From b5ec00a9771abe3ff737c8fcaa880c7a545ecdb6 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 08:39:32 +0000
Subject: [PATCH 1/9] Initial plan


From cc6f4cf7c4b37965142a3886b4b511b2b01d20c4 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 08:45:39 +0000
Subject: [PATCH 2/9] fix: decode special log records in ReadRange without
 status flags

Special log records (log-interrupted, buffer-purged, log-disabled) use
the log-status choice which does NOT include status flags. The previous
code unconditionally consumed the status flags bytes, causing it to read
into subsequent records and lose sync.

This fix:
- Validates closing tag 1 before consuming it
- Checks for context tag 2 (status flags) presence before decoding
- Adds support for log-status choice (context tag 0)
- Adds isLogStatus and logStatus fields to differentiate special records
- Adds comprehensive test for mixed normal and special log records

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts                      |  98 +++++++++++++++++++-----
 src/lib/services/WriteProperty.ts    |   8 +-
 test/unit/service-read-range.spec.ts | 109 +++++++++++++++++++++++++++
 3 files changed, 194 insertions(+), 21 deletions(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index eb50119e..49bb4f50 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -2475,10 +2475,30 @@ export const decodeRange = (
 		len += 2
 
 		// value payload (context specific)
+		// This is the log-datum CHOICE with options:
+		// [0] log-status (BACnetLogStatus bitstring - special records)
+		// [1] boolean-value
+		// [2] real-value
+		// [3] enum-value
+		// [4] unsigned-value
+		// ... and more per ASHRAE 135
 		tag = decodeTagNumberAndValue(buffer, offset + len)
 		len += tag.len
 		let value: ApplicationData | undefined
-		if (tag.tagNumber === 2 && tag.value === 4) {
+		let isLogStatus = false
+		if (tag.tagNumber === 0) {
+			// log-status choice: BACnetLogStatus bitstring
+			// These are special log records (log-disabled, buffer-purged, log-interrupted)
+			// They do NOT have status flags after the log-datum
+			value = bacappDecodeData(
+				buffer,
+				offset + len,
+				maxOffset,
+				ApplicationTag.BIT_STRING,
+				tag.value,
+			)
+			isLogStatus = true
+		} else if (tag.tagNumber === 2 && tag.value === 4) {
 			value = bacappDecodeData(
 				buffer,
 				offset + len,
@@ -2506,26 +2526,34 @@ export const decodeRange = (
 		if (!value) return undefined
 		len += value.len
 
-		// closing tag 1 + opening tag 2
-		tag = decodeTagNumberAndValue(buffer, offset + len)
-		len += tag.len
+		// closing tag 1 is required
+		if (!decodeIsClosingTagNumber(buffer, offset + len, 1)) {
+			return undefined
+		}
 		tag = decodeTagNumberAndValue(buffer, offset + len)
 		len += tag.len
 
-		// status flags
-		const status = bacappDecodeData(
-			buffer,
-			offset + len,
-			maxOffset,
-			ApplicationTag.BIT_STRING,
-			tag.value,
-		)
-		if (!status) return undefined
-		len += status.len
+		// context tag 2 (status flags) is optional for regular log records.
+		// Special log records (log-status choice) do NOT have status flags.
+		let status: ApplicationData | undefined
+		if (!isLogStatus && decodeIsContextTag(buffer, offset + len, 2)) {
+			tag = decodeTagNumberAndValue(buffer, offset + len)
+			len += tag.len
+
+			// status flags bitstring
+			status = bacappDecodeData(
+				buffer,
+				offset + len,
+				maxOffset,
+				ApplicationTag.BIT_STRING,
+				tag.value,
+			)
+			if (!status) return undefined
+			len += status.len
+		}
 
 		const d = date.value as Date
 		const t = time.value as Date
-		const statusBits = status.value as { value: number[] }
 		const timestamp = new Date(
 			d.getFullYear(),
 			d.getMonth(),
@@ -2535,16 +2563,48 @@ export const decodeRange = (
 			t.getSeconds(),
 			t.getMilliseconds(),
 		)
-		result.push({
+
+		const record: {
+			timestamp: Date
+			value: unknown
+			isLogStatus?: boolean
+			logStatus?: {
+				log_disabled: boolean
+				buffer_purged: boolean
+				log_interrupted: boolean
+			}
+			status?: {
+				out_of_service: boolean
+				overridden: boolean
+				fault: boolean
+				in_alarm: boolean
+			}
+		} = {
 			timestamp,
 			value: value.value,
-			status: {
+		}
+
+		if (isLogStatus) {
+			record.isLogStatus = true
+			const logStatusBits = value.value as { value: number[] }
+			record.logStatus = {
+				log_disabled: ((logStatusBits.value[0] >> 0) & 1) !== 0,
+				buffer_purged: ((logStatusBits.value[0] >> 1) & 1) !== 0,
+				log_interrupted: ((logStatusBits.value[0] >> 2) & 1) !== 0,
+			}
+		}
+
+		if (status) {
+			const statusBits = status.value as { value: number[] }
+			record.status = {
 				out_of_service: ((statusBits.value[0] >> 0) & 1) !== 0,
 				overridden: ((statusBits.value[0] >> 1) & 1) !== 0,
 				fault: ((statusBits.value[0] >> 2) & 1) !== 0,
 				in_alarm: ((statusBits.value[0] >> 3) & 1) !== 0,
-			},
-		})
+			}
+		}
+
+		result.push(record)
 	}
 
 	if (offset + len >= maxOffset) return undefined
diff --git a/src/lib/services/WriteProperty.ts b/src/lib/services/WriteProperty.ts
index e6c1dd2d..8f94d08d 100644
--- a/src/lib/services/WriteProperty.ts
+++ b/src/lib/services/WriteProperty.ts
@@ -108,7 +108,10 @@ export default class WriteProperty extends BacnetService {
 		)
 	}
 
-	private static writeDateBytes(buffer: EncodeBuffer, value: BACNetDateValue) {
+	private static writeDateBytes(
+		buffer: EncodeBuffer,
+		value: BACNetDateValue,
+	) {
 		if (WriteProperty.isRawDate(value)) {
 			WriteProperty.validateRawDateByte('year', value.year, 0, 255)
 			if (value.month !== 0xff) {
@@ -170,7 +173,8 @@ export default class WriteProperty extends BacnetService {
 		if (timeValue == null) {
 			throw new Error(`${errorPrefix} time is required`)
 		}
-		const normalized = timeValue instanceof Date ? timeValue : new Date(timeValue)
+		const normalized =
+			timeValue instanceof Date ? timeValue : new Date(timeValue)
 		if (Number.isNaN(normalized.getTime())) {
 			throw new Error(`${errorPrefix} time is invalid`)
 		}
diff --git a/test/unit/service-read-range.spec.ts b/test/unit/service-read-range.spec.ts
index 0255246a..803d115c 100644
--- a/test/unit/service-read-range.spec.ts
+++ b/test/unit/service-read-range.spec.ts
@@ -198,6 +198,115 @@ test.describe('ReadRangeAcknowledge', () => {
 		)
 	})
 
+	test('should decode special log-status records without status flags', () => {
+		// Build a log record with log-status choice (tag 0) instead of normal value
+		// Per ASHRAE 135, log-status records do NOT have status flags (context tag 2)
+		const applicationData = utils.getBuffer()
+
+		// First record: normal record with status flags
+		baAsn1.encodeOpeningTag(applicationData, 0)
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.DATE,
+			value: new Date(2024, 1, 3),
+		})
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.TIME,
+			value: new Date(2024, 1, 3, 12, 15, 30, 0),
+		})
+		baAsn1.encodeClosingTag(applicationData, 0)
+		baAsn1.encodeOpeningTag(applicationData, 1)
+		baAsn1.encodeTag(applicationData, 2, true, 4)
+		applicationData.buffer.writeFloatBE(42.5, applicationData.offset)
+		applicationData.offset += 4
+		baAsn1.encodeClosingTag(applicationData, 1)
+		baAsn1.encodeContextBitstring(applicationData, 2, {
+			bitsUsed: 4,
+			value: [0b0000],
+		})
+
+		// Second record: log-status (log-interrupted) without status flags
+		baAsn1.encodeOpeningTag(applicationData, 0)
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.DATE,
+			value: new Date(2024, 1, 3),
+		})
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.TIME,
+			value: new Date(2024, 1, 3, 12, 30, 0, 0),
+		})
+		baAsn1.encodeClosingTag(applicationData, 0)
+		baAsn1.encodeOpeningTag(applicationData, 1)
+		// log-status choice: context tag 0 with bitstring
+		// LOG_INTERRUPTED = bit 2 = 0b0100 = 4
+		baAsn1.encodeContextBitstring(applicationData, 0, {
+			bitsUsed: 3,
+			value: [0b0100],
+		})
+		baAsn1.encodeClosingTag(applicationData, 1)
+		// NO status flags for log-status records!
+
+		// Third record: another normal record with status flags
+		baAsn1.encodeOpeningTag(applicationData, 0)
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.DATE,
+			value: new Date(2024, 1, 3),
+		})
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.TIME,
+			value: new Date(2024, 1, 3, 12, 45, 0, 0),
+		})
+		baAsn1.encodeClosingTag(applicationData, 0)
+		baAsn1.encodeOpeningTag(applicationData, 1)
+		baAsn1.encodeTag(applicationData, 2, true, 4)
+		applicationData.buffer.writeFloatBE(99.9, applicationData.offset)
+		applicationData.offset += 4
+		baAsn1.encodeClosingTag(applicationData, 1)
+		baAsn1.encodeContextBitstring(applicationData, 2, {
+			bitsUsed: 4,
+			value: [0b0000],
+		})
+
+		const buffer = utils.getBuffer()
+		ReadRange.encodeAcknowledge(
+			buffer,
+			{ type: 20, instance: 0 },
+			131,
+			0xffffffff,
+			{ bitsUsed: 3, value: [0] },
+			3,
+			applicationData.buffer.slice(0, applicationData.offset),
+			ReadRangeType.BY_POSITION,
+			0,
+		)
+
+		const result = ReadRange.decodeAcknowledge(
+			buffer.buffer,
+			0,
+			buffer.offset,
+		)
+		assert.ok(result)
+		assert.ok(result.values)
+		assert.equal(result.values?.length, 3)
+
+		// First record: normal with value 42.5
+		assert.equal(result.values?.[0].value, 42.5)
+		assert.equal(result.values?.[0].isLogStatus, undefined)
+		assert.ok(result.values?.[0].status)
+
+		// Second record: log-status (log-interrupted)
+		assert.equal(result.values?.[1].isLogStatus, true)
+		assert.ok(result.values?.[1].logStatus)
+		assert.equal(result.values?.[1].logStatus?.log_interrupted, true)
+		assert.equal(result.values?.[1].logStatus?.log_disabled, false)
+		assert.equal(result.values?.[1].logStatus?.buffer_purged, false)
+		assert.equal(result.values?.[1].status, undefined)
+
+		// Third record: normal with value 99.9 (approximately)
+		assert.ok(Math.abs((result.values?.[2].value as number) - 99.9) < 0.01)
+		assert.equal(result.values?.[2].isLogStatus, undefined)
+		assert.ok(result.values?.[2].status)
+	})
+
 	test('should slice fallback rangeBuffer correctly with non-zero offset', () => {
 		const ackBuffer = utils.getBuffer()
 		ReadRange.encodeAcknowledge(

From 79a8503780ea807a48bc5afa57180e318104f5c8 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 08:48:24 +0000
Subject: [PATCH 3/9] refactor: extract LogRecord interface and improve test
 assertions

- Extract LogRecord, LogStatusFlags, LogRecordStatusFlags interfaces
- Update ReadRangeAcknowledge.values to use LogRecord[] instead of any[]
- Update decodeRange to return Decode<LogRecord[]>
- Use assert.strictEqual for undefined checks in tests

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts                      | 22 +++----------
 src/lib/types.ts                     | 49 +++++++++++++++++++++++++++-
 test/unit/service-read-range.spec.ts |  6 ++--
 3 files changed, 55 insertions(+), 22 deletions(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index 49bb4f50..567cd8bc 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -31,6 +31,7 @@ import {
 	BACNetDateValue,
 	BACNetEncodableAppData,
 	BACNetRawDate,
+	LogRecord,
 } from './types'
 import {
 	CharacterStringEncoding,
@@ -2425,11 +2426,11 @@ export const decodeRange = (
 	buffer: Buffer,
 	offset: number,
 	maxOffset: number,
-): Decode<any[]> | undefined => {
+): Decode<LogRecord[]> | undefined => {
 	// The payload for readRange ACK is expected to start with opening tag 0.
 	if (!decodeIsOpeningTagNumber(buffer, offset, 0)) return undefined
 	let len = 0
-	const result: any[] = []
+	const result: LogRecord[] = []
 
 	while (
 		offset + len < maxOffset &&
@@ -2564,22 +2565,7 @@ export const decodeRange = (
 			t.getMilliseconds(),
 		)
 
-		const record: {
-			timestamp: Date
-			value: unknown
-			isLogStatus?: boolean
-			logStatus?: {
-				log_disabled: boolean
-				buffer_purged: boolean
-				log_interrupted: boolean
-			}
-			status?: {
-				out_of_service: boolean
-				overridden: boolean
-				fault: boolean
-				in_alarm: boolean
-			}
-		} = {
+		const record: LogRecord = {
 			timestamp,
 			value: value.value,
 		}
diff --git a/src/lib/types.ts b/src/lib/types.ts
index 67042c9e..a04fc2d4 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -742,13 +742,60 @@ export interface ReadRangePayload extends BasicServicePayload {
 	values: BACNetAppData[]
 }
 
+/**
+ * Represents the log-status choice for special log records.
+ * These are status-only records without actual data values.
+ */
+export interface LogStatusFlags {
+	log_disabled: boolean
+	buffer_purged: boolean
+	log_interrupted: boolean
+}
+
+/**
+ * Represents the status flags for a normal log record.
+ */
+export interface LogRecordStatusFlags {
+	out_of_service: boolean
+	overridden: boolean
+	fault: boolean
+	in_alarm: boolean
+}
+
+/**
+ * Represents a single log record from a TREND_LOG.
+ * Can be either a normal data record or a special log-status record.
+ */
+export interface LogRecord {
+	/** Timestamp when the record was logged */
+	timestamp: Date
+	/**
+	 * The logged value. For normal records, this is the actual data (number, boolean, etc.).
+	 * For log-status records, this is the raw bitstring value.
+	 */
+	value: unknown
+	/**
+	 * True if this is a special log-status record (log-disabled, buffer-purged, log-interrupted).
+	 * Undefined for normal data records.
+	 */
+	isLogStatus?: boolean
+	/**
+	 * Present only for log-status records. Indicates which special status applies.
+	 */
+	logStatus?: LogStatusFlags
+	/**
+	 * Present only for normal data records. Contains the BACnet status flags.
+	 */
+	status?: LogRecordStatusFlags
+}
+
 export interface ReadRangeAcknowledge {
 	objectId: BACNetObjectID
 	property: BACNetPropertyID
 	resultFlag: BACNetBitString
 	itemCount: number
 	rangeBuffer: Buffer
-	values?: any[]
+	values?: LogRecord[]
 	len: number
 }
 
diff --git a/test/unit/service-read-range.spec.ts b/test/unit/service-read-range.spec.ts
index 803d115c..37a59d22 100644
--- a/test/unit/service-read-range.spec.ts
+++ b/test/unit/service-read-range.spec.ts
@@ -290,7 +290,7 @@ test.describe('ReadRangeAcknowledge', () => {
 
 		// First record: normal with value 42.5
 		assert.equal(result.values?.[0].value, 42.5)
-		assert.equal(result.values?.[0].isLogStatus, undefined)
+		assert.strictEqual(result.values?.[0].isLogStatus, undefined)
 		assert.ok(result.values?.[0].status)
 
 		// Second record: log-status (log-interrupted)
@@ -299,11 +299,11 @@ test.describe('ReadRangeAcknowledge', () => {
 		assert.equal(result.values?.[1].logStatus?.log_interrupted, true)
 		assert.equal(result.values?.[1].logStatus?.log_disabled, false)
 		assert.equal(result.values?.[1].logStatus?.buffer_purged, false)
-		assert.equal(result.values?.[1].status, undefined)
+		assert.strictEqual(result.values?.[1].status, undefined)
 
 		// Third record: normal with value 99.9 (approximately)
 		assert.ok(Math.abs((result.values?.[2].value as number) - 99.9) < 0.01)
-		assert.equal(result.values?.[2].isLogStatus, undefined)
+		assert.strictEqual(result.values?.[2].isLogStatus, undefined)
 		assert.ok(result.values?.[2].status)
 	})
 

From 56096123468361dc32c589c467f66491951d850e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 09:37:08 +0000
Subject: [PATCH 4/9] =?UTF-8?q?docs:=20add=20ASHRAE=20135=20=C2=A712.25=20?=
 =?UTF-8?q?standard=20references=20to=20LogRecord=20decoding?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Reference ASHRAE 135 Standard Section 12.25 for LogRecord structure
in JSDoc comments for decodeRange function and LogRecord types.

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts  | 19 +++++++++++++------
 src/lib/types.ts |  3 +++
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index 567cd8bc..187cdcb2 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -2422,6 +2422,14 @@ export const decodeCalendarDatelist = (
 	return { len, value: result }
 }
 
+/**
+ * Decodes LogRecord sequence from ReadRange ACK payload.
+ * Per ASHRAE 135 §12.25, LogRecord ::= SEQUENCE {
+ *   timestamp [0] BACnetDateTime,
+ *   logDatum  [1] CHOICE { log-status [0], boolean-value [1], real-value [2], ... },
+ *   statusFlags [2] BACnetStatusFlags OPTIONAL  -- NOT present for log-status choice
+ * }
+ */
 export const decodeRange = (
 	buffer: Buffer,
 	offset: number,
@@ -2475,22 +2483,21 @@ export const decodeRange = (
 		}
 		len += 2
 
-		// value payload (context specific)
-		// This is the log-datum CHOICE with options:
+		// log-datum [1] CHOICE per ASHRAE 135 §12.25:
 		// [0] log-status (BACnetLogStatus bitstring - special records)
 		// [1] boolean-value
 		// [2] real-value
 		// [3] enum-value
 		// [4] unsigned-value
-		// ... and more per ASHRAE 135
+		// ... and more
 		tag = decodeTagNumberAndValue(buffer, offset + len)
 		len += tag.len
 		let value: ApplicationData | undefined
 		let isLogStatus = false
 		if (tag.tagNumber === 0) {
-			// log-status choice: BACnetLogStatus bitstring
-			// These are special log records (log-disabled, buffer-purged, log-interrupted)
-			// They do NOT have status flags after the log-datum
+			// log-status choice: BACnetLogStatus bitstring per ASHRAE 135 §12.25
+			// Special log records (log-disabled, buffer-purged, log-interrupted)
+			// do NOT have statusFlags [2] after the log-datum
 			value = bacappDecodeData(
 				buffer,
 				offset + len,
diff --git a/src/lib/types.ts b/src/lib/types.ts
index a04fc2d4..cf8feb35 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -743,6 +743,7 @@ export interface ReadRangePayload extends BasicServicePayload {
 }
 
 /**
+ * BACnetLogStatus bitstring per ASHRAE 135 §12.25.
  * Represents the log-status choice for special log records.
  * These are status-only records without actual data values.
  */
@@ -753,6 +754,7 @@ export interface LogStatusFlags {
 }
 
 /**
+ * BACnetStatusFlags per ASHRAE 135 §12.25.
  * Represents the status flags for a normal log record.
  */
 export interface LogRecordStatusFlags {
@@ -763,6 +765,7 @@ export interface LogRecordStatusFlags {
 }
 
 /**
+ * LogRecord per ASHRAE 135 §12.25.
  * Represents a single log record from a TREND_LOG.
  * Can be either a normal data record or a special log-status record.
  */

From a33fbbb6359d2bf7d088f07350c9f0974a4d6014 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 09:44:47 +0000
Subject: [PATCH 5/9] refactor: use BACNetBitString for casts and add
 LogRecordValue type

Address code review comments:
- Use BACNetBitString for bitstring casts instead of { value: number[] }
- Add LogRecordValue union type to narrow LogRecord.value from unknown

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts  |  7 ++++---
 src/lib/types.ts | 16 ++++++++++++++--
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index 187cdcb2..5ab576a8 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -32,6 +32,7 @@ import {
 	BACNetEncodableAppData,
 	BACNetRawDate,
 	LogRecord,
+	LogRecordValue,
 } from './types'
 import {
 	CharacterStringEncoding,
@@ -2574,12 +2575,12 @@ export const decodeRange = (
 
 		const record: LogRecord = {
 			timestamp,
-			value: value.value,
+			value: value.value as LogRecordValue,
 		}
 
 		if (isLogStatus) {
 			record.isLogStatus = true
-			const logStatusBits = value.value as { value: number[] }
+			const logStatusBits = value.value as BACNetBitString
 			record.logStatus = {
 				log_disabled: ((logStatusBits.value[0] >> 0) & 1) !== 0,
 				buffer_purged: ((logStatusBits.value[0] >> 1) & 1) !== 0,
@@ -2588,7 +2589,7 @@ export const decodeRange = (
 		}
 
 		if (status) {
-			const statusBits = status.value as { value: number[] }
+			const statusBits = status.value as BACNetBitString
 			record.status = {
 				out_of_service: ((statusBits.value[0] >> 0) & 1) !== 0,
 				overridden: ((statusBits.value[0] >> 1) & 1) !== 0,
diff --git a/src/lib/types.ts b/src/lib/types.ts
index cf8feb35..ae0092c0 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -764,6 +764,18 @@ export interface LogRecordStatusFlags {
 	in_alarm: boolean
 }
 
+/**
+ * Union type for log record values per ASHRAE 135 §12.25.
+ * log-datum CHOICE can contain various types depending on the logged property.
+ */
+export type LogRecordValue =
+	| number // REAL, ENUMERATED, UNSIGNED_INTEGER, SIGNED_INTEGER
+	| boolean // BOOLEAN
+	| BACNetBitString // log-status bitstring
+	| null // NULL
+	| string // CHARACTER_STRING
+	| BACNetObjectID // OBJECTIDENTIFIER
+
 /**
  * LogRecord per ASHRAE 135 §12.25.
  * Represents a single log record from a TREND_LOG.
@@ -774,9 +786,9 @@ export interface LogRecord {
 	timestamp: Date
 	/**
 	 * The logged value. For normal records, this is the actual data (number, boolean, etc.).
-	 * For log-status records, this is the raw bitstring value.
+	 * For log-status records, this is a BACNetBitString.
 	 */
-	value: unknown
+	value: LogRecordValue
 	/**
 	 * True if this is a special log-status record (log-disabled, buffer-purged, log-interrupted).
 	 * Undefined for normal data records.

From f5bbc1fa9ed4b95027c27e1e15f131ba7ed45634 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 10:04:11 +0000
Subject: [PATCH 6/9] refactor: use camelCase for flag names and narrow
 LogRecordValue type

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts                      | 10 +++++-----
 src/lib/types.ts                     | 26 +++++++++++++-------------
 test/unit/service-read-range.spec.ts |  6 +++---
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index 5ab576a8..5bb64750 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -2582,19 +2582,19 @@ export const decodeRange = (
 			record.isLogStatus = true
 			const logStatusBits = value.value as BACNetBitString
 			record.logStatus = {
-				log_disabled: ((logStatusBits.value[0] >> 0) & 1) !== 0,
-				buffer_purged: ((logStatusBits.value[0] >> 1) & 1) !== 0,
-				log_interrupted: ((logStatusBits.value[0] >> 2) & 1) !== 0,
+				logDisabled: ((logStatusBits.value[0] >> 0) & 1) !== 0,
+				bufferPurged: ((logStatusBits.value[0] >> 1) & 1) !== 0,
+				logInterrupted: ((logStatusBits.value[0] >> 2) & 1) !== 0,
 			}
 		}
 
 		if (status) {
 			const statusBits = status.value as BACNetBitString
 			record.status = {
-				out_of_service: ((statusBits.value[0] >> 0) & 1) !== 0,
+				outOfService: ((statusBits.value[0] >> 0) & 1) !== 0,
 				overridden: ((statusBits.value[0] >> 1) & 1) !== 0,
 				fault: ((statusBits.value[0] >> 2) & 1) !== 0,
-				in_alarm: ((statusBits.value[0] >> 3) & 1) !== 0,
+				inAlarm: ((statusBits.value[0] >> 3) & 1) !== 0,
 			}
 		}
 
diff --git a/src/lib/types.ts b/src/lib/types.ts
index ae0092c0..78fb49f2 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -748,9 +748,9 @@ export interface ReadRangePayload extends BasicServicePayload {
  * These are status-only records without actual data values.
  */
 export interface LogStatusFlags {
-	log_disabled: boolean
-	buffer_purged: boolean
-	log_interrupted: boolean
+	logDisabled: boolean
+	bufferPurged: boolean
+	logInterrupted: boolean
 }
 
 /**
@@ -758,23 +758,23 @@ export interface LogStatusFlags {
  * Represents the status flags for a normal log record.
  */
 export interface LogRecordStatusFlags {
-	out_of_service: boolean
+	outOfService: boolean
 	overridden: boolean
 	fault: boolean
-	in_alarm: boolean
+	inAlarm: boolean
 }
 
 /**
  * Union type for log record values per ASHRAE 135 §12.25.
- * log-datum CHOICE can contain various types depending on the logged property.
+ * Currently supported log-datum CHOICE types decoded by decodeRange:
+ * - [0] log-status (BACNetBitString)
+ * - [2] real-value (number)
+ * - [3] enumerated-value (number)
+ * - [4] unsigned-value (number)
+ * Other CHOICE alternatives exist in the BACnet spec but are not currently decoded;
+ * for unsupported types, use the raw `rangeBuffer` from ReadRangeAcknowledge.
  */
-export type LogRecordValue =
-	| number // REAL, ENUMERATED, UNSIGNED_INTEGER, SIGNED_INTEGER
-	| boolean // BOOLEAN
-	| BACNetBitString // log-status bitstring
-	| null // NULL
-	| string // CHARACTER_STRING
-	| BACNetObjectID // OBJECTIDENTIFIER
+export type LogRecordValue = number | BACNetBitString
 
 /**
  * LogRecord per ASHRAE 135 §12.25.
diff --git a/test/unit/service-read-range.spec.ts b/test/unit/service-read-range.spec.ts
index 37a59d22..6835f692 100644
--- a/test/unit/service-read-range.spec.ts
+++ b/test/unit/service-read-range.spec.ts
@@ -296,9 +296,9 @@ test.describe('ReadRangeAcknowledge', () => {
 		// Second record: log-status (log-interrupted)
 		assert.equal(result.values?.[1].isLogStatus, true)
 		assert.ok(result.values?.[1].logStatus)
-		assert.equal(result.values?.[1].logStatus?.log_interrupted, true)
-		assert.equal(result.values?.[1].logStatus?.log_disabled, false)
-		assert.equal(result.values?.[1].logStatus?.buffer_purged, false)
+		assert.equal(result.values?.[1].logStatus?.logInterrupted, true)
+		assert.equal(result.values?.[1].logStatus?.logDisabled, false)
+		assert.equal(result.values?.[1].logStatus?.bufferPurged, false)
 		assert.strictEqual(result.values?.[1].status, undefined)
 
 		// Third record: normal with value 99.9 (approximately)

From f1f71764977ce3c08f52276cf348210f70e13b0e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 10:12:49 +0000
Subject: [PATCH 7/9] revert: keep snake_case property names to avoid breaking
 changes

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts                      | 10 +++++-----
 src/lib/types.ts                     | 26 +++++++++++++-------------
 test/unit/service-read-range.spec.ts |  6 +++---
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index 5bb64750..5ab576a8 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -2582,19 +2582,19 @@ export const decodeRange = (
 			record.isLogStatus = true
 			const logStatusBits = value.value as BACNetBitString
 			record.logStatus = {
-				logDisabled: ((logStatusBits.value[0] >> 0) & 1) !== 0,
-				bufferPurged: ((logStatusBits.value[0] >> 1) & 1) !== 0,
-				logInterrupted: ((logStatusBits.value[0] >> 2) & 1) !== 0,
+				log_disabled: ((logStatusBits.value[0] >> 0) & 1) !== 0,
+				buffer_purged: ((logStatusBits.value[0] >> 1) & 1) !== 0,
+				log_interrupted: ((logStatusBits.value[0] >> 2) & 1) !== 0,
 			}
 		}
 
 		if (status) {
 			const statusBits = status.value as BACNetBitString
 			record.status = {
-				outOfService: ((statusBits.value[0] >> 0) & 1) !== 0,
+				out_of_service: ((statusBits.value[0] >> 0) & 1) !== 0,
 				overridden: ((statusBits.value[0] >> 1) & 1) !== 0,
 				fault: ((statusBits.value[0] >> 2) & 1) !== 0,
-				inAlarm: ((statusBits.value[0] >> 3) & 1) !== 0,
+				in_alarm: ((statusBits.value[0] >> 3) & 1) !== 0,
 			}
 		}
 
diff --git a/src/lib/types.ts b/src/lib/types.ts
index 78fb49f2..ae0092c0 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -748,9 +748,9 @@ export interface ReadRangePayload extends BasicServicePayload {
  * These are status-only records without actual data values.
  */
 export interface LogStatusFlags {
-	logDisabled: boolean
-	bufferPurged: boolean
-	logInterrupted: boolean
+	log_disabled: boolean
+	buffer_purged: boolean
+	log_interrupted: boolean
 }
 
 /**
@@ -758,23 +758,23 @@ export interface LogStatusFlags {
  * Represents the status flags for a normal log record.
  */
 export interface LogRecordStatusFlags {
-	outOfService: boolean
+	out_of_service: boolean
 	overridden: boolean
 	fault: boolean
-	inAlarm: boolean
+	in_alarm: boolean
 }
 
 /**
  * Union type for log record values per ASHRAE 135 §12.25.
- * Currently supported log-datum CHOICE types decoded by decodeRange:
- * - [0] log-status (BACNetBitString)
- * - [2] real-value (number)
- * - [3] enumerated-value (number)
- * - [4] unsigned-value (number)
- * Other CHOICE alternatives exist in the BACnet spec but are not currently decoded;
- * for unsupported types, use the raw `rangeBuffer` from ReadRangeAcknowledge.
+ * log-datum CHOICE can contain various types depending on the logged property.
  */
-export type LogRecordValue = number | BACNetBitString
+export type LogRecordValue =
+	| number // REAL, ENUMERATED, UNSIGNED_INTEGER, SIGNED_INTEGER
+	| boolean // BOOLEAN
+	| BACNetBitString // log-status bitstring
+	| null // NULL
+	| string // CHARACTER_STRING
+	| BACNetObjectID // OBJECTIDENTIFIER
 
 /**
  * LogRecord per ASHRAE 135 §12.25.
diff --git a/test/unit/service-read-range.spec.ts b/test/unit/service-read-range.spec.ts
index 6835f692..37a59d22 100644
--- a/test/unit/service-read-range.spec.ts
+++ b/test/unit/service-read-range.spec.ts
@@ -296,9 +296,9 @@ test.describe('ReadRangeAcknowledge', () => {
 		// Second record: log-status (log-interrupted)
 		assert.equal(result.values?.[1].isLogStatus, true)
 		assert.ok(result.values?.[1].logStatus)
-		assert.equal(result.values?.[1].logStatus?.logInterrupted, true)
-		assert.equal(result.values?.[1].logStatus?.logDisabled, false)
-		assert.equal(result.values?.[1].logStatus?.bufferPurged, false)
+		assert.equal(result.values?.[1].logStatus?.log_interrupted, true)
+		assert.equal(result.values?.[1].logStatus?.log_disabled, false)
+		assert.equal(result.values?.[1].logStatus?.buffer_purged, false)
 		assert.strictEqual(result.values?.[1].status, undefined)
 
 		// Third record: normal with value 99.9 (approximately)

From 2125d039b66e89cbabb28885f84476c939dede5d Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 30 Mar 2026 12:13:44 +0000
Subject: [PATCH 8/9] fix: handle time-change records and make status flags
 optional for all record types

Agent-Logs-Url: https://github.com/bacnet-js/client/sessions/e153eab8-5232-426b-92f5-4cecd29c35b7

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts                      |  41 ++++++++--
 src/lib/types.ts                     |  15 +++-
 test/unit/service-read-range.spec.ts | 110 +++++++++++++++++++++++++++
 3 files changed, 155 insertions(+), 11 deletions(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index 5ab576a8..c89dfa10 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -2490,15 +2490,20 @@ export const decodeRange = (
 		// [2] real-value
 		// [3] enum-value
 		// [4] unsigned-value
-		// ... and more
+		// [5] signed-value
+		// [6] bitstring-value
+		// [7] null-value
+		// [8] failure (BACnetError)
+		// [9] time-change (REAL - seconds delta for clock adjustment)
+		// [10] any-value (ABSTRACT-SYNTAX.&Type)
 		tag = decodeTagNumberAndValue(buffer, offset + len)
 		len += tag.len
 		let value: ApplicationData | undefined
 		let isLogStatus = false
+		let isTimeChange = false
 		if (tag.tagNumber === 0) {
 			// log-status choice: BACnetLogStatus bitstring per ASHRAE 135 §12.25
 			// Special log records (log-disabled, buffer-purged, log-interrupted)
-			// do NOT have statusFlags [2] after the log-datum
 			value = bacappDecodeData(
 				buffer,
 				offset + len,
@@ -2507,7 +2512,8 @@ export const decodeRange = (
 				tag.value,
 			)
 			isLogStatus = true
-		} else if (tag.tagNumber === 2 && tag.value === 4) {
+		} else if (tag.tagNumber === 2) {
+			// real-value
 			value = bacappDecodeData(
 				buffer,
 				offset + len,
@@ -2515,7 +2521,8 @@ export const decodeRange = (
 				ApplicationTag.REAL,
 				tag.value,
 			)
-		} else if (tag.tagNumber === 4 && tag.value === 1) {
+		} else if (tag.tagNumber === 3) {
+			// enum-value
 			value = bacappDecodeData(
 				buffer,
 				offset + len,
@@ -2523,7 +2530,8 @@ export const decodeRange = (
 				ApplicationTag.ENUMERATED,
 				tag.value,
 			)
-		} else if (tag.tagNumber === 3 && tag.value === 1) {
+		} else if (tag.tagNumber === 4) {
+			// unsigned-value
 			value = bacappDecodeData(
 				buffer,
 				offset + len,
@@ -2531,6 +2539,17 @@ export const decodeRange = (
 				ApplicationTag.ENUMERATED,
 				tag.value,
 			)
+		} else if (tag.tagNumber === 9) {
+			// time-change: REAL value representing seconds the clock changed
+			// Per ASHRAE 135 §12.25, time-change records do not have status flags
+			value = bacappDecodeData(
+				buffer,
+				offset + len,
+				maxOffset,
+				ApplicationTag.REAL,
+				tag.value,
+			)
+			isTimeChange = true
 		}
 		if (!value) return undefined
 		len += value.len
@@ -2542,10 +2561,12 @@ export const decodeRange = (
 		tag = decodeTagNumberAndValue(buffer, offset + len)
 		len += tag.len
 
-		// context tag 2 (status flags) is optional for regular log records.
-		// Special log records (log-status choice) do NOT have status flags.
+		// context tag 2 (status flags) is OPTIONAL for ALL log record types.
+		// Per ASHRAE 135 §12.25 and bacnet-stack, status flags are only encoded
+		// when the ucStatus byte has bit 7 set. This means any record type
+		// (log-status, time-change, real-value, etc.) may or may not have status flags.
 		let status: ApplicationData | undefined
-		if (!isLogStatus && decodeIsContextTag(buffer, offset + len, 2)) {
+		if (decodeIsContextTag(buffer, offset + len, 2)) {
 			tag = decodeTagNumberAndValue(buffer, offset + len)
 			len += tag.len
 
@@ -2588,6 +2609,10 @@ export const decodeRange = (
 			}
 		}
 
+		if (isTimeChange) {
+			record.isTimeChange = true
+		}
+
 		if (status) {
 			const statusBits = status.value as BACNetBitString
 			record.status = {
diff --git a/src/lib/types.ts b/src/lib/types.ts
index ae0092c0..b3c8837d 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -779,7 +779,7 @@ export type LogRecordValue =
 /**
  * LogRecord per ASHRAE 135 §12.25.
  * Represents a single log record from a TREND_LOG.
- * Can be either a normal data record or a special log-status record.
+ * Can be either a normal data record, a special log-status record, or a time-change record.
  */
 export interface LogRecord {
 	/** Timestamp when the record was logged */
@@ -787,19 +787,28 @@ export interface LogRecord {
 	/**
 	 * The logged value. For normal records, this is the actual data (number, boolean, etc.).
 	 * For log-status records, this is a BACNetBitString.
+	 * For time-change records, this is the number of seconds the clock changed (REAL).
 	 */
 	value: LogRecordValue
 	/**
 	 * True if this is a special log-status record (log-disabled, buffer-purged, log-interrupted).
-	 * Undefined for normal data records.
+	 * Undefined for normal data records and time-change records.
 	 */
 	isLogStatus?: boolean
+	/**
+	 * True if this is a time-change record (clock adjustment).
+	 * Per ASHRAE 135 §12.25, time-change records contain a REAL value representing
+	 * the number of seconds the clock changed (positive or negative).
+	 * Undefined for normal data records and log-status records.
+	 */
+	isTimeChange?: boolean
 	/**
 	 * Present only for log-status records. Indicates which special status applies.
 	 */
 	logStatus?: LogStatusFlags
 	/**
-	 * Present only for normal data records. Contains the BACnet status flags.
+	 * Present only when status flags are encoded. Per ASHRAE 135 §12.25,
+	 * status flags are optional for ALL log record types.
 	 */
 	status?: LogRecordStatusFlags
 }
diff --git a/test/unit/service-read-range.spec.ts b/test/unit/service-read-range.spec.ts
index 37a59d22..53fbbecc 100644
--- a/test/unit/service-read-range.spec.ts
+++ b/test/unit/service-read-range.spec.ts
@@ -307,6 +307,116 @@ test.describe('ReadRangeAcknowledge', () => {
 		assert.ok(result.values?.[2].status)
 	})
 
+	test('should decode time-change records without status flags', () => {
+		// Build a log record with time-change choice (tag 9) per ASHRAE 135 §12.25
+		// Per the BACnet standard, time-change records do NOT have status flags
+		const applicationData = utils.getBuffer()
+
+		// First record: normal record with status flags
+		baAsn1.encodeOpeningTag(applicationData, 0)
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.DATE,
+			value: new Date(2024, 1, 3),
+		})
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.TIME,
+			value: new Date(2024, 1, 3, 12, 0, 0, 0),
+		})
+		baAsn1.encodeClosingTag(applicationData, 0)
+		baAsn1.encodeOpeningTag(applicationData, 1)
+		baAsn1.encodeTag(applicationData, 2, true, 4)
+		applicationData.buffer.writeFloatBE(42.5, applicationData.offset)
+		applicationData.offset += 4
+		baAsn1.encodeClosingTag(applicationData, 1)
+		baAsn1.encodeContextBitstring(applicationData, 2, {
+			bitsUsed: 4,
+			value: [0b0000],
+		})
+
+		// Second record: time-change (context tag 9) without status flags
+		// This represents a clock adjustment of 0.075 seconds
+		baAsn1.encodeOpeningTag(applicationData, 0)
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.DATE,
+			value: new Date(2024, 1, 3),
+		})
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.TIME,
+			value: new Date(2024, 1, 3, 12, 30, 0, 0),
+		})
+		baAsn1.encodeClosingTag(applicationData, 0)
+		baAsn1.encodeOpeningTag(applicationData, 1)
+		// time-change choice: context tag 9 with REAL value (seconds delta)
+		baAsn1.encodeTag(applicationData, 9, true, 4)
+		applicationData.buffer.writeFloatBE(0.075, applicationData.offset)
+		applicationData.offset += 4
+		baAsn1.encodeClosingTag(applicationData, 1)
+		// NO status flags for time-change records!
+
+		// Third record: another normal record with status flags
+		baAsn1.encodeOpeningTag(applicationData, 0)
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.DATE,
+			value: new Date(2024, 1, 3),
+		})
+		baAsn1.bacappEncodeApplicationData(applicationData, {
+			type: ApplicationTag.TIME,
+			value: new Date(2024, 1, 3, 12, 45, 0, 0),
+		})
+		baAsn1.encodeClosingTag(applicationData, 0)
+		baAsn1.encodeOpeningTag(applicationData, 1)
+		baAsn1.encodeTag(applicationData, 2, true, 4)
+		applicationData.buffer.writeFloatBE(99.9, applicationData.offset)
+		applicationData.offset += 4
+		baAsn1.encodeClosingTag(applicationData, 1)
+		baAsn1.encodeContextBitstring(applicationData, 2, {
+			bitsUsed: 4,
+			value: [0b0000],
+		})
+
+		const buffer = utils.getBuffer()
+		ReadRange.encodeAcknowledge(
+			buffer,
+			{ type: 20, instance: 0 },
+			131,
+			0xffffffff,
+			{ bitsUsed: 3, value: [0] },
+			3,
+			applicationData.buffer.slice(0, applicationData.offset),
+			ReadRangeType.BY_POSITION,
+			0,
+		)
+
+		const result = ReadRange.decodeAcknowledge(
+			buffer.buffer,
+			0,
+			buffer.offset,
+		)
+		assert.ok(result)
+		assert.ok(result.values)
+		assert.equal(result.values?.length, 3)
+
+		// First record: normal with value 42.5 and status flags
+		assert.equal(result.values?.[0].value, 42.5)
+		assert.strictEqual(result.values?.[0].isLogStatus, undefined)
+		assert.strictEqual(result.values?.[0].isTimeChange, undefined)
+		assert.ok(result.values?.[0].status)
+
+		// Second record: time-change with value 0.075 (seconds delta)
+		assert.equal(result.values?.[1].isTimeChange, true)
+		assert.strictEqual(result.values?.[1].isLogStatus, undefined)
+		assert.ok(
+			Math.abs((result.values?.[1].value as number) - 0.075) < 0.001,
+		)
+		assert.strictEqual(result.values?.[1].status, undefined)
+
+		// Third record: normal with value 99.9 and status flags
+		assert.ok(Math.abs((result.values?.[2].value as number) - 99.9) < 0.01)
+		assert.strictEqual(result.values?.[2].isLogStatus, undefined)
+		assert.strictEqual(result.values?.[2].isTimeChange, undefined)
+		assert.ok(result.values?.[2].status)
+	})
+
 	test('should slice fallback rangeBuffer correctly with non-zero offset', () => {
 		const ackBuffer = utils.getBuffer()
 		ReadRange.encodeAcknowledge(

From a648adef3b15d7659086d7127c88012e4297b552 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 30 Mar 2026 12:16:11 +0000
Subject: [PATCH 9/9] fix: use UNSIGNED_INTEGER for log-datum tag 4 per ASHRAE
 135

Agent-Logs-Url: https://github.com/bacnet-js/client/sessions/e153eab8-5232-426b-92f5-4cecd29c35b7

Co-authored-by: robertsLando <11502495+robertsLando@users.noreply.github.com>
---
 src/lib/asn1.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/lib/asn1.ts b/src/lib/asn1.ts
index c89dfa10..dff33e99 100644
--- a/src/lib/asn1.ts
+++ b/src/lib/asn1.ts
@@ -2536,7 +2536,7 @@ export const decodeRange = (
 				buffer,
 				offset + len,
 				maxOffset,
-				ApplicationTag.ENUMERATED,
+				ApplicationTag.UNSIGNED_INTEGER,
 				tag.value,
 			)
 		} else if (tag.tagNumber === 9) {