Codebase Modernizer

For a codebase you are returning to after a long gap, or one that has drifted through many unoptimized changes. It audits every applicable dimension, then converts the findings into a phased, sprint-sized, testable plan for a better, up-to-date version.

Produces exactly two files in the target repo root:

File	Contents
MODERNIZATION_REPORT.md	Baseline evidence + every finding, severity-ranked, each citing path:line
MODERNIZATION_PLAN.md	Phases → sprints → tasks → milestones, every task closing named findings

Read-only contract

This skill never modifies source code, dependencies, lockfiles, or configuration — no tracked file's content changes. On a clean tree that is git diff --stat empty. On a stale, already-dirty tree, git status --porcelain and git diff after the run must match a snapshot taken before it (declared artifacts set aside). Beyond the two reports, only two kinds of new file may appear, both enumerated in the report's Artifacts section: a declared delegate artifact (CODE_REVIEW.md, from code-review mode review) and probe byproducts (build dirs such as obj/, .dart_tool/, target/, .gradle/). Nothing else.

• Dependency upgrades become planned tasks with migration steps — never npm update, ncu -u, cargo update, poetry update, or any equivalent. A blind bulk upgrade on a stale tree produces a broken build and an unreviewable diff, which is exactly what the plan exists to prevent.
• Refactors, dead-code removal, and test generation are planned, not applied. Applying them is the delegate skills' job, run later against the plan.
• Agent environment files (CLAUDE.md, AGENTS.md) are planned via /agent-config create or /agent-config update in the plan's Pre step — never created or rewritten during the audit.
• If the user asks mid-run to start fixing, finish the report and plan first, then hand off to the delegate skill named in that task.

Dependency Preflight (mandatory)

This skill invokes the two skills declared in frontmatter dependencies: code-review (modes review and perf, for BUG and PERF) and dont-make-me-think (UX). Run this before Phase 0, the first phase that probes anything. Discovery acquires nothing:

if command -v asm >/dev/null && asm deps --help >/dev/null 2>&1; then
  asm deps discover codebase-modernizer --json || echo "discover failed; acquire at first use" >&2
  printf 'cm_session=%s\n' "codebase-modernizer-$(date +%s)-$$"   # record it; reuse it verbatim
else
  echo "asm deps unavailable: npm install -g agent-skill-manager@latest" >&2
fi

1. If the block prints asm deps unavailable, record every delegated dimension Not Assessed — skill unavailable, skip steps 2–5, and continue.
2. When Phase 2 first reaches BUG or PERF, run asm deps acquire code-review --session <cm_session> --json. When it first reaches UX, run the same command for dont-make-me-think. Never acquire for a dimension that is Not Assessed.
3. If the acquire exits 0, pass its returned skillMdPath to the dimension worker as delegate_skill_md. Read that path directly.
4. If the acquire exits non-zero, print the install hint in references/delegation-policy.md (Missing dependency). Record Not Assessed — skill unavailable for BUG and PERF (code-review) or UX (dont-make-me-think), continue, and name it in Limitations. A missing dependency is fail-soft, not fatal.
5. Release in finally. If any acquire ran, run asm deps release --session <cm_session> --json once at every terminal outcome (after Phase 5, on a stop, or on an error), before the final report. Put a failed release under Uncertainty:.

Lease-owned copies live outside the target repo, so they are not target artifacts. The six inline dimensions name their skill in a plan task and never invoke it, so they need no dependency entry.

Leading terms

Used throughout this skill and its references with these exact meanings:

• baseline-green — the recorded state where the project builds and its test suite runs to a known pass rate. Established in Phase 0; every P0–P4 task must assert it still holds. Pre is exempt when the baseline is RED — restore-green stays on P0 / Sprint 0.
• finding record — one normalized issue row with a stable finding ID (F-<DIM>-<NNN>, e.g. F-DEP-003). The report lists them; the plan's tasks close them by ID.
• Not Assessed — an explicit report verdict for a dimension that could not be checked (no tool, no UI, no network). Never replaced by a guess.
• fail-soft — probe whether a tool exists before using it; on absence, record Not Assessed with the reason and continue. A missing tool never aborts the run.
• upgrade wave — one batch of dependency upgrades that ships and is verified together: security patches → patch/minor batch → each major on its own.

Repo Sync Before Edits (mandatory)

Default: do not sync. This skill merges nothing and commits nothing — it writes two untracked report files. Rebasing mid-audit can pull in a year of upstream commits, invalidating every path:line citation and the recorded SHA. Audit the tree as you found it.

Sync only when the user asks for the reports committed or pushed. Then sync at the start of Phase 3, after the audit is recorded. Because HEAD moves, re-record the commit SHA and re-verify every citation. If any citation no longer resolves, stop with Result: BLOCKED — audit stale after sync and re-run the audit.

When syncing, sync the current branch with remote — stash first if the tree is not clean:

git stash push -u -m "pre-sync"   # only when `git status --porcelain` is non-empty
branch="$(git rev-parse --abbrev-ref HEAD)"
git fetch origin && git pull --rebase origin "$branch"
git stash pop                     # only if you stashed

If origin is missing, pull is unavailable, or rebase/stash conflicts occur, stop and ask the user before continuing. A dirty tree is common on a neglected repo — never discard uncommitted work.

Scope and branch selection

Resolve all nine branches in references/scope-detection.md before Phase 0. Each is a real branch in the workflow, not a preference. Check these two first, because they change what is obtainable at all:

• No Bash → record the whole baseline Not Assessed — no shell, audit only what static reading supports, and never fabricate a verdict.
• No UI detected → UI/UX dimensions are Not Assessed — no UI detected. Never invent UX findings.

If a branch was not checked, take its restrictive side.

What this skill owns, and what it delegates

The finding-generators already exist. This skill's own contribution is dependency and runtime currency, the baseline gate, and the audit → plan bridge. Everything else is delegated.

Dim	Dimension	Audited by	Skip when
DEP	Dependency + runtime currency	this skill — references/dependency-audit.md, scripts/dep_scan.sh	no manifest found
BUG	Bugs, security holes, quality	invoke code-review mode review	never
PERF	Bottlenecks, leaks, algorithmic waste	invoke code-review mode perf	never
UX	Usability and UI flow	invoke dont-make-me-think	no UI detected
CLEAN	Readability vs Clean Code standards	inline — plan task runs code-review mode clean	never
DEAD	Dead code, duplication, slop, weak types	inline — plan task runs code-review mode cleanup	never
TEST	Untested branches and edge cases	inline — plan task runs test-coverage	never — an absent suite is itself a Critical finding
CI	Pipelines, pre-commit, quality gates	inline — plan task runs devops-pipeline	never
SEC	Secrets, dependency vulnerabilities	inline — plan task runs security-setup	never
DOCS	Docs drifted from code	inline — plan task runs doc-manager	never

Delegation policy — one rule: a delegate is invoked only if it changes no tracked file.

• Invoked (BUG, PERF, UX) — normalize the output into finding records and record Path: delegated. Never let dont-make-me-think enter its Redesign Mode, which edits UI source files.
• Inline (CLEAN, DEAD, TEST, CI, SEC, DOCS) — these delegates write, so never invoke one during the audit. Audit the dimension with its checklist in references/dimension-map.md, record Path: inline, and name that skill in the plan task. inline is the expected path, not a degradation.

Read references/delegation-policy.md before Phase 2. It holds the invocation args, the CODE_REVIEW.md declared-artifact handling, the review-only rule for dont-make-me-think, the /agent-config Pre-step rule, and the Skill-tool-unavailable fallback (which is reduced depth).

Workflow

Phase 0 — Baseline (gate)

Follow references/baseline.md. Record each of these with the command that produced it: build status, test command and pass rate, coverage if obtainable, lint status, CI presence and last result, runtime/toolchain versions in use.

A RED baseline (does not build, tests do not run, there is no suite, or the build could not be probed at all) does not stop the audit. Record Baseline: RED, continue, and make restoring baseline-green the plan's Sprint 0 — nothing downstream is verifiable without it.

Probes must not mutate tracked files. A tracked file a probe changes is a finding. The snapshot procedure and the no-test-command fallback are in references/baseline.md (Phase 0 rules: tracked files and the no-test-command fallback).

Completion criteria: every row of the baseline table in references/baseline.md holds a recorded value or an explicit Not Assessed with a reason; the overall verdict is GREEN, AMBER, or RED; every value cites the command that produced it.

Phase 1 — Inventory and dimension selection

Detect stack, ecosystems, UI presence, repo size, and entry points. Produce the dimension worklist: each of the 10 dimensions marked audit or Not Assessed + reason. If a requested area maps to no dimension ID, or to more than one, ask the user once which to audit. Otherwise proceed without asking.

Completion criteria: all 10 dimensions have a disposition; every ecosystem with a manifest is listed; repo-size branch and Agent-tool branch are both resolved and stated.

Phase 2 — Dimension audits

Read references/delegation-policy.md before invoking any delegated dimension.

Run DEP first — its output feeds the plan's upgrade waves and often explains findings in other dimensions. Then run the remaining audited dimensions. If the Repo size and Agent tool branches select subagents, spawn one agents/dimension-auditor.md per dimension in parallel. Otherwise run them inline, one at a time.

• DEP uses agents/dependency-auditor.md and references/dependency-audit.md, one invocation per ecosystem. All DEP findings share the F-DEP- prefix, so allocate each ecosystem a distinct id_start (1, 101, 201, …) before spawning them; gaps in the numbering are fine, collisions are not.
• All other dimensions use agents/dimension-auditor.md with that dimension's row from references/dimension-map.md. Each has its own prefix and numbers from 1, so they need no ID coordination.
• No-fabrication rule: every finding record cites path:line (or a manifest entry and version for DEP), or it is dropped. A dimension that produced nothing citable is Not Assessed, not "no issues found".

Completion criteria: every dimension marked audit in Phase 1 returned either ≥ 1 finding record or an explicit "clean — checked X, found nothing" with the checks named; zero finding records lack evidence; finding IDs are unique and follow F-<DIM>-<NNN>.

Phase 3 — Write MODERNIZATION_REPORT.md

Merge all finding records into MODERNIZATION_REPORT.md using references/report-template.md. Rank by severity: Critical → High → Medium → Low.

Deduplicate before writing, by the Deduplication rule in references/report-template.md.

Completion criteria: the file exists at the repo root; it contains the baseline table, a dimension coverage table showing all 10 dispositions, and the full finding table; every finding has ID, dimension, severity, evidence, and fix direction; the counts in the summary equal the rows in the table.

Phase 4 — Write MODERNIZATION_PLAN.md

Spawn agents/plan-architect.md with the report path (or run it inline when the Agent tool is unavailable). It writes MODERNIZATION_PLAN.md from references/plan-template.md, using the fixed skeleton: unconditional Pre Agent environment (ME), then P0 Stabilize (M0), P1 Secure & Patch (M1), P2 Modernize (M2), P3 Clean & Harden (M3), and P4 Polish (M4). Do not rename or renumber P0–P4. Each phase's goal and exit milestone are in references/plan-template.md (The fixed phase skeleton). Phases split into sprints. Every task uses the tasks-generator task format so the plan interoperates with that skill, plus a Closes: line naming finding IDs.

Completion criteria: Pre is present and ordered before P0; every Critical and High finding is closed by ≥ 1 task; every task has ≥ 2 testable acceptance criteria; every P0–P4 task asserts baseline-green still holds; the dependency table references only task IDs that exist and has no cycles; the critical path is stated explicitly; Pre and each of P0–P4 have a milestone with a measurable exit condition. references/plan-template.md carries the task-ID format, the Pre create-vs-update rule, and the RED-baseline exemption.

Phase 5 — Validation pass

1. Spawn agents/plan-validator.md with fresh context, giving it both output files and the repo. It verifies evidence citations resolve, severities are defensible, no finding is orphaned, no task invents work not traceable to a finding or a milestone, and the stated critical path is actually the longest chain in the dependency table.
2. Apply each must-fix correction it returns.
3. If round 1 returned any must-fix, re-run the validator once. Never run a third round.
4. Record each must-fix still open after round 2 in the report's Limitations, with a reason.

Completion criteria: the validator has run at least twice when round 1 returned any must-fix; zero unresolved must-fix items remain, or each survivor is recorded in Limitations with a reason.

Step Completion Reports

After each phase, emit:

◆ [Phase Name] (phase N of 5 — [context])
··································································
  [Check 1]:          √ pass
  [Check 2]:          × fail — [reason]
  [Criteria]:         √ N/M met
  ____________________________
  Result:             PASS | FAIL | PARTIAL

Use the per-phase check names in references/output-format.md. Never report PASS while a phase completion criterion, required output file, or safety guardrail is unresolved.

Acceptance Criteria

Walk references/acceptance-criteria.md before writing the final report. It is the full run checklist: outputs, the read-only contract, findings, the plan, and an understandable final report. The two bars this skill exists to keep:

• No tracked file's content changed relative to the pre-run snapshot (Read-only contract).
• Every new file in git status --short is one of the two reports, a declared delegate artifact (CODE_REVIEW.md), or a probe byproduct listed in the report's Artifacts section.

If any criterion fails, report it as a FAIL row in the Step Completion Report and set Result: by the rules below.

Final report

End the run with one final report in chat. Its first four lines are fixed; field contents, the outcome table, and the format rule are in references/output-format.md.

Result: COMPLETE | PARTIAL — <reason> | BLOCKED — <reason>
Evidence: <checks that actually ran, and what each showed>
Uncertainty: <Not Assessed rows, degraded paths, untested items, labeled assumptions>
Decision: <approval needed, or "No approval needed."> Next: <remaining user action>

Set Result: with the first rule that matches:

1. BLOCKED — either output file is missing at the repo root, a tracked file's content changed during the run (even if restored), or the run stopped (sync conflict, stale citations, user stop).
2. PARTIAL — any of: a dimension is Not Assessed for an environment reason (no shell, offline, missing tool, missing skill); BUG, PERF, or UX ran inline at reduced depth; a huge-repo cap left paths unscanned; the read-only check could not run (not a git repo); a must-fix survived round 2; an acceptance criterion fails.
3. COMPLETE — every other run. A RED baseline, or Not Assessed because of no UI, no manifest, or the requested scope, is a finding or a scope choice, not a gap.

Expected Output

Result: COMPLETE — 47 findings; Pre + P0–P4 plan; 0 must-fix
Evidence: git status --porcelain and git diff match the pre-run snapshot; validator ran 1 round
Uncertainty: coverage Not Assessed (no coverage tool); no plan task was executed
Decision: No approval needed. Next: review MODERNIZATION_PLAN.md, then run Task Pre.1

The summary facts that follow these four lines (target, baseline, dimensions, findings, outputs, plan, validation, source files changed) are in references/output-format.md (Full example).

Edge Cases

Read references/edge-cases.md when a case arises: not a git repo, no manifest, no network, baseline RED, a huge repo, a narrowed dimension filter, a monorepo, or existing report files. A user asking mid-run to apply fixes is handled by the Read-only contract above.

Reference files

Read each file only when its phase needs it; that keeps the agent's context budget for the audit.

• references/scope-detection.md — the nine scope branches, detection, and resolution order.
• references/delegation-policy.md — invocation args, artifact handling, fallbacks per path.
• references/baseline.md — Phase 0 probe protocol per stack, and the baseline evidence table.
• references/dependency-audit.md — per-ecosystem fail-soft probes, classification schema, upgrade wave rules, and migration lookup for majors.
• references/dimension-map.md — the 10 dimensions: inline checklist, severity rubric, skip rules.
• references/report-template.md — report structure and the deduplication rule.
• references/plan-template.md — plan structure, task format, task-ID and Pre rules.
• references/acceptance-criteria.md — the full run checklist.
• references/output-format.md — Step Completion Report checks, final-report fields, format rule.
• references/edge-cases.md — the full edge-case list.
• scripts/dep_scan.sh — read-only ecosystem and dependency probe; prints a markdown summary.

Agents (spawn with the Agent tool; run inline if unavailable): agents/dependency-auditor.md (DEP), agents/dimension-auditor.md (one delegated dimension per invocation), agents/plan-architect.md (report → plan), agents/plan-validator.md (fresh-context validation).