diff --git a/go/default.nix b/go/default.nix
index 819ac13a9..598b9239e 100644
--- a/go/default.nix
+++ b/go/default.nix
@@ -262,6 +262,14 @@ let
   # gofumpt/gotools are the same igloo `pkgs` builds the dev-shell carries,
   # so the Go output matches the dev-loop formatter. null on the non-flake
   # `import ./go/default.nix` path (treelint absent).
+  # tommy's conformist codegen linter driver ([linter.tommy-codegen]), owned by
+  # the tommy flake so the pinned tommy input resolves which tommy backs it (no
+  # per-repo driver duplication). It bakes that tommy in and skips when go is
+  # absent. Regenerates the *_tommy.go companions so they land in the
+  # `conformist --commit` chore; `just build-go-generate` remains the
+  # NATO-ordered regen path.
+  tommyCodegen = tommy.packages.${system}.conformist-tommy-codegen;
+
   treelint-fmt =
     if treelint == null then
       null
@@ -275,6 +283,13 @@ let
           pkgs.nixfmt
           pkgs.shfmt
           pkgs.shellcheck
+          # tommy (TOML formatter, [formatter.tommy]) + go + the codegen driver
+          # ([linter.tommy-codegen]), so the wrapper resolves the formatter and
+          # the codegen repair regen. go is needed by `tommy generate`'s
+          # go/packages analysis in repair mode.
+          tommy.packages.${system}.default
+          pkgs.go_1_26
+          tommyCodegen
         ];
         text = ''exec conformist "$@"'';
       };
diff --git a/treelint.toml b/treelint.toml
index 218525362..95eaec681 100644
--- a/treelint.toml
+++ b/treelint.toml
@@ -53,6 +53,13 @@ command = "shfmt"
 options = ["-w", "-i", "2", "-s", "-ci"]
 includes = ["*.sh", "*.bash"]
 
+# TOML via tommy's CST-preserving formatter (`tommy fmt`). treelint.toml itself
+# is excluded above (intentional layout).
+[formatter.tommy]
+command = "tommy"
+options = ["fmt"]
+includes = ["*.toml"]
+
 # Linter: shellcheck runs read-only in `treelint check` (no repair-command, so
 # it is a no-op in repair mode). Catches shell bugs the formatters miss.
 [linter.shellcheck]
@@ -61,3 +68,19 @@ includes = ["*.sh", "*.bash"]
 # go/vimdiff.bash is the vendored upstream git-vimdiff mergetool test harness;
 # it carries ~40 shellcheck findings we don't own. shfmt still formats it.
 excludes = ["go/vimdiff.bash"]
+
+# tommy codegen as a REPAIR linter: `treelint` / `conformist --commit` runs
+# `tommy generate` for every `//go:generate tommy generate` source file, so the
+# regenerated *_tommy.go companions land in the auto-fix chore. The driver
+# self-gates on tommy + go (present on the treelint-fmt wrapper PATH), so it is a
+# no-op where the toolchain is absent. The CHECK command is a deliberate no-op
+# (`true`) so `treelint check` never reports false codegen drift — `tommy
+# generate --check` compares against tommy's raw render, which differs from the
+# committed file once it is re-run through gofumpt (see `just build-go-generate`
+# / `codemod-go-fmt`); true staleness stays gated by that recipe.
+# passes-files=false: the driver walks the tree for the directive itself.
+[linter.tommy-codegen]
+command = "true"
+repair-command = "conformist-tommy-codegen"
+includes = ["*.go", "**/*.go"]
+passes-files = false