diff --git a/.chronus/changes/python-regen-narrow-legacy-baseline-2026-6-3-12-0-0.md b/.chronus/changes/python-regen-narrow-legacy-baseline-2026-6-3-12-0-0.md
new file mode 100644
index 00000000000..8f22c76b273
--- /dev/null
+++ b/.chronus/changes/python-regen-narrow-legacy-baseline-2026-6-3-12-0-0.md
@@ -0,0 +1,7 @@
+---
+changeKind: internal
+packages:
+  - "@typespec/http-client-python"
+---
+
+Only copy the legacy code paths required for tests from the baseline sparse-checkout instead of copying the entire `azure/` and `unbranded/` baseline trees.
diff --git a/packages/http-client-python/eng/scripts/ci/regenerate-common.ts b/packages/http-client-python/eng/scripts/ci/regenerate-common.ts
index 5e6b2b9ed88..1fe6f17d63c 100644
--- a/packages/http-client-python/eng/scripts/ci/regenerate-common.ts
+++ b/packages/http-client-python/eng/scripts/ci/regenerate-common.ts
@@ -716,15 +716,31 @@ export async function prepareBaselineOfGeneratedCode(generatedFolder: string): P
     run(`git fetch --depth 1 origin ${branch}`);
     run(`git checkout FETCH_HEAD`);
 
+    // we don't copy whole generated folder, just the specific subfolders needed for tests
+    // to verify correct preservation/deletion of files and folders during regeneration,
+    // to avoid accidentally including any manually edited code that might be in the repo
+    // and cause confusion when it doesn't get updated during regeneration
+    const legacyCodePathNeededForTests = [
+      "azure/authentication-api-key",
+      "unbranded/authentication-api-key",
+      "azure/authentication-union",
+      "azure/generation-subdir",
+      "azure/generation-subdir2",
+      "unbranded/generation-subdir",
+      "unbranded/generation-subdir2",
+    ];
+
     const sourceRoot = join(tempDir, ...sourceSubdir.split("/"));
-    for (const flavor of ["azure", "unbranded"]) {
-      const src = join(sourceRoot, flavor);
-      const dest = join(testsGeneratedDir, flavor);
+    for (const subPath of legacyCodePathNeededForTests) {
+      const segments = subPath.split("/");
+      const src = join(sourceRoot, ...segments);
+      const dest = join(testsGeneratedDir, ...segments);
       if (!existsSync(src)) {
         console.warn(pc.yellow(`Baseline folder not found: ${src}`));
         continue;
       }
-      console.log(pc.dim(`Copying ${flavor}/ -> ${dest}`));
+      console.log(pc.dim(`Copying ${subPath} -> ${dest}`));
+      await mkdir(dirname(dest), { recursive: true });
       await cp(src, dest, { recursive: true });
     }
 
diff --git a/packages/http-client-python/generator/pygen/preprocess/__init__.py b/packages/http-client-python/generator/pygen/preprocess/__init__.py
index 1c1e575f44b..b2a90c78c47 100644
--- a/packages/http-client-python/generator/pygen/preprocess/__init__.py
+++ b/packages/http-client-python/generator/pygen/preprocess/__init__.py
@@ -171,9 +171,7 @@ def _get_etag_role(parameter: dict[str, Any]) -> Optional[str]:
     return parameter.get("etagRole")
 
 
-def _pick_etag_slot(
-    candidates: list[dict[str, Any]], standard_wire_name: str
-) -> Optional[dict[str, Any]]:
+def _pick_etag_slot(candidates: list[dict[str, Any]], standard_wire_name: str) -> Optional[dict[str, Any]]:
     """Choose which etag-typed header should be promoted to the etag/match_condition slot.
 
     When more than one etag-typed header is present in an operation, prefer the
@@ -258,15 +256,14 @@ def _process_operation_etag_headers(
             elif role == "ifNoneMatch":
                 if_none_match_candidates.append(p)
 
-    property_if_match, property_if_none_match = _resolve_etag_pair(
-        if_match_candidates, if_none_match_candidates
-    )
+    property_if_match, property_if_none_match = _resolve_etag_pair(if_match_candidates, if_none_match_candidates)
 
     if property_if_match and property_if_none_match:
         etag_params = {id(property_if_match), id(property_if_none_match)}
-        operation["parameters"] = [
-            item for item in operation["parameters"] if id(item) not in etag_params
-        ] + [property_if_match, property_if_none_match]
+        operation["parameters"] = [item for item in operation["parameters"] if id(item) not in etag_params] + [
+            property_if_match,
+            property_if_none_match,
+        ]
         operation["hasEtag"] = True
         client["hasEtag"] = True