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[BIP-119] Make it abundantly clear that policy and standard are recommendations.
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bip-0119.mediawiki

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@@ -274,14 +274,14 @@ For the avoidance of unclarity, the parameters to be determined are:
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consensus.vDeployments[Consensus::DEPLOYMENT_CHECKTEMPLATEVERIFY].min_activation_height = 0;
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Until BIP-119 reaches ACTIVE state and the
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SCRIPT_VERIFY_DEFAULT_CHECK_TEMPLATE_VERIFY_HASH flag is set, the network should
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execute a NOP4 as SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS for policy and a NOP for
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consensus.
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SCRIPT_VERIFY_DEFAULT_CHECK_TEMPLATE_VERIFY_HASH flag is enforced, node implementations should (are recommended to)
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execute a NOP4 as SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS (to deny entry to the mempool) for policy and must evaluate as
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a NOP for consensus (during block validation).
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In order to facilitate using CHECKTEMPLATEVERIFY, the common case of a
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PayToBareDefaultCheckTemplateVerifyHash
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with no scriptSig data shall be made standard to permit relaying. Future template types may be
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standardized later as policy changes.
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with no scriptSig data may (is recommended to) be made standard to permit relaying. Future template types may be
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standardized later as policy changes at the preference of the implementor.
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==Reference Implementation==
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@@ -592,12 +592,13 @@ reuse-unsafe.
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Because CHECKTEMPLATEVERIFY commits to the input index currently being spent, reused-keys are
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guaranteed to execute in separate transactions which reduces the risk of "half-spend" type issues.
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====NOP-Default and Standardness Rules====
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====NOP-Default and Recommended Standardness Rules====
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If the argument length is not exactly 32, CHECKTEMPLATEVERIFY treats it as a NOP.
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Many OP_NOP upgrades prefer to fail in such circumstances. In particular, for
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CHECKTEMPLATEVERIFY, making an invalid argument a NOP permits future soft-forks to upgrade the
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semantics or loosed restrictions around the value being previously pushed only.
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If the argument length is not exactly 32, CHECKTEMPLATEVERIFY treats it as a NOP during
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consensus validation. Implementations are recommended to fail in such circumstances during non-consensus
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relaying and mempool validation. In particular, making an invalid-length argument a failure aids future
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soft-forks upgrades to be able to rely on the tighter standard restrictions to safely loosen
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the restrictions for standardness while tightening them for consensus with the upgrade's rules.
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The standardness rules may lead an unscrupulous script developer to accidentally rely on the
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stricter standardness rules to be enforced during consensus. Should that developer submit a
@@ -713,8 +714,9 @@ for an OP_NOP are a soft fork, so existing software will be fully functional wit
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for mining and block validation. Similar soft forks for OP_CHECKSEQUENCEVERIFY and OP_CHECKLOCKTIMEVERIFY
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(see BIP-0065 and BIP-0112) have similarly changed OP_NOP semantics without introducing compatibility issues.
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In contrast to previous forks, OP_CHECKTEMPLATEVERIFY's implementation does not allow transactions with spending
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scripts using it to be accepted to the mempool or relayed under standard policy until the new rule is active.
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In contrast to previous forks, OP_CHECKTEMPLATEVERIFY's reference implementation does not allow transactions with spending
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scripts using it to be accepted to the mempool or relayed under standard policy until the new rule is active. Other implementations
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are recommended to follow this rule as well, but not required.
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Older wallet software will be able to accept spends from OP_CHECKTEMPLATEVERIFY outputs, but will
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require an upgrade in order to treat PayToBareDefaultCheckTemplateVerifyHash chains with a confirmed ancestor as

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