diff --git a/global/tools/code-modernization/SKILL.md b/global/tools/code-modernization/SKILL.md
index ace1213..7deed54 100644
--- a/global/tools/code-modernization/SKILL.md
+++ b/global/tools/code-modernization/SKILL.md
@@ -1,15 +1,173 @@
 ---
-name: code-modernization
-description: Modernize or refactor a legacy codebase incrementally while preserving business logic. Use for migrations (framework/language/version upgrades), killing tech debt, refactoring an old project, or "bring this up to date". Mirrors Anthropic's code-modernization methodology.
+name: code-modernizer
+description: >-
+  Modernize or refactor a legacy codebase incrementally while preserving business
+  logic. Replaces hand-rolled logic with the standard library, a native feature,
+  an already-installed dependency, or (only after live research) a well-vetted new
+  package, then applies minimal design patterns to whatever custom code remains.
+  Confirms scope first (full-codebase, one module/partial, or only the exact lines
+  named) and flags file count, line count, and breaking-change risk before
+  generating a large diff, asking instead of assuming when scope, a library choice,
+  or a behavior change is unclear.
+  Use for migrations (framework/language/version upgrades), killing tech debt,
+  refactoring an old project, or "bring this up to date". Use whenever the user
+  asks to refactor, modernize, de-bloat, clean up, simplify, upgrade, or audit
+  code; asks "is there a library for this", "don't reinvent the wheel", "replace
+  with a framework", "reduce boilerplate", or "apply proper design patterns"; wants
+  a root-cause fix over a quick patch; says "full upgrade" vs "partial upgrade" vs
+  "just fix this one thing"; or wants a legacy-code/tech-debt audit or a
+  dependency-choice recommendation.
+license: MIT
+attribution: >-
+  This skill's ladder is adapted from DietrichGebert/ponytail (MIT licensed).
+  See "Relationship to ponytail" below.
 ---
 
-# Code modernization
+# Code Modernizer
 
-For legacy/dated codebases (several of yours qualify). Modernize in safe,
-verifiable increments — never a big-bang rewrite. Keep a human in the loop at each
-gate.
+## Philosophy
 
-## 1. Assess (read-only first)
+A senior engineer isn't measured by how much code they wrote today, but by how
+little the system needs. Before touching anything, decide whether the code should
+be replaced with something already established. If custom code is genuinely
+necessary, write the least of it that solves the real problem without dropping
+behavior anyone relies on.
+
+This skill's core decision procedure is adapted from Dietrich Gebert's `ponytail`
+project (MIT licensed, github.com/DietrichGebert/ponytail). It extends ponytail
+two ways: it applies the same ladder retroactively to audit code that already
+exists, not just to gate new code being written, and it adds scope control, a
+pre-flight cost/impact gate, and a mandatory live-research step for whenever a
+genuinely new dependency is on the table. See "Relationship to ponytail" at the
+end.
+
+## The ladder
+
+Before writing, keeping, or replacing any piece of logic, stop at the first rung
+that holds:
+
+1. **Does this need to exist at all?** (YAGNI). If a feature isn't used, delete it
+   instead of modernizing it.
+2. **Already solved elsewhere in this codebase?** Reuse it, don't rewrite it.
+3. **Standard library does it?** Use it.
+4. **Native platform feature does it?** Use it. The browser already has
+   `<input type="date">`, so don't reach for a date-picker library.
+5. **Already-installed dependency does it?** Use it. Zero new install cost.
+6. **Is a new dependency genuinely justified?** Only after the research pass in
+   Step 3 below. Never skip straight here.
+7. **Can what's left be one line?** Make it one line.
+8. **Only then:** write the minimum code that works, shaped by whichever design
+   pattern (if any) removes real duplication. See
+   `references/design-patterns-cheatsheet.md`.
+
+The ladder runs after understanding the problem, not instead of it. Read the code
+and its tests before picking a rung (Step 2).
+
+## Two modes, same ladder
+
+- **Forward** (writing new code): apply the ladder before writing anything.
+- **Audit** (existing code): apply the same ladder retroactively. For every
+  hand-rolled block in scope, ask: "would rung 3, 4, 5, or a researched rung 6
+  now produce less code, or safer code, than what's already here?" If yes, and the
+  check in Step 4 clears it, propose the swap. This audit mode is the part
+  `ponytail` doesn't cover. It governs new code; this skill governs the code
+  that's already sitting in the repo.
+
+## Step 0: Scope handshake (every time, before any real work)
+
+Refactoring has a blast radius. Before generating anything beyond a one-file,
+one-function fix, pin down which of these three the user wants:
+
+- **Full**: a comprehensive pass across the named codebase or repo. Expect
+  multiple files and possibly breaking changes; produce a migration note.
+- **Partial**: bounded to one named module, directory, or feature area. No
+  drive-by edits outside that boundary, even if something nearby looks equally
+  outdated.
+- **Targeted**: only the exact file, function, or lines named. Nothing else
+  changes.
+
+If the request already states scope clearly ("just fix this function", "modernize
+the whole `utils/` folder"), proceed without asking. If it's ambiguous ("clean up
+this codebase", "make this better"), ask one direct question offering these three
+options before reading any more files than needed to ask it well. Don't default to
+Full because it seems more thorough. Full is the most expensive and highest-risk
+option, not the safe default.
+
+## Step 1: Pre-flight scan and cost/impact flag (Full/Partial only, skip for Targeted)
+
+Ground the estimate in real numbers instead of a guess. Run:
+
+```
+python3 scripts/preflight_scan.py <path>
+```
+
+It's stdlib-only Python, nothing to install. Report back to the user in a short
+block before generating anything:
+
+```
+Scope: <Full|Partial> on <path>
+~<N> files, ~<X> lines in range
+Dependencies already available: <short list from the manifest>
+Flagged high-cost: <any file over ~800 lines, or the pass touching 15-20+ files, name them>
+Estimated: <rough tool-call / diff count>, <low|medium|high> breaking-change risk
+Proceed as scoped, narrow it, or switch to Targeted?
+```
+
+Treat anything the scan flags as high-cost as its own decision point. Offer full
+detail there or a summarized diff, rather than silently generating all of it. Full
+rubric, including the flexibility trade-off, in `references/cost-impact-preflight.md`.
+
+## Step 2: Read before you touch (root cause, not a patch)
+
+Before proposing any swap, read what's actually there: the function, its tests,
+nearby comments, and the commit that introduced the "ugly" version if it's
+available. Hand-rolled code is sometimes just unmaintained. Sometimes it's
+load-bearing for an edge case the clean replacement doesn't handle. Confirm which
+one is in front of you before replacing it. If the tests don't cover a case the
+old code was clearly written for, say so instead of silently dropping it.
+
+## Step 3: Research before recommending a new dependency (mandatory, live)
+
+Rungs 1 through 5 need no research; they're free and already known to be safe.
+Rung 6, a genuinely new dependency, is the one place memory goes stale fast: a
+library that was the obvious choice eighteen months ago can be unmaintained,
+superseded, or carrying an open CVE today. Never recommend a package from memory
+alone. Check its current state first, live, with search. Checklist,
+current-as-of-lookup sources, and red/green flags are in
+`references/research-protocol.md`. Summarize the choice in one or two sentences
+per swap in the final answer; this step is not the place to write an essay.
+
+## Step 4: Impact vs. flexibility, before writing the change
+
+Before writing the replacement, work out:
+
+- who else calls this (the blast radius may be bigger than the one call site that
+  prompted the change),
+- what flexibility the current code buys and whether anyone actually uses it (grep
+  before removing), and
+- whether the migration cost (call-site updates, type changes, test churn) is
+  worth what's gained.
+
+If the trade isn't clearly worth it, say what was found and ask. The user knows
+release timing and risk appetite that the code alone doesn't reveal. Full rubric
+in `references/cost-impact-preflight.md`.
+
+## Step 5: Output discipline
+
+- Show the diff or the changed function, not the whole file, unless the whole file
+  is asked for.
+- One consolidated summary per batch of related changes, not a running commentary
+  per file.
+- Batch logically related edits together instead of narrating each one separately.
+- Don't restate the ladder or the research trail in the final answer. The user
+  needs the change and a one-line reason, not the process that produced it.
+
+## Incremental modernization methodology (Full/Partial scope)
+
+For legacy/dated codebases, modernize in safe, verifiable increments — never a
+big-bang rewrite. Keep a human in the loop at each gate.
+
+### Assess (read-only first)
 - Map dependencies and the module graph; identify dead code and the highest-churn,
   highest-complexity, highest-business-value hotspots.
 - Use the `serena` LSP + `scout` subagent so this exploration doesn't fill main
@@ -17,29 +175,101 @@ gate.
 - Verify target frameworks/versions with `tech-selector` (current best, not
   training-data defaults).
 
-## 2. Safety net before changing anything
+### Safety net before changing anything
 - Characterize current behavior with tests. If coverage is thin on the code you'll
   touch, add regression tests that pin the *existing* output first — so a refactor
   that changes behavior fails loudly.
 
-## 3. Transform incrementally
+### Transform incrementally
 - One bounded slice at a time (a module, a route, a component). Preserve business
   logic exactly; modernize the form around it.
 - After each slice: run tests + build + lint, and for UI use `ui-workflow`'s
   screenshot check. Commit per slice with a conventional message so each step is
   revertible.
 
-## 4. Verify each slice
+### Verify each slice
 - Tests green, build passes, behavior unchanged (diff against the pinned regression
   output). Use the `verifier` subagent on non-trivial slices.
 - Patch security issues surfaced along the way (semgrep is installed) but keep them
   as separate commits.
 
-## 5. Document
+### Document
 - Update `MODERNIZATION.md` with what changed and why; capture any institutional
   knowledge recovered from the old code before it's lost.
 
-## Guardrails
+### Guardrails
 - Business continuity first: if a slice can't be proven behavior-preserving, stop
   and surface it rather than guessing.
 - No scope creep — modernize what the slice covers, not everything you notice.
+
+## Never lazy about (unchanged from ponytail)
+
+Input validation at trust boundaries, error handling that prevents data loss,
+security, accessibility, and anything the user explicitly asked for. These are
+never traded away for a smaller diff, no matter which rung of the ladder applies.
+
+## Marking deferred opportunities
+
+When a swap is correct in principle but out of scope for a Targeted request, don't
+make it. Leave a one-line marker instead, mirroring ponytail's `ponytail:` comment:
+
+```js
+// modernize: could use structuredClone() (Node 17+) instead of this deep-clone helper
+```
+
+At the end of a session, list any `modernize:` markers left behind, so "later"
+leaves a paper trail instead of quietly becoming "never."
+
+## Ask, don't assume
+
+Stop and ask one direct question, don't proceed on a guess, when:
+
+- Scope isn't stated and can't be inferred confidently (Step 0).
+- Two well-maintained libraries are both reasonable and the right one depends on a
+  constraint the user hasn't stated (bundle size vs. features, already using a
+  sibling package from one ecosystem, etc.).
+- The swap is a breaking change to a public API or an exported function.
+- The "clean" replacement doesn't obviously cover an edge case the current code
+  handles.
+
+## Example
+
+**Request:** "This `debounce` function in `hooks/useDebounce.ts` looks
+hand-rolled, can you clean it up?"
+
+This names an exact file and function, so it's **Targeted**; skip Step 1. Step 2:
+read it and its tests; it correctly cancels on unmount, which a naive replacement
+might miss. Step 3: `lodash` is already an installed dependency (rung 5) with a
+well-tested `debounce`, so no new dependency and no research pass are needed.
+Step 4: one call site, low risk, no flexibility lost. Result: a 3-line wrapper
+around `lodash.debounce` that preserves the unmount-cancel behavior, with a
+one-line note on why. Not a rewrite, not an essay, not a new package.
+
+## Relationship to ponytail
+
+This skill deliberately does not re-implement ponytail's own commands
+(`/ponytail-review`, `/ponytail-audit`, `/ponytail-debt`, its lite/full/ultra
+intensity dial). That would be exactly the kind of reinventing this skill exists
+to prevent. For governing new code as it's written, install ponytail itself in
+Claude Code: it's free, MIT-licensed, actively maintained, and benchmarked at
+roughly half the code and 20% lower cost against a no-skill baseline.
+
+```
+/plugin marketplace add DietrichGebert/ponytail
+/plugin install ponytail@ponytail
+```
+
+The two compose cleanly. Ponytail keeps new code minimal as it's written; this
+skill audits and modernizes what's already in the repo, with the scope control,
+cost/impact gate, and live research discipline the ladder alone doesn't cover.
+
+## Reference files (load only when the step above points here)
+
+- `references/research-protocol.md`: vetting a candidate library, current sources
+  to check, red/green flags, decision template.
+- `references/design-patterns-cheatsheet.md`: smell → pattern → when to skip it,
+  compact table.
+- `references/cost-impact-preflight.md`: full pre-flight output template and the
+  impact/flexibility rubric.
+- `scripts/preflight_scan.py`: stdlib-only scanner for file count, LOC, and
+  dependency manifests.
diff --git a/global/tools/code-modernization/references/cost-impact-preflight.md b/global/tools/code-modernization/references/cost-impact-preflight.md
new file mode 100644
index 0000000..d5c663a
--- /dev/null
+++ b/global/tools/code-modernization/references/cost-impact-preflight.md
@@ -0,0 +1,54 @@
+# Cost / impact pre-flight and flexibility rubric
+
+## Pre-flight output template (Step 1)
+
+Run `python3 scripts/preflight_scan.py <path>` and report:
+
+```
+Scope: <Full|Partial> on <path>
+~<N> files, ~<X> lines in range
+Dependencies already available: <short list from the manifest>
+Flagged high-cost: <any file over ~800 lines, or the pass touching 15-20+ files, name them>
+Estimated: <rough tool-call / diff count>, <low|medium|high> breaking-change risk
+Proceed as scoped, narrow it, or switch to Targeted?
+```
+
+### Breaking-change risk levels
+
+| Level | Criteria |
+|---|---|
+| **Low** | Internal/private functions only; no exported API changes; no type signature changes |
+| **Medium** | Exported functions change signature but callers are all in-repo; or a dependency is swapped that has a slightly different API |
+| **High** | Public API / SDK changes; cross-repo consumers possible; type changes that propagate through generics; removal of a feature flag or config option |
+
+### High-cost file handling
+
+When a file exceeds ~800 lines or the total pass touches 15–20+ files:
+
+1. Name the files explicitly in the pre-flight report.
+2. Offer the user a choice: full detailed diff, summarized diff (key changes
+   only), or skip that file for now.
+3. Don't silently generate a massive diff — the user may want to split the work
+   across PRs.
+
+## Impact vs. flexibility rubric (Step 4)
+
+Before writing each swap, evaluate:
+
+| Question | If yes → | If no → |
+|---|---|---|
+| Does anyone else call this? | Check all call sites; mention them in the summary | Safe to change in isolation |
+| Does the current code handle edge cases the replacement doesn't? | Keep the edge-case handling; wrap the replacement if needed | Straight swap |
+| Does the current API surface offer flexibility someone might rely on? | Grep for usage of that flexibility; if unused, remove | Keep the simpler replacement |
+| Is the migration cost (call-site updates, type changes, test churn) < the maintenance cost of keeping the old code? | Proceed | Defer — leave a `// modernize:` marker |
+| Does the swap change observable behavior (return types, error messages, side effects)? | Treat as a breaking change; flag in the pre-flight report | Transparent swap |
+
+### When to defer instead of swap
+
+- The swap is correct but the module is in active development (merge conflicts).
+- The user said "Targeted" and the swap is outside the named scope.
+- The migration cost is high and the old code works fine — it's debt, not a bug.
+- Two equally good replacements exist and the choice depends on constraints the
+  user hasn't stated.
+
+In all these cases, leave a `// modernize:` marker and list it at session end.
diff --git a/global/tools/code-modernization/references/design-patterns-cheatsheet.md b/global/tools/code-modernization/references/design-patterns-cheatsheet.md
new file mode 100644
index 0000000..58f42f9
--- /dev/null
+++ b/global/tools/code-modernization/references/design-patterns-cheatsheet.md
@@ -0,0 +1,24 @@
+# Design patterns cheatsheet
+
+Apply a pattern only when it removes real duplication or coupling. If the code is
+already clear and short, a pattern adds ceremony for no gain — skip it.
+
+| Smell | Pattern | When to skip |
+|---|---|---|
+| Copy-pasted logic with minor variations | **Strategy** — extract the varying part into a function/object, pass it in | Fewer than 3 copies, or the variations are trivial one-liners |
+| Long `if/else` or `switch` choosing behavior by type/string | **Strategy** or **Map lookup** — a plain `Record<string, handler>` is usually enough | Only 2–3 branches and unlikely to grow |
+| Object construction with many optional params | **Builder** or plain options object | A single config object with defaults already reads well |
+| Multiple callers need the same setup/teardown around a core operation | **Template Method** (or just a higher-order function) | Only one caller — inline the setup |
+| Need to react to state changes across unrelated modules | **Observer / Event emitter** | Two modules — a direct callback is simpler |
+| Expensive object creation, same inputs → same output | **Flyweight / Cache / Memoize** | Object is cheap, or inputs rarely repeat |
+| Access to a resource that needs lifecycle management | **Dispose / using / context manager** | Resource is process-scoped (no cleanup needed) |
+| External API that doesn't match your domain model | **Adapter** | You control both sides — just change the source |
+| Deep nesting of decorators or wrappers | **Middleware / Pipeline** — compose a flat list | Two wrappers max — nesting is still readable |
+| Repeated null-checks or fallback chains | **Null Object** or optional chaining (`?.`) | Language already has `??` / `?.` — use it (rung 3/4) |
+
+## Anti-patterns to avoid
+
+- **Singleton for testability**: makes mocking hard. Prefer dependency injection.
+- **Factory for one type**: a constructor call is simpler.
+- **Abstract base class with one subclass**: remove the abstraction.
+- **Pattern just to match a textbook**: the code is the product, not the diagram.
diff --git a/global/tools/code-modernization/references/research-protocol.md b/global/tools/code-modernization/references/research-protocol.md
new file mode 100644
index 0000000..41a61c4
--- /dev/null
+++ b/global/tools/code-modernization/references/research-protocol.md
@@ -0,0 +1,42 @@
+# Research protocol — vetting a candidate library (rung 6)
+
+Only reach this file when rungs 1–5 failed and a new dependency is genuinely on
+the table. Never skip straight here.
+
+## Mandatory live checks
+
+Run these before recommending. Stale memory is the failure mode this protocol
+exists to prevent.
+
+| Check | Source | Red flag |
+|---|---|---|
+| Last commit / release | GitHub releases or npm/PyPI page | > 12 months with open issues |
+| Open CVEs | `npm audit` / `pip-audit` / Snyk DB / GitHub advisories | Any unpatched critical/high |
+| Maintenance signal | Issue tracker, PR merge cadence | Dozens of unanswered issues, no maintainer response in months |
+| Download trend | npm trends, PyPI stats | Steep decline or flatline vs. competitors |
+| License compatibility | `package.json` / `setup.cfg` license field | Copyleft (GPL) in an MIT project, or no license |
+| Bundle size (frontend) | bundlephobia.com or `import-cost` | > 50 kB gzipped for a single utility |
+| Peer / transitive deps | `npm ls` / `pip show` | Pulls in a heavy tree for a small task |
+
+## Green flags (not required, but strengthen the case)
+
+- Active maintainer with a history of responding to security reports.
+- TypeScript types shipped (not DefinitelyTyped-only).
+- Used by well-known projects (check dependents on GitHub).
+- Clear migration path if abandoned (small API surface, stdlib fallback exists).
+
+## Decision template (one per candidate)
+
+```
+Library: <name@version>
+Rung: 6 (new dependency)
+Replaces: <what hand-rolled code or older dep>
+Last release: <date>  |  Weekly downloads: <N>  |  License: <X>
+CVEs: <none | list>
+Bundle impact: <+N kB gzipped> (frontend only)
+Verdict: adopt / skip / ask user
+Reason (1–2 sentences): ...
+```
+
+Include this block in the final answer when recommending a new dependency. Keep it
+short — the user needs the decision, not the research log.
diff --git a/global/tools/code-modernization/scripts/preflight_scan.py b/global/tools/code-modernization/scripts/preflight_scan.py
new file mode 100755
index 0000000..1499037
--- /dev/null
+++ b/global/tools/code-modernization/scripts/preflight_scan.py
@@ -0,0 +1,190 @@
+#!/usr/bin/env python3
+"""Pre-flight scanner for code-modernizer skill.
+
+Stdlib-only — nothing to install.
+
+Usage:
+    python3 scripts/preflight_scan.py <path> [--json]
+
+Reports file count, total lines of code, detected dependency manifests,
+and flags high-cost files (> 800 lines).
+"""
+
+import json
+import os
+import sys
+from pathlib import Path
+
+SKIP_DIRS = {
+    "node_modules", ".git", "__pycache__", ".venv", "venv",
+    "dist", "build", ".next", ".nuxt", "coverage", ".tox",
+    "vendor", "target", "out", ".cache", ".turbo",
+}
+
+CODE_EXTENSIONS = {
+    ".js", ".jsx", ".ts", ".tsx", ".mjs", ".cjs",
+    ".py", ".pyx",
+    ".rs", ".go", ".java", ".kt", ".kts",
+    ".c", ".cpp", ".cc", ".h", ".hpp",
+    ".rb", ".php", ".swift", ".scala",
+    ".vue", ".svelte", ".astro",
+    ".css", ".scss", ".less",
+    ".sql", ".sh", ".bash", ".zsh",
+    ".lua", ".zig", ".nim", ".ex", ".exs",
+    ".cs", ".fs",
+}
+
+MANIFEST_FILES = {
+    "package.json", "package-lock.json", "yarn.lock", "pnpm-lock.yaml",
+    "requirements.txt", "pyproject.toml", "setup.py", "setup.cfg", "Pipfile",
+    "Cargo.toml", "go.mod", "Gemfile", "composer.json",
+    "build.gradle", "build.gradle.kts", "pom.xml",
+    "pubspec.yaml", "mix.exs",
+}
+
+HIGH_COST_THRESHOLD = 800
+
+
+def count_lines(path: Path) -> int:
+    try:
+        with open(path, "r", encoding="utf-8", errors="replace") as f:
+            return sum(1 for _ in f)
+    except (OSError, UnicodeDecodeError):
+        return 0
+
+
+def parse_dependencies(root: Path) -> list[str]:
+    deps = []
+    pkg = root / "package.json"
+    if pkg.is_file():
+        try:
+            data = json.loads(pkg.read_text(encoding="utf-8"))
+            for key in ("dependencies", "devDependencies"):
+                if key in data:
+                    deps.extend(data[key].keys())
+        except (json.JSONDecodeError, OSError):
+            pass
+
+    req = root / "requirements.txt"
+    if req.is_file():
+        try:
+            for line in req.read_text(encoding="utf-8").splitlines():
+                line = line.strip()
+                if line and not line.startswith("#") and not line.startswith("-"):
+                    name = line.split("==")[0].split(">=")[0].split("<=")[0].split("[")[0].strip()
+                    if name:
+                        deps.append(name)
+        except OSError:
+            pass
+
+    pyproject = root / "pyproject.toml"
+    if pyproject.is_file():
+        try:
+            content = pyproject.read_text(encoding="utf-8")
+            in_deps = False
+            for line in content.splitlines():
+                if line.strip().startswith("dependencies"):
+                    in_deps = True
+                    continue
+                if in_deps:
+                    if line.strip() == "]":
+                        in_deps = False
+                        continue
+                    dep = line.strip().strip('",').split(">=")[0].split("==")[0].split("<")[0].strip()
+                    if dep:
+                        deps.append(dep)
+        except OSError:
+            pass
+
+    return sorted(set(deps))
+
+
+def scan(root: Path) -> dict:
+    file_count = 0
+    total_lines = 0
+    high_cost_files = []
+    manifests_found = []
+
+    for dirpath, dirnames, filenames in os.walk(root):
+        dirnames[:] = [d for d in dirnames if d not in SKIP_DIRS]
+
+        for fname in filenames:
+            fpath = Path(dirpath) / fname
+
+            if fname in MANIFEST_FILES:
+                manifests_found.append(str(fpath.relative_to(root)))
+
+            if fpath.suffix.lower() in CODE_EXTENSIONS:
+                file_count += 1
+                lines = count_lines(fpath)
+                total_lines += lines
+                if lines > HIGH_COST_THRESHOLD:
+                    high_cost_files.append({
+                        "file": str(fpath.relative_to(root)),
+                        "lines": lines,
+                    })
+
+    deps = parse_dependencies(root)
+
+    return {
+        "root": str(root),
+        "file_count": file_count,
+        "total_lines": total_lines,
+        "manifests": manifests_found,
+        "dependencies": deps,
+        "high_cost_files": sorted(high_cost_files, key=lambda x: -x["lines"]),
+    }
+
+
+def format_report(result: dict) -> str:
+    lines = [
+        f"Scope: scan on {result['root']}",
+        f"~{result['file_count']} files, ~{result['total_lines']} lines of code",
+    ]
+
+    if result["dependencies"]:
+        dep_preview = result["dependencies"][:20]
+        dep_str = ", ".join(dep_preview)
+        if len(result["dependencies"]) > 20:
+            dep_str += f" (+{len(result['dependencies']) - 20} more)"
+        lines.append(f"Dependencies already available: {dep_str}")
+    else:
+        lines.append("Dependencies already available: (none detected)")
+
+    if result["high_cost_files"]:
+        hc = "; ".join(f"{f['file']} ({f['lines']} lines)" for f in result["high_cost_files"][:10])
+        lines.append(f"Flagged high-cost (>{HIGH_COST_THRESHOLD} lines): {hc}")
+    else:
+        lines.append(f"Flagged high-cost: none (all files <{HIGH_COST_THRESHOLD} lines)")
+
+    risk = "low"
+    if result["file_count"] > 20:
+        risk = "medium"
+    if result["file_count"] > 50 or result["total_lines"] > 20000:
+        risk = "high"
+
+    lines.append(f"Estimated breaking-change risk: {risk}")
+
+    return "\n".join(lines)
+
+
+def main():
+    if len(sys.argv) < 2:
+        print(f"Usage: {sys.argv[0]} <path> [--json]", file=sys.stderr)
+        sys.exit(1)
+
+    target = Path(sys.argv[1]).resolve()
+    if not target.is_dir():
+        print(f"Error: {target} is not a directory", file=sys.stderr)
+        sys.exit(1)
+
+    result = scan(target)
+
+    if "--json" in sys.argv:
+        print(json.dumps(result, indent=2))
+    else:
+        print(format_report(result))
+
+
+if __name__ == "__main__":
+    main()