@99percentpeople/pi-thinking-fold

Fold long, streaming reasoning blocks into a small live preview in Pi's TUI. The preview follows the latest terminal-visible lines instead of letting a reasoning trace continuously grow upward.

During thinking you see a compact tail preview with a live timer; afterwards it collapses to Thought for 12.3s. Press Ctrl+T anytime to expand the full reasoning trace. Behavior is tunable in /99settings (fold depth, while/ after-thinking strategies).

Demo

Trace models

A reasoning trace collapses to a stable tail preview with a timer, then to Thought for Xs (ctrl+t to expand) — no more scroll-storms:

Summary models

A reasoning summary keeps its content folded while the working row shows the latest summary headline, then collapses to the same completed timer:

Behavior

When While thinking is set to preview, the assistant Item contains a timed header and its latest terminal-visible lines:

Thinking 7.1s  (ctrl+t to expand)
  checking the final branch…
  validating the result…

The cursor working row separately displays the plain status Thinking.... Model behavior determines whether that row uses a summary headline (for example, Running focused tests) or Thinking.... With the default auto streaming behavior, summary content stays hidden while trace content shows a tail preview.

Cursor styling is intentionally outside this package. Install @99percentpeople/pi-cursor-effect to apply the optional wave effect to this and Pi's other main working-cursor labels.

The Item timer redraws only once per second. When reasoning finishes, the timer freezes as soon as answer text or a tool call starts. The default auto completion behavior hides content for every model, leaving a single line with precise elapsed time. This also handles OpenAI-compatible providers that delay their thinking_end event until the entire answer has streamed:

Thought for 12.3s  (ctrl+t to expand)

Additional behavior:

• The preview strategy shows the latest 5 visual lines by default, for traces and summaries alike.
• Preview content keeps Pi's native Markdown formatting. Each thinking section is rendered at the current terminal width first, then the preview retains its final terminal-visible rows. Fences, headings, tables, quotes, lists, syntax highlighting, wrapping, and future Markdown behavior therefore need no syntax-specific handling, while the folded height stays fixed as formatted constructs enter or leave the tail window.
• Pi's normalized thinking_start / thinking_delta / thinking_end events drive streaming and timing, so model IDs never need per-model adapters.
• While thinking defaults to auto: summaries show only the timer while traces show their latest lines. Explicit collapse and preview override that model-aware choice.
• After thinking defaults to auto, which hides completed content for both summaries and traces. Explicit collapse, preview, and full override it.
• An empty Pi thinking_start still creates the timed Item. If a provider emits its entire summary immediately before thinking_end, the cursor keeps that headline visible for at least one second before Responding….
• Models that expose neither a trace nor a summary transition directly to the normal Responding... working row without an extra availability warning.
• Ctrl+T (or the configured app.thinking.toggle binding) switches between the folded view and complete reasoning blocks. Its expansion hint appears only when content is actually hidden: by a collapse strategy, or because a thinking block exceeds the configured fold threshold. The chosen state persists across later turns until Ctrl+T is pressed again.
• Ctrl+O keeps its native Pi behavior and only expands tools and other expandable UI content.

The extension changes display-only message copies. Original assistant messages, reasoning signatures, session persistence, and model context are not modified. No extra session entries are added. After a reload, old durations are reconstructed from Pi's message timestamps and are therefore approximate.

Install

Build and install this checkout as a user-local development package:

bun run build:packages
bun run --cwd extensions/thinking-fold build
pi install ./extensions/thinking-fold

Or test without adding it to settings:

pi -e ./extensions/thinking-fold/index.ts

Remove the local package with:

pi remove ./extensions/thinking-fold

Settings

Run the shared /99settings menu. It lists installed @99percentpeople plugins that expose three independent display controls:

• Fold after lines (1–20): maximum terminal-visible lines retained by a preview display;
• While thinking: auto (hide summaries, preview traces), preview (latest lines), or collapse (timer only);
• After thinking: auto (hide every model), collapse (timer only), preview (latest lines), or full (all reasoning text).

Both behavior settings default to auto.

Settings persist globally in:

~/.pi/agent/99extensions.json

under the thinking-fold namespace. The model behavior is always resolved from the built-in model behavior configuration described below; an unmatched model uses trace. Existing previewLines and autoCollapse settings are migrated to the equivalent new values when next saved.

Model behavior configuration

model-behaviors.json is the package's single built-in compatibility table. A rule selects by any combination of case-insensitive JavaScript regular-expression sources in api, provider, and model:

{
  "version": 1,
  "rules": [
    {
      "id": "responses-summary",
      "api": "responses$",
      "behavior": "summary"
    },
    {
      "id": "deepseek-trace",
      "provider": "^deepseek$",
      "model": "^deepseek-.*$",
      "behavior": "trace"
    }
  ]
}

Patterns are regex source strings without /.../ delimiters; use ^ and $ when a full-field match is required. Invalid expressions fail validation at startup. Rules with more selectors win, then model is considered more specific than provider, and provider more specific than api; a later rule wins a remaining tie.

The built-in table uses conservative API-family baselines:

API/provider family	Behavior	Basis
OpenAI-compatible Chat Completions	trace	Pi reads reasoning_content, reasoning, or reasoning_text
Anthropic-compatible gateways	trace	Safe fallback because gateway semantics vary
Amazon Bedrock Converse	trace	Safe fallback because the model behind reasoningContent varies
Mistral Conversations	trace	Pi streams explicit thinking content items
pi-messages gateways	trace	Safe fallback for an intentionally generic protocol
OpenAI/Azure/Codex Responses	summary	Pi consumes reasoning_summary_text events
Google Generative AI/Vertex	summary	Pi consumes Google thought parts
First-party Anthropic	summary	Pi requests summarized thinking display

The conservative Trace rules cover common providers such as OpenRouter, Groq, Together, Fireworks, Cerebras, Hugging Face, Kimi, MiniMax, Moonshot, Qwen, xAI Chat Completions, Z.AI, Xiaomi, NVIDIA, Mistral, and Bedrock through their Pi API adapter. They do not claim that every routed model exposes a raw chain of thought; Trace is chosen because it preserves visible content if an untested backend differs. Provider/model-specific rules can override these API baselines later.

Only the previously exercised OpenAI Responses, Google, and DeepSeek paths have live model coverage in this repository. The additional families are validated against Pi 0.82.1 adapter source and static fixtures, not paid provider calls. The first config version intentionally supports only trace and summary, is shipped with the package, and has no user override file. This keeps compatibility data declarative and leaves provider/model names out of rendering code.

Compatibility

Pi currently exports AssistantMessageComponent but does not provide an extension hook for replacing normal assistant-message rendering. This package therefore installs a guarded compatibility patch around the component's public updateContent() method. It lets Pi create its native thinking Markdown component, then wraps that display-only child so render(width) is evaluated before its output is folded. The patch prevents duplicates across reloads and restores the original method during session shutdown.

The package is tested against Pi 0.83.0. If the public component API is missing, the extension disables itself and reports a warning. If Pi changes only the internal child layout, an affected message safely falls back to complete native rendering instead of exposing markers or modifying source content.