diff --git a/nibabies/cli/tests/test_parser.py b/nibabies/cli/tests/test_parser.py
index e2be6190..bd0c83ea 100644
--- a/nibabies/cli/tests/test_parser.py
+++ b/nibabies/cli/tests/test_parser.py
@@ -82,9 +82,9 @@ def test_parser_valid(tmp_path, args):
         ('1000MB', 1),
         ('1T', 1000),
         ('1TB', 1000),
-        ('%dK' % 1e6, 1),
-        ('%dKB' % 1e6, 1),
-        ('%dB' % 1e9, 1),
+        (f'{1e6:.0f}K', 1),
+        (f'{1e6:.0f}KB', 1),
+        (f'{1e9:.0f}B', 1),
     ],
 )
 def test_memory_arg(tmp_path, argval, gb):
diff --git a/nibabies/config.py b/nibabies/config.py
index 4c6263e7..70f309cb 100644
--- a/nibabies/config.py
+++ b/nibabies/config.py
@@ -130,11 +130,10 @@
     # Just get so analytics track one hit
     from contextlib import suppress
 
-    from requests import ConnectionError, ReadTimeout
-    from requests import get as _get_url
+    import requests
 
-    with suppress((ConnectionError, ReadTimeout)):
-        _get_url('https://rig.mit.edu/et/projects/nipy/nipype', timeout=0.05)
+    with suppress((requests.ConnectionError, requests.ReadTimeout)):
+        requests.get('https://rig.mit.edu/et/projects/nipy/nipype', timeout=0.05)
 
 # Execution environment
 _exec_env = os.name
diff --git a/nibabies/interfaces/reports.py b/nibabies/interfaces/reports.py
index c0e0c8a3..b99d921f 100644
--- a/nibabies/interfaces/reports.py
+++ b/nibabies/interfaces/reports.py
@@ -274,13 +274,13 @@ def _generate_segment(self):
         reg = {
             'FSL': [
                 'FSL <code>flirt</code> with boundary-based registration'
-                ' (BBR) metric - %d dof' % dof,
+                f' (BBR) metric - {dof} dof',
                 'FSL <code>flirt</code> rigid registration - 6 dof',
             ],
             'FreeSurfer': [
                 'FreeSurfer <code>bbregister</code> '
-                '(boundary-based registration, BBR) - %d dof' % dof,
-                'FreeSurfer <code>mri_coreg</code> - %d dof' % dof,
+                f'(boundary-based registration, BBR) - {dof} dof',
+                f'FreeSurfer <code>mri_coreg</code> - {dof} dof',
             ],
         }[self.inputs.registration][self.inputs.fallback]
 
diff --git a/nibabies/reports/core.py b/nibabies/reports/core.py
index 2b0c142e..ed7ccdd2 100644
--- a/nibabies/reports/core.py
+++ b/nibabies/reports/core.py
@@ -58,7 +58,7 @@ def generate_reports(
 
         logger = logging.getLogger('cli')
         error_list = ', '.join(
-            '%s (%d)' % (subid, err)
+            f'{subid} ({err})'
             for subid, err in zip(sub_ses_list, report_errors, strict=False)
             if err
         )
diff --git a/nibabies/workflows/bold/outputs.py b/nibabies/workflows/bold/outputs.py
index befeaa24..36884c4a 100644
--- a/nibabies/workflows/bold/outputs.py
+++ b/nibabies/workflows/bold/outputs.py
@@ -133,7 +133,7 @@ def prepare_timing_parameters(metadata: dict):
         if run_stc:
             first, last = st[0], st[-1]
             frac = config.workflow.slice_time_ref
-            tzero = np.round(first + frac * (last - first), 3)
+            tzero = float(np.round(first + frac * (last - first), 3))
             timing_parameters['StartTime'] = tzero
 
     return timing_parameters
diff --git a/nibabies/workflows/bold/stc.py b/nibabies/workflows/bold/stc.py
index 4c0ae8c8..92c0fe53 100644
--- a/nibabies/workflows/bold/stc.py
+++ b/nibabies/workflows/bold/stc.py
@@ -100,7 +100,7 @@ def init_bold_stc_wf(metadata, name='bold_stc_wf'):
     frac = config.workflow.slice_time_ref
     tzero = np.round(first + frac * (last - first), 3)
 
-    afni_ver = ''.join('%02d' % v for v in afni.Info().version() or [])
+    afni_ver = ''.join(f'{v:02d}' % v for v in afni.Info().version() or [])
     workflow = Workflow(name=name)
     workflow.__desc__ = f"""\
 BOLD runs were slice-time corrected to {tzero:0.3g}s ({frac:g} of slice acquisition range