Adds "prefix-threshold" to the valid disaggregation decider names in
bundle.go, enabling IsValidDisaggregationDecider() and
ValidDisaggregationDeciderNames() to recognize the new decider.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Adds PDPrefixThreshold int to DeploymentConfig for the prefix-threshold
decider's non-cached token threshold. Adds --pd-prefix-threshold CLI flag
(default 512) with >= 0 validation. Updates --pd-decider description to
include "prefix-threshold". Wires PDPrefixThreshold into the config
construction in cmd/root.go.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…rver

- cluster.go: branch on PDDecider=="prefix-threshold" to construct
  PrefixThresholdDecider(PDPrefixThreshold, BlockSizeTokens) directly;
  add notifyDisaggregationObserver helper
- cluster_event.go: call notifyDisaggregationObserver after RoutingDecisionEvent
  injection (standard routing path, BC-PD-28)
- pd_events.go: call notifyDisaggregationObserver after PrefillRoutingEvent
  injection (disaggregated path, BC-PD-28)
- disaggregation_test.go: add integration tests verifying wiring, high/low
  threshold behavior, observer call, and transfer conservation

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…reshold

Documents DisaggregationObserver interface, PrefixThresholdDecider, and
PDPrefixThreshold in the file organization table. Adds --pd-prefix-threshold
to the CLI flags list and the disaggregated data flow CLI flags summary.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Round 1 fixes:
- Update DisaggregationObserver docstring with R13 note and R17 signal
  freshness guarantee
- Add noopDisaggregationObserver to satisfy R13 (>=2 implementations)
- Add explicit comment in DecodeRoutingEvent explaining why observer
  is intentionally not called on the decode sub-path
- Add 'Adding New Disaggregation Deciders' section to extension-recipes.md
  covering both stateless and stateful patterns
- Fix Decide() docstring: clarify hash-reuse fires only on non-disaggregated
  path (disaggregated path receives prefill sub-request with different ID)

Round 2 fixes:
- Remove structural TestPrefixThreshold_DeciderWiredCorrectly; replace
  with compile-time interface assertion (behavioral coverage exists in
  ZeroThresholdAlwaysDisaggregates and HighThresholdNoDisaggregation)
- Add PDPrefixThreshold field to newTestDisaggDeploymentConfig (R4
  construction site audit)
- Add PD disaggregation row to CLI Flag Summary table in configuration.md
  including --pd-prefix-threshold and all PD flags introduced in PR1-PR4

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…ound 3)

- Add logrus.Warn when --pd-prefix-threshold is explicitly set but
  --pd-decider is not "prefix-threshold" (silent flag ignored, R3 spirit)
- Add PD Disaggregation section to docs/reference/configuration.md
  explaining decider options, prefix-threshold semantics (non-cached
  tokens vs total tokens), default value meaning, and all PD flags

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…arming effect

TestPrefixThreshold_ObserverWarmsCache replaces the previous
TestPrefixThreshold_ObserverCalledAfterRouting which only checked
causality invariants (TransferCompleteTime != 0) and did not verify
that the DisaggregationObserver actually warmed the prefix cache.

The new test uses two requests with a shared 192-token prefix
(threshold=150): req1 disaggregates (192 > 150 with empty cache),
observer records 12 blocks, req2 arrives later with the same prefix
(58 non-cached tokens ≤ 150) and is routed locally — proving the
observer was called and the cache was warmed.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…n.md cross-link

- extension-recipes.md: add missing step 4 (update configuration.md table) and
  fix touch-point count from 3 to 4 for stateless disaggregation deciders
- configuration.md: replace broken cross-link to non-existent
  architecture.md#pd-disaggregation with descriptive text documenting
  the pool topology constraint (prefill + decode <= num-instances)

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…tingEvent

- Restore droppedKVAllocations counter and DroppedKVAllocations() accessor
  (R1: count dropped requests — never silent)
- Move AssignedInstance/DecodeInstanceID/DecodeEnqueueTime assignment to
  after successful AllocateTransferredKV check to prevent inconsistent state
  on failure
- Restore DroppedKVAllocations() in cmd/root.go anomaly counter output
- Add INV-PD-1 through INV-PD-5 back to invariants.md for DRY compliance
  (these were in CLAUDE.md but not the canonical standards doc)

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

…uctural tests

Critical: Add CLI validation that --pd-decider other than "never" requires
--prefill-instances and --decode-instances to be set (R1: no silent config
failure).

Important:
- Remove superseded disaggregation decider recipe (incorrect field names,
  wrong flag names, stale purity contract) from extension-recipes.md
- Add prefix-threshold to first PD flags table in configuration.md
- Replace internal field accesses (cs.parentRequests, cs.transfersInitiated,
  cs.trace, cs.droppedAtDecodeKV) with public accessors (cs.ParentRequests(),
  cs.Trace(), cs.DroppedKVAllocations()) in disaggregation_test.go for
  refactor survival (BDD/TDD principle inference-sim#5)

Also includes minor comment condensations from code-simplifier agent.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Add the new PD-mode anomaly counter to the results guide so users
understand what it means when decode KV allocation fails.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>