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… of crashing _update_requests_with_invalid_blocks unpacks a single block-id list, so a hybrid (Mamba+attention) model attached to a KV connector crashes EngineCore with 'too many values to unpack' the first time a remote chunk fails to load. Multi-group requests now take a dedicated recovery path: - Group coverage uses the engine's own outer-spec rule (AttentionSpec scaled by DCP) over groups that participate in prefix caching, scanning only the possibly-externally-computed prefix. - A failure in any group invalidates every participating group's cached hashes (evict_blocks removes hashes only, never returning DMA-owned receive buffers to the pool), because state groups depend on the full-attention boundary state; partial resume is unsound. - Recompute policy marks the request skip_reading_prefix_cache, preempts RUNNING requests through the normal _preempt_request path back into the waiting queue, and resets async WAITING_FOR_REMOTE_KVS requests to zero so the existing finished-recv flow frees their groups. - Fail policy reports affected requests and the eviction set without touching recompute state; single-group requests keep the existing longest-valid-prefix and shared-block optimizations. Validated on GLM-5.3-Flash TP4 with a real external KV store: before the fix every hybrid chunk failure killed EngineCore; after it, requests recompute and the engine survives. A CPU-only AST regression suite exercises the six failure/async/preempt/fail-policy paths (pristine main fails with the unpack ValueError, patched passes 5/5).
Four CPU-only regressions through the real Scheduler with a two-group (attention + aligned mamba) KV cache config: - Failure in the attention group: the hybrid request replays from zero (PREEMPTED back to waiting, skip_reading_prefix_cache, zero computed tokens) and both groups' identifications are consistent; not the pre-fix ValueError from the single-list unpack and not a partial resume at the failed block index. - Failure inside the state (mamba) group is equally fatal to the shared prefix. - Async WAITING_FOR_REMOTE_KVS failure resets computed tokens to zero, keeps the queued buffers pending finished-recving, and leaves sibling requests untouched. - kv_load_failure_policy='fail' reports the request as FINISHED_ERROR with no silent recompute (HMA mock, since the upstream request_finished path fail-closes on non-HMA connectors for hybrid groups).
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Purpose
Scheduler._update_requests_with_invalid_blocksunpacks a single block-id list:For a hybrid (multi-group) model attached to a KV connector,
get_block_idsreturns one list per KV cache group, so the first failed remote chunk load kills EngineCore withValueError: too many values to unpack (expected 1, got N)— observed live on GLM-5.3-Flash TP4 (6 groups) with dfkv/Mooncake-style stores; the same crash reproduces with any KV connector on a hybrid model.Even without the crash, the single-group recovery semantics (truncate
num_computed_tokensat the first failed block and resume) are unsound for hybrid models: state groups (mamba) depend on the full-attention group's boundary state, so resuming one group at a partial prefix while another group failed produces silently inconsistent KV.This PR makes hybrid requests replay from zero with every participating group's prefix hashes invalidated:
kv_cache_manager.evict_blocks(hash-only: receive buffers the connector still owns are not returned to the allocator).recomputepolicy (default): the request is markedskip_reading_prefix_cache, RUNNING requests are preempted through the normal_preempt_requestpath back into the waiting queue, and asyncWAITING_FOR_REMOTE_KVSrequests reset to zero so the existing finished-recv flow frees their groups.failpolicy reports the affected requests and eviction set without touching recompute state; single-group requests keep the existing longest-valid-prefix and shared-block optimizations unchanged.No wire, connector, or allocator contracts change; non-hybrid models take exactly the previous code path (
len(group_block_ids) == 1).Test Plan
CPU-only regressions exercising the real Scheduler (not stubs) with a two-group config (full-attention + aligned mamba), through the existing
tests/v1/kv_connector/unitfixture utilities:num_computed_tokens == 0,skip_reading_prefix_cache is True, attention prefix hashes evicted (no partial resume)failpolicy → FINISHED_ERROR, no silent recompute (HMA connector mock: upstreamrequest_finishedfail-closes on non-SupportsHMA connectors for hybrid groups)Test Result
Before the fix, every scenario raises
ValueError: too many values to unpack (expected 1, got 6)— EngineCore dies on the first hybrid load failure. After:Both suites also passed on the deployment configuration where the crash was first observed (GLM-5.3-Flash TP4 + external KV store; failed chunk loads now recompute and the engine survives).