diff --git a/src/plugin-interface.test.ts b/src/plugin-interface.test.ts
index 4dac3f7be..fea4752e2 100644
--- a/src/plugin-interface.test.ts
+++ b/src/plugin-interface.test.ts
@@ -6,7 +6,6 @@ import { randomUUID } from "node:crypto"
 import { createPluginInterface } from "./plugin-interface"
 import { createAutoSlashCommandHook } from "./hooks/auto-slash-command"
 import { createStartWorkHook } from "./hooks/start-work"
-import { getAgentListDisplayName } from "./shared/agent-display-names"
 import { readBoulderState } from "./features/boulder-state"
 import {
   _resetForTesting,
diff --git a/src/plugin/chat-message.test.ts b/src/plugin/chat-message.test.ts
index 6dd7a0397..2d96f6065 100644
--- a/src/plugin/chat-message.test.ts
+++ b/src/plugin/chat-message.test.ts
@@ -9,7 +9,6 @@ import { createAutoSlashCommandHook } from "../hooks/auto-slash-command"
 import { createStartWorkHook } from "../hooks/start-work"
 import { readBoulderState } from "../features/boulder-state"
 import { _resetForTesting, setMainSession, subagentSessions, registerAgentName, updateSessionAgent, getSessionAgent } from "../features/claude-code-session-state"
-import { getAgentListDisplayName } from "../shared/agent-display-names"
 import { clearSessionModel, getSessionModel, setSessionModel } from "../shared/session-model-state"
 
 type ChatMessagePart = { type: string; text?: string; [key: string]: unknown }
@@ -403,7 +402,10 @@ describe("createChatMessageHandler - TUI variant passthrough", () => {
     expect(getSessionModel("test-session")).toEqual({ providerID: "openai", modelID: "gpt-5.4" })
   })
 
-  test("treats prefixed list-display agent names as explicit model overrides", async () => {
+  test("treats legacy ZWSP-prefixed agent names as explicit model overrides (GH-3259)", async () => {
+    // Users upgrading from v3.14.0-v3.16.0 may still have ZWSP-prefixed agent
+    // keys persisted in their session state. The handler must strip the
+    // prefix and resolve to the canonical display name.
     //#given
     setMainSession("test-session")
     setSessionModel("test-session", { providerID: "openai", modelID: "gpt-5.4" })
@@ -416,7 +418,7 @@ describe("createChatMessageHandler - TUI variant passthrough", () => {
       },
     })
     const handler = createChatMessageHandler(args)
-    const input = createMockInput(getAgentListDisplayName("prometheus"))
+    const input = createMockInput("\u200B\u200B\u200BPrometheus - Plan Builder")
     const output = createMockOutput()
 
     //#when
diff --git a/src/shared/agent-display-names.test.ts b/src/shared/agent-display-names.test.ts
index 353bfb31e..b77a5e1ff 100644
--- a/src/shared/agent-display-names.test.ts
+++ b/src/shared/agent-display-names.test.ts
@@ -183,30 +183,46 @@ describe("getAgentConfigKey", () => {
     expect(getAgentConfigKey("Sisyphus-Junior")).toBe("sisyphus-junior")
   })
 
-  it("resolves atlas even when the UI ordering prefix is present", () => {
-    expect(getAgentConfigKey(getAgentListDisplayName("atlas"))).toBe("atlas")
+  it("resolves atlas even when a legacy ZWSP sort prefix is present on the stored key", () => {
+    // Users who installed v3.14.0 through v3.16.0 may have ZWSP-prefixed agent
+    // names baked into their config.agent keys. The resolver must still find
+    // the canonical config key after strip.
+    expect(getAgentConfigKey("\u200B\u200B\u200B\u200BAtlas - Plan Executor")).toBe("atlas")
   })
 })
 
-describe("getAgentListDisplayName", () => {
-  it("applies invisible stable-sort prefixes to the core agent list", () => {
-    expect(getAgentListDisplayName("sisyphus")).toBe("\u200BSisyphus - Ultraworker")
-    expect(getAgentListDisplayName("hephaestus")).toBe("\u200B\u200BHephaestus - Deep Agent")
-    expect(getAgentListDisplayName("prometheus")).toBe("\u200B\u200B\u200BPrometheus - Plan Builder")
-    expect(getAgentListDisplayName("atlas")).toBe("\u200B\u200B\u200B\u200BAtlas - Plan Executor")
+describe("getAgentListDisplayName (deprecated alias, GH-3259)", () => {
+  it("returns plain display names without the legacy ZWSP sort prefix", () => {
+    // ZWSP prefixes were removed in #3242/#3259. This alias is retained for
+    // external callers that may still import it, but it now behaves
+    // identically to getAgentDisplayName.
+    expect(getAgentListDisplayName("sisyphus")).toBe("Sisyphus - Ultraworker")
+    expect(getAgentListDisplayName("hephaestus")).toBe("Hephaestus - Deep Agent")
+    expect(getAgentListDisplayName("prometheus")).toBe("Prometheus - Plan Builder")
+    expect(getAgentListDisplayName("atlas")).toBe("Atlas - Plan Executor")
   })
 
-  it("keeps non-core agents unprefixed for list display", () => {
+  it("matches getAgentDisplayName for unknown agents", () => {
     expect(getAgentListDisplayName("oracle")).toBe("oracle")
   })
+
+  it("contains no zero-width characters in any core agent output (GH-3259)", () => {
+    const coreAgents = ["sisyphus", "hephaestus", "prometheus", "atlas"]
+    for (const agent of coreAgents) {
+      const result = getAgentListDisplayName(agent)
+      expect(result).not.toMatch(/[\u200B\u200C\u200D\uFEFF]/)
+    }
+  })
 })
 
 describe("normalizeAgentForPrompt", () => {
-  it("strips core UI ordering prefixes back to canonical display names", () => {
-    expect(normalizeAgentForPrompt(getAgentListDisplayName("sisyphus"))).toBe("Sisyphus - Ultraworker")
-    expect(normalizeAgentForPrompt(getAgentListDisplayName("hephaestus"))).toBe("Hephaestus - Deep Agent")
-    expect(normalizeAgentForPrompt(getAgentListDisplayName("prometheus"))).toBe("Prometheus - Plan Builder")
-    expect(normalizeAgentForPrompt(getAgentListDisplayName("atlas"))).toBe("Atlas - Plan Executor")
+  it("strips legacy ZWSP sort prefixes from stored agent keys back to canonical display names", () => {
+    // Configs from v3.14.0-v3.16.0 may persist ZWSP-prefixed keys. The
+    // normalizer must restore the canonical name on read.
+    expect(normalizeAgentForPrompt("\u200BSisyphus - Ultraworker")).toBe("Sisyphus - Ultraworker")
+    expect(normalizeAgentForPrompt("\u200B\u200BHephaestus - Deep Agent")).toBe("Hephaestus - Deep Agent")
+    expect(normalizeAgentForPrompt("\u200B\u200B\u200BPrometheus - Plan Builder")).toBe("Prometheus - Plan Builder")
+    expect(normalizeAgentForPrompt("\u200B\u200B\u200B\u200BAtlas - Plan Executor")).toBe("Atlas - Plan Executor")
   })
 })
 
diff --git a/src/shared/agent-display-names.ts b/src/shared/agent-display-names.ts
index 426425851..2ccb545ad 100644
--- a/src/shared/agent-display-names.ts
+++ b/src/shared/agent-display-names.ts
@@ -26,13 +26,23 @@ export const AGENT_DISPLAY_NAMES: Record<string, string> = {
   "council-member": "council-member",
 }
 
-const AGENT_LIST_SORT_PREFIXES: Record<string, string> = {
-  sisyphus: "\u200B",
-  hephaestus: "\u200B\u200B",
-  prometheus: "\u200B\u200B\u200B",
-  atlas: "\u200B\u200B\u200B\u200B",
-}
-
+/**
+ * Strip the legacy zero-width-space sort prefix from an agent name.
+ *
+ * v3.14.0 through v3.16.0 prefixed the four core agents (Sisyphus,
+ * Hephaestus, Prometheus, Atlas) with U+200B Zero Width Space characters
+ * so they would sort ahead of user agents in the Tab cycle. Some terminal
+ * emulators (Ghostty, certain Windows Terminal builds) render ZWSP as a
+ * visible box or extra space, breaking the status bar layout (#3259), and
+ * the prefixes also leaked through the plugin API and broke prompt_async
+ * consumers (#3238).
+ *
+ * The prefixes are no longer injected anywhere (#3242 removed all call
+ * sites and #3259 removed the constant table). This helper remains so
+ * existing user configs that still have the ZWSP baked into their
+ * `config.agent` keys from an older install continue to resolve
+ * correctly after upgrading.
+ */
 export function stripAgentListSortPrefix(agentName: string): string {
   return agentName.replace(/^\u200B+/, "")
 }
@@ -58,17 +68,20 @@ export function getAgentDisplayName(configKey: string): string {
 }
 
 /**
- * @deprecated Do NOT use for config.agent keys or API-facing names.
- * ZWSP prefixes leak into the /agent API response and break prompt_async consumers.
- * Use getAgentDisplayName() instead. The `order` field injected by
- * reorderAgentsByPriority() handles sort ordering without invisible characters.
- * See: https://github.com/code-yeongyu/oh-my-openagent/issues/3238
+ * @deprecated Use {@link getAgentDisplayName} directly.
+ *
+ * Historically this returned the display name with a ZWSP sort prefix
+ * prepended so core agents would sort ahead of user agents in the Tab
+ * cycle. The ZWSP prefixes caused visible rendering artifacts in some
+ * terminals (#3259) and leaked into the plugin API surface (#3238), so
+ * they were removed in #3242/#3259. This function is now a thin alias
+ * over {@link getAgentDisplayName} that exists only for external
+ * callers that may still import it. Sort ordering is now handled by
+ * the `order` field injection in `reorderAgentsByPriority()` plus the
+ * core-first insertion order in the same helper.
  */
 export function getAgentListDisplayName(configKey: string): string {
-  const displayName = getAgentDisplayName(configKey)
-  const prefix = AGENT_LIST_SORT_PREFIXES[configKey.toLowerCase()]
-
-  return prefix ? `${prefix}${displayName}` : displayName
+  return getAgentDisplayName(configKey)
 }
 
 const REVERSE_DISPLAY_NAMES: Record<string, string> = Object.fromEntries(