diff --git a/src/agents/builtin-agents.ts b/src/agents/builtin-agents.ts
index 57e859c759..2d74a33dd7 100644
--- a/src/agents/builtin-agents.ts
+++ b/src/agents/builtin-agents.ts
@@ -12,6 +12,7 @@ import { createMetisAgent, metisPromptMetadata } from "./metis"
 import { createAtlasAgent, atlasPromptMetadata } from "./atlas"
 import { createMomusAgent, momusPromptMetadata } from "./momus"
 import { createHephaestusAgent } from "./hephaestus"
+import { createSisyphusJuniorAgentWithOverrides } from "./sisyphus-junior"
 import type { AvailableCategory } from "./dynamic-agent-prompt-builder"
 import {
   fetchAvailableModels,
@@ -41,6 +42,7 @@ const agentSources: Record<BuiltinAgentName, AgentSource> = {
   // Note: Atlas is handled specially in createBuiltinAgents()
   // because it needs OrchestratorContext, not just a model string
   atlas: createAtlasAgent as AgentFactory,
+  "sisyphus-junior": createSisyphusJuniorAgentWithOverrides as unknown as AgentFactory,
 }
 
 /**
diff --git a/src/agents/builtin-agents/general-agents.ts b/src/agents/builtin-agents/general-agents.ts
index 54f2ae3fb3..e75baa1467 100644
--- a/src/agents/builtin-agents/general-agents.ts
+++ b/src/agents/builtin-agents/general-agents.ts
@@ -50,6 +50,7 @@ export function collectPendingBuiltinAgents(input: {
     if (agentName === "sisyphus") continue
     if (agentName === "hephaestus") continue
     if (agentName === "atlas") continue
+    if (agentName === "sisyphus-junior") continue
     if (disabledAgents.some((name) => name.toLowerCase() === agentName.toLowerCase())) continue
 
     const override = agentOverrides[agentName]
diff --git a/src/agents/index.ts b/src/agents/index.ts
index 1eee7c3b27..6f2bbc1e74 100644
--- a/src/agents/index.ts
+++ b/src/agents/index.ts
@@ -2,3 +2,4 @@ export * from "./types"
 export { createBuiltinAgents } from "./builtin-agents"
 export type { AvailableAgent, AvailableCategory, AvailableSkill } from "./dynamic-agent-prompt-builder"
 export type { PrometheusPromptSource } from "./prometheus"
+export { createSisyphusJuniorAgentWithOverrides, SISYPHUS_JUNIOR_DEFAULTS } from "./sisyphus-junior"
diff --git a/src/agents/types.ts b/src/agents/types.ts
index 63e09b3f6a..acf4900074 100644
--- a/src/agents/types.ts
+++ b/src/agents/types.ts
@@ -113,7 +113,8 @@ export type BuiltinAgentName =
   | "multimodal-looker"
   | "metis"
   | "momus"
-  | "atlas";
+  | "atlas"
+  | "sisyphus-junior";
 
 export type OverridableAgentName = "build" | BuiltinAgentName;
 
diff --git a/src/config/schema/agent-names.ts b/src/config/schema/agent-names.ts
index 814077d88f..73e4f1f80a 100644
--- a/src/config/schema/agent-names.ts
+++ b/src/config/schema/agent-names.ts
@@ -11,6 +11,7 @@ export const BuiltinAgentNameSchema = z.enum([
   "metis",
   "momus",
   "atlas",
+  "sisyphus-junior",
 ])
 
 export const BuiltinSkillNameSchema = z.enum([
diff --git a/src/shared/model-requirements.test.ts b/src/shared/model-requirements.test.ts
index 29c4770572..992af79d8e 100644
--- a/src/shared/model-requirements.test.ts
+++ b/src/shared/model-requirements.test.ts
@@ -191,8 +191,8 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
     expect(hephaestus.requiresModel).toBeUndefined()
   })
 
-  test("all 10 builtin agents have valid fallbackChain arrays", () => {
-    // #given - list of 10 agent names
+  test("all 11 builtin agents have valid fallbackChain arrays", () => {
+    // #given - list of 11 agent names
     const expectedAgents = [
       "sisyphus",
       "hephaestus",
@@ -204,13 +204,14 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
       "metis",
       "momus",
       "atlas",
+      "sisyphus-junior",
     ]
 
     // when - checking AGENT_MODEL_REQUIREMENTS
     const definedAgents = Object.keys(AGENT_MODEL_REQUIREMENTS)
 
     // #then - all agents present with valid fallbackChain
-    expect(definedAgents).toHaveLength(10)
+    expect(definedAgents).toHaveLength(11)
     for (const agent of expectedAgents) {
       const requirement = AGENT_MODEL_REQUIREMENTS[agent]
       expect(requirement).toBeDefined()
diff --git a/src/shared/model-requirements.ts b/src/shared/model-requirements.ts
index 84ade08016..4c3f33b232 100644
--- a/src/shared/model-requirements.ts
+++ b/src/shared/model-requirements.ts
@@ -157,6 +157,19 @@ export const AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
       { providers: ["openai", "github-copilot", "opencode"], model: "gpt-5.4", variant: "medium" },
     ],
   },
+  "sisyphus-junior": {
+    fallbackChain: [
+      {
+        providers: ["anthropic", "github-copilot", "opencode"],
+        model: "claude-sonnet-4-6",
+      },
+      { providers: ["openai", "github-copilot", "opencode"], model: "gpt-5.4", variant: "medium" },
+      {
+        providers: ["google", "github-copilot", "opencode"],
+        model: "gemini-3-flash",
+      },
+    ],
+  },
 };
 
 export const CATEGORY_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {