---
status: current
last-verified: 2026-10-09
owner: active-agent
source: repository and regression evidence
---

# System patterns

## Architecture

| Component | Responsibility |
| --- | --- |
| `NTFSSecurity.psd1` | Root script, nested binary, initialization, types, help |
| `NTFSSecurity.Init.ps1` | Loads Security2/privilege assemblies and prepends formatting |
| `NTFSSecurity.dll` | 36 PowerShell cmdlets; BaseCmdlet path/privilege behavior |
| `Security2.dll` | DACL/SACL objects, owners, inheritance, effective access, Win32 |
| AlphaFS | Long-path files/directories/links |
| PrivilegeControl / ProcessPrivileges | Token privilege operations |
| `en-US/NTFSSecurity.dll-Help.xml` | Committed help generated from cmdlet Markdown |

## Decisions

Read only task-relevant records; the index controls routing.

| # | Decision |
| --- | --- |
| 1 | [Use the canonical Memory Bank base](decisions/0001-canonical-memory-bank.md) |
| 2 | [Cmdlet reference stays platyPS markdown](decisions/0002-platyps-cmdlet-reference.md) |
| 3 | [Document the source at HEAD](decisions/0003-document-source-at-head.md) |
| 4 | [Online help points to GitHub](decisions/0004-online-help-on-github.md) |
| 5 | [Document defects, don't fix them in docs work](decisions/0005-document-defects-separately.md) |
| 6 | [CI checks the docs against a build of the source](decisions/0006-ci-checks-docs-against-build.md) |
| 7 | [CHANGELOG lists user-visible changes only](decisions/0007-changelog-user-visible-only.md) |
| 8 | [Commit the generated help file and check it in CI](decisions/0008-commit-generated-help.md) |
| 9 | [Keep the documentation on GitHub](decisions/0009-docs-on-github.md) |
| 10 | [One version for the manifest, assemblies, and changelog](decisions/0010-one-version.md) |
| 11 | [CI and the wiki run on GitHub Actions](decisions/0011-github-actions.md) |
| 12 | [Releases are built and published by CI on a version tag](decisions/0012-ci-releases.md) |
| 13 | [Set-NTFSInheritance keeps entries like the dedicated cmdlets](decisions/0013-set-inheritance-keeps-entries.md) |
| 14 | [Repository hardening is optional](decisions/0014-repository-hardening-optional.md) |
| 15 | [Merge stacked pull requests in order with merge commits](decisions/0015-merge-stacks-with-merge-commits.md) |
| 16 | [Fix only reproducible bugs](decisions/0016-fix-reproducible-bugs-only.md) |
| 17 | [Issue labels](decisions/0017-issue-labels.md) |
| 18 | [NTFSSecurity will be archived](decisions/0018-archive-for-windowsaccesscontrol.md) |
| 19 | [Cmdlets write only the sections that they change](decisions/0019-write-only-changed-sections.md) |
| 20 | [Live tests in a lab live in Tests\Lab](decisions/0020-live-tests-in-tests-lab.md) |
| 21 | [A quality gate before 5.0.0](decisions/0021-quality-gate-before-5.0.0.md) |
| 22 | [The behavior changes of Phase 2 (proposed)](decisions/0022-phase-2-behavior-changes.md) |
| 23 | [Non-Windows file servers before 5.0.0, #34 (proposed)](decisions/0023-non-windows-file-servers.md) |

## Patterns

### Cmdlets and security sections

- BaseCmdlet resolves relative paths against the current filesystem
  location; file-object input binds FullName through path transformation.
- Write only changed/read sections (Decision 19); a descriptor parameter
  changes memory until `Set-NTFSSecurityDescriptor` persists it.
- Access denial can retry through InvokeAsOwner; restore the previous owner
  on every exit, except a successful descriptor write that intentionally
  sets the owner. Restoration failures must report RestoreOwnerError.
- Privilege cleanup runs in EndProcessing and Dispose, reads current states,
  attempts all cleanup, and preserves explicit enables. Dispose has no stream.
- Pipeline getters never throw; per-item errors name input and allow continuation.
- Folder moves never use CopyAllowed; preserve cross-volume source folders.
- Apply implied Hidden/Force before deciding to emit, including the first item.
- A catch-all for the failures of one item must pass on what a later command
  raises through a Write call. A downstream throw is an ordinary exception,
  so a type check finds only the end of the pipeline, break, and continue.
  BaseCmdlet notes the exception that its WriteObject, WriteError,
  WriteVerbose, and WriteDebug raised (WriteWarning is not noted: no catch-all
  encloses it); `IsFromLaterCommand` recognizes it, and the type check
  `PipelineControl.IsEnd` backs it up for other calls into PowerShell. A write
  inside a helper, such as the owner restore of `InvokeAsOwner`, is an
  accepted gap: its handler reports the item's own error, which raises too.
  Prefer writing outside the try. `Tests/PipelineControl.Tests.ps1` has rows
  for every cmdlet: add a row for a new one, and keep the typed-throw rows
  (they fail if PowerShell stops wrapping a thrown exception).
- Record an enabled privilege before the next write, which a later command
  can answer with an exception: Dispose disables only what is recorded.
- `Get-ChildItem2 -Filter` has two matchers: the AlphaFS enumeration, whose
  dot rules also differ from those of `Get-ChildItem` (probe: `Report.*` and
  `Rep*.` in both editions), and a PowerShell wildcard on the name, where only
  `*` and `?` are special. `*.*` is treated as `*`; the other dot patterns are
  pinned by `ItemCmdlets.Tests` and are an open maintainer decision.

### Tests and documentation

- Tests import Release in isolated processes, both editions and privilege
  modes. File/ACL/link fixtures use shared sandbox guards and cleanup.
  Privilege-dependent skips must have eligible counterparts in the matrix.
- Assert persisted state, errors/targets, continuation, and no failed
  PassThru output. Prove new characterization guards with bounded mutations;
  restore source exactly and rebuild before green validation or packaging.
  Apply the mutations of one round together only when no guard can fail
  because of another mutation; otherwise split the rounds.
- A test that arranges a retry asserts its precondition (the plain write is
  denied), or it can pass without reaching the retry.
- A test variable must not take the name of an automatic variable such as
  `$foreach`: Pester runs the block inside a foreach, and the value is lost.
- The CI scripts set `$ErrorActionPreference = 'Stop'`; focused runs do the
  same, and a test that needs a non-terminating error (for example to take it
  through `2>&1`) names `-ErrorAction Continue`.
- Fixture DACLs use .NET SetAccessControl, not Set-Acl's unintended SACL writes.
- Scope/descendant expectations are independent of the production converter.
- Drive-root tests map a sandbox folder with `subst` through
  `New-TestDriveMapping` (elevated only; the basic token cannot). Tests that
  need a letter without a volume take the lowest free one.
- Desktop platyPS: generate help, rebuild, round-trip unchanged, check links.
  platyPS 0.14.2 turns a pair of asterisks in a paragraph into emphasis, also
  inside backticks, and the help drops them: write the words, put patterns in
  example code blocks, and check the generated XML.
- Live tests use only approved lab targets, SMB then independent server state;
  Get/SetFileSecurity preserves stored DACLs; rights oracles use S4U tokens.
- A suite that is green on the development host and on CI says little about a
  feature that the environment lacks. The matrix found three defects that every
  earlier run had missed because the host is outside a domain and the CI
  runner's token differs: run the suite on a domain member, on other builds, and
  as a basic user before a release, and classify a failure by a probe under the
  real tokens (elevated, filtered, local standard, domain standard) before
  calling it a defect or a design.
- A fixture that deletes an account and creates it again with the same name
  gets the old SID and groups from Kerberos S4U logons (the oracle of the live
  tests, and the Authz functions behind `Get-NTFSEffectiveAccess`) on the
  domain controller and on member servers for more than seven minutes, and no
  cache flush helped (a ticket purge renews only the session's own token). A
  failure that follows the order of the cells and not the version of the
  module points to such state: run a loop probe with the baseline and the
  candidate side by side before blaming the code. The controller names the
  account of case 3 anew for each new fixture.

### CI results and publication

- Use Path.Combine then GetFullPath for a rooted-or-repository-relative
  result path; Join-Path appends even a rooted child and corrupts it.
- Discovery handles only expected PackageNotFound as absence; repository,
  authentication, and network errors remain failures.
- Rerun/uncertain-upload success requires Gallery SHA-512 equality with the
  exact build artifact. Base64 is case-sensitive: use ordinal comparison.
  Missing/different/unverifiable metadata preserves the upload error.
- Secrets stay by environment reference, never in process arguments/logs.
  Test all external publication commands with mocks; no test may upload.
- AltCover aggregates all four sequential runs without --save. Report
  sequence points, not unique source lines; keep unmatched paths visible.