diff --git a/src/cargo/core/manifest.rs b/src/cargo/core/manifest.rs
index f5f4217da81..93fac21fdf9 100644
--- a/src/cargo/core/manifest.rs
+++ b/src/cargo/core/manifest.rs
@@ -6,7 +6,6 @@ use rustc_serialize::{Encoder, Encodable};
 
 use core::{Dependency, PackageId, Summary, SourceId, PackageIdSpec};
 use core::WorkspaceConfig;
-use core::package_id::Metadata;
 
 pub enum EitherManifest {
     Real(Manifest),
@@ -159,7 +158,6 @@ pub struct Target {
     kind: TargetKind,
     name: String,
     src_path: PathBuf,
-    metadata: Option<Metadata>,
     tested: bool,
     benched: bool,
     doc: bool,
@@ -279,7 +277,6 @@ impl Target {
             kind: TargetKind::Bin,
             name: String::new(),
             src_path: PathBuf::new(),
-            metadata: None,
             doc: false,
             doctest: false,
             harness: true,
@@ -289,40 +286,35 @@ impl Target {
         }
     }
 
-    pub fn lib_target(name: &str, crate_targets: Vec<LibKind>,
-                      src_path: &Path,
-                      metadata: Metadata) -> Target {
+    pub fn lib_target(name: &str,
+                      crate_targets: Vec<LibKind>,
+                      src_path: &Path) -> Target {
         Target {
             kind: TargetKind::Lib(crate_targets),
             name: name.to_string(),
             src_path: src_path.to_path_buf(),
-            metadata: Some(metadata),
             doctest: true,
             doc: true,
             ..Target::blank()
         }
     }
 
-    pub fn bin_target(name: &str, src_path: &Path,
-                      metadata: Option<Metadata>) -> Target {
+    pub fn bin_target(name: &str, src_path: &Path) -> Target {
         Target {
             kind: TargetKind::Bin,
             name: name.to_string(),
             src_path: src_path.to_path_buf(),
-            metadata: metadata,
             doc: true,
             ..Target::blank()
         }
     }
 
     /// Builds a `Target` corresponding to the `build = "build.rs"` entry.
-    pub fn custom_build_target(name: &str, src_path: &Path,
-                               metadata: Option<Metadata>) -> Target {
+    pub fn custom_build_target(name: &str, src_path: &Path) -> Target {
         Target {
             kind: TargetKind::CustomBuild,
             name: name.to_string(),
             src_path: src_path.to_path_buf(),
-            metadata: metadata,
             for_host: true,
             benched: false,
             tested: false,
@@ -340,25 +332,21 @@ impl Target {
         }
     }
 
-    pub fn test_target(name: &str, src_path: &Path,
-                       metadata: Metadata) -> Target {
+    pub fn test_target(name: &str, src_path: &Path) -> Target {
         Target {
             kind: TargetKind::Test,
             name: name.to_string(),
             src_path: src_path.to_path_buf(),
-            metadata: Some(metadata),
             benched: false,
             ..Target::blank()
         }
     }
 
-    pub fn bench_target(name: &str, src_path: &Path,
-                        metadata: Metadata) -> Target {
+    pub fn bench_target(name: &str, src_path: &Path) -> Target {
         Target {
             kind: TargetKind::Bench,
             name: name.to_string(),
             src_path: src_path.to_path_buf(),
-            metadata: Some(metadata),
             tested: false,
             ..Target::blank()
         }
@@ -367,7 +355,6 @@ impl Target {
     pub fn name(&self) -> &str { &self.name }
     pub fn crate_name(&self) -> String { self.name.replace("-", "_") }
     pub fn src_path(&self) -> &Path { &self.src_path }
-    pub fn metadata(&self) -> Option<&Metadata> { self.metadata.as_ref() }
     pub fn kind(&self) -> &TargetKind { &self.kind }
     pub fn tested(&self) -> bool { self.tested }
     pub fn harness(&self) -> bool { self.harness }
diff --git a/src/cargo/core/mod.rs b/src/cargo/core/mod.rs
index 305b6ed7c74..e663dcdf270 100644
--- a/src/cargo/core/mod.rs
+++ b/src/cargo/core/mod.rs
@@ -2,7 +2,7 @@ pub use self::dependency::{Dependency, DependencyInner};
 pub use self::manifest::{Manifest, Target, TargetKind, Profile, LibKind, Profiles};
 pub use self::manifest::{EitherManifest, VirtualManifest};
 pub use self::package::{Package, PackageSet};
-pub use self::package_id::{PackageId, Metadata};
+pub use self::package_id::PackageId;
 pub use self::package_id_spec::PackageIdSpec;
 pub use self::registry::Registry;
 pub use self::resolver::Resolve;
diff --git a/src/cargo/core/package.rs b/src/cargo/core/package.rs
index 03ed7d88729..11e53cf2c9a 100644
--- a/src/cargo/core/package.rs
+++ b/src/cargo/core/package.rs
@@ -7,7 +7,7 @@ use std::path::{Path, PathBuf};
 use semver::Version;
 
 use core::{Dependency, Manifest, PackageId, SourceId, Target, TargetKind};
-use core::{Summary, Metadata, SourceMap};
+use core::{Summary, SourceMap};
 use ops;
 use util::{CargoResult, Config, LazyCell, ChainError, internal, human, lev_distance};
 use rustc_serialize::{Encoder,Encodable};
@@ -94,10 +94,6 @@ impl Package {
         self.targets().iter().any(|t| t.is_custom_build())
     }
 
-    pub fn generate_metadata(&self) -> Metadata {
-        self.package_id().generate_metadata()
-    }
-
     pub fn find_closest_target(&self, target: &str, kind: TargetKind) -> Option<&Target> {
         let targets = self.targets();
 
diff --git a/src/cargo/core/package_id.rs b/src/cargo/core/package_id.rs
index 8f1992a733e..d9224bae180 100644
--- a/src/cargo/core/package_id.rs
+++ b/src/cargo/core/package_id.rs
@@ -9,7 +9,7 @@ use regex::Regex;
 use rustc_serialize::{Encodable, Encoder, Decodable, Decoder};
 use semver;
 
-use util::{CargoResult, CargoError, short_hash, ToSemver};
+use util::{CargoResult, CargoError, ToSemver};
 use core::source::SourceId;
 
 /// Identifier for a specific version of a package in a specific source.
@@ -118,12 +118,6 @@ impl From<PackageIdError> for Box<CargoError> {
     fn from(t: PackageIdError) -> Box<CargoError> { Box::new(t) }
 }
 
-#[derive(PartialEq, Eq, Hash, Clone, RustcEncodable, Debug)]
-pub struct Metadata {
-    pub metadata: String,
-    pub extra_filename: String
-}
-
 impl PackageId {
     pub fn new<T: ToSemver>(name: &str, version: T,
                              sid: &SourceId) -> CargoResult<PackageId> {
@@ -141,13 +135,6 @@ impl PackageId {
     pub fn version(&self) -> &semver::Version { &self.inner.version }
     pub fn source_id(&self) -> &SourceId { &self.inner.source_id }
 
-    pub fn generate_metadata(&self) -> Metadata {
-        let metadata = short_hash(self);
-        let extra_filename = format!("-{}", metadata);
-
-        Metadata { metadata: metadata, extra_filename: extra_filename }
-    }
-
     pub fn with_precise(&self, precise: Option<String>) -> PackageId {
         PackageId {
             inner: Arc::new(PackageIdInner {
@@ -169,14 +156,6 @@ impl PackageId {
     }
 }
 
-impl Metadata {
-    pub fn mix<T: Hash>(&mut self, t: &T) {
-        let new_metadata = short_hash(&(&self.metadata, t));
-        self.extra_filename = format!("-{}", new_metadata);
-        self.metadata = new_metadata;
-    }
-}
-
 impl fmt::Display for PackageId {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "{} v{}", self.inner.name, self.inner.version)?;
diff --git a/src/cargo/ops/cargo_clean.rs b/src/cargo/ops/cargo_clean.rs
index 99b45f7c20a..fd270b79aba 100644
--- a/src/cargo/ops/cargo_clean.rs
+++ b/src/cargo/ops/cargo_clean.rs
@@ -73,11 +73,17 @@ pub fn clean(ws: &Workspace, opts: &CleanOptions) -> CargoResult<()> {
     cx.probe_target_info(&units)?;
 
     for unit in units.iter() {
-        let layout = cx.layout(unit);
-        rm_rf(&layout.proxy().fingerprint(&unit.pkg))?;
-        rm_rf(&layout.build(&unit.pkg))?;
+        rm_rf(&cx.fingerprint_dir(unit))?;
+        if unit.target.is_custom_build() {
+            if unit.profile.run_custom_build {
+                rm_rf(&cx.build_script_out_dir(unit))?;
+            } else {
+                rm_rf(&cx.build_script_dir(unit))?;
+            }
+            continue
+        }
 
-        for (src, link_dst, _) in cx.target_filenames(&unit)? {
+        for (src, link_dst, _) in cx.target_filenames(unit)? {
             rm_rf(&src)?;
             if let Some(dst) = link_dst {
                 rm_rf(&dst)?;
diff --git a/src/cargo/ops/cargo_rustc/context.rs b/src/cargo/ops/cargo_rustc/context.rs
index d95b7ee75c6..c0a92d643ec 100644
--- a/src/cargo/ops/cargo_rustc/context.rs
+++ b/src/cargo/ops/cargo_rustc/context.rs
@@ -1,19 +1,22 @@
+#![allow(deprecated)]
+
 use std::collections::{HashSet, HashMap, BTreeSet};
 use std::env;
+use std::fmt;
+use std::hash::{Hasher, Hash, SipHasher};
 use std::path::{Path, PathBuf};
 use std::str::{self, FromStr};
 use std::sync::Arc;
 
-
 use core::{Package, PackageId, PackageSet, Resolve, Target, Profile};
-use core::{TargetKind, Profiles, Metadata, Dependency, Workspace};
+use core::{TargetKind, Profiles, Dependency, Workspace};
 use core::dependency::Kind as DepKind;
-use util::{CargoResult, ChainError, internal, Config, profile, Cfg, human};
+use util::{self, CargoResult, ChainError, internal, Config, profile, Cfg, human};
 
 use super::TargetConfig;
 use super::custom_build::{BuildState, BuildScripts};
 use super::fingerprint::Fingerprint;
-use super::layout::{Layout, LayoutProxy};
+use super::layout::Layout;
 use super::links::Links;
 use super::{Kind, Compilation, BuildConfig};
 
@@ -53,6 +56,9 @@ struct TargetInfo {
     cfg: Option<Vec<Cfg>>,
 }
 
+#[derive(Clone)]
+pub struct Metadata(u64);
+
 impl<'a, 'cfg> Context<'a, 'cfg> {
     pub fn new(ws: &Workspace<'cfg>,
                resolve: &'a Resolve,
@@ -272,23 +278,61 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
     }
 
     /// Returns the appropriate directory layout for either a plugin or not.
-    pub fn layout(&self, unit: &Unit) -> LayoutProxy {
-        let primary = unit.pkg.package_id() == &self.current_package;
-        match unit.kind {
-            Kind::Host => LayoutProxy::new(&self.host, primary),
-            Kind::Target => LayoutProxy::new(self.target.as_ref()
-                                                 .unwrap_or(&self.host),
-                                             primary),
+    fn layout(&self, kind: Kind) -> &Layout {
+        match kind {
+            Kind::Host => &self.host,
+            Kind::Target => self.target.as_ref().unwrap_or(&self.host)
         }
     }
 
+    /// Returns the directories where Rust crate dependencies are found for the
+    /// specified unit.
+    pub fn deps_dir(&self, unit: &Unit) -> &Path {
+        self.layout(unit.kind).deps()
+    }
+
+    /// Returns the directory for the specified unit where fingerprint
+    /// information is stored.
+    pub fn fingerprint_dir(&mut self, unit: &Unit) -> PathBuf {
+        let dir = self.pkg_dir(unit);
+        self.layout(unit.kind).fingerprint().join(dir)
+    }
+
+    /// Returns the appropriate directory layout for either a plugin or not.
+    pub fn build_script_dir(&mut self, unit: &Unit) -> PathBuf {
+        assert!(unit.target.is_custom_build());
+        assert!(!unit.profile.run_custom_build);
+        let dir = self.pkg_dir(unit);
+        self.layout(Kind::Host).build().join(dir)
+    }
+
+    /// Returns the appropriate directory layout for either a plugin or not.
+    pub fn build_script_out_dir(&mut self, unit: &Unit) -> PathBuf {
+        assert!(unit.target.is_custom_build());
+        assert!(unit.profile.run_custom_build);
+        let dir = self.pkg_dir(unit);
+        self.layout(unit.kind).build().join(dir).join("out")
+    }
+
     /// Returns the appropriate output directory for the specified package and
     /// target.
-    pub fn out_dir(&self, unit: &Unit) -> PathBuf {
+    pub fn out_dir(&mut self, unit: &Unit) -> PathBuf {
         if unit.profile.doc {
-            self.layout(unit).doc_root()
+            self.layout(unit.kind).root().parent().unwrap().join("doc")
+        } else if unit.target.is_custom_build() {
+            self.build_script_dir(unit)
+        } else if unit.target.is_example() {
+            self.layout(unit.kind).examples().to_path_buf()
         } else {
-            self.layout(unit).out_dir(unit)
+            self.deps_dir(unit).to_path_buf()
+        }
+    }
+
+    fn pkg_dir(&mut self, unit: &Unit) -> String {
+        let name = unit.pkg.package_id().name();
+        match self.target_metadata(unit) {
+            Some(meta) => format!("{}-{}", name, meta),
+            None => format!("{}-{}", name, util::short_hash(unit.pkg)),
         }
     }
 
@@ -311,7 +355,7 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
     /// We build to the path: "{filename}-{target_metadata}"
     /// We use a linking step to link/copy to a predictable filename
     /// like `target/debug/libfoo.{a,so,rlib}` and such.
-    pub fn target_metadata(&self, unit: &Unit) -> Option<Metadata> {
+    pub fn target_metadata(&mut self, unit: &Unit) -> Option<Metadata> {
         // No metadata for dylibs because of a couple issues
         // - OSX encodes the dylib name in the executable
         // - Windows rustc multiple files of which we can't easily link all of them
@@ -336,56 +380,41 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
             return None;
         }
 
-        let metadata = unit.target.metadata().cloned().map(|mut m| {
-            if let Some(features) = self.resolve.features(unit.pkg.package_id()) {
-                let mut feat_vec: Vec<&String> = features.iter().collect();
-                feat_vec.sort();
-                for feat in feat_vec {
-                    m.mix(feat);
-                }
-            }
-            m.mix(unit.profile);
-            m
-        });
-        let mut pkg_metadata = {
-            let mut m = unit.pkg.generate_metadata();
-            if let Some(features) = self.resolve.features(unit.pkg.package_id()) {
+        let mut hasher = SipHasher::new_with_keys(0, 0);
+
+        // Unique metadata per (name, source, version) triple. This'll allow us
+        // to pull crates from anywhere w/o worrying about conflicts
+        unit.pkg.package_id().hash(&mut hasher);
+
+        // Also mix in enabled features to our metadata. This'll ensure that
+        // when changing feature sets each lib is separately cached.
+        match self.resolve.features(unit.pkg.package_id()) {
+            Some(features) => {
                 let mut feat_vec: Vec<&String> = features.iter().collect();
                 feat_vec.sort();
-                for feat in feat_vec {
-                    m.mix(feat);
-                }
+                feat_vec.hash(&mut hasher);
             }
-            m.mix(unit.profile);
-            m
-        };
-
-        if unit.target.is_lib() && unit.profile.test {
-            // Libs and their tests are built in parallel, so we need to make
-            // sure that their metadata is different.
-            metadata.map(|mut m| {
-                m.mix(&"test");
-                m
-            })
-        } else if unit.target.is_bin() && unit.profile.test {
-            // Make sure that the name of this test executable doesn't
-            // conflict with a library that has the same name and is
-            // being tested
-            pkg_metadata.mix(&format!("bin-{}", unit.target.name()));
-            Some(pkg_metadata)
-        } else if unit.pkg.package_id().source_id().is_path() &&
-                  !unit.profile.test {
-            Some(pkg_metadata)
-        } else {
-            metadata
+            None => Vec::<&String>::new().hash(&mut hasher),
         }
+
+        // Throw in the profile we're compiling with. This helps caching
+        // panic=abort and panic=unwind artifacts, additionally with various
+        // settings like debuginfo and whatnot.
+        unit.profile.hash(&mut hasher);
+
+        // Finally throw in the target name/kind. This ensures that concurrent
+        // compiles of targets in the same crate don't collide.
+        unit.target.name().hash(&mut hasher);
+        unit.target.kind().hash(&mut hasher);
+
+        Some(Metadata(hasher.finish()))
     }
 
     /// Returns the file stem for a given target/profile combo (with metadata)
-    pub fn file_stem(&self, unit: &Unit) -> String {
+    pub fn file_stem(&mut self, unit: &Unit) -> String {
         match self.target_metadata(unit) {
-            Some(ref metadata) => format!("{}{}", unit.target.crate_name(),
-                                          metadata.extra_filename),
+            Some(ref metadata) => format!("{}-{}", unit.target.crate_name(),
+                                          metadata),
             None => self.bin_stem(unit),
         }
     }
@@ -407,7 +436,7 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
 
     /// Returns an Option because in some cases we don't want to link
     /// (eg a dependent lib)
-    pub fn link_stem(&self, unit: &Unit) -> Option<(PathBuf, String)> {
+    pub fn link_stem(&mut self, unit: &Unit) -> Option<(PathBuf, String)> {
         let src_dir = self.out_dir(unit);
         let bin_stem = self.bin_stem(unit);
         let file_stem = self.file_stem(unit);
@@ -441,7 +470,7 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
     /// filename: filename rustc compiles to. (Often has metadata suffix).
     /// link_dst: Optional file to link/copy the result to (without metadata suffix)
     /// linkable: Whether possible to link against file (eg it's a library)
-    pub fn target_filenames(&self, unit: &Unit)
+    pub fn target_filenames(&mut self, unit: &Unit)
                             -> CargoResult<Vec<(PathBuf, Option<PathBuf>, bool)>> {
         let out_dir = self.out_dir(unit);
         let stem = self.file_stem(unit);
@@ -870,3 +899,9 @@ fn env_args(config: &Config,
 
     Ok(Vec::new())
 }
+
+impl fmt::Display for Metadata {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{:016x}", self.0)
+    }
+}
diff --git a/src/cargo/ops/cargo_rustc/custom_build.rs b/src/cargo/ops/cargo_rustc/custom_build.rs
index 375a6ea434c..eb62f38c522 100644
--- a/src/cargo/ops/cargo_rustc/custom_build.rs
+++ b/src/cargo/ops/cargo_rustc/custom_build.rs
@@ -82,11 +82,12 @@ pub fn prepare<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
 
 fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
                         -> CargoResult<(Work, Work)> {
-    let host_unit = Unit { kind: Kind::Host, ..*unit };
-    let (script_output, build_output) = {
-        (cx.layout(&host_unit).build(unit.pkg),
-         cx.layout(unit).build_out(unit.pkg))
-    };
+    let dependencies = cx.dep_run_custom_build(unit)?;
+    let build_script_unit = dependencies.iter().find(|d| {
+        !d.profile.run_custom_build && d.target.is_custom_build()
+    }).expect("running a script not depending on an actual script");
+    let script_output = cx.build_script_dir(build_script_unit);
+    let build_output = cx.build_script_out_dir(unit);
 
     // Building the command to execute
     let to_exec = script_output.join(unit.target.name());
@@ -150,7 +151,7 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
     // This information will be used at build-time later on to figure out which
     // sorts of variables need to be discovered at that time.
     let lib_deps = {
-        cx.dep_run_custom_build(unit)?.iter().filter_map(|unit| {
+        dependencies.iter().filter_map(|unit| {
             if unit.profile.run_custom_build {
                 Some((unit.pkg.manifest().links().unwrap().to_string(),
                       unit.pkg.package_id().clone()))
@@ -177,8 +178,8 @@ fn build_work<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
     };
     cx.build_explicit_deps.insert(*unit, (output_file.clone(), rerun_if_changed));
 
-    fs::create_dir_all(&cx.layout(&host_unit).build(unit.pkg))?;
-    fs::create_dir_all(&cx.layout(unit).build(unit.pkg))?;
+    fs::create_dir_all(&script_output)?;
+    fs::create_dir_all(&build_output)?;
 
     // Prepare the unit of "dirty work" which will actually run the custom build
     // command.
@@ -336,9 +337,8 @@ impl BuildOutput {
 
             match key {
                 "rustc-flags" => {
-                    let (libs, links) = 
-                        BuildOutput::parse_rustc_flags(value, &whence)
-                    ?;
+                    let (libs, links) =
+                        BuildOutput::parse_rustc_flags(value, &whence)?;
                     library_links.extend(links.into_iter());
                     library_paths.extend(libs.into_iter());
                 }
diff --git a/src/cargo/ops/cargo_rustc/fingerprint.rs b/src/cargo/ops/cargo_rustc/fingerprint.rs
index 6cc8f88c105..3d1f274498f 100644
--- a/src/cargo/ops/cargo_rustc/fingerprint.rs
+++ b/src/cargo/ops/cargo_rustc/fingerprint.rs
@@ -48,7 +48,7 @@ pub fn prepare_target<'a, 'cfg>(cx: &mut Context<'a, 'cfg>,
                                 unit: &Unit<'a>) -> CargoResult<Preparation> {
     let _p = profile::start(format!("fingerprint: {} / {}",
                                     unit.pkg.package_id(), unit.target.name()));
-    let new = dir(cx, unit);
+    let new = cx.fingerprint_dir(unit);
     let loc = new.join(&filename(cx, unit));
 
     debug!("fingerprint at: {}", loc.display());
@@ -426,7 +426,7 @@ pub fn prepare_build_cmd<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>)
                                    -> CargoResult<Preparation> {
     let _p = profile::start(format!("fingerprint build cmd: {}",
                                     unit.pkg.package_id()));
-    let new = dir(cx, unit);
+    let new = cx.fingerprint_dir(unit);
     let loc = new.join("build");
 
     debug!("fingerprint at: {}", loc.display());
@@ -507,13 +507,13 @@ fn write_fingerprint(loc: &Path, fingerprint: &Fingerprint) -> CargoResult<()> {
     debug!("write fingerprint: {}", loc.display());
     paths::write(&loc, util::to_hex(hash).as_bytes())?;
     paths::write(&loc.with_extension("json"),
-                      json::encode(&fingerprint).unwrap().as_bytes())?;
+                 json::encode(&fingerprint).unwrap().as_bytes())?;
     Ok(())
 }
 
 /// Prepare work for when a package starts to build
 pub fn prepare_init(cx: &mut Context, unit: &Unit) -> CargoResult<()> {
-    let new1 = dir(cx, unit);
+    let new1 = cx.fingerprint_dir(unit);
     let new2 = new1.clone();
 
     if fs::metadata(&new1).is_err() {
@@ -525,14 +525,9 @@ pub fn prepare_init(cx: &mut Context, unit: &Unit) -> CargoResult<()> {
     Ok(())
 }
 
-/// Return the (old, new) location for fingerprints for a package
-pub fn dir(cx: &Context, unit: &Unit) -> PathBuf {
-    cx.layout(unit).proxy().fingerprint(unit.pkg)
-}
-
 /// Returns the (old, new) location for the dep info file of a target.
-pub fn dep_info_loc(cx: &Context, unit: &Unit) -> PathBuf {
-    dir(cx, unit).join(&format!("dep-{}", filename(cx, unit)))
+pub fn dep_info_loc(cx: &mut Context, unit: &Unit) -> PathBuf {
+    cx.fingerprint_dir(unit).join(&format!("dep-{}", filename(cx, unit)))
 }
 
 fn compare_old_fingerprint(loc: &Path, new_fingerprint: &Fingerprint)
@@ -653,7 +648,7 @@ fn mtime_if_fresh<I>(output: &Path, paths: I) -> Option<FileTime>
     }
 }
 
-fn filename(cx: &Context, unit: &Unit) -> String {
+fn filename(cx: &mut Context, unit: &Unit) -> String {
     // file_stem includes metadata hash. Thus we have a different
     // fingerprint for every metadata hash version. This works because
     // even if the package is fresh, we'll still link the fresh target
diff --git a/src/cargo/ops/cargo_rustc/layout.rs b/src/cargo/ops/cargo_rustc/layout.rs
index cf0cec2df02..2b5cd7514d8 100644
--- a/src/cargo/ops/cargo_rustc/layout.rs
+++ b/src/cargo/ops/cargo_rustc/layout.rs
@@ -49,10 +49,8 @@ use std::fs;
 use std::io;
 use std::path::{PathBuf, Path};
 
-use core::{Package, Workspace};
+use core::Workspace;
 use util::{Config, FileLock, CargoResult, Filesystem, human};
-use util::hex::short_hash;
-use super::Unit;
 
 pub struct Layout {
     root: PathBuf,
@@ -64,11 +62,6 @@ pub struct Layout {
     _lock: FileLock,
 }
 
-pub struct LayoutProxy<'a> {
-    root: &'a Layout,
-    primary: bool,
-}
-
 impl Layout {
     pub fn new(ws: &Workspace,
                triple: Option<&str>,
@@ -127,58 +120,6 @@ impl Layout {
     pub fn deps(&self) -> &Path { &self.deps }
     pub fn examples(&self) -> &Path { &self.examples }
     pub fn root(&self) -> &Path { &self.root }
-
-    pub fn fingerprint(&self, package: &Package) -> PathBuf {
-        self.fingerprint.join(&self.pkg_dir(package))
-    }
-
-    pub fn build(&self, package: &Package) -> PathBuf {
-        self.build.join(&self.pkg_dir(package))
-    }
-
-    pub fn build_out(&self, package: &Package) -> PathBuf {
-        self.build(package).join("out")
-    }
-
-    fn pkg_dir(&self, pkg: &Package) -> String {
-        format!("{}-{}", pkg.name(), short_hash(pkg))
-    }
-}
-
-impl<'a> LayoutProxy<'a> {
-    pub fn new(root: &'a Layout, primary: bool) -> LayoutProxy<'a> {
-        LayoutProxy {
-            root: root,
-            primary: primary,
-        }
-    }
-
-    pub fn root(&self) -> &'a Path {
-        if self.primary {self.root.dest()} else {self.root.deps()}
-    }
-    pub fn deps(&self) -> &'a Path { self.root.deps() }
-
-    pub fn examples(&self) -> &'a Path { self.root.examples() }
-
-    pub fn build(&self, pkg: &Package) -> PathBuf { self.root.build(pkg) }
-
-    pub fn build_out(&self, pkg: &Package) -> PathBuf { self.root.build_out(pkg) }
-
-    pub fn proxy(&self) -> &'a Layout { self.root }
-
-    pub fn out_dir(&self, unit: &Unit) -> PathBuf {
-        if unit.target.is_custom_build() {
-            self.build(unit.pkg)
-        } else if unit.target.is_example() {
-            self.examples().to_path_buf()
-        } else {
-            self.deps().to_path_buf()
-        }
-    }
-
-    pub fn doc_root(&self) -> PathBuf {
-        // the "root" directory ends in 'debug' or 'release', and we want it to
-        // end in 'doc' instead
-        self.root.root().parent().unwrap().join("doc")
-    }
+    pub fn fingerprint(&self) -> &Path { &self.fingerprint }
+    pub fn build(&self) -> &Path { &self.build }
 }
diff --git a/src/cargo/ops/cargo_rustc/mod.rs b/src/cargo/ops/cargo_rustc/mod.rs
index 8155805c8ec..561949b7123 100644
--- a/src/cargo/ops/cargo_rustc/mod.rs
+++ b/src/cargo/ops/cargo_rustc/mod.rs
@@ -18,7 +18,6 @@ use self::job_queue::JobQueue;
 
 pub use self::compilation::Compilation;
 pub use self::context::{Context, Unit};
-pub use self::layout::{Layout, LayoutProxy};
 pub use self::custom_build::{BuildOutput, BuildMap, BuildScripts};
 
 mod compilation;
@@ -104,12 +103,6 @@ pub fn compile_targets<'a, 'cfg: 'a>(ws: &Workspace<'cfg>,
     queue.execute(&mut cx)?;
 
     for unit in units.iter() {
-        let out_dir = cx.layout(unit).build_out(unit.pkg)
-                        .display().to_string();
-        cx.compilation.extra_env.entry(unit.pkg.package_id().clone())
-          .or_insert(Vec::new())
-          .push(("OUT_DIR".to_string(), out_dir));
-
         for (dst, link_dst, _linkable) in cx.target_filenames(unit)? {
             let bindst = match link_dst {
                 Some(link_dst) => link_dst,
@@ -131,6 +124,13 @@ pub fn compile_targets<'a, 'cfg: 'a>(ws: &Workspace<'cfg>,
 
             // Include immediate lib deps as well
             for unit in cx.dep_targets(unit)?.iter() {
+                if unit.profile.run_custom_build {
+                    let out_dir = cx.build_script_out_dir(unit).display().to_string();
+                    cx.compilation.extra_env.entry(unit.pkg.package_id().clone())
+                      .or_insert(Vec::new())
+                      .push(("OUT_DIR".to_string(), out_dir));
+                }
+
                 let pkgid = unit.pkg.package_id();
                 if !unit.target.is_lib() { continue }
                 if unit.profile.doc { continue }
@@ -183,8 +183,7 @@ fn compile<'a, 'cfg: 'a>(cx: &mut Context<'a, 'cfg>,
     let (dirty, fresh, freshness) = if unit.profile.run_custom_build {
         custom_build::prepare(cx, unit)?
     } else {
-        let (freshness, dirty, fresh) = fingerprint::prepare_target(cx,
-                                                                         unit)?;
+        let (freshness, dirty, fresh) = fingerprint::prepare_target(cx, unit)?;
         let work = if unit.profile.doc {
             rustdoc(cx, unit)?
         } else {
@@ -421,7 +420,7 @@ fn add_plugin_deps(rustc: &mut ProcessBuilder,
     Ok(())
 }
 
-fn prepare_rustc(cx: &Context,
+fn prepare_rustc(cx: &mut Context,
                  crate_types: Vec<&str>,
                  unit: &Unit) -> CargoResult<ProcessBuilder> {
     let mut base = cx.compilation.rustc_process(unit.pkg)?;
@@ -465,10 +464,6 @@ fn rustdoc(cx: &mut Context, unit: &Unit) -> CargoResult<Work> {
 
     build_deps_args(&mut rustdoc, cx, unit)?;
 
-    if unit.pkg.has_custom_build() {
-        rustdoc.env("OUT_DIR", &cx.layout(unit).build_out(unit.pkg));
-    }
-
     rustdoc.args(&cx.rustdocflags_args(unit)?);
 
     let name = unit.pkg.name().to_string();
@@ -509,7 +504,7 @@ fn root_path(cx: &Context, unit: &Unit) -> PathBuf {
     }
 }
 
-fn build_base_args(cx: &Context,
+fn build_base_args(cx: &mut Context,
                    cmd: &mut ProcessBuilder,
                    unit: &Unit,
                    crate_types: &[&str]) {
@@ -610,8 +605,8 @@ fn build_base_args(cx: &Context,
 
     match cx.target_metadata(unit) {
         Some(m) => {
-            cmd.arg("-C").arg(&format!("metadata={}", m.metadata));
-            cmd.arg("-C").arg(&format!("extra-filename={}", m.extra_filename));
+            cmd.arg("-C").arg(&format!("metadata={}", m));
+            cmd.arg("-C").arg(&format!("extra-filename=-{}", m));
         }
         None => {
             cmd.arg("-C").arg(&format!("metadata={}", short_hash(unit.pkg)));
@@ -624,7 +619,7 @@ fn build_base_args(cx: &Context,
 }
 
 
-fn build_plugin_args(cmd: &mut ProcessBuilder, cx: &Context, unit: &Unit) {
+fn build_plugin_args(cmd: &mut ProcessBuilder, cx: &mut Context, unit: &Unit) {
     fn opt(cmd: &mut ProcessBuilder, key: &str, prefix: &str,
            val: Option<&OsStr>)  {
         if let Some(val) = val {
@@ -645,20 +640,18 @@ fn build_plugin_args(cmd: &mut ProcessBuilder, cx: &Context, unit: &Unit) {
     opt(cmd, "-C", "linker=", cx.linker(unit.kind).map(|s| s.as_ref()));
 }
 
-fn build_deps_args(cmd: &mut ProcessBuilder, cx: &Context, unit: &Unit)
+fn build_deps_args(cmd: &mut ProcessBuilder, cx: &mut Context, unit: &Unit)
                    -> CargoResult<()> {
-    let layout = cx.layout(unit);
     cmd.arg("-L").arg(&{
         let mut deps = OsString::from("dependency=");
-        deps.push(layout.deps());
+        deps.push(cx.deps_dir(unit));
         deps
     });
 
-    if unit.pkg.has_custom_build() {
-        cmd.env("OUT_DIR", &layout.build_out(unit.pkg));
-    }
-
     for unit in cx.dep_targets(unit)?.iter() {
+        if unit.profile.run_custom_build {
+            cmd.env("OUT_DIR", &cx.build_script_out_dir(unit));
+        }
         if unit.target.linkable() && !unit.profile.doc {
             link_to(cmd, cx, unit)?;
         }
@@ -666,7 +659,7 @@ fn build_deps_args(cmd: &mut ProcessBuilder, cx: &Context, unit: &Unit)
 
     return Ok(());
 
-    fn link_to(cmd: &mut ProcessBuilder, cx: &Context, unit: &Unit)
+    fn link_to(cmd: &mut ProcessBuilder, cx: &mut Context, unit: &Unit)
                -> CargoResult<()> {
         for (dst, _link_dst, linkable) in cx.target_filenames(unit)? {
             if !linkable {
diff --git a/src/cargo/ops/mod.rs b/src/cargo/ops/mod.rs
index ff4583c569a..902c72e3007 100644
--- a/src/cargo/ops/mod.rs
+++ b/src/cargo/ops/mod.rs
@@ -2,8 +2,8 @@ pub use self::cargo_clean::{clean, CleanOptions};
 pub use self::cargo_compile::{compile, compile_ws, resolve_dependencies, CompileOptions};
 pub use self::cargo_compile::{CompileFilter, CompileMode, MessageFormat};
 pub use self::cargo_read_manifest::{read_manifest,read_package,read_packages};
-pub use self::cargo_rustc::{compile_targets, Compilation, Layout, Kind, Unit};
-pub use self::cargo_rustc::{Context, LayoutProxy};
+pub use self::cargo_rustc::{compile_targets, Compilation, Kind, Unit};
+pub use self::cargo_rustc::Context;
 pub use self::cargo_rustc::{BuildOutput, BuildConfig, TargetConfig};
 pub use self::cargo_run::run;
 pub use self::cargo_install::{install, install_list, uninstall};
diff --git a/src/cargo/util/toml.rs b/src/cargo/util/toml.rs
index c5d70b7098b..5e5dc93a669 100644
--- a/src/cargo/util/toml.rs
+++ b/src/cargo/util/toml.rs
@@ -14,7 +14,6 @@ use core::{Summary, Manifest, Target, Dependency, DependencyInner, PackageId};
 use core::{EitherManifest, VirtualManifest};
 use core::dependency::{Kind, Platform};
 use core::manifest::{LibKind, Profile, ManifestMetadata};
-use core::package_id::Metadata;
 use sources::CRATES_IO;
 use util::{self, CargoResult, human, ToUrl, ToSemver, ChainError, Config};
 
@@ -437,7 +436,6 @@ impl TomlManifest {
         }
 
         let pkgid = project.to_package_id(source_id)?;
-        let metadata = pkgid.generate_metadata();
 
         // If we have no lib at all, use the inferred lib if available
         // If we have a lib with a path, we're done
@@ -550,8 +548,7 @@ impl TomlManifest {
                                 new_build,
                                 &examples,
                                 &tests,
-                                &benches,
-                                &metadata);
+                                &benches);
 
         if targets.is_empty() {
             debug!("manifest has no build targets");
@@ -1064,8 +1061,7 @@ fn normalize(lib: &Option<TomlLibTarget>,
              custom_build: Option<PathBuf>,
              examples: &[TomlExampleTarget],
              tests: &[TomlTestTarget],
-             benches: &[TomlBenchTarget],
-             metadata: &Metadata) -> Vec<Target> {
+             benches: &[TomlBenchTarget]) -> Vec<Target> {
     fn configure(toml: &TomlTarget, target: &mut Target) {
         let t2 = target.clone();
         target.set_tested(toml.test.unwrap_or(t2.tested()))
@@ -1080,9 +1076,7 @@ fn normalize(lib: &Option<TomlLibTarget>,
               });
     }
 
-    fn lib_target(dst: &mut Vec<Target>,
-                  l: &TomlLibTarget,
-                  metadata: &Metadata) {
+    fn lib_target(dst: &mut Vec<Target>, l: &TomlLibTarget) {
         let path = l.path.clone().unwrap_or(
             PathValue::Path(Path::new("src").join(&format!("{}.rs", l.name())))
         );
@@ -1095,14 +1089,8 @@ fn normalize(lib: &Option<TomlLibTarget>,
             }
         };
 
-        // Binaries, examples, etc, may link to this library. Their crate names
-        // have a high likelihood to being the same as ours, however, so we need
-        // some extra metadata in our name to ensure symbols won't collide.
-        let mut metadata = metadata.clone();
-        metadata.mix(&"lib");
         let mut target = Target::lib_target(&l.name(), crate_types,
-                                            &path.to_path(),
-                                            metadata);
+                                            &path.to_path());
         configure(l, &mut target);
         dst.push(target);
     }
@@ -1113,8 +1101,7 @@ fn normalize(lib: &Option<TomlLibTarget>,
             let path = bin.path.clone().unwrap_or_else(|| {
                 PathValue::Path(default(bin))
             });
-            let mut target = Target::bin_target(&bin.name(), &path.to_path(),
-                                                None);
+            let mut target = Target::bin_target(&bin.name(), &path.to_path());
             configure(bin, &mut target);
             dst.push(target);
         }
@@ -1124,7 +1111,7 @@ fn normalize(lib: &Option<TomlLibTarget>,
         let name = format!("build-script-{}",
                            cmd.file_stem().and_then(|s| s.to_str()).unwrap_or(""));
 
-        dst.push(Target::custom_build_target(&name, cmd, None));
+        dst.push(Target::custom_build_target(&name, cmd));
     }
 
     fn example_targets(dst: &mut Vec<Target>,
@@ -1141,40 +1128,29 @@ fn normalize(lib: &Option<TomlLibTarget>,
         }
     }
 
-    fn test_targets(dst: &mut Vec<Target>, tests: &[TomlTestTarget],
-                    metadata: &Metadata,
+    fn test_targets(dst: &mut Vec<Target>,
+                    tests: &[TomlTestTarget],
                     default: &mut FnMut(&TomlTestTarget) -> PathBuf) {
         for test in tests.iter() {
             let path = test.path.clone().unwrap_or_else(|| {
                 PathValue::Path(default(test))
             });
 
-            // make sure this metadata is different from any same-named libs.
-            let mut metadata = metadata.clone();
-            metadata.mix(&format!("test-{}", test.name()));
-
-            let mut target = Target::test_target(&test.name(), &path.to_path(),
-                                                 metadata);
+            let mut target = Target::test_target(&test.name(), &path.to_path());
             configure(test, &mut target);
             dst.push(target);
         }
     }
 
-    fn bench_targets(dst: &mut Vec<Target>, benches: &[TomlBenchTarget],
-                     metadata: &Metadata,
+    fn bench_targets(dst: &mut Vec<Target>,
+                     benches: &[TomlBenchTarget],
                      default: &mut FnMut(&TomlBenchTarget) -> PathBuf) {
         for bench in benches.iter() {
             let path = bench.path.clone().unwrap_or_else(|| {
                 PathValue::Path(default(bench))
             });
 
-            // make sure this metadata is different from any same-named libs.
-            let mut metadata = metadata.clone();
-            metadata.mix(&format!("bench-{}", bench.name()));
-
-            let mut target = Target::bench_target(&bench.name(),
-                                                  &path.to_path(),
-                                                  metadata);
+            let mut target = Target::bench_target(&bench.name(), &path.to_path());
             configure(bench, &mut target);
             dst.push(target);
         }
@@ -1183,7 +1159,7 @@ fn normalize(lib: &Option<TomlLibTarget>,
     let mut ret = Vec::new();
 
     if let Some(ref lib) = *lib {
-        lib_target(&mut ret, lib, metadata);
+        lib_target(&mut ret, lib);
         bin_targets(&mut ret, bins,
                     &mut |bin| Path::new("src").join("bin")
                                    .join(&format!("{}.rs", bin.name())));
@@ -1201,7 +1177,7 @@ fn normalize(lib: &Option<TomlLibTarget>,
                     &mut |ex| Path::new("examples")
                                    .join(&format!("{}.rs", ex.name())));
 
-    test_targets(&mut ret, tests, metadata, &mut |test| {
+    test_targets(&mut ret, tests, &mut |test| {
         if test.name() == "test" {
             Path::new("src").join("test.rs")
         } else {
@@ -1209,7 +1185,7 @@ fn normalize(lib: &Option<TomlLibTarget>,
         }
     });
 
-    bench_targets(&mut ret, benches, metadata, &mut |bench| {
+    bench_targets(&mut ret, benches, &mut |bench| {
         if bench.name() == "bench" {
             Path::new("src").join("bench.rs")
         } else {
diff --git a/tests/build-script.rs b/tests/build-script.rs
index 2a49e9972f7..46d8e144063 100644
--- a/tests/build-script.rs
+++ b/tests/build-script.rs
@@ -2288,3 +2288,49 @@ fn cfg_env_vars_available() {
     assert_that(build.cargo_process("bench"),
                 execs().with_status(0));
 }
+
+#[test]
+fn switch_features_rerun() {
+    let build = project("builder")
+        .file("Cargo.toml", r#"
+            [package]
+            name = "builder"
+            version = "0.0.1"
+            authors = []
+            build = "build.rs"
+
+            [features]
+            foo = []
+        "#)
+        .file("src/main.rs", r#"
+            fn main() {
+                println!(include_str!(concat!(env!("OUT_DIR"), "/output")));
+            }
+        "#)
+        .file("build.rs", r#"
+            use std::env;
+            use std::fs::File;
+            use std::io::Write;
+            use std::path::Path;
+
+            fn main() {
+                let out_dir = env::var_os("OUT_DIR").unwrap();
+                let out_dir = Path::new(&out_dir).join("output");
+                let mut f = File::create(&out_dir).unwrap();
+
+                if env::var_os("CARGO_FEATURE_FOO").is_some() {
+                    f.write_all(b"foo").unwrap();
+                } else {
+                    f.write_all(b"bar").unwrap();
+                }
+            }
+        "#);
+    build.build();
+
+    assert_that(build.cargo("run").arg("-v").arg("--features=foo"),
+                execs().with_status(0).with_stdout("foo\n"));
+    assert_that(build.cargo("run").arg("-v"),
+                execs().with_status(0).with_stdout("bar\n"));
+    assert_that(build.cargo("run").arg("-v").arg("--features=foo"),
+                execs().with_status(0).with_stdout("foo\n"));
+}