diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index 511dd51..2f8909f 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "2.6.0"
+  ".": "2.6.1"
 }
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8c1e698..6a74c18 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 2.6.1 (2026-02-07)
+
+Full Changelog: [v2.6.0...v2.6.1](https://github.com/moderation-api/sdk-ruby/compare/v2.6.0...v2.6.1)
+
+### Bug Fixes
+
+* **client:** loosen json header parsing ([58cc470](https://github.com/moderation-api/sdk-ruby/commit/58cc470e748a3b3ff04775cf68ef46e27df719a0))
+
 ## 2.6.0 (2026-02-06)
 
 Full Changelog: [v2.5.1...v2.6.0](https://github.com/moderation-api/sdk-ruby/compare/v2.5.1...v2.6.0)
diff --git a/Gemfile.lock b/Gemfile.lock
index f9938b8..968e41a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -11,7 +11,7 @@ GIT
 PATH
   remote: .
   specs:
-    moderation_api (2.6.0)
+    moderation_api (2.6.1)
       cgi
       connection_pool
 
diff --git a/README.md b/README.md
index c1176d3..aa920b7 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@ To use this gem, install via Bundler by adding the following to your application
 <!-- x-release-please-start-version -->
 
 ```ruby
-gem "moderation_api", "~> 2.6.0"
+gem "moderation_api", "~> 2.6.1"
 ```
 
 <!-- x-release-please-end -->
diff --git a/lib/moderation_api/internal/util.rb b/lib/moderation_api/internal/util.rb
index 65240ec..309c890 100644
--- a/lib/moderation_api/internal/util.rb
+++ b/lib/moderation_api/internal/util.rb
@@ -485,7 +485,7 @@ def writable_enum(&blk)
       end
 
       # @type [Regexp]
-      JSON_CONTENT = %r{^application/(?:vnd(?:\.[^.]+)*\+)?json(?!l)}
+      JSON_CONTENT = %r{^application/(?:[a-zA-Z0-9.-]+\+)?json(?!l)}
       # @type [Regexp]
       JSONL_CONTENT = %r{^application/(:?x-(?:n|l)djson)|(:?(?:x-)?jsonl)}
 
diff --git a/lib/moderation_api/version.rb b/lib/moderation_api/version.rb
index f613738..6d0d952 100644
--- a/lib/moderation_api/version.rb
+++ b/lib/moderation_api/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module ModerationAPI
-  VERSION = "2.6.0"
+  VERSION = "2.6.1"
 end
diff --git a/rbi/moderation_api/internal/util.rbi b/rbi/moderation_api/internal/util.rbi
index fa9e8b3..6d3d5f1 100644
--- a/rbi/moderation_api/internal/util.rbi
+++ b/rbi/moderation_api/internal/util.rbi
@@ -296,7 +296,7 @@ module ModerationAPI
       end
 
       JSON_CONTENT =
-        T.let(%r{^application/(?:vnd(?:\.[^.]+)*\+)?json(?!l)}, Regexp)
+        T.let(%r{^application/(?:[a-zA-Z0-9.-]+\+)?json(?!l)}, Regexp)
       JSONL_CONTENT =
         T.let(%r{^application/(:?x-(?:n|l)djson)|(:?(?:x-)?jsonl)}, Regexp)
 
diff --git a/test/moderation_api/internal/util_test.rb b/test/moderation_api/internal/util_test.rb
index e63af0e..e7de629 100644
--- a/test/moderation_api/internal/util_test.rb
+++ b/test/moderation_api/internal/util_test.rb
@@ -171,6 +171,8 @@ def test_json_content
     cases = {
       "application/json" => true,
       "application/jsonl" => false,
+      "application/arbitrary+json" => true,
+      "application/ARBITRARY+json" => true,
       "application/vnd.github.v3+json" => true,
       "application/vnd.api+json" => true
     }