[rudycelekli]

Problem

agentdb_graph-query accepts relation and advertises five-hop k-hop queries. The native backend ignores relation, while the SQL fallback executes at most three hops but reports the requested depth. A caller can treat an over-broad result or an incomplete cycle check as authoritative.

Change

Native graph-node now returns a machine-readable unsupported: "relation" error for filtered k-hop queries. Its kHopNeighbors API cannot filter, and the native and SQL stores are not an atomic mirror (agentdb_causal-edge writes SQL asynchronously), so silently switching to SQL could create a false negative. When native is unavailable, the SQL path still applies the relation predicate. Every successful k-hop response now reports appliedDepth; SQL responses set truncated: true when the existing three-hop bound clips the request. The tool description explains both limits.

Validation

• Focused Vitest regression: 6/6 pass, covering native unfiltered, native filtered refusal, SQL filtered, missing backends, and SQL depth 5 versus 2.
• The same test against origin/main fails 6/6 cases.
• git diff --check: pass.

The tests mock backend availability and inspect the SQL sent to the query layer; they do not claim a real native/SQLite integration run. The existing SQL depth bound is preserved to avoid expanding recursive-query cost in this fix.

Fixes #3202