diff --git a/plugins/codex/agents/codex-rescue.md b/plugins/codex/agents/codex-rescue.md
index 7009ec86..d8b06479 100644
--- a/plugins/codex/agents/codex-rescue.md
+++ b/plugins/codex/agents/codex-rescue.md
@@ -31,7 +31,7 @@ Forwarding rules:
 - If the user asks for `spark`, map that to `--model gpt-5.3-codex-spark`.
 - If the user asks for a concrete model name such as `gpt-5.4-mini`, pass it through with `--model`.
 - Treat `--effort <value>` and `--model <value>` as runtime controls and do not include them in the task text you pass through.
-- Default to a write-capable Codex run by adding `--write` unless the user explicitly asks for read-only behavior or only wants review, diagnosis, or research without edits.
+- Default to a write-capable Codex run by adding `--write` unless the user explicitly asks for read-only behavior or only wants review, diagnosis, or research without edits; in those cases, add `--read-only` instead.
 - Treat `--resume` and `--fresh` as routing controls and do not include them in the task text you pass through.
 - `--resume` means add `--resume-last`.
 - `--fresh` means do not add `--resume-last`.
diff --git a/plugins/codex/commands/rescue.md b/plugins/codex/commands/rescue.md
index 56de9555..920a586f 100644
--- a/plugins/codex/commands/rescue.md
+++ b/plugins/codex/commands/rescue.md
@@ -1,6 +1,6 @@
 ---
 description: Delegate investigation, an explicit fix request, or follow-up rescue work to the Codex rescue subagent
-argument-hint: "[--background|--wait] [--resume|--fresh] [--model <model|spark>] [--effort <none|minimal|low|medium|high|xhigh>] [what Codex should investigate, solve, or continue]"
+argument-hint: "[--background|--wait] [--read-only] [--resume|--fresh] [--model <model|spark>] [--effort <none|minimal|low|medium|high|xhigh>] [what Codex should investigate, solve, or continue]"
 allowed-tools: Bash(node:*), AskUserQuestion, Agent
 ---
 
@@ -17,7 +17,7 @@ Execution mode:
 - If the request includes `--wait`, run the `codex:codex-rescue` subagent in the foreground.
 - If neither flag is present, default to foreground.
 - `--background` and `--wait` are execution flags for Claude Code. Do not forward them to `task`, and do not treat them as part of the natural-language task text.
-- `--model` and `--effort` are runtime-selection flags. Preserve them for the forwarded `task` call, but do not treat them as part of the natural-language task text.
+- `--model` and `--effort` are runtime-selection flags. Preserve them and `--read-only` for the forwarded `task` call, but do not treat them as part of the natural-language task text.
 - If the request includes `--resume`, do not ask whether to continue. The user already chose.
 - If the request includes `--fresh`, do not ask whether to continue. The user already chose.
 - Otherwise, before starting Codex, check for a resumable rescue thread from this Claude session by running:
diff --git a/plugins/codex/scripts/codex-companion.mjs b/plugins/codex/scripts/codex-companion.mjs
index 83df468a..2ebfceea 100644
--- a/plugins/codex/scripts/codex-companion.mjs
+++ b/plugins/codex/scripts/codex-companion.mjs
@@ -79,7 +79,7 @@ function printUsage() {
       "  node scripts/codex-companion.mjs setup [--enable-review-gate|--disable-review-gate] [--json]",
       "  node scripts/codex-companion.mjs review [--wait|--background] [--base <ref>] [--scope <auto|working-tree|branch>]",
       "  node scripts/codex-companion.mjs adversarial-review [--wait|--background] [--base <ref>] [--scope <auto|working-tree|branch>] [focus text]",
-      "  node scripts/codex-companion.mjs task [--background] [--write] [--resume-last|--resume|--fresh] [--model <model|spark>] [--effort <none|minimal|low|medium|high|xhigh>] [prompt]",
+      "  node scripts/codex-companion.mjs task [--background] [--write] [--read-only] [--resume-last|--resume|--fresh] [--model <model|spark>] [--effort <none|minimal|low|medium|high|xhigh>] [prompt]",
       "  node scripts/codex-companion.mjs transfer [--source <claude-jsonl>] [--json]",
       "  node scripts/codex-companion.mjs status [job-id] [--all] [--json]",
       "  node scripts/codex-companion.mjs result [job-id] [--json]",
@@ -488,7 +488,7 @@ async function executeTaskRun(request) {
     defaultPrompt: resumeThreadId ? DEFAULT_CONTINUE_PROMPT : "",
     model: request.model,
     effort: request.effort,
-    sandbox: request.write ? "workspace-write" : "read-only",
+    sandbox: request.write ? "workspace-write" : request.readOnly ? "read-only" : null,
     onProgress: request.onProgress,
     persistThread: true,
     threadName: resumeThreadId ? null : buildPersistentTaskThreadName(request.prompt || DEFAULT_CONTINUE_PROMPT)
@@ -601,13 +601,14 @@ function buildTaskJob(workspaceRoot, taskMetadata, write) {
   });
 }
 
-function buildTaskRequest({ cwd, model, effort, prompt, write, resumeLast, jobId }) {
+function buildTaskRequest({ cwd, model, effort, prompt, write, readOnly, resumeLast, jobId }) {
   return {
     cwd,
     model,
     effort,
     prompt,
     write,
+    readOnly,
     resumeLast,
     jobId
   };
@@ -762,7 +763,7 @@ async function handleReview(argv) {
 async function handleTask(argv) {
   const { options, positionals } = parseCommandInput(argv, {
     valueOptions: ["model", "effort", "cwd", "prompt-file"],
-    booleanOptions: ["json", "write", "resume-last", "resume", "fresh", "background"],
+    booleanOptions: ["json", "write", "read-only", "resume-last", "resume", "fresh", "background"],
     aliasMap: {
       m: "model"
     }
@@ -780,6 +781,10 @@ async function handleTask(argv) {
     throw new Error("Choose either --resume/--resume-last or --fresh.");
   }
   const write = Boolean(options.write);
+  const readOnly = Boolean(options["read-only"]);
+  if (write && readOnly) {
+    throw new Error("Choose either --write or --read-only.");
+  }
   const taskMetadata = buildTaskRunMetadata({
     prompt,
     resumeLast
@@ -796,6 +801,7 @@ async function handleTask(argv) {
       effort,
       prompt,
       write,
+      readOnly,
       resumeLast,
       jobId: job.id
     });
@@ -814,6 +820,7 @@ async function handleTask(argv) {
         effort,
         prompt,
         write,
+        readOnly,
         resumeLast,
         jobId: job.id,
         onProgress: progress
diff --git a/plugins/codex/scripts/lib/codex.mjs b/plugins/codex/scripts/lib/codex.mjs
index fead00cc..31e21449 100644
--- a/plugins/codex/scripts/lib/codex.mjs
+++ b/plugins/codex/scripts/lib/codex.mjs
@@ -65,7 +65,7 @@ function buildThreadParams(cwd, options = {}) {
     cwd,
     model: options.model ?? null,
     approvalPolicy: options.approvalPolicy ?? "never",
-    sandbox: options.sandbox ?? "read-only",
+    sandbox: options.sandbox ?? null,
     serviceName: SERVICE_NAME,
     ephemeral: options.ephemeral ?? true
   };
@@ -78,7 +78,7 @@ function buildResumeParams(threadId, cwd, options = {}) {
     cwd,
     model: options.model ?? null,
     approvalPolicy: options.approvalPolicy ?? "never",
-    sandbox: options.sandbox ?? "read-only"
+    sandbox: options.sandbox ?? null
   };
 }
 
diff --git a/plugins/codex/scripts/stop-review-gate-hook.mjs b/plugins/codex/scripts/stop-review-gate-hook.mjs
index 2346bdcf..a5737b58 100644
--- a/plugins/codex/scripts/stop-review-gate-hook.mjs
+++ b/plugins/codex/scripts/stop-review-gate-hook.mjs
@@ -102,7 +102,7 @@ function runStopReview(cwd, input = {}) {
     ...process.env,
     ...(input.session_id ? { [SESSION_ID_ENV]: input.session_id } : {})
   };
-  const result = spawnSync(process.execPath, [scriptPath, "task", "--json", prompt], {
+  const result = spawnSync(process.execPath, [scriptPath, "task", "--json", "--read-only", prompt], {
     cwd,
     env: childEnv,
     encoding: "utf8",
diff --git a/plugins/codex/skills/codex-cli-runtime/SKILL.md b/plugins/codex/skills/codex-cli-runtime/SKILL.md
index 0e91bfb5..e1aa593d 100644
--- a/plugins/codex/skills/codex-cli-runtime/SKILL.md
+++ b/plugins/codex/skills/codex-cli-runtime/SKILL.md
@@ -21,7 +21,7 @@ Execution rules:
 - Leave `--effort` unset unless the user explicitly requests a specific effort.
 - Leave model unset by default. Add `--model` only when the user explicitly asks for one.
 - Map `spark` to `--model gpt-5.3-codex-spark`.
-- Default to a write-capable Codex run by adding `--write` unless the user explicitly asks for read-only behavior or only wants review, diagnosis, or research without edits.
+- Default to a write-capable Codex run by adding `--write` unless the user explicitly asks for read-only behavior or only wants review, diagnosis, or research without edits; in those cases, add `--read-only` instead.
 
 Command selection:
 - Use exactly one `task` invocation per rescue handoff.
diff --git a/tests/fake-codex-fixture.mjs b/tests/fake-codex-fixture.mjs
index f83c96a0..1411b906 100644
--- a/tests/fake-codex-fixture.mjs
+++ b/tests/fake-codex-fixture.mjs
@@ -312,6 +312,7 @@ rl.on("line", (line) => {
         if (requiresExperimental("persistExtendedHistory", message, state) || requiresExperimental("persistFullHistory", message, state)) {
           throw new Error("thread/start.persistFullHistory requires experimentalApi capability");
         }
+        state.lastThreadStart = { ...message.params };
         const thread = nextThread(state, message.params.cwd, message.params.ephemeral);
         send({ id: message.id, result: { thread: buildThread(thread), model: message.params.model || "gpt-5.4", modelProvider: "openai", serviceTier: null, cwd: thread.cwd, approvalPolicy: "never", sandbox: { type: "readOnly", access: { type: "fullAccess" }, networkAccess: false }, reasoningEffort: null } });
         send({ method: "thread/started", params: { thread: { id: thread.id } } });
@@ -344,6 +345,7 @@ rl.on("line", (line) => {
         if (requiresExperimental("persistExtendedHistory", message, state) || requiresExperimental("persistFullHistory", message, state)) {
           throw new Error("thread/resume.persistFullHistory requires experimentalApi capability");
         }
+        state.lastThreadResume = { ...message.params };
         const thread = ensureThread(state, message.params.threadId);
         thread.updatedAt = now();
         saveState(state);
diff --git a/tests/runtime.test.mjs b/tests/runtime.test.mjs
index 8f276835..c9617cdf 100644
--- a/tests/runtime.test.mjs
+++ b/tests/runtime.test.mjs
@@ -139,6 +139,7 @@ test("setup reports not ready when app-server config read fails", () => {
 test("review renders a no-findings result from app-server review/start", () => {
   const repo = makeTempDir();
   const binDir = makeTempDir();
+  const statePath = path.join(binDir, "fake-codex-state.json");
   installFakeCodex(binDir);
   initGitRepo(repo);
   fs.mkdirSync(path.join(repo, "src"));
@@ -155,6 +156,8 @@ test("review renders a no-findings result from app-server review/start", () => {
   assert.equal(result.status, 0);
   assert.match(result.stdout, /Reviewed uncommitted changes/);
   assert.match(result.stdout, /No material issues found/);
+  const fakeState = JSON.parse(fs.readFileSync(statePath, "utf8"));
+  assert.equal(fakeState.lastThreadStart.sandbox, "read-only");
 });
 
 test("task runs when the active provider does not require OpenAI login", () => {
@@ -369,6 +372,7 @@ test("review accepts the quoted raw argument style for built-in base-branch revi
 test("adversarial review renders structured findings over app-server turn/start", () => {
   const repo = makeTempDir();
   const binDir = makeTempDir();
+  const statePath = path.join(binDir, "fake-codex-state.json");
   installFakeCodex(binDir);
   initGitRepo(repo);
   fs.mkdirSync(path.join(repo, "src"));
@@ -384,6 +388,8 @@ test("adversarial review renders structured findings over app-server turn/start"
 
   assert.equal(result.status, 0);
   assert.match(result.stdout, /Missing empty-state guard/);
+  const fakeState = JSON.parse(fs.readFileSync(statePath, "utf8"));
+  assert.equal(fakeState.lastThreadStart.sandbox, "read-only");
 });
 
 test("adversarial review accepts the same base-branch targeting as review", () => {
@@ -482,6 +488,7 @@ test("review logs reasoning summaries and review output to the job log", () => {
 test("task --resume-last resumes the latest persisted task thread", () => {
   const repo = makeTempDir();
   const binDir = makeTempDir();
+  const statePath = path.join(binDir, "fake-codex-state.json");
   installFakeCodex(binDir);
   initGitRepo(repo);
   fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
@@ -501,6 +508,8 @@ test("task --resume-last resumes the latest persisted task thread", () => {
 
   assert.equal(result.status, 0, result.stderr);
   assert.equal(result.stdout, "Resumed the prior run.\nFollow-up prompt accepted.\n");
+  const fakeState = JSON.parse(fs.readFileSync(statePath, "utf8"));
+  assert.equal(fakeState.lastThreadResume.sandbox, null);
 });
 
 test("task-resume-candidate returns the latest rescue thread from the current session", () => {
@@ -701,6 +710,7 @@ test("session start hook exports the Claude session id, transcript path, and plu
 test("write task output focuses on the Codex result without generic follow-up hints", () => {
   const repo = makeTempDir();
   const binDir = makeTempDir();
+  const statePath = path.join(binDir, "fake-codex-state.json");
   installFakeCodex(binDir);
   initGitRepo(repo);
   fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
@@ -714,6 +724,8 @@ test("write task output focuses on the Codex result without generic follow-up hi
 
   assert.equal(result.status, 0, result.stderr);
   assert.equal(result.stdout, "Handled the requested task.\nTask prompt accepted.\n");
+  const fakeState = JSON.parse(fs.readFileSync(statePath, "utf8"));
+  assert.equal(fakeState.lastThreadStart.sandbox, "workspace-write");
 });
 
 test("task --resume acts like --resume-last without leaking the flag into the prompt", () => {
@@ -780,6 +792,7 @@ test("task forwards model selection and reasoning effort to app-server turn/star
 
   assert.equal(result.status, 0, result.stderr);
   const fakeState = JSON.parse(fs.readFileSync(statePath, "utf8"));
+  assert.equal(fakeState.lastThreadStart.sandbox, null);
   assert.equal(fakeState.lastTurnStart.model, "gpt-5.3-codex-spark");
   assert.equal(fakeState.lastTurnStart.effort, "low");
 });
@@ -920,16 +933,17 @@ test("task using the shared broker still completes when Codex spawns subagents",
   assert.equal(result.stdout, "Handled the requested task.\nTask prompt accepted.\n");
 });
 
-test("task --background enqueues a detached worker and exposes per-job status", async () => {
+test("task --background preserves --read-only through the detached worker", async () => {
   const repo = makeTempDir();
   const binDir = makeTempDir();
+  const fakeStatePath = path.join(binDir, "fake-codex-state.json");
   installFakeCodex(binDir, "slow-task");
   initGitRepo(repo);
   fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
   run("git", ["add", "README.md"], { cwd: repo });
   run("git", ["commit", "-m", "init"], { cwd: repo });
 
-  const launched = run("node", [SCRIPT, "task", "--background", "--json", "investigate the failing test"], {
+  const launched = run("node", [SCRIPT, "task", "--background", "--read-only", "--json", "investigate the failing test"], {
     cwd: repo,
     env: buildEnv(binDir)
   });
@@ -967,6 +981,63 @@ test("task --background enqueues a detached worker and exposes per-job status",
   assert.equal(resultPayload.job.id, launchPayload.jobId);
   assert.equal(resultPayload.job.status, "completed");
   assert.match(resultPayload.storedJob.rendered, /Handled the requested task/);
+  const fakeState = JSON.parse(fs.readFileSync(fakeStatePath, "utf8"));
+  assert.equal(fakeState.lastThreadStart.sandbox, "read-only");
+});
+
+test("task --read-only pins the app-server thread sandbox", () => {
+  const repo = makeTempDir();
+  const binDir = makeTempDir();
+  const statePath = path.join(binDir, "fake-codex-state.json");
+  installFakeCodex(binDir);
+  initGitRepo(repo);
+  fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
+  run("git", ["add", "README.md"], { cwd: repo });
+  run("git", ["commit", "-m", "init"], { cwd: repo });
+
+  const result = run("node", [SCRIPT, "task", "--read-only", "inspect the failing test"], {
+    cwd: repo,
+    env: buildEnv(binDir)
+  });
+
+  assert.equal(result.status, 0, result.stderr);
+  const fakeState = JSON.parse(fs.readFileSync(statePath, "utf8"));
+  assert.equal(fakeState.lastThreadStart.sandbox, "read-only");
+});
+
+test("task --read-only pins resumed app-server threads", () => {
+  const repo = makeTempDir();
+  const binDir = makeTempDir();
+  const statePath = path.join(binDir, "fake-codex-state.json");
+  installFakeCodex(binDir);
+  initGitRepo(repo);
+  fs.writeFileSync(path.join(repo, "README.md"), "hello\n");
+  run("git", ["add", "README.md"], { cwd: repo });
+  run("git", ["commit", "-m", "init"], { cwd: repo });
+
+  const firstRun = run("node", [SCRIPT, "task", "initial task"], {
+    cwd: repo,
+    env: buildEnv(binDir)
+  });
+  assert.equal(firstRun.status, 0, firstRun.stderr);
+
+  const result = run("node", [SCRIPT, "task", "--read-only", "--resume-last", "read-only follow up"], {
+    cwd: repo,
+    env: buildEnv(binDir)
+  });
+
+  assert.equal(result.status, 0, result.stderr);
+  const fakeState = JSON.parse(fs.readFileSync(statePath, "utf8"));
+  assert.equal(fakeState.lastThreadResume.sandbox, "read-only");
+});
+
+test("task rejects --write with --read-only", () => {
+  const result = run("node", [SCRIPT, "task", "--write", "--read-only", "inspect the failing test"], {
+    cwd: ROOT
+  });
+
+  assert.notEqual(result.status, 0);
+  assert.match(result.stderr, /Choose either --write or --read-only\./);
 });
 
 test("review rejects focus text because it is native-review only", () => {
@@ -1967,6 +2038,7 @@ test("stop hook runs a stop-time review task and blocks on findings when the rev
   assert.match(fakeState.lastTurnStart.prompt, /<compact_output_contract>/i);
   assert.match(fakeState.lastTurnStart.prompt, /Only review the work from the previous Claude turn/i);
   assert.match(fakeState.lastTurnStart.prompt, /I completed the refactor and updated the retry logic\./);
+  assert.equal(fakeState.lastThreadStart.sandbox, "read-only");
 
   const status = run("node", [SCRIPT, "status"], {
     cwd: repo,