diff --git a/Cargo.lock b/Cargo.lock
index b7ce6e6c10b..6c8217c3a7a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -12690,6 +12690,7 @@ version = "0.0.0"
 dependencies = [
  "blockifier",
  "blockifier_reexecution",
+ "cairo-lang-starknet-classes",
  "indexmap 2.12.0",
  "rstest",
  "starknet-rust",
diff --git a/crates/starknet_os_runner/Cargo.toml b/crates/starknet_os_runner/Cargo.toml
index 194798919ff..7331c690fa1 100644
--- a/crates/starknet_os_runner/Cargo.toml
+++ b/crates/starknet_os_runner/Cargo.toml
@@ -9,6 +9,7 @@ description = "Runs transactions through the Starknet OS and returns Cairo PIE a
 [dependencies]
 blockifier.workspace = true
 blockifier_reexecution.workspace = true
+cairo-lang-starknet-classes.workspace = true
 indexmap.workspace = true
 starknet-rust.workspace = true
 starknet-rust-core.workspace = true
diff --git a/crates/starknet_os_runner/src/classes_provider.rs b/crates/starknet_os_runner/src/classes_provider.rs
new file mode 100644
index 00000000000..88c9a9accaf
--- /dev/null
+++ b/crates/starknet_os_runner/src/classes_provider.rs
@@ -0,0 +1,26 @@
+use std::collections::{BTreeMap, HashSet};
+
+use cairo_lang_starknet_classes::casm_contract_class::CasmContractClass;
+use starknet_api::core::{ClassHash, CompiledClassHash};
+use starknet_api::deprecated_contract_class::ContractClass;
+
+use crate::errors::ClassesProviderError;
+
+/// The classes required for a Starknet OS run.
+/// Matches the fields in `StarknetOsInput` and `OsBlockInput`.
+pub struct ClassesInput {
+    /// Deprecated (Cairo 0) contract classes.
+    /// Maps ClassHash to the contract class definition.
+    pub deprecated_compiled_classes: BTreeMap<ClassHash, ContractClass>,
+    /// Cairo 1+ contract classes (CASM).
+    /// Maps CompiledClassHash to the CASM contract class definition.
+    pub compiled_classes: BTreeMap<CompiledClassHash, CasmContractClass>,
+}
+
+pub trait ClassesProvider {
+    /// Fetches all classes required for the OS run based on the executed class hashes.
+    fn get_classes(
+        &self,
+        executed_class_hashes: HashSet<ClassHash>,
+    ) -> Result<ClassesInput, ClassesProviderError>;
+}
diff --git a/crates/starknet_os_runner/src/errors.rs b/crates/starknet_os_runner/src/errors.rs
index 5b84cf13557..2c100af2d85 100644
--- a/crates/starknet_os_runner/src/errors.rs
+++ b/crates/starknet_os_runner/src/errors.rs
@@ -26,3 +26,9 @@ pub enum ProofProviderError {
     #[error("Invalid RPC proof response: {0}")]
     InvalidProofResponse(String),
 }
+
+#[derive(Debug, Error)]
+pub enum ClassesProviderError {
+    #[error("Failed to get classes: {0}")]
+    GetClassesError(String),
+}
diff --git a/crates/starknet_os_runner/src/lib.rs b/crates/starknet_os_runner/src/lib.rs
index 09d787718ad..1b836ca42de 100644
--- a/crates/starknet_os_runner/src/lib.rs
+++ b/crates/starknet_os_runner/src/lib.rs
@@ -1,3 +1,4 @@
+pub mod classes_provider;
 pub mod errors;
 pub mod storage_proofs;
 pub mod virtual_block_executor;