Documentation
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Overview ¶
Package contextwindow estimates token usage for a message history. The numbers are approximate — exact tokenization depends on the model's tokenizer and varies enough between providers that "good enough for a watermark" is the operative bar.
Two callers consume this:
- The TUI status bar, which colors the token counter when usage crosses a configurable warn_threshold.
- The auto-summarization trigger, which fires before the next turn when usage crosses auto_threshold.
Both treat the numbers as ratios, not absolute counts, so a 10–15% estimation error is harmless.
The companion question — how big IS the model's window — lives in the catalog package (catalog.ResolveWindow / WindowFor): the window is a per-model/per-deployment fact sourced from the catalog, the user's override, or a live probe, none of which belong in this leaf estimation package (which would otherwise drag the catalog's config/network deps in, and form an import cycle via adapter).
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
func EstimateText ¶ added in v0.3.0
EstimateText returns an approximate token count for an arbitrary string under the same heuristic EstimateTokens uses. /context calls this for the system-prompt and memory-file buckets where the input isn't a Message slice.
func EstimateTokens ¶
EstimateTokens returns an approximate token count for the given messages. Tool-call argument JSON and tool-result content are counted; role metadata is not (it's bounded and small).
func EstimateToolSchemas ¶ added in v0.3.0
EstimateToolSchemas counts what the adapter advertises per tool: the tool name, description, and the JSON-serialized parameter schema. Mirrors what's actually sent on the wire so the /context Tools bucket matches the real cost.
Marshal errors fall back to a zero contribution for the offending tool — a malformed schema would have failed at registration time, so in practice this branch only fires for tools that pass nil/non-JSON schemas (which the adapter would reject anyway).
func SplitMessages ¶ added in v0.3.0
SplitMessages partitions a message slice into the system-prompt prefix and the conversation body, returning estimated token counts for each bucket. The split is by role: every RoleSystem message (typically just one) goes into the system bucket, everything else into conversation. /context charges the two to different buckets so the user can see the always-present system overhead separately from the growing chat history.
Types ¶
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Source Files