diff --git a/Cargo.lock b/Cargo.lock
index ff8553d1..e3b9b449 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -365,7 +365,7 @@ dependencies = [
  "rpassword",
  "rusqlite",
  "serde_json",
- "sha2",
+ "sha2 0.11.1",
  "url",
  "zeroize",
 ]
@@ -528,7 +528,7 @@ dependencies = [
  "schemars",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.11.1",
  "subtle",
 ]
 
@@ -663,7 +663,6 @@ dependencies = [
  "block-buffer 0.10.4",
  "const-oid 0.9.6",
  "crypto-common 0.1.7",
- "subtle",
 ]
 
 [[package]]
@@ -983,11 +982,11 @@ checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
 [[package]]
 name = "hmac"
-version = "0.12.1"
+version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c49c37c09c17a53d937dfbb742eb3a961d65a994e6bcdcf37e7399d0cc8ab5e"
+checksum = "6303bc9732ae41b04cb554b844a762b4115a61bfaa81e3e83050991eeb56863f"
 dependencies = [
- "digest 0.10.7",
+ "digest 0.11.3",
 ]
 
 [[package]]
@@ -1236,7 +1235,7 @@ dependencies = [
  "rustls",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "thiserror",
  "tokio",
  "tokio-rustls",
@@ -1311,7 +1310,7 @@ dependencies = [
  "serde",
  "serde_json",
  "serde_yaml",
- "sha2",
+ "sha2 0.11.1",
  "tempfile",
  "thiserror",
  "tokio",
@@ -2424,6 +2423,7 @@ dependencies = [
  "core",
  "futures-util",
  "getrandom 0.4.3",
+ "hex",
  "http-body-util",
  "iphone-use-mcp",
  "libc",
@@ -2439,7 +2439,7 @@ dependencies = [
  "rustls",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.11.1",
  "tempfile",
  "tokio",
  "tokio-rustls",
@@ -2474,6 +2474,17 @@ dependencies = [
  "digest 0.10.7",
 ]
 
+[[package]]
+name = "sha2"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47d7069beb7d6ac7b9acd1039986e73443f24234f41074da099d6f994ac9ad19"
+dependencies = [
+ "cfg-if",
+ "cpufeatures 0.3.1",
+ "digest 0.11.3",
+]
+
 [[package]]
 name = "sharded-slab"
 version = "0.1.7"
diff --git a/crates/browser-session/Cargo.toml b/crates/browser-session/Cargo.toml
index fed1a789..22af8627 100644
--- a/crates/browser-session/Cargo.toml
+++ b/crates/browser-session/Cargo.toml
@@ -21,7 +21,7 @@ argon2 = "0.6"
 base64 = "0.22"
 rand = "0.10"
 serde_json = "1"
-sha2 = "0.10"
+sha2 = "0.11"
 hex = "0.4"
 zeroize = "1"
 clap = { version = "4", features = ["derive"], optional = true }
diff --git a/crates/core/Cargo.toml b/crates/core/Cargo.toml
index 74672349..d5ff16fd 100644
--- a/crates/core/Cargo.toml
+++ b/crates/core/Cargo.toml
@@ -6,8 +6,8 @@ license-file = "../../LICENSE"
 
 [dependencies]
 schemars = { version = "1", optional = true }
-hmac = "0.12"
-sha2 = "0.10"
+hmac = "0.13"
+sha2 = "0.11"
 subtle = "2"
 getrandom = "0.4"
 base64 = "0.22"
diff --git a/crates/core/src/auth.rs b/crates/core/src/auth.rs
index d90d72b6..d3265290 100644
--- a/crates/core/src/auth.rs
+++ b/crates/core/src/auth.rs
@@ -3,7 +3,7 @@
 /// Token format: `exp:nonce:sig`
 /// where `sig = base64url_nopad(HMAC_SHA256(secret, "exp:nonce"))`.
 use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine as _};
-use hmac::{Hmac, Mac};
+use hmac::{Hmac, KeyInit, Mac};
 use sha2::Sha256;
 use subtle::ConstantTimeEq;
 
diff --git a/crates/core/src/runner_auth.rs b/crates/core/src/runner_auth.rs
index 5d646bd4..b43ed384 100644
--- a/crates/core/src/runner_auth.rs
+++ b/crates/core/src/runner_auth.rs
@@ -20,7 +20,7 @@
 //! [`MAX_SKEW_SECS`] of its own clock, so a captured request cannot be
 //! replayed or altered.
 
-use hmac::{Hmac, Mac};
+use hmac::{Hmac, KeyInit, Mac};
 use sha2::{Digest, Sha256};
 use subtle::ConstantTimeEq;
 
diff --git a/crates/mcp/Cargo.toml b/crates/mcp/Cargo.toml
index 68d7dae6..0e9930d1 100644
--- a/crates/mcp/Cargo.toml
+++ b/crates/mcp/Cargo.toml
@@ -50,7 +50,7 @@ libc = "0.2"
 base64 = "0.22"
 
 # Registry checksums (flow update verifies every file against index.json)
-sha2 = "0.10"
+sha2 = "0.11"
 hex = "0.4"
 
 # `flow publish` clones the registry into a scratch directory
diff --git a/crates/mcp/src/task.rs b/crates/mcp/src/task.rs
index c0d1cd6a..5d49139f 100644
--- a/crates/mcp/src/task.rs
+++ b/crates/mcp/src/task.rs
@@ -369,7 +369,7 @@ pub fn start(
     }
     use sha2::{Digest, Sha256};
     // Keep only the digest; model keys and return parameters are never exposed.
-    let request_fingerprint = format!("{:x}", Sha256::digest(format!("{request:?}").as_bytes()));
+    let request_fingerprint = hex::encode(Sha256::digest(format!("{request:?}").as_bytes()));
     let id = new_id();
     let task = Arc::new(Task {
         state: Mutex::new(State {
@@ -1496,7 +1496,7 @@ mod tests {
     async fn request_id_deduplicates_and_pause_is_nonterminal() {
         let request=TaskRequest {goal:"synthetic goal".into(),client_request_id:Some("fixture-client".into()),..Default::default()};
         use sha2::{Digest, Sha256};
-        let request_fingerprint=format!("{:x}",Sha256::digest(format!("{request:?}").as_bytes()));
+        let request_fingerprint=hex::encode(Sha256::digest(format!("{request:?}").as_bytes()));
         let task=Arc::new(Task {
             state: Mutex::new(State {request_fingerprint,id:"fixture-dedup".into(),goal:"synthetic goal".into(),client_request_id:Some("fixture-client".into()),status:Status::Running,phase:"observing",planned_action:None,flow:None,steps:vec![],confirm:None,summary:None,error:None,started_at_ms:unix_ms(),started:Instant::now(),finished_ms:None,models_used:json!({})}),
             cancel:AtomicBool::new(false),paused:AtomicBool::new(false),cancel_signal:tokio::sync::Notify::new(),answer:Mutex::new(None),
diff --git a/crates/server/Cargo.toml b/crates/server/Cargo.toml
index c9d7174c..b0919a74 100644
--- a/crates/server/Cargo.toml
+++ b/crates/server/Cargo.toml
@@ -57,7 +57,8 @@ tempfile = "3"
 
 # runner (L2 element-tree control): screenshots arrive base64-encoded.
 base64 = "0.22"
-sha2 = "0.10"
+sha2 = "0.11"
+hex = "0.4"
 # ES256 tokens for the App Store Connect API (legacy iOS signing) and the
 # SHA-1 codesign takes; already in the tree through rustls.
 ring = "0.17"
diff --git a/crates/server/src/setup/embed.rs b/crates/server/src/setup/embed.rs
index a91b0e69..5e2c206d 100644
--- a/crates/server/src/setup/embed.rs
+++ b/crates/server/src/setup/embed.rs
@@ -170,9 +170,17 @@ fn usable(path: &Path) -> Result<EmbedLib, String> {
 }
 
 fn file_sha256(path: &Path) -> Option<String> {
+    use std::io::Read;
     let mut file = std::fs::File::open(path).ok()?;
     let mut digest = Sha256::new();
-    std::io::copy(&mut file, &mut digest).ok()?;
+    let mut buf = vec![0u8; 64 * 1024];
+    loop {
+        let n = file.read(&mut buf).ok()?;
+        if n == 0 {
+            break;
+        }
+        digest.update(&buf[..n]);
+    }
     Some(
         digest
             .finalize()
@@ -322,7 +330,7 @@ mod tests {
         );
         assert_eq!(
             cache_component(Some(&first)),
-            format!("embed:{:x}", Sha256::digest(b"one"))
+            format!("embed:{}", hex::encode(Sha256::digest(b"one")))
         );
         assert_eq!(cache_component(None), "embed:none");
         assert_eq!(
diff --git a/crates/server/src/setup/runner.rs b/crates/server/src/setup/runner.rs
index 9f7a41f6..c851cde3 100644
--- a/crates/server/src/setup/runner.rs
+++ b/crates/server/src/setup/runner.rs
@@ -1481,7 +1481,7 @@ mod tests {
             std::fs::write(&path, bytes).unwrap();
             super::super::embed::EmbedLib {
                 path: path.clone(),
-                sha256: format!("{:x}", <sha2::Sha256 as sha2::Digest>::digest(bytes)),
+                sha256: hex::encode(<sha2::Sha256 as sha2::Digest>::digest(bytes)),
             }
         };
         let component = super::super::embed::cache_component;