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Agent skill

Wf Spec Impact

by changkun in changkun/wallfacer

Blast radius of a change before it is made: which code and which other specs a proposed spec would touch, and which specs need updating as a consequence.

MITAuto-check passedDevelopment

Install Wf Spec Impact

skills CLI
$ npx skills add changkun/wallfacer --skill wf-spec-impact -a claude-code

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

GitHub CLI
$ gh skill install changkun/wallfacer wf-spec-impact --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/changkun/wallfacer.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/wf-spec-impact .claude/skills/wf-spec-impact && 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
wf-spec-impact
GitHub stars
112
Token cost
~1.4k tokens
SKILL.md length
629 words
Files
1
Skills in repo
14
Repo updated
First seen
Licence
MIT

At a glance

Blast radius of a change before it is made: which code and which other specs a proposed spec would touch, and which specs need updating as a consequence.

  • Works in 8 steps: Parse arguments → Read the spec → Map the code impact → …
  • Development work in your project
  • SKILL.md covers Step 0: Parse arguments, Step 1: Read the spec, Step 2: Map the code impact and Step 3: Check interface…, plus 5 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Wf Spec Impact is an agent skill from changkun/wallfacer. Blast radius of a change before it is made: which code and which other specs a proposed spec would touch, and which specs need updating as a consequence. Read-only. Use before implementing or breaking down, to size the work and surface hidden dependents.

Its SKILL.md is about 1.4k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development. The repository describes itself as: Chat, specs, tasks, and code. An autonomous engineering platform. Full autonomy when you trust it. Full control when you don't. The licence is MIT.

When your agent uses it

  • Development work in your project

Example prompts

  • “/wf-spec-impact”

Requirements

  • Pre-approved tools (allowed-tools): Read, Grep, Glob, Agent, Bash(git log *), Bash(ls *)

Workflow steps

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

  1. Parse arguments
  2. Read the spec
  3. Map the code impact
  4. Check interface stability
  5. Check spec cross-references (reverse dependency analysis)
  6. Check documentation impact
  7. Check test impact
  8. Generate report

What it can do on your machine

Read from SKILL.md and the folder at commit 5b3cea1. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Read
    • Grep
    • Glob
    • Agent
    • Bash(git log *)
    • Bash(ls *)

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

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

  • Network

    No URLs in SKILL.md.

    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

Wf Spec Impact loads about 1.4k tokens when it runs. Until then it costs about 67 tokens; SKILL.md has 629 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~67
When it runs · the whole SKILL.md, loaded when a task matches
~1.4k

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 changkun/wallfacer at commit 5b3cea1, republished under its MIT licence (© changkun). 629 words, ~1,419 tokens.

Download SKILL.mdSave it as .claude/skills/wf-spec-impact/SKILL.md (or your agent's skills folder).
name
wf-spec-impact
description
Blast radius of a change before it is made: which code and which other specs a proposed spec would touch, and which specs need updating as a consequence. Read-only. Use before implementing or breaking down, to size the work and surface hidden dependents.
allowed-tools
Read, Grep, Glob, Agent, Bash(git log *), Bash(ls *)
argument-hint
<spec-file.md>

Check Impact

Analyze the blast radius of a spec before implementation. Identify what existing code, tests, specs, and documentation will be affected.

Step 0: Parse arguments

Extract the spec file path from the first token.

Step 1: Read the spec

  1. Read the spec file in full. Parse YAML frontmatter to extract title, status, depends_on, affects, effort.
  2. Use the affects list from frontmatter as the primary set of code files and directories this spec touches.
  3. Extract additional file paths, package names, type names, function names, and interface names mentioned in the spec body.
  4. Identify the spec's deliverables: what new things it creates, what existing things it modifies.

Step 2: Map the code impact

For each file, type, or function the spec plans to modify:

  1. Find all callers and dependents using Grep/Glob:
    • Functions: grep for call sites across the codebase.
    • Types: grep for usage (field access, type assertions, interface implementations).
    • Interfaces: grep for implementations and consumers.
    • Packages: grep for imports.
  2. Build a dependency fan-out: "changing X affects Y, Z, W".
  3. Classify each affected file as:
    • Direct — mentioned in the spec, will be intentionally modified.
    • Ripple — not mentioned but uses something being changed; may need updates.
    • Test — test file that exercises affected code; may need updates.

Use Agent subagents (Explore type) for parallel searches across independent packages. Launch up to 3 concurrently.

Step 3: Check interface stability

For each interface or exported type the spec modifies:

  1. Find all implementations (for interfaces) or embeddings (for structs).
  2. Check if any are in other packages or other specs' deliverables.
  3. Flag breaking changes: method signature changes, removed fields, renamed types.
  4. For each breaking change, list every file that would need updating.

Step 4: Check spec cross-references (reverse dependency analysis)

Use two complementary approaches:

4a. Reverse depends_on scan

Grep all spec files for depends_on entries that reference this spec's path. These are specs that directly depend on this one. For each:

  • Check its status — if validated or later, it may be affected by changes.
  • If the dependent is already complete, flag it as potentially needing a stale review.
4b. affects overlap scan

Grep all spec files for affects entries that reference the same code paths as this spec. Specs with overlapping affects may conflict even without an explicit depends_on edge.

Show full SKILL.md (246 more words)Show less
4c. Transitive impact

Follow the reverse depends_on graph transitively: if spec A depends on this spec, and spec B depends on A, then B is transitively affected. Report both direct and transitive dependents.

4d. Body reference scan

Grep all other spec files for references to:

  • The spec being analyzed (by filename).
  • Types, interfaces, or packages the spec modifies. For each referencing spec, assess whether it:
  • Depends on the current shape of what's being changed (needs update).
  • Merely mentions it in passing (no action needed).
  • Has assumptions that conflict with the proposed changes.

Step 5: Check documentation impact

Scan documentation files for references to things being changed:

  1. Repository instructions such as AGENTS.md or CLAUDE.md.
  2. User-facing guides and reference documentation.
  3. Architecture or internals documentation.
  4. README.md and CONTRIBUTING.md at the project root when present.

Flag any doc sections that reference modified APIs, types, or behaviors.

Step 6: Check test impact

  1. Find test files in affected packages.
  2. Grep for test functions that reference modified types or functions.
  3. Estimate how many tests will need updating.
  4. Flag packages with low test coverage in the affected area (no existing tests for the code being changed).

Step 7: Generate report

## Impact Analysis: <spec-name>

### Direct Changes
Files the spec explicitly modifies:
- <file> — <what changes>

### Ripple Effects
Files not in the spec but affected by the changes:
- <file> — uses <thing being changed>, may need: <what>
- <file> — imports <package being changed>, may need: <what>

### Interface Changes
- <interface/type> — <N> implementations, <N> callers
  Breaking: <yes/no>, affected files: <list>

### Cross-Spec Impact
- <other-spec> — references <thing>, needs: <update/no action>

### Documentation Updates Needed
- <doc-file> — mentions <thing being changed>

### Test Impact
- <N> test files in affected packages
- <N> test functions reference modified code
- Packages with no tests in affected area: <list>

### Risk Assessment
- **Blast radius:** <Small (1-3 files) | Medium (4-10) | Large (10+)>
- **Breaking changes:** <None | <list>>
- **Highest risk area:** <description of what's most likely to break>

### Recommendations
- <actions to take before or during implementation>

Notes

  • This skill is read-only. It does not modify any files.
  • Focus on actionable findings. Don't flag every transitive import — focus on code that will actually need changes.
  • If the spec has a task breakdown, check impact per-task to identify which tasks carry the most risk.

© changkun, 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 .claude/skills/wf-spec-impact of changkun/wallfacer.

Open the folder on GitHubat commit 5b3cea1

Compare with similar skills

Wf Spec Impact 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.

Wf Spec Impact compared with similar skills
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Wf Spec Impact this skillchangkun/wallfacer112—~1.4kAutomated safety check: PassMIT
Vercel Composition Patternssupabase/supabase111k58 repos~726Automated safety check: PassMIT
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Typescript Advanced Typesrolling-scopes/rsschool-app10k25 repos~4.2kAutomated safety check: PassMPL-2.0
PR Babysitteropeninterpreter/openinterpreter69k3 repos~4.2kAutomated safety check: PassApache-2.0
Code Review ChecklistshareAI-lab/learn-claude-code78k5 repos~1.1kAutomated safety check: PassMIT

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Categories

Questions about Wf Spec Impact

What does Wf Spec Impact do?

Blast radius of a change before it is made: which code and which other specs a proposed spec would touch, and which specs need updating as a consequence. Wf Spec Impact is an agent skill from changkun/wallfacer. Blast radius of a change before it is made: which code and which other specs a proposed spec would touch, and which specs need updating as a consequence.

When should I use Wf Spec Impact?

Wf Spec Impact fits situations like: development work in your project.

How do I install Wf Spec Impact in Claude Code?

Run `npx skills add changkun/wallfacer --skill wf-spec-impact -a claude-code`. Or copy the skill folder (.claude/skills/wf-spec-impact in changkun/wallfacer) into .claude/skills/wf-spec-impact in your project. Claude Code loads it when a task matches its description.

How do I install Wf Spec Impact in Codex?

Run `npx skills add changkun/wallfacer --skill wf-spec-impact -a codex`. Or copy the skill folder (.claude/skills/wf-spec-impact in changkun/wallfacer) into .agents/skills/wf-spec-impact in your project. Codex loads it when a task matches its description.

Can I use Wf Spec Impact 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 changkun/wallfacer --skill wf-spec-impact -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/wf-spec-impact, .gemini/skills/wf-spec-impact, .github/skills/wf-spec-impact and .opencode/skills/wf-spec-impact in your project.

What does Wf Spec Impact need to run?

SKILL.md names no scripts, command-line tools or credentials: Wf Spec Impact is instructions for the agent only. Its frontmatter pre-approves these tools: Read, Grep, Glob, Agent, Bash(git log *), Bash(ls *).

Does Wf Spec Impact access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Wf Spec Impact 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 Wf Spec Impact use?

Wf Spec Impact 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 Wf Spec Impact use?

About 1.4k tokens (SKILL.md is roughly 5.7k 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 Wf Spec Impact?

Skills that share tags, products or a category with Wf Spec Impact: Vercel Composition Patterns (supabase/supabase, 111k stars), Finishing a Development Branch (obra/superpowers, 297k stars), Typescript Advanced Types (rolling-scopes/rsschool-app, 10k stars) and PR Babysitter (openinterpreter/openinterpreter, 69k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Wf Spec Impact?

changkun (a GitHub user) maintains it in changkun/wallfacer, which has 112 GitHub stars. The repository holds 14 skills in this directory. The repository was last updated on October 4, 2026.

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