The tool-result persistence budget was a fixed 100K chars/result and 200K
chars/turn regardless of the active model. On a small-context model (e.g. a
65K-token local model switched into mid-session) a single large tool result
(reporter: a 279K-char search result) or a full 200K-char turn (~50K tokens)
could by itself approach or exceed the window, forcing an oversized request
that the provider rejects as "Prompt too long".
- budget_config.budget_for_context_window() scales per-result/per-turn char
caps to a fraction of the model window, clamped to the historical 100K/200K
defaults (large models unchanged) and floored so small models stay usable.
- resolve_threshold() now caps the per-tool registry value at default_result_size
so tools that register a fixed 100K cap (web/terminal/x_search) don't re-inflate
a scaled-down budget. No-op for the default budget (both 100K).
- tool_executor wires the agent's live context_length (recomputed on model
switch) into all four persist/turn-budget call sites.
read_file stays inf-pinned (no persist loop). Verified E2E: a 279K-char result
against a 65K model collapses to a ~1.6K preview; a 200K model is byte-identical
to today.
