The page-freshness check carries the digest the client already holds (heads(expect=...)) instead of asking first and fetching afterwards. A page that has NOT changed costs one round trip as before; a page that HAS changed now costs one instead of two. Also corrects the record: the item-edit bench hang is pilot start-up flakiness, not the _prime/_grow concurrency I blamed it on — proved with a stack dump.

Result: {"status":"keep","total_ms":25121.9,"lg_boot_ms":694.8,"lg_decomp_ms":2370.8,"lg_graph_ms":917.1,"lg_hex_ms":456.1,"lg_index_ms":69.4,"lg_listing_cold_ms":442.7,"lg_listing_warm_ms":498.8,"lg_nav_ms":6548.8,"lg_palette_ms":4.8,"lg_rename_ms":711.4,"lg_render_ms":224.9,"lg_search_ms":3484.7,"lg_split_ms":2619.3,"pure_graph_ms":220.7,"sm_boot_ms":448.6,"sm_decomp_ms":1292.5,"sm_graph_ms":748.8,"sm_hex_ms":438.3,"sm_index_ms":2.4,"sm_listing_cold_ms":274.3,"sm_listing_warm_ms":266.5,"sm_nav_ms":302.7,"sm_palette_ms":0.3,"sm_rename_ms":392.5,"sm_render_ms":260.2,"sm_search_ms":59.6,"sm_split_ms":1370.9,"fails":0}

1 files changed, 14 insertions, 10 deletions

diff --git a/server/patch_server.py b/server/patch_server.py
index a991158..e860676 100644
--- a/server/patch_server.py
+++ b/server/patch_server.py
@@ -700,7 +700,7 @@ def heads(
     end: Annotated[str, "Optional exclusive end address; default = segment end"] = "",
     back: Annotated[bool, "Walk backwards: return the count heads ENDING just before addr, in forward order"] = False,
     annotate: Annotated[bool, "Emit IDA-style function boundary banner rows (kind sep/funchdr)"] = False,
-    digest: Annotated[bool, "Return only a digest+count of the rows, not the rows themselves"] = False,
+    expect: Annotated[str, "Digest a caller already holds: the rows are omitted when they still hash to it"] = "",
 ) -> dict:
     """Walk item heads from ``addr`` as a flat listing: every head is rendered
     (code OR data OR undefined) via generate_disasm_line and stepped with
@@ -824,15 +824,19 @@ def heads(
         rows.extend(_rows_for(ea, f))  # a struct head expands into member rows
         ea = _advance(ea, f)
     cursor = {"next": hex(ea)} if more else {"done": True}
-    out = {"addr": str(addr), "cursor": cursor,
-           "digest": _idatui_rows_digest(rows), "count": len(rows)}
-    # ``digest`` mode answers "is this page still exactly what you have?" without
-    # shipping it. The rows are built either way -- generate_disasm_line is the
-    # floor and there is no way to know a line is unchanged without rendering it
-    # -- but pickling several hundred rows with their colour spans, unpickling
-    # them and rebuilding Heads is about 40% of what a page costs, and after a
-    # rename almost every page comes back identical.
-    if not digest:
+    dig = _idatui_rows_digest(rows)
+    out = {"addr": str(addr), "cursor": cursor, "digest": dig, "count": len(rows)}
+    # ``expect`` says "I already hold a page that hashed to this". The rows are
+    # built either way -- generate_disasm_line is the floor and there is no way
+    # to know a line is unchanged without rendering it -- but pickling several
+    # hundred rows with their colour spans, unpickling them and rebuilding Heads
+    # is about 40% of what a page costs, and after a rename almost every page
+    # comes back identical.
+    #
+    # It carries the expected value rather than being a yes/no "digest mode" so
+    # that a page which HAS changed still costs one round trip: asking first and
+    # fetching afterwards made every changed page two.
+    if not (expect and str(dig) == expect):
         out["heads"] = rows
     return out