Instruction Set

29 assigned slots with fixed numbers, fixed spellings, and fixed semantics. Once assigned, a slot never changes.

The assigned slots

Slot	Op	Meaning
0	pulse	push a float onto the stack
1	pulse_str	push a string
2	sense	read a variable's value
3	hold	store a value into a variable
4	grow_organ	construct an organ (fields + methods)
5	read_field	read an organ field
6	write_field	write an organ field
7	grow_list	construct a list
8	probe	index into a list
9	combine	add
10	subtract	subtract
11	scale	multiply
12	divide	divide
13	signal	print / write to the screen
14	output	return a value / end a program
16	threshold_eq	equality test
17	threshold_ne	inequality test
18	threshold_lt	less-than
19	threshold_le	less-than-or-equal
20	threshold_gt	greater-than
21	threshold_ge	greater-than-or-equal
22	route	unconditional jump
23	gate	conditional branch
24	junction	block label / join point
25	dispatch	call a cell
27	builtin	host builtin (file, GPU, math)
28	implant	write into a list slot
62	checkret	return-type guard
63	checktype	argument-type guard

Reserved forever

Slot 15 was the old Return, merged into Output. It is reserved permanently and will never be reused. Assigning a new op to it is a build error, not a policy.

Slot 26 is reserved the same way: it was the old Ret, merged into Output. It keeps its number and is never reassigned.

The freeze

Five rules, enforced at compile time in the compiler's own source:

• Assigned slot numbers never change.
• New ops take unassigned slots only.
• Deprecated ops keep their tag and number forever.
• Alias spellings are part of the ABI (the serialized surface is load-bearing).
• Semantics never mutate; new behavior rides a new slot.

Changing an assigned slot's number or spelling fails the build. That is what makes BloodCode a contract instead of a convention.