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fix: coerce write_to_file content to string when model sends object #11041

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fix: coerce write_to_file content to string when model sends object #11041

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28 changes: 25 additions & 3 deletions src/core/assistant-message/NativeToolCallParser.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,25 @@ export class NativeToolCallParser {
return undefined
}

/**
* Coerce content to a string for write_to_file tool.
* Some models (e.g., GLM 4.7 via OpenAI Compatible API) incorrectly pass content
* as a JSON object instead of a string. This handles that case gracefully.
*/
private static coerceContentToString(value: unknown, toolName: string): string {
if (typeof value === "string") {
return value
}

// Value is not a string - convert it and log a warning
console.warn(
`[NativeToolCallParser] Model sent non-string content for '${toolName}' tool. ` +
`Expected string, received ${typeof value}. Converting to JSON string. ` +
`This may indicate the model is not following the tool schema correctly.`,
)
return JSON.stringify(value, null, 2)
}

/**
* Process a raw tool call chunk from the API stream.
* Handles tracking, buffering, and emits start/delta/end events.
Expand Down Expand Up @@ -401,10 +420,13 @@ export class NativeToolCallParser {
break

case "write_to_file":
if (partialArgs.path || partialArgs.content) {
if (partialArgs.path || partialArgs.content !== undefined) {
nativeArgs = {
path: partialArgs.path,
content: partialArgs.content,
content:
partialArgs.content !== undefined
? this.coerceContentToString(partialArgs.content, "write_to_file")
: undefined,
}
}
break
Expand Down Expand Up @@ -805,7 +827,7 @@ export class NativeToolCallParser {
if (args.path !== undefined && args.content !== undefined) {
nativeArgs = {
path: args.path,
content: args.content,
content: this.coerceContentToString(args.content, "write_to_file"),
} as NativeArgsFor<TName>
}
break
Expand Down
163 changes: 163 additions & 0 deletions src/core/assistant-message/__tests__/NativeToolCallParser.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -238,4 +238,167 @@ describe("NativeToolCallParser", () => {
})
})
})

describe("write_to_file tool - content type coercion", () => {
describe("parseToolCall", () => {
it("should handle content as a string (normal case)", () => {
const toolCall = {
id: "toolu_123",
name: "write_to_file" as const,
arguments: JSON.stringify({
path: "package.json",
content: '{\n "name": "test"\n}',
}),
}

const result = NativeToolCallParser.parseToolCall(toolCall)

expect(result).not.toBeNull()
expect(result?.type).toBe("tool_use")
if (result?.type === "tool_use") {
const nativeArgs = result.nativeArgs as { path: string; content: string }
expect(nativeArgs.path).toBe("package.json")
expect(nativeArgs.content).toBe('{\n "name": "test"\n}')
}
})

it("should coerce content from object to JSON string", () => {
// This simulates the bug where models like GLM 4.7 pass content as an object
const toolCall = {
id: "toolu_456",
name: "write_to_file" as const,
arguments: JSON.stringify({
path: "package.json",
content: { name: "sample-project", version: "1.0.0" },
}),
}

const consoleSpy = vi.spyOn(console, "warn").mockImplementation(() => {})

const result = NativeToolCallParser.parseToolCall(toolCall)

expect(result).not.toBeNull()
expect(result?.type).toBe("tool_use")
if (result?.type === "tool_use") {
const nativeArgs = result.nativeArgs as { path: string; content: string }
expect(nativeArgs.path).toBe("package.json")
// Content should be converted to a formatted JSON string
expect(nativeArgs.content).toBe(
JSON.stringify({ name: "sample-project", version: "1.0.0" }, null, 2),
)
}

// Should log a warning about the type coercion
expect(consoleSpy).toHaveBeenCalledWith(
expect.stringContaining("Model sent non-string content for 'write_to_file' tool"),
)

consoleSpy.mockRestore()
})

it("should coerce content from array to JSON string", () => {
const toolCall = {
id: "toolu_789",
name: "write_to_file" as const,
arguments: JSON.stringify({
path: "data.json",
content: [1, 2, 3, { key: "value" }],
}),
}

const consoleSpy = vi.spyOn(console, "warn").mockImplementation(() => {})

const result = NativeToolCallParser.parseToolCall(toolCall)

expect(result).not.toBeNull()
if (result?.type === "tool_use") {
const nativeArgs = result.nativeArgs as { path: string; content: string }
expect(nativeArgs.content).toBe(JSON.stringify([1, 2, 3, { key: "value" }], null, 2))
}

expect(consoleSpy).toHaveBeenCalled()
consoleSpy.mockRestore()
})

it("should coerce content from number to string", () => {
const toolCall = {
id: "toolu_num",
name: "write_to_file" as const,
arguments: JSON.stringify({
path: "number.txt",
content: 42,
}),
}

const consoleSpy = vi.spyOn(console, "warn").mockImplementation(() => {})

const result = NativeToolCallParser.parseToolCall(toolCall)

expect(result).not.toBeNull()
if (result?.type === "tool_use") {
const nativeArgs = result.nativeArgs as { path: string; content: string }
expect(nativeArgs.content).toBe("42")
}

expect(consoleSpy).toHaveBeenCalled()
consoleSpy.mockRestore()
})
})

describe("processStreamingChunk", () => {
it("should coerce content from object to JSON string during streaming", () => {
const id = "toolu_streaming_write"
NativeToolCallParser.startStreamingToolCall(id, "write_to_file")

const consoleSpy = vi.spyOn(console, "warn").mockImplementation(() => {})

const fullArgs = JSON.stringify({
path: "config.json",
content: { setting: true, value: 123 },
})

const result = NativeToolCallParser.processStreamingChunk(id, fullArgs)

expect(result).not.toBeNull()
if (result?.nativeArgs) {
const nativeArgs = result.nativeArgs as { path: string; content: string }
expect(nativeArgs.path).toBe("config.json")
expect(nativeArgs.content).toBe(JSON.stringify({ setting: true, value: 123 }, null, 2))
}

expect(consoleSpy).toHaveBeenCalled()
consoleSpy.mockRestore()
})
})

describe("finalizeStreamingToolCall", () => {
it("should coerce content from object to JSON string on finalize", () => {
const id = "toolu_finalize_write"
NativeToolCallParser.startStreamingToolCall(id, "write_to_file")

const consoleSpy = vi.spyOn(console, "warn").mockImplementation(() => {})

NativeToolCallParser.processStreamingChunk(
id,
JSON.stringify({
path: "tsconfig.json",
content: { compilerOptions: { strict: true } },
}),
)

const result = NativeToolCallParser.finalizeStreamingToolCall(id)

expect(result).not.toBeNull()
expect(result?.type).toBe("tool_use")
if (result?.type === "tool_use") {
const nativeArgs = result.nativeArgs as { path: string; content: string }
expect(nativeArgs.path).toBe("tsconfig.json")
expect(nativeArgs.content).toBe(JSON.stringify({ compilerOptions: { strict: true } }, null, 2))
}

expect(consoleSpy).toHaveBeenCalled()
consoleSpy.mockRestore()
})
})
})
})
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