diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
new file mode 100644
index 0000000..c8d09e8
--- /dev/null
+++ b/.github/copilot-instructions.md
@@ -0,0 +1,68 @@
+# Copilot PR-review instructions for ANcpLua.Roslyn.Utilities
+
+Utility library for Roslyn incremental generators, analyzers, and code-fix
+providers. Ships five NuGet packages: a binary library, a `Sources` source-only
+package (rewritten to `internal` at pack via `Transform-Sources.ps1`), `Polyfills`,
+`Testing` (analyzer/generator/codefix harness), and `Testing.Aot`. Main library +
+`Sources` target `netstandard2.0` so Roslyn-hosted consumers can absorb them;
+`Testing` targets `net10.0`. `TreatWarningsAsErrors=true` repo-wide; all analyzer
+diagnostics elevated to error in `.editorconfig`. This file scopes to PR review only.
+
+## Flag
+
+- New API in the main library (or `Sources`) that pulls in dependencies not
+  available on `netstandard2.0` — `System.Text.Json`, modern BCL methods, anything
+  ns2.1+. Such code can land in `Testing` or downstream consumers, but not in
+  the analyzer-hosted surface.
+- New `public` type or member added to the `Sources` project without a
+  `#if ANCPLUA_ROSLYN_PUBLIC public #else internal #endif` guard — the Sources
+  package rewrites visibility on pack, so adding bare `public` breaks the
+  internal-on-pack contract.
+- Storing `ISymbol`, `SyntaxNode`, `SyntaxTree`, or any Roslyn reference type as
+  a `HashSet<T>` / `Dictionary<TKey, …>` key — reference equality, cache misses
+  on rebuild, breaks generator incrementality.
+- New allocations in generator hot paths: `.ToArray()` / `.ToList()` on a `Span`
+  inside `Append` loops, capturing closures in `Dict.GetOrAdd`/`GetOrInsert`,
+  boxing of value types via `object`. The `closure-free` `GetOrInsert<TContext>`
+  + `static` lambda + `ValueStringBuilder` patterns are the established shape.
+- Public types intended for generator payloads added without value equality —
+  use `readonly record struct` (or `EquatableArray<T>` for collections), never
+  classes or non-record structs.
+- File-I/O via `System.IO.File` / `System.IO.Directory` outside `Guard.cs` —
+  `Guard.cs` is the single allow-listed call site (suppressed `RS1035`).
+
+## utilities-specific
+
+- The `Sources` package is for source generators that can't take a binary
+  reference. Any new helper meant for that consumer set goes in
+  `src/ANcpLua.Roslyn.Utilities/` (the shared tree) and gets exposed via the
+  `Sources` package on pack.
+- `Polyfills` package supplies `init`, `required`, `Index`/`Range`, nullable +
+  trim attributes for `netstandard2.0` consumers. Don't duplicate polyfills in
+  the main library.
+- `Testing` ships a fluent generator/analyzer/codefix harness. New test helpers
+  belong there, not in individual consumer test projects.
+- `EquatableArray<T>` is `ref`-struct-like (value-equality wrapper); use it for
+  collection fields in generator records, not `ImmutableArray<T>` (no equality)
+  or `T[]` (reference equality).
+
+## Do not flag
+
+- Allow-listed suppressions in `Guard.cs`: `#pragma warning disable RS1035`
+  (file I/O legal here, non-analyzer call sites only).
+- Polyfills suppressions: `CA1019`, `RCS1251`, `IDE0300`, `CA1064`, `CA1812`,
+  `SA1623`, `RCS1157` — all on shim types.
+- Testing-csproj suppressions: `NU1903`, `RS1036`, `RS1038`, `RS1041`, `CA1019`,
+  `NU5104`, `CA1859`, `RS0030`, `CA1307`, `IDE1006`, `CA1002`, `CA1000`,
+  `CS1574`, `CS1591` — test-infra concessions.
+- `[ExcludeFromCodeCoverage]` only appears on polyfills, not on mainline types
+  — that's intentional, mainline gets coverage.
+- `Testing` package's use of `System.Text.Json` and modern BCL — it's `net10.0`,
+  not the constrained surface.
+
+## Project context
+
+Solo-dev repo. The Sources package is consumed by `ANcpLua.Analyzers` and
+`ANcpLua.Agents.Testing` (and downstream generators); regressions ripple. Breaking
+changes are allowed in the same session — bump major, fix consumers, ship.
+Don't suggest backwards-compat shims or feature flags within a single PR.
diff --git a/.github/workflows/nuget-publish.yml b/.github/workflows/nuget-publish.yml
index dfe1c8e..343e0ca 100644
--- a/.github/workflows/nuget-publish.yml
+++ b/.github/workflows/nuget-publish.yml
@@ -49,7 +49,7 @@ jobs:
               MAJOR=${BASH_REMATCH[1]}
               MINOR=${BASH_REMATCH[2]}
               PATCH=${BASH_REMATCH[3]}
-              if git tag --points-at HEAD | grep -qx "$LATEST_TAG"; then
+              if git tag --points-at HEAD | grep -qFx "$LATEST_TAG"; then
                 VERSION="$MAJOR.$MINOR.$PATCH"
                 echo "HEAD is tagged $LATEST_TAG — reusing version: $VERSION"
               else
@@ -116,7 +116,7 @@ jobs:
   #   3. No NUGET_API_KEY secret required — OIDC handles auth.
   publish:
     needs: [version, build]
-    if: github.event_name == 'push' && github.ref == 'refs/heads/main' || github.event_name == 'workflow_dispatch'
+    if: (github.event_name == 'push' && github.ref == 'refs/heads/main') || github.event_name == 'workflow_dispatch'
     runs-on: ubuntu-latest
     environment: nuget
     permissions: