Enable iterative chart modifications via conversation history

[Copilot]

Users cannot iterate on charts with follow-up requests like "update the revenue axis to start at 4k" because the LLM receives no conversation context—each request is processed in isolation.

Changes

llmRouter.js

• Added chatHistory parameter to getUpdatedChartSpec() to pass full conversation context to LLM
• Updated system prompt with instructions for incremental modifications (preserve existing settings, apply only requested changes)
• Added error handling for non-serializable objects with descriptive messages
• Fallback to currentSpec when history unavailable (backward compatible)

main.js

• Pass state.chatHistory to getUpdatedChartSpec()

Example Flow

// Before: No context between requests
User: "generate chart showing revenue by quarter"
LLM receives: [system, user message]
→ Creates chart ✓

User: "update the revenue axis to start at 4k"  
LLM receives: [system, user message]  // No context!
→ Doesn't understand what to update ✗

// After: Full conversation context
User: "generate chart showing revenue by quarter"
LLM receives: [system, user message]
→ Creates chart ✓

User: "update the revenue axis to start at 4k"
LLM receives: [system, previous exchange, user message]
→ Modifies yaxis.range while preserving other settings ✓

The implementation handles edge cases (null values, arrays, circular references) and maintains the existing chat history structure in state.chatHistory.

Original prompt

i noticed that when i ask a follow up about the chart, like "change axis" or start axis at 4k "ou
generate a chart that shows revenue by quarter
Assistant
{
"title": "Revenue by Quarter",
"chartType": "bar",
"x": "Date",
"y": "Revenue",
"groupBy": {
"columns": [
"Date"
],
"aggregations": {
"Revenue": {
"func": "sum"
}
}
},
"layout": {
"xaxis": {
"tickformat": "%Y-Q%q"
}
}
}
You
update the revenue axis to start at 4k
Assistant
{
"title": "Revenue by Quarter",
"chartType": "bar",
"x": "Date",
"y": "Revenue",
"groupBy": {
"columns": [
"Date"
],
"aggregations": {
"Revenue": {
"func": "sum"
}
}
},
"layout": {
"xaxis": {
"tickformat": "%Y-Q%q"
},
"yaxis": {
"range": [
4000,
null
]
}
}
}" it doesnt update the chart, it responds back in chat, i don't think there is a method for the user to iterate on the chart that is in the visualization

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[evcatalyst]

@copilot Addendum: Vanilla static + browser-local requirements (paste into Update)
Hard constraints

Vanilla static site only:

No React / Vue / Svelte / Next.

Prefer zero build step (plain HTML/CSS/JS).

Use ES modules (type="module") and keep dependencies minimal.

If any dependencies are used, they must be either:

vendored into /vendor/ in the repo, or

loaded via stable CDNs with pinned versions.

Local-first:

App must work fully in-browser, including dataset storage and layout state.

Persist state using:

IndexedDB for datasets / large blobs (CSV, parsed tables, cached samples)

localStorage for lightweight settings (UI prefs, selected model, sampling preset, last layout)

Optional: Service worker for offline + caching static assets (no server required).

UI implementation approach

Use native Web Components (Custom Elements) for modularity instead of framework components:

, , , , , etc.

Keep styling with CSS variables + shadow DOM where useful (or light DOM if easier to theme globally).

Use a vanilla-compatible grid/drag/resize library (pick one and justify):

Grid/tile system candidates (must be framework-agnostic):

Gridstack.js (drag + resize dashboard tiles, widely used)

Muuri (great for draggable grids; pair with resize handling if needed)

Interact.js (low-level drag/resize; build custom grid behavior if needed)

Use a vanilla splitter for resizable chat drawer:

Split.js (simple resizable panes) or equivalent.

Chat drawer requirements (vanilla)

Chat is a toggleable, resizable side drawer:

Drawer open/close state persisted in localStorage

Drawer width persisted

Keyboard accessible (Esc closes, focus trap while open optional)

Chat messages can create/update tiles in the grid:

“Spawn chart tile”, “Spawn text tile”, “Update tile #n”

Natural language settings UI (vanilla)

Implement “natural language form” style controls as a lightweight custom element:

Inline sentence with editable tokens/selects

Styling inspired by Tympanus NaturalLanguageForm interaction pattern, but implemented without heavy dependencies.

Sampling control should be an LED/retro segmented UI:

Presets: 1%, 5%, 10%, 20%, 50%, 100%

Shows estimated token impact and warning states

Persist preset + last custom value in localStorage

Deliverables expected (vanilla-specific)

Provide:

Folder structure for a static site (/components, /styles, /vendor, /data, etc.)

State model for IndexedDB/localStorage (schema + keys)

Recommended grid library choice + rationale for vanilla use

Migration plan from current layout to the new workbench without rewriting the core ChartSpec engine