Connect Plaid

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Choose your path

1

Create your Plaid developer account

Trial counts 10 banks for the lifetime of the team. A bank you remove does not give the slot back. Plaid states it: “Removing Items created on a Trial plan (using /item/remove) will not allow you to create more Items.”A bank you already linked at my.plaid.com does not carry over to Postern. Postern reads only the banks you link through its own Plaid Link session. Linking such a bank again here spends another Trial slot.

Open dashboard.plaid.com and create an account.Plaid’s Trial plan covers US and Canada teams created on or after 2026-04-15. An older team uses paid Production access instead. Which plan you hold decides what this page costs you.

2

Copy your client ID and Production secret

The Console tells you where to go. Open Sources, press Add a source, then press Plaid.The card’s left column is headed Register your app, which the screen prints in capitals. It carries 3 numbered lines:

1. Sign in at dashboard.plaid.com → Team Settings → Keys.
2. Copy your client_id and the Production secret.
3. Request Production access if you haven’t — Plaid approves it.

The card’s first line is out of date. Plaid’s dashboard has no Team Settings item. Follow this page instead, and expect the card to be corrected.

In Plaid’s dashboard, the left rail groups its items. Under PLATFORM, open Developers and select Keys. The address is dashboard.plaid.com/developers/keys, which you can also open directly.The page is headed Keys and carries 3 cards, one under the next:

card	what it holds
Client ID	Readable on the page. One copy control beside it.
Production secret	Hidden behind dots. A control reveals it, a second copies it, and Rotate replaces it.
Sandbox secret	The same 3 controls, over a different value.

Copy the Client ID. Then copy the Production secret — the second card, not the third.Both secrets sit on this one page, a card apart, and they look identical once revealed. This is the step where the wrong one gets copied. A Sandbox secret is not refused loudly: Postern saves it, Plaid’s production host rejects the call, and no bank ever links.The Client ID is the same string in every Plaid environment. Each environment has its own secret. Postern saves what you paste here as a Production app, and the card’s own note says so: Console defaults to Production.

3

Save your app and open Plaid Link

Postern encrypts the secret and stores it on your own machine as you save. The Console never shows it again: the field afterwards reads already sealed — leave blank to keep. Plaid’s dashboard is the only other place you can read it.

The card’s right-hand panel is headed Configure the app, again in capitals on screen. It carries Client ID, Secret, and the button that opens Plaid Link.Paste the client_id into Client ID. Paste the Production secret into Secret. Press Save & add a bank.That button reads Save & add a bank until you save an app. After you save one it reads Add a bank, and Secret reads already sealed — leave blank to keep. Leave Secret blank to keep the stored secret.Postern opens Plaid Link in a new browser tab. The Console panel switches to Link your banks and reads waiting for the first bank.

If no new tab opened, a pop-up blocker stopped it. Press Re-open Plaid Link on the panel behind it. It opens the same address.That address works for 3 hours. After that, press Add a bank again.

4

Get past Plaid's phone screen and pick your bank

The new tab carries the title Connect with Plaid. Its first screen reads Postern uses Plaid to connect your account. Every Postern user sees that heading, because Postern sends the name.Plaid asks for a phone number first. You do not need one.Press Continue without phone number. It sits directly under the Continue button.

Type a number instead and Plaid may refuse it, even a working mobile. The screen then reads Invalid phone number over We couldn't verify that … is a valid number. Press Try again, then press Continue without phone number.

Plaid then shows Select your institution: a search field placeholdered Search, over a grid of bank tiles. Press your bank’s tile. The recorded run pressed CHASE.Postern sends the United States as the only country, so the grid offers US banks.Plaid may also show a banner that names your app and says it is testing something new. Plaid builds that line from the name Postern sends. It appears for an app without full Production access, and nothing in the Console turns it off.A bank can also need time at Plaid before it works with a new app. Minutes to hours is usual. Charles Schwab has taken up to about 6 weeks.

5

Sign in at your bank and choose the accounts

Plaid hands you to your bank. The handoff screen carries your bank’s name. In the recorded run it read Log into Chase, over After logging into Chase, make sure you check all these boxes:.

That screen shows one ticked box: Share all accounts to see all your financial info with Postern. Plaid’s own instruction is to check all the boxes it shows you. Do that at your bank before you finish.

Press Continue to login ⧉. Your bank’s own sign-in page opens.Sign in there with your bank’s own credentials. You never paste a bank password into Postern. Only a token for that one bank comes back. Nothing outside your home has to reach your machine for this to work.Your bank then asks which accounts to share. Tick every account you want an agent to read, and approve. Your bank names its own screens and its own controls, so this page names none of them.Whatever your bank offers to share, finance stays read-only. No agent can move money.Plaid takes you back and ends on a success page. The captures of that run hold 2 wordings for it:

• Success over Your account has been successfully linked to Postern
• Success! over Your information has been successfully shared. It's safe to close the browser now.

Plaid may then offer to save the bank to your own Plaid profile. That screen carries your bank’s name — Save Chase with Plaid in the recorded run — over Connect faster to 8,000+ Plaid-powered apps. Press Finish without saving to skip it. That offer is Plaid’s, not Postern’s.Close the Plaid tab and go back to the Console tab.

6

Watch the bank land in the Console

Leave the Link your banks panel open. It checks every few seconds, and reads waiting for the first bank until something lands.When you finish at Plaid, the bank appears on that panel with the status ok. The button changes from Continue in Sources to Done — go to Sources. Press it.Sources now carries a Plaid group. Its row reads byo app · finance and feeds 1 bank · every 6h, all of them, with Add a bank and Edit app beside it. Your bank sits beneath it as its own row.

A bank that has not synced yet reads 0 accounts under Coverage, and never under Last heard. The Finance sector reads Awaiting first sync. That is normal. Press Sync now, or wait.Postern checks every Plaid bank at the same rate: every 6 hours, and never faster than 15 minutes.A bank’s own page shows that rate under Poll cadence, read-only. Beside it sit — set once, for all Plaid banks and a link Change it on the Plaid group →. That link lands on Sources, which carries no cadence control for Plaid. You cannot change the rate from the Console today.

One trip through Plaid Link links one bank. The panel says bank(s) because that is Plaid’s wording. A multi-bank trip needs a Plaid user token Postern cannot get.For the next bank, open Sources, find the Plaid group header, and press Add a bank. Client ID is already filled and the secret stays stored, so leave Secret blank.

Close Plaid’s tab before you finish and nothing links. The panel still reads waiting for the first bank, its button changes to Done — go to Sources, and no bank row appears. You linked nothing and spent no slot. Press Add a bank and start again.

7

Reconnect a bank when its consent lapses

Bank consent expires about once a year, per bank. Capital One, Fidelity and Bank of America all enforce it. A lapsed bank returns empty pages, which reads like a quiet week. Postern checks each bank’s standing and shows it instead.In Sources, a lapsed bank’s Cadence cell reads consent lapsed. Its last cell reads Reconnect → rather than Manage →. Press Reconnect →.On the connection page, press Reconnect at Plaid. Postern opens Plaid’s re-approval page in a new tab and says Opened Plaid's re-approval page in a new tab. Sign in at your bank there and approve.

That re-approval address works for about 30 minutes, not 3 hours. This screen carries no re-open button. If a pop-up blocker eats the tab, press Reconnect at Plaid again.

The re-approval runs against the same Item. No re-paste, no fresh trip through Plaid Link. The Item keeps its identity, carries on from where it stopped, and fills in what it missed. The row clears at the next check, up to 6 hours away. Sync now, on the same page, checks at once.

Re-approval cannot fix these 2 cases.Plaid no longer holds that bank’s Item. Link the bank again: open Sources, then press Add a bank on the Plaid group. On a Trial team that costs a slot.Or your Plaid team hit its bank cap, or spent its credits. No re-link can work. Free a slot or change your Plaid plan first.A connection you disconnected has no credential left on your machine, and the Console says so rather than offer a reconnect that cannot work.

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Sandbox is for testing only

curl -s -X POST http://localhost:8787/api/plaid/app \
  -H 'content-type: application/json' \
  -d '{"clientId":"YOUR_PLAID_CLIENT_ID","clientSecret":"YOUR_PLAID_SANDBOX_SECRET","env":"sandbox"}'

• The grey bar names the only number Plaid accepts here: You are currently in Sandbox mode. Sandbox » phone number: 415-555-0011. You still do not need one — Continue without phone number works.
• Press any bank tile. Sandbox sends you to its own test bank, First Platypus Bank, whichever tile you pressed. Below that bank’s sign-in form sits a strip with an Error Selector and a Submit Error control, for forcing failures on purpose.
• The test bank takes any sign-in. The recorded run typed a username of its own. Plaid’s published test login is user_good / pass_good, and its published MFA code is 1234. Its account picker lists several invented accounts, Plaid Checking ··· ··· 0000 among them. None is a real account.

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Confirm it works

• Sources carries a Plaid group with one row per linked bank. The group’s own line says how many banks feed it.
• Each bank’s Cadence cell reads a time, not consent lapsed.
• Open Settings and find Provider apps: Plaid reads configured.
• After the first sync, a bank’s Coverage reads more than 0 accounts, and its Last heard reads a time rather than never.
• A bank that also arrives through SimpleFIN carries also arrives via SimpleFIN — served as one. Postern merges 2 rows on its own only when both providers publish the last 4 digits. Otherwise it asks Is this the same account, seen twice? on its own screen. Answer They’re the same account or Keep them separate, and it stays answered.
• Ask an agent with a finance grant: which finance sources can you see, and how fresh are they? It names the Plaid bank and its standing. It names the consent expiry date too, once Plaid publishes one. You grant finance at Agents & keys — Connect an agent.

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If something went wrong

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What you have now

• Plaid bills Production per linked bank, monthly, for as long as the bank stays linked.
• A balance an agent reads from the cache costs nothing. An explicit live balance costs money each time: it goes to a Plaid endpoint Plaid bills per call.
• Consent expires about once a year, per bank. Postern shows the lapse but cannot renew it — Reconnect a bank when its consent lapses.
• Disconnect a bank and Postern tells Plaid to cancel that Item. That also stops Plaid’s charge for it, and Postern leaves your other Plaid banks alone. It is one-way: you cannot reconnect a bank you disconnected or erased, only link it from the start, on a fresh slot.

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