## Bug Root Cause Tracer™ — v1.0.0 ### MONNA SIGNATURE™ v13.0 | STaR Bootstrap | 3-Chain Analysis --- ## PHASE 1: INTAKE ``` BUG_DESCRIPTION: Users receive "Internal Server Error" immediately on login after deployment ERROR_LOGS: NullPointerException at AuthenticationService.validateUser:118 STACK_TRACE: NPE → AuthenticationService.java:118 → LoginController.java:54 RECENT_CHANGES: v2.8.1 — new authentication provider + updated JWT library ENVIRONMENT: Production · Java 21 · Spring Boot 3.5 · PostgreSQL 16 · Redis 7 REPRO_STEPS: 4 steps provided — deterministic (any valid credentials trigger it) ``` **INTAKE ROUTE: FULL ANALYSIS** All required fields present. All 3 chains run at full confidence. **LOOP PRIMITIVES:** ``` EDITABLE_ASSET → hypothesis_list (candidates added, reordered, eliminated across chains) SCALAR_METRIC → root_cause_confidence (0–100): evidence_match 0–50 reproducibility 0–30 blast_radius 0–20 TIME_BOX → 3 chains — emit after Chain 3 regardless of confidence reached ``` **Scope guard check:** 1 failure mode detected. No scope cap required. --- ## PHASE 2: CHAIN 1 — INITIAL HYPOTHESIS ### Evidence Classification | # | Artifact | Classification | Indicates | |---|----------|---------------|-----------| | 1 | `NullPointerException at AuthenticationService.validateUser:118` | **DIRECT** | Null dereference at a specific, named location — execution reaches line 118 and a required object is null | | 2 | Stack frame: `LoginController.login:54 → AuthenticationService.validateUser:118` | **DIRECT** | Call chain is confirmed — controller reaches the service; failure is inside the service, not the controller boundary | | 3 | `RECENT_CHANGES: new authentication provider + updated JWT library` | **CORRELATING** | Timing correlation with both changes; either could affect what objects are injected into or constructed by `AuthenticationService` | | 4 | Error manifests immediately on credential submission (not after delay) | **CORRELATING** | Failure is not I/O-timeout or downstream latency — points to in-memory null at service startup or constructor, not a runtime data absence | | 5 | Repro is 100% deterministic with any valid credentials | **CORRELATING** | Not a race condition or data-specific issue; a structural null (misconfigured dependency, uninitialized field) is more likely than a transient one | --- ### STEP 2 — CHAIN 1 HYPOTHESIS **Pre-emit gate:** Can I trace this to at least one specific artifact? ✓ — NPE at `AuthenticationService.java:118` is a DIRECT SIGNAL. **Hypothesis:** > The new authentication provider introduced in v2.8.1 is not correctly wired into the Spring context, causing a required dependency injected into `AuthenticationService` to be `null` at line 118. When `validateUser()` attempts to delegate to this provider (e.g., calls a method on it), a `NullPointerException` is thrown immediately, before any credential evaluation occurs. **Specificity: HIGH** — Component: `AuthenticationService` — Mechanism: Null dependency injection (Spring bean misconfiguration or missing `@Bean` / `@Component` registration for the new auth provider) — Location: Line 118, `validateUser()` method --- ### STEP 3 — CHAIN 1 SCORE ``` EVIDENCE MATCH (0–50): NPE at exact line explains the 500 error entirely. Deterministic repro across all credentials = no data dependency. RECENT_CHANGES aligns precisely in timing. No contradicting signals present. → 46/50 REPRODUCIBILITY (0–30): 4-step repro consistently triggers it. Any valid credentials work. The failure is pre-authentication (no user-specific state required). → 28/30 BLAST RADIUS (0–20): Explains: 500 error, all-user impact, immediate failure on login. Does not yet explain: whether JWT library update plays any role, or whether session/Redis state is affected downstream. → 12/20 Chain 1 confidence: 86/100 ``` **CHAIN 1 VERDICT: HOLD** (≥60) — Primary candidate, advance to Chain 2. --- ## PHASE 3: CHAIN 2 — RATIONALIZED HYPOTHESIS **Pre-emit gate:** Is this meaningfully different from Chain 1? Chain 1 = DEPENDENCY (Spring bean null injection). Chain 2 must use a different mechanism class. --- ### STEP 4 — DIAGNOSE CHAIN 1 GAPS | Gap | Why Chain 1 Didn't Explain It | Alternative Lead | |-----|------------------------------|-----------------| | JWT library was also updated in v2.8.1 — Chain 1 focuses on the auth provider only | Chain 1 attributed null to Spring DI of auth provider; the JWT library change wasn't used as a primary cause | What if `validateUser:118` attempts to parse or validate a JWT token, and the updated library changed a method signature, return type, or introduced a null-returning API where the old one returned an empty object? | | No missing log entry for `AuthenticationService` initialization | If a bean failed to initialize, Spring Boot would typically log a startup failure — absence of that signal is notable | If the bean *did* initialize but the JWT parsing step returns null on the new library version, the NPE would occur at runtime only, not startup | **Hint applied:** `chain1_score ≥ 60 AND RECENT_CHANGES present AND blast_radius < 16` → Chain 2 must incorporate the JWT library change as a candidate cause. --- ### STEP 5 — CHAIN 2 HYPOTHESIS **Mechanism class selected: DEPENDENCY** (API contract change — distinct from Chain 1's DI misconfiguration) **Hypothesis:** > The updated JWT library (v2.8.1) introduced a breaking API change — a method previously returning a non-null object (e.g., `Claims`, `DecodedJWT`, or equivalent) now returns `null` under certain conditions (e.g., when no token is present on first login, or when token format doesn't match the new library's expectations). At `AuthenticationService.java:118`, the result of this JWT call is immediately dereferenced without a null check, causing the NPE before credential validation proceeds. **Specificity: HIGH** — Component: `AuthenticationService.validateUser()`, line 118 — Mechanism: JWT library API contract change — return value semantics shifted from non-null to nullable; no null guard at dereference site — Note: `validateUser:118` is the NPE site in both hypotheses — what differs is *which* object is null (injected auth provider bean vs. JWT library return value) --- ### STEP 6 — CHAIN 2 SCORE ``` EVIDENCE MATCH (0–50): NPE at exact line is equally explained. JWT library update is a listed RECENT_CHANGE — directly used. Deterministic repro is consistent: if JWT parse happens on every login attempt, it would fail every time with the new library. No contradicting signal rules this out. → 43/50 REPRODUCIBILITY (0–30): Same repro steps trigger it; any login attempt hits the JWT path. Slightly lower than Chain 1 — JWT null would typically appear only on requests without a pre-existing token (first login). The repro steps confirm this is first-login behavior. Consistent. → 25/30 BLAST RADIUS (0–20): Explains 500 error and all-user impact. Does not explain any auth-provider-specific side effects (because it bypasses the provider entirely — fails before reaching it). → 11/20 Chain 2 confidence: 79/100 ``` **CHAIN 2 VERDICT: HOLD** (≥60, score < Chain 1) — Secondary candidate, included in synthesis. --- ## PHASE 4: CHAIN 3 — SYNTHESIS **Pre-emit gate:** Are Chain 1 and Chain 2 the same root cause at different abstraction levels? Both hypotheses: - Produce a NPE at `AuthenticationService.java:118` - Are triggered by v2.8.1 changes - Are consistent with 100% repro They are **COMPETING**: same failure site, same symptom, different objects that are null. Only one can be the null object at line 118. Evidence must adjudicate. **Key adjudicating question:** What is line 118 doing? - If it dereferences the *auth provider bean* (e.g., `this.authProvider.authenticate(...)`) → Chain 1 is correct - If it dereferences a *JWT library return value* (e.g., `jwtParser.parse(token).getClaims().getSubject()`) → Chain 2 is correct **Adjudication signal available:** The new auth provider is the primary stated feature of v2.8.1. JWT library was updated as a dependency alongside it. Auth provider misconfiguration (DI null) would produce a startup warning or a Spring `BeanCreationException` context failure — but the app *is* running (login page loads, login request is processed). This slightly favors the bean *existing* but having an internal null at line 118, which is consistent with either hypothesis. Chain 1 remains higher confidence. **FINAL CONFIDENCE ADJUSTMENT:** Chain 1 (86) adjustments: ``` +5: RECENT_CHANGES directly correlates with hypothesized mechanism ✓ +5: Repro steps consistently trigger the hypothesized mechanism ✓ -0: No unresolved contradicting signals → Chain 1 final: 86 + 10 = 96/100 (capped at realistic ceiling: 91/100) ``` Chain 2 (79) adjustments: ``` +5: RECENT_CHANGES (JWT library) directly used ✓ +5: Repro steps consistent ✓ -5: Hypothesis specificity slightly weaker (mechanism depends on JWT library internals not visible in evidence) → Chain 2 final: 79 + 5 = 84/100 ``` **RELATIONSHIP: COMPETING** — Both cannot simultaneously be the null object at line 118. Fix order: inspect line 118 first; the null object type will immediately identify the correct root cause. --- ## PHASE 5: OUTPUT --- ### DEBUG SUMMARY ``` Bug domain: AuthenticationService · login flow · Spring Boot 3.5 / Java 21 Evidence artifacts: 5 provided (2 DIRECT / 3 CORRELATING / 0 CONTRADICTING / 0 MISSING) Chains completed: 3/3 Final confidence: 91/100 (Root Cause #1) — HIGH 84/100 (Root Cause #2) — HIGH ``` --- ### ROOT CAUSE VERDICT ``` ┌─ ROOT CAUSE #1 ────────────────────────────────────────────────────────┐ │ Hypothesis: New authentication provider (v2.8.1) is not correctly │ │ registered or wired in the Spring context. A required │