diff --git a/.github/workflows/functional-tests.yml b/.github/workflows/functional-tests.yml
index 6692a21..6c50833 100644
--- a/.github/workflows/functional-tests.yml
+++ b/.github/workflows/functional-tests.yml
@@ -4,21 +4,78 @@ on:
     branches: [main, master]
   pull_request:
     branches: [main, master]
+  # EduIDE-deployment calls this after it has deployed an environment, so the
+  # suite runs against the rollout that just went green rather than against
+  # whatever the repository variable happens to point at.
+  workflow_call:
+    inputs:
+      environment:
+        type: string
+        required: true
+        description: >-
+          Landing page hostname to test, e.g.
+          e2e.eduide.student.k8s.aet.cit.tum.de. In EduIDE-deployment the
+          environment name and the landing page hostname are the same string,
+          so the caller passes its environment name straight through.
+      artemis_url:
+        type: string
+        required: false
+        default: ''
+        description: >-
+          Artemis instance to integrate against, as a full URL, for example
+          https://artemis.tum.de. Environments front different Artemis
+          instances, so it belongs to the caller. Empty falls back to the
+          ARTEMIS_URL repository variable.
+    secrets:
+      KEYCLOAK_USER:
+        required: true
+      KEYCLOAK_PWD:
+        required: true
+      # A called workflow can only read secrets it declares. The functional
+      # project never touches Artemis, so these stay optional and simply stay
+      # empty for a caller that does not have them.
+      ARTEMIS_USER:
+        required: false
+      ARTEMIS_PWD:
+        required: false
 jobs:
   test:
     timeout-minutes: 60
-    runs-on: [self-hosted, e2e-test]
+    # Was `[self-hosted, e2e-test]`, which no registered runner answers to. The
+    # only self-hosted runners in this org are two ARC scale sets on the student
+    # cluster (`arc-buildkit-*-stud-amd64`), and an ARC scale-set runner is
+    # addressed by its scale set name, never by `self-hosted`. Every run since
+    # 2026-08-27 15:13 sat queued for that reason.
+    #
+    # The environments under test are reachable from the public internet - Let's
+    # Encrypt validates their certificates over HTTP-01 - so a hosted runner
+    # reaches them and needs no cluster access.
+    runs-on: ubuntu-latest
     env:
       KEYCLOAK_USER: ${{ secrets.KEYCLOAK_USER }}
       KEYCLOAK_PWD: ${{ secrets.KEYCLOAK_PWD }}
-      LANDINGPAGE_URL: ${{ vars.LANDINGPAGE_URL }}
-      ARTEMIS_URL: ${{ vars.ARTEMIS_URL }}
+      # Called: test what the caller just deployed. Triggered directly: there is
+      # no input, so keep using the repository variable as before.
+      LANDINGPAGE_URL: ${{ inputs.environment && format('https://{0}', inputs.environment) || vars.LANDINGPAGE_URL }}
+      # Configurable, so a caller can point the suite at its own Artemis.
+      # Falls back to the repository variable when triggered directly.
+      ARTEMIS_URL: ${{ inputs.artemis_url || vars.ARTEMIS_URL }}
       ARTEMIS_USER: ${{ secrets.ARTEMIS_USER }}
       ARTEMIS_PWD: ${{ secrets.ARTEMIS_PWD }}
       NUM_INSTANCES: 10
 
     steps:
+      # In a called workflow the github context belongs to the CALLER, so a bare
+      # checkout would clone the calling repository and leave no test suite to
+      # run. job.workflow_repository / job.workflow_sha point at the repo and
+      # commit this workflow file itself came from, which is what we want there.
+      # inputs.environment is only set when we are called, so direct push and
+      # pull_request runs keep checking out github.repository at github.sha
+      # exactly as before.
       - uses: actions/checkout@v4
+        with:
+          repository: ${{ inputs.environment && job.workflow_repository || github.repository }}
+          ref: ${{ inputs.environment && job.workflow_sha || github.sha }}
       - uses: actions/setup-node@v4
         with:
           node-version: lts/*
diff --git a/README.md b/README.md
index 1aa8cb1..538b903 100644
--- a/README.md
+++ b/README.md
@@ -140,6 +140,39 @@ This repository provides E2E integration tests for the [Theia Cloud IDE](https:/
 | artemis            | Runs the **integration** test with Artemis, either local or deployed depending on the URLs set in the env file.   | [![Playwright Tests](https://github.com/ls1intum/theia-scale-tests/actions/workflows/artemis-integration-tests.yml/badge.svg)](https://github.com/ls1intum/theia-scale-tests/actions/workflows/artemis-integration-tests.yml) |
 | \*-setup           | These are setup projects and not meant to be run on its own. Dependencies are already set.                        |
 
+### Running the functional suite from another repository
+
+`.github/workflows/functional-tests.yml` is also a reusable workflow, so a deployment pipeline can run the suite against the environment it has just rolled out. `EduIDE/EduIDE-deployment` uses it that way:
+
+```yaml
+e2e:
+  needs: deploy
+  uses: EduIDE/theia-scale-tests/.github/workflows/functional-tests.yml@main
+  with:
+    environment: e2e.eduide.student.k8s.aet.cit.tum.de
+    artemis_url: https://artemis.tum.de
+  secrets:
+    KEYCLOAK_USER: ${{ secrets.E2E_KEYCLOAK_USER }}
+    KEYCLOAK_PWD: ${{ secrets.E2E_KEYCLOAK_PWD }}
+```
+
+| Input | Required | |
+|---|---|---|
+| `environment` | yes | Landing page hostname. Becomes `LANDINGPAGE_URL` as `https://<environment>` |
+| `artemis_url` | no | Artemis instance to integrate against, as a full URL. Environments front different Artemis instances, so it belongs to the caller. Empty falls back to the `ARTEMIS_URL` repository variable |
+
+`KEYCLOAK_USER` and `KEYCLOAK_PWD` are required; `ARTEMIS_USER` and `ARTEMIS_PWD`
+are optional and only needed by suites that reach Artemis.
+
+The job runs on `ubuntu-latest`. It used to ask for `[self-hosted, e2e-test]`,
+which no registered runner answers to, so every run queued indefinitely. The
+environments under test are reachable from the public internet, so a hosted
+runner is enough.
+
+`environment` is the landing page hostname; the job turns it into `LANDINGPAGE_URL=https://<environment>`. In EduIDE-deployment the environment name under `environments/` and the landing page hostname are the same string, so the caller passes its environment name through unchanged. Pushes and pull requests on this repository send no input and keep reading `LANDINGPAGE_URL` from the repository variable.
+
+`ARTEMIS_USER` and `ARTEMIS_PWD` are declared as optional secrets. The `functional` project never touches Artemis, so a caller that does not have them can leave them out.
+
 ## Development
 
 - Single User Playwright Tests are run using a Test Account for Keycloak, to change the Test User, change the environment variables in GitHub Secrets \