diff --git a/src/hooks/prometheus-md-only/agent-matcher.ts b/src/hooks/prometheus-md-only/agent-matcher.ts
new file mode 100644
index 00000000..1932b5d4
--- /dev/null
+++ b/src/hooks/prometheus-md-only/agent-matcher.ts
@@ -0,0 +1,5 @@
+import { PROMETHEUS_AGENT } from "./constants"
+
+export function isPrometheusAgent(agentName: string | undefined): boolean {
+  return agentName?.toLowerCase().includes(PROMETHEUS_AGENT) ?? false
+}
diff --git a/src/hooks/prometheus-md-only/hook.ts b/src/hooks/prometheus-md-only/hook.ts
index d693836c..b0b5a01a 100644
--- a/src/hooks/prometheus-md-only/hook.ts
+++ b/src/hooks/prometheus-md-only/hook.ts
@@ -1,9 +1,10 @@
 import type { PluginInput } from "@opencode-ai/plugin"
-import { HOOK_NAME, PROMETHEUS_AGENT, BLOCKED_TOOLS, PLANNING_CONSULT_WARNING, PROMETHEUS_WORKFLOW_REMINDER } from "./constants"
+import { HOOK_NAME, BLOCKED_TOOLS, PLANNING_CONSULT_WARNING, PROMETHEUS_WORKFLOW_REMINDER } from "./constants"
 import { log } from "../../shared/logger"
 import { SYSTEM_DIRECTIVE_PREFIX } from "../../shared/system-directive"
 import { getAgentDisplayName } from "../../shared/agent-display-names"
 import { getAgentFromSession } from "./agent-resolution"
+import { isPrometheusAgent } from "./agent-matcher"
 import { isAllowedFile } from "./path-policy"
 
 const TASK_TOOLS = ["task", "call_omo_agent"]
@@ -16,7 +17,7 @@ export function createPrometheusMdOnlyHook(ctx: PluginInput) {
     ): Promise<void> => {
       const agentName = getAgentFromSession(input.sessionID, ctx.directory)
 
-      if (agentName !== PROMETHEUS_AGENT) {
+      if (!isPrometheusAgent(agentName)) {
         return
       }
 
diff --git a/src/hooks/prometheus-md-only/index.test.ts b/src/hooks/prometheus-md-only/index.test.ts
index ca9cd32f..2c99b6e5 100644
--- a/src/hooks/prometheus-md-only/index.test.ts
+++ b/src/hooks/prometheus-md-only/index.test.ts
@@ -30,11 +30,11 @@ describe("prometheus-md-only", () => {
     } as never
   }
 
-  function setupMessageStorage(sessionID: string, agent: string): void {
+  function setupMessageStorage(sessionID: string, agent: string | undefined): void {
     testMessageDir = join(MESSAGE_STORAGE, sessionID)
     mkdirSync(testMessageDir, { recursive: true })
     const messageContent = {
-      agent,
+      ...(agent ? { agent } : {}),
       model: { providerID: "test", modelID: "test-model" },
     }
     writeFileSync(
@@ -55,6 +55,122 @@ describe("prometheus-md-only", () => {
     rmSync(TEST_STORAGE_ROOT, { recursive: true, force: true })
   })
 
+  describe("agent name matching", () => {
+    test("should enforce md-only restriction for exact prometheus agent name", async () => {
+      //#given
+      setupMessageStorage(TEST_SESSION_ID, "prometheus")
+      const hook = createPrometheusMdOnlyHook(createMockPluginInput())
+      const input = {
+        tool: "Write",
+        sessionID: TEST_SESSION_ID,
+        callID: "call-1",
+      }
+      const output = {
+        args: { filePath: "/path/to/file.ts" },
+      }
+
+      //#when //#then
+      await expect(
+        hook["tool.execute.before"](input, output)
+      ).rejects.toThrow("can only write/edit .md files")
+    })
+
+    test("should enforce md-only restriction for Prometheus display name Plan Builder", async () => {
+      //#given
+      setupMessageStorage(TEST_SESSION_ID, "Prometheus (Plan Builder)")
+      const hook = createPrometheusMdOnlyHook(createMockPluginInput())
+      const input = {
+        tool: "Write",
+        sessionID: TEST_SESSION_ID,
+        callID: "call-1",
+      }
+      const output = {
+        args: { filePath: "/path/to/file.ts" },
+      }
+
+      //#when //#then
+      await expect(
+        hook["tool.execute.before"](input, output)
+      ).rejects.toThrow("can only write/edit .md files")
+    })
+
+    test("should enforce md-only restriction for Prometheus display name Planner", async () => {
+      //#given
+      setupMessageStorage(TEST_SESSION_ID, "Prometheus (Planner)")
+      const hook = createPrometheusMdOnlyHook(createMockPluginInput())
+      const input = {
+        tool: "Write",
+        sessionID: TEST_SESSION_ID,
+        callID: "call-1",
+      }
+      const output = {
+        args: { filePath: "/path/to/file.ts" },
+      }
+
+      //#when //#then
+      await expect(
+        hook["tool.execute.before"](input, output)
+      ).rejects.toThrow("can only write/edit .md files")
+    })
+
+    test("should enforce md-only restriction for uppercase PROMETHEUS", async () => {
+      //#given
+      setupMessageStorage(TEST_SESSION_ID, "PROMETHEUS")
+      const hook = createPrometheusMdOnlyHook(createMockPluginInput())
+      const input = {
+        tool: "Write",
+        sessionID: TEST_SESSION_ID,
+        callID: "call-1",
+      }
+      const output = {
+        args: { filePath: "/path/to/file.ts" },
+      }
+
+      //#when //#then
+      await expect(
+        hook["tool.execute.before"](input, output)
+      ).rejects.toThrow("can only write/edit .md files")
+    })
+
+    test("should not enforce restriction for non-Prometheus agent", async () => {
+      //#given
+      setupMessageStorage(TEST_SESSION_ID, "sisyphus")
+      const hook = createPrometheusMdOnlyHook(createMockPluginInput())
+      const input = {
+        tool: "Write",
+        sessionID: TEST_SESSION_ID,
+        callID: "call-1",
+      }
+      const output = {
+        args: { filePath: "/path/to/file.ts" },
+      }
+
+      //#when //#then
+      await expect(
+        hook["tool.execute.before"](input, output)
+      ).resolves.toBeUndefined()
+    })
+
+    test("should not enforce restriction when agent name is undefined", async () => {
+      //#given
+      setupMessageStorage(TEST_SESSION_ID, undefined)
+      const hook = createPrometheusMdOnlyHook(createMockPluginInput())
+      const input = {
+        tool: "Write",
+        sessionID: TEST_SESSION_ID,
+        callID: "call-1",
+      }
+      const output = {
+        args: { filePath: "/path/to/file.ts" },
+      }
+
+      //#when //#then
+      await expect(
+        hook["tool.execute.before"](input, output)
+      ).resolves.toBeUndefined()
+    })
+  })
+
    describe("with Prometheus agent in message storage", () => {
      beforeEach(() => {
        setupMessageStorage(TEST_SESSION_ID, "prometheus")