diff --git a/.github/actions/resolve-targets/action.yml b/.github/actions/resolve-targets/action.yml
new file mode 100644
index 00000000..cf9f57e4
--- /dev/null
+++ b/.github/actions/resolve-targets/action.yml
@@ -0,0 +1,28 @@
+name: Resolve fuzz target matrix
+description: >
+  Parse fuzz/Cargo.toml (the single source of truth) and emit every
+  `[[bin]] name = "fuzz_*"` target as a compact JSON array, ready to feed a
+  `strategy.matrix.target`. The repository must already be checked out.
+
+outputs:
+  targets:
+    description: JSON array of fuzz target names, in Cargo.toml order.
+    value: ${{ steps.list.outputs.targets }}
+
+runs:
+  using: composite
+  steps:
+    - id: list
+      shell: bash
+      run: |
+        # Same source of truth enforced by scripts/check_target_inventory.py.
+        targets=$(grep -oE 'name = "fuzz_[a-z0-9_]+"' fuzz/Cargo.toml \
+          | sed -E 's/.*"(fuzz_[a-z0-9_]+)"/\1/' \
+          | awk '!seen[$0]++' \
+          | jq -R -s -c 'split("\n") | map(select(length > 0))')
+        if [ "$targets" = "[]" ] || [ -z "$targets" ]; then
+          echo "ERROR: no fuzz_* [[bin]] targets found in fuzz/Cargo.toml" >&2
+          exit 1
+        fi
+        echo "targets=$targets" >> "$GITHUB_OUTPUT"
+        echo "Resolved targets: $targets"
diff --git a/.github/actions/setup-afl/action.yml b/.github/actions/setup-afl/action.yml
new file mode 100644
index 00000000..65ef59d7
--- /dev/null
+++ b/.github/actions/setup-afl/action.yml
@@ -0,0 +1,35 @@
+name: Set up AFL++ toolchain
+description: >
+  Build and install AFL++ from source, then install the Rust stable toolchain
+  and cargo-afl. The repository must already be checked out before this runs.
+
+inputs:
+  afl-version:
+    description: AFL++ git tag to build from source.
+    required: false
+    default: v4.40c
+
+runs:
+  using: composite
+  steps:
+    - name: Install AFL++ ${{ inputs.afl-version }} from source
+      shell: bash
+      run: |
+        sudo apt-get update -q
+        sudo apt-get install -y \
+          build-essential python3-dev automake cmake \
+          flex bison libglib2.0-dev libpixman-1-dev \
+          python3-setuptools ninja-build
+        git clone --depth 1 --branch ${{ inputs.afl-version }} \
+          https://github.com/AFLplusplus/AFLplusplus /tmp/aflplusplus
+        cd /tmp/aflplusplus
+        make distrib
+        sudo make install
+        afl-fuzz --version
+
+    - name: Install Rust (stable)
+      uses: dtolnay/rust-toolchain@stable
+
+    - name: Install cargo-afl
+      shell: bash
+      run: cargo install cargo-afl --locked
diff --git a/.github/actions/setup-libfuzzer/action.yml b/.github/actions/setup-libfuzzer/action.yml
new file mode 100644
index 00000000..3a22d865
--- /dev/null
+++ b/.github/actions/setup-libfuzzer/action.yml
@@ -0,0 +1,17 @@
+name: Set up libFuzzer toolchain
+description: >
+  Install the Rust nightly toolchain (with llvm-tools-preview, required by
+  cargo-fuzz and llvm-cov) and cargo-fuzz itself. The repository and
+  logos-execution-zone must already be checked out before this runs.
+
+runs:
+  using: composite
+  steps:
+    - name: Install Rust nightly + llvm-tools-preview
+      uses: dtolnay/rust-toolchain@nightly
+      with:
+        components: llvm-tools-preview
+
+    - name: Install cargo-fuzz
+      shell: bash
+      run: cargo install cargo-fuzz
diff --git a/.github/workflows/corpus-update.yml b/.github/workflows/corpus-update.yml
new file mode 100644
index 00000000..31a334d5
--- /dev/null
+++ b/.github/workflows/corpus-update.yml
@@ -0,0 +1,443 @@
+name: Corpus update
+
+# Fully-automated weekly corpus maintenance.
+#
+#   Every Sunday, for each fuzz target (libFuzzer + AFL++ lanes, in parallel):
+#     Phase 1 — GROW:     fuzz for 30 min starting from the checked-in corpus,
+#                         keeping every new input it discovers.
+#     Phase 2 — MINIMISE: re-minimise that target's *entire* corpus
+#                         (cmin / afl-cmin) so dominated inputs are dropped and
+#                         the tree never balloons.
+#
+#   Corpus minimisation is per-target by construction (each target has its own
+#   corpus dir + its own instrumented binary), so running Phase 2 right after
+#   Phase 1 inside the same job is equivalent to a separate global minimise pass
+#   — without shipping the whole corpus between jobs.
+#
+#   Every per-target result is uploaded as an artifact; a single `commit` job
+#   aggregates them into ONE pull request. Matrix jobs never push, so they never
+#   race on the branch. The PR is opened with a classic PAT (secret
+#   CORPUS_BOT_TOKEN).
+
+on:
+  schedule:
+    - cron: "0 3 * * 0"     # Sundays, 03:00 UTC
+  workflow_dispatch:
+    inputs:
+      duration:
+        description: "Seconds to fuzz per target in the grow phase"
+        required: false
+        default: "1800"
+      minimize_only:
+        description: "Skip fuzzing; only minimise the existing corpus"
+        type: boolean
+        default: false
+
+env:
+  RISC0_DEV_MODE: "1"
+  CARGO_TERM_COLOR: always
+
+permissions:
+  contents: read
+
+jobs:
+  # ── Resolve the target matrix + run parameters ────────────────────────────────
+  config:
+    name: Resolve matrix & config
+    runs-on: ubuntu-latest
+    outputs:
+      targets: ${{ steps.targets.outputs.targets }}
+      duration: ${{ steps.cfg.outputs.duration }}
+      minimize_only: ${{ steps.cfg.outputs.minimize_only }}
+    steps:
+      - uses: actions/checkout@v4
+      - id: targets
+        uses: ./.github/actions/resolve-targets
+      - id: cfg
+        run: |
+          if [ "${{ github.event_name }}" = "workflow_dispatch" ]; then
+            DUR="${{ inputs.duration }}"
+            MIN="${{ inputs.minimize_only }}"
+          else
+            DUR="1800"      # scheduled weekly grow: 30 minutes per target
+            MIN="false"
+          fi
+          [ -n "$DUR" ] || DUR="1800"
+          [ -n "$MIN" ] || MIN="false"
+          echo "duration=$DUR"          >> "$GITHUB_OUTPUT"
+          echo "minimize_only=$MIN"     >> "$GITHUB_OUTPUT"
+          echo "duration=${DUR}s minimize_only=${MIN}"
+
+  # ── libFuzzer lane: grow 30 min, then minimise ────────────────────────────────
+  libfuzz:
+    name: "libFuzzer — ${{ matrix.target }}"
+    needs: config
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        target: ${{ fromJSON(needs.config.outputs.targets) }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./.github/actions/checkout-lez
+      - name: Install logos-blockchain-circuits
+        uses: ./logos-execution-zone/.github/actions/install-logos-blockchain-circuits
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+      - uses: ./.github/actions/setup-libfuzzer
+
+      - name: Build fuzz target
+        run: cargo fuzz build ${{ matrix.target }}
+
+      - name: "Phase 1 — grow (fuzz ${{ needs.config.outputs.duration }}s)"
+        if: needs.config.outputs.minimize_only != 'true'
+        run: |
+          T="${{ matrix.target }}"
+          mkdir -p "corpus/libfuzz/$T"
+          before=$(ls "corpus/libfuzz/$T" | wc -l)
+          cargo fuzz run "$T" "corpus/libfuzz/$T" -- \
+            -max_total_time=${{ needs.config.outputs.duration }} -jobs=2 -workers=2
+          echo "grew corpus/libfuzz/$T: $before → $(ls "corpus/libfuzz/$T" | wc -l) inputs"
+
+      - name: "Phase 2 — minimise entire corpus (cmin)"
+        run: |
+          T="${{ matrix.target }}"
+          mkdir -p "corpus/libfuzz/$T"
+          before=$(ls "corpus/libfuzz/$T" | wc -l)
+          cargo fuzz cmin "$T" "corpus/libfuzz/$T"
+          echo "minimised corpus/libfuzz/$T: $before → $(ls "corpus/libfuzz/$T" | wc -l) inputs"
+
+      - name: Upload corpus
+        uses: actions/upload-artifact@v4
+        with:
+          name: libfuzz-corpus-${{ matrix.target }}
+          path: corpus/libfuzz/${{ matrix.target }}/
+          if-no-files-found: ignore
+
+      - name: Upload crash artifacts
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: libfuzz-crash-${{ matrix.target }}
+          path: fuzz/artifacts/${{ matrix.target }}/
+          if-no-files-found: ignore
+
+  # ── AFL++ lane: grow 30 min, then minimise ────────────────────────────────────
+  afl:
+    name: "AFL++ — ${{ matrix.target }}"
+    needs: config
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        target: ${{ fromJSON(needs.config.outputs.targets) }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./.github/actions/checkout-lez
+      - name: Install logos-blockchain-circuits
+        uses: ./logos-execution-zone/.github/actions/install-logos-blockchain-circuits
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+      - uses: ./.github/actions/setup-afl
+
+      - name: Build AFL++ target
+        run: |
+          cargo afl build \
+            --manifest-path fuzz/Cargo.toml \
+            --no-default-features \
+            --features fuzzer-afl \
+            --release \
+            --bin ${{ matrix.target }}
+
+      - name: Prepare seed corpus
+        if: needs.config.outputs.minimize_only != 'true'
+        run: |
+          T="${{ matrix.target }}"
+          SEEDS="afl-seeds/$T"
+          mkdir -p "$SEEDS"
+          for src in "corpus/libfuzz/$T" "corpus/afl/$T"; do
+            [ -d "$src" ] || continue
+            for f in "$src"/*; do [ -f "$f" ] && cp -n "$f" "$SEEDS/" 2>/dev/null || true; done
+          done
+          [ -n "$(ls -A "$SEEDS")" ] || echo -n "seed" > "$SEEDS/default_seed"
+          echo "Seed inputs: $(ls "$SEEDS" | wc -l)"
+
+      - name: "Phase 1 — grow (AFL++ ${{ needs.config.outputs.duration }}s)"
+        if: needs.config.outputs.minimize_only != 'true'
+        env:
+          AFL_SKIP_CPUFREQ: "1"
+          AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES: "1"
+        run: |
+          T="${{ matrix.target }}"
+          mkdir -p "afl-output/$T"
+          set +e
+          timeout ${{ needs.config.outputs.duration }} \
+            afl-fuzz -i "afl-seeds/$T" -o "afl-output/$T" -- "fuzz/target/release/$T"
+          rc=$?
+          set -e
+          # 124 = SIGALRM from timeout (expected end); 0 = clean exit; else real failure
+          [ $rc -eq 0 ] || [ $rc -eq 124 ] || exit $rc
+
+      - name: Sync new queue entries into corpus/afl
+        if: needs.config.outputs.minimize_only != 'true'
+        run: |
+          T="${{ matrix.target }}"
+          DEST="corpus/afl/$T"
+          mkdir -p "$DEST"
+          added=0
+          for instance_dir in "afl-output/$T"/*/; do
+            QUEUE="${instance_dir}queue"
+            [ -d "$QUEUE" ] || continue
+            for f in "$QUEUE"/id:*; do
+              [ -f "$f" ] || continue
+              HASH=$(sha1sum "$f" | cut -d' ' -f1)
+              if [ ! -f "$DEST/$HASH" ]; then
+                cp "$f" "$DEST/$HASH"
+                added=$((added + 1))
+              fi
+            done
+          done
+          echo "grew corpus/afl/$T → $(ls "$DEST" | wc -l) inputs (+$added new)"
+
+      - name: "Phase 2 — minimise entire corpus (afl-cmin)"
+        env:
+          AFL_SKIP_CPUFREQ: "1"
+          AFL_I_DONT_CARE_ABOUT_MISSING_CRASHES: "1"
+        run: |
+          T="${{ matrix.target }}"
+          SRC="corpus/afl/$T"
+          if [ ! -d "$SRC" ] || [ -z "$(ls -A "$SRC" 2>/dev/null)" ]; then
+            echo "corpus/afl/$T is empty — nothing to minimise."
+            exit 0
+          fi
+          before=$(ls "$SRC" | wc -l)
+          # afl-cmin can fail on pathological corpora; fall back to leaving SRC as-is.
+          if afl-cmin -i "$SRC" -o "afl-cmin/$T" -- "fuzz/target/release/$T"; then
+            rm -rf "$SRC"
+            mkdir -p "$SRC"
+            cp "afl-cmin/$T"/* "$SRC"/ 2>/dev/null || true
+          else
+            echo "afl-cmin failed — keeping corpus/afl/$T unchanged."
+          fi
+          echo "minimised corpus/afl/$T: $before → $(ls "$SRC" | wc -l) inputs"
+
+      - name: Upload corpus
+        uses: actions/upload-artifact@v4
+        with:
+          name: afl-corpus-${{ matrix.target }}
+          path: corpus/afl/${{ matrix.target }}/
+          if-no-files-found: ignore
+
+      - name: Package AFL findings on failure
+        if: failure()
+        run: |
+          T="${{ matrix.target }}"
+          # AFL filenames contain colons (forbidden by upload-artifact) — tar them.
+          tar -czf "afl-findings-$T.tar.gz" -C afl-output "$T" 2>/dev/null \
+            || tar -czf "afl-findings-$T.tar.gz" -T /dev/null
+      - name: Upload AFL findings on failure
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: afl-crash-${{ matrix.target }}
+          path: afl-findings-${{ matrix.target }}.tar.gz
+          if-no-files-found: ignore
+
+  # ── Aggregate every per-target corpus into ONE pull request ───────────────────
+  commit:
+    name: Open corpus update PR
+    needs: [config, libfuzz, afl]
+    # Run as long as config succeeded; individual matrix failures (fail-fast:false)
+    # must not block the PR for the targets that did succeed.
+    if: ${{ !cancelled() && needs.config.result == 'success' }}
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+
+      - name: Download corpus artifacts
+        uses: actions/download-artifact@v4
+        with:
+          path: corpus-artifacts
+          pattern: "*-corpus-*"     # libfuzz-corpus-* and afl-corpus-* only
+          merge-multiple: false
+        continue-on-error: true
+
+      - name: Apply corpus deltas to the working tree
+        run: |
+          shopt -s nullglob
+          applied=0
+          # Replace per-target dirs only for targets that produced an artifact, so a
+          # crashed/skipped target never has its checked-in corpus deleted. Replacing
+          # (rm + repopulate) lets cmin-driven deletions show up in the PR diff.
+          for d in corpus-artifacts/libfuzz-corpus-*; do
+            t="${d##*/libfuzz-corpus-}"
+            rm -rf "corpus/libfuzz/$t"; mkdir -p "corpus/libfuzz/$t"
+            cp "$d"/* "corpus/libfuzz/$t/" 2>/dev/null || true
+            applied=$((applied + 1))
+          done
+          for d in corpus-artifacts/afl-corpus-*; do
+            t="${d##*/afl-corpus-}"
+            rm -rf "corpus/afl/$t"; mkdir -p "corpus/afl/$t"
+            cp "$d"/* "corpus/afl/$t/" 2>/dev/null || true
+            applied=$((applied + 1))
+          done
+          echo "Applied corpus for $applied target lane(s)."
+          echo "Changed files: $(git status --porcelain corpus | wc -l)"
+
+      - name: Summarise corpus changes for the PR body
+        id: summary
+        env:
+          RUN_URL: "${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
+          RUN_ID: "${{ github.run_id }}"
+          DURATION: "${{ needs.config.outputs.duration }}"
+        run: |
+          set -euo pipefail
+
+          BODY="$RUNNER_TEMP/pr-body.md"
+          UNUSUAL="$RUNNER_TEMP/unusual.txt"
+          OUTSIDE="$RUNNER_TEMP/outside.txt"
+          : > "$UNUSUAL"; : > "$OUTSIDE"
+
+          # Scan the working tree (not just corpus/) so anything touched outside
+          # corpus/ is surfaced for the reviewer. Exclude corpus-artifacts.
+          mapfile -t changes < <(git status --porcelain --untracked-files=all -- ':(exclude)corpus-artifacts')
+
+          added=0; deleted=0; modified=0; other=0
+          declare -A tgt_add tgt_del tgt_mod
+          for line in "${changes[@]}"; do
+            x="${line:0:2}"
+            path="${line:3}"
+            # "old -> new" for renames; keep the destination path.
+            case "$path" in *" -> "*) path="${path##* -> }";; esac
+            # git C-quotes odd names — drop the surrounding quotes for display.
+            path="${path%\"}"; path="${path#\"}"
+
+            case "$x" in
+              "??"|"A "|"AM") added=$((added+1));    cls=add ;;
+              " D"|"D ")      deleted=$((deleted+1)); cls=del ;;
+              " M"|"M "|"MM") modified=$((modified+1)); cls=mod ;;
+              *)              other=$((other+1));     cls=other ;;
+            esac
+
+            case "$path" in
+              corpus/*) ;;
+              *) printf '%s  %s\n' "$x" "$path" >> "$OUTSIDE" ;;
+            esac
+
+            base="${path##*/}"
+            if [[ "$path" == corpus/* ]] && ! [[ "$base" =~ ^[0-9a-f]{40}$ ]]; then
+              printf '%s  %s\n' "$x" "$path" >> "$UNUSUAL"
+            fi
+
+            if [[ "$path" =~ ^corpus/(libfuzz|afl)/([^/]+)/ ]]; then
+              key="${BASH_REMATCH[1]}/${BASH_REMATCH[2]}"
+              case "$cls" in
+                add) tgt_add[$key]=$(( ${tgt_add[$key]:-0} + 1 )) ;;
+                del) tgt_del[$key]=$(( ${tgt_del[$key]:-0} + 1 )) ;;
+                mod) tgt_mod[$key]=$(( ${tgt_mod[$key]:-0} + 1 )) ;;
+              esac
+            fi
+          done
+          total=${#changes[@]}
+
+          {
+            echo "Automated weekly corpus update produced by"
+            echo "\`.github/workflows/corpus-update.yml\` (run [#${RUN_ID}](${RUN_URL}))."
+            echo
+            echo "Per target, in parallel: **Phase 1** fuzzed ${DURATION}s (libFuzzer + AFL++),"
+            echo "**Phase 2** re-minimised the entire corpus (\`cmin\` / \`afl-cmin\`)."
+            echo
+            echo "## Change statistics"
+            echo
+            echo "| Metric | Count |"
+            echo "| --- | ---: |"
+            echo "| Files changed | ${total} |"
+            echo "| Added | ${added} |"
+            echo "| Deleted | ${deleted} |"
+            echo "| Modified | ${modified} |"
+            [ "$other" -gt 0 ] && echo "| Other status | ${other} |"
+            echo
+          } > "$BODY"
+
+          if [ "${#tgt_add[@]}" -gt 0 ] || [ "${#tgt_del[@]}" -gt 0 ] || [ "${#tgt_mod[@]}" -gt 0 ]; then
+            {
+              echo "### Per target"
+              echo
+              echo "| Corpus | Added | Deleted | Modified |"
+              echo "| --- | ---: | ---: | ---: |"
+              printf '%s\n' "${!tgt_add[@]}" "${!tgt_del[@]}" "${!tgt_mod[@]}" \
+                | sort -u | while read -r key; do
+                  [ -n "$key" ] || continue
+                  echo "| \`$key\` | ${tgt_add[$key]:-0} | ${tgt_del[$key]:-0} | ${tgt_mod[$key]:-0} |"
+                done
+              echo
+            } >> "$BODY"
+          fi
+
+          # ── Reviewer flags ────────────────────────────────────────────────
+          emit_list() {  # title, file, intro
+            local title="$1" file="$2" intro="$3" n cap=50
+            n=$(wc -l < "$file" | tr -d ' ')
+            {
+              echo "### ⚠️ $title ($n)"
+              echo
+              echo "$intro"
+              echo
+              echo '```'
+              head -n "$cap" "$file"
+              [ "$n" -gt "$cap" ] && echo "... and $((n - cap)) more"
+              echo '```'
+              echo
+            } >> "$BODY"
+          }
+
+          flagged=0
+          if [ -s "$OUTSIDE" ]; then
+            flagged=1
+            emit_list "Files changed outside \`corpus/\`" "$OUTSIDE" \
+              "A corpus update should only touch \`corpus/\` — review these carefully."
+          fi
+          if [ -s "$UNUSUAL" ]; then
+            flagged=1
+            emit_list "Corpus files with unusual names" "$UNUSUAL" \
+              "Corpus inputs are normally named by their 40-char SHA-1. These are not:"
+          fi
+          if [ "$flagged" -eq 0 ]; then
+            echo "✅ All changes are under \`corpus/\` and named by SHA-1 as expected." >> "$BODY"
+            echo >> "$BODY"
+          fi
+
+          {
+            echo "---"
+            echo "Per-target corpora that crashed or were skipped are left untouched."
+            echo "Review the diff, confirm CI is green, and merge."
+          } >> "$BODY"
+
+          echo "body_path=$BODY" >> "$GITHUB_OUTPUT"
+          echo "::group::Generated PR body"; cat "$BODY"; echo "::endgroup::"
+
+      - name: Generate unique branch suffix
+        id: suffix
+        run: echo "value=$(LC_ALL=C tr -dc 'a-z' </dev/urandom | head -c 4)" >> "$GITHUB_OUTPUT"
+
+      - name: Create or update pull request
+        uses: peter-evans/create-pull-request@v6
+        with:
+          token: ${{ secrets.CORPUS_BOT_TOKEN }}
+          base: main
+          branch: automation/corpus-update-${{ steps.suffix.outputs.value }}
+          delete-branch: true
+          add-paths: |
+            corpus/libfuzz/**
+            corpus/afl/**
+          commit-message: "chore: weekly corpus update (grow + minimise)"
+          title: "chore: automated weekly corpus update"
+          labels: |
+            automation
+            corpus
+          body-path: ${{ steps.summary.outputs.body_path }}
diff --git a/.github/workflows/fuzz-afl.yml b/.github/workflows/fuzz-afl.yml
index dde2a9e7..d9188052 100644
--- a/.github/workflows/fuzz-afl.yml
+++ b/.github/workflows/fuzz-afl.yml
@@ -80,25 +80,8 @@ jobs:
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Install AFL++ v4.40c from source
-        run: |
-          sudo apt-get update -q
-          sudo apt-get install -y \
-            build-essential python3-dev automake cmake \
-            flex bison libglib2.0-dev libpixman-1-dev \
-            python3-setuptools ninja-build
-          git clone --depth 1 --branch v4.40c \
-            https://github.com/AFLplusplus/AFLplusplus /tmp/aflplusplus
-          cd /tmp/aflplusplus
-          make distrib
-          sudo make install
-          afl-fuzz --version
-
-      - name: Install Rust (stable)
-        uses: dtolnay/rust-toolchain@stable
-
-      - name: Install cargo-afl
-        run: cargo install cargo-afl --locked
+      - name: Set up AFL++ toolchain
+        uses: ./.github/actions/setup-afl
 
       - name: Build fuzz target
         run: |
diff --git a/.github/workflows/fuzz.yml b/.github/workflows/fuzz.yml
index b6b096cd..7a1046b0 100644
--- a/.github/workflows/fuzz.yml
+++ b/.github/workflows/fuzz.yml
@@ -55,11 +55,6 @@ jobs:
       - name: Checkout logos-execution-zone
         uses: ./.github/actions/checkout-lez
 
-      - name: Install Rust nightly (required by cargo-fuzz)
-        uses: dtolnay/rust-toolchain@nightly
-        with:
-          components: llvm-tools-preview
-
       - name: Cache cargo registry
         uses: actions/cache@v4
         with:
@@ -74,8 +69,7 @@ jobs:
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Install cargo-fuzz
-        run: cargo install cargo-fuzz
+      - uses: ./.github/actions/setup-libfuzzer
 
       - name: Build fuzz target
         run: cargo fuzz build ${{ matrix.target }}
@@ -242,14 +236,11 @@ jobs:
       - uses: actions/checkout@v4
       - name: Checkout logos-execution-zone
         uses: ./.github/actions/checkout-lez
-      - uses: dtolnay/rust-toolchain@nightly
-        with:
-          components: llvm-tools-preview
       - name: Install logos-blockchain-circuits
         uses: ./logos-execution-zone/.github/actions/install-logos-blockchain-circuits
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
-      - run: cargo install cargo-fuzz
+      - uses: ./.github/actions/setup-libfuzzer
       - name: Reproduce corpus
         run: |
           mkdir -p corpus/libfuzz/${{ matrix.target }}
@@ -282,14 +273,11 @@ jobs:
       - uses: actions/checkout@v4
       - name: Checkout logos-execution-zone
         uses: ./.github/actions/checkout-lez
-      - uses: dtolnay/rust-toolchain@nightly
-        with:
-          components: llvm-tools-preview
       - name: Install logos-blockchain-circuits
         uses: ./logos-execution-zone/.github/actions/install-logos-blockchain-circuits
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
-      - run: cargo install cargo-fuzz
+      - uses: ./.github/actions/setup-libfuzzer
       - name: Measure throughput (30 s per target)
         run: |
           for target in \
diff --git a/corpus/libfuzz/fuzz_multi_block_state_sequence/287c1358afcc2c83b86a03bd1f06e33811037527 b/corpus/libfuzz/fuzz_multi_block_state_sequence/287c1358afcc2c83b86a03bd1f06e33811037527
new file mode 100644
index 00000000..2d997a25
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diff --git a/corpus/libfuzz/fuzz_multi_block_state_sequence/957d6b0a369114d7315e4a379495636beabe3e5b b/corpus/libfuzz/fuzz_multi_block_state_sequence/957d6b0a369114d7315e4a379495636beabe3e5b
new file mode 100644
index 00000000..3e46c47c
Binary files /dev/null and b/corpus/libfuzz/fuzz_multi_block_state_sequence/957d6b0a369114d7315e4a379495636beabe3e5b differ
diff --git a/corpus/libfuzz/fuzz_multi_block_state_sequence/d2d347de29031b8ed90521f782aa96ec8bf3e83c b/corpus/libfuzz/fuzz_multi_block_state_sequence/d2d347de29031b8ed90521f782aa96ec8bf3e83c
new file mode 100644
index 00000000..7f2dee95
Binary files /dev/null and b/corpus/libfuzz/fuzz_multi_block_state_sequence/d2d347de29031b8ed90521f782aa96ec8bf3e83c differ
diff --git a/fuzz_props/src/generators.rs b/fuzz_props/src/generators.rs
index ca79628c..f1b6949d 100644
--- a/fuzz_props/src/generators.rs
+++ b/fuzz_props/src/generators.rs
@@ -59,19 +59,54 @@ pub struct FuzzAccount {
 /// conservation checks can therefore use `checked_add` instead of `saturating_add` to
 /// turn silent overflow into a detected violation, ruling out false-positive panics on
 /// legitimate fuzz inputs.
+///
+/// # Reserved-ID and duplicate exclusion
+///
+/// The cap above is only sound if every generated balance survives genesis construction
+/// unchanged.  Two failure modes break that:
+///
+/// * **Reserved system accounts.** [`nssa::V03State::new_with_genesis_accounts`] inserts
+///   the faucet account (`balance = u128::MAX`) and bridge account *after* the supplied
+///   genesis accounts, overwriting any generated account whose ID collides.  A fuzzer that
+///   lands on the faucet ID would make a caller read back `u128::MAX` instead of the capped
+///   balance it generated, overflowing the conservation sum — a harness false positive, not
+///   a protocol bug.
+/// * **Duplicate IDs.** Genesis stores accounts in a `HashMap` keyed by ID, so duplicate
+///   IDs collapse to a single (last-write-wins) account, while a caller's per-ID balance sum
+///   double-counts that account's balance.
+///
+/// Both are excluded here: generated IDs equal to a reserved system account, or already
+/// seen in this state, are skipped.  The result therefore contains only distinct,
+/// non-reserved IDs whose generated balances match what genesis stores — so `0..=8`
+/// accounts are returned (an empty state is a valid degenerate case).
 pub fn arbitrary_fuzz_state(u: &mut Unstructured<'_>) -> arbitrary::Result<Vec<FuzzAccount>> {
+    let reserved = [
+        nssa::system_faucet_account_id(),
+        nssa::system_bridge_account_id(),
+    ];
     let n = ((u8::arbitrary(u)? as usize) % 8) + 1; // 1..=8
-    std::iter::repeat_with(|| {
-        Ok(FuzzAccount {
-            account_id: ArbAccountId::arbitrary(u)?.0,
-            // Divide by 8 so the sum of 8 accounts is at most u128::MAX, preventing
-            // false-positive checked_add panics that would mask real inflation bugs.
-            balance: u128::arbitrary(u)? / 8,
-            private_key: ArbPrivateKey::arbitrary(u)?.0,
-        })
-    })
-    .take(n)
-    .collect()
+
+    let mut seen = std::collections::HashSet::with_capacity(n);
+    let mut accounts = Vec::with_capacity(n);
+    for _ in 0..n {
+        let account_id = ArbAccountId::arbitrary(u)?.0;
+        // Divide by 8 so the sum of 8 accounts is at most u128::MAX, preventing
+        // false-positive checked_add panics that would mask real inflation bugs.
+        let balance = u128::arbitrary(u)? / 8;
+        let private_key = ArbPrivateKey::arbitrary(u)?.0;
+
+        // Skip IDs that genesis would overwrite (reserved system accounts) or that would
+        // collapse on insertion (duplicates); see the doc comment above.
+        if reserved.contains(&account_id) || !seen.insert(account_id) {
+            continue;
+        }
+        accounts.push(FuzzAccount {
+            account_id,
+            balance,
+            private_key,
+        });
+    }
+    Ok(accounts)
 }
 
 /// Reduce raw fuzzer draws into a *biased-valid* `(nonce, amount)` pair.
diff --git a/fuzz_props/src/privacy.rs b/fuzz_props/src/privacy.rs
index 180700d7..5ae61a4c 100644
--- a/fuzz_props/src/privacy.rs
+++ b/fuzz_props/src/privacy.rs
@@ -230,7 +230,7 @@ pub fn arb_privacy_preserving_tx(
     }
     let n_extra = (u8::arbitrary(u)? as usize) % 4;
     for _ in 0..n_extra {
-        let id = if bool::arbitrary(u)? {
+        let id = if !accounts.is_empty() && bool::arbitrary(u)? {
             // a known fuzz account — its post-state change is observable in the snapshot
             accounts[(u8::arbitrary(u)? as usize) % accounts.len()].account_id
         } else {
diff --git a/fuzz_props/src/tests/generators.rs b/fuzz_props/src/tests/generators.rs
index ec5584b5..b3f2cfce 100644
--- a/fuzz_props/src/tests/generators.rs
+++ b/fuzz_props/src/tests/generators.rs
@@ -49,22 +49,37 @@ fn signer_ids_contains_the_signing_account() {
     );
 }
 
+/// A buffer whose bytes are all distinct within any 80-byte window (the per-account
+/// stride: 32 id + 16 balance + 32 key), so each generated account gets a distinct ID
+/// and the dedup pass in `arbitrary_fuzz_state` does not collapse the count.  Using
+/// `buf[i] = i` works because two account-ID windows starting at offsets `a` and `b`
+/// (both `< 256`) are equal only when `a ≡ b (mod 256)`, which never holds for the
+/// `1 + j*80` offsets of the first eight accounts.
+fn distinct_byte_buffer(len: usize) -> Vec<u8> {
+    (0_u8..=255).cycle().take(len).collect()
+}
+
 #[test]
-fn fuzz_state_never_empty() {
-    let buf = vec![0_u8; 1000];
+fn fuzz_state_never_empty_for_distinct_ids() {
+    // Selector byte 0 -> (0 % 8) + 1 = 1 account; distinct bytes keep it from being
+    // deduped away.  (An all-duplicate or all-reserved draw may legitimately return
+    // 0 accounts now — see `fuzz_state_dedups_account_ids` — so non-emptiness is only
+    // asserted for an input that yields distinct, non-reserved IDs.)
+    let buf = distinct_byte_buffer(1000);
     let mut u = Unstructured::new(&buf);
     let accounts = arbitrary_fuzz_state(&mut u).expect("should succeed");
     assert!(
         !accounts.is_empty(),
-        "arbitrary_fuzz_state must return at least 1 account (n = 1..=8); \
+        "arbitrary_fuzz_state must return at least 1 account for distinct-ID input; \
          returned 0 \u{2014} mutation: `+ 1` replaced by `* 1` or `Ok(vec![])`"
     );
 }
 
 #[test]
 fn fuzz_state_count_uses_modulo_not_div_or_add() {
-    // fill_buffer reads from the front; the first byte is the n-selector.
-    let mut buf = vec![0_u8; 1000];
+    // fill_buffer reads from the front; the first byte is the n-selector.  Distinct
+    // bytes give every account a unique ID so the count is not masked by dedup.
+    let mut buf = distinct_byte_buffer(1000);
     buf[0] = 8; // selector byte: 8 % 8 = 0, +1 -> n=1  |  8 / 8 = 1, +1 -> n=2  |  8 + 8 = 16, +1 -> n=17
     let mut u = Unstructured::new(&buf);
     let accounts = arbitrary_fuzz_state(&mut u).expect("should succeed");
@@ -76,6 +91,56 @@ fn fuzz_state_count_uses_modulo_not_div_or_add() {
     );
 }
 
+#[test]
+fn fuzz_state_excludes_reserved_system_ids() {
+    // Genesis overwrites the faucet (balance = u128::MAX) and bridge accounts after
+    // inserting the supplied genesis accounts; a generated account colliding with one
+    // would read back a balance the cap never produced, overflowing conservation sums.
+    // The generator must therefore never emit a reserved system ID.
+    let reserved = [
+        nssa::system_faucet_account_id(),
+        nssa::system_bridge_account_id(),
+    ];
+    let buf = distinct_byte_buffer(10_000);
+    let mut u = Unstructured::new(&buf);
+    let accounts = arbitrary_fuzz_state(&mut u).expect("should succeed");
+    for acc in &accounts {
+        assert!(
+            !reserved.contains(&acc.account_id),
+            "arbitrary_fuzz_state emitted reserved system account ID {:?} \u{2014} \
+             genesis would overwrite it and break the balance-conservation invariant",
+            acc.account_id
+        );
+    }
+}
+
+#[test]
+fn fuzz_state_dedups_account_ids() {
+    // All-identical bytes make every drawn account ID identical; genesis stores
+    // accounts in a HashMap (last-write-wins), so duplicate IDs would let a per-ID
+    // balance sum double-count one account.  The generator must collapse them to one.
+    let buf = vec![0xAB_u8; 10_000];
+    let mut u = Unstructured::new(&buf);
+    let accounts = arbitrary_fuzz_state(&mut u).expect("should succeed");
+    assert!(
+        accounts.len() <= 1,
+        "arbitrary_fuzz_state must dedup identical account IDs; got {} accounts",
+        accounts.len()
+    );
+
+    // Independent confirmation on a distinct-ID draw: no ID appears twice.
+    let distinct_buf = distinct_byte_buffer(10_000);
+    let mut distinct_u = Unstructured::new(&distinct_buf);
+    let distinct_accounts = arbitrary_fuzz_state(&mut distinct_u).expect("should succeed");
+    let unique: std::collections::HashSet<_> =
+        distinct_accounts.iter().map(|a| a.account_id).collect();
+    assert_eq!(
+        unique.len(),
+        distinct_accounts.len(),
+        "arbitrary_fuzz_state returned duplicate account IDs"
+    );
+}
+
 /// Verifies that each account's balance is <= `u128::MAX / 8`.
 #[test]
 fn fuzz_state_balances_bounded_by_max_div_8() {
diff --git a/fuzz_props/src/tests/privacy.rs b/fuzz_props/src/tests/privacy.rs
index ad4a0d08..847c4392 100644
--- a/fuzz_props/src/tests/privacy.rs
+++ b/fuzz_props/src/tests/privacy.rs
@@ -257,6 +257,41 @@ fn arb_validity_window_bounds_use_modulo_8() {
 /// Two flavours of check run here: per-iteration upper bounds that must hold for
 /// *every* generated transaction, and end-of-run reachability checks that confirm
 /// the interesting shapes actually occur across the sampled inputs.
+/// Which branches of the line-233 `if !accounts.is_empty() && bool::arbitrary(u)?` were
+/// observable across a transaction's non-signer "extra" public-account ids.
+#[derive(Default)]
+struct ExtraKinds {
+    /// At least one extra (non-signer id) was appended at all.
+    any: bool,
+    /// An extra equal to a *known* fuzz-account id (the `&&`-true branch).
+    known: bool,
+    /// An extra that is a *random* id (the `else` branch).
+    random: bool,
+}
+
+/// Classify a message's extras. A signer's public-account id is key-derived and independent
+/// of `FuzzAccount.account_id`, so any non-signer id present in `public_account_ids` was
+/// appended by the line-233 `if`; a *known* id can only come from its `&&`-true branch.
+fn classify_extras(
+    public_account_ids: &[AccountId],
+    signer_ids: &[AccountId],
+    known_ids: &std::collections::HashSet<AccountId>,
+) -> ExtraKinds {
+    let mut kinds = ExtraKinds::default();
+    for id in public_account_ids {
+        if signer_ids.contains(id) {
+            continue;
+        }
+        kinds.any = true;
+        if known_ids.contains(id) {
+            kinds.known = true;
+        } else {
+            kinds.random = true;
+        }
+    }
+    kinds
+}
+
 #[test]
 fn arb_privacy_preserving_tx_generator_invariants() {
     let accounts: Vec<FuzzAccount> = (1..=6_u8)
@@ -270,6 +305,9 @@ fn arb_privacy_preserving_tx_generator_invariants() {
         accounts.iter().map(|a| (a.account_id, a.balance)).collect();
     let state = V03State::new_with_genesis_accounts(&genesis, vec![], 0);
 
+    let known_ids: std::collections::HashSet<AccountId> =
+        accounts.iter().map(|a| a.account_id).collect();
+
     let mut rng = Rng::new();
     let mut buf = vec![0_u8; 8192];
 
@@ -277,6 +315,8 @@ fn arb_privacy_preserving_tx_generator_invariants() {
     let mut max_signers = 0_usize;
     let mut saw_signer = false;
     let mut saw_extra = false;
+    let mut saw_known_extra = false;
+    let mut saw_random_extra = false;
     let mut max_commitments = 0_usize;
     let mut max_nullifiers = 0_usize;
     let mut saw_empty_comm_nonempty_null = false;
@@ -344,14 +384,12 @@ fn arb_privacy_preserving_tx_generator_invariants() {
             msg.encrypted_private_post_states.len()
         );
 
-        // An id that is not a signer can only be present because an extra was appended.
-        if msg
-            .public_account_ids
-            .iter()
-            .any(|id| !signer_ids.contains(id))
-        {
-            saw_extra = true;
-        }
+        // Classify the non-signer "extras" by which branch of the line-233 `if` produced
+        // them — a *known* fuzz-account id, a *random* id, or both.
+        let extras = classify_extras(&msg.public_account_ids, &signer_ids, &known_ids);
+        saw_extra |= extras.any;
+        saw_known_extra |= extras.known;
+        saw_random_extra |= extras.random;
 
         max_commitments = max_commitments.max(msg.new_commitments.len());
         max_nullifiers = max_nullifiers.max(msg.new_nullifiers.len());
@@ -393,6 +431,19 @@ fn arb_privacy_preserving_tx_generator_invariants() {
         saw_extra,
         "the generator never appended an extra public account id"
     );
+    // Both branches `if !accounts.is_empty() && bool::arbitrary(u)?` must be
+    // reachable. The known-account branch must fire (else `delete !` — which short-circuits to
+    // the random branch when accounts are present — would be indistinguishable)
+    assert!(
+        saw_known_extra,
+        "the generator never appended a *known* fuzz-account id as an extra"
+    );
+    // …and the random branch must fire (else `&&`→`||` — which short-circuits to the known
+    // branch when accounts are present — would be indistinguishable).
+    assert!(
+        saw_random_extra,
+        "the generator never appended a *random* id as an extra"
+    );
     // Multiple distinct commitments must be reachable (the dedup must keep, not drop).
     assert!(
         max_commitments >= 2,