compressed repr. should store disc as part of data

Author: SwenSchaeferjohann

external/photon

@@ -63,15 +63,13 @@ impl AccountInterface {
     }
 
     /// Create a cold account interface for a PDA/mint.
+    ///
+    /// `data.data` contains the full on-chain account bytes as-is (no reassembly needed).
     pub fn cold(key: Pubkey, compressed: CompressedAccount, owner: Pubkey) -> Self {
         let data = compressed
             .data
             .as_ref()
-            .map(|d| {
-                let mut buf = d.discriminator.to_vec();
-                buf.extend_from_slice(&d.data);
-                buf
-            })
+            .map(|d| d.data.clone())
             .unwrap_or_default();
 
         Self {

sdk-libs/client/src/interface/account_interface.rs

@@ -3,6 +3,8 @@
 //! These functions are generic over account types and can be reused by the macro.
 //! The compress flow uses a dispatch callback pattern (same as decompress).
 
+use alloc::vec::Vec;
+
 use light_account_checks::AccountInfoTrait;
 use light_compressed_account::{
     address::derive_address,
@@ -111,8 +113,11 @@ where
     *compressed_data.compression_info_mut()? =
         crate::interface::account::compression_info::CompressionInfo::compressed();
 
-    // Hash the data (discriminator NOT included per protocol convention)
-    let data_bytes = borsh::to_vec(&compressed_data).map_err(|_| LightSdkTypesError::Borsh)?;
+    // Serialize with disc prefix: disc(8) + borsh(struct) — mirrors on-chain layout.
+    let borsh_bytes = borsh::to_vec(&compressed_data).map_err(|_| LightSdkTypesError::Borsh)?;
+    let mut data_bytes = Vec::with_capacity(8 + borsh_bytes.len());
+    data_bytes.extend_from_slice(&A::LIGHT_DISCRIMINATOR);
+    data_bytes.extend_from_slice(&borsh_bytes);
     let mut output_data_hash = Sha256::hash(&data_bytes).map_err(LightSdkTypesError::Hasher)?;
     output_data_hash[0] = 0; // Zero first byte per protocol convention
 

sdk-libs/sdk-types/src/interface/program/compression/pda.rs

@@ -92,11 +92,15 @@ where
         return Ok(());
     }
 
-    // 5. Hash with canonical CompressionInfo::compressed() for input verification
-    let data_bytes = account_data
+    // 5. Hash with canonical CompressionInfo::compressed() for input verification.
+    // data = disc(8) + borsh(struct) — mirrors on-chain layout.
+    let borsh_bytes = account_data
         .try_to_vec()
         .map_err(|_| LightSdkTypesError::Borsh)?;
-    let data_len = data_bytes.len();
+    let data_len = borsh_bytes.len();
+    let mut data_bytes = Vec::with_capacity(8 + data_len);
+    data_bytes.extend_from_slice(&<Data<SEED_COUNT, P> as LightDiscriminator>::LIGHT_DISCRIMINATOR);
+    data_bytes.extend_from_slice(&borsh_bytes);
     let mut input_data_hash = Sha256BE::hash(&data_bytes)?;
     input_data_hash[0] = 0; // Zero first byte per protocol convention