diff --git a/src/tools/call-omo-agent/background-agent-executor.test.ts b/src/tools/call-omo-agent/background-agent-executor.test.ts
index f6cda6b9e..181e8dd8a 100644
--- a/src/tools/call-omo-agent/background-agent-executor.test.ts
+++ b/src/tools/call-omo-agent/background-agent-executor.test.ts
@@ -152,4 +152,32 @@ describe("executeBackgroundAgent", () => {
     expect(secondResult).toContain("Task ID: task-2")
     expect(secondResult).not.toContain("interrupt")
   })
+
+  test("#given subagent_type is the lowercase config key 'hephaestus' #when executeBackgroundAgent runs #then BackgroundManager.launch receives the registered display name 'Hephaestus - Deep Agent'", async () => {
+    //#given
+    launchMock.mockClear()
+    launchMock.mockResolvedValueOnce({
+      id: "task-heph",
+      sessionId: "ses-heph",
+      description: "task",
+      agent: "Hephaestus - Deep Agent",
+      status: "pending",
+    })
+    getTaskMock.mockReturnValueOnce({
+      id: "task-heph",
+      sessionId: "ses-heph",
+      description: "task",
+      agent: "Hephaestus - Deep Agent",
+      status: "pending",
+    })
+    const args = { ...testArgs, subagent_type: "hephaestus" }
+
+    //#when
+    await executeBackgroundAgent(args, testContext, mockManager, mockClient)
+
+    //#then
+    const launchCall = launchMock.mock.calls.find(([input]) => (input as { agent: string }).agent !== undefined)
+    expect(launchCall).toBeDefined()
+    expect((launchCall![0] as { agent: string }).agent).toBe("Hephaestus - Deep Agent")
+  })
 })
diff --git a/src/tools/call-omo-agent/background-agent-executor.ts b/src/tools/call-omo-agent/background-agent-executor.ts
index 23cfbfc0d..196157e9a 100644
--- a/src/tools/call-omo-agent/background-agent-executor.ts
+++ b/src/tools/call-omo-agent/background-agent-executor.ts
@@ -7,6 +7,7 @@ import type { CallOmoAgentArgs } from "./types"
 import type { ToolContextWithMetadata } from "./tool-context-with-metadata"
 import { getMessageDir } from "./message-storage-directory"
 import { getSessionTools } from "../../shared/session-tools-store"
+import { getAgentDisplayName, stripAgentListSortPrefix } from "../../shared/agent-display-names"
 
 export async function executeBackgroundAgent(
 	args: CallOmoAgentArgs,
@@ -39,7 +40,7 @@ export async function executeBackgroundAgent(
 		const task = await manager.launch({
 			description: args.description,
 			prompt: args.prompt,
-			agent: args.subagent_type,
+			agent: getAgentDisplayName(stripAgentListSortPrefix(args.subagent_type)),
 			parentSessionId: toolContext.sessionID,
 			parentMessageId: toolContext.messageID,
 			parentAgent,
diff --git a/src/tools/call-omo-agent/background-executor.test.ts b/src/tools/call-omo-agent/background-executor.test.ts
index d92722245..68603bf49 100644
--- a/src/tools/call-omo-agent/background-executor.test.ts
+++ b/src/tools/call-omo-agent/background-executor.test.ts
@@ -126,7 +126,7 @@ describe("executeBackground", () => {
     if (!launchArgs) {
       throw new Error("Expected launch arguments")
     }
-    expect(launchArgs.agent).toBe("hephaestus")
+    expect(launchArgs.agent).toBe("Hephaestus - Deep Agent")
   })
 
   test("keeps launched background task alive when parent aborts before session id resolves", async () => {
@@ -210,4 +210,48 @@ describe("executeBackground", () => {
     expect(secondResult).toContain("Task ID: task-2")
     expect(secondResult).not.toContain("interrupt")
   })
+
+  test("#given subagent_type is the lowercase config key 'hephaestus' #when executeBackground runs #then BackgroundManager.launch receives the registered display name", async () => {
+    //#given
+    launchMock.mockClear()
+    launchMock.mockResolvedValueOnce({
+      id: "test-task-id",
+      sessionId: "sub-session",
+      description: "Test task",
+      agent: "Hephaestus - Deep Agent",
+      status: "pending",
+    })
+
+    //#when
+    await executeBackground({ ...testArgs, subagent_type: "hephaestus" }, testContext, mockManager, mockClient)
+
+    //#then
+    const latestCall = [...launchMock.mock.calls].pop()
+    if (!latestCall) throw new Error("Expected background manager launch to be called")
+    const launchArgs = latestCall[0]
+    if (!launchArgs) throw new Error("Expected launch arguments")
+    expect(launchArgs.agent).toBe("Hephaestus - Deep Agent")
+  })
+
+  test("#given subagent_type is a same-keyed agent 'explore' #when executeBackground runs #then BackgroundManager.launch receives the unchanged key (regression guard)", async () => {
+    //#given
+    launchMock.mockClear()
+    launchMock.mockResolvedValueOnce({
+      id: "test-task-id",
+      sessionId: "sub-session",
+      description: "Test task",
+      agent: "explore",
+      status: "pending",
+    })
+
+    //#when
+    await executeBackground({ ...testArgs, subagent_type: "explore" }, testContext, mockManager, mockClient)
+
+    //#then
+    const latestCall = [...launchMock.mock.calls].pop()
+    if (!latestCall) throw new Error("Expected background manager launch to be called")
+    const launchArgs = latestCall[0]
+    if (!launchArgs) throw new Error("Expected launch arguments")
+    expect(launchArgs.agent).toBe("explore")
+  })
 })
diff --git a/src/tools/call-omo-agent/background-executor.ts b/src/tools/call-omo-agent/background-executor.ts
index cae87c986..ed0c841e6 100644
--- a/src/tools/call-omo-agent/background-executor.ts
+++ b/src/tools/call-omo-agent/background-executor.ts
@@ -9,6 +9,7 @@ import { getSessionAgent } from "../../features/claude-code-session-state"
 import { getMessageDir } from "./message-dir"
 import { getSessionTools } from "../../shared/session-tools-store"
 import { sanitizeSubagentType } from "../delegate-task/subagent-discovery"
+import { getAgentDisplayName, stripAgentListSortPrefix } from "../../shared/agent-display-names"
 
 export async function executeBackground(
   args: CallOmoAgentArgs,
@@ -48,7 +49,7 @@ export async function executeBackground(
     const task = await manager.launch({
       description: args.description,
       prompt: args.prompt,
-      agent: sanitizeSubagentType(args.subagent_type),
+      agent: getAgentDisplayName(stripAgentListSortPrefix(sanitizeSubagentType(args.subagent_type))),
       parentSessionId: toolContext.sessionID,
       parentMessageId: toolContext.messageID,
       parentAgent,
diff --git a/src/tools/call-omo-agent/sync-executor.test.ts b/src/tools/call-omo-agent/sync-executor.test.ts
index fdd6cff0b..3b0e0db5f 100644
--- a/src/tools/call-omo-agent/sync-executor.test.ts
+++ b/src/tools/call-omo-agent/sync-executor.test.ts
@@ -141,6 +141,69 @@ describe("executeSync", () => {
     expect(promptInput?.body.agent).toBe("Sisyphus - Ultraworker")
   })
 
+  test("#given subagent_type is the lowercase config key 'hephaestus' #when executeSync runs #then promptAsync receives the registered display name 'Hephaestus - Deep Agent'", async () => {
+    //#given
+    const executeSync = await importExecuteSync()
+    const deps = createDependencies()
+    const toolContext = createToolContext()
+    const recorder = createPromptAsyncRecorder()
+    const args = {
+      subagent_type: "hephaestus",
+      description: "task",
+      prompt: "do the thing",
+      run_in_background: false,
+    }
+
+    //#when
+    await executeSync(args, toolContext, createContext(recorder.promptAsync) as never, deps)
+
+    //#then — SDK rejects raw config keys with UnknownError; the dispatch must translate
+    const promptInput = recorder.getCapturedInput()
+    expect(promptInput?.body.agent).toBe("Hephaestus - Deep Agent")
+  })
+
+  test("#given subagent_type is the lowercase config key 'sisyphus-junior' #when executeSync runs #then promptAsync receives the registered display name 'Sisyphus-Junior'", async () => {
+    //#given
+    const executeSync = await importExecuteSync()
+    const deps = createDependencies()
+    const toolContext = createToolContext()
+    const recorder = createPromptAsyncRecorder()
+    const args = {
+      subagent_type: "sisyphus-junior",
+      description: "task",
+      prompt: "do the thing",
+      run_in_background: false,
+    }
+
+    //#when
+    await executeSync(args, toolContext, createContext(recorder.promptAsync) as never, deps)
+
+    //#then
+    const promptInput = recorder.getCapturedInput()
+    expect(promptInput?.body.agent).toBe("Sisyphus-Junior")
+  })
+
+  test("#given subagent_type is already a display name like 'explore' (config key == display name) #when executeSync runs #then promptAsync receives 'explore' unchanged", async () => {
+    //#given a same-keyed agent must not be double-translated
+    const executeSync = await importExecuteSync()
+    const deps = createDependencies()
+    const toolContext = createToolContext()
+    const recorder = createPromptAsyncRecorder()
+    const args = {
+      subagent_type: "explore",
+      description: "task",
+      prompt: "do the thing",
+      run_in_background: false,
+    }
+
+    //#when
+    await executeSync(args, toolContext, createContext(recorder.promptAsync) as never, deps)
+
+    //#then
+    const promptInput = recorder.getCapturedInput()
+    expect(promptInput?.body.agent).toBe("explore")
+  })
+
   test("returns processed response with task metadata footer", async () => {
     //#given
     const executeSync = await importExecuteSync()
diff --git a/src/tools/call-omo-agent/sync-executor.ts b/src/tools/call-omo-agent/sync-executor.ts
index 640bdb15a..aec78b183 100644
--- a/src/tools/call-omo-agent/sync-executor.ts
+++ b/src/tools/call-omo-agent/sync-executor.ts
@@ -5,7 +5,7 @@ import { getAgentToolRestrictions, log } from "../../shared"
 import { applySessionPromptParams } from "../../shared/session-prompt-params-helpers"
 import type { DelegatedModelConfig } from "../../shared/model-resolution-types"
 import type { FallbackEntry } from "../../shared/model-requirements"
-import { stripAgentListSortPrefix } from "../../shared/agent-display-names"
+import { getAgentDisplayName, stripAgentListSortPrefix } from "../../shared/agent-display-names"
 import { promptAsyncAfterSessionIdle } from "../../hooks/shared/prompt-async-gate"
 import { waitForCompletion } from "./completion-poller"
 import { processMessages } from "./message-processor"
@@ -119,7 +119,7 @@ export async function executeSync(
         input: {
           path: { id: sessionID },
           body: {
-            agent: normalizedSubagentType,
+            agent: getAgentDisplayName(normalizedSubagentType),
             tools: {
               ...getAgentToolRestrictions(normalizedSubagentType),
               task: false,