diff --git a/docs/reference/spec-v01-backend-adapter.md b/docs/reference/spec-v01-backend-adapter.md
index b43ae62..564bfdb 100644
--- a/docs/reference/spec-v01-backend-adapter.md
+++ b/docs/reference/spec-v01-backend-adapter.md
@@ -52,6 +52,9 @@ Adapter 必须把 backend 错误映射为稳定 failureKind：
 | `provider-auth-failed` | provider credential 或 auth file 无效、上游返回 401/403。 |
 | `provider-rate-limited` | 上游限流或 quota 错误。 |
 | `backend-protocol-error` | backend 输出无法解析、协议字段缺失。 |
+| `backend-json-parse-error` | backend stdout 不是合法 JSON-RPC 行。 |
+| `backend-response-invalid` | backend JSON-RPC response/terminal notification 缺少必需字段。 |
+| `backend-spawn-failed` | backend app-server 进程无法启动。 |
 | `backend-failed` | backend 进程非零退出或 terminal error。 |
 | `backend-timeout` | executionPolicy timeout 触发。 |
 | `cancelled` | interrupt/cancel 生效。 |
diff --git a/docs/reference/spec-v01-backend-codex.md b/docs/reference/spec-v01-backend-codex.md
index a883064..ee34ba1 100644
--- a/docs/reference/spec-v01-backend-codex.md
+++ b/docs/reference/spec-v01-backend-codex.md
@@ -96,6 +96,7 @@ Run 的 `executionPolicy.secretScope` 应引用 `agentrun-v01-provider-codex` 
 | --- | --- | --- |
 | Codex backend 规格 | 已定义 | 本文为 v0.1 第一真实 backend 权威。 |
 | Codex Secret projection | 未实现 | 需要后续 Kubernetes Secret 和 runner/backend manifest。 |
-| Codex adapter | 未实现 | 需要后续代码实现。 |
+| Codex adapter | 已部分实现 | 当前代码已实现受控 `codex app-server --listen stdio://`、`initialize`/`thread/start`/`thread/resume`/`turn/start` response 校验、stderr 有界诊断、spawn/JSON parse/response invalid/timeout failureKind 和 fake app-server 自测试。 |
+| 错误可观测与脱敏 | 已部分实现 | child env、cwd、workspace 和 Codex home 只输出摘要；stderr tail 有界且标记截断；事件和 failure 统一走 redaction。 |
 | 真实 provider turn | 未实现 | 综合联调必须真实完成后才能发布通过。 |
 | hostPath `~/.codex` | 不采用 | 只能通过 Kubernetes Secret projection 注入。 |
diff --git a/src/backend/adapter.ts b/src/backend/adapter.ts
index d12ff54..cb8115c 100644
--- a/src/backend/adapter.ts
+++ b/src/backend/adapter.ts
@@ -21,6 +21,7 @@ export async function runBackendTurn(run: RunRecord, command: CommandRecord, opt
     timeoutMs: run.executionPolicy.timeoutMs,
   };
   if (typeof command.payload.model === "string") turnOptions.model = command.payload.model;
+  if (typeof command.payload.threadId === "string") turnOptions.threadId = command.payload.threadId;
   if (options.codexCommand) turnOptions.command = options.codexCommand;
   if (options.codexArgs) turnOptions.args = options.codexArgs;
   if (options.env) turnOptions.env = options.env;
diff --git a/src/backend/codex-stdio.ts b/src/backend/codex-stdio.ts
index c82365c..83ecbd4 100644
--- a/src/backend/codex-stdio.ts
+++ b/src/backend/codex-stdio.ts
@@ -1,13 +1,40 @@
 import { spawn, type ChildProcessWithoutNullStreams } from "node:child_process";
+import { createHash } from "node:crypto";
 import { accessSync, constants as fsConstants } from "node:fs";
+import path from "node:path";
 import * as readline from "node:readline";
 import type { BackendEvent, BackendTurnResult, FailureKind, JsonRecord, JsonValue, TerminalStatus } from "../common/types.js";
 import { redactJson, redactText } from "../common/redaction.js";
 
+const codexProtocol = "codex-app-server-jsonrpc-stdio";
+const defaultCodexArgs = ["app-server", "--listen", "stdio://"];
+const stderrBufferBytes = 64_000;
+const stderrEventChars = 4_000;
+const requestTimeoutCapMs = 30_000;
+
+const childEnvSummaryKeys = [
+  "CODEX_HOME",
+  "HOME",
+  "PATH",
+  "HTTP_PROXY",
+  "HTTPS_PROXY",
+  "ALL_PROXY",
+  "NO_PROXY",
+  "http_proxy",
+  "https_proxy",
+  "all_proxy",
+  "no_proxy",
+  "OPENAI_API_KEY",
+  "CODEX_API_KEY",
+  "GITHUB_TOKEN",
+  "GH_TOKEN",
+];
+
 export interface CodexStdioTurnOptions {
   prompt: string;
   cwd: string;
   model?: string;
+  threadId?: string;
   approvalPolicy: string;
   sandbox: string;
   timeoutMs: number;
@@ -18,48 +45,87 @@ export interface CodexStdioTurnOptions {
 }
 
 interface PendingRequest {
+  method: string;
+  timer: NodeJS.Timeout;
   resolve: (value: unknown) => void;
   reject: (error: Error) => void;
 }
 
+interface CodexStdioCloseInfo extends JsonRecord {
+  code: number | null;
+  signal: string | null;
+  stderrTail: string;
+  stderrBytes: number;
+  stderrTruncated: boolean;
+  failureKind: FailureKind | null;
+  message: string | null;
+}
+
+class CodexStdioFailure extends Error {
+  readonly failureKind: FailureKind;
+  readonly phase: string;
+  readonly details: JsonRecord;
+
+  constructor(failureKind: FailureKind, message: string, phase: string, details: JsonRecord = {}) {
+    super(redactText(message));
+    this.name = "CodexStdioFailure";
+    this.failureKind = failureKind;
+    this.phase = phase;
+    this.details = redactJson(details);
+  }
+}
+
 export class CodexStdioClient {
   private readonly child: ChildProcessWithoutNullStreams;
   private readonly pending = new Map<number, PendingRequest>();
-  private readonly stderrChunks: Buffer[] = [];
+  private stderrTailBuffer = Buffer.alloc(0);
+  private stderrBytes = 0;
   private nextId = 1;
   private closed = false;
-  readonly closedPromise: Promise<{ code: number | null; signal: string | null; stderrTail: string }>;
-  private closeResolve!: (value: { code: number | null; signal: string | null; stderrTail: string }) => void;
+  private closeFailure: CodexStdioFailure | null = null;
+  readonly closedPromise: Promise<CodexStdioCloseInfo>;
+  private closeResolve!: (value: CodexStdioCloseInfo) => void;
 
   constructor(options: { command?: string; args?: string[]; cwd: string; env?: NodeJS.ProcessEnv; onNotification: (message: JsonRecord) => void }) {
     this.closedPromise = new Promise((resolve) => { this.closeResolve = resolve; });
-    this.child = spawn(options.command ?? "codex", options.args ?? ["app-server", "--listen", "stdio://"], {
-      cwd: options.cwd,
-      env: options.env ?? process.env,
-      stdio: "pipe",
-    });
-    this.child.stderr.on("data", (chunk: Buffer) => {
-      this.stderrChunks.push(chunk);
-      while (Buffer.concat(this.stderrChunks).length > 64_000) this.stderrChunks.shift();
-    });
+    const command = options.command ?? "codex";
+    const args = options.args ?? defaultCodexArgs;
+    try {
+      this.child = spawn(command, args, {
+        cwd: options.cwd,
+        env: options.env ?? process.env,
+        stdio: "pipe",
+      });
+    } catch (error) {
+      throw spawnFailure(command, error);
+    }
+    this.child.stderr.on("data", (chunk: Buffer) => this.appendStderr(chunk));
     const rl = readline.createInterface({ input: this.child.stdout, crlfDelay: Infinity });
     void this.readLines(rl, options.onNotification);
     this.child.on("close", (code, signal) => this.handleClose(code, signal));
-    this.child.on("error", (error) => this.handleClose(127, error.message));
+    this.child.on("error", (error) => this.handleClose(127, null, spawnFailure(command, error)));
   }
 
-  request(method: string, params: JsonRecord): Promise<unknown> {
-    if (this.closed) return Promise.reject(new Error("codex app-server is closed"));
+  request(method: string, params: JsonRecord, timeoutMs = requestTimeoutCapMs): Promise<unknown> {
+    if (this.closed) return Promise.reject(this.closeFailure ?? new CodexStdioFailure("backend-failed", "codex app-server is closed", `request:${method}`));
     const id = this.nextId++;
     const message = { id, method, params };
+    const effectiveTimeoutMs = positiveTimeout(timeoutMs);
     return new Promise((resolve, reject) => {
-      this.pending.set(id, { resolve, reject });
-      this.child.stdin.write(`${JSON.stringify(message)}\n`);
+      const timer = setTimeout(() => {
+        this.rejectRequest(id, new CodexStdioFailure("backend-timeout", `Codex stdio request ${method} timed out after ${effectiveTimeoutMs}ms`, `request:${method}`, { method, timeoutMs: effectiveTimeoutMs }));
+      }, effectiveTimeoutMs);
+      this.pending.set(id, { method, timer, resolve, reject });
+      this.child.stdin.write(`${JSON.stringify(message)}\n`, "utf8", (error: Error | null | undefined) => {
+        if (!error) return;
+        this.rejectRequest(id, new CodexStdioFailure("backend-failed", `failed to write Codex stdio request ${method}: ${error.message}`, `request:${method}`, { method }));
+      });
     });
   }
 
   notify(method: string, params: JsonRecord = {}): void {
-    if (!this.closed) this.child.stdin.write(`${JSON.stringify({ method, params })}\n`);
+    if (this.closed) return;
+    this.child.stdin.write(`${JSON.stringify({ method, params })}\n`, "utf8", () => undefined);
   }
 
   stop(): void {
@@ -70,33 +136,65 @@ export class CodexStdioClient {
     }, 1500).unref?.();
   }
 
+  private appendStderr(chunk: Buffer): void {
+    this.stderrBytes += chunk.byteLength;
+    const next = Buffer.concat([this.stderrTailBuffer, chunk]);
+    this.stderrTailBuffer = next.byteLength > stderrBufferBytes ? next.subarray(next.byteLength - stderrBufferBytes) : next;
+  }
+
   private async readLines(rl: readline.Interface, onNotification: (message: JsonRecord) => void): Promise<void> {
     try {
       for await (const line of rl) {
         const trimmed = String(line).trim();
         if (trimmed.length === 0) continue;
-        const message = JSON.parse(trimmed) as JsonRecord;
-        const id = typeof message.id === "number" ? message.id : null;
-        const method = typeof message.method === "string" ? message.method : null;
-        if (id !== null && method === null) {
-          const pending = this.pending.get(id);
-          if (!pending) continue;
-          this.pending.delete(id);
-          if (message.error !== undefined) pending.reject(new Error(JSON.stringify(redactJson(message.error))));
-          else pending.resolve(message.result);
-          continue;
+        let message: JsonRecord;
+        try {
+          message = JSON.parse(trimmed) as JsonRecord;
+        } catch {
+          this.handleProtocolFailure(new CodexStdioFailure("backend-json-parse-error", "codex app-server emitted invalid JSON on stdout", "stdout:parse", { linePreview: redactText(trimmed.slice(0, 800)), lineChars: trimmed.length }));
+          break;
         }
-        if (id !== null && method !== null) {
-          this.handleServerRequest(id, method);
-          continue;
-        }
-        if (method !== null) onNotification(message);
+        this.handleMessage(message, onNotification);
       }
     } catch (error) {
-      this.rejectAll(error instanceof Error ? error : new Error(String(error)));
+      this.handleProtocolFailure(new CodexStdioFailure("backend-protocol-error", error instanceof Error ? error.message : String(error), "stdout:read"));
     }
   }
 
+  private handleMessage(message: JsonRecord, onNotification: (message: JsonRecord) => void): void {
+    const id = typeof message.id === "number" ? message.id : null;
+    const method = typeof message.method === "string" ? message.method : null;
+    if (id !== null && method === null) {
+      this.handleResponse(id, message);
+      return;
+    }
+    if (id !== null && method !== null) {
+      this.handleServerRequest(id, method);
+      return;
+    }
+    if (method !== null) {
+      onNotification(message);
+      return;
+    }
+    this.handleProtocolFailure(new CodexStdioFailure("backend-response-invalid", "codex app-server message had neither JSON-RPC id nor method", "stdout:message", { message }));
+  }
+
+  private handleResponse(id: number, message: JsonRecord): void {
+    const pending = this.pending.get(id);
+    if (!pending) return;
+    this.pending.delete(id);
+    clearTimeout(pending.timer);
+    if (message.error !== undefined) {
+      pending.reject(failureFromRpcError(pending.method, message.error));
+      return;
+    }
+    if (!("result" in message)) {
+      pending.reject(new CodexStdioFailure("backend-response-invalid", `codex app-server response for ${pending.method} omitted result and error`, `response:${pending.method}`, { method: pending.method }));
+      return;
+    }
+    pending.resolve(message.result);
+  }
+
   private handleServerRequest(id: number, method: string): void {
     if (method === "item/commandExecution/requestApproval" || method === "item/fileChange/requestApproval") {
       this.child.stdin.write(`${JSON.stringify({ id, result: { decision: "decline" } })}\n`);
@@ -105,92 +203,172 @@ export class CodexStdioClient {
     this.child.stdin.write(`${JSON.stringify({ id, error: { code: -32601, message: `Unsupported client-side request: ${method}` } })}\n`);
   }
 
+  private rejectRequest(id: number, error: CodexStdioFailure): void {
+    const pending = this.pending.get(id);
+    if (!pending) return;
+    this.pending.delete(id);
+    clearTimeout(pending.timer);
+    pending.reject(error);
+  }
+
   private rejectAll(error: Error): void {
-    for (const pending of this.pending.values()) pending.reject(error);
+    for (const pending of this.pending.values()) {
+      clearTimeout(pending.timer);
+      pending.reject(error);
+    }
     this.pending.clear();
   }
 
-  private handleClose(code: number | null, signal: string | null): void {
+  private handleProtocolFailure(error: CodexStdioFailure): void {
+    if (this.closed) return;
+    this.closeFailure = error;
+    this.rejectAll(error);
+    this.stop();
+  }
+
+  private handleClose(code: number | null, signal: string | null, failure: CodexStdioFailure | null = null): void {
     if (this.closed) return;
     this.closed = true;
-    const stderrTail = redactText(Buffer.concat(this.stderrChunks).toString("utf8").slice(-8000));
-    this.rejectAll(new Error(`codex app-server closed code=${code} signal=${signal}`));
-    this.closeResolve({ code, signal, stderrTail });
+    if (failure) this.closeFailure = failure;
+    const stderr = this.stderrInfo();
+    const closeInfo: CodexStdioCloseInfo = {
+      code,
+      signal,
+      stderrTail: stderr.stderrTail,
+      stderrBytes: this.stderrBytes,
+      stderrTruncated: stderr.stderrTruncated,
+      failureKind: this.closeFailure?.failureKind ?? null,
+      message: this.closeFailure?.message ?? null,
+    };
+    this.rejectAll(this.closeFailure ?? new CodexStdioFailure("backend-failed", `codex app-server closed code=${code} signal=${signal}`, "process:close", closeInfo));
+    this.closeResolve(closeInfo);
+  }
+
+  private stderrInfo(): { stderrTail: string; stderrTruncated: boolean } {
+    const buffered = this.stderrTailBuffer.toString("utf8");
+    const tail = buffered.slice(-8000);
+    return {
+      stderrTail: redactText(tail),
+      stderrTruncated: this.stderrBytes > this.stderrTailBuffer.byteLength || buffered.length > tail.length,
+    };
   }
 }
 
 export async function runCodexStdioTurn(options: CodexStdioTurnOptions): Promise<BackendTurnResult> {
-  const secretFailure = codexHomeReadiness(options.codexHome ?? options.env?.CODEX_HOME ?? `${options.env?.HOME ?? process.env.HOME ?? ""}/.codex`);
+  const codexHome = resolveCodexHome(options);
+  const secretFailure = codexHomeReadiness(codexHome);
   if (secretFailure) return secretFailure;
-  const events: BackendEvent[] = [{ type: "backend_status", payload: { phase: "codex-app-server-starting", protocol: "codex-app-server-jsonrpc-stdio" } }];
+  const env = childEnv(options, codexHome);
+  const events: BackendEvent[] = [{
+    type: "backend_status",
+    payload: {
+      phase: "codex-app-server-starting",
+      protocol: codexProtocol,
+      runtime: runtimeSummary(options, env, codexHome),
+    },
+  }];
   let assistantText = "";
-  let threadId: string | undefined;
+  let threadId: string | undefined = options.threadId;
   let turnId: string | undefined;
   let terminal: { status: TerminalStatus; failureKind: FailureKind | null; message: string | null } | null = null;
   let terminalResolve!: () => void;
   const terminalPromise = new Promise<void>((resolve) => { terminalResolve = resolve; });
-  const clientOptions: ConstructorParameters<typeof CodexStdioClient>[0] = {
-    cwd: options.cwd,
-    env: childEnv(options),
-    onNotification: (message) => {
-      const normalized = normalizeCodexNotification(message);
-      if (normalized.threadId) threadId = normalized.threadId;
-      if (normalized.turnId) turnId = normalized.turnId;
-      if (normalized.assistantDelta) assistantText += normalized.assistantDelta;
-      events.push(...normalized.events);
-      if (normalized.terminal) {
-        terminal = normalized.terminal;
-        terminalResolve();
-      }
-    },
-  };
-  if (options.command) clientOptions.command = options.command;
-  if (options.args) clientOptions.args = options.args;
-  const client = new CodexStdioClient(clientOptions);
+  let client: CodexStdioClient | null = null;
+  const requestTimeoutMs = Math.min(positiveTimeout(options.timeoutMs), requestTimeoutCapMs);
   const timeout = setTimeout(() => {
-    if (!terminal) {
-      terminal = { status: "failed", failureKind: "backend-timeout", message: `codex stdio turn timed out after ${options.timeoutMs}ms` };
-      events.push({ type: "error", payload: terminal });
-      client.stop();
-      terminalResolve();
-    }
-  }, options.timeoutMs);
+    if (terminal) return;
+    terminal = { status: "failed", failureKind: "backend-timeout", message: `codex stdio turn timed out after ${options.timeoutMs}ms` };
+    events.push({ type: "error", payload: { failureKind: terminal.failureKind, message: terminal.message, phase: "turn:timeout" } });
+    client?.stop();
+    terminalResolve();
+  }, positiveTimeout(options.timeoutMs));
   try {
-    await client.request("initialize", { clientInfo: { name: "agentrun", title: "AgentRun", version: "0.1.0" }, capabilities: { experimentalApi: true } });
-    const threadResponse = asResponseRecord(await client.request("thread/start", { model: options.model ?? "default", cwd: options.cwd, approvalPolicy: options.approvalPolicy, sandbox: options.sandbox, serviceName: "agentrun" }));
-    threadId = stringAt(asRecordAt(threadResponse, "thread"), "id") ?? threadId;
-    const turnResponse = asResponseRecord(await client.request("turn/start", { threadId: threadId ?? "", input: [{ type: "text", text: options.prompt, text_elements: [] }], cwd: options.cwd, approvalPolicy: options.approvalPolicy, model: options.model ?? "default" }));
-    turnId = stringAt(asRecordAt(turnResponse, "turn"), "id") ?? turnId;
-    await Promise.race([terminalPromise, client.closedPromise]);
-    if (!terminal) terminal = { status: "failed", failureKind: "backend-protocol-error", message: "codex app-server closed before turn/completed" };
+    const clientOptions: ConstructorParameters<typeof CodexStdioClient>[0] = {
+      cwd: options.cwd,
+      env,
+      onNotification: (message) => {
+        const normalized = normalizeCodexNotification(message);
+        if (normalized.threadId) threadId = normalized.threadId;
+        if (normalized.turnId) turnId = normalized.turnId;
+        if (normalized.assistantDelta) assistantText += normalized.assistantDelta;
+        events.push(...normalized.events);
+        if (normalized.terminal && !terminal) {
+          terminal = normalized.terminal;
+          terminalResolve();
+        }
+      },
+    };
+    if (options.command) clientOptions.command = options.command;
+    if (options.args) clientOptions.args = options.args;
+    client = new CodexStdioClient(clientOptions);
+    const initializeResult = requireResponseRecord(await client.request("initialize", { clientInfo: { name: "agentrun", title: "AgentRun", version: "0.1.0" }, capabilities: { experimentalApi: true } }, requestTimeoutMs), "initialize");
+    validateInitializeResponse(initializeResult);
+    client.notify("initialized", {});
+    events.push({ type: "backend_status", payload: { phase: "initialize:completed", protocol: codexProtocol } });
+
+    const threadMethod = options.threadId ? "thread/resume" : "thread/start";
+    const threadParams: JsonRecord = options.threadId
+      ? { threadId: options.threadId, model: options.model ?? "default", cwd: options.cwd, approvalPolicy: options.approvalPolicy, sandbox: options.sandbox }
+      : { model: options.model ?? "default", cwd: options.cwd, approvalPolicy: options.approvalPolicy, sandbox: options.sandbox, serviceName: "agentrun" };
+    const threadResponse = requireResponseRecord(await client.request(threadMethod, threadParams, requestTimeoutMs), threadMethod);
+    threadId = requireNestedId(threadResponse, threadMethod, "thread");
+    events.push({ type: "backend_status", payload: { phase: `${threadMethod}:completed`, threadId } });
+
+    const turnResponse = requireResponseRecord(await client.request("turn/start", { threadId, input: textInput(options.prompt), cwd: options.cwd, approvalPolicy: options.approvalPolicy, model: options.model ?? "default" }, requestTimeoutMs), "turn/start");
+    turnId = requireNestedId(turnResponse, "turn/start", "turn");
+    events.push({ type: "backend_status", payload: { phase: "turn/start:completed", turnId } });
+
+    const race = await Promise.race([
+      terminalPromise.then(() => ({ kind: "terminal" as const })),
+      client.closedPromise.then((closeInfo) => ({ kind: "closed" as const, closeInfo })),
+    ]);
+    if (race.kind === "closed" && !terminal) {
+      terminal = terminalFromClose(race.closeInfo);
+      events.push({ type: "error", payload: { failureKind: terminal.failureKind, message: terminal.message, phase: "transport:closed-before-terminal", appServerExit: closeEvent(race.closeInfo) } });
+    }
+    if (!terminal) terminal = { status: "failed", failureKind: "backend-response-invalid", message: "codex app-server did not emit turn/completed" };
   } catch (error) {
-    terminal = { status: "failed", failureKind: "backend-protocol-error", message: error instanceof Error ? error.message : String(error) };
-    events.push({ type: "error", payload: { failureKind: terminal.failureKind, message: terminal.message } });
+    if (!terminal) {
+      const failure = normalizeFailure(error);
+      terminal = { status: failure.failureKind === "secret-unavailable" ? "blocked" : "failed", failureKind: failure.failureKind, message: failure.message };
+      events.push({ type: "error", payload: { failureKind: failure.failureKind, message: failure.message, phase: failure.phase, details: failure.details } });
+    }
   } finally {
     clearTimeout(timeout);
-    client.stop();
+    if (client) {
+      client.stop();
+      const closeInfo = await client.closedPromise;
+      events.push({ type: "backend_status", payload: { phase: "codex-app-server-closed", appServerExit: closeEvent(closeInfo) } });
+    }
   }
+  if (!terminal) terminal = { status: "failed", failureKind: "backend-response-invalid", message: "codex app-server finished without terminal status" };
   if (assistantText.trim().length > 0) events.push({ type: "assistant_message", payload: { text: assistantText } });
   events.push({ type: "terminal_status", payload: { terminalStatus: terminal.status, failureKind: terminal.failureKind, message: terminal.message } });
   return { terminalStatus: terminal.status, failureKind: terminal.failureKind, failureMessage: terminal.message, events: events.map((event) => ({ ...event, payload: redactJson(event.payload) })), ...(threadId ? { threadId } : {}), ...(turnId ? { turnId } : {}) };
 }
 
 function codexHomeReadiness(codexHome: string): BackendTurnResult | null {
-  try {
-    accessSync(`${codexHome}/auth.json`, fsConstants.R_OK);
-    accessSync(`${codexHome}/config.toml`, fsConstants.R_OK);
-    return null;
-  } catch {
-    return {
-      terminalStatus: "blocked",
-      failureKind: "secret-unavailable",
-      failureMessage: "Codex auth.json or config.toml projection is not readable",
-      events: [
-        { type: "error", payload: { failureKind: "secret-unavailable", credentialSource: { codexHome, valuesPrinted: false } } },
-        { type: "terminal_status", payload: { terminalStatus: "blocked", failureKind: "secret-unavailable" } },
-      ],
-    };
-  }
+  const auth = fileReadable(`${codexHome}/auth.json`);
+  const config = fileReadable(`${codexHome}/config.toml`);
+  if (auth.readable && config.readable) return null;
+  const payload = {
+    failureKind: "secret-unavailable",
+    projection: {
+      codexHome: pathSummary(codexHome),
+      authJson: auth,
+      configToml: config,
+      valuesPrinted: false,
+    },
+  } satisfies JsonRecord;
+  return {
+    terminalStatus: "blocked",
+    failureKind: "secret-unavailable",
+    failureMessage: "Codex auth.json or config.toml projection is not readable",
+    events: [
+      { type: "error", payload },
+      { type: "terminal_status", payload: { terminalStatus: "blocked", failureKind: "secret-unavailable" } },
+    ],
+  };
 }
 
 function normalizeCodexNotification(message: JsonRecord): { events: BackendEvent[]; assistantDelta?: string; threadId?: string; turnId?: string; terminal?: { status: TerminalStatus; failureKind: FailureKind | null; message: string | null } } {
@@ -207,33 +385,163 @@ function normalizeCodexNotification(message: JsonRecord): { events: BackendEvent
   if (method === "item/agentMessage/delta") return { events: [], assistantDelta: typeof params.delta === "string" ? params.delta : "" };
   if (method === "item/commandExecution/outputDelta") return { events: [{ type: "command_output", payload: { stream: "stdout", text: typeof params.delta === "string" ? params.delta : "" } }] };
   if (method === "item/started" || method === "item/completed") return { events: [{ type: "tool_call", payload: { method, item: redactJson(asRecordAt(params, "item")) } }] };
-  if (method === "error") return { events: [{ type: "error", payload: { failureKind: "backend-failed", error: redactJson(params.error ?? params) } }] };
+  if (method === "error") {
+    const error = asRecordAt(params, "error");
+    const messageText = typeof error.message === "string" ? error.message : "Codex app-server error";
+    const failureKind = classifyMessageFailureKind(messageText, "backend-failed");
+    const terminal = params.willRetry === true ? undefined : { status: "failed" as const, failureKind, message: redactText(messageText) };
+    return { events: [{ type: "error", payload: { failureKind, error: redactJson(error), willRetry: params.willRetry === true } }], ...(terminal ? { terminal } : {}) };
+  }
   if (method === "turn/completed") {
     const turn = asRecordAt(params, "turn");
+    if (typeof turn.status !== "string") {
+      return { events: [{ type: "error", payload: { failureKind: "backend-response-invalid", message: "turn/completed notification omitted turn.status" } }], terminal: { status: "failed", failureKind: "backend-response-invalid", message: "turn/completed notification omitted turn.status" } };
+    }
     const status = terminalStatusFromValue(turn.status);
     const error = asRecordAt(turn, "error");
-    const messageText = typeof error.message === "string" ? error.message : null;
-    return { events: [{ type: "backend_status", payload: { phase: method, terminalStatus: status } }], terminal: { status, failureKind: status === "completed" ? null : "backend-failed", message: messageText } };
+    const messageText = typeof error.message === "string" ? redactText(error.message) : null;
+    return { events: [{ type: "backend_status", payload: { phase: method, terminalStatus: status } }], terminal: { status, failureKind: status === "completed" ? null : classifyMessageFailureKind(messageText ?? turn.status, "backend-failed"), message: messageText } };
   }
   return { events: [{ type: "backend_status", payload: { phase: method } }] };
 }
 
 function terminalStatusFromValue(value: unknown): TerminalStatus {
   if (value === "completed") return "completed";
-  if (value === "cancelled" || value === "canceled") return "cancelled";
+  if (value === "cancelled" || value === "canceled" || value === "interrupted") return "cancelled";
   if (value === "blocked") return "blocked";
   return "failed";
 }
 
-function childEnv(options: CodexStdioTurnOptions): NodeJS.ProcessEnv {
-  const env: NodeJS.ProcessEnv = { ...process.env, ...options.env };
-  const codexHome = options.codexHome ?? options.env?.CODEX_HOME;
-  if (codexHome) env.CODEX_HOME = codexHome;
-  return env;
+function childEnv(options: CodexStdioTurnOptions, codexHome: string): NodeJS.ProcessEnv {
+  return {
+    ...process.env,
+    ...options.env,
+    CODEX_HOME: codexHome,
+    CODEX_INTERNAL_ORIGINATOR_OVERRIDE: "agentrun",
+  };
 }
 
-function asResponseRecord(value: unknown): JsonRecord {
-  return typeof value === "object" && value !== null && !Array.isArray(value) ? value as JsonRecord : {};
+function resolveCodexHome(options: CodexStdioTurnOptions): string {
+  return options.codexHome ?? options.env?.CODEX_HOME ?? `${options.env?.HOME ?? process.env.HOME ?? ""}/.codex`;
+}
+
+function validateInitializeResponse(value: JsonRecord): void {
+  const serverInfo = value.serverInfo;
+  if (serverInfo !== undefined && (typeof serverInfo !== "object" || serverInfo === null || Array.isArray(serverInfo))) {
+    throw new CodexStdioFailure("backend-response-invalid", "initialize response serverInfo must be an object when present", "response:initialize", { response: value });
+  }
+}
+
+function requireResponseRecord(value: unknown, method: string): JsonRecord {
+  if (typeof value === "object" && value !== null && !Array.isArray(value)) return value as JsonRecord;
+  throw new CodexStdioFailure("backend-response-invalid", `${method} response result must be an object`, `response:${method}`);
+}
+
+function requireNestedId(value: JsonRecord, method: string, key: string): string {
+  const id = stringAt(asRecordAt(value, key), "id");
+  if (id) return id;
+  throw new CodexStdioFailure("backend-response-invalid", `${method} response did not include ${key}.id`, `response:${method}`, { response: value });
+}
+
+function textInput(text: string): JsonValue[] {
+  return [{ type: "text", text, text_elements: [] }];
+}
+
+function fileReadable(filePath: string): JsonRecord {
+  try {
+    accessSync(filePath, fsConstants.R_OK);
+    return { ...pathSummary(filePath), readable: true };
+  } catch {
+    return { ...pathSummary(filePath), readable: false };
+  }
+}
+
+function pathSummary(value: string): JsonRecord {
+  const raw = String(value || "");
+  const parts = raw.split(/[\\/]+/u).filter(Boolean);
+  return {
+    present: raw.trim().length > 0,
+    absolute: path.isAbsolute(raw),
+    basename: parts.at(-1) ?? null,
+    depth: parts.length,
+    fingerprint: shortHash(raw),
+    valuePrinted: false,
+  };
+}
+
+function runtimeSummary(options: CodexStdioTurnOptions, env: NodeJS.ProcessEnv, codexHome: string): JsonRecord {
+  return {
+    command: options.command ?? "codex",
+    args: options.args ?? defaultCodexArgs,
+    cwd: pathSummary(options.cwd),
+    workspace: pathSummary(options.cwd),
+    codexHome: pathSummary(codexHome),
+    env: envSummary(env),
+    valuesPrinted: false,
+  };
+}
+
+function envSummary(env: NodeJS.ProcessEnv): JsonRecord {
+  const keyState: Record<string, JsonValue> = {};
+  for (const key of childEnvSummaryKeys) keyState[key] = { present: typeof env[key] === "string" && String(env[key]).length > 0 };
+  const secretLikeKeyCount = Object.keys(env).filter((key) => /auth|authorization|api[_-]?key|token|password|secret|credential/iu.test(key)).length;
+  return {
+    keyCount: Object.keys(env).length,
+    trackedKeys: keyState,
+    secretLikeKeyCount,
+    valuesPrinted: false,
+  };
+}
+
+function closeEvent(closeInfo: CodexStdioCloseInfo): JsonRecord {
+  return {
+    code: closeInfo.code,
+    signal: closeInfo.signal,
+    failureKind: closeInfo.failureKind,
+    message: closeInfo.message,
+    stderrTail: closeInfo.stderrTail.slice(-stderrEventChars),
+    stderrBytes: closeInfo.stderrBytes,
+    stderrTruncated: closeInfo.stderrTruncated || closeInfo.stderrTail.length > stderrEventChars,
+  };
+}
+
+function terminalFromClose(closeInfo: CodexStdioCloseInfo): { status: TerminalStatus; failureKind: FailureKind; message: string } {
+  const baseMessage = `codex app-server closed before turn/completed code=${closeInfo.code} signal=${closeInfo.signal}`;
+  const combined = [closeInfo.message ?? "", closeInfo.stderrTail].filter(Boolean).join("\n");
+  const failureKind = closeInfo.failureKind ?? classifyMessageFailureKind(combined, "backend-response-invalid");
+  const stderrPreview = closeInfo.stderrTail.trim().length > 0 ? `; stderrTail=${closeInfo.stderrTail.slice(-1000)}` : "";
+  return { status: "failed", failureKind, message: redactText(`${baseMessage}${stderrPreview}`) };
+}
+
+function failureFromRpcError(method: string, value: unknown): CodexStdioFailure {
+  const error = typeof value === "object" && value !== null ? value as Record<string, unknown> : {};
+  const message = typeof error.message === "string" ? error.message : JSON.stringify(redactJson(value as JsonValue));
+  return new CodexStdioFailure(classifyMessageFailureKind(message, "backend-protocol-error"), `codex app-server ${method} error: ${message}`, `response:${method}`, { method, error: redactJson(value as JsonValue) });
+}
+
+function spawnFailure(command: string, error: unknown): CodexStdioFailure {
+  const message = error instanceof Error ? error.message : String(error);
+  const code = typeof error === "object" && error !== null && "code" in error ? String((error as { code?: unknown }).code ?? "") : "";
+  return new CodexStdioFailure("backend-spawn-failed", `failed to start Codex app-server command ${command}: ${message}`, "process:spawn", { command, code });
+}
+
+function normalizeFailure(error: unknown): CodexStdioFailure {
+  if (error instanceof CodexStdioFailure) return error;
+  const message = error instanceof Error ? error.message : String(error);
+  return new CodexStdioFailure(classifyMessageFailureKind(message, "backend-protocol-error"), message, "codex-stdio");
+}
+
+function classifyMessageFailureKind(message: string, fallback: FailureKind): FailureKind {
+  const text = String(message || "").toLowerCase();
+  if (/rate.?limit|too many requests|\b429\b/u.test(text)) return "provider-rate-limited";
+  if (/\b401\b|\b403\b|unauthori[sz]ed|forbidden|invalid api key|authentication|auth failed|oauth|access token/u.test(text)) return "provider-auth-failed";
+  if (/timed out|timeout|idle timeout/u.test(text)) return "backend-timeout";
+  if (/invalid json|json parse/u.test(text)) return "backend-json-parse-error";
+  return fallback;
+}
+
+function positiveTimeout(value: number): number {
+  return Number.isFinite(value) && value > 0 ? Math.max(1, Math.floor(value)) : requestTimeoutCapMs;
 }
 
 function asRecordAt(value: JsonRecord, key: string): JsonRecord {
@@ -242,5 +550,9 @@ function asRecordAt(value: JsonRecord, key: string): JsonRecord {
 }
 
 function stringAt(value: JsonRecord, key: string): string | null {
-  return typeof value[key] === "string" ? value[key] : null;
+  return typeof value[key] === "string" && String(value[key]).length > 0 ? String(value[key]) : null;
+}
+
+function shortHash(value: string): string {
+  return createHash("sha256").update(value).digest("hex").slice(0, 12);
 }
diff --git a/src/common/redaction.ts b/src/common/redaction.ts
index 43f06d1..6ba45b1 100644
--- a/src/common/redaction.ts
+++ b/src/common/redaction.ts
@@ -1,7 +1,8 @@
 export function redactText(value: string): string {
   return value
+    .replace(/\b(sk-[A-Za-z0-9_-]{8,}|ghp_[A-Za-z0-9_]{8,}|github_pat_[A-Za-z0-9_]+)\b/gu, "REDACTED")
     .replace(/(authorization\s*[:=]\s*)(bearer\s+)?[A-Za-z0-9._~+/=-]+/giu, "$1$2REDACTED")
-    .replace(/((?:api[_-]?key|token|password|secret)\s*[:=]\s*)[A-Za-z0-9._~+/=-]+/giu, "$1REDACTED")
+    .replace(/((?:api[_-]?key|token|password|secret)\s*["']?\s*[:=]\s*["']?)[A-Za-z0-9._~+/=-]+/giu, "$1REDACTED")
     .replace(/(postgres(?:ql)?:\/\/[^:\s/@]+:)[^@\s]+(@)/giu, "$1REDACTED$2")
     .replace(/(https?:\/\/[^:\s/@]+:)[^@\s]+(@)/giu, "$1REDACTED$2");
 }
diff --git a/src/common/types.ts b/src/common/types.ts
index 1ef153e..195f4c6 100644
--- a/src/common/types.ts
+++ b/src/common/types.ts
@@ -9,6 +9,9 @@ export type FailureKind =
   | "runner-lease-conflict"
   | "backend-failed"
   | "backend-protocol-error"
+  | "backend-spawn-failed"
+  | "backend-json-parse-error"
+  | "backend-response-invalid"
   | "backend-timeout"
   | "provider-auth-failed"
   | "provider-rate-limited"
diff --git a/src/selftest/fake-codex-app-server.ts b/src/selftest/fake-codex-app-server.ts
index 316a9b7..2f14559 100644
--- a/src/selftest/fake-codex-app-server.ts
+++ b/src/selftest/fake-codex-app-server.ts
@@ -1,6 +1,7 @@
 import * as readline from "node:readline";
 
 const rl = readline.createInterface({ input: process.stdin, crlfDelay: Infinity });
+const mode = process.env.AGENTRUN_FAKE_CODEX_MODE ?? "success";
 let threadCounter = 0;
 let turnCounter = 0;
 
@@ -9,6 +10,10 @@ for await (const line of rl) {
   if (trimmed.length === 0) continue;
   const message = JSON.parse(trimmed) as { id?: number; method?: string; params?: Record<string, unknown> };
   if (message.method === "initialize") {
+    if (mode === "invalid-json") {
+      process.stdout.write('{"token":"test-token-material"\n');
+      process.exit(0);
+    }
     respond(message.id, { serverInfo: { name: "fake-codex-app-server", version: "self-test" } });
     continue;
   }
@@ -26,6 +31,17 @@ for await (const line of rl) {
     continue;
   }
   if (message.method === "turn/start") {
+    if (mode === "missing-turn-result") {
+      respond(message.id, {});
+      continue;
+    }
+    if (mode === "missing-terminal") {
+      turnCounter += 1;
+      const turn = { id: `turn_selftest_${turnCounter}`, status: "running" };
+      notify("turn/started", { turn });
+      respond(message.id, { turn });
+      continue;
+    }
     turnCounter += 1;
     const turn = { id: `turn_selftest_${turnCounter}`, status: "completed" };
     notify("turn/started", { turn });
diff --git a/src/selftest/run.ts b/src/selftest/run.ts
index 655fd90..af3fbd2 100644
--- a/src/selftest/run.ts
+++ b/src/selftest/run.ts
@@ -7,6 +7,7 @@ import { startManagerServer } from "../mgr/server.js";
 import { ManagerClient } from "../mgr/client.js";
 import { runOnce } from "../runner/run-once.js";
 import { redactText } from "../common/redaction.js";
+import type { FailureKind, JsonRecord, TerminalStatus } from "../common/types.js";
 
 const root = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../..");
 const tmp = await mkdtemp(path.join(os.tmpdir(), "agentrun-selftest-"));
@@ -21,45 +22,133 @@ try {
   await writeFile(path.join(workspace, "README.md"), "self-test workspace\n");
 
   assert.equal(redactText("Authorization: Bearer abc123"), "Authorization: Bearer REDACTED");
+  assert.equal(redactText('{"token":"test-token-material"}').includes("test-token-material"), false);
 
   const server = await startManagerServer({ port: 0, host: "127.0.0.1", sourceCommit: "self-test" });
   try {
     const client = new ManagerClient(server.baseUrl);
     const health = await client.get("/health/readiness") as { database?: { adapter?: string } };
     assert.equal(health.database?.adapter, "memory-self-test");
-    const run = await client.post("/api/v1/runs", {
-      tenantId: "unidesk",
-      projectId: "pikasTech/unidesk",
-      workspaceRef: { kind: "host-path", path: workspace },
-      providerId: "G14",
-      backendProfile: "codex",
-      executionPolicy: {
-        sandbox: "workspace-write",
-        approval: "never",
-        timeoutMs: 15_000,
-        network: "default",
-        secretScope: { allowCredentialEcho: false, providerCredentials: [{ profile: "codex", secretRef: { name: "agentrun-v01-provider-codex", keys: ["auth.json", "config.toml"], mountPath: codexHome } }] },
-      },
-      traceSink: null,
-    }) as { id: string };
-    const command = await client.post(`/api/v1/runs/${run.id}/commands`, { type: "turn", payload: { prompt: "hello" }, idempotencyKey: "selftest-turn" }) as { id: string };
-    const duplicate = await client.post(`/api/v1/runs/${run.id}/commands`, { type: "turn", payload: { prompt: "hello" }, idempotencyKey: "selftest-turn" }) as { id: string };
-    assert.equal(duplicate.id, command.id);
     const fakePath = path.join(root, "src/selftest/fake-codex-app-server.ts");
     const fakeCommand = process.env.AGENTRUN_SELFTEST_CODEX_COMMAND ?? process.execPath;
     const fakeArgs = process.env.AGENTRUN_SELFTEST_CODEX_ARGS ? JSON.parse(process.env.AGENTRUN_SELFTEST_CODEX_ARGS) as string[] : [fakePath];
-    const result = await runOnce({ managerUrl: server.baseUrl, runId: run.id, codexCommand: fakeCommand, codexArgs: fakeArgs, codexHome, env: { CODEX_HOME: codexHome } });
+
+    const happy = await createRunWithCommand(client, workspace, codexHome, "hello", "selftest-turn", 15_000);
+    const result = await runOnce({ managerUrl: server.baseUrl, runId: happy.runId, codexCommand: fakeCommand, codexArgs: fakeArgs, codexHome, env: { CODEX_HOME: codexHome } });
     assert.equal(result.terminalStatus, "completed");
-    const events = await client.get(`/api/v1/runs/${run.id}/events?afterSeq=0&limit=100`) as { items?: Array<{ type: string; payload: unknown }> };
+    const events = await client.get(`/api/v1/runs/${happy.runId}/events?afterSeq=0&limit=100`) as { items?: Array<{ type: string; payload: unknown }> };
     assert.ok(events.items?.some((event) => event.type === "assistant_message"));
-    assert.equal(JSON.stringify(events).includes("test-token-material"), false);
-    assert.equal(JSON.stringify(events).includes("Bearer test-token"), false);
-    const finalRun = await client.get(`/api/v1/runs/${run.id}`) as { terminalStatus?: string };
+    assertNoSecretLeak(events);
+    const finalRun = await client.get(`/api/v1/runs/${happy.runId}`) as { terminalStatus?: string };
     assert.equal(finalRun.terminalStatus, "completed");
-    console.log(JSON.stringify({ ok: true, tests: ["manager-memory-lifecycle", "codex-stdio-fake-turn", "redaction"], runId: run.id }));
+
+    await runFailureCase({
+      client,
+      managerUrl: server.baseUrl,
+      workspace,
+      codexHome,
+      fakeCommand,
+      fakeArgs,
+      mode: "missing-turn-result",
+      expectedStatus: "failed",
+      expectedFailureKind: "backend-response-invalid",
+    });
+    await runFailureCase({
+      client,
+      managerUrl: server.baseUrl,
+      workspace,
+      codexHome,
+      fakeCommand,
+      fakeArgs,
+      mode: "invalid-json",
+      expectedStatus: "failed",
+      expectedFailureKind: "backend-json-parse-error",
+    });
+    await runFailureCase({
+      client,
+      managerUrl: server.baseUrl,
+      workspace,
+      codexHome,
+      fakeCommand,
+      fakeArgs,
+      mode: "missing-terminal",
+      expectedStatus: "failed",
+      expectedFailureKind: "backend-timeout",
+      timeoutMs: 500,
+    });
+    await runSpawnFailureCase({
+      client,
+      managerUrl: server.baseUrl,
+      workspace,
+      codexHome,
+    });
+
+    console.log(JSON.stringify({ ok: true, tests: ["manager-memory-lifecycle", "codex-stdio-fake-turn", "codex-stdio-missing-turn-result", "codex-stdio-invalid-json", "codex-stdio-timeout", "codex-stdio-spawn-failure", "redaction"], runId: happy.runId }));
   } finally {
     await new Promise<void>((resolve) => server.server.close(() => resolve()));
   }
 } finally {
   await rm(tmp, { recursive: true, force: true });
 }
+
+async function createRunWithCommand(client: ManagerClient, workspace: string, codexHome: string, prompt: string, idempotencyKey: string, timeoutMs: number): Promise<{ runId: string; commandId: string }> {
+  const run = await client.post("/api/v1/runs", {
+    tenantId: "unidesk",
+    projectId: "pikasTech/unidesk",
+    workspaceRef: { kind: "host-path", path: workspace },
+    providerId: "G14",
+    backendProfile: "codex",
+    executionPolicy: {
+      sandbox: "workspace-write",
+      approval: "never",
+      timeoutMs,
+      network: "default",
+      secretScope: { allowCredentialEcho: false, providerCredentials: [{ profile: "codex", secretRef: { name: "agentrun-v01-provider-codex", keys: ["auth.json", "config.toml"], mountPath: codexHome } }] },
+    },
+    traceSink: null,
+  }) as { id: string };
+  const command = await client.post(`/api/v1/runs/${run.id}/commands`, { type: "turn", payload: { prompt }, idempotencyKey }) as { id: string };
+  const duplicate = await client.post(`/api/v1/runs/${run.id}/commands`, { type: "turn", payload: { prompt }, idempotencyKey }) as { id: string };
+  assert.equal(duplicate.id, command.id);
+  return { runId: run.id, commandId: command.id };
+}
+
+async function runFailureCase(options: { client: ManagerClient; managerUrl: string; workspace: string; codexHome: string; fakeCommand: string; fakeArgs: string[]; mode: string; expectedStatus: TerminalStatus; expectedFailureKind: FailureKind; timeoutMs?: number }): Promise<void> {
+  const item = await createRunWithCommand(options.client, options.workspace, options.codexHome, `failure ${options.mode}`, `selftest-${options.mode}`, options.timeoutMs ?? 3_000);
+  const result = await runOnce({
+    managerUrl: options.managerUrl,
+    runId: item.runId,
+    codexCommand: options.fakeCommand,
+    codexArgs: options.fakeArgs,
+    codexHome: options.codexHome,
+    env: { CODEX_HOME: options.codexHome, AGENTRUN_FAKE_CODEX_MODE: options.mode },
+  }) as JsonRecord;
+  assert.equal(result.terminalStatus, options.expectedStatus, options.mode);
+  assert.equal(result.failureKind, options.expectedFailureKind, options.mode);
+  const events = await options.client.get(`/api/v1/runs/${item.runId}/events?afterSeq=0&limit=100`) as { items?: Array<{ type: string; payload: unknown }> };
+  assert.ok(events.items?.some((event) => event.type === "error"), options.mode);
+  assertNoSecretLeak(events);
+}
+
+async function runSpawnFailureCase(options: { client: ManagerClient; managerUrl: string; workspace: string; codexHome: string }): Promise<void> {
+  const item = await createRunWithCommand(options.client, options.workspace, options.codexHome, "failure spawn", "selftest-spawn-failure", 3_000);
+  const result = await runOnce({
+    managerUrl: options.managerUrl,
+    runId: item.runId,
+    codexCommand: path.join(os.tmpdir(), `agentrun-missing-codex-${process.pid}`),
+    codexArgs: [],
+    codexHome: options.codexHome,
+    env: { CODEX_HOME: options.codexHome },
+  }) as JsonRecord;
+  assert.equal(result.terminalStatus, "failed", "spawn failure");
+  assert.equal(result.failureKind, "backend-spawn-failed", "spawn failure");
+  const events = await options.client.get(`/api/v1/runs/${item.runId}/events?afterSeq=0&limit=100`) as { items?: Array<{ type: string; payload: unknown }> };
+  assert.ok(events.items?.some((event) => event.type === "error"), "spawn failure");
+  assertNoSecretLeak(events);
+}
+
+function assertNoSecretLeak(value: unknown): void {
+  const text = JSON.stringify(value);
+  assert.equal(text.includes("test-token-material"), false);
+  assert.equal(text.includes("Bearer test-token"), false);
+}