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feat: add TUI agent harness with MCP server#8

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feat/tui-harness
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feat: add TUI agent harness with MCP server#8
aidandaly24 wants to merge 5 commits into
mainfrom
feat/tui-harness

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Description

Adds a TUI agent harness that enables AI agents (Claude Code, Kiro) to programmatically interact with the AgentCore CLI's Terminal UI through headless pseudo-terminals.

Architecture:

  • Core library (src/tui-harness/lib/) — TuiSession class wrapping node-pty + @xterm/headless for headless terminal emulation. Provides sendKeys, sendSpecialKey, readScreen, waitFor, and close operations. Includes settling detection (waits for terminal output to stabilize), session management with signal-handler cleanup, and screen reading utilities.
  • MCP server (src/tui-harness/mcp/) — Exposes 7 tools (tui_launch, tui_send_keys, tui_read_screen, tui_wait_for, tui_screenshot, tui_close, tui_list_sessions) over stdio transport using @modelcontextprotocol/sdk. Built as a standalone binary at dist/mcp-harness/index.mjs.
  • DocumentationAGENTS.md updated with complete harness usage guide including screen identification markers, a 27-step create wizard example captured from ground truth, navigation patterns, and error recovery guidance.

Key design decisions:

  • @xterm/headless marked as external in esbuild (CJS-only package, bundling mangles default export)
  • SpecialKey type derived from SPECIAL_KEY_VALUES const array (single source of truth)
  • WaitForTimeoutError returns {found: false} from MCP layer, not isError — lets agents decide next action
  • tui_launch({}) defaults to node dist/cli/index.mjs for zero-config AgentCore CLI launching

Related Issue

Closes #

Documentation PR

N/A — documentation is inline in AGENTS.md and docs/TESTING.md

Type of Change

  • Bug fix
  • New feature
  • Breaking change
  • Documentation update
  • Other (please describe):

Testing

How have you tested the change?

  • I ran npm run test:unit and npm run test:integ
  • I ran npm run typecheck
  • I ran npm run lint
  • If I modified src/assets/, I ran npm run test:update-snapshots and committed the updated snapshots

Additional verification:

  • Both esbuild bundles (CLI + MCP harness) build successfully
  • MCP server starts and responds to stdio transport
  • Proof-of-concept unit tests pass (xterm standalone, PTY+xterm wiring, DSR/CPR handler)
  • Integration tests (27 tests across 5 suites) pass in follow-up PR Add dark mode support #2

Checklist

  • I have read the CONTRIBUTING document
  • I have added any necessary tests that prove my fix is effective or my feature works
  • I have updated the documentation accordingly
  • I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
  • My changes generate no new warnings
  • Any dependent changes have been merged and published

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the
terms of your choice.

aidandaly24 and others added 5 commits March 13, 2026 13:46
Headless terminal harness using node-pty + @xterm/headless that spawns
real CLI processes in a PTY and reads screen state programmatically.

Core components:
- TuiSession: spawn, sendKeys, sendSpecialKey, readScreen, waitFor, close
- SettlingMonitor: text-content comparison to filter cursor blink
- Screen reader: viewport/scrollback reading, numbered output
- Key map: named keys to escape sequence mapping
- Session manager: global registry with process-exit cleanup
- Availability check: graceful skip when node-pty is missing

waitFor() throws WaitForTimeoutError on timeout (not silent return).
launch() races settle vs process exit, throws LaunchError on crash.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
7 MCP tools exposed via stdio transport for AI agents to drive the TUI:
tui_launch, tui_send_keys, tui_read_screen, tui_wait_for,
tui_screenshot, tui_close, tui_list_sessions.

Session map with max 10 concurrent sessions. tui_wait_for catches
WaitForTimeoutError and returns {found: false} (not an MCP error).
tui_launch defaults to AgentCore CLI when no command specified.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
- devDependencies: @xterm/headless, @modelcontextprotocol/sdk
- optionalDependencies: node-pty (native addon, graceful skip)
- esbuild: second entry point for mcp-harness bundle
- vitest: new 'tui' project with fileParallelism: false
- .mcp.json: MCP server discovery for Claude Code
- package.json: bin entry + test:tui script

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
AGENTS.md: TUI harness section with MCP tool reference, complete 27-step
create wizard example (verified against real TUI), screen identification
markers table, screenshot format, error recovery patterns, navigation
patterns, and known limitations.

TESTING.md: TUI integration test guide with TuiSession API reference,
ScreenState type, special keys list, waitFor vs settling guidance,
WaitForTimeoutError output example, and LaunchError handling.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Move harness code from two separate directories (src/test-utils/tui-harness/
and src/mcp-harness/) into a single src/tui-harness/ directory with lib/ and
mcp/ subdirectories. Also cleans up dead code in tools.ts, derives SpecialKey
type from SPECIAL_KEY_VALUES array (single source of truth), and fixes
cross-boundary import of createMinimalProjectDir.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@aidandaly24 aidandaly24 mentioned this pull request Mar 17, 2026
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Coverage Report

Status Category Percentage Covered / Total
🔵 Lines 41.18% 3847 / 9340
🔵 Statements 40.8% 4056 / 9941
🔵 Functions 42.17% 749 / 1776
🔵 Branches 43.86% 2545 / 5802
Generated in workflow #20 for commit 4a80d1b by the Vitest Coverage Report Action

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