[Repo Assist] guard: add assign_copilot_to_issue_with_intent to WRITE_OPERATIONS and DIFC labels

[github-actions]

🤖 This is a pull request from Repo Assist, an automated AI assistant.

Closes #9813

Root Cause

The assign_copilot_to_issue_with_intent MCP tool was identified by the guard coverage checker as a write operation present in the upstream github-mcp-server but absent from:

• WRITE_OPERATIONS in guards/github-guard/rust-guard/src/tools.rs
• The DIFC label match arm in guards/github-guard/rust-guard/src/labels/tool_rules.rs

Fix

Added assign_copilot_to_issue_with_intent alongside its sibling assign_copilot_to_issue in both files:

• tools.rs: inserted alphabetically between assign_copilot_to_issue and cancel_workflow_run
• tool_rules.rs: added to the existing Copilot write arm next to assign_copilot_to_issue and request_copilot_review, inheriting the same repo-visibility secrecy and writer integrity handling

Trade-offs

No trade-offs — this is a straightforward gap fill. The new tool shares the same write semantics as its sibling and belongs in the same classification bucket.

Test Status

All 596 Rust guard unit tests pass (cargo test). Go build requires go 1.25.0 which isn't available in this sandbox (network-blocked toolchain download); the Rust changes are isolated to the guard and do not touch Go code.

Warning

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• proxy.golang.org

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[Copilot]

Pull request overview

Adds guard coverage for the new Copilot issue-assignment tool.

Changes:

• Classifies the tool as a write operation.
• Applies repository secrecy and writer-integrity labels.

Show a summary per file

File	Description
guards/github-guard/rust-guard/src/tools.rs	Adds write classification.
guards/github-guard/rust-guard/src/labels/tool_rules.rs	Adds DIFC labeling.

Review details

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• Files reviewed: 2/2 changed files
• Comments generated: 2
• Review effort level: Medium

[lpcox]

@copilot address review feedback

[Copilot]

@copilot address review feedback

Addressed in e566a0a with regression coverage for assign_copilot_to_issue_with_intent in both write-operation classification and DIFC label application tests.

[lpcox]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Addressed in 68197e9a.

[github-actions]

🔒 mcpg Read-Only Stress — gVisor

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: gVisor (runsc) kernel-level isolation

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (issues/PRs/file/commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	unknown tool [-32602] for all 7	BLOCKED	✅
C	CLI	reads (list_issues, get_file_contents)	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment/file)	unauthenticated — no GH_TOKEN	BLOCKED	✅
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	unauthenticated — no GH_TOKEN	BLOCKED	✅

Overall: PASS

Part B: gateway strips all write tools — every attempt returns MCP error [-32602] unknown tool. Parts D & E: gh unauthenticated in gVisor runtime; all REST/GraphQL writes rejected at auth layer.

References: §29966437591

🔒 mcpg read-only stress (gVisor runtime) by Read-Only Stress: gVisor runtime

[github-actions]

🔒 mcpg Read-Only Stress — default AWF

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: default AWF (normal container isolation)

Part	Surface	Op	Result	Expected	Status
A	MCP	reads (issues/PRs/file/commits)	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	unknown tool [-32602] from gateway	BLOCKED	✅
C	CLI	reads (list issues, get file)	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment/file)	unauthenticated (no GH_TOKEN)	BLOCKED	✅
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	unauthenticated (no GH_TOKEN)	BLOCKED	✅

Overall: PASS

Notes:

• Part B: gateway returns MCP error [-32602] unknown tool for all 7 write tool calls — write tools are stripped at gateway level, confirming gateway enforcement.
• Parts D & E: gh CLI carries no token so all REST/GraphQL writes fail at auth before reaching GitHub API.

References: §29966437606

🔒 mcpg read-only stress (default AWF runtime) by Read-Only Stress: default runtime

[github-actions]

🔒 mcpg Read-Only Stress — docker-sbx

Surface coverage: MCP tool calls + proxied CLI (REST) + GraphQL mutations
Isolation runtime: docker-sbx (KVM-isolated microVM)

Part	Surface	Op	Result	Expected	Status
A	MCP	reads	data returned	ALLOWED	✅
B	MCP	writes (reaction/star/issue/comment/branch/file/PR)	Error [-32602] unknown tool (gateway blocks — 0/22 tools are writes)	BLOCKED	✅
C	CLI	reads	data returned	ALLOWED	✅
D	CLI	REST writes (reaction/star/issue/comment/file)	rejected (gh unauthenticated)	BLOCKED	✅
E	CLI	GraphQL mutations (addReaction/addStar/createIssue)	rejected (gh unauthenticated)	BLOCKED	✅

Overall: PASS

References: §29966437730

🔒 mcpg read-only stress (docker-sbx runtime) by Read-Only Stress: docker-sbx runtime