EC-003: Engine-family check protocol

Paired WP: WP-005 Purpose: Procedural checklist for diffing Case File #1 and Case File #2 disc contents against Showdown, producing a binary engine-compatibility verdict per disc.

The trap this checklist exists to prevent: hand-waving “looks similar” verdicts. Compatibility is a structural question with a structural answer. If the answer comes back as “INDETERMINATE,” that’s a real verdict — record it; don’t fudge it to COMPATIBLE.

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Pre-flight

• Disc-mount tooling available (Windows native mount, WinCDEmu, or 7z l for direct ISO listing)
• Hex viewer available
• Showdown ISO mounted or extracted to known location; path: ____
• docs/findings/ directory exists (create if missing)

Step 1 — File listings (time-box: 30 min)

For each disc — Showdown (reference), Case File #1, Case File #2:

• Generate a file listing (name + size) of every file on the disc
• Save listings as docs/findings/disc-listing-showdown.txt, disc-listing-case-file-1.txt, disc-listing-case-file-2.txt
• Strip platform metadata noise (Windows thumbs.db, Mac DS_Store, autorun.inf) before diffing

Quick win: if a disc lacks TGIFILE.ART or Scooby.exe entirely, the verdict is immediately INCOMPATIBLE — no further work needed for that disc.

Step 2 — Filename-level diff (time-box: 15 min)

For each Case File disc:

• Compute: files in Showdown ∩ files in Case File (intersection)
• Compute: files in Showdown \ files in Case File (Showdown-only — could indicate missing engine pieces)
• Compute: files in Case File \ files in Showdown (Case-File-only — could indicate new engine pieces)
• Record intersection size and the two “missing” sets in docs/findings/case-file-disc-diff.md

Decision rule for this step:

Outcome	Action
TGIFILE.ART, Scooby.exe, object.ini all present in Case File	Continue to Step 3
Any of the three is absent	Verdict for this disc = INCOMPATIBLE; skip Step 3; document
All three present + intersection ≥ 80% of Showdown’s file count	High confidence in compatibility; continue to Step 3
All three present + intersection < 50%	Likely INCOMPATIBLE despite filename match; Step 3 will confirm

Step 3 — Structural spot-check (time-box: 1 hour total, ~20 min per disc)

For each Case File disc, hex-inspect the first 64 bytes of:

• TGIFILE.ART — compare against Showdown’s known opener:
  • First 4 bytes: should be 45 00 00 00 (69, little-endian) if same group count
  • Bytes 4–7 should look like a 4-byte value in the same range as Showdown’s group descriptors (0x34328117–0x44C440B9)
• Scooby.exe — compare PE header characteristics:
  • DOS stub identical?
  • PE signature offset identical?
  • Timestamp (different is expected — different build date)
  • Section count identical?
• object.ini — compare structurally (not byte-for-byte; content will differ):
  • First non-blank line: section header in [Name] format?
  • Same section names appearing (e.g. [Rooms], [Objects], [Cursors])?

Record each comparison as a row in docs/findings/case-file-disc-diff.md.

Step 4 — Verdict (time-box: 15 min)

For each of Case File #1 and Case File #2, produce one of three verdicts:

Verdict	Criteria
COMPATIBLE	All three files present; TGIFILE.ART opener matches Showdown’s structure; Scooby.exe PE structure consistent; object.ini uses same section naming
INCOMPATIBLE	Any of the three target files missing, OR TGIFILE.ART opener structurally divergent (different magic, different group descriptor range, clearly different format)
INDETERMINATE	Filenames match but structures disagree in ways that don’t cleanly resolve (e.g. TGIFILE.ART opener has same shape but different sized group descriptor table). Requires Ghidra session (extension of WP-001) on Case File Scooby.exe to settle.

Do not pick COMPATIBLE if the data is INDETERMINATE. The vision’s Phase 5 scope rule treats COMPATIBLE as a green light to ship those titles in the upstream PR — false COMPATIBLE = bad PR.

Step 5 — Document and propagate (time-box: 30 min)

• Final verdict per disc recorded in docs/findings/case-file-disc-diff.md
• docs/formats/tgifile-art.md → Findings → “Cross-title verification” populated with the comparison
• docs/01-VISION.md → Phase 5 scope rule updated:
  • If both COMPATIBLE: extend the “Extended” tier to include Case Files explicitly
  • If both INCOMPATIBLE: move Case Files to “Excluded” tier; PR scope is TerraGlyph trio only
  • If mixed: split — name which Case File goes where
  • If any INDETERMINATE: leave under “Conditional” with a note that WP-001 extension is the resolver
• WP-005 status updated to ✅ Done in WORK_INDEX.md

Definition of done

• docs/findings/case-file-disc-diff.md exists with binary verdicts for Case Files #1 and #2
• Vision doc Phase 5 scope rule reflects the verdicts
• WP-005 exit criteria #1–#5 satisfied