diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 677bc034..71d3683e 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -20,6 +20,7 @@ repos:
       - id: check-toml
       - id: check-added-large-files
         args: [--maxkb=5000]  # parity fixture parquets can be larger than default 500KB
+        exclude: ^tests/fixtures/parity/pinned_cache\.tar\.xz$  # 5.1MB pinned raw-source bundle (deliberate, documented in fixtures/parity/README.md)
 
   - repo: local
     hooks:
diff --git a/tests/fixtures/parity/README.md b/tests/fixtures/parity/README.md
index 718fa0b6..c36997a3 100644
--- a/tests/fixtures/parity/README.md
+++ b/tests/fixtures/parity/README.md
@@ -8,6 +8,102 @@
 > Do **NOT** regenerate these files in CI. They are settlement-grade
 > reference data; the bytes ARE the Day 3 hard-gate ground truth.
 
+## Pinned-input redesign (2026-07-15, operator-directed — release 1.17.0 gate)
+
+The parity gate now runs in TWO variants (see `tests/test_parity.py`):
+
+- **`test_parity_case_pinned` — the HARD gate.** Runs `research()` fully
+  OFFLINE (socket-level network block) and **CACHE-COLD** over
+  `pinned_cache.tar.xz` — a committed bundle of the RAW `v1/sources/`
+  fetch text (IEM CSV / GHCNh PSV / CLI JSON; 82 MB raw → 5.1 MB xz),
+  captured live on **2026-07-15** by `capture_pinned_cache.py` from main
+  @ `02580c3`. Cold replay forces the production parsers,
+  `merge_observations`/`merge_climate` SOURCE_PRIORITY logic, aggregation,
+  and the join to execute on every gate run (codex PR-124 CRITICAL:
+  pinning the derived parquet tiers instead would let the warm-cache path
+  skip all of them). Deterministic forever; lives in the default fast
+  suite (every CI push), not behind `-m live`. All-5-case replay ≈ 7 s.
+- **`test_parity_case_live` — the upstream-drift monitor** (`-m live`,
+  pre-publish). A failure here while the pinned gate is green means the
+  mutable IEM/AWC archive drifted since the pin — audit that the diff is
+  confined to count-consistent `obs_*` sum-aggregates (`cli_*` +
+  `obs_high_f`/`obs_low_f` MUST stay clean), then deliberately re-pin via
+  `capture_pinned_cache.py` and extend the audit table below.
+
+**Validation of the approach:** replaying the pinned inputs through current
+code reproduces the original v0.14.1 fixtures for cases 1/2/5 EXACTLY
+(within the standing ULP `atol`) — the code is byte-faithful to 0.14.1
+wherever the archive did not move.
+
+### Drifted-cell re-base audit (2026-07-15)
+
+Between the May-2026 capture and the 2026-07-15 pin, the upstream archive
+restated 1 KLAX day + 17 KMIA days (late/corrected METARs — every diff is
+count-consistent). The 55 cells below were re-based onto the pinned-archive
+values; **every other cell in every fixture remains original 0.14.1
+bytes.** Settlement-critical columns (`cli_high_f`/`cli_low_f`/
+`cli_report_type`/`obs_high_f`/`obs_low_f`) were untouched on all cases.
+The pre-patch parquets are preserved in git history (last at the
+`v1.17.0`-candidate merge `02580c3`).
+
+| case | date | column | v0.14.1 fixture value | pinned-archive value |
+|------|------|--------|-----------------------|----------------------|
+| case-3 | 2025-03-12 | obs_mean_f | 56.739999999999995 | 56.782641509433965 |
+| case-3 | 2025-03-12 | obs_mean_dewpoint_f | 52.61076923076923 | 52.61924528301887 |
+| case-3 | 2025-03-12 | obs_count | 52 | 53 |
+| case-4 | 2025-01-31 | obs_mean_f | 73.7235294117647 | 73.81714285714285 |
+| case-4 | 2025-02-07 | obs_mean_f | 74.67870967741935 | 74.846875 |
+| case-4 | 2025-02-09 | obs_mean_f | 75.6174193548387 | 75.784375 |
+| case-4 | 2025-02-10 | obs_mean_f | 75.41085714285714 | 75.54 |
+| case-4 | 2025-02-11 | obs_mean_f | 75.39696969696969 | 75.50235294117647 |
+| case-4 | 2025-02-20 | obs_mean_f | 71.244 | 71.3488888888889 |
+| case-4 | 2025-03-12 | obs_mean_f | 69.67548387096774 | 69.938125 |
+| case-4 | 2025-05-12 | obs_mean_f | 75.60444444444444 | 75.72086956521738 |
+| case-4 | 2025-06-02 | obs_mean_f | 77.77771428571428 | 77.64611111111111 |
+| case-4 | 2025-06-11 | obs_mean_f | 83.93935483870968 | 84.00424242424242 |
+| case-4 | 2025-06-16 | obs_mean_f | 84.48451612903226 | 84.565625 |
+| case-4 | 2025-06-21 | obs_mean_f | 84.06484848484848 | 84.15352941176471 |
+| case-4 | 2025-09-11 | obs_mean_f | 80.73441860465117 | 80.78454545454545 |
+| case-4 | 2025-10-19 | obs_mean_f | 80.77483870967743 | 80.8425 |
+| case-4 | 2025-10-31 | obs_mean_f | 69.70967741935483 | 69.841875 |
+| case-4 | 2025-11-07 | obs_mean_f | 79.54709677419355 | 79.653125 |
+| case-4 | 2025-11-08 | obs_mean_f | 80.47625 | 80.58363636363637 |
+| case-4 | 2025-01-31 | obs_mean_dewpoint_f | 66.08764705882353 | 66.08571428571429 |
+| case-4 | 2025-02-07 | obs_mean_dewpoint_f | 65.6116129032258 | 65.5625 |
+| case-4 | 2025-02-09 | obs_mean_dewpoint_f | 68.03225806451613 | 67.969375 |
+| case-4 | 2025-02-10 | obs_mean_dewpoint_f | 67.57771428571428 | 67.55944444444444 |
+| case-4 | 2025-02-11 | obs_mean_dewpoint_f | 66.38545454545454 | 66.28470588235294 |
+| case-4 | 2025-02-20 | obs_mean_dewpoint_f | 63.15657142857143 | 63.07111111111111 |
+| case-4 | 2025-03-12 | obs_mean_dewpoint_f | 53.189677419354844 | 53.2475 |
+| case-4 | 2025-05-12 | obs_mean_dewpoint_f | 72.41555555555556 | 72.40565217391304 |
+| case-4 | 2025-06-02 | obs_mean_dewpoint_f | 73.2782857142857 | 73.21666666666667 |
+| case-4 | 2025-06-11 | obs_mean_dewpoint_f | 73.61419354838709 | 73.60666666666667 |
+| case-4 | 2025-06-16 | obs_mean_dewpoint_f | 71.54645161290323 | 71.593125 |
+| case-4 | 2025-06-21 | obs_mean_dewpoint_f | 72.7248484848485 | 72.67588235294117 |
+| case-4 | 2025-09-11 | obs_mean_dewpoint_f | 75.52139534883722 | 75.465 |
+| case-4 | 2025-10-19 | obs_mean_dewpoint_f | 72.29290322580646 | 72.31625 |
+| case-4 | 2025-10-31 | obs_mean_dewpoint_f | 57.097419354838706 | 57.095 |
+| case-4 | 2025-11-07 | obs_mean_dewpoint_f | 68.94193548387096 | 68.9125 |
+| case-4 | 2025-11-08 | obs_mean_dewpoint_f | 72.12125 | 72.05636363636364 |
+| case-4 | 2025-09-11 | obs_total_precip_in | 2.08 | 2.1784251968503936 |
+| case-4 | 2025-01-31 | obs_count | 34 | 35 |
+| case-4 | 2025-02-07 | obs_count | 31 | 32 |
+| case-4 | 2025-02-09 | obs_count | 31 | 32 |
+| case-4 | 2025-02-10 | obs_count | 35 | 36 |
+| case-4 | 2025-02-11 | obs_count | 33 | 34 |
+| case-4 | 2025-02-20 | obs_count | 35 | 36 |
+| case-4 | 2025-03-12 | obs_count | 31 | 32 |
+| case-4 | 2025-05-12 | obs_count | 45 | 46 |
+| case-4 | 2025-06-02 | obs_count | 35 | 36 |
+| case-4 | 2025-06-11 | obs_count | 31 | 33 |
+| case-4 | 2025-06-16 | obs_count | 31 | 32 |
+| case-4 | 2025-06-21 | obs_count | 33 | 34 |
+| case-4 | 2025-09-11 | obs_count | 43 | 44 |
+| case-4 | 2025-10-19 | obs_count | 31 | 32 |
+| case-4 | 2025-10-31 | obs_count | 31 | 32 |
+| case-4 | 2025-11-07 | obs_count | 31 | 32 |
+| case-4 | 2025-11-08 | obs_count | 32 | 33 |
+
 ## Case-4 re-baseline (2026-07-09, operator-approved — release 1.13.0 gate)
 
 `case_4_KMIA_2024-12-01_2025-11-30.parquet` (and its derived
diff --git a/tests/fixtures/parity/capture_pinned_cache.py b/tests/fixtures/parity/capture_pinned_cache.py
new file mode 100644
index 00000000..23b9d40b
--- /dev/null
+++ b/tests/fixtures/parity/capture_pinned_cache.py
@@ -0,0 +1,87 @@
+"""Capture the PINNED-INPUT cache bundle for the parity gate.
+
+Fetches the 5 parity windows live via ``mostlyright.research()`` into a
+staging ``MOSTLYRIGHT_CACHE_DIR``, strips the cache to the RAW source tier
+(``v1/sources/`` — the fetched IEM CSV / GHCNh PSV / CLI JSON text), and
+writes it compressed to ``tests/fixtures/parity/pinned_cache.tar.xz``.
+
+RAW sources, deliberately NOT the derived parquet tiers (codex PR-124
+CRITICAL): the offline gate replays CACHE-COLD from the raw text, so the
+production parsers (``_fetch_iem_month``/GHCNh/CLI), ``merge_observations``
+/ ``merge_climate`` SOURCE_PRIORITY logic, aggregation, and the join all
+execute under the network block on every run — a parser or merge
+regression fails the gate. Pinning derived parquets instead would let the
+warm-cache path skip all of that. (82 MB raw → 5.1 MB xz; cold replay of
+all 5 cases ≈ 5 s.)
+
+Why this exists (2026-07-15): the live parity gate compared "today's code +
+today's IEM/AWC archive" against fixtures frozen from ``mostlyright==0.14.1``
+in May 2026. The upstream archive is MUTABLE — late/corrected METARs shift
+the sum-then-divide ``obs_*`` aggregates (KLAX 2025-03, KMIA 2024-12..2025-11
+drifted) — and the 0.14.1 oracle can never be re-captured
+(api.mostlyright.md was re-pointed in Phase 28). Pinning the INPUTS converts
+the gate into a deterministic test of OUR aggregation/join code against the
+0.14.1 outputs, which is what it was always meant to prove.
+
+Run (live network, ~50 min — KMIA is a year window)::
+
+    uv run python tests/fixtures/parity/capture_pinned_cache.py
+
+Re-running OVERWRITES the pinned bundle from today's archive — only do this
+deliberately (it re-bases the input ground truth) and re-run the pinned gate
+plus the drifted-cell audit in README.md afterwards.
+"""
+
+from __future__ import annotations
+
+import os
+import shutil
+import sys
+import tarfile
+import tempfile
+import time
+from pathlib import Path
+
+FIXTURES = Path(__file__).resolve().parent
+PINNED_TARBALL = FIXTURES / "pinned_cache.tar.xz"
+
+CASES: list[tuple[int, str, str, str]] = [
+    (1, "KNYC", "2025-01-06", "2025-01-12"),
+    (2, "KMDW", "2025-04-01", "2025-04-30"),
+    (3, "KLAX", "2025-03-01", "2025-03-31"),
+    (4, "KMIA", "2024-12-01", "2025-11-30"),
+    (5, "KMSY", "2024-09-08", "2024-09-22"),
+]
+
+#: The RAW source tier the cache-cold offline replay parses. Derived tiers
+#: (``v1/observations``/``v1/climate``) and ``provenance/`` are deliberately
+#: excluded — they are rebuilt from raw text at test time so the production
+#: parse+merge+aggregate code is exercised on every gate run.
+_KEEP_TIER = "v1/sources"
+
+
+def main() -> int:
+    staging = Path(tempfile.mkdtemp(prefix="mr-parity-pin-"))
+    os.environ["MOSTLYRIGHT_CACHE_DIR"] = str(staging)
+    import mostlyright
+
+    for num, station, frm, to in CASES:
+        t0 = time.time()
+        df = mostlyright.research(station, frm, to, label="cli")
+        print(f"case-{num} {station} {frm}..{to}: {len(df)} rows in {time.time() - t0:.0f}s")
+
+    src = staging / _KEEP_TIER
+    if not src.is_dir():
+        raise RuntimeError(f"expected raw-source cache tier missing: {src}")
+    files = [f for f in sorted(src.rglob("*")) if f.is_file()]
+    with tarfile.open(PINNED_TARBALL, "w:xz") as tar:
+        for f in files:
+            tar.add(f, arcname=str(f.relative_to(staging)))
+    size_mb = PINNED_TARBALL.stat().st_size / 1e6
+    print(f"pinned {len(files)} raw-source files -> {PINNED_TARBALL} ({size_mb:.1f} MB)")
+    shutil.rmtree(staging)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/tests/fixtures/parity/case_3_KLAX_2025-03-01_2025-03-31.parquet b/tests/fixtures/parity/case_3_KLAX_2025-03-01_2025-03-31.parquet
index 1930da37..05ef1799 100644
Binary files a/tests/fixtures/parity/case_3_KLAX_2025-03-01_2025-03-31.parquet and b/tests/fixtures/parity/case_3_KLAX_2025-03-01_2025-03-31.parquet differ
diff --git a/tests/fixtures/parity/case_4_KMIA_2024-12-01_2025-11-30.parquet b/tests/fixtures/parity/case_4_KMIA_2024-12-01_2025-11-30.parquet
index 4d940421..5754903e 100644
Binary files a/tests/fixtures/parity/case_4_KMIA_2024-12-01_2025-11-30.parquet and b/tests/fixtures/parity/case_4_KMIA_2024-12-01_2025-11-30.parquet differ
diff --git a/tests/fixtures/parity/pinned_cache.tar.xz b/tests/fixtures/parity/pinned_cache.tar.xz
new file mode 100644
index 00000000..80f74978
Binary files /dev/null and b/tests/fixtures/parity/pinned_cache.tar.xz differ
diff --git a/tests/fixtures/parity/ts/case_3_KLAX_2025-03-01_2025-03-31.json b/tests/fixtures/parity/ts/case_3_KLAX_2025-03-01_2025-03-31.json
index bd27652d..51cc64ae 100644
--- a/tests/fixtures/parity/ts/case_3_KLAX_2025-03-01_2025-03-31.json
+++ b/tests/fixtures/parity/ts/case_3_KLAX_2025-03-01_2025-03-31.json
@@ -253,13 +253,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-03-13T00:30:00Z",
-    "obs_count": 52,
+    "obs_count": 53,
     "obs_high_f": 60.08,
     "obs_low_f": 53.0,
     "obs_max_gust_kt": 31.0,
     "obs_max_wind_kt": 17,
-    "obs_mean_dewpoint_f": 52.61076923076923,
-    "obs_mean_f": 56.739999999999995,
+    "obs_mean_dewpoint_f": 52.61924528301887,
+    "obs_mean_f": 56.782641509433965,
     "obs_total_precip_in": 0.15000000000000002,
     "station": "LAX"
   },
diff --git a/tests/fixtures/parity/ts/case_4_KMIA_2024-12-01_2025-11-30.json b/tests/fixtures/parity/ts/case_4_KMIA_2024-12-01_2025-11-30.json
index 06bd8029..652e53b4 100644
--- a/tests/fixtures/parity/ts/case_4_KMIA_2024-12-01_2025-11-30.json
+++ b/tests/fixtures/parity/ts/case_4_KMIA_2024-12-01_2025-11-30.json
@@ -1353,13 +1353,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-01-31T21:30:00Z",
-    "obs_count": 34,
+    "obs_count": 35,
     "obs_high_f": 78.08,
     "obs_low_f": 69.0,
     "obs_max_gust_kt": 25.0,
     "obs_max_wind_kt": 15,
-    "obs_mean_dewpoint_f": 66.08764705882353,
-    "obs_mean_f": 73.7235294117647,
+    "obs_mean_dewpoint_f": 66.08571428571429,
+    "obs_mean_f": 73.81714285714285,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -1507,13 +1507,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-02-07T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 32,
     "obs_high_f": 81.0,
     "obs_low_f": 68.0,
     "obs_max_gust_kt": 16.0,
     "obs_max_wind_kt": 12,
-    "obs_mean_dewpoint_f": 65.6116129032258,
-    "obs_mean_f": 74.67870967741935,
+    "obs_mean_dewpoint_f": 65.5625,
+    "obs_mean_f": 74.846875,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -1551,13 +1551,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-02-09T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 32,
     "obs_high_f": 82.04,
     "obs_low_f": 71.0,
     "obs_max_gust_kt": 21.0,
     "obs_max_wind_kt": 10,
-    "obs_mean_dewpoint_f": 68.03225806451613,
-    "obs_mean_f": 75.6174193548387,
+    "obs_mean_dewpoint_f": 67.969375,
+    "obs_mean_f": 75.784375,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -1573,13 +1573,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-02-10T21:30:00Z",
-    "obs_count": 35,
+    "obs_count": 36,
     "obs_high_f": 82.04,
     "obs_low_f": 68.0,
     "obs_max_gust_kt": 17.0,
     "obs_max_wind_kt": 11,
-    "obs_mean_dewpoint_f": 67.57771428571428,
-    "obs_mean_f": 75.41085714285714,
+    "obs_mean_dewpoint_f": 67.55944444444444,
+    "obs_mean_f": 75.54,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -1595,13 +1595,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-02-11T21:30:00Z",
-    "obs_count": 33,
+    "obs_count": 34,
     "obs_high_f": 81.0,
     "obs_low_f": 71.96,
     "obs_max_gust_kt": 22.0,
     "obs_max_wind_kt": 14,
-    "obs_mean_dewpoint_f": 66.38545454545454,
-    "obs_mean_f": 75.39696969696969,
+    "obs_mean_dewpoint_f": 66.28470588235294,
+    "obs_mean_f": 75.50235294117647,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -1793,13 +1793,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-02-20T21:30:00Z",
-    "obs_count": 35,
+    "obs_count": 36,
     "obs_high_f": 76.0,
     "obs_low_f": 63.0,
     "obs_max_gust_kt": 18.0,
     "obs_max_wind_kt": 11,
-    "obs_mean_dewpoint_f": 63.15657142857143,
-    "obs_mean_f": 71.244,
+    "obs_mean_dewpoint_f": 63.07111111111111,
+    "obs_mean_f": 71.3488888888889,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -2233,13 +2233,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-03-12T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 32,
     "obs_high_f": 80.06,
     "obs_low_f": 60.980000000000004,
     "obs_max_gust_kt": 16.0,
     "obs_max_wind_kt": 11,
-    "obs_mean_dewpoint_f": 53.189677419354844,
-    "obs_mean_f": 69.67548387096774,
+    "obs_mean_dewpoint_f": 53.2475,
+    "obs_mean_f": 69.938125,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -3575,13 +3575,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-05-12T21:30:00Z",
-    "obs_count": 45,
+    "obs_count": 46,
     "obs_high_f": 84.0,
     "obs_low_f": 71.0,
     "obs_max_gust_kt": 31.0,
     "obs_max_wind_kt": 21,
-    "obs_mean_dewpoint_f": 72.41555555555556,
-    "obs_mean_f": 75.60444444444444,
+    "obs_mean_dewpoint_f": 72.40565217391304,
+    "obs_mean_f": 75.72086956521738,
     "obs_total_precip_in": 9.68,
     "station": "MIA"
   },
@@ -4037,13 +4037,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-06-02T21:30:00Z",
-    "obs_count": 35,
+    "obs_count": 36,
     "obs_high_f": 89.0,
     "obs_low_f": 72.0,
     "obs_max_gust_kt": 43.0,
     "obs_max_wind_kt": 15,
-    "obs_mean_dewpoint_f": 73.2782857142857,
-    "obs_mean_f": 77.77771428571428,
+    "obs_mean_dewpoint_f": 73.21666666666667,
+    "obs_mean_f": 77.64611111111111,
     "obs_total_precip_in": 6.92,
     "station": "MIA"
   },
@@ -4235,13 +4235,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-06-11T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 33,
     "obs_high_f": 89.06,
     "obs_low_f": 80.0,
     "obs_max_gust_kt": 21.0,
     "obs_max_wind_kt": 14,
-    "obs_mean_dewpoint_f": 73.61419354838709,
-    "obs_mean_f": 83.93935483870968,
+    "obs_mean_dewpoint_f": 73.60666666666667,
+    "obs_mean_f": 84.00424242424242,
     "obs_total_precip_in": 0.4,
     "station": "MIA"
   },
@@ -4345,13 +4345,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-06-16T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 32,
     "obs_high_f": 89.06,
     "obs_low_f": 78.0,
     "obs_max_gust_kt": 21.0,
     "obs_max_wind_kt": 13,
-    "obs_mean_dewpoint_f": 71.54645161290323,
-    "obs_mean_f": 84.48451612903226,
+    "obs_mean_dewpoint_f": 71.593125,
+    "obs_mean_f": 84.565625,
     "obs_total_precip_in": 0.12,
     "station": "MIA"
   },
@@ -4455,13 +4455,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-06-21T21:30:00Z",
-    "obs_count": 33,
+    "obs_count": 34,
     "obs_high_f": 87.08000000000001,
     "obs_low_f": 79.0,
     "obs_max_gust_kt": 19.0,
     "obs_max_wind_kt": 13,
-    "obs_mean_dewpoint_f": 72.7248484848485,
-    "obs_mean_f": 84.06484848484848,
+    "obs_mean_dewpoint_f": 72.67588235294117,
+    "obs_mean_f": 84.15352941176471,
     "obs_total_precip_in": 0.11,
     "station": "MIA"
   },
@@ -6259,14 +6259,14 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-09-11T21:30:00Z",
-    "obs_count": 43,
+    "obs_count": 44,
     "obs_high_f": 92.0,
     "obs_low_f": 76.0,
     "obs_max_gust_kt": 24.0,
     "obs_max_wind_kt": 16,
-    "obs_mean_dewpoint_f": 75.52139534883722,
-    "obs_mean_f": 80.73441860465117,
-    "obs_total_precip_in": 2.08,
+    "obs_mean_dewpoint_f": 75.465,
+    "obs_mean_f": 80.78454545454545,
+    "obs_total_precip_in": 2.1784251968503936,
     "station": "MIA"
   },
   {
@@ -7095,13 +7095,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-10-19T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 32,
     "obs_high_f": 85.0,
     "obs_low_f": 77.0,
     "obs_max_gust_kt": 22.0,
     "obs_max_wind_kt": 15,
-    "obs_mean_dewpoint_f": 72.29290322580646,
-    "obs_mean_f": 80.77483870967743,
+    "obs_mean_dewpoint_f": 72.31625,
+    "obs_mean_f": 80.8425,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -7359,13 +7359,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-10-31T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 32,
     "obs_high_f": 76.0,
     "obs_low_f": 64.94,
     "obs_max_gust_kt": 15.0,
     "obs_max_wind_kt": 8,
-    "obs_mean_dewpoint_f": 57.097419354838706,
-    "obs_mean_f": 69.70967741935483,
+    "obs_mean_dewpoint_f": 57.095,
+    "obs_mean_f": 69.841875,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -7513,13 +7513,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-11-07T21:30:00Z",
-    "obs_count": 31,
+    "obs_count": 32,
     "obs_high_f": 87.0,
     "obs_low_f": 75.0,
     "obs_max_gust_kt": null,
     "obs_max_wind_kt": 8,
-    "obs_mean_dewpoint_f": 68.94193548387096,
-    "obs_mean_f": 79.54709677419355,
+    "obs_mean_dewpoint_f": 68.9125,
+    "obs_mean_f": 79.653125,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
@@ -7535,13 +7535,13 @@
     "fcst_pop_6hr_pct": null,
     "fcst_qpf_6hr_in": null,
     "market_close_utc": "2025-11-08T21:30:00Z",
-    "obs_count": 32,
+    "obs_count": 33,
     "obs_high_f": 86.0,
     "obs_low_f": 75.92,
     "obs_max_gust_kt": 16.0,
     "obs_max_wind_kt": 10,
-    "obs_mean_dewpoint_f": 72.12125,
-    "obs_mean_f": 80.47625,
+    "obs_mean_dewpoint_f": 72.05636363636364,
+    "obs_mean_f": 80.58363636363637,
     "obs_total_precip_in": 0.0,
     "station": "MIA"
   },
diff --git a/tests/fixtures/parity/ts/manifest.json b/tests/fixtures/parity/ts/manifest.json
index 1855a1bb..5f512242 100644
--- a/tests/fixtures/parity/ts/manifest.json
+++ b/tests/fixtures/parity/ts/manifest.json
@@ -82,7 +82,7 @@
     },
     "from": "2025-03-01",
     "row_count": 31,
-    "sha256": "126e868501355c0fc861c8fc77ae16365c8367398bb87f6b3c2a5826c7880078",
+    "sha256": "4beef03dcc62b11af6c43e96cce9e50bf583dce7435622cbf0d684f30717a9f0",
     "station": "KLAX",
     "to": "2025-03-31"
   },
@@ -111,7 +111,7 @@
     },
     "from": "2024-12-01",
     "row_count": 365,
-    "sha256": "6d38652ecb1d83e6ad4d40b639a90923bf660255ab4f0895fabfa3e181c8d4e6",
+    "sha256": "9cf030452508f329823b4bdc3524541bb2d93b50a686052b698b098ba924e524",
     "station": "KMIA",
     "to": "2025-11-30"
   },
diff --git a/tests/test_parity.py b/tests/test_parity.py
index a8041d05..be80665a 100644
--- a/tests/test_parity.py
+++ b/tests/test_parity.py
@@ -1,13 +1,42 @@
-"""Day 3 HARD GATE - 5-fixture byte-equivalent parity vs mostlyright==0.14.1.
-
-This test IS the Sprint 0 parity gate. Sprint 0 ships only if all 5
-parametrized cases pass against the captured ``case_*.parquet`` fixtures.
-Each case calls ``mostlyright.research(station, frm, to)`` against the
-real public APIs (IEM ASOS, IEM CLI, GHCNh) and compares the returned
-DataFrame to the v0.14.1 ``client.pairs()`` output.
-
-Marked ``@pytest.mark.live`` per CLAUDE.md testing playbook - the default
-``-m "not live"`` pytest invocation skips this; run explicitly with::
+"""HARD GATE - 5-fixture byte-equivalent parity vs mostlyright==0.14.1.
+
+This test IS the parity gate. A release ships only if all 5 parametrized
+cases pass against the captured ``case_*.parquet`` fixtures (the last
+output ``mostlyright==0.14.1`` ever produced - the oracle is gone:
+``api.mostlyright.md`` was re-pointed in Phase 28, so the fixtures can
+never be re-captured).
+
+TWO variants (pinned-input redesign, 2026-07-15):
+
+- ``test_parity_case_pinned`` - **the HARD gate.** Runs ``research()``
+  fully OFFLINE (network hard-blocked) and CACHE-COLD over the committed
+  ``pinned_cache.tar.xz`` bundle - the RAW ``v1/sources/`` fetch text
+  (IEM CSV / GHCNh PSV / CLI JSON, captured 2026-07-15 by
+  ``fixtures/parity/capture_pinned_cache.py``). Cold replay means the
+  production parsers, ``merge_observations``/``merge_climate``
+  SOURCE_PRIORITY logic, aggregation, and the join ALL execute on every
+  run (codex PR-124 CRITICAL: pinning derived parquets would let the
+  warm-cache path skip them). Deterministic forever; runs in the default
+  fast suite. This tests OUR parse-merge-aggregate-join code against the
+  0.14.1 outputs - which is what the gate was always meant to prove.
+- ``test_parity_case_live`` - **the upstream-drift monitor** (marked
+  ``live``; pre-publish runbook only). Same assertions against the LIVE
+  IEM/AWC/GHCNh/CLI APIs. Because the upstream archive is MUTABLE
+  (late/corrected METARs move the sum-then-divide ``obs_*`` aggregates),
+  a failure here WHILE the pinned gate is green means the ARCHIVE
+  drifted, not the code: audit the diff (must be confined to ``obs_*``
+  count-consistent cells; ``cli_*``/``obs_high_f``/``obs_low_f`` clean),
+  then deliberately re-pin via ``capture_pinned_cache.py`` and document
+  the re-based cells in ``fixtures/parity/README.md``.
+
+The KLAX 2025-03-12 + 17 KMIA days drifted upstream between the May-2026
+fixture capture and 2026-07-15; those 55 cells (obs_mean_f /
+obs_mean_dewpoint_f / obs_total_precip_in / obs_count ONLY) were re-based
+onto the pinned archive - the per-cell audit lives in
+``fixtures/parity/README.md``. Every other cell remains original 0.14.1
+bytes, and cases 1/2/5 reproduce 0.14.1 EXACTLY from the pinned inputs.
+
+Run the live monitor explicitly with::
 
     uv run pytest tests/test_parity.py -m live -v
 
@@ -152,6 +181,18 @@ def _pd3_translate_expected(expected: dict[str, str], df: pd.DataFrame) -> dict[
         return expected
     out = dict(expected)
     for col, dtype_str in expected.items():
+        # pandas 3 default datetime resolution inference is MICROSECOND for
+        # freshly-CONSTRUCTED frames (research() output) but parquet-read
+        # frames stay nanosecond — the documented, lossless ns → us shift
+        # from coerce_pd3.py (second-resolution timestamps only in the
+        # v0.14.1 contract). Conditional on the actual frame, exactly like
+        # the string translation below: only ns and us are accepted — any
+        # other dtype still hard-fails.
+        if dtype_str.startswith("datetime64[ns") and col in df.columns:
+            actual_dt = str(df[col].dtype)
+            if actual_dt.startswith("datetime64[us"):
+                out[col] = dtype_str.replace("[ns", "[us", 1)
+            continue
         if dtype_str != "object" or col not in df.columns:
             continue
         non_null = df[col].dropna().head(5)
@@ -160,14 +201,115 @@ def _pd3_translate_expected(expected: dict[str, str], df: pd.DataFrame) -> dict[
     return out
 
 
+def _pd3_align_expected_frame(df: pd.DataFrame) -> pd.DataFrame:
+    """Coerce a pd2-written fixture frame's datetime columns ns → us under pd3.
+
+    The DATETIME half of the documented ``coerce_pd3.py`` bridge, applied
+    inline: a live/pinned ``research()`` frame under pandas 3 infers
+    microsecond resolution while the pd2-written parquet reads back as
+    nanoseconds. Lossless (the contract carries second-resolution
+    timestamps). The bridge's ``object → string`` half is deliberately NOT
+    applied - pandas 3's parquet reader already lands string columns on the
+    ``str`` dtype that live frames carry, and ``_pd3_translate_expected``
+    pins that expectation.
+    """
+    if not _PD3:
+        return df
+    out = df.copy()
+    for col in out.columns:
+        dtype_str = str(out[col].dtype)
+        if dtype_str.startswith("datetime64[ns"):
+            out[col] = out[col].astype(dtype_str.replace("[ns", "[us", 1))
+    return out
+
+
+PINNED_TARBALL = FIXTURES / "pinned_cache.tar.xz"
+
+
+@pytest.fixture(scope="module")
+def _pinned_cache_root(tmp_path_factory: pytest.TempPathFactory) -> Path:
+    """Unpack the pinned RAW-source bundle once for the module.
+
+    The bundle carries ONLY ``v1/sources/`` (the raw IEM CSV / GHCNh PSV /
+    CLI JSON text captured 2026-07-15) - NO derived parquet tiers - so every
+    gate run replays CACHE-COLD through the production parsers,
+    ``merge_observations``/``merge_climate`` SOURCE_PRIORITY logic,
+    aggregation, and the join (codex PR-124 CRITICAL: pinning the derived
+    tiers instead would let the warm-cache path skip all of that). Derived
+    rows written during replay land in this shared per-module root: within a
+    single case the 2nd/3rd ``research()`` calls go cache-warm (production
+    behavior), and the 5 cases never share a station.
+    """
+    import tarfile
+
+    assert PINNED_TARBALL.is_file(), (
+        "tests/fixtures/parity/pinned_cache.tar.xz missing - run "
+        "`uv run python tests/fixtures/parity/capture_pinned_cache.py`"
+    )
+    root = tmp_path_factory.mktemp("pinned-cache")
+    with tarfile.open(PINNED_TARBALL, "r:xz") as tar:
+        try:
+            tar.extractall(root, filter="data")
+        except TypeError:  # Python 3.11: no filter= kwarg
+            tar.extractall(root)
+    return root
+
+
+@pytest.fixture
+def _pinned_inputs(_pinned_cache_root: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    """Point the cache at the pinned raw-source root and hard-block the network.
+
+    The socket-level block makes any accidental fetch a loud ``RuntimeError``
+    instead of a silent live-dependency - a missing/incomplete bundle can
+    never quietly turn this gate back into a live test.
+    """
+    import socket
+
+    monkeypatch.setenv("MOSTLYRIGHT_CACHE_DIR", str(_pinned_cache_root))
+
+    def _no_net(self: object, *args: object, **kwargs: object) -> None:
+        raise RuntimeError(
+            "NETWORK BLOCKED - the pinned parity gate must run fully offline; "
+            "a fetch here means the pinned_cache bundle is incomplete"
+        )
+
+    monkeypatch.setattr(socket.socket, "connect", _no_net)
+    monkeypatch.setattr(
+        socket,
+        "create_connection",
+        lambda *a, **k: (_ for _ in ()).throw(RuntimeError("NETWORK BLOCKED")),
+    )
+
+
+@pytest.mark.parametrize(
+    "case_num,station,frm,to",
+    CASES,
+    ids=[f"case-{n}-{s}-{f}-{t}" for n, s, f, t in CASES],
+)
+def test_parity_case_pinned(
+    _pinned_inputs: None, case_num: int, station: str, frm: str, to: str
+) -> None:
+    """PARITY-01 + PARITY-02 (HARD gate): byte-equivalent vs v0.14.1
+    ``client.pairs()`` over the PINNED input archive - deterministic,
+    network-blocked, fast-suite resident."""
+    _assert_parity_case(case_num, station, frm, to)
+
+
 @pytest.mark.live
 @pytest.mark.parametrize(
     "case_num,station,frm,to",
     CASES,
     ids=[f"case-{n}-{s}-{f}-{t}" for n, s, f, t in CASES],
 )
-def test_parity_case(case_num: int, station: str, frm: str, to: str) -> None:
-    """PARITY-01 + PARITY-02: byte-equivalent vs v0.14.1 client.pairs()."""
+def test_parity_case_live(case_num: int, station: str, frm: str, to: str) -> None:
+    """Upstream-drift MONITOR: the same assertions against the LIVE public
+    APIs. A failure here while ``test_parity_case_pinned`` is green means
+    the upstream archive drifted since the pin - see the module docstring
+    for the audit + deliberate re-pin procedure."""
+    _assert_parity_case(case_num, station, frm, to)
+
+
+def _assert_parity_case(case_num: int, station: str, frm: str, to: str) -> None:
     expected = pd.read_parquet(FIXTURES / f"case_{case_num}_{station}_{frm}_{to}.parquet")
     # Phase 32 (32-02 / D-22) parity pin: pin ``label="cli"`` EXPLICITLY on both
     # parity calls. The D-22 default-label bridge flips the implicit default to
@@ -192,7 +334,7 @@ def test_parity_case(case_num: int, station: str, frm: str, to: str) -> None:
     assert_frame_equal(_canon(actual_daily), _canon(actual), check_dtype=True)
 
     actual_c = _canon(actual)
-    expected_c = _canon(expected)
+    expected_c = _pd3_align_expected_frame(_canon(expected))
 
     # PARITY-03: dtype ground truth.
     actual_dtypes = {col: str(dtype) for col, dtype in actual_c.dtypes.items()}