#26 · the return doer

1. 138Record #26 enters the logLOG · append

   a wave is settlingengine: next: #25membrane: waiting at #25

   1. #0a listener
   2. #1a doer
   3. #2listener: the charter
   4. #3doer: the author
   5. #4listener: charter seen
   6. #5listener: blueprint seen
   7. #6doer: the planner
   8. #7listener: assess · charter
   9. #8listener: assess · result
   10. #9doer: the evaluator
   11. #10the charter wanted
   12. #11the blueprint
   13. #12readiness
   14. #13readiness
   15. #14a request: a charter
   16. #15the charter proposed
   17. #16the charter defined
   18. #17readiness
   19. #18readiness
   20. #19a request: a Cell
   21. #20the seed
   22. #21the Cell is open
   23. #22inner listener
   24. #23inner doer
   25. #24the Cell's context
   26. #25return listenerenginemembrane
   27. #26return doernew
   28. ·end of the log

   What	before		after
   records in the log	26	→	27
   #26	—	→	return doer · sys.descriptor.defined

   The door adds #26: the return doer, which will ask for the answer to be presented again once the return listener is ready.

   Where it happens appendEmissions()Vol. 02 §4.1 · Vol. 03 §1

   The only function that adds records to the log. Each new record gets the next free number, at the end.

   Specification

   Vol. 02 §4.1 · Vol. 03 §1

   Code

   appendEmissions() in core/registers/append-emissions.ts, line 14: the new record gets the next free number

   Journal

   LOG · append · offset: 26, kind: sys.descriptor.defined · by engine

   Picture

   records in the log: 26 → 27

   1. 1// The one LOG writer (Vol. 02 §4.1, Vol. 03 §1): emissions become tuples by
   2. 2// receiving the next dense absolute offset — `base + window.length` — and
   3. 3// nothing else ever grows the log. Each append is journalled under the
   4. 4// ambient context, so a batch born of a propagated tuple carries that
   5. 5// tuple's offset as its cause — the cube's provenance line (ADR-002).
   6. 6
   7. 7import type { WaveEmission, WaveTuple } from "../wave/gate";
   8. 8import type { RegisterFile } from "./register-file";
   9. 9import { recordTransition } from "./record-transition";
   10. 10
   11. 11export function appendEmissions(file: RegisterFile, emissions: readonly WaveEmission[]): void {
   12. 12 const engine = file.registers.engine;
   13. 13 for (const emission of emissions) {
   14. 14 const tuple: WaveTuple = { ...emission, offset: engine.base + engine.window.length };↑ the new record gets the next free number
   15. 15 engine.window.push(tuple);↑ it is added at the end of the log
   16. 16 recordTransition(file, "engine", "LOG", "append", {↑ the change is written into the journal
   17. 17 offset: tuple.offset,
   18. 18 kind: tuple.kind
   19. 19 });
   20. 20 }
   21. 21}

   AGPL-3.0-onlyThe Lab's demonstration environment, as this fragment ran it (build 043cc8b). The code may change, and may differ from the code of a working machine.

   Nest VM core, incubated in the CoAgnes garden · build 043cc8b (2026-09-21) · this file last changed in f36e70d (2026-08-18)

when the engine took #26

1. 143The engine takes #26ENGINE.CURSOR · propagate

   a wave is settlingengine: working on #26membrane: waiting at #25

   1. #0a listener
   2. #1a doer
   3. #2listener: the charter
   4. #3doer: the author
   5. #4listener: charter seen
   6. #5listener: blueprint seen
   7. #6doer: the planner
   8. #7listener: assess · charter
   9. #8listener: assess · result
   10. #9doer: the evaluator
   11. #10the charter wanted
   12. #11the blueprint
   13. #12readiness
   14. #13readiness
   15. #14a request: a charter
   16. #15the charter proposed
   17. #16the charter defined
   18. #17readiness
   19. #18readiness
   20. #19a request: a Cell
   21. #20the seed
   22. #21the Cell is open
   23. #22inner listener
   24. #23inner doer
   25. #24the Cell's context
   26. #25return listenermembrane
   27. #26return doerengine · working
   28. #27the return address
   29. ·end of the log

   What	before		after
   pointer — the next record to take	#26	→	#27

   The engine moves on to #26, the return doer, and the machine reacts to it.

   Where it happens takeNextTuple()Vol. 02 §4.1

   The engine's step: take the record under its pointer and move the pointer on — or stop, if the pointer has reached the end.

   Specification

   Vol. 02 §4.1

   Code

   takeNextTuple() in core/registers/take-next-tuple.ts, line 15: at the end of the log, the engine stops

   Journal

   #26 · ENGINE.CURSOR · propagate · offset: 26 · by engine

   Picture

   pointer — the next record to take: #26 → #27

   1. 1// ENGINE.CURSOR advance (Vol. 02 §4.1) — the machine's instruction pointer:
   2. 2// returns the tuple at the cursor and moves it forward exactly once, or null
   3. 3// at quiescence. Advancing IS the context switch: the ambient wave context
   4. 4// moves to the propagated tuple in the same movement, so every transition
   5. 5// journalled during its propagation is attributed to it — the cube's spine.
   6. 6// The cursor never rewinds.
   7. 7
   8. 8import type { WaveTuple } from "../wave/gate";
   9. 9import type { RegisterFile } from "./register-file";
   10. 10import { recordTransition } from "./record-transition";
   11. 11import { setDriver, setWaveContext } from "./set-wave-context";
   12. 12
   13. 13export function takeNextTuple(file: RegisterFile): WaveTuple | null {
   14. 14 const engine = file.registers.engine;
   15. 15 if (engine.cursor >= engine.base + engine.window.length) return null;↑ at the end of the log, the engine stops
   16. 16 const tuple = engine.window[engine.cursor - engine.base];
   17. 17 engine.cursor += 1;↑ the engine's pointer moves on by one
   18. 18 setWaveContext(file, { offset: tuple.offset, phase: "propagate" });
   19. 19 setDriver(file, "engine");
   20. 20 recordTransition(file, "engine", "ENGINE.CURSOR", "propagate", { offset: tuple.offset });↑ the change is written into the journal
   21. 21 return tuple;
   22. 22}

   AGPL-3.0-onlyThe Lab's demonstration environment, as this fragment ran it (build 043cc8b). The code may change, and may differ from the code of a working machine.

   Nest VM core, incubated in the CoAgnes garden · build 043cc8b (2026-09-21) · this file last changed in 6730f58 (2026-09-13)

2. 144The return doer is added to the figureBIND.DEFS · register-descriptor

   a wave is settlingengine: working on #26membrane: waiting at #25

   1. #0a listener
   2. #1a doer
   3. #2listener: the charter
   4. #3doer: the author
   5. #4listener: charter seen
   6. #5listener: blueprint seen
   7. #6doer: the planner
   8. #7listener: assess · charter
   9. #8listener: assess · result
   10. #9doer: the evaluator
   11. #10the charter wanted
   12. #11the blueprint
   13. #12readiness
   14. #13readiness
   15. #14a request: a charter
   16. #15the charter proposed
   17. #16the charter defined
   18. #17readiness
   19. #18readiness
   20. #19a request: a Cell
   21. #20the seed
   22. #21the Cell is open
   23. #22inner listener
   24. #23inner doer
   25. #24the Cell's context
   26. #25return listenermembrane
   27. #26return doerengine · working
   28. #27the return address
   29. ·end of the log

   What	before		after
   doer return.cell-20	—	→	on return.cell-20.gate: writes represent.requested
   when return.cell-20.gate is ready, it wakes	—	→	return.cell-20

   The machine writes return.cell-20 into its list of doers. It is the simplest doer the machine has: no rendezvous, no scope — when its listener is ready, it writes one fact.

   Where it happens registerDescriptorDefinition()Vol. 02 §4.2

   Stores a doer's description under its name, and lists it under every listener it waits for.

   Specification

   Vol. 02 §4.2

   Code

   registerDescriptorDefinition() in core/registers/register-descriptor-definition.ts, line 19: the description is stored under its name

   Journal

   #26 · BIND.DEFS · register-descriptor · id: return.cell-20, interests: ["return.cell-20.gate"] · by region:root

   Picture

   doer return.cell-20: — → on return.cell-20.gate: writes represent.requested

   1. 1// BIND.DEFS and DISPATCH write (Vol. 02 §4.2): the registration payload
   2. 2// lands as data; the dispatch table indexes the descriptor id under every
   3. 3// declared interest (the activation knot plus every demand for an operator
   4. 4// bind, the one subscription for an emit descriptor). Duplicate-id rejection
   5. 5// is the station's verdict (ADR-011 finding 3) — this op only records an
   6. 6// accepted registration.
   7. 7
   8. 8import type { DescriptorDefinedPayload } from "../topology/gate";
   9. 9import type { TopologyRegisters } from "./topology-registers";
   10. 10import type { RegisterFile } from "./register-file";
   11. 11import { recordTransition } from "./record-transition";
   12. 12
   13. 13export function registerDescriptorDefinition(
   14. 14 file: RegisterFile,
   15. 15 region: TopologyRegisters,
   16. 16 payload: DescriptorDefinedPayload,
   17. 17 interests: readonly string[]
   18. 18): void {
   19. 19 region.bindDefs.set(payload.id, payload);↑ the description is stored under its name
   20. 20 for (const interest of interests) {
   21. 21 const list = region.dispatch.get(interest);
   22. 22 if (list) list.push(payload.id);
   23. 23 else region.dispatch.set(interest, [payload.id]);↑ listed under the listener it waits for
   24. 24 }
   25. 25 recordTransition(file, `topology:${region.regionId}`, "BIND.DEFS", "register-descriptor", {↑ the change is written into the journal
   26. 26 id: payload.id,
   27. 27 interests
   28. 28 });
   29. 29}

   AGPL-3.0-onlyThe Lab's demonstration environment, as this fragment ran it (build 043cc8b). The code may change, and may differ from the code of a working machine.

   Nest VM core, incubated in the CoAgnes garden · build 043cc8b (2026-09-21) · this file last changed in f36e70d (2026-08-18)

when the membrane passed #26

1. 149The membrane passes #26MEMBRANE.CURSOR · sweep

   a wave is settlingengine: at the endmembrane: passing #26

   1. #0a listener
   2. #1a doer
   3. #2listener: the charter
   4. #3doer: the author
   5. #4listener: charter seen
   6. #5listener: blueprint seen
   7. #6doer: the planner
   8. #7listener: assess · charter
   9. #8listener: assess · result
   10. #9doer: the evaluator
   11. #10the charter wanted
   12. #11the blueprint
   13. #12readiness
   14. #13readiness
   15. #14a request: a charter
   16. #15the charter proposed
   17. #16the charter defined
   18. #17readiness
   19. #18readiness
   20. #19a request: a Cell
   21. #20the seed
   22. #21the Cell is open
   23. #22inner listener
   24. #23inner doer
   25. #24the Cell's context
   26. #25return listener
   27. #26return doermembrane · passing
   28. #27the return address
   29. ·end of the logengine

   What	before		after
   pointer — the next record to pass	#26	→	#27

   #26 asks nothing of the world, so the membrane's pointer simply moves on.

   Where it happens sweepNextTuple()Vol. 02 §4.6 · Vol. 07 §3

   The membrane's step: pass over the record under its pointer and move the pointer on — exactly once per record.

   Specification

   Vol. 02 §4.6 · Vol. 07 §3

   Code

   sweepNextTuple() in core/registers/sweep-next-tuple.ts, line 16: the membrane's pointer moves on by one

   Journal

   #26 · MEMBRANE.CURSOR · sweep · offset: 26 · by membrane

   Picture

   pointer — the next record to pass: #26 → #27

   1. 1// MEMBRANE.CURSOR advance (Vol. 02 §4.6, Vol. 07 §3): the membrane's own
   2. 2// reading of the one log — the second reception of one publication, never a
   3. 3// second truth. The cursor advances exactly once per offset per machine:
   4. 4// the exactly-once discharge guarantee lives in this movement.
   5. 5
   6. 6import type { WaveTuple } from "../wave/gate";
   7. 7import type { RegisterFile } from "./register-file";
   8. 8import { recordTransition } from "./record-transition";
   9. 9import { setDriver, setWaveContext } from "./set-wave-context";
   10. 10
   11. 11export function sweepNextTuple(file: RegisterFile): WaveTuple | null {
   12. 12 const engine = file.registers.engine;
   13. 13 const membrane = file.registers.membrane;
   14. 14 if (membrane.cursor >= engine.base + engine.window.length) return null;
   15. 15 const tuple = engine.window[membrane.cursor - engine.base];
   16. 16 membrane.cursor += 1;↑ the membrane's pointer moves on by one
   17. 17 setWaveContext(file, { offset: tuple.offset, phase: "sweep" });
   18. 18 setDriver(file, "membrane");
   19. 19 recordTransition(file, "membrane", "MEMBRANE.CURSOR", "sweep", { offset: tuple.offset });↑ the change is written into the journal
   20. 20 return tuple;
   21. 21}

   AGPL-3.0-onlyThe Lab's demonstration environment, as this fragment ran it (build 043cc8b). The code may change, and may differ from the code of a working machine.

   Nest VM core, incubated in the CoAgnes garden · build 043cc8b (2026-09-21) · this file last changed in 6730f58 (2026-09-13)