diff --git a/CHANGELOG.md b/CHANGELOG.md
index e52e037..cadb53c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix browser extension losing connection and feedback after MCP reconnect (`/mcp`) — session IDs are now derived deterministically from the project directory, so reconnecting preserves WebSocket connections and pending feedback (#43)
+- Add process ID guard on session unregistration to prevent race conditions when old and new MCP processes overlap
+- Add feedback migration when a new session registers with the same project directory as an existing session
+- Browser extension now validates cached session IDs on page navigation and auto-refreshes stale sessions
+
 ## [0.6.5] - 2026-04-21
 
 ### Fixed
diff --git a/extension/background.js b/extension/background.js
index e6de1c9..549a7e4 100644
--- a/extension/background.js
+++ b/extension/background.js
@@ -105,6 +105,35 @@ async function resolveSessionForTab(tabUrl, serverUrl) {
   return null;
 }
 
+// Validate that a cached session still exists on the server; re-resolve if stale
+async function validateOrRefreshSession(tabId, cachedSessionId, serverUrl) {
+  if (!cachedSessionId) {
+    const tab = await chrome.tabs.get(tabId);
+    const resolved = await resolveSessionForTab(tab.url, serverUrl);
+    if (resolved) {
+      tabSessionMap.set(tabId, resolved);
+      persistActiveTabs();
+    }
+    return resolved;
+  }
+
+  const sessions = await fetchSessions(serverUrl);
+  if (sessions.length === 0) return cachedSessionId; // Server unreachable, keep cached
+
+  const stillExists = sessions.some(s => s.sessionId === cachedSessionId);
+  if (stillExists) return cachedSessionId;
+
+  // Session is stale — re-resolve by project URL
+  const tab = await chrome.tabs.get(tabId);
+  const resolved = await resolveSessionForTab(tab.url, serverUrl);
+  if (resolved) {
+    tabSessionMap.set(tabId, resolved);
+    persistActiveTabs();
+    console.log(`[Feedback Ext] Session refreshed: ${cachedSessionId.slice(0, 8)} -> ${resolved.slice(0, 8)}`);
+  }
+  return resolved || cachedSessionId;
+}
+
 // Toggle widget on a specific tab
 async function toggleTab(tabId) {
   const serverUrl = await getServerUrl();
@@ -155,11 +184,13 @@ chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
     // Called by content script on page load
     const tabId = sender.tab?.id;
     if (tabId && activeTabs.has(tabId)) {
-      getServerUrl().then((serverUrl) => {
+      getServerUrl().then(async (serverUrl) => {
+        const cachedSession = tabSessionMap.get(tabId) || null;
+        const sessionId = await validateOrRefreshSession(tabId, cachedSession, serverUrl);
         sendResponse({
           active: true,
           serverUrl,
-          sessionId: tabSessionMap.get(tabId) || null,
+          sessionId,
         });
       });
       return true; // async response
@@ -218,7 +249,8 @@ chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
 chrome.tabs.onUpdated.addListener(async (tabId, changeInfo) => {
   if (changeInfo.status === 'complete' && activeTabs.has(tabId)) {
     const serverUrl = await getServerUrl();
-    const sessionId = tabSessionMap.get(tabId) || null;
+    const cachedSession = tabSessionMap.get(tabId) || null;
+    const sessionId = await validateOrRefreshSession(tabId, cachedSession, serverUrl);
     updateBadge(tabId, true);
     await sendToTab(tabId, { action: 'activate', serverUrl, sessionId });
   }
diff --git a/src/server.js b/src/server.js
index 4b4f0f3..8be4028 100644
--- a/src/server.js
+++ b/src/server.js
@@ -14,7 +14,7 @@ import crypto from "node:crypto";
 import { fileURLToPath, pathToFileURL } from "url";
 import { createRequire } from "module";
 import { execFile } from "child_process";
-import { isValidSessionId, getPendingSummary, detectProjectUrl, formatFeedbackAsContent } from "./utils.js";
+import { deriveSessionId, isValidSessionId, getPendingSummary, detectProjectUrl, formatFeedbackAsContent } from "./utils.js";
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
@@ -23,8 +23,9 @@ const PORT = parseInt(process.env.FEEDBACK_PORT || "9877");
 const PKG_VERSION = JSON.parse(fs.readFileSync(path.join(__dirname, '..', 'package.json'), 'utf8')).version;
 
 // Session identity for this MCP server process
-const SESSION_ID = crypto.randomUUID();
 const PROJECT_DIR = process.cwd();
+const SESSION_ID = deriveSessionId(PROJECT_DIR);
+const PROCESS_ID = crypto.randomUUID();
 
 // Session registry (owner server only): sessionId -> metadata
 const sessionRegistry = new Map();
@@ -183,6 +184,7 @@ async function registerSessionViaHttp() {
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify({
         sessionId: SESSION_ID,
+        processId: PROCESS_ID,
         projectDir: PROJECT_DIR,
         projectUrl: detected.url,
         detectedFrom: detected.detectedFrom,
@@ -199,7 +201,7 @@ async function unregisterSessionViaHttp() {
     await fetch(`http://localhost:${PORT}/unregister-session`, {
       method: 'POST',
       headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ sessionId: SESSION_ID }),
+      body: JSON.stringify({ sessionId: SESSION_ID, processId: PROCESS_ID }),
     });
   } catch (err) {
     // Ignore errors during shutdown
@@ -371,8 +373,36 @@ const httpServer = http.createServer((req, res) => {
         res.end(JSON.stringify({ error: "Invalid session ID format" }));
         return;
       }
+      // Migrate feedback from any old session with the same projectDir but different sessionId
+      for (const [existingId, existingMeta] of sessionRegistry) {
+        if (existingId !== data.sessionId && existingMeta.projectDir === data.projectDir) {
+          const oldPending = pendingFeedbackBySession.get(existingId);
+          if (oldPending && oldPending.length > 0) {
+            getSessionPending(data.sessionId).push(...oldPending);
+          }
+          const oldReady = readyFeedbackBySession.get(existingId);
+          if (oldReady && oldReady.length > 0) {
+            getSessionReady(data.sessionId).push(...oldReady);
+          }
+          const oldClients = connectedClientsBySession.get(existingId);
+          if (oldClients && oldClients.size > 0) {
+            const newClients = getSessionClients(data.sessionId);
+            for (const client of oldClients) {
+              client._sessionId = data.sessionId;
+              newClients.add(client);
+            }
+          }
+          pendingFeedbackBySession.delete(existingId);
+          readyFeedbackBySession.delete(existingId);
+          feedbackResolversBySession.delete(existingId);
+          connectedClientsBySession.delete(existingId);
+          sessionRegistry.delete(existingId);
+          console.error(`[browser-feedback-mcp] Migrated session data: ${existingId} -> ${data.sessionId}`);
+        }
+      }
       sessionRegistry.set(data.sessionId, {
         sessionId: data.sessionId,
+        processId: data.processId || null,
         projectDir: data.projectDir,
         projectUrl: data.projectUrl || null,
         detectedFrom: data.detectedFrom || null,
@@ -396,6 +426,14 @@ const httpServer = http.createServer((req, res) => {
         res.end(JSON.stringify({ error: "Invalid session ID format" }));
         return;
       }
+      // Guard: skip deletion if a different process has re-registered this session
+      const existing = sessionRegistry.get(data.sessionId);
+      if (existing && data.processId && existing.processId && existing.processId !== data.processId) {
+        console.error(`[browser-feedback-mcp] Skipping unregister: session ${data.sessionId} owned by different process`);
+        res.writeHead(200, { "Content-Type": "application/json" });
+        res.end(JSON.stringify({ success: true, skipped: true }));
+        return;
+      }
       sessionRegistry.delete(data.sessionId);
       // Clean up session data
       pendingFeedbackBySession.delete(data.sessionId);
@@ -1719,8 +1757,11 @@ function shutdown(reason) {
 
   // Only close HTTP server if we own it
   if (isHttpServerOwner) {
-    // Remove own session from registry
-    sessionRegistry.delete(SESSION_ID);
+    // Remove own session from registry only if we still own it
+    const ownSession = sessionRegistry.get(SESSION_ID);
+    if (ownSession && ownSession.processId === PROCESS_ID) {
+      sessionRegistry.delete(SESSION_ID);
+    }
 
     // Close all WebSocket connections
     for (const client of connectedClients) {
@@ -1831,6 +1872,7 @@ async function main() {
     // Owner registers directly
     sessionRegistry.set(SESSION_ID, {
       sessionId: SESSION_ID,
+      processId: PROCESS_ID,
       projectDir: PROJECT_DIR,
       projectUrl: detected.url,
       detectedFrom: detected.detectedFrom,
diff --git a/src/utils.js b/src/utils.js
index 8af0679..8e7841a 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -1,5 +1,19 @@
 import fs from "fs";
 import path from "path";
+import crypto from "node:crypto";
+
+// Derive a deterministic session ID (UUID format) from the project directory.
+// Ensures reconnecting the same project reuses the same session ID.
+export function deriveSessionId(projectDir) {
+  const hash = crypto.createHash('sha256').update(projectDir).digest('hex');
+  return [
+    hash.slice(0, 8),
+    hash.slice(8, 12),
+    hash.slice(12, 16),
+    hash.slice(16, 20),
+    hash.slice(20, 32),
+  ].join('-');
+}
 
 // UUID format validation for session IDs
 const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
diff --git a/tests/http-endpoints.test.js b/tests/http-endpoints.test.js
index b8a9154..da96c51 100644
--- a/tests/http-endpoints.test.js
+++ b/tests/http-endpoints.test.js
@@ -125,6 +125,47 @@ describe('session registration', () => {
     expect(found).toBeUndefined();
   });
 
+  it('POST /unregister-session skips deletion when processId does not match', async () => {
+    const sessionId = crypto.randomUUID();
+
+    // Register with processId 'proc-1'
+    await fetch(`${BASE_URL}/register-session`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ sessionId, processId: 'proc-1', projectDir: '/tmp/guard-test' }),
+    });
+
+    // Re-register with processId 'proc-2' (simulates new process taking over)
+    await fetch(`${BASE_URL}/register-session`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ sessionId, processId: 'proc-2', projectDir: '/tmp/guard-test' }),
+    });
+
+    // Old process tries to unregister with 'proc-1' — should be skipped
+    const unregResp = await fetch(`${BASE_URL}/unregister-session`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ sessionId, processId: 'proc-1' }),
+    });
+    expect(unregResp.status).toBe(200);
+    const unregData = await unregResp.json();
+    expect(unregData.skipped).toBe(true);
+
+    // Session should still exist
+    const sessionsResp = await fetch(`${BASE_URL}/sessions`);
+    const sessionsData = await sessionsResp.json();
+    const found = sessionsData.sessions.find(s => s.sessionId === sessionId);
+    expect(found).toBeDefined();
+
+    // Clean up with correct processId
+    await fetch(`${BASE_URL}/unregister-session`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ sessionId, processId: 'proc-2' }),
+    });
+  });
+
   it('POST /unregister-session with invalid ID returns 400', async () => {
     const resp = await fetch(`${BASE_URL}/unregister-session`, {
       method: 'POST',
@@ -252,6 +293,65 @@ describe('WebSocket session routing', () => {
     }
   });
 
+  it('client reconnecting after session migration lands in correct bucket', async () => {
+    // Register session A with a projectDir, connect a WS client, submit feedback
+    const sessionA = crypto.randomUUID();
+    const sessionB = crypto.randomUUID();
+    const projectDir = '/tmp/migration-test-project';
+
+    await fetch(`${BASE_URL}/register-session`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ sessionId: sessionA, processId: 'proc-a', projectDir }),
+    });
+
+    // Connect WS client to session A and submit feedback
+    const { ws: wsA, msg: msgA } = await connectWs(sessionA);
+    expect(msgA.sessionId).toBe(sessionA);
+
+    wsA.send(JSON.stringify({
+      type: 'feedback',
+      payload: { id: 'fb-migrate-1', description: 'Test feedback for migration' },
+    }));
+
+    // Wait for feedback to be stored
+    await new Promise(r => setTimeout(r, 100));
+
+    // Verify feedback exists under session A
+    const respA = await fetch(`${BASE_URL}/status?session=${sessionA}`);
+    const dataA = await respA.json();
+    expect(dataA.pendingFeedback).toBe(1);
+
+    wsA.close();
+    await new Promise(r => setTimeout(r, 100));
+
+    // Register session B with same projectDir — should migrate feedback
+    const regResp = await fetch(`${BASE_URL}/register-session`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ sessionId: sessionB, processId: 'proc-b', projectDir }),
+    });
+    expect(regResp.status).toBe(200);
+
+    // Verify feedback migrated to session B
+    const respB = await fetch(`${BASE_URL}/status?session=${sessionB}`);
+    const dataB = await respB.json();
+    expect(dataB.pendingFeedback).toBe(1);
+
+    // Verify session A no longer exists
+    const sessionsResp = await fetch(`${BASE_URL}/sessions`);
+    const sessionsData = await sessionsResp.json();
+    const foundA = sessionsData.sessions.find(s => s.sessionId === sessionA);
+    expect(foundA).toBeUndefined();
+
+    // Clean up
+    await fetch(`${BASE_URL}/unregister-session`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ sessionId: sessionB, processId: 'proc-b' }),
+    });
+  });
+
   it('second client on same session triggers duplicate warning', async () => {
     const sessionId = crypto.randomUUID();
     const { ws: ws1, msg: msg1 } = await connectWs(sessionId);
diff --git a/tests/utils.test.js b/tests/utils.test.js
index 5b22fe0..dc8c5f6 100644
--- a/tests/utils.test.js
+++ b/tests/utils.test.js
@@ -3,12 +3,41 @@ import fs from 'fs';
 import os from 'os';
 import path from 'path';
 import {
+  deriveSessionId,
   isValidSessionId,
   getPendingSummary,
   detectProjectUrl,
   formatFeedbackAsContent,
 } from '../src/utils.js';
 
+// ============================================
+// deriveSessionId
+// ============================================
+
+describe('deriveSessionId', () => {
+  it('returns a valid UUID-formatted session ID', () => {
+    const id = deriveSessionId('/home/user/project');
+    expect(isValidSessionId(id)).toBe(true);
+  });
+
+  it('returns the same ID for the same project directory', () => {
+    const id1 = deriveSessionId('/home/user/project');
+    const id2 = deriveSessionId('/home/user/project');
+    expect(id1).toBe(id2);
+  });
+
+  it('returns different IDs for different project directories', () => {
+    const id1 = deriveSessionId('/home/user/project-a');
+    const id2 = deriveSessionId('/home/user/project-b');
+    expect(id1).not.toBe(id2);
+  });
+
+  it('returns lowercase hex characters', () => {
+    const id = deriveSessionId('/some/path');
+    expect(id).toMatch(/^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/);
+  });
+});
+
 // ============================================
 // isValidSessionId
 // ============================================