Finding 4: full-trace evidence — reconstructed and re-derived, not summarized

Removes the deferral. Each sampled execution's FULL trace (every graph edge,
count, weight) and delta are persisted as evidence; the independent attestor
reconstructs them, recomputes the canonical trace hash and delta hash, re-derives
the replay-record leaf, and confirms it is among the retained Merkle leaves the
root is built from. The behavior-fingerprint hash is re-derived from features
(not trusted), and f64 divergence is stored bit-exact for an identical hash.

- trace_model: ExecutionTrace::serialize/deserialize (round-trips canonical_hash;
  total on garbage). Test: full_trace_serialize_roundtrips_canonical_hash.
- world_model: WorldDelta::serialize/deserialize (round-trips hash).
- ci_reports: retains TRACE_EVIDENCE_SAMPLE full traces; writes
  evidence/traces.tsv.
- attestation: depends on trace_model/world_model; reconstructs each trace,
  recomputes the leaf, requires it to match the claimed leaf AND be a retained
  leaf. Negative control: tampered_trace_breaks_attestation (corrupting the full
  trace, leaving the claimed leaf, fails attestation).
- merge-gates: requires evidence/traces.tsv; the separate attest step verifies it.

End-to-end (fast profile): 256/256 full traces reconstructed and re-derived to
retained leaves; recomputed root matches the claim over 6600 leaves.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/ci_reports/src/lib.rs

@@ -659,8 +659,24 @@ pub struct CiResults {
     /// Every Merkle leaf (per-execution replay hash) actually produced. Retained
     /// so the root can be independently recomputed from the leaves (finding 3).
     pub merkle_leaves: Vec<Hash>,
+    /// A sample of FULL execution traces + deltas + seeds (finding 4). The
+    /// attestor reconstructs each trace, recomputes its canonical hash and the
+    /// replay-record leaf, and checks the leaf is in `merkle_leaves` — proving
+    /// the leaves are backed by full trace structure, not a summary.
+    pub trace_evidence: Vec<TraceEvidence>,
 }
 
+/// One sampled full-trace evidence record.
+#[derive(Clone, Debug)]
+pub struct TraceEvidence {
+    pub replay: trace_model::ReplayRecord,
+    pub trace: trace_model::ExecutionTrace,
+    pub delta: world_model::WorldDelta,
+}
+
+/// How many full traces to retain as evidence.
+pub const TRACE_EVIDENCE_SAMPLE: usize = 256;
+
 impl CiResults {
     pub fn all_failures(&self) -> Vec<(&'static str, &Vec<String>)> {
         vec![
@@ -746,6 +762,7 @@ pub fn run_all(scale: Scale) -> CiResults {
     // Provenance leaves: one per actually-committed execution (base + every
     // perturbation), so the Merkle root binds to all compared executions.
     let mut merkle_leaves: Vec<Hash> = Vec::with_capacity(scale.executions);
+    let mut trace_evidence: Vec<TraceEvidence> = Vec::with_capacity(TRACE_EVIDENCE_SAMPLE);
     let mut actual_executions = 0usize;
     let mut worlds_generated = 0usize;
     let mut programs_generated = 0usize;
@@ -870,6 +887,14 @@ pub fn run_all(scale: Scale) -> CiResults {
                 equiv_failures.push(format!("case {} (base) reference != runtime_under_test", i));
             }
             merkle_leaves.push(r.replay.hash());
+            // Retain a sample of FULL traces as independent evidence (finding 4).
+            if trace_evidence.len() < TRACE_EVIDENCE_SAMPLE {
+                trace_evidence.push(TraceEvidence {
+                    replay: r.replay,
+                    trace: r.trace.clone(),
+                    delta: r.delta.clone(),
+                });
+            }
             for (pinput, pref_canon, pleaf) in &pert_execs {
                 let prut = rut.resolve(pinput.clone());
                 equiv_total += 1;
@@ -1212,6 +1237,7 @@ pub fn run_all(scale: Scale) -> CiResults {
         replay,
         coverage,
         merkle_leaves: retained_leaves,
+        trace_evidence,
     }
 }
 

crates/ci_reports/src/main.rs

@@ -59,6 +59,28 @@ fn write_evidence(dir: &Path, r: &CiResults) {
         r.provenance.engines_agree,
     );
     fs::write(ev.join("claims.tsv"), claims).expect("write claims");
+
+    // Full-trace evidence (finding 4): each line is
+    //   ws ps cs prs future leaf <TAB> <full trace> <TAB> <full delta>
+    // The attestor reconstructs the trace + delta, recomputes the canonical
+    // trace hash and the replay-record leaf, and checks the leaf is among the
+    // retained leaves. This is the full trace, not a summary.
+    let mut traces = String::from("# full-trace evidence: header<TAB>trace<TAB>delta\n");
+    for ev_rec in &r.trace_evidence {
+        let rr = &ev_rec.replay;
+        traces.push_str(&format!(
+            "{:016x} {:016x} {:016x} {:016x} {:016x} {:016x}\t{}\t{}\n",
+            rr.world_seed,
+            rr.program_seed,
+            rr.contract_seed,
+            rr.perturbation_seed,
+            rr.future_hash.0,
+            rr.hash().0,
+            ev_rec.trace.serialize(),
+            ev_rec.delta.serialize(),
+        ));
+    }
+    fs::write(ev.join("traces.tsv"), traces).expect("write traces");
 }
 
 fn build_reports(dir: &Path, r: &CiResults) {