diff --git a/README.md b/README.md
index c460f2d..b727cf5 100644
--- a/README.md
+++ b/README.md
@@ -40,14 +40,31 @@ Then add `inputs.claudebox.packages.${system}.default` to your `environment.syst
 | `--gc` | Remove stale per-project instance dirs and exit |
 | `--` | Pass remaining args to Claude Code |
 
-## Extra env vars
+## Env vars
 
-Pass additional host variables into the sandbox:
+**Env files (preferred)** — define vars without polluting your shell:
 
+`~/.claudebox/env` — global, loaded on every launch:
+```bash
+ANTHROPIC_API_KEY=sk-ant-...
+MY_GLOBAL_VAR=value
+```
+
+`<project>/.claudebox.env` — per-project, loaded when present:
+```bash
+DATABASE_URL=postgres://localhost/myapp
+SOME_PROJECT_VAR=value
+```
+
+Add `.claudebox.env` to your `.gitignore` if it contains secrets.
+
+**Pass-through** — inject host vars already set in your shell:
 ```bash
 CLAUDEBOX_EXTRA_ENV=MY_VAR,OTHER_VAR claudebox
 ```
 
+All injected vars appear in the `[+]` section of the env audit.
+
 ## How it works
 
 ```
diff --git a/claudebox.sh b/claudebox.sh
index 73d1535..0b578fb 100644
--- a/claudebox.sh
+++ b/claudebox.sh
@@ -253,20 +253,29 @@ ENV_ARGS=(
   --setenv SHELL "$SANDBOX_BASH"
   --setenv TMPDIR /tmp
   --setenv XDG_RUNTIME_DIR /tmp
-  --setenv NIX_SSL_CERT_FILE /etc/ssl/certs/ca-certificates.crt
-  --setenv SSL_CERT_FILE /etc/ssl/certs/ca-certificates.crt
 )
 
 # Populate sandbox audit data
-AUDIT_SANDBOX_KEYS=(HOME USER PATH SHELL TMPDIR XDG_RUNTIME_DIR NIX_SSL_CERT_FILE SSL_CERT_FILE)
+AUDIT_SANDBOX_KEYS=(HOME USER PATH SHELL TMPDIR XDG_RUNTIME_DIR)
 AUDIT_SANDBOX_VALS[HOME]="$HOME"
 AUDIT_SANDBOX_VALS[USER]="$USER"
 AUDIT_SANDBOX_VALS[PATH]="$SANDBOX_PATH"
 AUDIT_SANDBOX_VALS[SHELL]="$SANDBOX_BASH"
 AUDIT_SANDBOX_VALS[TMPDIR]="/tmp"
 AUDIT_SANDBOX_VALS[XDG_RUNTIME_DIR]="/tmp"
-AUDIT_SANDBOX_VALS[NIX_SSL_CERT_FILE]="/etc/ssl/certs/ca-certificates.crt"
-AUDIT_SANDBOX_VALS[SSL_CERT_FILE]="/etc/ssl/certs/ca-certificates.crt"
+
+# SSL cert path: prefer host NIX_SSL_CERT_FILE (NixOS sets this to a nix store path);
+# fall back to /etc/ssl/certs/ca-certificates.crt for non-NixOS hosts.
+_SSL_CERT_DEFAULT="/etc/ssl/certs/ca-certificates.crt"
+_NIX_SSL_CERT="${NIX_SSL_CERT_FILE:-$_SSL_CERT_DEFAULT}"
+_SSL_CERT="${SSL_CERT_FILE:-$_NIX_SSL_CERT}"
+ENV_ARGS+=(
+  --setenv NIX_SSL_CERT_FILE "$_NIX_SSL_CERT"
+  --setenv SSL_CERT_FILE "$_SSL_CERT"
+)
+AUDIT_SANDBOX_KEYS+=(NIX_SSL_CERT_FILE SSL_CERT_FILE)
+AUDIT_SANDBOX_VALS[NIX_SSL_CERT_FILE]="$_NIX_SSL_CERT"
+AUDIT_SANDBOX_VALS[SSL_CERT_FILE]="$_SSL_CERT"
 
 # Allowlisted host vars -- only pass if set on host
 HOST_ALLOWLIST=(TERM EDITOR LANG LC_ALL ANTHROPIC_API_KEY)
@@ -291,6 +300,32 @@ if [[ -v CLAUDEBOX_EXTRA_ENV ]]; then
   done
 fi
 
+# Env files: ~/.claudebox/env (global) and <project>/.claudebox.env (per-project)
+# Format: KEY=VALUE lines; blank lines and lines starting with # are ignored.
+load_env_file() {
+  local file="$1"
+  [[ -f "$file" ]] || return 0
+  while IFS= read -r line || [[ -n "$line" ]]; do
+    # strip leading whitespace, skip blanks and comments
+    line="${line#"${line%%[! ]*}"}"
+    [[ -z "$line" || "$line" == '#'* ]] && continue
+    # require KEY=VALUE form
+    [[ "$line" != *=* ]] && continue
+    local key="${line%%=*}"
+    local val="${line#*=}"
+    # strip optional surrounding quotes from value
+    if [[ "$val" == '"'*'"' || "$val" == "'"*"'" ]]; then
+      val="${val:1:${#val}-2}"
+    fi
+    ENV_ARGS+=(--setenv "$key" "$val")
+    AUDIT_EXTRA_KEYS+=("$key")
+    AUDIT_EXTRA_VALS[$key]="$val"
+  done < "$file"
+}
+
+load_env_file "$HOME/.claudebox/env"
+load_env_file "$CANONICAL_ROOT/.claudebox.env"
+
 # Env audit display (D-01, D-02, D-03, D-04, D-07, UX-01)
 print_audit() {
   echo "${BOLD}${CYAN}=== Sandbox Environment ===${RESET}" >&2