AutopilotMonitor/docs/decisions/003-multi-signal-session-completion.md

ADR-003: Multi-Signal Session Completion

Status: Accepted Date: 2026-03

Context

Windows Autopilot enrollment can follow multiple paths, and no single event reliably indicates "enrollment is done" across all scenarios:

• ESP (Enrollment Status Page) may or may not be present
• Windows Hello provisioning may be skipped, succeed, or time out
• Windows Device Preparation (v2) has no ESP at all
• White Glove (Pre-Provisioning) splits enrollment into two distinct phases
• Devices may reboot mid-enrollment, losing in-memory state

Decision

Implement 3 independent completion paths, any of which can trigger enrollment_complete:

1. IME Pattern Path — The existing pattern-based detection from Intune Management Extension logs (legacy, most reliable for app-centric enrollments)

2. ESP + Hello Composite Path — ESP final exit event + Hello completion/skip/timeout. For device-only ESP (no Account Setup), a 5-minute timer after Device Setup exit classifies as device-only.

3. Desktop + Hello Path (No-ESP) — Desktop arrival (explorer.exe under real user) + Hello completion. Used when ESP is absent (e.g., WDP v2).

Supporting infrastructure:

• EnrollmentStatePersistence — crash recovery for completion signals (persists seen signals to disk)
• DesktopArrivalDetector — polls explorer.exe every 30s, validates user identity (excludes SYSTEM, DefaultUser*)
• Signal audit trail — terminal events include signalsSeen and signalTimestamps
• Completion check throttling — observability events at 1x/min/source
• WDP v2 gate skip — enrollmentType == "v2" skips desktop arrival gate

Hello behavior:

• HelloCompletionTimeoutSeconds = 300 (5 minutes)
• HelloOutcome tracks: completed, skipped, timed_out

Consequences

• Covers all known Autopilot enrollment paths (Classic ESP, WDP v2, White Glove, device-only)
• State persists across reboots — no lost completions
• Each path is independently testable
• Adding new completion signals requires only extending EnrollmentTracker.CompletionLogic.cs
• Complexity concentrated in one partial class file (~789 lines) — acceptable given the domain complexity