Performs safe, behavior-preserving refactoring of C#/.NET code, verified with build, tests, and analyzers. USE FOR: rename or move a symbol/type/file; extract a method/type/interface; inline a wrapper/method/local; merge or consolidate near-identical classes or duplicate helpers; split or modernize C# code; generated/partial declarations; public, serialized, friend-assembly, or multi-targeted contracts; and mixed requests where a feature, bug fix, package/framework upgrade, public nullability change, or other behavior/contract change is presented as a refactor and must be separated or declined. DO NOT USE FOR: ordinary feature or bug-fix requests not framed as refactoring; upgrades after reclassification (use dotnet-upgrade); new tests; or formatting-only passes (use dotnet format).
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Performs safe, behavior-preserving refactoring of C#/.NET code, verified with build, tests, and analyzers. USE FOR: rename or move a symbol/type/file; extract a method/type/interface; inline a wrapper/method/local; merge or consolidate near-identical classes or duplicate helpers; split or modernize C# code; generated/partial declarations; public, serialized, friend-assembly, or multi-targeted contracts; and mixed requests where a feature, bug fix, package/framework upgrade, public nullability change, or other behavior/contract change is presented as a refactor and must be separated or declined. DO NOT USE FOR: ordinary feature or bug-fix requests not framed as refactoring; upgrades after reclassification (use dotnet-upgrade); new tests; or formatting-only passes (use dotnet format).
A refactor changes structure, never observable . Do the edit with binding-aware tools, then confirm behavior held with a build + the relevant tests. Keep the effort proportional to the change: a one-line local rename does not need the ceremony a public multi-targeted change does.
Version history
Read only enough repository context to classify the request. Do this before restoring, building, or making an edit. If the entire requested operation changes behavior or cannot preserve the relevant public/source contract, the correct result of this skill is a decisive handoff, not an implementation attempt:
Not a behavior-preserving refactor: <specific reason>.No files changed.Next workflow: <workflow>. Then stop. Do not add manual implementation steps, alternatives,
an offer to proceed without the workflow, or a follow-up question — even when that workflow is unavailable.| Requested as a "refactor" | Classification and action |
|---|---|
| Framework or NuGet version change | Upgrade. Do not edit or validate the upgrade here; hand off to dotnet-upgrade. |
| New capability, flag, endpoint, tier, or behavior | Feature. Do not implement it here; hand off to the repository's feature workflow. |
| Threshold, rate, output, or bug-result change | Behavior change. Defer it and hand off to the repository's bug-fix or behavior-change workflow; still complete any clearly separable structural operation. |
| Tighten or loosen a shipped/public nullable annotation | Source-contract change. Leave the declaration and API record unchanged; hand off to the repository's API-contract workflow. |
The three-line stop response applies only when the entire request is outside behavior-preserving
refactoring. For a mixed request, perform only a clearly separable structural operation and explicitly
defer the behavior/contract change. Never state No files changed. after completing that structural
operation, and never modify tests to make an unauthorized behavior change appear preserved.
Resolve the repository root first (git rev-parse --show-toplevel) and resolve any prompt-provided
relative solution/project path inside that root. Search and edit only that workspace. Never use
filesystem-wide search or select a similarly named clone, temporary directory, build output, or
another worktree because a file also exists there. If the named path is absent from the current
repository, stop and report that mismatch instead of guessing another workspace.
The #1 way a "rename" silently corrupts code is editing textual matches (comments, strings, unrelated
overloads) instead of real bindings. Find every binding reference first, then edit semantically. Use
the strongest tool available: an IDE/Roslyn workspace refactoring, then the C# LSP the
dotnet plugin declares
(findReferences, goToDefinition, incomingCalls, rename code action), then analyzer code-fixes /
Roslynator, then compiler-validated edits (edit the true bindings, rebuild, let the compiler flag misses).
Plain find/replace only when scope is provably tiny and every hit is verified. Include every partial
declaration, and edit the generator input, never generated (*.g.cs) output.
For the operation → Roslyn-provider mapping and representative PRs, see references/operation-catalog.md.
When de-duplicating, preserve the ownership direction stated by the code or request. If B duplicates
an implementation already owned by A, keep A canonical and make B delegate to it; do not invert
the dependency merely because either direction compiles. Preserve public compatibility wrappers when
the duplicate surface is shipped, and migrate only in-repo callers that are safe to move.
Use the first matching row instead of applying the requested operation mechanically:
| Situation | Do | Never |
|---|---|---|
| Inline an internal, unshipped pass-through wrapper | Migrate every binding reference to the target, remove the wrapper, then compile to catch misses. | Keep dead indirection "for compatibility" when no compatibility boundary exists. |
| Inline or remove a shipped/public wrapper | Migrate ordinary in-repo callers, but retain an [Obsolete] forwarding entry point unless the request explicitly authorizes a breaking change. | Delete a shipped API merely because all current source callers were migrated. |
| Rename a member reached by a string, reflection, DI, or configuration | Rename binding-based callers; preserve the observed external name with a forwarding shim or metadata, and exercise the old-name path. | Rewrite an external/configured name just to make the new source name consistent. |
| Extract duplicated logic whose callers pass different values | Extract the algorithm and pass each caller's existing inputs through unchanged. | Collapse distinct inputs, evaluation order, rounding, or side effects into one caller's version. |
Rename code compiled under #if or multiple TFMs | Update every source branch and validate each target framework explicitly. | Treat a green default-target build as evidence for unbuilt branches. |
| Merge near-identical types | Parameterize only the values that differ, migrate every construction site, and preserve each old value exactly. If the old types are internal/unshipped and the request says to merge into one type, delete their declarations. | Retain unnecessary aliases, static holders, factories, or wrapper types that leave the requested merge incomplete; introduce a new hierarchy or behavior. |
Compilation proves binding compatibility, not every external contract. Before renaming or moving a
type/member, check whether its name or metadata is observed by serialization, reflection, dependency
injection, configuration binding, source generators, P/Invoke, or dynamic.
| Boundary | Required decision |
|---|---|
| Serialized/configuration name | Preserve the external name with the repository's existing mechanism (for example, JsonPropertyName) while migrating C# callers; run a focused round-trip or payload test. |
| Public nullable annotation | The mandatory classification gate applies: leave it unchanged and hand off as a source-contract change. |
| Uncovered reflection or runtime lookup | Do not guess that a compile-clean rename is safe. Preserve the observed name or stop and report the unverified runtime boundary. |
Confirm behavior is preserved after the edit — scaled to blast radius, not a fixed ceremony:
private member, one file, single target framework, no public
surface, no partial/generated/#if): skip a separate baseline unless the tree is already suspect.
Make the edit, then run the narrowest build and relevant tests once. Let the compiler catch missed
references.#if/platform branches, or
partial/generated code): establish a baseline, then run an explicit build and the relevant tests for
each target framework after the edit (a test command's implicit build is not separate build evidence;
a green default build can hide a break on another TFM), and run the hazards check below.Use the repo's own build/test workflow when it documents one (README/CONTRIBUTING, build.*, eng/,
global.json, .github/workflows); its instructions win over any generic command.
findReferences/goToDefinition/rename) and include all partial declarations.Otherwise:
dotnet build # 0 errors
dotnet test # stays green; same pass count as before
One operation per step; never mix a refactor and a behavior change in the same step. On red, stop and report the failure; repair only your edit without discarding unrelated worktree changes.
Keep the handoff concise and evidence-based:
If — and only if — the change touches a public symbol, a multi-targeted project, or
partial/generated code, some breaks won't show up as a failing test. Search the repo for the surface
that governs the symbol (don't assume): the public-API gate (PublicAPI.Shipped/Unshipped.txt for
PublicApiAnalyzers, and/or ApiCompat/<EnablePackageValidation> — not interchangeable),
<TargetFrameworks>/#if branches, and InternalsVisibleTo. Moving a public type to another assembly
needs [TypeForwardedTo] in the original assembly; a move within one assembly does not. A public
rename needs an [Obsolete] shim, not a forwarder. For a provably local/private change, skip these
checks.
dynamic,
P/Invoke) — flag it.In these kits
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