Add test coverage for with_unbundled_context and update CHANGELOG

- Added comprehensive test coverage for the with_unbundled_context wrapper
  to verify the Bundler API compatibility chain:
  * Tests with_unbundled_env (modern Bundler API)
  * Tests with_clean_env (legacy Bundler API)
  * Tests fallback when neither method is available
  * Tests execution when Bundler is not defined

- Updated CHANGELOG.md with bug fix entry for issue #2084

All 18 examples in pack_generator_spec.rb pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

CHANGELOG.md

@@ -27,6 +27,10 @@ Changes since the last non-beta release.
 
 - **CSP Nonce Support for Console Replay**: Added Content Security Policy (CSP) nonce support for the `consoleReplay` script generated during server-side rendering. When Rails CSP is configured, the console replay script will automatically include the nonce attribute, allowing it to execute under restrictive CSP policies like `script-src: 'self'`. The implementation includes cross-version Rails compatibility (5.2-7.x) and defense-in-depth nonce sanitization to prevent attribute injection attacks. [PR 2059](https://github.com/shakacode/react_on_rails/pull/2059) by [justin808](https://github.com/justin808).
 
+#### Bug Fixes
+
+- [PR 2085](https://github.com/shakacode/react_on_rails/pull/2085) by [justin808](https://github.com/justin808): Fix pack generation in bin/dev when running from Bundler context. Pack generation was failing with "Could not find command 'react_on_rails:generate_packs'" because Bundler was intercepting the subprocess call. The fix wraps the bundle exec call with `Bundler.with_unbundled_env` to prevent interception.
+
 ### [v16.2.0.beta.11] - 2025-11-19
 
 #### Added

spec/react_on_rails/dev/pack_generator_spec.rb

@@ -206,5 +206,90 @@
           .with("bundle", "exec", "rake", "react_on_rails:generate_packs")
       end
     end
+
+    context "when calling bundle exec from within Bundler context" do
+      before do
+        # Ensure we're not in Rails context to trigger bundle exec path
+        hide_const("Rails") if defined?(Rails)
+        allow(ReactOnRails::PackerUtils).to receive(:shakapacker_precompile_hook_configured?).and_return(false)
+      end
+
+      it "unwraps the Bundler context before executing with with_unbundled_env" do
+        bundler_module = Module.new do
+          def self.respond_to?(method, *)
+            method == :with_unbundled_env
+          end
+
+          def self.with_unbundled_env
+            yield
+          end
+        end
+        stub_const("Bundler", bundler_module)
+
+        allow(bundler_module).to receive(:with_unbundled_env).and_yield
+        allow(described_class).to receive(:system)
+          .with("bundle", "exec", "rake", "react_on_rails:generate_packs")
+          .and_return(true)
+
+        described_class.generate(verbose: true)
+
+        expect(bundler_module).to have_received(:with_unbundled_env)
+      end
+
+      it "falls back to with_clean_env when with_unbundled_env is not available" do
+        bundler_module = Module.new do
+          def self.respond_to?(method, *)
+            method == :with_clean_env
+          end
+
+          def self.with_clean_env
+            yield
+          end
+        end
+        stub_const("Bundler", bundler_module)
+
+        allow(bundler_module).to receive(:with_clean_env).and_yield
+        allow(described_class).to receive(:system)
+          .with("bundle", "exec", "rake", "react_on_rails:generate_packs")
+          .and_return(true)
+
+        described_class.generate(verbose: true)
+
+        expect(bundler_module).to have_received(:with_clean_env)
+      end
+
+      it "executes directly when neither with_unbundled_env nor with_clean_env are available" do
+        bundler_module = Module.new do
+          def self.respond_to?(_method, *)
+            false
+          end
+        end
+        stub_const("Bundler", bundler_module)
+
+        allow(described_class).to receive(:system)
+          .with("bundle", "exec", "rake", "react_on_rails:generate_packs")
+          .and_return(true)
+
+        expect { described_class.generate(verbose: true) }
+          .to output(/📦 Generating React on Rails packs.../).to_stdout_from_any_process
+
+        expect(described_class).to have_received(:system)
+          .with("bundle", "exec", "rake", "react_on_rails:generate_packs")
+      end
+
+      it "executes directly when Bundler is not defined" do
+        hide_const("Bundler") if defined?(Bundler)
+
+        allow(described_class).to receive(:system)
+          .with("bundle", "exec", "rake", "react_on_rails:generate_packs")
+          .and_return(true)
+
+        expect { described_class.generate(verbose: true) }
+          .to output(/📦 Generating React on Rails packs.../).to_stdout_from_any_process
+
+        expect(described_class).to have_received(:system)
+          .with("bundle", "exec", "rake", "react_on_rails:generate_packs")
+      end
+    end
   end
 end