diff --git a/clients/cascades-tucson/session-logs/2026-06/2026-06-08-howard-edge-unc-download-bug-diagnosis.md b/clients/cascades-tucson/session-logs/2026-06/2026-06-08-howard-edge-unc-download-bug-diagnosis.md new file mode 100644 index 0000000..80701f8 --- /dev/null +++ b/clients/cascades-tucson/session-logs/2026-06/2026-06-08-howard-edge-unc-download-bug-diagnosis.md @@ -0,0 +1,120 @@ +# Cascades of Tucson — Session Log 2026-06-08 — Edge UNC Download Bug Diagnosis + +## User +- **User:** Howard Enos (howard) +- **Machine:** Howard-Home +- **Role:** tech + +## Session Summary + +Diagnosed (no changes made) a user-reported issue at Cascades: Ashley Jensen +(DESKTOP-U2DHAP0, domain-joined, Downloads folder redirected to the `\\cs-server\homes` +UNC share) could not open Office downloads from the Microsoft Edge download list. Clicking +a downloaded `.xlsx`/`.docx` in Edge produced "Windows cannot find +'\\?\\\cs-server\homes\AshleyJensen\Downloads\'." Text files and PDFs opened fine +from the same Edge action; the same Office files opened fine when double-clicked from File +Explorer. Howard wanted root cause first, not a fix. + +Worked the symptom to a root cause: the `\\?\` is the Win32 extended-length path prefix, and +the error path is the malformed result of prepending `\\?\` to a UNC path (`\\?\` + `\\cs-server` += `\\?\\\cs-server`) instead of the correct `\\?\UNC\cs-server\...`. Confirmed with Howard's +test that Explorer double-click works and only the Edge download-list "open" fails — isolating +the fault to Edge's open-from-download invocation, not the file, share, or folder redirection. + +Howard found and supplied the canonical upstream bug: Chromium issue 519243472, "Can't open +downloaded file when Downloads folder is a UNC path (malformed `\\?\` path on open)" — Status +Fixed, P0/S2, component UI>Browser>Downloads. The report confirms the exact mechanism: a +**regression introduced in Chromium 149** (last good 148.0.7778.217, first bad 149.0.7827.54) +in the `LaunchShellExecuteViaExplorer` feature, which prepends `\\?\` to a UNC path without +converting to `\\?\UNC\`. Triggered specifically by Downloads redirected via Folder Redirection +to a network UNC path with no mapped drive — exactly Ashley's configuration. The earlier +"Open Office files in the browser" theory was retracted; that was not the cause. + +Confirmed applicability to Cascades: Ashley and Lois Lane are on **Edge 149.0.4022.52** (June 4, +2026 stable). Edge rides the Chromium 149 base, so it inherits the regression (the original +reporter thought Edge was immune, but bug comment #27, dated 2026-06-08, confirms Edge affected +in RDS/Citrix/AVD). The txt/pdf-work-Office-fails split is explained by only the external +ShellExecute launch path being broken (PDF opens in Edge's built-in viewer; Office routes +through the broken launch). Presented fix options ranked for the HIPAA environment: update Edge +forward into the fix, the `--disable-features=LaunchShellExecuteViaExplorer` flag, "Show in +folder" workaround, or a supported 149→148 MSI rollback. Howard asked about a simple +"uninstall the update" rollback; clarified Edge is not serviced via Windows Update so no +per-update revert exists — the MSI + `RollbackToTargetVersion` + version-pin is the only +supported downgrade. No changes were applied this session; decision on fix path left to Howard. + +## Key Decisions + +- Diagnosed root cause before proposing any fix, per Howard's explicit "no changes, figure out + the cause" instruction. Treated the Explorer-works / Edge-fails split as the key discriminator. +- Retracted the intermediate "Open Office files in the browser" hypothesis once the Chromium bug + report identified `LaunchShellExecuteViaExplorer` as the actual regression. Did not defend the + earlier guess. +- Recommended the lighter fixes (feature flag, wait for the fixed Edge 149.x, or "Show in folder") + over a full version rollback for HIPAA machines, because pinning to 148 forfeits 149 security + fixes and must be unwound later. Provided the full supported rollback procedure anyway since + Howard requested it. +- Flagged the issue as fleet-wide, not Ashley-specific: every Cascades user with Downloads + redirected to the `\\cs-server\homes` UNC share will hit it once on Edge 149 (the whole + domain-migrated set plus the caregiver/medtech machines using the same redirect pattern). + +## Problems Encountered + +- Could not fetch the Reddit thread or the Chromium tracker pages directly — Reddit is hard-blocked + for WebFetch, and `issues.chromium.org` / `issuetracker.google.com` are JS apps behind sign-in + that return only the login shell. Web search did not surface the specific issue. Resolved when + Howard copy-pasted the full bug report text, which provided the authoritative root cause, + regression range, and fix status. + +## Configuration Changes + +- None. Diagnostic-only session. No tenant, RMM, GPO, or repo config changed. +- This session log created: `clients/cascades-tucson/session-logs/2026-06/2026-06-08-howard-edge-unc-download-bug-diagnosis.md`. + +## Credentials & Secrets + +- None discovered or created this session. (Separately this day, the Lonestar Electrical Unraid + root password was read from the vault on request — entry `clients/lonestar/unraid-server.sops.yaml`; + not a Cascades item, value not reproduced here.) + +## Infrastructure & Servers + +- **Affected machines:** DESKTOP-U2DHAP0 (Ashley Jensen), DESKTOP-KQSL232 (Lois Lane) — both on Edge 149.0.4022.52. +- **Redirect target:** `\\cs-server\homes\\Downloads` (CS-SERVER 192.168.2.254, file server / homes share `D:\Homes`). No mapped drive — raw UNC, which is the bug's required trigger. +- **Edge stable app GUID (for EdgeUpdate pin):** `{56EB18F8-B008-4CBD-B6D2-8C97FE7E9062}`. + +## Commands & Outputs + +- Error dialog (verbatim from screenshot): `Windows cannot find '\\?\\cs-server\homes\AshleyJensen\Downloads\Resident Demographics Table.xlsx'. Make sure you typed the name correctly, and then try again.` +- Discriminator test (Howard): double-click the same xlsx from File Explorer at `\\cs-server\homes\AshleyJensen\Downloads` → opens normally. Only the Edge download-list "open" fails. +- Edge version check (Howard): Ashley + Lois both `149.0.4022.52`. + +### Fix options (reference — none applied) + +1. **Update Edge forward** into the fixed build (permanent; Chromium fix crrev 7900033 "Correctly handle UNC paths in InvokeShellExecute", merged M149/M150, verified Chromium 151.0.7875.0). Re-enabled the feature after fixing, so the code fix — not a disabled flag — is the real resolution. +2. **Feature flag (interim):** Edge shortcut target → + `"C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe" --disable-features=LaunchShellExecuteViaExplorer` + (fully quit Edge first; only applies to launches from that shortcut). +3. **"Show in folder"** in the Edge download list → open from Explorer (zero-config; confirmed working). +4. **Supported 149→148 rollback** (one major back is in-bounds): + - Download 148 stable **MSI** from https://www.microsoft.com/en-us/edge/business/download (Stable / 148 / Win x64). + - `HKLM\SOFTWARE\Policies\Microsoft\Edge` → `RollbackToTargetVersion` (DWORD) = 1 *(set BEFORE install; enables downgrade + preserves profile).* + - `HKLM\SOFTWARE\Policies\Microsoft\EdgeUpdate` → `TargetVersionPrefix{56EB18F8-B008-4CBD-B6D2-8C97FE7E9062}` (REG_SZ) = `148.` and `Update{56EB18F8-...}` (DWORD) = 2 (manual) *(pins it; else auto-update returns to 149).* + - Install 148 MSI → verify `edge://version` = 148.x and `edge://policy` shows the rollback + target-prefix active. + - Unwind later (`RollbackToTargetVersion=0`, remove `TargetVersionPrefix`) once a fixed Edge 149.x/150 ships. + +## Pending / Incomplete Tasks + +- **Decision pending (Howard):** pick fix path for Ashley + Lois — feature flag vs "Show in folder" vs 148 MSI rollback vs wait for fixed Edge 149.x. No changes made this session. +- **Fleet exposure:** all Cascades users with Downloads redirected to `\\cs-server\homes` + Edge 149 will hit this (Sharon Edwards, Crystal Rodriguez, Lauren Hasselman, Megan Hiatt, receptionist/nursestation, and the caregiver/medtech machines). Decide whether to fix fleet-wide (lean flag/wait, not a fleet-wide 148 pin, to avoid holding the fleet off security updates). +- **Offered, not yet run:** read-only RMM pull of Edge version + update channel across the Cascades agent fleet to quantify how many machines are on the affected 149 build. +- **Watch:** Edge stable release notes for the servicing build that carries the InvokeShellExecute UNC fix; flag it so pinned/rolled-back machines can go forward. +- Unrelated and still open from prior session: caregiver/medtech Monday go-live runbook (reboot/verify NURSESTATION lockdown, ALIS timeout 20→15, CA allow-list + GPO filter cutover, laptop hybrid-join gap). + +## Reference Information + +- **Chromium issue 519243472** — "Can't open downloaded file when Downloads folder is a UNC path (malformed `\\?\` path on open)". Status Fixed, P0/S2, UI>Browser>Downloads. Regression Chromium 149 (last good 148.0.7778.217, first bad 149.0.7827.54). Feature: `LaunchShellExecuteViaExplorer`. Fix: crrev 7900033, merged M149/M150, verified 151.0.7875.0. Related save-side bug: 40888395. +- Edge stable 149.0.4022.52 release notes: https://learn.microsoft.com/en-us/deployedge/microsoft-edge-relnote-stable-channel#version-1490402252-june-04-2026-stable +- Edge for Business download (MSI): https://www.microsoft.com/en-us/edge/business/download +- Chrome interim mitigation history (from bug): Finch/variations config disabling the feature pushed 2026-06-04 (no reboot if variations enabled); Edge delivers its own equivalent via `config.edge.skype.com`. +- Source Reddit thread (could not fetch; Howard-supplied): https://www.reddit.com/r/sysadmin/comments/1txi9ur/edge_downloads_location_with_unc_path/ +- Cascades wiki: `wiki/clients/cascades-tucson.md`. Ashley Jensen recorded there as DESKTOP-U2DHAP0 (domain-joined, folder redirect manually fixed); Lois Lane as DESKTOP-KQSL232 (CareTakers dept head).