https://en.bitcoin.it/w/index.php?action=history&feed=atom&title=Ephemeral_anchor
Ephemeral anchor - Revision history
2026-09-04T04:58:47Z
Revision history for this page on the wiki
MediaWiki 1.43.9
https://en.bitcoin.it/w/index.php?title=Ephemeral_anchor&diff=71141&oldid=prev
NotATether: expand: Lightning option_anchors (330 sats, OP_16 CSV) and ephemeral P2A
2026-09-03T10:02:28Z
<p>expand: Lightning option_anchors (330 sats, OP_16 CSV) and ephemeral P2A</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 10:02, 3 September 2026</td>
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<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>An '''ephemeral anchor''' is a <del style="font-weight: bold; text-decoration: none;">fee</del>-<del style="font-weight: bold; text-decoration: none;">bumping </del>output that is created and spent in the same unconfirmed package, so it never persists in the UTXO set. <del style="font-weight: bold; text-decoration: none;">The </del>parent transaction <del style="font-weight: bold; text-decoration: none;">may pay </del>a <del style="font-weight: bold; text-decoration: none;">zero fee</del>. A child spends the anchor <del style="font-weight: bold; text-decoration: none;">and pays </del>the fee <del style="font-weight: bold; text-decoration: none;">for both</del>. Bitcoin Core <del style="font-weight: bold; text-decoration: none;">policy does this </del>with version-3 <del style="font-weight: bold; text-decoration: none;">(TRUC) transactions</del>, <del style="font-weight: bold; text-decoration: none;">a keyless </del>Pay-to-anchor (<del style="font-weight: bold; text-decoration: none;">P2A</del>) <del style="font-weight: bold; text-decoration: none;">script, and </del>an <del style="font-weight: bold; text-decoration: none;">ephemeral</del>-dust <del style="font-weight: bold; text-decoration: none;">rule </del>that <del style="font-weight: bold; text-decoration: none;">allows a </del>zero<del style="font-weight: bold; text-decoration: none;">-</del>value <del style="font-weight: bold; text-decoration: none;">output </del>when a child in the same package spends it.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>An '''ephemeral anchor''' is a <ins style="font-weight: bold; text-decoration: none;">keyless Pay-to</ins>-<ins style="font-weight: bold; text-decoration: none;">anchor (P2A) </ins>output that is created and spent in the same unconfirmed <ins style="font-weight: bold; text-decoration: none;">[[TRUC]] </ins>package, so it never persists in the UTXO set. <ins style="font-weight: bold; text-decoration: none;">A child-pays-for-</ins>parent transaction <ins style="font-weight: bold; text-decoration: none;">can attach fees at broadcast time.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Lightning Network commitments used an earlier related form. BOLT 3 <code>option_anchors</code> puts </ins>a <ins style="font-weight: bold; text-decoration: none;">keyed 330-satoshi P2WSH on the commitment for each party. The owner can spend it immediately. After 16 blocks anyone can sweep it (<code>OP_16 CHECKSEQUENCEVERIFY</code>)</ins>.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">== Lightning option_anchors ==</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A <ins style="font-weight: bold; text-decoration: none;">Lightning commitment transaction is signed long before it is broadcast, so the feerate that will be required is unknown. BOLT 3 <code>option_anchors</code> adds <code>to_local_anchor</code> and <code>to_remote_anchor</code> outputs so each party can attach a </ins>child <ins style="font-weight: bold; text-decoration: none;">that pays fees.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Each output is a P2WSH whose witness script requires that party's funding key, or, after 16 blocks, any spend (<code>OP_16 CHECKSEQUENCEVERIFY</code>). The amount is fixed at 330 satoshis, the default dust limit for P2WSH. The owner can spend the anchor immediately with a signature. After 16 blocks anyone can sweep it, which limits UTXO-set pollution if it is left unspent.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The 1-block CSV delay in BOLT 3 applies to the <code>to_remote</code> output and to HTLC </ins>spends <ins style="font-weight: bold; text-decoration: none;">under <code>option_anchors</code>, not to </ins>the anchor <ins style="font-weight: bold; text-decoration: none;">itself.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Two keyed anchors exist so that a counterparty cannot occupy </ins>the <ins style="font-weight: bold; text-decoration: none;">only </ins>fee<ins style="font-weight: bold; text-decoration: none;">-bumping output</ins>. Bitcoin Core<ins style="font-weight: bold; text-decoration: none;">'s CPFP carve-out lets a second child attach despite ordinary descendant limits. Carve-out is not granted to [[TRUC]] transactions.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Lightning <code>zero_fee_commitments</code> replaces the two keyed anchors </ins>with <ins style="font-weight: bold; text-decoration: none;">a single shared P2A output on a </ins>version-3 <ins style="font-weight: bold; text-decoration: none;">commitment, described below.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">== Ephemeral anchors ==</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">An ephemeral anchor is created and spent in the same unconfirmed package</ins>, <ins style="font-weight: bold; text-decoration: none;">so it does not remain in the UTXO set. BIP 433 defines </ins>Pay-to-anchor <ins style="font-weight: bold; text-decoration: none;">as the native segwit script <code>OP_1 &lt;0x4e73&gt;</code> </ins>(<ins style="font-weight: bold; text-decoration: none;">mainnet address <code>bc1pfeessrawgf</code></ins>)<ins style="font-weight: bold; text-decoration: none;">. Spending it requires </ins>an <ins style="font-weight: bold; text-decoration: none;">empty witness. Anyone can attach the child.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Ephemeral</ins>-dust <ins style="font-weight: bold; text-decoration: none;">policy allows </ins>that <ins style="font-weight: bold; text-decoration: none;">output to be below dust, including </ins>zero value<ins style="font-weight: bold; text-decoration: none;">, </ins>when a child in the same package spends it<ins style="font-weight: bold; text-decoration: none;">. The parent may pay a zero fee. [[TRUC]] (BIP 431) restricts the package to one unconfirmed parent and one unconfirmed child, limits the parent to 10,000 vB and the child to 1,000 vB, and treats the transactions as replaceable. Those caps bound pinning of a keyless output by an oversized low-feerate child</ins>.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== See also ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== See also ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">* [[TRUC]]</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Lightning Network]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Lightning Network]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Transaction]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [[Transaction]]</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>== External links ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">* [https://github.com/lightning/bolts/blob/master/03-transactions.md BOLT 3: Bitcoin Transaction and Script Formats]</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [https://github.com/bitcoin/bips/blob/master/bip-0431.mediawiki BIP 431: Topology Restrictions for Pinning (TRUC)]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [https://github.com/bitcoin/bips/blob/master/bip-0431.mediawiki BIP 431: Topology Restrictions for Pinning (TRUC)]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [https://github.com/bitcoin/bips/blob/master/bip-0433.mediawiki BIP 433: Pay to Anchor (P2A)]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* [https://github.com/bitcoin/bips/blob/master/bip-0433.mediawiki BIP 433: Pay to Anchor (P2A)]</div></td></tr>
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NotATether
https://en.bitcoin.it/w/index.php?title=Ephemeral_anchor&diff=71138&oldid=prev
NotATether: stub: ephemeral anchor (P2A + ephemeral dust, spent in-package)
2026-09-03T07:17:25Z
<p>stub: ephemeral anchor (P2A + ephemeral dust, spent in-package)</p>
<p><b>New page</b></p><div>An '''ephemeral anchor''' is a fee-bumping output that is created and spent in the same unconfirmed package, so it never persists in the UTXO set. The parent transaction may pay a zero fee. A child spends the anchor and pays the fee for both. Bitcoin Core policy does this with version-3 (TRUC) transactions, a keyless Pay-to-anchor (P2A) script, and an ephemeral-dust rule that allows a zero-value output when a child in the same package spends it.<br />
<br />
== See also ==<br />
<br />
* [[Lightning Network]]<br />
* [[Transaction]]<br />
<br />
== External links ==<br />
<br />
* [https://github.com/bitcoin/bips/blob/master/bip-0431.mediawiki BIP 431: Topology Restrictions for Pinning (TRUC)]<br />
* [https://github.com/bitcoin/bips/blob/master/bip-0433.mediawiki BIP 433: Pay to Anchor (P2A)]<br />
* [https://bitcoinops.org/en/topics/ephemeral-anchors/ Bitcoin Optech: Ephemeral anchors]<br />
<br />
[[Category:Technical]]</div>
NotATether