# aish — Phase 8 Manifest **Project:** aish — AI-augmented conversational shell **Document:** Phase 8 Requirements, Architecture & Design Decisions **Status:** Plan + review fold-in (tree at `aa64ad3`) **Date:** 2026-05-16 **Review findings (independent Sonnet agent, 2026-05-16) — 2 BLOCKERs resolved in-place, 4 CONCERNs folded, 4 NITs applied:** R1 (BLOCKER, RESOLVED). **§5 pseudocode missing per-turn cache pattern.** The prose under the §5 code block correctly describes the cache, but the code block itself calls `self.tokenize_fn(t.content)` unconditionally — an implementer following the code would produce the O(N round-trips per call) behavior the prose flags as too slow. **Fix:** §5 code block updated to show the explicit cache-read-then-write pattern (`if t._tokens then ... else t._tokens = self.tokenize_fn(t.content) end`). §13 commit 2 row also calls this out explicitly. R2 (BLOCKER, RESOLVED). **enforce_budget loop can spin indefinitely when system_prompt alone exceeds token_budget.** If `[project]` block is 5000 tokens and `token_budget = 4096`, the loop's OR condition stays true even when `#turns == 0` — `table.remove` is a no-op, the loop never exits. **Fix:** §13 commit 3 row updated to specify the explicit guard: `while (#self.turns > self.max_turns or self:estimate_tokens() > self.token_budget) and #self.turns > 0 do`. When turns are exhausted, the loop exits gracefully even if the system prompt blows the budget (caller is on their own to reduce :project, :memory, etc.). R3 (CONCERN, FOLDED). **`:cost detail` comparison semantically undefined.** Sum-of-prompt_tokens across all calls (accumulator) vs current-snapshot estimate are incommensurable — sessions with evictions ALWAYS show divergence not because heuristic is wrong but because they measure different things. **Resolution:** §6 reworked to drop the per-slot `~est=N` inline annotation (which conflated the two); instead show a SINGLE trailing "[estimated session ctx: N tokens]" line under :cost detail. Cleanly separates the running-total accumulator from the current-snapshot estimate. §13 commit 4 already pointed to this direction — now §6 matches. R4 (CONCERN, FOLDED). **tokenize_fn closure must reference `active_cfg` by upvalue, not by value-capture.** If the implementer writes `local cfg = active_cfg; return function(text) ... cfg ... end`, the closure won't follow `:model` switches. **Fix:** §13 commit 4 row gains an explicit code note: the closure MUST be `function(text) return broker.token_count(active_cfg, text) end` — direct upvalue reference. A5 analysis verified upvalue semantics; now spelled out so the implementer doesn't subtly miss it. R5 (CONCERN, FOLDED). **2s tokenize timeout can spuriously cache as unsupported when llama.cpp is busy serving a concurrent completion.** llama.cpp is single-threaded for inference; a /tokenize request that arrives mid-generation queues behind inference and may exceed the 2s cap. The capability would then cache as `false` for the rest of the session, even though the endpoint IS capable. **Fix:** §9 risk row added documenting this. Mitigation: 2s is reasonable for IDLE responses but if practical problems surface, bump to 5s or make configurable (`cfg.tokenize.timeout_ms`). v1 ships 2s; revisit in verify if it bites. R6 (CONCERN, FOLDED). **Per-endpoint cache key conflates two same-endpoint/different-model presets.** B1 confirmed /tokenize ignores the model field, so two probes per session when one would suffice. **Fix:** §4 cache key SIMPLIFIED to just `model_cfg.endpoint` (B1-justified). Same-endpoint presets share one cache entry; one probe per endpoint per session, not per (endpoint, model). For a future broker that DOES honor the model field, this design choice would need revisiting — documented inline. R-N1..N4 (NITs, APPLIED): N1. §13 commit 3 condition uses uppercase `OR`/`AND` — corrected to Lua's lowercase `or`/`and`. N2. §10 Q-T5 row's "Resolution target" cell was empty; now reads "Baseline (B1)" for consistency. N3. §6 outdated inline `~est=N` description removed; new approach (single trailing summary line) is documented; §8 out-of-scope bullet about per-call comparison stays as the explicit "we considered, rejected" record. N4. PHASE8.md status header (formerly carrying a stale tree hash that would drift before implementation) now references the latest tree as of this fold-in (`aa64ad3`). Commit 5's status bump to "Implement" will refresh it again at that point. **Analyze findings (2026-05-16):** A1. **enforce_budget ONLY checks max_turns, not token_budget — major scope gap.** `Context:enforce_budget` (context.lua:319) iterates `while #self.turns > self.max_turns`; `self.token_budget = 4096` is set but NEVER consulted. So even with accurate tokenization, eviction decisions are unaffected — the new `estimate_tokens()` only feeds the prompt template's `{ctx_used}` display variable (repl.lua:630). **Resolution**: extend Phase 8 with a NEW pillar 5: make `enforce_budget` honor `token_budget` AS WELL AS max_turns — evict the oldest pair when EITHER threshold is exceeded. This is the real motivation for accurate tokenization; without it Phase 8 is largely cosmetic. Folded into §1 (5 pillars now), §3 (context.lua row), §9 (new risk row about under-eviction becoming over-eviction if tokenize_fn returns a much higher number than char/4). A2. **`ffi.curl.M.post` signature confirmed.** `(body, status)` on success, `(nil, err)` on failure. Matches the formulate-time sketch. status is the integer HTTP code. The probe checks `status == 200 and out` correctly. A3. **Single caller of `Context:estimate_tokens()` in tree.** Only `repl.lua:630` (prompt template `{ctx_used}` substitution) calls it. No internal callers in context.lua. This means: - The wiring point is ONE line in repl.lua (the prompt template already runs `ctx:estimate_tokens()` on every prompt render). - With A1's extension, `enforce_budget` becomes a SECOND caller — and a more frequent one (per turn, not per prompt render). - Per-turn `_tokens` cache becomes important for the enforce_budget path (called from ask_ai after every turn). A4. **Q-T1 RESOLVED**: per-turn `_tokens` cache lives on the turn dict. `:reset` clears `ctx.turns` so the cache dies with them. New turns get nil `_tokens`; lazy-set on first count. Trivial. A5. **Q-T2 RESOLVED**: tokenize_fn closure captures `active_cfg` as an UPVALUE. Upvalues are resolved at closure call time, not at definition time. When the user `:model cloud` switches, `active_cfg = config.models[name]` reassigns the local; subsequent tokenize_fn calls see the new value. Natural; no explicit re-binding needed. A6. **Q-T3 RESOLVED**: skip the probe entirely when `cfg.tokenize.use_endpoint = false` or unset. Don't even call `broker.token_count` — repl.lua won't wire `tokenize_fn` to Context.new in the first place. context.lua's tokenize_fn-nil branch handles it (char/4 fallback). A7. **Q-T6 RESOLVED (defer to follow-up)**: tools-schema tokens are a fixed cost per session (tools_schema doesn't change unless `:mcp connect/disconnect` lands a new session). The under-count is bounded and predictable. Defer to a future polish; v1 counts only messages. Document in §8 out-of-scope. A8. **Per-turn `_tokens` cache invalidation.** Turn `content` is immutable after append (we don't mutate stored turns). Cache is safe to live forever on the turn. The only invalidation event is `:reset` (clears turns wholesale). No other invalidation needed. A9. **Probe latency baseline** (Q-T4 deferred): probed manually during formulate — single tokenize call for ~50 char text ran in ~50ms locally. For 40 turns × 500 chars cached = 40 × 50ms = 2s ONLY on the first estimate after a fresh session. After caching, subsequent estimates are O(1) per turn (dict lookups). A10. **Streaming during `chat_stream` interleaves with tokenize?** No — `Context:estimate_tokens()` is called OUTSIDE the streaming callback (in the main loop, before/after broker calls). No concurrent network competition. A11. **MCP tool turn content** — `role:"tool"` turns have `content` strings too (the tool result). These get tokenized identically; no special-case needed. Cache key is the turn dict itself, so tool turns get their own `_tokens` slot. A12. **`include_usage` interaction with tokenize**: orthogonal. The tokenize probe uses a separate (non-streaming) `/tokenize` endpoint; never sees the chat completion's stream_options. PHASE0 is the locked substrate; PHASE1-7 are layered on top. This manifest specifies what Phase 8 adds — **accurate tokenization**: replace the char/4 heuristic on `Context:estimate_tokens()` with a per-broker `/tokenize` round-trip where supported, char/4 fallback otherwise. Resolves Q1 (`PHASE0.md §13`, originally targeted at Phase 3 — deferred forward across each phase). PHASE0 §11 amendment to add Phase 8 row lands in the same commit as this formulate doc. --- ## 1. Scope of Phase 8 Five pillars (A1 added pillar 5): 1. **Per-endpoint tokenize probe (cached)** — at first use, send a probe to the broker's tokenize endpoint with a tiny payload; if it returns `{tokens: [...]}` we mark the endpoint+model as tokenize- capable and use the actual count thereafter. If it 404s or errors, mark the slot as `tokenize_supported = false` and fall through to char/4 silently. Cached per `(endpoint, model)` for the session. 2. **`broker.token_count(model_cfg, text)`** — thin wrapper that returns an accurate token count when the (endpoint, model) is tokenize-capable, else the char/4 heuristic. Always returns a non-negative integer; never errors. The probe + fallback is transparent to callers. 3. **`Context:estimate_tokens()` widening** — currently char/4 over `system_prompt` + sum of `turn.content`s. The new shape accepts an optional `tokenize_fn` (callback) at `Context.new` time and uses it when present; falls back to char/4 when nil. `repl.lua` wires `tokenize_fn = function(text) return broker.token_count(active_cfg, text) end`. This means the active model's tokenizer is used for budgeting decisions, which matches the broker the next ask_ai will hit. 4. **`:cost detail` estimated-vs-actual column** — for each (model, category) slot in the accumulator, the actual `prompt_tokens` from broker usage is already stored. Add an estimated column computed via `broker.token_count` on the currently-buffered prompt-shape. Disagreement >10% surfaces in a tiny `~est=N` annotation so users can see when the heuristic diverges from reality. Display-only; no behavior change. 5. **`enforce_budget` consults `token_budget` (A1)** — currently `enforce_budget` only iterates `#turns > max_turns`. Extend to ALSO check `estimate_tokens() > token_budget`. Eviction fires when EITHER threshold is exceeded; the existing summarize-on- evict callback (Phase 5) still gets called per evicted pair. This is the real motivation for accurate tokenization — without it, the new token counts are display-only. Default budget (token_budget = 4096) was set at PHASE0 but never enforced; Phase 8 closes that gap. **Phase 8 is done when:** - A long-running session with the local `qwen-coder-7b-snappy-8k` model evicts at the RIGHT moment (token_budget=4096 hit triggers eviction via the new pillar 5 path) rather than only when max_turns is exceeded. - `broker.token_count(local_cfg, "hello world")` returns 2 (matches the live tokenize result, not the char/4=2 coincidence — verify via `:cost detail` against multi-paragraph text). - `broker.token_count(cloud_cfg, "hello world")` returns 2 (char/4 fallback when /tokenize 404s, which it does for OpenRouter). - Cached per-endpoint capability — the probe fires once per endpoint per session, not per call. - Existing configs without `cfg.tokenize` behave like Phase 7 (zero behavior change unless opted in via `cfg.tokenize.use_endpoint = true`). - `:cost detail` shows estimated-vs-actual where disagreement >10%, silent otherwise. --- ## 2. Technology Decisions (delta from Phase 7) | Decision | Choice | Rationale | |---|---|---| | Tokenize endpoint path | `/tokenize` (NOT `/v1/tokenize`) | Per real probe against hossenfelder: `/v1/tokenize` returns 404; `/tokenize` returns `{tokens: [...]}`. This is the llama.cpp server convention. | | Request body shape | `{"content": "", "model": ""}` | Local model echoed via `model`; llama.cpp ignores it but harmless. Probed shape works. | | Capability detection | Per-call optimistic probe; on 404/non-200, cache `tokenize_supported[endpoint][model] = false` and never retry that session | One round-trip cost on first miss; zero on subsequent. Sessions are short enough that re-probe across restarts is fine. | | Fallback heuristic | char/4 (Phase 0 §8 convention) | Established; underestimates ~10% on real code/prose per baseline B1, but acceptable when no better signal available. | | `Context:estimate_tokens` calling convention | Optional `tokenize_fn` callback at Context.new; absent = char/4 (existing behavior) | Backward-compatible; no caller break. Opt-in via repl.lua. | | Active-model tokenizer | repl.lua wires `tokenize_fn` against `active_cfg` (the currently active model), so eviction decisions match the broker the next call will hit | When the user `:model cloud` switches mid-session, subsequent estimates use cloud's tokenizer (which falls back to char/4 since OpenRouter has no /tokenize). | | Caching strategy | Endpoint+model capability flag only; NOT per-text token-count cache | Token counts depend on text content; caching adds memory + correctness risk for marginal speed. Probe latency dominates only on first call per endpoint. | | Per-text timeout cap | 2s for tokenize calls (much tighter than the model's normal timeout_ms) | Tokenize is a small, fast operation; if it doesn't respond in 2s, the endpoint is misbehaving. Bail to char/4. | | `:cost detail` est-vs-actual | Show only when disagreement >10%; format `(prompt: 558 ~est=508 / completion: 80)` for the disagreement case, `(prompt: 558 / completion: 80)` otherwise | Always-on noise; suppress when heuristic is close. | | New config key | `cfg.tokenize = { use_endpoint = true }` — default false until user opts in | Network round-trip cost; user-acknowledged behavior change. | --- ## 3. Module Changes | File | State after Phase 7 | Phase 8 changes | |---|---|---| | `broker.lua` | `chat`, `chat_stream`, `build_request` (opts-widened in Phase 7) | New `M.token_count(model_cfg, text)`: tries `/tokenize` once per (endpoint, model); caches capability; returns int. New `M.tokenize_supported(model_cfg)` introspection helper for tests. | | `context.lua` | `estimate_tokens()` char/4 sum over system_prompt + turn.contents; `enforce_budget()` only checks max_turns | Widen `estimate_tokens` to use `self.tokenize_fn(text)` if present; else char/4. Per-turn `_tokens` cache on each turn dict; lazy-set on first count. Extend `enforce_budget` to ALSO evict when `estimate_tokens() > token_budget` (A1 — pillar 5). | | `repl.lua` | wires Context.new with summarize_fn, hosts all metas | `tokenize_fn` wired into Context.new when `cfg.tokenize.use_endpoint = true`. `:cost detail` extended with est-vs-actual column. | | `config.lua` | Phase 7 cost block example | Add commented-out `tokenize = { use_endpoint = true }` block. | | `docs/PHASE0.md` | §11 lists phases 0-7 | Amendment: add Phase 8 row to §11. | No new module files. --- ## 4. Pillar 1+2 — `broker.token_count(model_cfg, text)` R6-revised — cache key is endpoint-only (B1: /tokenize ignores the model field so two presets sharing an endpoint share one cache entry): ```lua -- Per-endpoint capability cache (session-scoped local in broker.lua). -- Keyed by endpoint only (B1: hossenfelder's /tokenize ignores the -- model field; same endpoint -> same tokenization). If a future -- broker honors the model field, revisit this keying. local _tokenize_capable = {} -- [endpoint] = true | false function M.token_count(model_cfg, text) text = text or "" if text == "" then return 0 end if not (model_cfg and model_cfg.endpoint) then return math.floor(#text / 4) -- pure fallback end local ep = model_cfg.endpoint local cap = _tokenize_capable[ep] if cap == false then return math.floor(#text / 4) end -- cap == nil OR cap == true; try the endpoint. local url = ep:gsub("/+$", "") .. "/tokenize" local body = json.encode({ content = text, model = model_cfg.model }) local out, status = curl.post(url, body, { "Content-Type: application/json" }, 2000) -- 2s timeout if not (status == 200 and out) then _tokenize_capable[ep] = false return math.floor(#text / 4) end local doc = json.decode(out) local toks = doc and doc.tokens if type(toks) ~= "table" then _tokenize_capable[ep] = false return math.floor(#text / 4) end _tokenize_capable[ep] = true return #toks end function M.tokenize_supported(model_cfg) if not (model_cfg and model_cfg.endpoint) then return nil end return _tokenize_capable[model_cfg.endpoint] end ``` Uses Phase 1's `ffi/curl.M.post` (blocking POST, returns body + status). --- ## 5. Pillar 3 — `Context:estimate_tokens` widening R1-revised — cache pattern is IN the reference code, not just prose: ```lua function M.new(opts) ... return setmetatable({ ... -- Phase 8: optional callback that returns an accurate token -- count for a given text. Set by repl.lua when cfg.tokenize. -- use_endpoint=true, calling broker.token_count(active_cfg, ...). -- nil = char/4 fallback (Phase 0 §8 behavior). tokenize_fn = opts.tokenize_fn, }, Context) end function Context:estimate_tokens() if self.tokenize_fn then -- system_prompt is recomposed per call (memory/project/summary -- blocks are dynamic) — re-tokenize every estimate. Bounded -- by one round-trip. local n = self.tokenize_fn(self.system_prompt) -- R1: per-turn cache on the turn dict itself. Turn content -- is immutable after append (A8) so the cache never goes -- stale; turns dying with :reset takes the cache with them. for _, t in ipairs(self.turns) do if t._tokens == nil then t._tokens = self.tokenize_fn(t.content) end n = n + t._tokens end return n end -- char/4 fallback (existing behavior) local n = #self.system_prompt for _, t in ipairs(self.turns) do n = n + #t.content end return math.floor(n / 4) end ``` Performance: first call after a fresh session fires N+1 round-trips (N turns + 1 system prompt). Subsequent calls fire 1 (system prompt) + N dict lookups. For N=40, that's 40 × ~30ms = 1.2s one-time + ~30ms amortized per call — acceptable for the prompt-template render path AND the per-step Norris enforce_budget call. --- ## 6. Pillar 4 — `:cost detail` est-vs-actual Current `:cost detail` (Phase 7) shows: ``` anthropic/claude-haiku-4.5 main 1 calls, 179 / 8 tokens, $0.000219 ``` The `179 / 8` is `prompt_tokens / completion_tokens` SUMMED across all calls in that slot — including any turns later evicted from context. R3-revised Phase 8 extension: an inline per-slot "estimated" annotation would conflate two different things — the per-slot prompt_tokens is a cumulative running total (across calls AND past evicted turns), while `estimate_tokens()` is a current-snapshot measurement (in-memory turns ONLY). Comparing them directly is misleading; sessions with evictions would always show divergence. Instead, add a SINGLE trailing summary line after the slot rows: ``` ... per-slot rows ... [estimated session ctx: 412 tokens; token_budget=4096 (10% used)] ``` The estimate is `ctx:estimate_tokens()` over the current ctx (system prompt + live turns); the percentage gives at-a-glance budget utilization. This is purely informational; no annotation on the accumulator rows themselves. --- ## 7. UX Surface Summary | Meta | Behavior change | |---|---| | `:cost detail` | Adds `~est=N` annotation per slot when heuristic disagreement >10% | | (no new metas in v1) | | | Config | Default | Effect | |---|---|---| | `cfg.tokenize.use_endpoint` | false | When true, repl.lua wires `tokenize_fn` so context budgeting uses real token counts | The `cfg.tokenize` block being opt-in is conservative: enabling it means every `Context:estimate_tokens()` call may hit the broker. For local llama.cpp the cost is ~50ms; for cloud-only configurations there IS no /tokenize endpoint so we silently fall through to char/4 (cached after one probe). No surprise; document in config example. --- ## 8. Out of Scope (Phase 8) - **Cost preflight enforcement** — option 2 of the Phase 7 §12 candidates. The tokenize work here is a PREREQUISITE for accurate preflight cost estimation, but the enforcement layer itself (cap_at_dollars that REFUSES the call) is its own surface — defer to a separate phase. - **Cross-session cost rollup** — option 1 of Phase 7 §12 candidates. Independent of tokenization. - **Streaming tokenize** — some servers expose streaming tokenize endpoints for partial-prompt token counts during generation. Out of scope here; we use the blocking /tokenize for batch estimates. - **Multi-tokenizer support** (e.g. tiktoken for OpenAI compat, sentencepiece for HuggingFace) — would require vendoring a C library (violates PHASE0 §3) or shelling out to python. Endpoint-based is the only substrate-compliant option for accuracy beyond char/4. - **Tokenization for `:cost detail` rows that span multiple turns** — the actual `prompt_tokens` in the accumulator slot is the sum ACROSS calls; the estimate for comparison should be over the CURRENT ctx content. Show the per-call comparison only. --- ## 9. Risks | Risk | Mitigation | |---|---| | `/tokenize` 404 silently cached as `tokenize_supported = false` for a typo'd endpoint config | Per-session cache; restart re-probes. Acceptable. | | Tokenize round-trip on every prompt eviction check adds 50ms × N turns latency | `turn._tokens` per-turn cache set at append-time; only re-tokenize on cache miss. | | Hossenfelder proxy may forward `/tokenize` differently than direct llama.cpp (e.g., adds `/v1/` prefix expected) | B1 confirms `/tokenize` works against hossenfelder; other proxies untested but the design degrades gracefully (char/4 fallback). | | Cloud models without /tokenize emit no probes after first 404 — fine but `:cost detail` est-vs-actual will always agree (both are char/4 then) | Documented; no fix needed. Display annotation hides when est=actual exactly OR within 10%. | | `Context:estimate_tokens` callers downstream expect synchronous fast return (currently O(N) string ops); new path is O(N) round-trips | Per-turn cache makes amortized cost O(1) per turn after first count. | | Endpoint URL handling — currently `endpoint .. "/v1/chat/completions"` is hardcoded; tokenize uses `endpoint .. "/tokenize"` (no /v1) — asymmetric | Document the asymmetry inline; the llama.cpp convention is that completions go through /v1 (OpenAI compat) but server-internal endpoints like /tokenize do not. | | A1 pillar 5 — accurate tokenization could cause EARLIER eviction than the char/4 heuristic (real counts are higher per baseline). User session that fit in 4096 tokens under char/4 may now spill. | Default `token_budget = 4096` was set in Phase 0; accurate counts mean Phase 8 finally ENFORCES it. Users on `cfg.context.token_budget` defaults may see eviction earlier than before — document as intentional. Users can raise `token_budget` per their model's real context window. | | R5 — 2s tokenize timeout could spuriously cache-as-unsupported when the llama.cpp backend is busy with a concurrent completion (single-threaded inference, /tokenize queues behind it). Once cached false, char/4 takes over for the rest of the session even though the endpoint IS capable. | 2s is fine for idle responses; bumping to 5s or making it configurable (`cfg.tokenize.timeout_ms`) is a v1.1 polish if it bites in practice. Documented; revisit during verify. | --- ## 10. Open Questions (Phase 8) | # | Question | Impact | Resolution target | |---|---|---|---| | Q-T1 | Per-turn `_tokens` cache across `:reset` | A4 — dies with turns; new turns get nil and lazy-set on first count. Trivial. | | Q-T2 | `tokenize_fn` re-bind on `:model` switch | A5 — closure captures `active_cfg` upvalue; resolved at call time; follows `:model` switch naturally. No explicit re-binding needed. | | Q-T3 | Probe respects opt-out | A6 — when `cfg.tokenize.use_endpoint = false`, repl.lua doesn't wire `tokenize_fn`; context.lua's nil branch takes the char/4 fallback. No probe call at all. | | Q-T4 | Tokenize round-trip latency | A9 — ~50ms per call locally for typical ~500-char turn. With per-turn cache, amortized O(1) per turn after first count. | | Q-T5 | `/tokenize` honors `model` field | B1 RESOLVED — `/tokenize` IGNORES the model field; returns the loaded backend's tokenization. Acceptable (BPE >> char/4 even with wrong tokenizer); cache key simplified to endpoint-only per R6. | | Q-T6 | tools-schema tokens | A7 — deferred to follow-up. Tools schema is fixed per session (changes only on :mcp connect/disconnect); under-count is bounded. v1 counts messages only. | --- ## 11. Phase 8 → Phase 9+ Out-of-band Candidate follow-ups (non-binding): - **Phase 9**: cost preflight enforcement (Phase 7 §12 option 2) — uses Phase 8's accurate token counts to refuse calls that would cross `cap_at_dollars`. The accuracy work here is the foundation. - **Cross-session cost rollup** (Phase 7 §12 option 1) — independent; could land in parallel. - **Phase X**: project-local config overlay (`.aish.lua`) — was the alternative scope to Phase 7's cost work. Still valuable but independent of any current line. Phase 8 itself is self-contained — no upstream dependencies. --- ## 13. Implementation Plan (commit-by-commit) Bottom-up: broker first (the egress capability all callers depend on), then context (the consumer + the new pillar 5 budget extension), then repl.lua wiring + display, then config + status bump. Each commit leaves the tree green (existing tests + load smoke + per- commit feature smoke). ### Order 1. **`broker.lua` — `M.token_count` helper + per-endpoint capability cache.** - Module-local `_tokenize_capable` table keyed by `endpoint .. "/" .. model`. - `M.token_count(model_cfg, text)`: - empty text -> 0 - bad cfg (no endpoint) -> char/4 immediately - capability cache says `false` for this slot -> char/4 - otherwise: probe `/tokenize` with `{content, model}` body, 2s timeout. On `status == 200 + parseable {tokens=[...]}`: cache `true`, return `#tokens`. Anything else (non-200, parse fail, transport err): cache `false`, char/4. - `M.tokenize_supported(model_cfg)` returns the cache slot for introspection (tests + future :tokenize meta). - Smoke: hand-call `M.token_count(local_cfg, "hello world")` -> 2; `M.token_count(cloud_cfg, "hello world")` -> 2 (char/4 fallback; cache marks cloud as unsupported on first try). 2. **`context.lua` — estimate_tokens widening + per-turn cache.** - Context.new accepts `opts.tokenize_fn` -> stored as `self.tokenize_fn`. - `Context:estimate_tokens()`: - if `tokenize_fn` is nil: existing char/4 (no behavior change). - else: tokenize `system_prompt` (no caching — system prompt changes per turn due to dynamic blocks). For each turn: if `turn._tokens` is set use it; else compute via tokenize_fn AND cache on turn._tokens. - No new helper; the change is internal to estimate_tokens. - Smoke: synthetic Context with stub tokenize_fn that returns N=42 for every call; verify estimate sums correctly + cache populates turn._tokens. 3. **`context.lua` — enforce_budget honors token_budget (pillar 5).** - Existing `while #self.turns > self.max_turns` loop extended. **R2 guard** — when system_prompt alone exceeds budget AND turns are empty, the loop must exit (not spin trying to evict nothing). Correct condition: ```lua while (#self.turns > self.max_turns or self:estimate_tokens() > self.token_budget) and #self.turns > 0 do ``` Lowercase `or`/`and` per Lua syntax (N1). - Per-pair eviction otherwise unchanged (summarize callback, status_evictions). - The estimate_tokens call inside the loop is potentially expensive under tokenize_fn — but commit #2's per-turn cache means each iteration is O(#turns) dict-lookups after the first. Acceptable for the eviction hot path. - Smoke: (a) Context with `token_budget = 100`, max_turns = 100, fill with turns until `estimate_tokens() > 100`, then call enforce_budget — should evict until under budget. (b) R2 case: synthetic system_prompt of 500 chars (char/4 = 125 tokens) + token_budget = 100 + zero turns — call enforce_budget; must return immediately, not spin. 4. **`repl.lua` — tokenize_fn wiring + :cost detail estimate row.** - When `config.tokenize and config.tokenize.use_endpoint`, build `ctx_opts.tokenize_fn = function(text) return broker.token_count(active_cfg, text) end`. **R4: the closure body MUST reference `active_cfg` directly as an upvalue, NOT capture it by value** (`local cfg = active_cfg; return function() ... cfg ... end` would freeze to the value at closure-construction time and miss `:model` switches). A5 verified upvalue semantics in Lua. - `:cost detail` extension per R3: ONE trailing summary line under the existing per-slot rows showing `[estimated session ctx: N tokens; token_budget=M (X% used)]`. N comes from `ctx:estimate_tokens()` (current snapshot, NOT a comparison against the accumulator sum — they measure different things). M is `ctx.token_budget`. X% = N/M × 100. - Smoke: with use_endpoint=true on a local-only session, observe enforce_budget eviction timing vs disabled; observe :cost detail estimate row updates as turns accumulate. 5. **`config.lua` example block + `docs/PHASE8.md` status bump.** - Commented-out `tokenize = { use_endpoint = true }` block in config.lua with parity to Phase 1-7 example blocks. Document the per-endpoint network cost (one probe per session) and the implication: token_budget actually enforces now. - PHASE8.md status header -> **Implement**. ### Risk index per commit | Commit | Risk | Mitigation | |---|---|---| | 1 (broker) | Per-endpoint cache leaks across model_cfg deletions (e.g., user removes a model from config mid-session) | Cache is keyed by string; stale entries don't grow without bound (bounded by #configured models × 1). No GC needed. | | 1 (broker) | /tokenize probe blocks the calling thread for 2s on a misconfigured endpoint | 2s timeout is the cap; one-shot per endpoint per session. | | 2 (context) | per-turn `_tokens` cache miss on every estimate when no tokenize_fn -> existing perf preserved | Cache check is conditional on tokenize_fn presence; char/4 path untouched. | | 3 (context) | enforce_budget loop now calls estimate_tokens potentially every iteration; with tokenize_fn that's O(#turns) per iteration -> O(#turns^2) worst case | Per-turn cache makes this O(#turns) amortized after first fill. For typical max_turns=40 + token_budget=4096 sessions: ~40^2 dict lookups = 1600 ops in worst case, microsecond cost. | | 3 (context) | accurate counts mean token_budget=4096 (Phase 0 default) finally ENFORCES — sessions that fit under char/4 may now evict earlier | Documented in §9; user can raise token_budget to match their model's real context window. | | 4 (repl) | tokenize_fn closure binding to `active_cfg` upval — if upval somehow gets reassigned wrong, eviction uses wrong tokenizer | Lua upvalues are call-time-resolved; A5 verified. Test by smoke after `:model` switch. | | 5 (config + status) | none | | ### Tests + smoke per commit Each commit: - Pass `luajit test_safety.lua` (87/87) and `luajit test_router_model.lua` (31/31) - Load cleanly via `luajit -e 'package.path=...; require("repl"); print("ok")'` - Pass a per-feature smoke (described in each row above) ### Things deliberately NOT split - New module file for tokenize — small enough to live in broker.lua. - Per-text token cache (in addition to per-turn): not needed; turn content is immutable post-append. - :tokenize meta for introspecting the cache — `M.tokenize_supported` is exported for testing; if a user needs runtime visibility, that's a follow-up. ### Open at plan-time (resolve at implement) - :cost detail layout — how exactly to show "estimated session ctx" relative to the existing per-slot rows. Pick at commit 4 (likely a single trailing line under the detail table). - Whether to expose `:tokenize ` for direct-probe debugging. Nice-to-have; defer unless useful during verify.