src/pdu.ts

@@ -71,78 +71,68 @@ type ResolvedBody = {
 	tlvs: TlvInputs | undefined;
 };
 
+/**
+ * What the PDU's data_coding describes, and so what may set it: short_message wherever it holds an
+ * octet, since messageOctets() reads it there, and message_payload only where it does not.
+ */
+type CodingSource = 'message_payload' | 'short_message';
+
 function codingOf(params: Record<string, ParamValue | undefined>): number | undefined {
 	return typeof params.data_coding === 'number' ? params.data_coding : undefined;
 }
 
-/** messageOctets() reads short_message wherever it holds an octet, and the TLV only where it does not. */
+function resolveShortMessage(
-function carriesOctets(value: ParamValue | undefined): boolean {
+	params: Record<string, ParamValue | undefined>,
-	return Buffer.isBuffer(value) && value.length > 0;
+	definition: CommandDefinition,
+): Result<{ params: Record<string, ParamValue | undefined>; source: CodingSource }> {
+	// Only the short_message the command's own table will write, since writeParams() ignores any other.
+	const message = definition.params?.short_message === undefined ? undefined : params.short_message;
+
+	if (Buffer.isBuffer(message)) {
+		return {
+			params: params.sm_length === undefined ? { ...params, sm_length: message.length } : params,
+			source: message.length > 0 ? 'short_message' : 'message_payload',
+		};
+	}
+
+	if (typeof message !== 'string') return { params, source: 'message_payload' };
+
+	const encoded = encodeBody(message, codingOf(params));
+
+	if (encoded.err) {
+		return { err: new Error(`Parameter "short_message" of "${definition.command}": ${encoded.err.message}`) };
+	}
+
+	const written = { ...params, short_message: encoded.buffer, sm_length: encoded.buffer.length };
+
+	if (encoded.buffer.length === 0) return { params: written, source: 'message_payload' };
+
+	return { params: { ...written, data_coding: encoded.dataCoding }, source: 'short_message' };
 }
 
-/** The short_message the command's own table will write, since writeParams() ignores any other. */
-function writtenBody(definition: CommandDefinition, value: ParamValue | undefined): ParamValue | undefined {
-	return definition.params?.short_message === undefined ? undefined : value;
-}
-
-/** Encoded in place, settling data_coding where `settles` says no mandatory field will carry it. */
-function resolveCarried(
-	resolved: ResolvedBody,
-	inputs: TlvInputs | undefined,
-	dataCoding: number | undefined,
-	settles: boolean,
-): VoidResult {
-	const text = inputs?.message_payload?.tagValue;
-
-	if (typeof text !== 'string') return {};
-
-	const encoded = encodeBody(text, dataCoding);
-
-	if (encoded.err) return { err: new Error(`TLV "message_payload": ${encoded.err.message}`) };
-
-	if (settles) resolved.params.data_coding = encoded.dataCoding;
-
-	resolved.tlvs = { ...resolved.tlvs, message_payload: { tagValue: encoded.buffer } };
-
-	return {};
-}
-
-/** data_coding names the alphabet of the body, and short_message settles it where it carries octets. */
 function resolveBody(
 	params: Record<string, ParamValue | undefined>,
 	tlvs: TlvInputs | undefined,
 	definition: CommandDefinition,
 ): Result<ResolvedBody> {
-	const message = writtenBody(definition, params.short_message);
+	const shortMessage = resolveShortMessage(params, definition);
-	const resolved: ResolvedBody = { params: { ...params }, tlvs };
 
-	if (Buffer.isBuffer(message) && params.sm_length === undefined) {
+	if (shortMessage.err) return { err: shortMessage.err };
-		resolved.params.sm_length = message.length;
-	}
 
-	if (typeof message === 'string') {
+	const text = tlvs?.message_payload?.tagValue;
-		const encoded = encodeBody(message, codingOf(params));
 
-		if (encoded.err) {
+	if (typeof text !== 'string') return { params: shortMessage.params, tlvs };
-			return { err: new Error(`Parameter "short_message" of "${definition.command}": ${encoded.err.message}`) };
-		}
 
-		if (carriesOctets(encoded.buffer)) resolved.params.data_coding = encoded.dataCoding;
+	const encoded = encodeBody(text, codingOf(shortMessage.params));
 
-		resolved.params.short_message = encoded.buffer;
+	if (encoded.err) return { err: new Error(`TLV "message_payload": ${encoded.err.message}`) };
-		resolved.params.sm_length = encoded.buffer.length;
-	}
 
-	// Only octets the command's own table will write can settle the alphabet the PDU declares.
+	return {
-	const settles = !carriesOctets(writtenBody(definition, resolved.params.short_message));
+		params: shortMessage.source === 'message_payload'
-	const carried = resolveCarried(
+			? { ...shortMessage.params, data_coding: encoded.dataCoding }
-		resolved,
+			: shortMessage.params,
-		tlvs,
+		tlvs: { ...tlvs, message_payload: { tagValue: encoded.buffer } },
-		settles ? codingOf(params) : codingOf(resolved.params),
+	};
-		settles,
-	);
-
-	return carried.err ? { err: carried.err } : resolved;
 }
 
 function writeParams(

todo.md

@@ -190,8 +190,8 @@ A nine-reader comprehension panel read the whole project on 2026-09-20 and score
 mean 6.8. Navigation (7–8) capped nobody. **Locality capped every unit reader at 5–6 and Shape
 capped both architects at 6**, and those two are what this release lifts. The gate is 7 on all four
 dimensions, higher where it is cheap. Maintainer's call, 2026-09-20. A systems-architect review the
-same day returned ALIGN with one blocking-severity finding, which is the first item under Locality
+same day returned ALIGN with one blocking-severity finding, `resolveBody`'s `settles` boolean, which
-and is also what the panel ranked hardest — two methods, one answer.
+the panel also ranked hardest; it is now a named `CodingSource`.
 
 A four-seat scoring run on 2026-09-27 read #30 at 6, 6, 7 and 6, every seat capped by Locality in
 the held-message and shutdown code; #30 merged under the floor on condition that Locality is the
@@ -199,12 +199,9 @@ next work ([decision](docs/decisions.md#internals-and-tests)).
 
 ### Locality — next, ahead of everything below; 5–6 today, and the gate is 7
 
-- [ ] **Replace `resolveBody`'s `settles` boolean with the decision it stands for.** One boolean
+- [ ] **Lift the held-message and shutdown code to Locality 7, and confirm it with a scoring run.**
-      chooses both whether to overwrite `data_coding` and which params to read it from, across four
+      The 2026-09-27 run capped every seat there; a run reading 7.0 or above also retires the #30
-      helpers all named some abstraction of "body". Return a named source — `'short_message' |
+      decision.
-      'payload' | 'caller'` — and branch once. Ranked hardest by three readers and picked by one as
-      the unit they would least want to touch, because a mistake here does not throw, does not fail
-      the types, and reaches the peer as somebody's message rendered wrong.
 
 ### Correctness
 
@@ -299,11 +296,10 @@ next work ([decision](docs/decisions.md#internals-and-tests)).
 
 - [ ] **Move the one-line facts out of the decision log and back to the code.** Five of nine readers
       independently reported being sent to `docs/decisions.md` for a question they hit while reading,
-      with no link from the code; one counted roughly fifty index redirects. The four worth inlining
+      with no link from the code; one counted roughly fifty index redirects. The three left to inline
       as one line each: that `segmentUnits`' three numbers are in two units (septets and octets),
-      which body settles `data_coding`, that a receipt's body is read as octets whatever its
+      that a receipt's body is read as octets whatever its `data_coding` says, and the `<base>-<n>`
-      `data_coding` says, and the `<base>-<n>` id notation. The reasoning stays in the log; the
+      id notation. The reasoning stays in the log; the definition belongs at the code.
-      definition belongs at the code.
 
 - [ ] **Document the two delivery-receipt merge bounds.** `maxDlrMerges` (1000) and
       `dlrMergeTimeout` (24 h) are hardcoded, are not options, and appear in no README and no test —