# GTR016 — Inline deprecated interpreter= (runtime-gated)

**Contract:** behaviour-preserving (provable subset).
## Claim
`<command interpreter="I">S rest</command>` →
`<command>I '$__tool_directory__/S' rest</command>` reproduces legacy runtime
behaviour for **any non-empty** interpreter value when `S` is a literal leading
script token.

## Proof — verbatim interpolation in every composition form Galaxy ever shipped
- Prepend form: `command_line = interpreter + " " + command_line` after an
  unquoted abspath replace — **byte-identical** `release_16.04`
  (`evaluation.py:478-484`) through `release_20.01` (`:509-514`).
- Token-splice form:
  `replace(executable, f"{interpreter} {shlex.quote(abs_executable)}", 1)` —
  `release_20.09` (`:501`) through `dev:781-787` **today** (still honored for
  `legacy_defaults` tools; the attribute was never removed).
- The forms coincide exactly when the script is the rendered line's first
  content token — the bucket-A gate. Every form gates on `if interpreter:`,
  so an empty attribute was always ignored (the codemod bails).
- Positional splice anchored past leading `##` comments; mixed-content
  `<command>` skipped (the audited break classes).

## Scope boundary
Cheetah-leading commands (`split()[0]` of the *rendered* line is statically
unknowable) and `interpreter=""`. The `shlex.quote`-vs-literal-quote bound is
accepted and documented (admin-controlled install paths).

## History
Single-token-standard-interpreter conservatism removed by §39 (the
verbatim-composition proof); bucket C dissolved (25 → A, 26 → B).