forked from EduCraft/curriculum-project-hub
78 lines
3.7 KiB
Markdown
78 lines
3.7 KiB
Markdown
# ADR 0017: Agent Runtime — Claude Code SDK via OpenRouter
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## Status
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Accepted.
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## Context
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The original ADR-0017 mandated a provider-agnostic agent layer: any
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OpenAI-compatible model via OpenRouter, custom agent loop built on Vercel AI
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SDK's `streamText`. The motivation was to avoid vendor lock-in.
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In practice, the hand-rolled agent loop lacked capabilities that a production
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agent needs: context compaction (long conversations), tool approval flows,
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partial-message streaming, and a battle-tested multi-turn loop. Building these
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ourselves meant re-implementing what the Claude Code SDK already provides.
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The Feishu integration also proved costly to hand-roll — card schema quirks,
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patch limitations, file support — each API quirk cost a round-trip.
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## Decision
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Adopt `@anthropic-ai/claude-agent-sdk` as the agent runtime, routed through
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OpenRouter's **"Anthropic Skin"** (`https://openrouter.ai/api`).
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OpenRouter exposes an Anthropic Messages API-compatible endpoint. Claude Code
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SDK speaks its native protocol directly to OpenRouter — no proxy, no format
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conversion. The SDK's `query()` owns the agent loop (tool dispatch, compaction,
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streaming). Built-in tools (Read, Write, Bash, Glob, Grep) cover the entire
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tool surface — no custom tools needed. `cph check` / `cph build` run via Bash.
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The Hub `AgentSession` is provider/role/model-bound, and it must persist the
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provider runtime cursor needed to continue a conversation. For Claude Code SDK,
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that cursor is the `result.session_id`; store it in `AgentSession.metadata` as
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`claudeSessionId` and pass it back to the next `query()` call as
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`options.resume`. Role is part of the session binding because role prompts and
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tool surfaces can differ even when the underlying model is the same; `/draft`
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and `/review` must not resume the same Claude runtime cursor by accident.
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Role definitions are Organization-scoped runtime data. A role bundle selects
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its default model, system prompt, tool allowlist and installed Agent skill
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versions. PostgreSQL is authoritative for role composition and skill metadata;
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skill bytes live in a content-addressed persistent store selected only by the
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recorded SHA-256 digest. Updating a role or binding skills takes effect without
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a Hub release or process restart. A change to the role's execution surface
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(model, prompt, tools, selected skill content) archives its active sessions so
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the next run cannot resume a provider context created under stale instructions;
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label and ordering-only changes preserve conversational continuity.
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Environment variables:
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```
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ANTHROPIC_BASE_URL=https://openrouter.ai/api
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ANTHROPIC_AUTH_TOKEN=<OpenRouter API key>
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ANTHROPIC_API_KEY="" # must be explicitly empty
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```
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Model routing: `ANTHROPIC_DEFAULT_SONNET_MODEL` etc. accept OpenRouter model
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IDs (e.g. `z-ai/glm-4.7`, `anthropic/claude-sonnet-4-20250514`). This gives
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limited OpenRouter-level model routing, but the runtime is still Claude Agent
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SDK-shaped: non-Claude models are best-effort and may not support every
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Claude Code feature.
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## Consequences
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- Provider-agnosticism is not fully preserved. OpenRouter can route to GLM,
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Claude, GPT, etc., but the runtime protocol and agent loop remain Claude
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Agent SDK-bound.
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- The agent loop is Claude Code SDK's (compaction, tool approval, partial
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message streaming) — not hand-rolled.
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- Custom tools (read_file, write_file, cph_check, cph_build) are replaced by
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the SDK's built-in Read/Write/Bash/Glob/Grep.
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- The SSE event format matches Claude-to-IM's expected protocol natively.
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- Per-run model selection works via role→model mapping; models are OpenRouter
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IDs, not Anthropic-only aliases.
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- OpenRouter recommends setting Anthropic as the top-priority provider for
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Claude Code; non-Anthropic models may have reduced compatibility with some
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SDK features (e.g. thinking blocks).
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