diff --git a/Cargo.lock b/Cargo.lock
index c79c8e4..ce998dc 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1180,6 +1180,7 @@ dependencies = [
  "reqwest",
  "serde",
  "serde_json",
+ "sha2",
  "thiserror 2.0.17",
  "toml",
 ]
diff --git a/mlf-cli/Cargo.toml b/mlf-cli/Cargo.toml
index be1bec7..6219b41 100644
--- a/mlf-cli/Cargo.toml
+++ b/mlf-cli/Cargo.toml
@@ -23,6 +23,7 @@ toml = "0.8"
 reqwest = { version = "0.12", features = ["blocking", "json"] }
 chrono = { version = "0.4", features = ["serde"] }
 hickory-resolver = "0.24"
+sha2 = "0.10"
 
 # Optional code generator plugins
 mlf-codegen-typescript = { path = "../codegen-plugins/mlf-codegen-typescript", optional = true }
diff --git a/mlf-cli/src/fetch.rs b/mlf-cli/src/fetch.rs
index 86175e2..a82ca0b 100644
--- a/mlf-cli/src/fetch.rs
+++ b/mlf-cli/src/fetch.rs
@@ -4,6 +4,7 @@ use hickory_resolver::config::*;
 use hickory_resolver::Resolver;
 use miette::Diagnostic;
 use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
 use std::collections::HashMap;
 use std::path::Path;
 use thiserror::Error;
@@ -62,6 +63,8 @@ pub struct CacheEntry {
     pub nsid: String,
     pub fetched_at: DateTime<Utc>,
     pub did: String,
+    #[serde(default)]
+    pub hash: String,
 }
 
 impl LexiconCache {
@@ -83,13 +86,14 @@ impl LexiconCache {
         Ok(())
     }
 
-    pub fn add_entry(&mut self, nsid: String, did: String) {
+    pub fn add_entry(&mut self, nsid: String, did: String, hash: String) {
         self.lexicons.insert(
             nsid.clone(),
             CacheEntry {
                 nsid,
                 fetched_at: Utc::now(),
                 did,
+                hash,
             },
         );
     }
@@ -296,8 +300,11 @@ pub fn fetch_lexicon(nsid: &str, project_root: &std::path::Path) -> Result<(), F
         std::fs::write(&mlf_path, mlf_content)?;
         println!("    → Converted to MLF at {}", mlf_path.display());
 
+        // Calculate hash of JSON content
+        let hash = calculate_hash(&json_str);
+
         // Update cache
-        cache.add_entry(record_nsid.clone(), did.clone());
+        cache.add_entry(record_nsid.clone(), did.clone(), hash);
     }
 
     // Save cache
@@ -459,3 +466,10 @@ fn extract_nsid_from_record(record: &AtProtoRecord) -> Result<String, FetchError
         record.uri
     )))
 }
+
+/// Calculate SHA-256 hash of content
+fn calculate_hash(content: &str) -> String {
+    let mut hasher = Sha256::new();
+    hasher.update(content.as_bytes());
+    format!("{:x}", hasher.finalize())
+}