diff --git a/.gitignore b/.gitignore
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--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,7 @@
 # Dependencies
-.sisyphus/
+.sisyphus/*
+!.sisyphus/rules/
+!.sisyphus/rules/**
 node_modules/
 
 # Build output
diff --git a/.sisyphus/rules/test-discipline.md b/.sisyphus/rules/test-discipline.md
new file mode 100644
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+++ b/.sisyphus/rules/test-discipline.md
@@ -0,0 +1,68 @@
+---
+description: Test discipline — fires when reading or editing any test file in this repo
+globs:
+  - "**/*.test.ts"
+  - "**/__tests__/**/*.ts"
+  - "src/testing/**/*.ts"
+  - "test-setup.ts"
+  - "script/run-ci-tests.ts"
+---
+
+# Test Discipline (NON-NEGOTIABLE)
+
+**Every test in this repo MUST pass `bun test` in one process, in one go — no isolation flags, no retries, no special ordering.** That is the gate. A test that needs `--only`, its own process, or a specific run order to pass is **BROKEN**. Fix the test; do not pamper it.
+
+## FLAKY = FAILING
+
+A test that passes 9 of 10 times is **failing 10% of the time**. Not "occasional." **BROKEN.**
+
+**FORBIDDEN in test bodies** unless time itself is the system under test (`Date.now`, real timers, debounce/throttle windows):
+
+- `setTimeout(resolve, N)` / `await new Promise(r => setTimeout(r, N))` / `await sleep(N)`
+- "wait long enough for X to happen" — "enough" is a guess; CI machines are slower or faster than your laptop and the test WILL fail on someone else's box
+
+The replacement: **subscribe BEFORE the trigger, await the signal with an explicit timeout.**
+
+## EVENT TESTING — SUBSCRIBE-FIRST, TIMEOUT-BOUND
+
+When code under test emits an event, fires a callback, or resolves a promise:
+
+1. **Register the listener / construct the awaitable BEFORE you trigger the action.** Reverse order = lost event = flake.
+2. **Race against an explicit timeout.** On timeout, **fail with a useful message** (`"waited 5s for event 'X', never fired"`). NEVER silently retry, NEVER fall through.
+3. The timeout is a **circuit breaker**, not a synchronization primitive. If the assertion logic depends on the timeout firing first, the test is wrong.
+
+## NO ISOLATION CRUTCHES
+
+Tests must work under arbitrary parallel ordering in a single `bun test` run, **no matter how many mocks are involved.**
+
+FORBIDDEN:
+
+- `.only` / `.skip` to mask a flaky test
+- Running a test in its own process to "fix" a state leak. `script/run-ci-tests.ts` already auto-isolates files that use `mock.module()` — DO NOT add to that list to cover up a real cross-test bug
+- Reordering `describe` / `it` blocks to mask cross-test contamination
+- Relying on test A running before test B
+
+Cross-test contamination = **state leak**. Find the leak. Reset in `beforeEach`, add the reset to `test-setup.ts` if it is shared, or mock at the module boundary (`mock.module`) instead of mutating globals other tests will read.
+
+## PROMPT TESTS — ASSERT BEHAVIOR, NOT TEXT
+
+When testing code that builds an LLM prompt, **DO NOT pin the current wording.**
+
+**BANNED — these tests guard a diff, not behavior:**
+
+```ts
+expect(prompt).toContain("You are Sisyphus")
+expect(prompt).toMatchSnapshot()
+expect(prompt).toBe(EXPECTED_PROMPT)
+```
+
+The wording changes next sprint, the test fails, and the next engineer edits the assertion to match the new text without understanding what the test was guarding. **The test guarded nothing.**
+
+**REQUIRED — assert the structural invariant the prompt logic enforces:**
+
+- "When `teamMode.enabled === true`, the prompt MUST mention `team_send_message`" → test the conditional branch
+- "When `verbose === false`, the prompt MUST NOT include the debug directive" → test the negative branch
+- "API keys MUST NOT appear in the system message" → test the redaction
+- "Skill X's instructions MUST appear when the skill is loaded, and MUST NOT when it is not" → test inclusion + exclusion
+
+Test what would break the **behavior**. Never test what would only break a **diff**.