# Changelog State API – LangChain Change History

> Changelog State API – LangChain Change History is a paid API for AI agents from changelog-state-api.replit.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Returns detected changelog update history (new releases, version changes, breaking signals, etc.) for the LangChain vendor.

## Facts

- Endpoint: GET https://changelog-state-api.replit.app/api/monitors/langchain/changes
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/changelog-state-api-langchain-change-history-4f311a94
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Hsp3BHWJNldmMcsRQbqlL

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability changelog-state-api-langchain-change-history-4f311a94
```

Example prompt: Show me all detected changelog changes for LangChain since last Monday, filtering to only new_release events, up to 100 results.

## When to prefer this

Use this endpoint when you need a history of detected changelog mutations for LangChain specifically — including breaking signals, version bumps, and release events — with time-range and type filtering. Prefer this over the 'structured recent releases' sibling endpoint when you need raw change detection events rather than curated release summaries, or when you want to audit changelog mutations over time.

## Known failure modes

- Invalid slug format returns 400 (must be lowercase alphanumeric with dashes)
- Untracked vendor slug returns 404 or empty results
- since timestamp in wrong format (not ISO 8601) returns 400
- limit exceeding 200 returns 400 validation error
- Insufficient payment or failed x402 payment returns 402

## How this service works

Detected changelog update history for one tracked vendor.

## Output

A JSON array of detected changelog change records for LangChain, each including the change type (e.g. new_release, version_changed, breaking_signal), detection timestamp, and relevant metadata about what changed. Supports filtering by change type and time window.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "slug"
     ],
     "properties": {
      "slug": {
       "type": "string",
       "pattern": "^[a-z0-9][a-z0-9-]*$",
       "maxLength": 64,
       "minLength": 1,
       "description": "Vendor slug, lowercase alphanumeric with dashes."
      }
     }
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "type": {
       "enum": [
        "new_release",
        "version_changed",
        "date_changed",
        "title_changed",
        "breaking_signal"
       ],
       "type": "string",
       "description": "Restrict to a single change type."
      },
      "limit": {
       "type": "integer",
       "default": 50,
       "maximum": 200,
       "minimum": 1,
       "description": "Maximum number of change rows to return."
      },
      "since": {
       "type": "string",
       "format": "date-time",
       "description": "Only return changes detected at or after this instant."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "enum": [
      "json"
     ],
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   },
   "description": "Detected changelog update history (paid)"
  }
 },
 "description": "Call shape for GET /api/monitors/{slug}/changes."
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/changelog-state-api-langchain-change-history-4f311a94/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from changelog-state-api.replit.app](https://www.zero.xyz/host/changelog-state-api.replit.app/llms.txt)