Architect Build Specs

Output style (plain words, no dashes, no hyphens)

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Write everything this skill produces, files and messages alike, in plain simple language. Talk to the reader as you, warm and direct like a colleague, and present every step as a recommendation they may run or skip, never an order. Keep technical terms that carry real meaning; explain each in plain words. Never use a dash or a hyphen as punctuation: no em dash, no en dash, and no hyphenated compounds. Write read only, not read-only. Say it in simple words, or reword the sentence. Code, file paths, command flags, and values other skills match on keep their hyphens. Use short sentences, commas, or parentheses. Clear beats clever.

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What this skill does

Runs structured discovery, weighs options, and writes or updates a build spec in docs/specs/. The main thread writes; it offloads only reading the codebase or fetching the web to a cheap subagent (see Subagents). Four modes:

• Create: new decision → new spec with status Proposed
• Update: evolving an existing decision → edit existing spec in place
• Supersede: replacing a past decision → new spec + update old spec's status line
• Ratify: deliberating an Assumed spec that /develop recorded when the engineer chose to build before deciding → see Ratify an assumed decision below

Spec status behaves one of two ways, decided by whether a buildable scope feature links the spec (a docs/scope/ row whose spec cell points to it):

• Feature linked spec (typical FEATURE/ENHANCEMENT, or an ARCHITECTURE foundation that has a scope row): status mirrors the feature lifecycle. /architect creates it as Proposed and owns its content but never advances the status; /develop advances it to In Progress when the feature goes in-progress, then Accepted when built and verified (scope done). Engineer confirmation ratifies content only; Accepted means shipped.
• Standalone decision spec (foundational/stack or cross cutting standard, no scope row links it): decision status. Proposed when written, Accepted once the engineer ratifies it on confirmation (the decision is then in force). /develop does not advance it.

A spec documenting already shipped work (the "already built" path, or a linked feature already existing) is born Accepted.

The Assumed status. /develop may create a spec in status Assumed when the engineer chooses to build before a load bearing decision is deliberated. It records the assumption the build used, not a deliberated decision. The feature can still be marked done; the Assumed spec stays flagged as owing ratification and does not block it. Only /architect clears the Assumed status, by ratifying (below). /architect never creates an Assumed spec; it only deliberates one that already exists.

Writes no code. Never updates AGENTS.md/CLAUDE.md (/sync owns that).

Subagents (main thread writes; subagents only read, fetch, or cross check)

The main thread runs the conversation and writes the spec; it never hands the writing or any fix to a subagent. Every subagent it spawns is read only and never inherits the session model:

• Read the codebase (cheapest model, Claude Code haiku): a read only scan of existing code when the repo is large (ENHANCEMENT/CROSS-CUTTING). Claude Code: the scout type. Returns a compact map, never file dumps.
• Fetch from the web (cheapest model, Claude Code haiku): the current tool landscape check and the Agent Skill / MCP discovery, both during the design conversation (Stage c), when a decision needs current facts. Claude Code: the researcher type. Returns a compact summary, never raw pages.
• Cross check the drafted spec (its primary job is decision completeness: finding values an action must produce whose source the spec never names, and decisions the builder would otherwise invent): a read only pass that reads the finished spec and returns a critique, writing nothing. /architect always asks whether to run it (never runs or skips it on the engineer's behalf), recommending Another model strongly at GA/Beta (the tiers where these bugs live), offering it at Alpha, and recommending Skip at Prototype; any gap it finds is presented to the engineer with a recommended fix for them to decide, not auto resolved. See After the spec is written.

Web fetching happens once, when a decision needs it (the Stage (c) landscape and tool discovery checks). The links it returns go into the spec's References for a human to follow; the AI never fetches them again (not in the cross check, /develop, or /audit).

Asks vs acts

Ask targeted questions before you write the spec (and before spawning any read/fetch helper); spend the budget on substance. Sort every question:

• INFER: anything the prompt or codebase reveals (feature vs architecture, the stack, UI in scope, an already chosen provider). Derive, never ask.
• ASK: only what the engineer alone knows (requirements, preferences, business rules, compliance scope).
• RECOMMEND: anything expertise settles (which provider/library/pattern fits). State the pick, a one line why, and the runner up; they may override. Never a neutral menu, never a silent decision.

Never bundle a complete data model, full stack, or ready made acceptance criteria set into one accept or change panel, and never silently decide a tool, provider, or setup choice for them.

Recommendations align with the stack in use (on a BaaS, prefer its auth/storage over new external tools; reuse beats sprawl). Web or mobile alike: infer the platform, never assume web.

That is the intent, not the procedure. How to run the questioning lives in internal/design-conversation.md, which Execution below makes you read in full before you ask a single design question.

Artifact ownership

Spec files in docs/specs/, created or updated by this skill only, plus any supporting evidence it produces (inventories, audits), which lives in the spec's rationale.md (directory spec) or inline (single file spec), never in the scope folder (docs/scope/ is owned by /scope, not a spec).

Two independent choices, location (repo shape) and shape (decision size):

• Location = repo shape. Single repo → docs/specs/. Monorepo → docs/specs/<workspace>/ for a workspace decision, docs/specs/_root/ for a repo wide one (mirrors the scope). Numbering is per location (scan that dir for the next NNNN). Call the resolved location $SPEC_DIR.

• Shape = decision size, the same in any repo shape. Simple decision: one file $SPEC_DIR/NNNN-title.md (everything inline, written tight). An umbrella (related sub decisions), a heavy or foundational decision, or one that warrants a verify.md uses the directory shape: $SPEC_DIR/NNNN-title/ with index.md as its top file plus a rationale.md beside it (and child specs NNNN-<child>.md for an umbrella). Never double the name (NNNN-title/NNNN-title.md); the directory carries the number, the top file is index.md. Default to a single file.

  A directory spec always has exactly two core files (plus optional verify.md and child specs):

  • index.md: the build spec /develop reads: ## Summary, ## Requirements, ## Decision, the design/spec section, ## Build plan, ## Consequences, ## Follow-up, and a one line ## Rationale pointer to rationale.md. For an umbrella it also opens with a ## Structure manifest listing and linking every child spec (one line each: what it is plus which decision it supports), and holds any cross child contract.
  • rationale.md: the decision record /develop skips: ## Context, ## Options considered, ## Rationale, the ## References section, and any bulky evidence (inventories, audits) under its own subheading. There is no research/ folder; all evidence lives here.
  • Child specs (umbrella only) are flat NNNN-<child>.md files, each complete enough to build from on its own with a short inline rationale (not its own rationale.md); promote a child to its own directory only when it grows heavy. Cross child contracts live in the umbrella index.md.

• One narrow exception into the scope: after the spec is confirmed, update the matching feature to the ready to build shape (exact edits in After the spec is written, step 3). Never dump the atomic task list into the scope. No matching feature: offer to enroll one (see the derive tasks step).

Artifact base. specs live under docs/ by default. If docs/ is a published docs site (docusaurus.config.*, .vitepress/, mkdocs.yml, Astro Starlight, or Nextra detected), use .workflow/ instead (.workflow/specs/). Always follow whichever base already exists (paths here assume docs/).

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Portability (any OS, any agent)

• Commands: git is the only required CLI, same on every OS. Other shell snippets (mkdir -p, date, find, ls, cat, wc) are POSIX reference, not literal scripts; use your agent's cross platform file tools (read, search/glob, write, create dir) and your knowledge of today's date. Create docs/specs/ with your write tool, not mkdir.
• Bundled files: agent-prompt.md, agent-modes/*.md, and spec-template.md live at paths relative to this skill's folder. The main thread reads these itself right before it writes the spec (see Write the spec): agent-prompt.md (the persona, rules, and report format), the one matching agent-modes/<mode>.md, and spec-template.md (the section structure). Read them only at write time, not during pre-flight, so they don't sit in context through the whole interview.
• No interactive question support? Use whatever your agent provides (an options picker) and fall back only where missing: ask the question rounds as plain text with the same options.

Execution

Step 0: Topic check (before pre-flight)

If no design topic was provided (/architect with no argument or an empty description), stop and ask before doing anything else:

"What design decision do you want to work through? Describe the feature, system, or choice you need to design in one or two sentences."

Wait for the answer; use it as the design topic before pre-flight.

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Pre-flight (main model)

Run these steps (the git commands are literal; everything else uses your agent's file tools):

• Freshness (teams): git fetch quietly, pick the base branch (main if git rev-parse --verify main succeeds, else master), count commits behind with git rev-list --count HEAD..origin/<base>. If >0, warn "pull first" before deciding (a teammate may have added specs or changed this feature).
• Resolve the spec location (SPEC_DIR) = the scope workspace mirrored into docs/specs/: single repo → docs/specs/; monorepo workspace → docs/specs/<workspace>/; repo wide → docs/specs/_root/. Determine <workspace> as the scope does (topic/path/scope row). Create the directory if missing.
• Today's date: use today's date (inject it into the spec).
• List existing specs in this location: files named NNNN-*.md plus any index.md in $SPEC_DIR, for numbering (per location) and related decision detection.
• Count source files (e.g. .ts, .tsx, .js, .py, .go, .rs, .java), excluding node_modules/, .git/, dist/. Informs how much code there is to read, and whether to offload that reading to a scout subagent.
• Read project context, the source of truth for the stack and community skills: root AGENTS.md (fall back to CLAUDE.md, else MISSING), plus the nested <area>/AGENTS.md for this feature's area if one exists (e.g. src/auth/AGENTS.md for an auth feature).
• Read the build approach for THIS feature: the delivery strategy that governs how the spec's ## Build plan is ordered and sliced. Precedence: this feature's scope row Approach override if declared, else the project default (root AGENTS.md first, else the scope header in docs/scope/). A feature with its own approach is built by ITS approach; others use the project default. The four imply materially different ## Build plan orderings, not the same order relabeled: Tracer Bullet stands up a thin end to end thread through every layer first, then thickens; Skateboard builds the thinnest usable whole first, then grows; Facade leads with the UI shell on placeholder data and defers the migration (a prototype path); Journey completes one user path's tasks fully before the next. A project specific variant is possible. If neither records one, note the assumption and set the default by Staff/Principal judgment (prefer end to end Tracer Bullet slices for production work). Let the recorded approach visibly shape the ordering.
• Locate the linked scope feature (if any): cheaply scan docs/scope/ filenames/headings (including per workspace subdirs) for a feature matching this topic; open only the single scope file containing it (scope.md, or the matching <epic>.md in a split). If found, read that row's intent plus any acceptance criteria seeds (they seed Stage (a)) and remember the file/row for the derive tasks and linking steps; this also settles feature linked vs standalone status. If no row matches, note the standalone decision path and don't create one now.
• (Optional) list installed skills dirs for availability only (.claude/skills/, .agents/skills/, skills/). Relevance is decided by AGENTS.md plus the feature, not name matching.

From the spec list (paths relative to $SPEC_DIR):

• Next number: highest existing + 1, zero padded to 4 digits; 0001 if none (an umbrella directory counts as one number). Collision guard (teams): list again $SPEC_DIR immediately before you write; if the chosen NNNN exists, bump to the next free number. Never overwrite an existing spec; after writing, confirm no concurrent run took the same number.
• Filename / shape: kebab-case slug from the topic, max 5 words, no articles, lowercase.
  • Simple decision → $SPEC_DIR/NNNN-kebab-title.md.
  • Umbrella (splits into ≥2 related sub decisions) → directory $SPEC_DIR/NNNN-kebab-title/ with index.md (the umbrella decision listing its children), rationale.md (the reasoning + any inventories/audits), and child specs NNNN-child.md inside it. Decide from the topic's breadth before you write, and hold the shape in mind as you write.
• Related specs: go in two passes so this stays cheap as specs accumulate. First read only the title line of each existing spec (cheap even at dozens of them); then read the first 20 lines (title, status, opening of Context) of just the few whose title plausibly overlaps this topic, to confirm. Flag matches.
• Child of umbrella detection: if the topic is a sub decision of an existing umbrella ($SPEC_DIR/NNNN-<umbrella>/), e.g. one that surfaced while building under it, place the new spec inside that directory as the next child (NNNN-child.md) and add it to the umbrella's index.md list, not a new top level spec. Same path when /develop hits a decision partway through a build. Tell the engineer where it's going.
• Update/supersede detection: if an existing spec clearly overlaps the topic (same domain, system, decision), before the staged conversation present a decision panel (plain text options where the agent has no picker; the picker adds Other automatically): "I found an existing spec that may overlap: [path], [title]. How should I treat this?", options: New decision (create a new spec) · Update the existing spec in place · Supersede it (a new spec replaces it). Default to the "(recommended)" option by overlap strength (nearly identical → Update or Supersede; adjacent → New). On update/supersede: set OPERATION, read the existing spec in full, and skip the staged conversation for in place updates.
  • Assumed spec found: if the overlapping spec's **Status**: is Assumed, this is a ratify, not the panel above. Follow Ratify an assumed decision (run the design conversation, then either fill in the real content and clear Assumed, or supersede if the assumption was wrong).

Community skills come from the project's AGENTS.md, never a hardcoded name table (names and stacks change). Project wide skills/conventions live in root AGENTS.md, area specific ones in the nested <area>/AGENTS.md (maintained by /audit and /sync):

1. Read root AGENTS.md and the nested AGENTS.md for this feature's area; their ## Agent skills section lists each installed skill as a bullet with its location and a one line note on what it governs, so you can pick out the relevant ones and their paths directly.
2. Identify only the skills relevant to this feature. Take each relevant skill's path and note from that ## Agent skills bullet, and open it on demand while writing, only if it materially shapes the decision (see Write the spec, item 12). Skip skills the feature doesn't touch.
3. Available ≠ relevant. You may list the installed skills dirs to see what exists, but relevance comes from the feature plus AGENTS.md. If a clearly relevant skill is installed but not yet referenced in AGENTS.md, use it anyway and flag (spec Follow-up) that it belongs in the right context file: root if project wide, nested <area>/AGENTS.md if area specific.
4. Whatever the context files show the project already uses (a BaaS, an ORM, a payment provider, an auth library) is what your library/provider recommendation must build on or prefer, not an unrelated external tool. If a genuinely better option isn't installed, note it as a spec Follow-up rather than silently assuming it.

Workflow skills (never treat as community skills): audit, architect, scope, develop, check, test, document, debug, sync, plus new workflow skills as they're created.

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