fix(compression): address PR #1717 review feedback

- chatCore: remove shadowed const, update estimatedTokens after compression
- aggressive: fix techniquesUsed overwrite (.push), use estimateTokens() for savings
- toolResultCompressor: add estimateTokens helper, convert all saved: to token math
- progressiveAging: add estimateTokens helper, convert all saved += to token math

open-sse/handlers/chatCore.ts

@@ -1226,7 +1226,7 @@ export async function handleChatCore({
   const allMessages =
     body?.messages || body?.input || body?.contents || body?.request?.contents || [];
   if (body && Array.isArray(allMessages) && allMessages.length > 0) {
-    const estimatedTokens = estimateTokens(JSON.stringify(allMessages));
+    let estimatedTokens = estimateTokens(JSON.stringify(allMessages));
     let contextLimit = getTokenLimit(provider, effectiveModel);
 
     if (isCombo && comboName) {
@@ -1271,7 +1271,7 @@ export async function handleChatCore({
     // Prompt compression pipeline — Phase 1 (lite) + Phase 2 (standard/caveman)
     try {
       const compressionConfig = getCompressionSettings();
-      const estimatedTokens = estimateCompressionTokens(body);
+      estimatedTokens = estimateCompressionTokens(body);
       const mode = selectCompressionStrategy(compressionConfig, comboName ?? null, estimatedTokens);
       if (mode !== "off") {
         const compressionResult = applyCompression(body as Record<string, unknown>, mode, {
@@ -1281,6 +1281,7 @@ export async function handleChatCore({
         if (compressionResult.compressed && compressionResult.stats) {
           body = compressionResult.body as typeof body;
           const s = compressionResult.stats;
+          estimatedTokens = s.compressedTokens;
           log?.info?.(
             "COMPRESSION",
             `Prompt compression (${s.mode}): ${s.originalTokens} → ${s.compressedTokens} tokens (${s.savingsPercent}% savings, ${s.durationMs ?? 0}ms${

open-sse/services/compression/aggressive.ts

@@ -121,7 +121,7 @@ export function compressAggressive(
           preserveCode: true,
         });
         if (summary && summary.length < text.length) {
-          summarizerSavings += text.length - summary.length;
+          summarizerSavings += estimateTokens(text) - estimateTokens(summary);
           return setContent(msg, `[COMPRESSED:summary] ${summary}`);
         }
         return msg;
@@ -172,11 +172,11 @@ export function compressAggressive(
     }
   }
 
-  resultStats.techniquesUsed = [
+  resultStats.techniquesUsed.push(
     ...(toolResultSavings > 0 ? ["toolResult"] : []),
     ...(agingSavings > 0 ? ["aging"] : []),
-    ...(summarizerSavings > 0 ? ["summarizer"] : []),
-  ];
+    ...(summarizerSavings > 0 ? ["summarizer"] : [])
+  );
 
   resultStats.aggressive = {
     summarizerSavings,

open-sse/services/compression/progressiveAging.ts

@@ -5,6 +5,10 @@ import { cavemanCompress } from "./caveman.ts";
 
 const COMPRESSED_MARKER_RE = /^\[COMPRESSED:/;
 
+function estimateTokens(text: string): number {
+  return Math.ceil(text.length / 4);
+}
+
 interface ChatMessage {
   role: string;
   content?: string | Array<{ type: string; text?: string }>;
@@ -73,7 +77,7 @@ export function applyAging(
             ? compressed.body.messages[0].content
             : extractText(compressed.body.messages[0].content);
         const tagged = `[COMPRESSED:aging:light] ${newContent}`;
-        saved += text.length - tagged.length;
+        saved += estimateTokens(text) - estimateTokens(tagged);
         result.push(setContent(msg, tagged));
       } else {
         result.push(msg);
@@ -86,7 +90,7 @@ export function applyAging(
             ? compressed.body.messages[0].content
             : extractText(compressed.body.messages[0].content);
         const tagged = `[COMPRESSED:aging:moderate] ${newContent}`;
-        saved += text.length - tagged.length;
+        saved += estimateTokens(text) - estimateTokens(tagged);
         result.push(setContent(msg, tagged));
       } else {
         result.push(msg);
@@ -95,12 +99,12 @@ export function applyAging(
       if (msg.role === "assistant") {
         const summary = sum.summarize([msg]);
         const tagged = `[COMPRESSED:aging:fullSummary] ${summary}`;
-        saved += text.length - tagged.length;
+        saved += estimateTokens(text) - estimateTokens(tagged);
         result.push(setContent(msg, tagged));
       } else if (msg.role === "user") {
         const firstLine = text.split("\n")[0]?.slice(0, 120) ?? "";
         const tagged = `[COMPRESSED:aging:fullSummary] ${firstLine}`;
-        saved += text.length - tagged.length;
+        saved += estimateTokens(text) - estimateTokens(tagged);
         result.push(setContent(msg, tagged));
       } else {
         result.push(msg);

open-sse/services/compression/toolResultCompressor.ts

@@ -110,41 +110,63 @@ function compressErrorMessage(content: string): string | null {
   return result;
 }
 
-export function compressToolResult(content: string, opts: ToolStrategiesConfig): CompressionResult {
-  const originalLen = content.length;
+function estimateTokens(text: string): number {
+  return Math.ceil(text.length / 4);
+}
 
+export function compressToolResult(content: string, opts: ToolStrategiesConfig): CompressionResult {
   if (opts.fileContent) {
     const result = compressFileContent(content);
     if (result !== null) {
-      return { compressed: result, strategy: "fileContent", saved: originalLen - result.length };
+      return {
+        compressed: result,
+        strategy: "fileContent",
+        saved: estimateTokens(content) - estimateTokens(result),
+      };
     }
   }
 
   if (opts.grepSearch) {
     const result = compressGrepSearch(content);
     if (result !== null) {
-      return { compressed: result, strategy: "grepSearch", saved: originalLen - result.length };
+      return {
+        compressed: result,
+        strategy: "grepSearch",
+        saved: estimateTokens(content) - estimateTokens(result),
+      };
     }
   }
 
   if (opts.shellOutput) {
     const result = compressShellOutput(content);
     if (result !== null) {
-      return { compressed: result, strategy: "shellOutput", saved: originalLen - result.length };
+      return {
+        compressed: result,
+        strategy: "shellOutput",
+        saved: estimateTokens(content) - estimateTokens(result),
+      };
     }
   }
 
   if (opts.json) {
     const result = compressJson(content);
     if (result !== null) {
-      return { compressed: result, strategy: "json", saved: originalLen - result.length };
+      return {
+        compressed: result,
+        strategy: "json",
+        saved: estimateTokens(content) - estimateTokens(result),
+      };
     }
   }
 
   if (opts.errorMessage) {
     const result = compressErrorMessage(content);
     if (result !== null) {
-      return { compressed: result, strategy: "errorMessage", saved: originalLen - result.length };
+      return {
+        compressed: result,
+        strategy: "errorMessage",
+        saved: estimateTokens(content) - estimateTokens(result),
+      };
     }
   }