diff --git a/crates/aura-campaign/tests/metric_vocabulary_e2e.rs b/crates/aura-campaign/tests/metric_vocabulary_e2e.rs
new file mode 100644
index 0000000..5adcaba
--- /dev/null
+++ b/crates/aura-campaign/tests/metric_vocabulary_e2e.rs
@@ -0,0 +1,107 @@
+//! Cross-crate guard for #190: pins `aura_research::metric_vocabulary()` (the
+//! hand-written 17-name declared metric roster) against the ACTUAL scalar
+//! fields the three metric-bearing `aura-analysis` types serialize — not a
+//! second hand-list that could independently drift. `aura-campaign` is the
+//! one crate that already depends on both `aura-analysis` (the types) and
+//! `aura-research` (the vocabulary), so it is the only place this pin can be
+//! written today (`aura-research` deliberately has no `aura-analysis` dep —
+//! `metric_vocabulary`'s own doc comment names this as an accepted residual).
+
+use std::collections::BTreeSet;
+
+use aura_analysis::{summarize_r, FamilySelection, RunMetrics, SelectionMode};
+
+/// The names of every field of a serialized sample whose JSON value is a
+/// `Number` — i.e. a scalar metric readout, not a string/enum tag, a nested
+/// object, or an array (per-tercile / per-trade series).
+fn scalar_field_names(sample: &serde_json::Value) -> BTreeSet<String> {
+    sample
+        .as_object()
+        .expect("a metric-bearing type serializes to a JSON object")
+        .iter()
+        .filter(|(_, v)| v.is_number())
+        .map(|(k, _)| k.clone())
+        .collect()
+}
+
+/// Property: the declared metric vocabulary (`aura_research::metric_vocabulary()`)
+/// is exhaustive against — and carries no stale entry beyond — the scalar
+/// fields the three metric-bearing `aura-analysis` types
+/// (`RMetrics`/`RunMetrics`/`FamilySelection`) actually ship, enumerated via
+/// their real `serde::Serialize` impls rather than a second hand-copy.
+///
+/// If a field is added, renamed, or removed on any of the three types without
+/// updating `metric_vocabulary()`, this test goes red: a new metric becomes
+/// un-gateable (present in the type, absent from the vocabulary), or a stale
+/// entry survives the vocabulary after its field is gone (present in the
+/// vocabulary, absent from every type). Today the two rosters agree, so this
+/// is a drift guard, not a repro: it must pass on arrival.
+#[test]
+fn metric_vocabulary_covers_all_shipped_scalar_metrics() {
+    // RMetrics: the real empty-input reduction (`summarize_r(&[], &[])`) is a
+    // genuine producer, not a hand-typed literal — every scalar field is
+    // unconditionally present (no `Option`/`skip_serializing_if` on this type).
+    let r_metrics = summarize_r(&[], &[]);
+    // RunMetrics: `r: None` keeps the nested `RMetrics` block out of this
+    // sample's JSON entirely (an `Object`, not a `Number`, so it would be
+    // filtered out anyway; `None` just avoids double-counting its fields here).
+    let run_metrics = RunMetrics { total_pips: 0.0, max_drawdown: 0.0, bias_sign_flips: 0, r: None };
+    // FamilySelection: an explicit literal that populates exactly the three
+    // annotation SCORES the vocabulary declares (`deflated_score`,
+    // `overfit_probability`, `neighbourhood_score`) and leaves their sibling
+    // annotation IDENTIFIERS (`n_resamples`/`block_len`/`seed`/`n_neighbours`)
+    // absent — real producers never mix an Argmax score with a Plateau score,
+    // but this is a serde-shape probe, not a reproduction of a real selection
+    // run, so the mix is only used to exercise every annotation field name once.
+    let selection = FamilySelection {
+        selection_metric: "expectancy_r".to_string(),
+        n_trials: 4,
+        raw_winner_metric: 1.0,
+        mode: SelectionMode::Argmax,
+        deflated_score: Some(0.5),
+        overfit_probability: Some(0.1),
+        n_resamples: None,
+        block_len: None,
+        seed: None,
+        neighbourhood_score: Some(0.9),
+        n_neighbours: None,
+    };
+
+    let mut scalar_fields = BTreeSet::new();
+    scalar_fields.extend(scalar_field_names(&serde_json::to_value(&r_metrics).unwrap()));
+    scalar_fields.extend(scalar_field_names(&serde_json::to_value(&run_metrics).unwrap()));
+
+    let mut selection_scalars = scalar_field_names(&serde_json::to_value(&selection).unwrap());
+    // `n_trials` / `raw_winner_metric` are selection PROVENANCE (how many
+    // trials ran; the raw pre-deflation score) about which existing metric
+    // the selection optimized, not a metric readout in their own right --
+    // structurally the same exclusion the `Number` filter above already
+    // applies to `selection_metric` (a `String` naming that same metric) and
+    // `mode` (the selection rule tag). Never part of the declared vocabulary.
+    selection_scalars.remove("n_trials");
+    selection_scalars.remove("raw_winner_metric");
+    scalar_fields.extend(selection_scalars);
+
+    let vocabulary: BTreeSet<String> =
+        aura_research::metric_vocabulary().iter().map(|s| s.to_string()).collect();
+
+    let missing_from_vocabulary: Vec<_> = scalar_fields.difference(&vocabulary).collect();
+    let stale_in_vocabulary: Vec<_> = vocabulary.difference(&scalar_fields).collect();
+    assert!(
+        missing_from_vocabulary.is_empty(),
+        "shipped scalar metric(s) {missing_from_vocabulary:?} are un-gateable: \
+         absent from aura_research::metric_vocabulary()"
+    );
+    assert!(
+        stale_in_vocabulary.is_empty(),
+        "aura_research::metric_vocabulary() entry/entries {stale_in_vocabulary:?} are stale: \
+         no shipped scalar field of RMetrics/RunMetrics/FamilySelection carries that name"
+    );
+    assert_eq!(
+        vocabulary.len(),
+        17,
+        "sanity count: 11 RMetrics + 3 RunMetrics + 3 FamilySelection scalars \
+         (a mismatched count here means a field is nested/missed by this flat, \
+         top-level enumeration)"
+    );
+}