diff --git a/.github/problem-matchers/README.md b/.github/problem-matchers/README.md
index 6ef475f64..a9eab0358 100644
--- a/.github/problem-matchers/README.md
+++ b/.github/problem-matchers/README.md
@@ -20,13 +20,12 @@ license. The version of the files at the time they were copied was 2025.1.2.
 -   [`pylint.json`](https://github.com/home-assistant/core/blob/dev/.github/workflows/matchers/pylint.json)
 -   [`yamllint.json`](https://github.com/home-assistant/core/blob/dev/.github/workflows/matchers/yamllint.json)
 
-The Mypy and Pytest problem matchers files originally came from the
+The Pytest problem matcher file originally came from the
 [gh-problem-matcher-wrap](https://github.com/liskin/gh-problem-matcher-wrap/tree/master/problem-matchers)
-repository (copied 2025-03-04, version 3.0.0), and were subsequently modified by
-Michael Hucka. The original JSON files are Copyright © 2020 Tomáš Janoušek and
+repository (copied 2025-03-04, version 3.0.0), and was subsequently modified by
+Michael Hucka. The original JSON file is Copyright © 2020 Tomáš Janoušek and
 made available under the terms of the MIT license.
 
--   [`mypy.json`](https://github.com/liskin/gh-problem-matcher-wrap/blob/master/problem-matchers/mypy.json)
 -   [`pytest.json`](https://github.com/liskin/gh-problem-matcher-wrap/blob/master/problem-matchers/pytest.json)
 
 The actionlint problem matcher JSON file came from the
diff --git a/.github/problem-matchers/mypy.json b/.github/problem-matchers/mypy.json
deleted file mode 100644
index 027169219..000000000
--- a/.github/problem-matchers/mypy.json
+++ /dev/null
@@ -1,19 +0,0 @@
-{
-  "problemMatcher": [
-    {
-      "owner": "mypy",
-      "severity": "error",
-      "pattern": [
-        {
-          "regexp": "^([^:]*):(\\d+):(?:(\\d+):)?\\s(error|warning): (.*?)(?:  \\[(\\S+)\\])?$",
-          "file": 1,
-          "line": 2,
-          "column": 3,
-          "severity": 4,
-          "message": 5,
-          "code": 6
-        }
-      ]
-    }
-  ]
-}
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 9de1a40bd..9fa0612a6 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -46,7 +46,7 @@ env:
   # This is used by setup-python to check whether its cache needs updating.
   python-dep-files: >-
     dev_tools/requirements/envs/format.env.txt
-    dev_tools/requirements/envs/mypy.env.txt
+    dev_tools/requirements/envs/typecheck.env.txt
     dev_tools/requirements/envs/pylint.env.txt
     dev_tools/requirements/envs/pytest-extra.env.txt
     dev_tools/requirements/envs/pytest.env.txt
@@ -56,7 +56,8 @@ concurrency:
   cancel-in-progress: true
   group: ${{github.workflow}}-${{github.event.pull_request.number||github.ref}}
 
-permissions: read-all
+permissions:
+  contents: read
 
 jobs:
   python-checks:
@@ -83,7 +84,7 @@ jobs:
         run: |
           pip install -r dev_tools/requirements/envs/format.env.txt
           pip install -r dev_tools/requirements/envs/pylint.env.txt
-          pip install -r dev_tools/requirements/envs/mypy.env.txt
+          pip install -r dev_tools/requirements/envs/typecheck.env.txt
 
       - name: Check format
         run: |
@@ -96,9 +97,7 @@ jobs:
           check/pylint -j 0
 
       - name: Check type declarations
-        run: |
-          echo '::add-matcher::.github/problem-matchers/mypy.json'
-          check/mypy
+        run: check/typecheck --output-format github
 
   pytest:
     name: Unit tests
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 7c6cccb6c..1ce53fc92 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -170,6 +170,14 @@ repos:
         files: \.(cc|h|cu|py)$
         stages: [pre-push]
 
+      - id: typecheck
+        name: 'check/typecheck runs without errors'
+        entry: check/typecheck
+        language: script
+        pass_filenames: false
+        types: [python]
+        stages: [pre-push]
+
   - repo: https://github.com/Pierre-Sassoulas/copyright_notice_precommit
     rev: 'd9215b6b2a028d1614c92cf43a9fcff3b1dd889e'  # frozen: 0.1.2
     hooks:
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e4b603e49..c7456ce30 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -234,13 +234,15 @@ for information about how to set up a local copy of the software for development
 ### Type annotation conventions
 
 Code should have [type annotations](https://www.python.org/dev/peps/pep-0484/). We use
-[mypy](http://mypy-lang.org/) to check that type annotations are correct, and the following script
-to run it:
+[Pyrefly](https://pyrefly.org/) to check that type annotations are correct, and the following
+script to run it:
 
 ```shell
-check/mypy
+check/typecheck
 ```
 
+(`check/mypy` remains as a deprecated wrapper that forwards to `check/typecheck`.)
+
 ### Linting and formatting
 
 Code should meet common style standards for Python and be free of error-prone constructs. We use
diff --git a/check/all b/check/all
index 04946a011..79e053691 100755
--- a/check/all
+++ b/check/all
@@ -100,7 +100,7 @@ done
 declare -a errors=()
 declare -a pylint_j=()
 declare -a pytest_n=()
-declare -a mypy_n=()
+declare -a typecheck_j=()
 
 function run() {
     echo "~~~~ Running $* ~~~~"
@@ -112,11 +112,11 @@ function run() {
 cpus=$(python3 -c 'import psutil; print(psutil.cpu_count(logical=False))')
 
 if [[ -z "${no_parallel}" ]]; then
-    # Pylint & pytest can auto-detect the number of CPUs, but not mypy. To be
-    # consistent, this uses the same explicit number for all of them.
+    # Pylint & pytest can auto-detect the number of CPUs; pyrefly uses -j.
+    # To be consistent, this uses the same explicit number for all of them.
     pylint_j=("-j" "${cpus}")
     pytest_n=("-n" "${cpus}")
-    mypy_n=("-n" "${cpus}")
+    typecheck_j=("-j" "${cpus}")
 fi
 
 if [[ -n "${only_changed}" ]]; then
@@ -126,7 +126,7 @@ else
     run check/format-incremental "${rev[@]}" "${apply_arg[@]}" --all
     run check/pylint "${pylint_j[@]}" "${rev[@]}"
 fi
-run check/mypy "${mypy_n[@]}"
+run check/typecheck "${typecheck_j[@]}"
 run check/pytest-and-incremental-coverage "${pytest_n[@]}" "${rev[@]}"
 run check/shellcheck
 run check/nbformat
diff --git a/check/mypy b/check/mypy
index c9c72ac9c..0bd52ee21 100755
--- a/check/mypy
+++ b/check/mypy
@@ -14,19 +14,18 @@
 # limitations under the License.
 
 ################################################################################
-# Runs mypy on the repository starting from the root.
+# Deprecated wrapper that forwards to check/typecheck (Pyrefly).
 #
 # Usage:
 #     check/mypy [--flags]
 ################################################################################
 
+echo "Warning: 'check/mypy' is deprecated." \
+  "Please use 'check/typecheck' instead." >&2
+echo >&2
+
 # Get the working directory to the repo root.
 cd "$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )" || exit 1
 cd "$(git rev-parse --show-toplevel)" || exit 1
 
-echo -e -n "\033[31m"
-mypy "$@" .
-result=$?
-echo -e -n "\033[0m"
-
-exit ${result}
+exec check/typecheck "$@"
diff --git a/check/shellcheck b/check/shellcheck
index 85be18a98..a4b3a970b 100755
--- a/check/shellcheck
+++ b/check/shellcheck
@@ -62,6 +62,7 @@ required_shell_scripts=(
     check/pylint-changed-files
     check/pytest
     check/pytest-and-incremental-coverage
+    check/typecheck
 )
 
 scripts_not_found=$(comm -13 \
diff --git a/check/typecheck b/check/typecheck
new file mode 100755
index 000000000..a67d042c3
--- /dev/null
+++ b/check/typecheck
@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+################################################################################
+# Runs type checking on the repository using Pyrefly.
+#
+# Usage:
+#     check/typecheck [--flags]
+################################################################################
+
+# Get the working directory to the repo root.
+cd "$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )" || exit 1
+cd "$(git rev-parse --show-toplevel)" || exit 1
+
+# Ensure terminal color is reset even if interrupted.
+trap 'echo -e -n "\033[0m"' EXIT
+
+echo -e -n "\033[31m"
+pyrefly check "$@"
+result=$?
+exit ${result}
diff --git a/dev_tools/requirements/create-env-files.sh b/dev_tools/requirements/create-env-files.sh
index 2cdf4aa02..688ecff69 100755
--- a/dev_tools/requirements/create-env-files.sh
+++ b/dev_tools/requirements/create-env-files.sh
@@ -48,13 +48,13 @@ mkdir -p dev_tools/requirements/envs dev_tools/requirements/max_compat
 uv pip compile "$@" \
     -o dev_tools/requirements/envs/dev.env.txt \
     dev_tools/requirements/deps/format.txt \
-    dev_tools/requirements/deps/mypy.txt \
     dev_tools/requirements/deps/packaging.txt \
     dev_tools/requirements/deps/pylint.txt \
     dev_tools/requirements/deps/pytest.txt \
     dev_tools/requirements/deps/resource_estimates_runtime.txt \
     dev_tools/requirements/deps/runtime.txt \
-    dev_tools/requirements/deps/shellcheck.txt
+    dev_tools/requirements/deps/shellcheck.txt \
+    dev_tools/requirements/deps/typecheck.txt
 
 uv pip compile "$@" \
     -o dev_tools/requirements/envs/format.env.txt \
@@ -82,9 +82,9 @@ uv pip compile "$@" \
     dev_tools/requirements/deps/runtime.txt
 
 uv pip compile "$@" \
-    -o dev_tools/requirements/envs/mypy.env.txt \
+    -o dev_tools/requirements/envs/typecheck.env.txt \
     -c dev_tools/requirements/envs/dev.env.txt \
-    dev_tools/requirements/deps/mypy.txt \
+    dev_tools/requirements/deps/typecheck.txt \
     dev_tools/requirements/deps/runtime.txt
 
 uv pip compile "$@" \
diff --git a/dev_tools/requirements/deps/mypy.txt b/dev_tools/requirements/deps/mypy.txt
deleted file mode 100644
index 36826aaae..000000000
--- a/dev_tools/requirements/deps/mypy.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-mypy
-
-pandas-stubs
-types-requests
-types-setuptools
-types-networkx
diff --git a/dev_tools/requirements/deps/typecheck.txt b/dev_tools/requirements/deps/typecheck.txt
new file mode 100644
index 000000000..ff3c068c9
--- /dev/null
+++ b/dev_tools/requirements/deps/typecheck.txt
@@ -0,0 +1,3 @@
+pyrefly
+
+types-networkx
diff --git a/dev_tools/requirements/envs/dev.env.txt b/dev_tools/requirements/envs/dev.env.txt
index a28c00833..48d32be2d 100644
--- a/dev_tools/requirements/envs/dev.env.txt
+++ b/dev_tools/requirements/envs/dev.env.txt
@@ -42,7 +42,6 @@ ast-serialize==0.5.0 \
     --hash=sha256:e42d729ef2be96a14efbad355093284739e3670ece3e534f82cc8832790911d9 \
     --hash=sha256:f66173891548c9f2726bf27957b41cabce12fa679dc6da505ddbde4d4b3b31cf \
     --hash=sha256:f8015cd071ac1339924ee2b8098c93e00e155f30a16f40ec9816fcf84f4753f6
-    # via mypy
 astor==0.8.1 \
     --hash=sha256:070a54e890cefb5b3739d19f30f5a5ec840ffc9c50ffa7d23cc9fc1a38ebbfc5 \
     --hash=sha256:6a6effda93f4e1ce9f618779b2dd1d9d84f1e32812c23a29b3fff6fd7f63fa5e
@@ -1001,7 +1000,6 @@ librt==0.11.0 ; platform_python_implementation != 'PyPy' \
     --hash=sha256:f9743fc99135d5f78d2454435615f6dec0473ca507c26ce9d92b10b562a280d3 \
     --hash=sha256:fa475675db22290c3158e1d42326d0f5a65f04f44a0e68c3630a25b53560fb9c \
     --hash=sha256:ff0fbaf5f44a21beeb0110f2ab64f45135a9536a834b79c0d1ef018f2786bbfa
-    # via mypy
 markdown-it-py==4.2.0 \
     --hash=sha256:04a21681d6fbb623de53f6f364d352309d4094dd4194040a10fd51833e418d49 \
     --hash=sha256:9f7ebbcd14fe59494226453aed97c1070d83f8d24b6fc3a3bcf9a38092641c4a
@@ -1217,58 +1215,6 @@ mpmath==1.3.0 \
     --hash=sha256:7a28eb2a9774d00c7bc92411c19a89209d5da7c4c9a9e227be8330a23a25b91f \
     --hash=sha256:a0b2b9fe80bbcd81a6647ff13108738cfb482d481d826cc0e02f5b35e5c88d2c
     # via sympy
-mypy==2.1.0 \
-    --hash=sha256:022c771234936ceac541ebaf836fe9e2abeb3f5e09aff21588fe543ff006fe21 \
-    --hash=sha256:0b1a5260c95aa443083f9ed3592662941951bca3d4ca224a5dc517c38b7cf666 \
-    --hash=sha256:11a6beb180257a805961aea9ec591bbd0bd17f1e18d35b8456d57aee5bedfedc \
-    --hash=sha256:1a293c534adb55271fef24a26da04b855540a8c13cc07bc5917b9fd2c394f2ca \
-    --hash=sha256:20509760fd791c51579d573153407d226385ec1f8bcce55d730b354f3336bc22 \
-    --hash=sha256:244358bf1c0da7722230bce60683d52e8e9fd030554926f15b747a84efb5b3af \
-    --hash=sha256:35aac3bb114e03888f535d5eb51b8bafbb3266586b599da1940f9b1be3ec5bd5 \
-    --hash=sha256:3712c20deed54e814eaaa825603bada8ea1c390670a397c95b98405347acc563 \
-    --hash=sha256:47cebf61abde7c088a4e27718a8b13a81655686b2e9c251f5c0915a802248166 \
-    --hash=sha256:498207db725cec88829a6a5c2fc771205fd043719ef98bc49aba8fb9fc4e6d57 \
-    --hash=sha256:49890d4f76ac9e06ec117f9e09f3174da70a620a0c300953d8595c926e80947f \
-    --hash=sha256:4ec7c57657493c7a75534df2751c8ae2cda383c16ecc55d2106c54476b1b16f6 \
-    --hash=sha256:4f910fe825376a7b66ef7ca8c98e5a149e8cd64c19ae71d84047a74ee060d4e6 \
-    --hash=sha256:5431d42af987ebd92ba2f71d45c85ed41d8e6ca9f5fd209a69f68f707d2469e5 \
-    --hash=sha256:5fdf2941a07434af755837d9880f7d7d25f1dacb1af9dcd4b9b66f2220a3024e \
-    --hash=sha256:6753d0c1fdd6b1a23b9e4f283ce80b2153b724adcb2653b20b85a8a28ac6436b \
-    --hash=sha256:7354c5a7f69d9345c3d6e69921d57088eea3ddeeb6b20d34c1b3855b02c36ec2 \
-    --hash=sha256:7406f4d048e71e576f5356d317e5b0a9e666dfd966bd99f9d14ca06e1a341538 \
-    --hash=sha256:761be68e023ef5d94678772396a8af1220030f80837a3afd8d0aef3b419666f4 \
-    --hash=sha256:767fe8c66dc3e01e19e1737d4c38ebefead16125e1b8e58ad421903b376f5c65 \
-    --hash=sha256:7d5e5cad0efeba72b93cd17490cc0d69c5ac9ca132994fe3fb0314808aeeb83e \
-    --hash=sha256:81e76ad12c2d804512e9b13240d1588316531bfba07558286078bfbce9613633 \
-    --hash=sha256:82208da9e09414d520e912d3e462d454854bed0810b71540bb016dcbca7308fd \
-    --hash=sha256:8de55a8c861f2a49331f807be98d90caeceeef520bde13d43a160207f8af613e \
-    --hash=sha256:8ef78c1d306bbf9a8a12f526c44902c9c28dffd6c52c52bf6a72641ce18d3849 \
-    --hash=sha256:98ebb6589bb3b6d0c6f0c459d53ca55b8091fbc13d277c4041c885392e8195e8 \
-    --hash=sha256:a663814603a5c563fb87a4f96fb473eeb30d1f5a4885afcf44f9db000a366289 \
-    --hash=sha256:a683016b16fe2f572dc04c72be7ee0504ac1605a265d0200f5cea695fb788f41 \
-    --hash=sha256:aea7f7a8a55b459c34275fc468ada6ca7c173a5e43a68f5dbe588a563d8a06b8 \
-    --hash=sha256:b33b6cd332695bba180d55e717a79d3038e479a2c49cc5eb3d53603409b9a5d7 \
-    --hash=sha256:b84802e7b5a6daf1f5e15bc9fcd7ddae77be13981ffab037f1c67bb84d67d135 \
-    --hash=sha256:bf03e12003084a67395184d3eb8cbd6a489dc3655b5664b28c210a9e2403ab0b \
-    --hash=sha256:c209a90853081ff01d01ee895cafe10f7db1474e0d95beaeef0f6c1db9119bbd \
-    --hash=sha256:c90345fc182dc363b891350457ec69c35140858538f38b4540845afcc32b1aef \
-    --hash=sha256:c989640253f0d76843e9c6c1bbf4bd48c5e85ada61bde4beb37cb3eca035685e \
-    --hash=sha256:d57a90ae5e872138a425ec328edbc9b235d1934c4377881a33ec05b341acc9a8 \
-    --hash=sha256:d8161b6ff4392410023224f0969d17db93e1e154bc3e4ba62598e720723ae211 \
-    --hash=sha256:e0210d626fc8b31ccc90233754c7bc90e1f43205e85d96387f7db1285b55c398 \
-    --hash=sha256:e195b817c13f02352a9c124301f9f30f078405444679b6753c1b96b6eed37285 \
-    --hash=sha256:e583edc957cfb0deb142079162ae826f58449b116c1d442f2d91c69d9fced081 \
-    --hash=sha256:e79ebc1b904b84f0310dff7469655a9c36c7a68bddb37bdd42b67a332df61d08 \
-    --hash=sha256:ecfe70d43775ab99562ab128ce49854a362044c9f894961f68f898c23cb7429d \
-    --hash=sha256:fcaa0e479066e31f7cceb6a3bea39cb22b2ff51a6b2f24f193d19179ba17c389 \
-    --hash=sha256:ff715050c127d724fd260a2e666e7747fdd83511c0c47d449d98238970aef780
-    # via -r dev_tools/requirements/deps/mypy.txt
-mypy-extensions==1.1.0 \
-    --hash=sha256:1be4cccdb0f2482337c4743e60421de3a356cd97508abadd57d47403e94f5505 \
-    --hash=sha256:52e68efc3284861e772bbcd66823fde5ae21fd2fdb51c62a211403730b916558
-    # via
-    #   black
-    #   mypy
 nbformat==5.10.4 \
     --hash=sha256:322168b14f937a5d11362988ecac2a4952d3d8e3a2cbeb2319584631226d5b3a \
     --hash=sha256:3b48d6c8fbca4b299bf3982ea7db1af21580e4fec269ad087b9e81588891200b
@@ -1377,7 +1323,6 @@ numpy==2.2.6 \
     #   matplotlib
     #   ml-dtypes
     #   pandas
-    #   pandas-stubs
     #   pyscf
     #   scipy
     #   types-networkx
@@ -1453,16 +1398,11 @@ pandas==2.3.3 \
     --hash=sha256:f086f6fe114e19d92014a1966f43a3e62285109afe874f067f5abbdcbb10e59c \
     --hash=sha256:f8bfc0e12dc78f777f323f55c58649591b2cd0c43534e8355c51d3fede5f4dee
     # via cirq-core
-pandas-stubs==2.3.3.260113 \
-    --hash=sha256:076e3724bcaa73de78932b012ec64b3010463d377fa63116f4e6850643d93800 \
-    --hash=sha256:ec070b5c576e1badf12544ae50385872f0631fc35d99d00dc598c2954ec564d3
-    # via -r dev_tools/requirements/deps/mypy.txt
 pathspec==1.1.1 \
     --hash=sha256:17db5ecd524104a120e173814c90367a96a98d07c45b2e10c2f3919fff91bf5a \
     --hash=sha256:a00ce642f577bf7f473932318056212bc4f8bfdf53128c78bbd5af0b9b20b189
     # via
     #   black
-    #   mypy
 pillow==12.2.0 \
     --hash=sha256:00a2865911330191c0b818c59103b58a5e697cae67042366970a6b6f1b20b7f9 \
     --hash=sha256:01afa7cf67f74f09523699b4e88c73fb55c13346d212a59a2db1f86b0a63e8c5 \
@@ -2097,7 +2037,6 @@ tomli==2.4.1 ; python_full_version <= '3.11' \
     #   black
     #   build
     #   coverage
-    #   mypy
     #   pylint
     #   pytest
 tomlkit==0.15.0 \
@@ -2118,22 +2057,24 @@ twine==6.2.0 \
     --hash=sha256:418ebf08ccda9a8caaebe414433b0ba5e25eb5e4a927667122fbe8f829f985d8 \
     --hash=sha256:e5ed0d2fd70c9959770dce51c8f39c8945c574e18173a7b81802dab51b4b75cf
     # via -r dev_tools/requirements/deps/packaging.txt
-types-networkx==3.6.1.20260518 \
-    --hash=sha256:574304deea33828fb32cdca757af84f79b67bd80164aa1725c52a95d4a9347e6 \
-    --hash=sha256:af3ab153815b366c3695a0015cc75aece9b3eb0e5df56bb60ffee0b7cec8f630
-    # via -r dev_tools/requirements/deps/mypy.txt
-types-pytz==2026.2.0.20260518 \
-    --hash=sha256:3a12eaa38f476bd650902a9c9bb442f03f3c7dee2be5c5848bce61bd708d205a \
-    --hash=sha256:e5d254329e9c4e91f0781b22c43a4bb2d10bb044d97b24c4b05d45567b0eae16
-    # via pandas-stubs
-types-requests==2.33.0.20260518 \
-    --hash=sha256:626d697d1adaaff76e2044dc8c5c051d8f21abc157bdfe204a75558076fe0bf0 \
-    --hash=sha256:df7bd3bfe0ca8402dfb841e7d9be714bb5578203283d66d7dc4ef69343449a5e
-    # via -r dev_tools/requirements/deps/mypy.txt
-types-setuptools==82.0.0.20260518 \
-    --hash=sha256:31c04a62b57a653a5021caf191be0f10f70df890f813b51f02bab3969d300f20 \
-    --hash=sha256:3b743cfe63d0981ea4c15b90710fc1ed41e3464a537d51e705be514e891c1d07
-    # via -r dev_tools/requirements/deps/mypy.txt
+pyrefly==1.2.0 \
+    --hash=sha256:25822ea9505f589ea8a725e4268b475132fb89e038fbf092e446510443ac142a \
+    --hash=sha256:368aaf7eee4f511ddc0f8e564cf14e01ab2f10b0db9105c6d5b153bf498d07bf \
+    --hash=sha256:3a90bb8df39dfbac74b1f3b2e9d7c526b8f80568884c3944d955023a73ebf61e \
+    --hash=sha256:5485f960fc2481617068c918335c39ab1507ef90b6b5bd35bf57726e60e73185 \
+    --hash=sha256:5de7b2ad2bba5c8055181681a84b74143eac2234a48ba5d1b7ed7e7a722b02bd \
+    --hash=sha256:756f669b5555090f5c1a4fef30db1785fabe657764f7e4e6dc88994dfb8ca82d \
+    --hash=sha256:7f46d983ac49ddd2b043694960a01dc6a19a5cfd8eec609d6bd9c42866f91b4e \
+    --hash=sha256:8a8964c224ccc4882730130955815de21ff443c1ac3f0b90685b19bf63848170 \
+    --hash=sha256:8c90751de8506d938e8f802659c74cf35bd7a0036510ee6c634a38eebb280bfa \
+    --hash=sha256:90efe75e17491ef5d636e10469e9278d7d0256b3b4c5e1f4750069bf3ae0f5d1 \
+    --hash=sha256:d52d5da7bc65fb7675fbaa80eda879d4f8787c494f04cac21603330d3abbdbbe \
+    --hash=sha256:e3465812ce5ef4781fb592edbf2724547296f0a3124be115d73c7e8b2401862d
+    # via -r dev_tools/requirements/deps/typecheck.txt
+types-networkx==3.6.1.20260728 \
+    --hash=sha256:0be72ff7625dbdfcd2d76ed7662de96987d0d5433b7055c320065d5b3621f9f6 \
+    --hash=sha256:f193e4fc6a41c973c7d687fa3c12f8008d8e7dcd22b0ab62f0300cc47b65eb28
+    # via -r dev_tools/requirements/deps/typecheck.txt
 typing-extensions==4.15.0 \
     --hash=sha256:0cea48d173cc12fa28ecabc3b837ea3cf6f38c6d1136f85cbaaf598984861466 \
     --hash=sha256:f0fa19c6845758ab08074a0cfa8b7aecb71c999ca73d62883bc25cc018c4e548
@@ -2143,7 +2084,6 @@ typing-extensions==4.15.0 \
     #   cirq-core
     #   cryptography
     #   exceptiongroup
-    #   mypy
     #   pytest-asyncio
     #   referencing
     #   virtualenv
@@ -2158,7 +2098,6 @@ urllib3==2.7.0 \
     #   id
     #   requests
     #   twine
-    #   types-requests
 uv==0.11.20 \
     --hash=sha256:14026b64ccbe0174e4fcf107f585f5d23f0f5b9f5b3e8b28394fe63fff3e60ff \
     --hash=sha256:2d307d47b1a0cf8f76aa69bde850be407bca9482c13cff066142e586a5c57e77 \
diff --git a/dev_tools/requirements/envs/mypy.env.txt b/dev_tools/requirements/envs/typecheck.env.txt
similarity index 76%
rename from dev_tools/requirements/envs/mypy.env.txt
rename to dev_tools/requirements/envs/typecheck.env.txt
index cceab8c76..2eb2eb4dd 100644
--- a/dev_tools/requirements/envs/mypy.env.txt
+++ b/dev_tools/requirements/envs/typecheck.env.txt
@@ -1,42 +1,5 @@
 # This file was autogenerated by uv via the following command:
 #    dev_tools/requirements/create-env-files.sh
-ast-serialize==0.5.0 \
-    --hash=sha256:061ee58bdb52341c8201a6df41182a977736bae3b7ded87ca7176ca25a8a47ab \
-    --hash=sha256:0668aa9459cfa8c9c49ddd2163ebcf43088ba045ef7492af6fe22e0098303101 \
-    --hash=sha256:104e4a35bd7c124173c41760ef9aaea17ddb3f86c65cb643671d59afbe3ee94c \
-    --hash=sha256:143a4ef63285a075871908fda3672dc21864b83a8ec3ee12304aa3e4c5387b9a \
-    --hash=sha256:16db7c62ec0b8efe1d7afd283a388d8f74f2605d56032e5a37747d2de8dba027 \
-    --hash=sha256:1943db345233cc7194a470f13afa9c59772c0b123dea0c9414c4d4ca54369759 \
-    --hash=sha256:239a4c354e8d676e9d94631d1d4a64edc6b266f86ff3a5a80aedd344f342c01d \
-    --hash=sha256:2782c36237c46dd1674542f2109740ea5ea485a169bf1431939ada0434e17934 \
-    --hash=sha256:27d51654fc240a1e87e742d353d98eb45b75f62f129086b3596ab53df2ac2a43 \
-    --hash=sha256:36be371028fc1675acb38a331bde160dbab7ff907fdf00b67eb6911aa106951b \
-    --hash=sha256:5499e8797edff2a9186aa313ed382c6b422e798e9332d9953badcee6e69a88f2 \
-    --hash=sha256:5880091bfe6f4f986f22866375c2e884843e7a0b6343ae41aeea659613d879b6 \
-    --hash=sha256:6848f2a093fb5548751a9a09bff8fcd229e2bbeb0e3331f391b6ae6d26cd9903 \
-    --hash=sha256:787baedb0262cc49e8ce37cc15c00ae818e46a165a3b36f5e21ed174998104cb \
-    --hash=sha256:7d1a2de9de5be04652f0ed60738356ef94f66db37924a9499fffe98dc491aa0b \
-    --hash=sha256:832d4c998e0b091fd60a6d6bceee535483c4d490de9ba85003af835225719261 \
-    --hash=sha256:842d1c004bb466c7df036f95fabef789570541922b10976b12f5592a69cf0b38 \
-    --hash=sha256:8f5c14f169eb0972c0c21bada5358b23d6047c76583b005234f865b11f1fa00a \
-    --hash=sha256:92a31c9c20d25a076edaeec76b128a3535d74a24f340b9a8a7e96c9b86dc9642 \
-    --hash=sha256:9cc22cf0c9be65e71cf88fda130af60d61eb4a79370ad4cfe7900d48a4aa2211 \
-    --hash=sha256:b0c06d760909b095cc466356dfccd05a1c7233a6ca191c020dca2c6a6f16c24c \
-    --hash=sha256:b15219e9cdc9f53f6f4cb51c009203507228226148c05c5e8fe451c28b435eb3 \
-    --hash=sha256:b54f60c1d78767a53b67eaa663f0dfac3afe606aa07f1301572f588b73d64809 \
-    --hash=sha256:b725026bafa801dbd7310eb13a75f0a2e370e7e51b2cb225f9d21fcfadf919ee \
-    --hash=sha256:baf5eb061eb5bccade4128ad42da33787d72f6013809cd1b590376ece8b3c937 \
-    --hash=sha256:be5173fb66f9b49026d9d5a2ff0fc7c7009077107c0eb285b2d60fdf1fe10bd1 \
-    --hash=sha256:bf683d6363edf2b39eed6b6d4fe22d34b6203867a67e27134d9e2a2680c4bc4a \
-    --hash=sha256:cae65289fc456fde04af979a2be09302ef5d8ab92ef23e596d6746dc267ada27 \
-    --hash=sha256:cf25572c526add400f26a4750dc6ce0c3bb93fc1f75e7ae0cad4ce4f2cd5c590 \
-    --hash=sha256:df1c00022cbbcb064bfaa505aa9c9295362443ce5dacb459d1331d3da353f887 \
-    --hash=sha256:e42d729ef2be96a14efbad355093284739e3670ece3e534f82cc8832790911d9 \
-    --hash=sha256:f66173891548c9f2726bf27957b41cabce12fa679dc6da505ddbde4d4b3b31cf \
-    --hash=sha256:f8015cd071ac1339924ee2b8098c93e00e155f30a16f40ec9816fcf84f4753f6
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   mypy
 attrs==26.1.0 \
     --hash=sha256:c647aa4a12dfbad9333ca4e71fe62ddc36f4e63b2d260a37a8b83d2f043ac309 \
     --hash=sha256:d03ceb89cb322a8fd706d4fb91940737b6642aa36998fe130a9bc96c985eff32
@@ -182,12 +145,7 @@ charset-normalizer==3.4.7 \
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   requests
-cirq-core==1.5.0 ; python_full_version < '3.11' \
-    --hash=sha256:104a574c766011c979e897f0fb5e90eb69a2b58ec1dc389a73495e63124923d0
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   -r dev_tools/requirements/deps/runtime.txt
-cirq-core==1.6.1 ; python_full_version >= '3.11' \
+cirq-core==1.6.1 \
     --hash=sha256:fbc809d7c6a228762ad92bb7870dc16f55b76728fcc7ef4c7aaceb7e5c63e8e6
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
@@ -510,100 +468,6 @@ kiwisolver==1.5.0 \
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   matplotlib
-librt==0.11.0 ; platform_python_implementation != 'PyPy' \
-    --hash=sha256:05fb8fb2ab90e21c8d12ea240d744ad514da9baf381ebfa70d91d20d21713175 \
-    --hash=sha256:070aa8c26c0a74774317a72df8851facc7f0f012a5b406557ac56992d92e1ec8 \
-    --hash=sha256:075dc3ef4458a278e0195cbf6ac9d38808d9b906c5a6c7f7f79c3888276a3fb1 \
-    --hash=sha256:0827efe7854718f04aaddf6496e96960a956e676fe1d0f04eb41511fd8ad06d5 \
-    --hash=sha256:0add982e0e7b9fc14cf4b33789d5f13f66581889b88c2f58099f6ce8f92617bd \
-    --hash=sha256:0cad8a4d6a8ff03c9b76f9414caccd78e7cfbc8a2e12fa334d8e1d9932753783 \
-    --hash=sha256:0d1029d7e1ae1a7e647ed6fb5df8c4ce2dffefb7a9f5fd1376a4554d96dac09f \
-    --hash=sha256:0dc56b1f8d06e60db362cc3fdae206681817f86ce4725d34511473487f12a34b \
-    --hash=sha256:0ef69ac715f3cd8e5cd252cb2aebfa72c015492aacc339d5d7bf8fef3c62c677 \
-    --hash=sha256:11bd19822431cc21af9f27374e7ae2e58103c7d98bda823536a6c47f6bb2bb3d \
-    --hash=sha256:137e79445c896a0ea7b265f52d23954e05b64222ee1af69e2cb34219067cbb67 \
-    --hash=sha256:140695816ddf3c86eb972981a26f35efd871c44b0c3aed44c8cd01749386617f \
-    --hash=sha256:22bdf239b219d3993761a148ffa134b19e52e9989c84f845d5d7b71d70a17412 \
-    --hash=sha256:258d73a0aa66a055e65b2e4d1b8cdb23b9d132c5bb915d9547d804fcaed116cc \
-    --hash=sha256:28edb433edde181112a908c78907af28f964eabc15f4dd16c9d66c834302677c \
-    --hash=sha256:2b481d846ac894c4e8403c5fd0e87c5d11d6499e404b474602508a224ff531c8 \
-    --hash=sha256:2f10cf143e4a9bb0f4f5af568a00df94a2d69ef41c2579584454bb0fe5cc642c \
-    --hash=sha256:32bcc918c0148eb7e3d57385125bac7e5f9e4359d05f07448b09f6f778c2f31c \
-    --hash=sha256:40071fc5fe0ce8daa6de616702314a01e1250711682b0523d6ab8d4525910cb3 \
-    --hash=sha256:41dc19fe150b69716c8ece4f76773a9e8813fe3e35e032a58b4d46423fb8d7c0 \
-    --hash=sha256:461bbceede621f1ffb8839755f8663e886087ee7af16294cab7fb4d782c62eeb \
-    --hash=sha256:46c60b61e308eb535fbd6fa622b1ee1bb2815691c1ad9c98bf7b84952ec3bc8d \
-    --hash=sha256:4a017a95e5837dc15a8c5661d60e05daa96b90908b1aa6b7acdf443cd25c8ebd \
-    --hash=sha256:4a9a237d13addb93715b6fee74023d5ee3469b53fce527626c0e088aa585805f \
-    --hash=sha256:4ce1f21fbe589bc1afd7872dece84fb0e1144f794a288e58a10d2c54a55c43be \
-    --hash=sha256:4e8bd98ea9c47ae90b319a087ab28dac493f1ffbc1ecd1f28fcdbf3b7e1108d1 \
-    --hash=sha256:4ee278c769a713638cdacd4c0436d72156e75df3ebc0166ab2b9dc43acc386c9 \
-    --hash=sha256:557183ddc36babe46b27dd60facbd5adb4492181a5be887587d57cda6e092f21 \
-    --hash=sha256:5ba067f4aadae8fda802d91d2124c90c42195ff32d9161d3549e6d05cfe26f96 \
-    --hash=sha256:5d63c855d86938d9de93e265c9bd8c705b51ec494de5738340ee93767a686e4b \
-    --hash=sha256:5ddd17bd87b2c56ddd60e546a7984a2e64c4e8eab92fb4cf3830a48ad5469d51 \
-    --hash=sha256:621db29691044bdeda22e789e482e1b0f3a985d90e3426c9c6d17606416205ea \
-    --hash=sha256:624a40c4a4ad7773315c287276cd024509b2c66ff5904f504bfc08d2c70293ab \
-    --hash=sha256:65ac3bc20f78aa0ee5ae84baa68917f89fef4af63e941084dd019a0d0e749f0c \
-    --hash=sha256:6bd72d903911d995ab666dbd1871f8b1e80925a699af8063fbf50053329fb05f \
-    --hash=sha256:6bf14feb84b05ae945277395451998c89c54d0def4070eb5c08de544930b245a \
-    --hash=sha256:6e94ebfcfa2d5e9926d6c3b9aa4617ffc42a845b4321fb84021b872358c82a0f \
-    --hash=sha256:75672f0bc524ede266287d532d7923dbce94c7514ad07627bac3d0c6d92cc4d9 \
-    --hash=sha256:7753e57d6e12d019c0d8786f1c09c709f4c3fcc57c3887b24e36e6c06ec938b7 \
-    --hash=sha256:78dc31f7fdfe9c9d0eb0e8f42d139db230e826415bbcabd9f0e9faaaee909894 \
-    --hash=sha256:78fddc31cd4d3caa897ad5d31f856b1faadc9474021ad6cb182b9018793e254e \
-    --hash=sha256:7a80a71e1fda83cc752a9141e87aae7fef279538597564d670e9ce513f286192 \
-    --hash=sha256:7aef3cf1d5af86e770ab04bfd993dfc4ae8b8c17f66fb77dd4a7d50de7bbb1a3 \
-    --hash=sha256:7c39513d8b7477a2e1ed8c43fc21c524e8d5a0f8d4e8b7b074dbdbe7820a08e2 \
-    --hash=sha256:7da327dacd7be8f8ec36547373550744a3cc0e536d54665cd83f8bcd961200e8 \
-    --hash=sha256:7e82e642ab0f7608ce2fe53d76ca2280a9ee33a1b06556142c7c6fe80a86fc33 \
-    --hash=sha256:83d3e1f72bd42f6c5c0b7daec530c3f829bd02db42c70b8ddf0c2d90a2459930 \
-    --hash=sha256:84308fc49423ce6475d1c5d1985cd69a8ca9f0325fc7d5f81bb690a3f3625d4e \
-    --hash=sha256:88145c15c67731d54283d135b03244028c750cc9edc334a96a4f5950ebdb2884 \
-    --hash=sha256:8ca8aa88751a775870b764e93bad5135385f563cb8dcee399abf034ea4d3cb47 \
-    --hash=sha256:902e546ff044f579ff1c953ff5fce97b636fe9e3943996b2177710c6ef076f73 \
-    --hash=sha256:92f7ff819c197fc30473190a12c2856f325ac90aabfccbeb2072d28cc2e234e3 \
-    --hash=sha256:936c5995f3514a42111f20099397d8177c79b4d7e70961e396c6f5a0a3566766 \
-    --hash=sha256:93d95bd45b7d58343d8b90d904450a545144eec19a002511163426f8ab1fae29 \
-    --hash=sha256:94663a21534637f0e787ec2a2a756022df6e5b7b2335a5cdd7d8e33d68a2af89 \
-    --hash=sha256:96f044bb325fd9cf1a723015638c219e9143f0dfbc0ca54c565df2b7fc748b44 \
-    --hash=sha256:970b09f7044ea2b64c9da42fd3d335666518cfd1c6e8a182c95da73d0214b41e \
-    --hash=sha256:993f028be9e96a08d31df3479ac80d99be374d17f3b78e4796b3fd3c913d4e89 \
-    --hash=sha256:9bc0ca6ad9381cbe8e4aa6e5726e4c80c78115a6e9723c599ed1d73e092bc49d \
-    --hash=sha256:9c028a9442a18e266955d364ce42259136e79a7ba14d773e0d778d5f70cd56f1 \
-    --hash=sha256:9d36a51b3d93320b686588e27123f4995804dbf1bce81df78c02fc3c6eea9280 \
-    --hash=sha256:9f1692105a02bcf853f355032a5fdc5494358ef83d8fd22d16de375c85cec3f5 \
-    --hash=sha256:a9010e2ed5b3a9e158c5fd966b3ab7e834bb3d3aacc8f66c91dd4b57a3799230 \
-    --hash=sha256:aa0dd688aab3f7914d3e6e5e3554978e0383312fb8e771d84be008a35b9ee548 \
-    --hash=sha256:ab73e8db5e3f564d812c1f5c3a175930a5f9bc96ccb5e3b22a34d7858b401cf7 \
-    --hash=sha256:ae627397a2f351560440d872d6f7c8dbb4072e57868e7b2fc5b8b430fe489d45 \
-    --hash=sha256:aea3caa317752e3a466fa8af45d91ee0ea8c7fdd96e42b0a8dd9b76a7931eba1 \
-    --hash=sha256:b1ecbd9819deccc39b7542bf4d2a740d8a620694d39989e58661d3763458f8d4 \
-    --hash=sha256:b87504f1690a23b9a2cca841191a04f83895d4fc2dd04df91d82b1a04ca2ad46 \
-    --hash=sha256:bc3ce6b33c5828d9e80592011a5c584cb2ce86edbc4088405f70da47dc1d1b3b \
-    --hash=sha256:bd43992b4473d42f12ff9e68326079f0696d9d4e6000e8f39a0238d482ba6ee2 \
-    --hash=sha256:c1f708d8ae9c56cf38a903c44297243d2ec83fd82b396b977e0144a3e76217e3 \
-    --hash=sha256:cae74872be221df4374d10fec61f93ed1513b9546ea84f2c0bf73ab3e9bd0b03 \
-    --hash=sha256:cca6644054e78746d8d4ef238681f9c34ff8b584fe6b988ecebb8db3b15e622a \
-    --hash=sha256:d00f3ac06a2a8b246327f11e186a53a100a4d5c7ed52346367e5ec751d51586c \
-    --hash=sha256:d1b36540d7aaf9b9101b3a6f376c8d8e9f7a9aec93ed05918f2c69d493ffef72 \
-    --hash=sha256:d2277a05f6dcb9fd13db9566aac4fabd68c3ea1ea46ee5567d4eef8efa495a2f \
-    --hash=sha256:d5b0eea49f5562861ee8d757a32ef7d559c1d35be2aaaa1ec28941d74c9ffc8a \
-    --hash=sha256:dc329359321b67d24efdf4bc69012b0597001649544db662c001db5a0184794c \
-    --hash=sha256:de3bf945454d032f9e390b85c4072e0a0570bf825421c8be0e71209fa65e1abe \
-    --hash=sha256:dec7db73758c2b54953fd8b7fe348c45188fe26b39ee18446196edd08453a5d4 \
-    --hash=sha256:dee008f20b542e3cd162ba338a7f9ec0f6d23d395f66fe8aeeec3c9d067ea253 \
-    --hash=sha256:efbb343ab2ce3540f4ecbe6315d677ed70f37cd9a72b1e58066c918ca83acbaa \
-    --hash=sha256:f230cb1cbc9faaa616f9a678f530ebcf186e414b6bcbd88b960e4ba1b92428d5 \
-    --hash=sha256:f37aa505b3cf60701562eddb32df74b12a9e380c207fd8b06dd157a943ac7ea0 \
-    --hash=sha256:f5fb36b8c6c63fdcbb1d526d94c0d1331610d43f4118cc1beb4efef4f3faacb2 \
-    --hash=sha256:f8e3e8056dd674e279741485e2e512d6e9a751c7455809d0114e6ebf8d781085 \
-    --hash=sha256:f9743fc99135d5f78d2454435615f6dec0473ca507c26ce9d92b10b562a280d3 \
-    --hash=sha256:fa475675db22290c3158e1d42326d0f5a65f04f44a0e68c3630a25b53560fb9c \
-    --hash=sha256:ff0fbaf5f44a21beeb0110f2ab64f45135a9536a834b79c0d1ef018f2786bbfa
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   mypy
 matplotlib==3.10.9 \
     --hash=sha256:09218df8a93712bd6ea133e83a153c755448cf7868316c531cffcc43f69d1cc9 \
     --hash=sha256:10cc5ce06d10231c36f40e875f3c7e8050362a4ee8f0ee5d29a6b3277d57bb42 \
@@ -669,60 +533,6 @@ mpmath==1.3.0 \
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   sympy
-mypy==2.1.0 \
-    --hash=sha256:022c771234936ceac541ebaf836fe9e2abeb3f5e09aff21588fe543ff006fe21 \
-    --hash=sha256:0b1a5260c95aa443083f9ed3592662941951bca3d4ca224a5dc517c38b7cf666 \
-    --hash=sha256:11a6beb180257a805961aea9ec591bbd0bd17f1e18d35b8456d57aee5bedfedc \
-    --hash=sha256:1a293c534adb55271fef24a26da04b855540a8c13cc07bc5917b9fd2c394f2ca \
-    --hash=sha256:20509760fd791c51579d573153407d226385ec1f8bcce55d730b354f3336bc22 \
-    --hash=sha256:244358bf1c0da7722230bce60683d52e8e9fd030554926f15b747a84efb5b3af \
-    --hash=sha256:35aac3bb114e03888f535d5eb51b8bafbb3266586b599da1940f9b1be3ec5bd5 \
-    --hash=sha256:3712c20deed54e814eaaa825603bada8ea1c390670a397c95b98405347acc563 \
-    --hash=sha256:47cebf61abde7c088a4e27718a8b13a81655686b2e9c251f5c0915a802248166 \
-    --hash=sha256:498207db725cec88829a6a5c2fc771205fd043719ef98bc49aba8fb9fc4e6d57 \
-    --hash=sha256:49890d4f76ac9e06ec117f9e09f3174da70a620a0c300953d8595c926e80947f \
-    --hash=sha256:4ec7c57657493c7a75534df2751c8ae2cda383c16ecc55d2106c54476b1b16f6 \
-    --hash=sha256:4f910fe825376a7b66ef7ca8c98e5a149e8cd64c19ae71d84047a74ee060d4e6 \
-    --hash=sha256:5431d42af987ebd92ba2f71d45c85ed41d8e6ca9f5fd209a69f68f707d2469e5 \
-    --hash=sha256:5fdf2941a07434af755837d9880f7d7d25f1dacb1af9dcd4b9b66f2220a3024e \
-    --hash=sha256:6753d0c1fdd6b1a23b9e4f283ce80b2153b724adcb2653b20b85a8a28ac6436b \
-    --hash=sha256:7354c5a7f69d9345c3d6e69921d57088eea3ddeeb6b20d34c1b3855b02c36ec2 \
-    --hash=sha256:7406f4d048e71e576f5356d317e5b0a9e666dfd966bd99f9d14ca06e1a341538 \
-    --hash=sha256:761be68e023ef5d94678772396a8af1220030f80837a3afd8d0aef3b419666f4 \
-    --hash=sha256:767fe8c66dc3e01e19e1737d4c38ebefead16125e1b8e58ad421903b376f5c65 \
-    --hash=sha256:7d5e5cad0efeba72b93cd17490cc0d69c5ac9ca132994fe3fb0314808aeeb83e \
-    --hash=sha256:81e76ad12c2d804512e9b13240d1588316531bfba07558286078bfbce9613633 \
-    --hash=sha256:82208da9e09414d520e912d3e462d454854bed0810b71540bb016dcbca7308fd \
-    --hash=sha256:8de55a8c861f2a49331f807be98d90caeceeef520bde13d43a160207f8af613e \
-    --hash=sha256:8ef78c1d306bbf9a8a12f526c44902c9c28dffd6c52c52bf6a72641ce18d3849 \
-    --hash=sha256:98ebb6589bb3b6d0c6f0c459d53ca55b8091fbc13d277c4041c885392e8195e8 \
-    --hash=sha256:a663814603a5c563fb87a4f96fb473eeb30d1f5a4885afcf44f9db000a366289 \
-    --hash=sha256:a683016b16fe2f572dc04c72be7ee0504ac1605a265d0200f5cea695fb788f41 \
-    --hash=sha256:aea7f7a8a55b459c34275fc468ada6ca7c173a5e43a68f5dbe588a563d8a06b8 \
-    --hash=sha256:b33b6cd332695bba180d55e717a79d3038e479a2c49cc5eb3d53603409b9a5d7 \
-    --hash=sha256:b84802e7b5a6daf1f5e15bc9fcd7ddae77be13981ffab037f1c67bb84d67d135 \
-    --hash=sha256:bf03e12003084a67395184d3eb8cbd6a489dc3655b5664b28c210a9e2403ab0b \
-    --hash=sha256:c209a90853081ff01d01ee895cafe10f7db1474e0d95beaeef0f6c1db9119bbd \
-    --hash=sha256:c90345fc182dc363b891350457ec69c35140858538f38b4540845afcc32b1aef \
-    --hash=sha256:c989640253f0d76843e9c6c1bbf4bd48c5e85ada61bde4beb37cb3eca035685e \
-    --hash=sha256:d57a90ae5e872138a425ec328edbc9b235d1934c4377881a33ec05b341acc9a8 \
-    --hash=sha256:d8161b6ff4392410023224f0969d17db93e1e154bc3e4ba62598e720723ae211 \
-    --hash=sha256:e0210d626fc8b31ccc90233754c7bc90e1f43205e85d96387f7db1285b55c398 \
-    --hash=sha256:e195b817c13f02352a9c124301f9f30f078405444679b6753c1b96b6eed37285 \
-    --hash=sha256:e583edc957cfb0deb142079162ae826f58449b116c1d442f2d91c69d9fced081 \
-    --hash=sha256:e79ebc1b904b84f0310dff7469655a9c36c7a68bddb37bdd42b67a332df61d08 \
-    --hash=sha256:ecfe70d43775ab99562ab128ce49854a362044c9f894961f68f898c23cb7429d \
-    --hash=sha256:fcaa0e479066e31f7cceb6a3bea39cb22b2ff51a6b2f24f193d19179ba17c389 \
-    --hash=sha256:ff715050c127d724fd260a2e666e7747fdd83511c0c47d449d98238970aef780
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   -r dev_tools/requirements/deps/mypy.txt
-mypy-extensions==1.1.0 \
-    --hash=sha256:1be4cccdb0f2482337c4743e60421de3a356cd97508abadd57d47403e94f5505 \
-    --hash=sha256:52e68efc3284861e772bbcd66823fde5ae21fd2fdb51c62a211403730b916558
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   mypy
 networkx==3.4.2 \
     --hash=sha256:307c3669428c5362aab27c8a1260aa8f47c4e91d3891f48be0141738d8d053e1 \
     --hash=sha256:df5d4365b724cf81b8c6a7312509d0c22386097011ad1abe274afd5e9d3bbc5f
@@ -794,7 +604,6 @@ numpy==2.2.6 \
     #   h5py
     #   matplotlib
     #   pandas
-    #   pandas-stubs
     #   scipy
     #   types-networkx
 packaging==26.2 \
@@ -863,18 +672,6 @@ pandas==2.3.3 \
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   cirq-core
-pandas-stubs==2.3.3.260113 \
-    --hash=sha256:076e3724bcaa73de78932b012ec64b3010463d377fa63116f4e6850643d93800 \
-    --hash=sha256:ec070b5c576e1badf12544ae50385872f0631fc35d99d00dc598c2954ec564d3
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   -r dev_tools/requirements/deps/mypy.txt
-pathspec==1.1.1 \
-    --hash=sha256:17db5ecd524104a120e173814c90367a96a98d07c45b2e10c2f3919fff91bf5a \
-    --hash=sha256:a00ce642f577bf7f473932318056212bc4f8bfdf53128c78bbd5af0b9b20b189
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   mypy
 pillow==12.2.0 \
     --hash=sha256:00a2865911330191c0b818c59103b58a5e697cae67042366970a6b6f1b20b7f9 \
     --hash=sha256:01afa7cf67f74f09523699b4e88c73fb55c13346d212a59a2db1f86b0a63e8c5 \
@@ -982,6 +779,22 @@ pyparsing==3.3.2 \
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   matplotlib
+pyrefly==1.2.0 \
+    --hash=sha256:25822ea9505f589ea8a725e4268b475132fb89e038fbf092e446510443ac142a \
+    --hash=sha256:368aaf7eee4f511ddc0f8e564cf14e01ab2f10b0db9105c6d5b153bf498d07bf \
+    --hash=sha256:3a90bb8df39dfbac74b1f3b2e9d7c526b8f80568884c3944d955023a73ebf61e \
+    --hash=sha256:5485f960fc2481617068c918335c39ab1507ef90b6b5bd35bf57726e60e73185 \
+    --hash=sha256:5de7b2ad2bba5c8055181681a84b74143eac2234a48ba5d1b7ed7e7a722b02bd \
+    --hash=sha256:756f669b5555090f5c1a4fef30db1785fabe657764f7e4e6dc88994dfb8ca82d \
+    --hash=sha256:7f46d983ac49ddd2b043694960a01dc6a19a5cfd8eec609d6bd9c42866f91b4e \
+    --hash=sha256:8a8964c224ccc4882730130955815de21ff443c1ac3f0b90685b19bf63848170 \
+    --hash=sha256:8c90751de8506d938e8f802659c74cf35bd7a0036510ee6c634a38eebb280bfa \
+    --hash=sha256:90efe75e17491ef5d636e10469e9278d7d0256b3b4c5e1f4750069bf3ae0f5d1 \
+    --hash=sha256:d52d5da7bc65fb7675fbaa80eda879d4f8787c494f04cac21603330d3abbdbbe \
+    --hash=sha256:e3465812ce5ef4781fb592edbf2724547296f0a3124be115d73c7e8b2401862d
+    # via
+    #   -c dev_tools/requirements/envs/dev.env.txt
+    #   -r dev_tools/requirements/deps/typecheck.txt
 python-dateutil==2.9.0.post0 \
     --hash=sha256:37dd54208da7e1cd875388217d5e00ebd4179249f90fb72437e91a35459a0ad3 \
     --hash=sha256:a8b2bc7bffae282281c8140a97d3aa9c14da0b136dfe83f850eea9a5f7470427
@@ -1071,94 +884,24 @@ sympy==1.14.0 \
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   -r dev_tools/requirements/deps/runtime.txt
     #   cirq-core
-tomli==2.4.1 ; python_full_version < '3.11' \
-    --hash=sha256:01f520d4f53ef97964a240a035ec2a869fe1a37dde002b57ebc4417a27ccd853 \
-    --hash=sha256:0d85819802132122da43cb86656f8d1f8c6587d54ae7dcaf30e90533028b49fe \
-    --hash=sha256:136443dbd7e1dee43c68ac2694fde36b2849865fa258d39bf822c10e8068eac5 \
-    --hash=sha256:1d8591993e228b0c930c4bb0db464bdad97b3289fb981255d6c9a41aedc84b2d \
-    --hash=sha256:2190f2e9dd7508d2a90ded5ed369255980a1bcdd58e52f7fe24b8162bf9fedbd \
-    --hash=sha256:2c1c351919aca02858f740c6d33adea0c5deea37f9ecca1cc1ef9e884a619d26 \
-    --hash=sha256:36d2bd2ad5fb9eaddba5226aa02c8ec3fa4f192631e347b3ed28186d43be6b54 \
-    --hash=sha256:3d48a93ee1c9b79c04bb38772ee1b64dcf18ff43085896ea460ca8dec96f35f6 \
-    --hash=sha256:47149d5bd38761ac8be13a84864bf0b7b70bc051806bc3669ab1cbc56216b23c \
-    --hash=sha256:4ab97e64ccda8756376892c53a72bd1f964e519c77236368527f758fbc36a53a \
-    --hash=sha256:4b605484e43cdc43f0954ddae319fb75f04cc10dd80d830540060ee7cd0243cd \
-    --hash=sha256:504aa796fe0569bb43171066009ead363de03675276d2d121ac1a4572397870f \
-    --hash=sha256:51529d40e3ca50046d7606fa99ce3956a617f9b36380da3b7f0dd3dd28e68cb5 \
-    --hash=sha256:52c8ef851d9a240f11a88c003eacb03c31fc1c9c4ec64a99a0f922b93874fda9 \
-    --hash=sha256:559db847dc486944896521f68d8190be1c9e719fced785720d2216fe7022b662 \
-    --hash=sha256:5a881ab208c0baf688221f8cecc5401bd291d67e38a1ac884d6736cbcd8247e9 \
-    --hash=sha256:5cb41aa38891e073ee49d55fbc7839cfdb2bc0e600add13874d048c94aadddd1 \
-    --hash=sha256:5e262d41726bc187e69af7825504c933b6794dc3fbd5945e41a79bb14c31f585 \
-    --hash=sha256:5ee18d9ebdb417e384b58fe414e8d6af9f4e7a0ae761519fb50f721de398dd4e \
-    --hash=sha256:7008df2e7655c495dd12d2a4ad038ff878d4ca4b81fccaf82b714e07eae4402c \
-    --hash=sha256:734e20b57ba95624ecf1841e72b53f6e186355e216e5412de414e3c51e5e3c41 \
-    --hash=sha256:7c7e1a961a0b2f2472c1ac5b69affa0ae1132c39adcb67aba98568702b9cc23f \
-    --hash=sha256:7f86fd587c4ed9dd76f318225e7d9b29cfc5a9d43de44e5754db8d1128487085 \
-    --hash=sha256:7f94b27a62cfad8496c8d2513e1a222dd446f095fca8987fceef261225538a15 \
-    --hash=sha256:88dceee75c2c63af144e456745e10101eb67361050196b0b6af5d717254dddf7 \
-    --hash=sha256:8a650c2dbafa08d42e51ba0b62740dae4ecb9338eefa093aa5c78ceb546fcd5c \
-    --hash=sha256:8d65a2fbf9d2f8352685bc1364177ee3923d6baf5e7f43ea4959d7d8bc326a36 \
-    --hash=sha256:96481a5786729fd470164b47cdb3e0e58062a496f455ee41b4403be77cb5a076 \
-    --hash=sha256:a120733b01c45e9a0c34aeef92bf0cf1d56cfe81ed9d47d562f9ed591a9828ac \
-    --hash=sha256:b1d22e6e9387bf4739fbe23bfa80e93f6b0373a7f1b96c6227c32bef95a4d7a8 \
-    --hash=sha256:b8c198f8c1805dc42708689ed6864951fd2494f924149d3e4bce7710f8eb5232 \
-    --hash=sha256:c2541745709bad0264b7d4705ad453b76ccd191e64aa6f0fc66b69a293a45ece \
-    --hash=sha256:c742f741d58a28940ce01d58f0ab2ea3ced8b12402f162f4d534dfe18ba1cd6a \
-    --hash=sha256:c7f2c7f2b9ca6bdeef8f0fa897f8e05085923eb091721675170254cbc5b02897 \
-    --hash=sha256:d312ef37c91508b0ab2cee7da26ec0b3ed2f03ce12bd87a588d771ae15dcf82d \
-    --hash=sha256:d4d8fe59808a54658fcc0160ecfb1b30f9089906c50b23bcb4c69eddc19ec2b4 \
-    --hash=sha256:da25dc3563bff5965356133435b757a795a17b17d01dbc0f42fb32447ddfd917 \
-    --hash=sha256:eab21f45c7f66c13f2a9e0e1535309cee140182a9cdae1e041d02e47291e8396 \
-    --hash=sha256:eb0dc4e38e6a1fd579e5d50369aa2e10acfc9cace504579b2faabb478e76941a \
-    --hash=sha256:ec9bfaf3ad2df51ace80688143a6a4ebc09a248f6ff781a9945e51937008fcbc \
-    --hash=sha256:ede3e6487c5ef5d28634ba3f31f989030ad6af71edfb0055cbbd14189ff240ba \
-    --hash=sha256:f3c6818a1a86dd6dca7ddcaaf76947d5ba31aecc28cb1b67009a5877c9a64f3f \
-    --hash=sha256:f758f1b9299d059cc3f6546ae2af89670cb1c4d48ea29c3cacc4fe7de3058257 \
-    --hash=sha256:f8f0fc26ec2cc2b965b7a3b87cd19c5c6b8c5e5f436b984e85f486d652285c30 \
-    --hash=sha256:fd0409a3653af6c147209d267a0e4243f0ae46b011aa978b1080359fddc9b6cf \
-    --hash=sha256:ff18e6a727ee0ab0388507b89d1bc6a22b138d1e2fa56d1ad494586d61d2eae9 \
-    --hash=sha256:ff2983983d34813c1aeb0fa89091e76c3a22889ee83ab27c5eeb45100560c049
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   mypy
 tqdm==4.67.3 \
     --hash=sha256:7d825f03f89244ef73f1d4ce193cb1774a8179fd96f31d7e1dcde62092b960bb \
     --hash=sha256:ee1e4c0e59148062281c49d80b25b67771a127c85fc9676d3be5f243206826bf
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   cirq-core
-types-networkx==3.6.1.20260518 \
-    --hash=sha256:574304deea33828fb32cdca757af84f79b67bd80164aa1725c52a95d4a9347e6 \
-    --hash=sha256:af3ab153815b366c3695a0015cc75aece9b3eb0e5df56bb60ffee0b7cec8f630
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   -r dev_tools/requirements/deps/mypy.txt
-types-pytz==2026.2.0.20260518 \
-    --hash=sha256:3a12eaa38f476bd650902a9c9bb442f03f3c7dee2be5c5848bce61bd708d205a \
-    --hash=sha256:e5d254329e9c4e91f0781b22c43a4bb2d10bb044d97b24c4b05d45567b0eae16
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   pandas-stubs
-types-requests==2.33.0.20260518 \
-    --hash=sha256:626d697d1adaaff76e2044dc8c5c051d8f21abc157bdfe204a75558076fe0bf0 \
-    --hash=sha256:df7bd3bfe0ca8402dfb841e7d9be714bb5578203283d66d7dc4ef69343449a5e
-    # via
-    #   -c dev_tools/requirements/envs/dev.env.txt
-    #   -r dev_tools/requirements/deps/mypy.txt
-types-setuptools==82.0.0.20260518 \
-    --hash=sha256:31c04a62b57a653a5021caf191be0f10f70df890f813b51f02bab3969d300f20 \
-    --hash=sha256:3b743cfe63d0981ea4c15b90710fc1ed41e3464a537d51e705be514e891c1d07
+types-networkx==3.6.1.20260728 \
+    --hash=sha256:0be72ff7625dbdfcd2d76ed7662de96987d0d5433b7055c320065d5b3621f9f6 \
+    --hash=sha256:f193e4fc6a41c973c7d687fa3c12f8008d8e7dcd22b0ab62f0300cc47b65eb28
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
-    #   -r dev_tools/requirements/deps/mypy.txt
+    #   -r dev_tools/requirements/deps/typecheck.txt
 typing-extensions==4.15.0 \
     --hash=sha256:0cea48d173cc12fa28ecabc3b837ea3cf6f38c6d1136f85cbaaf598984861466 \
     --hash=sha256:f0fa19c6845758ab08074a0cfa8b7aecb71c999ca73d62883bc25cc018c4e548
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   cirq-core
-    #   mypy
 tzdata==2026.2 \
     --hash=sha256:9173fde7d80d9018e02a662e168e5a2d04f87c41ea174b139fbef642eda62d10 \
     --hash=sha256:bbe9af844f658da81a5f95019480da3a89415801f6cc966806612cc7169bffe7
@@ -1171,4 +914,3 @@ urllib3==2.7.0 \
     # via
     #   -c dev_tools/requirements/envs/dev.env.txt
     #   requests
-    #   types-requests
diff --git a/pyproject.toml b/pyproject.toml
index 72ba61d15..98a6b8d87 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,44 +31,60 @@ filterwarnings = [
     "ignore:Skipped assert_qasm_is_consistent_with_unitary because qiskit.*:UserWarning",
 ]
 
-[tool.mypy]
-implicit_optional = true
-ignore_errors = false
-
-[[tool.mypy.overrides]]
-module = "__main__"
-follow_imports = "silent"
-ignore_missing_imports = true
-
-[[tool.mypy.overrides]]
-module = [
+[tool.pyrefly]
+# Migrated from [tool.mypy] via `pyrefly init`. Preset "legacy" disables a few
+# Pyrefly-only checks so the first pass stays closer to mypy behavior.
+preset = "legacy"
+# Match mypy defaults: do not aggressively check unannotated defs / infer returns.
+check-unannotated-defs = false
+infer-return-types = "never"
+# Respect leftover `# type: ignore` / `# mypy: ignore` comments during migration.
+permissive-ignores = true
+project-includes = ["src"]
+project-excludes = [
+    "**/docs/**",
+    "**/*.ipynb",
+    "**/__pycache__/**",
+    "**/.venv/**",
+    "**/venv/**",
+]
+search-path = ["src"]
+# Optional or test-only imports without stubs; mirrors the old [tool.mypy.overrides].
+ignore-missing-imports = [
+    "__main__",
     "_pytest.*",
     "absl",
     "apiclient.*",
     "ase.*",
     "h5py",
+    "jax",
+    "jax.*",
     "numpy.*",
+    "pandas",
+    "pandas.*",
     "pubchempy",
     "pybtas",
+    "pyscf",
     "pyscf.*",
     "pytest.*",
     "scipy.*",
+    "sympy.*",
     "tensorflow_docs",
+    "tensorflow_docs.*",
+]
+# pyscf (and similar) may be installed in CI via other env files; their
+# factory callables (e.g. scf.HF) are not valid annotation forms for Pyrefly.
+replace-imports-with-any = [
+    "pyscf",
+    "pyscf.*",
 ]
-follow_imports = "silent"
-ignore_missing_imports = true
-
-[[tool.mypy.overrides]]
-module = "sympy.*"
-ignore_missing_imports = true
-
-[[tool.mypy.overrides]]
-module = "tensorflow_docs.*"
-ignore_missing_imports = true
 
-[[tool.mypy.overrides]]
-module = "deprecation"
-follow_untyped_imports = true
+# Pyrefly-only checks that currently flag ~15 Cirq/sympy Expr and EigenGate override
+# issues mypy did not report on main; re-enable in a follow-up once those are fixed.
+[tool.pyrefly.errors]
+unsupported-operation = false
+invalid-inheritance = false
+bad-override = false
 
 [tool.uv.pip]
 universal = true
diff --git a/src/openfermion/chem/pubchem.py b/src/openfermion/chem/pubchem.py
index ca365c431..fb1573e2c 100644
--- a/src/openfermion/chem/pubchem.py
+++ b/src/openfermion/chem/pubchem.py
@@ -11,7 +11,7 @@
 #   limitations under the License.
 
 
-def geometry_from_pubchem(name: str, structure: str = None):
+def geometry_from_pubchem(name: str, structure: str | None = None):
     """Function to extract geometry using the molecule's name from the PubChem
     database. The 'structure' argument can be used to specify which structure
     info to use to extract the geometry. If structure=None, the geometry will
@@ -52,6 +52,7 @@ def geometry_from_pubchem(name: str, structure: str = None):
         )
         return None
 
+    # pyrefly: ignore[no-matching-overload]
     pubchempy_geometry = pubchempy_molecule[0].to_dict(properties=['atoms'])['atoms']
     geometry = [
         (atom['element'], (atom['x'], atom['y'], atom.get('z', 0))) for atom in pubchempy_geometry
diff --git a/src/openfermion/circuits/gates/four_qubit_gates.py b/src/openfermion/circuits/gates/four_qubit_gates.py
index 429ec77e5..70476682f 100644
--- a/src/openfermion/circuits/gates/four_qubit_gates.py
+++ b/src/openfermion/circuits/gates/four_qubit_gates.py
@@ -27,7 +27,7 @@ class DoubleExcitationGate(cirq.EigenGate):
     def __init__(
         self,
         *,  # Forces keyword args.
-        exponent: Optional[Union[sympy.Symbol, float]] = None,
+        exponent: Optional[Union[sympy.Expr, float]] = None,
         rads: Optional[float] = None,
         degs: Optional[float] = None,
         duration: Optional[float] = None,
@@ -86,7 +86,7 @@ def _apply_unitary_(self, args: cirq.ApplyUnitaryArgs) -> Optional[np.ndarray]:
             args.target_tensor, inner_matrix, slices=[a, b], out=args.available_buffer
         )
 
-    def _with_exponent(self, exponent: Union[sympy.Symbol, float]) -> 'DoubleExcitationGate':
+    def _with_exponent(self, exponent: Union[sympy.Expr, float]) -> 'DoubleExcitationGate':
         return DoubleExcitationGate(exponent=exponent)
 
     def _decompose_(self, qubits):
diff --git a/src/openfermion/circuits/primitives/bogoliubov_transform.py b/src/openfermion/circuits/primitives/bogoliubov_transform.py
index c1d298d9a..07a53906a 100644
--- a/src/openfermion/circuits/primitives/bogoliubov_transform.py
+++ b/src/openfermion/circuits/primitives/bogoliubov_transform.py
@@ -170,7 +170,7 @@ def _is_spin_block_diagonal(matrix) -> bool:
         return False
     max_upper_right = numpy.max(numpy.abs(matrix[: n // 2, n // 2 :]))
     max_lower_left = numpy.max(numpy.abs(matrix[n // 2 :, : n // 2]))
-    return numpy.isclose(max_upper_right, 0.0) and numpy.isclose(max_lower_left, 0.0)
+    return bool(numpy.isclose(max_upper_right, 0.0) and numpy.isclose(max_lower_left, 0.0))
 
 
 def _preserves_parity(transformation_matrix: numpy.ndarray) -> bool:
@@ -194,7 +194,7 @@ def _preserves_parity(transformation_matrix: numpy.ndarray) -> bool:
     w1 = transformation_matrix[:, :n]
     w2 = transformation_matrix[:, n:]
     bogoliubov_de_gennes = numpy.block([[w1, w2], [numpy.conjugate(w2), numpy.conjugate(w1)]])
-    return numpy.isclose(numpy.linalg.det(bogoliubov_de_gennes), 1.0)
+    return bool(numpy.isclose(numpy.linalg.det(bogoliubov_de_gennes), 1.0))
 
 
 def _occupied_orbitals(computational_basis_state: int, n_qubits) -> List[int]:
diff --git a/src/openfermion/hamiltonians/jellium.py b/src/openfermion/hamiltonians/jellium.py
index a1ad64b72..9aecffca4 100644
--- a/src/openfermion/hamiltonians/jellium.py
+++ b/src/openfermion/hamiltonians/jellium.py
@@ -138,7 +138,7 @@ def plane_wave_kinetic(
 def plane_wave_potential(
     grid: Grid,
     spinless: bool = False,
-    e_cutoff: float = None,
+    e_cutoff: Optional[float] = None,
     non_periodic: bool = False,
     period_cutoff: Optional[float] = None,
 ) -> FermionOperator:
@@ -403,7 +403,7 @@ def jellium_model(
     spinless: bool = False,
     plane_wave: bool = True,
     include_constant: bool = False,
-    e_cutoff: float = None,
+    e_cutoff: Optional[float] = None,
     non_periodic: bool = False,
     period_cutoff: Optional[float] = None,
 ) -> FermionOperator:
diff --git a/src/openfermion/resource_estimates/pbc/sf/sf_integrals.py b/src/openfermion/resource_estimates/pbc/sf/sf_integrals.py
index f9d91e242..3daf710c1 100644
--- a/src/openfermion/resource_estimates/pbc/sf/sf_integrals.py
+++ b/src/openfermion/resource_estimates/pbc/sf/sf_integrals.py
@@ -11,6 +11,8 @@
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
 import itertools
+from typing import Optional
+
 import numpy as np
 import numpy.typing as npt
 
@@ -21,7 +23,7 @@
 
 # Single-Factorization
 class SingleFactorization:
-    def __init__(self, cholesky_factor: npt.NDArray, kmf: scf.HF, naux: int = None):
+    def __init__(self, cholesky_factor: npt.NDArray, kmf: scf.HF, naux: Optional[int] = None):
         """Class defining single-factorized ERIs.
 
         Args: