Claude Code Web gives you a coding assistant instantly—no install, no terminal, just open a browser and start asking questions. That’s exactly what you want for quick tasks. But when you need to run agents for hours, orchestrate multiple tools together, and connect to real services, you need infrastructure underneath.
This isn’t about which is “better.” Claude Code is a harness layer for AI coding. Islo is the runtime layer underneath—the infrastructure that makes harnesses like Claude Code and Cursor more capable.
Quick Comparison
| Aspect | Claude Code Web | Islo + Claude Code |
|---|
| Instant setup | ✓ | ✓ |
| Your exact environment | ✗ | ✓ |
| Hours-long sessions | ✗ | ✓ |
| Real service access | ✗ | ✓ |
| Multi-harness orchestration | ✗ | ✓ |
| Defense layer | ✗ | ✓ |
| Service fakes | ✗ | ✓ |
What Claude Code Web Does Well
Claude Code Web is optimized for accessibility and quick interactions:
- Zero friction - Open a browser tab, start coding. No CLI install, no API keys, no configuration.
- Quick help - Great for writing functions, debugging snippets, or understanding unfamiliar code.
- Works anywhere - Any device with a browser. Useful for quick questions from a phone or tablet.
- Immediate value - No setup cost. Ask a question, get an answer.
If you need to write a quick script, understand how some library works, or get help with syntax, Claude Code Web is built for that.
The Runtime Layer: What’s Missing
Harnesses like Claude Code and Cursor orchestrate LLM calls, manage context, and coordinate tools. But they need infrastructure to run on. Harnesses cloud environments provide basic infrastructure—but they’re limited:
Single-harness limitation - You can run Claude Code in Claude Code Web. But you can’t run Claude Code and Cursor together. You can’t have Claude Code design an architecture while Cursor implements it. Browser environments are single-tenant for a single harness.
Environment mismatch - Your project has specific Node versions, Python packages, system dependencies, config files. Claude Code Web gives you a generic environment. Every session starts with Claude reads and set ups the environment.
Not continuous - You can’t start locally and continue from another place, like your phone.
No defense layer - What happens when an agent tries something dangerous? Browser environments either block everything (constant approval prompts) or allow everything (dangerous). There’s no intelligent policy layer.
The Token Tax of Missing Context
Here’s what happens when an agent doesn’t have your environment:
Checking version of node to install..
I see you're using TypeScript. Checking tsconfig..
Found you're using Postgres 15, setting up...
Every session starts with this dance. You’re spending tokens—and time—re-establishing context that your local environment already has.
With Islo, islo start captures this once. The harness starts with your Node version, your package manager, your tsconfig, your database schema. The first message can be “add caching to the user lookup” instead of “here’s everything about my project.”
Multi-Harness Orchestration
This is where a proper runtime layer unlocks entirely new workflows. Different harnesses have different strengths. With Islo as the runtime, you compose these capabilities:
islo shell -- claude "Design the authentication overhaul"
islo shell -- cursor-cli "Implement the auth changes based on the design"
And you can use all the different harnesses that your organization uses.
Defense Layer
The ideal is that harnesses run freely, but dangerous operations get caught.
Browser environments typically offer two modes:
- Constant approval prompts - Every file write, every shell command needs your approval. Safe, but you’re babysitting.
- Skip all prompts -
--dangerously-skip-permissions or equivalent. Fast, but one bad command and your credentials are gone.
Islo’s defense layer is different. It runs at the runtime level, underneath all harnesses:
- Allow normal operations - File reads, writes, builds, tests run without interruption
- Block dangerous operations - Recursive deletes outside project, credential access, production database connections
- Flag for approval - High-risk but legitimate operations surface on your phone. “Agent wants to push to main” - approve or deny in 10 seconds.
The harness runs for hours unattended. You’re not watching logs. When something genuinely needs human judgment, you get a notification.
A Real Example: Database Migration
Let’s say you need to add a new column to your users table, backfill data, and update the API.
With Claude Code Web:
- Agent reads your database schema (tokens)
- Agent writes migration code but can’t run it
- Either it hallucinates results or spins up a new database—which takes time and isn’t your database
- You need to step in and run the migrations locally
You’re the executor. The harness is just suggesting.
With Islo + Claude Code:
- Environment is already synced with your dev environment—which has the database
- Agent writes migration
- Agent runs it against the database
- Agent verifies the backfill worked
- Agent updates the API
- Agent runs your test suite
You’re delegating. The harness is executing.
Service Fakes for Scale
When you’re running multiple harnesses in parallel, you hit rate limits fast. GitHub’s 5,000 requests/hour disappears when ten agents are all hitting the API.
Islo includes doubleagent—stateful fake servers for GitHub, Slack, Stripe, and other APIs. Any harness running on Islo can:
- Create PRs without hitting real GitHub
- Post messages without hitting real Slack
- Process payments without hitting real Stripe
The fakes maintain state (create a PR, read it back, merge it) and work with official SDKs. When you’re ready to go real, swap the endpoint.
This is infrastructure for AI-native development—building at a scale where multiple harnesses work in parallel on the same codebase.
Use Claude Code Web when:
- You need quick coding help or explanations
- You’re away from your dev machine
- You’re writing isolated snippets or prototypes
- The task is self-contained (no external services needed)
Use Islo when:
- You need your actual development environment
- You want to orchestrate multiple harnesses (Claude Code + Cursor + others)
- Security boundaries matter (production access, sensitive data)
Claude Code Web gives you a coding assistant instantly—no install, no terminal, just open a browser and start asking questions. That’s exactly what you want for quick tasks. But when you need to run agents for hours, orchestrate multiple tools together, and connect to real services, you need infrastructure underneath.
This isn’t about which is “better.” Claude Code is a harness layer for AI coding. Islo is the runtime layer underneath—the infrastructure that makes harnesses like Claude Code and Cursor more capable.
Quick Comparison
What Claude Code Web Does Well
Claude Code Web is optimized for accessibility and quick interactions:
If you need to write a quick script, understand how some library works, or get help with syntax, Claude Code Web is built for that.
The Runtime Layer: What’s Missing
Harnesses like Claude Code and Cursor orchestrate LLM calls, manage context, and coordinate tools. But they need infrastructure to run on. Harnesses cloud environments provide basic infrastructure—but they’re limited:
Single-harness limitation - You can run Claude Code in Claude Code Web. But you can’t run Claude Code and Cursor together. You can’t have Claude Code design an architecture while Cursor implements it. Browser environments are single-tenant for a single harness.
Environment mismatch - Your project has specific Node versions, Python packages, system dependencies, config files. Claude Code Web gives you a generic environment. Every session starts with Claude reads and set ups the environment.
Not continuous - You can’t start locally and continue from another place, like your phone.
No defense layer - What happens when an agent tries something dangerous? Browser environments either block everything (constant approval prompts) or allow everything (dangerous). There’s no intelligent policy layer.
The Token Tax of Missing Context
Here’s what happens when an agent doesn’t have your environment:
Every session starts with this dance. You’re spending tokens—and time—re-establishing context that your local environment already has.
With Islo,
islo startcaptures this once. The harness starts with your Node version, your package manager, your tsconfig, your database schema. The first message can be “add caching to the user lookup” instead of “here’s everything about my project.”Multi-Harness Orchestration
This is where a proper runtime layer unlocks entirely new workflows. Different harnesses have different strengths. With Islo as the runtime, you compose these capabilities:
And you can use all the different harnesses that your organization uses.
Defense Layer
The ideal is that harnesses run freely, but dangerous operations get caught.
Browser environments typically offer two modes:
--dangerously-skip-permissionsor equivalent. Fast, but one bad command and your credentials are gone.Islo’s defense layer is different. It runs at the runtime level, underneath all harnesses:
The harness runs for hours unattended. You’re not watching logs. When something genuinely needs human judgment, you get a notification.
A Real Example: Database Migration
Let’s say you need to add a new column to your users table, backfill data, and update the API.
With Claude Code Web:
You’re the executor. The harness is just suggesting.
With Islo + Claude Code:
You’re delegating. The harness is executing.
Service Fakes for Scale
When you’re running multiple harnesses in parallel, you hit rate limits fast. GitHub’s 5,000 requests/hour disappears when ten agents are all hitting the API.
Islo includes doubleagent—stateful fake servers for GitHub, Slack, Stripe, and other APIs. Any harness running on Islo can:
The fakes maintain state (create a PR, read it back, merge it) and work with official SDKs. When you’re ready to go real, swap the endpoint.
This is infrastructure for AI-native development—building at a scale where multiple harnesses work in parallel on the same codebase.
Pick the Right Tool
Use Claude Code Web when:
Use Islo when:
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