Remove Python 3.9 support (#19273)

Co-authored-by: Claude <[email protected]>

Author: desertaxle

.github/workflows/docker-images.yaml

@@ -26,7 +26,6 @@ jobs:
           - "prefecthq/prefect"
           - "prefecthq/prefect-client"
         python-version:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"

.github/workflows/integration-package-release.yaml

@@ -37,7 +37,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v6
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           cache: "pip"
           cache-dependency-path: "requirements*.txt"
 

.github/workflows/integration-package-tests.yaml

@@ -28,7 +28,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v6
         with:
-          python-version: "3.9"
+          python-version: "3.10"
       - name: Generate matrix
         id: set-matrix
         run: |

.github/workflows/prefect-aws-docker-images.yaml

@@ -30,7 +30,6 @@ jobs:
       fail-fast: false
       matrix:
         python-version:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"

.github/workflows/prefect-client.yaml

@@ -40,7 +40,7 @@ jobs:
         uses: astral-sh/setup-uv@v7
         with:
           enable-cache: true
-          python-version: "3.9"
+          python-version: "3.10"
           cache-dependency-glob: "pyproject.toml"
           activate-environment: true
 

.github/workflows/python-package.yaml

@@ -27,7 +27,7 @@ jobs:
         uses: astral-sh/setup-uv@v7
         with:
           enable-cache: true
-          python-version: "3.9"
+          python-version: "3.10"
           cache-dependency-glob: "pyproject.toml"
 
       - uses: actions/setup-node@v6

.github/workflows/python-tests.yaml

@@ -71,7 +71,6 @@ jobs:
           - "postgres:14"
           - "sqlite"
         python-version:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"
@@ -180,7 +179,6 @@ jobs:
         database:
           - "postgres:14"
         python-version:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"

.github/workflows/static-analysis.yaml

@@ -37,7 +37,7 @@ jobs:
       - name: Install uv and set the python version
         uses: astral-sh/setup-uv@v7
         with:
-          python-version: "3.9"
+          python-version: "3.10"
           enable-cache: true
           cache-dependency-glob: "pyproject.toml"
 

.github/workflows/windows-tests.yaml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       matrix:
         python-version:
-          - "3.9"
+          - "3.10"
           - "3.12"
           - "3.14"
 

AGENTS.md

@@ -43,7 +43,7 @@ prefect config view            # Inspect configuration
 
 ### Code Conventions
 
-- Python 3.9+ with modern typing (`list[int]`, `T | None`)
+- Python 3.10+ with modern typing (`list[int]`, `T | None`)
 - Private implementation details (`_private_method`)
 - No public API changes without approval
 - Use `uv` for dependency management, not `pip`