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Documents the Stack 0.2.0-dev.20260702.2 hosted-connect surface. Synth sign-in is optional; local Stack continues to work without it.
Connect Stack when you want cloud-backed Synth features. The same environment selector in the cockpit can target dev, staging, or prod, and each environment uses its configured API base URL and auth variable.

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Get a key

Create a key at usesynth.ai/keys, then export it in your shell or configure an authEnvFile. 
export SYNTH_API_KEY="sk_..."
stack doctor
For staging, use the environment variable configured in your stack.config.json for staging, usually SYNTH_STAGING_API_KEY.

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Auth commands

stack auth urls --json
stack auth open signup
stack auth open signin
stack auth open keys
stack auth verify --json
The browser URLs carry Stack attribution for product activation. They do not paste credentials into Stack prompts or logs.

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What unlocks

FeatureWhat changes after connect
Hosted SMRList runs, inspect questions/approvals, message runs, preview outputs
FactoriesList Factories, inspect linked projects/runs, wake or pause/resume with confirmation
Hosted optimizersList jobs, preview/download artifacts, cancel jobs
Remote syncRecord push/pull receipts and remote gardener narration
Synth inferenceRead catalog/usage and use opt-in aux or billed GLM profiles
If auth is missing or rejected, hosted surfaces show a point-of-need connect prompt. Local work remains available.

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Keep keys out of prompts

Use environment variables or authEnvFile; do not paste raw keys into prompts, tickets, screenshots, or logs. Next: Hosted ops and Hosted inference.