diff --git a/.gitignore b/.gitignore
index 967989d04c..4f16ccaf74 100644
--- a/.gitignore
+++ b/.gitignore
@@ -116,3 +116,16 @@ packages/desktop/deploy/
 # vi.mock interception for imports nested inside the bundle; see the script
 # comment (scripts/build-engine-core-gate-bundle.mjs) for the full repro.
 packages/core/.gate-bundle/
+
+# FNXC:KnowledgeGraph 2026-08-10-18:32:
+# `fn knowledge-graph build` output (FN-8920 memory epic). Deterministic and fully
+# regenerable from source, with SHA-256 fingerprints in the manifest driving
+# incremental rebuilds — so committing it preserves nothing that a rebuild cannot
+# reproduce. It is ~85MB (edges.json alone is 43MB, past GitHub's 50MB warning
+# threshold) and rewritten on every build, so tracking it would add irreversible,
+# compounding history bloat to every clone and CI checkout.
+# Operator decision, 2026-08-10: ignore it. docs/knowledge-graph.md previously said
+# "it is not ignored" and left committing to the operator; that guidance is updated
+# alongside this entry. An operator who does want a snapshot committed can still
+# force it with `git add -f .fusion-knowledge/graph`.
+.fusion-knowledge/
diff --git a/docs/knowledge-graph.md b/docs/knowledge-graph.md
index 264747c823..8bf2b49e8d 100644
--- a/docs/knowledge-graph.md
+++ b/docs/knowledge-graph.md
@@ -8,7 +8,9 @@
 
 The default `knowledgeGraphDir` is `.fusion-knowledge/graph`, deliberately outside ignored `.fusion/`. It contains `nodes.json`, `edges.json`, and `manifest.json`; all use sorted, LF JSON. Nodes and edges are written before the manifest so a torn write safely triggers a full rebuild. The manifest records SHA-256 fingerprints and import references, enabling changed files only to be re-extracted and deleted file ownership to be pruned.
 
-The artifact is intentionally not committed by this change. Operators may review and commit it with `git add .fusion-knowledge/graph`; it is not ignored.
+The artifact is not committed. As of 2026-08-10 `.fusion-knowledge/` is gitignored: the graph is deterministic and fully regenerable from source (the manifest's SHA-256 fingerprints drive incremental rebuilds), so tracking it preserves nothing a rebuild cannot reproduce, while costing ~85MB of irreversible, compounding history bloat on every clone and CI checkout — `edges.json` alone is 43MB, past GitHub's 50MB warning threshold. Regenerate it with `fn knowledge-graph build` rather than pulling it.
+
+An operator who explicitly wants a snapshot in history can still force one with `git add -f .fusion-knowledge/graph`; prefer a rebuild.
 
 ## Model