Episode 2 — React Frontend Architecture NextJS / 2.13 — Global State Management

2.13.b — Context providers & consumers: deep trees

Learning outcomes

Compose multiple providers without a pyramid of unreadable JSX.
Share state through deep trees without prop drilling—while keeping boundaries explicit.
Export custom hooks (useAuth) instead of raw context everywhere.

Provider composition pattern

export function AppProviders({ children }: { children: React.ReactNode }) {
  return (
    <QueryClientProvider client={queryClient}>
      <ThemeProvider>
        <AuthProvider>{children}</AuthProvider>
      </ThemeProvider>
    </QueryClientProvider>
  );
}

Order matters when inner providers depend on outer ones (e.g., auth client needing theme for branded errors—rare but real).

Deep trees: mental model

Consumers anywhere below a provider can read context. That is powerful and dangerous: implicit coupling replaces explicit props.

Mitigation: narrow context types, document allowed mutations, code-review provider changes.

Testing

Provide a renderWithProviders(ui, { authUser: ... }) helper so tests do not copy 40 lines of wrapping.

Appendix — Scenario bank (basic → advanced)

Each card: symptom → cause → fix → interview phrase. Drill five cards daily and explain aloud without reading.

GS1-001 — Providers & consumers #1

Level: Beginner
Symptom: subtree re-renders 13% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-002 — Providers & consumers #2

Level: Beginner+
Symptom: subtree re-renders 26% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-003 — Providers & consumers #3

Level: Intermediate
Symptom: subtree re-renders 39% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-004 — Providers & consumers #4

Level: Intermediate+
Symptom: subtree re-renders 52% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-005 — Providers & consumers #5

Level: Advanced
Symptom: subtree re-renders 65% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-006 — Providers & consumers #6

Level: Advanced+
Symptom: subtree re-renders 78% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-007 — Providers & consumers #7

Level: Beginner
Symptom: subtree re-renders 91% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-008 — Providers & consumers #8

Level: Beginner+
Symptom: subtree re-renders 104% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-009 — Providers & consumers #9

Level: Intermediate
Symptom: subtree re-renders 117% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-010 — Providers & consumers #10

Level: Intermediate+
Symptom: subtree re-renders 130% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-011 — Providers & consumers #11

Level: Advanced
Symptom: subtree re-renders 143% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-012 — Providers & consumers #12

Level: Advanced+
Symptom: subtree re-renders 156% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-013 — Providers & consumers #13

Level: Beginner
Symptom: subtree re-renders 169% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-014 — Providers & consumers #14

Level: Beginner+
Symptom: subtree re-renders 182% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-015 — Providers & consumers #15

Level: Intermediate
Symptom: subtree re-renders 195% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-016 — Providers & consumers #16

Level: Intermediate+
Symptom: subtree re-renders 8% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-017 — Providers & consumers #17

Level: Advanced
Symptom: subtree re-renders 21% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-018 — Providers & consumers #18

Level: Advanced+
Symptom: subtree re-renders 34% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-019 — Providers & consumers #19

Level: Beginner
Symptom: subtree re-renders 47% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-020 — Providers & consumers #20

Level: Beginner+
Symptom: subtree re-renders 60% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-021 — Providers & consumers #21

Level: Intermediate
Symptom: subtree re-renders 73% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-022 — Providers & consumers #22

Level: Intermediate+
Symptom: subtree re-renders 86% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-023 — Providers & consumers #23

Level: Advanced
Symptom: subtree re-renders 99% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-024 — Providers & consumers #24

Level: Advanced+
Symptom: subtree re-renders 112% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-025 — Providers & consumers #25

Level: Beginner
Symptom: subtree re-renders 125% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-026 — Providers & consumers #26

Level: Beginner+
Symptom: subtree re-renders 138% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-027 — Providers & consumers #27

Level: Intermediate
Symptom: subtree re-renders 151% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-028 — Providers & consumers #28

Level: Intermediate+
Symptom: subtree re-renders 164% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-029 — Providers & consumers #29

Level: Advanced
Symptom: subtree re-renders 177% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-030 — Providers & consumers #30

Level: Advanced+
Symptom: subtree re-renders 190% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-031 — Providers & consumers #31

Level: Beginner
Symptom: subtree re-renders 3% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-032 — Providers & consumers #32

Level: Beginner+
Symptom: subtree re-renders 16% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-033 — Providers & consumers #33

Level: Intermediate
Symptom: subtree re-renders 29% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-034 — Providers & consumers #34

Level: Intermediate+
Symptom: subtree re-renders 42% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-035 — Providers & consumers #35

Level: Advanced
Symptom: subtree re-renders 55% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-036 — Providers & consumers #36

Level: Advanced+
Symptom: subtree re-renders 68% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-037 — Providers & consumers #37

Level: Beginner
Symptom: subtree re-renders 81% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-038 — Providers & consumers #38

Level: Beginner+
Symptom: subtree re-renders 94% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-039 — Providers & consumers #39

Level: Intermediate
Symptom: subtree re-renders 107% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-040 — Providers & consumers #40

Level: Intermediate+
Symptom: subtree re-renders 120% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-041 — Providers & consumers #41

Level: Advanced
Symptom: subtree re-renders 133% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-042 — Providers & consumers #42

Level: Advanced+
Symptom: subtree re-renders 146% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-043 — Providers & consumers #43

Level: Beginner
Symptom: subtree re-renders 159% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-044 — Providers & consumers #44

Level: Beginner+
Symptom: subtree re-renders 172% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-045 — Providers & consumers #45

Level: Intermediate
Symptom: subtree re-renders 185% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-046 — Providers & consumers #46

Level: Intermediate+
Symptom: subtree re-renders 198% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-047 — Providers & consumers #47

Level: Advanced
Symptom: subtree re-renders 11% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-048 — Providers & consumers #48

Level: Advanced+
Symptom: subtree re-renders 24% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-049 — Providers & consumers #49

Level: Beginner
Symptom: subtree re-renders 37% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-050 — Providers & consumers #50

Level: Beginner+
Symptom: subtree re-renders 50% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-051 — Providers & consumers #51

Level: Intermediate
Symptom: subtree re-renders 63% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-052 — Providers & consumers #52

Level: Intermediate+
Symptom: subtree re-renders 76% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-053 — Providers & consumers #53

Level: Advanced
Symptom: subtree re-renders 89% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-054 — Providers & consumers #54

Level: Advanced+
Symptom: subtree re-renders 102% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-055 — Providers & consumers #55

Level: Beginner
Symptom: subtree re-renders 115% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-056 — Providers & consumers #56

Level: Beginner+
Symptom: subtree re-renders 128% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-057 — Providers & consumers #57

Level: Intermediate
Symptom: subtree re-renders 141% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-058 — Providers & consumers #58

Level: Intermediate+
Symptom: subtree re-renders 154% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-059 — Providers & consumers #59

Level: Advanced
Symptom: subtree re-renders 167% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-060 — Providers & consumers #60

Level: Advanced+
Symptom: subtree re-renders 180% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-061 — Providers & consumers #61

Level: Beginner
Symptom: subtree re-renders 193% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-062 — Providers & consumers #62

Level: Beginner+
Symptom: subtree re-renders 6% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-063 — Providers & consumers #63

Level: Intermediate
Symptom: subtree re-renders 19% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-064 — Providers & consumers #64

Level: Intermediate+
Symptom: subtree re-renders 32% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-065 — Providers & consumers #65

Level: Advanced
Symptom: subtree re-renders 45% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-066 — Providers & consumers #66

Level: Advanced+
Symptom: subtree re-renders 58% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-067 — Providers & consumers #67

Level: Beginner
Symptom: subtree re-renders 71% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-068 — Providers & consumers #68

Level: Beginner+
Symptom: subtree re-renders 84% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-069 — Providers & consumers #69

Level: Intermediate
Symptom: subtree re-renders 97% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-070 — Providers & consumers #70

Level: Intermediate+
Symptom: subtree re-renders 110% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-071 — Providers & consumers #71

Level: Advanced
Symptom: subtree re-renders 123% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-072 — Providers & consumers #72

Level: Advanced+
Symptom: subtree re-renders 136% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-073 — Providers & consumers #73

Level: Beginner
Symptom: subtree re-renders 149% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-074 — Providers & consumers #74

Level: Beginner+
Symptom: subtree re-renders 162% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-075 — Providers & consumers #75

Level: Intermediate
Symptom: subtree re-renders 175% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-076 — Providers & consumers #76

Level: Intermediate+
Symptom: subtree re-renders 188% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-077 — Providers & consumers #77

Level: Advanced
Symptom: subtree re-renders 1% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-078 — Providers & consumers #78

Level: Advanced+
Symptom: subtree re-renders 14% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-079 — Providers & consumers #79

Level: Beginner
Symptom: subtree re-renders 27% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-080 — Providers & consumers #80

Level: Beginner+
Symptom: subtree re-renders 40% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-081 — Providers & consumers #81

Level: Intermediate
Symptom: subtree re-renders 53% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-082 — Providers & consumers #82

Level: Intermediate+
Symptom: subtree re-renders 66% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-083 — Providers & consumers #83

Level: Advanced
Symptom: subtree re-renders 79% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-084 — Providers & consumers #84

Level: Advanced+
Symptom: subtree re-renders 92% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-085 — Providers & consumers #85

Level: Beginner
Symptom: subtree re-renders 105% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-086 — Providers & consumers #86

Level: Beginner+
Symptom: subtree re-renders 118% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-087 — Providers & consumers #87

Level: Intermediate
Symptom: subtree re-renders 131% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-088 — Providers & consumers #88

Level: Intermediate+
Symptom: subtree re-renders 144% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-089 — Providers & consumers #89

Level: Advanced
Symptom: subtree re-renders 157% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-090 — Providers & consumers #90

Level: Advanced+
Symptom: subtree re-renders 170% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-091 — Providers & consumers #91

Level: Beginner
Symptom: subtree re-renders 183% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-092 — Providers & consumers #92

Level: Beginner+
Symptom: subtree re-renders 196% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-093 — Providers & consumers #93

Level: Intermediate
Symptom: subtree re-renders 9% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-094 — Providers & consumers #94

Level: Intermediate+
Symptom: subtree re-renders 22% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-095 — Providers & consumers #95

Level: Advanced
Symptom: subtree re-renders 35% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-096 — Providers & consumers #96

Level: Advanced+
Symptom: subtree re-renders 48% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-097 — Providers & consumers #97

Level: Beginner
Symptom: subtree re-renders 61% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-098 — Providers & consumers #98

Level: Beginner+
Symptom: subtree re-renders 74% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-099 — Providers & consumers #99

Level: Intermediate
Symptom: subtree re-renders 87% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-100 — Providers & consumers #100

Level: Intermediate+
Symptom: subtree re-renders 100% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-101 — Providers & consumers #101

Level: Advanced
Symptom: subtree re-renders 113% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-102 — Providers & consumers #102

Level: Advanced+
Symptom: subtree re-renders 126% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-103 — Providers & consumers #103

Level: Beginner
Symptom: subtree re-renders 139% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-104 — Providers & consumers #104

Level: Beginner+
Symptom: subtree re-renders 152% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-105 — Providers & consumers #105

Level: Intermediate
Symptom: subtree re-renders 165% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-106 — Providers & consumers #106

Level: Intermediate+
Symptom: subtree re-renders 178% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-107 — Providers & consumers #107

Level: Advanced
Symptom: subtree re-renders 191% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-108 — Providers & consumers #108

Level: Advanced+
Symptom: subtree re-renders 4% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-109 — Providers & consumers #109

Level: Beginner
Symptom: subtree re-renders 17% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-110 — Providers & consumers #110

Level: Beginner+
Symptom: subtree re-renders 30% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-111 — Providers & consumers #111

Level: Intermediate
Symptom: subtree re-renders 43% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-112 — Providers & consumers #112

Level: Intermediate+
Symptom: subtree re-renders 56% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-113 — Providers & consumers #113

Level: Advanced
Symptom: subtree re-renders 69% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-114 — Providers & consumers #114

Level: Advanced+
Symptom: subtree re-renders 82% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-115 — Providers & consumers #115

Level: Beginner
Symptom: subtree re-renders 95% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-116 — Providers & consumers #116

Level: Beginner+
Symptom: subtree re-renders 108% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-117 — Providers & consumers #117

Level: Intermediate
Symptom: subtree re-renders 121% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-118 — Providers & consumers #118

Level: Intermediate+
Symptom: subtree re-renders 134% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-119 — Providers & consumers #119

Level: Advanced
Symptom: subtree re-renders 147% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-120 — Providers & consumers #120

Level: Advanced+
Symptom: subtree re-renders 160% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-121 — Providers & consumers #121

Level: Beginner
Symptom: subtree re-renders 173% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-122 — Providers & consumers #122

Level: Beginner+
Symptom: subtree re-renders 186% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-123 — Providers & consumers #123

Level: Intermediate
Symptom: subtree re-renders 199% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-124 — Providers & consumers #124

Level: Intermediate+
Symptom: subtree re-renders 12% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-125 — Providers & consumers #125

Level: Advanced
Symptom: subtree re-renders 25% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-126 — Providers & consumers #126

Level: Advanced+
Symptom: subtree re-renders 38% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-127 — Providers & consumers #127

Level: Beginner
Symptom: subtree re-renders 51% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-128 — Providers & consumers #128

Level: Beginner+
Symptom: subtree re-renders 64% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-129 — Providers & consumers #129

Level: Intermediate
Symptom: subtree re-renders 77% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-130 — Providers & consumers #130

Level: Intermediate+
Symptom: subtree re-renders 90% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-131 — Providers & consumers #131

Level: Advanced
Symptom: subtree re-renders 103% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-132 — Providers & consumers #132

Level: Advanced+
Symptom: subtree re-renders 116% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-133 — Providers & consumers #133

Level: Beginner
Symptom: subtree re-renders 129% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-134 — Providers & consumers #134

Level: Beginner+
Symptom: subtree re-renders 142% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-135 — Providers & consumers #135

Level: Intermediate
Symptom: subtree re-renders 155% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-136 — Providers & consumers #136

Level: Intermediate+
Symptom: subtree re-renders 168% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-137 — Providers & consumers #137

Level: Advanced
Symptom: subtree re-renders 181% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-138 — Providers & consumers #138

Level: Advanced+
Symptom: subtree re-renders 194% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-139 — Providers & consumers #139

Level: Beginner
Symptom: subtree re-renders 7% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-140 — Providers & consumers #140

Level: Beginner+
Symptom: subtree re-renders 20% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-141 — Providers & consumers #141

Level: Intermediate
Symptom: subtree re-renders 33% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-142 — Providers & consumers #142

Level: Intermediate+
Symptom: subtree re-renders 46% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-143 — Providers & consumers #143

Level: Advanced
Symptom: subtree re-renders 59% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-144 — Providers & consumers #144

Level: Advanced+
Symptom: subtree re-renders 72% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-145 — Providers & consumers #145

Level: Beginner
Symptom: subtree re-renders 85% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-146 — Providers & consumers #146

Level: Beginner+
Symptom: subtree re-renders 98% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-147 — Providers & consumers #147

Level: Intermediate
Symptom: subtree re-renders 111% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-148 — Providers & consumers #148

Level: Intermediate+
Symptom: subtree re-renders 124% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-149 — Providers & consumers #149

Level: Advanced
Symptom: subtree re-renders 137% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-150 — Providers & consumers #150

Level: Advanced+
Symptom: subtree re-renders 150% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-151 — Providers & consumers #151

Level: Beginner
Symptom: subtree re-renders 163% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-152 — Providers & consumers #152

Level: Beginner+
Symptom: subtree re-renders 176% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-153 — Providers & consumers #153

Level: Intermediate
Symptom: subtree re-renders 189% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Consumer hooks scattered without naming convention (useX).
Primary remediation: Export useTheme, useAuth hooks wrapping useContext for ergonomics + errors.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-154 — Providers & consumers #154

Level: Intermediate+
Symptom: subtree re-renders 2% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Rendering Provider inside a route that unmounts resets unrelated state unexpectedly.
Primary remediation: Build a renderWithProviders test utility with sensible defaults.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-155 — Providers & consumers #155

Level: Advanced
Symptom: subtree re-renders 15% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Passing unstable callbacks through createContext default instead of Provider value.
Primary remediation: Introduce facades or domain modules so consumers depend on narrow APIs.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-156 — Providers & consumers #156

Level: Advanced+
Symptom: subtree re-renders 28% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Provider nested 14 levels deep with duplicated boundaries confusing ownership.
Primary remediation: Compose providers with a single AppProviders module; document order dependencies.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-157 — Providers & consumers #157

Level: Beginner
Symptom: subtree re-renders 41% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Prop drilling replaced by context drilling without reducing coupling.
Primary remediation: Always supply value via Provider; keep defaults for tests only.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

GS1-158 — Providers & consumers #158

Level: Beginner+
Symptom: subtree re-renders 54% more than expected after a small unrelated UI change.
Architecture smell: unclear ownership of who may mutate shared state.
Root cause class: Testing becomes painful because every test must wrap the entire provider tree.
Primary remediation: Lift persistent providers to layout shell that does not unmount on navigation.
Proof: React DevTools highlight updates; split providers and re-measure.
Interview one-liner: Providers are boundaries—decide what crosses them as carefully as public APIs.

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