feat(discord): emit IMAGE markers for inbound image attachments (RMN-1826)

[xero7689]

Summary

• process_attachments() silently dropped image/* attachments with a debug log
• Add a 2-line image/* branch that emits [IMAGE:<cdn_url>] markers
• Follows the same pattern already used in qq.rs and linq.rs

Linked Issue

Closes #1825

Label Snapshot (required)

• Risk label: risk: low
• Size label: size: XS
• Scope labels: channel, tool: discord

Change Metadata

• Change type: feature
• Primary scope: channel

Validation Evidence (required)

cargo test process_attachments
# test channels::discord::tests::process_attachments_empty_list_returns_empty ... ok
# test channels::discord::tests::process_attachments_skips_unsupported_types ... ok
# test channels::discord::tests::process_attachments_image_produces_image_marker ... ok
# test channels::discord::tests::process_attachments_multiple_images_produce_markers ... ok
# test result: ok. 4 passed; 0 failed

cargo clippy -- -D warnings
# No new errors introduced by this PR.

cargo fmt --all -- --check
# No formatting issues.

Manually verified: sent image attachment over Discord, agent received [IMAGE:<cdn_url>] marker and forwarded to vision-capable provider successfully.

Security Impact (required)

• New permissions/capabilities? No.
• New external network calls? No — CDN URL is provided by Discord in the attachment payload; no additional fetch.
• Secrets/tokens handling changed? No.
• File system access scope changed? No.
• Risk description: No new attack surface. The CDN URL originates from Discord's own payload, not user-controlled input.

Privacy and Data Hygiene (required)

• Data-hygiene status: pass
• Test fixtures use cdn.discordapp.com placeholder paths and neutral filenames only.

Compatibility / Migration

• Backward compatible? Yes — additive only. Deployments without vision-capable providers are unaffected (marker is emitted but rejected at the provider layer with an existing error path).
• Config/env changes? No.
• Migration needed? No.

i18n Follow-Through (required)

• i18n follow-through triggered? No — no docs or user-facing wording changes.

Side Effects / Blast Radius (required)

• Affected subsystems: src/channels/discord.rs only.
• Potential unintended effects: Users with non-vision providers will see provider_capability_error when sending images. This is the existing behaviour for all other channels; tracked separately in feat(discord): emit IMAGE markers for inbound image attachments (RMN-1826) #1826.

Rollback Plan (required)

• Rollback: revert the image/* branch in process_attachments() — single focused change, no config impact.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Image attachments from Discord are now recognized and marked with identifiers in the output, providing consistent treatment with text attachments.

• Tests

  • Implemented tests to validate image attachment identification and marker generation, covering both individual and multiple image scenarios to ensure proper functionality.

Linear

Refs RMN-1826

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📝 Walkthrough

Walkthrough

The process_attachments() function in src/channels/discord.rs now handles image attachments by inserting [IMAGE:<url>] markers, extending existing support for text attachments. Two tests verify single and multiple image attachment handling.

Changes

Cohort / File(s)	Summary
Image Attachment Processing src/channels/discord.rs	Added image/* MIME type handling to process_attachments() to emit [IMAGE:<cdn_url>] markers for image attachments. Includes tests for single and multiple image attachment scenarios.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Suggested labels

size: XS

Suggested reviewers

• theonlyhennygod
• chumyin

Poem

🐰 A hop, a skip, through Discord's door,
Images now shine where none before!
[IMAGE:link] in markers we weave,
Vision-bound channels now truly believe. 🖼️✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR fully addresses all acceptance criteria from issue #1825: image/* attachments produce [IMAGE:<cdn_url>] markers, non-image attachments are skipped, tests cover single and multiple images, and the 2-line implementation matches the proposed solution.
Out of Scope Changes check	✅ Passed	All changes are in scope: only src/channels/discord.rs modified with the image/* branch addition and corresponding tests, matching the stated 2-line architecture impact.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Description check	✅ Passed	The pull request description is comprehensive and well-structured, covering all required template sections including summary, linked issues, labels, change metadata, validation evidence, security/privacy impact, compatibility, i18n assessment, and rollback plan.
Title check	✅ Passed	The title accurately and specifically describes the main change: adding IMAGE marker emission for inbound image attachments in the Discord channel handler.

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🧪 Generate unit tests (beta)

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[coderabbitai]

🧹 Nitpick comments (1)

src/channels/discord.rs (1)

1453-1454: Tighten multi-image assertion to enforce output contract.

contains checks can miss regressions in delimiter/order/extra content. Prefer asserting the full expected string.

Suggested test tightening

-        assert!(result.contains("[IMAGE:https://cdn.discordapp.com/attachments/1/2/a.jpg]"));
-        assert!(result.contains("[IMAGE:https://cdn.discordapp.com/attachments/1/2/b.png]"));
+        assert_eq!(
+            result,
+            "[IMAGE:https://cdn.discordapp.com/attachments/1/2/a.jpg]\n---\n[IMAGE:https://cdn.discordapp.com/attachments/1/2/b.png]"
+        );

As per coding guidelines, "Keep tests deterministic (no flaky timing/network dependence without guardrails)".

🤖 Prompt for AI Agents

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

In `@src/channels/discord.rs` around lines 1453 - 1454, The test currently uses
loose checks on the variable result via assert!(result.contains(...)) for two
image tokens; tighten it by asserting the exact expected output string
(including delimiters and order) instead of contains so regressions in
formatting or extra content fail the test—construct the exact expected value
containing
"[IMAGE:https://cdn.discordapp.com/attachments/1/2/a.jpg][IMAGE:https://cdn.discordapp.com/attachments/1/2/b.png]"
(or with the exact spacing/newline/delimiter your contract requires) and replace
the two contains assertions with a single equality assertion (e.g.,
assert_eq!(result, expected)) referring to result in the same test.

🤖 Prompt for all review comments with AI agents

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

Nitpick comments:
In `@src/channels/discord.rs`:
- Around line 1453-1454: The test currently uses loose checks on the variable
result via assert!(result.contains(...)) for two image tokens; tighten it by
asserting the exact expected output string (including delimiters and order)
instead of contains so regressions in formatting or extra content fail the
test—construct the exact expected value containing
"[IMAGE:https://cdn.discordapp.com/attachments/1/2/a.jpg][IMAGE:https://cdn.discordapp.com/attachments/1/2/b.png]"
(or with the exact spacing/newline/delimiter your contract requires) and replace
the two contains assertions with a single equality assertion (e.g.,
assert_eq!(result, expected)) referring to result in the same test.

---

ℹ️ Review info

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between d2b0593 and 862ba5e.

📒 Files selected for processing (1)

• src/channels/discord.rs

[dwillitzer]

Reviewed by ZeroClaw-Nigel team. Discord-only addition for IMAGE markers. Follows existing patterns. Safe to merge.

[github-actions]

PR intake checks found warnings (non-blocking)

Fast safe checks found advisory issues. CI lint/test/build gates still enforce merge quality.

• Incomplete required PR template fields: summary problem, summary why it matters, summary what changed, validation commands, security risk/mitigation, privacy status, rollback plan

Action items:

1. Complete required PR template sections/fields.
2. Link this PR to exactly one active Linear issue key (RMN-xxx/CDV-xxx/COM-xxx).
3. Remove tabs, trailing whitespace, and merge conflict markers from added lines.
4. Re-run local checks before pushing:
   • ./scripts/ci/rust_quality_gate.sh
   • ./scripts/ci/rust_strict_delta_gate.sh
   • ./scripts/ci/docs_quality_gate.sh

Detected Linear keys: RMN-1826

Run logs: https://github.com/zeroclaw-labs/zeroclaw/actions/runs/22543656370

Detected blocking line issues (sample):

• none

Detected advisory line issues (sample):

• none

[theonlyhennygod]

Approved for rebase/merge pass.