Count user image tokens in context estimates

closes #4983

packages/agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed context token estimates to count user image attachments consistently with tool result images ([#4983](https://github.com/earendil-works/pi/issues/4983)).
+
 ## [0.75.5] - 2026-05-23
 
 ## [0.75.4] - 2026-05-20

packages/agent/src/harness/compaction/compaction.ts

@@ -198,22 +198,33 @@ export function shouldCompact(contextTokens: number, contextWindow: number, sett
 	return contextTokens > contextWindow - settings.reserveTokens;
 }
 
+const ESTIMATED_IMAGE_CHARS = 4800;
+
+function estimateTextAndImageContentChars(content: string | Array<{ type: string; text?: string }>): number {
+	if (typeof content === "string") {
+		return content.length;
+	}
+
+	let chars = 0;
+	for (const block of content) {
+		if (block.type === "text" && block.text) {
+			chars += block.text.length;
+		} else if (block.type === "image") {
+			chars += ESTIMATED_IMAGE_CHARS;
+		}
+	}
+	return chars;
+}
+
 /** Estimate token count for one message using a conservative character heuristic. */
 export function estimateTokens(message: AgentMessage): number {
 	let chars = 0;
 
 	switch (message.role) {
 		case "user": {
-			const content = (message as { content: string | Array<{ type: string; text?: string }> }).content;
-			if (typeof content === "string") {
-				chars = content.length;
-			} else if (Array.isArray(content)) {
-				for (const block of content) {
-					if (block.type === "text" && block.text) {
-						chars += block.text.length;
-					}
-				}
-			}
+			chars = estimateTextAndImageContentChars(
+				(message as { content: string | Array<{ type: string; text?: string }> }).content,
+			);
 			return Math.ceil(chars / 4);
 		}
 		case "assistant": {
@@ -231,18 +242,7 @@ export function estimateTokens(message: AgentMessage): number {
 		}
 		case "custom":
 		case "toolResult": {
-			if (typeof message.content === "string") {
-				chars = message.content.length;
-			} else {
-				for (const block of message.content) {
-					if (block.type === "text" && block.text) {
-						chars += block.text.length;
-					}
-					if (block.type === "image") {
-						chars += 4800;
-					}
-				}
-			}
+			chars = estimateTextAndImageContentChars(message.content);
 			return Math.ceil(chars / 4);
 		}
 		case "bashExecution": {

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- Fixed context token estimates to count user image attachments consistently with tool result images ([#4983](https://github.com/earendil-works/pi/issues/4983)).
 - Fixed `RpcClient` to reject pending requests and consume stdin pipe errors when the child process exits unexpectedly ([#4764](https://github.com/earendil-works/pi/issues/4764)).
 - Fixed managed npm extension updates to avoid package managers installing or resolving pi host packages as peer dependencies ([#4907](https://github.com/earendil-works/pi/issues/4907)).
 - Fixed RPC mode raw stdout writes to retry transient backpressure errors and flush queued protocol output during shutdown ([#4897](https://github.com/earendil-works/pi/issues/4897)).

packages/coding-agent/src/core/compaction/compaction.ts

@@ -225,6 +225,24 @@ export function shouldCompact(contextTokens: number, contextWindow: number, sett
 // Cut point detection
 // ============================================================================
 
+const ESTIMATED_IMAGE_CHARS = 4800;
+
+function estimateTextAndImageContentChars(content: string | Array<{ type: string; text?: string }>): number {
+	if (typeof content === "string") {
+		return content.length;
+	}
+
+	let chars = 0;
+	for (const block of content) {
+		if (block.type === "text" && block.text) {
+			chars += block.text.length;
+		} else if (block.type === "image") {
+			chars += ESTIMATED_IMAGE_CHARS;
+		}
+	}
+	return chars;
+}
+
 /**
  * Estimate token count for a message using chars/4 heuristic.
  * This is conservative (overestimates tokens).
@@ -234,16 +252,9 @@ export function estimateTokens(message: AgentMessage): number {
 
 	switch (message.role) {
 		case "user": {
-			const content = (message as { content: string | Array<{ type: string; text?: string }> }).content;
-			if (typeof content === "string") {
-				chars = content.length;
-			} else if (Array.isArray(content)) {
-				for (const block of content) {
-					if (block.type === "text" && block.text) {
-						chars += block.text.length;
-					}
-				}
-			}
+			chars = estimateTextAndImageContentChars(
+				(message as { content: string | Array<{ type: string; text?: string }> }).content,
+			);
 			return Math.ceil(chars / 4);
 		}
 		case "assistant": {
@@ -261,18 +272,7 @@ export function estimateTokens(message: AgentMessage): number {
 		}
 		case "custom":
 		case "toolResult": {
-			if (typeof message.content === "string") {
-				chars = message.content.length;
-			} else {
-				for (const block of message.content) {
-					if (block.type === "text" && block.text) {
-						chars += block.text.length;
-					}
-					if (block.type === "image") {
-						chars += 4800; // Estimate images as 4000 chars, or 1200 tokens
-					}
-				}
-			}
+			chars = estimateTextAndImageContentChars(message.content);
 			return Math.ceil(chars / 4);
 		}
 		case "bashExecution": {