Patch Language Spec v1.3 — RepoPatch Docs

Top-Level Structure

A valid patchset document has exactly this shape:

PATCHSET PATCH path/to/file.py ... operation blocks ... ENDPATCH PATCH path/to/another_file.py ... operations ... ENDPATCH ENDPATCHSET

The file path on the PATCH line is the authoritative target — relative to the workspace root.
A PATCHSET may contain one or more PATCH blocks.
PATCH blocks are never nested.
Comments (# …) are only allowed as standalone lines outside PATCH blocks.
Inside any PATCH block, comment lines are forbidden — no exceptions.

Content Prefixes & Separator

Every content line inside an operation carries one of two prefixes. The prefix is determined solely by which block the line belongs to — not by whether the line is blank or non-blank.

OLD / ANCHOR block prefix: - (dash space) - def process_data(items): - return items - (blank old line → exactly "- ")

NEW / INSERT block prefix: . (dot space) . def process_data(items, validate=True): . return items . (blank new line → exactly ". ")

The separator between an old block and a new block must be exactly:

---

Blank Line Rule — Critical

A blank line in an old/anchor block → write as - (dash-space, nothing after). Never use . .
A blank line in a new/insert block → write as . (dot-space, nothing after). Never use - .
This rule applies in every operation — INSERT BEFORE, INSERT AFTER, DELETE, REPLACE, CREATEFILE — without exception.

Anchor Model & Uniqueness

v1.3 is anchor-first. An anchor block is a contiguous block of one or more - lines. The executor finds exactly one acceptable match for each anchor in the target file.

If an anchor block has zero matches, the operation fails — nothing is written.
If an anchor block matches more than once, the executor refuses to guess and the operation fails.
Authors should include enough surrounding old lines in anchors to make matches unique.
Line numbers are not part of Patch Language v1.3. The content itself is the locator.

Operations

INSERT BEFORE Insert

Adds new lines immediately before a matched anchor block.

INSERT BEFORE - anchor line 1 - anchor line 2 --- . new line 1 . new line 2

The executor locates a unique match for the anchor block.
New lines are inserted immediately before the first line of the matched anchor.
One or more . lines are required.

INSERT AFTER Insert

Adds new lines immediately after a matched anchor block.

INSERT AFTER - anchor line 1 - anchor line 2 --- . new line 1 . new line 2

New lines are inserted immediately after the last line of the matched anchor.
One or more . lines are required.

DELETE Remove

Removes an explicit old-content block from the file.

DELETE - old line 1 - old line 2 - old line 3

The - block is both the anchor and the deletion target.
On success, the matched lines are removed from the file.
No separator (---) or new block is used — DELETE has no new content.

REPLACE Swap

Swaps an explicit old block for a new block at the same logical location.

REPLACE - def foo(): - - pass --- . def foo(): . . return 42

In the example above, the second - line and the second . line each represent a blank line in the file.

The - block is the old-state anchor; the . block replaces it.
At least one line is required in each block.
One-line edits must use a sufficiently unique old block; if a single-line old block is not unique, include surrounding lines until it is.

CREATEFILE New File

Creates a brand-new file. The target file must not already exist in the workspace.

PATCH src/new_module.py CREATEFILE . """New module.""" . . MAX_RETRIES = 3 . TIMEOUT = 30 ENDPATCH

The authoritative file path is the one on the PATCH line.
One or more . lines are required — they form the full file content.
No separator or old block is used — CREATEFILE has no anchor.

DELETEFILE Delete File

Removes an entire file from the workspace. The target file must exist.

PATCH src/obsolete.py DELETEFILE ENDPATCH

DELETEFILE has no content block — no - or . lines.
The entire file is removed on Apply.

Executor Behaviour

For each operation the executor must:

Verify that every anchor or old block resolves to exactly one acceptable location.
If an anchor resolves to zero locations — fail.
If an anchor resolves to multiple plausible locations — refuse to guess.
In non-interactive execution, ambiguity is a hard failure.
In interactive execution, the executor may present candidate matches and require explicit user choice before proceeding.

Hard Limits

These rules are never violated, regardless of how a request is framed:

⛔ Must Never Do

Output git diff, unified diff, or context diff.
Output comments inside any PATCH block.
Include code fences or markdown formatting inside the PATCHSET body.
Omit required anchor or old blocks for INSERT, DELETE, or REPLACE.
Use line numbers as patch semantics.
Guess when an old block is ambiguous.
Renumber or rewrite the target file outside the requested operations.
Use . as the prefix for any line in an old or anchor block.
Use - as the prefix for any line in a new or insert block.

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