Project
Pi is an AI coding agent from Earendil Works that runs MCP tool calls in a sandbox, keeping their output out of the model's context.
Earendil's Pi 1.0, an agent harness whose website once advertised "No MCP", now builds MCP into its core. The team ties the reversal to Codemode, a JavaScript interpreter beside the harness loop that lets the model batch MCP calls into one script.
Reality
Kubernetes creators Craig McLuckie and Joe Beda's startup Stacklok is building Mecatl, a coding-agent harness designed to run in the cloud. It pulls tool calls, session state and memory out of the agent loop so each can be put into systems an operator can manage.
Reality
Pi shipped MCP in v0.99.0 using a sandbox that keeps tool schemas out of context, where three servers took 143,000 of Perplexity's 200,000 tokens. Other harnesses can copy the design if they are willing to host an interpreter that runs model-written code.
Reality
Bouras, Dai and Mechtaev found a static denylist let 46 of 75 prompt injections execute in a coding agent, against 3 under preflight-scoped capabilities. A same-day Google report of malware stealing OIDC tokens from GitHub Actions runners puts the outer limit on an agent in the CI job's permissions.
Reality
Earendil's Pi 1.0 coding agent ships native MCP support after more than a year of criticising the protocol, running tool calls inside a WASM sandbox. The team credits a more stateless July 2026 spec and a sandbox it already needed for non-LLM models, so MCP support was a small addition.
Reality
Pi Durable ports the Pi agent harness to TypeScript and checkpoints every step to one of three stores, so crashed agents resume where they stopped. Whether it can replace hand-built resume code depends on how it treats a tool call cut off mid-flight.
Reality
Pi made MCP a core feature in version 0.99.0 on September 29, 2026, after its creator Mario Zechner spent over a year arguing against the protocol. In Pi, models call MCP tools from JavaScript in a QuickJS sandbox, so tool schemas are not preloaded into context.
Reality
Portable Computer's harness is real engineering. The bill of materials starts at a $4,800 DGX Spark or a 24GB RTX card, which turns local agents into a hardware order.
Perspective Coverage
3 publishersReality
Jev answers propositions with calibrated probabilities, and the gate around it mirrors every threshold on 0.5, so a two-point tightening of the secret-egress cutoff deleted two thirds of the band that catches exfiltration.
Reality
Codex made the session Item a wire type and Pi gave every entry a nullable parentId, while Claude Code squeezes the transcript in five stages. The three designs diverge on what stays addressable after compaction.
Reality
A seven-part video walkthrough is packaging the Flask creator's Pi workflow for a general audience. The harness itself leaves isolation to the operator, and Earendil's own documentation says so plainly.
Reality
A frozen Claude Code session moved cleanly into seven rival agent formats. The approval and audit machinery wrapped around it moved into none of them.
Reality
A review of v0.84.2 is blunt: no built-in sandbox, no permission layer. Three of the four default tools change the machine, and whatever sits between them and your repo is code you own.
Reality
Oh-My-Pi makes a write conditional on the target lines still hashing the same, so the loser of a race gets an error instead of a wrecked file. The guarantee is paid for in retries.
Reality
A Cloudflare engineer argues web apps should let users generate their own missing features. The hard part is not the code generation, it is running that code beside live customer data.
Reality
A 2.5-year retrospective spanning more than 250 engineering teams credits a LiteLLM-based API proxy, stood up in January 2024, for metering adoption and forcing client upgrades.
Reality