Context File Budget

Each context-file section (SOUL, AGENTS chain sections, other injected files) is capped by a character budget.

Two names, two meanings

Name	Meaning
CONTEXT_FILE_MAX_CHARS (= 20_000)	Code constant: fallback value and the floor of the dynamic calculation
context_file_max_chars (config.yaml)	Optional explicit key: when set, it is the exact ceiling for every context file

Rules

Case 1 — context_file_max_chars set in config.yaml:

context_file_max_chars: 20000

20 000 is then an exact ceiling: no context file exceeds it in the prompt. The dynamic calculation is disabled.

Case 2 — key absent: Hermes computes a budget from the model context window:

candidate = window_tokens × 4 × 6 %
budget    = min(500 000, max(20 000, candidate))

• 20 000 is the floor of the dynamic mode only;
• 500 000 is the cap of the dynamic mode;
• when the model window is unknown, the budget is 20 000 characters.

Model window	Dynamic budget	Effective budget
40 000 tokens	9 600 chars	20 000 chars (floor)
128 000 tokens	30 720 chars	30 720 chars
2 000 000 tokens	480 000 chars	480 000 chars
3 000 000 tokens	720 000 chars	500 000 chars (cap)

Application

• The budget is in characters, per context section.
• The merged AGENTS chain receives a second global cap at the same effective budget.
• Truncation is deterministic, not sampling: 70 % of the head and 20 % of the tail are kept, the middle is replaced by a marker telling the agent the path of the full file.
• An explicit context_file_max_chars: 20000 is an exact ceiling, never merely a floor.