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Agent skill

Sync Syntax

by mimir in mimir/mimir

Propagate a change to Mim's surface syntax from the lexer/parser to the six downstream consumers - docs/langref.md, lit/docs/tutorial.mim, docs/mim.js, the vim-mim plugin, the tree-sitter-mim…

MITAuto-check passed

Install Sync Syntax

skills CLI
$ npx skills add mimir/mimir --skill sync-syntax -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install mimir/mimir sync-syntax --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/mimir/mimir.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/sync-syntax .claude/skills/sync-syntax && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
sync-syntax
GitHub stars
148
Token cost
~3.2k tokens
SKILL.md length
1,469 words
Files
2
Skills in repo
1
Repo updated
First seen
Licence
MIT

At a glance

Propagate a change to Mim's surface syntax from the lexer/parser to the six downstream consumers - docs/langref.md, lit/docs/tutorial.mim, docs/mim.js, the vim-mim plugin, the tree-sitter-mim…

  • Works in 5 steps: run the checker → what a change touches → the targets → …
  • SKILL.md covers Ground truth, Step 1: run the checker, Step 2: what a change touches and Step 3: the targets, plus 2 more sections
  • Runs Shell scripts from its folder; calls git, cmake and npm; reaches github.com; needs MIM_KEY

What it does

Sync Syntax is an agent skill from mimir/mimir. Propagate a change to Mim's surface syntax from the lexer/parser to the six downstream consumers - docs/langref.md, lit/docs/tutorial.mim, docs/mim.js, the vim-mim plugin, the tree-sitter-mim grammar, and the tree-sitter-mim-vscode extension. Use after touching include/mim/ast/{tok,lexer,parser}.h or src/mim/ast/{lexer,parser}.cpp or src/mim/ast/family.h, and whenever asked to check or re-sync those targets.

Its SKILL.md is about 3.2k tokens, which your agent loads only when the skill is triggered. The skill folder holds 1 other file (for example `check.sh`).

It works with Visual Studio Code and C++. The repository describes itself as: MimIR is my Intermediate Representation. The licence is MIT.

Example prompts

  • “/sync-syntax”

Requirements

  • Node.js
  • A Bash shell
  • A credential in MIM_KEY

Workflow steps

5 steps, taken from the step headings in SKILL.md.

  1. run the checker
  2. what a change touches
  3. the targets
  4. verify
  5. hand off

What it can do on your machine

Read from SKILL.md and the folder at commit 6f033e5. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships script files (Shell), which the agent can run.

    Shell commands in SKILL.md call:

    • git
    • cmake
    • npm
    • npx

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Hosts in commands or code, which the agent is likely to contact:

    • github.com

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names these keys or tokens, usually read from environment variables:

    • MIM_KEY

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Sync Syntax loads about 3.2k tokens when it runs. Until then it costs about 106 tokens; SKILL.md has 1,469 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~106
When it runs · the whole SKILL.md, loaded when a task matches
~3.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from mimir/mimir at commit 6f033e5, republished under its MIT licence (© mimir). 1,469 words, ~3,212 tokens.

Download SKILL.mdSave it as .claude/skills/sync-syntax/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
sync-syntax
description
Propagate a change to Mim's surface syntax from the lexer/parser to the six downstream consumers - docs/langref.md, lit/docs/tutorial.mim, docs/mim.js, the vim-mim plugin, the tree-sitter-mim grammar, and the tree-sitter-mim-vscode extension. Use after touching include/mim/ast/{tok,lexer,parser}.h or src/mim/ast/{lexer,parser}.cpp or src/mim/ast/family.h, and whenever asked to check or re-sync those targets.

sync-syntax

The lexer and the parser define Mim's surface syntax; six other places merely describe it and silently rot when they are not updated in the same breath.

Ground truth

FileWhat it settles
include/mim/ast/tok.hMIM_KEY (keywords), MIM_SUBST (lm/bot/top), MIM_TOK (every punctuation spelling), MIM_INFIX_SUGAR/MIM_INFIX_CORE, MIM_PREC (the precedence ladder and its associativity)
src/mim/ast/lexer.cppwhich byte sequence yields which tag (lex), the literal grammar (lex_lit, lex_digits, lex_exp), escapes (lex_char, unquote), comments and /// Markdown
src/mim/ast/parser.cppthe productions and the Prec bound each parse_expr/parse_ptrn passes
src/mim/ast/family.hwhich tags start which production (C_EXPR, C_DECL, C_LAM, …)

Start from git diff over those files - the diff, not the current state, is what tells you which of the six targets are in play.

Step 1: run the checker

sh
.claude/skills/sync-syntax/check.sh

It diffs the keyword and terminal tables of tok.h against the four targets that carry a flat word list and reports what is missing (in tok.h, not in the target) or stale (the other way round). It has nothing to say about lit/docs/tutorial.mim, and it only sees flat word lists - a new production, a changed precedence, or a new literal form passes it silently too. All of that needs the manual pass below. It also flags capture names that language-configs.json of the vscode extension maps but tree-sitter-mim/queries/highlights.scm no longer emits. VIM_MIM, TS_MIM, and VSC_MIM override the sibling checkouts (../vim-mim, ../tree-sitter-mim, ../tree-sitter-mim-vscode).

Step 2: what a change touches

Changelangreftutorialmim.jsvim-mimtree-sitter-mimvscode
keyword added/removed/renamed✓✓✓✓✓✓
new punctuation token or Unicode spelling✓✓✓✓✓✓
literal syntax✓✓✓✓✓✓
new/changed production✓✓--✓✓
comment syntax✓✓✓✓✓✓
precedence or associativity✓---✓✓
error message or diagnostic only------

The vscode column only means bump the submodule: the extension ships tree-sitter-mim verbatim, so anything that reaches the grammar reaches it. Its own files change only for brackets, comment markers, and renamed captures.

A construct that was removed or renamed reaches the tutorial no matter which row it sits in: the file is a lit test, so a stale line breaks the build rather than going unnoticed.

Step 3: the targets

docs/langref.md

The normative reference; the other four follow it, so do this one first.

  • Primary Terminals and Secondary Terminals mirror MIM_TOK and MIM_SUBST.
  • Keywords mirrors MIM_KEY; the predefined-alias table below it mirrors what bind.cpp expands.
  • Lexical Terminals is the EBNF for I, L, X_n, C, S and the bin/dec/id/op/esc shorthands - keep it matching lex_lit/lex_char literally. A new lexical terminal name also goes into LEXICAL in docs/ebnf.js, or it renders as a nonterminal.
  • The Grammar sections carry one EBNF block per construct plus a bullet per rule; a new production needs both.
  • The Precedence table mirrors MIM_PREC top to bottom, including which levels are pseudo levels.
  • Normalizations only changes when a normalizer does.
lit/docs/tutorial.mim

The tour: every construct langref defines must show up here, in a section following langref's own order. It is a lit test, not prose - each claim is a static refly assertion, so the file compiling at all is what tests it - and mim --output-md renders it into the docs as the Tutorial page, which is also the playground's landing example, so it is the first Mim anyone reads.

  • A /// line becomes Markdown prose and interrupts the surrounding mim code fence; a // comment stays inside it. So a section heading (/// ## …) and the sentence introducing a construct are ///, while a remark on a single line of code is a trailing //.
  • Show the new construct where it belongs, with a one-line // comment saying what it demonstrates. Match the surrounding density: one or two lines per construct, not a paragraph.
  • Assert wherever there is something to assert. refly.struc.e (a, b) states that two terms are the same node; where two types coincide, a lam whose parameter type and return type differ is the assertion - as in sigma_is_array, erased, and fuse. A construct with nothing to compare against just has to typecheck.
  • Both RUN lines matter: the second is %mim -p ll %s, so new code must also survive the ll backend. They live in an HTML comment at the top, so the docs page doesn't show them. Keep anything the backend chokes on - a runtime-size pack, say - out of an extern the emitter reaches.
  • Renaming or removing a construct breaks this file; fix it here rather than deleting the line, or the tour loses a section.
docs/mim.js

The highlighter for mim-fenced blocks in the docs and for the playground - web/CMakeLists.txt stages this very file as mim-code.js, so there is nothing separate to update under web/.

  • WORDS is probed in order and the set's name becomes the token kind, so put a new word in the right one: keyword, decl (that is C_DECL plus the parse_modifiers modifiers), type, literal, special.
  • TOKEN is a sticky alternation whose capture i yields KINDS[i]; a new Unicode operator joins the [«»‹›→←Π∀] class and a new word-like character the identifier class.
  • CLASS maps a kind to a Doxygen CSS class; a kind with no entry is left unhighlighted.
  • The machinery lives in docs/code.js - read it before adding a kind.
../vim-mim
  • syntax/mim.vim: the syn keyword lines, mimType/mimConstant for the Unicode spellings, the mimNumber/mimFloat/mimIndex patterns, and mimOperator/mimDelimiter. Multi-character operators must stay after the single-character ones (later item wins at equal position) and mimComment must stay before the / operator.
  • ftplugin/mim.vim: a token that has only a Unicode spelling needs an iabbrev and a matching iunabbrev in b:undo_ftplugin.
  • README.md: the abbreviation table, and the sentence listing which symbols have ASCII spellings.
Show full SKILL.md (582 more words)Show less
../tree-sitter-mim

Read ../tree-sitter-mim/CLAUDE.md first - it is the authority for that repo and explains the PREC mirror, the pattern/telescope split, and why */+/- are handled structurally.

  • grammar.js is the only hand-written grammar source; src/ is generated and committed, so tree-sitter generate is part of the change.
  • queries/highlights.scm (plus injections.scm, folds.scm) are the Neovim queries; renaming a grammar node breaks them and the external Helix ones.
  • The corpus under test/corpus/ is small - the real regression suite is this repo's .mim files.
../tree-sitter-mim-vscode

A fork of AlecGhost/tree-sitter-vscode that bundles two grammars as submodules and builds them to WASM with generate_wasm.sh; src/extension.ts is upstream's generic tree-sitter host. A sync is four jobs, in this order:

  1. Own repo. git pull --ff-only from origin (mimir/tree-sitter-mim-vscode) first, so nothing below lands on a stale base.
  2. Upstream. Add the remote once (git remote add upstream https://github.com/AlecGhost/tree-sitter-vscode.git), then git fetch upstream && git merge upstream/master. Conflicts concentrate in package.json (name, publisher, version, repository, the tree-sitter-mim-vscode.* configuration keys) and README.md: keep ours for identity, take theirs for dependencies, scripts, and engines. Upstream's tree-sitter-vscode.* setting and command ids must stay renamed to tree-sitter-mim-vscode.* in both package.json and src/extension.ts. Beyond the renames, src/extension.ts carries four Mim additions to re-apply when upstream rewrites the file: the bundled language-configs.json with its ${extension_dir} placeholder and per-language user overrides, last-match-wins among equal-range tokens, sorting tokens before splitToken, and the #lua-match? translation. package.json also keeps our languages contribution and runs ./generate_wasm.sh in its package script. A new upstream config key (e.g. a query file like folds) is only live once language-configs.json passes it for mim, and the .scm file is copied by generate_wasm.sh.
  3. tree-sitter-mim submodule. It must point at mimir/tree-sitter-mim, not the old fodinabor/tree-sitter-mim fork (whose history is unrelated): git submodule set-url tree-sitter-mim https://github.com/mimir/tree-sitter-mim, git submodule sync, then check out the commit the sibling ../tree-sitter-mim was just synced to. Then reconcile what the extension layers over the grammar:
    • language-configs.json: every semanticTokenTypeMappings key of the mim entry must be a capture queries/highlights.scm emits - check.sh lists the ones that are not; an unmapped capture falls back to VS Code's defaults, a stale key is dead.
    • mim-language-configuration.json: brackets/autoClosingPairs/surroundingPairs mirror the D_* delimiters of tok.h (<, >, <<, >> are operators, not brackets); comments mirrors the lexer's comment forms.
  4. tree-sitter-markdown submodule. Move it to the newest release tag of tree-sitter-grammars/tree-sitter-markdown (git -C tree-sitter-markdown fetch --tags, check out the highest v*); it only renders /// doc comments via queries/mim/injections.scm, so rename checks there are all it needs. The markdown/markdown-inline mappings in language-configs.json follow its queries/highlights.scm the same way.

Step 4: verify

sh
cmake --build build -j16                     # tok.h/lexer/parser still compile
cmake --build build --target mim_lit_tests   # re-stage lit before running it
cmake --build build --target lit             # tutorial.mim asserts the whole tour
cd lit && ../scripts/probe.sh tutorial.mim   # … or just that one, while iterating on it
cmake --build build --target docs            # langref + mim.js land in the doxygen site
.claude/skills/sync-syntax/check.sh          # tables agree again
sh
cd ../tree-sitter-mim
tree-sitter generate && tree-sitter test
tree-sitter parse -q $(find ../mimir/lit ../mimir/src/mim/plug -name '*.mim')
# expected: only lit/error/{insert_no_index,missing_name,path_member,
#           unanchored_delim,unterminated_string,where_semicolon}.mim report an ERROR
sh
cd ../tree-sitter-mim-vscode
npm install && npm run build       # tsc + webpack + prettier + eslint; `prebuild` stages web-tree-sitter.wasm into dist/
npx vsce package --no-dependencies # prepublish reruns the build and generate_wasm.sh (both grammars at ABI 15)
git -C tree-sitter-mim checkout -- .   # generate_wasm.sh leaves the submodule dirty

src/extension.ts rewrites Neovim's #lua-match?/#not-lua-match? into #match? before compiling highlights.scm; web-tree-sitter silently ignores unknown predicates, which would turn every identifier into @type and @constant. A new Lua character class in a query needs an entry in LUA_CLASSES there. Headless check without VS Code: load node_modules/web-tree-sitter/web-tree-sitter.cjs in node, parse the .mim files, run the translated query, and look at which capture wins per node.

Install the .vsix (code --install-extension …) and open lit/docs/tutorial.mim: keywords, literals, parameters, and the Markdown inside /// must all be coloured.

For vim-mim there is no test suite: open a .mim file and check with :syn list / :Inspect, or eyeball lit/docs/tutorial.mim.

Step 5: hand off

Four repos are involved, so this is up to four commits; in the vscode repo, keep the upstream merge a commit of its own, separate from the submodule bumps. Do not commit or push - report per repo what changed and what remains, and let Roland commit. Say explicitly if a target was left alone because the change did not reach it.

© mimir, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file in .claude/skills/sync-syntax of mimir/mimir.

  • SKILL.md
  • check.sh

Open the folder on GitHubat commit 6f033e5

Compare with similar skills

Sync Syntax next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

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Works with

Questions about Sync Syntax

What does Sync Syntax do?

Propagate a change to Mim's surface syntax from the lexer/parser to the six downstream consumers - docs/langref.md, lit/docs/tutorial.mim, docs/mim.js, the vim-mim plugin, the tree-sitter-mim…. Sync Syntax is an agent skill from mimir/mimir.js, the vim-mim plugin, the tree-sitter-mim grammar, and the tree-sitter-mim-vscode extension.

How do I install Sync Syntax in Claude Code?

Run `npx skills add mimir/mimir --skill sync-syntax -a claude-code`. Or copy the skill folder (.claude/skills/sync-syntax in mimir/mimir) into .claude/skills/sync-syntax in your project. Claude Code loads it when a task matches its description.

How do I install Sync Syntax in Codex?

Run `npx skills add mimir/mimir --skill sync-syntax -a codex`. Or copy the skill folder (.claude/skills/sync-syntax in mimir/mimir) into .agents/skills/sync-syntax in your project. Codex loads it when a task matches its description.

Can I use Sync Syntax in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add mimir/mimir --skill sync-syntax -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/sync-syntax, .gemini/skills/sync-syntax, .github/skills/sync-syntax and .opencode/skills/sync-syntax in your project.

What does Sync Syntax need to run?

Going by SKILL.md and its folder, Sync Syntax needs a shell for the scripts in its folder, the command-line tools its instructions call (git, cmake, npm and npx) and credentials named MIM_KEY. Our summary lists: Node.js; A Bash shell; A credential in MIM_KEY.

Does Sync Syntax access the network?

SKILL.md names 1 domain. In commands or code: github.com; the agent is likely to contact it when it follows the instructions. This is read from the text; nothing was executed.

Is Sync Syntax safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Sync Syntax use?

Sync Syntax is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Sync Syntax use?

About 3.2k tokens (SKILL.md is roughly 13k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Sync Syntax?

Skills that share tags, products or a category with Sync Syntax: Ray (Railly/tinte, 624 stars), Mspm0g Contest (2262727886-stack/mspm0g-contest-skill, 319 stars), Tilelang Debug Helper (tile-ai/tilelang-ascend, 400 stars) and Flutter Setting Up On Windows (btwld/superdeck, 130 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Sync Syntax?

mimir (a GitHub organization) maintains it in mimir/mimir, which has 148 GitHub stars. The repository was last updated on October 7, 2026.

Source: mimir/mimir on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.