diff --git a/lib/microwaveprop/partition_manager.ex b/lib/microwaveprop/partition_manager.ex
index d8235aa4..a92b81cf 100644
--- a/lib/microwaveprop/partition_manager.ex
+++ b/lib/microwaveprop/partition_manager.ex
@@ -40,6 +40,14 @@ defmodule Microwaveprop.PartitionManager do
 
   @default_parents ~w(hrrr_profiles hrdps_profiles)
 
+  @typedoc """
+  Per-partition result. `parent` is the parent table name, `name` is
+  the resolved child partition name, and the status flags whether
+  this call performed the CREATE or found an existing partition that
+  already covered the range.
+  """
+  @type result :: {parent :: String.t(), name :: String.t(), :created | :exists}
+
   @doc """
   For each configured parent table, ensure partitions covering the
   current quarter and the next `lookahead_quarters` quarters exist.
@@ -47,8 +55,7 @@ defmodule Microwaveprop.PartitionManager do
   Returns a list of `{parent, partition_name, :created | :exists}`
   entries so the worker can log a single summary line.
   """
-  @spec ensure_quarterly_partitions(non_neg_integer(), [String.t()]) ::
-          [{String.t(), String.t(), :created | :exists}]
+  @spec ensure_quarterly_partitions(non_neg_integer(), [String.t()]) :: [result()]
   def ensure_quarterly_partitions(lookahead_quarters \\ 4, parents \\ @default_parents)
       when is_integer(lookahead_quarters) and lookahead_quarters >= 0 and is_list(parents) do
     today = Date.utc_today()
@@ -59,10 +66,8 @@ defmodule Microwaveprop.PartitionManager do
     end
   end
 
-  # Public for direct access from tests / mix tasks. Returns
-  # `{parent, partition_name, :created | :exists}`.
-  @spec ensure_partition(String.t(), Date.t(), Date.t()) ::
-          {String.t(), String.t(), :created | :exists}
+  # Public for direct access from tests / mix tasks.
+  @spec ensure_partition(String.t(), Date.t(), Date.t()) :: result()
   def ensure_partition(parent, %Date{} = q_start, %Date{} = q_end) do
     name = partition_name(parent, q_start)
 
diff --git a/lib/microwaveprop/pskr/calibration_sampler.ex b/lib/microwaveprop/pskr/calibration_sampler.ex
index 9e6deb42..a2a20cfc 100644
--- a/lib/microwaveprop/pskr/calibration_sampler.ex
+++ b/lib/microwaveprop/pskr/calibration_sampler.ex
@@ -150,6 +150,7 @@ defmodule Microwaveprop.Pskr.CalibrationSampler do
   # a midpoint enqueue once, and let `HrrrPointEnqueuer.enqueue/1`
   # union the points into the existing `hrrr_fetch_tasks` row for
   # this hour rather than racing to insert duplicates.
+  @spec enqueue_missing_hrrr(map(), DateTime.t(), [map()]) :: :ok
   defp enqueue_missing_hrrr(cells, hour_utc, hrrr_index) do
     points =
       cells
diff --git a/lib/microwaveprop/workers/partition_maintenance_worker.ex b/lib/microwaveprop/workers/partition_maintenance_worker.ex
index b64cdc91..130aea6f 100644
--- a/lib/microwaveprop/workers/partition_maintenance_worker.ex
+++ b/lib/microwaveprop/workers/partition_maintenance_worker.ex
@@ -28,6 +28,7 @@ defmodule Microwaveprop.Workers.PartitionMaintenanceWorker do
   @lookahead_quarters 4
 
   @impl Oban.Worker
+  @spec perform(Oban.Job.t()) :: :ok
   def perform(%Oban.Job{args: args}) do
     lookahead = lookahead(args)
     results = PartitionManager.ensure_quarterly_partitions(lookahead)
@@ -46,6 +47,7 @@ defmodule Microwaveprop.Workers.PartitionMaintenanceWorker do
     :ok
   end
 
+  @spec lookahead(map()) :: non_neg_integer()
   defp lookahead(%{"lookahead_quarters" => n}) when is_integer(n) and n >= 0, do: n
   defp lookahead(_), do: @lookahead_quarters
 end
diff --git a/test/microwaveprop/pskr/calibration_sampler_test.exs b/test/microwaveprop/pskr/calibration_sampler_test.exs
index dd04ad1c..8872d818 100644
--- a/test/microwaveprop/pskr/calibration_sampler_test.exs
+++ b/test/microwaveprop/pskr/calibration_sampler_test.exs
@@ -205,6 +205,48 @@ defmodule Microwaveprop.Pskr.CalibrationSamplerTest do
       assert Enum.sort(sample.modes) == ["FT4", "FT8"]
     end
 
+    test "two-pass pipeline: first run NULL+enqueue, second run UPSERTs with HRRR" do
+      # End-to-end behaviour the producer was added for: a cell with no
+      # nearby HRRR profile gets a sample row written with NULL weather
+      # fields *and* a fetch task enqueued; once the Rust hrrr-point-worker
+      # delivers the profile (simulated here by directly inserting an
+      # hrrr_profiles row), the next sampler pass UPSERTs the same
+      # calibration_samples row, this time with non-NULL HRRR fields.
+      insert_spot!(%{midpoint_lat: 33.0, midpoint_lon: -97.0})
+
+      # ── Pass 1 ─────────────────────────────────────────────────
+      assert CalibrationSampler.build_for_hour(@hour) == 1
+      [first_sample] = Repo.all(CalibrationSample)
+      assert first_sample.surface_temp_c == nil
+      assert first_sample.hpbl_m == nil
+      assert Repo.aggregate(from(t in "hrrr_fetch_tasks"), :count) == 1
+
+      # ── Rust worker drains the task (simulated) ────────────────
+      insert_hrrr!(%{
+        lat: 33.0,
+        lon: -97.0,
+        surface_temp_c: 24.0,
+        surface_dewpoint_c: 18.0,
+        pwat_mm: 31.0,
+        min_refractivity_gradient: -120.0,
+        hpbl_m: 480.0,
+        ducting_detected: true
+      })
+
+      # ── Pass 2 ─────────────────────────────────────────────────
+      assert CalibrationSampler.build_for_hour(@hour) == 1
+      [second_sample] = Repo.all(CalibrationSample)
+
+      # Same row, UPSERTed (id preserved, weather populated).
+      assert second_sample.id == first_sample.id
+      assert second_sample.surface_temp_c == 24.0
+      assert second_sample.surface_dewpoint_c == 18.0
+      assert second_sample.pwat_mm == 31.0
+      assert second_sample.min_refractivity_gradient == -120.0
+      assert second_sample.hpbl_m == 480.0
+      assert second_sample.hrrr_ducting_detected == true
+    end
+
     test "is idempotent — re-running the same hour upserts the row" do
       insert_spot!(%{})
       insert_hrrr!(%{lat: 33.0, lon: -97.0})