feat: add experimental Caveman response style skill

.cspell/general-technical.txt

@@ -1623,3 +1623,4 @@ transitioner
 urlsafe
 wberry
 writeback
+Brussee

.github/skills/experimental/caveman/SKILL.md

@@ -0,0 +1,104 @@
+---
+name: caveman
+description: 'Ultra-compressed response style that reduces output token count while preserving technical accuracy, with intensity levels and auto-clarity safety rules - Brought to you by microsoft/hve-core'
+argument-hint: "[{lite|full|ultra|wenyan|off}]"
+license: MIT
+disable-model-invocation: true
+metadata:
+  authors: "microsoft/hve-core"
+  spec_version: "1.0"
+  last_updated: "2026-06-05"
+  content_based_on: "https://github.com/JuliusBrussee/caveman"
+---
+
+# Caveman Skill
+
+## Overview
+
+Caveman is an opt-in response style that reduces output verbosity while keeping technical content fully intact. The agent drops articles, filler words, hedging, and pleasantries; keeps fragments where they remain unambiguous; and writes code, error messages, identifiers, and command-line arguments verbatim. Use it when the user explicitly requests a terser response.
+
+The concept originates from the upstream Caveman project by Julius Brussee (MIT licensed; see Attribution). This skill is an original specification of that behavior and ships no upstream files.
+
+## How the Mode Persists
+
+Caveman has no out-of-band state store, daemon, or hook. Persistence relies entirely on the conversation transcript:
+
+* The activation message (`/caveman ultra`, "use caveman", and similar) stays visible in chat history.
+* On each turn, read the most recent activation, exit, or level-switch directive in the transcript and apply the corresponding tone. The latest matching directive wins.
+* The skill file is loaded on demand. Once the rules are in context, keep applying them without reloading. If context is trimmed and the rules drop out, reload `caveman/SKILL.md` the next time an active directive appears.
+* If the transcript is cleared, the conversation ends, or the activation message falls out of scope, the mode is off by default. The user re-invokes to turn it back on.
+
+State lives in chat, not in a file. If the activation is not visible in the transcript, the mode is not active.
+
+## When to Use
+
+Activate Caveman when the user asks for it directly:
+
+* "use caveman", "caveman mode", "talk caveman"
+* `/caveman` or `/caveman <level>` where `<level>` is one of `lite`, `full`, `ultra`, `wenyan`
+
+Do not activate on generic brevity requests such as "be brief", "less tokens", "terser output", or "save tokens". Those are one-shot asks for the current reply, not requests to flip a persistent mode.
+
+Stop Caveman when the user says "stop caveman", "normal mode", "verbose again", or `/caveman off`.
+
+## Intensity Levels
+
+| Level            | Behavior                                                         |
+|------------------|------------------------------------------------------------------|
+| `lite`           | Drop filler and hedging. Keep articles and full sentences.       |
+| `full` (default) | Drop articles. Sentence fragments allowed. Short synonyms.       |
+| `ultra`          | Telegraphic. One-word answers when sufficient. Arrows for flow.  |
+| `wenyan`         | Classical Chinese (文言) register layered on `full` compression. |
+
+If the user requests `/caveman` without a level, default to `full`. `/caveman wenyan` applies the wenyan register at `full` compression. Combine with another level for stronger compression, e.g. `/caveman wenyan ultra`.
+
+## Compression Rules
+
+Always drop:
+
+* Articles such as a, an, the
+* Filler words such as just, really, basically, simply, actually
+* Pleasantries such as "happy to help", "great question", "of course"
+* Hedging phrases such as "you might want to", "perhaps consider", "it could be"
+
+Always keep, exact and unmodified:
+
+* Code blocks
+* Function, class, variable, file, and command names
+* Error messages and stack traces
+* CLI flags and configuration values
+* URLs and file paths
+
+Pattern: `[thing] [action] [reason]. [next step].`
+
+## Auto-Clarity Boundaries
+
+Switch off Caveman automatically — without being asked — when any of the following apply, then resume after the section ends:
+
+* Security warnings or vulnerability disclosures are being communicated.
+* Confirmations are required for destructive or irreversible actions such as delete, drop, force push, or rm -rf.
+* Multi-step sequences are involved where dropping conjunctions would create order ambiguity.
+* Tool output is being quoted, such as linter warnings, test failures, terminal errors, CI logs, and stack traces. Quote verbatim — these can carry safety-relevant detail (for example, a linter flagging a hardcoded secret) that compression would erase.
+* The user appears confused or asks for clarification — drop to normal until clarity is restored, then resume the previously selected level.
+* Compression would make a technical instruction ambiguous.
+
+Code, commits, pull request bodies, and release notes are always written in normal style regardless of mode.
+
+## Examples
+
+Normal: "I'd be happy to help! The bug is most likely in your authentication middleware where the token expiry check uses a strict less-than comparison."
+
+Caveman (full): "Bug in auth middleware. Token expiry check uses `<` not `<=`. Fix:"
+
+Caveman (ultra): "Auth bug. `<` → `<=`. Fix:"
+
+## Limits
+
+* Caveman affects assistant prose only. It does not change generated code, commit messages, or PR descriptions.
+* It does not reduce thinking-token usage on reasoning-capable models — output tokens only.
+
+## Attribution
+
+Concept based on the [Caveman project](https://github.com/JuliusBrussee/caveman) (MIT license, Copyright (c) 2026 Julius Brussee). This SKILL.md is an original specification authored for hve-core; no upstream files are redistributed.
+
+> Brought to you by microsoft/hve-core

collections/experimental.collection.md

@@ -41,6 +41,7 @@ Experimental and preview artifacts not yet promoted to stable collections. Items
 
 | Name                     | Description                                                                                                                                                                           |
 |--------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| **caveman**              | Ultra-compressed response style that reduces output token count while preserving technical accuracy, with intensity levels and auto-clarity safety rules                              |
 | **customer-card-render** | Generate customer-card PowerPoint content YAML from Design Thinking canonical artifacts and build using the shared PowerPoint skill pipeline                                          |
 | **mural**                | Mural workspace, room, mural, and widget workflows via the Mural REST API exposed through a Python CLI. Use when you need to read or write Mural content or automate widget creation. |
 | **powerpoint**           | PowerPoint slide deck generation and management using python-pptx with YAML-driven content and styling                                                                                |

collections/experimental.collection.yml

@@ -14,6 +14,9 @@ items:
   - path: .github/agents/experimental/subagents/pptx-subagent.agent.md
     kind: agent
   # Skills
+  - path: .github/skills/experimental/caveman
+    kind: skill
+    maturity: experimental
   - path: .github/skills/experimental/customer-card-render
     kind: skill
   - path: .github/skills/experimental/powerpoint

collections/hve-core-all.collection.md

@@ -242,6 +242,7 @@ Use this edition when you want access to everything without choosing a focused c
 | **adr-author**                | Authoring skill for Architecture Decision Records (ADRs) supporting capture, from-planner-handoff, and adopt-template entry modes with selectable Y-Statement or MADR v4.0.0 output templates, supersession lineage, and ASR trigger evaluation - Brought to you by microsoft/hve-core.                               |
 | **architecture-diagrams**     | Architecture diagram authoring for cloud infrastructure: parse Azure IaC, map relationships, and render either ASCII block diagrams or Mermaid flowcharts based on the caller's chosen output format                                                                                                                  |
 | **backlog-templates**         | Shared work-item templates and conventions for ADO and GitHub backlog handoff across the RAI, Security, SSSC, and Accessibility planners                                                                                                                                                                              |
+| **caveman**                   | Ultra-compressed response style that reduces output token count while preserving technical accuracy, with intensity levels and auto-clarity safety rules                                                                                                                                                              |
 | **customer-card-render**      | Generate customer-card PowerPoint content YAML from Design Thinking canonical artifacts and build using the shared PowerPoint skill pipeline                                                                                                                                                                          |
 | **documentation**             | Canonical documentation capability for audit, drift, validate, and author modes in hve-core.                                                                                                                                                                                                                          |
 | **dt-coaching-foundation**    | Design Thinking coaching foundation knowledge: coach identity and philosophy, quality and fidelity constraints, method sequencing, coaching state schema, and the canonical deck workflow                                                                                                                             |

collections/hve-core-all.collection.yml

@@ -515,6 +515,9 @@ items:
 - path: .github/skills/design-thinking/dt-rpi-integration
   kind: skill
   maturity: preview
+- path: .github/skills/experimental/caveman
+  kind: skill
+  maturity: experimental
 - path: .github/skills/experimental/customer-card-render
   kind: skill
 - path: .github/skills/experimental/mural