Add Pi coding-agent provider

[ahmadaccino]

Summary

• Adds Pi (@earendil-works/pi-coding-agent) as a selectable coding-agent provider, alongside Codex / Claude / Cursor / Grok / OpenCode.
• Integrates via Pi's native pi --mode rpc JSONL protocol over the shared Effect ChildProcessSpawner. The Pi package is a types-only devDependency — the user's installed pi binary is the runtime, so nothing heavy is bundled.
• Disabled by default and gated behind the normal provider settings — no behavior change for anyone who doesn't enable Pi.
• Mirrors the existing providers' structure end-to-end (driver / adapter / provider snapshot / text generation / web settings) so Pi stays consistent and low-surprise — it is not a special case.

What's included

Server (apps/server)

• PiRpcClient — typed JSONL transport over ChildProcessSpawner (stdin-writer + stdout-reader fibers, request/response correlation, scoped teardown) plus pure, unit-tested parse/extract helpers.
• PiAdapter — per-thread sessions, text_delta streaming, tool lifecycle, finalize on agent_end, mid-turn steer, image attachments, in-session model switch + thinking level, and fork-based rollback. Emits the same canonical runtime events as the other adapters (including thread.started for projection parity, and exitKind: "error" on unexpected exit).
• Tool-approval gate driven by runtimeMode (like Claude/Cursor): a bundled, default-deny Pi extension is injected via --extension and verified with a get_commands load handshake (fail-closed), bridging Pi's extension_ui requests to the canonical approval / user-input events.
• PiProvider — pi --version probe, live model discovery (get_available_models), and a models-based auth verdict (mirrors OpenCode).
• PiTextGeneration — stateless RPC + get_last_assistant_text, reusing the shared JSON extractor.

Contracts & web

• PiSettings + driver-kind wiring; pi.rpc.* runtime raw sources.
• Pi surfaced in provider settings, the model picker, and icons — identical wiring to the other drivers.

Docs

• Adds docs/providers/pi.md; lists Pi (and Grok) in the README.

Testing

• vp check
• vp run typecheck
• vp test (server, contracts, and web suites; new Pi unit + integration tests included)
• Live-validated against a real pi install: session lifecycle, mid-turn steer, model/thinking switch, fork rollback, and the tool-approval round-trip (default-deny gate blocking bash).
• Not run: vp run lint:mobile (no native mobile changes).

Notes

• Early Access; disabled by default. Written in idiomatic effect-smol style (named Effect.fn, scoped fibers, Schema.TaggedErrorClass, no escape hatches) and reviewed for consistency with the existing providers.
• Consolidates the earlier community attempts (Add Hermes and Pi agent provider support #2748, feat(pi): add Pi provider settings and runtime support #2800, [codex] Add Pi provider integration #2831, [codex] add Pi provider driver (AGENT MISTAKE) #2856, Bscholar/pi rpc #2812) into a single consistency-first implementation.

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Note

Medium Risk
Large new subprocess and tool-approval path, but it mirrors existing providers, defaults off, and fails closed when the approval gate cannot load.

Overview
Adds Pi as a first-class, disabled-by-default coding-agent provider wired like Codex/Claude/Cursor: driver, adapter, health/model snapshot, text generation, contracts, settings UI, and docs.

The server talks to the user’s pi --mode rpc process over a new JSONL RPC transport, mapping Pi events into the shared runtime model (streaming, tools, approvals, user prompts, model/thinking switches, fork-based rollback). Tool approval loads a bundled Pi extension at build time and refuses to start gated sessions unless the extension registers its sentinel command. Pi is removed from the “coming soon” add-provider list and promoted to the live picker (Early Access).

^{Reviewed by Cursor Bugbot for commit ab7cefa. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Add Pi coding-agent as a provider with RPC adapter, text generation, and tool approval gate

• Adds a full Pi provider integration: settings schema, driver registration, UI icons, and model discovery via a short-lived pi --mode rpc session.
• Introduces PiAdapter that manages per-thread RPC sessions, streams assistant/reasoning events, and bridges tool approval and user-input requests via Pi's extension-ui protocol.
• Introduces PiTextGeneration that prompts the Pi CLI in RPC mode and returns schema-validated, sanitized commit messages, PR content, branch names, and thread titles.
• Bundles a t3-approvals Pi extension that blocks tool calls by default and requires explicit user confirmation unless T3_PI_APPROVAL_MODE=auto-accept-edits.
• For the pi provider, resolveModelSlug returns an empty string instead of falling back to a default model, since available models are discovered live per account.
• Risk: the Pi CLI binary must be installed and accessible; missing binary reports a distinct "not installed" status rather than a generic error.

^{Macroscope summarized ab7cefa.}

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[macroscopeapp]

Approvability

Verdict: Needs human review

4 blocking correctness issues found. Diff is too large for automated approval analysis. A human reviewer should evaluate this PR.

^{You can customize Macroscope's approvability policy. Learn more.}

[macroscopeapp]

Effect service conventions: two issues in the new PiTextGeneration.ts. Both have a canonical precedent in the same directory (OpenCodeTextGeneration.ts).

^{Posted via Macroscope — Effect Service Conventions}

[harshav167]

Hi @ahmadaccino, are you still actively maintaining this PR and open to contributions? I would like to help finish and harden the full Pi integration. If so, would you prefer focused PRs or commits against your feat/pi-provider branch, or should I continue the work on a separate branch?