Frontend MASP sustainability fee #4790

grarco · 2025-08-14T14:56:16Z

Describe your changes

Adds support for an optional masp frontend providers sustainability fees. This fee is supported as both a transparent and a shielded transfer (with the exception of incoming shielding IBC packets). To support it the followings have been changed:

Shielding and (IBC) unshielding

The sdk has been extended to allow specifying the entry for this fee. This is an optional target and a percentage which will be applied to all inputs. The sdk adjusts the input amounts to account for this extra fee.

There's one limitation for the IBC unshielding case. If the transaction ultimately fails (rejected by the target chain or timed out) we refund the amount of the unshielding to a disposable address. The frontend fees are not part of this amount and do not get refunded: to support this we'd need to temporarily escrow those tokens to an internal address and finalize the fee payment only once the target chain has confirmed the transaction to be successful (this would require some protocol support and should probably be done in conjunction with #4726). On top of this, the unshielding refunds are done to a disposable transparent address from which the user might want to reshield the tokens: this would incur in another frontend fee event leading to multiple fees applied to the same overall action.

Incoming IBC shielding packets

The optional target and percentage of the fee can be passed to the gen_ibc_shielding_transfer function. Since IBC is limited to a single token, the asset is automatically inferred to be the same of the transfer and fees are not supported when shielding nfts. The fee amount itself will be encoded as an additional shielded output of the MASP bundle so that we can avoid the need for protocol-breaking changes.

Osmosis swaps

Osmosis swaps are ultimately collapsed to the above ibc cases and so the same rules apply. In case the swap was fully shielded the frontend provider should refrain from charging a fee since this should count as a fully shielded transaction.

Checklist before merging

If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
- This will require 2 reviewers to approve the changes
If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
- Relevant PR if applies:
If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
- Relevant PR if applies:

crates/core/src/ibc.rs

mergify · 2025-08-21T17:30:08Z

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batconjurer · 2025-08-22T08:48:40Z

crates/apps_lib/src/cli.rs

                        .def()
                        .help(wrap!("The amount to transfer in decimal.")),
                )
+                .arg(__TEST_FRONTEND_SUS_FEE.def().help(wrap!(


should we bother exposing this in the cli as it's just for testing?

Yes we still need to expose them to run the integration and e2e tests

Is there a clever way to keep this from showing up in the cli help menu?

Hid them in e90c619

crates/sdk/src/tx.rs

crates/tests/src/integration/masp.rs

batconjurer

nits

batconjurer · 2025-09-09T13:51:41Z

crates/sdk/src/tx.rs

+                // NOTE: The frontend fee should NOT account for the masp fee
+                // payment amount
+                let sus_fee_amt = namada_token::Amount::from_uint(
+                    validated_amount


this block of code for the percentage calculation isn't nice looking and appears in a few spots. Can we hide it in the amount module?

Done in 3fe86a7, but the new function does also the validation part and lives in the same module

(cherry picked from commit a13d611)

Frontend MASP sustainability fee (backport #4790)

(cherry picked from commit a13d611) # Conflicts: # .changelog/libs-v0.251.2/features/4790-frontend-sus-fees.md

(cherry picked from commit a13d611)

…pr-4790 Frontend MASP sustainability fee (backport #4790)

grarco force-pushed the grarco/frontend-sus-fees branch 2 times, most recently from 82b94e5 to 4514cac Compare August 20, 2025 15:32

grarco added a commit that referenced this pull request Aug 21, 2025

Changelog #4790

cc897ad

grarco marked this pull request as ready for review August 21, 2025 16:41

grarco added enhancement New feature or request IBC MASP SDK breaking:consensus Consensus breaking change that requires a hard-fork breaking:SDK SDK breaking change labels Aug 21, 2025

github-actions bot added the breaking:api public API breaking change label Aug 21, 2025

grarco requested review from batconjurer, brentstone and yito88 August 21, 2025 17:09

grarco changed the title ~~Frontend MASP fee~~ Frontend MASP sustainability fee Aug 21, 2025

grarco commented Aug 21, 2025

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batconjurer requested changes Aug 22, 2025

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yito88 approved these changes Aug 25, 2025

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grarco added a commit that referenced this pull request Sep 6, 2025

Changelog #4790

66a008d

grarco force-pushed the grarco/frontend-sus-fees branch from cc897ad to abeb496 Compare September 6, 2025 10:12

grarco added a commit that referenced this pull request Sep 6, 2025

Changelog #4790

b6de931

grarco force-pushed the grarco/frontend-sus-fees branch from 9072bfd to b6de931 Compare September 6, 2025 12:50

grarco removed the breaking:consensus Consensus breaking change that requires a hard-fork label Sep 8, 2025

grarco requested a review from batconjurer September 8, 2025 13:37

batconjurer requested changes Sep 9, 2025

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brentstone added this to the Next Release milestone Sep 18, 2025

brentstone requested a review from batconjurer September 18, 2025 04:44

batconjurer approved these changes Sep 19, 2025

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grarco added a commit that referenced this pull request Sep 25, 2025

Changelog #4790

93ef3b3

grarco and others added 12 commits September 29, 2025 14:42

Shielded frontend fee target for incoming IBC packets

4b1398f

Adds support for shielded masp frontend fees

2418cf5

Adds tests for shielded masp frontend fees

8b38f4b

Forces ibc shielding target argument to be a payment address

3cacd32

Frontend MASP fee argument as a percentage

ce7150d

More masp frontened fee tests

718b77e

Refactors masp frontend fee handling in the sdk

8070560

Adds balance check when shielding with masp frontend fees

f0c4925

Tests insufficients masp sus fee balances

c5fef2b

Hides test cli arguments

2c82472

Refactors computation of the masp sus fee into a function

2757e68

Changelog #4790

a13d611

grarco force-pushed the grarco/frontend-sus-fees branch from d3f672b to a13d611 Compare September 29, 2025 12:42

mergify bot added the queued label Sep 29, 2025

mergify bot merged commit 58a926b into main Sep 29, 2025
27 checks passed

mergify bot deleted the grarco/frontend-sus-fees branch September 29, 2025 13:37

mergify bot removed the queued label Sep 29, 2025

tzemanovic restored the grarco/frontend-sus-fees branch October 7, 2025 14:34

tzemanovic added the backport-201.0 Backport to app 201.0 maintenance branch label Oct 7, 2025

mergify bot pushed a commit that referenced this pull request Oct 7, 2025

Changelog #4790

9c5d777

(cherry picked from commit a13d611)

mergify bot mentioned this pull request Oct 7, 2025

Frontend MASP sustainability fee (backport #4790) #4905

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3 tasks

tzemanovic pushed a commit that referenced this pull request Oct 8, 2025

Changelog #4790

a7b976b

(cherry picked from commit a13d611)

mergify bot added a commit that referenced this pull request Oct 8, 2025

Merge pull request #4905 from namada-net/mergify/bp/maint-201.0/pr-4790

d1ab01b

Frontend MASP sustainability fee (backport #4790)

sug0 mentioned this pull request Oct 28, 2025

Take sustainability fees from IBC shieldings #4944

Open

brentstone mentioned this pull request Nov 3, 2025

[Namadillo]: integrate tx-level fees namada-net/namada-interface#2316

Open

tzemanovic added the backport-libs-0.251 Backport libraries to 0.251 maintenance branch label Dec 2, 2025

mergify bot pushed a commit that referenced this pull request Dec 2, 2025

Changelog #4790

3147b50

(cherry picked from commit a13d611) # Conflicts: # .changelog/libs-v0.251.2/features/4790-frontend-sus-fees.md

mergify bot mentioned this pull request Dec 2, 2025

Frontend MASP sustainability fee (backport #4790) #4990

Merged

3 tasks

tzemanovic pushed a commit that referenced this pull request Dec 2, 2025

Changelog #4790

726af7c

(cherry picked from commit a13d611)

mergify bot added a commit that referenced this pull request Dec 2, 2025

Merge pull request #4990 from namada-net/mergify/bp/maint-libs-0.251/…

641a6c9

…pr-4790 Frontend MASP sustainability fee (backport #4790)

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grarco commented Aug 14, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Describe your changes

Shielding and (IBC) unshielding

Incoming IBC shielding packets

Osmosis swaps

Checklist before merging

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mergify bot commented Aug 21, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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