Audit Chain

Verify every receipt in the audit trail, not just a single receipt. protect-mcp 0.7.4 appends receipts to receipts.jsonl in ./receipts/ (or the specified directory), one per line, and this command checks the signature on each line.

Usage

/audit-chain                    # Verify all receipts in ./receipts/
/audit-chain --last 50          # Verify only the last 50 receipts
/audit-chain --dir /var/log/receipts  # Use a different directory

What This Command Does

1. Reads receipts.jsonl in the target directory
2. Keeps only the last N lines when --last N is given
3. Verifies each Ed25519 signature against the publicKey value in ./protect-mcp.key (or the file named by PROTECT_MCP_KEY)
4. Reports the line number of each receipt that fails. With --last N, the verifier numbers the selected lines from 1, so the command prints the offset to add to get the line in receipts.jsonl

protect-mcp 0.7.4 receipts carry no link to the previous receipt, so this check cannot detect a deleted, inserted, or reordered line. To detect deleted lines, keep a copy of the receipts file where the operator cannot change it.

Implementation

RECEIPT_DIR="./receipts"; N=""
while [ $# -gt 0 ]; do
    case "$1" in
        --last|--dir)
            if [ $# -lt 2 ]; then
                echo "usage: /audit-chain [--last N] [--dir path]" >&2; exit 2
            fi
            if [ "$1" = "--last" ]; then
                case "$2" in
                    ''|*[!0-9]*) echo "--last takes a positive whole number" >&2; exit 2 ;;
                esac
                N="$2"
            else
                RECEIPT_DIR="$2"
            fi
            shift 2 ;;
        *) shift ;;
    esac
done
FILE="$RECEIPT_DIR/receipts.jsonl"
if [ -n "$N" ]; then
    N=$((10#$N))
    [ "$N" -gt 0 ] || { echo "--last takes a positive whole number" >&2; exit 2; }
    TOTAL=$(wc -l < "$FILE"); OFFSET=$(( TOTAL > N ? TOTAL - N : 0 ))
    echo "Checking lines $((OFFSET + 1)) to $((TOTAL)). Add $OFFSET to each reported line number."
    TMP="$(mktemp)"; tail -n "$N" "$FILE" > "$TMP"; FILE="$TMP"
fi
PUB=$(node -p 'JSON.parse(require("fs").readFileSync(process.env.PROTECT_MCP_KEY || "./protect-mcp.key")).publicKey')
npx @veritasacta/verify@0.9.2 --replay-chain "$FILE" --key "$PUB"

Exit 0 means every receipt verified. Exit 1 means at least one receipt failed, because it was tampered with, a line is malformed, the key is wrong or missing, or the algorithm is unsupported. With --replay-chain, the verifier reports those cases per line with exit 1. Exit 2 means the check could not run, e.g., because the file could not be read or an option had no value.

npx downloads @veritasacta/verify@0.9.2 the first time it runs. For an offline machine, install it in the project first with npm install --no-save @veritasacta/verify@0.9.2, and npx then runs the local copy without network access.

What to Show the User

All receipts verify

Audit verification: PASSED

Scanned:     247 receipts in ./receipts/receipts.jsonl
Signatures:  247/247 valid ✓
Key:         0faf558a90dfbf88...

All 247 receipts verify. A deleted or reordered line would not show here,
because 0.7.4 receipts carry no link to the previous receipt.

Tampered receipt

Audit verification: FAILED

Scanned:     247 receipts
Signatures:  246/247 valid (1 failed)

FAILED at line 89: invalid_signature
  Request:     tu-1790427588265-c8x5
  Tool:        Bash
  Issued at:   2026-09-26T14:22:01Z

The signature on this line does not verify, so the receipt was modified
after signing, or the key is not the signer's key. Compare the line against
a known-good copy to find the altered field.

When to Run This

• Before shipping a release, to confirm that no development receipt was altered
• During security audits, to show auditors that every receipt verifies
• After incidents — verify logs were not tampered with during the incident
• Periodically — CI/CD job to catch silent corruption
• Before compliance reviews — provide evidence of continuous integrity

References

• @veritasacta/verify on npm
• Use /verify-receipt for single-receipt verification