diff --git a/include/ghostty-vt.h b/include/ghostty-vt.h
index 591b095a2..b61069058 100644
--- a/include/ghostty-vt.h
+++ b/include/ghostty-vt.h
@@ -7,6 +7,127 @@
 extern "C" {
 #endif
 
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+//-------------------------------------------------------------------
+// Types
+
+typedef struct GhosttyOscParser GhosttyOscParser;
+
+typedef enum {
+    GHOSTTY_VT_SUCCESS = 0,
+    GHOSTTY_VT_OUT_OF_MEMORY = -1,
+} GhosttyVtResult;
+
+typedef struct {
+    /**
+     * Return a pointer to `len` bytes with specified `alignment`, or return
+     * `NULL` indicating the allocation failed.
+     *
+     * @param ctx The allocator context
+     * @param len Number of bytes to allocate
+     * @param alignment Required alignment for the allocation. Guaranteed to
+     *   be a power of two between 1 and 16 inclusive.
+     * @param ret_addr First return address of the allocation call stack (0 if not provided)
+     * @return Pointer to allocated memory, or NULL if allocation failed
+     */
+    void* (*alloc)(void *ctx, size_t len, uint8_t alignment, uintptr_t ret_addr);
+    
+    /**
+     * Attempt to expand or shrink memory in place.
+     *
+     * `memory_len` must equal the length requested from the most recent
+     * successful call to `alloc`, `resize`, or `remap`. `alignment` must
+     * equal the same value that was passed as the `alignment` parameter to
+     * the original `alloc` call.
+     *
+     * `new_len` must be greater than zero.
+     *
+     * @param ctx The allocator context
+     * @param memory Pointer to the memory block to resize
+     * @param memory_len Current size of the memory block
+     * @param alignment Alignment (must match original allocation)
+     * @param new_len New requested size
+     * @param ret_addr First return address of the allocation call stack (0 if not provided)
+     * @return true if resize was successful in-place, false if relocation would be required
+     */
+    bool (*resize)(void *ctx, void *memory, size_t memory_len, uint8_t alignment, size_t new_len, uintptr_t ret_addr);
+    
+    /**
+     * Attempt to expand or shrink memory, allowing relocation.
+     *
+     * `memory_len` must equal the length requested from the most recent
+     * successful call to `alloc`, `resize`, or `remap`. `alignment` must
+     * equal the same value that was passed as the `alignment` parameter to
+     * the original `alloc` call.
+     *
+     * A non-`NULL` return value indicates the resize was successful. The
+     * allocation may have same address, or may have been relocated. In either
+     * case, the allocation now has size of `new_len`. A `NULL` return value
+     * indicates that the resize would be equivalent to allocating new memory,
+     * copying the bytes from the old memory, and then freeing the old memory.
+     * In such case, it is more efficient for the caller to perform the copy.
+     *
+     * `new_len` must be greater than zero.
+     *
+     * @param ctx The allocator context
+     * @param memory Pointer to the memory block to remap
+     * @param memory_len Current size of the memory block
+     * @param alignment Alignment (must match original allocation)
+     * @param new_len New requested size
+     * @param ret_addr First return address of the allocation call stack (0 if not provided)
+     * @return Pointer to resized memory (may be relocated), or NULL if manual copy is needed
+     */
+    void* (*remap)(void *ctx, void *memory, size_t memory_len, uint8_t alignment, size_t new_len, uintptr_t ret_addr);
+    
+    /**
+     * Free and invalidate a region of memory.
+     *
+     * `memory_len` must equal the length requested from the most recent
+     * successful call to `alloc`, `resize`, or `remap`. `alignment` must
+     * equal the same value that was passed as the `alignment` parameter to
+     * the original `alloc` call.
+     *
+     * @param ctx The allocator context
+     * @param memory Pointer to the memory block to free
+     * @param memory_len Size of the memory block
+     * @param alignment Alignment (must match original allocation)
+     * @param ret_addr First return address of the allocation call stack (0 if not provided)
+     */
+    void (*free)(void *ctx, void *memory, size_t memory_len, uint8_t alignment, uintptr_t ret_addr);
+} GhosttyVtAllocatorVtable;
+
+/**
+ * Custom memory allocator.
+ *
+ * Usage example:
+ * @code
+ * GhosttyVtAllocator allocator = {
+ *     .vtable = &my_allocator_vtable,
+ *     .ctx = my_allocator_state
+ * };
+ * @endcode
+ */
+typedef struct {
+    /**
+     * Opaque context pointer passed to all vtable functions.
+     * This allows the allocator implementation to maintain state
+     * or reference external resources needed for memory management.
+     */
+    void *ctx;
+
+    /**
+     * Pointer to the allocator's vtable containing function pointers
+     * for memory operations (alloc, resize, remap, free).
+     */
+    const GhosttyVtAllocatorVtable *vtable;
+} GhosttyVtAllocator;
+
+//-------------------------------------------------------------------
+// Functions
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/lib/allocator.zig b/src/lib/allocator.zig
new file mode 100644
index 000000000..ef296f23d
--- /dev/null
+++ b/src/lib/allocator.zig
@@ -0,0 +1,317 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const testing = std.testing;
+
+/// Useful alias since they're required to create Zig allocators
+pub const ZigVTable = std.mem.Allocator.VTable;
+
+/// The VTable required by the C interface.
+pub const VTable = extern struct {
+    alloc: *const fn (*anyopaque, len: usize, alignment: u8, ret_addr: usize) callconv(.c) ?[*]u8,
+    resize: *const fn (*anyopaque, memory: [*]u8, memory_len: usize, alignment: u8, new_len: usize, ret_addr: usize) callconv(.c) bool,
+    remap: *const fn (*anyopaque, memory: [*]u8, memory_len: usize, alignment: u8, new_len: usize, ret_addr: usize) callconv(.c) ?[*]u8,
+    free: *const fn (*anyopaque, memory: [*]u8, memory_len: usize, alignment: u8, ret_addr: usize) callconv(.c) void,
+};
+
+/// The Allocator interface for custom memory allocation strategies
+/// within C libghostty APIs.
+///
+/// This -- purposely -- matches the Zig allocator interface. We do this
+/// for two reasons: (1) Zig's allocator interface is well proven in
+/// the real world to be flexible and useful, and (2) it allows us to
+/// easily convert C allocators to Zig allocators and vice versa, since
+/// we're written in Zig.
+pub const Allocator = extern struct {
+    ctx: *anyopaque,
+    vtable: *const VTable,
+
+    /// vtable for the Zig allocator interface to map our extern
+    /// allocator to Zig's allocator interface.
+    pub const zig_vtable: ZigVTable = .{
+        .alloc = alloc,
+        .resize = resize,
+        .remap = remap,
+        .free = free,
+    };
+
+    /// Create a C allocator from a Zig allocator. This requires that
+    /// the Zig allocator be pointer-stable for the lifetime of the
+    /// C allocator.
+    pub fn fromZig(zig_alloc: *const std.mem.Allocator) Allocator {
+        return .{
+            .ctx = @ptrCast(@constCast(zig_alloc)),
+            .vtable = &ZigAllocator.vtable,
+        };
+    }
+
+    /// Create a Zig allocator from this C allocator. This requires
+    /// a pointer to a Zig allocator vtable that we can populate with
+    /// our callbacks.
+    pub fn zig(self: *const Allocator) std.mem.Allocator {
+        return .{
+            .ptr = @ptrCast(@constCast(self)),
+            .vtable = &zig_vtable,
+        };
+    }
+
+    fn alloc(
+        ctx: *anyopaque,
+        len: usize,
+        alignment: std.mem.Alignment,
+        ra: usize,
+    ) ?[*]u8 {
+        const self: *Allocator = @ptrCast(@alignCast(ctx));
+        return self.vtable.alloc(
+            self.ctx,
+            len,
+            @intFromEnum(alignment),
+            ra,
+        );
+    }
+
+    fn resize(
+        ctx: *anyopaque,
+        old_mem: []u8,
+        alignment: std.mem.Alignment,
+        new_len: usize,
+        ra: usize,
+    ) bool {
+        const self: *Allocator = @ptrCast(@alignCast(ctx));
+        return self.vtable.resize(
+            self.ctx,
+            old_mem.ptr,
+            old_mem.len,
+            @intFromEnum(alignment),
+            new_len,
+            ra,
+        );
+    }
+
+    fn remap(
+        ctx: *anyopaque,
+        old_mem: []u8,
+        alignment: std.mem.Alignment,
+        new_len: usize,
+        ra: usize,
+    ) ?[*]u8 {
+        const self: *Allocator = @ptrCast(@alignCast(ctx));
+        return self.vtable.remap(
+            self.ctx,
+            old_mem.ptr,
+            old_mem.len,
+            @intFromEnum(alignment),
+            new_len,
+            ra,
+        );
+    }
+
+    fn free(
+        ctx: *anyopaque,
+        old_mem: []u8,
+        alignment: std.mem.Alignment,
+        ra: usize,
+    ) void {
+        const self: *Allocator = @ptrCast(@alignCast(ctx));
+        self.vtable.free(
+            self.ctx,
+            old_mem.ptr,
+            old_mem.len,
+            @intFromEnum(alignment),
+            ra,
+        );
+    }
+};
+
+/// An allocator implementation that wraps a Zig allocator so that
+/// it can be exposed to C.
+const ZigAllocator = struct {
+    const vtable: VTable = .{
+        .alloc = alloc,
+        .resize = resize,
+        .remap = remap,
+        .free = free,
+    };
+
+    fn alloc(
+        ctx: *anyopaque,
+        len: usize,
+        alignment: u8,
+        ra: usize,
+    ) callconv(.c) ?[*]u8 {
+        const zig_alloc: *const std.mem.Allocator = @ptrCast(@alignCast(ctx));
+        return zig_alloc.vtable.alloc(
+            zig_alloc.ptr,
+            len,
+            @enumFromInt(alignment),
+            ra,
+        );
+    }
+
+    fn resize(
+        ctx: *anyopaque,
+        memory: [*]u8,
+        memory_len: usize,
+        alignment: u8,
+        new_len: usize,
+        ra: usize,
+    ) callconv(.c) bool {
+        const zig_alloc: *const std.mem.Allocator = @ptrCast(@alignCast(ctx));
+        return zig_alloc.vtable.resize(
+            zig_alloc.ptr,
+            memory[0..memory_len],
+            @enumFromInt(alignment),
+            new_len,
+            ra,
+        );
+    }
+
+    fn remap(
+        ctx: *anyopaque,
+        memory: [*]u8,
+        memory_len: usize,
+        alignment: u8,
+        new_len: usize,
+        ra: usize,
+    ) callconv(.c) ?[*]u8 {
+        const zig_alloc: *const std.mem.Allocator = @ptrCast(@alignCast(ctx));
+        return zig_alloc.vtable.remap(
+            zig_alloc.ptr,
+            memory[0..memory_len],
+            @enumFromInt(alignment),
+            new_len,
+            ra,
+        );
+    }
+
+    fn free(
+        ctx: *anyopaque,
+        memory: [*]u8,
+        memory_len: usize,
+        alignment: u8,
+        ra: usize,
+    ) callconv(.c) void {
+        const zig_alloc: *const std.mem.Allocator = @ptrCast(@alignCast(ctx));
+        return zig_alloc.vtable.free(
+            zig_alloc.ptr,
+            memory[0..memory_len],
+            @enumFromInt(alignment),
+            ra,
+        );
+    }
+};
+
+/// C allocator (libc)
+pub const CAllocator = struct {
+    comptime {
+        if (!builtin.link_libc) {
+            @compileError("C allocator is only available when linking against libc");
+        }
+    }
+
+    const vtable: VTable = .{
+        .alloc = alloc,
+        .resize = resize,
+        .remap = remap,
+        .free = free,
+    };
+
+    fn alloc(
+        ctx: *anyopaque,
+        len: usize,
+        alignment: u8,
+        ra: usize,
+    ) callconv(.c) ?[*]u8 {
+        return std.heap.c_allocator.vtable.alloc(
+            ctx,
+            len,
+            @enumFromInt(alignment),
+            ra,
+        );
+    }
+
+    fn resize(
+        ctx: *anyopaque,
+        memory: [*]u8,
+        memory_len: usize,
+        alignment: u8,
+        new_len: usize,
+        ra: usize,
+    ) callconv(.c) bool {
+        return std.heap.c_allocator.vtable.resize(
+            ctx,
+            memory[0..memory_len],
+            @enumFromInt(alignment),
+            new_len,
+            ra,
+        );
+    }
+
+    fn remap(
+        ctx: *anyopaque,
+        memory: [*]u8,
+        memory_len: usize,
+        alignment: u8,
+        new_len: usize,
+        ra: usize,
+    ) callconv(.c) ?[*]u8 {
+        return std.heap.c_allocator.vtable.remap(
+            ctx,
+            memory[0..memory_len],
+            @enumFromInt(alignment),
+            new_len,
+            ra,
+        );
+    }
+
+    fn free(
+        ctx: *anyopaque,
+        memory: [*]u8,
+        memory_len: usize,
+        alignment: u8,
+        ra: usize,
+    ) callconv(.c) void {
+        std.heap.c_allocator.vtable.free(
+            ctx,
+            memory[0..memory_len],
+            @enumFromInt(alignment),
+            ra,
+        );
+    }
+};
+
+pub const c_allocator: Allocator = .{
+    .ctx = undefined,
+    .vtable = &CAllocator.vtable,
+};
+
+/// Allocator that can be sent to the C API that does full
+/// leak checking within Zig tests. This should only be used from
+/// Zig tests.
+pub const test_allocator: Allocator = b: {
+    if (!builtin.is_test) @compileError("test_allocator can only be used in tests");
+    break :b .fromZig(&testing.allocator);
+};
+
+test "c allocator" {
+    if (!comptime builtin.link_libc) return error.SkipZigTest;
+
+    const alloc = c_allocator.zig();
+    const str = try alloc.alloc(u8, 10);
+    defer alloc.free(str);
+    try testing.expectEqual(10, str.len);
+}
+
+test "fba allocator" {
+    var buf: [1024]u8 = undefined;
+    var fba: std.heap.FixedBufferAllocator = .init(&buf);
+    const zig_alloc = fba.allocator();
+
+    // Convert the Zig allocator to a C interface
+    const c_alloc: Allocator = .fromZig(&zig_alloc);
+
+    // Convert back to Zig so we can test it.
+    const alloc = c_alloc.zig();
+    const str = try alloc.alloc(u8, 10);
+    defer alloc.free(str);
+    try testing.expectEqual(10, str.len);
+}
diff --git a/src/lib_vt.zig b/src/lib_vt.zig
index 98242ce78..19849805c 100644
--- a/src/lib_vt.zig
+++ b/src/lib_vt.zig
@@ -68,9 +68,16 @@ pub const Attribute = terminal.Attribute;
 comptime {
     // If we're building the C library (vs. the Zig module) then
     // we want to reference the C API so that it gets exported.
-    if (terminal.is_c_lib) _ = terminal.c_api;
+    if (terminal.is_c_lib) {
+        const c = terminal.c_api;
+        @export(&c.ghostty_vt_osc_new, .{ .name = "ghostty_vt_osc_new" });
+        @export(&c.ghostty_vt_osc_free, .{ .name = "ghostty_vt_osc_free" });
+    }
 }
 
 test {
     _ = terminal;
+
+    // Tests always test the C API
+    _ = terminal.c_api;
 }
diff --git a/src/terminal/c_api.zig b/src/terminal/c_api.zig
index 287711fec..079a16fb3 100644
--- a/src/terminal/c_api.zig
+++ b/src/terminal/c_api.zig
@@ -1,5 +1,44 @@
-pub export fn ghostty_hi() void {
-    // Does nothing, but you can see this symbol exists:
-    // nm -D --defined-only zig-out/lib/libghostty-vt.so | rg ' T '
-    // This is temporary as we figure out the API.
+const std = @import("std");
+const lib_alloc = @import("../lib/allocator.zig");
+const CAllocator = lib_alloc.Allocator;
+const osc = @import("osc.zig");
+
+pub const GhosttyOscParser = extern struct {
+    parser: *osc.Parser,
+};
+
+pub const Result = enum(c_int) {
+    success = 0,
+    out_of_memory = -1,
+};
+
+pub fn ghostty_vt_osc_new(
+    c_alloc: *const CAllocator,
+    result: *GhosttyOscParser,
+) callconv(.c) Result {
+    const alloc = c_alloc.zig();
+    const ptr = alloc.create(osc.Parser) catch return .out_of_memory;
+    ptr.* = .initAlloc(alloc);
+    result.* = .{ .parser = ptr };
+    return .success;
+}
+
+pub fn ghostty_vt_osc_free(parser: GhosttyOscParser) callconv(.c) void {
+    const alloc = parser.parser.alloc.?;
+    parser.parser.deinit();
+    alloc.destroy(parser.parser);
+}
+
+test {
+    _ = lib_alloc;
+}
+
+test "osc" {
+    const testing = std.testing;
+    var p: GhosttyOscParser = undefined;
+    try testing.expectEqual(Result.success, ghostty_vt_osc_new(
+        &lib_alloc.test_allocator,
+        &p,
+    ));
+    ghostty_vt_osc_free(p);
 }