diff --git a/desktop/package.json b/desktop/package.json
index 3dc8f70..71c9d9e 100644
--- a/desktop/package.json
+++ b/desktop/package.json
@@ -2,7 +2,7 @@
   "name": "simc-lab",
   "productName": "SimC Lab",
   "desktopName": "simc-lab.desktop",
-  "version": "1.33.0",
+  "version": "1.34.0",
   "description": "Local SimulationCraft workbench with upgrade finder and tank simulation.",
   "author": "Roburmaster",
   "private": true,
diff --git a/lib/analysis/compare.mjs b/lib/analysis/compare.mjs
new file mode 100644
index 0000000..866bede
--- /dev/null
+++ b/lib/analysis/compare.mjs
@@ -0,0 +1,77 @@
+// SimC beside a combat log: the simulation that matches a fight, and the two cast sequences set against each other.
+//
+// SimC's sequence is one sample iteration, with its own procs, crits and rage, so a single event that differs may be
+// chance rather than a mistake. Small shifts in time count as the same cast; only a difference that repeats through
+// the fight is marked as large.
+import {simKey} from './fury.mjs';
+
+// The simulation that matches a fight: the Silvermoon dummies when they were the targets, otherwise Patchwerk on as
+// many targets as were hit; as long as the player attacked, with the bleed tail after it; and no buffs, as on a dummy
+// (they can be turned on in Quick Sim).
+export function fightSetup(fight,data,analysis){
+  const names=[...data.targets.values()].map(t=>t.name);
+  const dummies=names.some(n=>/Cleave Training Dummy/i.test(n));
+  const busy=[...data.targets.values()].filter(t=>t.hits>=Math.max(5,0.05*Math.max(...[...data.targets.values()].map(x=>x.hits)))).length;
+  const attacking=Math.max(20,Math.round(analysis.length-(analysis.tail?.seconds||0)));
+  return {
+    style:dummies?'SilvermoonDummies':'Patchwerk',targets:dummies?5:Math.max(1,Math.min(20,busy)),duration:attacking,
+    ...(analysis.tail?.seconds>=5?{bleedTail:Math.min(60,Math.round(analysis.tail.seconds))}:{}),
+    ...(dummies?{dummyHealth:{mode:'held'}}:{}),
+    label:dummies?'Silvermoon dummies':`${fight.kind==='encounter'?fight.name:'Patchwerk'} · ${busy} target${busy===1?'':'s'}`
+  };
+}
+
+// What counts as a cast on each side. SimC's sequence also holds stance toggles and helper actions.
+const skip=/^(auto_attack|snapshot_stats|berserker_stance|battle_stance|defensive_stance|variable|call_action_list|run_action_list|use_items|wait|pool_resource)$/;
+export const simCasts=sequence=>sequence.filter(e=>!skip.test(e.name)).map(e=>({t:e.t,key:e.name,name:e.spell||e.name,rage:e.rage,buffs:e.buffs||[]}));
+// Charge logs two spells for one press; the same name within a moment is one cast.
+export const logCasts=casts=>casts.filter(c=>!/^(Battle Shout|Berserker Stance)$/.test(c.name)).filter((c,i,list)=>!(i&&list[i-1].name===c.name&&c.t-list[i-1].t<0.3)).map(c=>({t:c.t,key:simKey(c.name),name:c.name}));
+
+// Sets the two sequences against each other (an alignment: the same ability close in time is a match, everything else
+// is a cast only one side made). Both are timed from their own first cast.
+export function align(sim,log,{window=6}={}){
+  const zero=list=>{const t0=list[0]?.t??0;return list.map(e=>({...e,at:e.t-t0}));};
+  const a=zero(sim),b=zero(log),n=a.length,m=b.length,gap=1;
+  const cost=(x,y)=>x.key!==y.key?Infinity:Math.min(1.9,Math.abs(x.at-y.at)/window);
+  // Classic edit distance with a band in time, so a long fight stays quick.
+  const D=Array.from({length:n+1},()=>new Float64Array(m+1).fill(Infinity)),P=Array.from({length:n+1},()=>new Uint8Array(m+1));
+  D[0][0]=0;for(let i=1;i<=n;i++){D[i][0]=i*gap;P[i][0]=1;}for(let j=1;j<=m;j++){D[0][j]=j*gap;P[0][j]=2;}
+  for(let i=1;i<=n;i++)for(let j=1;j<=m;j++){
+    if(Math.abs(a[i-1].at-b[j-1].at)>30){if(b[j-1].at>a[i-1].at+30)break;}
+    let best=D[i-1][j]+gap,step=1;
+    if(D[i][j-1]+gap<best){best=D[i][j-1]+gap;step=2;}
+    const c=cost(a[i-1],b[j-1]);if(D[i-1][j-1]+c<best){best=D[i-1][j-1]+c;step=3;}
+    D[i][j]=best;P[i][j]=step;
+  }
+  const rows=[];let i=n,j=m;
+  while(i>0||j>0){
+    const step=i===0?2:j===0?1:P[i][j]||(D[i-1][j]<=D[i][j-1]?1:2);
+    if(step===3){rows.push({sim:a[i-1],log:b[j-1]});i--;j--;}else if(step===1){rows.push({sim:a[i-1],log:null});i--;}else{rows.push({sim:null,log:b[j-1]});j--;}
+  }
+  return classify(rows.reverse());
+}
+
+// Colours and words for every row. A cast SimC made that you did not (or the reverse) is large when the same thing
+// happens again and again over the fight, small when it is a one-off that may be chance.
+export function classify(rows){
+  const missed={},extra={};
+  for(const r of rows){if(r.sim&&!r.log)missed[r.sim.key]=(missed[r.sim.key]||0)+1;if(r.log&&!r.sim)extra[r.log.key]=(extra[r.log.key]||0)+1;}
+  const repeated=(counts,key)=>counts[key]>=3;
+  const near=(i,side)=>{for(let k=Math.max(0,i-2);k<=Math.min(rows.length-1,i+2);k++)if(k!==i&&rows[k][side]&&!rows[k][side==='log'?'sim':'log'])return rows[k][side];return null;};
+  const out=rows.map((r,i)=>{
+    if(r.sim&&r.log){
+      const dt=r.log.at-r.sim.at,abs=Math.abs(dt);
+      if(abs<1.5)return {...r,kind:'same',size:'none',note:`${r.log.name} as SimC.`};
+      return {...r,kind:dt>0?'late':'early',size:abs>=4?'large':'small',note:`${r.log.name} ${abs.toFixed(1)} s ${dt>0?'later':'earlier'} than SimC.${abs>=4&&dt>0?' Something else took its place first.':''}`};
+    }
+    if(r.sim){
+      const instead=near(i,'log');
+      return {...r,kind:'missed',size:repeated(missed,r.sim.key)?'large':'small',note:`SimC used ${r.sim.name} here${r.sim.rage!=null?` at ${Math.round(r.sim.rage)} rage`:''}; you did not${instead?`, you used ${instead.name} instead`:''}.${repeated(missed,r.sim.key)?` This happens ${missed[r.sim.key]} times in the fight.`:''}`};
+    }
+    const instead=near(i,'sim');
+    return {...r,kind:'extra',size:repeated(extra,r.log.key)?'large':'small',note:`You used ${r.log.name}; SimC did not${instead?` (it used ${instead.name})`:''}.${repeated(extra,r.log.key)?` You do this ${extra[r.log.key]} times.`:''}`};
+  });
+  const count=f=>out.filter(f).length;
+  return {rows:out,summary:{same:count(r=>r.kind==='same'),small:count(r=>r.size==='small'),large:count(r=>r.size==='large'),
+    missed:Object.entries(missed).sort((a,b)=>b[1]-a[1]),extra:Object.entries(extra).sort((a,b)=>b[1]-a[1])}};
+}
diff --git a/package-lock.json b/package-lock.json
index 071f21e..5bbb59d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "simc-lab",
-  "version": "1.33.0",
+  "version": "1.34.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "simc-lab",
-      "version": "1.33.0",
+      "version": "1.34.0",
       "license": "GPL-3.0-or-later",
       "devDependencies": {
         "luaparse": "^0.3.1",
diff --git a/package.json b/package.json
index e608a55..e959908 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "simc-lab",
-  "version": "1.33.0",
+  "version": "1.34.0",
   "private": true,
   "type": "module",
   "scripts": {
diff --git a/public/logs.js b/public/logs.js
index 0ef6068..e7aa7ba 100644
--- a/public/logs.js
+++ b/public/logs.js
@@ -11,7 +11,7 @@ const lanes=['Recklessness','Avatar','Bladestorm',"Odyn's Fury",'Thunderous Roar
 // Log Analysis: pick a combat log, a fight and a player, and see what the rotation did and what to change, beside a
 // finished simulation of the same character when one is chosen.
 export function logsUI({api,notice}){
-  let files=[],scan=null,polling=null,characters=[];
+  let files=[],scan=null,polling=null,characters=[],current=null;
   const store={get:k=>{try{return localStorage.getItem(k);}catch{return null;}},set:(k,v)=>{try{localStorage.setItem(k,v);}catch{}}};
   $('#history').insertAdjacentHTML('afterend',`<section id="logs-panel" class="panel logs-panel" hidden>
     <div class="panel-heading"><h2>Analyse a combat log</h2><span class="pill" id="logs-specs"></span></div>
@@ -67,16 +67,21 @@ export function logsUI({api,notice}){
   }
   async function analyse(id){
     const row=document.querySelector(`[data-analyse="${id}"]`).closest('tr');const player=row.dataset.player,name=row.dataset.playerName;
+    current={file:scan.file,fight:id,player,character:$('#log-character').value,name};
     // Finished simulations of the same character, newest first, to set the rotation beside.
     let sims=[];try{sims=(await api('/api/jobs')).filter(j=>['complete','partial'].includes(j.status)&&['quick','compare','enchants','talents'].includes(j.mode)&&String(j.name).toLowerCase()===name.toLowerCase()).sort((a,b)=>String(b.created).localeCompare(String(a.created)));}catch{}
     $('#log-report').innerHTML=`<div class="log-compare"><label>Compare with a simulation<select id="log-compare"><option value="">No comparison</option>${sims.map(j=>`<option value="${esc(j.id)}">${esc(j.name)} · ${when(j.created)}</option>`).join('')}</select></label><p class="hint">${sims.length?'SimC’s casts per minute from that simulation are shown beside yours.':`No finished simulation of ${esc(name)} yet. Run a Quick Sim of the same character (for dummies, the Silvermoon dummies fight style) to compare.`}</p></div><div id="log-result">Analysing …</div>`;
-    const run=async()=>{try{render(await api('/api/logs/analyse',{file:scan.file,fight:id,player,job:$('#log-compare').value||null}));}catch(e){$('#log-result').innerHTML=`<p class="notice">${esc(e.message)}</p>`;}};
+    const run=async()=>{try{render(await api('/api/logs/analyse',{file:scan.file,fight:id,player,job:$('#log-compare').value||null}));await sideBySide($('#log-compare').value||null);}catch(e){$('#log-result').innerHTML=`<p class="notice">${esc(e.message)}</p>`;}};
+    current.rerun=run;
     $('#log-compare').onchange=run;if(sims[0]){$('#log-compare').value=sims[0].id;}await run();
   }
+  let lastReport=null;
   function render(r){
+    lastReport=r;
     const icon={warning:'!',tip:'→',good:'✓'};
     const timeline=lanes.filter(l=>r.casts.some(c=>c.name===l)).map(l=>`<div class="lane"><span>${esc(l)}</span><div>${r.casts.filter(c=>c.name===l).map(c=>`<i style="left:${Math.max(0,Math.min(100,100*c.t/r.length)).toFixed(2)}%" title="${esc(l)} at ${c.t.toFixed(1)} s"></i>`).join('')}</div></div>`).join('');
-    $('#log-result').innerHTML=`<div class="log-summary"><div><strong>${number(r.dps)}</strong><span>DPS · ${esc(short(r.name))} · ${esc(r.spec)}</span></div><div><strong>${clock(r.length)}</strong><span>${r.targets} target${r.targets===1?'':'s'}</span></div><div><strong>${r.uptime.enrage}%</strong><span>Enrage</span></div><div><strong>${r.uptime.recklessness}%</strong><span>Recklessness</span></div>${r.compare?`<div><strong>${number(r.compare.dps)}</strong><span>SimC · ${esc(r.compare.scenario?.style||'')}</span></div>`:''}</div>
+    $('#log-result').innerHTML=`<div class="log-sim" id="log-sim"></div><div class="log-summary"><div><strong>${number(r.dps)}</strong><span>DPS · ${esc(short(r.name))} · ${esc(r.spec)}</span></div><div><strong>${clock(r.length)}</strong><span>${r.targets} target${r.targets===1?'':'s'}</span></div><div><strong>${r.uptime.enrage}%</strong><span>Enrage</span></div><div><strong>${r.uptime.recklessness}%</strong><span>Recklessness</span></div>${r.compare?`<div><strong>${number(r.compare.dps)}</strong><span>SimC · ${esc(r.compare.scenario?.style||'')}</span></div>`:''}</div>
+      <div id="log-side"></div>
       <h3 class="upgrade-heading">What to change</h3><div class="log-findings">${r.findings.map(f=>`<div class="finding ${f.severity}"><span>${icon[f.severity]}</span><div><strong>${esc(f.title)}</strong><p>${esc(f.detail)}</p></div></div>`).join('')}</div>
       <h3 class="upgrade-heading">Casts over the fight</h3><div class="cast-timeline">${timeline}</div>
       <h3 class="upgrade-heading">Casts per minute${r.compare?' · you and SimC':''}</h3><table class="result-table"><thead><tr><th>Ability</th><th>Casts</th><th>Per minute</th>${r.compare?'<th>SimC per minute</th>':''}<th>Damage</th></tr></thead><tbody>${r.abilities.map(a=>`<tr><td>${esc(a.name)}</td><td>${a.casts}</td><td>${a.cpm}</td>${r.compare?`<td>${a.simCpm??'—'}</td>`:''}<td>${a.share?a.share+'%':'—'}</td></tr>`).join('')}</tbody></table>
@@ -85,6 +90,59 @@ export function logsUI({api,notice}){
       <details class="environment-detail"><summary>Damage by spell</summary><table class="result-table"><thead><tr><th>Spell</th><th>Damage</th><th>Share</th><th>Hits</th><th>Crit</th></tr></thead><tbody>${r.spells.map(s=>`<tr><td>${esc(s.name)}</td><td>${number(s.amount)}</td><td>${s.share}%</td><td>${s.hits}</td><td>${s.crit}%</td></tr>`).join('')}</tbody></table></details>
       <p class="hint">Rage: ${number(r.rage.gained)} gained, ${number(r.rage.wasted)} lost to the cap. Buffs you already had when the log started (flask, food, rune) do not show in a log.</p>`;
   }
+  // Simulate the fight right here: the character's addon export on the same targets, as long as they attacked, with
+  // the bleed tail and no buffs; then set SimC beside the log.
+  async function simulate(){
+    const box=$('#log-sim');box.innerHTML='<p class="hint">Starting the simulation …</p>';
+    try{
+      const job=await api('/api/logs/simulate',{...current,iterations:Number($('#iterations')?.value)||10000,threads:Number($('#threads')?.value)||undefined});
+      const s=job.setup;
+      for(;;){
+        const j=await api(`/api/jobs/${job.id}`);
+        const pct=Math.round(100*(j.fraction||0));
+        box.innerHTML=`<p class="hint">Simulating ${esc(s.label)} · ${s.duration} s${s.bleedTail?` + ${s.bleedTail} s of bleeds`:''} · no buffs … ${pct}%</p><div class="progress-track live"><div class="progress-fill" style="width:${pct}%"></div></div>`;
+        if(['complete','partial'].includes(j.status))break;
+        if(['failed','cancelled','interrupted'].includes(j.status))throw new Error(j.error||j.results?.[0]?.error||'The simulation did not finish.');
+        await new Promise(r=>setTimeout(r,1500));
+      }
+      const select=$('#log-compare');select.insertAdjacentHTML('afterbegin',`<option value="${esc(job.id)}">${esc(current.name)} · this fight · just now</option>`);select.value=job.id;
+      await current.rerun();
+    }catch(e){box.innerHTML=`<p class="notice">${esc(e.message)}</p>`;}
+  }
+  // SimC's sample sequence on the left, the log on the right; Compare sets them against each other.
+  async function sideBySide(job){
+    const box=$('#log-side');if(!box)return;
+    $('#log-sim').innerHTML=`<div class="engine-actions"><button class="button small primary" data-log-simulate>Simulate this fight</button></div><p class="hint">Simulates ${esc(current.name)} from the SimCLab addon export on the same targets, for as long as you attacked, with your bleed tail and no buffs (turn buffs on in Quick Sim when you had them).</p>`;
+    if(!job){box.innerHTML='';return;}
+    let rot,me;
+    try{rot=await api(`/api/jobs/${job}/rotation`);}catch(e){box.innerHTML=`<p class="notice">${esc(e.message)}</p>`;return;}
+    me=lastReport.casts;
+    const simRows=(rot.sequence||[]).filter(e=>!/^(auto_attack|berserker_stance|variable|snapshot_stats)$/.test(e.name));
+    box.innerHTML=`<h3 class="upgrade-heading">SimC beside you</h3>
+      <div class="engine-actions"><button class="button small primary" data-log-compare>Compare events</button><label class="check"><input type="checkbox" id="log-timeline">Timeline view</label></div>
+      <div id="log-compare-view"><div class="side-by-side"><div><h5>SimC · ${Math.round(rot.dps).toLocaleString('en-US')} DPS · one sample iteration</h5><ol class="cast-list">${simRows.map(e=>`<li><span>${e.t.toFixed(1)}</span>${esc(e.spell||e.name)}${e.rage!=null?`<small>${Math.round(e.rage)} rage</small>`:''}</li>`).join('')}</ol></div>
+      <div><h5>You · ${lastReport.dps.toLocaleString('en-US')} DPS</h5><ol class="cast-list">${me.map(c=>`<li><span>${c.t.toFixed(1)}</span>${esc(c.name)}</li>`).join('')}</ol></div></div></div>`;
+    box.dataset.job=job;
+  }
+  const kinds={same:'Same',late:'Later',early:'Earlier',missed:'SimC only',extra:'You only'};
+  async function compareEvents(){
+    const box=$('#log-compare-view');box.innerHTML='<p class="hint">Setting the casts against each other …</p>';
+    try{
+      const r=await api('/api/logs/compare',{...current,job:$('#log-side').dataset.job});const timeline=$('#log-timeline').checked;
+      const legend=`<div class="cmp-legend"><span class="cmp same">Same (within 1.5 s)</span><span class="cmp small">Small: shifted 1.5–4 s, or a one-off that may be chance</span><span class="cmp large">Large: shifted 4 s or more, or the same difference again and again</span><span class="cmp extra">You only</span><span class="cmp missed">SimC only</span></div>
+        <p class="hint">${r.summary.same} casts the same, ${r.summary.small} small and ${r.summary.large} large differences. SimC's side is one sample iteration with its own procs, so look for what repeats: ${r.summary.missed.slice(0,3).map(([k,n])=>`SimC used ${k.replaceAll('_',' ')} ${n} times you did not`).join(', ')}${r.summary.extra.length?`; you used ${r.summary.extra.slice(0,3).map(([k,n])=>`${k.replaceAll('_',' ')} ${n} times`).join(', ')} where SimC did not`:''}.</p>`;
+      const cls=row=>row.kind==='same'?'same':row.size==='large'?'large':row.kind==='extra'?'extra':row.kind==='missed'?'missed':'small';
+      if(timeline){
+        const end=Math.max(...r.rows.map(x=>Math.max(x.sim?.at||0,x.log?.at||0)),1);const x=t=>(100*t/end).toFixed(2);
+        const marks=side=>r.rows.filter(row=>row[side]).map(row=>`<i class="cmp-mark ${cls(row)}" style="left:${x(row[side].at)}%" title="${esc(row[side].at.toFixed(1)+' s · '+row[side].name+' — '+row.note)}"></i>`).join('');
+        box.innerHTML=legend+`<div class="cmp-timeline"><div class="lane"><span>SimC</span><div>${marks('sim')}</div></div><div class="lane"><span>You</span><div>${marks('log')}</div></div></div><p class="hint">Point at a mark for what happened. The scale is ${Math.round(end)} s.</p>`;
+      }else{
+        box.innerHTML=legend+`<table class="result-table cmp-table"><thead><tr><th>SimC</th><th>You</th><th>What happened</th></tr></thead><tbody>${r.rows.map(row=>`<tr class="cmp-row ${cls(row)}"><td>${row.sim?`<b>${row.sim.at.toFixed(1)}</b> ${esc(row.sim.name)}`:''}</td><td>${row.log?`<b>${row.log.at.toFixed(1)}</b> ${esc(row.log.name)}`:''}</td><td><span class="cmp-tag">${kinds[row.kind]}${row.size==='large'?' · large':row.size==='small'?' · small':''}</span> ${esc(row.note)}</td></tr>`).join('')}</tbody></table>`;
+      }
+    }catch(e){box.innerHTML=`<p class="notice">${esc(e.message)}</p>`;}
+  }
+  document.addEventListener('click',e=>{if(e.target.closest('[data-log-simulate]'))simulate();if(e.target.closest('[data-log-compare]'))compareEvents();});
+  document.addEventListener('change',e=>{if(e.target.id==='log-timeline'&&$('#log-compare-view .cmp-legend'))compareEvents();});
   $('#log-refresh').onclick=refresh;$('#log-scan').onclick=startScan;
   $('#log-character').onchange=()=>{store.set('simc-lab-log-character',$('#log-character').value);$('#log-other-label').hidden=$('#log-character').value!=='other';$('#log-report').innerHTML='';if(scan)renderFights();};
   $('#log-other').oninput=()=>{if(scan)renderFights();};$('#log-bosses').onchange=()=>{if(scan)renderFights();};
diff --git a/public/style.css b/public/style.css
index 188ffe2..46e087a 100644
--- a/public/style.css
+++ b/public/style.css
@@ -134,3 +134,5 @@
 .logs-pick{display:flex;gap:10px;align-items:end;flex-wrap:wrap}.logs-pick label{flex:1;min-width:240px}.logs-pick .button{width:auto}.log-fights select{min-width:180px;font-size:12px;padding:6px}.log-fights td{vertical-align:middle}.log-compare{margin-top:22px;padding-top:18px;border-top:1px solid var(--line)}.log-summary{display:flex;flex-wrap:wrap;gap:12px;margin:18px 0}.log-summary>div{background:#131a24;border:1px solid #3b475b;border-radius:7px;padding:14px 18px;min-width:120px}.log-summary strong{display:block;font-size:24px;color:var(--amber);font-weight:600}.log-summary span{font-size:12px;color:var(--muted)}.log-findings{display:grid;gap:8px}.finding{display:flex;gap:12px;padding:12px 14px;border:1px solid var(--line);border-radius:7px;background:#141a25}.finding>span{width:22px;height:22px;border-radius:50%;display:grid;place-content:center;font-size:12px;flex-shrink:0}.finding strong{font-size:13px}.finding p{margin:4px 0 0;font-size:13px;color:var(--muted);line-height:1.6}.finding.warning{border-color:#805060}.finding.warning>span{background:#412b32;color:#f4b5be}.finding.tip>span{background:#302b23;color:var(--amber)}.finding.good>span{background:#1d3329;color:var(--green)}.cast-timeline{display:grid;gap:4px}.lane{display:grid;grid-template-columns:130px 1fr;gap:10px;align-items:center;font-size:11px;color:var(--muted)}.lane>div{position:relative;height:14px;background:#141a25;border:1px solid var(--line);border-radius:3px}.lane i{position:absolute;top:2px;width:2px;height:8px;background:var(--amber)}.rotation-view{margin-top:16px;padding:14px;border:1px solid var(--line);border-radius:7px;background:#141a25}.rotation-view h4{margin:0 0 10px;font-size:13px}.rotation-view h5{margin:0 0 8px;font-size:11px;letter-spacing:1px;color:var(--muted);text-transform:uppercase}.rotation-grid{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,2fr);gap:16px}.rotation-grid>div{max-height:420px;overflow:auto}.apl{background:#0f141d;padding:12px;max-height:360px;overflow:auto;white-space:pre-wrap;overflow-wrap:anywhere;font-size:11px;color:#aabbd2}@media(max-width:720px){.rotation-grid{grid-template-columns:1fr}.lane{grid-template-columns:90px 1fr}}
 .rotation-grid{grid-template-columns:repeat(auto-fit,minmax(280px,1fr))}.rotation-view .result-table td,.rotation-view .result-table th{text-align:left;white-space:normal}.rotation-view .result-table td:first-child{max-width:none}
 .bleed-tail{display:flex;align-items:center;gap:10px;margin-bottom:6px;flex-wrap:wrap}.bleed-tail .inline{display:flex;align-items:center;gap:6px;font-size:12px}.bleed-tail .inline input{width:64px;padding:6px}
+.side-by-side{display:grid;grid-template-columns:1fr 1fr;gap:14px}.side-by-side h5{margin:0 0 8px;font-size:11px;letter-spacing:1px;color:var(--muted);text-transform:uppercase}.cast-list{list-style:none;margin:0;padding:0;max-height:420px;overflow:auto;border:1px solid var(--line);border-radius:6px;font-size:12px}.cast-list li{display:flex;gap:10px;padding:5px 10px;border-bottom:1px solid #222b3a}.cast-list span{color:var(--muted);width:44px;flex-shrink:0;font-variant-numeric:tabular-nums}.cast-list small{margin-left:auto;color:var(--muted)}.cmp-legend{display:flex;flex-wrap:wrap;gap:6px;margin:12px 0}.cmp{font-size:11px;padding:4px 8px;border-radius:12px;border:1px solid var(--line)}.cmp.same,.cmp-row.same td:first-child,.cmp-mark.same{--c:#4f9d7c}.cmp.small,.cmp-row.small td:first-child,.cmp-mark.small{--c:#d9b45a}.cmp.large,.cmp-row.large td:first-child,.cmp-mark.large{--c:#e0745e}.cmp.extra,.cmp-row.extra td:first-child,.cmp-mark.extra{--c:#6b9bd9}.cmp.missed,.cmp-row.missed td:first-child,.cmp-mark.missed{--c:#b07fd6}.cmp{border-color:var(--c);color:var(--c)}.cmp-table td{text-align:left!important;white-space:normal!important;padding:8px 6px}.cmp-row td:first-child{border-left:3px solid var(--c)}.cmp-row b{color:var(--muted);font-weight:500;margin-right:4px}.cmp-row.same td{color:#9fb0c4}.cmp-tag{font-size:11px;color:var(--muted);margin-right:6px}.cmp-row.large .cmp-tag{color:#e0745e}.cmp-timeline{display:grid;gap:8px;margin-top:6px}.cmp-timeline .lane>div{height:22px}.cmp-mark{position:absolute;top:3px;width:3px;height:14px;background:var(--c);border-radius:1px;cursor:help}.cmp-mark.same{opacity:.55}@media(max-width:720px){.side-by-side{grid-template-columns:1fr}}
+#log-side .engine-actions .button,#log-sim .engine-actions .button{width:auto}.cmp-timeline{overflow-x:auto;padding-bottom:6px}.cmp-timeline .lane{grid-template-columns:60px minmax(1800px,1fr)}
diff --git a/server.mjs b/server.mjs
index e06b93d..b035a3e 100644
--- a/server.mjs
+++ b/server.mjs
@@ -27,6 +27,7 @@ import {identity,simEntry,trackTable,sendableModes} from './lib/wowdata.mjs';
 import {importArmory,isArmoryProfile} from './lib/armory.mjs';
 import {logsDir,listLogs,logPath,scanLog,readPlayer} from './lib/combatlog.mjs';
 import {analyserFor,supported as analysedSpecs,simCastsPerMinute,simRotation} from './lib/analysis/index.mjs';
+import {fightSetup,align,simCasts,logCasts} from './lib/analysis/compare.mjs';
 const port=Number(process.env.PORT || 8642);
 const pkg=JSON.parse(await fs.readFile(new URL('./package.json',import.meta.url),'utf8'));
 const appInfo={name:'SimC Lab',version:pkg.version,desktop:!!process.env.SIMC_LAB_DESKTOP,platform:process.platform};const token=randomBytes(32).toString('hex');
@@ -106,6 +107,32 @@ const server=http.createServer(async(req,res)=>{
     if(req.method==='GET'&&route==='/api/wow/captures')return json(res,200,await wow.captures());
     if(req.method==='GET'&&route==='/api/logs'){const dir=await logsDir(await engine.wowInstallDir());return json(res,200,{dir,files:await listLogs(dir),specs:analysedSpecs});}
     if(req.method==='POST'&&route==='/api/logs/scan'){const {file}=await body(req);return json(res,200,await startScan(file));}
+    // One fight read and analysed, for the simulation and the comparison that follow an analysis.
+    const loggedFight=async({file,fight:id,player})=>{
+      const state=await startScan(file);if(state.status!=='done')throw new Error('Scan the log first.');
+      const fight=state.scan.fights.find(f=>f.id===Number(id));if(!fight)throw new Error('Choose a fight.');
+      const data=await readPlayer(logPath(await logsDir(await engine.wowInstallDir()),file),fight,String(player));
+      const analyser=analyserFor(data);if(!analyser)throw new Error(`Rotation analysis is not available for this specialization yet. Analysed so far: ${analysedSpecs.join(', ')}.`);
+      return {fight,data,analysis:analyser.analyse(data)};
+    };
+    // Simulate the fight from the Log Analysis tab: the character's addon export, the matching fight, no buffs.
+    if(req.method==='POST'&&route==='/api/logs/simulate'){
+      ready();if(updater.switching)throw new Error('SimC is switching to the new engine. Try again in a moment.');
+      const input=await body(req);const {fight,data,analysis}=await loggedFight(input);
+      const capture=(await wow.captures()).characters?.find(c=>c.key===String(input.character));
+      if(!capture?.text)throw new Error('This character has no export from the SimCLab addon. Log in with it and type /simc, or use Quick Sim.');
+      const {label,...scenario}=fightSetup(fight,data,analysis);
+      const request={profile:capture.text,mode:'quick',iterations:Number(input.iterations)||10000,targetError:0.2,duration:scenario.duration,threads:Number(input.threads)||engine.maxThreads,
+        environment:{buffs:Object.fromEntries(buffs.map(b=>[b.id,false])),variation:0,bloodlust:{mode:'pull',value:0},consumables:{food:'none',flask:'none',potion:'none',augmentation:'none',main_hand_oil:'none',off_hand_oil:'none'}},scenarios:[scenario]};
+      const plan=await prepare(request,catalog,talentData,season);
+      return json(res,201,{...jobs.public(await jobs.add(plan,request)),setup:{...scenario,label}});
+    }
+    // SimC's sample sequence set against the log, cast by cast.
+    if(req.method==='POST'&&route==='/api/logs/compare'){
+      const input=await body(req);const {analysis}=await loggedFight(input);const {report,row}=await jobReport(input.job);
+      const rotation=simRotation(report);
+      return json(res,200,{...align(simCasts(rotation.sequence),logCasts(analysis.casts)),simDps:row.dps,logDps:analysis.dps,length:analysis.length});
+    }
     if(req.method==='POST'&&route==='/api/logs/analyse'){
       const {file,fight:id,player,job}=await body(req);const state=await startScan(file);if(state.status!=='done')throw new Error('Scan the log first.');
       const fight=state.scan.fights.find(f=>f.id===Number(id));if(!fight)throw new Error('Choose a fight.');
diff --git a/tests/compare.test.mjs b/tests/compare.test.mjs
new file mode 100644
index 0000000..1875a23
--- /dev/null
+++ b/tests/compare.test.mjs
@@ -0,0 +1,23 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import {align,simCasts,logCasts,fightSetup} from '../lib/analysis/compare.mjs';
+
+test('SimC and the log set side by side: same casts, shifts, and differences that repeat',()=>{
+  const sim=simCasts([{t:0,name:'auto_attack'},{t:0,name:'charge',spell:'Charge'},{t:1,name:'rampage',spell:'Rampage',rage:80},{t:2,name:'raging_blow',spell:'Raging Blow'},{t:3,name:'raging_blow',spell:'Raging Blow'},{t:4,name:'raging_blow',spell:'Raging Blow'},{t:9,name:'rampage',spell:'Rampage'}]);
+  const log=logCasts([{t:0,name:'Charge'},{t:0.1,name:'Charge'},{t:1.4,name:'Rampage'},{t:2,name:'Bloodthirst'},{t:3,name:'Bloodthirst'},{t:4,name:'Bloodthirst'},{t:14,name:'Rampage'}]);
+  assert.equal(log.length,6,'Charge logs twice for one press');
+  const r=align(sim,log);
+  const kinds=r.rows.map(x=>x.kind);
+  assert.equal(kinds.filter(k=>k==='same').length,2,'Charge and the first Rampage');
+  assert.ok(r.rows.some(x=>x.kind==='late'&&x.size==='large'&&/5\.0 s later/.test(x.note)),'the second Rampage, 5 s late');
+  const missed=r.rows.filter(x=>x.kind==='missed');assert.equal(missed.length,3);assert.ok(missed.every(x=>x.size==='large'),'three times is a pattern');
+  assert.match(missed[0].note,/SimC used Raging Blow here/);
+  assert.deepEqual(r.summary.extra,[['bloodthirst',3]]);
+});
+
+test('the simulation that matches a fight',()=>{
+  const targets=new Map([['a',{name:'Cleave Training Dummy',hits:100}],['b',{name:'Cleave Training Dummy',hits:90}]]);
+  assert.deepEqual(fightSetup({kind:'activity'},{targets},{length:170.6,tail:{seconds:20.1}}),{style:'SilvermoonDummies',targets:5,duration:151,bleedTail:20,dummyHealth:{mode:'held'},label:'Silvermoon dummies'});
+  const boss=fightSetup({kind:'encounter',name:'Nek’zali'},{targets:new Map([['x',{name:'Boss',hits:300}],['y',{name:'Add',hits:2}]])},{length:300,tail:{seconds:1}});
+  assert.equal(boss.style,'Patchwerk');assert.equal(boss.targets,1);assert.equal(boss.duration,299);assert.equal(boss.bleedTail,undefined);
+});