Agent Breaking Changes_

← Pi

Pi v0.99.2

2026-09-30 · official notes

Summary

Full notes

### New Features

- MCP servers stay out of the way: servers with the default `codemode` exposure are no longer listed in the `codemode` description and no longer block the first prompt. They appear in a short system prompt section, and scripts find their tools with `searchTools()` and `describeNamespace()`. See [Control tool exposure](https://github.com/earendil-works/pi/blob/v0.99.2/packages/coding-agent/docs/mcp.md#control-tool-exposure).
- More MCP authentication options: `oauth.clientName` for servers that only accept known OAuth clients, and `"auth": { "provider": "<provider>" }` to authenticate HTTP servers with a provider's `/login` token. See [Authenticate with OAuth](https://github.com/earendil-works/pi/blob/v0.99.2/packages/coding-agent/docs/mcp.md#authenticate-with-oauth).
- Anthropic workload identity federation from the Anthropic SDK environment variables. See [Use an API key from the environment](https://github.com/earendil-works/pi/blob/v0.99.2/packages/coding-agent/docs/providers.md#use-an-api-key-from-the-environment).
- `/reload` enables tools newly added to the `defaultTools` setting. See [Tools](https://github.com/earendil-works/pi/blob/v0.99.2/packages/coding-agent/docs/settings.md#tools).

### Added

- Added a `description` field for MCP servers (`pi mcp add --description`), shown with the server in the system prompt and used to rank its tools in tool search, and a `describeNamespace(name)` codemode helper that returns a namespace's instructions and tool names. `describeNamespace()` and `searchTools()` accept a namespace as `mcp__dev-radius`, `mcp__dev_radius`, `dev-radius`, or `dev_radius`.
- Added an `oauth.clientName` setting for MCP servers (`pi mcp add --oauth-client-name`) to change the client name sent during OAuth client registration, for servers that only accept known clients ([#10226](https://github.com/earendil-works/pi/issues/10226)).
- Added `"auth": { "provider": "<provider>" }` for HTTP MCP servers to send a provider's current `/login` token as the bearer token instead of using MCP OAuth. The token is read on every request, so provider refreshes apply. Only allowed in the global `mcp.json` and from extensions, and requires https except on loopback hosts.
- Added Anthropic workload identity federation from the `ANTHROPIC_FEDERATION_RULE_ID`, `ANTHROPIC_ORGANIZATION_ID`, and `ANTHROPIC_IDENTITY_TOKEN_FILE` environment variables (see [Providers](https://github.com/earendil-works/pi/blob/v0.99.2/packages/coding-agent/docs/providers.md)) ([#10177](https://github.com/earendil-works/pi/issues/10177), [#10242](https://github.com/earendil-works/pi/pull/10242) by [@philfreo](https://github.com/philfreo)).
- `/reload` now enables tools newly added to the `defaultTools` setting. Tools removed from it stay enabled, tools turned off during the session stay off unless newly added, and `--tools`, `--no-tools`, and `--no-builtin-tools` still override the setting ([#10245](https://github.com/earendil-works/pi/issues/10245)).

### Changed

- MCP servers with the default `codemode` exposure no longer appear in the `codemode` description; scripts find them with `searchTools()`. `codemode-deferred` is now an alias for `codemode`. Use `direct` exposure for tools the model should see without searching ([#10212](https://github.com/earendil-works/pi/issues/10212)).
- The `codemode` description no longer includes deferred tools, tool counts, or MCP server instructions, so it no longer changes when MCP servers connect or change their tools. The `tool_search` description no longer lists the servers whose tools it can load, for the same reason. Servers are listed instead in an `mcp_servers` system prompt section with a one-line summary, updated at the start of each prompt; a changed section is appended to the conversation. Scripts read server instructions with `describeNamespace()` ([#10212](https://github.com/earendil-works/pi/issues/10212)).
- The first prompt no longer waits for MCP servers without `direct` tools. They connect in the background and are waited for when a codemode script names them, a script searches tools, or `tool_search` runs ([#10212](https://github.com/earendil-works/pi/issues/10212)).

### Fixed

- Fixed new sessions intermittently ignoring the saved default model, or warning that no models are available, when it belongs to an extension-registered native provider with a stored credential ([#9962](https://github.com/earendil-works/pi/issues/9962), [#10190](https://github.com/earendil-works/pi/pull/10190) by [@davidbrai](https://github.com/davidbrai)).
- Fixed the `/mcp` sign-in URL not being clickable when it wraps across lines, by emitting it as a terminal hyperlink with a `Cmd/Ctrl+click to open` line like `/login` ([#10186](https://github.com/earendil-works/pi/issues/10186)).
- Fixed codemode `image()` accepting malformed base64 data or unsupported image types, which persisted an invalid image block that made every later provider request fail with HTTP 400 ([#10215](https://github.com/earendil-works/pi/issues/10215)).
- Fixed codemode failing to start its script worker from the standalone Windows executable ([#10204](https://github.com/earendil-works/pi/issues/10204)).
- Fixed prompt submission slowing down with session length, because resolving the session's model selection looked up the model catalog once per assistant message ([#10198](https://github.com/earendil-works/pi/issues/10198)).
- Fixed model lookups slowing down for providers with a refreshed pi.dev catalog, because merging remote catalog models took quadratic time.
- Fixed the `built-in-tool-renderer.ts` and `minimal-mode.ts` extension examples removing the built-in tools' summaries and guidelines from the system prompt ([#10072](https://github.com/earendil-works/pi/issues/10072), [#10193](https://github.com/earendil-works/pi/pull/10193) by [@christianklotz](https://github.com/christianklotz)).
- Fixed context overflow detection for Z.AI CN endpoint `Prompt exceeds max length` errors ([#10208](https://github.com/earendil-works/pi/issues/10208)).
- Fixed Anthropic requests failing when a tool schema uses keywords Anthropic strict tool use rejects, such as `minimum`/`maximum`; such tools are now sent non-strict ([#9953](https://github.com/earendil-works/pi/issues/9953)).
- Fixed provider retries firing immediately when a `Retry-After` header contains an unparseable date; they now use exponential backoff ([#9571](https://github.com/earendil-works/pi/issues/9571)).
- Fixed extension commands registered without a string name or handler crashing pi when typing `/`; the extension now fails to load with an error instead ([#10054](https://github.com/earendil-works/pi/issues/10054)).
- Fixed collapsed `codemode` and MCP tool results filling the screen when the output is one long line, such as minified JSON. Like bash output, the preview is now limited to wrapped lines instead of logical lines.
- Fixed `codemode.mode: "only"` listing `read`, `bash`, `edit`, and `write` in the system prompt's tool list although requests only declare `codemode` ([#10192](https://github.com/earendil-works/pi/issues/10192)).
- Fixed codemode scripts calling the wrong MCP tool when two tool names differ only in `-` and `_`, such as `read-file` and `read_file`. Like in Codex, MCP tool and namespace names now replace `-` with `_` (`mcp__my-server__x` is now `mcp__my_server__x`), colliding tools of a server all get a hash suffix, and server names that differ only in `-` and `_` are rejected ([#10239](https://github.com/earendil-works/pi/issues/10239)).
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