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Open Source and Local Code Mode MCP in Deno Sandboxes

portofcontext.com

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Re: Open Source and Local Code Mode MCP in Deno Sandboxes

#4

Post by thecopy »

Fannon wrote: post #3

This is interesting. Also "Discover tools on-demand". Are there any stats or estimates how many tools an LLM / agent could handle with this approach vs. loading them all into context as MCP tools?

What i have read its in the range of 60-80.

(shameless plug: im building an cloud based gateway where the set of servers given to an mcp client can be controlled using "profiles": https://docs.gatana.ai/profiles/)

Re: Open Source and Local Code Mode MCP in Deno Sandboxes

#6

Post by pmkelly4444 »

buremba wrote: post #5

Oh that’s great! I have been experimenting a similar approach with WASM, I convert MCP tools into Typescript files and expose a single tool to run JS at runtime. https://github.com/buremba/1mcp

nice! will follow your progress! love that this runs locally as well

Re: Open Source and Local Code Mode MCP in Deno Sandboxes

#7

Post by orliesaurus »

i love seeing experiments that make this stuff run locally… bridging an MCP client into a Deno sandbox feels like a natural step if you want the same ergonomics offline.

ALSO there's a bunch of interesting questions around security and permission models when code is pulled on demand. Running arbitrary tools in a sandbox is neat, BUT you still need to think about what those tools can access… environment variables, network, local file system… limiting that scope could make these experiments more viable for larger teams.

i'd be curious to see benchmarks for cold starts and memory usage in this model… as well as patterns for caching compiled tools so they aren't reloaded every time. Discovering tools on demand is one thing, making them feel instantaneous is another. HOWEVER it's exciting to see folks pushing on this area and sharing their work.

Re: Open Source and Local Code Mode MCP in Deno Sandboxes

#8

Post by pmkelly4444 »

orliesaurus wrote: post #7

i love seeing experiments that make this stuff run locally… bridging an MCP client into a Deno sandbox feels like a natural step if you want the same ergonomics offline. ALSO there's a bunch of interesting questions around security and permission models when code is pulled on demand. Running arbitrary tools in a sandbox is neat, BUT you still need to think about what those tools can access… environment variables, net…

thank you!

on your second point, check out how we lock down the sandbox with a custom deno runtime! https://github.com/portofcontext/pctx/tree/main/crates/pctx_...

on third, will def get some benchmarks out... we setup OTEL so we have the data

Re: Open Source and Local Code Mode MCP in Deno Sandboxes

#9

Post by ethmarks »

This is very interesting. So it's an MCP server that connects to what is effectively a sandboxed MCP "hub". This is a clever middle ground between using dozens of context-munching MCP servers and just giving the agent access to your command line.

One question: why is Deno used? I thought that it was a JavaScript runtime. Can pctx only run sandboxed JavaScript code? If so, what do you do if you need the agent to run a Python script? If not, I don't understand how using a sandboxed JavaScript runtime allows you to sandbox other things.

Re: Open Source and Local Code Mode MCP in Deno Sandboxes

#10

Post by ttoinou »

ethmarks wrote: post #9

This is very interesting. So it's an MCP server that connects to what is effectively a sandboxed MCP "hub". This is a clever middle ground between using dozens of context-munching MCP servers and just giving the agent access to your command line. One question: why is Deno used? I thought that it was a JavaScript runtime. Can pctx only run sandboxed JavaScript code? If so, what do you do if you need the agent to run a…

Deno wraps around the V8 engine to brings lots of APIs, features and native TypeScript, here I'm guessing the sandbox feature is using the ability to control what the running code has access to https://docs.deno.com/runtime/fundamentals/security/
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