From d0b702ddd4f705d553793aee6a53c464d0a40f09 Mon Sep 17 00:00:00 2001
From: Zak Peirce <plastikman@gmail.com>
Date: Mon, 12 Oct 2026 19:55:14 -0700
Subject: [PATCH 1/2] fix(tools): require original start g-code

---
 tests/start_gcode_helper.test.js      | 10 +++---
 tools/start-gcode-helper/README.md    | 12 ++++---
 tools/start-gcode-helper/index.html   |  1 +
 tools/start-gcode-helper/processor.js | 51 ++++++---------------------
 tools/start-gcode-helper/style.css    |  2 ++
 5 files changed, 24 insertions(+), 52 deletions(-)

diff --git a/tests/start_gcode_helper.test.js b/tests/start_gcode_helper.test.js
index c8062fd..c9a370a 100644
--- a/tests/start_gcode_helper.test.js
+++ b/tests/start_gcode_helper.test.js
@@ -19,12 +19,10 @@ assert.equal((result.text.match(/^M191 /gm) || []).length, 1);
 assert.match(result.text, /M140 .*\nM141 S\{overall_chamber_temperature\}/);
 assert.match(result.text, /G0 Z5 F10000\nM106 P2 S178\nM191 S\{overall_chamber_temperature\}\nM107 P2\n; WAIT_CHAMBER_TEMP TIMEOUT=180\nG28 Z/);
 
-const updated = processGcode(result.text, "55");
-assert.equal((updated.text.match(/^M141 /gm) || []).length, 1);
-assert.equal((updated.text.match(/^M191 /gm) || []).length, 1);
-assert.match(updated.text, /M141 S55/);
-assert.match(updated.text, /M106 P2 S178\nM191 S55\nM107 P2/);
-assert.equal((updated.text.match(/^; WAIT_CHAMBER_TEMP/gm) || []).length, 1);
+assert.throws(() => processGcode(result.text, "55"), /original, unmodified slicer start G-code/);
+assert.throws(() => processGcode(template.replace("M140", "M140\nM141 S50"), "55"), /already contains DragonBreath chamber commands/);
+assert.throws(() => processGcode(template.replace("G0 Z5 F10000", "G0 Z5 F10000\nM191 S50"), "55"), /already contains DragonBreath chamber commands/);
+assert.throws(() => processGcode(template.replace("G0 Z5 F10000", "G0 Z5 F10000\nM106 P2 S178"), "55"), /already contains DragonBreath chamber commands/);
 
 const outsideFan = template + "\nM106 P2 S255\n";
 assert.match(processGcode(outsideFan, "55").text, /M107 P2\n; WAIT_CHAMBER_TEMP TIMEOUT=180\nG28 Z[\s\S]*M106 P2 S255/);
diff --git a/tools/start-gcode-helper/README.md b/tools/start-gcode-helper/README.md
index ae6ab3a..9a39e70 100644
--- a/tools/start-gcode-helper/README.md
+++ b/tools/start-gcode-helper/README.md
@@ -4,6 +4,10 @@ A dependency-free static page for adding DragonBreath chamber control to a
 printer's start G-code. It runs completely in the browser; files are never
 uploaded to a server.
 
+Use only the original, unmodified slicer start G-code. Do not run the helper on
+code that already has DragonBreath chamber commands. It stops if it finds
+`M141`, `M191`, or the helper's `M106 P2 S178` fan command in the startup area.
+
 The helper places `M141 S<target>` after the first `M140`, then looks for the
 first `G0 Z5` after `M190` and adds this wait sequence beneath it:
 
@@ -15,11 +19,9 @@ M107 P2
 
 `S178` is 70% of the 0–255 fan scale. The target defaults to the Orca/Bambu
 template variable `{overall_chamber_temperature}`. For already-sliced G-code,
-enter the numeric chamber target instead. If a chamber wait already exists in
-the startup area, the helper updates it and its adjacent P2 fan commands rather
-than adding a second wait. It also comments out an active `WAIT_CHAMBER_TEMP`
-in that startup section because `M191` now performs the wait. Unrelated fan
-commands later in the print are kept.
+enter the numeric chamber target instead. It comments out an active
+`WAIT_CHAMBER_TEMP` in that startup section because `M191` now performs the
+wait. Unrelated fan commands later in the print are kept.
 
 The page expects start G-code containing `M140` and `M190`. Review the preview
 before downloading and using the updated file.
diff --git a/tools/start-gcode-helper/index.html b/tools/start-gcode-helper/index.html
index 153eae8..77a2fb0 100644
--- a/tools/start-gcode-helper/index.html
+++ b/tools/start-gcode-helper/index.html
@@ -17,6 +17,7 @@ <h1>Add chamber control to your start G-code</h1>
 
     <section class="card" aria-labelledby="upload-title">
       <h2 id="upload-title">1. Add your start G-code</h2>
+      <p class="warning"><strong>Use only original, unmodified slicer start G-code.</strong> Do not run this helper on code that already has DragonBreath chamber commands. The helper stops if it finds them.</p>
       <label class="dropzone" id="dropzone" for="file-input">
         <span class="upload-icon" aria-hidden="true">↑</span>
         <span><strong>Choose a file</strong> or drop it here</span>
diff --git a/tools/start-gcode-helper/processor.js b/tools/start-gcode-helper/processor.js
index 4ca4c71..0d1e6b4 100644
--- a/tools/start-gcode-helper/processor.js
+++ b/tools/start-gcode-helper/processor.js
@@ -13,14 +13,6 @@
     return new RegExp("^" + code + "(?:\\s|$)", "i").test(command(line));
   }
 
-  function isP2FanOn(line) {
-    return /^M106\s+.*\bP2\b/i.test(command(line));
-  }
-
-  function isP2FanOff(line) {
-    return /^M107\s+.*\bP2\b/i.test(command(line)) || /^M106\s+.*\bP2\b.*\bS0(?:\.0+)?\b/i.test(command(line));
-  }
-
   function isSafeTemperature(value) {
     const text = String(value).trim();
     if (/^\{[A-Za-z_][A-Za-z0-9_]*\}$/.test(text)) return true;
@@ -45,45 +37,22 @@
     if (bedWaitIndex < 0) bedWaitIndex = lines.findIndex((line) => isCommand(line, "M190"));
     if (bedWaitIndex < 0) throw new Error("Couldn’t find M190, which marks the bed wait. The file was left unchanged.");
 
-    const beforeBedWait = lines.slice(0, bedWaitIndex);
-    const existingM141 = beforeBedWait.findIndex((line) => isCommand(line, "M141"));
-    if (existingM141 >= 0) {
-      lines[existingM141] = "M141 S" + target;
-      for (let i = beforeBedWait.length - 1; i > existingM141; i--) {
-        if (isCommand(lines[i], "M141")) lines.splice(i, 1);
-      }
-    } else {
-      lines.splice(bedTargetIndex + 1, 0, "M141 S" + target);
-    }
-    bedWaitIndex = lines.findIndex((line, index) => index > bedTargetIndex && isCommand(line, "M190"));
-    if (bedWaitIndex < 0) bedWaitIndex = lines.findIndex((line) => isCommand(line, "M190"));
-
     let endIndex = lines.findIndex((line, index) => index > bedWaitIndex && (isCommand(line, "G28") || isCommand(line, "BED_MESH_CALIBRATE")));
     if (endIndex < 0) endIndex = lines.length;
-    const safeZIndex = lines.findIndex((line, index) => index > bedWaitIndex && index < endIndex && /^G0\s+Z5(?:\.0+)?(?:\s|$)/i.test(command(line)));
 
-    // Replace only an existing chamber-wait block in the startup area. Fan
-    // commands elsewhere in the print are left alone.
-    const existingWaits = [];
-    for (let i = bedWaitIndex + 1; i < endIndex; i++) if (isCommand(lines[i], "M191")) existingWaits.push(i);
-    let insertAt = safeZIndex >= 0 ? safeZIndex + 1 : bedWaitIndex + 1;
-    if (existingWaits.length) {
-      insertAt = safeZIndex >= 0 ? safeZIndex + 1 : existingWaits[0];
-      const remove = new Set();
-      for (const index of existingWaits) {
-        remove.add(index);
-        if (index > bedWaitIndex + 1 && isP2FanOn(lines[index - 1])) remove.add(index - 1);
-        if (index + 1 < endIndex && isP2FanOff(lines[index + 1])) remove.add(index + 1);
-      }
-      for (const index of [...remove].sort((a, b) => b - a)) {
-        lines.splice(index, 1);
-        if (index < insertAt) insertAt--;
-        if (index < endIndex) endIndex--;
-      }
+    const alreadyHasChamberTarget = lines.slice(0, endIndex).some((line) => isCommand(line, "M141"));
+    const alreadyHasChamberWait = lines.slice(0, endIndex).some((line) => isCommand(line, "M191"));
+    const alreadyHasHelperFan = lines.slice(bedWaitIndex + 1, endIndex).some((line) => /^M106\s+P2\s+S178(?:\s|$)/i.test(command(line)));
+    if (alreadyHasChamberTarget || alreadyHasChamberWait || alreadyHasHelperFan) {
+      throw new Error("This start G-code already contains DragonBreath chamber commands. Use the original, unmodified slicer start G-code; do not run this helper on code that has already been modified.");
     }
 
+    lines.splice(bedTargetIndex + 1, 0, "M141 S" + target);
+    if (bedTargetIndex < bedWaitIndex) bedWaitIndex++;
     endIndex = lines.findIndex((line, index) => index > bedWaitIndex && (isCommand(line, "G28") || isCommand(line, "BED_MESH_CALIBRATE")));
     if (endIndex < 0) endIndex = lines.length;
+    const safeZIndex = lines.findIndex((line, index) => index > bedWaitIndex && index < endIndex && /^G0\s+Z5(?:\.0+)?(?:\s|$)/i.test(command(line)));
+    let insertAt = safeZIndex >= 0 ? safeZIndex + 1 : bedWaitIndex + 1;
     let legacyWaitsCommented = 0;
     for (let i = bedWaitIndex + 1; i < endIndex; i++) {
       if (isCommand(lines[i], "WAIT_CHAMBER_TEMP")) {
@@ -97,7 +66,7 @@
     if (hadTrailingNewline) output += newline;
     return {
       text: output,
-      message: (existingWaits.length ? "Updated the chamber-wait block" : "Added the chamber target and 70% fan-assisted chamber wait") +
+      message: "Added the chamber target and 70% fan-assisted chamber wait" +
         (legacyWaitsCommented ? " and commented out the old WAIT_CHAMBER_TEMP." : ".")
     };
   }
diff --git a/tools/start-gcode-helper/style.css b/tools/start-gcode-helper/style.css
index 60f667a..0c4471b 100644
--- a/tools/start-gcode-helper/style.css
+++ b/tools/start-gcode-helper/style.css
@@ -37,6 +37,8 @@ textarea { min-height: 190px; resize: vertical; padding: 14px; tab-size: 2; }
 input[type="text"] { padding: 12px; }
 textarea:focus, input:focus { outline: 2px solid #559ee3; outline-offset: 1px; }
 .hint { margin: 8px 0 18px; font-size: .89rem; }
+.warning { margin: 0 0 16px; padding: 12px 14px; border: 1px solid #806333; border-radius: 10px; background: #332916; color: #ffe1a6; }
+.warning strong { color: #fff0cc; }
 code { color: #c7e2ff; }
 button { min-height: 46px; padding: 11px 18px; border: 1px solid transparent; border-radius: 10px; background: #3185d5; color: white; font: inherit; font-weight: 750; cursor: pointer; }
 button:hover { background: #4499e9; }

From 772790ffa364ef40198e9282bb863bd7c04cf1ca Mon Sep 17 00:00:00 2001
From: Zak Peirce <plastikman@gmail.com>
Date: Mon, 12 Oct 2026 19:58:59 -0700
Subject: [PATCH 2/2] docs(tools): clarify startup input limits

---
 tools/start-gcode-helper/README.md  |  7 ++++---
 tools/start-gcode-helper/app.js     | 16 +++++++++++++++-
 tools/start-gcode-helper/index.html |  5 +++--
 tools/start-gcode-helper/style.css  |  3 +++
 4 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/tools/start-gcode-helper/README.md b/tools/start-gcode-helper/README.md
index 9a39e70..91d56dc 100644
--- a/tools/start-gcode-helper/README.md
+++ b/tools/start-gcode-helper/README.md
@@ -4,9 +4,10 @@ A dependency-free static page for adding DragonBreath chamber control to a
 printer's start G-code. It runs completely in the browser; files are never
 uploaded to a server.
 
-Use only the original, unmodified slicer start G-code. Do not run the helper on
-code that already has DragonBreath chamber commands. It stops if it finds
-`M141`, `M191`, or the helper's `M106 P2 S178` fan command in the startup area.
+Start with the original, unmodified slicer start G-code. The helper cannot
+prove that a file is otherwise unmodified: it only checks the startup section
+for `M141`, `M191`, or the helper's `M106 P2 S178` fan command and stops if it
+finds one. Users must confirm they started from the original slicer code.
 
 The helper places `M141 S<target>` after the first `M140`, then looks for the
 first `G0 Z5` after `M190` and adds this wait sequence beneath it:
diff --git a/tools/start-gcode-helper/app.js b/tools/start-gcode-helper/app.js
index 7485667..0fd60fc 100644
--- a/tools/start-gcode-helper/app.js
+++ b/tools/start-gcode-helper/app.js
@@ -7,8 +7,16 @@
   const filename = document.getElementById("filename");
   const resultCard = document.getElementById("result-card");
   const output = document.getElementById("output");
+  const originalConfirmation = document.getElementById("confirm-original");
+  const processButton = document.getElementById("process");
   let downloadName = "start-gcode-updated.gcode";
 
+  function clearOriginalConfirmation() {
+    originalConfirmation.checked = false;
+    processButton.disabled = true;
+    resultCard.hidden = true;
+  }
+
   function showError(message) {
     status.textContent = message;
     status.classList.add("error");
@@ -24,6 +32,7 @@
     const reader = new FileReader();
     reader.onload = () => {
       source.value = String(reader.result || "");
+      clearOriginalConfirmation();
       downloadName = file.name.replace(/\.(?:gcode|gco|gc|g|txt)$/i, "") + "-updated.gcode";
       filename.textContent = file.name;
       status.textContent = "File loaded locally. Review the text, then add the commands.";
@@ -35,6 +44,7 @@
   }
 
   fileInput.addEventListener("change", () => readFile(fileInput.files[0]));
+  source.addEventListener("input", clearOriginalConfirmation);
   for (const eventName of ["dragenter", "dragover"]) {
     dropzone.addEventListener(eventName, (event) => {
       event.preventDefault();
@@ -49,7 +59,11 @@
   }
   dropzone.addEventListener("drop", (event) => readFile(event.dataTransfer.files[0]));
 
-  document.getElementById("process").addEventListener("click", () => {
+  originalConfirmation.addEventListener("change", () => {
+    processButton.disabled = !originalConfirmation.checked;
+  });
+
+  processButton.addEventListener("click", () => {
     try {
       const result = window.StartGcodeProcessor.processGcode(source.value, target.value);
       output.value = result.text;
diff --git a/tools/start-gcode-helper/index.html b/tools/start-gcode-helper/index.html
index 77a2fb0..37fe96d 100644
--- a/tools/start-gcode-helper/index.html
+++ b/tools/start-gcode-helper/index.html
@@ -17,7 +17,8 @@ <h1>Add chamber control to your start G-code</h1>
 
     <section class="card" aria-labelledby="upload-title">
       <h2 id="upload-title">1. Add your start G-code</h2>
-      <p class="warning"><strong>Use only original, unmodified slicer start G-code.</strong> Do not run this helper on code that already has DragonBreath chamber commands. The helper stops if it finds them.</p>
+      <p class="warning"><strong>Start from the original, unmodified slicer start G-code.</strong> This helper cannot prove a file is otherwise unmodified. It only checks the startup section for existing DragonBreath chamber commands and stops if it finds them.</p>
+      <label class="confirm-original"><input id="confirm-original" type="checkbox"> I’m using the original start G-code from my slicer, before adding these chamber commands.</label>
       <label class="dropzone" id="dropzone" for="file-input">
         <span class="upload-icon" aria-hidden="true">↑</span>
         <span><strong>Choose a file</strong> or drop it here</span>
@@ -34,7 +35,7 @@ <h2 id="settings-title">2. Set the chamber target</h2>
       <label for="target">Temperature command value</label>
       <input id="target" type="text" value="{overall_chamber_temperature}" autocomplete="off" spellcheck="false">
       <p class="hint">Keep the slicer variable for a start-G-code template. For an already-sliced file, enter its chamber temperature, for example <code>55</code>.</p>
-      <button id="process" type="button">Add chamber commands</button>
+      <button id="process" type="button" disabled>Add chamber commands</button>
       <p id="status" role="status" aria-live="polite"></p>
     </section>
 
diff --git a/tools/start-gcode-helper/style.css b/tools/start-gcode-helper/style.css
index 0c4471b..72ec015 100644
--- a/tools/start-gcode-helper/style.css
+++ b/tools/start-gcode-helper/style.css
@@ -39,6 +39,9 @@ textarea:focus, input:focus { outline: 2px solid #559ee3; outline-offset: 1px; }
 .hint { margin: 8px 0 18px; font-size: .89rem; }
 .warning { margin: 0 0 16px; padding: 12px 14px; border: 1px solid #806333; border-radius: 10px; background: #332916; color: #ffe1a6; }
 .warning strong { color: #fff0cc; }
+.confirm-original { display: flex; align-items: start; gap: 10px; margin: 0 0 12px; font-weight: 500; }
+.confirm-original input { width: 18px; height: 18px; flex: 0 0 auto; margin: 2px 0 0; accent-color: #3185d5; }
+button:disabled { background: #344253; color: #a6b1be; cursor: not-allowed; }
 code { color: #c7e2ff; }
 button { min-height: 46px; padding: 11px 18px; border: 1px solid transparent; border-radius: 10px; background: #3185d5; color: white; font: inherit; font-weight: 750; cursor: pointer; }
 button:hover { background: #4499e9; }