diff --git a/config/opencode/agents/test.md b/config/opencode/agents/test.md
index 3c4506f..54f7113 100644
--- a/config/opencode/agents/test.md
+++ b/config/opencode/agents/test.md
@@ -175,6 +175,27 @@ Rust:
 - Use `assert_eq!`, `assert_ne!`, `assert!` with informative messages.
 - Use existing test helpers from the crate's `tests/common/` module when present.
 
+### Test Naming
+
+In TDD, tests are *specifications*. The test name describes the **contract under test**, not the test machinery or the current RED state. The same name must be valid both before the body pass (RED) and after it (GREEN). If a name wouldn't survive the body pass, rename now.
+
+**Forbidden naming patterns:**
+- Anything referencing the stub mechanic: `..._panics_on_todo`, `..._fails_red`, `..._stub_works`, `..._not_yet_implemented`. These describe the RED state, which disappears once `@make` fills in the body.
+- Generic placeholders: `test_works`, `it_does_the_thing`, `basic_test`.
+- Vague verbs without an outcome: `..._handles_input`, `..._processes_data` — handles or processes how, with what observable result?
+- Implementation-detail names that leak internals: `..._calls_query_get_mut_three_times`, `..._uses_hashmap`.
+
+**Required form: action + observable outcome.** Examples:
+
+| Bad | Good |
+|---|---|
+| `move_enemies_following_path_panics_on_todo` | `move_enemies_advances_position_along_path` |
+| `path_types_randomly_assigned` | `spawn_in_special_stage_assigns_one_of_three_pattern_types` |
+| `spawn_enemies_special_stage_panics_on_todo` | `spawn_enemies_in_special_stage_attaches_flight_pattern_component` |
+| `weaving_test` | `weave_enemies_removes_weaving_component_after_duration` |
+
+The name should read like a sentence: "[subject] [verb] [observable outcome under condition]". When you can't write such a sentence, the test is testing too much (split it) or testing the wrong thing (revisit the spec).
+
 ### Devshell wrapping
 
 If the project has a `flake.nix` with a `devShells.default`, wrap every test/lint command with `nix develop -c …` (e.g. `nix develop -c cargo test`, `nix develop -c uv run pytest`). The devshell guarantees the right toolchain is on PATH.