Cohere

Lightweight, dependency-free, in-memory Cohere v2 API fake for testing code that uses the real cohere-ai SDK (and the language-agnostic v2 REST API). All generated content is deterministic — text, embedding vectors, and rerank scores are derived from a hash of the input.

Default port: 4754

Quick start

import { CohereServer } from "./services/cohere/src/server.js";

const server = new CohereServer(4754);
await server.start();
// ... run your app/tests ...
await server.stop();

Point the real cohere-ai client at it via environment:

import { CohereClientV2 } from "cohere-ai";

const cohere = new CohereClientV2({
  token: "parlel",
  environment: "http://127.0.0.1:4754",
});

const response = await cohere.chat({
  model: "command-r-plus",
  messages: [{ role: "user", content: "Hello Cohere" }],
});
// response.message.content[0].text => deterministic text

Implemented operations

All /v2/* routes require an Authorization: Bearer <key> header (any non-empty bearer token is accepted). State is in-memory and ephemeral.

POST /v2/chat — chat. Returns { id, message: { role, content: [{ type: "text", text }] }, finish_reason, usage }. Supports stream: true via the Cohere v2 SSE event types (message-start, content-start, content-delta, content-end, message-end), ending with data: [DONE].
POST /v2/embed — embeddings. Returns { id, embeddings: { float: [...] }, texts, meta } (deterministic 1024-dim vectors). Requires texts, model, input_type.
POST /v2/rerank — rerank documents against a query. Returns { id, results: [{ index, relevance_score }], meta }, sorted descending, honoring top_n.

Service & inspection operations (parlel extensions)

GET / — service metadata.
GET /health — health check ({ status: "ok" }).
POST /__parlel/reset — reset all in-memory state.
GET /__parlel/requests — list captured requests.
DELETE /__parlel/requests — clear the captured request log.

SDK usage example

import cohere

co = cohere.ClientV2(api_key="parlel", base_url="http://127.0.0.1:4754")
res = co.rerank(
    model="rerank-english-v3.0",
    query="What is parlel?",
    documents=["parlel is a tool", "unrelated", "another parlel mention"],
    top_n=2,
)
for r in res.results:
    print(r.index, r.relevance_score)

Access via MCP / preview URL

HTTP services are auto-exposed at the Daytona preview URL. Send requests to the preview URL with the x-daytona-preview-token header. Set COHERE_BASE_URL to the preview URL.

Surface coverage

This emulator faithfully replicates the API surface most application code and agents exercise. Anything below the supported lines is either an intentional design choice for a fast, zero-cost local emulator (✓ By design) or a candidate for a future release (⟳ Roadmap) — never a silent inaccuracy.

Legend: ✅ fully supported · ◐ accepted (stored, not strictly enforced) · ✓ by design · ⟳ on the roadmap.

Feature	Status
`v2/chat` (+ streaming SSE)	✅ Supported
`v2/embed` (deterministic float vectors)	✅ Supported
`v2/rerank` (sorted scores, `top_n`)	✅ Supported
Request inspection	✅ Supported (parlel extension)
Real model inference / quality	✓ By design — Deterministic stub output — repeatable assertions, no API spend
`tools` / connectors / web search	◐ Accepted, not executed
`int8` / `binary` embedding types	◐ Only `float` returned
Token / billing counts	◐ Approximate word-based
Bearer-token validity / quota	✓ By design — Never throttles — local tests run at full speed, zero cost

Manifest

See services/cohere/manifest.json:

name: cohere, image: parlel/cohere:1
port: 4754, protocol: http, healthcheck: /health, startup ≈ 100ms
env: COHERE_API_KEY, CO_API_KEY, COHERE_BASE_URL

Configuration — `test.env`

Copy these into your test.env (used by the bridge sidecar flow). Tokens are Parlel's seeded test credentials — any non-empty value is accepted by the emulator, so you rarely need to change them. Swap in real credentials only when pointing at the live service in prod.env.

COHERE_API_KEY=parlel
CO_API_KEY=parlel
COHERE_BASE_URL=http://parlel-bridge:4754