security: keep the API key out of Marshal and YAML

[simonx1]

Providers::Base#inspect has redacted the API key since the provider classes landed. Serialization does not go through inspect, and nothing covered it.

Verified on Ruby 3.2.11, 3.3.8 and 3.4.8:

p = RubyDecisionModel::Providers::Typesafe.new(api_key: "sk-SUPER-SECRET")

p.inspect
# => #<...Typesafe name=:typesafe base_url="https://api.typesafe.ai" api_key=[REDACTED]>

Marshal.dump(p).include?("sk-SUPER-SECRET")   # => true
YAML.dump(p)
# --- !ruby/object:RubyDecisionModel::Providers::Typesafe
# api_key: sk-SUPER-SECRET
# base_url:

YAML.dump(client) leaks too — it walks to the provider, where Marshal.dump(client) merely gives up on the Proc transport.

That is a plaintext key in a cache entry, a background-job argument, a config dump or a crash report, produced by an object that looks redacted when you print it.

The fix

Don't serialize the key. marshal_dump/encode_with write the base URL and nothing else; marshal_load/init_with read the key back from the provider's environment variable, which is where a long-lived process should be getting it anyway.

A provider restored without that variable set has no key, and building a Client from it raises ConfigurationError — a loud failure rather than a Bearer header with nothing after it. api_key stays readable in process; the leak was never deliberate access.

Tests

test/redaction_test.rb, 11 cases: both serializers for every registered provider, the client-level YAML walk, base URL survival, environment round-trip, and the no-key-in-env failure. Suite green on 3.2.11 / 3.3.8 / 3.4.8.

---

One of a series from a security and API-coverage audit. Branches are independent, each off main, so they can be taken in any order or individually.

🤖 Generated with Claude Code