pi-kiro-models

Bridge Kiro CLI's premium AI models into the pi coding agent via the Agent Client Protocol (ACP).

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Overview

pi is a terminal-based AI coding agent. Kiro is Amazon's AI coding agent that gives you access to 15 premium models (Claude Sonnet 5, Opus 4.8, DeepSeek V3.2, etc.) through a single subscription.

This extension bridges Kiro's models into pi. Once installed, you select a Kiro model in pi with /model and chat with it — token-by-token streaming, full conversation context, and the same workflow you use with any other provider.

How it works

pi TUI  →  Extension (streamSimple)  →  ACP Client (NDJSON over stdio)  →  kiro-cli-chat acp --agent pi-bridge  →  Kiro API

1. pi loads the extension, which registers a kiro provider with 15 models.
2. On the first prompt, the extension writes a pi-bridge Kiro agent config to ~/.config/kiro/agents/pi-bridge.json (idempotent) and spawns kiro-cli-chat acp --agent pi-bridge as a child process. It completes the ACP handshake (initialize + session/new), then issues session/set_model for the pi-selected model.
3. For each prompt, the extension renders pi's systemPrompt and any new turns in context.messages into a tagged transcript and sends only the delta as session/prompt. Kiro's own session state persists prior turns.
4. Kiro streams agent_message_chunk notifications, which the extension maps to pi's text_delta events.

Tools

Inference for Kiro models runs inside Kiro's own agent loop — Kiro executes tool calls itself and streams back text. pi forwards the transcript and displays the result; pi does not execute tools on Kiro's behalf.

Two classes of tools are available to the bridged model:

1. Kiro's native tools — fs_read, fs_write, execute_bash, glob, grep, web_fetch, web_search.
2. MCP servers you've configured — the bridge discovers every MCP server in your Kiro mcp.json files and forwards them to the session, so their tools are callable directly by the model. See MCP Tool Passthrough.

Why not forward pi's own tools? pi's ExtensionAPI exposes tool definitions (getAllTools()) but no way for one extension to execute another's tool, and Kiro — not pi — drives the agent loop for Kiro models. So pi's in-process tools (read/edit/etc.) can't be handed to Kiro generically. The forwardable, future-proof surface is MCP, which Kiro runs natively. Any tool you want available to a Kiro model should be exposed as an MCP server.

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Features

• 15 models from Kiro's catalog — Claude Sonnet 5, Opus 4.8/4.7/4.6/4.5, Sonnet 4.6/4.5/4, Haiku 4.5, DeepSeek V3.2, GLM-5, Qwen3 Coder Next, and more
• Dynamic MCP tool passthrough — every MCP server in your Kiro mcp.json is auto-forwarded to the bridged model. Add a server to mcp.json, restart pi, and its tools are callable — no bridge edits. See MCP Tool Passthrough.
• Model routing via session/set_model — pi's /model selection actually reaches Kiro (not just the auto default)
• Token-by-token streaming into pi's TUI
• Full pi context passthrough — systemPrompt, prior turns, tool calls, and tool results are rendered as a tagged transcript (<pi-system-prompt>, <pi-transcript>, <user>, <assistant>, <tool_call>, <tool_result>). Only the delta since the last send is forwarded per turn; Kiro's own session state persists prior turns.
• Automatic process management — spawns on first use, cleans up on pi exit, respawns if the child dies
• Ctrl+C cancellation — sends session/cancel to Kiro
• No API key needed — uses your existing Kiro CLI authentication (AWS IAM Identity Center)

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Stack

Component	Technology
Runtime	Node.js 20+ (loaded by pi's jiti)
Language	TypeScript
Protocol	Agent Client Protocol (ACP) over stdio
Framing	NDJSON (newline-delimited JSON-RPC 2.0)
Transport	Child process spawn with stdio pipes
Authentication	Inherited from kiro-cli (IAM Identity Center)

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Architecture

┌──────────────────────────────────────────────────────────┐
│ pi (host)                                                │
│  ┌────────────────────────────────────────────────────┐  │
│  │ kiro-provider extension (index.ts)                 │  │
│  │  ┌──────────────┐  ┌─────────────────────────────┐  │  │
│  │  │ 15 models    │  │ streamKiro() — bridges ACP  │  │  │
│  │  │ registered   │  │ to pi's AssistantMessage    │  │  │
│  │  └──────────────┘  │ EventStream                 │  │  │
│  │                    └──────────────┬──────────────┘  │  │
│  │  ┌─────────────────────────────────▼──────────────┐  │  │
│  │  │ ACPClient (NDJSON, request/response,           │  │  │
│  │  │ notification dispatch)                         │  │  │
│  │  └─────────────────────────────────┬──────────────┘  │  │
│  └────────────────────────────────────┼─────────────────┘  │
└─────────────────────────────────────┼────────────────────┘
                                      │ stdin/stdout (NDJSON)
                                      │
┌─────────────────────────────────────▼────────────────────┐
│ kiro-cli-chat acp (child process)                        │
│  - ACP session state                                     │
│  - Built-in tool execution (read, write, shell, etc.)   │
│  - IAM Identity Center auth                              │
└──────────────────────────────────────────────────────────┘

Data flow per prompt:

1. pi calls streamSimple(model, context, options)
2. Extension ensures the pi-bridge Kiro agent config exists at ~/.config/kiro/agents/pi-bridge.json and spawns kiro-cli-chat acp --agent pi-bridge on the first call (cached across turns). It forwards every MCP server found in your Kiro mcp.json files via session/new mcpServers, so their tools are callable by the model.
3. Extension issues session/set_model if pi's selected model differs from Kiro's current model.
4. Extension renders context.systemPrompt and any new context.messages into a tagged transcript (<pi-system-prompt>, <pi-transcript>, <user>, <assistant>, <tool_call>, <tool_result>) and sends it as session/prompt. Only the delta since the previous send is included — Kiro maintains its own session history for prior turns.
5. Kiro streams session/update notifications with agent_message_chunk.
6. Extension maps each chunk to a text_delta event on pi's stream.
7. Kiro responds to session/prompt with stopReason: "end_turn".
8. Extension pushes done, records lastMessageCount on the session, and ends the stream.

Context passthrough limits:

• pi's systemPrompt reaches the model as authoritative context (facts, conventions, project details) and is respected in the model's answers.
• Kiro's underlying agent has a fixed self-identity ("I'm Kiro") that its ACP --agent mode overlay does not override. Attempts to force identity change via pi's systemPrompt will be refused by the model. This is a Kiro-side limitation; pi's operational context still works.

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Models

All 15 models from the Kiro catalog:

Model	Context	Notes
auto	1M	Auto-routing
claude-sonnet-5	1M	Experimental preview
claude-opus-4.8	1M
claude-opus-4.7	1M
claude-opus-4.6	1M
claude-sonnet-4.6	1M
claude-opus-4.5	200K
claude-sonnet-4.5	200K
claude-sonnet-4	200K
claude-haiku-4.5	200K	Cheapest/fastest
deepseek-3.2	164K	Experimental
minimax-m2.5	196K
minimax-m2.1	196K	Experimental
glm-5	200K
qwen3-coder-next	256K	Experimental, cheap

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Prerequisites

• pi coding agent installed (pi on PATH)
• Kiro CLI installed (kiro-cli-chat available)
• Kiro CLI authenticated (kiro-cli-chat whoami shows your IAM user)
• An active Kiro subscription
• Node.js 20+ (bundled with pi's installer)

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Installation

Method 1: Clone from GitHub

cd ~/.pi/agent/extensions/
git clone https://github.com/yanralapdy/pi-kiro-models.git kiro-provider

Method 2: Symlink from a dev location

ln -s ~/sites/js/node/pi-kiro-models ~/.pi/agent/extensions/kiro-provider

Method 3: Register in settings.json

If auto-discovery doesn't pick up the extension, add it explicitly to ~/.config/pi/agent/settings.json:

{
  "extensions": [
    "~/sites/js/node/pi-kiro-models/index.ts"
  ]
}

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Usage

pi

In pi, run:

/model

Scroll to the kiro provider. Select any model (e.g., kiro/claude-haiku-4.5 for cheap/fast testing or kiro/claude-sonnet-5 for premium quality).

Start chatting. Text streams token-by-token. Ctrl+C cancels.

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MCP Tool Passthrough

The bridge gives Kiro models access to Model Context Protocol servers. On each session it discovers the MCP servers configured for Kiro and forwards them two ways:

• ACP session/new mcpServers — connects the servers for the bridged ACP session (the mechanism that makes the tools callable).
• @server entries in the generated pi-bridge agent config — allows the servers' tools.

This is fully dynamic: add a server to any Kiro mcp.json, start a fresh pi session, and the model can call its tools. No changes to this extension are needed for new tools.

Where servers are read from

Discovered and unioned by name (later overrides earlier, so a workspace entry overrides a global one):

1. ~/.config/kiro/settings/mcp.json (global)
2. ~/.kiro/settings/mcp.json (global)
3. <cwd>/.kiro/settings/mcp.json (per-project)

Only stdio (command-based) servers are forwarded. HTTP/SSE (url) servers are currently skipped.

Register a server

Use the Kiro CLI (writes global config unless run inside a project, which writes the workspace config):

# stdio server on PATH or by absolute path
kiro-cli-chat mcp add --name my-tool --command /absolute/path/to/my-mcp-server

# with arguments and environment variables
kiro-cli-chat mcp add --name notion \
  --command npx --args "-y,@notionhq/notion-mcp-server" \
  --env NOTION_TOKEN=secret

Or edit mcp.json directly:

{
  "mcpServers": {
    "my-tool": {
      "command": "/absolute/path/to/my-mcp-server",
      "args": [],
      "env": {}
    }
  }
}

Then start a fresh pi session. On startup you'll see the servers being forwarded:

[kiro-provider] Wrote Kiro agent config at ~/.config/kiro/agents/pi-bridge.json (mcp: notion, my-tool)
[kiro-provider] Forwarding 2 MCP server(s) to Kiro: notion, my-tool

Ask the model to call one of the server's tools to confirm.

Verify

# in pi, with a Kiro model selected
call the list_projects tool          # example: codebase-memory-mcp

Or test the underlying agent directly, bypassing pi:

kiro-cli-chat chat --agent pi-bridge --no-interactive --trust-all-tools \
  "Call the list_projects tool and paste its output."

Notes

• The pi-bridge agent config at ~/.config/kiro/agents/pi-bridge.json is generated — it's regenerated each session from your mcp.json. Don't hand-edit it; edit mcp.json instead.
• Servers with "disabled": true in mcp.json are skipped.
• Server env values are copied into the ACP session config; treat the Kiro config tree as you would any file holding secrets.

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Testing

Test scripts in test/:

# NDJSON framing with a mock echo process
jiti test/framing.test.ts

# ACP handshake with the real kiro-cli-chat binary
jiti test/lifecycle.test.ts

# Text streaming + Ctrl+C abort
jiti test/stream.test.ts
jiti test/abort.test.ts

# Respawn after external kill
jiti test/lifecycle-cleanup.test.ts

# Transcript rendering + delta-send prompt building (pure, no ACP)
jiti test/transcript.test.ts

# End-to-end multi-turn passthrough with a real Kiro session
jiti test/context.test.ts

Run with pi's bundled jiti:

/Users/tnkapdy/.nvm/versions/node/v24.17.0/lib/node_modules/@earendil-works/pi-coding-agent/node_modules/.bin/jiti test/framing.test.ts

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Troubleshooting

Symptom	Cause	Fix
[kiro-provider] Extension loaded not in output	Extension not discovered	Add path to settings.json → extensions
baseUrl is required error	Missing baseUrl in provider config	Update to latest version
Provider kiro: "baseUrl" is required when defining models	Same as above	Same
spawn ~/.local/bin/kiro-cli-chat ENOENT	Kiro CLI not installed or wrong path	Set KIRO_CLI_CHAT env var to absolute path
Authentication failed	Kiro not logged in	Run kiro-cli-chat login
Text doesn't stream, hangs for 30s	Kiro backend slow or network issue	Retry; check kiro-cli-chat whoami
Orphaned kiro-cli-chat processes after pi exit	Process exit handler not firing	Report an issue; manually pkill -f kiro-cli-chat
Model self-identifies as "Kiro" not pi	Kiro's built-in identity system prompt overrides pi-bridge mode overlay	Expected. pi's systemPrompt still delivers factual context (project name, tools, conventions). Identity swap is a Kiro-side limitation.
Selecting different kiro/* models has no effect	session/set_model failed silently	Check stderr for session/set_model failed; verify model id is in the Kiro model list; ensure Kiro subscription includes the model
pi's systemPrompt seems ignored	pi-bridge Kiro agent missing or stale	Delete ~/.config/kiro/agents/pi-bridge.json and let the extension recreate it on the next run
MCP tool not available to the model	Server not in a discovered mcp.json, is disabled, or is a url (HTTP/SSE) server	Add it to a discovered mcp.json as a stdio (command) server; check startup log for Forwarding N MCP server(s); start a fresh session
MCP server registered but tools still missing	Session started before the server was added	Restart pi — servers are forwarded at session creation

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Roadmap

• V1: Chat-only bridge with all 15 models
• MCP tool passthrough — dynamically forward configured MCP servers to the bridged model (session/new mcpServers + generated @server agent config)
• HTTP/SSE MCP server support (currently stdio only)
• Multi-session support (concurrent pi processes)
• Image input (Kiro ACP supports images; pi has ImageContent)

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Legal & Compliance

• This extension uses ACP, an official open protocol documented at agentclientprotocol.com
• Kiro CLI explicitly supports ACP for third-party integrations (see kiro.dev/docs/cli/acp)
• No reverse engineering or unofficial APIs used
• Requires valid Kiro subscription

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License

MIT

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Contributing

Issues and PRs welcome. Test with Kiro CLI v2.5.0+.