FixAV should detect zero-subscription state before diagnosing device issues

[JamesPHoughton]

Problem

When a participant's partner drops out of a video call, FixAV misdiagnoses the problem as a device issue (speakerNotSet) rather than recognizing that no remote participants are subscribed. This sends users down a futile device-fix path instead of surfacing the actual problem: their partner isn't in the call.

Evidence (Sentry event 83d27b6b, Feb 27)

A Listener in a 6-player storytelling study had their paired Storyteller drop out. The subscription system correctly set all 4 remaining remote participants to {audio: false, video: false} (none were the partner). But when the user reported "cant-see, cant-hear":

1. FixAV diagnosed speakerNotSet (because callObject.getOutputDevices() returned null)
2. Attempted speaker re-alignment — reported "success"
3. Validation showed speakerNotSet still present
4. Error reported to Sentry as a device failure

The real problem was never audio devices — it was that no one was subscribed because the partner was absent.

Why this matters

• Users waste time trying to fix audio when the real issue is a missing partner
• The reportMissing button may be turned off in some studies (e.g., to avoid spamming all participants), so users have no other signal
• These events pollute Sentry's PE/PG issue groups, obscuring real device problems
• ~25% of pre-crash PE events in our analysis were this pattern

Proposed Implementation

1. Add subscription-aware diagnosis to FixAV

In the diagnosis flow (FixAV.jsx), check desiredSubscriptions before running device diagnostics. If all remote participants have {audio: false, video: false}, surface a different diagnosis:

// New diagnosis: check if any remote participants are subscribed
const hasSubscribedParticipant = [...desiredSubscriptions.entries()].some(
  ([_, tracks]) => tracks.audio || tracks.video
);

if (!hasSubscribedParticipant && remoteParticipantCount > 0) {
  causes.push({
    id: "noSubscribedParticipants",
    description: "Your conversation partner hasn't joined the call yet",
    fixDescription: "Wait for your partner or report them as missing",
    fixable: false,  // not auto-fixable
    priority: 1,     // highest priority — show this instead of device issues
  });
  // Skip device diagnostics — they're irrelevant without subscriptions
  return causes;
}

2. Access desired subscriptions from FixAV

desiredSubscriptions is already stored in a module-level ref in Call.jsx (latestDesiredSubscriptions). Expose it to FixAV via the existing diagnostic data gathering:

// In FixAV's diagnostic data collection
desiredSubscriptions: Object.fromEntries(
  [...(latestDesiredSubscriptions.current?.entries() || [])]
),

This ref is already used for FixAV error reporting (Call.jsx line 451), so the plumbing partially exists.

3. UI treatment

When noSubscribedParticipants is diagnosed:

• Show a clear message: "Your conversation partner hasn't joined the call yet"
• Offer guidance: "You can wait for them to join, or use the Report Missing button if available"
• Do NOT show device fix options (they're irrelevant)
• Still log to Sentry, but at warning level instead of error, with the subscription state in extras

Test Plan

Add tests to playwright/component-tests/video-call/mocked/FixAV.ct.jsx:

FIXAV-NOSUB-001: Zero subscriptions diagnosed before device issues

• Mount VideoCall with multiple remote participants
• Set all desired subscriptions to {audio: false, video: false}
• Trigger FixAV with "cant-hear" report
• Assert: diagnosis includes noSubscribedParticipants
• Assert: diagnosis does NOT include speakerNotSet (early return skips device checks)

FIXAV-NOSUB-002: Normal subscriptions proceed to device diagnosis

• Mount VideoCall with at least one participant subscribed {audio: true, video: true}
• Trigger FixAV with "cant-hear" report
• Assert: diagnosis does NOT include noSubscribedParticipants
• Assert: device diagnostics run normally

FIXAV-NOSUB-003: Zero remote participants skips subscription check

• Mount VideoCall with no remote participants (solo in room)
• Trigger FixAV with "cant-hear" report
• Assert: diagnosis does NOT include noSubscribedParticipants (no one to subscribe to yet)
• Assert: device diagnostics run normally (problem may be that partner hasn't joined Daily at all)

FIXAV-NOSUB-004: Sentry capture uses warning level for no-subscription case

• Same setup as NOSUB-001
• Submit the FixAV report
• Assert: Sentry capture level is warning, not error
• Assert: extras include desiredSubscriptions state

Files to modify

• client/src/call/FixAV.jsx — add subscription check to diagnosis flow
• client/src/call/Call.jsx — expose latestDesiredSubscriptions to FixAV (may already be sufficient)
• playwright/component-tests/video-call/mocked/FixAV.ct.jsx — add NOSUB tests

Related

• Downstream of bug: speaker device alignment silently fails — users can't hear audio (Bluetooth) #1227 (speaker alignment investigation)
• Root cause found via Sentry event 83d27b6ba4fa4bb4b10ea4dd13cb8c97
• Report Missing feature (ReportMissing.jsx) is the correct user path but may be disabled in some studies