fix(compact): make config knobs explicit and flag two review smells

Address @tianyicui's minor-revision review on PR #110:

- Make every BasicCompactConfig knob required except `auto` (defaults
  true): there is no data yet to justify default thresholds/budgets, so
  a consumer states each value explicitly. Drop the DEFAULTS export and
  the constructor's `= {}` default; example cordis.yml, the compaction
  e2e, the README, and every test construction site now pass a complete
  config (tests route through a `cfg()` helper).
- Add a TODO on estimateContentTokens: char/4 is coarse; replace with a
  real tokenizer or post-response usage feedback in a follow-up.
- Add a TODO on the agent/pre-step `fullSystemPrompt` param flagging it
  as a smell on a generic per-step seam (compaction is its sole
  consumer); a `//` line comment so it stays out of the generated catalog.

packages/compact/compact-basic/src/index.ts

@@ -39,7 +39,7 @@ import type { BasicCompactConfig, ResolvedConfig } from './types.ts'
 import { resolveConfig } from './types.ts'
 
 export type { BasicCompactConfig, ResolvedConfig } from './types.ts'
-export { DEFAULTS, resolveConfig } from './types.ts'
+export { resolveConfig } from './types.ts'
 
 /** Per-block structural overhead for JSON framing / type tag. */
 const BLOCK_OVERHEAD = 4
@@ -155,10 +155,10 @@ function finishError(finish: FinishReason): Error | undefined {
 export class BasicCompactService extends CompactService {
   static inject = ['llm']
 
-  /** Resolved configuration (defaults applied). */
+  /** Resolved configuration (`auto` defaulted). */
   readonly config: ResolvedConfig
 
-  constructor(ctx: Context, config: BasicCompactConfig = {}) {
+  constructor(ctx: Context, config: BasicCompactConfig) {
     super(ctx)
     this.config = resolveConfig(config)
 
@@ -207,6 +207,9 @@ export class BasicCompactService extends CompactService {
 
   // ---- Token estimation (overridable hooks) ----
 
+  // TODO: char/4 is a coarse heuristic. Replace with an exact count — a real
+  // tokenizer, or the provider's post-response `usage` (input tokens) fed back
+  // as a correction — so threshold decisions match the model's actual budget.
   /**
    * Estimate the token count of content blocks — char/4 with per-block
    * overhead. Override in a subclass to plug in a real tokenizer.

packages/compact/compact-basic/src/types.ts

@@ -9,40 +9,34 @@
  * @module @deepseek-ai/dsh-compact-basic/types
  */
 
-/** Backend configuration — all optional with sensible defaults. */
+/**
+ * Backend configuration. Every knob is REQUIRED except `auto`: there is no
+ * concrete data yet to justify default thresholds/budgets, so a consumer must
+ * state each value explicitly rather than inherit a guessed default. `auto`
+ * alone defaults to `true` (auto-compaction is the intended posture).
+ */
 export interface BasicCompactConfig {
-  /** Context window size in tokens (default 128000). */
-  contextWindow?: number
-  /** Compact when estimated token usage exceeds this fraction of context window (default 0.8). */
-  thresholdRatio?: number
-  /** Number of tokens of recent context to retain during compaction (default 20480). */
-  retainTokens?: number
-  /** Model to use for summarization (default '' — uses the agent's model). */
-  summarizationModel?: string
-  /** Provider generation cap for the summarization call (default 8192). */
-  maxTokens?: number
-  /** Extra compaction attempts when the first compacted surface is still over threshold (default 1). */
-  compactionRetries?: number
+  /** Context window size in tokens. */
+  contextWindow: number
+  /** Compact when estimated token usage exceeds this fraction of context window. */
+  thresholdRatio: number
+  /** Number of tokens of recent context to retain during compaction. */
+  retainTokens: number
+  /** Model to use for summarization (`''` — uses the agent's model). */
+  summarizationModel: string
+  /** Provider generation cap for the summarization call. */
+  maxTokens: number
+  /** Extra compaction attempts when the first compacted surface is still over threshold. */
+  compactionRetries: number
   /** Enable automatic compaction on the `agent/pre-step` seam (default true). */
   auto?: boolean
 }
 
-/** Resolved config with all defaults applied. */
+/** Resolved config with `auto` defaulted. */
 export type ResolvedConfig = Required<BasicCompactConfig>
 
-/** Default configuration values. */
-export const DEFAULTS: ResolvedConfig = {
-  contextWindow: 128000,
-  thresholdRatio: 0.8,
-  retainTokens: 20480,
-  summarizationModel: '',
-  maxTokens: 8192,
-  compactionRetries: 1,
-  auto: true,
-}
-
 /**
- * Apply defaults to a partial config and reject nonsensical numeric knobs.
+ * Default `auto` when unset and reject nonsensical numeric knobs.
  *
  * Convergence is not a static config invariant: provider generation caps can be
  * spent on hidden or surfaced reasoning tokens, and the model may emit a summary
@@ -52,7 +46,7 @@ export const DEFAULTS: ResolvedConfig = {
  * throwing if the surface still exceeds the threshold.
  */
 export function resolveConfig(config: BasicCompactConfig): ResolvedConfig {
-  const resolved = { ...DEFAULTS, ...config }
+  const resolved: ResolvedConfig = { auto: true, ...config }
 
   assertPositiveInteger('contextWindow', resolved.contextWindow)
   assertRatio('thresholdRatio', resolved.thresholdRatio)