vercel · chris-olszewski · Apr 14, 2025 · Mar 26, 2025
@@ -24,6 +24,7 @@ struct ConfigOutput<'a> {
     scm_base: Option<&'a str>,
     scm_head: Option<&'a str>,
     cache_dir: &'a Utf8Path,
+    concurrency: Option<&'a str>,
 }
 
 pub async fn run(repo_root: AbsoluteSystemPathBuf, args: Args) -> Result<(), cli::Error> {
@@ -55,6 +56,7 @@ pub async fn run(repo_root: AbsoluteSystemPathBuf, args: Args) -> Result<(), cli
             scm_base: config.scm_base(),
             scm_head: config.scm_head(),
             cache_dir: config.cache_dir(),
+            concurrency: config.concurrency.as_deref()
         })?
     );
     Ok(())

@@ -122,6 +122,10 @@ impl CommandBase {
             )
             .with_run_summary(args.run_args().and_then(|args| args.summarize()))
             .with_allow_no_turbo_json(args.allow_no_turbo_json.then_some(true))
+            .with_concurrency(
+                args.execution_args()
+                    .and_then(|args| args.concurrency.clone()),
+            )
             .build()
     }
 

@@ -43,6 +43,7 @@ const TURBO_MAPPING: &[(&str, &str)] = [
     ("turbo_allow_no_turbo_json", "allow_no_turbo_json"),
     ("turbo_cache", "cache"),
     ("turbo_tui_scrollback_length", "tui_scrollback_length"),
+    ("turbo_concurrency", "concurrency"),
 ]
 .as_slice();
 
@@ -202,6 +203,12 @@ impl ResolvedConfigurationOptions for EnvVars {
                 )
             })?;
 
+        let concurrency = self
+            .output_map
+            .get("concurrency")
+            .filter(|s| !s.is_empty())
+            .cloned();
+
         let output = ConfigurationOptions {
             api_url: self.output_map.get("api_url").cloned(),
             login_url: self.output_map.get("login_url").cloned(),
@@ -210,6 +217,7 @@ impl ResolvedConfigurationOptions for EnvVars {
             token: self.output_map.get("token").cloned(),
             scm_base: self.output_map.get("scm_base").cloned(),
             scm_head: self.output_map.get("scm_head").cloned(),
+            concurrency,
             cache,
             // Processed booleans
             signature,
@@ -326,6 +334,7 @@ mod test {
         env.insert("turbo_allow_no_turbo_json".into(), "true".into());
         env.insert("turbo_remote_cache_upload_timeout".into(), "200".into());
         env.insert("turbo_tui_scrollback_length".into(), "2048".into());
+        env.insert("turbo_concurrency".into(), "50%".into());
 
         let config = EnvVars::new(&env)
             .unwrap()
@@ -354,6 +363,7 @@ mod test {
             config.root_turbo_json_path,
             Some(AbsoluteSystemPathBuf::new(root_turbo_json).unwrap())
         );
+        assert_eq!(config.concurrency, Some("50%".to_owned()));
     }
 
     #[test]
@@ -378,6 +388,7 @@ mod test {
         env.insert("turbo_run_summary".into(), "".into());
         env.insert("turbo_allow_no_turbo_json".into(), "".into());
         env.insert("turbo_tui_scrollback_length".into(), "".into());
+        env.insert("turbo_concurrency".into(), "".into());
 
         let config = EnvVars::new(&env)
             .unwrap()
@@ -405,5 +416,6 @@ mod test {
             config.tui_scrollback_length(),
             DEFAULT_TUI_SCROLLBACK_LENGTH
         );
+        assert_eq!(config.concurrency, None);
     }
 }
@@ -297,6 +297,7 @@ pub struct ConfigurationOptions {
     pub(crate) run_summary: Option<bool>,
     pub(crate) allow_no_turbo_json: Option<bool>,
     pub(crate) tui_scrollback_length: Option<u64>,
+    pub(crate) concurrency: Option<String>,
 }
 
 #[derive(Default)]

@@ -43,6 +43,7 @@ impl<'a> TurboJsonReader<'a> {
         opts.daemon = turbo_json.daemon.map(|daemon| *daemon.as_inner());
         opts.env_mode = turbo_json.env_mode;
         opts.cache_dir = cache_dir;
+        opts.concurrency = turbo_json.concurrency;
         Ok(opts)
     }
 }

@@ -312,7 +312,7 @@ impl<'a> TryFrom<OptsInputs<'a>> for RunOpts {
 
     fn try_from(inputs: OptsInputs) -> Result<Self, Self::Error> {
         let concurrency = inputs
-            .execution_args
+            .config
             .concurrency
             .as_deref()
             .map(parse_concurrency)

@@ -158,6 +158,9 @@ pub struct RawTurboJson {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub boundaries: Option<Spanned<BoundariesConfig>>,
 
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub concurrency: Option<String>,
+
     #[deserializable(rename = "//")]
     #[serde(skip)]
     _comment: Option<String>,

@@ -91,6 +91,22 @@ Select a terminal UI for the repository.
 }
 ```
 
+### `concurrency`
+
+Default: `"10"`
+
+Set/limit the maximum concurrency for task execution. Must be an integer greater than or equal to `1` or a percentage value like `50%`.
+
+- Use `1` to force serial execution (one task at a time).
+- Use `100%` to use all available logical processors.
+- This option is ignored if the [`--parallel`](#--parallel) flag is also passed.
+
+```jsonc title="./turbo.json"
+{
+  "concurrency": "1"
+}
+```
+
 ### `dangerouslyDisablePackageManagerCheck`
 
 Default: `false`

@@ -328,6 +328,16 @@ System environment variables are always overridden by flag values provided direc
         Enables TUI when passed true or 1, disables when passed false or 0.
       </td>
     </tr>
+    <tr id="turbo_concurrency">
+      <td>
+        <code>TURBO_CONCURRENCY</code>
+      </td>
+      <td>
+        Controls{' '}
+        <a href="/repo/docs/reference/run#--concurrency-number--percentage">concurrency</a>{' '}
+        settings in run or watch mode.
+      </td>
+    </tr>
   </tbody>
 </table>
 

@@ -19,7 +19,8 @@ Run test run
     "envMode": "strict",
     "scmBase": null,
     "scmHead": null,
-    "cacheDir": ".turbo[\\/]+cache" (re)
+    "cacheDir": ".turbo[\\/]+cache", (re)
+    "concurrency": null
   }
 
 Run test run with api overloaded
@@ -111,3 +112,15 @@ Add env var: `TURBO_CACHE_DIR`
 Add flag: `--cache-dir`
   $ ${TURBO} --cache-dir FifthDimension/Nebulo9 config | jq -r .cacheDir
   FifthDimension[\\/]Nebulo9 (re)
+
+No concurrency by default
+  $ ${TURBO} config | jq -r .concurrency
+  null
+
+Add env var: `TURBO_CONCURRENCY`
+  $ TURBO_CONCURRENCY=5 ${TURBO} config | jq -r .concurrency
+  5
+
+Add flag: `--concurrency`
+  $ ${TURBO} --concurrency=5 config | jq -r .concurrency
+  5
@@ -8,14 +8,32 @@
 
   [1]
 
+  $ TURBO_CONCURRENCY=1 ${TURBO} run build
+    x Invalid task configuration
+    `->   x You have 2 persistent tasks but `turbo` is configured for
+          | concurrency of 1. Set --concurrency to at least 3
+
+  [1]
+
   $ ${TURBO} run build --concurrency=2
     x Invalid task configuration
     `->   x You have 2 persistent tasks but `turbo` is configured for
           | concurrency of 2. Set --concurrency to at least 3
 
   [1]
 
+  $ TURBO_CONCURRENCY=2 ${TURBO} run build
+    x Invalid task configuration
+    `->   x You have 2 persistent tasks but `turbo` is configured for
+          | concurrency of 2. Set --concurrency to at least 3
+
+  [1]
+
   $ ${TURBO} run build --concurrency=3 > tmp.log 2>&1
   $ grep -E "2 successful, 2 total" tmp.log
    Tasks:    2 successful, 2 total
 
+  $ TURBO_CONCURRENCY=3 ${TURBO} run build > tmp-env.log 2>&1
+  $ grep -E "2 successful, 2 total" tmp-env.log
+   Tasks:    2 successful, 2 total
+