Release Ghostlink v1.16.0 · rwilliamspbg-ops/Ghostlink

[1.16.0] - 2026-08-05 (Reliability fixes: GPU probe timeout, TCP circuit breaker, model-list caching)

GPU hardware detection (system_profile.rs) had a probe-timeout regression: each probe_*_with_timeout wrapper unconditionally slept the full timeout duration before checking whether the probe had already finished, so every startup paid the full 5-10s per probe instead of returning as soon as the fast path completed. Replaced with a real bounded wait (detached thread + mpsc::recv_timeout) that returns immediately on completion and only blocks up to the timeout on a genuinely slow/hung probe. Full profile detection now completes in ~1.5s on a typical dev machine instead of a guaranteed multi-second floor.
GUI production build (npm run build) was broken: vite-plugin-monaco-editor-esm's built-in worker entries hardcode monaco-editor/esm/vs/... paths that, against monaco-editor's current package.json "exports" map, resolve to a doubled esm/vs/esm/vs/... path that doesn't exist ("Could not resolve"). Reconfigured ghostlink_gui_modern/vite.config.ts to supply the same 5 workers (editor core, CSS, HTML, JSON, TypeScript) via customWorkers with the prefix stripped, which the exports map re-adds correctly. Affects both npm run build and npm run dev; this was blocking the release-artifacts.yml CI gate outright.

circuit_breaker module in crates/ghostlink-core/src/circuit_breaker.rs: a 3-state (Closed/Open/Half-Open) circuit breaker with jittered exponential backoff. Wired into the TCP transport bridge's reconnect loop (crates/ghostlink-core/src/runtime.rs spawn_tcp_bridge) via a new per-node breaker registry on ClusterState (circuit_breaker_for) — failure history now persists across pipeline executions targeting the same remote node, so a chronically-unreachable node fails fast on later calls instead of repeating the full connect/backoff sequence every time. Opt-in per call site (Option<CircuitBreaker>); the loopback benchmarking path passes None and is unaffected.
api_response_cache module in crates/ghostlink-core/src/api_response_cache.rs: a TTL + ETag response cache. Wired into GET /api/models, which previously ran a real fs::read_dir/fs::metadata disk scan on every request — now cached for 5s and explicitly invalidated the moment a download completes or a model is deleted.
LayerKvCache::write_kv_batch in crates/ghostlink-core/src/kv_cache.rs: writes multiple tokens' KV entries under a single write-lock acquisition, validating every entry upfront so a bad entry fails the whole batch atomically. Available as a primitive; like the rest of kv_cache.rs, it has no current caller in runtime.rs (Ghostlink delegates model execution to an external inference engine).

Three modules from an in-progress performance pass didn't hold up under review and were cut before landing: a churn-coalescing module that duplicated ClusterState's existing lock-free snapshot cache, an MCP "server pool" that pooled against a per-call subprocess-spawn cost the real MCP client (mcp/registry.rs, persistent connections) doesn't have, and a protocol buffer pool targeting DiscoveryFrame::encode(), which already encodes into a stack buffer on a low-frequency discovery path.