diff --git a/packages/cli-workflow/src/commands/thread.ts b/packages/cli-workflow/src/commands/thread.ts
index 8a75d7c..eefb8ab 100644
--- a/packages/cli-workflow/src/commands/thread.ts
+++ b/packages/cli-workflow/src/commands/thread.ts
@@ -804,13 +804,11 @@ function spawnAgent(
   role: string,
   edgePrompt: string,
 ): CasRef {
-  const argv = [...agent.args, threadId, role];
-  const env = { ...process.env, UWF_EDGE_PROMPT: edgePrompt };
+  const argv = [...agent.args, "--thread", threadId, "--role", role, "--prompt", edgePrompt];
   let stdout: string;
   try {
     stdout = execFileSync(agent.command, argv, {
       encoding: "utf8",
-      env,
       stdio: ["ignore", "pipe", "pipe"],
       maxBuffer: 50 * 1024 * 1024, // 50 MB — stream-json output can be large
     });
diff --git a/packages/workflow-agent-kit/src/context.ts b/packages/workflow-agent-kit/src/context.ts
index 4c1647b..7c48b94 100644
--- a/packages/workflow-agent-kit/src/context.ts
+++ b/packages/workflow-agent-kit/src/context.ts
@@ -21,14 +21,6 @@ function fail(message: string): never {
   throw new Error(message);
 }
 
-function readEdgePrompt(): string {
-  const value = process.env.UWF_EDGE_PROMPT;
-  if (value === undefined || value === "") {
-    fail("UWF_EDGE_PROMPT environment variable is required");
-  }
-  return value;
-}
-
 function walkChain(store: Store, schemas: AgentStore["schemas"], headHash: CasRef): ChainState {
   const headNode = store.get(headHash);
   if (headNode === null) {
@@ -123,7 +115,11 @@ async function loadWorkflow(store: Store, schemas: AgentStore["schemas"], workfl
  * Build agent execution context from thread head in threads.yaml.
  * Walks the CAS chain from head to StartNode and expands step outputs.
  */
-export async function buildContext(threadId: ThreadId, role: string): Promise<AgentContext> {
+export async function buildContext(
+  threadId: ThreadId,
+  role: string,
+  edgePrompt: string,
+): Promise<AgentContext> {
   const storageRoot = resolveStorageRoot();
   const agentStore = await createAgentStore(storageRoot);
   const { store, schemas } = agentStore;
@@ -142,7 +138,6 @@ export async function buildContext(threadId: ThreadId, role: string): Promise<Ag
   }
 
   const steps = await buildHistory(store, chain.stepsNewestFirst);
-  const edgePrompt = readEdgePrompt();
   const isFirstVisit = !steps.some((s) => s.role === role);
 
   return {
@@ -172,6 +167,7 @@ export type BuildContextMeta = {
 export async function buildContextWithMeta(
   threadId: ThreadId,
   role: string,
+  edgePrompt: string,
 ): Promise<AgentContext & { meta: BuildContextMeta }> {
   const storageRoot = resolveStorageRoot();
   const agentStore = await createAgentStore(storageRoot);
@@ -191,7 +187,6 @@ export async function buildContextWithMeta(
   }
 
   const steps = await buildHistory(store, chain.stepsNewestFirst);
-  const edgePrompt = readEdgePrompt();
   const isFirstVisit = !steps.some((s) => s.role === role);
 
   return {
diff --git a/packages/workflow-agent-kit/src/run.ts b/packages/workflow-agent-kit/src/run.ts
index 2a3d8fb..391e3f8 100644
--- a/packages/workflow-agent-kit/src/run.ts
+++ b/packages/workflow-agent-kit/src/run.ts
@@ -22,16 +22,24 @@ function agentLabel(name: string): string {
   return `uwf-${name}`;
 }
 
-function parseArgv(argv: string[]): { threadId: ThreadId; role: string } {
-  const threadId = argv[2];
-  const role = argv[3];
-  if (threadId === undefined || threadId === "") {
-    fail("usage: <agent-cli> <thread-id> <role>");
+const USAGE = "usage: <agent-cli> --thread <id> --role <role> --prompt <text>";
+
+function getNamedArg(argv: string[], name: string): string {
+  const idx = argv.indexOf(name);
+  if (idx === -1 || idx + 1 >= argv.length) {
+    return "";
   }
-  if (role === undefined || role === "") {
-    fail("usage: <agent-cli> <thread-id> <role>");
-  }
-  return { threadId: threadId as ThreadId, role };
+  return argv[idx + 1];
+}
+
+function parseArgv(argv: string[]): { threadId: ThreadId; role: string; prompt: string } {
+  const threadId = getNamedArg(argv, "--thread");
+  const role = getNamedArg(argv, "--role");
+  const prompt = getNamedArg(argv, "--prompt");
+  if (threadId === "") fail(USAGE);
+  if (role === "") fail(USAGE);
+  if (prompt === "") fail(USAGE);
+  return { threadId: threadId as ThreadId, role, prompt };
 }
 
 function runWithMessage<T>(label: string, fn: () => Promise<T>): Promise<T> {
@@ -103,11 +111,11 @@ async function persistStep(options: {
 
 export function createAgent(options: AgentOptions): () => Promise<void> {
   return async function main(): Promise<void> {
-    const { threadId, role } = parseArgv(process.argv);
+    const { threadId, role, prompt } = parseArgv(process.argv);
     const storageRoot = resolveStorageRoot();
     loadDotenv({ path: getEnvPath(storageRoot) });
 
-    const ctx = await runWithMessage("context", () => buildContextWithMeta(threadId, role));
+    const ctx = await runWithMessage("context", () => buildContextWithMeta(threadId, role, prompt));
 
     const roleDef = ctx.workflow.roles[role];
     if (roleDef === undefined) {
diff --git a/packages/workflow-agent-kit/src/types.ts b/packages/workflow-agent-kit/src/types.ts
index 9a25918..42f8c1e 100644
--- a/packages/workflow-agent-kit/src/types.ts
+++ b/packages/workflow-agent-kit/src/types.ts
@@ -13,7 +13,7 @@ export type AgentContext = ModeratorContext & {
    */
   outputFormatInstruction: string;
   /**
-   * Edge prompt from the graph transition that led to this role (UWF_EDGE_PROMPT).
+   * Edge prompt from the graph transition that led to this role (--prompt CLI arg).
    * Always the real moderator instruction for this step.
    */
   edgePrompt: string;