diff --git a/README.md b/README.md
index e2e1322..ce50ba3 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ S3-backed repository layer and provider workflows around those trees.
 > repository is pre-1.0; tagged releases publish public GitHub release bundles,
 > while crates.io publication remains a separately controlled release step.
 
-![SILO architecture](diagram/prolly-s3-architecture.svg)
+![SILO architecture](diagram/prolly-s3-architecture.svg?rev=arrowhead-v2)
 
 ## Why SILO
 
diff --git a/diagram/prolly-s3-architecture.svg b/diagram/prolly-s3-architecture.svg
index ec0dece..e9940f4 100644
--- a/diagram/prolly-s3-architecture.svg
+++ b/diagram/prolly-s3-architecture.svg
@@ -4,8 +4,7 @@
   <defs>
     <linearGradient id="bg" x1="0" y1="0" x2="1" y2="1"><stop stop-color="#08111f"/><stop offset="1" stop-color="#111b34"/></linearGradient>
     <marker id="arrow" markerWidth="9" markerHeight="7" refX="9" refY="3.5" orient="auto"><path d="M0 0 9 3.5 0 7Z" fill="#6ee7f9"/></marker>
-    <marker id="history-arrow" markerWidth="10" markerHeight="10" refX="10" refY="5" orient="auto"><path d="M0 0 10 5 0 10Z" fill="#6ee7f9"/></marker>
-    <style>.h{font:700 22px ui-sans-serif,system-ui;fill:#f8fafc}.s{font:400 13px ui-sans-serif,system-ui;fill:#9fb0c8}.t{font:700 16px ui-sans-serif,system-ui;fill:#f8fafc}.b{font:400 13px ui-sans-serif,system-ui;fill:#c7d2e3}.k{font:600 12px ui-monospace,SFMono-Regular,monospace;fill:#7dd3fc}.box{fill:#12223b;stroke:#385173;stroke-width:1.5}.data{fill:#102f35;stroke:#2dd4bf;stroke-width:1.5}.meta{fill:#241d42;stroke:#a78bfa;stroke-width:1.5}.line{fill:none;stroke:#6ee7f9;stroke-width:2;marker-end:url(#arrow)}.history-line{marker-end:url(#history-arrow)}</style>
+    <style>.h{font:700 22px ui-sans-serif,system-ui;fill:#f8fafc}.s{font:400 13px ui-sans-serif,system-ui;fill:#9fb0c8}.t{font:700 16px ui-sans-serif,system-ui;fill:#f8fafc}.b{font:400 13px ui-sans-serif,system-ui;fill:#c7d2e3}.k{font:600 12px ui-monospace,SFMono-Regular,monospace;fill:#7dd3fc}.box{fill:#12223b;stroke:#385173;stroke-width:1.5}.data{fill:#102f35;stroke:#2dd4bf;stroke-width:1.5}.meta{fill:#241d42;stroke:#a78bfa;stroke-width:1.5}.line{fill:none;stroke:#6ee7f9;stroke-width:2;marker-end:url(#arrow)}.history-line{marker-end:none}</style>
   </defs>
   <rect width="1120" height="650" rx="18" fill="url(#bg)"/>
   <text x="50" y="55" class="h">Prolly is the history; S3 holds whole immutable payloads</text>
@@ -37,7 +36,9 @@
   <text x="785" y="534" class="b">retention pins + exact-version GC</text>
   <path d="M260 235H350" class="line"/><text x="305" y="222" text-anchor="middle" class="s">calls</text>
   <path d="M650 185H755" class="line"/><text x="702" y="169" text-anchor="middle" class="s">whole bytes</text>
-  <path d="M650 290C705 290 720 430 755 440" class="line history-line"/><text x="690" y="365" text-anchor="middle" class="s">history</text>
+  <path d="M650 290C705 290 720 430 755 440" class="line history-line"/>
+  <path d="M740 429L755 440L740 451Z" transform="rotate(16 755 440)" fill="#6ee7f9"/>
+  <text x="690" y="365" text-anchor="middle" class="s">history</text>
   <rect x="50" y="430" width="600" height="140" rx="14" fill="#0c192c" stroke="#334a69"/>
   <text x="80" y="468" class="t">Canonical read</text>
   <text x="80" y="500" class="b">1. Pin a Prolly commit and resolve the logical key.</text>