# Description of Changes
This pull request makes significant improvements to the Docker build
process for the embedded Stirling-PDF image, focusing on build
efficiency, runtime optimization, and maintainability. Key changes
include upgrading major tool versions, introducing optional stripping of
Calibre's WebEngine to reduce image size, consolidating ImageMagick
layers, and refining the Python environment build process. The runtime
image is now leaner, with clearer separation between build and runtime
dependencies, and improved caching for faster builds and pulls.
**Build and Dependency Management Improvements**
* Upgraded Calibre to version `9.4.0` and added support for the
`TARGETPLATFORM` build argument for multi-platform builds.
* Added an optional `CALIBRE_STRIP_WEBENGINE` build argument to strip
Chromium/WebEngine from Calibre, saving ~80 MB when PDF output via
Calibre is not needed.
* Consolidated ImageMagick outputs into a single staging directory
(`/magick-export`) to reduce Docker layers and improve caching
efficiency.
* Refactored Python virtual environment build: now built in a dedicated
stage with pre-built wheels and copied into the runtime image,
eliminating the need for build tools and pip installs at runtime.
**Runtime Image Optimization**
* Reduced installed system packages to only what is needed at runtime;
Python build tools and dev packages are no longer included.
* Cleaned up unnecessary runtime files, including removal of build-only
Python artifacts and system headers, for a smaller and more secure
image.
**Layer and Copy Optimization**
* Switched to `COPY --link` for all major external tool layers and
application files, enabling independent layer caching and parallel pulls
for faster builds.
**Runtime Configuration and Health**
* Improved runtime directory structure and permissions, added persistent
cache directories for Project Leyden AOT, and wrote the version tag to
`/etc/stirling_version` for easier script access.
* Updated the healthcheck to wait longer for startup and increased
timeout/retries for more robust readiness detection.
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## Checklist
### General
- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings
### Documentation
- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)
### Translations (if applicable)
- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)
### UI Changes (if applicable)
- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)
### Testing (if applicable)
- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.
---------
Signed-off-by: Balázs Szücs <bszucs1209@gmail.com>
