gerfru · gerfru · Aug 13, 2026 · Aug 13, 2026
diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
@@ -6,9 +6,9 @@
     {
       "name": "dev",
       "source": "./plugins/dev",
-      "description": "24 skills for software projects: Design (App, Secure, API, Data, Migration, UX, LLM, Observability, CI/CD, IaC), Review (App, Architecture, Security, UX, LLM), Tools (Debug, Test, Style, Accessibility, Performance), Meta. Grounded in MIT, CMU, Stanford curricula.",
+      "description": "27 skills for software projects: Design (App, Secure, API, Data, Migration, UX, LLM, Observability, CI/CD, IaC, Public), Review (App, Architecture, Security, UX, LLM, Public), Tools (Debug, Test, Style, Accessibility, Performance), Meta. Grounded in MIT, CMU, Stanford curricula. Works with Claude Code and GitHub Copilot CLI.",
       "category": "development",
-      "tags": ["best-practices", "security", "architecture", "llm", "accessibility", "performance", "ci-cd", "iac"]
+      "tags": ["best-practices", "security", "architecture", "llm", "accessibility", "performance", "ci-cd", "iac", "copilot-cli"]
     }
   ]
 }
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -7,6 +7,19 @@ Format: [Semantic Versioning](https://semver.org). Dates: YYYY-MM-DD.
 
 ## [Unreleased]
 
+### Added
+
+- GitHub Copilot CLI support: this plugin now works as a Copilot CLI plugin/marketplace as well as a Claude Code plugin, without a second manifest or generated duplicate tree
+- `meta-install --target claude|copilot-cli`, plus `--copilot-native` and `--standalone-skills` modes, for installing rules/skills into Copilot CLI projects
+- `validate-skills.sh`: new Copilot CLI compatibility checks (`${CLAUDE_PLUGIN_ROOT}` usage, `plugin.json` `skills` field, unsafe single-line `description:` colons)
+
+### Fixed
+
+- Skill `name:` frontmatter changed from `dev:<skill>` to `dev-<skill>` — Copilot CLI rejects `:` in skill names; verified this has no effect on Claude Code, whose `/dev:<skill>` invocation is driven by `commands/<skill>.md`, not this field
+- Three files (`review-app/SKILL.md`, `commands/meta-install.md`, `commands/meta-create-skill.md`) had unquoted single-line `description:` values containing a colon followed by a space, which breaks YAML parsing under Copilot CLI's stricter parser
+- Four `SKILL.md` files used `${CLAUDE_PLUGIN_ROOT}` (Claude Code-only template variable) for cross-file references — replaced with plain relative paths
+- Stale "24 skills" / "26 skills" counts corrected to 27 across `marketplace.json`, `plugin.json`, `CLAUDE.md`, `README.md`
+
 ---
 
 ## [2.0.0] — 2026-06-08

diff --git a/CLAUDE.md b/CLAUDE.md
@@ -1,6 +1,6 @@
 # Dev Best Practices
 
-This repo contains best-practice rules for software projects (RAG systems, AI agents, data pipelines, full-stack web apps) and a **Claude Code Plugin** with 26 skills.
+This repo contains best-practice rules for software projects (RAG systems, AI agents, data pipelines, full-stack web apps) and a **Claude Code Plugin** with 27 skills that also works as a **GitHub Copilot CLI plugin** (see "Copilot CLI Support" below).
 
 ## Repo Structure
 
@@ -10,9 +10,9 @@ This repo contains best-practice rules for software projects (RAG systems, AI ag
 
 plugins/dev/
   .claude-plugin/
-    plugin.json             # Plugin metadata (name: "dev", version: "3.0.0")
-  commands/                 # Slash command definitions (one file per skill)
-  skills/                   # Skill workflow definitions (auto-triggered)
+    plugin.json             # Plugin metadata (name: "dev", version: "3.0.0") — also read by Copilot CLI (fallback lookup path)
+  commands/                 # Slash command definitions (one file per skill) — Claude Code only, Copilot CLI has no equivalent
+  skills/                   # Skill workflow definitions (auto-triggered) — shared by Claude Code and Copilot CLI
   rules/                    # Mirror of claude/*.md (used by skills as reference)
 
 claude/                     # Condensed rules for Claude Code
@@ -33,7 +33,7 @@ scripts/
   validate-skills.sh        # Plugin structure validator (CI + pre-commit)
 ```
 
-## Plugin Skills (24)
+## Plugin Skills (27)
 
 ```text
 DESIGN:  design-app, design-secure, design-api, design-data, design-migration,
@@ -49,12 +49,40 @@ Navigation menu: `/dev:meta-help`
 
 ## Usage in Projects
 
-**Install plugin:** `claude plugin install dev@gerald-dev-best-practices`
+**Install plugin (Claude Code):** `claude plugin install dev@gerald-dev-best-practices`
+
+**Install plugin (GitHub Copilot CLI):** `copilot plugin marketplace add gerfru/dev-best-practices` then `copilot plugin install dev@gerald-dev-best-practices` — see "Copilot CLI Support" below.
 
 **Rules only (without plugin):** Copy `claude/essential-rules.md` into project CLAUDE.md, or use `/dev:meta-install`.
 
 **More detail:** Selectively add sections from `claude/app-rules.md`, `claude/github-rules.md`, `claude/architecture-rules.md`.
 
+## Copilot CLI Support
+
+This plugin is dual-compatible with Claude Code and GitHub Copilot CLI, since both tools
+converged on a near-identical plugin architecture:
+
+- **Manifests are reused as-is.** `plugins/dev/.claude-plugin/plugin.json` sits at one of
+  Copilot CLI's fallback lookup paths and has no `skills` field — the exact condition both
+  tools need (Claude Code rejects a `skills` field; Copilot CLI auto-discovers `skills/`
+  only when it's absent). `.claude-plugin/marketplace.json` is also a valid Copilot CLI
+  lookup path. No second manifest or generated duplicate tree exists in this repo.
+- **`SKILL.md` files use plain relative paths** (`../../rules/...`, `../other-skill/SKILL.md`)
+  for all cross-file references, never `${CLAUDE_PLUGIN_ROOT}` — that template variable is
+  Claude Code-only and Copilot CLI does not expand it. `${CLAUDE_PLUGIN_ROOT}` remains fine
+  inside `plugins/dev/commands/*.md`, which is Claude Code-only (Copilot CLI has no
+  slash-command-router concept — skills are natively slash-invocable there via discovery).
+- **`meta-install` supports `--target claude|copilot-cli`** — for Copilot CLI it writes into
+  the same `CLAUDE.md` by default (Copilot CLI reads it directly as an instructions file),
+  or `.github/copilot-instructions.md` with `--copilot-native`. A `--standalone-skills` mode
+  copies the skill library into a project's `.github/skills/`, `.claude/skills/`, or
+  `.agents/skills/` for Copilot CLI users not using the plugin/marketplace mechanism.
+- **Skill `name:` fields use `dev-<skill>` (hyphen, not colon).** Verified live: Copilot CLI
+  rejects `:` in skill names ("must contain only ASCII letters, numbers, hyphens,
+  underscores"); Claude Code's own `/dev:<skill>` slash-invocation is unaffected since it's
+  driven by `commands/<skill>.md` (plugin name + command filename), never by this
+  frontmatter field.
+
 ## Maintenance
 
 - Update `reference/` when best practices change

diff --git a/README.md b/README.md
@@ -4,12 +4,14 @@
 
 Opinionated best-practice rules for software projects — RAG systems, AI agents, data pipelines, full-stack web apps. Three detail levels: compact essential rules for `CLAUDE.md`, thematic rule files, and detailed reference docs.
 
-Also a **Claude Code plugin**: install once, get 24 skills in every project.
+Also a **Claude Code plugin**: install once, get 27 skills in every project. Also works as a **GitHub Copilot CLI plugin** — same repo, same skills.
 
 ---
 
 ## Quick Start
 
+### Claude Code
+
 ```bash
 # Add marketplace (once per machine)
 claude plugin marketplace add gerfru/dev-best-practices
@@ -23,6 +25,24 @@ claude plugin install dev@gerald-dev-best-practices
 
 **Windows (VS Code):** Claude icon → `/plugin` → Marketplaces → add `gerfru/dev-best-practices` → Plugins → Install `dev`.
 
+### GitHub Copilot CLI
+
+```bash
+# Add marketplace (once per machine)
+copilot plugin marketplace add gerfru/dev-best-practices
+
+# Install plugin
+copilot plugin install dev@gerald-dev-best-practices
+```
+
+Skills are then invocable directly, e.g. `/dev:design-api`, or auto-triggered from a
+natural-language prompt matching a skill's description — same as Claude Code.
+
+Not using Copilot's plugin/marketplace mechanism? Run `/dev:meta-install --target
+copilot-cli --standalone-skills` from a Claude Code session against your target project to
+copy the skill library into `.github/skills/`, `.claude/skills/`, or `.agents/skills/`,
+where Copilot CLI auto-discovers it.
+
 ---
 
 ## Skills
@@ -69,7 +89,7 @@ Or just describe what you need in natural language — Claude picks the right sk
 
 | Skill | What it does |
 |---|---|
-| `/dev:meta-help` | Navigation menu — shows all 24 skills, launches chosen one |
+| `/dev:meta-help` | Navigation menu — shows all 27 skills, launches chosen one |
 | `/dev:meta-install` | Insert `essential-rules.md` into project `CLAUDE.md` (detects install vs. update) |
 | `/dev:meta-drift` | Compare installed rules block against current rule files |
 | `/dev:meta-sync` | Repo-internal: check if `claude/*.md` still reflects `reference/*.md` |
@@ -85,9 +105,9 @@ Or just describe what you need in natural language — Claude picks the right sk
 
 plugins/dev/
   .claude-plugin/
-    plugin.json             Plugin metadata (name: "dev", version: "2.0.0")
-  commands/                 Slash-command definitions (one file per skill)
-  skills/                   Skill workflow definitions (auto-triggered)
+    plugin.json             Plugin metadata (name: "dev", version: "3.0.0") — also read by Copilot CLI
+  commands/                 Slash-command definitions (one file per skill) — Claude Code only
+  skills/                   Skill workflow definitions (auto-triggered) — shared with Copilot CLI
   rules/                    Mirror of claude/*.md (used by skills as reference)
 
 claude/                     Condensed rules for Claude Code

diff --git a/plugins/dev/.claude-plugin/plugin.json b/plugins/dev/.claude-plugin/plugin.json
@@ -1,6 +1,6 @@
 {
   "name": "dev",
   "version": "3.0.0",
-  "description": "26 Skills für Design (inkl. LLM-Engineering/RAG/Agents, Observability/SRE, CI/CD, IaC/GitOps, UX/Human-AI Interaction, Repo-Publication), Security-Review (ISEC/Stanford/MIT, OWASP LLM Top 10), App-Audit (OWASP ASVS 5.0, DORA), Architektur-Review, Debug, Test, Styling, Accessibility (WCAG 2.2), Performance Engineering (MIT 6.172, USE Method) und Skill-Erstellung.",
+  "description": "27 Skills für Design (inkl. LLM-Engineering/RAG/Agents, Observability/SRE, CI/CD, IaC/GitOps, UX/Human-AI Interaction, Repo-Publication), Security-Review (ISEC/Stanford/MIT, OWASP LLM Top 10), App-Audit (OWASP ASVS 5.0, DORA), Architektur-Review, Debug, Test, Styling, Accessibility (WCAG 2.2), Performance Engineering (MIT 6.172, USE Method) und Skill-Erstellung. Funktioniert mit Claude Code und GitHub Copilot CLI.",
   "author": { "name": "Gerald" }
 }
diff --git a/plugins/dev/commands/meta-create-skill.md b/plugins/dev/commands/meta-create-skill.md
@@ -1,5 +1,11 @@
 ---
-description: Creates a new skill for this plugin following the established methodology: topic → academic research (university curricula + canonical books) → SKILL.md + references/. Use this skill when you want to create a new /dev skill. Trigger: "create a new skill", "build a new skill", "create skill for X", "add a skill", "add skill", "new skill for X". Covers: topic clarification, academic research, structure decision, writing all files, housekeeping (commands/, meta-help, plugin.json).
+description: >
+  Creates a new skill for this plugin following the established methodology — topic →
+  academic research (university curricula + canonical books) → SKILL.md + references/.
+  Use this skill when you want to create a new /dev skill. Trigger phrases: "create a new
+  skill", "build a new skill", "create skill for X", "add a skill", "add skill",
+  "new skill for X". Covers topic clarification, academic research, structure decision,
+  writing all files, housekeeping (commands/, meta-help, plugin.json).
 argument-hint: "[optional: skill topic, e.g. 'LLM Engineering' or 'Performance Monitoring']"
 ---
 

diff --git a/plugins/dev/commands/meta-install.md b/plugins/dev/commands/meta-install.md
@@ -1,5 +1,8 @@
 ---
-description: Installs or updates dev best practices rules in CLAUDE.md. Automatically detects whether initial installation or update is needed. Flags: --essential (default), --full, --update, --section <name>.
+description: >
+  Installs or updates dev best practices rules in CLAUDE.md. Automatically detects
+  whether initial installation or update is needed. Flags — --essential (default),
+  --full, --update, --section <name>.
 argument-hint: "[--essential | --full | --update | --section <security|cicd|architecture>]"
 ---
 

diff --git a/plugins/dev/skills/design-api/SKILL.md b/plugins/dev/skills/design-api/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-api
+name: dev-design-api
 description: >
   API contract design skill grounded in CMU 17-625 (API Design, Swarnalatha Ashok /
   Bradley Schmerl) and Google API Design Guide. Use this skill whenever the user

diff --git a/plugins/dev/skills/design-app/SKILL.md b/plugins/dev/skills/design-app/SKILL.md
@@ -1,12 +1,12 @@
 ---
-name: dev:design-app
+name: dev-design-app
 description: From an app idea to well-founded architecture and stack decisions based on the Dev-Best-Practices rules. Use this skill whenever the user describes a new app idea and wants help choosing architecture, stack, structure, or a scaffolding plan; triggers on "new app", "app idea", "how do I structure", "which stack", "architecture for ...".
 ---
 
 # App Design (rule-based)
 
 Turns an app idea into justified decisions. Standard: the rule files
-under `${CLAUDE_PLUGIN_ROOT}/rules/` (especially architecture-rules.md, app-rules.md,
+under `../../rules/` (especially architecture-rules.md, app-rules.md,
 github-rules.md). No generic advice — every decision references the rule.
 
 ## Step 0 - Clarify Idea & Scope

diff --git a/plugins/dev/skills/design-cicd/SKILL.md b/plugins/dev/skills/design-cicd/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-cicd
+name: dev-design-cicd
 description: >
   CI/CD Pipeline Design grounded in "Accelerate" (Forsgren/Humble/Kim, IT Revolution 2018)
   and "Continuous Delivery" (Humble/Farley, Addison-Wesley 2010). Covers pipeline architecture,

diff --git a/plugins/dev/skills/design-data/SKILL.md b/plugins/dev/skills/design-data/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-data
+name: dev-design-data
 description: >
   Data model design skill grounded in CMU 15-445 (Database Systems, Prof. Andy Pavlo)
   and Stanford CS245. Use this skill whenever the user needs to design or review a

diff --git a/plugins/dev/skills/design-iac/SKILL.md b/plugins/dev/skills/design-iac/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-iac
+name: dev-design-iac
 description: >
   Infrastructure as Code Design grounded in "Infrastructure as Code" (Kief Morris,
   O'Reilly 2021) and NTNU IIKG3005 (the only dedicated academic IaC course worldwide).

diff --git a/plugins/dev/skills/design-llm/SKILL.md b/plugins/dev/skills/design-llm/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-llm
+name: dev-design-llm
 description: >
   LLM system design grounded in Stanford CS224N (Yang/Choi), CMU 11-667
   (Savelka/Kim) and Chip Huyen "Designing ML Systems". Use this skill whenever

diff --git a/plugins/dev/skills/design-migration/SKILL.md b/plugins/dev/skills/design-migration/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-migration
+name: dev-design-migration
 description: >
   Migration planning skill grounded in MIT 6.5840 (Distributed Systems, Morris/
   Kaashoek/Zeldovich) and Martin Fowler's migration patterns. Use this skill

diff --git a/plugins/dev/skills/design-observability/SKILL.md b/plugins/dev/skills/design-observability/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-observability
+name: dev-design-observability
 description: >
   Observability architecture grounded in the Google SRE Books (Beyer et al.) and
   Observability Engineering (Majors/Fong-Jones, O'Reilly 2022). Covers

diff --git a/plugins/dev/skills/design-public/SKILL.md b/plugins/dev/skills/design-public/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-public
+name: dev-design-public
 description: >
   Publication-readiness design skill grounded in OpenSSF Best Practices,
   GitHub Security Hardening docs, CISA Security-by-Design, OWASP DevSecOps

diff --git a/plugins/dev/skills/design-secure/SKILL.md b/plugins/dev/skills/design-secure/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-secure
+name: dev-design-secure
 description: >
   Security-first application design skill grounded in TU Graz ISEC Major curriculum
   and top-university references (Stanford CS255/CS355, MIT 6.566/6.5610).

diff --git a/plugins/dev/skills/design-ux/SKILL.md b/plugins/dev/skills/design-ux/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:design-ux
+name: dev-design-ux
 description: >
   Human-Centered UX Design skill grounded in the leading academic HCI curricula
   (CMU HCII, Stanford CS 247A/347, ETH, TU Wien, TU Graz) and the four canonical

diff --git a/plugins/dev/skills/meta-create-skill/SKILL.md b/plugins/dev/skills/meta-create-skill/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:meta-create-skill
+name: dev-meta-create-skill
 description: >
   Creates a new skill for this plugin following the established methodology:
   topic → academic research (university curricula + canonical books) → SKILL.md +
@@ -99,6 +99,11 @@ What belongs IN SKILL.md:
 - Standard finding format (for review-* skills)
 - Output format (which file, which structure)
 - References to references/ files
+- Cross-file references as **plain relative paths** (e.g. `../../rules/essential-rules.md`,
+  `../other-skill/SKILL.md`) — **never `${CLAUDE_PLUGIN_ROOT}`**. That variable is Claude
+  Code-only template syntax; it breaks silently under GitHub Copilot CLI, which also reads
+  this plugin's `skills/` directory but does not expand it. `${CLAUDE_PLUGIN_ROOT}` is
+  permitted only inside `commands/<name>.md` (a Claude-Code-only file Copilot never parses).
 
 What does NOT belong in SKILL.md (→ references/):
 - Lookup tables (Concept → course link)
@@ -173,7 +178,7 @@ Required elements:
 
 ```markdown
 ---
-name: <skill-name>
+name: dev-<skill-name>
 description: >
   <What the skill does>. Grounded in <primary source>.
   Trigger: "<Keyword 1>", "<Keyword 2>", ...
@@ -209,6 +214,18 @@ description: >
 - `references/<file>.md` — <what is in it>
 ```
 
+**Note:** `name:` uses `dev-<skill-name>` (hyphen, not colon). Verified against a live
+Copilot CLI install: `:` is rejected ("Skill name must start with an ASCII letter or
+number and contain only ASCII letters, numbers, hyphens, underscores"), so `dev:<name>`
+produced a load warning on every skill under Copilot CLI (non-fatal there — it fell back
+to the folder name — but still worth avoiding). `dev-<name>` is ASCII-clean for Copilot.
+Also verified live against Claude Code after this rename: `/dev:<skill-name>`
+slash-invocation is driven entirely by `commands/<skill-name>.md` (plugin name from
+`plugin.json` + the command file's own name) — it never reads this SKILL.md frontmatter
+field at all, so the rename has zero effect on Claude Code's routing. Any cross-file
+reference in the body must be a plain relative path regardless — see the rule under
+Step 2a.
+
 ### 3c — commands/<name>.md
 
 ```markdown

diff --git a/plugins/dev/skills/meta-drift/SKILL.md b/plugins/dev/skills/meta-drift/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:meta-drift
+name: dev-meta-drift
 description: Compares the dev-best-practices block in a project CLAUDE.md with the current state of the rule files and shows what is missing, outdated, or newly added. Use this skill whenever the user wants to update their project rules, check if rules are still current, or sync a CLAUDE.md with the latest best practices; triggers for "update rules", "are my rules still current", "drift", "sync CLAUDE.md", "update rules".
 ---
 
@@ -10,7 +10,7 @@ Shows the delta — without automatically overwriting.
 
 ## Step 0 — Load Sources
 
-1. **Current state (TARGET):** Rule files from `${CLAUDE_PLUGIN_ROOT}/rules/`
+1. **Current state (TARGET):** Rule files from `../../rules/`
    - `essential-rules.md` — always
    - `app-rules.md`, `github-rules.md`, `architecture-rules.md` — only if present in the project block
 

diff --git a/plugins/dev/skills/meta-help/SKILL.md b/plugins/dev/skills/meta-help/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: dev:meta-help
+name: dev-meta-help
 description: >
   Navigation menu for all Dev Best Practices skills. Shows all available skills
   grouped and starts the chosen one directly. Trigger for "which skill should I use",
@@ -61,9 +61,9 @@ Which skill should start?
 **With a description:** Choose the best matching skill, mention it briefly ("→ starting review-secure …"), then start directly.
 **With arguments:** Pass to the started skill.
 
-Load and follow exactly: `${CLAUDE_PLUGIN_ROOT}/skills/<chosen-skill>/SKILL.md`
+Load and follow exactly: `../<chosen-skill>/SKILL.md`
 
 ## Rules
 - Show menu immediately, no intro
 - After the choice: start directly, do not explain or ask again
-- Never load all 26 skills at once — always only the chosen one
+- Never load all 27 skills at once — always only the chosen one