diff --git a/plans/apl-on-sx.md b/plans/apl-on-sx.md
index d22cdd92..acff35ee 100644
--- a/plans/apl-on-sx.md
+++ b/plans/apl-on-sx.md
@@ -104,6 +104,16 @@ Core mapping:
 - [ ] Drive corpus to 100+ green
 - [ ] Idiom corpus — `lib/apl/tests/idioms.sx` covering classic Roger Hui / Phil Last idioms
 
+## SX primitive baseline
+
+Use vectors for arrays; numeric tower + rationals for numbers; ADTs for tagged data;
+coroutines for fibers; string-buffer for mutable string building; bitwise ops for bit
+manipulation; multiple values for multi-return; promises for lazy evaluation; hash tables
+for mutable associative storage; sets for O(1) membership; sequence protocol for
+polymorphic iteration; gensym for unique symbols; char type for characters; string ports
++ read/write for reader protocols; regexp for pattern matching; bytevectors for binary
+data; format for string templating.
+
 ## Progress log
 
 _Newest first._
diff --git a/plans/common-lisp-on-sx.md b/plans/common-lisp-on-sx.md
index 3b59215d..1f89d1b4 100644
--- a/plans/common-lisp-on-sx.md
+++ b/plans/common-lisp-on-sx.md
@@ -110,6 +110,16 @@ Core mapping:
 - [ ] FORMAT — basic directives `~A`, `~S`, `~D`, `~F`, `~%`, `~&`, `~T`, `~{...~}` (iteration), `~[...~]` (conditional), `~^` (escape), `~P` (plural)
 - [ ] Drive corpus to 200+ green
 
+## SX primitive baseline
+
+Use vectors for arrays; numeric tower + rationals for numbers; ADTs for tagged data;
+coroutines for fibers; string-buffer for mutable string building; bitwise ops for bit
+manipulation; multiple values for multi-return; promises for lazy evaluation; hash tables
+for mutable associative storage; sets for O(1) membership; sequence protocol for
+polymorphic iteration; gensym for unique symbols; char type for characters; string ports
++ read/write for reader protocols; regexp for pattern matching; bytevectors for binary
+data; format for string templating.
+
 ## Progress log
 
 _Newest first._
diff --git a/plans/ruby-on-sx.md b/plans/ruby-on-sx.md
index c10a4035..c5440d74 100644
--- a/plans/ruby-on-sx.md
+++ b/plans/ruby-on-sx.md
@@ -113,6 +113,16 @@ Core mapping:
 - [ ] `Integer`: `times`, `upto`, `downto`, `step`, `digits`, `gcd`, `lcm`
 - [ ] Drive corpus to 200+ green
 
+## SX primitive baseline
+
+Use vectors for arrays; numeric tower + rationals for numbers; ADTs for tagged data;
+coroutines for fibers; string-buffer for mutable string building; bitwise ops for bit
+manipulation; multiple values for multi-return; promises for lazy evaluation; hash tables
+for mutable associative storage; sets for O(1) membership; sequence protocol for
+polymorphic iteration; gensym for unique symbols; char type for characters; string ports
++ read/write for reader protocols; regexp for pattern matching; bytevectors for binary
+data; format for string templating.
+
 ## Progress log
 
 _Newest first._
diff --git a/plans/tcl-on-sx.md b/plans/tcl-on-sx.md
index ab472686..81d8f835 100644
--- a/plans/tcl-on-sx.md
+++ b/plans/tcl-on-sx.md
@@ -116,6 +116,16 @@ Core mapping:
 - [ ] Drive corpus to 150+ green
 - [ ] Idiom corpus — `lib/tcl/tests/idioms.sx` covering classic Welch/Jones idioms
 
+## SX primitive baseline
+
+Use vectors for arrays; numeric tower + rationals for numbers; ADTs for tagged data;
+coroutines for fibers; string-buffer for mutable string building; bitwise ops for bit
+manipulation; multiple values for multi-return; promises for lazy evaluation; hash tables
+for mutable associative storage; sets for O(1) membership; sequence protocol for
+polymorphic iteration; gensym for unique symbols; char type for characters; string ports
++ read/write for reader protocols; regexp for pattern matching; bytevectors for binary
+data; format for string templating.
+
 ## Progress log
 
 _Newest first._