diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 8a3dd7fe..5010cd8a 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -62,16 +62,8 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
-  # ubuntu-24.04, NOT ubuntu-latest (#1096). The Ubuntu 26.04 that
-  # `ubuntu-latest` now gives out runs this suite out of disk: #1092's run of
-  # this job (job 119050702775, image `ubuntu-26.04` version 20261012.163.1)
-  # ended `2436 failed, 11382 passed, 380 skipped, 5579 errors in 3048.23s`,
-  # with 28325 lines of `[Errno 122] Disk quota exceeded`, and later `No space
-  # left on device`, all under pytest's basetemp in /tmp,
-  # `/tmp/pytest-of-runner/pytest-0`. The same job passed on 24.04. It stays
-  # on 24.04 until the suite runs on 26.04, which #1096 tracks.
   tests:
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-latest
     steps:
       # PINNED BY COMMIT, not by tag — the rule this repository spends a
       # whole README section on. A tag can be moved and a commit cannot.
@@ -126,8 +118,37 @@ jobs:
             echo "GIT_COMMITTER_EMAIL=ci@openreposhape.invalid"
           } >> "$GITHUB_ENV"
 
+      # THE SUITE'S TEMPORARY FILES GO ON THE RUNNER'S DISK, NOT IN /tmp
+      # (#1096). On the Ubuntu 26.04 that `ubuntu-latest` now gives out, /tmp
+      # is a tmpfs of 7.9G, and the suite writes about 25G. #1092's run of
+      # this job (job 119050702775, image `ubuntu-26.04` 20261012.163.1)
+      # filled /tmp under pytest's default basetemp and ended `2436 failed,
+      # 11382 passed, 380 skipped, 5579 errors`, with 28325 lines of `Disk
+      # quota exceeded` and then `No space left on device`, all under
+      # `/tmp/pytest-of-runner/pytest-0`. With the basetemp below, #1097's
+      # round 3 (job 119263572144, `ubuntu-latest`, that same image) passed,
+      # and the `df` lines showed /tmp at 38M used before and after, and the
+      # runner's disk at 57G used before the suite and 83G after.
+      #
+      # So the basetemp is `$RUNNER_TEMP/pytest`, and `TMPDIR` is
+      # `runner.temp` for everything this step starts: `tests/conftest.py`
+      # points `TMPDIR` at `<basetemp>/tmpdir` once the session starts, and
+      # this one holds what is written before then and after, such as
+      # pytest's own capture files. `runner.temp` and NOT the workspace:
+      # the workspace is this checkout, a git work tree, and a test's folder
+      # inside it would be inside this repository for every git that looks
+      # upward from it. The `df` lines put the two filesystems' room in the
+      # log, before the suite and after it.
       - name: tests
-        run: python3 -m pytest tests -q
+        env:
+          TMPDIR: ${{ runner.temp }}
+        run: |
+          df -hT /tmp "$RUNNER_TEMP"
+          status=0
+          python3 -m pytest tests -q \
+              --basetemp="$RUNNER_TEMP/pytest" || status=$?
+          df -hT /tmp "$RUNNER_TEMP"
+          exit "$status"
 
       # PINNED, checksum-verified, no `go install`/`pip` package exists for
       # this: a static release binary downloaded straight from the tag this
@@ -282,9 +303,9 @@ jobs:
   # build for setup-python: its manifest lists 3.10 to 3.15 there, and 3.8 to
   # 3.15 for 24.04. A run that landed on a 26.04 runner failed in setup-python
   # with `The version '3.9' with architecture 'x64' was not found for Ubuntu
-  # 26.04.` The `tests` job above is on ubuntu-24.04 too, for a reason of its
-  # own (#1096), and `tests-git-bash` runs on windows-latest. In release.yml,
-  # `build` asks for `3.12` on ubuntu-latest, which 26.04 has.
+  # 26.04.` The other jobs keep their runners: `tests` here asks for `3.x`
+  # and release.yml's `build` for `3.12` on ubuntu-latest, both of which
+  # 26.04 has, and `tests-git-bash` runs on windows-latest.
   package:
     runs-on: ubuntu-24.04
     steps:
diff --git a/tests/test_doctor_legs_members_next.py b/tests/test_doctor_legs_members_next.py
index bd3749c8..f58480dd 100644
--- a/tests/test_doctor_legs_members_next.py
+++ b/tests/test_doctor_legs_members_next.py
@@ -34,7 +34,7 @@
 ask `quote_arg` for it (`platform="nt"`, from any host) and compare the
 string; no test here pastes a line into `powershell`. A Windows-only test
 would not change that, because no job runs this file on Windows: `tests.yml`
-runs the suite on ubuntu-24.04 alone (the macOS and Windows jobs were
+runs the suite on ubuntu-latest alone (the macOS and Windows jobs were
 dropped, #597), and its one Windows job, `tests-git-bash`, runs three files
 of the launcher's and the installer's suites and no other. A
 `skipif(os.name != "nt")` test added here would be skipped by every runner
diff --git a/tests/test_release_workflow.py b/tests/test_release_workflow.py
index 956f613c..4606097a 100644
--- a/tests/test_release_workflow.py
+++ b/tests/test_release_workflow.py
@@ -596,18 +596,6 @@ def test_the_package_job_runs_its_python_3_9_on_ubuntu_24_04():
     assert pythons == ["3.9"]
 
 
-def test_the_tests_job_runs_the_suite_on_ubuntu_24_04():
-    """#1096: `tests.yml`'s `tests` job runs the whole suite, and on the
-    Ubuntu 26.04 that `ubuntu-latest` now gives out it ended `2436 failed,
-    11382 passed, 380 skipped, 5579 errors`, with `[Errno 122] Disk quota
-    exceeded` under pytest's basetemp in `/tmp` and `No space left on
-    device` after it. The job is pinned to 24.04, where it passed, until
-    the suite runs on 26.04; the change that moves it back takes this test
-    with it."""
-    jobs = load_yaml(WORKFLOWS / "tests.yml")["jobs"]
-    assert jobs["tests"]["runs-on"] == "ubuntu-24.04"
-
-
 def setup_python_pairs():
     """Every (file, job, runner, Python) a setup-python step of `tests.yml`
     or `release.yml` asks for, as text. A job with an `include` matrix
@@ -658,6 +646,29 @@ def test_no_setup_python_on_ubuntu_latest_asks_for_a_python_26_04_lacks():
     assert ("release.yml", "install", "ubuntu-24.04", "3.9") in pairs
 
 
+def test_the_suite_keeps_its_temporary_files_on_the_runners_disk():
+    """#1096: on the Ubuntu 26.04 that `ubuntu-latest` now gives out, the
+    whole suite filled `/tmp` under pytest's default basetemp (`Disk quota
+    exceeded`, then `No space left on device`) and ended `2436 failed,
+    11382 passed, 380 skipped, 5579 errors`. `tests.yml`'s `tests` step
+    gives pytest a basetemp under `$RUNNER_TEMP`, on the runner's disk, and
+    sets `TMPDIR` to `runner.temp` for everything it starts, so nothing the
+    suite writes goes to `/tmp`. The step prints the room on both
+    filesystems after the suite as well, and still ends with the suite's
+    own exit status."""
+    steps = load_yaml(WORKFLOWS / "tests.yml")["jobs"]["tests"]["steps"]
+    [step] = [step for step in steps if step.get("name") == "tests"]
+    assert step["env"] == {"TMPDIR": "${{ runner.temp }}"}
+    lines = commands(step["run"])
+    assert lines == [
+        'df -hT /tmp "$RUNNER_TEMP"',
+        "status=0",
+        'python3 -m pytest tests -q --basetemp="$RUNNER_TEMP/pytest" '
+        "|| status=$?",
+        'df -hT /tmp "$RUNNER_TEMP"',
+        'exit "$status"']
+
+
 def test_the_header_says_how_to_release(workflow):
     """The release notes (`docs/release-notes/v1.1.0.md` and `v1.1.1.md`)
     point at this header for the steps, so it carries them: Brett Heap's