LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

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TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

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ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
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@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

Merged
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

@ldk-reviews-bot

ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
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@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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@tnull@ldk-reviews-bot@ldk-claude-review-bot@TheBlueMatt@jkczyz@joostjager@f3r10
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LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

Merged
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

@ldk-reviews-bot

ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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ldk-claude-review-bot commented Jun 2, 2026

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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
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@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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@tnull@ldk-reviews-bot@ldk-claude-review-bot@TheBlueMatt@jkczyz@joostjager@f3r10
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LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

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TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

@ldk-reviews-bot

ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
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@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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@tnull@ldk-reviews-bot@ldk-claude-review-bot@TheBlueMatt@jkczyz@joostjager@f3r10
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LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

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TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

@ldk-reviews-bot

ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
1 check passed
@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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@tnull@ldk-reviews-bot@ldk-claude-review-bot@TheBlueMatt@jkczyz@joostjager@f3r10
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LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

Merged
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

@ldk-reviews-bot

ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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ldk-claude-review-bot commented Jun 2, 2026

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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
1 check passed
@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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@tnull@ldk-reviews-bot@ldk-claude-review-bot@TheBlueMatt@jkczyz@joostjager@f3r10
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LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

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TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

@ldk-reviews-bot

ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
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@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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@tnull@ldk-reviews-bot@ldk-claude-review-bot@TheBlueMatt@jkczyz@joostjager@f3r10
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LSPS2 service: Treat replayed HTLCIntercepted events idempotently - #4656

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TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue
Jun 17, 2026
Merged

LSPS2 service: Treat replayed HTLCIntercepted events idempotently#4656
TheBlueMatt merged 4 commits into
lightningdevkit:mainfrom
tnull:2026-06-lsps2-replayed-htlc-queue

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@tnull

@tnulltnull commented Jun 2, 2026

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Fixes#4637.

Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.

Also:

Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.

@ldk-reviews-bot

ldk-reviews-bot commented Jun 2, 2026

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👋 Thanks for assigning @jkczyz as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 686c27d to 190b6afCompareJune 2, 2026 12:48
Comment threadlightning-liquidity/src/lsps2/service.rs Outdated
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I've reviewed the full PR against my prior analysis and the current code. The add_htlc dedup-by-intercept_id, remove_terminal_channel_state, and the channel_closed async/sync wrappers are all internally consistent, and the inner/outer map cleanup is symmetric.

No issues found.

The only finding from my prior review pass (the Vec-vs-HashSet lookup nit on the old prune_terminal_state_without_channels) is now resolved — that code was removed entirely and replaced by the event-driven channel_closed approach, so there is nothing left to address there.

One pre-existing limitation (not introduced by this PR, so not flagged inline): channels that close in a non-terminal state (after channel_ready but before PaymentForwarded) still leave stale peer_by_channel_id / intercept_scid_by_channel_id entries, since remove_terminal_channel_state only matches the PaymentForwarded arm. This is no worse than before the PR (there was no ChannelClosed handler previously).

@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 190b6af to 444c009CompareJune 2, 2026 13:04
/// - [`Event::ChannelReady`] to [`LSPS2ServiceHandler::channel_ready`]
/// - [`Event::HTLCHandlingFailed`] to [`LSPS2ServiceHandler::htlc_handling_failed`]
/// - [`Event::PaymentForwarded`] to [`LSPS2ServiceHandler::payment_forwarded`]
/// - [`Event::ChannelClosed`] to [`LSPS2ServiceHandler::channel_closed`]

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Could you add a pending changelog for this?

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For what exactly? For the fact that we expect users to now forward channel closed events? Or something else?

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Yeah, since the docs say "If the LSPS2 service is configured, users must forward the following parameters from LDK events:"

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Added.

Comment on lines +1283 to +1285
let Some(counterparty_node_id) = counterparty_node_id else {
return Ok(());
};

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Elsewhere we return APIError::APIMisuseError. Should we do the same here?

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Good question. We could for consistency, but honestly I'm regretting we moved away from having the event-handling-related API idempotent. It seems not having it idempotent might run into issues / unexpected errors in case events get replayed on restart? But maybe that's okay?

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Hmmm... yeah I guess we return Ok(()) for htlc_intercepted, so might also depend on the event.

Comment on lines +1301 to +1306
self.persist().await.map_err(|e| APIError::APIMisuseError {
err: format!(
"Failed to persist peer state after channel {} closed: {}",
channel_id, e
),
})?;

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I see we use this error elsewhere when persistence fails. Do we expect the caller to retry?

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Yeah, error types are unfortunately still a mess (see #4074). We hope to address that soon. We don't expect the caller to necessarily retry, the persistence will be automatically retried by the background processor eventually.

if let Some(intercept_scid) = removed_intercept_scid {
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
self.persist().await.map_err(|e| APIError::APIMisuseError {

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I have a question here. As I understand, self.persist() sweeps all peers triggering a global sweep. Would it not be better to use here self.persist_peer_state(counterparty_node_id).await ?

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Yeah, note that persist_peer_state will then leave pruning/cleanup to the background processor run, but that's probably fine. Now changing to the pattern we have elsewhere.

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Just one question between the difference between self.persist() and self.persist_peer_state(counterparty_node_id).await

@tnulltnull self-assigned this Jun 11, 2026
@tnulltnull moved this to Goal: Merge in Weekly GoalsJun 11, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

tnull added 3 commits June 17, 2026 14:23
Replayed intercepted HTLC events should not duplicate queued payments or
panic after restart. Ignore already-queued intercept IDs so persisted
queues remain stable across event replay.
Co-Authored-By: HAL 9000
Terminal JIT channel state is only useful while the forwarded channel
still exists. Drop completed LSPS2 mappings once the channel is gone so
persisted service state does not retain stale entries indefinitely.
Co-Authored-By: HAL 9000
Persisting LSPS2 service state can race with replayed intercepted HTLC
events after restart. Cover replaying the same intercepted HTLC after
restoring peer state so duplicate queueing is caught.
Co-Authored-By: HAL 9000
@tnull
tnullforce-pushed the 2026-06-lsps2-replayed-htlc-queue branch from 444c009 to 68e71c2CompareJune 17, 2026 13:06
@tnull

tnull commented Jun 17, 2026

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Please move the test commit so that its after the fix, rather than having an intermediate state that fails tests. Also please word-wrap commit messages. Do you think it makes sense to backport the last commit to 0.2? I presume not.

Done! Yeah, likely only the idempotency commit makes sense.

Also updated to use the persist_peer_state pattern rather than full persist:

diff --git a/lightning-liquidity/src/lsps2/service.rs b/lightning-liquidity/src/lsps2/service.rs
index e1373cfb1..4f338a5fd 100644
--- a/lightning-liquidity/src/lsps2/service.rs+++ b/lightning-liquidity/src/lsps2/service.rs@@ -1299,9 +1299,11 @@ where
self.peer_by_intercept_scid.write().unwrap().remove(&intercept_scid);
self.peer_by_channel_id.write().unwrap().remove(&channel_id);
- self.persist().await.map_err(|e| APIError::APIMisuseError {- err: format!(- "Failed to persist peer state after channel {} closed: {}",- channel_id, e- ),+ self.persist_peer_state(counterparty_node_id).await.map_err(|e| {+ APIError::APIMisuseError {+ err: format!(+ "Failed to persist peer state after channel {} closed: {}",+ channel_id, e+ ),+ }
})?;
}

@tnull
tnull requested a review from jkczyzJune 17, 2026 13:07
self.outbound_channels_by_intercept_scid.remove(&intercept_scid);
self.intercept_scid_by_channel_id.remove(&channel_id);
self.intercept_scid_by_user_channel_id.retain(|_, iscid| *iscid != intercept_scid);
self.needs_persist = true;

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Here is some overlap with #4703 perhaps.

@TheBlueMatt
TheBlueMatt merged commit 63fcc4f into lightningdevkit:mainJun 17, 2026
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@github-project-automationgithub-project-automationBot moved this from Goal: Merge to Done in Weekly GoalsJun 17, 2026
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Backported to 0.2 in #4706

TheBlueMatt added a commit to TheBlueMatt/rust-lightning that referenced this pull request Jun 23, 2026
v0.2.3 - Jun 18, 2026 - "Through the Loupe"
API Updates
===========
* `DefaultMessageRouter` will now always generate blinded message paths that
provide no privacy (where our node is the introduction node) for nodes with
public channels. This works around an issue which will appear for any nodes
with LND peers that enable onion messaging - such peers will refuse to
forward BOLT 12 messages from unknown third parties, which most BOLT 12
payers rely on today (lightningdevkit#4647).
* Explicit `amount_msats` of 0 is rejected in BOLT 12 `Offer`s; `OfferBuilder`
now maps 0-amounts to an amount of `None` (lightningdevkit#4324).
Bug Fixes
=========
* `Features::supports_zero_conf` no longer clears the `ZeroConf` features and
`Features::requires_zero_conf` now correctly reports required, rather than
supported, status (lightningdevkit#4517).
* If an MPP payment is claimed but `ChannelMonitorUpdate`s for some parts are
still being completed asynchronously, further channel updates (e.g.
forwarding another payment) are pending and the node restarts, the channel
could have become stuck (lightningdevkit#4520).
* The presence of unconfirmed transactions actually no longer causes
`ElectrumSyncClient` to spuriously fail to sync (lightningdevkit#4590).
* LSPS1, LSPS2, and LSPS5 persistence will no longer get stuck and refuse to
persist again after a single failure from the KVStore (lightningdevkit#4597, lightningdevkit#4282).
* Dropping the future returned by
`OutputSweeper::regenerate_and_broadcast_spend_if_necessary` no longer
results in future calls to the same method being spuriously ignored (lightningdevkit#4598).
* Used async-receive offers are no longer refreshed on every timer tick once
their refresh time is reached (lightningdevkit#4672).
* `FilesystemStore::list_all_keys` will no longer fail if there are stale
intermediate files lying around from a previous unclean shutdown (lightningdevkit#4618).
* When forwarding an HTLC while in a blinded path with proportional fees over
200%, LDK will no longer spuriously allow a forward that pays us 1 msat too
little in fees (lightningdevkit#4697).
* Fixed a rare case where a channel could get stuck on reconnect when using
both async `ChannelMonitorUpdate` persistence and async signing (lightningdevkit#4684).
* If we had exactly zero balance in a zero-fee-commitment channel, the
counterparty was able to splice all of their balance out, violating the
reserve requirements they'd otherwise be forced to keep (lightningdevkit#4580).
* Providing an `Event::HTLCIntercepted` to the `LSPS2ServiceHandler` twice no
longer results in spuriously opening a channel early (lightningdevkit#4656).
* `Event::PaymentSent::fee_paid_msat` is no longer `None` in cases where
`ChannelManager::abandon_payment` was called before the payment ultimately
completes anyway (lightningdevkit#4651).
* `AnchorDescriptor::previous_utxo` now provides the correct `script_pubkey`
for non-zero-commitment-fee anchor channels (lightningdevkit#4669).
* Syncing a `ChainMonitor` using the `Confirm` trait will no longer write some
full `ChannelMonitor`s to disk several times per block (lightningdevkit#4544).
* `OMDomainResolver` now correctly accounts for failed queries when rate
limiting, ensuring we continue to respond to queries after failures (lightningdevkit#4591).
* Calling `ChannelManager::send_payment_with_route` without a `route_params`
and with an invalid `Route` will no longer panic (lightningdevkit#4707).
* `LSPS2ServiceHandler::channel_open_failed` now correctly fails intercepted
HTLCs rather than allowing them to fail just before expiry (lightningdevkit#4677).
* `StaticInvoice::is_offer_expired` was corrected to check offer, rather than
static invoice, expiry (lightningdevkit#4594).
* `lightning-custom-message`'s handling of `peer_connected` events now ensures
that sub-handlers will see a `peer_disconnected` event if a different
sub-handler refused the connection by `Err`ing `peer_connected` (lightningdevkit#4595).
* Replay protection for LSPS5 signatures now detects replays which are only
different in the encoded signature's case (lightningdevkit#4701).
* When `lightning-liquidity` is configured in the background processor, there
is no longer a stream of `Persisting LiquidityManager...` log spam (lightningdevkit#4246).
* Incomplete MPP keysend payments will no longer see their HTLCs held until
expiry (lightningdevkit#4558).
* `InvoiceRequestBuilder` will no longer accept a `quantity` of `0` for a
BOLT 12 `Offer`, allowing any quantity up to a bound (lightningdevkit#4667).
* `lightning-custom-message` handlers that return `Ok(None)` when asked to
deserialize a message in their defined range no longer cause panics (lightningdevkit#4709).
* Several spurious debug assertions were fixed (lightningdevkit#4537, lightningdevkit#4618, lightningdevkit#4026)
Security
========
0.2.3 fixes several underestimates of the anchor reserves required to ensure we
can reliably close channels, several denial-of-service vulnerabilities and a
sanitization issue.
* `Bolt11Invoice::recover_payee_pub_key` no longer panics if called on an
invoice which set an explicit public key, rather than relying on public key
recovery. Note that this method is called from
`PaymentParameters::from_bolt11_invoice` (lightningdevkit#4717).
* Maliciously-crafted unpayable invoices which have overflowing feerates will
no longer cause an `unwrap` failure panic (lightningdevkit#4716).
* Parsing an `LSPSDateTime` which is before 1970 no longer panics. This is
reachable when parsing messages from counterparties (lightningdevkit#4715).
* `possiblyrandom` did not properly generate random data except when it was
explicitly configured to. By default this means LDK is vulnerable to various
HashDoS attacks (lightningdevkit#4719).
* `OMNameResolver` will no longer panic when looking up payment instructions
which include unicode characters at the start of a TXT record (lightningdevkit#4718).
* When using the `anchor_channel_reserves` module to calculate reserves
required to pay for fees when closing anchor channels, zero-fee-commitment
channels were not considered. This could allow a counterparty to open many
channels, leaving us unable to properly force-close (lightningdevkit#4592).
* The `anchor_channel_reserves` module overestimated the value of `Utxo`s in
the wallet by ignoring the `TxIn` cost to spend them (lightningdevkit#4670).
* `PrintableString` did not properly sanitize unicode format characters,
allowing an attacker to corrupt the rendering of logs or UI (lightningdevkit#4593, lightningdevkit#4605).
* RGS data is now limited in how large of a graph it is able to cause a client
to store in memory. Note that RGS data is still considered a DoS vector in
general and you should only use semi-trusted RGS data (lightningdevkit#4713).
* Counterparty-provided strings in failure messages are no longer logged in
full, reducing the ability of such a counterparty to spam our logs (lightningdevkit#4714).
* Reading a corrupted `ChannelManager` or `ProbabilisticScorer` can no longer
cause us to allocate large amounts of memory (lightningdevkit#4712).
Thanks to Project Loupe for reporting most of the issues fixed in this release.
Conflicts resolved in:
* lightning/src/chain/channelmonitor.rs
* lightning/src/events/mod.rs
* lightning/src/ln/channelmanager.rs
* lightning/src/ln/mod.rs
* lightning/src/ln/offers_tests.rs
* lightning/src/ln/onion_utils.rs
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LSP panics on restart due to stale LSPS2 payment queue entries (duplicate intercept_id assertion)

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@tnull@ldk-reviews-bot@ldk-claude-review-bot@TheBlueMatt@jkczyz@joostjager@f3r10