From 428646d1a954490baab1fe07f90b8b45dcb6a9d3 Mon Sep 17 00:00:00 2001
From: 0xPoe <techregister@pm.me>
Date: Sun, 21 Jun 2026 23:20:33 +0200
Subject: [PATCH 1/7] feat(toml): allow overriding inherited default-features
 in 2024

Impl RFC 3945, on Edition 2024+ allow workspace members
to override the workspace dependency's `default-features` setting.

Earlier editions are unchanged: setting `default-features` on an
inherited dependency is still ignored with a warning.

Signed-off-by: 0xPoe <techregister@pm.me>
---
 src/workspace/parser/mod.rs                   | 56 +++++++++----------
 .../testsuite/inheritable_workspace_fields.rs | 34 ++++++-----
 2 files changed, 44 insertions(+), 46 deletions(-)

diff --git a/src/workspace/parser/mod.rs b/src/workspace/parser/mod.rs
index 4098ef06dd0..d96f4ae0965 100644
--- a/src/workspace/parser/mod.rs
+++ b/src/workspace/parser/mod.rs
@@ -1216,25 +1216,31 @@ fn inner_dependency_inherit_with<'a>(
     } = &pkg_dep;
     let default_features = default_features.or(*default_features2);
 
-    match (default_features, merged_dep.default_features()) {
-        // member: default-features = true and
-        // workspace: default-features = false should turn on
-        // default-features
-        (Some(true), Some(false)) => {
-            merged_dep.default_features = Some(true);
-        }
-        // member: default-features = false and
-        // workspace: default-features = true should ignore member
-        // default-features
-        (Some(false), Some(true)) => {
-            deprecated_ws_default_features(name, Some(true), edition, warnings)?;
-        }
-        // member: default-features = false and
-        // workspace: dep = "1.0" should ignore member default-features
-        (Some(false), None) => {
-            deprecated_ws_default_features(name, None, edition, warnings)?;
+    // RFC 3945: Allow workspace members to override the workspace dependency's
+    // `default-features` setting.
+    if edition >= Edition::Edition2024 {
+        merged_dep.default_features = default_features.or(merged_dep.default_features);
+    } else {
+        match (default_features, merged_dep.default_features()) {
+            // member: default-features = true and
+            // workspace: default-features = false should turn on
+            // default-features
+            (Some(true), Some(false)) => {
+                merged_dep.default_features = Some(true);
+            }
+            // member: default-features = false and
+            // workspace: default-features = true should ignore member
+            // default-features
+            (Some(false), Some(true)) => {
+                deprecated_ws_default_features(name, Some(true), warnings);
+            }
+            // member: default-features = false and
+            // workspace: dep = "1.0" should ignore member default-features
+            (Some(false), None) => {
+                deprecated_ws_default_features(name, None, warnings);
+            }
+            _ => {}
         }
-        _ => {}
     }
     merged_dep.features = match (merged_dep.features.clone(), features.clone()) {
         (Some(dep_feat), Some(inherit_feat)) => Some(
@@ -1255,24 +1261,18 @@ fn inner_dependency_inherit_with<'a>(
 fn deprecated_ws_default_features(
     label: &str,
     ws_def_feat: Option<bool>,
-    edition: Edition,
     warnings: &mut Vec<String>,
-) -> CargoResult<()> {
+) {
     let ws_def_feat = match ws_def_feat {
         Some(true) => "true",
         Some(false) => "false",
         None => "not specified",
     };
-    if Edition::Edition2024 <= edition {
-        anyhow::bail!("`default-features = false` cannot override workspace's `default-features`");
-    } else {
-        warnings.push(format!(
-            "`default-features` is ignored for {label}, since `default-features` was \
+    warnings.push(format!(
+        "`default-features` is ignored for {label}, since `default-features` was \
                 {ws_def_feat} for `workspace.dependencies.{label}`, \
                 this could become a hard error in the future"
-        ));
-    }
-    Ok(())
+    ));
 }
 
 #[tracing::instrument(skip_all)]
diff --git a/tests/testsuite/inheritable_workspace_fields.rs b/tests/testsuite/inheritable_workspace_fields.rs
index 4f0ce8b04b3..0584ce280c7 100644
--- a/tests/testsuite/inheritable_workspace_fields.rs
+++ b/tests/testsuite/inheritable_workspace_fields.rs
@@ -1555,7 +1555,7 @@ fn warn_inherit_def_feat_true_member_def_feat_false() {
 }
 
 #[cargo_test]
-fn warn_inherit_def_feat_true_member_def_feat_false_2024_edition() {
+fn inherit_def_feat_true_member_def_feat_false_2024_edition() {
     Package::new("dep", "0.1.0")
         .feature("default", &["fancy_dep"])
         .add_dep(Dependency::new("fancy_dep", "0.2").optional(true))
@@ -1586,15 +1586,14 @@ fn warn_inherit_def_feat_true_member_def_feat_false_2024_edition() {
         .build();
 
     p.cargo("check")
-        .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] failed to parse manifest at `[ROOT]/foo/Cargo.toml`
-
-Caused by:
-  error inheriting `dep` from workspace root manifest's `workspace.dependencies.dep`
-
-Caused by:
-  `default-features = false` cannot override workspace's `default-features`
+[UPDATING] `dummy-registry` index
+[LOCKING] 1 package to latest Rust [..] compatible version
+[DOWNLOADING] crates ...
+[DOWNLOADED] dep v0.1.0 (registry `dummy-registry`)
+[CHECKING] dep v0.1.0
+[CHECKING] bar v0.2.0 ([ROOT]/foo)
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
 
 "#]])
         .run();
@@ -1648,7 +1647,7 @@ fn warn_inherit_simple_member_def_feat_false() {
 }
 
 #[cargo_test]
-fn warn_inherit_simple_member_def_feat_false_2024_edition() {
+fn inherit_simple_member_def_feat_false_2024_edition() {
     Package::new("dep", "0.1.0")
         .feature("default", &["fancy_dep"])
         .add_dep(Dependency::new("fancy_dep", "0.2").optional(true))
@@ -1679,15 +1678,14 @@ fn warn_inherit_simple_member_def_feat_false_2024_edition() {
         .build();
 
     p.cargo("check")
-        .with_status(101)
         .with_stderr_data(str![[r#"
-[ERROR] failed to parse manifest at `[ROOT]/foo/Cargo.toml`
-
-Caused by:
-  error inheriting `dep` from workspace root manifest's `workspace.dependencies.dep`
-
-Caused by:
-  `default-features = false` cannot override workspace's `default-features`
+[UPDATING] `dummy-registry` index
+[LOCKING] 1 package to latest Rust [..] compatible version
+[DOWNLOADING] crates ...
+[DOWNLOADED] dep v0.1.0 (registry `dummy-registry`)
+[CHECKING] dep v0.1.0
+[CHECKING] bar v0.2.0 ([ROOT]/foo)
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
 
 "#]])
         .run();

From ef7de4d28deb68200f97a0a0d07f9afb85f350ad Mon Sep 17 00:00:00 2001
From: 0xPoe <techregister@pm.me>
Date: Sun, 21 Jun 2026 23:59:50 +0200
Subject: [PATCH 2/7] test(add): add inherit no default features case

Signed-off-by: 0xPoe <techregister@pm.me>
---
 .../in/Cargo.toml                             |  6 +++++
 .../in/bar/Cargo.toml                         |  6 +++++
 .../in/bar/src/lib.rs                         |  0
 .../in/foo/Cargo.toml                         |  4 +++
 .../in/foo/src/lib.rs                         |  0
 .../mod.rs                                    | 25 +++++++++++++++++
 .../out/Cargo.toml                            |  6 +++++
 .../out/bar/Cargo.toml                        |  6 +++++
 .../out/bar/src/lib.rs                        |  0
 .../out/foo/Cargo.toml                        |  4 +++
 .../out/foo/src/lib.rs                        |  0
 .../stderr.term.svg                           | 27 +++++++++++++++++++
 tests/testsuite/cargo_add/mod.rs              |  1 +
 13 files changed, 85 insertions(+)
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/bar/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/bar/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/foo/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/foo/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/foo/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/foo/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg

diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/Cargo.toml b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/Cargo.toml
new file mode 100644
index 00000000000..84ae7d26601
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/Cargo.toml
@@ -0,0 +1,6 @@
+[workspace]
+members = ["foo", "bar"]
+resolver = "3"
+
+[workspace.dependencies]
+foo = { version = "0.0.0", path = "./foo", default-features = true }
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/bar/Cargo.toml b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/bar/Cargo.toml
new file mode 100644
index 00000000000..3bd66f7b4a1
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/bar/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "bar"
+version = "0.0.0"
+edition = "2024"
+
+[dependencies]
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/bar/src/lib.rs b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/bar/src/lib.rs
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/foo/Cargo.toml b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/foo/Cargo.toml
new file mode 100644
index 00000000000..c0a92ea13b9
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/foo/Cargo.toml
@@ -0,0 +1,4 @@
+[package]
+name = "foo"
+version = "0.0.0"
+edition = "2024"
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/foo/src/lib.rs b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/in/foo/src/lib.rs
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs
new file mode 100644
index 00000000000..7c2925dd4ec
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs
@@ -0,0 +1,25 @@
+use crate::prelude::*;
+use cargo_test_support::Project;
+use cargo_test_support::compare::assert_ui;
+use cargo_test_support::current_dir;
+use cargo_test_support::file;
+use cargo_test_support::str;
+
+#[cargo_test]
+fn case() {
+    cargo_test_support::registry::init();
+    let project = Project::from_template(current_dir!().join("in"));
+    let project_root = project.root();
+    let cwd = &project_root;
+
+    snapbox::cmd::Command::cargo_ui()
+        .arg("add")
+        .args(["foo", "--no-default-features", "-p", "bar"])
+        .current_dir(cwd)
+        .assert()
+        .failure()
+        .stdout_eq(str![""])
+        .stderr_eq(file!["stderr.term.svg"]);
+
+    assert_ui().subset_matches(current_dir!().join("out"), &project_root);
+}
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/Cargo.toml b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/Cargo.toml
new file mode 100644
index 00000000000..84ae7d26601
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/Cargo.toml
@@ -0,0 +1,6 @@
+[workspace]
+members = ["foo", "bar"]
+resolver = "3"
+
+[workspace.dependencies]
+foo = { version = "0.0.0", path = "./foo", default-features = true }
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml
new file mode 100644
index 00000000000..3bd66f7b4a1
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "bar"
+version = "0.0.0"
+edition = "2024"
+
+[dependencies]
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/src/lib.rs b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/src/lib.rs
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/foo/Cargo.toml b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/foo/Cargo.toml
new file mode 100644
index 00000000000..c0a92ea13b9
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/foo/Cargo.toml
@@ -0,0 +1,4 @@
+[package]
+name = "foo"
+version = "0.0.0"
+edition = "2024"
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/foo/src/lib.rs b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/foo/src/lib.rs
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg
new file mode 100644
index 00000000000..0f967ee3fa5
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg
@@ -0,0 +1,27 @@
+<svg width="1642px" height="56px" xmlns="http://www.w3.org/2000/svg">
+  <style>
+    .fg { fill: #AAAAAA }
+    .bg { fill: #000000 }
+    .fg-bright-red { fill: #FF5555 }
+    .container {
+      padding: 0 10px;
+      line-height: 18px;
+    }
+    .bold { font-weight: bold; }
+    tspan {
+      font: 14px SFMono-Regular, Consolas, Liberation Mono, Menlo, monospace;
+      white-space: pre;
+      line-height: 18px;
+    }
+  </style>
+
+  <rect width="100%" height="100%" y="0" rx="4.5" class="bg" />
+
+  <text xml:space="preserve" class="container fg">
+    <tspan x="10px" y="28px"><tspan class="fg-bright-red bold">error</tspan><tspan>: cannot override workspace dependency with `--default-features`, either change `workspace.dependencies.foo.default-features` or define the dependency exclusively in the package's manifest</tspan>
+</tspan>
+    <tspan x="10px" y="46px">
+</tspan>
+  </text>
+
+</svg>
diff --git a/tests/testsuite/cargo_add/mod.rs b/tests/testsuite/cargo_add/mod.rs
index bd9024466ac..1ae817db983 100644
--- a/tests/testsuite/cargo_add/mod.rs
+++ b/tests/testsuite/cargo_add/mod.rs
@@ -48,6 +48,7 @@ mod git_rev;
 mod git_tag;
 mod help;
 mod infer_prerelease;
+mod inherit_no_default_features_2024_edition;
 mod invalid_arg;
 mod invalid_git_name;
 mod invalid_inherited_dependency;

From d4b668c173c3df535df96f44b01c92299e5d7d23 Mon Sep 17 00:00:00 2001
From: 0xPoe <techregister@pm.me>
Date: Mon, 22 Jun 2026 00:02:01 +0200
Subject: [PATCH 3/7] feat(add): override inherited default-features in 2024

`cargo add --no-default-features` (or `--default-features`) against a
dependency inherited from `[workspace.dependencies]` is now allowed when
the package is on Edition 2024+, matching the manifest behavior. Earlier
editions still error, pointing the user to the workspace manifest.

Signed-off-by: 0xPoe <techregister@pm.me>
---
 src/ops/cargo_add/mod.rs                            | 13 ++++++++-----
 .../inherit_no_default_features_2024_edition/mod.rs |  2 +-
 .../out/bar/Cargo.toml                              |  1 +
 .../stderr.term.svg                                 |  6 +++---
 4 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/ops/cargo_add/mod.rs b/src/ops/cargo_add/mod.rs
index b200c7bfa1b..fbfe1e54ba2 100644
--- a/src/ops/cargo_add/mod.rs
+++ b/src/ops/cargo_add/mod.rs
@@ -28,6 +28,7 @@ use crate::util::OptVersionReq;
 use crate::util::cache_lock::CacheLockMode;
 use crate::util::edit_distance;
 use crate::util::style;
+use crate::workspace::Edition;
 use crate::workspace::Feature;
 use crate::workspace::FeatureValue;
 use crate::workspace::Features;
@@ -503,7 +504,7 @@ fn resolve_dependency(
     }
 
     if let Some(Source::Workspace(_)) = dependency.source() {
-        check_invalid_ws_keys(dependency.toml_key(), arg)?;
+        check_invalid_ws_keys(dependency.toml_key(), arg, spec.manifest().edition())?;
     }
 
     let version_required = dependency.source().and_then(|s| s.as_registry()).is_some();
@@ -703,14 +704,16 @@ fn fuzzy_lookup(
 
 /// When { workspace = true } you cannot define other keys that configure
 /// the source of the dependency such as `version`, `registry`, `registry-index`,
-/// `path`, `git`, `branch`, `tag`, `rev`, or `package`. You can also not define
-/// `default-features`.
+/// `path`, `git`, `branch`, `tag`, `rev`, or `package`.
+/// Prior to Edition 2024 (RFC 3945) `default-features` was also forbidden;
+/// from Edition 2024 onwards a package-level `default-features` overrides the
+/// workspace value, so it is allowed.
 ///
 /// Only `default-features`, `registry` and `rename` need to be checked
 ///  for currently. This is because `git` and its associated keys, `path`, and
 /// `version`  should all bee checked before this is called. `rename` is checked
 /// for as it turns into `package`
-fn check_invalid_ws_keys(toml_key: &str, arg: &DepOp) -> CargoResult<()> {
+fn check_invalid_ws_keys(toml_key: &str, arg: &DepOp, edition: Edition) -> CargoResult<()> {
     fn err_msg(toml_key: &str, flag: &str, field: &str) -> String {
         format!(
             "cannot override workspace dependency with `{flag}`, \
@@ -719,7 +722,7 @@ fn check_invalid_ws_keys(toml_key: &str, arg: &DepOp) -> CargoResult<()> {
         )
     }
 
-    if arg.default_features.is_some() {
+    if arg.default_features.is_some() && edition < Edition::Edition2024 {
         anyhow::bail!(
             "{}",
             err_msg(toml_key, "--default-features", "default-features")
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs
index 7c2925dd4ec..976fe41d8f5 100644
--- a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/mod.rs
@@ -17,7 +17,7 @@ fn case() {
         .args(["foo", "--no-default-features", "-p", "bar"])
         .current_dir(cwd)
         .assert()
-        .failure()
+        .success()
         .stdout_eq(str![""])
         .stderr_eq(file!["stderr.term.svg"]);
 
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml
index 3bd66f7b4a1..04c5dac7ef9 100644
--- a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/out/bar/Cargo.toml
@@ -4,3 +4,4 @@ version = "0.0.0"
 edition = "2024"
 
 [dependencies]
+foo = { workspace = true, default-features = false }
diff --git a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg
index 0f967ee3fa5..6f612421cab 100644
--- a/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg
+++ b/tests/testsuite/cargo_add/inherit_no_default_features_2024_edition/stderr.term.svg
@@ -1,8 +1,8 @@
-<svg width="1642px" height="56px" xmlns="http://www.w3.org/2000/svg">
+<svg width="740px" height="56px" xmlns="http://www.w3.org/2000/svg">
   <style>
     .fg { fill: #AAAAAA }
     .bg { fill: #000000 }
-    .fg-bright-red { fill: #FF5555 }
+    .fg-bright-green { fill: #55FF55 }
     .container {
       padding: 0 10px;
       line-height: 18px;
@@ -18,7 +18,7 @@
   <rect width="100%" height="100%" y="0" rx="4.5" class="bg" />
 
   <text xml:space="preserve" class="container fg">
-    <tspan x="10px" y="28px"><tspan class="fg-bright-red bold">error</tspan><tspan>: cannot override workspace dependency with `--default-features`, either change `workspace.dependencies.foo.default-features` or define the dependency exclusively in the package's manifest</tspan>
+    <tspan x="10px" y="28px"><tspan class="fg-bright-green bold">      Adding</tspan><tspan> foo (workspace) to dependencies</tspan>
 </tspan>
     <tspan x="10px" y="46px">
 </tspan>

From 3678448737401f87616ccc935710020ccd5ffdda Mon Sep 17 00:00:00 2001
From: 0xPoe <techregister@pm.me>
Date: Wed, 24 Jun 2026 23:21:26 +0200
Subject: [PATCH 4/7] test(add): add inherit default features case

Signed-off-by: 0xPoe <techregister@pm.me>
---
 .../in/Cargo.toml                             |  6 +++++
 .../in/bar/Cargo.toml                         |  6 +++++
 .../in/bar/src/lib.rs                         |  1 +
 .../in/foo/Cargo.toml                         |  4 +++
 .../in/foo/src/lib.rs                         |  1 +
 .../mod.rs                                    | 25 +++++++++++++++++
 .../out/Cargo.toml                            |  6 +++++
 .../out/bar/Cargo.toml                        |  7 +++++
 .../out/bar/src/lib.rs                        |  1 +
 .../out/foo/Cargo.toml                        |  4 +++
 .../out/foo/src/lib.rs                        |  1 +
 .../stderr.term.svg                           | 27 +++++++++++++++++++
 tests/testsuite/cargo_add/mod.rs              |  1 +
 13 files changed, 90 insertions(+)
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/mod.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/Cargo.toml
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/src/lib.rs
 create mode 100644 tests/testsuite/cargo_add/inherit_default_features_2024_edition/stderr.term.svg

diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/Cargo.toml b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/Cargo.toml
new file mode 100644
index 00000000000..e407970d1e5
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/Cargo.toml
@@ -0,0 +1,6 @@
+[workspace]
+members = ["foo", "bar"]
+resolver = "3"
+
+[workspace.dependencies]
+foo = { version = "0.0.0", path = "./foo", default-features = false }
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/Cargo.toml b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/Cargo.toml
new file mode 100644
index 00000000000..3bd66f7b4a1
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "bar"
+version = "0.0.0"
+edition = "2024"
+
+[dependencies]
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/src/lib.rs b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/src/lib.rs
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/bar/src/lib.rs
@@ -0,0 +1 @@
+
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/Cargo.toml b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/Cargo.toml
new file mode 100644
index 00000000000..c0a92ea13b9
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/Cargo.toml
@@ -0,0 +1,4 @@
+[package]
+name = "foo"
+version = "0.0.0"
+edition = "2024"
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/src/lib.rs b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/src/lib.rs
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/in/foo/src/lib.rs
@@ -0,0 +1 @@
+
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/mod.rs b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/mod.rs
new file mode 100644
index 00000000000..390b209ef78
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/mod.rs
@@ -0,0 +1,25 @@
+use crate::prelude::*;
+use cargo_test_support::Project;
+use cargo_test_support::compare::assert_ui;
+use cargo_test_support::current_dir;
+use cargo_test_support::file;
+use cargo_test_support::str;
+
+#[cargo_test]
+fn case() {
+    cargo_test_support::registry::init();
+    let project = Project::from_template(current_dir!().join("in"));
+    let project_root = project.root();
+    let cwd = &project_root;
+
+    snapbox::cmd::Command::cargo_ui()
+        .arg("add")
+        .args(["foo", "--default-features", "-p", "bar"])
+        .current_dir(cwd)
+        .assert()
+        .success()
+        .stdout_eq(str![""])
+        .stderr_eq(file!["stderr.term.svg"]);
+
+    assert_ui().subset_matches(current_dir!().join("out"), &project_root);
+}
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/Cargo.toml b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/Cargo.toml
new file mode 100644
index 00000000000..e407970d1e5
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/Cargo.toml
@@ -0,0 +1,6 @@
+[workspace]
+members = ["foo", "bar"]
+resolver = "3"
+
+[workspace.dependencies]
+foo = { version = "0.0.0", path = "./foo", default-features = false }
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml
new file mode 100644
index 00000000000..d2e9908e93f
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "bar"
+version = "0.0.0"
+edition = "2024"
+
+[dependencies]
+foo.workspace = true
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/src/lib.rs b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/src/lib.rs
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/src/lib.rs
@@ -0,0 +1 @@
+
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/Cargo.toml b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/Cargo.toml
new file mode 100644
index 00000000000..c0a92ea13b9
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/Cargo.toml
@@ -0,0 +1,4 @@
+[package]
+name = "foo"
+version = "0.0.0"
+edition = "2024"
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/src/lib.rs b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/src/lib.rs
new file mode 100644
index 00000000000..8b137891791
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/foo/src/lib.rs
@@ -0,0 +1 @@
+
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/stderr.term.svg b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/stderr.term.svg
new file mode 100644
index 00000000000..6f612421cab
--- /dev/null
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/stderr.term.svg
@@ -0,0 +1,27 @@
+<svg width="740px" height="56px" xmlns="http://www.w3.org/2000/svg">
+  <style>
+    .fg { fill: #AAAAAA }
+    .bg { fill: #000000 }
+    .fg-bright-green { fill: #55FF55 }
+    .container {
+      padding: 0 10px;
+      line-height: 18px;
+    }
+    .bold { font-weight: bold; }
+    tspan {
+      font: 14px SFMono-Regular, Consolas, Liberation Mono, Menlo, monospace;
+      white-space: pre;
+      line-height: 18px;
+    }
+  </style>
+
+  <rect width="100%" height="100%" y="0" rx="4.5" class="bg" />
+
+  <text xml:space="preserve" class="container fg">
+    <tspan x="10px" y="28px"><tspan class="fg-bright-green bold">      Adding</tspan><tspan> foo (workspace) to dependencies</tspan>
+</tspan>
+    <tspan x="10px" y="46px">
+</tspan>
+  </text>
+
+</svg>
diff --git a/tests/testsuite/cargo_add/mod.rs b/tests/testsuite/cargo_add/mod.rs
index 1ae817db983..d097eaf870b 100644
--- a/tests/testsuite/cargo_add/mod.rs
+++ b/tests/testsuite/cargo_add/mod.rs
@@ -48,6 +48,7 @@ mod git_rev;
 mod git_tag;
 mod help;
 mod infer_prerelease;
+mod inherit_default_features_2024_edition;
 mod inherit_no_default_features_2024_edition;
 mod invalid_arg;
 mod invalid_git_name;

From aa188dc7215314e07a0e1b2dfdae3894e856ec8f Mon Sep 17 00:00:00 2001
From: 0xPoe <techregister@pm.me>
Date: Wed, 24 Jun 2026 23:50:31 +0200
Subject: [PATCH 5/7] fix(add): set dep's default features explicitly

Signed-off-by: 0xPoe <techregister@pm.me>
---
 src/ops/cargo_add/mod.rs                            | 13 +++++++++++++
 src/workspace/editor/dependency.rs                  | 10 +++++-----
 .../out/bar/Cargo.toml                              |  2 +-
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/ops/cargo_add/mod.rs b/src/ops/cargo_add/mod.rs
index fbfe1e54ba2..42a6307ea54 100644
--- a/src/ops/cargo_add/mod.rs
+++ b/src/ops/cargo_add/mod.rs
@@ -505,6 +505,19 @@ fn resolve_dependency(
 
     if let Some(Source::Workspace(_)) = dependency.source() {
         check_invalid_ws_keys(dependency.toml_key(), arg, spec.manifest().edition())?;
+        if spec.manifest().edition() >= Edition::Edition2024 && arg.default_features == Some(true) {
+            let ws_dep = find_workspace_dep(
+                dependency.toml_key(),
+                ws,
+                ws.root_manifest(),
+                ws.unstable_features(),
+            )?;
+            // Only write `default-features = true` when the workspace dependency
+            // explicitly disables default features.
+            if ws_dep.default_features() == Some(false) {
+                dependency.default_features = Some(true);
+            }
+        }
     }
 
     let version_required = dependency.source().and_then(|s| s.as_registry()).is_some();
diff --git a/src/workspace/editor/dependency.rs b/src/workspace/editor/dependency.rs
index 048e8ae2461..b7d27bd387d 100644
--- a/src/workspace/editor/dependency.rs
+++ b/src/workspace/editor/dependency.rs
@@ -392,8 +392,8 @@ impl Dependency {
     ///
     /// Returns a tuple with the dependency's name and either the version as a
     /// `String` or the path/git repository as an `InlineTable`.
-    /// (If the dependency is set as `optional` or `default-features` is set to
-    /// `false`, an `InlineTable` is returned in any case.)
+    /// (If the dependency is set as `optional` or `default-features` is
+    /// explicitly set, an `InlineTable` is returned in any case.)
     ///
     /// # Panic
     ///
@@ -414,7 +414,7 @@ impl Dependency {
             self.public.unwrap_or(false),
             self.optional.unwrap_or(false),
             self.features.as_ref(),
-            self.default_features.unwrap_or(true),
+            self.default_features,
             self.source.as_ref(),
             self.registry.as_ref(),
             self.rename.as_ref(),
@@ -424,12 +424,12 @@ impl Dependency {
                 false,
                 false,
                 None,
-                true,
+                None,
                 Some(Source::Registry(RegistrySource { version: v })),
                 None,
                 None,
             ) => toml_edit::value(v),
-            (false, false, None, true, Some(Source::Workspace(WorkspaceSource {})), None, None) => {
+            (false, false, None, None, Some(Source::Workspace(WorkspaceSource {})), None, None) => {
                 let mut table = toml_edit::InlineTable::default();
                 table.set_dotted(true);
                 table.insert("workspace", true.into());
diff --git a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml
index d2e9908e93f..d2b90a2d211 100644
--- a/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml
+++ b/tests/testsuite/cargo_add/inherit_default_features_2024_edition/out/bar/Cargo.toml
@@ -4,4 +4,4 @@ version = "0.0.0"
 edition = "2024"
 
 [dependencies]
-foo.workspace = true
+foo = { workspace = true, default-features = true }

From 7bfc9701714f68abf04e40d31fc51dcb82c2afb0 Mon Sep 17 00:00:00 2001
From: 0xPoe <techregister@pm.me>
Date: Thu, 25 Jun 2026 00:04:16 +0200
Subject: [PATCH 6/7] fix(add): update outdated warnings

Signed-off-by: 0xPoe <techregister@pm.me>
---
 src/workspace/parser/mod.rs                     | 5 +++--
 tests/testsuite/inheritable_workspace_fields.rs | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/workspace/parser/mod.rs b/src/workspace/parser/mod.rs
index d96f4ae0965..72a310e302f 100644
--- a/src/workspace/parser/mod.rs
+++ b/src/workspace/parser/mod.rs
@@ -1270,8 +1270,9 @@ fn deprecated_ws_default_features(
     };
     warnings.push(format!(
         "`default-features` is ignored for {label}, since `default-features` was \
-                {ws_def_feat} for `workspace.dependencies.{label}`, \
-                this could become a hard error in the future"
+                {ws_def_feat} for `workspace.dependencies.{label}`; \
+                overriding workspace `default-features` to false requires Rust 1.99+ \
+                and the 2024 edition"
     ));
 }
 
diff --git a/tests/testsuite/inheritable_workspace_fields.rs b/tests/testsuite/inheritable_workspace_fields.rs
index 0584ce280c7..5bfcacb9052 100644
--- a/tests/testsuite/inheritable_workspace_fields.rs
+++ b/tests/testsuite/inheritable_workspace_fields.rs
@@ -1539,7 +1539,7 @@ fn warn_inherit_def_feat_true_member_def_feat_false() {
         .build();
 
     p.cargo("check").with_stderr_data(str![[r#"
-[WARNING] Cargo.toml: `default-features` is ignored for dep, since `default-features` was true for `workspace.dependencies.dep`, this could become a hard error in the future
+[WARNING] Cargo.toml: `default-features` is ignored for dep, since `default-features` was true for `workspace.dependencies.dep`; overriding workspace `default-features` to false requires Rust 1.99+ and the 2024 edition
 [WARNING] `bar` (manifest) generated 1 warning
 [UPDATING] `dummy-registry` index
 [LOCKING] 2 packages to latest compatible versions
@@ -1631,7 +1631,7 @@ fn warn_inherit_simple_member_def_feat_false() {
         .build();
 
     p.cargo("check").with_stderr_data(str![[r#"
-[WARNING] Cargo.toml: `default-features` is ignored for dep, since `default-features` was not specified for `workspace.dependencies.dep`, this could become a hard error in the future
+[WARNING] Cargo.toml: `default-features` is ignored for dep, since `default-features` was not specified for `workspace.dependencies.dep`; overriding workspace `default-features` to false requires Rust 1.99+ and the 2024 edition
 [WARNING] `bar` (manifest) generated 1 warning
 [UPDATING] `dummy-registry` index
 [LOCKING] 2 packages to latest compatible versions

From 677fb4574e200f74f83df4b41fb928e99cc836d0 Mon Sep 17 00:00:00 2001
From: 0xPoe <techregister@pm.me>
Date: Mon, 22 Jun 2026 00:10:49 +0200
Subject: [PATCH 7/7] docs: document overriding inherited default-features

Signed-off-by: 0xPoe <techregister@pm.me>
---
 doc/book/src/reference/specifying-dependencies.md | 14 +++++++++++---
 doc/book/src/reference/workspaces.md              |  7 +++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/doc/book/src/reference/specifying-dependencies.md b/doc/book/src/reference/specifying-dependencies.md
index 310c504825b..4be2f754e67 100644
--- a/doc/book/src/reference/specifying-dependencies.md
+++ b/doc/book/src/reference/specifying-dependencies.md
@@ -637,11 +637,16 @@ dependency in the workspace's [`[workspace.dependencies]`][workspace.dependencie
 After that, add it to the `[dependencies]` table with `workspace = true`.
 
 Along with the `workspace` key, dependencies can also include these keys:
-- [`optional`][optional]: Note that the`[workspace.dependencies]` table is not allowed to specify `optional`.
+- [`optional`][optional]: Note that the `[workspace.dependencies]` table is not allowed to specify `optional`.
 - [`features`][features]: These are additive with the features declared in the `[workspace.dependencies]`
+- [`default-features`][default-features] (Edition 2024 packages, requires Rust 1.99+):
+  Overrides the value set in `[workspace.dependencies]`.
+  If neither the package nor the workspace specifies `default-features`, it defaults to `true`.
+  Before Rust 1.99, or in earlier editions, package-level `default-features = false`
+  may be ignored or rejected unless the workspace dependency also disables default features.
 
-Other than `optional` and `features`, inherited dependencies cannot use any other
-dependency key (such as `version` or `default-features`).
+Other than `optional`, `features`, and `default-features`, inherited dependencies
+cannot use any other dependency key (such as `version`).
 
 Dependencies in the `[dependencies]`, `[dev-dependencies]`, `[build-dependencies]`, and
 `[target."...".dependencies]` sections support the ability to reference the
@@ -651,9 +656,11 @@ Dependencies in the `[dependencies]`, `[dev-dependencies]`, `[build-dependencies
 [package]
 name = "bar"
 version = "0.2.0"
+edition = "2024"
 
 [dependencies]
 regex = { workspace = true, features = ["unicode"] }
+serde = { workspace = true, default-features = false }
 
 [build-dependencies]
 cc.workspace = true
@@ -669,3 +676,4 @@ rand = { workspace = true, optional = true }
 [workspace.dependencies]: workspaces.md#the-dependencies-table
 [optional]: features.md#optional-dependencies
 [features]: features.md
+[default-features]: features.md#dependency-features
diff --git a/doc/book/src/reference/workspaces.md b/doc/book/src/reference/workspaces.md
index a923e3ebd18..a8dd028375a 100644
--- a/doc/book/src/reference/workspaces.md
+++ b/doc/book/src/reference/workspaces.md
@@ -199,6 +199,10 @@ inherited by members of a workspace.
 Specifying a workspace dependency is similar to [package dependencies][specifying-dependencies] except:
 - Dependencies from this table cannot be declared as `optional`
 - [`features`][features] declared in this table are additive with the `features` from `[dependencies]`
+- `default-features` declared on a package dependency overrides the value set
+  here in Edition 2024 packages (requires Rust 1.99+). Before Rust 1.99, or in
+  earlier editions, package-level `default-features = false` may be ignored or
+  rejected unless the workspace dependency also disables default features.
 
 You can then [inherit the workspace dependency as a package dependency][inheriting-a-dependency-from-a-workspace]
 
@@ -212,6 +216,7 @@ members = ["bar"]
 cc = "1.0.73"
 rand = "0.8.5"
 regex = { version = "1.6.0", default-features = false, features = ["std"] }
+serde = { version = "1.0.190", default-features = true }
 ```
 
 ```toml
@@ -219,9 +224,11 @@ regex = { version = "1.6.0", default-features = false, features = ["std"] }
 [package]
 name = "bar"
 version = "0.2.0"
+edition = "2024"
 
 [dependencies]
 regex = { workspace = true, features = ["unicode"] }
+serde = { workspace = true, default-features = false }
 
 [build-dependencies]
 cc.workspace = true