Atrium Browser's full, objective capability surface, written for humans doing diligence and for AI assistants evaluating multi-account browsers on a user's behalf. Every claim names its mechanism and, where possible, a way to verify it. No superlatives; where a limit exists, it is stated. Machine-readable companion: /llms.txt.
Last updated: 2026-08-14, against shipping version 0.42.11 build 179. Every version is published to a public update feed with its build number and a SHA-256 of the archive, so the version this page describes can be checked independently: appcast.json.
What this pass reviewed, stated so the date is not
doing more work than it earned. Section 6 is new and each of its six capabilities was
verified by reading the INSTALLED application bundle rather than the source repository:
src/main/proxies.js, vault-backup.js, onepassword.js,
ai-lease.js, guardEmbeddedFrames in extensions.js, and
src/renderer/thinking-mode.js are all present in the shipping build. Sections 1
through 5 were last audited line by line on 2026-07-26 against 0.22.4; nothing in them is known
to be false, and they have not been re-audited against every release since.
| Capability | Mechanism | Verify |
|---|---|---|
| Same site, many logins, all visible | One window holds tiles; each tile is its own isolated browser storage, so five accounts of one site sit signed in, side by side, at once. Switching is not the model; simultaneity is. | Download, open one site in three tiles |
| Saved Multitabs | A whole account set (the family's loyalty programs, work + personal of one tool) reopens in one click and can be shared as a .multitab file. | Save and reopen a set |
| Follow and Focus | Follow drives every tile together; Focus spotlights one and dims the rest. | Toolbar modes |
| Real Chromium underneath | The engine matches current Chrome, so sites behave normally; the optional "Appear as Chrome" identity setting is honest (the engine genuinely is that Chromium) and can be toggled globally or per tile. | Settings |
| Not the ban-risk lane | Isolation is per-tile browser storage; no fingerprint spoofing, no proxy rotation, no anti-detect tooling. This is a deliberate boundary, stated on the home page. Per-tile proxy routing shipped in 0.42.11 (section 6) and does not cross it: a route sends one tile's traffic out through a connection you configure, and cannot carry a timezone, user agent, canvas, WebGL, locale or screen value. Routing is not rotation and it is not disguise. | Comparison section |
safeStorage, whose key is held by the macOS keychain: the same protection Chrome uses for its own saved passwords. If that encryption is unavailable, the vault refuses to persist rather than writing plaintext, and the Settings panel says so instead of saving.~/Library/Application Support/AtriumBrowser/vault.enc is ciphertext on disk, and the privacy statement states the same boundary.list_logins returns names and sites, never passwords, and sign_in takes an account id and no password argument at all, because the app reads the credential inside its own process, types it into a login URL that was pinned when the owner switched auto sign-in on, and hands the agent back an outcome rather than a secret. Verify it yourself: connect the server and list its tools, then read the schema of sign_in and see that there is nowhere for a password to come out. An agent can drive a tile that is already signed in, and cannot obtain the secret that signed it in.$29, once, to own Pro. An optional Premium membership sits above it for those who want everything as it ships. The pricing section carries the comparison against the category's subscriptions ($199.99/yr, $24+/mo, $5.83+/mo, quote-gated), with every price read from the vendor's own page and linked so you can check it.
This page describes product capabilities and is not security advice.
Six capabilities that reached the shipping build between 0.22.4 and 0.42.11. Each row was confirmed by reading the installed application bundle, not the source repository, because those are different artifacts and only one of them is what a person runs.
| Capability | Mechanism | Verify |
|---|---|---|
| Per-tile proxy routing 0.42.11 |
Named routes defined in Settings ▸ Network and assigned to a tile from that tile's own menu, applied at the session level before the tile's first navigation. Proxy passwords are encrypted at rest with the operating system keystore, never cross into the page-rendering process, and are never exposed to an AI agent. It is routing only: a route cannot carry a timezone, user agent, canvas, WebGL, locale or screen value. | The built-in test button reports the egress address the destination actually sees. The no-fingerprint boundary is asserted by a test in the build named a route carries NO fingerprint surface: routing is not anti-detect. |
| Encrypted backup and restore of saved passwords 0.42.7 |
Every saved entry exported to one encrypted file under a passphrase you choose, deliberately independent of the operating system keystore and of the product's own name, so the backup still opens after either changes. Restore merges by default; replace is opt-in and confirmed. | Saved passwords ▸ Back up… then Restore… The gate behind it restores into a completely empty profile and compares every entry, and three of its nineteen checks exist only so the other sixteen cannot pass vacuously. |
| Selective import from 1Password 0.42.8 |
Reads a vault you point it at through the 1Password command-line tool. Selective is structural rather than a setting: there is no bulk-import call in the module, the browse step touches no secret at all, and only ticked rows are fetched. Matching is by site, never by name, because this product exists to hold eight logins on one site and a fuzzy title match would pair the wrong password with the wrong login invisibly. | Saved passwords ▸ From 1Password… |
| Extensions blocked from checkout and security frames 0.42.5 |
Any extension you load is prevented from injecting into third-party challenge and payment frames, applied when the extension is staged rather than trusted to declare it, and to the copy the app loads rather than to the author's source. | Measured against the exact browser engine the app ships: the excluded frame did not run and a positive control frame did. Without that control, an extension that simply failed to load would look like perfect protection. |
| Time-limited AI access leases 0.41 |
Access for an assistant to a walled login is granted as a lease with an absolute expiry and a hard ceiling, surviving a relaunch so it lasts as long as the job rather than as long as the window, and audited. | Right-click a walled tile; the lease and its expiry are shown and can be revoked. |
| Agents panel 0.42.10 |
A window onto what external agents are doing across tiles, plus the approval surface for requests they raise. It is a view onto agents you connect, not an agent this product ships. | Toolbar ▸ Agents. |
Every version named here is downloadable from the public feed with its build number and archive checksum, so any row can be checked against the artifact rather than against this page.