diff --git a/job_filter.mjs b/job_filter.mjs
index bb18b53..461923e 100644
--- a/job_filter.mjs
+++ b/job_filter.mjs
@@ -100,7 +100,7 @@ async function collect(state, settings) {
   }
 
   console.log(`  Batch ended. Downloading results...`);
-  const results = await downloadResults(state.batch_id, apiKey);
+  const results = await downloadResults(state.batch_id, apiKey, state.id_map || {});
 
   const searchConfig = loadConfig(resolve(__dir, 'config/search_config.json'));
   const globalMin = searchConfig.filter_min_score ?? 5;
@@ -195,7 +195,7 @@ async function submit(settings, searchConfig, candidateProfile) {
   const model = settings.filter?.model || DEFAULT_MODEL;
   console.log(`🚀 Submitting batch — ${filterable.length} jobs, model: ${model}`);
 
-  const batchId = await submitBatch(filterable, jobProfilesByTrack, searchConfig, candidateProfile, model, apiKey);
+  const { batchId, idMap } = await submitBatch(filterable, jobProfilesByTrack, searchConfig, candidateProfile, model, apiKey);
 
   const submittedAt = new Date().toISOString();
   writeState({
@@ -204,6 +204,7 @@ async function submit(settings, searchConfig, candidateProfile) {
     job_count: filterable.length,
     model,
     tracks: Object.keys(jobProfilesByTrack),
+    id_map: idMap,
   });
 
   console.log(`  Batch submitted: ${batchId}`);
diff --git a/lib/filter.mjs b/lib/filter.mjs
index a92ec3f..12c4150 100644
--- a/lib/filter.mjs
+++ b/lib/filter.mjs
@@ -62,11 +62,16 @@ Penalize heavily for:
 Return ONLY a JSON object: {"score": <0-10>, "reason": "<one line>"}`;
 }
 
+function sanitize(str) {
+  // Remove lone surrogates and other invalid Unicode that breaks JSON encoding
+  return (str || '').replace(/[\uD800-\uDFFF]/g, '').replace(/\0/g, '');
+}
+
 function buildJobMessage(job) {
-  const desc = (job.description || '').substring(0, DESC_MAX_CHARS).replace(/\s+/g, ' ').trim();
-  return `Title: ${job.title}
-Company: ${job.company || 'Unknown'}
-Location: ${job.location || 'Unknown'}
+  const desc = sanitize(job.description).substring(0, DESC_MAX_CHARS).replace(/\s+/g, ' ').trim();
+  return `Title: ${sanitize(job.title)}
+Company: ${sanitize(job.company) || 'Unknown'}
+Location: ${sanitize(job.location) || 'Unknown'}
 Description: ${desc}
 
 Return ONLY: {"score": <0-10>, "reason": "<one line>"}`;
@@ -94,6 +99,7 @@ export async function submitBatch(jobs, jobProfilesByTrack, searchConfig, candid
   const globalMin = searchConfig.filter_min_score ?? 5;
 
   const requests = [];
+  const idMap = {}; // custom_id → job.id (handles truncation edge cases)
 
   for (const job of jobs) {
     const track = job.track || 'ae';
@@ -101,9 +107,12 @@ export async function submitBatch(jobs, jobProfilesByTrack, searchConfig, candid
     if (!jobProfile) continue; // no profile → skip (caller handles this)
 
     const systemPrompt = buildSystemPrompt(jobProfile, candidateProfile);
+    // Anthropic custom_id max 64 chars
+    const customId = job.id.length <= 64 ? job.id : job.id.substring(0, 64);
+    idMap[customId] = job.id;
 
     requests.push({
-      custom_id: job.id,
+      custom_id: customId,
       params: {
         model,
         max_tokens: 128,
@@ -123,6 +132,7 @@ export async function submitBatch(jobs, jobProfilesByTrack, searchConfig, candid
 
   if (requests.length === 0) throw new Error('No requests to submit — check job profiles are configured');
 
+  // Return idMap alongside batch ID so collector can resolve truncated IDs
   const res = await fetch(BATCH_API, {
     method: 'POST',
     headers: apiHeaders(apiKey),
@@ -135,7 +145,7 @@ export async function submitBatch(jobs, jobProfilesByTrack, searchConfig, candid
   }
 
   const data = await res.json();
-  return data.id; // msgbatch_...
+  return { batchId: data.id, idMap };
 }
 
 /**
@@ -159,7 +169,7 @@ export async function checkBatch(batchId, apiKey) {
 /**
  * Download and parse batch results. Returns array of { jobId, score, reason, error }
  */
-export async function downloadResults(batchId, apiKey) {
+export async function downloadResults(batchId, apiKey, idMap = {}) {
   const res = await fetch(`${BATCH_API}/${batchId}/results`, {
     headers: apiHeaders(apiKey),
   });
@@ -173,7 +183,8 @@ export async function downloadResults(batchId, apiKey) {
   for (const line of lines) {
     try {
       const entry = JSON.parse(line);
-      const jobId = entry.custom_id;
+      // Resolve truncated custom_id back to original job ID
+      const jobId = idMap[entry.custom_id] || entry.custom_id;
 
       if (entry.result?.type === 'succeeded') {
         const content = entry.result.message?.content?.[0]?.text || '';