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title Virtual Participant Local Development

Virtual Participant Local Development

This guide describes how to run and iterate on the LMA Virtual Participant (VP) locally against a deployed LMA CloudFormation stack. The VP is a headless-Chromium-on-Linux Playwright app that normally runs in ECS (Fargate or EC2), so the most realistic local environment is a Linux EC2 instance that mirrors the ECS task's runtime — edited via VSCode Remote-SSH and previewed via VNC.

Table of Contents

Why not just run it on your laptop?

The VP container bundles a specific Linux + Chromium + audio-stack combination that closely matches what ECS runs in production. Running Docker on macOS or Windows (even via WSL or Docker Desktop) introduces subtle differences in:

  • Chromium/Playwright behavior and fonts
  • Audio device enumeration and virtual sinks
  • CPU architecture (Apple Silicon vs. x86_64)
  • Networking and DNS resolution inside the container

Reproducing ECS-specific bugs locally on a laptop is unreliable. Running on a Linux EC2 that uses the same base image/arch as the ECS task is the closest match to production.

Recommended Setup

1. EC2 instance

Launch an EC2 instance that mirrors your VP ECS task configuration:

  • Same architecture (x86_64 is the default)
  • Instance size large enough to run the container comfortably (e.g. c5.xlarge or m5.xlarge if you are testing Voice Assistant + Simli avatar)
  • Docker installed and running
  • AWS CLI installed and configured with credentials that can describe-stacks, list-stack-resources, get-graphql-api on the target LMA stack
  • Open SSH inbound (nothing else — VNC will be tunneled through SSH)

2. VSCode Remote-SSH

From your laptop:

  1. Install the Remote - SSH VSCode extension.
  2. Add an SSH host entry for your EC2 instance.
  3. Connect — VSCode opens a remote workspace running on the EC2.
  4. Clone this repo onto the EC2 and open it in the remote VSCode window.

3. TigerVNC (or any VNC viewer) on your laptop

Install TigerVNC Viewer (or RealVNC / macOS Screen Sharing with vnc://localhost:5900). You will not connect it to the EC2 directly — VSCode forwards the container's VNC ports back to your laptop automatically.

Running the VP Locally

From the repository root on the EC2:

make vp-start STACK_NAME=LMA-dev-stack PLATFORM=WEBEX MEETING_ID=25523622514

With a password:

make vp-start STACK_NAME=LMA-dev-stack PLATFORM=ZOOM MEETING_ID=123456789 MEETING_PASSWORD=abc123  # pragma: allowlist secret

The vp-start target wraps lma-virtual-participant-stack/backend/local-test.sh, which:

  1. Reads your deployed LMA stack via CloudFormation (Kinesis stream, S3 bucket, AppSync endpoints, VP Task Registry table, Nova Sonic config, Simli config, etc.)
  2. Writes everything to lma-virtual-participant-stack/backend/.env.local
  3. Builds the VP Docker image (lma-vp-local)
  4. Runs the container with your AWS credentials mounted read-only and ports 5900 (VNC) and 5901 (noVNC) exposed

Accepted PLATFORM values: WEBEX, ZOOM, TEAMS, CHIME.

Managing Secrets (--reuse-env)

local-test.sh discovers most configuration from CloudFormation, but some values are not stored in the stack and must be set manually in .env.local. These currently include:

  • ELEVENLABS_API_KEY — ElevenLabs Conversational AI API key
  • SIMLI_API_KEY — Simli avatar API key
  • ZOOM_MEETING_SDK_CLIENT_ID / ZOOM_MEETING_SDK_CLIENT_SECRET — Zoom Meeting SDK app credentials. When both are set, Zoom meetings join via the Web SDK (see Zoom Meeting SDK Join); MEETING_ZOOM_METHOD (auto/sdk/dom) can force a method.
  • Any other workflow-specific overrides you want to test (e.g. a custom MEETING_NAME to target an existing real meeting so Nova Sonic / ElevenLabs tool calls work end-to-end)

Workflow

  1. First run — let the script generate a fresh .env.local from CloudFormation:

    make vp-start STACK_NAME=LMA-dev-stack PLATFORM=WEBEX MEETING_ID=25523622514

  2. Stop the container (Ctrl+C, or make vp-stop).

  3. Edit lma-virtual-participant-stack/backend/.env.local — fill in the blank secret values:

    ELEVENLABS_API_KEY=sk-...         # pragma: allowlist secret
SIMLI_API_KEY=simli_...           # pragma: allowlist secret
# Optionally pin MEETING_NAME to an existing meeting so tool calls can resolve it:
MEETING_NAME=MyRealMeeting-LMA

  4. Subsequent runs — use REUSE_ENV=1 so your edits are preserved. The script only updates MEETING_PLATFORM, MEETING_ID, MEETING_PASSWORD, MEETING_TIME, and DEV_MODE:

    make vp-start-reuse STACK_NAME=LMA-dev-stack PLATFORM=WEBEX MEETING_ID=25523622514

    Equivalent long form:

    make vp-start REUSE_ENV=1 STACK_NAME=LMA-dev-stack PLATFORM=WEBEX MEETING_ID=25523622514

Tip: If the stack's CloudFormation values change (e.g. you redeployed and table names or endpoints rotated), drop REUSE_ENV=1 once to regenerate .env.local, then re-add your secrets.

Note on MEETING_NAME: The local-test.sh --reuse-env path intentionally does not overwrite MEETING_NAME by default so that if you have pointed it at a real meeting ID (to exercise Nova Sonic / ElevenLabs tool calls), your pin is preserved across runs. See the comment in local-test.sh near the MEETING_NAME sed line.

Dev Mode (auto-reload)

Dev mode mounts lma-virtual-participant-stack/backend/src into the container and auto-rebuilds / restarts when TypeScript files change.

make vp-start-dev STACK_NAME=LMA-dev-stack PLATFORM=WEBEX MEETING_ID=25523622514

Or combined with reusing your .env.local:

make vp-start-dev REUSE_ENV=1 STACK_NAME=LMA-dev-stack PLATFORM=WEBEX MEETING_ID=25523622514

Dev mode runs the container as lma-vp-local-test (named, persistent). Once it's running:

make vp-logs      # tail container logs
make vp-shell     # exec into the container
make vp-stop      # stop and remove the container

VNC Preview and VSCode Port Forwarding

When the container starts, VNC is available on:

VSCode's Remote-SSH session automatically forwards these ports from the EC2 back to your laptop, so localhost:5900 on your laptop reaches the container on the EC2.

⚠️ Stale port forwarding gotcha

VSCode's auto-forwarded ports can become stale from day to day (especially after disconnects, EC2 reboots, or long idle sessions). Symptom:

TigerVNC Viewer connects to localhost:5900 and hangs indefinitely. No error, no timeout, just a spinner.

Fix: delete the stale forwarded ports and let VSCode recreate them.

  1. In VSCode, open the Ports panel (View → Terminal, then the PORTS tab next to TERMINAL / OUTPUT).
  2. Right-click ports 5900 and 5901 and choose Stop Forwarding Port.
  3. Stop the VP container (make vp-stop) and start it again (make vp-start-reuse ...). VSCode will detect the listening ports and auto-forward them fresh.
  4. Reconnect TigerVNC to localhost:5900 — it should connect immediately.

If auto-forward doesn't kick in, click Forward a Port in the Ports panel and manually add 5900 and 5901.

Useful make Targets

Target Purpose
make vp-start STACK_NAME=… PLATFORM=… MEETING_ID=… Build and run the VP container locally
make vp-start-dev STACK_NAME=… PLATFORM=… MEETING_ID=… Same, but dev mode (source mounted, auto-reload)
make vp-start-reuse STACK_NAME=… PLATFORM=… MEETING_ID=… Reuse existing .env.local (preserves manually-set secrets)
make vp-stop Stop and remove the lma-vp-local-test container
make vp-logs Tail container logs
make vp-shell Open a bash shell inside the running container
make build-vp TypeScript build of the VP backend (no Docker)

All vp-start* targets accept:

Variable Required Description
STACK_NAME yes LMA CloudFormation stack name
PLATFORM yes WEBEX, ZOOM, TEAMS, or CHIME
MEETING_ID yes Meeting ID to join
MEETING_PASSWORD no Meeting password, if the platform requires one
DEV=1 no Enable dev mode (implied by vp-start-dev)
REUSE_ENV=1 no Reuse .env.local (implied by vp-start-reuse)

Troubleshooting

  • "Could not fetch all required CloudFormation resources" — verify STACK_NAME is correct and the stack is fully deployed. Check your AWS credentials on the EC2: aws sts get-caller-identity.
  • "Container 'lma-vp-local-test' already exists" — run make vp-stop and retry. Happens in non-dev mode when a previous dev-mode container was left running.
  • TigerVNC hangs on connect — delete stale forwarded ports in the VSCode Ports panel (see above).
  • Changes to .ts not picked up — make sure you're running in dev mode (DEV=1 / make vp-start-dev). Production mode does not mount src.
  • Voice Assistant not working — confirm ELEVENLABS_API_KEY or relevant Nova Sonic config is present in .env.local and that you used REUSE_ENV=1 on your follow-up run so the key isn't wiped.
  • AWS creds not found inside the container — the script mounts ~/.aws read-only. Ensure ~/.aws/credentials or ~/.aws/config exists on the EC2, or use an instance profile (the container inherits the EC2's role via IMDS only if you remove the -v ~/.aws:/root/.aws:ro mount — the simplest is to write credentials into ~/.aws on the EC2).

See Also