diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f00c38b7..91780179 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -50,6 +50,7 @@ env:
   FROST: 'no'
   CHILLDKG: 'no'
   ICEBERG: 'no'
+  PREFRACTAL: 'no'
   ### test options
   SECP256K1_TEST_ITERS: 64
   BENCH: 'yes'
@@ -107,14 +108,14 @@ jobs:
       matrix:
         configuration:
           - env_vars: { WIDEMUL: 'int64',  RECOVERY: 'yes' }
-          - env_vars: { WIDEMUL: 'int64',                   ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes'}
+          - env_vars: { WIDEMUL: 'int64',                   ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes'}
           - env_vars: { WIDEMUL: 'int128' }
           - env_vars: { WIDEMUL: 'int128_struct',                                                                           ELLSWIFT: 'yes' }
           - env_vars: { WIDEMUL: 'int128', RECOVERY: 'yes',              EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes' }
-          - env_vars: { WIDEMUL: 'int128',                  ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes',                  EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes'}
+          - env_vars: { WIDEMUL: 'int128',                  ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes',                  EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes'}
           - env_vars: { WIDEMUL: 'int128', ASM: 'x86_64',                                                                   ELLSWIFT: 'yes' }
-          - env_vars: {                    RECOVERY: 'yes',              EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes',                  EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes'}
-          - env_vars: { CTIMETESTS: 'no',  RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes',                  EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', CPPFLAGS: '-DVERIFY' }
+          - env_vars: {                    RECOVERY: 'yes',              EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes',                  EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', PREFRACTAL: 'yes'}
+          - env_vars: { CTIMETESTS: 'no',  RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes',                  EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes', CPPFLAGS: '-DVERIFY' }
           - env_vars: { BUILD: 'distcheck', WITH_VALGRIND: 'no', CTIMETESTS: 'no', BENCH: 'no' }
           - env_vars: { CPPFLAGS: '-DDETERMINISTIC' }
           - env_vars: { CFLAGS: '-O0', CTIMETESTS: 'no' }
@@ -183,6 +184,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CC: ${{ matrix.cc }}
 
     steps:
@@ -223,6 +225,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CTIMETESTS: 'no'
 
     steps:
@@ -265,6 +268,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CTIMETESTS: 'no'
 
     steps:
@@ -298,6 +302,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CTIMETESTS: 'no'
       CC: ${{ matrix.cc }}
 
@@ -350,6 +355,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CTIMETESTS: 'no'
 
     steps:
@@ -407,6 +413,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CTIMETESTS: 'no'
       SECP256K1_TEST_ITERS: 2
 
@@ -448,6 +455,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CTIMETESTS: 'no'
       CFLAGS: '-fsanitize=undefined,address -g'
       UBSAN_OPTIONS: 'print_stacktrace=1:halt_on_error=1'
@@ -506,6 +514,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CC: ${{ matrix.cc }}
       SECP256K1_TEST_ITERS: 32
       ASM: 'no'
@@ -543,6 +552,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
       CTIMETESTS: 'no'
 
     strategy:
@@ -575,15 +585,15 @@ jobs:
       fail-fast: false
       matrix:
         env_vars:
-          - { WIDEMUL: 'int64',  RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes' }
+          - { WIDEMUL: 'int64',  RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes' }
           - { WIDEMUL: 'int128_struct', ECMULTGENKB: 2, ECMULTWINDOW: 4 }
-          - { WIDEMUL: 'int128',                  ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes' }
+          - { WIDEMUL: 'int128',                  ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes' }
           - { WIDEMUL: 'int128', RECOVERY: 'yes' }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes' }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', CC: 'gcc' }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes',  WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', CC: 'gcc', WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
-          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', CPPFLAGS: '-DVERIFY', CTIMETESTS: 'no' }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes' }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes', CC: 'gcc' }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes',  WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes', CC: 'gcc', WRAPPER_CMD: 'valgrind --error-exitcode=42', SECP256K1_TEST_ITERS: 2 }
+          - { WIDEMUL: 'int128', RECOVERY: 'yes', ECDH: 'yes', EXTRAKEYS: 'yes', SCHNORRSIG: 'yes', MUSIG: 'yes', ELLSWIFT: 'yes', EXPERIMENTAL: 'yes', ECDSA_S2C: 'yes', RANGEPROOF: 'yes', SURJECTIONPROOF: 'yes', WHITELIST: 'yes', GENERATOR: 'yes', ECDSAADAPTOR: 'yes', BPPP: 'yes', SCHNORRSIG_HALFAGG: 'yes', FROST: 'yes', CHILLDKG: 'yes', ICEBERG: 'yes', PREFRACTAL: 'yes', CPPFLAGS: '-DVERIFY', CTIMETESTS: 'no' }
           - BUILD: 'distcheck'
 
     steps:
@@ -762,6 +772,7 @@ jobs:
       FROST: 'yes'
       CHILLDKG: 'yes'
       ICEBERG: 'yes'
+      PREFRACTAL: 'yes'
 
     steps:
       - *CHECKOUT
diff --git a/README.md b/README.md
index 68ebc17b..dfc21c4a 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,7 @@ Added features:
 * Experimental module for [FROST (BIP 445)](src/modules/frost/frost.md).
 * Experimental module for [ChillDKG](src/modules/chilldkg/chilldkg.md), distributed key generation for FROST (bip-frost-dkg draft).
 * Experimental module for [Iceberg](doc/iceberg.md), a threshold scheme that lets a group of parties stand in for a single MuSig2 (BIP 327) participant.
+* Experimental module for [Prefractal](doc/prefractal.md), a nested FROST+MuSig2 signer that lets a FROST group occupy one participant slot of an ordinary MuSig2 (BIP 327) session.
 
 Experimental features are made available for testing and review by the community. The APIs of these features should not be considered stable.
 
diff --git a/ci/ci.sh b/ci/ci.sh
index e3bab1a6..b11e220c 100755
--- a/ci/ci.sh
+++ b/ci/ci.sh
@@ -15,7 +15,7 @@ print_environment() {
             ECMULTWINDOW ECMULTGENKB ASM WIDEMUL WITH_VALGRIND EXTRAFLAGS \
             EXPERIMENTAL ECDH RECOVERY EXTRAKEYS SCHNORRSIG MUSIG SCHNORRSIG_HALFAGG ELLSWIFT \
             ECDSA_S2C GENERATOR RANGEPROOF SURJECTIONPROOF WHITELIST ECDSAADAPTOR BPPP \
-            FROST CHILLDKG ICEBERG SECP256K1_TEST_ITERS BENCH SECP256K1_BENCH_ITERS CTIMETESTS SYMBOL_CHECK \
+            FROST CHILLDKG ICEBERG PREFRACTAL SECP256K1_TEST_ITERS BENCH SECP256K1_BENCH_ITERS CTIMETESTS SYMBOL_CHECK \
             EXAMPLES \
             HOST WRAPPER_CMD \
             CC CFLAGS CPPFLAGS AR NM \
@@ -72,6 +72,7 @@ fi
     --enable-module-frost="$FROST" \
     --enable-module-chilldkg="$CHILLDKG" \
     --enable-module-iceberg="$ICEBERG" \
+    --enable-module-prefractal="$PREFRACTAL" \
     --enable-examples="$EXAMPLES" \
     --enable-ctime-tests="$CTIMETESTS" \
     --with-valgrind="$WITH_VALGRIND" \