diff --git a/.github/workflows/workflow-metrics.yml b/.github/workflows/workflow-metrics.yml
index bcf0e25..293997a 100644
--- a/.github/workflows/workflow-metrics.yml
+++ b/.github/workflows/workflow-metrics.yml
@@ -48,6 +48,7 @@ jobs:
           METRIC_NAMESPACE: ${{ inputs.namespace }}
           OS: ${{ inputs.os }}
           WORKFLOW_NAME: ${{ github.event.workflow_run.name }}
+          BRANCH: ${{ github.event.workflow_run.head_branch }}
           RESULT: ${{ github.event.workflow_run.conclusion }}
           RUN_STARTED_AT: ${{ github.event.workflow_run.run_started_at }}
           RUN_COMPLETED_AT: ${{ github.event.workflow_run.updated_at }}
@@ -58,6 +59,7 @@ jobs:
           fi
           metric_data=$(jq -nc \
             --arg workflow "$WORKFLOW_NAME" \
+            --arg branch "$BRANCH" \
             --arg result "${RESULT:-Unknown}" \
             --arg os "$OS" \
             --arg timestamp "$RUN_COMPLETED_AT" \
@@ -66,6 +68,7 @@ jobs:
               MetricName: "WorkflowRunDuration",
               Dimensions: [
                 {Name: "WorkflowName", Value: $workflow},
+                {Name: "Branch", Value: $branch},
                 {Name: "Result", Value: $result},
                 {Name: "OS", Value: $os}
               ],
diff --git a/README.md b/README.md
index d359b09..c4dacd1 100644
--- a/README.md
+++ b/README.md
@@ -10,9 +10,10 @@ The `.github/workflows/` directory contains reusable workflows. Each is invoked
 callers retain their event triggers and repository-specific prompts.
 
 `workflow-metrics.yml` emits `WorkflowRunDuration` for a completed
-`workflow_run`. Callers provide the namespace, OS, and writer-role secret name,
-grant `id-token: write`, and pass `WORKFLOW_SECRETS_READER_ROLE_ARN`. Pin the
-workflow to a full commit SHA. The writer role needs `cloudwatch:PutMetricData`.
+`workflow_run`, with `WorkflowName`, `Branch`, `Result`, and `OS` dimensions.
+Callers provide the namespace, OS, and writer-role secret name, grant
+`id-token: write`, and pass `WORKFLOW_SECRETS_READER_ROLE_ARN`. Pin the workflow
+to a full commit SHA. The writer role needs `cloudwatch:PutMetricData`.
 
 ```yaml
 on: