feat: enhance mode routing with track_progress and context preservation

This PR implements enhanced mode routing to address two critical v1 migration issues:
1. Lost GitHub context when using custom prompts in tag mode
2. Missing tracking comments for automatic PR reviews

Changes:
- Add track_progress input to force tag mode with tracking comments for PR/issue events
- Support custom prompt injection in tag mode via <custom_instructions> section
- Inject GitHub context as environment variables in agent mode
- Validate track_progress usage (only allowed for PR/issue events)
- Comprehensive test coverage for new routing logic

Event Routing:
- Comment events: Default to tag mode, switch to agent with explicit prompt
- PR/Issue events: Default to agent mode, switch to tag mode with track_progress
- Custom prompts can now be used in tag mode without losing context

This ensures backward compatibility while solving context preservation and tracking visibility issues reported in discussions #490 and #491.

src/create-prompt/types.ts

@@ -99,4 +99,5 @@ export type EventData =
 // Combined type with separate eventData field
 export type PreparedContext = CommonFields & {
   eventData: EventData;
+  githubContext?: import("../github/context").GitHubContext;
 };

src/github/context.ts

@@ -75,6 +75,7 @@ type BaseContext = {
     useStickyComment: boolean;
     useCommitSigning: boolean;
     allowedBots: string;
+    trackProgress: boolean;
   };
 };
 
@@ -122,6 +123,7 @@ export function parseGitHubContext(): GitHubContext {
       useStickyComment: process.env.USE_STICKY_COMMENT === "true",
       useCommitSigning: process.env.USE_COMMIT_SIGNING === "true",
       allowedBots: process.env.ALLOWED_BOTS ?? "",
+      trackProgress: process.env.TRACK_PROGRESS === "true",
     },
   };
 

src/modes/agent/index.ts

@@ -5,6 +5,37 @@ import type { PreparedContext } from "../../create-prompt/types";
 import { prepareMcpConfig } from "../../mcp/install-mcp-server";
 import { parseAllowedTools } from "./parse-tools";
 import { configureGitAuth } from "../../github/operations/git-config";
+import type { GitHubContext } from "../../github/context";
+import { isEntityContext } from "../../github/context";
+
+/**
+ * Extract GitHub context as environment variables for agent mode
+ */
+function extractGitHubContext(context: GitHubContext): Record<string, string> {
+  const envVars: Record<string, string> = {};
+  
+  // Basic repository info
+  envVars.GITHUB_REPOSITORY = context.repository.full_name;
+  envVars.GITHUB_TRIGGER_ACTOR = context.actor;
+  envVars.GITHUB_EVENT_NAME = context.eventName;
+  
+  // Entity-specific context (PR/issue numbers, branches, etc.)
+  if (isEntityContext(context)) {
+    if (context.isPR) {
+      envVars.GITHUB_PR_NUMBER = String(context.entityNumber);
+      
+      // Extract branch info from payload if available
+      if (context.payload && 'pull_request' in context.payload && context.payload.pull_request) {
+        envVars.GITHUB_BASE_REF = context.payload.pull_request.base?.ref || '';
+        envVars.GITHUB_HEAD_REF = context.payload.pull_request.head?.ref || '';
+      }
+    } else {
+      envVars.GITHUB_ISSUE_NUMBER = String(context.entityNumber);
+    }
+  }
+  
+  return envVars;
+}
 
 /**
  * Agent mode implementation.
@@ -136,6 +167,14 @@ export const agentMode: Mode = {
   },
 
   generatePrompt(context: PreparedContext): string {
+    // Inject GitHub context as environment variables
+    if (context.githubContext) {
+      const envVars = extractGitHubContext(context.githubContext);
+      for (const [key, value] of Object.entries(envVars)) {
+        core.exportVariable(key, value);
+      }
+    }
+
     // Agent mode uses prompt field
     if (context.prompt) {
       return context.prompt;

src/modes/detector.ts

@@ -3,31 +3,60 @@ import {
   isEntityContext,
   isIssueCommentEvent,
   isPullRequestReviewCommentEvent,
+  isPullRequestEvent,
+  isIssuesEvent,
+  isPullRequestReviewEvent,
 } from "../github/context";
 import { checkContainsTrigger } from "../github/validation/trigger";
 
 export type AutoDetectedMode = "tag" | "agent";
 
 export function detectMode(context: GitHubContext): AutoDetectedMode {
-  // If prompt is provided, use agent mode for direct execution
-  if (context.inputs?.prompt) {
-    return "agent";
+  // Validate track_progress usage
+  if (context.inputs.trackProgress) {
+    validateTrackProgressEvent(context);
   }
 
-  // Check for @claude mentions (tag mode)
+  // If track_progress is set for PR/issue events, force tag mode
+  if (context.inputs.trackProgress && isEntityContext(context)) {
+    if (isPullRequestEvent(context) || isIssuesEvent(context)) {
+      return "tag";
+    }
+  }
+
+  // Comment events (current behavior - unchanged)
   if (isEntityContext(context)) {
     if (
       isIssueCommentEvent(context) ||
-      isPullRequestReviewCommentEvent(context)
+      isPullRequestReviewCommentEvent(context) ||
+      isPullRequestReviewEvent(context)
     ) {
+      // If prompt is provided on comment events, use agent mode
+      if (context.inputs.prompt) {
+        return "agent";
+      }
+      // Default to tag mode if @claude mention found
       if (checkContainsTrigger(context)) {
         return "tag";
       }
     }
+  }
 
-    if (context.eventName === "issues") {
-      if (checkContainsTrigger(context)) {
-        return "tag";
+  // Issue events
+  if (isEntityContext(context) && isIssuesEvent(context)) {
+    // Check for @claude mentions or labels/assignees
+    if (checkContainsTrigger(context)) {
+      return "tag";
+    }
+  }
+
+  // PR events (opened, synchronize, etc.)
+  if (isEntityContext(context) && isPullRequestEvent(context)) {
+    const supportedActions = ["opened", "synchronize", "ready_for_review", "reopened"];
+    if (context.eventAction && supportedActions.includes(context.eventAction)) {
+      // If prompt is provided, use agent mode (default for automation)
+      if (context.inputs.prompt) {
+        return "agent";
       }
     }
   }
@@ -47,6 +76,28 @@ export function getModeDescription(mode: AutoDetectedMode): string {
   }
 }
 
+function validateTrackProgressEvent(context: GitHubContext): void {
+  // track_progress is only valid for pull_request and issue events
+  const validEvents = ["pull_request", "issues"];
+  if (!validEvents.includes(context.eventName)) {
+    throw new Error(
+      `track_progress is only supported for pull_request and issue events. ` +
+      `Current event: ${context.eventName}`
+    );
+  }
+  
+  // Additionally validate PR actions
+  if (context.eventName === "pull_request" && context.eventAction) {
+    const validActions = ["opened", "synchronize", "ready_for_review", "reopened"];
+    if (!validActions.includes(context.eventAction)) {
+      throw new Error(
+        `track_progress for pull_request events is only supported for actions: ` +
+        `${validActions.join(", ")}. Current action: ${context.eventAction}`
+      );
+    }
+  }
+}
+
 export function shouldUseTrackingComment(mode: AutoDetectedMode): boolean {
   return mode === "tag";
 }

src/modes/tag/index.ts

@@ -177,7 +177,18 @@ export const tagMode: Mode = {
     githubData: FetchDataResult,
     useCommitSigning: boolean,
   ): string {
-    return generateDefaultPrompt(context, githubData, useCommitSigning);
+    const defaultPrompt = generateDefaultPrompt(context, githubData, useCommitSigning);
+    
+    // If a custom prompt is provided, inject it into the tag mode prompt
+    if (context.githubContext?.inputs?.prompt) {
+      return defaultPrompt + `
+
+<custom_instructions>
+${context.githubContext.inputs.prompt}
+</custom_instructions>`;
+    }
+    
+    return defaultPrompt;
   },
 
   getSystemPrompt() {