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snapshot: docs.riftenlabs.com/cauldron/ (28 pages) - author: Riften Labs Backup of Cauldron docs at snapshot time. Canonical source of truth: https://docs.riftenlabs.com/cauldron/ Includes: whitepaper, liquidity/swap/yield/wallets, developer resources, knowledge base, and the full API section (bcmr, broadcast, cauldron, contract-subscribe, ido, moria_v11, oracle, root, tokenbch, tokentoken). Supporting CSS/JS bundle preserved so pages render offline.
2026-09-02 04:05:04 +02:00
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Transaction Broadcast API
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Unsubscribing
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Available Electrum Servers
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Notes
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DApp Integration
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HD Wallet &amp; Derivation Paths
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Token Rating
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Moria Protocol
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Borrowing, redeeming and liquidations
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<article class="md-content__inner md-typeset">
<h2 id="real-time-cauldron-tracking-api">Real-time Cauldron tracking API</h2>
<h1 id="cauldroncontractsubscribe">cauldron.contract.subscribe</h1>
<p><strong>Method:</strong> <code>cauldron.contract.subscribe</code></p>
<p><strong>Description:</strong> Subscribe to real-time notifications for Cauldron contract changes for a specific token. This is an Electrum API method that provides both initial state and ongoing updates when contracts are created, modified, or withdrawn.</p>
<h2 id="parameters">Parameters</h2>
<ul>
<li><code>contract_version</code> (integer): The contract version to subscribe to. Currently only version <code>2</code> is supported.</li>
<li><code>token_id</code> (string): The 32-byte token ID (category) to monitor for contract changes.</li>
</ul>
<h2 id="response">Response</h2>
<h3 id="initial-response">Initial Response</h3>
<p>When first subscribing, the server returns the current state of all active contracts for the specified token:</p>
<div class="highlight"><pre><span></span><code><span class="p">{</span>
<span class="w"> </span><span class="nt">"utxos"</span><span class="p">:</span><span class="w"> </span><span class="p">[</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="nt">"pkh"</span><span class="p">:</span><span class="w"> </span><span class="s2">"36c0020dd39e7cd66c21f237dc53d384661a557f"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"is_withdrawn"</span><span class="p">:</span><span class="w"> </span><span class="kc">false</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"spent_utxo_hash"</span><span class="p">:</span><span class="w"> </span><span class="s2">"0000000000000000000000000000000000000000000000000000000000000000"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"new_utxo_hash"</span><span class="p">:</span><span class="w"> </span><span class="s2">"a1b2c3d4e5f6789012345678901234567890123456789012345678901234567890"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"new_utxo_txid"</span><span class="p">:</span><span class="w"> </span><span class="s2">"94a933a0fa55093a0965eb867f1b9cac2bb07488ced4825bc31f86c9371f76aa"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"new_utxo_n"</span><span class="p">:</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"token_id"</span><span class="p">:</span><span class="w"> </span><span class="s2">"b79bfc8246b5fc4707e7c7dedcb6619ef1ab91f494a790c20b0f4c422ed95b92"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"sats"</span><span class="p">:</span><span class="w"> </span><span class="mi">776661580</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"token_amount"</span><span class="p">:</span><span class="w"> </span><span class="mi">16</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">],</span>
<span class="w"> </span><span class="nt">"type"</span><span class="p">:</span><span class="w"> </span><span class="s2">"initial"</span>
<span class="p">}</span>
</code></pre></div>
<h3 id="update-notifications">Update Notifications</h3>
<p>After the initial response, the client will receive JSON-RPC notifications whenever contracts change:</p>
<div class="highlight"><pre><span></span><code><span class="p">{</span>
<span class="w"> </span><span class="nt">"jsonrpc"</span><span class="p">:</span><span class="w"> </span><span class="s2">"2.0"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"method"</span><span class="p">:</span><span class="w"> </span><span class="s2">"cauldron.contract.subscribe"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"params"</span><span class="p">:</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="nt">"utxos"</span><span class="p">:</span><span class="w"> </span><span class="p">[</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="nt">"pkh"</span><span class="p">:</span><span class="w"> </span><span class="s2">"36c0020dd39e7cd66c21f237dc53d384661a557f"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"is_withdrawn"</span><span class="p">:</span><span class="w"> </span><span class="kc">false</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"spent_utxo_hash"</span><span class="p">:</span><span class="w"> </span><span class="s2">"0000000000000000000000000000000000000000000000000000000000000000"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"new_utxo_hash"</span><span class="p">:</span><span class="w"> </span><span class="s2">"a1b2c3d4e5f6789012345678901234567890123456789012345678901234567890"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"new_utxo_txid"</span><span class="p">:</span><span class="w"> </span><span class="s2">"94a933a0fa55093a0965eb867f1b9cac2bb07488ced4825bc31f86c9371f76aa"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"new_utxo_n"</span><span class="p">:</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"token_id"</span><span class="p">:</span><span class="w"> </span><span class="s2">"b79bfc8246b5fc4707e7c7dedcb6619ef1ab91f494a790c20b0f4c422ed95b92"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"sats"</span><span class="p">:</span><span class="w"> </span><span class="mi">776661580</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"token_amount"</span><span class="p">:</span><span class="w"> </span><span class="mi">16</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">],</span>
<span class="w"> </span><span class="nt">"type"</span><span class="p">:</span><span class="w"> </span><span class="s2">"update"</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
<h2 id="field-descriptions">Field Descriptions</h2>
<h3 id="contract-object-fields">Contract Object Fields</h3>
<ul>
<li><code>pkh</code> (string): The public key hash of the contract owner in hex format</li>
<li><code>is_withdrawn</code> (boolean): Whether the contract has been withdrawn</li>
<li><code>spent_utxo_hash</code> (string): Hash of the UTXO that was spent to create this contract (all zeros for new contracts)</li>
<li><code>new_utxo_hash</code> (string): Hash of the UTXO containing this contract</li>
<li><code>new_utxo_txid</code> (string): Transaction ID of the transaction containing this contract</li>
<li><code>new_utxo_n</code> (integer): Output index of the contract in the transaction</li>
<li><code>token_id</code> (string): The 32-byte token ID this contract is for</li>
<li><code>sats</code> (integer): Amount of satoshis locked in the contract</li>
<li><code>token_amount</code> (integer): Amount of tokens locked in the contract</li>
</ul>
<h3 id="utxo-hash-calculation">UTXO Hash Calculation</h3>
<p>Both <code>spent_utxo_hash</code> and <code>new_utxo_hash</code> are computed using the same algorithm:</p>
<div class="highlight"><pre><span></span><code>utxo_hash = sha256(txid + n)
</code></pre></div>
<p>Where:
- <code>txid</code> is the transaction ID (32 bytes, in internal byte order)
- <code>n</code> is the output index as a <strong>little-endian 32-bit unsigned integer</strong> (4 bytes)
- The result is a single SHA-256 hash (not double-SHA256)</p>
<h4 id="examples">Examples</h4>
<p><strong>Example 1: New Contract</strong></p>
<p>For a newly created contract:
- <code>spent_utxo_hash</code> = <code>"0000000000000000000000000000000000000000000000000000000000000000"</code> (all zeros, indicating no previous UTXO)
- <code>new_utxo_hash</code> is calculated from the contract's UTXO:
- txid: <code>94a933a0fa55093a0965eb867f1b9cac2bb07488ced4825bc31f86c9371f76aa</code>
- output index (<code>n</code>): <code>0</code>
- Calculate: <code>sha256(txid_bytes + little_endian_u32(0))</code></p>
<p><strong>Example 2: Modified Contract</strong></p>
<p>When a contract is modified (e.g., liquidity added/removed):
- <code>spent_utxo_hash</code> = hash of the previous contract UTXO (the one being spent)
- <code>new_utxo_hash</code> = hash of the new contract UTXO (the one being created)</p>
<h4 id="code-example">Code Example</h4>
<p><strong>Python:</strong>
<div class="highlight"><pre><span></span><code><span class="kn">import</span><span class="w"> </span><span class="nn">hashlib</span>
<span class="kn">import</span><span class="w"> </span><span class="nn">struct</span>
<span class="k">def</span><span class="w"> </span><span class="nf">calculate_utxo_hash</span><span class="p">(</span><span class="n">txid_hex</span><span class="p">:</span> <span class="nb">str</span><span class="p">,</span> <span class="n">output_index</span><span class="p">:</span> <span class="nb">int</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">str</span><span class="p">:</span>
<span class="w"> </span><span class="sd">"""Calculate UTXO hash from txid and output index.</span>
<span class="sd"> Args:</span>
<span class="sd"> txid_hex: Transaction ID as hex string (64 chars)</span>
<span class="sd"> output_index: Output index (0-based)</span>
<span class="sd"> Returns:</span>
<span class="sd"> UTXO hash as hex string (64 chars)</span>
<span class="sd"> """</span>
<span class="c1"># Convert txid from hex to bytes (internal byte order)</span>
<span class="n">txid_bytes</span> <span class="o">=</span> <span class="nb">bytes</span><span class="o">.</span><span class="n">fromhex</span><span class="p">(</span><span class="n">txid_hex</span><span class="p">)</span>
<span class="c1"># Convert output index to little-endian 32-bit unsigned int</span>
<span class="n">index_bytes</span> <span class="o">=</span> <span class="n">struct</span><span class="o">.</span><span class="n">pack</span><span class="p">(</span><span class="s1">'&lt;I'</span><span class="p">,</span> <span class="n">output_index</span><span class="p">)</span>
<span class="c1"># Concatenate and hash</span>
<span class="n">combined</span> <span class="o">=</span> <span class="n">txid_bytes</span> <span class="o">+</span> <span class="n">index_bytes</span>
<span class="n">utxo_hash</span> <span class="o">=</span> <span class="n">hashlib</span><span class="o">.</span><span class="n">sha256</span><span class="p">(</span><span class="n">combined</span><span class="p">)</span><span class="o">.</span><span class="n">digest</span><span class="p">()</span>
<span class="k">return</span> <span class="n">utxo_hash</span><span class="o">.</span><span class="n">hex</span><span class="p">()</span>
<span class="c1"># Example usage:</span>
<span class="n">txid</span> <span class="o">=</span> <span class="s2">"94a933a0fa55093a0965eb867f1b9cac2bb07488ced4825bc31f86c9371f76aa"</span>
<span class="n">output_index</span> <span class="o">=</span> <span class="mi">0</span>
<span class="n">hash_result</span> <span class="o">=</span> <span class="n">calculate_utxo_hash</span><span class="p">(</span><span class="n">txid</span><span class="p">,</span> <span class="n">output_index</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="sa">f</span><span class="s2">"UTXO hash: </span><span class="si">{</span><span class="n">hash_result</span><span class="si">}</span><span class="s2">"</span><span class="p">)</span>
</code></pre></div></p>
<h4 id="important-notes">Important Notes</h4>
<ul>
<li><strong>Byte Order:</strong> The txid must be in internal byte order (as stored in blocks/transactions), not display/RPC order. Most libraries handle this correctly when parsing hex txids.</li>
<li><strong>Index Encoding:</strong> The output index must be encoded as a <strong>little-endian</strong> 32-bit unsigned integer (4 bytes).</li>
<li><strong>Single SHA-256:</strong> Use SHA-256 once, not double-SHA256 (which is used elsewhere in Bitcoin Cash).</li>
<li><strong>All Zeros:</strong> A <code>spent_utxo_hash</code> of all zeros (<code>0000...0000</code>) indicates a newly created contract with no previous UTXO.</li>
</ul>
<h2 id="client-side-utxo-tracking">Client-Side UTXO Tracking</h2>
<p><strong>Important:</strong> You must track UTXOs client-side and update your local state from the notifications. The server does not topologically sort changes, so you need to process updates in two steps:</p>
<ol>
<li><strong>First, add all new UTXOs</strong> from the notification</li>
<li><strong>Then, remove all used UTXOs</strong> (those with <code>spent_utxo_hash</code> not all zeros)</li>
</ol>
<p>This two-step process ensures that UTXOs that are created and used within the same update are properly created and removed from local state.</p>
<h2 id="unsubscribing">Unsubscribing</h2>
<p>To stop receiving notifications, use the <code>cauldron.contract.unsubscribe</code> method:</p>
<div class="highlight"><pre><span></span><code><span class="p">{</span>
<span class="w"> </span><span class="nt">"jsonrpc"</span><span class="p">:</span><span class="w"> </span><span class="s2">"2.0"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"id"</span><span class="p">:</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"method"</span><span class="p">:</span><span class="w"> </span><span class="s2">"cauldron.contract.unsubscribe"</span><span class="p">,</span>
<span class="w"> </span><span class="nt">"params"</span><span class="p">:</span><span class="w"> </span><span class="p">[</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="s2">"b79bfc8246b5fc4707e7c7dedcb6619ef1ab91f494a790c20b0f4c422ed95b92"</span><span class="p">]</span>
<span class="p">}</span>
</code></pre></div>
<h2 id="available-electrum-servers">Available Electrum Servers</h2>
<p>You can connect to the following Electrum server that supports this API:</p>
<ul>
<li><strong>wss://rostrum.riften.net:443</strong></li>
</ul>
<h2 id="notes">Notes</h2>
<ul>
<li>This is an Electrum API method that uses WebSocket connections</li>
<li>The server maintains subscription limits per connection to prevent abuse</li>
<li>Notifications are sent in real-time as transactions are seen in the mempool.</li>
<li>The <code>type</code> field distinguishes between initial state (<code>"initial"</code>) and updates (<code>"update"</code>)</li>
<li>Contract withdrawals will have <code>is_withdrawn: true</code> in update notifications</li>
<li>Only contracts for the specified token ID will be included in notifications</li>
<li><strong>Important:</strong> Process UTXO updates in two steps: add new UTXOs first, then remove spent UTXOs</li>
</ul>
<h2 id="dapp-integration">DApp Integration</h2>
<p>If your dapp uses this API, please let us know. We need to know if the API should be maintained.</p>
<p>We're also interested to hear who would wants to host a Rostrum server with Cauldron subscription API. This feedback will be used as grounds open-sourcing such server software.</p>
<h2 id="error-handling">Error Handling</h2>
<p>Common error responses:</p>
<ul>
<li><code>Invalid contract version</code>: Only version 2 is currently supported</li>
<li><code>Invalid token ID</code>: The provided token ID is not a valid 32-byte hex string</li>
<li><code>Subscription limit exceeded</code>: Too many active subscriptions for this connection</li>
</ul>
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