Add MiniMax provider support (#656 by @dannote)

- Add minimax to KnownProvider and Api types
- Add MINIMAX_API_KEY to getEnvApiKey()
- Generate MiniMax-M2 and MiniMax-M2.1 models
- Add context overflow detection pattern
- Add tests to all required test files
- Update README and CHANGELOG with attribution

Also fixes:
- Bedrock duplicate toolResult ID when content has multiple blocks
- Sandbox extension unused parameter lint warning

packages/coding-agent/README.md

@@ -167,6 +167,7 @@ Add API keys to `~/.pi/agent/auth.json`:
 | xAI | `xai` | `XAI_API_KEY` |
 | OpenRouter | `openrouter` | `OPENROUTER_API_KEY` |
 | ZAI | `zai` | `ZAI_API_KEY` |
+| MiniMax | `minimax` | `MINIMAX_API_KEY` |
 
 Auth file keys take priority over environment variables.
 
@@ -1142,7 +1143,7 @@ pi [options] [@files...] [messages...]
 
 | Option | Description |
 |--------|-------------|
-| `--provider <name>` | Provider: `anthropic`, `openai`, `openai-codex`, `google`, `mistral`, `xai`, `groq`, `cerebras`, `openrouter`, `zai`, `github-copilot`, `google-gemini-cli`, `google-antigravity`, or custom |
+| `--provider <name>` | Provider: `anthropic`, `openai`, `openai-codex`, `google`, `google-vertex`, `amazon-bedrock`, `mistral`, `xai`, `groq`, `cerebras`, `openrouter`, `zai`, `minimax`, `github-copilot`, `google-gemini-cli`, `google-antigravity`, or custom |
 | `--model <id>` | Model ID |
 | `--api-key <key>` | API key (overrides environment) |
 | `--system-prompt <text\|file>` | Custom system prompt (text or file path) |

packages/coding-agent/examples/extensions/sandbox/index.ts

@@ -211,7 +211,7 @@ export default function (pi: ExtensionAPI) {
 	pi.registerTool({
 		...localBash,
 		label: "bash (sandboxed)",
-		async execute(id, params, onUpdate, ctx, signal) {
+		async execute(id, params, onUpdate, _ctx, signal) {
 			if (!sandboxEnabled || !sandboxInitialized) {
 				return localBash.execute(id, params, signal, onUpdate);
 			}

packages/coding-agent/src/cli/args.ts

@@ -243,6 +243,8 @@ ${chalk.bold("Environment Variables:")}
   XAI_API_KEY             - xAI Grok API key
   OPENROUTER_API_KEY      - OpenRouter API key
   ZAI_API_KEY             - ZAI API key
+  MISTRAL_API_KEY         - Mistral API key
+  MINIMAX_API_KEY         - MiniMax API key
   AWS_PROFILE             - AWS profile for Amazon Bedrock
   AWS_ACCESS_KEY_ID       - AWS access key for Amazon Bedrock
   AWS_SECRET_ACCESS_KEY   - AWS secret key for Amazon Bedrock

packages/coding-agent/src/core/model-resolver.ts

@@ -26,6 +26,7 @@ export const defaultModelPerProvider: Record<KnownProvider, string> = {
 	cerebras: "zai-glm-4.6",
 	zai: "glm-4.6",
 	mistral: "devstral-medium-latest",
+	minimax: "MiniMax-M2.1",
 	opencode: "claude-opus-4-5",
 };