From 8db566f4d50c3952eb81d628d1640d166e2d8df5 Mon Sep 17 00:00:00 2001
From: Radonirinaunimi <rrabeman@nikhef.nl>
Date: Sun, 21 Jun 2026 01:04:38 +0200
Subject: [PATCH 1/2] Fix intrinsic bottom/top leakage

---
 src/pineko/evolve.py | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/pineko/evolve.py b/src/pineko/evolve.py
index e8d8029a..a7b9b893 100644
--- a/src/pineko/evolve.py
+++ b/src/pineko/evolve.py
@@ -27,6 +27,16 @@
 
 logger = logging.getLogger(__name__)
 
+# EKO marks any heavy quark flavor with index > nf as "intrinsic" (i.e. frozen,
+# identity-evolved) at every scale. However, intrinsic bottom and top must never
+# leak into the FK table, so their flavor-basis columns are masked whenever EKO
+# would otherwise treat them as intrinsic (flavor index > nf). Charm is excluded
+# here, since intrinsic charm is the supported feature.
+_INTRINSIC_HEAVY_FLAVOR_IDX = {
+    5: tuple(basis_rotation.flavor_basis_pids.index(pid) for pid in (-5, 5)),
+    6: tuple(basis_rotation.flavor_basis_pids.index(pid) for pid in (-6, 6)),
+}
+
 
 def sv_scheme(tcard):
     """Infere the factorization scale_variation scheme to be used from the theory card.
@@ -479,7 +489,7 @@ def evolve_grid(
 
     def prepare(operator, convolution_types):
         """Match the raw operator with its relevant metadata."""
-        for (q2, _), op in operator.items():
+        for (q2, nf), op in operator.items():
             # reshape the x-grid output
             op = manipulate.xgrid_reshape(
                 op,
@@ -487,6 +497,11 @@ def prepare(operator, convolution_types):
                 opcard.configs.interpolation_polynomial_degree,
                 targetgrid=XGrid(x_grid),
             )
+            # mask out intrinsic bottom/top before they get mixed into the
+            # evolution basis by `to_evol`
+            for intr_fl, flavor_idx in _INTRINSIC_HEAVY_FLAVOR_IDX.items():
+                if intr_fl > nf:
+                    op.operator[:, :, flavor_idx, :] = 0.0
             # rotate the input to evolution basis
             op = manipulate.to_evol(op, source=True)
             check.check_grid_and_eko_compatible(grid, x_grid, q2, xif, max_as, max_al)

From f8f5f1d1e32e8d788b14c51bebecabe23f0cef24 Mon Sep 17 00:00:00 2001
From: Radonirinaunimi <rrabeman@nikhef.nl>
Date: Sun, 21 Jun 2026 21:57:00 +0200
Subject: [PATCH 2/2] rely on `pixi` to run the isolated regression tests

---
 .github/workflows/regression.yml |   6 +
 .gitignore                       |   3 +
 pixi.lock                        | 303 +++++++++++++++++++++++++++++++
 pixi.toml                        |  13 ++
 4 files changed, 325 insertions(+)
 create mode 100644 pixi.lock
 create mode 100644 pixi.toml

diff --git a/.github/workflows/regression.yml b/.github/workflows/regression.yml
index c90e4363..dcb92bc0 100644
--- a/.github/workflows/regression.yml
+++ b/.github/workflows/regression.yml
@@ -16,6 +16,12 @@ jobs:
         with:
           # tags needed for dynamic versioning
           fetch-depth: 0
+      - name: Setup pixi 📦
+        uses: prefix-dev/setup-pixi@v0.8.8
+        with:
+          pixi-version: v0.65.0
+          cache: true
+          activate-environment: true
       - name: Install and configure Poetry
         uses: snok/install-poetry@v1
         with:
diff --git a/.gitignore b/.gitignore
index 939b2538..e3958b0b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -133,3 +133,6 @@ dmypy.json
 # Benchmark files
 benchmarks/data_files
 benchmarks/fakepdfs
+# pixi environments
+.pixi/*
+!.pixi/config.toml
diff --git a/pixi.lock b/pixi.lock
new file mode 100644
index 00000000..fa2af969
--- /dev/null
+++ b/pixi.lock
@@ -0,0 +1,303 @@
+version: 6
+environments:
+  default:
+    channels:
+    - url: https://conda.anaconda.org/conda-forge/
+    options:
+      pypi-prerelease-mode: if-necessary-or-explicit
+    packages:
+      linux-64:
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/_openmp_mutex-4.5-20_gnu.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/bzip2-1.0.8-hda65f42_9.conda
+      - conda: https://conda.anaconda.org/conda-forge/noarch/ca-certificates-2026.6.17-hbd8a1cb_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/ld_impl_linux-64-2.45.1-default_hbd61a6d_102.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/lhapdf-6.5.6-py313hc8edb43_2.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libexpat-2.8.1-hecca717_1.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libffi-3.5.2-h3435931_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libgcc-15.2.0-he0feb66_19.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libgomp-15.2.0-he0feb66_19.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/liblzma-5.8.3-hb03c661_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libmpdec-4.0.0-hb03c661_1.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libsqlite-3.53.2-h0c1763c_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libstdcxx-15.2.0-h934c35e_19.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libuuid-2.42.2-h5347b49_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/libzlib-1.3.2-h25fd6f3_2.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/ncurses-6.6-hdb14827_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/openssl-3.6.3-h35e630c_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/noarch/pip-26.1.2-pyh145f28c_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/python-3.13.14-h6add32d_100_cp313.conda
+      - conda: https://conda.anaconda.org/conda-forge/noarch/python_abi-3.13-8_cp313.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/readline-8.3-h853b02a_0.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/tk-8.6.13-noxft_h366c992_103.conda
+      - conda: https://conda.anaconda.org/conda-forge/noarch/tzdata-2025c-hc9c84f9_1.conda
+      - conda: https://conda.anaconda.org/conda-forge/linux-64/zstd-1.5.7-hb78ec9c_6.conda
+packages:
+- conda: https://conda.anaconda.org/conda-forge/linux-64/_openmp_mutex-4.5-20_gnu.conda
+  build_number: 20
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+  timestamp: 1770939786096
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+  license_family: BSD
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+  timestamp: 1771350215188
+- conda: https://conda.anaconda.org/conda-forge/noarch/ca-certificates-2026.6.17-hbd8a1cb_0.conda
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+  - __unix
+  license: ISC
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+  depends:
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+  license: GPL-3.0-only
+  license_family: GPL
+  size: 728002
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+  sha256: 8a506caa0cdace6c18dd15da107139c775da1d7836d59fc5de7b64a819cf8886
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+  depends:
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+  - libstdcxx >=14
+  - libgcc >=14
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+  license: GPL-3.0-only
+  license_family: GPL
+  size: 668216
+  timestamp: 1775783127262
+- conda: https://conda.anaconda.org/conda-forge/linux-64/libexpat-2.8.1-hecca717_1.conda
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+  depends:
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+  constrains:
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+  license: MIT
+  license_family: MIT
+  size: 77856
+  timestamp: 1781203599810
+- conda: https://conda.anaconda.org/conda-forge/linux-64/libffi-3.5.2-h3435931_0.conda
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+  depends:
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+  constrains:
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+  - libgomp 15.2.0 he0feb66_19
+  license: GPL-3.0-only WITH GCC-exception-3.1
+  license_family: GPL
+  size: 1041084
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+- conda: https://conda.anaconda.org/conda-forge/linux-64/libzlib-1.3.2-h25fd6f3_2.conda
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+  license_family: Other
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+- conda: https://conda.anaconda.org/conda-forge/linux-64/ncurses-6.6-hdb14827_0.conda
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diff --git a/pixi.toml b/pixi.toml
new file mode 100644
index 00000000..cdd47404
--- /dev/null
+++ b/pixi.toml
@@ -0,0 +1,13 @@
+[workspace]
+authors = ["Tanjona R. Rabemananjara <tanjona.hepc@gmail.com>"]
+channels = ["conda-forge"]
+name = "pineko"
+platforms = ["linux-64"]
+version = "0.1.0"
+
+[tasks]
+
+[dependencies]
+python = "3.13.*"
+lhapdf = ">=6.5.6,<7"
+pip = ">=26.1.2,<27"