fix(libsy): preserve provider events when escalation serves a buffered reply - #636
fix(libsy): preserve provider events when escalation serves a buffered reply#636linj-glitch wants to merge 1 commit into
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…d reply The escalation router calls the efficient tier, buffers the reply so the judge can read the completed turn, then serves that same reply when the judge declines. It rebuilt the served stream with AggLlmResponse::into_stream(), which is documented as lossy: it emits synthetic chunks and drops response extensions and preservation metadata. into_agg() consumed only each event's normalized chunks and discarded its preservation payload, so the payload was already gone by the time the response was rebuilt. Every unlatched escalation turn therefore reached the outbound codec without the provider bodies it uses for faithful same-format responses. Escalation is the only route that buffers, so no other route was affected. Add LlmResponse::into_agg_retaining_events(), which aggregates for the judge while optionally retaining the original events, and replay_stream_events(), which serves them verbatim. Escalation now replays the originals when the request is streaming and keeps returning the aggregate otherwise. Signed-off-by: Lin Jia <linj@nvidia.com>
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WalkthroughThe protocol now retains and replays original provider stream events during escalation classification. Non-escalated streaming responses preserve provider payloads, while non-streaming responses and error handling keep their existing behavior. ChangesProvider event replay
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: 🟡 Moderate · up to Streaming escalation requests can return an empty response when the efficient model supplies an aggregate result and the judge declines escalation. Preserve aggregate results by converting them to a synthetic stream in this case before merge. Poem
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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✨ Finishing Touches 💡 1🛠️ Fix failing CI checks 💡
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In `@crates/libsy/src/algorithms/escalation.rs`:
- Around line 145-146: Update the streaming response handling in
Driver::call_model to preserve LlmResponse::Agg values by converting the
aggregate with agg.into_stream() instead of replaying retained events; retain
replay_stream_events for event-based responses and add a regression test
covering an aggregate response when streaming is enabled.
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crates/libsy/src/algorithms/escalation.rscrates/protocol/src/stream.rs
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| llm_response: if streaming { | ||
| LlmResponse::Stream(replay_stream_events(retained_events)) |
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🎯 Functional Correctness | 🟠 Major | ⚡ Quick win
🔎 Supported by static analysis
🏁 Script executed:
#!/bin/bash
set -euo pipefail
# Find the Driver call contract and response construction paths.
rg -n -C 8 --glob '*.rs' '\bfn\s+call_model\b|\bcall_model\s*\(' crates
# Inspect whether streaming requests can return an aggregate response.
rg -n -C 8 --glob '*.rs' 'LlmResponse::Agg|llm_request\.stream' cratesRepository: NVIDIA-NeMo/Switchyard
Length of output: 50378
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf '%s\n' '--- escalation classifier ---'
sed -n '70,175p' crates/libsy/src/algorithms/escalation.rs
printf '%s\n' '--- Driver::call_model implementation ---'
sed -n '145,215p' crates/libsy/src/core/algorithm.rs
printf '%s\n' '--- response normalization helpers ---'
sed -n '135,225p' crates/protocol/src/stream.rs
printf '%s\n' '--- request-stream handling in client routing ---'
rg -n -C 6 --glob '*.rs' 'llm_request\.stream|request\.stream|LlmResponse::Stream|LlmResponse::Agg' crates/libsy-llm-client/src crates/libsy/src/core crates/libsy/src/algorithms/escalation.rsRepository: NVIDIA-NeMo/Switchyard
Length of output: 36083
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#!/bin/bash
set -euo pipefail
printf '%s\n' '--- escalation test fixtures and streaming cases ---'
sed -n '180,470p' crates/libsy/src/algorithms/escalation.rs
printf '%s\n' '--- client response-shape selection ---'
sed -n '430,510p' crates/libsy-llm-client/src/client.rs
printf '%s\n' '--- protocol aggregate stream conversion ---'
sed -n '216,275p' crates/protocol/src/stream.rsRepository: NVIDIA-NeMo/Switchyard
Length of output: 17426
Preserve aggregate responses in streaming mode.
Driver::call_model forwards LlmResponse::Agg unchanged. into_agg_retaining_events returns no events for an aggregate response, so line 146 replays an empty stream when request.llm_request.stream is true. Return agg.into_stream() for an aggregate source, and add a regression test.
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In `@crates/libsy/src/algorithms/escalation.rs` around lines 145 - 146, Update the
streaming response handling in Driver::call_model to preserve LlmResponse::Agg
values by converting the aggregate with agg.into_stream() instead of replaying
retained events; retain replay_stream_events for event-based responses and add a
regression test covering an aggregate response when streaming is enabled.
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Converting to draft: this change regresses in end-to-end testing and is not ready to merge. The underlying defect is real — Benchmarking the escalation router with Codex against a Kimi-K3 efficient tier, the same five tasks behave as follows:
So replaying the original events changes what the client records for the assistant turn, and the tool-call/tool-result pairing in the client's next request no longer resolves upstream. The synthetic path, whatever else it loses, at least emits tool calls in a shape the client echoes back correctly. Leaving this open as a draft because the preservation loss is worth fixing; the fix needs to keep the replayed items consistent with what the outbound codec and client expect, which this does not yet do. I will update once I have a version that holds up end to end. |
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Closing this. I found why the change regresses, and the approach is wrong. Replaying the retained provider events serves the upstream body verbatim, which bypasses Reproduced by diffing the upstream request bodies with and without the change, on the same client session. The conversation the client replays differs: End to end against a Kimi-K3 efficient tier, the same five tasks go from 5/5 evaluations completing (unchanged) to 3/5 failing outright, with the upstream returning: So the lossiness documented on The underlying observation still stands and may be worth addressing separately: Worth noting the passthrough route serves the same provider events without this problem, so whatever passthrough does differently is probably the right model for a future fix. |
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Problem
The escalation router calls the efficient tier, buffers the reply so the trajectory judge can read the completed turn, and then serves that same buffered reply whenever the judge declines. It rebuilt the served stream with
AggLlmResponse::into_stream(), which documents itself as lossy:The loss happened one step earlier as well.
LlmResponse::into_agg()consumed only each event'snormalizedchunks and dropped itspreservationpayload, so the original provider bodies were already discarded before the response was rebuilt.The result is that every unlatched escalation turn reached the outbound codec as synthetic chunks with no preserved provider bodies, so the codec could not produce a faithful same-format response. Escalation is the only route type that buffers a reply and then serves it, so no other route is affected. Latched turns are also unaffected, because a confirmed session returns before the buffering path.
This is invisible in normal operation: the requests all succeed, and the degradation only shows up as reduced agent quality on the turns that were served from the buffer.
Change
LlmResponse::into_agg_retaining_events(retain_events)aggregates as before, and optionally returns the original stream events alongside the aggregate.into_agg()now delegates to it and keeps its existing behaviour.replay_stream_events()serves previously buffered events verbatim, sopreservationsurvives.The judge still reads the aggregated reply, so verdict behaviour is unchanged.
Testing
retained_events_replay_with_preservation_intactasserts both halves of the contract: replayed events keep the provider payload, and theinto_stream()path still emits synthetic events without preservation.cargo test -p switchyard-protocol -p switchyard-libsy --libpasses: 306 tests, 0 failures.Found while benchmarking the escalation router with Codex on DeepSWE-v1.1, where the buffered path is taken on every turn until a session latches.
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