diff --git a/packages/opencode/src/config/config.ts b/packages/opencode/src/config/config.ts
index 261731b8b0a4..27176e8a6003 100644
--- a/packages/opencode/src/config/config.ts
+++ b/packages/opencode/src/config/config.ts
@@ -177,8 +177,18 @@ export namespace Config {
     }
 
     // Inline config content overrides all non-managed config sources.
+    // Route through load() to enable {env:} and {file:} token substitution.
+    // Use a path within Instance.directory so relative {file:} paths resolve correctly.
+    // The filename "OPENCODE_CONFIG_CONTENT" appears in error messages for clarity.
     if (Flag.OPENCODE_CONFIG_CONTENT) {
-      result = merge(result, JSON.parse(Flag.OPENCODE_CONFIG_CONTENT))
+      // Parse and ensure $schema is present to prevent Bun.write() from creating a file
+      const parsed = JSON.parse(Flag.OPENCODE_CONFIG_CONTENT)
+      if (!parsed.$schema) parsed.$schema = "https://opencode.ai/config.json"
+
+      result = merge(
+        result,
+        await load(JSON.stringify(parsed), path.join(Instance.directory, "OPENCODE_CONFIG_CONTENT")),
+      )
       log.debug("loaded custom config from OPENCODE_CONFIG_CONTENT")
     }
 
diff --git a/packages/opencode/src/flag/flag.ts b/packages/opencode/src/flag/flag.ts
index 0049d716d095..4f4520f4386e 100644
--- a/packages/opencode/src/flag/flag.ts
+++ b/packages/opencode/src/flag/flag.ts
@@ -8,7 +8,7 @@ export namespace Flag {
   export const OPENCODE_GIT_BASH_PATH = process.env["OPENCODE_GIT_BASH_PATH"]
   export const OPENCODE_CONFIG = process.env["OPENCODE_CONFIG"]
   export declare const OPENCODE_CONFIG_DIR: string | undefined
-  export const OPENCODE_CONFIG_CONTENT = process.env["OPENCODE_CONFIG_CONTENT"]
+  export declare const OPENCODE_CONFIG_CONTENT: string | undefined
   export const OPENCODE_DISABLE_AUTOUPDATE = truthy("OPENCODE_DISABLE_AUTOUPDATE")
   export const OPENCODE_DISABLE_PRUNE = truthy("OPENCODE_DISABLE_PRUNE")
   export const OPENCODE_DISABLE_TERMINAL_TITLE = truthy("OPENCODE_DISABLE_TERMINAL_TITLE")
@@ -95,3 +95,14 @@ Object.defineProperty(Flag, "OPENCODE_CLIENT", {
   enumerable: true,
   configurable: false,
 })
+
+// Dynamic getter for OPENCODE_CONFIG_CONTENT
+// This must be evaluated at access time, not module load time,
+// because external tooling may set this env var at runtime
+Object.defineProperty(Flag, "OPENCODE_CONFIG_CONTENT", {
+  get() {
+    return process.env["OPENCODE_CONFIG_CONTENT"]
+  },
+  enumerable: true,
+  configurable: false,
+})
diff --git a/packages/opencode/test/config/config.test.ts b/packages/opencode/test/config/config.test.ts
index 91b87f6498c4..331e05d5a7b3 100644
--- a/packages/opencode/test/config/config.test.ts
+++ b/packages/opencode/test/config/config.test.ts
@@ -1800,3 +1800,68 @@ describe("OPENCODE_DISABLE_PROJECT_CONFIG", () => {
     }
   })
 })
+
+// OPENCODE_CONFIG_CONTENT should support {env:} and {file:} token substitution
+// just like file-based config sources do.
+describe("OPENCODE_CONFIG_CONTENT token substitution", () => {
+  test("substitutes {env:} tokens in OPENCODE_CONFIG_CONTENT", async () => {
+    const originalEnv = process.env["OPENCODE_CONFIG_CONTENT"]
+    const originalTestVar = process.env["TEST_CONFIG_VAR"]
+    process.env["TEST_CONFIG_VAR"] = "test_api_key_12345"
+    process.env["OPENCODE_CONFIG_CONTENT"] = JSON.stringify({
+      $schema: "https://opencode.ai/config.json",
+      theme: "{env:TEST_CONFIG_VAR}",
+    })
+
+    try {
+      await using tmp = await tmpdir()
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const config = await Config.get()
+          expect(config.theme).toBe("test_api_key_12345")
+        },
+      })
+    } finally {
+      if (originalEnv !== undefined) {
+        process.env["OPENCODE_CONFIG_CONTENT"] = originalEnv
+      } else {
+        delete process.env["OPENCODE_CONFIG_CONTENT"]
+      }
+      if (originalTestVar !== undefined) {
+        process.env["TEST_CONFIG_VAR"] = originalTestVar
+      } else {
+        delete process.env["TEST_CONFIG_VAR"]
+      }
+    }
+  })
+
+  test("substitutes {file:} tokens in OPENCODE_CONFIG_CONTENT", async () => {
+    const originalEnv = process.env["OPENCODE_CONFIG_CONTENT"]
+
+    try {
+      await using tmp = await tmpdir({
+        init: async (dir) => {
+          await Bun.write(path.join(dir, "api_key.txt"), "secret_key_from_file")
+          process.env["OPENCODE_CONFIG_CONTENT"] = JSON.stringify({
+            $schema: "https://opencode.ai/config.json",
+            theme: "{file:./api_key.txt}",
+          })
+        },
+      })
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const config = await Config.get()
+          expect(config.theme).toBe("secret_key_from_file")
+        },
+      })
+    } finally {
+      if (originalEnv !== undefined) {
+        process.env["OPENCODE_CONFIG_CONTENT"] = originalEnv
+      } else {
+        delete process.env["OPENCODE_CONFIG_CONTENT"]
+      }
+    }
+  })
+})