Concurrent session limit reached (429 concurrency-limit)
You might be here because: “You already have as many sessions open, or AI tasks running, as your account allows” · “A usage limit was reached. Wait a moment or review your plan” · “Concurrent session limit reached” · “it won’t let me launch another profile” · “says I already have sessions running but I don’t see any” · “429 concurrency-limit” · “how many sessions can I run at once” · “launch button does nothing / greyed out”
Short answer
Your plan allows a fixed number of sessions open at the same time, and you already have that many. Nothing is broken: end a session you started (or wait for one to finish), then launch again. The limit is per account, so a teammate’s sessions count too: ask them before you stop one of theirs.
Check first
- Signed in to the right account? Team members launch on the team owner’s plan, so the owner’s open sessions count.
- Open the Sessions tab and look for anything still running, including sessions that are still starting (“provisioning” counts against the limit).
- A session that was closed from a script or another computer may need a refresh before the app shows the slot as free.
- In older app versions, “A usage limit was reached…” covers four limits. What were you doing? Launching a profile → sessions at once (Concurrent session limit reached (429 concurrency-limit)) or, after a plan change, After a downgrade only the most recently used profiles and proxies can launch; creating or duplicating a profile → Cannot create a profile: plan’s saved-profile limit reached; sending a message to the AI → ‘3 AI tasks are already running’ (AI task limit).
Likely causes and fixes
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You are at your plan’s limit. The server refuses the next launch with HTTP 429
concurrency-limit, title “Concurrent session limit reached”, detail “Account already has N active sessions; tier permits N”. The desktop app shows “You already have as many sessions open, or AI tasks running, as your account allows. Stop one or wait for one to finish, then try again.” (older versions: “A usage limit was reached…”). Limits per plan: Trial 1, Starter 1, Pro 3, Team 6, Scale 12; Enterprise is set by contract. Legacy Free is 1. Fix: stop a session you started and no longer need, then launch. -
A session is still open somewhere else. Sessions started from code or a second computer hold a slot until they are closed. If you started them, stop them from the Sessions tab, or close them from the code that started them. If a teammate or their script did, ask them, or wait for one to end.
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A session is stuck ending. A session counts until it reaches a terminal state. Wait a minute and refresh; if it still shows as running and you started it, use Stop on its row; if someone else did, ask them.
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You need more sessions at once. The only way past the limit is a plan with a higher number. To move to Starter, Pro or Team, open the dashboard → Billing → Choose a plan (or Change plan if you pay by card), then Choose … (or Upgrade to …) on the plan you want (self-serve). Scale and Enterprise, refunds, disputed charges and “I paid but the plan is not active” are handled by a person.
If it still fails
Press Talk to a person in this chat (or open Help) and include: the plan you are on, what the Sessions tab shows as running, and the exact message. If a session shows as running but cannot be stopped, that is something a person looks at directly.