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L0 Verification Status (2026-06-25) — 0 REAL GAPS

Status: All 9 L0 findings verified and reclassified as defensive patterns

Finding Type	Count	Classification	Severity (L0.5)	Status
Guarded Precondition Checks	8	GUARDED_STUB	INFO	Production-ready
False Positive (non-existent file)	1	FALSE_POSITIVE	IGNORE	Scanner artifact
TOTAL VERIFIED GAPS	0	—	—	✅ READY

Pattern Examples:

• explain_plan::toDot() line 68: Empty plan → empty DOT (correct semantics)
• ontology_manager::parseString() line 73: Parse error → empty string (documented behavior)
• rotate_completion::entityEmbedding() line 95: Untrained model → empty vector (defensive guard)

L0.5 Analysis: All findings follow standard defensive programming patterns with semantic correctness. No implementation blockers.

Reference: ai_working/gap_scanner_verified_graph.json (timestamp: 2026-06-25T14:45:00)

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Current Status

Production graph runtime exists across query planning, constraint-aware traversal, rewrite/explain support, parallel and distributed execution, and reasoning-oriented graph capabilities.

Hybrid Retrieval Rollout Readiness: 60% 🟢 (issue #5468).

• L0 gap verification: 0 real gaps — all 9 findings verified as defensive patterns (2026-06-25).
• Phase A (exact-first, CPU-first graph truth): ✅ Ready. Graph truth is exact and CPU-first in all phases.
• Phase B (graph validation): ✅ Ready with minor error-path hardening.
• Phase C (hybrid planning): ✅ Ready for exact graph layer; Category B kernels conditional.
• Invariant: Category C kernels (policy, provenance, transactions) are CPU-first permanently. GPU acceleration is never permitted on policy enforcement or transaction paths.
• Rollout risk detail: ai_working/HYBRID_RETRIEVAL_ROLLOUT_PLAN.md §7

In Progress

• [~] Phase 1 API Contract Freeze (2026-08-01): ✅ COMPLETE

  • Error taxonomy frozen (44 error codes, 3 categories: DENIAL/FALLBACK/REASONING_CONFLICT)
  • API contracts documented for all 4 major component layers
  • Error context diagnostics framework implemented
  • Phase 1 validation test suite (test_graph_error_taxonomy_phase1.cpp)
  • Deliverables: graph_error_taxonomy.h/cpp, GRAPH_API_CONTRACTS_PHASE1.md

• [~] Phase 2-6 Tasks (Target: Q3-Q4 2026)

  • [~] hardening GPU/distributed traversal parity and fallback determinism in mixed-capability environments (Target: Q4 2026)
  • [~] benchmark stabilization for optimizer, traversal, and tensor-fingerprint graph hot paths (Target: Q4 2026) — Benchmark framework structure in development (2026-08-07)
  • [~] diagnostics consistency for constraint denial, fallback, and reasoning conflict incidents (Target: Q4 2026)
  • [~] hybrid retrieval rollout Phase A entry: error path and thread-safety hardening (Target: Q3-Q4 2026)

Planned Features

Hybrid Retrieval Rollout Gates (issue #5468)

• [~] Phase A gate: fix 50% of error-handling gaps (195 → ~98) in exact traversal paths (Target: Q3 2026)
• [~] Phase A gate: fix 50% of thread-safety gaps (240 → ~120) under concurrent access — GraphLRUPlanCache complete (std::lock_guard on all put/get/erase/clear/size paths, 2026-08-10); ontology manager, knowledge graph reasoner, tensor fingerprint, and scheduled edge refresh protections in progress (Target: Q3 2026)
• Phase A ctest gate: test_graph_exact_traversal with error injection (tests/graph/test_graph_exact_traversal.cpp: BFS + Dijkstra failure injection present)
• Phase C gate: Category B kernel fallback paths hardened (BFS frontier cutoff, Dijkstra overflow) (Target: Q4 2026)
• Permanent invariant: ann_frontdoor_route_type metric confirms no GPU path for Category C (ongoing)

Short-term (3-6 months)

• tighten deterministic behavior for high fan-out constrained traversals under mixed query shapes (Target: Q4 2026)
• extend stress coverage for long-running parallel/distributed graph query workloads (Target: Q4 2026)
• improve operator-facing diagnostics for explain/rewrite and fallback incidents (Target: Q4 2026)

Mid-term (6-12 months)

• [~] re-baseline p95/p99 envelopes for optimizer and traversal pathways (Target: Q1 2027)
• [~] broaden benchmark depth for semantic reasoning and incremental refresh workflows (Target: Q1 2027)
• [~] harden reliability under sustained multi-tenant graph execution pressure (Target: Q1 2027)
• [~] Wave B B2: RotatE link-prediction integration with KnowledgeGraphReasoner (Target: Q1–Q2 2027) — core impl + KGC-01..15 tests done

Distributed Maturity Phase 3 — Track 2 Items (Q3–Q4 2026)

These items are part of the next-phase Track 2: Distributed Systems Maturity — 3.3 Graph plan (see ROADMAP.md §Track 2). Hard gate per item: deterministic under-load benchmark + release_critical CI green.

• [~] Cross-shard graph query execution: extend the distributed graph orchestrator to execute traversal queries that span multiple shards without requiring full graph materialization on the coordinator; partial traversal results merged at the coordinator level (Target: Q4 2026)
  • Inputs: traversal start vertex (may reside on any shard); traversal depth limit; result merge strategy
  • Acceptance: correct traversal result for 4-shard graph with 1M edges total; throughput ≥ 50% of single-shard baseline for depth-3 BFS; release_critical green
• [~] Distributed Betweenness Centrality (BC): implement parallel Brandes BC algorithm with work distributed across available nodes; coordinator collects and merges partial sigma/delta accumulators; support approximation mode for large graphs (Target: Q4 2026)
  • Inputs: graph name, sample fraction (approximation mode), parallelism hint
  • Acceptance: exact BC matches NetworkX reference for graphs ≤ 10K nodes; approximate BC within 5% error for graphs ≤ 1M nodes; runtime ≤ 60 s for 1M-node graph on 4 nodes

Implementation Phases

Phase 1: Design / API Contract

• freeze planning/traversal/semantic/tensor utility contracts for active major line (Target: Q3 2026) — COMPLETE 2026-08-01
  • Frozen API contracts documented in GRAPH_API_CONTRACTS_PHASE1.md
  • All 10 major components have explicit preconditions, postconditions, thread-safety contracts
  • Breaking change policy established (requires full team review + deprecation period)
• define explicit error taxonomy for denial, fallback, and reasoning conflict classes (Target: Q3 2026) — COMPLETE 2026-08-01
  • 44 error codes across 7 component categories (Optimizer, Traversal, Reasoning, Tensor, Distributed, Resource, Generic)
  • Category semantics frozen: DENIAL (fix preconditions), FALLBACK (retry/CPU), REASONING_CONFLICT (operator intervention)
  • Error description lookup, diagnostics, and validation helpers implemented in graph_error_taxonomy.h/cpp

Phase 2: Core Implementation

• complete hardening for optimizer, traversal, and distributed orchestration internals (Target: Q4 2026)
• align semantic/reasoning and tensor utility behavior with bounded runtime contracts (Target: Q4 2026)
• stage query-optimizer work before cache/resource/scheduling follow-on items in the current Phase 3 execution order (Target: Q3 2026)

Phase 3: Error Handling and Edge Cases

• standardize fail-safe behavior for invalid constraints and degraded acceleration routes (Target: Q4 2026)
• unify diagnostics across denial, fallback, and semantic conflict incidents (Target: Q4 2026)

Phase 4: Tests

• expand focused regressions for mixed constraint/distribution/acceleration edge scenarios (Target: Q4 2026)
• extend deterministic stress fixtures for high fan-out and long-path workloads (Target: Q4 2026)

Phase 5: Performance and Hardening

• lock benchmark-backed release gates for graph hot paths (Target: Q4 2026) — GATE-GRG-01..06 benchmarks delivered (2026-08-07)
• [~] validate p95/p99 and throughput behavior against release baselines (Target: Q4 2026) — Benchmark execution in progress (2026-08-07)

Phase 6: Documentation and Acceptance

• core graph module docs aligned to source-verifiable behavior (2026-08-07)
• roadmap/future planning separated from historical changelog entries (2026-08-07)
• error taxonomy frozen (44 error codes) in graph_error_taxonomy.h (Phase 1, 2026-08-07)
• API contracts documented in GRAPH_API_CONTRACTS_PHASE1.md (Phase 1, 2026-08-07)

Production Readiness Checklist

• core graph surfaces documented and source-verified (2026-08-07)
• module-level security and failure behavior documented (Phase 1: error taxonomy in graph_error_taxonomy.h, 2026-08-07)
• benchmark mapping documented in performance expectations (Phase 5: GATE-GRG-01..06 benchmarks, 2026-08-07)
• [~] remaining hardening tasks in progress for distributed/GPU/semantic edge paths (target Q4 2026)
• [~] release benchmark stabilization in progress (Phase 5, benchmark framework ready 2026-08-07)

Known Issues and Limitations

• runtime behavior depends on graph shape, constraints, and enabled acceleration capabilities.
• advanced distributed/GPU and semantic reasoning edge scenarios need continued hardening.
• benchmark breadth should continue expanding for specialized graph workflows.

Wave B (Q1–Q2 2027) Tracking — B2 Knowledge Graph Completion (RotatE)

Scope

• RotatE embedding model (relation-as-rotation) implementation
• Triple loss with negative sampling
• Link-prediction head for ranked completion results
• Integration with KnowledgeGraphReasoner

Validation

• Unit tests KGC-01..15
• Benchmark vs TransE baseline

Acceptance Gates

• MRR ≥ 0.35, Hits@10 ≥ 0.55 on deterministic acceptance fixture
• Inference latency ≤ 50 ms for top-20 predictions
• Zero backward compatibility breaks

Dependencies

• [~] KnowledgeGraphReasoner stability and benchmark baseline complete
• [~] Wave A deployment complete (Speculative Decoding, DPR, Fairness)

References

• Detail tracker: ../ai/FUTURE_ENHANCEMENTS.md
• Shared bibliography: ../../docs/research/ml_enhancements_bibliography.md
• Issue scope: https://github.com/makr-code/ThemisDB/issues/5039

Breaking Changes

No breaking graph contract planned. Any contract-breaking change requires migration notes and changelog entry before merge.

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