diff --git a/playground/js/shapeseq/delta.js b/playground/js/shapeseq/delta.js
new file mode 100644
index 0000000..1597964
--- /dev/null
+++ b/playground/js/shapeseq/delta.js
@@ -0,0 +1,50 @@
+/**
+ * ShapeSeq DeltaController — MLP delta application with boundary enforcement
+ *
+ * Applies MLP output deltas to frozen param values for live (unfrozen) params.
+ * Frozen params pass through unchanged. Live params get:
+ *   frozenValue + (mlpValue - 0.5) * 2 * deltaScale
+ * with per-param boundary enforcement (clamp, wrap, scaled).
+ *
+ * @module shapeseq/delta
+ */
+
+import { applyBoundary } from './primitive.js';
+
+export class DeltaController {
+  /**
+   * Compute effective params by applying MLP-derived deltas to frozen values.
+   *
+   * For frozen params: returns the frozen value unchanged.
+   * For live params: frozenValue + delta, with boundary enforcement.
+   *
+   * The delta is derived from the MLP output: delta = (mlpValue - 0.5) * 2 * deltaScale
+   * This maps MLP [0,1] output to a [-deltaScale, +deltaScale] range centered on the frozen value.
+   *
+   * @param {Float32Array} frozenParams - captured param values from FreezeManager
+   * @param {Uint8Array} liveFlags - 1=live, 0=frozen from FreezeManager
+   * @param {Float32Array} mlpParams - current MLP-mapped param values [0,1]
+   * @param {Array<{schema: {boundary: string, scaledRange?: number}}>} paramSchemas - from chain.getParamSchemas()
+   * @param {number} deltaScale - global delta sensitivity (default 0.3)
+   * @returns {Float32Array} effective params ready for chain.evaluate()
+   */
+  static computeEffective(frozenParams, liveFlags, mlpParams, paramSchemas, deltaScale = 0.3) {
+    const count = frozenParams.length;
+    const result = new Float32Array(count);
+
+    for (let i = 0; i < count; i++) {
+      if (!liveFlags[i]) {
+        // Frozen: passthrough
+        result[i] = frozenParams[i];
+      } else {
+        // Live: apply delta with boundary enforcement
+        const delta = (mlpParams[i] - 0.5) * 2 * deltaScale;
+        const raw = frozenParams[i] + delta;
+        const schema = paramSchemas[i]?.schema || { boundary: 'clamp' };
+        result[i] = applyBoundary(raw, schema, frozenParams[i]);
+      }
+    }
+
+    return result;
+  }
+}
diff --git a/playground/js/shapeseq/freeze.js b/playground/js/shapeseq/freeze.js
new file mode 100644
index 0000000..4c56f42
--- /dev/null
+++ b/playground/js/shapeseq/freeze.js
@@ -0,0 +1,246 @@
+/**
+ * ShapeSeq FreezeManager — freeze-as-algorithm and freeze-as-pattern
+ *
+ * Two freeze modes:
+ *
+ * - **algorithm**: Captures all primitive param values + PRNG seeds.
+ *   Frozen params hold their captured values; individual params can
+ *   be selectively re-exposed as "live" for ML-driven exploration.
+ *
+ * - **pattern**: Captures the realized note pattern (the actual step
+ *   events for one full loop). The sequencer bypasses the primitive
+ *   chain entirely and just loops the frozen pattern.
+ *
+ * Delta math (proper delta+boundary logic) is a separate issue (meml-7goy).
+ * This module provides the simple version: frozen params use captured values,
+ * live params pass through current ML values.
+ *
+ * @module shapeseq/freeze
+ */
+
+import { clonePattern } from './pattern.js';
+
+export class FreezeManager {
+  constructor() {
+    /** @private */ this._frozen = false;
+    /** @private @type {'algorithm'|'pattern'|null} */ this._freezeMode = null;
+    /** @private @type {Float32Array|null} */ this._frozenParams = null;
+    /** @private @type {Array<number>|null} */ this._frozenSeeds = null;
+    /** @private @type {Array<Object>|null} */ this._frozenStates = null;
+    /** @private @type {Uint8Array|null} */ this._liveFlags = null;
+    /** @private @type {number|null} */ this._masterSeed = null;
+    /** @private @type {Object|null} */ this._frozenPattern = null;
+  }
+
+  // ── Freeze / unfreeze ───────────────────────────────────────────────
+
+  /**
+   * Capture a full snapshot of the current state.
+   *
+   * In **algorithm** mode (default): captures params, seeds, and states.
+   * All params start frozen (liveFlags = 0); use toggleParam() or
+   * setParamLive() to selectively re-expose params for ML control.
+   *
+   * In **pattern** mode: captures the realized note pattern via deep clone.
+   * The primitive chain is bypassed entirely — the sequencer just loops
+   * the frozen pattern.
+   *
+   * @param {import('./chain.js').Chain|null} chain
+   * @param {Float32Array|Array<number>|null} currentParams - flat param array
+   * @param {number|null} masterSeed
+   * @param {'algorithm'|'pattern'} [mode='algorithm']
+   * @param {Object|null} [currentPattern=null] - required when mode is 'pattern'
+   */
+  freeze(chain, currentParams, masterSeed, mode = 'algorithm', currentPattern = null) {
+    this._freezeMode = mode;
+
+    if (mode === 'pattern') {
+      // Pattern mode: capture the realized pattern, bypass chain
+      if (!currentPattern) {
+        throw new Error('freeze: pattern mode requires a currentPattern');
+      }
+      this._frozenPattern = clonePattern(currentPattern);
+      // Clear algorithm-mode state
+      this._frozenParams = null;
+      this._frozenSeeds = null;
+      this._frozenStates = null;
+      this._liveFlags = null;
+      this._masterSeed = null;
+    } else {
+      // Algorithm mode: existing behavior
+      // Copy param values
+      this._frozenParams = new Float32Array(currentParams.length);
+      for (let i = 0; i < currentParams.length; i++) {
+        this._frozenParams[i] = currentParams[i];
+      }
+
+      // Capture per-primitive seeds
+      this._frozenSeeds = chain.getPrimitives().map(p => p.getSeed());
+
+      // Capture per-primitive states
+      this._frozenStates = chain.getState();
+
+      // Store master seed
+      this._masterSeed = masterSeed;
+
+      // All params frozen by default
+      this._liveFlags = new Uint8Array(currentParams.length);
+
+      // Clear pattern-mode state
+      this._frozenPattern = null;
+    }
+
+    this._frozen = true;
+  }
+
+  /**
+   * Clear all captured state and return to unfrozen mode.
+   */
+  unfreeze() {
+    this._frozen = false;
+    this._freezeMode = null;
+    this._frozenParams = null;
+    this._frozenSeeds = null;
+    this._frozenStates = null;
+    this._liveFlags = null;
+    this._masterSeed = null;
+    this._frozenPattern = null;
+  }
+
+  // ── Per-param live/frozen control ──────────────────────────────────
+
+  /**
+   * Toggle a param between frozen (0) and live (1).
+   * Only valid when frozen; throws if not frozen.
+   *
+   * @param {number} flatIndex - index into the flat param array
+   */
+  toggleParam(flatIndex) {
+    if (!this._frozen) {
+      throw new Error('toggleParam: cannot toggle when not frozen');
+    }
+    const idx = flatIndex | 0;
+    if (idx < 0 || idx >= this._liveFlags.length) {
+      throw new RangeError('toggleParam: index ' + flatIndex + ' out of range [0, ' + (this._liveFlags.length - 1) + ']');
+    }
+    this._liveFlags[idx] = this._liveFlags[idx] ? 0 : 1;
+  }
+
+  /**
+   * Explicitly set a param's live state.
+   * Only valid when frozen; throws if not frozen.
+   *
+   * @param {number} flatIndex - index into the flat param array
+   * @param {boolean} isLive - true = live (receives ML values), false = frozen
+   */
+  setParamLive(flatIndex, isLive) {
+    if (!this._frozen) {
+      throw new Error('setParamLive: cannot set when not frozen');
+    }
+    const idx = flatIndex | 0;
+    if (idx < 0 || idx >= this._liveFlags.length) {
+      throw new RangeError('setParamLive: index ' + flatIndex + ' out of range [0, ' + (this._liveFlags.length - 1) + ']');
+    }
+    this._liveFlags[idx] = isLive ? 1 : 0;
+  }
+
+  // ── Getters ────────────────────────────────────────────────────────
+
+  /** @returns {boolean} */
+  get isFrozen() {
+    return this._frozen;
+  }
+
+  /**
+   * Returns the current freeze mode, or null if not frozen.
+   * @returns {'algorithm'|'pattern'|null}
+   */
+  get freezeMode() {
+    return this._freezeMode;
+  }
+
+  /**
+   * Returns the captured pattern (pattern mode only), or null.
+   * @returns {Object|null}
+   */
+  getFrozenPattern() {
+    return this._frozenPattern;
+  }
+
+  /**
+   * Returns the captured param values, or null if not frozen.
+   * @returns {Float32Array|null}
+   */
+  getFrozenParams() {
+    return this._frozenParams;
+  }
+
+  /**
+   * Returns the live flags array, or null if not frozen.
+   * @returns {Uint8Array|null}
+   */
+  getLiveFlags() {
+    return this._liveFlags;
+  }
+
+  /**
+   * Returns the captured per-primitive PRNG seeds, or null if not frozen.
+   * @returns {Array<number>|null}
+   */
+  getFrozenSeeds() {
+    return this._frozenSeeds;
+  }
+
+  /**
+   * Returns the captured per-primitive states, or null if not frozen.
+   * @returns {Array<Object>|null}
+   */
+  getFrozenStates() {
+    return this._frozenStates;
+  }
+
+  /**
+   * Returns the captured master seed, or null if not frozen.
+   * @returns {number|null}
+   */
+  getMasterSeed() {
+    return this._masterSeed;
+  }
+
+  // ── Effective params ───────────────────────────────────────────────
+
+  /**
+   * Given current MLP-derived params, return the effective param array:
+   * frozen params use captured values, live params use currentMLParams.
+   *
+   * This is the simple version. The delta controller (meml-7goy) will
+   * replace this with proper delta+boundary logic later.
+   *
+   * Returns null if not frozen.
+   *
+   * @param {Float32Array|Array<number>} currentMLParams
+   * @returns {Float32Array|null}
+   */
+  getEffectiveParams(currentMLParams) {
+    if (!this._frozen) return null;
+    if (this._freezeMode === 'pattern') return null;
+
+    const result = new Float32Array(this._frozenParams.length);
+    for (let i = 0; i < result.length; i++) {
+      result[i] = this._liveFlags[i] ? currentMLParams[i] : this._frozenParams[i];
+    }
+    return result;
+  }
+
+  // ── Sequencer integration ──────────────────────────────────────────
+
+  /**
+   * Returns true when frozen — freeze-as-algorithm suppresses per-loop
+   * re-evaluation. The sequencer's _handleLoopStart should check this.
+   *
+   * @returns {boolean}
+   */
+  shouldSuppressReEval() {
+    return this._frozen;
+  }
+}
diff --git a/playground/js/shapeseq/sequencer.js b/playground/js/shapeseq/sequencer.js
index 311645e..5b8ba42 100644
--- a/playground/js/shapeseq/sequencer.js
+++ b/playground/js/shapeseq/sequencer.js
@@ -33,6 +33,8 @@ import {
   IntervalLock,
   VelocityShaper,
 } from './primitives.js';
+import { FreezeManager } from './freeze.js';
+import { DeltaController } from './delta.js';
 
 // ── Defaults ─────────────────────────────────────────────────────────
 
@@ -63,6 +65,15 @@ export class ShapeSeqEngine {
 
     /** @private */ this._outputCount = SEQ_DEFAULT_OUTPUT_COUNT;
     /** @private */ this._stepCount = DEFAULT_STEP_COUNT;
+
+    // Freeze-as-algorithm manager
+    /** @private */ this._freezeManager = new FreezeManager();
+
+    // Last evaluated params — needed for freeze snapshot
+    /** @private @type {Float32Array|null} */ this._lastEvaluatedParams = null;
+
+    // Last projected pattern — needed for freeze-as-pattern snapshot
+    /** @private @type {Object|null} */ this._lastPattern = null;
     /** @private */ this._masterSeed = DEFAULT_MASTER_SEED;
     /** @private */ this._playing = false;
     /** @private */ this._initialized = false;
@@ -267,6 +278,51 @@ export class ShapeSeqEngine {
   /** @returns {WasmIML} */
   getSequenceIML() { return this._sequenceIML; }
 
+  /** @returns {FreezeManager} */
+  get freezeManager() { return this._freezeManager; }
+
+  // ── Freeze-as-algorithm ────────────────────────────────────────────
+
+  /**
+   * Freeze the current state.
+   *
+   * In **algorithm** mode (default): capture param values, seeds, and states.
+   * All params start frozen; use toggleParamFreeze() to re-expose
+   * individual params for ML-driven exploration.
+   *
+   * In **pattern** mode: capture the last projected pattern. The sequencer
+   * bypasses the primitive chain entirely and loops the frozen pattern.
+   *
+   * @param {'algorithm'|'pattern'} [mode='algorithm']
+   */
+  freeze(mode = 'algorithm') {
+    if (mode === 'pattern') {
+      // Need the last evaluated pattern
+      this._freezeManager.freeze(null, null, null, 'pattern', this._lastPattern);
+    } else {
+      if (!this._chain) return;
+      const currentParams = this._lastEvaluatedParams || new Float32Array(this._chain.totalParamCount);
+      this._freezeManager.freeze(this._chain, currentParams, this._masterSeed, 'algorithm');
+    }
+  }
+
+  /**
+   * Unfreeze: clear captured state and return to normal ML control.
+   */
+  unfreeze() {
+    this._freezeManager.unfreeze();
+    this._bumpGeneration();
+  }
+
+  /**
+   * Toggle a single param between frozen and live.
+   * @param {number} flatIndex
+   */
+  toggleParamFreeze(flatIndex) {
+    this._freezeManager.toggleParam(flatIndex);
+    this._bumpGeneration();
+  }
+
   // ── Input routing ──────────────────────────────────────────────────
 
   /**
@@ -280,6 +336,11 @@ export class ShapeSeqEngine {
   setSequenceInputs(values) {
     if (!this._initialized || !this._sequenceIML) return;
 
+    // Freeze-as-pattern: skip entire pipeline, just keep looping frozen pattern
+    if (this._freezeManager.isFrozen && this._freezeManager.freezeMode === 'pattern') {
+      return;
+    }
+
     // Dirty-check: skip re-evaluation if inputs AND config haven't changed
     const EPS = 1e-5;
     const inputsSame = Math.abs(values[0] - this._lastInputs[0]) < EPS &&
@@ -298,20 +359,49 @@ export class ShapeSeqEngine {
     // 2. Run MLP inference
     this._sequenceIML.process();
 
-    // 3. Get the 16 MLP outputs
+    // 3. Get the MLP outputs
     const mlpOutputs = this._sequenceIML.getOutputs();
 
-    // 4. Map 16 outputs to N primitive params
-    const paramCount = this._chain.totalParamCount;
-    const mappedParams = map(mlpOutputs, paramCount);
+    // 4–7. Run downstream pipeline
+    this._runPipeline(mlpOutputs);
+  }
 
-    // 5. Evaluate the chain to produce a pattern description
+  /**
+   * Shared downstream pipeline: param mapping -> chain -> projection -> clock.
+   *
+   * @private
+   * @param {Float32Array} mlpOutputs - raw MLP outputs (sequence slice)
+   */
+  _runPipeline(mlpOutputs) {
+    // Map N outputs to M primitive params
+    const paramCount = this._chain.totalParamCount;
+    let mappedParams = map(mlpOutputs, paramCount);
+
+    // Apply freeze: frozen params use captured values, live params get delta control
+    if (this._freezeManager.isFrozen) {
+      const schemas = this._chain.getParamSchemas();
+      mappedParams = DeltaController.computeEffective(
+        this._freezeManager.getFrozenParams(),
+        this._freezeManager.getLiveFlags(),
+        mappedParams,
+        schemas,
+        0.3 // deltaScale — could be configurable later
+      );
+    }
+
+    // Track last evaluated params for freeze snapshot
+    this._lastEvaluatedParams = mappedParams;
+
+    // Evaluate the chain to produce a pattern description
     const patternDesc = this._chain.evaluate(mappedParams, this._stepCount, this._masterSeed);
 
-    // 6. Apply projection transforms
+    // Apply projection transforms
     const projectedPattern = applyProjection(this._projectionChain, patternDesc);
 
-    // 7. Schedule the pattern on the clock
+    // Track last pattern for freeze-as-pattern snapshot
+    this._lastPattern = projectedPattern;
+
+    // Schedule the pattern on the clock
     this._clock.schedulePattern(projectedPattern);
   }
 
@@ -345,6 +435,7 @@ export class ShapeSeqEngine {
    */
   _handleLoopStart() {
     if (!this._initialized || !this._chain || !this._sequenceIML) return;
+    if (this._freezeManager.shouldSuppressReEval()) return;
     if (!this._chain.hasReEvalPrimitives()) return;
 
     // Bump the generation counter so the next setSequenceInputs() call
diff --git a/playground/js/shapeseq/tests/delta.test.js b/playground/js/shapeseq/tests/delta.test.js
new file mode 100644
index 0000000..b7c8734
--- /dev/null
+++ b/playground/js/shapeseq/tests/delta.test.js
@@ -0,0 +1,193 @@
+import { describe, it } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { DeltaController } from '../delta.js';
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+const EPS = 1e-6;
+
+function approxEqual(actual, expected, msg) {
+  assert.ok(
+    Math.abs(actual - expected) < EPS,
+    `${msg || ''} expected ${expected}, got ${actual}`
+  );
+}
+
+function makeSchemas(count, boundary = 'clamp', scaledRange) {
+  const schemas = [];
+  for (let i = 0; i < count; i++) {
+    const entry = { boundary };
+    if (boundary === 'scaled' && scaledRange !== undefined) {
+      entry.scaledRange = scaledRange;
+    }
+    schemas.push({ schema: entry });
+  }
+  return schemas;
+}
+
+// ---------------------------------------------------------------------------
+// Tests
+// ---------------------------------------------------------------------------
+
+describe('DeltaController.computeEffective', () => {
+
+  it('all frozen (liveFlags all 0): output === frozenParams', () => {
+    const frozen = new Float32Array([0.2, 0.5, 0.8]);
+    const live = new Uint8Array([0, 0, 0]);
+    const mlp = new Float32Array([0.0, 1.0, 0.5]);
+    const schemas = makeSchemas(3);
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas);
+
+    approxEqual(result[0], 0.2, 'param 0');
+    approxEqual(result[1], 0.5, 'param 1');
+    approxEqual(result[2], 0.8, 'param 2');
+  });
+
+  it('all live with clamp boundary: delta applied, result clamped to [0,1]', () => {
+    const frozen = new Float32Array([0.9, 0.1]);
+    const live = new Uint8Array([1, 1]);
+    const mlp = new Float32Array([1.0, 0.0]); // max positive, max negative
+    const schemas = makeSchemas(2, 'clamp');
+    const deltaScale = 0.3;
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas, deltaScale);
+
+    // param 0: 0.9 + (1.0 - 0.5)*2*0.3 = 0.9 + 0.3 = 1.2 -> clamped to 1.0
+    approxEqual(result[0], 1.0, 'param 0 clamped high');
+    // param 1: 0.1 + (0.0 - 0.5)*2*0.3 = 0.1 - 0.3 = -0.2 -> clamped to 0.0
+    approxEqual(result[1], 0.0, 'param 1 clamped low');
+  });
+
+  it('live with wrap boundary: values wrap around', () => {
+    const frozen = new Float32Array([0.9, 0.1]);
+    const live = new Uint8Array([1, 1]);
+    const mlp = new Float32Array([1.0, 0.0]);
+    const schemas = makeSchemas(2, 'wrap');
+    const deltaScale = 0.3;
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas, deltaScale);
+
+    // param 0: 0.9 + 0.3 = 1.2 -> wrap -> 0.2
+    approxEqual(result[0], 0.2, 'param 0 wrapped high');
+    // param 1: 0.1 - 0.3 = -0.2 -> wrap -> 0.8
+    approxEqual(result[1], 0.8, 'param 1 wrapped low');
+  });
+
+  it('live with scaled boundary: delta operates within scaledRange of frozen value', () => {
+    const frozen = new Float32Array([0.5]);
+    const live = new Uint8Array([1]);
+    // With scaled boundary, applyBoundary maps [0,1] input to [frozen-range, frozen+range]
+    // The raw value passed to applyBoundary is frozen + delta
+    // For scaled: lo = 0.5 - 0.3 = 0.2, hi = 0.5 + 0.3 = 0.8
+    // mapped = 0.2 + raw * 0.6
+    const mlp = new Float32Array([0.75]); // delta = (0.75 - 0.5)*2*0.3 = 0.15, raw = 0.65
+    const schemas = makeSchemas(1, 'scaled', 0.3);
+    const deltaScale = 0.3;
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas, deltaScale);
+
+    // raw = 0.5 + 0.15 = 0.65
+    // scaled: lo = 0.5 - 0.3 = 0.2, hi = 0.5 + 0.3 = 0.8
+    // mapped = 0.2 + 0.65 * (0.8 - 0.2) = 0.2 + 0.39 = 0.59
+    approxEqual(result[0], 0.59, 'scaled boundary');
+  });
+
+  it('MLP value 0.5 produces zero delta (frozen value unchanged)', () => {
+    const frozen = new Float32Array([0.3, 0.7]);
+    const live = new Uint8Array([1, 1]);
+    const mlp = new Float32Array([0.5, 0.5]);
+    const schemas = makeSchemas(2, 'clamp');
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas);
+
+    approxEqual(result[0], 0.3, 'param 0 unchanged');
+    approxEqual(result[1], 0.7, 'param 1 unchanged');
+  });
+
+  it('MLP value 0.0 produces max negative delta', () => {
+    const frozen = new Float32Array([0.5]);
+    const live = new Uint8Array([1]);
+    const mlp = new Float32Array([0.0]);
+    const schemas = makeSchemas(1, 'clamp');
+    const deltaScale = 0.3;
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas, deltaScale);
+
+    // 0.5 + (0.0 - 0.5)*2*0.3 = 0.5 - 0.3 = 0.2
+    approxEqual(result[0], 0.2, 'max negative delta');
+  });
+
+  it('MLP value 1.0 produces max positive delta', () => {
+    const frozen = new Float32Array([0.5]);
+    const live = new Uint8Array([1]);
+    const mlp = new Float32Array([1.0]);
+    const schemas = makeSchemas(1, 'clamp');
+    const deltaScale = 0.3;
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas, deltaScale);
+
+    // 0.5 + (1.0 - 0.5)*2*0.3 = 0.5 + 0.3 = 0.8
+    approxEqual(result[0], 0.8, 'max positive delta');
+  });
+
+  it('mixed frozen/live params', () => {
+    const frozen = new Float32Array([0.2, 0.5, 0.8, 0.4]);
+    const live = new Uint8Array([0, 1, 0, 1]);
+    const mlp = new Float32Array([0.9, 0.5, 0.1, 0.75]);
+    const schemas = makeSchemas(4, 'clamp');
+    const deltaScale = 0.3;
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas, deltaScale);
+
+    // param 0: frozen -> 0.2
+    approxEqual(result[0], 0.2, 'frozen param 0');
+    // param 1: live, mlp=0.5 -> zero delta -> 0.5
+    approxEqual(result[1], 0.5, 'live param 1 zero delta');
+    // param 2: frozen -> 0.8
+    approxEqual(result[2], 0.8, 'frozen param 2');
+    // param 3: live, 0.4 + (0.75 - 0.5)*2*0.3 = 0.4 + 0.15 = 0.55
+    approxEqual(result[3], 0.55, 'live param 3');
+  });
+
+  it('deltaScale affects magnitude', () => {
+    const frozen = new Float32Array([0.5]);
+    const live = new Uint8Array([1]);
+    const mlp = new Float32Array([1.0]); // max positive
+    const schemas = makeSchemas(1, 'clamp');
+
+    const r1 = DeltaController.computeEffective(frozen, live, mlp, schemas, 0.1);
+    const r2 = DeltaController.computeEffective(frozen, live, mlp, schemas, 0.5);
+
+    // scale 0.1: 0.5 + 0.1 = 0.6
+    approxEqual(r1[0], 0.6, 'small deltaScale');
+    // scale 0.5: 0.5 + 0.5 = 1.0
+    approxEqual(r2[0], 1.0, 'large deltaScale');
+  });
+
+  it('defaults deltaScale to 0.3 when not provided', () => {
+    const frozen = new Float32Array([0.5]);
+    const live = new Uint8Array([1]);
+    const mlp = new Float32Array([1.0]);
+    const schemas = makeSchemas(1, 'clamp');
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas);
+
+    // 0.5 + (1.0 - 0.5)*2*0.3 = 0.8
+    approxEqual(result[0], 0.8, 'default deltaScale 0.3');
+  });
+
+  it('falls back to clamp when schema is missing', () => {
+    const frozen = new Float32Array([0.9]);
+    const live = new Uint8Array([1]);
+    const mlp = new Float32Array([1.0]);
+    const schemas = []; // empty — no schema for this index
+
+    const result = DeltaController.computeEffective(frozen, live, mlp, schemas, 0.3);
+
+    // 0.9 + 0.3 = 1.2 -> clamped to 1.0
+    approxEqual(result[0], 1.0, 'missing schema falls back to clamp');
+  });
+});
diff --git a/playground/js/shapeseq/tests/freeze-pattern.test.js b/playground/js/shapeseq/tests/freeze-pattern.test.js
new file mode 100644
index 0000000..96c66e6
--- /dev/null
+++ b/playground/js/shapeseq/tests/freeze-pattern.test.js
@@ -0,0 +1,217 @@
+import { describe, it } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { FreezeManager } from '../freeze.js';
+import { Chain } from '../chain.js';
+import { EuclideanRhythm, ProbabilityGate, PitchWalker } from '../primitives.js';
+import { createPattern, clonePattern } from '../pattern.js';
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+function makeTestChain() {
+  const chain = new Chain();
+  chain.addPrimitive(new EuclideanRhythm());
+  chain.addPrimitive(new ProbabilityGate());
+  chain.addPrimitive(new PitchWalker());
+  return { chain, paramCount: chain.totalParamCount };
+}
+
+function makeParams(count) {
+  const params = new Float32Array(count);
+  for (let i = 0; i < count; i++) {
+    params[i] = (i + 1) / (count + 1);
+  }
+  return params;
+}
+
+/**
+ * Create a pattern with some non-default step data for testing.
+ */
+function makeTestPattern(stepCount) {
+  const pattern = createPattern(stepCount);
+  for (let i = 0; i < stepCount; i++) {
+    pattern.steps[i].trigger = i % 2 === 0;
+    pattern.steps[i].pitch = (i + 1) / (stepCount + 1);
+    pattern.steps[i].velocity = 0.5 + (i * 0.05);
+    pattern.steps[i].accent = i === 0;
+    pattern.steps[i].midiNote = 60 + i;
+  }
+  pattern.metadata.source = 'test';
+  return pattern;
+}
+
+// ---------------------------------------------------------------------------
+// freeze with mode='pattern' captures the pattern
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager freeze-as-pattern', () => {
+  it('freeze with mode=pattern captures the pattern', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(8);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+
+    assert.strictEqual(fm.isFrozen, true);
+    const frozen = fm.getFrozenPattern();
+    assert.ok(frozen !== null, 'frozen pattern should not be null');
+    assert.strictEqual(frozen.stepCount, 8);
+    assert.strictEqual(frozen.steps.length, 8);
+  });
+
+  it('getFrozenPattern returns the captured pattern', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(4);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+
+    const frozen = fm.getFrozenPattern();
+    // Verify step data matches
+    for (let i = 0; i < 4; i++) {
+      assert.strictEqual(frozen.steps[i].trigger, pattern.steps[i].trigger,
+        'step ' + i + ' trigger should match');
+      assert.strictEqual(frozen.steps[i].pitch, pattern.steps[i].pitch,
+        'step ' + i + ' pitch should match');
+      assert.strictEqual(frozen.steps[i].velocity, pattern.steps[i].velocity,
+        'step ' + i + ' velocity should match');
+      assert.strictEqual(frozen.steps[i].midiNote, pattern.steps[i].midiNote,
+        'step ' + i + ' midiNote should match');
+    }
+    assert.strictEqual(frozen.metadata.source, 'test');
+  });
+
+  it('freezeMode is pattern', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(8);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+
+    assert.strictEqual(fm.freezeMode, 'pattern');
+  });
+
+  it('getEffectiveParams returns null in pattern mode', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(8);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+
+    const result = fm.getEffectiveParams(new Float32Array(8));
+    assert.strictEqual(result, null);
+  });
+
+  it('shouldSuppressReEval returns true in pattern mode', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(8);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+
+    assert.strictEqual(fm.shouldSuppressReEval(), true);
+  });
+
+  it('unfreeze clears frozen pattern', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(8);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+    assert.strictEqual(fm.isFrozen, true);
+    assert.ok(fm.getFrozenPattern() !== null);
+
+    fm.unfreeze();
+
+    assert.strictEqual(fm.isFrozen, false);
+    assert.strictEqual(fm.freezeMode, null);
+    assert.strictEqual(fm.getFrozenPattern(), null);
+    assert.strictEqual(fm.getFrozenParams(), null);
+    assert.strictEqual(fm.getFrozenSeeds(), null);
+    assert.strictEqual(fm.getFrozenStates(), null);
+    assert.strictEqual(fm.getMasterSeed(), null);
+  });
+
+  it('freeze with mode=algorithm still works (backward compat)', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const params = makeParams(paramCount);
+
+    fm.freeze(chain, params, 42, 'algorithm');
+
+    assert.strictEqual(fm.isFrozen, true);
+    assert.strictEqual(fm.freezeMode, 'algorithm');
+    assert.ok(fm.getFrozenParams() instanceof Float32Array);
+    assert.strictEqual(fm.getFrozenParams().length, paramCount);
+    assert.ok(Array.isArray(fm.getFrozenSeeds()));
+    assert.ok(Array.isArray(fm.getFrozenStates()));
+    assert.strictEqual(fm.getMasterSeed(), 42);
+    assert.strictEqual(fm.getFrozenPattern(), null);
+  });
+
+  it('freeze with default mode is algorithm (backward compat)', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const params = makeParams(paramCount);
+
+    // Call without mode argument — should default to 'algorithm'
+    fm.freeze(chain, params, 42);
+
+    assert.strictEqual(fm.freezeMode, 'algorithm');
+    assert.ok(fm.getFrozenParams() instanceof Float32Array);
+    assert.strictEqual(fm.getFrozenPattern(), null);
+  });
+
+  it('frozen pattern is a deep clone (mutating original does not affect frozen)', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(4);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+
+    // Mutate the original
+    pattern.steps[0].trigger = !pattern.steps[0].trigger;
+    pattern.steps[0].pitch = 0.999;
+    pattern.steps[0].midiNote = 127;
+    pattern.metadata.source = 'mutated';
+
+    // Frozen should be unaffected
+    const frozen = fm.getFrozenPattern();
+    assert.strictEqual(frozen.steps[0].trigger, true, 'frozen trigger should be unchanged');
+    assert.notStrictEqual(frozen.steps[0].pitch, 0.999, 'frozen pitch should be unchanged');
+    assert.strictEqual(frozen.steps[0].midiNote, 60, 'frozen midiNote should be unchanged');
+    assert.strictEqual(frozen.metadata.source, 'test', 'frozen metadata should be unchanged');
+  });
+
+  it('pattern mode throws if currentPattern is null', () => {
+    const fm = new FreezeManager();
+    assert.throws(
+      () => fm.freeze(null, null, null, 'pattern', null),
+      /pattern mode requires a currentPattern/
+    );
+  });
+
+  it('freezeMode is null when not frozen', () => {
+    const fm = new FreezeManager();
+    assert.strictEqual(fm.freezeMode, null);
+  });
+
+  it('getFrozenPattern returns null when not frozen', () => {
+    const fm = new FreezeManager();
+    assert.strictEqual(fm.getFrozenPattern(), null);
+  });
+
+  it('getFrozenPattern returns null in algorithm mode', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42, 'algorithm');
+    assert.strictEqual(fm.getFrozenPattern(), null);
+  });
+
+  it('algorithm-mode state is null in pattern mode', () => {
+    const fm = new FreezeManager();
+    const pattern = makeTestPattern(8);
+
+    fm.freeze(null, null, null, 'pattern', pattern);
+
+    assert.strictEqual(fm.getFrozenParams(), null);
+    assert.strictEqual(fm.getFrozenSeeds(), null);
+    assert.strictEqual(fm.getFrozenStates(), null);
+    assert.strictEqual(fm.getLiveFlags(), null);
+    assert.strictEqual(fm.getMasterSeed(), null);
+  });
+});
diff --git a/playground/js/shapeseq/tests/freeze.test.js b/playground/js/shapeseq/tests/freeze.test.js
new file mode 100644
index 0000000..a3a490d
--- /dev/null
+++ b/playground/js/shapeseq/tests/freeze.test.js
@@ -0,0 +1,293 @@
+import { describe, it } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { FreezeManager } from '../freeze.js';
+import { Chain } from '../chain.js';
+import { EuclideanRhythm, ProbabilityGate, PitchWalker } from '../primitives.js';
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+/**
+ * Create a chain with known primitives for testing.
+ * Returns { chain, paramCount }.
+ */
+function makeTestChain() {
+  const chain = new Chain();
+  chain.addPrimitive(new EuclideanRhythm());
+  chain.addPrimitive(new ProbabilityGate());
+  chain.addPrimitive(new PitchWalker());
+  return { chain, paramCount: chain.totalParamCount };
+}
+
+/**
+ * Create a Float32Array of params with sequential values for easy identification.
+ */
+function makeParams(count) {
+  const params = new Float32Array(count);
+  for (let i = 0; i < count; i++) {
+    params[i] = (i + 1) / (count + 1); // spread across (0, 1)
+  }
+  return params;
+}
+
+// ---------------------------------------------------------------------------
+// freeze() captures params, seeds, states correctly
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager.freeze()', () => {
+  it('captures params as a Float32Array copy', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const params = makeParams(paramCount);
+    const masterSeed = 42;
+
+    fm.freeze(chain, params, masterSeed);
+
+    const frozen = fm.getFrozenParams();
+    assert.ok(frozen instanceof Float32Array, 'should be Float32Array');
+    assert.strictEqual(frozen.length, paramCount);
+
+    // Values should match
+    for (let i = 0; i < paramCount; i++) {
+      assert.strictEqual(frozen[i], params[i], 'param ' + i + ' should match');
+    }
+
+    // Should be a copy, not the same reference
+    assert.notStrictEqual(frozen, params);
+  });
+
+  it('captures per-primitive seeds', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const params = makeParams(paramCount);
+
+    // Set known seeds
+    const prims = chain.getPrimitives();
+    prims[0].setSeed(100);
+    prims[1].setSeed(200);
+    prims[2].setSeed(300);
+
+    fm.freeze(chain, params, 42);
+
+    const seeds = fm.getFrozenSeeds();
+    assert.ok(Array.isArray(seeds));
+    assert.strictEqual(seeds.length, 3);
+    assert.strictEqual(seeds[0], 100);
+    assert.strictEqual(seeds[1], 200);
+    assert.strictEqual(seeds[2], 300);
+  });
+
+  it('captures per-primitive states', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const params = makeParams(paramCount);
+
+    fm.freeze(chain, params, 42);
+
+    const states = fm.getFrozenStates();
+    assert.ok(Array.isArray(states));
+    assert.strictEqual(states.length, 3);
+  });
+
+  it('captures master seed', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const params = makeParams(paramCount);
+
+    fm.freeze(chain, params, 12345);
+    assert.strictEqual(fm.getMasterSeed(), 12345);
+  });
+
+  it('initializes all live flags to 0 (frozen)', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const params = makeParams(paramCount);
+
+    fm.freeze(chain, params, 42);
+
+    const flags = fm.getLiveFlags();
+    assert.ok(flags instanceof Uint8Array);
+    assert.strictEqual(flags.length, paramCount);
+    for (let i = 0; i < paramCount; i++) {
+      assert.strictEqual(flags[i], 0, 'param ' + i + ' should be frozen');
+    }
+  });
+});
+
+// ---------------------------------------------------------------------------
+// isFrozen
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager.isFrozen', () => {
+  it('returns false initially', () => {
+    const fm = new FreezeManager();
+    assert.strictEqual(fm.isFrozen, false);
+  });
+
+  it('returns true after freeze()', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+    assert.strictEqual(fm.isFrozen, true);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// toggleParam
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager.toggleParam()', () => {
+  it('flips a param from frozen to live and back', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+
+    assert.strictEqual(fm.getLiveFlags()[0], 0);
+
+    fm.toggleParam(0);
+    assert.strictEqual(fm.getLiveFlags()[0], 1);
+
+    fm.toggleParam(0);
+    assert.strictEqual(fm.getLiveFlags()[0], 0);
+  });
+
+  it('only affects the targeted param', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+
+    fm.toggleParam(2);
+    const flags = fm.getLiveFlags();
+    assert.strictEqual(flags[0], 0);
+    assert.strictEqual(flags[1], 0);
+    assert.strictEqual(flags[2], 1);
+    assert.strictEqual(flags[3], 0);
+  });
+
+  it('throws when not frozen', () => {
+    const fm = new FreezeManager();
+    assert.throws(() => fm.toggleParam(0), /cannot toggle when not frozen/);
+  });
+
+  it('throws on out-of-range index', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+    assert.throws(() => fm.toggleParam(paramCount + 10), /out of range/);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// setParamLive
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager.setParamLive()', () => {
+  it('explicitly sets live state', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+
+    fm.setParamLive(1, true);
+    assert.strictEqual(fm.getLiveFlags()[1], 1);
+
+    fm.setParamLive(1, false);
+    assert.strictEqual(fm.getLiveFlags()[1], 0);
+  });
+
+  it('throws when not frozen', () => {
+    const fm = new FreezeManager();
+    assert.throws(() => fm.setParamLive(0, true), /cannot set when not frozen/);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// getEffectiveParams
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager.getEffectiveParams()', () => {
+  it('returns frozen values for frozen params, current for live', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    const frozenParams = makeParams(paramCount);
+
+    fm.freeze(chain, frozenParams, 42);
+
+    // Make param 2 live
+    fm.toggleParam(2);
+
+    // Create different "current" ML params
+    const currentParams = new Float32Array(paramCount);
+    for (let i = 0; i < paramCount; i++) {
+      currentParams[i] = 0.99;
+    }
+
+    const effective = fm.getEffectiveParams(currentParams);
+    assert.ok(effective instanceof Float32Array);
+    assert.strictEqual(effective.length, paramCount);
+
+    // Param 0: frozen -> uses frozen value
+    assert.strictEqual(effective[0], frozenParams[0]);
+    // Param 1: frozen -> uses frozen value
+    assert.strictEqual(effective[1], frozenParams[1]);
+    // Param 2: live -> uses current ML value (Float32 precision)
+    assert.ok(Math.abs(effective[2] - 0.99) < 1e-5, 'live param should use current ML value');
+    // Param 3: frozen -> uses frozen value
+    assert.strictEqual(effective[3], frozenParams[3]);
+  });
+
+  it('returns null when not frozen', () => {
+    const fm = new FreezeManager();
+    const result = fm.getEffectiveParams(new Float32Array(4));
+    assert.strictEqual(result, null);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// unfreeze
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager.unfreeze()', () => {
+  it('clears all captured state', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+
+    assert.strictEqual(fm.isFrozen, true);
+
+    fm.unfreeze();
+
+    assert.strictEqual(fm.isFrozen, false);
+    assert.strictEqual(fm.getFrozenParams(), null);
+    assert.strictEqual(fm.getLiveFlags(), null);
+    assert.strictEqual(fm.getFrozenSeeds(), null);
+    assert.strictEqual(fm.getFrozenStates(), null);
+    assert.strictEqual(fm.getMasterSeed(), null);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// shouldSuppressReEval
+// ---------------------------------------------------------------------------
+
+describe('FreezeManager.shouldSuppressReEval()', () => {
+  it('returns true when frozen', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+    assert.strictEqual(fm.shouldSuppressReEval(), true);
+  });
+
+  it('returns false when not frozen', () => {
+    const fm = new FreezeManager();
+    assert.strictEqual(fm.shouldSuppressReEval(), false);
+  });
+
+  it('returns false after unfreeze', () => {
+    const fm = new FreezeManager();
+    const { chain, paramCount } = makeTestChain();
+    fm.freeze(chain, makeParams(paramCount), 42);
+    fm.unfreeze();
+    assert.strictEqual(fm.shouldSuppressReEval(), false);
+  });
+});