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Orbis AI Media OS β€” Complete Documentation

Version: 1.0 Β· Last updated: 2026-05-12
Stack: FastAPI Β· PostgreSQL Β· LangGraph Β· Pillow Β· APScheduler Β· React Β· Cloudinary Β· Railway + Netlify


Table of Contents

  1. What This System Does
  2. Architecture Overview
  3. Tech Stack
  4. Database Schema
  5. Content Generation Pipeline
  6. Post Types
  7. text_image β€” PIL Card System
  8. Scheduler β€” Automated Publishing
  9. LLM Agent & Model Fallbacks
  10. API Reference
  11. WebSocket Real-Time Updates
  12. Frontend Pages
  13. Environment Variables
  14. Deployment Guide
  15. Local Development
  16. Key Design Decisions
  17. Known Limitations & TODOs

1. What This System Does

Orbis AI Media OS is a fully automated social media content engine. It:

  1. Discovers trending topics (Reddit, manual seeds)
  2. Generates platform-native posts using an LLM agent (OpenRouter / Groq)
  3. Creates or sources images (Pollinations AI)
  4. Burns text directly onto images for text_image posts using Pillow (quote-card style)
  5. Uploads final media to Cloudinary CDN
  6. Saves drafts for human review in a web dashboard
  7. Publishes approved posts to Instagram (LinkedIn, Twitter wired but not yet active)

Everything runs autonomously on a schedule. A human moderator approves posts via the dashboard before they go live (unless AUTO_APPROVE=true).


2. Architecture Overview

β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
β”‚                        SCHEDULER (APScheduler)                  β”‚
β”‚   Every 6h: Fetch Trends   β”‚   Daily: Generate Posts (N/day)   β”‚
β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜
                β”‚                         β”‚
                β–Ό                         β–Ό
         β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”            β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
         β”‚  Trends  β”‚            β”‚  LLM Agent      β”‚
         β”‚  Table   │──────────▢ β”‚  (LangGraph)    β”‚
         β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜            β”‚  OpenRouter     β”‚
                                 β””β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”˜
                                          β”‚ caption + image_prompt
                                          β–Ό
                                 β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
                                 β”‚ Image Generation β”‚
                                 β”‚ Pollinations AI  β”‚
                                 β””β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”˜
                                          β”‚ raw image URL
                                          β–Ό
                              β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
                              β”‚  PIL Card Generator  β”‚ (text_image only)
                              β”‚  typography card     β”‚
                              β”‚  editorial photo cardβ”‚
                              β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜
                                         β”‚ composited image
                                         β–Ό
                                β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
                                β”‚   Cloudinary    β”‚
                                β”‚   CDN Upload    β”‚
                                β””β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”˜
                                         β”‚ permanent URL
                                         β–Ό
                               β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
                               β”‚  Post Draft (DB) β”‚
                               β”‚  status=draft    β”‚
                               β”‚  approval=pendingβ”‚
                               β””β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜
                                        β”‚
               β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”Όβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
               β”‚                        β”‚                        β”‚
               β–Ό                        β–Ό                        β–Ό
    β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”     β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”   β”Œβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”
    β”‚  React Dashboardβ”‚     β”‚  PostgreSQL NOTIFY  β”‚   β”‚  Instagram API   β”‚
    β”‚  (Netlify/Vite) │◀────│  WebSocket push     β”‚   β”‚  on approval     β”‚
    β”‚  Human review   β”‚     β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜   β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜
    β””β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”˜

Request Flow (Generate via Dashboard)

User clicks "Generate" β†’ GenerateModal (pick type + platform)
  β†’ POST /api/workflows/trigger  {post_type, platform}
  β†’ pipeline.generate_post_content()   [LLM]
  β†’ pipeline.generate_images()         [Pollinations]
  β†’ pipeline.store_media_to_cdn()      [Cloudinary]
  β†’ pipeline.save_post_draft()         [Pillow overlay if text_image]
  β†’ DB INSERT post (status=draft)
  β†’ PG NOTIFY posts_changed
  β†’ WebSocket push to browser
  β†’ React Query cache updates
  β†’ Post appears in dashboard grid

3. Tech Stack

Backend

Layer Technology
API server FastAPI (Python 3.11+)
Database PostgreSQL (Neon on Railway)
ORM SQLAlchemy 2.x async
Scheduler APScheduler (AsyncIOScheduler)
LLM framework LangGraph + LangChain
LLM providers OpenRouter (primary), Groq (fallback)
Image generation Pollinations AI (free, no key needed)
Image processing Pillow (PIL)
CDN Cloudinary
Social publishing Instagram Graph API
HTTP client httpx (async)
Logging Loguru
Config Pydantic BaseSettings

Frontend

Layer Technology
Framework React 18 + Vite
State / data TanStack Query (React Query)
Routing React Router v6
Charts Recharts
Real-time Native WebSocket
Styling Custom CSS variables (dark-first)
Deployment Netlify

Infrastructure

Service Provider
Backend hosting Railway
Database Neon PostgreSQL (via Railway)
Frontend hosting Netlify
Media CDN Cloudinary
Font delivery GitHub rsms/inter (downloaded at runtime)

4. Database Schema

agents

Column Type Notes
id PK
name VARCHAR e.g. "Default Agent"
description TEXT
is_active BOOL default true

agent_versions

Column Type Notes
id PK
agent_id FK β†’ agents
version INT
config JSON {model, temperature, ...}

trends

Column Type Notes
id PK
topic VARCHAR e.g. "AI in healthcare 2025"
source VARCHAR reddit, manual, rss
score FLOAT relevance score
status VARCHAR pending / used / skipped
raw_data JSON source-specific metadata
created_at TIMESTAMP

posts

Column Type Notes
id PK
trend_id FK β†’ trends
agent_version_id FK β†’ agent_versions
content TEXT final caption
post_type VARCHAR image / text_only / carousel / text_image / link
status VARCHAR draft / scheduled / published
approval_status VARCHAR pending / approved / rejected
platform VARCHAR instagram / twitter / linkedin
image_url VARCHAR Cloudinary URL
carousel_urls JSON list of URLs (carousel only)
video_url VARCHAR
link_url VARCHAR link posts
link_title VARCHAR
link_description VARCHAR
platform_post_id VARCHAR IG media ID after publish
published_at TIMESTAMP
token_count INT LLM tokens used
generation_cost FLOAT USD
hallucination_score FLOAT 0–1
created_at TIMESTAMP auto

media

Column Type Notes
id PK
post_id FK β†’ posts
url VARCHAR CDN URL
media_type VARCHAR image / video
nsfw_score FLOAT AWS Rekognition
is_approved BOOL

Supporting tables

  • workflow_executions β€” Temporal workflow IDs and statuses
  • observability_traces β€” Langfuse trace IDs, token counts, costs
  • api_usage β€” Per-service usage tracking for cost monitoring
  • system_alerts β€” Severity-tagged alerts with resolved status
  • users β€” Firebase-authenticated dashboard users
  • platform_configs β€” Per-platform OAuth tokens / credentials
  • model_configs β€” Primary + fallback model configuration per agent
  • notifications β€” In-app notifications (approval needed, publish failed)

5. Content Generation Pipeline

A single end-to-end run (triggered by scheduler or manually):

Step 1 β€” Pick a Trend

# scheduler.py
trend = session.execute(
    select(Trend)
    .where(Trend.status == "pending")
    .order_by(Trend.score.desc())
    .limit(1)
)

Step 2 β€” Generate Post Content (LLM)

pipeline.generate_post_content(GeneratePostInput)
  β†’ post_generator.generate_post_with_agent(trend_dict, agent_version_id)
    β†’ _pick_post_type()           weighted random: text_image 70%, image 10%, text_only 10%, carousel 5%, link 5%
    β†’ _build_system_prompt(post_type, trend)
    β†’ LLM.invoke([SystemMessage])
    β†’ _parse_image_post() / _parse_link_post()
  β†’ returns PostData(content, post_type, image_prompt, ...)

Step 3 β€” Generate Image

pipeline.generate_images(GenerateImagesInput)
  β†’ builds Pollinations AI URL with encoded prompt
  β†’ GET https://image.pollinations.ai/prompt/{encoded}?width=1080&height=1080&model=flux
  β†’ retries up to 3Γ— with increasing timeout (60s, 90s, 120s)
  β†’ returns {"image_1": url}

Step 4 β€” Upload to CDN

pipeline.store_media_to_cdn(StoreMediaInput)
  β†’ cloudinary.uploader.upload(url, folder="ai_media_os/post_{id}")
  β†’ returns {"image_1": cloudinary_secure_url}

Step 5 β€” Save Draft

pipeline.save_post_draft(SavePostDraftInput)
  β†’ if post_type == "text_image":
      apply_text_overlay(raw_url, caption)  ← PIL card generation
  β†’ INSERT INTO posts (status="draft", approval_status="pending")
  β†’ PG NOTIFY posts_changed

6. Post Types

Type Description Has Image
image Photo + caption Yes (Pollinations)
text_only Pure text, no image No
text_image Text burned onto image (PIL quote card) Yes (composited)
carousel Multi-slide swipeable post Yes (multiple)
link Link preview card + caption No

Weighted Distribution (default)

POST_TYPE_WEIGHTS = {
    "text_image":  70,   # dominant β€” best engagement
    "image":       10,
    "text_only":   10,
    "carousel":     5,
    "link":         5,
}

7. text_image β€” PIL Card System

File: src/utils/image_overlay.py

The text overlay system generates social cards that look hand-crafted, not AI-generated. It automatically chooses one of two layouts based on caption length.

Layout Selection

hook_word_count = len(hook.split())
if hook_word_count <= 9:
    canvas = _make_typo_card(hook, body, tags)      # Layout A
else:
    canvas = await _make_photo_card(hook, body, tags, image_url)  # Layout B

Layout A β€” Typography Card (short hooks ≀ 9 words)

  • Size: 1080Γ—1080 (square, ideal for quotes)
  • Background: Vertical gradient (no photo)
  • 6 colour palettes: warm parchment, deep purple night, dark forest, dark amber, cool lavender, cream rust
  • Text: Auto-sized hook fills ~60% of width; body text at 1/3 hook size
  • Accents: Horizontal bar above hook, bottom line, brand @orbis bottom-right
  • Best for: "Stop scrolling hooks", quotes, bold statements

Layout B β€” Editorial Photo Card (longer hooks > 9 words)

  • Size: 1080Γ—1350 (portrait, 4:5 ratio)
  • Background: Full-bleed Pollinations photo, fill-cropped
  • Scrims: Top 22% dark scrim (title area) + bottom 50% dark scrim (text area)
  • Headline: hook.upper(), auto-sized to fill bottom zone, white text with dark shadow + accent bar left
  • Body: 2 sub-lines below headline at 40px
  • Top bar: ORBIS STUDIO brand + accent line
  • Best for: News stories, editorial content, longer captions

Font Loading Chain

1. System fonts (Linux paths + Windows C:/Windows/Fonts/)
2. /tmp/orbis_fonts/Inter-Bold.ttf  ← downloaded from GitHub rsms/inter on first run
3. PIL default bitmap (tiny fallback β€” only if download fails)

Font loading is cached in _FONT_CACHE dict to avoid repeated disk reads.

Caption Parsing

Before rendering, the caption is cleaned of LLM structural labels:

clean = re.sub(
    r"(?im)^(HOOK|SLIDE\s*\d+[:\.\-]?[^|\n]*\|?|CAPTION|IMAGE_PROMPT)[:\s]*",
    "", caption
)

Then split into: hook (line 1), body (lines 2–3), tags (hashtag line).


8. Scheduler β€” Automated Publishing

File: src/services/scheduler.py

Jobs

Job Schedule What it does
run_trend_fetch Every 6h (0, 6, 12, 18 UTC) Fetches fresh trends from all sources
run_post_generation N times/day (from POSTS_PER_DAY) Full pipeline run for one trend
run_auto_publish Triggered by generation if AUTO_APPROVE=true Publishes draft immediately

Post Scheduling Times

# POSTS_PER_DAY=4  β†’ 8am, 12pm, 4pm, 8pm UTC
hour = 8 + (i * (16 / posts_per_day))

Auto-Approve vs Manual Review

AUTO_APPROVE Behaviour
false (default) Posts saved as draft, wait in dashboard for human approval
true Posts auto-published immediately after generation

Dev / Prod Safety

In non-production environments (ENVIRONMENT != "production"), all published posts get a [TEST] prefix so they're identifiable on real Instagram accounts:

if settings.environment != "production":
    text = f"[TEST] {text}"

9. LLM Agent & Model Fallbacks

File: src/agents/post_generator.py

Primary Model

Set via OPENAI_MODEL env var. Defaults to whatever is configured (typically a Groq or OpenRouter model).

API endpoint set via OPENAI_API_BASE (supports any OpenAI-compatible API).

Automatic Fallback Chain

If the primary model returns a 429 (rate limit) or 404/400 error, the agent automatically tries these free OpenRouter models in order:

FREE_MODEL_FALLBACKS = [
    "nousresearch/hermes-3-llama-3.1-405b:free",
    "arcee-ai/trinity-large-thinking:free",
    "meta-llama/llama-3.3-70b-instruct:free",
    "google/gemma-4-31b-it:free",
    # ... more
]

LangGraph Pipeline

StateGraph:
  process_trend_node  β†’ LLM invoke, parse output
  determine_images_node β†’ set images_needed count
  finalize_node β†’ set status="ready_for_moderation"

Prompt Engineering

Each post type has a dedicated system prompt. Key rules enforced:

  • text_image: "THIS IS A SINGLE-IMAGE POST. Do NOT write SLIDE 1/2/3 content."
  • All image types: "No human faces. No text in image."
  • LLM output parser strips echoed structural labels (HOOK:, SLIDE N:, CAPTION:, IMAGE_PROMPT:)

10. API Reference

Base URL: https://<your-railway-domain>/api

Posts

Method Path Description
GET /posts List posts (filter: status, platform, post_type, pagination)
GET /posts/{id} Get single post
POST /posts/{id}/approve Approve β†’ triggers Instagram publish
POST /posts/{id}/reject Reject draft
POST /posts/{id}/discard Hard-delete a draft post

GET /posts params

Param Default Notes
status (all) draft / scheduled / published
platform (all) instagram / twitter / linkedin
post_type (all) image / text_image / etc.
limit 20
offset 0

GET /posts response

{
  "posts": [...],
  "total": 5,
  "all_total": 12
}

total = filtered count, all_total = unfiltered across all statuses (used for header badge).

Workflows

Method Path Description
POST /workflows/trigger Manually trigger post generation

POST /workflows/trigger body

{
  "trend_id": 3,
  "agent_version_id": 1,
  "platform": "instagram",
  "post_type": "text_image"
}

If trend_id is omitted, the scheduler picks the highest-scoring pending trend.

Trends

Method Path Description
GET /trends List trends
POST /trends Create manual trend

Agents

Method Path Description
GET /agents List agents
GET /agents/{id}/versions Get agent versions

Moderator

Method Path Description
GET /moderator/dashboard Posts pending approval + stats

Health

GET /health
β†’ { "status": "healthy", "database": "ok", "scheduler": "running" }

11. WebSocket Real-Time Updates

File: src/api/routes/ws.py + src/services/notification_listener.py

How it works

  1. PostgreSQL triggers fire NOTIFY posts_changed on INSERT/UPDATE to posts
  2. Python asyncpg listener receives the notification
  3. Sets an asyncio.Event dirty flag
  4. WebSocket hub checks dirty flag and broadcasts {"type": "posts_changed"} to all connected browsers
  5. React Query receives the message and calls queryClient.invalidateQueries(["posts"])
  6. Dashboard re-fetches and updates without a page reload

WebSocket endpoint

ws://<host>/api/ws/updates

React connection (frontend)

const ws = new WebSocket(`${WS_BASE}/api/ws/updates`);
ws.onmessage = (e) => {
  const msg = JSON.parse(e.data);
  if (msg.type === "posts_changed") {
    queryClient.invalidateQueries(["posts"]);
  }
};

12. Frontend Pages

All pages use TanStack Query for data fetching and live updates.

Dashboard (/)

  • Scheduler strip: running status, posts/day, today's generated + published count, next run time
  • Pipeline visualization: shows 5 pipeline steps (Trend β†’ LLM β†’ Image β†’ CDN β†’ Draft)
  • KV stats: total posts, published today, pending approval, trends available
  • Area chart: post volume over last 7 days

Posts (/posts)

  • Grid of PostCards: thumbnail, type badge, status badge, time ago
  • Filter bar: by status and post type
  • Header badge: total post count (unfiltered)
  • Generate button: opens GenerateModal
  • PostCard actions: Preview (eye), Approve (check), Reject (Γ—), Discard (trash) β€” contextual by status
  • GenerateModal: 6 post type options (grid), 4 platform pills, Generate button

Preview Modal

  • Full-size image
  • Caption text
  • Post type and status chips
  • Approve / Reject / Discard buttons with loading state
  • Prevents double-click via isPending flags + backend idempotency guard

Trends (/trends)

  • List of detected trends with source, score, status
  • Manual trend creation form

Analytics (/analytics)

  • Charts for post volume, engagement by type, cost tracking

Workflows (/workflows)

  • Workflow execution history
  • Manual trigger panel

Settings (/settings)

  • Environment config display
  • Platform connection status

13. Environment Variables

Copy .env.example to .env and fill in:

Required

DATABASE_URL=postgresql+asyncpg://user:pass@host/db
OPENAI_API_KEY=sk-...           # OpenRouter key (despite name)
OPENAI_API_BASE=https://openrouter.ai/api/v1
OPENAI_MODEL=meta-llama/llama-3.3-70b-instruct:free

CLOUDINARY_CLOUD_NAME=your_cloud
CLOUDINARY_API_KEY=123456
CLOUDINARY_API_SECRET=abc...

INSTAGRAM_ACCESS_TOKEN=EAA...
INSTAGRAM_BUSINESS_ACCOUNT_ID=17841...

Optional (with defaults)

ENVIRONMENT=development          # production β†’ removes [TEST] prefix
AUTO_APPROVE=false               # true β†’ publish immediately after generation
POSTS_PER_DAY=4                  # how many posts to generate per day
POST_PLATFORM=instagram

ALLOWED_ORIGINS=https://your-netlify-app.netlify.app

LOG_LEVEL=INFO

Unused / future

TEMPORAL_HOST=localhost:7233     # Temporal removed in favour of direct pipeline
REDIS_URL=localhost:6379
ANTHROPIC_API_KEY=
LANGFUSE_PUBLIC_KEY=
R2_ACCOUNT_ID=                   # Cloudflare R2 (replaced by Cloudinary)
AWS_ACCESS_KEY_ID=               # Rekognition (NSFW β€” not active)

14. Deployment Guide

Backend (Railway)

  1. Connect GitHub repo to Railway
  2. Set all environment variables in Railway dashboard
  3. Railway auto-detects Procfile:
    web: python -m uvicorn src.api.main:app --host 0.0.0.0 --port $PORT --access-log --use-colors 2>&1
    
  4. On first deploy, startup migrations run automatically:
    • src/utils/migrate.py executes ALTER TABLE ADD COLUMN IF NOT EXISTS for all columns
    • Safe to run on every deploy β€” no-ops if columns already exist

Startup sequence

init_db()           β†’ create tables if not exist (SQLAlchemy)
run_migrations()    β†’ add any missing columns (idempotent)
install_triggers()  β†’ PG NOTIFY triggers on posts table
start_listener()    β†’ asyncpg LISTEN for notifications
scheduler.start()   β†’ APScheduler jobs begin

Frontend (Netlify)

  1. Connect GitHub repo, set build command: cd frontend && npm run build
  2. Set publish directory: frontend/dist
  3. Set env var: VITE_API_BASE_URL=https://your-railway-domain.up.railway.app
  4. Deploy

Font availability on Railway

On startup (first text_image post), the system downloads Inter fonts from GitHub to /tmp/orbis_fonts/:

  • Inter-Regular.otf β†’ /tmp/orbis_fonts/Inter-Regular.ttf
  • Inter-Bold.otf β†’ /tmp/orbis_fonts/Inter-Bold.ttf

This is automatic. No manual setup needed. Fonts are cached in memory (_FONT_CACHE) for the process lifetime.


15. Local Development

Requirements

  • Python 3.11+
  • Node.js 18+
  • PostgreSQL (local or Neon free tier)

Backend

# Create virtual environment
python -m venv venv
source venv/bin/activate   # Windows: venv\Scripts\activate

# Install dependencies
pip install -r requirements.txt

# Create .env
cp .env.example .env
# Fill in DATABASE_URL, OPENAI_API_KEY, etc.

# Run
uvicorn src.api.main:app --reload --port 8000

Frontend

cd frontend
npm install

# Create .env.local
echo "VITE_API_BASE_URL=http://localhost:8000" > .env.local

npm run dev
# β†’ http://localhost:5173

Generate a test post manually

curl -X POST http://localhost:8000/api/workflows/trigger \
  -H "Content-Type: application/json" \
  -d '{"agent_version_id": 1, "platform": "instagram", "post_type": "text_image"}'

VSCode Python setup

If Pyrefly shows PIL import errors, select the venv interpreter:

  • Ctrl+Shift+P β†’ "Python: Select Interpreter" β†’ choose .venv/Scripts/python.exe

16. Key Design Decisions

Why not Temporal?

The original design used Temporal for durable workflow orchestration. It was removed because:

  • Railway free tier can't run a separate Temporal server
  • The pipeline is short enough (~30s) that durability isn't critical
  • APScheduler + direct async functions are simpler and free

Temporal stubs remain in the codebase (src/temporal_workflows/) but the functions inside are standalone async functions called directly.

Why Cloudinary over R2?

Cloudinary was chosen because:

  • Free tier (25GB storage, 25GB bandwidth)
  • Python SDK with single-call upload from URL or BytesIO
  • PIL output is uploaded directly as BytesIO without temp files

R2 env vars are in config but the upload path uses Cloudinary.

Why Pollinations AI for images?

  • Completely free, no API key
  • Supports flux model with 1080px output
  • URL-based (no SDK) β€” just build a URL, fetch, get image
  • Sufficient quality for social cards

Why PIL for text overlay instead of Cloudinary transformations?

Cloudinary text overlays are possible but:

  • Limited typography control
  • Can't do gradient backgrounds or custom layout logic
  • PIL gives full pixel control for the typography card layout
  • Output is uploaded to Cloudinary after compositing

Why ALTER TABLE ADD COLUMN IF NOT EXISTS on every startup?

Railway reuses the same PostgreSQL database across deploys. New columns added in code would cause column does not exist errors if migrations weren't run. Running idempotent IF NOT EXISTS migrations on every startup ensures the schema is always in sync without a separate migration tool.

Why datetime.utcnow() + "Z" for timestamps?

Python's datetime.utcnow() returns a naive datetime with no timezone indicator. JavaScript's new Date("2025-01-01T10:00:00") without a Z or +offset is treated as local time by browsers. In IST (UTC+5:30) this made posts appear 5.5h older than they were. Appending Z before parsing forces UTC interpretation.

Why [TEST] prefix for non-prod publishing?

When ENVIRONMENT != "production", any post that gets approved and published will have [TEST] prepended to its caption. This lets you test the full approval β†’ publish flow against a real Instagram account without the post looking like real content to followers.


17. Known Limitations & TODOs

Item Status
Twitter/LinkedIn publishing Wired in model, not yet active
AWS Rekognition NSFW moderation Code exists, not enabled by default
Carousel image generation Only generates 1 image; needs multi-image support
Video post type Schema ready, generation not implemented
Firebase auth on frontend Schema has users table; login UI not built
Langfuse observability Config wired; traces not actively sent
Rate limiting on API Not implemented
link post type LLM generates content; link_url not auto-fetched
Trend sources Reddit and manual only; RSS/Twitter not active
Font persistence /tmp is ephemeral on Railway; fonts re-download on each dyno restart (cached for process lifetime)

Documentation generated 2026-05-12. For questions, open an issue on the GitHub repo or contact the maintainer.