diff --git a/scripts/auto-fix-issue.mjs b/scripts/auto-fix-issue.mjs
index cab7f44..9216362 100755
--- a/scripts/auto-fix-issue.mjs
+++ b/scripts/auto-fix-issue.mjs
@@ -3,7 +3,19 @@ import { writeFile } from "node:fs/promises"
 
 const anthropicToken = process.env.ANTHROPIC_AUTH_TOKEN
 const anthropicBaseUrl = process.env.ANTHROPIC_BASE_URL || "https://api.anthropic.com"
-const anthropicModel = process.env.ANTHROPIC_MODEL || "claude-opus-4.1"
+
+const defaultHaikuModel = process.env.ANTHROPIC_DEFAULT_HAIKU_MODEL || "claude-haiku-4.5"
+const defaultOpusModel = process.env.ANTHROPIC_DEFAULT_OPUS_MODEL || "claude-opus-4.6"
+const defaultSonnetModel = process.env.ANTHROPIC_DEFAULT_SONNET_MODEL || "claude-sonnet-4.6"
+
+// Priority: explicit model override -> sonnet default -> haiku -> opus.
+const anthropicModel = process.env.ANTHROPIC_MODEL || defaultSonnetModel || defaultHaikuModel || defaultOpusModel
+
+const timeoutMs = Number(process.env.ANTHROPIC_TIMEOUT_MS || "180000")
+const maxRetries = Number(process.env.ANTHROPIC_MAX_RETRIES || "3")
+const retryBaseMs = Number(process.env.ANTHROPIC_RETRY_BASE_MS || "2000")
+const maxTokens = Number(process.env.ANTHROPIC_MAX_TOKENS || "2048")
+
 const issueNumber = process.env.ISSUE_NUMBER || ""
 const issueTitle = process.env.ISSUE_TITLE || ""
 const issueBody = process.env.ISSUE_BODY || ""
@@ -15,6 +27,26 @@ if (!anthropicToken) {
   process.exit(1)
 }
 
+if (!Number.isFinite(timeoutMs) || timeoutMs <= 0) {
+  console.error(`Invalid ANTHROPIC_TIMEOUT_MS: ${process.env.ANTHROPIC_TIMEOUT_MS}`)
+  process.exit(1)
+}
+
+if (!Number.isFinite(maxRetries) || maxRetries < 1) {
+  console.error(`Invalid ANTHROPIC_MAX_RETRIES: ${process.env.ANTHROPIC_MAX_RETRIES}`)
+  process.exit(1)
+}
+
+if (!Number.isFinite(retryBaseMs) || retryBaseMs < 0) {
+  console.error(`Invalid ANTHROPIC_RETRY_BASE_MS: ${process.env.ANTHROPIC_RETRY_BASE_MS}`)
+  process.exit(1)
+}
+
+if (!Number.isFinite(maxTokens) || maxTokens < 1) {
+  console.error(`Invalid ANTHROPIC_MAX_TOKENS: ${process.env.ANTHROPIC_MAX_TOKENS}`)
+  process.exit(1)
+}
+
 const prompt = [
   "You are a senior software engineer fixing a GitHub issue.",
   "Return ONLY strict JSON with keys: summary, patch.",
@@ -29,33 +61,87 @@ const prompt = [
   issueBody || "(empty)",
 ].join("\n")
 
-const response = await fetch(`${anthropicBaseUrl.replace(/\/$/, "")}/v1/messages`, {
-  method: "POST",
-  headers: {
-    "Content-Type": "application/json",
-    "x-api-key": anthropicToken,
-    "anthropic-version": "2023-06-01",
-  },
-  body: JSON.stringify({
-    model: anthropicModel,
-    max_tokens: 4096,
-    temperature: 0.2,
-    messages: [
-      {
-        role: "user",
-        content: prompt,
-      },
-    ],
-  }),
-})
+function sleep(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms))
+}
 
-if (!response.ok) {
-  const errText = await response.text()
-  console.error(`Anthropic API error: ${response.status} ${errText}`)
+function shouldRetry(status) {
+  return status === 408 || status === 429 || status >= 500
+}
+
+async function requestClaude() {
+  const endpoint = `${anthropicBaseUrl.replace(/\/$/, "")}/v1/messages`
+
+  for (let attempt = 1; attempt <= maxRetries; attempt += 1) {
+    const controller = new AbortController()
+    const timer = setTimeout(() => controller.abort(), timeoutMs)
+
+    try {
+      const response = await fetch(endpoint, {
+        method: "POST",
+        headers: {
+          "Content-Type": "application/json",
+          "x-api-key": anthropicToken,
+          "anthropic-version": "2023-06-01",
+        },
+        body: JSON.stringify({
+          model: anthropicModel,
+          max_tokens: maxTokens,
+          temperature: 0.2,
+          messages: [
+            {
+              role: "user",
+              content: prompt,
+            },
+          ],
+        }),
+        signal: controller.signal,
+      })
+
+      const rawText = await response.text()
+
+      if (!response.ok) {
+        if (attempt < maxRetries && shouldRetry(response.status)) {
+          const delay = retryBaseMs * 2 ** (attempt - 1)
+          console.warn(`Anthropic returned ${response.status}, retrying in ${delay}ms (attempt ${attempt}/${maxRetries})`)
+          await sleep(delay)
+          continue
+        }
+
+        console.error(`Anthropic API error: ${response.status} ${rawText}`)
+        process.exit(1)
+      }
+
+      try {
+        return JSON.parse(rawText)
+      } catch {
+        console.error("Anthropic API returned non-JSON response")
+        console.error(rawText)
+        process.exit(1)
+      }
+    } catch (error) {
+      const isAbort = error instanceof Error && error.name === "AbortError"
+      if (attempt < maxRetries) {
+        const delay = retryBaseMs * 2 ** (attempt - 1)
+        console.warn(
+          `${isAbort ? "Request timed out" : "Request failed"}, retrying in ${delay}ms (attempt ${attempt}/${maxRetries})`,
+        )
+        await sleep(delay)
+        continue
+      }
+
+      console.error(isAbort ? `Anthropic request timeout after ${timeoutMs}ms` : `Anthropic request failed: ${String(error)}`)
+      process.exit(1)
+    } finally {
+      clearTimeout(timer)
+    }
+  }
+
+  console.error("Anthropic request exhausted retries")
   process.exit(1)
 }
 
-const data = await response.json()
+const data = await requestClaude()
 const outputText = Array.isArray(data?.content)
   ? data.content
       .filter((part) => part?.type === "text" && typeof part?.text === "string")
@@ -89,4 +175,4 @@ if (!parsed.patch || typeof parsed.patch !== "string") {
 
 await writeFile("/tmp/issue-autofix.patch", parsed.patch)
 await writeFile("/tmp/issue-autofix-summary.txt", String(parsed.summary || ""))
-console.log("Generated patch at /tmp/issue-autofix.patch")
+console.log(`Generated patch at /tmp/issue-autofix.patch using model ${anthropicModel}`)