feat!: remove the Apple Containers backend

.dap/review/engineering.md

@@ -38,18 +38,18 @@ and is never read at the boundary produces a devcontainer that silently ignores
   devcontainers — the daemon came up unprivileged and its entrypoint never ran (#103).
 - The inverse counts too: a value read at the boundary that no parsing path can ever set.
 
-## R2. Path parity — native, shell-out, and each backend
+## R2. Path parity — native, shell-out, and the backend boundary
 
 Refines `D1`. This repository implements the same behaviour more than once by design.
 
 - **compose** has a native orchestrator (`compose/orchestrator.go`) and a shell-out path
   (`docker compose`). A fix, guard, or flag added to one and not the other is a finding —
   name the sibling call site and say what it does instead. Both paths carried the same
   recreate bug (#71, #72) and the same entrypoint gap (#103).
-- **runtime** has `docker` and `applecontainer` backends behind one interface.
-  A change to shared orchestration must state what each backend does with it; a change
-  inside one backend must say whether the other needs the same. Apple diverges from
-  Docker in ways that have already broken workspaces (below).
+- **runtime** has one backend today — `docker` — behind the `runtime.Runtime`
+  interface. Shared orchestration (engine, compose) must reach it through that
+  interface; a diff that leaks Docker-specific behaviour into shared code is a
+  finding, because the interface is what keeps a second backend possible.
 - A capability flag on `Capabilities()` (`ServiceNameDNS`, for instance) is the
   legitimate way to encode divergence. A silent assumption that all backends behave like
   Docker is not.
@@ -150,4 +150,3 @@ Do not file these here:
   documented `Known limitations` in the CHANGELOG. Absence of a non-goal is not a defect.
 - Dependency version bumps with no code change, beyond an actual incompatibility you can
   point at in the diff.
-- The Swift bridge under `applecontainer-bridge/` unless the diff touches it.

.devcontainer/README.md

@@ -39,16 +39,11 @@ The prebuild image provides everything the Linux CI jobs need:
   `docker` / `docker compose` from inside the container.
 - **GitHub CLI** and `make`.
 
-> The Apple `container` backend (`runtime/applecontainer`) is darwin/arm64-only
-> and cannot be built inside this Linux container — exactly as on the Linux CI
-> jobs, where `make bridge` is a no-op. Use a native macOS checkout for that
-> backend.
-
 ## Common tasks
 
 ```bash
 make lint              # golangci-lint run ./...
-make test              # go test -race ./...   (bridge is a no-op on Linux)
+make test              # go test -race ./...
 make test-integration  # docker-backed integration suite
 ```
 

.gitignore

@@ -33,6 +33,3 @@ go.work.sum
 # work-in-progress drafts, milestone trackers, etc.
 PRD.md
 design/private/
-
-# Local applecontainer working directory (not committed).
-examples/applecontainer-spike/

CHANGELOG.md

@@ -9,6 +9,23 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Removed
 
+- **BREAKING — the Apple Containers backend is removed.** `runtime/applecontainer`
+  and the `applecontainer-bridge` Swift package (reached through a cgo shim) are
+  deleted, along with the `--runtime applecontainer` CLI value: `--runtime` now
+  accepts `docker` only, and any other value is refused with
+  `unknown runtime %q (want docker)`. The backend was darwin/arm64-only, could not
+  be built or exercised on Linux CI. Its CI jobs were already removed earlier in
+  this same unreleased line, which is also when Docker became the only documented
+  backend. Also gone:
+  the `bridge` / `bridge-clean` Makefile targets (and the `test` /
+  `test-integration` dependency on them, so neither target shells out to `swift`
+  any more) and the eight `test/integration/applecontainer_*_test.go` suites.
+- The design record `design/runtime-applecontainer.md` is deleted with the code it
+  described, and its row removed from the `design/` index. It remains readable in
+  git history at tag `v0.4.3`. `design/compose-native.md` keeps its Apple sections:
+  per `design/README.md` those records document the state of the world when
+  written, and the probe results and rejected alternatives in them are still the
+  reasoning behind the compose orchestrator's shape.
 - **BREAKING — checkpoint/restore is gone.** The feature only ever
   worked on Podman (docker's restore is broken upstream on
   containerd-integrated engines), and the Podman backend existed to

Makefile

@@ -1,4 +1,4 @@
-.PHONY: all test test-integration lint fmt vet tidy clean tools bridge bridge-clean
+.PHONY: all test test-integration lint fmt vet tidy clean tools
 
 GO ?= go
 GOLANGCI_LINT ?= golangci-lint
@@ -12,13 +12,10 @@ all: lint test
 tools:
 	$(GO) install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@$(GOLANGCI_LINT_VERSION)
 
-# test depends on bridge so the embedded dylib is present on
-# darwin/arm64 (go:embed fails the build if the file is missing). On
-# other platforms bridge is a no-op so this dependency is free.
-test: bridge
+test:
 	$(GO) test -race -count=1 ./...
 
-test-integration: bridge
+test-integration:
 	$(GO) test -race -count=1 -tags=integration -timeout=10m ./test/integration/...
 
 lint:
@@ -36,26 +33,3 @@ tidy:
 clean:
 	$(GO) clean -testcache
 
-# bridge builds libACBridge.dylib via SwiftPM and copies it into
-# runtime/applecontainer/embed/ where go:embed picks it up. Required
-# before any Go build that imports runtime/applecontainer on
-# darwin/arm64. On other platforms it's a no-op so this target can be
-# unconditionally listed as a dependency by `test` / `test-integration`
-# without burdening Linux CI.
-bridge:
-	@if [ "$$(uname -s)" = "Darwin" ] && [ "$$(uname -m)" = "arm64" ]; then \
-		cd applecontainer-bridge && swift build -c release && \
-		mkdir -p ../runtime/applecontainer/embed && \
-		cp .build/arm64-apple-macosx/release/libACBridge.dylib \
-		   ../runtime/applecontainer/embed/libACBridge.dylib; \
-	else \
-		echo "bridge: skipped (requires darwin/arm64)"; \
-	fi
-
-bridge-clean:
-	@if [ "$$(uname -s)" = "Darwin" ] && [ "$$(uname -m)" = "arm64" ]; then \
-		(cd applecontainer-bridge && swift package clean && rm -rf .build) && \
-		rm -f runtime/applecontainer/embed/libACBridge.dylib; \
-	else \
-		echo "bridge-clean: skipped (requires darwin/arm64)"; \
-	fi