Pi Web vs Zero: Features, Pricing & Which Is Better (2026)

A side-by-side comparison of Pi Web and Zero — features, pricing, and ideal use cases — to help you decide which AI tool fits your workflow.

Pi Web

agegr

Free

Local web UI for the Pi coding agent — browse sessions, switch worktrees, manage models, and chat beside your project files in a browser.

Session Browser: Reads local Pi session files and organizes prior conversations by project for quick resume.
Fork and Continue: Continue from any earlier message or fork a session into a separate route to try alternatives safely.
Git Worktree Switcher: Switch between Git worktrees from the sidebar to work on multiple branches in parallel.
File Preview: Side-by-side chat and project file browser that previews source, docs, images, audio, and PDFs.
Model and Skill Manager: Configure models, API keys, run model tests, and toggle skills from the web UI instead of CLI flags.
Local-Only Runtime: Runs on http://127.0.0.1 by default so session data and code never leave the developer's machine.

Resume Prior Work: Reopen a conversation from last week by project instead of scrolling terminal history.
Safe Experimentation: Fork a session to try a risky refactor without losing the original conversation state.
Parallel Branch Work: Switch Git worktrees mid-session to jump between feature branches in one workspace.
Model Comparison: Rerun the same task against different configured models to compare output quality.
In-Browser Code Review: Preview generated diffs and project files beside the chat without leaving the browser.

Vercel Labs

Free

An experimental graph-first programming language where agents edit a compiler-checked program graph instead of raw source text.

Graph as the Program: A compiler-owned semantic graph of symbols, calls, types, effects and node IDs is the source of truth, so agents reason over program structure rather than parsing and regenerating text.
Hash-Guarded Patches: Every edit carries an expected graph hash and expected field values, so a stale or conflicting patch is rejected before it reaches the store instead of silently corrupting the program.
Compiler in the Loop: Shape, type, stale-state and repository metadata checks run as part of applying a patch, collapsing the write-build-test-inspect cycle into a single checked operation.
Readable Text Projections: The graph renders to reviewable .0 source projections so humans can read diffs, audit what an agent changed and make rare manual edits.
Structured JSON Diagnostics: The compiler emits machine-readable diagnostics rather than prose error text, so agents can act on failures without parsing terminal output.
Explicit Effects via World: Side effects are passed through an explicit World capability parameter, making what a function can touch visible in its signature.
Runtime Constraints by Design: Targets token efficiency, low memory, fast startup, fast builds, low latency and zero dependencies rather than relaxing systems goals for agent ergonomics.
Query and Patch CLI: zero init, zero query, zero patch and zero run give agents a direct command surface over the graph, with agent skills carrying the graph discipline instead of rigid human prompts.

Reliable Agent Code Edits: Let a coding agent make semantic changes that are rejected outright if its view of the program is stale, instead of producing plausible-looking but broken text diffs.
Reducing Agent Token Spend: Query the specific symbols, types and nodes relevant to a task rather than feeding whole files into context on every turn.
Outcome-Driven Development: Describe a desired result in conversation — add auth, fix a failing route, build a CRM API — and review the resulting projection rather than writing the code.
Auditable AI-Written Code: Review what changed through readable .0 projections and graph hashes, keeping a human checkpoint over agent-authored programs.
Language and Tooling Research: Explore what a compiler and program representation look like when machine editors, not human typists, are the primary writers.
Sandboxed Experimentation: Prototype agent-driven codebases in an isolated environment where breaking changes and pre-1.0 churn are acceptable.