@baggiiiie/pi-context-chart

A pi package that visualises context usage two ways:

• A live chart rendered in a Glimpse window.
• A live footer showing the current context-window mix and totals.

Both surfaces share a single computation, so they stay consistent and only recompute once per session event.

Install

pi install npm:@baggiiiie/pi-context-chart

Usage

/context-chart           Open the live context usage chart
/context-chart close     Close the chart window
/context-chart footer    Toggle the context footer on/off
/context-chart refresh   Recompute context state (updates chart + footer)
/context-chart help      Show the in-app help widget
/context-chart clear     Hide the help widget

The footer is on by default. Override the startup behavior with:

export PI_CONTEXT_CHART_FOOTER=off   # disable footer on launch (default: on)

How tokens are calculated

Estimation method

Token counts are estimated locally — no tokenizer or API call is involved at estimation time. The primary method is estimateTokens(message) exported by @mariozechner/pi-coding-agent. If that throws (e.g. for an unrecognized message shape), the fallback is Math.ceil(textContent.length / 4) (a rough chars-to-tokens heuristic).

Message categorization

Each message in the reconstructed context array is classified into one of five buckets based on its role:

| Role | Category | Description | |------|----------|-------------| | user | User input | User prompts and follow-ups | | assistant | Agent output | Model responses, tool-call blocks, thinking | | toolResult, bashExecution | Tools | Tool/command outputs returned to the model | | compactionSummary, branchSummary, custom | Memory | Carried context from compaction or branch summaries | | (system prompt) | System instructions | Estimated separately from the resolved system prompt string |

The snapshot total is the sum of all five categories:

total = systemInstructions + userInput + agentOutput + tools + memory

Reconciliation with actual usage

When pi reports real token counts via ctx.getContextUsage() (returned by the provider after a request), the footer uses the actual tokens value as the authoritative total. The category breakdown is then scaled proportionally to match that real total using the largest-remainder method (each category keeps its relative share, with rounding residuals distributed to the largest fractional remainders). This avoids the breakdown summing to a different number than what the provider reported.

If getContextUsage() is unavailable (e.g. right after compaction, or for live in-flight snapshots), the local estimate is used and marked as "approximate" (~ prefix in the footer).

Per-turn history

For the chart, each historical turn's snapshot is built by calling buildSessionContext(entries, parentId, byId) which reconstructs the full message array that was sent to the model for that specific turn. This means each data point reflects the cumulative context size at that moment, not just the incremental addition.

Cache hit rate

The footer displays a prompt cache hit rate after the context breakdown. It is calculated as:

hitRate = cacheRead / (input + cacheRead + cacheWrite)

Values are taken from the model's reported usage metadata accumulated across all assistant turns in the current branch. The rate is color-coded: green (≥70%), yellow (≥30%), or dim (<30%). Shows -- if no prompt tokens have been reported yet.

Notes

• Requires pi
• The chart requires Glimpse to be installed where Node can resolve it, or GLIMPSE_PATH set to .../glimpseui/src/glimpse.mjs
• Footer uses pi's ctx.getContextUsage() when available, with a local estimate fallback (e.g. right after compaction)