Docs

• The x12-tidy Method
  The one idea the other notes hang off — earn the four delimiters from structure first, and then everything downstream is ordinary parsing plus repair. Read this first.
  ~1,100 words  ·  Markdown  ·  PDF
• Finding the Elusive ISA Line
  Locating the ISA line in a file that strips it, prepends to it and re-encodes it — why fixed byte offsets and a regex both fail, and the five techniques that replace them.
  ~2,400 words  ·  Markdown  ·  PDF
• Those Pesky Delimiters
  Reading the four X12 delimiters — element, repetition, component, terminator — out of that run when every byte offset the standard uses has moved.
  ~1,900 words  ·  Markdown  ·  PDF
• Reconstructing the ISA Line
  Once the delimiters are trusted, rebuilding the canonical 105-byte line — and why that is a total function: non-fatal in, one canonical line out, everything else a named fatal.
  ~1,500 words  ·  Markdown  ·  PDF
• Reassembling the Interchange
  Turning a reconstructed ISA line and a pile of raw segments into one cleansed payload — split into segments, empties dropped, rejoined on the sender's own terminator — and why doing the location work twice is free.
  ~1,400 words  ·  Markdown
• Auditing the Envelope
  Once a payload exists, checking whether the interchange's own bookkeeping is honest — envelope pairing, counts, control-number agreement, identifier shape, version agreement — and why “fatal” stops meaning stop.
  ~1,400 words  ·  Markdown

More as the build moves forward — multiple interchanges in one file, the recovery path.