diff --git a/.changeset/grid-phase-fields.md b/.changeset/grid-phase-fields.md
new file mode 100644
index 0000000..26510a2
--- /dev/null
+++ b/.changeset/grid-phase-fields.md
@@ -0,0 +1,5 @@
+---
+"ftw-webapp": patch
+---
+
+Name the grid's three phase currents and the main fuse in the shared contract, as field ids 11 to 14 after the frozen set. The box sends them for a node's own view; this app does not draw them yet.
diff --git a/contract/registry.yaml b/contract/registry.yaml
index 18f3cd5..0cfdaec 100644
--- a/contract/registry.yaml
+++ b/contract/registry.yaml
@@ -49,6 +49,29 @@ frozen_fields:
   # by the site convention: the charger consumes like any other load.
   10: { name: ev_w, kind: power, unit: W }
 
+# ---------------------------------------------------------------------------
+# Field ids after the frozen set. They travel like the frozen ids, in lane
+# 0's delta and in FTW Cloud's live body, under the same rules: integers,
+# sent only while the box has the reading, and an id never changes meaning.
+# They are depth for a node's own view, not the core view, so an app draws
+# Now without them and a box may stop sending one. Lane 0 drops the highest
+# id first when a delta does not fit its bucket, so these give way first.
+#
+# The grid's phase currents come from the site meter in tenths of an ampere,
+# signed by the site convention: positive while the phase draws from the
+# grid. A meter that gives magnitudes and no power per phase sends positive
+# values both ways, so a positive current alone does not prove import. The
+# box sends only the phases the site has, each while the meter is online and
+# reports it, and their freshness is the grid meter's. grid_fuse_da is the
+# main fuse per phase from the box's config, sent with the phases as their
+# scale.
+# ---------------------------------------------------------------------------
+extra_fields:
+  11: { name: grid_l1_da, kind: current, unit: dA }
+  12: { name: grid_l2_da, kind: current, unit: dA }
+  13: { name: grid_l3_da, kind: current, unit: dA }
+  14: { name: grid_fuse_da, kind: current, unit: dA }
+
 # ---------------------------------------------------------------------------
 # Capabilities. A set of names, not version numbers. Absent means the box does
 # not have it; the UI hides the feature and never crashes.
diff --git a/docs/protocol.md b/docs/protocol.md
index 48e09ce..f11a741 100644
--- a/docs/protocol.md
+++ b/docs/protocol.md
@@ -126,6 +126,12 @@ battery power, battery state of charge, load power, and their source ids. Any
 app, however old, can draw the core view. Freezing them now is free; doing it
 later is not.
 
+Ids after the frozen set live in the registry's `extra_fields`: depth for a
+node's own view, such as the grid's phase currents and the main fuse. They
+travel in the same `delta` and follow the same rules, but an app draws the
+core view without them and a box may stop sending one. A delta that does not
+fit drops the highest id first, so they give way before the core view.
+
 ## Freshness
 
 Every reading points at a **source**, not at its own timestamp:
diff --git a/tests/registry-contract.test.ts b/tests/registry-contract.test.ts
index 87484bc..5284125 100644
--- a/tests/registry-contract.test.ts
+++ b/tests/registry-contract.test.ts
@@ -283,6 +283,36 @@ describe('frozen field ids', () => {
     const table = Object.entries(FID).map(([name, id]) => `${id}: ${name.toLowerCase()}`)
     expect(table.sort()).toEqual(declared.sort())
   })
+
+  /**
+   * extra_fields share the frozen set's id space on the wire: a delta and
+   * FTW Cloud's live body key both by id alone. An id or a name in both
+   * blocks would be two meanings for one number. They also sit above the
+   * frozen set, because lane 0 drops the highest id first when a delta does
+   * not fit, and the core view must be the last thing to go.
+   */
+  it('leave the extra fields above the frozen set, with ids and names of their own', () => {
+    const entries = (name: string) =>
+      block(name).map((line) => {
+        const m = /^ {2}(\d+): \{ name: ([a-z0-9_]+),/.exec(line)
+        expect(m, `unreadable ${name} line: ${line}`).not.toBeNull()
+        return { id: Number(m![1]), name: m![2]! }
+      })
+    const frozen = entries('frozen_fields')
+    const extra = entries('extra_fields')
+    expect(extra.length, 'no extra fields were found to check').toBeGreaterThan(0)
+
+    const highestFrozen = Math.max(...frozen.map((f) => f.id))
+    const ids = new Set(frozen.map((f) => f.id))
+    const names = new Set(frozen.map((f) => f.name))
+    for (const f of extra) {
+      expect(f.id, `${f.name} sits among the frozen ids`).toBeGreaterThan(highestFrozen)
+      expect(ids.has(f.id), `field id ${f.id} is declared twice`).toBe(false)
+      expect(names.has(f.name), `field name ${f.name} is declared twice`).toBe(false)
+      ids.add(f.id)
+      names.add(f.name)
+    }
+  })
 })
 
 describe('capabilities the app gates on', () => {