@fractaal/pi-claude-bridge

Run Claude Code as a Pi provider using your Claude subscription. Adds claude-bridge/* models to /model while keeping Pi's tools and TUI.

Maintained from @vanillagreen/pi-claude-bridge, itself forked from elidickinson/pi-claude-bridge. The fractaal fork tracks current Pi APIs and can use Pi's complete system prompt without embedding host-specific policy.

Highlights

• claude-bridge/claude-fable-5, Opus 5, Sonnet 5, Opus 4.8, Opus 4.7, Sonnet 4.6, and Haiku in /model.
• Pi tool calls run on Pi; Claude Code handles reasoning.
• Tool-use turns block until Pi-delivered tool results reach Claude Code, including persistent subagent panes.
• Session continuity across normal turns, /compact, tree navigation, and abort recovery.
• Steering: a message sent while a tool runs reaches Claude in the same turn, right after the tool result.
• Requests with a session id other than the Pi session's own (an extension's side conversation, such as /btw) run in their own Claude Code session, alongside the main turn without touching it.
• When a session outgrows the context window Claude Code allows for your account, Pi compacts and continues the turn automatically.
• Thinking-level forwarding with summarized Opus thinking display.
• Optional Claude effort overrides (xhigh → max for Opus 4.8).
• MCP isolation and Claude cloud-MCP suppression to keep tokens lean.
• Tools Pi declares to its model always load. Tools Pi keeps behind its own search (MCP servers set to deferred or codemode in mcp.json) wait behind Claude Code's tool search until Claude needs them; hidden tools and Pi's tool_search and codemode tools are not offered, because Claude Code's tool search replaces them. A deferred tool Claude loads and calls becomes active in Pi, so Pi's transcript declares it from then on. Claude Code turns tool search on by itself only for a first-party Anthropic endpoint, so a host routing Claude through a proxy enables it with ENABLE_TOOL_SEARCH=true in env when the proxy forwards Anthropic requests unchanged.
• Opt-in forwarding of APPEND_SYSTEM.md and recognized Pi prompt hooks.

Requirements

Bridge 2.x requires the Pi 1.x provider API as shipped by the fractaal fork 0.86 or newer. It relies on 0.86 resolving a call to a tool activated mid-turn, or registered with deferred/codemode exposure, in the same turn; upstream Pi 1.0.4 lacks that, so a deferred tool Claude loads would fail its first call there. Use bridge 1.12.x with Pi 0.85 and older.

Install

Via npm:

pi install npm:@fractaal/pi-claude-bridge

Restart Pi after installation.

Model discovery

On Pi model-catalog refresh, the bridge asks its selected Claude Code executable (including the SDK-bundled CLI on managed hosts) for its supported models through a short-lived initialization: no prompt, tools, MCP servers, hooks, or persisted conversation. It resolves aliases to canonical IDs and uses pi.dev's Anthropic catalog for context/output limits and pricing. Prices are list-price estimates, not a statement of subscription charges. Neither credentials nor provider request headers are sent to pi.dev.

Discovered models are additive and stored in Pi's existing ModelsStore; the bundled list is an offline baseline, not an inclusion limit. Cache-only startup performs no discovery, ordinary refreshes reuse a four-hour cache, and Pi's forced refresh bypasses that interval. Failed discovery keeps the last-known catalog. If a newly advertised model has no usable limit metadata yet, the bridge reports it through the UI and claude-bridge:model-discovery-warning rather than inventing capabilities; later refreshes can add it once metadata is available.

Embedding hosts use Pi's refresh lifecycle and publish the resulting registry changes. Discovery uses the same executable and per-runtime environment as inference, without reinitializing an active inference Query. A new model requiring a newer Claude Code protocol can still require updating Claude Code.

Prompt context

systemPromptMode has two modes:

• claude-code (default): use Claude Code's preset prompt and optionally append selected Pi context.
• pi: pass Pi's complete system prompt through unchanged and disable Claude filesystem setting sources, avoiding duplicate instructions and MCP discovery.

The bridge only provides this mechanism. Pi installations and embedding hosts choose the mode through normal package settings.

Embedding hosts that run multiple sibling Pi runtimes in one process should use @fractaal/pi-claude-bridge/isolated. Every factory invocation owns independent session, tool, UI, and query state. The default package entry preserves personal Pi's nested-agent behavior, where reloaded extension instances share one model registry.

The factory also accepts env, an optional map of Claude child-process environment overrides. Hosts can supply a runtime-specific gateway endpoint, credential or CLAUDE_CONFIG_DIR without changing process.env or another runtime. Setting an entry to undefined suppresses its inherited value. Overrides are copied when the extension is registered; executable discovery, native session-copy paths and Claude subprocesses use the same effective environment. Normal Pi configuration and the bridge's tool/MCP isolation remain unchanged. Keep credentials in the host's runtime configuration, not persisted bridge settings or source.

Settings

Open /extensions:settings; settings appear under the Claude Bridge tab.

Project settings in .pi/settings.json apply only after Pi marks the workspace trusted; before trust, vstack Pi extensions read user/global settings only.

General

Setting	What it does
Enable Claude bridge provider	Register claude-bridge/* models. Reload required.

Base prompt

Setting	What it does
System prompt	Choose Claude Code's preset prompt or Pi's complete system prompt.
Forward AGENTS.md + skills	In Claude Code mode, append AGENTS.md and Pi's skills block.

Pi prompt context

Setting	What it does
Forward APPEND_SYSTEM.md	Forward project/global APPEND_SYSTEM.md content.

Pi prompt hooks

Setting	What it does
Forward project agents hook	Forward pi-agents-tmux Project Agents/Subagents list.
Forward task panel hook	Forward pi-task-panel workflow reminders.
Forward caveman hook	Forward pi-caveman response-style directives.

Claude Code

Setting	What it does
Strict MCP config	Block filesystem MCP auto-loads; Pi owns tools.
Allow extra usage helper	Let the bridge launch Claude Code's /usage-credits flow when a request needs usage credits. Billing/admin approval still happens in Claude's browser page.
Fast mode	Enable Claude Code fast mode for bridge requests when the selected model supports it.
Force Claude effort	Override Pi's thinking-level mapping for every claude-bridge request. none keeps Pi's selected level; max sends Claude Code --effort max.
Model effort overrides	JSON object mapping model IDs to Claude Code efforts, e.g. {"claude-opus-4-8":"max"}. Per-model entries beat the global force setting.
Claude executable path	Explicit claude binary path; empty auto-detects.

Pi 0.80.6 and newer expose native max thinking. Fable 5 bridge metadata forwards both xhigh and max; Force Claude effort and Model effort overrides remain available when one bridge model needs a different fixed effort. For example, to force only Opus 4.8 to max:

{"claude-opus-4-8":"max"}

Keys may be bare model IDs (claude-opus-4-8), claude-bridge/<id>, or * for all bridge models. Values are low, medium, high, xhigh, or max.

Fable 5 caveat

The bridge registers claude-bridge/claude-fable-5, claude-bridge/claude-opus-5-5, claude-bridge/claude-opus-5, claude-bridge/claude-sonnet-5, and claude-bridge/claude-opus-4-8 even when Pi's Anthropic model registry has not shipped those entries yet. For Fable 5, the bridge asks Claude Code to use Opus 4.8 as the availability fallback and preserves Claude Code's content-safety fallback events so Pi labels rerouted turns as Opus 4.8. Content-safety fallback still depends on Claude Code's own Fable 5 support; use Claude Code 2.1.170 or newer, and set ANTHROPIC_DEFAULT_FABLE_MODEL / ANTHROPIC_DEFAULT_OPUS_MODEL yourself when routing provider-specific model IDs through Bedrock, Vertex, or Foundry.

Extra usage and rate limits

Claude Code's /usage-credits local command (formerly /extra-usage) works through the Claude Agent SDK. In Pi, use /claude-bridge:extra to run that flow from claude-bridge. With Allow extra usage helper on in /extensions:settings, the bridge also launches it automatically when Claude Code reports that a request needs usage credits: a rejection with the credits_required error code, or a long-context request that needs usage credits. An ordinary session or weekly limit does not launch it.

When Claude Code reports a rate-limit reset time, the bridge shows one clear [rate-limit] warning with timezone context and avoids repeating the same error line. If pi-qol is installed, it can use the reset time to resume later.

Approaching a plan limit is shown the way Claude Code shows it. Claude Code reports utilization as a fraction of the limit; from 70% the bridge shows a warning such as You've used 91% of your weekly limit, and below 70% it shows nothing.

Plan usage for hosts

On a Claude subscription, the bridge reads Claude Code's plan usage during turns (at most once a minute) and emits claude-bridge:usage on Pi's extension event bus: { provider: "anthropic-claude-code", observedAt, planType, windows: [{ id: "five_hour" | "weekly", label, windowSeconds, usedPercent, resetAt }] }. Hosts such as Aria Local Runtime can show it as quota. For steady pacing, hosts can instead poll createClaudeUsageProbe() from @fractaal/pi-claude-bridge/usage-probe about once a minute: it keeps one idle Claude Code process (no prompt, tools, MCP servers, or user settings, so no model calls) while reads continue and closes it about two minutes after they stop. Claude Code marks the underlying API experimental, so the bridge stops reading for the rest of the process if the call disappears, keeps failing, or returns an unexpected shape. API-key, Bedrock, and Vertex sessions emit nothing.

Debugging

Set CLAUDE_BRIDGE_DEBUG=1 to write bridge logs to ~/.pi/agent/claude-bridge.log and per-query Claude Code CLI logs under ~/.pi/agent/cc-cli-logs/.

Tool-result integrity problems are recorded even when debug logging is off, in the private diagnostic file ~/.pi/agent/claude-bridge-diag.log. They are not shown in the conversation: the bridge rebuilds Claude's session from Pi history before the next turn.

Startup failures include the resolved Claude executable and working directory, which makes missing binaries and wrong launch directories easier to fix.

Contributor-facing stream, tool-result, and startup diagnostics are documented in DEVELOPMENT.md.