diff --git a/apps/ui/src/constants.test.ts b/apps/ui/src/constants.test.ts
new file mode 100644
index 00000000..51c98365
--- /dev/null
+++ b/apps/ui/src/constants.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, test } from "bun:test";
+import { avatarInitial } from "./constants";
+
+describe("avatarInitial", () => {
+	test("uppercases a plain handle's first letter", () => {
+		expect(avatarInitial("Mintaka")).toBe("M");
+	});
+
+	test("uppercases a lowercase handle", () => {
+		expect(avatarInitial("rigel")).toBe("R");
+	});
+
+	test("empty string falls back to ?", () => {
+		expect(avatarInitial("")).toBe("?");
+	});
+
+	test("whitespace-only falls back to ?", () => {
+		expect(avatarInitial("   ")).toBe("?");
+	});
+
+	// An emoji carries no Latin letter, so it clamps to ? on its own merits.
+	test("emoji-leading handle falls back to ?", () => {
+		expect(avatarInitial("🚀ocket")).toBe("?");
+	});
+
+	// Guards the grapheme read: this astral char NFKD-folds to plain "A", so a
+	// regression to .at(0) would split the surrogate pair and return ? instead.
+	test("astral first character is read whole, not as half a surrogate", () => {
+		expect(avatarInitial("𝐀lpha")).toBe("A");
+	});
+
+	test("accented Latin handle strips the diacritic", () => {
+		expect(avatarInitial("Émile")).toBe("E");
+	});
+
+	test("non-Latin script (Cyrillic) falls back to ?", () => {
+		expect(avatarInitial("Живко")).toBe("?");
+	});
+
+	// ß uppercases to "SS"; we keep the FIRST resulting char, not ?, so a real
+	// letter still distinguishes the agent.
+	test("uppercase-expanding character keeps its first char", () => {
+		expect(avatarInitial("ßravo")).toBe("S");
+	});
+
+	// A digit is a printable ASCII char and survives the clamp — a handle like
+	// "3pio" tabs as "3", which tells it apart better than ?.
+	test("digit-leading handle keeps the digit", () => {
+		expect(avatarInitial("3pio")).toBe("3");
+	});
+
+	// Punctuation is likewise printable ASCII and kept — the derivation only
+	// falls back to ? for non-ASCII-representable scripts, not for ASCII symbols.
+	test("punctuation-leading handle keeps the punctuation", () => {
+		expect(avatarInitial("_hidden")).toBe("_");
+	});
+});
diff --git a/apps/ui/src/constants.ts b/apps/ui/src/constants.ts
index e849da0d..c41e9880 100644
--- a/apps/ui/src/constants.ts
+++ b/apps/ui/src/constants.ts
@@ -123,6 +123,21 @@ export const RIGHT_SIDEBAR_TAB_BY_ID: {
 export const RIGHT_SIDEBAR_ISSUE_ITEMS: readonly ActivityBarItem[] =
 	Object.values(RIGHT_SIDEBAR_TAB_BY_ID).filter((t) => t.group === "issue");
 
+/** Derive an agent's activity-bar avatar initial from its handle, per D1 of
+ *  design compass-glyph-primitives. Handles are charset-unconstrained (proto
+ *  `from_handle`, no schema validation), so both activity-bar constructors
+ *  derive through here — and the ASCII clamp is what lets the Unifont pin
+ *  retire. An uppercase that expands (`ß`→`SS`) keeps the first letter rather
+ *  than `?`, since the initial exists to tell agents apart; the tab's title
+ *  carries the full handle either way. */
+export function avatarInitial(handle: string): string {
+	const first = Array.from(handle.trim())[0];
+	if (first === undefined) return "?";
+	const folded = first.normalize("NFKD").replace(/\p{M}/gu, "").toUpperCase();
+	const ascii = Array.from(folded)[0];
+	return ascii !== undefined && /^[\x21-\x7e]$/.test(ascii) ? ascii : "?";
+}
+
 /** Build the fleet activity-bar item for a RESOLVABLE pinned agent (Record A
  *  §T2; RIG-1645 P1). The tab id is the `agent:`-prefixed account id (the open
  *  arm of `RightSidebarTab`); the icon is the agent handle's initial (matching
@@ -134,7 +149,7 @@ export const RIGHT_SIDEBAR_ISSUE_ITEMS: readonly ActivityBarItem[] =
 export function fleetItemForAgent(agent: Agent): ActivityBarItem {
 	return {
 		id: `agent:${agent.account.id}`,
-		icon: (agent.account.handle.at(0) ?? "?").toUpperCase(),
+		icon: avatarInitial(agent.account.handle),
 		title: agent.account.handle,
 		group: "fleet",
 		agentId: agent.account.id,
@@ -151,7 +166,7 @@ export function fleetItemForAgent(agent: Agent): ActivityBarItem {
 export function unreachableFleetItem(pin: PinnedAgent): ActivityBarItem {
 	return {
 		id: `agent:${pin.id}`,
-		icon: (pin.handle.at(0) ?? "?").toUpperCase(),
+		icon: avatarInitial(pin.handle),
 		title: pin.handle,
 		group: "fleet",
 		agentId: pin.id,