diff --git a/hooks/rules/__init__.py b/hooks/rules/__init__.py
index b4c6e124..d5859886 100644
--- a/hooks/rules/__init__.py
+++ b/hooks/rules/__init__.py
@@ -37,6 +37,7 @@ def get_rules_for_event(event):
     from .new_file_advisory import NewFileAdvisoryRule
     from .nextjs_typecheck import NextjsTypecheckRule
     from .pnpm_lockfile_guard import PnpmLockfileGuardRule
+    from .post_commit_briefing import PostCommitBriefingRule
     from .prompt_context import UserPromptContextRule
     from .read_before_edit import ReadBeforeEditRule
     from .read_tracker import ReadTrackerRule
@@ -88,6 +89,7 @@ def get_rules_for_event(event):
         SkillUsageRule(),  # Issue #119: event-level skill usage tracking
         TokenTrackerRule(),  # Issue #84: token usage tracking (postToolUse)
         EpisodeBatcherRule(),  # Issue #394: batch episode auto-learn (opt-in)
+        PostCommitBriefingRule(),  # Issue #804: scoped mini-briefing after git commit
         # VerificationGateRule also handles postToolUse (already registered above)
         # errorOccurred
         ErrorKBRule(),
diff --git a/hooks/rules/post_commit_briefing.py b/hooks/rules/post_commit_briefing.py
new file mode 100644
index 00000000..b8b984b5
--- /dev/null
+++ b/hooks/rules/post_commit_briefing.py
@@ -0,0 +1,112 @@
+"""PostToolUse hook: emit scoped mini-briefing when git commit completes.
+
+Triggers on ``postToolUse`` for the ``bash`` tool when the command contains
+``git commit``.  Queries ``knowledge_entries`` for entries whose
+``code_location`` or ``content`` references the files changed in that commit,
+then emits a lean ``additionalContext`` block so the LLM sees relevant past
+mistakes and patterns.
+
+Fail-open: any exception returns ``None`` to keep the dispatch chain unblocked.
+Silent when no relevant entries are found (no noise).
+"""
+
+import re
+import sqlite3
+import subprocess
+from pathlib import Path
+
+from . import Rule
+from .common import TOOLS_DIR, context
+
+DB_PATH = TOOLS_DIR / "knowledge.db"
+_MAX_ENTRIES = 8
+_GIT_COMMIT_RE = re.compile(r"\bgit\s+commit\b")
+
+
+def _get_changed_files() -> list[str]:
+    """Return file paths changed in the most recent commit."""
+    try:
+        result = subprocess.run(
+            ["git", "diff", "HEAD~1..HEAD", "--name-only"],
+            capture_output=True,
+            text=True,
+            timeout=10,
+        )
+        if result.returncode == 0 and result.stdout.strip():
+            return [f.strip() for f in result.stdout.splitlines() if f.strip()]
+    except Exception:
+        pass
+    return []
+
+
+def _get_entries_for_files(db: sqlite3.Connection, file_paths: list[str]) -> list[dict]:
+    """Query knowledge_entries matching changed files (by path or basename)."""
+    entries: list[dict] = []
+    seen_ids: set[int] = set()
+    for fp in file_paths[:10]:
+        basename = Path(fp).name
+        rows = db.execute(
+            "SELECT id, category, title, substr(content, 1, 200) FROM knowledge_entries "
+            "WHERE (code_location LIKE ? OR content LIKE ?) "
+            "AND category IN ('mistake', 'pattern', 'decision') "
+            "ORDER BY confidence DESC, last_seen DESC LIMIT 3",
+            (f"%{fp}%", f"%{basename}%"),
+        ).fetchall()
+        for row in rows:
+            if row[0] not in seen_ids:
+                seen_ids.add(row[0])
+                entries.append(
+                    {
+                        "id": row[0],
+                        "category": row[1],
+                        "title": row[2],
+                        "content": row[3],
+                    }
+                )
+    return entries[:_MAX_ENTRIES]
+
+
+class PostCommitBriefingRule(Rule):
+    """Emit a scoped mini-briefing via additionalContext after a git commit."""
+
+    name = "post-commit-briefing"
+    events = ["postToolUse"]
+    tools = ["bash"]
+
+    def evaluate(self, event, data):  # noqa: ARG002
+        try:
+            tool_args = data.get("toolArgs", {})
+            if not isinstance(tool_args, dict):
+                return None
+
+            cmd = tool_args.get("command", tool_args.get("cmd", ""))
+            if not isinstance(cmd, str) or not _GIT_COMMIT_RE.search(cmd):
+                return None
+
+            changed_files = _get_changed_files()
+            if not changed_files:
+                return None
+
+            if not DB_PATH.exists():
+                return None
+
+            with sqlite3.connect(DB_PATH) as db:
+                entries = _get_entries_for_files(db, changed_files)
+
+            if not entries:
+                return None
+
+            # Build a lean briefing label
+            names = [Path(f).name for f in changed_files[:3]]
+            files_label = ", ".join(names)
+            if len(changed_files) > 3:
+                files_label += f" +{len(changed_files) - 3} more"
+
+            lines = [f"📚 sk post-commit briefing ({files_label}):"]
+            for e in entries:
+                emoji = "⚠️" if e["category"] == "mistake" else "✅"
+                lines.append(f"  {emoji} [{e['category']}] #{e['id']} — {e['title'][:60]}")
+
+            return context("\n".join(lines))
+        except Exception:
+            return None