Use Environment Variable Substitution for All Secrets

Plano supports $VAR_NAME substitution in config values. This applies to access_key fields, connection_string for state storage, and http_headers in prompt targets and endpoints. Never hardcode credentials — Plano reads them from environment variables or a .env file at startup via planoai up.

Incorrect (hardcoded secrets):

yaml

version: v0.3.0

model_providers:
  - model: openai/gpt-4o
    access_key: abcdefghijklmnopqrstuvwxyz...   # Hardcoded — never do this

state_storage:
  type: postgres
  connection_string: "postgresql://admin:mysecretpassword@prod-db:5432/plano"

prompt_targets:
  - name: get_data
    endpoint:
      name: my_api
      http_headers:
        Authorization: "Bearer abcdefghijklmnopqrstuvwxyz"   # Hardcoded token

Correct (environment variable substitution):

yaml

version: v0.3.0

model_providers:
  - model: openai/gpt-4o
    access_key: $OPENAI_API_KEY
    default: true

  - model: anthropic/claude-sonnet-4-20250514
    access_key: $ANTHROPIC_API_KEY

state_storage:
  type: postgres
  connection_string: "postgresql://${DB_USER}:${DB_PASS}@${DB_HOST}:5432/${DB_NAME}"

prompt_targets:
  - name: get_data
    endpoint:
      name: my_api
      http_headers:
        Authorization: "Bearer $MY_API_TOKEN"

.env file pattern (loaded automatically by planoai up):

bash

# .env — add to .gitignore
OPENAI_API_KEY=sk-proj-...
ANTHROPIC_API_KEY=sk-ant-...
DB_USER=plano
DB_PASS=secure-password
DB_HOST=localhost
MY_API_TOKEN=tok_live_...

Plano also accepts keys set directly in the shell environment. Variables referenced in config but not found at startup cause planoai up to fail with a clear error listing the missing keys.

Reference: https://github.com/katanemo/archgw