feat(web): expose get_diff on MCP server by msukkari · Pull Request #1142 · sourcebot-dev/sourcebot · GitHub

Fixes SOU-968

Summary

add a new get_diff MCP tool that returns structured git diff data between base and head
register get_diff in the Sourcebot MCP server toolset
document get_diff in MCP docs with parameters aligned to the public API diff schema

Test plan

run yarn workspace @sourcebot/web lint
verify MCP descriptor includes get_diff with repo, base, head
call MCP get_diff for main~1..main and verify non-empty diff output
compare MCP get_diff output for HEAD~5..HEAD with git diff file set and stats

Made with Cursor

Summary by CodeRabbit

New Features
- Added a new MCP tool, "get_diff", to return structured git diffs between two refs (repo, base, head), including changed files, hunks, line ranges, and patch content.
UI
- Chat now displays a compact "Compared base to head in repo" summary with changed-file counts and a dedicated tool output renderer.
Documentation
- Added user docs and changelog entry describing the new get_diff tool.

Add a new get_diff MCP tool backed by the existing git diff API so agents can request structured diffs between refs. Document the tool in MCP docs with parameters aligned to the public API spec. Made-with: Cursor

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Project	Status	Preview	Updated (UTC)
sourcebot	🟢 Ready	View Preview	Apr 21, 2026, 5:24 PM

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Caution

Review failed

The pull request is closed.

ℹ️ Recent review info ⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 278f62cc-74d6-4442-bb7a-414d44b0eee3

📥 Commits

Reviewing files that changed from the base of the PR and between f401c24 and a7511d7.

📒 Files selected for processing (4)

packages/web/src/features/chat/agent.ts
packages/web/src/features/chat/components/chatThread/detailsCard.tsx
packages/web/src/features/chat/components/chatThread/tools/getDiffToolComponent.tsx
packages/web/src/features/chat/tools.ts

Walkthrough

Adds a new MCP tool get_diff that returns a structured git diff between two refs; includes tool implementation, schema, MCP registration, UI rendering, docs, and changelog entry. (50 words)

Changes

Cohort / File(s)	Summary
Documentation docs/docs/features/mcp-server.mdx, packages/web/src/features/tools/getDiff.txt	Added documentation for the get_diff tool, describing purpose and required parameters: repo, base, head.
Tool Implementation packages/web/src/features/tools/getDiff.ts	New tool definition getDiffDefinition with request schema, logging, call to getDiff, service-error handling, JSON-stringified output, and enriched metadata.
Tool Barrel & Server Registration packages/web/src/features/tools/index.ts, packages/web/src/features/mcp/server.ts	Re-exported getDiff from tools barrel and registered get_diff with the MCP server.
Chat Integration & UI packages/web/src/features/chat/tools.ts, packages/web/src/features/chat/components/chatThread/detailsCard.tsx, packages/web/src/features/chat/components/chatThread/tools/getDiffToolComponent.tsx, packages/web/src/features/chat/agent.ts	Added chat/tool mapping, UI part type, rendering case for tool-get_diff, new GetDiffToolComponent, and updated system prompt examples to include get_diff.
Changelog CHANGELOG.md	Added Unreleased note recording the new get_diff MCP tool (#1142).

Sequence Diagram(s)

sequenceDiagram
    participant Client as Client
    participant MCP as MCP Server
    participant Tool as get_diff Tool
    participant DiffSvc as Diff Service

    Client->>MCP: Request get_diff(repo, base, head)
    MCP->>Tool: invoke handler with params
    Tool->>DiffSvc: getDiff(repo, base, head)
    DiffSvc-->>Tool: diff result / error
    alt success
        Tool-->>MCP: return JSON output + metadata
        MCP-->>Client: 200 + diff payload
    else service error
        Tool-->>MCP: throw Error(response.message)
        MCP-->>Client: 5xx error
    end

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

feat(web): add GET /api/diff endpoint #1063: Implements a core getDiff API and GET /api/diff endpoint that this tool integrates with.
feat(web): expose get_diff on MCP server #1142: Adds the get_diff MCP tool, docs, changelog, and UI — closely overlaps with these changes.
feat(mcp): hide ask_codebase tool when no LLM providers configured #1018: Changes MCP server/tool-registration code; touches the same server registration area updated here.

Suggested reviewers

brendan-kellam

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat(web): expose get_diff on MCP server' clearly and concisely summarizes the main change: adding and exposing the get_diff tool to the MCP server.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Commit unit tests in branch michael/expose-mcp-get-diff-sou-968

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Document the new MCP get_diff capability under Unreleased using the repository changelog format and PR link. Made-with: Cursor

🧹 Nitpick comments (1)

packages/web/src/features/tools/getDiff.ts (1)
21-39: Consider size limits for large diffs.

JSON.stringify(response) returns the full diff with no truncation or size cap. For large base..head ranges this could produce very large outputs that exceed MCP client limits or consume excessive tokens. Consider adding a max file/hunk cap or a size guard, similar to the limit parameters on other tools (grep, glob, list_commits).
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In `@packages/web/src/features/tools/getDiff.ts` around lines 21 - 39, The execute
handler currently returns the full diff (JSON.stringify(response)) which can be
arbitrarily large; update the execute implementation in getDiff.ts (the execute
function that calls getDiff and uses isServiceError) to enforce a size/entry
cap: either pass a new limit parameter into getDiff (e.g., file/hunk limit) or
truncate the response before stringifying (e.g., keep first N files/hunks and
set a truncated=true flag), and include metadata that indicates truncation along
with repo/base/head; ensure you still throw on isServiceError(response) and
preserve the existing metadata merge but replace output with the
capped/truncated JSON to avoid oversized payloads.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@packages/web/src/features/tools/getDiff.ts`:
- Around line 21-39: The execute handler currently returns the full diff
(JSON.stringify(response)) which can be arbitrarily large; update the execute
implementation in getDiff.ts (the execute function that calls getDiff and uses
isServiceError) to enforce a size/entry cap: either pass a new limit parameter
into getDiff (e.g., file/hunk limit) or truncate the response before
stringifying (e.g., keep first N files/hunks and set a truncated=true flag), and
include metadata that indicates truncation along with repo/base/head; ensure you
still throw on isServiceError(response) and preserve the existing metadata merge
but replace output with the capped/truncated JSON to avoid oversized payloads.

ℹ️ Review info ⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 53057228-4605-4cf8-8dea-8558c9bc0381

📥 Commits

Reviewing files that changed from the base of the PR and between 48ad44d and a23c35a.

📒 Files selected for processing (5)

docs/docs/features/mcp-server.mdx
packages/web/src/features/mcp/server.ts
packages/web/src/features/tools/getDiff.ts
packages/web/src/features/tools/getDiff.txt
packages/web/src/features/tools/index.ts

Register get_diff in the Ask agent toolset and render its output in the details panel so chat workflows can compare refs directly. Made-with: Cursor

feat(web): expose get_diff on MCP server

a23c35a

Add a new get_diff MCP tool backed by the existing git diff API so agents can request structured diffs between refs. Document the tool in MCP docs with parameters aligned to the public API spec. Made-with: Cursor

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chore: add changelog entry for MCP get_diff tool

f401c24

Document the new MCP get_diff capability under Unreleased using the repository changelog format and PR link. Made-with: Cursor

mintlify Bot deployed to staging - docs April 21, 2026 17:24 View deployment

coderabbitai Bot reviewed Apr 21, 2026

View reviewed changes

brendan-kellam previously approved these changes Apr 21, 2026

View reviewed changes

feat(chat): expose get_diff tool in Ask agent

a7511d7

Register get_diff in the Ask agent toolset and render its output in the details panel so chat workflows can compare refs directly. Made-with: Cursor

msukkari dismissed brendan-kellam’s stale review via a7511d7 April 21, 2026 17:31

msukkari merged commit 14ca65d into main Apr 21, 2026
6 of 7 checks passed

github-actions Bot mentioned this pull request Apr 21, 2026

Sourcebot Roadmap 🚀 #459

Open

coderabbitai Bot mentioned this pull request Apr 23, 2026

feat: improve diff tool display and token efficiency #1146

Merged

coderabbitai Bot mentioned this pull request May 15, 2026

fix(web): preserve source revisions in chat citation links #1205

Merged

coderabbitai Bot mentioned this pull request Aug 19, 2026

feat(web): add list branches tool to MCP and Ask Sourcebot #1609

Merged

feat(web): expose get_diff on MCP server by msukkari · Pull Request #1142 · sourcebot-dev/sourcebot · GitHub

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feat(web): expose get_diff on MCP server - #1142

feat(web): expose get_diff on MCP server#1142
msukkari merged 3 commits into
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feat(web): expose get_diff on MCP server by msukkari · Pull Request #1142 · sourcebot-dev/sourcebot · GitHub

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feat(web): expose get_diff on MCP server - #1142

feat(web): expose get_diff on MCP server#1142msukkari merged 3 commits intomainsourcebot-dev/sourcebot:mainfrom michael/expose-mcp-get-diff-sou-968sourcebot-dev/sourcebot:michael/expose-mcp-get-diff-sou-968Copy head branch name to clipboard

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Walkthrough

Changes

Sequence Diagram(s)

Estimated code review effort

Possibly related PRs

Suggested reviewers

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feat(web): expose get_diff on MCP server#1142
msukkari merged 3 commits into
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msukkari commented Apr 21, 2026 •
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