Solution Design

Solution Design → SOLUTION.md

The skill creates or fully rewrites SOLUTION.md in the directory returned by pwd.

SOLUTION.md answers the questions: what to change, why this way, which contracts must survive, what is out of scope, how to prove correctness.

It does not answer "which files to change, step by step" — that is $planf3's job.

The resulting file is always two-block:

1. Block 1. For the human — a short, readable summary without architectural overload.
2. Block 2. For the agent — the complete contract for planning and implementation.

Hard boundaries

You may modify only SOLUTION.md.

Forbidden:

• writing code;
• modifying tests, configs, schemas, dependencies;
• creating implementation phases or a file-by-file checklist;
• automatically launching $codebase-analysis or $planf3;
• overwriting CURRENT_STATE.md;
• adding future-proofing to the chosen solution;
• turning a local task into a subsystem/platform/framework.

Launch contract

The skill requires a concrete task: a feature, a bug fix, a refactoring goal, a migration, a product change, a greenfield system.

If there is no goal — do not create a general architecture document. Ask for the task.

At the start:

1. Run pwd.
2. Find the Git roots and the initial working tree status.
3. Read the local instructions and the relevant docs/manifests.
4. Find and classify CURRENT_STATE.md: CURRENT, PARTIAL, STALE, IRRELEVANT, ABSENT.
5. Determine the mode: existing, greenfield, hybrid.
6. Determine whether this is one coherent change set or independent workstreams.

Primary objective function

Not "the most correct architecture", but the minimal sufficient solution.

A solution is better if it:

• fulfills the observable requirements;
• preserves the existing contracts;
• uses the project's current patterns;
• adds fewer files, dependencies, layers, and state;
• is easier to review, test, and delete;
• explicitly moves future work outside the current task.

If the correct solution looks overbuilt, the status must be BLOCKED_BY_SCOPE_OVERDESIGN, not READY_FOR_PLANF3.

Mandatory minimality

SOLUTION.md must contain:

• the smallest acceptable option;
• explicit non-goals;
• rejected overengineering;
• a complexity budget;
• a future work parking lot;
• a justification for every new dependency/subsystem/persistent state/abstraction, if any are needed.

Interview rounds

Open questions to the user are asked as a design tree worked in rounds (after grilling, mattpocock/skills):

• The frontier is every question whose prerequisites are already settled. Ask the whole frontier in one round; a question that depends on another still open one belongs to a later round.
• Every question carries a stable code (Q1, Q2, …) and your recommended answer with the reason; the user may reply Q1 ок, Q2: <answer>.
• Facts are yours to find (code, docs, tools, a sub-agent) — never ask the user for something you can look up. Decisions are the user's — put each to them and wait.
• The interview is done when the frontier is empty: nothing left silently assumed. Anything still open at that point goes into SOLUTION.md as an explicit assumption with how it will be verified, not as a decision.

Delegation

Use subagents only when they add value:

• context explorer;
• domain/doc researcher;
• design challenger;
• lean challenger.

For a non-trivial solution, these are mandatory:

1. a fresh Design Challenger — hunts for correctness/contract gaps;
2. a Lean Challenger — hunts for overengineering/scope creep.

Both work read-only. Only the coordinator writes the final SOLUTION.md.

If the harness does not provide an isolated-subagent tool (for example, Pi) — run the challengers inline: two separate passes, each outputting only findings in the delegation-policy format, then the coordinator responds. Do not simulate spawning subagents and do not claim they were launched.

What to read

• context-modes.md
• design-workflow.md
• design-readiness-gate.md
• evidence-policy.md
• solution-lenses.md
• delegation-policy.md
• SOLUTION.template.md

Language

Write SOLUTION.md and all reports in the user's language — the language of the user's request and conversation, not the language of these instructions. If the request is in Russian, the artifact is in Russian. Do not translate file names, symbols, commands, statuses, or APIs.

Completion criteria

SOLUTION.md is done only if:

• there is a short human block;
• the agent block contains verifiable requirements, contracts, decisions, risks, validation;
• the minimal sufficient approach is chosen;
• the non-goals and rejected overengineering are explicit;
• every material requirement has observable verification;
• PlanF3 will not have to reinvent the architecture;
• the final status is exactly one of: READY_FOR_PLANF3, BLOCKED, BLOCKED_BY_SCOPE_OVERDESIGN.