refactor: unify system directive prefix for keyword-detector filtering

- Add shared/system-directive.ts with SYSTEM_DIRECTIVE_PREFIX constant
- Unify all system message prefixes to [SYSTEM DIRECTIVE: OH-MY-OPENCODE - ...]
- Add isSystemDirective() filter to keyword-detector to skip system messages
- Update prometheus-md-only tests to use new prefix constants

src/hooks/compaction-context-injector/index.ts

@@ -1,5 +1,6 @@
 import { injectHookMessage } from "../../features/hook-message-injector"
 import { log } from "../../shared/logger"
+import { createSystemDirective, SystemDirectiveTypes } from "../../shared/system-directive"
 
 export interface SummarizeContext {
   sessionID: string
@@ -9,7 +10,7 @@ export interface SummarizeContext {
   directory: string
 }
 
-const SUMMARIZE_CONTEXT_PROMPT = `[COMPACTION CONTEXT INJECTION]
+const SUMMARIZE_CONTEXT_PROMPT = `${createSystemDirective(SystemDirectiveTypes.COMPACTION_CONTEXT)}
 
 When summarizing this session, you MUST include the following sections in your summary:
 

src/hooks/context-window-monitor.ts

@@ -1,4 +1,5 @@
 import type { PluginInput } from "@opencode-ai/plugin"
+import { createSystemDirective, SystemDirectiveTypes } from "../shared/system-directive"
 
 const ANTHROPIC_DISPLAY_LIMIT = 1_000_000
 const ANTHROPIC_ACTUAL_LIMIT =
@@ -8,7 +9,7 @@ const ANTHROPIC_ACTUAL_LIMIT =
     : 200_000
 const CONTEXT_WARNING_THRESHOLD = 0.70
 
-const CONTEXT_REMINDER = `[SYSTEM REMINDER - 1M Context Window]
+const CONTEXT_REMINDER = `${createSystemDirective(SystemDirectiveTypes.CONTEXT_WINDOW_MONITOR)}
 
 You are using Anthropic Claude with 1M context window.
 You have plenty of context remaining - do NOT rush or skip tasks.

src/hooks/keyword-detector/index.ts

@@ -1,6 +1,7 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import { detectKeywordsWithType, extractPromptText, removeCodeBlocks } from "./detector"
 import { log } from "../../shared"
+import { isSystemDirective } from "../../shared/system-directive"
 import { getMainSessionID } from "../../features/claude-code-session-state"
 import type { ContextCollector } from "../../features/context-injector"
 
@@ -23,6 +24,12 @@ export function createKeywordDetectorHook(ctx: PluginInput, collector?: ContextC
       }
     ): Promise<void> => {
       const promptText = extractPromptText(output.parts)
+
+      if (isSystemDirective(promptText)) {
+        log(`[keyword-detector] Skipping system directive message`, { sessionID: input.sessionID })
+        return
+      }
+
       let detectedKeywords = detectKeywordsWithType(removeCodeBlocks(promptText), input.agent)
 
       if (detectedKeywords.length === 0) {

src/hooks/prometheus-md-only/constants.ts

@@ -1,3 +1,5 @@
+import { createSystemDirective, SystemDirectiveTypes } from "../../shared/system-directive"
+
 export const HOOK_NAME = "prometheus-md-only"
 
 export const PROMETHEUS_AGENTS = ["Prometheus (Planner)"]
@@ -12,7 +14,7 @@ export const PLANNING_CONSULT_WARNING = `
 
 ---
 
-[SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION]
+${createSystemDirective(SystemDirectiveTypes.PROMETHEUS_READ_ONLY)}
 
 You are being invoked by Prometheus (Planner), a READ-ONLY planning agent.
 

src/hooks/prometheus-md-only/index.test.ts

@@ -3,6 +3,7 @@ import { mkdirSync, rmSync, writeFileSync } from "node:fs"
 import { join } from "node:path"
 import { createPrometheusMdOnlyHook } from "./index"
 import { MESSAGE_STORAGE } from "../../features/hook-message-injector"
+import { SYSTEM_DIRECTIVE_PREFIX, createSystemDirective, SystemDirectiveTypes } from "../../shared/system-directive"
 
 describe("prometheus-md-only", () => {
   const TEST_SESSION_ID = "test-session-prometheus"
@@ -167,7 +168,7 @@ describe("prometheus-md-only", () => {
       await hook["tool.execute.before"](input, output)
 
       // #then
-      expect(output.args.prompt).toContain("[SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION]")
+      expect(output.args.prompt).toContain(SYSTEM_DIRECTIVE_PREFIX)
       expect(output.args.prompt).toContain("DO NOT modify any files")
     })
 
@@ -187,7 +188,7 @@ describe("prometheus-md-only", () => {
       await hook["tool.execute.before"](input, output)
 
       // #then
-      expect(output.args.prompt).toContain("[SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION]")
+      expect(output.args.prompt).toContain(SYSTEM_DIRECTIVE_PREFIX)
     })
 
     test("should inject read-only warning when Prometheus calls call_omo_agent", async () => {
@@ -206,7 +207,7 @@ describe("prometheus-md-only", () => {
       await hook["tool.execute.before"](input, output)
 
       // #then
-      expect(output.args.prompt).toContain("[SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION]")
+      expect(output.args.prompt).toContain(SYSTEM_DIRECTIVE_PREFIX)
     })
 
     test("should not double-inject warning if already present", async () => {
@@ -217,7 +218,7 @@ describe("prometheus-md-only", () => {
         sessionID: TEST_SESSION_ID,
         callID: "call-1",
       }
-      const promptWithWarning = "Some prompt [SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION] already here"
+      const promptWithWarning = `Some prompt ${SYSTEM_DIRECTIVE_PREFIX} already here`
       const output = {
         args: { prompt: promptWithWarning },
       }
@@ -226,7 +227,7 @@ describe("prometheus-md-only", () => {
       await hook["tool.execute.before"](input, output)
 
       // #then
-      const occurrences = (output.args.prompt as string).split("[SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION]").length - 1
+      const occurrences = (output.args.prompt as string).split(SYSTEM_DIRECTIVE_PREFIX).length - 1
       expect(occurrences).toBe(1)
     })
   })
@@ -272,7 +273,7 @@ describe("prometheus-md-only", () => {
 
       // #then
       expect(output.args.prompt).toBe(originalPrompt)
-      expect(output.args.prompt).not.toContain("[SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION]")
+      expect(output.args.prompt).not.toContain(SYSTEM_DIRECTIVE_PREFIX)
     })
   })
 

src/hooks/prometheus-md-only/index.ts

@@ -5,6 +5,7 @@ import { HOOK_NAME, PROMETHEUS_AGENTS, ALLOWED_EXTENSIONS, ALLOWED_PATH_PREFIX,
 import { findNearestMessageWithFields, findFirstMessageWithAgent, MESSAGE_STORAGE } from "../../features/hook-message-injector"
 import { getSessionAgent } from "../../features/claude-code-session-state"
 import { log } from "../../shared/logger"
+import { SYSTEM_DIRECTIVE_PREFIX } from "../../shared/system-directive"
 
 export * from "./constants"
 
@@ -89,7 +90,7 @@ export function createPrometheusMdOnlyHook(ctx: PluginInput) {
       // Inject read-only warning for task tools called by Prometheus
       if (TASK_TOOLS.includes(toolName)) {
         const prompt = output.args.prompt as string | undefined
-        if (prompt && !prompt.includes("[SYSTEM DIRECTIVE - READ-ONLY PLANNING CONSULTATION]")) {
+        if (prompt && !prompt.includes(SYSTEM_DIRECTIVE_PREFIX)) {
           output.args.prompt = prompt + PLANNING_CONSULT_WARNING
           log(`[${HOOK_NAME}] Injected read-only planning warning to ${toolName}`, {
             sessionID: input.sessionID,

src/hooks/ralph-loop/index.ts

@@ -2,6 +2,7 @@ import type { PluginInput } from "@opencode-ai/plugin"
 import { existsSync, readFileSync, readdirSync } from "node:fs"
 import { join } from "node:path"
 import { log } from "../../shared/logger"
+import { SYSTEM_DIRECTIVE_PREFIX } from "../../shared/system-directive"
 import { readState, writeState, clearState, incrementIteration } from "./storage"
 import {
   HOOK_NAME,
@@ -42,7 +43,7 @@ interface OpenCodeSessionMessage {
   }>
 }
 
-const CONTINUATION_PROMPT = `[RALPH LOOP - ITERATION {{ITERATION}}/{{MAX}}]
+const CONTINUATION_PROMPT = `${SYSTEM_DIRECTIVE_PREFIX} - RALPH LOOP {{ITERATION}}/{{MAX}}]
 
 Your previous attempt did not output the completion promise. Continue working on the task.
 

src/hooks/sisyphus-orchestrator/index.ts

@@ -10,6 +10,7 @@ import {
 import { getMainSessionID, subagentSessions } from "../../features/claude-code-session-state"
 import { findNearestMessageWithFields, MESSAGE_STORAGE } from "../../features/hook-message-injector"
 import { log } from "../../shared/logger"
+import { createSystemDirective, SYSTEM_DIRECTIVE_PREFIX, SystemDirectiveTypes } from "../../shared/system-directive"
 import type { BackgroundManager } from "../../features/background-agent"
 
 export const HOOK_NAME = "sisyphus-orchestrator"
@@ -28,7 +29,7 @@ const DIRECT_WORK_REMINDER = `
 
 ---
 
-[SYSTEM REMINDER - DELEGATION REQUIRED]
+${createSystemDirective(SystemDirectiveTypes.DELEGATION_REQUIRED)}
 
 You just performed direct file modifications outside \`.sisyphus/\`.
 
@@ -52,7 +53,7 @@ You should NOT:
 ---
 `
 
-const BOULDER_CONTINUATION_PROMPT = `[SYSTEM REMINDER - BOULDER CONTINUATION]
+const BOULDER_CONTINUATION_PROMPT = `${createSystemDirective(SystemDirectiveTypes.BOULDER_CONTINUATION)}
 
 You have an active work plan with incomplete tasks. Continue working.
 
@@ -107,7 +108,7 @@ const ORCHESTRATOR_DELEGATION_REQUIRED = `
 
 ---
 
-⚠️⚠️⚠️ [CRITICAL SYSTEM DIRECTIVE - DELEGATION REQUIRED] ⚠️⚠️⚠️
+⚠️⚠️⚠️ ${createSystemDirective(SystemDirectiveTypes.DELEGATION_REQUIRED)} ⚠️⚠️⚠️
 
 **STOP. YOU ARE VIOLATING ORCHESTRATOR PROTOCOL.**
 
@@ -155,7 +156,7 @@ sisyphus_task(
 
 const SINGLE_TASK_DIRECTIVE = `
 
-[SYSTEM DIRECTIVE - SINGLE TASK ONLY]
+${createSystemDirective(SystemDirectiveTypes.SINGLE_TASK_ONLY)}
 
 **STOP. READ THIS BEFORE PROCEEDING.**
 
@@ -626,7 +627,7 @@ export function createSisyphusOrchestratorHook(
       // Check sisyphus_task - inject single-task directive
       if (input.tool === "sisyphus_task") {
         const prompt = output.args.prompt as string | undefined
-        if (prompt && !prompt.includes("[SYSTEM DIRECTIVE - SINGLE TASK ONLY]")) {
+        if (prompt && !prompt.includes(SYSTEM_DIRECTIVE_PREFIX)) {
           output.args.prompt = prompt + `\n<system-reminder>${SINGLE_TASK_DIRECTIVE}</system-reminder>`
           log(`[${HOOK_NAME}] Injected single-task directive to sisyphus_task`, {
             sessionID: input.sessionID,

src/hooks/todo-continuation-enforcer.ts

@@ -9,6 +9,7 @@ import {
     type ToolPermission,
 } from "../features/hook-message-injector"
 import { log } from "../shared/logger"
+import { createSystemDirective, SystemDirectiveTypes } from "../shared/system-directive"
 
 const HOOK_NAME = "todo-continuation-enforcer"
 
@@ -40,7 +41,7 @@ interface SessionState {
   abortDetectedAt?: number
 }
 
-const CONTINUATION_PROMPT = `[SYSTEM REMINDER - TODO CONTINUATION]
+const CONTINUATION_PROMPT = `${createSystemDirective(SystemDirectiveTypes.TODO_CONTINUATION)}
 
 Incomplete tasks remain in your todo list. Continue working on the next pending task.
 

src/shared/index.ts

@@ -24,3 +24,4 @@ export * from "./zip-extractor"
 export * from "./agent-variant"
 export * from "./session-cursor"
 export * from "./shell-env"
+export * from "./system-directive"

src/shared/system-directive.ts

@@ -0,0 +1,40 @@
+/**
+ * Unified system directive prefix for oh-my-opencode internal messages.
+ * All system-generated messages should use this prefix for consistent filtering.
+ *
+ * Format: [SYSTEM DIRECTIVE: OH-MY-OPENCODE - {TYPE}]
+ */
+
+export const SYSTEM_DIRECTIVE_PREFIX = "[SYSTEM DIRECTIVE: OH-MY-OPENCODE"
+
+/**
+ * Creates a system directive header with the given type.
+ * @param type - The directive type (e.g., "TODO CONTINUATION", "RALPH LOOP")
+ * @returns Formatted directive string like "[SYSTEM DIRECTIVE: OH-MY-OPENCODE - TODO CONTINUATION]"
+ */
+export function createSystemDirective(type: string): string {
+  return `${SYSTEM_DIRECTIVE_PREFIX} - ${type}]`
+}
+
+/**
+ * Checks if a message starts with the oh-my-opencode system directive prefix.
+ * Used by keyword-detector and other hooks to skip system-generated messages.
+ * @param text - The message text to check
+ * @returns true if the message is a system directive
+ */
+export function isSystemDirective(text: string): boolean {
+  return text.trimStart().startsWith(SYSTEM_DIRECTIVE_PREFIX)
+}
+
+export const SystemDirectiveTypes = {
+  TODO_CONTINUATION: "TODO CONTINUATION",
+  RALPH_LOOP: "RALPH LOOP",
+  BOULDER_CONTINUATION: "BOULDER CONTINUATION",
+  DELEGATION_REQUIRED: "DELEGATION REQUIRED",
+  SINGLE_TASK_ONLY: "SINGLE TASK ONLY",
+  COMPACTION_CONTEXT: "COMPACTION CONTEXT",
+  CONTEXT_WINDOW_MONITOR: "CONTEXT WINDOW MONITOR",
+  PROMETHEUS_READ_ONLY: "PROMETHEUS READ-ONLY",
+} as const
+
+export type SystemDirectiveType = (typeof SystemDirectiveTypes)[keyof typeof SystemDirectiveTypes]