From 773cfe113be8cb12a570b21f5a205db8a10679ce Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 21 Apr 2026 05:58:34 +0300
Subject: [PATCH] builtin: fix runtime.nr_jobs assert without VJOBS env
 variable (fixes #26798)

---
 vlib/runtime/runtime.v      |  2 +-
 vlib/runtime/runtime_test.v | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/vlib/runtime/runtime.v b/vlib/runtime/runtime.v
index 3e2346995..dd33dafeb 100644
--- a/vlib/runtime/runtime.v
+++ b/vlib/runtime/runtime.v
@@ -17,7 +17,7 @@ pub fn nr_jobs() int {
 		// in its cgen stage. Returning 1 here, increases the chances of it working on non linux systems.
 		return 1
 	}
-	mut cpus := nr_cpus() - 1
+	mut cpus := nr_cpus()
 	// allow for overrides, for example using `VJOBS=32 ./v test .`
 	vjobs := os.getenv('VJOBS').int()
 	if vjobs > 0 {
diff --git a/vlib/runtime/runtime_test.v b/vlib/runtime/runtime_test.v
index 01a2f8303..fd6aa452c 100644
--- a/vlib/runtime/runtime_test.v
+++ b/vlib/runtime/runtime_test.v
@@ -1,3 +1,4 @@
+import os
 import runtime
 
 fn test_physical_memory() {
@@ -26,6 +27,37 @@ fn test_nr_jobs() {
 	assert nr_jobs > 0
 }
 
+fn test_nr_jobs_matches_nr_cpus_without_vjobs() {
+	env := os.environ()
+	had_vjobs := 'VJOBS' in env
+	saved_vjobs := env['VJOBS']
+	defer {
+		if had_vjobs {
+			os.setenv('VJOBS', saved_vjobs, true)
+		} else {
+			os.unsetenv('VJOBS')
+		}
+	}
+	os.unsetenv('VJOBS')
+	assert runtime.nr_jobs() == runtime.nr_cpus()
+}
+
+fn test_nr_jobs_uses_vjobs_override() {
+	env := os.environ()
+	had_vjobs := 'VJOBS' in env
+	saved_vjobs := env['VJOBS']
+	defer {
+		if had_vjobs {
+			os.setenv('VJOBS', saved_vjobs, true)
+		} else {
+			os.unsetenv('VJOBS')
+		}
+	}
+	expected_jobs := runtime.nr_cpus() + 1
+	os.setenv('VJOBS', expected_jobs.str(), true)
+	assert runtime.nr_jobs() == expected_jobs
+}
+
 fn test_is_32bit() {
 	x := runtime.is_32bit().str()
 	println('    is_32bit: ${x}')
-- 
2.39.5