docs: add 'Porting Superpowers to a New Harness' guide

An evergreen guide for adding support for a new harness (IDE, CLI, or agent
runner). Teaches the invariants — automatic session-start bootstrap, skill
discovery/invocation, tool mapping, the acceptance test — and points at the
closest reference integration shape (shell-hook, in-process plugin,
instructions-file / declared context file) to copy. Covers discovery, build,
local install, tmux-driven verification, distribution, and PR submission, with a
live reference-integration index and a gotchas appendix.

Two non-negotiable rules: (1) never edit skill bodies; (2) everything ships
through the harness's own install mechanism — never edit the user's config. When
a plugin installer strips undeclared files, declare the bootstrap as a recognized
component (a manifest contextFileName-style context file the installer preserves
and the harness loads every session), generated at install time from the live
SKILL.md + tool mapping. Surfaced-skill-description bootstrap is the softer
fallback.

Hardened against real end-to-end ports (Antigravity CLI): shapes can compose; a
fork doesn't inherit its parent's behavior; a hook system != a usable
session-start event; verify @-includes AND context-file preservation with a
marker; web-search the docs and study existing plugins; reverse-engineer
undocumented harnesses; print/headless modes may hang; workspace-trust gates
stall tmux; declared context files survive plugin install while undeclared files
are stripped; skills-path registration is per-harness.

docs/porting-to-a-new-harness.md

@@ -0,0 +1,826 @@
+# Porting Superpowers to a New Harness
+
+This guide explains how to add support for a new harness — an IDE, CLI, or
+agent runner that isn't Claude Code — so that Superpowers skills auto-trigger
+there the same way they do natively.
+
+It is written in two layers. **Part 1–3** explain how the system works and how
+to tell whether a harness can be supported at all; read these before you touch
+anything. **Part 4–8** are a prescriptive procedure for an agent (supervised by
+a human partner) to execute the port end to end, through distribution. An
+appendix indexes the current reference integrations so you can copy the closest
+one.
+
+The integration mechanism differs across harnesses, and it will keep changing.
+This guide deliberately teaches the **invariants** — the things that must be
+true no matter the mechanism — and points you at a live reference implementation
+to copy. When this guide and the code disagree, the code wins; fix the guide.
+
+## Before you start
+
+Adding a harness is the highest-stakes contribution type in this repo. Before
+writing anything:
+
+- Read `CLAUDE.md` and `.github/PULL_REQUEST_TEMPLATE.md` in full — the
+  contributor rules and the new-harness PR requirements are not optional.
+- Search open **and closed** PRs for a prior attempt at this harness. If one
+  exists, understand why it stalled before starting your own.
+
+---
+
+## Part 1 — How Superpowers works across harnesses
+
+Superpowers is the same content everywhere. What changes per harness is the thin
+layer that delivers that content to the model and translates its instructions
+into the harness's native tools. Three components:
+
+1. **Skills (harness-agnostic).** Everything in `skills/` is the source of
+   truth, shared verbatim by every harness. Skills are written to describe
+   *actions* — "invoke a skill", "read a file", "dispatch a subagent", "create a
+   todo" — and never name a specific tool. This is what lets one skill body run
+   on Claude Code, Codex, Gemini, pi, and the rest without edits.
+
+2. **Tool mapping (per-harness).** Each harness needs the action vocabulary
+   translated into its real tool names. That translation lives in
+   `skills/using-superpowers/references/<harness>-tools.md` and/or inline in the
+   harness's bootstrap injector (see Part 5). It says, e.g., "*dispatch a
+   subagent* → call `task` with `subagent_type`."
+
+3. **Bootstrap (per-harness).** At the start of every session, the full
+   `skills/using-superpowers/SKILL.md` is injected into the model's context,
+   wrapped in `<EXTREMELY_IMPORTANT>` tags, with the tool mapping appended. That
+   injected skill is what teaches the model that skills exist and that it must
+   check for a relevant skill before acting. **The bootstrap is the entire
+   integration.** Without it, the skill files are inert — present on disk, never
+   invoked.
+
+### Two rules that make this work
+
+**1. Skills name actions, not tools.** Do **not** edit skill bodies to fit your
+harness. Porting adds a tool-mapping reference and a bootstrap injector; it
+never reaches into `skills/*/SKILL.md` to swap tool names. (The project's
+contributor guidelines treat skill content as carefully-tuned behavior-shaping
+code; rewording it for "compliance" is rejected on sight.)
+
+**2. Everything ships through the harness's own install mechanism. Never edit the
+user's files.** The bootstrap, the skills, and the tool mapping all get delivered
+*as part of what the harness installs* — a plugin, an extension, a marketplace
+entry, an extension-bundled context file. A port **must not** reach into a user's
+global or personal config (`~/.gemini/config/AGENTS.md`, `settings.json`,
+`trustedFolders.json`, a hand-edited `~/.bashrc`, etc.) to inject anything. The
+harness owns what it loads; your install artifact is the only thing you get to
+write. If the install mechanism genuinely can't carry the bootstrap, that is a
+limitation to surface (Part 6) — never a license to hand-edit the user's config.
+(Shape C is *not* an exception: Gemini's context file is fine because it ships
+*inside the installed extension* and is declared by the manifest's
+`contextFileName` — the harness loads the extension's own file, not a file you
+edited in the user's home.)
+
+---
+
+## Part 2 — Can this harness be supported?
+
+A harness can support Superpowers only if it can do all of the following. Check
+these before writing code — if the first one fails, stop.
+
+### Hard requirement: automatic session-start injection
+
+The harness must let you inject text into the model's context **at the start of
+every session, with no per-session opt-in by your human partner.** This is the
+one non-negotiable capability. It can take any form:
+
+- a **hook/event system** that runs a shell command at session start and reads
+  its stdout (Claude Code, Codex, Cursor, Copilot CLI), or
+- an **in-process plugin/extension** with a session-start or message lifecycle
+  callback that can mutate the message array (OpenCode, pi), or
+- an **instructions-file** convention where the harness loads a context file that
+  *your installed extension ships and declares* (e.g. Gemini's `contextFileName`
+  pointing at the extension's own `GEMINI.md`) — not a file you edit in the user's
+  home.
+
+If the only way to get Superpowers in front of the model is for your human
+partner to opt in each session (paste a prompt, run a command, enable a mode),
+the harness
+**cannot** be properly supported. The acceptance test in Part 3 will fail, and
+the PR will be closed. This is the single most common reason a "port" isn't a
+real port.
+
+### The rest of the capability checklist
+
+| Capability | Why it's needed | If absent |
+|---|---|---|
+| **Skill discovery + invocation** | The model must be able to load a skill's full content on demand | If there's no native skill tool, the sanctioned fallback is to `read` the relevant `SKILL.md` directly — see Part 5. A harness with neither a skill tool nor file-read cannot work. |
+| **File read / write / edit** | Nearly every skill manipulates files | Essential. No workaround. |
+| **Run shell commands** | TDD, verification, git workflows | Essential. |
+| **Subagent / task dispatch** | `dispatching-parallel-agents`, `subagent-driven-development` | Degradable: if unavailable, those specific skills tell the model to do the work inline or report the missing capability — *never* to invent a `Task` call. Some harnesses gate this behind a config flag (e.g. Codex needs multi-agent enabled). |
+| **Todo / task tracking** | Progress tracking in several skills | Degradable: fall back to a plan file or `TODO.md`. |
+| **Web fetch / search** | A few skills | Degradable. |
+| **Shell or polyglot script execution (Windows)** | Only for the shell-hook shape, only if you want Windows support | See Part 7. In-process-plugin harnesses sidestep this entirely. |
+
+"Degradable" means: the skill already has fallback wording for the missing
+tool. Your job in the tool mapping is to point at the real tool when it exists
+and reuse that fallback wording when it doesn't.
+
+### You may not need a new directory at all
+
+Some "new harnesses" are really existing integrations under a different
+installer. Factory's Droid, for example, consumes the Claude Code plugin via its
+own `plugin install` command and needs no new files here. Before building,
+check whether the harness can simply load an existing manifest. A port that adds
+nothing to this repo but a paragraph in the README is a perfectly good outcome.
+
+---
+
+## Part 3 — Definition of done
+
+A port is finished when **all** of these are true:
+
+1. The `using-superpowers` bootstrap loads at session start, every session, with
+   no per-session opt-in.
+2. A tool mapping exists for the harness (in
+   `references/<harness>-tools.md`, inline in the bootstrap, or both — per Part 5).
+3. Skills can actually be invoked — natively, or via the documented
+   read-`SKILL.md` fallback — and the model follows them.
+4. **The acceptance test passes.** In a clean session, the user message:
+
+   > Let's make a react todo list
+
+   auto-triggers the `brainstorming` skill *before any code is written*. Capture
+   the full transcript — the PR requires it.
+5. Tests cover the integration (Part 5) and pass.
+6. A real user can install it through the harness's own mechanism (not by
+   hand-copying files), and the version is tracked in `.version-bump.json` where
+   applicable (Part 6). Note that some installers rewrite or strip the manifest on
+   install (one drops it to just `{"name": …}`), so "the *installed* files report
+   the repo version" is not always achievable — track the version at the source
+   manifest and don't treat a rewritten installed manifest as a failure.
+
+A quick smoke check before the full acceptance test: start a session and ask the
+model to describe its superpowers. If the bootstrap injected, it knows it has
+them. (OpenCode's install doc uses `opencode run --print-logs "hello" 2>&1 |
+grep -i superpowers` for the same goal via a different mechanism — log-grep
+rather than asking the model; the `2>&1` matters because logs go to stderr. Find
+your harness's equivalent.)
+
+---
+
+## Part 4 — Choose your integration shape
+
+There are three structural shapes, distinguished by *how you get the bootstrap
+in front of the model*. Pick the one that matches what your harness exposes,
+then copy that reference implementation. The shape determines almost everything
+in Part 5 — the steps below branch on it.
+
+### How to tell which shape you have
+
+Before routing, learn the harness's *actual* mechanism — and don't assume it's
+well documented or that it behaves like whatever harness it forked from.
+
+**Find the surface:**
+
+- **Search the web for the harness's docs** (extension / plugin / hook / skill /
+  MCP / "context file" / "rules file"). Vendor tools change fast; search rather
+  than trust training knowledge.
+- **Find and read an existing third-party extension/plugin for the harness.** A
+  real working example beats docs — it shows the manifest shape, the install
+  command, and which components the harness actually loads.
+- Check what the harness loads at startup: a settings file? an extensions
+  directory? a per-project or global instructions file (`AGENTS.md`, `<NAME>.md`)?
+
+**If it's underdocumented, reverse-engineer it empirically** (a real porter has
+had to do every one of these):
+
+- `strings` the binary / grep the install tree for hook event names, config
+  paths, and the instructions file it reads.
+- **Ask the running model to enumerate its own tool names** — e.g. "list the
+  exact machine names of every tool you can call." This is the authoritative way
+  to get tool names without inventing them (see Step 4).
+- Prove every assumption with a **unique-marker test**: inject a nonsense token
+  through the mechanism you think works, start a fresh session, and confirm the
+  token actually reached the model.
+
+**A fork does not inherit its parent's behavior.** A harness derived from another
+(e.g. a Gemini-derived CLI) may expose the parent's manifest fields and
+`@`-include syntax and *still not honor them the same way*. Verify with a marker;
+never assume the parent's recipe transfers.
+
+Then route to a shape:
+
+- Shell command at session start whose stdout is read → **Shape A**.
+- Plugin/extension module with lifecycle callbacks you run code in → **Shape B**.
+- Only ever an always-on instructions file, no hook and no code plugin →
+  **Shape C**.
+
+**Shapes compose — they are not mutually exclusive.** The *skill-discovery*
+mechanism and the *bootstrap* mechanism need not be the same shape — but **both
+must still ride the install mechanism** (rule 2). Decide the two questions
+separately: *where do skills get discovered?* and *how does the bootstrap reach
+the model every session?* A harness might install skills via a plugin yet need
+the bootstrap delivered another install-shipped way (an extension-declared
+context file, or — see below — by the harness surfacing the installed
+`using-superpowers` skill's own description at session start). If more than one
+install-mechanism surface injects automatically, prefer the most reliable. What
+you may **not** do is bridge a gap by editing the user's global config.
+
+### Shape A — Shell-hook
+
+The harness has a hook system that runs a shell command at session start and
+reads JSON from its stdout. The configured command runs `run-hook.cmd`, a
+polyglot wrapper that just locates bash and dispatches the named script; the
+script (`hooks/session-start`, or a harness-specific variant like
+`hooks/session-start-codex`) is what reads `using-superpowers/SKILL.md` and
+prints a JSON object whose **field name and nesting differ per harness**.
+
+- Reference: `hooks/session-start` (and `hooks/session-start-codex`),
+  `hooks/run-hook.cmd`, and the per-harness hook config `hooks/hooks.json`
+  (Claude Code), `hooks/hooks-codex.json` (Codex), `hooks/hooks-cursor.json`
+  (Cursor).
+- Manifests: `.codex-plugin/plugin.json`, `.cursor-plugin/plugin.json` point the
+  harness at `./skills/` and the right `hooks-*.json`. (Claude Code's
+  `.claude-plugin/plugin.json` sets neither field — it auto-discovers `skills/`
+  and `hooks/hooks.json` by convention.)
+
+> **A hook *system* is not a session-start *event*.** A harness can have a
+> `hooks.json` mechanism — and even contain the literal string `SessionStart` in
+> its binary — while having no hook event that fires at session start and can
+> inject context. (One real harness only exposed pre/post-tool and stop events;
+> the `SessionStart` strings were telemetry.) Confirm the *specific event* you
+> need exists and can write to the model's context before committing to Shape A.
+> If it can't, the bootstrap belongs in an instructions file (Shape C) instead.
+
+### Shape B — In-process plugin / extension
+
+The harness loads a JS/TS module that exposes lifecycle callbacks. You register
+the skills directory through the harness's API and inject the bootstrap by
+mutating the message array in code.
+
+- Reference: `.opencode/plugins/superpowers.js` (JavaScript) and
+  `.pi/extensions/superpowers.ts` (TypeScript). pi is the closest reference for
+  any harness that has **no native skill tool**.
+
+### Shape C — Instructions-file
+
+The harness has neither a shell hook nor a code plugin — its session-start
+surface is a context file that *your installed extension ships and the manifest
+declares* (e.g. Gemini's `contextFileName` → the extension's own `GEMINI.md`).
+You can't run code or mutate messages; the extension's context file points at the
+bootstrap. There is no injector to assemble a string or strip frontmatter — the
+harness loads the referenced content as-is. **This works only because the file is
+part of the installed extension** — never substitute "edit the user's global
+`GEMINI.md`/`AGENTS.md`" for shipping your own (rule 2).
+
+- Reference: `gemini-extension.json` (manifest, with `contextFileName`),
+  `GEMINI.md` (two `@`-includes — the bootstrap skill and the tool-mapping
+  reference), `skills/using-superpowers/references/gemini-tools.md`.
+- Note: `@`-include is a Gemini feature. If your harness loads an instructions
+  file but has no include syntax, you must inline the bootstrap content into the
+  file instead.
+- **Don't trust that an `@`-include is actually expanded — prove it.** A
+  Gemini-*derived* harness can accept `@./path` syntax yet treat it as a *hint
+  the model may choose to read* (it emits a file-read tool call) rather than a
+  guaranteed inline expansion. That's the difference between the bootstrap being
+  reliably present every session and the model maybe-reading it. Run a
+  unique-marker test: if the marker isn't in context *without* a tool call,
+  **inline the content** rather than `@`-include it.
+
+### Routing table
+
+| If the harness… | Use shape | Copy from |
+|---|---|---|
+| runs a shell command at session start and reads its stdout | A (shell-hook) | Codex (`hooks/session-start-codex` + `hooks/hooks-codex.json` + `.codex-plugin/`) |
+| is a JS/TS plugin host with session/message lifecycle callbacks | B (in-process) | OpenCode (`.opencode/`) — or pi (`.pi/`) if it has no native skill tool |
+| ships an extension-declared context file it always loads | C (instructions-file) | Gemini (`gemini-extension.json` + `GEMINI.md` + `references/gemini-tools.md`) |
+| has a plugin install command and a manifest `contextFileName` (or equivalent) the installer keeps | C via the plugin installer | Antigravity (`.antigravity-plugin/` — `agy plugin install` ships a generated context file; verify the installer preserves it — Part 6) |
+
+Most real harnesses fit one row cleanly; the last is the hybrid case (rule 2 still
+holds — the bootstrap rides the install mechanism, never a user-config edit).
+
+---
+
+## Part 5 — The porting procedure
+
+### Step 1 — Study the closest reference implementation
+
+Open the files named in Part 4 for your shape and read them end to end. The
+patterns below are summaries; the code is the spec.
+
+### Step 2 — Create the manifest / entry point
+
+Create whatever the harness uses to recognize the plugin. Match the existing
+ones in spirit:
+
+- **Shape A:** a `*-plugin/plugin.json` (see `.codex-plugin/plugin.json`) with
+  `name`, `version`, `description`, author/license/keywords, `"skills":
+  "./skills/"`, and `"hooks": "./hooks/hooks-<harness>.json"`. Plus the
+  `hooks-<harness>.json` itself, registering a session-start hook whose command
+  invokes `run-hook.cmd`.
+- **Shape B:** the module the harness loads (e.g. `.<harness>/plugins/*.js`) plus
+  whatever package metadata it needs to be discovered. The committed package
+  metadata is the **repo-root `package.json`**: `main` points at the OpenCode
+  plugin, the `pi` field (`pi.extensions`, `pi.skills`) plus the `pi-package`
+  keyword declare the pi extension. Per-harness local manifests and lockfiles are
+  kept out of git — `.opencode/.gitignore` excludes `node_modules`,
+  `package.json`, and lockfiles. Do the same for your harness's *local* install
+  artifacts so they don't pollute the repo — but never gitignore the repo-root
+  `package.json`, which is the tracked source of truth.
+  - **Build/dependency check.** Decide how the harness loads your module:
+    does it run the source directly (pi's `.ts` is referenced as-is from
+    `package.json`; OpenCode ships plain `.js`), or does it need a transpile/build
+    step? Superpowers is zero-runtime-dependency. pi's `import type
+    { ExtensionAPI }` works specifically because the harness runs the `.ts`
+    directly, supplies that type at load, and the repo never type-checks the file
+    in CI — the import isn't even declared as a dependency. If *your* harness
+    actually type-checks or bundles the plugin, that breaks: an undeclared type
+    import fails, and the PR rules only carve out *runtime* deps for new
+    harnesses, not dev/type packages. If you hit this, confirm the approach with
+    the maintainer rather than quietly adding a dependency. Keep any build output
+    out of git and document the command.
+- **Shape C (instructions-file):** a small manifest (see `gemini-extension.json`:
+  `name`, `description`, `version`, `contextFileName`) plus the context file
+  itself (`GEMINI.md` is just two `@`-includes: the bootstrap skill and the
+  tool-mapping reference). The Gemini manifest has no `skills` field — Gemini
+  auto-discovers the `skills/` directory bundled in the installed extension. If
+  your harness has a native skill tool but no manifest field to register the
+  directory, you must find its discovery convention (read its extension docs),
+  then verify empirically: after wiring, ask the model to list its available
+  skills — if the bundled skills don't appear, discovery isn't working yet.
+
+### Step 3 — Wire the bootstrap injection
+
+This is the heart of the port. The shared goal: at session start, get the
+`using-superpowers` skill content (wrapped in `<EXTREMELY_IMPORTANT>` tags) plus
+the harness's tool mapping in front of the model, with a note that the skill is
+already active so the model doesn't try to load it again. *How* you do that —
+and what you assemble vs. what the harness loads raw — depends entirely on your
+shape. Do **not** apply one shape's recipe to another.
+
+**Shape A — a script reads `SKILL.md` and prints the harness's JSON.** The
+dispatched script (`hooks/session-start`) `cat`s the whole `SKILL.md` (frontmatter
+included — that's fine; it's emitted verbatim), wraps it with the "You have
+superpowers… for all other skills use the Skill tool" preamble, escapes it, and
+prints the harness's JSON shape. The tool mapping for Shape A does **not** go
+inline here — it lives in `references/<harness>-tools.md` (Step 4). Get the JSON
+output shape exactly right. `hooks/session-start`
+detects the harness from environment variables and prints *one of three* shapes:
+
+- Cursor (`CURSOR_PLUGIN_ROOT` set): `{ "additional_context": "…" }`
+- Claude Code (`CLAUDE_PLUGIN_ROOT` set, `COPILOT_CLI` unset):
+  `{ "hookSpecificOutput": { "hookEventName": "SessionStart", "additionalContext": "…" } }`
+- Copilot CLI / SDK standard (else): `{ "additionalContext": "…" }`
+
+This is a trap. Emitting the wrong field, or an extra one, means the bootstrap
+either never injects or injects twice (Claude Code reads both
+`additional_context` and `hookSpecificOutput` without de-duplicating, so emitting
+both double-injects). Find the
+exact field, nesting, and event-matcher values your harness expects. Then
+decide: add a fourth branch to `hooks/session-start`, or — if the harness needs
+a different bootstrap message or env contract — add a dedicated
+`hooks/session-start-<harness>` script, the way Codex did. If you add a branch
+and your harness *also* sets an env var an earlier branch keys on (some harnesses
+set `CLAUDE_PLUGIN_ROOT` too), order your branch before the one that would
+otherwise shadow it. Match the harness's
+own event-matcher strings (Claude Code uses `startup|clear|compact`, Codex
+`startup|resume|clear`, Cursor `sessionStart`); wrong matchers mean the hook
+silently never fires.
+
+The **hook-config schema itself varies per harness** — don't assume the
+Claude/Codex shape is universal. Compare `hooks/hooks.json`,
+`hooks/hooks-codex.json`, and `hooks/hooks-cursor.json`: Cursor's uses
+`"version": 1`, a lowercase `sessionStart` key, a relative
+`./hooks/run-hook.cmd` command, and omits the `matcher`/`type`/`async` fields the
+others use. Match your `hooks-<harness>.json` to whichever existing file is
+closest, not to a single canonical template.
+
+The hook **command string references a harness-provided plugin-root variable**,
+and its name differs per harness: `hooks.json` uses `${CLAUDE_PLUGIN_ROOT}`,
+`hooks-codex.json` uses `${PLUGIN_ROOT}`, Cursor uses a relative path. Use
+whatever your harness exports. (The `session-start` script re-derives the root
+itself via `dirname`, so the script body doesn't depend on this — but the
+command in the manifest does.)
+
+**Discovering the harness's contract.** The three facts above — env var, JSON
+field/nesting, matcher strings — are the harness's contract, not Superpowers',
+so you have to source them. Read the harness's hook docs, or find out
+empirically: register a throwaway session-start hook that dumps its environment
+and emits a marker, then observe which env var identifies the harness and
+whether/how the harness ingests your stdout. Pin these down before writing the
+real branch.
+
+**Shape B — assemble the string in code, then inject as a user message.** Here
+you build the bootstrap yourself: read `SKILL.md`, strip its YAML frontmatter,
+and assemble `<EXTREMELY_IMPORTANT>` + a short preamble that the skill is already
+loaded and must not be re-invoked + the stripped body + the inline tool mapping +
+`</EXTREMELY_IMPORTANT>`. One subtlety the references disagree on: OpenCode's
+preamble says "do NOT use the skill tool…" (assumes a `skill` tool exists), while
+pi's just says "do not try to load using-superpowers again." If your harness has
+no skill tool, use pi's wording, not OpenCode's.
+
+Inject the result as a **user-role message, not a system message** — system
+messages bloat tokens when repeated every turn (#750) and multiple system
+messages break some models (#894). Three things you must replicate:
+
+- **Dedup guard.** The lifecycle callback can fire repeatedly (OpenCode's
+  transform runs on *every* agent step; pi's `context` fires per turn). Before
+  injecting, check whether a bootstrap marker is already present and skip if so.
+  (The references pick different markers — pi a custom string, OpenCode the
+  `EXTREMELY_IMPORTANT` tag; matching the tag is more robust since it needs no
+  harness-specific constant.) Cache the bootstrap content at module level so
+  you're not re-reading and re-parsing `SKILL.md` on every call (#1202).
+- **Compaction.** If the harness compacts/summarizes history, re-inject
+  afterward. pi sets an `injectBootstrap` flag on `session_start` and
+  `session_compact`, clears it on `agent_end`, and inserts the message *after*
+  any leading compaction-summary messages. OpenCode relies on its per-step
+  re-injection plus the dedup guard.
+- **Message-object shape is per-harness — discover yours, don't copy a literal.**
+  The two references use *incompatible* shapes: pi builds
+  `{ role, content: [{ type, text }], timestamp }`; OpenCode manipulates
+  `message.info.role` and `message.parts[]`. Find your harness's message shape
+  from its API; copying a reference's object literal verbatim will fail silently.
+
+**Shape C — point your extension's context file at the bootstrap; assemble
+nothing.** There is no injector, so you do *not* strip frontmatter or build a
+wrapped string. The context file your extension ships (declared by the manifest —
+*not* the user's own global file) pulls in two things: the `using-superpowers`
+skill and the harness's tool-mapping reference. `GEMINI.md`
+does this with two `@`-includes (`@./skills/using-superpowers/SKILL.md` and
+`@./skills/using-superpowers/references/<harness>-tools.md`); the harness loads
+them raw, frontmatter and all, and `SKILL.md` already carries its own
+`<EXTREMELY-IMPORTANT>` block internally. If your harness has no include syntax,
+inline the content into the instructions file instead. Gemini ships **no**
+"already loaded, don't re-invoke" preamble — for an `@`-include harness the
+content is the active instruction set, not a skill the model would re-load. If
+you find your harness does try to re-invoke, add that note as a literal line in
+the instructions file (you have no code to add it any other way).
+
+### Step 4 — Write the tool mapping
+
+Translate the action vocabulary into the harness's real tools. Cover every one
+of these actions (omit only what genuinely doesn't apply):
+
+- read a file
+- create / edit / delete a file (one `apply_patch`-style tool, or separate
+  write/edit?)
+- run a shell command
+- search file contents / find files by name (grep, glob)
+- fetch a URL / web search
+- **dispatch a subagent**, including how to pass the agent type — and any config
+  flag needed to enable it
+- **create / update todos** (treat older `TodoWrite` references as this action)
+- **invoke a skill** — see Step 5
+
+**Get the real tool names from the harness; never invent them.** If the docs
+don't list them, the authoritative source is the harness itself: in a live
+session, ask the model to "list the exact machine names of every tool you can
+call, one per line" and use what it reports.
+
+**How the harness finds the `skills/` directory is itself per-harness** — confirm
+it, don't assume. Possibilities: a manifest `skills` path field (Codex's
+`"skills": "./skills/"`); a *co-located* `skills/` the harness auto-scans (where a
+path field is **ignored** — one real harness only scanned a `skills/` sitting next
+to `plugin.json`); an API/registration call (OpenCode, pi); or you stage an
+install dir that pairs the manifest with a **symlink to the repo's `skills/`** and
+point the installer at the staging dir (verify the installer *dereferences* the
+symlink and copies the real files — confirm with `agy plugin validate`/`install`
+or the equivalent before relying on it). A `skills` path field is *not* portable.
+
+Where the mapping lives depends on shape:
+
+- **Shape A:** put it in `skills/using-superpowers/references/<harness>-tools.md`.
+  The agent reaches it from the bootstrap — `SKILL.md`'s "Platform Adaptation"
+  section links the per-harness references files. (Shape A harnesses have no
+  instructions file; the mapping is *not* inlined into the hook output.)
+- **Shape B:** the mapping is typically inlined into the bootstrap string you
+  inject (see the `toolMapping` constant in `superpowers.js`). pi keeps it in
+  *both* places — `piToolMapping()` inline **and** `references/pi-tools.md`. If
+  you maintain it in two places, update both, or the port is half-done.
+- **Shape C:** put it in `references/<harness>-tools.md` and pull it into the
+  always-loaded instructions file (e.g. `GEMINI.md` `@`-includes
+  `gemini-tools.md`).
+
+You may also add a one-line pointer to your harness in `SKILL.md`'s "Platform
+Adaptation" section so an agent reading the bootstrap knows where its mapping
+lives. This is the one edit to a `SKILL.md` a port may make — and only because
+that section is a pointer list, not behavior-shaping content. It does not violate
+the "don't edit skill bodies" rule (Part 1); do not touch anything else in any
+skill. (The list is a convenience pointer, not an exhaustive registry — not every
+harness is listed.)
+
+### Step 5 — Handle a harness with no native skill tool
+
+`using-superpowers/SKILL.md` tells the model to *never read skill files manually
+with file tools — always use your platform's skill-loading mechanism.* The point
+is "don't bypass the mechanism," not "never use file-read." What counts as "your
+platform's mechanism" depends on the harness — and for a harness with no skill
+tool, the documented mechanism *is* reading `SKILL.md`. So reading it there
+honors the rule rather than breaking it. Distinguish three cases:
+
+1. **Native `Skill`-style tool** (Claude Code, Copilot CLI, Gemini's
+   `activate_skill`): point the mapping at that tool.
+2. **Native skill *discovery* but no `Skill` tool** (pi, Antigravity): the harness
+   can find and list skills, but the model can't call a tool to load one. Get the
+   skills installed where the harness scans (pi registers via `resources_discover`
+   → `skillPaths`; OpenCode via its `config` hook; `agy plugin install` copies
+   them in), and tell the model to load a skill by **reading its `SKILL.md` with
+   the file-read tool when the skill applies** — the sanctioned mechanism here,
+   the way `references/pi-tools.md` states it.
+
+   **For the bootstrap itself, prefer a declared context file (Part 6).** If the
+   harness has a `contextFileName`-style manifest field — as Antigravity does —
+   ship a generated context file through the installer: it's guaranteed-loaded and
+   carries both the `using-superpowers` content and the tool mapping. That is the
+   strong, preferred path.
+
+   **Fallback — the surfaced skill index.** If there's no context-file field but
+   the harness surfaces each installed skill's name + description at session start,
+   you need *neither* a built index nor a runtime-list instruction — the harness
+   is the index, and `using-superpowers`'s own surfaced description can be what
+   triggers the model to load it. This is softer than a declared context file;
+   two things it does **not** give you, versus a context file / hook / in-process
+   injector — account for both:
+   - **It bootstraps *triggering*, not the *tool mapping*.** An injector prepends
+     `<harness>-tools.md` alongside `using-superpowers` every session. Here nothing
+     injects the mapping — the model only sees skill *descriptions* and must *read*
+     your `references/<harness>-tools.md` when it needs tool names. It works
+     because skills name actions (the model reads the mapping when it acts), but
+     it's softer than injection. Make sure the mapping is reachable from what the
+     model loads — e.g. linked from `SKILL.md`'s Platform Adaptation section and
+     installed alongside the skills — not just sitting in the repo.
+   - **There's no structural guarantee the trigger fires.** No `<EXTREMELY_IMPORTANT>`
+     wrapper, no dedup, no re-injection after compaction — firing depends on the
+     model choosing to act on a description it sees in the index. This is exactly
+     why the acceptance test is mandatory here: it is the *only* guarantee, so run
+     it on the model(s) your users will actually use, not just the strongest one.
+3. **No skill system at all:** there is nothing to register, and the *only*
+   mechanism is the model reading `SKILL.md` on demand. But the model can't read
+   what it can't find: `using-superpowers/SKILL.md` does **not** enumerate the
+   available skills, so on its own the model won't know which skills exist or
+   their triggers. You must supply a discovery path. Two options, and they differ
+   in durability: (a) generate a skill index (each `skills/*/SKILL.md`'s `name` +
+   `description` frontmatter) and place it *inside* the `<EXTREMELY_IMPORTANT>`
+   wrapper alongside the tool mapping (Shape B recipe above) so it's covered by
+   the dedup guard — but a build-time index goes stale as skills are added; or
+   (b) instruct the model to list `skills/*/SKILL.md` at runtime and read their
+   frontmatter to find a match — slower but never stale. Prefer (b) unless you
+   have a reason not to. Without either, a no-skill-system port loads the
+   bootstrap but silently never triggers any other skill.
+
+In cases 2 and 3, say plainly in your tool mapping that reading `SKILL.md` is the
+blessed path, so the model doesn't think it's violating the "never read skill
+files" rule. Don't go hunting for a `skillPaths`-style registration API in a
+harness that has no skill system — case 3 has none.
+
+### Step 6 — Add tests
+
+Match the existing per-harness test style:
+
+- **Shape A:** assert the hook's stdout has the exact JSON shape your harness
+  consumes, and that it contains the bootstrap. See `tests/hooks/test-session-start.sh`,
+  which validates each harness's output shape.
+- **Shape B:** a unit test that fakes the harness's plugin API and asserts the
+  lifecycle handlers register, the bootstrap injects once, the dedup guard
+  works, and (if relevant) compaction re-injection works. See
+  `tests/pi/test-pi-extension.mjs`. Add an isolated-install integration check in
+  the style of `tests/opencode/`.
+- If the bootstrap is cached, test that the cache behaves when the file is
+  missing (see the OpenCode caching tests).
+
+These automated tests cover the wiring; the live tmux run in Step 7 is what
+proves the integration actually triggers skills.
+
+### Step 7 — Install locally, then drive a live instance to verify
+
+You cannot confirm a port works by reading code. You have to run the harness with
+your in-progress port loaded and watch a real session — which is also how you
+produce the transcript the PR requires.
+
+**Install locally.** Point a *local* instance of the harness at your working
+tree, not a published build:
+
+- **Shape A / C:** install the plugin/extension from this repo's local path (or
+  symlink its directory into wherever the harness looks). Find the harness's
+  "install from a local directory / git checkout" path in its docs.
+- **Shape B:** register the local module — e.g. an `opencode.json` `plugin`
+  entry pointing at the local path, or pi resolving the `package.json` fields
+  from the repo.
+
+Reinstall after each change and restart the harness, since the bootstrap loads at
+startup.
+
+**Drive it with tmux.** Most harnesses are interactive REPLs/TUIs that can't be
+driven by piping stdin, so run the harness inside a detached tmux session and
+control it with `send-keys` / `capture-pane`. A harness may advertise a
+non-interactive "run one prompt" mode (e.g. `opencode run "..."`) — try it for the
+quick smoke check, but **don't depend on it**: these modes are frequently flaky,
+auth-gated, or trust-gated (one real harness's `--print` mode hung and timed out
+with no output every time). Be ready to do *everything*, including the smoke
+check, through tmux.
+
+**Clear the gates first, or tmux stalls silently.** Many harnesses block on
+first-run onboarding, a "do you trust this folder?" prompt, a sandbox mode, or a
+permission gate — and a detached tmux session will just sit there with no error
+while it waits. Before the run, pre-trust your scratch directory (in the harness's
+settings/config) or be prepared to answer those prompts via `send-keys`, and
+account for the harness's startup time in your first `sleep`.
+
+```bash
+# 1. Launch the harness detached, in a throwaway project dir
+mkdir -p /tmp/port-smoke
+tmux new-session -d -s port-test -c /tmp/port-smoke '<harness-launch-command>'
+
+# 2. Let it initialize — real TUIs take longer than you think (10s+ with a model
+#    handshake); tune this. THEN capture and clear any blocking modal before you
+#    type a prompt: first-run onboarding and "trust this folder?" are modal, so
+#    keystrokes sent during them select menu items instead of typing your prompt.
+sleep 12
+tmux capture-pane -t port-test -p          # onboarding / trust prompt? answer it via send-keys first
+# (e.g. tmux send-keys -t port-test Enter   # to accept a trust prompt — inspect before assuming)
+
+# 3. Smoke check: does the model know it has superpowers?
+#    Send the text and Enter as SEPARATE send-keys with a beat between them —
+#    sending them together races on some TUIs (Enter arrives before the text lands).
+tmux send-keys -t port-test 'What are your superpowers?'; sleep 0.4; tmux send-keys -t port-test Enter
+sleep 5
+tmux capture-pane -t port-test -p          # reply should show it knows its skills
+
+# 4. Acceptance test: exact prompt (note the escaped apostrophe), fresh session
+tmux send-keys -t port-test 'Let'\''s make a react todo list'; sleep 0.4; tmux send-keys -t port-test Enter
+# poll until the turn finishes — re-capture every few seconds, don't capture once
+sleep 8
+tmux capture-pane -t port-test -p          # PASS = brainstorming triggers BEFORE any code
+
+# 5. Save the transcript for the PR, then clean up
+tmux capture-pane -t port-test -p > /tmp/port-smoke/transcript.txt
+tmux kill-session -t port-test
+```
+
+tmux gotchas that bite here: wait after launch before the first capture; send the
+prompt text and `Enter` as *separate* `send-keys` calls with a short `sleep`
+between them (sending them together races on some TUIs), and `Enter` is a key name
+not `\n`; the agent's turn takes time, so **poll `capture-pane` in a loop** rather
+than capturing once; `capture-pane` shows only the visible pane, so for a long
+conversation use the harness's own transcript/log file as the record of truth;
+always `kill-session` when done.
+
+If the smoke check shows the model *doesn't* know it has superpowers, the
+bootstrap isn't loading — fix that before bothering with the acceptance test.
+
+---
+
+## Part 6 — Distribution and release
+
+A working integration in this repo isn't usable until a real user can install
+it. Distribution differs per harness ecosystem — find yours:
+
+| Channel | Example | What you do |
+|---|---|---|
+| Native plugin marketplace | Claude Code | Register in `.claude-plugin/marketplace.json`; users `/plugin install`. The external `superpowers-marketplace` repo is the source of truth users install from — see the release steps in `CLAUDE.md`. |
+| External marketplace fork, synced by script | Codex | `scripts/sync-to-codex-plugin.sh` rsyncs the tracked plugin files into a separate fork repo and opens a PR. Read its include/exclude list so you ship the right tree (it deliberately drops repo-internal dirs and other harnesses' dotdirs). |
+| Git-URL extension install | Gemini, OpenCode | Users install from a git URL (`gemini extensions install …`; an `opencode.json` `plugin` array entry). Document the exact command. |
+| Package-manifest fields | pi | Declared through fields in the repo-root `package.json`; users install via the harness's package command. |
+| Local installer (plugin install) | Antigravity (`agy`) | A small `install.sh` that runs the harness's own `agy plugin install` against a staging dir holding the manifest, the skills, and a generated `contextFileName` context file (the bootstrap). Everything arrives through the install mechanism — *not* by editing the user's config (see below). |
+
+Then:
+
+- **A plugin installer may silently strip *undeclared* files — so make the
+  bootstrap a file the installer *recognizes*, never a user-config edit.** A
+  `plugin install` typically copies only the components it knows about
+  (skills/agents/commands/mcp/hooks/context) and discards anything else, so a
+  context file the manifest doesn't declare just vanishes from the install. The
+  fix is **not** to give up and write into the user's config (**rule 2**) — it's
+  to declare the bootstrap as a recognized component. In escalation order:
+  - **Ship a context file the manifest declares.** If the harness has a
+    `contextFileName`-style field (an extension-declared file it loads every
+    session), that is the strongest clean bootstrap: declare it, and the installer
+    preserves it *and* the harness loads it. Generate it at install time from the
+    live `using-superpowers/SKILL.md` + the tool mapping (wrapped in
+    `<EXTREMELY_IMPORTANT>`) so the installed bootstrap never drifts. This is what
+    `.antigravity-plugin/install.sh` does — `agy plugin install` reports
+    `✔ context : ANTIGRAVITY.md`, and a clean session reads `using-superpowers`'s
+    SKILL.md, loads `brainstorming`, and enters the brainstorming flow before any
+    code. **Verify with a marker** that the installer keeps the file and the
+    harness loads it: one porter wrongly concluded it couldn't, because they
+    shipped the file *without* declaring `contextFileName` and it was stripped as
+    unrecognized.
+  - **Otherwise lean on the installed `using-superpowers` skill itself.** If the
+    harness surfaces each installed skill's name + description at session start,
+    the `using-superpowers` description ("Use when starting any conversation…")
+    can prompt the model to load it — installing the skill *is* the bootstrap.
+    Softer (no guaranteed wrapper; it carries triggering but not the tool mapping
+    — see Step 5), so prefer the declared context file when available.
+  - If neither works, the harness cannot be cleanly supported yet — **say so**
+    and raise it, rather than hand-editing the user's config.
+
+- **Write install docs.** A `docs/README.<harness>.md` and/or a
+  `.<harness>/INSTALL.md` (see `docs/README.opencode.md` and
+  `.opencode/INSTALL.md`), plus an install section in the top-level `README.md`.
+  The only supported install action is **running the harness's own install
+  command** (`agy plugin install`, `gemini extensions install`, `/plugin
+  install`, etc.). Hand-copying skill files and editing the user's global/personal
+  config are *both* off-limits (rule 2 / the PR rules). If the harness has no
+  install command at all — its only surface is a user-owned config file — then it
+  fails the "deliver via install mechanism" rule, and you should raise that rather
+  than ship an installer that edits the user's files.
+- **Register the version.** If your harness introduces a *new* versioned
+  manifest, add its path and version field to `.version-bump.json` so
+  `scripts/bump-version.sh` keeps it in lockstep (read that file to see what's
+  currently tracked). A new manifest that isn't registered there will ship a
+  stale version. If your harness instead rides an already-tracked file — pi
+  declares itself in the repo-root `package.json`, which is already listed —
+  there's nothing new to add.
+- **If no existing channel fits, you're standing up a new one.** None of the four
+  rows may match your harness. If it needs a Codex-style external fork sync,
+  `scripts/sync-to-codex-plugin.sh` is the template to clone (note its anchored
+  include/exclude list and its PR automation). And whenever you add a new
+  per-harness directory, add it to the *other* harnesses' sync excludes (e.g. the
+  EXCLUDES list in `sync-to-codex-plugin.sh`) so your dotdir doesn't leak into
+  their distributions.
+
+---
+
+## Part 7 — Cross-platform / Windows
+
+Only relevant to the shell-hook shape. `hooks/run-hook.cmd` is a polyglot: a
+single file that's valid as both a Windows batch script and a Unix shell script.
+On Windows, `cmd.exe` runs the batch portion, which locates `bash` (Git for
+Windows, then `bash` on PATH) and runs the named hook script; if no bash is
+found it exits cleanly so the harness still works, just without injection. On
+Unix, the leading `:` makes the batch block a no-op and the shell runs the
+script directly.
+
+Two rules this enforces, which you must respect:
+
+- **Hook scripts are extensionless** (`session-start`, not `session-start.sh`).
+  Claude Code's Windows handling prepends `bash` to any command containing
+  `.sh`, which would double-invoke. Name your hook script without an extension.
+- Don't write per-OS variants of the hook script. One extensionless bash script
+  plus the polyglot wrapper covers all three platforms.
+
+`hooks/run-hook.cmd` itself is the authoritative implementation — read it.
+(`docs/windows/polyglot-hooks.md` covers the background and rationale but
+describes an earlier per-script `.cmd`/`.sh` variant, so trust the code over that
+doc where they differ.)
+
+---
+
+## Part 8 — Submitting the PR
+
+- Target the **`dev`** branch. One harness per PR.
+- Fill in the PR template's **"New harness support"** section and paste the
+  complete acceptance-test transcript (the "Let's make a react todo list"
+  session showing `brainstorming` auto-triggering). A PR without this proof will
+  be closed.
+- Superpowers is a zero-dependency plugin. Don't add a third-party runtime
+  dependency. Adding a new harness is the one carve-out the contributor rules
+  allow, and even then keep it to what the integration strictly requires —
+  type-only imports that compile away are fine; runtime packages are not.
+- Don't touch skill bodies (Part 1). If you found yourself editing a `SKILL.md`
+  to make the port work, the fix belongs in your tool mapping instead.
+
+---
+
+## Appendix A — Reference integrations (current)
+
+Use this as the live index; when in doubt, read the files, not this table.
+
+| Harness | Entry point | Bootstrap mechanism | Tool mapping | Tests | Distribution |
+|---|---|---|---|---|---|
+| Claude Code | `.claude-plugin/plugin.json` + `hooks/hooks.json` | shell hook → `hooks/session-start` (`hookSpecificOutput.additionalContext`) | native `Skill` tool; `references/claude-code-tools.md` | `tests/hooks/` | marketplace |
+| Codex | `.codex-plugin/plugin.json` + `hooks/hooks-codex.json` | shell hook → `hooks/session-start-codex` | `references/codex-tools.md` | `tests/codex-plugin-sync/`, `tests/hooks/` | fork sync (`scripts/sync-to-codex-plugin.sh`) |
+| Cursor | `.cursor-plugin/plugin.json` + `hooks/hooks-cursor.json` | shell hook → `hooks/session-start` (`additional_context`) | `references/claude-code-tools.md` | `tests/hooks/` | hand-authored |
+| Copilot CLI | (shares Claude Code hook path; `COPILOT_CLI` env) | shell hook → `hooks/session-start` (`additionalContext`) | `references/copilot-tools.md` | `tests/hooks/` | — |
+| Gemini CLI | `gemini-extension.json` + `GEMINI.md` | instructions file `@`-includes bootstrap + mapping | `references/gemini-tools.md` | — | `gemini extensions install` |
+| OpenCode | `.opencode/plugins/superpowers.js` (declared via root `package.json` `main`) | in-process: `config` hook registers skills dir; `experimental.chat.messages.transform` injects user message | inline in `superpowers.js` | `tests/opencode/` | `opencode.json` plugin git URL |
+| pi | `.pi/extensions/superpowers.ts` | in-process: `resources_discover` registers skills; `context` event injects user message; lifecycle-flag + compaction-aware | `piToolMapping()` inline **and** `references/pi-tools.md` | `tests/pi/` | repo-root `package.json` fields |
+
+## Appendix B — Gotchas that have bitten porters
+
+- **Opt-in isn't a port.** If your human partner has to do anything per session
+  to get Superpowers, the acceptance test fails. Re-read Part 2.
+- **Wrong JSON field → silent failure or double injection.** Shape A only.
+  Confirm the exact field/nesting; Claude Code reads two fields without dedup.
+- **Hook-config schema varies per harness.** Shape A. Cursor's `hooks-cursor.json`
+  looks nothing like the Claude/Codex one (`version`, lowercase `sessionStart`,
+  relative command, no `matcher`/`type`/`async`). Match the closest existing file.
+- **Plugin-root env var differs per harness.** Shape A. The hook command uses
+  `${CLAUDE_PLUGIN_ROOT}` (Claude), `${PLUGIN_ROOT}` (Codex), or a relative path
+  (Cursor). Use what your harness exports; the script re-derives the root itself.
+- **System-message injection.** Shape B injects a *user* message on purpose
+  (#750, #894). Don't "fix" it to a system message.
+- **Per-step vs per-turn callbacks.** OpenCode fires every step (per-call dedup
+  guard); pi fires per turn (lifecycle flag + `agent_end` reset). Copying one
+  harness's dedup strategy onto the other's callback frequency breaks injection.
+- **Message-object shape is per-harness.** Shape B. pi and OpenCode use
+  incompatible shapes; discover yours, don't copy a reference's object literal.
+- **Hunting for a skill-registration API that doesn't exist.** A harness with no
+  skill system (not just no `Skill` tool) has nothing to register — the model
+  reads `SKILL.md` on demand. Don't assume a `skillPaths` equivalent exists.
+- **Mapping in two places.** For in-process plugins the mapping may live both
+  inline and in a `references/` file (pi). Update both.
+- **The "never read skill files" line.** It means "don't bypass your platform's
+  skill-loading mechanism," not "never use file-read." On a no-skill-tool harness
+  that mechanism *is* reading `SKILL.md` — say so explicitly in the mapping
+  (Part 5).
+- **`.sh` on Windows.** Keep hook scripts extensionless (Part 7).
+- **Unregistered version.** A new manifest not added to `.version-bump.json`
+  ships stale (Part 6).
+- **Editing skills to fit the harness.** Never. The fix goes in the tool mapping.