feat(hot-state): section-aware greedy renderer, accounting types, fix docs drift

Replace blunt .slice(0, maxRenderedChars) truncation with a greedy line
accumulator that fits whole lines and suppresses header-only sections.
Add accountHotSessionStateRender() returning prompt + omitted[] accounting.
Export HotStateSection, HotStateOmissionReason, HotStateOmittedItem,
HotSessionStateRenderAccounting types for v2 evidence extension.
Fix configuration.md ranking formula (ACTION_WEIGHT + count*3, weights
50/45/30/20). Clarify README injection order. Add 9 unit tests.

README.md

@@ -85,11 +85,13 @@ OpenCode Working Memory adds durable memory without making extra LLM/API calls.
                    ▼
 ┌──────────────────────────────────────┐
 │ ⚡ Prompt Context                     │
-│ system[1]: frozen workspace memory   │
+│ system[1]*: frozen workspace memory  │
-│ system[2+]: hot session state        │
+│ system[2+]*: hot session state       │
 └──────────────────────────────────────┘
 ```
 
+\* Conceptually, workspace memory is pushed first when it is non-empty, and hot session state is pushed after workspace memory. If workspace memory is empty, hot state may be the first plugin-added system message. Actual `system[]` indices also depend on OpenCode and other plugins, so `system[1]` / `system[2+]` is a simplified model.
+
 **Zero extra API calls:** OpenCode Working Memory does not call the model on its own. Memory extraction is folded into OpenCode's built-in compaction request.
 
 **Cache-friendly layout:** durable workspace memory is rendered as a stable frozen snapshot for the session, while fast-changing hot session state is appended separately. Compaction starts a new cache epoch, refreshing the workspace snapshot after pending memories are promoted.

docs/configuration.md

@@ -87,16 +87,33 @@ const HOT_STATE_LIMITS = {
 
 ## Active File Scoring
 
-Files are ranked by action type:
+Files are ranked by action type plus repeated access count:
 
 | Action | Weight | Description |
 |--------|--------|-------------|
-| `write` | 4 | File created/overwritten |
+| `edit` | 50 | File modified |
-| `edit` | 3 | File modified |
+| `write` | 45 | File created/overwritten |
-| `read` | 2 | File read |
+| `grep` | 30 | Grep searched in file |
-| `grep` | 1 | Grep searched in file |
+| `read` | 20 | File read |
 
-Score formula: `count * action_weight * recency_decay`
+Score formula: `ACTION_WEIGHT[action] + count * 3`
+
+When scores tie, the most recent `lastSeen` timestamp sorts first. There is no recency decay factor in the score itself.
+
+## Hot Session State Truncation
+
+Hot state rendering applies section caps before the character budget:
+
+| Section | Rendered cap |
+|---------|--------------|
+| `active_files` | 8 |
+| `open_errors` | 3 |
+| `recent_decisions` | 8 |
+| `pending_memories` | 6 |
+
+After section caps, the renderer applies the 700-character budget with whole-line inclusion only. The prefix line is counted against the budget, and a section heading is emitted only when at least one entry from that section fits; header-only sections are suppressed.
+
+`accountHotSessionStateRender()` returns prompt and omission accounting for future diagnostics. Evidence event integration for hot-state render omissions is planned for v2.
 
 ## Error Categories
 

src/session-state.ts

@@ -189,49 +189,150 @@ export function clearErrorsForSuccessfulCommand(state: SessionState, command: st
   state.updatedAt = new Date().toISOString();
 }
 
+export type HotStateSection = "active_files" | "open_errors" | "recent_decisions" | "pending_memories";
+
+export type HotStateOmissionReason = "section_cap" | "char_budget";
+
+export type HotStateOmittedItem = {
+  section: HotStateSection;
+  reason: HotStateOmissionReason;
+  text: string;
+  memoryId?: string;
+};
+
+export type HotSessionStateRenderAccounting = {
+  prompt: string;
+  omitted: HotStateOmittedItem[];
+  maxRenderedChars: number;
+};
+
+type HotStateRenderItem = {
+  section: HotStateSection;
+  line: string;
+  memoryId?: string;
+};
+
+type HotStateRenderSection = {
+  heading: `${HotStateSection}:`;
+  items: HotStateRenderItem[];
+};
+
+const HOT_STATE_PREFIX = "Hot session state (current session):";
+
+export function accountHotSessionStateRender(state: SessionState, workspaceRoot: string): HotSessionStateRenderAccounting {
+  const maxRenderedChars = HOT_STATE_LIMITS.maxRenderedChars;
+  const omitted: HotStateOmittedItem[] = [];
+  const sections = buildHotStateRenderSections(state, workspaceRoot, omitted);
+
+  if (sections.every(section => section.items.length === 0)) {
+    return { prompt: "", omitted, maxRenderedChars };
+  }
+
+  const lines: string[] = [HOT_STATE_PREFIX];
+  let renderedEntryCount = 0;
+
+  for (const section of sections) {
+    let headingRendered = false;
+
+    for (const item of section.items) {
+      if (headingRendered) {
+        if (wouldFit(lines, item.line, maxRenderedChars)) {
+          lines.push(item.line);
+          renderedEntryCount += 1;
+        } else {
+          omitted.push(omitHotStateItem(item, "char_budget"));
+        }
+        continue;
+      }
+
+      if (wouldFit(lines, section.heading, maxRenderedChars)
+        && wouldFit([...lines, section.heading], item.line, maxRenderedChars)) {
+        lines.push(section.heading, item.line);
+        headingRendered = true;
+        renderedEntryCount += 1;
+      } else {
+        omitted.push(omitHotStateItem(item, "char_budget"));
+      }
+    }
+  }
+
+  if (renderedEntryCount === 0) return { prompt: "", omitted, maxRenderedChars };
+
+  return { prompt: lines.join("\n"), omitted, maxRenderedChars };
+}
+
 export function renderHotSessionState(state: SessionState, workspaceRoot: string): string {
-  const activeFiles = rankActiveFiles(state.activeFiles).slice(0, HOT_STATE_LIMITS.maxActiveFilesRendered);
+  return accountHotSessionStateRender(state, workspaceRoot).prompt;
+}
+
+function buildHotStateRenderSections(
+  state: SessionState,
+  workspaceRoot: string,
+  omitted: HotStateOmittedItem[],
+): HotStateRenderSection[] {
+  const activeFiles = rankActiveFiles(state.activeFiles).map(item => ({
+    section: "active_files" as const,
+    line: `- ${displayPath(workspaceRoot, item.path)} (${item.action}, ${item.count}x)`,
+  }));
   const openErrors = [...state.openErrors]
     .sort((a, b) => b.lastSeen - a.lastSeen)
-    .slice(0, HOT_STATE_LIMITS.maxOpenErrorsRendered);
+    .map(err => ({
-  const decisions = state.recentDecisions.slice(-HOT_STATE_LIMITS.maxRecentDecisionsStored);
+      section: "open_errors" as const,
-  const pendingMemories = dedupePendingMemories(state.pendingMemories)
+      line: `- [${err.category}] ${err.summary}`,
-    .slice(-HOT_STATE_LIMITS.maxPendingMemoriesRendered);
+    }));
+  const decisions = state.recentDecisions.map(item => ({
+    section: "recent_decisions" as const,
+    line: `- ${item.text}`,
+  }));
+  const pendingMemories = dedupePendingMemories(state.pendingMemories).map(item => ({
+    section: "pending_memories" as const,
+    line: `- [${item.type}] ${item.text}`,
+    memoryId: item.id,
+  }));
 
-  if (activeFiles.length === 0 && openErrors.length === 0 && decisions.length === 0 && pendingMemories.length === 0) return "";
+  const renderedActiveFiles = capHotStateItems(activeFiles, HOT_STATE_LIMITS.maxActiveFilesRendered, "start", omitted);
+  const renderedOpenErrors = capHotStateItems(openErrors, HOT_STATE_LIMITS.maxOpenErrorsRendered, "start", omitted);
+  const renderedDecisions = capHotStateItems(decisions, HOT_STATE_LIMITS.maxRecentDecisionsStored, "end", omitted);
+  const renderedPendingMemories = capHotStateItems(
+    pendingMemories,
+    HOT_STATE_LIMITS.maxPendingMemoriesRendered,
+    "end",
+    omitted,
+  );
 
-  const lines: string[] = ["Hot session state (current session):"];
+  return [
+    { heading: "active_files:", items: renderedActiveFiles },
+    { heading: "open_errors:", items: renderedOpenErrors },
+    { heading: "recent_decisions:", items: renderedDecisions },
+    { heading: "pending_memories:", items: renderedPendingMemories },
+  ];
+}
 
-  if (activeFiles.length > 0) {
+function capHotStateItems(
-    lines.push("active_files:");
+  items: HotStateRenderItem[],
-    for (const item of activeFiles) {
+  cap: number,
-      const viewPath = displayPath(workspaceRoot, item.path);
+  keep: "start" | "end",
-      lines.push(`- ${viewPath} (${item.action}, ${item.count}x)`);
+  omitted: HotStateOmittedItem[],
-    }
+): HotStateRenderItem[] {
-  }
+  if (items.length <= cap) return items;
 
-  if (openErrors.length > 0) {
+  const renderedItems = keep === "start" ? items.slice(0, cap) : items.slice(-cap);
-    lines.push("open_errors:");
+  const omittedItems = keep === "start" ? items.slice(cap) : items.slice(0, items.length - cap);
-    for (const err of openErrors) {
+  omitted.push(...omittedItems.map(item => omitHotStateItem(item, "section_cap")));
-      lines.push(`- [${err.category}] ${err.summary}`);
+  return renderedItems;
-    }
+}
-  }
 
-  if (decisions.length > 0) {
+function omitHotStateItem(item: HotStateRenderItem, reason: HotStateOmissionReason): HotStateOmittedItem {
-    lines.push("recent_decisions:");
+  return {
-    for (const decision of decisions) {
+    section: item.section,
-      lines.push(`- ${decision.text}`);
+    reason,
-    }
+    text: item.line,
-  }
+    ...(item.memoryId ? { memoryId: item.memoryId } : {}),
+  };
+}
 
-  if (pendingMemories.length > 0) {
+function wouldFit(lines: string[], nextLine: string, maxRenderedChars: number): boolean {
-    lines.push("pending_memories:");
+  return [...lines, nextLine].join("\n").length <= maxRenderedChars;
-    for (const memory of pendingMemories) {
-      lines.push(`- [${memory.type}] ${memory.text}`);
-    }
-  }
-
-  return lines.join("\n").slice(0, HOT_STATE_LIMITS.maxRenderedChars);
 }
 
 function rankActiveFiles(activeFiles: ActiveFile[]): ActiveFile[] {

tests/session-state.test.ts

@@ -0,0 +1,210 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import * as sessionStateModule from "../src/session-state.ts";
+import type { HotSessionStateRenderAccounting } from "../src/session-state.ts";
+import type { ActiveFile, LongTermMemoryEntry, OpenError, SessionDecision, SessionState } from "../src/types.ts";
+import { HOT_STATE_LIMITS } from "../src/types.ts";
+
+type AccountHotSessionStateRender = (state: SessionState, workspaceRoot: string) => HotSessionStateRenderAccounting;
+
+const accountHotSessionStateRender = (
+  sessionStateModule as typeof sessionStateModule & { accountHotSessionStateRender: AccountHotSessionStateRender }
+).accountHotSessionStateRender;
+
+const { createEmptySessionState, renderHotSessionState } = sessionStateModule;
+
+const root = "/repo";
+
+function state(overrides: Partial<SessionState> = {}): SessionState {
+  return {
+    version: 1,
+    sessionID: "session-state-test",
+    turn: 0,
+    updatedAt: "2026-05-05T00:00:00.000Z",
+    activeFiles: [],
+    openErrors: [],
+    recentDecisions: [],
+    pendingMemories: [],
+    ...overrides,
+  };
+}
+
+function activeFile(path: string, action: ActiveFile["action"], count: number, lastSeen: number): ActiveFile {
+  return { path, action, count, lastSeen };
+}
+
+function openError(id: string, summary: string, lastSeen: number): OpenError {
+  return {
+    id,
+    category: "test",
+    summary,
+    fingerprint: `fingerprint-${id}`,
+    status: "open",
+    firstSeen: lastSeen - 1,
+    lastSeen,
+    seenCount: 1,
+  };
+}
+
+function decision(id: string, text: string, createdAt: number): SessionDecision {
+  return { id, text, source: "assistant", createdAt };
+}
+
+function memory(id: string, text: string, type: LongTermMemoryEntry["type"] = "decision"): LongTermMemoryEntry {
+  return {
+    id,
+    type,
+    text,
+    source: "compaction",
+    confidence: 0.75,
+    status: "active",
+    createdAt: "2026-05-05T00:00:00.000Z",
+    updatedAt: "2026-05-05T00:00:00.000Z",
+  };
+}
+
+test("accountHotSessionStateRender returns empty prompt and no omissions for empty state", () => {
+  const accounting = accountHotSessionStateRender(createEmptySessionState("empty-session"), root);
+
+  assert.equal(accounting.prompt, "");
+  assert.deepEqual(accounting.omitted, []);
+  assert.equal(accounting.maxRenderedChars, HOT_STATE_LIMITS.maxRenderedChars);
+});
+
+test("accountHotSessionStateRender renders hot-state sections in stable order", () => {
+  const accounting = accountHotSessionStateRender(state({
+    activeFiles: [activeFile("/repo/src/a.ts", "read", 1, 1)],
+    openErrors: [openError("err-1", "one failing test", 2)],
+    recentDecisions: [decision("dec-1", "Keep renderer simple", 3)],
+    pendingMemories: [memory("mem-1", "Promote useful fact")],
+  }), root);
+
+  assert.ok(accounting.prompt.startsWith("Hot session state (current session):"));
+  assert.ok(accounting.prompt.indexOf("active_files:") < accounting.prompt.indexOf("open_errors:"));
+  assert.ok(accounting.prompt.indexOf("open_errors:") < accounting.prompt.indexOf("recent_decisions:"));
+  assert.ok(accounting.prompt.indexOf("recent_decisions:") < accounting.prompt.indexOf("pending_memories:"));
+});
+
+test("accountHotSessionStateRender ranks active files by score then lastSeen descending", () => {
+  const accounting = accountHotSessionStateRender(state({
+    activeFiles: [
+      activeFile("/repo/src/edit.ts", "edit", 1, 400),
+      activeFile("/repo/src/write.ts", "write", 5, 200),
+      activeFile("/repo/src/grep.ts", "grep", 10, 300),
+      activeFile("/repo/src/read.ts", "read", 12, 100),
+    ],
+  }), root);
+
+  const lines = accounting.prompt.split("\n");
+  const activeLines = lines.filter(line => line.startsWith("- src/"));
+  assert.deepEqual(activeLines, [
+    "- src/grep.ts (grep, 10x)",
+    "- src/write.ts (write, 5x)",
+    "- src/read.ts (read, 12x)",
+    "- src/edit.ts (edit, 1x)",
+  ]);
+});
+
+test("accountHotSessionStateRender reports section-cap omissions for every capped section", () => {
+  const accounting = accountHotSessionStateRender(state({
+    activeFiles: Array.from({ length: 9 }, (_, index) => activeFile(`/repo/a${index}.ts`, "read", 1, 100 - index)),
+    openErrors: Array.from({ length: 4 }, (_, index) => openError(`err-${index}`, `e${index}`, 100 - index)),
+    recentDecisions: Array.from({ length: 9 }, (_, index) => decision(`dec-${index}`, `d${index}`, index)),
+    pendingMemories: Array.from({ length: 7 }, (_, index) => memory(`mem-${index}`, `m${index}`)),
+  }), root);
+
+  const sectionCapOmissions = accounting.omitted.filter(item => item.reason === "section_cap");
+  assert.deepEqual(
+    sectionCapOmissions.map(item => item.section).sort(),
+    ["active_files", "open_errors", "pending_memories", "recent_decisions"].sort(),
+  );
+  assert.equal(sectionCapOmissions.find(item => item.section === "pending_memories")?.memoryId, "mem-0");
+});
+
+test("accountHotSessionStateRender omits over-budget entries without cutting rendered lines", () => {
+  const longPath = `/repo/${"x".repeat(650)}.ts`;
+  const accounting = accountHotSessionStateRender(state({
+    activeFiles: [
+      activeFile("/repo/src/short.ts", "read", 1, 20),
+      activeFile(longPath, "read", 1, 10),
+    ],
+  }), root);
+
+  assert.equal(accounting.prompt, [
+    "Hot session state (current session):",
+    "active_files:",
+    "- src/short.ts (read, 1x)",
+  ].join("\n"));
+  assert.equal(accounting.omitted.length, 1);
+  assert.equal(accounting.omitted[0]?.reason, "char_budget");
+  assert.equal(accounting.omitted[0]?.section, "active_files");
+  assert.ok(!accounting.prompt.includes("x".repeat(20)));
+});
+
+test("accountHotSessionStateRender includes exact 700-char prompt but omits one additional character", () => {
+  const fixedPrompt = [
+    "Hot session state (current session):",
+    "pending_memories:",
+    "- [decision] ",
+  ].join("\n");
+  const exactText = "x".repeat(HOT_STATE_LIMITS.maxRenderedChars - fixedPrompt.length);
+  const exactAccounting = accountHotSessionStateRender(state({
+    pendingMemories: [memory("mem-exact", exactText)],
+  }), root);
+
+  assert.equal(exactAccounting.prompt.length, HOT_STATE_LIMITS.maxRenderedChars);
+  assert.equal(exactAccounting.omitted.length, 0);
+
+  const overAccounting = accountHotSessionStateRender(state({
+    pendingMemories: [memory("mem-over", `${exactText}y`)],
+  }), root);
+
+  assert.equal(overAccounting.prompt, "");
+  assert.equal(overAccounting.omitted.length, 1);
+  assert.equal(overAccounting.omitted[0]?.reason, "char_budget");
+  assert.equal(overAccounting.omitted[0]?.memoryId, "mem-over");
+});
+
+test("accountHotSessionStateRender suppresses header-only sections when no entries fit", () => {
+  const accounting = accountHotSessionStateRender(state({
+    activeFiles: [activeFile(`/repo/${"z".repeat(720)}.ts`, "read", 1, 1)],
+  }), root);
+
+  assert.equal(accounting.prompt, "");
+  assert.equal(accounting.omitted.length, 1);
+  assert.equal(accounting.omitted[0]?.reason, "char_budget");
+  assert.ok(!accounting.prompt.includes("active_files:"));
+});
+
+test("renderHotSessionState delegates to accounted renderer prompt for empty and seeded states", () => {
+  const empty = createEmptySessionState("compat-empty");
+  const seeded = state({
+    activeFiles: [activeFile("/repo/src/a.ts", "edit", 2, 1)],
+    pendingMemories: [memory("mem-compat", "Compatibility prompt")],
+  });
+
+  assert.equal(renderHotSessionState(empty, root), accountHotSessionStateRender(empty, root).prompt);
+  assert.equal(renderHotSessionState(seeded, root), accountHotSessionStateRender(seeded, root).prompt);
+});
+
+test("accountHotSessionStateRender counts newline separators in the 700-char budget", () => {
+  const fixedPrompt = [
+    "Hot session state (current session):",
+    "recent_decisions:",
+    "- ",
+  ].join("\n");
+  const exactText = "n".repeat(HOT_STATE_LIMITS.maxRenderedChars - fixedPrompt.length);
+
+  const exactAccounting = accountHotSessionStateRender(state({
+    recentDecisions: [decision("dec-exact", exactText, 1)],
+  }), root);
+  assert.equal(exactAccounting.prompt.length, HOT_STATE_LIMITS.maxRenderedChars);
+  assert.equal(exactAccounting.omitted.length, 0);
+
+  const overAccounting = accountHotSessionStateRender(state({
+    recentDecisions: [decision("dec-over", `${exactText}!`, 1)],
+  }), root);
+  assert.equal(overAccounting.prompt, "");
+  assert.equal(overAccounting.omitted.length, 1);
+  assert.equal(overAccounting.omitted[0]?.reason, "char_budget");
+});