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+# ADR-0005: Inherit from Cortex patterns (R1-R19)
+
+**Status:** Accepted
+**Date:** 2026-04-23
+**Deciders:** Jacob
+
+## Context
+
+Cortex's `docs/future-plans/texting-bot-groups/` directory contains ~100 numbered requirements (R1-R19) developed over the past month, covering per-chat workspace isolation, attention gating, sharing bridge, phone-OTP identity, and so on. They are the most thought-through design for this problem anywhere Jacob has access to.
+
+The options are:
+
+1. **Re-derive from scratch.** Rejected: wastes weeks re-litigating decisions Cortex already made.
+2. **Copy-paste R1-R19 into picortex docs verbatim.** Rejected: stale-on-day-one; no attribution; muddles diff-with-Cortex reviews.
+3. **Inherit by reference.** Mark each Cortex requirement as one of: `adopt`, `adapt`, `reject`, `defer`. Document divergences in an inheritance map.
+
+## Decision
+
+Inherit by reference. Maintain [`docs/wiki/cortex-inheritance.md`](../wiki/cortex-inheritance.md) as a living map. Every Cortex requirement gets one of four labels:
+
+- **adopt** — use as-is; cite Cortex doc path.
+- **adapt** — use the idea, change implementation (e.g. Linux users instead of Docker).
+- **reject** — does not apply to picortex (e.g. enterprise billing flow).
+- **defer** — applies but post-v0.1.
+
+When Cortex updates a requirement, the inheritance map gets re-reviewed at quarterly diff checkpoints (see [ADR-0001](0001-standalone-project-not-noos-fork.md) "Mitigations").
+
+## Consequences
+
+### Positive
+
+- Zero re-derivation cost.
+- Clear audit trail for why each decision was made: "we adopted R4.3" or "we adapted R2.1 from Docker to Linux users (see ADR-0002)."
+- Cortex's language (e.g. `WorkspaceAccessResolver`, `BridgeEvent`) can be reused — agents writing code for picortex recognize it.
+- Forces explicit decision on every requirement — no silent drift.
+
+### Negative
+
+- Requires reading Cortex's plan-jacob-unified.md + requirements.md in full to build the map.
+- If Cortex's R-numbers ever reshuffle, the map breaks. Needs timestamped snapshot column.
+- Divergences have to be maintained in *two* places (ADR + inheritance map) — unavoidable but notable.
+
+### Mitigations
+
+- Inheritance map pins Cortex git SHA on adoption (e.g. "as of `e55f129`, 2026-04-23").
+- Every 3 months, re-diff against latest Cortex and update.
+
+## Related
+
+- [Cortex inheritance map](../wiki/cortex-inheritance.md) — the actual mapping
+- [ADR-0001](0001-standalone-project-not-noos-fork.md) — why standalone not fork
+- Cortex source: `IdeaFlowCo/cortex` @ `~/code/cortex/docs/future-plans/texting-bot-groups/`
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