fix: Claude model compatibility for Antigravity proxy

- Add textPartModels config: configurable model patterns that use text
  parts instead of synthetic tool parts for context injection, preventing
  Claude VALIDATED mode tool_use/tool_result pairing errors (default:
  ['antigravity-claude'])

- Fix pruneFullTool: replace edit/write tool part content with
  placeholders instead of removing parts entirely, preserving tool
  pairing integrity required by Claude's VALIDATED mode

- Fix distill/prune Invalid IDs: rebuild toolIdList after
  syncToolCache in executePruneOperation to prevent stale/empty
  ID list after session reinitialization

Author: anilcancakir

README.md

@@ -110,6 +110,11 @@ DCP uses its own config file:
 >             "contextLimit": 100000,
 >             // Additional tools to protect from pruning
 >             "protectedTools": [],
+>             // Model name patterns that should use text parts instead of tool parts
+>             // for DCP context injection. Prevents 400 errors with providers that use
+>             // strict tool call/result pairing (e.g., Antigravity Claude models).
+>             // Uses case-insensitive substring matching against the model ID.
+>             "textPartModels": ["antigravity-claude"],
 >         },
 >         // Distills key findings into preserved knowledge before removing raw content
 >         "distill": {

lib/config.ts

@@ -28,6 +28,7 @@ export interface ToolSettings {
     nudgeFrequency: number
     protectedTools: string[]
     contextLimit: number | `${number}%`
+    textPartModels: string[]
 }
 
 export interface Tools {
@@ -107,6 +108,7 @@ export const VALID_CONFIG_KEYS = new Set([
     "tools.settings.nudgeFrequency",
     "tools.settings.protectedTools",
     "tools.settings.contextLimit",
+    "tools.settings.textPartModels",
     "tools.distill",
     "tools.distill.permission",
     "tools.distill.showDistillation",
@@ -303,6 +305,16 @@ function validateConfigTypes(config: Record<string, any>): ValidationError[] {
                     })
                 }
             }
+            if (
+                tools.settings.textPartModels !== undefined &&
+                !Array.isArray(tools.settings.textPartModels)
+            ) {
+                errors.push({
+                    key: "tools.settings.textPartModels",
+                    expected: "string[]",
+                    actual: typeof tools.settings.textPartModels,
+                })
+            }
         }
         if (tools.distill) {
             if (tools.distill.permission !== undefined) {
@@ -505,6 +517,7 @@ const defaultConfig: PluginConfig = {
             nudgeFrequency: 10,
             protectedTools: [...DEFAULT_PROTECTED_TOOLS],
             contextLimit: 100000,
+            textPartModels: ["antigravity-claude"],
         },
         distill: {
             permission: "allow",
@@ -684,6 +697,7 @@ function mergeTools(
                 ]),
             ],
             contextLimit: override.settings?.contextLimit ?? base.settings.contextLimit,
+            textPartModels: override.settings?.textPartModels ?? base.settings.textPartModels,
         },
         distill: {
             permission: override.distill?.permission ?? base.distill.permission,
@@ -724,6 +738,7 @@ function deepCloneConfig(config: PluginConfig): PluginConfig {
             settings: {
                 ...config.tools.settings,
                 protectedTools: [...config.tools.settings.protectedTools],
+                textPartModels: [...config.tools.settings.textPartModels],
             },
             distill: { ...config.tools.distill },
             compress: { ...config.tools.compress },

lib/messages/inject.ts

@@ -253,13 +253,19 @@ export const insertPruneToolContext = (
 
     // When following a user message, append a synthetic text part since models like Claude
     // expect assistant turns to start with reasoning parts which cannot be easily faked.
+    // For models listed in textPartModels, always use text parts to avoid tool pairing issues.
     // For all other cases, append a synthetic tool part to the last message which works
     // across all models without disrupting their behavior.
-    if (lastNonIgnoredMessage.info.role === "user") {
+    const modelID = userInfo.model?.modelID || ""
+    const lowerModelID = modelID.toLowerCase()
+    const useTextPart = config.tools.settings.textPartModels.some(
+        (pattern) => lowerModelID.includes(pattern.toLowerCase()),
+    )
+
+    if (lastNonIgnoredMessage.info.role === "user" || useTextPart) {
         const textPart = createSyntheticTextPart(lastNonIgnoredMessage, combinedContent)
         lastNonIgnoredMessage.parts.push(textPart)
     } else {
-        const modelID = userInfo.model?.modelID || ""
         const toolPart = createSyntheticToolPart(lastNonIgnoredMessage, combinedContent, modelID)
         lastNonIgnoredMessage.parts.push(toolPart)
     }

lib/messages/prune.ts

@@ -24,15 +24,14 @@ export const prune = (
 }
 
 const pruneFullTool = (state: SessionState, logger: Logger, messages: WithParts[]): void => {
-    const messagesToRemove: string[] = []
+    let prunedCount = 0
 
     for (const msg of messages) {
         if (isMessageCompacted(state, msg)) {
             continue
         }
 
         const parts = Array.isArray(msg.parts) ? msg.parts : []
-        const partsToRemove: string[] = []
 
         for (const part of parts) {
             if (part.type !== "tool") {
@@ -45,26 +44,27 @@ const pruneFullTool = (state: SessionState, logger: Logger, messages: WithParts[
                 continue
             }
 
-            partsToRemove.push(part.callID)
-        }
-
-        if (partsToRemove.length === 0) {
-            continue
-        }
-
-        msg.parts = parts.filter(
-            (part) => part.type !== "tool" || !partsToRemove.includes(part.callID),
-        )
+            // Instead of removing the tool part entirely (which breaks Claude's
+            // tool_use/tool_result pairing in VALIDATED mode), replace the content
+            // with a placeholder. This preserves the tool part structure so the
+            // model-level conversion still generates matched functionCall/functionResponse pairs.
+            if (part.state?.input && typeof part.state.input === "object") {
+                for (const key of Object.keys(part.state.input)) {
+                    if (typeof part.state.input[key] === "string") {
+                        part.state.input[key] = PRUNED_TOOL_ERROR_INPUT_REPLACEMENT
+                    }
+                }
+            }
+            if (part.state?.status === "completed") {
+                part.state.output = PRUNED_TOOL_OUTPUT_REPLACEMENT
+            }
 
-        if (msg.parts.length === 0) {
-            messagesToRemove.push(msg.info.id)
+            prunedCount++
         }
     }
 
-    if (messagesToRemove.length > 0) {
-        const result = messages.filter((msg) => !messagesToRemove.includes(msg.info.id))
-        messages.length = 0
-        messages.push(...result)
+    if (prunedCount > 0) {
+        logger.info(`Pruned content for ${prunedCount} edit/write tool parts`)
     }
 }
 

lib/tools/prune-shared.ts

@@ -9,6 +9,7 @@ import { ensureSessionInitialized } from "../state"
 import { saveSessionState } from "../state/persistence"
 import { calculateTokensSaved, getCurrentParams } from "../strategies/utils"
 import { getFilePathsFromParameters, isProtected } from "../protected-file-patterns"
+import { buildToolIdList } from "../messages/utils"
 
 // Shared logic for executing prune operations.
 export async function executePruneOperation(
@@ -47,10 +48,11 @@ export async function executePruneOperation(
     })
     const messages: WithParts[] = messagesResponse.data || messagesResponse
 
-    await ensureSessionInitialized(ctx.client, state, sessionId, logger, messages)
-    await syncToolCache(state, config, logger, messages)
+     await ensureSessionInitialized(ctx.client, state, sessionId, logger, messages)
+     await syncToolCache(state, config, logger, messages)
+     buildToolIdList(state, messages, logger)
 
-    const currentParams = getCurrentParams(state, messages, logger)
+     const currentParams = getCurrentParams(state, messages, logger)
 
     const toolIdList = state.toolIdList