diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b1c7e5f..2733d61 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -62,6 +62,7 @@ jobs:
   test-fuzz:
     name: Test - fuzzer
     runs-on: ubuntu-latest
+    needs: test-stable
 
     steps:
     - name: Checkout
diff --git a/Cargo.lock b/Cargo.lock
index f175d7e..88ff0a1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -510,7 +510,7 @@ dependencies = [
 [[package]]
 name = "simplicity-lang"
 version = "0.2.0"
-source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=713842937ab0b5e0b1a343e19fdee6634b7a6add#713842937ab0b5e0b1a343e19fdee6634b7a6add"
+source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=0594aaf004c1a28904e2242d0b319241b1560390#0594aaf004c1a28904e2242d0b319241b1560390"
 dependencies = [
  "bitcoin",
  "bitcoin_hashes",
@@ -526,7 +526,7 @@ dependencies = [
 [[package]]
 name = "simplicity-sys"
 version = "0.2.0"
-source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=713842937ab0b5e0b1a343e19fdee6634b7a6add#713842937ab0b5e0b1a343e19fdee6634b7a6add"
+source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=0594aaf004c1a28904e2242d0b319241b1560390#0594aaf004c1a28904e2242d0b319241b1560390"
 dependencies = [
  "bitcoin_hashes",
  "cc",
diff --git a/Cargo.toml b/Cargo.toml
index 0bd12d4..76803cf 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,7 +7,7 @@ homepage = "https://github.com/BlockstreamResearch/simfony/"
 repository = "https://github.com/BlockstreamResearch/simfony/"
 description = "Rust-like language that compiles to Simplicity bytecode."
 edition = "2021"
-rust-version = "1.61.0"
+rust-version = "1.63.0"
 
 [lib]
 name = "simfony"
@@ -24,7 +24,7 @@ pest = "2.1.3"
 pest_derive = "2.7.1"
 serde = { version = "1.0.188", features = ["derive"] }
 serde_json = "1.0.105"
-simplicity-lang = { git = "https://github.com/BlockstreamResearch/rust-simplicity", rev = "713842937ab0b5e0b1a343e19fdee6634b7a6add" }
+simplicity-lang = { git = "https://github.com/BlockstreamResearch/rust-simplicity", rev = "0594aaf004c1a28904e2242d0b319241b1560390" }
 miniscript = "11.0.0"
 either = "1.12.0"
 itertools = "0.13.0"
diff --git a/README.md b/README.md
index 6daba02..b0a1b32 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ Take a look at the [example programs](https://github.com/BlockstreamResearch/sim
 
 ## MSRV
 
-This crate should compile with any feature combination on **Rust 1.61.0** or higher.
+This crate should compile with any feature combination on **Rust 1.63.0** or higher.
 
 ## Simplicity's need for a high-level language
 
diff --git a/bitcoind-tests/Cargo.lock b/bitcoind-tests/Cargo.lock
index 61ab274..016ca01 100644
--- a/bitcoind-tests/Cargo.lock
+++ b/bitcoind-tests/Cargo.lock
@@ -769,7 +769,7 @@ dependencies = [
 [[package]]
 name = "simplicity-lang"
 version = "0.2.0"
-source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=713842937ab0b5e0b1a343e19fdee6634b7a6add#713842937ab0b5e0b1a343e19fdee6634b7a6add"
+source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=0594aaf004c1a28904e2242d0b319241b1560390#0594aaf004c1a28904e2242d0b319241b1560390"
 dependencies = [
  "bitcoin 0.31.2",
  "bitcoin_hashes 0.13.0",
@@ -785,7 +785,7 @@ dependencies = [
 [[package]]
 name = "simplicity-sys"
 version = "0.2.0"
-source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=713842937ab0b5e0b1a343e19fdee6634b7a6add#713842937ab0b5e0b1a343e19fdee6634b7a6add"
+source = "git+https://github.com/BlockstreamResearch/rust-simplicity?rev=0594aaf004c1a28904e2242d0b319241b1560390#0594aaf004c1a28904e2242d0b319241b1560390"
 dependencies = [
  "bitcoin_hashes 0.13.0",
  "cc",
diff --git a/clippy.toml b/clippy.toml
index f5fcb56..b3c3a24 100644
--- a/clippy.toml
+++ b/clippy.toml
@@ -1 +1 @@
-msrv = "1.61.0"
+msrv = "1.63.0"
diff --git a/codegen/Cargo.toml b/codegen/Cargo.toml
index 089bb2f..28778e9 100644
--- a/codegen/Cargo.toml
+++ b/codegen/Cargo.toml
@@ -2,7 +2,7 @@
 name = "codegen"
 version = "0.1.0"
 edition = "2021"
-rust-version = "1.61.0"
+rust-version = "1.63.0"
 description = "Generator of Rust code as interface between Simfony and Rust."
 publish = false
 
diff --git a/codegen/src/jet.rs b/codegen/src/jet.rs
index 79c0fd5..5350445 100644
--- a/codegen/src/jet.rs
+++ b/codegen/src/jet.rs
@@ -414,6 +414,7 @@ This jet should not be used directly."#,
         // Bitcoin (without primitives)
         Elements::ParseLock => "Parse an integer as a consensus-encoded Bitcoin lock time.",
         Elements::ParseSequence => "Parse an integer as a consensus-encoded Bitcoin sequence number.",
+        Elements::TapdataInit => r#"Create a SHA256 context, initialized with a "TapData" tag."#,
         // Signature hash modes
         Elements::AnnexHash => r#"Continue a SHA256 hash with an optional hash by appending the following:
 - If there is no hash, then the byte `0x00`.
@@ -433,6 +434,14 @@ This builds a taproot from two branches."#,
 - The lexicographically larger of the two inputs (32 bytes).
 
 This builds a taproot from two branches."#,
+        Elements::BuildTaptweak => r#"Implementation of `taproot_tweak_pubkey` from BIP-0341.
+
+## Panics
+1. The input x-only public key is off curve or exceeds the field size.
+2. The internal hash value `t` exceeds the secp256k1 group order.
+3. The generated tweaked point is infinity, and thus has no valid x-only public key.
+
+Note that situations 2 and 3 are cryptographically impossible to occur."#,
         Elements::InputAmountsHash => "Return the SHA256 hash of the serialization of each input UTXO's asset and amount fields.",
         Elements::InputAnnexesHash => r#"Return the SHA256 hash of the concatenation of the following for every input:
 - If the input has no annex, or isn't a taproot spend, then the byte `0x00`.
@@ -953,13 +962,13 @@ const DIGITAL_SIGNATURES: [Elements; 1] = [
     Elements::Bip0340Verify
 ];
 #[rustfmt::skip]
-const BITCOIN: [Elements; 2] = [
-    Elements::ParseLock, Elements::ParseSequence
+const BITCOIN: [Elements; 3] = [
+    Elements::ParseLock, Elements::ParseSequence, Elements::TapdataInit,
 ];
 // Elements
 #[rustfmt::skip]
-const SIGNATURE_HASH_MODES: [Elements; 34] = [
-    Elements::AnnexHash, Elements::AssetAmountHash, Elements::BuildTapbranch, Elements::BuildTapleafSimplicity, Elements::InputAmountsHash, Elements::InputAnnexesHash, Elements::InputHash, Elements::InputOutpointsHash, Elements::InputScriptSigsHash, Elements::InputScriptsHash, Elements::InputSequencesHash, Elements::InputUtxoHash, Elements::InputUtxosHash, Elements::InputsHash, Elements::IssuanceAssetAmountsHash, Elements::IssuanceBlindingEntropyHash, Elements::IssuanceHash, Elements::IssuanceRangeProofsHash, Elements::IssuanceTokenAmountsHash, Elements::IssuancesHash, Elements::NonceHash, Elements::OutpointHash, Elements::OutputAmountsHash, Elements::OutputHash, Elements::OutputNoncesHash, Elements::OutputRangeProofsHash, Elements::OutputScriptsHash, Elements::OutputSurjectionProofsHash, Elements::OutputsHash, Elements::SigAllHash, Elements::TapEnvHash, Elements::TapleafHash, Elements::TappathHash, Elements::TxHash
+const SIGNATURE_HASH_MODES: [Elements; 35] = [
+    Elements::AnnexHash, Elements::AssetAmountHash, Elements::BuildTapbranch, Elements::BuildTapleafSimplicity, Elements::BuildTaptweak, Elements::InputAmountsHash, Elements::InputAnnexesHash, Elements::InputHash, Elements::InputOutpointsHash, Elements::InputScriptSigsHash, Elements::InputScriptsHash, Elements::InputSequencesHash, Elements::InputUtxoHash, Elements::InputUtxosHash, Elements::InputsHash, Elements::IssuanceAssetAmountsHash, Elements::IssuanceBlindingEntropyHash, Elements::IssuanceHash, Elements::IssuanceRangeProofsHash, Elements::IssuanceTokenAmountsHash, Elements::IssuancesHash, Elements::NonceHash, Elements::OutpointHash, Elements::OutputAmountsHash, Elements::OutputHash, Elements::OutputNoncesHash, Elements::OutputRangeProofsHash, Elements::OutputScriptsHash, Elements::OutputSurjectionProofsHash, Elements::OutputsHash, Elements::SigAllHash, Elements::TapEnvHash, Elements::TapleafHash, Elements::TappathHash, Elements::TxHash
 ];
 #[rustfmt::skip]
 const TIME_LOCKS: [Elements; 9] = [
diff --git a/flake.nix b/flake.nix
index 6a2d429..8840745 100644
--- a/flake.nix
+++ b/flake.nix
@@ -39,6 +39,7 @@
             defaultRust
             pkgs.just
             pkgs.gdb
+            pkgs.cargo-hack
           ] ++ (
             if with_elements then [ elementsd-simplicity ] else []
           );
@@ -57,11 +58,12 @@
           buildInputs = [
             (mkRust "stable" "latest" "default" [])
             pkgs.just
+            pkgs.cargo-hack
           ];
         };
         msrv = pkgs.mkShell {
           buildInputs = [
-            (mkRust "stable" "1.61.0" "minimal" [])
+            (mkRust "stable" "1.63.0" "minimal" [])
             pkgs.just
           ];
         };
diff --git a/justfile b/justfile
index 3fac561..4b37a21 100644
--- a/justfile
+++ b/justfile
@@ -10,6 +10,10 @@ fmtcheck:
 lint:
     cargo clippy --all-targets --workspace -- --deny warnings
 
+# Build code with all feature combinations
+build_features:
+    cargo hack check --feature-powerset --no-dev-deps
+
 # Run unit tests
 test:
     cargo test --workspace
@@ -20,6 +24,7 @@ check:
     rustc --version
     just fmtcheck
     just lint
+    just build_features
     just test
 
 # Run fuzz test for 30 seconds
diff --git a/src/ast.rs b/src/ast.rs
index 32a1aec..8d97a8f 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -20,7 +20,7 @@ use crate::value::{UIntValue, Value};
 use crate::{impl_eq_hash, parse};
 
 /// Map of witness names to their expected type, as declared in the program.
-#[derive(Clone, Debug, Eq, PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq, Default)]
 pub struct DeclaredWitnesses(HashMap<WitnessName, ResolvedType>);
 
 impl DeclaredWitnesses {
diff --git a/src/jet.rs b/src/jet.rs
index f088815..cf6a1fc 100644
--- a/src/jet.rs
+++ b/src/jet.rs
@@ -404,6 +404,7 @@ pub fn source_type(jet: Elements) -> Vec<AliasedType> {
         /*
          * Bitcoin (without primitives)
          */
+        Elements::TapdataInit => vec![],
         Elements::ParseLock | Elements::ParseSequence => vec![U32.into()],
         /*
          * ==============================
@@ -444,6 +445,7 @@ pub fn source_type(jet: Elements) -> Vec<AliasedType> {
         Elements::AnnexHash => vec![Ctx8.into(), option(U256)],
         Elements::BuildTapleafSimplicity => vec![U256.into()],
         Elements::BuildTapbranch => vec![U256.into(), U256.into()],
+        Elements::BuildTaptweak => vec![Pubkey.into(), U256.into()],
         /*
          * Time locks
          */
@@ -911,6 +913,7 @@ pub fn target_type(jet: Elements) -> AliasedType {
          */
         Elements::ParseLock => either(Height, Time),
         Elements::ParseSequence => option(either(Distance, Duration)),
+        Elements::TapdataInit => Ctx8.into(),
         /*
          * ==============================
          *         Elements jets
@@ -943,7 +946,8 @@ pub fn target_type(jet: Elements) -> AliasedType {
         | Elements::TapleafHash
         | Elements::TappathHash
         | Elements::BuildTapleafSimplicity
-        | Elements::BuildTapbranch => U256.into(),
+        | Elements::BuildTapbranch
+        | Elements::BuildTaptweak => U256.into(),
         Elements::OutpointHash
         | Elements::AssetAmountHash
         | Elements::NonceHash
diff --git a/src/lib.rs b/src/lib.rs
index 30fd4d5..b33c76e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,6 +39,17 @@ pub struct CompiledProgram {
     debug_symbols: DebugSymbols,
 }
 
+impl Default for CompiledProgram {
+    fn default() -> Self {
+        use simplicity::node::CoreConstructible;
+        Self {
+            simplicity: ProgNode::unit(&simplicity::types::Context::new()),
+            witness_types: DeclaredWitnesses::default(),
+            debug_symbols: DebugSymbols::default(),
+        }
+    }
+}
+
 impl CompiledProgram {
     /// Parse and compile a Simfony program from the given string.
     ///
diff --git a/src/value.rs b/src/value.rs
index b30e9fc..26b9191 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -58,8 +58,8 @@ impl fmt::Display for UIntValue {
             UIntValue::U16(n) => <u16 as fmt::Display>::fmt(n, f),
             UIntValue::U32(n) => <u32 as fmt::Display>::fmt(n, f),
             UIntValue::U64(n) => <u64 as fmt::Display>::fmt(n, f),
-            UIntValue::U128(n) => write!(f, "{}", n.to_be_bytes().as_hex()),
-            UIntValue::U256(n) => write!(f, "{}", n.as_ref().as_hex()),
+            UIntValue::U128(n) => write!(f, "0x{}", n.to_be_bytes().as_hex()),
+            UIntValue::U256(n) => write!(f, "0x{}", n.as_ref().as_hex()),
         }
     }
 }