diff --git a/compose_api/environments/compliance.py b/compose_api/environments/compliance.py
index e6ae73cc..cf10d052 100644
--- a/compose_api/environments/compliance.py
+++ b/compose_api/environments/compliance.py
@@ -137,7 +137,8 @@ class Expectation(BaseModel):
     - ``reference``: every column of ``reference`` (a CSV in the case, with a time column first) matches the result
       at the reference's times, within the tolerance.
     - ``scalar``: the emitted number ``field`` in row ``row`` (the last when omitted) is ``expected``, within the
-      tolerance: for a component whose stores are plain numbers rather than a ``numeric_result``.
+      tolerance: for a component whose stores are plain numbers rather than a ``numeric_result``. ``field`` may be a
+      dotted path into lists and maps, ``values.2.0`` (composition 7c-4: an ensemble's per-seed values).
     """
 
     kind: Literal["rows", "value", "reference", "scalar"]
@@ -237,8 +238,10 @@ def _check_scalar(expectation: Expectation, rows: list[Any]) -> list[str]:
     if expectation.expected is None:
         return ["a scalar expectation needs `expected`"]
     try:
-        row = rows[expectation.row]
-        actual = float(row[expectation.field])
+        found: Any = rows[expectation.row]
+        for step in expectation.field.split("."):
+            found = found[int(step)] if isinstance(found, list) else found[step]
+        actual = float(found)
     except (IndexError, KeyError, TypeError, ValueError) as e:
         return [f"{where}: no number ({type(e).__name__}: {e})"]
     if _close(actual, expectation.expected, expectation.rel, expectation.abs):
diff --git a/compose_api/registry/compliance/viva-pde-particle/fokker-planck-ensemble/case.yaml b/compose_api/registry/compliance/viva-pde-particle/fokker-planck-ensemble/case.yaml
new file mode 100644
index 00000000..207e7f3f
--- /dev/null
+++ b/compose_api/registry/compliance/viva-pde-particle/fokker-planck-ensemble/case.yaml
@@ -0,0 +1,18 @@
+description: >-
+  viva-pde-particle's own example (compose_runner.write_example): FokkerPlanckEnsemble runs four trials, seeds 1 to 4, of
+  the Fokker-Planck benchmark's trial_rho (test4, tau 0.2, dtau 1e-3), each a PDE solve co-simulated with Smoldyn (built
+  with OPTION_VCELL), and emits each seed's two values. The emitter is named fully qualified (composition D7c.2). The
+  values are seeded, so exact: these are what its prebuilt image's runner and compose-api's runner gave in the
+  registry_env@5 + viva-pde-particle environment, identically (2026-10-27, docs/plan-environment-composition.md 7c).
+document: document.pbg
+interval: 1
+expect:
+  - {kind: rows, emitter: emitter, min: 2}
+  - {kind: scalar, emitter: emitter, field: seeds.0, expected: 1}
+  - {kind: scalar, emitter: emitter, field: seeds.3, expected: 4}
+  - {kind: scalar, emitter: emitter, field: values.0.0, expected: 0.07137369415367853, rel: 1.0e-6}
+  - {kind: scalar, emitter: emitter, field: values.0.1, expected: 0.0004004746655585104, rel: 1.0e-6}
+  - {kind: scalar, emitter: emitter, field: values.1.0, expected: 0.0, abs: 1.0e-12}
+  - {kind: scalar, emitter: emitter, field: values.2.0, expected: 0.09234150979599469, rel: 1.0e-6}
+  - {kind: scalar, emitter: emitter, field: values.2.1, expected: 0.0020975747341526988, rel: 1.0e-6}
+  - {kind: scalar, emitter: emitter, field: values.3.0, expected: 0.0, abs: 1.0e-12}
diff --git a/compose_api/registry/compliance/viva-pde-particle/fokker-planck-ensemble/document.pbg b/compose_api/registry/compliance/viva-pde-particle/fokker-planck-ensemble/document.pbg
new file mode 100644
index 00000000..911a9677
--- /dev/null
+++ b/compose_api/registry/compliance/viva-pde-particle/fokker-planck-ensemble/document.pbg
@@ -0,0 +1,46 @@
+{
+  "state": {
+    "seeds": [],
+    "values": [],
+    "ensemble": {
+      "_type": "process",
+      "address": "local:viva_pde_particle.ensemble.FokkerPlanckEnsemble",
+      "config": {
+        "params": "{\"test\": \"test4\", \"tau\": 0.2, \"dtau\": 0.001}",
+        "seeds": [
+          1,
+          4
+        ],
+        "workers": 0
+      },
+      "interval": 1.0,
+      "inputs": {},
+      "outputs": {
+        "seeds": [
+          "seeds"
+        ],
+        "values": [
+          "values"
+        ]
+      }
+    },
+    "emitter": {
+      "_type": "step",
+      "address": "local:process_bigraph.emitter.RAMEmitter",
+      "config": {
+        "emit": {
+          "seeds": "list[integer]",
+          "values": "list[list[float]]"
+        }
+      },
+      "inputs": {
+        "seeds": [
+          "seeds"
+        ],
+        "values": [
+          "values"
+        ]
+      }
+    }
+  }
+}
diff --git a/compose_api/registry/environments.py b/compose_api/registry/environments.py
index 37647318..fdb40a43 100644
--- a/compose_api/registry/environments.py
+++ b/compose_api/registry/environments.py
@@ -100,11 +100,13 @@ def spec_problems(spec: EnvironmentSpec, manifest: Manifest, *, bundled: bool =
 
 def members_of(spec: EnvironmentSpec, manifest: Manifest) -> frozenset[str]:
     """The registry entries an environment provides: those it is composed of, or, for a prebuilt image (which lists
-    none), the entries bundled in it. Core entries are left out: every environment that can run their classes
+    none), the entries bundled in it and what they require, which the image installs its own way (viva-pde-particle's
+    Smoldyn and engines: composition 7c-4). Core entries are left out: every environment that can run their classes
     provides them, so they never tell environments apart (composition 7c-1)."""
-    return frozenset(spec.entries) or frozenset(
-        e.id for e in manifest.entries if spec.name in e.bundles and e.kind != "core"
-    )
+    if spec.entries:
+        return frozenset(spec.entries)
+    bundled = {e.id for e in manifest.entries if spec.name in e.bundles and e.kind != "core"}
+    return frozenset(manifest.with_requirements(bundled))
 
 
 def _unlisted_requirements(spec: EnvironmentSpec, by_id: dict[str, RegistryEntry]) -> list[str]:
diff --git a/compose_api/registry/manifest.yaml b/compose_api/registry/manifest.yaml
index 7cf1f636..5759b47b 100644
--- a/compose_api/registry/manifest.yaml
+++ b/compose_api/registry/manifest.yaml
@@ -77,12 +77,40 @@ entries:
   - id: viva-pde-particle
     package: viva-pde-particle
     source: https://github.com/vivarium-collective/viva-pde-particle
-    # the commit behind the deployed image (PREBUILT_SIMULATORS pins its digest, tagged sha-8c16827)
-    commit: 8c168271e3b48ac667cde9092ca025be0f444d65
+    # viva-pde-particle#67's merge (2026-10-27): each trial function its own Ensemble class, so no document's config
+    # names what is imported. What a composed environment installs, and the commit of the prebuilt image
+    # (viva-pde-particle-compose:sha-21dfe46) registered as viva-pde-particle@2
+    commit: 21dfe468455b3a8746b184469651494f4b06b4a4
+    # composed too (docs/plan-environment-composition.md 7c, D7c.1-D7c.3): its engines from conda-forge, as its own
+    # pixi.toml's `compose` environment has them, less the Smoldyn toolchain; Smoldyn is the smoldyn-vcell wheel
+    install:
+      git: https://github.com/vivarium-collective/viva-pde-particle
+      commit: 21dfe468455b3a8746b184469651494f4b06b4a4
+      extras: [reference]
+    conda:
+      fenics-dolfinx: "0.10.*"
+      mpich: "*"
+      gmsh: "*"
+      python-gmsh: "*"
+      h5py: "*"
+      netgen: ">=6.2.2602,<7"
+      scikit-image: "*"
+      pydantic: ">=2.10,<3"
+      vtk: "*"
+      pyvista: ">=0.49.0,<0.50"
+      imageio: ">=2.38.0,<3"
+    # what its pixi.toml adds beyond its package metadata: Smoldyn, the VCell solver and geometry, results bundles
+    requires:
+      - smoldyn-vcell
+      - vcell-fenics
+      - pyvcell-fvsolver
+      - zarr
+      - pyvcell
+      - libvcell
     module_roots:
       - viva_pde_particle
     level: tested
-    # its own prebuilt image, not registry_env: it runs only with `simulator=viva-pde-particle`
+    # its own prebuilt image runs a document of its classes alone (D7c.3); composed, they join a mash-up
     bundles:
       - viva-pde-particle
     evidence:
@@ -91,6 +119,11 @@ entries:
         package's own CI on every push to main (.github/workflows/compose-image.yml): a smoke ensemble in Docker,
         then this service's exact job contract under `apptainer run --compat` with /experiment bound, before the
         image is pushed. The pinned digest passed both.
+      - >-
+        Composed on 2026-10-27 (7c-4): with registry_env@5's entries in one pixi lock (472 packages, no conflict), its
+        example ensemble (four PDE + Smoldyn trials) gave values identical to its prebuilt image's through
+        compose-api's runner. In a composed version its compliance case (registry/compliance/viva-pde-particle)
+        decides its level.
 
   - id: biosim-toolkit
     package: biosim-toolkit
@@ -160,6 +193,58 @@ entries:
   # Pinned to what registry_env@1 actually ran (read back from its image, 2026-10-25), not to the old library list,
   # which said tellurium 2.2.11.1 and python-copasi 4.46.300 while the image held these.
 
+  - id: smoldyn-vcell
+    kind: library
+    package: smoldyn
+    # Smoldyn's Python module built with OPTION_VCELL (the hybrid ValueProvider hooks) from the virtualcell fork's
+    # pyhybrid branch, by its .github/workflows/vcell-hybrid-wheel.yml (composition 7c-3, D7c.1): on no index
+    source: https://github.com/virtualcell/Smoldyn/releases/tag/vcell-pyhybrid-e86d552
+    version: "2.76.dev0+vcell.e86d552"
+    install:
+      url: https://github.com/virtualcell/Smoldyn/releases/download/vcell-pyhybrid-e86d552/smoldyn-2.76.dev0%2Bvcell.e86d552-cp312-cp312-linux_x86_64.whl
+      sha256: bb033bccff9481a075603d4a79fefe249b152fac5544a716adf16761adc29d14
+    level: installable
+    evidence:
+      - >-
+        Built at e86d552 by the fork's workflow and released 2026-10-27; the hash is the release asset's, checked on
+        download. CPython 3.12 on Linux x86-64; it links libpython, which composed images put on LD_LIBRARY_PATH.
+
+  - id: vcell-fenics
+    kind: library
+    package: vcell-fenics
+    source: https://github.com/virtualcell/vcell-fenics/tree/4dab281e1ed3f7c2b2bb60c6c2d1a8ccb251ca17
+    commit: 4dab281e1ed3f7c2b2bb60c6c2d1a8ccb251ca17
+    install:
+      git: https://github.com/virtualcell/vcell-fenics
+      commit: 4dab281e1ed3f7c2b2bb60c6c2d1a8ccb251ca17
+    level: installable
+    evidence:
+      - The commit viva-pde-particle's pixi.toml pins (main, the merge of #211); its geometry formalism and Netgen realization.
+
+  - id: pyvcell-fvsolver
+    kind: library
+    package: pyvcell-fvsolver
+    source: https://pypi.org/project/pyvcell-fvsolver/0.11.1/
+    version: "0.11.1"
+    install:
+      pypi: pyvcell-fvsolver
+      version: "0.11.1"
+    level: installable
+    evidence:
+      - viva-pde-particle's pixi.toml floor (>=0.11.1, the hybrid fixes vcell-fvsolver#32-#34); what the 2026-10-27 lock resolved.
+
+  - id: zarr
+    kind: library
+    package: zarr
+    source: https://pypi.org/project/zarr/3.4.1/
+    version: "3.4.1"
+    install:
+      pypi: zarr
+      version: "3.4.1"
+    level: installable
+    evidence:
+      - viva-pde-particle's results bundles are zarr groups (its pixi.toml, >=3.1,<4); what the 2026-10-27 lock resolved.
+
   - id: tellurium
     kind: library
     package: tellurium
diff --git a/docs/plan-environment-composition.md b/docs/plan-environment-composition.md
index 1f11642f..60dc8d2e 100644
--- a/docs/plan-environment-composition.md
+++ b/docs/plan-environment-composition.md
@@ -480,10 +480,42 @@
        - a compliance case kept with it: a short PDE + Smoldyn ensemble with fixed seeds, the emitter fully
          qualified, and its expected values;
        - tested locally (lock, install, the case) before merge.
+       - *As built (2026-10-27):*
+         - **The wheel:** release `vcell-pyhybrid-e86d552` of `virtualcell/Smoldyn`, built by its workflow (#1, 7c-3).
+           sha256 `bb033bcc…`, checked on download. Builds are not bit-reproducible, so the entry takes the release
+           asset's hash.
+         - **The entries:**
+           - `smoldyn-vcell` (by URL), `vcell-fenics` (git `4dab281`), `pyvcell-fvsolver` 0.11.1 and `zarr` 3.4.1;
+           - viva-pde-particle gains `install` (git `21dfe46`, viva-pde-particle#67's merge, below), the
+             `reference` extra, its conda engines, and `requires`.
+         - **`members_of` for a prebuilt image** now includes its bundled entries' requirements, which the image
+           installs its own way. Without that, a document of viva-pde-particle's classes alone would no longer be
+           covered by its image and would make a mash-up, breaking D7c.3.
+         - **Compliance case `viva-pde-particle/fokker-planck-ensemble`:** its own example (four seeded PDE + Smoldyn
+           trials) with the emitter fully qualified. A `scalar` expectation's `field` may now be a path
+           (`values.2.0`).
+         - **Checked with compose-api's own code, in Docker:**
+           - a document of its ensemble, `CopasiUTCStep` and RAMEmitter needs ten entries; no declared environment
+             covers them; they are composable, so `mash-05956395cf`;
+           - its generated workspace locked in 45 s (462 packages);
+           - the definition's URL check passed against the release;
+           - `pixi install --frozen` succeeded;
+           - compose-api's runner ran both cases, and its evaluator passed both: viva-pde-particle's nine
+             expectations, and pbsim-common's COPASI case against its reference;
+           - validation admits the case document in the mash-up.
+         - **`EnsembleRunner` imported its config (decided 2026-10-27).** Its `trial: "module:function"` imported
+           and called whatever a document named, which the address check never sees. Jim chose a fix in the class
+           (vivarium-collective/viva-pde-particle#67, merged as `21dfe46`): each trial function has its own
+           `Ensemble` subclass naming it in code (`FokkerPlanckEnsemble` for `trial_rho`), so the document picks the
+           trial by its address, its config is only `params`, `seeds` and `workers`, and `EnsembleRunner` is gone.
+           The same PR names the emitter fully qualified in `ensemble_document`. The case document moved to
+           `local:viva_pde_particle.ensemble.FokkerPlanckEnsemble`, and its values are unchanged.
+         - **The prebuilt image** (viva-pde-particle@1, `sha-8c16827`) still has `EnsembleRunner`, and a prebuilt
+           run's classes are not looked up. After the release, `environments create viva-pde-particle --image
+           …viva-pde-particle-compose@sha256:<sha-21dfe46's digest>` makes @2; it becomes the default, `environments
+           inspect` reads it back, and @1 is retired.
      - **7c-5. Live:** a release, then a document combining viva-pde-particle's processes with `CopasiUTCStep`,
        submitted signed in. It creates its mash-up, locks and builds it (expect a large image), and runs.
-     - **Optional, vivarium-collective with Jim's go-ahead:** viva-pde-particle's `ensemble_document` writes the fully
-       qualified emitter (`ensemble.py`, one line), so documents it generates pass validation as they are.
 
 8. **Retire** what composition replaced (surveyed 2026-10-26, when registry_env@5, composed, became the default).
 
diff --git a/tests/api/test_submission_rejection.py b/tests/api/test_submission_rejection.py
index 27df89a4..3481ede2 100644
--- a/tests/api/test_submission_rejection.py
+++ b/tests/api/test_submission_rejection.py
@@ -131,7 +131,8 @@ async def test_a_run_naming_no_environment_goes_where_its_classes_are(
     http_api_client: httpx.AsyncClient, database_service: DatabaseService
 ) -> None:
     """Step 7a (D7.1): a document using only viva-pde-particle's classes is inferred to run in its image when the
-    deployment offers it, as if it had named it; offered nowhere, the shared environment refuses it as before."""
+    deployment offers it, as if it had named it. Offered nowhere, its classes are composable since composition 7c-4,
+    so the run needs a mash-up, which only a signed-in caller may cause (D7.4): an anonymous one is told to sign in."""
     await register_prebuilt(database_service, PREBUILT, PDE_IMAGE)
     inferred = await http_api_client.post(
         "/simulation/run", files={"uploaded_file": ("doc.pbg", pbg(PDE), "application/json")}
@@ -141,9 +142,9 @@ async def test_a_run_naming_no_environment_goes_where_its_classes_are(
     refused = await http_api_client.post(
         "/simulation/run", files={"uploaded_file": ("doc.pbg", pbg(PDE), "application/json")}
     )
-    assert refused.status_code == 400
-    (violation,) = refused.json()["detail"]["violations"]
-    assert "not installed in the environment `registry_env`" in violation["reason"]
+    assert refused.status_code == 401, refused.text
+    detail = refused.json()["detail"]
+    assert "viva-pde-particle" in detail and "sign in to have one made" in detail
 
 
 @pytest.mark.asyncio
diff --git a/tests/environments/test_compliance.py b/tests/environments/test_compliance.py
index aa6c4858..22afb637 100644
--- a/tests/environments/test_compliance.py
+++ b/tests/environments/test_compliance.py
@@ -140,3 +140,23 @@ def test_viva_basic_processes_case_checks_plain_numbers() -> None:
     assert not outcome.passed and outcome.failures == ["emitter.y in row -1: 33.0, expected 34.0"]
     missing = evaluate(case, {"emitter": [{"x": 1.0}]})
     assert any("no number" in f for f in missing.failures)
+
+
+def test_viva_pde_particles_case_reads_an_ensembles_values_by_path() -> None:
+    """Its emitter records each seed's values as lists, so `scalar` reads `values.2.0`: a path into lists and maps
+    (composition 7c-4). The rows are what compose-api's runner emitted for this document in the registry_env@5 +
+    viva-pde-particle environment on 2026-10-27, identical to its prebuilt image's."""
+    (case,) = load_cases("viva-pde-particle")
+    assert compliance.case_problems(case) == []
+    values = [[0.07137369415367853, 0.0004004746655585104], [0.0, 0.0],
+              [0.09234150979599469, 0.0020975747341526988], [0.0, 0.0]]  # fmt: skip
+    rows = [{"seeds": [], "values": []}, {"seeds": [1, 2, 3, 4], "values": values}]
+    assert evaluate(case, {"emitter": rows}).passed
+    off = [rows[0], {"seeds": [1, 2, 3, 4], "values": [values[0], values[1], [0.09, 0.002], values[3]]}]
+    outcome = evaluate(case, {"emitter": off})
+    assert not outcome.passed and any(f.startswith("emitter.values.2.0 in row -1: 0.09") for f in outcome.failures)
+    short = evaluate(case, {"emitter": [rows[0], {"seeds": [1], "values": [values[0]]}]})
+    assert any("no number (IndexError" in f for f in short.failures)
+    # the document names its emitter fully qualified (D7c.2), never viva-pde-particle's own short `ram-emitter`
+    document = json.loads(case.path(case.document).read_text())
+    assert document["state"]["emitter"]["address"] == "local:process_bigraph.emitter.RAMEmitter"
diff --git a/tests/environments/test_mash_up_creation.py b/tests/environments/test_mash_up_creation.py
index 7c47dc6c..fd1259ba 100644
--- a/tests/environments/test_mash_up_creation.py
+++ b/tests/environments/test_mash_up_creation.py
@@ -115,7 +115,8 @@ def test_a_mash_up_is_named_by_its_entries_and_only_composable_ones_qualify() ->
     assert lifecycle.composable(NEEDED, manifest) == []
     (listed,) = lifecycle.composable({"viva-tellurium"}, manifest)  # a catalog wrapper: no install, `listed`
     assert "does not say how it installs" in listed
-    assert any("cannot be composed" in p for p in lifecycle.composable({"viva-pde-particle"}, manifest))
+    # viva-pde-particle is composable since composition 7c-4: its classes may join a mash-up
+    assert lifecycle.composable(manifest.with_requirements({"viva-pde-particle"}), manifest) == []
 
 
 def test_declared_environments_cover_before_mash_ups() -> None:
diff --git a/tests/environments/test_url_installs.py b/tests/environments/test_url_installs.py
index ba4ef3e7..5bb62f33 100644
--- a/tests/environments/test_url_installs.py
+++ b/tests/environments/test_url_installs.py
@@ -83,7 +83,8 @@ def test_the_check_passes_the_wheel_or_fails_the_build(tmp_path: Path, matches:
 
 
 def test_a_mash_up_may_list_a_url_entry() -> None:
-    manifest = Manifest(entries=[*load_manifest().entries, _smoldyn()])
+    others = [e for e in load_manifest().entries if e.id != "smoldyn-vcell"]
+    manifest = Manifest(entries=[*others, _smoldyn()])
     spec = EnvironmentSpec(name="mash-x", kind="mash-up", python=["python"], entries=["smoldyn-vcell"])
     composed = ComposedSpec.of(spec, manifest, COMPOSITION, WHEN)
     assert composed.as_json()["entries"][0]["install"] == {"url": WHEEL, "sha256": SHA}
diff --git a/tests/registry/test_core_entries.py b/tests/registry/test_core_entries.py
index a1a86a09..92ce0236 100644
--- a/tests/registry/test_core_entries.py
+++ b/tests/registry/test_core_entries.py
@@ -92,3 +92,22 @@ def test_a_core_entry_needs_module_roots() -> None:
         RegistryEntry(
             id="x", package="x", source="s", kind="core", version="1", level=CurationLevel.TESTED, module_roots=[]
         )
+
+
+def test_viva_pde_particle_and_copasi_make_a_mash_up_that_admits_them() -> None:
+    """The motivating mash-up (composition 7c): viva-pde-particle's ensemble beside pbsim-common's COPASI step, with
+    process-bigraph's emitter. No declared environment covers both, so a mash-up of exactly what they need is made,
+    and its version admits every address. Locked, built and run in Docker on 2026-10-27 (7c-4)."""
+    from compose_api.environments import lifecycle
+    from compose_api.registry.resolver import covering_environment
+
+    manifest = load_manifest()
+    targets = ["viva_pde_particle.ensemble.FokkerPlanckEnsemble", COPASI[6:], RAM[6:]]
+    needed = needed_entries(targets, manifest)
+    assert {"viva-pde-particle", "smoldyn-vcell", "pbsim-common", "python-copasi"} <= needed
+    assert "process-bigraph-emitters" not in needed
+    assert covering_environment(needed, manifest, load_environments()) is None
+    assert lifecycle.composable(needed, manifest) == []
+    standing = Standing(label=f"{lifecycle.mash_up_name(needed)}@1", members=frozenset(needed))
+    for address in ("local:viva_pde_particle.ensemble.FokkerPlanckEnsemble", COPASI, RAM):
+        assert _reason(address, standing) is None, address
diff --git a/tests/registry/test_environments.py b/tests/registry/test_environments.py
index 81402354..c21b3fdd 100644
--- a/tests/registry/test_environments.py
+++ b/tests/registry/test_environments.py
@@ -154,7 +154,9 @@ def test_summaries_describe_the_default_versions_manifest() -> None:
     current = summarize(spec, {"viva-pde-particle": PDE_IMAGE}, manifest)
     assert current is not None
     assert (current.simulator, current.components, current.errors, current.stale) == ("viva-pde-particle", 2, 1, False)
-    assert current.process_bigraph == "1.8.5" and [e.id for e in current.entries] == ["viva-pde-particle"]
+    # its entry and what it requires, which its image installs (composition 7c-4), as registry_env lists its libraries
+    assert current.process_bigraph == "1.8.5" and "viva-pde-particle" in [e.id for e in current.entries]
+    assert {"smoldyn-vcell", "vcell-fenics"} <= {e.id for e in current.entries}
 
     shared = next(e for e in load_environments().environments if e.kind == "shared")
     listed = summarize(shared, {}, None)
diff --git a/tests/registry/test_resolver.py b/tests/registry/test_resolver.py
index d0fad80a..a57ded0b 100644
--- a/tests/registry/test_resolver.py
+++ b/tests/registry/test_resolver.py
@@ -38,7 +38,9 @@ def test_every_class_registry_env_provides_still_runs_there() -> None:
 def test_a_prebuilt_environments_classes_go_to_it_when_it_is_offered() -> None:
     manifest = load_manifest()
     needed = needed_entries([PDE], manifest)
-    assert needed == {"viva-pde-particle"}
+    # its requirements come with it (composition 7c-4: it is composable now), and its image provides them, so a
+    # document of its classes alone still runs in its prebuilt image (D7c.3), not in a mash-up
+    assert "viva-pde-particle" in needed and "smoldyn-vcell" in needed
     assert choose_environment(needed, manifest, EVERYWHERE).name == "viva-pde-particle"
     # not offered here: the shared environment, whose validation then says the entry is not installed in it
     assert choose_environment(needed, manifest, EVERYWHERE, offered=lambda spec: False).name == "registry_env"