diff --git a/lib/config.py b/lib/config.py
index d5bbf7f..9f1b401 100644
--- a/lib/config.py
+++ b/lib/config.py
@@ -200,6 +200,9 @@ MERGE_INTERVAL = 30
 FIX_INTERVAL = 60
 HEALTH_CHECK_INTERVAL = 60
 
+# --- Extraction gates ---
+EXTRACTION_COOLDOWN_HOURS = 4  # Skip sources with any PR activity in this window. Defense-in-depth for DB-status filter.
+
 # --- Retrieval (Telegram bot) ---
 RETRIEVAL_RRF_K = 20  # RRF smoothing constant — tuned for 5-10 results per source
 RETRIEVAL_ENTITY_BOOST = 1.5  # RRF score multiplier for claims wiki-linked from matched entities
diff --git a/lib/extract.py b/lib/extract.py
index a1bdc78..a1e017f 100644
--- a/lib/extract.py
+++ b/lib/extract.py
@@ -572,6 +572,18 @@ async def _extract_one_source(
 
     if not files_written:
         logger.info("No files written for %s — cleaning up", source_file)
+        # Path B null-result: enrichments existed but all targets missing in worktree.
+        # No PR, no cooldown match — without DB update this re-extracts every 60s.
+        # (Ganymede review, commit 469cb7f follow-up.)
+        try:
+            conn.execute(
+                """INSERT INTO sources (path, status, updated_at) VALUES (?, 'null_result', datetime('now'))
+                   ON CONFLICT(path) DO UPDATE SET status='null_result', updated_at=datetime('now')""",
+                (source_path,),
+            )
+            conn.commit()
+        except Exception:
+            logger.debug("Failed to mark source as null_result (path B)", exc_info=True)
         await _git("checkout", "main", cwd=str(EXTRACT_WORKTREE))
         await _git("branch", "-D", branch, cwd=str(EXTRACT_WORKTREE))
         await _archive_source(source_path, domain, "null-result")
@@ -688,6 +700,19 @@ async def _extract_one_source(
             for c in claims_raw if c.get("title") or c.get("filename")
         )
 
+        # Success path: mark source as 'extracting' so queue scan's DB-status filter
+        # skips it between PR creation and merge. Without this, cooldown is load-bearing
+        # (Ganymede review, commit 469cb7f follow-up).
+        try:
+            conn.execute(
+                """INSERT INTO sources (path, status, updated_at) VALUES (?, 'extracting', datetime('now'))
+                   ON CONFLICT(path) DO UPDATE SET status='extracting', updated_at=datetime('now')""",
+                (source_path,),
+            )
+            conn.commit()
+        except Exception:
+            logger.debug("Failed to mark source as extracting", exc_info=True)
+
         # Upsert: if discover_external_prs already created the row, update it;
         # if not, create a partial row that discover will complete.
         source_channel = classify_source_channel(branch)
@@ -931,16 +956,17 @@ async def extract_cycle(conn, max_workers=None) -> tuple[int, int]:
         if skipped:
             logger.info("Skipped %d source(s) with existing open PRs", skipped)
 
-    # Emergency cooldown: skip sources with ANY PR (merged/closed/open) in last 4h.
-    # Prevents runaway re-extraction when archive step lags behind merge.
-    # Root cause: source file remains in inbox/queue/ after PR merges until
-    # _archive_source moves it — next daemon tick extracts the same source again.
+    # Cooldown: skip sources with ANY PR in last EXTRACTION_COOLDOWN_HOURS.
+    # Defense-in-depth for DB-status filter — catches the window between PR
+    # creation and DB status update if anything races.
     if unprocessed:
+        cooldown_hours = config.EXTRACTION_COOLDOWN_HOURS
         recent_source_paths = {
             r["source_path"] for r in conn.execute(
                 """SELECT DISTINCT source_path FROM prs
                    WHERE source_path IS NOT NULL
-                   AND created_at > datetime('now', '-4 hours')"""
+                   AND created_at > datetime('now', ? || ' hours')""",
+                (f"-{cooldown_hours}",),
             ).fetchall() if r["source_path"]
         }
         if recent_source_paths:
@@ -951,7 +977,7 @@ async def extract_cycle(conn, max_workers=None) -> tuple[int, int]:
             ]
             cooled = before - len(unprocessed)
             if cooled:
-                logger.info("Cooldown: skipped %d source(s) with PRs in last 4h", cooled)
+                logger.info("Cooldown: skipped %d source(s) with PRs in last %dh", cooled, cooldown_hours)
 
     # ── Check for re-extraction sources (must run even when queue is empty) ──
     reextract_rows = conn.execute(