Fix remote build context identity and preserve hard-linked files

Author: Dingway98

README.md

@@ -352,6 +352,42 @@ for event in connection.events():
     print(event)
 ```
 
+### Cache remote Dockerfile builds
+
+Use the public context fingerprint when deriving a cache name. It uses the same
+Dockerfile source selection and `.dockerignore` rules as remote packaging,
+including file contents, modes, paths, and symlinks. It ignores timestamps and
+does not compress or stage the context on disk.
+
+```python
+from hyperbrowser.build_context import docker_build_context_fingerprint
+
+fingerprint = docker_build_context_fingerprint("./app")
+# Include build options such as platform and image_init in your cache key too.
+image_name = f"app-{fingerprint[:32]}"
+build = client.sandboxes.build_image_from_dockerfile(
+    context_path="./app",
+    image_name=image_name,
+    expected_context_fingerprint=fingerprint,
+)
+```
+
+If the archived inputs differ from the fingerprint, the SDK raises
+`DockerBuildContextChangedError` before creating or uploading a build. Compute a
+fresh fingerprint and repeat the lookup/build operation. Use the same `dockerfile`
+and `force_full_context` selection when fingerprinting and building (the latter
+is named `remote_full_context` on the build method). The expected fingerprint is
+supported only for remote builds.
+
+Fingerprinting streams included files and performs blocking I/O. Async callers
+should use `await asyncio.to_thread(docker_build_context_fingerprint, "./app")`
+(Python 3.9+) or an executor. It does not resolve mutable base-image tags or
+network resources fetched by a Dockerfile; rebuild explicitly when those change.
+
+Image listings distinguish `ready` from `uploaded`: a completed team image can
+be ready to launch before its durability backup is uploaded. `ready` is `None`
+when talking to an older server. Keep the returned image ID to pin that revision.
+
 ## License
 
 This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.

hyperbrowser/build_context.py

@@ -0,0 +1,8 @@
+"""Public helpers for identifying inputs to remote Dockerfile builds."""
+
+from .client.managers.sandboxes.image_build import (
+    DockerBuildContextChangedError,
+    docker_build_context_fingerprint,
+)
+
+__all__ = ["DockerBuildContextChangedError", "docker_build_context_fingerprint"]

hyperbrowser/client/managers/async_manager/sandbox.py

@@ -725,6 +725,7 @@ async def _build_image_from_remote_dockerfile(
         dockerfile,
         platform: str,
         remote_full_context: bool,
+        expected_context_fingerprint: Optional[str],
         image_init: Optional[Union[SandboxImageInitDict, SandboxImageInit]],
         image_config_user: Optional[str],
         builder_cpus: Optional[int],
@@ -741,6 +742,7 @@ async def _build_image_from_remote_dockerfile(
             context_path,
             dockerfile=dockerfile,
             force_full_context=remote_full_context,
+            expected_context_fingerprint=expected_context_fingerprint,
             temp_dir=temp_dir,
         )
         build_id = None
@@ -803,6 +805,7 @@ async def build_image_from_dockerfile(
         dockerfile="Dockerfile",
         remote: bool = True,
         remote_full_context: bool = False,
+        expected_context_fingerprint: Optional[str] = None,
         docker_tag: Optional[str] = None,
         platform: str = IMAGE_BUILD_SOURCE_PLATFORM,
         build_args: Optional[Dict[str, str]] = None,
@@ -829,6 +832,7 @@ async def build_image_from_dockerfile(
                 dockerfile=dockerfile,
                 platform=platform,
                 remote_full_context=remote_full_context,
+                expected_context_fingerprint=expected_context_fingerprint,
                 image_init=image_init,
                 image_config_user=image_config_user,
                 builder_cpus=builder_cpus,
@@ -840,6 +844,8 @@ async def build_image_from_dockerfile(
                 temp_dir=temp_dir,
                 upload_timeout=upload_timeout,
             )
+        if expected_context_fingerprint is not None:
+            raise ValueError("expected_context_fingerprint requires remote=True")
         tag = docker_tag or make_temp_docker_tag()
         remove_tag = docker_tag is None
         try: