office-addin-debugging 5.x / 6.x doesn't sideload on LTSC 2024 Mac

[zsy619]

Summary

office-addin-debugging start (verified on 5.1.6 and 6.1.1) writes only
2 of the 6 SQL rows that the WEF scanner on Office LTSC 2024 Mac
requires to register a dev catalog. After registration, the dev add-in
is invisible to Excel's Insert > Add-ins > My Add-ins, no WefProcess
is spawned, no HTTP request reaches the dev server, and Excel's
diagnostic log contains zero references to the add-in GUID or the dev
server URL.

The same project on Microsoft 365 Mac sideloads normally (the dev
catalog gets auto-injected as a custom ribbon tab). The gap is specific
to LTSC 2024 Mac (which moved WEF storage to a WebView2-backed
on-disk layout the tooling doesn't populate).

Environment

• Office LTSC Standard for Mac 2024, version 16.110.2, build 26062818
• macOS 15.5
• office-addin-debugging@5.1.6 and 6.1.1 (both reproduce identically)
• office-addin-dev-settings@2.3.6 and 3.1.1 (the dev-settings-mac.js
  write path is byte-equivalent between these versions)
• Excel is the only Office process running; no WefProcess child is ever spawned
• Dev server: webpack serve on https://127.0.0.1:3000 (the dev cert
  from office-addin-dev-certs install is in the system keychain)

Repro

# 1. New project
mkdir repro && cd repro
# (initialize a taskpane add-in via Yo Office with manifest id e504fb41-...)

# 2. Start dev server
npm run dev-server &  # listens on https://127.0.0.1:3000

# 3. Sideload
./node_modules/.bin/office-addin-debugging start manifest.xml \
  --app excel --source-bundle-url-host 127.0.0.1 --source-bundle-url-port 3000 --no-debug

# 4. Open Excel
open -a "Microsoft Excel"
sleep 15

# 5. Observe:
#  - Insert > Add-ins > My Add-ins: dev add-in is NOT listed
#  - ps -ax | grep WefProcess: 0 matches (no child process)
#  - Dev server log: 0 requests from WefProcess
#  - Excel log: 0 references to the add-in GUID

Expected

After office-addin-debugging start, the dev catalog should be
discoverable by Excel's WEF scanner and the add-in should appear in
Insert > Add-ins > My Add-ins. WefProcess should spawn and load
taskpane.html from the dev server.

Actual

The dev catalog is registered in
~/Library/Group Containers/UBF8T346G9.Office/MicrosoftRegistrationDB/MicrosoftRegistrationDB_19413899015.reg
at HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Wef\Providers\<catalog-hash>,
but only with these 2 values:

Value	Type	Size
Entitlements	REG_QWORD	8 (FILETIME)
UniqueId	REG_SZ	9 ("developer")

Compare to a working Omex catalog (geLWvPTNy9pxk4xxzFEGHw==) on the
same machine, which has 4 values + an AppStates child node:

Value	Type
BlockForMinor	REG_DWORD
Entitlements	REG_QWORD (FILETIME)
EntitlementsInvalid	REG_SZ
UniqueId	REG_SZ (LiveId, not "developer")
+ child: AppStates with <assetid>_<ver> REG_QWORD per add-in

The on-disk WEF layout at
~/Library/Containers/com.microsoft.Excel/Data/Library/Application Support/Microsoft/Office/16.0/Wef/{EC993EB3-E226-5544-8239-1F3370D3A9CD}/<catalog-hash>/
is also never created for dev catalogs (Omex catalogs have a full
10-subdir layout with Manifests/, AppStates/, Tokens/,
Metadata/, Html/, TrustedApps/, etc.).

Suggested fix

office-addin-debugging should detect LTSC 2024+ Mac installs (e.g.
Excel.app/Contents/Info.plist CFBundleVersion >= 16.110) and on
register, in addition to the current 2 SQL rows:

1. Write BlockForMinor=0 (REG_DWORD)
2. Write EntitlementsInvalid={unique-guid} (REG_SZ)
3. Create AppStates child node under the catalog with
   <assetid>_<ver> REG_QWORD FILETIME per add-in
4. Create the 10-subdir on-disk layout
   (Wef/{EC993EB3-...}/<catalog-hash>/) and populate
   Manifests/<aid>_<ver> (the manifest XML), AppStates/<aid>_<ver>
   (XML <o:results>), Tokens/<aid>_<ver> (XML <o:assets>),
   Metadata/<aid>_<ver>_<locale> (JSON), Html/<aid>_<ver>_<locale>
   (HTML redirector), and TrustedApps/<aid>_<ver> (empty marker).
5. Set UniqueId to the user's LiveId rather than the literal
   "developer" (or add a fallback scan path that matches on
   UniqueId being absent).

The dev-settings-mac.js write path would also need to be updated to
target the new on-disk path; the legacy ~/Documents/wef/
fs.ensureLinkSync symlink is no longer read by LTSC 2024 Mac.

Related

• See also: LTSC 2024 Mac WefProcess rejects manually-registered dev
  catalog (issue TBD) — even with all 5 preconditions written manually
  • the manifest signed, the WefProcess still does not spawn.
• See also: Omex manifest signing not reproducible for non-Microsoft
  add-ins (issue TBD) — production Omex add-ins ship with XAdES-T
  signatures from CN=Microsoft Corporation Third-Party App Distribution,
  which no third party can obtain.