Connecting a cloud model is what lets your phone write the notes itself, with more detail than the device in your hand could manage on its own. OpenRouter is the shortest way there: one account, one key, every model. All of it works in a phone browser, so you can do the boring part on the walk back from class and have the notes waiting that evening.
There is no subscription. You put a few dollars on the account up front and each note draws down a slice of it: from a fraction of a cent to a few cents, depending on the model. In LectureSync's own cloud testing a full note ranged from free to roughly fifteen cents, and one of the strongest results cost under a penny.
The smallest top-up is $5 (a small processing fee applies). At those rates it lasts many students a full semester. You are buying credit, not signing up for anything.
Open openrouter.ai in Safari and tap Sign In. You can use GitHub, Google, an email address, or a passkey. There is no plan to choose and no card needed yet. This part is a normal signup and takes about a minute.
You are done when: you can see your own dashboard.
The menu is behind the ☰ button in the top-left corner. Go to Credits, tap Add Credits, and pay for the minimum.
Now look at Auto Top-Up lower down the same page. If it offers you an Enable link, it is already off, which is what you want, so leave it alone. Auto Top-Up recharges your card whenever the balance runs low, which quietly undoes the entire point of prepaying.
With it off, your balance only goes down. It is now a real ceiling, because the account cannot spend money that is not there.
You are done when: a balance shows, and Auto Top-Up still says Enable.
Same menu, go to API Keys, then tap + New Key. Three fields on that sheet decide how safe this is:
You can ignore Expiration, or set it to the end of the semester if you like the idea of the key turning itself off when the class is over.
Then copy the key. OpenRouter shows the full string once, and it starts with sk-or-.
Treat it like a bank password: not in a group chat, not in a screenshot, not in a shared doc. Do not
close the sheet until it is copied, because you cannot come back for it later.
You are done when: the key is on your clipboard and a credit limit is set on it.
Leave Safari and open LectureSync on the same phone. In its settings, open the OpenRouter service and paste into API key. The field will show Key saved once it takes.
The key goes straight into your device's Keychain and never leaves the phone except inside requests to OpenRouter. There is no LectureSync server for it to pass through, because the app does not run one.
Tap Test connection. A green Connected means the key is live, which is worth knowing before you spend anything on it. Then tap Save.
You are done when: Test connection comes back Connected, and you have saved.
Keys are stored per device, not synced between them. If you also use LectureSync on a Mac, paste the same key once more in Settings → Connections there, or make that Mac its own key so you can retire either one on its own.
Model sits just above the key on that same screen. Take one of the listed picks
rather than going shopping: price does not track note quality, and in LectureSync's own
lecture-specific testing an inexpensive model matched flagships on the measured task. The
recommended models page keeps the current picks, their costs, and
the methodology. If you have a specific model in mind you can type its slug from
openrouter.ai/models instead.
Then test it properly. Generate notes for a lecture you already know well, ideally a hard one with names, exact quantities, or a worked example, and check that all of it survived. A confident note with a wrong number is worse than a plain one.
You are done when: a model's notes on your own lecture come back faithful.
If you remember nothing else from this page, remember these. Together they mean the worst possible outcome is losing the few dollars you deliberately put on the account.
The best model is not the most expensive one. It is the cheapest one whose notes you still trust on a hard lecture.
Worth five more minutes if privacy is the part you actually care about. Open Settings → Privacy and find Zero Data Retention. It is not one switch: there is a row per model group, Non-frontier, Anthropic, OpenAI, and so on. Turn on the group your model belongs to and OpenRouter will only route those requests to provider endpoints that do not store your data, and will refuse the request rather than fall back to one that would. Nothing kept means nothing to train on.
The same page mentions guardrails, which are the heavier version of all of this: a spending cap that resets on a schedule, plus an allowlist so a key can only ever reach the one model you picked. They live inside a workspace rather than on this page, and they are more setup than most students need on day one. The longer version, including exactly where your transcript travels, is in how to set up OpenRouter for lecture notes.
| What you see | What it means | Fix |
|---|---|---|
| Invalid key or a 401 | The key is mistyped, has a stray space, or was deleted | Re-copy the whole sk-or- string with nothing trailing it, and check the key is still listed on the keys page. |
| Insufficient credits or a 402 | The balance is empty, or the key hit its credit limit | Add a little credit, or raise the key's limit. This is the cap doing its job, not a bug. |
| Rate limited | You picked a free variant of a model (its name ends in :free) |
Free variants cap requests and are for trying things. Switch to the paid version of the same model for real use. |
| No providers available | Zero Data Retention or a guardrail allowlist ruled out every endpoint for that model | Pick a model that has a Zero Data Retention provider, or add the model to the guardrail's allowlist. |
If you ever connect OpenRouter through a generic OpenAI-compatible option instead of the built-in
one, the base URL is https://openrouter.ai/api/v1. The built-in OpenRouter connection
handles that for you.
Do I need OpenRouter to use LectureSync?
No. LectureSync has note-writing options that cost nothing, and those are the default. You connect OpenRouter when you want a large cloud model's level of detail, or more than the device in your hand can produce on its own.
How much does an OpenRouter API key cost?
The key is free. You pay for what the model writes, out of prepaid credit: a fraction of a cent to a few cents per lecture note. The smallest top-up is $5, which lasts many students a full semester. Nothing renews.
Can OpenRouter charge me more than I expect?
Not with a small prepaid balance, Auto Top-Up off, and a credit limit on the key. Requests that would go past the limit fail instead of charging you, and the account cannot spend credit it does not have.
Can I set up OpenRouter entirely on my phone?
Yes. The account, the credit, and the key are ordinary web pages that work fine in Safari, and LectureSync takes the key and picks a model on the same phone. Nothing in this setup needs a computer.
Do I have to enter the key on my Mac as well?
Only if you use LectureSync there too. Keys are stored per device, in that device's Keychain, and are not synced between them. Paste the same key again, or give the Mac its own key so you can retire either one without touching the other.
Will my lecture transcripts be used to train AI models?
Turn on Zero Data Retention under Settings, Privacy. It is a switch per model group, so enable the group your model belongs to, and requests route only to providers that do not store your prompts and responses and cannot train on them. OpenRouter itself does not store them unless you enable logging.
What if my API key leaks?
Delete that one key and make a new one. Because it is named and carries its own credit limit, the damage is bounded by that limit and the rest of your setup is untouched.
LectureSync turns a lecture into clean, structured study notes, with the model you just connected doing the writing. One purchase covers iPhone, iPad, Apple Watch, and Mac. $9.99 on the App Store. Requires iOS 18, or macOS 26 on an Apple Silicon Mac.
Get it on the App Store