4.6",
         "pdfjs-dist": "5.4.296",
         "postgres": "^3.4.9",
+        "posthog-js": "^1.386.8",
         "react": "19.2.4",
         "react-dom": "19.2.4",
         "react-markdown": "^10.1.0",
@@ -2251,7 +2252,9 @@
       }
     },
     "node_modules/@ontos-ai/knowhere-sdk": {
-      "version": "0.4.0",
+      "version": "0.6.0",
+      "resolved": "https://registry.npmjs.org/@ontos-ai/knowhere-sdk/-/knowhere-sdk-0.6.0.tgz",
+      "integrity": "sha512-YqDgg+BKwGp7NepD50aquhEOmUgdDAQxpoyttqh0d+4tWjOgkSo74vEGiJVxt8v+LAcA/5CmxPeghX1Hx0v3wQ==",
       "license": "MIT",
       "dependencies": {
         "axios": "^1.15.2",
@@ -2310,6 +2313,21 @@
         "node": ">=18"
       }
     },
+    "node_modules/@posthog/core": {
+      "version": "1.32.5",
+      "resolved": "https://registry.npmjs.org/@posthog/core/-/core-1.32.5.tgz",
+      "integrity": "sha512-Vmr6LZms7QEP1ljfTRRBVtLkeEHMrTmLECt0FXPLwUIgPwxOgvBdAYwRMWyP13WuN/XQweo1tJ9J1DxHNAF3qg==",
+      "license": "MIT",
+      "dependencies": {
+        "@posthog/types": "^1.386.4"
+      }
+    },
+    "node_modules/@posthog/types": {
+      "version": "1.386.4",
+      "resolved": "https://registry.npmjs.org/@posthog/types/-/types-1.386.4.tgz",
+      "integrity": "sha512-UgE9+5+wkZg7yc2MpW5G32/6zYW8fAbXJkG8WGnrb4X8OKWzNa9cWeNCd82vKok+TSoRpM4qiYQFtBSpJS1dsw==",
+      "license": "MIT"
+    },
     "node_modules/@radix-ui/number": {
       "version": "1.1.1",
       "license": "MIT"
@@ -5114,6 +5132,17 @@
         "node": ">=6.6.0"
       }
     },
+    "node_modules/core-js": {
+      "version": "3.49.0",
+      "resolved": "https://registry.npmjs.org/core-js/-/core-js-3.49.0.tgz",
+      "integrity": "sha512-es1U2+YTtzpwkxVLwAFdSpaIMyQaq0PBgm3YD1W3Qpsn1NAmO3KSgZfu+oGSWVu6NvLHoHCV/aYcsE5wiB7ALg==",
+      "hasInstallScript": true,
+      "license": "MIT",
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/core-js"
+      }
+    },
     "node_modules/core-util-is": {
       "version": "1.0.3",
       "license": "MIT"
@@ -7567,6 +7596,12 @@
         "node": "^12.20 || >= 14.13"
       }
     },
+    "node_modules/fflate": {
+      "version": "0.4.8",
+      "resolved": "https://registry.npmjs.org/fflate/-/fflate-0.4.8.tgz",
+      "integrity": "sha512-FJqqoDBR00Mdj9ppamLa/Y7vxm+PRmNWA67N846RvsoYVMKB4q3y/de5PA7gUmRMYK/8CMz2GDZQmCRN1wBcWA==",
+      "license": "MIT"
+    },
     "node_modules/figures": {
       "version": "6.1.0",
       "dev": true,
@@ -11462,6 +11497,22 @@
         "url": "https://github.com/sponsors/porsager"
       }
     },
+    "node_modules/posthog-js": {
+      "version": "1.386.8",
+      "resolved": "https://registry.npmjs.org/posthog-js/-/posthog-js-1.386.8.tgz",
+      "integrity": "sha512-L4cJD1sleUULE7K4mZQI5wpS24NHGtNmFw1rPHruc579unVzHuooHiVDEHp/qyNnhNxtNE6alBTiVORbYnRTSw==",
+      "license": "SEE LICENSE IN LICENSE",
+      "dependencies": {
+        "@posthog/core": "^1.32.4",
+        "@posthog/types": "^1.386.4",
+        "core-js": "^3.38.1",
+        "dompurify": "^3.3.2",
+        "fflate": "^0.4.8",
+        "preact": "^10.28.2",
+        "query-selector-shadow-dom": "^1.0.1",
+        "web-vitals": "^5.1.0"
+      }
+    },
     "node_modules/powershell-utils": {
       "version": "0.1.0",
       "dev": true,
@@ -11473,6 +11524,16 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/preact": {
+      "version": "10.29.2",
+      "resolved": "https://registry.npmjs.org/preact/-/preact-10.29.2.tgz",
+      "integrity": "sha512-7tNmwg/7mzzAoB/8kSg6Hl37JraAZw3Z3A0JSY7VXlZwo82Xn0G7wKbNNs2qoF4ZEEsQGTwDAroNdqKs1ofJxQ==",
+      "license": "MIT",
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/preact"
+      }
+    },
     "node_modules/prelude-ls": {
       "version": "1.2.1",
       "dev": true,
@@ -11623,6 +11684,12 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/query-selector-shadow-dom": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/query-selector-shadow-dom/-/query-selector-shadow-dom-1.0.1.tgz",
+      "integrity": "sha512-lT5yCqEBgfoMYpf3F2xQRK7zEr1rhIIZuceDK6+xRkJQ4NMbHTwXqk4NkwDwQMNqXgG9r9fyHnzwNVs6zV5KRw==",
+      "license": "MIT"
+    },
     "node_modules/queue-microtask": {
       "version": "1.2.3",
       "dev": true,
@@ -14917,6 +14984,12 @@
         "node": ">= 8"
       }
     },
+    "node_modules/web-vitals": {
+      "version": "5.3.0",
+      "resolved": "https://registry.npmjs.org/web-vitals/-/web-vitals-5.3.0.tgz",
+      "integrity": "sha512-q6LWsLatGYZp5VGBIOvbTj6JBV2nOmC8KvWztXBmwJcfFAzhwKwbOxhUH306XY3CcaZDUlSmSuNPBsCn0bFu+g==",
+      "license": "Apache-2.0"
+    },
     "node_modules/webidl-conversions": {
       "version": "8.0.1",
       "dev": true,
@@ -15268,111 +15341,6 @@
         "type": "github",
         "url": "https://github.com/sponsors/wooorm"
       }
-    },
-    "node_modules/@next/swc-darwin-x64": {
-      "version": "16.2.4",
-      "resolved": "https://registry.npmjs.org/@next/swc-darwin-x64/-/swc-darwin-x64-16.2.4.tgz",
-      "integrity": "sha512-XhpVnUfmYWvD3YrXu55XdcAkQtOnvaI6wtQa8fuF5fGoKoxIUZ0kWPtcOfqJEWngFF/lOS9l3+O9CcownhiQxQ==",
-      "cpu": [
-        "x64"
-      ],
-      "optional": true,
-      "os": [
-        "darwin"
-      ],
-      "engines": {
-        "node": ">= 10"
-      }
-    },
-    "node_modules/@next/swc-linux-arm64-gnu": {
-      "version": "16.2.4",
-      "resolved": "https://registry.npmjs.org/@next/swc-linux-arm64-gnu/-/swc-linux-arm64-gnu-16.2.4.tgz",
-      "integrity": "sha512-Mx/tjlNA3G8kg14QvuGAJ4xBwPk1tUHq56JxZ8CXnZwz1Etz714soCEzGQQzVMz4bEnGPowzkV6Xrp6wAkEWOQ==",
-      "cpu": [
-        "arm64"
-      ],
-      "optional": true,
-      "os": [
-        "linux"
-      ],
-      "engines": {
-        "node": ">= 10"
-      }
-    },
-    "node_modules/@next/swc-linux-arm64-musl": {
-      "version": "16.2.4",
-      "resolved": "https://registry.npmjs.org/@next/swc-linux-arm64-musl/-/swc-linux-arm64-musl-16.2.4.tgz",
-      "integrity": "sha512-iVMMp14514u7Nup2umQS03nT/bN9HurK8ufylC3FZNykrwjtx7V1A7+4kvhbDSCeonTVqV3Txnv0Lu+m2oDXNg==",
-      "cpu": [
-        "arm64"
-      ],
-      "optional": true,
-      "os": [
-        "linux"
-      ],
-      "engines": {
-        "node": ">= 10"
-      }
-    },
-    "node_modules/@next/swc-linux-x64-gnu": {
-      "version": "16.2.4",
-      "resolved": "https://registry.npmjs.org/@next/swc-linux-x64-gnu/-/swc-linux-x64-gnu-16.2.4.tgz",
-      "integrity": "sha512-EZOvm1aQWgnI/N/xcWOlnS3RQBk0VtVav5Zo7n4p0A7UKyTDx047k8opDbXgBpHl4CulRqRfbw3QrX2w5UOXMQ==",
-      "cpu": [
-        "x64"
-      ],
-      "optional": true,
-      "os": [
-        "linux"
-      ],
-      "engines": {
-        "node": ">= 10"
-      }
-    },
-    "node_modules/@next/swc-linux-x64-musl": {
-      "version": "16.2.4",
-      "resolved": "https://registry.npmjs.org/@next/swc-linux-x64-musl/-/swc-linux-x64-musl-16.2.4.tgz",
-      "integrity": "sha512-h9FxsngCm9cTBf71AR4fGznDEDx1hS7+kSEiIRjq5kO1oXWm07DxVGZjCvk0SGx7TSjlUqhI8oOyz7NfwAdPoA==",
-      "cpu": [
-        "x64"
-      ],
-      "optional": true,
-      "os": [
-        "linux"
-      ],
-      "engines": {
-        "node": ">= 10"
-      }
-    },
-    "node_modules/@next/swc-win32-arm64-msvc": {
-      "version": "16.2.4",
-      "resolved": "https://registry.npmjs.org/@next/swc-win32-arm64-msvc/-/swc-win32-arm64-msvc-16.2.4.tgz",
-      "integrity": "sha512-3NdJV5OXMSOeJYijX+bjaLge3mJBlh4ybydbT4GFoB/2hAojWHtMhl3CYlYoMrjPuodp0nzFVi4Tj2+WaMg+Ow==",
-      "cpu": [
-        "arm64"
-      ],
-      "optional": true,
-      "os": [
-        "win32"
-      ],
-      "engines": {
-        "node": ">= 10"
-      }
-    },
-    "node_modules/@next/swc-win32-x64-msvc": {
-      "version": "16.2.4",
-      "resolved": "https://registry.npmjs.org/@next/swc-win32-x64-msvc/-/swc-win32-x64-msvc-16.2.4.tgz",
-      "integrity": "sha512-kMVGgsqhO5YTYODD9IPGGhA6iprWidQckK3LmPeW08PIFENRmgfb4MjXHO+p//d+ts2rpjvK5gXWzXSMrPl9cw==",
-      "cpu": [
-        "x64"
-      ],
-      "optional": true,
-      "os": [
-        "win32"
-      ],
-      "engines": {
-        "node": ">= 10"
-      }
     }
   }
 }
diff --git a/package.json b/package.json
index aca7377..8449b3b 100644
--- a/package.json
+++ b/package.json
@@ -52,6 +52,7 @@
     "next-themes": "^0.4.6",
     "pdfjs-dist": "5.4.296",
     "postgres": "^3.4.9",
+    "posthog-js": "^1.386.8",
     "react": "19.2.4",
     "react-dom": "19.2.4",
     "react-markdown": "^10.1.0",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index d6213a9..484f2fd 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -104,6 +104,9 @@ importers:
       postgres:
         specifier: ^3.4.9
         version: 3.4.9
+      posthog-js:
+        specifier: ^1.386.8
+        version: 1.386.8
       react:
         specifier: 19.2.4
         version: 19.2.4
@@ -1434,6 +1437,12 @@ packages:
     engines: {node: '>=18'}
     hasBin: true
 
+  '@posthog/core@1.32.5':
+    resolution: {integrity: sha512-Vmr6LZms7QEP1ljfTRRBVtLkeEHMrTmLECt0FXPLwUIgPwxOgvBdAYwRMWyP13WuN/XQweo1tJ9J1DxHNAF3qg==}
+
+  '@posthog/types@1.386.4':
+    resolution: {integrity: sha512-UgE9+5+wkZg7yc2MpW5G32/6zYW8fAbXJkG8WGnrb4X8OKWzNa9cWeNCd82vKok+TSoRpM4qiYQFtBSpJS1dsw==}
+
   '@radix-ui/number@1.1.1':
     resolution: {integrity: sha512-MkKCwxlXTgz6CFoJx3pCwn07GKp36+aZyu/u2Ln2VrA5DcdyCZkASEDBTd8x5whTQQL5CiYf4prXKLcgQdv29g==}
 
@@ -2716,6 +2725,9 @@ packages:
     resolution: {integrity: sha512-ei8Aos7ja0weRpFzJnEA9UHJ/7XQmqglbRwnf2ATjcB9Wq874VKH9kfjjirM6UhU2/E5fFYadylyhFldcqSidQ==}
     engines: {node: '>=18'}
 
+  core-js@3.49.0:
+    resolution: {integrity: sha512-es1U2+YTtzpwkxVLwAFdSpaIMyQaq0PBgm3YD1W3Qpsn1NAmO3KSgZfu+oGSWVu6NvLHoHCV/aYcsE5wiB7ALg==}
+
   core-util-is@1.0.3:
     resolution: {integrity: sha512-ZQBvi1DcpJ4GDqanjucZ2Hj3wEO5pZDS89BWbkcrvdxksJorwUDDZamX9ldFkp9aw2lmBDLgkObEA4DWNJ9FYQ==}
 
@@ -3312,6 +3324,9 @@ packages:
     resolution: {integrity: sha512-7yAQpD2UMJzLi1Dqv7qFYnPbaPx7ZfFK6PiIxQ4PfkGPyNyl2Ugx+a/umUonmKqjhM4DnfbMvdX6otXq83soQQ==}
     engines: {node: ^12.20 || >= 14.13}
 
+  fflate@0.4.8:
+    resolution: {integrity: sha512-FJqqoDBR00Mdj9ppamLa/Y7vxm+PRmNWA67N846RvsoYVMKB4q3y/de5PA7gUmRMYK/8CMz2GDZQmCRN1wBcWA==}
+
   figures@6.1.0:
     resolution: {integrity: sha512-d+l3qxjSesT4V7v2fh+QnmFnUWv9lSpjarhShNTgBOfA0ttejbQUAlHLitbjkoRiDulW0OPoQPYIGhIC8ohejg==}
     engines: {node: '>=18'}
@@ -4520,10 +4535,16 @@ packages:
     resolution: {integrity: sha512-GD3qdB0x1z9xgFI6cdRD6xu2Sp2WCOEoe3mtnyB5Ee0XrrL5Pe+e4CCnJrRMnL1zYtRDZmQQVbvOttLnKDLnaw==}
     engines: {node: '>=12'}
 
+  posthog-js@1.386.8:
+    resolution: {integrity: sha512-L4cJD1sleUULE7K4mZQI5wpS24NHGtNmFw1rPHruc579unVzHuooHiVDEHp/qyNnhNxtNE6alBTiVORbYnRTSw==}
+
   powershell-utils@0.1.0:
     resolution: {integrity: sha512-dM0jVuXJPsDN6DvRpea484tCUaMiXWjuCn++HGTqUWzGDjv5tZkEZldAJ/UMlqRYGFrD/etByo4/xOuC/snX2A==}
     engines: {node: '>=20'}
 
+  preact@10.29.2:
+    resolution: {integrity: sha512-7tNmwg/7mzzAoB/8kSg6Hl37JraAZw3Z3A0JSY7VXlZwo82Xn0G7wKbNNs2qoF4ZEEsQGTwDAroNdqKs1ofJxQ==}
+
   prelude-ls@1.2.1:
     resolution: {integrity: sha512-vkcDPrRZo1QZLbn5RLGPpg/WmIQ65qoWWhcGKf/b5eplkkarX0m9z8ppCat4mlOqUsWpyNuYgO3VRyrYHSzX5g==}
     engines: {node: '>= 0.8.0'}
@@ -4568,6 +4589,9 @@ packages:
     resolution: {integrity: sha512-6YHEFRL9mfgcAvql/XhwTvf5jKcOiiupt2FiJxHkiX1z4j7WL8J/jRHYLluORvc1XxB5rV20KoeK00gVJamspg==}
     engines: {node: '>=0.6'}
 
+  query-selector-shadow-dom@1.0.1:
+    resolution: {integrity: sha512-lT5yCqEBgfoMYpf3F2xQRK7zEr1rhIIZuceDK6+xRkJQ4NMbHTwXqk4NkwDwQMNqXgG9r9fyHnzwNVs6zV5KRw==}
+
   queue-microtask@1.2.3:
     resolution: {integrity: sha512-NuaNSa6flKT5JaSYQzJok04JzTL1CA6aGhv5rfLW3PgqA+M2ChpZQnAC8h8i4ZFkBS8X5RqkDBHA7r4hej3K9A==}
 
@@ -5310,6 +5334,9 @@ packages:
     resolution: {integrity: sha512-d2JWLCivmZYTSIoge9MsgFCZrt571BikcWGYkjC1khllbTeDlGqZ2D8vD8E/lJa8WGWbb7Plm8/XJYV7IJHZZw==}
     engines: {node: '>= 8'}
 
+  web-vitals@5.3.0:
+    resolution: {integrity: sha512-q6LWsLatGYZp5VGBIOvbTj6JBV2nOmC8KvWztXBmwJcfFAzhwKwbOxhUH306XY3CcaZDUlSmSuNPBsCn0bFu+g==}
+
   webidl-conversions@8.0.1:
     resolution: {integrity: sha512-BMhLD/Sw+GbJC21C/UgyaZX41nPt8bUTg+jWyDeg7e7YN4xOM05YPSIXceACnXVtqyEw/LMClUQMtMZ+PGGpqQ==}
     engines: {node: '>=20'}
@@ -6396,6 +6423,12 @@ snapshots:
     dependencies:
       playwright: 1.58.2
 
+  '@posthog/core@1.32.5':
+    dependencies:
+      '@posthog/types': 1.386.4
+
+  '@posthog/types@1.386.4': {}
+
   '@radix-ui/number@1.1.1': {}
 
   '@radix-ui/primitive@1.1.3': {}
@@ -7579,6 +7612,8 @@ snapshots:
 
   cookie@1.1.1: {}
 
+  core-js@3.49.0: {}
+
   core-util-is@1.0.3: {}
 
   cors@2.8.6:
@@ -8317,6 +8352,8 @@ snapshots:
       node-domexception: 1.0.0
       web-streams-polyfill: 3.3.3
 
+  fflate@0.4.8: {}
+
   figures@6.1.0:
     dependencies:
       is-unicode-supported: 2.1.0
@@ -9709,8 +9746,21 @@ snapshots:
 
   postgres@3.4.9: {}
 
+  posthog-js@1.386.8:
+    dependencies:
+      '@posthog/core': 1.32.5
+      '@posthog/types': 1.386.4
+      core-js: 3.49.0
+      dompurify: 3.4.2
+      fflate: 0.4.8
+      preact: 10.29.2
+      query-selector-shadow-dom: 1.0.1
+      web-vitals: 5.3.0
+
   powershell-utils@0.1.0: {}
 
+  preact@10.29.2: {}
+
   prelude-ls@1.2.1: {}
 
   pretty-format@27.5.1:
@@ -9753,6 +9803,8 @@ snapshots:
     dependencies:
       side-channel: 1.1.0
 
+  query-selector-shadow-dom@1.0.1: {}
+
   queue-microtask@1.2.3: {}
 
   range-parser@1.2.1: {}
@@ -10654,6 +10706,8 @@ snapshots:
 
   web-streams-polyfill@3.3.3: {}
 
+  web-vitals@5.3.0: {}
+
   webidl-conversions@8.0.1: {}
 
   whatwg-mimetype@5.0.0: {}
diff --git a/src/app/layout.tsx b/src/app/layout.tsx
index afbda8b..6520102 100644
--- a/src/app/layout.tsx
+++ b/src/app/layout.tsx
@@ -2,6 +2,7 @@ import type { Metadata } from "next";
 import { Geist, Geist_Mono } from "next/font/google";
 import { ThemeProvider } from "@/components/theme-provider";
 import { appMetadata } from "@/lib/app-metadata";
+import { PostHogInitializer } from "@/providers/posthog-initializer";
 import "./globals.css";
 
 const geistSans = Geist({
@@ -34,7 +35,7 @@ export default function RootLayout({
           enableSystem
           disableTransitionOnChange
         >
-          {children}
+          <PostHogInitializer>{children}</PostHogInitializer>
         </ThemeProvider>
       </body>
     </html>
diff --git a/src/components/chat-composer.tsx b/src/components/chat-composer.tsx
index 807f298..8f1de60 100644
--- a/src/components/chat-composer.tsx
+++ b/src/components/chat-composer.tsx
@@ -21,7 +21,6 @@ import {
 import { Spinner } from "@/components/ui/spinner";
 import { Textarea } from "@/components/ui/textarea";
 import { chatPromptTemplates } from "@/domains/chat/prompt-templates";
-
 const chatComposerId = "chat-composer";
 const placeholderPattern = /(\[[^\]\r\n]{1,80}\])/gu;
 const placeholderSegmentPattern = /^\[[^\]\r\n]{1,80}\]$/u;
diff --git a/src/components/chat-panel.test.ts b/src/components/chat-panel.test.ts
index 1d9736e..cc39fc2 100644
--- a/src/components/chat-panel.test.ts
+++ b/src/components/chat-panel.test.ts
@@ -4,6 +4,15 @@ import { cleanup, render, screen, within } from "@testing-library/react";
 import userEvent from "@testing-library/user-event";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
+const analyticsMocks = vi.hoisted(() => ({
+  trackNotebookAssistantQuestionSubmitted: vi.fn(),
+}));
+
+vi.mock("@/lib/posthog", () => ({
+  trackNotebookAssistantQuestionSubmitted:
+    analyticsMocks.trackNotebookAssistantQuestionSubmitted,
+}));
+
 import { workspaceClient } from "@/domains/workspace/client";
 import { ChatPanel } from "./chat-panel";
 
@@ -23,6 +32,7 @@ describe("ChatPanel", () => {
       disconnect() {}
     };
     vi.mocked(workspaceClient.createChatDiagram).mockReset();
+    analyticsMocks.trackNotebookAssistantQuestionSubmitted.mockReset();
     mockVisibleVirtualViewport();
   });
 
@@ -242,11 +252,56 @@ describe("ChatPanel", () => {
     await user.click(screen.getByRole("button", { name: "Send message" }));
 
     expect(onSend).not.toHaveBeenCalled();
+    expect(
+      analyticsMocks.trackNotebookAssistantQuestionSubmitted,
+    ).not.toHaveBeenCalled();
     expect(workspaceClient.createChatDiagram).toHaveBeenCalledWith({
       answer: "Cloud revenue was 42 and Ads revenue was 28.",
     });
   });
 
+  it("tracks normal composer sends as assistant questions", async () => {
+    const user = userEvent.setup();
+    const onSend = vi.fn();
+
+    render(
+      React.createElement(C, {
+        activeThreadId: "thread_1",
+        analyticsContext: {
+          workspaceId: "workspace_1",
+          workspaceNamespace: "demo",
+          userId: "user_1",
+          isGuest: false,
+        },
+        selectedSourcesCount: 2,
+        sourceCount: 4,
+        onSend,
+      }),
+    );
+
+    await user.type(
+      screen.getByPlaceholderText("Ask a question about your documents…"),
+      "Summarize revenue",
+    );
+    await user.click(screen.getByRole("button", { name: "Send message" }));
+
+    expect(onSend).toHaveBeenCalledWith("Summarize revenue");
+    expect(
+      analyticsMocks.trackNotebookAssistantQuestionSubmitted,
+    ).toHaveBeenCalledWith({
+      context: {
+        workspaceId: "workspace_1",
+        workspaceNamespace: "demo",
+        userId: "user_1",
+        isGuest: false,
+      },
+      threadId: "thread_1",
+      selectedSourcesCount: 2,
+      sourceCountSnapshot: 4,
+      messageLength: "Summarize revenue".length,
+    });
+  });
+
   it("uses Notebook source titles for generated Knowhere citation filenames", () => {
     const { container } = render(
       React.createElement(C, {
diff --git a/src/components/chat-panel.tsx b/src/components/chat-panel.tsx
index 1aeb897..7600cf0 100644
--- a/src/components/chat-panel.tsx
+++ b/src/components/chat-panel.tsx
@@ -38,6 +38,10 @@ import type {
   ChatThreadView,
 } from "@/domains/chat/types";
 import { workspaceClient } from "@/domains/workspace/client";
+import {
+  trackNotebookAssistantQuestionSubmitted,
+  type AnalyticsContext,
+} from "@/lib/posthog";
 
 export type ChatPanelProps = {
   messages: ChatMessageView[];
@@ -51,6 +55,8 @@ export type ChatPanelProps = {
   onLoginClick?: () => void;
   sourceTitlesByDocumentId?: Readonly<Record<string, string>>;
   sourceCount?: number;
+  selectedSourcesCount?: number;
+  analyticsContext?: AnalyticsContext;
   isSending?: boolean;
   isHistoryLoading?: boolean;
   isCreatingThread?: boolean;
@@ -73,6 +79,8 @@ export function ChatPanel({
   onLoginClick,
   sourceTitlesByDocumentId = {},
   sourceCount = 0,
+  selectedSourcesCount = 0,
+  analyticsContext,
   isSending = false,
   isHistoryLoading = false,
   isCreatingThread = false,
@@ -150,6 +158,13 @@ export function ChatPanel({
       return;
     }
 
+    void trackNotebookAssistantQuestionSubmitted({
+      context: analyticsContext,
+      threadId: activeThreadId,
+      selectedSourcesCount,
+      sourceCountSnapshot: sourceCount,
+      messageLength: text.length,
+    });
     onSend?.(text);
   }
 
diff --git a/src/components/chunks-panel.tsx b/src/components/chunks-panel.tsx
index 7d5b853..fd9e7a0 100644
--- a/src/components/chunks-panel.tsx
+++ b/src/components/chunks-panel.tsx
@@ -43,6 +43,7 @@ import { useSourceOriginalPreviewWarmup } from "@/components/source-original-pre
 import { sourceOriginalPreviewModel } from "@/components/source-original-preview-model";
 import type { ParsedChunkView } from "@/domains/chunks/types";
 import type { SourceOriginalFileView, SourceView } from "@/domains/sources/types";
+import type { AnalyticsContext } from "@/lib/posthog";
 import { cn } from "@/lib/utils";
 
 export type ChunksPanelProps = {
@@ -60,6 +61,8 @@ export type ChunksPanelProps = {
   onLoadAllChunks?: () => void;
   onLoginClick?: () => void;
   onSourceUploaded?: (source: SourceView) => void;
+  analyticsContext?: AnalyticsContext;
+  sourceCountSnapshot?: number;
 };
 
 type ChunkDisplayMode = "list" | "tree";
@@ -85,6 +88,8 @@ export function ChunksPanel({
   onLoadAllChunks,
   onLoginClick,
   onSourceUploaded,
+  analyticsContext,
+  sourceCountSnapshot = 0,
 }: Partial<ChunksPanelProps> = {}) {
   const originalPreviewCacheKey = selectedSourceFile?.url ?? null;
   const isOriginalPreviewAvailable =
@@ -362,6 +367,8 @@ export function ChunksPanel({
                   <EmptySourceUploadState
                     onLoginClick={onLoginClick}
                     onSourceUploaded={onSourceUploaded}
+                    analyticsContext={analyticsContext}
+                    sourceCountSnapshot={sourceCountSnapshot}
                   />
                 )
               ) : isTreeModeVisible ? (
@@ -967,11 +974,15 @@ function truncateTreeLabel(value: string): string {
 }
 
 function EmptySourceUploadState({
+  analyticsContext,
   onLoginClick,
   onSourceUploaded,
+  sourceCountSnapshot = 0,
 }: {
+  readonly analyticsContext?: AnalyticsContext;
   readonly onLoginClick?: () => void;
   readonly onSourceUploaded?: (source: SourceView) => void;
+  readonly sourceCountSnapshot?: number;
 }): ReactNode {
   if (onLoginClick) {
     return (
@@ -999,6 +1010,8 @@ function EmptySourceUploadState({
   return (
     <SourceUploadDialog
       onSourceUploaded={onSourceUploaded}
+      analyticsContext={analyticsContext}
+      sourceCountSnapshot={sourceCountSnapshot}
       renderTrigger={({ onClick, onDragOver, onDrop }) => (
         <button
           type="button"
diff --git a/src/components/source-upload-dialog-workflow.test.ts b/src/components/source-upload-dialog-workflow.test.ts
index 3544a79..b5cadbb 100644
--- a/src/components/source-upload-dialog-workflow.test.ts
+++ b/src/components/source-upload-dialog-workflow.test.ts
@@ -3,6 +3,17 @@ import React, { type ReactElement } from "react";
 import { cleanup, fireEvent, render, screen, waitFor } from "@testing-library/react";
 import { afterEach, describe, expect, it, vi } from "vitest";
 
+const mocks = vi.hoisted(() => ({
+  trackNotebookDocumentUploadCompleted: vi.fn(),
+  trackNotebookDocumentUploadFailed: vi.fn(),
+}));
+
+vi.mock("@/lib/posthog", () => ({
+  trackNotebookDocumentUploadCompleted:
+    mocks.trackNotebookDocumentUploadCompleted,
+  trackNotebookDocumentUploadFailed: mocks.trackNotebookDocumentUploadFailed,
+}));
+
 import type { SourceView } from "@/domains/sources/types";
 import { useSourceUploadDialogWorkflow } from "./source-upload-dialog-workflow";
 
@@ -53,6 +64,14 @@ describe("useSourceUploadDialogWorkflow", () => {
       expect(onSourceUploaded).toHaveBeenCalledWith(uploadedSource);
     });
     expect(uploadSource).toHaveBeenCalledWith(file);
+    expect(mocks.trackNotebookDocumentUploadCompleted).toHaveBeenCalledWith({
+      context: undefined,
+      uploadedCount: 1,
+      fileType: "application/pdf",
+      fileSizeBytes: 5,
+      sourceCountBefore: 0,
+      sourceCountAfter: 1,
+    });
     expect(screen.getByTestId("is-dialog-open").textContent).toBe("false");
     expect(screen.getByTestId("selected-file-name").textContent).toBe("");
   });
@@ -115,6 +134,40 @@ describe("useSourceUploadDialogWorkflow", () => {
       "Choose a document to upload.",
     );
   });
+
+  it("classifies local upload validation failures separately from server failures", async () => {
+    const uploadSource = vi.fn(async () => ({
+      status: 400,
+      body: { message: "Unsupported file type." },
+    }));
+    const file = new File(["hello"], "notes.exe", {
+      type: "application/x-msdownload",
+    });
+
+    render(
+      React.createElement(SourceUploadDialogWorkflowHarness, {
+        uploadSource,
+      }),
+    );
+
+    fireEvent.change(screen.getByLabelText("file-input"), {
+      target: { files: [file] },
+    });
+    fireEvent.submit(screen.getByTestId("upload-form"));
+
+    await waitFor(() => {
+      expect(mocks.trackNotebookDocumentUploadFailed).toHaveBeenCalledWith({
+        context: undefined,
+        fileType: "application/x-msdownload",
+        fileSizeBytes: 5,
+        errorType: "validation",
+        errorMessage: "Unsupported file type.",
+      });
+    });
+    expect(screen.getByTestId("upload-message").textContent).toBe(
+      "Unsupported file type.",
+    );
+  });
 });
 
 function SourceUploadDialogWorkflowHarness({
diff --git a/src/components/source-upload-dialog-workflow.ts b/src/components/source-upload-dialog-workflow.ts
index cd56159..40a731a 100644
--- a/src/components/source-upload-dialog-workflow.ts
+++ b/src/components/source-upload-dialog-workflow.ts
@@ -11,6 +11,11 @@ import {
 
 import type { SourceView } from "@/domains/sources/types";
 import { postSourceUpload } from "@/domains/sources/upload-request";
+import {
+  trackNotebookDocumentUploadCompleted,
+  trackNotebookDocumentUploadFailed,
+  type AnalyticsContext,
+} from "@/lib/posthog";
 
 type SourceUploadResponseBody = {
   readonly message?: string;
@@ -30,7 +35,9 @@ type SourceUploadDialogMessage = {
 };
 
 type SourceUploadDialogWorkflowInput = {
+  readonly analyticsContext?: AnalyticsContext;
   readonly onSourceUploaded?: (source: SourceView) => void;
+  readonly sourceCountBefore?: number;
   readonly uploadSource?: UploadSource;
 };
 
@@ -52,7 +59,9 @@ const defaultUploadFailureMessage =
   "Upload failed. Try again or choose another file.";
 
 export function useSourceUploadDialogWorkflow({
+  analyticsContext,
   onSourceUploaded,
+  sourceCountBefore = 0,
   uploadSource = postSourceUpload,
 }: SourceUploadDialogWorkflowInput): SourceUploadDialogWorkflow {
   const inputRef = useRef<HTMLInputElement>(null);
@@ -89,6 +98,13 @@ export function useSourceUploadDialogWorkflow({
       const { body } = response;
 
       if (!isSuccessfulStatus(response.status) || !body.source) {
+        void trackNotebookDocumentUploadFailed({
+          context: analyticsContext,
+          fileType: file.type || null,
+          fileSizeBytes: file.size,
+          errorType: getUploadFailureErrorType(response.status),
+          errorMessage: body.message ?? defaultUploadFailureMessage,
+        });
         setMessage({
           isSuccess: false,
           text: body.message ?? defaultUploadFailureMessage,
@@ -97,9 +113,24 @@ export function useSourceUploadDialogWorkflow({
       }
 
       clearSelectedFile();
+      void trackNotebookDocumentUploadCompleted({
+        context: analyticsContext,
+        uploadedCount: 1,
+        fileType: file.type,
+        fileSizeBytes: file.size,
+        sourceCountBefore,
+        sourceCountAfter: sourceCountBefore + 1,
+      });
       onSourceUploaded?.(body.source);
       setIsDialogOpen(false);
     } catch {
+      void trackNotebookDocumentUploadFailed({
+        context: analyticsContext,
+        fileType: file.type || null,
+        fileSizeBytes: file.size,
+        errorType: "network",
+        errorMessage: defaultUploadFailureMessage,
+      });
       setMessage({
         isSuccess: false,
         text: defaultUploadFailureMessage,
@@ -175,6 +206,12 @@ function isSuccessfulStatus(status: number): boolean {
   return status >= 200 && status < 300;
 }
 
+function getUploadFailureErrorType(
+  status: number,
+): "validation" | "server" {
+  return status === 400 ? "validation" : "server";
+}
+
 function hasDraggedFiles(event: DragEvent<HTMLElement>): boolean {
   return Array.from(event.dataTransfer.types).includes("Files");
 }
diff --git a/src/components/source-upload-dialog.test.ts b/src/components/source-upload-dialog.test.ts
index b55a072..6c8aea5 100644
--- a/src/components/source-upload-dialog.test.ts
+++ b/src/components/source-upload-dialog.test.ts
@@ -13,12 +13,22 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 const mocks = vi.hoisted(() => ({
   uploadBlob: vi.fn(),
+  trackNotebookUploadButtonClicked: vi.fn(),
+  trackNotebookDocumentUploadCompleted: vi.fn(),
+  trackNotebookDocumentUploadFailed: vi.fn(),
 }));
 
 vi.mock("@vercel/blob/client", () => ({
   upload: mocks.uploadBlob,
 }));
 
+vi.mock("@/lib/posthog", () => ({
+  trackNotebookUploadButtonClicked: mocks.trackNotebookUploadButtonClicked,
+  trackNotebookDocumentUploadCompleted:
+    mocks.trackNotebookDocumentUploadCompleted,
+  trackNotebookDocumentUploadFailed: mocks.trackNotebookDocumentUploadFailed,
+}));
+
 import { SourceUploadDialog } from "./source-upload-dialog";
 
 describe("SourceUploadDialog", () => {
@@ -60,6 +70,7 @@ describe("SourceUploadDialog", () => {
     render(React.createElement(SourceUploadDialog, { onSourceUploaded }));
 
     await user.click(screen.getByRole("button", { name: "Upload Document" }));
+    expect(mocks.trackNotebookUploadButtonClicked).toHaveBeenCalledOnce();
     const dialog = screen.getByRole("dialog");
     const file = new File(["hello"], "drop.pdf", { type: "application/pdf" });
     const dropEvent = createFileDropEvent(file);
diff --git a/src/components/source-upload-dialog.tsx b/src/components/source-upload-dialog.tsx
index 8c3165b..911e6df 100644
--- a/src/components/source-upload-dialog.tsx
+++ b/src/components/source-upload-dialog.tsx
@@ -19,9 +19,15 @@ import {
 import { useSourceUploadDialogWorkflow } from "@/components/source-upload-dialog-workflow";
 import type { SourceView } from "@/domains/sources/types";
 import { MAX_UPLOAD_MB } from "@/domains/sources/validation";
+import {
+  trackNotebookUploadButtonClicked,
+  type AnalyticsContext,
+} from "@/lib/posthog";
 
 export type SourceUploadDialogProps = {
   readonly onSourceUploaded?: (source: SourceView) => void;
+  readonly analyticsContext?: AnalyticsContext;
+  readonly sourceCountSnapshot?: number;
   readonly renderTrigger?: (props: SourceUploadDialogTriggerProps) => ReactElement;
 };
 
@@ -34,6 +40,8 @@ export type SourceUploadDialogTriggerProps = {
 
 export function SourceUploadDialog({
   onSourceUploaded,
+  analyticsContext,
+  sourceCountSnapshot = 0,
   renderTrigger,
 }: SourceUploadDialogProps): ReactElement {
   const {
@@ -48,8 +56,19 @@ export function SourceUploadDialog({
     handleFileInputChange,
     handleSubmit,
     handleUploadDialogOpen,
-  } = useSourceUploadDialogWorkflow({ onSourceUploaded });
+  } = useSourceUploadDialogWorkflow({
+    onSourceUploaded,
+    analyticsContext,
+    sourceCountBefore: sourceCountSnapshot,
+  });
   const fileInputId = useId();
+  const handleOpenUploadDialog = (): void => {
+    void trackNotebookUploadButtonClicked({
+      context: analyticsContext,
+      sourceCountSnapshot,
+    });
+    handleUploadDialogOpen();
+  };
 
   return (
     <Dialog
@@ -59,14 +78,14 @@ export function SourceUploadDialog({
       {renderTrigger ? (
         renderTrigger({
           isUploading,
-          onClick: handleUploadDialogOpen,
+          onClick: handleOpenUploadDialog,
           onDragOver: handleUploadDragOver,
           onDrop: handleUploadDrop,
         })
       ) : (
         <Button
           type="button"
-          onClick={handleUploadDialogOpen}
+          onClick={handleOpenUploadDialog}
           onDragOver={handleUploadDragOver}
           onDrop={handleUploadDrop}
           size="sm"
diff --git a/src/components/sources-panel.tsx b/src/components/sources-panel.tsx
index 6f38735..477244f 100644
--- a/src/components/sources-panel.tsx
+++ b/src/components/sources-panel.tsx
@@ -25,6 +25,7 @@ import type {
   OfficialLibrarySourceView,
   SourceView,
 } from "@/domains/sources/types";
+import type { AnalyticsContext } from "@/lib/posthog";
 
 export type SourcesPanelProps = {
   readonly isNarrow?: boolean;
@@ -40,6 +41,8 @@ export type SourcesPanelProps = {
   onLibraryOpen?: () => void;
   onOfficialLibrarySourceAdd?: (demoSourceId: string) => void;
   archivingSourceIds?: readonly string[];
+  analyticsContext?: AnalyticsContext;
+  sourceCountSnapshot?: number;
   /** When provided, the Upload button redirects to login instead of opening the dialog. */
   onLoginClick?: () => void;
 };
@@ -56,6 +59,8 @@ export function SourcesPanel({
   onArchiveSource,
   onLibraryOpen,
   archivingSourceIds = [],
+  analyticsContext,
+  sourceCountSnapshot = sources.length,
   onLoginClick,
 }: Partial<SourcesPanelProps> = {}): ReactElement {
   const [confirmSourceId, setConfirmSourceId] = useState<string | null>(null);
@@ -139,6 +144,8 @@ export function SourcesPanel({
         ) : isNarrow ? (
           <SourceUploadDialog
             onSourceUploaded={onSourceUploaded}
+            analyticsContext={analyticsContext}
+            sourceCountSnapshot={sourceCountSnapshot}
             renderTrigger={({ isUploading, onClick, onDragOver, onDrop }) => (
               <Button
                 type="button"
@@ -160,7 +167,11 @@ export function SourcesPanel({
             )}
           />
         ) : (
-          <SourceUploadDialog onSourceUploaded={onSourceUploaded} />
+          <SourceUploadDialog
+            onSourceUploaded={onSourceUploaded}
+            analyticsContext={analyticsContext}
+            sourceCountSnapshot={sourceCountSnapshot}
+          />
         )}
       </div>
       <ScrollArea className="flex-1">
diff --git a/src/components/top-nav.test.ts b/src/components/top-nav.test.ts
index e67a3fa..e07c634 100644
--- a/src/components/top-nav.test.ts
+++ b/src/components/top-nav.test.ts
@@ -4,6 +4,14 @@ import userEvent from "@testing-library/user-event"
 import { createElement } from "react"
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest"
 
+const mocks = vi.hoisted(() => ({
+  trackNotebookDashboardLinkClicked: vi.fn(),
+}))
+
+vi.mock("@/lib/posthog", () => ({
+  trackNotebookDashboardLinkClicked: mocks.trackNotebookDashboardLinkClicked,
+}))
+
 import { ThemeProvider } from "@/components/theme-provider"
 import { TopNav, type TopNavProps } from "./top-nav"
 
@@ -23,6 +31,7 @@ describe("TopNav", () => {
 
   afterEach(() => {
     cleanup()
+    vi.clearAllMocks()
     vi.unstubAllGlobals()
   })
 
@@ -43,6 +52,16 @@ describe("TopNav", () => {
     const link = screen.getByRole("link", { name: "Open Dashboard" })
 
     expect(link.getAttribute("href")).toBe("https://dashboard.example.test")
+    await user.click(link)
+    expect(mocks.trackNotebookDashboardLinkClicked).toHaveBeenCalledWith(
+      {
+        context: undefined,
+        targetUrl: "https://dashboard.example.test",
+        fromPage: "/",
+        hasSources: false,
+        hasChats: false,
+      },
+    )
     await user.click(screen.getByRole("button", { name: "Toggle theme" }))
 
     expect(screen.getByRole("menuitem", { name: "Light" })).toBeTruthy()
diff --git a/src/components/top-nav.tsx b/src/components/top-nav.tsx
index 487fcc2..5c32df8 100644
--- a/src/components/top-nav.tsx
+++ b/src/components/top-nav.tsx
@@ -1,11 +1,18 @@
 import { NotebookLogoMark } from "@/components/notebook-logo-mark";
 import { Separator } from "@/components/ui/separator";
 import { ThemeToggle } from "@/components/theme-toggle";
+import {
+  trackNotebookDashboardLinkClicked,
+  type AnalyticsContext,
+} from "@/lib/posthog";
 import { ExternalLink } from "lucide-react";
 import type { ReactElement } from "react";
 
 export type TopNavProps = {
   dashboardUrl?: string | null;
+  analyticsContext?: AnalyticsContext;
+  hasChats?: boolean;
+  hasSources?: boolean;
   userInitials?: string;
   userName?: string;
   userTierLabel?: string;
@@ -14,6 +21,9 @@ export type TopNavProps = {
 
 export function TopNav({
   dashboardUrl,
+  analyticsContext,
+  hasChats = false,
+  hasSources = false,
   userInitials,
   userName,
   userTierLabel,
@@ -39,6 +49,18 @@ export function TopNav({
           <a
             href={dashboardUrl}
             aria-label="Open Dashboard"
+            onClick={() => {
+              void trackNotebookDashboardLinkClicked({
+                context: analyticsContext,
+                targetUrl: dashboardUrl,
+                fromPage:
+                  typeof window !== "undefined"
+                    ? window.location.pathname
+                    : "notebook",
+                hasSources,
+                hasChats,
+              });
+            }}
             className="flex items-center gap-1.5 rounded-md px-2 py-1.5 text-xs font-medium text-muted-foreground transition-colors hover:text-foreground hover:underline focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-[#8e51ff]/25"
           >
             <span className="hidden sm:inline">Dashboard</span>
diff --git a/src/components/workspace-chat-workflow.ts b/src/components/workspace-chat-workflow.ts
index 405516f..c108134 100644
--- a/src/components/workspace-chat-workflow.ts
+++ b/src/components/workspace-chat-workflow.ts
@@ -5,6 +5,12 @@ import useSWR, { useSWRConfig } from "swr"
 import useSWRMutation from "swr/mutation"
 
 import { workspaceChatState } from "@/components/workspace-chat-state"
+import {
+  trackNotebookAssistantAnswerCompleted,
+  trackNotebookAssistantAnswerFailed,
+  trackNotebookWorkspaceFirstQuestionAsked,
+  type AnalyticsContext,
+} from "@/lib/posthog"
 import { workspaceClient } from "@/domains/workspace/client"
 import {
   workspaceClientCache,
@@ -19,6 +25,7 @@ import type { SourceView } from "@/domains/sources/types"
 
 type WorkspaceChatWorkflowInput = {
   readonly activeChatThreadId?: string | null
+  readonly analyticsContext?: AnalyticsContext
   readonly initialChatMessages?: readonly ChatMessageView[]
   readonly initialChatThreads?: readonly ChatThreadView[]
   readonly isGuest?: boolean
@@ -50,6 +57,7 @@ const archiveChatThreadSWRKey = workspaceClient.keys.archiveChatThread
 
 export function useWorkspaceChatWorkflow({
   activeChatThreadId = null,
+  analyticsContext,
   initialChatMessages = [],
   initialChatThreads = [],
   isGuest = false,
@@ -65,6 +73,7 @@ export function useWorkspaceChatWorkflow({
     ),
   )
   const optimisticMessageSequence = useRef(0)
+  const didTrackFirstQuestionRef = useRef(initialChatMessages.length > 0)
   const { cache, mutate: mutateSWR } = useSWRConfig()
   const initialThreadRows = useMemo(
     () => [...initialChatThreads],
@@ -239,6 +248,10 @@ export function useWorkspaceChatWorkflow({
   }
 
   async function handleChatSend(text: string): Promise<void> {
+    const sendStart = Date.now()
+    const selectedSourcesCount = sources.filter(
+      (source) => source.status === "ready" && !source.excludedFromQuery,
+    ).length
     const demoSourceIds = getMaterializableDemoSourceIds(sources)
     if (demoSourceIds.length > 0) {
       setChat((current) =>
@@ -289,6 +302,13 @@ export function useWorkspaceChatWorkflow({
       })
 
       if (!body.threadId || !Array.isArray(body.messages)) {
+        void trackNotebookAssistantAnswerFailed({
+          context: analyticsContext,
+          threadId: chat.threadId,
+          latencyMs: Date.now() - sendStart,
+          errorType: "server",
+          errorMessage: body.message ?? "The assistant could not answer right now.",
+        })
         setChat((current) => ({
           ...workspaceChatState.failSend(current, optimisticId),
           error: body.message ?? "The assistant could not answer right now.",
@@ -296,6 +316,19 @@ export function useWorkspaceChatWorkflow({
         return
       }
 
+      if (!didTrackFirstQuestionRef.current) {
+        didTrackFirstQuestionRef.current = true
+        void trackNotebookWorkspaceFirstQuestionAsked({
+          context: analyticsContext,
+          selectedSourcesCount,
+        })
+      }
+      void trackNotebookAssistantAnswerCompleted({
+        context: analyticsContext,
+        threadId: body.threadId,
+        latencyMs: Date.now() - sendStart,
+      })
+
       void mutateChatThreads(
         (current = []) =>
           workspaceChatState.upsertThreadAfterSend(
@@ -325,6 +358,13 @@ export function useWorkspaceChatWorkflow({
         )
       }
     } catch {
+      void trackNotebookAssistantAnswerFailed({
+        context: analyticsContext,
+        threadId: chat.threadId,
+        latencyMs: Date.now() - sendStart,
+        errorType: "network",
+        errorMessage: "The assistant could not answer right now.",
+      })
       setChat((current) => workspaceChatState.failSend(current, optimisticId))
     }
   }
diff --git a/src/components/workspace-shell-layout.tsx b/src/components/workspace-shell-layout.tsx
index 6108d9b..cb49fdd 100644
--- a/src/components/workspace-shell-layout.tsx
+++ b/src/components/workspace-shell-layout.tsx
@@ -13,6 +13,7 @@ import { MobileTabBar } from "@/components/mobile-tab-bar"
 import { OfficialLibraryPanel } from "@/components/official-library-panel"
 import { SourcesPanel } from "@/components/sources-panel"
 import { TopNav } from "@/components/top-nav"
+import type { AnalyticsContext } from "@/lib/posthog"
 import { useWorkspaceResizeHandleWorkflow } from "@/components/workspace-resize-handle-workflow"
 import { workspaceShellState } from "@/components/workspace-shell-state"
 import type {
@@ -85,6 +86,7 @@ export type WorkspaceShellLayoutProps = {
   readonly sources: readonly SourceView[]
   readonly officialLibrarySources: readonly OfficialLibrarySourceView[]
   readonly user: WorkspaceShellUser | undefined
+  readonly analyticsContext?: AnalyticsContext
   readonly onArchiveChatThread: (threadId: string) => void | Promise<void>
   readonly onArchiveSource: (sourceId: string) => void | Promise<void>
   readonly onChatSend: (text: string) => void | Promise<void>
@@ -129,6 +131,9 @@ export function WorkspaceShellLayout(
   const { onDesktopLayoutElementChange } = props
   const addingLibrarySourceIds = props.addingLibrarySourceIds ?? []
   const officialLibrarySources = props.officialLibrarySources ?? []
+  const selectedSourcesCount = props.sources.filter(
+    (source) => !source.excludedFromQuery && source.status === "ready",
+  ).length
   const isSourcesPanelCollapsed =
     props.desktopPanelWidths.sources <=
     workspaceShellState.desktopSidePanelCompactThreshold
@@ -147,6 +152,9 @@ export function WorkspaceShellLayout(
     <div className="flex h-screen w-full flex-col overflow-hidden bg-background">
       <TopNav
         dashboardUrl={props.dashboardUrl}
+        analyticsContext={props.analyticsContext}
+        hasChats={props.chatThreads.length > 0}
+        hasSources={props.readySourceCount > 0}
         userInitials={props.user ? initialsOf(props.user) : undefined}
         userName={
           props.user ? (props.user.name ?? props.user.email ?? undefined) : undefined
@@ -190,6 +198,8 @@ export function WorkspaceShellLayout(
                 officialLibrarySources={[...officialLibrarySources]}
                 isLibraryOpen={props.contentView === "library"}
                 isNarrow={isSourcesPanelNarrow}
+                analyticsContext={props.analyticsContext}
+                sourceCountSnapshot={props.sources.length}
                 onSourceUploaded={
                   props.isGuest ? undefined : props.onSourceUploaded
                 }
@@ -259,6 +269,8 @@ export function WorkspaceShellLayout(
                 onSourceUploaded={
                   props.isGuest ? undefined : props.onSourceUploaded
                 }
+                analyticsContext={props.analyticsContext}
+                sourceCountSnapshot={props.sources.length}
               />
             )}
           </div>
@@ -307,6 +319,8 @@ export function WorkspaceShellLayout(
                 pendingCitationId={props.pendingCitationId}
                 pendingStatusText={props.chat.pendingStatusText}
                 sourceCount={props.readySourceCount}
+                analyticsContext={props.analyticsContext}
+                selectedSourcesCount={selectedSourcesCount}
                 onSend={props.onChatSend}
                 onNewChat={props.isGuest ? undefined : props.onCreateChatThread}
                 onThreadSelect={
@@ -334,6 +348,8 @@ export function WorkspaceShellLayout(
       >
         <SourcesPanel
           sources={[...props.sources]}
+          analyticsContext={props.analyticsContext}
+          sourceCountSnapshot={props.sources.length}
           officialLibrarySources={[...officialLibrarySources]}
           isLibraryOpen={props.contentView === "library"}
           onSourceUploaded={props.isGuest ? undefined : props.onSourceUploaded}
@@ -389,6 +405,8 @@ export function WorkspaceShellLayout(
             onLoadMore={props.onLoadMoreChunks}
             onLoginClick={props.isGuest ? props.onLoginClick : undefined}
             onSourceUploaded={props.isGuest ? undefined : props.onSourceUploaded}
+            analyticsContext={props.analyticsContext}
+            sourceCountSnapshot={props.sources.length}
           />
         )}
       </div>
@@ -413,6 +431,8 @@ export function WorkspaceShellLayout(
           pendingCitationId={props.pendingCitationId}
           pendingStatusText={props.chat.pendingStatusText}
           sourceCount={props.readySourceCount}
+          analyticsContext={props.analyticsContext}
+          selectedSourcesCount={selectedSourcesCount}
           onSend={props.onChatSend}
           onNewChat={props.isGuest ? undefined : props.onCreateChatThread}
           onThreadSelect={props.isGuest ? undefined : props.onSelectChatThread}
diff --git a/src/components/workspace-shell.tsx b/src/components/workspace-shell.tsx
index da9edcd..01bd98e 100644
--- a/src/components/workspace-shell.tsx
+++ b/src/components/workspace-shell.tsx
@@ -1,7 +1,8 @@
 "use client"
 
-import { useMemo, useState } from "react"
+import { useEffect, useMemo, useRef, useState } from "react"
 import type { ReactElement } from "react"
+import { usePathname } from "next/navigation"
 import { SWRConfig } from "swr"
 import {
   WorkspaceShellLayout,
@@ -13,6 +14,13 @@ import { useWorkspaceCitationFocus } from "@/components/workspace-citation-focus
 import { useWorkspaceChatWorkflow } from "@/components/workspace-chat-workflow"
 import { useWorkspaceSourceWorkflow } from "@/components/workspace-source-workflow"
 import { workspaceShellState } from "@/components/workspace-shell-state"
+import {
+  identifyUser,
+  resetUser,
+  trackNotebookWorkspaceFirstDocumentUploaded,
+  trackPageView,
+  type AnalyticsContext,
+} from "@/lib/posthog"
 import { workspaceClient } from "@/domains/workspace/client"
 import type {
   ChatMessageView,
@@ -76,6 +84,7 @@ function WorkspaceShellContent({
   activeChatThreadId,
   chatMessages: initialChatMessages,
   dashboardUrl,
+  workspace,
   initialPrefetchedChunksBySourceId,
   isGuest = false,
   loginUrl,
@@ -83,11 +92,21 @@ function WorkspaceShellContent({
   const [mobilePanel, setMobilePanel] = useState<PanelId>(
     isGuest ? "content" : "chat",
   )
+  const pathname = usePathname()
   const [contentView, setContentView] = useState<ContentView>("chunks")
   const sourceWorkflow = useWorkspaceSourceWorkflow({
     initialSources: initialSources ?? [],
     isGuest,
   })
+  const analyticsContext = useMemo<AnalyticsContext>(
+    () => ({
+      workspaceId: workspace?.id,
+      workspaceNamespace: workspace?.namespace,
+      userId: user?.id,
+      isGuest,
+    }),
+    [isGuest, user?.id, workspace?.id, workspace?.namespace],
+  )
   const citationFocus = useWorkspaceCitationFocus({
     fetchChunks: workspaceClient.fetchChunks,
     initialPrefetchedChunksBySourceId:
@@ -98,6 +117,7 @@ function WorkspaceShellContent({
   })
   const chatWorkflow = useWorkspaceChatWorkflow({
     activeChatThreadId: activeChatThreadId ?? null,
+    analyticsContext,
     initialChatMessages: initialChatMessages ?? [],
     initialChatThreads: initialChatThreads ?? [],
     isGuest,
@@ -147,6 +167,42 @@ function WorkspaceShellContent({
   }
 
   const hasMessages = chatWorkflow.chat.messages.length > 0
+  const didTrackFirstDocumentRef = useRef(false)
+  const analyticsContextRef = useRef(analyticsContext)
+  const userId = user?.id
+  const userEmail = user?.email
+  const userName = user?.name
+
+  useEffect(() => {
+    analyticsContextRef.current = analyticsContext
+  }, [analyticsContext])
+
+  useEffect(() => {
+    if (isGuest || !userId) {
+      void resetUser()
+      return
+    }
+
+    void identifyUser({
+      id: userId,
+      email: userEmail,
+      name: userName,
+    })
+  }, [isGuest, userEmail, userId, userName])
+
+  useEffect(() => {
+    void trackPageView(analyticsContextRef.current)
+  }, [pathname])
+
+  function handleSourceUploaded(source: SourceView): void {
+    if (!didTrackFirstDocumentRef.current && sourceWorkflow.sources.length === 0) {
+      didTrackFirstDocumentRef.current = true
+      void trackNotebookWorkspaceFirstDocumentUploaded({
+        context: analyticsContext,
+      })
+    }
+    sourceWorkflow.handleSourceUploaded(source)
+  }
 
   return (
     <WorkspaceShellLayout
@@ -180,6 +236,7 @@ function WorkspaceShellContent({
       sources={sourceWorkflow.sources}
       officialLibrarySources={officialLibrarySources ?? []}
       user={user}
+      analyticsContext={analyticsContext}
       onArchiveChatThread={chatWorkflow.handleArchiveChatThread}
       onArchiveSource={sourceWorkflow.handleArchiveSource}
       onChatSend={chatWorkflow.handleChatSend}
@@ -199,7 +256,7 @@ function WorkspaceShellContent({
       onSelectChatThread={chatWorkflow.handleSelectChatThread}
       onSourceSelected={handleSourceSelected}
       onOfficialLibrarySourceAdd={handleOfficialLibrarySourceAdd}
-      onSourceUploaded={sourceWorkflow.handleSourceUploaded}
+      onSourceUploaded={handleSourceUploaded}
       onToggleIncluded={sourceWorkflow.handleToggleIncluded}
     />
   )
diff --git a/src/lib/posthog.test.ts b/src/lib/posthog.test.ts
new file mode 100644
index 0000000..0d4304f
--- /dev/null
+++ b/src/lib/posthog.test.ts
@@ -0,0 +1,139 @@
+// @vitest-environment jsdom
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+const mocks = vi.hoisted(() => ({
+  capture: vi.fn(),
+  identify: vi.fn(),
+  init: vi.fn(),
+  reset: vi.fn(),
+}));
+
+vi.mock("posthog-js", () => ({
+  default: {
+    capture: mocks.capture,
+    identify: mocks.identify,
+    init: mocks.init,
+    reset: mocks.reset,
+  },
+}));
+
+import {
+  identifyUser,
+  initPostHogClient,
+  isPostHogEnabled,
+  resetUser,
+} from "./posthog";
+
+describe("posthog", () => {
+  const originalKey = process.env.NEXT_PUBLIC_POSTHOG_KEY;
+  const originalHost = process.env.NEXT_PUBLIC_POSTHOG_HOST;
+
+  afterEach(() => {
+    vi.clearAllMocks();
+    if (originalKey === undefined) {
+      delete process.env.NEXT_PUBLIC_POSTHOG_KEY;
+    } else {
+      process.env.NEXT_PUBLIC_POSTHOG_KEY = originalKey;
+    }
+    if (originalHost === undefined) {
+      delete process.env.NEXT_PUBLIC_POSTHOG_HOST;
+    } else {
+      process.env.NEXT_PUBLIC_POSTHOG_HOST = originalHost;
+    }
+  });
+
+  it("returns false when no key is configured", () => {
+    delete process.env.NEXT_PUBLIC_POSTHOG_KEY;
+    expect(isPostHogEnabled()).toBe(false);
+  });
+
+  it("returns true when a key is configured", () => {
+    process.env.NEXT_PUBLIC_POSTHOG_KEY = "phc_test_key";
+    expect(isPostHogEnabled()).toBe(true);
+  });
+
+  it("identifies and resets users when key is configured", async () => {
+    process.env.NEXT_PUBLIC_POSTHOG_KEY = "phc_test_key";
+    await initPostHogClient();
+    await identifyUser({
+      id: "user_1",
+      email: "user@example.com",
+      name: "User One",
+    });
+    await resetUser();
+
+    expect(mocks.init).toHaveBeenCalledOnce();
+    expect(mocks.identify).toHaveBeenCalledWith("user_1", {
+      email: "user@example.com",
+      name: "User One",
+    });
+    expect(mocks.reset).toHaveBeenCalledOnce();
+  });
+
+  it("falls back to default host when NEXT_PUBLIC_POSTHOG_HOST is blank", async () => {
+    vi.resetModules();
+    process.env.NEXT_PUBLIC_POSTHOG_KEY = "phc_test_key";
+    process.env.NEXT_PUBLIC_POSTHOG_HOST = "   ";
+    const { initPostHogClient: initClient } = await import("./posthog");
+    await initClient();
+
+    expect(mocks.init).toHaveBeenCalledWith(
+      "phc_test_key",
+      expect.objectContaining({
+        api_host: "https://us.i.posthog.com",
+      }),
+    );
+  });
+
+  it("resets guest identity before capturing a pageview in the same effect flush", async () => {
+    vi.resetModules();
+    process.env.NEXT_PUBLIC_POSTHOG_KEY = "phc_test_key";
+    const { resetUser: resetGuest, trackPageView: trackView } =
+      await import("./posthog");
+    window.history.pushState({}, "", "/workspace/guest");
+
+    resetGuest();
+    await trackView({
+      isGuest: true,
+    });
+
+    expect(mocks.reset).toHaveBeenCalledOnce();
+    expect(mocks.capture).toHaveBeenCalledWith(
+      "$pageview",
+      expect.objectContaining({
+        $pathname: "/workspace/guest",
+        is_guest: true,
+      }),
+    );
+    expect(mocks.reset.mock.invocationCallOrder[0]).toBeLessThan(
+      mocks.capture.mock.invocationCallOrder[0],
+    );
+  });
+
+  it("tracks pageview with full url metadata", async () => {
+    vi.resetModules();
+    process.env.NEXT_PUBLIC_POSTHOG_KEY = "phc_test_key";
+    const { initPostHogClient: initClient, trackPageView: trackView } =
+      await import("./posthog");
+    window.history.pushState({}, "", "/workspace/test");
+    await initClient();
+    await trackView({
+      workspaceId: "ws_1",
+      isGuest: false,
+    });
+
+    expect(mocks.capture).toHaveBeenCalledWith(
+      "$pageview",
+      expect.objectContaining({
+        $current_url: window.location.href,
+        $pathname: "/workspace/test",
+        workspace_id: "ws_1",
+        is_guest: false,
+      }),
+    );
+    const payload = mocks.capture.mock.calls[0]?.[1] as
+      | Record<string, unknown>
+      | undefined;
+    expect(payload).not.toHaveProperty("from_page");
+  });
+});
diff --git a/src/lib/posthog.ts b/src/lib/posthog.ts
new file mode 100644
index 0000000..65baf5c
--- /dev/null
+++ b/src/lib/posthog.ts
@@ -0,0 +1,221 @@
+"use client";
+
+import posthog, { type Properties } from "posthog-js";
+let isInitialized = false;
+
+const POSTHOG_CLOUD_HOST: string = "https://us.i.posthog.com";
+
+export type AnalyticsContext = {
+  readonly workspaceId?: string;
+  readonly workspaceNamespace?: string;
+  readonly userId?: string;
+  readonly isGuest?: boolean;
+};
+
+type AnalyticsEnvelope = {
+  readonly context?: AnalyticsContext;
+};
+
+function getPostHogKey(): string | null {
+  const key = process.env.NEXT_PUBLIC_POSTHOG_KEY;
+  return key && key.trim().length > 0 ? key : null;
+}
+
+function getPostHogHost(): string {
+  const host = process.env.NEXT_PUBLIC_POSTHOG_HOST?.trim();
+  return host && host.length > 0 ? host : POSTHOG_CLOUD_HOST;
+}
+
+export function isPostHogEnabled(): boolean {
+  return getPostHogKey() !== null;
+}
+
+export function initPostHogClient(): void {
+  const key = getPostHogKey();
+  if (!key) return;
+  if (typeof window === "undefined" || isInitialized) return;
+
+  posthog.init(key, {
+    api_host: getPostHogHost(),
+    person_profiles: "identified_only",
+    capture_pageview: false,
+    capture_pageleave: true,
+  });
+  isInitialized = true;
+}
+
+function ensurePostHogClient(): boolean {
+  if (typeof window === "undefined" || !isPostHogEnabled()) return false;
+  if (!isInitialized) initPostHogClient();
+  return isInitialized;
+}
+
+export function trackEvent(
+  eventName: string,
+  properties?: Properties,
+): Promise<void> {
+  if (!ensurePostHogClient()) return Promise.resolve();
+  posthog.capture(eventName, properties);
+  return Promise.resolve();
+}
+
+function buildBaseProperties(context?: AnalyticsContext): Properties {
+  return {
+    surface: "notebook",
+    timestamp: new Date().toISOString(),
+    workspace_id: context?.workspaceId,
+    workspace_namespace: context?.workspaceNamespace,
+    user_id: context?.userId,
+    is_guest: context?.isGuest,
+  };
+}
+
+export function identifyUser(input: {
+  id: string;
+  email?: string | null;
+  name?: string | null;
+}): void {
+  if (!ensurePostHogClient()) return;
+
+  posthog.identify(input.id, {
+    email: input.email ?? undefined,
+    name: input.name ?? undefined,
+  });
+}
+
+export function resetUser(): void {
+  if (!ensurePostHogClient()) return;
+  posthog.reset();
+}
+
+export function trackPageView(
+  context?: AnalyticsContext,
+): Promise<void> {
+  if (typeof window === "undefined") return Promise.resolve();
+  return trackEvent("$pageview", {
+    ...buildBaseProperties(context),
+    $current_url: window.location.href,
+    $pathname: window.location.pathname,
+  });
+}
+
+export function trackNotebookUploadButtonClicked(
+  input: AnalyticsEnvelope & { readonly sourceCountSnapshot: number },
+): Promise<void> {
+  return trackEvent("notebook_upload_button_clicked", {
+    ...buildBaseProperties(input.context),
+    source_count_snapshot: input.sourceCountSnapshot,
+  });
+}
+
+export function trackNotebookDocumentUploadCompleted(input: {
+  readonly context?: AnalyticsContext;
+  uploadedCount: number;
+  fileType: string;
+  fileSizeBytes: number;
+  sourceCountBefore: number;
+  sourceCountAfter: number;
+}): Promise<void> {
+  return trackEvent("notebook_document_upload_completed", {
+    ...buildBaseProperties(input.context),
+    uploaded_count: input.uploadedCount,
+    file_types: [input.fileType || "unknown"],
+    total_size_bytes: input.fileSizeBytes,
+    source_count_before: input.sourceCountBefore,
+    source_count_after: input.sourceCountAfter,
+  });
+}
+
+export function trackNotebookAssistantQuestionSubmitted(input: {
+  readonly context?: AnalyticsContext;
+  readonly threadId?: string | null;
+  selectedSourcesCount: number;
+  sourceCountSnapshot: number;
+  messageLength: number;
+}): Promise<void> {
+  return trackEvent("notebook_assistant_question_submitted", {
+    ...buildBaseProperties(input.context),
+    thread_id: input.threadId,
+    selected_sources_count: input.selectedSourcesCount,
+    source_count_snapshot: input.sourceCountSnapshot,
+    message_length: input.messageLength,
+  });
+}
+
+export function trackNotebookDashboardLinkClicked(input: {
+  readonly context?: AnalyticsContext;
+  readonly targetUrl: string;
+  readonly fromPage: string;
+  readonly hasSources: boolean;
+  readonly hasChats: boolean;
+}): Promise<void> {
+  return trackEvent("notebook_dashboard_link_clicked", {
+    ...buildBaseProperties(input.context),
+    from_page: input.fromPage,
+    target_url: input.targetUrl,
+    has_sources: input.hasSources,
+    has_chats: input.hasChats,
+  });
+}
+
+export function trackNotebookDocumentUploadFailed(input: {
+  readonly context?: AnalyticsContext;
+  readonly fileType: string | null;
+  readonly fileSizeBytes: number | null;
+  readonly errorType: "network" | "validation" | "server" | "unknown";
+  readonly errorMessage: string;
+}): Promise<void> {
+  return trackEvent("notebook_document_upload_failed", {
+    ...buildBaseProperties(input.context),
+    file_type: input.fileType,
+    file_size_bytes: input.fileSizeBytes,
+    error_type: input.errorType,
+    error_message: input.errorMessage.slice(0, 200),
+  });
+}
+
+export function trackNotebookAssistantAnswerCompleted(input: {
+  readonly context?: AnalyticsContext;
+  readonly threadId: string;
+  readonly latencyMs: number;
+}): Promise<void> {
+  return trackEvent("notebook_assistant_answer_completed", {
+    ...buildBaseProperties(input.context),
+    thread_id: input.threadId,
+    latency_ms: input.latencyMs,
+  });
+}
+
+export function trackNotebookAssistantAnswerFailed(input: {
+  readonly context?: AnalyticsContext;
+  readonly threadId?: string | null;
+  readonly latencyMs: number;
+  readonly errorType: "network" | "validation" | "server" | "unknown";
+  readonly errorMessage: string;
+}): Promise<void> {
+  return trackEvent("notebook_assistant_answer_failed", {
+    ...buildBaseProperties(input.context),
+    thread_id: input.threadId,
+    latency_ms: input.latencyMs,
+    error_type: input.errorType,
+    error_message: input.errorMessage.slice(0, 200),
+  });
+}
+
+export function trackNotebookWorkspaceFirstDocumentUploaded(input: {
+  readonly context?: AnalyticsContext;
+}): Promise<void> {
+  return trackEvent("notebook_workspace_first_document_uploaded", {
+    ...buildBaseProperties(input.context),
+  });
+}
+
+export function trackNotebookWorkspaceFirstQuestionAsked(input: {
+  readonly context?: AnalyticsContext;
+  readonly selectedSourcesCount: number;
+}): Promise<void> {
+  return trackEvent("notebook_workspace_first_question_asked", {
+    ...buildBaseProperties(input.context),
+    selected_sources_count: input.selectedSourcesCount,
+  });
+}
diff --git a/src/providers/posthog-initializer.tsx b/src/providers/posthog-initializer.tsx
new file mode 100644
index 0000000..d72d102
--- /dev/null
+++ b/src/providers/posthog-initializer.tsx
@@ -0,0 +1,16 @@
+"use client";
+
+import { type ReactNode, useEffect } from "react";
+import { initPostHogClient } from "@/lib/posthog";
+
+export function PostHogInitializer({
+  children,
+}: {
+  children: ReactNode;
+}): ReactNode {
+  useEffect(() => {
+    void initPostHogClient();
+  }, []);
+
+  return children;
+}