[Slush97]

A mod that ships a game .vdata_c (scripts/heroes.vdata_c, scripts/abilities.vdata_c) replaces the whole file in game, so anything Valve added after the mod was built is gone. This adds a check for that.

vpkmerge_core::check_vdata(mod, pak01) decodes each .vdata_c the mod ships and the game's copy as KV3 and diffs the trees. One VdataReport per entry:

• missing: paths the game has and the mod lacks (what the mod deletes), shallowest first so a whole missing hero comes before its fields
• extra: paths only the mod has (the game dropped them)
• changed: leaf values that differ

Arrays count as structure. Equal-length arrays diff by index. When lengths differ, arrays of plain values are matched by value and reported as path[=value], because Valve inserts mid-array (the 2026-09-29 batch added EHeroSpiritLifestealEffectiveness inside every hero's m_vecDisplayStats). Arrays of objects report the tail as path[i].

Status is outdated (any missing or extra), modified (values only), current, not-in-game (compiler leftovers like panorama/image_compiler.vdata_c) or undecodable.

modified is not proof a mod is current: it can't separate the mod's intended edits from values Valve rebalanced since. That needs the build the mod was made against.

VdataChecker checks many mods against one pak: it opens the pak only once a mod actually ships a .vdata_c, and reads and decodes each game file once. check_vdata wraps it for a single mod.

CLI:

vpkmerge vdata-check --base <pak01_dir.vpk> <MOD_dir.vpk>... [--limit N] [--json]

--json prints the full untruncated reports. A mod that fails to open gets an error field and the exit code stays 0, so one bad file never hides the rest of a batch. Text mode exits non-zero if any mod failed to open.

Testing

• 11 unit tests for the tree diff (incl. mid-array insertion, shrunk arrays, object-array tails), plus tests/vdata_check_live.rs against the real pak (gated on DEADLOCK_PAK). Both pass, along with clippy (lib/bins/tests) and fmt.
• Ran it over the 68 mod VPKs in a real install plus a junk VPK: 0.1 s (was 2.5 s before the shared checker), exit 0, the junk file reported per mod. Two mods flagged: an emotes mod whose heroes.vdata_c predates the 2026-09-29 hero batch (104 missing, including Rat King's ability slots and the new lifesteal stat in every hero) and a Plague Doctor Graves skin missing 9 whole heroes.
• Linux CI is red on pre-existing morphic pedantic lints (kv3/patch.rs, reader.rs, rewrap.rs, model/glb.rs), same as main since fix: open VPKs that omit the optional v2 MD5 section #45. Nothing in this PR trips clippy.

Notes

• Grimoire uses this to flag outdated mods on the Installed page (feat(installed): flag mods that ship outdated vdata grimoire#419). It needs a vpkmerge release with this subcommand, then a pin bump in grimoire's scripts/fetch-vpkmerge.mjs.
• This is the core + CLI part of d312f40 on the local mcp-server branch. That commit also wires the check into the MCP inspect_mod tool. That part stays with the MCP server work, since vpkmerge-mcp isn't on main.