diff --git a/Cargo.lock b/Cargo.lock
index dd33b7672..18d0531a6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2457,6 +2457,7 @@ dependencies = [
  "pyo3",
  "pyo3-log",
  "regex",
+ "schemars",
  "serde",
  "serde_json",
  "testing_logger",
@@ -4598,6 +4599,8 @@ dependencies = [
  "fs-err",
  "insta",
  "install-wheel-rs",
+ "pep508_rs",
+ "pypi-types",
  "serde",
  "url",
  "uv-cache",
diff --git a/crates/pep508-rs/Cargo.toml b/crates/pep508-rs/Cargo.toml
index 9b9b18ea7..8718af923 100644
--- a/crates/pep508-rs/Cargo.toml
+++ b/crates/pep508-rs/Cargo.toml
@@ -26,6 +26,7 @@ pep440_rs = { workspace = true }
 pyo3 = { workspace = true, optional = true, features = ["abi3", "extension-module"] }
 pyo3-log = { workspace = true, optional = true }
 regex = { workspace = true }
+schemars = { workspace = true, optional = true }
 serde = { workspace = true, features = ["derive", "rc"] }
 serde_json = { workspace = true, optional = true }
 thiserror = { workspace = true }
@@ -44,6 +45,7 @@ testing_logger = { version = "0.1.1" }
 [features]
 pyo3 = ["dep:pyo3", "pep440_rs/pyo3", "pyo3-log", "tracing", "tracing/log"]
 tracing = ["dep:tracing", "pep440_rs/tracing"]
+schemars = ["dep:schemars"]
 # PEP 508 allows only URLs such as `foo @ https://example.org/foo` or `foo @ file:///home/ferris/foo`, and
 # arguably does not allow relative paths in file URLs (`foo @ file://./foo`,
 # `foo @ file:foo-3.0.0-py3-none-any.whl`, `foo @ file://foo-3.0.0-py3-none-any.whl`), as they are not part of the
diff --git a/crates/pep508-rs/src/lib.rs b/crates/pep508-rs/src/lib.rs
index ffdc95f72..3e27464c0 100644
--- a/crates/pep508-rs/src/lib.rs
+++ b/crates/pep508-rs/src/lib.rs
@@ -33,6 +33,8 @@ use pyo3::{
     create_exception, exceptions::PyNotImplementedError, pyclass, pyclass::CompareOp, pymethods,
     pymodule, types::PyModule, IntoPy, PyObject, PyResult, Python,
 };
+use schemars::gen::SchemaGenerator;
+use schemars::schema::Schema;
 use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
 use thiserror::Error;
 use url::Url;
@@ -489,6 +491,25 @@ impl Reporter for TracingReporter {
     }
 }
 
+#[cfg(feature = "schemars")]
+impl<T: Pep508Url> schemars::JsonSchema for Requirement<T> {
+    fn schema_name() -> String {
+        "Requirement".to_string()
+    }
+
+    fn json_schema(_gen: &mut SchemaGenerator) -> Schema {
+        schemars::schema::SchemaObject {
+            instance_type: Some(schemars::schema::InstanceType::String.into()),
+            metadata: Some(Box::new(schemars::schema::Metadata {
+                description: Some("A PEP 508 dependency specifier".to_string()),
+                ..schemars::schema::Metadata::default()
+            })),
+            ..schemars::schema::SchemaObject::default()
+        }
+        .into()
+    }
+}
+
 impl<T: Pep508Url> FromStr for Requirement<T> {
     type Err = Pep508Error<T>;
 
diff --git a/crates/uv-cli/Cargo.toml b/crates/uv-cli/Cargo.toml
index 0083cacc8..063490dd1 100644
--- a/crates/uv-cli/Cargo.toml
+++ b/crates/uv-cli/Cargo.toml
@@ -16,12 +16,14 @@ workspace = true
 [dependencies]
 distribution-types = { workspace = true }
 install-wheel-rs = { workspace = true, features = ["clap"], default-features = false }
+pep508_rs = { workspace = true }
+pypi-types = { workspace = true }
 uv-cache = { workspace = true, features = ["clap"] }
 uv-configuration = { workspace = true, features = ["clap"] }
 uv-normalize = { workspace = true }
+uv-python = { workspace = true, features = ["clap", "schemars"]}
 uv-resolver = { workspace = true, features = ["clap"] }
 uv-settings = { workspace = true, features = ["schemars"] }
-uv-python = { workspace = true, features = ["clap", "schemars"]}
 uv-version = { workspace = true }
 uv-warnings = { workspace = true }
 
diff --git a/crates/uv-cli/src/lib.rs b/crates/uv-cli/src/lib.rs
index f94d3af33..6ae5c0dfe 100644
--- a/crates/uv-cli/src/lib.rs
+++ b/crates/uv-cli/src/lib.rs
@@ -7,6 +7,8 @@ use anyhow::{anyhow, Result};
 use clap::{Args, Parser, Subcommand};
 
 use distribution_types::{FlatIndexLocation, IndexUrl};
+use pep508_rs::Requirement;
+use pypi_types::VerbatimParsedUrl;
 use uv_cache::CacheArgs;
 use uv_configuration::{
     ConfigSettingEntry, IndexStrategy, KeyringProviderType, PackageNameSpecifier, TargetTriple,
@@ -300,7 +302,7 @@ pub enum PipCommand {
         after_help = "Use `uv help pip sync` for more details.",
         after_long_help = ""
     )]
-    Sync(PipSyncArgs),
+    Sync(Box<PipSyncArgs>),
     /// Install packages into an environment.
     #[command(
         after_help = "Use `uv help pip install` for more details.",
@@ -2408,7 +2410,7 @@ pub struct ResolverArgs {
     /// Allow upgrades for a specific package, ignoring pinned versions in any existing output
     /// file.
     #[arg(long, short = 'P')]
-    pub upgrade_package: Vec<PackageName>,
+    pub upgrade_package: Vec<Requirement<VerbatimParsedUrl>>,
 
     /// The strategy to use when resolving against multiple index URLs.
     ///
@@ -2484,7 +2486,7 @@ pub struct ResolverInstallerArgs {
     /// Allow upgrades for a specific package, ignoring pinned versions in any existing output
     /// file.
     #[arg(long, short = 'P')]
-    pub upgrade_package: Vec<PackageName>,
+    pub upgrade_package: Vec<Requirement<VerbatimParsedUrl>>,
 
     /// Reinstall all packages, regardless of whether they're already installed.
     #[arg(long, alias = "force-reinstall", overrides_with("no_reinstall"))]
diff --git a/crates/uv-configuration/Cargo.toml b/crates/uv-configuration/Cargo.toml
index e1e3bdc6c..894237547 100644
--- a/crates/uv-configuration/Cargo.toml
+++ b/crates/uv-configuration/Cargo.toml
@@ -13,7 +13,7 @@ license = { workspace = true }
 workspace = true
 
 [dependencies]
-pep508_rs = { workspace = true }
+pep508_rs = { workspace = true, features = ["schemars"] }
 platform-tags = { workspace = true }
 pypi-types = { workspace = true }
 uv-auth = { workspace = true }
diff --git a/crates/uv-configuration/src/constraints.rs b/crates/uv-configuration/src/constraints.rs
index 10150f1ec..4bea7359b 100644
--- a/crates/uv-configuration/src/constraints.rs
+++ b/crates/uv-configuration/src/constraints.rs
@@ -1,8 +1,10 @@
-use either::Either;
-use pep508_rs::MarkerTree;
-use pypi_types::Requirement;
-use rustc_hash::{FxBuildHasher, FxHashMap};
 use std::borrow::Cow;
+
+use either::Either;
+use rustc_hash::FxHashMap;
+
+use pep508_rs::MarkerTree;
+use pypi_types::{Requirement, RequirementSource};
 use uv_normalize::PackageName;
 
 /// A set of constraints for a set of requirements.
@@ -11,10 +13,16 @@ pub struct Constraints(FxHashMap<PackageName, Vec<Requirement>>);
 
 impl Constraints {
     /// Create a new set of constraints from a set of requirements.
-    pub fn from_requirements(requirements: Vec<Requirement>) -> Self {
-        let mut constraints: FxHashMap<PackageName, Vec<Requirement>> =
-            FxHashMap::with_capacity_and_hasher(requirements.len(), FxBuildHasher);
+    pub fn from_requirements(requirements: impl Iterator<Item = Requirement>) -> Self {
+        let mut constraints: FxHashMap<PackageName, Vec<Requirement>> = FxHashMap::default();
         for requirement in requirements {
+            // Skip empty constraints.
+            if let RequirementSource::Registry { specifier, .. } = &requirement.source {
+                if specifier.is_empty() {
+                    continue;
+                }
+            }
+
             constraints
                 .entry(requirement.name.clone())
                 .or_default()
diff --git a/crates/uv-configuration/src/package_options.rs b/crates/uv-configuration/src/package_options.rs
index e9b5bd56d..928f03aef 100644
--- a/crates/uv-configuration/src/package_options.rs
+++ b/crates/uv-configuration/src/package_options.rs
@@ -1,6 +1,8 @@
+use either::Either;
 use pep508_rs::PackageName;
 
-use rustc_hash::FxHashSet;
+use pypi_types::Requirement;
+use rustc_hash::FxHashMap;
 
 /// Whether to reinstall packages.
 #[derive(Debug, Default, Clone)]
@@ -54,12 +56,12 @@ pub enum Upgrade {
     All,
 
     /// Allow package upgrades, but only for the specified packages.
-    Packages(FxHashSet<PackageName>),
+    Packages(FxHashMap<PackageName, Vec<Requirement>>),
 }
 
 impl Upgrade {
     /// Determine the upgrade strategy from the command-line arguments.
-    pub fn from_args(upgrade: Option<bool>, upgrade_package: Vec<PackageName>) -> Self {
+    pub fn from_args(upgrade: Option<bool>, upgrade_package: Vec<Requirement>) -> Self {
         match upgrade {
             Some(true) => Self::All,
             Some(false) => Self::None,
@@ -67,7 +69,15 @@ impl Upgrade {
                 if upgrade_package.is_empty() {
                     Self::None
                 } else {
-                    Self::Packages(upgrade_package.into_iter().collect())
+                    Self::Packages(upgrade_package.into_iter().fold(
+                        FxHashMap::default(),
+                        |mut map, requirement| {
+                            map.entry(requirement.name.clone())
+                                .or_default()
+                                .push(requirement);
+                            map
+                        },
+                    ))
                 }
             }
         }
@@ -82,4 +92,28 @@ impl Upgrade {
     pub fn is_all(&self) -> bool {
         matches!(self, Self::All)
     }
+
+    /// Returns `true` if the specified package should be upgraded.
+    pub fn contains(&self, package_name: &PackageName) -> bool {
+        match &self {
+            Self::None => false,
+            Self::All => true,
+            Self::Packages(packages) => packages.contains_key(package_name),
+        }
+    }
+
+    /// Returns an iterator over the constraints.
+    ///
+    /// When upgrading, users can provide bounds on the upgrade (e.g., `--upgrade-package flask<3`).
+    pub fn constraints(&self) -> impl Iterator<Item = &Requirement> {
+        if let Self::Packages(packages) = self {
+            Either::Right(
+                packages
+                    .values()
+                    .flat_map(|requirements| requirements.iter()),
+            )
+        } else {
+            Either::Left(std::iter::empty())
+        }
+    }
 }
diff --git a/crates/uv-requirements/src/upgrade.rs b/crates/uv-requirements/src/upgrade.rs
index 5e22b854b..2b1cfc6d5 100644
--- a/crates/uv-requirements/src/upgrade.rs
+++ b/crates/uv-requirements/src/upgrade.rs
@@ -56,7 +56,7 @@ pub async fn read_requirements_txt(
         // Ignore pinned versions for the specified packages.
         Upgrade::Packages(packages) => preferences
             .into_iter()
-            .filter(|preference| !packages.contains(preference.name()))
+            .filter(|preference| !packages.contains_key(preference.name()))
             .collect(),
     })
 }
@@ -68,11 +68,7 @@ pub fn read_lock_requirements(lock: &Lock, upgrade: &Upgrade) -> LockedRequireme
 
     for dist in lock.distributions() {
         // Skip the distribution if it's not included in the upgrade strategy.
-        if match upgrade {
-            Upgrade::None => false,
-            Upgrade::All => true,
-            Upgrade::Packages(packages) => packages.contains(dist.name()),
-        } {
+        if upgrade.contains(dist.name()) {
             continue;
         }
 
diff --git a/crates/uv-resolver/src/exclusions.rs b/crates/uv-resolver/src/exclusions.rs
index 34593af9d..59a4864b2 100644
--- a/crates/uv-resolver/src/exclusions.rs
+++ b/crates/uv-resolver/src/exclusions.rs
@@ -26,7 +26,7 @@ impl Exclusions {
                 };
 
             if let Upgrade::Packages(packages) = upgrade {
-                exclusions.extend(packages);
+                exclusions.extend(packages.into_keys());
             };
 
             if exclusions.is_empty() {
diff --git a/crates/uv-settings/src/settings.rs b/crates/uv-settings/src/settings.rs
index 83212c92f..e7a9e8e7b 100644
--- a/crates/uv-settings/src/settings.rs
+++ b/crates/uv-settings/src/settings.rs
@@ -4,6 +4,7 @@ use serde::Deserialize;
 
 use distribution_types::{FlatIndexLocation, IndexUrl};
 use install_wheel_rs::linker::LinkMode;
+use pep508_rs::Requirement;
 use pypi_types::VerbatimParsedUrl;
 use uv_configuration::{
     ConfigSettings, IndexStrategy, KeyringProviderType, PackageNameSpecifier, TargetTriple,
@@ -105,7 +106,7 @@ pub struct ResolverOptions {
     pub exclude_newer: Option<ExcludeNewer>,
     pub link_mode: Option<LinkMode>,
     pub upgrade: Option<bool>,
-    pub upgrade_package: Option<Vec<PackageName>>,
+    pub upgrade_package: Option<Vec<Requirement<VerbatimParsedUrl>>>,
     pub no_build: Option<bool>,
     pub no_build_package: Option<Vec<PackageName>>,
     pub no_binary: Option<bool>,
@@ -132,7 +133,7 @@ pub struct ResolverInstallerOptions {
     pub link_mode: Option<LinkMode>,
     pub compile_bytecode: Option<bool>,
     pub upgrade: Option<bool>,
-    pub upgrade_package: Option<Vec<PackageName>>,
+    pub upgrade_package: Option<Vec<Requirement<VerbatimParsedUrl>>>,
     pub reinstall: Option<bool>,
     pub reinstall_package: Option<Vec<PackageName>>,
     pub no_build: Option<bool>,
@@ -193,7 +194,7 @@ pub struct PipOptions {
     pub compile_bytecode: Option<bool>,
     pub require_hashes: Option<bool>,
     pub upgrade: Option<bool>,
-    pub upgrade_package: Option<Vec<PackageName>>,
+    pub upgrade_package: Option<Vec<Requirement<VerbatimParsedUrl>>>,
     pub reinstall: Option<bool>,
     pub reinstall_package: Option<Vec<PackageName>>,
     pub concurrent_downloads: Option<NonZeroUsize>,
diff --git a/crates/uv/src/commands/pip/operations.rs b/crates/uv/src/commands/pip/operations.rs
index 0fd4cff54..29bb58548 100644
--- a/crates/uv/src/commands/pip/operations.rs
+++ b/crates/uv/src/commands/pip/operations.rs
@@ -180,7 +180,11 @@ pub(crate) async fn resolve<InstalledPackages: InstalledPackagesProvider>(
     .await?;
 
     // Collect constraints and overrides.
-    let constraints = Constraints::from_requirements(constraints);
+    let constraints = Constraints::from_requirements(
+        constraints
+            .into_iter()
+            .chain(upgrade.constraints().cloned()),
+    );
     let overrides = Overrides::from_requirements(overrides);
     let preferences = Preferences::from_iter(preferences, markers);
 
diff --git a/crates/uv/src/settings.rs b/crates/uv/src/settings.rs
index fc896f108..215809156 100644
--- a/crates/uv/src/settings.rs
+++ b/crates/uv/src/settings.rs
@@ -798,7 +798,7 @@ pub(crate) struct PipSyncSettings {
 
 impl PipSyncSettings {
     /// Resolve the [`PipSyncSettings`] from the CLI and filesystem configuration.
-    pub(crate) fn resolve(args: PipSyncArgs, filesystem: Option<FilesystemOptions>) -> Self {
+    pub(crate) fn resolve(args: Box<PipSyncArgs>, filesystem: Option<FilesystemOptions>) -> Self {
         let PipSyncArgs {
             src_file,
             constraint,
@@ -829,7 +829,7 @@ impl PipSyncSettings {
             no_strict,
             dry_run,
             compat_args: _,
-        } = args;
+        } = *args;
 
         Self {
             src_file,
@@ -1384,7 +1384,10 @@ impl ResolverSettings {
                 args.upgrade.combine(upgrade),
                 args.upgrade_package
                     .combine(upgrade_package)
-                    .unwrap_or_default(),
+                    .into_iter()
+                    .flatten()
+                    .map(Requirement::from)
+                    .collect(),
             ),
             build_options: BuildOptions::new(
                 NoBinary::from_args(
@@ -1522,7 +1525,10 @@ impl ResolverInstallerSettings {
                 args.upgrade.combine(upgrade),
                 args.upgrade_package
                     .combine(upgrade_package)
-                    .unwrap_or_default(),
+                    .into_iter()
+                    .flatten()
+                    .map(Requirement::from)
+                    .collect(),
             ),
             reinstall: Reinstall::from_args(
                 args.reinstall.combine(reinstall),
@@ -1841,7 +1847,10 @@ impl PipSettings {
                 args.upgrade.combine(upgrade),
                 args.upgrade_package
                     .combine(upgrade_package)
-                    .unwrap_or_default(),
+                    .into_iter()
+                    .flatten()
+                    .map(Requirement::from)
+                    .collect(),
             ),
             reinstall: Reinstall::from_args(
                 args.reinstall.combine(reinstall),
diff --git a/crates/uv/tests/pip_compile.rs b/crates/uv/tests/pip_compile.rs
index c55dadd8b..693d27fa4 100644
--- a/crates/uv/tests/pip_compile.rs
+++ b/crates/uv/tests/pip_compile.rs
@@ -4770,6 +4770,61 @@ fn upgrade_package() -> Result<()> {
     Ok(())
 }
 
+/// Upgrade a package with a constraint on the allowed upgrade.
+#[test]
+fn upgrade_constraint() -> Result<()> {
+    let context = TestContext::new("3.12");
+    let requirements_in = context.temp_dir.child("requirements.in");
+    requirements_in.write_str("iniconfig")?;
+
+    let requirements_txt = context.temp_dir.child("requirements.txt");
+    requirements_txt.write_str(indoc! {r"
+        # This file was autogenerated by uv via the following command:
+        #    uv pip compile requirements.in --python-version 3.12 --cache-dir [CACHE_DIR]
+        iniconfig==1.0.0
+    "})?;
+
+    uv_snapshot!(context.pip_compile()
+            .arg("requirements.in")
+            .arg("--output-file")
+            .arg("requirements.txt")
+            .arg("--upgrade-package")
+            .arg("iniconfig<2"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt --upgrade-package iniconfig<2
+    iniconfig==1.1.1
+        # via -r requirements.in
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    "###
+    );
+
+    uv_snapshot!(context.pip_compile()
+            .arg("requirements.in")
+            .arg("--output-file")
+            .arg("requirements.txt")
+            .arg("--upgrade-package")
+            .arg("iniconfig"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    # This file was autogenerated by uv via the following command:
+    #    uv pip compile --cache-dir [CACHE_DIR] requirements.in --output-file requirements.txt --upgrade-package iniconfig
+    iniconfig==2.0.0
+        # via -r requirements.in
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    "###
+    );
+
+    Ok(())
+}
+
 /// Attempt to resolve a requirement at a path that doesn't exist.
 #[test]
 fn missing_path_requirement() -> Result<()> {
diff --git a/uv.schema.json b/uv.schema.json
index 61e7b2d7b..2f1f309a2 100644
--- a/uv.schema.json
+++ b/uv.schema.json
@@ -267,7 +267,7 @@
         "null"
       ],
       "items": {
-        "$ref": "#/definitions/PackageName"
+        "$ref": "#/definitions/Requirement"
       }
     },
     "workspace": {
@@ -826,7 +826,7 @@
             "null"
           ],
           "items": {
-            "$ref": "#/definitions/PackageName"
+            "$ref": "#/definitions/Requirement"
           }
         }
       },
@@ -933,6 +933,10 @@
       "type": "string",
       "pattern": "^3\\.\\d+(\\.\\d+)?$"
     },
+    "Requirement": {
+      "description": "A PEP 508 dependency specifier",
+      "type": "string"
+    },
     "ResolutionMode": {
       "oneOf": [
         {