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Agent skill

Polylith Migrate Split Component Internals

by DavidVujic in DavidVujic/python-polylith

[Internal sub-skill of polylith-migrate-orchestrator. An agent skill from DavidVujic/python-polylith.

MITAuto-check passed

Install Polylith Migrate Split Component Internals

skills CLI
$ npx skills add DavidVujic/python-polylith --skill polylith-migrate-split-component-internals -a claude-code

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

GitHub CLI
$ gh skill install DavidVujic/python-polylith polylith-migrate-split-component-internals --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/DavidVujic/python-polylith.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/polylith/migrate-project/polylith-migrate-split-component-internals .claude/skills/polylith-migrate-split-component-internals && 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
polylith-migrate-split-component-internals
GitHub stars
553
Token cost
~988 tokens
SKILL.md length
429 words
Files
1
Skills in repo
37
Repo updated
First seen
Licence
MIT

At a glance

[Internal sub-skill of polylith-migrate-orchestrator. An agent skill from DavidVujic/python-polylith.

  • Works in 5 steps: Identify Candidates → Group Definitions by Domain → Create New Modules → …
  • SKILL.md covers Goal, Inputs, Steps and Verify, plus 2 more sections
  • Calls git

What it does

Polylith Migrate Split Component Internals is an agent skill from DavidVujic/python-polylith. [Internal sub-skill of polylith-migrate-orchestrator. Do not load directly — load polylith-migrate-orchestrator first, which drives all phases.] Split monolithic core.py files in shared components into domain-focused modules.

Its SKILL.md is about 990 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: Tooling support for the Polylith Architecture in Python. The licence is MIT.

Example prompts

  • “/polylith-migrate-split-component-internals”

Requirements

  • Python 3

Workflow steps

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

  1. Identify Candidates
  2. Group Definitions by Domain
  3. Create New Modules
  4. Update init.py
  5. Handle core.py

What it can do on your machine

Read from SKILL.md and the folder at commit a7a80f2. 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

    Shell commands in SKILL.md call:

    • git

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

  • Network

    No URLs in SKILL.md. Its commands use git, which can reach the network depending on how they are called.

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

  • Credentials

    Names no API keys, tokens, secrets or passwords.

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

Context cost

Polylith Migrate Split Component Internals loads about 988 tokens when it runs. Until then it costs about 69 tokens; SKILL.md has 429 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~69
When it runs · the whole SKILL.md, loaded when a task matches
~988

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 DavidVujic/python-polylith at commit a7a80f2, republished under its MIT licence (© DavidVujic). 429 words, ~988 tokens.

Download SKILL.mdSave it as .claude/skills/polylith-migrate-split-component-internals/SKILL.md (or your agent's skills folder).
name
polylith-migrate-split-component-internals
description
[Internal sub-skill of `polylith-migrate-orchestrator`. Do not load directly — load `polylith-migrate-orchestrator` first, which drives all phases.] Split monolithic `core.py` files in shared components into domain-focused modules.

Skill: polylith-migrate-split-component-internals

📐 Scope vs sibling skills. This skill operates inside one already-extracted component, splitting its core.py into multiple sibling Python files. No new components are created — only the internal file layout changes. Don't confuse with:

  • polylith-migrate-split-big-component — splits one component into multiple components. Use that when the unit being broken up is a component, not a file.
  • polylith-migrate-isolate-shared-and-project-logic — separates shared vs project-specific code across components and projects; may create new components.
  • polylith-migrate-extract-standalone-modules — pulls foundational modules out of the residual big component into new standalone components.

Goal

Split monolithic core.py files in shared components (e.g., models_shared, schemas_shared, or similar) into domain-focused modules. This skill ensures that shared components remain well-organized and maintainable.

Inputs

From migration/<PROJECT>/state.md:

  • TARGET_TOP_NS
  • Verification commands.

From migration/<PROJECT>/manifest.md:

  • Current component list and structure.

All inputs from state.md are assumed to satisfy the validation rules in polylith-migrate-discover (### Validation rules). Validate before proceeding.

Steps

1. Identify Candidates
  • Scan components for large core.py files.
  • A component is a candidate if:
    • The file contains definitions from multiple domains.
    • The file contains helper/utility functions alongside class definitions.
    • The file exceeds a reasonable size threshold.
2. Group Definitions by Domain
  • Group definitions by the domain concept they serve.
  • Example domains: ORM models, schema/dataclass clusters, helper functions.
3. Create New Modules
  • Create domain-focused modules (e.g., merchant.py, transaction.py).
  • Move relevant definitions from core.py to the new modules.
4. Update __init__.py
  • Re-export public names from the new modules in __init__.py.
5. Handle core.py
  • Delete core.py if all definitions have been moved.
  • Keep core.py if it serves as a composition point.

Verify

  • RUN_TEST_CMD succeeds.
  • If set, RUN_LINT_CMD and RUN_TYPECHECK_CMD succeed.
Show full SKILL.md (169 more words)Show less

Common failure modes

SymptomLikely causeRemediation
core.py is small (<100 lines) but mixes two domainsThe component itself is too small to warrant an internal split.Leave it. Splitting adds indirection without benefit at this size; revisit when the file grows.
After splitting, an import like from <ns>.<component> import <symbol> fails__init__.py was not updated to re-export the symbol from its new module.Add from <ns>.<component>.<new_module> import <symbol> to __init__.py. The component's public API must remain stable across the split.
New files inside the component now circularly import each other (e.g., models/user.py ↔ models/transaction.py)Domain split was too aggressive; the two files genuinely share a concept.Extract the shared concept into a third file (e.g., models/_base.py) and have both depend on it.

Commit

After verification passes, commit this phase to the migration branch:

bash
git add -A && git commit -m "migrate(<PROJECT>): phase <N> — split-component-internals"

Substitute <PROJECT>, <N>, and <phase-name> from state.md and the orchestrator's phase table. Do not proceed to the next phase without a clean commit — the per-phase commit is the rollback point for the next phase's failure-mode tables.

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

Files

Just SKILL.md in .agents/skills/polylith/migrate-project/polylith-migrate-split-component-internals of DavidVujic/python-polylith.

Open the folder on GitHubat commit a7a80f2

Compare with similar skills

Polylith Migrate Split Component Internals 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.

Polylith Migrate Split Component Internals compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Polylith Migrate Split Component Internals this skillDavidVujic/python-polylith553—~988Automated safety check: PassMIT
Migrate Internal Package into GhostTryGhost/Ghost55k—~3.8kAutomated safety check: PassMIT
Reversible MigrationJuliusBrussee/caveman110k1 repos~196Automated safety check: PassApache-2.0
Database Migrationsaffaan-m/ECC274k4 repos~3kAutomated safety check: PassMIT
Database Migrationsaffaan-m/ECC274k1 repos~2.4kAutomated safety check: PassMIT
Safe Database Migration Patternsaffaan-m/ECC274k—~3.3kAutomated safety check: PassMIT

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Questions about Polylith Migrate Split Component Internals

What does Polylith Migrate Split Component Internals do?

[Internal sub-skill of polylith-migrate-orchestrator. An agent skill from DavidVujic/python-polylith. Polylith Migrate Split Component Internals is an agent skill from DavidVujic/python-polylith. [Internal sub-skill of polylith-migrate-orchestrator.

How do I install Polylith Migrate Split Component Internals in Claude Code?

Run `npx skills add DavidVujic/python-polylith --skill polylith-migrate-split-component-internals -a claude-code`. Or copy the skill folder (.agents/skills/polylith/migrate-project/polylith-migrate-split-component-internals in DavidVujic/python-polylith) into .claude/skills/polylith-migrate-split-component-internals in your project. Claude Code loads it when a task matches its description.

How do I install Polylith Migrate Split Component Internals in Codex?

Run `npx skills add DavidVujic/python-polylith --skill polylith-migrate-split-component-internals -a codex`. Or copy the skill folder (.agents/skills/polylith/migrate-project/polylith-migrate-split-component-internals in DavidVujic/python-polylith) into .agents/skills/polylith-migrate-split-component-internals in your project. Codex loads it when a task matches its description.

Can I use Polylith Migrate Split Component Internals 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 DavidVujic/python-polylith --skill polylith-migrate-split-component-internals -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/polylith-migrate-split-component-internals, .gemini/skills/polylith-migrate-split-component-internals, .github/skills/polylith-migrate-split-component-internals and .opencode/skills/polylith-migrate-split-component-internals in your project.

What does Polylith Migrate Split Component Internals need to run?

Going by SKILL.md and its folder, Polylith Migrate Split Component Internals needs the command-line tools its instructions call (git). Our summary lists: Python 3.

Does Polylith Migrate Split Component Internals access the network?

SKILL.md contains no URLs. Its commands use git, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Polylith Migrate Split Component Internals 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 Polylith Migrate Split Component Internals use?

Polylith Migrate Split Component Internals 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 Polylith Migrate Split Component Internals use?

About 988 tokens (SKILL.md is roughly 4k 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 Polylith Migrate Split Component Internals?

Skills that share tags, products or a category with Polylith Migrate Split Component Internals: Migrate Internal Package into Ghost (TryGhost/Ghost, 55k stars), Reversible Migration (JuliusBrussee/caveman, 110k stars), Database Migrations (affaan-m/ECC, 274k stars) and Database Migrations (affaan-m/ECC, 274k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Polylith Migrate Split Component Internals?

DavidVujic (a GitHub user) maintains it in DavidVujic/python-polylith, which has 553 GitHub stars. The repository holds 37 skills in this directory. The repository was last updated on October 4, 2026.

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