feat: protect file operations from pruning

README.md

@@ -75,6 +75,9 @@ DCP uses its own config file:
         "enabled": false,
         "turns": 4,
     },
+    // Protect file operations from pruning via glob patterns
+    // Patterns match tool parameters.filePath (e.g. read/write/edit)
+    "protectedFilePatterns": [],
     // LLM-driven context pruning tools
     "tools": {
         // Shared settings for all prune tools

lib/config.ts

@@ -50,6 +50,7 @@ export interface PluginConfig {
     debug: boolean
     pruneNotification: "off" | "minimal" | "detailed"
     turnProtection: TurnProtection
+    protectedFilePatterns: string[]
     tools: Tools
     strategies: {
         deduplication: Deduplication
@@ -79,6 +80,7 @@ export const VALID_CONFIG_KEYS = new Set([
     "turnProtection",
     "turnProtection.enabled",
     "turnProtection.turns",
+    "protectedFilePatterns",
     "tools",
     "tools.settings",
     "tools.settings.nudgeEnabled",
@@ -151,6 +153,22 @@ function validateConfigTypes(config: Record<string, any>): ValidationError[] {
         }
     }
 
+    if (config.protectedFilePatterns !== undefined) {
+        if (!Array.isArray(config.protectedFilePatterns)) {
+            errors.push({
+                key: "protectedFilePatterns",
+                expected: "string[]",
+                actual: typeof config.protectedFilePatterns,
+            })
+        } else if (!config.protectedFilePatterns.every((v) => typeof v === "string")) {
+            errors.push({
+                key: "protectedFilePatterns",
+                expected: "string[]",
+                actual: "non-string entries",
+            })
+        }
+    }
+
     // Top-level turnProtection validator
     if (config.turnProtection) {
         if (
@@ -371,6 +389,7 @@ const defaultConfig: PluginConfig = {
         enabled: false,
         turns: 4,
     },
+    protectedFilePatterns: [],
     tools: {
         settings: {
             nudgeEnabled: true,
@@ -480,6 +499,9 @@ function createDefaultConfig(): void {
     "enabled": false,
     "turns": 4
   },
+  // Protect file operations from pruning via glob patterns
+  // Patterns match tool parameters.filePath (e.g. read/write/edit)
+  "protectedFilePatterns": [],
   // LLM-driven context pruning tools
   "tools": {
     // Shared settings for all prune tools
@@ -615,6 +637,7 @@ function deepCloneConfig(config: PluginConfig): PluginConfig {
     return {
         ...config,
         turnProtection: { ...config.turnProtection },
+        protectedFilePatterns: [...config.protectedFilePatterns],
         tools: {
             settings: {
                 ...config.tools.settings,
@@ -670,6 +693,12 @@ export function getConfig(ctx: PluginInput): PluginConfig {
                     enabled: result.data.turnProtection?.enabled ?? config.turnProtection.enabled,
                     turns: result.data.turnProtection?.turns ?? config.turnProtection.turns,
                 },
+                protectedFilePatterns: [
+                    ...new Set([
+                        ...config.protectedFilePatterns,
+                        ...(result.data.protectedFilePatterns ?? []),
+                    ]),
+                ],
                 tools: mergeTools(config.tools, result.data.tools as any),
                 strategies: mergeStrategies(config.strategies, result.data.strategies as any),
             }
@@ -706,6 +735,12 @@ export function getConfig(ctx: PluginInput): PluginConfig {
                     enabled: result.data.turnProtection?.enabled ?? config.turnProtection.enabled,
                     turns: result.data.turnProtection?.turns ?? config.turnProtection.turns,
                 },
+                protectedFilePatterns: [
+                    ...new Set([
+                        ...config.protectedFilePatterns,
+                        ...(result.data.protectedFilePatterns ?? []),
+                    ]),
+                ],
                 tools: mergeTools(config.tools, result.data.tools as any),
                 strategies: mergeStrategies(config.strategies, result.data.strategies as any),
             }
@@ -739,6 +774,12 @@ export function getConfig(ctx: PluginInput): PluginConfig {
                     enabled: result.data.turnProtection?.enabled ?? config.turnProtection.enabled,
                     turns: result.data.turnProtection?.turns ?? config.turnProtection.turns,
                 },
+                protectedFilePatterns: [
+                    ...new Set([
+                        ...config.protectedFilePatterns,
+                        ...(result.data.protectedFilePatterns ?? []),
+                    ]),
+                ],
                 tools: mergeTools(config.tools, result.data.tools as any),
                 strategies: mergeStrategies(config.strategies, result.data.strategies as any),
             }

lib/messages/inject.ts

@@ -4,6 +4,7 @@ import type { PluginConfig } from "../config"
 import type { UserMessage } from "@opencode-ai/sdk/v2"
 import { loadPrompt } from "../prompts"
 import { extractParameterKey, buildToolIdList, createSyntheticUserMessage } from "./utils"
+import { getFilePathFromParameters, isProtectedFilePath } from "../protected-file-patterns"
 import { getLastUserMessage } from "../shared-utils"
 
 const getNudgeString = (config: PluginConfig): string => {
@@ -62,6 +63,11 @@ const buildPrunableToolsList = (
             return
         }
 
+        const filePath = getFilePathFromParameters(toolParameterEntry.parameters)
+        if (isProtectedFilePath(filePath, config.protectedFilePatterns)) {
+            return
+        }
+
         const numericId = toolIdList.indexOf(toolCallId)
         if (numericId === -1) {
             logger.warn(`Tool in cache but not in toolIdList - possible stale entry`, {

lib/protected-file-patterns.ts

@@ -0,0 +1,82 @@
+function normalizePath(input: string): string {
+    return input.replaceAll("\\\\", "/")
+}
+
+function escapeRegExpChar(ch: string): string {
+    return /[\\.^$+{}()|\[\]]/.test(ch) ? `\\${ch}` : ch
+}
+
+/**
+ * Basic glob matching with support for `**`, `*`, and `?`.
+ *
+ * Notes:
+ * - Matching is performed against the full (normalized) string.
+ * - `*` and `?` do not match `/`.
+ * - `**` matches across `/`.
+ */
+export function matchesGlob(inputPath: string, pattern: string): boolean {
+    if (!pattern) return false
+
+    const input = normalizePath(inputPath)
+    const pat = normalizePath(pattern)
+
+    let regex = "^"
+
+    for (let i = 0; i < pat.length; i++) {
+        const ch = pat[i]
+
+        if (ch === "*") {
+            const next = pat[i + 1]
+            if (next === "*") {
+                const after = pat[i + 2]
+                if (after === "/") {
+                    // **/  (zero or more directories)
+                    regex += "(?:.*/)?"
+                    i += 2
+                    continue
+                }
+
+                // **
+                regex += ".*"
+                i++
+                continue
+            }
+
+            // *
+            regex += "[^/]*"
+            continue
+        }
+
+        if (ch === "?") {
+            regex += "[^/]"
+            continue
+        }
+
+        if (ch === "/") {
+            regex += "/"
+            continue
+        }
+
+        regex += escapeRegExpChar(ch)
+    }
+
+    regex += "$"
+
+    return new RegExp(regex).test(input)
+}
+
+export function getFilePathFromParameters(parameters: unknown): string | undefined {
+    if (typeof parameters !== "object" || parameters === null) {
+        return undefined
+    }
+
+    const filePath = (parameters as Record<string, unknown>).filePath
+    return typeof filePath === "string" && filePath.length > 0 ? filePath : undefined
+}
+
+export function isProtectedFilePath(filePath: string | undefined, patterns: string[]): boolean {
+    if (!filePath) return false
+    if (!patterns || patterns.length === 0) return false
+
+    return patterns.some((pattern) => matchesGlob(filePath, pattern))
+}

lib/strategies/deduplication.ts

@@ -2,6 +2,7 @@ import { PluginConfig } from "../config"
 import { Logger } from "../logger"
 import type { SessionState, WithParts } from "../state"
 import { buildToolIdList } from "../messages/utils"
+import { getFilePathFromParameters, isProtectedFilePath } from "../protected-file-patterns"
 import { calculateTokensSaved } from "./utils"
 
 /**
@@ -50,6 +51,11 @@ export const deduplicate = (
             continue
         }
 
+        const filePath = getFilePathFromParameters(metadata.parameters)
+        if (isProtectedFilePath(filePath, config.protectedFilePatterns)) {
+            continue
+        }
+
         const signature = createToolSignature(metadata.tool, metadata.parameters)
         if (!signatureMap.has(signature)) {
             signatureMap.set(signature, [])

lib/strategies/purge-errors.ts

@@ -2,6 +2,7 @@ import { PluginConfig } from "../config"
 import { Logger } from "../logger"
 import type { SessionState, WithParts } from "../state"
 import { buildToolIdList } from "../messages/utils"
+import { getFilePathFromParameters, isProtectedFilePath } from "../protected-file-patterns"
 import { calculateTokensSaved } from "./utils"
 
 /**
@@ -52,6 +53,11 @@ export const purgeErrors = (
             continue
         }
 
+        const filePath = getFilePathFromParameters(metadata.parameters)
+        if (isProtectedFilePath(filePath, config.protectedFilePatterns)) {
+            continue
+        }
+
         // Only process error tools
         if (metadata.status !== "error") {
             continue

lib/strategies/supersede-writes.ts

@@ -2,6 +2,7 @@ import { PluginConfig } from "../config"
 import { Logger } from "../logger"
 import type { SessionState, WithParts } from "../state"
 import { buildToolIdList } from "../messages/utils"
+import { getFilePathFromParameters, isProtectedFilePath } from "../protected-file-patterns"
 import { calculateTokensSaved } from "./utils"
 
 /**
@@ -50,11 +51,15 @@ export const supersedeWrites = (
             continue
         }
 
-        const filePath = metadata.parameters?.filePath
+        const filePath = getFilePathFromParameters(metadata.parameters)
         if (!filePath) {
             continue
         }
 
+        if (isProtectedFilePath(filePath, config.protectedFilePatterns)) {
+            continue
+        }
+
         if (metadata.tool === "write") {
             if (!writesByFile.has(filePath)) {
                 writesByFile.set(filePath, [])

lib/strategies/tools.ts

@@ -9,6 +9,7 @@ import { saveSessionState } from "../state/persistence"
 import type { Logger } from "../logger"
 import { loadPrompt } from "../prompts"
 import { calculateTokensSaved, getCurrentParams } from "./utils"
+import { getFilePathFromParameters, isProtectedFilePath } from "../protected-file-patterns"
 
 const DISCARD_TOOL_DESCRIPTION = loadPrompt("discard-tool-spec")
 const EXTRACT_TOOL_DESCRIPTION = loadPrompt("extract-tool-spec")
@@ -88,6 +89,17 @@ async function executePruneOperation(
             })
             return "Invalid IDs provided. Only use numeric IDs from the <prunable-tools> list."
         }
+
+        const filePath = getFilePathFromParameters(metadata.parameters)
+        if (isProtectedFilePath(filePath, config.protectedFilePatterns)) {
+            logger.debug("Rejecting prune request - protected file path", {
+                index,
+                id,
+                tool: metadata.tool,
+                filePath,
+            })
+            return "Invalid IDs provided. Only use numeric IDs from the <prunable-tools> list."
+        }
     }
 
     const pruneToolIds: string[] = numericToolIds.map((index) => toolIdList[index])