research(nightly): global-min-cut gated streaming memory admission (ADR-344)

Cargo.toml

@@ -329,6 +329,7 @@ members = [
     "crates/ruvector-cluster-rag",
     # S-T mincut namespace routing for multi-namespace search (ADR-299)
     "crates/ruvector-namespace-merge",
+    "crates/ruvector-memory-admission",
     # Semantic query-result reuse for repeated agent-memory queries (ADR-301)
     "crates/ruvector-query-cache",
     # Reservoir-sampled adaptive product quantization under drift (ADR-302)

crates/ruvector-memory-admission/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "ruvector-memory-admission"
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+license.workspace = true
+repository.workspace = true
+description = "Global min-cut gated write-time cluster admission for streaming agent memory in RuVector"
+readme = "README.md"
+keywords = ["vector-search", "agent-memory", "mincut", "streaming", "clustering"]
+categories = ["algorithms", "data-structures"]
+
+[[bin]]
+name = "benchmark"
+path = "src/bin/benchmark.rs"
+
+[dependencies]
+
+[lints.rust]
+dead_code = "allow"
+unused_variables = "allow"

crates/ruvector-memory-admission/README.md

@@ -0,0 +1,39 @@
+# ruvector-memory-admission
+
+Global-min-cut gated write-time cluster admission for streaming agent memory.
+
+`ruvector-namespace-merge` (ADR-299) uses S-T max-flow/min-cut to answer a
+**read-time** question: given a query and a fixed namespace set, which
+namespaces should be searched? This crate answers the dual **write-time**
+question, which has no natural source/sink to fix the flow terminals on:
+given a stream of incoming agent-memory vectors and a growing set of
+clusters, should the next vector merge into an existing cluster, or does it
+belong to a new one?
+
+A fixed cosine-to-nearest-centroid threshold (the obvious baseline) only
+looks at one edge. The **global** minimum cut (Stoer-Wagner, no source/sink)
+of the (existing centroids + candidate point) similarity graph looks at the
+whole structure: it finds the single weakest link in the graph and checks
+whether the candidate sits on the weak side of it.
+
+Three policies implement `AdmissionPolicy`:
+
+1. `NearestCentroidThreshold` — baseline: merge into the nearest centroid if
+   cosine similarity clears a fixed threshold, else spawn a new cluster.
+2. `MincutGatedAdmission` — candidate A: global min-cut over centroids +
+   candidate, gated on the cut's average crossing-edge weight against a
+   fixed `tau`.
+3. `AdaptiveMincutAdmission` — candidate B: same mechanism, but `tau` is set
+   online from a running mean/std of previously observed cut weights
+   (Welford's algorithm) instead of a hand-tuned constant.
+
+Run the benchmark:
+
+```bash
+cargo run --release -p ruvector-memory-admission --bin benchmark
+```
+
+See `docs/research/nightly/2026-09-02-mincut-streaming-memory-admission/README.md`
+for the full hypothesis, methodology, and measured results, and
+`docs/adr/ADR-344-mincut-gated-streaming-memory-admission.md` for the
+architecture decision record.