diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - Deprecated `GOOGLE_VERTEX_THINKING_BUDGET_TOKENS` environment variable in favor of per-model `thinkingBudget` config. [#1110](https://github.com/sourcebot-dev/sourcebot/pull/1110)
 - Removed `GOOGLE_VERTEX_INCLUDE_THOUGHTS` environment variable. Thoughts are now always included. [#1110](https://github.com/sourcebot-dev/sourcebot/pull/1110)
+- Renamed and consolidated PostHog chat events (`wa_chat_thread_created` -> `ask_thread_created`, `wa_chat_message_sent` -> `ask_message_sent`, `wa_chat_tool_used` -> `tool_used`), added unified `tool_used` tracking across the ask agent and MCP server, and removed the redundant `api_code_search_request` event. [#1111](https://github.com/sourcebot-dev/sourcebot/pull/1111)
 
 ## [4.16.8] - 2026-04-09
 

diff --git a/CLAUDE.md b/CLAUDE.md
@@ -57,6 +57,12 @@ if (!value) { return; }
 if (condition) doSomething();
 ```
 
+## PostHog Event Naming
+
+- The `wa_` prefix is reserved for events that can ONLY be fired from the web app (e.g., `wa_login_with_github`, `wa_chat_feedback_submitted`).
+- Events fired from multiple sources (web app, MCP server, API) must NOT use the `wa_` prefix (e.g., `ask_message_sent`, `tool_used`).
+- Multi-source events should include a `source` property to identify the origin (e.g., `'sourcebot-web-client'`, `'sourcebot-mcp-server'`, `'sourcebot-ask-agent'`).
+
 ## Tailwind CSS
 
 Use Tailwind color classes directly instead of CSS variable syntax:

diff --git a/packages/web/src/app/api/(server)/chat/route.ts b/packages/web/src/app/api/(server)/chat/route.ts
@@ -91,12 +91,15 @@ export const POST = apiHandler(async (req: NextRequest) => {
                 return [];
             }))).flat();
 
-            await captureEvent('wa_chat_message_sent', {
+            const source = req.headers.get('X-Sourcebot-Client-Source') ?? undefined;
+
+            await captureEvent('ask_message_sent', {
                 chatId: id,
                 messageCount: messages.length,
                 selectedReposCount: expandedRepos.length,
+                source,
                 ...(env.EXPERIMENT_ASK_GH_ENABLED === 'true' ? { selectedRepos: expandedRepos } : {}),
-            } );
+            });
 
             const stream = await createMessageStream({
                 chatId: id,

diff --git a/packages/web/src/app/api/(server)/search/route.ts b/packages/web/src/app/api/(server)/search/route.ts
@@ -2,7 +2,6 @@
 
 import { search, searchRequestSchema } from "@/features/search";
 import { apiHandler } from "@/lib/apiHandler";
-import { captureEvent } from "@/lib/posthog";
 import { requestBodySchemaValidationError, serviceErrorResponse } from "@/lib/serviceError";
 import { isServiceError } from "@/lib/utils";
 import { NextRequest } from "next/server";
@@ -21,12 +20,6 @@ export const POST = apiHandler(async (request: NextRequest) => {
         ...options
     } = parsed.data;
 
-    const source = request.headers.get('X-Sourcebot-Client-Source') ?? 'unknown';
-    await captureEvent('api_code_search_request', {
-        source,
-        type: 'blocking',
-    });
-
     const response = await search({
         queryType: 'string',
         query,

diff --git a/packages/web/src/app/api/(server)/stream_search/route.ts b/packages/web/src/app/api/(server)/stream_search/route.ts
@@ -2,7 +2,6 @@
 
 import { streamSearch, searchRequestSchema } from '@/features/search';
 import { apiHandler } from '@/lib/apiHandler';
-import { captureEvent } from '@/lib/posthog';
 import { requestBodySchemaValidationError, serviceErrorResponse } from '@/lib/serviceError';
 import { isServiceError } from '@/lib/utils';
 import { NextRequest } from 'next/server';
@@ -20,12 +19,6 @@ export const POST = apiHandler(async (request: NextRequest) => {
         ...options
     } = parsed.data;
 
-    const source = request.headers.get('X-Sourcebot-Client-Source') ?? 'unknown';
-    await captureEvent('api_code_search_request', {
-        source,
-        type: 'streamed',
-    });
-
     const stream = await streamSearch({
         queryType: 'string',
         query,

diff --git a/packages/web/src/features/chat/actions.ts b/packages/web/src/features/chat/actions.ts
@@ -49,9 +49,10 @@ export const createChat = async ({ source }: { source?: string } = {}) => sew(()
             });
         }
 
-        await captureEvent('wa_chat_thread_created', {
+        await captureEvent('ask_thread_created', {
             chatId: chat.id,
             isAnonymous: isGuestUser,
+            source,
         });
 
         return {

diff --git a/packages/web/src/features/chat/agent.ts b/packages/web/src/features/chat/agent.ts
@@ -1,7 +1,6 @@
 import { SBChatMessage, SBChatMessageMetadata } from "@/features/chat/types";
 import { getAnswerPartFromAssistantMessage } from "@/features/chat/utils";
 import { getFileSource } from '@/features/git';
-import { captureEvent } from "@/lib/posthog";
 import { isServiceError } from "@/lib/utils";
 import { LanguageModelV3 as AISDKLanguageModelV3 } from "@ai-sdk/provider";
 import { ProviderOptions } from "@ai-sdk/provider-utils";
@@ -210,13 +209,7 @@ const createAgentStream = async ({
         ],
         toolChoice: "auto",
         onStepFinish: ({ toolResults }) => {
-            toolResults.forEach(({ toolName, output, dynamic }) => {
-                captureEvent('wa_chat_tool_used', {
-                    chatId,
-                    toolName,
-                    success: !isServiceError(output),
-                });
-
+            toolResults.forEach(({ output, dynamic }) => {
                 if (dynamic || isServiceError(output)) {
                     return;
                 }

diff --git a/packages/web/src/features/chat/components/chatThread/chatThread.tsx b/packages/web/src/features/chat/components/chatThread/chatThread.tsx
@@ -102,6 +102,9 @@ export const ChatThread = ({
         messages: initialMessages,
         transport: new DefaultChatTransport({
             api: '/api/chat',
+            headers: {
+                'X-Sourcebot-Client-Source': 'sourcebot-web-client',
+            },
         }),
         onData: (dataPart) => {
             // Keeps sources added by the assistant in sync.

diff --git a/packages/web/src/features/mcp/askCodebase.ts b/packages/web/src/features/mcp/askCodebase.ts
@@ -86,9 +86,10 @@ export const askCodebase = (params: AskCodebaseParams): Promise<AskCodebaseResul
                 },
             });
 
-            await captureEvent('wa_chat_thread_created', {
+            await captureEvent('ask_thread_created', {
                 chatId: chat.id,
                 isAnonymous: !user,
+                source,
             });
 
             if (user) {
@@ -137,10 +138,11 @@ export const askCodebase = (params: AskCodebaseParams): Promise<AskCodebaseResul
 
             let finalMessages: SBChatMessage[] = [];
 
-            await captureEvent('wa_chat_message_sent', {
+            await captureEvent('ask_message_sent', {
                 chatId: chat.id,
                 messageCount: 1,
                 selectedReposCount: selectedRepos.length,
+                source,
                 ...(env.EXPERIMENT_ASK_GH_ENABLED === 'true' ? {
                     selectedRepos: selectedRepos.map(r => r.value)
                 } : {}),

diff --git a/packages/web/src/features/mcp/server.ts b/packages/web/src/features/mcp/server.ts
@@ -2,6 +2,7 @@ import {
     languageModelInfoSchema,
 } from '@/features/chat/types';
 import { askCodebase } from '@/features/mcp/askCodebase';
+import { captureEvent } from '@/lib/posthog';
 import { isServiceError } from '@/lib/utils';
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { ChatVisibility } from '@sourcebot/db';
@@ -57,6 +58,11 @@ export async function createMcpServer(): Promise<McpServer> {
         },
         async () => {
             const models = await getConfiguredLanguageModelsInfo();
+            captureEvent('tool_used', {
+                toolName: 'list_language_models',
+                source: 'sourcebot-mcp-server',
+                success: true,
+            });
             return { content: [{ type: "text", text: JSON.stringify(models) }] };
         }
     );
@@ -101,11 +107,22 @@ export async function createMcpServer(): Promise<McpServer> {
                 });
 
                 if (isServiceError(result)) {
+                    captureEvent('tool_used', {
+                        toolName: 'ask_codebase',
+                        source: 'sourcebot-mcp-server',
+                        success: false,
+                    });
                     return {
                         content: [{ type: "text", text: `Failed to ask codebase: ${result.message}` }],
                     };
                 }
 
+                captureEvent('tool_used', {
+                    toolName: 'ask_codebase',
+                    source: 'sourcebot-mcp-server',
+                    success: true,
+                });
+
                 const formattedResponse = dedent`
                 ${result.answer}
 

diff --git a/packages/web/src/features/tools/adapters.ts b/packages/web/src/features/tools/adapters.ts
@@ -1,6 +1,7 @@
 import { tool } from "ai";
 import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
 import { z } from "zod";
+import { captureEvent } from "@/lib/posthog";
 import { ToolContext, ToolDefinition } from "./types";
 
 export function toVercelAITool<TName extends string, TShape extends z.ZodRawShape, TMetadata>(
@@ -11,7 +12,21 @@ export function toVercelAITool<TName extends string, TShape extends z.ZodRawShap
         description: def.description,
         inputSchema: def.inputSchema,
         title: def.title,
-        execute: (input) => def.execute(input, context),
+        execute: async (input) => {
+            let success = true;
+            try {
+                return await def.execute(input, context);
+            } catch (error) {
+                success = false;
+                throw error;
+            } finally {
+                captureEvent('tool_used', {
+                    toolName: def.name,
+                    source: context.source ?? 'unknown',
+                    success,
+                });
+            }
+        },
         toModelOutput: ({ output }) => ({
             type: "content",
             value: [{ type: "text", text: output.output }],
@@ -38,13 +53,21 @@ export function registerMcpTool<TName extends string, TShape extends z.ZodRawSha
             },
         },
         async (input) => {
+            let success = true;
             try {
                 const parsed = def.inputSchema.parse(input);
                 const result = await def.execute(parsed, context);
                 return { content: [{ type: "text" as const, text: result.output }] };
             } catch (error) {
+                success = false;
                 const message = error instanceof Error ? error.message : String(error);
                 return { content: [{ type: "text" as const, text: `Tool "${def.name}" failed: ${message}` }], isError: true };
+            } finally {
+                captureEvent('tool_used', {
+                    toolName: def.name,
+                    source: context.source ?? 'unknown',
+                    success,
+                });
             }
         },
     );

diff --git a/packages/web/src/lib/apiHandler.ts b/packages/web/src/lib/apiHandler.ts
@@ -47,9 +47,7 @@ export function apiHandler<H extends AnyHandler>(
             const source = request.headers.get('X-Sourcebot-Client-Source') ?? 'unknown';
 
             // Fire and forget - don't await to avoid blocking the request
-            captureEvent('api_request', { path, method, source }).catch(() => {
-                // Silently ignore tracking errors
-            });
+            captureEvent('api_request', { path, method, source });
         }
 
         // Call the original handler with all arguments

diff --git a/packages/web/src/lib/posthog.ts b/packages/web/src/lib/posthog.ts
@@ -1,11 +1,12 @@
 import { PostHog } from 'posthog-node'
-import { env, SOURCEBOT_VERSION } from '@sourcebot/shared'
+import { createLogger, env, SOURCEBOT_VERSION } from '@sourcebot/shared'
 import { RequestCookies } from 'next/dist/compiled/@edge-runtime/cookies';
 import * as Sentry from "@sentry/nextjs";
 import { PosthogEvent, PosthogEventMap } from './posthogEvents';
 import { cookies, headers } from 'next/headers';
-import { auth } from '@/auth';
-import { getVerifiedApiObject } from '@/middleware/withAuth';
+import { getAuthenticatedUser } from '@/middleware/withAuth';
+
+const logger = createLogger('posthog');
 
 /**
  * @note: This is a subset of the properties stored in the
@@ -53,28 +54,19 @@ const getPostHogCookie = (cookieStore: Pick<RequestCookies, 'get'>): PostHogCook
  * Attempts to retrieve the distinct id of the current user.
  */
 export const tryGetPostHogDistinctId = async () => {
-    // First, attempt to retrieve the distinct id from the cookie.
+    // First, attempt to retrieve the distinct id from the PostHog cookie
+    // (set by the client-side PostHog SDK). This preserves identity
+    // continuity between client-side and server-side events.
     const cookieStore = await cookies();
     const cookie = getPostHogCookie(cookieStore);
     if (cookie) {
         return cookie.distinct_id;
     }
 
-    // Next, from the session.
-    const session = await auth();
-    if (session) {
-        return session.user.id;
-    }
-
-    // Finally, from the api key.
-    const headersList = await headers();
-    const apiKeyString = headersList.get("X-Sourcebot-Api-Key") ?? undefined;
-    if (!apiKeyString) {
-        return undefined;
-    }
-
-    const apiKey = await getVerifiedApiObject(apiKeyString);
-    return apiKey?.createdById;
+    // Fall back to the authenticated user's ID. This covers all auth
+    // methods: session cookies, OAuth Bearer tokens, and API keys.
+    const authResult = await getAuthenticatedUser();
+    return authResult?.user.id;
 }
 
 export const createPostHogClient = async () => {
@@ -88,24 +80,28 @@ export const createPostHogClient = async () => {
 }
 
 export async function captureEvent<E extends PosthogEvent>(event: E, properties: PosthogEventMap[E]) {
-    if (env.SOURCEBOT_TELEMETRY_DISABLED === 'true') {
-        return;
-    }
+    try {
+        if (env.SOURCEBOT_TELEMETRY_DISABLED === 'true') {
+            return;
+        }
 
-    const distinctId = await tryGetPostHogDistinctId();
-    const posthog = await createPostHogClient();
-
-    const headersList = await headers();
-    const host = headersList.get("host") ?? undefined;
-
-    posthog.capture({
-        event,
-        properties: {
-            ...properties,
-            sourcebot_version: SOURCEBOT_VERSION,
-            install_id: env.SOURCEBOT_INSTALL_ID,
-            $host: host,
-        },
-        distinctId,
-    });
+        const distinctId = await tryGetPostHogDistinctId();
+        const posthog = await createPostHogClient();
+
+        const headersList = await headers();
+        const host = headersList.get("host") ?? undefined;
+
+        posthog.capture({
+            event,
+            properties: {
+                ...properties,
+                sourcebot_version: SOURCEBOT_VERSION,
+                install_id: env.SOURCEBOT_INSTALL_ID,
+                $host: host,
+            },
+            distinctId,
+        });
+    } catch (error) {
+        logger.error('Failed to capture PostHog event:', error);
+    }
 }