Enable Hex dependency cooldown - #4971
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Adds hex: [cooldown: "1w"] to mix.exs so newly-resolved dependency versions must have existed for at least a week before Hex will pull them in, mitigating supply-chain attacks that get caught and retired within days. Normal builds against an intact mix.lock are unaffected. Older Hex silently ignores the cooldown config, so bin/bootstrap now enforces Hex >= 2.5.0, auto-upgrading and failing fast if it can't.
stuartc
marked this pull request as ready for review
July 14, 2026 18:47
Security Review ✅
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Fixes a pre-existing Credo --strict refactoring finding that was failing the lint CI job.
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Description
This PR adds Hex 2.5.0's dependency release-age cooldown to Lightning.
Setting
hex: [cooldown: "1w"]inmix.exsmeans Hex won't resolve to a package version until it has existed for at least a week. This mitigates the common supply-chain attack where a compromised release is pulled into builds before anyone notices and retires it — most such incidents are caught within days. Lightning only consumes dependencies (it doesn't publish), so this only affects what we pull in, never what we ship.Day-to-day impact is basically nil:
mix deps.getagainst an intactmix.lockbypasses the cooldown entirely, so normal builds and CI are unchanged. The cooldown only bites when resolving something new (mix deps.update, adding a dep, ordeps.getafter unlocking). Security fixes for a dep we're already locked to re-resolve past the cooldown automatically; a genuinely urgent fresh fix can be forced for a single command withHEX_COOLDOWN=0d mix deps.update <pkg>.The catch: Hex older than 2.5.0 silently ignores the config, giving false confidence. So:
bin/bootstrapnow enforces Hex>= 2.5.0for local dev, auto-upgrading and failing fast if it can't.mix local.hex --force, so it's covered.Validation steps
< 2.5.0, runbin/bootstrapand confirm it upgrades Hex and reports>= 2.5.0.>= 2.5.0, runmix deps.getagainst the committedmix.lockand confirm it resolves unchanged (cooldown does not bite locked versions).mix hex.outdatedand confirm any versions inside the 1-week window are annotated(cooldown).Additional notes for the reviewer
1w— covers all-but-one of the analysed supply-chain incidents while costing us almost nothing for an app that doesn't ship on every dependency bump.ensure_hex_versioninbin/bootstrap.d/common.shusessort -Vso it treats e.g. 2.10 as newer than 2.5.AI Usage
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