diff --git a/src/hooks/context-window-monitor.ts b/src/hooks/context-window-monitor.ts
index ce8d756..d2a7af2 100644
--- a/src/hooks/context-window-monitor.ts
+++ b/src/hooks/context-window-monitor.ts
@@ -1,7 +1,11 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 
 const ANTHROPIC_DISPLAY_LIMIT = 1_000_000
-const ANTHROPIC_ACTUAL_LIMIT = 200_000
+const ANTHROPIC_ACTUAL_LIMIT =
+  process.env.ANTHROPIC_1M_CONTEXT === "true" ||
+  process.env.VERTEX_ANTHROPIC_1M_CONTEXT === "true"
+    ? 1_000_000
+    : 200_000
 const CONTEXT_WARNING_THRESHOLD = 0.70
 
 const CONTEXT_REMINDER = `[SYSTEM REMINDER - 1M Context Window]
diff --git a/src/hooks/preemptive-compaction/index.ts b/src/hooks/preemptive-compaction/index.ts
index ecf2c22..91890f4 100644
--- a/src/hooks/preemptive-compaction/index.ts
+++ b/src/hooks/preemptive-compaction/index.ts
@@ -48,7 +48,11 @@ interface MessageWrapper {
 }
 
 const CLAUDE_MODEL_PATTERN = /claude-(opus|sonnet|haiku)/i
-const CLAUDE_DEFAULT_CONTEXT_LIMIT = 200_000
+const CLAUDE_DEFAULT_CONTEXT_LIMIT =
+  process.env.ANTHROPIC_1M_CONTEXT === "true" ||
+  process.env.VERTEX_ANTHROPIC_1M_CONTEXT === "true"
+    ? 1_000_000
+    : 200_000
 
 function isSupportedModel(modelID: string): boolean {
   return CLAUDE_MODEL_PATTERN.test(modelID)
diff --git a/src/shared/dynamic-truncator.ts b/src/shared/dynamic-truncator.ts
index 84a4e6e..33481ea 100644
--- a/src/shared/dynamic-truncator.ts
+++ b/src/shared/dynamic-truncator.ts
@@ -1,6 +1,10 @@
 import type { PluginInput } from "@opencode-ai/plugin";
 
-const ANTHROPIC_ACTUAL_LIMIT = 200_000;
+const ANTHROPIC_ACTUAL_LIMIT =
+  process.env.ANTHROPIC_1M_CONTEXT === "true" ||
+  process.env.VERTEX_ANTHROPIC_1M_CONTEXT === "true"
+    ? 1_000_000
+    : 200_000;
 const CHARS_PER_TOKEN_ESTIMATE = 4;
 const DEFAULT_TARGET_MAX_TOKENS = 50_000;