diff --git a/dcp.schema.json b/dcp.schema.json
index e25f09b1..fc2e6e78 100644
--- a/dcp.schema.json
+++ b/dcp.schema.json
@@ -121,6 +121,11 @@
                                     "pattern": "^\\d+(?:\\.\\d+)?%$"
                                 }
                             ]
+                        },
+                        "contextLimitFallback": {
+                            "description": "Fallback token limit when model context window is unknown and percentage-based contextLimit is used (defaults to 100000)",
+                            "type": "number",
+                            "default": 100000
                         }
                     }
                 },
diff --git a/lib/config.ts b/lib/config.ts
index 1a60307f..b1a14eff 100644
--- a/lib/config.ts
+++ b/lib/config.ts
@@ -28,6 +28,7 @@ export interface ToolSettings {
     nudgeFrequency: number
     protectedTools: string[]
     contextLimit: number | `${number}%`
+    contextLimitFallback?: number
 }
 
 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.contextLimitFallback",
     "tools.distill",
     "tools.distill.permission",
     "tools.distill.showDistillation",
@@ -303,6 +305,15 @@ function validateConfigTypes(config: Record<string, any>): ValidationError[] {
                     })
                 }
             }
+            if (tools.settings.contextLimitFallback !== undefined) {
+                if (typeof tools.settings.contextLimitFallback !== "number") {
+                    errors.push({
+                        key: "tools.settings.contextLimitFallback",
+                        expected: "number",
+                        actual: typeof tools.settings.contextLimitFallback,
+                    })
+                }
+            }
         }
         if (tools.distill) {
             if (tools.distill.permission !== undefined) {
@@ -684,6 +695,8 @@ function mergeTools(
                 ]),
             ],
             contextLimit: override.settings?.contextLimit ?? base.settings.contextLimit,
+            contextLimitFallback:
+                override.settings?.contextLimitFallback ?? base.settings.contextLimitFallback,
         },
         distill: {
             permission: override.distill?.permission ?? base.distill.permission,
diff --git a/lib/messages/inject.ts b/lib/messages/inject.ts
index 3f0c60b1..92978816 100644
--- a/lib/messages/inject.ts
+++ b/lib/messages/inject.ts
@@ -68,11 +68,14 @@ Context management was just performed. Do NOT use the ${toolName} again. A fresh
 
 const resolveContextLimit = (config: PluginConfig, state: SessionState): number | undefined => {
     const configLimit = config.tools.settings.contextLimit
+    const contextLimitFallback = config.tools.settings.contextLimitFallback
+    const DEFAULT_FALLBACK = 100_000 // 100k tokens hardcoded fallback
 
     if (typeof configLimit === "string") {
         if (configLimit.endsWith("%")) {
             if (state.modelContextLimit === undefined) {
-                return undefined
+                const fallback = contextLimitFallback ?? DEFAULT_FALLBACK
+                return parsePercentageString(configLimit, fallback)
             }
             return parsePercentageString(configLimit, state.modelContextLimit)
         }