Completes the reviewer requirement from PR #1190 review that was carried
over but not implemented in #1230:
> "The hard max is a function-local constant. For this setting, the ceiling
> should be configurable or at least represented as a named setting/default
> with tests."
— review on #1190#1230 shipped the adaptive auto-derivation but left `DEFAULT_HARD_MAX = 200_000`
as a hardcoded module constant in src/context_budget.py. Admins on premium
APIs with large context windows (kimi-k2 / minimax-m3 at 1M, etc.) can use
their full window today only by setting `agent_input_token_budget`
explicitly — which then takes them off the adaptive auto-path entirely.
## What this PR changes
- src/settings.py: register `agent_input_token_hard_max` in
DEFAULT_SETTINGS, default 200_000 (matches `DEFAULT_HARD_MAX`). Inline
comment documents the no-op semantics in the explicit branch.
- src/agent_loop.py: read the setting at the call site and pass it as the
`hard_max` kwarg of `compute_input_token_budget`. Defensive parsing —
missing / non-int / zero values fall back to `DEFAULT_HARD_MAX`, so a
misconfig cannot silently zero the budget.
- src/tool_implementations.py: three friendly aliases for `manage_settings`:
- "hard max" -> agent_input_token_hard_max
- "token budget cap" -> agent_input_token_hard_max
- "input budget cap" -> agent_input_token_hard_max
Plus the existing "token budget" -> agent_input_token_budget keeps a
matching shorter alias "input budget".
- tests/test_context_budget.py: 6 new tests on top of the existing 6:
- hard_max raises the auto ceiling (1M ctx + raised cap -> 85% of ctx)
- hard_max lowers the auto ceiling (128K ctx + 50K cap -> 50K)
- hard_max has no effect on the explicit branch
- DEFAULT_SETTINGS contains the new key
- manage_settings aliases are registered
- the live get_setting path returns the override value, and malformed
values fall back per the agent_loop defensive parsing
12 passed in 0.04s. No changes to the pure helper signature or semantics;
#1230's behavior is the default when the new setting is unset.
## How it lets users drop the explicit override
Before this PR, on a 1M-context model:
agent_input_token_budget = 900_000 (explicit) -> 900K [user override]
agent_input_token_budget = <unset> (auto) -> 200K [HARD_MAX]
After this PR, same model:
agent_input_token_budget = <unset>
agent_input_token_hard_max = 900_000
-> min(1M * 0.85, 900K) = 850K [auto, no override needed]
The explicit-override path keeps working unchanged for users who prefer it.
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