diff --git a/AGENTS.md b/AGENTS.md
index 370cfd8..fbf0aba 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -237,5 +237,7 @@ Rules:
 5. **Keep AGENTS.md a map, not an encyclopedia.** New deep content goes into `docs/`. Add an entry to "Where to find each topic" instead of pasting prose into this file. The "Always-on rules" section is the exception — it's for invariants that should always be in scope.
 6. **Re-read on schema/query/IR changes.** Edits to `schema.pest`, `query.pest`, `ir/lower.rs`, `query/typecheck.rs`, or `query/lint.rs` should trigger a re-read of [docs/schema-language.md](docs/schema-language.md), [docs/query-language.md](docs/query-language.md), and [docs/execution.md](docs/execution.md) to confirm they still describe reality.
 7. **Always make smaller commits.** Each commit does one thing, compiles, and passes tests; mechanical refactors land separately from the behavior changes they enable.
+8. **Test-first for bug fixes.** When fixing an identified bug, write a regression test that reproduces the failure first. Confirm it fails against the current code with the predicted symptom (not an unrelated error). Then land the fix in a separate commit and confirm the test turns green. The test commit lands just before the fix commit so the red → green pair is visible in `git log` and a reviewer can check out the test commit alone and reproduce the failure.
+9. **Correct by design over symptomatic patches.** When a bug surfaces, identify the root cause and make the fix correct by construction. Don't patch the symptom. If the design admits the bug class, the fix is to close the class, not to add a guard around the latest instance. A symptomatic patch is acceptable only as a stop-gap, with an explicit note in the commit message and a follow-up issue tracking the design fix.
 
 CI check: `scripts/check-agents-md.sh` verifies that every `docs/*.md` link in this file resolves and that every doc in the canonical set is linked. Run it locally before opening a PR if you've moved or renamed docs.