diff --git a/.gitignore b/.gitignore
index 5c53913..b86b887 100644
--- a/.gitignore
+++ b/.gitignore
@@ -23,6 +23,12 @@ _testmain.go
 *.test
 *.prof
 
+# Config test fixtures use a .yml.test suffix and must be tracked even though
+# the *.test rule above (for compiled Go test binaries) would otherwise ignore
+# them. Without this negation a plain `git add` silently drops them and the
+# cmd/go-mutesting config tests fail on a fresh checkout.
+!testdata/configs/*.yml.test
+
 # go-mutesting build output and run artifacts
 /go-mutesting
 report.json
diff --git a/CHANGELOG.md b/CHANGELOG.md
index bfe6e01..8df0776 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,13 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/). This pr
 
 ---
 
+## [v2.6.16] — 2026-05-29
+
+### Fixed
+- Hardened the `cmd/go-mutesting` config test fixtures against the `*.test` `.gitignore` rule. The fixtures (`testdata/configs/*.yml.test`) are already tracked, but their `.yml.test` suffix matches the `*.test` rule meant for compiled Go test binaries, so any future `git rm` + re-add would silently drop them and leave a clean clone with a red test suite. A `.gitignore` negation now keeps them tracked.
+
+---
+
 ## [v2.6.15] — 2026-05-26
 
 ### Fixed
@@ -326,3 +333,4 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/). This pr
 [v2.6.13]: https://github.com/jonbaldie/go-mutesting/compare/v2.6.12...v2.6.13
 [v2.6.14]: https://github.com/jonbaldie/go-mutesting/compare/v2.6.13...v2.6.14
 [v2.6.15]: https://github.com/jonbaldie/go-mutesting/compare/v2.6.14...v2.6.15
+[v2.6.16]: https://github.com/jonbaldie/go-mutesting/compare/v2.6.15...v2.6.16
diff --git a/CLAUDE.md b/CLAUDE.md
index b30dfff..6c8ba6a 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -16,11 +16,14 @@ All packages pass. `internal/importing` and `internal/parser` were once broken i
 | Package | What it does |
 | :--- | :--- |
 | `cmd/go-mutesting/` | Binary entrypoint; all flag wiring and orchestration |
-| `mutator/` | Mutator implementations (arithmetic, branch, expression, loop, numbers, statement) |
+| `mutator/` | Mutator implementations (arithmetic, branch, concurrency, conditional, expression, loop, numbers, select, statement) |
 | `internal/models/` | `Report`, `Stats`, `Mutant` types; MSI and quality gate logic |
 | `internal/gitdiff/` | Git diff line filter for `--git-diff-lines` |
 | `internal/filter/` | Annotation and skip filters |
 | `internal/coverage/` | Coverage profile parsing (`--coverage`) and per-test coverage map (`--per-test`) |
+| `internal/parser/` | Package loading and the AST cache (`ClearPackageCache`) |
+| `internal/annotation/` | Comment-directive filters (block, chain, function, line, regex) |
+| `internal/reportmaker/` | JSON / HTML / agentic report generation |
 
 ## Self-mutation and quality gates