fix(app): ZEB-1038 serve reset-chain links one per frame with a group-total ingest cap - #785
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…-total ingest cap The catch-up ResetChain frame packed ALL selected links into one body, making the link-COUNT cap (8) the wrong bound: a link is O(N²) bytes in committee size (one dk event per confirming member, each carrying the full N-entry verifying-share list), so at N≈16 a 3-link chain already exceeded the 64KiB frame cap and catchup_respond dropped the WHOLE frame — and select_reset_chain rebuilt the same oversized set every round, permanently wedging that requester/responder pair's reset-chain healing. - Responder: serve ONE link per ResetChain frame (the module's existing one-event-per-frame idiom for dk/vb), oldest-first, fit-testing each candidate with encode_frame — the same gate dfrost_catchup_seal_reply re-runs, so an accepted frame cannot be dropped at sealing. STOP at the first link that does not fit alone (never skip: markers must apply in epoch order, so links past a gap are wasted requester verify work). Residual: a committee so large ONE link exceeds the frame (payload N in the low 40s) — documented on the cap constant; the quorum-trim lever (O(N²) → O(t·N) per link) is ZEB-1045. - Requester: the decode+verify link cap becomes GROUP-TOTAL across all of a responder group's ResetChain frames — per-link frames make multi-frame chains the legitimate shape, and a per-frame take would let a hostile responder multiply the Ed25519 verify work the ZEB-1031 I3 cap exists to bound. - Docs: real sizing math on MAX_RESET_CHAIN_LINKS_PER_RESPONSE and the frame-cap constant (per-link weight, overflow thresholds, residual). Wire-compatible both directions: an old requester already accumulates links across frames (per-frame cap 8 ≥ 1); an old responder's single frame stays within the new group budget. Tests: reset_chain_served_one_link_per_frame_zeb1038 (20-member 3-reset fixture whose combined body exceeds the cap — the exact shape the pre-fix code dropped whole), reset_chain_single_oversize_link_ stops_at_first_misfit_zeb1038, reset_chain_group_total_link_cap_ zeb1038. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MsT6ZD7kqbpbKoeenyQPtc
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📝 WalkthroughWalkthroughReset-chain catch-up responses now send one link per size-checked frame in epoch order. Serving stops at the first oversized link. Request decoding applies the link limit across all frames from one responder group. Regression tests cover framing, termination, and cumulative limits. ChangesReset-chain catch-up
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to This change improves reset-chain recovery by splitting links across frames, but invalid links can still cause repeated verification work and out-of-order frames can prevent an otherwise valid recovery chain from advancing. Merge should wait for bounded-attempt accounting and sequence handling, or obtain explicit owner acceptance of these risks. Sequence Diagram(s)sequenceDiagram
participant Responder
participant catchup_respond
participant encode_frame
participant Requester
Responder->>catchup_respond: select reset-chain links oldest-first
catchup_respond->>encode_frame: encode one link
encode_frame-->>catchup_respond: return fitting frame or size failure
catchup_respond->>Requester: send each fitting frame
catchup_respond->>catchup_respond: stop at first oversized link
Requester->>Requester: apply cumulative group-total link budget
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| Category | Suggestion | Impact | Generated at (UTC) |
| Comment mismatch |
The claimed group-total cap only limits successfully verified links; malformed links
| Major | 2026-08-31 19:16
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Inline comments:
In `@src-tauri/src/community_dfrost_log_engine.rs`:
- Around line 3979-4001: Update the reset-chain ingestion flow around
group_frames and the links loop to track attempted links per responder group,
rather than deriving the remaining budget from reset_chain.len(). Increment the
attempt counter before marker and dk signature verification, cap processing
against that counter across all frames for the group, and add a test covering
invalid signatures repeated across multiple frames.
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src-tauri/src/community_dfrost_log_engine.rssrc-tauri/src/community_dfrost_catchup.rs
🔇 Additional comments (4)
src-tauri/src/community_dfrost_catchup.rs (1)
36-40: LGTM!Also applies to: 76-107
src-tauri/src/community_dfrost_log_engine.rs (3)
3822-3875: LGTM!
4946-4949: LGTM!
11012-11266: LGTM!
…d links, not accepted CodeRabbit and CodeAnt converged on the same defect in the new group-total cap: the budget was derived from reset_chain.len(), which counts ACCEPTED links. Invalid-signature links never enter the accepted set, so a hostile responder sending frame after frame of garbage links saw a fresh budget of 8 every frame — re-bounding the per-group Ed25519 verify work by the 16 MiB round cap (~55k minimal links) instead of by MAX_RESET_CHAIN_LINKS_PER_RESPONSE. The budget now charges ATTEMPTED links, counted before verification: a group serving garbage burns through its 8 attempts and is done. Honest multi-frame serving is unchanged (every honest link is attempted once and accepted once). Docs on the cap constant updated to say attempt-counted and why. Test: reset_chain_attempted_links_consume_group_budget_zeb1038 — two frames of invalid links exhaust the budget, so a third frame of VALID links gets zero verify attempts (accepted set stays empty). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01MsT6ZD7kqbpbKoeenyQPtc
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Closes ZEB-1038.
The bug
The catch-up
ResetChainframe packed all selected links into one body, so the link-count cap (8) was bounding the wrong dimension: a link is O(N²) bytes in committee size — onedkevent per confirming member, each carrying the full N-entry verifying-share list (~N × (55N + 300) bytes/link: ~6KiB at N=8, ~35KiB at N=20). At N≈16, a 3-link chain already exceeded the 64KiB frame cap,catchup_responddropped the whole frame, andselect_reset_chainrebuilt the same oversized set every round — that requester/responder pair's reset-chain healing was permanently wedged.The fix
Two code facts reshaped this away from the ticket's shrink-retry sketch:
ResetChainframes in a response group — multi-frame serving is legal wire shape, no schema change.So:
catchup_respond): one link perResetChainframe, oldest-first, each candidate fit-tested withencode_frame— the same gatedfrost_catchup_seal_replyre-runs before sealing, so an accepted frame can't be dropped downstream. Stop at the first link that doesn't fit alone, never skip: markers must apply in ascending epoch order (apply_reset_chainwalks in order; a post-gap marker fails RS-M2 against pre-gap state), so links past a misfit are wasted requester verify work. This heals up to the full 8-link cap per round at any committee size where one link fits — strictly better than count-halving, which degrades to 1 link/round and dies at the same single-link bound.catchup_decode_and_verify): the link cap becomes group-total across all of a responder group'sResetChainframes. With per-link frames legitimate, the old per-frametake(8)would let a hostile responder pack every frame full and multiply the Ed25519 verify work the ZEB-1031 review-I3 cap exists to bound; the group budget keeps the verify-work ceiling exactly where it was.MAX_RESET_CHAIN_LINKS_PER_RESPONSEand the frame-cap constant now carry the real sizing math, the serving shape, and the residual.Residual + follow-up: a committee so large that a single link exceeds the frame (payload N in the low 40s) still can't be served — distinct warn at the responder. The lever is trimming each link's dk set to a threshold-quorum subset (
adopt_initial_quorumrequires onlythresholddistinct actors), flattening a link to O(t·N) — filed as ZEB-1045.Wire compatibility, both directions: an old requester already accumulates links across frames (its per-frame cap 8 ≥ 1); an old responder's single frame stays within the new group budget.
Tests (TDD — written first, failed on the pre-fix shape)
reset_chain_served_one_link_per_frame_zeb1038— 20-member, 3-reset fixture whose combined body exceeds the cap (asserted in-test; the exact shape the pre-fix code dropped whole): now 3 frames, one link each, oldest-first, each passingencode_frame.reset_chain_single_oversize_link_stops_at_first_misfit_zeb1038— 700-member first link, tiny second: zero chain frames (no skip-ahead), rest of the reply still serves.reset_chain_group_total_link_cap_zeb1038— 3 frames × 4 valid links: exactly 8 survive decode+verify.Gates
cargo fmtclean; clippy--all-targets -D warningsclean; catchup/reset seam sweep 86/86;scripts/test-select --context task1132/1132.🤖 Generated with Claude Code
https://claude.ai/code/session_01MsT6ZD7kqbpbKoeenyQPtc
Summary by CodeRabbit
Bug Fixes
Documentation