diff --git a/src/cli/run/agent-resolver.test.ts b/src/cli/run/agent-resolver.test.ts
new file mode 100644
index 000000000..234db1db1
--- /dev/null
+++ b/src/cli/run/agent-resolver.test.ts
@@ -0,0 +1,88 @@
+/// <reference types="bun-types" />
+
+import { afterEach, describe, expect, it, mock, spyOn } from "bun:test"
+import type { OhMyOpenCodeConfig } from "../../config"
+import { resolveRunAgent } from "./agent-resolver"
+
+const createConfig = (overrides: Partial<OhMyOpenCodeConfig> = {}): OhMyOpenCodeConfig => ({
+  ...overrides,
+})
+
+describe("resolveRunAgent", () => {
+  afterEach(() => {
+    mock.restore()
+  })
+
+  it("preserves unknown explicit agents while honoring priority over env and config", () => {
+    //#given
+    const config = createConfig({ default_run_agent: "prometheus" })
+    const env = { OPENCODE_DEFAULT_AGENT: "Atlas" }
+
+    //#when
+    const agent = resolveRunAgent({ message: "test", agent: "  custom-agent  " }, config, env)
+
+    //#then
+    expect(agent).toBe("custom-agent")
+  })
+
+  it("falls back when an env-selected display-name agent is disabled", () => {
+    //#given
+    const config = createConfig({ disabled_agents: ["Atlas (Plan Executor)"] })
+    const env = { OPENCODE_DEFAULT_AGENT: "Atlas (Plan Executor)" }
+    const logSpy = spyOn(console, "log").mockImplementation(mock(() => undefined))
+
+    //#when
+    const agent = resolveRunAgent({ message: "test" }, config, env)
+
+    //#then
+    expect(agent).toBe("Sisyphus (Ultraworker)")
+    expect(logSpy).toHaveBeenCalledTimes(1)
+    expect(String(logSpy.mock.calls[0]?.[0] ?? "")).toContain("disabled")
+    expect(String(logSpy.mock.calls[0]?.[0] ?? "")).toContain("Sisyphus")
+  })
+
+  it("treats sisyphus_agent.disabled as disabling the config default agent", () => {
+    //#given
+    const config = createConfig({
+      default_run_agent: "sisyphus",
+      sisyphus_agent: { disabled: true },
+    })
+    const logSpy = spyOn(console, "log").mockImplementation(mock(() => undefined))
+
+    //#when
+    const agent = resolveRunAgent({ message: "test" }, config, {})
+
+    //#then
+    expect(agent).toBe("Hephaestus (Deep Agent)")
+    expect(logSpy).toHaveBeenCalledTimes(1)
+    expect(String(logSpy.mock.calls[0]?.[0] ?? "")).toContain("disabled")
+    expect(String(logSpy.mock.calls[0]?.[0] ?? "")).toContain("Hephaestus")
+  })
+
+  it("falls back to the default core agent when a requested core agent is disabled", () => {
+    //#given
+    const config = createConfig({ disabled_agents: ["Hephaestus"] })
+
+    //#when
+    const agent = resolveRunAgent({ message: "test", agent: "Hephaestus" }, config, {})
+
+    //#then
+    expect(agent).toBe("Sisyphus (Ultraworker)")
+  })
+
+  it("still returns sisyphus when every core agent is disabled", () => {
+    //#given
+    const config = createConfig({
+      disabled_agents: ["sisyphus", "hephaestus", "prometheus", "atlas"],
+    })
+    const logSpy = spyOn(console, "log").mockImplementation(mock(() => undefined))
+
+    //#when
+    const agent = resolveRunAgent({ message: "test", agent: "Atlas" }, config, {})
+
+    //#then
+    expect(agent).toBe("Sisyphus (Ultraworker)")
+    expect(logSpy).toHaveBeenCalledTimes(1)
+    expect(String(logSpy.mock.calls[0]?.[0] ?? "")).toContain("no enabled core agent was found")
+  })
+})