THE VAULT
Drop your save folder in once. The Vault parses every .run
file and hands you back winrate, current streak, PB floor, per-character
splits, every fight filterable. Sign in with Steam and the same app
shows you who else is around right now looking for a co-op run. Free,
no signup, your saves stay on your machine. The actual game invite
still goes through Steam — we just help you find each other.
Checking who's around… · Open source on GitHub
Mega Crit's call to gate multiplayer through Steam friends is correct. It stops random griefers and keeps the experience tight. But it creates a chicken-and-egg problem: before you can play with someone, you need to already know them. If you didn't bring an STS2-loving friend to launch night, your only option today is the global Discord, and good luck filtering that for "someone pushing A10 who's online right now."
Spire Vault sits between "I want to play co-op" and "I have a Steam friend to play with." It doesn't host games, route invites, or replace anything Mega Crit built. It just shows you who's around, what tier they're at, and how to reach out. Steam takes it from there — same Steam invite, same in-game experience.
The whole thing is open source. The desktop apps only read files already on your computer. Co-op uses Steam OpenID, so your password never touches the server. Every line of code is on GitHub, and the full threat model is in SECURITY.md. Audit anything before you install.
Points at your STS2 save folder, parses every .run file in it, builds a private history out of the lot. Winrate, max ascension, character splits, every relic you've touched. No upload, no signup, nothing leaves your computer. Re-scans silently in the background every 30 seconds.
One-click PNG of any run with the actual relic icons and card art baked in — not just text. Drop straight into Discord, Reddit, or X. Markdown export ships in the same modal.
Classic Co-op is the live roster — sign in with Steam, see who's around, fire a canned invite. Lobby Beta is the new path: post the run you actually want to play (character + ascension target), browse Open Run Lobbies, check Best Matches, accept or decline. Both feeds run side by side, both end in a Steam invite, both are free.
Six-card KPI strip (current streak, last-10 form, PB floor, fastest win, this week, best streak), winrate-over-time chart, floor-death histogram. Filter chips on Recent Runs by character, outcome, ascension. Export to CSV anytime.
Run tracking works fully offline. Co-op uses Steam OpenID, no password ever leaves Valve. The public landing-page presence count is anonymized server-side — only signed-in users see the full roster. Cloud sync is keyed to your Steam ID and survives a clean install on any device.
MIT licensed. macOS app, Windows app, web companion, the matchmaking Worker — all in one repo on GitHub. Read it, fork it, host your own. No hidden binary, no proprietary service.
A small floating window that sits over Slay the Spire 2, glances at your screen when you ask, and tells you the best card to take, relic to swap, or path to push. Streamer-safe by default (invisible to OBS, Discord, Game Bar). Bring your own OpenAI or Anthropic key; nothing goes through our servers. See it in detail →
Run Coach is a small always-on-top panel that lives over Slay the Spire 2 — same idea as Cluely for code interviews, but pointed at deck-building decisions. Tap a chip, ask a question. It reads your live save (character, HP, gold, deck, relics, floor) and grabs the current frame of your screen, then tells you exactly which card to pick, which boss relic to grab, or whether to go left or right at the fork. Bring your own OpenAI or Anthropic key. Nothing routes through our servers.
Defect A6 · F12 · 57/75 · 145g), and a
420×540 chat card that unfolds when you ask for help.
Drag either to position once; it survives relaunches.
NSWindow.sharingType=.none, so
it's invisible to OBS, Discord, and QuickTime captures.
Toggle the switch under Beta → Run Coach
if you actually want it on stream.
.run JSON files that the run tracker reads.
It does not modify the game, inject DLLs, or touch process
memory. Mega Crit-friendly by construction.
Launch a Slay the Spire 2 run, then tap a chip below — Coach will read your save and give you specific advice.
Real captures from the web companion at app.spirevault.app. Every screenshot below is the actual app on sample data — including the Share-Run card, which renders real relic icons and card art straight into the canvas.
STS2 multiplayer is friend-gated through Steam — no third-party tool can route those invites, and we don't try. The Vault solves the actual problem: finding someone at your level who's around right now.
Pick your platform. Mac and Windows get native apps with run tracking, Run Coach, and Share-Run cards. The web companion covers Linux, Chromebooks, and anywhere else with a browser. All three share the same co-op feed and the same stats — sign in once, your runs sync across every device.
Run tracker · co-op feed · Share-Run cards
Run tracker · co-op feed · Run Coach
%APPDATA%\SlayTheSpire2Linux, Chromebook, anywhere with a browser
.run
Power user? Build from source
with git clone + make run (macOS) or cargo tauri build (Windows).
Sign-in is Steam OpenID — the same flow Steam uses for every other site. Your password never reaches our server. We store the minimum required for matchmaking, and the entire codebase is on GitHub.
No. Spire Vault is an unofficial, fan-made companion. Mega Crit owns Slay the Spire. We don't host games, route invites, or replace anything they built — we just help players find each other before Steam takes over.
Run Coach is an opt-in floating panel that sits on top of Slay the Spire 2 — a 260×40 pill that collapses to a 420×540 chat card. Ask it something and it grabs the current frame of your screen, sends the question + the screenshot to your chosen AI (OpenAI or Anthropic) using your own API key, and shows you what the model says back. That's it.
It's marked Beta on purpose and ships on both macOS and Windows.
What it doesn't do: modify the game, read game
memory, hook the process, talk to a Vault-hosted AI, or spend
money on your behalf. Nothing about Run Coach changes how runs
are tracked. The overlay is streamer-safe by default (hidden
from screen recordings via
NSWindow.sharingType=.none) — toggle it
under Beta → Run Coach if you do want
it on stream.
Classic Co-op is the live roster you've probably seen: sign in with Steam, see who's around, fire a canned invite. The Lobby Beta is the alternate path. You post the run you actually want to play — character, ascension target, vibe — and the page shows a board of Open Run Lobbies, a Best Matches rail picked by the server, and a request-to-join flow with accept / decline.
Classic stays the default. Flip the Lobby Beta on under the Beta tab (or the in-tab toggle on the Co-op page), flip it off whenever. Same Steam sign-in, same live presence underneath, same Steam invite to start the actual game.
No, it's not a mod. Spire Vault doesn't modify
Slay the Spire 2, doesn't inject into the game process, doesn't load
DLLs or use ModTheSpire, and doesn't touch game memory. It only reads
the .run JSON files Slay the Spire 2 itself writes to your
save folder after each run — the same files you could open in any
text editor.
Run-history readers like this have existed for the original Slay the Spire for years (Sky Diving, Mintotaur, etc.) and are universally accepted by Mega Crit and the community. The macOS app has read-only access to one folder. The web companion never touches your filesystem at all.
Yes — same backend (Cloudflare Worker), same UI (app.spirevault.app
embedded in a WebView2), same Run Coach overlay, same bring-your-own-key flow, same
co-op feed. The native layer is rewritten in Rust (Tauri 2) instead of Swift, but
everything the player sees and every API call it makes is identical. Auto-updates
ship through GitHub Releases on the same tag cadence as the macOS DMG.
The one current difference: the Windows build is ad-hoc signed, so SmartScreen will show "More info → Run anyway" on first launch — same energy as the macOS "right-click → Open" step. Once the installer builds reputation (~50 installs), SmartScreen clears automatically.
For the run tracker, no — it works fully offline. For co-op you sign in via Steam OpenID, which is Valve-hosted and never sees your password. Sign out any time and your session disappears.
$0 to use. No tier, no premium, no donation gate, no "supporter" perks dangled in front of free features. I cover hosting (Cloudflare costs me a few dollars a month) and the $14/year domain — that's the entire bill. It's MIT licensed, so even if I disappear, anyone can fork the repo and keep it running for themselves and their friends.
Yes, and the entire stack is designed for it. The marketing
site is a static page (any host works), the web companion is also
static, and the matchmaking server is a single Cloudflare Worker
with a KV namespace. The
repo
includes a Makefile that deploys all three with
wrangler; bring your own Steam Web API key and
you're done. There's no hidden binary, no proprietary service,
nothing that only works on my domain.
You sign in with Steam, set your status (Looking · Playing · Idle), optionally add a Discord handle. Your client heartbeats your presence every minute. The feed shows everyone heartbeating in the last few minutes, with a button to open their Steam profile or copy their Discord. The actual game session goes through Steam friends like normal.
If you opt into the Co-op Lobby Beta, the same presence layer is what decides whether your posted lobby shows up in someone else's Open Run Lobbies board. Drop offline, the lobby drops off the board.
No. Every write to the server requires a signed Steam OpenID verification — the server checks the signature with Valve directly. Your session token can only be issued after that verification. Threat model details in SECURITY.md.
You don't have to. Sign-in is Steam OpenID, which means your password is typed into Steam's login page, not mine — the server only ever sees the verified Steam ID Valve hands back. The whole stack is on GitHub; every outbound network call from the app is documented in SECURITY.md. The desktop apps make zero network calls except to the matchmaking server, and only when you're signed in. Read the code, build it yourself, file an issue if something looks wrong.
STS run tracker for iPhone and iPad. The Vault parsing library feeds its stats tab. On the App Store now.