diff --git a/Cargo.lock b/Cargo.lock
index 4b1503c..d55096e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "aho-corasick"
@@ -1033,8 +1033,7 @@ dependencies = [
 [[package]]
 name = "simplicity-lang"
 version = "0.7.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "70e57bd4d84853974a212eab24ed89da54f49fbccf5e33e93bcd29f0a6591cd5"
+source = "git+https://github.com/stringhandler/rust-simplicity.git?branch=feat%2Fadd-annex#7ce98ca88b5845de64dd630c890ba899efeaf54d"
 dependencies = [
  "bitcoin",
  "bitcoin_hashes 0.14.0",
@@ -1051,9 +1050,8 @@ dependencies = [
 
 [[package]]
 name = "simplicity-sys"
-version = "0.6.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "875630d128f19818161cefe0a3d910b6aae921d8246711db574a689cb2c11747"
+version = "0.6.1"
+source = "git+https://github.com/stringhandler/rust-simplicity.git?branch=feat%2Fadd-annex#7ce98ca88b5845de64dd630c890ba899efeaf54d"
 dependencies = [
  "bitcoin_hashes 0.14.0",
  "cc",
diff --git a/Cargo.toml b/Cargo.toml
index 27e870d..b5a9cee 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -45,7 +45,9 @@ serde_yaml = "0.8.8"
 hex = "0.3.2"
 
 elements = { version = "0.25.2", features = [ "serde", "base64" ] }
-simplicity = { package = "simplicity-lang", version = "0.7.0", features = [ "base64", "serde" ] }
+# simplicity = { package = "simplicity-lang", version = "0.7.0", features = [ "base64", "serde" ] }
+simplicity = { package="simplicity-lang", git="https://github.com/stringhandler/rust-simplicity.git", branch="feat/add-annex", features = ["base64", "serde"]}
+
 thiserror = "2.0.17"
 
 # Daemon-only dependencies
diff --git a/src/actions/simplicity/info.rs b/src/actions/simplicity/info.rs
index c1754e3..27eb58f 100644
--- a/src/actions/simplicity/info.rs
+++ b/src/actions/simplicity/info.rs
@@ -2,6 +2,7 @@ use crate::hal_simplicity::{elements_address, Program};
 use crate::simplicity::hex::parse::FromHex as _;
 use crate::simplicity::{jet, Amr, Cmr, Ihr};
 use serde::Serialize;
+use simplicity::NodeBounds;
 
 #[derive(Debug, thiserror::Error)]
 pub enum SimplicityInfoError {
@@ -18,6 +19,7 @@ pub struct RedeemInfo {
 	pub witness_hex: String,
 	pub amr: Amr,
 	pub ihr: Ihr,
+	pub bounds: NodeBounds,
 }
 
 #[derive(Serialize)]
@@ -56,6 +58,7 @@ pub fn simplicity_info(
 			witness_hex,
 			amr: node.amr(),
 			ihr: node.ihr(),
+			bounds: node.bounds(),
 		}
 	});
 
diff --git a/src/actions/simplicity/pset/finalize.rs b/src/actions/simplicity/pset/finalize.rs
index 8b7d984..cdfd370 100644
--- a/src/actions/simplicity/pset/finalize.rs
+++ b/src/actions/simplicity/pset/finalize.rs
@@ -1,6 +1,8 @@
 // Copyright 2025 Andrew Poelstra
 // SPDX-License-Identifier: CC0-1.0
 
+use elements::bitcoin::taproot::TAPROOT_ANNEX_PREFIX;
+
 use crate::hal_simplicity::Program;
 use crate::simplicity::jet;
 
@@ -25,6 +27,11 @@ pub enum PsetFinalizeError {
 
 	#[error("failed to prune program: {0}")]
 	ProgramPrune(simplicity::bit_machine::ExecutionError),
+
+	#[error("cost of transaction exceeds budget. Suggested annex padding bytes to add (including prefix): {padding_required}")]
+	CostExceedsBudget {
+		padding_required: usize,
+	},
 }
 
 /// Attach a Simplicity program and witness to a PSET input
@@ -33,6 +40,7 @@ pub fn pset_finalize(
 	input_idx: &str,
 	program: &str,
 	witness: &str,
+	annex_padding_size: usize,
 	genesis_hash: Option<&str>,
 ) -> Result<UpdatedPset, PsetFinalizeError> {
 	// 1. Parse everything.
@@ -56,7 +64,26 @@ pub fn pset_finalize(
 	let (prog, witness) = pruned.to_vec_with_witness();
 	// If `execution_environment` above succeeded we are guaranteed that this index is in bounds.
 	let input = &mut pset.inputs_mut()[input_idx_usize];
-	input.final_script_witness = Some(vec![witness, prog, tap_leaf.into_bytes(), cb_serialized]);
+
+	let final_script_witness = if annex_padding_size == 0 {
+		vec![witness, prog, tap_leaf.into_bytes(), cb_serialized]
+	} else {
+		let mut annex = vec![0u8; annex_padding_size];
+		annex[0] = TAPROOT_ANNEX_PREFIX;
+
+		vec![witness, prog, tap_leaf.into_bytes(), cb_serialized, annex]
+	};
+
+	// Calculate the budget and warn the user if it is not enough.
+	let cost = pruned.bounds().cost;
+	if !cost.is_budget_valid(&final_script_witness) {
+		let padding_required = cost.get_padding(&final_script_witness).map(|bytes| bytes.len());
+		return Err(PsetFinalizeError::CostExceedsBudget {
+			padding_required: padding_required.unwrap_or_default(),
+		});
+	}
+
+	input.final_script_witness = Some(final_script_witness);
 
 	let updated_values = vec!["final_script_witness"];
 
diff --git a/src/actions/simplicity/sighash.rs b/src/actions/simplicity/sighash.rs
index 6ac9640..841bc3c 100644
--- a/src/actions/simplicity/sighash.rs
+++ b/src/actions/simplicity/sighash.rs
@@ -1,3 +1,4 @@
+use crate::hex_or_base64;
 use crate::simplicity::bitcoin::secp256k1::{
 	schnorr, Keypair, Message, Secp256k1, SecretKey, XOnlyPublicKey,
 };
@@ -12,6 +13,7 @@ use elements::bitcoin::secp256k1;
 use elements::hashes::Hash as _;
 use elements::pset::PartiallySignedTransaction;
 use serde::Serialize;
+use simplicity::base64;
 
 use crate::simplicity::elements::taproot::ControlBlock;
 use crate::simplicity::jet::elements::ElementsEnv;
@@ -92,6 +94,9 @@ pub enum SimplicitySighashError {
 
 	#[error("invalid input UTXO: {0}")]
 	InputUtxoParsing(ParseElementsUtxoError),
+
+	#[error("annex was not valid hex or base64:{0}")]
+	AnnexParsing(base64::DecodeError),
 }
 
 #[derive(Serialize)]
@@ -113,6 +118,7 @@ pub fn simplicity_sighash(
 	public_key: Option<&str>,
 	signature: Option<&str>,
 	input_utxos: Option<&[&str]>,
+	annex: Option<&str>,
 ) -> Result<SighashInfo, SimplicitySighashError> {
 	let secp = Secp256k1::new();
 
@@ -214,15 +220,11 @@ pub fn simplicity_sighash(
 		]),
 	};
 
-	let tx_env = ElementsEnv::new(
-		&tx,
-		input_utxos,
-		input_idx,
-		cmr,
-		control_block,
-		None, // FIXME populate this; needs https://github.com/BlockstreamResearch/rust-simplicity/issues/315 first
-		genesis_hash,
-	);
+	let annex = annex
+		.map(|v| hex_or_base64(v).map_err(SimplicitySighashError::AnnexParsing))
+		.transpose()?;
+	let tx_env =
+		ElementsEnv::new(&tx, input_utxos, input_idx, cmr, control_block, annex, genesis_hash);
 
 	let (pk, sig) = match (public_key, signature) {
 		(Some(pk), None) => (
diff --git a/src/bin/hal-simplicity/cmd/simplicity/pset/finalize.rs b/src/bin/hal-simplicity/cmd/simplicity/pset/finalize.rs
index 8e3a694..78a23e7 100644
--- a/src/bin/hal-simplicity/cmd/simplicity/pset/finalize.rs
+++ b/src/bin/hal-simplicity/cmd/simplicity/pset/finalize.rs
@@ -22,6 +22,8 @@ pub fn cmd<'a>() -> clap::App<'a, 'a> {
 			)
 			.short("g")
 			.required(false),
+			cmd::arg("padding-bytes", "The number of padding bytes to add to the annex to allow the cost of the program to fall in budget. This number should include the prefix byte.").alias("padding")
+			.short("a").required(false)
 		])
 }
 
@@ -31,12 +33,15 @@ pub fn exec<'a>(matches: &clap::ArgMatches<'a>) {
 	let program = matches.value_of("program").expect("program is mandatory");
 	let witness = matches.value_of("witness").expect("witness is mandatory");
 	let genesis_hash = matches.value_of("genesis-hash");
+	let padding_bytes =
+		matches.value_of("padding-bytes").map(|b| b.parse().ok()).flatten().unwrap_or_default();
 
 	match hal_simplicity::actions::simplicity::pset::pset_finalize(
 		pset_b64,
 		input_idx,
 		program,
 		witness,
+		padding_bytes,
 		genesis_hash,
 	) {
 		Ok(info) => cmd::print_output(matches, &info),
diff --git a/src/bin/hal-simplicity/cmd/simplicity/sighash.rs b/src/bin/hal-simplicity/cmd/simplicity/sighash.rs
index a685f9e..5478204 100644
--- a/src/bin/hal-simplicity/cmd/simplicity/sighash.rs
+++ b/src/bin/hal-simplicity/cmd/simplicity/sighash.rs
@@ -38,6 +38,7 @@ pub fn cmd<'a>() -> clap::App<'a, 'a> {
 				.multiple(true)
 				.number_of_values(1)
 				.required(false),
+			cmd::opt("annex", "addition annex, as hex. Mainly used to add padding for CPU intensive programs").required(false)
 		])
 }
 
@@ -51,6 +52,7 @@ pub fn exec<'a>(matches: &clap::ArgMatches<'a>) {
 	let public_key = matches.value_of("public-key");
 	let signature = matches.value_of("signature");
 	let input_utxos: Option<Vec<_>> = matches.values_of("input-utxo").map(|vals| vals.collect());
+	let annex = matches.value_of("annex");
 
 	match hal_simplicity::actions::simplicity::simplicity_sighash(
 		tx_hex,
@@ -62,6 +64,7 @@ pub fn exec<'a>(matches: &clap::ArgMatches<'a>) {
 		public_key,
 		signature,
 		input_utxos.as_deref(),
+		annex,
 	) {
 		Ok(info) => cmd::print_output(matches, &info),
 		Err(e) => cmd::print_output(