Bench 4.0.0 alongside master in the version throughput benchmark

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 #### Features
 
+* [#2914](https://github.com/ruby-grape/grape/pull/2914): Bench 4.0.0 in the version throughput benchmark - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
 
 #### Fixes

benchmark/version_throughput/README.md

@@ -14,7 +14,7 @@ Cross-version throughput benchmark for Grape. Measures `BenchAPI.call(env)` requ
 ## Usage
 
 ```sh
-# default: 3.0.1, 3.1.1, 3.2.1, 3.3.5, master
+# default: 3.0.1, 3.1.1, 3.2.1, 3.3.5, 4.0.0, master
 ruby benchmark/version_throughput/run.rb
 
 # subset
@@ -41,6 +41,7 @@ YJIT columns are only emitted if the running Ruby was built with YJIT support (`
 ## Interpreting results
 
 - **Noise floor is ~5-8%.** A single 5s window on macOS can easily move a few percent under thermal throttling or background load. Rerun before drawing conclusions on small deltas.
+- **`master` right after a release benches the same code twice.** When nothing has landed on `master` since the newest benched release, the two rows exercise identical code and their spread is a direct read of that session's noise floor — not a regression or a win.
 - **Run on a quiet machine.** Close other apps, plug in the laptop, don't touch the keyboard during the run. Each version takes ~14s of wall-clock measurement plus bundle install on first use.
 - **`master` vs released gems is not apples-to-apples for code paths that changed.** If a refactor moved code between files, both numbers still measure the same `app.rb` request — that's the point — but interpret deltas as "end-to-end request cost" rather than per-method.
 - **YJIT speedup is `(yjit_ips - no_yjit_ips) / no_yjit_ips`.** Both passes share the same Ruby binary; only the `--yjit` flag differs.

benchmark/version_throughput/RESULTS.md

@@ -1,6 +1,6 @@
 # Grape throughput by version
 
-Generated: 2026-09-07 17:13:53 CEST  
+Generated: 2026-09-07 18:16:50 CEST  
 Ruby: ruby 4.0.6 (2026-07-14 revision 03b6d3f889) +PRISM [arm64-darwin25]  
 Host: Darwin 25.6.0 arm64  
 YJIT available: true
@@ -9,13 +9,14 @@ Single-threaded `Benchmark.ips`, 2s warmup + 5s measure, `BenchAPI.call(env)` ag
 
 | Version | No-YJIT (i/s) | μs/req | vs prev | vs 3.0.1 | YJIT (i/s) | μs/req | vs prev | vs 3.0.1 | YJIT speedup |
 | --- | ---: | ---: | ---: | ---: | ---: | ---: | ---: | ---: | ---: |
-| 3.0.1 | 34,512 | 28.98 | — | — | 52,487 | 19.05 | — | — | +52.1% |
-| 3.1.1 | 45,656 | 21.90 | +32.3% | +32.3% | 85,284 | 11.73 | +62.5% | +62.5% | +86.8% |
-| 3.2.1 | 47,440 | 21.08 | +3.9% | +37.5% | 90,745 | 11.02 | +6.4% | +72.9% | +91.3% |
-| 3.3.5 | 67,834 | 14.74 | +43.0% | +96.6% | 137,675 | 7.26 | +51.7% | +162.3% | +103.0% |
-| master | 120,877 | 8.27 | +78.2% | +250.2% | 230,153 | 4.34 | +67.2% | +338.5% | +90.4% |
+| 3.0.1 | 34,255 | 29.19 | — | — | 54,997 | 18.18 | — | — | +60.6% |
+| 3.1.1 | 43,711 | 22.88 | +27.6% | +27.6% | 84,743 | 11.80 | +54.1% | +54.1% | +93.9% |
+| 3.2.1 | 45,470 | 21.99 | +4.0% | +32.7% | 89,697 | 11.15 | +5.8% | +63.1% | +97.3% |
+| 3.3.5 | 67,602 | 14.79 | +48.7% | +97.3% | 135,813 | 7.36 | +51.4% | +146.9% | +100.9% |
+| 4.0.0 | 123,107 | 8.12 | +82.1% | +259.4% | 233,841 | 4.28 | +72.2% | +325.2% | +89.9% |
+| master | 122,134 | 8.19 | -0.8% | +256.5% | 235,134 | 4.25 | +0.6% | +327.5% | +92.5% |
 
-Over time, 3.0.1 → master: **+250.2%** without YJIT, **+338.5%** with YJIT.
+Over time, 3.0.1 → master: **+256.5%** without YJIT, **+327.5%** with YJIT.
 
 ## Notes
 - All versions exercised through the same `BenchAPI` definition (kept stable in `app.rb`).

benchmark/version_throughput/run.rb

@@ -30,7 +30,7 @@
 HERE = __dir__
 TMP  = File.join(ROOT, 'tmp', 'bench-versions')
 
-DEFAULT_VERSIONS = %w[3.0.1 3.1.1 3.2.1 3.3.5 master].freeze
+DEFAULT_VERSIONS = %w[3.0.1 3.1.1 3.2.1 3.3.5 4.0.0 master].freeze
 versions = (ENV['GRAPE_VERSIONS']&.split(',')&.map(&:strip) || DEFAULT_VERSIONS).freeze
 
 def gemfile_for(version)