feat(chat): experimental caveman mode 🪨

[vibegui]

Summary

Adds an opt-in caveman mode to the chat — a fun, experimental easter egg inspired by JuliusBrussee/caveman. When activated, the model responds in terse caveman-speak ("why use many token when few token do trick") and the context-window ring + cost tooltips re-skin themselves with a stone-and-clay palette.

Two-tier toggle:

1. Settings → Profile & Preferences → Experimental → Caveman mode — gates the feature (off by default).
2. 🪨 button in the chat input footer — only appears when the experimental flag is on; click to activate the skin and inject the caveman system prompt for the next message.

What changes when active

• A <caveman-mode> system prompt is appended to the chat's system string, instructing the model to drop articles/filler, stay technically accurate, sprinkle 🪨, and skip greetings/sign-offs.
• The context-window ring (SessionStats) turns clay-brown / warm-clay / burnt-umber by fill tier, with a butt linecap and a 🪨 prefix on the percentage.
• The session, per-message, and thinking tooltips switch to a dark-stone background with parchment text. Labels swap: context→rock full, tokens→words, cost→shiny, in/out→ear/mouth, think/thinking→ponder. Numbers stay numeric.

Two preference keys (experimental_caveman and caveman_active) live in usePreferences() and follow the existing experimental_vibecode pattern. No backend, migration, or new dependency.

Files

• apps/mesh/src/web/lib/caveman-mode.ts (new) — CAVEMAN_SYSTEM_PROMPT, CAVEMAN_LABELS, CAVEMAN_RING_COLORS, useCavemanMode, useCavemanFeatureEnabled, useCavemanToggle.
• apps/mesh/src/web/hooks/use-preferences.ts — adds experimental_caveman and caveman_active.
• apps/mesh/src/web/views/settings/profile-preferences.tsx — Switch row in ExperimentalSection + tracking event.
• apps/mesh/src/web/components/chat/input.tsx — 🪨 toggle button in the left actions, gated on the experimental flag.
• apps/mesh/src/web/components/chat/usage-stats.tsx — SessionStats / MessageUsageStats / MessageStatsBar branch on useCavemanMode().
• apps/mesh/src/web/components/chat/chat-context.tsx — appends CAVEMAN_SYSTEM_PROMPT to the system string in sendMessageInternal when both flags are on.

Test plan

• Toggle off (default): chat looks/behaves identically to main.
• Enable Settings → Experimental → Caveman mode, return to chat: 🪨 button appears in the input footer next to Tools.
• Click 🪨: button expands to a clay-colored "Caveman" pill (matches Plan/Image/Web mode pill styling).
• Send a message: response comes back in caveman-speak; cost/tokens tooltip shows rock full, words, shiny, ear, mouth, ponder.
• After the assistant replies: ring indicator shows clay-brown stroke + 🪨 % label.
• Click X on the pill (or click the pill again): toggle deactivates; subsequent messages return to normal.
• Disable the experimental flag in Settings: 🪨 button disappears even if caveman_active was on; messages stop carrying the caveman prompt.

bun run fmt ✅. bun run check clean for files in this PR (the only error — task-row.tsx avatar "xs", from commit 61a4d81 — is pre-existing on main and untouched here).

🤖 Generated with Claude Code

---

Summary by cubic

Adds an opt-in caveman mode for chat. A Settings flag unlocks a 🪨 button that injects a caveman system prompt and re-skins usage stats with a stone-and-clay look.

• New Features
  • Settings: adds experimental_caveman (flag) and caveman_active (per-chat toggle) in preferences; off by default.
  • Chat: shows a 🪨 button in the input footer when the flag is on; toggling applies/removes caveman mode.
  • Prompt: when both flags are true, appends CAVEMAN_SYSTEM_PROMPT to the system string for outgoing messages.
  • UI: SessionStats, MessageUsageStats, and MessageStatsBar get a stone palette, butt linecap, and caveman labels (context→rock full, tokens→words, cost→shiny, in/out→ear/mouth, think(ing)→ponder); numbers unchanged.

^{Written for commit 04d9f93. Summary will update on new commits. Review in cubic}

[github-actions]

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[github-actions]

Release Options

Suggested: Minor (2.280.0) — based on feat: prefix

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