Exercises new TriggerClient(...) — the explicit, per-instance management client introduced alongside the global configure() API. Useful when a single process needs to talk to multiple projects, environments, or preview branches without globally mutating SDK state.

• src/trigger/echo.ts — a trivial task that returns its payload (the trigger target for the external scripts and the fan-out task).
• src/trigger/fanOut.ts — runs inside a task and triggers echo through two different TriggerClient instances in parallel.
• src/external/main.ts — external Node script. Two clients with different secrets (and optionally different preview branches), triggers echo sequentially and concurrently, logs every outgoing request's authorization + x-trigger-branch headers.
• src/external/isolation.ts — interleaves the global configure() API and an instance call, asserts via the captured fetches that neither side leaks into the other.

Boot the webapp (pnpm dev --filter webapp) and trigger dev in this workspace as usual, then run the scripts against http://localhost:3030:

TRIGGER_API_URL=http://localhost:3030 \
TRIGGER_PRIMARY_KEY=tr_dev_... \
TRIGGER_SECONDARY_KEY=tr_dev_... \
TRIGGER_SECONDARY_BRANCH=signup-flow \
pnpm trigger:external

TRIGGER_API_URL=http://localhost:3030 \
TRIGGER_GLOBAL_KEY=tr_dev_... \
TRIGGER_INSTANCE_KEY=tr_dev_... \
TRIGGER_INSTANCE_BRANCH=preview-x \
pnpm trigger:isolation

The fan-out task is exercised by triggering it through the dashboard or via the Trigger MCP after setting TRIGGER_FAN_OUT_PRIMARY_KEY and TRIGGER_FAN_OUT_SECONDARY_KEY in the dev env.