diff --git a/scripts/src/agentrun.ts b/scripts/src/agentrun.ts
index 27747841..7ccfdae2 100644
--- a/scripts/src/agentrun.ts
+++ b/scripts/src/agentrun.ts
@@ -3321,7 +3321,8 @@ function yamlLaneBuildImageSubmitScript(spec: AgentRunLaneSpec, sourceCommit: st
     "process.stdout.write(hash.digest('hex').slice(0, 24));",
     "NODE",
     ")",
-    "job_id=\"${source_commit:0:12}-$env_identity\"",
+    "source_short=$(printf '%s' \"$source_commit\" | cut -c1-12)",
+    "job_id=\"$source_short-$env_identity\"",
     "status_file=\"$state_dir/$job_id.json\"",
     "stdout_file=\"$state_dir/$job_id.stdout.log\"",
     "stderr_file=\"$state_dir/$job_id.stderr.log\"",