Lab L8 — Harness Adapter Interface & Cross-Harness Execution Engine

Phase 6 · MULTI-HARNESS — Lab L8
Status: Authored & Empirically Verified.
Student Lab Package: Authenticated Direct Download from VTAlgo Platform
Branches: main (starter template) · solution (reference architecture).
Video Master: 04:45 min @ 1080p FHD 60fps NVENC · Audio Elmer Oficial (-16 LUFS, Zero BGM) · Curated Synchronized Subtitles (ASS).
Canonical Path: Student repo only — not E:\bridle, not the Kratos live product.

1. Laboratory Objective

Construct from scratch in pure Go an industrial-grade Multi-Harness Adapter Interface & Cross-Harness Execution Engine, proving empirically that enterprise multi-agent systems require capability negotiation via bitmasks, non-blocking ring-buffered stdio isolation, clean OS process group teardown, and transactional cascade failover with atomic workspace rollback.

The student implements:

• An immutable canonical adapter interface (Adapter) with strongly-typed capability bitmasks (Capability).
• $O(1)$ capability probing and dynamic handshake negotiation rejecting incompatible engines before task dispatch.
• A high-fidelity mock adapter with simulated latency, token accounting, and programmatic fault injection (timeouts, exit code failures, syntax panics).
• A safe subprocess CLI adapter with concurrent stdout/stderr scanners streaming into a bounded 4 MB circular ring buffer.
• Robust OS process group tree termination preventing orphan zombie processes upon context deadline cancellation.
• A thread-safe dispatcher coordinating cascade fallbacks, atomic workspace rollback hooks, and redundant execution cross-validation.
• A 10/10 deterministic in-memory test suite executing in $<300$ ms with zero data races.

2. The Four Cardinal Subsystems

┌──────────────────────────────────────────────────────────────────────────┐
│        MULTI-HARNESS ADAPTER INTERFACE & DISPATCH ENGINE (PURE GO)       │
│                                                                          │
│  ┌─────────────────────────┐           ┌──────────────────────────────┐  │
│  │  1. Adapter & Bitmasks  │           │  2. In-Memory Mock Adapter   │  │
│  │     TaskEnvelope        ├──────────►│     Fault Injection Engine   │  │
│  │  (O(1) Capability Probe)│           │  (Timeouts/Crashes/Tokens)   │  │
│  └───────────┬─────────────┘           └──────────────┬───────────────┘  │
│              │                                        │                  │
│              ▼                                        ▼                  │
│  ┌─────────────────────────┐           ┌──────────────────────────────┐  │
│  │  3. Subprocess Adapter  │           │  4. Resilient Dispatcher     │  │
│  │     Bounded Ring Buffer ├──────────►│     Cascade Fallback Engine  │  │
│  │  (Process Tree Teardown)│           │  (Atomic Rollback / Auditing)│  │
│  └───────────┬─────────────┘           └──────────────┬───────────────┘  │
│              │                                        │                  │
│              ▼                                        ▼                  │
│  ┌────────────────────────────────────────────────────────────────────┐  │
│  │  5. 10/10 Deterministic Test Suite in <300ms (ThreadSanitizer)     │  │
│  └────────────────────────────────────────────────────────────────────┘  │
└──────────────────────────────────────────────────────────────────────────┘

1. Canonical Adapter Interface (pkg/adapter)

• Exposes the canonical Adapter interface with Name, Execute, Cancel, and Capabilities.
• Encodes engine capabilities as strongly-typed 64-bit bitmasks (CapTerminal, CapTools, CapMCP, CapGitPatches, CapStreaming, CapCheckpoints).
• Defines immutable TaskEnvelope ingress with strict validation (task ID, prompt, timeout, capability requirements).
• Defines normalized ExecutionResult egress with sanitized stdout/stderr (ANSI sequence stripping) and distilled output tokens.

2. Mock Adapter & Fault Injection (pkg/mock)

• Simulates realistic harness behavior without incurring third-party API billing or network jitter.
• Configurable simulated latency, token consumption accounting, and deterministic synthetic git patch output.
• Programmatic fault injection modes: forced timeout deadline expiration, non-zero process exit codes, and synthetic crash panics.

3. Subprocess CLI Adapter & Ring Buffers (pkg/subprocess)

• Wraps arbitrary OS command-line tools within a monitored execution boundary.
• Concurrent background scanner goroutines continuously drain stdout and stderr into non-blocking bounded circular ring buffers (4 MB cap) to avoid unbounded heap growth.
• Guarantees clean OS process group teardown on Windows (taskkill /F /T) and POSIX (syscall.Kill(-pid, SIGKILL)), preventing orphan zombie processes when context deadlines expire.

4. Resilient Dispatcher & Cascade Fallback (pkg/dispatcher)

• Thread-safe adapter registry managing multiple heterogeneous harness runtimes concurrently.
• Dynamic capability negotiation matching task requirements against engine bitmasks in $O(1)$ time.
• Autonomous cascade fallback protocol: when the primary harness faults or times out, the dispatcher triggers an atomic rollback hook, discards dirty state, and fails over to the next qualified secondary harness.
• Redundant dual-dispatch mode executing identical tasks concurrently across distinct engines to detect divergence in non-deterministic environments.

3. Verification & Testing Invariants

cd hefesto-lab8-harness-adapter
go test -v ./...

Expected output:

• 10/10 PASS across all packages (pkg/adapter, pkg/mock, pkg/subprocess, pkg/dispatcher).
• Total test execution time $<300$ milliseconds.
• Zero data races under concurrent dispatch workloads.
• Process group teardown verified under induced timeout faults.

4. Interactive CLI Tool

The lab includes an interactive demonstration binary in cmd/adapter-cli:

# Standard end-to-end multi-stage pipeline run:
go run ./cmd/adapter-cli

# Demonstrate cascade fallback with atomic rollback:
go run ./cmd/adapter-cli -mode fallback-demo

# Demonstrate redundant cross-harness divergence verification:
go run ./cmd/adapter-cli -mode redundant-demo