diff --git a/.github/workflows/_checks.yml b/.github/workflows/_checks.yml
index 2a98dda..0f7b3c1 100644
--- a/.github/workflows/_checks.yml
+++ b/.github/workflows/_checks.yml
@@ -88,14 +88,16 @@ jobs:
     # The declared floors are part of what we ship, and nothing else in CI installs
     # them: `pytest` and `scheduled-dep-check` both resolve highest. That is how
     # 0.13.2 shipped `faststream>=0.7.1` and stayed green until 0.7.6 broke a user.
-    # This leg resolves the lower bound instead. One interpreter per distinct floor
-    # set: 3.11 for the unmarked floors, 3.13 and 3.14 for the marked ones.
+    # This leg resolves the lower bound instead, on every supported interpreter:
+    # a floor's wheel coverage is per-interpreter, so two interpreters resolving
+    # the same versions can still disagree on whether those versions install.
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
         python-version:
           - "3.11"
+          - "3.12"
           - "3.13"
           - "3.14"
     services:
@@ -120,7 +122,10 @@ jobs:
           cache-dependency-glob: "**/pyproject.toml"
       - run: uv python install ${{ matrix.python-version }}
       - run: uv python pin ${{ matrix.python-version }}
-      - run: uv sync --all-extras --no-install-project --resolution lowest-direct
+      # --no-build: a floor with no wheel for this interpreter must fail here rather
+      # than quietly compile its sdist. Without it the leg passes on a floor that
+      # still breaks anyone installing into an image with no build toolchain.
+      - run: uv sync --all-extras --no-install-project --resolution lowest-direct --no-build
       # fastapi's floor pulls a starlette whose TestClient predates httpx2 support.
       # Installed here rather than declared in the dev group: at the resolved-highest
       # end starlette takes the httpx2 that group already declares, and adding httpx
diff --git a/pyproject.toml b/pyproject.toml
index 4201234..7422f43 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,10 +36,10 @@ dependencies = [
     # Not imported here: faststream pulls pydantic through fast-depends[pydantic], which allows it
     # back to 1.x. FastStream's serializer calls model_dump, so publishing a model raises
     # AttributeError on pydantic 1 — v2 is a real requirement of ours, not a preference. The two
-    # marked floors are wheel coverage: pydantic-core ships no cp313 wheel before pydantic 2.8
-    # and no cp314 wheel before 2.12.
+    # marked floors are wheel coverage: pydantic-core ships no cp313 wheel before pydantic 2.8.1
+    # (2.8.0 carries pydantic-core 2.20.0, which has none) and no cp314 wheel before 2.12.
     "pydantic>=2; python_version < '3.13'",
-    "pydantic>=2.8; python_version == '3.13'",
+    "pydantic>=2.8.1; python_version == '3.13'",
     "pydantic>=2.12; python_version >= '3.14'",
     # 4.12.2, not 4.12.0: pydantic requires >=4.12.2 on 3.13+, and pinning 4.12.0 drags pydantic
     # back to a build whose pydantic-core has no cp313 wheel either.