Chapter 6: PWA, Telegram, and Extensions

Welcome to Chapter 6: PWA, Telegram, and Extensions. In this part of HAPI Tutorial: Remote Control for Local AI Coding Sessions, you will build an intuitive mental model first, then move into concrete implementation details and practical production tradeoffs.

HAPI supports multiple control surfaces so users can choose the right experience for context and urgency.

Client Surface Comparison

Surface	Best For
PWA	full mobile/desktop remote session control
Telegram Mini App	fast approvals and notification-first workflow
terminal + runner	machine-level orchestration and spawning

PWA Operations

• install as home-screen app for fast access
• use notification permissions for approval alerts
• rely on cached UI for degraded connectivity scenarios

Extension Opportunities

Use runner + machine identities to route new sessions to specific hosts based on performance, policy, or ownership.

Summary

You can now align HAPI interfaces with operator roles and team workflow needs.

Next: Chapter 7: Configuration and Security

What Problem Does This Solve?

Most teams struggle here because the hard part is not writing more code, but deciding clear boundaries for core abstractions in this chapter so behavior stays predictable as complexity grows.

In practical terms, this chapter helps you avoid three common failures:

• coupling core logic too tightly to one implementation path
• missing the handoff boundaries between setup, execution, and validation
• shipping changes without clear rollback or observability strategy

After working through this chapter, you should be able to reason about Chapter 6: PWA, Telegram, and Extensions as an operating subsystem inside HAPI Tutorial: Remote Control for Local AI Coding Sessions, with explicit contracts for inputs, state transitions, and outputs.

Use the implementation notes around execution and reliability details as your checklist when adapting these patterns to your own repository.

How it Works Under the Hood

Under the hood, Chapter 6: PWA, Telegram, and Extensions usually follows a repeatable control path:

1. Context bootstrap: initialize runtime config and prerequisites for core component.
2. Input normalization: shape incoming data so execution layer receives stable contracts.
3. Core execution: run the main logic branch and propagate intermediate state through state model.
4. Policy and safety checks: enforce limits, auth scopes, and failure boundaries.
5. Output composition: return canonical result payloads for downstream consumers.
6. Operational telemetry: emit logs/metrics needed for debugging and performance tuning.

When debugging, walk this sequence in order and confirm each stage has explicit success/failure conditions.

Chapter Connections

• Tutorial Index
• Previous Chapter: Chapter 5: Permissions and Approval Workflow
• Next Chapter: Chapter 7: Configuration and Security
• Main Catalog
• A-Z Tutorial Directory

Source Code Walkthrough

cli/src/persistence.ts

The readRunnerState function in cli/src/persistence.ts handles a key part of this chapter's functionality:

 * Read runner state from local file
 */
export async function readRunnerState(): Promise<RunnerLocallyPersistedState | null> {
  try {
    if (!existsSync(configuration.runnerStateFile)) {
      return null;
    }
    const content = await readFile(configuration.runnerStateFile, 'utf-8');
    return JSON.parse(content) as RunnerLocallyPersistedState;
  } catch (error) {
    // State corrupted somehow :(
    console.error(`[PERSISTENCE] Runner state file corrupted: ${configuration.runnerStateFile}`, error);
    return null;
  }
}

/**
 * Write runner state to local file (synchronously for atomic operation)
 */
export function writeRunnerState(state: RunnerLocallyPersistedState): void {
  writeFileSync(configuration.runnerStateFile, JSON.stringify(state, null, 2), 'utf-8');
}

/**
 * Clean up runner state file and lock file
 */
export async function clearRunnerState(): Promise<void> {
  if (existsSync(configuration.runnerStateFile)) {
    await unlink(configuration.runnerStateFile);
  }
  // Also clean up lock file if it exists (for stale cleanup)
  if (existsSync(configuration.runnerLockFile)) {

This function is important because it defines how HAPI Tutorial: Remote Control for Local AI Coding Sessions implements the patterns covered in this chapter.

cli/src/persistence.ts

The writeRunnerState function in cli/src/persistence.ts handles a key part of this chapter's functionality:

 * Write runner state to local file (synchronously for atomic operation)
 */
export function writeRunnerState(state: RunnerLocallyPersistedState): void {
  writeFileSync(configuration.runnerStateFile, JSON.stringify(state, null, 2), 'utf-8');
}

/**
 * Clean up runner state file and lock file
 */
export async function clearRunnerState(): Promise<void> {
  if (existsSync(configuration.runnerStateFile)) {
    await unlink(configuration.runnerStateFile);
  }
  // Also clean up lock file if it exists (for stale cleanup)
  if (existsSync(configuration.runnerLockFile)) {
    try {
      await unlink(configuration.runnerLockFile);
    } catch {
      // Lock file might be held by running runner, ignore error
    }
  }
}

/**
 * Acquire an exclusive lock file for the runner.
 * The lock file proves the runner is running and prevents multiple instances.
 * Returns the file handle to hold for the runner's lifetime, or null if locked.
 */
export async function acquireRunnerLock(
  maxAttempts: number = 5,
  delayIncrementMs: number = 200
): Promise<FileHandle | null> {

This function is important because it defines how HAPI Tutorial: Remote Control for Local AI Coding Sessions implements the patterns covered in this chapter.

cli/src/persistence.ts

The clearRunnerState function in cli/src/persistence.ts handles a key part of this chapter's functionality:

 * Clean up runner state file and lock file
 */
export async function clearRunnerState(): Promise<void> {
  if (existsSync(configuration.runnerStateFile)) {
    await unlink(configuration.runnerStateFile);
  }
  // Also clean up lock file if it exists (for stale cleanup)
  if (existsSync(configuration.runnerLockFile)) {
    try {
      await unlink(configuration.runnerLockFile);
    } catch {
      // Lock file might be held by running runner, ignore error
    }
  }
}

/**
 * Acquire an exclusive lock file for the runner.
 * The lock file proves the runner is running and prevents multiple instances.
 * Returns the file handle to hold for the runner's lifetime, or null if locked.
 */
export async function acquireRunnerLock(
  maxAttempts: number = 5,
  delayIncrementMs: number = 200
): Promise<FileHandle | null> {
  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
    try {
      // 'wx' ensures we only create if it doesn't exist (atomic lock acquisition)
      const fileHandle = await open(configuration.runnerLockFile, 'wx');
      // Write PID to lock file for debugging
      await fileHandle.writeFile(String(process.pid));
      return fileHandle;

This function is important because it defines how HAPI Tutorial: Remote Control for Local AI Coding Sessions implements the patterns covered in this chapter.

cli/src/persistence.ts

The acquireRunnerLock function in cli/src/persistence.ts handles a key part of this chapter's functionality:

 * Returns the file handle to hold for the runner's lifetime, or null if locked.
 */
export async function acquireRunnerLock(
  maxAttempts: number = 5,
  delayIncrementMs: number = 200
): Promise<FileHandle | null> {
  for (let attempt = 1; attempt <= maxAttempts; attempt++) {
    try {
      // 'wx' ensures we only create if it doesn't exist (atomic lock acquisition)
      const fileHandle = await open(configuration.runnerLockFile, 'wx');
      // Write PID to lock file for debugging
      await fileHandle.writeFile(String(process.pid));
      return fileHandle;
    } catch (error: any) {
      if (error.code === 'EEXIST') {
        // Lock file exists, check if process is still running
        try {
          const lockPid = readFileSync(configuration.runnerLockFile, 'utf-8').trim();
          if (lockPid && !isNaN(Number(lockPid))) {
            if (!isProcessAlive(Number(lockPid))) {
              // Process doesn't exist, remove stale lock
              unlinkSync(configuration.runnerLockFile);
              continue; // Retry acquisition
            }
          }
        } catch {
          // Can't read lock file, might be corrupted
        }
      }

      if (attempt === maxAttempts) {
        return null;

This function is important because it defines how HAPI Tutorial: Remote Control for Local AI Coding Sessions implements the patterns covered in this chapter.

How These Components Connect

flowchart TD
    A[readRunnerState]
    B[writeRunnerState]
    C[clearRunnerState]
    D[acquireRunnerLock]
    E[releaseRunnerLock]
    A --> B
    B --> C
    C --> D
    D --> E