State of TypeScript Architecture 2026

Executive summary

Findings below are computed at build time from frozen Observatory analysis snapshots. No estimates or synthetic statistics.

• 11 open-source repositories with complete structural proof (Proof Density Rule: module and edge counts both greater than zero).
• 5,585 modules and 14,245 dependency edges traced across included snapshots.
• Architecture scores in this dataset range from 68.5 to 97 (0–100 scale from arc analyze snapshots).
• Highest recorded fan-in: 225 dependents on `src/types` in Payload CMS.
• Largest blast radius: 495 downstream modules from `src/errors/APIError` in Payload CMS.
• 8 of 11 snapshots report one or more dependency cycles.

Dataset

Repositories included in this edition — each passes the Proof Density Rule and links to a public proof page.

Fan-in analysis

Highest fan-in modules across all included snapshots (from highRiskModules fields). Fan-in counts direct dependents in each repository's traced subgraph.

1. 01fan-in 225

   src/types

   Payload CMS · CRITICAL

2. 02fan-in 154

   src

   Payload CMS · CRITICAL

3. 03fan-in 142

   src/config/types

   Payload CMS · CRITICAL

4. 04fan-in 128

   src/collections/config/types

   Payload CMS · CRITICAL

5. 05fan-in 124

   src/fields/config/types

   Payload CMS · CRITICAL

6. 06fan-in 123

   src/config/nx-json

   Nx · CRITICAL

7. 07fan-in 112

   src/utils/workspace-root

   Nx · CRITICAL

8. 08fan-in 105

   src/config/project-graph

   Nx · CRITICAL

9. 09fan-in 104

   src/logger

   Directus · CRITICAL

10. 10fan-in 102

    src/utils/output

    Nx · CRITICAL

11. 11fan-in 80

    src/api/utils/validators

    Medusa · CRITICAL

12. 12fan-in 71

    src/utils/fileutils

    Nx · CRITICAL

Blast radius analysis

Largest blast-radius modules (from hotspots fields) — downstream modules reachable when a node changes.

1. 01blast radius 495

   src/errors/APIError

   Payload CMS · fan-in 41 · CRITICAL

2. 02blast radius 478

   src/utils/fileutils

   Nx · fan-in 71 · CRITICAL

3. 03blast radius 477

   src/utilities/isNumber

   Payload CMS · fan-in 14 · CRITICAL

4. 04blast radius 477

   src/versions/types

   Payload CMS · fan-in 16 · CRITICAL

5. 05blast radius 476

   src/utils/workspace-root

   Nx · fan-in 112 · CRITICAL

6. 06blast radius 476

   src

   Payload CMS · fan-in 154 · CRITICAL

7. 07blast radius 476

   src/config/types

   Payload CMS · fan-in 142 · CRITICAL

8. 08blast radius 476

   src/types

   Payload CMS · fan-in 225 · CRITICAL

9. 09blast radius 467

   src/utils/versions

   Nx · fan-in 21 · CRITICAL

10. 10blast radius 465

    src/native

    Nx · fan-in 64 · CRITICAL

11. 11blast radius 454

    src/utils/path

    Nx · fan-in 26 · CRITICAL

12. 12blast radius 453

    src/config/task-graph

    Nx · fan-in 38 · CRITICAL

Architecture score distribution

Score spread across included repositories (arc analyze snapshot, 0–100). Range: 68.5 – 97.

• Cal.com
  97
• Strapi
  94.4
• Supabase
  93.9
• Turborepo
  93.7
• Medusa
  91
• Next.js
  89
• Prisma
  87.1
• tRPC
  79.3
• Directus
  75.1
• Payload CMS
  71.1
• Nx
  68.5

Common structural patterns

Recurring hotspots and shared characteristics counted from snapshot fields — not inferred from industry samples.

• Documented change-risk zones

  Every snapshot with structural proof lists at least one change-risk zone (11 of 11).

  • Cal.com · components/booking/actions/bookingActions
  • Directus · src/utils/get-config-from-env
  • Medusa · src/api/utils/validators
  • Next.js · src/types
  • Nx · src/utils/fileutils

• God-module gravity centers

  Primary gravity center role is "god-module" in 9 of 11 snapshots.

  • Directus · src/utils/get-config-from-env
  • Medusa · src/api/utils/validators
  • Nx · src/utils/fileutils
  • Payload CMS · src/errors/APIError
  • Prisma · src/runtime/core/errorRendering/base

• Types modules as top fan-in signal

  Highest fan-in module path contains "types" in 5 of 11 snapshots.

  • Next.js · src/shared/lib/app-router-types
  • Payload CMS · src/types
  • Prisma · src/runtime/core/engines/common/types/Transaction
  • Strapi · src/cli/types
  • Turborepo · src/types

• Utils modules as top fan-in signal

  Highest fan-in module path contains "utils" or "util" in 4 of 11 snapshots.

  • Medusa · src/api/utils/validators
  • Nx · src/utils/workspace-root
  • Supabase · src/lib/utils/cn
  • tRPC · src/unstable-core-do-not-import/utils

Key takeaways

• ·High fan-in modules are change-risk signals — inspect impact paths before refactoring shared types, utils, or config modules surfaced in this dataset.
• ·9 of 11 snapshots label the primary gravity center as a god-module — a single module carrying disproportionate structural pull.
• ·2 of 11 snapshots report layer violations — boundary crossings worth mapping before large moves.
• ·Each row in this report links to a frozen repository proof page — rerun arc impact locally on the module you plan to change before merge.

Methodology

Source repository proofs

• Cal.com
• Directus
• Medusa
• Next.js
• Nx
• Payload CMS
• Prisma
• Strapi
• Supabase
• tRPC
• Turborepo