Stack detection fix

docker/stacks/jvm/Dockerfile.fragment

@@ -13,13 +13,14 @@
 
 USER root
 
-# OpenJDK 21 (current LTS) and Maven for build support.
+# OpenJDK 17 (Bookworm's default LTS) and Maven for build support.
 RUN apt-get update && apt-get install -y --no-install-recommends \
-        openjdk-21-jdk-headless \
+        openjdk-17-jdk-headless \
         maven \
     && rm -rf /var/lib/apt/lists/*
 
-ENV JAVA_HOME="/usr/lib/jvm/java-21-openjdk-amd64"
+RUN ln -s /usr/lib/jvm/java-17-openjdk-* /usr/lib/jvm/java-17-openjdk
+ENV JAVA_HOME="/usr/lib/jvm/java-17-openjdk"
 
 # Eclipse JDT Language Server — canonical LSP for Java/JVM (Java, Kotlin, Groovy).
 # Pin to a specific release; update JDTLS_VERSION + JDTLS_BUILD for upgrades.

server/src/chat/transport/matrix/new_project.rs

@@ -417,6 +417,20 @@ fn apply_project_toml_key(
     Ok(format!("Set `{key} = {toml_value}` in `project.toml`."))
 }
 
+/// Return the path to `docker/stacks/` in the huskies source tree.
+///
+/// Uses `CARGO_MANIFEST_DIR` (baked in at compile time) to find the workspace
+/// root, which is correct regardless of which project directory the gateway is
+/// running from.
+pub fn stacks_dir() -> std::path::PathBuf {
+    let manifest_dir = std::path::Path::new(env!("CARGO_MANIFEST_DIR"));
+    manifest_dir
+        .parent()
+        .expect("CARGO_MANIFEST_DIR has no parent")
+        .join("docker")
+        .join("stacks")
+}
+
 /// Scan `stacks_dir` for per-stack `markers` files and detect which stacks
 /// match the given project directory.
 ///
@@ -693,10 +707,9 @@ async fn handle_adopt_project(
     crate::service::gateway::io::init_wizard_state(host_path);
 
     // ── Detect or validate stack ─────────────────────────────────────────────
-    let stacks_dir = config_dir.join("docker").join("stacks");
     let (resolved_stack, detect_warnings) = match stack {
         Some(s) => (Some(s.to_string()), vec![]),
-        None => detect_stack(host_path, &stacks_dir),
+        None => detect_stack(host_path, &stacks_dir()),
     };
     let stack_image = image_for_stack(resolved_stack.as_deref());
     let image = match build_project_image(host_path, &stack_image, name).await {
@@ -1038,10 +1051,9 @@ pub async fn handle_new_project(
 
     // ── Detect or validate stack ─────────────────────────────────────────────
 
-    let stacks_dir = config_dir.join("docker").join("stacks");
     let (resolved_stack, detect_warnings) = match stack {
         Some(s) => (Some(s.to_string()), vec![]),
-        None => detect_stack(&host_path, &stacks_dir),
+        None => detect_stack(&host_path, &stacks_dir()),
     };
     let stack_image = image_for_stack(resolved_stack.as_deref());
     let image = match build_project_image(&host_path, &stack_image, name).await {

server/src/chat/transport/matrix/project_rebuild.rs

@@ -154,8 +154,8 @@ pub async fn handle_project_rebuild(
     }
 
     // ── 3. Build new image ───────────────────────────────────────────────────
-    let stacks_dir = config_dir.join("docker").join("stacks");
-    let (resolved_stack, _warnings) = super::new_project::detect_stack(host_path, &stacks_dir);
+    let (resolved_stack, _warnings) =
+        super::new_project::detect_stack(host_path, &super::new_project::stacks_dir());
     let base_image = super::new_project::image_for_stack(resolved_stack.as_deref());
 
     let image = match super::new_project::build_project_image(host_path, &base_image, name).await {