Most coding assistants solve the problem for you. CodeTutor AI teaches you to solve it yourself — the tutor knows your lesson, your current code, and how many times you've tried, and escalates hints accordingly. You write the answer; it makes sure you understand why.
Lesson workspace — instructions, editor, and an AI tutor that guides without spoiling.
A full coding workspace across nine languages. Each comes with a starter project so you can jump right in.
- Professional editor — syntax highlighting, autocomplete, multi-file projects, light + dark themes
- Instant run — sandboxed container returns stdout, stderr, and execution time
- Highlight + ask — select any code and press Cmd+K / Ctrl+K to ask the tutor about it
- Dedicated stdin — sample input pre-filled per language, or paste your own
- First-time tour — walks you through the workspace on your first visit
Two structured beginner courses today: 12-lesson Python Fundamentals (through a mini-project + two capstones) and 8-lesson JavaScript Fundamentals (through a habit-tracker mini-project). Shared content pipeline, per-language test harness, and authoring scripts. (More courses on the way.)
- Learn by doing — read, write, run, check your work. Loop.
- Tutor that teaches, not solves — knows your lesson context, gives escalating hints, never spoils the answer
- Instant validation — "Check My Work" runs your code against the lesson's completion rules and shows what to fix
- Visible + hidden tests — capstone lessons show example test cases you can run any time; "Check My Work" also runs hidden cases
- Practice mode — 30+ bite-sized challenges (3 per lesson) reinforce each concept with a different twist
- Progress that sticks — code, completions, and progress save to your account and sync across devices
- Guided onboarding — contextual nudges and a spotlight tour introduce the workspace on your first lesson
- Learning dashboard — see what's next, recent activity, and lessons worth revisiting
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Adaptive AI tutor — adjusts vocabulary and depth to your experience level (beginner, intermediate, advanced). |
Highlight + ask — select code and press Cmd+K / Ctrl+K to ask about it anywhere in the app. |
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Stuckness detection — repeated failures on the same step unlock stronger hints and concrete next steps. |
Tutor access — signed-in learners get a small daily allowance on the hosted tier. Bring your own OpenAI key for unlimited use — encrypted at rest, never surfaced back. Editor and run always work without either. |
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Light & dark themes — follows your system by default, or pick one in Settings. Editor and app chrome switch together. |
Accessible by default — WCAG AA contrast, keyboard-navigable splitters, full ARIA labeling on every interactive surface. |
A full-stack TypeScript product shipping to real users at codetutor.msrivas.com.
%%{init: {
'theme': 'base',
'themeVariables': {
'primaryColor': '#1e293b',
'primaryTextColor': '#f8fafc',
'primaryBorderColor': '#334155',
'lineColor': '#64748b',
'clusterBkg': '#0f172a',
'clusterBorder': '#334155'
},
'flowchart': {
'curve': 'basis',
'htmlLabels': true,
'nodeSpacing': 55,
'rankSpacing': 70
}
}}%%
flowchart LR
U((User<br/>Browser))
SWA[Static Web Apps<br/>frontend bundle]
subgraph CLOUD[Cloud services]
direction TB
SB[(Supabase<br/>Auth + Postgres)]
AI[OpenAI<br/>Responses API]
KV[Key Vault<br/>runtime secrets]
end
subgraph VM[Azure VM · Ubuntu 24.04]
direction TB
CD[Caddy<br/>TLS + reverse proxy]
subgraph BECTR[Backend container · Express + TS]
direction TB
API[HTTP / SSE routes]
SM[SessionManager<br/>userId to runnerId]
EB[ExecutionBackend<br/>Dockerode client]
SW[Idle sweeper<br/>45 s tick]
API --> SM
SM --> EB
SW -. reaps idle .-> SM
end
SP[socket-proxy<br/>endpoint allowlist]
subgraph POOL[Runner pool · one per session]
direction TB
R1[Runner A<br/>non-root · no net<br/>read-only rootfs]
R2[Runner B]
R3[Runner ...]
end
CD --> API
EB -->|tcp:2375| SP
SP -->|docker.sock| R1
SP --> R2
SP --> R3
end
U --> SWA
U ==>|HTTPS / SSE| CD
U -.->|auth| SB
API -->|JWKS + DB| SB
EB --> AI
EB -. boot time .-> KV
classDef user fill:#1e293b,stroke:#0f172a,color:#f8fafc,stroke-width:2px
classDef edge fill:#0284c7,stroke:#0369a1,color:#fff,stroke-width:2px
classDef svc fill:#0078d4,stroke:#005a9e,color:#fff,stroke-width:2px
classDef proxy fill:#f59e0b,stroke:#b45309,color:#0f172a,stroke-width:2px
classDef runner fill:#10b981,stroke:#047857,color:#fff,stroke-width:2px
classDef external fill:#475569,stroke:#334155,color:#fff,stroke-width:2px
class U user
class SWA edge
class CD,API,SM,EB,SW,KV svc
class SP proxy
class R1,R2,R3 runner
class SB,AI external
Session lifecycle — create → snapshot → run → reap
%%{init: {
'theme': 'base',
'themeVariables': {
'fontFamily': '-apple-system, BlinkMacSystemFont, Segoe UI, sans-serif',
'fontSize': '13px',
'primaryColor': '#0284c7',
'primaryTextColor': '#f8fafc',
'primaryBorderColor': '#0369a1',
'lineColor': '#64748b',
'actorBkg': '#1e293b',
'actorTextColor': '#f8fafc',
'actorBorder': '#334155',
'signalColor': '#cbd5e1',
'signalTextColor': '#e2e8f0',
'noteBkgColor': '#fef3c7',
'noteTextColor': '#78350f',
'noteBorderColor': '#f59e0b',
'sequenceNumberColor': '#f8fafc',
'activationBkgColor': '#10b981'
}
}}%%
sequenceDiagram
autonumber
participant U as Browser
participant BE as Backend
participant SM as SessionManager
participant SP as socket-proxy
participant RN as Runner
U->>BE: POST /api/session (JWT)
BE->>SM: create(userId)
SM->>SP: /containers/create (allowlist check)
SP->>RN: spawn · non-root · --network none · read-only
RN-->>SP: containerId
SP-->>SM: handle
SM-->>BE: sessionId
BE-->>U: { sessionId }
U->>BE: POST /api/project/snapshot (files)
BE->>RN: write workspace
U->>BE: POST /api/execution/run (code, stdin)
BE->>SP: exec
SP->>RN: run · CPU · mem · PID capped
RN-->>BE: stdout · stderr (SSE)
BE-->>U: streamed output
Note over SM,RN: Idle sweeper ticks every 45 s —<br/>reaps sessions past idle timeout
SM->>SP: /containers/{id} DELETE
SP->>RN: stop · remove
| Layer | Stack |
|---|---|
| Frontend | React + Vite + Tailwind + Monaco + Zustand. React Router, SSE streaming, optimistic DB writes with server reconciliation. |
| Backend | Node + Express + TypeScript. Auth + Postgres via Supabase. OpenAI Responses API with strict json_schema + intent classifier (debug · concept · howto · walkthrough · checkin). |
| Execution | Per-session Docker runner container — non-root, --network none, read-only rootfs, CPU / memory / PID capped. Dockerode goes through a socket-proxy sidecar with an endpoint allowlist, not the raw socket. |
| Content pipeline | File-based courses with Zod schemas, a concept graph (used-before-taught detection), per-language function-test harness with HMAC-signed result envelopes, and golden-solution verification in CI. |
| Infra | Azure VM + Static Web Apps + Key Vault (managed-identity secret delivery); Caddy + Let's Encrypt TLS. GHCR images, OIDC deploys, Log Analytics + scheduled-query + availability alerts + weekly VM backups. |
| Tests | Vitest (unit) + content validation + Playwright (end-to-end, real Docker stack). |
Full system design, security posture, and API surface: docs/ARCHITECTURE.md.
Tip
You don't need to install anything. Click the live link, sign in, and you're coding in seconds — a small daily allowance of tutor questions is included.
Head to codetutor.msrivas.com and sign in with an email magic-link or Google OAuth. The editor and run-code work instantly; drop in your own OpenAI API key for unlimited tutor use.
Full dev setup (Docker Desktop + Supabase project credentials + frontend/backend install) is documented in docs/DEVELOPMENT.md. Content authoring (lessons + practice exercises) is in docs/CONTENT_AUTHORING.md.
Copyright © 2026 Mehul Srivastava. All rights reserved. Source available for personal viewing and learning. See LICENSE.