diff --git a/firmware/open_evse/open_evse.h b/firmware/open_evse/open_evse.h
index 53dbceaa..c591d893 100644
--- a/firmware/open_evse/open_evse.h
+++ b/firmware/open_evse/open_evse.h
@@ -527,7 +527,13 @@ extern AutoCurrentCapacityController g_ACCController;
 // 10-byte MCU id needs only 33 for $GI, so the LCD-derived 34 still fits;
 // keep AVR unchanged so its RAM footprint does not grow. See the matching
 // #error guard in rapi_proc.cpp.
-#ifdef TARGET_SAMD
+//
+// Select from the MCU id length rather than the target name: take the
+// LCD-derived size unless the $GI reply needs more. Values are unchanged
+// from when this was keyed on TARGET_SAMD -- a 16-byte id needs 45 and so
+// selects 48, a 10-byte id needs 33 and so keeps the LCD-derived 34.
+#define TMP_BUF_GI_REPLYLEN (3 + 1 + (2*MCU_ID_LEN) + 4 + 4 + 1)
+#if defined(MCU_ID_LEN) && (TMP_BUF_GI_REPLYLEN > ((LCD_MAX_CHARS_PER_LINE+1)*2))
 #define TMP_BUF_SIZE 48
 #else
 #define TMP_BUF_SIZE ((LCD_MAX_CHARS_PER_LINE+1)*2)
diff --git a/firmware/open_evse/rapi_proc.h b/firmware/open_evse/rapi_proc.h
index 1bf02146..c6e4535c 100644
--- a/firmware/open_evse/rapi_proc.h
+++ b/firmware/open_evse/rapi_proc.h
@@ -487,11 +487,17 @@ Z0 closems holdpwm
 
 // buffer[] holds an inbound RAPI command and is reused to build the
 // outbound response text. The longest response text is $GI (get MCU id),
-// whose #else branch writes 2*MCU_ID_LEN hex chars plus a NUL. On SAMD
-// MCU_ID_LEN is 16, so that is 2*16+1 = 33 bytes and the historic 32-byte
-// buffer overflowed by one, corrupting the adjacent bufCnt member. Size
-// per target so AVR RAM cost stays zero.
-#ifdef TARGET_SAMD
+// whose #else branch writes 2*MCU_ID_LEN hex chars plus a NUL. With a
+// 16-byte MCU id that is 2*16+1 = 33 bytes and the historic 32-byte buffer
+// overflowed by one, corrupting the adjacent bufCnt member.
+//
+// Size from the MCU id length rather than the target name, so any target
+// inherits the right buffer automatically. The values are unchanged from
+// when this was keyed on TARGET_SAMD: a 16-byte id selects 40, a 10-byte
+// id selects 32, so AVR RAM cost stays zero (ESRAPI_BUFLEN sizes three
+// buffers there -- buffer[], g_rapiSerialBuffer and g_rapiI2ClBuffer).
+#define ESRAPI_GI_RESPLEN (2*MCU_ID_LEN + 1)
+#if defined(MCU_ID_LEN) && (ESRAPI_GI_RESPLEN > 32)
 #define ESRAPI_BUFLEN 40
 #else
 #define ESRAPI_BUFLEN 32