refactor(package): rename traits and switch dep maps to IndexMap

Rename Package/CompletePackage to PackageInterface/CompletePackageInterface
to mirror Composer's interface names, and split each into its own module
under crates/mozart-core/src/package/.

Switch dependency-link and metadata maps from BTreeMap to indexmap::IndexMap
so serialized JSON preserves the original key ordering rather than sorting
alphabetically — matching PHP associative-array semantics. The
--sort-packages behaviour in `require` is preserved via sort_unstable_keys.

16 files changed, 222 insertions, 244 deletions

diff --git a/crates/mozart/src/commands/audit.rs b/crates/mozart/src/commands/audit.rs
index 0b84ccf..f543cb4 100644
--- a/crates/mozart/src/commands/audit.rs
+++ b/crates/mozart/src/commands/audit.rs
@@ -194,8 +194,6 @@ fn load_locked_packages(working_dir: &Path, no_dev: bool) -> anyhow::Result<Vec<
 
 #[cfg(test)]
 mod tests {
-    use std::collections::BTreeMap;
-
     use super::*;
     use mozart_core::repository::lockfile::{LockFile, LockedPackage};
 
@@ -242,7 +240,7 @@ mod tests {
             aliases: vec![],
             homepage: None,
             support: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         });
         installed.write(&vendor_dir).unwrap();
 
@@ -273,7 +271,7 @@ mod tests {
             aliases: vec![],
             homepage: None,
             support: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         });
         installed.upsert(mozart_core::repository::installed::InstalledPackageEntry {
             name: "phpunit/phpunit".to_string(),
@@ -287,7 +285,7 @@ mod tests {
             aliases: vec![],
             homepage: None,
             support: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         });
         installed
             .dev_package_names
@@ -315,11 +313,11 @@ mod tests {
                 version_normalized: Some("3.0.0.0".to_string()),
                 source: None,
                 dist: None,
-                require: BTreeMap::new(),
-                require_dev: BTreeMap::new(),
-                conflict: BTreeMap::new(),
-                provide: BTreeMap::new(),
-                replace: BTreeMap::new(),
+                require: indexmap::IndexMap::new(),
+                require_dev: indexmap::IndexMap::new(),
+                conflict: indexmap::IndexMap::new(),
+                provide: indexmap::IndexMap::new(),
+                replace: indexmap::IndexMap::new(),
                 suggest: None,
                 package_type: None,
                 autoload: None,
@@ -332,7 +330,7 @@ mod tests {
                 support: None,
                 funding: None,
                 time: None,
-                extra_fields: BTreeMap::new(),
+                extra_fields: indexmap::IndexMap::new(),
             }],
             packages_dev: None,
             aliases: vec![],
@@ -370,11 +368,11 @@ mod tests {
                 version_normalized: None,
                 source: None,
                 dist: None,
-                require: BTreeMap::new(),
-                require_dev: BTreeMap::new(),
-                conflict: BTreeMap::new(),
-                provide: BTreeMap::new(),
-                replace: BTreeMap::new(),
+                require: indexmap::IndexMap::new(),
+                require_dev: indexmap::IndexMap::new(),
+                conflict: indexmap::IndexMap::new(),
+                provide: indexmap::IndexMap::new(),
+                replace: indexmap::IndexMap::new(),
                 suggest: None,
                 package_type: None,
                 autoload: None,
@@ -387,7 +385,7 @@ mod tests {
                 support: None,
                 funding: None,
                 time: None,
-                extra_fields: BTreeMap::new(),
+                extra_fields: indexmap::IndexMap::new(),
             }],
             packages_dev: Some(vec![LockedPackage {
                 name: "phpunit/phpunit".to_string(),
@@ -395,11 +393,11 @@ mod tests {
                 version_normalized: None,
                 source: None,
                 dist: None,
-                require: BTreeMap::new(),
-                require_dev: BTreeMap::new(),
-                conflict: BTreeMap::new(),
-                provide: BTreeMap::new(),
-                replace: BTreeMap::new(),
+                require: indexmap::IndexMap::new(),
+                require_dev: indexmap::IndexMap::new(),
+                conflict: indexmap::IndexMap::new(),
+                provide: indexmap::IndexMap::new(),
+                replace: indexmap::IndexMap::new(),
                 suggest: None,
                 package_type: None,
                 autoload: None,
@@ -412,7 +410,7 @@ mod tests {
                 support: None,
                 funding: None,
                 time: None,
-                extra_fields: BTreeMap::new(),
+                extra_fields: indexmap::IndexMap::new(),
             }]),
             aliases: vec![],
             minimum_stability: "stable".to_string(),
diff --git a/crates/mozart/src/commands/browse.rs b/crates/mozart/src/commands/browse.rs
index e3eae22..957f4bc 100644
--- a/crates/mozart/src/commands/browse.rs
+++ b/crates/mozart/src/commands/browse.rs
@@ -4,7 +4,7 @@ use mozart_core::console::IoInterface;
 use mozart_core::console_writeln;
 use mozart_core::console_writeln_error;
 use mozart_core::exit_code;
-use mozart_core::package::Package as _;
+use mozart_core::package::PackageInterface as _;
 use mozart_core::repository::browse_repos::{BrowseRepos, CompletePackageView};
 use mozart_core::repository::cache::{Cache, build_cache_config};
 use mozart_core::repository::installed::InstalledPackages;
diff --git a/crates/mozart/src/commands/bump.rs b/crates/mozart/src/commands/bump.rs
index 351be01..2d6eea8 100644
--- a/crates/mozart/src/commands/bump.rs
+++ b/crates/mozart/src/commands/bump.rs
@@ -3,7 +3,7 @@ use clap::Args;
 use indexmap::IndexMap;
 use mozart_core::composer::LocalRepository;
 use mozart_core::console::IoInterface;
-use mozart_core::package::{Link, Package as _};
+use mozart_core::package::PackageInterface as _;
 use mozart_core::{console_writeln, console_writeln_error};
 use std::collections::BTreeMap;
 use std::path::Path;
@@ -151,7 +151,7 @@ pub async fn do_bump(
         }
     }
 
-    let mut tasks: Vec<(&'static str, &BTreeMap<String, Link>)> = Vec::new();
+    let mut tasks = Vec::new();
     if !dev_only {
         tasks.push(("require", composer.package().requires()));
     }
@@ -386,11 +386,11 @@ mod tests {
             version_normalized: Some(format!("{version}.0")),
             source: None,
             dist: None,
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
-            provide: BTreeMap::new(),
-            replace: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
+            provide: indexmap::IndexMap::new(),
+            replace: indexmap::IndexMap::new(),
             suggest: None,
             package_type: None,
             autoload: None,
@@ -403,7 +403,7 @@ mod tests {
             support: None,
             funding: None,
             time: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         }
     }
 
diff --git a/crates/mozart/src/commands/check_platform_reqs.rs b/crates/mozart/src/commands/check_platform_reqs.rs
index 2dbcd3b..f6731d7 100644
--- a/crates/mozart/src/commands/check_platform_reqs.rs
+++ b/crates/mozart/src/commands/check_platform_reqs.rs
@@ -3,7 +3,6 @@ use mozart_core::console::IoInterface;
 use mozart_core::console_writeln;
 use mozart_core::console_writeln_error;
 use mozart_core::installer::{InstalledCandidate, InstalledRepoLite};
-use std::collections::BTreeMap;
 use std::path::Path;
 
 #[derive(Args)]
@@ -75,7 +74,7 @@ pub async fn execute(
     let installed_path = vendor_dir.join("composer/installed.json");
 
     let mut installed_repo = InstalledRepoLite::new();
-    let mut requires: BTreeMap<String, Vec<Link>> = BTreeMap::new();
+    let mut requires = indexmap::IndexMap::new();
 
     if args.lock {
         if !lock_path.exists() {
@@ -141,8 +140,8 @@ pub async fn execute(
             pretty_name: pkg.name,
             version: pkg.version.clone(),
             pretty_version: pkg.version,
-            provides: BTreeMap::new(),
-            replaces: BTreeMap::new(),
+            provides: indexmap::IndexMap::new(),
+            replaces: indexmap::IndexMap::new(),
         });
     }
 
@@ -251,7 +250,7 @@ fn load_lock(
     lock_path: &Path,
     no_dev: bool,
     repo: &mut InstalledRepoLite,
-    requires: &mut BTreeMap<String, Vec<Link>>,
+    requires: &mut indexmap::IndexMap<String, Vec<Link>>,
 ) -> anyhow::Result<()> {
     let lock = mozart_core::repository::lockfile::LockFile::read_from_file(lock_path)?;
 
@@ -282,7 +281,7 @@ fn load_installed(
     installed: &mozart_core::repository::installed::InstalledPackages,
     no_dev: bool,
     repo: &mut InstalledRepoLite,
-    requires: &mut BTreeMap<String, Vec<Link>>,
+    requires: &mut indexmap::IndexMap<String, Vec<Link>>,
 ) {
     let dev_names: indexmap::IndexSet<String> = installed
         .dev_package_names
@@ -334,10 +333,10 @@ fn add_root_as_candidate(
 }
 
 fn string_map_from_extra(
-    extra: &BTreeMap<String, serde_json::Value>,
+    extra: &indexmap::IndexMap<String, serde_json::Value>,
     key: &str,
-) -> BTreeMap<String, String> {
-    let mut out: BTreeMap<String, String> = BTreeMap::new();
+) -> indexmap::IndexMap<String, String> {
+    let mut out = indexmap::IndexMap::new();
     if let Some(val) = extra.get(key)
         && let Some(obj) = val.as_object()
     {
@@ -351,7 +350,7 @@ fn string_map_from_extra(
 }
 
 fn push_platform_link(
-    requires: &mut BTreeMap<String, Vec<Link>>,
+    requires: &mut indexmap::IndexMap<String, Vec<Link>>,
     source: &str,
     target: &str,
     constraint: &str,
@@ -470,7 +469,6 @@ fn print_table(
 mod tests {
     use super::*;
     use mozart_core::console::Console;
-    use std::collections::BTreeMap;
     use tempfile::tempdir;
 
     fn test_console() -> std::sync::Arc<std::sync::Mutex<Box<dyn IoInterface>>> {
@@ -481,22 +479,26 @@ mod tests {
 
     fn write_lock(
         path: &Path,
-        packages: &[(&str, BTreeMap<String, String>)],
-        dev_packages: &[(&str, BTreeMap<String, String>)],
+        packages: &[(&str, indexmap::IndexMap<String, String>)],
+        dev_packages: &[(&str, indexmap::IndexMap<String, String>)],
     ) {
         write_lock_with(path, packages, dev_packages, &[]);
     }
 
     fn write_lock_with(
         path: &Path,
-        packages: &[(&str, BTreeMap<String, String>)],
-        dev_packages: &[(&str, BTreeMap<String, String>)],
-        provides: &[(&str, BTreeMap<String, String>, BTreeMap<String, String>)], // (name, provide, replace)
+        packages: &[(&str, indexmap::IndexMap<String, String>)],
+        dev_packages: &[(&str, indexmap::IndexMap<String, String>)],
+        provides: &[(
+            &str,
+            indexmap::IndexMap<String, String>,
+            indexmap::IndexMap<String, String>,
+        )], // (name, provide, replace)
     ) {
         let make_pkg = |name: &str,
-                        require: BTreeMap<String, String>,
-                        provide: BTreeMap<String, String>,
-                        replace: BTreeMap<String, String>| {
+                        require: indexmap::IndexMap<String, String>,
+                        provide: indexmap::IndexMap<String, String>,
+                        replace: indexmap::IndexMap<String, String>| {
             serde_json::json!({
                 "name": name,
                 "version": "1.0.0",
@@ -508,15 +510,34 @@ mod tests {
 
         let mut pkgs_json: Vec<serde_json::Value> = packages
             .iter()
-            .map(|(name, req)| make_pkg(name, req.clone(), BTreeMap::new(), BTreeMap::new()))
+            .map(|(name, req)| {
+                make_pkg(
+                    name,
+                    req.clone(),
+                    indexmap::IndexMap::new(),
+                    indexmap::IndexMap::new(),
+                )
+            })
             .collect();
         for (name, prov, repl) in provides {
-            pkgs_json.push(make_pkg(name, BTreeMap::new(), prov.clone(), repl.clone()));
+            pkgs_json.push(make_pkg(
+                name,
+                indexmap::IndexMap::new(),
+                prov.clone(),
+                repl.clone(),
+            ));
         }
 
         let dev_pkgs_json: Vec<serde_json::Value> = dev_packages
             .iter()
-            .map(|(name, req)| make_pkg(name, req.clone(), BTreeMap::new(), BTreeMap::new()))
+            .map(|(name, req)| {
+                make_pkg(
+                    name,
+                    req.clone(),
+                    indexmap::IndexMap::new(),
+                    indexmap::IndexMap::new(),
+                )
+            })
             .collect();
 
         let lock_json = serde_json::json!({
@@ -565,7 +586,7 @@ mod tests {
         let dir = tempdir().unwrap();
         let lock_path = dir.path().join("composer.lock");
 
-        let mut pkg_require = BTreeMap::new();
+        let mut pkg_require = indexmap::IndexMap::new();
         pkg_require.insert("php".to_string(), ">=8.1".to_string());
         pkg_require.insert("ext-json".to_string(), "*".to_string());
         pkg_require.insert("monolog/monolog".to_string(), "^3.0".to_string()); // not platform
@@ -573,7 +594,7 @@ mod tests {
         write_lock(&lock_path, &[("vendor/pkg", pkg_require)], &[]);
 
         let mut repo = InstalledRepoLite::new();
-        let mut requires: BTreeMap<String, Vec<Link>> = BTreeMap::new();
+        let mut requires = indexmap::IndexMap::new();
         load_lock(&lock_path, false, &mut repo, &mut requires).unwrap();
 
         assert!(requires.contains_key("php"));
@@ -591,10 +612,10 @@ mod tests {
         let dir = tempdir().unwrap();
         let lock_path = dir.path().join("composer.lock");
 
-        let mut prod_require = BTreeMap::new();
+        let mut prod_require = indexmap::IndexMap::new();
         prod_require.insert("php".to_string(), ">=8.0".to_string());
 
-        let mut dev_require = BTreeMap::new();
+        let mut dev_require = indexmap::IndexMap::new();
         dev_require.insert("ext-xdebug".to_string(), "*".to_string());
 
         write_lock(
@@ -604,13 +625,13 @@ mod tests {
         );
 
         let mut repo = InstalledRepoLite::new();
-        let mut requires: BTreeMap<String, Vec<Link>> = BTreeMap::new();
+        let mut requires = indexmap::IndexMap::new();
         load_lock(&lock_path, true, &mut repo, &mut requires).unwrap();
         assert!(requires.contains_key("php"));
         assert!(!requires.contains_key("ext-xdebug"));
 
         let mut repo2 = InstalledRepoLite::new();
-        let mut requires2: BTreeMap<String, Vec<Link>> = BTreeMap::new();
+        let mut requires2 = indexmap::IndexMap::new();
         load_lock(&lock_path, false, &mut repo2, &mut requires2).unwrap();
         assert!(requires2.contains_key("ext-xdebug"));
     }
@@ -626,10 +647,10 @@ mod tests {
             pretty_name: "vendor/pkg".into(),
             version: "1.0.0".into(),
             pretty_version: "1.0.0".into(),
-            provides: BTreeMap::new(),
-            replaces: BTreeMap::new(),
+            provides: indexmap::IndexMap::new(),
+            replaces: indexmap::IndexMap::new(),
         });
-        let mut polyfill_provides = BTreeMap::new();
+        let mut polyfill_provides = indexmap::IndexMap::new();
         polyfill_provides.insert("ext-mbstring".to_string(), "*".to_string());
         repo.add_candidate(InstalledCandidate {
             name: "symfony/polyfill-mbstring".into(),
@@ -637,7 +658,7 @@ mod tests {
             version: "1.30.0".into(),
             pretty_version: "1.30.0".into(),
             provides: polyfill_provides,
-            replaces: BTreeMap::new(),
+            replaces: indexmap::IndexMap::new(),
         });
 
         let candidates = repo.find_with_replacers_and_providers("ext-mbstring");
@@ -652,7 +673,7 @@ mod tests {
 
     #[test]
     fn test_replacer_candidate_satisfies_require() {
-        let mut replaces = BTreeMap::new();
+        let mut replaces = indexmap::IndexMap::new();
         replaces.insert("ext-mbstring".to_string(), "1.0".to_string());
 
         let mut repo = InstalledRepoLite::new();
@@ -661,7 +682,7 @@ mod tests {
             pretty_name: "vendor/legacy-replacement".into(),
             version: "2.0.0".into(),
             pretty_version: "2.0.0".into(),
-            provides: BTreeMap::new(),
+            provides: indexmap::IndexMap::new(),
             replaces,
         });
 
diff --git a/crates/mozart/src/commands/dependency.rs b/crates/mozart/src/commands/dependency.rs
index 70d1644..5766b08 100644
--- a/crates/mozart/src/commands/dependency.rs
+++ b/crates/mozart/src/commands/dependency.rs
@@ -9,7 +9,6 @@ use indexmap::IndexSet;
 use mozart_core::console::IoInterface;
 use mozart_core::console_format;
 use mozart_core::console_writeln;
-use std::collections::BTreeMap;
 use std::path::Path;
 
 /// Inputs for [`do_execute`], collected from the `depends` / `prohibits` CLI args.
@@ -160,11 +159,11 @@ pub struct PackageInfo {
     pub name: String,
     pub version: String,
     /// Runtime requirements (`require` section).
-    pub require: BTreeMap<String, String>,
+    pub require: indexmap::IndexMap<String, String>,
     /// Dev requirements (`require-dev`) — only non-empty for the root package.
-    pub require_dev: BTreeMap<String, String>,
+    pub require_dev: indexmap::IndexMap<String, String>,
     /// Conflict declarations (`conflict` section).
-    pub conflict: BTreeMap<String, String>,
+    pub conflict: indexmap::IndexMap<String, String>,
     /// Whether this is the root `composer.json` package.
     pub is_root: bool,
 }
@@ -218,9 +217,9 @@ pub fn load_packages(working_dir: &Path, locked: bool) -> Result<Vec<PackageInfo
         packages.push(PackageInfo {
             name: pp.name.clone(),
             version: pp.version.clone(),
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
             is_root: false,
         });
     }
@@ -230,7 +229,7 @@ pub fn load_packages(working_dir: &Path, locked: bool) -> Result<Vec<PackageInfo
         && let Ok(root) = mozart_core::package::read_from_file(&composer_json_path)
     {
         // Extract conflict from extra_fields if present
-        let conflict: BTreeMap<String, String> = root
+        let conflict = root
             .extra_fields
             .get("conflict")
             .and_then(|v| v.as_object())
@@ -267,7 +266,7 @@ fn load_from_lockfile(lock_path: &Path) -> Result<Vec<PackageInfo>> {
             name: pkg.name.clone(),
             version: pkg.version.clone(),
             require: pkg.require.clone(),
-            require_dev: BTreeMap::new(), // locked packages don't expose require-dev
+            require_dev: indexmap::IndexMap::new(), // locked packages don't expose require-dev
             conflict: pkg.conflict.clone(),
             is_root: false,
         });
@@ -279,7 +278,7 @@ fn load_from_lockfile(lock_path: &Path) -> Result<Vec<PackageInfo>> {
                 name: pkg.name.clone(),
                 version: pkg.version.clone(),
                 require: pkg.require.clone(),
-                require_dev: BTreeMap::new(),
+                require_dev: indexmap::IndexMap::new(),
                 conflict: pkg.conflict.clone(),
                 is_root: false,
             });
@@ -325,7 +324,7 @@ fn load_from_installed(working_dir: &Path) -> Result<Vec<PackageInfo>> {
                 name: p.name.clone(),
                 version: p.version.clone(),
                 require,
-                require_dev: BTreeMap::new(),
+                require_dev: indexmap::IndexMap::new(),
                 conflict,
                 is_root: false,
             }
@@ -367,7 +366,7 @@ fn get_dependents_forward(
     let needle_set: IndexSet<String> = needles.iter().map(|n| n.to_lowercase()).collect();
 
     // Build name→PackageInfo lookup
-    let pkg_map: BTreeMap<String, &PackageInfo> = packages
+    let pkg_map: indexmap::IndexMap<_, _> = packages
         .iter()
         .map(|p| (p.name.to_lowercase(), p))
         .collect();
@@ -448,7 +447,7 @@ fn collect_direct_requires(packages: &[PackageInfo], needle: &str) -> Vec<Depend
 fn recurse_dependents(
     packages: &[PackageInfo],
     needle: &str,
-    pkg_map: &BTreeMap<String, &PackageInfo>,
+    pkg_map: &indexmap::IndexMap<String, &PackageInfo>,
     visited: &mut IndexSet<String>,
     _original_needles: &IndexSet<String>,
 ) -> Vec<DependencyResult> {
@@ -760,7 +759,7 @@ mod tests {
                 .iter()
                 .map(|(k, v)| (k.to_string(), v.to_string()))
                 .collect(),
-            require_dev: BTreeMap::new(),
+            require_dev: indexmap::IndexMap::new(),
             conflict: conflict
                 .iter()
                 .map(|(k, v)| (k.to_string(), v.to_string()))
diff --git a/crates/mozart/src/commands/diagnose.rs b/crates/mozart/src/commands/diagnose.rs
index a1d655f..6b2817a 100644
--- a/crates/mozart/src/commands/diagnose.rs
+++ b/crates/mozart/src/commands/diagnose.rs
@@ -8,7 +8,7 @@ use mozart_core::console::IoInterface;
 use mozart_core::console_writeln;
 use mozart_core::factory::create_config;
 use mozart_core::http::HttpDownloader;
-use mozart_core::package::CompletePackage as _;
+use mozart_core::package::CompletePackageInterface as _;
 use std::borrow::Cow;
 use std::path::Path;
 
diff --git a/crates/mozart/src/commands/exec.rs b/crates/mozart/src/commands/exec.rs
index f2a9c55..1078158 100644
--- a/crates/mozart/src/commands/exec.rs
+++ b/crates/mozart/src/commands/exec.rs
@@ -1,6 +1,6 @@
 use crate::composer::Composer;
 use clap::Args;
-use mozart_core::package::Package as _;
+use mozart_core::package::PackageInterface as _;
 use mozart_core::{console::IoInterface, console_writeln};
 use std::path::{Path, PathBuf};
 
diff --git a/crates/mozart/src/commands/init.rs b/crates/mozart/src/commands/init.rs
index 0e16054..4598d39 100644
--- a/crates/mozart/src/commands/init.rs
+++ b/crates/mozart/src/commands/init.rs
@@ -425,7 +425,7 @@ async fn build_interactive(
             "Would you like to define your dev dependencies (require-dev) interactively [<comment>yes</comment>]?"
         ))
     {
-        let all_required: BTreeMap<String, String> = require
+        let all_required: indexmap::IndexMap<_, _> = require
             .iter()
             .chain(require_dev.iter())
             .map(|(k, v)| (k.clone(), v.clone()))
@@ -493,7 +493,7 @@ async fn build_interactive(
 /// Returns a map of package name → version constraint selected by the user.
 async fn interactive_search_packages(
     label: &str,
-    already_required: &BTreeMap<String, String>,
+    already_required: &indexmap::IndexMap<String, String>,
     preferred_stability: Stability,
     repo_cache: &mozart_core::repository::cache::Cache,
     io: &std::sync::Arc<std::sync::Mutex<Box<dyn IoInterface>>>,
@@ -749,8 +749,8 @@ fn get_git_config_value(key: &str) -> Option<String> {
     get_git_config().get(key).cloned().filter(|v| !v.is_empty())
 }
 
-fn parse_requirements(reqs: &[String]) -> anyhow::Result<BTreeMap<String, String>> {
-    let mut map = BTreeMap::new();
+fn parse_requirements(reqs: &[String]) -> anyhow::Result<indexmap::IndexMap<String, String>> {
+    let mut map = indexmap::IndexMap::new();
     for req in reqs {
         let (name, version) =
             validation::parse_require_string(req).map_err(|e| anyhow::anyhow!(e))?;
@@ -761,7 +761,7 @@ fn parse_requirements(reqs: &[String]) -> anyhow::Result<BTreeMap<String, String
 
 fn build_autoload(path: &str, package_name: &str) -> Option<RawAutoload> {
     let namespace = validation::namespace_from_package_name(package_name)?;
-    let mut psr4 = BTreeMap::new();
+    let mut psr4 = indexmap::IndexMap::new();
     psr4.insert(format!("{namespace}\\"), path.to_string());
     Some(RawAutoload { psr4 })
 }
diff --git a/crates/mozart/src/commands/install.rs b/crates/mozart/src/commands/install.rs
index 54256e2..709b934 100644
--- a/crates/mozart/src/commands/install.rs
+++ b/crates/mozart/src/commands/install.rs
@@ -2,7 +2,7 @@ use clap::Args;
 use indexmap::IndexSet;
 use mozart_core::console::IoInterface;
 use mozart_core::console_format;
-use mozart_core::package::{Package as _, RootPackage as _, RootPackageData};
+use mozart_core::package::{PackageInterface as _, RootPackage as _, RootPackageData};
 use mozart_core::repository::installed;
 use mozart_core::repository::installer_executor::{
     Action, ExecuteContext, FilesystemExecutor, InstallerExecutor, PackageOperation,
@@ -11,7 +11,6 @@ use mozart_core::repository::installer_executor::{
     locked_to_installed_entry, previously_installed_alias_versions,
 };
 use mozart_core::repository::lockfile;
-use std::collections::BTreeMap;
 use std::path::Path;
 
 #[derive(Args)]
@@ -212,7 +211,7 @@ fn verify_lock_platform_problems(
 /// `provide` is intentionally excluded — `getNames(false)` excludes it, and
 /// virtual `provide` targets allow multiple co-installed providers.
 fn verify_lock_same_name_problems(lock: &lockfile::LockFile, dev_mode: bool) -> Vec<String> {
-    let mut providers: BTreeMap<String, Vec<String>> = BTreeMap::new();
+    let mut providers: indexmap::IndexMap<_, Vec<_>> = indexmap::IndexMap::new();
 
     let mut all_pkgs: Vec<&lockfile::LockedPackage> = lock.packages.iter().collect();
     if dev_mode {
@@ -397,8 +396,8 @@ fn combine_platform_requirements(
     root: &RootPackageData,
     lock: &lockfile::LockFile,
     dev_mode: bool,
-) -> BTreeMap<String, String> {
-    let mut combined: BTreeMap<String, String> = BTreeMap::new();
+) -> indexmap::IndexMap<String, String> {
+    let mut combined = indexmap::IndexMap::new();
 
     if let Some(obj) = lock.platform.as_object() {
         for (name, val) in obj {
@@ -434,7 +433,7 @@ fn combine_platform_requirements(
 }
 
 fn check_platform_requirements_against(
-    combined: &BTreeMap<String, String>,
+    combined: &indexmap::IndexMap<String, String>,
     platform: &[mozart_core::platform::PlatformPackage],
     ignore_platform_reqs: bool,
     ignore_platform_req: &[String],
@@ -1081,7 +1080,6 @@ pub async fn run(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::collections::BTreeMap;
     use tempfile::tempdir;
 
     fn make_locked_package(name: &str, version: &str) -> lockfile::LockedPackage {
@@ -1091,11 +1089,11 @@ mod tests {
             version_normalized: None,
             source: None,
             dist: None,
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
-            provide: BTreeMap::new(),
-            replace: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
+            provide: indexmap::IndexMap::new(),
+            replace: indexmap::IndexMap::new(),
             suggest: None,
             package_type: Some("library".to_string()),
             autoload: None,
@@ -1108,7 +1106,7 @@ mod tests {
             support: None,
             funding: None,
             time: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         }
     }
 
@@ -1125,7 +1123,7 @@ mod tests {
             aliases: vec![],
             homepage: None,
             support: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         }
     }
 
@@ -1506,9 +1504,10 @@ mod tests {
 
     #[test]
     fn check_platform_requirements_reports_missing_extension() {
-        let combined: BTreeMap<String, String> = [("ext-foo".to_string(), "^10".to_string())]
-            .into_iter()
-            .collect();
+        let combined: indexmap::IndexMap<String, String> =
+            [("ext-foo".to_string(), "^10".to_string())]
+                .into_iter()
+                .collect();
         let platform = vec![pp("php", "8.2.0")];
         let problems = check_platform_requirements_against(&combined, &platform, false, &[]);
 
@@ -1521,7 +1520,7 @@ mod tests {
 
     #[test]
     fn check_platform_requirements_reports_unsatisfied_php() {
-        let combined: BTreeMap<String, String> = [("php".to_string(), "^20".to_string())]
+        let combined: indexmap::IndexMap<String, String> = [("php".to_string(), "^20".to_string())]
             .into_iter()
             .collect();
         let platform = vec![pp("php", "8.2.0")];
@@ -1536,9 +1535,10 @@ mod tests {
 
     #[test]
     fn check_platform_requirements_satisfied_returns_empty() {
-        let combined: BTreeMap<String, String> = [("php".to_string(), "^8.0".to_string())]
-            .into_iter()
-            .collect();
+        let combined: indexmap::IndexMap<String, String> =
+            [("php".to_string(), "^8.0".to_string())]
+                .into_iter()
+                .collect();
         let platform = vec![pp("php", "8.2.0")];
         let problems = check_platform_requirements_against(&combined, &platform, false, &[]);
 
@@ -1547,9 +1547,10 @@ mod tests {
 
     #[test]
     fn check_platform_requirements_ignore_platform_reqs_short_circuits() {
-        let combined: BTreeMap<String, String> = [("ext-foo".to_string(), "^10".to_string())]
-            .into_iter()
-            .collect();
+        let combined: indexmap::IndexMap<String, String> =
+            [("ext-foo".to_string(), "^10".to_string())]
+                .into_iter()
+                .collect();
         let platform: Vec<mozart_core::platform::PlatformPackage> = vec![];
         let problems = check_platform_requirements_against(&combined, &platform, true, &[]);
 
@@ -1558,7 +1559,7 @@ mod tests {
 
     #[test]
     fn check_platform_requirements_specific_ignore_filters_named_packages() {
-        let combined: BTreeMap<String, String> = [
+        let combined: indexmap::IndexMap<String, String> = [
             ("ext-foo".to_string(), "^10".to_string()),
             ("ext-bar".to_string(), "^10".to_string()),
         ]
diff --git a/crates/mozart/src/commands/licenses.rs b/crates/mozart/src/commands/licenses.rs
index 73f2018..0e4ea0b 100644
--- a/crates/mozart/src/commands/licenses.rs
+++ b/crates/mozart/src/commands/licenses.rs
@@ -4,14 +4,13 @@ use indexmap::IndexMap;
 use mozart_core::console::IoInterface;
 use mozart_core::console::hyperlink;
 use mozart_core::console_writeln;
-use mozart_core::package::Package as _;
+use mozart_core::package::PackageInterface as _;
 use mozart_core::package_info;
 use mozart_core::package_info::PackageUrls;
 use mozart_core::package_sorter::sort_packages_alphabetically;
 use mozart_core::repository_utils;
 use mozart_core::repository_utils::Required;
 use serde::Serialize as _;
-use std::collections::BTreeMap;
 
 #[derive(Args)]
 pub struct LicensesArgs {
@@ -38,7 +37,7 @@ struct LicenseEntry {
     name: String,
     version: String,
     licenses: Vec<String>,
-    requires: BTreeMap<String, String>,
+    requires: indexmap::IndexMap<String, String>,
     support_source: Option<String>,
     source_url: Option<String>,
     homepage: Option<String>,
@@ -48,7 +47,7 @@ impl Required for LicenseEntry {
     fn package_name(&self) -> &str {
         &self.name
     }
-    fn requires(&self) -> &BTreeMap<String, String> {
+    fn requires(&self) -> &indexmap::IndexMap<String, String> {
         &self.requires
     }
 }
@@ -144,7 +143,7 @@ fn read_root_licenses(composer_json_path: &std::path::Path) -> anyhow::Result<Ve
 
 fn load_installed_entries<V>(
     working_dir: &std::path::Path,
-    root_requires: &BTreeMap<String, V>,
+    root_requires: &indexmap::IndexMap<String, V>,
     no_dev: bool,
 ) -> anyhow::Result<Vec<LicenseEntry>> {
     let vendor_dir = working_dir.join("vendor");
@@ -453,7 +452,6 @@ fn tally_licenses(entries: &[LicenseEntry]) -> Vec<(String, usize)> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::collections::BTreeMap;
 
     fn entry(name: &str, licenses: &[&str]) -> LicenseEntry {
         LicenseEntry {
@@ -461,7 +459,7 @@ mod tests {
             name: name.to_lowercase(),
             version: "1.0.0".to_string(),
             licenses: licenses.iter().map(|s| s.to_string()).collect(),
-            requires: BTreeMap::new(),
+            requires: indexmap::IndexMap::new(),
             support_source: None,
             source_url: None,
             homepage: None,
@@ -547,7 +545,7 @@ mod tests {
     #[test]
     fn installed_to_entry_extracts_require_and_license() {
         use mozart_core::repository::installed::InstalledPackageEntry;
-        let mut extra = BTreeMap::new();
+        let mut extra = indexmap::IndexMap::new();
         extra.insert("license".to_string(), serde_json::json!(["MIT"]));
         extra.insert(
             "require".to_string(),
@@ -587,7 +585,7 @@ mod tests {
             aliases: vec![],
             homepage: Some("https://example.com/".to_string()),
             support: Some(serde_json::json!({"source": "https://github.com/v/p"})),
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         };
         let e = installed_to_entry(&pkg);
         assert_eq!(e.support_source.as_deref(), Some("https://github.com/v/p"));
@@ -630,7 +628,7 @@ mod tests {
             aliases: vec![],
             homepage: None,
             support: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         });
         installed.upsert(mozart_core::repository::installed::InstalledPackageEntry {
             name: "b/b".to_string(),
@@ -644,11 +642,11 @@ mod tests {
             aliases: vec![],
             homepage: None,
             support: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         });
         installed.write(&vendor_dir).unwrap();
 
-        let mut root_req = BTreeMap::new();
+        let mut root_req = indexmap::IndexMap::new();
         root_req.insert("a/a".to_string(), "*".to_string());
 
         let kept = load_installed_entries(working_dir, &root_req, true).unwrap();
@@ -679,11 +677,11 @@ mod tests {
                 version_normalized: None,
                 source: None,
                 dist: None,
-                require: BTreeMap::new(),
-                require_dev: BTreeMap::new(),
-                conflict: BTreeMap::new(),
-                provide: BTreeMap::new(),
-                replace: BTreeMap::new(),
+                require: indexmap::IndexMap::new(),
+                require_dev: indexmap::IndexMap::new(),
+                conflict: indexmap::IndexMap::new(),
+                provide: indexmap::IndexMap::new(),
+                replace: indexmap::IndexMap::new(),
                 suggest: None,
                 package_type: None,
                 autoload: None,
@@ -696,7 +694,7 @@ mod tests {
                 support: None,
                 funding: None,
                 time: None,
-                extra_fields: BTreeMap::new(),
+                extra_fields: indexmap::IndexMap::new(),
             }],
             packages_dev: Some(vec![LockedPackage {
                 name: "phpunit/phpunit".to_string(),
@@ -704,11 +702,11 @@ mod tests {
                 version_normalized: None,
                 source: None,
                 dist: None,
-                require: BTreeMap::new(),
-                require_dev: BTreeMap::new(),
-                conflict: BTreeMap::new(),
-                provide: BTreeMap::new(),
-                replace: BTreeMap::new(),
+                require: indexmap::IndexMap::new(),
+                require_dev: indexmap::IndexMap::new(),
+                conflict: indexmap::IndexMap::new(),
+                provide: indexmap::IndexMap::new(),
+                replace: indexmap::IndexMap::new(),
                 suggest: None,
                 package_type: None,
                 autoload: None,
@@ -721,7 +719,7 @@ mod tests {
                 support: None,
                 funding: None,
                 time: None,
-                extra_fields: BTreeMap::new(),
+                extra_fields: indexmap::IndexMap::new(),
             }]),
             aliases: vec![],
             minimum_stability: "stable".to_string(),
diff --git a/crates/mozart/src/commands/remove.rs b/crates/mozart/src/commands/remove.rs
index 5bb3be3..938a5d1 100644
--- a/crates/mozart/src/commands/remove.rs
+++ b/crates/mozart/src/commands/remove.rs
@@ -154,7 +154,7 @@ pub async fn execute(
         if args.dev {
             if composer.require_dev.contains_key(&name) {
                 console_writeln!(io, "<info>Removing {name} from require-dev</info>");
-                composer.require_dev.remove(&name);
+                composer.require_dev.shift_remove(&name);
                 packages_removed.push(name);
             } else {
                 io.lock().unwrap().info(&console_format!(
@@ -163,11 +163,11 @@ pub async fn execute(
             }
         } else if composer.require.contains_key(&name) {
             console_writeln!(io, "<info>Removing {name} from require</info>");
-            composer.require.remove(&name);
+            composer.require.shift_remove(&name);
             packages_removed.push(name);
         } else if composer.require_dev.contains_key(&name) {
             console_writeln!(io, "<info>Removing {name} from require-dev</info>");
-            composer.require_dev.remove(&name);
+            composer.require_dev.shift_remove(&name);
             packages_removed.push(name);
         } else {
             io.lock().unwrap().info(&console_format!(
@@ -682,7 +682,6 @@ mod tests {
     use super::*;
     use mozart_core::package::RawPackageData;
     use mozart_core::repository::lockfile;
-    use std::collections::BTreeMap;
 
     fn make_locked_package(name: &str, version: &str) -> lockfile::LockedPackage {
         lockfile::LockedPackage {
@@ -691,11 +690,11 @@ mod tests {
             version_normalized: Some(format!("{}.0", version)),
             source: None,
             dist: None,
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
-            provide: BTreeMap::new(),
-            replace: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
+            provide: indexmap::IndexMap::new(),
+            replace: indexmap::IndexMap::new(),
             suggest: None,
             package_type: Some("library".to_string()),
             autoload: None,
@@ -708,7 +707,7 @@ mod tests {
             support: None,
             funding: None,
             time: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         }
     }
 
@@ -746,7 +745,7 @@ mod tests {
 
         assert!(composer.require.contains_key("psr/log"));
 
-        composer.require.remove("psr/log");
+        composer.require.shift_remove("psr/log");
 
         assert!(
             !composer.require.contains_key("psr/log"),
@@ -771,7 +770,7 @@ mod tests {
 
         assert!(composer.require_dev.contains_key("phpunit/phpunit"));
 
-        composer.require_dev.remove("phpunit/phpunit");
+        composer.require_dev.shift_remove("phpunit/phpunit");
 
         assert!(
             !composer.require_dev.contains_key("phpunit/phpunit"),
@@ -792,8 +791,8 @@ mod tests {
             .insert("psr/log".to_string(), "^3.0".to_string());
 
         let name = "nonexistent/package";
-        let found_in_require = composer.require.remove(name).is_some();
-        let found_in_require_dev = composer.require_dev.remove(name).is_some();
+        let found_in_require = composer.require.shift_remove(name).is_some();
+        let found_in_require_dev = composer.require_dev.shift_remove(name).is_some();
 
         assert!(!found_in_require);
         assert!(!found_in_require_dev);
@@ -814,9 +813,9 @@ mod tests {
             .insert("phpunit/phpunit".to_string(), "^11.0".to_string());
 
         let name = "psr/log";
-        let removed_from_require = composer.require.remove(name).is_some();
+        let removed_from_require = composer.require.shift_remove(name).is_some();
         let removed_from_dev = if !removed_from_require {
-            composer.require_dev.remove(name).is_some()
+            composer.require_dev.shift_remove(name).is_some()
         } else {
             false
         };
@@ -842,9 +841,9 @@ mod tests {
             .insert("phpunit/phpunit".to_string(), "^11.0".to_string());
 
         let name = "phpunit/phpunit";
-        let removed_from_require = composer.require.remove(name).is_some();
+        let removed_from_require = composer.require.shift_remove(name).is_some();
         let removed_from_dev = if !removed_from_require {
-            composer.require_dev.remove(name).is_some()
+            composer.require_dev.shift_remove(name).is_some()
         } else {
             false
         };
@@ -894,8 +893,8 @@ mod tests {
 
         // A glob-style name: not a valid exact package name, not in require either.
         let name = "vendor/*";
-        let found =
-            composer.require.remove(name).is_some() || composer.require_dev.remove(name).is_some();
+        let found = composer.require.shift_remove(name).is_some()
+            || composer.require_dev.shift_remove(name).is_some();
 
         // Should NOT be found (falls through to "not required" warning), not panicked/bailed.
         assert!(!found, "glob name should not match any package");
@@ -1001,7 +1000,7 @@ mod tests {
             .write_to_file(&lock_path)
             .expect("should write initial lock file");
 
-        composer.require.remove("psr/log");
+        composer.require.shift_remove("psr/log");
         package::write_to_file(&composer, &composer_path).unwrap();
 
         let request2 = ResolveRequest {
@@ -1084,7 +1083,7 @@ mod tests {
         std::fs::write(&composer_path, content).unwrap();
 
         let mut composer: RawPackageData = serde_json::from_str(content).unwrap();
-        composer.require.remove("psr/log");
+        composer.require.shift_remove("psr/log");
         package::write_to_file(&composer, &composer_path).unwrap();
 
         assert!(
diff --git a/crates/mozart/src/commands/require.rs b/crates/mozart/src/commands/require.rs
index 3d5fcd6..f92442c 100644
--- a/crates/mozart/src/commands/require.rs
+++ b/crates/mozart/src/commands/require.rs
@@ -1026,9 +1026,9 @@ pub async fn execute(
     // Remove from the opposite section before inserting into the target.
     for pkg in &inconsistent {
         if args.dev {
-            raw.require.remove(pkg.as_str());
+            raw.require.shift_remove(pkg.as_str());
         } else {
-            raw.require_dev.remove(pkg.as_str());
+            raw.require_dev.shift_remove(pkg.as_str());
         }
     }
 
@@ -1066,10 +1066,8 @@ pub async fn execute(
     let sort_packages = args.sort_packages || config_sort_packages;
 
     if sort_packages {
-        let sorted_require: std::collections::BTreeMap<_, _> = raw.require.clone();
-        raw.require = sorted_require;
-        let sorted_dev: std::collections::BTreeMap<_, _> = raw.require_dev.clone();
-        raw.require_dev = sorted_dev;
+        raw.require.sort_unstable_keys();
+        raw.require_dev.sort_unstable_keys();
     }
 
     // --- Write composer.json (unless --dry-run) ---
@@ -1129,7 +1127,6 @@ pub async fn execute(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::collections::BTreeMap;
 
     fn make_locked_package(name: &str, version: &str) -> lockfile::LockedPackage {
         lockfile::LockedPackage {
@@ -1138,11 +1135,11 @@ mod tests {
             version_normalized: Some(format!("{}.0", version)),
             source: None,
             dist: None,
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
-            provide: BTreeMap::new(),
-            replace: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
+            provide: indexmap::IndexMap::new(),
+            replace: indexmap::IndexMap::new(),
             suggest: None,
             package_type: Some("library".to_string()),
             autoload: None,
@@ -1155,7 +1152,7 @@ mod tests {
             support: None,
             funding: None,
             time: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         }
     }
 
@@ -1176,35 +1173,6 @@ mod tests {
         }
     }
 
-    /// Verify that --sort-packages sorts both require and require-dev maps.
-    #[test]
-    fn test_sort_packages_sorts_both_sections() {
-        use mozart_core::package::RawPackageData;
-
-        let mut raw = RawPackageData::new("test/project".to_string());
-        raw.require
-            .insert("z/package".to_string(), "^1.0".to_string());
-        raw.require
-            .insert("a/package".to_string(), "^2.0".to_string());
-        raw.require
-            .insert("m/package".to_string(), "^3.0".to_string());
-        raw.require_dev
-            .insert("z/dev".to_string(), "^1.0".to_string());
-        raw.require_dev
-            .insert("a/dev".to_string(), "^2.0".to_string());
-
-        let sorted_require: BTreeMap<String, String> = raw.require.clone();
-        raw.require = sorted_require;
-        let sorted_dev: BTreeMap<String, String> = raw.require_dev.clone();
-        raw.require_dev = sorted_dev;
-
-        let require_keys: Vec<_> = raw.require.keys().collect();
-        assert_eq!(require_keys, vec!["a/package", "m/package", "z/package"]);
-
-        let dev_keys: Vec<_> = raw.require_dev.keys().collect();
-        assert_eq!(dev_keys, vec!["a/dev", "z/dev"]);
-    }
-
     /// Verify that compute_update_changes produces correct Install entries for new packages.
     #[test]
     fn test_require_change_report_new_packages() {
diff --git a/crates/mozart/src/commands/show.rs b/crates/mozart/src/commands/show.rs
index d0a2218..81eaaad 100644
--- a/crates/mozart/src/commands/show.rs
+++ b/crates/mozart/src/commands/show.rs
@@ -6,7 +6,6 @@ use mozart_core::console_writeln;
 use mozart_core::console_writeln_error;
 use mozart_core::matches_wildcard;
 use mozart_core::platform::is_platform_package;
-use std::collections::BTreeMap;
 use std::path::Path;
 
 #[derive(Default, Args)]
@@ -255,15 +254,15 @@ struct PackageDetail {
     support: Option<serde_json::Value>,
     /// A13: autoload rules.
     autoload: Option<serde_json::Value>,
-    require: BTreeMap<String, String>,
-    require_dev: BTreeMap<String, String>,
+    require: indexmap::IndexMap<String, String>,
+    require_dev: indexmap::IndexMap<String, String>,
     /// A12: conflict links.
-    conflict: BTreeMap<String, String>,
+    conflict: indexmap::IndexMap<String, String>,
     /// A12: provide links.
-    provide: BTreeMap<String, String>,
+    provide: indexmap::IndexMap<String, String>,
     /// A12: replace links.
-    replace: BTreeMap<String, String>,
-    suggest: BTreeMap<String, String>,
+    replace: indexmap::IndexMap<String, String>,
+    suggest: indexmap::IndexMap<String, String>,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -1132,7 +1131,7 @@ async fn print_package_detail(
 /// Print a named section of package links (requires, conflict, etc.).
 fn print_links_section(
     label: &str,
-    links: &BTreeMap<String, String>,
+    links: &indexmap::IndexMap<String, String>,
     io: std::sync::Arc<std::sync::Mutex<Box<dyn IoInterface>>>,
 ) {
     if links.is_empty() {
@@ -2077,7 +2076,7 @@ fn get_installed_release_date(
 fn get_installed_link_map(
     pkg: &mozart_core::repository::installed::InstalledPackageEntry,
     key: &str,
-) -> BTreeMap<String, String> {
+) -> indexmap::IndexMap<String, String> {
     pkg.extra_fields
         .get(key)
         .and_then(|v| v.as_object())
@@ -2092,7 +2091,7 @@ fn get_installed_link_map(
 /// Extract a map of `{package: reason}` from an installed package's suggest field.
 fn get_installed_suggest_map(
     pkg: &mozart_core::repository::installed::InstalledPackageEntry,
-) -> BTreeMap<String, String> {
+) -> indexmap::IndexMap<String, String> {
     pkg.extra_fields
         .get("suggest")
         .and_then(|v| v.as_object())
@@ -2268,8 +2267,7 @@ mod tests {
 
     #[test]
     fn test_get_installed_description_present() {
-        use std::collections::BTreeMap;
-        let mut extra = BTreeMap::new();
+        let mut extra = indexmap::IndexMap::new();
         extra.insert(
             "description".to_string(),
             serde_json::Value::String("A logging library".to_string()),
@@ -2293,7 +2291,6 @@ mod tests {
 
     #[test]
     fn test_get_installed_description_absent() {
-        use std::collections::BTreeMap;
         let pkg = mozart_core::repository::installed::InstalledPackageEntry {
             name: "psr/log".to_string(),
             version: "3.0.0".to_string(),
@@ -2306,15 +2303,14 @@ mod tests {
             aliases: vec![],
             homepage: None,
             support: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         };
         assert_eq!(get_installed_description(&pkg), "");
     }
 
     #[test]
     fn test_get_installed_keywords() {
-        use std::collections::BTreeMap;
-        let mut extra = BTreeMap::new();
+        let mut extra = indexmap::IndexMap::new();
         extra.insert(
             "keywords".to_string(),
             serde_json::json!(["log", "psr3", "logging"]),
diff --git a/crates/mozart/src/commands/suggests.rs b/crates/mozart/src/commands/suggests.rs
index b882f5c..ca8e5fe 100644
--- a/crates/mozart/src/commands/suggests.rs
+++ b/crates/mozart/src/commands/suggests.rs
@@ -235,11 +235,10 @@ fn build_root_info(root: Option<&mozart_core::package::RawPackageData>) -> RootI
 mod tests {
     use super::*;
     use mozart_core::installer::{HasSuggests, InstalledRepoLite, RootInfo};
-    use std::collections::BTreeMap;
 
     fn make_locked_package(
         name: &str,
-        suggest: Option<BTreeMap<String, String>>,
+        suggest: Option<indexmap::IndexMap<String, String>>,
     ) -> mozart_core::repository::lockfile::LockedPackage {
         mozart_core::repository::lockfile::LockedPackage {
             name: name.to_string(),
@@ -247,11 +246,11 @@ mod tests {
             version_normalized: None,
             source: None,
             dist: None,
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
-            provide: BTreeMap::new(),
-            replace: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
+            provide: indexmap::IndexMap::new(),
+            replace: indexmap::IndexMap::new(),
             suggest,
             package_type: None,
             autoload: None,
@@ -264,15 +263,15 @@ mod tests {
             support: None,
             funding: None,
             time: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         }
     }
 
     fn make_installed_entry(
         name: &str,
-        suggest: Option<BTreeMap<String, String>>,
+        suggest: Option<indexmap::IndexMap<String, String>>,
     ) -> mozart_core::repository::installed::InstalledPackageEntry {
-        let mut extra_fields: BTreeMap<String, serde_json::Value> = BTreeMap::new();
+        let mut extra_fields = indexmap::IndexMap::new();
         if let Some(s) = suggest {
             let map: serde_json::Map<String, serde_json::Value> = s
                 .into_iter()
@@ -322,7 +321,7 @@ mod tests {
 
     #[test]
     fn locked_package_implements_has_suggests() {
-        let mut suggest = BTreeMap::new();
+        let mut suggest = indexmap::IndexMap::new();
         suggest.insert("ext-intl".to_string(), "for i18n".to_string());
         suggest.insert("ext-redis".to_string(), "for cache".to_string());
         let pkg = make_locked_package("vendor/a", Some(suggest));
@@ -333,7 +332,7 @@ mod tests {
 
     #[test]
     fn installed_entry_reads_suggest_from_extra_fields() {
-        let mut suggest = BTreeMap::new();
+        let mut suggest = indexmap::IndexMap::new();
         suggest.insert("ext-redis".to_string(), "for cache".to_string());
         let entry = make_installed_entry("vendor/cache", Some(suggest));
         let pairs = entry.suggests();
@@ -413,15 +412,15 @@ mod tests {
             license: None,
             authors: vec![],
             minimum_stability: None,
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
-            provide: BTreeMap::new(),
-            replace: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
+            provide: indexmap::IndexMap::new(),
+            replace: indexmap::IndexMap::new(),
             repositories: vec![],
             autoload: None,
             bin: vec![],
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         };
         root.require.insert("vendor/a".into(), "^1.0".into());
         root.require_dev.insert("vendor/b".into(), "^2.0".into());
@@ -437,7 +436,7 @@ mod tests {
         let console = console();
         let mut reporter = SuggestedPackagesReporter::new(&console);
 
-        let mut suggest = BTreeMap::new();
+        let mut suggest = indexmap::IndexMap::new();
         suggest.insert("ext-intl".to_string(), "for i18n".to_string());
         suggest.insert("vendor/optional".to_string(), "Optional".to_string());
         let pkg = make_locked_package("vendor/a", Some(suggest));
@@ -452,7 +451,7 @@ mod tests {
         let console = console();
         let mut reporter = SuggestedPackagesReporter::new(&console);
 
-        let mut suggest = BTreeMap::new();
+        let mut suggest = indexmap::IndexMap::new();
         suggest.insert("vendor/already-here".to_string(), "".to_string());
         suggest.insert("vendor/not-here".to_string(), "".to_string());
         let pkg = make_locked_package("vendor/a", Some(suggest));
diff --git a/crates/mozart/src/commands/update.rs b/crates/mozart/src/commands/update.rs
index f482272..334e221 100644
--- a/crates/mozart/src/commands/update.rs
+++ b/crates/mozart/src/commands/update.rs
@@ -1803,7 +1803,6 @@ pub async fn run(
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::collections::BTreeMap;
 
     fn make_locked_package(name: &str, version: &str) -> lockfile::LockedPackage {
         lockfile::LockedPackage {
@@ -1812,11 +1811,11 @@ mod tests {
             version_normalized: Some(format!("{}.0", version)),
             source: None,
             dist: None,
-            require: BTreeMap::new(),
-            require_dev: BTreeMap::new(),
-            conflict: BTreeMap::new(),
-            provide: BTreeMap::new(),
-            replace: BTreeMap::new(),
+            require: indexmap::IndexMap::new(),
+            require_dev: indexmap::IndexMap::new(),
+            conflict: indexmap::IndexMap::new(),
+            provide: indexmap::IndexMap::new(),
+            replace: indexmap::IndexMap::new(),
             suggest: None,
             package_type: Some("library".to_string()),
             autoload: None,
@@ -1829,7 +1828,7 @@ mod tests {
             support: None,
             funding: None,
             time: None,
-            extra_fields: BTreeMap::new(),
+            extra_fields: indexmap::IndexMap::new(),
         }
     }
 
diff --git a/crates/mozart/src/factory.rs b/crates/mozart/src/factory.rs
index 41f157a..581b53a 100644
--- a/crates/mozart/src/factory.rs
+++ b/crates/mozart/src/factory.rs
@@ -368,7 +368,7 @@ mod tests {
             r#"{"name": "acme/app", "require": {"vendor/pkg": "^1.0"}}"#,
         );
 
-        use mozart_core::package::Package;
+        use mozart_core::package::PackageInterface;
         let composer = Composer::require(io(), dir.path()).unwrap();
         assert_eq!(composer.package().name(), "acme/app");
         assert_eq!(