reopen main for development (#15373)

Bump the version to 51.0.0-dev1 and add a changelog section for the next
release.


Claude-Session: https://claude.ai/code/session_01XFSYJJ1k7PDnNV7stHJgLg

Co-authored-by: Claude <noreply@anthropic.com>

Author: alex

CHANGELOG.rst

@@ -1,6 +1,13 @@
 Changelog
 =========
 
+.. _v51-0-0:
+
+51.0.0 - `main`_
+~~~~~~~~~~~~~~~~
+
+.. note:: This version is not yet released and is under active development.
+
 .. _v50-0-0:
 
 50.0.0 - 2026-07-31

Cargo.lock

@@ -12,7 +12,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.50.0"
+version = "0.51.0-dev1"
 authors = ["The cryptography developers <cryptography-dev@python.org>"]
 edition = "2021"
 publish = false

Cargo.toml

@@ -16,7 +16,7 @@ build-backend = "maturin"
 
 [project]
 name = "cryptography"
-version = "50.0.0"
+version = "51.0.0-dev1"
 authors = [
     { name = "The Python Cryptographic Authority and individual contributors", email = "cryptography-dev@python.org" },
 ]
@@ -76,7 +76,7 @@ dev = [
 ]
 nox = ["nox[uv] >=2024.04.15"]
 test = [
-    "cryptography_vectors==50.0.0",
+    "cryptography_vectors",
     "pytest >=7.4.0",
     "pytest-benchmark >=4.0",
     "pytest-cov >=2.10.1",

pyproject.toml

@@ -10,7 +10,7 @@
     "__version__",
 ]
 
-__version__ = "50.0.0"
+__version__ = "51.0.0-dev1"
 
 
 __author__ = "The Python Cryptographic Authority and individual contributors"

src/cryptography/__about__.py

@@ -6,4 +6,4 @@
     "__version__",
 ]
 
-__version__ = "50.0.0"
+__version__ = "51.0.0-dev1"

vectors/cryptography_vectors/__about__.py

@@ -6,7 +6,7 @@ build-backend = "uv_build"
 
 [project]
 name = "cryptography_vectors"
-version = "50.0.0"
+version = "51.0.0-dev1"
 authors = [
     {name = "The Python Cryptographic Authority and individual contributors", email = "cryptography-dev@python.org"}
 ]