feat: replace LangChainProvider with Runner protocol implementation (AIC-2388) by jsonbailey · Pull Request #1338 · launchdarkly/js-core

jsonbailey · 2026-04-28T23:24:26Z

Summary

Replaces the legacy LangChainProvider extension model with the Runner protocol for the LangChain provider package. This is a breaking change — LangChainProvider is removed.

Removed:

LangChainProvider class and its tests — callers must migrate to the new factory/runner pattern

Added:

LangChainModelRunner — Runner for chat completions; run(input: string | LDMessage[], outputType?) returns RunnerResult { content, metrics, raw, parsed? }. Structured output is parsed via withStructuredOutput.
LangChainAgentRunner — Runner for a single agent. Runs a tool-calling loop using LangChain's native bindTools and ToolMessage. Tool definitions come from config.model.parameters.tools; tool callables come from a caller-supplied ToolRegistry. Populates LDAIMetrics.toolCalls with the names of tools invoked.
LangChainRunnerFactory — extends AIProvider; exposes createModel(config) and createAgent(config, tools?). Applies OpenTelemetry instrumentation (via @traceloop/instrumentation-langchain) fire-and-forget in the constructor if available.

Renamed / moved:

langchainHelper.ts → LangChainHelper.ts (casing fix)
createLangChainModel moved from LangChainRunnerFactory into LangChainHelper and exported from the package

Renamed:

mapProvider → mapProviderName in helper exports

Test plan

yarn workspace @launchdarkly/server-sdk-ai-langchain test — all tests pass
yarn workspace @launchdarkly/server-sdk-ai-langchain lint — clean
yarn workspace @launchdarkly/server-sdk-ai-langchain run build — clean

🤖 Generated with Claude Code

Note

High Risk
High risk because this is a breaking API change that removes LangChainProvider in favor of new runner/factory entrypoints, requiring downstream code migration. It also changes how tools, metrics (usage/toolCalls), and structured output are produced/returned.

Overview
Breaking change: removes the LangChainProvider class (and its tests) and replaces it with a Runner-protocol integration.

Adds LangChainRunnerFactory to create either a LangChainModelRunner (chat completions) or LangChainAgentRunner (agent execution via createAgent), including optional OpenTelemetry ESM instrumentation. Introduces LangChainHelper utilities for provider mapping, message conversion, tool wrapping (buildStructuredTools), tool-call extraction, and token-usage aggregation, and updates package exports to expose the new factory/runners/helpers.

^{Reviewed by Cursor Bugbot for commit 3b1aa33. Bugbot is set up for automated code reviews on this repo. Configure here.}

accidental

Adds LangChainModelRunner, LangChainAgentRunner, and LangChainRunnerFactory that implement the Runner protocol introduced in JS PR 6. The runners take an LDAICompletionConfig / LDAIAgentConfig at construction and expose run(prompt: string) returning RunnerResult. LangChainModelRunner.run(prompt) prepends the config's messages before the user prompt. LangChainAgentRunner uses LangChain's native bindTools to run a tool-calling loop, populating LDAIMetrics.toolCalls with the names of tools the model invoked. Tool implementations are supplied via a ToolRegistry passed to LangChainRunnerFactory.createAgent. mapProvider is renamed to mapProviderName on both the helper module and the LangChainProvider class; the old mapProvider name is kept as a deprecated alias. The deprecated LangChainProvider class is preserved so AIProviderFactory continues to work during the migration. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

…] input handling

…ent on construction Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Previously the tool-calling loop fell off the end silently and returned success=true. Now only the clean-exit path (no more tool calls) sets success=true; hitting the iteration cap returns success=false with a logger warning. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

JSON.stringify(undefined) returns undefined (not a string), producing a malformed ToolMessage content. Nullish-coalesce to empty string so the message content is always a valid string. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lots of changes

…AIC-2388) (#1338)

… (AIC-2388) Now that all provider packages (#1337 OpenAI, #1338 LangChain, #1339 Vercel) have migrated to the Runner protocol, the deprecated compatibility surface on the umbrella `feat/next-ai-release` branch can be removed. BREAKING CHANGE: Removes the following deprecated APIs: AIProvider abstract base class: - `invokeModel()` and `invokeStructuredModel()` instance methods - `static create()` factory method - `protected logger` field on the constructor (provider subclasses now declare their own private `_logger` field) LDAIClient deprecated method aliases: - `config()` (use `completionConfig`) - `agent()` (use `agentConfig`) - `agents()` (use `agentConfigs`) - `createChat()` and `initChat()` (use `createModel`) Public types: - `StructuredResponse` (only consumed by the removed `invokeStructuredModel` method) Type narrowing on `AIProvider` and `RunnerFactory`: - `createModel(config: LDAICompletionConfig | LDAIJudgeConfig)` - `createAgent(config: LDAIAgentConfig)` - `createAgentGraph(graphDef: AgentGraphDefinition)` Previously these accepted the wider `LDAIConfigKind` union; the new signatures mirror what the provider subclasses already declared and surface mode mismatches at the type level. Also updates README examples to use `createModel`/`run()` and removes the stale `_LegacyProviderAdapter` references in `RunnerFactory` doc comments. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…AIC-2388) (#1338)

🤖 I have created a release *beep* *boop* --- <details><summary>server-sdk-ai: 0.20.0</summary> ## [0.20.0](server-sdk-ai-v0.19.1...server-sdk-ai-v0.20.0) (2026-05-07) ### ⚠ BREAKING CHANGES * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) * Use LDAIGraphMetricSummary for graph metric summary ([#1362](#1362)) ### Features * add Evaluator class for judge orchestration ([#1331](#1331)) ([54faa69](54faa69)) * add ManagedAgent with evaluations support ([#1334](#1334)) ([7f09c46](7f09c46)) * add ManagedGraphResult, GraphMetricSummary, and ManagedAgentGraph ([#1335](#1335)) ([09fa1db](09fa1db)) * introduce ManagedResult, RunnerResult, and LDAIMetricSummary ([#1332](#1332)) ([5040122](5040122)) * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) ([ad66314](ad66314)) * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) ([ff932b7](ff932b7)) * Replace OpenAIProvider with Runner protocol implementation (AIC-2388) ([#1337](#1337)) ([e32a955](e32a955)) ### Bug Fixes * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) ([c90034b](c90034b)) * Use LDAIGraphMetricSummary for graph metric summary ([#1362](#1362)) ([76a4bf2](76a4bf2)) </details> <details><summary>server-sdk-ai-langchain: 0.7.0</summary> ## [0.7.0](server-sdk-ai-langchain-v0.6.3...server-sdk-ai-langchain-v0.7.0) (2026-05-07) ### ⚠ BREAKING CHANGES * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) ### Features * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) ([ad66314](ad66314)) * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) ([ff932b7](ff932b7)) * Replace LangChainProvider with Runner protocol implementation (AIC-2388) ([#1338](#1338)) ([113a0d2](113a0d2)) ### Bug Fixes * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) ([c90034b](c90034b)) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/server-sdk-ai bumped from ^0.19.1 to ^0.20.0 * peerDependencies * @launchdarkly/server-sdk-ai bumped from ^0.19.1 to ^0.20.0 </details> <details><summary>server-sdk-ai-openai: 0.6.0</summary> ## [0.6.0](server-sdk-ai-openai-v0.5.10...server-sdk-ai-openai-v0.6.0) (2026-05-07) ### ⚠ BREAKING CHANGES * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) ### Features * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) ([ad66314](ad66314)) * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) ([ff932b7](ff932b7)) * Replace OpenAIProvider with Runner protocol implementation (AIC-2388) ([#1337](#1337)) ([e32a955](e32a955)) ### Bug Fixes * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) ([c90034b](c90034b)) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/server-sdk-ai bumped from ^0.19.1 to ^0.20.0 * peerDependencies * @launchdarkly/server-sdk-ai bumped from ^0.19.1 to ^0.20.0 </details> <details><summary>server-sdk-ai-vercel: 0.6.0</summary> ## [0.6.0](server-sdk-ai-vercel-v0.5.10...server-sdk-ai-vercel-v0.6.0) (2026-05-07) ### ⚠ BREAKING CHANGES * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) ### Features * Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) ([#1363](#1363)) ([ad66314](ad66314)) * Rename LDAIMetrics.usage and LDAIGraphMetrics.usage to .tokens ([#1366](#1366)) ([ff932b7](ff932b7)) * replace VercelProvider with Runner protocol implementation (AIC-2388) ([#1339](#1339)) ([d5a62de](d5a62de)) ### Bug Fixes * add zod devDependency to Vercel provider (peer dep of ai v5) ([aab6226](aab6226)) * Build judge input as string and strip legacy judge config messages ([#1364](#1364)) ([c90034b](c90034b)) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/server-sdk-ai bumped from ^0.19.1 to ^0.20.0 * peerDependencies * @launchdarkly/server-sdk-ai bumped from ^0.19.1 to ^0.20.0 </details> --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).  --- > [!NOTE] > **Medium Risk** > This is primarily a versioning/release metadata update, but it ships breaking API changes in `@launchdarkly/server-sdk-ai` and provider packages that may require consumer code updates (e.g., metrics field rename and deprecated method removals). > > **Overview** > Publishes a new release for `@launchdarkly/server-sdk-ai` (`0.19.1` → `0.20.0`) and the provider packages (`server-sdk-ai-langchain` `0.6.3` → `0.7.0`, `server-sdk-ai-openai`/`server-sdk-ai-vercel` `0.5.10` → `0.6.0`), updating `.release-please-manifest.json`, package versions, and `sdkInfo.ts`. > > Updates provider `peerDependencies`/`devDependencies` to require `@launchdarkly/server-sdk-ai@^0.20.0`, and bumps all `server-ai` examples to depend on the new SDK/provider versions. Changelogs highlight *breaking changes* including renaming metrics `usage` → `tokens`, removing deprecated `AIProvider` methods/aliases, and judge-input/config cleanup (plus additional `server-sdk-ai` graph/managed result summary changes). > > <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit cb3aebc. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup>  Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

jsonbailey force-pushed the jb/aic-2388/js-openai-runner branch from 07f1af2 to 66bb862 Compare May 1, 2026 14:10

jsonbailey force-pushed the jb/aic-2388/js-langchain-runner branch from 7a6a7b8 to 58f8249 Compare May 1, 2026 14:13

jsonbailey mentioned this pull request May 1, 2026

chore: Next AI SDK Release #1347

Closed

jsonbailey force-pushed the jb/aic-2388/js-openai-runner branch from 66bb862 to c9d433a Compare May 4, 2026 21:59

jsonbailey force-pushed the jb/aic-2388/js-langchain-runner branch from 58f8249 to fa4a5cf Compare May 4, 2026 21:59

jsonbailey force-pushed the jb/aic-2388/js-openai-runner branch from c9d433a to 42f17c6 Compare May 5, 2026 14:13

jsonbailey force-pushed the jb/aic-2388/js-langchain-runner branch from fa4a5cf to 1b5dcc1 Compare May 5, 2026 14:13

jsonbailey force-pushed the jb/aic-2388/js-openai-runner branch from 42f17c6 to 6902ffa Compare May 5, 2026 17:10

jsonbailey force-pushed the jb/aic-2388/js-langchain-runner branch from 1b5dcc1 to 175c210 Compare May 5, 2026 17:30

jsonbailey changed the base branch from jb/aic-2388/js-openai-runner to next-ai-release May 5, 2026 18:50

jsonbailey changed the title ~~feat: add LangChain Runner protocol implementation (AIC-2388)~~ feat: replace LangChainProvider with Runner protocol implementation (AIC-2388) May 5, 2026

jsonbailey marked this pull request as ready for review May 5, 2026 20:16

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jsonbailey and others added 7 commits May 6, 2026 14:29

fix: rename LangChainHelper, remove LangChainProvider, fix LDMessage[…

db8adb7

…] input handling

refactor: remove static create() from LangChainRunnerFactory; instrum…

94fc74b

…ent on construction Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

refactor: LangChainRunnerFactory extends AIProvider

7d8a246

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

refactor: move createLangChainModel to LangChainHelper

26741bc

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

jsonbailey force-pushed the jb/aic-2388/js-langchain-runner branch from 2479fb2 to d297039 Compare May 6, 2026 19:35

Use langchain agents

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addresss feedback

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remove zod dependency

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strip model tools

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jsonbailey added 2 commits May 6, 2026 16:44

address feedback

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address feedback

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jsonbailey merged commit f065743 into next-ai-release May 6, 2026
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jsonbailey deleted the jb/aic-2388/js-langchain-runner branch May 6, 2026 21:57

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feat: Replace LangChainProvider with Runner protocol implementation (…

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…AIC-2388) (#1338)

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chore: Next AI SDK Release #1361

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feat!: Remove AIProvider deprecated methods and create*/init* aliases (AIC-2388) #1363

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feat: Replace LangChainProvider with Runner protocol implementation (…

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…AIC-2388) (#1338)

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chore: release main #1369

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