overleaf/overleaf · error

invalid session

Error message

invalid session

What it means

Warning logged in the socket.io connection handler when the session lookup fails with 'could not look up session by key' — the client presented an expired, revoked or unknown session key (typical after server restarts or session TTL expiry). The connection is rejected with 'invalid session' so the client re-authenticates; this is expected behavior, not a server fault.

Source

Thrown at services/real-time/app/js/Router.js:169

          if (client.connected) {
            client.emit('reconnectGracefully')
            client.disconnect()
          }
        })
      }

      if (settings.shutDownInProgress) {
        client.emit('connectionRejected', { message: 'retry' })
        client.disconnect()
        return
      }

      if (
        client &&
        error &&
        error.message.match(/could not look up session by key/)
      ) {
        logger.warn(
          { err: error, client: !!client, session: !!session },
          'invalid session'
        )
        // tell the client to reauthenticate if it has an invalid session key
        client.emit('connectionRejected', { message: 'invalid session' })
        client.disconnect()
        return
      }

      if (error) {
        logger.err(
          { err: error, client: !!client, session: !!session },
          'error when client connected'
        )
        if (client) {
          client.emit('connectionRejected', { message: 'error' })
        }
        if (client) {

View on GitHub (pinned to 28ad3b03b7)

Solutions

1. Have the client obtain a fresh session key (re-login) and reconnect
2. Verify the session store (redis) is reachable and in sync across real-time instances
3. Check session TTL settings versus expected connection lifetimes
4. Ignore as routine noise unless it spikes, which indicates session-store issues

When it happens

Trigger: Thrown at services/real-time/app/js/Router.js:169 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of overleaf/overleaf@28ad3b03b7 (2026-09-03). Data as JSON: /api/errors/090d6995484455f7. Report an issue: GitHub.