Tes5Mod:Mod File Format/PACK

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PACK records describe AI packages, which are used to control the behavior and activities of NPCs.

PACK records use a moderately complex structure, with various fields that occur multiple times and have different meanings depending upon where they occur within the overall structure. The records also seem to generally contain a large amount of unnecessary and/or obsolete content -- deleted activities never seem to actually be deleted from the game data; some sections are required even though they are entirely empty in 99.9% of the PACK records. As a result, a large fraction of the data in a given PACK record may not be visible in the CK editor.


These fields are always found at the start of the PACK record.

C SubRecord Name Type/Size Info
+ EDID editorId zstring Editor id
- VMAD script info VMAD script info
* CTDA conditions struct[32] Conditions controlling when the package can be active. CTDA fields can also be found in the Procedure Tree section of the record, in which case the conditions are specific to that branch of the procedure tree.
Variable name? zstring Auxiliary data for CTDA.
Variable name? zstring Auxiliary data for CTDA.
- IDLC Idle Count uint8 Number of formids found in subsequent IDLA field
- IDLA Idle formid[IDLC] 1 or more IDLE formids
- IDLF Idle Flags uint8 Flags:
0x01: If set: Run In Sequence. If not set: Random
0x04: Do Once
0x08: Unknown
- IDLT Idle Time float
- QNAM Owner Quest formid QNAM can only appear once in the header section. However, it can also appear in the Begin/End/Change section, with a different format and meaning.
+ PKCU PKCU field struct[12]
ulong Unknown, possibly flags. Values range from 1 to 34.
Package Template
formid Formid for another PACK record that is used as a template. This value can only be provided in records that are identified with Package Type "Package", and only templates with type "Package Template" are valid entries.
ulong Unknown, possibly flags. Values range from 0 to 29.
+ PKDT Package Flags struct[12]
Misc Flags
uint32 Only flags that have a visible effect in the CK are listed here. Many other flags may be set in the game data, but they are probably hold-overs from Oblivion that were phased out during development.
0x04 = Must Complete
0x08 = Maintain Speed at Goal
0x40 = At Package Start Unlock Doors
0x80 = On Package Change Unlock Doors
0x400 = Once Per Day
0x2000 = Preferred Speed (although choice of Walk/Fast Walk/Jog/Run is stored separately, see below)
0x20000 = Always Sneak
0x40000 = Allow Swimming
0x100000 = Ignore Combat
0x200000 = Weapons Unequipped
0x800000 = Weapon Drawn
0x8000000 = No Combat Alert
0x20000000 = Wear Sleep Outfit
Package Type
uint8 Only the first bit is relevant:
0x01 = Package Template (if not set, type is "Package")

0x12 is always set.

Interrupt Override
uint8 Only observed values are 0 (None) and 4 (Combat)
Preferred Speed
uint8 This value is only relevant if the Preferred Speed Misc Flag is set (0x2000 above)
0 = Walk
1 = Jog
2 = Run
3 = Fast Walk
uint8 Possibly padding
Interrupt Flags
0x01 = Hellos to player
0x02 = Random conversations
0x04 = Observe combat behavior
0x08 = Greet corpse behavior
0x10 = Reaction to player actions
0x20 = Friendly fire comments
0x40 = Aggro Radius Behavior
0x80 = Allow Idle Chatter
0x200 = World Interactions

The remainder of the bits (0xFC00) can also be set, but they appear to be "extra" interrupt flags: the "Set all interrupt flags" sets the flags to 0xFFFF, and "Clear all interrupt flags" sets them to 0x0000, but the higher bits do not correspond to any displayed flags in the CK editor.

+ PSDT Schedule struct[12] Information on when package is allowed to be active
byte Any=-1 (only value currently being used in Skyrim)
Day of week
byte Day of week
7=Weekdays: MTMTF
8=Weekends: Loredas, Sundas
9=Morndas, Middas, Fredas
10=Tirdas, Turdas
byte Date (day of month); Any=0
byte Start hour (0-23); Any=-1
byte Start minutes (0-59); Any=-1
byte[3] Probably unused padding (although values are typically not zero)
uint32 Duration in minutes, although the value is displayed in the CK using decimal hours

Public Package Data[edit]

The section providing the public package data is located after the fields listed for the header, and extends until an XNAM field is encountered. It provides a list of activities and parameters controlling those activities, all of which are listed in the "Public Package Data" section of the CK edit interface.

The section is made up of a series of ANAM fields, each of which is followed by various other fields providing the activity parameters corresponding to that ANAM field. Then the section contains a series of UNAM fields, each of which provides the activity name corresponding to one of the previous ANAM fields.

Note that ANAM fields are also found in the Procedure Tree section, if one exists.

C SubRecord Name Type/Size Info
* ANAM Activity Type zstring A string identifying the type of data stored in this activity entry. Each ANAM field is followed by one field that provides data with the given type. Possible values in this section, and the associated field, are:
  • Bool: CNAM field, CNAM type=uint8
  • Float: CNAM field, CNAM type=float
  • Int: CNAM field, CNAM type=int32
  • Location: PLDT field
  • ObjectList: CNAM field, CNAM type=float
  • SingleRef: PTDA field
  • TargetSelector: PTDA field
  • Topic: PDTO field or TPIC field (only one instance of a TPIC field)

One and only one of the following fields is found after each ANAM field. (Other values for ANAM are only found in the Procedure Tree section of the record.)

Numeric Value variable CNAM is 1-4 bytes in size, and the type of data in CNAM depends upon the previous ANAM field; see above.
Topic Value struct[8] Note that PDTO fields can also occur in the Begin/End/Change section
0 = Dialogue
1 = Topic Subtype
Topic Value
formid/char[4] Formid for a DIAL record when type=0; 4-character string for type=1 (e.g. "HELO" for "Hello" subtype)
Location Value struct[12]
0=Near reference, Location=formid
1=In cell, Location=formid
2=Near package start location, Location=unused
3=Near editor location, Location=unused
6=Near linked reference, Location=formid of a KYWD record
8=Alias (reference), Location=uint32 providing an AliasID
9=Alias (location), Location=formid
12=Near Self, Location=unused
variable Location; always 4 bytes in length, but format depends upon Type as listed above. If Location is unused, then value is empty.
long Radius
Target Value struct[12]
0=Specific reference, Target=formid
1=Object ID, Target=formid
2=Object Type, Target=uint32
3=Linked Reference, Target=formid
4=Ref Alias, Target=uint32 providing an AliasID
6=Self, Target=unused
formid/long Target; always 4 bytes in length, but format depends upon Type as listed above. If Location is unused, then value is empty.

For Object Type, number appears to be a lookup value. Known values are:

11 = Weapons: Any
long Count (0 in all Skyrim records)
Unknown formid DIAL record
* UNAM Activity ID uint8 Each UNAM field provides a numerical ID; that ID can be looked up in the Package Template to determine the Name of the activity as listed in the CK.

Although the UNAM fields are listed after all of the ANAM fields for this section, each UNAM field provides the name for one of the previous ANAM fields. The first UNAM field corresponds to the first ANAM field, etc.

+ XNAM Unknown int8 Number ranging from -77 to 99. There is always one XNAM field in a PACK record, and it is always located at the end of the Public Package Data section.

Procedure Tree[edit]

This section is the first of two sections that are only found in template packages. This section defines the structure of the procedure tree used by this template and all packages based upon this template.

As with the Public Package Data section, this section is also made up of a series of ANAM fields. However, a completely different set of ANAM values appear in this section, and each ANAM section contains multiple fields, all of which are different than those found in Public Package Data.

This section ends when a UNAM field is found, signaling the start of the Procedure Data section.

C SubRecord Name Type/Size Info
* ANAM Branch Type zstring A string identifying the type of branch data stored in the following section. Possible values found in this section are:
  • Procedure: Basic element of the tree (only non-branch element). All individual activities (PKC2 fields) are contained with Procedures.
  • Random: Top-level branch that can contain multiple Procedures.
  • Sequence: Top-level branch that can contain multiple Procedures.
  • Simultaneous: Top-level branch that can contain multiple Procedures.
  • Stacked: Top-level branch that can contain multiple Procedures.

Each ANAM entry is followed by multiple fields. The count column for the following entries is relative to a given ANAM field -- overall these fields can always occur 0 or many times in a given record.

Condition Count uint32 Number of conditions (CTDA fields) in this branch. Can be 0, in which case there are no CTDA fields.
Conditions struct[32] Conditions controlling when this branch can be active. Note that conditions relevant to the overall package are provided using CTDA fields that appear in the header section.
Unknown struct[8] Appears to be two uint32 values
Procedure Type zstring Note that PNAM fields also appear in the Procedure Data Section, in which case formats other than zstring are possible
Flag uint32 Flag. Only one bit is in use:
0x01=Success Completes Package
Activity ID uint8 The PKC2 fields provide a list of all the activity IDs found in this branch. Note that a given activity ID can occur multiple times within the Procedure Tree Section, in particular if that activity is part of multiple branches.
Unknown struct[16]
Unknown struct[12]

Procedure Data[edit]

This section is also only found in template packages. It provides the name associated with each activity ID. It consists of a series of UNAM fields, each followed by one BNAM field and one PNAM field.

C SubRecord Name Type/Size Info
* UNAM Activity ID uint8 This is the same activity ID provided in both the Public Package Data and Procedure Tree sections. However, many additional activity IDs can also possibly appear; any additional IDs correspond to activities that were deleted from the package and are no longer accessible through the CK edit interface.
Activity Name zstring The activity name as displayed in the CK
Unknown uint32 Probably a flag: only values are 0 or 1. Note that the PNAM fields also appear in the Procedure Tree section, but have a completely different format and meaning.


This section provides the 'On Begin', 'On End', and 'On Change' actions for this package. It is always present at the end of all PACK records (for both standard packages and template packages -- even though the CK editor does not display this section for template packages).

It consists of three marker fields (POBA, POEA, POCA), each of which is always followed by an INAM and a PDTO field. Each marker may also be followed by an old scripting (SCHR) field.

C SubRecord Name Type/Size Info
+ POBA or On Begin 0-size Marks start of 'On Begin' actions
POEA or On End 0-size Marks start of 'On End' actions
POCA On Change 0-size Marks start of 'On Change' actions
+ INAM Idle formid IDLE record. Field is always present but its value is 0 if there is no idle action.
- SCHR Old Script SCHR Old scripting field.
- TNAM Unknown int32 Seen only on a single PACK record ("Say" / 0x0001CB6) - always 0.
+ PDTO Topic struct[8] Field is always present but is entirely 0 if there is no topic. Note that PDTO fields also appear in Public Package Data section; the same structure is probably used in both cases.