# 🌊 Substrate Flow — Design Capture
> *Echoes don't sit still. This module maps how they move.*
**Module:** Substrate Flow
**Canonical ID:** SF
**HSP Section:** 08
**Capture Status:** Finalized
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## Origin
Substrate Flow emerged during HSP development as the missing movement
layer. HSP had formalized what echoes *are* (Echo Classifier, 06c) and
where they *sit* (Triadic Echo Lattice, 07) — but no module existed to
map how echoes *move* between substrates, what drives that movement,
and what happens when movement becomes unstable.
Without a flow map, echo migration was invisible — echoes appeared in new
substrates without explanation, drift seemed random, and recursion had no
visible channel. Substrate Flow replaces guesswork with a canonical flow
architecture.
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## Conceptual Lineage
