feat: MCP server — agents can search and reuse session history across tools

[aytzey]

What

showagent mcp — a stdio MCP server so any MCP-capable agent (Claude Code, Codex, ...) can search every past coding session on the machine, across all supported agents, and pull one in as context or convert it to continue there.

Built on the official MCP Go SDK (github.com/modelcontextprotocol/go-sdk v1.6.1) — the one new dependency.

Tools

Tool	Does
list_sessions	provider / workspace-substring / free-text filters (workspace + first/last user message), newest first, limit default 25 / max 100, returns pre-limit total
get_transcript	user/assistant turns; max_turns keeps the most recent N (default 50) with total_turns/truncated markers
branch_session	fork via session.Branch; returns new id + file + resume command
convert_session	rewrite via session.Convert; returns new id + file + resume command
resume_command	exact shell command + cwd, returned as a string — never executed

No delete tool by design — destructive actions stay behind the TUI's two-press confirm. Branch/convert only ever write new files through the existing atomic paths.

Testing

• In-memory MCP client against the real server: filter/search, end-truncation, branch, convert, unknown-id/provider tool errors, and a test pinning that no delete tool is exposed. Hermetic via the provider home env overrides.
• Live smoke test over raw stdio JSON-RPC against demo/fixtures/gen.sh fixtures: initialize → tools/list → list_sessions {"query":"rate limit"} → resume_command latest, all sane.
• gofmt / go vet / golangci-lint clean, go test ./... -race green, CGO-free cross-compile for linux/darwin/windows amd64.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added MCP support to showagent, including a new command to expose session history through agent-friendly tools.
  • Introduced tools to list sessions, view transcripts, branch sessions, convert sessions, and retrieve resume commands.

• Documentation

  • Updated the README with MCP setup instructions, example agent configurations, tool descriptions, and safety notes.

• Bug Fixes

  • Help output and command handling now correctly include the new MCP command.
  • Added coverage for argument validation and MCP behavior to improve reliability.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds an internal/mcpserver package implementing an MCP server exposing session history tools (list_sessions, get_transcript, branch_session, convert_session, resume_command) over stdio, wires a new showagent mcp CLI subcommand, updates go.mod dependencies, and documents MCP usage in README.md.

Changes

MCP session server

Layer / File(s)	Summary
Dependency updates go.mod	Adds github.com/modelcontextprotocol/go-sdk and related indirect dependencies.
Server construction and registration internal/mcpserver/server.go	Constructs the MCP server, registers tool annotations, and adds a Run entrypoint starting the stdio transport.
list_sessions and get_transcript tools internal/mcpserver/server.go	Implements discovery-based session listing with filters/limits and transcript retrieval with truncation and resolveRow session lookup.
branch_session, convert_session, resume_command tools internal/mcpserver/server.go	Implements forking/converting sessions into new session records and returning exact resume commands without executing them.
Server test suite internal/mcpserver/server_test.go	Adds fixture setup, an in-memory MCP client/server harness, and tests covering all tools, resolveRow, and matchesFilters.
CLI mcp subcommand cmd/showagent/main.go, cmd/showagent/main_test.go	Adds mcp subcommand dispatch, help text, runMCP entrypoint, and tests for help output and argument rejection.
MCP documentation README.md	Documents showagent mcp, configuration examples, and the tool list.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Sequence Diagram(s)

sequenceDiagram
    participant Agent as Claude/Codex Agent
    participant CLI as showagent CLI
    participant MCPServer as mcpserver.Server
    participant Store as Session Storage

    Agent->>CLI: showagent mcp
    CLI->>MCPServer: mcpserver.Run(ctx, version)
    MCPServer->>MCPServer: register tools (list_sessions, get_transcript, branch_session, convert_session, resume_command)
    Agent->>MCPServer: call list_sessions(filters)
    MCPServer->>Store: discover sessions
    Store-->>MCPServer: session rows
    MCPServer-->>Agent: filtered/sorted summaries + total

    Agent->>MCPServer: call get_transcript(id or "latest")
    MCPServer->>Store: resolveRow(id)
    Store-->>MCPServer: session row
    MCPServer-->>Agent: transcript turns (truncated)

    Agent->>MCPServer: call branch_session(id)
    MCPServer->>Store: resolveRow(id) + write new session file
    Store-->>MCPServer: new session id/path
    MCPServer-->>Agent: new session id + resume command

Loading

Possibly related PRs

• aytzey/showagent#1: Both PRs modify cmd/showagent/main.go's CLI dispatcher and help output, extending the same subcommand routing structure.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 28.57% 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 matches the main change: adding an MCP server for agents to search and reuse session history across tools.
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.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/mcp-server

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[coderabbitai]

🧹 Nitpick comments (1)

cmd/showagent/main.go (1)

326-341: 🩺 Stability & Availability | 🔵 Trivial | 💤 Low value

Consider handling SIGTERM as well as SIGINT
signal.NotifyContext only listens for os.Interrupt, so the MCP server won’t exit gracefully when a supervisor sends SIGTERM. Adding syscall.SIGTERM here is a small robustness win for containerized deployments.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@cmd/showagent/main.go` around lines 326 - 341, runMCP currently only listens
for os.Interrupt via signal.NotifyContext, so it won’t shut down gracefully on
SIGTERM. Update the signal setup in runMCP to include syscall.SIGTERM alongside
os.Interrupt, keeping the rest of the mcpserver.Run flow unchanged so the MCP
server exits cleanly under container/supervisor shutdown.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@cmd/showagent/main.go`:
- Around line 326-341: runMCP currently only listens for os.Interrupt via
signal.NotifyContext, so it won’t shut down gracefully on SIGTERM. Update the
signal setup in runMCP to include syscall.SIGTERM alongside os.Interrupt,
keeping the rest of the mcpserver.Run flow unchanged so the MCP server exits
cleanly under container/supervisor shutdown.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 94d3b0a2-009e-47d9-9d00-553a9b6efed5

📥 Commits

Reviewing files that changed from the base of the PR and between dfabdf1 and 4619c7c.

⛔ Files ignored due to path filters (1)

• go.sum is excluded by !**/*.sum

📒 Files selected for processing (6)

• README.md
• cmd/showagent/main.go
• cmd/showagent/main_test.go
• go.mod
• internal/mcpserver/server.go
• internal/mcpserver/server_test.go