diff --git a/src/core/BlockUnit.ts b/src/core/BlockUnit.ts
index 7b9df93..7985e09 100644
--- a/src/core/BlockUnit.ts
+++ b/src/core/BlockUnit.ts
@@ -10,6 +10,11 @@ function makeSeededRandom(seed: number): () => number {
   };
 }
 
+/**
+ * Block-level trial controller (browser counterpart of Python's BlockUnit).
+ *
+ * Generates a shuffled, weighted condition sequence for a block of trials.
+ */
 export class BlockUnit {
   block_id: string;
   block_idx: number;
@@ -37,6 +42,12 @@ export class BlockUnit {
     this.seed = Number(seeds[block_idx] ?? settings.overall_seed ?? 2025);
   }
 
+  /**
+   * Generate a shuffled condition sequence for this block.
+   *
+   * Uses weighted sampling to distribute remainder trials, then Fisher-Yates shuffle.
+   * Pass `func` to delegate generation to a custom function instead.
+   */
   generate_conditions(options: {
     weights?: number[] | null;
     func?: (...args: any[]) => string[];
diff --git a/src/core/StimBank.ts b/src/core/StimBank.ts
index 60371a4..ca48880 100644
--- a/src/core/StimBank.ts
+++ b/src/core/StimBank.ts
@@ -16,6 +16,12 @@ function formatTemplate(template: string, vars: Record<string, unknown>): string
   });
 }
 
+/**
+ * Immutable stimulus registry (browser counterpart of Python's StimBank).
+ *
+ * Holds {@link StimSpec} definitions keyed by name.  Returns {@link StimRef}
+ * handles from {@link get} that are resolved to concrete specs at runtime.
+ */
 export class StimBank {
   private readonly config: Record<string, StimSpec>;
 
@@ -23,6 +29,7 @@ export class StimBank {
     this.config = config;
   }
 
+  /** Return a {@link StimRef} handle for a named stimulus. Throws if not found. */
   get(key: string): StimRef {
     if (!this.config[key]) {
       throw new Error(`Stimulus '${key}' not found.`);
@@ -30,6 +37,7 @@ export class StimBank {
     return { kind: "stim_ref", key };
   }
 
+  /** Resolve a ref or key to a deep-cloned {@link StimSpec}. Throws if not found. */
   resolve(ref: StimRef | string): StimSpec {
     const key = typeof ref === "string" ? ref : ref.key;
     const spec = this.config[key];
@@ -59,6 +67,10 @@ export class StimBank {
     return this.format(name, vars);
   }
 
+  /**
+   * Register `<key>_voice` entries for the given text stimuli.
+   * Uses pre-recorded audio assets when available, falls back to Web Speech API.
+   */
   convert_to_voice(
     keys: string[] | string,
     options: {
@@ -140,6 +152,10 @@ export class StimBank {
   }
 }
 
+/**
+ * Resolve a potentially late-bound stimulus input to a concrete {@link StimSpec}.
+ * Handles {@link Resolver} functions, {@link StateRef} lookups, string keys, and {@link StimRef} handles.
+ */
 export function resolveStimInput(
   input: Resolvable<StimRef | StimSpec | null>,
   snapshot: TrialSnapshot,
diff --git a/src/core/StimUnit.ts b/src/core/StimUnit.ts
index 44e71b5..5924d9c 100644
--- a/src/core/StimUnit.ts
+++ b/src/core/StimUnit.ts
@@ -11,6 +11,12 @@ import { TrialBuilder } from "./TrialBuilder";
 
 type StageStatePatch = Record<string, Resolvable<unknown>>;
 
+/**
+ * Builder for a single trial stage (browser counterpart of Python's StimUnit).
+ *
+ * Chain `.addStim()` → `.show()` / `.captureResponse()` / `.waitAndContinue()` →
+ * optionally `.set_state()` / `.to_dict()` → then call `.compile()` to produce a {@link CompiledStage}.
+ */
 export class StimUnit {
   readonly label: string;
   private readonly trial: TrialBuilder;
@@ -125,6 +131,7 @@ export class StimUnit {
     return this;
   }
 
+  /** Create a {@link StateRef} pointing to a key in this unit's runtime state. */
   ref<T = unknown>(key: string): StateRef<T> {
     return {
       kind: "state_ref",
diff --git a/src/core/SubInfo.ts b/src/core/SubInfo.ts
index f8a1cf5..9127eb1 100644
--- a/src/core/SubInfo.ts
+++ b/src/core/SubInfo.ts
@@ -11,6 +11,12 @@ function coerceFieldValue(field: SubInfoField, raw: string): string | number {
   return raw;
 }
 
+/**
+ * Participant information form (browser counterpart of Python's SubInfo).
+ *
+ * Renders an HTML form from field definitions and returns validated responses
+ * as a Promise resolved on submit.
+ */
 export class SubInfo {
   private readonly fields: SubInfoField[];
   private readonly mapping: Record<string, string>;
@@ -25,6 +31,7 @@ export class SubInfo {
     this.mapping = config.subinfo_mapping;
   }
 
+  /** Render the participant form into `container` and resolve with validated responses on submit. */
   collect(container: HTMLElement): Promise<Record<string, string | number>> {
     container.innerHTML = "";
     const wrapper = document.createElement("div");
diff --git a/src/core/TaskSettings.ts b/src/core/TaskSettings.ts
index f6a87af..4506b91 100644
--- a/src/core/TaskSettings.ts
+++ b/src/core/TaskSettings.ts
@@ -18,6 +18,12 @@ function makeSeededRandom(seed: number): () => number {
   };
 }
 
+/**
+ * Experiment configuration container (browser counterpart of Python's TaskSettings).
+ *
+ * Create via {@link TaskSettings.from_dict} with a parsed YAML config object.
+ * Holds window display, block/trial structure, seeding, and condition weights.
+ */
 export class TaskSettings {
   [key: string]: unknown;
 
@@ -38,6 +44,10 @@ export class TaskSettings {
   trial_per_block?: number;
   subject_id?: string;
 
+  /**
+   * Create a TaskSettings from a flat config dictionary.
+   * Validates `trial_per_block` consistency and initialises block seeds.
+   */
   static from_dict(config: SettingsLike): TaskSettings {
     const settings = new TaskSettings();
     Object.assign(settings, config);
@@ -71,6 +81,7 @@ export class TaskSettings {
       .map(() => Math.floor(rng() * 100000));
   }
 
+  /** Merge participant info into settings and derive per-subject seeds when `seed_mode` is `"same_within_sub"`. */
   add_subinfo(subinfo: Record<string, unknown>): void {
     Object.assign(this, subinfo);
     const subjectId = String(subinfo.subject_id ?? "");
@@ -88,6 +99,7 @@ export class TaskSettings {
     }
   }
 
+  /** Return validated weight vector aligned to `conditions`, or `null` for equal weighting. */
   resolve_condition_weights(): number[] | null {
     const raw = this.condition_weights;
     if (raw == null) {
diff --git a/src/core/TrialBuilder.ts b/src/core/TrialBuilder.ts
index 910a04e..4721db1 100644
--- a/src/core/TrialBuilder.ts
+++ b/src/core/TrialBuilder.ts
@@ -6,6 +6,11 @@ import type {
 } from "./types";
 import { StimUnit } from "./StimUnit";
 
+/**
+ * Builds a single {@link CompiledTrial} from an ordered sequence of {@link StimUnit} stages.
+ *
+ * Typical usage: `new TrialBuilder(meta).unit("fixation").addStim(...).show()...build()`
+ */
 export class TrialBuilder {
   readonly trial_id: number | string;
   readonly block_id: string | null;
@@ -27,6 +32,7 @@ export class TrialBuilder {
     this.condition = meta.condition;
   }
 
+  /** Create and register a new {@link StimUnit} stage with the given label. */
   unit(label: string): StimUnit {
     const unit = new StimUnit(label, this);
     this.units.push(unit);
@@ -42,6 +48,7 @@ export class TrialBuilder {
     this.trialState[key] = value;
   }
 
+  /** Compile all registered units into a {@link CompiledTrial}. */
   build(): CompiledTrial {
     return {
       trial_id: this.trial_id,
diff --git a/src/core/reducer.ts b/src/core/reducer.ts
index 27e468c..173b6a0 100644
--- a/src/core/reducer.ts
+++ b/src/core/reducer.ts
@@ -38,6 +38,10 @@ const RAW_FIELDS = new Set([
   "task_factors"
 ]);
 
+/**
+ * Resolve a {@link Resolvable} value: call it if it's a {@link Resolver},
+ * look up state if it's a {@link StateRef}, or return it as-is.
+ */
 export function resolveValue<T>(
   value: Resolvable<T>,
   snapshot: TrialSnapshot,
@@ -63,6 +67,12 @@ export function splitRawExtraData(unitState: Record<string, unknown>): Record<st
   return extra;
 }
 
+/**
+ * Records trial execution data and produces raw JSONL + reduced CSV output.
+ *
+ * Implements {@link RuntimeView} so that Resolvers and finalizers can query
+ * accumulated results during execution.
+ */
 export class ExecutionRecorder implements RuntimeView {
   private readonly trialStore = new Map<
     number | string,
diff --git a/src/core/types.ts b/src/core/types.ts
index 0ee8d27..1980935 100644
--- a/src/core/types.ts
+++ b/src/core/types.ts
@@ -1,10 +1,27 @@
+/**
+ * Core type definitions for the psyflow-web runtime.
+ *
+ * Key concepts:
+ * - **StimRef / StimSpec**: references to stimuli vs. their concrete specs
+ * - **StateRef / Resolver / Resolvable**: late-bound values resolved at runtime
+ * - **CompiledTrial / CompiledStage**: the fully-built trial structure executed by the runtime
+ * - **RawStageRow / ReducedTrialRow**: output data shapes (per-stage vs. per-trial)
+ *
+ * @module
+ */
+
 export type Primitive = string | number | boolean | null;
 
+/** Reference to a named stimulus in a {@link StimBank}. Resolved to a concrete {@link StimSpec} at runtime. */
 export interface StimRef {
   kind: "stim_ref";
   key: string;
 }
 
+/**
+ * Late-bound reference to a value stored in another StimUnit's state.
+ * Resolved during trial execution via {@link resolveValue}.
+ */
 export interface StateRef<T = unknown> {
   kind: "state_ref";
   unit_label: string;
@@ -12,6 +29,7 @@ export interface StateRef<T = unknown> {
   __type?: T;
 }
 
+/** Read-only snapshot of a trial's accumulated state, passed to Resolvers and finalizers. */
 export interface TrialSnapshot {
   trial_id: number | string;
   block_id: string | null;
@@ -21,12 +39,18 @@ export interface TrialSnapshot {
   trial_state: Record<string, unknown>;
 }
 
+/** Read-only view of the execution recorder, available to Resolvers and finalizers. */
 export interface RuntimeView {
   getReducedRows(): ReducedTrialRow[];
   sumReducedField(field: string): number;
 }
 
+/** A function that computes a value at runtime from the current trial state. */
 export type Resolver<T> = (snapshot: TrialSnapshot, runtime: RuntimeView) => T;
+/**
+ * A value that may be literal, a {@link StateRef} to another unit's state,
+ * or a {@link Resolver} function evaluated at runtime.
+ */
 export type Resolvable<T> = T | StateRef<T> | Resolver<T>;
 
 export type StimSpec =
@@ -117,6 +141,7 @@ export interface SpeechStimSpec extends BaseStimSpec {
   volume?: number;
 }
 
+/** Configuration for keyboard response capture during a trial stage. */
 export interface ResponseConfig {
   keys: string[];
   correct_keys?: string[];
@@ -138,6 +163,10 @@ export interface TrialContextSpec {
   stim_features?: Record<string, unknown> | null;
 }
 
+/**
+ * A single stage within a compiled trial (e.g. show stimulus, capture response, wait).
+ * Built by {@link StimUnit} and executed by the jsPsych plugin.
+ */
 export interface CompiledStage {
   unit_label: string;
   op: "show" | "capture_response" | "wait_and_continue";
@@ -163,6 +192,7 @@ export type TrialFinalizer = (
   helpers: TrialFinalizeHelpers
 ) => void;
 
+/** A fully compiled trial containing an ordered list of stages, built by {@link TrialBuilder}. */
 export interface CompiledTrial {
   trial_id: number | string;
   block_id: string | null;
@@ -173,6 +203,7 @@ export interface CompiledTrial {
   finalizers: TrialFinalizer[];
 }
 
+/** One row of raw JSONL output, recorded per-stage during execution. */
 export interface RawStageRow {
   trial_id: number | string;
   block_id: string | null;
@@ -202,8 +233,10 @@ export interface RawStageRow {
   extra_data: Record<string, unknown>;
 }
 
+/** One row of the reduced CSV output, recorded per-trial after finalization. */
 export type ReducedTrialRow = Record<string, unknown>;
 
+/** Structured result of parsing a psyflow YAML config file. */
 export interface ParsedConfig {
   raw: Record<string, unknown>;
   task_config: Record<string, unknown>;
diff --git a/src/index.ts b/src/index.ts
index 0bbfbc3..d8efe8d 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,3 +1,14 @@
+/**
+ * psyflow-web — browser runtime for auditable psychology experiments.
+ *
+ * **For task authors**: use {@link TaskSettings}, {@link BlockUnit}, {@link StimBank},
+ * {@link StimUnit}, {@link TrialBuilder}, and {@link SubInfo} to define trials.
+ *
+ * **For runtime consumers**: use {@link runPsyflowExperiment} or {@link mountTaskApp}.
+ *
+ * @module
+ */
+
 export { parsePsyflowConfig } from "./core/config";
 export { TaskSettings } from "./core/TaskSettings";
 export { BlockUnit } from "./core/BlockUnit";