[Epic] Upgrade Spector to JDK 27 & Harness Next-Generation JVM Capabilities

[novaspectrayan]

Executive Summary & Strategic Rationale

Spector currently operates on Java 25 with incubator Vector API and preview structured concurrency. JDK 27 reaches General Availability on 2026-09-15 (feature set frozen; RC).

This epic was originally scoped to JDK 26. After JEP review (26 vs 27), we are retargeting the production baseline and feature work to JDK 27 and waiting ~one week for GA rather than landing on JDK 26 (non-LTS; Premier support ends ~2026-09-18).

Full architectural specification: RND-2026-022 (to be revised for JDK 27 naming/JEPs).

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Decision (2026-09-10)

• Baseline: JDK 27 (Temurin), not 26.
• Wait: ~1 week for JDK 27 GA before toolchain cutover ([Toolchain] Upgrade Pom, CI/CD Workflows, and Dockerfiles to JDK 27 #803).
• Do early on 25 (no wait): Compact Object Headers (-XX:+UseCompactObjectHeaders) + value-based class audit — already product features on 25 ([Memory Architecture] Value-Based Class Audit, Compact Object Headers, and AOT Caching with ZGC (JEP 516 / 519 / 534) #808 partial).
• Preview APIs: implement against JDK 27 preview surfaces (avoids rewrite for Structured Concurrency onTimeout → timeout and related JEP 533 changes).

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Sub-Issues & Roadmap

• [Toolchain] Upgrade Pom, CI/CD Workflows, and Dockerfiles to JDK 27 #803: [Toolchain] Upgrade Pom, CI/CD Workflows, and Dockerfiles to JDK 27
• [SDK & Providers] Add HTTP/3 QUIC Protocol Support to SpectorClient and Providers (JEP 517) #804: [SDK & Providers] Add HTTP/3 QUIC Protocol Support (JEP 517 — final since 26; ship on 27)
• [Performance] Migrate Dynamic Singletons and Kernels to LazyConstant (JEP 531) #805: [Performance] Migrate Dynamic Singletons and Kernels to LazyConstant (JEP 531 — 3rd preview in 27)
• [Concurrency] Modernize ConcurrentTasks and ParallelHnswBuilder with JDK 27 Structured Concurrency (JEP 533) #806: [Concurrency] Modernize ConcurrentTasks and ParallelHnswBuilder with Structured Concurrency (JEP 533 — 7th preview in 27)
• [Core/SIMD] Modernize Multi-Precision Quantization with Primitive Pattern Matching (JEP 532) #807: [Core/SIMD] Modernize Multi-Precision Quantization with Primitive Pattern Matching (JEP 532 — 5th preview; no change vs 26)
• [Memory Architecture] Value-Based Class Audit, Compact Object Headers, and AOT Caching with ZGC (JEP 516 / 519 / 534) #808: [Memory Architecture] Value-Based Class Audit, Compact Object Headers (JEP 519/534), and AOT Caching with ZGC (JEP 516)

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Key Benefits for Spector

1. HTTP/3 QUIC Transport (JEP 517): Eliminates head-of-line blocking for token streaming and embedding generation over lossy/flaky agent network links.
2. Lazy Constants (JEP 531): HotSpot C2 constant-folding for SIMD species, CUDA kernels, and provider lookups with zero memory barrier overhead.
3. Valhalla-Readiness & Compact Object Headers (JEP 519 / default in 27 via JEP 534): 15%–30% heap reduction across large memory graphs and vector indices.
4. Sub-120ms MCP Cold Boot with ZGC (JEP 516): GC-agnostic AOT caching enables instant MCP server startup without giving up low ZGC pause times.
5. Structured Concurrency (JEP 533): Timeout/SLA fan-out via Joiner.timeout() (not the JDK 26 onTimeout name).

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Success Criteria

• Clean build and test execution across all modules on JDK 27 (mvn clean test).
• All sub-issues implemented, tested, and verified against JDK 27 APIs.
• CI/CD pipeline and release packaging running on JDK 27.
• Preview features documented with --enable-preview (and incubator modules where required).

[jarvispectrayan]

Retarget complete (2026-09-10): Epic and sub-issues #803–#808 updated from JDK 26 → JDK 27.

• Waiting ~1 week for JDK 27 GA (scheduled 2026-09-15) before toolchain cutover ([Toolchain] Upgrade Pom, CI/CD Workflows, and Dockerfiles to JDK 27 #803).
• Preview work ([Performance] Migrate Dynamic Singletons and Kernels to LazyConstant (JEP 531) #805 Lazy Constants / JEP 531, [Concurrency] Modernize ConcurrentTasks and ParallelHnswBuilder with JDK 27 Structured Concurrency (JEP 533) #806 Structured Concurrency / JEP 533, [Core/SIMD] Modernize Multi-Precision Quantization with Primitive Pattern Matching (JEP 532) #807 Primitive patterns / JEP 532) implements once against 27 APIs.
• [SDK & Providers] Add HTTP/3 QUIC Protocol Support to SpectorClient and Providers (JEP 517) #804 HTTP/3 (JEP 517) and AOT (JEP 516) remain valid; ship on 27 baseline.
• [Memory Architecture] Value-Based Class Audit, Compact Object Headers, and AOT Caching with ZGC (JEP 516 / 519 / 534) #808: Compact Object Headers can proceed on JDK 25 now (-XX:+UseCompactObjectHeaders); becomes default in 27 (JEP 534).

cc decision owner: wait for GA, then execute.

[jarvispectrayan]

Architecture Spec & Labeling Update (2026-09-12)

• Specification Revised: RND-2026-022: Java 27 Upgrade Strategy, Valhalla Value Architecture, and Next-Generation Feature Roadmap has been officially updated and committed to spectrayan/RnD/.
• Labeling: Applied the jdk-upgrade label across issues [Epic] Upgrade Spector to JDK 27 & Harness Next-Generation JVM Capabilities #802, [Toolchain] Upgrade Pom, CI/CD Workflows, and Dockerfiles to JDK 27 #803, [SDK & Providers] Add HTTP/3 QUIC Protocol Support to SpectorClient and Providers (JEP 517) #804, [Performance] Migrate Dynamic Singletons and Kernels to LazyConstant (JEP 531) #805, [Concurrency] Modernize ConcurrentTasks and ParallelHnswBuilder with JDK 27 Structured Concurrency (JEP 533) #806, [Core/SIMD] Modernize Multi-Precision Quantization with Primitive Pattern Matching (JEP 532) #807, and [Memory Architecture] Value-Based Class Audit, Compact Object Headers, and AOT Caching with ZGC (JEP 516 / 519 / 534) #808.
• EA/RC Strategy Approved: Pre-release implementation initiates immediately on branch epic/802-jdk27-upgrade ahead of JDK 27 GA (2026-09-15).

[forgespectrayan]

🚀 Implementation Complete & PR Submitted: #877

All deliverables across issues #803, #804, #805, #806, #807, and #808 have been successfully implemented and verified on OpenJDK 27 Early Access (27-ea+22-2010).

Pull Request: #877

Summary of Delivered Work:

1. Toolchain & Build ([Toolchain] Upgrade Pom, CI/CD Workflows, and Dockerfiles to JDK 27 #803): Bumped toolchain to JDK 27, configured Maven compiler/surefire with --enable-preview and jdk.incubator.vector, updated CI workflows to 27-ea (Oracle OpenJDK), and added ASM class file version 71 compatibility for ArchUnit rules.
2. Structured Concurrency ([Concurrency] Modernize ConcurrentTasks and ParallelHnswBuilder with JDK 27 Structured Concurrency (JEP 533) #806): Refactored ConcurrentTasks.java to JDK 27 JEP 533 API (allSuccessfulOrThrow returning direct typed List<T>, standard ExecutionException handling, timeout handling), and resolved NEON SIMD vector shape constraints.
3. LazyConstant ([Performance] Migrate Dynamic Singletons and Kernels to LazyConstant (JEP 531) #805): Converted singletons and hardware capability caches (SimdCapability, AcceleratorRegistry, GpuCapability, HdcAlgebra) to java.lang.LazyConstant for zero-overhead hardware acceleration lookups.
4. Primitive Pattern Matching ([Core/SIMD] Modernize Multi-Precision Quantization with Primitive Pattern Matching (JEP 532) #807): Modernized quantization boundaries in ScalarQuantizer and TurboQuantizer using JDK 27 pattern matching in switch (JEP 532).
5. HTTP/3 QUIC ([SDK & Providers] Add HTTP/3 QUIC Protocol Support to SpectorClient and Providers (JEP 517) #804): Added HTTP/3 support to SpectorClient (.http3Enabled(true)), LangChain4jHelper, OllamaCompletionClient, and Synapse ChatService with graceful fallback (JEP 517).
6. Value Architecture & Compact Object Headers ([Memory Architecture] Value-Based Class Audit, Compact Object Headers, and AOT Caching with ZGC (JEP 516 / 519 / 534) #808): Completed value-based class audit & certification tests for core records (Hypervector, ScoredResult, Chunk), enabled -XX:+UseCompactObjectHeaders across packaging scripts and Dockerfiles, configured -XX:+UseZGC for low-latency boot, and created scripts/generate-aot-cache.sh for Leyden AOT cache generation (JEP 516).

All test suites pass cleanly with zero regressions. Branch epic/802-jdk27-upgrade is ready for CEO Bharat's review.