From 3c26b44cccfeea354e98d07a38eceb324acf1ec4 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 14:55:41 +0000
Subject: [PATCH 01/17] Add pinned dev version of ast_serialize to CI

---
 .github/workflows/test.yml | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 92aa38f437db4..f071795845053 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -213,6 +213,28 @@ jobs:
         pip install -r test-requirements.txt
         CC=clang MYPYC_OPT_LEVEL=0 MYPY_USE_MYPYC=1 pip install -e .
 
+    # To speed-up process until ast_serialize is on PyPI.
+    - name: Checkout pinned ast_serialize
+      uses: actions/checkout@v4
+      with:
+        persist-credentials: false
+        repository: mypyc/ast_serialize
+        ref: 038d30db8c3428310a5d69c151feeebf31160a08
+        path: ast_serialize
+
+    - run: |
+        cd ast_serialize
+
+    - name: Install development version of ast_serialize
+      uses: PyO3/maturin-action@v1
+      with:
+        command: develop
+        args: --release
+
+    - run: |
+        cd ..
+        python3 -c 'import ast_serialize; print(ast_serialize("no way")[1])'
+
     - name: Setup tox environment
       run: |
         tox run -e ${{ matrix.toxenv }} --notest

From 51fa0edd31ff433bb12b336ffdc0c24a4a38fb53 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:22:00 +0000
Subject: [PATCH 02/17] Try a different way

---
 .github/workflows/test.yml | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f071795845053..92b22b3a9d0d2 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -215,6 +215,7 @@ jobs:
 
     # To speed-up process until ast_serialize is on PyPI.
     - name: Checkout pinned ast_serialize
+      if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       uses: actions/checkout@v4
       with:
         persist-credentials: false
@@ -222,16 +223,21 @@ jobs:
         ref: 038d30db8c3428310a5d69c151feeebf31160a08
         path: ast_serialize
 
-    - run: |
+    - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
+      run: |
         cd ast_serialize
 
     - name: Install development version of ast_serialize
+      іf: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       uses: PyO3/maturin-action@v1
       with:
-        command: develop
-        args: --release
+        target: aarch64
+        args: --release --out dist
 
-    - run: |
+    - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
+      run: |
+        ls dist
+        pip install dist/*
         cd ..
         python3 -c 'import ast_serialize; print(ast_serialize("no way")[1])'
 

From 28396a14ed8a3ff0d260d42b8a0d211aa3ceb008 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:29:31 +0000
Subject: [PATCH 03/17] Hm...

---
 .github/workflows/test.yml | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 92b22b3a9d0d2..0753366642afc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -227,8 +227,7 @@ jobs:
       run: |
         cd ast_serialize
 
-    - name: Install development version of ast_serialize
-      іf: ${{ matrix.os == 'ubuntu-24.04-arm' }}
+    - іf: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       uses: PyO3/maturin-action@v1
       with:
         target: aarch64

From 55a22eb0f77e300905aee5dffa0ffe82802123cc Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:32:19 +0000
Subject: [PATCH 04/17] I have no idea how I did this

---
 .github/workflows/test.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 0753366642afc..a857f264023dc 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -227,7 +227,7 @@ jobs:
       run: |
         cd ast_serialize
 
-    - іf: ${{ matrix.os == 'ubuntu-24.04-arm' }}
+    - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       uses: PyO3/maturin-action@v1
       with:
         target: aarch64

From f415ee79dcbe064481fc69621106c4d29d71a7d3 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:36:47 +0000
Subject: [PATCH 05/17] Try doing it normally

---
 .github/workflows/test.yml | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index a857f264023dc..3b8b2244917f4 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -223,21 +223,17 @@ jobs:
         ref: 038d30db8c3428310a5d69c151feeebf31160a08
         path: ast_serialize
 
-    - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
-      run: |
-        cd ast_serialize
-
     - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       uses: PyO3/maturin-action@v1
       with:
         target: aarch64
         args: --release --out dist
+        working-directory: ast_serialize
 
     - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       run: |
         ls dist
         pip install dist/*
-        cd ..
         python3 -c 'import ast_serialize; print(ast_serialize("no way")[1])'
 
     - name: Setup tox environment

From ab4dadb995f8351a2efd7d19bb66ea6f5065de75 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:41:23 +0000
Subject: [PATCH 06/17] Again

---
 .github/workflows/test.yml | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3b8b2244917f4..8d82cb32592b8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -232,8 +232,7 @@ jobs:
 
     - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       run: |
-        ls dist
-        pip install dist/*
+        pip install ast_serialize/dist/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
         python3 -c 'import ast_serialize; print(ast_serialize("no way")[1])'
 
     - name: Setup tox environment

From 25096574fd8151f3dfd260582c586e55e0baf61f Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:44:09 +0000
Subject: [PATCH 07/17] Too many dist

---
 .github/workflows/test.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 8d82cb32592b8..d7d25f7f0e198 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -232,7 +232,7 @@ jobs:
 
     - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       run: |
-        pip install ast_serialize/dist/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
+        pip install ast_serialize/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
         python3 -c 'import ast_serialize; print(ast_serialize("no way")[1])'
 
     - name: Setup tox environment

From b9e7cd07e0b73931c99a2c43b0218272379389b6 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:48:15 +0000
Subject: [PATCH 08/17] Fingers crossed

---
 .github/workflows/test.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index d7d25f7f0e198..f72602becfdf3 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -233,7 +233,7 @@ jobs:
     - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       run: |
         pip install ast_serialize/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
-        python3 -c 'import ast_serialize; print(ast_serialize("no way")[1])'
+        python3 -c 'import ast_serialize; print(ast_serialize.parse("no way")[1])'
 
     - name: Setup tox environment
       run: |

From 9957a43db8681cf97c63a494700d25a36f0de935 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 15:52:27 +0000
Subject: [PATCH 09/17] Oh, right

---
 .github/workflows/test.yml | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f72602becfdf3..323a2b225a5c3 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -233,7 +233,9 @@ jobs:
     - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
       run: |
         pip install ast_serialize/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
-        python3 -c 'import ast_serialize; print(ast_serialize.parse("no way")[1])'
+        echo 'no way' > test_ast_serialize.py
+        python3 -c 'import ast_serialize; print(ast_serialize.parse("test_ast_serialize.py")[1])'
+        rm test_ast_serialize.py
 
     - name: Setup tox environment
       run: |

From a005fc9876decca27fd7fb67da03bb242fd97851 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Tue, 17 Feb 2026 16:22:54 +0000
Subject: [PATCH 10/17] Skip free-threaded build

---
 .github/workflows/test.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 323a2b225a5c3..c87a98de21ff7 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -215,7 +215,7 @@ jobs:
 
     # To speed-up process until ast_serialize is on PyPI.
     - name: Checkout pinned ast_serialize
-      if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
+      if: ${{ matrix.os == 'ubuntu-24.04-arm' && matrix.python != '3.14t' }}
       uses: actions/checkout@v4
       with:
         persist-credentials: false
@@ -223,14 +223,14 @@ jobs:
         ref: 038d30db8c3428310a5d69c151feeebf31160a08
         path: ast_serialize
 
-    - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
+    - if: ${{ matrix.os == 'ubuntu-24.04-arm' && matrix.python != '3.14t' }}
       uses: PyO3/maturin-action@v1
       with:
         target: aarch64
         args: --release --out dist
         working-directory: ast_serialize
 
-    - if: ${{ matrix.os == 'ubuntu-24.04-arm' }}
+    - if: ${{ matrix.os == 'ubuntu-24.04-arm' && matrix.python != '3.14t' }}
       run: |
         pip install ast_serialize/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
         echo 'no way' > test_ast_serialize.py

From f2c955046a1054269d46718a3ccd10a3d3e6ee4c Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Wed, 4 Mar 2026 23:47:00 +0000
Subject: [PATCH 11/17] Use native parser for parallel tests; skip some tests

---
 .github/workflows/test.yml           | 10 ++++++----
 mypy/message_registry.py             |  2 +-
 mypy/test/testcheck.py               |  4 ++++
 test-data/unit/check-columns.test    |  6 +++---
 test-data/unit/check-errorcodes.test | 20 ++++++++++----------
 test-data/unit/check-fastparse.test  | 14 +++++++-------
 test-data/unit/check-literal.test    |  8 ++++----
 test-data/unit/check-statements.test | 14 +++++++-------
 8 files changed, 42 insertions(+), 36 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index c87a98de21ff7..ef02e899f6953 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -106,12 +106,14 @@ jobs:
           os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
+          dev_ast_serialize: true
         - name: Parallel tests with py314-ubuntu, mypyc-compiled
           python: '3.14'
           os: ubuntu-24.04-arm
           toxenv: py
           tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           test_mypyc: true
+          dev_ast_serialize: true
         - name: Parallel tests with py314-windows-64, interpreted
           python: '3.14'
           os: windows-latest
@@ -215,22 +217,22 @@ jobs:
 
     # To speed-up process until ast_serialize is on PyPI.
     - name: Checkout pinned ast_serialize
-      if: ${{ matrix.os == 'ubuntu-24.04-arm' && matrix.python != '3.14t' }}
+      if: ${{ matrix.dev_ast_serialize }}
       uses: actions/checkout@v4
       with:
         persist-credentials: false
         repository: mypyc/ast_serialize
-        ref: 038d30db8c3428310a5d69c151feeebf31160a08
+        ref: da5a16cf268dbec63ed6b2e6b715470576e2d1a6
         path: ast_serialize
 
-    - if: ${{ matrix.os == 'ubuntu-24.04-arm' && matrix.python != '3.14t' }}
+    - if: ${{ matrix.dev_ast_serialize }}
       uses: PyO3/maturin-action@v1
       with:
         target: aarch64
         args: --release --out dist
         working-directory: ast_serialize
 
-    - if: ${{ matrix.os == 'ubuntu-24.04-arm' && matrix.python != '3.14t' }}
+    - if: ${{ dev_ast_serialize }}
       run: |
         pip install ast_serialize/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
         echo 'no way' > test_ast_serialize.py
diff --git a/mypy/message_registry.py b/mypy/message_registry.py
index 9de31514b6bd1..8140e28e16d7a 100644
--- a/mypy/message_registry.py
+++ b/mypy/message_registry.py
@@ -303,7 +303,7 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
     "Condition can't be inferred, unable to merge overloads"
 )
 TYPE_IGNORE_WITH_ERRCODE_ON_MODULE: Final = ErrorMessage(
-    "type ignore with error code is not supported for modules; "
+    "Type ignore with error code is not supported for modules; "
     'use `# mypy: disable-error-code="{}"`',
     codes.SYNTAX,
 )
diff --git a/mypy/test/testcheck.py b/mypy/test/testcheck.py
index 54cdb38596bfe..cbb9c0235feda 100644
--- a/mypy/test/testcheck.py
+++ b/mypy/test/testcheck.py
@@ -141,12 +141,16 @@ def run_case_once(
 
         if options.num_workers:
             options.fixed_format_cache = True
+            options.native_parser = True
             if testcase.output_files:
                 raise pytest.skip("Reports are not supported in parallel mode")
             # Note: do not use this unless really needed!
             if testcase.name.endswith("_no_parallel"):
                 raise pytest.skip("Test not supported in parallel mode yet")
 
+        if options.native_parser and testcase.name.endswith("_no_native_parse"):
+            raise pytest.skip("Test not supported by native parser yet")
+
         # Enable some options automatically based on test file name.
         if "columns" in testcase.file:
             options.show_column_numbers = True
diff --git a/test-data/unit/check-columns.test b/test-data/unit/check-columns.test
index c38d69a9c3a89..6ce0571f546ec 100644
--- a/test-data/unit/check-columns.test
+++ b/test-data/unit/check-columns.test
@@ -1,6 +1,6 @@
 # Test column numbers in messages. --show-column-numbers is enabled implicitly by test runner.
 
-[case testColumnsSyntaxError]
+[case testColumnsSyntaxError_no_native_parse]
 f()
 1 +
 [out]
@@ -146,7 +146,7 @@ if int():
     def f(a: 'A') -> None: pass
     (f(b=object())) # E:6: Unexpected keyword argument "b" for "f"
 
-[case testColumnInvalidType]
+[case testColumnInvalidType_no_native_parse]
 
 from typing import Iterable
 
@@ -342,7 +342,7 @@ if int():
 main:2:11: error: Syntax error in type annotation
 main:2:11: note: Suggestion: Is there a spurious trailing comma?
 
-[case testColumnSyntaxErrorInTypeAnnotation2]
+[case testColumnSyntaxErrorInTypeAnnotation2_no_native_parse]
 if int():
     # TODO: It would be better to point to the type comment
     xyz = 0  # type: blurbnard blarb
diff --git a/test-data/unit/check-errorcodes.test b/test-data/unit/check-errorcodes.test
index 26f43ebeadd4e..f02daea40fd12 100644
--- a/test-data/unit/check-errorcodes.test
+++ b/test-data/unit/check-errorcodes.test
@@ -30,21 +30,21 @@ class A:
 [case testErrorCodeNoteHasNoCode]
 reveal_type(1) # N: Revealed type is "Literal[1]?"
 
-[case testErrorCodeSyntaxError]
+[case testErrorCodeSyntaxError_no_native_parse]
 1 ''
 [out]
 main:1: error: Invalid syntax  [syntax]
 [out version==3.10.0]
 main:1: error: Invalid syntax. Perhaps you forgot a comma?  [syntax]
 
-[case testErrorCodeSyntaxError2]
+[case testErrorCodeSyntaxError2_no_native_parse]
 def f(): # E: Type signature has too many parameters  [syntax]
     # type: (int) -> None
     1
 
 x = 0  # type: x y  # E: Syntax error in type comment "x y"  [syntax]
 
-[case testErrorCodeSyntaxError3]
+[case testErrorCodeSyntaxError3_no_native_parse]
 # This is a bit inconsistent -- syntax error would be more logical?
 x: 'a b'  # E: Invalid type comment or annotation  [valid-type]
 for v in x:  # type: int, int  # E: Syntax error in type annotation  [syntax] \
@@ -208,7 +208,7 @@ def h(x  # type: xyz  # type: ignore[foo]  # E: Name "xyz" is not defined  [name
 import nostub  # type: ignore[import]
 from defusedxml import xyz  # type: ignore[import]
 
-[case testErrorCodeBadIgnore]
+[case testErrorCodeBadIgnore_no_native_parse]
 import nostub # type: ignore xyz  # E: Invalid "type: ignore" comment  [syntax] \
                                   # E: Cannot find implementation or library stub for module named "nostub"  [import-not-found] \
                                   # N: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
@@ -226,7 +226,7 @@ def f(x,  # type: int  # type: ignore[  # E: Invalid "type: ignore" comment  [sy
     # type: (...) -> None
     pass
 
-[case testErrorCodeBadIgnoreNoExtraComment]
+[case testErrorCodeBadIgnoreNoExtraComment_no_native_parse]
 # Omit the E: ... comments, as they affect parsing
 import nostub # type: ignore xyz
 import nostub # type: ignore[xyz
@@ -762,7 +762,7 @@ main:1: error: Name "y" is not defined  [name-defined]
 main:2: error: Name "ignored" is not defined  [name-defined]
 main:2: error: Name "y" is not defined  [name-defined]
 
-[case testErrorCodeTypeIgnoreMisspelled2]
+[case testErrorCodeTypeIgnoreMisspelled2_no_native_parse]
 x = y  # type: int  # type: ignored[foo]
 x = y  # type: int  # type: ignored [foo]
 [out]
@@ -1014,7 +1014,7 @@ def f(arg: int) -> int:
 def f(arg: str) -> str:
     ...
 
-[case testSliceInDictBuiltin]
+[case testSliceInDictBuiltin_no_native_parse]
 # flags: --show-column-numbers
 b: dict[int, x:y]
 c: dict[x:y]
@@ -1027,7 +1027,7 @@ main:3:4: error: "dict" expects 2 type arguments, but 1 given  [type-arg]
 main:3:9: error: Invalid type comment or annotation  [valid-type]
 main:3:9: note: did you mean to use ',' instead of ':' ?
 
-[case testSliceInDictTyping]
+[case testSliceInDictTyping_no_native_parse]
 # flags: --show-column-numbers
 from typing import Dict
 b: Dict[int, x:y]
@@ -1067,11 +1067,11 @@ def f(d: D, s: str) -> None:
 [typing fixtures/typing-typeddict.pyi]
 
 [case testRecommendErrorCode]
-# type: ignore[whatever]  # E: type ignore with error code is not supported for modules; use `# mypy: disable-error-code="whatever"`  [syntax]
+# type: ignore[whatever]  # E: Type ignore with error code is not supported for modules; use `# mypy: disable-error-code="whatever"`  [syntax]
 1 + "asdf"
 
 [case testRecommendErrorCode2]
-# type: ignore[whatever, other]  # E: type ignore with error code is not supported for modules; use `# mypy: disable-error-code="whatever, other"`  [syntax]
+# type: ignore[whatever, other]  # E: Type ignore with error code is not supported for modules; use `# mypy: disable-error-code="whatever, other"`  [syntax]
 1 + "asdf"
 
 [case testShowErrorCodesInConfig]
diff --git a/test-data/unit/check-fastparse.test b/test-data/unit/check-fastparse.test
index a0b619349d23f..7ee5a9c432169 100644
--- a/test-data/unit/check-fastparse.test
+++ b/test-data/unit/check-fastparse.test
@@ -1,8 +1,8 @@
-[case testFastParseSyntaxError]
+[case testFastParseSyntaxError_no_native_parse]
 
 1 +  # E: Invalid syntax
 
-[case testFastParseTypeCommentSyntaxError]
+[case testFastParseTypeCommentSyntaxError_no_native_parse]
 
 x = None # type: a : b  # E: Syntax error in type comment "a : b"
 
@@ -12,13 +12,13 @@ x = None # type: a + b  # E: Invalid type comment or annotation
 
 -- Function type comments are attributed to the function def line.
 -- This happens in both parsers.
-[case testFastParseFunctionAnnotationSyntaxError]
+[case testFastParseFunctionAnnotationSyntaxError_no_native_parse]
 
 def f():  # E: Syntax error in type comment "None -> None" # N: Suggestion: wrap argument types in parentheses
   # type: None -> None
   pass
 
-[case testFastParseFunctionAnnotationSyntaxErrorSpaces]
+[case testFastParseFunctionAnnotationSyntaxErrorSpaces_no_native_parse]
 
 def f():  # E: Syntax error in type comment "None -> None" # N: Suggestion: wrap argument types in parentheses
   # type:             None -> None
@@ -156,7 +156,7 @@ def f(a,        # type: A
 [builtins fixtures/dict.pyi]
 [out]
 
-[case testFastParsePerArgumentAnnotationsWithAnnotatedBareStar]
+[case testFastParsePerArgumentAnnotationsWithAnnotatedBareStar_no_native_parse]
 
 def f(*, # type: int  # E: Bare * has associated type comment
       x  # type: str
@@ -194,7 +194,7 @@ def f(x, y):  # E: Type signature has too few parameters
 f(1, 2)
 f(1) # E: Missing positional argument "y" in call to "f"
 
-[case testFasterParseTypeErrorCustom]
+[case testFasterParseTypeErrorCustom_no_native_parse]
 
 from typing import TypeVar, Generic
 T = TypeVar('T')
@@ -275,7 +275,7 @@ def f7(x: int):  # E: Function has duplicate type signatures
   # type: (int) -> int
   pass
 
-[case testFastParserDuplicateNames]
+[case testFastParserDuplicateNames_no_native_parse]
 
 def f(x, y, z):
   pass
diff --git a/test-data/unit/check-literal.test b/test-data/unit/check-literal.test
index 0b779f57b6150..f795f1f5b354b 100644
--- a/test-data/unit/check-literal.test
+++ b/test-data/unit/check-literal.test
@@ -224,7 +224,7 @@ accepts_bytes(c_alias)
 [builtins fixtures/tuple.pyi]
 [out]
 
-[case testLiteralMixingUnicodeAndBytesPython3ForwardStrings]
+[case testLiteralMixingUnicodeAndBytesPython3ForwardStrings_no_native_parse]
 from typing import Literal, TypeVar, Generic
 
 a_unicode_wrapper: u"Literal[u'foo']"
@@ -577,7 +577,7 @@ reveal_type(d)      # N: Revealed type is "Any"
 [builtins fixtures/primitives.pyi]
 [out]
 
-[case testLiteralDisallowFloatsAndComplex]
+[case testLiteralDisallowFloatsAndComplex_no_native_parse]
 
 from typing import Literal
 a1: Literal[3.14]    # E: Parameter 1 of Literal[...] cannot be of type "float"
@@ -601,7 +601,7 @@ d2: d2t              # E: Variable "__main__.d2t" is not valid as a type \
 [builtins fixtures/complex_tuple.pyi]
 [out]
 
-[case testLiteralDisallowComplexExpressions]
+[case testLiteralDisallowComplexExpressions_no_native_parse]
 from typing import Literal
 def dummy() -> int: return 3
 a: Literal[3 + 4]               # E: Invalid type: Literal[...] cannot contain arbitrary expressions
@@ -2460,7 +2460,7 @@ expect_2(final_set_2.pop())  # E: Argument 1 to "expect_2" has incompatible type
 -- Tests for Literals and enums
 --
 
-[case testLiteralWithEnumsBasic]
+[case testLiteralWithEnumsBasic_no_native_parse]
 from typing import Literal
 from enum import Enum
 
diff --git a/test-data/unit/check-statements.test b/test-data/unit/check-statements.test
index 5b1a59e359c19..0b768908a4487 100644
--- a/test-data/unit/check-statements.test
+++ b/test-data/unit/check-statements.test
@@ -164,7 +164,7 @@ while None:
 [builtins fixtures/bool.pyi]
 [out]
 
-[case testForStatementTypeComments]
+[case testForStatementTypeComments_no_native_parse]
 
 from typing import List, Union
 x = []  # type: List[int]
@@ -182,7 +182,7 @@ for v in x:  # type: int, int  # E: Syntax error in type annotation # N: Suggest
     pass
 [builtins fixtures/list.pyi]
 
-[case testForStatementMultipleTypeComments]
+[case testForStatementMultipleTypeComments_no_native_parse]
 
 from typing import List, Tuple
 x = []  # type: List[Tuple[int, int]]
@@ -1360,7 +1360,7 @@ def f() -> Iterator[List[int]]:
 [builtins fixtures/for.pyi]
 [out]
 
-[case testYieldFromNotAppliedToNothing]
+[case testYieldFromNotAppliedToNothing_no_native_parse]
 def h():
     yield from  # E: Invalid syntax
 [out]
@@ -1492,7 +1492,7 @@ with A() as (a, b):
     a = b # E: Incompatible types in assignment (expression has type "str", variable has type "int")
 [builtins fixtures/tuple.pyi]
 
-[case testWithStmtTypeComment]
+[case testWithStmtTypeComment_no_native_parse]
 
 from typing import Union
 class A:
@@ -1514,7 +1514,7 @@ with A() as c:  # type: int, int  # E: Syntax error in type annotation # N: Sugg
 with A() as d:  # type: Union[int, str]
     reveal_type(d)  # N: Revealed type is "builtins.int | builtins.str"
 
-[case testWithStmtTupleTypeComment]
+[case testWithStmtTupleTypeComment_no_native_parse]
 
 from typing import Tuple
 class A:
@@ -1546,7 +1546,7 @@ with A() as (k, l):  # type: int, str  # E: Incompatible types in assignment (ex
     pass
 [builtins fixtures/tuple.pyi]
 
-[case testWithStmtComplexTypeComment]
+[case testWithStmtComplexTypeComment_no_native_parse]
 
 from typing import Tuple
 class A:
@@ -2244,7 +2244,7 @@ N = TypedDict('N', {'x': int})
 [typing fixtures/typing-full.pyi]
 [out]
 
-[case testForwardRefsInWithStatement]
+[case testForwardRefsInWithStatement_no_native_parse]
 from typing import ContextManager, Any, TypedDict
 cm: ContextManager[Any]
 

From 53b5e6c150f40fc2d87095e715282012c1010c10 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Wed, 4 Mar 2026 23:49:46 +0000
Subject: [PATCH 12/17] Fix yaml

---
 .github/workflows/test.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index ef02e899f6953..5db9035e11406 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -232,7 +232,7 @@ jobs:
         args: --release --out dist
         working-directory: ast_serialize
 
-    - if: ${{ dev_ast_serialize }}
+    - if: ${{ matrix.dev_ast_serialize }}
       run: |
         pip install ast_serialize/dist/ast_serialize-0.1.0-cp39-abi3-manylinux_2_34_aarch64.whl
         echo 'no way' > test_ast_serialize.py

From 215b2e142098bc4ac9756301147d7331990dab74 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Wed, 4 Mar 2026 23:55:38 +0000
Subject: [PATCH 13/17] Check the problem

---
 .github/workflows/test.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 5db9035e11406..1a68a00296642 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -105,13 +105,13 @@ jobs:
           python: '3.14'
           os: ubuntu-24.04-arm
           toxenv: py
-          tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
+          tox_extra_args: "-x -n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           dev_ast_serialize: true
         - name: Parallel tests with py314-ubuntu, mypyc-compiled
           python: '3.14'
           os: ubuntu-24.04-arm
           toxenv: py
-          tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
+          tox_extra_args: "-x -n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           test_mypyc: true
           dev_ast_serialize: true
         - name: Parallel tests with py314-windows-64, interpreted

From d3131267d792a4c63336f5fa375dbf0ec2d8a004 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Thu, 5 Mar 2026 00:18:43 +0000
Subject: [PATCH 14/17] Try fixing tox

---
 .github/workflows/test.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 1a68a00296642..6b6d005d4de75 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -141,6 +141,7 @@ jobs:
     timeout-minutes: 60
     env:
       TOX_SKIP_MISSING_INTERPRETERS: False
+      VIRTUALENV_SYSTEM_SITE_PACKAGES: ${{ matrix.dev_ast_serialize && 1 || 0 }}
       # Rich (pip) -- Disable color for windows + pytest
       FORCE_COLOR: ${{ !(startsWith(matrix.os, 'windows-') && startsWith(matrix.toxenv, 'py')) && 1 || 0 }}
       # Tox

From 707c8dc770f0e0f884016d5588ceb7b87a05e911 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Thu, 5 Mar 2026 18:28:47 +0000
Subject: [PATCH 15/17] Skip remainig tests; skip Windows for now

---
 .github/workflows/test.yml                 | 11 ++++++-----
 test-data/unit/check-annotated.test        |  2 +-
 test-data/unit/check-async-await.test      |  4 ++--
 test-data/unit/check-basic.test            |  2 +-
 test-data/unit/check-expressions.test      |  4 ++--
 test-data/unit/check-functions.test        |  8 ++++----
 test-data/unit/check-ignore.test           |  4 ++--
 test-data/unit/check-incremental.test      |  2 +-
 test-data/unit/check-namedtuple.test       |  2 +-
 test-data/unit/check-newsemanal.test       |  2 +-
 test-data/unit/check-newsyntax.test        |  4 ++--
 test-data/unit/check-python312.test        |  6 +++---
 test-data/unit/check-python39.test         |  2 +-
 test-data/unit/check-type-aliases.test     |  2 +-
 test-data/unit/check-typeddict.test        |  2 +-
 test-data/unit/check-unreachable-code.test |  6 +++---
 16 files changed, 32 insertions(+), 31 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 6b6d005d4de75..4eca8a79083d5 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -114,11 +114,12 @@ jobs:
           tox_extra_args: "-x -n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           test_mypyc: true
           dev_ast_serialize: true
-        - name: Parallel tests with py314-windows-64, interpreted
-          python: '3.14'
-          os: windows-latest
-          toxenv: py
-          tox_extra_args: "-n 2 --mypy-num-workers=2 mypy/test/testcheck.py -k 'incremental or modules or classes'"
+        # Skip Windows tests until we publish ast_serialize wheels on PyPI.
+        # - name: Parallel tests with py314-windows-64, interpreted
+        #   python: '3.14'
+        #   os: windows-latest
+        #   toxenv: py
+        #   tox_extra_args: "-n 2 --mypy-num-workers=2 mypy/test/testcheck.py -k 'incremental or modules or classes'"
 
         - name: Type check our own code (py310-ubuntu)
           python: '3.10'
diff --git a/test-data/unit/check-annotated.test b/test-data/unit/check-annotated.test
index d4de3f7b5043f..7ef46e9417843 100644
--- a/test-data/unit/check-annotated.test
+++ b/test-data/unit/check-annotated.test
@@ -17,7 +17,7 @@ x: Annotated[int, THESE, ARE, IGNORED, FOR, NOW]
 reveal_type(x)  # N: Revealed type is "builtins.int"
 [builtins fixtures/tuple.pyi]
 
-[case testAnnotated3]
+[case testAnnotated3_no_native_parse]
 from typing_extensions import Annotated
 x: Annotated[int, -+~12.3, "som"[e], more(anno+a+ions, that=[are]), (b"ignored",), 4, N.O.W, ...]
 reveal_type(x)  # N: Revealed type is "builtins.int"
diff --git a/test-data/unit/check-async-await.test b/test-data/unit/check-async-await.test
index 242461af8a1cf..907bf6027f657 100644
--- a/test-data/unit/check-async-await.test
+++ b/test-data/unit/check-async-await.test
@@ -192,7 +192,7 @@ async def f() -> None:
 [builtins fixtures/async_await.pyi]
 [typing fixtures/typing-async.pyi]
 
-[case testAsyncForTypeComments]
+[case testAsyncForTypeComments_no_native_parse]
 
 from typing import AsyncIterator, Union
 class C(AsyncIterator[int]):
@@ -342,7 +342,7 @@ async def f() -> None:
 [builtins fixtures/async_await.pyi]
 [typing fixtures/typing-async.pyi]
 
-[case testAsyncWithTypeComments]
+[case testAsyncWithTypeComments_no_native_parse]
 
 class C:
     async def __aenter__(self) -> int: pass
diff --git a/test-data/unit/check-basic.test b/test-data/unit/check-basic.test
index c2818b27b007d..b91a2343a0b25 100644
--- a/test-data/unit/check-basic.test
+++ b/test-data/unit/check-basic.test
@@ -286,7 +286,7 @@ x = 1
 x in 1,  # E: Unsupported right operand type for in ("int")
 [builtins fixtures/tuple.pyi]
 
-[case testTrailingCommaInIfParsing]
+[case testTrailingCommaInIfParsing_no_native_parse]
 if x in 1, : pass
 [out]
 main:1: error: Invalid syntax
diff --git a/test-data/unit/check-expressions.test b/test-data/unit/check-expressions.test
index 1acda7079cc85..17ce4cd596590 100644
--- a/test-data/unit/check-expressions.test
+++ b/test-data/unit/check-expressions.test
@@ -1456,7 +1456,7 @@ if int():
     b = (x for x in a)  # E: Generator has incompatible item type "Callable[[], str]"; expected "Callable[[], int]"
 [builtins fixtures/list.pyi]
 
-[case testGeneratorNoSpuriousError]
+[case testGeneratorNoSpuriousError_no_native_parse]
 from typing import Iterable, overload
 
 @overload
@@ -1915,7 +1915,7 @@ None == None
 None < None  # E: Unsupported left operand type for < ("None")
 [builtins fixtures/ops.pyi]
 
-[case testDictWithStarExpr]
+[case testDictWithStarExpr_no_native_parse]
 
 b = {'z': 26, *a}  # E: Invalid syntax
 [builtins fixtures/dict.pyi]
diff --git a/test-data/unit/check-functions.test b/test-data/unit/check-functions.test
index 542cbb3fd22c9..6d5d472ca2b17 100644
--- a/test-data/unit/check-functions.test
+++ b/test-data/unit/check-functions.test
@@ -774,7 +774,7 @@ class A:
 main:6: error: Incompatible types in assignment (expression has type "int", variable has type "A")
 main:8: error: Argument 1 to "g" has incompatible type "A"; expected "int"
 
-[case testNestedFunctionInMethodWithTooFewArgumentsInTypeComment]
+[case testNestedFunctionInMethodWithTooFewArgumentsInTypeComment_no_native_parse]
 class A:
     def f(self):
         # type: () -> None
@@ -795,7 +795,7 @@ class A:
             arg.B  # E: "object" has no attribute "B"
 [file mod.py]
 
-[case testDeepNestedFunctionWithTooFewArgumentsInTypeComment]
+[case testDeepNestedFunctionWithTooFewArgumentsInTypeComment_no_native_parse]
 class A:
     def f(self):
         # type: () -> None
@@ -2139,13 +2139,13 @@ class A:
         pass
 [builtins fixtures/staticmethod.pyi]
 
-[case testEllipsisWithSomethingAfterItFails]
+[case testEllipsisWithSomethingAfterItFails_no_native_parse]
 def f(x, y, z): # type: (..., int) -> None
     pass
 [out]
 main:1: error: Ellipses cannot accompany other parameter types in function type signature
 
-[case testEllipsisWithSomethingBeforeItFails]
+[case testEllipsisWithSomethingBeforeItFails_no_native_parse]
 def f(x, y, z): # type: (int, ...) -> None
     pass
 [out]
diff --git a/test-data/unit/check-ignore.test b/test-data/unit/check-ignore.test
index 0d44c1f966c97..2bcf6e0884966 100644
--- a/test-data/unit/check-ignore.test
+++ b/test-data/unit/check-ignore.test
@@ -32,7 +32,7 @@ from xyz_m import * # type: ignore
 x   # E: Name "x" is not defined
 1() # E: "int" not callable
 
-[case testIgnoreImportBadModule]
+[case testIgnoreImportBadModule_no_native_parse]
 import m # type: ignore
 from m import a # type: ignore
 [file m.py]
@@ -54,7 +54,7 @@ foo = 3
 [builtins fixtures/module_all.pyi]
 [out]
 
-[case testIgnoreImportStarFromBadModule]
+[case testIgnoreImportStarFromBadModule_no_native_parse]
 from m import * # type: ignore
 [file m.py]
 +
diff --git a/test-data/unit/check-incremental.test b/test-data/unit/check-incremental.test
index 8b77c9be7f615..5b256b1731e01 100644
--- a/test-data/unit/check-incremental.test
+++ b/test-data/unit/check-incremental.test
@@ -7264,7 +7264,7 @@ bar: int = foo
 [out3]
 tmp/bar.py:2: error: Incompatible types in assignment (expression has type "str", variable has type "int")
 
-[case testIncrementalBlockingErrorRepeatAndUndo]
+[case testIncrementalBlockingErrorRepeatAndUndo_no_native_parse]
 import m
 [file m.py]
 import f
diff --git a/test-data/unit/check-namedtuple.test b/test-data/unit/check-namedtuple.test
index ccabda405563a..6eb1c322cee69 100644
--- a/test-data/unit/check-namedtuple.test
+++ b/test-data/unit/check-namedtuple.test
@@ -1374,7 +1374,7 @@ class Test:
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-namedtuple.pyi]
 
-[case testNoClassKeywordsForNamedTuple]
+[case testNoClassKeywordsForNamedTuple_no_native_parse]
 from typing import NamedTuple
 class Test1(NamedTuple, x=1, y=2):  # E: Unexpected keyword argument "x" for "__init_subclass__" of "NamedTuple" \
                                     # E: Unexpected keyword argument "y" for "__init_subclass__" of "NamedTuple"
diff --git a/test-data/unit/check-newsemanal.test b/test-data/unit/check-newsemanal.test
index 856d7be0ebac6..ad3ea03110c0b 100644
--- a/test-data/unit/check-newsemanal.test
+++ b/test-data/unit/check-newsemanal.test
@@ -1657,7 +1657,7 @@ tmp/a.py: note: In member "g" of class "A":
 tmp/a.py:10: error: Type argument "str" of "C" must be a subtype of "int"
 tmp/a.py:11: error: Type argument "str" of "C" must be a subtype of "int"
 
-[case testNewAnalyzerTypeArgBoundCheckDifferentNodes]
+[case testNewAnalyzerTypeArgBoundCheckDifferentNodes_no_native_parse]
 from typing import TypeVar, TypedDict, Generic, NamedTuple, NewType, Union, Any, cast, overload
 
 T = TypeVar('T', bound=int)
diff --git a/test-data/unit/check-newsyntax.test b/test-data/unit/check-newsyntax.test
index df36a1ce4dd22..3df0d03c96e10 100644
--- a/test-data/unit/check-newsyntax.test
+++ b/test-data/unit/check-newsyntax.test
@@ -1,4 +1,4 @@
-[case testNewSyntaxSyntaxError]
+[case testNewSyntaxSyntaxError_no_native_parse]
 x: int: int  # E: Invalid syntax
 [out]
 
@@ -122,7 +122,7 @@ reveal_type(f'{v}') # N: Revealed type is "builtins.str"
 reveal_type(f'{1}') # N: Revealed type is "builtins.str"
 [builtins fixtures/f_string.pyi]
 
-[case testFeatureVersionSuggestion]
+[case testFeatureVersionSuggestion_no_native_parse]
 # flags: --python-version 3.99
 x *** x this is what future python looks like public static void main String[] args await goto exit
 [out]
diff --git a/test-data/unit/check-python312.test b/test-data/unit/check-python312.test
index 39b57d1bb6f04..122bf5df14e7c 100644
--- a/test-data/unit/check-python312.test
+++ b/test-data/unit/check-python312.test
@@ -1622,7 +1622,7 @@ reveal_type(a)  # N: Revealed type is "builtins.list[builtins.int]"
 def f[T](x: foobar, y: T) -> T: ...  # E: Name "foobar" is not defined
 reveal_type(f)  # N: Revealed type is "def [T] (x: Any, y: T`-1) -> T`-1"
 
-[case testPEP695WrongNumberOfConstrainedTypes]
+[case testPEP695WrongNumberOfConstrainedTypes_no_native_parse]
 type A[T: ()] = list[T]  # E: Type variable must have at least two constrained types
 a: A[int]
 reveal_type(a)  # N: Revealed type is "builtins.list[builtins.int]"
@@ -1771,7 +1771,7 @@ type Y[T] = {"item": T, **Y[T]}  # E: Overwriting TypedDict field "item" while m
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-full.pyi]
 
-[case testPEP695UsingIncorrectExpressionsInTypeVariableBound]
+[case testPEP695UsingIncorrectExpressionsInTypeVariableBound_no_native_parse]
 type X[T: (yield 1)] = Any  # E: Yield expression cannot be used as a type variable bound
 type Y[T: (yield from [])] = Any # E: Yield expression cannot be used as a type variable bound
 type Z[T: (a := 1)] = Any  # E: Named expression cannot be used as a type variable bound
@@ -1802,7 +1802,7 @@ def fooy_nested[T: (1 + (yield from []))](): pass  # E: Yield expression cannot
 def fooz_nested[T: (1 + (a := 1))](): pass  # E: Named expression cannot be used as a type variable bound
 def fook_nested[T: (1 +(await 1))](): pass  # E: Await expression cannot be used as a type variable bound
 
-[case testPEP695UsingIncorrectExpressionsInTypeAlias]
+[case testPEP695UsingIncorrectExpressionsInTypeAlias_no_native_parse]
 type X = (yield 1)  # E: Yield expression cannot be used within a type alias
 type Y = (yield from []) # E: Yield expression cannot be used within a type alias
 type Z = (a := 1)  # E: Named expression cannot be used within a type alias
diff --git a/test-data/unit/check-python39.test b/test-data/unit/check-python39.test
index 86a9126ff483a..236482229a6ee 100644
--- a/test-data/unit/check-python39.test
+++ b/test-data/unit/check-python39.test
@@ -1,4 +1,4 @@
-[case testGivingSameKeywordArgumentTwice]
+[case testGivingSameKeywordArgumentTwice_no_native_parse]
 # This test was originally in check-kwargs.test
 # Python 3.9's new parser started producing a different error message here. Since this isn't the
 # most important test, to deal with this we'll only run this test with Python 3.9 and later.
diff --git a/test-data/unit/check-type-aliases.test b/test-data/unit/check-type-aliases.test
index 61eda2bd77747..69474e2850055 100644
--- a/test-data/unit/check-type-aliases.test
+++ b/test-data/unit/check-type-aliases.test
@@ -1164,7 +1164,7 @@ reveal_type(xp)  # N: Revealed type is "__main__.G[[builtins.int], builtins.str]
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-full.pyi]
 
-[case testTypeAliasTypeInvalidGeneric]
+[case testTypeAliasTypeInvalidGeneric_no_native_parse]
 from typing_extensions import TypeAliasType, TypeVarTuple, ParamSpec
 from typing import Callable, Dict, Generic, TypeVar, Tuple, Unpack
 
diff --git a/test-data/unit/check-typeddict.test b/test-data/unit/check-typeddict.test
index 3fcd9eda58f7d..eb6a4d08b978d 100644
--- a/test-data/unit/check-typeddict.test
+++ b/test-data/unit/check-typeddict.test
@@ -3749,7 +3749,7 @@ B = TypedDict("B", {  # E: Type of a TypedDict key becomes "Any" due to an unfol
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]
 
-[case testTypedDictWithClassLevelKeywords]
+[case testTypedDictWithClassLevelKeywords_no_native_parse]
 from typing import TypedDict, Generic, TypeVar
 
 T = TypeVar('T')
diff --git a/test-data/unit/check-unreachable-code.test b/test-data/unit/check-unreachable-code.test
index f02eb2bd55c47..1888a6595b61b 100644
--- a/test-data/unit/check-unreachable-code.test
+++ b/test-data/unit/check-unreachable-code.test
@@ -452,7 +452,7 @@ reveal_type(x)  # N: Revealed type is "builtins.str"
 [builtins fixtures/ops.pyi]
 [out]
 
-[case testCustomSysPlatform2]
+[case testCustomSysPlatform2_no_native_parse]
 # flags: --platform win32
 import sys
 if sys.platform == 'linux':
@@ -463,7 +463,7 @@ reveal_type(x)  # N: Revealed type is "builtins.int"
 [builtins fixtures/ops.pyi]
 [out]
 
-[case testCustomSysPlatformStartsWith]
+[case testCustomSysPlatformStartsWith_no_native_parse]
 # flags: --platform win32
 import sys
 if sys.platform.startswith('win'):
@@ -887,7 +887,7 @@ def baz(x: int) -> int:
         return x
 [builtins fixtures/exception.pyi]
 
-[case testUnreachableFlagIgnoresSemanticAnalysisUnreachable]
+[case testUnreachableFlagIgnoresSemanticAnalysisUnreachable_no_native_parse]
 # flags: --warn-unreachable --python-version 3.9 --platform win32 --always-false FOOBAR
 import sys
 from typing import TYPE_CHECKING

From 6a3420f62dd89275b2e4eb2da84ff3a067dfe9fd Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Thu, 5 Mar 2026 18:32:25 +0000
Subject: [PATCH 16/17] Undo fail fast logic

---
 .github/workflows/test.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 4eca8a79083d5..f227fc95e7aa1 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -105,13 +105,13 @@ jobs:
           python: '3.14'
           os: ubuntu-24.04-arm
           toxenv: py
-          tox_extra_args: "-x -n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
+          tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           dev_ast_serialize: true
         - name: Parallel tests with py314-ubuntu, mypyc-compiled
           python: '3.14'
           os: ubuntu-24.04-arm
           toxenv: py
-          tox_extra_args: "-x -n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
+          tox_extra_args: "-n 4 --mypy-num-workers=4 mypy/test/testcheck.py"
           test_mypyc: true
           dev_ast_serialize: true
         # Skip Windows tests until we publish ast_serialize wheels on PyPI.

From 0226445601dbad804263612b4ea958ba49d94d72 Mon Sep 17 00:00:00 2001
From: Ivan Levkivskyi <levkivskyi@gmail.com>
Date: Thu, 5 Mar 2026 19:02:11 +0000
Subject: [PATCH 17/17] Skip t-strings tests for now

---
 test-data/unit/check-python314.test | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/test-data/unit/check-python314.test b/test-data/unit/check-python314.test
index c6944013c1d83..688541d7c39a0 100644
--- a/test-data/unit/check-python314.test
+++ b/test-data/unit/check-python314.test
@@ -1,4 +1,4 @@
-[case testTemplateStringBasics]
+[case testTemplateStringBasics_no_native_parse]
 reveal_type(t"foobar")  # N: Revealed type is "string.templatelib.Template"
 t"{'foobar'}"
 t"foo{'bar'}"
@@ -14,32 +14,32 @@ a = t"foobar"
 a = t"{'foobar'}"
 [builtins fixtures/f_string.pyi]
 
-[case testTemplateStringWithoutExplicitImport]
+[case testTemplateStringWithoutExplicitImport_no_native_parse]
 reveal_type(t"implicit import works")  # N: Revealed type is "string.templatelib.Template"
 [builtins fixtures/f_string.pyi]
 
-[case testTemplateStringExpressionsOk]
+[case testTemplateStringExpressionsOk_no_native_parse]
 t".{1 + 1}."
 t".{1 + 1}.{'foo' + 'bar'}"
 [builtins fixtures/f_string.pyi]
 
-[case testTemplateStringExpressionsErrors]
+[case testTemplateStringExpressionsErrors_no_native_parse]
 t"{1 + ''}"   # E: Unsupported operand types for + ("int" and "str")
 t".{1 + ''}"  # E: Unsupported operand types for + ("int" and "str")
 [builtins fixtures/f_string.pyi]
 
-[case testTemplateStringParseFormatOptions]
+[case testTemplateStringParseFormatOptions_no_native_parse]
 value = 10.5142
 width = 10
 precision = 4
 t"result: {value:{width}.{precision}}"
 [builtins fixtures/f_string.pyi]
 
-[case testTemplateStringNestedExpressionsTypeChecked]
+[case testTemplateStringNestedExpressionsTypeChecked_no_native_parse]
 t"{2:{3 + ''}}"  # E: Unsupported operand types for + ("int" and "str")
 [builtins fixtures/f_string.pyi]
 
-[case testIncrementalTemplateStringImplicitDependency]
+[case testIncrementalTemplateStringImplicitDependency_no_native_parse]
 import m
 reveal_type(m.x)
 [file m.py]