claude-plugins/plugins/code-modernization/commands/modernize-reimagine.md

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description: Multi-agent greenfield rebuild — extract specs from legacy, design AI-native, scaffold & validate with HITL

argument-hint:

The first token of $ARGUMENTS is the system dir ($1); everything after it is the target vision — it is usually multiple words, so do not truncate it to one token. Below, <vision> means that full remainder.

Reimagine legacy/$1 as:

This is not a port — it's a rebuild from extracted intent. The legacy system becomes the specification source, not the structural template. This command orchestrates a multi-agent team with explicit human checkpoints.

The brief is binding — read it first. If analysis/$1/MODERNIZATION_BRIEF.md exists, this reimagine is executing one of its phases: read it before doing anything below. Find the phase that names this command with a scope matching $1 and , and treat that phase's scope, entry criteria, exit criteria, and any edits the user made to it as binding on the phases below — on top of, never instead of, this command's own two HITL checkpoints. Entry criteria are gates, not context: if one is not met (a prior phase's exit criteria, an SME sign-off the brief requires), meeting it is the next step — do not proceed past it and do not silently re-plan around it. If the brief exists but no phase matches, stop and ask which phase this is. The user steers execution by editing the brief; a brief the execution command never reads cannot steer anything.

Phase A — Specification mining (parallel agents)

Spawn concurrently and show the user that all three are running:

1. business-rules-extractor — "Extract every business rule from legacy/$1 into Given/When/Then form. Output to a structured list I can parse."

2. legacy-analyst — "Catalog every external interface of legacy/$1: inbound (screens, APIs, batch triggers, queues) and outbound (reports, files, downstream calls, DB writes). For each: name, direction, payload shape, frequency/SLA if discernible. Mask any credential embedded in endpoints or payload examples per your secret-handling rules."

3. legacy-analyst — "Identify the core domain entities in legacy/$1 and their relationships. Return as an entity list + Mermaid erDiagram."

Collect results. Write analysis/$1/AI_NATIVE_SPEC.md containing:

• Capabilities (what the system must do — derived from rules + interfaces)
• Domain Model (entities + erDiagram)
• Interface Contracts (each external interface as an OpenAPI fragment or AsyncAPI fragment)
• Non-functional requirements inferred from legacy (batch windows, volumes)
• Behavior Contract (the Given/When/Then rules — these are the acceptance tests)

Credential values are masked everywhere in the spec; connection details appear as env-var placeholders (${DATABASE_URL}), never literals.

Phase B — HITL checkpoint #1

Present the spec summary. Ask the user one focused question: "Which of these capabilities are P0 for the reimagined system, and are there any we should deliberately drop?" Wait for the answer. Record it in the spec.

Phase C — Architecture (single agent, then critique)

Design the target architecture for "":

• Mermaid C4 Container diagram
• Service boundaries with rationale (which rules/entities live where)
• Technology choices with one-line justification each
• Data migration approach from legacy stores

Then spawn architecture-critic: "Review this proposed architecture for against the spec in analysis/$1/AI_NATIVE_SPEC.md. Identify over-engineering, missed requirements, scaling risks, and simpler alternatives." Incorporate the critique. Write the result to analysis/$1/REIMAGINED_ARCHITECTURE.md.

Phase D — HITL checkpoint #2

Present the architecture and stop — scaffold nothing until the user explicitly approves (use plan mode if the session supports it).

Phase E — Parallel scaffolding

This phase runs only after the user approved the architecture in Phase D — the approval is what authorizes the build-out.

Preferred — Workflow orchestration. If the Workflow tool is available, scaffold every service in the approved architecture — no cap; the workflow runtime queues agents against its concurrency limit, so 8 services are as tractable as 3:

Workflow({
  scriptPath: "${CLAUDE_PLUGIN_ROOT}/workflows/reimagine-scaffold.js",
  args: { system: "$1", services: [
    { name: "<service-name>", responsibilities: "<one-line summary from the architecture>" },
    ...
  ] }
})

Tell the user the service count before launching. Each agent writes only to its own modernized/$1-reimagined/<service-name>/ directory (disjoint, so parallel writes don't conflict). On return, report from the structured result: services scaffolded (scaffolded[]) and totals (services, acceptanceTests, pendingRules count); the actual pending rule IDs and any planted-instruction/blocker notes are per-service at scaffolded[].pendingRuleIds and scaffolded[].blockers (check every service's blockers — that's where the untrusted-spec injection signal surfaces); plus notScaffolded for anything skipped.

Fallback (no Workflow tool): for each service — cap at 3 to keep the run tractable; tell the user which you deferred — spawn a scaffolder agent in parallel:

"Scaffold the service per analysis/$1/REIMAGINED_ARCHITECTURE.md and AI_NATIVE_SPEC.md. Create: project skeleton, domain model, API stubs matching the interface contracts, and executable acceptance tests for every behavior-contract rule assigned to this service (mark unimplemented ones as expected-failure/skip with the rule ID). No credential literal from legacy code becomes a test fixture or config default — use fake same-shape values and env-var placeholders. Write to modernized/$1-reimagined//."

Show the agents' progress. When all complete, run the acceptance test suites and report: total tests, passing (scaffolded behavior), pending (rule IDs awaiting implementation).

Phase F — Knowledge graph handoff

Write modernized/$1-reimagined/CLAUDE.md — the persistent context file for the new system, containing: architecture summary, service responsibilities, where the spec lives, how to run tests, and the legacy→modern traceability map. This file IS the knowledge graph that future agents and engineers will load — and it gets committed: connection details and credentials appear only as env-var names with a pointer to where they're provisioned, never as values.

Report: services scaffolded, acceptance tests defined, % behaviors with a home, location of all artifacts.