fix: scrub OpenCode prompts routed through LiteLLM

README.md

@@ -70,7 +70,7 @@ Verify at `http://localhost:3456/plugins` — you should see `opencode-scrub` li
 | OpenCode prompt + user CLAUDE.md additions | identity stripped, all user content preserved |
 | OpenCode environment preamble + `<env>` | duplicate preamble and redundant fields removed; bare `Working directory` retained for Meridian's cwd extraction |
 
-The plugin is scoped to `adapters: ["opencode"]`, so it has no effect on requests from pi, Crush, Droid, ForgeCode, or the passthrough adapter.
+The plugin runs for the `opencode` adapter and for `passthrough` requests that still carry an OpenCode-specific identity or runtime marker. This covers OpenCode routed through LiteLLM when its client headers are removed. Other passthrough prompts, including genuine Claude Code prompts with an `<env>` block, remain byte-for-byte unchanged.
 
 ## Rules
 

src/__tests__/plugin.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, it } from "bun:test"
+import plugin from "../index.js"
+import type { RequestContext } from "../types.js"
+
+const opencodePrompt = `You are powered by the model named claude-haiku-4-5. The exact model ID is anthropic/claude-haiku-4-5
+Here is some useful information about the environment you are running in:
+<env>
+  Working directory: /client/project
+  Platform: darwin
+</env>`
+
+describe("opencode-scrub adapter boundary", () => {
+  it("includes LiteLLM's passthrough classification and scrubs OpenCode content", () => {
+    expect(plugin.adapters).toContain("passthrough")
+    const ctx: RequestContext = { adapter: "passthrough", systemContext: opencodePrompt, metadata: {} }
+    const result = plugin.onRequest?.(ctx)
+    expect(result?.systemContext).not.toContain("You are powered by the model named")
+    expect(result?.systemContext).not.toContain("Here is some useful information")
+    expect(result?.systemContext).toContain("Working directory: /client/project")
+  })
+
+  it("preserves genuine Claude Code passthrough prompts byte-for-byte", () => {
+    const systemContext = "You are Claude Code.\n\n\nHere is some useful information about the environment you are running in:\n<env>\n  Working directory: /client/project\n</env>\n\n"
+    const ctx: RequestContext = { adapter: "passthrough", systemContext, metadata: {} }
+    expect(plugin.onRequest?.(ctx)).toBe(ctx)
+    expect(ctx.systemContext).toBe(systemContext)
+  })
+
+  it("preserves incidental OpenCode mentions in other passthrough prompts", () => {
+    const systemContext = "Compare OpenCode and other editors.\n\n\nKeep this formatting.\n"
+    const ctx: RequestContext = { adapter: "passthrough", systemContext, metadata: {} }
+    expect(plugin.onRequest?.(ctx)).toBe(ctx)
+  })
+
+  it("keeps the existing direct OpenCode adapter behavior", () => {
+    const ctx: RequestContext = { adapter: "opencode", systemContext: opencodePrompt, metadata: {} }
+    const result = plugin.onRequest?.(ctx)
+    expect(result?.systemContext).not.toContain("Here is some useful information")
+    expect(result?.systemContext).toContain("Working directory: /client/project")
+  })
+})

src/index.ts

@@ -1,23 +1,31 @@
 /**
  * Meridian plugin: strip opencode-identifying fingerprints from the system prompt.
  *
- * Scoped to the `opencode` adapter. Runs on every opencode request — the
- * scrub is idempotent, so fork/subagent replays produce identical output.
+ * Runs on the `opencode` adapter and on `passthrough` requests carrying an
+ * OpenCode-specific marker. LiteLLM can remove the client headers that let
+ * Meridian identify OpenCode, so its requests arrive as `passthrough`.
  */
 
 import type { Transform, RequestContext } from "./types.js"
 import { scrubOpencodeFingerprints } from "./scrub.js"
 
 export type { Transform, RequestContext } from "./types.js"
 
+// The duplicate <env> preamble is shared with genuine Claude Code traffic.
+// Require an independent OpenCode/OMO marker before touching passthrough
+// requests, so unrelated clients keep their original prompt bytes.
+const PASSTHROUGH_OPENCODE_MARKER =
+  /You are OpenCode, the best coding agent on the planet\.|You are powered by the model named |<omo-env>|<agent-identity>|You are (?:"|\*\*)Sisyphus(?:"|\*\*)[^\n]*OhMyOpenCode/
+
 const plugin: Transform = {
   name: "opencode-scrub",
   version: "0.1.0",
   description: "Strip opencode-identifying fingerprints from the system prompt before it reaches Claude",
-  adapters: ["opencode"],
+  adapters: ["opencode", "passthrough"],
 
   onRequest(ctx: RequestContext): RequestContext {
     if (!ctx.systemContext) return ctx
+    if (ctx.adapter === "passthrough" && !PASSTHROUGH_OPENCODE_MARKER.test(ctx.systemContext)) return ctx
     const scrubbed = scrubOpencodeFingerprints(ctx.systemContext)
     if (scrubbed === ctx.systemContext) return ctx
     return { ...ctx, systemContext: scrubbed }