fix(context-pruning): cover image-only tool-result pruning

CHANGELOG.md

@@ -93,6 +93,7 @@ Docs: https://docs.openclaw.ai
 - Gateway/session reset auth: split conversation `/new` and `/reset` handling away from the admin-only `sessions.reset` control-plane RPC so write-scoped gateway callers can no longer reach the privileged reset path through `agent`. Thanks @tdjackey for reporting.
 - Telegram/final preview delivery followup: keep ambiguous missing-`message_id` finals only when a preview was already visible, while first-preview/no-id cases still fall back so Telegram users do not lose the final reply. (#41932) thanks @hougangdev.
 - Agents/Azure OpenAI Responses: include the `azure-openai` provider in the Responses API store override so Azure OpenAI multi-turn cron jobs and embedded agent runs no longer fail with HTTP 400 "store is set to false". (#42934, fixes #42800) Thanks @ademczuk.
+- Agents/context pruning: prune image-only tool results during soft-trim, align context-pruning coverage with the new tool-result contract, and extend historical image cleanup to the same screenshot-heavy session path. (#42212) Thanks @MoerAI.
 
 ## 2026.3.8
 

src/agents/pi-extensions/context-pruning.test.ts

@@ -358,21 +358,26 @@ describe("context-pruning", () => {
     expect(toolText(findToolResult(next, "t2"))).toContain("y".repeat(20_000));
   });
 
-  it("skips tool results that contain images (no soft trim, no hard clear)", () => {
+  it("replaces image blocks in tool results during soft trim", () => {
     const messages: AgentMessage[] = [
       makeUser("u1"),
       makeImageToolResult({
         toolCallId: "t1",
         toolName: "exec",
-        text: "x".repeat(20_000),
+        text: "visible tool text",
       }),
     ];
 
-    const next = pruneWithAggressiveDefaults(messages);
+    const next = pruneWithAggressiveDefaults(messages, {
+      hardClearRatio: 10.0,
+      hardClear: { enabled: false, placeholder: "[cleared]" },
+      softTrim: { maxChars: 200, headChars: 100, tailChars: 100 },
+    });
 
     const tool = findToolResult(next, "t1");
-    expect(tool.content.some((b) => b.type === "image")).toBe(true);
-    expect(toolText(tool)).toContain("x".repeat(20_000));
+    expect(tool.content.some((b) => b.type === "image")).toBe(false);
+    expect(toolText(tool)).toContain("[image removed during context pruning]");
+    expect(toolText(tool)).toContain("visible tool text");
   });
 
   it("soft-trims across block boundaries", () => {

src/agents/pi-extensions/context-pruning/pruner.test.ts

@@ -165,6 +165,41 @@ describe("pruneContextMessages", () => {
     );
   });
 
+  it("replaces image-only tool results with placeholders even when text trimming is not needed", () => {
+    const messages: AgentMessage[] = [
+      makeUser("summarize this"),
+      makeToolResult([{ type: "image", data: "img", mimeType: "image/png" }]),
+      makeAssistant([{ type: "text", text: "done" }]),
+    ];
+
+    const result = pruneContextMessages({
+      messages,
+      settings: {
+        ...DEFAULT_CONTEXT_PRUNING_SETTINGS,
+        keepLastAssistants: 1,
+        softTrimRatio: 0,
+        hardClearRatio: 10,
+        hardClear: {
+          ...DEFAULT_CONTEXT_PRUNING_SETTINGS.hardClear,
+          enabled: false,
+        },
+        softTrim: {
+          maxChars: 5_000,
+          headChars: 2_000,
+          tailChars: 2_000,
+        },
+      },
+      ctx: CONTEXT_WINDOW_1M,
+      isToolPrunable: () => true,
+      contextWindowTokensOverride: 1,
+    });
+
+    const toolResult = result[1] as Extract<AgentMessage, { role: "toolResult" }>;
+    expect(toolResult.content).toEqual([
+      { type: "text", text: "[image removed during context pruning]" },
+    ]);
+  });
+
   it("hard-clears image-containing tool results once ratios require clearing", () => {
     const messages: AgentMessage[] = [
       makeUser("summarize this"),

src/agents/pi-extensions/context-pruning/pruner.ts

@@ -205,18 +205,25 @@ function softTrimToolResultMessage(params: {
   settings: EffectiveContextPruningSettings;
 }): ToolResultMessage | null {
   const { msg, settings } = params;
-  const parts = hasImageBlocks(msg.content)
+  const hasImages = hasImageBlocks(msg.content);
+  const parts = hasImages
     ? collectPrunableToolResultSegments(msg.content)
     : collectTextSegments(msg.content);
   const rawLen = estimateJoinedTextLength(parts);
   if (rawLen <= settings.softTrim.maxChars) {
-    return null;
+    if (!hasImages) {
+      return null;
+    }
+    return { ...msg, content: [asText(parts.join("\n"))] };
   }
 
   const headChars = Math.max(0, settings.softTrim.headChars);
   const tailChars = Math.max(0, settings.softTrim.tailChars);
   if (headChars + tailChars >= rawLen) {
-    return null;
+    if (!hasImages) {
+      return null;
+    }
+    return { ...msg, content: [asText(parts.join("\n"))] };
   }
 
   const head = takeHeadFromJoinedText(parts, headChars);