audit: trace-identity cycle close — C29 honoured, code twins back in lockstep

The drift review found the run handle keying on the blueprint's *content* id,
which hashes `doc` fields and every other C23 debug symbol. C29's Id treatment
forbids a description influencing an identity, and the repository already
carried the right projection unused. The digest now substitutes
`blueprint_identity_json`'s debug-symbol-blind projection (#171) for
`topology_hash` in the hashed value. `manifest.topology_hash` itself is
untouched, so #343's reference semantics and the committed record-line
fingerprint both stand.

That projection blanks more than descriptions — the render name and node, role,
output, tap and gang names — while param openness stays identity-bearing. This
is correct rather than incidental: names are non-load-bearing debug symbols
(C8/C23), so blueprints differing only in them compute bit-identically and one
address is the right answer. The reach is now stated in C22 and in the digest's
own doc, together with the one observable consequence: two structurally
identical blueprints whose declared tap names differ share a directory while
writing differently named tap files, since the write path never prunes (#352).

Two code twins the cycle left stale are corrected. `name_gate`'s doc comment
still carried the C23 clause this cycle superseded and moved to its sidecar,
and the authoring guide claimed a same-identity re-run replaces the directory's
contents — it does not, for the same non-pruning reason.

Bench is report-only and all five fingerprints are unchanged. `campaign_sweep`
reports a peak-RSS NOTICE (+12.8%); the campaign leg is untouched by this cycle
and its fingerprint is stable, so nothing is ratified against it here.

Routed rather than fixed: #353 — naming authority for one flat namespace is
spelled in three crates and the single-run leg has no claim path — filed into
the recorded-stream-store milestone, where the container consolidates anyway; a
data-identity seam recorded on #320 (a run's identity carries the window, never
the data's content, so a corrected archive is a silent overwrite until that
store supplies a recording identity); and a second instance of the non-pruning
class on #352.

The cycle's spec and plan are removed — git-ignored working files, read by the
drift review before deletion.

refs #311

crates/aura-cli/src/main.rs

@@ -19,7 +19,7 @@ use aura_core::Cell;
 #[cfg(test)]
 use aura_composites::StopRule;
 use aura_engine::{
-    blueprint_from_json, blueprint_to_json, f64_field, join_on_ts,
+    blueprint_from_json, blueprint_identity_json, blueprint_to_json, f64_field, join_on_ts,
     JoinedRow,
     SelectionMode,
 };
@@ -1447,13 +1447,21 @@ fn exec_blueprint_leg(path: &str, overrides: &[String], tap: &[String], env: &au
         // `&cell.strategy_id`, the stored base document's id, as `topo` even
         // for a reopened member). Computed here, over the still-unreopened
         // `signal`, before `reopen_all` consumes it, and threaded into
-        // `run_signal_r`'s own `topo` parameter so every consumer inside that
+        // `run_signal_r`'s own `refs` parameter so every consumer inside that
         // function — the record line AND the trace-store persistence
         // (`bound.finish`, `aura-registry::trace_store`) — sees the base
         // document's hash from the start; no post-hoc manifest mutation
         // after the run, which would miss the already-persisted `index.json`.
+        // `base_identity` is the sibling #171 identity projection, computed
+        // over the SAME un-reopened `signal` for the same reason (2026-07-27,
+        // C29): the reopened variant would show the overridden param as OPEN
+        // rather than bound, which would split a no-op `--override` from the
+        // un-overridden run it is identical to (`run_identity_digest`'s doc
+        // comment).
         let base_topo =
             content_id(&blueprint_to_json(&signal).expect("a buildable signal serializes"));
+        let base_identity =
+            content_id(&blueprint_identity_json(&signal).expect("a buildable signal serializes"));
         let signal = reopen_all(signal, &paths);
         // An out-of-domain override value fails a node's own domain check at
         // bootstrap (e.g. `Sma::new`'s `assert!`, or a negative length
@@ -1466,7 +1474,10 @@ fn exec_blueprint_leg(path: &str, overrides: &[String], tap: &[String], env: &au
         // refusal (exit 1, C14 partition) instead of an uncaught exit 101 —
         // the input was well-formed argv; the value is what the node refuses.
         let outcome = match aura_campaign::catch_member_panic(|| {
-            run_signal_r(signal, &params, RunData::Synthetic, 0, env, tap_plan, Some(&base_topo))
+            run_signal_r(
+                signal, &params, RunData::Synthetic, 0, env, tap_plan,
+                Some((&base_topo, &base_identity)),
+            )
         })
         .unwrap_or_else(|msg| {
             eprintln!("aura: {}", panic_refusal_prose(&msg));

crates/aura-cli/tests/exec.rs

@@ -721,6 +721,69 @@ same effective params must mint the same handle: base {base_out} / overridden {o
     );
 }
 
+/// C29 audit fix (2026-07-27): a blueprint's composite-level `doc` field is a
+/// CONTENT-id key (`blueprint_to_json` serializes it, so it changes
+/// `topology_hash`) but an identity-BLIND debug symbol
+/// (`blueprint_identity_json`/`strip_debug_symbols` blanks it) — C29's own Id
+/// treatment: "description fields … are blanked for the identity id". Two
+/// blueprints differing ONLY in that field are, by that rule, the SAME run and
+/// must land in the SAME trace directory, even though their `topology_hash`es
+/// genuinely differ (proving the two documents are not byte-identical, so this
+/// is not a vacuous pass).
+#[test]
+fn exec_blueprint_description_only_edit_lands_in_the_same_trace_directory() {
+    let cwd = temp_cwd("doc-only-same-dir");
+    let bare_path = cwd.join("bare.json");
+    std::fs::write(&bare_path, tap_blueprint_json()).expect("write bare blueprint");
+    let mut with_doc: serde_json::Value =
+        serde_json::from_str(&tap_blueprint_json()).expect("parse tapped blueprint");
+    with_doc["blueprint"]["doc"] = serde_json::json!("an authored one-line rationale");
+    let doc_path = cwd.join("with_doc.json");
+    std::fs::write(&doc_path, serde_json::to_string(&with_doc).expect("re-serialize doc'd blueprint"))
+        .expect("write doc'd blueprint");
+
+    let (base_out, base_code) =
+        run_code_in(&cwd, &["exec", bare_path.to_str().expect("utf-8 path")]);
+    assert_eq!(base_code, Some(0), "stdout/stderr: {base_out}");
+    let base_line = base_out.lines().find(|l| l.starts_with('{')).expect("record line");
+    let base_v: serde_json::Value = serde_json::from_str(base_line).expect("record parses");
+    let base_handle =
+        base_v["trace_name"].as_str().expect("a recording run prints its trace_name").to_string();
+    let base_topo =
+        base_v["manifest"]["topology_hash"].as_str().expect("base topology_hash").to_string();
+
+    let (doc_out, doc_code) =
+        run_code_in(&cwd, &["exec", doc_path.to_str().expect("utf-8 path")]);
+    assert_eq!(doc_code, Some(0), "stdout/stderr: {doc_out}");
+    let doc_line = doc_out.lines().find(|l| l.starts_with('{')).expect("record line");
+    let doc_v: serde_json::Value = serde_json::from_str(doc_line).expect("record parses");
+    let doc_handle =
+        doc_v["trace_name"].as_str().expect("a recording run prints its trace_name").to_string();
+    let doc_topo =
+        doc_v["manifest"]["topology_hash"].as_str().expect("doc'd topology_hash").to_string();
+
+    assert_ne!(
+        base_topo, doc_topo,
+        "a doc edit DOES change the content id (C24/C29) — the two documents are not \
+byte-identical: {base_out} / {doc_out}"
+    );
+    assert_eq!(
+        base_handle, doc_handle,
+        "a description-only edit must not mint a new trace directory (C29's Id treatment): \
+base {base_out} / with-doc {doc_out}"
+    );
+
+    let entries: Vec<_> = std::fs::read_dir(cwd.join("runs/traces"))
+        .expect("read traces dir")
+        .map(|e| e.expect("dir entry").file_name())
+        .collect();
+    assert_eq!(
+        entries.len(),
+        1,
+        "one identity, one directory — found {entries:?} under runs/traces"
+    );
+}
+
 /// A malformed override token (no `NODE.PARAM=VALUE` shape) refuses as usage.
 #[test]
 fn exec_override_malformed_token_refuses_with_usage() {

crates/aura-engine/src/blueprint.rs

@@ -198,8 +198,10 @@ pub struct GangMember {
 /// Deterministic shape gate for authored composite render names (#331) —
 /// shape only, never content judgement (C29 discipline): non-empty, no path
 /// separator (`/` or `\`), and not the special segments `.` or `..`. The rule
-/// exists because the name keys a trace directory on disk unsanitized
-/// (`traces/<name>/`, `crates/aura-registry/src/trace_store.rs`). Applied at
+/// exists because the name has an operational run-time role: it prefixes a
+/// run's identity-keyed trace directory on disk unsanitized
+/// (`traces/<name>-<id8>/`, #311; `crates/aura-registry/src/trace_store.rs`),
+/// not the whole directory component as before #311. Applied at
 /// both data-borne birth routes for a name (the skeptic's two-seam finding):
 /// the `Op::Name` op intake (`construction.rs`) and the CLI's
 /// blueprint-envelope root-name intake — never at store read-back (C29:

crates/aura-runner/src/lib.rs

@@ -101,7 +101,33 @@ pub struct RunnerError {
 /// serde_json's map is sorted, so re-serialising a parsed value yields
 /// deterministic bytes — the same technique aura-bench uses for its record-line
 /// fingerprint (`crates/aura-bench/src/surfaces/fixed_cost.rs`).
-pub fn run_identity_digest(manifest: &aura_engine::RunManifest) -> String {
+///
+/// **`topology_hash` is not hashed as-is — `identity_hash` stands in for it
+/// (2026-07-27 audit fix, C29).** `manifest.topology_hash` is a **content** id
+/// (`content_id_of(blueprint_to_json(..))`, #158/C24): the canonical bytes it
+/// hashes include a blueprint's `doc` field — an authored one-line rationale,
+/// C29 — and every other C23 debug symbol (render name, instance names, bound
+/// param/role/output/tap/gang names). A description-only (or name-only) edit
+/// to an otherwise bit-identical blueprint therefore changes `topology_hash`,
+/// which would mint a fresh trace directory for what is, by C29's own Id
+/// treatment ("description fields … are blanked for the identity id"), the
+/// SAME run — a description influencing an identity id is exactly what C29
+/// forbids. The caller passes `identity_hash` — the #171
+/// `blueprint_identity_json` projection (debug-symbol-blind by construction)
+/// — and this function substitutes it for whatever `manifest.topology_hash`
+/// carries in the hashed value; `manifest.topology_hash` itself is untouched
+/// (it keeps its own #343 reference-semantics content id — the reproduction
+/// store still keys on it byte-exact). **The blanking is wholesale, not
+/// description-only:** `identity_hash` is blind to the render name and every
+/// node/role/output/tap/gang name too, because none of these carry run
+/// semantics (a bound param's *openness* stays identity-bearing) — two
+/// blueprints identical in every load-bearing respect but differing only in
+/// such names correctly compute the same `identity_hash`, one directory, not
+/// two. Both mint sites
+/// (`aura-runner::member::run_signal_r`, `aura-runner::measure::run_measurement`)
+/// compute `identity_hash` from the SAME blueprint reference they already hash
+/// for `topology_hash`, so the two can never drift.
+pub fn run_identity_digest(manifest: &aura_engine::RunManifest, identity_hash: &str) -> String {
     use aura_engine::Scalar;
     use sha2::{Digest, Sha256};
 
@@ -124,6 +150,10 @@ pub fn run_identity_digest(manifest: &aura_engine::RunManifest) -> String {
             "params".to_string(),
             serde_json::to_value(&merged).expect("the merged param vec serializes"),
         );
+        obj.insert(
+            "topology_hash".to_string(),
+            serde_json::Value::String(identity_hash.to_string()),
+        );
     }
     let canonical = serde_json::to_string(&v).expect("re-serializing a parsed value cannot fail");
     let hex = format!("{:x}", Sha256::digest(canonical.as_bytes()));
@@ -135,6 +165,15 @@ mod tests {
     use super::run_identity_digest;
     use aura_engine::{ProjectProvenance, RunManifest, Scalar, Timestamp};
 
+    /// A fixed `identity_hash` stand-in used by every case below that does not
+    /// itself vary the blueprint's identity projection — held equal across both
+    /// calls being compared so the case tests exactly the field it names, not an
+    /// incidental `identity_hash` difference. Shaped like a real SHA-256 hex
+    /// digest (64 lowercase hex chars) but not a real hash of anything.
+    fn identity_hash() -> String {
+        "beef".repeat(16)
+    }
+
     /// A manifest with every field populated the way a real single run stamps
     /// them — the base each case below perturbs by exactly one field.
     fn manifest() -> RunManifest {
@@ -158,7 +197,7 @@ mod tests {
 
     #[test]
     fn run_identity_digest_is_eight_lowercase_hex() {
-        let d = run_identity_digest(&manifest());
+        let d = run_identity_digest(&manifest(), &identity_hash());
         assert_eq!(d.len(), 8, "the handle suffix is 8 hex chars: {d}");
         assert!(
             d.bytes().all(|b| b.is_ascii_hexdigit() && !b.is_ascii_uppercase()),
@@ -172,8 +211,8 @@ mod tests {
         let mut b = manifest();
         b.commit = "0123456789abcdef".to_string();
         assert_eq!(
-            run_identity_digest(&a),
-            run_identity_digest(&b),
+            run_identity_digest(&a, &identity_hash()),
+            run_identity_digest(&b, &identity_hash()),
             "manifest.commit is the binary's build provenance, not the run's identity"
         );
     }
@@ -185,8 +224,8 @@ mod tests {
         b.project.as_mut().expect("base manifest carries provenance").commit =
             Some("deadbeef-dirty".to_string());
         assert_eq!(
-            run_identity_digest(&a),
-            run_identity_digest(&b),
+            run_identity_digest(&a, &identity_hash()),
+            run_identity_digest(&b, &identity_hash()),
             "project.commit is re-derived per invocation; editing the worktree is not a new run"
         );
     }
@@ -200,8 +239,8 @@ mod tests {
         let mut b = manifest();
         b.project.as_mut().expect("base manifest carries provenance").commit = None;
         assert_eq!(
-            run_identity_digest(&a),
-            run_identity_digest(&b),
+            run_identity_digest(&a, &identity_hash()),
+            run_identity_digest(&b, &identity_hash()),
             "a derivable HEAD and an underivable one are the same run"
         );
     }
@@ -212,8 +251,8 @@ mod tests {
         let mut b = manifest();
         b.params = vec![("fast.length".to_string(), Scalar::I64(3))];
         assert_ne!(
-            run_identity_digest(&a),
-            run_identity_digest(&b),
+            run_identity_digest(&a, &identity_hash()),
+            run_identity_digest(&b, &identity_hash()),
             "params are identity-bearing — this is the headline case"
         );
     }
@@ -233,8 +272,8 @@ mod tests {
             ("bias.scale".to_string(), Scalar::F64(0.5)),
         ];
         assert_eq!(
-            run_identity_digest(&a),
-            run_identity_digest(&b),
+            run_identity_digest(&a, &identity_hash()),
+            run_identity_digest(&b, &identity_hash()),
             "same effective params, different params/defaults partition — same run"
         );
     }
@@ -248,17 +287,40 @@ mod tests {
         b.project.as_mut().expect("base manifest carries provenance").dylib_sha256 =
             Some("ff00".to_string());
         assert_ne!(
-            run_identity_digest(&a),
-            run_identity_digest(&b),
+            run_identity_digest(&a, &identity_hash()),
+            run_identity_digest(&b, &identity_hash()),
             "dylib_sha256 is exactly what C13 hot-reload varies"
         );
     }
 
+    /// C29 audit fix (2026-07-27): `topology_hash` is a CONTENT id — it hashes
+    /// a blueprint's `doc` field (and every other C23 debug symbol) along with
+    /// its structure — so a description-only edit changes `manifest.
+    /// topology_hash` even though the run is otherwise bit-identical. The
+    /// digest must not tell these two manifests apart: it hashes the caller's
+    /// `identity_hash`, not `manifest.topology_hash`, so two manifests whose
+    /// `topology_hash` fields differ (as a real doc-only edit would produce)
+    /// digest the same as long as the SAME `identity_hash` is supplied — which
+    /// is exactly what `blueprint_identity_json` (doc-blind) computes for both.
+    #[test]
+    fn run_identity_digest_ignores_topology_hash_content_id_when_identity_hash_agrees() {
+        let a = manifest(); // topology_hash: "0f1e2d3c"
+        let mut b = manifest();
+        b.topology_hash = Some("ffffffff".to_string()); // as if a doc-only edit changed the content id
+        assert_eq!(
+            run_identity_digest(&a, &identity_hash()),
+            run_identity_digest(&b, &identity_hash()),
+            "a description-only edit changes topology_hash (a content id, C29) but not \
+             the blueprint's identity projection — the digest must not tell these apart"
+        );
+    }
+
     /// The absolute property every other case in this module only tests
     /// relationally: ONE fully-populated manifest (every field set, including
     /// a `project` with `namespace`, `dylib_sha256` AND `commit` all present)
-    /// yields this ONE specific 8-hex value — stably, across builds and
-    /// processes, since the whole trace store's addressing rests on it.
+    /// plus one fixed `identity_hash` yields this ONE specific 8-hex value —
+    /// stably, across builds and processes, since the whole trace store's
+    /// addressing rests on it.
     ///
     /// If this literal ever needs to change, that change is NOT a casual
     /// update: it means `run_identity_digest`'s canonicalisation shifted
@@ -285,8 +347,8 @@ mod tests {
             }),
         };
         assert_eq!(
-            run_identity_digest(&m),
-            "3d080714",
+            run_identity_digest(&m, &"c0ffee00".repeat(8)),
+            "8cfcc5fc",
             "the digest for this fixed manifest must be stable across builds and processes"
         );
     }

crates/aura-runner/src/measure.rs

@@ -90,10 +90,15 @@ pub fn run_measurement(
     // topology_hash's own two-line body, inlined (mirrors member::run_signal_r):
     // `content_id_of` over the canonical (#164) blueprint JSON — the CLI shell's
     // `topology_hash` helper is the same primitive, kept single-sourced at
-    // `aura_research`.
+    // `aura_research`. `identity_hash` is the sibling #171 projection over the
+    // SAME `signal`, feeding `run_identity_digest` in place of `topology_hash`
+    // (2026-07-27, C29) — see that function's doc comment.
     let topo = aura_research::content_id_of(
         &aura_engine::blueprint_to_json(&signal).expect("a buildable signal serializes"),
     ); // before signal is consumed
+    let identity_hash = aura_research::content_id_of(
+        &aura_engine::blueprint_identity_json(&signal).expect("a buildable signal serializes"),
+    ); // before signal is consumed
     // #311 (mirrors run_signal_r): the render name is the readable prefix; the
     // directory is minted from the manifest below.
     let render_name = signal.name().to_string();
@@ -131,7 +136,8 @@ pub fn run_measurement(
     manifest.defaults = defaults;
     manifest.topology_hash = Some(topo);
     manifest.project = env.provenance();
-    let run_name = format!("{}-{}", render_name, crate::run_identity_digest(&manifest));
+    let run_name =
+        format!("{}-{}", render_name, crate::run_identity_digest(&manifest, &identity_hash));
 
     // Bind each declared tap per the plan's subscription (mirrors
     // run_signal_r — the shared bind_tap_plan/BoundTaps pair IS the mirror).

crates/aura-runner/src/member.rs

@@ -540,19 +540,24 @@ fn compile_error_prose(e: &CompileError, names: &[String], params: &[Scalar]) ->
 /// The single construction+run path shared by the `aura run <blueprint.json>` CLI
 /// arm and its bit-identical test.
 ///
-/// `topo`: `None` computes `topology_hash` inline from `signal` as always
-/// (every existing caller); `Some(hash)` overrides it with the caller's own
-/// **reference-semantics** hash (#343, revised) — the exec blueprint leg's
-/// `--override` branch passes the loaded base document's content id, computed
-/// BEFORE `reopen_all`, so the manifest reaching every consumer inside this
-/// function (the record line AND the trace-store persistence below) carries
-/// the base document's id, never the reopened topology's own, exactly as the
-/// campaign leg's `run_blueprint_member` has always taken its `topo` as a
-/// caller-supplied reference (`runner.rs`'s `&cell.strategy_id`).
+/// `refs`: `None` computes both `topology_hash` (the content id) and the run
+/// identity's `identity_hash` (the #171 `blueprint_identity_json` projection —
+/// debug-symbol-blind, including to a C29 description) inline from `signal`,
+/// as always (every existing caller). `Some((topo, identity))` overrides BOTH
+/// with the caller's own **reference-semantics** hashes (#343, revised): the
+/// exec blueprint leg's `--override` branch computes them from the loaded base
+/// document BEFORE `reopen_all`, so every consumer inside this function (the
+/// record line, the trace-store persistence below, AND the #311 handle) sees
+/// the base document's hashes, never the reopened topology's own — computing
+/// `identity_hash` from the REOPENED signal instead would show the overridden
+/// param as open rather than bound, which would split a no-op `--override`
+/// (one that reopens a param only to rebind it to its own default) from the
+/// un-overridden run it is identical to. Mirrors the campaign leg's own
+/// precedent for `topo` alone (`runner.rs`'s `&cell.strategy_id`).
 #[allow(clippy::type_complexity)]
 pub fn run_signal_r(
     signal: Composite, params: &[Scalar], data: RunData, seed: u64, env: &Env,
-    plan: TapPlan, topo: Option<&str>,
+    plan: TapPlan, refs: Option<(&str, &str)>,
 ) -> Result<crate::RunOutcome<RunReport>, RunnerError> {
     // #297 fieldtest finding B1 (milestone-safe-to-embed): mirror the CLI's
     // own `exec_blueprint_leg` exposes-neither guard (`aura-cli/src/main.rs`,
@@ -574,13 +579,20 @@ pub fn run_signal_r(
     // topology_hash's own two-line body, inlined: `content_id_of` over the
     // canonical (#164) blueprint JSON — the CLI shell's `topology_hash`
     // helper is the same primitive, kept single-sourced at `aura_research`.
-    // Skipped when the caller already supplies a reference-semantics hash
-    // (`topo: Some(..)`) — no need to hash a signal whose own topology_hash
-    // will be overridden anyway.
-    let topo: String = match topo {
-        Some(t) => t.to_string(),
-        None => aura_research::content_id_of(
-            &aura_engine::blueprint_to_json(&signal).expect("a buildable signal serializes"),
+    // `identity_hash` is the sibling #171 projection, over the SAME `signal`
+    // reference, feeding `run_identity_digest` in place of `topology_hash`
+    // (2026-07-27, C29). Both skipped when the caller already supplies
+    // reference-semantics hashes (`refs: Some(..)`) — no need to hash a
+    // signal whose own topology_hash/identity_hash will be overridden anyway.
+    let (topo, identity_hash): (String, String) = match refs {
+        Some((t, i)) => (t.to_string(), i.to_string()),
+        None => (
+            aura_research::content_id_of(
+                &aura_engine::blueprint_to_json(&signal).expect("a buildable signal serializes"),
+            ),
+            aura_research::content_id_of(
+                &aura_engine::blueprint_identity_json(&signal).expect("a buildable signal serializes"),
+            ),
         ), // before signal is consumed
     };
     // #311: the render name is only the readable PREFIX of the run's directory
@@ -632,7 +644,8 @@ pub fn run_signal_r(
     manifest.broker = r_sma_broker_label(pip_size);
     manifest.topology_hash = Some(topo);
     manifest.project = env.provenance();
-    let run_name = format!("{}-{}", render_name, crate::run_identity_digest(&manifest));
+    let run_name =
+        format!("{}-{}", render_name, crate::run_identity_digest(&manifest, &identity_hash));
     // Bind each declared tap per the plan's subscription, before bootstrap
     // (#283): typed refusals for bad plans, record consumers hold their
     // streaming writer in-graph, folds accumulate O(1), live closures run

docs/authoring-guide.md

@@ -257,10 +257,14 @@ overwrote an earlier one's trace — is **resolved** (#311), and no longer
 depends on naming at all: a run's trace directory is keyed by the run's own
 identity (`traces/<name>-<id8>/`, a digest over its manifest), so two runs
 that differ in any identity-bearing input — a different topology, an
-`--override` value, the data window, the seed — land in two directories,
-while two runs that differ in nothing land in one and the later simply
-rewrites what the earlier wrote. The render name survives as the directory's
-readable prefix, and `aura chart <name>` lists the runs recorded under it.
+`--override` value, the data window, the seed — land in two directories, and
+two runs that differ in nothing land in the same one. That directory's
+*contents* are not wholesale-replaced on the second write, though: the
+declared tap *plan* (which of a blueprint's taps this invocation subscribes)
+is not itself identity-bearing, so a same-identity pair that persists a
+different tap subset can strand an earlier tap file beside the later run's
+own — tracked as #352. The render name survives as the directory's readable
+prefix, and `aura chart <name>` lists the runs recorded under it.
 
 Value forms are the typed-tag representations used everywhere in this
 family of artifacts:

docs/design/contracts/c18-registry.history.md

@@ -295,3 +295,10 @@ aggregate** over those members, not a persisted family-level record."
 #319 sugar retirement, 2026-07-25):** "`aura campaign run <file|content-id>`
 executes a campaign (a file is register-then-run sugar; the content id is
 canonical): a zero-fault referential gate, then the process pipeline."
+
+**Current-state "Single-run trace identity (#311)" clause (superseded
+2026-07-27 — the audit that closed the #311 cycle found `topology_hash`
+itself, a C24 content id, feeding the digest, in violation of C29's Id
+treatment):** "What remains — the merged params, window, seed, broker,
+instrument, `topology_hash`, and the project's `namespace`/`dylib_sha256` (the
+C13 hot-reload discriminator) — is identity-bearing."

docs/design/contracts/c18-registry.md

@@ -263,9 +263,18 @@ partition between them records *how* a bound value was supplied (varied vs. held
 at its default, #246) rather than *what* the run's effective parameterisation is —
 the same provenance-not-identity distinction, applied to a different pair of keys;
 the merge is lossless since the two vectors are disjoint by construction. What
-remains — the merged params, window, seed, broker, instrument, `topology_hash`,
-and the project's `namespace`/`dylib_sha256` (the C13 hot-reload discriminator) —
-is identity-bearing. The two provenance keys are removed rather than blanked
+remains — the merged params, window, seed, broker, instrument, and the
+project's `namespace`/`dylib_sha256` (the C13 hot-reload discriminator) — is
+identity-bearing, with one substitution (2026-07-27, C29): `topology_hash` is
+a **content** id (`content_id_of(blueprint_to_json(..))`, #158/C24) that also
+hashes a blueprint's `doc` field and every other C23 debug symbol, so a
+description-only edit would otherwise mint a fresh directory for a
+bit-identical run — forbidden by C29's own Id treatment ("description fields
+… are blanked for the identity id"). The digest hashes
+`blueprint_identity_json`'s debug-symbol-blind projection (#171) in
+`topology_hash`'s place instead; `manifest.topology_hash` itself is
+untouched, keeping its own #343 reference-semantics content id. The two
+provenance keys are removed rather than blanked
 because `ProjectProvenance.commit` skips serializing when it is `None`: blanking
 would canonicalise an absent key to `null` and split one identity in two.
 `aura-runner::run_identity_digest` is the single implementation; both single-run

docs/design/contracts/c22-playground-traces.history.md

@@ -146,6 +146,12 @@ run's own name, on both shapes: …"
 "file I/O is `aura-registry::TraceStore`, persisting each run under
 `runs/traces/<name>/` beside the run registry's `runs.jsonl`"
 
+**Current-state "Single-run trace identity (#311)" clause (superseded
+2026-07-27 — the audit that closed the #311 cycle found `topology_hash`
+itself, a C24 content id, feeding the digest, in violation of C29's Id
+treatment):** "Everything else the manifest carries is identity-bearing,
+`project.dylib_sha256` included (it is what C13 hot-reload varies)."
+
 **Current-state "Single run" + "Families" + "Newcomer" clauses (superseded by
 the #319 sugar retirement, 2026-07-25):** "**Single run.** `aura run
 <blueprint.json>` persists every tap the blueprint declares to the trace

docs/design/contracts/c22-playground-traces.md

@@ -92,7 +92,22 @@ different pair: `params`/`defaults` record *how* a bound value was supplied
 (varied vs. held at its default, #246), not *what* the run's effective
 parameterisation is, and the two vectors are disjoint by construction, so the
 merge is lossless. Everything else the manifest carries is identity-bearing,
-`project.dylib_sha256` included (it is what C13 hot-reload varies). The
+`project.dylib_sha256` included (it is what C13 hot-reload varies) —
+**except** `topology_hash` (2026-07-27, C29): it is a **content** id
+(`content_id_of(blueprint_to_json(..))`, #158/C24) that also hashes a
+blueprint's `doc` field and every other C23 debug symbol, so a
+description-only edit would otherwise mint a fresh directory for a
+bit-identical run, which C29's own Id treatment forbids. The digest hashes
+`blueprint_identity_json`'s debug-symbol-blind projection (#171) in
+`topology_hash`'s place instead; `manifest.topology_hash` itself is
+untouched. That projection blanks every C23 debug symbol, not descriptions
+alone — the render name, and node, role, output, tap and gang names — while
+param openness stays identity-bearing; two blueprints differing only in
+such names compute bit-identically, so one address is the correct answer.
+One observable consequence: two structurally identical blueprints whose
+declared *tap names* differ share a directory while writing differently
+named tap files, and the later run's `index.json` lists only its own, since
+the write path never prunes (tracked as #352, unchanged here). The
 manifest is assembled *before* the tap bind and the same value is reused for
 the record, so the handle can never name a directory whose identity the
 stored record does not describe. Consequences: two runs of one blueprint

docs/design/contracts/c29-self-description.md

@@ -60,6 +60,11 @@ content id and are blanked for the identity id, exactly as `Composite.doc`
 ([C24](c24-blueprint-data.md)), so node docs move no id. Documents have no
 identity projection — their pair is: absent `description` is byte-identical
 to the field-less form (existing content ids stable), present participates.
+A single `aura exec` run's #311 trace-directory handle honours this same
+treatment (2026-07-27 audit fix): its digest hashes the blueprint's identity
+projection, not `manifest.topology_hash` (a content id), so a
+description-only blueprint edit mints no fresh directory for a bit-identical
+run (`aura-runner::run_identity_digest`, [C18](c18-registry.md)).
 
 **Forbids.** The engine evaluating description text — the gate is
 deterministic string shape, never content judgement (no freetext logic