diff --git a/docs/adr/0017-agent-session-is-provider-bound.md b/docs/adr/0017-agent-session-is-provider-bound.md
index 331cf3a..47805b4 100644
--- a/docs/adr/0017-agent-session-is-provider-bound.md
+++ b/docs/adr/0017-agent-session-is-provider-bound.md
@@ -1,8 +1,8 @@
-# ADR 0017: Agent Runtime — Claude Code SDK
+# ADR 0017: Agent Runtime — Claude Code SDK via OpenRouter
 
 ## Status
 
-Accepted — supersedes the original ADR-0017 (provider-agnostic session).
+Accepted.
 
 ## Context
 
@@ -16,38 +16,42 @@ partial-message streaming, and a battle-tested multi-turn loop. Building these
 ourselves meant re-implementing what the Claude Code SDK already provides.
 
 The Feishu integration also proved costly to hand-roll — card schema quirks,
-patch limitations, file support — each API quirk cost a round-trip. The
-Claude-to-IM library (2.7K stars) has already solved these, but its
-LLMProvider interface expects Claude Code SDK's SSE event format. Using it with
-a generic provider would require a conversion layer.
+patch limitations, file support — each API quirk cost a round-trip.
 
 ## Decision
 
-Adopt `@anthropic-ai/claude-agent-sdk` as the agent runtime. The SDK's `query()`
-function owns the agent loop (tool dispatch, compaction, streaming). Built-in
-tools (Read, Write, Bash, Glob, Grep) cover the entire tool surface — no custom
-tools needed. `cph check` / `cph build` run via Bash.
+Adopt `@anthropic-ai/claude-agent-sdk` as the agent runtime, routed through
+OpenRouter's **"Anthropic Skin"** (`https://openrouter.ai/api`).
 
-This means:
-- The agent layer is **Anthropic-specific**, not provider-agnostic. Claude Code
-  SDK speaks the Anthropic Messages API and cannot be pointed at OpenRouter
-  (which is OpenAI-compatible).
-- An Anthropic API key (or OAuth via Claude Pro/Max) is required.
-- Model selection is within the Anthropic model family (Sonnet, Haiku, Opus),
-  not across vendors.
+OpenRouter exposes an Anthropic Messages API-compatible endpoint. Claude Code
+SDK speaks its native protocol directly to OpenRouter — no proxy, no format
+conversion. The SDK's `query()` owns the agent loop (tool dispatch, compaction,
+streaming). Built-in tools (Read, Write, Bash, Glob, Grep) cover the entire
+tool surface — no custom tools needed. `cph check` / `cph build` run via Bash.
+
+Environment variables:
+```
+ANTHROPIC_BASE_URL=https://openrouter.ai/api
+ANTHROPIC_AUTH_TOKEN=<OpenRouter API key>
+ANTHROPIC_API_KEY=""  # must be explicitly empty
+```
+
+Model routing: `ANTHROPIC_DEFAULT_SONNET_MODEL` etc. accept OpenRouter model
+IDs (e.g. `z-ai/glm-4.7`, `anthropic/claude-sonnet-4-20250514`). This means
+**provider-agnosticism is preserved** — any OpenRouter model that supports tool
+use can be used, not just Anthropic models.
 
 ## Consequences
 
-- We lose the ability to route to GLM or other non-Anthropic models via
-  OpenRouter. This is the accepted cost of getting a mature agent loop.
-- The Vercel AI SDK dependency is dropped.
+- Provider-agnosticism preserved via OpenRouter — GLM, Claude, GPT, etc. all
+  work as long as the model supports tool use.
+- The agent loop is Claude Code SDK's (compaction, tool approval, partial
+  message streaming) — not hand-rolled.
 - Custom tools (read_file, write_file, cph_check, cph_build) are replaced by
   the SDK's built-in Read/Write/Bash/Glob/Grep.
-- The SSE event format matches Claude-to-IM's expected protocol natively —
-  adopting Claude-to-IM for Feishu integration is a direct fit, no conversion.
-- Per-run model selection still works (role→model mapping), but models are
-  Anthropic aliases, not OpenRouter routing IDs.
-- If provider-agnosticism becomes a hard requirement again, the migration path
-  is: replace `query()` with a Vercel AI SDK `streamText` call + an SSE format
-  converter (~100 lines). The rest of the architecture (trigger, lock,
-  permission, Feishu client) is provider-agnostic already.
+- The SSE event format matches Claude-to-IM's expected protocol natively.
+- Per-run model selection works via role→model mapping; models are OpenRouter
+  IDs, not Anthropic-only aliases.
+- OpenRouter recommends setting Anthropic as the top-priority provider for
+  Claude Code; non-Anthropic models may have reduced compatibility with some
+  SDK features (e.g. thinking blocks).
diff --git a/hub/.env.example b/hub/.env.example
index 62ee565..73d9d30 100644
--- a/hub/.env.example
+++ b/hub/.env.example
@@ -1,28 +1,31 @@
 # Hub runtime configuration. Copy to .env and fill in.
-#
-# For local dev: `cp .env.example .env` then edit.
-# For tests:     integration tests read from .env via dotenv.
 
 # PostgreSQL connection string.
 DATABASE_URL="postgresql://paradigm:paradigm@127.0.0.1:5432/paradigm"
 
-# OpenRouter (or any OpenAI-compatible) API key.
+# OpenRouter API key — used as ANTHROPIC_AUTH_TOKEN for Claude Code SDK.
+# OpenRouter's "Anthropic Skin" (https://openrouter.ai/api) is Anthropic-API
+# compatible, so Claude Code SDK speaks its native protocol directly.
 # Get one at https://openrouter.ai/keys
-# The agent layer is provider-agnostic (ADR-0017); OpenRouter routes to any model.
 OPENROUTER_API_KEY=""
 
-# Optional: override the base URL (e.g. direct vendor API, local gateway).
-# OPENROUTER_BASE_URL="https://openrouter.ai/api/v1"
+# Claude Code SDK auth — derived from OpenRouter. Do NOT set ANTHROPIC_API_KEY
+# to a real value; it must be explicitly empty to avoid auth conflicts.
+ANTHROPIC_BASE_URL="https://openrouter.ai/api"
+ANTHROPIC_AUTH_TOKEN=""  # Set to same value as OPENROUTER_API_KEY
+ANTHROPIC_API_KEY=""
 
-# Feishu (lark) bot credentials. Create a self-built app at
-# https://open.feishu.cn/app, add the "Bot" capability, subscribe to
-# im.message.receive_v1, then fill these in.
+# Model override (optional). Defaults to Claude Sonnet. To use GLM:
+# ANTHROPIC_DEFAULT_SONNET_MODEL="z-ai/glm-4.7"
+# ANTHROPIC_DEFAULT_OPUS_MODEL="z-ai/glm-4.7"
+# ANTHROPIC_DEFAULT_HAIKU_MODEL="z-ai/glm-4.6"
+
+# Feishu (lark) bot credentials.
 FEISHU_APP_ID=""
 FEISHU_APP_SECRET=""
 FEISHU_BOT_OPEN_ID=""
 
-# Path to the `cph` binary (the Courseware-side checker, ADR-0016).
-# Defaults to `cph` on PATH if unset.
+# Path to the `cph` binary (ADR-0016). Defaults to `cph` on PATH.
 # CPH_BIN="/usr/local/bin/cph"
 
 # Hub server port. Defaults to 8788.
diff --git a/hub/src/server.ts b/hub/src/server.ts
index 54e6c23..56b183a 100644
--- a/hub/src/server.ts
+++ b/hub/src/server.ts
@@ -29,6 +29,14 @@ function requireEnv(name: string): string {
 async function main(): Promise<void> {
   const databaseUrl = requireEnv("DATABASE_URL");
   void databaseUrl;
+
+  // Claude Code SDK auth via OpenRouter's Anthropic Skin. The SDK reads
+  // ANTHROPIC_BASE_URL + ANTHROPIC_AUTH_TOKEN from env. ANTHROPIC_API_KEY
+  // must be explicitly empty to avoid auth conflicts.
+  const openrouterKey = requireEnv("OPENROUTER_API_KEY");
+  process.env["ANTHROPIC_BASE_URL"] ??= "https://openrouter.ai/api";
+  process.env["ANTHROPIC_AUTH_TOKEN"] ??= openrouterKey;
+  process.env["ANTHROPIC_API_KEY"] ??= "";
   const feishuAppId = requireEnv("FEISHU_APP_ID");
   const feishuAppSecret = requireEnv("FEISHU_APP_SECRET");
   const feishuBotOpenId = requireEnv("FEISHU_BOT_OPEN_ID");