diff --git a/crates/aura-cli/src/main.rs b/crates/aura-cli/src/main.rs
index 88c82e4..39a5bff 100644
--- a/crates/aura-cli/src/main.rs
+++ b/crates/aura-cli/src/main.rs
@@ -3154,6 +3154,36 @@ fn run_blueprint_member(
     RunReport { manifest, metrics: m }
 }
 
+/// The exact wrapped probe the loaded-blueprint sweep resolves its axes
+/// against: the loaded signal wrapped in the stage1-r scaffolding (stop bound,
+/// reduce, no cost), taps discarded. `param_space()` on it is the axis
+/// namespace `--axis` binds; `.axis()` consumes it to seed a sweep. Single
+/// source for the sweep terminal, the MC closed-check, AND `--list-axes`, so
+/// the listed names track the swept names by construction (incl. across #159's
+/// harness retirement). The reload is infallible under the SAME
+/// dispatch-boundary contract the callers already rely on: the doc is
+/// `blueprint_from_json`-validated at the `["sweep", ..]` / `["mc", ..]`
+/// boundary before this runs, so a malformed doc has already exited 2 and
+/// never reaches the `.expect`.
+fn blueprint_axis_probe(doc: &str) -> Composite {
+    let signal = blueprint_from_json(doc, &|t| std_vocabulary(t))
+        .expect("doc parse-validated at the dispatch boundary; reload is infallible");
+    let (tx_eq, _) = mpsc::channel();
+    let (tx_ex, _) = mpsc::channel();
+    let (tx_r, _) = mpsc::channel();
+    let (tx_req, _) = mpsc::channel();
+    wrap_stage1r(signal, tx_eq, tx_ex, tx_r, tx_req, false, true, None)
+}
+
+/// `aura sweep <blueprint.json> --list-axes`: one `<name>:<kind>` line per open
+/// sweepable knob, in `param_space()` order; a closed blueprint prints nothing.
+/// Names are exactly what `--axis` binds (same probe as the sweep terminal).
+fn list_blueprint_axes(doc: &str) {
+    for p in blueprint_axis_probe(doc).param_space() {
+        println!("{}:{:?}", p.name, p.kind); // ScalarKind Debug -> I64/F64/Bool/Timestamp
+    }
+}
+
 /// Sweep a serialized signal `doc` over user-named param-space axes — the structural
 /// twin of [`stage1_r_sweep_family`], with three deviations. (1) The signal source is
 /// `wrap_stage1r(blueprint_from_json(doc))` — a loaded blueprint, not the Rust-built
@@ -3180,14 +3210,9 @@ fn blueprint_sweep_family(
     let pip = data.pip_size();
     let window = data.full_window();
     // a single throwaway floated build, only to resolve param_space (borrow) then seed
-    // the named axes (move) — its taps are never drained. Mirrors stage1_r_sweep_family:
-    // param_space takes &self, .axis() consumes self, so one build suffices. The signal
-    // is wrapped exactly as the single run wraps it (stop bound, reduce, no cost).
-    let (tx_eq, _) = mpsc::channel();
-    let (tx_ex, _) = mpsc::channel();
-    let (tx_r, _) = mpsc::channel();
-    let (tx_req, _) = mpsc::channel();
-    let probe = wrap_stage1r(reload(doc), tx_eq, tx_ex, tx_r, tx_req, false, true, None);
+    // the named axes (move) — its taps are never drained. The wrapped probe is the one
+    // `blueprint_axis_probe` single-sources (identical `false, true, None` wrap).
+    let probe = blueprint_axis_probe(doc);
     let space = probe.param_space();
     // seed the named axes verbatim: the first via Composite::axis (consumes the probe),
     // the rest via SweepBinder::axis. resolve_axes name- and kind-checks them at the
@@ -3231,13 +3256,9 @@ fn blueprint_mc_family(doc: &str, n_seeds: u64, data: &DataSource) -> Result<McF
     };
     let topo = topology_hash(&reload(doc));
     let pip = data.pip_size();
-    // probe the wrapped param_space (as blueprint_sweep_family does); MC needs it empty.
-    let (tx_eq, _) = mpsc::channel();
-    let (tx_ex, _) = mpsc::channel();
-    let (tx_r, _) = mpsc::channel();
-    let (tx_req, _) = mpsc::channel();
-    let space =
-        wrap_stage1r(reload(doc), tx_eq, tx_ex, tx_r, tx_req, false, true, None).param_space();
+    // probe the wrapped param_space (the same probe the sweep resolves against);
+    // MC needs it empty. `blueprint_axis_probe` is the single source of that wrap.
+    let space = blueprint_axis_probe(doc).param_space();
     if !space.is_empty() {
         // Exit-free like blueprint_sweep_family: the builder's single error contract is this
         // returned message (no hidden process exit), so the rejection is unit-testable; the IO
@@ -3909,6 +3930,7 @@ struct SweepBlueprintArgs {
     name: String,
     persist: bool,
     data: DataChoice,
+    list_axes: bool,
 }
 
 /// Parse the `aura sweep <blueprint.json> …` tail: repeatable `--axis <name>=<csv>`
@@ -3919,8 +3941,14 @@ fn parse_sweep_blueprint_args(rest: &[&str]) -> Result<SweepBlueprintArgs, Strin
     let mut axes: Vec<(String, Vec<Scalar>)> = Vec::new();
     let mut name: Option<(String, bool)> = None; // (name, persist)
     let mut data = RealWindowGrammar::default();
+    let mut list_axes = false;
     let mut tail = rest;
     while let Some((flag, t)) = tail.split_first() {
+        if *flag == "--list-axes" {
+            list_axes = true;
+            tail = t;
+            continue;
+        }
         let (value, t) = t.split_first().ok_or_else(usage)?;
         if data.accept(flag, value, &usage)? {
             tail = t;
@@ -3939,9 +3967,22 @@ fn parse_sweep_blueprint_args(rest: &[&str]) -> Result<SweepBlueprintArgs, Strin
         }
         tail = t;
     }
+    if list_axes {
+        // A query, not a sweep: it must stand alone (the flags tail is only itself).
+        if rest.len() != 1 {
+            return Err("--list-axes lists axes and takes no other flags".to_string());
+        }
+        return Ok(SweepBlueprintArgs {
+            axes,
+            name: "sweep".to_string(),
+            persist: false,
+            data: data.finish(&usage)?,
+            list_axes: true,
+        });
+    }
     if axes.is_empty() { return Err(usage()); } // a sweep needs at least one axis
     let (name, persist) = name.unwrap_or_else(|| ("sweep".to_string(), false));
-    Ok(SweepBlueprintArgs { axes, name, persist, data: data.finish(&usage)? })
+    Ok(SweepBlueprintArgs { axes, name, persist, data: data.finish(&usage)?, list_axes: false })
 }
 
 /// Parsed tail of `aura mc <blueprint.json> …`: the seed count + the family name.
@@ -4109,11 +4150,15 @@ fn main() {
                     eprintln!("aura: {path}: {e:?}");
                     std::process::exit(2);
                 }
-                let SweepBlueprintArgs { axes, name, persist, data } =
+                let SweepBlueprintArgs { axes, name, persist, data, list_axes } =
                     parse_sweep_blueprint_args(&rest[1..]).unwrap_or_else(|msg| {
                         eprintln!("aura: {msg}");
                         std::process::exit(2);
                     });
+                if list_axes {
+                    list_blueprint_axes(&doc);
+                    return;
+                }
                 run_blueprint_sweep(&doc, &axes, &name, persist, DataSource::from_choice(data));
                 return;
             }
@@ -5294,6 +5339,23 @@ mod tests {
         assert!(parse_sweep_blueprint_args(&["--axis", "x=1", "--name", "a", "--trace", "b"]).is_err());  // name + trace together
     }
 
+    /// Property: `--list-axes` is a standalone query sub-mode — it parses alone
+    /// (setting `list_axes` and binding no axes), is mutually exclusive with a real
+    /// sweep in either flag order, and its absence leaves `list_axes` false while a
+    /// bare sweep still requires >= 1 axis.
+    #[test]
+    fn parse_sweep_blueprint_args_list_axes_is_standalone() {
+        let a = parse_sweep_blueprint_args(&["--list-axes"]).expect("--list-axes alone parses");
+        assert!(a.list_axes);
+        assert!(a.axes.is_empty());
+        // mutually exclusive with a real sweep, in either order:
+        assert!(parse_sweep_blueprint_args(&["--list-axes", "--axis", "stage1_signal.fast.length=2,3"]).is_err());
+        assert!(parse_sweep_blueprint_args(&["--axis", "stage1_signal.fast.length=2,3", "--list-axes"]).is_err());
+        // a bare sweep (no --list-axes) still requires >= 1 axis and reports list_axes=false:
+        let b = parse_sweep_blueprint_args(&["--axis", "stage1_signal.fast.length=2,3"]).expect("bare sweep parses");
+        assert!(!b.list_axes);
+    }
+
     /// Property: the `aura mc <blueprint.json>` grammar requires `--seeds <n>` with
     /// `n >= 1`, defaults the family name to "mc", and — synthetic-only this cycle —
     /// rejects `--real` (and any other unknown flag) as a strict usage error, never a
@@ -5377,6 +5439,22 @@ mod tests {
         assert_ne!(k4, k6, "distinct grid points key distinctly");
     }
 
+    #[test]
+    fn blueprint_axis_probe_lists_prefixed_open_knobs() {
+        // The open fixture's two SMA lengths are the sweepable knobs; the probe
+        // wraps the signal (name "stage1_signal") so the names are prefixed —
+        // exactly what `--axis` binds.
+        let open = include_str!("../tests/fixtures/stage1_signal_open.json");
+        let space = blueprint_axis_probe(open).param_space();
+        let names: Vec<&str> = space.iter().map(|p| p.name.as_str()).collect();
+        assert_eq!(names, ["stage1_signal.fast.length", "stage1_signal.slow.length"]);
+        assert!(space.iter().all(|p| matches!(p.kind, ScalarKind::I64)));
+
+        // A closed blueprint (both lengths bound) has no open axes.
+        let closed = include_str!("../tests/fixtures/stage1_signal.json");
+        assert!(blueprint_axis_probe(closed).param_space().is_empty());
+    }
+
     #[test]
     fn blueprint_mc_family_seeds_differ() {
         // MC over a CLOSED signal (both SMA knobs bound): 3 seeds -> 3 draws, one shared
diff --git a/crates/aura-cli/tests/cli_run.rs b/crates/aura-cli/tests/cli_run.rs
index c07bb0e..2a6cdff 100644
--- a/crates/aura-cli/tests/cli_run.rs
+++ b/crates/aura-cli/tests/cli_run.rs
@@ -3631,3 +3631,121 @@ fn aura_reproduce_rejects_a_missing_stored_blueprint() {
     );
     let _ = std::fs::remove_dir_all(&cwd);
 }
+
+/// E2E (#169): `aura sweep <open blueprint.json> --list-axes` prints one
+/// `<name>:<kind>` line per open sweepable knob, in `param_space()` order, and
+/// exits 0. The names are prefixed by the wrapping (stage1_signal.*) — exactly
+/// the strings `--axis` binds — so a user can discover then sweep without guessing.
+#[test]
+fn aura_sweep_list_axes_prints_prefixed_names() {
+    let bp = format!("{}/tests/fixtures/stage1_signal_open.json", env!("CARGO_MANIFEST_DIR"));
+    let out = std::process::Command::new(env!("CARGO_BIN_EXE_aura"))
+        .args(["sweep", &bp, "--list-axes"])
+        .output()
+        .expect("spawn aura sweep --list-axes");
+    assert_eq!(out.status.code(), Some(0));
+    let stdout = String::from_utf8(out.stdout).expect("utf-8");
+    assert_eq!(stdout, "stage1_signal.fast.length:I64\nstage1_signal.slow.length:I64\n");
+}
+
+/// E2E (#169): `--list-axes` on a CLOSED blueprint (all knobs bound) prints
+/// nothing and exits 0 — an empty axis set is the honest answer, not an error.
+#[test]
+fn aura_sweep_list_axes_closed_is_empty() {
+    let bp = format!("{}/tests/fixtures/stage1_signal.json", env!("CARGO_MANIFEST_DIR"));
+    let out = std::process::Command::new(env!("CARGO_BIN_EXE_aura"))
+        .args(["sweep", &bp, "--list-axes"])
+        .output()
+        .expect("spawn aura sweep --list-axes (closed)");
+    assert_eq!(out.status.code(), Some(0));
+    assert!(out.stdout.is_empty(), "a closed blueprint has no open axes");
+}
+
+/// E2E (#169): `--list-axes` is a standalone query — combining it with a real
+/// sweep flag (`--axis`) is a usage error (exit 2), naming that it lists axes
+/// and takes no other flags. A query cannot also seed a sweep.
+#[test]
+fn aura_sweep_list_axes_rejects_other_flags() {
+    let bp = format!("{}/tests/fixtures/stage1_signal_open.json", env!("CARGO_MANIFEST_DIR"));
+    let out = std::process::Command::new(env!("CARGO_BIN_EXE_aura"))
+        .args(["sweep", &bp, "--list-axes", "--axis", "stage1_signal.fast.length=2,3"])
+        .output()
+        .expect("spawn aura sweep --list-axes + --axis");
+    assert_eq!(out.status.code(), Some(2));
+    let stderr = String::from_utf8(out.stderr).expect("utf-8");
+    assert!(stderr.contains("--list-axes lists axes"), "stderr was: {stderr}");
+}
+
+/// E2E (#169, safety): `--list-axes` over a malformed blueprint rejects cleanly
+/// (exit 2, naming UnknownNodeType) rather than panicking — the axis probe reloads
+/// the doc, so the dispatch-boundary validation must run first, never a raw `.expect`.
+#[test]
+fn aura_sweep_list_axes_rejects_malformed_blueprint() {
+    let bp = format!("{}/tests/fixtures/unknown_node.json", env!("CARGO_MANIFEST_DIR"));
+    let out = std::process::Command::new(env!("CARGO_BIN_EXE_aura"))
+        .args(["sweep", &bp, "--list-axes"])
+        .output()
+        .expect("spawn aura sweep --list-axes (malformed)");
+    assert_eq!(out.status.code(), Some(2), "malformed blueprint must be rejected, not panic");
+    let stderr = String::from_utf8(out.stderr).expect("utf-8");
+    assert!(stderr.contains("UnknownNodeType"), "stderr was: {stderr}");
+    assert!(!stderr.contains("panicked"), "must reject cleanly, not panic: {stderr}");
+}
+
+/// E2E (#169, the load-bearing "listed == swept" invariant): a name emitted by
+/// `--list-axes` is accepted VERBATIM by `--axis` — the discovered axis namespace
+/// and the swept axis namespace are the same set (shared-probe construction). The
+/// axis names here are DERIVED from the `--list-axes` output, never hardcoded, then
+/// fed straight back into a real sweep: the sweep exits 0 and persists a `Sweep`
+/// family, proving every listed name resolved (no UnknownKnob). This is the
+/// discovery-removes-guessing property #169 exists to close — were the list and
+/// sweep surfaces ever to diverge, a discovered name would be rejected here and this
+/// round-trip would fail, whereas the literal-pinned per-surface tests could not see it.
+#[test]
+fn aura_sweep_list_axes_names_round_trip_into_a_working_sweep() {
+    let cwd = temp_cwd("blueprint-list-axes-roundtrip");
+    let bp = format!("{}/tests/fixtures/stage1_signal_open.json", env!("CARGO_MANIFEST_DIR"));
+
+    // 1) discover the axis names (do NOT hardcode them) — this is what a user reads.
+    let list = Command::new(BIN)
+        .args(["sweep", &bp, "--list-axes"])
+        .output()
+        .expect("spawn aura sweep --list-axes");
+    assert_eq!(list.status.code(), Some(0));
+    let listed = String::from_utf8(list.stdout).expect("utf-8");
+    let names: Vec<String> = listed
+        .lines()
+        .map(|l| l.split(':').next().expect("a `name:kind` line").to_string())
+        .collect();
+    assert!(!names.is_empty(), "the open fixture must list >= 1 axis");
+
+    // 2) feed the DISCOVERED names straight back into a real sweep. Values are
+    //    position-assigned (first axis small, rest large) to stay in a non-degenerate
+    //    SMA regime without re-hardcoding the names; each axis takes two values.
+    let mut args: Vec<String> = vec!["sweep".into(), bp.clone()];
+    for (i, name) in names.iter().enumerate() {
+        args.push("--axis".into());
+        args.push(format!("{name}={}", if i == 0 { "2,4" } else { "8,16" }));
+    }
+    let sweep = Command::new(BIN)
+        .args(&args)
+        .current_dir(&cwd)
+        .output()
+        .expect("spawn aura sweep over discovered axes");
+    assert!(
+        sweep.status.success(),
+        "every listed name must be a valid --axis; exit={:?} stderr={}",
+        sweep.status,
+        String::from_utf8_lossy(&sweep.stderr)
+    );
+
+    // 3) the sweep persisted a Sweep family whose grid spans exactly the discovered
+    //    axes (each bound to two values -> 2^k members) — the names resolved end-to-end.
+    let fams = Command::new(BIN).args(["runs", "families"]).current_dir(&cwd).output().expect("spawn families");
+    let fo = String::from_utf8(fams.stdout).expect("utf-8");
+    assert!(fo.contains("\"kind\":\"Sweep\""), "families: {fo}");
+    let expected = 1usize << names.len(); // two values per discovered axis
+    assert!(fo.contains(&format!("\"members\":{expected}")), "grid over the discovered axes: {fo}");
+
+    let _ = std::fs::remove_dir_all(&cwd);
+}