diff --git a/crates/aura-cli/src/graph.rs b/crates/aura-cli/src/graph.rs
index c21dd83..b277efa 100644
--- a/crates/aura-cli/src/graph.rs
+++ b/crates/aura-cli/src/graph.rs
@@ -99,8 +99,9 @@ fn collect_distinct_composites(bp: &Blueprint) -> Vec<&Composite> {
 }
 
 /// Render one composite's interior as a flat graph: interior leaves as `[type]`,
-/// nested composites as opaque `[name]`, plus an `[in:k]` entry marker per input
-/// role (wired to its interior targets) and an `[out:<name>]` marker per
+/// nested composites as opaque `[name]`, plus an `[in:<name>]` entry marker per
+/// input role (wired to its interior targets), a `[param:<name>]` marker per param
+/// alias (wired to the leaf it relabels), and an `[out:<name>]` marker per
 /// re-exported output field (wired from its producer). Prefixed `"<name>:\n"`.
 fn render_definition(c: &Composite) -> String {
     let mut labels: Vec<String> = Vec::with_capacity(c.nodes().len());
@@ -114,13 +115,18 @@ fn render_definition(c: &Composite) -> String {
     for e in c.edges() {
         edges.push((e.from, e.to));
     }
-    for (role, targets) in c.input_roles().iter().enumerate() {
+    for role in c.input_roles() {
         let in_id = labels.len();
-        labels.push(format!("in:{role}"));
-        for t in targets {
+        labels.push(format!("in:{}", role.name));
+        for t in &role.targets {
             edges.push((in_id, t.node));
         }
     }
+    for a in c.params() {
+        let p_id = labels.len();
+        labels.push(format!("param:{}", a.name));
+        edges.push((p_id, a.node));
+    }
     for of in c.output() {
         let out_id = labels.len();
         labels.push(format!("out:{}", of.name));
diff --git a/crates/aura-cli/src/main.rs b/crates/aura-cli/src/main.rs
index 6cdd8c7..bba70fc 100644
--- a/crates/aura-cli/src/main.rs
+++ b/crates/aura-cli/src/main.rs
@@ -11,7 +11,7 @@ mod graph;
 use aura_core::{Firing, Scalar, ScalarKind, Timestamp};
 use aura_engine::{
     f64_field, summarize, Blueprint, BlueprintNode, Composite, Edge, Harness, OutField,
-    RunManifest, RunReport, SourceSpec, Target,
+    ParamAlias, Role, RunManifest, RunReport, SourceSpec, Target,
 };
 use aura_std::{Ema, Exposure, Recorder, SimBroker, Sma, Sub};
 use std::sync::mpsc::{self, Receiver};
@@ -126,7 +126,11 @@ fn sma_cross(name: &str) -> Composite {
             Edge { from: 0, to: 2, slot: 0, from_field: 0 },
             Edge { from: 1, to: 2, slot: 1, from_field: 0 },
         ],
-        vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+        vec![Role {
+            name: "price".into(),
+            targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+        }],
+        vec![],
         vec![OutField { node: 2, field: 0, name: "cross".into() }],
     )
 }
@@ -200,10 +204,18 @@ fn macd(name: &str) -> Composite {
             Edge { from: 2, to: 4, slot: 0, from_field: 0 }, // line   → histogram[0]
             Edge { from: 3, to: 4, slot: 1, from_field: 0 }, // signal → histogram[1]
         ],
-        vec![vec![
-            Target { node: 0, slot: 0 }, // price → fast EMA
-            Target { node: 1, slot: 0 }, // price → slow EMA
-        ]],
+        vec![Role {
+            name: "price".into(),
+            targets: vec![
+                Target { node: 0, slot: 0 }, // price → fast EMA
+                Target { node: 1, slot: 0 }, // price → slow EMA
+            ],
+        }],
+        vec![
+            ParamAlias { name: "fast".into(), node: 0, slot: 0 },   // fast EMA length
+            ParamAlias { name: "slow".into(), node: 1, slot: 0 },   // slow EMA length
+            ParamAlias { name: "signal".into(), node: 3, slot: 0 }, // signal EMA length
+        ],
         vec![
             OutField { node: 2, field: 0, name: "macd".into() },      // the MACD line
             OutField { node: 3, field: 0, name: "signal".into() },    // the signal line
@@ -379,7 +391,7 @@ mod tests {
         let out = graph::render_blueprint(&sample_blueprint());
         // the sma_cross body is defined exactly once, with its interior + ports
         assert_eq!(out.matches("sma_cross:").count(), 1, "definition not rendered once:\n{out}");
-        for needle in ["[SMA]", "[Sub]", "[in:0]", "[out:cross]"] {
+        for needle in ["[SMA]", "[Sub]", "[in:price]", "[out:cross]"] {
             assert!(out.contains(needle), "missing {needle} in definition:\n{out}");
         }
     }
@@ -392,14 +404,16 @@ mod tests {
             "inner",
             vec![Sma::factory().into()],
             vec![],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 0, field: 0, name: "out".into() }],
         );
         let outer = Composite::new(
             "outer",
             vec![BlueprintNode::Composite(inner), Sub::factory().into()],
             vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 1, field: 0, name: "out".into() }],
         );
         let bp = Blueprint::new(
@@ -490,7 +504,7 @@ mod tests {
 where:
 
 sma_cross:
-     [in:0]
+   [in:price]
     ┌───└───┐
     ↓       ↓
   [SMA]   [SMA]
@@ -566,6 +580,34 @@ sma_cross:
         assert!(out.contains("[macd]"), "missing opaque macd node:\n{out}");
         assert_eq!(out.matches("macd:").count(), 1, "macd defined once:\n{out}");
         assert!(out.contains("[EMA]"), "macd interior must show EMA leaves:\n{out}");
+        assert!(out.contains("[in:price]"), "named MACD input role: {out}");
+        assert!(out.contains("[param:fast]"), "aliased fast length: {out}");
+        assert!(out.contains("[param:slow]"), "aliased slow length: {out}");
+        assert!(out.contains("[param:signal]"), "aliased signal length: {out}");
+    }
+
+    /// E2E acceptance (#41 / spec 0019, the worked example): the real MACD strategy
+    /// blueprint's swept param surface relabels the three otherwise-indistinguishable
+    /// EMA `length` slots to `macd.fast` / `macd.slow` / `macd.signal` — the named
+    /// composite boundary visible end-to-end through `param_space()`, with the slot
+    /// count and order unchanged (C23 — pure naming overlay, not curation: every
+    /// interior slot stays sweepable, the `scale` knob is unaffected).
+    #[test]
+    fn macd_param_space_surfaces_the_three_named_aliases() {
+        let names: Vec<String> =
+            macd_blueprint().param_space().into_iter().map(|p| p.name).collect();
+        // three aliased composite slots, in declared (fast, slow, signal) order,
+        // then the strategy-level Exposure `scale` (outside the composite, unaliased).
+        assert_eq!(
+            names,
+            vec![
+                "macd.fast".to_string(),
+                "macd.slow".to_string(),
+                "macd.signal".to_string(),
+                "scale".to_string(),
+            ],
+            "MACD param surface must expose the three named EMA lengths + scale",
+        );
     }
 
     #[test]
diff --git a/crates/aura-engine/src/blueprint.rs b/crates/aura-engine/src/blueprint.rs
index 7e39bb9..cd4c92e 100644
--- a/crates/aura-engine/src/blueprint.rs
+++ b/crates/aura-engine/src/blueprint.rs
@@ -41,6 +41,26 @@ impl From<LeafFactory> for BlueprintNode {
     }
 }
 
+/// One named input role: role `r` (by position) fans the source value into
+/// `targets`. The `name` is a non-load-bearing render symbol (C23); identity is
+/// the role index, which survives lowering — the name does not.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Role {
+    pub name: String,
+    pub targets: Vec<Target>,
+}
+
+/// A composite-level alias relabelling one interior leaf param slot's surface
+/// name in `param_space()`. `node` is the interior item index, `slot` the param
+/// slot within that leaf. Pure legibility: the alias relabels in place and never
+/// reorders, adds, or removes a slot (C23 — identity stays the slot).
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ParamAlias {
+    pub name: String,
+    pub node: usize,
+    pub slot: usize,
+}
+
 /// A reusable sub-graph fragment compiled away by inlining (C9/C23). It is **not**
 /// a [`Node`]: it is never `eval`'d. It holds interior items (local indices),
 /// interior edges (local indices), input roles (role `r` fans into the interior
@@ -50,7 +70,8 @@ pub struct Composite {
     name: String,
     nodes: Vec<BlueprintNode>,
     edges: Vec<Edge>,
-    input_roles: Vec<Vec<Target>>,
+    input_roles: Vec<Role>,
+    params: Vec<ParamAlias>,
     output: Vec<OutField>,
 }
 
@@ -63,10 +84,11 @@ impl Composite {
         name: impl Into<String>,
         nodes: Vec<BlueprintNode>,
         edges: Vec<Edge>,
-        input_roles: Vec<Vec<Target>>,
+        input_roles: Vec<Role>,
+        params: Vec<ParamAlias>,
         output: Vec<OutField>,
     ) -> Self {
-        Self { name: name.into(), nodes, edges, input_roles, output }
+        Self { name: name.into(), nodes, edges, input_roles, params, output }
     }
 
     /// The authored render name (cluster title, #13). Non-load-bearing.
@@ -81,10 +103,17 @@ impl Composite {
     pub fn edges(&self) -> &[Edge] {
         &self.edges
     }
-    /// The input roles: role `r` fans into `input_roles()[r]` interior targets.
-    pub fn input_roles(&self) -> &[Vec<Target>] {
+    /// The input roles: role `r` fans into `input_roles()[r].targets` interior
+    /// targets, under the boundary name `input_roles()[r].name` (C23 — name is a
+    /// render symbol, identity is the role index).
+    pub fn input_roles(&self) -> &[Role] {
         &self.input_roles
     }
+    /// The param aliases: each relabels one interior leaf param slot's surface
+    /// name in `param_space()` (pure naming overlay; identity stays the slot, C23).
+    pub fn params(&self) -> &[ParamAlias] {
+        &self.params
+    }
     /// The exposed output record: each entry re-exports one interior
     /// `(node, output-field)` under a boundary name (C8 — one port, K columns).
     pub fn output(&self) -> &[OutField] {
@@ -148,7 +177,7 @@ impl Blueprint {
     /// same-type siblings in one composite share a name — uniqueness is at the slot.
     pub fn param_space(&self) -> Vec<ParamSpec> {
         let mut out = Vec::new();
-        collect_params(&self.nodes, "", &mut out);
+        collect_params(&self.nodes, "", &[], &mut out);
         out
     }
 
@@ -218,17 +247,32 @@ impl Blueprint {
 
 /// Recursive read-only walk for `Blueprint::param_space`: a leaf contributes its
 /// declared params under the running path prefix; a composite pushes its `name()`
-/// onto the path and recurses. Order mirrors `lower_items` (items in declared order,
-/// composites depth-first) so a param's slot matches the later flat-node order.
-fn collect_params(items: &[BlueprintNode], prefix: &str, out: &mut Vec<ParamSpec>) {
-    for item in items {
+/// onto the path and recurses, passing its own param aliases down. A leaf param
+/// slot matched by an `(node, slot)` alias is relabelled in place (C23 — pure
+/// naming overlay; the slot stays, order is untouched). Order mirrors `lower_items`
+/// (items in declared order, composites depth-first) so a param's slot matches the
+/// later flat-node order.
+fn collect_params(
+    items: &[BlueprintNode],
+    prefix: &str,
+    aliases: &[ParamAlias],
+    out: &mut Vec<ParamSpec>,
+) {
+    for (i, item) in items.iter().enumerate() {
         match item {
             BlueprintNode::Leaf(factory) => {
-                for p in factory.params() {
+                for (s, p) in factory.params().iter().enumerate() {
+                    // an alias for this exact (node, slot) relabels in place;
+                    // otherwise the factory param name, as today.
+                    let local = aliases
+                        .iter()
+                        .find(|a| a.node == i && a.slot == s)
+                        .map(|a| a.name.as_str())
+                        .unwrap_or(p.name.as_str());
                     let name = if prefix.is_empty() {
-                        p.name.clone()
+                        local.to_string()
                     } else {
-                        format!("{prefix}.{}", p.name)
+                        format!("{prefix}.{local}")
                     };
                     out.push(ParamSpec { name, kind: p.kind });
                 }
@@ -239,7 +283,7 @@ fn collect_params(items: &[BlueprintNode], prefix: &str, out: &mut Vec<ParamSpec
                 } else {
                     format!("{prefix}.{}", c.name())
                 };
-                collect_params(c.nodes(), &child, out);
+                collect_params(c.nodes(), &child, c.params(), out);
             }
         }
     }
@@ -306,9 +350,22 @@ fn inline_composite(
 ) -> Result<ItemLowering, CompileError> {
     // `name` is the non-load-bearing render symbol (#13); it dissolves at inline
     // (C23 — the boundary does not reach the compilat), so it is not destructured.
-    let Composite { name: _, nodes, edges, input_roles, output } = c;
+    // `params` here are the composite's ParamAlias overlay (renamed to avoid
+    // shadowing the injected scalar `params: &[Scalar]` arg consumed by
+    // `lower_items` below).
+    let Composite { name: _, nodes, edges, input_roles, params: param_aliases, output } = c;
     let item_count = nodes.len();
 
+    // an alias must name a real interior leaf param slot (C23 — names are cosmetic
+    // but a dangling handle is an author error). Mirrors the output range-check.
+    for a in &param_aliases {
+        let ok = a.node < item_count
+            && matches!(&nodes[a.node], BlueprintNode::Leaf(f) if a.slot < f.params().len());
+        if !ok {
+            return Err(CompileError::BadInteriorIndex);
+        }
+    }
+
     // recursively lower interior items, then rewrite interior edges through them
     let interior = lower_items(nodes, params, cursor, flat_nodes, flat_edges)?;
     for e in &edges {
@@ -342,7 +399,7 @@ fn inline_composite(
     let mut roles: Vec<Vec<Target>> = Vec::with_capacity(input_roles.len());
     for (r, role) in input_roles.iter().enumerate() {
         let mut flat_targets: Vec<Target> = Vec::new();
-        for t in role {
+        for t in &role.targets {
             flat_targets.extend(resolve_target(t, &interior)?);
         }
         if let Some((first, rest)) = flat_targets.split_first() {
@@ -529,7 +586,11 @@ mod tests {
                 Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                 Edge { from: 1, to: 2, slot: 1, from_field: 0 },
             ],
-            vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![],
             vec![OutField { node: 2, field: 0, name: "out".into() }],
         )
     }
@@ -573,9 +634,10 @@ mod tests {
             vec![pass1(), pass1()],
             vec![],
             vec![
-                vec![Target { node: 0, slot: 0 }],
-                vec![Target { node: 1, slot: 0 }],
+                Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] },
+                Role { name: "price2".into(), targets: vec![Target { node: 1, slot: 0 }] },
             ],
+            vec![],
             vec![
                 OutField { node: 0, field: 0, name: "a".into() },
                 OutField { node: 1, field: 0, name: "b".into() },
@@ -623,7 +685,8 @@ mod tests {
             "outer",
             vec![BlueprintNode::Composite(inner)],
             vec![],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 0, field: 0, name: "out".into() }],
         );
         let bp = Blueprint::new(
@@ -658,9 +721,10 @@ mod tests {
             vec![pass1(), pass1()],
             vec![],
             vec![
-                vec![Target { node: 0, slot: 0 }],
-                vec![Target { node: 1, slot: 0 }],
+                Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] },
+                Role { name: "price2".into(), targets: vec![Target { node: 1, slot: 0 }] },
             ],
+            vec![],
             vec![
                 OutField { node: 0, field: 0, name: "a".into() },
                 OutField { node: 1, field: 0, name: "b".into() },
@@ -671,9 +735,10 @@ mod tests {
             vec![BlueprintNode::Composite(inner)],
             vec![],
             vec![
-                vec![Target { node: 0, slot: 0 }], // outer role 0 -> inner role 0
-                vec![Target { node: 0, slot: 1 }], // outer role 1 -> inner role 1
+                Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }, // outer role 0 -> inner role 0
+                Role { name: "price2".into(), targets: vec![Target { node: 0, slot: 1 }] }, // outer role 1 -> inner role 1
             ],
+            vec![],
             vec![
                 OutField { node: 0, field: 0, name: "x".into() }, // inner field 0
                 OutField { node: 0, field: 1, name: "y".into() }, // inner field 1 (nested arm)
@@ -708,7 +773,8 @@ mod tests {
             "c",
             vec![pass1()],
             vec![Edge { from: 0, to: 9, slot: 0, from_field: 0 }],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 0, field: 0, name: "out".into() }],
         );
         let bp = Blueprint::new(vec![BlueprintNode::Composite(c)], vec![], vec![]);
@@ -723,7 +789,11 @@ mod tests {
             "c",
             vec![pass1(), sink_i64()],
             vec![],
-            vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![],
             vec![OutField { node: 0, field: 0, name: "out".into() }],
         );
         let bp = Blueprint::new(vec![BlueprintNode::Composite(c)], vec![], vec![]);
@@ -738,7 +808,8 @@ mod tests {
             "c",
             vec![pass1()],
             vec![],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 0, field: 5, name: "out".into() }],
         );
         let bp = Blueprint::new(vec![BlueprintNode::Composite(c)], vec![], vec![]);
@@ -754,7 +825,8 @@ mod tests {
             "c",
             vec![pass1()],
             vec![],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 0, field: 0, name: "a".into() }],
         );
         let bp = Blueprint::new(
@@ -852,7 +924,11 @@ mod tests {
                 Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                 Edge { from: 1, to: 2, slot: 1, from_field: 0 },
             ],
-            vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![],
             vec![OutField { node: 2, field: 0, name: "out".into() }],
         )
     }
@@ -940,9 +1016,10 @@ mod tests {
             vec![Sma::factory().into(), Sma::factory().into()],
             vec![],
             vec![
-                vec![Target { node: 0, slot: 0 }],
-                vec![Target { node: 1, slot: 0 }],
+                Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] },
+                Role { name: "price2".into(), targets: vec![Target { node: 1, slot: 0 }] },
             ],
+            vec![],
             vec![
                 OutField { node: 0, field: 0, name: "a".into() },
                 OutField { node: 1, field: 0, name: "b".into() },
@@ -1079,6 +1156,108 @@ mod tests {
         );
     }
 
+    #[test]
+    fn param_alias_relabels_param_space_name_in_place() {
+        // two Sma leaves (each one `length` param) under a composite that aliases
+        // slot 0 of node 0 -> "shortLen" and slot 0 of node 1 -> "longLen".
+        let c = Composite::new(
+            "cross",
+            vec![Sma::factory().into(), Sma::factory().into(), Sub::factory().into()],
+            vec![
+                Edge { from: 0, to: 2, slot: 0, from_field: 0 },
+                Edge { from: 1, to: 2, slot: 1, from_field: 0 },
+            ],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![
+                ParamAlias { name: "shortLen".into(), node: 0, slot: 0 },
+                ParamAlias { name: "longLen".into(), node: 1, slot: 0 },
+            ],
+            vec![OutField { node: 2, field: 0, name: "out".into() }],
+        );
+        let bp = Blueprint::new(vec![BlueprintNode::Composite(c)], vec![], vec![]);
+        let names: Vec<String> = bp.param_space().into_iter().map(|p| p.name).collect();
+        // aliased in place: names are the aliases, NOT two duplicate "cross.length".
+        assert_eq!(names, vec!["cross.shortLen".to_string(), "cross.longLen".to_string()]);
+    }
+
+    #[test]
+    fn out_of_range_param_alias_rejected() {
+        // alias names node 9 (no such interior item) -> caught at compile.
+        let c = Composite::new(
+            "cross",
+            vec![Sma::factory().into(), Sma::factory().into(), Sub::factory().into()],
+            vec![
+                Edge { from: 0, to: 2, slot: 0, from_field: 0 },
+                Edge { from: 1, to: 2, slot: 1, from_field: 0 },
+            ],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![ParamAlias { name: "bogus".into(), node: 9, slot: 0 }],
+            vec![OutField { node: 2, field: 0, name: "out".into() }],
+        );
+        let bp = Blueprint::new(
+            vec![BlueprintNode::Composite(c)],
+            vec![SourceSpec { kind: ScalarKind::F64, targets: vec![] }],
+            vec![],
+        );
+        // two Sma leaves => two i64 length slots; supply a matching vector so the
+        // ONLY error is the bad alias, not arity. (The Ok arm holds Box<dyn Node>,
+        // not Debug, so assert via the Err arm — as the other reject tests do.)
+        assert_eq!(
+            bp.compile_with_params(&[Scalar::I64(2), Scalar::I64(4)]).err(),
+            Some(CompileError::BadInteriorIndex),
+        );
+    }
+
+    #[test]
+    fn unaliased_params_keep_factory_names() {
+        // no aliases => param_space identical to the pre-#41 path-qualified names.
+        let c = Composite::new(
+            "cross",
+            vec![Sma::factory().into(), Sma::factory().into(), Sub::factory().into()],
+            vec![
+                Edge { from: 0, to: 2, slot: 0, from_field: 0 },
+                Edge { from: 1, to: 2, slot: 1, from_field: 0 },
+            ],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![],
+            vec![OutField { node: 2, field: 0, name: "out".into() }],
+        );
+        let bp = Blueprint::new(vec![BlueprintNode::Composite(c)], vec![], vec![]);
+        let names: Vec<String> = bp.param_space().into_iter().map(|p| p.name).collect();
+        assert_eq!(names, vec!["cross.length".to_string(), "cross.length".to_string()]);
+    }
+
+    #[test]
+    fn partial_aliasing_relabels_only_the_named_slot() {
+        // alias node 0 only; node 1 keeps its factory name; order intact.
+        let c = Composite::new(
+            "cross",
+            vec![Sma::factory().into(), Sma::factory().into(), Sub::factory().into()],
+            vec![
+                Edge { from: 0, to: 2, slot: 0, from_field: 0 },
+                Edge { from: 1, to: 2, slot: 1, from_field: 0 },
+            ],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![ParamAlias { name: "shortLen".into(), node: 0, slot: 0 }],
+            vec![OutField { node: 2, field: 0, name: "out".into() }],
+        );
+        let bp = Blueprint::new(vec![BlueprintNode::Composite(c)], vec![], vec![]);
+        let names: Vec<String> = bp.param_space().into_iter().map(|p| p.name).collect();
+        assert_eq!(names, vec!["cross.shortLen".to_string(), "cross.length".to_string()]);
+    }
+
     #[test]
     fn param_space_is_flat_path_qualified_and_slot_disambiguated() {
         use aura_std::{LinComb, Sma, Sub};
@@ -1090,7 +1269,11 @@ mod tests {
                 Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                 Edge { from: 1, to: 2, slot: 1, from_field: 0 },
             ],
-            vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![],
             vec![OutField { node: 2, field: 0, name: "out".into() }],
         );
         // outer composite "strategy": the inner composite + a LinComb([1,-1])
@@ -1098,7 +1281,8 @@ mod tests {
             "strategy",
             vec![BlueprintNode::Composite(fast_slow), LinComb::factory(2).into()],
             vec![],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 0, field: 0, name: "out".into() }],
         );
         let bp = Blueprint::new(vec![BlueprintNode::Composite(strategy)], vec![], vec![]);
@@ -1141,7 +1325,11 @@ mod tests {
                 Edge { from: 0, to: 2, slot: 0, from_field: 0 },
                 Edge { from: 1, to: 2, slot: 1, from_field: 0 },
             ],
-            vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+            vec![Role {
+                name: "price".into(),
+                targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+            }],
+            vec![],
             vec![OutField { node: 2, field: 0, name: "out".into() }],
         );
         // outer composite "strategy": the inner composite + a LinComb([1,-1])
@@ -1149,7 +1337,8 @@ mod tests {
             "strategy",
             vec![BlueprintNode::Composite(fast_slow), LinComb::factory(2).into()],
             vec![],
-            vec![vec![Target { node: 0, slot: 0 }]],
+            vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+            vec![],
             vec![OutField { node: 0, field: 0, name: "out".into() }],
         );
         let bp = Blueprint::new(vec![BlueprintNode::Composite(strategy)], vec![], vec![]);
diff --git a/crates/aura-engine/src/lib.rs b/crates/aura-engine/src/lib.rs
index b4ce7f3..fa234c2 100644
--- a/crates/aura-engine/src/lib.rs
+++ b/crates/aura-engine/src/lib.rs
@@ -35,7 +35,7 @@ mod blueprint;
 mod harness;
 mod report;
 
-pub use blueprint::{Blueprint, BlueprintNode, CompileError, Composite, OutField};
+pub use blueprint::{Blueprint, BlueprintNode, CompileError, Composite, OutField, ParamAlias, Role};
 pub use harness::{BootstrapError, Edge, Harness, SourceSpec, Target};
 pub use report::{f64_field, summarize, RunManifest, RunMetrics, RunReport};
 // #29: re-export the core scalar vocabulary a Blueprint builder needs
diff --git a/fieldtests/milestone-construction-layer/mc_1_composite_build_run.rs b/fieldtests/milestone-construction-layer/mc_1_composite_build_run.rs
index 9bb1036..d239776 100644
--- a/fieldtests/milestone-construction-layer/mc_1_composite_build_run.rs
+++ b/fieldtests/milestone-construction-layer/mc_1_composite_build_run.rs
@@ -17,7 +17,7 @@
 use std::sync::mpsc;
 
 use aura_core::{Firing, Scalar, ScalarKind, Timestamp};
-use aura_engine::{Blueprint, BlueprintNode, Composite, Edge, OutField, SourceSpec, Target};
+use aura_engine::{Blueprint, BlueprintNode, Composite, Edge, OutField, Role, SourceSpec, Target};
 use aura_std::{Exposure, Recorder, SimBroker, Sma, Sub};
 
 fn main() {
@@ -41,10 +41,15 @@ fn main() {
             Edge { from: 1, to: 2, slot: 1, from_field: 0 },
         ],
         // input role 0 (price) fans into Sma(2).slot0 AND Sma(4).slot0
-        vec![vec![
-            Target { node: 0, slot: 0 },
-            Target { node: 1, slot: 0 },
-        ]],
+        vec![Role {
+            name: "price".into(),
+            targets: vec![
+                Target { node: 0, slot: 0 },
+                Target { node: 1, slot: 0 },
+            ],
+        }],
+        // no param aliases
+        vec![],
         // single exposed output: Sub's output field 0
         vec![OutField { node: 2, field: 0, name: "out".into() }],
     );
diff --git a/fieldtests/milestone-construction-layer/mc_2_miswire_render.rs b/fieldtests/milestone-construction-layer/mc_2_miswire_render.rs
index 8a0a938..5a84865 100644
--- a/fieldtests/milestone-construction-layer/mc_2_miswire_render.rs
+++ b/fieldtests/milestone-construction-layer/mc_2_miswire_render.rs
@@ -12,7 +12,7 @@
 // Public interface only: Composite / Blueprint accessors + Node::label() via
 // the boxed node; ledger C8-refinement (label is the disambiguating symbol).
 
-use aura_engine::{BlueprintNode, Composite, Edge, OutField, Target};
+use aura_engine::{BlueprintNode, Composite, Edge, OutField, Role, Target};
 // NB: `node.label()` on a `&Box<dyn Node>` leaf dispatches via the trait object
 // without an explicit `use aura_core::Node` (the method is in scope through the
 // boxed trait object). A consumer does not need to import the Node trait to read
@@ -43,7 +43,11 @@ fn cross(swap: bool) -> Composite {
             Sub::factory().into(),
         ],
         vec![e_fast, e_slow],
-        vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+        vec![Role {
+            name: "price".into(),
+            targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+        }],
+        vec![],
         vec![OutField { node: 2, field: 0, name: "out".into() }],
     )
 }
diff --git a/fieldtests/milestone-construction-layer/mc_3_nested_composite.rs b/fieldtests/milestone-construction-layer/mc_3_nested_composite.rs
index 4894c6d..f5da3bc 100644
--- a/fieldtests/milestone-construction-layer/mc_3_nested_composite.rs
+++ b/fieldtests/milestone-construction-layer/mc_3_nested_composite.rs
@@ -15,7 +15,7 @@
 use std::sync::mpsc;
 
 use aura_core::{Firing, Scalar, ScalarKind, Timestamp};
-use aura_engine::{Blueprint, BlueprintNode, Composite, Edge, OutField, SourceSpec, Target};
+use aura_engine::{Blueprint, BlueprintNode, Composite, Edge, OutField, Role, SourceSpec, Target};
 use aura_std::{Exposure, Recorder, SimBroker, Sma, Sub};
 
 /// Inner composite: the SMA(2)/SMA(4) cross (one price role -> spread output).
@@ -31,7 +31,11 @@ fn inner_cross() -> Composite {
             Edge { from: 0, to: 2, slot: 0, from_field: 0 },
             Edge { from: 1, to: 2, slot: 1, from_field: 0 },
         ],
-        vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+        vec![Role {
+            name: "price".into(),
+            targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+        }],
+        vec![],
         vec![OutField { node: 2, field: 0, name: "out".into() }],
     )
 }
@@ -48,7 +52,9 @@ fn strategy() -> Composite {
             Exposure::factory().into(),
         ],
         vec![Edge { from: 0, to: 1, slot: 0, from_field: 0 }], // cross -> Exposure
-        vec![vec![Target { node: 0, slot: 0 }]],               // price -> inner role 0
+        // price -> inner role 0
+        vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }] }],
+        vec![],
         vec![OutField { node: 1, field: 0, name: "out".into() }],
     )
 }
diff --git a/fieldtests/milestone-construction-layer/mc_4_introspect_graph.rs b/fieldtests/milestone-construction-layer/mc_4_introspect_graph.rs
index 4840e52..12c75e7 100644
--- a/fieldtests/milestone-construction-layer/mc_4_introspect_graph.rs
+++ b/fieldtests/milestone-construction-layer/mc_4_introspect_graph.rs
@@ -10,7 +10,7 @@
 // Public interface only.
 
 use aura_core::ScalarKind;
-use aura_engine::{Blueprint, BlueprintNode, Composite, Edge, OutField, SourceSpec, Target};
+use aura_engine::{Blueprint, BlueprintNode, Composite, Edge, OutField, Role, SourceSpec, Target};
 // NB (fieldtest finding): `aura_engine::ScalarKind` does NOT resolve — the
 // construction surface (aura-engine) does not re-export the core scalar
 // vocabulary (ScalarKind / Scalar / Firing) that a graph-builder needs. A
@@ -30,7 +30,11 @@ fn sma_cross() -> Composite {
             Edge { from: 0, to: 2, slot: 0, from_field: 0 },
             Edge { from: 1, to: 2, slot: 1, from_field: 0 },
         ],
-        vec![vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }]],
+        vec![Role {
+            name: "price".into(),
+            targets: vec![Target { node: 0, slot: 0 }, Target { node: 1, slot: 0 }],
+        }],
+        vec![],
         vec![OutField { node: 2, field: 0, name: "out".into() }],
     )
 }
@@ -63,8 +67,8 @@ fn describe_node(prefix: &str, n: &BlueprintNode) {
             for inner in c.nodes() {
                 describe_node(&format!("{prefix}  "), inner);
             }
-            for (r, targets) in c.input_roles().iter().enumerate() {
-                println!("{prefix}  role[{r}] fans into {targets:?}");
+            for (r, role) in c.input_roles().iter().enumerate() {
+                println!("{prefix}  role[{r}] {:?} fans into {:?}", role.name, role.targets);
             }
             for e in c.edges() {
                 println!("{prefix}  interior edge {e:?}");
@@ -107,7 +111,8 @@ fn main() {
         assert_eq!(c.name(), "sma_cross");
         assert_eq!(c.nodes().len(), 3, "composite interior should have 3 items");
         assert_eq!(c.input_roles().len(), 1, "one price role");
-        assert_eq!(c.input_roles()[0].len(), 2, "price fans into both SMAs");
+        assert_eq!(c.input_roles()[0].name, "price", "the role carries its boundary name");
+        assert_eq!(c.input_roles()[0].targets.len(), 2, "price fans into both SMAs");
         let out = c.output();
         assert_eq!(out.len(), 1, "the cross re-exports one output field");
         assert_eq!((out[0].node, out[0].field), (2, 0), "Sub output is the port");