The snapshot/restore machinery added in the previous commit
(ca988b7) to implement MDK-style `stageCommit` + `mergeStagedCommit`
introduced a tree-rebuild path (RatchetTree.decodeTls followed by a
fresh SecretTree construction) that, in production, caused a
recursive StackOverflowError in `SecretTree.getNodeSecret` during
encryption after a second add-member cycle. The unit test flow did
not exercise it and couldn't reproduce.
Keep the underlying fix — outer-encrypt outbound kind:445 commits
with the PRE-commit (epoch-N) exporter secret — but deliver it with
far less machinery:
- `CommitResult.preCommitExporterSecret` now carries the
`MLS-Exporter("marmot", "group-event", 32)` value captured inside
`MlsGroup.commit()` BEFORE any state mutation. It's the key
existing members still at epoch N hold, so the outer kind:445
wrap with it is decryptable to them (RFC 9420 §12.4 + MDK parity).
- `MlsGroup.commit()` captures this exporter once at the top of the
function, threads it into the returned `CommitResult`.
- `MarmotManager.addMember / removeMember / updateGroupMetadata`
read `commitResult.preCommitExporterSecret` and pass it to
`MarmotOutboundProcessor.buildCommitEvent(..., exporterKey=...)`.
The eager `group.addMember` / etc. continue to advance the local
epoch immediately — the same behavior as before the previous
commit, which was proven safe under production load.
Removed:
- `MlsGroup.stageCommit` / `mergeStagedCommit` / `stageAddMember` /
`stageRemoveMember` and their snapshot/restore helpers.
- `MlsGroupSnapshot` / `StagedCommit` types.
- `MlsGroupManager.stageAddMember` / `stageRemoveMember` /
`stageRotateSigningKey` / `stageUpdateGroupExtensions` /
`mergeStagedCommit`.
- `tree` back to `val` in `MlsGroup`.
Kept from the previous commit:
- `MarmotOutboundProcessor.buildCommitEvent(... exporterKey: ByteArray?)`
with default falling back to `groupManager.exporterSecret(...)`.
- `MlsGroupManager.processCommit` retains epoch secrets AFTER
successful apply (was a secondary bug polluting the retention
window with duplicates of the current key when a commit failed).
- `pushRetainedEpoch` helper that accepts a pre-captured
RetainedEpochSecrets, used throughout instead of the old
`retainEpochSecrets(nostrGroupId, group)`.
Test updated:
- `testCreatorCanAddTwoMembersAndAllDecryptFollowingMessage` now
uses the eager `addMember` path and asserts that the member still
at the old epoch can outer-decrypt with the pre-commit key shipped
back via `CommitResult`. Also decrypts Alice's self-echo and
sends multiple follow-up messages — this is the scenario that
triggered the production stack overflow before the revert.
- `testAddMemberExposesPreCommitExporterSecret` (renamed) confirms
`CommitResult.preCommitExporterSecret` equals the exporter the
group had immediately before the call, and that the post-commit
exporter differs from it (proves we actually rotated).
https://claude.ai/code/session_014zfdNeeKAfU1zGGyFw4bUL
Claude
b039543807