Backward call-chain tracing - systematically trace bugs from error location back through call stack to original trigger. Adds instrumentation when needed.
Traces bugs backward through call chains to find original triggers and adds instrumentation when needed.
npx claudepluginhub lerianstudio/ringThis skill inherits all available tools. When active, it can use any tool Claude has access to.
find-polluter.shBugs often manifest deep in the call stack (git init in wrong directory, file created in wrong location, database opened with wrong path). Your instinct is to fix where the error appears, but that's treating a symptom.
Core principle: Trace backward through the call chain until you find the original trigger, then fix at the source.
Use root-cause-tracing when:
Relationship with systematic-debugging:
When NOT to use:
Error: git init failed in /Users/jesse/project/packages/coreawait execFileAsync('git', ['init'], { cwd: projectDir })WorktreeManager.createSessionWorktree(projectDir) → Session.initializeWorkspace() → Session.create() → test at Project.create()projectDir = '' (empty!) → resolves to process.cwd() → source code directory!const context = setupCoreTest() returns { tempDir: '' } → accessed before beforeEach!When you can't trace manually, add instrumentation before the problematic operation:
console.error('DEBUG git init:', { directory, cwd: process.cwd(), stack: new Error().stack });
Critical: Use console.error() in tests (logger may not show). Run: npm test 2>&1 | grep 'DEBUG'
Analyze: Look for test file names, line numbers, patterns (same test? same parameter?).
If something appears during tests but you don't know which test:
Use the bisection script: @find-polluter.sh
./find-polluter.sh '.git' 'src/**/*.test.ts'
Runs tests one-by-one, stops at first polluter. See script for usage.
Symptom: .git in packages/core/ (source code)
Trace chain: git init in process.cwd() ← empty cwd ← WorktreeManager ← Session.create() ← test accessed context.tempDir before beforeEach ← setupCoreTest() returns { tempDir: '' }
Root cause: Top-level variable initialization accessing empty value
Fix: Made tempDir a getter that throws if accessed before beforeEach
Defense-in-depth: (1) Project.create() validates (2) WorkspaceManager validates (3) NODE_ENV guard (4) Stack trace logging
Flow: Found immediate cause → Can trace up? (yes → trace backwards) → Is this source? (no → keep tracing | yes → fix at source) → Add validation at each layer → Bug impossible
NEVER fix just where the error appears. Trace back to find the original trigger.
console.error() not logger (may be suppressed)new Error().stack shows complete chain5-level trace → fixed at source (getter validation) → 4 layers defense → 1847 tests, zero pollution
STOP and report if:
| Decision Type | Blocker Condition | Required Action |
|---|---|---|
| Incomplete trace | Cannot trace call chain back to original trigger | STOP and add instrumentation before proceeding |
| Missing source access | Cannot access code that calls problematic function | STOP and report missing context |
| Complex async flow | Call chain involves async/event-driven code that breaks linear trace | STOP and instrument with timestamps before continuing |
| External dependency | Root cause appears to be in external library or service | STOP and report external dependency issue |
The following requirements CANNOT be waived:
| Severity | Condition | Required Action |
|---|---|---|
| CRITICAL | Error causes data corruption or test pollution across suite | MUST trace to source immediately, cannot proceed until resolved |
| HIGH | Error affects multiple call sites or components | MUST complete full trace before any fix attempt |
| MEDIUM | Error isolated to single execution path | MUST trace at least 3 levels up before fixing |
| LOW | Error is cosmetic or easily reproducible | Should trace to source, can fix incrementally |
| User Says | Your Response |
|---|---|
| "Just fix it where the error appears" | "MUST NOT fix at symptom location. Tracing to root cause prevents the bug from manifesting elsewhere." |
| "We don't have time for full tracing" | "CANNOT skip tracing. Fixing symptoms creates whack-a-mole debugging that takes longer overall." |
| "The fix works in my test" | "MUST verify fix eliminates root cause, not just masks symptom in one scenario." |
| "Add a try-catch and move on" | "CANNOT suppress errors without tracing. Error indicates invalid state that will cause problems elsewhere." |
| Rationalization | Why It's WRONG | Required Action |
|---|---|---|
| "The error message tells us enough" | Error location ≠ error source. Message describes symptom, not cause. | MUST trace call chain backward |
| "I know this code, the fix is obvious" | Familiarity breeds assumptions. Obvious fixes often mask deeper issues. | MUST verify with actual tracing |
| "Tracing is overkill for this simple bug" | Simple symptoms often have complex causes. Skipping trace leads to regression. | MUST trace regardless of apparent simplicity |
| "Adding logging slows things down" | Temporary instrumentation is cheap. Untraced bugs cause expensive debugging sessions. | MUST add instrumentation when needed |
| "The stack trace shows the problem" | Stack trace shows where, not why. Original invalid data may be layers above. | MUST trace data flow, not just call stack |
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