---
phase: 13-slider-persistence-hardening
verified: 2026-04-05T23:00:00Z
status: passed
score: 4/4 must-haves verified
re_verification: false
---

# Phase 13: Slider Persistence and Hardening Verification Report

**Phase Goal:** IPD changes made via the SteamVR slider persist to the headset's lighthouse config so they survive SteamVR restarts
**Verified:** 2026-04-05T23:00:00Z
**Status:** passed
**Re-verification:** No — initial verification

## Goal Achievement

### Observable Truths

| # | Truth | Status | Evidence |
|---|-------|--------|----------|
| 1 | IPD changes during a session are written to headset flash via lighthouse_console on SteamVR shutdown | VERIFIED | `Cleanup()` calls `PersistIpdToConfig()` inside `#ifdef ENABLE_IPD_PERSIST` guard (device_provider.cpp:114-115); `PersistIpdToConfig()` runs full download-modify-upload cycle via `RunLighthouseCommand()` using `CreateProcessA` with stdin pipes (lines 1072-1210) |
| 2 | If IPD did not change during the session, no persistence write occurs | VERIFIED | Change detection at lines 1075-1081: skips if `m_fCurrentIpd <= 0.0f`, `m_fStartupIpd <= 0.0f`, or `fabsf(m_fCurrentIpd - m_fStartupIpd) < 0.0001f`; logs "No change during session, skipping"; hardware-confirmed (SUMMARY: "logs No change during session, skipping") |
| 3 | If lighthouse_console fails or times out, SteamVR shutdown completes normally and failure is logged | VERIFIED | All 12 error paths in `PersistIpdToConfig()` (lines 1080-1201) use `return` or `goto cleanup` — none throw; `RunLighthouseCommand()` returns bool; `TerminateProcess` handles process that fails to exit (line 1062); `Cleanup()` continues to `DestroyPipeServer()` etc. regardless |
| 4 | Building with ENABLE_IPD_PERSIST=OFF compiles cleanly with no persistence code | VERIFIED | All persistence code in device_provider.h (lines 46-51) and device_provider.cpp (lines 85-87, 114-116, 208-213, 929-1212) wrapped in `#ifdef ENABLE_IPD_PERSIST` / `#endif`; SUMMARY documents hardware-verified ON/OFF builds both succeeded |

**Score:** 4/4 truths verified

### Required Artifacts

| Artifact | Expected | Status | Details |
|----------|----------|--------|---------|
| `CMakeLists.txt` | ENABLE_IPD_PERSIST CMake option defaulting to ON | VERIFIED | Lines 58-62: `option(ENABLE_IPD_PERSIST "Enable IPD persistence to lighthouse config on shutdown" ON)` + `target_compile_definitions(${DRIVER_NAME} PRIVATE ENABLE_IPD_PERSIST)` inside `if(ENABLE_IPD_PERSIST)` |
| `src/driver/device_provider.h` | m_fStartupIpd field, PersistIpdToConfig and FindLighthouseConsole declarations | VERIFIED | Lines 46-51: all three declared inside `#ifdef ENABLE_IPD_PERSIST` block; `float m_fStartupIpd = 0.0f`, `void PersistIpdToConfig()`, `std::string FindLighthouseConsole()` |
| `src/driver/device_provider.cpp` | PersistIpdToConfig implementation with CreateProcess pipe spawning, download-modify-upload cycle, Cleanup hook | VERIFIED | `FindLighthouseConsole()` at line 931; `RunLighthouseCommand()` static helper at line 975 with `CreateProcessA`, stdin/stdout pipes, `TerminateProcess` on timeout; `PersistIpdToConfig()` at line 1072 with full DL-modify-UL cycle; `Cleanup()` hook at line 114; `m_fStartupIpd` capture in `ApplyIpd()` at lines 208-213 |

### Key Link Verification

| From | To | Via | Status | Details |
|------|----|-----|--------|---------|
| `Cleanup()` | `PersistIpdToConfig()` | `#ifdef ENABLE_IPD_PERSIST` guard | VERIFIED | device_provider.cpp:114-116: `#ifdef ENABLE_IPD_PERSIST` / `PersistIpdToConfig();` / `#endif` directly before `DestroyPipeServer()` |
| `PersistIpdToConfig()` | `lighthouse_console.exe` | `CreateProcessA` with stdin pipe | VERIFIED | `RunLighthouseCommand()` at line 1004: `CreateProcessA(exePath.c_str(), NULL, NULL, NULL, TRUE, CREATE_NO_WINDOW, NULL, NULL, &si, &pi)` with `STARTF_USESTDHANDLES` |
| `Init()` / `ApplyIpd()` | `m_fStartupIpd` | snapshot of `m_fCurrentIpd` after reading initial IPD | VERIFIED | Init() at lines 85-87: `m_fStartupIpd = ipd` inside `#ifdef`; ApplyIpd() at lines 208-213: `if (m_fStartupIpd <= 0.0f) m_fStartupIpd = ipdMeters` (deviation from plan: captures on first successful apply, not only Init, to handle VREvent_IpdChanged path) |

### Data-Flow Trace (Level 4)

Not applicable. Phase produces a driver DLL with no UI components — all logic is business/control flow, not rendering pipeline. IPD value flows: `m_fCurrentIpd` (in-memory float) -> `ipdMm = m_fCurrentIpd * 1000.0f` -> `snprintf(buf, "%.1f", ipdMm)` -> `configStr.replace()` -> written to temp file -> sent to `lighthouse_console uploadconfig`. Data source is the live in-memory IPD state updated by `ApplyIpd()`.

### Behavioral Spot-Checks

Hardware testing completed by user per SUMMARY (hardware testing is the authoritative verification for this phase — no server can be started in this environment):

| Behavior | Method | Result | Status |
|----------|--------|--------|--------|
| IPD persists across SteamVR restart | Set to 62mm, restarted SteamVR, queried IPD | 62mm preserved | PASS (hardware-verified) |
| No-change detection fires correctly | Session with no IPD change, checked logs | "No change during session, skipping" logged | PASS (hardware-verified) |
| Persistence timing | Measured end-to-end | ~5s total (DL ~2.5s + UL ~2.5s) | PASS (hardware-verified) |
| Error paths non-blocking | All `return`/`goto cleanup` paths checked | No throws, Cleanup() continues | PASS (static analysis) |

Automated build artifact spot-check:

| Behavior | Command | Result | Status |
|----------|---------|--------|--------|
| Driver DLL exists and is current | `ls -la build/driver/.../driver_BeyondProximity.dll` | 113152 bytes, Apr 5 22:19 | PASS |
| Commit 4a2f5af exists | `git show --stat 4a2f5af` | feat(13-01) commit confirmed | PASS |
| Commit 8722008 exists | `git show --stat 8722008` | fix(phase-13) commit confirmed | PASS |

### Requirements Coverage

| Requirement | Source Plan | Description | Status | Evidence |
|-------------|-------------|-------------|--------|----------|
| SLIDER-03 | 13-01-PLAN.md | Slider-initiated IPD changes persist to headset lighthouse config (`default_mm` field) via lighthouse_console | SATISFIED | `PersistIpdToConfig()` searches for `"default_mm"` at line 1146, replaces value with `snprintf(buf, "%.1f", ipdMm)` at line 1180, uploads via `RunLighthouseCommand()` at line 1198; hardware test confirmed persistence |
| SLIDER-04 | 13-01-PLAN.md | Driver reads headset lighthouse serial from HID config data for lighthouse_console invocation | SATISFIED | `m_sTrackingSerial` set from HID user flash tag 0x09 (`m_pHidDevice->GetTrackingSerial()`) at device_provider.cpp:804-814; used in `serialCmd = "serial " + m_sTrackingSerial` at line 1111; check at line 1084 guards against empty serial |
| HARD-03 | 13-01-PLAN.md | Lighthouse_console persistence failures are logged but do not block live IPD change | SATISFIED | 12 error paths in `PersistIpdToConfig()` all use `return` or `goto cleanup` — function is `void`, never throws; `Cleanup()` continues unconditionally after the `#ifdef` block |

All three requirement IDs declared in PLAN frontmatter are satisfied. No orphaned requirements for Phase 13 in REQUIREMENTS.md (traceability table confirms SLIDER-03, SLIDER-04, HARD-03 all map to Phase 13).

### Anti-Patterns Found

| File | Line | Pattern | Severity | Impact |
|------|------|---------|----------|--------|
| device_provider.cpp | 1026, 1029 | `goto` for error handling inside `RunLighthouseCommand` | Info | Idiomatic Win32 resource-cleanup pattern; all handles closed in `done:` block; not a stub |

No TODOs, FIXMEs, placeholder returns, or empty implementations found in the persistence code paths.

**Deviation from plan spec — not a gap:** The plan specified `WaitForSingleObject(pi.hProcess, 10000)` for process exit. The implementation uses `GetExitCodeProcess` polling with `Sleep(1)` up to 10000 iterations (effective 10s cap), then `TerminateProcess`. This is the HMDUtility reference pattern and was documented as an intentional architectural change in SUMMARY key-decisions. The functional contract (10s cap + forced termination + non-blocking on timeout) is identical.

### Human Verification Required

The following items were already completed by the user during hardware testing:

1. **IPD persistence across SteamVR restart**
   - Test: Set IPD to 62mm via slider, close SteamVR, restart, query IPD
   - Result: 62mm confirmed preserved
   - Completed: 2026-04-05 per SUMMARY

2. **ENABLE_IPD_PERSIST=OFF clean build**
   - Test: Configure with `-DENABLE_IPD_PERSIST=OFF`, build Release
   - Result: Build succeeded (SUMMARY: "All phases 10-13 shipped, both ON/OFF builds succeed")
   - Completed: 2026-04-05 per SUMMARY

No outstanding human verification items remain.

### Gaps Summary

No gaps. All four observable truths are verified. All three artifacts are substantive (full implementations, not stubs), wired into the call graph, and carry real data flow. All three requirement IDs are satisfied. Hardware testing is complete.

---

_Verified: 2026-04-05T23:00:00Z_
_Verifier: Claude (gsd-verifier)_