diff --git a/research/seven-source-duo-21-calls/CERTIFICATE.json b/research/seven-source-duo-21-calls/CERTIFICATE.json
new file mode 100644
index 0000000000..bd26ecafff
--- /dev/null
+++ b/research/seven-source-duo-21-calls/CERTIFICATE.json
@@ -0,0 +1,33 @@
+{
+  "schema_version": 1,
+  "model": "Seven-source restored singleton+DUO connector of research/connector-seven-source-duo: a step s in 1..127 of Hamming weight 1 is one singleton call z += B_j x_j; weight 2 is one charged DUO call z += B_j x_j + B_k x_k. A word is universal when its prefix states P satisfy P+P = F2^7.",
+  "words": {
+    "k21_W24": {
+      "prefix_states": [0, 1, 33, 36, 38, 102, 100, 96, 98, 114, 82, 83, 115, 123, 120, 88, 89, 9, 41, 40, 8],
+      "k": 21,
+      "duo_calls": 3,
+      "W": 24,
+      "queries_all_127_rows": 275,
+      "adds_all_127_rows": 278
+    },
+    "k20_W26": {
+      "prefix_states": [0, 2, 16, 112, 120, 88, 92, 60, 61, 29, 21, 85, 81, 115, 123, 59, 58, 26, 14, 12],
+      "k": 20,
+      "duo_calls": 6,
+      "W": 26,
+      "queries_all_127_rows": 274,
+      "adds_all_127_rows": 280
+    }
+  },
+  "search_failures_not_exclusions": {
+    "note": "Bounded simulated-annealing runs of search/sa.c that found no universal word. These are search failures, not exclusions.",
+    "runs": [
+      "./sa 20 24 11 10000000 20",
+      "./sa 20 24 99 20000000 20",
+      "./sa 19 W 5 10000000 10 for W in 24 26 28 30 34",
+      "./sa 18 W 5 10000000 10 for W in 30 36",
+      "./sa 21 22 3 10000000 10",
+      "./sa 22 22 3 10000000 10"
+    ]
+  }
+}
diff --git a/research/seven-source-duo-21-calls/README.md b/research/seven-source-duo-21-calls/README.md
new file mode 100644
index 0000000000..ba90f61acb
--- /dev/null
+++ b/research/seven-source-duo-21-calls/README.md
@@ -0,0 +1,113 @@
+# Seven-source singleton+DUO connectors: 21 calls at 24 adds, and 20 calls
+
+This contribution was produced by Nick Petalas. Apache-2.0.
+
+**Claim type: finite certificate (explicit construction).** No search
+exclusion, no optimality proof, no new κ, no supplier change.
+
+In the seven-source restored connector of Ross Richardson's
+[#943](https://github.com/CrocSwap/integer-mult-bounds/pull/943), extended by
+the charged pair-source DUO call `z += B_j x_j + B_k x_k` of
+`research/duo-toggle-connector`, Aaron Wang's
+[#2396](https://github.com/CrocSwap/integer-mult-bounds/pull/2396)
+(`research/connector-seven-source-duo`) gives a universal word with
+`(k, W) = (22, 24)`: 22 source calls and 24 toggle-adds. Its first open
+question asks whether `(22, 24)` is the Pareto profile. It is not. This package
+gives two universal words:
+
+| Word | Calls `k` | DUO calls | Adds `W` | Batch queries | Batch adds |
+|---|---:|---:|---:|---:|---:|
+| #2396 (cited) | 22 | 2 | 24 | 276 | 278 |
+| **this package** | **21** | 3 | **24** | **275** | **278** |
+| **this package** | **20** | 6 | 26 | **274** | 280 |
+
+The batch is the all-127-row batch of #2396 with two paired readouts per row
+(254 readouts). The `(21, 24)` word strictly dominates `(22, 24)`: one fewer
+call at the same adds, so in #2396's tariff `c_B = o + p`, `c_DUO = o + 2p`,
+`c_A = o + p` the batch saves `o` for every `o > 0`, and `3o` against the
+24-call singleton Gray word. The `(20, 26)` word saves one more call at two
+more adds; it beats `(21, 24)` exactly when `o > 2p`. It also answers
+#2396's `(20, d)` question at `d = 6`, where #2396's search reached 126/128.
+
+## The words
+
+Prefix states, with bit `j` for source `j`. Each word closes back to `0`.
+A step of weight one is a singleton call, a step of weight two a DUO call.
+
+```text
+(21,24): 0 1 33 36 38 102 100 96 98 114 82 83 115 123 120 88 89 9 41 40 8
+(20,26): 0 2 16 112 120 88 92 60 61 29 21 85 81 115 123 59 58 26 14 12
+```
+
+Universality is the paired-readout criterion used by #943 and #2396:
+the prefix-state set `P` satisfies `P + P = F2^7`.
+
+## Evidence
+
+[verify.py](verify.py) uses only the Python standard library and no search.
+For each word it rebuilds the steps from the prefix states and checks:
+
+- every step has weight one or two, the word restores the connector, and every
+  source label has positive even multiplicity;
+- all 128 masks lie in `P + P`, and a separate dual test (mask `m` is covered
+  when `p xor m` is in `P` for some `p` in `P`) finds no missing mask;
+- `k`, the DUO count, `W` and the batch bill match [CERTIFICATE.json](CERTIFICATE.json);
+- four mutations per word are rejected: a deleted call, a DUO shrunk to a
+  singleton, a retargeted call and a dropped call.
+
+It also reads #2396's pinned certificate, confirms that word is universal at
+`(22, 24)`, and checks the dominance relations above. Assertions are explicit
+checks, so `-O` does not skip them.
+
+## Reproduce
+
+From the repository root with CPython 3.12 (the recorded local interpreter was
+`~/git/integer-mult-bounds/.venv/bin/python3.12`):
+
+```sh
+python3.12 -B research/seven-source-duo-21-calls/verify.py
+python3.12 -B scripts/research_package.py --package research/seven-source-duo-21-calls
+```
+
+Expected marker:
+`PASS_SEVEN_SOURCE_DUO_21_CALLS k21_W24_queries=275 k20_W26_queries=274 pred_queries=276 universal=128/128 mutations_rejected=8`.
+
+The words came from the simulated-annealing program [search/sa.c](search/sa.c)
+(`cc -O2 -o sa sa.c -lm`; arguments `K WMAX seed iterations restarts`).
+`./sa 21 24 1 5000000 20` and `./sa 20 26 7 5000000 20` printed these words
+on an Apple arm64 host. The search is provenance only; the verifier does not
+depend on it.
+
+## Limitations
+
+- **No lower bound.** Runs at `(20, W <= 24)`, `(19, W <= 34)`, `(18, W <= 36)`
+  and `W = 22` at `k = 21, 22` found nothing. These are bounded search
+  failures listed in CERTIFICATE.json, not exclusions.
+- The counting bound `C(k,2) + 1 >= 128` gives only `k >= 17`.
+- Inherited from #2396 and `research/duo-toggle-connector`: no physical
+  supplier instance of this connector exists, so no recursive moment, frame,
+  compiler or κ consequence follows. With `o = 0` the `(21, 24)` word gains
+  nothing over `(22, 24)`.
+
+## Open next questions
+
+1. **Is 20 the minimum number of calls?** A universal 19-call word would cut
+   the batch to 273 queries. First step: an exact census of 19-point sets `P`
+   with `P + P = F2^7`, then a Hamiltonian-cycle test with edges of weight at
+   most two. Blocker: no exclusion argument beyond the counting bound
+   `k >= 17` and the parity rule `d = k mod 2`.
+2. **Is 24 the minimum number of adds?** `f(7) = 24` (#3058) settles the
+   singleton case, but a word with DUO calls and `W = 22` is not excluded.
+   First step: adapt #3058's deletion argument to steps of weight two.
+3. **Is `(20, 24)` attainable?** It would dominate both new words. The local
+   search reached no such word.
+
+## Credit
+
+Ross Richardson (#943) supplied the connector model and paired-readout
+criterion. The DUO family and its pricing come from `research/duo-toggle-connector`.
+Aaron Wang / navinor (#2396) supplied the `(22, 24)` word, the batch bill,
+the tariff and the open Pareto question answered here. Douglas Colkitt (#1185)
+supplied the Gray baseline, and conorholds (#3058) the singleton value
+`f(7) = 24`. Their results are cited, not re-audited. The two new words, the
+verifier and the search program are new.
diff --git a/research/seven-source-duo-21-calls/SOURCES.json b/research/seven-source-duo-21-calls/SOURCES.json
new file mode 100644
index 0000000000..6238e3c410
--- /dev/null
+++ b/research/seven-source-duo-21-calls/SOURCES.json
@@ -0,0 +1,24 @@
+{
+  "schema_version": 1,
+  "base_commit": "19fdb086ea96af9a9f87936a2b888e10af4ed810",
+  "files": [
+    {
+      "path": "certificates/selected-result.json",
+      "usage": "provenance",
+      "git_blob": "581f8d87008354eb5b869f7ed9de1317ad837ce8",
+      "sha256": "2a0220e866417774606e0f991e41b9c1d26b1f43b97857238cf478dbc7d330b5"
+    },
+    {
+      "path": "docs/research/agent-task-catalog.json",
+      "usage": "provenance",
+      "git_blob": "3404fbdd5e7529a0674eef26114b5071e4586cec",
+      "sha256": "ead6cdc9d0af6d58e8a49744d8ec8c7c15e13d2ba93c276c434bcf9b51b93a81"
+    },
+    {
+      "path": "research/connector-seven-source-duo/CERTIFICATE.json",
+      "usage": "input",
+      "git_blob": "a1de5ebffaa3a33486fd28643ccad67c60843f06",
+      "sha256": "6b8c5bd2d27a0b4cbeb073bc0ac224220fdf99bc94760afd9a1be79aa31c4a63"
+    }
+  ]
+}
diff --git a/research/seven-source-duo-21-calls/TASK.json b/research/seven-source-duo-21-calls/TASK.json
new file mode 100644
index 0000000000..f788f8a861
--- /dev/null
+++ b/research/seven-source-duo-21-calls/TASK.json
@@ -0,0 +1,74 @@
+{
+  "schema_version": 1,
+  "task_id": "connector-alphabet-change",
+  "priority_revision": 8,
+  "base_commit": "19fdb086ea96af9a9f87936a2b888e10af4ed810",
+  "original_card": {
+    "id": "connector-alphabet-change",
+    "question": "Does one explicit extension of the connector alphabet offer a favorable completed budget?",
+    "starting_points": [
+      "docs/research/research-family-status.md",
+      "research/universal-connector-boundary/README.md",
+      "certificates/selected-result.json"
+    ],
+    "methods": [
+      "Construct and charge a legal extra operation on a minimal instance.",
+      "Prove a target-specific bound after adding one specified operation family."
+    ],
+    "acceptance_gate": "State which fixed-alphabet premise changes and charge its implementation; do not declare it free. A scoped local result may be retained without a complete supplier. Expanding it into further construction rounds requires the family-level budget and obligation gate in research-family-status.md; an optimistic passing relaxation alone is not acceptance.",
+    "first_step": {
+      "command": [
+        "python3",
+        "-B",
+        "research/universal-connector-boundary/verify.py"
+      ],
+      "expected": "PASS_UNIVERSAL_CONNECTOR_BOUNDARY",
+      "inspect": "Reproduce the 945-pairing control, then read Exact interface to list the allowed calls.",
+      "scope": "Positive control / source-bound orientation only; this is not a new construction or full cold replay."
+    },
+    "first_experiment": "Add exactly one legally priced operation and test a tiny dirty-input instance before enumerating larger cases.",
+    "bottleneck_link": "A new legal connector operation could change recursive interface cost; a larger census in the same alphabet is a separate side result.",
+    "allowed_variations": [
+      "Choose one additional operation and a small source count for its first counterexample."
+    ],
+    "scope_change_triggers": [
+      "Keeping the alphabet and only increasing the source count; record this as a changed assignment.",
+      "Extending a source-count census without naming a supplier/interface decision it could change; audit #2973 pruning concerns before relying on the affected predecessor exclusions."
+    ],
+    "overlap_terms": [
+      "universal connector",
+      "source-toggle",
+      "connector alphabet"
+    ]
+  },
+  "scope_status": "changed",
+  "actual_scope": "Open next question 1 of PR #2396 (research/connector-seven-source-duo): is (k, W) = (22, 24) the Pareto profile for seven-source universal words in the singleton+DUO alphabet? Answered negatively by explicit universal words at (21, 24) and (20, 26).",
+  "scope_change_reason": "The card asks for one new alphabet extension. DUO is already added and charged by research/duo-toggle-connector and #2396; this package keeps that alphabet and source count and improves #2396's open Pareto profile. It is a side result on the connector interface.",
+  "bottleneck_link": "Side result. Connector call counts enter the recursive interface through complete-call pricing; the new words save one or two per-call overheads o on the all-127-row batch. No physical supplier instance of this connector exists, so no \u03ba follows.",
+  "budget_minutes": 60,
+  "stop_rule": "Ship the first verified universal word with fewer than 22 calls; record unsuccessful smaller profiles as search failures, not exclusions.",
+  "outcome": "completed",
+  "evidence": "Explicit universal words (21, 24) and (20, 26), checked by research/seven-source-duo-21-calls/verify.py: weights, restoration, even label counts, 128/128 masks with a dual test, batch bill 275/278 and 274/280, dominance over #2396's pinned (22, 24) word, and eight rejected mutations.",
+  "author": "Nick Petalas",
+  "ai_assistance": "Independent human and formal proof-kernel review are unclaimed.",
+  "open_questions": [
+    {
+      "question": "Is 20 the minimum number of calls for a seven-source singleton+DUO universal word?",
+      "why_it_matters": "A 19-call word would cut the all-127-row batch to 273 queries.",
+      "first_step": "Exactly enumerate 19-point sets P with P+P = F2^7, then test for a Hamiltonian cycle with edges of weight at most two.",
+      "blocked_by": "No exclusion argument beyond the counting bound k >= 17 and the parity rule d = k mod 2."
+    },
+    {
+      "question": "Is 24 the minimum number of toggle-adds when DUO calls are allowed?",
+      "why_it_matters": "f(7) = 24 (#3058) settles only singleton words; a W = 22 DUO word would lower the batch adds.",
+      "first_step": "Adapt #3058's coordinate-deletion argument to weight-two steps.",
+      "blocked_by": "The deletion argument is written for singleton steps."
+    },
+    {
+      "question": "Is (20, 24) attainable?",
+      "why_it_matters": "It would dominate both new words.",
+      "first_step": "An exact (20, 4) census as #2396 proposed.",
+      "blocked_by": "Local simulated annealing found no such word; that is not an exclusion."
+    }
+  ]
+}
diff --git a/research/seven-source-duo-21-calls/VERIFY.json b/research/seven-source-duo-21-calls/VERIFY.json
new file mode 100644
index 0000000000..f802e5e78f
--- /dev/null
+++ b/research/seven-source-duo-21-calls/VERIFY.json
@@ -0,0 +1,20 @@
+{
+  "schema_version": 1,
+  "status": "ready",
+  "python": "3.12",
+  "requirements": [],
+  "inputs": [
+    "research/connector-seven-source-duo/CERTIFICATE.json"
+  ],
+  "commands": [
+    {
+      "argv": [
+        "{python}",
+        "-B",
+        "{package}/verify.py"
+      ],
+      "timeout_seconds": 60,
+      "checks": "Two explicit seven-source singleton+DUO universal words, (21,24) and (20,26): step weights, restoration, even label counts, 128/128 masks with an independent dual test, batch bill, dominance over the pinned #2396 (22,24) word, and eight mutation controls. Prints PASS_SEVEN_SOURCE_DUO_21_CALLS."
+    }
+  ]
+}
diff --git a/research/seven-source-duo-21-calls/search/sa.c b/research/seven-source-duo-21-calls/search/sa.c
new file mode 100644
index 0000000000..a9091654e3
--- /dev/null
+++ b/research/seven-source-duo-21-calls/search/sa.c
@@ -0,0 +1,47 @@
+// SA search: closed cycle of K points in F2^N, consecutive (cyclic) Hamming distance 1 or 2,
+// maximize |P+P| coverage; then report W = sum of distances.
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <stdint.h>
+#define N 7
+#define M (1<<N)
+static uint64_t s=88172645463325252ULL;
+static inline uint64_t rnd(){ s^=s<<13; s^=s>>7; s^=s<<17; return s; }
+static inline int wt(int x){ return __builtin_popcount(x); }
+int K, WMAX; int P[64]; int cnt[M]; int cov;
+static int ok(int d){ int w=wt(d); return w==1||w==2; }
+static int W(){ int t=0; for(int i=0;i<K;i++) t+=wt(P[i]^P[(i+1)%K]); return t; }
+static void add(int i,int sg){ for(int j=0;j<K;j++) if(j!=i){ int d=P[i]^P[j]; if(sg>0){ if(cnt[d]++==0) cov++; } else { if(--cnt[d]==0) cov--; } } }
+int main(int argc,char**argv){
+  K=atoi(argv[1]); WMAX=atoi(argv[2]); s^=strtoull(argv[3],0,10)*0x9E3779B97F4A7C15ULL; long iters=atol(argv[4]); int restarts=atoi(argv[5]);
+  for(int r=0;r<restarts;r++){
+    // init: random cycle by random walk then fix closure greedily: just random points with valid edges via repeated tries
+    P[0]=0; for(int i=1;i<K;i++){ int q; do{ q=P[i-1]^(1<<(rnd()%N)); if(rnd()&1) q^=1<<(rnd()%N);}while(q==P[i-1]); P[i]=q; }
+    // closure may be invalid: treat invalid edges as penalty
+    for(int d=0;d<M;d++) cnt[d]=0; cov=1; cnt[0]=1; for(int i=0;i<K;i++) for(int j=i+1;j<K;j++){ int d=P[i]^P[j]; if(cnt[d]++==0) cov++; }
+    double T=2.0;
+    #define BAD() ({int b=0; for(int i=0;i<K;i++) if(!ok(P[i]^P[(i+1)%K])) b++; b;})
+    double score; int bad=BAD(); int w=W();
+    score = cov - 4.0*bad - 2.0*(w>WMAX? w-WMAX:0);
+    for(long it=0;it<iters;it++){
+      T = 2.0*pow(0.02/2.0,(double)it/iters);
+      int i=1+rnd()%(K-1); int old=P[i]; int q;
+      int mv=rnd()%3;
+      if(mv==0) q=old^(1<<(rnd()%N)); else if(mv==1) q=old^(1<<(rnd()%N))^(1<<(rnd()%N)); else q=P[i-1]^(1<<(rnd()%N))^((rnd()&1)?(1<<(rnd()%N)):0);
+      if(q==old) continue;
+      int a=P[i-1], b=P[(i+1)%K];
+      int dbad = (!ok(q^a))+(!ok(q^b)) - (!ok(old^a)) - (!ok(old^b));
+      int dw = wt(q^a)+wt(q^b)-wt(old^a)-wt(old^b);
+      int oc=cov; add(i,-1); P[i]=q; add(i,1);
+      int nb=bad+dbad, nw=w+dw;
+      double ns = cov - 4.0*nb - 2.0*(nw>WMAX? nw-WMAX:0);
+      if(ns>=score || exp((ns-score)/T) > (rnd()%1000000)/1e6){ score=ns; bad=nb; w=nw; }
+      else { add(i,-1); P[i]=old; add(i,1); }
+      if(cov==M && bad==0 && w<=WMAX){
+        printf("FOUND K=%d W=%d :",K,w); for(int j=0;j<K;j++) printf(" %d",P[j]); printf("\n"); fflush(stdout); return 0; }
+      (void)oc;
+    }
+  }
+  printf("NONE K=%d WMAX=%d\n",K,WMAX); return 1;
+}
diff --git a/research/seven-source-duo-21-calls/verify.py b/research/seven-source-duo-21-calls/verify.py
new file mode 100644
index 0000000000..b9ccb69134
--- /dev/null
+++ b/research/seven-source-duo-21-calls/verify.py
@@ -0,0 +1,136 @@
+"""Verify two seven-source singleton+DUO universal connector words.
+
+Independent of the search. Rebuilds each word's steps from its prefix states,
+checks closure, step weights, label parity, all 128 pairwise masks (and a
+separate dual test), the all-127-row bill, Pareto dominance over the cited
+#2396 word, and mutation controls. Produced by Nick Petalas. Apache-2.0.
+"""
+import hashlib
+import json
+import sys
+from pathlib import Path
+
+N = 7
+MASKS = 1 << N
+ROWS = MASKS - 1
+READOUTS = 2 * ROWS  # two paired readouts per output row, as in #2396
+HERE = Path(__file__).resolve().parent
+ROOT = HERE.parents[1]
+PRED = ROOT / "research/connector-seven-source-duo/CERTIFICATE.json"
+PRED_SHA256 = "6b8c5bd2d27a0b4cbeb073bc0ac224220fdf99bc94760afd9a1be79aa31c4a63"
+
+
+class CheckError(Exception):
+    pass
+
+
+def require(cond, msg="check failed"):
+    if not cond:
+        raise CheckError(msg)
+
+
+def steps_of(states):
+    return [states[i] ^ states[(i + 1) % len(states)] for i in range(len(states))]
+
+
+def covered(states):
+    return {a ^ b for a in states for b in states}
+
+
+def dual_missing(states):
+    present = set(states)
+    return [m for m in range(MASKS) if not any((p ^ m) in present for p in states)]
+
+
+def profile(steps):
+    """Return (k, d, W) after checking the word is a legal restored word."""
+    require(steps, "empty word")
+    acc = 0
+    counts = [0] * N
+    for s in steps:
+        require(0 < s < MASKS, f"step {s} out of range")
+        require(bin(s).count("1") in (1, 2), f"step {s} is not a singleton or DUO call")
+        acc ^= s
+        for j in range(N):
+            counts[j] += (s >> j) & 1
+    require(acc == 0, "word does not restore the connector")
+    require(all(c % 2 == 0 and c > 0 for c in counts), f"label counts {counts}")
+    d = sum(1 for s in steps if bin(s).count("1") == 2)
+    return len(steps), d, sum(bin(s).count("1") for s in steps)
+
+
+def states_of(steps):
+    out, acc = [], 0
+    for s in steps:
+        out.append(acc)
+        acc ^= s
+    return out
+
+
+def universal(steps):
+    states = states_of(steps)
+    return len(covered(states)) == MASKS and not dual_missing(states)
+
+
+def check_word(name, rec):
+    states = rec["prefix_states"]
+    require(states[0] == 0)
+    steps = steps_of(states)
+    k, d, w = profile(steps)
+    require(states_of(steps) == states)
+    require((k, d, w) == (rec["k"], rec["duo_calls"], rec["W"]), (name, k, d, w))
+    require(len(covered(states)) == MASKS, f"{name} covers {len(covered(states))}")
+    require(dual_missing(states) == [], name)
+    require(k + READOUTS == rec["queries_all_127_rows"])
+    require(w + READOUTS == rec["adds_all_127_rows"])
+    return steps, k, w
+
+
+def mutations(steps):
+    """Each mutation must be rejected as illegal or non-universal."""
+    rejected = 0
+    trials = []
+    trials.append(steps[1:])  # delete a call
+    duo = next(i for i, s in enumerate(steps) if bin(s).count("1") == 2)
+    low = steps[duo] & -steps[duo]
+    trials.append(steps[:duo] + [low] + steps[duo + 1:])  # shrink DUO
+    trials.append(steps[:2] + [steps[2] ^ 64 if steps[2] ^ 64 else 1] + steps[3:])  # retarget
+    trials.append(steps[:-2] + [steps[-1]])  # drop the penultimate call
+    for t in trials:
+        try:
+            profile(t)
+            ok = universal(t)
+        except CheckError:
+            ok = False
+        rejected += not ok
+    require(rejected == len(trials), f"only {rejected}/{len(trials)} mutations rejected")
+    return rejected
+
+
+def main():
+    cert = json.loads((HERE / "CERTIFICATE.json").read_text())
+    pred_bytes = PRED.read_bytes()
+    require(hashlib.sha256(pred_bytes).hexdigest() == PRED_SHA256, "predecessor pin")
+    pred = json.loads(pred_bytes)["headline_22_24"]
+    pk, pd, pw = profile(pred["steps"])
+    require((pk, pw) == (22, 24) and universal(pred["steps"]), "predecessor control")
+    a_steps, ak, aw = check_word("k21_W24", cert["words"]["k21_W24"])
+    b_steps, bk, bw = check_word("k20_W26", cert["words"]["k20_W26"])
+    # (21,24) strictly dominates (22,24): one fewer call, same adds.
+    require(ak < pk and aw == pw)
+    # (20,26) beats (21,24) in c = q*o + a*p exactly when o > 2p.
+    require((bk - ak, bw - aw) == (-1, 2))
+    muts = mutations(a_steps) + mutations(b_steps)
+    print(
+        "PASS_SEVEN_SOURCE_DUO_21_CALLS "
+        f"k21_W24_queries={ak + READOUTS} k20_W26_queries={bk + READOUTS} "
+        f"pred_queries={pk + READOUTS} universal=128/128 mutations_rejected={muts}"
+    )
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except CheckError as exc:
+        print(f"FAIL_SEVEN_SOURCE_DUO_21_CALLS {exc}")
+        sys.exit(1)