Integrate package context into fee and weight calculations; add absolute fee target#38
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evanlinjin wants to merge 3 commits intobitcoindevkit:masterfrom
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Integrate package context into fee and weight calculations; add absolute fee target#38evanlinjin wants to merge 3 commits intobitcoindevkit:masterfrom
evanlinjin wants to merge 3 commits intobitcoindevkit:masterfrom
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When a Package is set via with_package(), all fee and weight calculations now automatically include parent transaction context: - weight() returns child_weight + parent_weight - fee() returns child_fee + parent_fee - implied_feerate() returns package feerate New methods for when child-only values are needed: - weight_without_package() - fee_without_package() - package() accessor RBF calculations (replacement_excess) use child weight only since Bitcoin's RBF rule 4 applies to the replacing transaction, not the package. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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Tests cover: - weight() includes parent_weight when package is set - weight_without_package() returns child weight only - fee() includes parent_fee when package is set - fee_without_package() returns child fee only - implied_feerate() returns package feerate - package() accessor - with_package() auto-selects link indices - No package behaves normally (backwards compatible) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
aagbotemi
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Feb 16, 2026
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The approach of adding Package to CoinSelector is good one and works well for the UTXO selection for CPFP use case.
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I also want to add an absolute fee target. Payjoin (BIP 78): The payjoin proposal MUST NOT decrease the absolute fee of the original transaction. Some users may want to select their fee based on an absolute value (not sure why, but some wallets provide this feature). |
Add a `TargetFee::absolute` field that acts as a minimum absolute fee floor, checked independently alongside the existing feerate and replacement constraints. This supports use cases like Payjoin (BIP 78), where the receiver must not decrease the original transaction's absolute fee, and application-level policy minimums. Changes: - Add `absolute: u64` field to `TargetFee` - Add `CoinSelector::absolute_excess()` method - Integrate absolute excess into `CoinSelector::excess()` via `.min()` - Account for absolute fee in `CoinSelector::implied_fee()` - Handle absolute constraint in `LowestFee::bound()` for correct branch-and-bound behavior
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aagbotemi
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Mar 24, 2026
| /// How much the current selection overshoots the value need to satisfy `target.fee.rate` and | ||
| /// `target.value` (while ignoring `target.min_fee`). | ||
| /// `target.value` (while ignoring `target.fee.absolute`). | ||
| pub fn rate_excess(&self, target: Target, drain: Drain) -> i64 { |
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rate_excess includes parent_weight in the required fee via implied_fee_from_feerate() -> weight() but doesn't include parent_fee in the actual fee, so the excess is parent_fee sats too low.
This was referenced Mar 30, 2026
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Closing in favor of #43. |
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b8db9e9 feat: Add absolute fee target to TargetFee (志宇) Pull request description: ## Summary - Adds `TargetFee::absolute` field as a minimum absolute fee floor, checked independently alongside the existing feerate and replacement constraints - Adds `CoinSelector::absolute_excess()` method and integrates it into `excess()` via `.min()` so the most binding constraint wins - Handles the absolute constraint in `LowestFee::bound()` for correct branch-and-bound behavior **Use cases:** - **Payjoin (BIP 78):** The receiver must not decrease the original transaction's absolute fee when adding inputs - **Application-level policy minimums:** Supports `bdk_wallet`'s `TxBuilder::fee_absolute()` API where users set a fee floor regardless of feerate Extracted from #38 (package context changes excluded). ## Test plan - [x] `cargo test` — all existing tests pass - [x] `cargo test --no-default-features` — no_std builds pass - [x] `cargo clippy` — clean 🤖 Generated with [Claude Code](https://claude.com/claude-code) Top commit has no ACKs. Tree-SHA512: a2465c64a73a09b533f2f6d103137846684daad95e6019fbc34f663e4493fbb4ea2e4ad9cb764a4ec5febf041157c9a539e08b343fc5c291de58cb19f7bd6c1b
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Package context for CPFP
When a
Packageis set viawith_package(), all fee and weight calculations now automatically include parent transaction context:weight()returnschild_weight + parent_weightfee()returnschild_fee + parent_feeimplied_feerate()returns package feerateNew methods for when child-only values are needed:
weight_without_package()fee_without_package()package()accessorRBF calculations (
replacement_excess) use child weight only since Bitcoin's RBF rule 4 applies to the replacing transaction, not the package.Absolute fee target
Adds a
TargetFee::absolutefield that acts as a minimum absolute fee floor, checked independently alongside the existing feerate and replacement constraints.Use cases:
bdk_wallet'sTxBuilder::fee_absolute()API where users set a fee floor regardless of feerate.Changes:
TargetFee::absolute: u64— minimum absolute fee the transaction must payCoinSelector::absolute_excess()— how much the selection overshoots the absolute fee requirementabsolute_excessintegrated intoexcess()via.min()so the most binding constraint winsimplied_fee()accounts forabsolutevia.max()LowestFee::bound()handles the absolute constraint for correct branch-and-bound behaviorNote: absolute fee is complementary to package context, not a replacement. Package context changes how the feerate constraint itself scales with child weight (the parent's fee/weight are inside the feerate calculation). An absolute fee floor is an independent constraint for cases where a fixed sat minimum comes from an external source.