diff --git a/Cargo.lock b/Cargo.lock
index 846cea9..0e746b3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3037,9 +3037,9 @@ dependencies = [
 
 [[package]]
 name = "tx3-tir"
-version = "0.17.0"
+version = "0.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "152e332c5ab744e8f17d54dfa4b6e3e177d5055141a1f37625303d4613277a72"
+checksum = "4bd8b43d04c3d116e901407cf4c6fa4949938f8904dddf7088cb97efcacd8bb2"
 dependencies = [
  "ciborium",
  "hex",
diff --git a/bin/tx3c/Cargo.toml b/bin/tx3c/Cargo.toml
index 1bfc9de..e089e5a 100644
--- a/bin/tx3c/Cargo.toml
+++ b/bin/tx3c/Cargo.toml
@@ -12,7 +12,7 @@ homepage.workspace = true
 readme.workspace = true
 
 [dependencies]
-tx3-tir = "0.17.0"
+tx3-tir = "0.18.0"
 tx3-lang = { path = "../../crates/tx3-lang" }
 tx3-cardano = { path = "../../crates/tx3-cardano" }
 clap = { version = "4.5", features = ["derive"] }
diff --git a/bin/tx3c/src/tii/schema.rs b/bin/tx3c/src/tii/schema.rs
index 817bbda..2e3c336 100644
--- a/bin/tx3c/src/tii/schema.rs
+++ b/bin/tx3c/src/tii/schema.rs
@@ -73,6 +73,14 @@ impl<'a> SchemaCtx<'a> {
                 "type": "object",
                 "additionalProperties": self.map_type(value)
             }),
+            // A tuple is a fixed-length, positionally-typed array.
+            ast::Type::Tuple(elements) => json!({
+                "type": "array",
+                "prefixItems": elements.iter().map(|t| self.map_type(t)).collect::<Vec<_>>(),
+                "items": false,
+                "minItems": elements.len(),
+                "maxItems": elements.len()
+            }),
             ast::Type::Custom(id) => self.map_custom(&id.value),
             ast::Type::Undefined => json!({"type": "null"}),
             ast::Type::Utxo => {
diff --git a/crates/tx3-cardano/Cargo.toml b/crates/tx3-cardano/Cargo.toml
index faae070..dd7815f 100644
--- a/crates/tx3-cardano/Cargo.toml
+++ b/crates/tx3-cardano/Cargo.toml
@@ -17,7 +17,7 @@ pallas = { version = "1.0.0" }
 # pallas = { version = ">=1.0.0-alpha, <2.0.0", path = "../../../../txpipe/pallas/pallas" }
 # pallas = { git = "https://github.com/txpipe/pallas.git" }
 
-tx3-tir = "0.17.0"
+tx3-tir = "0.18.0"
 
 hex = "0.4.3"
 thiserror = "2.0.11"
diff --git a/crates/tx3-lang/Cargo.toml b/crates/tx3-lang/Cargo.toml
index da892c4..d2ffa90 100644
--- a/crates/tx3-lang/Cargo.toml
+++ b/crates/tx3-lang/Cargo.toml
@@ -18,7 +18,7 @@ trait-variant = { workspace = true }
 hex = { workspace = true }
 serde = { workspace = true }
 
-tx3-tir = "0.17.0"
+tx3-tir = "0.18.0"
 
 miette = { version = "7.4.0", features = ["fancy"] }
 pest = { version = "2.7.15", features = ["miette-error", "pretty-print"] }
diff --git a/crates/tx3-resolver/Cargo.toml b/crates/tx3-resolver/Cargo.toml
index 126dcdf..36e0b1e 100644
--- a/crates/tx3-resolver/Cargo.toml
+++ b/crates/tx3-resolver/Cargo.toml
@@ -13,7 +13,7 @@ homepage.workspace = true
 readme.workspace = true
 
 [dependencies]
-tx3-tir = "0.17.0"
+tx3-tir = "0.18.0"
 
 thiserror = { workspace = true }
 trait-variant = { workspace = true }