docs(guide, glossary): pin each ArgKind's lexical canonical form

Fieldtest spec-gap ratified: Count is a plain positive decimal with no
sign and no leading zeros ('03' refuses) — and the per-kind asymmetry
against TimeOfDay's required zero-pad is deliberate, pinned with its
rationale: canonical is each domain's conventional notation,
fixed-width for wall-clock times, minimal for numbers.

refs #271

Cargo.lock

@@ -160,6 +160,7 @@ dependencies = [
  "aura-core",
  "aura-engine",
  "aura-ingest",
+ "aura-market",
  "aura-measurement",
  "aura-registry",
  "aura-research",
@@ -167,6 +168,7 @@ dependencies = [
  "aura-std",
  "aura-strategy",
  "aura-vocabulary",
+ "chrono-tz",
  "clap",
  "data-server",
  "libc",
@@ -192,6 +194,7 @@ dependencies = [
 name = "aura-core"
 version = "0.1.0"
 dependencies = [
+ "chrono-tz",
  "serde",
  "serde_json",
 ]
@@ -307,8 +310,6 @@ dependencies = [
  "aura-backtest",
  "aura-core",
  "aura-strategy",
- "chrono",
- "chrono-tz",
 ]
 
 [[package]]

README.md

@@ -122,7 +122,9 @@ The op kinds are `source`, `input`, `add`, `feed`, `connect`, `expose`, `tap`,
 `gang`, `doc`, and `use` (`tap` declares a recorded measurement point on an
 interior wire; `doc` declares the composite's one-line meaning, required at
 register — C29; `use` splices a registered blueprint in as a nested composite,
-by content id or label; see the authoring guide). See
+by content id or label; `add` additionally takes an `args` object for
+**arg-bearing** types (`Session`, `LinComb`, `CostSum`) — structural,
+non-scalar construction consumed before `bind`; see the authoring guide). See
 `aura graph introspect --node <T>` for a type's exact ports and the op-script
 grammar in the design ledger for the full semantics.
 

crates/aura-cli/Cargo.toml

@@ -65,6 +65,15 @@ zip = "2"
 # (#[cfg(test)] use aura_composites::StopRule in main.rs's ic_tests module),
 # so this rides the same dev-only-edge idiom as `aura-analysis`/`sha2` below.
 aura-composites = { path = "../aura-composites" }
+# aura-market: the shell's own use is test-only (#271's identity-bridge test,
+# `identity_id_bridges_the_rust_configured_session_and_args_script`, needs
+# `Session::configured` as the Rust-authored twin of the args op-script path)
+# — rides the same dev-only-edge idiom as `aura-composites`/`aura-analysis`.
+aura-market = { path = "../aura-market" }
+# chrono-tz: the SAME identity-bridge test needs a `chrono_tz::Tz` to pass
+# `Session::configured` — test-only, pinned to the same version every other
+# crate's chrono-tz entry uses.
+chrono-tz = { version = "0.10", default-features = false }
 # aura-analysis: pearson_corr, used only by the ic_tests unit-test fixtures
 # (mod ic_tests in main.rs) — a test-only edge, not a production one.
 aura-analysis = { path = "../aura-analysis" }

crates/aura-cli/src/graph_construct.rs

@@ -8,8 +8,9 @@ use std::collections::BTreeMap;
 use std::path::Path;
 
 use aura_engine::{
-    blueprint_from_json, blueprint_identity_json, blueprint_to_json, replay, BindOpError,
-    BlueprintDoc, CompileError, Composite, GraphSession, LoadError, Op, OpError, Scalar, ScalarKind,
+    blueprint_from_json, blueprint_identity_json, blueprint_to_json, replay, ArgOpError,
+    BindOpError, BlueprintDoc, CompileError, Composite, GraphSession, LoadError, Op, OpError,
+    Scalar, ScalarKind,
 };
 use serde::Deserialize;
 
@@ -30,6 +31,9 @@ pub const OP_REFERENCE: &str = r#"Op-list reference (stdin: a JSON array of op o
       declare an open input role (wired by an enclosing graph)
   {"op":"add","type":"SMA","name":"fast","bind":{"length":{"I64":2}}}
       instantiate a node ("name" optional; "bind" maps param -> typed scalar)
+  {"op":"add","type":"Session","name":"ny","args":{"tz":"America/New_York","open":"09:30"},"bind":{"period_minutes":{"I64":15}}}
+      an arg-bearing type applies "args" (closed, per-type-declared string
+      pairs) BEFORE "bind" — see graph introspect --node <T> for its args
   {"op":"feed","role":"price","into":["fast.series","slow.series"]}
       wire a role into one or more input slots
   {"op":"connect","from":"fast.value","to":"sub.lhs"}
@@ -64,6 +68,12 @@ enum OpDoc {
         // naming, not an aliasing (contrast `expose`'s `as`, which is a real alias).
         #[serde(rename = "name", default)]
         as_name: Option<String>,
+        // Construction args (#271) — the typed, closed channel applied BEFORE
+        // `bind`. A `BTreeMap` (deterministic iteration order into `Op::Add`'s
+        // `Vec`, mirroring `bind`'s own convention) — absent for every
+        // args-free type, so an old-style `add` document is unaffected.
+        #[serde(default)]
+        args: BTreeMap<String, String>,
         #[serde(default)]
         bind: BTreeMap<String, Scalar>,
     },
@@ -151,9 +161,12 @@ impl From<OpDoc> for Op {
         match d {
             OpDoc::Source { role, kind } => Op::Source { role, kind },
             OpDoc::Input { role } => Op::Input { role },
-            OpDoc::Add { type_id, as_name, bind } => {
-                Op::Add { type_id, as_name, bind: bind.into_iter().collect() }
-            }
+            OpDoc::Add { type_id, as_name, args, bind } => Op::Add {
+                type_id,
+                as_name,
+                args: args.into_iter().collect(),
+                bind: bind.into_iter().collect(),
+            },
             OpDoc::Feed { role, into } => Op::Feed { role, into },
             OpDoc::Connect { from, to } => Op::Connect { from, to },
             OpDoc::Expose { from, as_name } => Op::Expose { from, as_name },
@@ -172,6 +185,24 @@ impl From<OpDoc> for Op {
     }
 }
 
+/// Phrase one `ArgOpError` (#271) as a human cause, WITHOUT the node prefix —
+/// shared by `format_op_error`'s `BadArg` arm (the `add`-op path) and
+/// `blueprint_load_prose`'s `BadArg` arm (the blueprint LOAD path), so the two
+/// error families cannot phrase the same fault differently. Exhaustive over
+/// `ArgOpError`; `BadValue` names the arg, its declared `ArgKind`, AND the
+/// closed per-kind `hint()` line (the same hint `introspect --node` shows).
+fn arg_op_error_prose(err: &ArgOpError) -> String {
+    match err {
+        ArgOpError::NotArgBearing => "takes no construction args".to_string(),
+        ArgOpError::UnknownArg(a) => format!("has no construction arg {a:?}"),
+        ArgOpError::DuplicateArg(a) => format!("was given arg {a:?} more than once"),
+        ArgOpError::MissingArg(a) => format!("is missing required arg {a:?}"),
+        ArgOpError::BadValue { arg, kind, got } => {
+            format!("arg {arg:?} expects {kind:?} ({}) — got {got:?}", kind.hint())
+        }
+    }
+}
+
 /// Phrase one `OpError` as a human cause (the engine error types are
 /// `Display`-free by convention; this is the CLI's presentation layer). The
 /// exhaustive match means a new `OpError` variant forces an update here.
@@ -204,6 +235,7 @@ fn format_op_error(e: &OpError) -> String {
                 format!("cannot bind {node}.{param} — member of gang {gang:?}")
             }
         },
+        OpError::BadArg { node, err } => format!("node {node} {}", arg_op_error_prose(err)),
         OpError::UnconnectedPort { node, slot } => format!("slot {node}.{slot} is unconnected"),
         OpError::RoleKindMismatch { role } => format!("input role {role} fans into slots of differing kinds"),
         OpError::GangKindMismatch { member, expected, got } => {
@@ -439,6 +471,17 @@ pub fn introspect_node(type_id: &str, env: &aura_runner::project::Env) -> Result
     let schema = builder.schema();
     // C29 (#315): the head line carries the node's one-line meaning.
     let mut out = format!("{} — {}\n", builder.label(), schema.doc);
+    // #271: an arg-bearing (pending) type declares its ArgSpecs but no real
+    // ports/params yet — those form only once `try_args` runs (`make`). Show
+    // the arg rows first (they must be supplied before anything else can be
+    // discovered) plus the one-line note the spec's worked discovery example
+    // pins.
+    for spec in builder.arg_specs() {
+        out.push_str(&format!("  arg    {}: {:?}   ({})\n", spec.name, spec.kind, spec.kind.hint()));
+    }
+    if builder.is_pending() {
+        out.push_str("  note   ports and params form at construction; args are required\n");
+    }
     for port in &schema.inputs {
         out.push_str(&format!("  in   {}:{:?}\n", port.name, port.kind));
     }
@@ -662,6 +705,7 @@ pub(crate) fn blueprint_load_prose(e: &LoadError) -> String {
         }
         LoadError::UnknownNodeType(t) => format!("unknown node type {t:?}"),
         LoadError::Gang(e) => format!("gang section invalid: {}", gang_fault_prose(e)),
+        LoadError::BadArg(e) => format!("construction args invalid: {}", arg_op_error_prose(e)),
     }
 }
 

crates/aura-cli/src/main.rs

@@ -3809,6 +3809,54 @@ mod tests {
         );
     }
 
+    /// #271 (cross-path identity, extending #171's bridge pattern to an
+    /// arg-bearing type): the Rust-authored `Session::configured` builder and
+    /// its `add`-op `args` twin differ in canonical bytes (debug names) —
+    /// distinct content ids — but project to the same identity JSON, one
+    /// identity id across authoring paths even though the construction
+    /// channel (Rust call vs `args` object) differs.
+    #[test]
+    fn identity_id_bridges_the_rust_configured_session_and_args_script() {
+        use aura_market::Session;
+
+        let rust_built = Composite::new(
+            "sess",
+            vec![Session::configured(9, 30, chrono_tz::Europe::Berlin, 15).into()],
+            vec![],
+            vec![aura_engine::Role {
+                name: "trigger".into(),
+                targets: vec![aura_engine::Target { node: 0, slot: 0 }],
+                source: Some(ScalarKind::F64),
+            }],
+            vec![aura_engine::OutField { node: 0, field: 0, name: "bars".into() }],
+        );
+
+        let doc = r#"[
+            {"op":"source","role":"trigger","kind":"F64"},
+            {"op":"add","type":"Session","name":"sess",
+             "args":{"tz":"Europe/Berlin","open":"09:30"},
+             "bind":{"period_minutes":{"I64":15}}},
+            {"op":"feed","role":"trigger","into":["sess.trigger"]},
+            {"op":"expose","from":"sess.bars_since_open","as":"bars"}
+        ]"#;
+        let env = aura_runner::project::Env::std();
+        let json = crate::graph_construct::build_from_str(doc, &env).expect("args op-script twin builds");
+        assert_ne!(
+            content_id(&json),
+            content_id(&blueprint_to_json(&rust_built).expect("serializes")),
+            "authoring paths keep distinct content ids (debug names differ)"
+        );
+        let loaded = blueprint_from_json(&json, &|t| std_vocabulary(t)).expect("twin reloads");
+        let identity = |c: &Composite| {
+            content_id(&aura_engine::blueprint_identity_json(c).expect("identity-serializes"))
+        };
+        assert_eq!(
+            identity(&loaded),
+            identity(&rust_built),
+            "one topology -> one identity id, Rust-configured vs args op-script"
+        );
+    }
+
     #[test]
     fn mc_r_bootstrap_json_carries_every_bootstrap_field_under_the_mc_r_bootstrap_key() {
         // Property: the `mc_r_bootstrap` output line is the full RBootstrap shape —

crates/aura-cli/tests/graph_construct.rs

@@ -170,8 +170,9 @@ fn graph_introspect_vocabulary_lists_exactly_the_closed_roster_count() {
     let lines: Vec<&str> = stdout.lines().filter(|l| !l.is_empty()).collect();
     assert_eq!(
         lines.len(),
-        33,
-        "the std-only (no project) vocabulary has exactly the roster's 33 entries: {stdout}"
+        36,
+        "the std-only (no project) vocabulary has exactly the roster's 36 entries (#271: \
+         Session/LinComb/CostSum moved in): {stdout}"
     );
 }
 
@@ -183,6 +184,78 @@ fn graph_introspect_node_answers_ports_without_a_build() {
     assert!(stdout.contains("value"), "lists the output field: {stdout}");
 }
 
+/// #271 acceptance criterion 1: an op-script reaching BOTH new arg-bearing
+/// roster entries (a `Session` for any IANA timezone/open, a `LinComb` of any
+/// arity — no Rust authored) builds via `aura graph build`; the emitted
+/// blueprint is `"version": 2` (the args-bearing tier) and carries the
+/// accepted timezone verbatim.
+///
+/// Deviation from the spec's literal worked example
+/// (`docs/specs/construction-args.md` §"The user-facing program"): that JSON
+/// wires `ny.bars_since_open` (`Session`'s I64 output) directly into
+/// `mix.term[0]` (`LinComb`'s F64 input) — a genuine kind mismatch the
+/// engine's eager `connect` gate refuses (I64 != F64), not a property of
+/// this feature. This fixture keeps every construction-args property the
+/// criterion asks for (Session + args, LinComb + args, version 2, tz
+/// carried) but feeds `LinComb` from two same-kind SMAs and exposes
+/// `ny.bars_since_open` at the boundary directly (`expose` has no kind
+/// constraint) instead of wiring it into the mismatched slot.
+#[test]
+fn graph_build_accepts_the_session_args_example() {
+    let doc = r#"[
+        {"op":"source","role":"price","kind":"F64"},
+        {"op":"add","type":"Session","name":"ny",
+         "args":{"tz":"America/New_York","open":"09:30"},
+         "bind":{"period_minutes":{"I64":15}}},
+        {"op":"add","type":"SMA","name":"fast","bind":{"length":{"I64":2}}},
+        {"op":"add","type":"SMA","name":"slow","bind":{"length":{"I64":4}}},
+        {"op":"add","type":"LinComb","name":"mix","args":{"arity":"2"},
+         "bind":{"weights[0]":{"F64":1.0},"weights[1]":{"F64":0.25}}},
+        {"op":"add","type":"Bias"},
+        {"op":"feed","role":"price","into":["ny.trigger","fast.series","slow.series"]},
+        {"op":"connect","from":"fast.value","to":"mix.term[0]"},
+        {"op":"connect","from":"slow.value","to":"mix.term[1]"},
+        {"op":"connect","from":"mix.value","to":"bias.signal"},
+        {"op":"expose","from":"bias.bias","as":"bias"},
+        {"op":"expose","from":"ny.bars_since_open","as":"session_bar"},
+        {"op":"doc","text":"NY-session-gated SMA blend"}
+    ]"#;
+    let (stdout, stderr, ok) = run(&["graph", "build"], doc);
+    assert!(ok, "the worked example builds: {stderr}");
+    assert!(stdout.contains(r#""format_version":2"#), "an args-bearing document is version 2: {stdout}");
+    assert!(stdout.contains("America/New_York"), "carries the accepted tz verbatim: {stdout}");
+}
+
+/// #271: a malformed construction-arg value (a bad IANA tz string) refuses at
+/// the `add` op with exit 1, naming the offending arg (not a Debug leak).
+#[test]
+fn graph_build_bad_tz_is_exit_1_naming_the_arg() {
+    let doc = r#"[
+        {"op":"add","type":"Session","name":"ny",
+         "args":{"tz":"not_a_zone","open":"09:30"}}
+    ]"#;
+    let (stderr, code) = run_code(&["graph", "build"], doc);
+    assert_eq!(code, Some(1), "a construction-arg fault is exit 1: {stderr}");
+    assert!(stderr.contains("tz"), "names the offending arg: {stderr}");
+    assert!(!stderr.contains("{"), "no Debug-struct leak: {stderr}");
+}
+
+/// #271: `graph introspect --node Session` self-describes its declared
+/// construction args (name, kind, hint) plus the pending note — the
+/// discovery surface an author reads before writing the `args` object.
+#[test]
+fn graph_introspect_node_session_lists_arg_rows() {
+    let (stdout, _stderr, ok) = run(&["graph", "introspect", "--node", "Session"], "");
+    assert!(ok, "exit success");
+    assert!(stdout.contains("tz"), "lists the tz arg: {stdout}");
+    assert!(stdout.contains("open"), "lists the open arg: {stdout}");
+    assert!(stdout.contains("IANA timezone"), "shows the tz hint: {stdout}");
+    assert!(
+        stdout.contains("ports and params form at construction"),
+        "shows the pending note: {stdout}"
+    );
+}
+
 #[test]
 fn graph_introspect_unwired_reports_open_slots() {
     let doc = r#"[

crates/aura-composites/src/lib.rs

@@ -52,8 +52,8 @@ fn vol_stop_inner(knobs: Option<(i64, f64)>) -> Composite {
     let sqrt = g.add(Sqrt::builder()); // → σ (price units)
     // k·σ: weights[0] bound (Some) or open and named `stop_k` (None).
     let scale = g.add(match knobs {
-        Some((_, k)) => LinComb::builder(1).bind("weights[0]", Scalar::f64(k)),
-        None => LinComb::builder(1).named("stop_k"),
+        Some((_, k)) => LinComb::configured(1).bind("weights[0]", Scalar::f64(k)),
+        None => LinComb::configured(1).named("stop_k"),
     });
     g.feed(price, [delay.input("series"), sub.input("lhs")]);
     g.connect(delay.output("value"), sub.input("rhs"));
@@ -174,7 +174,7 @@ pub fn cost_graph(cost_nodes: Vec<PrimitiveBuilder>) -> Composite {
     let entry = g.input_role("entry_price");
     let stop = g.input_role("stop_price");
 
-    let agg = g.add(CostSum::builder(n));
+    let agg = g.add(CostSum::configured(n));
 
     // Per-role geometry fan targets, collected across all nodes, fed once per role.
     let mut closed_t = Vec::with_capacity(n);

crates/aura-core/Cargo.toml

@@ -7,6 +7,10 @@ publish.workspace = true
 
 [dependencies]
 serde = { workspace = true }
+# ArgValue::Tz carries chrono_tz::Tz (the closed IANA table, exact names only) —
+# already a workspace dependency of four other crates (see docs/specs/
+# construction-args.md § Dependency note).
+chrono-tz = { version = "0.10", default-features = false }
 
 [dev-dependencies]
 serde_json = { workspace = true }

crates/aura-core/src/lib.rs

@@ -44,8 +44,9 @@ pub use column::{Column, Window};
 pub use ctx::Ctx;
 pub use error::KindMismatch;
 pub use node::{
-    doc_gate, zip_params, BindOpError, BoundParam, DocGateFault, FieldSpec, Firing, Node,
-    NodeSchema, ParamSpec, PortSpec, PrimitiveBuilder,
+    doc_gate, zip_params, ArgKind, ArgOpError, ArgSpec, ArgValue, BindOpError, BoundParam,
+    ConstructionArg, DocGateFault, FieldSpec, Firing, Node, NodeSchema, ParamSpec, PortSpec,
+    PrimitiveBuilder,
 };
 pub use scalar::{Scalar, ScalarKind, Timestamp};
 pub use series_fold::SeriesFold;

crates/aura-core/src/node.rs

@@ -112,6 +112,7 @@ pub struct PrimitiveBuilder {
     instance_name: Option<String>,
     schema: NodeSchema,
     bound: Vec<BoundParam>,
+    args: ArgsState, // NEW: `Plain` for every existing (non-arg-bearing) node
     // The build closure's type is exactly the recipe contract (a param slice in, a
     // boxed node out); a type alias would not clarify it.
     #[allow(clippy::type_complexity)]
@@ -127,7 +128,108 @@ impl PrimitiveBuilder {
         schema: NodeSchema,
         build: impl Fn(&[Cell]) -> Box<dyn Node> + 'static,
     ) -> Self {
-        Self { name, instance_name: None, schema, bound: Vec::new(), build: Box::new(build) }
+        Self { name, instance_name: None, schema, bound: Vec::new(), args: ArgsState::Plain, build: Box::new(build) }
+    }
+
+    /// An arg-bearing recipe: introspectable (doc + declared `ArgSpec`s) but
+    /// not yet constructible. `schema` carries only the doc line (empty
+    /// inputs/output/params — the real signature forms inside `make`, once
+    /// `try_args` has parsed values to hand it); `build` on a pending builder
+    /// panics (the `bind` panic-contract twin) — the data path always goes
+    /// through `try_args` first, so no pending builder ever reaches `build`.
+    pub fn pending(
+        name: &'static str,
+        doc: &'static str,
+        specs: &'static [ArgSpec],
+        make: fn(&[(String, ArgValue)]) -> PrimitiveBuilder,
+    ) -> Self {
+        Self {
+            name,
+            instance_name: None,
+            schema: NodeSchema { doc, ..Default::default() },
+            bound: Vec::new(),
+            args: ArgsState::Pending { specs, make },
+            build: Box::new(move |_| {
+                panic!(
+                    "PrimitiveBuilder::build: `{name}` is an unconfigured arg-bearing type — \
+                     call try_args first"
+                )
+            }),
+        }
+    }
+
+    /// Validate raw `(name, value)` pairs against the declared `ArgSpec`s
+    /// (strict form — see `ArgKind::parse`), then run `make`, returning the
+    /// configured builder (`args: Configured{..}`) with this builder's
+    /// `instance_name` carried over. `Plain` + empty raw is `Ok(self)`
+    /// (uniform op application, #157's try_bind precedent); `Plain` +
+    /// non-empty raw is `NotArgBearing`. Validation order (deterministic):
+    /// first unknown arg name, then a duplicate, then the first spec-order
+    /// missing arg, then per-kind parse failures (`BadValue`).
+    pub fn try_args(self, raw: &[(String, String)]) -> Result<Self, ArgOpError> {
+        let (specs, make) = match &self.args {
+            ArgsState::Plain | ArgsState::Configured { .. } => {
+                return if raw.is_empty() { Ok(self) } else { Err(ArgOpError::NotArgBearing) };
+            }
+            ArgsState::Pending { specs, make } => (*specs, *make),
+        };
+
+        for (name, _) in raw {
+            if !specs.iter().any(|s| s.name == name.as_str()) {
+                return Err(ArgOpError::UnknownArg(name.clone()));
+            }
+        }
+        for i in 0..raw.len() {
+            if raw[i + 1..].iter().any(|(n, _)| n == &raw[i].0) {
+                return Err(ArgOpError::DuplicateArg(raw[i].0.clone()));
+            }
+        }
+        for spec in specs {
+            if !raw.iter().any(|(n, _)| n.as_str() == spec.name) {
+                return Err(ArgOpError::MissingArg(spec.name.to_string()));
+            }
+        }
+
+        let mut values = Vec::with_capacity(specs.len());
+        let mut accepted = Vec::with_capacity(specs.len());
+        for spec in specs {
+            let raw_val = &raw.iter().find(|(n, _)| n.as_str() == spec.name).expect("presence checked above").1;
+            let value = spec.kind.parse(raw_val).map_err(|()| ArgOpError::BadValue {
+                arg: spec.name.to_string(),
+                kind: spec.kind,
+                got: raw_val.clone(),
+            })?;
+            values.push((spec.name.to_string(), value));
+            accepted.push(ConstructionArg { name: spec.name.to_string(), value: raw_val.clone() });
+        }
+
+        let mut built = make(&values);
+        built.instance_name = self.instance_name;
+        built.args = ArgsState::Configured { values: accepted };
+        Ok(built)
+    }
+
+    /// The declared construction-arg specs (a view into the pending recipe);
+    /// empty unless this builder `is_pending()`.
+    pub fn arg_specs(&self) -> &[ArgSpec] {
+        match &self.args {
+            ArgsState::Pending { specs, .. } => specs,
+            _ => &[],
+        }
+    }
+
+    /// The accepted, verbatim construction-arg pairs (the serialize surface);
+    /// empty unless this builder was configured via `try_args`.
+    pub fn construction_args(&self) -> &[ConstructionArg] {
+        match &self.args {
+            ArgsState::Configured { values } => values,
+            _ => &[],
+        }
+    }
+
+    /// True for an arg-bearing recipe not yet configured via `try_args`.
+    pub fn is_pending(&self) -> bool {
+        matches!(self.args, ArgsState::Pending { .. })
     }
     /// Set this node instance's explicit name. Must be non-empty: the name forms
     /// a knob-address segment (`<composite>.<name>.<param>`, via `node_name()` in
@@ -344,6 +446,135 @@ pub enum BindOpError {
     AlreadyGanged { param: String, gang: String },
 }
 
+/// Closed construction-arg kinds (spec §Closedness) — deliberately NOT
+/// `ScalarKind`: the four scalar kinds are the streamed set (invariant 4); args
+/// are bootstrap metadata, never streamed, so the two closedness axes stay
+/// separate types.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ArgKind {
+    /// An IANA timezone name (`chrono_tz::Tz`'s own parser — exact, case-sensitive).
+    Tz,
+    /// A local wall-clock time, strict zero-padded `HH:MM` (00-23 / 00-59).
+    TimeOfDay,
+    /// A plain positive decimal count (>= 1, no leading zeros).
+    Count,
+}
+
+impl ArgKind {
+    /// Parse `raw` in this kind's strict canonical form. The accepted form IS
+    /// the canonical form (spec §Closedness) — there is no normalization
+    /// layer, so a near-miss string refuses rather than being silently
+    /// rewritten (content ids stay input-variance-free by refusal).
+    // The spec's pinned shape (`Result<ArgValue, ()>`, mirroring `ArgOpError`'s
+    // caller-side `BadValue` wrapping the plain refusal): the unit error carries
+    // no information of its own — `try_args` is the only caller and always maps
+    // it to `ArgOpError::BadValue`, which is where the real detail lives.
+    #[allow(clippy::result_unit_err)]
+    pub fn parse(&self, raw: &str) -> Result<ArgValue, ()> {
+        match self {
+            ArgKind::Tz => raw.parse::<chrono_tz::Tz>().map(ArgValue::Tz).map_err(|_| ()),
+            ArgKind::TimeOfDay => {
+                let bytes = raw.as_bytes();
+                if bytes.len() != 5 || bytes[2] != b':' {
+                    return Err(());
+                }
+                let (h, m) = (&raw[0..2], &raw[3..5]);
+                if !h.bytes().all(|b| b.is_ascii_digit()) || !m.bytes().all(|b| b.is_ascii_digit()) {
+                    return Err(());
+                }
+                let hour: u32 = h.parse().map_err(|_| ())?;
+                let minute: u32 = m.parse().map_err(|_| ())?;
+                if hour > 23 || minute > 59 {
+                    return Err(());
+                }
+                Ok(ArgValue::TimeOfDay { hour, minute })
+            }
+            ArgKind::Count => {
+                if raw.is_empty() || !raw.bytes().all(|b| b.is_ascii_digit()) {
+                    return Err(());
+                }
+                if raw.len() > 1 && raw.starts_with('0') {
+                    return Err(()); // leading zero: not the canonical form
+                }
+                let n: usize = raw.parse().map_err(|_| ())?;
+                if n == 0 {
+                    return Err(()); // Count is >= 1
+                }
+                Ok(ArgValue::Count(n))
+            }
+        }
+    }
+
+    /// The static, per-kind hint line (introspection surface, C29) — a closed
+    /// table keyed only by `ArgKind`, never per-entry freetext.
+    pub fn hint(&self) -> &'static str {
+        match self {
+            ArgKind::Tz => "IANA timezone name, e.g. Europe/Berlin",
+            ArgKind::TimeOfDay => "local wall-clock HH:MM",
+            ArgKind::Count => "positive integer count",
+        }
+    }
+}
+
+/// One declared construction arg of an arg-bearing `PrimitiveBuilder` (the
+/// pending recipe's twin of `ParamSpec`): its render name and closed `ArgKind`.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ArgSpec {
+    pub name: &'static str,
+    pub kind: ArgKind,
+}
+
+/// A parsed, validated construction-arg value (in-memory only; documents carry
+/// the canonical string form in [`ConstructionArg`]).
+#[derive(Clone, Debug, PartialEq)]
+pub enum ArgValue {
+    Tz(chrono_tz::Tz),
+    TimeOfDay { hour: u32, minute: u32 },
+    Count(usize),
+}
+
+/// A consumed construction arg — the id-bearing, serialized twin of
+/// `BoundParam`. `value` is the accepted strict-form string, stored verbatim
+/// (never re-normalized — see `ArgKind::parse`).
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ConstructionArg {
+    pub name: String,
+    pub value: String,
+}
+
+/// A fallible-`try_args` fault — the construction-arg twin of `BindOpError`,
+/// for the data-level construction surface.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ArgOpError {
+    /// Args were given, but this type declares none (a `Plain` builder).
+    NotArgBearing,
+    /// A given arg name is not among the declared `ArgSpec`s.
+    UnknownArg(String),
+    /// The same arg name was given more than once.
+    DuplicateArg(String),
+    /// A declared arg has no value in the given set.
+    MissingArg(String),
+    /// A given value failed its declared kind's strict-form parse.
+    BadValue { arg: String, kind: ArgKind, got: String },
+}
+
+/// The args-channel state of a [`PrimitiveBuilder`] (private: callers only
+/// ever observe it through `arg_specs`/`construction_args`/`is_pending`).
+enum ArgsState {
+    /// No construction args declared (every existing node, unaffected).
+    Plain,
+    /// An arg-bearing recipe: declared `ArgSpec`s and the `make` that turns a
+    /// parsed value set into the real, configured builder.
+    Pending {
+        specs: &'static [ArgSpec],
+        #[allow(clippy::type_complexity)]
+        make: fn(&[(String, ArgValue)]) -> PrimitiveBuilder,
+    },
+    /// A configured arg-bearing builder: the accepted, verbatim (name, value)
+    /// pairs — the render/serialize surface (`construction_args`).
+    Configured { values: Vec<ConstructionArg> },
+}
+
 /// A node's declared interface: its inputs (in order) and its output record — an
 /// ordered list of named base columns; length 1 is a scalar (the degenerate
 /// case), and an **empty** `output` (`vec![]`) declares a **pure consumer**
@@ -844,6 +1075,132 @@ mod tests {
     fn doc_gate_accepts_a_meaning_line() {
         assert_eq!(doc_gate("EMA", "exponential moving average over the input series"), Ok(()));
     }
+
+    // --- construction args (ArgKind/ArgSpec/ArgValue/ConstructionArg/ArgOpError) ---
+
+    const DEMO_ARG_SPECS: &[ArgSpec] =
+        &[ArgSpec { name: "tz", kind: ArgKind::Tz }, ArgSpec { name: "open", kind: ArgKind::TimeOfDay }];
+
+    /// A minimal `make`: the fixture does not need `values` to shape a real
+    /// schema (that's `Session::make`'s job, Task 2) — it only proves
+    /// `try_args` reaches `make` with parsed values and carries the result
+    /// forward as `Configured`.
+    fn demo_make(values: &[(String, ArgValue)]) -> PrimitiveBuilder {
+        let _ = values;
+        PrimitiveBuilder::new(
+            "Demo",
+            NodeSchema { inputs: vec![], output: vec![], params: vec![], doc: "test-only arg-bearing schema" },
+            |_| Box::new(Bare),
+        )
+    }
+
+    fn demo_pending() -> PrimitiveBuilder {
+        PrimitiveBuilder::pending("Demo", "test-only arg-bearing schema", DEMO_ARG_SPECS, demo_make)
+    }
+
+    #[test]
+    fn try_args_not_arg_bearing_on_a_plain_builder_with_args() {
+        let plain = PrimitiveBuilder::new("Bare", NodeSchema::default(), |_| Box::new(Bare));
+        assert_eq!(
+            plain.try_args(&[("x".into(), "1".into())]).err(),
+            Some(ArgOpError::NotArgBearing),
+        );
+    }
+
+    #[test]
+    fn try_args_plain_with_empty_raw_is_ok_unchanged() {
+        let plain = PrimitiveBuilder::new(
+            "Bare",
+            NodeSchema { inputs: vec![], output: vec![], params: vec![], doc: "plain doc" },
+            |_| Box::new(Bare),
+        );
+        let after = plain.try_args(&[]).expect("empty raw against a Plain builder is Ok(self)");
+        assert_eq!(after.schema().doc, "plain doc");
+        assert!(after.construction_args().is_empty());
+    }
+
+    #[test]
+    fn try_args_unknown_arg_names_the_first_unknown() {
+        assert_eq!(
+            demo_pending()
+                .try_args(&[("nope".into(), "x".into()), ("tz".into(), "Europe/Berlin".into())])
+                .err(),
+            Some(ArgOpError::UnknownArg("nope".into())),
+        );
+    }
+
+    #[test]
+    fn try_args_duplicate_arg_names_the_repeated_name() {
+        assert_eq!(
+            demo_pending()
+                .try_args(&[
+                    ("tz".into(), "Europe/Berlin".into()),
+                    ("tz".into(), "Europe/Berlin".into()),
+                    ("open".into(), "09:30".into()),
+                ])
+                .err(),
+            Some(ArgOpError::DuplicateArg("tz".into())),
+        );
+    }
+
+    #[test]
+    fn try_args_missing_arg_names_the_first_missing_in_spec_order() {
+        assert_eq!(
+            demo_pending().try_args(&[("tz".into(), "Europe/Berlin".into())]).err(),
+            Some(ArgOpError::MissingArg("open".into())),
+        );
+    }
+
+    #[test]
+    fn try_args_bad_value_names_arg_kind_and_the_rejected_string() {
+        assert_eq!(
+            demo_pending()
+                .try_args(&[("tz".into(), "berlin".into()), ("open".into(), "09:30".into())])
+                .err(),
+            Some(ArgOpError::BadValue { arg: "tz".into(), kind: ArgKind::Tz, got: "berlin".into() }),
+        );
+    }
+
+    /// Strict form IS the canonical form (spec §Closedness): no normalization
+    /// layer, so a near-miss string refuses rather than being rewritten.
+    #[test]
+    fn arg_kind_parse_strict_form_refusals_and_accepts() {
+        assert!(ArgKind::TimeOfDay.parse("9:30").is_err(), "not zero-padded");
+        assert!(ArgKind::Tz.parse("berlin").is_err(), "not the exact IANA name");
+        assert!(ArgKind::Count.parse("02").is_err(), "leading zero");
+        assert!(ArgKind::TimeOfDay.parse("09:30").is_ok());
+        assert!(ArgKind::Tz.parse("Europe/Berlin").is_ok());
+        assert!(ArgKind::Count.parse("2").is_ok());
+    }
+
+    #[test]
+    fn try_args_accepts_a_valid_set_and_echoes_verbatim_pairs() {
+        let configured = demo_pending()
+            .try_args(&[("tz".into(), "America/New_York".into()), ("open".into(), "09:30".into())])
+            .expect("a full valid set configures");
+        assert!(!configured.is_pending());
+        assert_eq!(
+            configured.construction_args(),
+            &[
+                ConstructionArg { name: "tz".into(), value: "America/New_York".into() },
+                ConstructionArg { name: "open".into(), value: "09:30".into() },
+            ],
+        );
+    }
+
+    #[test]
+    fn pending_arg_specs_are_visible_before_configuration() {
+        let pending = demo_pending();
+        assert!(pending.is_pending());
+        assert_eq!(pending.arg_specs().iter().map(|s| s.name).collect::<Vec<_>>(), ["tz", "open"]);
+        assert!(pending.construction_args().is_empty());
+    }
+
+    #[test]
+    #[should_panic(expected = "unconfigured")]
+    fn pending_build_panics() {
+        let _ = demo_pending().build(&[]);
+    }
 }
 
 #[cfg(test)]

crates/aura-engine/src/blueprint.rs

@@ -1821,7 +1821,7 @@ mod tests {
         Composite::new(
             "sig3",
             vec![
-                LinComb::builder(2).into(),
+                LinComb::configured(2).into(),
                 Bias::builder().into(),
                 Sma::builder().named("c").into(),
             ],
@@ -1860,7 +1860,7 @@ mod tests {
         Composite::new(
             "sig3",
             vec![
-                LinComb::builder(2).into(),
+                LinComb::configured(2).into(),
                 Bias::builder().into(),
                 Sma::builder().named("c").into(),
             ],
@@ -3233,7 +3233,7 @@ mod tests {
         // outer composite "strategy": the inner composite + a LinComb([1,-1])
         let strategy = Composite::new(
             "strategy",
-            vec![BlueprintNode::Composite(fast_slow), LinComb::builder(2).into()],
+            vec![BlueprintNode::Composite(fast_slow), LinComb::configured(2).into()],
             vec![],
             vec![Role { name: "price".into(), targets: vec![Target { node: 0, slot: 0 }], source: None }],
             vec![OutField { node: 0, field: 0, name: "out".into() }],
@@ -3441,7 +3441,7 @@ mod tests {
         // outer composite "strategy": the inner composite + a LinComb([1,-1])
         let strategy = Composite::new(
             "strategy",
-            vec![BlueprintNode::Composite(fast_slow), LinComb::builder(2).into()],
+            vec![BlueprintNode::Composite(fast_slow), LinComb::configured(2).into()],
             // fan fast_slow's output into both LinComb terms so every interior slot
             // is wired (the totality check, cycle 0040); param order is unaffected.
             vec![
@@ -3501,7 +3501,7 @@ mod tests {
         use aura_std::{LinComb, Sma};
         let bp = Composite::new(
             "root",
-            vec![Sma::builder().into(), LinComb::builder(2).into()],
+            vec![Sma::builder().into(), LinComb::configured(2).into()],
             vec![],
             vec![],
             vec![], // output

crates/aura-engine/src/blueprint_serde.rs

@@ -7,18 +7,29 @@
 //! closure and the declared schema are re-derived on load from the injected
 //! resolver. This is the inverse of the lossy render half (`model_to_json`); it
 //! carries no node logic (C17) and references a closed vocabulary (C24).
+//!
+//! Construction args (#271) are structural, id-bearing data — like `bound`
+//! values, unlike debug-symbol names — so `strip_debug_symbols` leaves
+//! `PrimitiveData.args` untouched.
 
 use crate::blueprint::{BlueprintNode, Composite, Gang, OutField, Role};
 use crate::harness::Edge;
-use aura_core::{BoundParam, PrimitiveBuilder};
+use aura_core::{BoundParam, ConstructionArg, PrimitiveBuilder};
 
-/// The format version the loader understands. Bumped only by a load-bearing
-/// (Tier-2) change; additive optional fields do not bump it (#156). Pre-ship
-/// dormancy (#61, 2026-07-10): while the project is unshipped every document
-/// lives in-repo and reader/writer change atomically, so the Tier-2 bump
-/// discipline activates at the first external ship — which consciously
-/// freezes v1 (gangs included).
-pub const BLUEPRINT_FORMAT_VERSION: u32 = 1;
+/// The CEILING format version this build's loader understands (and the
+/// writer may ever emit) — bumped only by a load-bearing (Tier-2) change;
+/// additive optional fields do not bump it (#156). Pre-ship dormancy (#61,
+/// 2026-07-10): while the project is unshipped every document lives in-repo
+/// and reader/writer change atomically, so the Tier-2 bump discipline
+/// activates at the first external ship.
+///
+/// #271 (data-driven version): the writer no longer emits a single fixed
+/// version. A document emits `1` when args-free (byte-identical to every
+/// pre-#271 document — content ids stable, C18) and `2` the moment any
+/// primitive, at any nesting depth, carries construction `args` — the
+/// must-understand signal a pre-#271 loader needs. The loader accepts the
+/// closed range `1..=BLUEPRINT_FORMAT_VERSION`.
+pub const BLUEPRINT_FORMAT_VERSION: u32 = 2;
 
 /// Top-level envelope: the version is read before the payload is interpreted.
 #[derive(serde::Serialize, serde::Deserialize)]
@@ -61,17 +72,33 @@ pub enum NodeData {
 }
 
 /// A primitive node as data: its compiled-in type identity, optional instance
-/// name, and bound params. The schema + build closure are re-derived on load.
+/// name, its accepted construction args (#271), and bound params. The schema
+/// + build closure are re-derived on load.
 #[derive(serde::Serialize, serde::Deserialize)]
 pub struct PrimitiveData {
     #[serde(rename = "type")]
     pub type_id: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub name: Option<String>,
+    /// The consumed `(name, value)` construction-arg pairs (#271) — the
+    /// id-bearing, serialized twin of `bound`. Additive-optional: absent
+    /// (empty) for every args-free primitive, so a document with no args
+    /// anywhere stays byte-identical to its pre-#271 form.
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub args: Vec<ArgData>,
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub bound: Vec<BoundParam>,
 }
 
+/// One serialized construction-arg pair (#271) — the wire twin of
+/// [`aura_core::ConstructionArg`]: `value` is the accepted strict-form
+/// string, stored verbatim (never re-normalized).
+#[derive(Clone, serde::Serialize, serde::Deserialize)]
+pub struct ArgData {
+    pub name: String,
+    pub value: String,
+}
+
 /// Serializer failure (typed, named).
 #[derive(Debug)]
 pub enum SerializeError {
@@ -111,9 +138,19 @@ fn project_node(n: &BlueprintNode) -> NodeData {
             // construction once a multi-param node enters the vocabulary.
             let mut bound = b.bound_params().to_vec();
             bound.sort_by_key(|bp| bp.pos);
+            // Construction args (#271) are declared in a fixed `ArgSpec` order
+            // (not player-chosen like binds), so no re-canonicalization is
+            // needed — `construction_args()` already returns them in that
+            // deterministic order.
+            let args: Vec<ArgData> = b
+                .construction_args()
+                .iter()
+                .map(|ConstructionArg { name, value }| ArgData { name: name.clone(), value: value.clone() })
+                .collect();
             NodeData::Primitive(PrimitiveData {
                 type_id: b.label(),
                 name: b.instance_name().map(str::to_string),
+                args,
                 bound,
             })
         }
@@ -121,8 +158,32 @@ fn project_node(n: &BlueprintNode) -> NodeData {
     }
 }
 
+/// Any primitive, at any nesting depth, carries construction args (#271) —
+/// the must-understand signal for the data-driven version (spec §Data-driven
+/// format version).
+fn has_args(b: &CompositeData) -> bool {
+    b.nodes.iter().any(|n| match n {
+        NodeData::Primitive(p) => !p.args.is_empty(),
+        NodeData::Composite(c) => has_args(c),
+    })
+}
+
+/// The version THIS document must declare (#271): `1` for an args-free
+/// document (byte-identical to every pre-#271 document, C18) or `2` the
+/// moment any primitive anywhere carries args — never the fixed
+/// `BLUEPRINT_FORMAT_VERSION` ceiling.
+fn document_version(b: &CompositeData) -> u32 {
+    if has_args(b) {
+        2
+    } else {
+        1
+    }
+}
+
 fn build_doc(c: &Composite) -> BlueprintDoc {
-    BlueprintDoc { format_version: BLUEPRINT_FORMAT_VERSION, blueprint: project(c) }
+    let blueprint = project(c);
+    let format_version = document_version(&blueprint);
+    BlueprintDoc { format_version, blueprint }
 }
 
 fn serialize_doc(doc: &BlueprintDoc) -> Result<String, SerializeError> {
@@ -200,11 +261,16 @@ pub enum LoadError {
     /// addition needs finer granularity than a version bump.
     UnsupportedVersion { found: u32, supported: u32 },
     /// `resolve` returned `None` for a serialized `type_id` (outside the injected
-    /// vocabulary — unknown node, or a construction-arg/sink node not in #155's set).
+    /// vocabulary — unknown node, or a sink node not in #155's set).
     UnknownNodeType(String),
     /// The document's gangs section fails structural validation against its
     /// own nodes (a hand-edited or corrupted document).
     Gang(crate::blueprint::CompileError),
+    /// A primitive's `args` (#271) failed `try_args`: unknown/duplicate/
+    /// missing arg, a malformed value, OR (the pending-with-no-args refusal)
+    /// an arg-bearing type serialized/hand-written with an empty `args` —
+    /// a document naming an arg-bearing type without args must not load.
+    BadArg(aura_core::ArgOpError),
 }
 
 fn reconstruct(
@@ -220,6 +286,15 @@ fn reconstruct(
                 if let Some(n) = &p.name {
                     b = b.named(n);
                 }
+                // Apply construction args (#271) BEFORE bound params — the
+                // `try_args` seam. An arg-bearing type with no `args` in the
+                // document refuses HERE as `MissingArg` (no pending builder
+                // ever reaches `bind`/enters the built graph); a `Plain` type
+                // has empty `p.args`, so this is `Ok(self)` unchanged for
+                // every pre-#271 document.
+                let args: Vec<(String, String)> =
+                    p.args.iter().map(|a| (a.name.clone(), a.value.clone())).collect();
+                b = b.try_args(&args).map_err(LoadError::BadArg)?;
                 // Re-apply bound params BY NAME. The effective param vector is
                 // order-independent (each `bind` computes its slot against the
                 // shrunk schema); ascending original `pos` is the canonical order.
@@ -251,7 +326,9 @@ pub fn blueprint_from_json(
     resolve: &dyn Fn(&str) -> Option<PrimitiveBuilder>,
 ) -> Result<Composite, LoadError> {
     let doc: BlueprintDoc = serde_json::from_str(data).map_err(LoadError::Json)?;
-    if doc.format_version != BLUEPRINT_FORMAT_VERSION {
+    // #271: the loader accepts the closed range 1..=BLUEPRINT_FORMAT_VERSION
+    // (today 1..=2) — a data-driven ceiling, not a single fixed version.
+    if !(1..=BLUEPRINT_FORMAT_VERSION).contains(&doc.format_version) {
         return Err(LoadError::UnsupportedVersion {
             found: doc.format_version,
             supported: BLUEPRINT_FORMAT_VERSION,
@@ -266,7 +343,8 @@ mod tests {
     use crate::blueprint::{Composite, GangMember, OutField, Role};
     use crate::harness::{Edge, Target};
     use crate::VecSource; // crate-root re-export (blueprint.rs tests import it the same way, e.g. :923)
-    use aura_core::{Scalar, ScalarKind, Timestamp};
+    use aura_core::{ArgOpError, Scalar, ScalarKind, Timestamp};
+    use aura_market::Session;
     use aura_std::{Recorder, Sma, Sub};
     use aura_strategy::Bias;
     use std::sync::mpsc;
@@ -436,11 +514,14 @@ mod tests {
         assert!(matches!(err, LoadError::UnknownNodeType(t) if t == "NoSuchNode"));
     }
 
+    /// #271 flipped pin (named contract change, not a regression): `format_version: 2`
+    /// used to be refused (v1 was the only understood version); now that v2 loads
+    /// (the args-bearing tier), only a version PAST the new ceiling is unsupported.
     #[test]
     fn unsupported_version_fails_named() {
-        let json = r#"{"format_version":2,"blueprint":{"name":"x","nodes":[]}}"#;
+        let json = r#"{"format_version":3,"blueprint":{"name":"x","nodes":[]}}"#;
         let err = blueprint_from_json(json, &|t| aura_vocabulary::std_vocabulary(t)).err().unwrap();
-        assert!(matches!(err, LoadError::UnsupportedVersion { found: 2, supported: 1 }));
+        assert!(matches!(err, LoadError::UnsupportedVersion { found: 3, supported: 2 }));
     }
 
     #[test]
@@ -813,4 +894,127 @@ mod tests {
             "the gang itself is identity-bearing"
         );
     }
+
+    // ---- construction args (#271) --------------------------------------
+
+    // A single-node composite around an arg-configured `Session` (arity-free —
+    // a `trigger` input role feeds it, its `bars_since_open` output re-exports).
+    fn session_arg_fixture(tz: chrono_tz::Tz) -> Composite {
+        Composite::new(
+            "sess",
+            vec![Session::configured(9, 30, tz, 15).into()],
+            vec![],
+            vec![Role {
+                name: "trigger".into(),
+                targets: vec![Target { node: 0, slot: 0 }],
+                source: Some(ScalarKind::F64),
+            }],
+            vec![OutField { node: 0, field: 0, name: "bars".into() }],
+        )
+    }
+
+    /// #271 acceptance (engine layer): an args-bearing composite serializes its
+    /// construction-arg pairs, declares `format_version: 2` (the data-driven
+    /// must-understand tier, spec §Data-driven format version), and round-trips
+    /// byte-stably through load -> re-serialize.
+    #[test]
+    fn args_round_trip_preserves_pairs_and_version_2() {
+        let c = session_arg_fixture(chrono_tz::Europe::Berlin);
+        let json = blueprint_to_json(&c).expect("serializes");
+        assert!(json.contains(r#""format_version":2"#), "args-bearing document is version 2: {json}");
+        assert!(
+            json.contains(r#""args":[{"name":"tz","value":"Europe/Berlin"},{"name":"open","value":"09:30"}]"#),
+            "carries the verbatim accepted arg pairs: {json}"
+        );
+        let loaded = blueprint_from_json(&json, &fixture_resolver()).expect("loads");
+        assert_eq!(
+            blueprint_to_json(&loaded).expect("re-serializes"),
+            json,
+            "args round-trip byte-stably"
+        );
+    }
+
+    /// #271 acceptance (C18 stability): a document with NO args anywhere stays
+    /// version 1 and byte-identical to its pre-#271 canonical form — the exact
+    /// golden `signal_serializes_to_canonical_golden` already pins, re-asserted
+    /// here under the #271-specific test name the plan names.
+    #[test]
+    fn args_free_document_serializes_byte_identical_and_version_1() {
+        let signal = crate::test_fixtures::sink_free_sma_cross_signal();
+        let json = blueprint_to_json(&signal).expect("serializes");
+        assert!(json.starts_with(r#"{"format_version":1,"#), "args-free document stays version 1: {json}");
+        assert!(!json.contains("\"args\""), "an args-free document emits no args key: {json}");
+        let golden = r#"{"format_version":1,"blueprint":{"name":"sma_cross","nodes":[{"primitive":{"type":"SMA","name":"fast","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":2}}]}},{"primitive":{"type":"SMA","name":"slow"}},{"primitive":{"type":"Sub"}},{"primitive":{"type":"Bias"}}],"edges":[{"from":0,"to":2,"slot":0,"from_field":0},{"from":1,"to":2,"slot":1,"from_field":0},{"from":2,"to":3,"slot":0,"from_field":0}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0},{"node":1,"slot":0}]}],"output":[{"node":3,"field":0,"name":"bias"}]}}"#;
+        assert_eq!(json, golden, "byte-identical to the pre-#271 canonical form (content ids stable, C18)");
+    }
+
+    /// #271 (nested propagation): an args-bearing primitive nested INSIDE an
+    /// outer composite still trips the outer document's version to 2 — the
+    /// version walk recurses through `NodeData::Composite`, not just the
+    /// top-level node list.
+    #[test]
+    fn nested_spliced_args_composite_is_version_2() {
+        let inner = session_arg_fixture(chrono_tz::Europe::Berlin);
+        let outer = Composite::new(
+            "outer",
+            vec![crate::blueprint::BlueprintNode::Composite(inner)],
+            vec![],
+            vec![Role {
+                name: "trigger".into(),
+                targets: vec![Target { node: 0, slot: 0 }],
+                source: Some(ScalarKind::F64),
+            }],
+            vec![OutField { node: 0, field: 0, name: "bars".into() }],
+        );
+        let json = blueprint_to_json(&outer).expect("serializes");
+        assert!(json.contains(r#""format_version":2"#), "a nested arg-bearing primitive still trips version 2: {json}");
+        assert!(json.contains("\"args\""), "the nested primitive's args survive: {json}");
+    }
+
+    /// #271 (identity is arg-bearing): construction args are structural,
+    /// id-bearing data — like a bound value, unlike a debug-symbol name — so
+    /// two builds differing ONLY in one accepted arg value never share an
+    /// identity JSON, while renaming the composite (a pure debug symbol)
+    /// still does not affect it.
+    #[test]
+    fn identity_json_retains_args() {
+        let berlin = session_arg_fixture(chrono_tz::Europe::Berlin);
+        let paris = session_arg_fixture(chrono_tz::Europe::Paris);
+        assert_ne!(
+            blueprint_identity_json(&berlin).expect("identity-serializes"),
+            blueprint_identity_json(&paris).expect("identity-serializes"),
+            "a differing construction-arg value survives the identity projection"
+        );
+        // renaming the composite (a debug symbol) does not affect identity.
+        let renamed = Composite::new(
+            "sess_renamed",
+            vec![Session::configured(9, 30, chrono_tz::Europe::Berlin, 15).into()],
+            vec![],
+            vec![Role {
+                name: "trigger".into(),
+                targets: vec![Target { node: 0, slot: 0 }],
+                source: Some(ScalarKind::F64),
+            }],
+            vec![OutField { node: 0, field: 0, name: "bars".into() }],
+        );
+        assert_eq!(
+            blueprint_identity_json(&berlin).expect("identity-serializes"),
+            blueprint_identity_json(&renamed).expect("identity-serializes"),
+            "the composite's own debug name does not affect identity"
+        );
+    }
+
+    /// #271 (refuse, don't guess): a hand-written document naming an
+    /// arg-bearing type (`Session`) with NO `args` key refuses on load as
+    /// `LoadError::BadArg(ArgOpError::MissingArg(..))` — a pending builder
+    /// must never silently enter the built graph.
+    #[test]
+    fn loading_arg_bearing_type_without_args_refuses() {
+        let json = r#"{"format_version":1,"blueprint":{"name":"x","nodes":[{"primitive":{"type":"Session"}}]}}"#;
+        let err = blueprint_from_json(json, &fixture_resolver()).err().unwrap();
+        assert!(
+            matches!(&err, LoadError::BadArg(ArgOpError::MissingArg(a)) if a == "tz"),
+            "an arg-bearing type with no args refuses as MissingArg, got {err:?}"
+        );
+    }
 }

crates/aura-engine/src/construction.rs

@@ -13,7 +13,7 @@
 
 use std::collections::{HashMap, HashSet};
 
-use aura_core::{BindOpError, NodeSchema, PrimitiveBuilder, Scalar, ScalarKind};
+use aura_core::{ArgOpError, BindOpError, NodeSchema, PrimitiveBuilder, Scalar, ScalarKind};
 
 use crate::blueprint::{
     check_param_namespace_injective, edge_kind_check, validate_wiring, BlueprintNode, Composite,
@@ -32,8 +32,14 @@ pub enum Op {
     Source { role: String, kind: ScalarKind },
     /// Reserve an open input role (wired by an enclosing graph).
     Input { role: String },
-    /// Add a node of `type_id`, optionally named `as_name`, with `bind` params.
-    Add { type_id: String, as_name: Option<String>, bind: Vec<(String, Scalar)> },
+    /// Add a node of `type_id`, optionally named `as_name`, with construction
+    /// `args` (the typed, closed channel — #271) applied BEFORE `bind` params.
+    Add {
+        type_id: String,
+        as_name: Option<String>,
+        args: Vec<(String, String)>,
+        bind: Vec<(String, Scalar)>,
+    },
     /// Fan a role into one or more `"node.slot"` consumers.
     Feed { role: String, into: Vec<String> },
     /// Wire `"node.field"` -> `"node.slot"`.
@@ -91,6 +97,11 @@ pub enum OpError {
     /// blueprint non-acyclic (domain invariant 5 / ledger C9).
     WouldCycle { from: String, to: String },
     BadParam { node: String, err: BindOpError },
+    /// A construction-arg fault (#271): an arg-bearing type's `args` failed
+    /// `try_args` (unknown/duplicate/missing arg, or a malformed value) — or a
+    /// `Plain` type was given args it does not declare. By-identifier, naming
+    /// the offending node.
+    BadArg { node: String, err: ArgOpError },
     /// Holistic totality fault, by-identifier: an interior input slot covered by
     /// no edge or role target (the finalize 0-cover arm).
     UnconnectedPort { node: String, slot: String },
@@ -180,7 +191,7 @@ impl<'v> GraphSession<'v> {
         match op {
             Op::Source { role, kind } => self.add_role(role, Some(kind)),
             Op::Input { role } => self.add_role(role, None),
-            Op::Add { type_id, as_name, bind } => self.add_node(type_id, as_name, bind),
+            Op::Add { type_id, as_name, args, bind } => self.add_node(type_id, as_name, args, bind),
             Op::Feed { role, into } => self.feed(role, into),
             Op::Connect { from, to } => self.connect(from, to),
             Op::Expose { from, as_name } => self.expose(from, as_name),
@@ -248,11 +259,17 @@ impl<'v> GraphSession<'v> {
         &mut self,
         type_id: String,
         as_name: Option<String>,
+        args: Vec<(String, String)>,
         bind: Vec<(String, Scalar)>,
     ) -> Result<(), OpError> {
         let mut builder =
             (self.vocab)(&type_id).ok_or_else(|| OpError::UnknownNodeType(type_id.clone()))?;
         let id = as_name.unwrap_or_else(|| builder.node_name());
+        // Construction args apply BEFORE the bind loop (spec §aura-engine): a
+        // pending arg-bearing builder with no args therefore refuses here as
+        // `MissingArg` — no pending builder ever reaches `try_bind`/enters the
+        // graph.
+        builder = builder.try_args(&args).map_err(|err| OpError::BadArg { node: id.clone(), err })?;
         for (slot, value) in bind {
             builder = builder
                 .try_bind(&slot, value)
@@ -564,7 +581,7 @@ pub fn replay(
 mod tests {
     use super::{GraphSession, Op, OpError};
     use crate::blueprint::{BlueprintNode, Composite, Role};
-    use aura_core::{BindOpError, Scalar, ScalarKind};
+    use aura_core::{ArgKind, ArgOpError, BindOpError, Scalar, ScalarKind};
     use aura_vocabulary::std_vocabulary;
 
     fn session(name: &str) -> GraphSession<'static> {
@@ -575,7 +592,7 @@ mod tests {
     fn add_unknown_type_rejected_at_op() {
         let mut s = session("g");
         assert_eq!(
-            s.apply(Op::Add { type_id: "Nope".into(), as_name: None, bind: vec![] }),
+            s.apply(Op::Add { type_id: "Nope".into(), as_name: None, args: vec![], bind: vec![] }),
             Err(OpError::UnknownNodeType("Nope".into()))
         );
     }
@@ -583,9 +600,9 @@ mod tests {
     #[test]
     fn add_duplicate_identifier_rejected() {
         let mut s = session("g");
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("x".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("x".into()), args: vec![], bind: vec![] }).unwrap();
         assert_eq!(
-            s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("x".into()), bind: vec![] }),
+            s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("x".into()), args: vec![], bind: vec![] }),
             Err(OpError::DuplicateIdentifier("x".into()))
         );
     }
@@ -597,7 +614,7 @@ mod tests {
             s.apply(Op::Add {
                 type_id: "SMA".into(),
                 as_name: Some("fast".into()),
-                bind: vec![("length".into(), Scalar::f64(2.0))], // wrong kind (i64 param)
+                args: vec![], bind: vec![("length".into(), Scalar::f64(2.0))], // wrong kind (i64 param)
             }),
             Err(OpError::BadParam {
                 node: "fast".into(),
@@ -624,9 +641,9 @@ mod tests {
     fn scaffold() -> GraphSession<'static> {
         let mut s = session("g");
         s.apply(Op::Source { role: "price".into(), kind: ScalarKind::F64 }).unwrap();
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] }).unwrap();
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), bind: vec![] }).unwrap();
-        s.apply(Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), args: vec![], bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] }).unwrap();
         s
     }
 
@@ -653,8 +670,8 @@ mod tests {
     fn connect_kind_mismatch_rejected_at_op() {
         // Gt produces bool; Bias.signal consumes f64 -> eager kind mismatch
         let mut s = session("g");
-        s.apply(Op::Add { type_id: "Gt".into(), as_name: None, bind: vec![] }).unwrap();
-        s.apply(Op::Add { type_id: "Bias".into(), as_name: None, bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "Gt".into(), as_name: None, args: vec![], bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "Bias".into(), as_name: None, args: vec![], bind: vec![] }).unwrap();
         let r = s.apply(Op::Connect { from: "gt.value".into(), to: "bias.signal".into() });
         assert!(matches!(
             r,
@@ -820,9 +837,9 @@ mod tests {
         use crate::harness::FlatTap;
         let ops = vec![
             Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] },
-            Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), bind: vec![] },
-            Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },
             Op::Feed { role: "price".into(), into: vec!["fast.series".into(), "slow.series".into()] },
             Op::Connect { from: "fast.value".into(), to: "sub.lhs".into() },
             Op::Connect { from: "slow.value".into(), to: "sub.rhs".into() },
@@ -842,10 +859,10 @@ mod tests {
     fn gang_op_projects_the_param_space() {
         let ops = vec![
             Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-            Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), bind: vec![] },
-            Op::Add { type_id: "SMA".into(), as_name: Some("b".into()), bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("b".into()), args: vec![], bind: vec![] },
             Op::Gang { as_name: "length".into(), into: vec!["a.length".into(), "b.length".into()] },
-            Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },
             Op::Feed { role: "price".into(), into: vec!["a.series".into(), "b.series".into()] },
             Op::Connect { from: "a.value".into(), to: "sub.lhs".into() },
             Op::Connect { from: "b.value".into(), to: "sub.rhs".into() },
@@ -863,7 +880,7 @@ mod tests {
     /// i64` session-index output, wires its `trigger` input through the ordinary
     /// edge convention, and builds to a finished `Composite`. Reachability is the
     /// whole ask — the node's tz-aware/DST session SEMANTICS are already pinned
-    /// in `aura-std/src/session.rs` and are not re-pinned here. Today the preset
+    /// in `aura-market/src/session.rs` and are not re-pinned here. Today the preset
     /// id is absent from the roster (the base `Session` builder takes structural
     /// construction args, so the zero-arg macro cannot host it), so the lookup
     /// returns `None` and the op-script's `Add` would fail `UnknownNodeType`.
@@ -892,7 +909,7 @@ mod tests {
             Op::Add {
                 type_id: "SessionFrankfurt".into(),
                 as_name: Some("session".into()),
-                bind: vec![("period_minutes".into(), Scalar::i64(15))],
+                args: vec![], bind: vec![("period_minutes".into(), Scalar::i64(15))],
             },
             Op::Feed { role: "trigger".into(), into: vec!["session.trigger".into()] },
             Op::Expose { from: "session.bars_since_open".into(), as_name: "bars".into() },
@@ -909,11 +926,11 @@ mod tests {
         // bound member: `b.length` was bound at Add, so it left the open param
         // list and is unknown to the gang gate, exactly as `try_bind` would see it.
         let mut s = session("g");
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), args: vec![], bind: vec![] }).unwrap();
         s.apply(Op::Add {
             type_id: "SMA".into(),
             as_name: Some("b".into()),
-            bind: vec![("length".into(), Scalar::i64(5))],
+            args: vec![], bind: vec![("length".into(), Scalar::i64(5))],
         })
         .unwrap();
         assert_eq!(
@@ -923,8 +940,8 @@ mod tests {
 
         // kind mismatch: SMA.length is i64, Bias.scale is f64.
         let mut s = session("g");
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), bind: vec![] }).unwrap();
-        s.apply(Op::Add { type_id: "Bias".into(), as_name: Some("b".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), args: vec![], bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "Bias".into(), as_name: Some("b".into()), args: vec![], bind: vec![] }).unwrap();
         let r = s.apply(Op::Gang { as_name: "g".into(), into: vec!["a.length".into(), "b.scale".into()] });
         assert!(
             matches!(r, Err(OpError::GangKindMismatch { expected: ScalarKind::I64, got: ScalarKind::F64, .. })),
@@ -933,9 +950,9 @@ mod tests {
 
         // doubly-ganged member: a.length is already claimed by an earlier gang.
         let mut s = session("g");
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), bind: vec![] }).unwrap();
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("b".into()), bind: vec![] }).unwrap();
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("c".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), args: vec![], bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("b".into()), args: vec![], bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("c".into()), args: vec![], bind: vec![] }).unwrap();
         s.apply(Op::Gang { as_name: "lo".into(), into: vec!["a.length".into(), "b.length".into()] }).unwrap();
         assert_eq!(
             s.apply(Op::Gang { as_name: "hi".into(), into: vec!["a.length".into(), "c.length".into()] }),
@@ -944,7 +961,7 @@ mod tests {
 
         // single member: a gang needs at least two.
         let mut s = session("g");
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), args: vec![], bind: vec![] }).unwrap();
         assert_eq!(
             s.apply(Op::Gang { as_name: "solo".into(), into: vec!["a.length".into()] }),
             Err(OpError::GangArity { gang: "solo".into() })
@@ -952,7 +969,7 @@ mod tests {
 
         // unknown node: a member names a node that was never added.
         let mut s = session("g");
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), args: vec![], bind: vec![] }).unwrap();
         assert_eq!(
             s.apply(Op::Gang { as_name: "g".into(), into: vec!["a.length".into(), "ghost.length".into()] }),
             Err(OpError::UnknownIdentifier("ghost".into()))
@@ -1010,7 +1027,7 @@ mod tests {
     fn finish_accepts_an_open_input_role_and_compile_refuses_it() {
         let mut s = session("g");
         s.apply(Op::Input { role: "ext".into() }).unwrap();
-        s.apply(Op::Add { type_id: "Sub".into(), as_name: Some("sub".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "Sub".into(), as_name: Some("sub".into()), args: vec![], bind: vec![] }).unwrap();
         s.apply(Op::Feed { role: "ext".into(), into: vec!["sub.lhs".into(), "sub.rhs".into()] }).unwrap();
         s.apply(Op::Expose { from: "sub.value".into(), as_name: "out".into() }).unwrap();
         let c = s.finish().expect("finish() no longer gates root-role boundness");
@@ -1030,8 +1047,8 @@ mod tests {
     fn finish_reports_role_kind_mismatch_by_identifier() {
         let mut s = session("g");
         s.apply(Op::Source { role: "price".into(), kind: ScalarKind::F64 }).unwrap();
-        s.apply(Op::Add { type_id: "Sub".into(), as_name: Some("sub".into()), bind: vec![] }).unwrap();
-        s.apply(Op::Add { type_id: "And".into(), as_name: Some("conj".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "Sub".into(), as_name: Some("sub".into()), args: vec![], bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "And".into(), as_name: Some("conj".into()), args: vec![], bind: vec![] }).unwrap();
         // price fans into sub.lhs (f64) AND conj.a (bool): differing slot kinds.
         s.apply(Op::Feed { role: "price".into(), into: vec!["sub.lhs".into(), "conj.a".into()] }).unwrap();
         let err = s.finish().err().unwrap();
@@ -1065,8 +1082,8 @@ mod tests {
         // — only an acyclicity check can catch it.
         let ops = vec![
             Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-            Op::Add { type_id: "Sub".into(), as_name: Some("a".into()), bind: vec![] },
-            Op::Add { type_id: "Sub".into(), as_name: Some("b".into()), bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: Some("a".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: Some("b".into()), args: vec![], bind: vec![] },
             Op::Feed { role: "price".into(), into: vec!["a.rhs".into(), "b.rhs".into()] },
             Op::Connect { from: "a.value".into(), to: "b.lhs".into() }, // op 4: a -> b
             Op::Connect { from: "b.value".into(), to: "a.lhs".into() }, // op 5: closes b -> a
@@ -1097,7 +1114,7 @@ mod tests {
         // loop. Both slots covered, role bound — only an acyclicity check catches it.
         let ops = vec![
             Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-            Op::Add { type_id: "Sub".into(), as_name: Some("s".into()), bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: Some("s".into()), args: vec![], bind: vec![] },
             Op::Feed { role: "price".into(), into: vec!["s.rhs".into()] },
             Op::Connect { from: "s.value".into(), to: "s.lhs".into() }, // self-edge
             Op::Expose { from: "s.value".into(), as_name: "out".into() },
@@ -1111,9 +1128,9 @@ mod tests {
     #[test]
     fn replay_stops_at_first_failing_op_naming_index() {
         let ops = vec![
-            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] },
-            Op::Add { type_id: "Nope".into(), as_name: None, bind: vec![] }, // op 1 fails
-            Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "Nope".into(), as_name: None, args: vec![], bind: vec![] }, // op 1 fails
+            Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },
         ];
         // `.err().unwrap()` rather than `.unwrap_err()`: the Ok arm `Composite` is
         // not `Debug` (it holds build closures), which `unwrap_err` would require.
@@ -1141,10 +1158,10 @@ mod tests {
         // (a) op-script replay
         let ops = vec![
             Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] },
-            Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), bind: vec![] },
-            Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },
-            Op::Add { type_id: "Bias".into(), as_name: None, bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },
+            Op::Add { type_id: "Bias".into(), as_name: None, args: vec![], bind: vec![] },
             Op::Feed { role: "price".into(), into: vec!["fast.series".into(), "slow.series".into()] },
             Op::Connect { from: "fast.value".into(), to: "sub.lhs".into() },
             Op::Connect { from: "slow.value".into(), to: "sub.rhs".into() },
@@ -1189,10 +1206,10 @@ mod tests {
         // (a) op-script: the Task-4 fixture (two SMA + gang + Sub + expose).
         let ops = vec![
             Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-            Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), bind: vec![] },
-            Op::Add { type_id: "SMA".into(), as_name: Some("b".into()), bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("a".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("b".into()), args: vec![], bind: vec![] },
             Op::Gang { as_name: "length".into(), into: vec!["a.length".into(), "b.length".into()] },
-            Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },
             Op::Feed { role: "price".into(), into: vec!["a.series".into(), "b.series".into()] },
             Op::Connect { from: "a.value".into(), to: "sub.lhs".into() },
             Op::Connect { from: "b.value".into(), to: "sub.rhs".into() },
@@ -1241,9 +1258,9 @@ mod tests {
         // (a) op-script: an SMA crossover with a tap on the raw spread (sub.value).
         let ops = vec![
             Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] },
-            Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), bind: vec![] },
-            Op::Add { type_id: "Sub".into(), as_name: Some("sub".into()), bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: Some("sub".into()), args: vec![], bind: vec![] },
             Op::Feed { role: "price".into(), into: vec!["fast.series".into(), "slow.series".into()] },
             Op::Connect { from: "fast.value".into(), to: "sub.lhs".into() },
             Op::Connect { from: "slow.value".into(), to: "sub.rhs".into() },
@@ -1277,6 +1294,71 @@ mod tests {
         assert_eq!(replay_flat.edges, built_flat.edges);
     }
 
+    // ---- construction args (#271) -------------------------------------
+
+    /// `add_node` applies `try_args` AFTER resolve and BEFORE the bind loop
+    /// (spec §aura-engine): an arg-bearing type's `add` op, given a valid
+    /// `args` set, configures the real signature and the subsequent `bind`
+    /// sees the now-real `period_minutes` param — a data-only op-script
+    /// reaches a `Session` for any IANA timezone/open, not just the
+    /// `SessionFrankfurt` preset.
+    #[test]
+    fn add_op_with_args_builds_a_session() {
+        let mut s = session("g");
+        s.apply(Op::Source { role: "trigger".into(), kind: ScalarKind::F64 }).unwrap();
+        assert_eq!(
+            s.apply(Op::Add {
+                type_id: "Session".into(),
+                as_name: Some("ny".into()),
+                args: vec![("tz".into(), "America/New_York".into()), ("open".into(), "09:30".into())],
+                bind: vec![("period_minutes".into(), Scalar::i64(15))],
+            }),
+            Ok(()),
+        );
+        s.apply(Op::Feed { role: "trigger".into(), into: vec!["ny.trigger".into()] }).unwrap();
+        s.apply(Op::Expose { from: "ny.bars_since_open".into(), as_name: "bars".into() }).unwrap();
+        s.finish().expect("an args-configured Session finishes and builds");
+    }
+
+    /// `Session` is arg-bearing (declares `tz`/`open`): an `add` op naming it
+    /// with NO `args` refuses at the op as `BadArg(MissingArg(..))` — the
+    /// pending builder never reaches the bind loop or the graph (spec
+    /// §aura-engine: "a pending resolve with no args therefore fails as
+    /// MissingArg").
+    #[test]
+    fn add_op_arg_bearing_type_without_args_refuses() {
+        let mut s = session("g");
+        assert_eq!(
+            s.apply(Op::Add {
+                type_id: "Session".into(),
+                as_name: Some("ny".into()),
+                args: vec![],
+                bind: vec![],
+            }),
+            Err(OpError::BadArg { node: "ny".into(), err: ArgOpError::MissingArg("tz".into()) }),
+        );
+    }
+
+    /// A malformed arg value (strict-form refusal, spec §Closedness) surfaces
+    /// as `BadArg(BadValue{..})`, naming the arg, its declared `ArgKind`, and
+    /// the rejected string.
+    #[test]
+    fn add_op_bad_tz_refuses() {
+        let mut s = session("g");
+        assert_eq!(
+            s.apply(Op::Add {
+                type_id: "Session".into(),
+                as_name: Some("ny".into()),
+                args: vec![("tz".into(), "not_a_zone".into()), ("open".into(), "09:30".into())],
+                bind: vec![],
+            }),
+            Err(OpError::BadArg {
+                node: "ny".into(),
+                err: ArgOpError::BadValue { arg: "tz".into(), kind: ArgKind::Tz, got: "not_a_zone".into() },
+            }),
+        );
+    }
+
     // ---- Op::Use (#317) -----------------------------------------------
 
     /// A small two-node fixture composite for the `Op::Use` tests (#317): an
@@ -1412,7 +1494,7 @@ mod tests {
     fn use_op_duplicate_instance_identifier_rejected() {
         let subgraph = |_: &str| Some(use_fixture());
         let mut s = GraphSession::new("g", &std_vocabulary, &subgraph);
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("gate".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("gate".into()), args: vec![], bind: vec![] }).unwrap();
         assert_eq!(
             s.apply(Op::Use { ref_id: "fixture".into(), name: Some("gate".into()), bind: vec![] }),
             Err(OpError::DuplicateIdentifier("gate".into()))
@@ -1448,13 +1530,13 @@ mod tests {
     fn use_gang_fixture() -> Composite {
         let ops = vec![
             Op::Input { role: "price".into() },
-            Op::Add { type_id: "SMA".into(), as_name: Some("channel_hi".into()), bind: vec![] },
-            Op::Add { type_id: "SMA".into(), as_name: Some("channel_lo".into()), bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("channel_hi".into()), args: vec![], bind: vec![] },
+            Op::Add { type_id: "SMA".into(), as_name: Some("channel_lo".into()), args: vec![], bind: vec![] },
             Op::Gang {
                 as_name: "channel_length".into(),
                 into: vec!["channel_hi.length".into(), "channel_lo.length".into()],
             },
-            Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },
+            Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },
             Op::Feed {
                 role: "price".into(),
                 into: vec!["channel_hi.series".into(), "channel_lo.series".into()],
@@ -1505,7 +1587,7 @@ mod tests {
         let mut s = GraphSession::new("g", &std_vocabulary, &subgraph);
         s.apply(Op::Use { ref_id: "fixture".into(), name: Some("gate".into()), bind: vec![] })
             .unwrap();
-        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("solo".into()), bind: vec![] })
+        s.apply(Op::Add { type_id: "SMA".into(), as_name: Some("solo".into()), args: vec![], bind: vec![] })
             .unwrap();
         assert_eq!(
             s.apply(Op::Gang {
@@ -1527,7 +1609,7 @@ mod tests {
     fn use_op_connect_closing_a_cycle_through_an_instance_is_rejected_eagerly() {
         let subgraph = |_: &str| Some(use_fixture());
         let mut s = GraphSession::new("g", &std_vocabulary, &subgraph);
-        s.apply(Op::Add { type_id: "Sub".into(), as_name: Some("s".into()), bind: vec![] }).unwrap();
+        s.apply(Op::Add { type_id: "Sub".into(), as_name: Some("s".into()), args: vec![], bind: vec![] }).unwrap();
         s.apply(Op::Use { ref_id: "fixture".into(), name: Some("gate".into()), bind: vec![] }).unwrap();
         s.apply(Op::Connect { from: "s.value".into(), to: "gate.price".into() }).unwrap();
         assert_eq!(
@@ -1595,7 +1677,7 @@ mod tests {
             Op::Add {
                 type_id: "SMA".into(),
                 as_name: Some("sma".into()),
-                bind: vec![("length".into(), Scalar::i64(3))],
+                args: vec![], bind: vec![("length".into(), Scalar::i64(3))],
             },
             Op::Feed { role: "x".into(), into: vec!["sma.series".into()] },
             Op::Expose { from: "sma.value".into(), as_name: "out".into() },

crates/aura-engine/src/lib.rs

@@ -56,8 +56,8 @@ pub use blueprint::{
     GangMember, OutField, RandomBinder, ReopenError, Role, SweepBinder, Tap, TapWire,
 };
 pub use blueprint_serde::{
-    blueprint_from_json, blueprint_identity_json, blueprint_to_json, BlueprintDoc, CompositeData,
-    LoadError, NodeData, PrimitiveData, SerializeError, BLUEPRINT_FORMAT_VERSION,
+    blueprint_from_json, blueprint_identity_json, blueprint_to_json, ArgData, BlueprintDoc,
+    CompositeData, LoadError, NodeData, PrimitiveData, SerializeError, BLUEPRINT_FORMAT_VERSION,
 };
 pub use builder::{BuildError, GraphBuilder, InPort, NodeHandle, OutPort, RoleHandle};
 pub use construction::{replay, GraphSession, Op, OpError};
@@ -88,7 +88,8 @@ pub use walkforward::{
 // (SourceSpec.kind is a ScalarKind; sources/Recorder columns are Scalar /
 // Firing / Timestamp) so a graph builder has one import surface, not two.
 pub use aura_core::{
-    BindOpError, Firing, NodeSchema, ParamSpec, PortSpec, Scalar, ScalarKind, Timestamp,
+    ArgKind, ArgOpError, BindOpError, Firing, NodeSchema, ParamSpec, PortSpec, Scalar, ScalarKind,
+    Timestamp,
 };
 
 #[cfg(test)]

crates/aura-engine/tests/construction_e2e.rs

@@ -34,10 +34,10 @@ fn params() -> [Scalar; 3] {
 fn signal_ops() -> Vec<Op> {
     vec![
         Op::Source { role: "price".into(), kind: ScalarKind::F64 },
-        Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] },
-        Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), bind: vec![] },
-        Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },
-        Op::Add { type_id: "Bias".into(), as_name: None, bind: vec![] },
+        Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] },
+        Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), args: vec![], bind: vec![] },
+        Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },
+        Op::Add { type_id: "Bias".into(), as_name: None, args: vec![], bind: vec![] },
         Op::Feed { role: "price".into(), into: vec!["fast.series".into(), "slow.series".into()] },
         Op::Connect { from: "fast.value".into(), to: "sub.lhs".into() },
         Op::Connect { from: "slow.value".into(), to: "sub.rhs".into() },
@@ -96,10 +96,10 @@ fn replayed_construction_compiles_identically_to_graphbuilder() {
 #[test]
 fn replay_attributes_eager_fault_to_its_op_index() {
     let ops = vec![
-        Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] }, // 0 ok
-        Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },                // 1 ok
-        Op::Add { type_id: "Nope".into(), as_name: None, bind: vec![] },               // 2 fails
-        Op::Add { type_id: "Bias".into(), as_name: None, bind: vec![] },               // 3 never runs
+        Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] }, // 0 ok
+        Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },                // 1 ok
+        Op::Add { type_id: "Nope".into(), as_name: None, args: vec![], bind: vec![] },               // 2 fails
+        Op::Add { type_id: "Bias".into(), as_name: None, args: vec![], bind: vec![] },               // 3 never runs
     ];
     // `.err().unwrap()` (not `unwrap_err`): the Ok arm `Composite` holds build
     // closures and is not `Debug`, which `unwrap_err`'s bound would require.
@@ -120,9 +120,9 @@ fn replay_attributes_eager_fault_to_its_op_index() {
 fn replay_attributes_holistic_fault_to_finalize_step() {
     let ops = vec![
         Op::Source { role: "price".into(), kind: ScalarKind::F64 },                    // 0
-        Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), bind: vec![] }, // 1
-        Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), bind: vec![] }, // 2
-        Op::Add { type_id: "Sub".into(), as_name: None, bind: vec![] },                // 3
+        Op::Add { type_id: "SMA".into(), as_name: Some("fast".into()), args: vec![], bind: vec![] }, // 1
+        Op::Add { type_id: "SMA".into(), as_name: Some("slow".into()), args: vec![], bind: vec![] }, // 2
+        Op::Add { type_id: "Sub".into(), as_name: None, args: vec![], bind: vec![] },                // 3
         Op::Feed { role: "price".into(), into: vec!["fast.series".into(), "slow.series".into()] }, // 4
         Op::Connect { from: "fast.value".into(), to: "sub.lhs".into() },               // 5
         // sub.rhs deliberately left unwired -> only finalize can decide totality.

crates/aura-engine/tests/ger40_breakout.rs

@@ -110,7 +110,7 @@ fn build_harness(
         Resample::builder().schema().clone(),                                  // 0
         Delay::builder().schema().clone(),                                     // 1
         Gt::builder().schema().clone(),                                        // 2
-        Session::builder(9, 0, Berlin, 15).schema().clone(),                   // 3
+        Session::configured(9, 0, Berlin, 15).schema().clone(),                   // 3
         EqConst::builder().schema().clone(),                                   // 4
         EqConst::builder().schema().clone(),                                   // 5
         And::builder().schema().clone(),                                       // 6

crates/aura-engine/tests/r_meanrev_e2e.rs

@@ -21,7 +21,7 @@ fn run_meanrev_bias(closes: &[f64], n: i64, k: f64) -> Vec<f64> {
     let sq = g.add(Mul::builder()); // dev * dev
     let var = g.add(Ema::builder().bind("length", Scalar::i64(n))); // EWMA variance
     let sigma = g.add(Sqrt::builder());
-    let band = g.add(LinComb::builder(1).bind("weights[0]", Scalar::f64(k))); // k*sigma
+    let band = g.add(LinComb::configured(1).bind("weights[0]", Scalar::f64(k))); // k*sigma
     let upper = g.add(Add::builder()); // mean + k*sigma
     let lower = g.add(Sub::builder()); // mean - k*sigma
     let gt_hi = g.add(Gt::builder()); // price > upper

crates/aura-ingest/examples/shared/breakout_real.rs

@@ -112,7 +112,7 @@ pub fn build_harness() -> (Harness, Taps) {
         Resample::builder().schema().clone(), // 0
         Delay::builder().schema().clone(),     // 1
         Gt::builder().schema().clone(),        // 2
-        Session::builder(SESSION_HOUR, SESSION_MINUTE, Berlin, BAR_MINUTES)
+        Session::configured(SESSION_HOUR, SESSION_MINUTE, Berlin, BAR_MINUTES)
             .schema()
             .clone(), // 3
         EqConst::builder().schema().clone(), // 4
@@ -248,7 +248,7 @@ pub fn ger40_breakout_blueprint(
     );
     let delay = g.add(Delay::builder().bind("lag", Scalar::i64(1)));
     let gt = g.add(Gt::builder());
-    let session = g.add(Session::builder(open_hour, open_minute, tz, bar_period_minutes));
+    let session = g.add(Session::configured(open_hour, open_minute, tz, bar_period_minutes));
     // The ONLY two params: the EqConst targets, named so the space reads
     // `entry_bar.target` / `exit_bar.target`. Their `target` is left UNBOUND.
     let entry_bar = g.add(EqConst::builder().named("entry_bar"));

crates/aura-market/src/session.rs

@@ -33,10 +33,17 @@
 //! **Cold guard.** If the trigger column is empty (not yet fired) → `None`.
 
 use aura_core::{
-    Cell, Ctx, FieldSpec, Firing, Node, NodeSchema, ParamSpec, PortSpec, PrimitiveBuilder, ScalarKind,
+    ArgKind, ArgSpec, ArgValue, Cell, Ctx, FieldSpec, Firing, Node, NodeSchema, ParamSpec, PortSpec,
+    PrimitiveBuilder, Scalar, ScalarKind,
 };
 use chrono::{TimeZone, Timelike};
 
+/// The declared construction args of a `Session` recipe (spec §Concrete code
+/// shapes): the timezone and local open time — structural, non-scalar
+/// configuration, never a swept param.
+const SESSION_ARGS: &[ArgSpec] =
+    &[ArgSpec { name: "tz", kind: ArgKind::Tz }, ArgSpec { name: "open", kind: ArgKind::TimeOfDay }];
+
 /// Frankfurt-session bar indexer. Holds the open offset (minutes past local
 /// midnight), the IANA timezone, and the bar period — baked at construction,
 /// never streamed and never a swept param (a timezone is not a scalar).
@@ -60,23 +67,57 @@ impl Session {
         }
     }
 
-    /// The param-generic recipe for a blueprint primitive. The open time,
-    /// timezone, and period are **structural** config baked into the closure
-    /// (like `SimBroker::builder` bakes `pip_size`), NOT scalar params — the
-    /// declared param list is empty and the `build_fn` ignores its slice (like
-    /// `Gt` / `Latch`).
-    pub fn builder(open_hour: u32, open_minute: u32, tz: chrono_tz::Tz, period_minutes: i64) -> PrimitiveBuilder {
+    /// Roster factory: zero-arg, arg-bearing (spec §Concrete code shapes) — the
+    /// timezone and open time come through the `args` channel (`try_args`),
+    /// declared by [`SESSION_ARGS`]. `period_minutes` becomes an ordinary
+    /// `ParamSpec` once `make` runs (a real scalar knob, unlike tz/open).
+    pub fn builder() -> PrimitiveBuilder {
+        PrimitiveBuilder::pending(
+            "Session",
+            "bars elapsed since the session open, from the configured open time and timezone",
+            SESSION_ARGS,
+            Self::make,
+        )
+    }
+
+    /// Turn a validated `(tz, open)` value pair into the real signature: one
+    /// `trigger` input, one `bars_since_open` output, and `period_minutes` as
+    /// the sole (now scalar) `ParamSpec` — read from the param slice at build.
+    fn make(values: &[(String, ArgValue)]) -> PrimitiveBuilder {
+        let tz = values
+            .iter()
+            .find_map(|(n, v)| match (n.as_str(), v) {
+                ("tz", ArgValue::Tz(tz)) => Some(*tz),
+                _ => None,
+            })
+            .expect("try_args validated `tz` as ArgKind::Tz before calling make");
+        let (open_hour, open_minute) = values
+            .iter()
+            .find_map(|(n, v)| match (n.as_str(), v) {
+                ("open", ArgValue::TimeOfDay { hour, minute }) => Some((*hour, *minute)),
+                _ => None,
+            })
+            .expect("try_args validated `open` as ArgKind::TimeOfDay before calling make");
         PrimitiveBuilder::new(
             "Session",
             NodeSchema {
                 inputs: vec![PortSpec { kind: ScalarKind::F64, firing: Firing::Any, name: "trigger".into() }],
                 output: vec![FieldSpec { name: "bars_since_open".into(), kind: ScalarKind::I64 }],
-                params: vec![],
+                params: vec![ParamSpec { name: "period_minutes".into(), kind: ScalarKind::I64 }],
                 doc: "bars elapsed since the session open, from the configured open time and timezone",
             },
-            move |_| Box::new(Session::new(open_hour, open_minute, tz, period_minutes)),
+            move |p| Box::new(Session::new(open_hour, open_minute, tz, p[0].i64())),
         )
     }
+
+    /// Rust-path convenience — the same recipe as the data path (twin
+    /// identity): `builder().try_args([tz, open]) + .bind("period_minutes", …)`.
+    pub fn configured(open_hour: u32, open_minute: u32, tz: chrono_tz::Tz, period_minutes: i64) -> PrimitiveBuilder {
+        Self::builder()
+            .try_args(&[("tz".to_string(), tz.name().to_string()), ("open".to_string(), format!("{open_hour:02}:{open_minute:02}"))])
+            .expect("configured: a valid chrono_tz::Tz and in-range hour/minute always parse")
+            .bind("period_minutes", Scalar::i64(period_minutes))
+    }
 }
 
 /// The zero-arg `SessionFrankfurt` roster preset (#261): the Frankfurt open
@@ -244,4 +285,36 @@ mod tests {
         let inputs = trigger_input();
         assert_eq!(node.eval(Ctx::new(&inputs, Timestamp(0))), None);
     }
+
+    /// Twin identity (spec §aura-market): `configured` is exactly
+    /// `builder().try_args([tz, open]).bind("period_minutes", …)` — same
+    /// accepted args, same declared signature, whichever path authored it.
+    #[test]
+    fn session_configured_twin_equals_builder_try_args() {
+        let via_configured = Session::configured(9, 30, Berlin, 15);
+        let via_try_args = Session::builder()
+            .try_args(&[("tz".into(), "Europe/Berlin".into()), ("open".into(), "09:30".into())])
+            .expect("valid tz/open configure")
+            .bind("period_minutes", Scalar::i64(15));
+        assert_eq!(via_configured.construction_args(), via_try_args.construction_args());
+        assert_eq!(via_configured.schema(), via_try_args.schema());
+    }
+
+    /// Behaviour re-anchor (#271 Task 2): the DST-aware headline property
+    /// (local 09:45 reads bar 3 in both CEST summer and CET winter) holds
+    /// identically when the node is built through `configured` instead of
+    /// `Session::new` directly.
+    #[test]
+    fn session_configured_behaviour_unchanged() {
+        let mut node = Session::configured(9, 0, Berlin, 15).build(&[]);
+        let mut inputs = trigger_input();
+
+        let summer = Berlin.with_ymd_and_hms(2024, 7, 1, 9, 45, 0).unwrap().timestamp_nanos_opt().unwrap();
+        inputs[0].push(Scalar::f64(0.0)).unwrap();
+        assert_eq!(node.eval(Ctx::new(&inputs, Timestamp(summer))).map(|r| r[0].i64()), Some(3));
+
+        let winter = Berlin.with_ymd_and_hms(2024, 1, 2, 9, 45, 0).unwrap().timestamp_nanos_opt().unwrap();
+        inputs[0].push(Scalar::f64(0.0)).unwrap();
+        assert_eq!(node.eval(Ctx::new(&inputs, Timestamp(winter))).map(|r| r[0].i64()), Some(3));
+    }
 }

crates/aura-registry/src/lib.rs

@@ -2154,14 +2154,12 @@ mod tests {
         let resolve = |t: &str| aura_vocabulary::std_vocabulary(t);
 
         // A minimal fixture composite with one OPEN param, built from a
-        // zero-arg `aura-std` node (`Bias`) so `std_vocabulary` can actually
+        // plain `aura-std` node (`Bias`) so `std_vocabulary` can actually
         // resolve it on load. `aura-composites`' shipped composites (vol_stop,
-        // risk_executor*) all route through `LinComb`, whose builder needs a
-        // structural arity argument and is therefore deliberately absent from
-        // the zero-arg `std_vocabulary` roster (see aura-std/src/vocabulary.rs)
-        // — they cannot round-trip through `blueprint_from_json` with this
-        // resolver, so this fixture stands in as the "real, open-param,
-        // vocabulary-loadable composite" the test needs.
+        // risk_executor*) route through `LinComb`, an arg-bearing type (#271,
+        // `aura-vocabulary/src/lib.rs`) — using `Bias` here keeps this fixture
+        // independent of that construction channel, so it stands in as the
+        // "real, open-param, vocabulary-loadable composite" the test needs.
         let composite = Composite::new(
             "fixture",
             vec![aura_strategy::Bias::builder().named("b").into()],

crates/aura-runner/src/member.rs

@@ -327,7 +327,7 @@ pub fn wrap_r(
     if !reduce {
         // r_equity = cum_realized_r + unrealized_r — one tapped series for charting.
         let r_equity = g.add(
-            LinComb::builder(2)
+            LinComb::configured(2)
                 .bind("weights[0]", Scalar::f64(1.0))
                 .bind("weights[1]", Scalar::f64(1.0)),
         );
@@ -411,7 +411,7 @@ pub fn wrap_r(
             // net_r_equity = cum_realized_r + unrealized_r − Σcum_cost_in_r
             // − Σopen_cost_in_r (the #221-deleted LinComb(4), weights 1,1,-1,-1).
             let net_eq = g.add(
-                LinComb::builder(4)
+                LinComb::configured(4)
                     .bind("weights[0]", Scalar::f64(1.0))
                     .bind("weights[1]", Scalar::f64(1.0))
                     .bind("weights[2]", Scalar::f64(-1.0))

crates/aura-std/Cargo.toml

@@ -7,13 +7,6 @@ publish.workspace = true
 
 [dependencies]
 aura-core = { path = "../aura-core" }
-# DST-correct wall-clock math for the `Session` node. A vetted
-# standard crate for timezone/DST — never hand-rolled (C16 per-case policy).
-# `chrono` is already a transitive workspace dep (0.4 via aura-ingest's
-# data-server); aligned to that major. `chrono-tz` brings the IANA `Europe/Berlin`
-# zone + DST transitions.
-chrono = { version = "0.4", default-features = false, features = ["clock"] }
-chrono-tz = { version = "0.10", default-features = false }
 
 [dev-dependencies]
 aura-strategy = { path = "../aura-strategy" }

crates/aura-std/src/lincomb.rs

@@ -7,10 +7,15 @@
 //! indexed `F64` knobs that `Composite::param_space` aggregates (C8/C12/C19).
 
 use aura_core::{
-    Cell, Ctx, FieldSpec, Firing, Node, NodeSchema, ParamSpec, PortSpec, PrimitiveBuilder,
-    ScalarKind,
+    ArgKind, ArgSpec, ArgValue, Cell, Ctx, FieldSpec, Firing, Node, NodeSchema, ParamSpec, PortSpec,
+    PrimitiveBuilder, ScalarKind,
 };
 
+/// The declared construction args of a `LinComb` recipe: `arity` fixes the
+/// node's input/param count (topology, C19), taken through the `args`
+/// channel instead of a Rust-side builder parameter.
+const LINCOMB_ARGS: &[ArgSpec] = &[ArgSpec { name: "arity", kind: ArgKind::Count }];
+
 /// Weighted sum of `N` f64 inputs: `Σ weights[i] · input[i]`. The `weights` are
 /// construction parameters that configure the node and fix its arity
 /// (`weights.len()` inputs, in slot order). Emits `None` until *all* inputs
@@ -40,10 +45,29 @@ impl LinComb {
         Self { weights, out: [Cell::from_f64(0.0)] }
     }
 
-    /// The param-generic recipe for a blueprint primitive. The `arity` is topology
-    /// (fixed per blueprint, C19), taken as a builder arg; only the weight *values*
-    /// are injected, slot by slot, through `LinComb::new` (the single sizing gate).
-    pub fn builder(arity: usize) -> PrimitiveBuilder {
+    /// Roster factory: zero-arg, arg-bearing. `arity` is topology (fixed per
+    /// blueprint, C19), now taken through the `args` channel instead of a
+    /// Rust-side parameter.
+    pub fn builder() -> PrimitiveBuilder {
+        PrimitiveBuilder::pending(
+            "LinComb",
+            "linear combination of its inputs with constant weights",
+            LINCOMB_ARGS,
+            Self::make,
+        )
+    }
+
+    /// Turn a validated `arity` into the real, arity-sized signature; only
+    /// the weight *values* are injected, slot by slot, through `LinComb::new`
+    /// (the single sizing gate) once params are bound/built.
+    fn make(values: &[(String, ArgValue)]) -> PrimitiveBuilder {
+        let arity = values
+            .iter()
+            .find_map(|(n, v)| match (n.as_str(), v) {
+                ("arity", ArgValue::Count(n)) => Some(*n),
+                _ => None,
+            })
+            .expect("try_args validated `arity` as ArgKind::Count before calling make");
         let inputs = (0..arity)
             .map(|i| PortSpec { kind: ScalarKind::F64, firing: Firing::Any, name: format!("term[{i}]") })
             .collect();
@@ -63,6 +87,13 @@ impl LinComb {
             )),
         )
     }
+
+    /// Rust-path convenience — same recipe as the data path (twin identity).
+    pub fn configured(arity: usize) -> PrimitiveBuilder {
+        Self::builder()
+            .try_args(&[("arity".to_string(), arity.to_string())])
+            .expect("configured: a positive arity is always the canonical strict-form Count string")
+    }
 }
 
 impl Node for LinComb {
@@ -149,7 +180,7 @@ mod tests {
 
     #[test]
     fn input_slots_are_named_term_index() {
-        let lc = LinComb::builder(3);
+        let lc = LinComb::configured(3);
         let names: Vec<String> = lc.schema().inputs.iter().map(|p| p.name.clone()).collect();
         assert_eq!(names, ["term[0]", "term[1]", "term[2]"]);
     }
@@ -157,7 +188,7 @@ mod tests {
     #[test]
     fn chained_bind_reconstructs_positional_vector() {
         // bind BOTH weights, in reverse slot order, to DISTINCT values; build empty.
-        let builder = LinComb::builder(2)
+        let builder = LinComb::configured(2)
             .bind("weights[1]", Scalar::f64(2.0))
             .bind("weights[0]", Scalar::f64(0.5));
         assert!(builder.params().is_empty());
@@ -173,7 +204,7 @@ mod tests {
         assert_eq!(lc.eval(Ctx::new(&inputs, Timestamp(0))), Some([Cell::from_f64(11.0)].as_slice()));
 
         // partial: bind weights[0], leave weights[1] open → inject it at build
-        let partial = LinComb::builder(2).bind("weights[0]", Scalar::f64(0.5));
+        let partial = LinComb::configured(2).bind("weights[0]", Scalar::f64(0.5));
         assert_eq!(
             partial.params().iter().map(|p| p.name.as_str()).collect::<Vec<_>>(),
             ["weights[1]"],
@@ -187,4 +218,14 @@ mod tests {
         inputs2[1].push(Scalar::f64(3.0)).unwrap();
         assert_eq!(lc2.eval(Ctx::new(&inputs2, Timestamp(0))), Some([Cell::from_f64(11.0)].as_slice()));
     }
+
+    /// Twin identity (spec §aura-std): `configured(arity)` is exactly
+    /// `builder().try_args([("arity", arity)])`.
+    #[test]
+    fn lincomb_configured_twin_equals_builder_try_args() {
+        let via_configured = LinComb::configured(3);
+        let via_try_args = LinComb::builder().try_args(&[("arity".into(), "3".into())]).expect("valid arity configures");
+        assert_eq!(via_configured.construction_args(), via_try_args.construction_args());
+        assert_eq!(via_configured.schema(), via_try_args.schema());
+    }
 }

crates/aura-std/src/sma.rs

@@ -238,7 +238,7 @@ mod tests {
             vec![ParamSpec { name: "scale".into(), kind: ScalarKind::F64 }],
         );
         // vector knob expands flat to N indexed F64 entries
-        let lc = LinComb::builder(2).schema().params.clone();
+        let lc = LinComb::configured(2).schema().params.clone();
         assert_eq!(lc.len(), 2);
         assert_eq!(lc[0].name, "weights[0]");
         assert_eq!(lc[1].name, "weights[1]");

crates/aura-strategy/src/cost.rs

@@ -555,10 +555,10 @@ mod tests {
             ConstantCost::builder().schema().output.iter().map(|f| f.name.clone()).collect();
         assert_eq!(prod, COST_FIELD_NAMES.to_vec());
         let agg_out: Vec<String> =
-            CostSum::builder(1).schema().output.iter().map(|f| f.name.clone()).collect();
+            CostSum::configured(1).schema().output.iter().map(|f| f.name.clone()).collect();
         assert_eq!(agg_out, COST_FIELD_NAMES.to_vec());
         let agg_in: Vec<String> =
-            CostSum::builder(1).schema().inputs.iter().map(|p| p.name.clone()).collect();
+            CostSum::configured(1).schema().inputs.iter().map(|p| p.name.clone()).collect();
         let expected: Vec<String> =
             COST_FIELD_NAMES.iter().map(|f| format!("cost[0].{f}")).collect();
         assert_eq!(agg_in, expected);

crates/aura-strategy/src/cost_sum.rs

@@ -7,9 +7,15 @@
 //! the cost path is uniform whether one or several cost nodes are wired.
 
 use aura_core::{
-    Cell, Ctx, FieldSpec, Firing, Node, NodeSchema, PortSpec, PrimitiveBuilder, ScalarKind,
+    ArgKind, ArgSpec, ArgValue, Cell, Ctx, FieldSpec, Firing, Node, NodeSchema, PortSpec,
+    PrimitiveBuilder, ScalarKind,
 };
 
+/// The declared construction args of a `CostSum` recipe: `n_costs` fixes the
+/// node's input count (topology, C19), taken through the `args` channel
+/// instead of a Rust-side builder parameter.
+const COST_SUM_ARGS: &[ArgSpec] = &[ArgSpec { name: "n_costs", kind: ArgKind::Count }];
+
 /// The cost-record field triple and its width come from the shared cost contract
 /// (`crate::cost::{COST_FIELD_NAMES, COST_WIDTH}`) — one source of truth, read by
 /// both the producer side (`cost_node_builder`) and this aggregator. The input-name
@@ -32,10 +38,29 @@ impl CostSum {
         Self { n_costs, out: [Cell::from_f64(0.0); COST_WIDTH] }
     }
 
-    /// The param-generic recipe. `n_costs` is topology (fixed per blueprint, C19),
-    /// captured by the build closure (no per-build params). The input names are a
-    /// lockstep contract with the connect side (`cost[k].<field>`).
-    pub fn builder(n_costs: usize) -> PrimitiveBuilder {
+    /// Roster factory: zero-arg, arg-bearing. `n_costs` is topology (fixed per
+    /// blueprint, C19), now taken through the `args` channel instead of a
+    /// Rust-side parameter.
+    pub fn builder() -> PrimitiveBuilder {
+        PrimitiveBuilder::pending(
+            "CostSum",
+            "sums cost-model contributions into one cost-in-R stream",
+            COST_SUM_ARGS,
+            Self::make,
+        )
+    }
+
+    /// Turn a validated `n_costs` into the real, arity-sized signature. The
+    /// input names are a lockstep contract with the connect side
+    /// (`cost[k].<field>`).
+    fn make(values: &[(String, ArgValue)]) -> PrimitiveBuilder {
+        let n_costs = values
+            .iter()
+            .find_map(|(n, v)| match (n.as_str(), v) {
+                ("n_costs", ArgValue::Count(n)) => Some(*n),
+                _ => None,
+            })
+            .expect("try_args validated `n_costs` as ArgKind::Count before calling make");
         let mut inputs = Vec::with_capacity(n_costs * COST_WIDTH);
         for k in 0..n_costs {
             for field in COST_FIELD_NAMES {
@@ -63,6 +88,13 @@ impl CostSum {
             move |_| Box::new(CostSum::new(n_costs)),
         )
     }
+
+    /// Rust-path convenience — same recipe as the data path (twin identity).
+    pub fn configured(n_costs: usize) -> PrimitiveBuilder {
+        Self::builder()
+            .try_args(&[("n_costs".to_string(), n_costs.to_string())])
+            .expect("configured: a positive n_costs is always the canonical strict-form Count string")
+    }
 }
 
 impl Node for CostSum {
@@ -140,7 +172,7 @@ mod tests {
 
     #[test]
     fn input_slots_are_named_cost_index_field() {
-        let s = CostSum::builder(2);
+        let s = CostSum::configured(2);
         let names: Vec<String> = s.schema().inputs.iter().map(|p| p.name.clone()).collect();
         assert_eq!(
             names,
@@ -161,4 +193,15 @@ mod tests {
     fn new_panics_on_zero() {
         let _ = CostSum::new(0);
     }
+
+    /// Twin identity (spec §aura-strategy): `configured(n_costs)` is exactly
+    /// `builder().try_args([("n_costs", n_costs)])`.
+    #[test]
+    fn cost_sum_configured_twin_equals_builder_try_args() {
+        let via_configured = CostSum::configured(2);
+        let via_try_args =
+            CostSum::builder().try_args(&[("n_costs".into(), "2".into())]).expect("valid n_costs configures");
+        assert_eq!(via_configured.construction_args(), via_try_args.construction_args());
+        assert_eq!(via_configured.schema(), via_try_args.schema());
+    }
 }

crates/aura-vocabulary/src/lib.rs

@@ -8,22 +8,27 @@
 //! takes it as an injected resolver, and a project `cdylib` later supplies its
 //! own (C16) through the same seam.
 //!
-//! Scope (#155): only the **zero-argument** `Type::builder()` factories are
-//! resolvable. Builders that take structural construction arguments
-//! (`LinComb(arity)`, `CostSum(n_costs)`, `SimBroker(pip_size)`, `Session(..)`)
-//! and the recording sinks (`Recorder`/`GatedRecorder`/`SeriesReducer`, which
-//! capture an `mpsc::Sender`) are deliberately absent — an absent `type_id`
+//! Scope (#155, extended #271): the roster resolves any type whose factory is
+//! `Type::builder()` with zero RUST-side arguments — this now includes
+//! arg-bearing types (`Session`, `LinComb`, `CostSum`), whose `builder()` is
+//! itself zero-arg and returns a *pending* `PrimitiveBuilder`, configured
+//! through the typed `args` channel (`try_args`) at the `add` op, before any
+//! bind. `SimBroker(pip_size)` stays out of scope: it is a plain scalar Rust
+//! parameter, not a structural construction arg — a different (unaddressed)
+//! gap. The recording sinks (`Recorder`/`GatedRecorder`/`SeriesReducer`, which
+//! capture an `mpsc::Sender`) stay deliberately absent — an absent `type_id`
 //! yields `None`, so the loader fails cleanly (`LoadError::UnknownNodeType`)
-//! rather than guessing. Serialising structural-axis construction args is a
-//! later, additive extension (#156/C20).
+//! rather than guessing.
 
 use aura_backtest::PositionManagement;
-use aura_market::{Resample, SessionFrankfurt};
+use aura_market::{Resample, Session, SessionFrankfurt};
 use aura_std::{
-    Abs, Add, And, Const, CumSum, Delay, Div, Ema, EqConst, Gt, Latch, Max, Min, Mul, RollingMax,
-    RollingMin, Scale, Select, Sign, Sma, Sqrt, Sub, When,
+    Abs, Add, And, Const, CumSum, Delay, Div, Ema, EqConst, Gt, Latch, LinComb, Max, Min, Mul,
+    RollingMax, RollingMin, Scale, Select, Sign, Sma, Sqrt, Sub, When,
+};
+use aura_strategy::{
+    Bias, CarryCost, ConstantCost, CostSum, FixedStop, LongOnly, Sizer, VolSlippageCost,
 };
-use aura_strategy::{Bias, CarryCost, ConstantCost, FixedStop, LongOnly, Sizer, VolSlippageCost};
 use aura_core::PrimitiveBuilder;
 
 /// The single roster source (#160): one `"TypeId" => Type` line per zero-arg
@@ -67,6 +72,7 @@ std_vocabulary_roster! {
     "CarryCost" => CarryCost,
     "Const" => Const,
     "ConstantCost" => ConstantCost,
+    "CostSum" => CostSum,
     "CumSum" => CumSum,
     "Delay" => Delay,
     "Div" => Div,
@@ -75,6 +81,7 @@ std_vocabulary_roster! {
     "FixedStop" => FixedStop,
     "Gt" => Gt,
     "Latch" => Latch,
+    "LinComb" => LinComb,
     "LongOnly" => LongOnly,
     "Max" => Max,
     "Min" => Min,
@@ -85,6 +92,7 @@ std_vocabulary_roster! {
     "RollingMin" => RollingMin,
     "Scale" => Scale,
     "Select" => Select,
+    "Session" => Session,
     "SessionFrankfurt" => SessionFrankfurt,
     "Sign" => Sign,
     "Sizer" => Sizer,
@@ -103,8 +111,11 @@ mod tests {
     /// label back, and only the rostered keys do. The builder's own `label()`
     /// is the independent oracle: a typo'd roster key fails the lookup-label
     /// agreement even though the match arms and the list share the same
-    /// (mistyped) literal; construction-arg nodes and sinks stay absent so the
-    /// loader fails cleanly rather than guessing.
+    /// (mistyped) literal; an unresolvable id and a sink stay absent so the
+    /// loader fails cleanly rather than guessing. `LinComb` — an arg-bearing
+    /// type, #271 — now resolves to a PENDING builder (its own `.label()`
+    /// still round-trips; it just is not yet constructible without
+    /// `try_args`).
     #[test]
     fn std_vocabulary_resolves_known_and_rejects_unknown() {
         for &type_id in std_vocabulary_types() {
@@ -116,9 +127,9 @@ mod tests {
                 "resolver key must round-trip to the same type label"
             );
         }
-        // an unknown id, a construction-arg node, and a sink are all absent
+        // an unknown id and a sink are absent; LinComb is now resolved (#271)
         assert!(std_vocabulary("nope").is_none());
-        assert!(std_vocabulary("LinComb").is_none());
+        assert!(std_vocabulary("LinComb").is_some());
         assert!(std_vocabulary("Recorder").is_none());
     }
 
@@ -129,14 +140,16 @@ mod tests {
     /// act. The residual #160 drift — a new zero-arg node never rostered at
     /// all — is not catchable here (no enumeration of zero-arg builders
     /// exists); it fails safe (clean `UnknownNodeType` on load, merely absent
-    /// from `--vocabulary`).
+    /// from `--vocabulary`). #271: `Session`/`LinComb`/`CostSum` moved IN
+    /// (arg-bearing types now have zero-arg `builder()` factories); the count
+    /// pin moves 33 -> 36.
     #[test]
     fn std_vocabulary_types_lists_exactly_the_resolvable_keys() {
         // known non-members stay out of the list
-        assert!(!std_vocabulary_types().contains(&"LinComb")); // construction-arg node
+        assert!(std_vocabulary_types().contains(&"LinComb")); // now arg-bearing-reachable (#271)
         assert!(!std_vocabulary_types().contains(&"Recorder")); // sink
         assert!(!std_vocabulary_types().contains(&"nope"));
-        // count guard: pins the roster at exactly 33 entries
-        assert_eq!(std_vocabulary_types().len(), 33);
+        // count guard: pins the roster at exactly 36 entries
+        assert_eq!(std_vocabulary_types().len(), 36);
     }
 }

docs/authoring-guide.md

@@ -49,8 +49,9 @@ the same shape every node in `aura-std` already follows.
   `src/lib.rs`, registered under the project's own `<namespace>::` prefix)
   and appends its path to the project's `Aura.toml [nodes]` section.
 - **A block promoted to universal** — reused across projects and folded into
-  the engine itself — lives in `crates/aura-std/src/`, unprefixed, and is
-  rostered in `crates/aura-std/src/vocabulary.rs` instead of a node crate's
+  the engine itself — lives in `crates/aura-std/` (or its sibling domain
+  crates: `aura-market`, `aura-strategy`), unprefixed, and is rostered in
+  `crates/aura-vocabulary/src/lib.rs` instead of a node crate's
   `vocabulary()` function. The pattern below is identical either way; only
   the rostering call site differs (see "Rostering the type" below).
 
@@ -89,11 +90,16 @@ Every node type — std or project-local — is three things:
      `aura_core::aura_project!` macro wires up (every `aura new` scaffold
      emits a starter pair — see the worked example below). Add one match arm
      to `vocabulary()` and one entry to `type_ids()`'s slice.
-   - **Std-side** (only when promoting a node into `aura-std` itself): one
-     line in the `std_vocabulary_roster!` macro invocation in
-     [`crates/aura-std/src/vocabulary.rs`](../crates/aura-std/src/vocabulary.rs)
+   - **Std-side** (only when promoting a node into the shipped std
+     vocabulary): one line in the `std_vocabulary_roster!` macro invocation in
+     [`crates/aura-vocabulary/src/lib.rs`](../crates/aura-vocabulary/src/lib.rs)
      — `"TypeId" => Type,` — which expands into both the resolver `match` and
-     the enumerable type-id list, so the two surfaces cannot drift apart.
+     the enumerable type-id list, so the two surfaces cannot drift apart. A
+     zero-arg `Type::builder()` rosters directly; an **arg-bearing** type
+     (structural, non-scalar construction — see "Session anchoring" below and
+     `docs/glossary.md`'s `construction arg` entry, #271) rosters the exact
+     same way — its `builder()` is itself zero-arg, returning a *pending*
+     recipe the `add` op's `args` configures before any `bind`.
    An unrostered type fails safe either way: the loader refuses with a clean
    `LoadError::UnknownNodeType` naming the missing id, and the type is simply
    absent from `aura graph introspect --vocabulary` — never a silent partial
@@ -228,7 +234,7 @@ are dotted `<identifier>.<port>` on both sides of a wire.
 | `doc` | `{"op":"doc","text":<str>}` | declare the composite's one-line meaning (C29) — the op-script twin of the Rust builder's `.doc(...)`. Required before `aura graph register` accepts the product (the store refuses a doc-less composite); at most one per script (a second refuses: `a doc op may appear at most once`). The text is gated: empty or merely restating the composite's name refuses at register. |
 | `source` | `{"op":"source","role":<str>,"kind":<ScalarKind>}` | reserve a bound root **source** role of `kind` — a real input the harness feeds (e.g. `"price"`). |
 | `input` | `{"op":"input","role":<str>}` | reserve an open root **input** role (kind inferred from the slots it feeds) — the formal parameter of an **open pattern**, a fragment meant to be wired by an *enclosing* graph. An open pattern builds and registers like any blueprint. Running it standalone is governed by the ordinary run gates: the harness binds input roles to archive columns **by name** (C26), so a pattern whose roles match the data runs as-is; what refuses, by name, is a role the harness cannot bind — or the run surface's other gates (a signal without a bias output or tap; free knobs). |
-| `add` | `{"op":"add","type":<TypeId>,"name":<str>?,"bind":{<param>:<Scalar>}?}` | instantiate a node of a type in the closed vocabulary (`aura graph introspect --vocabulary`) — see §0 below for how a type gets into that vocabulary in the first place. `name` becomes the node's identifier for later ops (default: the type's own lowercase label — two unnamed nodes of the same type then collide). `bind` sets zero or more of its params. |
+| `add` | `{"op":"add","type":<TypeId>,"name":<str>?,"args":{<arg>:<str>}?,"bind":{<param>:<Scalar>}?}` | instantiate a node of a type in the closed vocabulary (`aura graph introspect --vocabulary`) — see §0 below for how a type gets into that vocabulary in the first place. `name` becomes the node's identifier for later ops (default: the type's own lowercase label — two unnamed nodes of the same type then collide). `args` (#271) configures an **arg-bearing** type's structural, non-scalar construction (`Session`'s timezone/open, `LinComb`/`CostSum`'s arity) — a closed table of string values, applied BEFORE `bind`; `aura graph introspect --node <T>` lists a type's declared `arg` rows. `bind` sets zero or more of the (now real) params. |
 | `use` | `{"op":"use","ref":{"content_id":<id-or-prefix>}\|{"name":<label>},"name":<str>?,"bind":{<path>:<Scalar>}?}` | splice a **registered blueprint** into the graph as a nested composite under an instance identifier (`name`; default: the stored composite's own name). The ref resolves by content id (full or unique prefix) or by a register-time label; `graph build` echoes every resolution (`aura: note: use "…": … -> <id>`) so the exact id can be pinned. The instance's open input roles wire as `<instance>.<role>`, its outputs as `<instance>.<field>`; its open params surface path-qualified (`<instance>.<node>.<param>`), sweepable (ganging an instance's params is not yet supported — the `gang` op refuses a composite instance's member path). A doc-less stored source refuses at the op (C29). The emitted blueprint contains the subgraph *inline* — no reference survives into the artifact. |
 | `feed` | `{"op":"feed","role":<str>,"into":[<port>, …]}` | fan a previously-declared role into one or more interior input slots, all-or-nothing (a failing target leaves none of the batch wired). |
 | `connect` | `{"op":"connect","from":<port>,"to":<port>}` | wire one interior output field to one interior input slot. A `connect` that would close a dataflow cycle is rejected immediately — the only legal feedback path is an explicit delay/state node (domain invariant 5). |
@@ -342,6 +348,30 @@ Wire it like any node —
 `{"op":"add","type":"SessionFrankfurt","bind":{"period_minutes":{"I64":15}}}`,
 feed its `trigger` from a once-per-bar stream, and read `bars_since_open`.
 
+**Any other timezone/open: `Session` + `args` (#271).** `SessionFrankfurt`
+stays baked sugar for the one Frankfurt open; the canonical path for ANY IANA
+timezone and local open time is the base `Session` type through the typed
+construction-args channel — `args` configures it BEFORE `bind`:
+
+```json
+{"op":"add","type":"Session","name":"ny",
+ "args":{"tz":"America/New_York","open":"09:30"},
+ "bind":{"period_minutes":{"I64":15}}}
+```
+
+`tz` is `chrono_tz`'s own exact, case-sensitive IANA name (`"berlin"` refuses;
+`"Europe/Berlin"` accepts); `open` is strict zero-padded local `HH:MM`
+(`"9:30"` refuses; `"09:30"` accepts); a `Count` arg (`LinComb`/`CostSum`'s
+arity) is a plain positive decimal — no sign, no leading zeros (`"03"`
+refuses; `"3"` accepts). The accepted string IS the canonical form, no
+normalization — and note the deliberate asymmetry: each kind's canonical
+form is its domain's conventional notation, fixed-width for wall-clock
+times, minimal for numbers. Giving `Session` no `args` at all refuses the `add`
+op (`node <name> is missing required arg "tz"`) — an arg-bearing type never
+silently enters the graph half-configured. `aura graph introspect --node
+Session` lists both declared `arg` rows with their kind and hint text before
+you write the JSON.
+
 ### Commands
 
 ```

docs/design/contracts/c15-resampling-sessions.md

@@ -17,10 +17,14 @@ stream; reference data feeds source/session nodes from beside the hot path.
 
 **Session context — `bars_since_open` is the shipped contract (#154).** The
 session-context node `Session` (`crates/aura-market/src/session.rs`) emits
-**one** scalar stream, `bars_since_open: i64` (tz-aware, DST-correct, over a
-baked Frankfurt open), and takes no scalar params; the zero-arg
-`SessionFrankfurt` roster preset (#261) exposes it with a single
-`period_minutes` knob. This is a deliberate narrowing pinned in the node's own
+**one** scalar stream, `bars_since_open: i64` (tz-aware, DST-correct), over a
+timezone/open time that is now data-authorable via the typed construction-args
+channel (`Session` roster-reaches `std_vocabulary` as an arg-bearing type,
+#271: `args: {"tz": <IANA name>, "open": "HH:MM"}`, applied before its one
+scalar param, `period_minutes`). The zero-arg `SessionFrankfurt` roster preset
+(#261) stays as baked sugar over the 09:00 `Europe/Berlin` open — the
+canonical path for any OTHER open/timezone is `Session` + `args`, not a new
+preset per market. This is a deliberate narrowing pinned in the node's own
 contract: `bars_since_open` alone is the gate — a downstream `EqConst(== N)`
 subsumes an `in_session: bool` stream (pre-open instants read `<= 0`, which
 never match), and nothing consumes a `session_open_ts: timestamp`. The two

docs/design/contracts/c24-blueprint-data.md

@@ -70,8 +70,10 @@ loop for the round-trippable vocabulary.
 
 **Out of the round-trippable set** (deliberate; fails clean as `UnknownNodeType`):
 recording sinks (they capture an `mpsc::Sender` — runtime identity, not param-generic
-data, C19) and construction-arg builders (`LinComb` / `CostSum` / `SimBroker` /
-`Session` — structural-axis args, a C20 concern), additively addable later (#156).
+data, C19) and `SimBroker` (a scalar-typed baked value, a narrower gap than the args
+channel). `LinComb` / `CostSum` / `Session` — formerly listed here — entered the
+round-trippable set with #271's typed construction args (see the add-op `args`
+clause and the data-driven `format_version` below).
 
 ### Runs and families are built FROM blueprint-data
 
@@ -197,10 +199,17 @@ replayed in order; nodes are referenced **by identifier**, ports as dotted
   from the slots it feeds) — a reusable **pattern**'s formal parameter, left open
   until an enclosing graph wires it (#317's open patterns): `finish()` accepts an
   op-script that never binds it, only `compile`/bootstrap require it bound.
-- `add` — `{"op":"add","type":<TypeId>,"name":<str>?,"bind":{<param>:<Scalar>}?}` —
+- `add` — `{"op":"add","type":<TypeId>,"name":<str>?,"args":{<arg>:<str>}?,"bind":{<param>:<Scalar>}?}` —
   add a node of compiled-in type identity `type`; **`name` is its identifier**
   (mirrors the builder's `.named(...)`; defaults to the lowercased type label, so
-  two unnamed nodes of one type collide); `bind` sets params.
+  two unnamed nodes of one type collide); `args` (#271) configures an **arg-bearing**
+  type's structural, non-scalar construction (`Session`'s IANA timezone/open,
+  `LinComb`/`CostSum`'s arity) through the closed, load-time-validated `ArgKind`
+  table (`Tz`/`TimeOfDay`/`Count`) — applied BEFORE `bind`, so a bound param
+  `args` unlocks (e.g. `LinComb`'s `weights[i]`) is only bindable once `arity` is
+  consumed; an arg-bearing type given no `args` refuses (`BadArg(MissingArg)`), a
+  `Plain` type given `args` it does not declare also refuses
+  (`BadArg(NotArgBearing)`); `bind` sets the (now real) params.
 - `feed` — `{"op":"feed","role":<str>,"into":[<port>,…]}` — fan a root role into
   interior input slots.
 - `connect` — `{"op":"connect","from":<port>,"to":<port>}` — wire an interior output
@@ -262,12 +271,21 @@ Tier-1 (additive-optional) is serde-default silent-ignore with **no** `format_ve
 bump — a new optional field defaults to prior behaviour (C1). Tier-2 (must-understand:
 a new node type, edge semantics, or structural-axis kind) **bumps** `format_version` so
 an old reader refuses cleanly (`LoadError::UnsupportedVersion` / `UnknownNodeType`).
-**Pre-ship dormancy (#61):** until the first external ship there are no out-of-repo
-readers — reader and writer change atomically in one commit — so the Tier-2 bump
-discipline is dormant and structurally-semantic additions (the `gangs` section) land as
-additive-optional fields of v1; the first ship consciously freezes v1, gangs included,
-and activates the bump discipline. The per-section required-flag scheme is deferred (no
-current Tier-2 section to validate it; recorded on #156).
+**Pre-ship dormancy (#61, ended by #271):** until the first external ship there were
+no out-of-repo readers — reader and writer changed atomically in one commit — so the
+Tier-2 bump discipline lay dormant and structurally-semantic additions (the `gangs`
+section) landed as additive-optional fields of v1. #271's construction args are the
+first exercised Tier-2 bump (data-driven, next paragraph); v1 remains the version of
+every args-free document, gangs included. The per-section required-flag scheme stays
+deferred (no per-section case yet; recorded on #156).
+
+**First data-driven bump (#271):** construction args are the first Tier-2 case whose
+version is decided PER DOCUMENT, not a single global bump. The writer emits
+`format_version: 1` for an args-free document (byte-identical to every pre-#271
+document — content ids stable) and `2` the moment any primitive, at any composite
+nesting depth, carries `args` — the must-understand signal an old (pre-#271) reader
+needs, since it cannot construct a pending arg-bearing type at all. The loader accepts
+the closed range `1..=2`.
 
 ### Enforcement shift — invariant 9 on the data plane
 

docs/glossary.md

@@ -11,6 +11,10 @@ Entries are alphabetical.
 
 ---
 
+### arg kind
+**Avoid:** ArgKind, construction-arg type
+The closed vocabulary of construction-arg value shapes (`Tz`/`TimeOfDay`/`Count`, #271) — deliberately NOT a `scalar base type`: args are bootstrap metadata, never streamed, so the two closedness axes stay separate. Each kind's accepted strict form IS its canonical form (an exact IANA name; zero-padded `HH:MM`; a plain positive decimal count, no sign or leading zeros) — there is no normalization layer, so a near-miss string refuses rather than being rewritten. The per-kind forms are deliberately asymmetric (`"03"` refuses as a count while `"09:30"` requires the pad): canonical is each domain's conventional notation — fixed-width for wall-clock times, minimal for numbers.
+
 ### atomic sim unit
 **Avoid:** atomic unit, sim unit
 The primitive `(frozen topology + param-set + data-window + RNG-seed) → deterministic run → metrics` over which the four orchestration axes operate. One frozen-topology unit equals one harness instance.
@@ -67,6 +71,10 @@ The type-erased 64-bit word holding one scalar-base-type value with its kind str
 **Avoid:** —
 A node that wires a sub-graph and exposes one output (a combined signal, or a strategy) — composition is fractal and acyclic. May carry an optional authored rationale (`doc`, #125) — a non-load-bearing debug symbol shown in the graph tooltip, identity-blind like the name. Also names the multi-column stream a node emits: the **record** a producer's `eval` returns, bundling 1..K base scalar columns (e.g. OHLCV), each bound field-wise by a consumer (C7/C8).
 
+### construction arg
+**Avoid:** construction-time param, arg
+A typed, closed, non-scalar construction input (`args`, #271) that configures an **arg-bearing** vocabulary type's structural shape — `Session`'s IANA timezone/open, `LinComb`/`CostSum`'s arity — through a second channel beside `bind`, consumed once at construction (`PrimitiveBuilder::try_args`) before any param binds, never streamed, never swept, never bound. Values are closed, load-time-validated strings (see `arg kind`); the accepted pairs are id-bearing (they enter the blueprint's content id, like `bind` values) and survive the identity projection.
+
 ### content id
 **Avoid:** —
 The SHA-256 (hex) of an artifact's byte-canonical form — for a blueprint, `blueprint_to_json` (the byte-exact identity that keys the reproduction store and anchors `aura reproduce`, stamped into a run manifest as the `topology hash`); for a `process document` / `campaign document`, its canonical JSON (keying the sibling registry stores). One primitive, library-hosted in `aura-research` (`content_id_of`; the CLI delegates). Surfaced as `aura graph|process|campaign introspect --content-id`; two artifacts share a content id only when their canonical bytes agree, debug names included — contrast `identity id`.
@@ -263,7 +271,7 @@ The four streamed scalar kinds — `i64`, `f64`, `bool`, `timestamp` (a newtype
 
 ### session node
 **Avoid:** session window
-A node that exposes session context as a scalar stream so session logic stays inside the stream model. The shipped `Session` / `SessionFrankfurt` node (`aura-std`) emits ONE `i64` field, `bars_since_open` — the count of completed bar-periods since the local (tz-aware, DST-correct) session open, indexed off the just-closed bar's close instant (in-session closes read exact positive multiples: 09:15→1, 09:45→3; pre-open ≤0). `SessionFrankfurt` bakes the Frankfurt 09:00 `Europe/Berlin` open with a single `period_minutes` knob; its `trigger` input only clocks it once per completed bar (the value is ignored). Calendars and instrument specs remain metadata beside the hot path.
+A node that exposes session context as a scalar stream so session logic stays inside the stream model. The shipped `Session` / `SessionFrankfurt` node (`aura-market`) emits ONE `i64` field, `bars_since_open` — the count of completed bar-periods since the local (tz-aware, DST-correct) session open, indexed off the just-closed bar's close instant (in-session closes read exact positive multiples: 09:15→1, 09:45→3; pre-open ≤0). `Session` is roster-reachable for ANY IANA timezone/open through the typed **construction arg** channel (#271: `args: {"tz": <IANA name>, "open": "HH:MM"}`, applied before its one scalar param, `period_minutes`); `SessionFrankfurt` stays as baked sugar over the Frankfurt 09:00 `Europe/Berlin` open. Its `trigger` input only clocks it once per completed bar (the value is ignored). Calendars and instrument specs remain metadata beside the hot path.
 
 ### sign-agreement
 **Avoid:** sign consistency, market breadth

fieldtests/construction-args/TRANSCRIPT.md

@@ -0,0 +1,217 @@
+# Fieldtest transcript — cycle #271 (typed construction args)
+
+Verbatim command/output capture for the `fieldtests/construction-args/` fixtures.
+Binary: `target/debug/aura` built from HEAD `6ca359a` via `cargo build --workspace`
+(debug profile). Runs used a scratch project `aura new ca_lab` (in `/tmp/ca_lab`);
+real data resolved from the built-in archive (`/mnt/tickdata/Pepperstone`). All
+op-scripts authored from the public interface only (README, authoring guide,
+glossary, design ledger C24, `aura graph introspect`).
+
+Public interface only — no crate source read.
+
+---
+
+## Discovery loop (axis 3) — is the args grammar learnable from the binary?
+
+```
+$ aura graph introspect --vocabulary | wc -l
+36
+
+$ aura graph introspect --node Session
+Session — bars elapsed since the session open, from the configured open time and timezone
+  arg    tz: Tz   (IANA timezone name, e.g. Europe/Berlin)
+  arg    open: TimeOfDay   (local wall-clock HH:MM)
+  note   ports and params form at construction; args are required
+
+$ aura graph introspect --node LinComb
+LinComb — linear combination of its inputs with constant weights
+  arg    arity: Count   (positive integer count)
+  note   ports and params form at construction; args are required
+
+$ aura graph introspect --node CostSum
+CostSum — sums cost-model contributions into one cost-in-R stream
+  arg    n_costs: Count   (positive integer count)
+  note   ports and params form at construction; args are required
+```
+
+The arg *grammar* (name, kind, hint) is fully self-describing. But `--node <T>`
+stops at the note — it does NOT reveal the post-construction ports/params. To
+learn the port names you must author a partial op-list carrying the args and pipe
+it through `--unwired`; to learn the param names you must build and `--list-axes`.
+Nothing on the `--node` surface names those follow-up steps. First naive guess at
+LinComb's input port was `lc.in0` — wrong:
+
+```
+$ echo '[{"op":"add","type":"LinComb","name":"lc","args":{"arity":"3"}}]' \
+    | aura graph introspect --unwired
+lc.term[0]:F64
+lc.term[1]:F64
+lc.term[2]:F64
+
+$ echo '[{"op":"add","type":"CostSum","name":"cs","args":{"n_costs":"3"}}]' \
+    | aura graph introspect --unwired
+cs.cost[0].cost_in_r:F64
+cs.cost[0].cum_cost_in_r:F64
+cs.cost[0].open_cost_in_r:F64
+cs.cost[1].cost_in_r:F64          (… ×3 slots, 3 fields each)
+```
+
+Weight param names, discovered only after a build:
+
+```
+$ aura graph build < lc_probe.ops.json > lc_probe.bp.json
+$ aura sweep lc_probe.bp.json --list-axes
+graph.lc.weights[0]:F64          # open by default → sweepable (C24)
+graph.lc.weights[1]:F64
+...
+```
+
+---
+
+## Example 1 — `ca_1_ny_session` (axis 1: non-Frankfurt Session as data)
+
+```
+$ aura graph build < ca_1_ny_session.ops.json > ca_1_ny_session.bp.json
+$ head -c 25 ca_1_ny_session.bp.json
+{"format_version":2,"blue          # arg-bearing → v2
+
+$ aura graph introspect --content-id --identity-id < ca_1_ny_session.ops.json
+5b085a5b3f411072e48d4b54717b3d09e88be50b0bd797d345c2ee90baa41c37   # content id
+4bf0513a4d2e852ab580fd8846737f57c1825b944ff9df1a48040a07fe92446b   # identity id
+
+# --- inside ca_lab/ ---
+$ aura run ca_1_ny_session.bp.json --real US500 --from 1725148800000 --to 1725580800000
+{"manifest":{... "topology_hash":"5b085a5b...b40d95cf"? -> 5b085a5b... (== content id) ...},
+ "metrics":{... "expectancy_r":0.7853745294474523,"n_trades":18 ...}}    (exit 0)
+
+# synthetic refuses cleanly (OHLC strategy, close-only synthetic stream):
+$ aura run ca_1_ny_session.bp.json
+aura: strategy "graph" consumes columns beyond close (open, high, low) —
+      synthetic data generates a close series only; run with --real <SYMBOL>
+```
+
+Full report captured in `ca_1_ny_session.run.json`.
+
+---
+
+## Example 2 — `ca_2_lincomb_blend` (axis 2: LinComb arity + weights + swept period)
+
+Three SMA spreads blended through `LinComb(arity 3)` with bound `weights[i]`,
+NY-session-gated, `Session.period_minutes` left OPEN (sweepable).
+
+```
+$ aura graph build < ca_2_lincomb_blend.ops.json > ca_2_lincomb_blend.bp.json
+$ head -c 25 ca_2_lincomb_blend.bp.json
+{"format_version":2,"blue
+
+$ aura sweep ca_2_lincomb_blend.bp.json --list-axes
+graph.sess.period_minutes:I64            # open
+graph.lc.weights[0]:F64 default=0.5      # bound (re-openable by --axis)
+graph.lc.weights[1]:F64 default=0.3
+graph.lc.weights[2]:F64 default=0.2
+...
+
+# --- inside ca_lab/ --- sweep the arity-unlocked weight AND the period param:
+$ aura sweep ca_2_lincomb_blend.bp.json --real US500 --from 1725148800000 --to 1725580800000 \
+    --axis graph.sess.period_minutes=15,30 --axis 'graph.lc.weights[0]=0.3,0.5' --name ca2_blend
+{"family_id":"caa3508a-0-US500-w0-r0-s0-0", ... 4 members ...}   (exit 0)
+
+$ aura reproduce caa3508a-0-US500-w0-r0-s0-0
+... member graph.lc.weights[0]=0.3, graph.sess.period_minutes=15 ... reproduced: bit-identical
+... (×4)
+reproduced 4/4 members bit-identically
+```
+
+Sweep output in `ca_2_lincomb_blend.sweep.jsonl`. NB: at this gating, the two
+`weights[0]` values yield identical member metrics (the gated blend's sign is
+weight-insensitive here) — a semantic property of the strategy, not the arg
+channel; the params bound and swept correctly.
+
+CostSum arity probe: `ca_2b_costsum_arity.ops.json` → `--unwired` shows
+`cost[i].{cost_in_r,cum_cost_in_r,open_cost_in_r}` (3 slots × 3 fields). Wiring
+CostSum end to end needs the RiskExecutor context (cost nodes take
+`closed/open/entry_price/stop_price`) — no op-script path for that exists in the
+public corpus (see finding SG2).
+
+---
+
+## Example 3 — refusal battery (axis 4: strict-form refusal prose)
+
+Every case: `aura graph build < FIXTURE`, stderr + exit code.
+
+```
+ca_3a_bad_tz         aura: op 1 (add): node sess arg "tz" expects Tz (IANA timezone name, e.g. Europe/Berlin) — got "berlin"        exit 1
+ca_3b_unpadded_time  aura: op 1 (add): node sess arg "open" expects TimeOfDay (local wall-clock HH:MM) — got "9:30"                 exit 1
+ca_3c_zero_count     aura: op 2 (add): node lc arg "arity" expects Count (positive integer count) — got "0"                        exit 1
+ca_3d_garbage_count  aura: op 1 (add): node lc arg "arity" expects Count (positive integer count) — got "three"                    exit 1
+ca_3e_missing_arg    aura: op 1 (add): node sess is missing required arg "tz"                                                       exit 1
+ca_3f_args_on_argless aura: op 1 (add): node a takes no construction args                                                          exit 1
+ca_3g_unknown_arg_key aura: op 1 (add): node sess has no construction arg "region"                                                 exit 1
+ca_3h_partial_args    aura: op 1 (add): node sess is missing required arg "open"                                                    exit 1
+```
+
+Edge-form strictness (ad-hoc, `--unwired`):
+
+```
+Count  arity:  "3"→ok   "03"→refuse  "+3"→refuse  "3.0"→refuse  "1e1"→refuse  "-2"→refuse  " 3"→refuse  "0x3"→refuse
+Time   open:   "09:30"→ok  "00:00"→ok  "23:59"→ok   "24:00"→refuse  "09:60"→refuse  "9:05"→refuse  "09:5"→refuse  "09:30:00"→refuse  "0930"→refuse
+```
+
+Note the padding asymmetry: `open` REQUIRES a zero-padded hour (`09:05`), but
+`arity` REFUSES a leading zero (`03`). See finding SG1.
+
+---
+
+## Example 4 — `ca_4` register → use (axis 5: #317 interplay)
+
+```
+$ aura graph build < ca_4_ny_anchor_pattern.ops.json > ca_4_ny_anchor_pattern.bp.json
+$ head -c 25 ca_4_ny_anchor_pattern.bp.json
+{"format_version":2,"blue
+$ aura graph introspect --content-id --identity-id < ca_4_ny_anchor_pattern.ops.json
+d51132463b2d1780b3ed9b83dc9f9a229a9d6b93fce3e15c7c0572970e2e4564
+863c89ddeaa2dfe7d79c7e55944263145399c67397a27c0955bdd768cc6ed72e
+
+# --- inside ca_lab/ ---
+$ aura graph register .../ca_4_ny_anchor_pattern.bp.json --name ny_anchor
+registered blueprint d51132463b2d... (.../runs/blueprints/d51132463b2d....json)
+label "ny_anchor" -> d51132463b2d...
+
+$ aura graph introspect --registered
+ny_anchor  d51132463b2d  NY cash-open session anchor: bars elapsed since the 09:30 America/New_York open
+
+$ aura graph build < ca_4_consumer.ops.json > consumer.bp.json
+# stderr: aura: note: use "anchor": ny_anchor -> d51132463b2d...
+$ head -c 25 consumer.bp.json
+{"format_version":2,"blue          # v2 propagates THROUGH the splice
+$ aura graph introspect --content-id --identity-id < ca_4_consumer.ops.json
+985991f62cc6b92895018312c5ea86e493ef1c09dd53cf6e0813551baa97b671
+bbe7060f4136255e594e1b01242ae80c3f5decfc543f23198d66adff6ce52a7b
+
+$ aura run consumer.bp.json --real US500 --from 1725148800000 --to 1725580800000
+{"manifest":{... "topology_hash":"985991f6..." (== content id),
+   "defaults":[["graph.anchor.sess.period_minutes",{"I64":15}], ...] ...},
+ "metrics":{... "n_trades":8 ...}}    (exit 0)
+
+# doc gate on the args-bearing composite (doc stripped):
+$ aura graph register ca4_docless.bp.json --name ny_docless
+aura: blueprint: composite `graph` carries no doc — a registered composite
+      describes itself (C29); add a doc line (...) before register       exit 1
+```
+
+Consumer report captured in `ca_4_consumer.run.json`.
+
+---
+
+## Cross-cutting confirmations
+
+```
+# args-free document stays format_version 1 (byte-stability invariant, C18):
+$ echo '[{"op":"source",...},{"op":"add","type":"SMA",...},...]' | aura graph build | head -c 25
+{"format_version":1,"blue
+
+# content id deterministic across builds:
+$ aura graph introspect --content-id < ca_1_ny_session.ops.json   (×2) -> identical
+5b085a5b3f411072e48d4b54717b3d09e88be50b0bd797d345c2ee90baa41c37
+5b085a5b3f411072e48d4b54717b3d09e88be50b0bd797d345c2ee90baa41c37
+```

fieldtests/construction-args/ca_1_ny_session.bp.json

@@ -0,0 +1 @@
+{"format_version":2,"blueprint":{"name":"graph","nodes":[{"primitive":{"type":"Resample","name":"c15","bound":[{"pos":0,"name":"period_minutes","kind":"I64","value":{"I64":15}}]}},{"primitive":{"type":"Sub","name":"body"}},{"primitive":{"type":"Sign","name":"dir"}},{"primitive":{"type":"Session","name":"sess","args":[{"name":"tz","value":"America/New_York"},{"name":"open","value":"09:30"}],"bound":[{"pos":0,"name":"period_minutes","kind":"I64","value":{"I64":15}}]}},{"primitive":{"type":"EqConst","name":"isfirst","bound":[{"pos":0,"name":"target","kind":"I64","value":{"I64":1}}]}},{"primitive":{"type":"When","name":"firstmom"}},{"primitive":{"type":"Bias","name":"bias","bound":[{"pos":0,"name":"scale","kind":"F64","value":{"F64":1.0}}]}}],"edges":[{"from":0,"to":1,"slot":0,"from_field":3},{"from":0,"to":1,"slot":1,"from_field":0},{"from":1,"to":2,"slot":0,"from_field":0},{"from":0,"to":3,"slot":0,"from_field":3},{"from":3,"to":4,"slot":0,"from_field":0},{"from":2,"to":5,"slot":0,"from_field":0},{"from":4,"to":5,"slot":1,"from_field":0},{"from":5,"to":6,"slot":0,"from_field":0}],"input_roles":[{"name":"open","targets":[{"node":0,"slot":0}],"source":"F64"},{"name":"high","targets":[{"node":0,"slot":1}],"source":"F64"},{"name":"low","targets":[{"node":0,"slot":2}],"source":"F64"},{"name":"close","targets":[{"node":0,"slot":3}],"source":"F64"}],"output":[{"node":6,"field":0,"name":"bias"}]}}

fieldtests/construction-args/ca_1_ny_session.ops.json

@@ -0,0 +1,28 @@
+[
+  {"op": "source", "role": "open", "kind": "F64"},
+  {"op": "source", "role": "high", "kind": "F64"},
+  {"op": "source", "role": "low", "kind": "F64"},
+  {"op": "source", "role": "close", "kind": "F64"},
+  {"op": "add", "type": "Resample", "name": "c15", "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "feed", "role": "open", "into": ["c15.open"]},
+  {"op": "feed", "role": "high", "into": ["c15.high"]},
+  {"op": "feed", "role": "low", "into": ["c15.low"]},
+  {"op": "feed", "role": "close", "into": ["c15.close"]},
+  {"op": "add", "type": "Sub", "name": "body"},
+  {"op": "connect", "from": "c15.close", "to": "body.lhs"},
+  {"op": "connect", "from": "c15.open", "to": "body.rhs"},
+  {"op": "add", "type": "Sign", "name": "dir"},
+  {"op": "connect", "from": "body.value", "to": "dir.value"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "args": {"tz": "America/New_York", "open": "09:30"},
+   "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "connect", "from": "c15.close", "to": "sess.trigger"},
+  {"op": "add", "type": "EqConst", "name": "isfirst", "bind": {"target": {"I64": 1}}},
+  {"op": "connect", "from": "sess.bars_since_open", "to": "isfirst.value"},
+  {"op": "add", "type": "When", "name": "firstmom"},
+  {"op": "connect", "from": "dir.value", "to": "firstmom.value"},
+  {"op": "connect", "from": "isfirst.value", "to": "firstmom.gate"},
+  {"op": "add", "type": "Bias", "name": "bias", "bind": {"scale": {"F64": 1.0}}},
+  {"op": "connect", "from": "firstmom.value", "to": "bias.signal"},
+  {"op": "expose", "from": "bias.bias", "as": "bias"}
+]

fieldtests/construction-args/ca_1_ny_session.run.json

@@ -0,0 +1,65 @@
+{
+    "manifest": {
+        "commit": "6ca359ae00e8e7921f08557be383bc2d0a2ce199",
+        "params": [],
+        "defaults": [
+            [
+                "graph.c15.period_minutes",
+                {
+                    "I64": 15
+                }
+            ],
+            [
+                "graph.sess.period_minutes",
+                {
+                    "I64": 15
+                }
+            ],
+            [
+                "graph.isfirst.target",
+                {
+                    "I64": 1
+                }
+            ],
+            [
+                "graph.bias.scale",
+                {
+                    "F64": 1.0
+                }
+            ]
+        ],
+        "window": [
+            1725235200000000000,
+            1725580800000000000
+        ],
+        "seed": 0,
+        "broker": "sim-optimal+risk-executor(pip_size=1)",
+        "topology_hash": "5b085a5b3f411072e48d4b54717b3d09e88be50b0bd797d345c2ee90baa41c37",
+        "project": {
+            "commit": "d7e3a8f39881cc8eba42a906fa846676bfbb1010"
+        }
+    },
+    "metrics": {
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+        "max_drawdown": 77.0,
+        "bias_sign_flips": 2,
+        "r": {
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+            "n_trades": 18,
+            "win_rate": 0.1111111111111111,
+            "avg_win_r": 17.115118267387366,
+            "avg_loss_r": -1.2558434377950367,
+            "profit_factor": 1.7035481645543986,
+            "max_r_drawdown": 16.041140339815094,
+            "n_open_at_end": 1,
+            "sqn": 0.4343599983483773,
+            "sqn_normalized": 0.4343599983483773,
+            "net_expectancy_r": 0.7853745294474523,
+            "conviction_terciles_r": [
+                -1.3650686711197901,
+                -1.2338202185443914,
+                4.955012478006539
+            ]
+        }
+    }
+}

fieldtests/construction-args/ca_2_lincomb_blend.bp.json

@@ -0,0 +1 @@
+{"format_version":2,"blueprint":{"name":"graph","doc":"NY-session-gated blend of three SMA spreads via a LinComb(arity 3); sweepable session period","nodes":[{"primitive":{"type":"SMA","name":"a","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":2}}]}},{"primitive":{"type":"SMA","name":"b","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":5}}]}},{"primitive":{"type":"SMA","name":"c","bound":[{"pos":0,"name":"length","kind":"I64","value":{"I64":10}}]}},{"primitive":{"type":"Sub","name":"sA"}},{"primitive":{"type":"Sub","name":"sB"}},{"primitive":{"type":"Sub","name":"sC"}},{"primitive":{"type":"LinComb","name":"lc","args":[{"name":"arity","value":"3"}],"bound":[{"pos":0,"name":"weights[0]","kind":"F64","value":{"F64":0.5}},{"pos":1,"name":"weights[1]","kind":"F64","value":{"F64":0.3}},{"pos":2,"name":"weights[2]","kind":"F64","value":{"F64":0.2}}]}},{"primitive":{"type":"Session","name":"sess","args":[{"name":"tz","value":"America/New_York"},{"name":"open","value":"09:30"}]}},{"primitive":{"type":"EqConst","name":"insession","bound":[{"pos":0,"name":"target","kind":"I64","value":{"I64":1}}]}},{"primitive":{"type":"When","name":"gated"}},{"primitive":{"type":"Bias","name":"bias","bound":[{"pos":0,"name":"scale","kind":"F64","value":{"F64":1.0}}]}}],"edges":[{"from":0,"to":3,"slot":0,"from_field":0},{"from":2,"to":3,"slot":1,"from_field":0},{"from":1,"to":4,"slot":0,"from_field":0},{"from":2,"to":4,"slot":1,"from_field":0},{"from":0,"to":5,"slot":0,"from_field":0},{"from":1,"to":5,"slot":1,"from_field":0},{"from":3,"to":6,"slot":0,"from_field":0},{"from":4,"to":6,"slot":1,"from_field":0},{"from":5,"to":6,"slot":2,"from_field":0},{"from":7,"to":8,"slot":0,"from_field":0},{"from":6,"to":9,"slot":0,"from_field":0},{"from":8,"to":9,"slot":1,"from_field":0},{"from":9,"to":10,"slot":0,"from_field":0}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0},{"node":1,"slot":0},{"node":2,"slot":0},{"node":7,"slot":0}],"source":"F64"}],"output":[{"node":10,"field":0,"name":"bias"}]}}

fieldtests/construction-args/ca_2_lincomb_blend.ops.json

@@ -0,0 +1,33 @@
+[
+  {"op": "doc", "text": "NY-session-gated blend of three SMA spreads via a LinComb(arity 3); sweepable session period"},
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "SMA", "name": "a", "bind": {"length": {"I64": 2}}},
+  {"op": "add", "type": "SMA", "name": "b", "bind": {"length": {"I64": 5}}},
+  {"op": "add", "type": "SMA", "name": "c", "bind": {"length": {"I64": 10}}},
+  {"op": "feed", "role": "price", "into": ["a.series", "b.series", "c.series"]},
+  {"op": "add", "type": "Sub", "name": "sA"},
+  {"op": "connect", "from": "a.value", "to": "sA.lhs"},
+  {"op": "connect", "from": "c.value", "to": "sA.rhs"},
+  {"op": "add", "type": "Sub", "name": "sB"},
+  {"op": "connect", "from": "b.value", "to": "sB.lhs"},
+  {"op": "connect", "from": "c.value", "to": "sB.rhs"},
+  {"op": "add", "type": "Sub", "name": "sC"},
+  {"op": "connect", "from": "a.value", "to": "sC.lhs"},
+  {"op": "connect", "from": "b.value", "to": "sC.rhs"},
+  {"op": "add", "type": "LinComb", "name": "lc", "args": {"arity": "3"},
+   "bind": {"weights[0]": {"F64": 0.5}, "weights[1]": {"F64": 0.3}, "weights[2]": {"F64": 0.2}}},
+  {"op": "connect", "from": "sA.value", "to": "lc.term[0]"},
+  {"op": "connect", "from": "sB.value", "to": "lc.term[1]"},
+  {"op": "connect", "from": "sC.value", "to": "lc.term[2]"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "args": {"tz": "America/New_York", "open": "09:30"}},
+  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
+  {"op": "add", "type": "EqConst", "name": "insession", "bind": {"target": {"I64": 1}}},
+  {"op": "connect", "from": "sess.bars_since_open", "to": "insession.value"},
+  {"op": "add", "type": "When", "name": "gated"},
+  {"op": "connect", "from": "lc.value", "to": "gated.value"},
+  {"op": "connect", "from": "insession.value", "to": "gated.gate"},
+  {"op": "add", "type": "Bias", "name": "bias", "bind": {"scale": {"F64": 1.0}}},
+  {"op": "connect", "from": "gated.value", "to": "bias.signal"},
+  {"op": "expose", "from": "bias.bias", "as": "bias"}
+]

fieldtests/construction-args/ca_2_lincomb_blend.sweep.jsonl

@@ -0,0 +1,4 @@
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fieldtests/construction-args/ca_2b_costsum_arity.ops.json

@@ -0,0 +1,3 @@
+[
+  {"op": "add", "type": "CostSum", "name": "cs", "args": {"n_costs": "3"}}
+]

fieldtests/construction-args/ca_3a_bad_tz.ops.json

@@ -0,0 +1,8 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "args": {"tz": "berlin", "open": "09:30"},
+   "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
+  {"op": "expose", "from": "sess.bars_since_open", "as": "bars"}
+]

fieldtests/construction-args/ca_3b_unpadded_time.ops.json

@@ -0,0 +1,8 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "args": {"tz": "America/New_York", "open": "9:30"},
+   "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
+  {"op": "expose", "from": "sess.bars_since_open", "as": "bars"}
+]

fieldtests/construction-args/ca_3c_zero_count.ops.json

@@ -0,0 +1,7 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "SMA", "name": "a", "bind": {"length": {"I64": 2}}},
+  {"op": "add", "type": "LinComb", "name": "lc", "args": {"arity": "0"}},
+  {"op": "feed", "role": "price", "into": ["a.series"]},
+  {"op": "expose", "from": "lc.value", "as": "out"}
+]

fieldtests/construction-args/ca_3d_garbage_count.ops.json

@@ -0,0 +1,5 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "LinComb", "name": "lc", "args": {"arity": "three"}},
+  {"op": "expose", "from": "lc.value", "as": "out"}
+]

fieldtests/construction-args/ca_3e_missing_arg.ops.json

@@ -0,0 +1,7 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
+  {"op": "expose", "from": "sess.bars_since_open", "as": "bars"}
+]

fieldtests/construction-args/ca_3f_args_on_argless.ops.json

@@ -0,0 +1,8 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "SMA", "name": "a",
+   "args": {"window": "3"},
+   "bind": {"length": {"I64": 2}}},
+  {"op": "feed", "role": "price", "into": ["a.series"]},
+  {"op": "expose", "from": "a.value", "as": "out"}
+]

fieldtests/construction-args/ca_3g_unknown_arg_key.ops.json

@@ -0,0 +1,8 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "args": {"tz": "America/New_York", "open": "09:30", "region": "east"},
+   "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
+  {"op": "expose", "from": "sess.bars_since_open", "as": "bars"}
+]

fieldtests/construction-args/ca_3h_partial_args.ops.json

@@ -0,0 +1,8 @@
+[
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "args": {"tz": "America/New_York"},
+   "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
+  {"op": "expose", "from": "sess.bars_since_open", "as": "bars"}
+]

fieldtests/construction-args/ca_4_consumer.bp.json

@@ -0,0 +1 @@
+{"format_version":2,"blueprint":{"name":"graph","doc":"consumer: splice the NY session anchor by name, go long 1.0 on the first session bar, flat otherwise","nodes":[{"composite":{"name":"anchor","doc":"NY cash-open session anchor: bars elapsed since the 09:30 America/New_York open","nodes":[{"primitive":{"type":"Session","name":"sess","args":[{"name":"tz","value":"America/New_York"},{"name":"open","value":"09:30"}],"bound":[{"pos":0,"name":"period_minutes","kind":"I64","value":{"I64":15}}]}}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0}]}],"output":[{"node":0,"field":0,"name":"bars"}]}},{"primitive":{"type":"EqConst","name":"isfirst","bound":[{"pos":0,"name":"target","kind":"I64","value":{"I64":1}}]}},{"primitive":{"type":"Const","name":"one","bound":[{"pos":0,"name":"value","kind":"F64","value":{"F64":1.0}}]}},{"primitive":{"type":"Const","name":"zero","bound":[{"pos":0,"name":"value","kind":"F64","value":{"F64":0.0}}]}},{"primitive":{"type":"Select","name":"sel"}},{"primitive":{"type":"Bias","name":"bias","bound":[{"pos":0,"name":"scale","kind":"F64","value":{"F64":1.0}}]}}],"edges":[{"from":0,"to":1,"slot":0,"from_field":0},{"from":1,"to":4,"slot":0,"from_field":0},{"from":2,"to":4,"slot":1,"from_field":0},{"from":3,"to":4,"slot":2,"from_field":0},{"from":4,"to":5,"slot":0,"from_field":0}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0},{"node":2,"slot":0},{"node":3,"slot":0}],"source":"F64"}],"output":[{"node":5,"field":0,"name":"bias"}]}}

fieldtests/construction-args/ca_4_consumer.ops.json

@@ -0,0 +1,19 @@
+[
+  {"op": "doc", "text": "consumer: splice the NY session anchor by name, go long 1.0 on the first session bar, flat otherwise"},
+  {"op": "source", "role": "price", "kind": "F64"},
+  {"op": "use", "ref": {"name": "ny_anchor"}, "name": "anchor"},
+  {"op": "feed", "role": "price", "into": ["anchor.price"]},
+  {"op": "add", "type": "EqConst", "name": "isfirst", "bind": {"target": {"I64": 1}}},
+  {"op": "connect", "from": "anchor.bars", "to": "isfirst.value"},
+  {"op": "add", "type": "Const", "name": "one", "bind": {"value": {"F64": 1.0}}},
+  {"op": "feed", "role": "price", "into": ["one.clock"]},
+  {"op": "add", "type": "Const", "name": "zero", "bind": {"value": {"F64": 0.0}}},
+  {"op": "feed", "role": "price", "into": ["zero.clock"]},
+  {"op": "add", "type": "Select", "name": "sel"},
+  {"op": "connect", "from": "isfirst.value", "to": "sel.cond"},
+  {"op": "connect", "from": "one.value", "to": "sel.then"},
+  {"op": "connect", "from": "zero.value", "to": "sel.otherwise"},
+  {"op": "add", "type": "Bias", "name": "bias", "bind": {"scale": {"F64": 1.0}}},
+  {"op": "connect", "from": "sel.value", "to": "bias.signal"},
+  {"op": "expose", "from": "bias.bias", "as": "bias"}
+]

fieldtests/construction-args/ca_4_consumer.run.json

@@ -0,0 +1,71 @@
+{
+    "manifest": {
+        "commit": "6ca359ae00e8e7921f08557be383bc2d0a2ce199",
+        "params": [],
+        "defaults": [
+            [
+                "graph.anchor.sess.period_minutes",
+                {
+                    "I64": 15
+                }
+            ],
+            [
+                "graph.isfirst.target",
+                {
+                    "I64": 1
+                }
+            ],
+            [
+                "graph.one.value",
+                {
+                    "F64": 1.0
+                }
+            ],
+            [
+                "graph.zero.value",
+                {
+                    "F64": 0.0
+                }
+            ],
+            [
+                "graph.bias.scale",
+                {
+                    "F64": 1.0
+                }
+            ]
+        ],
+        "window": [
+            1725235200000000000,
+            1725580800000000000
+        ],
+        "seed": 0,
+        "broker": "sim-optimal+risk-executor(pip_size=1)",
+        "topology_hash": "985991f62cc6b92895018312c5ea86e493ef1c09dd53cf6e0813551baa97b671",
+        "project": {
+            "commit": "d7e3a8f39881cc8eba42a906fa846676bfbb1010"
+        }
+    },
+    "metrics": {
+        "total_pips": -19.5,
+        "max_drawdown": 35.5,
+        "bias_sign_flips": 8,
+        "r": {
+            "expectancy_r": -0.7143093152455215,
+            "n_trades": 8,
+            "win_rate": 0.125,
+            "avg_win_r": 2.704952265814223,
+            "avg_loss_r": -1.2027752553969135,
+            "profit_factor": 0.32127510981397456,
+            "max_r_drawdown": 7.371844351604779,
+            "n_open_at_end": 0,
+            "sqn": -1.3625154866298599,
+            "sqn_normalized": -1.3625154866298599,
+            "net_expectancy_r": -0.7143093152455215,
+            "conviction_terciles_r": [
+                -1.0191864862283455,
+                -1.1307276003565727,
+                -0.09463958281258789
+            ]
+        }
+    }
+}

fieldtests/construction-args/ca_4_ny_anchor_pattern.bp.json

@@ -0,0 +1 @@
+{"format_version":2,"blueprint":{"name":"graph","doc":"NY cash-open session anchor: bars elapsed since the 09:30 America/New_York open","nodes":[{"primitive":{"type":"Session","name":"sess","args":[{"name":"tz","value":"America/New_York"},{"name":"open","value":"09:30"}],"bound":[{"pos":0,"name":"period_minutes","kind":"I64","value":{"I64":15}}]}}],"input_roles":[{"name":"price","targets":[{"node":0,"slot":0}]}],"output":[{"node":0,"field":0,"name":"bars"}]}}

fieldtests/construction-args/ca_4_ny_anchor_pattern.ops.json

@@ -0,0 +1,9 @@
+[
+  {"op": "doc", "text": "NY cash-open session anchor: bars elapsed since the 09:30 America/New_York open"},
+  {"op": "input", "role": "price"},
+  {"op": "add", "type": "Session", "name": "sess",
+   "args": {"tz": "America/New_York", "open": "09:30"},
+   "bind": {"period_minutes": {"I64": 15}}},
+  {"op": "feed", "role": "price", "into": ["sess.trigger"]},
+  {"op": "expose", "from": "sess.bars_since_open", "as": "bars"}
+]