Prompt ownership matrix (MIN-379)

Defines which layer owns which instruction so composed system prompts do not repeat the same rule 2–4 times.

Layers

Layer	Owns	Does not own
base	Identity, session context, communication style, safety/trust (destructive commands, secrets, untrusted data), resource awareness	Tool mechanics, mode workflow, deliverable schemas
tool-usage (default)	Read-before-write, never-invent-output, shell/Windows/build-output/background commands, parallel calls, failure policy (interactive vs autonomous), working directory	Mode-specific deliverables, plan schemas
tool-usage (fragments)	Conditional features: fact-verification ladder, mode-handoff, ask-question enforcement, browser allowlist, sub-agent delegation, Context7, settings, launch-app	Content duplicated in base or mode
mode	Mode mechanics only: tool policy deltas, handoff triggers, mode-specific reporting (e.g. READY FOR VERIFICATION), todo_write when no default work-agent	Full implementation how-to when default work-agent is active
work-agent	Deliverable spec: Builder persistence/diagnostics, Planner plan schema, Orchestrator board workflow	Base safety, generic shell rules
memory	Brain wiki layout, routing table, save_memory / brain_write rules, brain-before-web	Base one-line pointer to memory section

Suppression rules (composer)

When workAgentId matches defaultForModes for the active mode, the mode part is omitted — the work-agent carries deliverable instructions (e.g. Build + Builder, Plan + Planner, Orchestrate + Orchestrator).

Dedupe checklist

• Security/git destructive rules: base + tool-usage rule 7 only (mode/work-agent reference base).
• Verify-before-build ladder: fact-verification fragment only (base = one-line pointer).
• ask_question mandatory usage: ask-question-enforcement (+ browser allowlist when browser tools enabled).
• Memory save/search rules: memory part only (base = one-line pointer).
• Shell/Windows/test guidance: tool-usage default only.
• Plan schema with Build/Test/Accept: planner work-agent when auto-selected; plan mode when planner is not active.

Lite profile

Every fragment that can be injected in lite profile must ship a .lite.md variant. Parts without a lite variant are omitted (not truncated mid-sentence).

Compose-time hygiene

• HTML comments (<!-- MINNOW_MODE_MARKER: … -->) are stripped before the model sees the prompt.
• Dead interpolation tokens are removed from the composer.