diff --git a/src/tests/modules/punk/ansi/testsuites/ansi/grepstr.test b/src/tests/modules/punk/ansi/testsuites/ansi/grepstr.test
index d2593606..d09e3d75 100644
--- a/src/tests/modules/punk/ansi/testsuites/ansi/grepstr.test
+++ b/src/tests/modules/punk/ansi/testsuites/ansi/grepstr.test
@@ -70,6 +70,15 @@ namespace eval ::testspace {
         if {$code} {
             return -options $ropts $r
         }
+        if {[string first \x00 $caught] >= 0} {
+            #stderr backed by a windows console: the pushed transform receives the console
+            #driver's utf-16le wide-char byte stream rather than encoded bytes (each ascii
+            #char arrives NUL-interleaved), so content assertions never match - decode.
+            #(found 2026-07-19 via the sibling helper in punk/args dynamic.test failing in
+            #console-attached singleproc runs; piped stderr and -jobs children are unaffected)
+            set enc [expr {"utf-16le" in [encoding names] ? "utf-16le" : "unicode"}]
+            set caught [encoding convertfrom $enc $caught]
+        }
         return $caught
     }
 
diff --git a/src/tests/modules/punk/args/testsuites/args/dynamic.test b/src/tests/modules/punk/args/testsuites/args/dynamic.test
index db073022..940aaa29 100644
--- a/src/tests/modules/punk/args/testsuites/args/dynamic.test
+++ b/src/tests/modules/punk/args/testsuites/args/dynamic.test
@@ -34,6 +34,15 @@ namespace eval ::testspace {
         if {$code} {
             return -options $ropts $r
         }
+        if {[string first \x00 $caught] >= 0} {
+            #stderr backed by a windows console: the pushed transform receives the console
+            #driver's utf-16le wide-char byte stream rather than encoded bytes (each ascii
+            #char arrives NUL-interleaved), so content assertions never match - decode.
+            #(found 2026-07-19: dynamic_bad_tag_warns_once failed ONLY in console-attached
+            #singleproc runs; piped/file stderr and -jobs child processes deliver plain bytes)
+            set enc [expr {"utf-16le" in [encoding names] ? "utf-16le" : "unicode"}]
+            set caught [encoding convertfrom $enc $caught]
+        }
         return $caught
     }
 
diff --git a/src/tests/modules/punk/ns/testsuites/ns/corp.test b/src/tests/modules/punk/ns/testsuites/ns/corp.test
index 74681831..4bdd024e 100644
--- a/src/tests/modules/punk/ns/testsuites/ns/corp.test
+++ b/src/tests/modules/punk/ns/testsuites/ns/corp.test
@@ -198,6 +198,15 @@ namespace eval ::testspace {
         if {$code} {
             return -options $ropts $r
         }
+        if {[string first \x00 $caught] >= 0} {
+            #stderr backed by a windows console: the pushed transform receives the console
+            #driver's utf-16le wide-char byte stream rather than encoded bytes (each ascii
+            #char arrives NUL-interleaved), so content assertions never match - decode.
+            #(found 2026-07-19 via the sibling helper in punk/args dynamic.test failing in
+            #console-attached singleproc runs; piped stderr and -jobs children are unaffected)
+            set enc [expr {"utf-16le" in [encoding names] ? "utf-16le" : "unicode"}]
+            set caught [encoding convertfrom $enc $caught]
+        }
         return $caught
     }
     #sp n - n plain spaces (keeps expected values reviewable)