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Document config-shaping env vars delivered via loadEnv .env files #564

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067593e
Document config-shaping env vars via loadEnv (harper#1580)
nizzlenitz Jul 2, 2026
938746d
Clarify override belongs to the loadEnv config block
nizzlenitz Jul 2, 2026
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13 changes: 13 additions & 0 deletions reference/environment-variables/overview.md
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Expand Up @@ -78,6 +78,19 @@ loadEnv:

Files are loaded in the order specified.

## Config-Shaping Variables

<VersionBadge type="changed" version="v5.2.0" />

The three configuration env vars — `HARPER_DEFAULT_CONFIG`, `HARPER_CONFIG`, and `HARPER_SET_CONFIG` (see [Configuration](../configuration/overview.md)) — shape Harper's root configuration, which is composed once at startup, before components load. When one of these is delivered through a `loadEnv` `.env` file, Harper applies it before composing the configuration, so `.env` delivery behaves the same as setting a real process environment variable. (Prior to 5.2.0, these variables silently had no effect when delivered via `.env`, because they were read after the configuration had already been composed.)

Notes and limitations:

- A real process environment variable still takes precedence over the `.env` value, unless `loadEnv` is configured with `override: true`.
- Encrypted (`enc:v1:`) values cannot shape configuration — secret decryptors are not registered until components load. Such values are skipped with an error log.
- `componentsRoot` cannot be redirected this way: Harper discovers the `.env` files by scanning the components root from the config file, so a `componentsRoot` override delivered via env var or `.env` cannot change where that scan looks.
- Only these three variables are applied early. All other `.env` keys load at component-load time as usual.

## Related

- [Components Overview](../components/overview.md)
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