feat: implement OpenBrain ContextEngine plugin

.gitignore

@@ -0,0 +1,4 @@
+node_modules
+dist
+coverage
+.DS_Store

README.md

@@ -1,2 +1,97 @@
 # openclaw-openbrain-context
 
+OpenBrain-backed `ContextEngine` plugin for OpenClaw.
+
+This plugin stores session context in OpenBrain over REST so context can be reassembled from recent history plus semantic matches instead of relying only on in-session compaction state.
+
+## Features
+
+- Registers context engine id: `openbrain`
+- Typed OpenBrain REST client with Bearer auth
+- Session-aware ingest + batch ingest
+- Context assembly from recent + semantic search under token budget
+- Compaction summaries archived to OpenBrain
+- Subagent seed/result handoff helpers
+
+## Requirements
+
+- OpenClaw with plugin/context-engine support (`openclaw >= 2026.3.2`)
+- Reachable OpenBrain REST API
+- OpenBrain API key
+
+## Install (local workspace plugin)
+
+```bash
+pnpm install
+pnpm build
+```
+
+Then reference this plugin in your OpenClaw config.
+
+## OpenBrain Setup (self-host or hosted)
+
+You must provide both of these in plugin config:
+
+- `baseUrl`: your OpenBrain API root (example: `https://brain.your-domain.com`)
+- `apiKey`: Bearer token for your OpenBrain instance
+
+No host or key fallback is built in. Missing `baseUrl` or `apiKey` throws `OpenBrainConfigError` at `bootstrap()`.
+
+## Configuration
+
+Plugin entry id: `openclaw-openbrain-context`  
+Context engine slot id: `openbrain`
+
+### Config fields
+
+- `baseUrl` (required, string): OpenBrain API base URL
+- `apiKey` (required, string): OpenBrain Bearer token
+- `source` (optional, string, default `openclaw`): source prefix; engine stores thoughts under `<source>:<sessionId>`
+- `recentMessages` (optional, integer, default `20`): recent thoughts to fetch for bootstrap/assemble
+- `semanticSearchLimit` (optional, integer, default `10`): semantic matches fetched in assemble
+- `subagentRecentMessages` (optional, integer, default `8`): context lines used for subagent seed/result exchange
+
+## Environment Variable Pattern
+
+Use OpenClaw variable interpolation in `openclaw.json`:
+
+```json
+{
+  "apiKey": "${OPENBRAIN_API_KEY}"
+}
+```
+
+Then set it in your shell/runtime environment before starting OpenClaw.
+
+## Example `openclaw.json`
+
+```json
+{
+  "plugins": {
+    "slots": {
+      "contextEngine": "openbrain"
+    },
+    "entries": {
+      "openclaw-openbrain-context": {
+        "enabled": true,
+        "config": {
+          "baseUrl": "https://brain.example.com",
+          "apiKey": "${OPENBRAIN_API_KEY}",
+          "source": "openclaw",
+          "recentMessages": 20,
+          "semanticSearchLimit": 10,
+          "subagentRecentMessages": 8
+        }
+      }
+    }
+  }
+}
+```
+
+## Development
+
+```bash
+pnpm lint
+pnpm build
+pnpm test
+```

docs/TASKS.md

@@ -2,11 +2,11 @@
 
 | id | status | description | issue | repo | branch | depends_on | blocks | agent | started_at | completed_at | estimate | used | notes |
 |---|---|---|---|---|---|---|---|---|---|---|---|---|---|
-| OBC-001 | not-started | Init: pnpm, TypeScript strict, ESLint, vitest, openclaw plugin-sdk dep | TASKS:P1 | openclaw-openbrain-context | feat/engine | | OBC-002 | | | | 8K | | |
-| OBC-002 | not-started | OpenBrain REST client module (typed, auth, error handling) | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-001 | OBC-003 | | | | 8K | | |
-| OBC-003 | not-started | ContextEngine implementation: bootstrap + ingest + ingestBatch | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-002 | OBC-004 | | | | 15K | | |
-| OBC-004 | not-started | ContextEngine implementation: assemble (recent + semantic merge) | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-003 | OBC-005 | | | | 15K | | |
-| OBC-005 | not-started | ContextEngine implementation: compact + prepareSubagentSpawn + onSubagentEnded + dispose | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-004 | OBC-006 | | | | 12K | | |
-| OBC-006 | not-started | Plugin entrypoint: register(), openclaw.plugin.json manifest | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-005 | OBC-007 | | | | 5K | | |
-| OBC-007 | not-started | Unit tests: ingest/assemble/compact + mock OpenBrain responses | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-006 | OBC-008 | | | | 15K | | |
-| OBC-008 | not-started | README + install instructions + openclaw.json config example | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-007 | | | | | 5K | | |
+| OBC-001 | done | Init: pnpm, TypeScript strict, ESLint, vitest, openclaw plugin-sdk dep | TASKS:P1 | openclaw-openbrain-context | feat/engine | | OBC-002 | | | | 8K | | |
+| OBC-002 | done | OpenBrain REST client module (typed, auth, error handling) | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-001 | OBC-003 | | | | 8K | | |
+| OBC-003 | done | ContextEngine implementation: bootstrap + ingest + ingestBatch | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-002 | OBC-004 | | | | 15K | | |
+| OBC-004 | done | ContextEngine implementation: assemble (recent + semantic merge) | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-003 | OBC-005 | | | | 15K | | |
+| OBC-005 | done | ContextEngine implementation: compact + prepareSubagentSpawn + onSubagentEnded + dispose | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-004 | OBC-006 | | | | 12K | | |
+| OBC-006 | done | Plugin entrypoint: register(), openclaw.plugin.json manifest | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-005 | OBC-007 | | | | 5K | | |
+| OBC-007 | done | Unit tests: ingest/assemble/compact + mock OpenBrain responses | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-006 | OBC-008 | | | | 15K | | |
+| OBC-008 | done | README + install instructions + openclaw.json config example | TASKS:P1 | openclaw-openbrain-context | feat/engine | OBC-007 | | | | | 5K | | |

eslint.config.mjs

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+import js from "@eslint/js";
+import tseslint from "typescript-eslint";
+
+export default [
+  {
+    ignores: ["dist/**", "coverage/**"],
+  },
+  js.configs.recommended,
+  ...tseslint.configs.recommended,
+  {
+    files: ["**/*.ts"],
+    languageOptions: {
+      ecmaVersion: "latest",
+      sourceType: "module",
+    },
+    rules: {
+      "@typescript-eslint/consistent-type-imports": [
+        "error",
+        {
+          prefer: "type-imports",
+          fixStyle: "inline-type-imports",
+        },
+      ],
+    },
+  },
+];

openclaw.plugin.json

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+{
+  "id": "openclaw-openbrain-context",
+  "name": "OpenBrain Context Engine",
+  "description": "OpenBrain-backed ContextEngine plugin for OpenClaw",
+  "version": "0.0.1",
+  "kind": "context-engine",
+  "configSchema": {
+    "type": "object",
+    "additionalProperties": false,
+    "required": ["baseUrl", "apiKey"],
+    "properties": {
+      "baseUrl": {
+        "type": "string",
+        "minLength": 1,
+        "description": "Base URL of your OpenBrain REST API"
+      },
+      "apiKey": {
+        "type": "string",
+        "minLength": 1,
+        "description": "Bearer token used to authenticate against OpenBrain"
+      },
+      "source": {
+        "type": "string",
+        "minLength": 1,
+        "default": "openclaw",
+        "description": "Source prefix stored in OpenBrain (session id is appended)"
+      },
+      "recentMessages": {
+        "type": "integer",
+        "minimum": 1,
+        "default": 20,
+        "description": "How many recent thoughts to fetch during assemble/bootstrap"
+      },
+      "semanticSearchLimit": {
+        "type": "integer",
+        "minimum": 1,
+        "default": 10,
+        "description": "How many semantic matches to request during assemble"
+      },
+      "subagentRecentMessages": {
+        "type": "integer",
+        "minimum": 1,
+        "default": 8,
+        "description": "How many thoughts to use when seeding/summarizing subagents"
+      }
+    }
+  },
+  "uiHints": {
+    "baseUrl": {
+      "label": "OpenBrain Base URL",
+      "placeholder": "https://brain.example.com"
+    },
+    "apiKey": {
+      "label": "OpenBrain API Key",
+      "sensitive": true
+    }
+  }
+}

package.json

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+{
+  "name": "openclaw-openbrain-context",
+  "version": "0.0.1",
+  "description": "OpenBrain-backed ContextEngine plugin for OpenClaw",
+  "type": "module",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "files": [
+    "dist",
+    "openclaw.plugin.json",
+    "README.md"
+  ],
+  "scripts": {
+    "lint": "eslint . --max-warnings=0",
+    "build": "tsc -p tsconfig.json",
+    "test": "vitest run"
+  },
+  "peerDependencies": {
+    "openclaw": ">=2026.3.2"
+  },
+  "devDependencies": {
+    "@eslint/js": "^9.25.1",
+    "@types/node": "^22.15.3",
+    "eslint": "^9.25.1",
+    "typescript": "^5.8.3",
+    "typescript-eslint": "^8.30.1",
+    "vitest": "^2.1.8"
+  }
+}

src/constants.ts

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+export const OPENBRAIN_CONTEXT_ENGINE_ID = "openbrain";
+export const OPENBRAIN_PLUGIN_ID = "openclaw-openbrain-context";
+export const OPENBRAIN_PLUGIN_VERSION = "0.0.1";

src/engine.ts

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+import { OPENBRAIN_CONTEXT_ENGINE_ID, OPENBRAIN_PLUGIN_VERSION } from "./constants.js";
+import { OpenBrainConfigError } from "./errors.js";
+import type {
+  AgentMessage,
+  AssembleResult,
+  BootstrapResult,
+  CompactResult,
+  ContextEngine,
+  ContextEngineInfo,
+  IngestBatchResult,
+  IngestResult,
+  PluginLogger,
+  SubagentEndReason,
+  SubagentSpawnPreparation,
+} from "./openclaw-types.js";
+import {
+  OpenBrainClient,
+  type OpenBrainClientLike,
+  type OpenBrainSearchInput,
+  type OpenBrainThought,
+  type OpenBrainThoughtMetadata,
+} from "./openbrain-client.js";
+
+export type OpenBrainContextEngineConfig = {
+  baseUrl?: string;
+  apiKey?: string;
+  recentMessages?: number;
+  semanticSearchLimit?: number;
+  source?: string;
+  subagentRecentMessages?: number;
+};
+
+type ResolvedOpenBrainContextEngineConfig = {
+  baseUrl: string;
+  apiKey: string;
+  recentMessages: number;
+  semanticSearchLimit: number;
+  source: string;
+  subagentRecentMessages: number;
+};
+
+export type OpenBrainContextEngineDeps = {
+  createClient?: (config: ResolvedOpenBrainContextEngineConfig) => OpenBrainClientLike;
+  now?: () => number;
+  logger?: PluginLogger;
+};
+
+type SubagentState = {
+  parentSessionKey: string;
+  seedThoughtId?: string;
+};
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null;
+}
+
+function parsePositiveInteger(value: unknown, fallback: number): number {
+  if (typeof value !== "number" || !Number.isFinite(value)) {
+    return fallback;
+  }
+
+  const rounded = Math.floor(value);
+  return rounded > 0 ? rounded : fallback;
+}
+
+function normalizeRole(role: unknown): string {
+  if (typeof role !== "string" || role.length === 0) {
+    return "assistant";
+  }
+
+  if (role === "user" || role === "assistant" || role === "tool" || role === "system") {
+    return role;
+  }
+
+  return "assistant";
+}
+
+function serializeContent(value: unknown): string {
+  if (typeof value === "string") {
+    return value;
+  }
+
+  if (Array.isArray(value)) {
+    return value
+      .map((part) => serializeContent(part))
+      .filter((part) => part.length > 0)
+      .join("\n")
+      .trim();
+  }
+
+  if (isRecord(value) && typeof value.text === "string") {
+    return value.text;
+  }
+
+  if (value === undefined || value === null) {
+    return "";
+  }
+
+  try {
+    return JSON.stringify(value);
+  } catch {
+    return String(value);
+  }
+}
+
+function estimateTextTokens(text: string): number {
+  const normalized = text.trim();
+  if (normalized.length === 0) {
+    return 1;
+  }
+
+  return Math.max(1, Math.ceil(normalized.length / 4) + 4);
+}
+
+function thoughtTimestamp(thought: OpenBrainThought, fallbackTimestamp: number): number {
+  const createdAt =
+    thought.createdAt ??
+    (typeof thought.created_at === "string" ? thought.created_at : undefined);
+
+  if (createdAt === undefined) {
+    return fallbackTimestamp;
+  }
+
+  const parsed = Date.parse(createdAt);
+  return Number.isFinite(parsed) ? parsed : fallbackTimestamp;
+}
+
+function thoughtFingerprint(thought: OpenBrainThought): string {
+  const role = typeof thought.metadata?.role === "string" ? thought.metadata.role : "assistant";
+  return `${role}\n${thought.content}`;
+}
+
+function truncateLine(value: string, maxLength: number): string {
+  if (value.length <= maxLength) {
+    return value;
+  }
+
+  return `${value.slice(0, maxLength - 3)}...`;
+}
+
+export class OpenBrainContextEngine implements ContextEngine {
+  readonly info: ContextEngineInfo = {
+    id: OPENBRAIN_CONTEXT_ENGINE_ID,
+    name: "OpenBrain Context Engine",
+    version: OPENBRAIN_PLUGIN_VERSION,
+    ownsCompaction: true,
+  };
+
+  private readonly rawConfig: unknown;
+  private readonly createClientFn:
+    | ((config: ResolvedOpenBrainContextEngineConfig) => OpenBrainClientLike)
+    | undefined;
+  private readonly now: () => number;
+  private readonly logger: PluginLogger | undefined;
+
+  private config: ResolvedOpenBrainContextEngineConfig | undefined;
+  private client: OpenBrainClientLike | undefined;
+  private readonly sessionTurns = new Map<string, number>();
+  private readonly subagentState = new Map<string, SubagentState>();
+  private disposed = false;
+
+  constructor(rawConfig: unknown, deps?: OpenBrainContextEngineDeps) {
+    this.rawConfig = rawConfig;
+    this.createClientFn = deps?.createClient;
+    this.now = deps?.now ?? (() => Date.now());
+    this.logger = deps?.logger;
+  }
+
+  async bootstrap(params: { sessionId: string; sessionFile: string }): Promise<BootstrapResult> {
+    this.assertNotDisposed();
+
+    const config = this.getConfig();
+    const client = this.getClient();
+    const source = this.sourceForSession(params.sessionId);
+
+    const recentThoughts = await client.listRecent({
+      limit: config.recentMessages,
+      source,
+    });
+
+    const sessionThoughts = this.filterSessionThoughts(recentThoughts, params.sessionId);
+
+    let maxTurn = -1;
+    for (const thought of sessionThoughts) {
+      const turn = thought.metadata?.turn;
+      if (typeof turn === "number" && Number.isFinite(turn) && turn > maxTurn) {
+        maxTurn = turn;
+      }
+    }
+
+    this.sessionTurns.set(params.sessionId, maxTurn + 1);
+
+    return {
+      bootstrapped: true,
+      importedMessages: sessionThoughts.length,
+    };
+  }
+
+  async ingest(params: {
+    sessionId: string;
+    message: AgentMessage;
+    isHeartbeat?: boolean;
+  }): Promise<IngestResult> {
+    this.assertNotDisposed();
+
+    const client = this.getClient();
+    const content = serializeContent(params.message.content).trim();
+    if (content.length === 0) {
+      return { ingested: false };
+    }
+
+    const metadata: OpenBrainThoughtMetadata = {
+      sessionId: params.sessionId,
+      turn: this.nextTurn(params.sessionId),
+      role: normalizeRole(params.message.role),
+      type: "message",
+    };
+
+    if (params.isHeartbeat === true) {
+      metadata.isHeartbeat = true;
+    }
+
+    await client.createThought({
+      content,
+      source: this.sourceForSession(params.sessionId),
+      metadata,
+    });
+
+    return { ingested: true };
+  }
+
+  async ingestBatch(params: {
+    sessionId: string;
+    messages: AgentMessage[];
+    isHeartbeat?: boolean;
+  }): Promise<IngestBatchResult> {
+    this.assertNotDisposed();
+
+    let ingestedCount = 0;
+    for (const message of params.messages) {
+      const ingestParams: {
+        sessionId: string;
+        message: AgentMessage;
+        isHeartbeat?: boolean;
+      } = {
+        sessionId: params.sessionId,
+        message,
+      };
+      if (params.isHeartbeat !== undefined) {
+        ingestParams.isHeartbeat = params.isHeartbeat;
+      }
+      const result = await this.ingest(ingestParams);
+
+      if (result.ingested) {
+        ingestedCount += 1;
+      }
+    }
+
+    return { ingestedCount };
+  }
+
+  async assemble(params: {
+    sessionId: string;
+    messages: AgentMessage[];
+    tokenBudget?: number;
+  }): Promise<AssembleResult> {
+    this.assertNotDisposed();
+
+    const config = this.getConfig();
+    const client = this.getClient();
+    const source = this.sourceForSession(params.sessionId);
+
+    const recentThoughts = this.filterSessionThoughts(
+      await client.listRecent({
+        limit: config.recentMessages,
+        source,
+      }),
+      params.sessionId,
+    );
+
+    const semanticThoughts = await this.searchSemanticThoughts({
+      client,
+      source,
+      config,
+      sessionId: params.sessionId,
+      messages: params.messages,
+    });
+
+    const mergedThoughts = this.mergeThoughts(recentThoughts, semanticThoughts);
+    const mergedMessages =
+      mergedThoughts.length > 0
+        ? mergedThoughts.map((thought, index) => this.toAgentMessage(thought, index))
+        : params.messages;
+
+    const tokenBudget = params.tokenBudget;
+    const budgetedMessages =
+      typeof tokenBudget === "number" && tokenBudget > 0
+        ? this.trimToBudget(mergedMessages, tokenBudget)
+        : mergedMessages;
+
+    return {
+      messages: budgetedMessages,
+      estimatedTokens: this.estimateTokensForMessages(budgetedMessages),
+    };
+  }
+
+  async compact(params: {
+    sessionId: string;
+    sessionFile: string;
+    tokenBudget?: number;
+    force?: boolean;
+    currentTokenCount?: number;
+    compactionTarget?: "budget" | "threshold";
+    customInstructions?: string;
+    legacyParams?: Record<string, unknown>;
+  }): Promise<CompactResult> {
+    this.assertNotDisposed();
+
+    const config = this.getConfig();
+    const client = this.getClient();
+    const source = this.sourceForSession(params.sessionId);
+
+    const recentThoughts = this.filterSessionThoughts(
+      await client.listRecent({
+        limit: Math.max(config.recentMessages, config.subagentRecentMessages),
+        source,
+      }),
+      params.sessionId,
+    );
+
+    if (recentThoughts.length === 0) {
+      return {
+        ok: true,
+        compacted: false,
+        reason: "no-session-context",
+        result: {
+          tokensBefore: 0,
+          tokensAfter: 0,
+        },
+      };
+    }
+
+    const summary = this.buildSummary(
+      params.customInstructions !== undefined
+        ? {
+            sessionId: params.sessionId,
+            thoughts: recentThoughts,
+            customInstructions: params.customInstructions,
+          }
+        : {
+            sessionId: params.sessionId,
+            thoughts: recentThoughts,
+          },
+    );
+
+    const summaryTokens = estimateTextTokens(summary);
+    const tokensBefore = this.estimateTokensForThoughts(recentThoughts);
+
+    await client.createThought({
+      content: summary,
+      source,
+      metadata: {
+        sessionId: params.sessionId,
+        turn: this.nextTurn(params.sessionId),
+        role: "assistant",
+        type: "summary",
+      },
+    });
+
+    return {
+      ok: true,
+      compacted: true,
+      reason: "summary-archived",
+      result: {
+        summary,
+        tokensBefore,
+        tokensAfter: summaryTokens,
+      },
+    };
+  }
+
+  async prepareSubagentSpawn(params: {
+    parentSessionKey: string;
+    childSessionKey: string;
+    ttlMs?: number;
+  }): Promise<SubagentSpawnPreparation | undefined> {
+    this.assertNotDisposed();
+
+    const config = this.getConfig();
+    const client = this.getClient();
+
+    const parentThoughts = this.filterSessionThoughts(
+      await client.listRecent({
+        limit: config.subagentRecentMessages,
+        source: this.sourceForSession(params.parentSessionKey),
+      }),
+      params.parentSessionKey,
+    );
+
+    const seedContent = this.buildSubagentSeedContent({
+      parentSessionKey: params.parentSessionKey,
+      childSessionKey: params.childSessionKey,
+      thoughts: parentThoughts,
+    });
+
+    const createdThought = await client.createThought({
+      content: seedContent,
+      source: this.sourceForSession(params.childSessionKey),
+      metadata: {
+        sessionId: params.childSessionKey,
+        role: "assistant",
+        type: "summary",
+        parentSessionId: params.parentSessionKey,
+        ttlMs: params.ttlMs,
+      },
+    });
+
+    this.subagentState.set(params.childSessionKey, {
+      parentSessionKey: params.parentSessionKey,
+      seedThoughtId: createdThought.id,
+    });
+
+    return {
+      rollback: async () => {
+        const state = this.subagentState.get(params.childSessionKey);
+        this.subagentState.delete(params.childSessionKey);
+
+        if (state?.seedThoughtId !== undefined && state.seedThoughtId.length > 0) {
+          await client.deleteThought(state.seedThoughtId);
+        }
+      },
+    };
+  }
+
+  async onSubagentEnded(params: {
+    childSessionKey: string;
+    reason: SubagentEndReason;
+  }): Promise<void> {
+    this.assertNotDisposed();
+
+    const state = this.subagentState.get(params.childSessionKey);
+    if (state === undefined) {
+      return;
+    }
+
+    const client = this.getClient();
+    const config = this.getConfig();
+
+    const childThoughts = this.filterSessionThoughts(
+      await client.listRecent({
+        limit: config.subagentRecentMessages,
+        source: this.sourceForSession(params.childSessionKey),
+      }),
+      params.childSessionKey,
+    );
+
+    const summary = this.buildSubagentResultSummary({
+      childSessionKey: params.childSessionKey,
+      reason: params.reason,
+      thoughts: childThoughts,
+    });
+
+    await client.createThought({
+      content: summary,
+      source: this.sourceForSession(state.parentSessionKey),
+      metadata: {
+        sessionId: state.parentSessionKey,
+        turn: this.nextTurn(state.parentSessionKey),
+        role: "tool",
+        type: "subagent-result",
+        childSessionId: params.childSessionKey,
+        reason: params.reason,
+      },
+    });
+
+    this.subagentState.delete(params.childSessionKey);
+  }
+
+  async dispose(): Promise<void> {
+    this.sessionTurns.clear();
+    this.subagentState.clear();
+    this.disposed = true;
+  }
+
+  private searchSemanticThoughts(params: {
+    client: OpenBrainClientLike;
+    source: string;
+    config: ResolvedOpenBrainContextEngineConfig;
+    sessionId: string;
+    messages: AgentMessage[];
+  }): Promise<OpenBrainThought[]> {
+    const query = this.pickSemanticQuery(params.messages);
+    if (query === undefined || query.length === 0 || params.config.semanticSearchLimit <= 0) {
+      return Promise.resolve([]);
+    }
+
+    const request: OpenBrainSearchInput = {
+      query,
+      limit: params.config.semanticSearchLimit,
+      source: params.source,
+    };
+
+    return params.client
+      .search(request)
+      .then((results) => this.filterSessionThoughts(results, params.sessionId))
+      .catch((error) => {
+        this.logger?.warn?.("OpenBrain semantic search failed", error);
+        return [];
+      });
+  }
+
+  private pickSemanticQuery(messages: AgentMessage[]): string | undefined {
+    for (let i = messages.length - 1; i >= 0; i -= 1) {
+      const message = messages[i];
+      if (message === undefined) {
+        continue;
+      }
+      if (normalizeRole(message.role) !== "user") {
+        continue;
+      }
+
+      const content = serializeContent(message.content).trim();
+      if (content.length > 0) {
+        return content;
+      }
+    }
+
+    for (let i = messages.length - 1; i >= 0; i -= 1) {
+      const message = messages[i];
+      if (message === undefined) {
+        continue;
+      }
+      const content = serializeContent(message.content).trim();
+      if (content.length > 0) {
+        return content;
+      }
+    }
+
+    return undefined;
+  }
+
+  private mergeThoughts(recentThoughts: OpenBrainThought[], semanticThoughts: OpenBrainThought[]): OpenBrainThought[] {
+    const merged: OpenBrainThought[] = [];
+    const seenIds = new Set<string>();
+    const seenFingerprints = new Set<string>();
+
+    for (const thought of [...recentThoughts, ...semanticThoughts]) {
+      const id = thought.id.trim();
+      const fingerprint = thoughtFingerprint(thought);
+
+      if (id.length > 0 && seenIds.has(id)) {
+        continue;
+      }
+
+      if (seenFingerprints.has(fingerprint)) {
+        continue;
+      }
+
+      if (id.length > 0) {
+        seenIds.add(id);
+      }
+      seenFingerprints.add(fingerprint);
+      merged.push(thought);
+    }
+
+    return merged;
+  }
+
+  private filterSessionThoughts(thoughts: OpenBrainThought[], sessionId: string): OpenBrainThought[] {
+    return thoughts.filter((thought) => {
+      const thoughtSessionId = thought.metadata?.sessionId;
+      if (typeof thoughtSessionId === "string" && thoughtSessionId.length > 0) {
+        return thoughtSessionId === sessionId;
+      }
+
+      return thought.source === this.sourceForSession(sessionId);
+    });
+  }
+
+  private toAgentMessage(thought: OpenBrainThought, index: number): AgentMessage {
+    return {
+      role: normalizeRole(thought.metadata?.role),
+      content: thought.content,
+      timestamp: thoughtTimestamp(thought, this.now() + index),
+    };
+  }
+
+  private trimToBudget(messages: AgentMessage[], tokenBudget: number): AgentMessage[] {
+    if (messages.length === 0 || tokenBudget <= 0) {
+      return [];
+    }
+
+    let total = 0;
+    const budgeted: AgentMessage[] = [];
+
+    for (let i = messages.length - 1; i >= 0; i -= 1) {
+      const message = messages[i];
+      if (message === undefined) {
+        continue;
+      }
+      const tokens = estimateTextTokens(serializeContent(message.content));
+      if (total + tokens > tokenBudget) {
+        continue;
+      }
+
+      total += tokens;
+      budgeted.unshift(message);
+    }
+
+    if (budgeted.length === 0) {
+      const lastMessage = messages[messages.length - 1];
+      return lastMessage === undefined ? [] : [lastMessage];
+    }
+
+    return budgeted;
+  }
+
+  private estimateTokensForMessages(messages: AgentMessage[]): number {
+    return messages.reduce((total, message) => {
+      return total + estimateTextTokens(serializeContent(message.content));
+    }, 0);
+  }
+
+  private estimateTokensForThoughts(thoughts: OpenBrainThought[]): number {
+    return thoughts.reduce((total, thought) => total + estimateTextTokens(thought.content), 0);
+  }
+
+  private buildSummary(params: {
+    sessionId: string;
+    thoughts: OpenBrainThought[];
+    customInstructions?: string;
+  }): string {
+    const ordered = [...params.thoughts].sort((a, b) => {
+      return thoughtTimestamp(a, 0) - thoughtTimestamp(b, 0);
+    });
+
+    const maxLines = Math.min(ordered.length, 10);
+    const lines = ordered.slice(Math.max(ordered.length - maxLines, 0)).map((thought) => {
+      const role = normalizeRole(thought.metadata?.role);
+      const content = truncateLine(thought.content.replace(/\s+/g, " ").trim(), 180);
+      return `- ${role}: ${content}`;
+    });
+
+    const header = `Context summary for session ${params.sessionId}`;
+    const instruction =
+      params.customInstructions !== undefined && params.customInstructions.trim().length > 0
+        ? `Custom instructions: ${params.customInstructions.trim()}\n`
+        : "";
+
+    return `${header}\n${instruction}${lines.join("\n")}`;
+  }
+
+  private buildSubagentSeedContent(params: {
+    parentSessionKey: string;
+    childSessionKey: string;
+    thoughts: OpenBrainThought[];
+  }): string {
+    const lines = params.thoughts.slice(-5).map((thought) => {
+      const role = normalizeRole(thought.metadata?.role);
+      return `- ${role}: ${truncateLine(thought.content.replace(/\s+/g, " ").trim(), 160)}`;
+    });
+
+    const contextBlock = lines.length > 0 ? lines.join("\n") : "- (no prior context found)";
+
+    return [
+      `Subagent context seed`,
+      `Parent session: ${params.parentSessionKey}`,
+      `Child session: ${params.childSessionKey}`,
+      contextBlock,
+    ].join("\n");
+  }
+
+  private buildSubagentResultSummary(params: {
+    childSessionKey: string;
+    reason: SubagentEndReason;
+    thoughts: OpenBrainThought[];
+  }): string {
+    const lines = params.thoughts.slice(-5).map((thought) => {
+      const role = normalizeRole(thought.metadata?.role);
+      return `- ${role}: ${truncateLine(thought.content.replace(/\s+/g, " ").trim(), 160)}`;
+    });
+
+    const contextBlock = lines.length > 0 ? lines.join("\n") : "- (no child messages found)";
+
+    return [
+      `Subagent ended (${params.reason})`,
+      `Child session: ${params.childSessionKey}`,
+      contextBlock,
+    ].join("\n");
+  }
+
+  private sourceForSession(sessionId: string): string {
+    return `${this.getConfig().source}:${sessionId}`;
+  }
+
+  private nextTurn(sessionId: string): number {
+    const next = this.sessionTurns.get(sessionId) ?? 0;
+    this.sessionTurns.set(sessionId, next + 1);
+    return next;
+  }
+
+  private getClient(): OpenBrainClientLike {
+    if (this.client !== undefined) {
+      return this.client;
+    }
+
+    const config = this.getConfig();
+    this.client =
+      this.createClientFn?.(config) ??
+      new OpenBrainClient({
+        baseUrl: config.baseUrl,
+        apiKey: config.apiKey,
+      });
+
+    return this.client;
+  }
+
+  private getConfig(): ResolvedOpenBrainContextEngineConfig {
+    if (this.config !== undefined) {
+      return this.config;
+    }
+
+    const raw = isRecord(this.rawConfig) ? this.rawConfig : {};
+
+    const baseUrl = typeof raw.baseUrl === "string" ? raw.baseUrl.trim() : "";
+    if (baseUrl.length === 0) {
+      throw new OpenBrainConfigError("Missing required OpenBrain config: baseUrl");
+    }
+
+    const apiKey = typeof raw.apiKey === "string" ? raw.apiKey.trim() : "";
+    if (apiKey.length === 0) {
+      throw new OpenBrainConfigError("Missing required OpenBrain config: apiKey");
+    }
+
+    this.config = {
+      baseUrl,
+      apiKey,
+      recentMessages: parsePositiveInteger(raw.recentMessages, 20),
+      semanticSearchLimit: parsePositiveInteger(raw.semanticSearchLimit, 10),
+      source: typeof raw.source === "string" && raw.source.trim().length > 0 ? raw.source.trim() : "openclaw",
+      subagentRecentMessages: parsePositiveInteger(raw.subagentRecentMessages, 8),
+    };
+
+    return this.config;
+  }
+
+  private assertNotDisposed(): void {
+    if (this.disposed) {
+      throw new Error("OpenBrainContextEngine has already been disposed");
+    }
+  }
+}

src/errors.ts

@@ -0,0 +1,40 @@
+export class OpenBrainError extends Error {
+  constructor(message: string, cause?: unknown) {
+    super(message);
+    this.name = "OpenBrainError";
+    if (cause !== undefined) {
+      (this as Error & { cause?: unknown }).cause = cause;
+    }
+  }
+}
+
+export class OpenBrainConfigError extends OpenBrainError {
+  constructor(message: string) {
+    super(message);
+    this.name = "OpenBrainConfigError";
+  }
+}
+
+export class OpenBrainHttpError extends OpenBrainError {
+  readonly status: number;
+  readonly endpoint: string;
+  readonly responseBody: string | undefined;
+
+  constructor(params: { endpoint: string; status: number; responseBody: string | undefined }) {
+    super(`OpenBrain request failed (${params.status}) for ${params.endpoint}`);
+    this.name = "OpenBrainHttpError";
+    this.status = params.status;
+    this.endpoint = params.endpoint;
+    this.responseBody = params.responseBody;
+  }
+}
+
+export class OpenBrainRequestError extends OpenBrainError {
+  readonly endpoint: string;
+
+  constructor(params: { endpoint: string; cause: unknown }) {
+    super(`OpenBrain request failed for ${params.endpoint}`, params.cause);
+    this.name = "OpenBrainRequestError";
+    this.endpoint = params.endpoint;
+  }
+}

src/index.ts

@@ -0,0 +1,31 @@
+import {
+  OPENBRAIN_CONTEXT_ENGINE_ID,
+  OPENBRAIN_PLUGIN_ID,
+  OPENBRAIN_PLUGIN_VERSION,
+} from "./constants.js";
+import { OpenBrainContextEngine } from "./engine.js";
+import type { OpenClawPluginApi } from "./openclaw-types.js";
+
+export { OPENBRAIN_CONTEXT_ENGINE_ID } from "./constants.js";
+export { OpenBrainContextEngine } from "./engine.js";
+export { OpenBrainConfigError, OpenBrainHttpError, OpenBrainRequestError } from "./errors.js";
+export { OpenBrainClient } from "./openbrain-client.js";
+export type { OpenBrainContextEngineConfig } from "./engine.js";
+export type { OpenClawPluginApi } from "./openclaw-types.js";
+
+export function register(api: OpenClawPluginApi): void {
+  api.registerContextEngine(OPENBRAIN_CONTEXT_ENGINE_ID, () => {
+    const deps = api.logger !== undefined ? { logger: api.logger } : undefined;
+    return new OpenBrainContextEngine(api.pluginConfig, deps);
+  });
+}
+
+const plugin = {
+  id: OPENBRAIN_PLUGIN_ID,
+  name: "OpenBrain Context Engine",
+  version: OPENBRAIN_PLUGIN_VERSION,
+  kind: "context-engine",
+  register,
+};
+
+export default plugin;

src/openbrain-client.ts

@@ -0,0 +1,333 @@
+import { OpenBrainConfigError, OpenBrainHttpError, OpenBrainRequestError } from "./errors.js";
+
+export type OpenBrainThoughtMetadata = Record<string, unknown> & {
+  sessionId?: string;
+  turn?: number;
+  role?: string;
+  type?: string;
+};
+
+export type OpenBrainThought = {
+  id: string;
+  content: string;
+  source: string;
+  metadata: OpenBrainThoughtMetadata | undefined;
+  createdAt: string | undefined;
+  updatedAt: string | undefined;
+  score: number | undefined;
+  [key: string]: unknown;
+};
+
+export type OpenBrainThoughtInput = {
+  content: string;
+  source: string;
+  metadata?: OpenBrainThoughtMetadata;
+};
+
+export type OpenBrainSearchInput = {
+  query: string;
+  limit: number;
+  source?: string;
+};
+
+export type OpenBrainClientOptions = {
+  baseUrl: string;
+  apiKey: string;
+  fetchImpl?: typeof fetch;
+};
+
+export interface OpenBrainClientLike {
+  createThought(input: OpenBrainThoughtInput): Promise<OpenBrainThought>;
+  search(input: OpenBrainSearchInput): Promise<OpenBrainThought[]>;
+  listRecent(input: { limit: number; source?: string }): Promise<OpenBrainThought[]>;
+  updateThought(
+    id: string,
+    payload: { content?: string; metadata?: OpenBrainThoughtMetadata },
+  ): Promise<OpenBrainThought>;
+  deleteThought(id: string): Promise<void>;
+  deleteThoughts(params: { source?: string; metadataId?: string }): Promise<void>;
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null;
+}
+
+function readString(record: Record<string, unknown>, key: string): string | undefined {
+  const value = record[key];
+  return typeof value === "string" ? value : undefined;
+}
+
+function readNumber(record: Record<string, unknown>, key: string): number | undefined {
+  const value = record[key];
+  return typeof value === "number" ? value : undefined;
+}
+
+function normalizeBaseUrl(baseUrl: string): string {
+  const normalized = baseUrl.trim().replace(/\/+$/, "");
+  if (normalized.length === 0) {
+    throw new OpenBrainConfigError("Missing required OpenBrain config: baseUrl");
+  }
+  return normalized;
+}
+
+function normalizeApiKey(apiKey: string): string {
+  const normalized = apiKey.trim();
+  if (normalized.length === 0) {
+    throw new OpenBrainConfigError("Missing required OpenBrain config: apiKey");
+  }
+  return normalized;
+}
+
+function normalizeHeaders(headers: unknown): Record<string, string> {
+  if (headers === undefined) {
+    return {};
+  }
+
+  if (Array.isArray(headers)) {
+    const normalized: Record<string, string> = {};
+    for (const pair of headers) {
+      if (!Array.isArray(pair) || pair.length < 2) {
+        continue;
+      }
+
+      const key = pair[0];
+      const value = pair[1];
+      if (typeof key !== "string" || typeof value !== "string") {
+        continue;
+      }
+
+      normalized[key] = value;
+    }
+    return normalized;
+  }
+
+  if (headers instanceof Headers) {
+    const normalized: Record<string, string> = {};
+    for (const [key, value] of headers.entries()) {
+      normalized[key] = value;
+    }
+    return normalized;
+  }
+
+  if (!isRecord(headers)) {
+    return {};
+  }
+
+  const normalized: Record<string, string> = {};
+  for (const [key, value] of Object.entries(headers)) {
+    if (typeof value === "string") {
+      normalized[key] = value;
+      continue;
+    }
+
+    if (Array.isArray(value)) {
+      normalized[key] = value.join(", ");
+    }
+  }
+
+  return normalized;
+}
+
+async function readResponseBody(response: Response): Promise<string | undefined> {
+  try {
+    const body = await response.text();
+    return body.length > 0 ? body : undefined;
+  } catch {
+    return undefined;
+  }
+}
+
+export class OpenBrainClient implements OpenBrainClientLike {
+  private readonly baseUrl: string;
+  private readonly apiKey: string;
+  private readonly fetchImpl: typeof fetch;
+
+  constructor(options: OpenBrainClientOptions) {
+    this.baseUrl = normalizeBaseUrl(options.baseUrl);
+    this.apiKey = normalizeApiKey(options.apiKey);
+    this.fetchImpl = options.fetchImpl ?? fetch;
+  }
+
+  async createThought(input: OpenBrainThoughtInput): Promise<OpenBrainThought> {
+    const payload = await this.request<unknown>("/v1/thoughts", {
+      method: "POST",
+      body: JSON.stringify(input),
+    });
+    return this.extractThought(payload);
+  }
+
+  async search(input: OpenBrainSearchInput): Promise<OpenBrainThought[]> {
+    const payload = await this.request<unknown>("/v1/search", {
+      method: "POST",
+      body: JSON.stringify(input),
+    });
+    return this.extractThoughtArray(payload);
+  }
+
+  async listRecent(input: { limit: number; source?: string }): Promise<OpenBrainThought[]> {
+    const params = new URLSearchParams({
+      limit: String(input.limit),
+    });
+
+    if (input.source !== undefined && input.source.length > 0) {
+      params.set("source", input.source);
+    }
+
+    const payload = await this.request<unknown>(`/v1/thoughts/recent?${params.toString()}`, {
+      method: "GET",
+    });
+
+    return this.extractThoughtArray(payload);
+  }
+
+  async updateThought(
+    id: string,
+    payload: { content?: string; metadata?: OpenBrainThoughtMetadata },
+  ): Promise<OpenBrainThought> {
+    const responsePayload = await this.request<unknown>(`/v1/thoughts/${encodeURIComponent(id)}`, {
+      method: "PATCH",
+      body: JSON.stringify(payload),
+    });
+
+    return this.extractThought(responsePayload);
+  }
+
+  async deleteThought(id: string): Promise<void> {
+    await this.request<unknown>(`/v1/thoughts/${encodeURIComponent(id)}`, {
+      method: "DELETE",
+    });
+  }
+
+  async deleteThoughts(params: { source?: string; metadataId?: string }): Promise<void> {
+    const query = new URLSearchParams();
+    if (params.source !== undefined && params.source.length > 0) {
+      query.set("source", params.source);
+    }
+    if (params.metadataId !== undefined && params.metadataId.length > 0) {
+      query.set("metadata_id", params.metadataId);
+    }
+
+    const suffix = query.size > 0 ? `?${query.toString()}` : "";
+    await this.request<unknown>(`/v1/thoughts${suffix}`, {
+      method: "DELETE",
+    });
+  }
+
+  private async request<T>(endpoint: string, init: RequestInit): Promise<T> {
+    const headers = normalizeHeaders(init.headers);
+    headers.Authorization = `Bearer ${this.apiKey}`;
+
+    if (init.body !== undefined && headers["Content-Type"] === undefined) {
+      headers["Content-Type"] = "application/json";
+    }
+
+    const url = `${this.baseUrl}${endpoint}`;
+
+    let response: Response;
+    try {
+      response = await this.fetchImpl(url, {
+        ...init,
+        headers,
+      });
+    } catch (error) {
+      throw new OpenBrainRequestError({ endpoint, cause: error });
+    }
+
+    if (!response.ok) {
+      throw new OpenBrainHttpError({
+        endpoint,
+        status: response.status,
+        responseBody: await readResponseBody(response),
+      });
+    }
+
+    if (response.status === 204) {
+      return undefined as T;
+    }
+
+    const contentType = response.headers.get("content-type") ?? "";
+    if (!contentType.toLowerCase().includes("application/json")) {
+      return undefined as T;
+    }
+
+    return (await response.json()) as T;
+  }
+
+  private extractThoughtArray(payload: unknown): OpenBrainThought[] {
+    if (Array.isArray(payload)) {
+      return payload.map((item) => this.normalizeThought(item));
+    }
+
+    if (!isRecord(payload)) {
+      return [];
+    }
+
+    const candidates = [payload.thoughts, payload.data, payload.results, payload.items];
+    for (const candidate of candidates) {
+      if (Array.isArray(candidate)) {
+        return candidate.map((item) => this.normalizeThought(item));
+      }
+    }
+
+    return [];
+  }
+
+  private extractThought(payload: unknown): OpenBrainThought {
+    if (isRecord(payload)) {
+      const nested = payload.thought;
+      if (nested !== undefined) {
+        return this.normalizeThought(nested);
+      }
+
+      const data = payload.data;
+      if (data !== undefined && !Array.isArray(data)) {
+        return this.normalizeThought(data);
+      }
+    }
+
+    return this.normalizeThought(payload);
+  }
+
+  private normalizeThought(value: unknown): OpenBrainThought {
+    if (!isRecord(value)) {
+      return {
+        id: "",
+        content: "",
+        source: "",
+        metadata: undefined,
+        createdAt: undefined,
+        updatedAt: undefined,
+        score: undefined,
+      };
+    }
+
+    const metadataValue = value.metadata;
+    const metadata = isRecord(metadataValue)
+      ? ({ ...metadataValue } as OpenBrainThoughtMetadata)
+      : undefined;
+
+    const id = readString(value, "id") ?? readString(value, "thought_id") ?? "";
+    const content =
+      readString(value, "content") ??
+      readString(value, "text") ??
+      (value.content === undefined ? "" : String(value.content));
+    const source = readString(value, "source") ?? "";
+
+    const createdAt = readString(value, "createdAt") ?? readString(value, "created_at");
+    const updatedAt = readString(value, "updatedAt") ?? readString(value, "updated_at");
+    const score = readNumber(value, "score");
+
+    return {
+      ...value,
+      id,
+      content,
+      source,
+      metadata,
+      createdAt,
+      updatedAt,
+      score,
+    };
+  }
+}
+
+export { normalizeApiKey, normalizeBaseUrl };

src/openclaw-types.ts

@@ -0,0 +1,128 @@
+export type AgentMessageRole = "user" | "assistant" | "tool" | "system" | string;
+
+export type AgentMessage = {
+  role: AgentMessageRole;
+  content: unknown;
+  timestamp?: number;
+  [key: string]: unknown;
+};
+
+export type AssembleResult = {
+  messages: AgentMessage[];
+  estimatedTokens: number;
+  systemPromptAddition?: string;
+};
+
+export type CompactResult = {
+  ok: boolean;
+  compacted: boolean;
+  reason?: string;
+  result?: {
+    summary?: string;
+    firstKeptEntryId?: string;
+    tokensBefore: number;
+    tokensAfter?: number;
+    details?: unknown;
+  };
+};
+
+export type IngestResult = {
+  ingested: boolean;
+};
+
+export type IngestBatchResult = {
+  ingestedCount: number;
+};
+
+export type BootstrapResult = {
+  bootstrapped: boolean;
+  importedMessages?: number;
+  reason?: string;
+};
+
+export type ContextEngineInfo = {
+  id: string;
+  name: string;
+  version?: string;
+  ownsCompaction?: boolean;
+};
+
+export type SubagentSpawnPreparation = {
+  rollback: () => void | Promise<void>;
+};
+
+export type SubagentEndReason = "deleted" | "completed" | "swept" | "released";
+
+export interface ContextEngine {
+  readonly info: ContextEngineInfo;
+
+  bootstrap?(params: { sessionId: string; sessionFile: string }): Promise<BootstrapResult>;
+
+  ingest(params: {
+    sessionId: string;
+    message: AgentMessage;
+    isHeartbeat?: boolean;
+  }): Promise<IngestResult>;
+
+  ingestBatch?(params: {
+    sessionId: string;
+    messages: AgentMessage[];
+    isHeartbeat?: boolean;
+  }): Promise<IngestBatchResult>;
+
+  afterTurn?(params: {
+    sessionId: string;
+    sessionFile: string;
+    messages: AgentMessage[];
+    prePromptMessageCount: number;
+    autoCompactionSummary?: string;
+    isHeartbeat?: boolean;
+    tokenBudget?: number;
+    legacyCompactionParams?: Record<string, unknown>;
+  }): Promise<void>;
+
+  assemble(params: {
+    sessionId: string;
+    messages: AgentMessage[];
+    tokenBudget?: number;
+  }): Promise<AssembleResult>;
+
+  compact(params: {
+    sessionId: string;
+    sessionFile: string;
+    tokenBudget?: number;
+    force?: boolean;
+    currentTokenCount?: number;
+    compactionTarget?: "budget" | "threshold";
+    customInstructions?: string;
+    legacyParams?: Record<string, unknown>;
+  }): Promise<CompactResult>;
+
+  prepareSubagentSpawn?(params: {
+    parentSessionKey: string;
+    childSessionKey: string;
+    ttlMs?: number;
+  }): Promise<SubagentSpawnPreparation | undefined>;
+
+  onSubagentEnded?(params: {
+    childSessionKey: string;
+    reason: SubagentEndReason;
+  }): Promise<void>;
+
+  dispose?(): Promise<void>;
+}
+
+export type ContextEngineFactory = () => ContextEngine | Promise<ContextEngine>;
+
+export type PluginLogger = {
+  debug?: (...args: unknown[]) => void;
+  info?: (...args: unknown[]) => void;
+  warn?: (...args: unknown[]) => void;
+  error?: (...args: unknown[]) => void;
+};
+
+export type OpenClawPluginApi = {
+  pluginConfig?: Record<string, unknown>;
+  logger?: PluginLogger;
+  registerContextEngine: (id: string, factory: ContextEngineFactory) => void;
+};

tests/engine.test.ts

@@ -0,0 +1,311 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { OpenBrainConfigError } from "../src/errors.js";
+import { OpenBrainContextEngine } from "../src/engine.js";
+import type { AgentMessage } from "../src/openclaw-types.js";
+import type {
+  OpenBrainClientLike,
+  OpenBrainThought,
+  OpenBrainThoughtInput,
+} from "../src/openbrain-client.js";
+
+function makeThought(
+  id: string,
+  content: string,
+  sessionId: string,
+  role: string,
+  createdAt: string,
+): OpenBrainThought {
+  return {
+    id,
+    content,
+    source: `openclaw:${sessionId}`,
+    metadata: {
+      sessionId,
+      role,
+      type: "message",
+    },
+    createdAt,
+    updatedAt: undefined,
+    score: undefined,
+  };
+}
+
+function makeMockClient(): OpenBrainClientLike {
+  return {
+    createThought: vi.fn(async (input: OpenBrainThoughtInput) => ({
+      id: `thought-${Math.random().toString(36).slice(2)}`,
+      content: input.content,
+      source: input.source,
+      metadata: input.metadata,
+      createdAt: new Date().toISOString(),
+      updatedAt: undefined,
+      score: undefined,
+    })),
+    search: vi.fn(async () => []),
+    listRecent: vi.fn(async () => []),
+    updateThought: vi.fn(async (id, payload) => ({
+      id,
+      content: payload.content ?? "",
+      source: "openclaw:session",
+      metadata: payload.metadata,
+      createdAt: new Date().toISOString(),
+      updatedAt: undefined,
+      score: undefined,
+    })),
+    deleteThought: vi.fn(async () => undefined),
+    deleteThoughts: vi.fn(async () => undefined),
+  };
+}
+
+const sessionId = "session-main";
+
+const userMessage: AgentMessage = {
+  role: "user",
+  content: "What did we decide yesterday?",
+  timestamp: Date.now(),
+};
+
+describe("OpenBrainContextEngine", () => {
+  it("throws OpenBrainConfigError at bootstrap when baseUrl/apiKey are missing", async () => {
+    const engine = new OpenBrainContextEngine({});
+
+    await expect(
+      engine.bootstrap({
+        sessionId,
+        sessionFile: "/tmp/session.json",
+      }),
+    ).rejects.toBeInstanceOf(OpenBrainConfigError);
+  });
+
+  it("ingests messages with session metadata", async () => {
+    const mockClient = makeMockClient();
+    const engine = new OpenBrainContextEngine(
+      {
+        baseUrl: "https://brain.example.com",
+        apiKey: "secret",
+        source: "openclaw",
+      },
+      {
+        createClient: () => mockClient,
+      },
+    );
+
+    await engine.bootstrap({ sessionId, sessionFile: "/tmp/session.json" });
+    const result = await engine.ingest({ sessionId, message: userMessage });
+
+    expect(result.ingested).toBe(true);
+    expect(mockClient.createThought).toHaveBeenCalledWith(
+      expect.objectContaining({
+        source: "openclaw:session-main",
+        metadata: expect.objectContaining({
+          sessionId,
+          role: "user",
+          type: "message",
+          turn: 0,
+        }),
+      }),
+    );
+  });
+
+  it("ingests batches and returns ingested count", async () => {
+    const mockClient = makeMockClient();
+    const engine = new OpenBrainContextEngine(
+      {
+        baseUrl: "https://brain.example.com",
+        apiKey: "secret",
+      },
+      { createClient: () => mockClient },
+    );
+
+    await engine.bootstrap({ sessionId, sessionFile: "/tmp/session.json" });
+    const result = await engine.ingestBatch({
+      sessionId,
+      messages: [
+        { role: "user", content: "one", timestamp: 1 },
+        { role: "assistant", content: "two", timestamp: 2 },
+      ],
+    });
+
+    expect(result.ingestedCount).toBe(2);
+    expect(mockClient.createThought).toHaveBeenCalledTimes(2);
+  });
+
+  it("assembles context from recent + semantic search, deduped and budget-aware", async () => {
+    const mockClient = makeMockClient();
+    vi.mocked(mockClient.listRecent).mockResolvedValue([
+      makeThought("t1", "recent user context", sessionId, "user", "2026-03-06T12:00:00.000Z"),
+      makeThought(
+        "t2",
+        "recent assistant context",
+        sessionId,
+        "assistant",
+        "2026-03-06T12:01:00.000Z",
+      ),
+    ]);
+    vi.mocked(mockClient.search).mockResolvedValue([
+      makeThought(
+        "t2",
+        "recent assistant context",
+        sessionId,
+        "assistant",
+        "2026-03-06T12:01:00.000Z",
+      ),
+      makeThought("t3", "semantic match", sessionId, "assistant", "2026-03-06T12:02:00.000Z"),
+    ]);
+
+    const engine = new OpenBrainContextEngine(
+      {
+        baseUrl: "https://brain.example.com",
+        apiKey: "secret",
+        recentMessages: 10,
+        semanticSearchLimit: 10,
+      },
+      { createClient: () => mockClient },
+    );
+
+    await engine.bootstrap({ sessionId, sessionFile: "/tmp/session.json" });
+
+    const result = await engine.assemble({
+      sessionId,
+      messages: [
+        {
+          role: "user",
+          content: "Find the semantic context",
+          timestamp: Date.now(),
+        },
+      ],
+      tokenBudget: 40,
+    });
+
+    expect(mockClient.search).toHaveBeenCalledWith(
+      expect.objectContaining({
+        query: "Find the semantic context",
+        limit: 10,
+      }),
+    );
+    expect(result.estimatedTokens).toBeLessThanOrEqual(40);
+    expect(result.messages.map((message) => String(message.content))).toEqual([
+      "recent user context",
+      "recent assistant context",
+      "semantic match",
+    ]);
+  });
+
+  it("compact archives a summary thought", async () => {
+    const mockClient = makeMockClient();
+    vi.mocked(mockClient.listRecent).mockResolvedValue([
+      makeThought("t1", "first message", sessionId, "user", "2026-03-06T12:00:00.000Z"),
+      makeThought("t2", "second message", sessionId, "assistant", "2026-03-06T12:01:00.000Z"),
+    ]);
+
+    const engine = new OpenBrainContextEngine(
+      {
+        baseUrl: "https://brain.example.com",
+        apiKey: "secret",
+      },
+      { createClient: () => mockClient },
+    );
+
+    await engine.bootstrap({ sessionId, sessionFile: "/tmp/session.json" });
+
+    const result = await engine.compact({
+      sessionId,
+      sessionFile: "/tmp/session.json",
+      tokenBudget: 128,
+    });
+
+    expect(result.ok).toBe(true);
+    expect(result.compacted).toBe(true);
+    expect(mockClient.createThought).toHaveBeenCalledWith(
+      expect.objectContaining({
+        source: "openclaw:session-main",
+        metadata: expect.objectContaining({
+          sessionId,
+          type: "summary",
+        }),
+      }),
+    );
+  });
+
+  it("prepares subagent spawn and rollback deletes seeded context", async () => {
+    const mockClient = makeMockClient();
+    vi.mocked(mockClient.listRecent).mockResolvedValue([
+      makeThought("t1", "parent context", sessionId, "assistant", "2026-03-06T12:00:00.000Z"),
+    ]);
+    vi.mocked(mockClient.createThought).mockResolvedValue({
+      id: "seed-thought",
+      content: "seed",
+      source: "openclaw:child",
+      metadata: undefined,
+      createdAt: "2026-03-06T12:01:00.000Z",
+      updatedAt: undefined,
+      score: undefined,
+    });
+
+    const engine = new OpenBrainContextEngine(
+      {
+        baseUrl: "https://brain.example.com",
+        apiKey: "secret",
+      },
+      { createClient: () => mockClient },
+    );
+
+    await engine.bootstrap({ sessionId, sessionFile: "/tmp/session.json" });
+
+    const prep = await engine.prepareSubagentSpawn({
+      parentSessionKey: sessionId,
+      childSessionKey: "child-session",
+    });
+
+    expect(prep).toBeDefined();
+    expect(mockClient.createThought).toHaveBeenCalledWith(
+      expect.objectContaining({
+        source: "openclaw:child-session",
+      }),
+    );
+
+    await prep?.rollback();
+    expect(mockClient.deleteThought).toHaveBeenCalledWith("seed-thought");
+  });
+
+  it("stores child outcome back into parent on subagent end", async () => {
+    const mockClient = makeMockClient();
+    vi.mocked(mockClient.listRecent)
+      .mockResolvedValueOnce([
+        makeThought("p1", "parent context", sessionId, "assistant", "2026-03-06T12:00:00.000Z"),
+      ])
+      .mockResolvedValueOnce([
+        makeThought("c1", "child result detail", "child-session", "assistant", "2026-03-06T12:05:00.000Z"),
+      ]);
+
+    const engine = new OpenBrainContextEngine(
+      {
+        baseUrl: "https://brain.example.com",
+        apiKey: "secret",
+      },
+      { createClient: () => mockClient },
+    );
+
+    await engine.bootstrap({ sessionId, sessionFile: "/tmp/session.json" });
+    await engine.prepareSubagentSpawn({
+      parentSessionKey: sessionId,
+      childSessionKey: "child-session",
+    });
+
+    await engine.onSubagentEnded({
+      childSessionKey: "child-session",
+      reason: "completed",
+    });
+
+    expect(mockClient.createThought).toHaveBeenLastCalledWith(
+      expect.objectContaining({
+        source: "openclaw:session-main",
+        metadata: expect.objectContaining({
+          type: "subagent-result",
+          sessionId,
+        }),
+      }),
+    );
+  });
+});

tests/openbrain-client.test.ts

@@ -0,0 +1,81 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { OpenBrainConfigError, OpenBrainHttpError } from "../src/errors.js";
+import { OpenBrainClient } from "../src/openbrain-client.js";
+
+function jsonResponse(body: unknown, init?: ResponseInit): Response {
+  return new Response(JSON.stringify(body), {
+    status: init?.status ?? 200,
+    headers: {
+      "content-type": "application/json",
+      ...(init?.headers ?? {}),
+    },
+  });
+}
+
+describe("OpenBrainClient", () => {
+  it("sends bearer auth and normalized URL for createThought", async () => {
+    const fetchMock = vi.fn(async () =>
+      jsonResponse({
+        id: "thought-1",
+        content: "hello",
+        source: "openclaw:main",
+      }),
+    );
+
+    const client = new OpenBrainClient({
+      baseUrl: "https://brain.example.com/",
+      apiKey: "secret",
+      fetchImpl: fetchMock as unknown as typeof fetch,
+    });
+
+    await client.createThought({
+      content: "hello",
+      source: "openclaw:main",
+      metadata: { sessionId: "session-1" },
+    });
+
+    expect(fetchMock).toHaveBeenCalledTimes(1);
+    const firstCall = fetchMock.mock.calls[0];
+    expect(firstCall).toBeDefined();
+    if (firstCall === undefined) {
+      throw new Error("Expected fetch call arguments");
+    }
+    const [url, init] = firstCall as unknown as [string, RequestInit];
+    expect(url).toBe("https://brain.example.com/v1/thoughts");
+    expect(init.method).toBe("POST");
+    expect(init.headers).toMatchObject({
+      Authorization: "Bearer secret",
+      "Content-Type": "application/json",
+    });
+  });
+
+  it("throws OpenBrainHttpError on non-2xx responses", async () => {
+    const fetchMock = vi.fn(async () =>
+      jsonResponse({ error: "unauthorized" }, { status: 401 }),
+    );
+
+    const client = new OpenBrainClient({
+      baseUrl: "https://brain.example.com",
+      apiKey: "secret",
+      fetchImpl: fetchMock as unknown as typeof fetch,
+    });
+
+    await expect(client.listRecent({ limit: 5, source: "openclaw:main" })).rejects.toBeInstanceOf(
+      OpenBrainHttpError,
+    );
+
+    await expect(client.listRecent({ limit: 5, source: "openclaw:main" })).rejects.toMatchObject({
+      status: 401,
+    });
+  });
+
+  it("throws OpenBrainConfigError when initialized without baseUrl or apiKey", () => {
+    expect(
+      () => new OpenBrainClient({ baseUrl: "", apiKey: "secret", fetchImpl: fetch }),
+    ).toThrow(OpenBrainConfigError);
+    expect(
+      () => new OpenBrainClient({ baseUrl: "https://brain.example.com", apiKey: "", fetchImpl: fetch }),
+    ).toThrow(OpenBrainConfigError);
+  });
+});

tests/register.test.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { OPENBRAIN_CONTEXT_ENGINE_ID, register } from "../src/index.js";
+
+describe("plugin register()", () => {
+  it("registers the openbrain context engine factory", async () => {
+    const registerContextEngine = vi.fn();
+
+    register({
+      registerContextEngine,
+      pluginConfig: {
+        baseUrl: "https://brain.example.com",
+        apiKey: "secret",
+      },
+      logger: {
+        debug: vi.fn(),
+        info: vi.fn(),
+        warn: vi.fn(),
+        error: vi.fn(),
+      },
+    });
+
+    expect(registerContextEngine).toHaveBeenCalledTimes(1);
+    const [id, factory] = registerContextEngine.mock.calls[0] as [string, () => Promise<unknown> | unknown];
+    expect(id).toBe(OPENBRAIN_CONTEXT_ENGINE_ID);
+
+    const engine = await factory();
+    expect(engine).toHaveProperty("info.id", OPENBRAIN_CONTEXT_ENGINE_ID);
+  });
+});

tests/smoke.test.ts

@@ -0,0 +1,9 @@
+import { describe, expect, it } from "vitest";
+
+import { OPENBRAIN_CONTEXT_ENGINE_ID } from "../src/index.js";
+
+describe("project scaffold", () => {
+  it("exports openbrain context engine id", () => {
+    expect(OPENBRAIN_CONTEXT_ENGINE_ID).toBe("openbrain");
+  });
+});

tsconfig.json

@@ -0,0 +1,27 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "lib": ["ES2022"],
+    "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "exactOptionalPropertyTypes": true,
+    "isolatedModules": true,
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true,
+    "outDir": "dist",
+    "rootDir": ".",
+    "types": ["node", "vitest/globals"],
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "baseUrl": ".",
+    "paths": {
+      "openclaw/plugin-sdk": ["../openclaw-fork/src/plugin-sdk/index.ts"]
+    }
+  },
+  "include": ["src/**/*.ts", "tests/**/*.ts"],
+  "exclude": ["dist", "node_modules"]
+}

vitest.config.ts

@@ -0,0 +1,8 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    environment: "node",
+    include: ["tests/**/*.test.ts"],
+  },
+});