diff --git a/.wolf/buglog.json b/.wolf/buglog.json
index 980d5598..f3b502d6 100644
--- a/.wolf/buglog.json
+++ b/.wolf/buglog.json
@@ -18144,6 +18144,26 @@
       "related_bugs": [],
       "occurrences": 1,
       "last_seen": "2026-08-21T00:00:00Z"
+    },
+    {
+      "id": "bug-1620",
+      "timestamp": "2026-08-21T15:56:00Z",
+      "error_message": "ERROR: Unknown option: \"dirty_fingerprint\".",
+      "file": "src/tools/xce-build.sh (setup_build, --incremental path)",
+      "root_cause": "`xce-build.sh worker asan --incremental` runs `meson setup --reconfigure \"$BUILD_DIR\" -Dcommit_id=... -Dbuild_time=... -Ddirty_fingerprint=...` against a pre-existing xce.build dir that was configured before commit a860141b (feat(dirty-content-fingerprint): add dirty_fingerprint meson option). Meson 1.9.1 validates -D flags on `--reconfigure` against the OLD cached coredata BEFORE re-reading meson.options to pick up newly-added options, so any brand-new option name passed via -D on the same reconfigure invocation is rejected as unknown -- even though the option genuinely exists in the current src/meson.options (confirmed: `intro-buildoptions.json` in the stale build dir only listed commit_id/build_time, not dirty_fingerprint). Pure staleness in the incremental build dir vs. the current option surface, unrelated to any C source edit.",
+      "fix": "Ran `meson setup --reconfigure xce.build` once with NO -D overrides first -- this successfully re-reads meson.options and registers the new dirty_fingerprint option in cached coredata (confirmed via intro-buildoptions.json). A subsequent normal `xce-build.sh worker asan --incremental` (which does pass -Ddirty_fingerprint=...) then succeeded cleanly. General recipe: if `--incremental` reconfigure fails with 'Unknown option: \"X\"' for an option that IS defined in src/meson.options, the build dir predates that option's introduction -- do one plain `meson setup --reconfigure <build_dir>` with no -D args to register it, then retry the real build. Rebuilding without --incremental (full rm -rf + fresh setup) also fixes it but wipes any other component's binaries sharing that dir (see bug-1565).",
+      "tags": [
+        "meson",
+        "reconfigure",
+        "incremental-build",
+        "dirty_fingerprint",
+        "xce-build.sh",
+        "worker",
+        "stale-build-dir"
+      ],
+      "related_bugs": ["bug-1565"],
+      "occurrences": 1,
+      "last_seen": "2026-08-21T15:56:00Z"
     }
   ]
 }