Re-request undecryptable messages from the phone instead of dropping them

[6justgotme]

Problem

When a message can't be decrypted, whatsmeow emits events.UndecryptableMessage. In pkg/whatsmeow/service/whatsmeow.go the handler for that event only forwards a webhook when it's a view_once message (and reconnects for IDs starting with 66/67). Every other undecryptable message is logged and dropped — no webhook, and nothing is done to recover it.

Where this bites in practice is the first message from a brand-new contact. A new contact has no Signal session yet, so the first inbound message can fail to decrypt on the linked device; when it does, it's silently lost. The rest of the conversation decrypts fine once the session is established, so from the outside it looks like "the first message never arrives." Click-to-WhatsApp ad leads make this very visible, since every lead is a first-contact by definition.

Cause

Evolution Go runs as a companion/linked device, so it has no local history to fall back on. whatsmeow already handles this case: if the sender doesn't resend within RequestFromPhoneDelay (~5s), it can re-request the message from the account's own phone (the primary device, which already decrypted it). That path is gated behind Client.AutomaticMessageRerequestFromPhone, and the service never enables it — so the fallback never runs and the message stays lost.

Fix

Enable whatsmeow's AutomaticMessageRerequestFromPhone in StartClient, gated behind a new REREQUEST_FROM_PHONE env var so it's opt-in per deployment (default off):

client.AutomaticMessageRerequestFromPhone = w.config.RerequestFromPhone

With REREQUEST_FROM_PHONE=true, an undecryptable message gets re-requested from the phone and comes back through as a normal events.Message, so the webhook fires as expected.

Notes

• Off by default — no behavior change unless an operator sets REREQUEST_FROM_PHONE=true.
• Recovered messages arrive with up to ~5s of extra latency (the delay window before falling back to the phone). Fine trade-off versus losing them.
• No change for messages that decrypt normally.
• Requires the account's phone to be reachable to answer the re-request, which is the normal case.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

This PR enables automatic re-requesting of undecryptable messages from the primary phone so that previously dropped first-contact messages are recovered and delivered as normal events.

Sequence diagram for automatic rerequest of undecryptable messages

sequenceDiagram
  actor Sender
  participant WhatsAppServer
  participant PrimaryPhone
  participant LinkedDevice
  participant WebhookEndpoint

  Sender->>WhatsAppServer: send_message
  WhatsAppServer->>PrimaryPhone: deliver_message
  PrimaryPhone->>WhatsAppServer: sync_decrypted_message
  WhatsAppServer->>LinkedDevice: deliver_message
  LinkedDevice->>LinkedDevice: events.UndecryptableMessage

  alt [AutomaticMessageRerequestFromPhone enabled]
    LinkedDevice->>PrimaryPhone: AutomaticMessageRerequestFromPhone
    PrimaryPhone->>WhatsAppServer: resend_message
    WhatsAppServer->>LinkedDevice: events.Message
    LinkedDevice->>WebhookEndpoint: webhook_POST
  else [AutomaticMessageRerequestFromPhone disabled]
    LinkedDevice->>LinkedDevice: log_and_drop_message
  end

Loading

File-Level Changes

Change	Details	Files
Enable automatic re-request of undecryptable messages from the primary device instead of silently dropping them.	Set the WhatsApp client option AutomaticMessageRerequestFromPhone to true during client initialization. Document in comments that undecryptable messages (including first CTWA lead messages) are now recovered via re-request from the phone after RequestFromPhoneDelay instead of being discarded without a webhook.	pkg/whatsmeow/service/whatsmeow.go

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[sourcery-ai]

Hey - I've left some high level feedback:

• Consider making AutomaticMessageRerequestFromPhone configurable via ClientData or service options instead of hardcoding it to true, so operators can explicitly opt in or out of the rerequest behavior per deployment.
• The new inline comment is in Portuguese; for consistency across the codebase, consider rewriting it in the predominant project language and briefly summarizing the behavior change rather than its full rationale.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Consider making `AutomaticMessageRerequestFromPhone` configurable via `ClientData` or service options instead of hardcoding it to true, so operators can explicitly opt in or out of the rerequest behavior per deployment.
- The new inline comment is in Portuguese; for consistency across the codebase, consider rewriting it in the predominant project language and briefly summarizing the behavior change rather than its full rationale.

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[6justgotme]

Thanks for the review — addressed both points and pushed as 3f84b3c:

• Configurable instead of hardcoded: it's now behind a REREQUEST_FROM_PHONE env var, read in config.Load and applied in StartClient (client.AutomaticMessageRerequestFromPhone = w.config.RerequestFromPhone). Default off, so behavior is unchanged unless an operator opts in.
• Comment language: rewrote the inline comment in English and trimmed it to what the line does.