feat: Add ce:ideate open-ended ideation skill

Overview

Add a new ce:ideate skill to the compound-engineering plugin that performs open-ended, divergent-then-convergent idea generation for any project. The skill deeply scans the codebase, generates ~30 ideas, self-critiques and filters them, and presents the top 5-7 as a ranked list with structured analysis. It uses agent intelligence to improve the candidate pool without replacing the core prompt mechanism, writes a durable artifact to docs/ideation/ after the survivors have been reviewed, and hands off selected ideas to ce:brainstorm.

Problem Frame

The ce:* workflow pipeline has a gap at the very beginning. ce:brainstorm requires the user to bring an idea — it refines but doesn't generate. Users who want the AI to proactively suggest improvements must resort to ad-hoc prompting, which lacks codebase grounding, structured output, durable artifacts, and pipeline integration. (see origin: docs/brainstorms/2026-03-15-ce-ideate-skill-requirements.md)

Requirements Trace

• R1. Standalone skill in plugins/compound-engineering/skills/ce-ideate/
• R2. Optional freeform argument as focus hint (concept, path, constraint, or empty)
• R3. Deep codebase scan via research agents before generating ideas
• R4. Preserve the proven prompt mechanism: many ideas first, then brutal filtering, then detailed survivors
• R5. Self-critique with explicit rejection reasoning
• R6. Present top 5-7 with structured analysis (description, rationale, downsides, confidence 0-100%, complexity)
• R7. Rejection summary (one-line per rejected idea)
• R8. Durable artifact in docs/ideation/YYYY-MM-DD-<topic>-ideation.md
• R9. Volume overridable via argument
• R10. Handoff: brainstorm an idea, refine, share to Proof, or end session
• R11. Always route to ce:brainstorm for follow-up on selected ideas
• R12. Offer commit on session end
• R13. Resume from existing ideation docs (30-day recency window)
• R14. Present survivors before writing the durable artifact
• R15. Write artifact before handoff/share/end
• R16. Update doc in place on refine when preserving refined state
• R17. Use agent intelligence as support for the core mechanism, not a replacement
• R18. Use research agents for grounding; ideation/critique sub-agents are prompt-defined roles
• R19. Pass grounding summary, focus hint, and volume target to ideation sub-agents
• R20. Focus hints influence both generation and filtering
• R21. Use standardized structured outputs from ideation sub-agents
• R22. Orchestrator owns final scoring, ranking, and survivor decisions
• R23. Use broad prompt-framing methods to encourage creative spread without over-constraining ideation
• R24. Use the smallest useful set of sub-agents rather than a hardcoded fixed count
• R25. Mark ideas as "explored" when brainstormed

Scope Boundaries

• No external research (competitive analysis, similar projects) in v1 (see origin)
• No configurable depth modes — fixed volume with argument-based override (see origin)
• No modifications to ce:brainstorm — discovery via skill description only (see origin)
• No deprecated workflows:ideate alias — the workflows:* prefix is deprecated
• No references/ split — estimated skill length ~300 lines, well under the 500-line threshold

Context & Research

Relevant Code and Patterns

• plugins/compound-engineering/skills/ce-brainstorm/SKILL.md — Closest sibling. Mirror: resume behavior (Phase 0.1), artifact frontmatter (date + topic), handoff options via platform question tool, document-review integration, Proof sharing
• plugins/compound-engineering/skills/ce-plan/SKILL.md — Agent dispatch pattern: Task compound-engineering:research:repo-research-analyst(context) running in parallel. Phase 0.2 upstream document detection
• plugins/compound-engineering/skills/ce-work/SKILL.md — Session completion: incremental commit pattern, staging specific files, conventional commit format
• plugins/compound-engineering/skills/ce-compound/SKILL.md — Parallel research assembly: subagents return text only, orchestrator writes the single file
• plugins/compound-engineering/skills/document-review/SKILL.md — Utility invocation: "Load the document-review skill and apply it to..." Returns "Review complete" signal
• plugins/compound-engineering/skills/deepen-plan/SKILL.md — Broad parallel agent dispatch pattern
• PR #277 (fix: codex workflow conversion for compound-engineering) — establishes the Codex model for canonical ce:* workflows: prompt wrappers for canonical entrypoints, transformed intra-workflow handoffs, and omission of deprecated workflows:* aliases

Institutional Learnings

• docs/solutions/plugin-versioning-requirements.md — Do not bump versions or cut changelog entries in feature PRs. Do update README counts and plugin.json descriptions.
• docs/solutions/codex-skill-prompt-entrypoints.md (from PR #277) — for compound-engineering workflows in Codex, prompts are the canonical user-facing entrypoints and copied skills are the reusable implementation units underneath them

Key Technical Decisions

• Agent dispatch for codebase scan: Use repo-research-analyst + learnings-researcher in parallel (matches ce:plan Phase 1.1). Skip git-history-analyzer by default — marginal ideation value for the cost. The focus hint (R2) is passed as context to both agents.
• Core mechanism first, agents second: The core design is still the user's proven prompt pattern: generate many ideas, reject aggressively, then explain only the survivors. Agent intelligence improves the candidate pool and critique quality, but does not replace this mechanism.
• Prompt-defined ideation and critique sub-agents: Use prompt-shaped sub-agents with distinct framing methods for ideation and optional skeptical critique, rather than forcing reuse of existing named review agents whose purpose is different.
• Orchestrator-owned synthesis and scoring: The orchestrator merges and dedupes sub-agent outputs, applies one consistent rubric, and decides final scoring/ranking. Sub-agents may emit lightweight local signals, but not authoritative final rankings.
• Artifact frontmatter: date, topic, focus (optional). Minimal, paralleling the brainstorm date + topic pattern.
• Volume override via natural language: The skill instructions tell Claude to interpret number patterns in the argument ("top 3", "100 ideas") as volume overrides. No formal parsing.
• Artifact timing: Present survivors first, allow brief questions or lightweight clarification, then write/update the durable artifact before any handoff, Proof share, or session end.
• No disable-model-invocation: The skill should be auto-loadable when users say things like "what should I improve?", "give me ideas for this project", "ideate on improvements". Following the same pattern as ce:brainstorm.
• Commit pattern: Stage only docs/ideation/<filename>, use conventional format docs: add ideation for <topic>, offer but don't force.
• Relationship to PR #277: ce:ideate must follow the same Codex workflow model as the other canonical ce:* workflows. Why: without #277's prompt-wrapper and handoff-rewrite model, a copied workflow skill can still point at Claude-style slash handoffs that do not exist coherently in Codex. ce:ideate should be introduced as another canonical ce:* workflow on that same surface, not as a one-off pass-through skill.

Open Questions

Resolved During Planning

• Which agents for codebase scan? → repo-research-analyst + learnings-researcher. Rationale: same proven pattern as ce:plan, covers both current code and institutional knowledge.
• Additional analysis fields per idea? → Keep as specified in R6. "What this unlocks" bleeds into brainstorm scope. YAGNI.
• Volume override detection? → Natural language interpretation. The skill instructions describe how to detect overrides. No formal parsing needed.
• Artifact frontmatter fields? → date, topic, focus (optional). Follows brainstorm pattern.
• Need references/ split? → No. Estimated ~300 lines, under the 500-line threshold.
• Need deprecated alias? → No. workflows:* is deprecated; new skills go straight to ce:*.
• How should docs regeneration be represented in the plan? → The checked-in tree does not currently contain the previously assumed generated files (docs/index.html, docs/pages/skills.html). Treat /release-docs as a repo-maintenance validation step that may update tracked generated artifacts, not as a guaranteed edit to predetermined file paths.
• How should skill counts be validated across artifacts? → Do not force one unified count across every surface. The plugin manifests should reflect parser-discovered skill directories, while plugins/compound-engineering/README.md should preserve its human-facing taxonomy of workflow commands vs. standalone skills.
• What is the dependency on PR #277? → Treat #277 as an upstream prerequisite for Codex correctness. If it merges first, ce:ideate should slot into its canonical ce:* workflow model. If it does not merge first, equivalent Codex workflow behavior must be included before ce:ideate is considered complete.
• How should agent intelligence be applied? → Research agents are used for grounding, prompt-defined sub-agents are used to widen the candidate pool and critique it, and the orchestrator remains the final judge.
• Who should score the ideas? → The orchestrator, not the ideation sub-agents and not a separate scoring sub-agent by default.
• When should the artifact be written? → After the survivors are presented and reviewed enough to preserve, but always before handoff, sharing, or session end.

Deferred to Implementation

• Exact wording of the divergent ideation prompt section: The plan specifies the structure and mechanisms, but the precise phrasing will be refined during implementation. This is an inherently iterative design element.
• Exact wording of the self-critique instructions: Same — structure is defined, exact prose is implementation-time.

Implementation Units

• Unit 1: Create the ce:ideate SKILL.md

Goal: Write the complete skill definition with all phases, the ideation prompt structure, optional sub-agent support, artifact template, and handoff options.

Requirements: R1-R25 (all requirements — this is the core deliverable)

Dependencies: None

Files:

• Create: plugins/compound-engineering/skills/ce-ideate/SKILL.md
• Test (conditional): tests/claude-parser.test.ts, tests/cli.test.ts

Approach:

• Keep this unit primarily content-only unless implementation discovers a real parser or packaging gap. loadClaudePlugin() already discovers any skills/*/SKILL.md, and most target converters/writers already pass plugin.skills through as skillDirs.
• Do not rely on pure pass-through for Codex. Because PR #277 gives compound-engineering ce:* workflows a canonical prompt-wrapper model in Codex, ce:ideate must be validated against that model and may require Codex-target updates if #277 is not already present.
• Treat artifact lifecycle rules as part of the skill contract, not polish: resume detection, present-before-write, refine-in-place, and brainstorm handoff state all live inside this SKILL.md and must be internally consistent.
• Keep the prompt sections grounded in Phase 1 findings so ideation quality does not collapse into generic product advice.
• Keep the user's original prompt mechanism as the backbone of the workflow. Extra agent structure should strengthen that mechanism rather than replacing it.
• When sub-agents are used, keep them prompt-defined and lightweight: shared grounding/focus/volume input, structured output, orchestrator-owned merge/dedupe/scoring.

The skill follows the ce:brainstorm phase structure but with fundamentally different phases:

Phase 0: Resume and Route
  0.1 Check docs/ideation/ for recent ideation docs (R13)
  0.2 Parse argument — extract focus hint and any volume override (R2, R9)
  0.3 If no argument, proceed with fully open ideation (no blocking ask)

Phase 1: Codebase Scan
  1.1 Dispatch research agents in parallel (R3):
      - Task compound-engineering:research:repo-research-analyst(focus context)
      - Task compound-engineering:research:learnings-researcher(focus context)
  1.2 Consolidate scan results into a codebase understanding summary

Phase 2: Divergent Generation (R4, R17-R21, R23-R24)
  Core ideation instructions tell Claude to:
  - Generate ~30 ideas (or override amount) as a numbered list
  - Each idea is a one-liner at this stage
  - Push past obvious suggestions — the first 10-15 will be safe/obvious,
    the interesting ones come after
  - Ground every idea in specific codebase findings from Phase 1
  - Ideas should span multiple dimensions where justified
  - If a focus area was provided, weight toward it but don't exclude
    other strong ideas
  - Preserve the user's original many-ideas-first mechanism
  Optional sub-agent support:
  - If the platform supports it, dispatch a small useful set of ideation
    sub-agents with the same grounding summary, focus hint, and volume target
  - Give each one a distinct prompt framing method (e.g. friction, unmet
    need, inversion, assumption-breaking, leverage, extreme case)
  - Require structured idea output so the orchestrator can merge and dedupe
  - Do not use sub-agents to replace the core ideation mechanism

Phase 3: Self-Critique and Filter (R5, R7, R20-R22)
  Critique instructions tell Claude to:
  - Go through each idea and evaluate it critically
  - For each rejection, write a one-line reason
  - Rejection criteria: not actionable, too vague, too expensive relative
    to value, already exists, duplicates another idea, not grounded in
    actual codebase state
  - Target: keep 5-7 survivors (or override amount)
  - If more than 7 pass scrutiny, do a second pass with higher bar
  - If fewer than 5 pass, note this honestly rather than lowering the bar
  Optional critique sub-agent support:
  - Skeptical sub-agents may attack the merged list from distinct angles
  - The orchestrator synthesizes critiques and owns final scoring/ranking

Phase 4: Present Results (R6, R7, R14)
  - Display ranked survivors with structured analysis per idea:
    title, description (2-3 sentences), rationale, downsides,
    confidence (0-100%), estimated complexity (low/medium/high)
  - Display rejection summary: collapsed section, one-line per rejected idea
  - Allow brief questions or lightweight clarification before archival write

Phase 5: Write Artifact (R8, R15, R16)
  - mkdir -p docs/ideation/
  - Write the ideation doc after survivors are reviewe