fix(calling): handle 409 error for keepalive by rarajes2 · Pull Request #5172 · webex/webex-js-sdk

rarajes2 · 2026-08-17T08:50:32Z

COMPLETES #< SPARK-832708 >

This pull request addresses

When Mobius answers a keepalive (device_status) with 409 Conflict, the device registration
is gone but the same user still holds an active registration elsewhere — typically calling
opened in a second browser tab, which superseded this one. Previously a 409 fell through to the
default branch of handleRegistrationErrors, so the SDK re-registered. That unregistered the
other tab, which then re-registered and unregistered this one, producing a registration
ping-pong between tabs.

by making the following changes

A 409 on keepalive is now a hard stop: the keepalive worker is terminated, no re-registration is
attempted, the Mobius WebSocket is closed, and the app is notified that its session was
superseded.

register.ts — the KEEPALIVE_FAILURE branch short-circuits to a new
handle409KeepaliveFailure before handleRegistrationErrors runs, so no retry, failover, or
restore path can execute. The worker is stopped up front (before waiting on the shared mutex)
so no further keepalive can be sent.
performRegistrationDownCleanup → performHardStopCleanup(caller, hardStop), now shared with
the 409 path. A HardStop discriminated union (registration/types.ts) makes it impossible to
signal a superseded session without the LineError the consumer receives, and its
HARD_STOP_REASON values double as the log label. Teardown is unchanged: timers cleared,
transient flags and failover cache reset, status INACTIVE, WebSocket closed with the existing
permanent code {code: 3050, reason: 'done (permanent)'}.
Observability: submits the existing KEEPALIVE_ERROR / KEEPALIVE_FAILURE registration metric
and calls uploadLogs().

Public API (additive)

New LINE_EVENTS.SESSION_SUPERSEDED = 'session_superseded', typed in LineEventTypes as
(error: LineError) => void.
New ERROR_TYPE.SESSION_SUPERSEDED and ERROR_CODE.CONFLICT = 409.
For backward compatibility unregistered still fires first, followed by session_superseded
with the error. Line.lineEmitter re-emits it through the same guarded branch as error.

No existing event, payload, or status transition changed. Keepalive 404 / 429 / 5xx and the
registration, restoration, failover, and failback paths are untouched — the short-circuit is
scoped to the keepalive worker's failure branch only.

Notes

The LineError message comes from a new SESSION_SUPERSEDED_MESSAGE constant rather than
Mobius's data.message: the keepalive worker's failure envelope forwards only headers/status, and
adding the response body would have silently changed the 403 device-limit branch in
handleRegistrationErrors. Detection relies solely on the status code.

Change Type

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to change)
Documentation update
Tooling change
Internal code refactor

The following scenarios were tested

Vidcast - https://app.vidcast.io/share/d6bda2af-24a9-4cee-ab69-d9a2da283aa3

Further Testing

User registers in different session with old session having active call - with http/mercury and without 409 handling
https://app.vidcast.io/share/7fbc2f34-ec31-459c-bfc2-5a92c3a11383

User registers in different session with old session having active call - with mobius socket and 409 handling
https://app.vidcast.io/share/a8a4ea5c-792d-45f1-b343-59128d55e903

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I have read and followed contributing guidelines
I discussed changes with code owners prior to submitting this pull request
I have not skipped any automated checks
All existing and new tests passed
I have updated the documentation accordingly

Make sure to have followed the contributing guidelines before submitting.

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chatgpt-codex-connector · 2026-08-17T08:53:40Z

+    await this.performHardStopCleanup(METHODS.HANDLE_409_KEEPALIVE_FAILURE, {
+      reason: HARD_STOP_REASON.SESSION_SUPERSEDED,
+      error: lineError,
+    });


End active calls when the session is superseded

When a second tab or device supersedes a registration during an active call, this path marks the line inactive and disconnects its transport without ending the call retained by CallManager. Unlike handleRegistrationDownEvent(), which explicitly calls activeCall?.end(), the 409 path leaves the call, media connection, and call timers alive even though no further Mobius events can arrive, so consumers may continue displaying a stale established call. End the active call(s) before performing this hard-stop cleanup.

Useful? React with 👍 / 👎.

It's already handled. SDK receives "normal_disconnect" event from mercury and mobius-socket as soon as the same user registers in a different session. Vidcast is attached in the PR description.

aws-amplify-us-east-2 · 2026-08-17T09:00:22Z

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Kesari3008

Let's discuss the comments if needed

Kesari3008 · 2026-08-19T05:03:28Z

                logContext
              );

+              if (Number(error.statusCode) === ERROR_CODE.CONFLICT) {


Why are we not adding a separate switchcase in handleRegistrationError itself where we are addressing all the error codes for this error as well. We should move the handling there. Anyway it seems all we need to do is invoke the handler

Kesari3008 · 2026-08-19T05:16:07Z

        this.emit(event);
        break;
      case LINE_EVENTS.ERROR:
+      case LINE_EVENTS.SESSION_SUPERSEDED:


Why do we need to define new event for just handling this error ? If 409 is received for keepalive, we are to assume that in this tab registration doesn't exist so sending Unregistered event back to the application should be enough. We can add reason for deregistration in the payload for Unregistered event but a new event just for keepalive failure is not required

Kesari3008 · 2026-08-19T05:18:19Z

  RECONNECTING = 'reconnecting',
  REGISTERED = 'registered',
  UNREGISTERED = 'unregistered',
+  SESSION_SUPERSEDED = 'session_superseded',


Kesari3008 · 2026-08-19T05:27:07Z

+   * @param hardStop - Why the registration is being torn down as {@link HardStop}.
   */
-  private async performRegistrationDownCleanup(caller: string): Promise<void> {
+  private async performHardStopCleanup(caller: string, hardStop: HardStop): Promise<void> {


If we really wanna rename this method, registrationCleanup is enough. Also the changes with respect to new event are not needed. Noticed that we are already emitting Unregistered event here after cleaning everything up and after sedning unregistered, we send Session_Superseded again which is not ok by design. After receiving Unregistered event, no events should be emitted and application wont be handling it coz ideally they are supposed to destroy the line object post receiving Unregistered event

Renamed to registrationCleanup

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chatgpt-codex-connector · 2026-08-23T05:11:03Z

      }

-      this.lineEmitter(LINE_EVENTS.UNREGISTERED);
+      this.lineEmitter(LINE_EVENTS.UNREGISTERED, undefined, hardStop.error);


Deduplicate concurrent supersession cleanup

When another session supersedes this one while a keepalive is in flight, Mobius can deliver both the normal registration.down event and the keepalive 409; each path enters registrationCleanup, and the mutex only serializes them, so this unconditional emission fires twice. If the registration-down path runs last, its undefined error also replaces the useful supersession reason in consumers such as the updated sample, reverting the displayed status to generic “Not Registered.” Make the hard-stop cleanup idempotent or preserve the terminal reason across the second signal.

AGENTS.md reference: packages/calling/AGENTS.md:L80-L85

Useful? React with 👍 / 👎.

fix(calling): handle 409 error for keepalive

65f0ca8

rarajes2 requested a review from a team as a code owner August 17, 2026 08:50

rarajes2 added the validated If the pull request is validated for automation. label Aug 17, 2026

chatgpt-codex-connector Bot reviewed Aug 17, 2026

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Kesari3008 requested changes Aug 19, 2026

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fix(calling): address review comments

6423b24

github-actions Bot removed the validated If the pull request is validated for automation. label Aug 23, 2026

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COMPLETES #< SPARK-832708 >

This pull request addresses

by making the following changes

Public API (additive)

Notes

Change Type

The following scenarios were tested

The GAI Coding Policy And Copyright Annotation Best Practices

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rarajes2 commented Aug 17, 2026 •

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