diff --git a/lib/galaxy/dependencies/pinned-requirements.txt b/lib/galaxy/dependencies/pinned-requirements.txt
index e7d54ba104c..04631006923 100644
--- a/lib/galaxy/dependencies/pinned-requirements.txt
+++ b/lib/galaxy/dependencies/pinned-requirements.txt
@@ -102,7 +102,7 @@ groq==1.2.0
 grpcio==1.80.0
 grpcio-status==1.80.0
 gunicorn==26.0.0
-gxformat2==0.26.0
+gxformat2==0.24.0
 h11==0.16.0
 h5grove==4.0.0
 h5py==3.16.0
diff --git a/packages/app/setup.cfg b/packages/app/setup.cfg
index c455dc2cec4..c82489d1449 100644
--- a/packages/app/setup.cfg
+++ b/packages/app/setup.cfg
@@ -51,7 +51,7 @@ install_requires =
     cloudauthz==0.6.0
     cwl-utils
     dparse
-    gxformat2>=0.23.0
+    gxformat2>=0.23.0,!=0.25.0,!=0.26.0
     kombu>=5.3
     lagom
     lxml!=4.2.2
diff --git a/packages/test_base/setup.cfg b/packages/test_base/setup.cfg
index 543e650140c..810482c387b 100644
--- a/packages/test_base/setup.cfg
+++ b/packages/test_base/setup.cfg
@@ -35,7 +35,7 @@ install_requires =
     galaxy-util
     bioblend
     cwltest>=2.5.20240906231108
-    gxformat2>=0.23.0
+    gxformat2>=0.23.0,!=0.25.0,!=0.26.0
     pytest
     pytest-celery
     PyYAML
diff --git a/packages/test_selenium/setup.cfg b/packages/test_selenium/setup.cfg
index ddd713719ea..991e9db1ffb 100644
--- a/packages/test_selenium/setup.cfg
+++ b/packages/test_selenium/setup.cfg
@@ -36,7 +36,7 @@ install_requires =
     galaxy-selenium
     galaxy-test-base
     galaxy-util
-    gxformat2>=0.23.0
+    gxformat2>=0.23.0,!=0.25.0,!=0.26.0
     pytest
     PyYAML
     requests
diff --git a/packages/web_apps/setup.cfg b/packages/web_apps/setup.cfg
index 00da0e5cd05..79f20124f60 100644
--- a/packages/web_apps/setup.cfg
+++ b/packages/web_apps/setup.cfg
@@ -45,7 +45,7 @@ install_requires =
     fastapi>=0.124.0
     gunicorn!=25.1.0
     httpx
-    gxformat2>=0.23.0
+    gxformat2>=0.23.0,!=0.25.0,!=0.26.0
     Mako
     MarkupSafe
     Paste
diff --git a/pyproject.toml b/pyproject.toml
index c3ec9ed16cf..ee17764d0c2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,7 +43,7 @@ dependencies = [
     "future>=1.0.0",  # Python 3.12 support
     "gravity>=1.2.0",  # Python 3.14 support
     "gunicorn!=25.1.0",  # https://github.com/benoitc/gunicorn/discussions/3509
-    "gxformat2>=0.23.0",
+    "gxformat2>=0.23.0,!=0.25.0,!=0.26.0",  # https://github.com/galaxyproject/gxformat2/issues/204
     "h5grove>=1.2.1",
     "h5py>=3.12",  # Python 3.13 support
     "httpx",