| 💾 Saved. d722711 k33g 4h ago | 1 | // Package compact keeps the conversation history inside the model's context |
| 2 | // window. When the history grows past a threshold, the OLD question turns are |
| 3 | // replaced by ONE summary written by the model itself, and the last N turns |
| 4 | // stay raw — the hybrid of CONTEXT_WINDOW.md § 2.e. |
| 5 | // |
| 6 | // Why it exists: nothing in the agent ever shortens `messages`. Measured with |
| 7 | // the fake engine of part 03, the history sent to the model grew 2 → 5 → 7 → 9 |
| 8 | // messages over four requests, and every `bash` output (up to maxOutput |
| 9 | // characters) stays until /quit. On a local model the window is fixed at load |
| 10 | // time, so a long session first shows up as a false watchdog stall, then as a |
| 11 | // 400 from the engine. |
| 12 | // |
| 13 | // The package never calls the model directly: it builds the summary request |
| 14 | // and hands it to a Summarizer (engine.Summarize in production, a function |
| 15 | // returning a fixed text in tests). It knows nothing about the screen either — |
| 16 | // the report line is the agent's job. |
| 17 | package compact |
| 18 | |
| 19 | import ( |
| 20 | "context" |
| 21 | "encoding/json" |
| 22 | "errors" |
| 23 | "fmt" |
| 24 | "slices" |
| 25 | "strings" |
| 26 | "time" |
| 27 | |
| 28 | "mm/internal/config" |
| 29 | |
| 30 | "github.com/firebase/genkit/go/ai" |
| 31 | ) |
| 32 | |
| 33 | // Summarizer answers a request built by this package — a system message, the |
| 34 | // old turns, then the prompt as a user message — with plain text. |
| 35 | type Summarizer func(ctx context.Context, request []*ai.Message) (string, error) |
| 36 | |
| 37 | // Result describes one compression, for the one-line report. |
| 38 | type Result struct { |
| 39 | Messages []*ai.Message |
| 40 | Compressed int // messages replaced by the summary pair |
| 41 | Kept int // raw messages kept after the summary (system excluded) |
| 42 | Before int // estimated tokens before |
| 43 | After int // estimated tokens after |
| 44 | Elapsed time.Duration |
| 45 | } |
| 46 | |
| 47 | // Report is the one-line account of a compression, shared by the two front |
| 48 | // ends so the terminal and the editor say the same thing: |
| 49 | // |
| 50 | // compressed 12 messages → 1 summary + 4 kept (18.2k → 6.1k tokens, 3.4s) |
| 51 | func (r Result) Report() string { |
| 52 | return fmt.Sprintf("compressed %d messages → 1 summary + %d kept (%s → %s tokens, %s)", |
| 53 | r.Compressed, r.Kept, kilo(r.Before), kilo(r.After), seconds(r.Elapsed)) |
| 54 | } |
| 55 | |
| 56 | // kilo prints a token count the way the banner does: 18.2k, not 18234. |
| 57 | func kilo(n int) string { |
| 58 | if n < 1000 { |
| 59 | return fmt.Sprintf("%d", n) |
| 60 | } |
| 61 | return fmt.Sprintf("%.1fk", float64(n)/1000) |
| 62 | } |
| 63 | |
| 64 | // seconds prints a duration with one decimal under ten seconds, none above. |
| 65 | func seconds(d time.Duration) string { |
| 66 | if d < 10*time.Second { |
| 67 | return fmt.Sprintf("%.1fs", d.Seconds()) |
| 68 | } |
| 69 | return fmt.Sprintf("%ds", int(d.Seconds())) |
| 70 | } |
| 71 | |
| 72 | // ErrNothingToCompact is returned when the history holds no turn older than |
| 73 | // the ones to keep. It is not a failure: the threshold can be reached inside a |
| 74 | // single long turn, and there is then nothing to summarise yet. |
| 75 | var ErrNothingToCompact = errors.New("nothing to compact") |
| 76 | |
| 77 | // metaKey marks the two messages a compression inserts, so that a later |
| 78 | // compression recognises an earlier summary (and merges it instead of |
| 79 | // summarising it a second time — detail decays exponentially otherwise). |
| 80 | const metaKey = "compact" |
| 81 | |
| 82 | // Decision says whether to compress before the next question, and on what |
| 83 | // grounds. Tokens is the figure that was compared to the threshold; it is |
| 84 | // reported even when nothing triggers, for the /context-style displays. |
| 85 | type Decision struct { |
| 86 | Compact bool |
| 87 | Tokens int |
| 88 | Reason string // "tokens", "messages", or "" when nothing triggered |
| 89 | } |
| 90 | |
| 91 | // Decide applies the automatic trigger. |
| 92 | // |
| 93 | // `measured` is the input-token count the engine reported for the last call |
| 94 | // to the model (0 when it reported nothing, as the fake engine does). The |
| 95 | // larger of it and the local estimate is used: the measure sees what the |
| 96 | // estimate cannot (the tools' JSON, the chat template), but it lags one call |
| 97 | // behind and dies with the compression that made it stale — the caller |
| 98 | // forgets it after a successful compression. |
| 99 | // |
| 100 | // `window` is the served context size as far as the agent knows it: the |
| 101 | // yaml's `contextWindow`, or what the provider's probe learned from the server |
| 102 | // (llama-server's /props) — see engine.Engine.ContextWindow. 0 = unknown, and |
| 103 | // then only MaxMessages can trigger. |
| 104 | func Decide(msgs []*ai.Message, measured, window int, cfg config.ContextConfig) Decision { |
| 105 | d := Decision{Tokens: max(Estimate(msgs), measured)} |
| 106 | if !cfg.Enabled { |
| 107 | return d |
| 108 | } |
| 109 | switch { |
| 110 | // Cross-multiplied to stay in integers: tokens ≥ window × threshold / 100. |
| 111 | case window > 0 && d.Tokens*100 >= window*cfg.Threshold: |
| 112 | d.Compact, d.Reason = true, "tokens" |
| 113 | case cfg.MaxMessages > 0 && len(msgs) >= cfg.MaxMessages: |
| 114 | d.Compact, d.Reason = true, "messages" |
| 115 | } |
| 116 | return d |
| 117 | } |
| 118 | |
| 119 | // Compact replaces every turn but the last cfg.KeepLastTurns by a summary pair |
| 120 | // (a user message carrying the notes, a short model acknowledgement), inserted |
| 121 | // right after the system prompt. The kept turns are reused as they are, so the |
| 122 | // tool_call/tool_result pairs inside them cannot be split; the cut itself falls |
| 123 | // on a turn boundary, never on a message count. |
| 124 | // |
| 125 | // On any error the caller's history is left untouched: the returned Result is |
| 126 | // empty and `msgs` was never modified. |
| 127 | func Compact(ctx context.Context, msgs []*ai.Message, cfg config.ContextConfig, summarize Summarizer) (Result, error) { |
| 128 | start := time.Now() |
| 129 | |
| 130 | head, turns := Split(msgs) |
| 131 | keep := max(cfg.KeepLastTurns, 1) |
| 132 | if len(turns) <= keep { |
| 133 | return Result{}, ErrNothingToCompact |
| 134 | } |
| 135 | old, recent := turns[:len(turns)-keep], turns[len(turns)-keep:] |
| 136 | |
| 137 | // An earlier summary that is the only old turn: re-summarising a summary |
| 138 | // loses detail and gains nothing. |
| 139 | merge := IsSummary(old[0][0]) |
| 140 | if merge && len(old) == 1 { |
| 141 | return Result{}, ErrNothingToCompact |
| 142 | } |
| 143 | |
| 144 | oldMsgs := flatten(old) |
| 145 | text, err := summarize(ctx, Request(oldMsgs, cfg.Prompt, merge)) |
| 146 | if err != nil { |
| 147 | return Result{}, err |
| 148 | } |
| 149 | if strings.TrimSpace(text) == "" { |
| 150 | return Result{}, errors.New("empty summary") |
| 151 | } |
| 152 | |
| 153 | questions := len(old) |
| 154 | if merge { |
| 155 | questions-- // the summary pair is not a question the user asked |
| 156 | } |
| 157 | pair := SummaryPair(text, len(oldMsgs), questions, commands(oldMsgs)) |
| 158 | |
| 159 | out := make([]*ai.Message, 0, len(head)+len(pair)+len(msgs)) |
| 160 | out = append(out, head...) |
| 161 | out = append(out, pair...) |
| 162 | kept := flatten(recent) |
| 163 | out = append(out, kept...) |
| 164 | |
| 165 | // The safety net: the cut above cannot split a pair, but the check is |
| 166 | // cheap and the failure it guards against is a 400 on the next question. |
| 167 | if err := Valid(out); err != nil { |
| 168 | return Result{}, fmt.Errorf("compressed history is invalid: %w", err) |
| 169 | } |
| 170 | |
| 171 | return Result{ |
| 172 | Messages: out, |
| 173 | Compressed: len(oldMsgs), |
| 174 | Kept: len(kept), |
| 175 | Before: Estimate(msgs), |
| 176 | After: Estimate(out), |
| 177 | Elapsed: time.Since(start), |
| 178 | }, nil |
| 179 | } |
| 180 | |
| 181 | // Split separates the leading system message(s) from the question turns. A |
| 182 | // turn starts at a user message and runs until the next one, so it holds the |
| 183 | // whole model ↔ tools exchange the question caused; an earlier summary pair is |
| 184 | // a turn of its own, since it starts with a user message too. |
| 185 | // |
| 186 | // Every strategy of CONTEXT_WINDOW.md cuts on these boundaries: cutting on a |
| 187 | // message count can leave a `tool` message without the `assistant` that asked |
| 188 | // for it, which the OpenAI API refuses outright. |
| 189 | func Split(msgs []*ai.Message) (head []*ai.Message, turns [][]*ai.Message) { |
| 190 | i := 0 |
| 191 | for i < len(msgs) && msgs[i].Role == ai.RoleSystem { |
| 192 | i++ |
| 193 | } |
| 194 | head = msgs[:i] |
| 195 | for _, m := range msgs[i:] { |
| 196 | if m.Role == ai.RoleUser || len(turns) == 0 { |
| 197 | turns = append(turns, nil) |
| 198 | } |
| 199 | turns[len(turns)-1] = append(turns[len(turns)-1], m) |
| 200 | } |
| 201 | return head, turns |
| 202 | } |
| 203 | |
| 204 | // Valid checks what an OpenAI-compatible server checks before answering: the |
| 205 | // history starts with the system prompt, every tool request sits in a model |
| 206 | // message, and every tool response answers a request seen earlier — paired by |
| 207 | // Ref when the server set one, by tool name otherwise (same rule as |
| 208 | // engine.executed). |
| 209 | func Valid(msgs []*ai.Message) error { |
| 210 | if len(msgs) == 0 || msgs[0].Role != ai.RoleSystem { |
| 211 | return errors.New("history does not start with the system prompt") |
| 212 | } |
| 213 | type call struct{ ref, name string } |
| 214 | var pending []call |
| 215 | for i, m := range msgs { |
| 216 | for _, p := range m.Content { |
| 217 | switch { |
| 218 | case p.IsToolRequest() && p.ToolRequest != nil: |
| 219 | if m.Role != ai.RoleModel { |
| 220 | return fmt.Errorf("message %d: tool request in a %s message", i, m.Role) |
| 221 | } |
| 222 | pending = append(pending, call{p.ToolRequest.Ref, p.ToolRequest.Name}) |
| 223 | case p.IsToolResponse() && p.ToolResponse != nil: |
| 224 | r := p.ToolResponse |
| 225 | j := slices.IndexFunc(pending, func(c call) bool { |
| 226 | if r.Ref != "" { |
| 227 | return c.ref == r.Ref |
| 228 | } |
| 229 | return c.name == r.Name |
| 230 | }) |
| 231 | if j < 0 { |
| 232 | return fmt.Errorf("message %d: tool response %q answers no pending request", i, r.Name) |
| 233 | } |
| 234 | pending = slices.Delete(pending, j, j+1) |
| 235 | } |
| 236 | } |
| 237 | } |
| 238 | return nil |
| 239 | } |
| 240 | |
| 241 | // Estimate approximates the token count of a history without asking the |
| 242 | // engine: characters divided by 3.5, plus a few tokens of framing per message. |
| 243 | // |
| 244 | // 4 characters per token holds for English prose; code, JSON, paths and French |
| 245 | // tokenise closer to 3. Taking 3.5 over-estimates prose a little, which is the |
| 246 | // safe side for a threshold. The engine's own count, when it reports one, is |
| 247 | // preferred by Decide — this is the fallback, and the number the report shows |
| 248 | // for a history that was never sent. |
| 249 | func Estimate(msgs []*ai.Message) int { |
| 250 | chars := 0 |
| 251 | for _, m := range msgs { |
| 252 | for _, p := range m.Content { |
| 253 | switch { |
| 254 | case p.IsText(): |
| 255 | chars += len(p.Text) |
| 256 | case p.IsToolRequest() && p.ToolRequest != nil: |
| 257 | chars += len(p.ToolRequest.Name) + len(jsonOf(p.ToolRequest.Input)) |
| 258 | case p.IsToolResponse() && p.ToolResponse != nil: |
| 259 | chars += len(p.ToolResponse.Name) + len(jsonOf(p.ToolResponse.Output)) |
| 260 | } |
| 261 | } |
| 262 | } |
| 263 | return (chars*2+6)/7 + 4*len(msgs) |
| 264 | } |
| 265 | |
| 266 | // jsonOf renders a tool payload the way the request will carry it. A string |
| 267 | // output is taken as-is: marshalling it would count the escaping twice. |
| 268 | func jsonOf(v any) string { |
| 269 | if s, ok := v.(string); ok { |
| 270 | return s |
| 271 | } |
| 272 | b, err := json.Marshal(v) |
| 273 | if err != nil { |
| 274 | return fmt.Sprint(v) |
| 275 | } |
| 276 | return string(b) |
| 277 | } |
| 278 | |
| 279 | // IsSummary reports whether a message is the notes half of a summary pair. |
| 280 | func IsSummary(m *ai.Message) bool { |
| 281 | return m != nil && m.Role == ai.RoleUser && m.Metadata[metaKey] == "summary" |
| 282 | } |
| 283 | |
| 284 | // flatten joins turns back into one message list. |
| 285 | func flatten(turns [][]*ai.Message) []*ai.Message { |
| 286 | var out []*ai.Message |
| 287 | for _, t := range turns { |
| 288 | out = append(out, t...) |
| 289 | } |
| 290 | return out |
| 291 | } |
| 292 | |
| 293 | // commands counts the bash commands that actually ran in a history — one per |
| 294 | // response of the `bash` tool, the same measure as engine.Commands. It is not |
| 295 | // imported from engine so that this package stays free of Genkit's wiring and |
| 296 | // testable with a plain function. |
| 297 | func commands(msgs []*ai.Message) int { |
| 298 | n := 0 |
| 299 | for _, m := range msgs { |
| 300 | for _, p := range m.Content { |
| 301 | if p.IsToolResponse() && p.ToolResponse != nil && p.ToolResponse.Name == "bash" { |
| 302 | n++ |
| 303 | } |
| 304 | } |
| 305 | } |
| 306 | return n |
| 307 | } |