diff --git a/plans/prolog-on-sx.md b/plans/prolog-on-sx.md
index d47009d9..e2ebdda1 100644
--- a/plans/prolog-on-sx.md
+++ b/plans/prolog-on-sx.md
@@ -88,6 +88,7 @@ Representation choices (finalise in phase 1, document here):
 
 _Newest first. Agent appends on every commit._
 
+- 2026-04-25 — `sub_atom/5` (non-deterministic substring enumeration; CPS loop over all (start,sublen) pairs; trail-undo only on backtrack) + `aggregate_all/3` (6 templates: count/bag/sum/max/min/set; uses `pl-collect-solutions`). 25 tests in `tests/string_agg.sx`. Total **496** (+25).
 - 2026-04-25 — `:-` operator + assert with rules: added `(list ":-" 1200 "xfx")` to `pl-op-table`; fixed `pl-token-op` to accept `"op"` token type (tokenizer emits `:-` as `"op"`, not `"atom"`). `pl-build-clause` already handled `("compound" ":-" ...)`. `assert((head :- body))` now works for facts+rules. 15 tests in `tests/assert_rules.sx`. Total **471** (+15).
 - 2026-04-25 — IO/term predicates: `term_to_atom/2` (bidirectional: format term or parse atom), `term_string/2` (alias), `with_output_to/2` (atom/string sinks — saves/restores `pl-output-buffer`), `writeln/1`, `format/1` (~n/~t/~~), `format/2` (~w/~a/~d pull from arg list). 24 tests in `tests/io_predicates.sx`. Total **456** (+24).
 - 2026-04-25 — Char predicates: `char_type/2` (9 modes: alpha/alnum/digit/digit(N)/space/white/upper(L)/lower(U)/ascii(C)/punct), `upcase_atom/2`, `downcase_atom/2`, `string_upper/2`, `string_lower/2`. 10 helpers using `char-code`/`char-from-code` SX primitives. 27 tests in `tests/char_predicates.sx`. Total **432** (+27).