feat(agents): add Hephaestus - autonomous deep worker agent (#1287)

* refactor(keyword-detector): split constants into domain-specific modules

* feat(shared): add requiresAnyModel and isAnyFallbackModelAvailable

* feat(config): add hephaestus to agent schemas

* feat(agents): add Hephaestus autonomous deep worker

* feat(cli): update model-fallback for hephaestus support

* feat(plugin): add hephaestus to config handler with ordering

* test(delegate-task): update tests for hephaestus agent

* docs: update AGENTS.md files for hephaestus

* docs: add hephaestus to READMEs

* chore: regenerate config schema

* fix(delegate-task): bypass requiresModel check when user provides explicit config

* docs(hephaestus): add 4-part context structure for explore/librarian prompts

* docs: fix review comments from cubic (non-breaking changes)

- Move Hephaestus from Primary Agents to Subagents (uses own fallback chain)
- Fix Hephaestus fallback chain documentation (claude-opus-4-5 → gemini-3-pro)
- Add settings.local.json to claude-code-hooks config sources
- Fix delegate_task parameters in ultrawork prompt (agent→subagent_type, background→run_in_background, add load_skills)
- Update line counts in AGENTS.md (index.ts: 788, manager.ts: 1440)

* docs: fix additional documentation inconsistencies from oracle review

- Fix delegate_task parameters in Background Agents example (docs/features.md)
- Fix Hephaestus fallback chain in root AGENTS.md to match model-requirements.ts

* docs: clarify Hephaestus has no fallback (requires gpt-5.2-codex only)

Hephaestus uses requiresModel constraint - it only activates when gpt-5.2-codex
is available. The fallback chain in code is unreachable, so documentation
should not mention fallbacks.

* fix(hephaestus): remove unreachable fallback chain entries

Hephaestus has requiresModel: gpt-5.2-codex which means the agent only
activates when that specific model is available. The fallback entries
(claude-opus-4-5, gemini-3-pro) were unreachable and misleading.

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>

src/plugin-handlers/config-handler.test.ts

@@ -106,6 +106,45 @@ afterEach(() => {
 })
 
 describe("Plan agent demote behavior", () => {
+  test("orders core agents as sisyphus -> hephaestus -> prometheus -> atlas", async () => {
+    // #given
+    const createBuiltinAgentsMock = agents.createBuiltinAgents as unknown as {
+      mockResolvedValue: (value: Record<string, unknown>) => void
+    }
+    createBuiltinAgentsMock.mockResolvedValue({
+      sisyphus: { name: "sisyphus", prompt: "test", mode: "primary" },
+      hephaestus: { name: "hephaestus", prompt: "test", mode: "primary" },
+      oracle: { name: "oracle", prompt: "test", mode: "subagent" },
+      atlas: { name: "atlas", prompt: "test", mode: "primary" },
+    })
+    const pluginConfig: OhMyOpenCodeConfig = {
+      sisyphus_agent: {
+        planner_enabled: true,
+      },
+    }
+    const config: Record<string, unknown> = {
+      model: "anthropic/claude-opus-4-5",
+      agent: {},
+    }
+    const handler = createConfigHandler({
+      ctx: { directory: "/tmp" },
+      pluginConfig,
+      modelCacheState: {
+        anthropicContext1MEnabled: false,
+        modelContextLimitsCache: new Map(),
+      },
+    })
+
+    // #when
+    await handler(config)
+
+    // #then
+    const keys = Object.keys(config.agent as Record<string, unknown>)
+    const coreAgents = ["sisyphus", "hephaestus", "prometheus", "atlas"]
+    const ordered = keys.filter((key) => coreAgents.includes(key))
+    expect(ordered).toEqual(coreAgents)
+  })
+
   test("plan agent should be demoted to subagent mode when replacePlan is true", async () => {
     // given
     const pluginConfig: OhMyOpenCodeConfig = {
@@ -173,6 +212,41 @@ describe("Plan agent demote behavior", () => {
   })
 })
 
+describe("Agent permission defaults", () => {
+  test("hephaestus should allow delegate_task", async () => {
+    // #given
+    const createBuiltinAgentsMock = agents.createBuiltinAgents as unknown as {
+      mockResolvedValue: (value: Record<string, unknown>) => void
+    }
+    createBuiltinAgentsMock.mockResolvedValue({
+      sisyphus: { name: "sisyphus", prompt: "test", mode: "primary" },
+      hephaestus: { name: "hephaestus", prompt: "test", mode: "primary" },
+      oracle: { name: "oracle", prompt: "test", mode: "subagent" },
+    })
+    const pluginConfig: OhMyOpenCodeConfig = {}
+    const config: Record<string, unknown> = {
+      model: "anthropic/claude-opus-4-5",
+      agent: {},
+    }
+    const handler = createConfigHandler({
+      ctx: { directory: "/tmp" },
+      pluginConfig,
+      modelCacheState: {
+        anthropicContext1MEnabled: false,
+        modelContextLimitsCache: new Map(),
+      },
+    })
+
+    // #when
+    await handler(config)
+
+    // #then
+    const agentConfig = config.agent as Record<string, { permission?: Record<string, string> }>
+    expect(agentConfig.hephaestus).toBeDefined()
+    expect(agentConfig.hephaestus.permission?.delegate_task).toBe("allow")
+  })
+})
+
 describe("Prometheus category config resolution", () => {
   test("resolves ultrabrain category config", () => {
     // given