marfrit
10848645af
Phase 0 implementation per PHASE0.md §6, §8.
Context.new(opts) constructs with the §6 default system prompt (the
`CMD: ` extraction contract is hard-coded in there per §3 — locked
substrate, do not edit). opts overrides: system_prompt, max_turns
(default 40), token_budget (default 4096; visibility only in Phase 0
per Q1, deferred to Phase 3 for accurate tokenization).
API:
ctx:append({role, content}) record a turn
ctx:to_messages() [{system,...}, ...turns] for broker.chat
ctx:enforce_budget() evict pairs (user+assistant) until
#turns <= max_turns; returns count
ctx:estimate_tokens() char/4 heuristic
ctx:reset() drop all turns (system_prompt kept)
System prompt is the §6 phrasing verbatim including the `CMD: ` clause
— stored on the context, NOT in self.turns, so it is prepended freshly
on every to_messages() call.
Smoke covers basic ops, no-evict-at-max, evict-on-overflow, bulk
eviction (14 turns -> 4), reset.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
78 lines
2.6 KiB
Lua
78 lines
2.6 KiB
Lua
-- context.lua — in-memory conversation history + token budget.
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-- Phase 0: ordered turn list, sliding-window eviction by max_turns.
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-- Tokenization is char/4 heuristic in Phase 0; accurate count is Phase 3 (Q1).
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-- See docs/PHASE0.md §6, §8.
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local M = {}
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-- The §6 default system prompt. The `CMD: ` (exact prefix, single space)
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-- contract is locked per §3 invariants — do not edit without amending PHASE0.
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local DEFAULT_SYSTEM_PROMPT = [[
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You are aish, an AI-augmented shell assistant. You help the user execute shell
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commands, write and debug code, and re-engineer software. When suggesting shell
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commands, output them on a line beginning with exactly "CMD: " so aish can
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identify and optionally execute them. Be concise. Prefer concrete actions over
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explanations unless asked.]]
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local Context = {}
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Context.__index = Context
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function M.new(opts)
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opts = opts or {}
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return setmetatable({
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system_prompt = opts.system_prompt or DEFAULT_SYSTEM_PROMPT,
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turns = {},
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max_turns = opts.max_turns or 40,
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token_budget = opts.token_budget or 4096,
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}, Context)
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end
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function Context:append(turn)
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assert(type(turn) == "table" and turn.role and turn.content,
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"context:append requires { role = ..., content = ... }")
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self.turns[#self.turns + 1] = { role = turn.role, content = turn.content }
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end
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-- Render the messages array for broker.chat (system prompt prepended; turns
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-- in order). The system prompt is NOT stored in self.turns per §6.
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function Context:to_messages()
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local msgs = { { role = "system", content = self.system_prompt } }
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for _, t in ipairs(self.turns) do
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msgs[#msgs + 1] = { role = t.role, content = t.content }
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end
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return msgs
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end
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-- Evict the oldest pair (user + assistant) while we exceed max_turns. Returns
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-- total turns evicted. Caller is responsible for rendering the §8 status line.
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function Context:enforce_budget()
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local evicted = 0
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while #self.turns > self.max_turns do
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table.remove(self.turns, 1)
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evicted = evicted + 1
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if #self.turns > self.max_turns or evicted % 2 == 1 then
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if #self.turns > 0 then
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table.remove(self.turns, 1)
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evicted = evicted + 1
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end
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end
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end
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return evicted
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end
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-- Coarse char/4 token estimate per §8. Phase 0 visibility only; accurate
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-- tokenization is Q1 (target Phase 3).
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function Context:estimate_tokens()
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local n = #self.system_prompt
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for _, t in ipairs(self.turns) do
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n = n + #t.content
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end
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return math.floor(n / 4)
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end
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function Context:reset()
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self.turns = {}
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end
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return M
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