feat: RooMessage type system and storage layer for ModelMessage migration

[daniel-lxs]

Summary

Adds foundation infrastructure for migrating message storage from Anthropic format to AI SDK ModelMessage format (EXT-646).

No behavior change — purely additive. Existing code paths are untouched.

What's Added

Type System (rooMessage.ts)

• RooMessage = AI SDK ModelMessage + Roo metadata (ts, condenseId, truncationId, etc.)
• Uses AI SDK types directly (UserModelMessage, AssistantModelMessage, ToolModelMessage from "ai")
• Only custom additions: RooMessageMetadata and RooReasoningMessage (encrypted reasoning)
• Type guards: isRooUserMessage(), isRooAssistantMessage(), isRooToolMessage(), isRooReasoningMessage()

Legacy Converter (converters/anthropicToRoo.ts)

• convertAnthropicToRooMessages() — Converts old Anthropic-format conversations to RooMessage on first open
• Handles all content types: text, images, tool_use/tool_result, thinking/reasoning blocks, signatures, provider options
• Tool name resolution via first-pass tool call ID mapping
• Metadata preservation (ts, condense, truncation fields)

Versioned Storage (apiMessages.ts)

• readRooMessages() — Reads JSON, auto-detects format (v2 envelope vs legacy Anthropic array), converts on read
• saveRooMessages() — Writes in v2 format: { version: 2, messages: [...] }
• detectFormat() — Format detection utility
• Existing readApiMessages()/saveApiMessages() untouched

Utility (messageUtils.ts)

• flattenModelMessagesToStringContent() — For providers needing string content (e.g., DeepSeek on SambaNova)

Design Principles

1. Store as ModelMessage — Messages use AI SDK format directly, passed to streamText() with zero conversion
2. Forward-only migration — Old conversations convert on read; no backward path to Anthropic format
3. No type duplication — Content parts (TextPart, ImagePart, ToolCallPart, etc.) come from the "ai" package

Test Coverage

• 101 tests across 6 test files
• All 5536 existing tests continue to pass

Next Steps

• EXT-647: Wire Task.ts to use readRooMessages()/saveRooMessages() and construct RooMessage directly
• EXT-648: Delete per-provider converters (convertToAiSdkMessages, convertToOpenAiMessages, etc.)

Resolves EXT-646

Important

Introduces RooMessage type system and storage layer for migrating from Anthropic to AI SDK ModelMessage format, with conversion functions and comprehensive tests.

• Type System:
  • Introduces RooMessage types in rooMessage.ts, extending AI SDK ModelMessage with metadata.
  • Adds type guards: isRooUserMessage(), isRooAssistantMessage(), isRooToolMessage(), isRooReasoningMessage().
• Conversion:
  • Adds convertAnthropicToRooMessages() in converters/anthropicToRoo.ts to convert Anthropic-format messages to RooMessage.
  • Handles all content types and preserves metadata.
• Storage:
  • Implements readRooMessages() and saveRooMessages() in apiMessages.ts for versioned message storage.
  • Detects format and converts legacy messages on read.
• Utilities:
  • Adds flattenModelMessagesToStringContent() in messageUtils.ts for flattening message content.
• Tests:
  • 101 new tests across 6 files, ensuring comprehensive coverage.
  • Tests for type guards, conversion logic, storage functions, and utilities.

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[roomote]

Rooviewer   See task

Reviewed 1 changed file in the latest commit (mocked safeWriteJson in the write-failure test for cross-platform reliability). No new issues found.

Previous reviews

• 14cfae1: Review #1
• f59ffad: Review #2

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[daniel-lxs]

The platform-unit-test (windows-latest) job is failing on one test:

rooMessages.spec.ts > saveRooMessages > returns false on write failure (line 222)

Root cause

The test expects saveRooMessages to throw (and return false) when given globalStoragePath: "/nonexistent/readonly/path". The intent is that getTaskDirectoryPath or safeWriteJson will fail on a nonexistent/invalid path.

However, getTaskDirectoryPath calls fs.mkdir(taskDir, { recursive: true }), which successfully creates the directory on Windows because /nonexistent/readonly/path resolves to a valid absolute path on the current drive (e.g. D:\nonexistent\readonly\path\tasks\task-fail). Unlike Linux/macOS where writing to /nonexistent/... requires root, Windows happily creates it under the current drive root. So the write succeeds and the function returns true.

Fix

The test needs a path that will reliably fail on all platforms. Two options:

1. Use a path with invalid characters that will fail on Windows, e.g. globalStoragePath: path.join(os.tmpdir(), "roo-test-\0-invalid") (null byte is invalid everywhere).

2. Mock getTaskDirectoryPath or safeWriteJson to throw, rather than relying on filesystem behavior. This is the more robust approach since it doesn't depend on OS-specific path validation. For example:

import * as storage from "../../utils/storage"

vi.spyOn(storage, "getTaskDirectoryPath").mockRejectedValueOnce(new Error("simulated write failure"))

Option 2 is probably the better path since the test is checking the error-handling logic in saveRooMessages, not the OS filesystem behavior.

[daniel-lxs]

@roomote Fix the test based on my comment

[roomote]

Fixaroo   See task

Fixed the cross-platform test failure by mocking safeWriteJson instead of relying on OS-specific filesystem behavior. All tests and checks pass.

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