Bump to 6.2.0: Python 3.15 (3.15.2) as a pre-release line

Adds 3.15 to the generated version tables. They are generated from
python-build's `support-py3.15` manifest on top of the pinned release
date 20261027, which is otherwise identical to that release's manifest:
CPython 3.15.2, PBS 20261026, Pyodide 315.0.0a2 with wheel tag
pyemscripten-2026.5-wasm32, and all three Android ABIs. The row is
`prerelease: true`, so 3.15 is opt-in (`--python-version 3.15` /
SERIOUS_PYTHON_VERSION=3.15) and 3.14 stays the default. Pyodide 3.15 is
still an alpha and pypi.flet.dev has no cp315 mobile wheels yet.

The 3.15 runtimes and the Android `-py3.15` dart_bridge binaries exist
only as python-build / dart-bridge CI artifacts until those repos cut
releases. To build against them:

* Android: new SERIOUS_PYTHON_ANDROID_PYTHON_DIST=<dir> takes the
  `python-android-dart-<full>-<abi>.tar.gz` archives from <dir>
  instead of the release, the counterpart of the existing
  SERIOUS_PYTHON_DART_BRIDGE_DIST. Seeding the cache doesn't work here
  because the Gradle download task re-checks the release URL
  (onlyIfModified) and 404s. SERIOUS_PYTHON_BUILD_DIST doesn't fit
  either, because it skips the stdlib/site-packages staging.
* Darwin/iOS/Linux/Windows already skip the download when the cached
  file exists.
* `.github/scripts/seed_unreleased_runtimes.sh <platform>` does both
  from GitHub Actions run artifacts. Assets the pinned releases already
  publish are left alone, so it is a no-op for 3.12-3.14.

CI:
* 3.15 joins every bridge_example matrix (macOS and iOS x
  cocoapods/spm, Android, Windows, Linux amd64/arm64). Each job runs
  the seeding step with PYTHON_BUILD_RUN_ID / DART_BRIDGE_RUN_ID set to
  the python-build and dart-bridge `support-py3.15` runs. Clear both
  once 3.15 is released.
* version_tables_in_sync compares against PYTHON_BUILD_MANIFEST_URL
  (the python-build branch manifest) when set, again on top of the
  pinned date.

Windows: CPython 3.15 bundles Tcl/Tk 9 (`tcl90.dll`, `tcl9tk90.dll`,
`libtommath.dll`). The Tk cleanup now drops them like it drops the 8.6
DLLs.

No Dart or native logic needed to change for the new minor. Wheel tags,
the extension-suffix regex, the sitecustomize shims and _sp_bootstrap's
importlib hooks are minor-agnostic and unchanged in 3.15.2.

Author: ndonkoHenri

.github/scripts/seed_unreleased_runtimes.sh

@@ -0,0 +1,137 @@
+#!/usr/bin/env bash
+# Make runtimes that the pinned releases don't publish yet available to a build,
+# by taking them from GitHub Actions runs of flet-dev/python-build and
+# flet-dev/dart-bridge.
+#
+# serious_python downloads its Python runtime from the python-build release in
+# `python_build_release_date` and its dart_bridge binary from dart-bridge
+# release `v<dart_bridge_version>` (the generated python_versions.properties).
+# A new Python minor is added to those tables before either release exists, so
+# a build of that minor needs the files from CI artifacts instead:
+#
+#   * Darwin / iOS / Linux / Windows skip the download when the file is already
+#     in serious_python's cache, so the artifact is placed there.
+#   * Android re-checks the URL even when cached, so the archives are put in a
+#     directory exported as SERIOUS_PYTHON_ANDROID_PYTHON_DIST (and the
+#     dart_bridge .so files as SERIOUS_PYTHON_DART_BRIDGE_DIST).
+#
+# Files the releases already have are left alone, so this is a no-op for
+# released minors and when both run ids are empty.
+#
+# Usage: seed_unreleased_runtimes.sh <Darwin|iOS|Android|Linux|Windows>
+# Env:   SERIOUS_PYTHON_VERSION (short version), PYTHON_BUILD_RUN_ID, DART_BRIDGE_RUN_ID, GH_TOKEN,
+#        FLET_CACHE_DIR (optional), GITHUB_ENV / RUNNER_TEMP (set by Actions).
+set -euo pipefail
+
+platform="${1:?platform}"
+short="${SERIOUS_PYTHON_VERSION:?SERIOUS_PYTHON_VERSION is required}"
+root=$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)
+props="$root/src/serious_python_linux/linux/python_versions.properties"
+
+prop() { sed -n "s/^$1=//p" "$props" | tr -d '\r'; }
+full=$(prop "$short.full_version")
+date=$(prop python_build_release_date)
+dart_bridge=$(prop dart_bridge_version)
+if [ -z "$full" ]; then
+    echo "::error::$props has no $short.full_version"
+    exit 1
+fi
+
+cache="${FLET_CACHE_DIR:-$HOME/.flet/cache}"
+pb_cache="$cache/python-build/v$full-$date"
+tmp="${RUNNER_TEMP:-${TMPDIR:-/tmp}}/sp-unreleased"
+mkdir -p "$tmp"
+
+release_assets() { # repo tag
+    gh release view "$2" --repo "$1" --json assets --jq '.assets[].name' 2>/dev/null || true
+}
+pb_assets=$(release_assets flet-dev/python-build "$date")
+db_assets=$(release_assets flet-dev/dart-bridge "v$dart_bridge")
+has() { grep -qxF "$2" <<<"$1"; }
+
+# download_artifact <repo> <run id> <artifact> -> prints the directory it is in.
+download_artifact() {
+    local dir="$tmp/$3"
+    if [ ! -d "$dir" ]; then
+        if [ -z "$2" ]; then
+            echo "::error::$1 has not released $3's files and no run id is set to take them from" >&2
+            return 1
+        fi
+        echo "Downloading artifact $3 from $1 run $2" >&2
+        gh run download "$2" --repo "$1" --name "$3" --dir "$dir" >&2
+    fi
+    echo "$dir"
+}
+
+# seed_python <artifact> <file> <dest dir>
+seed_python() {
+    if has "$pb_assets" "$2"; then
+        return 0
+    fi
+    local dir
+    dir=$(download_artifact flet-dev/python-build "${PYTHON_BUILD_RUN_ID:-}" "$1")
+    mkdir -p "$3"
+    cp "$dir/$2" "$3/$2"
+    echo "Seeded $3/$2 (python-build run ${PYTHON_BUILD_RUN_ID})"
+}
+
+export_env() {
+    echo "$1=$2"
+    if [ -n "${GITHUB_ENV:-}" ]; then
+        echo "$1=$2" >> "$GITHUB_ENV"
+    fi
+}
+
+case "$platform" in
+    Darwin)
+        seed_python "darwin-unsigned-$full" "python-macos-dart-$full.tar.gz" "$pb_cache"
+        ;;
+    iOS)
+        seed_python "darwin-unsigned-$full" "python-ios-dart-$full.tar.gz" "$pb_cache"
+        ;;
+    Linux)
+        case "$(uname -m)" in
+            x86_64 | amd64) arch=x86_64 ;;
+            aarch64 | arm64) arch=aarch64 ;;
+            *) echo "::error::unsupported Linux arch $(uname -m)"; exit 1 ;;
+        esac
+        seed_python "python-linux-$full" "python-linux-dart-$full-$arch.tar.gz" "$pb_cache"
+        ;;
+    Windows)
+        seed_python "python-windows-$full" "python-windows-for-dart-$full.zip" "$pb_cache"
+        ;;
+    Android)
+        abis=$(prop "$short.android_abis" | tr ',' ' ')
+        py_dist="$tmp/android-python-dist"
+        bridge_dist="$tmp/android-dart-bridge-dist"
+        need_py=0
+        need_bridge=0
+        for abi in $abis; do
+            has "$pb_assets" "python-android-dart-$full-$abi.tar.gz" || need_py=1
+            has "$db_assets" "libdart_bridge-android-$abi-py$short.so" || need_bridge=1
+        done
+        if [ "$need_py" = 1 ]; then
+            # SERIOUS_PYTHON_ANDROID_PYTHON_DIST replaces the download for every
+            # ABI, so the directory gets all of them.
+            dir=$(download_artifact flet-dev/python-build "${PYTHON_BUILD_RUN_ID:-}" "python-android-$full")
+            mkdir -p "$py_dist"
+            for abi in $abis; do
+                cp "$dir/python-android-dart-$full-$abi.tar.gz" "$py_dist/"
+            done
+            export_env SERIOUS_PYTHON_ANDROID_PYTHON_DIST "$py_dist"
+        fi
+        if [ "$need_bridge" = 1 ]; then
+            mkdir -p "$bridge_dist"
+            for abi in $abis; do
+                name="libdart_bridge-android-$abi-py$short"
+                dir=$(download_artifact flet-dev/dart-bridge "${DART_BRIDGE_RUN_ID:-}" "$name")
+                cp "$dir/$name.so" "$bridge_dist/"
+            done
+            export_env SERIOUS_PYTHON_DART_BRIDGE_DIST "$bridge_dist"
+        fi
+        ;;
+    *)
+        echo "::error::unknown platform $platform"
+        exit 1
+        ;;
+esac

.github/workflows/ci.yml

@@ -30,6 +30,13 @@ env:
   # older flet whose transitive deps (e.g. msgpack) have wheels for the
   # target python_version / platform, leaving the two halves mismatched.
   FLET_VERSION: "0.85.3"
+  # GitHub Actions runs that supply runtimes the pinned releases don't publish
+  # yet (see .github/scripts/seed_unreleased_runtimes.sh): the python-build and
+  # dart-bridge `support-py3.15` runs that built Python 3.15.2 and its Android
+  # dart_bridge binaries. Clear both once python-build and dart-bridge releases
+  # carry 3.15; the seeding step is a no-op for released files.
+  PYTHON_BUILD_RUN_ID: "42319861949"
+  DART_BRIDGE_RUN_ID: "42321036158"
 
 permissions:
   contents: read
@@ -54,10 +61,21 @@ jobs:
 
       - name: Regenerate version tables and check for drift
         working-directory: src/serious_python
+        env:
+          # Unreleased minors: compare against python-build's `support-py3.15`
+          # branch manifest (on top of the pinned release date) instead of the
+          # release's. Clear once a python-build release lists 3.15.
+          PYTHON_BUILD_MANIFEST_URL: "https://raw.githubusercontent.com/flet-dev/python-build/support-py3.15/manifest.json"
         run: |
           set -euo pipefail
           flutter pub get >/dev/null
-          dart run serious_python:gen_version_tables
+          if [ -n "$PYTHON_BUILD_MANIFEST_URL" ]; then
+            curl -fsSL -o "$RUNNER_TEMP/manifest.json" "$PYTHON_BUILD_MANIFEST_URL"
+            date=$(sed -n 's/^const pythonReleaseDate = "\([0-9]*\)";$/\1/p' lib/src/python_versions.dart)
+            dart run serious_python:gen_version_tables --manifest "$RUNNER_TEMP/manifest.json" --release-date "$date"
+          else
+            dart run serious_python:gen_version_tables
+          fi
           if ! git diff --quiet; then
             echo "::error::Generated Python version tables are out of date."
             echo "The committed lib/src/python_versions.dart and the four"
@@ -105,7 +123,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python_version: ['3.12', '3.13', '3.14']
+        python_version: ['3.12', '3.13', '3.14', '3.15']
         build_system: ['cocoapods', 'spm']
     env:
       SERIOUS_PYTHON_VERSION: ${{ matrix.python_version }}
@@ -133,6 +151,12 @@ jobs:
           # Avoid release-time cache poisoning.
           lookup-only: ${{ startsWith(github.ref, 'refs/tags/') }}
 
+      - name: Seed unreleased runtimes
+        shell: bash
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: bash .github/scripts/seed_unreleased_runtimes.sh Darwin
+
       - name: Configure ${{ matrix.build_system }}
         run: |
           if [ "${{ matrix.build_system }}" = "spm" ]; then
@@ -202,7 +226,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python_version: ['3.12', '3.13', '3.14']
+        python_version: ['3.12', '3.13', '3.14', '3.15']
         build_system: ['cocoapods', 'spm']
     env:
       SERIOUS_PYTHON_VERSION: ${{ matrix.python_version }}
@@ -229,6 +253,12 @@ jobs:
           # Avoid release-time cache poisoning.
           lookup-only: ${{ startsWith(github.ref, 'refs/tags/') }}
 
+      - name: Seed unreleased runtimes
+        shell: bash
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: bash .github/scripts/seed_unreleased_runtimes.sh iOS
+
       - name: Setup iOS Simulator
         id: simulator
         uses: futureware-tech/simulator-action@e89aa8f93d3aec35083ff49d2854d07f7186f7f5 # v5
@@ -287,7 +317,7 @@ jobs:
       matrix:
         # x86_64 matches the emulator architecture; only build/install for
         # that ABI to keep CI fast.
-        python_version: ['3.12', '3.13', '3.14']
+        python_version: ['3.12', '3.13', '3.14', '3.15']
     env:
       SERIOUS_PYTHON_VERSION: ${{ matrix.python_version }}
     steps:
@@ -313,6 +343,12 @@ jobs:
           # Avoid release-time cache poisoning.
           lookup-only: ${{ startsWith(github.ref, 'refs/tags/') }}
 
+      - name: Seed unreleased runtimes
+        shell: bash
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: bash .github/scripts/seed_unreleased_runtimes.sh Android
+
       - name: Enable KVM
         run: |
           echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' | sudo tee /etc/udev/rules.d/99-kvm4all.rules
@@ -395,7 +431,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python_version: ['3.12', '3.13', '3.14']
+        python_version: ['3.12', '3.13', '3.14', '3.15']
     env:
       SERIOUS_PYTHON_VERSION: ${{ matrix.python_version }}
       BRIDGE_EXAMPLE_TEST_PYDANTIC: "1"
@@ -422,6 +458,12 @@ jobs:
           # Avoid release-time cache poisoning.
           lookup-only: ${{ startsWith(github.ref, 'refs/tags/') }}
 
+      - name: Seed unreleased runtimes
+        shell: bash
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: bash .github/scripts/seed_unreleased_runtimes.sh Windows
+
       - name: Package + run integration test
         working-directory: "src/serious_python/example/bridge_example"
         shell: bash
@@ -464,7 +506,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python_version: ['3.12', '3.13', '3.14']
+        python_version: ['3.12', '3.13', '3.14', '3.15']
         arch: [amd64, arm64]
         include:
           - arch: amd64
@@ -506,6 +548,12 @@ jobs:
           # Read-only on tag/release builds to avoid cache poisoning.
           lookup-only: ${{ startsWith(github.ref, 'refs/tags/') }}
 
+      - name: Seed unreleased runtimes
+        shell: bash
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: bash .github/scripts/seed_unreleased_runtimes.sh Linux
+
       - name: Install Linux desktop build deps
         run: |
           sudo apt-get update --allow-releaseinfo-change

src/serious_python/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 6.2.0
+
+* **Python 3.15 (3.15.2) as a pre-release line.** Select it with `--python-version 3.15` / `SERIOUS_PYTHON_VERSION=3.15`. It is never the default: 3.14 stays the default until Pyodide 3.15 is final and `pypi.flet.dev` has cp315 mobile wheels. Web builds use Pyodide `315.0.0a2` (wheel tag `pyemscripten-2026.5-wasm32`). The 3.15 runtimes and Android `dart_bridge` binaries come from python-build and dart-bridge releases that are not cut yet. Until then, build 3.15 against their CI artifacts (see "Testing unreleased runtimes" in the README).
+* New `SERIOUS_PYTHON_ANDROID_PYTHON_DIST` env var points Android builds at a directory of runtime archives instead of the python-build release. See serious_python_android 6.2.0.
+
 ## 6.1.3
 
 * Fix the `package` command hiding why a step failed when the error went to stdout, such as the `SyntaxError` from compiling an app file, which made `flet build` fail with no explanation unless run with `-vv` ([#262](https://github.com/flet-dev/serious-python/pull/262), [flet-dev/flet#7029](https://github.com/flet-dev/flet/issues/7029)).

src/serious_python/README.md

@@ -27,6 +27,7 @@ is specified.
 | 3.12  | 3.12.16         | 0.27.8        | `pyodide-2024.0-wasm32`           |
 | 3.13  | 3.13.18         | 0.29.5        | `pyemscripten-2025.0-wasm32`      |
 | 3.14  | 3.14.10         | 314.0.7       | `pyemscripten-2026.0-wasm32`      |
+| 3.15  | 3.15.2 (pre-release) | 315.0.0a2 | `pyemscripten-2026.5-wasm32`      |
 
 The default is the latest stable row (currently **3.14**) when neither
 `--python-version` nor `SERIOUS_PYTHON_VERSION` is set. When running through
@@ -49,7 +50,9 @@ in each platform package (read by the native build configs). To bump versions
 see [CONTRIBUTING.md](CONTRIBUTING.md); never hand-edit the generated files.
 Pre-release CPython lines are marked `prerelease: true`, so they're opt-in via
 explicit `--python-version` (or `requires-python = "==3.15.*"`) without becoming
-the auto-resolved default.
+the auto-resolved default. 3.15 is such a line: CPython 3.15 itself is final,
+but its Pyodide is still an alpha and the mobile wheel index
+(`pypi.flet.dev`) has no cp315 builds yet.
 
 ## Usage
 
@@ -134,7 +137,7 @@ dart run serious_python:main package --asset assets/myapp.zip app/src -p Emscrip
 
 Pick which CPython line to bundle with the **`SERIOUS_PYTHON_VERSION`
 environment variable** (supported short versions today are **3.12**, **3.13**,
-**3.14**; the default is the latest stable):
+**3.14**, and **3.15** as a pre-release; the default is the latest stable):
 
 ```
 export SERIOUS_PYTHON_VERSION=3.13
@@ -162,6 +165,26 @@ and Pyodide releases.
 > `flutter clean`) so stale compiled bytecode from the previous version isn't
 > reused.
 
+#### Testing unreleased runtimes
+
+The native builds download the Python runtime from the pinned python-build
+release and dart_bridge from the pinned dart-bridge release. To build against
+files that aren't released yet (e.g. a python-build or dart-bridge CI run):
+
+* **Darwin, iOS, Linux, Windows** skip the download when the file is already in
+  the cache: place it at
+  `~/.flet/cache/python-build/v<full>-<python_build_release_date>/<asset>` (or
+  `dart-bridge/v<dart_bridge_version>/<asset>`; `FLET_CACHE_DIR` moves
+  `~/.flet/cache`).
+* **Android** always re-checks the release URL, so point it at local files
+  instead: `SERIOUS_PYTHON_ANDROID_PYTHON_DIST=<dir>` for
+  `python-android-dart-<full>-<abi>.tar.gz` and
+  `SERIOUS_PYTHON_DART_BRIDGE_DIST=<dir>` for
+  `libdart_bridge-android-<abi>-py<X.Y>.so`.
+
+`.github/scripts/seed_unreleased_runtimes.sh` does this from GitHub Actions run
+artifacts. CI uses it to test a Python minor before its runtimes are released.
+
 #### Installing requirements
 
 Python app dependencies are installed with the `--requirements` option (alias `-r`). The value is passed verbatim to `pip`, so any flag pip accepts works. Pass each dependency as its own option to support specifiers that contain commas:

src/serious_python/analysis_options.yaml

@@ -1,3 +1,6 @@
+analyzer:
+  exclude:
+    - build/**
 include: package:flutter_lints/flutter.yaml
 
 # Additional information about this file can be found at

src/serious_python/lib/src/python_versions.dart

@@ -61,4 +61,12 @@ const pythonReleases = <String, PythonRelease>{
     androidAbis: ["arm64-v8a", "x86_64", "armeabi-v7a"],
     prerelease: false,
   ),
+  "3.15": PythonRelease(
+    standaloneVersion: "3.15.2",
+    standaloneReleaseDate: "20261026",
+    pyodideVersion: "315.0.0a2",
+    pyodidePlatformTag: "pyemscripten-2026.5-wasm32",
+    androidAbis: ["arm64-v8a", "x86_64", "armeabi-v7a"],
+    prerelease: true,
+  ),
 };

src/serious_python/pubspec.yaml

@@ -2,7 +2,7 @@ name: serious_python
 description: A cross-platform plugin for adding embedded Python runtime to your Flutter apps.
 homepage: https://flet.dev
 repository: https://github.com/flet-dev/serious-python
-version: 6.1.3
+version: 6.2.0
 
 platforms:
   ios:

src/serious_python_android/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 6.2.0
+
+* Python 3.15 runtimes (`arm64-v8a`, `armeabi-v7a`, `x86_64`), pre-release.
+* `SERIOUS_PYTHON_ANDROID_PYTHON_DIST=<dir>` makes the build take `python-android-dart-<full>-<abi>.tar.gz` from `<dir>` instead of downloading it from the python-build release. It mirrors `SERIOUS_PYTHON_DART_BRIDGE_DIST`. Unlike `SERIOUS_PYTHON_BUILD_DIST`, the archives still go through the normal stdlib/site-packages staging. The cached download can't be used for this because the build re-checks the release URL even when the file is cached.
+
 ## 6.1.3
 
 * Align with the serious_python **6.1.3** release ([#262](https://github.com/flet-dev/serious-python/pull/262)).