rea/docs/ines-containers.md

Classic iNES container inspection

REA recognizes classic iNES from the NES + 0x1a byte signature, independently of the file extension. This read-only container inspection uses portable Node.js file reads; it needs neither Ghidra nor an emulator.

rea inspect-artifact ./cartridge.nes --json
rea extract-artifact ./cartridge.nes --json

Through MCP, call open_binary with the local path, then inspect_artifact. Use extract_artifact to materialize the regions in the fresh directory named by its result. The caller owns that successful extraction directory.

Header and file regions

Inspection returns container-header and reconstruction observations inline. The single inventory Evidence under substeps[].evidence.normalized_result contains the complete graph and an ines object:

• ines.header: original 16-byte header_hex, PRG/CHR file-unit counts, mapper, raw flags 6/7, trainer and battery flags, and the declared mirroring mode.
• occurrences[]: each region's path, source_location.offset and source_location.length in the original container. Follow artifact_id to the node's observed SHA-256 and byte count.
• ines.reconstruction: ordered region paths, concatenated byte count, SHA-256 and verified: true. REA streams the actual region bytes in physical order and compares their concatenation with the original whole-file digest. No reconstructed file is written during inspection.

Regions are header.bin, optional trainer.bin (512 bytes), prg/000.bin onward (16 KiB each), chr/000.bin onward (8 KiB each), and optional trailing.bin. Every input byte is retained, including unused header fields and uninterpreted trailing data. Zero CHR-ROM units create no CHR region; REA does not fabricate CHR-RAM contents.

After extraction, concatenate the materialized files in ines.reconstruction.region_order from the inspection inventory. Their bytes reproduce the input exactly. Graph path order is lexical and is not physical file order; use the explicit region order or source offsets.

Supported boundary

This increment supports classic iNES with a complete 16-byte header, nonzero PRG count, complete declared trainer/PRG/CHR payload, and zero reserved bytes 12–15. Dirty legacy headers are refused because their upper mapper bits are ambiguous; REA does not silently repair them. NES 2.0 and UNIF signatures, unsupported header variants and truncated payloads are explicitly refused. An arbitrary file named .nes is not admitted as iNES.

The PRG/CHR units describe file storage, not mapper bank sizes or CPU windows. The mapper number and flags are header declarations, not proof of cartridge hardware or runtime behavior. Bank switching, 6502/65816 disassembly, emulator sessions and interpretation of console-specific trailing data remain outside this lane. Raw-binary Ghidra analysis is a separate workflow.

Source-owned byte fixtures verify original offsets and hashes, extraction and byte-exact reconstruction, CLI/stdio MCP parity, malformed/unsupported inputs, failed target-switch recovery, cancellation and source identity. These checks do not establish emulator behavior or compatibility with every historical ROM. The workflow has been executed on native Windows x64; Linux and macOS execution remain unverified for this increment.

Format references: iNES and NES 2.0.