diff --git a/arena_studio.html b/arena_studio.html
index 9a14e24..dc56446 100644
--- a/arena_studio.html
+++ b/arena_studio.html
@@ -2917,7 +2917,7 @@ <h2 id="modalTitle">Import error</h2>
 </div>
 
 <footer id="footer">
-  <span class="foot-left">Arena Studio v0.70 | 2026-09-04 12:14 ET · <a href="https://github.com/reiserlab/webDisplayTools" target="_blank" rel="noopener" title="webDisplayTools on GitHub: source, issues, and release notes (docs/development/arena-studio-release-notes.md)">GitHub</a></span>
+  <span class="foot-left">Arena Studio v0.71 | 2026-09-04 16:39 ET · <a href="https://github.com/reiserlab/webDisplayTools" target="_blank" rel="noopener" title="webDisplayTools on GitHub: source, issues, and release notes (docs/development/arena-studio-release-notes.md)">GitHub</a></span>
   <!-- Course-repo quick-links: open protocols / logs / patterns in a new tab.
        Hrefs built from the configured repo + bench id (updateGhQuickLinks). -->
   <span id="ghQuickLinks" title="Open the course repo on GitHub (new tab)">
diff --git a/docs/development/arena-studio-release-notes.md b/docs/development/arena-studio-release-notes.md
index bb0bc1a..45db836 100644
--- a/docs/development/arena-studio-release-notes.md
+++ b/docs/development/arena-studio-release-notes.md
@@ -4,6 +4,16 @@ The Studio's footer used to carry the full changelog inline; it now shows one li
 history lives here. Newest first. (Per-session engineering detail stays in
 `arena-studio-handover.md` and the design docs — this file is the user-facing what-changed list.)
 
+## v0.71 (2026-09-04) · Closed-loop apply is reset at run start and abort
+
+- **No more error floods at the start of a run.** If FicTrac closed-loop "apply"
+  had been left on (Console use, or a run that aborted mid-trial), the next run
+  pushed ball-tracking frames into its opening Mode-2 step and the controller
+  rejected every one — hundreds of error lines in the first seconds (seen on
+  rig03-sr, 2026-09-04). The runner now forces apply off at sequence start, at
+  sequence end, and whenever a run aborts or the link drops. Protocol data and
+  timing are unchanged.
+
 ## v0.70 (2026-09-04) · Metadata pick-lists restored; course age/sex/fly# lists load; token guidance
 
 - **The Experimenter dropdown is populated again when no data repo is signed in.**
diff --git a/js/arena-runner-g6.js b/js/arena-runner-g6.js
index 2f30032..401ffaa 100644
--- a/js/arena-runner-g6.js
+++ b/js/arena-runner-g6.js
@@ -858,9 +858,23 @@ var ArenaRunnerG6 = (function () {
             this._active = false;
             this._conditionName = null;
             this._clearLedActivator(); // guarded: no-op send when the link is gone
+            this._disarmClosedLoop();
             this._emit = null;
         }
 
+        /** Force the shared bridge's closed-loop apply OFF (idempotent, never
+         *  throws). Called at sequence start, at sequence end/abort, and on
+         *  disconnect so a stale apply=true from Console use or an aborted run
+         *  cannot drive frames into the next run's non-Mode-3 steps. */
+        _disarmClosedLoop() {
+            if (!this._bridge || typeof this._bridge.setApply !== 'function') return;
+            try {
+                this._bridge.setApply(false);
+            } catch (_) {
+                /* best-effort */
+            }
+        }
+
         // ---- conditional LED activation (install / teardown) --------------
         // Installed by a Mode-3 trialParams carrying led_activation; driven by
         // the bridge's per-frame 'applied' event; sends SET_AO_VOLTAGE only on
@@ -1004,6 +1018,11 @@ var ArenaRunnerG6 = (function () {
 
             this._active = true;
             this._abort = false;
+            // A stale closed-loop apply (left on by Console use or an aborted run)
+            // would push FicTrac frames into the opening Mode-2 step — the firmware
+            // rejects each 0x70 with status 1 and the log fills with errors
+            // (rig03-sr, 2026-09-04: 304 rejects in the first 3 s). Start clean.
+            this._disarmClosedLoop();
             const summary = {
                 completed: false,
                 aborted: false,
@@ -1204,6 +1223,7 @@ var ArenaRunnerG6 = (function () {
                 this._conditionName = null;
                 this._resolveSleep();
                 this._clearLedActivator(); // LED off + stop gating on completion/abort
+                this._disarmClosedLoop(); // never leak apply=true into the next run
                 try {
                     if (this._link && this._link.connected) {
                         await this._link.send(this._wire.encodeStop());
diff --git a/tests/test-arena-runner-g6.js b/tests/test-arena-runner-g6.js
index ed248e3..1dde3a5 100644
--- a/tests/test-arena-runner-g6.js
+++ b/tests/test-arena-runner-g6.js
@@ -1275,9 +1275,11 @@ async function main() {
             }
         });
         check('bridge.connect called once', bridge.connectCalls, 1);
+        // Runner disarms at sequence start and again at sequence end, so the
+        // protocol's own true/false sits between two safety falses.
         checkBool(
-            'apply toggled true then false',
-            JSON.stringify(bridge.applyStates) === JSON.stringify([true, false]),
+            'apply disarmed at start, toggled true then false, disarmed at end',
+            JSON.stringify(bridge.applyStates) === JSON.stringify([false, true, false, false]),
             bridge.applyStates.join(',')
         );
         checkBool(
@@ -1297,6 +1299,126 @@ async function main() {
         check('closed-loop timing = 2s (fictrac ops add no time)', slept, 2000);
     }
 
+    console.log('\n=== FicTrac closed-loop: stale apply is disarmed before the first step ===');
+    {
+        // Regression for rig03-sr 2026-09-04: apply left ON from earlier Console use
+        // pushed 0x70 frames into the opening Mode-2 step (304 firmware rejects).
+        const order = [];
+        const link = makeFakeLink();
+        const origSend = link.send.bind(link);
+        link.send = (bytes) => {
+            order.push('send:0x' + bytes[1].toString(16));
+            return origSend(bytes);
+        };
+        const bridge = {
+            apply: true, // stale state from before the run
+            connect() {},
+            disconnect() {},
+            setApply(on) {
+                this.apply = !!on;
+                order.push('apply:' + this.apply);
+            },
+            setConfig() {},
+            log() {}
+        };
+        const runner = new Runner.ArenaRunner(link, Wire, bridge);
+        const steps = [{ kind: 'ref', conditionName: 'bg', label: 'bg', seqIdx: 0, dur: 1 }];
+        const conditionsByName = new Map([
+            [
+                'bg',
+                {
+                    name: 'bg',
+                    commands: [
+                        {
+                            type: 'controller',
+                            command_name: 'trialParams',
+                            mode: 2,
+                            frame_rate: 10,
+                            gain: 0,
+                            frame_index: 0,
+                            duration: 1,
+                            pattern: 'p'
+                        },
+                        { type: 'wait', duration: 1 }
+                    ]
+                }
+            ]
+        ]);
+        const summary = await runner.runSequence({
+            steps,
+            conditionsByName,
+            resolvePatternId: () => 1,
+            sleep: () => Promise.resolve()
+        });
+        check('run completed', summary.completed, true);
+        check('first bridge/link action is apply:false', order[0], 'apply:false');
+        checkBool(
+            'apply:false precedes the first controller send',
+            order.indexOf('apply:false') < order.findIndex((o) => o.startsWith('send:')),
+            order.slice(0, 3).join(' → ')
+        );
+        check('apply is OFF after the run', bridge.apply, false);
+    }
+
+    console.log('\n=== FicTrac closed-loop: abort mid-trial leaves apply OFF ===');
+    {
+        const link = makeFakeLink();
+        const bridge = {
+            apply: false,
+            states: [],
+            connect() {},
+            disconnect() {},
+            setApply(on) {
+                this.apply = !!on;
+                this.states.push(!!on);
+            },
+            setConfig() {},
+            log() {}
+        };
+        const runner = new Runner.ArenaRunner(link, Wire, bridge);
+        const steps = [{ kind: 'ref', conditionName: 'cl', label: 'cl', seqIdx: 0, dur: 20 }];
+        const conditionsByName = new Map([
+            [
+                'cl',
+                {
+                    name: 'cl',
+                    commands: [
+                        {
+                            type: 'controller',
+                            command_name: 'trialParams',
+                            mode: 3,
+                            frame_rate: 0,
+                            gain: 0,
+                            frame_index: 0,
+                            duration: 20,
+                            pattern: 'p'
+                        },
+                        { type: 'plugin', plugin_name: 'fictrac', command_name: 'startClosedLoop' },
+                        { type: 'wait', duration: 20 },
+                        { type: 'plugin', plugin_name: 'fictrac', command_name: 'stopClosedLoop' }
+                    ]
+                }
+            ]
+        ]);
+        let applyDuringWait = null;
+        const summary = await runner.runSequence({
+            steps,
+            conditionsByName,
+            resolvePatternId: () => 1,
+            fictracPluginNames: new Set(['fictrac']),
+            sleep: () => {
+                // Mid-closed-loop the apply must be ON; then the link drops.
+                applyDuringWait = bridge.apply;
+                runner.abort();
+                return Promise.resolve();
+            }
+        });
+        check('apply was ON during the closed-loop wait', applyDuringWait, true);
+        check('run reported aborted', summary.aborted, true);
+        check('apply is OFF after the abort', bridge.apply, false);
+        check('last apply state recorded is false', bridge.states[bridge.states.length - 1], false);
+    }
+
     console.log('\n=== Summary ===');
     console.log(`${totalChecks - failures} / ${totalChecks} checks passed`);
     process.exit(failures === 0 ? 0 : 1);