diff --git a/README.md b/README.md
index 95a5bc1..9874813 100644
--- a/README.md
+++ b/README.md
@@ -132,6 +132,7 @@ When running from source (`bun src/loop.ts`), auto-update is disabled — use `g
 - `-a, --agent <claude|codex>`: agent to run (default: `codex`)
 - `-p, --prompt <text|.md file>`: prompt text or a `.md` prompt file path. Plain text auto-creates `PLAN.md` first.
 - `--proof <text>`: required proof criteria for task completion
+- `--codex-model <model>`: set the model passed to codex (`LOOP_CODEX_MODEL` can also set this by default)
 - `-m, --max-iterations <number>`: max loop count (default: infinite)
 - `-d, --done <signal>`: done signal string (default: `<promise>DONE</promise>`)
 - `--format <pretty|raw>`: output format (default: `pretty`)
diff --git a/src/loop/args.ts b/src/loop/args.ts
index 88ca332..4363a6d 100644
--- a/src/loop/args.ts
+++ b/src/loop/args.ts
@@ -69,6 +69,14 @@ const applyValueFlag = (
     opts.proof = trimmed;
     return;
   }
+  if (flag === "codexModel") {
+    const trimmed = value.trim();
+    if (!trimmed) {
+      throw new Error("Invalid --codex-model value: cannot be empty");
+    }
+    opts.model = trimmed;
+    return;
+  }
   opts.format = parseFormat(value);
 };
 
@@ -116,6 +124,11 @@ const consumeArg = (
     return { nextIndex: argv.length, stop: true };
   }
 
+  if (arg.startsWith("--codex-model=")) {
+    applyValueFlag("codexModel", arg.slice("--codex-model=".length), opts);
+    return { nextIndex: index + 1, stop: false };
+  }
+
   if (arg === "--review" || arg.startsWith("--review=")) {
     return {
       nextIndex: parseReviewArg(argv, index, opts, arg) + 1,
diff --git a/src/loop/constants.ts b/src/loop/constants.ts
index 495d5eb..6544df0 100644
--- a/src/loop/constants.ts
+++ b/src/loop/constants.ts
@@ -20,8 +20,8 @@ Options:
   -p, --prompt <text|.md file>      Prompt text or path to a .md prompt file
   -m, --max-iterations <number>.    Max loops (default: infinite)
   -d, --done <signal>               Done signal (default: <promise>DONE</promise>)
-      CODEX_TRANSPORT=app-server|exec  Codex transport mode (default: app-server)
   --proof <text>                    Proof requirements for task completion (required)
+  --codex-model <model>             Override codex model (default: ${DEFAULT_CODEX_MODEL})
   --format <pretty|raw>             Log format (default: pretty)
   --review [claude|codex|claudex]   Review on done (default: claudex)
   --tmux                            Run in a detached tmux session (name: repo-loop-X)
@@ -48,5 +48,6 @@ export const VALUE_FLAGS: Record<string, ValueFlag> = {
   "-d": "done",
   "--done": "done",
   "--proof": "proof",
+  "--codex-model": "codexModel",
   "--format": "format",
 };
diff --git a/src/loop/main.ts b/src/loop/main.ts
index 2438ad3..8cc992f 100644
--- a/src/loop/main.ts
+++ b/src/loop/main.ts
@@ -6,6 +6,17 @@ import { runAgent } from "./runner";
 import type { Options } from "./types";
 import { hasSignal } from "./utils";
 
+const doneSignalText = (doneSignal: string) => `done signal "${doneSignal}"`;
+const doneSignalMissingText = (signal: string) =>
+  `\n[loop] ${doneSignalText(signal)} detected, stopping.`;
+const doneSignalPassedText = (signal: string) =>
+  `\n[loop] ${doneSignalText(signal)} detected and review passed, stopping.`;
+const doneSignalExitText = (doneSignal: string, exitCode: number) =>
+  `[loop] ${doneSignalText(doneSignal)} seen despite exit code ${exitCode}.`;
+const bothReviewersNotes = (notes: string): string =>
+  "Both reviewers requested changes. Decide for each comment whether to address it now. " +
+  `If you skip one, explain why briefly. If both reviews found the same issue, it might be worth addressing.\n\n${notes}`;
+
 const runIterations = async (
   task: string,
   opts: Options,
@@ -13,7 +24,8 @@ const runIterations = async (
   hasExistingPr = false
 ): Promise<boolean> => {
   let reviewNotes = "";
-  const stopMessage = `\n[loop] done signal "${opts.doneSignal}" detected`;
+  const shouldReview = reviewers.length > 0;
+  const doneSignal = opts.doneSignal;
   console.log(`\n[loop] PLAN.md:\n\n${task}`);
   for (let i = 1; i <= opts.maxIterations; i++) {
     const tag = Number.isFinite(opts.maxIterations)
@@ -28,28 +40,31 @@ const runIterations = async (
     );
     reviewNotes = "";
     const result = await runAgent(opts.agent, prompt, opts);
-    if (result.exitCode !== 0) {
+    const output = `${result.parsed}\n${result.combined}`;
+    const done = hasSignal(output, doneSignal);
+    if (!done && result.exitCode !== 0) {
       throw new Error(
         `[loop] ${opts.agent} exited with code ${result.exitCode}`
       );
     }
-    if (!hasSignal(`${result.parsed}\n${result.combined}`, opts.doneSignal)) {
+    if (!done) {
       continue;
     }
-    if (reviewers.length === 0) {
-      console.log(`${stopMessage}, stopping.`);
+    if (result.exitCode !== 0) {
+      console.log(doneSignalExitText(doneSignal, result.exitCode));
+    }
+    if (!shouldReview) {
+      console.log(doneSignalMissingText(doneSignal));
       return true;
     }
     const review = await runReview(reviewers, task, opts);
     if (review.approved) {
       await runDraftPrStep(task, opts, hasExistingPr);
-      console.log(`${stopMessage} and review passed, stopping.`);
+      console.log(doneSignalPassedText(opts.doneSignal));
       return true;
     }
     if (review.consensusFail) {
-      reviewNotes =
-        "Both reviewers requested changes. Decide for each comment whether to address it now. " +
-        `If you skip one, explain why briefly. If both reviews found the same issue, it might be worth addressing.\n\n${review.notes}`;
+      reviewNotes = bothReviewersNotes(review.notes);
       console.log(
         "\n[loop] both reviews collected. original agent deciding what to address."
       );
@@ -68,14 +83,9 @@ export const runLoop = async (task: string, opts: Options): Promise<void> => {
     ? createInterface({ input: process.stdin, output: process.stdout })
     : undefined;
   let hasExistingPr = false;
-  let currentTask = task;
+  let loopTask = task;
   while (true) {
-    const done = await runIterations(
-      currentTask,
-      opts,
-      reviewers,
-      hasExistingPr
-    );
+    const done = await runIterations(loopTask, opts, reviewers, hasExistingPr);
     if (reviewers.length > 0 && done) {
       hasExistingPr = true;
     }
@@ -98,6 +108,6 @@ export const runLoop = async (task: string, opts: Options): Promise<void> => {
       rl.close();
       return;
     }
-    currentTask = `${currentTask}\n\nFollow-up:\n${followUp}`;
+    loopTask = `${loopTask}\n\nFollow-up:\n${followUp}`;
   }
 };
diff --git a/src/loop/types.ts b/src/loop/types.ts
index 4752984..1a68694 100644
--- a/src/loop/types.ts
+++ b/src/loop/types.ts
@@ -7,6 +7,7 @@ export type ValueFlag =
   | "max"
   | "done"
   | "proof"
+  | "codexModel"
   | "format";
 
 export interface Options {
diff --git a/tests/loop/args.test.ts b/tests/loop/args.test.ts
index 93feefa..1c924ba 100644
--- a/tests/loop/args.test.ts
+++ b/tests/loop/args.test.ts
@@ -89,6 +89,24 @@ test("parseArgs uses LOOP_CODEX_MODEL when present", () => {
   expect(opts.model).toBe("test-model");
 });
 
+test("parseArgs uses --codex-model when provided", () => {
+  const opts = parseArgs([
+    "--codex-model",
+    "custom-model",
+    "--proof",
+    "verify",
+  ]);
+
+  expect(opts.model).toBe("custom-model");
+});
+
+test("parseArgs with --codex-model= overrides LOOP_CODEX_MODEL", () => {
+  process.env.LOOP_CODEX_MODEL = "env-model";
+  const opts = parseArgs(["--codex-model=flag-model", "--proof", "verify"]);
+
+  expect(opts.model).toBe("flag-model");
+});
+
 test("parseArgs handles all value flags and explicit reviewer", () => {
   const opts = parseArgs([
     "--agent",
@@ -104,6 +122,8 @@ test("parseArgs handles all value flags and explicit reviewer", () => {
     "--format",
     "pretty",
     "--review=claudex",
+    "--codex-model",
+    "custom-model",
   ]);
 
   expect(opts.agent).toBe("claude");
@@ -113,6 +133,7 @@ test("parseArgs handles all value flags and explicit reviewer", () => {
   expect(opts.proof).toBe("verify this");
   expect(opts.format).toBe("pretty");
   expect(opts.review).toBe("claudex");
+  expect(opts.model).toBe("custom-model");
 });
 
 test("parseArgs treats bare --review as claudex when no reviewer follows", () => {
diff --git a/tests/loop/main.test.ts b/tests/loop/main.test.ts
index cc77d51..a1b4c26 100644
--- a/tests/loop/main.test.ts
+++ b/tests/loop/main.test.ts
@@ -92,6 +92,19 @@ test("runLoop stops immediately on done signal when review is disabled", async (
   expect(runDraftPrStep).not.toHaveBeenCalled();
 });
 
+test("runLoop stops on done signal even if agent exits non-zero when review is disabled", async () => {
+  const { runLoop, runAgent, runReview, runDraftPrStep } = await loadRunLoop({
+    resolveReviewers: () => [],
+    runAgent: async () => makeRunResult("<done/>", "", 1),
+  });
+
+  await runLoop("Ship feature", makeOptions({ review: undefined }));
+
+  expect(runAgent).toHaveBeenCalledTimes(1);
+  expect(runReview).not.toHaveBeenCalled();
+  expect(runDraftPrStep).not.toHaveBeenCalled();
+});
+
 test("runLoop creates draft PR when done signal is reviewed and approved", async () => {
   const opts = makeOptions({ review: "claudex" });
   const { runLoop, runAgent, runReview, runDraftPrStep } = await loadRunLoop({
@@ -116,6 +129,31 @@ test("runLoop creates draft PR when done signal is reviewed and approved", async
   );
 });
 
+test("runLoop creates draft PR when done signal is reviewed and approved even if agent exits non-zero", async () => {
+  const opts = makeOptions({ review: "claudex" });
+  const { runLoop, runAgent, runReview, runDraftPrStep } = await loadRunLoop({
+    resolveReviewers: () => ["codex", "claude"],
+    runAgent: async () => makeRunResult("<done/>", "", 1),
+    runReview: async () => ({
+      approved: true,
+      consensusFail: false,
+      notes: "",
+    }),
+  });
+
+  await runLoop("Ship feature", opts);
+
+  expect(runAgent).toHaveBeenCalledTimes(1);
+  expect(runReview).toHaveBeenCalledTimes(1);
+  expect(runDraftPrStep).toHaveBeenCalledTimes(1);
+  expect(runDraftPrStep).toHaveBeenNthCalledWith(
+    1,
+    "Ship feature",
+    opts,
+    false
+  );
+});
+
 test("runLoop uses follow-up commit prompt after a PR is already created", async () => {
   const answers = ["Update docs", ""];
   const { runLoop, runAgent, runReview, runDraftPrStep } = await loadRunLoop({