inspect_image

Send a local image file to a vision-capable model and return text analysis.

Source

• Entry: packages/coding-agent/src/tools/inspect-image.ts
• Model-facing prompt: packages/coding-agent/src/prompts/tools/inspect-image.md
• Key collaborators:
  • packages/coding-agent/src/tools/inspect-image-renderer.ts — TUI call/result rendering.
  • packages/coding-agent/src/utils/image-loading.ts — path resolution, type detection, size gate, optional resize.
  • packages/coding-agent/src/utils/image-resize.ts — downscale and recompress oversized images.
  • packages/coding-agent/src/tools/path-utils.ts — resolve input path relative to session cwd.
  • packages/utils/src/mime.ts — detect supported image formats from file bytes.

Inputs

Field	Type	Required	Description
path	string	Yes	Image path passed to loadImageInput; resolved relative to session.cwd by resolveReadPath(...).
question	string	Yes	User prompt sent as a text content block alongside the image.

Outputs

The tool returns a single AgentToolResult:

• content: one text block, [{ type: "text", text }], where text is the concatenated assistant text content from the model response.
• details:
  • model: <provider>/<id> of the selected model.
  • imagePath: resolved filesystem path returned by loadImageInput(...).
  • mimeType: MIME type actually sent to the model after optional resize/re-encode.

Model-visible output is single-shot, not streamed by this tool.

TUI rendering adds presentation-only truncation from packages/coding-agent/src/tools/inspect-image-renderer.ts:

• call preview truncates question to 100 columns,
• result view shows 4 lines collapsed or 16 lines expanded,
• each rendered output line is truncated to 120 columns,
• footer metadata shows model · mimeType when present.

Flow

1. InspectImageTool.execute(...) rejects immediately if images.blockImages is enabled in session settings.
2. It reads session.modelRegistry; missing registry, empty registry, missing API key, or unresolved model each raise ToolError from packages/coding-agent/src/tools/inspect-image.ts.
3. Model selection tries, in order, pi/vision, pi/default, the active model string from the session, then availableModels[0]. expandRoleAlias(...) and resolveModelFromString(...) handle each lookup.
4. The chosen model must advertise input.includes("image"); otherwise execution fails before reading the file.
5. loadImageInput(...) in packages/coding-agent/src/utils/image-loading.ts resolves the path with resolveReadPath(...), detects MIME type with readImageMetadata(...), and rejects files larger than MAX_IMAGE_INPUT_BYTES (20 * 1024 * 1024, 20 MiB) using ImageInputTooLargeError.
6. readImageMetadata(...) in packages/utils/src/mime.ts inspects file headers only. Supported detected MIME types are image/png, image/jpeg, image/gif, and image/webp.
7. If images.autoResize is true, loadImageInput(...) calls resizeImage(...). Resize failures are swallowed there and the original bytes are kept.
8. If MIME detection returned no supported image type, execute(...) throws ToolError("inspect_image only supports PNG, JPEG, GIF, and WEBP files detected by file content.").
9. The tool calls instrumentedCompleteSimple(...) with one user message containing two content parts in order:
   • { type: "image", data: imageInput.data, mimeType: imageInput.mimeType }
   • { type: "text", text: params.question }
10. systemPrompt is a one-element array rendered from packages/coding-agent/src/prompts/tools/inspect-image-system.md; telemetry is tagged with oneshot kind inspect_image.
11. If the model response stop reason is error or aborted, the tool maps that to ToolError.
12. extractResponseText(...) concatenates only text content blocks from the assistant message, trims the result, and fails if nothing remains.
13. Success returns the text plus details; inspectImageToolRenderer formats the result for the TUI.

Modes / Variants

• Original image path: images.autoResize disabled. The original file bytes are base64-encoded and sent with the detected MIME type.
• Auto-resized path: images.autoResize enabled. resizeImage(...) may downscale and re-encode the image before upload.
• Unsupported image path: file exists but header sniffing does not identify PNG/JPEG/GIF/WEBP. The tool returns a ToolError before any model call.
• Oversize image path: file size exceeds 20 MiB before upload. The tool returns a ToolError before any model call.

Side Effects

• Filesystem
  • Resolves and reads the target image from disk.
  • Stats the file once with Bun.file(...).stat() and reads it fully with fs.readFile(...).
• Network
  • Sends the final base64 image payload plus question text to the selected model through instrumentedCompleteSimple(...) / the configured simple completion implementation.
• Session state
  • Reads session settings, active model preferences, cwd, and model registry.
• Background work / cancellation
  • Passes the caller AbortSignal into instrumentedCompleteSimple(...) and the configured simple completion implementation.
  • Image preprocessing is local and not cancellation-aware in these helpers.

Limits & Caps

• Supported detected input formats: image/png, image/jpeg, image/gif, image/webp (SUPPORTED_IMAGE_MIME_TYPES in packages/utils/src/mime.ts).
• Metadata sniff cap: DEFAULT_IMAGE_METADATA_HEADER_BYTES = 256 * 1024 bytes. Format detection only reads up to 256 KiB from the file header.
• Upload input cap: MAX_IMAGE_INPUT_BYTES = 20 * 1024 * 1024 bytes (20 MiB) in packages/coding-agent/src/utils/image-loading.ts.
• Auto-resize defaults in packages/coding-agent/src/utils/image-resize.ts:
  • maxWidth: 1568
  • maxHeight: 1568
  • maxBytes: 500 * 1024 bytes (500 KiB target)
  • jpegQuality: 75
• Resize fast path: if the original image is already within 1568x1568 and within maxBytes / 4 (125 KiB by default), resizeImage(...) returns the original bytes unchanged.
• Resize quality ladder: after the first encode pass, lossy retries use qualities [70, 60, 50, 40].
• Resize dimension ladder: if quality reduction still misses the byte target, retries scale dimensions by [1.0, 0.75, 0.5, 0.35, 0.25] and stop if either dimension would fall below 100 pixels.
• First resize pass encodes PNG, JPEG, and WebP, then keeps the smallest encoded buffer. Fallback passes encode JPEG and WebP only, again keeping the smaller output.
• Renderer caps:
  • INSPECT_QUESTION_PREVIEW_WIDTH = 100
  • INSPECT_OUTPUT_COLLAPSED_LINES = 4
  • INSPECT_OUTPUT_EXPANDED_LINES = 16
  • INSPECT_OUTPUT_LINE_WIDTH = 120

Errors

• Settings gate:
  • Image submission is disabled by settings (images.blockImages=true). Disable it to use inspect_image.
• Model resolution / capability:
  • Model registry is unavailable for inspect_image.
  • No models available for inspect_image.
  • Unable to resolve a model for inspect_image.
  • Resolved model <provider>/<id> does not support image input. Configure a vision-capable model for modelRoles.vision.
  • No API key available for <provider>/<id>. Configure credentials for this provider or choose another vision-capable model.
• Input file:
  • Image file too large: <size> exceeds <limit> limit. from ImageInputTooLargeError, remapped to ToolError.
  • inspect_image only supports PNG, JPEG, GIF, and WEBP files detected by file content. when header sniffing fails.
• Model call:
  • inspect_image request failed. if the response stop reason is error without a provider message.
  • Provider errorMessage is passed through when present.
  • inspect_image request aborted. on aborted responses.
  • inspect_image model returned no text output. when the assistant message contains no text blocks after filtering.

Failures surface as thrown ToolErrors from execute(...); the normal success return shape is not used for error reporting.

Notes

• The tool schema is not marked strict in InspectImageTool; callers should still treat only path and question as supported inputs because the implementation reads no other fields.
• The model-facing prompt path on disk is packages/coding-agent/src/prompts/tools/inspect-image.md; the assignment's underscore form does not exist.
• Format support is based on file content, not filename extension. Renaming a non-image file to .png does not make it valid.
• resolveReadPath(...) tries macOS-specific path variants: shell-unescaped spaces, AM/PM narrow no-break-space filenames, NFD normalization, and curly-quote variants.
• loadImageInput(...) also computes textNote, dimensionNote, and final bytes, but inspect_image does not include those in tool output.
• Auto-resize can change the MIME type sent to the model. A JPEG or GIF input may be uploaded as PNG, JPEG, or WebP depending on which encoder output is smallest.
• If resizeImage(...) throws or cannot decode the image, loadImageInput(...) silently keeps the original base64 payload instead of failing.