diff --git a/compiler/ccgcalls.nim b/compiler/ccgcalls.nim
index 6ffe561df7..30326c8db0 100644
--- a/compiler/ccgcalls.nim
+++ b/compiler/ccgcalls.nim
@@ -230,20 +230,29 @@ proc genOpenArraySlice(p: BProc; q: PNode; formalType, destType: PType; prepareF
   of tyString, tySequence:
     let atyp = skipTypes(a.t, abstractInst)
     if formalType.skipTypes(abstractInst).kind in {tyVar} and atyp.kind == tyString and
-        optSeqDestructors in p.config.globalOptions:
+        optSeqDestructors in p.config.globalOptions and not p.config.isDefined("nimsso"):
       let bra = byRefLoc(p, a)
       p.s(cpsStmts).addCallStmt(cgsymValue(p.module, "nimPrepareStrMutationV2"),
         bra)
-    var val: Snippet
-    if atyp.kind in {tyVar} and not compileToCpp(p.module):
-      val = cDeref(ra)
+    if p.config.isDefined("nimsso") and
+        skipTypes(a.t, abstractVar + abstractInst).kind == tyString:
+      let strPtr = if atyp.kind in {tyVar} and not compileToCpp(p.module): ra
+                   else: addrLoc(p.config, a)
+      result = (
+        cCast(ptrType(dest), cOp(Add, NimInt,
+          cCall(cgsymValue(p.module, "nimStrData"), strPtr), rb)),
+        lengthExpr)
     else:
-      val = ra
-    result = (
-      cIfExpr(dataFieldAccessor(p, val),
-        cCast(ptrType(dest), cOp(Add, NimInt, dataField(p, val), rb)),
-        NimNil),
-      lengthExpr)
+      var val: Snippet
+      if atyp.kind in {tyVar} and not compileToCpp(p.module):
+        val = cDeref(ra)
+      else:
+        val = ra
+      result = (
+        cIfExpr(dataFieldAccessor(p, val),
+          cCast(ptrType(dest), cOp(Add, NimInt, dataField(p, val), rb)),
+          NimNil),
+        lengthExpr)
   else:
     result = ("", "")
     internalError(p.config, "openArrayLoc: " & typeToString(a.t))
@@ -287,11 +296,22 @@ proc openArrayLoc(p: BProc, formalType: PType, n: PNode; result: var Builder) =
     of tyString, tySequence:
       let ntyp = skipTypes(n.typ, abstractInst)
       if formalType.skipTypes(abstractInst).kind in {tyVar} and ntyp.kind == tyString and
-          optSeqDestructors in p.config.globalOptions:
+          optSeqDestructors in p.config.globalOptions and not p.config.isDefined("nimsso"):
         let bra = byRefLoc(p, a)
         p.s(cpsStmts).addCallStmt(cgsymValue(p.module, "nimPrepareStrMutationV2"),
           bra)
-      if ntyp.kind in {tyVar} and not compileToCpp(p.module):
+      if p.config.isDefined("nimsso") and
+          skipTypes(n.typ, abstractVar + abstractInst).kind == tyString:
+        if ntyp.kind in {tyVar} and not compileToCpp(p.module):
+          let ra = a.rdLoc
+          result.add(cCall(cgsymValue(p.module, "nimStrData"), ra))
+          result.addArgumentSeparator()
+          result.add(cCall(cgsymValue(p.module, "nimStrLen"), cDeref(ra)))
+        else:
+          result.add(cCall(cgsymValue(p.module, "nimStrData"), addrLoc(p.config, a)))
+          result.addArgumentSeparator()
+          result.add(lenExpr(p, a))
+      elif ntyp.kind in {tyVar} and not compileToCpp(p.module):
         let ra = a.rdLoc
         var t = TLoc(snippet: cDeref(ra))
         let lt = lenExpr(p, t)
@@ -315,9 +335,14 @@ proc openArrayLoc(p: BProc, formalType: PType, n: PNode; result: var Builder) =
         let ra = a.rdLoc
         var t = TLoc(snippet: cDeref(ra))
         let lt = lenExpr(p, t)
-        result.add(cIfExpr(dataFieldAccessor(p, t.snippet), dataField(p, t.snippet), NimNil))
-        result.addArgumentSeparator()
-        result.add(lt)
+        if p.config.isDefined("nimsso"):
+          result.add(cCall(cgsymValue(p.module, "nimStrData"), ra))
+          result.addArgumentSeparator()
+          result.add(cCall(cgsymValue(p.module, "nimStrLen"), t.snippet))
+        else:
+          result.add(cIfExpr(dataFieldAccessor(p, t.snippet), dataField(p, t.snippet), NimNil))
+          result.addArgumentSeparator()
+          result.add(lt)
       of tyArray:
         let ra = rdLoc(a)
         result.add(ra)
diff --git a/compiler/ccgliterals.nim b/compiler/ccgliterals.nim
index 9913ba147e..ac252f95f2 100644
--- a/compiler/ccgliterals.nim
+++ b/compiler/ccgliterals.nim
@@ -160,6 +160,23 @@ proc ssoPayloadLit(src: string; maxLen: int): string =
     result.add(ssoCharLit(ch))
   result.add('}')
 
+proc ssoMoreLit(m: BModule; s: string): string =
+  ## For medium string literals (AlwaysAvail < len <= PayloadSize), encode
+  ## chars[AlwaysAvail..ptrSize-1] in the 'more' pointer field bit-pattern.
+  ## The last pointer byte is always '\0' (null terminator), guaranteed by
+  ## PayloadSize = AlwaysAvail + ptrSize - 1.  slen <= PayloadSize guards
+  ## prevent any code from dereferencing this as an actual pointer.
+  const AlwaysAvail = 7
+  let ptrSize = m.g.config.target.ptrSize
+  var val: uint64 = 0
+  for i in 0..<ptrSize:
+    let ch: uint64 = if AlwaysAvail + i < s.len: uint64(s[AlwaysAvail + i]) else: 0
+    if CPU[m.g.config.target.targetCPU].endian == littleEndian:
+      val = val or (ch shl (uint(i) * 8))
+    else:
+      val = val or (ch shl (uint(ptrSize - 1 - i) * 8))
+  result = cCast(ptrType("LongString"), "(uintptr_t)" & $val)
+
 proc genStringLiteralV3Const(m: BModule; n: PNode; isConst: bool; result: var Builder) =
   # Inline SmallString struct initializer for use inside const aggregate types.
   # Short strings (<=7 chars) embed all chars directly. Long strings reference
@@ -170,6 +187,7 @@ proc genStringLiteralV3Const(m: BModule; n: PNode; isConst: bool; result: var Bu
   cgsym(m, "SmallString")
   cgsym(m, "LongString")
 
+  let payloadSize = AlwaysAvail + m.g.config.target.ptrSize - 1
   var si: StructInitializer
   result.addStructInitializer(si, kind = siOrderedStruct):
     if s.len <= AlwaysAvail:
@@ -179,6 +197,14 @@ proc genStringLiteralV3Const(m: BModule; n: PNode; isConst: bool; result: var Bu
         result.add(ssoPayloadLit(s, s.len))
       result.addField(si, name = "more"):
         result.add(NimNil)
+    elif s.len <= payloadSize:
+      # Medium string: encode remaining chars in 'more' pointer bytes — no heap block.
+      result.addField(si, name = "slen"):
+        result.addIntValue(s.len)
+      result.addField(si, name = "payload"):
+        result.add(ssoPayloadLit(s, s.len))
+      result.addField(si, name = "more"):
+        result.add(ssoMoreLit(m, s))
     else:
       # Emit the LongString block into cfsStrData and reference it inline.
       let dataName = getTempName(m)
@@ -224,6 +250,7 @@ proc genStringLiteralV3(m: BModule; n: PNode; isConst: bool; result: var Builder
   cgsym(m, "SmallString")
   cgsym(m, "LongString")
 
+  let payloadSize = AlwaysAvail + m.g.config.target.ptrSize - 1
   var res = newBuilder("")
   if s.len <= AlwaysAvail:
     # Short: all chars fit in payload, more = NULL.
@@ -238,6 +265,19 @@ proc genStringLiteralV3(m: BModule; n: PNode; isConst: bool; result: var Builder
           res.add(ssoPayloadLit(s, s.len))
         res.addField(si, name = "more"):
           res.add(NimNil)
+  elif s.len <= payloadSize:
+    # Medium: encode remaining chars in 'more' pointer bytes — no heap block needed.
+    res.addVarWithInitializer(
+        if isConst: AlwaysConst else: Global,
+        name = tmp, typ = "SmallString"):
+      var si: StructInitializer
+      res.addStructInitializer(si, kind = siOrderedStruct):
+        res.addField(si, name = "slen"):
+          res.addIntValue(s.len)
+        res.addField(si, name = "payload"):
+          res.add(ssoPayloadLit(s, s.len))
+        res.addField(si, name = "more"):
+          res.add(ssoMoreLit(m, s))
   else:
     # Long: cache the LongString block to emit it only once per module per string.
     # Always generate a fresh SmallString pointing at the (possibly cached) block.
diff --git a/lib/system/strs_v3.nim b/lib/system/strs_v3.nim
index 53db3117be..30ccc3a994 100644
--- a/lib/system/strs_v3.nim
+++ b/lib/system/strs_v3.nim
@@ -34,35 +34,14 @@ proc resize(old: int): int {.inline.} =
   elif old <= high(int16): result = old * 2
   else: result = old div 2 + old
 
-proc `=destroy`*(s: var SmallString) =
+# No Nim lifecycle hooks: the compiler calls the compilerRtl procs directly
+# for tyString variables (nimDestroyStrV1, nimAsgnStrV2).
+
+proc nimDestroyStrV1(s: SmallString) {.compilerRtl, inline.} =
   if int(s.slen) > PayloadSize and (s.more.capImpl and 1) == 1:
     if atomicSubFetch(s.more.rc, 1) == 0:
       dealloc(s.more)
 
-proc `=wasMoved`*(s: var SmallString) {.inline.} =
-  s.slen = 0
-
-proc `=sink`*(dst: var SmallString; src: SmallString) =
-  `=destroy`(dst)
-  copyMem(addr dst, unsafeAddr src, sizeof(SmallString))
-
-proc `=copy`*(dst: var SmallString; src: SmallString) =
-  if int(src.slen) <= PayloadSize:
-    `=destroy`(dst)  # dst may have been a long string
-    copyMem(addr dst, unsafeAddr src, sizeof(SmallString))
-  else:
-    if addr(dst) == unsafeAddr(src): return
-    `=destroy`(dst)
-    # COW: share the block, bump refcount — no allocation needed
-    if (src.more.capImpl and 1) == 1:
-      discard atomicAddFetch(src.more.rc, 1)
-    copyMem(addr dst, unsafeAddr src, sizeof(SmallString))
-
-proc `=dup`*(src: SmallString): SmallString =
-  copyMem(addr result, unsafeAddr src, sizeof(SmallString))
-  if int(src.slen) > PayloadSize and (src.more.capImpl and 1) == 1:
-    discard atomicAddFetch(src.more.rc, 1)
-
 proc ensureUniqueLong(s: var SmallString; oldLen, newLen: int) =
   # Ensure s.more is a unique (rc=1) heap block with capacity >= newLen, preserving existing data.
   # s must already be a long string on entry.
@@ -72,7 +51,7 @@ proc ensureUniqueLong(s: var SmallString; oldLen, newLen: int) =
   if unique and newLen <= cap:
     s.more.fullLen = newLen
   else:
-    let newCap = max(newLen, oldLen * 2)
+    let newCap = max(newLen, resize(cap))
     let p = cast[ptr LongString](alloc(sizeof(int) * 3 + newCap + 1))
     p.rc = 1
     p.fullLen = newLen
@@ -83,7 +62,7 @@ proc ensureUniqueLong(s: var SmallString; oldLen, newLen: int) =
       dealloc(old)
     s.more = p
 
-proc len*(s: SmallString): int {.inline.} =
+proc len(s: SmallString): int {.inline.} =
   result = int s.slen
   if result > PayloadSize:
     result = s.more.fullLen
@@ -95,7 +74,7 @@ template guts(s: SmallString): (int, ptr UncheckedArray[char]) =
   else:
     (slen, cast[ptr UncheckedArray[char]](addr s.payload[0]))
 
-proc `[]`*(s: SmallString; i: int): char {.inline.} =
+proc `[]`(s: SmallString; i: int): char {.inline.} =
   let slen = int s.slen
   if slen <= PayloadSize:
     # unchecked: when i >= 7 we store into the `more` overlay
@@ -105,7 +84,7 @@ proc `[]`*(s: SmallString; i: int): char {.inline.} =
   else:
     result = s.more.data[i]
 
-proc `[]=`*(s: var SmallString; i: int; c: char) =
+proc `[]=`(s: var SmallString; i: int; c: char) =
   let slen = int s.slen
   if slen <= PayloadSize:
     # unchecked: when i >= 7 we store into the `more` overlay
@@ -248,24 +227,6 @@ proc `&`*(a, b: SmallString): SmallString =
   result = a
   result.add(b)
 
-proc toSmallString*(s: openArray[char]): SmallString =
-  let l = s.len
-  if l == 0: return
-  if l <= PayloadSize:
-    result.slen = byte(l)
-    let inl = cast[ptr UncheckedArray[char]](addr result.payload[0])
-    copyMem(inl, unsafeAddr s[0], l)
-    inl[l] = '\0'
-  else:
-    let p = cast[ptr LongString](alloc(sizeof(int) * 3 + l + 1))
-    p.rc = 1
-    p.fullLen = l
-    p.capImpl = (l shl 1) or 1
-    copyMem(addr p.data[0], unsafeAddr s[0], l)
-    p.data[l] = '\0'
-    copyMem(addr result.payload[0], unsafeAddr s[0], AlwaysAvail)
-    result.slen = byte(PayloadSize + 1)
-    result.more = p
 
 {.push overflowChecks: off, rangeChecks: off.}
 
@@ -277,7 +238,7 @@ proc prepareAddLong(s: var SmallString; newLen: int) =
     discard  # already unique with sufficient capacity
   else:
     let oldLen = s.more.fullLen
-    let newCap = max(newLen, oldLen * 2)
+    let newCap = max(newLen, resize(cap))
     let p = cast[ptr LongString](alloc(sizeof(int) * 3 + newCap + 1))
     p.rc = 1
     p.fullLen = oldLen  # logical length unchanged — caller sets it after writing data
@@ -288,7 +249,7 @@ proc prepareAddLong(s: var SmallString; newLen: int) =
       dealloc(old)
     s.more = p
 
-proc prepareAdd*(s: var SmallString; addLen: int) {.compilerRtl.} =
+proc prepareAdd(s: var SmallString; addLen: int) {.compilerRtl.} =
   ## Ensure s has room for addLen more characters without changing its length.
   let slen = int(s.slen)
   let curLen = if slen > PayloadSize: s.more.fullLen else: slen
@@ -309,11 +270,11 @@ proc prepareAdd*(s: var SmallString; addLen: int) {.compilerRtl.} =
   else:
     prepareAddLong(s, newLen)
 
-proc nimAddCharV1*(s: var SmallString; c: char) {.compilerRtl, inline.} =
+proc nimAddCharV1(s: var SmallString; c: char) {.compilerRtl, inline.} =
   prepareAdd(s, 1)
   s.add(c)
 
-proc toNimStr*(str: cstring; len: int): SmallString {.compilerproc.} =
+proc toNimStr(str: cstring; len: int): SmallString {.compilerproc.} =
   if len <= 0: return
   if len <= PayloadSize:
     result.slen = byte(len)
@@ -331,11 +292,11 @@ proc toNimStr*(str: cstring; len: int): SmallString {.compilerproc.} =
     result.slen = byte(PayloadSize + 1)
     result.more = p
 
-proc cstrToNimstr*(str: cstring): SmallString {.compilerRtl.} =
+proc cstrToNimstr(str: cstring): SmallString {.compilerRtl.} =
   if str == nil: return
   toNimStr(str, str.len)
 
-proc nimToCStringConv*(s: var SmallString): cstring {.compilerproc, nonReloadable, inline.} =
+proc nimToCStringConv(s: var SmallString): cstring {.compilerproc, nonReloadable, inline.} =
   ## Returns a null-terminated C string pointer into s's data.
   ## Takes by var (pointer) so addr s.payload[0] is always into the caller's SmallString.
   if int(s.slen) > PayloadSize:
@@ -343,13 +304,13 @@ proc nimToCStringConv*(s: var SmallString): cstring {.compilerproc, nonReloadabl
   else:
     cast[cstring](addr s.payload[0])
 
-proc appendString*(dest: var SmallString; src: SmallString) {.compilerproc, inline.} =
+proc appendString(dest: var SmallString; src: SmallString) {.compilerproc, inline.} =
   dest.add(src)
 
-proc appendChar*(dest: var SmallString; c: char) {.compilerproc, inline.} =
+proc appendChar(dest: var SmallString; c: char) {.compilerproc, inline.} =
   dest.add(c)
 
-proc rawNewString*(space: int): SmallString {.compilerproc.} =
+proc rawNewString(space: int): SmallString {.compilerproc.} =
   ## Returns an empty SmallString with capacity reserved for `space` chars (newStringOfCap).
   if space <= 0: return
   if space <= PayloadSize:
@@ -363,7 +324,7 @@ proc rawNewString*(space: int): SmallString {.compilerproc.} =
     result.more = p
     result.slen = byte(PayloadSize + 1)
 
-proc mnewString*(len: int): SmallString {.compilerproc.} =
+proc mnewString(len: int): SmallString {.compilerproc.} =
   ## Returns a SmallString of `len` zero characters (newString).
   if len <= 0: return
   if len <= PayloadSize:
@@ -379,7 +340,7 @@ proc mnewString*(len: int): SmallString {.compilerproc.} =
     result.more = p
     result.slen = byte(PayloadSize + 1)
 
-proc setLengthStrV2*(s: var SmallString; newLen: int) {.compilerRtl.} =
+proc setLengthStrV2(s: var SmallString; newLen: int) {.compilerRtl.} =
   ## Sets the length of s to newLen, zeroing new bytes on growth.
   let slen = int(s.slen)
   let curLen = if slen > PayloadSize: s.more.fullLen else: slen
@@ -391,7 +352,7 @@ proc setLengthStrV2*(s: var SmallString; newLen: int) {.compilerRtl.} =
         s.more.data[0] = '\0'
       else:
         # shared block: detach and go back to empty inline
-        `=destroy`(s)
+        nimDestroyStrV1(s)
         s.slen = 0
     else:
       s.slen = 0
@@ -408,7 +369,7 @@ proc setLengthStrV2*(s: var SmallString; newLen: int) {.compilerRtl.} =
       s.slen = byte(newLen)
     else:
       # grow into long
-      let newCap = newLen * 2
+      let newCap = resize(newLen)
       let p = cast[ptr LongString](alloc0(sizeof(int) * 3 + newCap + 1))
       p.rc = 1
       p.fullLen = newLen
@@ -436,8 +397,17 @@ proc setLengthStrV2*(s: var SmallString; newLen: int) {.compilerRtl.} =
       s.more.data[newLen] = '\0'
       s.more.fullLen = newLen
 
-proc nimAsgnStrV2*(a: var SmallString; b: SmallString) {.compilerRtl.} =
-  `=copy`(a, b)
+proc nimAsgnStrV2(a: var SmallString; b: SmallString) {.compilerRtl.} =
+  if int(b.slen) <= PayloadSize:
+    nimDestroyStrV1(a)
+    copyMem(addr a, unsafeAddr b, sizeof(SmallString))
+  else:
+    if addr(a) == unsafeAddr(b): return
+    nimDestroyStrV1(a)
+    # COW: share the block, bump refcount — no allocation needed
+    if (b.more.capImpl and 1) == 1:
+      discard atomicAddFetch(b.more.rc, 1)
+    copyMem(addr a, unsafeAddr b, sizeof(SmallString))
 
 proc nimPrepareStrMutationImpl(s: var SmallString) =
   # Called when s holds a static (non-heap) LongString block. COW: allocate a fresh copy.
@@ -450,7 +420,7 @@ proc nimPrepareStrMutationImpl(s: var SmallString) =
   copyMem(addr p.data[0], addr old.data[0], oldLen + 1)
   s.more = p
 
-proc nimPrepareStrMutationV2*(s: var SmallString) {.compilerRtl, inline.} =
+proc nimPrepareStrMutationV2(s: var SmallString) {.compilerRtl, inline.} =
   if int(s.slen) > PayloadSize and (s.more.capImpl and 1) == 0:
     nimPrepareStrMutationImpl(s)
 
@@ -458,15 +428,10 @@ proc prepareMutation*(s: var string) {.inline.} =
   {.cast(noSideEffect).}:
     nimPrepareStrMutationV2(cast[ptr SmallString](addr s)[])
 
-proc nimAddStrV1*(s: var SmallString; src: SmallString) {.compilerRtl, inline.} =
+proc nimAddStrV1(s: var SmallString; src: SmallString) {.compilerRtl, inline.} =
   s.add(src)
 
-proc nimDestroyStrV1*(s: SmallString) {.compilerRtl, inline.} =
-  if int(s.slen) > PayloadSize and (s.more.capImpl and 1) == 1:
-    if atomicSubFetch(s.more.rc, 1) == 0:
-      dealloc(s.more)
-
-proc nimStrAtLe*(s: SmallString; idx: int; ch: char): bool {.compilerRtl, inline.} =
+proc nimStrAtLe(s: SmallString; idx: int; ch: char): bool {.compilerRtl, inline.} =
   let l = s.len
   result = idx < l and s[idx] <= ch
 
@@ -478,18 +443,18 @@ func capacity*(self: SmallString): int {.inline.} =
   else:
     PayloadSize
 
-proc nimStrLen*(s: SmallString): int {.compilerproc, inline.} =
+proc nimStrLen(s: SmallString): int {.compilerproc, inline.} =
   ## Returns the length of s. Called by the codegen for `mLen` on strings with -d:nimsso.
   s.len
 
-proc nimStrData*(s: var SmallString): ptr UncheckedArray[char] {.compilerproc, inline.} =
+proc nimStrData(s: var SmallString): ptr UncheckedArray[char] {.compilerproc, inline.} =
   ## Returns a pointer to the char data of s. Called by codegen for subscript and slice with -d:nimsso.
   let slen = int(s.slen)
   if slen > PayloadSize: cast[ptr UncheckedArray[char]](addr s.more.data[0])
   else: cast[ptr UncheckedArray[char]](addr s.payload[0])
 
-proc eqStrings*(a, b: SmallString): bool {.compilerproc, inline.} = a == b
+proc eqStrings(a, b: SmallString): bool {.compilerproc, inline.} = a == b
 
-proc cmpStrings*(a, b: SmallString): int {.compilerproc, inline.} = cmp(a, b)
+proc cmpStrings(a, b: SmallString): int {.compilerproc, inline.} = cmp(a, b)
 
 {.pop.}