diff --git a/fuzzers/baby_fuzzer_multi/.gitignore b/fuzzers/baby_fuzzer_multi/.gitignore
new file mode 100644
index 0000000000..a977a2ca5b
--- /dev/null
+++ b/fuzzers/baby_fuzzer_multi/.gitignore
@@ -0,0 +1 @@
+libpng-*
\ No newline at end of file
diff --git a/fuzzers/baby_fuzzer_multi/Cargo.toml b/fuzzers/baby_fuzzer_multi/Cargo.toml
new file mode 100644
index 0000000000..04ab2364b4
--- /dev/null
+++ b/fuzzers/baby_fuzzer_multi/Cargo.toml
@@ -0,0 +1,24 @@
+[package]
+name = "baby_fuzzer_multi"
+version = "0.10.0"
+authors = ["Andrea Fioraldi <andreafioraldi@gmail.com>", "Dominik Maier <domenukk@gmail.com>", "Addison Crump <me@addisoncrump.info>"]
+edition = "2021"
+
+[features]
+default = ["std"]
+tui = []
+std = []
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"
+lto = true
+codegen-units = 1
+opt-level = 3
+debug = true
+
+[dependencies]
+libafl = { path = "../../libafl/", features = ["multipart_inputs"] }
+libafl_bolts = { path = "../../libafl_bolts/" }
diff --git a/fuzzers/baby_fuzzer_multi/README.md b/fuzzers/baby_fuzzer_multi/README.md
new file mode 100644
index 0000000000..74e1b50932
--- /dev/null
+++ b/fuzzers/baby_fuzzer_multi/README.md
@@ -0,0 +1,10 @@
+# Baby fuzzer multi
+
+This is a minimalistic example about how to create a libafl based fuzzer for targets with multipart inputs.
+
+It runs on a single core until a crash occurs and then exits.
+
+The tested program is a simple Rust function without any instrumentation.
+For real fuzzing, you will want to add some sort to add coverage or other feedback.
+
+You can run this example using `cargo run`, and you can enable the TUI feature by running `cargo run --features tui`.
\ No newline at end of file
diff --git a/fuzzers/baby_fuzzer_multi/src/main.rs b/fuzzers/baby_fuzzer_multi/src/main.rs
new file mode 100644
index 0000000000..f462c20b70
--- /dev/null
+++ b/fuzzers/baby_fuzzer_multi/src/main.rs
@@ -0,0 +1,164 @@
+#[cfg(windows)]
+use std::ptr::write_volatile;
+use std::{path::PathBuf, ptr::write};
+
+#[cfg(feature = "tui")]
+use libafl::monitors::tui::{ui::TuiUI, TuiMonitor};
+#[cfg(not(feature = "tui"))]
+use libafl::monitors::SimpleMonitor;
+use libafl::{
+    corpus::{InMemoryCorpus, OnDiskCorpus},
+    events::SimpleEventManager,
+    executors::{inprocess::InProcessExecutor, ExitKind},
+    feedback_or_fast,
+    feedbacks::{CrashFeedback, MaxMapFeedback, MinMapFeedback},
+    fuzzer::{Fuzzer, StdFuzzer},
+    inputs::{BytesInput, HasTargetBytes, MultipartInput},
+    mutators::scheduled::{havoc_mutations, StdScheduledMutator},
+    observers::StdMapObserver,
+    schedulers::QueueScheduler,
+    stages::mutational::StdMutationalStage,
+    state::StdState,
+    Evaluator,
+};
+use libafl_bolts::{current_nanos, rands::StdRand, tuples::tuple_list, AsSlice};
+
+/// Coverage map with explicit assignments due to the lack of instrumentation
+static mut SIGNALS: [u8; 128] = [0; 128];
+static mut SIGNALS_PTR: *mut u8 = unsafe { SIGNALS.as_mut_ptr() };
+
+/// "Coverage" map for count, just to help things along
+static mut LAST_COUNT: [usize; 1] = [usize::MAX];
+static mut LAST_COUNT_PTR: *mut usize = unsafe { LAST_COUNT.as_mut_ptr() };
+
+/// Assign a signal to the signals map
+fn signals_set(idx: usize) {
+    unsafe { write(SIGNALS_PTR.add(idx), 1) };
+}
+
+/// Assign a count to the count "map"
+fn count_set(count: usize) {
+    unsafe { LAST_COUNT[0] = count };
+}
+
+#[allow(clippy::similar_names, clippy::manual_assert)]
+pub fn main() {
+    // The closure that we want to fuzz
+    let mut harness = |input: &MultipartInput<BytesInput>| {
+        let mut count = input.parts().len();
+        for (i, input) in input.parts().iter().enumerate() {
+            let target = input.target_bytes();
+            let buf = target.as_slice();
+            signals_set(i * 8);
+            if !buf.is_empty() && buf[0] == b'a' {
+                signals_set(1 + i * 8);
+                if buf.len() > 1 && buf[1] == b'b' {
+                    signals_set(2 + i * 8);
+                    if buf.len() > 2 && buf[2] == b'c' {
+                        count -= 1;
+                    }
+                }
+            }
+        }
+        if count == 0 {
+            #[cfg(unix)]
+            panic!("Artificial bug triggered =)");
+
+            // panic!() raises a STATUS_STACK_BUFFER_OVERRUN exception which cannot be caught by the exception handler.
+            // Here we make it raise STATUS_ACCESS_VIOLATION instead.
+            // Extending the windows exception handler is a TODO. Maybe we can refer to what winafl code does.
+            // https://github.com/googleprojectzero/winafl/blob/ea5f6b85572980bb2cf636910f622f36906940aa/winafl.c#L728
+            #[cfg(windows)]
+            unsafe {
+                write_volatile(0 as *mut u32, 0);
+            }
+        }
+
+        // without this, artificial bug is not found
+        // maybe interesting to try to auto-derive this, researchers! :)
+        count_set(count);
+
+        ExitKind::Ok
+    };
+
+    // Create an observation channel using the signals map
+    let signals_observer =
+        unsafe { StdMapObserver::from_mut_ptr("signals", SIGNALS_PTR, SIGNALS.len()) };
+    let mut count_observer =
+        unsafe { StdMapObserver::from_mut_ptr("count", LAST_COUNT_PTR, LAST_COUNT.len()) };
+    *count_observer.initial_mut() = usize::MAX; // we are minimising!
+
+    // Feedback to rate the interestingness of an input
+    let signals_feedback = MaxMapFeedback::new(&signals_observer);
+    let count_feedback = MinMapFeedback::new(&count_observer);
+
+    let mut feedback = feedback_or_fast!(count_feedback, signals_feedback);
+
+    // A feedback to choose if an input is a solution or not
+    let mut objective = CrashFeedback::new();
+
+    // create a State from scratch
+    let mut state = StdState::new(
+        // RNG
+        StdRand::with_seed(current_nanos()),
+        // Corpus that will be evolved, we keep it in memory for performance
+        InMemoryCorpus::new(),
+        // Corpus in which we store solutions (crashes in this example),
+        // on disk so the user can get them after stopping the fuzzer
+        OnDiskCorpus::new(PathBuf::from("./crashes")).unwrap(),
+        // States of the feedbacks.
+        // The feedbacks can report the data that should persist in the State.
+        &mut feedback,
+        // Same for objective feedbacks
+        &mut objective,
+    )
+    .unwrap();
+
+    // The Monitor trait define how the fuzzer stats are displayed to the user
+    #[cfg(not(feature = "tui"))]
+    let mon = SimpleMonitor::new(|s| println!("{s}"));
+    #[cfg(feature = "tui")]
+    let ui = TuiUI::with_version(String::from("Baby Fuzzer"), String::from("0.0.1"), false);
+    #[cfg(feature = "tui")]
+    let mon = TuiMonitor::new(ui);
+
+    // The event manager handle the various events generated during the fuzzing loop
+    // such as the notification of the addition of a new item to the corpus
+    let mut mgr = SimpleEventManager::new(mon);
+
+    // A queue policy to get testcasess from the corpus
+    let scheduler = QueueScheduler::new();
+
+    // A fuzzer with feedbacks and a corpus scheduler
+    let mut fuzzer = StdFuzzer::new(scheduler, feedback, objective);
+
+    // Create the executor for an in-process function with just one observer
+    let mut executor = InProcessExecutor::new(
+        &mut harness,
+        tuple_list!(signals_observer, count_observer),
+        &mut fuzzer,
+        &mut state,
+        &mut mgr,
+    )
+    .expect("Failed to create the Executor");
+
+    // a generator here is not generalisable
+    let initial = MultipartInput::from([
+        ("part", BytesInput::new(vec![b'h', b'e', b'l', b'l', b'o'])),
+        ("part", BytesInput::new(vec![b'h', b'e', b'l', b'l', b'o'])),
+        ("part", BytesInput::new(vec![b'h', b'e', b'l', b'l', b'o'])),
+        ("part", BytesInput::new(vec![b'h', b'e', b'l', b'l', b'o'])),
+    ]);
+
+    fuzzer
+        .evaluate_input(&mut state, &mut executor, &mut mgr, initial)
+        .unwrap();
+
+    // Setup a mutational stage with a basic bytes mutator
+    let mutator = StdScheduledMutator::new(havoc_mutations());
+    let mut stages = tuple_list!(StdMutationalStage::new(mutator));
+
+    fuzzer
+        .fuzz_loop(&mut stages, &mut executor, &mut state, &mut mgr)
+        .expect("Error in the fuzzing loop");
+}
diff --git a/libafl/Cargo.toml b/libafl/Cargo.toml
index c313f264da..e0a79e8c5a 100644
--- a/libafl/Cargo.toml
+++ b/libafl/Cargo.toml
@@ -85,6 +85,8 @@ tui_monitor = ["ratatui", "crossterm"]
 ## Enables `StringClassificationStage` and associated mutators, which allow for mutations which preserve the Unicode property data
 unicode = ["libafl_bolts/alloc", "ahash/std", "serde/rc", "bitvec", "reqwest", "zip"]
 
+## Enable multi-part input formats and mutators
+multipart_inputs = ["arrayvec", "rand_trait"]
 
 #! ## LibAFL-Bolts Features
 
@@ -186,6 +188,8 @@ libcasr = { version = "2.7", optional = true }
 
 bitvec = { version = "1.0", optional = true, features = ["serde"] } # used for string range storage
 
+arrayvec = { version = "0.7.4", optional = true, default-features = false } # used for fixed-len collects
+
 # optional-dev deps (change when target.'cfg(accessible(::std))'.test-dependencies will be stable)
 serial_test = { version = "2", optional = true, default-features = false, features = ["logging"] }
 
diff --git a/libafl/src/inputs/mod.rs b/libafl/src/inputs/mod.rs
index 08fa39caea..883537d882 100644
--- a/libafl/src/inputs/mod.rs
+++ b/libafl/src/inputs/mod.rs
@@ -12,8 +12,14 @@ pub use gramatron::*;
 pub mod generalized;
 pub use generalized::*;
 
+#[cfg(feature = "multipart_inputs")]
+pub mod multi;
+#[cfg(feature = "multipart_inputs")]
+pub use multi::*;
+
 #[cfg(feature = "nautilus")]
 pub mod nautilus;
+
 use alloc::{
     boxed::Box,
     string::{String, ToString},
diff --git a/libafl/src/inputs/multi.rs b/libafl/src/inputs/multi.rs
new file mode 100644
index 0000000000..750495ae64
--- /dev/null
+++ b/libafl/src/inputs/multi.rs
@@ -0,0 +1,165 @@
+//! Definitions for inputs which have multiple distinct subcomponents.
+//!
+//! Unfortunately, since both [`serde::de::Deserialize`] and [`Clone`] require [`Sized`], it is not
+//! possible to dynamically define a single input with dynamic typing. As such, [`MultipartInput`]
+//! requires that each subcomponent be the same subtype.
+
+use alloc::{
+    string::{String, ToString},
+    vec::Vec,
+};
+
+use arrayvec::ArrayVec;
+use serde::{Deserialize, Serialize};
+
+use crate::inputs::Input;
+
+/// An input composed of multiple parts. Use in situations where subcomponents are not necessarily
+/// related, or represent distinct parts of the input.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct MultipartInput<I> {
+    parts: Vec<I>,
+    names: Vec<String>,
+}
+
+impl<I> Default for MultipartInput<I> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<I> MultipartInput<I> {
+    /// Create a new multipart input.
+    #[must_use]
+    pub fn new() -> Self {
+        Self {
+            parts: Vec::new(),
+            names: Vec::new(),
+        }
+    }
+
+    fn idxs_to_skips(idxs: &mut [usize]) {
+        for following in (1..idxs.len()).rev() {
+            let first = idxs[following - 1];
+            let second = idxs[following];
+
+            idxs[following] = second
+                .checked_sub(first)
+                .expect("idxs was not sorted")
+                .checked_sub(1)
+                .expect("idxs had duplicate elements");
+        }
+    }
+
+    /// Get the individual parts of this input.
+    #[must_use]
+    pub fn parts(&self) -> &[I] {
+        &self.parts
+    }
+
+    /// Access multiple parts mutably.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if idxs is not sorted, has duplicate elements, or any entry is out of bounds.
+    #[must_use]
+    pub fn parts_mut<const N: usize>(&mut self, mut idxs: [usize; N]) -> [&mut I; N] {
+        Self::idxs_to_skips(&mut idxs);
+
+        let mut parts = self.parts.iter_mut();
+        if let Ok(arr) = idxs
+            .into_iter()
+            .map(|i| parts.nth(i).expect("idx had an out of bounds entry"))
+            .collect::<ArrayVec<_, N>>()
+            .into_inner()
+        {
+            arr
+        } else {
+            // avoid Debug trait requirement for expect/unwrap
+            panic!("arrayvec collection failed somehow")
+        }
+    }
+
+    /// Get a specific part of this input by index.
+    pub fn part_mut(&mut self, idx: usize) -> Option<&mut I> {
+        self.parts.get_mut(idx)
+    }
+
+    /// Get the names associated with the subparts of this input. Used to distinguish between the
+    /// input components in the case where some parts may or may not be present, or in different
+    /// orders.
+    #[must_use]
+    pub fn names(&self) -> &[String] {
+        &self.names
+    }
+
+    /// Gets a reference to each part with the provided name.
+    pub fn parts_by_name<'a, 'b>(
+        &'b self,
+        name: &'a str,
+    ) -> impl Iterator<Item = (usize, &'b I)> + 'a
+    where
+        'b: 'a,
+    {
+        self.names()
+            .iter()
+            .zip(&self.parts)
+            .enumerate()
+            .filter_map(move |(i, (s, item))| (s == name).then_some((i, item)))
+    }
+
+    /// Gets a mutable reference to each part with the provided name.
+    pub fn parts_by_name_mut<'a, 'b>(
+        &'b mut self,
+        name: &'a str,
+    ) -> impl Iterator<Item = (usize, &'b mut I)> + 'a
+    where
+        'b: 'a,
+    {
+        self.names
+            .iter()
+            .zip(&mut self.parts)
+            .enumerate()
+            .filter_map(move |(i, (s, item))| (s == name).then_some((i, item)))
+    }
+
+    /// Adds a part to this input, potentially with the same name as an existing part.
+    pub fn add_part(&mut self, name: String, part: I) {
+        self.parts.push(part);
+        self.names.push(name);
+    }
+
+    /// Iterate over the parts of this input; no order is specified.
+    pub fn iter(&self) -> impl Iterator<Item = (&str, &I)> {
+        self.names.iter().map(String::as_ref).zip(self.parts())
+    }
+}
+
+impl<I, It, S> From<It> for MultipartInput<I>
+where
+    It: IntoIterator<Item = (S, I)>,
+    S: AsRef<str>,
+{
+    fn from(parts: It) -> Self {
+        let mut input = MultipartInput::new();
+        for (name, part) in parts {
+            input.add_part(name.as_ref().to_string(), part);
+        }
+        input
+    }
+}
+
+impl<I> Input for MultipartInput<I>
+where
+    I: Input,
+{
+    fn generate_name(&self, idx: usize) -> String {
+        self.names
+            .iter()
+            .cloned()
+            .zip(self.parts.iter().map(|i| i.generate_name(idx)))
+            .map(|(name, generated)| format!("{name}-{generated}"))
+            .collect::<Vec<_>>()
+            .join(",")
+    }
+}
diff --git a/libafl/src/mutators/mod.rs b/libafl/src/mutators/mod.rs
index e3560bd673..7232b0e800 100644
--- a/libafl/src/mutators/mod.rs
+++ b/libafl/src/mutators/mod.rs
@@ -25,8 +25,14 @@ pub mod string;
 #[cfg(feature = "unicode")]
 pub use string::*;
 
+#[cfg(feature = "multipart_inputs")]
+pub mod multi;
+#[cfg(feature = "multipart_inputs")]
+pub use multi::*;
+
 #[cfg(feature = "nautilus")]
 pub mod nautilus;
+
 use alloc::vec::Vec;
 
 use libafl_bolts::{tuples::HasConstLen, Named};
diff --git a/libafl/src/mutators/multi.rs b/libafl/src/mutators/multi.rs
new file mode 100644
index 0000000000..838703a8f6
--- /dev/null
+++ b/libafl/src/mutators/multi.rs
@@ -0,0 +1,330 @@
+//! Mutator definitions for [`MultipartInput`]s. See [`crate::inputs::multi`] for details.
+
+use core::cmp::{min, Ordering};
+
+use libafl_bolts::{rands::Rand, Error};
+
+use crate::{
+    corpus::{Corpus, CorpusId},
+    impl_default_multipart,
+    inputs::{multi::MultipartInput, HasBytesVec, Input},
+    mutators::{
+        mutations::{
+            rand_range, BitFlipMutator, ByteAddMutator, ByteDecMutator, ByteFlipMutator,
+            ByteIncMutator, ByteInterestingMutator, ByteNegMutator, ByteRandMutator,
+            BytesCopyMutator, BytesDeleteMutator, BytesExpandMutator, BytesInsertCopyMutator,
+            BytesInsertMutator, BytesRandInsertMutator, BytesRandSetMutator, BytesSetMutator,
+            BytesSwapMutator, CrossoverInsertMutator, CrossoverReplaceMutator, DwordAddMutator,
+            DwordInterestingMutator, QwordAddMutator, WordAddMutator, WordInterestingMutator,
+        },
+        token_mutations::{I2SRandReplace, TokenInsert, TokenReplace},
+        MutationResult, Mutator,
+    },
+    random_corpus_id,
+    state::{HasCorpus, HasMaxSize, HasRand},
+};
+
+/// Marker trait for if the default multipart input mutator implementation is appropriate.
+///
+/// You should implement this type for your mutator if you just want a random part of the input to
+/// be selected and mutated. Use [`impl_default_multipart`] to implement this marker trait for many
+/// at once.
+pub trait DefaultMultipartMutator {}
+
+impl<I, M, S> Mutator<MultipartInput<I>, S> for M
+where
+    M: DefaultMultipartMutator + Mutator<I, S>,
+    S: HasRand,
+{
+    fn mutate(
+        &mut self,
+        state: &mut S,
+        input: &mut MultipartInput<I>,
+        stage_idx: i32,
+    ) -> Result<MutationResult, Error> {
+        if input.parts().is_empty() {
+            Ok(MutationResult::Skipped)
+        } else {
+            let selected = state.rand_mut().below(input.parts().len() as u64) as usize;
+            let mutated = input.part_mut(selected).unwrap();
+            self.mutate(state, mutated, stage_idx)
+        }
+    }
+
+    fn post_exec(
+        &mut self,
+        state: &mut S,
+        stage_idx: i32,
+        corpus_idx: Option<CorpusId>,
+    ) -> Result<(), Error> {
+        M::post_exec(self, state, stage_idx, corpus_idx)
+    }
+}
+
+mod macros {
+    /// Implements the marker trait [`super::DefaultMultipartMutator`] for one to many types, e.g.:
+    ///
+    /// ```rs
+    /// impl_default_multipart!(
+    ///     // --- havoc ---
+    ///     BitFlipMutator,
+    ///     ByteAddMutator,
+    ///     ByteDecMutator,
+    ///     ByteFlipMutator,
+    ///     ByteIncMutator,
+    ///     ...
+    /// );
+    /// ```
+    #[macro_export]
+    macro_rules! impl_default_multipart {
+        ($mutator: ty, $($mutators: ty),+$(,)?) => {
+            impl $crate::mutators::multi::DefaultMultipartMutator for $mutator {}
+            impl_default_multipart!($($mutators),+);
+        };
+
+        ($mutator: ty) => {
+            impl $crate::mutators::multi::DefaultMultipartMutator for $mutator {}
+        };
+    }
+}
+
+impl_default_multipart!(
+    // --- havoc ---
+    BitFlipMutator,
+    ByteAddMutator,
+    ByteDecMutator,
+    ByteFlipMutator,
+    ByteIncMutator,
+    ByteInterestingMutator,
+    ByteNegMutator,
+    ByteRandMutator,
+    BytesCopyMutator,
+    BytesDeleteMutator,
+    BytesExpandMutator,
+    BytesInsertCopyMutator,
+    BytesInsertMutator,
+    BytesRandInsertMutator,
+    BytesRandSetMutator,
+    BytesSetMutator,
+    BytesSwapMutator,
+    // crossover has a custom implementation below
+    DwordAddMutator,
+    DwordInterestingMutator,
+    QwordAddMutator,
+    WordAddMutator,
+    WordInterestingMutator,
+    // --- token ---
+    TokenInsert,
+    TokenReplace,
+    // ---  i2s  ---
+    I2SRandReplace,
+);
+
+impl<I, S> Mutator<MultipartInput<I>, S> for CrossoverInsertMutator<I>
+where
+    S: HasCorpus<Input = MultipartInput<I>> + HasMaxSize + HasRand,
+    I: Input + HasBytesVec,
+{
+    fn mutate(
+        &mut self,
+        state: &mut S,
+        input: &mut MultipartInput<I>,
+        _stage_idx: i32,
+    ) -> Result<MutationResult, Error> {
+        // we can eat the slight bias; number of parts will be small
+        let name_choice = state.rand_mut().next() as usize;
+        let part_choice = state.rand_mut().next() as usize;
+
+        // We special-case crossover with self
+        let idx = random_corpus_id!(state.corpus(), state.rand_mut());
+        if let Some(cur) = state.corpus().current() {
+            if idx == *cur {
+                let choice = name_choice % input.names().len();
+                let name = input.names()[choice].clone();
+
+                let other_size = input.parts()[choice].bytes().len();
+                if other_size < 2 {
+                    return Ok(MutationResult::Skipped);
+                }
+
+                let parts = input.parts_by_name(&name).count() - 1;
+
+                if parts == 0 {
+                    return Ok(MutationResult::Skipped);
+                }
+
+                let maybe_size = input
+                    .parts_by_name(&name)
+                    .filter(|&(p, _)| p != choice)
+                    .nth(part_choice % parts)
+                    .map(|(idx, part)| (idx, part.bytes().len()));
+
+                if let Some((part_idx, size)) = maybe_size {
+                    let target = state.rand_mut().below(size as u64) as usize;
+                    let range = rand_range(state, other_size, min(other_size, size - target));
+
+                    let [part, chosen] = match part_idx.cmp(&choice) {
+                        Ordering::Less => input.parts_mut([part_idx, choice]),
+                        Ordering::Equal => {
+                            unreachable!("choice should never equal the part idx!")
+                        }
+                        Ordering::Greater => {
+                            let [chosen, part] = input.parts_mut([choice, part_idx]);
+                            [part, chosen]
+                        }
+                    };
+
+                    return Ok(Self::crossover_insert(part, size, target, range, chosen));
+                }
+
+                return Ok(MutationResult::Skipped);
+            }
+        }
+
+        let mut other_testcase = state.corpus().get(idx)?.borrow_mut();
+        let other = other_testcase.load_input(state.corpus())?;
+
+        let choice = name_choice % other.names().len();
+        let name = &other.names()[choice];
+
+        let other_size = other.parts()[choice].bytes().len();
+        if other_size < 2 {
+            return Ok(MutationResult::Skipped);
+        }
+
+        let parts = input.parts_by_name(name).count();
+
+        if parts > 0 {
+            let (_, part) = input
+                .parts_by_name_mut(name)
+                .nth(part_choice % parts)
+                .unwrap();
+            drop(other_testcase);
+            let size = part.bytes().len();
+
+            let target = state.rand_mut().below(size as u64) as usize;
+            let range = rand_range(state, other_size, min(other_size, size - target));
+
+            let other_testcase = state.corpus().get(idx)?.borrow_mut();
+            // No need to load the input again, it'll still be cached.
+            let other = other_testcase.input().as_ref().unwrap();
+
+            Ok(Self::crossover_insert(
+                part,
+                size,
+                target,
+                range,
+                &other.parts()[choice],
+            ))
+        } else {
+            // just add it!
+            input.add_part(name.clone(), other.parts()[choice].clone());
+
+            Ok(MutationResult::Mutated)
+        }
+    }
+}
+
+impl<I, S> Mutator<MultipartInput<I>, S> for CrossoverReplaceMutator<I>
+where
+    S: HasCorpus<Input = MultipartInput<I>> + HasMaxSize + HasRand,
+    I: Input + HasBytesVec,
+{
+    fn mutate(
+        &mut self,
+        state: &mut S,
+        input: &mut MultipartInput<I>,
+        _stage_idx: i32,
+    ) -> Result<MutationResult, Error> {
+        // we can eat the slight bias; number of parts will be small
+        let name_choice = state.rand_mut().next() as usize;
+        let part_choice = state.rand_mut().next() as usize;
+
+        // We special-case crossover with self
+        let idx = random_corpus_id!(state.corpus(), state.rand_mut());
+        if let Some(cur) = state.corpus().current() {
+            if idx == *cur {
+                let choice = name_choice % input.names().len();
+                let name = input.names()[choice].clone();
+
+                let other_size = input.parts()[choice].bytes().len();
+                if other_size < 2 {
+                    return Ok(MutationResult::Skipped);
+                }
+
+                let parts = input.parts_by_name(&name).count() - 1;
+
+                if parts == 0 {
+                    return Ok(MutationResult::Skipped);
+                }
+
+                let maybe_size = input
+                    .parts_by_name(&name)
+                    .filter(|&(p, _)| p != choice)
+                    .nth(part_choice % parts)
+                    .map(|(idx, part)| (idx, part.bytes().len()));
+
+                if let Some((part_idx, size)) = maybe_size {
+                    let target = state.rand_mut().below(size as u64) as usize;
+                    let range = rand_range(state, other_size, min(other_size, size - target));
+
+                    let [part, chosen] = match part_idx.cmp(&choice) {
+                        Ordering::Less => input.parts_mut([part_idx, choice]),
+                        Ordering::Equal => {
+                            unreachable!("choice should never equal the part idx!")
+                        }
+                        Ordering::Greater => {
+                            let [chosen, part] = input.parts_mut([choice, part_idx]);
+                            [part, chosen]
+                        }
+                    };
+
+                    return Ok(Self::crossover_replace(part, target, range, chosen));
+                }
+
+                return Ok(MutationResult::Skipped);
+            }
+        }
+
+        let mut other_testcase = state.corpus().get(idx)?.borrow_mut();
+        let other = other_testcase.load_input(state.corpus())?;
+
+        let choice = name_choice % other.names().len();
+        let name = &other.names()[choice];
+
+        let other_size = other.parts()[choice].bytes().len();
+        if other_size < 2 {
+            return Ok(MutationResult::Skipped);
+        }
+
+        let parts = input.parts_by_name(name).count();
+
+        if parts > 0 {
+            let (_, part) = input
+                .parts_by_name_mut(name)
+                .nth(part_choice % parts)
+                .unwrap();
+            drop(other_testcase);
+            let size = part.bytes().len();
+
+            let target = state.rand_mut().below(size as u64) as usize;
+            let range = rand_range(state, other_size, min(other_size, size - target));
+
+            let other_testcase = state.corpus().get(idx)?.borrow_mut();
+            // No need to load the input again, it'll still be cached.
+            let other = other_testcase.input().as_ref().unwrap();
+
+            Ok(Self::crossover_replace(
+                part,
+                target,
+                range,
+                &other.parts()[choice],
+            ))
+        } else {
+            // just add it!
+            input.add_part(name.clone(), other.parts()[choice].clone());
+
+            Ok(MutationResult::Mutated)
+        }
+    }
+}
diff --git a/libafl/src/mutators/mutations.rs b/libafl/src/mutators/mutations.rs
index 2e19892873..935973f6a5 100644
--- a/libafl/src/mutators/mutations.rs
+++ b/libafl/src/mutators/mutations.rs
@@ -1,13 +1,13 @@
 //! A wide variety of mutations used during fuzzing.
 
 use alloc::{borrow::ToOwned, vec::Vec};
-use core::{cmp::min, mem::size_of, ops::Range};
+use core::{cmp::min, marker::PhantomData, mem::size_of, ops::Range};
 
 use libafl_bolts::{rands::Rand, Named};
 
 use crate::{
     corpus::Corpus,
-    inputs::HasBytesVec,
+    inputs::{HasBytesVec, Input},
     mutators::{MutationResult, Mutator},
     random_corpus_id,
     state::{HasCorpus, HasMaxSize, HasRand},
@@ -1085,12 +1085,45 @@ impl BytesSwapMutator {
 
 /// Crossover insert mutation for inputs with a bytes vector
 #[derive(Debug, Default)]
-pub struct CrossoverInsertMutator;
+pub struct CrossoverInsertMutator<I> {
+    phantom: PhantomData<I>,
+}
+
+impl<I: HasBytesVec> CrossoverInsertMutator<I> {
+    pub(crate) fn crossover_insert(
+        input: &mut I,
+        size: usize,
+        target: usize,
+        range: Range<usize>,
+        other: &I,
+    ) -> MutationResult {
+        input.bytes_mut().resize(size + range.len(), 0);
+        unsafe {
+            buffer_self_copy(
+                input.bytes_mut(),
+                target,
+                target + range.len(),
+                size - target,
+            );
+        }
+
+        unsafe {
+            buffer_copy(
+                input.bytes_mut(),
+                other.bytes(),
+                range.start,
+                target,
+                range.len(),
+            );
+        }
+        MutationResult::Mutated
+    }
+}
 
-impl<S> Mutator<S::Input, S> for CrossoverInsertMutator
+impl<I, S> Mutator<I, S> for CrossoverInsertMutator<I>
 where
-    S: HasCorpus + HasRand + HasMaxSize,
-    S::Input: HasBytesVec,
+    S: HasCorpus<Input = I> + HasRand + HasMaxSize,
+    I: Input + HasBytesVec,
 {
     fn mutate(
         &mut self,
@@ -1125,55 +1158,60 @@ where
         let range = rand_range(state, other_size, min(other_size, max_size - size));
         let target = state.rand_mut().below(size as u64) as usize;
 
-        input.bytes_mut().resize(size + range.len(), 0);
-        unsafe {
-            buffer_self_copy(
-                input.bytes_mut(),
-                target,
-                target + range.len(),
-                size - target,
-            );
-        }
-
         let other_testcase = state.corpus().get(idx)?.borrow_mut();
         // No need to load the input again, it'll still be cached.
         let other = other_testcase.input().as_ref().unwrap();
 
-        unsafe {
-            buffer_copy(
-                input.bytes_mut(),
-                other.bytes(),
-                range.start,
-                target,
-                range.len(),
-            );
-        }
-        Ok(MutationResult::Mutated)
+        Ok(Self::crossover_insert(input, size, target, range, other))
     }
 }
 
-impl Named for CrossoverInsertMutator {
+impl<I> Named for CrossoverInsertMutator<I> {
     fn name(&self) -> &str {
         "CrossoverInsertMutator"
     }
 }
 
-impl CrossoverInsertMutator {
+impl<I> CrossoverInsertMutator<I> {
     /// Creates a new [`CrossoverInsertMutator`].
     #[must_use]
     pub fn new() -> Self {
-        Self
+        Self {
+            phantom: PhantomData,
+        }
     }
 }
 
 /// Crossover replace mutation for inputs with a bytes vector
 #[derive(Debug, Default)]
-pub struct CrossoverReplaceMutator;
+pub struct CrossoverReplaceMutator<I> {
+    phantom: PhantomData<I>,
+}
 
-impl<S> Mutator<S::Input, S> for CrossoverReplaceMutator
+impl<I: HasBytesVec> CrossoverReplaceMutator<I> {
+    pub(crate) fn crossover_replace(
+        input: &mut I,
+        target: usize,
+        range: Range<usize>,
+        other: &I,
+    ) -> MutationResult {
+        unsafe {
+            buffer_copy(
+                input.bytes_mut(),
+                other.bytes(),
+                range.start,
+                target,
+                range.len(),
+            );
+        }
+        MutationResult::Mutated
+    }
+}
+
+impl<I, S> Mutator<I, S> for CrossoverReplaceMutator<I>
 where
-    S: HasCorpus + HasRand,
-    S::Input: HasBytesVec,
+    S: HasCorpus<Input = I> + HasRand,
+    I: Input + HasBytesVec,
 {
     fn mutate(
         &mut self,
@@ -1210,30 +1248,23 @@ where
         // No need to load the input again, it'll still be cached.
         let other = other_testcase.input().as_ref().unwrap();
 
-        unsafe {
-            buffer_copy(
-                input.bytes_mut(),
-                other.bytes(),
-                range.start,
-                target,
-                range.len(),
-            );
-        }
-        Ok(MutationResult::Mutated)
+        Ok(Self::crossover_replace(input, target, range, other))
     }
 }
 
-impl Named for CrossoverReplaceMutator {
+impl<I> Named for CrossoverReplaceMutator<I> {
     fn name(&self) -> &str {
         "CrossoverReplaceMutator"
     }
 }
 
-impl CrossoverReplaceMutator {
+impl<I> CrossoverReplaceMutator<I> {
     /// Creates a new [`CrossoverReplaceMutator`].
     #[must_use]
     pub fn new() -> Self {
-        Self
+        Self {
+            phantom: PhantomData,
+        }
     }
 }
 
diff --git a/libafl/src/mutators/scheduled.rs b/libafl/src/mutators/scheduled.rs
index 3627d9fee8..ffdab9e92d 100644
--- a/libafl/src/mutators/scheduled.rs
+++ b/libafl/src/mutators/scheduled.rs
@@ -258,10 +258,11 @@ pub type HavocMutationsNoCrossoverType = tuple_list_type!(
 );
 
 /// Tuple type of the mutations that compose the Havoc mutator's crossover mutations
-pub type HavocCrossoverType = tuple_list_type!(CrossoverInsertMutator, CrossoverReplaceMutator);
+pub type HavocCrossoverType<I> =
+    tuple_list_type!(CrossoverInsertMutator<I>, CrossoverReplaceMutator<I>);
 
 /// Tuple type of the mutations that compose the Havoc mutator
-pub type HavocMutationsType = tuple_list_type!(
+pub type HavocMutationsType<I> = tuple_list_type!(
     BitFlipMutator,
     ByteFlipMutator,
     ByteIncMutator,
@@ -287,8 +288,8 @@ pub type HavocMutationsType = tuple_list_type!(
     BytesCopyMutator,
     BytesInsertCopyMutator,
     BytesSwapMutator,
-    CrossoverInsertMutator,
-    CrossoverReplaceMutator,
+    CrossoverInsertMutator<I>,
+    CrossoverReplaceMutator<I>,
 );
 
 /// Get the mutations that compose the Havoc mutator (only applied to single inputs)
@@ -325,7 +326,7 @@ pub fn havoc_mutations_no_crossover() -> HavocMutationsNoCrossoverType {
 
 /// Get the mutations that compose the Havoc mutator's crossover strategy
 #[must_use]
-pub fn havoc_crossover() -> HavocCrossoverType {
+pub fn havoc_crossover<I>() -> HavocCrossoverType<I> {
     tuple_list!(
         CrossoverInsertMutator::new(),
         CrossoverReplaceMutator::new(),
@@ -334,14 +335,14 @@ pub fn havoc_crossover() -> HavocCrossoverType {
 
 /// Get the mutations that compose the Havoc mutator
 #[must_use]
-pub fn havoc_mutations() -> HavocMutationsType {
+pub fn havoc_mutations<I>() -> HavocMutationsType<I> {
     havoc_mutations_no_crossover().merge(havoc_crossover())
 }
 
 /// Get the mutations that uses the Tokens metadata
 #[must_use]
 pub fn tokens_mutations() -> tuple_list_type!(TokenInsert, TokenReplace) {
-    tuple_list!(TokenInsert::new(), TokenReplace::new(),)
+    tuple_list!(TokenInsert::new(), TokenReplace::new())
 }
 
 /// A logging [`Mutator`] that wraps around a [`StdScheduledMutator`].
@@ -617,7 +618,7 @@ pub mod pybind {
     /// Python class for StdHavocMutator
     pub struct PythonStdHavocMutator {
         /// Rust wrapped StdHavocMutator object
-        pub inner: StdScheduledMutator<BytesInput, HavocMutationsType, PythonStdState>,
+        pub inner: StdScheduledMutator<BytesInput, HavocMutationsType<BytesInput>, PythonStdState>,
     }
 
     #[pymethods]
diff --git a/libafl/src/observers/map.rs b/libafl/src/observers/map.rs
index 50becd968b..ed68926378 100644
--- a/libafl/src/observers/map.rs
+++ b/libafl/src/observers/map.rs
@@ -542,6 +542,11 @@ where
         )
     }
 
+    /// Gets the initial value for this map, mutably
+    pub fn initial_mut(&mut self) -> &mut T {
+        &mut self.initial
+    }
+
     /// Gets the backing for this map
     pub fn map(&self) -> &OwnedMutSlice<'a, T> {
         &self.map