Roadmap

🗺️ Roadmap

Spector is under active development. This page details planned improvements, their projected impact, and implementation status.

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Compression & Quantization

✅ SVASQ-4 — Half-Precision SVASQ (INT4 Codes) {#svasq-4}

success: Completed Implemented and merged. Available via SpectorEngine.builder().svasq4() or QuantizedHnswIndex.svasq4(...).

Replace INT8 [-127, 127] codes with INT4 [-7, 7] codes in the SVASQ pipeline. The FWHT rotation still equalizes variance, so INT4 quantization error remains uniformly distributed — just at a coarser granularity (15 levels vs 255).

Memory layout:

[float32 normSq (4 bytes)] [INT4 × paddedDim nibble-packed (paddedDim/2 bytes)]

Dims	Current SVASQ-8	SVASQ-4	Compression vs float32
384 → 512	516 B	260 B	5.9×
768 → 1024	1028 B	516 B	6.0×
4096	4100 B	2052 B	8.0×

Recall:

• Without rescore: ~95–97% recall@10
• With 3× oversampling rescore: ~97–99% recall@10

Key design decisions:

• Separate Svasq4Encoder / Svasq4SimdKernel classes (not parameterizing SVASQ-8) to avoid impacting existing code
• Offset encoding [0, 14] keeps byte values non-negative for correct castShape sign extension
• Deinterleaved hi/lo query arrays match nibble layout for natural SIMD ILP
• Tighter clipping (2.5σ vs 3.0σ) optimizes for 15 quantization levels

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🔜 Padding-Aware Storage — Skip Zero Dimensions {#padding-aware}

info: Status: Planned (next) Low effort, zero recall loss for L2 distance. Highest ROI pending improvement.

SVASQ pads vectors to the next power-of-two dimensionality (e.g., 768 → 1024), adding wasted bytes. The padded dimensions are zero-filled before FWHT, so their rotated codes are predictable. We can store only the first originalDim codes and reconstruct padded codes at query time.

Dims	paddedDim	Current SVASQ-8	Padding-Aware	Savings
384	512	516 B	388 B	25%
768	1024	1028 B	772 B	25%
1536	2048	2052 B	1540 B	25%
4096	4096	4100 B	4100 B	0% (already pow2)

Recall impact: None for L2 distance — padded dimensions contribute a constant offset that doesn't affect ranking.

warning: SIMD Tail Loop The current SIMD kernel exploits paddedDim % VL == 0 to avoid tail loops. Storing only originalDim codes breaks this, requiring either a scalar tail loop or alignment padding to the next SIMD boundary (e.g., round up to multiple of 16 bytes).

Changes required:

• SvasqEncoder / Svasq4Encoder: Store only originalDim codes, update bytesPerVector()
• SvasqSimdKernel / Svasq4SimdKernel: Handle non-power-of-2 loop bound (SIMD-aligned padding recommended)

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🔜 Norm Header Compression — float32 → float16 {#norm-f16}

info: Status: Planned (next) Very low effort. Negligible recall impact.

The 4-byte float32 exactNormSq header can be compressed to 2 bytes using float16 (half-precision). Java 21+ provides Float.floatToFloat16() and Float.float16ToFloat() for lossless conversion.

Savings: 2 bytes per vector. Small absolute savings but trivial to implement.

Combined with	Before	After	Savings
SVASQ-8 (768-dim)	1028 B	1026 B	0.2%
SVASQ-4 (768-dim)	516 B	514 B	0.4%
Padding-aware SVASQ-8 (768-dim)	772 B	770 B	0.3%

Recall impact: < 0.01% — float16 has ~3 decimal digits of precision. For L2 ranking, the norm header is a per-vector constant that shifts all distances equally.

Changes required:

• SvasqEncoder / Svasq4Encoder: Use Float.floatToFloat16() for 2-byte header write
• SvasqSimdKernel / Svasq4SimdKernel: Read with Float.float16ToFloat(segment.get(JAVA_SHORT, offset))

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🔬 SVASQ-PQ Hybrid — Product Quantization of SVASQ Residuals {#svasq-pq}

note: Status: Future Research Very high implementation effort. Most aggressive compression option.

After FWHT rotation, instead of scalar INT8/INT4 quantization, apply Product Quantization to the rotated coordinates. The FWHT rotation makes coordinates near-independent (isotropized), which is the ideal input distribution for PQ — similar to how Optimized PQ (OPQ) works with learned rotations, but using FWHT instead of an expensive SVD-based rotation matrix.

Memory layout:

[float32 normSq (4 bytes)] [PQ codes: M bytes (one centroid ID per subspace)]

With M=16 subspaces, K=256 centroids:

Dims	Float32	SVASQ-8	SVASQ-PQ (M=16)	Compression vs float32
768	3,072 B	1,028 B	20 B	154×
4096	16,384 B	4,100 B	68 B	241×

Recall impact:

• PQ on FWHT-rotated residuals: ~85–93% recall@10
• FWHT rotation gives ~3–5% recall advantage over naive PQ (pre-decorrelates dimensions)
• Rescore with exact float32 residuals pushes recall to 95%+

Why it works: The FWHT rotation is essentially a free, lossless "Optimized PQ" rotation — it decorrelates dimensions without requiring an expensive SVD or learned rotation matrix. This means PQ subspaces can be independent slices of the rotated vector, which is information-theoretically optimal.

Implementation scope:

• Train PQ codebooks per shard (or globally after FWHT rotation)
• Asymmetric Distance Computation (ADC) lookup tables during search
• New SIMD kernel for PQ distance computation
• Integration with existing ProductQuantizer in spector-index

danger: Complexity Warning This is essentially building a new quantization mode. The existing ProductQuantizer could be adapted, but integrating it with the FWHT rotation pipeline is non-trivial. Estimated effort: 2–4 weeks.

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🔬 Flat-Mode SVASQ — Compress Flat-Shard Storage {#flat-svasq}

note: Status: Future Research Medium effort, good payoff for large flat shards.

In SpectorShard's flat mode, residuals are stored as raw float32[]. Since all residuals in a shard share the same centroid, they have similar statistical distributions. SVASQ quantization of flat residuals could compress flat-mode storage by ~3× without changing the shard architecture.

Savings:

Scenario	Current (float32)	With SVASQ	Savings
10K vectors × 768 dims	30 MB/shard	10 MB/shard	3×
50K vectors × 4096 dims	781 MB/shard	195 MB/shard	4×

Recall impact:

• If applied only to storage (decode for search): None — search uses decoded float32
• If applied to search (scan quantized codes directly): Same as SVASQ-8 (~99.5%)

Implementation scope:

• Integrate SVASQ encoding into the flat-mode ingestion path
• Modify SpectorShard.flatScan() to use the SVASQ SIMD kernel directly
• Per-shard calibration using the shard's centroid residuals

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🔴 Adaptive Bit-Width SVASQ {#adaptive-bw}

warning: Status: Not Recommended Very high effort, marginal benefit due to FWHT already equalizing variance.

Instead of uniform INT8 across all dimensions, assign more bits to high-variance dimensions and fewer to low-variance ones (after FWHT rotation):

• Dimensions with σ > 2× median: 8 bits
• Dimensions with σ < 0.5× median: 4 bits
• Others: 6 bits

Projected savings: ~10–15% additional compression.

Recall impact: Minimal (< 0.5%) — allocating bits proportionally to variance is information-theoretically optimal.

Why it's not recommended: FWHT already equalizes variance by design, so the marginal gain from adaptive bit-widths is small. The implementation requires variable-length encoding, non-aligned SIMD reads, and per-dimension bit-width bookkeeping — the worst effort-to-benefit ratio of all proposed improvements.

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Agentic AI

✅ Native MCP Server {#mcp-server}

success: Completed Implemented in spector-mcp module. 6 tools, stdio transport, agent-native search.

Built-in Model Context Protocol server that gives AI agents (Claude Desktop, Cursor, autonomous agents) direct, in-process access to Spector’s search engine. Zero network overhead — tool handlers call SpectorEngine directly via virtual threads.

Tools: semantic_search, hybrid_search, rag_query, ingest_document, delete_document, engine_status

Architecture:

• McpToolHandler abstract base class (common timing, error handling, arg parsing)
• ToolSchemaBuilder fluent JSON schema construction
• SpectorToolRegistry for extensible tool registration
• SpectorResourceProvider + SpectorPromptProvider for MCP resources/prompts
• ResultFormatter shared formatting utilities

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🔜 Streamable HTTP Transport {#mcp-http}

info: Status: Planned (next) Stdio covers Claude Desktop, Cursor, and all local agents. HTTP needed for cloud/remote deployments.

Add HTTP-based MCP transport for scenarios where the agent and Spector run on different machines. The official MCP SDK supports Streamable HTTP transport — Spector would expose the same 6 tools over an HTTP endpoint.

Use cases: Cloud deployments, remote agent connections, multi-agent architectures.

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🔬 LoRA Adapter Routing {#lora-routing}

note: Status: Future Research Requires LoRA weight format specification and SIMD matrix multiply implementation.

Multi-tenant query projection via SIMD matrix multiply. Instead of creating separate indexes per tenant, store one base index and apply per-tenant LoRA weight matrices at query time using Panama FMA loops.

How it works:

• Ingest base model embeddings once
• Each tenant uploads a small LoRA matrix ($W_A$, typically 768×32 or similar)
• At query time: $q_{tenant} = q_{base} \times W_A$ (microseconds via Panama SIMD)
• Search the same index with the projected query

Expected impact: Zero-downtime multi-tenant customization without index duplication.

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🔬 ColBERT Late Interaction Reranking {#colbert}

note: Status: Future Research Requires token-level vector storage and MaxSim SIMD kernel.

Native ColBERT reranking using Panama FMA loops. ColBERT stores a vector for every token in a document, then computes relevance via MaxSim (maximum similarity per query token). Python struggles with this due to GIL contention when routing massive matrices between C++ and Python memory.

Spector advantage: Off-heap MemorySegment arrays and Fused-Multiply-Add Panama loops can natively execute ColBERT MaxSim reranking faster than almost any competitor.

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Cognitive Graph Memory

✅ 3-Layer Cognitive Graph {#cognitive-graph}

success: Completed All four phases implemented and merged. 357 tests pass, 0 failures.

Full graph augmentation layer for spector-memory — three biologically-inspired graph structures that augment vector recall with associative, temporal, and relational signals.

Architecture:

RecallPipeline
  Step 5a: Habituation + Inhibition of Return
  Step 5b: STDP causal boost (CoActivationTracker)
  Step 5c: Hebbian spreading activation (HebbianGraph, depth=2)
  Step 5d: Temporal chain extension (TemporalChain, maxHops=3)
  Step 5e: Entity graph traversal (EntityGraph, 2-hop BFS)

Layer 1 — Hebbian Association Graph:

• Off-heap adjacency list (164B/node, MAX_DEGREE=20) via Panama MemorySegment
• Edge strengthening, decay (0.9 factor per consolidation), spreading activation
• Persistence via HGPH magic header, chunked 64KB FileChannel I/O
• CoActivationTracker migrated to off-heap: OffHeapPairTable (32B/slot) + OffHeapEdgeTable (40B/slot)
• Persistence via COAX magic header with hash→tag reverse map

Layer 2 — Entity-Relationship Graph:

• Off-heap entity store (48B/entity, 16B/edge), BFS traversal with typed edge filtering
• 22 entity types × 21 relation types
• EntityExtractor SPI with LlmEntityExtractor (externalized prompt template) and NoOpEntityExtractor
• Persistence via ENTG magic header with nameIndex reconstruction

Layer 3 — Temporal Causal Chain:

• Off-heap linked list (16B/node: prevIdx + nextIdx + sessionId + pad)
• Session-local memory linking at ingestion, forward/backward traversal at recall
• Persistence via TPCH magic header

Error framework: 6 error codes (SPE-310-006..011), 7 granular exception classes extending SpectorGraphException. All catch sites use catch(RuntimeException) → create exception → log(ex.getMessage()). No string concatenation.

Each graph step is additive and gracefully degrading — if the graph is null/empty or the operation throws, the step is a no-op.

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🔜 Temporal Chain Pruning {#temporal-pruning}

info: Status: Planned (next) Low effort. Prevents unbounded temporal chain growth.

Temporal chain links are permanent — unlike Hebbian edges which decay via decayEdges(0.9f), temporal links have no homeostasis mechanism. Old session-local links waste slots indefinitely.

Design:

• Add pruneOlderThan(long cutoffEpochMs) to TemporalChain
• Replace the pad:4B field in the 16B node layout with epochSec:4B (seconds since epoch, ~136 year range)
• Integrate into DefaultSpectorMemory.reflect() after Hebbian decay
• Configurable retention period via Builder: temporalRetentionDays(int) (default: 7)

Effort: ~0.5 day

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🔜 Cross-Layer Promotion (Hebbian → Entity) {#cross-layer-promotion}

info: Status: Planned (next) Medium effort. Enables automatic knowledge graph construction from statistical patterns.

Promote strong statistical Hebbian associations into explicit entity relations during sleep consolidation — analogous to hippocampal replay.

Design:

• During reflect(), scan HebbianGraph for edges with weight ≥ 0.8 AND activationCount ≥ 5
• For each strong edge, look up shared entities via EntityGraph.memoriesForEntity()
• If shared entities exist, strengthen the entity relation edge; if none, create a RELATED_TO relation
• Add promotionThreshold(float) and promotionMinActivations(int) to Builder config
• Add PromotionReport record for observability: promotedCount, strengthenedCount, skippedCount

Effort: ~1-2 days

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🔜 Entity Graph Decay + Node Merging {#entity-decay}

info: Status: Planned Medium effort. Prevents entity graph bloat.

Entity graph edges accumulate without decay. Near-duplicate entities (e.g., "John Smith" and "J. Smith") should be merged during consolidation.

Design:

• Add decayRelations(float factor) to EntityGraph — multiplicative decay, prune below threshold
• Add mergeEntities(int sourceId, int targetId) — redirect all edges and memory links
• Fuzzy name matching via Levenshtein distance during consolidation
• Integrate into reflect() cycle

Effort: ~1-2 days

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🔜 Graph-Aware Scoring Weights {#graph-scoring}

info: Status: Planned Low effort. Highest ROI among remaining graph improvements.

Extract hardcoded graph score attenuation factors into a configurable GraphScoringPolicy.

Current hardcoded values:

Factor	Current Value	Used In
Hebbian boost	0.3f	RecallPipeline Step 5c
Temporal forward	0.8f	RecallPipeline Step 5d
Temporal backward	0.7f	RecallPipeline Step 5d
Entity hop attenuation	0.25f	RecallPipeline Step 5e

Design:

public record GraphScoringPolicy(
    float hebbianBoostFactor,     // default 0.3
    float temporalForwardFactor,  // default 0.8
    float temporalBackwardFactor, // default 0.7
    float entityHopAttenuation,   // default 0.25
    int hebbianMaxDepth,          // default 2
    int temporalMaxHops,          // default 3
    int entityMaxHops             // default 2
) {}

• Configurable via Builder: graphScoringPolicy(GraphScoringPolicy)
• Future: online tuning based on user reinforcement/suppression feedback

Effort: ~0.5 day

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Compute & Hardware

🔜 GPU Kernel Dispatch {#gpu-dispatch}

info: Status: Infrastructure Ready CUDA context management and Panama FFM bridge are implemented. The compute kernel dispatch is pending.

Ship actual CUDA compute kernels for batch cosine similarity and HNSW neighbor selection. The existing spector-gpu module provides context management, memory allocation, and kernel loading via Panama FFM — the remaining work is the CUDA kernel code itself.

Prerequisites: CUDA Toolkit 12+ on the host machine.

Expected impact: 10–100× throughput improvement for batch similarity computation on large datasets (> 100K vectors).

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🔬 NPU Acceleration {#npu}

note: Status: Exploratory Depends on Intel/AMD NPU SDK maturity.

Leverage Intel NPU (via OpenVINO) or AMD XDNA (via DirectML) for INT8 batch operations. NPUs are optimized for low-precision matrix operations, making them ideal for quantized SVASQ distance computation.

Target workloads: INT8/INT4 batch similarity, SVASQ kernel offload.

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Runtime & Deployment

🔬 WASM Runtime for Edge Deployment {#wasm}

note: Status: Exploratory Depends on GraalWasm or Chicory maturity for JVM → WASM compilation.

Compile the core SIMD kernels and HNSW index to WebAssembly for browser-based or edge deployment. This would enable client-side semantic search without a server round-trip.

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🔬 Project Valhalla Value Classes {#valhalla}

note: Status: Future Research Exploratory evaluation of JEP 401 (Value Classes and Objects). Requires Project Valhalla Early-Access builds.

Migrate hot-path intermediate records (e.g., CognitiveResult, candidate pairs, search options) to value class (or value record). This will allow the JVM JIT compiler to perform aggressive scalar replacement and store value arrays contiguously in memory, eliminating garbage collection overhead and pointer-chasing latency during HNSW index traversals.

Benefits:

• Zero-GC Hot Path: Short-lived search results and option records are stack-allocated, avoiding the JVM heap.
• Cache Locality: Contiguous storage of value structures inside arrays prevents pointer chasing.
• Header Elimination: Removes standard 12-to-16-byte JVM object headers for inline arrays.

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✅ Structured Concurrency (JEP 505) {#structured-concurrency}

success: Completed Implemented via ConcurrentTasks in spector-commons. Dual-mode: structured concurrency (default) with classic ExecutorService fallback via -Dspector.concurrency.structured=false.

Migrated all 6 concurrency sites from unstructured ExecutorService + Future to the JEP 505 StructuredTaskScope API, centralized in ConcurrentTasks:

Site	Module	Pattern	Benefit
HybridSearchOrchestrator	spector-query	2-way fan-out (keyword ∥ vector)	Auto-cancel sibling on failure
ClusterCoordinator	spector-node	N-way shard fan-out	Auto-cancel all on shard failure
DistributedQueryCoordinator	spector-node	N-way with timeout + partial results	Clean timeout via awaitAll() + withTimeout()
ParallelEmbeddingPipeline	spector-embed-api	N-way batch embedding	Scope-per-call, no executor lifecycle
ParallelPqTrainer	spector-index	M-way K-Means subspace training	All-or-nothing structured scope
BM25Index	spector-index	Parallel term scoring	Auto-cancel with sequential fallback

Key design decisions:

• Centralized in ConcurrentTasks (spector-commons) for single-point updates when JEP finalizes
• Feature flag: -Dspector.concurrency.structured=false for fallback to classic virtual threads
• forkJoinAll(): all-or-nothing with auto-cancel (uses awaitAllSuccessfulOrThrow Joiner)
• forkJoinPartial(): deadline-based with LabeledTask/PartialResult records (uses awaitAll Joiner + Configuration.withTimeout())

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Summary Table

#	Improvement	Category	Effort	Status
1	SVASQ-4	Compression	Medium	✅ Done
2	Native MCP Server	Agentic AI	Medium	✅ Done
3	3-Layer Cognitive Graph	Graph Memory	High	✅ Done
4	Structured Concurrency	Runtime	Low	✅ Done
5	Padding-aware storage	Compression	Low	🔜 Next
6	Norm header f16	Compression	Very Low	🔜 Next
7	Temporal chain pruning	Graph Memory	Low	🔜 Next
8	Cross-layer promotion	Graph Memory	Medium	🔜 Planned
9	Entity graph decay + merging	Graph Memory	Medium	🔜 Planned
10	Graph scoring weights	Graph Memory	Low	🔜 Planned
11	Streamable HTTP transport	Agentic AI	Medium	🔜 Planned
12	GPU kernel dispatch	Compute	Medium	🔜 Infra ready
13	SVASQ-PQ hybrid	Compression	Very High	🔬 Research
14	Flat-mode SVASQ	Compression	Medium	🔬 Research
15	LoRA adapter routing	Agentic AI	High	🔬 Research
16	ColBERT late interaction	Agentic AI	High	🔬 Research
17	NPU acceleration	Compute	High	🔬 Exploratory
18	WASM edge runtime	Runtime	High	🔬 Exploratory
19	Project Valhalla	Runtime	Medium	🔬 Research
20	Adaptive bit-width	Compression	Very High	🔴 Not planned