sdcorejs-debug

name	sdcorejs-debug
description	Systematic debugging skill for root-cause/fix of concrete bugs and failing tests. Use for debug, investigate, resolve, fix, root-cause, wrong behavior, flaky/CI/prod-only failure, runtime/build error, or performance anomaly. Use sdcorejs-test for write/run/plan tests without fix intent. Runtime-localized.

Codex path resolution: Resolve ../_refs/... relative to this SKILL.md. Resolve another SDCoreJS skill by opening the sibling folder ../<skill-name>/SKILL.md.

Debug - Evidence-Driven Root-Cause Workflow

Purpose

sdcorejs-debug owns safe root-cause analysis for concrete failures:

• reproduce locally or evidence-confirm the bug;
• isolate the smallest failing case;
• classify debug_mode, bug_class, stack_profile, repro_status, and environment;
• form and falsify hypotheses with a visible Hypothesis Ledger;
• add temporary diagnostic instrumentation only when needed and track it;
• apply the smallest safe fix for the confirmed root cause;
• add or update a focused regression test when feasible;
• verify the original repro and regression surface;
• hand off to sdcorejs-ship before any commit, PR, changelog, or release flow.

It does not own broad feature implementation, unrelated test-plan generation, large new test suites, new test infrastructure, speculative fixes, direct Git artifacts, destructive production reproduction, or weakening tests to get a green result.

Shared Protocols

Before executing this skill:

1. Read and apply ../_refs/shared/tasklist.md for non-trivial execution tasks.
2. Read and apply ../_refs/shared/persona.md if a project persona exists.
3. Read and apply ../_refs/shared/project-context.md for project memory, resume checkpoints, summaries, specs/plans, tasks, and relevant memories.
4. Current user request, current files, diffs, logs, failing tests, and command output override stored context.
5. Before presenting user-facing choices, approval gates, yes/no questions, or mode selections, read and apply ../_refs/shared/user-choice-prompt.md so options are presented as sequential numbered choices.

After the shared protocols and before edits, read these debugging refs:

• ../_refs/shared/debugging-discipline.md
• ../_refs/shared/debug-command-discovery.md
• ../_refs/shared/debug-environment-guard.md
• ../_refs/shared/debug-context.md

Routing Boundary

Use sdcorejs-debug for root-cause analysis and fixing bugs, including failing tests when the user asks to debug, fix, investigate, resolve, or find root cause.

Correct routing:

• "debug this failing test", "fix this failing Jest test", "root-cause this test failure", "investigate flaky test" -> sdcorejs-debug.
• "write tests for X", "add unit tests", "run the test suite", "create UAT cases", "what should be tested?" -> sdcorejs-test.
• sdcorejs-test may do read-only failing-output triage only when the user asks to explain, classify, or summarize output without changes.
• When failing output implies a production bug or needs source changes, sdcorejs-test hands off to sdcorejs-debug with test_context, test_evidence, and the smallest failing command.
• sdcorejs-debug may add or update a small focused regression test during a bug fix when the existing runner and test style are clear. Large suites, new infrastructure, multiple test levels, complex UAT/e2e coverage, dependency installs, or browser binary installs belong to sdcorejs-test.

Do not invoke for feature requests phrased as new behavior, broad performance tuning without a concrete anomaly, review findings sets that belong to sdcorejs-repair-loop, or readiness/delivery checks that belong to sdcorejs-ship.

Step 0 - Working-Tree And Context Preflight

Before any source edit, inspect and record:

git branch --show-current
git rev-parse HEAD
git status --short
git diff --staged --stat
git diff --staged --name-status
git diff --stat
git ls-files --others --exclude-standard

Preflight output must include:

working_tree_preflight:
  branch:
  current_HEAD:
  staged_diffstat:
  unstaged_diffstat:
  untracked_files:
  allowed_edit_scope:
  unrelated_dirty_files:
  generated_vendor_build_outputs:

Rules:

• If unrelated dirty files exist and this task did not already approve the dirty baseline, stop and ask one numbered choice:
  1. Continue but restrict edits to bug-scoped files.
  2. Continue and allow touching selected dirty files.
  3. Stop so the user can clean or stash changes first.
• If the workflow already approved dirty state for this task, record the baseline and proceed inside the allowed edit scope.
• Do not stage, commit, push, or create PRs from sdcorejs-debug.
• Do not modify generated, vendor, build, coverage, cache, or runner output unless the bug is explicitly in generated artifacts and the repo convention supports editing them.

Step 1 - Classify The Debug Session

Classify before applying stack-specific guidance or editing files. Unknown is valid when evidence is insufficient, and classifications may change when new evidence arrives.

Required debug_mode values:

runtime-error | failing-test | wrong-behavior | flaky | ci-only | prod-only |
performance-anomaly | environment-config | dependency-regression |
security-sensitive | data-integrity | build-compile |
browser-device-specific | unknown

Required bug_class values:

null-or-undefined | async-race | state-lifecycle | validation |
permission-authz | authentication | routing | database-query |
transaction-consistency | serialization-deserialization | caching-staleness |
timezone-locale | dependency-version | configuration | environment |
network-third-party | type-contract | test-contract |
performance-regression | memory-leak | unknown

Required stack_profile values:

core-ui-angular | legacy-core-ui-angular | plain-angular |
sdcorejs-nestjs | plain-nestjs |
nextjs-build-website | plain-nextjs |
react-vite | react-cra | react-next-generic |
node-general | general

Required repro_status values:

local-confirmed | evidence-confirmed | flaky-confirmed | blocked

Environment values:

local | dev | staging | prod | unknown | mock

Classification rules:

• Evidence decides the label. Do not choose stack-specific bug classes or stack probes unless the target project uses that stack or dependency.
• For mixed or unknown stacks, use general or node-general and shared debugging rules.
• Do not let unknown become an excuse to patch. Gather evidence until a hypothesis is testable or mark repro_status: blocked.

Step 2 - Profile-Aware Stack Detection

Detect the target stack from files, dependencies, imports, test files, runner config, approved plans, and current error evidence.

Angular:

• Detect Angular from angular.json, @angular/core, components, modules, routes, or Angular tests.
• Use core-ui-angular only if @sdcorejs/angular is installed or the target code imports/uses it.
• Use legacy-core-ui-angular only if @sd-angular/core is installed or the target code imports/uses it.
• Use plain-angular when Angular is present but neither Core UI package is detected.
• Do not assume Core UI components, Sd* services, SD_API_CONFIGURATION, src/libs/**/features/**, or admin portal patterns for plain-angular.

NestJS:

• Detect NestJS from nest-cli.json, @nestjs/* dependencies, modules, controllers, providers, or Nest tests.
• Use sdcorejs-nestjs only if @sdcorejs/nestjs or strong SDCoreJS Nest conventions are detected.
• Use plain-nestjs when NestJS is present without SDCoreJS Nest evidence.
• Do not assume TypeORM, PostgreSQL, Zod, SdContext, @HasPermission, or @sdcorejs/nestjs for plain-nestjs unless detected.
• For plain NestJS, inspect the actual stack first: Prisma, Mongoose, TypeORM, class-validator/class-transformer, Zod, Fastify/Express, Passport/JWT, guards, interceptors, and pipes.

Next.js:

• Detect Next.js from next.config.*, next dependency, app/pages router files, page.tsx, layout.tsx, route.ts, or Next tests.
• Use nextjs-build-website only with strong build-website/public-site evidence such as [locale] i18n routing, typed i18n navigation, content/public-site structure, or prior sdcorejs-nextjs build-website context.
• Use plain-nextjs otherwise.
• Do not assume [locale], setRequestLocale, typed i18n navigation, sitemap/public-site metadata, or build-website caching rules for plain-nextjs.

React and general:

• Use react-vite, react-cra, or react-next-generic only when the project signals that profile.
• Use node-general for Node tools, libraries, CLIs, scripts, or servers without a stronger framework profile.
• Use general for unsupported or mixed projects and debug from direct evidence only.

Step 3 - Command Discovery And Environment Guard

Use ../_refs/shared/debug-command-discovery.md as the canonical command policy. Before running repro or verification, discover the package manager, lockfiles, workspace config, relevant package.json scripts, runner configs, original failing command, and CI output. Prefer focused repro first, focused regression second, and broader existing checks last. Do not mix package managers, invent scripts, assume npm/npx/tsc commands, install tools, or run browser installs without explicit approval; record missing, unsafe, or environment-blocked commands in commands_skipped.

Use ../_refs/shared/debug-environment-guard.md as the canonical environment policy. Before any repro touches browsers, APIs, databases, external systems, or persistent state, classify the environment as local | dev | staging | prod | unknown | mock, block destructive production/external side effects, and record seed/setup/cleanup or blocked evidence in debug_context.

Step 4 - Reproduce Or Evidence-Confirm

Use evidence-aware reproduction, not a rigid "must run locally" rule:

repro_status	Definition	Verification rule
local-confirmed	The bug reproduces locally with a focused command or manual step.	Prefer 3/3 consistent repro when cheap and appropriate.
evidence-confirmed	Local execution is unavailable, but stack traces, CI logs, production logs, screenshots, sanitized payloads, or failing output isolate a likely root cause.	Mark confidence and do not claim the original environment is fixed until verified there.
flaky-confirmed	Repeated runs or logs show nondeterministic failure.	Treat nondeterminism as the bug; record pass/fail counts and do not claim fixed from one passing run.
blocked	Evidence is insufficient or required environment/data/access is unavailable.	Do not patch speculatively. Ask for missing evidence or propose safe instrumentation.

Capture:

• observed behavior: exact redacted error, stack, command output, network response, screenshot summary, or input;
• expected behavior in the user's words or the contract;
• input/data/environment that triggered it;
• confidence: high, medium, or low.

Step 5 - Maintain The Hypothesis Ledger

Before any fix, create and update a visible Hypothesis Ledger:

ID	Observation	Hypothesis	Predicted evidence	Falsification probe	Result	Status
H1	Stack trace points to user.name	user is undefined when lookup returns 404	missing-user repro throws before guard	run focused missing-user test	confirmed	ROOT

Rules:

• Do not patch until at least one hypothesis is confirmed, unless the user explicitly approves a tactical mitigation.
• Do not keep more than 3 live hypotheses without gathering new evidence.
• Mark hypotheses as confirmed, falsified, inconclusive, or root.
• If all hypotheses are inconclusive, gather more evidence or escalate.
• Avoid shotgun debugging. Apply one coherent root-cause fix at a time.
• The final report must identify the root hypothesis or explain why root cause remains uncertain.

Step 6 - Track Diagnostic Instrumentation

When adding logs, probes, temporary assertions, breakpoints, tracing, throw probes, or debug-only assertions, maintain this ledger:

Diagnostic Instrumentation Ledger:
- file:
- line_or_scope:
- purpose:
- sensitive_values_redacted:
- cleanup_required:
- cleanup_done:
- permanent_observability_approved:

Rules:

• Temporary instrumentation must be removed before final verification unless the user explicitly approves permanent observability.
• Do not leave noisy logs in production code.
• Do not log secrets, tokens, cookies, credentials, PII, full request bodies, or raw SQL parameter dumps.
• Permanent observability must be intentional, minimal, redacted, and consistent with project logging conventions.
• Final report must state whether diagnostic instrumentation remains.

Step 7 - Fix Scope And Regression Tests

Fix the root cause with the smallest safe patch:

• Do not perform broad refactors during debugging.
• Do not apply multiple unrelated fixes in one pass.
• Do not hide symptoms with optional chaining, default values, catch-and-swallow blocks, retries, or null guards unless the confirmed hypothesis proves that this is the correct contract.
• Do not change public API, schema, security, permissions, migration behavior, or product contract without explicit approval.
• If the bug reveals a broader design issue, apply only the minimal safe mitigation and propose follow-up planning.

Regression test ownership:

• Add or update a small focused regression test when the existing runner and style are clear, the repro is cheap to capture, the file scope is obvious, and no new infrastructure is needed.
• Delegate to sdcorejs-test when new infrastructure, multiple test levels, a broad suite, complex UAT/e2e coverage, dependency installs, or browser binaries are needed.
• Do not add test dependencies from sdcorejs-debug without explicit approval.
• Do not weaken tests, delete tests, skip tests, loosen assertions, increase timeouts blindly, or mock away the behavior under test.
• If an existing test is wrong because of an approved contract change, require explicit approval before updating the expectation.

Step 8 - Mode-Specific Rules

Flaky:

• Treat nondeterminism as the bug.
• Run repeated focused repro when cheap and record pass/fail counts.
• Look for shared state, timing, clock, random, order dependency, retries, race conditions, external services, and cleanup leaks.
• Do not claim fixed from a single passing run.

CI-only:

• Use CI logs, config, and environment differences as evidence.
• Compare package manager, Node/browser/OS versions, env vars, timezones, caches, parallelism, workspace paths, and lockfiles.
• If local repro is impossible, use evidence-confirmed and require CI verification before claiming fixed.

Prod-only:

• Require sanitized logs and payloads.
• Prefer safe instrumentation or feature-flagged diagnostics.
• Do not use raw production secrets/data or destructive production repro.
• Mark the fix unverified until production or staging confirmation exists.

Performance-anomaly:

• Debug only concrete wrong behavior or regression, not broad optimization.
• Use measured evidence such as timings, profiles, query plans, traces, or before/after command output.
• Avoid broad rewrites unless root cause requires them and the user approves.

Security-sensitive:

• Redact aggressively.
• Avoid printing exploit payloads, secrets, or sensitive identifiers unnecessarily.
• Consider a follow-up sdcorejs-review security review after the fix.
• Do not weaken auth, permission, validation, or crypto checks to make a path pass.

Data-integrity:

• Treat migrations, schema changes, backfills, deletions, and transactional fixes as high risk.
• Prefer read-only inspection first.
• Do not run destructive data changes without explicit approval plus backup/rollback strategy.

Dependency-regression:

• Isolate version and config changes before changing dependencies.
• Do not update or downgrade dependencies casually.
• If a dependency change is required, route delivery through sdcorejs-ship dependency-update discipline when present.
• Record lockfile, package manager, and changelog/migration evidence.

Step 9 - Redaction Protocol

Never echo secret or PII values from .env, local config, CI files, shell output, source files, stack traces, network logs, request payloads, cookies, authorization headers, JWTs, refresh tokens, database URLs, API keys, passwords, private keys, customer PII, production data, or git diffs.

Rules:

• Never print full lines that contain likely secret values.
• For suspected secrets, report only file path, line number when available, key/category name, risk reason, and redacted evidence such as API_KEY=[REDACTED].
• If a grep/rg command would print secret values, do not run it raw. Use safer summaries or redacted inspection.
• Do not include secret values in debug_context, final summaries, auto-docs, task tracker, commit messages, PR bodies, or changelog entries.
• If suspected secrets are part of the bug, stop before shipping and require remediation.

Step 10 - Verify And Tail Chain

After the fix:

1. Re-run the original repro or evidence-equivalent focused repro.
2. Run the focused regression test if available.
3. Run broader existing checks when appropriate and available.
4. Remove or explicitly approve diagnostic instrumentation.
5. Emit final debug_context.
6. Run auto-docs, task tracker, and memories only when durable debug knowledge or changed artifacts justify them and normal tail policy allows it.
7. Run sdcorejs-ship (verify-before-done mode) when acceptance criteria, a bug contract, or source changes exist.
8. Run sdcorejs-ship (branch-ready mode) as the final read-only gate over the final diff before any Git artifact path. No writes after branch-ready unless branch-ready is run again.
9. Invoke sdcorejs-git only after ship and branch-ready gates have passed for the current HEAD or diff and the user explicitly asks for commit, PR, changelog, release-note, or workspace artifacts.

If invoked from sdcorejs-repair-loop, preserve repair_source, review_context, original finding ID/source, package-manager evidence, and verification commands. After the debug fix, return to the caller's tail chain.

If verification is blocked, say blocked/unverified and do not claim the bug is fixed. If repro_status is evidence-confirmed or blocked, do not overclaim confidence.

Required Output

Every sdcorejs-debug session ends with a redacted debug_context block. The canonical schema lives in ../_refs/shared/debug-context.md; do not duplicate or drift it in this skill body. The final block must include at minimum:

source, debug_mode, bug_class, stack_profile, repro_status, observed, expected,
root_cause, root_hypothesis_id, confidence, files_touched,
diagnostic_instrumentation, regression_tests, commands_run, commands_skipped,
package_manager, environment, secret_redaction, verification, ship_handoff

Rules:

• commands_run includes only commands actually run.
• Do not claim tests, build, lint, repro, or CI passed unless they were actually run and passed.
• If verification was skipped or blocked, record why.
• debug_context must not contain secrets, PII, raw production data, or full secret-bearing lines.

Rules

MUST DO

• Run working-tree preflight before edits.
• Classify debug_mode, bug_class, stack_profile, repro_status, and environment before stack-specific probes.
• Use package-manager/script-aware command discovery.
• Redact secrets and PII in logs, stack traces, network output, grep output, diffs, and final reports.
• Maintain the Hypothesis Ledger and Diagnostic Instrumentation Ledger.
• Confirm or evidence-confirm the bug before patching, or mark blocked.
• Fix the root cause, not the symptom.
• Add/update focused regression coverage when feasible, or delegate to sdcorejs-test.
• Verify original repro plus regression surface.
• Run sdcorejs-ship (verify-before-done mode) and sdcorejs-ship (branch-ready mode) before Git artifacts when source or contract changes exist.

MUST NOT

• Patch speculatively when repro_status: blocked.
• Use shotgun debugging.
• Silence errors with broad try/catch, optional chaining, default values, retries, or null guards without a confirmed root-cause contract.
• Disable, skip, weaken, or rewrite tests only to make output green.
• Run destructive production repro or use production data unsafely.
• Leave temporary diagnostic logs behind.
• Hardcode one package manager or invent scripts.
• Use --no-verify to bypass hooks.
• Stage, commit, push, or create PRs.

Cross-references

• sdcorejs-test - owns writing/running/planning tests without root-cause/fix intent and receives delegated large test work.
• sdcorejs-ship - consumes debug evidence for verify-before-done and branch-ready gates.
• sdcorejs-review - optional follow-up review, especially for security/performance-sensitive fixes.
• sdcorejs-repair-loop - can call debug for a single verified bug while preserving repair_source and review_context.
• sdcorejs-git - creates artifacts only after ship gates pass and the user explicitly requests them.