[hyperpolymath]

What & why

First v0.5 "engine depth" increment. Overlays could already add rules; now they can override base rules — the piece real multi-context policies need. Deliberately touches none of the v0.4 wire contracts (facts/diff/findings/SARIF unchanged).

Semantics

• override-rules { ids } — removes those base rules from the effective set. Use it to exempt a context (a vendored or generated zone) from a base rule.
• Override + add-rules (same id) — replaces a rule: e.g. keep the check but drop its severity from error to warning for one context.
• modify-rules stays reserved — its diff semantics are genuinely underspecified, and load-time rejection keeps evaluate total.

[[overlays.effects]]
type = "override-rules"
ids = ["readme-present"]     # this context doesn't require a README

Implementation (three places, kept consistent)

• schema.rs — accepts override-rules; each overridden id must name a real base rule (OverrideUnknownRule otherwise). The duplicate-id check now operates over effective base ids (base minus overridden) plus overlay-added ids, so a same-id replacement is legal rather than a false collision. Overridden base rules are still fully validated at load — evaluation skips them, but a later un-override must not resurrect a malformed rule.
• eval.rs — effective_rules drops overridden base rules; promoted to pub(crate).
• action.rs — the planner's rule_index now reuses effective_rules, so evaluator and planner share exactly one set and a finding can never resolve to an overridden-away rule.

Verification

• cargo test --workspace — 93 tests (5 new: override-disables and override-with-replacement at the eval level; unknown-id, same-id-replacement, and modify-rules-still-reserved at the schema level)
• cargo clippy --workspace --all-targets -- -D warnings and cargo fmt --check clean
• Live demo: a README-less repo fails the base readme-present rule, then passes clean (exit 0) once an overlay overrides that rule away
• plasma check . self-check: 0 violations, 110 rules satisfied

Next in v0.5 (not in this PR)

Content facts + file-matches-pattern is the other big depth item — but it adds a file_contents layer to the FactSet, which ripples into the frozen plasma facts/plasma diff wire contracts (snapshot size vs. completeness is a real tradeoff). I've left it for a deliberate decision rather than bundling it here. More fix action types (CreateFile) also remain.

🤖 Generated with Claude Code

https://claude.ai/code/session_01JSVSF9HhKUhDrEV4xkMEXq

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