Add a new Bundler config to control how many specs are fetched:

- ### Problem

  In #9071, I increased the API_REQUEST_SIZE constants to fetch 100
  specifications at once instead of 50.
  Worth to remember that this codepath is exclusively used for servers
  that don't implement the compact index API and where Bundler has to
  fallback on the `/v1/dependencies` endpoint.

  Fetching 100 gems at once seems not supported by some gem servers.
  See #9345

  ### Solution

  I'd like to provide a new Bundler configuration
  `BUNDLE_API_REQUEST_SIZE` to let users of those servers control how
  many dependencies should be fetched at once.

  ### Alternatives

  The other alternative is to revert #9071 and always fetch 50 specs.
  I tried the number 100 on a single rubygem registry (cloudsmith),
  and I don't have data point to know whether this value is supported
  by most registries.

Author: Edouard-chin

bundler/lib/bundler/fetcher/dependency.rb

@@ -50,7 +50,7 @@ def dependency_specs(gem_names)
 
       def unmarshalled_dep_gems(gem_names)
         gem_list = []
-        gem_names.each_slice(Source::Rubygems::API_REQUEST_SIZE) do |names|
+        gem_names.each_slice(api_request_size) do |names|
           marshalled_deps = downloader.fetch(dependency_api_uri(names)).body
           gem_list.concat(Bundler.safe_load_marshal(marshalled_deps))
         end
@@ -74,6 +74,12 @@ def dependency_api_uri(gem_names = [])
         uri.query = "gems=#{CGI.escape(gem_names.sort.join(","))}" if gem_names.any?
         uri
       end
+
+      private
+
+      def api_request_size
+        Bundler.settings[:api_request_size]&.to_i || Source::Rubygems::API_REQUEST_SIZE
+      end
     end
   end
 end

bundler/lib/bundler/man/bundle-config.1

@@ -1,6 +1,6 @@
 .\" generated with Ronn-NG/v0.10.1
 .\" http://github.com/apjanke/ronn-ng/tree/0.10.1
-.TH "BUNDLE\-CONFIG" "1" "February 2026" ""
+.TH "BUNDLE\-CONFIG" "1" "March 2026" ""
 .SH "NAME"
 \fBbundle\-config\fR \- Set bundler configuration options
 .SH "SYNOPSIS"
@@ -70,6 +70,9 @@ Any periods in the configuration keys must be replaced with two underscores when
 .SH "LIST OF AVAILABLE KEYS"
 The following is a list of all configuration keys and their purpose\. You can learn more about their operation in bundle install(1) \fIbundle\-install\.1\.html\fR\.
 .TP
+\fBapi_request_size\fR (\fBBUNDLE_API_REQUEST_SIZE\fR)
+Configure how many dependencies to fetch when resolving the specifications\. This configuration is only used when fetchig specifications from RubyGems servers that didn't implement the Compact Index API\. Defaults to 100\.
+.TP
 \fBauto_install\fR (\fBBUNDLE_AUTO_INSTALL\fR)
 Automatically run \fBbundle install\fR when gems are missing\.
 .TP

bundler/lib/bundler/man/bundle-config.1.ronn

@@ -106,6 +106,11 @@ the environment variable `BUNDLE_LOCAL__RACK`.
 The following is a list of all configuration keys and their purpose. You can
 learn more about their operation in [bundle install(1)](bundle-install.1.html).
 
+* `api_request_size` (`BUNDLE_API_REQUEST_SIZE`):
+   Configure how many dependencies to fetch when resolving the specifications.
+   This configuration is only used when fetchig specifications from RubyGems
+   servers that didn't implement the Compact Index API.
+   Defaults to 100.
 * `auto_install` (`BUNDLE_AUTO_INSTALL`):
    Automatically run `bundle install` when gems are missing.
 * `bin` (`BUNDLE_BIN`):

bundler/spec/bundler/fetcher/dependency_spec.rb

@@ -222,6 +222,18 @@
       expect(Bundler).to receive(:safe_load_marshal).with(fetch_response.body).and_return([unmarshalled_gems])
       expect(subject.unmarshalled_dep_gems(gem_names)).to eq([unmarshalled_gems])
     end
+
+    it "should fetch as many dependencies as specified" do
+      allow(subject).to receive(:dependency_api_uri).with([%w[foo bar]]).and_return(dep_api_uri)
+      allow(subject).to receive(:dependency_api_uri).with([%w[bundler rubocop]]).and_return(dep_api_uri)
+
+      expect(downloader).to receive(:fetch).twice.with(dep_api_uri).and_return(fetch_response)
+      expect(Bundler).to receive(:safe_load_marshal).twice.with(fetch_response.body).and_return([unmarshalled_gems])
+
+      Bundler.settings.temporary(api_request_size: 1) do
+        expect(subject.unmarshalled_dep_gems(gem_names)).to eq([unmarshalled_gems, unmarshalled_gems])
+      end
+    end
   end
 
   describe "#get_formatted_specs_and_deps" do