diff --git a/scripts/candidate-github.mjs b/scripts/candidate-github.mjs
index 25b2ca4..b7f0913 100644
--- a/scripts/candidate-github.mjs
+++ b/scripts/candidate-github.mjs
@@ -23,9 +23,9 @@ export function safeArchiveNames(text) {
 }
 function http(token) {
   demand(typeof token==='string' && token.length>0,'GitHub token required');
-  async function call(url,{method='GET',body,octet=false,limit=20*1024**2}={}) {
+  async function call(url,{method='GET',body,octet=false,accept=octet?'application/octet-stream':'application/vnd.github+json',limit=20*1024**2}={}) {
     demand(url.startsWith(base+'/') || url.startsWith(`https://uploads.github.com/repos/${repo}/`),'unexpected GitHub request destination');
-    const response=await fetch(url,{method,headers:{Authorization:`Bearer ${token}`,Accept:octet?'application/octet-stream':'application/vnd.github+json','X-GitHub-Api-Version':'2022-11-28',...(body?{'Content-Type':Buffer.isBuffer(body)?'application/octet-stream':'application/json'}:{})},body:body?(Buffer.isBuffer(body)?body:JSON.stringify(body)):undefined,signal:AbortSignal.timeout(180000)});
+    const response=await fetch(url,{method,headers:{Authorization:`Bearer ${token}`,Accept:accept,'X-GitHub-Api-Version':'2022-11-28',...(body?{'Content-Type':Buffer.isBuffer(body)?'application/octet-stream':'application/json'}:{})},body:body?(Buffer.isBuffer(body)?body:JSON.stringify(body)):undefined,signal:AbortSignal.timeout(180000)});
     if(!response.ok)throw Object.assign(Error(`GitHub ${method} operation failed (HTTP ${response.status})`),{status:response.status});
     demand(Number(response.headers.get('content-length')??0)<=limit,'GitHub response exceeds size bound');
     const chunks=[];let size=0;
@@ -38,7 +38,9 @@ export async function acquireCandidate(a,pubkey,token) {
   demand(positive(a.prepareRunId) && positive(a.prepareAttempt) && positive(a.artifactId) && /^[a-f0-9]{40}$/.test(a.sourceSha) && /^[a-f0-9]{64}$/.test(a.artifactSha256),'explicit acquisition pins required');
   const call=http(token),run=await call(`${base}/actions/runs/${a.prepareRunId}`);verifyPrepareRun(run,a);
   const asset=await call(`${base}/actions/artifacts/${a.artifactId}`);verifyArtifact(asset,a);
-  const archive=await call(`${base}/actions/artifacts/${a.artifactId}/zip`,{octet:true,limit:2*1024**3});
+  // Actions negotiates its archive redirect through the JSON API media type;
+  // the redirected response is still binary. Release assets use octet-stream.
+  const archive=await call(`${base}/actions/artifacts/${a.artifactId}/zip`,{octet:true,accept:'application/vnd.github+json',limit:2*1024**3});
   demand(sha256(archive)===a.artifactSha256,'downloaded ZIP SHA differs');
   const temporary=mkdtempSync(join(tmpdir(),'tenebra-candidate-')),zip=join(temporary,'candidate.zip');
   const files=new Map();
diff --git a/scripts/candidate-github.test.mjs b/scripts/candidate-github.test.mjs
index efa8b75..7b6cf03 100644
--- a/scripts/candidate-github.test.mjs
+++ b/scripts/candidate-github.test.mjs
@@ -1,8 +1,42 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { verifyPrepareRun, verifyArtifact, safeArchiveNames, publisher } from './candidate-github.mjs';
+import { verifyPrepareRun, verifyArtifact, safeArchiveNames, publisher, acquireCandidate } from './candidate-github.mjs';
 import {sha256} from './signed-candidate.mjs';
 const source='a'.repeat(40), acceptance={prepareRunId:123,prepareAttempt:2,sourceSha:source,artifactId:456,artifactSha256:'b'.repeat(64)};
+test('Actions archive uses JSON API negotiation but verifies the downloaded binary before extraction',async t=>{
+  const requests=[];
+  t.mock.method(globalThis,'fetch',async(url,options)=>{
+    requests.push({url,method:options.method,accept:options.headers.Accept});
+    assert.equal(options.method,'GET');
+    if(url.endsWith('/actions/runs/123'))return new Response(JSON.stringify({id:123,run_attempt:2,event:'workflow_dispatch',head_branch:'main',head_sha:source,path:'.github/workflows/desktop-candidate.yml',status:'completed',conclusion:'success',repository:{full_name:'Divaaaan/tenebra'}}));
+    if(url.endsWith('/actions/artifacts/456'))return new Response(JSON.stringify({id:456,name:'tenebra-signed-desktop-123-2',expired:false,digest:'sha256:'+acceptance.artifactSha256,size_in_bytes:5,workflow_run:{id:123,head_sha:source,head_branch:'main'}}));
+    if(url.endsWith('/actions/artifacts/456/zip')){
+      // Matches the live Actions endpoint: octet-stream negotiation returns 415.
+      if(options.headers.Accept!=='application/vnd.github+json')return new Response('{}',{status:415});
+      // Deliberately invalid digest; must reach binary SHA verification, never
+      // parse this non-JSON body or invoke unzip/candidate verification on it.
+      return new Response(Buffer.from([0x50,0x4b,0xff,0x00,0xfe]),{headers:{'Content-Type':'application/zip'}});
+    }
+    throw Error('unexpected request');
+  });
+  await assert.rejects(()=>acquireCandidate(acceptance,'unused-key','test-token'),/downloaded ZIP SHA differs/);
+  assert.equal(requests.length,3);
+  assert.ok(requests.every(r=>r.accept==='application/vnd.github+json'));
+});
+test('release asset byte verification still requests octet-stream',async t=>{
+  const notes=Buffer.from('# Tenebra 0.6.0\n\nNotes.\n'),promotionId='c'.repeat(64),bytes=Buffer.from([0xff,0x00,0x7b,0xfe]);
+  const candidate={version:'0.6.0',sourceSha:source,files:[{name:'release-notes.md',sha256:sha256(notes)}]};
+  let downloaded=false;
+  t.mock.method(globalThis,'fetch',async(url,options)=>{
+    assert.equal(options.method,'GET');
+    if(url.endsWith('/git/ref/tags/v0.6.0'))return new Response(JSON.stringify({object:{type:'commit',sha:source}}));
+    if(url.endsWith('/releases/42'))return new Response(JSON.stringify({id:42,tag_name:'v0.6.0',prerelease:false,draft:true,body:`<!-- tenebra-promotion-sha256:${promotionId} -->\n${notes}`,assets:[{id:8,name:'file.exe',state:'uploaded',size:bytes.length}]}));
+    if(url.endsWith('/releases/assets/8')){assert.equal(options.headers.Accept,'application/octet-stream');downloaded=true;return new Response(bytes);}
+    throw Error('unexpected request');
+  });
+  await publisher('test-token',candidate,notes).verifyUploaded(42,new Map([['file.exe',bytes]]),{promotionId});
+  assert.equal(downloaded,true);
+});
 test('artifact acquisition pins an actual completed main dispatch, not a PR/tree-equivalent build',()=>{
   const run={id:123,run_attempt:2,event:'workflow_dispatch',head_branch:'main',head_sha:source,path:'.github/workflows/desktop-candidate.yml',status:'completed',conclusion:'success',repository:{full_name:'Divaaaan/tenebra'}};
   assert.equal(verifyPrepareRun(run,acceptance),true);