• Extends email tracking code format to optionally include distinct_id while keeping backward compatibility with existing functionId:invocationId payloads.
• Updates tracking-code parsing to safely reconstruct distinct_id when it contains colons, and propagates distinct_id through pixel URL generation.
• Adds standard PostHog event capture on email send/fail in the send path with workflow and email metadata properties.

This chunk extends the email tracking identifier format so one ph_id token can carry functionId, invocationId, and optionally distinctId, while still accepting legacy two-part payloads. In tracking-code.ts, the helper API is made explicit with ParsedTrackingCode, generation methods now accept an optional distinctId, and parsing uses a fixed-first-two + rest rejoin strategy to preserve distinctId values that may contain :. The overall pattern remains a compact URL-safe base64 transport format, so existing links/tags continue to work and old payloads decode without schema migration.

In email.service.ts, the send path now propagates invocation.state.globals.event.distinct_id into the SES ph_id email tag (generateEmailTrackingCode(result.invocation, distinctId)), which is the critical integration point for later asynchronous SES webhook attribution. The same method also appends standard PostHog capture events ($messaging_email_sent / $messaging_email_failed) to result.capturedPostHogEvents with workflow and email metadata, but only when a distinct ID exists. This follows the existing invocation-result contract rather than introducing a direct side-effect call inside the service.

Architecturally, this chunk connects synchronous send execution and downstream telemetry pipelines: EmailService.executeSendEmail is called by HogExecutor, returned results are consumed by cyclotron worker processing, and capturedPostHogEvents are ultimately emitted via HogFunctionMonitoringService + InternalCaptureService. On the tracking side, the updated token format is consumed by SES webhook parsing and direct pixel/redirect handlers through shared helper functions, giving one consistent identity propagation path across direct opens/clicks and SES-originated engagement signals. There is one existing review-thread nit in this chunk about clarifying the inline colon-rejoin comment, but no architectural disagreement in the discussion.

• Adds queuePostHogEvent to HogFunctionMonitoringService to enqueue arbitrary PostHog events by resolving team token and normalizing timestamp.
• Enhances SES webhook processing to return distinct_id and engagement properties ($email_to, optional $link_url) alongside metric mapping.
• Refactors email tracking handlers to parse combined ph_id (with legacy ph_fn_id/ph_inv_id fallback), emit standardized $messaging_email_* events, and attach source/workflow/link properties for opens, clicks, and SES events.
• Review hotspot: email-tracking currently calls async queuePostHogEvent without await before flush, which can cause dropped events.

This chunk extends the CDP messaging pipeline so asynchronous email engagement signals (pixel opens, redirect clicks, SES webhooks) are emitted as first-class PostHog events, not only as workflow app metrics. The architectural addition is queuePostHogEvent on HogFunctionMonitoringService, which reuses the existing buffered monitoring pattern (eventsToCapture + flush) but accepts a team_id, resolves the team API token through TeamManager, normalizes timestamp, and queues an InternalCaptureEvent for InternalCaptureService. This is the missing path for events that happen after the original invocation lifecycle, where capturedPostHogEvents on invocation results is no longer available.

EmailTrackingService is refactored into a normalization/dispatch layer: tracking URLs now encode ph_id with optional distinct_id, request handlers decode either the new combined ph_id format or legacy ph_fn_id/ph_inv_id, and trackMetric resolves whether the source ID belongs to a Hog function or Hog flow before emitting data. It still queues legacy app metrics (metric_kind: "email") for existing monitoring, and now additionally emits standardized $messaging_email_* events with consistent properties ($workflow_id, $messaging_source, plus optional $link_url/$email_to). This keeps backward compatibility while aligning engagement telemetry with standard PostHog event semantics for insights, funnels, and automation triggers.

SesWebhookHandler is upgraded from metric-name mapping to richer event extraction: it now returns distinctId and event properties from SES records, including recipient and clicked link. That output feeds directly into EmailTrackingService.handleSesWebhook, which iterates metrics and forwards them through the same trackMetric pipeline used by pixel/redirect endpoints, giving one integration path for direct and SES sources. The main implementation caveat already identified in review is that queuePostHogEvent is async but currently called without await before flush, creating a race where PostHog events can be dropped if flush executes before queueing completes.