Add environment variable support for parallelism field

schema.json

@@ -23,6 +23,24 @@
       "description": "Whether to proceed with this step and further steps if a step named in the depends_on attribute fails",
       "default": false
     },
+    "envVarString": {
+      "type": "string",
+      "description": "An environment variable reference that will be substituted at runtime",
+      "pattern": "^\\$[A-Z_][A-Z0-9_]*$",
+      "examples": ["$PARALLELISM", "$NUMBER_OF_JOBS"]
+    },
+    "integerOrEnvVar": {
+      "oneOf": [
+        {
+          "type": "integer",
+          "description": "A literal integer value"
+        },
+        {
+          "$ref": "#/definitions/envVarString"
+        }
+      ],
+      "description": "Either an integer value or an environment variable reference"
+    },
     "image": {
       "type": "string",
       "description": "(Kubernetes stack only) The container image to use for this pipeline or step",
@@ -910,9 +928,9 @@
           }
         },
         "parallelism": {
-          "type": "integer",
+          "$ref": "#/definitions/integerOrEnvVar",
           "description": "The number of parallel jobs that will be created based on this step",
-          "examples": [42]
+          "examples": [42, "$PARALLELISM"]
         },
         "plugins": {
           "anyOf": [

test/schema.test.js

@@ -50,6 +50,9 @@ describe("schema.json", function () {
   it("should validate matrix", function () {
     validate("matrix.yml");
   });
+  it("should validate environment variables in parallelism field", function () {
+    validate("parallelism-env-vars.yml");
+  });
 
   it("should verify groupStep.steps uses the same-ish items as root steps", function () {
     const mainList = schema.properties.steps.items.anyOf;

test/valid-pipelines/parallelism-env-vars.yml

@@ -0,0 +1,16 @@
+steps:
+  # Test parallelism with environment variable
+  - command: "echo 'Testing parallelism with env var'"
+    parallelism: $PARALLELISM
+
+  # Test parallelism with literal value
+  - command: "echo 'Testing parallelism with literal'"
+    parallelism: 5
+
+  # Test mixed usage (parallelism with env var, other properties with literals)
+  - command: "echo 'Testing mixed configuration'"
+    parallelism: $PARALLELISM
+    concurrency: 2
+    concurrency_group: "test-group"
+    timeout_in_minutes: 30
+    priority: 1