feat(agent): merge grok ceremony lines into the one residual

Author: TheGreatAxios

src/agent/model-family-policy.ts

@@ -109,6 +109,34 @@ const MUSE_POLICY: Omit<ModelFamilyPolicy, "family"> = {
   toolDisciplineRules: MUSE_TOOL_DISCIPLINE_RULES,
 };
 
+// Single grok prompt residual (CL-8296): the finish-bias bullets plus the
+// three ceremony lines from the CL-7768 design (no git, no pre-plan, verify
+// once), merged into one block with no line twice. The don't re-read idea
+// appears exactly once (the "re-open paths" bullet) — it is not repeated.
+// Grok-only: detectModelFamily has no glm family, so per the <30min rule no
+// GLM row ships here. The text lives here once; buildGrokLeafAntiThrashNote
+// (prompts.ts) returns it verbatim, so the prompt carries exactly one grok
+// residual and the sibling CL-8297 hook resolves to the same block.
+const GROK_PROMPT_RESIDUAL = [
+  "Finish bias (xAI / Grok worker):",
+  "- Once you can answer the dispatch brief, prefer the structured report over another speculative tool call.",
+  "- If the next call would only re-open paths you already read, write the report instead.",
+  "- When the dispatch brief's done-definition is met, write the report envelope instead of making one more search or micro-edit.",
+  "- Route file and web work through the dedicated tools, never run_shell — mining showed grok reaching for shell first when a typed tool already covered the job.",
+  "- Never run git add, git commit, git stash, or any other state-changing git command unless the user asks.",
+  "- Do not narrate a plan before acting on a small task; act, then report.",
+  "- Verify with the test command once at the end, not after every edit.",
+].join("\n");
+
+/**
+ * Minimal per-family prompt residual hook. The sibling CL-8297 owns the
+ * canonical hook; this local copy keeps the branch self-contained so tests
+ * pass standalone — the two reconcile when CL-8297 lands.
+ */
+export function promptResidual(family: ModelFamily): string {
+  return family === "grok" ? GROK_PROMPT_RESIDUAL : "";
+}
+
 export function resolveModelFamilyPolicy(input: {
   providerName: string;
   model?: string;

src/agent/prompts.ts

@@ -11,6 +11,7 @@ import {
   buildWorkerContract,
   buildWorkerToolNames,
 } from "./worker-contract.js";
+import { promptResidual } from "./model-family-policy.js";
 
 // Advertise every gated core tool when the caller has no session-start facts
 // (tests, ad-hoc prompt previews) — except wait_agents, which is mount-gated:
@@ -511,14 +512,12 @@ export function buildSubAgentReportContract(
 // Tiny residual for Grok/xAI workers: mining showed higher tools-only thrash
 // than Codex on the same harness. Shared thrash harness + spawn contracts do
 // the structural work; this is only a finish-bias nudge, not a full rewrite.
+// Single source of truth is the promptResidual("grok") block in
+// model-family-policy.ts (CL-8296 merged the three ceremony lines into it);
+// this composes that block verbatim so the prompt carries one grok residual
+// with no line twice.
 export function buildGrokLeafAntiThrashNote(): string {
-  return [
-    "Finish bias (xAI / Grok worker):",
-    "- Once you can answer the dispatch brief, prefer the structured report over another speculative tool call.",
-    "- If the next call would only re-open paths you already read, write the report instead.",
-    "- When the dispatch brief's done-definition is met, write the report envelope instead of making one more search or micro-edit.",
-    "- Route file and web work through the dedicated tools, never run_shell — mining showed grok reaching for shell first when a typed tool already covered the job.",
-  ].join("\n");
+  return promptResidual("grok");
 }
 
 export function buildSubAgentSystemPrompt(