EnvShield

Environment variables, as a version-controlled configuration contract.

.env files and environment variables have no contract. Nothing declares what a project actually needs, what's required where, or whether a change to one breaks another service. EnvShield gives that contract a real, committed file — env.schema.toml — and everything else follows from it: validating a local file against it, discovering what code actually reads that the schema doesn't know about, and reviewing how the contract itself changes across git revisions. Secret handling is one part of that contract, not the product's center of gravity.

Free, open source (MIT), and fully local. EnvShield never sends your configuration or secrets anywhere.

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Why EnvShield?

Environment variables tend to go through the same decay, on every real project:

.env / os.environ
    → undocumented      (what does this app actually need?)
    → inconsistent      (staging has it, local doesn't)
    → undeclared        (new code reads a var nobody wrote down)
    → accidentally exposed   (a real key ends up in a commit)
    → hard to review    ("what did this PR actually change about config?")

EnvShield's answer is to make the configuration contract a real, versioned file, and let every other command work from it:

env.schema.toml
    → contract          (types, required/optional, defaults, conditional requirements)
    → validation        (check, doctor, setup)
    → usage discovery   (undeclared — what does the code actually read?)
    → schema diff       (what changed to the contract, across two git revisions?)
    → secret safety     (scan — a supporting check, not the product)

env.schema.toml is the product. Everything above reads from that one file; nothing above it invents its own idea of what your configuration is supposed to be.

Quick Start

pipx install envshield

Prefer an existing Python/pip workflow instead? pip install envshield works the same way, as an alternative.

In an existing project:

envshield init

init looks for a real config source — a .env, .env.example, or a recognizable Python config module — and builds env.schema.toml from your actual variables (classifying secrets, suggesting defaults, inferring types where the shape is unambiguous). A brand-new project with nothing to read yet gets a framework-aware starting template instead.

envshield setup      # interactive wizard: fills in your local .env from the schema
envshield check      # validate your local file against the schema

That's the whole loop for a single-service project. Everything past this point — multiple services, schema composition, CI, deployment manifests — is opt-in.

The Schema

env.schema.toml is plain TOML, meant to be committed to git and hand-edited. It declares shape, never secret values:

[DATABASE_URL]
description = "PostgreSQL connection string"
type = "url"
secret = true

[APP_ENV]
description = "Deployment environment"
enum = ["local", "staging", "production"]
defaultValue = "local"

[PORT]
description = "Port the API listens on"
type = "port"
defaultValue = "8000"

[DEBUG]
description = "Enable debug mode"
type = "bool"
defaultValue = "false"

[ADMIN_EMAIL]
description = "Where alerts get sent"
type = "email"

[STRIPE_SECRET_KEY]
description = "Stripe secret key"
secret = true
requiredIf = { var = "PAYMENTS_ENABLED", equals = "true" }

What each field actually means:

There is no separate required = true/false field. Requiredness is derived: unconditional by default, waived by a defaultValue, or made conditional by requiredIf — see below.

Conditional requirements (requiredIf)

A variable that's only relevant behind a feature flag doesn't need to be required unconditionally. requiredIf = { var = "OTHER_VAR", equals = "some value" } makes a field required only when that condition holds — with no defaultValue and no requiredIf, a variable stays required unconditionally, exactly as before this existed:

[PAYMENTS_ENABLED]
type = "bool"
defaultValue = "false"

[STRIPE_SECRET_KEY]
secret = true
requiredIf = { var = "PAYMENTS_ENABLED", equals = "true" }

With PAYMENTS_ENABLED=false, STRIPE_SECRET_KEY is optional. Flip the flag in any environment, and check/doctor/setup immediately start requiring it there.

Composing schemas (extends)

A monorepo with several services usually shares a handful of variables. Factor them into a base schema and extend it — the child's own definition always wins on a conflict, no per-field merging:

# services/api/env.schema.toml
extends = "../../shared/base.schema.toml"

[DATABASE_URL]
secret = true

Core workflow

Four stages, in order: define the contract, validate against it, discover what code actually depends on, review how the contract itself changes.

Define

env.schema.toml (see The Schema above) is what you define. envshield init/envshield import <file> build it from your real, existing configuration — see Existing projects.

Validate

envshield check — validate local configuration, and commonly-used Docker Compose and Kubernetes deployment-manifest patterns, against the same schema (see Known limitations).

$ envshield check
┌───────────────────┬────────────────┬────────────────────────────────────┐
│ Status             │ Variable Name  │ Source                              │
├───────────────────┼────────────────┼────────────────────────────────────┤
│ Missing in Local   │ DATABASE_URL   │ env.schema.toml (Required)          │
│ Invalid Value      │ PORT           │ must be a port number from 1-65535  │
└───────────────────┴────────────────┴────────────────────────────────────┘

envshield setup — interactive onboarding: fills in whatever's missing, blank, or now-invalid in your local file, prompting with each variable's description.

envshield doctor — a full health check on your project's EnvShield setup at once (config files present, schema/template in sync, deployment manifest registered and valid, and more). --fix offers to fix what it can.

Want typed, validated config code instead of raw os.getenv() calls? envshield generate compiles the schema into a Python (pydantic-settings) or TypeScript (zod) module — a secondary, opt-in convenience once the contract exists, not a separate thing to learn.

Discover

envshield undeclared — catch a new environment-variable read that isn't in the schema yet, before you commit it. Compares source code between two git revisions (or your working tree against HEAD by default):

$ envshield undeclared
┌────────────────┬─────────────┬──────┬───────────┬──────────────────────┐
│ Variable       │ File        │ Line │ Access    │ Contract status      │
├────────────────┼─────────────┼──────┼───────────┼──────────────────────┤
│ ANALYTICS_KEY  │ app/main.py │ 42   │ os.getenv │ missing declaration  │
└────────────────┴─────────────┴──────┴───────────┴──────────────────────┘

envshield explain VARIABLE — everything EnvShield knows about one variable: its contract, where it's declared, what source code reads it, and which deployment manifests reference it.

Review / govern

envshield schema diff — compare the schema contract between two git revisions, classified by impact:

$ envshield schema diff origin/main HEAD
┌───────────────┬──────────┬───────────────────────────────────────────┐
│ Variable      │ Category │ Description                                │
├───────────────┼──────────┼───────────────────────────────────────────┤
│ PORT          │ BREAKING │ lost its default and is now always         │
│               │          │ required                                   │
│ STRIPE_KEY    │ SECURITY │ secret classification WEAKENED             │
└───────────────┴──────────┴───────────────────────────────────────────┘

This is the schema functioning as a real contract: a change to it is reviewable on a PR, the same way an API contract change would be — not just a local file that happens to agree with itself.

envshield service discover / service add register services in a multi-service project — see Monorepos. A supporting safety check, scan, exists alongside all of this — see Secret safety.

Every command above documents its own options with --help; the full reference is in the docs.

Git / CI workflow

This is where the schema stops being documentation and starts being enforcement. Three concrete things EnvShield catches in a PR:

A new environment variable used in code but missing from the schema:

envshield undeclared origin/main HEAD --service api

A schema contract change:

envshield schema diff origin/main HEAD --service api

A secret accidentally introduced into a commit — the pre-commit hook runs scan --staged automatically:

envshield hook install

In CI, diff against the merge-base, not the base branch's current tip (which can move while the PR is open):

# .github/workflows/envshield.yml
on: pull_request
jobs:
  contract-check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with: { fetch-depth: 0 }
      - run: pipx install envshield
      - run: |
          BASE=$(git merge-base "origin/${{ github.base_ref }}" HEAD)
          envshield schema diff "$BASE" HEAD
          envshield undeclared "$BASE" HEAD

Both commands exit non-zero on a real finding — nothing beyond the exit code is required to gate a PR. Add --json if you want to post a custom summary instead.

Existing projects

Adopting EnvShield into a project that already has configuration doesn't require rewriting anything:

.env (existing)
    ↓
envshield import .env
    ↓
review env.schema.toml       (fix classifications, add descriptions)
    ↓
envshield check               (confirm your local file already satisfies it)
    ↓
envshield undeclared          (confirm nothing's silently missing)
    ↓
CI: schema diff + undeclared  (governance from here on)

import reads your real values and does most of the schema-writing for you — it always leaves a "TODO: Add description." marker as a nudge to review, and any automatic secret/type classification is a starting point, not a final answer. Not using a .env file? envshield import config/settings.py reads a Python config module's assignments via its AST (never executes the file).

Monorepos / services

If a repo has more than one service, envshield.yml registers each one with its own schema:

services:
  api:
    schema: services/api/env.schema.toml
    local_file: services/api/.env
  worker:
    schema: services/worker/env.schema.toml

envshield service discover     # finds service-like directories, registers + seeds each one
envshield service list
envshield check --service api

Every command is service-aware. --service is optional with exactly one service configured, inferred automatically when you're standing inside a registered service's own directory, and only prompted for interactively when there's more than one and neither applies.

Discovering reads in a shared library (additional_source_roots)

undeclared and explain only walk a service's own directory by default. If part of a service's real configuration is read from a shared internal library that lives outside that directory — a common-utilities package imported by several services, say — those reads are invisible to both commands, for every service that imports the library.

additional_source_roots widens a service's discovery scope to cover extra directories:

services:
  api:
    schema: services/api/env.schema.toml
    additional_source_roots:
      - libs/shared

undeclared --service api and explain --service api now also look inside libs/shared — a variable read there counts toward api's own discovery results exactly as if it lived in services/api/ itself. The same directory can be listed by more than one service; each one independently sees the reads it contains. A path that doesn't exist yet contributes nothing (no error); a path resolving outside the project is refused, the same protection every other path in envshield.yml already has. scan is unaffected — it's already repository-wide.

Multiple sources per service (completeness: union)

By default, every registered source for a service — its local_file, each registered deployment manifest — is validated independently against the whole schema: check/doctor expect any one of them to be self-sufficient on its own. Some services genuinely don't work that way: part of the configuration lives in a local config file, the rest is supplied by a deployment manifest. Under the default model, a variable that only ever lives in one of them shows up as "missing" everywhere else, even though nothing is actually wrong.

Set completeness: union on a service to validate against the combined presence of all its registered sources instead — a variable satisfied by any one of them satisfies the service as a whole:

services:
  api:
    schema: services/api/env.schema.toml
    local_file: services/api/config/settings.py
    completeness: union
manifests:
  - file: docker-compose.yml
    containers:
      api: api

[DB_HOST]
description = "set in config/settings.py"

[FEATURE_MODE]
description = "set via docker-compose.yml"

With completeness: union, check/doctor stop expecting config/settings.py to declare FEATURE_MODE, or docker-compose.yml to set DB_HOST — the schema is satisfied as long as every variable is present somewhere among the registered sources. envshield schema sync respects this too: it only ever appends a variable to a Python local_file that's genuinely missing from every registered source, never one that another source already covers.

A few things worth knowing:

• Opt-in, per service. Unset (the default) means every source must be independently self-sufficient, exactly as before this existed — nothing changes unless you set the key.
• Union means presence, not values. Whether an ordinary variable is satisfied depends only on whether it's present (and valid) somewhere — never on merging, comparing, or picking between its values across sources. A blank or invalid value is still reported, wherever it occurs. The one deliberate exception is a requiredIf trigger's own value (see next) — deciding whether a condition currently holds has always meant reading one specific value, even before completeness: union existed; union only extends where that one value may come from, it doesn't turn this into general value merging.
• A requiredIf condition (see Conditional requirements above) is resolved against the union too — if the variable a condition depends on lives in a different source than the one being checked, completeness: union still finds it. Sources that agree on the trigger's value resolve normally; if two sources genuinely disagree, EnvShield reports it as an explicit conflict rather than guessing which one wins — registration order is never used as a tiebreaker.
• A source that fails to load is always a failure, even if the sources that did load happen to satisfy the schema between them. doctor reports this as two separate signals for a union-mode service — source health (does this file exist and parse) and registered-source completeness (does the union satisfy the schema) — so one can never quietly hide behind the other. check --json reflects the same split: each source's own result is still reported individually, plus one combined entry per union-mode service carrying the aggregate verdict.

Supported languages / discovery

Source-code discovery (what powers undeclared and explain's "used in source" section) is AST-based for Python (os.environ.get, os.getenv, os.environ[...]) and pattern-based for JavaScript/TypeScript (process.env.X, process.env["X"], import.meta.env.X, including single-level destructuring). No other language is discovered yet — the schema and validation commands work with any stack, but undeclared/explain can only see what's read from these two.

explain additionally recognizes Flask's current_app.config[...]/.get(...) in Python — including the common from flask import current_app as <alias> import form — and reports it at medium confidence, shown inline as (medium confidence): it's one level of indirection through a config object whose contents could come from anywhere, not a direct environment read. This recognition is deliberately explain-only — it never affects undeclared's or scan's pass/fail signal, so a Flask-config read can never quietly satisfy (or break) a completeness check the way a direct os.environ/os.getenv read does.

Secret safety

A supporting check alongside the contract, not the product itself. secret = true on a field tells EnvShield (and setup, and code generation) that it's sensitive — the schema records that fact, never the actual value. On top of that:

• envshield scan looks for hardcoded secrets by pattern (Stripe, AWS, GitHub tokens, and more), and for env-var reads the schema doesn't declare, in one pass. Values are always redacted in output — a Stripe publishable key (pk_...) is never flagged, since detection matches the secret-key pattern (sk_...) by shape, not the variable's name.
• envshield hook install wires scan --staged into a pre-commit hook, so a real secret is caught before it's committed, not after.

Removing EnvShield

envshield uninstall

Removes EnvShield's Git hook integration while preserving your project configuration — it does not delete envshield.yml, any env.schema.toml, .env.example, any registered local configuration file (.env, a Python config module, etc.), .gitignore, or any code envshield generate has produced, regardless of whether EnvShield originally created any of it. Those are your project's own configuration contract and application config, not disposable installation artifacts.

The only thing uninstall ever deletes is a Git hook whose content exactly matches what EnvShield would generate right now — the same ownership rule hook remove already uses. A hand-modified hook, a foreign hook (even one that happens to contain EnvShield's marker comment), or an EnvShield hook that's gone stale relative to your current envshield.yml (e.g. after registering a new service) is left in place and reported, never deleted or silently regenerated.

envshield uninstall --yes    # skip the confirmation prompt

--yes only skips the prompt — it never overrides the ownership check; a modified, foreign, or stale hook is preserved with --yes exactly as it is interactively. There is no --force and no --purge: uninstall is intentionally not a "delete everything EnvShield ever created" command. To remove EnvShield's configuration from a project entirely, delete envshield.yml and the schema files yourself once you're sure you no longer need them.

Known limitations

EnvShield is built around the patterns real projects actually use. A few narrower cases aren't handled yet — none of them let a secret leak or let a genuinely missing required variable pass as clean:

• Docker Compose: ${VAR}, ${VAR:-default}, and the no-colon ${VAR-default} form are all supported. The ${VAR:?}/${VAR:+} forms and embedded/multiple interpolation references in one value aren't evaluated yet.
• Kubernetes: env[].valueFrom.secretKeyRef/configMapKeyRef are matched by the container's environment-variable name (env[].name) — name your schema variable after the env var, not the key — and, when the referenced Secret/ConfigMap is defined in the same manifest, the referenced key is validated to actually exist there. envFrom.prefix is applied. initContainers are selectable via --container but never auto-selected by default.
• Source discovery: Python is AST-based; JavaScript/TypeScript is pattern-based. No other language is discovered yet.
• .env: multiline quoted values aren't supported.

These are bounded, tracked engineering work — see the roadmap for what's next and what EnvShield deliberately isn't building.

Documentation

This README is enough to get real value out of EnvShield. For the full command reference, every schema field, envshield.yml structure, exit codes, and JSON output shapes, see the documentation.

License

MIT — see LICENSE.md.