diff --git a/src/plugin-handlers/agent-config-handler.ts b/src/plugin-handlers/agent-config-handler.ts
index 8a8d9ea1d..38e576692 100644
--- a/src/plugin-handlers/agent-config-handler.ts
+++ b/src/plugin-handlers/agent-config-handler.ts
@@ -163,10 +163,15 @@ export async function applyAgentConfig(params: {
         getAgentDisplayName("sisyphus");
     }
 
+    // Assembly order: Sisyphus -> Hephaestus -> Prometheus -> Atlas
     const agentConfig: Record<string, unknown> = {
       sisyphus: builtinAgents.sisyphus,
     };
 
+    if (builtinAgents.hephaestus) {
+      agentConfig["hephaestus"] = builtinAgents.hephaestus;
+    }
+
     agentConfig["sisyphus-junior"] = createSisyphusJuniorAgentWithOverrides(
       params.pluginConfig.agents?.["sisyphus-junior"],
       (builtinAgents.atlas as { model?: string } | undefined)?.model,
@@ -248,7 +253,7 @@ export async function applyAgentConfig(params: {
     params.config.agent = {
       ...agentConfig,
       ...Object.fromEntries(
-        Object.entries(builtinAgents).filter(([key]) => key !== "sisyphus"),
+        Object.entries(builtinAgents).filter(([key]) => key !== "sisyphus" && key !== "hephaestus"),
       ),
       ...filterDisabledAgents(filteredUserAgents),
       ...filterDisabledAgents(filteredProjectAgents),
diff --git a/src/plugin-handlers/config-handler.test.ts b/src/plugin-handlers/config-handler.test.ts
index e4d681104..72681de0f 100644
--- a/src/plugin-handlers/config-handler.test.ts
+++ b/src/plugin-handlers/config-handler.test.ts
@@ -1205,8 +1205,8 @@ describe("per-agent todowrite/todoread deny when task_system enabled", () => {
   const AGENTS_WITH_TODO_DENY = new Set([
     getAgentListDisplayName("sisyphus"),
     getAgentListDisplayName("hephaestus"),
-    getAgentListDisplayName("atlas"),
     getAgentListDisplayName("prometheus"),
+    getAgentListDisplayName("atlas"),
     getAgentListDisplayName("sisyphus-junior"),
   ])
 
@@ -1218,8 +1218,8 @@ describe("per-agent todowrite/todoread deny when task_system enabled", () => {
     createBuiltinAgentsMock.mockResolvedValue({
       sisyphus: { name: "sisyphus", prompt: "test", mode: "primary" },
       hephaestus: { name: "hephaestus", prompt: "test", mode: "primary" },
-      atlas: { name: "atlas", prompt: "test", mode: "primary" },
       prometheus: { name: "prometheus", prompt: "test", mode: "primary" },
+      atlas: { name: "atlas", prompt: "test", mode: "primary" },
       "sisyphus-junior": { name: "sisyphus-junior", prompt: "test", mode: "subagent" },
       oracle: { name: "oracle", prompt: "test", mode: "subagent" },
     })
diff --git a/src/shared/agent-config-integration.test.ts b/src/shared/agent-config-integration.test.ts
index 1340dda7f..25cd14a26 100644
--- a/src/shared/agent-config-integration.test.ts
+++ b/src/shared/agent-config-integration.test.ts
@@ -86,15 +86,16 @@ describe("Agent Config Integration", () => {
   describe("Display name resolution", () => {
     test("returns correct display names for all builtin agents", () => {
       // given - lowercase config keys
-      const agents = ["sisyphus", "atlas", "prometheus", "metis", "momus", "oracle", "librarian", "explore", "multimodal-looker"]
+      const agents = ["sisyphus", "hephaestus", "prometheus", "atlas", "metis", "momus", "oracle", "librarian", "explore", "multimodal-looker"]
 
       // when - display names are requested
       const displayNames = agents.map((agent) => getAgentDisplayName(agent))
 
       // then - display names are correct
       expect(displayNames).toContain("Sisyphus (Ultraworker)")
-      expect(displayNames).toContain("Atlas (Plan Executor)")
+      expect(displayNames).toContain("Hephaestus (Deep Agent)")
       expect(displayNames).toContain("Prometheus (Plan Builder)")
+      expect(displayNames).toContain("Atlas (Plan Executor)")
       expect(displayNames).toContain("Metis (Plan Consultant)")
       expect(displayNames).toContain("Momus (Plan Critic)")
       expect(displayNames).toContain("oracle")
@@ -145,7 +146,7 @@ describe("Agent Config Integration", () => {
 
     test("model requirements include all builtin agents", () => {
       // given - expected builtin agents
-      const expectedAgents = ["sisyphus", "atlas", "prometheus", "metis", "momus", "oracle", "librarian", "explore", "multimodal-looker"]
+      const expectedAgents = ["sisyphus", "hephaestus", "prometheus", "atlas", "metis", "momus", "oracle", "librarian", "explore", "multimodal-looker"]
 
       // when - checking AGENT_MODEL_REQUIREMENTS
       const agentKeys = Object.keys(AGENT_MODEL_REQUIREMENTS)