diff --git a/recipe_modules/bazel/api.py b/recipe_modules/bazel/api.py
index 97ceb53..1e534c5 100644
--- a/recipe_modules/bazel/api.py
+++ b/recipe_modules/bazel/api.py
@@ -24,7 +24,7 @@
 from recipe_engine import recipe_api
 
 if TYPE_CHECKING:  # pragma: no cover
-    from typing import Any, Sequence
+    from typing import Any, Callable, Sequence
     from recipe_engine import config_types
     from RECIPE_MODULES.pigweed.checkout import api as checkout_api
 
@@ -222,6 +222,7 @@
 class UpdateCommitHashResult:
     old_revision: str
     project_name: str | None
+    finalize: Callable[[], None] | None = None
 
 
 class LineProxy:
@@ -382,6 +383,7 @@
         num_nearby_lines: int = 10,
         path: config_types.Path | None,
         replace_remote: bool = False,
+        delay_write: bool = False,
     ) -> UpdateCommitHashResult | None:
         if not path:
             path = checkout.root / 'WORKSPACE'
@@ -457,17 +459,28 @@
                     project_names.append(match.group('name'))
                     break
 
-        self.m.file.write_text(
-            f'write new {path.name}',
-            path,
-            ''.join(
-                f'{x}\n'
-                for x in lines[num_nearby_lines:-num_nearby_lines]
-                if x is not None
-            ),
-        )
+        def write():
+            self.m.file.write_text(
+                f'write new {path.name}',
+                path,
+                ''.join(
+                    f'{x}\n'
+                    for x in lines[num_nearby_lines:-num_nearby_lines]
+                    if x is not None
+                ),
+            )
 
-        return UpdateCommitHashResult(
-            old_revision=old_revision,
-            project_name=', '.join(project_names),
-        )
+        if delay_write:
+            return UpdateCommitHashResult(
+                old_revision=old_revision,
+                project_name=', '.join(project_names),
+                finalize=write,
+            )
+
+        else:
+            write()
+
+            return UpdateCommitHashResult(
+                old_revision=old_revision,
+                project_name=', '.join(project_names),
+            )
diff --git a/recipe_modules/bazel/tests/update_commit_hash.proto b/recipe_modules/bazel/tests/update_commit_hash.proto
index 84123ca..71bb3c8 100644
--- a/recipe_modules/bazel/tests/update_commit_hash.proto
+++ b/recipe_modules/bazel/tests/update_commit_hash.proto
@@ -22,4 +22,7 @@
 
   // Repository referred to by the WORKSPACE file.
   string project_remote = 2;
+
+  // Provide a callback to write data instead of writing it immediately.
+  bool delay_write = 3;
 }
diff --git a/recipe_modules/bazel/tests/update_commit_hash.py b/recipe_modules/bazel/tests/update_commit_hash.py
index 80ec58b..6cf9dff 100644
--- a/recipe_modules/bazel/tests/update_commit_hash.py
+++ b/recipe_modules/bazel/tests/update_commit_hash.py
@@ -66,9 +66,13 @@
         new_revision='ffffffffffffffffffffffffffffffffffffffff',
         path=path,
         replace_remote=True,
+        delay_write=props.delay_write,
     )
 
     if update_result:
+        if update_result.finalize:
+            update_result.finalize()
+
         with api.step.nest('update result'):
             api.step.empty(f'old revision {update_result.old_revision}')
             api.step.empty(f'project name {update_result.project_name}')
@@ -112,7 +116,10 @@
 
     yield api.test(
         'multiple',
-        properties(project_remote=_url('pigweed/pigweed')),
+        properties(
+            project_remote=_url('pigweed/pigweed'),
+            delay_write=True,
+        ),
         api.step_data(
             'read old WORKSPACE',
             api.file.read_text(api.bazel.MULTIPLE_ROLL_WORKSPACE_FILE),