Pin libplctag ab_server to v2.6.16 — real release tag + SHA256 hashes for all three Windows arches. Closes the "pick a current version + pin" deferral left by the #180 PR docs stub. Verified the release lands ab_server.exe inside libplctag_2.6.16_windows_<arch>_tools.zip alongside plctag.dll + list_tags_* helpers by downloading each tools zip + unzip -l'ing to confirm ab_server.exe is present at 331264 bytes. New ci/ab-server.lock.json is the single source of truth — one file the CI YAML reads via ConvertFrom-Json instead of duplicating the hash across the workflow + the docs. Structure: repo (libplctag/libplctag) + tag (v2.6.16) + published date (2026-03-29) + assets keyed by platform (windows-x64 / windows-x86 / windows-arm64) each carrying filename + sha256. docs/v2/test-data-sources.md §2.CI updated — replaces the prior placeholder (ver = '<pinned libplctag release tag>', expected = '<pinned sha256>') with the real v2.6.16 + 9b78a3de... hashes pinned table, and replaces the hardcoded URL with a lockfile-driven pwsh step that picks windows-x64 by default but swaps to x86/arm64 by changing one line for non-x64 CI runners. Hash-mismatch path throws with both the expected + actual values so on the first drift the CI log tells the maintainer exactly what to update in the lockfile. Two verification notes from the release fetch: (1) libplctag v2.6.16 tools zips ship ab_server.exe + plctag.dll together — tests don't need a separate libplctag NuGet download for the integration path, the extracted tools dir covers both the simulator + the driver's native dependency; (2) the three Windows arches all carry ab_server.exe, so ARM64 Windows GitHub runners (when they arrive) can run the integration suite without changes beyond swapping the asset key. No code changes in this PR — purely docs + the new lockfile. Admin tests + Core tests unchanged + passing per the prior commit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/v2/test-data-sources.md

@@ -196,22 +196,30 @@ The integration harness at `tests/ZB.MOM.WW.OtOpcUa.Driver.AbCip.IntegrationTest
 - **`AbServerFixture(AbServerProfile)`** — starts the simulator with the CLI args composed from the profile's `--plc` family + seed-tag set. One fixture instance per family, one simulator process per test case (smoke tier). For larger suites that can share a simulator across several reads/writes, use a `IClassFixture<AbServerFixture>` wrapper per family.
 - **`KnownProfiles.{ControlLogix, CompactLogix, Micro800, GuardLogix}`** — the four per-family profiles. Drives the simulator's `--plc` mode + the preseed `--tag name:type[:size]` set. Micro800 + GuardLogix fall back to `controllogix` under the hood because ab_server has no dedicated mode for them — the driver-side family profile still enforces the narrower connection shape / safety classification separately.
 
-**CI step (intended — fleet-ops to wire):**
+**Pinned version** (recorded in `ci/ab-server.lock.json` so drift is one-file visible):
+
+- `libplctag` **v2.6.16** (published 2026-03-29) — `ab_server.exe` ships inside the `_tools.zip` asset alongside `plctag.dll` + two `list_tags_*` helpers.
+- Windows x64: `libplctag_2.6.16_windows_x64_tools.zip` — SHA256 `9b78a3dee73d9cd28ca348c090f453dbe3ad9d07ad6bf42865a9dc3a79bc2232`
+- Windows x86: `libplctag_2.6.16_windows_x86_tools.zip` — SHA256 `fdfefd58b266c5da9a1ded1a430985e609289c9e67be2544da7513b668761edf`
+- Windows ARM64: `libplctag_2.6.16_windows_arm64_tools.zip` — SHA256 `d747728e4c4958bb63b4ac23e1c820c4452e4778dfd7d58f8a0aecd5402d4944`
+
+**CI step:**
 
 ```yaml
 # GitHub Actions step placed before `dotnet test`:
-- name: Fetch ab_server
+- name: Fetch ab_server (libplctag v2.6.16)
   shell: pwsh
   run: |
-    $ver = '<pinned libplctag release tag>'
-    $url = "https://github.com/libplctag/libplctag/releases/download/$ver/ab_server-windows-x64.zip"
-    Invoke-WebRequest $url -OutFile $env:RUNNER_TEMP/ab_server.zip
-    # SHA256 check against a pinned value recorded in this repo's CI lockfile — drift = fail closed
-    $expected = '<pinned sha256>'
-    $actual = (Get-FileHash -Algorithm SHA256 $env:RUNNER_TEMP/ab_server.zip).Hash
-    if ($expected -ne $actual) { throw "ab_server hash mismatch" }
-    Expand-Archive $env:RUNNER_TEMP/ab_server.zip -DestinationPath $env:RUNNER_TEMP/ab_server
-    echo "$env:RUNNER_TEMP/ab_server" >> $env:GITHUB_PATH
+    $pin = Get-Content ci/ab-server.lock.json | ConvertFrom-Json
+    $asset = $pin.assets.'windows-x64'       # swap to windows-x86 / windows-arm64 on non-x64 runners
+    $url = "https://github.com/libplctag/libplctag/releases/download/$($pin.tag)/$($asset.file)"
+    $zip = Join-Path $env:RUNNER_TEMP 'libplctag-tools.zip'
+    Invoke-WebRequest $url -OutFile $zip
+    $actual = (Get-FileHash -Algorithm SHA256 $zip).Hash.ToLower()
+    if ($actual -ne $asset.sha256) { throw "libplctag tools SHA256 mismatch: expected $($asset.sha256), got $actual" }
+    $dest = Join-Path $env:RUNNER_TEMP 'libplctag-tools'
+    Expand-Archive $zip -DestinationPath $dest
+    Add-Content $env:GITHUB_PATH $dest
 ```
 
 The fixture's `LocateBinary()` picks the binary up off PATH so the C# harness doesn't own the download — CI YAML is the right place for version pinning + hash verification. Developer workstations install the binary once from source (`cmake + make ab_server` under a libplctag clone) and the same fixture works identically.