Implement experimental file-based encrypted private chat

Add fixed-suite Rust/WASI identity files, signed challenge authentication, ciphertext-only SQLite storage, a minimal LibreJS-compatible interface, and consistent backup snapshots. Keep production unchanged and document the local workflow, limits, source distribution, and browser recovery tests.

5 files changed, 515 insertions, 0 deletions

diff --git a/crates/chat-server/web/app.js b/crates/chat-server/web/app.js
new file mode 100644
index 0000000..c06116b
--- /dev/null
+++ b/crates/chat-server/web/app.js
@@ -0,0 +1,325 @@
+// Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+// @license magnet:?xt=urn:btih:0b31508aeb0634b347b8270c7bee4d411b5d4109&dn=agpl-3.0.txt AGPL-3.0
+
+const element = id => document.getElementById(id);
+const show = (id, visible = true) => { element(id).hidden = !visible; };
+const status = message => { element('status').textContent = message; };
+let config;
+let wasm;
+let credentials;
+let session;
+let selected;
+let before = 0;
+let pendingFile;
+let setupToken;
+let pendingSend;
+let generation = 0;
+let busy = false;
+const workers = new Map();
+const blobs = new Set();
+
+async function api(request) {
+    const current = generation;
+    const response = await fetch('/api', {
+        method: 'POST', credentials: 'omit', cache: 'no-store', redirect: 'error',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ ...request, token: session?.token }),
+        signal: AbortSignal.timeout(20000),
+    });
+    const result = await response.json();
+    if (current !== generation) throw new Error('Session locked');
+    if (!response.ok || result.error) throw new Error(result.error || 'Server request failed');
+    return result;
+}
+
+async function cryptoOperation(request) {
+    const current = generation;
+    const bytes = await wasm;
+    if (current !== generation) throw new Error('Session locked');
+    return new Promise((resolve, reject) => {
+        const worker = new Worker('/worker.js');
+
+        const stop = () => { worker.terminate(); workers.delete(worker); clearTimeout(timer); };
+        const timer = setTimeout(() => { stop(); reject(new Error('Cryptographic operation timed out')); }, 90000);
+        workers.set(worker, () => { stop(); reject(new Error('Session locked')); });
+        worker.onerror = () => { stop(); reject(new Error('Cryptographic worker failed')); };
+        worker.onmessage = event => {
+            stop();
+            if (current !== generation) { reject(new Error('Session locked')); return; }
+            if (event.data.error) reject(new Error(event.data.error)); else resolve(event.data.result);
+        };
+        worker.postMessage({ bytes, request });
+    });
+}
+
+function protectRequest(op, fields) {
+    if (!credentials) throw new Error('Unlock your identity file first');
+    return { op, ...credentials, origin: location.origin, ...fields };
+}
+
+function clearState() {
+    generation += 1;
+    busy = false;
+    for (const button of document.querySelectorAll('button')) button.disabled = false;
+    for (const cancel of workers.values()) cancel();
+    workers.clear();
+    for (const url of blobs) URL.revokeObjectURL(url);
+    blobs.clear();
+    credentials = undefined;
+    session = undefined;
+    selected = undefined;
+    pendingFile = undefined;
+    pendingSend = undefined;
+    setupToken = undefined;
+    before = 0;
+    for (const input of document.querySelectorAll('input,textarea')) {
+        if (input.id === 'history-count') input.value = '0'; else input.value = '';
+    }
+    for (const id of ['messages', 'conversations', 'who', 'fingerprint', 'counts', 'thread-name', 'conversation-fingerprint']) element(id).replaceChildren();
+    for (const id of ['create', 'unlock', 'chat', 'thread', 'inbox', 'older', 'retry']) show(id, false);
+    show('entry', Boolean(config?.owner));
+    status('Locked. Select your file and enter its password to return.');
+}
+
+function action(id, callback) {
+    element(id).addEventListener(id.endsWith('-form') ? 'submit' : 'click', async event => {
+        event.preventDefault();
+        if (busy) return;
+        busy = true;
+        status('Working locally...');
+        const current = generation;
+        for (const button of document.querySelectorAll('button:not(#lock)')) button.disabled = true;
+        try { await callback(); }
+        catch (error) { if (generation === current) status(error.message); }
+        finally {
+            if (generation === current) {
+                busy = false;
+                for (const button of document.querySelectorAll('button')) button.disabled = false;
+            }
+        }
+    });
+}
+
+function download(file) {
+    const url = URL.createObjectURL(new Blob([file], { type: 'application/octet-stream' }));
+    blobs.add(url);
+    const link = document.createElement('a');
+    link.href = url;
+    link.download = 'stack-chat-identity.chat';
+    link.click();
+    setTimeout(() => { URL.revokeObjectURL(url); blobs.delete(url); }, 30000);
+}
+
+async function createIdentity() {
+    const password = element('new-password').value;
+    if (password !== element('confirm-password').value) throw new Error('Passwords do not match');
+    if (!config.owner && location.hash !== '#setup') throw new Error('Owner setup is required first');
+    setupToken = !config.owner ? element('setup-token').value : undefined;
+    status('Generating your purpose-specific identity and protecting its file...');
+    const result = await cryptoOperation({ op: 'create', origin: location.origin, name: element('name').value, password, owner: config.owner || '' });
+    pendingFile = result.file;
+    download(result.file);
+    element('create-form').reset();
+    show('create', false);
+    show('unlock');
+    element('reopen-note').textContent = 'Your file was downloaded. Reopen that exact saved file and enter its password before any message can be sent. Keep a safe backup.';
+    status('Reopen your downloaded identity file to verify recovery.');
+}
+
+async function unlockIdentity() {
+    const file = element('file').files[0];
+    if (!file || file.size > 262144) throw new Error('Choose an identity file no larger than 256 KiB');
+    const fileText = await file.text();
+    if (pendingFile && fileText !== pendingFile) throw new Error('Reopen the exact identity file you just downloaded');
+    const candidate = { file: fileText, password: element('password').value };
+    element('unlock-form').reset();
+    status('Unlocking locally and verifying your identity...');
+    const identity = await cryptoOperation({ op: 'open', ...candidate, origin: location.origin });
+    if (config.owner && identity.owner !== config.owner) throw new Error('Pinned owner key differs from this server. Stop and verify the change with Doan.');
+    const challenge = await api({ op: 'challenge', public: identity.public, setup_token: setupToken });
+    const proof = await cryptoOperation({ op: 'proof', ...candidate, origin: location.origin, challenge: challenge.challenge });
+    const authenticated = await api({ op: 'authenticate', id: challenge.id, signature: proof.signature });
+    if (authenticated.id !== identity.fingerprint || typeof authenticated.owner !== 'boolean') throw new Error('Authenticated identity mismatch');
+    credentials = candidate;
+    session = { ...identity, ...authenticated };
+    pendingFile = undefined;
+    setupToken = undefined;
+    config = await api({ op: 'config' });
+    show('entry', false);
+    show('unlock', false);
+    show('chat');
+    element('who').textContent = `${identity.name} [${session.owner === true ? 'OWNER' : 'VISITOR'}]`;
+    element('fingerprint').textContent = `Identity: ${identity.fingerprint}`;
+    if (authenticated.owner) {
+        session.owner = true;
+        show('inbox');
+        await inbox();
+    } else {
+        session.owner = false;
+        const profile = await cryptoOperation(protectRequest('encrypt', { recipient: config.owner, payload: JSON.stringify({ v: 1, kind: 'profile', origin: location.origin, conversation: session.id, sender: session.id, name: identity.name }) }));
+        await api({ op: 'profile', conversation: session.id, ciphertext: profile.ciphertext });
+        selected = { id: session.id, public: identity.public };
+        element('conversation-fingerprint').textContent = `Conversation: ${session.id}`;
+        show('thread');
+        element('thread-name').textContent = 'You <-> Doan';
+        await history(0);
+    }
+    status('Unlocked in memory only. No history loaded automatically. Lock or leave to forget this session.');
+}
+
+function checkedPayload(payload, kind, conversation, sender) {
+    const value = JSON.parse(payload);
+    if (value.v !== 1 || value.kind !== kind || value.origin !== location.origin || value.conversation !== conversation || value.sender !== sender) throw new Error('Signed message binding mismatch');
+    return value;
+}
+
+async function inbox() {
+    const result = await api({ op: 'inbox' });
+    element('conversations').replaceChildren();
+    for (const conversation of result.conversations) {
+        const button = document.createElement('button');
+        button.textContent = `${conversation.id.slice(0, 12)} / ${conversation.total} messages`;
+        button.addEventListener('click', async () => {
+            if (busy) return;
+            if (pendingSend) { status('Retry the pending message, or lock before switching conversations.'); return; }
+            busy = true;
+            const current = generation;
+            status('Opening conversation...');
+            try {
+                selected = conversation;
+                element('conversation-fingerprint').textContent = `Conversation: ${conversation.id}`;
+                element('thread-name').textContent = `Doan <-> ${conversation.id.slice(0, 12)}`;
+                pendingSend = undefined;
+                element('text').value = '';
+                show('retry', false);
+                element('messages').replaceChildren();
+                show('thread');
+                let name = conversation.id.slice(0, 12);
+                if (conversation.profile) {
+                    const result = await cryptoOperation(protectRequest('decrypt', { sender: conversation.public, ciphertext: conversation.profile }));
+                    if (result.signer !== conversation.id) throw new Error('Profile signer fingerprint mismatch');
+                    const profile = checkedPayload(result.payload, 'profile', conversation.id, conversation.id);
+                    if (typeof profile.name !== 'string' || profile.name.length > 80) throw new Error('Invalid encrypted profile');
+                    name = profile.name;
+                }
+                element('thread-name').textContent = `Doan <-> ${name}`;
+                await history(0);
+                status('Conversation opened. Choose how many messages to load.');
+            } catch (error) { status(error.message); }
+            finally { if (generation === current) busy = false; }
+        });
+        element('conversations').append(button);
+    }
+}
+
+function counters(conversation) {
+    const sent = session.owner ? conversation.owner_sent : conversation.visitor_sent;
+    const received = session.owner ? conversation.visitor_sent : conversation.owner_sent;
+    element('counts').textContent = `Total: ${conversation.total} | Sent: ${sent} | Received: ${received}`;
+}
+
+async function history(count, cursor = 0) {
+    if (!selected) throw new Error('Choose a conversation first');
+    if (!Number.isSafeInteger(count) || count < 0 || count > 50) throw new Error('Choose 0 to 50 messages');
+    const result = await api({ op: 'history', conversation: selected.id, count, before: cursor });
+    counters(result.conversation);
+    if (!cursor) element('messages').replaceChildren();
+    if (result.messages.length) {
+        status('Decrypting and verifying selected messages locally...');
+        const requests = result.messages.map(message => ({ sender: message.sender === selected.id ? selected.public : config.owner, ciphertext: message.ciphertext }));
+        const decrypted = await cryptoOperation(protectRequest('decrypt_batch', { messages: requests }));
+        for (let index = 0; index < result.messages.length; index += 1) {
+            const message = result.messages[index];
+            const item = document.createElement('li');
+            const label = document.createElement('small');
+            label.textContent = `#${message.seq} / ${message.sender === session.id ? 'YOU' : 'THEM'}`;
+            const text = document.createElement('p');
+            try {
+                const entry = decrypted.messages[index];
+                if (entry.signer !== message.sender) throw new Error('Sender fingerprint mismatch');
+                if (entry.error) throw new Error('Invalid ciphertext or signature');
+                const payload = checkedPayload(entry.payload, 'message', selected.id, message.sender);
+                if (payload.id !== message.id || typeof payload.text !== 'string' || new TextEncoder().encode(payload.text).length > 8192) throw new Error('Message binding mismatch');
+                text.textContent = payload.text;
+            } catch { text.textContent = '[Message rejected: invalid ciphertext, signature, or conversation binding.]'; }
+            item.append(label, text);
+            element('messages').prepend(item);
+        }
+        before = Math.min(...result.messages.map(message => message.seq));
+    }
+    show('older', count > 0 && result.messages.length === count);
+    status(count === 0 ? 'No message history loaded.' : 'Selected history decrypted and verified locally.');
+}
+
+async function submitPending() {
+    if (!pendingSend) throw new Error('No pending message');
+    const result = await api(pendingSend);
+    counters(result.conversation);
+    pendingSend = undefined;
+    element('text').value = '';
+    show('retry', false);
+    status('Encrypted message stored. Load history to read messages.');
+}
+
+async function send() {
+    if (!selected) throw new Error('Choose a conversation first');
+    if (pendingSend) throw new Error('Retry or lock before composing another message');
+    const text = element('text').value;
+    if (!text.trim() || new TextEncoder().encode(text).length > 8192) throw new Error('Enter 1 to 8192 UTF-8 bytes of text');
+    const id = Array.from(crypto.getRandomValues(new Uint8Array(32)), byte => byte.toString(16).padStart(2, '0')).join('');
+    const recipient = session.owner ? selected.public : config.owner;
+    status('Signing and encrypting for both participants locally...');
+    const result = await cryptoOperation(protectRequest('encrypt', { recipient, payload: JSON.stringify({ v: 1, kind: 'message', origin: location.origin, conversation: selected.id, sender: session.id, id, text }) }));
+    pendingSend = { op: 'send', conversation: selected.id, id, ciphertext: result.ciphertext };
+    show('retry');
+    await submitPending();
+}
+
+action('create-choice', async () => { show('entry', false); show('create'); status('Create a purpose-specific protected identity file.'); });
+action('open-choice', async () => { show('entry', false); show('unlock'); status('Select your saved identity file.'); });
+action('create-form', createIdentity);
+action('unlock-form', unlockIdentity);
+action('history-form', () => history(Number(element('history-count').value)));
+action('send-form', send);
+action('retry', submitPending);
+action('refresh-inbox', inbox);
+action('older', () => history(Number(element('history-count').value), before));
+element('lock').addEventListener('click', () => { if (session) api({ op: 'lock' }).catch(() => {}); clearState(); });
+window.addEventListener('pagehide', clearState);
+window.addEventListener('pageshow', event => { if (event.persisted) clearState(); });
+
+async function start() {
+    wasm = fetch('/crypto.wasm', { cache: 'no-store', credentials: 'omit' }).then(response => {
+        if (!response.ok) throw new Error('Build the WASI cryptographic module first');
+        return response.arrayBuffer();
+    });
+    await wasm;
+    config = await api({ op: 'config' });
+    if (config.origin !== location.origin) throw new Error('Server origin mismatch');
+    if (!config.owner) {
+        if (location.hash === '#setup') {
+            show('create');
+            show('setup-label');
+            element('create-title').textContent = 'Create the dedicated owner identity';
+            status('Owner setup. Keep this identity separate from your canonical OpenPGP key.');
+        } else { status('Owner setup is not complete. Please return later.'); }
+    } else { show('entry'); status('Choose CREATE NEW CHAT or OPEN CHAT FILE.'); }
+}
+
+start().catch(error => status(error.message));
+
+// @license-end
diff --git a/crates/chat-server/web/index.html b/crates/chat-server/web/index.html
new file mode 100644
index 0000000..9783789
--- /dev/null
+++ b/crates/chat-server/web/index.html
@@ -0,0 +1,82 @@
+<!--
+Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as
+published by the Free Software Foundation, either version 3 of the
+License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+-->
+<!doctype html>
+<html lang="en">
+<head>
+<meta charset="utf-8">
+<meta name="viewport" content="width=device-width, initial-scale=1">
+<title>Message Me | Doan Luu Duc Tai</title>
+<link rel="stylesheet" href="/style.css">
+<script src="/app.js" defer></script>
+</head>
+<body>
+<main>
+<header><a href="https://doan.luuduct.ai/">~doan</a> / message me <span class="status">EXPERIMENTAL / LOCAL TEST</span></header>
+<h1>[ private chat ]</h1>
+<p>Text only. A dedicated identity file. Encrypted for you and Doan.</p>
+<p class="notice">This is an experimental application, not an audited messenger. <a href="/LIMITATIONS.txt">Read its limitations</a> before use. Keep your file and password safe: there is no account recovery.</p>
+<p id="status" role="status" aria-live="polite">Loading cryptographic module...</p>
+<section id="entry" hidden>
+<button id="create-choice">CREATE NEW CHAT</button>
+<button id="open-choice">OPEN CHAT FILE</button>
+</section>
+<section id="create" hidden>
+<h2 id="create-title">Create a new chat</h2>
+<form id="create-form" autocomplete="off">
+<label>Display name <input id="name" maxlength="80" required autocomplete="off"></label>
+<label>Password <input id="new-password" type="password" minlength="12" maxlength="1024" required autocomplete="off"></label>
+<label>Confirm password <input id="confirm-password" type="password" minlength="12" required autocomplete="off"></label>
+<label id="setup-label" hidden>Owner setup token from the root .env <input id="setup-token" type="password" autocomplete="off"></label>
+<p>Use a strong, unique passphrase. This identity is solely for this chat; do not reuse it elsewhere.</p>
+<button type="submit">GENERATE AND DOWNLOAD IDENTITY FILE</button>
+</form>
+</section>
+<section id="unlock" hidden>
+<h2>Open your saved identity file</h2>
+<p id="reopen-note">Your file is opened locally. The file and password are never uploaded.</p>
+<form id="unlock-form" autocomplete="off">
+<label>Identity file <input id="file" type="file" required></label>
+<label>Password <input id="password" type="password" required autocomplete="off"></label>
+<button type="submit">UNLOCK CHAT</button>
+</form>
+</section>
+<section id="chat" hidden>
+<div class="chat-heading"><h2 id="who"></h2><button id="lock">LOCK / FORGET</button></div>
+<p id="fingerprint"></p>
+<section id="inbox" hidden><h3>Conversations</h3><button id="refresh-inbox">REFRESH INBOX</button><div id="conversations"></div></section>
+<section id="thread" hidden>
+<h3 id="thread-name"></h3>
+<p id="conversation-fingerprint"></p>
+<p id="counts"></p>
+<form id="history-form"><label>Latest messages to load (0–50) <input id="history-count" type="number" min="0" max="50" step="1" value="0" required></label><button type="submit">LOAD HISTORY</button></form>
+<button id="older" hidden>LOAD OLDER</button>
+<ol id="messages" aria-label="Messages"></ol>
+<form id="send-form" autocomplete="off"><label>Plain text message (up to 8192 UTF-8 bytes) <textarea id="text" rows="5" required maxlength="8192" autocomplete="off"></textarea></label><button type="submit">ENCRYPT AND SEND</button></form>
+<button id="retry" hidden>RETRY THE SAME ENCRYPTED MESSAGE</button>
+</section>
+</section>
+<noscript>This chat requires free JavaScript and WebAssembly for local cryptography. The main website remains JavaScript-free.</noscript>
+<footer>
+<p><a class="badge" href="https://www.gnu.org/software/librejs/" aria-describedby="js-warning">GNU LibreJS-compliant</a><span id="js-warning" role="tooltip">LibreJS compliance concerns software freedom, not a guarantee of privacy or security. Review the source code, dependencies, and scripts delivered to your browser. Server-delivered code can change between visits; free software can still track users or behave maliciously.</span></p>
+<a href="https://www.gnu.org/licenses/agpl-3.0.html">LICENSE</a>
+<a href="/THIRD-PARTY-LICENSES.html">THIRD PARTY LICENSES</a>
+<a href="/SOURCE.tar.gz">CORRESPONDING SOURCE CODE</a>
+<a href="/javascript.html" rel="jslicense">JAVASCRIPT LICENSES / RAW SOURCE</a>
+</footer>
+</main>
+</body>
+</html>
diff --git a/crates/chat-server/web/javascript.html b/crates/chat-server/web/javascript.html
new file mode 100644
index 0000000..927a678
--- /dev/null
+++ b/crates/chat-server/web/javascript.html
@@ -0,0 +1,28 @@
+<!--
+Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as
+published by the Free Software Foundation, either version 3 of the
+License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+-->
+<!doctype html>
+<html lang="en"><head><meta charset="utf-8"><title>JavaScript licenses</title><link rel="stylesheet" href="/style.css"></head><body><main>
+<h1>JavaScript licenses and source</h1>
+<p>All first-party scripts are available under the GNU Affero General Public License, version 3 or, at your option, any later version. The table uses the license identifiers recognized by GNU LibreJS.</p>
+<table id="jslicense-labels1"><thead><tr><th>Script / raw file</th><th>License</th><th>Corresponding source</th></tr></thead><tbody>
+<tr><td><a href="/app.js">app.js</a></td><td><a href="https://www.gnu.org/licenses/agpl-3.0.html">GNU-AGPL-3.0</a></td><td><a href="/SOURCE.tar.gz">Complete corresponding source</a></td></tr>
+<tr><td><a href="/worker.js">worker.js</a></td><td><a href="https://www.gnu.org/licenses/agpl-3.0.html">GNU-AGPL-3.0</a></td><td><a href="/SOURCE.tar.gz">Complete corresponding source</a></td></tr>
+<tr><td><a href="/wasi.mjs">wasi.mjs</a></td><td><a href="https://www.gnu.org/licenses/agpl-3.0.html">GNU-AGPL-3.0</a></td><td><a href="/SOURCE.tar.gz">Complete corresponding source</a></td></tr>
+</tbody></table>
+<p>The WebAssembly module is compiled from the Rust workspace and unmodified OpenSSL 3.6.5, under their respective free software licenses. The source archive includes first-party sources, Cargo dependencies, the OpenSSL source archive, build scripts, and notices. General-purpose Rust and WASI SDK tools are documented with verified download locations in CHAT-OPENSSL-MIGRATION.txt.</p>
+<p><a href="/THIRD-PARTY-LICENSES.html">Third-party licenses</a> / <a href="/SOURCE.tar.gz">Source archive</a> / <a href="/">Return</a></p>
+</main></body></html>
diff --git a/crates/chat-server/web/style.css b/crates/chat-server/web/style.css
new file mode 100644
index 0000000..0983b2e
--- /dev/null
+++ b/crates/chat-server/web/style.css
@@ -0,0 +1,49 @@
+/*
+Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as
+published by the Free Software Foundation, either version 3 of the
+License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+* { box-sizing: border-box; }
+:root { color-scheme: dark; font-family: "Courier New", monospace; background: #131715; color: #d4d8cd; line-height: 1.6; }
+body { margin: 0; }
+main { max-width: 58rem; margin: 2rem auto; padding: 0 1.25rem; }
+header, footer { border-top: 1px solid #667367; padding-top: 1rem; }
+header { display: flex; flex-wrap: wrap; gap: .6rem; }
+h1 { font-size: 1.8rem; color: #e3e3ce; }
+h2, h3 { font-size: 1.05rem; }
+a { color: #aec2a5; text-underline-offset: .2rem; }
+.status, .badge { color: #e0c46d; }
+.status { margin-left: auto; }
+.notice { border-left: 2px solid #c5ad68; padding-left: 1rem; }
+button, input, textarea { font: inherit; color: inherit; background: #1c231e; border: 1px solid #667367; border-radius: 0; padding: .55rem .7rem; }
+button { cursor: pointer; margin: .4rem .6rem .4rem 0; }
+button:hover, button:focus-visible { border-color: #d7c884; color: #f0e5b0; }
+button:disabled { opacity: .5; cursor: wait; }
+input, textarea { display: block; width: 100%; margin: .35rem 0 1rem; }
+input[type=number] { width: 8rem; }
+label { display: block; }
+section { margin: 1.5rem 0; }
+[hidden] { display: none !important; }
+.chat-heading { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: center; }
+#fingerprint, #conversation-fingerprint { overflow-wrap: anywhere; font-size: .8rem; }
+#messages { padding: 0; list-style: none; }
+#messages li { border-top: 1px dashed #48564a; padding: 1rem 0; }
+#messages p { white-space: pre-wrap; overflow-wrap: anywhere; margin: .4rem 0; }
+#messages small { color: #a8b39e; }
+#status { min-height: 1.6rem; color: #e0c46d; }
+footer { margin-top: 3rem; padding-bottom: 2rem; }
+footer > a { display: block; width: fit-content; }
+footer p { position: relative; }
+#js-warning { display: none; max-width: 48rem; border: 1px solid #c5ad68; background: #1c231e; padding: 1rem; margin: .8rem 0; }
+.badge:hover + #js-warning, .badge:focus-visible + #js-warning { display: block; }
diff --git a/crates/chat-server/web/worker.js b/crates/chat-server/web/worker.js
new file mode 100644
index 0000000..64e0795
--- /dev/null
+++ b/crates/chat-server/web/worker.js
@@ -0,0 +1,31 @@
+// Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+// @license magnet:?xt=urn:btih:0b31508aeb0634b347b8270c7bee4d411b5d4109&dn=agpl-3.0.txt AGPL-3.0
+
+importScripts('/wasi.mjs');
+
+self.onmessage = async event => {
+    try {
+        const result = await self.stackChatWasi.runCommand(event.data.bytes, event.data.request);
+        self.postMessage({ result });
+    } catch {
+        self.postMessage({ error: 'Cryptographic operation failed. Check your file, password, origin, and sender.' });
+    } finally {
+        self.close();
+    }
+};
+
+// @license-end